JP2016225567A - Cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely remove a reaction product that is deposited on a processing container.SOLUTION: A cleaning method includes: a first step for supplying a gas via a plurality of gas passages that are divided into a first region corresponding to a first in-plane position of a substrate and a second region corresponding to a second in-plane position for which an in-plane position of the substrate is different from the first in-plane position, and cleaning the inside of the processing container with a plasma of a gas containing a fluorine-containing gas and an oxygen-containing gas; a second step for making a pressure within the processing container lower than a pressure in the first cleaning step, and cleaning the gas passage in the first region with the plasma of the gas for which a flow rate of the oxygen-containing gas to be supplied to the first region is lower than a flow rate in the second region; a third step for cleaning the gas passage in the second region with the plasma of the gas for which the flow rate of the oxygen-containing gas to be supplied to the first region is higher than the flow rate in the second region; and a fourth step for cleaning the inside of the processing container with the plasma of the gas including an NFgas.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a cleaning method.

  2. Description of the Related Art Plasma processing apparatuses that perform plasma processing such as plasma etching on a semiconductor device substrate using plasma are widely known. The plasma processing apparatus, for example, supplies gas via a gas supply hole to a processing container in which plasma is generated inside, an upper electrode and a lower electrode provided opposite to each other, and a space sandwiched between the upper electrode and the lower electrode. It has a gas supply part. Then, high-frequency power is applied to at least one of the upper electrode and the lower electrode, the gas is excited by the electric field energy to generate plasma, and the substrate is subjected to plasma treatment by the generated discharge plasma.

  When plasma etching is performed using a deposition gas, a reaction product generated during the process adheres to the inner wall of the processing vessel or the gas supply hole. The attached reaction product becomes particles and causes a defect in the semiconductor device or causes a failure of the plasma processing apparatus. For this reason, cleaning for removing reaction products adhering to a processing container or the like has been proposed (see, for example, Patent Document 1).

JP 2015-18836 A

  However, in the method of Patent Document 1, the etching rate may shift in plasma etching before and after cleaning. Thus, when the characteristics of plasma etching change before and after cleaning, stable production of semiconductor devices is hindered, and productivity may be reduced.

  In view of the above problems, in one aspect, the present invention aims to prevent a shift in etching rate in plasma etching before and after cleaning.

In order to solve the above-described problem, according to one aspect, a first region provided in a processing container and corresponding to a first in-plane position of a substrate, and the first in-plane position are defined on the substrate. A cleaning method of a plasma processing apparatus for supplying gas via a plurality of gas flow paths partitioned into a second region corresponding to a second in-plane position having a different in-plane position, wherein the inside of the processing vessel A first cleaning step of supplying a first gas containing a fluorine-containing gas and an oxygen-containing gas to the inside of the processing vessel with the plasma of the first gas, and after the first cleaning step, The pressure in the processing container is controlled to be lower than the pressure in the processing container in the first cleaning step, and the flow rate of the oxygen-containing gas supplied to the first region is controlled to include oxygen to supply the second region. Smaller than gas flow A second cleaning step of cleaning the gas flow path corresponding to the first region by the plasma of the second gas, and a flow rate of the oxygen-containing gas supplied to the first region after the second cleaning step. A third cleaning step of cleaning a gas flow path corresponding to the second region with a plasma of a third gas that is larger than the flow rate of the oxygen-containing gas supplied to the second region; And a fourth cleaning step of supplying a fourth gas containing nitrogen trifluoride (NF ₃ ) gas after the cleaning step and cleaning the inside of the processing container with plasma of the fourth gas. A method is provided.

  According to one aspect, shift of the etching rate can be prevented in plasma etching before and after cleaning.

The figure which shows an example of the longitudinal cross-section of the plasma processing apparatus which concerns on one Embodiment. The figure for demonstrating an example of the structure of the gas hole which concerns on one Embodiment, and the effect of a cleaning. The figure which shows the etching process and DC process which concern on one Embodiment. 6 is a flowchart illustrating an example of cleaning according to an embodiment. Diagram for explaining a first step the effect of endpoint detection and NF ₃ addition of the DC according to the embodiment. The figure which shows an example of the shift of the etching rate before and behind the cleaning which concerns on one Embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, in this specification and drawing, about the substantially same structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Configuration of plasma processing apparatus]
First, the configuration of a plasma processing apparatus 1 according to an embodiment of the present invention will be described with reference to an example of a longitudinal section of the plasma processing apparatus in FIG. In the present embodiment, as an example of the plasma processing apparatus 1, a capacitively coupled plasma etching apparatus is exemplified.

  The plasma processing apparatus 1 that executes the cleaning method according to the present embodiment is not particularly limited, but plasma processing such as RIE (Reactive Ion Etching) processing or ashing processing is performed on a semiconductor wafer W (hereinafter also referred to as “wafer W”). A parallel plate type (also referred to as capacitive coupling type) plasma processing apparatus can be used.

  The plasma processing apparatus 1 includes a processing container (chamber) 10 made of a conductive material such as aluminum, and a gas supply source 15 that supplies gas into the processing container 10. As the supplied gas, a gas suitable as an etching gas or a cleaning gas is appropriately selected.

  The processing container 10 is electrically grounded, and a lower electrode 20 and an upper electrode 25 disposed in parallel to face the lower electrode 20 are provided in the processing container 10. The lower electrode 20 also functions as a mounting table on which the wafer W is mounted. A power supply device 30 is connected to at least one of the lower electrode 20 and the upper electrode 25, in FIG. 1, the lower electrode 20. The power supply device 30 includes a first high-frequency power source 32 that supplies a first high-frequency power (plasma generation high-frequency power) having a first frequency, and a second high-frequency power (for generating a bias voltage) that is lower than the first frequency. And a second high frequency power supply 34 for supplying high frequency power). The first high frequency power supply 32 is connected to the lower electrode 20 via the first matching unit 33. The second high frequency power supply 34 is connected to the lower electrode 20 via the second matching unit 35. The first matching unit 33 and the second matching unit 35 are for matching the load impedance to the internal (or output) impedance of the first high frequency power source 32 and the second high frequency power source 34, respectively. When plasma is generated in the processing container 10, the first high frequency power supply 32 and the second high frequency power supply 34 function so that the internal impedance and the load impedance seem to coincide with each other.

  The upper electrode 25 is attached to the ceiling portion of the processing container 10 via a shield ring 40 that covers the peripheral edge portion thereof. The upper electrode 25 is provided with a diffusion chamber 50 for diffusing the gas introduced from the gas supply source 15. In the diffusion chamber 50, as shown in an example in FIG. 1, one or more annular partition members 26 made of O-rings are provided. The one or more annular partition members 26 are arranged at different positions in the radial direction of the upper electrode 25, that is, in the in-plane position of the wafer W to be processed. In the example of FIG. 1, the annular partition member 26 includes a first annular partition member 26a, a second annular partition member 26b, and a third annular partition member 26c from the center side with respect to the radial direction of the upper electrode 25. Has been. Thereby, the diffusion chamber 50 is divided into a first diffusion chamber 50a, a second diffusion chamber 50b, a third diffusion chamber 50c, and a fourth diffusion chamber 50d from the center side. In this case, for example, the first diffusion chamber 50a corresponds to the center portion of the wafer W to be processed, the second diffusion chamber 50b corresponds to the middle portion, and the third diffusion chamber corresponds to the edge portion. The fourth diffusion chamber 50d is formed corresponding to the belly edge portion 50c.

  The number of the annular partition members 26 is not particularly limited as long as it is one or more. For example, by disposing N annular partition members 26, the diffusion chamber 50 divided into N + 1 pieces can be installed. Gas diffusion ports 45a to 45d are respectively formed in the diffusion chambers 50a to 50d, and various gases can be introduced from the gas supply source 15 into the diffusion chambers 50a to 50d via the gas introduction ports 45a to 45d. it can.

  In the upper electrode 25, a large number of gas flow paths 55a for supplying the gas from the diffusion chamber 50 into the processing container 10 are formed. As shown in the enlarged view of the vicinity of the gas flow path 55a in FIG. 2, the upper electrode 25 has a surface on the lower electrode 20 side to protect the upper electrode 25 from plasma and scratches and to suppress metal contamination. A cover member 27 made of an insulating ceramic such as quartz is disposed. Also in the cover member 27, a gas channel 55 b is formed corresponding to the gas channel 55 a of the upper electrode 25. The gas channel 55 a of the upper electrode 25 has a configuration in which the hole diameter on the side close to the cover member 27 is smaller than the hole diameter on the side far from the cover member 27. Thereby, mixing of the leakage gas from the outside can be reduced.

  The gas from the gas supply source 15 is first distributed and supplied to the diffusion chambers 50a to 50d via the gas inlets 45a to 45d shown in FIG. The gas supplied to the diffusion chamber 50 is supplied into the processing container 10 via the gas supply holes 28 formed in the cover member 27 via the gas flow paths 55a and 55b shown in FIG. From the above, the upper electrode 25 having such a configuration also functions as a gas shower head that supplies gas.

  Returning to FIG. 1, an exhaust port 60 is formed on the bottom surface of the processing container 10, and the inside of the processing container 10 is exhausted by an exhaust device 65 connected to the exhaust port 60. Thereby, the inside of the processing container 10 can be maintained at a predetermined degree of vacuum.

  A gate valve G is provided on the side wall of the processing vessel 10. The gate valve G opens and closes the loading / unloading port when loading and unloading the wafer W from the processing container 10. Further, around the processing vessel 10, magnets (not shown) extending in a ring shape or concentric shape may be arranged, for example, in two upper and lower stages. When the magnet is disposed, an RF electric field is formed in the vertical direction by the high frequency power and a magnetic field is formed in the horizontal direction in the space between the lower electrode 20 and the upper electrode 25. By magnetron discharge using these orthogonal electromagnetic fields, high-density plasma can be formed near the surface of the lower electrode 20.

  The plasma processing apparatus 1 is provided with a control unit 100 that controls the operation of the entire apparatus. The control unit 100 includes a CPU (Central Processing Unit) 105 and recording areas of a ROM (Read Only Memory) 110 and a RAM (Random Access Memory) 115.

  The CPU 105 executes various plasma processes (cleaning, etching process, ashing process, etc.) according to various recipes stored in these storage areas. The recipe includes process time, pressure (gas exhaust), high-frequency power and voltage, various process gas flow rates, chamber temperature (for example, upper electrode temperature, chamber side wall temperature, ESC temperature) which are control information of the apparatus for process conditions. Etc. are described. Note that recipes indicating these programs and processing conditions may be stored in a hard disk or a semiconductor memory. Further, the recipe may be set at a predetermined position in the storage area while being stored in a storage medium readable by a portable computer such as a CD-ROM or DVD.

  In the plasma processing 1, a light emitting sensor 108 capable of measuring the intensity of light of each wavelength in the plasma in the processing container 10 through the quartz window 109 is attached. Detection values relating to the intensity of light of each wavelength in the plasma detected by the light emission sensor 108 are sent to the control unit 100. The control unit 100 measures the emission spectrum of each wavelength based on the detection value detected by the light emission sensor 108, and detects the end point of the cleaning process described later.

[Etching treatment and cleaning]
Next, an outline of etching processing and dry cleaning (hereinafter also referred to as “cleaning”) according to the present embodiment using the plasma processing apparatus 1 will be described with reference to FIG. First, the wafer W is carried into the processing container 10 and placed on the lower electrode 20 (mounting table) (step S1). Next, a predetermined etching gas is supplied, plasma is generated by the applied high frequency power, and the wafer W is etched by the etching gas plasma (step S2). Next, the wafer W is carried out of the processing container 10 (step S3). Next, a predetermined cleaning gas is supplied, and plasma is generated by the applied high frequency power. The inner wall and the like are cleaned (step S4). After cleaning, the process returns to step S1, and the next wafer W is carried into the processing container 10 and the next wafer W is etched. The timing at which the cleaning is performed is not limited to after the etching of one wafer W, but may be after the etching of a plurality of wafers W, or the etching of the wafers W included in one lot is performed. It may be after.

  The cleaning in step S4 may be performed in a state where the cleaning wafer is placed, or may be performed in a state where the cleaning wafer is not placed (waferless dry cleaning: WLDC).

[First to fifth cleaning steps]
Next, details of the cleaning shown in step S4 of FIG. 3 will be described with reference to the flowchart of FIG. In the cleaning of FIG. 4, the first to fifth cleaning steps are executed in order from the first step to the fifth step.

  In the etching process performed before cleaning according to the present embodiment, for example, a hydrofluorocarbon gas or a fluorocarbon gas is used as an etching gas. When the wafer W is etched by the plasma generated from the etching gas, a reaction product of mainly polymer generated from the etching gas is formed on the surface of the upper electrode 25, the side wall of the processing vessel 10, the inner surface of the gas supply hole 28, and the like. Adhere to. For this purpose, the following first to fifth cleaning steps are performed.

<First cleaning step: Cleaning of processing container>
When the cleaning according to the present embodiment is started, first, a first cleaning process is executed in step S10. In the first cleaning step, the entire processing container 10 is cleaned.

In the first cleaning process, a first gas containing a fluorine-containing gas and an oxygen-containing gas is introduced into the processing container 10. The first gas may be a gas containing nitrogen trifluoride (NF ₃ ) gas and oxygen (O ₂ ) gas. The first gas is ionized and dissociated by high-frequency power for plasma generation applied to the lower electrode 20 to generate plasma. The plasma generated from the first gas contains oxygen radicals and fluorine radicals. Oxygen radicals and fluorine radicals react with reaction products adhering to the inner wall of the processing vessel 10 and the surface of the upper electrode 25, and the reaction products are decomposed and removed. The decomposed reaction product is discharged from the exhaust port 60 by the exhaust device 65.

  An example of the end point detection result of the first cleaning process according to the present embodiment is shown in FIG. 5 together with a comparative example. During the first cleaning process, the emission intensity of a predetermined wavelength generated by the reaction between the plasma of the first gas containing fluorine gas and oxygen gas and the reaction product is detected.

  End point detection (EPD) is performed by measuring the intensity of light of each wavelength in the plasma using a light emitting sensor 108 attached to the plasma processing apparatus 1. The control unit 100 generates a reaction between a polymer reaction product in the processing container produced by etching and fluorine and oxygen components contained in the plasma from the measured emission spectrum in the plasma in the processing container 10. The emission intensity of the carbon oxide radical (483 nm) is detected. When the slope of the emission intensity of the predetermined wavelength with respect to time becomes 0, the control unit 100 determines end point detection EPD (End Point Detection).

Wafer No. of FIG. The end point detection times C and E for 3 and 5 are examples of the end point detection result by the first cleaning process according to the present embodiment. That is, as an example of the following process conditions, it is an example of an end point detection result when cleaning is performed by plasma of a gas containing an oxygen-containing gas and nitrogen trifluoride (NF ₃ ) gas.
-Process conditions for detecting end points of “C” and “E” (first cleaning step)
Pressure: 800 mT (106.7 Pa)
Gas type: O ₂ / He / NF ₃
HF (high frequency power for plasma generation): 3000 W
It can be determined that there is almost no polymer that is a reaction product in the processing vessel 10 when the slope of the observed emission intensity of the predetermined wavelength with respect to time becomes almost zero. As described above, the control unit 100 according to the present embodiment determines the end point detection when the slope of the observed emission intensity of the predetermined wavelength with respect to the time becomes almost zero, thereby determining the cleaning time of the first cleaning process. In fact, the time can be optimized when the polymer is almost removed. Thereby, it is possible to proceed to the second cleaning step after substantially removing the polymer.

  In the first cleaning step, HF (high frequency power for plasma generation) may be 3000 W or more.

On the other hand, wafer no. End point detection times A, B, and D for 1, 2, and 4 are examples of end point detection results by the cleaning process of the comparative example, and include oxygen-containing gas and nitrogen trifluoride (NF ₃ ) as shown below. ) Cleaning is performed by a gas plasma containing no gas.
-Process conditions for detecting the end point of “A” Pressure: 800 mT (106.7 Pa)
Gas type: O ₂ / He
HF (high frequency power for plasma generation): 3000 W
・ Process conditions for detecting end points of “B” and “D” Pressure: 800 mT (106.7 Pa)
Gas type: O ₂ / He / N ₂
HF: 3000W
According to the result of FIG. 5, compared with the case where the nitrogen trifluoride (NF ₃ ) gas of the comparative example is not added, in the first cleaning process according to the present embodiment, nitrogen trifluoride (NF ₃ ). It has been found that the cleaning time is shortened by adding the gas to the oxygen-containing gas.

  Usually, in the process of cleaning the entire inside of the processing container 10, the cleaning time becomes longer and the productivity is lowered. However, in the first cleaning step according to this embodiment, the cleaning time can be shortened by adding the fluorine-containing gas to the oxygen-containing gas, and the productivity can be improved.

  Note that the first gas supplied in the first cleaning step is a gas containing a fluorine-containing gas such as nitrogen trifluoride gas and an oxygen-containing gas such as oxygen gas.

<Second and third cleaning steps: cleaning of gas supply holes>
(Second cleaning process)
In the first cleaning step of Step S10, the entire inside of the processing container 10 can be cleaned, but it is difficult to remove the reaction product attached to the inner surface of the gas supply hole 28 or the like. For example, in FIG. 2 that schematically shows the vicinity of the gas supply hole 28 of the plasma processing apparatus 1, a downward arrow schematically shows the moving direction of the cleaning gas. The upward arrow schematically shows the direction of radical movement in the plasma generated from the cleaning gas.

  As shown in FIG. 2A, in the conventional cleaning method, oxygen gas as a cleaning gas is supplied from the diffusion chamber 50 to the processing container 10 through the gas flow paths 55a and 55b at a high flow rate. For this reason, it is difficult for oxygen radicals in the plasma generated in the processing container 10 to enter the gas flow paths 55b and 55a from the processing container 10. Therefore, the reaction product R adhering to the wall surface of the gas channel 55 remains without being completely removed in the first cleaning step.

  Therefore, in this embodiment, with respect to the diffusion chamber 50 partitioned into at least two or more regions by the annular partition member 26, a region where the flow rate of the supplied cleaning gas is large and a region where the flow rate of the supplied cleaning gas is small The cleaning gas is supplied so as to occur. That is, with respect to the diffusion chamber 50 divided into at least two or more zones by the annular partition member 26, the cleaning gas is supplied to the first region corresponding to the first in-plane position of the wafer W at the first flow rate. At the same time, the cleaning gas is supplied to the second region corresponding to the second in-plane position, which is different from the first in-plane position in the in-plane position of the wafer W, at the second flow rate that is larger than the first flow rate. Supply. In other words, the second cleaning step is performed by setting the first flow rate to be smaller than the second flow rate.

  In the gas supply hole 28 corresponding to the second region into which the cleaning gas has been introduced at the second flow rate, as described with reference to FIG. It is difficult to enter the flow paths 55a and 55b. However, in the gas supply hole 28 corresponding to the first region into which the cleaning gas is introduced at the first flow rate that is smaller than the second flow rate, the radicals in the plasma are converted into the processing container as shown in FIG. 10 can easily enter the gas flow paths 55a and 55b. Incoming radicals decompose and remove the reaction product R adhering to the inner surface of the gas channel 55. As a result, the gas flow path 55 corresponding to the first region is cleaned by the entered radicals.

Returning to FIG. 4, after the first cleaning step, the second cleaning step described above is executed (step S11). An example of process conditions in the second cleaning step is shown below.
・ Process conditions (second cleaning process)
Pressure: 200 mT (26.7 Pa)
Gas type: O ₂
HF: 3000W
Gas flow ratio Center part: Middle part: Edge part: Belly edge part = 48: 2: 48: 2
According to this, the pressure in the processing container 10 in the second cleaning process is controlled to be lower than the pressure in the processing container 10 in the first cleaning process. In the second cleaning step, the pressure in the processing container 10 is lowered and the first flow rate (here, the gas flow rate supplied to the gas flow path 55 in the middle portion and the belly edge portion) is changed to the second flow rate (here. Is lower than the gas flow rate supplied to the gas flow paths 55 at the center and the edge.

  In the second cleaning step, the first region where the cleaning gas is introduced at the first flow rate is communicated with the second diffusion chamber 50b corresponding to the middle portion and the fourth diffusion chamber 50d corresponding to the belly edge portion. The gas flow path 55 is used. Further, the second region into which the cleaning gas is introduced at the second flow rate is a gas flow path 55 that communicates with the first diffusion chamber 50a corresponding to the center portion and the third diffusion chamber 50c corresponding to the edge portion. .

  The plasma of the second gas in which the flow rate (first flow rate) of the oxygen-containing gas supplied to the first region is smaller than the flow rate (second flow rate) of the oxygen-containing gas supplied to the second region. As a result, the gas flow path corresponding to the first region is cleaned. At this time, oxygen radicals can enter the gas flow path 55 corresponding to the first region. For this reason, the inside of the gas channel 55 of the middle part and the belly edge part corresponding to the first region can be cleaned. In step S11, the flow rate ratio between the first flow rate supplied to the middle portion and the belly edge portion and the second flow rate supplied to the center portion and the edge portion is, for example, in the range of 0: 100 to 40:60. It is preferable to be inside.

(Third cleaning step)
Returning to FIG. 4, after the second cleaning step, the third cleaning step is executed (step S12). The process conditions in the third cleaning step are different from those in the second cleaning step only in the gas flow rate ratio.
・ Process conditions (third cleaning process)
Pressure: 200 mT (26.7 Pa)
Gas type: O ₂
HF: 3000W
Gas flow ratio Center part: Middle part: Edge part: Belly edge part = 2: 48: 2: 48
In the third cleaning process, the pressure in the processing container 10 is maintained at the pressure in the processing container 10 in the second cleaning process. That is, also in the third cleaning process, the pressure in the processing container 10 is controlled to be lower than the pressure in the processing container 10 in the first cleaning process.

  In the third cleaning step, the flow rate of the oxygen-containing gas supplied to the first region (first flow rate) is set to be larger than the flow rate of the oxygen-containing gas supplied to the second region (second flow rate). The gas flow path corresponding to the second region is cleaned by the plasma of the third gas. That is, when oxygen radicals enter the gas flow path 55 corresponding to the second region, the center and edge gas flow paths 55 corresponding to the second region are cleaned. In step S12, the flow rate ratio between the first flow rate supplied to the middle portion and the belly edge portion and the second flow rate supplied to the center portion and the edge portion is, for example, in the range of 100: 0 to 60:40. It is preferable to be inside.

  In the present embodiment, the first region is the gas channel 55 communicating with the second diffusion chamber 50b corresponding to the middle portion and the fourth diffusion chamber 50d corresponding to the belly edge portion, and the first region Were supplied with the same flow rate of oxygen gas. However, the present invention is not limited to this, and different flow rates are provided for the gas channel 55 communicating with the second diffusion chamber 50b corresponding to the middle portion and the gas channel 55 communicating with the fourth diffusion chamber 50d corresponding to the belly edge portion. The oxygen gas may be supplied. Similarly, a gas flow path 55 communicating with the first diffusion chamber 50a corresponding to the center portion constituting the second region, and a gas flow path 55 communicating with the third diffusion chamber 50c corresponding to the edge portion. Different flow rates of oxygen gas may be supplied. The reaction product R attached to the gas flow path 55 differs depending on the process conditions of the etching process using the plasma processing apparatus 1 of FIG. Therefore, it is important to sufficiently remove the reaction product R in the gas flow path 55 by adjusting the flow rate ratio and the cleaning time described above according to the type of the reaction product R and the adhesion amount.

  In the present embodiment, the diffusion chamber 50 is divided into at least two zones by the annular partition member 26. For example, by using one annular partition member 26, the diffusion chamber 50 can be divided into two zones corresponding to the center portion and the edge portion of the wafer W, for example. Also in this case, the flow rate ratio of oxygen gas supplied to the first region and the second region is made different to supply oxygen gas at an optimal flow rate ratio. As a result, oxygen radicals enter the gas flow path 55 corresponding to the region to which a small amount of oxygen gas is supplied, whereby the gas flow channel 55 corresponding to the region is cleaned.

  From the above, according to the second and third cleaning steps, oxygen gas having a different flow rate ratio is supplied to the gas flow paths 55 in a plurality of regions connected to the diffusion chamber 50 partitioned into two or more zones. To do. Thereby, the inside of the gas flow path 55 and the gas supply hole 28 are cleaned by making it easy for oxygen radicals to enter the gas flow path 55 having a small flow rate.

  In another form, by using the two annular partition members 26, the diffusion chamber 50 can be divided into three zones corresponding to, for example, the center portion, the middle portion, and the edge portion of the wafer W. In this case, for example, the first region may correspond to the center portion, and the second region may correspond to the middle portion and the edge portion, or vice versa. Further, the first region may correspond to the center portion and the middle portion, and the second region may correspond to the edge portion, or vice versa. Furthermore, the first region may correspond to the center portion and the edge portion, and the second region may correspond to the middle portion, or vice versa.

  In addition, by using the three annular partition members 26, for example, when the zone is divided into four zones corresponding to the center portion, the middle portion, the edge portion, and the belly edge portion of the wafer W, the first region and the second region are also provided. The allocation of the areas may be any combination.

  That is, for example, when N + 1 divided diffusion chambers 50 are installed by arranging N annular partition members 26, those skilled in the art appropriately define N + 1 diffusion chambers as the first region and the second region. Can be assigned to an area. When the first flow rate is relatively smaller than the second flow rate, first, the gas flow path 55 corresponding to the first region is cleaned in step S11. Thereafter, in step S12, the first flow rate is controlled to be relatively larger than the second flow rate, and the gas flow path 55 corresponding to the second region is cleaned.

  According to the second and third cleaning steps of the present embodiment, it is possible to remove the reaction product in the gas flow channel 55 that has been difficult to remove by the conventional cleaning method without remaining. As a result, it is possible to increase productivity by suppressing abnormal discharge in the gas flow path 55, reducing particles, and shortening the cleaning time.

  After cleaning the gas flow path 55 in the second and third cleaning steps, the gas flow path 55 and the gas supply hole 28 formed in the upper electrode 25 and the cover member 27 were visually confirmed. Adhesion of product R was not confirmed. On the other hand, after the first cleaning process, the reaction product R remained in the gas flow path when the second and third cleaning processes were not performed. From this, it is understood that the gas flow path 55 and the gas supply hole 28 can be reliably cleaned by the second and third cleaning steps according to the present embodiment.

<4th cleaning process: Improvement of etching shift>
Returning to FIG. 4, after the third cleaning step, in the fourth cleaning step, as shown in step S13, a fourth gas containing nitrogen trifluoride (NF ₃ ) gas is supplied and generated plasma is used. Residue in the processing container 10 is removed (step S13). Process conditions in the fourth cleaning step are shown below.
・ Process conditions (fourth cleaning process)
Pressure: 200 mT (26.7 Pa)
Gas type: NF ₃ / O ₂
HF: 1500W
In the fourth cleaning step, the plasma generated from nitrogen trifluoride gas and oxygen gas decomposes the residue mainly containing carbon (C) remaining in the processing container 10 after the second and third cleaning steps. And remove. As the fourth gas, a gas containing nitrogen trifluoride gas and oxygen gas is preferable to nitrogen trifluoride gas and argon gas. By supplying nitrogen trifluoride gas and oxygen gas in the fourth cleaning step, particles can be reduced at the same time.

(Effect of the fourth cleaning process)
In the fourth cleaning step, the residue is removed from the processing container 10 to improve the etching rate shift in the next etching. FIG. 6A shows the etching rate of the resist film (PR) when carbon tetrafluoride (CF ₄ ) gas and oxygen gas are supplied to the cleaning gas as cleaning of the comparative example. FIG. 6B shows the etching rate of the resist film when nitrogen trifluoride gas and argon gas are supplied in the fourth cleaning step according to the present embodiment. In any case, the pressure in the processing container 10 is 200 mT. The resist film is an organic film or an amorphous carbon film.

  6A and 6B, the horizontal axis indicates the radial position of the wafer W, and the vertical axis indicates the etching rate of the resist film. Etching rates in the X-axis direction and the Y-axis direction perpendicular to the X-axis in the radial direction of the wafer W are plotted.

In the case of the comparative example shown in FIG. 6A, carbon tetrafluoride (CF ₄ ) gas is used as the fluorine-containing gas. In this case, the etching rate on the edge side of the wafer W is higher when the cumulative time of etching and cleaning is 1.5 h than when the cleaning is performed only by etching (0 h). Thus, the average value “35.6 nm / min” of the etching rate when the cumulative time is 1.5 h is higher than the average value “26.1 nm / min” of the etching rate when the cleaning time is 0 h. Yes. That is, it can be seen that in the fourth cleaning step, the etching rate shifts when carbon tetrafluoride (CF ₄ ) gas is used as the fluorine-containing gas. Due to the shift of the etching rate, for example, the hole diameter of the mask is increased or the etching shape is deteriorated. For this reason, it is preferable to eliminate the phenomenon that the etching rate on the edge side of the wafer W becomes high and improve the shift of the etching rate.

  Therefore, in the fourth cleaning step according to the present embodiment shown in FIG. 6B, nitrogen trifluoride gas is used as the fluorine-containing gas in order to improve the etching rate shift. In the result of FIG. 6B, the average value of the respective etching rates when the accumulated time is 4.5 h is “32.8 nm / min”, and the average value of the etching rates is the case where the cleaning time is 0 h. The etching rate is substantially the same as “32.6 nm / min”. In addition, the variation from the average value “32.8 nm / min” of the etching rate when the cumulative time is 4.5 h is “± 45.7%”, and the average value of the etching rate when the cleaning time is 0 h “ The variation from “32.6 nm / min” is almost the same as “± 43.0%”. From this result, according to the fourth cleaning process of the present embodiment, the phenomenon that the etching rate on the edge side of the wafer W becomes high can be eliminated.

  Thereby, according to the 4th cleaning process concerning this embodiment, it turns out that the shift of an etching rate is improved in the following etching process. That is, when a cleaning process using carbon tetrafluoride gas is executed after the second and third cleaning processes, the inside of the processing container 10 is cleaned, but an etching rate shift occurs in the next etching process. In contrast, in the cleaning method according to the present embodiment, after the second and third cleaning steps, the residue is removed by executing the fourth cleaning step using nitrogen trifluoride gas, and the inside of the processing container 10 The atmosphere can be stabilized. As a result, the shift of the etching rate can be improved in the next etching step, the semiconductor device can be stably manufactured, and the productivity can be improved. Note that the fourth gas used in the fourth cleaning step includes nitrogen trifluoride gas, and the shift of the etching rate can be improved even if other gases such as oxygen gas are not included.

<Fifth cleaning step: removal of fluorine-based material>
Returning to FIG. 4, after the fourth cleaning step, in the fifth cleaning step, a fifth gas containing an oxygen-containing gas is supplied, and the fluorine-based material in the processing container 10 is removed by the generated plasma (step). S14). The process conditions in the fifth cleaning step are shown below.
・ Process conditions (fifth cleaning step)
Pressure: 800 mT (106.7 Pa)
Gas type: O ₂ / He
HF: 3000W
As shown in the process conditions, in the fifth cleaning process, the pressure in the processing container 10 is controlled to be higher than the pressure in the processing container 10 in the fourth cleaning process.

  In the fifth cleaning step, the fluorine-based substance (F) in the processing container 10 can be removed by plasma generated from the fifth gas including oxygen gas and helium gas. And the cleaning method of this embodiment is complete | finished. Note that the fifth gas includes an oxygen-containing gas and does not need to include a helium gas.

(Effect of the fifth cleaning step)
In the fifth cleaning step, the fluorine-based material remaining in the processing container 10 in the fourth cleaning step can be removed. When carbon tetrafluoride gas and oxygen gas are supplied in the fourth cleaning step, the main cleaning ends with the reaction product remaining. For this reason, in the fifth cleaning step, it was necessary to completely remove the residue containing carbon (C) with O ₂ plasma generated from oxygen gas. On the other hand, in this embodiment, nitrogen trifluoride gas was supplied instead of carbon tetrafluoride gas in the fourth cleaning step. Therefore, the fifth cleaning process according to the present embodiment is performed not for removing the residue containing carbon (C) but for removing the fluorine (F) -based material in the processing container 10. Thereby, it can be avoided that fluorine (F) remains in the processing container 10 and affects the next etching.

  In the etching process after the first cleaning process to the fourth cleaning process, the voltage value HF Vpp of the high frequency power for plasma excitation applied to the lower electrode 20 and the voltage value LF Vpp of the high frequency power for biasing fluctuate. It was. This indicates that the fluorine (F) -based material remains in the processing container 10.

  On the other hand, the fifth cleaning process is performed after the fourth cleaning process according to the present embodiment, and the voltage value HF Vpp and bias of the plasma excitation high frequency power applied to the lower electrode 20 in the subsequent etching process. No fluctuation occurs in the voltage value LF Vpp of the high-frequency power for use.

  As described above, nitrogen trifluoride gas and oxygen gas are supplied in the fourth cleaning step, and cleaning is performed by plasma generated from these gases. In the fifth cleaning step, cleaning is performed by plasma generated from oxygen gas and helium gas. In the fifth cleaning step, cleaning for removing fluorine (F) in the processing container 10 is executed.

  The result that there is no fluctuation in the voltage values HF Vpp and LF Vpp of the high-frequency power in the etching after the fifth cleaning step indicates that the impedance during the etching is stable and the plasma is stably generated. . In other words, according to the fourth and fifth cleaning steps of the present embodiment, by performing etching after removing fluorine (F) in the processing container 10, stable and good plasma processing can be performed in the next etching. Can do.

  Although the cleaning method and the plasma processing method have been described in the above embodiment, the cleaning method according to the present invention is not limited to the above embodiment, and various modifications and improvements can be made within the scope of the present invention. is there. The matters described in the above embodiments can be combined within a consistent range.

  For example, the cleaning method and the plasma processing method according to the present invention can be applied not only to a capacitively coupled plasma (CCP) apparatus but also to other plasma processing. Other plasma processing apparatuses include inductively coupled plasma (ICP), a plasma processing apparatus using a radial line slot antenna, a helicon wave excited plasma (HWP) apparatus, an electron cyclotron resonance plasma ( An ECR (Electron Cyclotron Resonance Plasma) apparatus or the like may be used.

  In this specification, the semiconductor wafer W has been described as an object to be etched, but various substrates used for LCD (Liquid Crystal Display), FPD (Flat Panel Display), etc., photomasks, CD substrates, printed boards, etc. good.

1: Plasma processing apparatus 10: Processing vessel 15: Gas supply source 20: Lower electrode 25: Upper electrode 26: Annular partition member 26a: First annular partition member 26b: Second annular partition member 27: Cover member 26c: No. 3 annular partition members 30: power supply device 32: first high frequency power supply 34: second high frequency power supply 45a to 45d: gas inlet 50: diffusion chamber 50a: first diffusion chamber 50b: second diffusion chamber 50c: first 3 diffusion chamber 50d: fourth diffusion chamber 55, 55a, 55b: gas flow path 100: control unit

Claims (6)

A first region corresponding to the first in-plane position of the substrate provided in the processing container and a first in-plane position corresponding to a second in-plane position different from the first in-plane position of the substrate. A method of cleaning a plasma processing apparatus that supplies gas through a plurality of gas flow paths partitioned into two regions,
Supplying a first gas containing a fluorine-containing gas and an oxygen-containing gas into the processing container, and cleaning the inside of the processing container with the plasma of the first gas;
After the first cleaning step, the pressure in the processing container is controlled to be lower than the pressure in the processing container in the first cleaning step, and the flow rate of the oxygen-containing gas supplied to the first region is A second cleaning step of cleaning the gas flow path corresponding to the first region with a plasma of a second gas that is smaller than the flow rate of the oxygen-containing gas supplied to the second region;
After the second cleaning step, the second gas plasma is supplied by the third gas plasma in which the flow rate of the oxygen-containing gas supplied to the first region is larger than the flow rate of the oxygen-containing gas supplied to the second region. A third cleaning step for cleaning the gas flow path corresponding to the region;
After the third cleaning step, a fourth cleaning step of supplying a fourth gas containing nitrogen trifluoride (NF ₃ ) gas and cleaning the inside of the processing container with the plasma of the fourth gas;
A cleaning method. After the fourth cleaning step, the method includes a fifth cleaning step of supplying a fifth gas containing an oxygen-containing gas and removing fluorine-based material from the processing container by the plasma of the fifth gas.
The cleaning method according to claim 1. The fifth cleaning step includes
Controlling the pressure in the processing container to be higher than the pressure in the processing container in the fourth cleaning step;
The cleaning method according to claim 2. The first gas is a gas containing nitrogen trifluoride (NF ₃ ) gas and oxygen (O ₂ ) gas.
The cleaning method as described in any one of Claims 1-3. The first in-plane position is one of the center part and the edge part when the substrate is partitioned into a center part and an edge part from the center side,
The second in-plane position is the other of the center part and the edge part,
The cleaning method as described in any one of Claims 1-4. The first in-plane position is determined when the substrate is partitioned into a center portion, a middle portion, an edge portion, and a belly edge portion from the center side. Including at least one or two regions,
The second in-plane position is the remaining area of the center part, the middle part, the edge part, and the belly edge part,
The cleaning method as described in any one of Claims 1-4.

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