Film-forming method and film-forming apparatus

Abstract

To provide a technique capable of controlling crystallinity of a silicon film.SOLUTION: A film-forming method according to an aspect of the present disclosure includes the steps of: forming a seed layer over a substrate; supplying a silicon-containing gas to the substrate and forming, over the seed layer, a bulk layer containing silicon; and thermally treating the substrate and crystallizing the bulk layer. The step of forming the bulk layer includes supplying an impurity-containing gas during at least a part of a supply period of the silicon-containing gas.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] A technique is known in which an amorphous silicon film doped with impurities that suppress the progress of crystallization and an undoped amorphous silicon film are stacked in this order on an insulating film, and then the stacked amorphous silicon films are crystallized (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-115435 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can control the crystallinity of a silicon film. [Means for solving the problem]

[0005] A film formation method according to one aspect of the present disclosure includes the steps of forming a seed layer on a substrate, supplying a silicon-containing gas to the substrate to form a bulk layer containing silicon on the seed layer, and heat-treating the substrate to crystallize the bulk layer, wherein the step of forming the bulk layer includes supplying an impurity-containing gas for at least a portion of the supply period of the silicon-containing gas. [Effects of the Invention]

[0006] According to the present disclosure, the crystallinity of the silicon film can be controlled. [Brief explanation of the drawings]

[0007] [Figure 1]2 is a flowchart illustrating a film forming method according to an embodiment. [Figure 2] 1A to 1C are cross-sectional views illustrating a film forming method according to an embodiment. [Figure 3] 3 is a cross-sectional view showing a first example of a bulk layer forming step in the film forming method of FIG. 2. FIG. [Figure 4] 3 is a cross-sectional view showing a second example of the bulk layer forming step in the film forming method of FIG. 2. FIG. [Figure 5] 1 is a vertical cross-sectional view showing a film forming apparatus according to an embodiment. [Figure 6] 1 is a horizontal cross-sectional view showing a film forming apparatus according to an embodiment. [Figure 7] FIG. 10 is a diagram comparing carbon concentrations of amorphous silicon films. [Figure 8] FIG. 10 is a diagram comparing the extinction coefficients of polycrystalline silicon films. [Figure 9] FIG. 10 is a diagram comparing weighted average crystal grain sizes of polycrystalline silicon films. 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 formation method according to an embodiment will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a flowchart showing the film formation method according to an embodiment. Fig. 2 is a cross-sectional view showing the film formation method according to an embodiment. As shown in Fig. 1, the film formation method according to an embodiment includes a preparation step S1, a seed layer formation step S2, a bulk layer formation step S3, and a crystallization step S4.

[0010] As shown in FIG. 2(a), the preparation step S1 includes preparing a substrate 100 having an insulating film 110 formed on its surface. The substrate 100 is, for example, a semiconductor substrate such as a silicon substrate. The insulating film 110 is, for example, a silicon oxide film. The insulating film 110 may also be a silicon nitride film, a silicon oxynitride film, or the like.

[0011] The seed layer forming step S2 is performed after the preparation step S1. As shown in FIG. 2(b), the seed layer forming step S2 includes supplying a first silicon-containing gas to the substrate 100 to form a seed layer 120 on the insulating film 110. The first silicon-containing gas is, for example, an aminosilane-based gas. Examples of the aminosilane-based gas include DIPAS (diisopropylaminosilane) gas, 3DMAS (trisdimethylaminosilane) gas, and BTBAS (bisterialbutylaminosilane) gas. The first silicon-containing gas may be a higher order silane-based gas containing two or more silicon atoms (Si) in one molecule. Examples of the higher order silane-based gas include disilane (Si2H6) gas, trisilane (Si3H8) gas, and tetrasilane (Si4H 10 ) gas. The seed layer 120 is not limited to a single layer film, and may be a laminated film. The seed layer 120 may be a laminated film in which a first seed layer formed using an aminosilane-based gas and a second seed layer formed using a high-order silane-based gas are laminated in this order. The seed layer formation step S2 may include maintaining the substrate 100 at a first temperature. The first temperature is, for example, 300°C or higher and 400°C or lower.

[0012] The bulk layer formation step S3 is performed after the seed layer formation step S2. As shown in FIG. 2(c), the bulk layer formation step S3 includes supplying a second silicon-containing gas to the substrate 100 to form a bulk layer 130 containing silicon on the seed layer 120. The second silicon-containing gas is, for example, monosilane (SiH4) gas. The second silicon-containing gas may also be a higher silane-based gas such as disilane gas, trisilane gas, or tetrasilane gas.

[0013] The bulk layer formation step S3 includes supplying an impurity-containing gas during at least a portion of the supply period of the second silicon-containing gas. The at least a portion of the supply period is, for example, 10% to 20% of the supply period of the second silicon-containing gas. The impurity-containing gas is, for example, ethylene (C2H2) gas. The impurity-containing gas may be a carbon-containing gas other than ethylene gas. The impurity contained in the impurity-containing gas may be at least one element selected from the group consisting of phosphorus (P), boron (B), fluorine (F), chlorine (Cl), oxygen (O), nitrogen (N), and hydrogen. The bulk layer formation step S3 may include maintaining the substrate 100 at a second temperature. The second temperature is higher than the first temperature. The second temperature is, for example, 400°C to 500°C.

[0014] FIG. 3 is a cross-sectional view showing a first example of the bulk layer formation step S3 in the film formation method of FIG. 2. In the first example of the bulk layer formation step S3, first, as shown in FIG. 3(a), monosilane gas is supplied to the substrate 100 to form a first amorphous silicon film 131 on the seed layer 120. After a first time has elapsed since the start of the supply of monosilane gas, as shown in FIG. 3(b), the supply of ethylene gas is started while the supply of monosilane gas is continued, to form a second amorphous silicon film 132 doped with carbon on the first amorphous silicon film 131. This results in the formation of a bulk layer 130 in which the first amorphous silicon film 131 and the second amorphous silicon film 132 are stacked in this order. The first time is, for example, a time longer than half of the entire period of the bulk layer formation step S3. Thus, in the example of FIG. 3, the supply of ethylene gas is started midway through the supply period of monosilane gas and stopped at the end of the supply period of monosilane gas.

[0015] 4 is a cross-sectional view showing a second example of the bulk layer formation step S3 in the film formation method of FIG. 2. In the second example of the bulk layer formation step S3, first, as shown in FIG. 4(a), monosilane gas is supplied to the substrate 100 to form a first amorphous silicon film 131 on the seed layer 120. After a second time has elapsed since the start of the supply of monosilane gas, as shown in FIG. 4(b), the supply of ethylene gas is started while the supply of monosilane gas is continued, to form a second amorphous silicon film 132 doped with carbon on the first amorphous silicon film 131. After a third time has elapsed since the start of the supply of ethylene gas, the supply of ethylene gas is stopped while the supply of monosilane gas is continued, to form a third amorphous silicon film 133 on the second amorphous silicon film 132, as shown in FIG. 4(b). This results in a bulk layer 130 in which a first amorphous silicon film 131, a second amorphous silicon film 132, and a third amorphous silicon film 133 are stacked in this order. The period from when the supply of ethylene gas is stopped to when the supply of monosilane gas ends is the same as, for example, the period from when the supply of monosilane gas begins to when the supply of ethylene gas starts. The period from when the supply of ethylene gas is stopped to when the supply of monosilane gas ends may be longer or shorter than the period from when the supply of monosilane gas begins to when the supply of ethylene gas starts. Thus, in the example of FIG. 4, the supply of ethylene gas starts midway through the supply of monosilane gas and is stopped midway through the supply of monosilane gas.

[0016] The crystallization step S4 is performed after the bulk layer formation step S3. As shown in FIG. 2(d), the crystallization step S4 includes heat-treating the substrate 100 to crystallize the bulk layer 130 to form a polycrystalline silicon film 140. In the crystallization step S4, the substrate 100 is heated to and maintained at a third temperature that is equal to or higher than the crystallization temperature of the bulk layer 130. The third temperature is higher than the second temperature, and is, for example, equal to or higher than 550°C and equal to or lower than 900°C.

[0017] As described above, according to the film formation method of the embodiment, the seed layer formation step S2, the bulk layer formation step S3, and the crystallization step S4 are performed in this order. The bulk layer formation step S3 includes supplying an impurity-containing gas during at least a portion of the supply period of the second silicon-containing gas. In this case, the crystallinity of the polycrystalline silicon film 140 can be controlled by changing the time or timing of supplying the impurity-containing gas. For example, when the polycrystalline silicon film 140 is used as a channel layer of a transistor, increasing the crystal grain size of the polycrystalline silicon film 140 increases carrier mobility and improves transistor performance.

[0018] [Film forming equipment] The film forming apparatus 1 according to the embodiment will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a vertical cross-sectional view showing the film forming apparatus 1 according to the embodiment. Fig. 6 is a horizontal cross-sectional view showing the film forming apparatus 1 according to the embodiment.

[0019] The film forming apparatus 1 is a batch type apparatus that processes a plurality of substrates W at once. The substrates W are, for example, semiconductor wafers. The film forming apparatus 1 includes a processing chamber 10, a gas supply unit 30, an exhaust unit 40, a heating unit 50, and a control unit 80.

[0020] The processing vessel 10 can have its interior depressurized. The processing vessel 10 accommodates a substrate W. The processing vessel 10 has an inner tube 11 and an outer tube 12. The inner tube 11 has a cylindrical shape with a ceiling and an open lower end. The outer tube 12 has a cylindrical shape with a ceiling and an open lower end that covers the outside of the inner tube 11. The inner tube 11 and the outer tube 12 are made of a heat-resistant material such as quartz. The inner tube 11 and the outer tube 12 have a double-tube structure arranged coaxially.

[0021] A storage section 13 for storing a gas supply pipe is formed along the longitudinal direction (vertical direction) on the side wall of the inner pipe 11. For example, a part of the side wall of the inner pipe 11 is protruded outward to form a convex section 14, and the inside of the convex section 14 is formed as the storage section 13.

[0022] A rectangular opening 15 is formed along the longitudinal direction in the side wall of the inner tube 11. The opening 15 faces the storage portion 13.

[0023] The opening 15 is a gas exhaust port formed so as to be able to exhaust gas from the inner tube 11. The length of the opening 15 is the same as the length of the boat 16, or is formed so as to extend in the vertical direction longer than the length of the boat 16.

[0024] The lower end of the processing vessel 10 is supported by a cylindrical manifold 17. The manifold 17 is made of, for example, stainless steel. A flange 18 is formed at the upper end of the manifold 17. The flange 18 supports the lower end of the outer tube 12. A seal member 19, such as an O-ring, is provided between the flange 18 and the lower end of the outer tube 12. This keeps the inside of the outer tube 12 airtight.

[0025] An annular support member 20 is provided on the inner wall of the upper portion of the manifold 17. The support member 20 supports the lower end of the inner tube 11. A lid member 21 is airtightly attached to the opening at the lower end of the manifold 17 via a sealing member 22 such as an O-ring. This airtightly closes the opening at the lower end of the processing vessel 10, i.e., the opening of the manifold 17. The lid member 21 is made of, for example, stainless steel.

[0026] A rotating shaft 24 is provided in the center of the lid 21, penetrating through the lid 21 via a magnetic fluid seal 23. The lower part of the rotating shaft 24 is rotatably supported by an arm 25A of an elevation mechanism 25 made up of a boat elevator.

[0027] A rotating plate 26 is provided at the upper end of the rotating shaft 24. A boat 16 holding substrates W is placed on the rotating plate 26 via a quartz heat retention stand 27. The boat 16 rotates by rotating the rotating shaft 24. The boat 16 moves up and down integrally with the lid 21 by raising and lowering the lifting mechanism 25. This allows the boat 16 to be inserted into and removed from the processing vessel 10. The boat 16 can be accommodated within the processing vessel 10. The boat 16 holds multiple (e.g., 50 to 150) substrates W in a shelf-like manner. The boat 16 holds the multiple substrates W approximately horizontally with spacing between them in the vertical direction.

[0028] The gas supply unit 30 is configured to be able to introduce various process gases into the inner pipe 11. The gas supply unit 30 includes a DIPAS supply unit 31, a disilane supply unit 32, a monosilane supply unit 33, and an ethylene supply unit .

[0029] The DIPAS supply unit 31 includes a gas supply pipe 31a inside the processing vessel 10 and a supply flow path 31b outside the processing vessel 10. A DIPAS source 31c, a mass flow controller 31d, and a valve 31e are installed in the supply flow path 31b, in this order from upstream to downstream in the gas flow direction. The supply timing of the DIPAS gas from the DIPAS source 31c is controlled by the valve 31e, and the mass flow controller 31d adjusts the flow rate to a predetermined value. The DIPAS gas flows from the supply flow path 31b into the gas supply pipe 31a and is then discharged from the gas supply pipe 31a into the processing vessel 10. The DIPAS gas is an example of a first silicon-containing gas used in the seed layer formation process S2.

[0030] The disilane supply unit 32 includes a gas supply pipe 32a inside the processing vessel 10 and a supply flow path 32b outside the processing vessel 10. A disilane source 32c, a mass flow controller 32d, and a valve 32e are installed in the supply flow path 32b, in this order from upstream to downstream in the gas flow direction. The supply timing of disilane gas from the disilane source 32c is controlled by the valve 32e, and the flow rate is adjusted to a predetermined value by the mass flow controller 32d. The disilane gas flows from the supply flow path 32b into the gas supply pipe 32a and is then discharged from the gas supply pipe 32a into the processing vessel 10. The disilane gas is an example of a first silicon-containing gas used in the seed layer formation process S2.

[0031] The monosilane supply unit 33 includes a gas supply pipe 33a inside the processing vessel 10 and a supply flow path 33b outside the processing vessel 10. A monosilane source 33c, a mass flow controller 33d, and a valve 33e are installed in the supply flow path 33b, in this order from upstream to downstream in the gas flow direction. The supply timing of the monosilane gas from the monosilane 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 monosilane gas flows from the supply flow path 33b into the gas supply pipe 33a and is then discharged from the gas supply pipe 33a into the processing vessel 10. The monosilane gas is an example of a second silicon-containing gas used in the bulk layer formation process S3.

[0032] The ethylene supply unit 34 includes a gas supply pipe 34a inside the processing vessel 10 and a supply flow path 34b outside the processing vessel 10. An ethylene source 34c, a mass flow controller 34d, and a valve 34e are installed in the supply flow path 34b, in this order from upstream to downstream in the gas flow direction. The supply timing of ethylene gas from the ethylene 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 ethylene gas flows from the supply flow path 34b into the gas supply pipe 34a and is discharged from the gas supply pipe 34a into the processing vessel 10. The ethylene gas is an example of an impurity-containing gas used in the bulk layer formation process S3.

[0033] The gas supply pipes 31a, 32a, 33a, and 34a are fixed to the manifold 17. The gas supply pipes 31a, 32a, 33a, and 34a are made of, for example, quartz. The gas supply pipes 31a, 32a, 33a, and 34a extend linearly in the vertical direction near the inner pipe 11, and then bend in an L-shape within the manifold 17 and extend horizontally, thereby penetrating the manifold 17. The gas supply pipes 31a, 32a, 33a, and 34a are arranged side by side along the circumferential direction of the inner pipe 11 and are formed at the same height.

[0034] A plurality of discharge ports 31f, 32f, 33f, and 34f are provided in the gas supply pipes 31a, 32a, 33a, and 34a at positions within the inner pipe 11. The discharge ports 31f, 32f, 33f, and 34f are formed at predetermined intervals along the extension direction of the gas supply pipes 31a, 32a, 33a, and 34a. Each discharge port 31f, 32f, 33f, and 34f discharges gas horizontally toward the substrate W from the radially outer side of the substrate W. Each discharge port 31f, 32f, 33f, and 34f discharges gas parallel to the main surface of the substrate W. The intervals between the discharge ports are set to, for example, the same as the intervals between the substrates W held in the boat 16. The height position of each discharge port is set to, for example, the midpoint between vertically adjacent substrates W. In this case, each discharge port can efficiently supply gas to the opposing surfaces of adjacent substrates W.

[0035] The gas supply unit 30 may mix multiple types of gases and discharge the mixed gas from a single gas supply pipe. The gas supply pipes 31a, 32a, 33a, and 34a may have different shapes and arrangements. The gas supply unit 30 may further include a gas supply pipe that supplies another gas, such as an inert gas.

[0036] The exhaust unit 40 exhausts gas that is discharged from the inner tube 11 through the opening 15 and then discharged from a gas outlet 41 via a space P1 between the inner tube 11 and the outer tube 12. The gas outlet 41 is formed on the side wall of the upper part of the manifold 17, above the support unit 20. An exhaust flow path 42 is connected to the gas outlet 41. A pressure adjustment valve 43 and a vacuum pump 44 are sequentially disposed in the exhaust flow path 42, so that the inside of the processing chamber 10 can be exhausted.

[0037] The heating unit 50 is provided around the outer tube 12. The heating unit 50 is provided, for example, on the base plate 28. The heating unit 50 has a cylindrical shape so as to cover the outer tube 12. The heating unit 50 includes, for example, a heating element, and heats each substrate W in the processing vessel 10.

[0038] The control unit 80 controls the operation of each part of the film forming apparatus 1. The control unit 80 may be, for example, a computer. A computer program that controls the operation of each part of the film forming apparatus 1 is stored in a storage medium 90. The storage medium 90 may be, for example, a flexible disk, a compact disk, a hard disk, a flash memory, a DVD, or the like.

[0039] [Operation of the Film Forming Apparatus] The operation of the film forming apparatus 1 when carrying out the film forming method according to the embodiment will be described.

[0040] First, the control unit 80 controls the lifting mechanism 25 to load the boat 16 holding multiple substrates W into the processing vessel 10, and then airtightly closes the opening at the bottom of the processing vessel 10 with the lid 21. Next, the control unit 80 controls the exhaust unit 40 to reduce the pressure inside the processing vessel 10, and controls the heating unit 50 to adjust the temperature of the substrates W to a first temperature. Each substrate W may be the substrate 100 described above.

[0041] Next, the seed layer formation step S2 is performed. The control unit 80 controls the heating unit 50 to maintain the temperature of the substrate W at the first temperature, controls the gas supply unit 30 to supply DIPAS gas into the processing chamber 10, and controls the exhaust unit 40 to maintain the interior of the processing chamber 10 at a predetermined pressure. As a result, a first seed layer is formed on the insulating film 110. The first seed layer functions as a part of the seed layer 120. When forming the first seed layer, an inert gas such as nitrogen gas may be supplied into the processing chamber 10 together with the DIPAS gas.

[0042] Next, the control unit 80 controls the heating unit 50 to maintain the temperature of the substrate W at the first temperature, controls the gas supply unit 30 to supply disilane gas into the processing vessel 10, and controls the exhaust unit 40 to maintain the interior of the processing vessel 10 at a predetermined pressure. As a result, a second seed layer is formed on the first seed layer. The second seed layer functions as part of the seed layer 120. When forming the second seed layer, an inert gas such as nitrogen gas may be supplied into the processing vessel 10 together with the disilane gas.

[0043] Next, the bulk layer formation process S3 is performed. The control unit 80 controls the heating unit 50 to adjust the temperature of the substrate W from the first temperature to the second temperature. Subsequently, while controlling the heating unit 50 to maintain the temperature of the substrate W at the second temperature, the control unit 80 controls the gas supply unit 30 to supply monosilane gas into the processing vessel 10 and controls the exhaust unit 40 to maintain a predetermined pressure inside the processing vessel 10. At this time, ethylene gas is supplied during at least a portion of the supply period of monosilane gas. As a result, a bulk layer 130 is formed on the seed layer 120. When forming the bulk layer 130, an inert gas such as nitrogen gas may be supplied into the processing vessel 10 together with the monosilane gas and ethylene gas.

[0044] Next, a crystallization step S4 is performed. The control unit 80 controls the gas supply unit 30 to supply an inert gas into the processing chamber 10, and controls the heating unit 50 to adjust and maintain the temperature of the substrate W from the second temperature to the third temperature. As a result, the substrate 100 is heat-treated, and the bulk layer 130 is crystallized to form a polycrystalline silicon film 140.

[0045] Next, the control unit 80 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 25 to unload the boat 16 from the processing vessel 10 .

[0046] As described above, the film formation method according to the embodiment can be carried out in the film formation apparatus 1. In the above example, the seed layer formation step S2, the bulk layer formation step S3, and the crystallization step S4 are performed in the film formation apparatus 1, but some of the steps may be performed in a separate apparatus. For example, the seed layer formation step S2 and the bulk layer formation step S3 may be performed in the film formation apparatus 1, and the crystallization step S4 may be performed in a separate apparatus.

[0047] [Example] Example 1 In Example 1, a silicon substrate having an oxide film on its surface was prepared, and the prepared silicon substrate was placed in the processing chamber 10 of the film-forming apparatus 1. An amorphous silicon film was formed on the oxide film under the following conditions 1R and 1A. Then, the carbon (C) concentration in the amorphous silicon film was measured by secondary ion mass spectrometry (SIMS).

[0048] <Condition 1R> In condition 1R, a seed layer was formed on an oxide film, and then monosilane gas was supplied to the silicon substrate to form an amorphous silicon film on the seed layer.

[0049] <Condition 1A> In condition 1A, a seed layer was formed on an oxide film, and then monosilane gas and ethylene gas were simultaneously supplied to the silicon substrate to form an amorphous silicon film on the seed layer. Condition 1A was the same as condition 1R, except that monosilane gas and ethylene gas were simultaneously supplied when forming the amorphous silicon film.

[0050] FIG. 7 is a diagram comparing the carbon concentration of the amorphous silicon film. As shown in FIG. 7, the carbon concentration of the amorphous silicon film was 2.28×10 19 atoms / cm 2 In the case of condition 1A, it is 8.39 × 10 20 atoms / cm 2 This result indicates that the amorphous silicon film is doped with carbon by simultaneously supplying monosilane gas and ethylene gas when forming the amorphous silicon film.

[0051] Example 2 In Example 2, a silicon substrate having an oxide film on its surface was prepared. The prepared silicon substrate was placed in the processing chamber 10 of the film-forming apparatus 1. A seed layer and an amorphous silicon film were formed on the oxide film in this order, and the amorphous silicon film was then heat-treated to form a polycrystalline silicon film. In Example 2, an amorphous silicon film was formed under Conditions 2R, 2A, and 2B shown below. The extinction coefficient (k value) of the polycrystalline silicon film was then determined using spectroscopic ellipsometry. The extinction coefficient was close to 0.25 when the silicon film was amorphous, and approached 0.05 as the crystallinity of the silicon film increased. In Example 2, the extinction coefficient was measured at multiple time points during which the amorphous silicon film was heat-treated for different periods of time.

[0052] <Condition 2R> Under condition 2R, an amorphous silicon film was formed on the seed layer by supplying monosilane gas to the silicon substrate. In this case, the amorphous silicon film was a non-doped layer.

[0053] <Condition 2A> Under condition 2A, monosilane gas was supplied to the silicon substrate, and ethylene gas was supplied during the monosilane gas supply period, and the ethylene gas supply was stopped at the end of the monosilane gas supply period, thereby forming an amorphous silicon film. In this case, the amorphous silicon film includes an undoped layer and a doped layer in this order.

[0054] <Condition 2B> Under condition 2B, monosilane gas was supplied to the silicon substrate, and ethylene gas was supplied during the monosilane gas supply period, and the ethylene gas supply was stopped during the monosilane gas supply period, thereby forming an amorphous silicon film. In this case, the amorphous silicon film included an undoped layer, a doped layer, and another undoped layer, in that order. Under condition 2B, the thickness of the undoped layer located at the bottom was set to be the same as the thickness of the undoped layer located at the top, and the thickness of the doped layer was set to be thinner than the thickness of the undoped layer.

[0055] 8 is a diagram comparing the extinction coefficients of polycrystalline silicon films, in which the vertical axis represents the extinction coefficient (k value) of the polycrystalline silicon film, and the horizontal axis represents the heat treatment time of the amorphous silicon film.

[0056] As shown in Figure 8, the time from the start of heat treatment of the amorphous silicon film until the extinction coefficient approaches 0.05, i.e., the time until the amorphous silicon film crystallizes, is longer under Condition 2R, Condition 2A, and Condition 2B. This result indicates that introducing a doped layer into the amorphous silicon film reduces the crystallization rate of the amorphous silicon film. In particular, when the doped layer is introduced at the middle position in the thickness direction of the amorphous silicon film (Condition 2B), the crystallization rate of the amorphous silicon film is slower than when the doped layer is introduced at the top of the amorphous silicon film (Condition 2A). It is thought that a slower crystallization rate of the amorphous silicon film makes it easier for the crystal grain size of the polycrystalline silicon film to increase.

[0057] Example 3 In Example 3, a silicon substrate having an oxide film on its surface was prepared. The prepared silicon substrate was placed in the processing chamber 10 of the film-forming apparatus 1. A seed layer and an amorphous silicon film were formed on the oxide film in this order, and the amorphous silicon film was heat-treated to form a polycrystalline silicon film. In Example 3, the amorphous silicon film was formed under the following conditions: 3R, 3A, 3B, 3C, 3D, and 3E. The thickness of the amorphous silicon film was set to the same under all conditions. Next, the weighted average crystal grain size of the polycrystalline silicon film was determined by electron backscatter diffraction (EBSD). The weighted average crystal grain size was calculated using an area-weighted method.

[0058] <Condition 3R> Under condition 3R, an amorphous silicon film was formed on the seed layer by supplying monosilane gas to the silicon substrate. In this case, the amorphous silicon film was a non-doped layer.

[0059] <Condition 3A> Under condition 3A, monosilane gas was supplied to the silicon substrate, and ethylene gas was supplied during the monosilane gas supply period, and the ethylene gas supply was stopped at the end of the monosilane gas supply period, thereby forming an amorphous silicon film. In this case, the amorphous silicon film includes an undoped layer and a doped layer in this order.

[0060] <Condition 3B> Under condition 3B, an amorphous silicon film was formed by supplying monosilane gas to the silicon substrate while starting the supply of ethylene gas midway through the monosilane gas supply period and then stopping the ethylene gas supply midway through the monosilane gas supply period. In this case, the amorphous silicon film included a non-doped layer, a doped layer, and another non-doped layer, in that order. Under condition 3B, the timing of starting and stopping the supply of ethylene gas was controlled so that the doped layer was located closer to the top surface than the middle position in the thickness direction of the amorphous silicon film. The thickness of the doped layer was the same as that of the doped layer under condition 3A.

[0061] <Condition 3C> Under condition 3C, the timing of starting and stopping the supply of ethylene gas was controlled so that the doped layer was positioned at the middle position in the thickness direction of the amorphous silicon film. The other conditions were the same as those under condition 3B.

[0062] <Condition 3D> In condition 3D, the timing of starting and stopping the supply of ethylene gas was controlled so that the doped layer was located closer to the bottom surface than the middle position in the thickness direction of the amorphous silicon film. Other conditions were the same as in condition 3B.

[0063] <Condition 3E> Under condition 3E, monosilane gas was supplied to the silicon substrate, and ethylene gas was supplied at the beginning of the monosilane gas supply period, and the ethylene gas supply was stopped midway through the monosilane gas supply period to form an amorphous silicon film. In this case, the amorphous silicon film included a doped layer and a non-doped layer in that order. The thickness of the doped layer was the same as that of the doped layer under condition 3A.

[0064] Figure 9 is a diagram comparing the weighted average grain size of polycrystalline silicon films. In Figure 9, the vertical axis represents the weighted average grain size of the polycrystalline silicon film, and the weighted average grain size of the polycrystalline silicon film under conditions 3A to 3E is shown as a relative value, with the weighted average grain size of the polycrystalline silicon film under conditions 3A to 3E being set at "1." In Figure 9, the horizontal axis represents the position of the doped layer.

[0065] As shown in Figure 9, it can be seen that the weighted average crystal grain size changes by changing the position of the doped layer in the thickness direction of the polycrystalline silicon film. This result shows that the crystallinity of the polycrystalline silicon film can be controlled by changing the position of the doped layer in the thickness direction of the polycrystalline silicon film.

[0066] As shown in Figure 9, when a doped layer is introduced from the top surface to the middle of the polycrystalline silicon film in the thickness direction, the weighted average grain size becomes larger than that of a polycrystalline silicon film that does not contain a doped layer. In particular, when a doped layer is introduced at the middle of the thickness direction of the polycrystalline silicon film, a weighted average grain size 1.8 times larger than that of a polycrystalline silicon film that does not contain a doped layer is obtained.

[0067] As shown in FIG. 9, when a doped layer is introduced closer to the bottom surface than to the middle position of the polycrystalline silicon film in the thickness direction of the polycrystalline silicon film, the weighted average grain size becomes smaller than that of a polycrystalline silicon film that does not include a doped layer.

[0068] 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.

[0069] In the above embodiment, the processing vessel is a vessel with a double-pipe structure, but the present disclosure is not limited to this. For example, the processing vessel may be a vessel with a single-pipe structure.

[0070] In the above embodiment, the film formation apparatus is described as an apparatus that supplies gas from a gas supply pipe arranged along the longitudinal direction of the processing vessel and exhausts the gas from a slit arranged opposite the gas supply pipe, but the present disclosure is not limited to this. For example, the film formation apparatus may be an apparatus that supplies gas from a gas supply pipe arranged along the longitudinal direction of a boat and exhausts the gas from an exhaust port arranged above the boat. Also, for example, the film formation apparatus may be an apparatus that supplies processing gas from a gas supply pipe arranged below the processing vessel and exhausts the gas from an exhaust port arranged above the processing vessel.

[0071] In the above embodiment, a batch-type apparatus that processes multiple substrates at once has been described, but the present disclosure is not limited to this. For example, the film formation apparatus may be a single-wafer-type apparatus that processes substrates one by one. For example, the film formation apparatus may be a semi-batch-type apparatus that processes the substrates by rotating a turntable on which multiple substrates are placed, causing each substrate to revolve and repeatedly passing through a process gas supply region arranged along the radial direction of the turntable. [Explanation of symbols]

[0072] 100 boards 120 seed layer 130 Bulk Layer 140 Polycrystalline silicon film S2 Seed layer formation process S3 Bulk layer formation process S4 Crystallization process

Claims

1. forming a seed layer on a substrate; supplying a silicon-containing gas to the substrate to form a bulk layer comprising silicon on the seed layer; heat-treating the substrate to crystallize the bulk layer; and the step of forming the bulk layer includes supplying an impurity-containing gas during at least a portion of a supply period of the silicon-containing gas; Film formation method.

2. the supply of the impurity-containing gas is started midway through a period during which the silicon-containing gas is supplied; The film forming method according to claim 1 .

3. the supply of the impurity-containing gas is stopped midway through the supply period of the silicon-containing gas; The film forming method according to claim 1 or 2.

4. a period from the time when the supply of the impurity-containing gas is stopped to the time when the supply period of the silicon-containing gas is ended is the same as a period from the time when the supply period of the silicon-containing gas is started to the time when the supply of the impurity-containing gas is started; The film forming method according to claim 3 .

5. The supply of the impurity-containing gas is stopped at the end of the supply period of the silicon-containing gas. The film forming method according to claim 1 or 2.

6. the substrate has an insulating film on its surface; the seed layer is formed on the insulating film. The film forming method according to claim 1 .

7. the silicon-containing gas is monosilane gas; The impurity-containing gas is ethylene gas. The film forming method according to claim 1 .

8. a processing vessel for accommodating a substrate; a supply unit that supplies a silicon-containing gas and an impurity-containing gas into the processing vessel; an exhaust unit that exhausts the inside of the processing vessel; a heating unit that heats the substrate; a control unit that controls the supply unit, the exhaust unit, and the heating unit; Equipped with The control unit forming a seed layer over the substrate; supplying the silicon-containing gas to the substrate to form a bulk layer comprising silicon on the seed layer; heat-treating the substrate to crystallize the bulk layer; configured to: the control unit is configured to supply the impurity-containing gas during at least a part of a supply period of the silicon-containing gas in the step of forming the bulk layer. Film deposition equipment.

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