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 doped with Ga or F by the mist CVD method.

Description

Method for manufacturing semiconductor thin films and substrates with semiconductor thin films

[0001] This invention relates to a method for manufacturing a semiconductor thin film and a substrate with a semiconductor thin film.

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

[0003] Japanese Patent Publication No. 2024-114114

[0004] By the way, in order to apply this to semiconductor devices made of crystalline oxides as described in Patent Document 1, it is necessary to realize a crystalline oxide that contains an n-type dopant or a p-type dopant.

[0005] This invention has been made in view of the above reasons, and includes r-GeO containing a dopant. ２ The objective is to provide a method for manufacturing semiconductor thin films and a substrate with a semiconductor thin film, which can realize high-quality semiconductor devices comprising semiconductor thin films made of crystals.

[0006] The semiconductor thin film manufacturing method according to the present invention comprises a substrate preparation step of preparing a substrate formed from an oxide crystal, and a mist CVD method of doping the substrate with Ga or F into r-GeO ２ The process includes a thin-film formation step of forming a semiconductor thin film made of crystals.

[0007] From another perspective, the semiconductor thin film substrate according to the present invention comprises a substrate formed from an oxide crystal and a Ga or F-doped r-GeO film formed on top of the substrate. ２ It comprises a semiconductor thin film made of crystals.

[0008] According to the present invention, r-GeO containing p-type or n-type impurities is formed on a substrate made from an oxide crystal. ２ Since it is possible to fabricate semiconductor thin films with relatively high crystallinity made of crystals, r-GeO ２ This makes it possible to realize high-quality semiconductor devices that incorporate semiconductor thin films made of crystals.

[0009] It is a cross-sectional view showing an example of a substrate with a semiconductor thin film according to Embodiment 1. It is a schematic configuration diagram of a mist CVD apparatus according to Embodiment 1. It is a cross-sectional view showing an example of a substrate with a semiconductor thin film according to Embodiment 2. It is a diagram showing XRD results of samples according to a comparative example and Examples 1 to 3. It is a diagram showing r-GeO of XRD for samples according to a comparative example and Examples 1 to 3 ２ It is a diagram showing the full width at half maximum of the corresponding peak.

[0010] (Embodiment 1) 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 the present embodiment includes a substrate made of an oxide crystal, a Ge formed on the substrate ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ N buffer layers made of crystal (N is an integer of 2 or greater), and a semiconductor thin film formed on the buffer layer group. Here, the N buffer layers constitute a so-called graded buffer layer in which the Ge composition ratio of each buffer layer is changed such that a buffer layer having a Ge composition ratio closer to that of the semiconductor layer has a smaller Ge composition ratio. Here, of two buffer layers adjacent to each other in the stacking direction, the Ge that forms one on the substrate side ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ crystal and the Ge forming the other ｘ［ｉ＋１］ Sn １－ｘ［ｉ＋１］ O ２ the relationship X[i] < X[i+1] holds between them. Further, for the buffer layer located closest to the substrate side, the Ge composition ratio X[1] is preferably 0.3 or less, and for the buffer layer located closest to the semiconductor thin film side, the Ge composition ratio X[N] is preferably 0.2 or more, and more preferably 0.4 or more.

[0011] The substrate with a semiconductor thin film according to the present embodiment includes six buffer layers L21, L22, ..., L26 formed on a substrate Sub1, as shown in FIG. 1, for example. The substrate Sub1 is TiO ２ crystal, sapphire (Al ２ O ３It 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 ２ It consists of crystals (x[4] < X[5] < 1). The buffer layer L26 is stacked on 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 and contains either n-type impurities (F) or p-type impurities (Ga).

[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 containing n-type or p-type impurities is placed on the buffer layers. ２A 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 ), GeI ４ , 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, when the conductivity type of the semiconductor thin film L1 is made p-type, a second compound consisting of one or more alcohol compounds selected from alcohol compounds and gallium (Ga) is dissolved in the raw material solution 32. This second compound may be gallium acetylacetonate (Ga(C)). ５ H ７ O ２ ) ３ ), GaCl ３ GaBr ３ GaI ３The following are examples. In addition, the Ga concentration in the raw material solution 32 is set to be 0.1 at.% or more and 10 at.% or less. On the other hand, when the conductivity type of the semiconductor thin film L1 is n-type, ammonium fluoride (NH4) is added to the raw material solution 32. ３ F) Dissolve hydrogen fluoride (HF).

[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] Here, we will explain the operation of the mist CVD apparatus. First, the ultrasonic transducer 35 vibrates, transmitting vibrational energy to the raw material solution 32 via matching water 34, and this vibrational energy turns the raw material solution 32 into a mist. Then, the misted raw material solution 32 is sent into the reaction vessel 41 through the second gas supply pipe P2 by carrier gas supplied from the gas supply source 21 into the raw material supply container 31. At this time, the amount of raw material solution sent into the reaction vessel 41 is adjusted by adjusting the flow rate of the carrier gas flowing through the first gas supply pipe P1 while checking the flow meter 23. The misted raw material solution sent into the reaction vessel 41 is supplied to the surface of the substrate 1 supported by the susceptor 43 inside the reaction vessel 41. When the misted raw material solution supplied to the surface of the substrate Sub1 is heated by the heater 42, the metal compounds and solvent in the raw material solution chemically react, and a buffer layer and a semiconductor thin film grow on top of the substrate Sub1. Here, the substrate Sub1 is heated to a temperature within the range of 550°C to 950°C.

[0018] In the semiconductor thin film manufacturing method according to this embodiment, after performing a substrate preparation step to prepare a substrate formed from an oxide crystal, a buffer layer formation step is first performed in which the aforementioned multiple buffer layers are formed on the substrate by mist CVD. Subsequently, r-GeO doped with Ga or F is formed on the substrate by mist CVD. ２ A thin film formation process is carried out to form a semiconductor thin film made of crystals. Here, Ga-doped r-GeO ２ When a semiconductor thin film made of crystals is formed, a heat treatment step may be performed to heat the semiconductor thin film. This makes it possible to remove hydrogen incorporated into the semiconductor thin film during the thin film formation process.

[0019] As described above, in the semiconductor thin film manufacturing method according to this embodiment, r-GeO containing p-type or n-type impurities is placed on a substrate formed from an oxide crystal. ２ Since it is possible to fabricate semiconductor thin films with relatively high crystallinity made of crystals, r-GeO ２ This makes it possible to realize high-quality semiconductor devices that incorporate semiconductor thin films made of crystals.

[0020] Furthermore, since the mist CVD method employed in the semiconductor thin film manufacturing method according to this embodiment is a non-vacuum process, it does not require a configuration to realize a vacuum atmosphere, thus simplifying the apparatus.

[0021] (Embodiment 2) The semiconductor thin film substrate according to this embodiment comprises, for example, a substrate Sub1 made of an oxide crystal and a semiconductor thin film L1 formed on the substrate Sub1, as shown in Figure 3. Here, the substrate Sub1 is the same as the substrate Sub1 described in Embodiment 1, and TiO ２ It is formed from crystals, sapphires, etc.

[0022] The semiconductor thin film L1 is r-GeO, similar to Embodiment 1. ２ (Rutile structure Ge0 ２ The semiconductor thin film L1 is made of crystals and contains either an n-type impurity, F, or a p-type impurity, Ga.

[0023] In the semiconductor thin film manufacturing method according to this embodiment, similar to Embodiment 1, a mist CVD method is used to directly place r-GeO containing n-type or p-type impurities onto the substrate Sub1. ２ A semiconductor thin film made of crystals is deposited. In this embodiment, for example, a mist CVD apparatus as shown in Figure 2 is used. In this embodiment, the substrate W is heated to a temperature within the range of 550°C to 950°C.

[0024] In the semiconductor thin film manufacturing method according to this embodiment, r-GeO containing p-type or n-type impurities is placed on a substrate formed from an oxide crystal. ２ Since it is possible to fabricate semiconductor thin films with relatively high crystallinity made of crystals, r-GeO ２ This makes it possible to realize high-quality semiconductor devices that incorporate semiconductor thin films made of crystals.

[0025] This invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent meaning of the invention are considered to be within the scope of the invention.

[0026] The method for manufacturing a semiconductor thin film according to the present invention will be described based on examples. However, the present invention is not limited to the examples described below.

[0027] The samples in Comparative Example 1 and Examples 1 to 4 all have a structure in which multiple buffer layers and a semiconductor thin film are formed on the substrate described in Embodiment 1. The substrate is a TiO2 substrate with the (001) plane exposed on its surface. ２ A substrate made of crystal was used.

[0028] The buffer layers and semiconductor thin films according to Comparative Example 1 and Examples 1 to 4 were formed by the manufacturing method described in Embodiment 1. Here, an ultrasonic vibrator that vibrates at a frequency of 2.4 MHz (HM-2412, manufactured by Honda Electronics Co., Ltd.) was employed as the ultrasonic vibrator of the aforementioned mist CVD apparatus. In the buffer layer forming steps according to Comparative Example 1 and Examples 1 to 5, bis[2-carboxyethylgermanium] sesquioxide (C 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.) dissolved in deionized water and adjusted to a concentration of 0.025 mol / L was used. Then, six types of raw material solutions were prepared such that the ratio of Ge to Sn present in the raw material solutions was 70:30, 75:25, 80:20, 85:15, 90:10, and 95:5, and six buffer layers were formed using each raw material solution in order. Thereby, on the substrate, Ge ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ Six buffer layers composed of i crystals (1≦i≦6) were formed. Here, the Ge composition ratios x[1], x[2], x[3], x[4], x[5], x[6] in each buffer layer are such that the Ge ｘ［１］ Sn １－ｘ［１］ O ２ crystal buffer layer is located closest to the substrate side, and were "0.4", "0.55", "0.7", "0.8", "0.9", and "0.95", respectively.

[0029] Next, in the thin film forming step according to Comparative Example 1, as the raw material solution, the aforementioned C ６ H １０ Ge ２ O ７ An aqueous solution with a concentration of 0.025 mol / L obtained by dissolving in deionized water was used. In the thin film forming steps according to Examples 1 to 3, as the raw material solution, the aforementioned C ６ H １０ Ge ２ O ７ and Ga(C ５ H ７ O ２ )３ manufactured by Kenei X Co., Ltd.) were dissolved in deionized water to obtain an aqueous solution with a concentration of 0.025 mol / L, and this aqueous solution was used. In the raw material solution according to Example 1, the concentration of Ga(C ５ H ７ O ２ ) ３ was adjusted such that the Ga concentration was 0.1 at.%. Further, in the raw material solution according to Example 2, the concentration of Ga(C ５ H ７ O ２ ) ３ was adjusted such that the Ga concentration was 1 at.%. Furthermore, in the raw material solution according to Example 3, the concentration of Ga(C ５ H ７ O ２ ) ３ was adjusted such that the Ga concentration was 10 at.%. Further, in the thin film forming step according to Example 4, as the raw material solution, the aforementioned C ６ H １０ Ge ２ O ７ and NH ４ F (manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in deionized water to obtain an aqueous solution with a concentration of 5 mol / L, and this aqueous solution was used. Nitrogen was used as the carrier gas and the dilution gas. The flow rate of the carrier gas during film formation was set to 2.5 L / min, and the flow rate of the dilution gas was set to 4.5 L / min. The film formation temperatures for the buffer layers and semiconductor thin films according to Comparative Example 1 and Examples 1 to 3 were all set to 850°C. The film formation temperature of the buffer layer according to Example 4 was set to 825°C, and the film formation temperature of the semiconductor thin film was set to 650°C. Furthermore, for each of the six buffer layers according to Comparative Example 1 and Examples 1 to 4, the film formation time was set to 2 min, and the film formation time of the semiconductor thin film was set to 30 min. Further, in Examples 1 to 3, after the thin film forming step, a heat treatment step was performed in which the substrate having the buffer layer and the semiconductor thin film formed thereon was maintained at 800°C for 20 min.

[0030] Furthermore, the crystalline structure of the semiconductor thin films was evaluated for each sample in Comparative Example 1 and Examples 1 to 3. The resistivity, carrier concentration, and mobility were also evaluated for each sample in Examples 3 and 4. The crystalline structure of the semiconductor thin films in Comparative Example 1 and Examples 1 to 3 was confirmed by the position of the diffraction peaks measured using an X-ray diffraction (XRD) analyzer (BRUKER D8 DISCOVER). The resistivity of the semiconductor thin films in Examples 3 and 4 was measured using the van der Paul method, and the carrier concentration and mobility were measured using the Hall effect. The thickness of the semiconductor thin films was set to 500 nm.

[0031] The results of the evaluations performed on the samples related to Comparative Example 1 and Examples 1 to 3 will be described in detail below. As shown in Figure 4A, according to the XRD results for each of the samples related to Comparative Example 1 and Examples 1 to 3, r-GeO was present at approximately 65.2 degrees at 2θ in all cases. ２ A peak originating from the 002 plane was observed. Furthermore, as shown in Figure 4B, the full width at half maximum of this peak was between 0.3 and 0.5 degrees. From this, it can be concluded that doping with Ga results in r-GeO ２ It was found that no decrease in crystallinity was observed.

[0032] The resistivity of the semiconductor thin film sample in Example 3 is 6.42 × 10⁻⁶. －２ The density is Ω·cm, and the carrier concentration is 1.0 × 10⁻⁶. １８ / cm ３ The range of motion is 96 cm. ２ The value was / Vs. Furthermore, since the semiconductor thin film according to Example 3 exhibits a p-type structure in the Hall effect measurement, it can be seen that Ga functions as a p-type acceptor. In addition, the resistivity of the semiconductor thin film of the sample according to Example 4 was 3.4 × 10⁻⁶. －２ The density is Ω·cm, and the carrier concentration is 1.1 × 10⁻⁶. ２０ / cm ３ The mobility is 1.7 cm. ２ The value was / Vs. Furthermore, since the semiconductor thin film according to Example 4 exhibits an n-type configuration in the Hall effect measurement, it can be said that F functions as an n-type donor.

[0033] This application is based on Japanese Patent Application No. 2025-042020, filed on 17 March 2025. The entire specification, claims, and drawings of Japanese Patent Application No. 2025-042020 are incorporated herein by reference.

[0034] 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.

[0035] 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 in which a substrate formed from oxide crystals is prepared, and r-GeO doped with Ga or F on top of the substrate by mist CVD. ２ A method for manufacturing a semiconductor thin film, comprising a thin film formation step for forming a semiconductor thin film made of crystals.

2. After said substrate preparation step and before said thin film forming step, further comprising a buffer layer forming step of forming a buffer layer of N layers (N is an integer of 2 or more, 1≦i≦N) consisting of Ge ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ crystals on said substrate by a mist CVD method, wherein among two buffer layers adjacent to each other in the lamination direction, Ge forming one buffer layer 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, the method for producing a semiconductor thin film according to claim 1.

3. The method for manufacturing a semiconductor thin film according to claim 1 or 2, wherein in the thin film formation step, a precursor raw material comprising a first compound containing Ge and a second compound of Ga and one or more alcohol compounds selected from alcohol compounds 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 ), GeI ４ , GeBr ４ , GeO ２ The second compound is at least one selected from the following, and the second compound is gallium acetylacetonate (Ga(C) ５ H ７ O ２ ) ３ ), GaCl ３ GaBr ３ GaI ３ A method for manufacturing a semiconductor thin film according to claim 3, wherein the method is at least one selected from the following.

5. In the thin film formation step, a first compound containing Ge and NH ４ A method for manufacturing a semiconductor thin film according to claim 1 or 2, comprising supplying a precursor raw material containing F or HF to the surface of the substrate.

6. The method for manufacturing a semiconductor thin film according to claim 3, 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.

7. The substrate is TiO ２ Crystal or Al ２ O ３ A method for manufacturing a semiconductor thin film according to claim 1 or 2, which is formed from a crystal.

8. The substrate is r-GeO ２ A method for manufacturing a semiconductor thin film according to claim 1, which is formed from a crystal.

9. The semiconductor thin film is Ga-doped r-GeO ２ A method for manufacturing a semiconductor thin film according to claim 1 or 2, further comprising, in the case where the semiconductor thin film is made of crystals, a heat treatment step of maintaining the semiconductor thin film in a heated state for a predetermined time after the thin film formation step.

10. A substrate formed from an oxide crystal, and a Ga or F-doped r-GeO formed above the substrate. ２ A semiconductor thin film substrate comprising a semiconductor thin film made of crystals.

11. Ge interposed between the substrate and the semiconductor thin film ｘ［ｉ］ Sn １－ｘ［ｉ］ O ２ The layer further comprises an N (where N is an integer greater than or equal to 2, 1 ≤ i ≤ N) buffer layer made of crystal, and one of the two adjacent buffer layers in the stacking direction, on the substrate side, is formed by Ge 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 according to claim 10, wherein the relationship X[i] < X[i+1] holds between the two.

12. The substrate is TiO ２ Crystal or Al ２ O ３ A substrate with a semiconductor thin film according to claim 10 or 11, formed from a crystal.

13. The substrate is r-GeO ２ A semiconductor thin film substrate according to claim 10, formed from a crystal.

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