Cleaning method and method for manufacturing semiconductor device

Abstract

A cleaning method according to one embodiment of the present disclosure cleans an electrostatic chuck by exposing the electrostatic chuck to plasma and maintaining a relationship between a potential of the electrostatic chuck and a potential of the plasma such that an electron current flows from the plasma toward the electrostatic chuck.

Description

Technical Field

[0001] The present disclosure relates to a cleaning method and a method for manufacturing a semiconductor device. Background Art

[0002] A technique is known in which argon ions generated by plasma discharge collide with an electrostatic chuck to perform plasma etching on contaminants attached to the electrostatic chuck (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-280365 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] The present disclosure provides a technology capable of suppressing damage to the surface of an electrostatic chuck and removing matter attached to the electrostatic chuck.

[0008] Solutions for solving problems

[0009] A cleaning method according to one embodiment of the present disclosure cleans an electrostatic chuck by exposing the electrostatic chuck to plasma and maintaining a relationship between a potential of the electrostatic chuck and a potential of the plasma such that an electron current flows from the plasma toward the electrostatic chuck.

[0010] Effects of the Invention

[0011] According to the present disclosure, it is possible to suppress damage to the surface of the electrostatic chuck and remove matter attached to the electrostatic chuck. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram showing an example of a film forming apparatus according to an embodiment.

[0013] Figure 2 This is a flowchart showing an example of a method for manufacturing a semiconductor device according to an embodiment. DETAILED DESCRIPTION

[0014] Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all the drawings, the same or corresponding components or parts are denoted by the same or corresponding reference numerals, and repeated descriptions are omitted.

[0015] 〔Film forming device〕

[0016] Reference Figure 1 An example of a film forming apparatus according to an embodiment will be described. Figure 1 This is a schematic diagram showing an example of a film forming apparatus according to an embodiment. In the following embodiment, a case where the film forming apparatus is a plasma CVD apparatus that forms a titanium (Ti) film on a substrate by plasma CVD (PECVD: Plasma-Enhanced Chemical Vapor Deposition) is exemplified and described.

[0017] The film forming apparatus 1 includes a processing chamber 11 formed of a processing container, which is a substantially cylindrical container formed airtightly. In the processing chamber 11, a stage 12 for horizontally adsorbing and holding a semiconductor wafer (hereinafter referred to as "wafer W") as an example of a substrate is arranged in a state supported by a substantially cylindrical support member 13 provided at the lower center thereof.

[0018] The stage 12 is made of conductive ceramic such as aluminum nitride (AlN). A guide ring 14 for guiding the wafer W is provided on the outer edge of the stage 12 .

[0019] The stage 12 includes a heater 15 embedded therein. The heater 15 is powered by a heater power source 40 to heat the wafer W to a predetermined temperature. In the present embodiment, the heater power source 40 includes an AC power source 40a, a thyristor 40b, and a noise filter (NF) 40c.

[0020] In the stage 12, the lower electrode 16 is embedded in the heater 15. The lower electrode 16 is connected to the chuck control mechanism 70 described later, and the stage 12 and the lower electrode 16 function as an electrostatic chuck. In the present embodiment, the electrostatic chuck is a Johnson-Rahbek type (JR type: Johnsen-Rahbek type).

[0021] A shower head 20 is provided on the ceiling 11A of the processing chamber 11 via an insulating member 19. The shower head 20 includes an upper base member 21 and a shower plate 22 mounted below the base member 21. A heater 23 for heating the shower head 20 is embedded in the base member 21. The heater 23 heats the shower head 20 to a predetermined temperature by receiving power from a heater power source 41.

[0022] The shower plate 22 is formed with a plurality of ejection holes 24 for ejecting gas into the processing chamber 11. Each ejection hole 24 is connected to a gas diffusion space 25 formed between the base member 21 and the shower plate 22. A gas inlet 26 for supplying a processing gas to the gas diffusion space 25 is provided in the central portion of the base member 21. The gas inlet 26 is connected to a mixed gas supply line 38 of a gas supply unit 30 described later.

[0023] The gas supply unit 30 includes a TiCl 4 gas supply source 31 for supplying TiCl 4 gas as a Ti compound gas, an Ar gas supply source 32 for supplying Ar gas, and an H 2 gas supply source 33 for supplying H 2 gas as a reducing gas.

[0024] The TiCl4 gas supply source 31 is connected to the TiCl4 gas supply line 31L, the Ar gas supply source 32 is connected to the Ar gas supply line 32L, and the H2 gas supply source 33 is connected to the H2 gas supply line 33L. The gas line 31L is provided with a mass flow controller (MFC) 31C and two valves 31V sandwiching the mass flow controller 31C, the gas line 32L is provided with a mass flow controller (MFC) 32C and two valves 32V sandwiching the mass flow controller 32C, and the gas line 33L is provided with a mass flow controller (MFC) 33C and two valves 33V sandwiching the mass flow controller 33C.

[0025] The gas mixing unit 37 has the function of mixing the above-mentioned processing gases and supplying them to the shower head 20. The gas inflow side of the gas mixing unit 37 is connected to the TiCl4 gas supply source 31, the Ar gas supply source 32, and the H2 gas supply source 33 via the gas pipelines 31L to 33L. The gas outflow side of the gas mixing unit 37 is connected to the shower head 20 via the mixed gas supply pipeline 38.

[0026] During the treatment, one gas or a mixed gas of the TiCl 4 gas, Ar gas and H 2 gas is introduced into the processing chamber 11 from the plurality of ejection holes 24 through the gas inlet 26 of the shower head 20 and the gas diffusion space 25 .

[0027] As described above, in the present embodiment, the shower head 20 is configured as a so-called premix type in which the process gases are mixed in advance and then supplied into the process chamber 11 . However, the shower head 20 may be configured as a postmix type in which each process gas is independently supplied into the process chamber 11 .

[0028] The shower head 20 is connected to the high-frequency power supply 43 via the matching device 42. When the processing gas is supplied to the processing chamber 11, a high-frequency power of, for example, 450 kHz is supplied from the high-frequency power supply 43 to the shower head 20, so that plasma is generated between the shower head 20 and the lower electrode 16. In this way, the shower head 20 functions as an upper electrode arranged opposite to the lower electrode. From the perspective of being able to efficiently attract electrons to the electrostatic chuck side in the cleaning process described later, the distance between the upper surface of the stage 12 and the lower surface of the shower plate 22 (the distance between a pair of electrodes) is preferably 80 mm or less. In addition, the high-frequency power is not limited to 450 kHz, and for example, 2 MHz, 13.56 MHz, 27 MHz, 60 MHz, 100 MHz, etc. can be appropriately used.

[0029] A circular opening 17 is formed in the center of the bottom wall 11B of the processing chamber 11, and an exhaust chamber 50 protruding downward is provided on the bottom wall 11B in a manner covering the opening 17. An exhaust pipe 51 is connected to the side of the exhaust chamber 50, and the exhaust pipe 51 is connected to an exhaust device 52. The exhaust device 52 reduces the pressure in the processing chamber 11 to a predetermined vacuum pressure.

[0030] A plurality of (e.g., three) lift pins 60 for supporting and lifting the wafer W are provided on the stage 12 so as to protrude or retract relative to the surface of the stage 12. The lift pins 60 are fixed to a support plate 61. The lift pins 60 are lifted and lowered by a drive mechanism 62 such as an air cylinder via the support plate 61. A loading and unloading port 18 for loading and unloading the wafer W and a gate valve G for opening and closing the loading and unloading port 18 are provided on the side wall 11C of the processing chamber 11.

[0031] When the wafer W is moved in or out of the processing chamber 11, the lifting pins 60 are raised and lowered. Specifically, when the wafer W is moved into the processing chamber 11, the lifting pins 60 are raised. Then, the wafer W is moved in from the loading and unloading port 18 by a transfer arm (not shown) and placed on the lifting pins 60. Next, the lifting pins 60 are lowered to place the wafer W on the stage 12. In addition, when the wafer W is moved out of the processing chamber 11, the lifting pins 60 are raised to lift the wafer W. Then, the wafer W is received by the transfer arm (not shown) and moved out from the loading and unloading port 18.

[0032] The film forming apparatus 1 includes a control unit 90. The control unit 90 controls the operation of each unit of the film forming apparatus 1. The control unit 90 is, for example, a computer. The control unit 90 includes a program, a memory, and a data processing unit composed of a CPU. The program includes commands (various steps) so that a control signal is sent from the control unit 90 to each unit of the film forming apparatus 1 to execute the cleaning method of the electrostatic chuck described later. The program is stored in a storage medium such as a flash memory, a hard disk, or an optical disk and installed in the control unit 90.

[0033] 〔Suction cup control mechanism〕

[0034] The chuck control mechanism 70 is electrically connected to the lower electrode 16. The chuck control mechanism 70 includes a power supply 71, a grounding box 72, a variable impedance device 73, and a current sensor 74.

[0035] The power supply 71 applies an anode voltage to the stage 12 via the lower electrode 16. In the present embodiment, the power supply 71 is a high voltage (HV) power supply, and applies a high voltage of, for example, 400V to 600V to the stage 12 via the lower electrode 16. By setting the anode voltage to, for example, 400V to 600V, the relationship between the potential of the stage 12 and the potential of the plasma can be maintained in a relationship in which an electron current flows from the plasma toward the stage 12. In addition, the power supply 71 may also include an RF filter (not shown) for cutting off high-frequency power flowing from the stage 12 side to the power supply 71.

[0036] The grounding box 72 is provided between the power supply 71 and the lower electrode 16. The grounding box 72 is configured to be switchable between a state in which the lower electrode 16 is grounded and a state in which the lower electrode 16 is not grounded. In the present embodiment, the grounding box 72 includes a switch 72a and a switch 72b. The switch 72a switches the state of electrical connection between the power supply 71 and the lower electrode 16. The power supply 71 and the lower electrode 16 are electrically connected by turning on the switch 72a, and the electrical connection between the power supply 71 and the lower electrode 16 is cut off by turning off the switch 72a. The switch 72b switches the state of grounding of the lower electrode 16. The lower electrode 16 is grounded by turning on the switch 72b.

[0037] The variable impedance device 73 is provided between the power supply 71 and the ground box 72. The variable impedance device 73 is used to adjust the impedance on the stage 12 side. In the present embodiment, the variable impedance device 73 includes a capacitor 73a and a variable coil 73b connected in series, and the impedance on the stage 12 side is adjusted by adjusting the inductance of the variable coil 73b. In addition, the variable impedance device 73 includes a current sensor 73c. ​​The current sensor 73c is, for example, an AC current sensor such as a CT (Current Transformer) type current sensor.

[0038] The current sensor 74 detects the current flowing from the lower electrode 16 toward the power source 71. In other words, the current sensor 74 detects the electron current flowing from the plasma space toward the electrostatic chuck. The current sensor 74 is, for example, an AC current sensor such as a CT current sensor.

[0039] [Method for manufacturing semiconductor device]

[0040] Reference Figure 2An example of a method for manufacturing a semiconductor device including a cleaning method according to an embodiment will be described. Figure 2 1 is a flowchart showing an example of a method for manufacturing a semiconductor device according to an embodiment. In the following description, the method for manufacturing a semiconductor device is described as follows: at the start of the method for manufacturing a semiconductor device, the exhaust device 52 is used to make the inside of the processing chamber 11 a vacuum environment.

[0041] First, the control unit 90 moves the wafer W into the processing chamber 11 (step S1). In the present embodiment, the control unit 90 uses a transfer arm (not shown) to move the wafer W into the processing chamber 11, transfers the wafer W to the lift pins 60, and places it on the stage 12. Next, the control unit 90 closes the gate valve G. Next, the control unit 90 controls the exhaust device 52 to reduce the pressure in the processing chamber 11 to a specified pressure. In addition, the control unit 90 controls the AC power supply 40a and the heater power supply 41 to heat the stage 12 and the shower head 20 to a specified temperature.

[0042] Next, the control unit 90 performs film forming processing on the wafer W adsorbed and held on the stage 12 (step S2). In the present embodiment, the control unit 90 controls the gas supply unit 30 to supply TiCl4 gas and H2 gas into the processing chamber 11. In addition, the control unit 90 controls the power supply 71 and the ground box 72 to apply voltage to the lower electrode 16, and uses the high-frequency power supply 43 to supply high-frequency power of a specified frequency to the shower head 20. As a result, the wafer W is adsorbed and held on the stage 12 (electrostatic chuck), and plasma is generated between the electrostatic chuck and the shower head 20, and the TiCl4 gas reacts with the H2 gas to form a Ti film on the wafer W.

[0043] When the film forming process is completed, the control unit 90 carries out the wafer W with the Ti film formed thereon from the processing chamber 11 (step S3). In the present embodiment, the control unit 90 controls the grounding box 72 to ground the lower electrode 16, thereby releasing the adsorption of the wafer W to the stage 12. Next, the control unit 90 opens the gate valve G. Next, the wafer W in the processing chamber 11 is carried out by a transfer arm (not shown).

[0044] After the wafer W is unloaded from the processing chamber 11 , the control unit 90 determines whether the electrostatic chuck needs to be cleaned (step S4 ). For example, the control unit 90 determines whether the electrostatic chuck needs to be cleaned based on the number of times or time of film formation processing.

[0045] If it is determined in step S4 that the electrostatic chuck does not need to be cleaned, the control unit 90 returns the process to step S1. That is, the control unit 90 carries the wafer W to be processed next into the processing chamber 11 and performs the film forming process without performing the electrostatic chuck cleaning process.

[0046] On the other hand, when it is determined in step S4 that the electrostatic chuck needs to be cleaned, the control unit 90 performs a cleaning process (cleaning method) on the electrostatic chuck (step S5). In the cleaning process, the electrostatic chuck is cleaned by exposing the electrostatic chuck to plasma in a state where there is no wafer W on the electrostatic chuck, and maintaining the relationship between the potential of the electrostatic chuck and the potential of the plasma in a relationship in which the electron current flows from the plasma toward the electrostatic chuck. In the present embodiment, the control unit 90 switches the switch 72a to on, switches the switch 72b to off, and controls the power supply 71 to apply an anode voltage of, for example, 400V to 600V to the lower electrode 16. In addition, the control unit 90 controls the gas supply unit 30 to supply Ar gas into the processing chamber 11, and controls the high-frequency power supply 43 to supply, for example, 450kH of high-frequency power to the shower head 20 to generate plasma. In addition, the control unit 90 controls the variable impedance device 73 to adjust the impedance on the electrostatic chuck side, thereby stabilizing the plasma generated between a pair of electrodes arranged opposite to each other.

[0047] In this way, by keeping the relationship between the potential of the electrostatic chuck and the potential of the plasma in a relationship in which the electron current flows from the plasma toward the electrostatic chuck, the surface of the electrostatic chuck is charged positively (+), so that the electrons contained in the plasma are attracted to the surface of the electrostatic chuck. That is, the electron current flows from the plasma toward the electrostatic chuck (lower electrode 16). As a result, electron collisions occur on the surface of the electrostatic chuck, and the attachments attached to the electrostatic chuck are removed. At this time, since the surface of the electrostatic chuck is positively charged, it is difficult for high-energy cations (such as Ar) to occur on the surface of the electrostatic chuck. + ). In this way, it is possible to selectively allow low-energy electrons to collide with the surface of the electrostatic chuck while suppressing the collision of high-energy cations with the surface of the electrostatic chuck. As a result, it is possible to suppress damage to the surface of the electrostatic chuck and remove deposits attached to the electrostatic chuck.

[0048] When the cleaning process is completed, the control unit 90 ends the process.

[0049] As described above, according to the embodiment, the electrostatic chuck is exposed to plasma, and the relationship between the potential of the electrostatic chuck and the potential of the plasma is maintained so that the electron current flows from the plasma toward the electrostatic chuck. As a result, electrons are attracted from the plasma space to the electrostatic chuck side, and the attracted electrons collide with the surface of the electrostatic chuck, so that the attached matter attached to the electrostatic chuck can be removed. As described above, according to the embodiment, since the collision of electrons with the surface of the electrostatic chuck is mainly used, compared with using cations (such as Ar) +For example, in the case of collision with cations, the outermost surface of the dielectric layer of the electrostatic chuck (such as the sintering aid) is etched due to the impact of the cations, and impurities such as particles are easily generated.

[0050] Furthermore, according to the embodiment, since the attached matter attached to the electrostatic chuck can be removed using plasma, the frequency of regenerating (repairing) the electrostatic chuck after the electrostatic chuck is removed from the film forming apparatus 1 can be reduced, thereby improving productivity.

[0051] In addition, according to the embodiment, plasma is generated in a narrow space where the distance between a pair of electrodes is 80 mm or less, and the electrostatic chuck is cleaned by the plasma. This can efficiently attract electrons to the electrostatic chuck side, thereby improving the ability to remove attached matter on the electrostatic chuck.

[0052] In addition, according to the embodiment, the impedance of the electrostatic chuck can be adjusted using a variable impedance device connected to the electrostatic chuck. Thus, even when the anode voltage applied to the lower electrode 16 is changed, the impedance of the electrostatic chuck can be adjusted, thereby generating stable plasma.

[0053] [Example]

[0054] In the embodiment, the electrostatic chuck with the deposits attached to the surface was subjected to the cleaning process described above in the film forming apparatus 1. The surface resistance of the electrostatic chuck was measured before and after the cleaning process. The cleaning process conditions and the surface resistance measurement conditions were as follows.

[0055] (Conditions of cleaning treatment)

[0056] Distance between a pair of electrodes: 10mm~50mm

[0057] Output of high frequency power supply 43: 450kHz, 500W

[0058] Output of power supply 71: 500V

[0059] Pressure in processing chamber 11: 5 Torr (667 Pa)

[0060] Processing time: 60 seconds x 10 cycles

[0061] (Measurement conditions of surface resistance)

[0062] Applied voltage: 1000V

[0063] The results of comparing the surface resistance of the electrostatic chuck before and after the cleaning process are shown in the following Table 1. In Table 1, the measurement positions refer to different positions within the surface of the electrostatic chuck.

[0064] [Table 1]

[0065] Determine the location Before cleaning After cleaning 1 77.9M 2T 2 44.0M 2T 3 25.8M 2T 4 9.3M 2T 5 2.8M 2T 6 8.15M 2T 7 24.6M 2T 8 65.7M 2T 9 42.9M 2T 10 22.3M 2T 11 44.0M 2T 12 13.4M 2T 13 18.0M 2T 14 23.9M 2T 15 39.5M 2T 16 9.8M 2T 17 10.6M 2T 18 132M 2T 19 5.71M 2T

[0066] As shown in Table 1, it can be seen that the surface resistance of the electrostatic chuck before the cleaning process is 2.8MΩ to 132MΩ, while the surface resistance of the electrostatic chuck after the cleaning process is above the upper limit of the measurement (2TΩ). Based on this result, it can be considered that by performing the above-mentioned cleaning process on the electrostatic chuck, the attached matter on the electrostatic chuck can be removed, so that the surface resistance of the electrostatic chuck becomes higher.

[0067] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive. The embodiments described above may be omitted, replaced, or modified in various ways without departing from the appended claims and the gist thereof.

[0068] The present international application claims the benefit of priority based on Japanese Patent Application No. 2020-046448, filed on March 17, 2020, the entire contents of which are incorporated herein by reference.

[0069] Description of Reference Numerals

[0070] 12: stage; 16: lower electrode; 20: shower head; 73: variable impedance device; W: wafer.

Claims

1. A cleaning method, The electrostatic chuck is exposed to plasma and the relationship between the potential of the electrostatic chuck and the potential of the plasma is maintained in a relationship in which an electron current flows from the plasma toward the electrostatic chuck, so that electrons contained in the plasma are attracted to the surface of the electrostatic chuck to collide with the surface of the electrostatic chuck, thereby removing the attached matter attached to the electrostatic chuck and cleaning the electrostatic chuck. in, The plasma is formed between a pair of electrodes arranged opposite to each other, high-frequency power is applied to one of the pair of electrodes, and an anode voltage of 400V to 600V is applied to the other electrode, the anode voltage is controlled based on the electron current flowing toward the electrostatic chuck, and the distance between the pair of electrodes is 80 mm or less, The electrostatic chuck is connected to a variable impedance device for adjusting impedance, and the impedance on the electrostatic chuck side is adjusted by controlling the variable impedance device to stabilize the plasma formed between the pair of electrodes.

2. The cleaning method according to claim 1, wherein: The electrostatic chuck is of the Johnson-Rabbeck type.

3. The cleaning method according to claim 1 or 2, wherein: The cleaning method is performed in a state where no substrate is on the electrostatic chuck.

4. A method for manufacturing a semiconductor device, comprising the following steps: Adsorbing and holding the substrate on an electrostatic chuck to form a film; and exposing the electrostatic chuck to plasma without a substrate on the electrostatic chuck, in, The step of exposing the electrostatic chuck to the plasma includes the following steps: maintaining the relationship between the potential of the electrostatic chuck and the potential of the plasma in a relationship in which an electron current flows from the plasma toward the electrostatic chuck, so that electrons contained in the plasma are attracted to the surface of the electrostatic chuck to collide with the surface of the electrostatic chuck, thereby removing attachments attached to the electrostatic chuck and cleaning the electrostatic chuck, The plasma is formed between a pair of electrodes arranged opposite to each other, high-frequency power is applied to one of the pair of electrodes, and an anode voltage of 400V to 600V is applied to the other, the anode voltage is controlled based on the electron current flowing toward the electrostatic chuck, and the distance between the pair of electrodes is less than 80 mm. The electrostatic chuck is connected to a variable impedance device for adjusting impedance, and the impedance on the electrostatic chuck side is adjusted by controlling the variable impedance device to stabilize the plasma formed between the pair of electrodes.

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