Film deposition method and film deposition apparatus

Abstract

To provide a film deposition method and film deposition apparatus that suppresses the occurrence of voids when embedding a film into a recess.SOLUTION: A deposition method has a process for preparing a substrate having a recess covered with a first silicon containing film, a process for supplying a first etching gas to the substrate maintained at a first temperature to partially etch the first silicon containing film, a process for supplying a second etching gas to the substrate maintained at a second temperature higher than the first temperature to partially etch the first silicon containing film, and a process for forming a second silicon containing film on top of the first silicon containing film remaining within the recess, and an each etching process is performed without using plasma, the first etching process is performed under a first condition where the first silicon containing film formed on the upper part of the recess is more readily etched than the first silicon containing film formed on the lower part of the recess, and the second etching process is performed under a second condition where the first silicon containing film formed at the lower part of the recess is more readily etched than under the first condition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] BACKGROUND ART A technique is known in which a film is filled into recesses formed on the surface of a substrate by alternately repeating film formation and etching (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-199306 [Patent Document 2] Japanese Patent Publication No. 2022-184550 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can suppress the occurrence of voids when a film is filled into a recess. [Means for solving the problem]

[0005] A film formation method according to one embodiment of the present disclosure includes the steps of: (a) preparing a substrate having a recess covered with a first silicon-containing film; (b) supplying a first etching gas to the substrate maintained at a first temperature to partially etch the first silicon-containing film; (c) supplying a second etching gas to the substrate maintained at a second temperature higher than the first temperature to partially etch the first silicon-containing film; and (d) forming a second silicon-containing film on the first silicon-containing film remaining in the recess, wherein steps (b) and (c) are performed without using plasma, and step (b) is performed under first conditions under which the first silicon-containing film formed in the upper part of the recess is more easily etched than the first silicon-containing film formed in the lower part of the recess, and step (c) is performed under second conditions under which the first silicon-containing film formed in the lower part of the recess is more easily etched than the first conditions. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to suppress the occurrence of voids when a film is filled into a recess. [Brief explanation of the drawings]

[0007] [Figure 1] 2 is a flowchart illustrating a film forming method according to an embodiment. [Figure 2] 1 is a cross-sectional view (1) showing a film forming method according to an embodiment. [Figure 3] FIG. 2 is a cross-sectional view (2) showing the film forming method according to the embodiment. [Figure 4] 10 is a flowchart illustrating a film forming method according to a modified example of the embodiment. [Figure 5] 1 is a vertical cross-sectional view showing a film forming apparatus according to a first example of an embodiment. [Figure 6] 1 is a horizontal cross-sectional view showing a film forming apparatus according to a first example of an embodiment. [Figure 7] FIG. 4 is a vertical cross-sectional view showing a film forming apparatus according to a second example of the embodiment. [Figure 8] FIG. 10 is a diagram showing an etching shape when a first etching step is performed. [Figure 9] FIG. 10 is a diagram showing an etching shape when a second etching step is performed. DETAILED DESCRIPTION OF THE INVENTION

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

[0009] [Film formation method] A film forming method according to an embodiment will be described with reference to Figures 1 to 3. As shown in Figure 1, the film forming method according to the embodiment includes a preparation step S11, a film forming step S12, a first etching step S13, a second etching step S14, and a filling step S15.

[0010] The preparation step S11 includes preparing a substrate 100, as shown in FIG. 2(a). The substrate 100 has a recess 110 on its surface. The substrate 100 is, for example, a semiconductor wafer such as a silicon wafer. The recess 110 extends, for example, along a first direction parallel to the main surface of the substrate 100. A plurality of recesses 110 are provided, for example, along a second direction parallel to the main surface of the substrate 100 and perpendicular to the first direction. The recess 110 has, for example, a narrowed portion 111. The narrowed portion 111 is a portion with a narrow opening width (width in the second direction). The narrowed portion 111 is provided, for example, at an upper portion in the depth direction of the recess 110. The narrowed portion 111 may be provided midway between the upper and lower portions in the depth direction of the recess 110. The recess 110 does not necessarily have to have a narrowed portion 111. The recess 110 is, for example, a trench.

[0011] The film formation step S12 is performed after the preparation step S11. As shown in FIG. 2(b), the film formation step S12 includes forming a silicon nitride film 120 to cover the bottom surface 110a, the side surface 110b, and the top surface 110c of the recess 110. The silicon nitride film 120 can be formed by alternately supplying dichlorosilane (DCS) gas to the substrate 100 and exposing the substrate 100 to plasma generated from ammonia gas while maintaining the substrate 100 at a first film formation temperature. In this case, the silicon nitride film 120 can be formed to approximately the same thickness on each of the bottom surface 110a, the side surface 110b, and the top surface 110c of the recess 110. In other words, the silicon nitride film 120 can be formed conformally along the surface of the recess 110. The first film formation temperature is, for example, 300°C or higher and 650°C or lower. The film forming step S12 may include forming the silicon nitride film 120 until the top of the recess 110 is closed, as shown in FIG. 2(c).

[0012] The first etching step S13 is performed after the film formation step S12. The first etching step S13 is performed, for example, in the same processing chamber as the film formation step S12. The first etching step S13 may be performed in a processing chamber different from that of the film formation step S12. As shown in FIG. 3(a), the first etching step S13 includes supplying a first etching gas to the substrate 100 maintained at a first etching temperature to partially etch the silicon nitride film 120. The first etching temperature is a temperature lower than the first film formation temperature. The first etching temperature is, for example, not lower than 50°C and not higher than 90°C. The first etching temperature is an example of the first temperature. The first etching step S13 may include partially etching the silicon nitride film 120 by anisotropic etching. The first etching step S13 is performed under first conditions under which the silicon nitride film 120 formed in the upper part of the recess 110 is more easily etched than the silicon nitride film 120 formed in the lower part of the recess 110.

[0013] The first condition is a condition for etching the silicon nitride film 120 by chemical etching without using plasma. The first condition may include a process of supplying a mixed gas of a halogen-containing gas and a basic gas to the substrate 100 to chemically react the silicon nitride film 120 with the mixed gas and generate a reaction product. The halogen-containing gas is, for example, hydrogen fluoride gas. The basic gas is, for example, ammonia gas. In this case, a reaction product containing mainly ammonium silicofluoride [(NH4)2SiF6] and water (H2O) is generated. The halogen-containing gas may be chlorine gas or chlorine trifluoride gas. The mixed gas is an example of a first etching gas.

[0014] The first etching step S13 may include removing the silicon nitride film 120 formed on the upper surface 110c of the recess 110 to expose at least a portion of the upper surface 110c of the recess 110. As shown in FIG. 3(a), the first etching step S13 may include removing the silicon nitride film 120 formed on the upper surface 110c of the recess 110 to expose the entire upper surface 110c of the recess 110.

[0015] The second etching step S14 is performed after the first etching step S13. As shown in FIG. 3(b), the second etching step S14 includes supplying a second etching gas to the substrate 100 maintained at a second etching temperature to partially etch the silicon nitride film 120. The second etching temperature is higher than the first etching temperature. The second etching temperature is, for example, a temperature equal to or higher than the sublimation temperature of the reaction product generated in the first etching step S13. In this case, the reaction product sublimes and is removed from the surface of the recess 110. The second etching temperature is, for example, the same temperature as the second film formation temperature described below. In this case, the filling step S15 can be performed without changing the temperature after the second etching step S14, thereby improving productivity. The second etching temperature is, for example, 300°C or higher and 650°C or lower. The second etching temperature is an example of the second temperature. The second etching step S14 may be performed under a higher pressure atmosphere than the first etching step S13. The second etching step S14 may include isotropically etching the silicon nitride film 120. The second etching step S14 is performed under second conditions under which the silicon nitride film 120 formed in the recess 110 is more easily etched than under the first conditions.

[0016] The second condition is a condition for etching the silicon nitride film 120 by chemical etching without using plasma. The second condition may include a process of supplying a halogen-containing gas to the substrate 100 without supplying a basic gas, thereby causing a chemical reaction between the silicon nitride film 120 and the halogen-containing gas and generating a volatile substance. Because the volatile substance does not deposit on the surface of the recess 110, the silicon nitride film 120 can be removed without blocking the upper part of the recess 110 during etching. The halogen-containing gas is, for example, hydrogen fluoride gas. In this case, a volatile substance containing mainly silicon tetrafluoride (SiF4) is generated. The halogen-containing gas may be chlorine gas or chlorine trifluoride gas.

[0017] The second etching step S14 may include removing the silicon nitride film 120 that blocks the upper portion of the recess 110. In this case, in the filling step S15, the silicon nitride film 120 is also deposited on the bottom surface 110a of the recess 110, making it easy to form the silicon nitride film 120 in the recess 110 in a bottom-up manner. This makes it possible to prevent voids from being formed in the recess 110. As shown in FIG. 3(b), the second etching step S14 may include removing the silicon nitride film 120 to a position that is the same depth as the narrowing portion 111 or a position that is deeper than the narrowing portion 111. In this case, in the filling step S15, it is easy to form the silicon nitride film 120 in the recess 110 in a bottom-up manner.

[0018] The second etching step S14 is performed, for example, in the same processing chamber as the first etching step S13. In this case, a step of increasing the temperature of the substrate 100 from the first etching temperature to the second etching temperature may be included between the first etching step S13 and the second etching step S14.

[0019] The filling step S15 is performed after the second etching step S14. As shown in FIG. 3(c), the filling step S15 includes forming another silicon nitride film 120 on the silicon nitride film 120 remaining in the recess 110, thereby filling the recess 110 with the silicon nitride film 120. The silicon nitride film 120 can be formed by alternately repeating supplying dichlorosilane gas to the substrate 100 and exposing the substrate 100 to plasma generated from ammonia gas while maintaining the substrate 100 at a second film formation temperature. The second film formation temperature may be the same as the first film formation temperature. The second film formation temperature is an example of a third temperature.

[0020] As described above, according to the film forming method of the embodiment, the silicon nitride film 120 covering the recess 110 is etched by two-stage etching at different etching temperatures, and then the silicon nitride film 120 is embedded in the recess 110. That is, the first etching step S13 and the second etching step S14 are performed in this order. In this case, the silicon nitride film 120 can be removed without blocking the upper part of the recess 110 during the etching. Therefore, it is possible to suppress the generation of voids when the silicon nitride film 120 is embedded in the recess 110.

[0021] In contrast, if only the first etching step S13 is performed on the silicon nitride film 120 covering the recess 110, reaction products generated by the chemical reaction between the silicon nitride film 120 and the first etching gas may accumulate on the upper part of the recess 110, causing blockage. In particular, ammonium silicofluoride has large crystal grains, so blockage is likely to occur on the upper part of the recess 110.

[0022] A film formation method according to a modified embodiment will be described with reference to Fig. 4. The film formation method shown in Fig. 4 differs from the film formation method shown in Fig. 1 in that the second etching step S24 and the second film formation step S25 are repeated in this order until the first number of times is reached. As shown in Fig. 4, the film formation method according to the modified embodiment includes a preparation step S21, a first film formation step S22, a first etching step S23, a second etching step S24, a second film formation step S25, and a determination step S26.

[0023] The preparation step S21, the first film formation step S22, the first etching step S23, and the second etching step S24 may be the same as the preparation step S11, the film formation step S12, the first etching step S13, and the second etching step S14, respectively.

[0024] The second film formation step S25 is performed after the second etching step S24. The second film formation step S25 includes forming a silicon nitride film 120 on the silicon nitride film 120 remaining in the recess 110. The silicon nitride film 120 can be formed by alternately repeating the supply of dichlorosilane gas to the substrate 100 and the exposure of the substrate 100 to plasma generated from ammonia gas while maintaining the substrate 100 at the second film formation temperature.

[0025] The determination step S26 is performed after the second film-forming step S25. The determination step S26 includes determining whether the second etching step S24 and the second film-forming step S25 have been performed a first number of times in this order. If it is determined that the second etching step S24 and the second film-forming step S25 have not been performed a first number of times in this order, the second etching step S24 and the second film-forming step S25 are performed again in this order. If it is determined that the second etching step S24 and the second film-forming step S25 have been performed a first number of times in this order, the process ends.

[0026] The first number of times is, for example, two or more times. The first number of times may be one time. The first number of times is determined in advance depending on, for example, the opening width of the recess 110, the depth of the recess 110, the presence or absence of the narrowed portion 111, the position of the narrowed portion 111, the opening width of the narrowed portion 111, etc. For example, the first number of times when the opening width of the recess 110 is a first width is set to a value larger than the first number of times when the opening width of the recess 110 is a second width that is wider than the first width. For example, the first number of times when the narrowed portion 111 is present is set to a value larger than the first number of times when the narrowed portion 111 is not present. For example, the first number of times when the narrowed portion 111 is provided midway between the upper and lower portions in the depth direction of the recess 110 is set to a value larger than the first number of times when the narrowed portion 111 is provided at the upper portion in the depth direction of the recess 110.

[0027] As described above, according to the film forming method of the modified embodiment, the silicon nitride film 120 covering the recess 110 is etched by two-stage etching using different etching temperatures, and then the silicon nitride film 120 is embedded in the recess 110. That is, the first etching step S23 and the second etching step S24 are performed in this order. Furthermore, the second etching step S24 and the second film forming step S25 are repeated a first number of times depending on the opening width of the recess 110, the depth of the recess 110, the presence or absence of the narrowed portion 111, the position of the narrowed portion 111, the opening width of the narrowed portion 111, and the like. In this case, the silicon nitride film 120 can be removed without blocking the upper portion of the recess 110 during etching. This prevents voids from being generated when the silicon nitride film 120 is embedded in the recess 110.

[0028] [Film forming equipment] (Example 1) A film forming apparatus 1 according to a first embodiment will be described with reference to Figures 5 and 6. As shown in Figures 5 and 6, the film forming apparatus 1 is configured as a batch-type apparatus that processes a plurality of substrates W at once. The substrates W are, for example, semiconductor wafers.

[0029] The film forming apparatus 1 includes a processing chamber 10, a gas supply unit 30, an exhaust unit 40, a heating unit 50, a plasma generating mechanism 60, and a control unit 90.

[0030] The processing vessel 10 has a vertical cylindrical shape with a ceiling and an open bottom end. The processing vessel 10 is made of, for example, quartz. A quartz ceiling plate 11 is provided near the upper end of the processing vessel 10, and the area below the ceiling plate 11 is sealed. A cylindrical manifold 12 is connected to the opening at the lower end of the processing vessel 10 via a sealing member 13 such as an O-ring. The manifold 12 is made of, for example, metal.

[0031] The manifold 12 supports the lower end of the processing vessel 10. The boat 14 is inserted into the processing vessel 10 from below the manifold 12. The boat 14 holds multiple substrates W at intervals in the vertical direction. The boat 14 holds each substrate W in a horizontal position. The boat 14 is made of, for example, quartz. The boat 14 has, for example, three support columns 15. Grooves (not shown) are formed in each support column 15 at predetermined intervals in the vertical direction. The boat 14 holds multiple substrates W using the grooves.

[0032] The boat 14 is placed on a table 17 via a quartz heat-insulating tube 16. The table 17 is supported on a rotary shaft 19 that passes through a lid 18. The lid 18 opens and closes the opening at the bottom end of the manifold 12. The lid 18 is made of, for example, stainless steel.

[0033] A magnetic fluid seal 20 is provided at the penetration portion of the rotating shaft 19. The magnetic fluid seal 20 airtightly seals the rotating shaft 19 and rotatably supports it. A seal member 21 is provided between the peripheral portion of the lid 18 and the lower end of the manifold 12. The seal member 21 maintains the airtightness of the inside of the processing vessel 10. The seal member 21 is, for example, an O-ring.

[0034] The rotation shaft 19 is attached to the tip of an arm 22 supported by a lifting mechanism (not shown), such as a boat elevator. This allows the boat 14 and the lid 18 to be raised and lowered as a unit and inserted into and removed from the processing vessel 10.

[0035] An opening 23 and an exhaust port 24 are provided in the side wall of the processing vessel 10. The opening 23 is formed to be elongated in the vertical direction so as to be able to cover all of the substrates W supported by the boat 14 in the vertical direction. The exhaust port 24 is provided, for example, at a position opposite the opening 23. The exhaust port 24 is formed to be elongated in the vertical direction so as to be able to cover all of the substrates W supported by the boat 14 in the vertical direction.

[0036] The gas supply unit 30 is configured to be able to introduce various process gases used in the above-described film formation method into the process vessel 10. The gas supply unit 30 includes a DCS supply unit 31, a hydrogen fluoride supply unit 32, an ammonia supply unit 33, and a nitrogen supply unit 34.

[0037] The DCS supply unit 31 includes a supply pipe 31a inside the processing vessel 10 and a supply path 31b outside the processing vessel 10. A DCS supply source 31c, a mass flow controller 31d, and a valve 31e are installed on the supply path 31b, in this order from upstream to downstream in the gas flow direction. The supply timing of DCS gas from the DCS supply source 31c is controlled by the valve 31e, and the flow rate is adjusted to a predetermined value by the mass flow controller 31d. The DCS gas flows from the supply path 31b into the supply pipe 31a and is then discharged from the supply pipe 31a into the processing vessel 10.

[0038] The hydrogen fluoride supply unit 32 includes a supply pipe 32a inside the processing vessel 10 and a supply path 32b outside the processing vessel 10. A hydrogen fluoride source 32c, a mass flow controller 32d, and a valve 32e are installed on the supply path 32b, in this order from upstream to downstream in the gas flow direction. Thus, the supply timing of the hydrogen fluoride gas from the hydrogen fluoride source 32c is controlled by the valve 32e, and the mass flow controller 32d adjusts the flow rate to a predetermined value. The hydrogen fluoride gas flows from the supply path 32b into the supply pipe 32a and is then discharged from the supply pipe 32a into the processing vessel 10.

[0039] The ammonia supply unit 33 includes a supply pipe 33a inside the processing vessel 10 and a supply path 33b outside the processing vessel 10. An ammonia source 33c, a mass flow controller 33d, and a valve 33e are installed on the supply path 33b, in this order from upstream to downstream in the gas flow direction. Thus, the supply timing of ammonia gas from the ammonia source 33c is controlled by the valve 33e, and the flow rate is adjusted to a predetermined value by the mass flow controller 33d. The ammonia gas flows from the supply path 33b into the supply pipe 33a and is discharged from the supply pipe 33a into the processing vessel 10.

[0040] The nitrogen supply unit 34 includes a supply pipe 34a inside the processing vessel 10 and a supply path 34b outside the processing vessel 10. A nitrogen source 34c, a mass flow controller 34d, and a valve 34e are installed on the supply path 34b, in this order from upstream to downstream in the gas flow direction. The supply timing of nitrogen gas from the nitrogen source 34c is controlled by the valve 34e, and the flow rate is adjusted to a predetermined value by the mass flow controller 34d. The nitrogen gas flows from the supply path 34b into the supply pipe 34a and is then discharged from the supply pipe 34a into the processing vessel 10.

[0041] Each of the supply pipes 31a, 32a extends vertically along the inner wall of the processing vessel 10, has its base end bent in an L-shape and extends horizontally, and is supported to penetrate the manifold 12. A plurality of outlets 31f, 32f are provided in each of the supply pipes 31a, 32a located within the processing vessel 10. The supply pipe 33a extends vertically along a plasma partition wall 61 into the plasma generation space P (described later), has its base end bent in an L-shape and extends horizontally, and is supported to penetrate the manifold 12. A plurality of outlets 33f are provided in each of the supply pipes 33a located within the processing vessel 10. The supply pipe 34a extends horizontally within the processing vessel 10 and is supported to penetrate the side wall of the manifold 12. The supply pipe 34a has an open end and discharges nitrogen gas from the open end. Each of the supply pipes 31a, 32a, 33a, 34a is made of, for example, quartz.

[0042] The discharge ports 31f, 32f, and 33f are formed at predetermined intervals along the extension direction of the respective supply pipes 31a, 32a, and 33a. Each discharge port 31f, 32f, and 33f discharges gas in the horizontal direction. The intervals between the discharge ports 31f, 32f, and 33f are set to be the same as the intervals between the substrates W held in the boat 14, for example. The height positions of each discharge port 31f, 32f, and 33f are set to be midpoints between vertically adjacent substrates W. This allows each discharge port to efficiently supply gas to the opposing surfaces between adjacent substrates W.

[0043] The gas supply unit 30 may mix multiple types of gases and discharge the mixed gas from a single supply pipe. The supply pipes 31a, 32a, 33a, and 34a may have different shapes and arrangements. The gas supply unit 30 may include a supply unit that supplies another gas in addition to DCS gas, hydrogen fluoride gas, ammonia gas, and nitrogen gas.

[0044] The exhaust unit 40 includes a cover member 41, an exhaust pipe 42, a pressure control valve 43, and a vacuum pump 44. The cover member 41 is attached to a portion of the processing vessel 10 corresponding to the exhaust port 24 so as to cover the exhaust port 24. The cover member 41 extends vertically along the outer wall of the processing vessel 10. The exhaust pipe 42 is connected to a lower portion of the cover member 41. The pressure control valve 43 and the vacuum pump 44 are provided on the exhaust pipe 42. The pressure control valve 43 controls the pressure inside the processing vessel 10. The vacuum pump 44 evacuates the processing vessel 10.

[0045] The heating unit 50 is provided around the processing chamber 10. The heating unit 50 includes, for example, a heater. The heater heats each substrate W in the processing chamber 10 to a predetermined temperature by controlling the output.

[0046] The plasma generation mechanism 60 is provided on a part of the sidewall of the processing vessel 10. The plasma generation mechanism 60 generates plasma from the ammonia gas supplied through the supply pipe 33a. The plasma generation mechanism 60 includes a plasma partition wall 61, a pair of plasma electrodes 62, a power supply line 63, an RF power supply 64, and an insulating protective cover 65.

[0047] The plasma compartment wall 61 is hermetically welded to the outer wall of the processing vessel 10. The plasma compartment wall 61 is made of, for example, quartz. The plasma compartment wall 61 has a concave shape in horizontal cross section. The plasma compartment wall 61 covers the opening 23. The plasma compartment wall 61 forms a plasma generation space P that communicates with the inside of the processing vessel 10.

[0048] The pair of plasma electrodes 62 each have a shape elongated in the vertical direction. The pair of plasma electrodes 62 are provided on the outer surfaces of opposing walls of the plasma compartment wall 61. The pair of plasma electrodes 62 are disposed opposite each other with the opposing wall of the plasma compartment wall 61 and the plasma generation space P interposed therebetween. A power supply line 63 is connected to the lower end of each plasma electrode 62.

[0049] The power supply line 63 electrically connects each plasma electrode 62 to an RF power supply 64. For example, one end of the power supply line 63 is connected to the lower end of each plasma electrode 62, and the other end is connected to the RF power supply 64.

[0050] An RF power supply 64 is connected to the lower end of each plasma electrode 62 via a power supply line 63. The RF power supply 64 supplies RF power of, for example, 13.56 MHz to the pair of plasma electrodes 62. As a result, RF power is applied to the plasma generation space P, and plasma is generated from the ammonia gas supplied to the plasma generation space P.

[0051] The insulating protective cover 65 is attached to the outside of the plasma compartment wall 61 so as to cover the plasma compartment wall 61. A coolant passage (not shown) may be provided inside the insulating protective cover 65. In this case, the plasma electrode 62 can be cooled by flowing a coolant through the coolant passage.

[0052] The control unit 90 is, for example, a computer. The control unit 90 includes a CPU (Central Processing Unit), RAM (Random Access Memory), 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 1. The control unit 90 may be provided inside or outside the film forming apparatus 1. When the control unit 90 is provided outside the film forming apparatus 1, the control unit 90 can control the film forming apparatus 1 via communication means such as wired or wireless.

[0053] Next, an example of the operation of the film forming apparatus 1 when carrying out the film forming method according to the embodiment will be described.

[0054] First, the control unit 90 controls the lifting mechanism (not shown) to load the boat 14 holding multiple substrates W into the processing vessel 10, and then airtightly closes and seals the opening at the bottom of the processing vessel 10 with the lid 18. This causes multiple substrates W to be accommodated in the processing vessel 10. Next, the control unit 90 controls the exhaust unit 40 to reduce the pressure inside the processing vessel 10. The control unit 90 also controls the heating unit 50 to adjust the temperature of the substrates W to the first film formation temperature. Each substrate W may be the substrate 100 described above (preparation step S11).

[0055] Next, the control unit 90 controls the heating unit 50 to maintain the temperature of the substrate W at the first film formation temperature, and controls the gas supply unit 30 to alternately and repeatedly supply DCS gas and ammonia gas into the processing chamber 10. As a result, a silicon nitride film 120 is formed to cover the bottom surface 110a, the side surface 110b, and the top surface 110c of the recess 110 (film formation step S12).

[0056] Next, the control unit 90 controls the heating unit 50 to change the temperature of the substrate W from the first film formation temperature to the first etching temperature, and while maintaining the temperature of the substrate W at the first etching temperature, controls the gas supply unit 30 to supply hydrogen fluoride gas and ammonia gas into the processing chamber 10. As a result, the silicon nitride film 120 is partially etched (first etching step S13).

[0057] Next, the control unit 90 controls the heating unit 50 to change the temperature of the substrate W from the first etching temperature to the second etching temperature, and while maintaining the temperature of the substrate W at the second etching temperature, controls the gas supply unit 30 to supply hydrogen fluoride gas into the processing chamber 10. As a result, the silicon nitride film 120 is partially etched (second etching step S14).

[0058] Next, the control unit 90 controls the heating unit 50 to maintain the temperature of the substrate W at the second film formation temperature, and controls the gas supply unit 30 to alternately and repeatedly supply DCS gas and ammonia gas into the processing chamber 10. As a result, a silicon nitride film 120 is further formed on the silicon nitride film 120 remaining in the recess 110, and the silicon nitride film 120 is embedded in the recess 110 (embedding step S15).

[0059] Next, the control unit 90 increases the pressure inside the processing vessel 10 to atmospheric pressure and decreases the temperature inside the processing vessel 10 to the unloading temperature, and then controls the lifting mechanism to unload the boat 14 from the processing vessel 10. This completes the processing of the multiple substrates W held in the boat 14.

[0060] (Example 2) A film formation apparatus 200 according to a second example of the embodiment will be described with reference to Fig. 7. Fig. 7 is a vertical cross-sectional view showing the film formation apparatus 200 according to the second example of the embodiment. As shown in Fig. 7, the film formation apparatus 200 is configured as a single-wafer type apparatus that processes substrates W one by one.

[0061] The film forming apparatus 200 includes a substantially cylindrical airtight processing chamber 220. An exhaust chamber 221 is provided in the center of the bottom wall of the processing chamber 220.

[0062] The exhaust chamber 221 has, for example, a substantially cylindrical shape that protrudes downward. An exhaust flow path 222 is connected to the exhaust chamber 221, for example, at a side surface of the exhaust chamber 221.

[0063] An exhaust unit 224 is connected to the exhaust flow path 222 via a pressure adjustment unit 223. The pressure adjustment unit 223 includes a pressure adjustment valve such as a butterfly valve. The exhaust flow path 222 is configured so that the pressure inside the processing vessel 220 can be reduced by the exhaust unit 224. A transfer port 225 is provided on the side of the processing vessel 220. The transfer port 225 is configured to be freely opened and closed by a gate valve 226. The substrate W is loaded and unloaded between the processing vessel 220 and a transfer chamber (not shown) via the transfer port 225.

[0064] A mounting table 230 for holding the substrate W substantially horizontally is provided within the processing chamber 220. The mounting table 230 is formed in a substantially circular shape in a plan view and is supported by a support member 231. A substantially circular recess 232 for mounting the substrate W, for example, having a diameter of 300 mm, is formed in the surface of the mounting table 230. The recess 232 has an inner diameter that is slightly larger (for example, about 1 mm to 4 mm) than the diameter of the substrate W. The depth of the recess 232 is configured to be substantially the same as the thickness of the substrate W. The mounting table 230 is formed of a ceramic material such as aluminum nitride (AlN). The mounting table 230 may also be formed of a metal material such as nickel (Ni). Instead of the recess 232, a guide ring for guiding the substrate W may be provided around the periphery of the surface of the mounting table 230.

[0065] A grounded lower electrode 233 is embedded in the mounting table 230, for example. A temperature adjustment mechanism 234 is embedded below the lower electrode 233. The temperature adjustment mechanism 234 adjusts the mounting table 230 or the substrate W placed thereon to a set temperature based on a control signal from the control unit 290. If the mounting table 230 is made entirely of metal, the entire mounting table 230 functions as the lower electrode, and the lower electrode 233 does not need to be embedded in the mounting table 230. The mounting table 230 is provided with a plurality of (for example, three) lift pins 241 for holding and lifting the substrate W placed on the mounting table 230. The lift pins 241 may be made of, for example, ceramics such as alumina (Al2O3), quartz, or the like. The lower ends of the lift pins 241 are attached to a support plate 242. The support plate 242 is connected to a lifting mechanism 244 provided outside the processing vessel 220 via a lifting shaft 243 .

[0066] The lifting mechanism 244 is installed, for example, at the bottom of the exhaust chamber 221. The bellows 245 is provided between the lifting mechanism 244 and an opening 211 for the lifting shaft 243 formed in the bottom surface of the exhaust chamber 221. The support plate 242 may be shaped so that it can be raised and lowered without interfering with the support member 231 of the mounting table 230. The lifting pins 241 are configured to be able to be raised and lowered between an upper side and a lower side of the surface of the mounting table 230 by the lifting mechanism 244. In other words, the lifting pins 241 are configured to be able to protrude from the top surface of the mounting table 230.

[0067] An upper electrode (gas supply unit 250) is provided on a ceiling wall 227 of the processing vessel 220 via an insulating member 228. The gas supply unit 250 constitutes the upper electrode and faces the lower electrode 233. An RF power supply 251 is connected to the gas supply unit 250 via a matching unit 252. The frequency band of the RF power supply 251 is, for example, 450 kHz to 2.45 GHz. By supplying RF power from the RF power supply 251 to the upper electrode (gas supply unit 250), an RF electric field is generated between the upper electrode (gas supply unit 250) and the lower electrode 233. The gas supply unit 250 includes a hollow gas diffusion chamber 253. A number of holes 254 for dispersing and supplying the processing gas into the processing vessel 220 are arranged, for example, evenly, on the bottom surface of the gas diffusion chamber 253. A heating mechanism 255 is embedded in the gas supply unit 250, for example, above the gas diffusion chamber 253. The heating mechanism 255 is heated to a set temperature by being supplied with power from a power supply unit (not shown) based on a control signal from the control unit 290 .

[0068] A gas supply path 260 is provided in the gas diffusion chamber 253. The gas supply path 260 is connected to the gas diffusion chamber 253. A gas source 261 is connected to the upstream side of the gas supply path 260 via a gas line 262. The gas source 261 includes, for example, various processing gas supply sources, mass flow controllers, and valves (none of which are shown). The processing gas includes the gases used in the above-mentioned film formation methods. The processing gas is introduced from the gas source 261 through the gas line 262 into the gas diffusion chamber 253. The processing gas includes, for example, DCS gas, hydrogen fluoride gas, and ammonia gas.

[0069] The film forming apparatus 200 includes a control unit 290. The control unit 290 is, for example, a computer. The control unit 290 includes a CPU, RAM, ROM, 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 200. The control unit 290 may be provided inside or outside the film forming apparatus 200. When the control unit 290 is provided outside the film forming apparatus 200, the control unit 290 can control the film forming apparatus 200 via communication means such as wired or wireless.

[0070] Next, an example of the operation of the film forming apparatus 200 when carrying out the film forming method according to the embodiment will be described.

[0071] First, the control unit 290 opens the gate valve 226 and causes a transfer mechanism (not shown) to transfer the substrate W into the processing vessel 220 and place it on the mounting table 230. The control unit 290 then retracts the transfer mechanism from the processing vessel 220, and closes the gate valve 226. Next, the control unit 290 controls the exhaust unit 224 to reduce the pressure inside the processing vessel 220. The control unit 290 also controls the temperature adjustment mechanism 234 to adjust the temperature of the substrate W to the first film formation temperature. The substrate W may be the substrate 100 described above (preparation step S11).

[0072] Next, the control unit 290 controls the temperature adjustment mechanism 234 to maintain the temperature of the substrate W at the first film formation temperature, and controls the gas source 261 to alternately and repeatedly supply DCS gas and ammonia gas into the processing chamber 220. As a result, a silicon nitride film 120 is formed to cover the bottom surface 110a, the side surface 110b, and the top surface 110c of the recess 110 (film formation step S12).

[0073] Next, the control unit 290 controls the temperature adjustment mechanism 234 to change the temperature of the substrate W from the first film formation temperature to the first etching temperature, and while maintaining the temperature of the substrate W at the first etching temperature, controls the gas source 261 to supply hydrogen fluoride gas and ammonia gas into the processing container 220. As a result, the silicon nitride film 120 is partially etched (first etching step S13).

[0074] Next, the control unit 290 controls the temperature adjustment mechanism 234 to change the temperature of the substrate W from the first etching temperature to the second etching temperature, and while maintaining the temperature of the substrate W at the second etching temperature, controls the gas source 261 to supply hydrogen fluoride gas into the processing container 220. As a result, the silicon nitride film 120 is partially etched (second etching step S14).

[0075] Next, the control unit 290 controls the temperature adjustment mechanism 234 to maintain the temperature of the substrate W at the second film formation temperature, and controls the gas source 261 to alternately and repeatedly supply DCS gas and ammonia gas into the processing vessel 220. As a result, a silicon nitride film 120 is further formed on the silicon nitride film 120 remaining in the recess 110, and the silicon nitride film 120 is embedded in the recess 110 (embedding step S15).

[0076] Next, the control unit 290 unloads the substrate W from the processing vessel 220 in the reverse order to the loading of the substrate W into the processing vessel 220. With the above, the processing for one substrate W is completed.

[0077] [Experimental results] (Experiment A) In experiment A, a silicon wafer having a trench covered with a silicon nitride film was prepared, and the silicon nitride film was etched by performing the first etching step S13 on the prepared silicon wafer.

[0078] The conditions for the first etching step S13 are as follows. First etching gas: A mixture of hydrogen fluoride and ammonia gases First etching temperature: 66℃ to 69℃ Pressure: 0.2 Torr (26.7 Pa)

[0079] In Experiment A, a cross section of the silicon wafer before etching the silicon nitride film and a cross section of the silicon wafer after etching the silicon nitride film were observed using a scanning electron microscope (SEM).

[0080] 8A and 8B are diagrams showing the etched shape when the first etching step S13 is performed, in which Fig. 8A is a cross-sectional SEM image of the silicon wafer before etching the silicon nitride film, and Fig. 8B is a cross-sectional SEM image of the silicon wafer after etching the silicon nitride film.

[0081] As shown in Figure 8(a), a silicon nitride film is formed conformally along the surface of the trench before etching. As shown in Figure 8(b), after etching, a silicon nitride film is present on the bottom and side surfaces of the trench, but not on the top surface of the trench. These results demonstrate that by using a mixture of hydrogen fluoride gas and ammonia gas under low processing temperatures and low processing pressures, it is possible to selectively etch the silicon nitride film formed on the top of the trench relative to the silicon nitride film formed on the bottom.

[0082] (Experiment B) In experiment B, a silicon wafer having a trench covered with a silicon nitride film was prepared, and the silicon nitride film was etched by performing the second etching step S14 on the prepared silicon wafer.

[0083] The conditions for the second etching step S14 are as follows. Second etching gas: A mixture of hydrogen fluoride and nitrogen gases Second etching temperature: 550℃ Pressure: 1 Torr to 100 Torr (133 Pa to 133 kPa)

[0084] In Experiment B, the cross section of the silicon wafer before the silicon nitride film was etched and the cross section of the silicon wafer after the silicon nitride film was etched were observed by SEM.

[0085] 9A and 9B are diagrams showing the etched shape when the second etching step S14 is performed, in which Fig. 9A is a cross-sectional SEM image of the silicon wafer before etching the silicon nitride film, and Fig. 9B is a cross-sectional SEM image of the silicon wafer after etching the silicon nitride film.

[0086] As shown in Figure 9(a), before etching, a silicon nitride film is formed conformally along the surface of the trench. As shown in Figure 9(b), after etching, the thickness of the silicon nitride film is reduced almost uniformly over the entire bottom, side, and top surfaces of the trench. These results demonstrate that by using a high processing temperature and a mixed gas of hydrogen fluoride gas and nitrogen gas, a silicon nitride film can be etched conformally along the surface of the trench.

[0087] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0088] In the above embodiment, the first silicon-containing film and the second silicon-containing film are silicon nitride films, but the present disclosure is not limited thereto. The first silicon-containing film and the second silicon-containing film are films containing at least one of nitrogen atoms, oxygen atoms, and carbon atoms. The first silicon-containing film and the second silicon-containing film may be silicon oxide films. The first silicon-containing film and the second silicon-containing film may be silicon oxynitride films.

[0089] In the above embodiment, the batch-type film forming apparatus 1 and the single-wafer-type film forming apparatus 200 are described, but the present disclosure is not limited thereto. For example, the present disclosure may be an apparatus in which multiple substrates (e.g., two to six) are placed on a mounting table and multiple substrates are processed at once. [Explanation of symbols]

[0090] 100 boards 110 recess 120 Silicon nitride film S11 Preparation process S12 Film formation process S13 First etching process S14 Second etching process S15 Embedding process S21 Preparation process S22 1st film formation process S23 First etching process S24 Second etching process S25 2nd film formation process S26 Judgment process

Claims

1. (a) providing a substrate having a recess covered with a first silicon-containing film; (b) supplying a first etching gas to the substrate maintained at a first temperature to partially etch the first silicon-containing film; (c) supplying a second etching gas to the substrate maintained at a second temperature higher than the first temperature to partially etch the first silicon-containing film; (d) forming a second silicon-containing film on the first silicon-containing film remaining in the recess; and The steps (b) and (c) are performed without using plasma; the step (b) is performed under first conditions under which the first silicon-containing film formed in the upper portion of the recess is more easily etched than the first silicon-containing film formed in the lower portion of the recess; the step (c) is performed under second conditions under which the first silicon-containing film formed in the lower portion of the recess is more easily etched than under the first conditions; Film formation method.

2. The steps (b), (c), and (d) are carried out in this order. The film forming method according to claim 1 .

3. The steps (c) and (d) are repeated in this order. The film forming method according to claim 2 .

4. an upper surface of the recess is covered with the first silicon-containing film; the step (b) includes removing the first silicon-containing film formed on the upper surface of the recessed portion to expose at least a portion of the upper surface of the recessed portion; The film forming method according to claim 1 .

5. an upper portion of the recess is closed by the first silicon-containing film; the step (c) includes removing the first silicon-containing film that closes an upper portion of the recess; The film forming method according to claim 1 .

6. the step (b) includes etching the first silicon-containing film by anisotropic etching; the step (c) includes etching the first silicon-containing film by isotropic etching; The film forming method according to claim 1 .

7. The step (c) is carried out under a higher pressure atmosphere than the step (b). The film forming method according to claim 1 .

8. (e) between the step (b) and the step (c), a step of increasing the temperature of the substrate from the first temperature to the second temperature; The film forming method according to claim 1 .

9. step (d) includes maintaining the substrate at a third temperature; The second temperature is the same as the third temperature. The film forming method according to claim 1 .

10. the first temperature is equal to or higher than 50°C and equal to or lower than 90°C, The second temperature is 300°C or higher and 650°C or lower. The film forming method according to claim 1 .

11. the first etching gas includes a halogen-containing gas and a basic gas; the second etching gas does not contain a basic gas but contains a halogen-containing gas; The film forming method according to claim 1 .

12. the first silicon-containing film and the second silicon-containing film are films containing at least one of nitrogen atoms, oxygen atoms, and carbon atoms; The film forming method according to claim 1 .

13. a processing vessel for accommodating a substrate; a gas supply unit that supplies a gas into the processing chamber; a heating unit that heats the substrate accommodated in the processing vessel; A control unit; Equipped with The control unit (a) providing a substrate having a recess covered with a first silicon-containing film; (b) supplying a first etching gas to the substrate maintained at a first temperature to partially etch the first silicon-containing film; (c) supplying a second etching gas to the substrate maintained at a second temperature higher than the first temperature to partially etch the first silicon-containing film; (d) forming a second silicon-containing film on the first silicon-containing film remaining in the recess; and controlling the gas supply unit and the heating unit to perform the steps of: The steps (b) and (c) are performed without using plasma; the step (b) is performed under first conditions under which the first silicon-containing film formed in the upper portion of the recess is more easily etched than the first silicon-containing film formed in the lower portion of the recess; the step (c) is performed under second conditions under which the first silicon-containing film formed in the lower portion of the recess is more easily etched than under the first conditions; Film deposition equipment.

Images