Nitride film forming method and plasma processing apparatus

Abstract

To reform a nitride film while controlling the stress of the nitride film.SOLUTION: Provided is a nitride film forming method including: (a) a step for preparing a substrate; (b) a step for supplying a halogen-containing raw-material gas into a processing container; and (c) a step for supplying a nitride-containing gas into the processing container. A cycle comprising the step of (b) and the step of (c) is repeated a set number of times to form a nitride film. The nitride film forming method further includes (d) a step for reforming the nitride film by supplying, between the step of (b) and the step of (c), a hydrogen-containing gas to the processing container to generate a hydrogen radical by a DC pulsed voltage.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a nitride film forming method and a plasma processing apparatus. [Background technology]

[0002] For example, Patent Document 1 proposes a method for forming a high-stress silicon nitride film at low temperatures in a batch-type apparatus. In Patent Document 1, dichlorosilane is supplied to a wafer, and a reaction product is formed on the wafer by reacting with the dichlorosilane. Next, hydrogen radicals are supplied to remove chlorine contained in the reaction product. Subsequently, ammonia radicals are supplied into the reaction tube to form a silicon nitride film on the substrate W. This process is repeated multiple times to form the desired silicon nitride film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-283385 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can modify a nitride film while controlling the film stress of the nitride film. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, a method includes the steps of: (a) providing a substrate; and (b) disposing a substrate in a processing chamber. Contains halogen-containing silicon compounds or halogen-containing germanium compounds (c) supplying a halogen-containing source gas into the processing chamber; and (d) supplying a hydrogen-containing gas into the processing chamber between the steps (b) and (c) to generate hydrogen radicals by applying a DC pulse voltage, thereby modifying the nitride film. The nitride film is a silicon nitride film or a germanium nitride film.A method for depositing a nitride film is provided. [Effects of the Invention]

[0006] According to one aspect, the nitride film can be modified while controlling the film stress of the nitride film. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing an example of a plasma processing apparatus according to an embodiment; [Figure 2] FIG. 4 is a diagram showing an example of a DC pulse voltage according to the embodiment. [Figure 3] 1 is a flowchart showing a method for forming a nitride film according to an embodiment. [Figure 4] 4 is a time chart showing a method for forming a nitride film according to an embodiment. [Figure 5] 10A and 10B are diagrams showing an example of hydrogen radical purging, film quality of a nitride film, and film stress. [Figure 6] 10A and 10B are diagrams showing an example of hydrogen radical purging, film quality of a nitride film, and film stress. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0009] [Plasma processing equipment] First, an example of the configuration of a plasma processing apparatus 1 according to an embodiment will be described with reference to FIG. 1. The plasma processing apparatus 1 is an example of an apparatus that performs a nitride film forming method according to an embodiment described below. The plasma processing apparatus 1 has a substantially cylindrical metal processing chamber 10. The processing chamber 10 is grounded. Inside the processing chamber 10, a metal mounting table 2 on which a substrate W is placed is provided. The mounting table 2 also functions as a lower electrode.

[0010] The mounting table 2 may have a heating mechanism, such as a heater. In addition, a plurality of lift pins (not shown) are inserted into the mounting table 2 so as to be protruding and retracting from the upper surface thereof, and the substrate W is transferred to and from the mounting table 2 by the lifting mechanism (not shown) raising and lowering the plurality of lift pins.

[0011] An opening is formed in the top of the processing vessel 10, and a shower head 15 is fitted into the opening via an insulating member 9 so as to face the mounting table 2. The shower head 15 is made of metal, has a cylindrical overall shape, and functions as the upper electrode 60. A part or all of the shower head 15 may serve as the upper electrode 60. The shower head 15 has a main body 11 having an opening at the bottom, and a shower plate 12 provided to close the opening of the main body 11, and the internal space between them functions as a gas diffusion space. A plurality of gas ejection holes 13 are formed in the shower plate 12.

[0012] The shower head 15 is formed with a gas inlet hole 14, and a processing gas supplied from a gas supply unit 20 is introduced into the shower head 15 through the gas inlet hole 14. The processing gas introduced into the shower head 15 is discharged into the processing chamber 10 through the gas discharge holes 13 and supplied to the space between the shower head 15, which functions as an upper electrode, and the mounting table 2, which functions as a lower electrode.

[0013] The gas supply unit 20 supplies a plurality of gases used in the plasma processing, such as a processing gas, a plasma generating gas, and a purge gas. An appropriate processing gas is selected depending on the plasma processing to be performed. The gas supply unit 20 has a plurality of gas supply sources and gas supply pipes, and the gas supply pipes are provided with valves and flow rate controllers such as mass flow controllers.

[0014] A high-frequency power supply 30 is connected to approximately the center of the showerhead 15 via a power supply line 87. The high-frequency power supply 30 preferably supplies high-frequency power with a frequency of 400 kHz or higher. When high-frequency power is supplied from the high-frequency power supply 30 to the showerhead 15, a capacitively coupled plasma is generated between the showerhead 15 and the mounting table 2.

[0015] The high frequency power supply 30 is connected to the upper electrode 60 via a matching circuit 34 and a power supply line 87. The high frequency power supply 30 supplies a high frequency voltage that contributes to plasma generation to the upper electrode 60 via the matching circuit 34. A filter 86 prevents the high frequency voltage from being transmitted to the variable DC power supply 80. The matching circuit 34 matches the impedance on the high frequency power supply 30 side with the impedance on the load side (mainly the electrode, plasma, and processing chamber).

[0016] An output terminal of the variable DC power supply 80 is connected to a pulse generator 89, and the variable DC power supply 80 outputs a negative DC voltage (DC voltage) to the pulse generator 89. The pulse generator 89 generates a DC pulse voltage using the negative DC voltage input from the variable DC power supply 80 and supplies the generated DC pulse voltage to the upper electrode 60 via a voltage limiter 88 and a filter 86. The DC pulse voltage periodically repeats an ON state in which a negative DC voltage is applied to the upper electrode 60 and an OFF state in which the DC voltage applied to the upper electrode 60 is set to approximately 0 V. When a negative DC voltage is continuously applied to the upper electrode 60 to excite plasma, abnormal discharge (arcing) is likely to occur. In contrast, when a negative DC pulse voltage is applied to the upper electrode 60, discharge occurs intermittently, and therefore, the occurrence of abnormal discharge is suppressed compared to when a negative DC voltage is continuously applied. However, when a DC pulse voltage is applied, if the voltage of the upper electrode 60 swings significantly to a positive voltage due to overshoot when transitioning from the on state to the off state, the energy of the ions incident on the substrate W increases.

[0017] The voltage limiter 88 propagates a negative voltage to the upper electrode 60 to generate plasma while the DC pulse voltage is in the ON state. Meanwhile, while the DC pulse voltage is in the OFF state, the voltage limiter 88 functions to prevent the voltage of the upper electrode 60 from swinging too far to the positive due to overshoot. For example, the overshoot voltage is limited to 100 V or less. This prevents the plasma potential from rising in the processing space. Meanwhile, because the mounting table 2 facing the upper electrode 60 is grounded, the potential of the substrate W placed on it is also fixed at 0 V. The potential difference between the substrate W and the plasma potential is the ion acceleration voltage. Since the voltage limiter 88 prevents the plasma potential from rising to 100 V or less, the ion acceleration voltage is also suppressed, resulting in a reduction in the energy of ions incident on the substrate W. By depositing a film with an ion energy of 100 eV or less, the film stress can be maintained at tensile stress. To keep the ion energy incident on the substrate W at 100 eV or less, the overshoot voltage should be set to 100 V or less. That is, by controlling the overshoot voltage to 100 V or less by the voltage limiter 88, the energy of the ions incident on the substrate W is reduced to 100 eV or less, and the stress of the film on the substrate W can be maintained at tensile stress.

[0018] An example of a DC pulse voltage according to this embodiment is shown in FIG. 2. The horizontal axis in FIG. 2 represents time, and the vertical axis represents the voltage of the upper electrode 60. The DC pulse voltage supplied to the upper electrode 60 alternates between an ON state and an OFF state at a predetermined duty ratio. When transitioning from the ON state to the OFF state, the function of the voltage limiter 88 suppresses overshoot of the DC pulse voltage, controlling it to a DC pulse voltage of 100 V or less. In FIG. 2, the overshoot is suppressed to about 20 V.

[0019] The frequency of the DC pulse voltage is preferably 10 kHz to 1 MHz, and the duty ratio is preferably 10% to 90%.

[0020] 1, an exhaust port 41 is provided at the bottom of processing vessel 10. An exhaust device 43 is connected to exhaust port 41 via an exhaust pipe 42. Exhaust device 43 evacuates the inside of processing vessel 10.

[0021] A switch 94 is provided between the mounting table 2 and the ground via the power supply line 36, and the switch 94 switches the connection of the mounting table 2 between the ground and the impedance adjustment circuit 93. The impedance adjustment circuit 93 uses the resonance of an LC circuit to control the high frequency power from the high frequency power supply 30 to flow efficiently from the upper electrode 60 side to the mounting table 2 side.

[0022] The control unit 100 controls the individual operations of the components in the plasma processing apparatus 1 (e.g., the exhaust device 43, the high frequency power supply 30, the variable DC power supply 80, the gas supply unit 20, the heating mechanism, etc.) and the overall operation (sequence) of the plasma processing apparatus 1. The control unit is realized by, for example, a microcomputer.

[0023] [Nitride film formation method] Next, a nitride film forming method that can be performed in the plasma processing apparatus 1 will be described with reference to FIGS. 3 and 4. FIG. 3 is a flowchart showing the nitride film forming method according to an embodiment. FIG. 4 is a time chart showing the nitride film forming method according to an embodiment. The film forming method of FIG. 3 is executed by the control unit 100.

[0024] When the process of FIG. 3 starts, the control unit 100 loads the substrate W into the processing chamber 10 and places it on the mounting table 2 in step S1.

[0025] 3 and 4, the source gas and argon (Ar) gas, which are film-forming raw materials, are supplied into the processing chamber 10 from the gas supply unit 20 at a predetermined flow rate, and the pressure inside the processing chamber 10 is adjusted to a set value by the exhaust device 43. Also, by switching the switch 94, the mounting table 2 is grounded via the switch 94 and the power supply line 36. The Ar gas is continuously supplied during the processing of steps S2 to S7 shown in FIG. 3, which will be described later.

[0026] In this manner, in step S2 of FIG. 3, the control unit 100 supplies a source gas to be adsorbed onto the substrate W. For example, when forming a silicon nitride film, a halogen-containing source gas is supplied as the source gas to be adsorbed onto the substrate W. A silicon (Si) compound containing chlorine (Cl) can be used as the halogen-containing source gas. In this disclosure, hexachlorodisilane (HCD; Si2Cl6) is used as an example of the source gas. Other examples of the source gas include dichlorosilane (DCS; SiH2Cl2), monochlorosilane (MCS; SiH3Cl), trichlorosilane (TCS; SiHCl3), silicon tetrachloride (STC; SiCl4), etc. However, the halogen-containing source gas is not limited to these, and may be a silicon compound containing iodine (I) or bromine (Br). Furthermore, the halogen-containing source gas is not limited to silicon, but may also be a halogen-containing germanium (Ge) compound.

[0027] After a predetermined time has elapsed since the start of step S2, the control unit 100 stops the supply of the source gas as shown in FIG. 4, and in step S3 of FIG. 3, a mixed gas of Ar gas and H2 gas is supplied as a purge gas. However, the purge gas is not limited to this, and Ar gas, H2 gas, N2 gas, a mixed gas of Ar gas and N2 gas, a mixed gas of H2 gas and N2 gas, etc. may also be used. As a result, the source gas in the processing chamber 10 is replaced with Ar gas and H2 gas. Furthermore, the surface of the substrate W is purged with Ar gas and H2 gas, and excess source gas molecules adhering to the surface of the substrate W are removed. Purge gases such as Ar gas and H2 gas and a nitrogen-containing gas, which will be described later, may be supplied from a gas supply pipe (not shown) located near the substrate W.

[0028] After a predetermined time has elapsed since the start of step S3, the control unit 100 supplies a DC pulse voltage from the variable DC power supply 80 to the upper electrode 60 in step S4 while continuing to supply H 2 gas and Ar gas.

[0029] The H2 gas is converted into plasma in the plasma generation space, generating hydrogen radicals. The hydrogen radicals reach the substrate W in the processing chamber 10, where chlorine contained in HCD (Si2Cl6) adsorbed on the substrate W reacts with the hydrogen, replacing the chlorine with hydrogen. Si-Cl is replaced with Si-H, modifying the silicon-containing film. Note that, in this disclosure, H2 gas is used as an example of a hydrogen-containing gas that generates hydrogen radicals, but this is not limiting.

[0030] After a predetermined time has elapsed since the start of step S4, the supply of DC pulse voltage from the variable DC power supply 80 is stopped as shown in FIG. 4, and the supply of H2 gas is stopped. However, the supply of Ar gas is continued. In step S5, the control unit 100 starts the supply of NH3 gas. As a result, the hydrogen gas in the processing chamber 10 is replaced with Ar gas and NH3 gas.

[0031] After a predetermined time has elapsed since the start of step S5, in step S6, the control unit 100 continues to supply Ar gas and NH gas, an example of a nitrogen-containing gas, into the processing chamber 10 and switches the switch 94 to connect the mounting table 2 to the impedance adjustment circuit 93. The control unit 100 then supplies a high-frequency voltage from the high-frequency power supply 30 to the upper electrode 60. This generates a plasma of NH gas, which reacts with the silicon-containing film modified by the hydrogen radicals to nitride the HCD adsorbed on the substrate W. This increases the nitrogen concentration in the silicon-containing film, resulting in the formation of a silicon nitride film. The nitrogen-containing gas is not limited to NH gas; nitrogen (N), diazene (N2H2), hydrazine (N2H4), or an organic hydrazine compound such as monomethylhydrazine (CH3(NH)NH2) can also be used. Note that the high-frequency voltage does not necessarily need to be supplied from the high-frequency power supply 30 in step S6.

[0032] 4, after a predetermined time has elapsed since the start of step S6, the supply of NH3 gas is stopped, the supply of high-frequency voltage from the high-frequency power supply 30 is stopped, and the mounting table 2 is grounded using the switch 94. In step S7, the control unit 100 continues to supply Ar gas. As a result, the NH3 gas in the processing chamber 10 is replaced with Ar gas. However, the purge gas is not limited to Ar gas, and may be H2 gas, N2 gas, a mixed gas of H2 gas and Ar gas, a mixed gas of Ar gas and N2 gas, or a mixed gas of H2 gas and N2 gas.

[0033] After a predetermined time has elapsed since the start of step S7, in step S8, the control unit 100 determines whether the nitride film formation process (steps S2 to S7) has been performed a predetermined number of times as one cycle. If the control unit 100 determines that the film formation process has not been performed the set number of times, it returns to step S2 and performs one cycle of steps S2 to S7. This repeats the silicon nitride film formation process. By repeating the film formation process the set number of times, a silicon nitride film of a predetermined thickness is formed. If the control unit 100 determines that the film formation process has been performed the set number of times, it unloads the substrate W and ends this process.

[0034] 4, for example, the source gas adsorption step of step S2 is performed for 2 seconds, step S3 is performed for 5 seconds, the hydrogen radical purging step of step S4 is performed for 2 seconds, step S5 is performed for 2 seconds, the nitriding step of step S6 is performed for 4 seconds, and step S7 is performed for 2 seconds. This makes it possible to form a silicon nitride film with good film quality on the surface of the substrate W. Note that the execution times of steps S2 to S7 are not limited to this example.

[0035] According to the nitride film forming method described above, a direct current pulse voltage is supplied between the source gas adsorption process of step S2 and the nitridation process of step S6, and hydrogen radical purging is performed in step S4 to generate hydrogen radicals, thereby modifying the silicon nitride film. By performing the hydrogen radical purging in step S4 after the supply of the chlorine-containing silicon source gas in step S2 and before the nitridation process of step S6, a silicon nitride film with the best film quality can be formed.

[0036] However, the hydrogen radical purge in step S4 may be performed at any time between steps S2 and S6. For example, the hydrogen radical purge in step S4 may be performed after the nitridation in step S6 and before the source gas adsorption in the next step S2.

[0037] Furthermore, according to the nitride film forming method described above, the stress of the silicon nitride film formed after performing the processes of steps S2, S4, and S6 a set number of times (one or more times) is tensile stress. When forming a silicon nitride film, film stress is one of the important indicators for evaluating film quality. For example, in the case of a silicon nitride film, it is generally preferable that the film stress is tensile stress. When a silicon nitride film is formed without performing hydrogen radical purging (S4 and S5 in FIG. 3 are omitted), the film stress is generally tensile stress. It is preferable to maintain tensile stress even when modifying the film by hydrogen radical purging.

[0038] In a conventional nitride film formation method, a hydrogen radical purge is performed using capacitively coupled plasma to form a silicon nitride film on a substrate W. In this case, the stress of the silicon nitride film shifts from tensile stress to compressive stress by irradiating the substrate W with high-energy ions. There is a strong correlation between the film stress and the ion energy in plasma irradiation during hydrogen radical purging, and by suppressing the ion energy, the film stress of the silicon nitride film formed on the substrate W can be made tensile even when hydrogen radical purging is performed.

[0039] One possible method for suppressing ion energy is to increase the frequency of the radio frequency power supplied from the radio frequency power supply 30 (increasing the frequency). However, increasing the frequency of the radio frequency voltage poses problems in terms of cost and changes to the hardware specifications of the radio frequency power supply, etc.

[0040] Therefore, in the film formation method of the present disclosure, in step S4 of the hydrogen radical purge, instead of supplying a high-frequency voltage from the high-frequency power supply 30 to the upper electrode 60, the variable DC power supply 80 supplies a DC pulse voltage with a positive overshoot of 100 V or less. By supplying a negative DC pulse voltage instead of a high-frequency voltage, the ion energy during plasma irradiation can be reduced. Furthermore, by controlling the DC pulse voltage using the voltage limiter 88 so that it does not exceed a positive value of 100 V, plasma with low ion energy can be generated. In other words, when a DC pulse voltage with a positive overshoot of 100 V or less is supplied, hydrogen plasma with lower ion energy can be generated than hydrogen plasma generated by supplying a high-frequency voltage from the high-frequency power supply 30. Furthermore, hydrogen plasma with a high radical density capable of modifying a silicon nitride film can be generated, equivalent to that generated when a high-frequency voltage is supplied from the high-frequency power supply 30. This allows the silicon nitride film to be modified while maintaining tensile stress.

[0041] As described above, according to the film deposition method of the present disclosure, hydrogen plasma with low ion energy and high radical density can be generated by supplying a DC pulse voltage, and therefore a silicon nitride film with good film stress of tensile stress can be deposited.

[0042] The mounting table 2 of the plasma processing apparatus 1 is an example of a first electrode on which a substrate is placed in the processing chamber 10, and the upper electrode 60 is an example of a second electrode facing the first electrode. The variable DC power supply 80 and the pulse generator 89 are an example of a power supply system that supplies a DC pulse voltage to the second electrode.

[0043] [Experimental Results] An experiment was conducted on the film characteristics of a silicon nitride film formed by the film forming method according to the present embodiment of Fig. 3 using the plasma processing apparatus 1. The results will be described with reference to Fig. 5 and Fig. 6. Fig. 5 and Fig. 6 are diagrams showing an example of the relationship between hydrogen radical purging and the film quality (refractive index) and film stress of the nitride film.

[0044] 5(a) shows the state of a silicon nitride film when step S4 (hydrogen radical purging) in FIG. 3 is not performed. FIG. 5(b) shows the state of a silicon nitride film when hydrogen radical purging is performed by supplying a high-frequency voltage from the high-frequency power supply 30. FIG. 5(c) shows the state of a silicon nitride film when hydrogen radical purging is performed by supplying a DC pulse voltage from the variable DC power supply 80. FIG. 5(c) shows an evaluation of the film quality and film stress of a silicon nitride film formed by the nitride film forming method according to the present embodiment shown in FIG. 3. FIG. 5(b) is a reference example, showing an evaluation of the film quality and film stress of a silicon nitride film when hydrogen radical purging is performed by supplying a high-frequency voltage from the high-frequency power supply 30.

[0045] The process conditions for the hydrogen radical purge of the reference example shown in FIG. 5(b) and the hydrogen radical purge of this embodiment shown in FIG. 5(c) are as follows.

[0046] <Reference example: Hydrogen radical purge process conditions> Supply voltage: High frequency voltage (frequency 40MHz) Power: 200W Pressure 4 Torr (533 Pa) <Present embodiment: Hydrogen radical purge process conditions> Supply voltage: DC pulse voltage (280V) Power: 200W Pressure 4 Torr

[0047] When the film stress has a negative value, it indicates compressive stress, and when it has a positive value, it indicates tensile stress.

[0048] The silicon nitride film formed on the substrate W without hydrogen radical purging shown in Figure 5(a) has a tensile film stress of 991 MPa. The refractive index (RI), which indicates the film quality, is 1.91. The closer the RI is to a value of 2, the better the film quality.

[0049] The film obtained by hydrogen radical purging in the reference example shown in Figure 5(b) is compared with the film obtained by hydrogen radical purging in this embodiment shown in Figure 5(c). The film obtained by hydrogen radical purging in this embodiment shown in Figure 5(c) has a tensile film stress of 924 MPa, and the film stress does not change significantly even after hydrogen radical purging, maintaining a tensile stress. Furthermore, the refractive index (RI) is 1.94, indicating that hydrogen radical purging improves the film quality.

[0050] These results demonstrate that hydrogen radical purging using a DC pulse voltage can form a high-quality silicon nitride film having a tensile film stress. In other words, it is possible to form a high-quality silicon nitride film having a tensile film stress at low cost without significantly changing the hardware configuration of the plasma processing apparatus.

[0051] In contrast, the film obtained by hydrogen radical purging in the reference example shown in Figure 5(b) has a compressive film stress of -272 MPa, and the direction of the film stress has changed significantly due to the hydrogen radical purging. The refractive index (RI) is 1.95, and the film quality has been improved.

[0052] In addition, in the silicon nitride film obtained by the hydrogen radical purging of the reference example, film peeling, which resembles blisters on the film surface, may occur, called blisters. On the other hand, in the film obtained by the hydrogen radical purging of this embodiment, blisters do not occur. This phenomenon is also thought to be caused by the irradiation of plasma with high ion energy.

[0053] 6 shows experimental results regarding the power dependency of the pressure inside the processing vessel 10 and the DC pulse voltage in the hydrogen radical purging using the DC pulse voltage according to this embodiment. The process conditions for the hydrogen radical purging according to this embodiment shown in FIGS. 6(a) to 6(c) are as follows:

[0054] <Present embodiment: Process conditions for hydrogen radical purge in FIG. 6(a)> Supply voltage: DC pulse voltage (310V) Power: 200W Pressure 1.5 Torr (200 Pa) <Present embodiment: Process conditions for hydrogen radical purge in FIG. 6(b)> Supply voltage: DC pulse voltage (280V) Power: 200W Pressure 4 Torr <Present embodiment: Process conditions for hydrogen radical purge in FIG. 6(c)> Supply voltage: DC pulse voltage (380V) Power: 400W Pressure 4 Torr

[0055] The experimental results showed that when hydrogen radical purging was performed under the process conditions of Figure 6(a), the film had a compressive film stress indicated by "-208 MPa" and a refractive index (RI) of "1.95," indicating that the film quality was improved.

[0056] When hydrogen radical purging was performed under the process conditions of Figure 6(b), the film had a tensile film stress of 924 MPa when the pressure was increased from 1.5 Torr to 4 Torr compared to Figure 6(a).The refractive index (RI) was also 1.93, indicating an improvement in film quality.

[0057] When hydrogen radical purging was performed under the process conditions of Figure 6(c), the film had a tensile film stress of 725 MPa when the power (power of DC pulse voltage) was doubled compared to Figure 6(b).The refractive index (RI) was also 1.94, and the film quality was improved.

[0058] In the case of Figure 6(a), the film stress is compressive stress. However, a comparison of the experimental results shown in Figures 6(a) and 6(b) shows that the film stress can be controlled by changing the pressure at which the hydrogen radical purge is performed. Furthermore, a comparison of the experimental results shown in Figures 6(b) and 6(c) shows that the film stress can be controlled by changing the DC pulse voltage. From the above, it can be seen that in this embodiment, the hydrogen radical purge step can control the stress of the silicon nitride film by adjusting at least one of the pressure in the processing chamber 10 and the power of the DC pulse voltage.

[0059] Furthermore, the results in Figure 6(c) show that tensile stress can be maintained when the DC pulse voltage power is set to 400 W, suggesting that the DC pulse voltage power for the hydrogen radical purge step can be increased beyond 400 W. In this case, it is believed that the film modification efficiency can be further improved while controlling the stress in the silicon nitride film to tensile stress.

[0060] As described above, the nitride film forming method and plasma processing apparatus of this embodiment can modify the silicon nitride film while controlling the film stress of the nitride film.

[0061] The nitride film forming method and plasma processing apparatus according to the presently disclosed embodiments should be considered to be illustrative in all respects and not restrictive. The embodiments can be modified and improved in various ways without departing from the spirit and scope of the appended claims. The features described in the above embodiments can be configured in other ways within a consistent range, and can be combined within a consistent range.

[0062] In the above embodiment, the plasma processing apparatus is described as a single-wafer processing apparatus that processes wafers one by one, but the present disclosure is not limited to this. For example, the plasma processing apparatus may be a multi-wafer deposition apparatus equipped with multiple mounting tables in a single processing chamber. Furthermore, for example, the plasma processing apparatus may be a semi-batch processing apparatus that processes wafers by rotating multiple wafers placed on a turntable in a processing chamber using the turntable, passing the wafers sequentially through an area where a first gas is supplied and an area where a second gas is supplied.

[0063] In addition, there is a plasma processing apparatus in which a wafer boat containing multiple substrates arranged vertically is loaded into a processing chamber and plasma processing is performed thereon, and plasma is supplied into the processing chamber from a plasma box connected to the processing chamber. In this apparatus configuration, the stress of the silicon nitride film does not shift toward compressive stress. This is thought to be due to the remote plasma type apparatus configuration in which the plasma generation region is far from the substrate, so the stress of the silicon nitride film does not shift toward compressive stress. Therefore, the nitride film formation method of this embodiment is suitable for use in a single-wafer deposition apparatus in which the plasma generation region is relatively close to the substrate. This is not limited to a single-wafer deposition apparatus that deposits films one by one, but may also be a multi-wafer deposition apparatus that simultaneously processes multiple substrates arranged horizontally relative to the mounting surface of the mounting table. [Explanation of symbols]

[0064] 1. Plasma processing equipment 2 Mounting table 10 Processing container 60 Upper electrode 80 Variable DC power supply 88 Voltage Limiter 100 control section

Claims

1. (a) providing a substrate; (b) supplying a halogen-containing source gas containing a halogen-containing silicon compound or a halogen-containing germanium compound into a processing vessel; (c) supplying a nitrogen-containing gas into the processing vessel; a cycle including the step (b) and the step (c) is repeated a predetermined number of times to form a nitride film; (d) between the step (b) and the step (c), a step of supplying a hydrogen-containing gas to the processing vessel and generating hydrogen radicals by a DC pulse voltage to modify the nitride film; The nitride film is a silicon nitride film or a germanium nitride film. A method for forming a nitride film.

2. the stress of the nitride film formed by performing the steps (b), (c), and (d) is a tensile stress; The film forming method according to claim 1 .

3. the step (d) controls the stress of the nitride film by adjusting at least one of the pressure in the processing chamber and the power of the DC pulse voltage. The film forming method according to claim 1 or 2.

4. A plasma processing apparatus including a first electrode on which a substrate is placed in a processing chamber, a second electrode facing the first electrode, and a DC power supply supplying a DC voltage to the second electrode, The step (d) controls the DC power supply to supply the DC pulse voltage to the second electrode. The film forming method according to any one of claims 1 to 3.

5. In the step (d), the DC pulse voltage is supplied so that the positive voltage overshoot value is 100 V or less. The film forming method according to claim 4.

6. the plasma processing apparatus has a voltage limiter connected to the DC power supply; In the step (d), the DC pulse voltage is controlled by the voltage limiter so that a voltage overshoot value is 100 V or less, and is supplied to the second electrode. The film forming method according to claim 5 .

7. The step (c) generates plasma of the nitrogen-containing gas by supplying a high-frequency voltage; The step (d) generates hydrogen radicals by supplying a DC pulse voltage. The film forming method according to claim 5 or 6.

8. repeating the steps (b), (d), and (c) in this order a set number of times; The film forming method according to any one of claims 1 to 7.

9. A plasma processing apparatus having a processing vessel, a DC power supply that supplies a DC pulse voltage, a high frequency power supply, and a control unit, The control unit A plasma processing apparatus that controls the steps (a), (b), (c), and (d) of the film forming method according to any one of claims 1 to 8.

10. In step (c), the high-frequency power supply generates plasma of the nitrogen-containing gas by supplying a high-frequency voltage; In step (d), the DC power supply generates hydrogen radicals by supplying a DC pulse voltage. The plasma processing apparatus according to claim 9 .

Images