Film forming method

Abstract

To provide a film forming method that restrains occurrence of voids when a film is embedded into a recess portion including a narrow portion.SOLUTION: A film forming method for filling a substrate having a recess portion including a narrowed portion, includes (a) a step S2 of supplying a first silicon-containing gas and a first nitrogen-containing gas to the substrate such that a first film is thicker at an opening portion of the recess portion than at a bottom portion of the recess portion, a step S3 of supplying a second silicon-containing gas and a second nitrogen-containing gas to the substrate to form a second film having the same thickness at the bottom portion and the opening portion of the recess portion or to form the second film that is thicker at the bottom portion of the recess portion than at the opening portion of the recess portion, a step S4 of partially etching the first film and the second film formed in the recess portion, and a step S6 of performing a cycle of steps S3 and S4 at plural times, after performing the cycle at plural times, supplying a third silicon-containing gas and a third nitrogen-containing gas to the substrate to form a third film having the same thickness at the bottom portion and the opening portion of the recess portion or to form the third film that is thicker at the bottom portion of the recess portion than at the opening portion of the recess portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a film forming method.

Background Art

[0002] In the semiconductor manufacturing process, as the structure is miniaturized, it is required to fill a recess with a high aspect ratio without voids (gaps). As an example of a process for filling a recess with a film, a technique is known in which deposition and etching are alternately repeated to fill the film bottom-up from the bottom of the recess (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of suppressing the generation of voids when filling a film into a recess having a constricted portion.

Means for Solving the Problems

[0005] A film formation method according to an aspect of the present disclosure is a film formation method for embedding a film in a recess of a substrate in which a recess including a constriction is formed, the method including: (a) supplying a first silicon-containing gas and a first nitrogen-containing gas to the substrate to form a first film thicker at an opening than at a bottom of the recess; (b) supplying a second silicon-containing gas and a second nitrogen-containing gas to the substrate to form a second film having the same thickness at the bottom and the opening of the recess, or forming the second film thicker at the bottom than at the opening of the recess; (c) partially etching the first film and the second film formed in the recess; and (d) supplying a third silicon-containing gas and a third nitrogen-containing gas to the substrate to form a third film having the same thickness at the bottom and the opening of the recess, or forming the third film thicker at the bottom than at the opening of the recess, wherein a plurality of cycles each including the steps (b) and (c) are performed, and the step (d) is performed after the plurality of cycles are performed.

Advantages of the Invention

[0006] According to the present disclosure, generation of voids can be suppressed when embedding a film in a recess having a constriction.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Best Mode for Carrying Out 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 members or components are denoted by the same or corresponding reference numerals, and duplicate explanations are omitted.

[0009] 〔Embedding Process〕 In semiconductor manufacturing processes, as the structures are miniaturized, it is required to embed a film in a recess having a high aspect ratio without voids (gaps). As an example of a process for embedding a film in a recess, a technique of embedding a film bottom-up from the bottom of the recess by alternately repeating deposition and etching (hereinafter also referred to as the "DED process") is known. By using the DED process, the generation of voids can be suppressed.

[0010] However, when a film is embedded in a recess of a substrate in which a recess including a constricted portion is formed using the DED process, damage may occur to the base layer at the opening of the recess. Hereinafter, with reference to FIG. 7, the reason why damage may occur to the base layer will be explained. FIG. 7 is a diagram for explaining the embedding characteristics when a film is embedded in a recess including a constricted portion by a conventional film formation method.

[0011] FIG. 7(a) is a schematic cross-sectional view of a substrate in which a recess including a constricted portion is formed. As shown in FIG. 7(a), the substrate 900 has a base layer 920 in which a recess 910 is formed. The recess 910 includes an opening 911, a constricted portion 912, and a bottom 913. The opening 911 is a portion that opens at the upper part of the recess 910. The constricted portion 912 is formed midway from the opening 911 to the bottom 913, and is a portion having a narrower width in cross-section than the opening 911 and the bottom 913. The bottom 913 is a portion including the bottom surface 914 of the recess 910 at the lower part of the recess 910.

[0012] FIG. 7(b) is a schematic cross-sectional view of a substrate when a film is conformally formed in the recess shown in FIG. 7(a), showing the state after deposition in the DED process. As shown in FIG. 7(b), in the recess 910 of the substrate 900, a film 930 is conformally formed to such an extent that the constricted portion 912 is not blocked.

[0013] FIG. 7(c) is a schematic cross-sectional view of a substrate when dry etching is performed on a substrate on which a film is conformally formed in a recess, showing the state after etching in the DED process. As shown in FIG. 7(c), in the substrate 900 in which the recess 910 including the constricted portion 912 is formed, in order to embed the film 930 in the bottom 913 by deposition after etching, it is preferable to etch and remove the film 930 deposited on the constricted portion 912. By the way, in the etching of the DED process, the film 930 conformally formed in the recess 910 is etched in a V shape in cross-sectional view. That is, the etching is performed under the condition that the etching rate of the opening 911 with respect to the film 930 is higher than that of the bottom 913. Therefore, before removing the film 930 deposited on the constricted portion 912, the film 930 deposited on the opening 911 is removed. Then, if dry etching is continued in a state where the film 930 deposited on the opening 911 is removed, damage occurs to the underlying layer 920, such as a part of the underlying layer 920 being scraped off. This is because the selectivity ratio to the underlying layer is not infinite.

[0014] Hereinafter, a film formation method according to an embodiment that can embed a film without voids while suppressing damage to the underlying layer in a recess having a constricted portion will be described.

[0015] 〔Film Formation Method〕 With reference to FIGS. 1 and 2, an example of the film formation method according to the embodiment will be described. Hereinafter, the case of forming and embedding a silicon nitride film (SiN film) in a recess will be described as an example.

[0016] (Step S1) First, in step S1, a substrate having a recess including a constriction is prepared. As shown in FIG. 2(a), the substrate 100 has a base 120 in which a recess 110 is formed. The recess 110 includes an opening 111, a constriction 112, and a bottom 113. The opening 111 is a portion that opens at the upper part of the recess 110. The constriction 112 is formed midway from the opening 111 to the bottom 113, and is a portion having a width narrower than that of the opening 111 and the bottom 113 in a cross-sectional view. The bottom 113 is a portion including the bottom surface 114 of the recess 110 at the lower part of the recess 110. In the illustrated example, the recess 110 has a shape that continuously narrows from the opening 111 toward the constriction 112 and continuously expands from the constriction 112 toward the bottom 113. However, the recess 110 is not limited to the illustrated shape, and may have another shape including the constriction 112 midway from the opening 111 to the bottom 113. The recess 110 is a trench, a hole, or the like. The base 120 is made of, for example, silicon or an insulating film, and may partially contain a metal or a metal compound.

[0017] (Step S2) Next, in step S2, as shown in FIG. 2(b), a SiN film 130 is formed in the recess 110 under the condition of being formed thicker at the opening 111 than at the bottom 113 of the recess 110 (hereinafter also referred to as the "low coverage condition").

[0018] Step S2 may include forming the SiN film 130 by, for example, atomic layer deposition (ALD: Atomic Layer Deposition).

[0019] When forming the SiN film 130 by ALD, it is preferable to alternately repeat the steps of supplying a silicon-containing gas to the substrate 100 and exposing the substrate 100 to plasma generated from a gas containing N2. In the step of supplying a silicon-containing gas to the substrate 100, the silicon-containing gas is adsorbed on the substrate 100, and in the step of exposing the substrate 100 to plasma generated from a gas containing N2, the silicon-containing gas adsorbed on the substrate 100 is nitrided to form a SiN layer. Here, since the radicals in the plasma generated from the gas containing N2 have a short lifetime, it is difficult to reach the bottom 113 of the recess 110. Therefore, the SiN film 130 formed at the bottom 113 of the recess 110 becomes thin. As a result, the SiN film 130 can be formed particularly thick at the opening 111 rather than at the bottom 113 of the recess 110. The gas containing N2 may be, for example, only N2 gas, or may further contain NH3 or H2. However, from the viewpoint of increasing the film thickness difference between the bottom 113 and the opening 111, the gas containing N2 is preferably only N2.

[0020] Also, when forming the SiN film 130 by ALD, it is preferable to alternately repeat the steps of supplying a silicon-containing gas to the substrate 100 in a supply rate-limiting state and supplying a nitrogen-containing gas to the substrate 100. The supply rate-limiting state means a region where the amount of the processing gas supplied into the processing vessel in which the substrate 100 is accommodated is very small, and the film formation rate is mainly dominated by the supply amount of the processing gas. For example, the supply rate-limiting state can be realized by reducing the supply amount of the processing gas and increasing the processing temperature. By supplying the silicon-containing gas to the substrate 100 in a supply rate-limiting state, the silicon-containing gas supplied to the recess 110 is adsorbed and consumed by the opening 111 and the constriction 112 before reaching the bottom 113. As a result, the SiN film 130 can be formed particularly thick at the opening 111 rather than at the bottom 113 of the recess 110. The gas supplied to the substrate 100 in a supply rate-limiting state is not limited to the silicon-containing gas, and may be a nitrogen-containing gas, or may be both the silicon-containing gas and the nitrogen-containing gas.

[0021] Also, when forming the SiN film 130 by ALD, the process may include a step of forming the SiN film 130 and a step of etching the SiN film 130. The step of forming the SiN film 130 includes repeating a cycle including a step of supplying a silicon-containing gas to the substrate 100 and a step of supplying a nitrogen-containing gas to the substrate 100, and may further include a step of exposing the substrate 100 to plasma generated from a gas containing He. In the step of supplying the silicon-containing gas to the substrate 100, the silicon-containing gas is adsorbed on the substrate 100, and in the step of supplying the nitrogen-containing gas to the substrate 100, the silicon-containing gas adsorbed on the substrate 100 is nitrided to form a SiN layer. Also, in the step of exposing the substrate 100 to plasma generated from a gas containing He, the SiN layer and / or the SiN film 130 is modified into a film with high etching resistance. Here, in the modification by plasma generated from a gas containing He, the opening 111 is more likely to be modified into a film with high etching resistance than the bottom 113 of the recess 110. Therefore, in the step of etching the SiN film 130 performed after the step of forming the SiN film 130, the amount of etching of the SiN film 130 at the bottom 113 of the recess 110 is larger than that at the opening 111. As a result, the SiN film 130 can be formed particularly thick at the opening 111 rather than the bottom 113 of the recess 110. Note that the step of supplying the nitrogen-containing gas to the substrate 100 may be changed to a step of exposing the substrate 100 to plasma generated from the nitrogen-containing gas. Also, the gas containing He may contain, for example, Ar. Also, the step of etching the SiN film 130 may be either dry etching or wet etching. When etching the SiN film 130 by dry etching, NF3, a CHF-based gas, etc. can be used as the etching gas. Also, gases such as O2, N2, and H2 may be added to those etching gases. When etching the SiN film 130 by wet etching, diluted hydrofluoric acid (DHF) etc. can be used.

[0022] Further, step S2 may include forming the SiN film 130 by chemical vapor deposition (CVD). By forming the SiN film 130 by CVD, the SiN film 130 can be formed thicker at the opening 111 than at the bottom 113 of the recess 110.

[0023] When forming the SiN film 130 by CVD, it may include forming the SiN film 130 by thermal CVD (Th-CVD) in which the reaction between the silicon-containing gas and the nitrogen-containing gas is carried out by heat. That is, it may include forming the SiN film 130 by supplying the silicon-containing gas and the nitrogen-containing gas to the substrate 100.

[0024] Also, when forming the SiN film 130 by CVD, it may include forming the SiN film 130 by plasma CVD (PE-CVD) in which the reaction between the silicon-containing gas and the nitrogen-containing gas is assisted by plasma. That is, it may include forming the SiN film 130 by exposing the substrate 100 to the plasma generated from the silicon-containing gas and the nitrogen-containing gas.

[0025] Also, when forming the SiN film 130 by CVD, it is preferable to supply the silicon-containing gas and the nitrogen-containing gas to the substrate 100 in a rate-determining state. By supplying the silicon-containing gas and the nitrogen-containing gas to the substrate 100 in a rate-determining state, the silicon-containing gas and the nitrogen-containing gas supplied to the recess 110 are consumed at the opening 111 and the constriction 112 before reaching the bottom 113. As a result, the SiN film 130 can be formed particularly thicker at the opening 111 than at the bottom 113 of the recess 110.

[0026] In addition, as the silicon-containing gas used in step S2, for example, one or more gases selected from the group consisting of hexachlorodisilane (HCD), monosilane [SiH4], disilane [Si2H6], dichlorosilane (DCS), hexaethylaminodisilane, hexamethyldisilazane (HMDS), tetrachlorosilane (TCS), disilylamine (DSA), trisilylamine (TSA), bistart-butylaminosilane (BTBAS), butylaminosilane, dimethylaminosilane, bisdimethylaminosilane, trimethylaminosilane, diethylaminosilane, bisdiethylaminosilane, dipropylaminosilane, diisopropylaminosilane, hexakisethylaminodisilane, etc. can be used.

[0027] In addition, as the nitrogen-containing gas used in step S2, for example, one or more gases selected from the group consisting of nitrogen (N2), ammonia (NH3), diazene (N2H2), hydrazine (N2H4), and organic hydrazine compounds such as monomethylhydrazine (CH3(NH)NH2) can be used.

[0028] (Step S3) Next, in step S3, as shown in FIG. 2(c), the SiN film 140 is formed in the recess 110 under the condition that the bottom 113 and the opening 111 of the recess 110 are formed to have the same thickness, or under the condition that the bottom 113 of the recess 110 is formed thicker than the opening 111 of the recess 110.

[0029] Step S3 may include, for example, forming the SiN film 140 by ALD. By forming the SiN film 140 by ALD, the SiN film 140 can be formed with the same thickness (conformal) at the bottom 113 and the opening 111 of the recess 110.

[0030] When forming the SiN film 140 by ALD, it may include forming the SiN film 140 by thermal ALD (Th-ALD) in which the reaction between the silicon-containing gas and the nitrogen-containing gas is carried out by heat. That is, it may include forming the SiN film 140 by alternately repeating the step of supplying the silicon-containing gas to the substrate 100 and the step of supplying the nitrogen-containing gas to the substrate 100. In the step of supplying the silicon-containing gas to the substrate 100, the silicon-containing gas is adsorbed on the substrate 100, and in the step of supplying the nitrogen-containing gas to the substrate 100, the silicon-containing gas adsorbed on the substrate 100 is nitrided to form a SiN layer. As the nitrogen-containing gas used in thermal ALD, NH3, N2H4, etc. can be used.

[0031] Also, when forming the SiN film 140 by ALD, it may include forming the SiN film 140 by plasma ALD (PE-ALD) in which the reaction between the silicon-containing gas and the nitrogen-containing gas is assisted by plasma. That is, it may include alternately repeating the step of supplying the silicon-containing gas to the substrate 100 and the step of exposing the substrate 100 to the plasma generated from the gas containing the nitrogen-containing gas. As the nitrogen-containing gas used in plasma ALD, for example, 1 or more gases selected from the group consisting of NH3, N2 / H2, and NH3 / N2 / H2 can be used. A noble gas may be added to the nitrogen-containing gas.

[0032] Also, when forming the SiN film 140 by ALD, the SiN layer and / or the SiN film 140 may be modified into a film with high etching resistance by exposing the substrate 100 to the plasma generated from the modifying gas. That is, it may include repeating the step of supplying the silicon-containing gas to the substrate 100, the step of exposing the substrate 100 to the plasma generated from the gas containing the nitrogen-containing gas, and the step of exposing the substrate 100 to the plasma generated from the modifying gas. Examples of the modifying gas may include He, H2, etc.

[0033] Further, step S3 may include a step of forming an inhibition region that inhibits the deposition of the SiN film on the side that opens above the constriction portion 112 in the recess 110 (that is, the opening portion 111 side shallower than the constriction portion 112). Thereby, since the deposition of the SiN film 140 on the opening portion 111 of the recess 110 is inhibited, the SiN film 140 can be formed thicker at the bottom 113 than at the opening portion 111 of the recess 110. The step of forming the inhibition region may include, for example, exposing the substrate 100 to plasma generated from a gas containing a halogen. As the gas containing a halogen, for example, fluorine gas (F2), chlorine gas (Cl2), hydrogen fluoride gas (HF), etc. can be used. Further, the step of forming the inhibition region may include, for example, exposing the substrate 100 to plasma generated from a gas containing N2.

[0034] Note that, as the silicon-containing gas used in step S3, for example, the same gas as the silicon-containing gas used in step S2 can be used, and silicon halide, aminosilane, etc. can be used.

[0035] (Step S4) Next, in step S4, as shown in FIG. 2(d), the SiN films 130 and 140 formed in the recess 110 are etched under etching conditions where the etching rate of the opening portion 111 is higher than that of the bottom 113, and the SiN films 130 and 140 are partially removed. Thereby, since the opening portion 111 and the constriction portion 112 expand, the SiN film 140 can be embedded on the side of the bottom 113 rather than the constriction portion 112 in step S3 performed again later.

[0036] In step S4, since the etching of the SiN films 130 and 140 is performed under the condition that the etching rate of the opening 111 with respect to the SiN film 130 is higher than that of the bottom 113, the amount of etching of the SiN films 130 and 140 in the opening 111 becomes larger than that in the constriction 112. Therefore, before removing the SiN films 130 and 140 formed in the constriction 112, the SiN films 130 and 140 formed in the opening 111 may be removed and the base 120 may be exposed. However, in the present embodiment, the SiN film 130 is formed thicker in the opening 111 than at the bottom 113 of the recess 110 in step S2. Thereby, before the SiN films 130 and 140 formed in the constriction 112 are removed, it is possible to suppress the removal of the SiN films 130 and 140 formed in the opening 111. Therefore, it is possible to suppress the exposure of the base 120 in the opening 111. As a result, even when the selectivity to the base is not infinite, it is possible to suppress damage to the base 120 in the opening 111.

[0037] Step S4 may include supplying NF3 or a CHF-based gas to the substrate 100. Thereby, the SiN films 130 and 140 formed in the recess 110 can be etched under the etching conditions in which the etching rate of the opening 111 is higher than that of the bottom 113.

[0038] Also, step S4 may include supplying NF3 or a CHF-based gas to the substrate 100 in a rate-determining state. Thereby, the SiN films 130 and 140 formed in the recess 110 can be etched under the etching conditions in which the etching rate of the opening 111 is higher than that of the bottom 113.

[0039] (Step S5) Next, in step S5, it is determined whether the number of repetitions of the cycle including steps S3 and S4 has reached a predetermined number. If the number of repetitions of the cycle including steps S3 and S4 has not reached the predetermined number, steps S3 and S4 are performed again. That is, until the predetermined number is reached, the film formation of the conformal or thin SiN film 140 in the opening 111 and the etching of the SiN films 130 and 140 are repeated. As a result, as shown in FIG. 2(e), a voidless SiN film 140 can be embedded on the bottom 113 side rather than the constriction 112 in the recess 110. When the number of repetitions of the cycle including steps S3 and S4 reaches the predetermined number, the process proceeds to step S6. The predetermined number is one or more.

[0040] Also, when the SiN film 130 formed in the opening 111 in step S4 is removed and the base 120 is exposed, or there is a possibility of exposure, step S2 may be performed after step S4 and before step S3 while steps S3 and S4 are being repeated. That is, a part of a plurality of cycles each including steps S3 and S4 may include step S2.

[0041] (Step S6) Next, in step S6, the SiN film 140 is formed in the recess 110 under the condition that the bottom 113 of the recess 110 and the opening 111 are formed to have the same thickness, or under the condition that the bottom 113 is formed thicker than the opening 111 of the recess 110. As a result, as shown in FIG. 2(f), a voidless SiN film 140 can be embedded in the recess 110.

[0042] Step S6 may include, for example, forming the SiN film 140 by ALD. By forming the SiN film 140 by ALD, the SiN film 140 can be formed to have the same thickness (conformal) at the bottom 113 and the opening 111 of the recess 110. Also, by forming the SiN film 140 by ALD, a SiN film 140 can be formed in which the bottom 113 of the recess 110 is thicker than the opening 111. The method of forming the SiN film 140 by ALD may be the same as the method of forming the SiN film 140 by ALD in step S3.

[0043] According to the embodiment described above, for a substrate having a concave portion including a constricted portion, an SiN film is formed under low coverage conditions, and then conformal or thin-opening SiN film deposition and etching of the SiN film are repeated to embed the SiN film in the concave portion. As a result, the SiN film formed under low coverage conditions during etching of the SiN film functions as a protective film that prevents exposure of the underlying layer. Thereby, it is possible to suppress damage to the underlying layer during etching of the SiN film. Further, since the SiN film is formed in the concave portion while repeating conformal or thin-opening SiN film deposition and etching of the SiN film, blockage of the constricted portion can be prevented. As a result, generation of voids when embedding the film in the concave portion can be suppressed.

[0044] 〔Processing System〕 With reference to FIG. 3, an example of a processing system for implementing the film deposition method of the embodiment will be described.

[0045] The processing system PS includes processing apparatuses PM1 to PM4, a vacuum transfer chamber VTM, load lock chambers LL1 to LL3, an atmospheric transfer chamber LM, load ports LP1 to LP3, and an overall control unit CU0.

[0046] The processing apparatuses PM1 to PM4 are each connected to the vacuum transfer chamber VTM via gate valves G11 to G14. The interiors of the processing apparatuses PM1 to PM4 are depressurized to a predetermined vacuum atmosphere, and a desired process is performed on the substrate W therein.

[0047] The interior of the vacuum transfer chamber VTM is depressurized to a predetermined vacuum atmosphere. The vacuum transfer chamber VTM is provided with a transfer mechanism TR1 capable of transferring the substrate W in a depressurized state. The transfer mechanism TR1 transfers the substrate W to the processing apparatuses PM1 to PM4 and the load lock chambers LL1 to LL3. The transfer mechanism TR1 has, for example, two transfer arms FK11 and FK12 that can move independently.

[0048] The load lock chambers LL1 to LL3 are each connected to the vacuum transfer chamber VTM via gate valves G21 to G23 and to the atmospheric transfer chamber LM via gate valves G31 to G33. The inside of the load lock chambers LL1 to LL3 can be switched between an atmospheric atmosphere and a vacuum atmosphere.

[0049] The inside of the atmospheric transfer chamber LM is in an atmospheric atmosphere, and for example, a downflow of clean air is formed. An aligner AN for aligning the substrate W is provided inside the atmospheric transfer chamber LM. Also, a transfer mechanism TR2 is provided in the atmospheric transfer chamber LM. The transfer mechanism TR2 transfers the substrate W to the load lock chambers LL1 to LL3, the carriers C of the load ports LP1 to LP3 described later, and the aligner AN.

[0050] The load ports LP1 to LP3 are provided on the long side wall surface of the atmospheric transfer chamber LM. The load ports LP1 to LP3 are attached with the carrier C in which the substrate W is accommodated or an empty carrier C. As the carrier C, for example, a FOUP (Front Opening Unified Pod) can be used.

[0051] The overall control unit CU may be, for example, a computer. The overall control unit CU 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 each part of the processing system PS. For example, the overall control unit CU executes the operations of the processing devices PM1 to PM4, the operations of the transfer mechanisms TR1 and TR2, the opening and closing of the gate valves G11 to G14, G21 to G23, G31 to G33, the switching of the atmosphere inside the load lock chambers LL1 to LL3, etc.

[0052] In the processing system PS of the embodiment, at least one of the processing apparatuses PM1 to PM4 is used to continuously perform steps S2 to S4 and S6 in the film forming method of the embodiment in a reduced pressure atmosphere. For example, steps S2 to S4 and S6 may be continuously performed using one of the processing apparatuses PM1 to PM4. Further, for example, steps S2 and S3 may be continuously performed using one of the processing apparatuses PM1 to PM4, step S4 may be performed using another one, and step S6 may be performed using still another one. Further, for example, the processing apparatuses PM1 to PM4 may each perform different steps S2 to S4 and S6.

[0053] 〔Processing Apparatus〕 With reference to FIG. 4, an example of the processing apparatus used as the processing apparatuses PM1 to PM4 included in the processing system PS of FIG. 3 will be described.

[0054] The processing apparatus includes a processing chamber 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.

[0055] The processing chamber 1 is made of a metal such as aluminum and has a substantially cylindrical shape. The processing chamber 1 houses a substrate W. The substrate W is, for example, a semiconductor wafer. An inlet / outlet 11 for loading or unloading the substrate W is formed in the side wall of the processing chamber 1. The inlet / outlet 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 chamber 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 top wall 14 is provided on the upper surface of the exhaust duct 13 so as to close the upper opening of the processing chamber 1 via an insulator member 16. The space between the exhaust duct 13 and the insulator member 16 is hermetically sealed by a seal ring 15. A partitioning member 17 divides the inside of the processing chamber 1 vertically when the mounting table 2 (and the cover member 22) rises to a processing position described later.

[0056] The mounting stage 2 horizontally supports the substrate W inside the processing container 1. The mounting stage 2 is formed in a disc shape with a size corresponding to the substrate W and is supported by the support member 23. The mounting stage 2 is made of a ceramic material such as AlN, or a metal material such as aluminum or nickel alloy, and a heater 21 for heating the substrate W is embedded inside. The heater 21 is supplied with power from a heater power source (not shown) and generates heat. Then, by controlling the output of the heater 21 based on the temperature signal of a thermocouple (not shown) provided near the upper surface of the mounting stage 2, the substrate W is controlled to a predetermined temperature. The mounting stage 2 is provided with a cover member 22 formed of a ceramic such as alumina so as to cover the outer peripheral region and the side surface of the upper surface.

[0057] A support member 23 for supporting the mounting stage 2 is provided on the bottom surface of the mounting stage 2. The support member 23 extends downward from the center of the bottom surface of the mounting stage 2 through a hole formed in the bottom wall of the processing container 1 and is connected to the lifting mechanism 24 at its lower end. The mounting stage 2 is lifted and lowered by the lifting mechanism 24 via the support member 23 between the processing position shown in FIG. 1 and the transfer position where the substrate W can be transferred shown by the two-dot chain line below. A flange portion 25 is attached below the processing container 1 of the support member 23. A bellows 26 is provided between the bottom surface of the processing container 1 and the flange portion 25. The bellows 26 partitions the atmosphere inside the processing container 1 from the outside air and expands and contracts as the mounting stage 2 moves up and down.

[0058] Near the bottom surface of the processing container 1, three (only two are shown) wafer support pins 27 are provided so as to protrude upward from the lifting plate 27a. The wafer support pins 27 are lifted and lowered via the lifting plate 27a by a lifting mechanism 28 provided below the processing container 1. The wafer support pins 27 are inserted into through holes 2a provided in the mounting stage 2 at the transfer position and can protrude and retract with respect to the upper surface of the mounting stage 2. By lifting and lowering the wafer support pins 27, the substrate W is transferred between the transfer mechanism (not shown) and the mounting stage 2.

[0059] The shower head 3 supplies the processing gas in a shower form into the processing vessel 1. The shower head 3 is made of metal, is provided so as to face the mounting table 2, and has substantially the same diameter as the mounting table 2. The shower head 3 has a main body portion 31 and a shower plate 32. The main body portion 31 is fixed to the top wall 14 of the processing vessel 1. The shower plate 32 is connected below the main body portion 31. A gas diffusion space 33 is formed between the main body portion 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 top wall 14 of the processing vessel 1 and the main body portion 31. An annular protrusion 34 protruding downward is formed at the peripheral edge of the shower plate 32. Gas discharge holes 35 are formed in the flat portion inside the annular protrusion 34. In a state where the mounting table 2 is present at the processing position, a processing space 38 is formed between the mounting table 2 and the shower plate 32, and an annular gap 39 is formed by the upper surface of the cover member 22 and the annular protrusion 34 being close to each other.

[0060] The exhaust section 4 exhausts the inside of the processing vessel 1. The exhaust section 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, the gas in the processing vessel 1 reaches the exhaust duct 13 through the slit 13a, and is exhausted by the exhaust mechanism 42 through the exhaust pipe 41 from the exhaust duct 13.

[0061] The gas supply section 5 supplies various processing gases to the shower head 3. The gas supply section 5 includes a gas source 51 and a gas line 52. The gas source 51 includes, for example, a supply source of various processing gases, a mass flow controller, and valves (none of which are shown). The various processing gases include the gases used in the film forming method of the above-described embodiment. The various gases are introduced from the gas source 51 into the gas diffusion space 33 through the gas line 52 and the gas introduction hole 36.

[0062] Further, the processing apparatus is a capacitively coupled plasma apparatus, where 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 directly without a capacitor, for example, 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.

[0063] 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 matcher 82, and a power supply line 83. The RF power source 81 is a power source that generates RF power. The RF power has a frequency suitable for plasma generation. The frequency of the RF power is, for example, within the 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 matcher 82 and the power supply line 83. The matcher 82 has a circuit for matching the load impedance to the internal impedance of the RF power source 81. Although the RF power supply unit 8 has been described as supplying RF power to the shower head 3 serving as the upper electrode, it is not limited thereto. A configuration that supplies RF power to the mounting table 2 serving as the lower electrode may also be adopted.

[0064] 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 processing apparatus. The control unit 9 may be provided inside the processing apparatus or outside it. When the control unit 9 is provided outside the processing apparatus, the control unit 9 can control the processing apparatus by means of communication means such as wired or wireless communication.

[0065] 〔Evaluation Results〕 Referring to FIGS. 5 and 6, a SiN film was formed in the recess (trench) under low coverage conditions used in step S2 of the film forming method of the embodiment, and the formed SiN film was observed with an electron microscope.

[0066] First, a substrate including a recess formed by an amorphous silicon (a-Si) film was prepared on the SiN film. Next, as the low coverage conditions, a step of supplying a silicon-containing gas to the substrate and a step of exposing the substrate to plasma generated from a gas containing N2 were alternately repeated to form a SiN film in the recess. As the silicon-containing gas, bisdiethylaminosilane (BDEAS) was used. As the gas containing N2, a mixed gas of N2 and Ar was used. Specifically, in a processing apparatus as shown in FIG. 4, for example, while maintaining the pressure at 0.1 to 50 Torr (1.3×10 1 ~6.7×10 3 Pa), a step of supplying BDEAS at a specific flow rate for 0.05 to 1.0 seconds and a step of exposing the substrate to plasma of 10 to 1000 W power generated from a specific flow rate of N2 for 0.1 to 6.0 seconds were alternately repeated to form a SiN film in the recess.

[0067] FIG. 5 is a diagram showing the result of forming a SiN film in the recess under low coverage conditions, and shows the observation result by a scanning electron microscope (SEM).

[0068] As shown in FIG. 5, it can be seen that a SiN film is formed thicker at the opening than at the bottom of the recess. From this result, it was shown that by alternately repeating the step of supplying a silicon-containing gas to the substrate and the step of exposing the substrate to plasma generated from a gas containing N2, a SiN film can be formed thicker at the opening than at the bottom of the recess.

[0069] Next, a substrate including a recess formed of crystalline silicon (Si) was prepared. Then, as low coverage conditions, a step of forming a SiN film and a step of etching the SiN film were performed in this order to form a SiN film in the recess. In the step of forming the SiN film, a cycle including a step of supplying a silicon-containing gas to the substrate, a step of exposing the substrate to plasma generated from a nitrogen-containing gas, and a step of exposing the substrate to plasma generated from a gas containing He was repeated. In the step of etching the SiN film, wet etching using hydrofluoric acid was performed. Dichlorosilane (DCS) was used as the silicon-containing gas. NH3 was used as the nitrogen-containing gas. A mixed gas of He and Ar was used as the gas containing He. Specifically, in a processing apparatus as shown in FIG. 4, for example, while maintaining the pressure at 0.1 to 50 Torr (1.3×10 1 ~6.7×10 3 Pa), a step of supplying DCS at a specific flow rate for 0.05 to 1.0 seconds, a step of exposing to plasma of 100 to 3000 W of power generated from a specific flow rate of NH3 for 1.0 to 10.0 seconds, and a step of exposing to plasma of 10 to 1000 W of power generated from a specific flow rate of He for 1.0 to 10.0 seconds were repeated to form a SiN film in the recess.

[0070] FIG. 6 is a diagram showing the result of forming a SiN film in the recess under low coverage conditions, and shows the observation result by a transmission electron microscope (TEM: Transmission Electron Microscope). FIG. 6(a) shows the observation result by TEM after the step of forming the SiN film, and FIG. 6(b) shows the observation result by TEM after the step of etching the SiN film.

[0071] As shown in Fig. 6(a), it can be seen that a conformal SiN film is formed in the recess after the step of forming the SiN film. Also, as shown in Fig. 6(b), it can be seen that most of the SiN film formed at the bottom of the recess is removed and the SiN film formed at the opening of the recess remains after the step of etching the SiN film. From these results, it was shown that by exposing the substrate to plasma generated from a gas containing He in the step of forming the SiN film and then etching the SiN film formed in the step of forming the SiN film, a thicker SiN film can be formed at the opening than at the bottom of the recess.

[0072] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The above embodiments may be omitted, substituted, or changed in various forms without departing from the scope and spirit of the appended claims.

[0073] In the above embodiments, the case where the processing apparatus is a capacitively coupled plasma apparatus has been described, but the present disclosure is not limited thereto. For example, a plasma apparatus using inductively coupled plasma, surface wave plasma (microwave plasma), magnetron plasma, remote plasma, etc. as a plasma source may also be used.

[0074] In the above embodiments, as an example of the film formation method, the case of embedding a SiN film in the recess has been described, but the present disclosure is not limited thereto. For example, the film to be embedded in the recess may be a silicon oxide film (SiO2 film), a metal nitride film, or a metal oxide film.

[0075] In the above-described embodiment, the case where the processing 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 processing apparatus may be a batch type apparatus that processes a plurality of wafers at once. Further, for example, the processing apparatus may be a semi-batch type apparatus that revolves a plurality of wafers arranged on a rotating table in a processing container by the rotating table and passes the region where the first gas is supplied and the region where the second gas is supplied in order to process the wafers. Further, it may be a multi-wafer processing apparatus including a plurality of mounting tables in one processing container.

Explanation of Reference Numerals

[0076] 100 Substrate 110 Concave portion 111 Opening 112 Narrow portion 113 Bottom 130 SiN film 140 SiN film

Claims

1. 1. A film forming method for filling a film in a recess of a substrate having a recess including a narrowed portion, the method comprising the steps of: (a) supplying a first silicon-containing gas and a first nitrogen-containing gas to the substrate to form a first film thicker at the opening of the recess than at a bottom of the recess; (b) supplying a second silicon-containing gas and a second nitrogen-containing gas to the substrate to form a second film having the same thickness at the bottom and the opening of the recess, or forming the second film to be thicker at the bottom of the recess than at the opening; (c) partially etching the first film and the second film formed in the recess; (d) supplying a third silicon-containing gas and a third nitrogen-containing gas to the substrate to form a third film having the same thickness at the bottom and the opening of the recess, or forming a third film having a greater thickness at the bottom of the recess than at the opening; having performing a plurality of cycles each including the step (b) and the step (c); and performing the step (d) after performing the plurality of cycles. Film formation method.

2. The film forming method according to claim 1 , wherein at least a portion of the multiple cycles includes the step (a).

3. 2. The method of claim 1, wherein the step (a) comprises forming the first film by alternately repeating the supply of the first silicon-containing gas and the supply of the first nitrogen-containing gas.

4. The supply of the first nitrogen-containing gas in the step (a) is ２ The method of claim 3 , further comprising exposing the substrate to a plasma generated from a gas containing:

5. The film forming method according to claim 1 , wherein the step (a) further comprises exposing the substrate to plasma generated from a modifying gas to modify the first film.

6. The film forming method according to claim 1 , wherein the step (a) further comprises supplying an etching gas to the substrate to etch the first film.

7. 2. The method of claim 1, wherein the step (a) comprises simultaneously supplying the first silicon-containing gas and the first nitrogen-containing gas to form the first film.

8. 2. The method of claim 1, wherein the step (a) includes exposing the substrate to plasma generated from the first silicon-containing gas and the first nitrogen-containing gas to form the first film.

9. 2 . The film forming method according to claim 1 , wherein at least one of the first silicon-containing gas and the first nitrogen-containing gas in the step (a) is supplied in a supply-rate-limited state.

10. 2. The film forming method according to claim 1, wherein the step (b) comprises forming the second film by alternately repeating the supply of the second silicon-containing gas and the supply of the second nitrogen-containing gas.

11. 11. The film forming method according to claim 10, wherein the supply of the second nitrogen-containing gas in the step (b) includes exposing the substrate to plasma generated from the second nitrogen-containing gas.

12. The film forming method according to claim 1 , wherein the step (b) further comprises exposing the substrate to plasma generated from a modifying gas to modify the second film.

13. The film forming method according to claim 1 , wherein the step (b) includes forming an inhibition region that inhibits deposition of the film on a side of the opening of the recess relative to the narrowed portion.

14. 2. The method of claim 1, wherein the step (d) comprises forming the third film by alternately repeating the supply of the third silicon-containing gas and the supply of the third nitrogen-containing gas.

15. 15. The film forming method according to claim 14, wherein the supplying of the third nitrogen-containing gas in the step (d) includes exposing the substrate to plasma generated from the third nitrogen-containing gas.

16. The film forming method according to claim 1 , wherein the step (d) further comprises exposing the substrate to plasma generated from a modifying gas to modify the third film.

17. The film forming method according to claim 1 , wherein the step (d) includes forming an inhibition region that inhibits deposition of the film on a side of the opening of the recess relative to the narrowed portion.

18. 2. The method of claim 1, wherein the first film, the second film, and the third film are silicon nitride films.

19. The film forming method according to claim 1 , wherein the steps (a), (b), (c), and (d) are successively performed under a reduced pressure atmosphere.

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