JP5036143B2 - Plasma processing apparatus, plasma processing method, and computer-readable storage medium - Google Patents

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method for performing plasma processing on a substrate to be processed such as a semiconductor substrate, and a computer-readable storage medium.

  For example, in a manufacturing process of a semiconductor device, in order to form a predetermined pattern on a predetermined layer formed on a semiconductor wafer that is a substrate to be processed, a plasma etching process is often used in which etching is performed with plasma using a resist as a mask.

  Various plasma etching apparatuses for performing such plasma etching are used, and among them, a capacitively coupled parallel plate plasma processing apparatus is the mainstream.

  In the capacitively coupled parallel plate plasma etching apparatus, a pair of parallel plate electrodes (upper and lower electrodes) are arranged in a chamber, a processing gas is introduced into the chamber, and a high frequency is applied to one of the electrodes to be interposed between the electrodes. A high frequency electric field is formed, plasma of a processing gas is formed by the high frequency electric field, and plasma etching is performed on a predetermined layer of the semiconductor wafer.

  Specifically, a plasma etching apparatus is known that forms a plasma by applying a high frequency for plasma formation to the upper electrode and applying a high frequency for ion attraction to the lower electrode. Thus, an etching process with a high selectivity and high reproducibility is possible (for example, Patent Document 1).

  By the way, in response to the recent demand for microfabrication, the thickness of the photoresist used as a mask is reduced, and the photoresist used is also exposed with KrF photoresist (that is, with a laser beam using KrF gas as a light source). Photoresists) are being transferred to ArF photoresists that can form pattern openings of about 0.13 μm or less (that is, photoresists that are exposed to shorter wavelength laser light using ArF gas as the light source). .

  However, since the ArF photoresist has low plasma resistance, there is a problem that the surface becomes rough during the etching, which is hardly generated in the KrF resist. For this reason, problems such as vertical streaks entering the inner wall surface of the opening or spreading of the opening (expansion of CD) occur, which is favorable in combination with the thin film thickness of the photoresist. There is a disadvantage that the etching holes cannot be formed with the etching selectivity.

  On the other hand, in this type of etching apparatus, when the high frequency power for plasma generation supplied to the upper electrode is small, deposits (depots) adhere to the upper electrode after the etching is completed, and process characteristics change and particle There are concerns. Also, when the power is high, the electrode is scraped, and the process characteristics change from when the power is low. Since the appropriate range of the power from the high-frequency power source is determined by the process, it is desirable that the process does not vary with any power. Furthermore, deposits occur on the chamber wall during etching, and in the case of a continuous etching process, the influence of the previous process remains and a memory effect that adversely affects the next process occurs. Elimination of adhesion is also required.

Further, in such a parallel plate type capacitively coupled etching apparatus, when the pressure in the chamber is high and the etching gas to be used is a negative gas (for example, C _x F _y , O _2, etc.), the central portion of the chamber In such a case, it is difficult to control the plasma density.
JP 2000-173993 A

  The present invention has been made in view of such circumstances, and can maintain high plasma resistance of an organic mask layer such as a resist layer and perform etching at a high selection ratio, or adhere deposits to electrodes. It is an object of the present invention to provide a plasma processing apparatus and a plasma processing method that can be effectively eliminated, can perform high-speed etching, or can perform uniform etching on a substrate to be processed.

In order to solve the above problems, according to a first aspect of the present invention, a substrate to be processed is accommodated, a processing container capable of being evacuated, and a first electrode and a substrate to be processed that are disposed to face each other in the processing container are supported. A second high frequency power application unit that applies a first high frequency power having a relatively high frequency to the second electrode, and a second high frequency power having a relatively low frequency to the second electrode. A second high-frequency power application unit that applies DC, a DC power source that applies DC voltage to the first electrode, a processing gas supply unit that supplies a processing gas into the processing container, and the first electrode is grounded And a variable device that can be changed between a floating state and a grounded state, and when a DC voltage is applied to the first electrode based on a command from the overall control device, the variable device is the first device. Electrode ground potential The plasma processing apparatus in a floating state, wherein when the DC voltage is not applied to the first electrode changing device is characterized in that either a floating state or a ground state said first electrode with respect to the ground potential for I will provide a.

  In the plasma processing apparatus according to the first aspect, any one of an applied voltage, an applied current, and an applied power to the first electrode is variable, and the DC power source is applied to the first electrode from the DC power source. It can be set as the structure further equipped with the control apparatus which controls either a voltage, an applied current, and applied power. In addition, the surface of the first electrode facing the second electrode can be formed of a silicon-containing material.

  In the plasma processing apparatus of the first aspect, in order to release a current based on a DC voltage from the DC power source applied to the first electrode through the plasma, a conductive member that is always grounded is provided in the processing container. Can be provided inside. In this case, the first electrode may be an upper electrode, the second electrode may be a lower electrode, and the conductive member may be installed around the second electrode. The first electrode may be an upper electrode, the second electrode may be a lower electrode, and the conductive member may be disposed in the vicinity of the first electrode. In this case, the conductive member can be arranged in a ring shape outside the first electrode.

  In the plasma processing apparatus according to the first aspect, grounding is performed based on a command from the overall control apparatus in order to release a current based on a DC voltage from the DC power source applied to the first electrode through the plasma. A conductive member can be provided in the processing container. In this case, the conductive member can be grounded during plasma etching.

  A DC voltage or an AC voltage can be applied to the conductive member, and the surface is sputtered or etched by applying the DC voltage or the AC voltage based on a command from the overall control device. can do. In this case, it is preferable that a DC voltage or an AC voltage is applied to the conductive member during cleaning. Further, a switching mechanism for switching the connection of the conductive member between the DC power source side and the ground line is further provided, and when the conductive member is connected to the DC power source side by the switching mechanism, By applying a DC voltage or an AC voltage to the conductive member, the surface can be sputtered or etched. In such a configuration, it is preferable that a negative DC voltage can be applied to the conductive member. In such a configuration in which a negative DC voltage can be applied, the processing container is grounded to discharge a DC electron current that flows when a negative DC voltage is applied to the conductive member. It is preferable to provide a conductive auxiliary member.

  In the plasma processing apparatus according to the first aspect, the first grounded in order to release the DC current from the DC power source supplied to the first electrode via the plasma based on a command from the overall control apparatus. A conductive member that takes one of the following conditions: a DC voltage applied from the DC power supply and a second state in which the surface is sputtered or etched; and a negative electrode of the DC power supply is applied to the processing container A first connection connected to an electrode and the conductive member is connected to a ground line; a positive electrode of the DC power supply is connected to the first electrode; and a negative electrode of the DC power supply is connected to the conductive member. And a connection switching mechanism that can form the first state and the second state by the switching, respectively. Can. In this case, the first state is preferably formed during plasma etching, and the second state is preferably formed during cleaning of the conductive member.

In the second aspect of the present invention, a first electrode and a second electrode that supports a substrate to be processed are disposed opposite to each other in a processing container, and the first high-frequency power having a relatively high frequency is disposed on the second electrode. And supplying a processing gas into the processing container while applying a second high-frequency power having a relatively low frequency, generating plasma of the processing gas, and applying to the substrate to be processed supported by the second electrode. A plasma processing method for performing plasma processing, comprising: applying a DC voltage to the first electrode; and applying a plasma process to the substrate to be processed while applying a DC voltage to the first electrode. The first electrode can be changed between a floating state that is not grounded and a grounded state, and when a DC voltage is applied to the first electrode based on a command from the overall control device, the first electrode 1 electrode to ground potential And a low coating state, to provide a plasma processing method which is characterized in that either a floating state or the grounded state the first electrode when the DC voltage to the first electrode is not applied with respect to the ground potential.

  In the plasma processing method according to the second aspect, a conductive member that is always grounded is provided in the processing container, and a current based on a DC voltage applied to the first electrode is released through the plasma. Is preferred. Alternatively, it is preferable that a conductive member to be grounded is provided in the processing container based on a command from the overall control device, and a current based on a DC voltage applied to the first electrode is released via plasma.

In the plasma processing method according to the second aspect, when the insulating film of the substrate to be processed supported by the second electrode is etched, in order to increase the selection ratio of the insulating film to the base film, Process gases include C ₅ F ₈ , Ar, N ₂ , and C ₄ F ₈ , Ar, N ₂ , and C ₄ F ₈ , Ar, N ₂ , O ₂ , and C ₄ F ₈ , Ar, N ₂ , Any combination of CO can be used. Similarly, in order to increase the selectivity with respect to the mask of the insulating film when etching the insulating film of the substrate to be processed supported by the second electrode, as the processing gas, CF ₄ , CF ₄ , Ar , And any combination of N ₂ and H ₂ can also be used. Further, when etching the organic antireflection film on the insulating film of the substrate to be processed supported by the second electrode, CF ₄ , CF ₄ , C ₃ F ₈ , and CF ₄ , C _{4 are used} as the processing gas. Any combination of F ₈ and CF ₄ , C ₄ F ₆ can be used. Furthermore, when the insulating film of the substrate to be processed supported by the second electrode is etched, in order to increase the etching rate of the insulating film, as the processing gas, C ₄ F ₆ , CF ₄ , Ar, O ₂ and C ₄ F ₆ , C ₃ F ₈ , Ar, O ₂ , and C ₄ F ₆ , C ₄ F ₈ , Ar, O ₂ , and C ₄ F ₆ , C ₂ F ₆ , Ar, O ₂ , And any combination of C ₄ F ₈ , Ar, O ₂ can be used.

  According to a third aspect of the present invention, there is provided a computer storage medium storing a control program that runs on a computer, and the control program is executed so that the plasma processing method according to the second aspect is performed at the time of execution. A computer readable storage medium is provided that controls the plasma processing apparatus.

  According to the present invention, the first high-frequency power application unit that applies the first high-frequency power having a relatively high frequency to the second electrode that supports the substrate to be processed, and the second high-frequency power application unit that has a relatively low frequency. A second high frequency power application unit that applies high frequency power is connected, and a DC power source that applies a DC voltage is connected to the first electrode, so that the frequency from the first and second high frequency power application units is connected to the second electrode. By applying a DC voltage to the first electrode when forming plasma of a processing gas by applying different high frequency powers and performing plasma etching while attracting ions to the substrate to be processed, (1) the self of the first electrode Sputtering effect on the surface of the first electrode by increasing the absolute value of the bias voltage, (2) Effect of expanding the plasma sheath in the first electrode and reducing the plasma to be formed, (3) First The effect of irradiating a substrate to be processed with electrons generated in the vicinity of the substrate, (4) the effect of controlling the plasma potential, (5) the effect of increasing the electron (plasma) density, and (6) increasing the plasma density at the center. At least one of the effects can be achieved.

  Due to the effect (1) above, even when a polymer derived from the process gas and a polymer from the photoresist adhere to the surface of the first electrode, the surface of the electrode can be cleaned by sputtering the polymer. At the same time, an optimal polymer can be supplied onto the substrate to eliminate the roughness of the photoresist film. Further, when the electrode itself is sputtered, an electrode material can be supplied onto the substrate to strengthen an organic mask such as a photoresist film.

  In addition, due to the effect (2), the effective residence time on the substrate to be processed is reduced, and the plasma is concentrated on the substrate to be processed, so that the diffusion is suppressed and the exhaust space is reduced. Dissociation is suppressed, and an organic mask such as a photoresist film is hardly etched.

  Furthermore, due to the effect (3), the mask composition on the substrate to be processed is modified, and the roughness of the photoresist film can be eliminated. In addition, since the substrate to be processed is irradiated with high-speed electrons, the shading effect is suppressed and the fine workability of the substrate to be processed is improved.

  Furthermore, due to the effect of (4) above, the plasma potential is appropriately controlled so that etching by-products adhere to the inner members of the processing vessel such as electrodes, chamber walls (depot shields, etc.) and insulating materials in the processing vessel. Can be suppressed.

  Furthermore, the etching rate (etching rate) for the substrate to be processed can be increased by the effect (5).

Furthermore, due to the effect of (6) above, even when the pressure in the processing container is high and the etching gas used is a negative gas, the plasma density in the central part in the processing container is lower than the surroundings. The plasma density can be controlled so that the plasma density can be made uniform.

  Thereby, the plasma resistance of the organic mask layer such as a resist layer can be maintained high and etching can be performed with a high selectivity. Or adhesion of the deposit to an electrode can be canceled effectively. Alternatively, high-speed etching can be performed, or uniform etching can be performed on the substrate to be processed.

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view schematically showing a plasma etching apparatus according to an embodiment of the present invention. As shown in this figure, this apparatus applies, for example, 40 MHz high frequency (RF) power for plasma generation from the first high frequency power supply 89 to the susceptor 16 which is the lower electrode, and ion from the second high frequency power supply 90. A plasma etching apparatus of a lower RF 2 frequency application type that applies a high frequency (RF) power of, for example, 2 MHz for pulling in, and a variable direct current power source 50 is connected to the upper electrode 34 as shown in the figure, and a predetermined direct current (DC) voltage is applied. Is a plasma etching apparatus to which is applied. This plasma etching apparatus will be further described in detail with reference to FIG.

  FIG. 2 is a schematic sectional view showing a plasma etching apparatus according to one embodiment of the present invention. This plasma etching apparatus is configured as a capacitively coupled parallel plate plasma etching apparatus, and has a substantially cylindrical chamber (processing vessel) 10 made of aluminum whose surface is anodized, for example. The chamber 10 is grounded for safety.

  A cylindrical susceptor support 14 is disposed at the bottom of the chamber 10 via an insulating plate 12 made of ceramics or the like, and a susceptor 16 made of, for example, aluminum is provided on the susceptor support 14. The susceptor 16 constitutes a lower electrode, on which a semiconductor wafer W as a substrate to be processed is placed.

  On the upper surface of the susceptor 16, an electrostatic chuck 18 that holds the semiconductor wafer W by electrostatic force is provided. The electrostatic chuck 18 has a structure in which an electrode 20 made of a conductive film is sandwiched between a pair of insulating layers or insulating sheets, and a DC power source 22 is electrically connected to the electrode 20. The semiconductor wafer W is attracted and held on the electrostatic chuck 18 by an electrostatic force such as a Coulomb force generated by a DC voltage from the DC power supply 22.

  A conductive focus ring (correction ring) 24 made of, for example, silicon is disposed on the upper surface of the susceptor 16 around the electrostatic chuck 18 (semiconductor wafer W) to improve etching uniformity. A cylindrical inner wall member 26 made of, for example, quartz is provided on the side surfaces of the susceptor 16 and the susceptor support 14.

  Inside the susceptor support 14, for example, a coolant chamber 28 is provided on the circumference. A coolant having a predetermined temperature, for example, cooling water, is circulated and supplied to the coolant chamber from a chiller unit (not shown) provided outside through the pipes 30a and 30b, and the processing temperature of the semiconductor wafer W on the susceptor is controlled by the coolant temperature. Can be controlled.

  Further, a heat transfer gas, for example, He gas, from a heat transfer gas supply mechanism (not shown) is supplied between the upper surface of the electrostatic chuck 18 and the back surface of the semiconductor wafer W via the gas supply line 32.

  Above the susceptor 16 that is the lower electrode, an upper electrode 34 is provided in parallel so as to face the susceptor 16. A space between the upper and lower electrodes 34 and 16 becomes a plasma generation space. The upper electrode 34 faces the semiconductor wafer W on the susceptor 16 that is the lower electrode, and forms a surface that is in contact with the plasma generation space, that is, a facing surface.

  The upper electrode 34 is supported on the upper portion of the chamber 10 via an insulating shielding member 42, and forms an opposing surface to the susceptor 16 and has a number of discharge holes 37, and the electrode plate 36 is detachably supported, and is constituted by a water-cooled electrode support 38 made of a conductive material, for example, aluminum whose surface is anodized. The electrode plate 36 is preferably a low-resistance conductor or semiconductor with low Joule heat, and a silicon-containing material is preferable from the viewpoint of strengthening the resist as will be described later. From such a viewpoint, the electrode plate 36 is preferably made of silicon or SiC. A gas diffusion chamber 40 is provided inside the electrode support 38, and a number of gas flow holes 41 communicating with the gas discharge holes 37 extend downward from the gas diffusion chamber 40.

The electrode support 38 is formed with a gas inlet 62 for introducing a processing gas to the gas diffusion chamber 40, and a gas supply pipe 64 is connected to the gas inlet 62, and a processing gas supply source is connected to the gas supply pipe 64. 66 is connected. The gas supply pipe 64 is provided with a mass flow controller (MFC) 68 and an opening / closing valve 70 in order from the upstream side. Then, as a processing gas for etching, a fluorocarbon gas (C _x F _y ) such as C ₄ F ₈ gas reaches the gas diffusion chamber 40 from the gas supply pipe 64 from the processing gas supply source 66, and the gas flow It is discharged into the plasma generation space in the form of a shower through the hole 41 and the gas discharge hole 37. That is, the upper electrode 34 functions as a shower head for supplying the processing gas.

  A variable DC power supply 50 is electrically connected to the upper electrode 34 via a low pass filter (LPF) 46a. The variable DC power supply 50 may be a bipolar power supply. The variable DC power supply 50 can be turned on / off by an on / off switch 52. The polarity and current / voltage of the variable DC power supply 50 and on / off of the on / off switch 52 are controlled by a controller (control device) 51.

  The low-pass filter (LPF) 46a is for trapping high frequencies from first and second high-frequency power sources, which will be described later, and is preferably composed of an LR filter or an LC filter.

  A cylindrical ground conductor 10 a is provided so as to extend upward from the side wall of the chamber 10 above the height position of the upper electrode 34. The cylindrical ground conductor 10a has a top wall at the top.

  A first high-frequency power source 89 is electrically connected to the susceptor 16, which is the lower electrode, via a matching unit 87, and a second high-frequency power source 90 is connected via a matching unit 88. The first high frequency power supply 89 outputs a high frequency power of 27 MHz or higher, for example, 40 MHz. The second high frequency power supply 90 outputs a high frequency power of 13.56 MHz or less, for example, 2 MHz.

  Matching devices 87 and 88 are used to match the load impedance to the internal (or output) impedances of the first and second high-frequency power sources 89 and 90, respectively, and are used when the plasma is generated in the chamber 10. Also, the internal impedance and the load impedance of the second high-frequency power supplies 89 and 90 function so as to coincide with each other.

An exhaust port 80 is provided at the bottom of the chamber 10, and an exhaust device 84 is connected to the exhaust port 80 via an exhaust pipe 82. The exhaust device 84 includes a vacuum pump such as a turbo molecular pump, and can reduce the pressure in the chamber 10 to a desired degree of vacuum. Further, a loading / unloading port 85 for the semiconductor wafer W is provided on the side wall of the chamber 10, and the loading / unloading port 85 can be opened and closed by a gate valve 86. A deposition shield 11 is detachably provided along the inner wall of the chamber 10 for preventing the etching byproduct (depot) from adhering to the chamber 10. That is, the deposition shield 11 forms a chamber wall. The deposition shield 11 is also provided on the outer periphery of the inner wall member 26. An exhaust plate 83 is provided between the deposition shield 11 on the chamber wall side at the bottom of the chamber 10 and the deposition shield 11 on the inner wall member 26 side. As the deposition shield 11 and the exhaust plate 83, an aluminum material coated with ceramics such as Y ₂ O ₃ can be suitably used.

  A conductive member (GND block) 91 connected to the ground in a DC manner is provided at a portion substantially the same height as the wafer W that constitutes the chamber inner wall of the deposition shield 11. Demonstrate the effect of preventing abnormal discharge.

  Each component of the plasma etching apparatus is connected to and controlled by a control unit (overall control device) 95. In addition, the control unit 95 includes a user interface 96 including a keyboard on which a process manager inputs commands to manage the plasma etching apparatus, a display that visualizes and displays the operating status of the plasma processing apparatus, and the like. It is connected.

  Furthermore, the control unit 95 causes each component of the plasma etching apparatus to execute processes according to a control program for realizing various processes executed by the plasma etching apparatus under the control of the control unit 95 and processing conditions. A storage unit 97 that stores a program for storing the recipe, that is, a recipe, is connected. The recipe may be stored in a hard disk or semiconductor memory, or set at a predetermined position in the storage unit 97 while being stored in a portable computer-readable storage medium such as a CDROM or DVD. Also good.

  Then, if necessary, an arbitrary recipe is called from the storage unit 97 by an instruction from the user interface 96 and is executed by the control unit 95, so that a desired value in the plasma etching apparatus is controlled under the control of the control unit 95. Processing is performed. Note that the plasma processing apparatus (plasma etching apparatus) described in the embodiment of the present invention includes the control unit 95.

When performing the etching process in the plasma etching apparatus configured as described above, first, the gate valve 86 is opened, and the semiconductor wafer W to be etched is loaded into the chamber 10 via the loading / unloading port 85, and the susceptor is loaded. 16 is mounted. Then, a processing gas for etching is supplied from the processing gas supply source 66 to the gas diffusion chamber 40 at a predetermined flow rate, and is supplied into the chamber 10 through the gas flow holes 41 and the gas discharge holes 37, while being exhausted. The chamber 10 is evacuated by 84, and the pressure therein is set to a set value within a range of 0.1 to 150 Pa, for example. Here, various conventionally used gases can be employed as the processing gas. For example, a gas containing a halogen element typified by a fluorocarbon gas (C _x F _y ) such as C ₄ F ₈ gas. Can be suitably used. Furthermore, other gases such as Ar gas and O ₂ gas may be contained.

  With the etching gas introduced into the chamber 10 as described above, high-frequency power for plasma generation is applied from the first high-frequency power supply 88 to the susceptor 16 as the lower electrode at a predetermined power, and the second high-frequency power supply From 90, high-frequency power for ion attraction is applied at a predetermined power. Then, a predetermined DC voltage is applied to the upper electrode 34 from the variable DC power supply 50. Further, a DC voltage is applied from the DC power source 22 for the electrostatic chuck 18 to the electrode 20 of the electrostatic chuck 18 to fix the semiconductor wafer W to the susceptor 16.

  The processing gas discharged from the gas discharge hole 37 formed in the electrode plate 36 of the upper electrode 34 is turned into plasma in the glow discharge between the upper electrode 34 and the lower electrode susceptor 16 generated by the high frequency power. The surface to be processed of the semiconductor wafer W is etched by the generated radicals and ions.

  In this plasma etching apparatus, high frequency power in a high frequency region (for example, 10 MHz or more) is supplied from the first high frequency power supply 89 to the susceptor 16 that is the lower electrode. And high density plasma can be formed even under lower pressure conditions.

In this embodiment, when plasma is formed in this way, a DC voltage having a predetermined polarity and magnitude is applied to the upper electrode 34 from the variable DC power supply 50. At this time, the self-bias voltage V _dc on the surface becomes deep enough to obtain a predetermined (moderate) sputtering effect on the surface of the upper electrode 34 that is the application electrode, that is, the surface of the electrode plate 36, that is, the upper electrode 34. It is preferable to control the voltage applied from the variable DC power supply 50 by the controller 51 so that the absolute value of V _{dc on} the surface becomes large. When plasma is generated by applying a high frequency from the first high frequency power supply 89, polymer may adhere to the upper electrode 34. By applying an appropriate DC voltage from the variable DC power supply 50, the upper electrode 34 can be applied. The surface of the upper electrode 34 can be cleaned by sputtering the polymer adhering to the surface. At the same time, an optimum amount of polymer can be supplied onto the semiconductor wafer W to eliminate the surface roughness of the photoresist film. Further, by adjusting the voltage from the variable DC power supply 50 and sputtering the upper electrode 34 itself so as to supply the electrode material itself to the surface of the semiconductor wafer W, a carbide is formed on the surface of the photoresist film to thereby form the photoresist. The film is strengthened, and the sputtered electrode material reacts with F in the fluorocarbon-based processing gas and is exhausted, whereby the F ratio in the plasma is reduced and the photoresist film becomes difficult to be etched. When the electrode plate 36 is a silicon-containing material such as silicon or SiC, the silicon sputtered on the surface of the electrode plate 36 reacts with the polymer to form SiC on the surface of the photoresist film, and the photoresist film is extremely strong. Moreover, since Si easily reacts with F, the above effect is particularly great. Accordingly, the material of the electrode plate 36 is preferably a silicon-containing substance. In this case, the applied current or the applied power may be controlled instead of controlling the applied voltage from the variable DC power supply 50.

Thus, when the DC voltage is applied to the upper electrode 34 and the self-bias voltage V _dc becomes deeper, the thickness of the plasma sheath formed on the upper electrode 34 side increases as shown in FIG. When the plasma sheath becomes thicker, the plasma is reduced by that amount. For example, when no DC voltage is applied to the upper electrode 34, the V _dc on the upper electrode side is, for example, −100 V, and the plasma has a thin sheath thickness d ₀ as shown in FIG. However, when a DC voltage of −900 V is applied to the upper electrode 34, the V _dc on the upper electrode side becomes −900 V, and the thickness of the plasma sheath is proportional to 3/4 of the absolute value of V _dc . as shown in b), is thicker plasma sheath d ₁ is formed, correspondingly plasma is shrink. By forming such a thick plasma sheath and appropriately reducing the plasma, the effective residence time on the semiconductor wafer W is reduced, and the plasma is concentrated on the wafer W to suppress diffusion and to provide a dissociation space. Decrease. As a result, dissociation of the fluorocarbon-based processing gas is suppressed, and the photoresist film becomes difficult to be etched. Therefore, the voltage applied from the variable DC power supply 50 is preferably controlled by the controller 51 so that the thickness of the plasma sheath in the upper electrode 34 becomes thick enough to form a desired reduced plasma. Also in this case, the applied current or the applied power may be controlled instead of controlling the applied voltage from the variable DC power supply 50.

  Further, when plasma is formed, electrons are generated in the vicinity of the upper electrode 34. When a DC voltage is applied to the upper electrode 34 from the variable DC power supply 50, electrons are accelerated in the vertical direction of the processing space due to the potential difference between the applied DC voltage value and the plasma potential. The semiconductor wafer W is irradiated with electrons by setting the polarity, voltage value, and current value of the variable DC power supply 50 as desired. The irradiated electrons modify the composition of the photoresist film as a mask, and the photoresist film is strengthened. Therefore, by controlling the amount of electrons generated in the vicinity of the upper electrode 34 by the applied voltage value and the applied current value of the variable DC power supply 50 and the acceleration voltage of such electrons to the wafer W, a predetermined amount for the photoresist film is controlled. It can be strengthened.

  In particular, when the photoresist film on the semiconductor wafer W is a photoresist film for ArF excimer laser (wavelength 193 nm) (hereinafter referred to as ArF resist film), the polymer structure of the ArF resist film has the following chemical formula (1) Through the reaction shown in (2), electrons are irradiated to form a structure as shown on the right side of the chemical formula (3). In other words, when irradiated with electrons, the composition of the ArF resist film is modified (resist cross-linking reaction) as shown in part d of the chemical formula (3). Since this d portion has a function of greatly increasing the etching resistance (plasma resistance), the etching resistance of the ArF resist film is remarkably increased. For this reason, the surface roughness of the ArF resist film can be suppressed, and the etching selectivity of the etching target layer with respect to the ArF resist film can be increased.

  Therefore, it is preferable to control the applied voltage value and current value from the variable DC power supply 50 by the controller 51 so that the etching resistance of the photoresist film (particularly, ArF resist film) is enhanced by electron irradiation. As described above, when a DC voltage is applied to the upper electrode 34, electrons generated in the vicinity of the upper electrode 34 when plasma is formed are accelerated in the vertical direction of the processing space. By making the polarity, voltage value, and current value as desired, electrons can reach the hole of the semiconductor wafer W, the shading effect can be suppressed, and a good processing shape without bowing can be obtained. The uniformity of the processed shape can be improved.

When an electron current amount I _DC due to a DC voltage is used as an electron amount of electrons whose acceleration voltage is controlled to be incident on the wafer W, assuming that an ion current amount I _ion incident on the wafer from the plasma is I _DC > (1 / 2) It is preferable to satisfy _Iion . I _ion = Zρv _ion (where Z is the number of charges, ρ is the flow velocity density, v _{ion is the} ion velocity, e is the charge amount of electrons 1.6 × 10 ⁻¹⁹ C), and ρ is proportional to the electron density Ne. Therefore, I _ion is proportional to Ne.

  In this way, the DC voltage applied to the upper electrode 34 is controlled, the sputtering function of the upper electrode 34 or the plasma reduction function, and a large amount of electrons generated by the upper electrode 34 to the semiconductor wafer W. By providing the supply function, it is possible to strengthen the photoresist film, supply the optimum polymer, suppress dissociation of the processing gas, etc., and suppress the surface roughness of the photoresist. The etching selectivity can be increased. At the same time, the spread of the CD in the opening portion of the photoresist can be suppressed, and more accurate pattern formation can be realized. In particular, such an effect can be further enhanced by controlling the DC voltage so that the three functions of the sputtering function, the plasma reduction function, and the electron supply function are appropriately exhibited.

  Note that which of the above functions is dominant depends on processing conditions and the like, and the voltage applied from the variable DC power supply 50 is controlled by the controller so that one or more of these functions can be exhibited and the above effects can be effectively achieved. It is preferable to control by 51.

  Further, the plasma potential can be controlled by adjusting the DC voltage applied to the upper electrode 34. Thereby, it has a function which suppresses adhesion of the etching by-product to the deposition shield 11, the inner wall member 26, and the insulating shielding member 42 which comprise the upper electrode 34 and a chamber wall.

When the etching by-product adheres to the upper electrode 34, the deposition shield 11 constituting the chamber wall, etc., there is a risk of change in process characteristics and particle. In particular, when the multilayer film is continuously etched, when the multilayer film in which the Si-based organic film (SiOC), the SiN film, the SiO ₂ film, and the photoresist are sequentially stacked on the semiconductor wafer W is continuously etched, Since the etching conditions differ for each film, the effect of the previous process remains and a memory effect that adversely affects the next process occurs.

  Since the adhesion of such etching by-products is affected by the potential difference between the plasma potential and the upper electrode 34, the chamber wall, etc., if the plasma potential can be controlled, the adhesion of such etching products is suppressed. be able to.

  As described above, by controlling the voltage applied from the variable DC power supply 50 to the upper electrode 34, the plasma potential can be lowered, and the deposition shield 11 constituting the upper electrode 34 and the chamber wall, and further the insulating material in the chamber 10. The adhesion of etching by-products to (members 26 and 42) can be suppressed. The value of the plasma potential Vp is preferably in the range of 80V ≦ Vp ≦ 200V.

  Furthermore, another effect obtained by applying a DC voltage to the upper electrode 34 is that plasma is formed by the applied DC voltage, thereby increasing the plasma density and increasing the etching rate.

  This is because when a negative DC voltage is applied to the upper electrode, electrons hardly enter the upper electrode, and the disappearance of the electrons is suppressed, and when ions are accelerated and enter the upper electrode, the electrons can exit the electrode. This is because the electrons are accelerated at a high speed by the difference between the plasma potential and the applied voltage value, and the neutral gas is ionized (plasmaized), thereby increasing the electron density (plasma density).

This will be described based on experimental results.
FIG. 4 shows the condition of HARC etching with the first high frequency power applied to the lower electrode susceptor 16 having a frequency of 40 MHz, a second high frequency power of 3.2 MHz, and a pressure of 4 Pa. It is a figure which shows the relationship between the output of each high frequency electric power, and electron density distribution when changing the absolute value of the negative DC voltage to apply to 0V, 300V, 600V, and 900V. FIG. 5 also shows that the absolute value of the DC voltage applied to the upper electrode is 0V, 300V, 600V, and 900V under the conditions of Via etching with a pressure of 6.7 Pa when two high-frequency powers having the same frequency are applied. It is a figure which shows the relationship between the output of each high frequency electric power and electron density distribution at the time of changing. As shown in these figures, it can be seen that the electron density (plasma density) increases as the absolute value of the applied DC voltage increases. FIG. 6 is a diagram showing an electron density distribution in the wafer radial direction when the first high frequency power is 3000 W and the second high frequency power is 4000 W by the HARC etching. As shown in this figure, it can be seen that the electron density increases as the absolute value of the applied DC voltage increases.

  Furthermore, when plasma is formed, by applying a DC voltage from the variable DC power supply 50 to the upper electrode 34, it is possible to increase the plasma density particularly in the center during trench etching. When the pressure in the chamber 10 is high and the etching gas to be used is a negative gas, such as the conditions during trench etching, the plasma density in the center of the chamber 10 tends to be low. By applying a DC voltage to the upper electrode 34 to increase the plasma density at the center, the plasma density can be controlled so that the plasma density becomes uniform.

This will be explained by experimental results.
In the apparatus of FIG. 2, a semiconductor wafer is loaded into a chamber and placed on a susceptor, and CF ₄ gas, CHF ₃ gas, Ar gas, and N ₂ gas are introduced into the chamber as processing gases. The DC voltage applied to the upper electrode under the conditions of trench etching in which the pressure is 26.6 Pa, the first high-frequency power is 300 W at 40 MHz, and the second high-frequency power is 1000 W at 3.2 MHz and applied to the susceptor as the lower electrode. The electron density (plasma density) distribution in the wafer radial direction was measured when no power was applied and when −600 W was applied. The result is shown in FIG. As shown in this figure, when a DC voltage is not applied, the electron density at the center of the wafer is lower than the other parts, whereas by applying a DC voltage, the electron density at the center of the wafer is increased. The electron density was confirmed to be uniform. Further, the application of a DC voltage increased the electron density as a whole.

  As described above, by controlling the DC voltage applied to the upper electrode 34, the above-mentioned sputtering function of the upper electrode 34, the plasma reduction function, the electron supply function, the plasma potential control function, the electron density (plasma density). It is possible to effectively exhibit at least one of the ascending function and the plasma density control function.

  In the foregoing, the operation and effect when a direct current (DC) voltage is applied to the upper electrode 34 has been described.

  In this embodiment, as a plasma etching apparatus that applies a DC voltage to an upper electrode, a lower part that applies a first radio frequency (RF) power for plasma formation and a second radio frequency (RF) power for ion attraction to the lower electrode. Although the description has been made using the RF dual frequency application type plasma etching apparatus, the advantages of the lower RF dual frequency application type plasma etching apparatus over other capacitively coupled plasma etching apparatuses include the following.

  First, by applying high-frequency power for plasma formation to the lower electrode as in this embodiment, plasma can be formed at a location closer to the wafer, so that the plasma does not diffuse to a wide area and the processing gas is dissociated. Therefore, the etching rate for the wafer can be increased even under conditions where the pressure in the processing chamber is high and the plasma density is low. In addition, even when the frequency of the high-frequency power for plasma formation is high, a relatively large ion energy can be secured, which is highly efficient. In contrast, in an apparatus of a type that applies high-frequency power for plasma formation to the upper electrode, plasma is generated in the vicinity of the upper electrode. Therefore, under conditions where the pressure in the processing vessel is high and the plasma density is low, the wafer is It is difficult to increase the etching rate with respect to.

  In addition, as in this embodiment, the plasma formation function and the ion attraction function necessary for plasma etching can be independently performed by separately applying high frequency power for plasma formation and high frequency power for ion attraction to the lower electrode. It becomes possible to control. On the other hand, in a device of a type that applies high frequency power of one frequency to the lower electrode, it is impossible to independently control the function of plasma formation and the function of ion attraction, and high fine workability is required. It is difficult to satisfy the etching conditions.

  As described above, it is possible to form a plasma near the wafer, the plasma is not diffused over a wide area, and the plasma forming function and the ion drawing function can be independently controlled. By applying a DC voltage to the upper electrode in a frequency-applied plasma etching apparatus, the upper electrode sputtering function, plasma reduction function, electron supply function to the wafer, plasma potential control function, plasma density control Since it becomes possible to have at least one of the ascending function and the plasma density control function, it is possible to provide a plasma etching apparatus having higher performance adapted to the recent etching fine processing.

  Note that the application of a DC voltage to the upper electrode 34 may be selective. In etching conditions that require application of a DC voltage to the upper electrode 34, the variable DC power supply 50 and the relay switch 52 shown in FIG. 2 are turned on, and in etching conditions that do not require application of a DC voltage to the upper electrode 34. The variable DC power supply 50 and the relay switch 52 may be turned off.

  Further, when a DC voltage is applied to the upper electrode 34, if the upper electrode 34 is grounded, the function of DC voltage application is lost, and therefore the upper electrode 34 needs to be DC floating. FIG. 8 shows a schematic diagram. In FIG. 8, the portions where the capacitors 501, 502, and 503 are electrically formed actually contain a dielectric, and the upper electrode 34 is connected to the processing container 10 and the ground conductor 10a via the dielectric. DC floating. The high-frequency power applied to the lower electrode 16 from the high-frequency power sources 89 and 90 reaches the upper electrode 34 through the processing space, and is grounded through the capacitors 501, 502, and 503 and the grounded processing container 10 and the ground conductor. Reach 10a.

  When the variable DC power supply 50 and the relay switch 52 are turned off and no DC voltage is applied to the upper electrode 34, the upper electrode 34 may be variable to either the ground state or the DC floating state. In the example of FIG. 9, when a DC voltage is not applied to the upper electrode 34, the ground conductor 10a and the upper electrode 34 are short-circuited by a switch (variable device) 504 so that the upper electrode 34 is grounded. ) 504 may be turned off, and the upper electrode 34 may be in a DC floating state.

  Further, as shown in FIG. 10, a portion where the capacitor 501 is electrically formed may be configured such that the capacitance can be electrically varied. Thereby, the potential of the upper electrode can be varied.

  As shown in FIG. 11, for example, a detector 55 that detects the state of plasma from the plasma detection window 10 a is provided, and the controller 51 controls the variable DC power supply 50 based on the detection signal, so that It is possible to automatically apply a direct current voltage to the upper electrode 34 so as to effectively perform the function.

  Further, a detector for detecting the sheath thickness or a detector for detecting the electron density may be provided, and the controller 51 may control the variable DC power supply 50 based on the detection signal.

  Here, in a plasma etching apparatus that applies a DC voltage to the upper electrode with a lower RF dual frequency application type, it is used as a processing gas when etching an insulating film (for example, a low-k film) formed on the wafer W. Examples of particularly preferred gas combinations are given below.

As a combination of processing gases preferably used during over-etching under the conditions of via etching, (C ₅ F ₈ , Ar, N ₂ ) or (C ₄ F ₈ , Ar, N ₂ ) or (C ₄ F ₈ , Ar, N ₂ , O ₂ ) or (C ₄ F ₈ , Ar, N ₂ , CO). Thereby, the selection ratio of the insulating film to the base film (SiC, SiN, etc.) can be increased.

Moreover, CF ₄ or (CF ₄ , Ar) or (N ₂ , H ₂ ) can be given as a combination of processing gases that are preferably used under the conditions of trench etching. Thereby, the selection ratio of the insulating film to the mask can be increased.

Further, under the conditions for etching the organic antireflection film on the insulating film, CF ₄ or (CF ₄ , C ₃ F ₈ ) or (CF ₄ , C ₄ F ₈ ) or (CF ₄ , C ₄ F ₆ ).

In addition, in the condition of HARC etching, a combination of processing gases preferably used is (C ₄ F ₆ , CF ₄ , Ar, O ₂ ) or (C ₄ F ₆ , C ₃ F ₈ , Ar, O ₂ ). Or (C ₄ F ₆ , C ₄ F ₈ , Ar, O ₂ ) or (C ₄ F ₆ , C ₂ F ₆ , Ar, O ₂ ) or (C ₄ F ₈ , Ar, O ₂ ). Thereby, the etching rate of the insulating film can be increased.

The present invention is not limited to the above, and it is possible to use (a combination of C _x H _y F _z gas / addition gas / dilution gas such as N ₂ and O ₂ ).

  By the way, when a DC voltage is applied to the upper electrode 34, electrons accumulate in the upper electrode 34, and abnormal discharge may occur between the inner wall of the chamber 10 and the like. In order to suppress such abnormal discharge, in this embodiment, a GND block (conductive member) 91 which is a part grounded in a DC manner is provided on the deposition shield 11 on the chamber wall side. This GND block 91 is exposed to the plasma surface, and is electrically connected to the conductive portion inside the deposition shield 11, and the DC voltage and current applied from the variable DC power supply 50 to the upper electrode 34 passes through the processing space. Then, it reaches the GND block 91 and is grounded via the deposition shield 11. The GND block 91 is a conductor, and is preferably a silicon-containing material such as Si or SiC. C can also be suitably used. With this GND block 91, electrons accumulated in the upper electrode 34 can be released, and abnormal discharge can be prevented. The protruding length of the GND block 91 is preferably 10 mm or more.

  In order to prevent abnormal discharge, when a DC voltage is applied to the upper electrode 34, an extremely short reverse polarity pulse as shown in FIG. A method of neutralizing electrons is also effective.

As long as the GND block 91 is provided in the plasma formation region, the position is not limited to the position shown in FIG. 1. For example, as shown in FIG. 13, the GND block 91 is provided around the susceptor 16. Alternatively, as shown in FIG. 14, it may be provided in the vicinity of the upper electrode 34, for example, in the form of a ring outside the upper electrode 34. However, when the plasma is formed, if Y ₂ O ₃ or polymer coated on the deposition shield 11 or the like flies and adheres to the GND block 91, it will not be grounded in a DC manner, and an abnormal discharge prevention effect will be obtained. Since it becomes difficult to exhibit, it is important that these do not adhere easily. For this purpose, the GND block 91 is preferably located away from the member covered with Y ₂ O ₃ or the like, and the adjacent parts are preferably Si-containing substances such as Si or quartz (SiO ₂ ). For example, as shown in FIG. 15A, it is preferable to provide a Si-containing member 93 around the GND block 91. In this case, it is preferable that the length L of the lower part of the Si-containing member 93 below the GND block 91 is equal to or longer than the protruding length M of the GND block 91. Further, in order to suppress the functional deterioration due to the adhesion of Y ₂ O ₃ or polymer, it is effective to provide a recess 91a as a GND block 91 to which flying objects are difficult to adhere as shown in FIG. . It is also effective to increase the surface area of the GND block 91 so that it is not easily covered with Y ₂ O ₃ or a polymer. In addition, a high temperature is effective for suppressing deposits, but high-frequency power for plasma formation is supplied to the upper electrode 34, and the temperature in the vicinity thereof increases. From the viewpoint of preventing the attachment of the kimono, it is also preferable to provide it near the upper electrode 34 as shown in FIG. In this case, in particular, as shown in FIG. 14, it is more preferable to provide a ring shape outside the upper electrode 34.

In order to more effectively eliminate the influence of deposits on the GND block 91 due to the flight of Y ₂ O ₃ or polymer coated on the deposition shield 11 or the like, as shown in FIG. It is effective to make it possible to apply a negative DC voltage. That is, by applying a negative DC voltage to the GND block 91, the deposits adhered thereto are sputtered or etched, and the surface of the GND block 91 can be cleaned. In the configuration of FIG. 16, a switching mechanism 53 is provided to switch the connection of the GND block 91 between the variable DC power supply 50 side and the ground line so that a voltage can be applied to the GND block 91 from the variable DC power supply 50. There is provided a grounded conductive auxiliary member 91b for allowing a direct current electronic current generated when a negative direct current voltage is applied to the GND block 91 to flow. The switching mechanism 53 includes a first switch 53a for switching the connection of the variable DC power supply 50 between the matching unit 46 side and the GND block 91 side, and a second switch 53b for turning on / off the connection of the GND block 91 to the ground line. And have. In the example of FIG. 16 , the GND block 91 is provided in a ring shape outside the upper electrode 34, and the conductive auxiliary member 91 b is provided on the outer periphery of the susceptor 16, and this arrangement is preferable. It may not be an arrangement.

In the apparatus having the configuration of FIG. 16, during plasma etching, the first switch 53 a of the switching mechanism 53 is normally connected to the upper electrode 34 side and the variable DC power supply 50 is connected to the upper electrode 34 as shown in FIG. The second switch 53b is turned on, and the GND block 91 is connected to the ground line side. In this state, power is supplied from the variable DC power supply 50 to the upper electrode 34, when the first RF power supply 89 is supplying power to the susceptor 16 serving as the lower electrode plasma is formed, a DC electron current through the plasma Then, it flows into the GND block 91 and the conductive auxiliary member 91b that are grounded from the upper electrode 34 (the direction of the positive ion current flows in the opposite direction). At this time, the surface of the GND block 91 may be covered with the deposit such as Y ₂ O ₃ or polymer as described above.

For this reason, such deposits are cleaned. At the time of such cleaning, as shown in FIG. 17B, the first switch 53a of the switching mechanism 53 is switched to the GND block 91 side, and the second switch 53b is turned off. In this state, power is supplied from the first high frequency power supply 89 to the susceptor 16 as the lower electrode to form cleaning plasma, and a negative DC voltage is applied from the variable DC power supply 50 to the GND block 91. As a result, the DC electron current flows from the GND block 91 into the conductive auxiliary member 91b. Conversely, positive ions flow into the GND block 91. For this reason, the surface of the GND block 91 can be ion-sputtered by adjusting the DC voltage and controlling the incident energy of positive ions to the GND block 91, thereby removing the deposits on the surface of the GND block 91. Can do.

  Further, in a part of the period during the plasma etching, as shown in FIG. 18, the second switch 53b may be turned off and the GND block 91 may be in a floating state. At this time, the DC electron current flows from the upper electrode 34 into the conductive auxiliary member 91b via the plasma (the direction of the positive ion current is reversed). At this time, a self-bias voltage is applied to the GND block 91, and positive ions are incident with the corresponding energy, so that the GND block 91 can be cleaned during plasma etching.

  During the cleaning, the applied DC voltage may be small, and the DC electron current at that time is small. For this reason, in the configuration of FIG. 16, the conductive auxiliary member 91 b is not necessarily required when electric charges are not accumulated in the GND block 91 due to the leakage current.

In the example of FIG. 16 described above, at the time of cleaning, the connection of the variable DC power supply 50 is switched from the upper electrode 34 side to the GND electrode 91 side, and a DC electron current when a DC voltage is applied is transferred from the GND block 91 to the conductive auxiliary member 91b . However, the positive electrode of the variable DC power supply 50 is connected to the upper electrode 34, the negative electrode is connected to the GND block 91, and a DC electron current when a DC voltage is applied flows from the GND block 91 to the upper electrode 34. It may be. In this case, the conductive auxiliary member is not necessary. Such a configuration is shown in FIG. In the configuration of FIG. 19, the negative electrode of the variable DC power supply 50 is connected to the upper electrode 34 and the GND block 91 is connected to the ground line during plasma etching, and the positive electrode of the variable DC power supply 50 is connected to the upper electrode 34 during cleaning. A connection switching mechanism 57 for switching the connection is provided so that the negative electrode is connected to the GND block 91. The connection switching mechanism 57 includes a first switch 57a for switching the connection of the variable DC power supply 50 to the upper electrode 34 between the positive electrode and the negative electrode, and a connection of the variable DC power supply 50 to the GND block 91 between the positive electrode and the negative electrode. A second switch 57b for switching and a third switch 57c for grounding the positive electrode or the negative electrode of the variable DC power supply 50 are provided. The first switch 57a and the second switch 57b are configured such that when the first switch 57a is connected to the positive electrode of the variable DC power supply 50, the second switch 57b is connected to the negative electrode of the DC power supply, and the first switch 57a is variable. When connected to the negative electrode of the DC power supply 50, an interlocking switch is configured to interlock so that the second switch 57b is turned off.

In the apparatus having the configuration shown in FIG. 19, during plasma etching, as shown in FIG. 20A, the first switch 57 a of the connection switching mechanism 57 is connected to the negative electrode side of the variable DC power supply 50, and the negative electrode of the variable DC power supply 50 is connected. Is connected to the upper electrode 34 side, the second switch 57b is connected to the positive side of the variable DC power supply 50, and the third switch 57c is connected to the positive side of the variable DC power supply 50 (of the variable DC power supply 50). The GND block 91 is connected to the ground line side. In this state, power is supplied from the variable DC power supply 50 to the upper electrode 34, when the first RF power supply 89 is supplying power to the susceptor 16 serving as the lower electrode plasma is formed, a DC electron current through the plasma Then, it flows into the GND block 91 that is grounded from the upper electrode 34 (the direction of the positive ion current flow is reversed). At this time, the surface of the GND block 91 may be covered with the deposit such as Y ₂ O ₃ or polymer as described above.

On the other hand, at the time of cleaning, as shown in FIG. 20B, the first switch 57a of the connection switching mechanism 57 is switched to the positive side of the variable DC power supply 50, and the second switch 57b is switched to the negative side of the variable DC power supply 50. Further, the third switch 57c is brought into an unconnected state. In this state, power is supplied from the first high frequency power supply 89 to the susceptor 16 which is the lower electrode, and cleaning plasma is formed. The GND block 91 has the variable DC power supply 50 from the negative electrode and the upper electrode 34 has the variable DC power supply 50. A DC voltage is applied from the positive electrode, and a DC electron current flows from the GND block 91 to the upper electrode 34 due to a potential difference therebetween, and conversely, positive ions flow into the GND block 91. For this reason, the surface of the GND block 91 can be ion-sputtered by adjusting the DC voltage and controlling the incident energy of positive ions to the GND block 91, thereby removing the deposits on the surface of the GND block 91. Can do. In this case, the variable DC power supply 50 is apparently in a floating state. However, since the power supply is generally provided with a frame ground line, it is safe.

In the above example, the third switch 57c is not connected, but may be connected to the positive side of the variable DC power supply 50 (the positive electrode of the variable DC power supply 50 is grounded). In this state, power is supplied from the first high frequency power supply 89 to the susceptor 16 as the lower electrode to form a cleaning plasma. A DC voltage is applied to the GND block 91 from the negative electrode of the variable DC power supply 50, and the DC electron current is The plasma flows from the GND block 91 to the upper electrode 34, and conversely, positive ions flow into the GND block 91. Even in this case, the surface of the GND block 91 can be ion-sputtered by adjusting the DC voltage and controlling the incident energy of positive ions to the GND block 91, thereby removing the deposit on the surface of the GND block 91. can do.

  In the examples of FIGS. 16 and 19, a DC voltage is applied to the GND block 91 during cleaning, but an AC voltage may be applied. In the example of FIG. 16, the voltage is applied to the GND block 91 using the variable DC power supply 50 for applying a DC voltage to the upper electrode, but the voltage may be applied from another power supply. In the examples of FIGS. 16 and 19, the GND block 91 is grounded during plasma etching and a negative DC voltage is applied to the GND block 91 during cleaning. However, the present invention is not limited to this. For example, a negative DC voltage may be applied to the GND block 91 during plasma etching. Further, the above cleaning may be replaced during ashing. Further, when a bipolar power source is used as the variable DC power source 50, a complicated switching operation like the connection switching mechanism 57 is not necessary.

  The switching operation of the switching mechanism 53 in the example of FIG. 16 and the connection switching mechanism 57 in the example of FIG. 19 is performed based on a command from the control unit 95.

When the plasma is formed, from the viewpoint of easily preventing Y ₂ O ₃ or the polymer from adhering to the GND block 91 from being DC grounded, a part of the GND block 91 is covered with another member. It is effective to expose a new surface of the GND block 91 by causing relative movement therebetween. Specifically, as shown in FIG. 21, the GND block 91 has a relatively large area, and a part of the surface of the GND block 91 that is exposed to plasma is covered with a mask material 211 that can move in the direction of the arrow, and this protective plate 211 It is possible to change the portion exposed to the plasma on the surface of the GND block 91 by moving. In this case, if the drive mechanism is provided in the chamber 10, there is a concern that the generation of particles may occur. Further, as shown in FIG. 22, for example, a cylindrical GND block 191 is rotatably provided, and is covered with a mask material 212 so that only a part of the outer peripheral surface of the GND block 191 can be exposed. It is also effective to change the part exposed to the plasma by rotating it. In this case, the drive mechanism can be provided outside the chamber 10. As the mask materials 211 and 212, a high plasma resistance material, for example, an aluminum plate sprayed with ceramics such as Y ₂ O ₃ can be used.

  Similarly, as another method for easily preventing the GND block 91 from being DC-grounded by the deposit, a part of the GND block 91 is covered with another member, and plasma is used as the other member. It is effective that the surface where the GND block 91 does not always lose conductivity is exposed by using what is gradually etched. For example, as shown in FIG. 23A, a part of the surface of the GND block 91 is covered with a stepped protective film 213, and the initial exposed surface 91c has a grounding function. When the plasma treatment is performed for 200 hours in this state, for example, as shown in FIG. 23B, the initial exposed surface 91c of the GND block 91 loses conductivity, but at that time, a thin portion of the stepped protective film 213 is formed. Is etched so that a new exposed surface 91d of the GND block 91 appears. As a result, the new exposed surface 91d exhibits a grounding function. Such a protective film 213 has the effect of preventing the wall surface material from adhering to the GND block 91 and the effect of reducing the inflow of ions to the GND block 91 to prevent contamination.

  In actual application, as shown in FIG. 24, it is preferable to use a protective film 213a in which a large number of thin layers 214 are stacked and each layer is slightly shifted. In this case, assuming that the time until one layer 214 disappears by etching with plasma is Te and the time until the exposed surface of the GND block 91 is contaminated and loses conductivity is Tp, it always satisfies Te <Tp. By setting the thickness of the layer 214 as described above, it is possible to ensure a surface that is always conductive in the GND block 91. The number of layers 214 is preferably selected so that the lifetime of the GND block 91 is longer than the maintenance cycle. In order to improve maintainability, one layer 214a with a different color as shown in the figure is provided as shown in the figure. For example, the layer 214a is replaced when the layer 214a exceeds a certain area. You can grasp the time.

  As the protective films 213 and 213a, those which are appropriately etched by plasma are preferable. For example, a photoresist film can be suitably used.

  As yet another method for easily preventing the GND block 91 from being grounded in a DC manner due to deposits, a plurality of GND blocks 91 are provided, and the ones having a grounding function are sequentially switched. Can be mentioned. For example, as shown in FIG. 25, three GND blocks 91 are provided, and a changeover switch 215 is provided so that only one of them is grounded. Further, a current sensor 217 is provided on the common ground line 216, and a direct current flowing therethrough is monitored. The current of the grounded GND block 91 is monitored by the current sensor 217, and when the current value becomes lower than a predetermined value, the grounding function is not performed and switching to another GND block 91 is performed. Note that the number of the GND blocks 91 may be selected in a range of about 3 to 10.

  In the above example, the GND block that is not grounded is in an electrically floating state, but from the viewpoint of protecting the GND block that is not used, a potential for protection is applied instead of providing the changeover switch 215. You may be able to do it. An example is shown in FIG. In FIG. 26, variable DC power supplies 219 are provided on the ground lines 218 individually connected to the GND blocks 91, respectively. As a result, the voltage of the variable DC power supply 219 corresponding to the GND block 91 that should exhibit the grounding function is controlled to be 0V, and other GND blocks 91 are set to a voltage at which no current flows, for example, 100V. The voltage of the corresponding variable DC power supply 219 is controlled so as to be. Then, when the current value of the current sensor 217 provided in the ground line 218 connected to the GND block 91 that should exhibit the grounding function becomes lower than a predetermined value, it is determined that the grounding function is not performed. The voltage value of the variable DC power supply 219 corresponding to the GND block 91 is controlled to a value at which the GND block performs the ground function.

  In this way, by setting the applied voltage from the DC power supply 219 to a negative value of about −1 kV, the GND block 219 connected thereto can function as an electrode for applying a DC voltage to the plasma. However, even if this value is too large, it will adversely affect the plasma. Further, by controlling the voltage applied to the GND block 91, a cleaning effect on the GND block 91 can be achieved.

  In addition, when the frequency which the said 1st high frequency power and the 2nd high frequency power can take is illustrated, as the 1st high frequency power, 13.56MHz, 27MHz, 40MHz, 60MHz, 80MHz, 100MHz, 160MHz can be mentioned. Examples of the second high-frequency power include 380 kHz, 800 kHz, 1 MHz, 2 MHz, 3.2 MHz, and 13.56 MHz, and they can be used in an appropriate combination depending on the process.

  In the above description, the plasma etching apparatus has been described as an example. However, the present invention can also be applied to an apparatus for processing a semiconductor substrate using another plasma. For example, a plasma film forming apparatus can be mentioned.

1 is a schematic sectional view showing a plasma etching apparatus according to an embodiment of the present invention. 1 is a schematic sectional view showing a plasma etching apparatus according to an embodiment of the present invention. The figure which shows the change of _Vdc and plasma sheath thickness at the time of applying a DC voltage to an upper electrode in the plasma etching apparatus of FIG. The figure which shows the change of the electron density at the time of changing the direct-current voltage to be applied using the conditions of HARC etching in the plasma etching apparatus of FIG. The figure which shows the change of the electron density at the time of changing the applied DC voltage using the conditions of Via etching in the plasma etching apparatus of FIG. The figure which shows the electron density distribution of a wafer radial direction at the time of making the 1st high frequency electric power 3000W and the 2nd high frequency electric power 4000W by the said HARC etching. The figure which shows the result of having measured the electron density distribution of the wafer radial direction by the case where a DC voltage is applied and the case where it does not apply using the conditions of trench etching. The figure showing the electrical state of an upper electrode in the plasma etching apparatus of FIG. The figure showing the electrical state of an upper electrode in the plasma etching apparatus of FIG. The figure showing the electrical state of an upper electrode in the plasma etching apparatus of FIG. Sectional drawing which shows the state which provided the detector which detects a plasma in the plasma etching apparatus of FIG. The figure which shows the waveform for suppressing abnormal discharge, when applying a DC voltage to an upper electrode in the plasma etching apparatus of FIG. Schematic which shows the other example of arrangement | positioning of a GND block. Schematic which shows the further example of arrangement | positioning of a GND block. The figure for demonstrating the adhesion prevention example of a GND block. Schematic which shows an example of the apparatus structure which can remove the deposit | attachment of a GND block. The schematic for demonstrating the state at the time of the plasma etching in the apparatus of FIG. 18, and the state at the time of cleaning. Schematic diagram showing another state during the plasma etching in g in the apparatus of FIG. 18. Schematic which shows the other example of the apparatus structure which can remove the deposit | attachment of a GND block. Schematic for demonstrating the state at the time of plasma etching and the state at the time of cleaning in the apparatus of FIG. The schematic diagram which shows an example of the GND block provided with the function which prevents that it is no longer grounded by DC. The schematic diagram which shows the other example of the GND block provided with the function which prevents that it is no longer grounded by DC. The schematic diagram which shows the further another example of the GND block provided with the function which prevents that it is not grounded like DC. The schematic diagram which shows the further another example of the GND block provided with the function which prevents that it is not grounded like DC. The schematic diagram which shows the further another example of the GND block provided with the function which prevents that it is not grounded like DC. The schematic diagram which shows the further another example of the GND block provided with the function which prevents that it is not grounded like DC.

Explanation of symbols

10 ... Chamber (processing container)
16 ... susceptor (lower electrode)
34 ... Upper electrode 46a ... Low pass filter 50 ... Variable DC power supply 51 ... Controller 52 ... On / off switch 66 ... Processing gas supply source 84 ... Exhaust device 89 ... First high frequency power supply 90 ... Second high frequency power supply 91 ... GND block W: Semiconductor wafer (substrate to be processed)

Claims (24)

A processing container in which a substrate to be processed is accommodated and evacuated;
A first electrode disposed opposite to the processing container and a second electrode for supporting the substrate to be processed;
A first high-frequency power application unit that applies a first high-frequency power having a relatively high frequency to the second electrode;
A second high-frequency power application unit that applies a second high-frequency power having a relatively low frequency to the second electrode;
A DC power supply for applying a DC voltage to the first electrode;
A processing gas supply unit for supplying a processing gas into the processing container ;
A variable device capable of changing between a floating state in which the first electrode is not grounded and a grounded state ;
Based on a command from the overall control device, when a DC voltage is applied to the first electrode, the variable device places the first electrode in a floating state with respect to a ground potential and applies the DC voltage to the first electrode. The plasma processing apparatus is characterized in that the variable device puts the first electrode in a floating state or a grounded state with respect to a ground potential when it is not .   The DC power supply is variable in any one of applied voltage, applied current and applied power to the first electrode, and controls any one of applied voltage, applied current and applied power from the DC power supply to the first electrode. The plasma processing apparatus according to claim 1, further comprising a control device that performs the control.   The plasma processing apparatus according to claim 1, wherein a surface of the first electrode facing the second electrode is formed of a silicon-containing material. 2. A conductive member that is always grounded is provided in the processing vessel in order to release a current based on a DC voltage from the DC power source applied to the first electrode through plasma. The plasma processing apparatus according to claim 3 . 5. The plasma processing apparatus of claim 4 , wherein the first electrode is an upper electrode, the second electrode is a lower electrode, and the conductive member is disposed around the second electrode. 6. . The plasma processing apparatus according to claim 4 , wherein the first electrode is an upper electrode, the second electrode is a lower electrode, and the conductive member is disposed in the vicinity of the first electrode. . The plasma processing apparatus according to claim 6 , wherein the conductive member is arranged in a ring shape outside the first electrode. In order to release the current based on the DC voltage from the DC power source applied to the first electrode through the plasma, a conductive member that is grounded based on a command from the overall control device is provided in the processing container. The plasma processing apparatus according to any one of claims 1 to 7 , wherein: The plasma processing apparatus according to claim 8 , wherein the conductive member is grounded during plasma etching. A DC voltage or an AC voltage can be applied to the conductive member, and the surface is sputtered or etched by applying the DC voltage or the AC voltage based on a command from the overall control device. the plasma processing apparatus according to claim 8 or claim 9, characterized. The plasma processing apparatus according to claim 10 , wherein a DC voltage or an AC voltage is applied to the conductive member during cleaning. A switching mechanism for switching the connection of the conductive member between the DC power source side and the ground line is further provided. When the conductive member is connected to the DC power source side by the switching mechanism, the conductive member is connected from the DC power source to the conductive member. The plasma processing apparatus according to claim 10 , wherein the surface is sputtered or etched by applying a DC voltage or an AC voltage to the conductive member. The plasma processing apparatus according to claim 10 , wherein a negative DC voltage can be applied to the conductive member. A grounded conductive auxiliary member is provided in the processing container to discharge a direct current electron current flowing into the processing container when a negative DC voltage is applied to the conductive member. The plasma processing apparatus according to claim 13 . Based on a command from the overall control device, a first state in which a DC current from the DC power source supplied to the first electrode is grounded to escape via plasma is applied, and a DC voltage is applied from the DC power source. A conductive member that takes one of the second states in which the surface is sputtered or etched is provided in the processing vessel, the negative electrode of the DC power supply is connected to the first electrode, and the conductive member is Switchable between a first connection connected to a ground line and a second connection in which the positive electrode of the DC power supply is connected to the first electrode and the negative electrode of the DC power supply is connected to the conductive member , and the by the switching, further be provided with a respective said first state and said second state capable of forming connection switching mechanism from claim 1, wherein according to any one of claims 3 Plasma processing apparatus. The plasma processing apparatus according to claim 15 , wherein the first state is formed at the time of plasma etching, and the second state is formed at the time of cleaning the conductive member. A first electrode and a second electrode that supports the substrate to be processed are disposed opposite to each other in the processing container, and a first high-frequency power having a relatively high frequency and a second having a relatively low frequency are disposed on the second electrode. In this plasma processing method, a processing gas is supplied into the processing vessel while applying a high-frequency power, and plasma of the processing gas is generated to perform plasma processing on the substrate to be processed supported by the second electrode. And
Applying a DC voltage to the first electrode; and applying a plasma treatment to the substrate to be processed while applying a DC voltage to the first electrode;
The first electrode can be changed between a floating state that is not grounded and a grounded state, and the first electrode is applied when a DC voltage is applied to the first electrode based on a command from the overall control device. The plasma is characterized in that the electrode is in a floating state with respect to a ground potential, and the first electrode is in a floating state or a ground state with respect to the ground potential when no DC voltage is applied to the first electrode. Processing method. The plasma processing method according to claim 17 , wherein a conductive member that is always grounded is provided in the processing container, and a current based on a DC voltage applied to the first electrode is released through the plasma. A conductive member to be grounded based on a command from the total control unit provided in the processing vessel, according to claim 17, characterized in that escape through the plasma current based on the DC voltage applied to the first electrode The plasma processing method as described in any one of Claims 1-3. When etching the insulating film of the substrate to be processed supported by the second electrode, in order to increase the selection ratio of the insulating film to the base film, as the processing gas, C ₅ F ₈ , Ar, N ₂ , And any combination of C ₄ F ₈ , Ar, N ₂ , and C ₄ F ₈ , Ar, N ₂ , O ₂ , and C ₄ F ₈ , Ar, N ₂ , CO The plasma processing method according to any one of claims 17 to 19 . When etching the insulating film of the substrate to be processed supported by the second electrode, CF ₄ , CF ₄ , Ar, and N are used as the processing gas in order to increase the selection ratio with the mask of the insulating film. _2, the plasma processing method according to any one of claims 19 claim 17, wherein the use of any combination of H _2. When the organic antireflection film on the insulating film of the substrate to be processed supported by the second electrode is etched, CF ₄ , CF ₄ , C ₃ F ₈ , and CF ₄ , C ₄ F _{8 are used} as the processing gas. , and _{CF 4,} C 4 plasma processing method according to any one of claims 19 claim 17, wherein the use of any combination of _{F 6.} When etching the insulating film of the substrate to be processed supported by the second electrode, in order to increase the etching rate of the insulating film, C ₄ F ₆ , CF ₄ , Ar, O ₂ , and _{C 4 F 6, C 3 F} 8, Ar, O 2, and _{C 4 F 6, C 4 F} 8, Ar, O 2, and _{C 4 F 6, C 2 F} 6, Ar, O 2, and _{C 4} F _8, Ar, plasma processing method according to claims 17 to any one of claims 19, wherein the use of any combination of O _2. A computer storage medium storing a control program that runs on a computer,
24. A computer-readable storage medium, wherein the control program controls the plasma processing apparatus so that the plasma processing method according to any one of claims 17 to 23 is performed at the time of execution.

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