Plasma processing method and plasma processing device

Abstract

One illustrative embodiment of the present invention provides a plasma processing method. This method includes: a) a step in which at least one temperature detection element provided in an upper electrode of a plasma processing device is used to acquire temperature information of a reaction chamber during plasma processing, as information describing the state of plasma density; and b) a step for converting the temperature information into power information, and on the basis of the power information, adjusting power supplied from the high-frequency power supply to the reaction chamber via the upper electrode so as to reduce the plasma density distribution bias along the electrode surface of the upper electrode. The upper electrode has a gap provided adjacent to and above the electrode surface exposed to the reaction chamber, and the at least one temperature detection element includes a first temperature detection element arranged so as to measure the temperature at the bottom part of the gap.

Description

Plasma processing method and plasma processing apparatus

[0001] SUMMARY OF THE INVENTION An exemplary embodiment of the present disclosure relates to a plasma processing method and a plasma processing apparatus.

[0002] In the manufacture of electronic devices such as semiconductor devices, for example, parallel plate plasma processing apparatuses are used. In plasma processing apparatuses, it is required to make the plasma distribution uniform on the wafer, and techniques for adjusting the electromagnetic waves used to generate the plasma in order to make the plasma distribution uniform are disclosed in Patent Documents 1 to 3.

[0003] JP 2003-73836 A JP 2016-31955 A JP 2022-520797 A

[0004] The present disclosure provides a technique for reducing the bias in the plasma density distribution in a reaction chamber.

[0005] In one exemplary embodiment, a plasma processing method is provided. The plasma processing method includes steps a) and b). In step a), temperature information of a reaction chamber during plasma processing is obtained as information indicating a state of plasma density using at least one temperature detection element provided in an upper electrode of the plasma processing apparatus. In step b), the temperature information is converted into power information, and based on the power information, power supplied from a high-frequency power source to the reaction chamber via the upper electrode is adjusted so as to reduce bias in the plasma density distribution along the electrode surface of the upper electrode. The upper electrode has a gap provided adjacent to the electrode surface above the electrode surface exposed to the reaction chamber. The at least one temperature detection element includes a first temperature detection element positioned to measure the temperature at the bottom of the gap.

[0006] According to one exemplary embodiment, the bias in the plasma density distribution in the reaction chamber can be reduced.

[0007] 1 is a diagram illustrating a plasma processing method according to an exemplary embodiment, a diagram illustrating a plasma processing apparatus according to an exemplary embodiment, a diagram illustrating an example of the arrangement of two temperature detection elements shown in FIG. 1, and a diagram illustrating variations in the planar shape of a gap in which the temperature detection elements are arranged.

[0008] Various exemplary embodiments are described below.

[0009] Various exemplary embodiments will be described in detail below with reference to the drawings, in which the same or equivalent parts are designated by the same reference numerals.

[0010] A plasma processing method (method MT) that can be performed using the plasma processing apparatus 1 will be described below with reference to Fig. 1. Fig. 1 is a flow chart showing a plasma processing method according to an exemplary embodiment, and the method MT shown in Fig. 1 is a method for processing a wafer.

[0011] FIG. 2 is a diagram showing an example of a plasma processing apparatus according to an exemplary embodiment. FIG. 2 schematically shows a cross-sectional structure of a plasma processing apparatus 1 that can be used in various embodiments of a method for processing a workpiece. The plasma processing apparatus 1 shown in FIG. 2 is a parallel plate type plasma processing apparatus. The plasma processing apparatus 1 includes a processing chamber 2, a mounting table 3, a lower electrode 3a, an upper electrode 5, a gas supply unit 13, a high frequency power supply 10, and a shower unit SH.

[0012] The processing vessel 2 is configured to perform plasma processing and is electrically conductive. The processing vessel 2 has a lid 2a and a sidewall 2b. The sidewall 2b and the lid 2a are made of a conductor such as aluminum and are electrically connected to ground potential. At least the portion of the sidewall 2b of the processing vessel 2 that is exposed to plasma is covered with a liner made of a plasma-resistant material or a liner on which a thermal spray coating made of a plasma-resistant material is formed.

[0013] The processing vessel 2 is hollow (cylindrical with a bottom). The central axis of the processing vessel 2 coincides with the central axis of the side wall 2b. An exhaust device 15 is connected to the bottom of the processing vessel 2 via a gas exhaust port 14 in order to reduce the pressure in the processing vessel 2, specifically, in the reaction chamber 4.

[0014] The cover 2a is formed in a disk shape with a through-hole 7c in the center. The cover 2a is provided above the side wall 2b. The central axes of the cover 2a and the through-hole 7c coincide with the central axis of the side wall 2b.

[0015] A reaction chamber 4 is provided in the processing vessel 2 between a mounting table 3 and an upper electrode 5, both of which are provided in the processing vessel 2. The mounting table 3 has a temperature control mechanism and is included in a lower electrode 3a.

[0016] The mounting table 3 is configured to mount the wafer W below the reaction chamber 4 in the processing vessel 2. The mounting table 3 is supported by a support member 21 that stands in the center of the bottom of the processing vessel 2.

[0017] The mounting table 3 may be provided with a heater (not shown) for heating the wafer W. Instead of a heating mechanism such as a heater, a cooling mechanism having a coolant flow path (not shown) through which a cooling coolant flows may be provided, or both a heating mechanism and a cooling mechanism may be provided. The mounting table 3 is provided with substrate support pins (not shown) that are movable up and down. The substrate support pins are used to transfer the wafer W between the mounting table 3 and a wafer transfer device (not shown) that is inserted into the processing chamber 2 from outside the processing chamber 2.

[0018] An upper electrode 5 is provided above the mounting table 3 (above the reaction chamber 4) so ​​as to face the mounting table 3. The upper electrode 5 includes a conductive material such as aluminum, and has a disk shape.

[0019] The upper electrode 5 is supported by the processing vessel 2 via a dielectric ring 6. The dielectric ring 6 is configured to seal the space between the waveguide 8 and the reaction chamber 4 and to supply high-frequency power in the VHF band to the reaction chamber 4. The upper electrode 5 and the dielectric ring 6 separate an upper space from a lower space within the processing vessel 2. The interior of the processing vessel 2 is sealed by the upper electrode 5 and the dielectric ring 6 so that when the interior of the processing vessel 2 is depressurized by the exhaust device 15, only the lower space is depressurized. The central axis of the upper electrode 5 coincides with the central axis of the processing vessel 2.

[0020] A process gas dispersion unit 12 having a substantially disk shape is provided inside the upper electrode 5. The process gas dispersion unit 12 is a space for diffusing gas introduced from the gas supply unit 13 so that the gas can be supplied into the reaction chamber 4 from the shower unit SH. The upper electrode 5 includes a shower unit SH provided below the upper electrode 5, i.e., on the reaction chamber 4 side. The shower unit SH is configured to supply the process gas from the gas supply unit 13 to the reaction chamber 4. The shower unit SH is provided with a plurality of gas outlets 11 communicating with the process gas dispersion unit 12. The process gas dispersion unit 12 is connected to the gas supply unit 13 provided outside the processing vessel 2. The plasma processing gas supplied from the gas supply unit 13 is supplied to the process gas dispersion unit 12 and then discharged into the reaction chamber 4 through the gas outlets 11.

[0021] The plasma processing apparatus 1 includes at least one temperature detection element provided in the upper electrode 5 (particularly in the shower section SH). In one embodiment, the plasma processing apparatus 1 may include a temperature sensor T1 (first temperature detection element) and a temperature sensor T2 (second temperature detection element) as shown in FIGS. 2 and 3 . That is, the at least one temperature detection element of the plasma processing apparatus 1 may include the temperature sensor T1 and / or the temperature sensor T2. The shower section SH of the upper electrode 5 has a temperature measurement space 5b, which is a gap provided above and adjacent to the electrode surface 5a exposed to the reaction chamber 4. The temperature sensor T1 is positioned to measure the temperature at the bottom of the temperature measurement space 5b. The shorter the distance from the bottom (bottom surface) of the temperature measurement space 5b to the electrode surface 5a (i.e., the distance from the temperature sensor T1 to the electrode surface 5a), the better. In this case, the temperature detected by the temperature sensor T1 will be closer to the temperature inside the reaction chamber 4. The temperature sensors T1 and T2 may be, for example, thermocouples, optical fiber thermometers, or radiation thermometers.

[0022] The shape of the temperature measurement space 5b can vary widely, as shown in FIG. 4. FIG. 4 illustrates various examples of the planar shape of the temperature measurement space 5b as viewed from the electrode surface 5a. The temperature measurement space 5b is disposed in the region AR of the electrode surface 5a. The planar shape of the temperature measurement space 5b can be, for example, a perfect circle 5b1, a regular hexagon 5b2, or a rhombus 5b3. Furthermore, the planar shape of the temperature measurement space 5b can be, for example, a rectangular shape 5b4, a square shape 5b5, a sector shape 5b6, or a perfect circle with a gas discharge port 11 provided within the temperature measurement space 5b 5b7. Furthermore, the planar shape of the temperature measurement space 5b can be, for example, an ellipse 5b8, a shape similar to a rectangle with its long sides curved to avoid the gas discharge port 11 5b9, or an equilateral triangle 5b10.

[0023] 2 and 3, the temperature sensor T1 and the temperature measurement space 5b are provided above a region in the reaction chamber 4 that includes a peak in the plasma density distribution measured in advance during plasma processing. The temperature sensor T2 is provided at a distance from the temperature sensor T1. The temperature sensor T2 is provided above a region in the reaction chamber 4 that has a flat distribution in the plasma density distribution measured in advance. Note that the plasma density distribution in this disclosure refers to the ion current [μA / cm 2 ] in the plasma in the direction along the electrode surface 5a. ２ ] means the distribution of

[0024] The temperature sensors T1 and T2 are connected to the temperature information acquisition unit 16 via a dielectric tube TB. The dielectric tube TB is a tube through which wiring passes that connects the temperature sensors T1 and T2 to the temperature information acquisition unit 16. The temperature information acquisition unit 16 is configured to acquire temperature information of the reaction chamber 4 based on temperature signals output from the temperature sensors T1 and T2 (at least one temperature detection element).

[0025] As one example, the temperature information acquired by the temperature information acquiring unit 16 may be a difference obtained by subtracting the second temperature detected by the temperature sensor T2 from the first temperature detected by the temperature sensor T1. The temperature information relating to the difference may be acquired by the temperature information acquiring unit 16 at the timing when high frequency power is supplied from the high frequency power supply 10 to the upper electrode 5 at the start of plasma processing (or several seconds after the timing, for example, 4 to 6 seconds after the timing).

[0026] As another example, the temperature information acquired by the temperature information acquisition unit 16 may be a difference obtained by subtracting a first temperature detected by the temperature sensor T1 at a first timing from a second temperature detected by the temperature sensor T1 at a second timing after the first timing. The first timing may be the timing at which high-frequency power is supplied from the high-frequency power supply 10 to the upper electrode 5 at the start of plasma processing (or within a range of several seconds from that timing, for example, 0 to 0.3 seconds). The time from the first timing to the second timing may be, for example, approximately 0.4 to 0.8 seconds.

[0027] The temperature information acquisition unit 16 is connected to a power adjustment unit 17 that can control the power output from the high-frequency power supply 10. The power adjustment unit 17 converts the temperature information acquired by the temperature information acquisition unit 16 into power information. Based on the power information, the power adjustment unit 17 controls the high-frequency power supply 10 so as to reduce the bias in the plasma density distribution along the electrode surface 5a of the upper electrode 5 (shower unit SH). By controlling the high-frequency power supply 10 in this manner, the power adjustment unit 17 is configured to adjust the power supplied from the high-frequency power supply 10 to the reaction chamber 4 via the upper electrode 5. In this way, the temperature information of the reaction chamber 4 is converted into power information, and the power information is fed back to the high-frequency power supply 10 to adjust the power supplied to the reaction chamber 4, thereby reducing the bias in the plasma density distribution.

[0028] The temperature information can be converted into power information using, for example, a table created in advance for each plasma processing apparatus 1. This table is provided to reduce bias in the plasma density distribution and can be stored in the memory of the power adjustment unit 17.

[0029] The dielectric ring 6 is provided along the side wall 2b so as to cover the outer peripheral surface of the upper electrode 5. The dielectric ring 6 transmits electromagnetic waves propagating through the waveguide 8 from the high frequency power source 10 via the high frequency matching box 9 into the reaction chamber 4.

[0030] The plasma processing apparatus 1 includes an antenna unit 7. The antenna unit 7 has an inner conductor 7a, an outer conductor 7b, and a through hole 7c.

[0031] The inner conductor 7a is an inner conductor of a coaxial waveguide that is connected to the high-frequency matching box 9. One end of the inner conductor 7a is connected to the center of the upper surface of the upper electrode 5. The central axis of the inner conductor 7a coincides with the central axis of the processing chamber 2. The other end of the inner conductor 7a is electrically connected to the high-frequency power supply 10 via the high-frequency matching box 9.

[0032] The outer conductor 7b is connected to the upper surface of the lid 2a. The central axis of the outer conductor 7b coincides with the central axis of the side wall 2b. The inner diameter of the outer conductor 7b is approximately the same as the diameter of the through hole 7c of the lid 2a.

[0033] The plasma processing apparatus 1 has a waveguide 8. The waveguide 8 propagates electromagnetic waves generated based on high frequency power output from a high frequency power supply 10 to the reaction chamber 4 via the dielectric ring 6. The waveguide 8 has a first waveguide 8a and a second waveguide 8b.

[0034] The first waveguide 8a is defined by the outer peripheral surface of the inner conductor 7a, the inner peripheral surface of the outer conductor 7b, etc. The first waveguide 8a propagates the electromagnetic wave in the axial direction (vertically downward) along the inner conductor 7a. The second waveguide 8b is continuous with the first waveguide 8a and is defined by the lower surface of the lid 2a and the upper surface of the upper electrode 5. The second waveguide 8b propagates the electromagnetic wave horizontally outward along the radial direction in a plan view.

[0035] The high frequency power supply 10 is electrically connected to the upper electrode 5 and is configured to generate plasma of the processing gas supplied from the gas supply device 13 by supplying high frequency power to the upper electrode 5. The high frequency power output from the high frequency power supply 10 is supplied to the upper electrode 5 via a high frequency matching box 9. The high frequency power supply 10 can output high frequency power in the VHF band, UHF band, or HF band. The high frequency power in the VHF band, UHF band, or HF band is applied to the plasma processing device 1.

[0036] The gas supply device 13 is configured to supply a processing gas to the reaction chamber 4 between the upper electrode 5 and the mounting table 3 .

[0037] In the plasma processing apparatus 1, plasma is generated in the reaction chamber 4 by a process gas supplied from the gas supply device 13 and discharged into the reaction chamber 4 from the gas discharge port 11, and by electromagnetic waves propagating to the reaction chamber 4 via the dielectric ring 6. To attract ions and the like in the plasma to the wafer W, for example, a high-frequency power supply (not shown) for RF bias may be electrically connected to the mounting table 3 via a matching box.

[0038] The plasma processing apparatus 1 further includes a control unit (not shown). The control unit includes a computer having, for example, a CPU, a memory, etc., and has a program storage unit. The program storage unit stores programs for executing various processes in the plasma processing apparatus 1.

[0039] 1 , the method MT will be described. The method MT includes steps ST1 to ST4 and can be performed each time a plasma process is performed. For example, when an atomic layer deposition (ALD) method is used in the film formation process, the method MT can be performed each time a plasma process is repeated multiple times.

[0040] In step ST1, plasma processing is started. In step ST2, the temperature information acquiring unit 16 acquires temperature information of the reaction chamber during plasma processing as information indicating the state of plasma density using at least one temperature detection element (e.g., temperature sensor T1 and temperature sensor T2) provided in the upper electrode 5 (shower part SH). As an example, the temperature information acquiring unit 16 can acquire temperature information when the high-frequency power supply 10 is turned on at the start of plasma processing.

[0041] In step ST3 following step ST2, the power adjustment unit 17 converts the temperature information acquired by the temperature information acquisition unit 16 into power information. In step ST4 following step ST3, the power adjustment unit 17 controls the high-frequency power supply 10 based on the power information so as to reduce the bias in the plasma density distribution along the electrode surface 5a of the upper electrode 5 (shower unit SH). In this way, the power adjustment unit 17 adjusts the power supplied from the high-frequency power supply 10 to the reaction chamber 4 via the upper electrode 5.

[0042] According to the above-described method MT and plasma processing apparatus 1, the deviation of the plasma density distribution can be reduced by the temperature information in the reaction chamber 4 during plasma processing, and a uniform plasma can be obtained. Furthermore, since a thermocouple, an optical fiber thermometer, or the like can be used as a temperature detection element (e.g., temperature sensors T1, T2), the method MT and plasma processing apparatus 1 can be realized with a simple structure and system at low cost.

[0043] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various additions, omissions, substitutions, and modifications may be made. Furthermore, elements in different embodiments may be combined to form other embodiments.

[0044] Various exemplary embodiments included in the present disclosure are now described in [E1] to [E6] below.

[0045] [E1] A plasma processing method comprising: a) a step of acquiring temperature information of a reaction chamber during plasma processing as information indicating a state of plasma density using at least one temperature detection element provided in an upper electrode of a plasma processing apparatus; and b) a step of converting the temperature information into power information and adjusting, based on the power information, power supplied from a high-frequency power source to the reaction chamber via the upper electrode so as to reduce bias in plasma density distribution along an electrode surface of the upper electrode; wherein the upper electrode has a gap provided adjacent to and above the electrode surface exposed to the reaction chamber, and the at least one temperature detection element includes a first temperature detection element positioned to measure a temperature at a bottom of the gap.

[0046] [E2] The plasma processing method according to [E1], wherein the first temperature detection element is provided above a region including a peak of a plasma density distribution measured in advance during plasma processing.

[0047] [E3] The plasma processing method according to [E1] or [E2], wherein the at least one temperature detection element includes a second temperature detection element provided at a distance from the first temperature detection element, and the second temperature detection element is provided above a flat region of the pre-measured plasma density distribution.

[0048] [E4] The plasma processing method according to [E3], wherein the temperature information acquired in the step a) is a difference obtained by subtracting a second temperature detected by the second temperature detection element from a first temperature detected by the first temperature detection element.

[0049] [E5] The plasma processing method according to [E1] or [E2], wherein the temperature information acquired in the step a) is a difference obtained by subtracting a first temperature detected by the first temperature detection element at a first timing from a second temperature detected by the first temperature detection element at a second timing after the first timing.

[0050] [E6] A processing vessel configured to perform plasma processing, a mounting table provided in the processing vessel and configured to mount a wafer thereon, an upper electrode provided in the processing vessel and positioned above the mounting table so as to face the mounting table, a gas supply unit configured to supply a processing gas to a reaction chamber between the upper electrode and the mounting table, a high frequency power supply electrically connected to the upper electrode and configured to generate plasma of the processing gas by supplying high frequency power to the upper electrode, at least one temperature detection element provided in the upper electrode, a temperature information acquisition unit configured to acquire temperature information of the reaction chamber based on a temperature signal output from the at least one temperature detection element, and a power adjustment unit configured to convert the temperature information acquired by the temperature information acquisition unit into power information and to adjust the power supplied from the high frequency power supply to the reaction chamber via the upper electrode based on the power information so as to reduce bias in plasma density distribution along an electrode surface of the upper electrode, wherein the upper electrode has a gap provided above and adjacent to the electrode surface exposed to the reaction chamber, The plasma processing apparatus, wherein the at least one temperature sensing element includes a first temperature sensing element positioned to measure a temperature at a bottom of the gap.

[0051] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims.

[0052] 1...plasma processing apparatus, 10...high frequency power supply, 11...gas outlet, 12...processing gas dispersion unit, 13...gas supply unit, 14...gas exhaust port, 15...exhaust unit, 16...temperature information acquisition unit, 17...power adjustment unit, 2...processing vessel, 21...support member, 2a...lid, 2b...side wall, 3...mounting table, 3a...lower electrode, 4...reaction chamber, 5...upper electrode, 5a...electrode surface, 5b...temperature measurement space, 6...dielectric ring, 7...antenna unit, 7a...inner conductor, 7b...outer conductor, 7c...through hole, 8...waveguide, 8a...first waveguide, 8b...second waveguide, 9...high frequency matching unit, AR...area, MT...method, SH...shower unit, T1...temperature sensor, T2...temperature sensor, TB...dielectric tube, W...wafer.

Claims

1. A plasma processing method comprising: a) a step of acquiring temperature information of a reaction chamber during plasma processing as information indicating a state of plasma density using at least one temperature detection element provided in an upper electrode of a plasma processing apparatus; and b) a step of converting the temperature information into power information and adjusting the power supplied from a high frequency power source to the reaction chamber via the upper electrode based on the power information so as to reduce bias in plasma density distribution along the electrode surface of the upper electrode, wherein the upper electrode has a gap provided adjacent to and above the electrode surface exposed to the reaction chamber, and the at least one temperature detection element includes a first temperature detection element arranged to measure a bottom temperature of the gap.

2. The plasma processing method according to claim 1, wherein the first temperature detection element is provided above a region including a peak of a plasma density distribution previously measured during plasma processing.

3. The plasma processing method according to claim 2, wherein the at least one temperature detection element includes a second temperature detection element spaced apart from the first temperature detection element, and the second temperature detection element is provided above a flat region of the previously measured plasma density distribution.

4. The plasma processing method according to claim 3, wherein the temperature information acquired in step a) is a difference obtained by subtracting a second temperature detected by the second temperature detection element from a first temperature detected by the first temperature detection element.

5. A plasma processing method as described in claim 1 or 2, wherein the temperature information acquired in step a) is a difference obtained by subtracting a first temperature detected by the first temperature detection element at a first timing from a second temperature detected by the first temperature detection element at a second timing after the first timing.

6. A processing vessel configured to perform plasma processing, a mounting stage provided within the processing vessel and configured to mount a wafer thereon, an upper electrode provided within the processing vessel and arranged above the mounting stage so as to face the mounting stage, a gas supply unit configured to supply a processing gas to a reaction chamber between the upper electrode and the mounting stage, a high frequency power source electrically connected to the upper electrode and configured to generate plasma of the processing gas by supplying high frequency power to the upper electrode, at least one temperature detection element provided within the upper electrode, a temperature information acquisition unit configured to acquire temperature information of the reaction chamber based on a temperature signal output from the at least one temperature detection element, and a power adjustment unit configured to convert the temperature information acquired by the temperature information acquisition unit into power information and to adjust the power supplied from the high frequency power source to the reaction chamber via the upper electrode based on the power information so as to reduce bias in plasma density distribution along an electrode surface of the upper electrode, wherein the upper electrode has a gap provided above and adjacent to the electrode surface exposed to the reaction chamber, The at least one temperature sensing element includes a first temperature sensing element positioned to measure a temperature at a bottom of the gap.

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