Substrate processing method, semiconductor device manufacturing method, substrate processing apparatus, and program

Abstract

A semiconductor device manufacturing method according to the present invention comprises: (a) a step for nitriding the inner surface of a concave structure formed on a substrate to modify at least a portion of the inner surface to a nitride layer; and (b) a step for oxidizing the inner surface including the nitride layer to modify the inner surface to an oxide layer, where in (a), the thickness distribution of the nitride layer on the inner surface is set to a distribution such that the thickness distribution of the oxide layer on the inner surface is a desired distribution.

Description

[Technical Field]

[0001] The present disclosure provides: Substrate processing method , Semiconductor device manufacturing method , a substrate processing apparatus, and a program. [Background technology]

[0002] As one step in the manufacturing process of a semiconductor device, a process of forming an oxide layer on the inner surface of a recessed structure formed on a substrate is sometimes performed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 125606 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a technique that allows the thickness of an oxide layer formed on the inner surface of a recessed structure formed on a substrate to have a desired thickness distribution. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; and In (a), a technique is provided for adjusting the thickness distribution of the nitride layer on the inner surface so that the thickness distribution of the oxide layer on the inner surface becomes a desired distribution. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to provide a technique that allows the thickness of an oxide layer formed on the inner surface of a recessed structure formed on a substrate to have a desired thickness distribution. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a substrate processing apparatus 100 suitably used in one embodiment of the present disclosure, showing a processing furnace 202 portion in vertical cross section. [Figure 2] FIG. 2 is an explanatory diagram illustrating the plasma generation principle in the substrate processing apparatus 100 suitably used in one embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic configuration diagram of the controller 221 provided in the substrate processing apparatus 100 suitably used in one embodiment of the present disclosure, and is a block diagram showing the control system of the controller 221. [Figure 4] Fig. 4(a) is a partially enlarged cross-sectional view of wafer 200 having trench 301 formed therein. Fig. 4(b) is a partially enlarged cross-sectional view of wafer 200 after at least a portion of the inner surface of trench 301 has been modified into nitride layer 401. Fig. 4(c) is a partially enlarged cross-sectional view of wafer 200 in the process of modifying the inner surface of trench 301, including nitride layer 401, into oxide layer 402. Fig. 4(d) is a partially enlarged cross-sectional view of wafer 200 after the inner surface of trench 301, including nitride layer 401, has been modified into oxide layer 402. DETAILED DESCRIPTION OF THE INVENTION

[0008] <One aspect of the present disclosure> Hereinafter, one embodiment of the present disclosure will be described mainly with reference to Figures 1 to 3 and 4(a) to 4(d). Note that the drawings used in the following description are all schematic, and the dimensional relationships between elements, the ratios of elements, etc. shown in the drawings do not necessarily match those in reality. Furthermore, the dimensional relationships between elements, the ratios of elements, etc. do not necessarily match between multiple drawings.

[0009] (1) Configuration of the substrate processing equipment 1, the substrate processing apparatus 100 includes a processing furnace 202 that accommodates wafers 200 as substrates and performs plasma processing on them. The processing furnace 202 includes a processing container 203 that forms a processing chamber 201. The processing container 203 includes a dome-shaped upper container 210 that serves as a first container, and a bowl-shaped lower container 211 that serves as a second container. The processing chamber 201 is formed by the upper container 210 covering the lower container 211. The upper container 210 is made of a non-metallic material such as aluminum oxide (Al2O3) or quartz (SiO2), and the lower container 211 is made of aluminum (Al), for example.

[0010] A gate valve 244 serving as a loading / unloading port (gate valve) is provided on a lower sidewall of the lower vessel 211. When the gate valve 244 is opened, the wafer 200 can be loaded into or unloaded from the processing chamber 201 via the loading / unloading port 245. When the gate valve 244 is closed, the inside of the processing chamber 201 can be kept airtight.

[0011] 2, the processing chamber 201 has a plasma generation space 201a and a substrate processing space 201b that communicates with the plasma generation space 201a and processes the wafer 200. The plasma generation space 201a is a space where plasma is generated, and refers to the space within the processing chamber 201 above the lower end of the resonance coil 212 (indicated by the dashed dotted line in FIG. 1). On the other hand, the substrate processing space 201b is a space where the substrate is processed by plasma and refers to the space below the lower end of the resonance coil 212.

[0012] A susceptor 217 serving as a substrate mounting portion for mounting the wafer 200 is disposed at the center of the bottom side of the processing chamber 201. The susceptor 217 is made of a non-metallic material such as aluminum nitride (AlN), ceramics, or quartz.

[0013] A heater 217b serving as a heating mechanism is integrally embedded inside the susceptor 217. By supplying power to the heater 217b via a heater power adjustment mechanism 276, the surface of the wafer 200 can be heated to a predetermined temperature within a range of, for example, 25°C to 1000°C.

[0014] The susceptor 217 is electrically insulated from the lower vessel 211. An impedance adjustment electrode 217c is provided inside the susceptor 217. The impedance adjustment electrode 217c is grounded via an impedance variable mechanism 275 serving as an impedance adjuster. The impedance variable mechanism 275 includes a coil, a variable capacitor, and the like, and is configured to be able to change the impedance of the impedance adjustment electrode 217c within a range from approximately 0 Ω to the parasitic impedance value of the processing chamber 201 by controlling the inductance and resistance of the coil, the capacitance value of the variable capacitor, and the like. This makes it possible to control the potential (bias voltage) of the wafer 200 during plasma processing via the impedance adjustment electrode 217c and the susceptor 217.

[0015] A susceptor lifting mechanism 268 for lifting and lowering the susceptor is provided below the susceptor 217. The susceptor 217 has through holes 217a. Support pins 266 serving as supports for supporting the wafers 200 are provided on the bottom surface of the lower vessel 211. At least three through holes 217a and three support pins 266 are provided in positions facing each other. When the susceptor 217 is lowered by the susceptor lifting mechanism 268, the support pins 266 pass through the through holes 217a without coming into contact with the susceptor 217. This makes it possible to hold the wafers 200 from below.

[0016] A gas supply head 236 is provided above the processing chamber 201, i.e., on top of the upper vessel 210. The gas supply head 236 includes a cap-shaped lid 233, a gas inlet 234, a buffer chamber 237, an opening 238, a shielding plate 240, and a gas outlet 239, and is configured to supply gas into the processing chamber 201. The buffer chamber 237 functions as a dispersion space that disperses the reaction gas introduced from the gas inlet 234.

[0017] The downstream end of gas supply pipe 232a for supplying a nitrogen-containing gas, the downstream end of gas supply pipe 232b for supplying an oxygen-containing gas, and gas supply pipe 232c for supplying an inert gas are connected to gas inlet 234 so that they converge. Gas supply pipe 232a is provided with, from upstream to downstream, a nitrogen-containing gas supply source 250a, a mass flow controller (MFC) 252a as a flow rate control device, and a valve 253a as an on-off valve. Gas supply pipe 232b is provided with, from upstream to downstream, an oxygen-containing gas supply source 250b, an MFC 252b as a flow rate control device, and a valve 253b as an on-off valve. Gas supply pipe 232c is provided with, from upstream to downstream, an inert gas supply source 250c, an MFC 252c as a flow rate control device, and a valve 253c as an on-off valve. A valve 243a is provided downstream of the junction of the gas supply pipe 232a, the gas supply pipe 232b, and the supply pipe 232c, and is connected to the upstream end of the gas inlet 234. By opening and closing the valves 253a to 253c and 243a, the nitrogen-containing gas, the oxygen-containing gas, and the inert gas can be supplied into the processing chamber 201 via the gas supply pipes 232a, 232b, and 232c, respectively, while the flow rates of the respective gases are adjusted by the MFCs 252a to 252c.

[0018] A nitrogen-containing gas supply system is mainly composed of gas supply head 236 (lid 233, gas inlet 234, buffer chamber 237, opening 238, shielding plate 240, gas outlet 239), gas supply pipe 232a, MFC 252a, and valves 253a and 243a. An oxygen-containing gas supply system is mainly composed of gas supply head 236, gas supply pipe 232b, MFC 252b, and valves 253b and 243a. An inert gas supply system is mainly composed of gas supply head 236, gas supply pipe 232c, MFC 252c, and valves 253c and 243a.

[0019] An exhaust port 235 for exhausting the inside of the processing chamber 201 is provided on a sidewall of the lower vessel 211. The upstream end of an exhaust pipe 231 is connected to the exhaust port 235. The exhaust pipe 231 is provided with, in this order from the upstream side, an APC (Auto Pressure Controller) valve 242 serving as a pressure regulator (pressure adjustment unit), a valve 243b, and a vacuum pump 246 serving as a vacuum exhaust device.

[0020] An exhaust unit is mainly composed of the exhaust port 235, the exhaust pipe 231, the APC valve 242, and the valve 243b. A vacuum pump 246 may also be included in the exhaust unit.

[0021] A spiral resonant coil 212 is provided on the outer periphery of the processing chamber 201, i.e., on the outside of the sidewall of the upper vessel 210, so as to surround the processing chamber 201. An RF (Radio Frequency) sensor 272, a high-frequency power supply 273, and a frequency matching box 274 (frequency control unit) are connected to the resonant coil 212. A shielding plate 223 is provided on the outer periphery of the resonant coil 212.

[0022] High frequency power supply 273 is configured to supply high frequency power to resonance coil 212. RF sensor 272 is provided on the output side of high frequency power supply 273. RF sensor 272 is configured to monitor information on forward waves and reflected waves of high frequency power supplied from high frequency power supply 273. Frequency matching device 274 is configured to match the frequency of the high frequency power output from high frequency power supply 273 based on the information on reflected wave power monitored by RF sensor 272 so as to minimize the reflected wave.

[0023] Both ends of resonance coil 212 are electrically grounded. One end of resonance coil 212 is grounded via movable tap 213. The other end of resonance coil 212 is grounded via fixed ground 214. Between these ends of resonance coil 212, movable tap 215 is provided, which allows the position at which power is supplied from high frequency power supply 273 to be set arbitrarily.

[0024] An excitation unit (plasma generating unit) that excites each of the gases supplied from the nitrogen-containing gas supply system and the oxygen-containing gas supply system is mainly configured by the resonant coil 212, the RF sensor 272, and the frequency matching box 274. The excitation unit may also include a high-frequency power supply 273 and a shielding plate 223.

[0025] Below, we will use Figure 2 to provide further details about the operation of the excitation unit and the properties of the generated plasma.

[0026] The resonant coil 212 is configured to function as a high-frequency inductively coupled plasma (ICP) electrode. The resonant coil 212 forms a standing wave of a predetermined wavelength and has its winding diameter, winding pitch, number of turns, and the like set so as to resonate in a full-wavelength mode. The electrical length of the resonant coil 212, i.e., the electrode length between the resonant coil and the ground, is adjusted to be an integer multiple of the wavelength of the high-frequency power supplied from the high-frequency power supply 273. These configurations, the power supplied to the resonant coil 212, and the magnetic field strength generated by the resonant coil 212 are appropriately determined taking into consideration the outer shape of the substrate processing apparatus 100, the processing contents, and the like. As an example, the coil diameter of the resonant coil 212 is 200 to 500 mm, and the number of turns of the coil is 2 to 60.

[0027] High frequency power supply 273 includes a power supply control means and an amplifier. The power supply control means is configured to output a predetermined high frequency signal (control signal) to the amplifier based on output conditions related to power and frequency preset through an operation panel. The amplifier is configured to amplify the control signal received from the power supply control means and output the obtained high frequency power to resonance coil 212 via a transmission line.

[0028] The frequency matching device 274 receives a voltage signal related to the reflected wave power from the RF sensor 272, and performs correction control to increase or decrease the frequency (oscillation frequency) of the high frequency power output by the high frequency power supply 273 so that the reflected wave power is minimized.

[0029] With the above configuration, the induction plasma excited in the plasma generation space 201a is of high quality, with almost no capacitive coupling with the inner wall of the processing chamber 201 or the susceptor 217. In the plasma generation space 201a, plasma with an extremely low electric potential and a doughnut shape in plan view is generated.

[0030] 3, the controller 221 serving as a control unit is configured as a computer including a CPU (Central Processing Unit) 221a, a RAM (Random Access Memory) 221b, a storage device 221c, and an I / O port 221d. The RAM 221b, the storage device 221c, and the I / O port 221d are configured to be able to exchange data with the CPU 221a via an internal bus 221e. The controller 221 may be connected to an input / output device 225 such as a touch panel, a mouse, a keyboard, or an operation terminal. The controller 221 may be connected to a display unit such as a display.

[0031] The storage device 221c is configured with, for example, a flash memory, an HDD (Hard Disk Drive), a CD-ROM, etc. The storage device 221c readably stores a control program for controlling the operation of the substrate processing apparatus 100, a process recipe describing the procedures and conditions for substrate processing, etc. The process recipe is a combination of procedures in the substrate processing step described below that are executed by the controller 221 configured as a computer in the substrate processing apparatus 100 to obtain a predetermined result, and functions as a program. Hereinafter, the process recipe, the control program, etc. are collectively referred to simply as a program. Note that, when the term "program" is used in this specification, it may include only the process recipe, only the control program, or both. The RAM 221b is configured as a memory area (work area) for temporarily storing programs, data, etc. read by the CPU 221a.

[0032] The I / O port 221d is connected to the above-mentioned MFCs 252a to 252c, valves 253a to 253c, 243a, 243b, gate valve 244, APC valve 242, vacuum pump 246, heater 217b, RF sensor 272, high-frequency power supply 273, frequency matching box 274, susceptor lifting mechanism 268, impedance variable mechanism 275, etc.

[0033] The CPU 221a is configured to read and execute a control program from the storage device 221c, and also to read a process recipe from the storage device 221c in response to an input of an operation command from the input / output device 225, etc. As shown in FIG. 1, the CPU 221a is configured to be able to control, in accordance with the contents of the read process recipe, the opening adjustment operation of the APC valve 242, the opening / closing operation of the valve 243b, and the start / stop of the vacuum pump 246 via the I / O port 221d and signal line A, the lifting operation of the susceptor lifting mechanism 268 via signal line B, the adjustment operation (temperature adjustment operation) of the amount of power supplied to the heater 217b based on a temperature sensor by the heater power adjustment mechanism 276 and the impedance value adjustment operation by the impedance variable mechanism 275 via signal line C, the opening / closing operation of the gate valve 244 via signal line D, the operations of the RF sensor 272, the frequency matching box 274, and the high-frequency power supply 273 via signal line E, and the flow rate adjustment operation of various gases by the MFCs 252a to 252c and the opening / closing operations of the valves 253a to 253c and 243a via signal line F.

[0034] The controller 221 is not limited to being configured as a dedicated computer, but may also be configured as a general-purpose computer. For example, the controller 221 according to this embodiment can be configured by preparing an external storage device 226 (e.g., a magnetic tape, a magnetic disk such as a flexible disk or a hard disk, an optical disk such as a CD or a DVD, a magneto-optical disk such as an MO, or a semiconductor memory such as a USB memory or a memory card) storing the above-described program and installing the program into a general-purpose computer using the external storage device 226. The means for supplying the program to the computer is not limited to supplying the program via the external storage device 226. For example, the program may be supplied via a communication means such as the Internet or a dedicated line, without going through the external storage device 226. The storage device 221c and the external storage device 226 are configured as computer-readable recording media. Hereinafter, these will be collectively referred to simply as recording media. In this specification, the term "recording medium" may refer to the storage device 221c alone, the external storage device 226 alone, or both.

[0035] (2) Substrate processing process An example of a substrate processing sequence for processing a wafer 200 as a substrate using the above-described substrate processing apparatus 100 as one step in the manufacturing process of a semiconductor device, specifically, an example of a sequence for forming an oxide layer on the inner surface of a recessed structure formed on the surface of the wafer 200, will be described mainly with reference to Figures 4(a), 4(b), 4(c), and 4(d). In the following description, the operation of each component of the substrate processing apparatus 100 is controlled by a controller 221.

[0036] In the substrate processing sequence of this embodiment, Step a) of nitriding the inner surface of the recessed structure formed on the wafer 200 to modify at least a part of the inner surface into a nitride layer; Step b: oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; The following will be implemented.

[0037] In step a, the thickness distribution of the nitride layer on the inner surface is adjusted so that the thickness distribution of the oxide layer on the inner surface, i.e., the oxide layer formed by performing step b, becomes a desired distribution.

[0038] In this specification, the term "wafer" may refer to the wafer itself or a laminate of the wafer and a predetermined layer or film formed on its surface. In this specification, the term "surface of a wafer" may refer to the surface of the wafer itself or the surface of a predetermined layer or the like formed on the wafer. In this specification, the phrase "forming a predetermined layer on a wafer" may mean forming a predetermined layer directly on the surface of the wafer itself or forming a predetermined layer on a layer or the like formed on the wafer. In this specification, the term "substrate" is also synonymous with the term "wafer".

[0039] (Wafer loading) With the susceptor 217 lowered to a predetermined transfer position, the gate valve 244 is opened, and the wafer 200 to be processed is loaded into the processing chamber 201 by a transfer robot (not shown). The wafer 200 loaded into the processing chamber 201 is supported in a horizontal position on support pins 266 protruding from the surface of the susceptor 217. After the wafer 200 has been loaded into the processing chamber 201, the arm of the transfer robot is retracted from the processing chamber 201, and the gate valve 244 is closed. Thereafter, the susceptor 217 is raised to a predetermined processing position, and the wafer 200 to be processed is transferred from the support pins 266 onto the susceptor 217. The wafer may be loaded while the processing chamber 201 is purged with an inert gas or the like.

[0040] As described above, a concave structure such as a trench or a hole is formed in advance on the surface of the wafer 200 to be processed. In this embodiment, as shown in Fig. 4(a), an example will be described in which a trench 301 is formed in advance as a concave structure on the surface of the wafer 200. In this embodiment, the inner surface of the trench 301 is formed of a Si layer made of simple Si (single crystal Si, polycrystalline Si, or amorphous silicon), for example.

[0041] (pressure and temperature regulation) Next, the processing chamber 201 is evacuated by the vacuum pump 246 to a desired processing pressure. The pressure inside the processing chamber 201 is measured by a pressure sensor, and the APC valve 242 is feedback-controlled based on this measured pressure information. The wafer 200 is also heated by the heater 217b to a desired processing temperature. Once the processing chamber 201 has reached the desired processing pressure and the temperature of the wafer 200 has reached and stabilized at the desired processing temperature, the nitriding process described below is started. The vacuum pump 246 is kept operating until the wafer is completely unloaded, described below.

[0042] Then, the following steps a and b are executed in sequence.

[0043] [Step a: Nitriding] In step a, a nitrogen-containing gas is excited into plasma and supplied to the wafer 200 in the processing chamber 201 .

[0044] Specifically, the valve 253a is opened to allow a nitrogen-containing gas to flow into the gas supply pipe 232a. The nitrogen-containing gas has a flow rate adjusted by the MFC 252a, is supplied into the processing chamber 201 via the buffer chamber 237, and is exhausted from the exhaust port 235. At this time, the nitrogen-containing gas is supplied onto the wafer 200 from above the wafer 200 (nitrogen-containing gas supply). At this time, the valve 243c may be opened to supply an inert gas into the processing chamber 201 via the buffer chamber 237.

[0045] At this time, radio frequency (RF) power is applied to the resonant coil 212 from the radio frequency power supply 273. As a result, induction plasma having a doughnut shape in a plan view is excited at the upper and lower ground points and at a height position corresponding to the electrical midpoint of the resonant coil 212 in the plasma generation space 201a. The excitation of the induction plasma activates the nitrogen-containing gas, generating nitriding species. The nitriding species includes excited N atoms (N * ), and ionized N atoms. Note that * means a radical. The same applies to the following explanation. When a gas containing hydrogen (H) is used as the nitrogen-containing gas, the nitriding species further includes excited NH groups (NH * ), and ions containing N and H. Furthermore, in this case, excited H atoms (H * ) and ionized H atoms may also be generated. These reactive species can be considered as part of the nitriding species.

[0046] The processing conditions in this step are as follows: Treatment temperature: room temperature to 1000°C, preferably 650 to 900°C Treatment pressure: 1 to 100 Pa, preferably 3 to 10 Pa Nitrogen-containing gas supply flow rate: 0.1 to 10 slm, preferably 0.15 to 0.5 slm Nitrogen-containing gas supply time: 10 to 600 seconds, preferably 20 to 50 seconds Inert gas supply flow rate: 0 to 10 slm RF power: 100-5000W, preferably 500-3500W RF frequency: 800kHz~50MHz is exemplified.

[0047] In this specification, when a numerical range such as "650 to 900°C" is expressed, it means that the lower limit and the upper limit are included in the range. Therefore, for example, "650 to 900°C" means "650°C or higher and 900°C or lower." The same applies to other numerical ranges. In this specification, the processing temperature means the temperature of the wafer 200 or the temperature inside the processing chamber 201, and the processing pressure means the pressure inside the processing chamber 201. A gas supply flow rate of 0 slm means that the gas is not supplied. These also apply to the following explanations.

[0048] By supplying a nitrogen-containing gas excited by plasma to the wafer 200 under the above-described processing conditions, nitriding species are supplied to the inner surface of the trench 301. The supplied nitriding species nitrides the inner surface of the trench 301, and at least a portion of the inner surface is modified into a nitride layer 401 (see FIG. 4(b)).

[0049] As one example, the thickness distribution of the nitride layer 401 can be such that it gradually becomes thinner from the opening 301a toward the bottom 301b of the trench 301 (see FIG. 4(b)). As another example, the inner surface of the trench 301 near the opening 301a can be modified into the nitride layer 401, while the inner surface near the bottom 301b can be unmodified into the nitride layer 401 (see FIG. 4(b)). The reason why the thickness distribution of the nitride layer 401 can be such is that the nitriding species supplied to the inner surface of the trench 301 reacts preferentially with and is consumed by the inner surface near the opening 301a, and the amount of the nitriding species supplied gradually decreases from the opening 301a toward the bottom 301b. Another reason is that the nitriding species supplied to the inner surface of trench 301 are deactivated as they move from near opening 301a to bottom 301b, and the amount of nitriding species supplied gradually decreases as they move from opening 301a to bottom 301b.

[0050] The thickness of the nitride layer 401 at the opening 301a of the trench 301 can be, for example, 1 to 3 nm. Regardless of its size (thinness), the thickness of the nitride layer 401 has the effect of controlling (suppressing) the oxidation rate in step b, as will be described later. However, to significantly obtain the effect of controlling (suppressing) the oxidation rate, it is preferable that the thickness of the nitride layer 401 be 1 nm or more. If the thickness is less than 1 nm, the effect in step b may not be sufficiently obtained.

[0051] In this step, the processing pressure is set to a relatively high pressure to ensure that the thickness distribution of the nitride layer 401 is as described above. Specifically, when the processing pressure at which the thickness distribution of the nitride layer 401 formed by performing step a is uniform across the entire inner surface of the trench 301 is defined as a "first pressure," the processing pressure is set to a second pressure higher than the first pressure. By increasing the processing pressure in this manner, the mean free path of the nitride species in the processing chamber 201 can be shortened, thereby reducing the probability that the nitride species will reach the bottom 301b of the trench 301. As a result, it is possible to more reliably achieve a thickness distribution of the nitride layer 401 that gradually becomes thinner from the opening 301a to the bottom 301b of the trench 301.

[0052] After the above-described nitriding process is completed, the valve 253a is closed to stop the supply of nitrogen-containing gas into the process chamber 201, and the supply of RF power to the resonance coil 212 is stopped. Then, the process chamber 201 is evacuated to remove gases remaining in the process chamber 201. At this time, the valve 253c is opened to supply an inert gas into the process chamber 201. The inert gas acts as a purge gas, and thereby the process chamber 201 is purged (purged).

[0053] Examples of the nitrogen-containing gas include nitrogen (N2) gas, ammonia (NH3) gas, diazene (N2H2) gas, hydrazine (N2H4) gas, and hydrogen nitride gas such as N3H8 gas. One or more of these can be used as the nitrogen-containing gas. Also, a mixed gas of a nitrogen-containing gas and a hydrogen-containing gas, such as a mixed gas of N2 gas and hydrogen (H2) gas, can be used as the nitrogen-containing gas.

[0054] When a gas containing hydrogen is used as the nitrogen-containing gas, the nitridation rate of a simple film such as a Si film tends to be higher than the nitridation rate of an oxide film such as a SiO film, compared to when a gas not containing hydrogen is used as the nitrogen-containing gas. Therefore, if a native oxide film with an uneven thickness is formed on the inner surface of trench 301, the influence of the native oxide film may make it difficult to control the thickness distribution of nitride layer 401 formed on the surface of wafer 200. In this case, using a gas not containing H (e.g., N gas) as the nitrogen-containing gas is preferable because it can suppress the influence of the native oxide film and improve the controllability of the thickness distribution of nitride layer 401 formed on the surface of wafer 200.

[0055] As the inert gas, for example, N2 gas or a rare gas such as argon (Ar) gas, helium (He) gas, neon (Ne) gas, or xenon (Xe) gas can be used. One or more of these can be used as the inert gas. This also applies to each step described below.

[0056] [Step b: Oxidation treatment] In step b, an oxygen-containing gas is excited into plasma and supplied to the wafer 200 in the processing chamber 201 .

[0057] Specifically, the valve 253b is opened to allow an oxygen-containing gas to flow into the gas supply pipe 232b. The oxygen-containing gas has a flow rate adjusted by the MFC 252b, is supplied into the processing chamber 201 via the buffer chamber 237, and is exhausted from the exhaust port 235. At this time, the oxygen-containing gas is supplied to the wafers 200 from above the wafers 200 (oxygen-containing gas supply). At this time, the valve 243c may be opened to supply an inert gas into the processing chamber 201 via the buffer chamber 237.

[0058] At this time, RF power is applied to the resonant coil 212 from the high frequency power supply 273. This excites the induction plasma in the same manner as in step a. The excitation of the induction plasma activates the oxygen-containing gas, generating oxidizing species. The oxidizing species include excited O atoms (O * ) and ionized O atoms. When a gas containing H is used as the oxygen-containing gas, the oxidizing species further includes excited OH groups (OH * ), and ions containing O and H. Furthermore, in this case, excited H atoms (H * Reactive species such as ions and ionized H atoms may also be produced. These reactive species can also be considered part of the oxidizing species.

[0059] The processing conditions in this step are as follows: Treatment temperature: room temperature to 1000°C, preferably 650 to 900°C Treatment pressure: 1 to 1000 Pa, preferably 100 to 200 Pa Oxygen-containing gas supply flow rate: 0.1 to 10 slm, preferably 0.2 to 0.5 slm Oxygen-containing gas supply time: 10 to 400 seconds, preferably 20 to 50 seconds Other processing conditions are the same as those used when supplying the nitrogen-containing gas in step a.

[0060] By supplying an oxygen-containing gas excited by plasma to the wafer 200 under the above-described processing conditions, oxidizing species are supplied to the inner surface of the trench 301. The supplied oxidizing species oxidize the inner surface of the trench 301, including the nitride layer 401, and the inner surface is modified to an oxide layer 402 (see FIG. 4(c)).

[0061] At this time, the nitride layer 401 can be modified into an oxide layer 402 over the entire thickness of the nitride layer 401. Preferably, of the inner surface of the trench 301, the nitride layer 401 and a predetermined region (an underlying region into which N is not diffused) that is deeper than the nitride layer 401 in the thickness direction of the nitride layer 401 and has not been modified into the nitride layer 401 can each be modified into an oxide layer 402. That is, the inner surface modified into the nitride layer 401 by performing step a and the inner surface that has not been modified into the nitride layer 401 even by performing step a can each be modified into an oxide layer 402.

[0062] In this case, the thickness distribution of the oxide layer 402 can be such that it gradually becomes thicker from the opening 301a of the trench 301 toward the bottom 301b, and preferably becomes thickest at the bottom 301b (see FIG. 4(d)).

[0063] One reason for this is that the rate (oxidation rate (oxidation speed)) when silicon nitride (SiN) is converted to silicon oxide (SiO) is smaller than the rate (oxidation rate) when silicon (Si) is converted to silicon oxide (SiO). In other words, there is selectivity in the oxidation process, where oxidation of elemental Si proceeds more efficiently than oxidation of SiN.

[0064] Another reason is that the thickness distribution of nitride layer 401 formed in step a is such that it gradually becomes thinner from opening 301a to bottom 301b of trench 301. Also, it is preferable that the inner surface of trench 301 near bottom 301b is not modified into nitride layer 401.

[0065] For these reasons, the oxidation rate at the opening 301a of the trench 301 is smaller than the oxidation rate at the bottom 301b of the trench 301. The oxidation rate on the inner surface of the trench 301 is, for example, smallest at the opening 301a of the trench 301 and gradually increases from the opening 301a toward the bottom 301b.

[0066] As a result, for example, in step b, the thickness distribution of oxide layer 402 can be adjusted to gradually increase from opening 301a to bottom 301b of trench 301, with oxide layer 402 being thickest at bottom 301b of trench 301. That is, in step a, the thickness distribution of nitride layer 401 can be adjusted so that in step b, the thickness distribution of oxide layer 402 gradually increases from opening 301a to bottom 301b of trench 301 and / or so that oxide layer 402 is thickest at bottom 301b of trench 301. In this case, the thickness of oxide layer 402 at bottom 301b of trench 301 can be, for example, 5 to 7 nm.

[0067] Also, for example, it is possible to adjust the thickness distribution of oxide layer 402 formed in step b to be uniform over the entire inner surface of trench 301. That is, in step a, the thickness distribution of nitride layer 401 can be adjusted so that the thickness distribution of oxide layer 402 formed in step b is uniform over the entire inner surface of trench 301.

[0068] After the above-described oxidation process is completed, the valve 253b is closed to stop the supply of the oxygen-containing gas into the processing chamber 201, and the supply of RF power to the resonance coil 212 is stopped.

[0069] Examples of oxygen-containing gases that can be used include oxygen (O2) gas, ozone (O3) gas, O2 gas + hydrogen (H2) gas, water vapor (H2O), hydrogen peroxide (H2O2) gas, etc. One or more of these can be used as the oxygen-containing gas.

[0070] In order to enhance the oxidizing power of the oxygen-containing gas and ensure oxidation of the outermost surface of the trench 301, it is preferable to use a gas containing hydrogen (H) in addition to oxygen (O), for example, O2 gas + H2 gas, as the oxygen-containing gas. In this case, by increasing the ratio of H component to O component contained in the oxygen-containing gas, the selectivity of the oxidation process for simple Si can be increased, that is, the oxidation rate R when modifying SiN to SiO can be reduced. SiN The oxidation rate R when converting Si to SiO Si The ratio (R Si / R SiN This makes it easier to improve the controllability of the thickness distribution of the oxide layer 402 formed by performing step b, for example, to increase the thickness of the oxide layer 402 at the bottom 301b of the trench 301.

[0071] (After purging, atmospheric pressure recovery) After step b is completed, the processing chamber 201 is evacuated to remove gases and other substances remaining in the processing chamber 201. Then, using the same processing procedures and conditions as those for the above-described purge, gaseous substances and other substances remaining in the processing chamber 201 are removed from the processing chamber 201 (after-purging). Thereafter, the atmosphere in the processing chamber 201 is replaced with a purge gas, and the pressure in the processing chamber 201 is returned to normal pressure (return to atmospheric pressure).

[0072] (Wafer removal) Next, the susceptor 217 is lowered to a predetermined transfer position, and the wafer 200 is transferred from the susceptor 217 onto the support pins 266. Thereafter, the gate valve 244 is opened, and the processed wafer 200 is transferred out of the processing chamber 201 using a transfer robot (not shown). This completes the substrate processing process according to this embodiment.

[0073] (3) Effects of this mode According to this aspect, one or more of the following effects can be obtained.

[0074] (a) By performing step a before performing step b and by performing step a to form nitride layer 401 with a predetermined thickness distribution, it is possible to form oxide layer 402 with a desired thickness distribution by performing step b.

[0075] For example, in step a, the inner surface (particularly the sidewall surface) of trench 301 near opening 301a is modified into nitride layer 401, while the inner surface near bottom 301b of trench 301 is not modified into nitride layer 401. This makes it possible to achieve a thickness distribution of oxide layer 402 formed by performing step b such that the thickness near bottom 301b is greater than the thickness near opening 301a. Furthermore, in step a, the inner surface (particularly the sidewall surface) of trench 301 is modified into nitride layer 401 so that the thickness distribution gradually becomes thinner from opening 301a to bottom 301b, while the inner surface near bottom 301b of trench 301 is not modified into nitride layer 401. This makes it possible to make the thickness distribution of the oxide layer 402 formed by performing step b gradually thicker from the opening 301a of the trench 301 toward the bottom 301b, and to make it thickest at the bottom 301b.

[0076] Also, for example, in step a, the entire inner surface of trench 301 (including the sidewall and bottom surfaces) is modified to nitride layer 401, while the thickness of nitride layer 401 is set to a predetermined distribution that gradually becomes thinner from opening 301a toward bottom 301b of trench 301. This makes it possible to make the thickness distribution of oxide layer 402 formed by performing step b uniform over the entire inner surface of trench 301.

[0077] (b) In step a, the nitrogen-containing gas is excited by applying energy such as plasma, heat, or light to generate nitriding species, and these nitriding species are supplied to the wafer 200, thereby enabling efficient formation of the nitride layer 401. Furthermore, by utilizing the fact that the generated nitriding species have a short lifespan, it is possible to improve the controllability of the thickness distribution of the nitride layer 401 formed by performing step a, and in turn improve the controllability of the thickness distribution of the oxide layer 402 formed by performing step b.

[0078] (c) In step b, the oxygen-containing gas is excited by applying energy using plasma, heat, light, etc. to generate oxidizing species, and these oxidizing species are supplied to the wafer 200, thereby enabling the efficient formation of the oxide layer 402.

[0079] (d) In steps a and b, the nitrogen-containing gas and the oxygen-containing gas are excited by plasma, respectively, so that the nitride layer 401 and the oxide layer 402 can be formed under relatively low temperature conditions, thereby reducing the thermal history of the wafer 200.

[0080] (e) In step a, by using a gas that does not contain H as the nitrogen-containing gas, the influence of the native oxide film having an uneven thickness formed on the inner surface of trench 301 can be suppressed, and it becomes possible to improve the controllability of the thickness distribution of nitride layer 401 formed on the inner surface of trench 301, and ultimately the controllability of the thickness distribution of oxide layer 402.

[0081] (f) In step b, by using a gas containing H as the oxygen-containing gas, it is possible to increase the oxidizing power of the oxygen-containing gas and improve the efficiency of the oxidation treatment.

[0082] In this case, by increasing the ratio of H components (the number of H atoms) to O components (the number of O atoms) contained in the oxygen-containing gas, the selectivity of oxidation treatment to Si elemental material (non-nitride) relative to oxidation treatment to SiN (nitride) can be improved (see the above-mentioned R Si / RSiN (This can increase the ratio of H component.) Therefore, for example, if the thickness of nitride layer 401 formed at bottom 301b of trench 301 is small or if nitride layer 401 is formed so that nitride layer 401 is not formed in step a, the thickness of oxide layer 402 formed at bottom 301b can be adjusted to be more selectively increased by increasing the ratio of H component. Similarly, for example, if nitride layer 401 is formed at step a so that it has a thickness distribution that gradually becomes thinner from opening 301a toward bottom 301b, the thickness gradient of oxide layer 402, which becomes thicker from opening 301a toward bottom 301b, can be adjusted to be even greater by increasing the ratio of H component.

[0083] In this way, for trench 301 in which nitride layer 401 is formed in step a so as to have a predetermined thickness distribution, adjusting the ratio of H component in step b makes it possible to further control the thickness distribution of oxide layer 402. In other words, adjusting the ratio of H component makes it possible to improve the controllability of the thickness distribution of oxide layer 402 formed by performing step b.

[0084] (g) In step b, the nitride layer 401 is modified into the oxide layer 402 throughout the entire thickness of the nitride layer 401, thereby making it possible to prevent N from substantially remaining in the oxide layer 402.

[0085] Preferably, in step b, the nitride layer 401 and a predetermined region (the underlying region into which N has not diffused) that is deeper than the nitride layer 401 in the thickness direction of the nitride layer 401 on the inner surface of the trench 301 are each modified into an oxide layer 402, thereby making it possible to more reliably prevent N from remaining in the oxide layer 402.

[0086] (h) The above-mentioned effects can be similarly obtained when a predetermined substance (gaseous substance, liquid substance) is arbitrarily selected from the above-mentioned oxygen-containing gas group, nitrogen-containing gas group, and inert gas group.

[0087] (4) Variations The substrate processing sequence in this embodiment can be modified as shown in the following variations. These variations can be combined as desired. Unless otherwise specified, the processing procedures and processing conditions for each step in each variation can be the same as the processing procedures and processing conditions for each step in the substrate processing sequence described above.

[0088] (Variation 1) In step a, the processing pressure may be set to a relatively low pressure to reduce the amount of nitriding species generated and control the thickness distribution of the nitride layer 401 and, in turn, the thickness distribution of the oxide layer 402. Specifically, the processing pressure is set to a third pressure that is lower than the "first pressure" mentioned in the description of the above embodiment.

[0089] This modification also provides the same effects as those of the above-described embodiment. Furthermore, this modification reduces the amount of nitriding species supplied to the wafer 200, allowing most of the nitriding species to be consumed near the opening 301a of the trench 301 and preventing the nitriding species from reaching the bottom 301b. As a result, it becomes easy to achieve a thickness distribution of the nitride layer 401 that gradually becomes thinner from the opening 301a toward the bottom 301b of the trench 301.

[0090] (Variation 2) In step a, the RF power may be set relatively low to reduce the amount of nitride species generated and control the thickness distribution of nitride layer 401 and, in turn, the thickness distribution of oxide layer 402. Specifically, when the RF power value that makes nitride layer 401 formed by performing step a have a uniform thickness distribution over the entire inner surface of trench 301 is set to a "first power value," the RF power value is set to a second power value that is lower than this first power value.

[0091] This modification also provides the same effects as those of the above-described embodiment. Furthermore, this modification reduces the amount of nitriding species supplied to the wafer 200, allowing most of the nitriding species to be consumed near the opening 301a of the trench 301 and preventing the nitriding species from reaching the bottom 301b. As a result, it becomes easy to achieve a thickness distribution of the nitride layer 401 that gradually becomes thinner from the opening 301a toward the bottom 301b of the trench 301.

[0092] (Variation 3) In step a, the supply time of the nitrogen-containing gas may be relatively short to reduce the amount of nitriding species supplied to the wafer 200, thereby controlling the thickness distribution of the nitride layer 401 and, in turn, the thickness distribution of the oxide layer 402. Specifically, when the supply time for which the nitride layer 401 formed by performing step a has a uniform thickness distribution over the entire inner surface of the trench 301 is defined as a "first supply time," the supply time is set to a second supply time that is shorter than the first supply time.

[0093] This modification also provides the same effects as those of the above-described embodiment. Furthermore, this modification reduces the amount of nitriding species supplied to the wafer 200, allowing most of the nitriding species to be consumed near the opening 301a of the trench 301 and preventing the nitriding species from reaching the bottom 301b. As a result, it becomes easy to achieve a thickness distribution of the nitride layer 401 that gradually becomes thinner from the opening 301a toward the bottom 301b of the trench 301.

[0094] (Variation 4) In step a, ion components such as ionized N atoms may be used as the nitriding species supplied to the wafer 200 to control the thickness distribution of the nitride layer 401, and therefore the thickness distribution of the oxide layer 402. Specifically, the impedance variable mechanism 275 is adjusted to control the potential (bias voltage) of the wafer 200 in step a via the impedance adjustment electrode 217c and the susceptor 217. This adjusts the distribution of nitridation by the ion components of the nitriding species drawn into the trench 301 so that the thickness distribution of the nitride layer 401 becomes a desired distribution.

[0095] This modification also provides the same effects as the above-described embodiment. Furthermore, ion components such as ionized N atoms have a short mean free path, even if the processing pressure is reduced, and therefore tend to react preferentially with the inner surface near the opening 301a of the trench 301. As a result, it becomes easy to achieve a thickness distribution of the nitride layer 401 that gradually becomes thinner from the opening 301a toward the bottom 301b of the trench 301.

[0096] (Variation 5) In step a, the flow rate of the nitrogen-containing gas may be set relatively high to control the thickness distribution of the nitride layer 401, and therefore the thickness distribution of the oxide layer 402. Specifically, when a "first flow rate" is set to a flow rate that makes the thickness distribution of the nitride layer 401 formed by performing step a uniform over the entire inner surface of the trench 301, the flow rate is set to a second flow rate that is higher than the first flow rate. The flow rate of the nitrogen-containing gas is adjusted, for example, by controlling the flow rate of the nitrogen-containing gas supplied into the processing chamber 201.

[0097] This modification also provides the same effects as those of the above-described embodiment. Furthermore, according to this modification, by increasing the flow rate of the nitriding species, the flow rate of the nitriding species near the bottom 301b can be reduced relative to the flow rate of the nitriding species near the opening 301a, thereby enabling preferential nitriding of the inner surface near the opening 301a of the trench 301. As a result, it becomes easy to achieve a thickness distribution of the nitride layer 401 that gradually becomes thinner from the opening 301a of the trench 301 toward the bottom 301b.

[0098] <Other Aspects of the Present Disclosure> Although the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the above embodiments and can be modified in various ways without departing from the spirit and scope of the present disclosure.

[0099] In the above embodiment, an example has been described in which a portion of the inner surface of trench 301 is modified into nitride layer 401 in step a. However, the present disclosure is not limited to this. For example, the entire inner surface of trench 301 may be modified into nitride layer 401. In this case, the same effects as those of the above embodiment can be obtained.

[0100] In the above-described embodiment, an example in which the nitrogen-containing gas and the oxygen-containing gas are excited by plasma has been described, but the present disclosure is not limited thereto. For example, the nitrogen-containing gas and the oxygen-containing gas may be excited by heat or light. In this case, the same effects as those of the above-described embodiment can be obtained. In addition, it is possible to avoid plasma damage to the wafer 200, etc.

[0101] In the above-described embodiment, trench 301 has been described as an example of the recessed structure, but the present disclosure is not limited thereto. For example, a hole may be formed as the recessed structure in the surface of wafer 200. The recessed structure may be formed so that it becomes wider from opening 301a to bottom 301b (so that the distance between opposing inner surfaces gradually increases). The recessed structure may also be formed so that it becomes narrower from opening 301a to bottom 301b (so that the distance between opposing inner surfaces gradually decreases). In these cases, the same effects as those of the above-described embodiment can be obtained.

[0102] Although not described in the above embodiment, the present disclosure can use a wafer 200 in which trenches 301 having an aspect ratio of 10 or more, or 20 or more are formed. According to the present disclosure, even when a wafer 200 having such a high aspect ratio is used, the same effects as those of the above embodiment can be obtained.

[0103] In the above embodiment, an example has been described in which the inner surface of trench 301 is formed of a Si layer made of simple Si, but the present disclosure is not limited to this. For example, the inner surface of trench 301 may be formed of a Si-containing material (Si compound) such as silicon carbide (SiC) or silicon germanium (SiGe). Furthermore, the inner surface of trench 301 may be formed of a metal containing aluminum (Al), titanium (Ti), hafnium (Hf), or zirconium (Zr), or a compound thereof. However, it is preferable that the inner surface of trench 301 be formed of a material other than an oxide or nitride of these metals.

[0104] In the above embodiment, an example in which the nitriding treatment (step a) and the oxidation treatment (step b) are performed consecutively in a single treatment chamber (i.e., treatment chamber 201) has been described, but the present disclosure is not limited to this. For example, after the nitriding treatment (step a) is performed on the substrate, the substrate may be transferred from the treatment chamber in which the nitriding treatment was performed to a transfer chamber that is not open to the atmosphere. The substrate may then be transferred into another treatment chamber, where the oxidation treatment (step b) is performed.

[0105] In the above-described embodiment, for example, an example of substrate processing using a single-wafer substrate processing apparatus that processes one or several substrates at a time has been described. The present disclosure is not limited to the above-described embodiment, and can also be suitably applied to a case where a batch-type substrate processing apparatus that processes multiple substrates at a time is used.

[0106] Even when using these substrate processing apparatuses, each process can be performed using the same processing procedures and conditions as those in the above-mentioned embodiments and variations, and the same effects as those in the above-mentioned embodiments and variations can be obtained. [Explanation of symbols]

[0107] 200 wafers (substrates) 301 Trench (concave structure) 401 nitride layer 402 Oxide layer

Claims

1. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; and In (a), the thickness distribution of the nitride layer on the inner surface is set to be gradually thinner from the opening portion of the recessed structure toward the bottom portion, the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; A substrate processing method, wherein the rate at which the nitride layer is oxidized in (b) is lower than the rate at which the material constituting the inner surface is oxidized in (b).

2. 2. The substrate processing method according to claim 1, wherein in step (a), a nitrogen-containing gas is excited to generate nitriding species, and the nitriding species is supplied to the substrate.

3. 3. The substrate processing method according to claim 2, wherein in step (a), the nitrogen-containing gas is excited by plasma or heat.

4. 4. The substrate processing method according to claim 2, wherein the nitrogen-containing gas is a gas that does not contain hydrogen.

5. 5. The substrate processing method according to claim 1, wherein in (a), the entire inner surface is modified to the nitride layer.

6. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; and In (a), the inner surface near the opening of the recessed structure is modified to the nitride layer, and the inner surface near the bottom of the recessed structure is not modified to the nitride layer; the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; A substrate processing method, wherein the rate at which the nitride layer is oxidized in (b) is lower than the rate at which the material constituting the inner surface is oxidized in (b).

7. 6. The substrate processing method according to claim 1, wherein the material that forms the inner surface that is nitrided in (a) contains silicon.

8. 8. The substrate processing method according to claim 1, wherein in step (b), an oxygen-containing gas is excited to generate oxidizing species, and the oxidizing species are supplied to the substrate.

9. 9. The substrate processing method according to claim 8, wherein in step (b), the oxygen-containing gas is excited by plasma or heat.

10. 10. The substrate processing method according to claim 8, wherein the oxygen-containing gas is a gas containing hydrogen.

11. 11. The substrate processing method according to claim 10, wherein in step (b), the thickness distribution of the oxide layer is controlled by adjusting the ratio of hydrogen to oxygen contained in the oxygen-containing gas.

12. 6. The substrate processing method according to claim 1, wherein in step (b), the nitride layer is modified into the oxide layer over the entire thickness of the nitride layer.

13. In (b), the thickness of the oxide layer is distributed so that it gradually becomes thicker from the opening of the recessed structure toward the bottom, and is thickest at the bottom.

14. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; and In (a), the thickness distribution of the nitride layer is set so that the thickness distribution of the oxide layer formed in (b) gradually increases from the opening of the recessed structure toward the bottom, and is the thickest at the bottom; the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; A substrate processing method, wherein the rate at which the nitride layer is oxidized in (b) is lower than the rate at which the material constituting the inner surface is oxidized in (b).

15. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; and In (a), the thickness distribution of the nitride layer on the inner surface is set to be gradually thinner from the opening portion of the recessed structure toward the bottom portion, the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; A method for manufacturing a semiconductor device, wherein the rate at which the nitride layer is oxidized in (b) is lower than the rate at which the material constituting the inner surface is oxidized in (b).

16. a nitrogen-containing gas supply system for supplying a nitrogen-containing gas to the substrate; an oxygen-containing gas supply system for supplying an oxygen-containing gas to the substrate; an excitation unit that excites the gases supplied from the nitrogen-containing gas supply system and the oxygen-containing gas supply system; a control unit configured to be able to control the nitrogen-containing gas supply system, the oxygen-containing gas supply system, and the excitation unit so that in (a), the thickness distribution of the nitride layer on the inner surface becomes gradually thinner from the opening of the recessed structure toward the bottom, and the nitrogen-containing gas supply system, the oxygen-containing gas supply system, and the excitation unit perform the following processes: (a) supplying nitriding species generated by exciting the nitrogen-containing gas to the substrate having a recessed structure formed on its surface, nitriding the inner surface of the recessed structure, and modifying at least a portion of the inner surface into a nitride layer; and (b) supplying oxidizing species generated by exciting the oxygen-containing gas to the substrate, and oxidizing the inner surface including the nitride layer, and modifying the inner surface into an oxide layer. and The inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof, and the rate at which the nitride layer is oxidized in (b) is lower than the rate at which the material that makes up the inner surface is oxidized in (b).

17. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; (a) a step of distributing the thickness of the nitride layer on the inner surface so that the thickness gradually becomes thinner from the opening of the recessed structure toward the bottom; Including, the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; A program that causes a substrate processing apparatus to execute, by a computer, a procedure in which the rate at which the nitride layer is oxidized in (b) is lower than the rate at which the material that constitutes the inner surface is oxidized in (b).

18. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; and In (a), the inner surface near the opening of the recessed structure is modified to the nitride layer, and the inner surface near the bottom of the recessed structure is not modified to the nitride layer; the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; A method for manufacturing a semiconductor device, wherein the rate at which the nitride layer is oxidized in (b) is lower than the rate at which the material constituting the inner surface is oxidized in (b).

19. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; and In (a), the thickness distribution of the nitride layer is set so that the thickness distribution of the oxide layer formed in (b) gradually increases from the opening of the recessed structure toward the bottom, and is the thickest at the bottom; the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; A method for manufacturing a semiconductor device, wherein the rate at which the nitride layer is oxidized in (b) is lower than the rate at which the material constituting the inner surface is oxidized in (b).

20. a nitrogen-containing gas supply system for supplying a nitrogen-containing gas to the substrate; an oxygen-containing gas supply system for supplying an oxygen-containing gas to the substrate; an excitation unit that excites the gases supplied from the nitrogen-containing gas supply system and the oxygen-containing gas supply system; a control unit configured to be able to control the nitrogen-containing gas supply system, the oxygen-containing gas supply system, and the excitation unit so that in (a), the inner surface near an opening of the recessed structure is modified to the nitride layer, and the inner surface near a bottom of the recessed structure is not modified to the nitride layer; and and the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; The substrate processing apparatus according to claim 1, wherein the rate at which the nitride layer is oxidized in step (b) is lower than the rate at which the material constituting the inner surface is oxidized in step (b).

21. a nitrogen-containing gas supply system for supplying a nitrogen-containing gas to the substrate; an oxygen-containing gas supply system for supplying an oxygen-containing gas to the substrate; an excitation unit that excites the gases supplied from the nitrogen-containing gas supply system and the oxygen-containing gas supply system; a control unit configured to be able to control the nitrogen-containing gas supply system, the oxygen-containing gas supply system, and the excitation unit so as to perform the following processes: (a) supplying nitriding species generated by exciting the nitrogen-containing gas to the substrate having a recessed structure formed on its surface, nitriding an inner surface of the recessed structure, and modifying at least a portion of the inner surface into a nitride layer; and (b) supplying oxidizing species generated by exciting the oxygen-containing gas to the substrate, oxidizing the inner surface including the nitride layer, and modifying the inner surface into an oxide layer, wherein the thickness distribution of the nitride layer in (a) is such that the thickness distribution of the oxide layer formed in (b) gradually increases from the opening of the recessed structure toward a bottom portion, and is thickest at the bottom portion; and the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; The substrate processing apparatus according to claim 1, wherein the rate at which the nitride layer is oxidized in step (b) is lower than the rate at which the material constituting the inner surface is oxidized in step (b).

22. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; (a) is a step of modifying the inner surface of the recessed structure near an opening portion thereof into the nitride layer, and not modifying the inner surface of the recessed structure near a bottom portion thereof into the nitride layer; Including, the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; a step of oxidizing the nitride layer in (b) at a rate lower than a rate at which the material constituting the inner surface is oxidized in (b); A program executed by a computer in a substrate processing apparatus.

23. (a) nitriding an inner surface of a recessed structure formed on a substrate to modify at least a portion of the inner surface into a nitride layer; (b) oxidizing the inner surface including the nitride layer to modify the inner surface into an oxide layer; (a) forming a thickness distribution of the nitride layer such that the thickness distribution of the oxide layer formed in (b) gradually increases from the opening of the recessed structure toward the bottom, and is thickest at the bottom; Including, the inner surface is made of a material that is silicon, aluminum, titanium, or hafnium, or a compound thereof; a step of oxidizing the nitride layer in (b) at a rate lower than a rate at which the material constituting the inner surface is oxidized in (b); A program executed by a computer in a substrate processing apparatus.

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