Film formation method

Abstract

To provide a technology that can improve the quality of silicon nitride film to be deposited.SOLUTION: A deposition method is a deposition method for depositing a silicon nitride film on a substrate, and comprises the steps of (a) supplying a silicon-containing gas into a processing vessel containing the substrate, and (b) supplying a nitrogen-containing gas into the processing vessel containing the substrate after the step of (a). In the deposition method, the internal pressure of the processing vessel in the step (b) is greater than the internal pressure of the processing vessel in the step (a).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a film formation method. [Background technology]

[0002] Patent Document 1 discloses a film formation method for forming a silicon nitride film (SiN film) on a substrate. In this type of film formation method, when a nitriding process is performed using heat, there is an advantage that nitriding of the base layer of the substrate can be suppressed more than when a nitriding process is performed using plasma.

[0003] However, thermal nitriding is weak and the quality of the silicon nitride film tends to be poor. In particular, the leakage current of a silicon nitride film that has been subjected to thermal nitriding is larger than that of a silicon nitride film that has been subjected to plasma nitriding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-153711 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique that can improve the film quality of a silicon nitride film to be formed. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a method for forming a silicon nitride film on a substrate, the method comprising: (a) supplying a silicon-containing gas into a processing vessel containing the substrate; and (b) after the step (a), supplying a nitrogen-containing gas into the processing vessel containing the substrate. before the step (b), a step of exhausting gas from the processing vessel while supplying the inert gas; and setting the internal pressure of the processing vessel in the step (b) to be higher than the internal pressure of the processing vessel in the step (a). death , The step (b) includes a step of increasing the internal pressure of the processing vessel to a target pressure and a step of stabilizing the internal pressure of the processing vessel at the target pressure, wherein in the step of increasing the internal pressure to the target pressure, the inert gas is supplied together with the nitrogen-containing gas, and the flow rate of the inert gas is set to be greater than the flow rate of the inert gas in the step (c).A deposition method is provided. [Effects of the Invention]

[0007] According to one aspect, the quality of the silicon nitride film to be formed can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] Fig. 1(A) is a schematic cross-sectional view showing a substrate on which a silicon nitride film has been formed by a film formation method according to an embodiment, and Fig. 1(B) is a flowchart showing steps of the film formation method according to an embodiment. [Figure 2] 1 is a vertical cross-sectional view schematically showing the configuration of a film formation apparatus for performing a film formation method. [Figure 3] Fig. 3(A) is a graph showing the internal pressure of the processing chamber in each step of the film forming method, and Fig. 3(B) is a graph showing the relationship between the supply time of the nitrogen-containing gas into the processing chamber and the leakage current. [Figure 4] FIG. 10 is an explanatory diagram illustrating a nitrogen-containing gas supply process according to a reference example and a nitrogen-containing gas supply process according to this embodiment, in which the nitrogen-containing gas supply process is evacuated. [Figure 5] Fig. 5(A) is a graph showing the flow rates of the nitrogen-containing gas and the inert gas during the pressure increase step, and Fig. 5(B) is a graph showing the pressure change during the pressure increase step. [Figure 6] 10 is a flowchart showing steps of a film forming method according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] 1(A), a film formation method according to an embodiment of the present disclosure forms a silicon nitride film 120 on the surface of a substrate 100. To this end, as shown in FIG. 1(B), the film formation method includes a purging step (step S1), a silicon-containing gas supplying step (step S2), a purging step (step S3), and a nitrogen-containing gas supplying step (step S4). In addition, in the film formation method, steps S1 to S4 are repeated in order until the silicon nitride film 120 reaches a desired thickness and the end of the film formation process is determined in the determination step of step S5.

[0011] The substrate 100 on which the silicon nitride film 120 is formed may be, for example, a semiconductor wafer used in a memory. The substrate 100 is formed of, for example, polycrystalline silicon. The silicon nitride film 120 is used as an insulating film that insulates the gate of the memory. Of course, the substrate 100 on which the silicon nitride film 120 is formed may also be used in semiconductors other than memories. For example, the silicon nitride film 120 can be used as a stop layer in etching during substrate processing.

[0012] The silicon nitride film 120 formed by the film forming method according to this embodiment is a SiN film. The type of the silicon nitride film 120 is not particularly limited, and may be a SiCN film, a SiBCN film, a SiON film, a SiOCN film, or the like, as will be described later.

[0013] An underlayer 110 is formed in advance on the surface of the substrate 100 on which the silicon nitride film 120 is to be formed. The underlayer 110 may be, for example, a silicon oxide film (SiO2 film). The silicon oxide film may be a natural oxidation film of silicon. On the other hand, an amorphous silicon film (not shown) is formed on top of the silicon nitride film 120 after the film formation.

[0014] In addition, the film formation method employs a film formation apparatus 1 that performs ALD (Atomic Layer Deposition), as shown in Fig. 2. Next, to facilitate understanding of the present disclosure, the configuration of the film formation apparatus 1 that performs the film formation method will be described.

[0015] The film formation apparatus 1 includes a processing vessel 10 that accommodates a plurality of substrates 100, a gas supply unit 30 that supplies gas into the processing vessel 10, a gas exhaust unit 40 that exhausts the gas inside the processing vessel 10, a heater 50 that heats the processing vessel 10, and a controller 80 that controls each component of the apparatus. The film formation apparatus 1 according to this embodiment is a thermal ALD type apparatus that performs a film formation process by heating the substrates 100 with the heater 50 without using plasma.

[0016] The processing vessel 10 is formed in a cylindrical shape with a central axis extending in the vertical direction so that multiple substrates 100 can be arranged vertically. For example, the processing vessel 10 includes a cylindrical inner cylinder 11 having a ceiling and an open bottom, and a cylindrical outer cylinder 12 that covers the outside of the inner cylinder 11, has a ceiling, and is also open at the bottom. The inner cylinder 11 and the outer cylinder 12 are made of a heat-resistant material such as quartz and have a double structure arranged coaxially. Note that the processing vessel 10 is not limited to a double structure, and may be a single-cylinder structure or a multiple structure consisting of three or more cylinders.

[0017] The inner cylinder 11 has a flat ceiling, while the outer cylinder 12 has a dome-shaped ceiling. A housing portion 13 for housing the gas nozzle 31 is formed in the vertical direction at a predetermined circumferential position of the inner cylinder 11. As an example, the housing portion 13 is formed inside a protrusion 14 that protrudes part of the side wall of the inner cylinder 11 radially outward.

[0018] A vertically long opening 15 is formed in the side wall of the inner cylinder 11 on the side opposite to the accommodation section 13. The opening 15 exhausts gas inside the inner cylinder 11 to the space P1 between the inner cylinder 11 and the outer cylinder 12. The vertical length of the opening 15 is preferably the same as the vertical length of the wafer boat 16 or is longer than the vertical length of the wafer boat 16.

[0019] The lower end of the processing vessel 10 is supported by a cylindrical manifold 17 made of, for example, stainless steel. A flange 18 is formed at the upper end of the manifold 17, and the flange 18 supports a flange 12f at the lower end of the outer cylinder 12. A seal member 19 is provided between the flange 12f and the flange 18 to airtightly seal the inside of the outer cylinder 12 and the manifold 17.

[0020] An annular support portion 20 protrudes radially inward from the inner wall of the upper portion of the manifold 17, and the support portion 20 supports the lower end of the inner cylinder 11. A lid body 21 is airtightly attached to the opening at the lower end of the manifold 17 via a seal member 22. That is, the lid body 21 airtightly closes the opening on the lower end side of the manifold 17. The lid body 21 is formed into a flat plate shape from, for example, stainless steel.

[0021] A rotation shaft 24 that rotatably supports the wafer boat 16 via a magnetic fluid seal 23 penetrates the center of the lid 21. The rotation shaft 24 rotates about its central axis based on a rotational driving force from a drive source and a drive transmission unit (not shown), thereby rotating the wafer boat 16 about a vertical axis.

[0022] The lower part of the rotation shaft 24 is supported by an arm 25A of a lifting mechanism 25 configured by a boat elevator or the like. In the film forming apparatus 1, by raising and lowering the arm 25A of the lifting mechanism 25, the lid 21 and the wafer boat 16 are moved up and down together, and the wafer boat 16 can be inserted into and removed from the processing vessel 10.

[0023] A rotating plate 26 is provided at the upper end of the rotating shaft 24, and a wafer boat 16 that holds the substrates 100 is placed on the rotating plate 26 via a heat insulating unit 27. The wafer boat 16 is a substrate holder that holds the substrates 100 at predetermined intervals in the vertical direction. The wafer boat 16 holds each substrate 100 so that it is aligned horizontally.

[0024] The gas supply unit 30 is inserted into the processing vessel 10 via the manifold 17. The gas supply unit 30 introduces gases such as a processing gas, a purge gas, and a cleaning gas into the inner cylinder 11. For example, the gas supply unit 30 includes a gas nozzle 31 that introduces the processing gas and a gas nozzle 33 that introduces the purge gas.

[0025] The gas nozzles 31 and 33 are quartz injector tubes that extend vertically within the inner cylinder 11, bend at their lower ends into an L-shape, and penetrate the manifold 17 from the inside to the outside. The gas nozzle 31 has a plurality of gas holes 32 spaced at predetermined intervals along the vertical direction, and discharges a process gas horizontally through each gas hole 34. Similarly, the gas nozzle 33 has a plurality of gas holes 34 spaced at predetermined intervals along the vertical direction, and discharges a purge gas horizontally through each gas hole 34. The predetermined intervals are set to be the same as the intervals between the substrates 100 supported on the wafer boat 16, for example. The vertical positions of the gas holes 32 are set to be midway between vertically adjacent substrates 100, allowing gas to flow smoothly through the spaces between the substrates 100.

[0026] The gas supply unit 30 supplies a processing gas to a gas nozzle 31 inside the processing vessel 10 while controlling the flow rate outside the processing vessel 10. The gas supply unit 30 also supplies a purge gas to a gas nozzle 33 inside the processing vessel 10 while controlling the flow rate outside the processing vessel 10. When forming a silicon nitride film 120 (see FIG. 1(A)), a silicon-containing gas and a nitrogen-containing gas are used as the processing gas.

[0027] The silicon-containing gas is not particularly limited, but suitable examples include chlorine-containing silane compounds such as dichlorosilane (DCS; SiH2Cl2), monochlorosilane (MCS; SiClH3), trichlorosilane (TCS; SiHCl3), silicon tetrachloride (STC; SiCl4), and hexachlorodisilane (HCD; Si2Cl6). The nitrogen-containing gas may also be selected appropriately depending on the silicon-containing gas. For example, ammonia gas (NH3 gas), hydrazine (NH2H4) gas, or its derivatives, such as monomethylhydrazine (MMH) gas, may be used. Note that the nitrogen-containing gas in this embodiment does not include simple nitrogen molecule (N2) gas. For example, an inert gas such as nitrogen (N2) gas or argon (Ar) gas may be used as the purge gas.

[0028] 1, the gas supply unit 30 is not limited to a configuration in which the silicon-containing gas, the nitrogen-containing gas, and the purge gas are supplied into the processing vessel 10 by two gas nozzles 31 and 33. For example, the gas supply unit 30 may be configured to supply the silicon-containing gas, the nitrogen-containing gas, and the purge gas by one common gas nozzle, or may be configured to supply each gas separately by three or more gas nozzles.

[0029] The gas exhaust unit 40 exhausts gas inside the processing vessel 10 to the outside. The gas supplied by the gas supply unit 30 flows from the opening 15 of the inner cylinder 11 into the space P1 between the inner cylinder 11 and the outer cylinder 12 and is exhausted through the gas outlet 41. The gas outlet 41 is formed on the side wall of the upper part of the manifold 17, above the support unit 20. An exhaust path 42 of the gas exhaust unit 40 is connected to the gas outlet 41. The gas exhaust unit 40 includes, in order from upstream to downstream of the exhaust path 42, a pressure adjustment valve 43 and a vacuum pump 44. The gas exhaust unit 40 sucks gas inside the processing vessel 10 using the vacuum pump 44 and adjusts the flow rate of the exhausted gas using the pressure adjustment valve 43, thereby adjusting the pressure inside the processing vessel 10 (internal pressure).

[0030] A temperature sensor (not shown) is provided inside the processing vessel 10 to detect the temperature inside the processing vessel 10. The temperature sensor may be a thermocouple, a resistance temperature detector, or the like, and transmits the detected temperature to the control unit 80.

[0031] The heater 50 is formed in a cylindrical shape that surrounds the processing vessel 10, and heats the substrate 100 in the processing vessel 10 under the control of the controller 80. The heater 50 may also have a temperature control function that supplies a cooling gas between the processing vessel 10 and the heater 50 in order to cool the substrate 100 in the processing vessel 10.

[0032] The control unit 80 may be a computer having a processor 81, memory 82, an input / output interface (not shown), etc. The processor 81 is a combination of one or more of a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), a circuit made up of a plurality of discrete semiconductors, etc. The memory 82 is an appropriate combination of a volatile memory and a non-volatile memory (for example, a compact disc, a DVD (Digital Versatile Disc), a hard disk, a flash memory, etc.).

[0033] The memory 82 stores a program for operating the film forming apparatus 1 and a recipe for process conditions for substrate processing, etc. The processor 81 reads and executes the program from the memory 82 to control each component of the film forming apparatus 1. The control unit 80 may be configured by a host computer or multiple client computers that communicate with each other via a network.

[0034] 1(B) by controlling each component of the film formation apparatus 1 in the film formation process, thereby forming a silicon nitride film 120 on the substrate 100. That is, the control unit 80 controls the purge step (step S1), the silicon-containing gas supply step (step S2), the purge step (step S3), and the nitrogen-containing gas supply step (step S4) to be performed in this order. Furthermore, the control unit 80 repeats steps S1 to S4 multiple times until it determines in the determination step (step S5) that the film formation process is complete.

[0035] More specifically, in the purge process (step S1), the control unit 80 controls the gas exhaust unit 40 to exhaust gas from the processing vessel 10 accommodating a plurality of substrates 100. Furthermore, the control unit 80 controls the gas supply unit 30 to supply a purge gas into the processing vessel 10 via the gas nozzle 33. As a result, the silicon-containing gas, nitrogen-containing gas, and other reaction products remaining in the processing vessel 10 are exhausted and replaced with the purge gas.

[0036] At this time, the control unit 80 controls the pressure regulating valve 43 to adjust the amount of gas discharged so that the pressure (internal pressure) in the processing vessel 10 becomes the target pressure in the purging process. Furthermore, the control unit 80 controls the heater 50 while monitoring the temperature detected by the temperature sensor, so that the temperature in the processing vessel 10 becomes the target temperature in the purging process.

[0037] After the purging step is performed for a predetermined period of time, the film forming method proceeds to a silicon-containing gas supplying step (step S2). In the silicon-containing gas supplying step, the control unit 80 controls the gas supplying unit 30 to supply a silicon-containing gas into the processing chamber 10 through the gas nozzle 31. As a result, the silicon-containing gas is adsorbed onto the surface of the substrate 100 (underlying layer 110) in the processing chamber 10, forming a silicon adsorption film.

[0038] Furthermore, the control unit 80 according to this embodiment controls the gas supply unit 30, the gas exhaust unit 40, and the heater 50 in the silicon-containing gas supply step so as to achieve the following process conditions. Process gas: silicon-containing gas Temperature inside the processing vessel 10: 550°C or higher and 630°C or lower Pressure inside the processing vessel 10: 3 Torr (≒ 400 Pa) or less (HCD) 8Torr (≒1.07kPa) or less (DCS, TCS, STC) Processing gas flow rate: 100sccm to 3000sccm (HCD) After filling the tank with 200cc to 700cc, open the secondary valve to introduce the gas into the furnace (DCS, TCS, STC).

[0039] After the silicon-containing gas supply process is performed for a predetermined period of time, the film forming method proceeds to a purge process (step S3). In this purge process, the control unit 80 controls the gas supply unit 30 to supply a purge gas into the processing vessel 10 and the gas exhaust unit 40 to exhaust the gas from the processing vessel 10, similar to step S1.

[0040] After the purging step is performed for a predetermined period of time, the film forming method proceeds to a nitrogen-containing gas supplying step (step S4). In the nitrogen-containing gas supplying step, the control unit 80 controls the gas supplying unit 30 to supply a nitrogen-containing gas into the processing chamber 10 through the gas nozzle 31. As a result, the silicon-containing gas adsorbed on the surface of the substrate 100 reacts with the nitrogen-containing gas to form a silicon nitride film 120. As will be described later, in the nitrogen-containing gas supplying step, the control unit 80 also supplies an inert gas (N gas: the same type of gas as the purge gas) through the gas nozzle 33.

[0041] The control unit 80 according to this embodiment controls the gas supply unit 30, the gas exhaust unit 40, and the heater 50 in the nitrogen-containing gas supply step so as to satisfy the following process conditions. Process gas: Nitrogen-containing gas Temperature inside the processing vessel 10: 550°C or higher and 630°C or lower Pressure inside the processing vessel 10: 8 Torr (≒ 1.07 kPa) or more and 100 Torr (≒ 13.3 kPa) or less Processing gas flow rate: 6000sccm or more and 13000sccm or less

[0042] 3A, the film forming method according to this embodiment is configured to change the internal pressure of the processing vessel 10 in the nitrogen-containing gas supply step to a higher pressure than the internal pressure of the processing vessel 10 in the silicon-containing gas supply step. The significance of increasing the pressure of the processing vessel 10 in the nitrogen-containing gas supply step will be described below with reference to FIG. 3B.

[0043] FIG. 3(B) is a graph showing the relationship between the supply time of the nitrogen-containing gas and the leakage current of the silicon nitride film 120, with the horizontal axis representing the supply time and the vertical axis representing the leakage current. The nitrogen-containing gas used in the experiment was ammonia (NH3) gas. In FIG. 3(B), the different colors or shapes of the points indicate different internal pressures. Specifically, the black circles represent 0.75 Torr, the white circles represent 8 Torr, the white triangles represent 12 Torr, the white squares represent 30 Torr, and the white stars represent 50 Torr.

[0044] The silicon nitride film 120 formed as an insulating film can be said to have poor film quality if the leakage current is large because it leaks electrons. Therefore, the film formation method is required to control the film formation so as to reduce the leakage current.

[0045] 3B, when the internal pressure of the processing vessel 10 is 0.75 Torr, the leakage current is large even when the nitrogen-containing gas is supplied for a predetermined period (near time tx) to form the silicon nitride film 120. In contrast, when the internal pressure is 8 Torr, the leakage current is significantly reduced when the nitrogen-containing gas is supplied for a predetermined period. In other words, when the internal pressure of the processing vessel 10 is high, the leakage current of the silicon nitride film 120 can be reduced even if the nitrogen-containing gas is supplied for a short period.

[0046] That is, if the internal pressure of the processing vessel 10 is high during the stage of supplying the nitrogen-containing gas, the concentration of nitrogen penetrating into the silicon adsorption film adsorbed on the surface of the substrate 100 increases (becomes nitrogen-rich). Therefore, it can be inferred that the nitridation of the silicon-containing gas is further promoted (intensified) on the surface of the substrate 100, and the film quality of the silicon nitride film 120 improves.

[0047] From this, it can be said that by setting the internal pressure in the nitrogen-containing gas supplying step higher than the internal pressure in the silicon-containing gas supplying step, it is possible to improve the film quality of the silicon nitride film 120. In particular, referring to the graph of Figure 3(B), it can be said that it is preferable to set the internal pressure in the nitrogen-containing gas supplying step to 8 Torr or more.

[0048] Furthermore, Figure 3(B) shows that the leakage current is low even when the internal pressure is 30 Torr or 50 Torr. Therefore, the upper limit of the internal pressure in the nitrogen-containing gas supply process can be set to the withstand pressure limit of the processing vessel 10 (e.g., 100 Torr). However, as can be seen from the decreasing trend of the leakage current when the internal pressure is 12 Torr, the rate of decrease in leakage current decreases as the pressure increases. Therefore, it is more preferable that the internal pressure in the nitrogen-containing gas supply process be in the range of 8 Torr to 30 Torr. For example, as can be seen from the graph, there is not much difference in the leakage current at an internal pressure of 50 Torr and at an internal pressure of 30 Torr.

[0049] Furthermore, the ratio of the internal pressure in the nitrogen-containing gas supply process to the internal pressure in the silicon-containing gas supply process is preferably in the range of 8 to 40 times. This makes it possible to stably improve the film quality of the silicon nitride film 120 in the nitrogen-containing gas supply process while realizing efficient film formation. If the internal pressure ratio is less than 8 times, it may take time for the nitridation of the silicon nitride film 120 to proceed. On the other hand, if the internal pressure ratio is greater than 40 times, it may take time for the internal pressure to reach the target pressure, which may ultimately result in processing delays.

[0050] 3(A), in the film forming apparatus 1, the internal pressure of the processing vessel 10 is slightly reduced during the purging process (step S3) after the silicon-containing gas supplying process (step S2). This is to sufficiently discharge the silicon-containing gas remaining in the processing vessel 10.

[0051] As shown in FIG. 4, in the nitrogen-containing gas supplying step, the control unit 80 performs control to shorten the period from the internal pressure in this purge step until the target pressure in the nitrogen-containing gas supplying step is reached.

[0052] Specifically, the control unit 80 performs a pressure increase step, a constant pressure step, and a pressure decrease step in order to adjust the internal pressure of the processing vessel 10 to the target pressure in the silicon-containing gas supply process. For example, in the pressure increase step (upper diagram in FIG. 4) according to the reference example, a nitrogen-containing gas is supplied at the same flow rate as the silicon-containing gas in the silicon-containing gas supply process. In this case, during the pressure increase step period TM', it takes a significantly long time to reach the target pressure.

[0053] In contrast, in the pressure increasing step (lower diagram in FIG. 4) according to this embodiment, a gas is supplied at a flow rate greater than the flow rate of the silicon-containing gas in the silicon-containing gas supplying step. This shortens the period TM of the pressure increasing step, thereby shortening the overall processing time for steps S1 to S4. In particular, in the film forming process, steps S1 to S4 are repeated multiple times, so the overall processing time for the film forming process can be significantly shortened.

[0054] 5A, the control unit 80 simultaneously supplies both a nitrogen-containing gas (NH gas) and an inert gas (N gas) in the pressure increasing step of the nitrogen-containing gas supply process. That is, the film forming apparatus 1 supplies the nitrogen-containing gas through the gas nozzle 31 and also supplies the inert gas through the gas nozzle 33. In this pressure increasing step, the film forming apparatus 1 may continuously supply the inert gas from the purge process, while setting the flow rate of the inert gas to be greater than the flow rate of the purge gas (inert gas) in the purge process.

[0055] In particular, in this embodiment, the control unit 80 adjusts the flow rates of the nitrogen-containing gas and the inert gas to be substantially the same and supplies them to the processing chamber 10. For example, the nitrogen-containing gas is adjusted to a flow rate of 6000 sccm, and the inert gas is adjusted to a flow rate of 6500 sccm.

[0056] Here, the control unit 80 is configured to supply the nitrogen-containing gas at 6000 sccm and the inert gas at 500 sccm during the constant pressure step of the nitrogen-containing gas supply process. In this case, the concentration of the nitrogen-containing gas is 92%. Therefore, as a reference example, it is also possible to supply the nitrogen-containing gas at similar flow rates (nitrogen-containing gas: 6000 sccm, inert gas: 500 sccm) during the pressure increase step. However, if the gases are supplied at the same flow rates as in the constant pressure step, the pressure increase step takes time, as shown in FIG. 5(B), and the start time t1′ of the constant pressure step is delayed.

[0057] 5A and 5B, the control unit 80 according to this embodiment sets the flow rate of the inert gas to 6500 sccm. This allows the total flow rate of the nitrogen-containing gas and the inert gas in the pressure-increasing step to be at least twice the total flow rate of the nitrogen-containing gas and the inert gas in the constant-pressure step, which allows the internal pressure of the processing vessel 10 to reach the target pressure quickly. As a result, the internal pressure of the processing vessel 10 increases to the target pressure in a short time, and the start time t1 of the constant-pressure step is advanced.

[0058] Furthermore, in the constant pressure step, the flow rate of the inert gas, which was set to 6500 sccm in the pressure increase step, is switched to 500 sccm. The flow rate of the inert gas is maintained at 6000 sccm. As a result, in the constant pressure step after the internal pressure has stabilized at the target pressure, the concentration of the nitrogen-containing gas is increased to 92%, which promotes the reaction between the silicon adsorption film and the nitrogen-containing gas. Even when the concentration of the nitrogen-containing gas is diluted and the supply rate is increased in the pressure increase step, increasing the concentration of the nitrogen-containing gas in the constant pressure step did not cause a deterioration in the film quality (increase in leakage current) of the silicon nitride film 120 after film formation.

[0059] To summarize the above-described control of the nitrogen-containing gas and the inert gas, the control unit 80 controls the flow rate of the nitrogen-containing gas in the pressure-increasing step to be equal to or less than the flow rate of the inert gas, and controls the flow rate of the nitrogen-containing gas in the constant-pressure step to be greater than the flow rate of the inert gas. This allows the film forming apparatus 1 to increase the internal pressure in the nitrogen-containing gas supply step and shorten the period of the nitrogen-containing gas supply step (pressure-increasing step). As a result, the film forming apparatus 1 can improve the film quality of the silicon nitride film 120 while increasing the efficiency of the film forming process.

[0060] The film formation method according to the present disclosure is not limited to the above-described embodiment, and various modifications are possible. For example, the film formation apparatus 1 is not limited to an apparatus that processes a plurality of substrates 100 arranged simultaneously, but may be a single-wafer type apparatus that processes the substrates 100 one by one. Furthermore, for example, the film formation apparatus 1 is not limited to a vertical processing apparatus that arranges a plurality of substrates 100 vertically, but may be a horizontal processing apparatus that arranges a plurality of substrates 100 horizontally. In short, the film formation apparatus 1 may be any of various apparatuses as long as it can implement the above-described film formation method.

[0061] Furthermore, in the pressure increasing step in the nitrogen-containing gas supply process, the control unit 80 may control the gas exhaust unit 40 to perform a gas exhaust restriction operation to reduce the amount of gas exhausted (or temporarily stop the gas exhaust). This allows the internal pressure of the processing vessel 10 to increase in a short period of time. The control unit 80 may perform the gas exhaust restriction operation while increasing the supply amount of inert gas in the pressure increasing step compared to the supply amount in the constant pressure step, or may perform the gas exhaust restriction operation while keeping the supply amount in the pressure increasing step the same as the supply amount in the constant pressure step.

[0062] In the film formation method, the processing time may be shortened by performing a pressure reduction step, which is performed when the nitrogen-containing gas supply step is completed, to rapidly reduce the internal pressure of the processing vessel 10. For example, in the pressure reduction step, the control unit 80 may stop the gas supply from the gas supply unit 30 while increasing the rotation speed of the vacuum pump 44 of the gas exhaust unit 40 to be higher than that during the silicon-containing gas supply step, thereby reducing the internal pressure of the processing vessel 10.

[0063] The film formation method according to the present disclosure is not limited to a configuration in which a SiN film is formed as the silicon nitride film 120 on the substrate 100, and may be a configuration in which a silicon nitride film 120 containing other atoms is formed. For example, the film formation method may perform the same process as described above when forming a SiCN film, a SiBN film, a SiBCN film, a SiON film, a SiOCN film, or the like as the silicon nitride film 120. Hereinafter, an example of a film formation method for forming a SiCN film (nitrogen-added silicon carbide film) will be described with reference to FIG. 6.

[0064] In the SiCN film forming method, a purge step (step S11), a silicon-containing gas supply step (step S12), a purge step (step S13), a carbon-containing gas supply step (step S14), a purge step (step S15), and a nitrogen-containing gas supply step (step S16) are performed in this order. Also in the SiCN film forming method, the internal pressure of the processing chamber 10 in the nitrogen-containing gas supply step is set higher than the internal pressure of the processing chamber 10 in the silicon-containing gas supply step.

[0065] In the carbon-containing gas supplying step (step S14), the film forming apparatus 1 supplies a carbon-containing gas, such as ethylene gas (C2H4 gas), into the processing chamber 10 via the gas nozzle 31 of the gas supply unit 30. At this time, the control unit 80 may control the internal pressure of the processing chamber 10 to be equal to or lower than the internal pressure of the processing chamber 10 in the nitrogen-containing gas supplying step. The silicon-containing gas supplying step (step S12), the nitrogen-containing gas supplying step (step S16), and the purging step (steps S11, S13, and S15) may be performed under the same process conditions as those of the SiN film formation method described above. Furthermore, when forming a SiBN film, a SiBCN film, a SiON film, or a SiOCN film, a process of supplying a processing gas containing one or more of a carbon-containing gas, a boron-containing gas, and an oxygen-containing gas in combination may be appropriately performed instead of the carbon gas supplying step.

[0066] In the above-described film formation method, the nitrogen-containing gas supplied in the nitrogen-containing gas supply step (step S16) nitrides silicon carbide formed on the substrate 100, thereby forming a SiCN film. Furthermore, the film formation method according to this embodiment makes it possible to create a nitrogen-rich state on the substrate 100 by increasing the internal pressure in the nitrogen-containing gas supply step. As a result, the quality of the SiCN film is improved.

[0067] Here, compared to SiN films, SiCN films have the advantages of higher etching resistance and a lower k value (dielectric constant), but their range of use has been limited due to their large leakage current. By adopting the film formation method according to this embodiment, it is possible to improve the film quality of the SiCN film and reduce the leakage current. For example, by using the film formation method, the leakage current of the SiCN film can be reduced to the same level as that of the SiN film, allowing the SiCN film to be used in a wider range of applications.

[0068] The technical ideas and effects of the present disclosure explained in the above embodiments will be described below.

[0069] One aspect of the present disclosure is a film formation method for forming a silicon nitride film 120 on a substrate 100, comprising: (a: silicon-containing gas supply step) a step of supplying a silicon-containing gas into a processing vessel 10 containing the substrate 100; and (b: nitrogen-containing gas supply step) a step of supplying a nitrogen-containing gas into the processing vessel 10 containing the substrate 100 after step (a), wherein the internal pressure of the processing vessel 10 in step (b) is made higher than the internal pressure of the processing vessel 10 in step (a).

[0070] As described above, the film formation method can improve the quality of the silicon nitride film 120 formed by increasing the internal pressure of the processing vessel 10 in the step (b: nitrogen-containing gas supply step) compared to the internal pressure of the processing vessel 10 in the step (a: silicon-containing gas supply step). That is, the film formation method promotes nitridation by increasing the internal pressure of the processing vessel 10 when supplying a nitrogen-containing gas to nitride the silicon adsorption film. This improves the efficiency of the film formation process, and the formed silicon nitride film 120 can significantly reduce leakage current. Therefore, the silicon nitride film 120 can be used effectively as an insulating film with high insulating performance, for example.

[0071] The process (b: nitrogen-containing gas supply process) includes a step of increasing the internal pressure of the processing vessel 10 to a target pressure (pressure increase step) and a step of stabilizing the internal pressure of the processing vessel 10 at the target pressure (constant pressure step), and in the step of increasing the pressure to the target pressure, an inert gas is supplied together with the nitrogen-containing gas. This allows the film formation method to shorten the time required for the step of increasing the pressure to the target pressure.

[0072] Furthermore, the total flow rate of the nitrogen-containing gas and the inert gas in the step of increasing the pressure to the target pressure (pressure increase step) is at least twice the total flow rate of the nitrogen-containing gas and the inert gas in the step of stabilizing the pressure at the target pressure, thereby enabling the film forming method to further shorten the time required for the step of increasing the pressure to the target pressure.

[0073] Furthermore, the flow rate of the nitrogen-containing gas in the step of increasing the pressure to the target pressure (pressure increase step) is equal to or less than the flow rate of the inert gas, and the flow rate of the nitrogen-containing gas in the step of stabilizing the pressure at the target pressure (constant pressure step) is greater than the flow rate of the inert gas. This makes it possible for the film formation method to shorten the time required for the step of increasing the pressure to the target pressure and to increase the concentration of the nitrogen-containing gas in the step of stabilizing the pressure at the target pressure. Therefore, the film formation method can effectively improve the film quality of the silicon nitride film 120 while improving the processing efficiency.

[0074] Furthermore, in the step of increasing the pressure to the target pressure, the flow rate of the gas discharged from the processing vessel 10 is set to be less than the flow rate of the gas discharged from the processing vessel 10 in the step of stabilizing the pressure at the target pressure, or the gas discharge is stopped. This allows the film forming method to increase the internal pressure of the processing vessel in a shorter time in the step (b: nitrogen-containing gas supply step).

[0075] Furthermore, before the steps (c: purging step) and (b: nitrogen-containing gas supply step), a step of exhausting gas from the processing vessel while supplying an inert gas is included, and in the step of increasing the pressure to a target pressure (pressure increase step), the flow rate of the inert gas is set to be greater than the flow rate of the inert gas in step (c). This allows the film forming method to smoothly increase the flow rate of the inert gas being supplied to the processing vessel 10.

[0076] Furthermore, the internal pressure of the processing chamber 10 in the step (b: nitrogen-containing gas supply step) is 8 Torr or more and 30 Torr or less, so that the film forming method can more reliably improve the film quality of the silicon nitride film 120 to be formed.

[0077] Furthermore, before the steps (d: carbon-containing gas supply step) and (b: nitrogen-containing gas supply step), a step of supplying a process gas that is a combination of one or more of a carbon-containing gas, a boron-containing gas, and an oxygen-containing gas is included. This allows the film formation method to improve the film quality of the silicon nitride film 120 to be formed, even when forming a SiCN film, a SiBN film, a SiBCN film, a SiON film, or a SiOCN film.

[0078] The film forming methods according to the embodiments disclosed herein are illustrative in all respects and are not limiting. 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 as long as they are not inconsistent, and can be combined as long as they are not inconsistent. [Explanation of symbols]

[0079] 10 Processing container 100 boards 120 Silicon nitride film

Claims

1. A method for forming a silicon nitride film on a substrate, comprising: (a) supplying a silicon-containing gas into a processing vessel containing the substrate; (b) after the step (a), supplying a nitrogen-containing gas into the processing vessel containing the substrate; (c) before the step (b), a step of exhausting gas from the processing vessel while supplying an inert gas, The internal pressure of the processing vessel in the step (b) is set to be higher than the internal pressure of the processing vessel in the step (a); The step (b) includes a step of increasing the internal pressure of the processing vessel to a target pressure; and a step of stabilizing the internal pressure of the processing vessel at the target pressure, In the step of increasing the pressure to the target pressure, the inert gas is supplied together with the nitrogen-containing gas, and the flow rate of the inert gas is set to be greater than the flow rate of the inert gas in the step (c). Film formation method.

2. a total flow rate of the nitrogen-containing gas and the inert gas in the step of increasing the pressure to the target pressure is at least twice as large as a total flow rate of the nitrogen-containing gas and the inert gas in the step of stabilizing the pressure at the target pressure; The film forming method according to claim 1 .

3. a flow rate of the nitrogen-containing gas in the step of increasing the pressure to the target pressure is equal to or less than a flow rate of the inert gas; a flow rate of the nitrogen-containing gas in the step of stabilizing the pressure at the target pressure being greater than a flow rate of the inert gas; The film forming method according to claim 1 .

4. In the step of increasing the pressure to the target pressure, a flow rate of the gas discharged from the processing vessel is made smaller than a flow rate of the gas discharged from the processing vessel in the step of stabilizing the pressure at the target pressure, or the discharge of the gas is stopped. The film forming method according to claim 1 .

5. The internal pressure of the processing vessel in the step (b) is 8 Torr or more and 30 Torr or less. The film forming method according to claim 1 .

6. (d) before the step (b), a step of supplying a process gas comprising a combination of one or more of a carbon-containing gas, a boron-containing gas, and an oxygen-containing gas; The film forming method according to claim 1 .

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