Method for producing polycrystalline film, and polycrystalline film

Abstract

According to this method for producing polycrystalline films 100, 300, and 400, a plurality of second seed crystals 22 that are different from a plurality of first seed crystals 12 and are formed of the same material as the plurality of first seed crystals 12 are grown above a first polycrystalline layer 10 by a chemical vapor deposition method so as to form a second polycrystalline layer 20 which is laminated on the first polycrystalline layer 10 and is formed of the same material as the first polycrystalline layer 10.

Description

Method for producing polycrystalline film and polycrystalline film

[0001] The present invention relates to a method for producing a polycrystalline film and a polycrystalline film, and particularly relates to a method for producing a polycrystalline film formed by chemical vapor deposition and a polycrystalline film.

[0002] Conventionally, polycrystalline films formed by chemical vapor deposition are known (for example, refer to Patent Document 1).

[0003] The above Patent Document 1 discloses a method for manufacturing a vibration element substrate including a polysilicon film (polycrystalline film). This polysilicon film is formed to a thickness of about 3 μm by chemical vapor deposition.

[0004] Japanese Unexamined Patent Publication No. 2020-151796

[0005] Here, for a polysilicon film as described in the above Patent Document 1, it is sometimes desired to increase the thickness to 3 μm or more for the purpose of improving mechanical strength and the like. However, although not explicitly stated in the above Patent Document 1, when an attempt is made to thicken a polysilicon film to 3 μm or more, the polysilicon film (polycrystalline film) may be damaged due to mutual pressing between adjacently growing polysilicon crystals. Therefore, there is a demand for a method for producing a polycrystalline film and a polycrystalline film that can be thickened while suppressing damage.

[0006] The present invention has been made to solve the above problems, and one object of the present invention is to provide a method for producing a polycrystalline film and a polycrystalline film that can be thickened while suppressing damage.

[0007] In order to achieve the above object, a method for producing a polycrystalline film according to a first aspect of the present invention comprises: a first polycrystalline layer forming step of forming a first polycrystalline layer by growing a plurality of first-type crystals by chemical vapor deposition; and a second polycrystalline layer forming step of, above the first polycrystalline layer, growing a plurality of second-type crystals that are different from the plurality of first-type crystals and are made of the same material as the plurality of first-type crystals by chemical vapor deposition, thereby laminating the second polycrystalline layer on the first polycrystalline layer and forming the second polycrystalline layer made of the same material as the first polycrystalline layer.

[0008] In the method for manufacturing a polycrystalline film according to the first aspect of this invention, as described above, multiple second-seed crystals, which are different from and made of the same material as the multiple first-seed crystals, are grown above the first polycrystalline layer by chemical vapor deposition, thereby stacking them on the first polycrystalline layer and forming a second polycrystalline layer made of the same material as the first polycrystalline layer. As a result, the polycrystalline film can be thickened by stacking the first and second polycrystalline layers, which are formed by growing different seed crystals from each other, thus eliminating the need to thicken only the first or second polycrystalline layer. Therefore, it is possible to suppress damage to the thickened first or second polycrystalline layer due to pressure between adjacent growing crystals. As a result, the polycrystalline film can be thickened while suppressing damage.

[0009] In the method for manufacturing a polycrystalline film according to the first aspect described above, preferably, between the first polycrystalline layer formation step and the second polycrystalline layer formation step, the method further includes a seed crystal reset step in which the seed crystals to be grown are reset from a plurality of first seed crystals to a plurality of second seed crystals, and a second seed crystal growth preparation step after the seed crystal reset step in which preparations are made to start the growth of the plurality of second seed crystals by chemical vapor deposition in the second polycrystalline layer formation step, wherein the seed crystal reset step includes the step of forming a seed crystal reset layer on the first polycrystalline layer. With this configuration, a plurality of second seed crystals can be easily grown above the first polycrystalline layer to form a second polycrystalline layer by the seed crystal reset step, which includes the step of forming a seed crystal reset layer, and the second seed crystal growth preparation step.

[0010] In this case, preferably, the seed crystal reset step includes at least one of the steps of stopping the introduction of reaction gas into the furnace for chemical vapor deposition, lowering the temperature inside the furnace, and increasing the pressure inside the furnace, and the second seed crystal growth preparation step includes returning at least one of the changes made in the seed crystal reset step—the introduction of reaction gas into the furnace, the temperature inside the furnace, and the pressure inside the furnace—to the state before the seed crystal reset step. With this configuration, the growth of multiple first seed crystals can be easily stopped by changing the state inside the furnace for chemical vapor deposition. Furthermore, by returning the state inside the furnace to the state before the seed crystal reset step, the growth of the second seed crystal by chemical vapor deposition can be easily started.

[0011] In a method for manufacturing a polycrystalline film, the above seed crystal reset step includes at least one of the steps of stopping the introduction of reaction gas into the furnace of the chemical vapor deposition method, lowering the temperature inside the furnace, and increasing the pressure inside the furnace, and the second seed crystal growth preparation step includes a step of returning at least one of the changes made in the seed crystal reset step—the introduction of reaction gas into the furnace, the temperature inside the furnace, and the pressure inside the furnace—to the state before the seed crystal reset step, preferably, the second polycrystalline layer formation step includes a step of returning the introduction of reaction gas into the furnace, the temperature inside the furnace, and the pressure inside the furnace to the state before the seed crystal reset step. With this configuration, even if not all of the changes made in the seed crystal reset step—the introduction of reaction gas into the furnace, the temperature inside the furnace, and the pressure inside the furnace—have returned to the state before the seed crystal reset step in the second seed crystal growth preparation step, the second polycrystalline layer can be easily formed in the second polycrystalline layer formation step.

[0012] In a method for manufacturing a polycrystalline film, the above seed crystal reset step includes at least one of the steps of stopping the introduction of reaction gas into the furnace of the chemical vapor deposition method, lowering the temperature inside the furnace, and increasing the pressure inside the furnace, and the second seed crystal growth preparation step includes a step of returning at least one of the changes made in the seed crystal reset step (the introduction of reaction gas into the furnace, the temperature inside the furnace, and the pressure inside the furnace) to the state before the seed crystal reset step, preferably the seed crystal reset step includes at least a step of increasing the pressure inside the furnace, and the second seed crystal growth preparation step or the second polycrystalline layer formation step includes at least a step of returning the pressure inside the furnace to the state before the seed crystal reset step. With this configuration, the growth of multiple first seed crystals can be easily stopped by increasing the pressure inside the furnace of the chemical vapor deposition method. Furthermore, by returning the pressure inside the furnace to the state before the seed crystal reset step, the growth of the second seed crystal by chemical vapor deposition can be easily started.

[0013] In a method for manufacturing a polycrystalline film, further comprising the above-described seed crystal reset step and second seed crystal growth preparation step, wherein the seed crystal reset step includes a step of forming a seed crystal reset layer on the first polycrystalline layer, preferably, the first polycrystalline layer formation step, the seed crystal reset step, the second seed crystal growth preparation step, and the second polycrystalline layer formation step are carried out consecutively in a common chemical vapor deposition furnace. With this configuration, the time and effort required throughout the entire process can be reduced compared to the case where the first polycrystalline layer formation step, the seed crystal reset step, the second seed crystal growth preparation step, and the second polycrystalline layer formation step are carried out in different locations.

[0014] In a method for manufacturing a polycrystalline film, further comprising the above-described seed crystal reset step and a second seed crystal growth preparation step, wherein the seed crystal reset step includes a step of forming a seed crystal reset layer on a first polycrystalline layer, preferably, the first polycrystalline layer and the second polycrystalline layer are formed from silicon, and the seed crystal reset layer contains at least one of impurity-diffusing silicon, silicon oxide, silicon nitride, CF polymer, and amorphous silicon. With this configuration, the growth of polycrystalline silicon can be reset by the seed crystal reset layer containing at least one of impurity-diffusing silicon, silicon oxide, silicon nitride, CF polymer, and amorphous silicon, thereby easily creating a thick polycrystalline silicon film while suppressing damage caused by adjacent crystals pushing against each other.

[0015] A method for manufacturing a polycrystalline film further comprising the above-described seed crystal reset step and a second seed crystal growth preparation step, wherein the seed crystal reset step includes a step of forming a seed crystal reset layer on a first polycrystalline layer, preferably further comprising a seed crystal reset layer removal step of removing the seed crystal reset layer before the second seed crystal growth preparation step, and the second polycrystalline layer formation step includes a step of forming a second polycrystalline layer that is stacked so as to be in contact with the first polycrystalline layer by growing a plurality of second seed crystals by chemical vapor deposition above the first polycrystalline layer. With this configuration, it is possible to suppress a decrease in the overall performance of the thickened polycrystalline film due to the remaining seed crystal reset layer between the first polycrystalline layer and the second polycrystalline layer.

[0016] In a method for producing a polycrystalline film, the above seed crystal reset step includes at least a step of increasing the pressure inside the furnace, and the second seed crystal growth preparation step or second polycrystalline layer formation step includes at least a step of returning the pressure inside the furnace to the state before the seed crystal reset step, preferably, the step of increasing the pressure inside the furnace includes a reaction gas replacement step of replacing the reaction gas inside the furnace with at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride, and the second seed crystal growth preparation step or second polycrystalline layer formation step includes a step of replacing at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride with a reaction gas. With this configuration, the pressure inside the furnace can be easily increased by chemical vapor deposition by replacing the reaction gas inside the furnace with at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride, and a seed crystal reset layer consisting of at least one of oxides, nitrides, impurity diffusers, and CF polymers can be easily formed on the first polycrystalline layer. Furthermore, by replacing at least one of the oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride in the furnace with a reaction gas, the growth of Type II crystals by chemical vapor deposition can be easily initiated.

[0017] The polycrystalline film according to the second aspect of this invention comprises a first polycrystalline layer formed by growing a plurality of first type crystals, and a second polycrystalline layer laminated on the first polycrystalline layer and formed by growing a plurality of second type crystals which are different from the plurality of first type crystals but are made of the same material as the plurality of first type crystals, and which are made of the same material as the first polycrystalline layer.

[0018] In the polycrystalline film according to the second aspect of this invention, a first polycrystalline layer and a second polycrystalline layer formed by growing different seed crystals are stacked to create a thick polycrystalline film, eliminating the need to thicken only the first polycrystalline layer or only the second polycrystalline layer. Therefore, when manufacturing the polycrystalline film, it is possible to suppress damage to the thickened first polycrystalline layer or the second polycrystalline layer caused by adjacent growing crystals pushing against each other. As a result, it is possible to provide a polycrystalline film that can be thickened while suppressing damage.

[0019] In the polycrystalline film with the second surface described above, preferably, a seed crystal reset layer is provided between the first polycrystalline layer and the second polycrystalline layer and further comprises at least one of impurity-diffusing silicon, silicon oxide, silicon nitride, CF polymer, and amorphous silicon. With this configuration, when manufacturing the polycrystalline film, the growth of the polycrystalline silicon is reset by the seed crystal reset layer comprising at least one of impurity-diffusing silicon, silicon oxide, silicon nitride, CF polymer, and amorphous silicon, thereby suppressing damage caused by adjacent crystals pushing against each other and making it easy to create a thick polycrystalline silicon film.

[0020] According to the present invention, as described above, it is possible to increase the thickness of the polycrystalline film while suppressing damage to the film.

[0021] This is a perspective view showing a polycrystalline film according to the first embodiment of the present invention. This is an enlarged side view of a polycrystalline film according to the first embodiment of the present invention. This is a flowchart showing the method for manufacturing a polycrystalline film according to the first embodiment of the present invention. This is a flowchart showing the subroutine for step S2 in Figure 3. This is a flowchart showing the subroutine for step S4 in Figure 3. This is a flowchart showing the subroutine for step S5 in Figure 3. This is a diagram showing the manufacturing process of a polycrystalline film corresponding to the flowchart in Figure 3 ((a), (b): step S1, (c): step S2, (d): step S3, (e), (f): step S5). This is a perspective view showing a polycrystalline film in the case of six layers according to the first embodiment of the present invention. This is a perspective view showing a polycrystalline film according to the second embodiment of the present invention. This is a flowchart showing the method for manufacturing a polycrystalline film according to the second embodiment of the present invention. This is a flowchart showing the subroutine for step S102 in Figure 10. This is a flowchart showing the subroutine for step S103 in Figure 10. This is a diagram showing the manufacturing process of a polycrystalline film corresponding to the flowchart in Figure 10 ((a), (b): step S101, (c): step S102, (d), (e): step S104).

[0022] The following describes embodiments of the present invention based on the drawings.

[0023] [First Embodiment] (Polycrystalline Film Structure) The structure of the polycrystalline film 100 according to the first embodiment will be described with reference to Figures 1 and 2.

[0024] As shown in Figure 1, the polycrystalline film 100 comprises a first polycrystalline layer 10 and a second polycrystalline layer 20. The polycrystalline film 100 (first polycrystalline layer 10 and second polycrystalline layer 20) is formed from, for example, silicon. In other words, the polycrystalline film 100 (first polycrystalline layer 10 and second polycrystalline layer 20) is so-called polysilicon. In the drawing, the thickness direction of the polycrystalline film 100 is defined as the Z direction. Within the Z direction, the upward direction is defined as the Z1 direction and the downward direction as the Z2 direction.

[0025] As shown in Figure 1, the first polycrystalline layer 10 and the second polycrystalline layer 20 overlap along the thickness direction (Z direction) of the polycrystalline film 100. As shown in Figure 2, the first polycrystalline layer 10 contains a plurality of first crystals 11. The plurality of first crystals 11 have a conical shape with their apex pointing downward (Z2 direction). The plurality of first crystals 11 are arranged adjacent to each other in a direction perpendicular to the thickness direction (Z direction) of the polycrystalline film 100. The arrangement of a plurality of first crystals 11 with a conical shape in this manner is a characteristic unique to polycrystalline layers formed by chemical vapor deposition.

[0026] Furthermore, as shown in Figure 2, the second polycrystalline layer 20 has a structure similar to that of the first polycrystalline layer 10. Specifically, the second polycrystalline layer 20 contains a plurality of second crystals 21. The plurality of second crystals 21 have a conical shape with their apex pointing downwards (Z2 direction). The plurality of second crystals 21 are arranged adjacent to each other in a direction perpendicular to the thickness direction (Z direction) of the polycrystalline film 100. The arrangement of a plurality of second crystals 21 with a conical shape in this manner is a characteristic unique to polycrystalline layers formed by chemical vapor deposition.

[0027] As shown in Figure 2, the thickness t1 of the first polycrystalline layer 10 and the thickness t2 of the second polycrystalline layer 20 are approximately equal. Here, the first polycrystalline layer 10 and the second polycrystalline layer 20 formed by chemical vapor deposition grow in a direction perpendicular to the thickness direction (Z direction) as their thickness increases. Therefore, once they exceed a predetermined thickness, multiple crystals growing adjacent to each other (first crystals 11 and second crystals 21) may break due to the pressure they exert on each other. This predetermined thickness is approximately 3 μm. For this reason, there are no particular restrictions on the thickness t1 of the first polycrystalline layer 10 and the thickness t2 of the second polycrystalline layer 20, but it is preferable to keep them less than approximately 3 μm.

[0028] (Method for Manufacturing Polycrystalline Films) Next, a method for manufacturing polycrystalline films 100 and 300 (see Figure 8) according to the first embodiment will be described with reference to Figures 3 to 8. Note that the method for manufacturing polycrystalline films 100 and 300 described below is carried out by a control unit of a device not shown.

[0029] As shown in Figures 3, 7(a), and 7(b), in step S1, the control unit forms the first polycrystalline layer 10. Specifically, as shown in Figures 7(a) and 7(b), the control unit grows a plurality of first type crystals 12 on the substrate 1 in the vacuum furnace 200 to form a first crystal 11 having a conical shape, and the first polycrystalline layer 10 is formed by the aggregation of a plurality of these first crystals 11. In step S1, the control unit reduces the pressure inside the vacuum furnace 200 from atmospheric pressure and maintains a temperature inside the vacuum furnace 200 that is heated from room temperature. Specifically, in step S1, the control unit reduces the pressure inside the vacuum furnace 200 to, for example, about 10 Pa and maintains a temperature inside the vacuum furnace 200 that is heated to, for example, about 800°C. Also in step S1, the control unit maintains a state in which the vacuum furnace 200 is filled with reaction gas 2. The reaction gas 2 includes, for example, monosilane, dichlorosilane, disilane, etc. The first type crystal 12 is formed from silicon contained in the reaction gas 2 that has crystallized. In other words, the first type crystal 12 is made of silicon. Accordingly, in step S1, the control unit forms the first polycrystalline layer 10 by low-pressure chemical vapor deposition (LPCVD). The vacuum furnace 200 is an example of a "furnace" in the claims. Also, step S1 is an example of a "first polycrystalline layer formation step" in the claims.

[0030] Next, as shown in Figures 3 and 7(c), in step S2, the control unit forms a seed crystal reset layer 30 on the first polycrystalline layer 10. Once formed, the seed crystal reset layer 30 resets the seed crystal to be grown from a plurality of first seed crystals 12 to a plurality of second seed crystals 22, which will be described later. Step S2 is an example of the "seed crystal reset process" within the claims.

[0031] As shown in Figure 4, step S2 includes step S21, step S22, or step S23, and terminates after either step S21 or step S23 and both step S22 have been completed. The control unit may process each of steps S21, S22, and S23 in parallel or sequentially.

[0032] As shown in Figure 4, in step S21, the control unit lowers the temperature inside the vacuum furnace 200 (see Figure 7). Specifically, the control unit stops heating inside the vacuum furnace 200 and lowers the temperature inside the vacuum furnace 200 to, for example, room temperature. Step S21 is an example of the "step of lowering the temperature inside the furnace of a chemical vapor deposition method" as described in the claims.

[0033] Furthermore, as shown in Figure 4, in step S22, the control unit stops the operation of introducing the reaction gas 2 (see Figure 7) into the vacuum furnace 200 (see Figure 7). Step S22 is an example of the "step of stopping the operation of introducing the reaction gas into the furnace of a chemical vapor deposition method" as described in the claims.

[0034] Furthermore, as shown in Figure 4, in step S23, the control unit increases the pressure inside the vacuum furnace 200 (see Figure 7). Specifically, as shown in Figure 7(c), the control unit increases the pressure inside the vacuum furnace 200 to near atmospheric pressure by introducing the seed crystal reset gas 3 into the vacuum furnace 200. At that time, the control unit replaces the reaction gas 2 (see Figure 7(b)) inside the vacuum furnace 200 with the seed crystal reset gas 3. The seed crystal reset gas 3 is, for example, at least one of oxygen, nitrogen, or doping gases for silicon such as phosphine, boron trichloride, and carbon fluoride. Carbon fluoride is, for example, C ２ F ６ and CF ４ And so on. Step S23 is an example of the "step of increasing the pressure inside the furnace for chemical vapor deposition" and the "step of replacing the reaction gas" as described in the claims.

[0035] By performing step S22 and either step S21 or step S23, the control unit stops the growth of the first seed crystal 12 (see Figure 7(a)) and the first crystal 11, and a seed crystal reset layer 30 is formed on the upper surface (Z1 side surface) of the multiple first crystals 11 (first polycrystalline layer 10) whose growth has stopped. If the control unit does not perform step S23, the control unit introduces the seed crystal reset gas 3 into the vacuum furnace 200 in parallel with steps S21 and S22 without increasing the pressure inside the vacuum furnace 200. If the seed crystal reset gas 3 is oxygen, the seed crystal reset layer 30 becomes silicon oxide. If the seed crystal reset gas 3 is nitrogen, the seed crystal reset layer 30 becomes silicon nitride. If the seed crystal reset gas 3 is a silicon doping gas such as phosphine or boron trichloride, the seed crystal reset layer 30 becomes a silicon impurity diffusion film. Furthermore, if the seed crystal reset gas 3 is carbon fluoride, the seed crystal reset layer 30 becomes a CF polymer. Then, when any of the above steps S21, S22, and S23 are completed, step S2 is completed.

[0036] Next, as shown in Figures 3 and 7(d), in step S3, the control unit removes the seed crystal reset layer 30. Specifically, if the seed crystal reset layer 30 is a CF polymer, the control unit removes the seed crystal reset layer 30 by raising the temperature inside the vacuum furnace 200 to, for example, 800°C or higher. If the seed crystal reset layer 30 is a silicon oxide or silicon nitride, the seed crystal reset layer 30 is removed by etching outside the vacuum furnace 200. Note that if the seed crystal reset layer 30 is impurity-diffusing silicon, it does not need to be removed because the impurity-diffusing silicon is formed by diffusion into the silicon surface layer. Note that step S3 is an example of the "seed crystal reset layer removal step" of the claims.

[0037] Next, as shown in Figure 3, in step S4, the control unit prepares to grow a new crystal from the seed crystal. Step S4 is an example of the "second seed crystal growth preparation step" in the claims.

[0038] As shown in Figure 5, step S4 includes step S41, step S42, or step S43, and terminates after any of steps S41, S42, and S43 have been completed. The control unit may process each of steps S41, S42, and S43 in parallel or sequentially. In step S2, at least one of the steps for returning any of the environments inside the vacuum reactor 200 that were changed by the selected step from steps S21, S22, and S23 back to the state before step S2 is selected as step S4 from steps S41, S42, and S43.

[0039] As shown in Figure 5, in step S41, the control unit raises the temperature inside the vacuum furnace 200 (see Figure 7). Specifically, the control unit starts (restarts) heating inside the vacuum furnace 200, which was stopped in step S2, and raises the temperature inside the vacuum furnace 200 to, for example, 800°C. In other words, in the first embodiment, step S41 (step S4) includes the step of returning the temperature inside the vacuum furnace 200 to the state before step S2.

[0040] Furthermore, as shown in Figure 5, in step S42, the control unit starts the operation of introducing the reaction gas 2 (see Figure 7) into the vacuum furnace 200 (see Figure 7). Specifically, the control unit restarts the operation of introducing the reaction gas 2, which was stopped in step S2. In other words, in the first embodiment, step S42 (step S4) includes the step of returning the operation of introducing the reaction gas 2 into the vacuum furnace 200 to the state before step S2.

[0041] Furthermore, as shown in Figure 5, in step S43, the control unit reduces the pressure inside the depressurizing furnace 200 (see Figure 7). Specifically, the control unit reduces the pressure inside the depressurizing furnace 200 to approximately 10 Pa. In other words, in the first embodiment, step S43 (step S4) includes the step of returning the pressure inside the depressurizing furnace 200 to the state before step S2.

[0042] When the control unit performs step S41, step S42, or step S43, conditions for forming a second-type crystal 22 described later are satisfied. Then, when any one of step S41, step S42, and step S43 is completed, step S4 is completed.

[0043] Next, as shown in FIG. 3, FIG. 7(e) and FIG. 7(f), in step S5, the control unit forms a second polycrystalline layer 20.

[0044] Note that, as shown in FIG. 6, step S5 includes step S51 and step S52, and the control unit performs step S51 and step S52 in this order. As shown in FIG. 6 and FIG. 7(e), in step S51, the control unit maintains the state after the completion of step S4, thereby forming, on the upper surface (surface on the Z1 side) of the first polycrystalline layer 10, a plurality of second-type crystals 22 that are different from the first-type crystals 12 and made of the same material as the first-type crystals 12. In other words, the second-type crystals 22 are made of silicon.

[0045] Next, as shown in FIG. 6, in step S52, the control unit grows a second crystal 21 (see FIG. 7(f)) by growing a second-type crystal 22. Note that for the second crystal 21 to grow, it is necessary that a step for returning all the environments in the reduced pressure furnace 200 changed by the step selected in step S2 in step S4 to the state before step S2 be selected (performed). Therefore, in step S52, if there is any step that has not been performed yet among the steps for returning any of the environments in the reduced pressure furnace 200 changed by the step selected in step S2 to the state before step S2 in step S4 (steps S41, S42 and S43), the control unit performs the step that has not been performed yet. As a result, in step S52, all the steps for returning all the environments in the reduced pressure furnace 200 changed by the step selected in step S2 among step S4 to the state before step S2 are performed, and as shown in FIG. 7(e) and FIG. 7(f), the second-type crystal 22 and the second crystal 21 grow. Note that in step S4, if the steps for returning all the environments in the reduced pressure furnace 200 changed by the step selected in step S2 to the state before step S2 have been selected (performed), step S52 proceeds immediately after the completion of step S51.

[0046] Through the above steps S51 and S52, as shown in FIG. 7(e) and FIG. 7(f), the control unit forms a plurality of second-type crystals 22 that are different from the first-type crystals 12 and made of the same material as the first-type crystals 12 on the upper surface (surface on the Z1 side) of the first polycrystalline layer 10, and grows the second-type crystals 22 to form the second polycrystalline layer 20. Note that conditions such as pressure and temperature in the reduced pressure furnace 200 in step S52 are the same as those in step S1. Note that step S5 is an example of the "second polycrystalline layer forming step" in the claims.

[0047] The control unit repeats steps S2 to S5 a predetermined number of times, reinterpreting each step as adding 1 to the number of the polycrystalline layer. When the control unit repeats steps S2 to S5 five times, as shown in Figure 8, the polycrystalline film 300 has a structure in which the first polycrystalline layer 10, the second polycrystalline layer 20, the third polycrystalline layer 40, the fourth polycrystalline layer 50, the fifth polycrystalline layer 60, and the sixth polycrystalline layer 70 are stacked in this order (six layers). After the control unit repeats steps S2 to S5 a predetermined number of times, the manufacturing method for the polycrystalline film 100 is completed. When the seed crystal reset layer 30 is a CF polymer, the control unit performs all of steps S1 to S5 consecutively in a common vacuum furnace 200.

[0048] (Effects of the First Embodiment) Next, the effects of the first embodiment will be described.

[0049] In the first embodiment, as described above, multiple second seed crystals 22, which are different from the multiple first seed crystals 12 but made of the same material (silicon) as the multiple first seed crystals 12, are grown on top of the first polycrystalline layer 10 by chemical vapor deposition, thereby stacking them on the first polycrystalline layer 10 and forming a second polycrystalline layer 20 made of the same material (silicon) as the first polycrystalline layer 10. As a result, the polycrystalline film 100 can be made thicker by stacking the first polycrystalline layer 10 and the second polycrystalline layer 20, which are formed by growing different seed crystals from each other, thus eliminating the need to thicken only the first polycrystalline layer 10 or the second polycrystalline layer 20. Therefore, it is possible to suppress damage to the thickened first polycrystalline layer 10 or the second polycrystalline layer 20 due to adjacent crystals pushing against each other. As a result, the polycrystalline film 100 can be made thicker while suppressing damage.

[0050] Furthermore, in the first embodiment, as described above, between the first polycrystalline layer formation step (step S1) and the second polycrystalline layer formation step (step S5), there is a seed crystal reset step (step S2) in which the seed crystals to be grown are reset from a plurality of first seed crystals 12 to a plurality of second seed crystals 22, and after the seed crystal reset step (step S2), there is a second seed crystal growth preparation step (step S4) in which preparations are made to start the growth of the plurality of second seed crystals 22 by chemical vapor deposition in the second polycrystalline layer formation step (step S5), wherein the seed crystal reset step (step S2) includes the step of forming a seed crystal reset layer 30 on the first polycrystalline layer 10. As a result, the seed crystal reset step (step S2), which includes the step of forming a seed crystal reset layer 30, and the second seed crystal growth preparation step (step S4) make it possible to easily grow a plurality of second seed crystals 22 on top of the first polycrystalline layer 10 to form a second polycrystalline layer 20.

[0051] Furthermore, in the first embodiment, as described above, the seed crystal reset step (step S2) includes at least one of the following: stopping the introduction of reaction gas 2 into the vacuum furnace 200 (step S22), lowering the temperature inside the vacuum furnace 200 (step S21), and increasing the pressure inside the vacuum furnace 200 (step S23). The second seed crystal growth preparation step (step S4) includes returning at least one of the following, which were changed in the seed crystal reset step (step S2): the introduction of reaction gas 2 into the vacuum furnace 200, the temperature inside the vacuum furnace 200, and the pressure inside the vacuum furnace 200, back to the state before the seed crystal reset step (step S2). This makes it easy to stop the growth of multiple first seed crystals 12 by changing the state inside the vacuum furnace 200. Also, by returning the state inside the vacuum furnace 200 to the state before the seed crystal reset step (step S2), it is easy to start the growth of the second seed crystal 22 by chemical vapor deposition.

[0052] Furthermore, in the first embodiment, as described above, the second polycrystalline layer formation step (step S5) includes a step of returning the operation of introducing the reaction gas 2 into the vacuum furnace 200, the temperature inside the vacuum furnace 200, and the pressure inside the vacuum furnace 200 to the state before the seed crystal reset step (step S2). As a result, even if, in the second seed crystal growth preparation step (step S4), not all of the operations of introducing the reaction gas 2 into the vacuum furnace 200, the temperature inside the vacuum furnace 200, and the pressure inside the vacuum furnace 200 that were changed in the seed crystal reset step (step S2) have returned to the state before the seed crystal reset step (step S2), the second polycrystalline layer 20 can be easily formed in the second polycrystalline layer formation step (step S5).

[0053] Furthermore, in the first embodiment, as described above, the seed crystal reset step (step S2) includes at least a step of increasing the pressure inside the depressurized furnace 200, and the second seed crystal growth preparation step (step S4), or the second polycrystalline layer formation step (step S5), includes at least a step of returning the pressure inside the depressurized furnace 200 to the state before the seed crystal reset step (step S2). As a result, by increasing the pressure inside the depressurized furnace 200, the growth of the multiple first seed crystals 12 can be easily stopped. Also, by returning the pressure inside the depressurized furnace 200 to the state before the seed crystal reset step (step S2), the growth of the second seed crystal 22 by chemical vapor deposition can be easily started.

[0054] Furthermore, in the first embodiment, as described above, the first polycrystalline layer formation step (step S1), the seed crystal reset step (step S2), the second seed crystal growth preparation step (step S4), and the second polycrystalline layer formation step (step S5) are carried out consecutively within a common vacuum furnace 200. This reduces the time and effort required throughout the entire process compared to the case where the first polycrystalline layer formation step (step S1), the seed crystal reset step (step S2), the second seed crystal growth preparation step (step S4), and the second polycrystalline layer formation step (step S5) are carried out in different locations.

[0055] Furthermore, in the first embodiment, as described above, the first polycrystalline layer 10 and the second polycrystalline layer 20 are formed from silicon, and the seed crystal reset layer 30 contains at least one of impurity-diffusing silicon, silicon oxide, silicon nitride, and CF polymer. As a result, by resetting the growth of polycrystalline silicon with the seed crystal reset layer 30 containing at least one of impurity-diffusing silicon, silicon oxide, silicon nitride, and CF polymer, the polycrystalline film 100 can be easily made thicker while suppressing damage caused by adjacent crystals (first crystals 11 and second crystals 21) pushing against each other.

[0056] Furthermore, in the first embodiment, as described above, the process further includes a seed crystal reset layer removal step (step S3) to remove the seed crystal reset layer 30 before the second seed crystal growth preparation step (step S4), and the second polycrystalline layer formation step (step S5) includes a step of forming a second polycrystalline layer 20 that is stacked in contact with the first polycrystalline layer 10 by growing a plurality of second seed crystals 22 on top of the first polycrystalline layer 10 by chemical vapor deposition. This makes it possible to suppress a decrease in the overall performance of the thickened polycrystalline film 100 due to the seed crystal reset layer 30 remaining between the first polycrystalline layer 10 and the second polycrystalline layer 20.

[0057] Furthermore, in the first embodiment, as described above, the step of increasing the pressure in the depressurized furnace 200 (step S23) includes a reaction gas replacement step of replacing the reaction gas 2 in the depressurized furnace 200 with a seed crystal reset gas 3 containing at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride, and the second seed crystal growth preparation step (step S4) or the second polycrystalline layer formation step (step S5) includes a step of replacing the seed crystal reset gas 3 containing at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride in the depressurized furnace 200 with the reaction gas 2 (step S43). As a result, by replacing the reaction gas 2 in the vacuum furnace 200 with a seed crystal reset gas 3 containing at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride, the pressure in the vacuum furnace 200 can be easily increased, and a seed crystal reset layer 30 consisting of at least one of oxides, nitrides, impurity diffusers, and CF polymers can be easily formed on the first polycrystalline layer 10. Furthermore, by replacing the seed crystal reset gas 3 containing at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride in the vacuum furnace 200 with the reaction gas 2, the growth of the second seed crystal 22 by chemical vapor deposition can be easily initiated.

[0058] Furthermore, in the first embodiment, as described above, the polycrystalline film 100 comprises a first polycrystalline layer 10 formed by growing a plurality of first seed crystals 12, and a second polycrystalline layer 20 formed by growing a plurality of second seed crystals 22 which are different from the plurality of first seed crystals 12 but are made of the same material (silicon) as the plurality of first seed crystals 12, and which is laminated on the first polycrystalline layer 10, and is made of the same material (silicon) as the first polycrystalline layer 10. As a result, the polycrystalline film 100 can be made thicker by laminating the first polycrystalline layer 10 and the second polycrystalline layer 20 which are formed by growing different seed crystals from each other, so that it is not necessary to make only the first polycrystalline layer 10 or the second polycrystalline layer 20 thicker. For this reason, when manufacturing the polycrystalline film 100, it is possible to suppress damage to the thickened first polycrystalline layer 10 or the second polycrystalline layer 20 due to adjacent crystals growing against each other. As a result, it is possible to provide a polycrystalline film 100 that can be made thicker while suppressing damage.

[0059] [Second Embodiment] Next, the polycrystalline film 400 according to the second embodiment and the method for manufacturing the same will be described with reference to Figures 9 to 13. Components similar to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0060] (Polycrystalline film structure) The structure of the polycrystalline film 400 according to the second embodiment will be described with reference to Figure 9.

[0061] In the second embodiment, unlike the first embodiment in which the first polycrystalline layer 10 and the second polycrystalline layer 20 are stacked in contact with each other, a seed crystal reset layer 80 exists between the first polycrystalline layer 10 and the second polycrystalline layer 20. Specifically, the first polycrystalline layer 10, the seed crystal reset layer 80, and the second polycrystalline layer 20 are stacked in this order. The seed crystal reset layer 80 is made of amorphous silicon, for example.

[0062] (Method for Manufacturing Polycrystalline Films) Next, a method for manufacturing the polycrystalline film 400 according to the second embodiment will be described with reference to Figures 10 to 13. Note that the method for manufacturing the polycrystalline film 400 shown below is carried out by the control unit of a device not shown.

[0063] In the second embodiment, unlike the first embodiment in which the seed crystal reset layer includes at least one of impurity-diffusing silicon, silicon oxide, silicon nitride, and CF polymer, the seed crystal reset layer is made of amorphous silicon. Also, in the second embodiment, unlike the first embodiment in which the control unit removes the seed crystal reset layer, the control unit does not remove the seed crystal reset layer.

[0064] As shown in Figures 10, 13(a), and 13(b), in step S101, the control unit forms the first polycrystalline layer 10. The details are the same as in the first embodiment, so the explanation is omitted. Step S101 is an example of the "first polycrystalline layer formation step" of the claims.

[0065] Next, as shown in Figures 10 and 13(c), in step S102, the control unit forms a seed crystal reset layer 80 on the first polycrystalline layer 10. Once formed, the seed crystal reset layer 80 resets the seed crystal to be grown from a plurality of first seed crystals 12 to a plurality of second seed crystals 22. Step S102 is an example of the "seed crystal reset step" of the claims.

[0066] As shown in Figure 11, step S102 includes steps S1021 and S1022, and terminates after both steps S1021 and S1022 have been completed. The control unit may process steps S1021 and S1022 in parallel or sequentially.

[0067] As shown in Figure 11, in step S1021, the control unit lowers the temperature inside the vacuum furnace 200 (see Figure 7). Specifically, the control unit reduces the degree of heating inside the vacuum furnace 200 to lower the temperature inside the vacuum furnace 200 to, for example, 500°C. Step S1021 is an example of the "step for lowering the temperature inside the furnace of a chemical vapor deposition method" as described in the claims.

[0068] Furthermore, as shown in Figure 11, in step S1022, the control unit stops the operation of introducing the reaction gas 2 (see Figure 13) into the vacuum furnace 200 (see Figure 13). Step S1022 is an example of the "step of stopping the operation of introducing the reaction gas into the furnace of a chemical vapor deposition method" as described in the claims.

[0069] Steps S1021 and S1022 are performed by the control unit, which stops the growth of the first seed crystal 12 (see Figure 13(a)) and the first crystal 11 (see Figure 13), and a seed crystal reset layer 80 is formed on the upper surface (Z1 side surface) of the multiple first crystals 11 (first polycrystalline layer 10) whose growth has stopped. The seed crystal reset layer 80 is made of amorphous silicon. When both steps S1021 and S1022 are completed, step S102 is completed.

[0070] Next, as shown in Figure 10, in step S103, the control unit prepares to grow a new crystal from the seed crystal. Step S103 is an example of the "second seed crystal growth preparation step" in the claims.

[0071] As shown in Figure 12, step S103 includes steps S1031 and S1032, and terminates after both steps S1031 and S1032 have been completed. The control unit may process steps S1031 and S1032 in parallel or sequentially.

[0072] As shown in Figure 12, in step S1031, the control unit raises the temperature inside the vacuum furnace 200 (see Figure 13). Specifically, the control unit increases the degree of heating into the vacuum furnace 200, which was reduced in step S2, to raise the temperature inside the vacuum furnace 200 to, for example, 800°C. In other words, in the second embodiment, step S1031 (step S103) includes the step of returning the temperature inside the vacuum furnace 200 to the state before step S102.

[0073] Furthermore, as shown in Figure 12, in step S1032, the control unit starts the operation of introducing the reaction gas 2 (see Figure 13) into the vacuum furnace 200 (see Figure 13). Specifically, the control unit restarts the operation of introducing the reaction gas 2, which was stopped in step S102. In other words, in the second embodiment, step S1032 (step S103) includes the step of returning the operation of introducing the reaction gas 2 into the vacuum furnace 200 to the state before step S102.

[0074] The control unit performs steps S1031 and S1032, thereby creating the conditions for growing crystals again by chemical vapor deposition. Once steps S1031 and S1032 are completed, step S103 is terminated.

[0075] Next, as shown in Figures 10, 13(d), and 13(e), in step S104, the control unit forms a second polycrystalline layer 20. Specifically, as shown in Figures 13(d) and 13(e), the control unit forms a second polycrystalline layer 20 by growing a plurality of second seed crystals 22 on the upper surface (Z1 side surface) of the seed crystal reset layer 80, which are different from the first seed crystal 12 but made of the same material as the first seed crystal 12. In other words, the second seed crystals 22 are made of silicon. The pressure, temperature, and other conditions inside the vacuum furnace 200 in step S104 are the same as in step S101. Step S104 is an example of the "second polycrystalline layer formation step" of the claims.

[0076] The control unit repeats steps S102 to S104 a predetermined number of times, reinterpreting the number of the polycrystalline layer as incrementing by 1. After the control unit has repeated steps S102 to S104 a predetermined number of times, the manufacturing method for the polycrystalline film 400 is completed. The control unit performs all of steps S101 to S104 consecutively within a common vacuum furnace 200.

[0077] (Effects of the second embodiment) Next, the effects of the second embodiment will be described.

[0078] In the second embodiment, as described above, the first polycrystalline layer 10 and the second polycrystalline layer 20 are formed from silicon, and the seed crystal reset layer 80 is made of amorphous silicon. As a result, the seed crystal reset layer 80 made of amorphous silicon, which is formed on the first polycrystalline layer 10 made of silicon, can easily reset the growing seed crystal from a plurality of first seed crystals 12 to a plurality of second seed crystals 22.

[0079] Furthermore, in the second embodiment, as described above, the polycrystalline film 400 includes a seed crystal reset layer 80 made of amorphous silicon, which is provided between the first polycrystalline layer 10 and the second polycrystalline layer 20. This allows the polycrystalline film 400 to be easily made thicker while suppressing damage caused by adjacent crystals (first crystals 11 and second crystals 21) pushing against each other, by resetting the growth of the polycrystalline silicon with the seed crystal reset layer 80 made of amorphous silicon when manufacturing the polycrystalline film 400. The other effects of the second embodiment are the same as those of the first embodiment.

[0080] [Modifications] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the description of the embodiments above, and further includes all modifications (modifications) within the meaning and scope equivalent to the claims.

[0081] In the first and second embodiments described above, the first polycrystalline layer 10 and the second polycrystalline layer 20 are shown to be formed from silicon, but the present invention is not limited thereto. For example, the first polycrystalline layer 10 and the second polycrystalline layer 20 may be formed from, for example, silicon germanium.

[0082] Furthermore, in the first embodiment described above, an example was shown where the thickness t1 of the first polycrystalline layer 10 and the thickness t2 of the second polycrystalline layer 20 are approximately equal, but the present invention is not limited to this. For example, the thickness t1 of the first polycrystalline layer 10 and the thickness t2 of the second polycrystalline layer 20 may be different.

[0083] Furthermore, while the first and second embodiments described above show examples of forming seed crystal reset layers 30 and 80, the present invention is not limited thereto. For example, if the growing seed crystal can be reset from a plurality of first seed crystals 12 to a plurality of second seed crystals 22, it is not necessary to form a seed crystal reset layer.

[0084] Furthermore, although the first embodiment described above shows an example in which the manufacturing method of the polycrystalline films 100 and 300 includes a step of removing the seed crystal reset layer 30 (step S3), the present invention is not limited thereto. For example, the manufacturing method of the polycrystalline films 100 and 300 does not have to include a step of removing the seed crystal reset layer 30 (step S3). In that case, regardless of whether the seed crystal reset layer 30 is impurity-diffusing silicon, silicon oxide, silicon nitride, or CF polymer, the control unit performs all of steps S1 to S5 continuously in a common vacuum furnace 200.

[0085] Furthermore, in the first embodiment described above, the control unit is shown to form a seed crystal reset layer 30 made of silicon oxide by replacing the reaction gas 2 in the vacuum furnace 200 with a seed crystal reset gas 3 made of oxygen, but the present invention is not limited thereto. For example, the seed crystal reset layer 30 made of silicon oxide may be formed by an apparatus or worker (not shown) removing the first polycrystalline layer 10 from inside the vacuum furnace 200 to the outside and exposing it to outside air containing oxygen.

[0086] 2. Reaction gas 3. Seed crystal reset gas (at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride) 10. First polycrystalline layer 12. First seed crystal 20. Second polycrystalline layer 22. Second seed crystal 30, 80. Seed crystal reset layer 100, 300, 400. Polycrystalline film 200. Vacuum reactor (chemical vapor deposition reactor)

Claims

1. A method for manufacturing a polycrystalline film, comprising: a first polycrystalline layer formation step of forming a first polycrystalline layer by growing a plurality of first type crystals by chemical vapor deposition; and a second polycrystalline layer formation step of stacking a plurality of second type crystals, which are different from the plurality of first type crystals but made of the same material as the plurality of first type crystals, on the first polycrystalline layer by chemical vapor deposition above the first polycrystalline layer, thereby forming a second polycrystalline layer made of the same material as the first polycrystalline layer.

2. The method for manufacturing a polycrystalline film according to claim 1, further comprising: a seed crystal reset step between the first polycrystalline layer formation step and the second polycrystalline layer formation step, in which the seed crystals to be grown are reset from the plurality of first seed crystals to the plurality of second seed crystals; and a second seed crystal growth preparation step after the seed crystal reset step, in which preparations are made to initiate the growth of the plurality of second seed crystals in the second polycrystalline layer formation step by chemical vapor deposition, wherein the seed crystal reset step includes the step of forming a seed crystal reset layer on the first polycrystalline layer.

3. The method for producing a polycrystalline film according to claim 2, wherein the seed crystal reset step includes at least one of the steps of stopping the introduction of a reaction gas into the furnace of the chemical vapor deposition method, lowering the temperature inside the furnace, and increasing the pressure inside the furnace, and the second seed crystal growth preparation step includes a step of returning at least one of the changes made in the seed crystal reset step—the introduction of the reaction gas into the furnace, the temperature inside the furnace, and the pressure inside the furnace—to the state before the seed crystal reset step.

4. The method for producing a polycrystalline film according to claim 3, wherein the second polycrystalline layer formation step includes a step of returning the operation of introducing the reaction gas into the furnace, the temperature inside the furnace, and the pressure inside the furnace to the state before the seed crystal reset step.

5. The method for manufacturing a polycrystalline film according to claim 3, wherein the seed crystal reset step includes at least a step of increasing the pressure inside the furnace, and the second seed crystal growth preparation step or the second polycrystalline layer formation step includes at least a step of returning the pressure inside the furnace to the state before the seed crystal reset step.

6. The method for producing a polycrystalline film according to claim 2, wherein the first polycrystalline layer formation step, the seed crystal reset step, the second seed crystal growth preparation step, and the second polycrystalline layer formation step are carried out consecutively in a common chemical vapor deposition furnace.

7. The method for producing a polycrystalline film according to claim 2, wherein the first polycrystalline layer and the second polycrystalline layer are formed from silicon, and the seed crystal reset layer comprises at least one of impurity-diffused silicon, silicon oxide, silicon nitride, CF polymer, and amorphous silicon.

8. The method for producing a polycrystalline film according to claim 2, further comprising a seed crystal reset layer removal step of removing the seed crystal reset layer before the second seed crystal growth preparation step, wherein the second polycrystalline layer formation step includes a step of forming the second polycrystalline layer which is stacked in contact with the first polycrystalline layer by growing the plurality of second seed crystals above the first polycrystalline layer by chemical vapor deposition.

9. The method for producing a polycrystalline film according to claim 5, wherein the step of increasing the pressure inside the furnace includes a reaction gas replacement step of replacing the reaction gas inside the furnace with at least one of oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride, and the second type crystal growth preparation step or the second polycrystalline layer formation step includes a step of replacing at least one of the oxygen, nitrogen, phosphine, boron trichloride, and carbon fluoride inside the furnace with the reaction gas.

10. A polycrystalline film comprising: a first polycrystalline layer formed by growing a plurality of first type crystals; and a second polycrystalline layer laminated on the first polycrystalline layer and formed by growing a plurality of second type crystals which are different from the plurality of first type crystals but made of the same material as the plurality of first type crystals, and which is made of the same material as the first polycrystalline layer.

11. The polycrystalline film according to claim 10, further comprising a seed crystal reset layer provided between the first polycrystalline layer and the second polycrystalline layer, the seed crystal reset layer comprising at least one of impurity-diffusing silicon, silicon oxide, silicon nitride, CF polymer, and amorphous silicon.

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