Semiconductor thin film production method and substrate with semiconductor thin film

Abstract

A semiconductor thin film production method according to the present invention comprises: a substrate preparation step for preparing a substrate (Sub1) formed of an oxide crystal; a buffer layer formation step for forming, on the substrate (Sub1), six buffer layers (L21, L22, ..., L26) composed of Gex[i]Sn1−x[i]O2 (1 ≤ i ≤ N) crystals by a mist CVD method; and a thin film formation step for forming, on the buffer layer (L26), a semiconductor thin film composed of an r-GeO2 crystal by the mist CVD method.

Description

Method for producing semiconductor thin film and substrate with semiconductor thin film

[0001] The present invention relates to a method for producing a semiconductor thin film and a substrate with a semiconductor thin film.

[0002] M ２ O ３ (where M is a Group 13 metal of the periodic table) as a main component, a laminated structure in which a crystalline oxide film containing GeO ２ is laminated on the crystal substrate has been proposed (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Publication No. 2024-114114

[0004] However, in the case of the laminated structure described in Patent Document 1, the degree of lattice mismatch between the crystal substrate and the crystalline oxide film is relatively large. Therefore, unless the growth temperature for growing the crystalline oxide film on the crystal substrate is controlled within a relatively narrow range, it may be difficult to produce a crystalline oxide film with good crystallinity.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a semiconductor thin film and a substrate with a semiconductor thin film, which can produce a high-quality semiconductor thin film made of r-GeO ２ crystals with good crystallinity.

[0006] The method for producing a semiconductor thin film according to the present invention comprises: a substrate preparation step of preparing a substrate formed of an oxide crystal; and after the substrate preparation step, forming, on the substrate by mist CVD method, Ge ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ a buffer layer forming step of forming N buffer layers (N is an integer of 2 or more, 1≦i≦N) made of crystal; and a thin film forming step of forming a semiconductor thin film made of r-GeO ２ crystal on the N buffer layers by mist CVD method, wherein between Ge ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ crystal forming one of two buffer layers adjacent in a lamination direction on the substrate side, and Ge ｘ［ｉ＋１］ Sn １－ｘ［ｉ＋１］ O ２ forming the other of the two buffer layers, a relationship of X[i]<X[i+1] holds.

[0007] From another perspective, the semiconductor thin film substrate according to the present invention comprises a substrate formed from an oxide crystal and a Ge formed on the substrate. ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ A buffer layer of N (where N is an integer of 2 or more, 1 ≤ i ≤ N) crystalline layers, and r-GeO formed on the N-layer buffer layer. ２ A semiconductor thin film made of crystals, comprising Ge forming one of two adjacent buffer layers in the stacking direction, on the substrate side. ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ The crystal and the Ge that forms the other ｘ［ｉ＋１］ Sn １－ｘ［ｉ＋１］ O ２ The relationship X[i] < X[i+1] holds between these two points.

[0008] According to the present invention, Ge is applied to a substrate by the mist CVD method. ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ After forming an N-layer buffer layer made of crystals, r-GeO is deposited on the N-layer buffer layer by mist CVD. ２ A semiconductor thin film made of crystals is formed. This allows the strain in the semiconductor thin film caused by lattice mismatch between the substrate and the semiconductor thin film to be gradually relieved by the N-layer buffer layer, resulting in a high-quality r-GeO with good crystallinity. ２ It is possible to fabricate semiconductor thin films made of crystals.

[0009] This is a schematic cross-sectional view of an example of a substrate with a semiconductor thin film according to the embodiment. This is a schematic configuration diagram of a mist CVD apparatus according to the embodiment. These are schematic cross-sectional views of samples according to Comparative Examples 1 to 6. This figure shows the results of 2θ-ωXRD of the sample according to Comparative Example 1 immediately after semiconductor thin film growth and after immersion in deionized water. This figure shows the results of XRD of the sample according to Example 1 immediately after semiconductor thin film growth and after immersion in deionized water. This figure shows the results of Φ scan XRD of the sample according to Example 1. This figure shows the reciprocal lattice map of the sample according to Example 1. (A) to (C) are SEM images of the surface of the sample according to Comparative Example 1 immediately after semiconductor thin film growth, and (D) to (F) are SEM images of the surface of the sample according to Comparative Example 1 after immersion in deionized water. (A) is a photograph of the surface of the sample according to Comparative Example 1 after immersion in deionized water, (B) is an image showing the EDX mapping results for Ge of the sample according to Comparative Example 1 after immersion in deionized water, (C) is an image showing the EDX mapping results for O of the sample according to Comparative Example 1 after immersion in deionized water, and (D) is an image showing the EDX mapping results for Ti of the sample according to Comparative Example 1 after immersion in deionized water. This is an SEM image of the surface of the sample according to Example 1 immediately after growth. This is an SEM image of the surface of the sample according to Example 1 after immersion in deionized water. This figure shows the Raman spectroscopy measurement results of the sample according to Example 2. This figure shows the XRD results of the samples according to Comparative Examples 2 to 7. This figure shows the XRD results of the samples according to Comparative Example 8 and Examples 2 to 6. XRD r-GeO of the samples according to Examples 2 to 6 ２This figure shows the full width at half maximum of the rocking curve of the corresponding peak. (A) is an SEM image of the surface of the sample according to Comparative Example 8 immediately after semiconductor thin film growth, (B) is an SEM image of the surface of the sample according to Example 6 immediately after semiconductor thin film growth, (C) is an SEM image of the surface of the sample according to Example 5 immediately after semiconductor thin film growth, (D) is an SEM image of the surface of the sample according to Example 4 immediately after semiconductor thin film growth, (E) is an SEM image of the surface of the sample according to Example 3 immediately after semiconductor thin film growth, and (F) is an SEM image of the surface of the sample according to Example 2 immediately after semiconductor thin film growth. This is an SEM image of the surface of the sample according to Example 6 after immersion in deionized water. This is an SEM image of the surface of the sample according to Example 2 after immersion in deionized water. This figure shows the XRD results of the sample according to Example 7. This figure shows the XRD results of the sample according to Example 8. This figure shows the XRD results of the sample according to Example 9. This figure shows the XRD results of the sample according to Example 10. This figure shows the Φ scan XRD results of the sample according to Example 7. This figure shows the results of the Φ scan XRD of the sample according to Example 8. This figure shows the results of the Φ scan XRD of the sample according to Example 9. This figure shows the results of the Φ scan XRD of the sample according to Example 10. This is an SEM image of the surface of the sample according to Example 7. This is an SEM image of the surface of the sample according to Example 8. This is an SEM image of the surface of the sample according to Example 9. This is an SEM image of the surface of the sample according to Example 10. This figure shows the XRD results of the samples according to Examples 11 to 15. XRD results of r-GeO of the samples according to Example 1 and Examples 11 to 15. ２ This figure shows the full width at half maximum of the rocking curve of the corresponding peak. This figure shows the sheet resistance values ​​of the samples according to Examples 13 to 15. This figure shows the results of the SIMS analysis of the sample according to Example 14.

[0010] Hereinafter, a method for manufacturing a semiconductor thin film and a substrate with a semiconductor thin film according to an embodiment of the present invention will be described with reference to the drawings. The substrate with a semiconductor thin film according to this embodiment is a substrate made of oxide crystal and Ge formed on the substrate ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２The device comprises an N (where N is an integer of 2 or more) layer buffer layer made of crystal, and a semiconductor thin film formed on the buffer layer group. Here, the N layer buffer layer is a so-called gradient buffer layer in which the composition ratio of Ge is varied in each buffer layer such that the Ge composition ratio decreases as the buffer layer gets closer to the semiconductor layer. Here, Ge forms one of the two adjacent buffer layers in the stacking direction that is on the substrate side. ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ The crystal and the Ge that forms the other ｘ［ｉ＋１］ Sn １－ｘ［ｉ＋１］ O ２ The relationship X[i] < X[i+1] holds between these two points. Furthermore, for the buffer layer located closest to the substrate, the Ge composition ratio X[1] is preferably 0.3 or less, and for the buffer layer located closest to the semiconductor thin film, the Ge composition ratio X[N] is preferably 0.2 or more, and more preferably 0.4 or more.

[0011] The semiconductor thin film substrate according to this embodiment comprises six buffer layers L21, L22, ..., L26 formed on the substrate Sub1, as shown in Figure 1, for example. ２ Crystal, sapphire (Al ２ O ３ It is formed from crystals, etc. The buffer layer L21 is stacked on the substrate Sub1, Ge ｘ［１］ Sn １－ｘ［１］ O ２ It consists of crystals (0 < x[1] < 1). The buffer layer L22 is stacked on the buffer layer L21, Ge ｘ［２］ Sn １－ｘ［２］ O ２ It consists of crystals (x[1] < X[2] < 1). The buffer layer L23 is stacked on the buffer layer L22, Ge ｘ［３］ Sn １－ｘ［３］ O ２ It consists of crystals (x[2] < X[3] < 1). The buffer layer L24 is stacked on the buffer layer L23, Ge ｘ［４］ Sn １－ｘ［４］ O ２ It consists of crystals (x[3] < X[4] < 1). The buffer layer L25 is stacked on top of the buffer layer L24, Ge ｘ［５］ Sn １－ｘ［５］ O ２It consists of crystals (x[4] < X[5] < 1). The buffer layer L26 is stacked on top of the buffer layer L25, Ge ｘ［６］ Sn １－ｘ［６］ O ２ The crystal consists of x[5] < x[6] < 1. The relationship x[1] < x[2] < x[3] < x[4] < x[5] < x[6] holds between x[1], x[2], x[3], x[4], x[5], and x[6], respectively, and these are set to, for example, "0.4", "0.55", "0.7", "0.8", "0.9", and "0.95".

[0012] The semiconductor thin film L1 is r-GeO ２ (Rutile structure Ge0 ２ ) It consists of crystals. Here, the semiconductor thin film L1 may contain Sb, which is an n-type impurity.

[0013] In the semiconductor thin film manufacturing method according to this embodiment, a plurality of buffer layers are formed on the aforementioned substrate using the mist CVD (Chemical Vapor Deposition) method, and then r-GeO is placed on the buffer layers. ２ A semiconductor thin film made of crystals is deposited. Here, for example, a mist CVD apparatus as shown in Figure 2 is used. This mist CVD apparatus comprises a gas supply source 21, a flow meter 23, a raw material supply container 31, a water storage container 33, an ultrasonic transducer 35, a reaction vessel 41, a heater 42, and a susceptor 43. The gas supply source 21 and the raw material supply container 31 are connected via a first gas supply pipe P1. The raw material supply container 31 and the reaction vessel 41 are connected via a second gas supply pipe P2. In addition, an exhaust pipe P3 for discharging excess gas from inside the reaction vessel 41 is connected to the reaction vessel 41.

[0014] The raw material supply container 31 stores a raw material solution 32 obtained by dissolving the precursor raw materials of the oxide that will form the buffer layer or semiconductor thin film in a solvent. As the precursor raw materials for the oxide that will form the buffer layer, compounds containing germanium (Ge) and compounds containing tin (Sn) are used. As a compound containing Ge, bis[2-carboxyethylgermanium]sesquioxide (C ６ H １０ Ge ２ O ７ ), GeI４ , GeBr ４ , GeO ２ Examples include tin chloride pentahydrate (SnCl). ４ ・5H ２ O) is one example. As precursor raw materials for oxides that form semiconductor thin films, compounds of one or more alcohol compounds selected from alcohol compounds and Ge are examples. As solvents, deionized water, alcohol, etc. are examples.

[0015] Then, to make the conductivity type of the semiconductor thin film L1 n-type, a compound containing antimony (Sb) is dissolved in the raw material solution 32. This compound is, for example, antimony chloride (SbCl ４ ), antimony acetate (III) (Sb(CH) ３ COO) ３ ), antimony acetylacetonate (C １５ H ２ 10 ６ Sb) is used. In this case, an aqueous hydrochloric acid solution is used as the solvent, and C is added to the aqueous hydrochloric acid solution. ６ H １０ Ge ２ O ７ ) and SbCl ４ The two are dissolved. Furthermore, the Sb concentration in the raw material solution 32 is set to be 0.01 at.% or more and 1.0 at.% or less.

[0016] The gas supply source 21 supplies a carrier gas such as air, nitrogen, or oxygen to the raw material supply container 31 for sending the atomized raw material solution into the reaction vessel 41. The water storage container 33 contains water 34 for ultrasonic matching, and the raw material supply container 31 is positioned inside the water storage container 33 with a portion of it submerged in the water 34 stored in the water storage container 33. An ultrasonic transducer 35 is fixed to the water storage container 33. The ultrasonic waves generated by the ultrasonic transducer 35 are transmitted to the raw material solution 32 stored in the raw material supply container 31 via the matching water 34 stored in the water storage container 33.

[0017] The operation of the mist CVD apparatus will be described here. First, vibration of the ultrasonic vibrator 35 transmits vibration energy to the raw material solution 32 via the matching water 34, and the vibration energy atomizes the raw material solution 32 into a mist. The atomized raw material solution 32 is then fed into the reaction vessel 41 through the second gas supply pipe P2 by the carrier gas supplied from the gas supply source 21 into the raw material supply container 31. At this time, by adjusting the flow rate of the carrier gas flowing through the first gas supply pipe P1 while checking the flow meter 23, the amount of the raw material solution fed into the reaction vessel 41 is adjusted. The atomized raw material solution fed into the reaction vessel 41 is supplied onto the surface of the substrate 1 supported by the susceptor 43 in the reaction vessel 41. When the atomized raw material solution supplied onto the surface of the substrate Sub1 is heated by the heater 42, the metal compound in the raw material solution chemically reacts with the solvent, and a buffer layer and a semiconductor thin film grow above the substrate Sub1. Here, the substrate Sub1 is heated to a temperature within a temperature range of not lower than 550°C and not higher than 950°C.

[0018] In the method for manufacturing a semiconductor thin film according to the present embodiment, after performing a substrate preparation step of preparing a substrate formed of an oxide crystal, first, a buffer layer formation step of forming the plurality of buffer layers described above on the substrate is performed by mist CVD. Thereafter, r-GeO is formed on the substrate by mist CVD ２ A thin film formation step of forming a semiconductor thin film made of a crystal is performed.

[0019] As described above, in the method for manufacturing a semiconductor thin film according to the present embodiment, Ge is deposited on a substrate by mist CVD ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ After forming an N-layer buffer layer made of a crystal, r-GeO is formed on the N-layer buffer layer by mist CVD ２ A semiconductor thin film made of a crystal is formed. Accordingly, strain in the semiconductor thin film caused by lattice mismatch between the substrate and the semiconductor thin film can be gradually relaxed by the N-layer buffer layer, so that high-quality r-GeO with good crystallinity ２ A semiconductor thin film made of a crystal can be manufactured.

[0020] Furthermore, since the mist CVD method employed in the method for manufacturing a semiconductor thin film according to the present embodiment is a non-vacuum process, no configuration for achieving a vacuum atmosphere is required, thereby enabling simplification of the apparatus.

[0021] Various embodiments and modifications of the present invention are possible without departing from the broad spirit and scope of the present invention. Further, the above-described embodiments are intended to illustrate the present invention, and do not limit the scope of the present invention. That is, the scope of the present invention is defined by the claims, not by the embodiments. Various modifications implemented within the scope of the claims and within the scope of equivalent meaning of the invention are considered to be within the scope of the present invention.

[0022] The method for manufacturing a semiconductor thin film according to the present invention will be described based on examples. Note that the present invention is not limited to the examples described below.

[0023] All samples according to Comparative Examples 1 to 6 have a structure in which a semiconductor thin film L1 is formed on a substrate Sub1, as shown in FIG. All samples according to Comparative Example 7 and Examples 1 to 13 have a structure in which six buffer layers L21, L22, ..., L26 and a semiconductor thin film L1 are formed on a substrate Sub1, as shown in FIG. 1 described in Embodiment 1. In the samples according to Comparative Examples 1 to 7, Examples 1 to 5, and Examples 10 to 13, a TiO with a (001) plane exposed on the surface is used as the substrate ２ single crystal substrate (manufactured by Furuuchi Chemical Corporation) is employed. Further, in the sample according to Example 6, an Al with a c-plane exposed on the surface ２ O ３ single crystal substrate (manufactured by Kyocera Corporation) is employed, and in the sample according to Example 7, an Al with an a-plane exposed on the surface ２ O ３ single crystal substrate (manufactured by Kyocera Corporation) is employed. Furthermore, in the sample according to Example 8, an Al with an m-plane exposed on the surface ２ O ３ single crystal substrate (manufactured by Kyocera Corporation) is employed, and in the sample according to Example 9, an Al with an r-plane exposed on the surface ２ O ３ single crystal substrate (manufactured by Kyocera Corporation) is employed.

[0024] The semiconductor thin films of the samples in Comparative Examples 1 to 6 were prepared by mist CVD on a substrate using r-GeO ２ The semiconductor thin films were formed by creating a crystalline semiconductor thin film. The buffer layers and semiconductor thin films in Comparative Example 7 and Examples 1 to 13 were formed by the manufacturing method described in Embodiment 1. Here, an ultrasonic transducer vibrating at a frequency of 2.4 MHz (Honda Electronics Co., Ltd., HM-2412) was used as the ultrasonic transducer of the mist CVD apparatus mentioned above. In the buffer layer formation process in Comparative Examples 1 to 7 and Examples 1 to 13, bis[2-carboxyethylgermanium]sesquioxide (C) was used as the raw material solution. ６ H １０ Ge ２ O ７ ) (manufactured by Tokyo Chemical Industry Co., Ltd.) and tin chloride pentahydrate (SnCl ４ ・5H ２ O) (manufactured by Kishida Chemical Co., Ltd.) was dissolved in deionized water to prepare a solution with a concentration of 0.025 mol / L. Six types of raw material solutions were prepared, with Ge to Sn ratios of 70:30, 75:25, 80:20, 85:15, 90:20, and 95:5. Six buffer layers were formed by using each raw material solution in sequence. As a result, Ge was applied to the substrate. ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ Six buffer layers were formed, consisting of crystals (1 ≤ i ≤ 6). Here, the composition ratios of Ge in each buffer layer, x[1], x[2], x[3], x[4], x[5], x[6], are Ge ｘ［１］ Sn １－ｘ［１］ O ２ Assuming that the crystalline buffer layer is located closest to the substrate, the values ​​were "0.4", "0.55", "0.7", "0.8", "0.9", and "0.95", respectively.

[0025] Next, in the formation of semiconductor thin films according to Comparative Examples 1 to 7 and Examples 1 to 9, the raw material solution is the aforementioned C ６ H １０ Ge ２ O ７An aqueous solution with a concentration of 0.025 mol / L was used, obtained by dissolving in deionized water. In the formation of semiconductor thin films according to Comparative Examples 1 to 7 and Examples 1 to 9, the above-mentioned C was used as the raw material solution. ６ H １０ Ge ２ O ７ A solution prepared by dissolving in deionized water to a concentration of 0.025 mol / L was used. In the formation of semiconductor thin films according to Examples 10 to 13, the above-mentioned C was used as the raw material solution. ６ H １０ Ge ２ O ７ And, antimony chloride (SbCl ４ ) (manufactured by Fujifilm Wako Chemical Co., Ltd.) was dissolved in a deionized aqueous solution containing 34% hydrochloric acid to prepare a solution with a concentration of 0.0125 mol. The concentrations of Sb in the raw material solutions for Examples 10 to 13 were 0.01 at.%, 0.1 at.%, 0.5 at.%, and 1.0 at.%, respectively. Nitrogen was used as the carrier gas and dilution gas. The flow rate of the carrier gas during film formation was 2.0 L / min. In the process of forming the semiconductor thin film, the substrate Sub1 was placed in the film formation chamber S11 and then heated to the growth temperature described later by the heater 42. The film formation time for Comparative Example 1 and Example 1 was set so that the thickness of the semiconductor thin film was approximately 1.0 μm and the total film thickness of the six buffer layers was 94 nm. For Comparative Examples 2 to 8, Examples 2 to 6, and Examples 11 to 15, the film deposition time was set so that the thickness of the semiconductor thin film was approximately 500 nm and the total film thickness of the six buffer layers was 50 nm. For Examples 7 to 10, the film deposition time was set so that the thickness of the semiconductor thin film was approximately 500 nm and the total film thickness of the six buffer layers was 94 nm. Here, the growth temperatures in the semiconductor thin film formation process for Comparative Examples 1 to 7 were 825°C, 850°C, 825°C, 750°C, 650°C, 550°C, and 450°C, respectively. Furthermore, the growth temperatures in the semiconductor thin film formation process for Examples 1 to 6 were 825°C, 850°C, 825°C, 750°C, 650°C, and 550°C, respectively. In addition, the growth temperature in the semiconductor thin film formation process for Comparative Example 8 was 450°C. Furthermore, the growth temperature in the semiconductor thin film formation process for Examples 7 to 15 was 850°C in all cases.

[0026] The crystalline structure of the semiconductor thin films was evaluated for each of the samples related to Comparative Examples 1 to 8 and Examples 1 to 15. For the samples related to Comparative Example 1 and Example 1, the crystalline structure was evaluated before and after immersion in deionized water for 1 hour. The sheet resistance value was measured for each of the samples related to Examples 11 to 15. The crystalline structure of the semiconductor thin films related to Comparative Examples 1 to 8 and Examples 1 to 15 was confirmed by the results measured using an X-ray diffraction (XRD) analyzer (BRUKER D8 DISCOVER). For the sample related to Example 14, the resistivity of the semiconductor thin film was measured by the van der Pauw method, and the carrier concentration and mobility were measured by Hall effect measurement. The thickness of the semiconductor thin film was set to 510 nm. Table 1 below summarizes the preparation conditions for the samples related to Comparative Examples 1 to 8 and Examples 1 to 15.

[0027]

[0028] In Table 1, under "Substrate Type", the following is listed: "TiO ２ " is a TiO with the (001) plane exposed on its surface. ２ This refers to a substrate made of single crystal, and "c-aspp." indicates that the c-plane is exposed on the surface of Al ２ O ３ This refers to a substrate made of single crystal (sapphire substrate), and "a-aspp." indicates that the a-plane is exposed on the surface. ２ O ３ This represents a substrate made of single crystal. Furthermore, "m-aspp." indicates an Al substrate with the m-plane exposed on its surface. ２ O ３ This refers to a substrate made of single crystal, and "r-aspp." indicates that the r-plane is exposed on the surface of Al. ２ O ３ This represents a substrate made of single crystal. Furthermore, the concentration indicated in "Sb concentration" represents the concentration of Sb contained in the raw material solution.

[0029] The results of the evaluations performed on the samples related to Comparative Example 1 and Example 1 will be described in detail below. In the XRD2θ-ω measurements of the semiconductor thin films of the samples related to Comparative Example 1 and Example 1 immediately after growth, as shown in Figures 4A and 4B, in both cases, r-GeO was found at around 65.2 degrees. ２ A sharp peak corresponding to the (002) plane of the crystal was observed. Furthermore, as shown in Figure 4B, a broad peak corresponding to the buffer layer was also observed in the sample according to Example 1. Here, the r-GeO of the sample according to Example 1 ２ The peak intensity corresponding to the (002) plane of the crystal is the same as that of the r-GeO sample in Comparative Example 1. ２ It was found that the peak intensity was larger than that corresponding to the (002) plane of the crystal. Furthermore, as shown in Figure 4A, when the sample according to Comparative Example 1 was immersed in deionized water for 1 hour and then XRD2θ-ω measurement was performed, r-GeO ２ The peak intensity corresponding to the (002) plane of the crystal decreased. On the other hand, as shown in Figure 4B, the sample according to Example 1 did not show r-GeO even after being immersed in deionized water for 1 hour. ２ The peak intensity corresponding to the (002) plane of the crystal hardly changed. This suggests that when a semiconductor thin film is grown directly on a substrate, as in the sample of Comparative Example 1, r-GeO ２ Crystal (Rutile-type GeO ２ Not only crystals, but also water-soluble α-quartz type GeO ２ Crystalline, amorphous GeO ２ It is thought that it contains. On the other hand, in the sample according to Example 1, GeO having a water-soluble structure in the semiconductor thin film ２ It was found that there was almost no presence of this substance, resulting in high stability underwater.

[0030] In the Φ scan XRD of the sample according to Example 1, as shown in Figure 5A, TiO ２ The substrate and r-GeO ２ For each of the semiconductor thin films, four symmetrical diffraction peaks were observed at 90-degree intervals. Here, TiO ２ The peak position corresponding to the substrate and r-GeO ２ The peak position corresponds to that of the semiconductor thin film, and from this, it can be concluded that r-GeO ２The semiconductor thin film is TiO ２ It can be seen that it grew on the substrate with the same in-plane orientation as the substrate. In other words, from the results of 2θ-ωXRD and Φ scan XRD shown in Figure 4B, r-GeO ２ The semiconductor thin film is TiO ２ It can be seen that it is epitaxially grown on a buffer layer formed on the substrate.

[0031] Furthermore, analysis of the reciprocal lattice pattern reveals that, as shown in Figure 5B, TiO ２ The spot corresponding to the substrate and r-GeO ２ Spots corresponding to the (112) plane of the semiconductor thin film and were observed. Between the two aforementioned spots, spots corresponding to each of the multiple buffer layers were observed. From this, it was found that the lattice constant of the buffer layer is the Ge forming the buffer layer. ｘ Sn １－ｘ O ２ It can be seen that it depends on the composition ratio of Ge and Sn in r-GeO ２ The position of the spot corresponding to the (112) plane of the semiconductor thin film is in the unstrained state of r-GeO ２ The value of qx in reciprocal lattice space is small and the value of qy is large compared to the spot position, which indicates that the r-GeO on the buffer layer ２ This indicates that the semiconductor thin film is expanded in the

[110] direction and compressed in the

[001] direction. On the other hand, an analysis of the reciprocal lattice pattern of Comparative Example 1 shows that r-GeO ２ The position of the spot corresponding to the (112) plane of the semiconductor thin film is in the unstrained state of r-GeO ２ It roughly coincided with the spot location. TiO ２ tor-GeO ２ It is thought that the strain caused by lattice mismatch in semiconductor thin films is relieved by dislocations and other mechanisms.

[0032] Furthermore, as shown in Figures 6(A) to (C), when the surface morphology of the semiconductor thin film of the sample according to Comparative Example 1 was observed immediately after growth, granular and leaf-like regions were observed. When the sample according to Comparative Example 1 was immersed in deionized water for one hour, the granular regions were removed, as shown in Figures 6(D) to (F). From this, it can be inferred that these granular regions were amorphous GeO ２ , α-quartz structure GeO ２ It is thought to be composed of the following. Furthermore, from the results of Figures 6(B) and (E) and other SEM observations, a decrease in the average diameter of the leaf-like region from 60 μm to 42 μm was confirmed. From this, it can be inferred that the leaf-like region is composed of water-soluble α-quartz structured GeO ２ It is thought to be composed of these elements.

[0033] Next, we will explain the results of EDX mapping measurements performed to analyze the rectangular region of the sample according to Comparative Example 1 shown in Figure 7(A) after immersion in deionized water for one hour. As shown in Figures 7(B) and (C), signals corresponding to Ge and O were detected in the rectangular region, and as shown in Figure 7(D), no signal corresponding to Ti was detected. Therefore, the rectangular region is GeO ２ It can be seen that it is formed by r-GeO. Furthermore, the rectangular region remains even after immersion in deionized water, indicating that it is formed by r-GeO. ２ It is a crystalline structure, and the alignment of the extension directions of the edges of multiple rectangular regions suggests that it was epitaxially grown on the substrate.

[0034] On the other hand, as shown in Figures 8A and 8B, in the sample according to Example 1, almost no change in surface morphology was observed before and after immersion in deionized water.

[0035] Furthermore, as shown in Figure 9, in the Raman scattering spectroscopic measurement of the sample according to Example 2, the value indicated by the arrow at 690 cm² was obtained. ―１ r-GeO ２ Peaks corresponding to the Eg mode and A1g mode were observed. This also indicates that the semiconductor thin film layer of the sample according to Example 1 contains r-GeO ２ It can be seen that crystals are present.

[0036] In the XRD2θ-ω measurements of each sample in Comparative Examples 2 to 7 immediately after the growth of the semiconductor thin film, as shown in Figure 10, only the sample in Example 2 showed r-GeO at around 65.2 degrees. ２ A peak corresponding to the (002) plane of the crystal was observed. In Comparative Example 3, r-GeO ２ Although the peak corresponding to the (002) plane of the crystal is not clearly observed, the same peak is observed in Comparative Example 1, which was grown at the same growth temperature of 825°C. This is thought to be because the peak intensity is weak in both Comparative Examples 1 and 3, and whether or not it is observed depends on the difference in scan speed during XRD measurement. From this, as shown in Figure 3, TiO ２ Directly onto the substrate r-GeO ２ When growing a semiconductor thin film made of crystals, it is necessary to maintain the growth temperature at a relatively high temperature of 825°C or higher. On the other hand, as shown in Figure 11A, according to the XRD results of each sample from Comparative Example 8 and Examples 2 to 6, all of the samples from Examples 2 to 6 had r-GeO at 2θ around 65.2 degrees. ２ A sharp peak corresponding to the (002) plane was observed. From this, it was found that by forming a buffer layer on the substrate, the allowable range of growth temperature can be extended to 550°C or higher. As shown in Figure 11B, r-GeO ２ The full width at half maximum of the rocking curve of the peak corresponding to the (002) plane was narrowest in Example 2 and widest in Example 6, and a tendency was observed for the full width at half maximum to decrease as the growth temperature increased.

[0037] As shown in Figures 12(A) to (E), no rectangular regions were observed on the surface of the semiconductor thin film of the sample according to Comparative Example 8 immediately after growth. However, interconnected rectangular regions were observed on the surface of the semiconductor thin films of each of the samples according to Examples 2 to 5 immediately after growth. Furthermore, as shown in Figures 12(B) and (D), and Figures 13A and 13B, there was almost no change in the surface state of the semiconductor thin films of the samples according to Examples 2 and 4 before and after immersion in deionized water for one hour.

[0038] In the XRD2θ-ω measurement of the semiconductor thin film sample according to Example 7 immediately after growth, as shown in Figure 14A, r-GeO２ A sharp peak corresponding to the (200) plane of the crystal was observed. Furthermore, in the 2θ-ωXRD measurements of each semiconductor thin film in the sample according to Example 8 immediately after growth, as shown in Figure 14B, r-GeO ２ A sharp peak corresponding to the (101) plane of the crystal was observed. In the XRD2θ-ω measurement of the semiconductor thin film of the sample according to Example 9 immediately after growth, as shown in Figure 15A, r-GeO ２ A sharp peak corresponding to the (002) plane of the crystal was observed. Furthermore, in the XRD2θ-ω measurement of each sample of the semiconductor thin film according to Example 10 immediately after growth, as shown in Figure 15B, r-GeO ２ A sharp peak corresponding to the (101) plane of the crystal was observed.

[0039] Furthermore, in the XRDΦ scan measurement of the sample according to Example 7, as shown in Figure 16A, α-Al ２ O ３ Crystal substrate and r-GeO ２ Six symmetric diffraction peaks were observed at 60-degree intervals for each crystalline semiconductor thin film. Here, α-Al ２ O ３ The peak position corresponding to the substrate and r-GeO ２ The peak position corresponds to that of the semiconductor thin film in the crystal, and from this, r-GeO ２ The semiconductor thin film of the crystal is α-Al ２ O ３ It can be seen that the crystal grew in a consistent in-plane direction on the substrate. In other words, from the XRD2θ-ω result shown in Figure 14A and the XRDΦ scan result shown in Figure 16A, r-GeO ２ A crystalline semiconductor thin film is α-Al ２ O ３ It can be seen that epitaxial growth is occurring on a buffer layer formed on a crystalline substrate. Furthermore, in the XRDΦ scan measurement of the sample according to Example 8, as shown in Figure 16B, α-Al ２ O ３ Regarding the crystalline substrate, two symmetrical diffraction peaks were observed at 180-degree intervals, and r-GeO ２ In the crystalline semiconductor thin film, two symmetrical diffraction peaks were observed at 180-degree intervals and shifted by 40 degrees. From this, Al ２O ３ r-GeO ２ It can be seen that the crystal rotated and the atomic arrangement matched, indicating epitaxial growth. Furthermore, in the XRDΦ scan measurement of the sample according to Example 9, as shown in Figure 17A, α-Al ２ O ３ Regarding the substrate, one diffraction peak was observed, and r-GeO ２ Four symmetrical diffraction peaks were observed at 90-degree intervals in the crystalline semiconductor thin film. α-Al ２ O ３ Diffraction peaks of the substrate and r-GeO ２ The fact that one of the diffraction peaks coincide indicates that epitaxial growth is occurring. Furthermore, in the XRDΦ scan measurement of the sample according to Example 10, as shown in Figure 17B, α-Al ２ O ３ Regarding the crystalline substrate, one diffraction peak was observed, and r-GeO ２ Two diffraction peaks were observed at 100-degree intervals in the crystalline semiconductor thin film. ２ The diffraction peaks of the crystals are α-Al ２ O ３ Since it is located at a position shifted 50 degrees from the diffraction peak of the crystal, α-Al ２ O ３ Crystal and r-GeO ２ It is believed that the semiconductor thin film is growing epitaxially, rotated 50 degrees in plane.

[0040] Furthermore, as shown in Figures 18A to 19B, when the surface morphology of the semiconductor thin films of the samples according to Examples 7 to 10 was observed immediately after growth, all showed α-Al ２ O ３ A structure reflecting the surface orientation exposed on the surface of the crystal substrate was observed. From these findings, it was observed that even when a buffer layer is formed on a sapphire substrate, r-GeO ２ It has been found that semiconductor thin films made of crystals can be grown.

[0041] In the 2θ-ωXRD measurements of each semiconductor thin film sample in Examples 11 to 15 immediately after growth, as shown in Figure 20A, r-GeO was found at around 65.2 degrees in all cases. ２A peak corresponding to the (002) plane of the crystal was observed. Also, as shown in Figure 20B, the r-GeO of each sample from Examples 11 to 15 ２ The full width at half maximum of the rocking curve of the peak corresponding to the (002) plane was between 0.25 degrees and 0.35 degrees. From this, it can be seen that doping with Sb results in r-GeO ２ It was found that no decrease in crystallinity was observed.

[0042] Furthermore, as shown in Figure 21, the sheet resistance of the semiconductor thin film sample according to Example 13 is approximately 1 × 10⁻⁶. ７ Although it was Ω□, the sheet resistance of the semiconductor thin film samples in Examples 14 and 15 was approximately 1 × 10⁻⁶. ２ The value was Ω□. Furthermore, the carrier concentration of the semiconductor thin film sample in Example 14 was 1.3 × 10⁻⁶. ２０ / cm ３ The mobility is 2.6 cm. ２ The value was / Vs. Furthermore, since the semiconductor thin films according to Examples 11 to 13 exhibit an n-type in Hall effect measurements, it can be said that Sb functions as an n-type donor. Moreover, as shown in Figure 22, in the sample according to Example 14, Sb was uniformly distributed throughout the semiconductor thin film at a concentration of 1.2 × 10⁻¹⁰. ２１ [atom / cm] ３ It was found that it was incorporated into [].

[0043] This application is based on Japanese Patent Application No. 2025-050927, filed on 26 March 2025. The entire specification, claims, and drawings of Japanese Patent Application No. 2025-050927 are incorporated herein by reference.

[0044] This invention is suitable as a method for manufacturing semiconductor devices using so-called power semiconductors, which are used in automotive electrical components, consumer electronics, and the like.

[0045] 21: Gas supply source, 23: Flow meter, 31: Raw material supply container, 32: Raw material solution, 33: Water storage container, 34: Water, 35: Ultrasonic transducer, 41: Reaction vessel, 42: Heater, 43: Susceptor, P1: First gas supply pipe, P2: Second gas supply pipe, P3: Exhaust pipe, Sub1: Substrate, L1: Semiconductor thin film, L21, L22, L23, L24, L25, L26: Buffer layers

Claims

1. A substrate preparation step of preparing a substrate formed from an oxide crystal; after the substrate preparation step, Ge on the substrate by mist CVD ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ A buffer layer forming step of forming an N-layer buffer layer (N is an integer of 2 or more, 1≦i≦N) made of crystal; a thin film forming step of forming a semiconductor thin film made of r-GeO ２ crystal on the N-layer buffer layer by mist CVD, wherein Ge forming one of the two buffer layers adjacent in the lamination direction on the substrate side ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ crystal and Ge forming the other buffer layer ｘ［ｉ＋１］ Sn １－ｘ［ｉ＋１］ O ２ satisfy the relationship X[i] < X[i+1] therebetween. A method for producing a semiconductor thin film.

2. In the thin film formation process, Sb-doped r-GeO ２ A method for manufacturing a semiconductor thin film according to claim 1, comprising forming a semiconductor thin film made of crystals.

3. The method for manufacturing a semiconductor thin film according to claim 1, wherein in the thin film formation step, a precursor raw material containing a first compound containing Ge and a second compound containing Sb is supplied to the surface of the substrate.

4. The first compound is bis[2-carboxyethylgermanium]sesquioxide (C ６ H １０ Ge ２ O ７ The second compound is antimony chloride (SbCl ４ The method for manufacturing a semiconductor thin film according to claim 3.

5. The method for manufacturing a semiconductor thin film according to claim 3 or 4, wherein in the thin film formation step, a raw material solution obtained by dissolving the precursor raw material in deionized water is supplied to the surface of the substrate in the form of a mist.

6. The substrate is TiO ２ Crystal or Al ２ O ３ A method for manufacturing a semiconductor thin film according to any one of claims 1 to 4, which is formed from a crystal.

7. The method for manufacturing a semiconductor thin film according to any one of claims 1 to 4, wherein in the thin film formation step, the growth temperature is 550°C or higher and 850°C or lower.

8. A substrate formed from an oxide crystal, and Ge formed on the substrate. ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ A buffer layer of N (where N is an integer of 2 or more, 1 ≤ i ≤ N) crystalline layers, and r-GeO formed on the N-layer buffer layer. ２ A semiconductor thin film made of crystals, comprising Ge forming one of two adjacent buffer layers in the stacking direction, on the substrate side. ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ The crystal and the Ge that forms the other ｘ［ｉ＋１］ Sn １－ｘ［ｉ＋１］ O ２ A semiconductor thin film substrate such that the relationship X[i] < X[i+1] holds between it and the given point.

9. The semiconductor thin film is doped with Sb, the semiconductor thin film substrate according to claim 8.

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