Silicon nitride film forming method and film forming apparatus

Abstract

To provide a technique capable of embedding a high-quality silicon nitride film in a recess.SOLUTION: A silicon nitride film forming method according to one aspect of the present disclosure is a method for forming a silicon nitride film in a recess formed on a surface of a substrate includes the steps of: exposing the substrate to plasma generated from adsorption-inhibiting gas containing halogen gas and non-halogen gas to form an adsorption-inhibiting region; adsorbing silicon-containing gas to a region excluding the adsorption-inhibition region; and exposing the substrate to which the silicon-containing gas has been adsorbed to plasma generated from nitrogen-containing gas to form a silicon nitride film.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In semiconductor manufacturing processes, as structures become finer, there is a demand for filling recesses with a film without leaving voids (gaps) in recesses with high aspect ratios. As one example of a process for filling a recess with a film, a technique is known in which a film is filled from the bottom up by alternately repeating deposition and etching (see, for example, Patent Document 1). As another example of a process for filling a recess with a film, a technique is known in which an adsorption inhibitor gas is adsorbed near the opening of the recess to suppress deposition of the film near the opening, thereby filling the recess with a film from the bottom up (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-112668 A [Patent Document 2] JP 2018-137369 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can fill a recess with a high-quality silicon nitride film. [Means for solving the problem]

[0005] A method for forming a silicon nitride film according to one aspect of the present disclosure is a method for forming a silicon nitride film in a recess formed on a surface of a substrate, the method comprising exposing the substrate to plasma generated from an adsorption inhibitor gas containing a halogen gas and a non-halogen gas. adsorbing active species generated from the halogen gas and the non-halogen gas;The method includes the steps of forming an adsorption inhibition region, adsorbing a silicon-containing gas to a region other than the adsorption inhibition region, and exposing the substrate on which the silicon-containing gas has been adsorbed to plasma generated from a nitrogen-containing gas to form a silicon nitride film. Effect of the Invention

[0006] According to the present disclosure, a high-quality silicon nitride film can be embedded in the recess. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a film forming apparatus according to an embodiment. [Diagram 2] 1 is a flowchart showing an example of a method for forming a silicon nitride film according to an embodiment of the present invention. [Diagram 3] 1 is a flowchart showing another example of a method for forming a silicon nitride film according to an embodiment of the present invention. [Figure 4] 1 is a flowchart showing yet another example of a method for forming a silicon nitride film according to an embodiment. [Diagram 5] 1 is a flowchart showing yet another example of a method for forming a silicon nitride film according to an embodiment. [Figure 6] 1 is a flowchart showing yet another example of a method for forming a silicon nitride film according to an embodiment. [Figure 7] FIG. 1 shows the results of evaluation of the embedding characteristics of a silicon nitride film in a trench. [Figure 8] Figure showing the evaluation results of WER of silicon nitride film buried in trenches DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all of the accompanying drawings, the same or corresponding members or parts are designated by the same or corresponding reference numerals, and duplicated descriptions will be omitted.

[0009] [Film forming equipment] An example of a film forming apparatus according to an embodiment will be described with reference to Fig. 1. The film forming apparatus includes a processing vessel 1, a mounting table 2, a shower head 3, an exhaust unit 4, a gas supply unit 5, an RF power supply unit 8, a control unit 9, and the like.

[0010] The processing vessel 1 is made of a metal such as aluminum and has a substantially cylindrical shape. The processing vessel 1 accommodates a wafer W, which is an example of a substrate. A loading / unloading port 11 is formed in a side wall of the processing vessel 1 for loading or unloading the wafer W. The loading / unloading port 11 is opened and closed by a gate valve 12. An annular exhaust duct 13 having a rectangular cross section is provided on the main body of the processing vessel 1. A slit 13a is formed along the inner peripheral surface of the exhaust duct 13. An exhaust port 13b is formed in the outer wall of the exhaust duct 13. A ceiling wall 14 is provided on the upper surface of the exhaust duct 13 so as to close the upper opening of the processing vessel 1 via an insulating member 16. A seal ring 15 is used to hermetically seal the space between the exhaust duct 13 and the insulating member 16. The partition member 17 partitions the inside of the processing vessel 1 into upper and lower sections when the mounting table 2 (and the cover member 22) is raised to a processing position described later.

[0011] The mounting table 2 horizontally supports the wafer W in the processing chamber 1. The mounting table 2 is formed in a disk shape having a size corresponding to the wafer W, and is supported by a support member 23. The mounting table 2 is made of a ceramic material such as AlN or a metal material such as an aluminum or nickel alloy, and has a heater 21 embedded therein for heating the wafer W. The heater 21 generates heat when power is supplied from a heater power source (not shown). The wafer W is controlled to a predetermined temperature by controlling the output of the heater 21 using a temperature signal from a thermocouple (not shown) provided near the upper surface of the mounting table 2. The mounting table 2 is provided with a cover member 22 made of ceramic such as alumina so as to cover the outer peripheral region of the upper surface and the side surfaces.

[0012] A support member 23 for supporting the mounting table 2 is provided on the bottom surface of the mounting table 2. The support member 23 extends from the center of the bottom surface of the mounting table 2 through a hole formed in the bottom wall of the processing vessel 1 to below the processing vessel 1, and its lower end is connected to a lifting mechanism 24. The lifting mechanism 24 raises and lowers the mounting table 2 via the support member 23 between a processing position shown in FIG. 1 and a transfer position shown by a two-dot chain line below the processing position where the wafer W can be transferred. A flange 25 is attached to the support member 23 below the processing vessel 1. A bellows 26 is provided between the bottom surface of the processing vessel 1 and the flange 25. The bellows 26 separates the atmosphere inside the processing vessel 1 from the outside air, and expands and contracts with the lifting and lowering operation of the mounting table 2.

[0013] Three wafer support pins 27 (only two shown) are provided near the bottom surface of the processing vessel 1 so as to protrude upward from a lift plate 27a. The wafer support pins 27 are raised and lowered via the lift plate 27a by a lift mechanism 28 provided below the processing vessel 1. The wafer support pins 27 are inserted into through holes 2a provided in the mounting table 2 at the transfer position, and can be protruded and retracted from the upper surface of the mounting table 2. The wafer W is transferred between the transfer mechanism (not shown) and the mounting table 2 by raising and lowering the wafer support pins 27.

[0014] The shower head 3 supplies a processing gas into the processing vessel 1 in a shower-like manner. The shower head 3 is made of metal, is provided to face the mounting table 2, and has approximately the same diameter as the mounting table 2. The shower head 3 has a main body 31 and a shower plate 32. The main body 31 is fixed to the ceiling wall 14 of the processing vessel 1. The shower plate 32 is connected below the main body 31. A gas diffusion space 33 is formed between the main body 31 and the shower plate 32. A gas introduction hole 36 is provided in the gas diffusion space 33 so as to penetrate the center of the ceiling wall 14 and the main body 31 of the processing vessel 1. An annular protrusion 34 protruding downward is formed on the periphery of the shower plate 32. A gas discharge hole 35 is formed on the inner flat portion of the annular protrusion 34. When the mounting table 2 is in the processing position, a processing space 38 is formed between the mounting table 2 and the shower plate 32, and the upper surface of the cover member 22 and the annular protrusion 34 are close to each other to form an annular gap 39.

[0015] The exhaust unit 4 exhausts the inside of the processing vessel 1. The exhaust unit 4 has an exhaust pipe 41 connected to the exhaust port 13b, and an exhaust mechanism 42 having a vacuum pump, a pressure control valve, etc. connected to the exhaust pipe 41. During processing, gas inside the processing vessel 1 reaches the exhaust duct 13 through the slit 13a, and is exhausted by the exhaust mechanism 42 from the exhaust duct 13 through the exhaust pipe 41.

[0016] The gas supply unit 5 supplies various process gases to the shower head 3. The gas supply unit 5 includes a gas source 51 and a gas line 52. The gas source 51 includes, for example, various process gas supply sources, a mass flow controller, and a valve (none of which are shown). The various process gases include an adsorption inhibitor gas, a silicon-containing gas, a nitrogen-containing gas, a modifying gas, and a purge gas used in a method for forming a silicon nitride film in an embodiment described below. The various gases are introduced from the gas source 51 through the gas line 52 and the gas introduction hole 36 into the gas diffusion space 33.

[0017] The adsorption inhibitory gas includes halogen gas and non-halogen gas. Examples of halogen gas include fluorine gas (F2), chlorine gas (Cl2), and hydrogen fluoride gas (HF). Examples of non-halogen gas include nitrogen gas (N2) and silane coupling agents. Examples of silicon-containing gas include gases containing halogens such as chlorine (Cl), bromine (Br), and iodine (I) and silicon (Si). Examples of nitrogen-containing gas include ammonia gas (NH3) and hydrazine gas (N2H4). Examples of modifying gas include hydrogen gas (H2). Examples of purge gas include nitrogen gas (N2) and argon gas (Ar).

[0018] The film forming apparatus is a capacitively coupled plasma apparatus, in which the mounting table 2 functions as a lower electrode and the shower head 3 functions as an upper electrode. The mounting table 2 is grounded via a capacitor (not shown). However, the mounting table 2 may be grounded, for example, without a capacitor, or may be grounded via a circuit combining a capacitor and a coil. The shower head 3 is connected to an RF power supply unit 8.

[0019] The RF power supply unit 8 supplies high frequency power (hereinafter also referred to as "RF power") to the shower head 3. The RF power supply unit 8 includes an RF power source 81, a matching box 82, and a feed line 83. The RF power source 81 is a power source that generates RF power. The RF power has a frequency suitable for generating plasma. The frequency of the RF power is, for example, within a range from 450 KHz in the low frequency band to 2.45 GHz in the microwave band. The RF power source 81 is connected to the main body 31 of the shower head 3 via the matching box 82 and the feed line 83. The matching box 82 includes a circuit for matching the load impedance to the internal impedance of the RF power source 81. Note that the RF power supply unit 8 has been described as supplying RF power to the shower head 3 serving as the upper electrode, but is not limited thereto. It may be configured to supply RF power to the mounting table 2 serving as the lower electrode.

[0020] The control unit 9 is, for example, a computer, and includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an auxiliary storage device, etc. The CPU operates based on a program stored in the ROM or the auxiliary storage device, and controls the operation of the film forming apparatus. The control unit 9 may be provided inside the film forming apparatus, or may be provided outside the film forming apparatus. When the control unit 9 is provided outside the film forming apparatus, the control unit 9 can control the film forming apparatus by a communication means such as a wired or wireless communication means.

[0021] [Method of forming silicon nitride film] 2, an example of a method for forming a silicon nitride film according to an embodiment will be described using the above-mentioned film forming apparatus. In this embodiment, a silicon wafer is used as the wafer W, and a trench is formed as a recess in the silicon wafer. The inside of the trench and the surface of the wafer W are made of, for example, silicon or an insulating film, and may partially contain a metal or a metal compound.

[0022] First, the control unit 9 loads the wafer W having a trench formed on its surface into the processing vessel 1. The control unit 9 controls the lifting mechanism 24 to lower the mounting table 2 to the transfer position, and then opens the gate valve 12. Next, the wafer W is loaded into the processing vessel 1 via the load / unload port 11 by the transfer arm (not shown), and placed on the mounting table 2 heated to a predetermined temperature (for example, 600° C. or less) by the heater 21. Next, the control unit 9 controls the lifting mechanism 24 to raise the mounting table 2 to the processing position, and reduces the pressure inside the processing vessel 1 to a predetermined vacuum level by the exhaust mechanism 42.

[0023] Subsequently, a Cl2 plasma step S11 is performed as a step of forming an adsorption inhibition region. In the Cl2 plasma step S11, the wafer W is exposed to plasma generated from chlorine gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. In this embodiment, the control unit 9 supplies chlorine gas from the gas supply unit 5 through the shower head 3 into the processing vessel 1, and then supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from the chlorine gas in the processing vessel 1, and active species (reactive species) such as chlorine radicals and chlorine ions are supplied to the surface of the trench formed in the wafer W. The active species are physically or chemically adsorbed on the surface. The adsorbed chlorine has a function of inhibiting the adsorption of DCS in the Si precursor adsorption step S15 described later, so that the region where chlorine is adsorbed becomes an adsorption inhibition region for DCS. Here, the active species easily reach the surface of the wafer W and the upper part of the trench, but do not reach the depth of the trench, that is, the lower part near the bottom, in large numbers. Since the aspect ratio of the trench is high, most of the active species are adsorbed or deactivated before reaching the depth of the trench. Therefore, chlorine is adsorbed at a high density on the surface of the wafer W and the upper part of the trench, but a large amount of unadsorbed chlorine remains in the lower part of the trench, and the density of adsorbed chlorine is low.

[0024] The RF power in the Cl2 plasma step S11 is preferably smaller than the RF power in the nitridation step S17 described below. This is because the dose of active species needs to be relatively limited in the Cl2 plasma step S11 to form a gradient of adsorbed chlorine density inside the trench, whereas the nitridation step S17 sufficiently nitrides the entire film inside the trench.

[0025] Moreover, the process conditions in the Cl2 plasma step S11 are, for example, as follows: Time: 0.05 seconds to 6 seconds ·RF power: 10W~500W Pressure: 0.1 Torr (13.3 Pa) to 50 Torr (6.7 kPa)

[0026] Subsequently, a purge step S12 is performed. In the purge step S12, gas remaining in the processing vessel 1 after the Cl2 plasma step S11 is removed. In this embodiment, the control unit 9 supplies argon gas from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and exhausts the processing vessel 1 using the exhaust unit 4. As a result, gas remaining in the processing vessel 1 is exhausted together with the argon gas. Note that the purge step S12 may be omitted.

[0027] Next, an N2 plasma step S13 is performed as a step of forming an adsorption inhibition region. In the N2 plasma step S13, the wafer W is exposed to plasma generated from nitrogen gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. In this embodiment, the control unit 9 supplies nitrogen gas from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and then supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from the nitrogen gas in the processing vessel 1, and active species such as nitrogen radicals and nitrogen ions are supplied into the trench formed on the surface of the wafer W. The active species are physically or chemically adsorbed to sites where chlorine is not adsorbed in the Cl2 plasma step S11. The adsorbed nitrogen has a function of inhibiting the adsorption of DCS in the Si precursor adsorption step S15 described later, so that the region where nitrogen is adsorbed becomes an adsorption inhibition region for DCS. Here, the active species easily reach the surface of the wafer W and the upper part of the trench, but do not reach the depth of the trench, that is, the lower part near the bottom, in large numbers. Since the aspect ratio of the trench is high, many of the active species are adsorbed or deactivated before reaching the depth of the trench. Therefore, nitrogen is adsorbed at a high density on the surface of the wafer W and the upper part of the trench, but a large amount of unadsorbed nitrogen remains in the lower part of the trench, and the density of adsorbed nitrogen is low.

[0028] The RF power in the N2 plasma step S13 is preferably smaller than the RF power in the nitridation step S17 described below. This is because the dose of active species needs to be relatively limited in the N2 plasma step S13 to form a gradient of adsorbed nitrogen density inside the trench, whereas the nitridation step S17 sufficiently nitrides the entire film inside the trench.

[0029] Moreover, the process conditions in the N2 plasma step S13 are, for example, as follows. Time: 0.1 seconds to 6 seconds ·RF power: 10W~1kW Pressure: 0.1 Torr (13.3 Pa) to 50 Torr (6.7 kPa)

[0030] Subsequently, a purge step S14 is performed. In the purge step S14, gas remaining in the processing vessel 1 after the N2 plasma step S13 is removed. In this embodiment, the control unit 9 supplies argon gas from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and exhausts the processing vessel 1 using the exhaust unit 4. As a result, gas remaining in the processing vessel 1 is exhausted together with the argon gas. Note that the purge step S14 may be omitted.

[0031] Subsequently, a Si precursor adsorption step S15 is performed. In the Si precursor adsorption step S15, DCS is supplied to the wafer W, and DCS is adsorbed in the region other than the adsorption inhibition region to form a Si-containing layer. In this embodiment, the control unit 9 supplies DCS from the gas supply unit 5 into the processing vessel 1 via the shower head 3. DCS is not adsorbed much in the region where adsorbed chlorine and adsorbed nitrogen having an adsorption inhibition function are present, but is adsorbed more in the region where no adsorption inhibition group is present. Therefore, DCS is adsorbed more near the bottom of the trench, and not much on the surface of the wafer W and the upper part of the trench. In other words, DCS is adsorbed at a high density near the bottom of the trench, and DCS is adsorbed at a low density on the upper part of the trench and on the surface of the wafer W.

[0032] Next, a purging step S16 is performed. In the purging step S16, gas remaining in the processing vessel 1 after the Si precursor adsorption step S15 is removed. In this embodiment, the control unit 9 supplies argon gas from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and exhausts the processing vessel 1 using the exhaust unit 4. As a result, gas remaining in the processing vessel 1 is exhausted together with the argon gas. Note that the purging step S16 may be omitted.

[0033] Subsequently, a nitridation step S17 is performed. In the nitridation step S17, the wafer W is exposed to plasma generated from ammonia gas to nitride the Si-containing layer formed on the surface of the wafer W and in the trench, thereby forming a silicon nitride film. In this embodiment, the control unit 9 supplies ammonia gas from the gas supply unit 5 into the processing chamber 1 via the shower head 3, and then supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from the ammonia gas in the processing chamber 1, and active species for nitridation are supplied to the surface of the wafer W and into the trench. The active species react with the Si-containing layer formed in the trench, and a molecular layer of the silicon nitride film is formed as a reaction product. Here, since the Si-containing layer is formed in large amounts near the bottom of the trench, a silicon nitride film is formed in large amounts near the bottom of the trench. This enables filling film formation with a high bottom-up effect.

[0034] The process conditions in the nitriding step S17 are, for example, as follows. Time: 1 second to 10 seconds ·RF power: 100W~3kW Pressure: 0.1 Torr (13.3 Pa) to 50 Torr (6.7 kPa)

[0035] Subsequently, a purging step S18 is performed. In the purging step S18, gas remaining in the processing vessel 1 after the nitriding step S17 is removed. In this embodiment, the control unit 9 supplies argon gas from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and exhausts the processing vessel 1 using the exhaust unit 4. As a result, gas remaining in the processing vessel 1 is exhausted together with the argon gas. Note that the purging step S18 may be omitted.

[0036] Next, a judgment step S19 is performed. In the judgment step S19, the control unit 9 judges whether the number of repetitions from the Cl2 plasma step S11 to the purge step S18 has reached a set number. The set number is determined, for example, according to the film thickness of the silicon nitride film to be formed. If it is judged in the judgment step S19 that the number of repetitions has reached the set number, the process ends. On the other hand, if it is judged in the judgment step S19 that the number of repetitions has not reached the set number, the process returns to the Cl2 plasma step S11.

[0037] In this manner, the Cl2 plasma process S11 to the purge process S18 are repeated, and the silicon nitride film is deposited from the bottom side without blocking the opening of the trench. Thus, a silicon nitride film with high bottom-up properties that does not block the opening while forming a V-shaped cross section can be formed. As a result, a high-quality silicon nitride film can be embedded in the trench without generating voids.

[0038] Next, another example of the method for forming a silicon nitride film according to the embodiment will be described with reference to Fig. 3. The method shown in Fig. 3 differs from the method shown in Fig. 2 in that the wafer W is exposed to plasma generated from chlorine gas and nitrogen gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. The other points are the same as those in the method shown in Fig. 2. Therefore, the following description will focus on the points that are different from the method shown in Fig. 2.

[0039] First, the control unit 9 loads the wafer W having a trench formed on its surface into the processing vessel 1. The method of loading the wafer W into the processing vessel 1 may be the same as the method shown in FIG.

[0040] Subsequently, a Cl2 / N2 plasma process S21 is performed as a process for forming an adsorption inhibition region. In the Cl2 / N2 plasma process S21, the wafer W is exposed to plasma generated from chlorine gas and nitrogen gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. In this embodiment, the control unit 9 simultaneously supplies chlorine gas and nitrogen gas from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and then supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from chlorine gas and nitrogen gas in the processing vessel 1, and active species are supplied into the trench formed on the surface of the wafer W. The active species are physically or chemically adsorbed on the surface. Since the adsorbed chlorine has a function of inhibiting the adsorption of DCS in the Si precursor adsorption process S23 described later, the region where chlorine is adsorbed becomes an adsorption inhibition region for DCS. Nitrogen is also physically or chemically adsorbed on the surface like chlorine. Since the adsorbed nitrogen has a function of inhibiting the adsorption of DCS in the Si precursor adsorption process S23 described later, the region where nitrogen is adsorbed becomes an adsorption inhibition region for DCS. Here, the active species easily reach the surface of the wafer W and the upper part of the trench, but not many reach the depth of the trench, i.e., the lower part near the bottom. Since the aspect ratio of the trench is high, most of the active species are adsorbed or deactivated before reaching the depth of the trench. Therefore, chlorine and nitrogen are adsorbed at high density on the surface of the wafer W and the upper part of the trench, but many unadsorbed portions remain in the lower part of the trench, and the density of adsorbed chlorine and adsorbed nitrogen is low.

[0041] It is preferable that the RF power in the Cl2 / N2 plasma step S21 is smaller than the RF power in the nitridation step S25. This is because the Cl2 / N2 plasma step S21 forms a gradient of chlorine and nitrogen adsorption density inside the trench, whereas the nitridation step S25 sufficiently nitrides the entire film inside the trench.

[0042] Moreover, the process conditions in the Cl2 / N2 plasma step S21 may be the same as the process conditions in the Cl2 plasma step S11 or the N2 plasma step S13, for example.

[0043] Subsequently, a purging step S22, a Si precursor adsorption step S23, a purging step S24, a nitriding step S25, a purging step S26, and a determination step S27 are performed in this order. The purging step S22, the Si precursor adsorption step S23, the purging step S24, the nitriding step S25, the purging step S26, and the determination step S27 may be the same as the purging step S14, the Si precursor adsorption step S15, the purging step S16, the nitriding step S17, the purging step S18, and the determination step S19 shown in FIG.

[0044] In this manner, the Cl2 / N2 plasma process S21 to the purge process S26 are repeated, and the silicon nitride film is deposited from the bottom side without blocking the opening of the trench. This allows the formation of a silicon nitride film with high bottom-up properties that does not block the opening while forming a V-shaped cross section. As a result, a high-quality silicon nitride film can be embedded in the trench without generating voids.

[0045] Next, referring to Fig. 4, another example of the method for forming a silicon nitride film according to the embodiment will be described. The method shown in Fig. 4 differs from the method shown in Fig. 2 in that the wafer W is exposed to plasma generated from chlorine gas and nitrogen gas, and then exposed to plasma generated from nitrogen gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. The other points are the same as those of the method shown in Fig. 2. Therefore, the following description will focus on the points that are different from the method shown in Fig. 2.

[0046] First, the control unit 9 loads the wafer W having a trench formed on its surface into the processing vessel 1. The method of loading the wafer W into the processing vessel 1 may be the same as the method shown in FIG.

[0047] Subsequently, a Cl2 / N2 plasma process S31 is performed. In the Cl2 / N2 plasma process S31, the wafer W is exposed to plasma generated from chlorine gas and nitrogen gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. In this embodiment, the control unit 9 simultaneously supplies chlorine gas and nitrogen gas from the gas supply unit 5 into the processing chamber 1 via the shower head 3, and then supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from chlorine gas and nitrogen gas in the processing chamber 1, and active species are supplied onto the base film in the trench formed on the surface of the wafer W. The active species are physically or chemically adsorbed on the surface. Since the adsorbed chlorine has a function of inhibiting the adsorption of DCS in the Si precursor adsorption process S34 described later, the region where chlorine is adsorbed becomes an adsorption inhibition region for DCS. Nitrogen is also physically or chemically adsorbed on the surface like chlorine. Since the adsorbed nitrogen has a function of inhibiting the adsorption of DCS in the Si precursor adsorption process S34 described later, the region where nitrogen is adsorbed becomes an adsorption inhibition region for DCS. Here, the active species easily reach the surface of the wafer W and the upper part of the trench, but not many reach the depth of the trench, i.e., the lower part near the bottom. Since the aspect ratio of the trench is high, most of the active species are adsorbed or deactivated before reaching the depth of the trench. Therefore, chlorine and nitrogen are adsorbed at high density on the surface of the wafer W and the upper part of the trench, but many unadsorbed portions remain in the lower part of the trench, and the density of adsorbed chlorine and adsorbed nitrogen is low.

[0048] It is preferable that the RF power in the Cl2 / N2 plasma step S31 is smaller than the RF power in the nitridation step S36. This is because the Cl2 / N2 plasma step S31 forms an adsorption density gradient of chlorine and nitrogen inside the trench, whereas the nitridation step S36 sufficiently nitrides the entire film inside the trench.

[0049] Moreover, the process conditions in the Cl2 / N2 plasma step S31 may be the same as the process conditions in the Cl2 plasma step S11 or the N2 plasma step S13, for example.

[0050] Next, the N2 plasma process S32 is performed. In the N2 plasma process S32, the wafer W is exposed to plasma generated from nitrogen gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. In this embodiment, the control unit 9 supplies nitrogen gas from the gas supply unit 5 into the processing chamber 1 via the shower head 3, and also supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from the nitrogen gas in the processing chamber 1, and active species are supplied onto the base film in the trench formed on the surface of the wafer W. The active species are physically or chemically adsorbed to sites where chlorine and nitrogen are not adsorbed in the Cl2 / N2 plasma process S31. The adsorbed nitrogen has a function of inhibiting the adsorption of DCS in the Si precursor adsorption process S34 described later, so that the region where nitrogen is adsorbed becomes an adsorption inhibition region for DCS. Here, the active species easily reach the surface of the wafer W and the upper part of the trench, but do not reach the depth of the trench, that is, the lower part near the bottom, in large numbers. Since the aspect ratio of the trench is high, many of the active species are adsorbed or deactivated before reaching the depth of the trench. Therefore, nitrogen is adsorbed at a high density on the surface of the wafer W and the upper part of the trench, but a large amount of unadsorbed nitrogen remains in the lower part of the trench, and the density of adsorbed nitrogen is low.

[0051] It is preferable that the RF power in the N2 plasma step S32 is smaller than the RF power in the nitridation step S36. This is because the N2 plasma step S32 forms a nitrogen adsorption density gradient inside the trench, whereas the nitridation step S36 sufficiently nitrides the entire film inside the trench.

[0052] Moreover, the process conditions in the N2 plasma step S32 may be the same as the process conditions in the N2 plasma step S13, for example.

[0053] Also, when transitioning from the Cl2 / N2 plasma process S31 to the N2 plasma process S32, for example, while maintaining the supply of RF power, only the supply of chlorine gas is stopped, and transition to the N2 plasma process S32 is made. Also, when transitioning from the Cl2 / N2 plasma process S31 to the N2 plasma process S32, for example, the supply of RF power, the supply of chlorine gas, and the supply of nitrogen gas may be stopped once, and then transition to the N2 plasma process S32 may be made. Also, when transitioning from the Cl2 / N2 plasma process S31 to the N2 plasma process S32, for example, the supply of RF power and the supply of chlorine gas may be stopped once, and a state in which nitrogen gas is supplied may be maintained for a certain period of time, and then transition to the N2 plasma process S32 may be made.

[0054] Also, for example, a purge step may be performed between the Cl2 / N2 plasma step S31 and the N2 plasma step S32.

[0055] Subsequently, a purging step S33, a Si precursor adsorption step S34, a purging step S35, a nitriding step S36, a purging step S37, and a determination step S38 are performed in this order. The purging step S33, the Si precursor adsorption step S34, the purging step S35, the nitriding step S36, the purging step S37, and the determination step S38 may be the same as the purging step S14, the Si precursor adsorption step S15, the purging step S16, the nitriding step S17, the purging step S18, and the determination step S19 shown in FIG.

[0056] In this way, the Cl2 / N2 plasma process S31 to the purge process S37 are repeated, and the silicon nitride film is deposited from the bottom side without blocking the opening of the trench. This allows the formation of a silicon nitride film with high bottom-up properties that does not block the opening while forming a V-shaped cross section. As a result, a high-quality silicon nitride film can be embedded in the trench without generating voids.

[0057] Next, another example of the method for forming a silicon nitride film according to the embodiment will be described with reference to Fig. 5. The method shown in Fig. 5 differs from the method shown in Fig. 4 in that a Cl2 plasma step S42 is performed instead of the N2 plasma step S32. Other points are the same as the method shown in Fig. 4. Therefore, the following description will focus on the points that are different from the method shown in Fig. 4.

[0058] First, the control unit 9 loads the wafer W having a trench formed on its surface into the processing vessel 1. The method of loading the wafer W into the processing vessel 1 may be the same as the method shown in FIG.

[0059] Then, a Cl2 / N2 plasma step S41 is performed. The Cl2 / N2 plasma step S41 may be the same as the Cl2 / N2 plasma step S31.

[0060] Subsequently, a Cl2 plasma process S42 is performed. In the Cl2 plasma process S42, the wafer W is exposed to plasma generated from chlorine gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. In this embodiment, the control unit 9 supplies chlorine gas from the gas supply unit 5 into the processing vessel 1 via the shower head 3, and then supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from the chlorine gas in the processing vessel 1, and active species are supplied onto the base film in the trench formed on the surface of the wafer W. The active species are physically or chemically adsorbed to sites where chlorine and nitrogen are not adsorbed in the Cl2 / N2 plasma process S41. The adsorbed chlorine has a function of inhibiting the adsorption of DCS in the Si precursor adsorption process S44 described later, so that the region where chlorine is adsorbed becomes an adsorption inhibition region for DCS. Here, the active species easily reach the surface of the wafer W and the upper part of the trench, but do not reach the depth of the trench, that is, the lower part near the bottom, in large numbers. Since the aspect ratio of the trench is high, most of the active species are adsorbed or deactivated before reaching the depth of the trench. Therefore, chlorine is adsorbed at a high density on the surface of the wafer W and the upper part of the trench, but a large amount of unadsorbed chlorine remains in the lower part of the trench, and the density of adsorbed chlorine is low.

[0061] It is preferable that the RF power in the Cl2 plasma step S42 is smaller than the RF power in the nitridation step S46. This is because the Cl2 plasma step S42 forms a chlorine adsorption density gradient inside the trench, whereas the nitridation step S46 sufficiently nitrides the entire film inside the trench.

[0062] Moreover, the process conditions in the Cl2 plasma step S42 may be the same as the process conditions in the Cl2 plasma step S11, for example.

[0063] Also, when transitioning from the Cl2 / N2 plasma process S41 to the Cl2 plasma process S42, for example, while maintaining the supply of RF power, only the supply of nitrogen gas is stopped, and transition to the Cl2 plasma process S42 is made. Also, when transitioning from the Cl2 / N2 plasma process S41 to the Cl2 plasma process S42, for example, the supply of RF power, the supply of chlorine gas, and the supply of nitrogen gas may be stopped once, and then transition to the Cl2 plasma process S42 may be made. Also, when transitioning from the Cl2 / N2 plasma process S41 to the Cl2 plasma process S42, for example, the supply of RF power and the supply of nitrogen gas may be stopped once, and a state in which chlorine gas is supplied may be maintained for a certain period of time, and then transition to the Cl2 plasma process S42 may be made.

[0064] Also, for example, a purge step may be performed between the Cl2 / N2 plasma step S41 and the Cl2 plasma step S42.

[0065] Subsequently, a purging step S43, a Si precursor adsorption step S44, a purging step S45, a nitriding step S46, a purging step S47, and a determination step S48 are performed in this order. The purging step S43, the Si precursor adsorption step S44, the purging step S45, the nitriding step S46, the purging step S47, and the determination step S48 may be the same as the purging step S33, the Si precursor adsorption step S34, the purging step S35, the nitriding step S36, the purging step S37, and the determination step S38 shown in FIG.

[0066] In this manner, the Cl2 / N2 plasma process S41 to the purge process S47 are repeated, and the silicon nitride film is deposited from the bottom side without blocking the opening of the trench. This allows the formation of a silicon nitride film with high bottom-up properties that does not block the opening while forming a V-shaped cross section. As a result, a high-quality silicon nitride film can be embedded in the trench without generating voids.

[0067] Next, another example of the method for forming a silicon nitride film according to the embodiment will be described with reference to Fig. 6. The method shown in Fig. 6 differs from the method shown in Fig. 2 in that the wafer W is exposed to plasma generated from nitrogen gas and then to plasma generated from chlorine gas to form an adsorption inhibition region on the upper part of the trench and on the surface of the wafer W. The other points are the same as those of the method shown in Fig. 2.

[0068] First, the control unit 9 loads the wafer W having a trench formed on its surface into the processing vessel 1. The method of loading the wafer W into the processing vessel 1 may be the same as the method shown in FIG.

[0069] Subsequently, the N2 plasma step S51, the purge step S52, the Cl2 plasma step S53, the purge step S54, the Si precursor adsorption step S55, the purge step S56, the nitridation step S57, the purge step S58, and the judgment step S59 are performed in this order. The N2 plasma step S51, the purge step S52, the Cl2 plasma step S53, the purge step S54, the Si precursor adsorption step S55, the purge step S56, the nitridation step S57, the purge step S58, and the judgment step S59 may be the same as the N2 plasma step S13, the purge step S12, the Cl2 plasma step S11, the purge step S14, the Si precursor adsorption step S15, the purge step S16, the nitridation step S17, the purge step S18, and the judgment step S19 shown in FIG.

[0070] In this manner, the N2 plasma process S51 to the purge process S58 are repeated, and the silicon nitride film is deposited from the bottom side without blocking the opening of the trench. Thus, a silicon nitride film with high bottom-up properties that does not block the opening while forming a V-shaped cross section can be formed. As a result, a high-quality silicon nitride film can be embedded in the trench without generating voids.

[0071] Various steps for forming an adsorption inhibition region have been described above with reference to FIG. 2 to FIG. 6, but are not limited thereto. For example, a Cl2 plasma step may be performed followed by a Cl2 / N2 plasma step, or a Cl2 / N2 plasma step may be performed followed by an N2 plasma step. An adsorption inhibition region may also be formed by combining a Cl2 plasma step, an N2 plasma step, and a Cl2 / N2 plasma step. For example, a Cl2 plasma step may be performed followed by an N2 plasma step, and a Cl2 plasma step may be performed, or a Cl2 plasma step may be performed followed by an N2 plasma step, and a Cl2 plasma step may be performed. For example, a Cl2 plasma step may be performed followed by a Cl2 / N2 plasma step, and a Cl2 plasma step may be performed, or a N2 plasma step may be performed followed by a Cl2 / N2 plasma step, and a Cl2 plasma step may be performed. As long as the combination of a Cl2 plasma step, an N2 plasma step, and a Cl2 / N2 plasma step is used, it is not limited to the above, and a combination of three or more steps is also included.

[0072] The silicon film forming method of the embodiment may further include a modification step. The modification step is performed, for example, after the step of forming an adsorption inhibition region, after the Si precursor adsorption step, and / or after the nitriding step. In the modification step S17, the wafer W is exposed to plasma generated from hydrogen gas to modify the Si-containing layer and the SiN film. In this embodiment, the control unit 9 supplies hydrogen gas from the gas supply unit 5 through the shower head 3 into the processing chamber 1, and then supplies RF power to the shower head 3 by the RF power supply unit 8. As a result, plasma is generated from the hydrogen gas in the processing chamber 1, and active species such as hydrogen radicals and hydrogen ions are supplied to the surface of the wafer W and into the trench. As a result, the Si-containing film is modified. The modification of the Si-containing film includes, for example, removing halogen contained in the Si-containing film. In addition, in the second cycle and thereafter, halogen and excess NH in the SiN film are removed. x This also includes removing halogens and excess NH x By removing the groups, for example, the wet etching rate can be improved.

[0073] [Example] An example will be described in which embedding characteristics of a silicon nitride film formed in a trench formed in the surface of a wafer W by the method for forming a silicon nitride film according to the above-described embodiment are evaluated.

[0074] In Example 1, a silicon nitride film was formed in a trench by the method of forming a silicon nitride film shown in FIG. 2. That is, in Example 1, a Cl2 plasma step S11 and an N2 plasma step S13 were performed in this order to form an adsorption inhibition region on the wafer W, and then a Si precursor adsorption step S15 and a nitridation step S17 were performed. Then, six positions Z1 to Z6 were defined from the shallowest depth in the trench, and the thickness of the deposited silicon nitride film was measured at each of them. In addition, the film formation amount per cycle of the silicon nitride film (hereinafter referred to as "GPC (Growth Per Cycle)") was calculated by dividing the measured thickness of the silicon nitride film by the number of repetitions from the Cl2 plasma step S11 to the purge step S18. In addition, the etching rate (hereinafter referred to as "WER (Wet Etching Rate)") when the silicon nitride film formed in the trench was etched with 0.5% dilute hydrofluoric acid (DHF) was measured.

[0075] In Example 2, a silicon nitride film was formed in a trench by the method of forming a silicon nitride film shown in FIG. 4. That is, in Example 2, an adsorption inhibition region was formed by performing Cl2 / N2 plasma step S31 and N2 plasma step S32 in this order, and then a Si precursor adsorption step S34 and a nitridation step S36 were performed. Next, six positions Z1 to Z6 were defined from the shallowest depth in the trench, and the thickness of the silicon nitride film was measured at each of them, and the GPC was calculated by dividing the thickness by the number of repetitions from the Cl2 / N2 plasma step S31 to the purge step S37. In addition, the WER was measured when the silicon nitride film formed in the trench was etched with 0.5% DHF.

[0076] In Comparative Example 1, a silicon nitride film was formed in a trench without performing the N2 plasma step S13 and the purge step S14 in the silicon nitride film forming method shown in Fig. 2. That is, in Comparative Example 1, the wafer W was exposed to plasma generated from chlorine gas to form an adsorption inhibition region, and then the Si precursor adsorption step S15 and the nitridation step S17 were performed. Next, six positions Z1 to Z6 were defined from the shallowest depth in the trench, and the film thickness of the silicon nitride film was measured at each of them, and the GPC was calculated by dividing the thickness by the number of repetitions from the Cl2 plasma step S11 to the purge step S18. In addition, the WER was measured when the silicon nitride film formed in the trench was etched with 0.5% DHF.

[0077] In Comparative Example 2, a silicon nitride film was formed in a trench without performing the Cl2 plasma step S11 and the purge step S12 in the silicon nitride film forming method shown in Fig. 2. That is, in Comparative Example 2, a wafer W was exposed to plasma generated from nitrogen gas to form an adsorption inhibition region, and then a Si precursor adsorption step S15 and a nitridation step S17 were performed. Next, six positions Z1 to Z6 were defined from the shallowest depth in the trench, and the thickness of the silicon nitride film was measured at each of the positions, and the GPC was calculated by dividing the measured thickness by the number of repetitions from the N2 plasma step S13 to the purge step S18.

[0078] Fig. 7 is a diagram showing the evaluation results of the embedding characteristics of the silicon nitride film in the trench. In Fig. 7, among positions Z1 to Z6, position Z1 is the shallowest position, i.e., the position at the top of the trench, and position Z6 is the deepest position, i.e., the position at the bottom of the trench. Fig. 7 also shows the GPC normalized at position Z6 in all of Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

[0079] 7, it can be seen that the cycle rate decreases from position Z6 to position Z1 (from the bottom to the top of the trench) in all of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. This result shows that in all of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, a silicon nitride film can be formed while forming a V-shaped cross section.

[0080] It is also found that the GPC is particularly small in the upper part of the trench (where the trench is shallow) in Example 1 and Example 2 compared to Comparative Example 1 and Comparative Example 2. From this result, it was shown that in Example 1 and Example 2, the opening angle of the V-shape in the cross section of the silicon nitride film embedded in the trench is larger than in Comparative Example 1 and Comparative Example 2, and a silicon nitride film with high bottom-up properties can be formed.

[0081] Thus, according to the first and second embodiments, a silicon nitride film having high bottom-up properties can be formed, so that the generation of voids can be more effectively suppressed. Furthermore, since the aspect ratio in the pattern can be kept relatively low, radicals can be more easily supplied to the seam. Therefore, a high-quality silicon nitride film can be embedded in the trench, and it is considered that, for example, wet etching resistance is improved. In particular, when a silicon nitride film is formed at a low temperature (for example, less than 400° C.), it is known that insufficient nitriding is likely to occur, and wet etching is likely to progress from the seam as a starting point. Since the first and second embodiments can keep the aspect ratio in the pattern relatively low, it is considered that the generation of voids can be more effectively suppressed even when the bowing shape of the trench is large.

[0082] 8 is a diagram showing the evaluation results of the wet etching rate (WER) of the silicon nitride film embedded in the trench. In FIG. 8, the wet etching rates (WER) of Example 1, Example 2, and Comparative Example 1 are shown when normalized with the wet etching rate (WER) of Comparative Example 1.

[0083] 8, it can be seen that the wet etching rates (WER) of Example 1 and Example 2 are less than half of the wet etching rate (WER) of Comparative Example 1. This result shows that the wet etching resistance is improved in Example 1 and Example 2 compared to Comparative Example 1. In particular, the wet etching rate (WER) of Example 2 is about 1 / 3 of the wet etching rate (WER) of Comparative Example 1, showing that the wet etching resistance is particularly improved.

[0084] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims.

[0085] In the above embodiment, the film forming apparatus is a capacitively coupled plasma apparatus, but the present disclosure is not limited to this. For example, the film forming apparatus may be a plasma apparatus using an inductively coupled plasma, a surface wave plasma (microwave plasma), a magnetron plasma, a remote plasma, or the like as a plasma source.

[0086] In the above embodiment, the case where the film forming apparatus is a single-wafer type apparatus that processes wafers one by one has been described, but the present disclosure is not limited thereto. For example, the film forming apparatus may be a batch type apparatus that processes multiple wafers at once. Also, for example, the film forming apparatus may be a semi-batch type apparatus that revolves multiple wafers placed on a turntable in a processing vessel by the turntable, and processes the wafers by passing them in order through an area where a first gas is supplied and an area where a second gas is supplied. Also, for example, the film forming apparatus may be a multiple-wafer film forming apparatus equipped with multiple mounting tables in one processing vessel. [Explanation of symbols]

[0087] 1 Processing vessel 5 Gas supply section 9. Control Unit

Claims

1. 1. A method for forming a silicon nitride film in a recess formed in a surface of a substrate, comprising: exposing the substrate to plasma generated from an adsorption inhibition gas containing a halogen gas and a non-halogen gas to adsorb active species generated from the halogen gas and the non-halogen gas to form an adsorption inhibition region; adsorbing a silicon-containing gas in an area other than the adsorption inhibition area; exposing the substrate on which the silicon-containing gas is adsorbed to plasma generated from a nitrogen-containing gas to form a silicon nitride film; The method for forming a silicon nitride film comprises the steps of:

2. repeating a cycle including the steps of forming the adsorption inhibiting region, adsorbing the silicon-containing gas, and forming the silicon nitride film; 2. The method for forming a silicon nitride film according to claim 1.

3. The step of forming the adsorption-inhibited region includes exposing the substrate to plasma generated from the halogen gas, and then exposing the substrate to plasma generated from the non-halogen gas.

3. The method for forming a silicon nitride film according to claim 1.

4. the step of forming the adsorption-inhibiting region includes exposing the substrate to plasma generated from the halogen gas, then exposing the substrate to plasma generated from the non-halogen gas, and then exposing the substrate to plasma generated from the halogen gas; 4. The method for forming a silicon nitride film according to claim 3.

5. The step of forming the adsorption-inhibiting region includes exposing the substrate to plasma generated from the non-halogen gas, and then exposing the substrate to plasma generated from the halogen gas.

3. The method for forming a silicon nitride film according to claim 1.

6. The step of forming the adsorption-inhibiting region includes exposing the substrate to plasma generated from the non-halogen gas, then exposing the substrate to plasma generated from the halogen gas, and then exposing the substrate to plasma generated from the non-halogen gas.

6. The method for forming a silicon nitride film according to claim 5.

7. The step of forming the adsorption inhibition region includes exposing the substrate to plasma generated from the halogen gas and the non-halogen gas.

3. The method for forming a silicon nitride film according to claim 1.

8. The step of forming the adsorption inhibition region includes exposing the substrate to plasma generated from the halogen gas and the non-halogen gas, and then exposing the substrate to plasma generated from either the halogen gas or the non-halogen gas.

8. The method for forming a silicon nitride film according to claim 7.

9. The step of forming the adsorption inhibition region includes exposing the substrate to plasma generated from either the halogen gas or the non-halogen gas, and then exposing the substrate to plasma generated from the halogen gas and the non-halogen gas.

3. The method for forming a silicon nitride film according to claim 1.

10. The step of forming the adsorption-inhibiting region comprises: exposing the substrate to a plasma generated from the halogen gas and the non-halogen gas; exposing the substrate to a plasma generated from either the halogen gas or the non-halogen gas; exposing the substrate to a plasma generated from the one or the other of the halogen gas and the non-halogen gas; Including, 3. The method for forming a silicon nitride film according to claim 1.

11. a power supplied for generating plasma in the step of forming the adsorption inhibition region is smaller than a power supplied for generating plasma in the step of forming the silicon nitride film; The method for forming a silicon nitride film according to claim 1 .

12. The temperature of the substrate is set to 600° C. or less. The method for forming a silicon nitride film according to claim 1 .

13. the halogen gas is chlorine gas, The non-halogen gas is nitrogen gas.

13. The method for forming a silicon nitride film according to claim 1.

14. The method further includes a modification step of modifying the substrate by exposing the substrate to plasma generated from hydrogen gas.

14. The method for forming a silicon nitride film according to claim 1.

15. the modifying step is carried out after at least one of the steps of forming the adsorption inhibiting region, the step of adsorbing the silicon-containing gas, and the step of forming the silicon nitride film. The method for forming a silicon nitride film according to claim 14.

16. a processing vessel for accommodating a substrate having a recess formed on a surface thereof; a gas supply unit for supplying an adsorption inhibitor gas, a silicon-containing gas, and a nitrogen-containing gas into the processing vessel; A control unit; Equipped with The adsorption inhibitor gas includes a halogen gas and a non-halogen gas, The control unit is exposing the substrate to plasma generated from the adsorption inhibiting gas to adsorb active species generated from the halogen gas and the non-halogen gas to form an adsorption inhibiting region; adsorbing the silicon-containing gas in a region other than the adsorption inhibition region; exposing the substrate on which the silicon-containing gas is adsorbed to plasma generated from the nitrogen-containing gas to form a silicon nitride film; configured to control the gas supply to implement Film deposition equipment.

Images