JPH0269956A - Method and apparatus for electrostatically chucking - Google Patents

Abstract

PURPOSE:To maintain similar attraction force to that of first substrate irrespective of an increase in the number of the substrates to be treated, and to enhance the reliability of a producing apparatus by applying a voltage having a reverse symbol to that of an electrostatically chucking electrode during the processing of the electrode before the substrate to be treated is peeled from the electrode. CONSTITUTION:A wafer 18 to be treated is conveyed externally into a vessel 11, and placed on an electrostatically chucking electrode 17 on an electrode 14. Here, the electrode 14 is water-cooled, and a metal foil, not shown, for applying a DC high voltage is provided on the electrode 17. Then, when the process is of etching, halogen element is introduced into the vessel 11, a magnetic field is applied together with a high frequency power between electrodes 13 and 14 to generate an electrostatically chucking operation, thereby attracting fixedly the wafer 18 onto the electrode 17. Then, when the etching is finished, the wafer 18 is peeled from the electrode 17, and it is transferred to a next process. In this case, a reverse voltage to that during etching is temporarily applied to the metal foil on the electrode 17 to easily peel it. Thus, the attracting force of the electrode 17 is always maintained.

Description

[Detailed Description of the Invention] [Objective of the Invention 1] The present invention is used in a semiconductor integrated circuit manufacturing apparatus, etc. that performs various treatments on a semiconductor substrate, and in particular, an apparatus that holds the semiconductor substrate on a temperature-controlled stage. The present invention relates to an electrostatic chuck method and an electrostatic chuck device.

(Prior Art) In recent years, semiconductor integrated circuits have undergone rapid development, and LSIs having submicron-sized elements are now being prototyped. On the other hand, in order to improve production efficiency, Si wafers are becoming larger in diameter, and 6-inch and 8-inch wafers will soon become mainstream.

With the increase in the diameter of wafers, the forms of various processing apparatuses are also changing as follows.

Taking etching equipment as an example, conventionally, a hatch type etching system with a large processing chamber was used to process small diameter wafers.
It was possible to process many sheets at once with the device. However, it is extremely difficult to process many large-diameter wafers at once with good uniformity and reproducibility in one chamber. For this reason, instead of the batch method, single-wafer etching systems that process wafers one by one are increasingly being used.

This single-wafer type etching apparatus requires higher etching speed than the batch type in order to increase productivity.

In order to obtain high etching speed in reactive ion etching equipment (RIE), which performs etching by irradiating reactive gas ions, high-density plasma is formed by increasing the high-frequency power applied to the electrodes. , a large amount of ions must be irradiated onto the wafer. As a result, a large amount of high-frequency current flows through the wafer, which inevitably causes a rise in temperature.

The resist used as an etching mask in RIE or the like is sensitive to heat, and even if a heat-resistant mask is used, the etching characteristics change significantly as the temperature rises. Therefore,
It is important to cool the wafer sufficiently. In order to cool the wafer, the wafer must be brought into close contact with the surface of the electrode whose temperature is controlled by flowing cooling water inside. In order to bring the wafer into close contact with the electrode surface, is there a way to press the periphery of the Uni-No with metal claws? In this method, the presence of the claws may disturb the distribution of plasma, become a source of contamination, or the claws themselves may be exposed to elevated temperatures. There are many problems such as heating up and becoming a new heat source.

The above problems are the same in process equipment other than etching equipment, and it is important to control the wafer temperature without such problems. Therefore, recently, an electrostatic chuck device has been devised that uses electric force to suck and fix the wafer. In this electrostatic chuck device, the wafer can be firmly attracted to the electrode by simply providing the electrostatic chuck electrode on the cooling electrode, without the need to provide a new structure on the surface side of the wafer. In addition, in order to improve the thermal conductivity between the wafer and the electrostatic chuck electrode, a few Torr was applied to the back surface of the wafer.
This has made it possible to significantly improve the cooling efficiency of UNINO\.

However, this type of method has the following problems. In other words, when an electrostatic chuck is actually used in a reactive ion etching device for etching, the adsorption force of the electrostatic chuck is sufficient for the first sheet 1, but for the second sheet, As the third sheet is etched, the suction power decreases.

Eventually, the wafer cannot withstand the pressure of the cooling gas introduced between the sea urchin and the electrostatic chuck electrode, and the wafer is etched and peeled off from the electrostatic chuck electrode.

(Problem to be solved by the invention) As described above, in conventional electrostatic chuck devices, as the number of processed substrates increases, the adsorption force decreases, and during processing, the electrostatic chuck electrode There was a problem with it peeling off. For this reason, it has been difficult to apply it to production equipment that requires high reliability.

The present invention has been made in consideration of the above circumstances.
The aim is to develop an electrostatic chuck method and method that can maintain the same suction force as a single substrate regardless of the increase in the number of substrates to be processed, and can be applied to various production equipment. An object of the present invention is to provide an electrostatic chuck device.

[Structure of the Invention] (Means for Solving the Problems) An object of the present invention is to fix the substrate to a predetermined electrode or the like using an electrostatic chuck and process the substrate. What is the process mentioned above on the electrostatic chuck electrode before it is peeled off from the electrostatic chuck electrode? The key is to apply the opposite voltage.

That is, the present invention provides an electrostatic chuck method for fixing a substrate to be processed on a stage, after placing the substrate to be processed on an electrostatic chuck electrode on a temperature-controlled stage.
A predetermined voltage is applied between the electrostatic chuck electrode and the substrate to be processed, the substrate is attracted to the electrode by electrostatic force, and then the substrate to be processed is subjected to a predetermined process (for example,
After processing (e.g. etching, thin film deposition, impurity addition, etc.), a voltage of the opposite sign to the voltage applied during processing of the substrate is temporarily applied between the electrostatic chuck electrode and the substrate to be processed. In this method, the substrate to be processed is peeled off from the electrostatic chuck electrode.

The present invention also provides an electrostatic chuck device for carrying out the above method, including an electrostatic chuck electrode provided on a temperature-controlled stage, this electrostatic chuck electrode, and a workpiece placed on the electrode. means for applying a predetermined voltage between the electrostatic chuck electrode and the substrate to be processed; means for temporarily applying a voltage of No. 70 opposite to the voltage between the electrostatic chuck electrode and the substrate to be processed; and the substrate to be processed; and means for peeling off the electrostatic chuck electrode from the electrostatic chuck electrode.

(Function) According to the present invention, before peeling off the substrate to be processed after performing a predetermined process, between the substrate to be processed and the electrostatic chuck electrode,
By applying a voltage opposite to the r voltage during processing, the electrostatic chuck electrode can be returned to its initial state. Therefore, even if the number of sheets to be processed increases, it is possible to always maintain the same suction force for each sheet 1-1. In other words, the substrate to be processed can be fixed onto the electrostatic chuck electrode with the same adsorption force with good reproducibility, and it is possible to prevent the substrate to be processed from peeling off during processing.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing a dry etching device using an electrostatic chuck device according to an embodiment of the present invention. In the figure, reference numeral 11 denotes a vacuum container, and an electrode (anode) 13 is attached to the upper opening of the container 11 via an insulating ring 12. An electrode (cathode) 14 serving as a stage is provided at a position in the container 1 facing the electrode 13. Inside the electrode 14 there is a channel 15 for passing cooling water.
is formed, and this flow path 15 is connected to a cooling water pipe 16. and the electrode via the cooling water pipe 16]
The electrode 14 is cooled by flowing cooling water through the flow path 15 in the electrode 4 .

An electrostatic chuck electrode [7] is fixed on the electrostatic chuck electrode [4], and a wafer 18 to be processed is placed on this electrostatic chuck electrode [17]. As shown in FIG. 2, this electrostatic chuck electrode 17 has a structure in which a metal foil 41 made of copper or the like with good thermal conductivity is covered with an insulating film 42 such as a polyimide film, and is fixed onto the electrode 14 by adhesive or the like. . Quiet? If chuck electrode 1
A DC power supply (chuck power supply) 20 is connected to the metal foil 41 of No. 7 through a high frequency filter 19.
As a result, a high melting pressure is selectively applied to the metal foil 41.

Further, a through hole is provided in the center of the electrostatic chuck electrode 17, and a gas supply pipe 21 is connected to this through hole. A gas source 22, a vacuum pump 23 such as a rotary pump, and a pressure sensor 24 are connected to the pipe 21. A cooling gas (for example, He, N2) is supplied from the gas source 22 into the pipe 21, and the gas is exhausted by the vacuum pump 23 according to the pressure detected by the pressure sensor 24, thereby causing the electrostatic chuck electrode to 17 and wafer 1
Cooling scum is supplied at a constant pressure into the minute gap between the 8 and 8.

On the other hand, the electrode 1B is grounded, and a high frequency power source 26 is connected to the electrode 14 via a matching circuit 25. Further, a magnetic field generating device 27 made of a permanent magnet, an electromagnet, etc. is installed on the atmospheric side of the electrode 13. Further, an etching gas is supplied into the container 11 from the waste introduction port 28, and the gas supplied into the container 1 is exhausted from the υ1 air port 29. By supplying the gas, applying high-frequency power, and applying a magnetic field, a Macnetron discharge occurs between the electrodes 13 and 14, and plasma is generated.

The matching circuit 25 is connected to the electrode 4 via the pipe 2. Further, in the figure, reference numeral 30 indicates a plasma region caused by discharge, 31 an insulator, and 32 a metal mesh for preventing plasma from entering the exhaust port. In addition, although not shown in FIGS. 1 and 2, there is a pusher pin 43 for peeling off the wafer to be processed 8 from the electrostatic chuck electrode 17, or a pusher pin 43 provided through the electrostatic chuck electrode 17. .

In such a configuration, the wafer 18 to be processed is transported from the outside of the container 11 into the container 1 by a transport mechanism (not shown) and placed on the electrostatic chuck electrode 17 of the electrode 14''. on the other hand,? The metal foil 4 of the electrostatic chuck [small pole] 7 is cooled by the flow of cooling water.
] A high DC voltage (-15 to -3 KV) is applied. Thereafter, a predetermined gas (for example, a gas containing a halogen element such as chlorine or fluorine) is introduced into the container 1], and a magnetic field is applied together with high frequency power between the electrodes 1.3 and 1.4.

As a result, plasma is generated between the electrodes 1, 3 and 14 by magnetron discharge, and this plasma causes the wafer to
8 or etched.

At this time, the wafer to be processed 18 and fIb are connected to each other through plasma.
Conductivity is established with the pole 13, and as a result, a high DC voltage is applied between the wafer [8] and the metal foil 41 of the electrostatic chuck electrode 17, the electrostatic chuck acts, and the wafer 18 is connected to the electrostatic chuck electrode]7. ” It is fixed by suction. Here, the electrostatic chuck electrode 17 is fixed on the cooled electrode 14, and He or N2 with good thermal conductivity is supplied as a cooling gas to the minute gap between the electrostatic chuck electrode 17 and the wafer 18. .

Thermal conductivity due to this gas is proportional to the gas pressure if it is smaller than the distance between the wafer to be processed [8] and the electrostatic chuck electrode]7 or the mean free path of the dregs. Therefore, by controlling the gas pressure, it is possible to control the temperature of the sea urchin.

After the etching is completed, the wafer 18 to be processed is peeled off from the electrostatic chuck electrode 17 using a pushpin 43 or the like and the next wafer is processed. The adsorption force by the chuck electrode 17 was weakened, and the wafer] 8 was sometimes peeled off from the electrostatic chuck electrode 17 during processing. Therefore, in this embodiment, after etching is completed, a voltage of 10, which is opposite to that during etching, is temporarily applied to the metal foil 4 of the electrostatic chuck electrode 7. Thereafter, the wafer 18 to be processed is pushed up with the push pin 43, etc., without being peeled off from the electrostatic chuck electrode 17.

By repeating the above steps, it became possible to adsorb the wafer 18 to be processed onto the electrostatic chuck electrode] 7 with good reproducibility. Note that the voltage applied to the metal foil 41 of the electrostatic chuck electrode 17 after etching is a voltage of the same magnitude as the previously applied voltage (I, 5 to 3 KV), but with the opposite sign.
That's fine.

Further, the application time was sufficiently effective for a short period of about several seconds.

Next, the reason why the suction force decreases due to repeated processing of the wafer to be processed] 8 and the reason why the reproducibility of suction is improved by the present invention will be explained with reference to the drawings.

FIG. 3 shows that when a high voltage (+) is applied to the electrostatic chuck electrode 17 to attract a wafer 18 to be processed using a conventional electronic chuck,
The output current of the electrostatic chuck electrode 17 is etched once,
This is the result of monitoring. The horizontal axis is time, and the vertical axis is current value. The respective peaks are: (1) when the wafer 18 is placed on the electrostatic chuck electrode 17; (2) when a high voltage is applied to the electrostatic chuck electrode 17; (2) when an etching gas is introduced into the container]1; ■ When high frequency power is applied between the electrodes 13 and 14; ■ When the high voltage of the electrostatic chuck electrode 17 is turned off; ■ When the high frequency power is turned off; ■ When the wafer 18 is peeled off from the electrostatic chuck electrode 17. corresponds to each.

Wafer to be processed 18 and metal foil 41 of electrostatic chuck electrode 17
Since it basically constitutes a capacitor, there is no steady DC current, but only a current that accumulates or discharges charges due to the potential difference between the UNO\] 8 and the metal foil 41 flows.

When etching was repeated and the data was collected, it was found that there were only peaks of ■ and ■ as shown in Figure 4, or that there were changes as shown below. Regarding (2), no peak is observed at first, but as the etching process is repeated, - current gradually begins to appear, and the electrostatic chuck electrode 17
This shows that the ten charges placed on the top are returned to the chuck power supply 20. As shown in FIG. 5(a), the electrostatic chuck electrode 17 is
One charge 5] remains on the surface of the
5 The opposite side of the insulating film 42 of the electrostatic chuck electrode 17 (metal foil 4
This is thought to be because there was a charge of 52 on That is,
When the wafer 18 is transferred, a new charge 53 is induced on the back side of the wafer 18 near the one charge 51 as shown in FIG.
). As a result, the electrostatic chuck electrode 1
It is considered that the electric charge 52 of the metal foil 41 of No. 7 returns to the power source 20 (at this time, the ammeter 44 swings to one side).

On the other hand, in FIG. 4, for ■, the peak height initially appeared largely on the negative side, but the peak height gradually decreased. It was also found that the wafer 18 is no longer attracted when the value is below a certain value. This means that even after the high voltage of the electrostatic chuck electrode 17 is turned off as shown in FIG. always remains, and this is in a state of attraction. Here, the wafer 18 is removed from the electrostatic chuck electrode 7 by the push pin 43 (FIG. 6(b)), and the residual charges 54.55 on the wafer 18 and the metal foil 41 are removed by the push pin 43, respectively.
(ground) and escapes to the chuck power supply 20. Therefore,
The fact that the charge 56 escaping to the chuck power supply 20 decreases as the number of etching increases is due to the residual charge (-charge) 5] on the electrostatic chuck electrode 17 after the wafer 18 is peeled off. This means that there has been an increase. because,
This is because the remaining charge 57 (charge of the metal foil 41) is attracted to the - charge 51 and does not return to the power supply 20. That is, it is considered that, as in case (2), the waste particles 51 remain on the electrostatic chuck electrode 17, and the number of gourds increases further.

There may be various reasons why a single charge 51 remains on the electrostatic chuck electrode 17.For example, as shown in FIG. This causes charge transfer 73 from the wafer 18 to the electrostatic chuck electrode 17, and when the wafer 18 is peeled off, the wafer 18 and the electrostatic chuck electrode 17
It is not clear whether it is conceivable that the distance between the two, the gas pressure, the electric field, or other conditions that are likely to cause a discharge would cause a short-term discharge to occur, resulting in the movement of charge.

In FIG. 7, 74 indicates ten ions dissociated by radiation, and 75 indicates electrons.

As mentioned above, the residual charge 5 on the surface of the electrostatic chuck electrode 17
1 exists, when the wafer 18 is next transported and attracted as shown in FIG.
Even if the same high voltage 8] is applied between the wafer 18 and the wafer 18, the charge 82 actually induced in the wafer 18 is reduced by the residual charge 5]. Therefore, the suction force 83 acting on the wafer 18 is also reduced accordingly. As the residual charge 51 gradually increases, the attraction force 83 decreases, and eventually the wafer 18 is no longer attracted.

In this embodiment, before peeling off the wafer 18, etching,
Electrostatic chuck electrode 1 during the opposite voltage (etching, during
If 7 is 10, -) is applied for a short time (several seconds). As a result, even after the high frequency power is turned off, a certain electric field is applied between the wafer 18 and the electrostatic chuck electrode 17.
As shown in Figure (a), the wafer 18 and the electrostatic chuck electrode 1
An electric charge is generated at 7. In addition, 93 in the figure is the space capacity, 9
4 indicates ten charges generated on the wafer 18, and 95 indicates one charge generated on the static chuck electrode 17. and,
As shown in FIG. 9(b), after the wafer 18 is peeled off, a positive charge 91 is intentionally transferred using a mechanism similar to the above-mentioned charge movement.
can remain on the electrostatic chuck electrode 17.

That is, it is possible to leave a charge opposite to that in the conventional case. In the figure, 96 indicates charges that escape to the power source 20, and 97 indicates charges remaining on the metal foil 4 of the electrostatic chuck electrode 17 due to residual charges 91 on the surface of the electrostatic chuck electrode 17. Also,
If you switch to the reverse voltage before turning off the high-frequency power, you can more easily eliminate the residual reverse charge. However, in that case, the cooling gas must be turned off before switching the voltage.

In this way, when the next wafer 18 is transferred with a charge opposite to that during etching remaining and is placed on the electrostatic chuck electrode 17, the peak marked ■ in FIG. 3 appears in the opposite direction. Next, a positive voltage is applied to the electrostatic chuck electrode 17, and then the high frequency power is turned on. At this time, the electric field between the wafer 18 and the metal foil 41 of the electrostatic chuck electrode]7 is opposite to the electric field formed by the remaining charges, and the latter substantially causes the electric field between the wafer 18 and the electrostatic chuck electrode]7 The Coulomb force acting between the two is not weakened at all.

Etching, including wafer 18 and electrostatic chuck electrode 17
It is thought that a certain amount of charge transfer occurs between the wafer 18 and the wafer 18, so that the residual charge decreases and one charge begins to accumulate.In one etching, the amount is small and the wafer 18 will not be peeled off. .

According to experiments conducted by the present inventors, when the current value (■) was measured when the wafer 18 was peeled off from the electrostatic chuck electrode 17 after etching in the same manner as before, as shown in FIG. A large peak of 71+11 was observed, and it was confirmed that the peak value did not change even if etching was repeated. In other words, it was confirmed that blue absorption of the wafer 18 could be achieved with good reproducibility.

Contrary to the above example, one voltage is applied to the electrostatic chuck electrode 17 during etching, ten voltages are applied to the wafer 18, and the opposite voltages are applied after etching, and the current values are observed. It was also confirmed that the wafer 18 could be suctioned without any change. When the present invention is not used, it takes longer for the wafer to peel off if one voltage is applied to the electrostatic chuck electrode 17 during etching. This is considered to be because the movement of charges due to electron emission from the wafer 18 is eliminated by setting the wafer 18 to the + side. Therefore, in the present invention, the electrostatic chuck electrode 17 is etched during etching.
It is preferable to apply one voltage to

Note that the present invention is not limited to the embodiments described above. In the embodiments, an apparatus using magnetron discharge that applies a magnetic field to plasma to form high-density plasma has been described, but the present invention can of course be applied to ordinary etching apparatuses.

Furthermore, the present invention is not limited to etching devices, but can be similarly applied to deposition devices using plasma, impurity addition devices, and the like. Further, even without using plasma, the present invention can be implemented in an apparatus that electrostatically attracts and fixes a wafer as long as it is provided with a means for applying a voltage to the wafer. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, by applying a voltage having a sign opposite to that during the processing to the electrostatic chuck electrode before peeling off the substrate to be processed from the electrostatic chuck electrode, Regardless of the increase in the number of substrates to be processed, it is possible to maintain the same adsorption force as that of the first substrate to be processed. Therefore, the substrate to be processed can be fixed on the electrostatic chuck electrode with the same adsorption force with good reproducibility, and it is possible to prevent the substrate from peeling off during processing, making it reliable for various production equipment. It can be easily applied.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing dry etching using an electrostatic chuck device according to an embodiment of the present invention, and FIG.
The figure is an enlarged cross-sectional view showing the structure of the electrostatic chuck part and the cathode part of the above-mentioned apparatus, and FIGS. 3 to 10 are for explaining the operation of this embodiment, respectively.
A characteristic diagram showing changes in the output current of the chuck power supply during the process. Figure 4 is a characteristic diagram showing changes in current peak value depending on etching and number of times in the conventional method. Figures 5 to 9.
The figure is a schematic diagram showing the residual and movement of charges, and FIG. 10 is a characteristic diagram showing the change in current peak value depending on the number of times of etching in the method of this embodiment. 11... Vacuum container, 13... Electrode (anode), 14...
・Stage electrode (cathode), ]6...Cooling water piping,
17... Electrostatic chuck device, 18... Wafer to be processed, 20... Power source for chuck, 21... Gas supply piping, 26... High frequency power source, 27... Magnetic field generator, 41
Metal foil, 42/insulating film. Applicant's agent Patent attorney Takehiko Suzue

Claims (7)

[Claims] (1) A process of placing a substrate to be processed on an electrostatic chuck electrode on a temperature-controlled stage, and applying a predetermined voltage between the electrostatic chuck electrode and the substrate to be processed, and applying an electrostatic force to the substrate. and applying the voltage between the electrostatic chuck electrode and the substrate to be processed after performing a predetermined process on the substrate while the substrate is attracted to the electrostatic chuck electrode. An electrostatic chucking method characterized by comprising the steps of: temporarily applying a voltage with a sign opposite to that of the electrostatic chuck electrode; and then peeling off the substrate to be processed from the electrostatic chuck electrode. (2) The electrostatic chuck method according to claim 1, wherein the processing performed on the substrate to be processed is etching, thin film deposition, or impurity addition. (3) A cooling gas is introduced between the electrostatic chuck electrode and the substrate to be processed during processing of the substrate to be processed, and the gas pressure is kept constant. electrostatic chuck method. (4) The voltage applied between the electrostatic chuck electrode and the processed electrode during processing of the processed substrate is negative on the processed substrate side with respect to the electrostatic chuck electrode. Electrostatic chuck method described. (5) The stage and the electrostatic chuck electrode are housed in a processing container, and the voltage applied to the substrate to be processed is
2. The electrostatic chuck method according to claim 1, wherein the electrostatic chuck is supplied from the inner wall of the processing container via plasma formed in the processing container which is under reduced pressure. (6) means for applying a predetermined voltage between an electrostatic chuck electrode provided on a temperature-controlled stage and a substrate to be processed placed on the electrostatic chuck electrode;
The method includes means for temporarily applying a voltage having a sign opposite to the voltage between the electrostatic chuck electrode and the substrate to be processed, and a means for peeling the substrate to be processed from the electrostatic chuck electrode. An electrostatic chuck device characterized by: (7) The electrostatic chuck device according to claim 6, wherein the electrostatic chuck electrode has a structure in which a conductive thin film is sandwiched between insulating thin films, and is adhesively fixed on the stage.