Semiconductor device and method for manufacturing the same

Abstract

To provide semiconductor devices with lower hole density than conventional devices by suppressing crystal defects in polycrystalline Ge films.SOLUTION: A semiconductor device 100 of the present invention has a base material 101 and a semiconductor film (semiconductor thin film) 102 formed (synthesized) on one surface 101a of the base material, and the semiconductor film 102 is a non-doped polycrystalline Ge film comprising crystal particles having an average particle size of 1 μm or more, and the hole density of the semiconductor film 102 is 1×1017 cm-3 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device used in thin-film transistors, solar cells, light-receiving sensors, and the like, and a method for manufacturing the same. [Background technology]

[0002] Semiconductor films synthesized on insulators (such as SiO2, glass, and plastic) are being actively researched as key components for realizing three-dimensional integrated circuits (LSIs) and improving the performance and cost of information terminals and solar cells.

[0003] Ge and SiGe, which are Group IV semiconductors, are expected to be next-generation semiconductor materials because they have high affinity with the existing material Si, and also possess higher carrier mobility and lower crystallization temperatures than Si. However, it is known that polycrystalline Ge or polycrystalline SiGe, after crystallization, exhibits p-type conduction even in an undoped state, as the defect levels in its crystals act as holes. This tendency is more pronounced in polycrystalline SiGe as the Ge content increases. Therefore, the lower limit of the range of p-type hole density that can be adjusted by doping depends on the amount of crystal defects in the polycrystalline Ge or polycrystalline SiGe immediately after formation. The hole density of polycrystalline Ge is at the lowest level of 3 × 10⁻⁶. 17 cm -3 This is known (see Patent Document 1).

[0004] Furthermore, polycrystalline Ge or polycrystalline SiGe that exhibits p-type properties without doping remain p-type even when a small amount of group V elements, which are n-type dopants, are injected, and do not become n-type. To exhibit n-type conduction, it is necessary to generate more electrons than holes. Therefore, the lower limit of the range of n-type electron density that can be adjusted by doping depends on the amount of crystal defects in the polycrystalline Ge or polycrystalline Ge immediately after formation. The electron density of Sb-doped n-type polycrystalline Ge is at the lowest level of 5 × 10⁻⁶. 17 cm -3 This is known (see Non-Patent Document 1).

[0005] Polycrystalline silicon contains grain boundaries and intragranular defects, which form localized energy levels. These localized levels contribute to a decrease in carrier mobility and an increase in leakage current, thus degrading the properties of semiconductor devices. It is known that adding hydrogen to polycrystalline silicon makes the grain boundaries and intragranular defects electrically inactive, improving the properties of semiconductor devices (see Patent Document 2).

[0006] Patent Document 3 describes that by subjecting polycrystalline Ge or polycrystalline SiGe containing a group V element, which is an n-type dopant, to hydrogen treatment, the p-type defect levels are reduced, the effect of the group V element becomes apparent, and the material exhibits n-type properties. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-142672 [Patent Document 2] Japanese Patent Publication No. 62-84562 [Patent Document 3] Japanese Patent Publication No. 2004-335494 [Non-patent literature]

[0008] [Non-Patent Document 1] D. Takahara, K. Moto, T. Imajo, T. Suemasu, and K. Toko, Appl. Phys. Lett. 114, 082105 (2019) [Overview of the project] [Problems that the invention aims to solve]

[0009] As mentioned above, although it was known that hydrogen treatment reduces p-type defect levels (in other words, reduces hole density), research on Ge thin-film devices has not progressed sufficiently until now. This is mainly because the effect was not sufficient.

[0010] A method has been developed to produce large-grained polycrystalline Ge or polycrystalline SiGe, consisting of crystalline particles with an average particle size of 1 μm or more, based on the solid-phase growth method (see Patent Document 1).

[0011] This invention has been made in view of the above circumstances, and aims to provide a semiconductor device and a method for manufacturing the same, in which crystal defects are suppressed in a polycrystalline Ge film and which has a lower hole density than conventional devices. [Means for solving the problem]

[0012] To solve the above problems, the present invention provides the following means.

[0013] A semiconductor device according to a first aspect of the present invention comprises a substrate and a semiconductor film formed on one surface of the substrate, wherein the semiconductor film is a non-doped polycrystalline Ge film composed of crystalline particles with an average particle size of 1 μm or more, and the hole density of the semiconductor film is 1 × 10⁻¹⁶ 17 cm -3 The following applies:

[0014] In the semiconductor device according to the above embodiment, the semiconductor film may contain Ge crystal particles with a maximum particle size of 5 μm or more.

[0015] A semiconductor device according to a second aspect of the present invention comprises a substrate and a semiconductor film formed on one surface of the substrate, wherein the semiconductor film is a non-doped polycrystalline Ge film composed of crystalline particles with an average particle size of 1 μm or more, and the hydrogen concentration of the semiconductor film is 1 × 10⁻⁶ 19 cm -3 That's all.

[0016] In the semiconductor device according to the above embodiment, the semiconductor film may contain Ge crystal particles with a maximum particle size of 5 μm or more.

[0017] The semiconductor device according to the above embodiment may exhibit a p-type conduction by containing a group III element as an impurity in the semiconductor layer.

[0018] The semiconductor device according to the above aspect has a hole density in the semiconductor layer of 1×10 15 cm -3 or more and 1×10 23 cm -3 or less, which may be acceptable.

[0019] The semiconductor device according to the above aspect may have a hole mobility in the semiconductor film of 25 cm 2 / V·s or more.

[0020] The semiconductor device according to the above aspect may be of an n-type conductivity type by containing a Group V element as an impurity in the semiconductor layer.

[0021] The semiconductor device according to the above aspect has an electron density in the semiconductor layer of 1×10 16 cm -3 or more and 1×10 23 bcm -3 or less, which may be acceptable.

[0022] The semiconductor device according to the above aspect may have an electron mobility in the semiconductor layer of 50 cm 2 / V·s or more.

[0023] The method for manufacturing a semiconductor device according to the third aspect of the present invention is a method for manufacturing a semiconductor device having a substrate and a semiconductor film formed on one surface of the substrate, wherein the semiconductor film is a polycrystalline film composed of crystal grains having an average particle diameter of 1 μm or more, and includes a first step of forming an amorphous semiconductor film on one surface of the substrate while heating the substrate, a second step of heating the semiconductor film to promote solid-phase growth of the semiconductor film, and a fourth step of introducing hydrogen into the semiconductor film. The semiconductor film is a Ge film, and the heating temperature in the first step is adjusted to be 50% or more and less than 100% of the temperature at which crystal angles occur in the semiconductor film, and the heating temperature in the first step is adjusted such that the density of the particles constituting the semiconductor film is 98% or more and less than 102% of the density of the particles in a crystal of the same material.

[0024] The method for manufacturing a semiconductor device according to the above embodiment may include a third step between the second step and the fourth step, in which the conductivity is adjusted by doping the semiconductor film with a group III element or a group V element.

[0025] In the semiconductor device manufacturing method according to the above embodiment, the third step may be carried out simultaneously with the first step, and a group III element or a group V element may be deposited onto an amorphous semiconductor film.

[0026] In the method for manufacturing a semiconductor device according to the above embodiment, the fourth step may be one or more of the following processes: hydrogen plasma treatment, hydrogen radical treatment, hydrogen ion implantation treatment, hydrogen ion beam manipulation treatment, halogen plasma treatment, halogen radical treatment, halogen ion implantation treatment, and halogen ion beam scanning treatment.

[0027] In the method for manufacturing a semiconductor device according to the above embodiment, the fourth step may involve plasmaizing an inert gas containing 5% hydrogen and exposing the surface side of the semiconductor film to the plasma. [Effects of the Invention]

[0028] According to the present invention, the hole density dependent on the p-type defect level in the undoped state after crystallization of polycrystalline Ge or polycrystalline SiGe can be reduced. As a result, the range of p-type or n-type carrier concentrations that can be controlled by doping can be broadened compared to conventional polycrystalline Ge or polycrystalline SiGe, thereby improving the performance of semiconductor devices containing Ge. [Brief explanation of the drawing]

[0029] [Figure 1] This is a schematic cross-sectional view of a semiconductor device according to the first embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of a modified example of the semiconductor device according to the first embodiment of the present invention. [Figure 3] This is a schematic cross-sectional view of a semiconductor device according to a second embodiment of the present invention. [Figure 4]This figure illustrates the manufacturing process of a semiconductor device according to the first or second embodiment. [Figure 5] This is a schematic cross-sectional view of a semiconductor device according to a third embodiment of the present invention. [Figure 6] This is a schematic cross-sectional view of a semiconductor device according to a fourth embodiment of the present invention. [Figure 7] This figure illustrates the manufacturing process of a semiconductor device according to the third or fourth embodiment. [Figure 8] This graph shows the results of analyzing the concentration of hydrogen in the depth direction within a polycrystalline Ge film obtained after hydrogen plasma treatment, using secondary ion mass spectrometry. [Figure 9] This graph shows the change in hole density of a polycrystalline Ge film obtained after hydrogen plasma treatment. [Figure 10] This graph shows the relationship between the hole density of a polycrystalline Ge film obtained after hydrogen plasma treatment and the hydrogen plasma treatment time. [Figure 11] This graph shows the relationship between the electron density of an Sb-doped n-type polycrystalline Ge film obtained after hydrogen plasma treatment and the hydrogen plasma treatment time. [Figure 12] This is the EBSD image (grain map) from Example 3. [Modes for carrying out the invention]

[0030] The present invention will be described in detail below, with reference to the figures as appropriate. The figures used in the following description may be enlarged for convenience to clearly illustrate the features of the present invention, and the dimensional ratios of each component may differ from those in reality. Furthermore, the materials, dimensions, etc., exemplified in the following description are merely examples, and the present invention is not limited to them. It is possible to modify and implement the invention as appropriate within the scope of achieving its effects.

[0031] [Semiconductor device (first embodiment)] Figure 1 is a cross-sectional view of a semiconductor device 100 according to the first embodiment of the present invention. The semiconductor device 100 according to the first embodiment comprises a substrate 101 and a semiconductor film (semiconductor thin film) 102 formed (synthesized) on one surface 101a of the substrate. The semiconductor film 102 is a non-doped polycrystalline Ge film composed of crystalline particles with an average particle size of 1 μm or more, and the hole density of the semiconductor film 102 is 1 × 10⁻⁶ 17 cm -3 The following applies:

[0032] In this specification, the "average grain size" of Ge crystal grains in a semiconductor film refers to the average of the diameters (equivalent circle diameters) of each crystal grain when viewed as a circle with an equivalent area in an electron microscope image or EBSD image. This average may be calculated automatically by analysis software. The average should be taken from 10 or more crystal grains. The Ge crystal grains used for the average grain size calculation may be selected from one image or from multiple images. If an image shows 10 crystal grains, the average of all visible crystal grains will be used to determine the "average grain size" of the Ge crystal grains in that semiconductor film. Since only a portion of the Ge crystal grains may be visible in an image, the "average grain size" of Ge crystal grains obtained using this definition will be smaller than the "average grain size" of the Ge crystal grains used for the average grain size calculation. Therefore, the "average grain size" of Ge crystal grains in the examples shown later is the lower limit of the "average grain size" of the Ge crystal grains used for the average grain size calculation. Furthermore, in this specification, the "maximum particle size" of Ge crystal particles in a semiconductor film refers to the particle size of the largest crystal particle when each crystal particle is represented as a circle with an equivalent area in an electron microscope image or EBSD image. Alternatively, the largest particle size among 10 or more crystal particles in an image is defined as the "maximum particle size" of Ge crystal particles in the semiconductor film. Since the Ge crystal particles visible in the image are only a portion of the Ge crystal particles in the semiconductor film, and the semiconductor film may contain Ge crystal particles larger than the determined "maximum particle size," the "maximum particle size" determined in this way can be considered the lower limit of the "maximum particle size" of Ge crystal particles in the semiconductor film.

[0033] As the substrate 101, known substrates for forming semiconductor films can be used, and examples include insulators such as SiO2, glass, and plastic, substrates on which these are mounted, or LSI chips.

[0034] Furthermore, the substrate 101 may be an inorganic material substrate (e.g., a silicon substrate) or an organic material substrate on which an insulating layer has been formed. The insulating layer may be any known insulating layer on which polycrystalline Ge can be formed, and for example, an insulating layer made of SiO2, Al2O3, or a compound containing Ge (e.g., GeO2) can be used.

[0035] The semiconductor film 102, in its undoped state, is a polycrystalline film composed of large-particle germanium crystals. This undoped polycrystalline film may contain elements unrelated to its function as impurities, to the extent that it does not affect its function. The average particle size of the Ge crystal particles constituting the polycrystalline Ge film is 1 μm or larger. Preferably, the average particle size of the Ge crystal particles is 3 μm or larger, more preferably 5 μm, and even more preferably 10 μm or larger. In this specification, "large particle size" means that the crystalline particles constituting the polycrystalline film are 1 μm or larger.

[0036] The particle size of the crystalline grains constituting a polycrystalline film can be evaluated, for example, by electron microscopy observation of the film cross-section or by electron diffraction (e.g., electron backscatter diffraction (EBSD)). Electron beam backscatter diffraction (EBSD) is an electron diffraction method capable of measuring crystal orientation texture. It is typically used in conjunction with a scanning electron microscope, allowing for simultaneous scanning and observation of the sample surface with an electron microscope image while performing crystal orientation analysis. This enables indexing of crystals at each measurement point, allowing for the determination of a distribution map of crystal grains, where regions surrounded by grain boundaries (random grain boundaries) where adjacent crystal orientations differ at unspecified angles are treated as single crystal grains. This mapping image is called a grain map, but in this specification, it will be referred to as an EBSD image.

[0037] The semiconductor film 102 may contain Ge crystal particles with a maximum particle size of 5 μm or more. The inclusion of Ge crystal grains with a large maximum particle size leads to a reduction in the number of grain boundaries, which is desirable for a semiconductor film. The semiconductor film 102 preferably contains Ge crystal particles with a maximum particle size of 10 μm or more, more preferably contains Ge crystal particles with a maximum particle size of 15 μm or more, and even more preferably contains Ge crystal particles with a maximum particle size of 20 μm or more.

[0038] The hole density of semiconductor film 102 is 1 × 10⁻⁶ 17 cm -3 The following applies: As mentioned above, polycrystalline Ge films are known to exhibit p-type conductivity even in an undoped state, as the defect levels of their crystals act as holes. Even undoped polycrystalline Ge films made of small-grained crystals, prior to the development of the large-grain technology by the inventors, had a hole density of 1 × 10⁻⁶. 18 cm -3 The hole density is approximately 3 × 10⁶, and in large-grained, undoped polycrystalline Ge films, the lowest hole density is 3 × 10⁶. 17 cm -3 That was the case. In contrast, by introducing hydrogen into the polycrystalline Ge film, we were able to obtain a polycrystalline Ge film with a hole density significantly lower than that of conventional films. As will be shown later, in the large-particle, undoped polycrystalline Ge film developed by the inventors, 2 × 10 15 cm -3 We have also obtained hole densities of a certain degree, achieving a reduction of about three orders of magnitude compared to conventional undoped polycrystalline Ge films made of small-grained crystalline particles. The hole density of semiconductor film 102 is 1 × 10⁻⁶ 16 cm -3 The following 2 x 10 15 cm -3 It is preferable that the above is true, 2 × 10 15 cm -3 The following is more preferable:

[0039] The hole mobility of semiconductor film 102 is 25 cm². 2 It is preferable that it be 50cm or more / V·s 2 / V·s or more 125cm 2 It is more preferable that it be less than or equal to / V·s, or 125cm 2 It is even more preferable that it be greater than or equal to / V·s.

[0040] As shown in Figure 2, the semiconductor film 102 may be composed of multiple polycrystalline Ge films with different hole densities. Figures 2(a) and (b) illustrate the case where the semiconductor film 102 consists of three polycrystalline Ge films (102-1, 102-2, and 102-3). Multiple polycrystalline Ge films with different hole densities can be obtained by adjusting the hydrogen treatment conditions for each layer, such as changing the hydrogen treatment time and the microwave power output for hydrogen treatment. Other layers (103-1, 103-2) may be provided between adjacent polycrystalline Ge films. For example, a hydrogen diffusion prevention layer may be provided between adjacent polycrystalline Ge films to prevent hydrogen movement. Figure 2(b) illustrates the case where there are two other layers. Known materials can be used as the hydrogen diffusion prevention layer, for example, SiO2, GeO2, and Al2O3. In this case, the semiconductor film 102 is composed of multiple polycrystalline Ge films with different hole densities, and layers other than the polycrystalline Ge films, such as the hydrogen diffusion prevention layer, do not constitute the semiconductor film 102.

[0041] [Semiconductor device (second embodiment)] The semiconductor device according to the second embodiment will be described using Figure 3. Configurations common to the semiconductor device according to the first embodiment will be omitted from the explanation as appropriate.

[0042] The semiconductor device 200 according to the second embodiment comprises a substrate 201 and a semiconductor film (semiconductor thin film) 202 formed (synthesized) on one surface 201a of the substrate, wherein the semiconductor film 202 is a non-doped polycrystalline Ge film composed of crystalline particles with an average particle size of 1 μm or more, and the hydrogen concentration of the semiconductor film 202 is 1 × 10⁻⁶ 19 cm -3 That's all.

[0043] In the semiconductor device 200, the average particle size of the Ge crystal particles constituting the polycrystalline Ge film is 1 μm or more. Preferably, the average particle size of the Ge crystal particles is 3 μm or more, more preferably 5 μm, even more preferably 7 μm or more, and most preferably 10 μm or more.

[0044] In the semiconductor device 200, the semiconductor film 202 may contain Ge crystal particles with a maximum particle size of 5 μm or more. The inclusion of Ge crystal grains with a large maximum particle size leads to a reduction in the number of grain boundaries, which is desirable for a semiconductor film. The semiconductor film 202 preferably contains Ge crystal particles with a maximum particle size of 10 μm or more, more preferably contains Ge crystal particles with a maximum particle size of 15 μm or more, and even more preferably contains Ge crystal particles with a maximum particle size of 20 μm or more.

[0045] The hydrogen concentration of semiconductor film 202 is 1 × 10⁻⁶ 19 cm -3 That's all. 1 x 10 19 cm -3 By containing hydrogen at the above atomic concentrations, the polycrystalline Ge film 202 has a hole density significantly lower than that of conventional films. The hydrogen concentration of semiconductor film 202 is 1 × 10⁻⁶ 20 cm -3 The above 1 x 10 22 cm -3 The following is preferable: 1 × 10 22 cm -3 It is more preferable that the above conditions are met.

[0046] The hole mobility of semiconductor film 202 is 25 cm². 2 / V·s or greater is sufficient. 50cm 2 / V·s or more 125cm 2 / V·s or less is more preferable, 125cm 2 / V·s or higher is even preferable.

[0047] The semiconductor film 202 may be composed of multiple polycrystalline Ge films with different hydrogen concentrations (see Figure 2). Multiple polycrystalline Ge films with different hydrogen concentrations can be obtained by adjusting the hydrogen treatment conditions for each layer, such as changing the hydrogen treatment time or the microwave power output for hydrogen treatment. Other layers may be provided between adjacent polycrystalline Ge films (see Figure 2(b)), for example, a hydrogen migration prevention layer may be provided to prevent the movement of hydrogen introduced between adjacent polycrystalline Ge films. Known materials can be used as the hydrogen migration prevention layer, for example, SiO2, GeO2, and Al2O3.

[0048] [Method for manufacturing a semiconductor device (first embodiment)] The three main steps for manufacturing the semiconductor device 100 or the semiconductor device 200 described above will be explained with reference to Figure 4. Although Figure 4 describes the semiconductor device 100, the semiconductor device 200 can also be manufactured using the same steps.

[0049] (Amorphous film formation process) While heating the substrate 101, Ge particles 102A are deposited on one surface 101a of the substrate to form an amorphous semiconductor film 102B (left side of Figure 4).

[0050] The heating method and deposition method are not particularly limited, and general methods (molecular beam deposition, CVD, sputtering, etc.) can be used. When using molecular beam deposition, particles 102A are deposited in a high vacuum to form an amorphous film 102B. This method allows for setting a low film deposition temperature, making it a preferred method when depositing films on substrates with low heat resistance, such as plastics, or on LSI chips.

[0051] The heating temperature during the amorphous film formation process is adjusted so that the resulting amorphous film 102B has a particle number density as close as possible to that of a crystal (98% to less than 102% of the particle density in a crystal of the same material), and so that no crystal nuclei are formed. In other words, the temperature is adjusted to be as high as possible while still preventing the formation of crystal nuclei in the amorphous film 102B.

[0052] In practice, the temperature should be adjusted to be between 30% and 100% of the temperature at which crystal nuclei form in the amorphous film 102B, and more preferably between 50% and 100%. Specifically, this is generally between 100°C and 700°C. This temperature is adjusted according to the material and thickness of the semiconductor film 102 to be formed. For example, when forming a semiconductor film 102 with a thickness of 100 nm, the temperature should be 100 to 150°C.

[0053] (Solid phase growth process) A heat treatment (regardless of atmosphere) is performed to promote solid-phase growth of the amorphous semiconductor film 102B formed in the amorphous film formation process, thereby synthesizing a polycrystalline semiconductor film (polycrystalline film) 102C (center of Figure 4). In the solid-phase growth process, the heating temperature is preferably 350°C to 800°C, and the heating time is preferably 0.1 hours to 300 hours.

[0054] By adjusting the heating temperature during amorphous film formation as described above, the resulting semiconductor film 102C becomes a polycrystalline film composed of large-particles of 1 μm or larger.

[0055] (Hydrogen treatment process) The polycrystalline semiconductor film (polycrystalline film) 102C formed in the solid-phase growth process is subjected to a process to introduce hydrogen element 102D, thereby synthesizing a polycrystalline semiconductor film 102E into which hydrogen has been introduced (right side of Figure 4).

[0056] The method for introducing hydrogen is not particularly limited, and general methods (such as hydrogen plasma treatment, hydrogen annealing, and thermal diffusion) can be used. When using hydrogen plasma treatment, hydrogen-containing Ar is converted into plasma in a high vacuum, and this is exposed to one surface 102a of the substrate, thereby introducing hydrogen into the polycrystalline film 102C and forming a hydrogen-treated polycrystalline film 102E. This method allows for the control of the amount of hydrogen element introduced by adjusting the mixing ratio of hydrogen and argon and the exposure time to the hydrogen plasma.

[0057] The semiconductor device 100 obtained through the processes of amorphous film formation and solid-phase growth has a polycrystalline semiconductor film 102C obtained by forming an amorphous film 102B with a density close to that of a crystal in a range where no crystal nuclei are generated during the manufacturing process, and then growing this amorphous film in solid phase. Since this semiconductor film 102C is a polycrystalline film composed of large-particle crystalline grains of 1 μm or more, the amount of hydrogen introduced in the hydrogen introduction process can be increased compared to conventional polycrystalline Ge films with small particle sizes of 1 μm or less.

[0058] If the particle size of the crystal grains constituting the semiconductor film 102 is smaller than 1 μm, it is not possible to reduce the hole density to the same extent as in the present invention.

[0059] As described above, the semiconductor device 100 according to this embodiment has a semiconductor 102E in which a large-grained polycrystalline film 102C is formed during the manufacturing process and hydrogen is introduced into it to reduce the hole density. Since this semiconductor film 102E is a polycrystalline film made up of large-grained crystalline particles of 1 μm or more, it is possible to achieve a lower hole density than conventional films. In addition to the process described in Patent Document 1, further increases in particle size can be achieved by (i) gradually changing the deposition temperature in the amorphous film formation (deposition) process, and (ii) using a substrate on which a Ge-containing underlayer has been formed on the surface. As for (i), for example, a high-density layer can be used as the nucleation layer (for example, deposited at 150°C), and a low-density layer can be used as the nucleation suppression layer on top of it (for example, deposited at 75°C).

[0060] When the semiconductor film 102 is composed of multiple polycrystalline Ge films with different hole densities or multiple polycrystalline Ge films with different hydrogen concentrations, the hydrogen treatment process consists of sub-steps in which the hydrogen treatment conditions are adjusted for each polycrystalline Ge film.

[0061] [Semiconductor device (third embodiment)] Figure 5 is a cross-sectional view of the semiconductor device 300 according to the third embodiment. The configuration common to the semiconductor device according to the above embodiment will not be described.

[0062] The semiconductor device 300 according to the third embodiment comprises a substrate 301 and a semiconductor film (semiconductor thin film) 302 formed (synthesized) on one surface 301a of the substrate, wherein the semiconductor film 302 is a polycrystalline Ge film composed of crystalline particles with an average particle size of 1 μm or more, and the hydrogen concentration of the semiconductor film 302 is 1 × 10⁻¹⁶ 19 cm -3 The above explains why the semiconductor film 302 exhibits a p-type conduction mechanism by containing a group III element as an impurity.

[0063] The semiconductor film 302 is a polycrystalline germanium film composed of large-particle-sized crystalline grains. The average particle size of the Ge crystalline grains constituting the polycrystalline Ge film is 1 μm or larger. Preferably, the average particle size of the Ge crystalline grains is 3 μm or larger, more preferably 5 μm, and even more preferably 10 μm or larger.

[0064] In the semiconductor device 300, the semiconductor film 302 may contain Ge crystal particles with a maximum particle size of 5 μm or more. The inclusion of Ge crystal grains with a large maximum particle size leads to a reduction in the number of grain boundaries, which is desirable for a semiconductor film. The semiconductor film 302 preferably contains Ge crystal particles with a maximum particle size of 10 μm or more, more preferably contains Ge crystal particles with a maximum particle size of 15 μm or more, and even more preferably contains Ge crystal particles with a maximum particle size of 20 μm or more.

[0065] The semiconductor film 302 is a polycrystalline Ge film exhibiting p-type conductivity and containing group III elements. Examples of group III elements include boron (B) and aluminum (Al). The hole density of semiconductor film 302 is 1 × 10⁻⁶ 15 cm -3 The above 1 x 10 23 cm -3 The following is preferable:

[0066] The hole mobility of semiconductor film 302 is 25 cm². 2 It is preferable that it is / V·s or greater.

[0067] The semiconductor film 302 may be composed of multiple polycrystalline Ge films with different hole densities (see Figure 2). Multiple polycrystalline Ge films with different hole densities can be obtained by adjusting the hydrogen treatment conditions for each layer, such as changing the hydrogen treatment time or the microwave power output for hydrogen treatment. Other layers may be provided between adjacent polycrystalline Ge films (see Figure 2(b)), for example, a hydrogen migration prevention layer may be provided between adjacent polycrystalline Ge films to prevent hydrogen migration. Known materials can be used as the hydrogen migration prevention layer, for example, SiO2, GeO2, and Al2O3.

[0068] [Semiconductor device (fourth embodiment)] The semiconductor device according to the fourth embodiment will be described using Figure 6. The configurations common to the semiconductor device according to the third embodiment will not be explained. The semiconductor device 400 according to the fourth embodiment comprises a substrate 401 and a semiconductor film (semiconductor thin film) 402 formed (synthesized) on one surface 401a of the substrate, wherein the semiconductor film 402 is a polycrystalline Ge film composed of crystalline particles with an average particle size of 1 μm or more, and the hydrogen concentration of the semiconductor film 402 is 1 × 10⁻¹⁶ 19 cm -3 The above describes how the semiconductor film 402 exhibits an n-type conduction pattern by containing a group V element as an impurity.

[0069] The semiconductor film 402 is a polycrystalline germanium film composed of large-particle-sized crystalline grains. The average particle size of the Ge crystalline grains constituting the polycrystalline Ge film is 1 μm or larger. Preferably, the average particle size of the Ge crystalline grains is 3 μm or larger, more preferably 5 μm, and even more preferably 10 μm or larger.

[0070] In the semiconductor device 400, the semiconductor film 402 may contain Ge crystal particles with a maximum particle size of 5 μm or more. The inclusion of Ge crystal grains with a large maximum particle size leads to a reduction in the number of grain boundaries, which is desirable for a semiconductor film. The semiconductor film 402 preferably contains Ge crystal particles with a maximum particle size of 10 μm or more, more preferably contains Ge crystal particles with a maximum particle size of 15 μm or more, and even more preferably contains Ge crystal particles with a maximum particle size of 20 μm or more.

[0071] The semiconductor film 402 is a polycrystalline Ge film exhibiting an n-type conductivity, containing group V elements. Examples of Group V elements include phosphorus (P), arsenic (As), and antimony (Sb). The electron density of semiconductor film 402 is 1 × 10⁻⁶ 16 cm -3 The above 1 x 10 23 cm -3 The following is preferable:

[0072] The electron mobility of semiconductor film 402 is 50 cm². 2 / V·s or greater is sufficient, 100cm 2 / V·s or more 200cm 2 / V·s or less is more preferable, and 200cm 2 / V·s or higher is even preferable.

[0073] The semiconductor film 402 in the semiconductor device according to the fourth embodiment may be composed of multiple polycrystalline Ge films with different electron densities. Multiple polycrystalline Ge films with different electron densities can be obtained by adjusting the hydrogen treatment conditions for each layer, such as changing the hydrogen treatment time or the microwave output for hydrogen treatment. In this configuration, other layers may be provided between adjacent polycrystalline Ge films. For example, a hydrogen transfer prevention layer may be provided between adjacent polycrystalline Ge films to prevent hydrogen migration. Known materials can be used as the hydrogen transfer prevention layer, for example, SiO2, GeO2, and Al2O3.

[0074] [Method for manufacturing a semiconductor device (second embodiment)] The four main steps for manufacturing the semiconductor device 300 or 400 will be explained with reference to Figure 7. Although Figure 7 describes the semiconductor device 300, the semiconductor device 400 can be manufactured using the same steps. In addition to the semiconductor device manufacturing method of the first embodiment, a step of introducing impurities to make it a p-type or n-type conduction type is added. Steps common to the semiconductor device manufacturing method of the first embodiment will be explained in a simplified or omitted manner as appropriate.

[0075] (Amorphous film formation and impurity introduction process) The method for introducing impurities is not particularly limited, and general methods (ion implantation, thermal diffusion, impurity deposition, etc.) can be used.

[0076] When using the impurity deposition method, in the step of forming an amorphous film, Ge particles 302A are deposited on one surface 301a of the substrate 301 while the substrate 301 is heated, and at the same time, impurity elements 302B are deposited. Subsequently, in the solid-phase growth step, heat treatment is performed to simultaneously achieve polycrystallization and doping. When using the ion implantation method or the thermal diffusion method, after polycrystallization in the solid-phase growth step, the ion implantation method or the thermal diffusion method is performed as an impurity introduction step.

[0077] The impurity elements are not particularly limited; for example, impurity elements for creating a p-type conduction system can be B, Al, Ga, In, and Tl, while impurity elements for creating an n-type conduction system can be P, As, Sb, and Bi.

[0078] The heating temperature during the amorphous film formation process is adjusted so that the resulting amorphous film 302C has a particle number density as close as possible to that of a crystal (98% to less than 102% of the particle density in a crystal of the same material), and so that no crystal nuclei are formed. In other words, the temperature is adjusted to be as high as possible while still preventing the formation of crystal nuclei in the amorphous film 302C.

[0079] In practice, the temperature should be adjusted to be between 30% and 100% of the temperature at which crystal nuclei form in the amorphous film 302C, and more preferably between 50% and 100%. Specifically, this is generally between 100°C and 700°C. This temperature is adjusted according to the material and thickness of the semiconductor film 302 to be formed. For example, when forming a semiconductor film 302 with a thickness of 100 nm, the temperature should be 100 to 150°C.

[0080] (Solid phase growth process) Similar to the solid-phase growth process in the first embodiment of the semiconductor device manufacturing method, heat treatment (regardless of atmosphere) is performed to promote solid-phase growth of the amorphous semiconductor film 302C formed in the amorphous film formation process, thereby synthesizing a polycrystalline semiconductor film (polycrystalline film) 302D (center of Figure 7). In the solid-phase growth process, the heating temperature is preferably 350°C or higher and 800°C or lower, and the heating time is preferably 0.1 hours or higher and 300 hours or lower.

[0081] By adjusting the heating temperature during amorphous film formation as described above, the resulting semiconductor film 302D becomes a polycrystalline film composed of large-particles of 1 μm or larger.

[0082] (Hydrogen treatment process) Similar to the hydrogen treatment step in the manufacturing method of the semiconductor device of the first embodiment, a hydrogen element 302E is introduced into the impurity-introduced polycrystalline semiconductor film 302D formed in the solid-phase growth step, thereby synthesizing an impurity-introduced polycrystalline semiconductor film (hydrogen-treated polycrystalline film) 302F into which hydrogen has been introduced.

[0083] Similar to the process described above, when using hydrogen plasma treatment, hydrogen-containing Ar is converted into plasma in a high vacuum, and this plasma is exposed to one surface 302a of the substrate, thereby introducing hydrogen into the polycrystalline film 302D and forming a hydrogen-treated polycrystalline film 302F. This method allows for control of the amount of hydrogen element introduced by adjusting the mixing ratio of hydrogen and argon and the exposure time to the hydrogen plasma.

[0084] The semiconductor device 300 has a polycrystalline semiconductor film 302D obtained by forming an amorphous film 302C with a density close to that of a crystal in a range where no crystal nuclei are generated during its manufacturing process, and then growing this amorphous film in solid phase. Since this semiconductor film 302D is a polycrystalline film composed of large-particle crystalline grains of 1 μm or more, the amount of hydrogen introduced in the hydrogen introduction process can be increased compared to conventional polycrystalline Ge films with small particle sizes of 1 μm or less.

[0085] The above-described method for manufacturing semiconductor devices can be applied by replacing the polycrystalline Ge film with a polycrystalline SiGe film. [Examples]

[0086] The effects of the present invention will be made clearer by the following examples. However, the present invention is not limited to the following examples and can be modified as appropriate without altering its essence.

[0087] (Example 1) A 100 nm thick amorphous Ge film was formed on a quartz glass substrate by molecular beam deposition (MDE) while the substrate temperature Td was set within the range of 125°C. The deposition rate was 1 nm / min, and the deposition time was 100 minutes.

[0088] Subsequently, the amorphous Ge film was introduced into an electric furnace under a nitrogen atmosphere and subjected to heat treatment at 450°C for 5 hours to promote solid-phase growth, thereby obtaining a polycrystalline Ge thin film.

[0089] For the obtained polycrystalline Ge thin film, electron beam backscatter diffraction measurements were performed, and the average particle size of the Ge crystal grains was automatically calculated using analysis software based on the EBSD image (grain map), which was found to be 3.6 μm. The maximum particle size was 6.2 μm. Note that the average particle size obtained by automatic calculation is not the average particle size divided by the number of particles, but rather the average particle size weighted by area, thus minimizing the influence of minute particles (such as minute particles caused by unavoidable impurities that may occur in each experiment).

[0090] Defects in polycrystalline Ge thin films act as acceptors (holes), and the hole density after the formation of the polycrystalline Ge film is 3 × 10⁻¹⁶. 17 cm -3 That was the case.

[0091] Subsequently, the polycrystalline Ge film was introduced into a vacuum chamber where a plasma was generated by irradiating Ar gas containing 5% hydrogen with electromagnetic waves at an output of 150W to 450W under vacuum. After standing for 20 minutes, the polycrystalline Ge film surface was subjected to hydrogen plasma treatment to introduce hydrogen.

[0092] Figure 8 is a graph showing the depth-direction hydrogen concentration in a polycrystalline Ge film obtained after hydrogen plasma treatment (300W output, 20 minutes), as analyzed by secondary ion mass spectrometry (SIMS). The horizontal axis of the graph represents the thickness [nm] of the sample in the depth direction, with the polycrystalline Ge film surface set to 0, and the vertical axis represents the hydrogen concentration [cm³]. -3 This indicates [...].

[0093] Without hydrogen plasma treatment, the hydrogen concentration in the polycrystalline Ge thin film is 10 19 [cm -3 The order of magnitude was 1 × 10⁻¹⁰ (lower limit of detection sensitivity). On the other hand, in this embodiment where hydrogen plasma treatment was performed, the maximum value on the polycrystalline Ge thin film surface was 1 × 10⁻¹⁰. 23 [cm -3 This shows a value that decreases with depth, and has a minimum value of 2 × 10 near the interface with the glass substrate. 19 [cm -3 This indicates that hydrogen has been introduced into the polycrystalline Ge film by hydrogen plasma treatment.

[0094] The electrical properties of the polycrystalline Ge film according to Example 1 were calculated using the van der Pauw method. FIG. 9 is a graph showing the change in hole density of the polycrystalline Ge film obtained through hydrogen plasma treatment. The horizontal axis of the graph indicates the presence or absence of hydrogen treatment, and the vertical axis indicates the hole density [cm -3 . Here, the polycrystalline Ge film with large particles having an average particle size of 3.6 μm and the polycrystalline Ge film with small particles having an average particle size of 0.5 μm according to Example 1 are shown by round plots and triangular plots, respectively.

[0095] The hole density of the polycrystalline Ge film according to Example 1 was 3×10 17 [cm -3 before hydrogen plasma treatment and 3×10 15 [cm -3 after hydrogen plasma treatment, showing a significant decrease. On the other hand, for the conventional polycrystalline Ge film with small particle sizes, although it decreased from 9×10 17 [cm -3 before hydrogen plasma treatment, it was 2×10 17 [cm -3 after hydrogen plasma treatment. The polycrystalline Ge film according to Example 1 has a greater effect of reducing hole density by hydrogen treatment than that of the conventional polycrystalline Ge film with small particle sizes.

[0096] FIG. 10 is a graph showing the relationship between the hole density of the polycrystalline Ge film obtained through hydrogen plasma treatment and the hydrogen plasma treatment time. The horizontal axis of the graph indicates the hydrogen treatment time [minutes], and the vertical axis indicates the hole mobility [cm -3 . Here, the hole densities when the microwave output in the hydrogen treatment process was 150 W, 300 W, and 450 W are shown by square plots, round plots, and triangular plots, respectively.

[0097] The hole density of the polycrystalline Ge film strongly depends on the hydrogen plasma treatment time and reaches a minimum value of 2×10 15 [cm -3This result shows that the amount of hydrogen introduced increases with increasing hydrogen plasma processing time, and when the hydrogen plasma processing time is the same, the amount of hydrogen introduced increases with increasing plasma output.

[0098] The hole mobility of the polycrystalline Ge film according to Example 1 is 125 [cm²]. 2 [V·s] has been obtained.

[0099] (Example 2) A 100 nm thick amorphous Ge film was formed by depositing Ge particles onto a quartz glass substrate using molecular beam deposition (MDE) at a substrate temperature Td of 125°C (amorphous film formation process). The deposition rate was 1 nm / min, and the deposition time was 100 minutes.

[0100] Simultaneously with the deposition of Ge particles, Sb particles were deposited as an n-type dopant (impurity introduction step). The temperature of the K cell for evaporating Sb was set to 290°C, the deposition rate to 1.0 nm / min, and the deposition time to 100 minutes. This deposition amount corresponds to the amount by which holes originating from crystal defects in the polycrystalline Ge film are deactivated, causing the p-type semiconductor to invert into an n-type semiconductor.

[0101] Subsequently, the amorphous Ge film was introduced into an electric furnace under a nitrogen atmosphere and subjected to heat treatment at 450°C for 5 hours to promote solid-phase growth. This heat treatment caused the amorphous Ge to crystallize into polycrystalline Ge, and at the same time, n-type dopant Sb particles diffused into the polycrystalline Ge film, forming an Sb-doped n-type polycrystalline Ge film exhibiting n-type conductivity.

[0102] The electron density of the Sb-doped n-type polycrystalline Ge film, calculated using the van der Pauw method, is 3 × 10⁻¹⁰. 18 [cm -3 ] was.

[0103] Thereafter, the Sb-doped n-type polycrystalline Ge thin film was introduced into a vacuum chamber in which Ar gas containing 5% hydrogen was irradiated with electromagnetic waves with an output of 300 W to generate plasma, and then left standing for 20 minutes to perform hydrogen plasma treatment on the surface of the Ge thin film, thereby adding hydrogen.

[0104] Figure 11 is a graph showing the relationship between the electron density of the Sb-doped n-type polycrystalline Ge film obtained through hydrogen plasma treatment and the hydrogen plasma treatment time. The horizontal axis indicates the hydrogen treatment time [minutes], and the vertical axis indicates the electron density [cm -3 .

[0105] The electron density of the polycrystalline Ge film strongly depends on the hydrogen plasma treatment time, and reaches a minimum value (1×10 16 [cm -3 ) when the hydrogen plasma treatment time is 20 minutes. This result shows that the amount of hydrogen introduced increases according to the length of the hydrogen plasma treatment time, and when the hydrogen plasma treatment time is the same, the amount of hydrogen introduced increases according to the magnitude of the plasma output. The decrease in the hole density of the non-doped polycrystalline Ge film due to hydrogen plasma treatment indicates that the n-type electron density has decreased. As a result, the controllable range of the n-type electron density has been expanded.

[0106] The electron mobility of the Sb-doped n-type polycrystalline Ge film according to this example is 200 [cm 2 / V·s].

[0107] (Example 3) In Example 3, a polycrystalline Ge film was obtained under the same conditions as in Example 1, except that a substrate on which a GeO2 film (film thickness: 100 nm) was formed on a quartz glass substrate was used, and a solid-phase growth process was performed under heat treatment conditions of 375 °C for 150 hours. When electron backscatter diffraction measurement was performed on the polycrystalline Ge film before hydrogen plasma treatment, the average grain size of the Ge crystal particles was 10.1 μm, and the maximum grain size was 17.5 μm. Fig. 12 shows an example of the obtained EBSD image (grain map). Ten Ge crystal particles can be seen in the EBSD image, and the maximum grain size in this image is 17.5 μm. [Industrial applicability]

[0108] This invention can be widely used in applications such as "development of high-speed, low-power thin-film transistors," "high-efficiency, low-cost multi-junction thin-film solar cells," "three-dimensional and multi-functional integrated circuits," and "near-infrared light receiving sensors for optical communications." [Explanation of symbols]

[0109] 100 semiconductor devices, 101 Base material, 102 Semiconductor film, 200 semiconductor equipment, 201 Base material, 202 Semiconductor film, 300 semiconductor equipment, 301 base material, 302 Semiconductor film 400 semiconductor devices, 401 Base material, 402 Semiconductor film

Claims

1. The substrate and the semiconductor film formed on one surface of the substrate, The semiconductor film is a polycrystalline Ge film composed of crystalline particles with an average particle size of 1 μm or more. The semiconductor film contains Ge crystal particles with a maximum particle size of 5 μm or more. The aforementioned semiconductor film contains a group III element as an impurity, thereby exhibiting a p-type conduction mechanism. A semiconductor device having a hole density of 1 × 10¹⁵ cm⁻³ or more and 1 × 10²³ cm⁻³ or less.

2. The hole mobility of the semiconductor film is 25 cm ２ The semiconductor device according to claim 1, wherein the s value is 1 / V·s or greater.

3. A substrate and a semiconductor film formed on one surface of the substrate, The semiconductor film is a polycrystalline Ge film composed of crystalline particles with an average particle size of 1 μm or more. The semiconductor film contains Ge crystal particles with a maximum particle size of 5 μm or more. The aforementioned semiconductor film contains a group V element as an impurity, thereby exhibiting an n-type conduction mechanism. A semiconductor device having an electron density of 1 × 10¹⁶ cm⁻³ or more and 1 × 10²³ cm⁻³ or less.

4. The electron mobility of the semiconductor film is 50 cm². ２ The semiconductor device according to claim 3, wherein the value is / V·s or greater.

5. A method for manufacturing a semiconductor device according to claim 1 or 2, A method for manufacturing a semiconductor device comprising a substrate and a semiconductor film formed on one surface of the substrate, wherein the semiconductor film is a polycrystalline film composed of crystalline particles with an average particle size of 1 μm or more, A first step involves heating the substrate while forming an amorphous semiconductor film on one surface of the substrate, A second step involves heating the semiconductor film to promote solid-phase growth of the semiconductor film, The fourth step involves introducing hydrogen into the semiconductor film, The semiconductor film is a Ge film, The heating temperature in the first step is adjusted to be 50% or more but less than 100% of the temperature at which crystal nuclei are generated in the semiconductor film. The heating temperature in the first step is adjusted so that the density of the particles constituting the semiconductor film is 98% or more and less than 102% of the density of particles in a crystal of the same material. A method for manufacturing a semiconductor device, wherein the introduction of impurities is performed by doping the semiconductor film with a Group III element between the second and fourth steps, or by depositing a Group III element onto an amorphous semiconductor film in the first step.

6. A method for manufacturing a semiconductor device according to claim 3 or 4, A method for manufacturing a semiconductor device comprising a substrate and a semiconductor film formed on one surface of the substrate, wherein the semiconductor film is a polycrystalline film composed of crystalline particles with an average particle size of 1 μm or more, A first step involves heating the substrate while forming an amorphous semiconductor film on one surface of the substrate, A second step involves heating the semiconductor film to promote solid-phase growth of the semiconductor film, The fourth step involves introducing hydrogen into the semiconductor film, The semiconductor film is a Ge film, The heating temperature in the first step is adjusted to be 50% or more but less than 100% of the temperature at which crystal nuclei are generated in the semiconductor film. The heating temperature in the first step is adjusted so that the density of the particles constituting the semiconductor film is 98% or more and less than 102% of the density of particles in a crystal of the same material. A method for manufacturing a semiconductor device, wherein the introduction of impurities is performed by doping the semiconductor film with a group V element between the second step and the fourth step, or by depositing a group V element onto an amorphous semiconductor film in the first step.

7. The method for manufacturing a semiconductor device according to claim 5 or 6, wherein the fourth step is one or more of the following: hydrogen plasma treatment, hydrogen radical treatment, hydrogen ion implantation treatment, hydrogen ion beam scanning treatment, halogen plasma treatment, halogen radical treatment, halogen ion implantation treatment, and halogen ion beam scanning treatment.

8. The method for manufacturing a semiconductor device according to claim 5 or 6, wherein the fourth step involves plasma-generating an inert gas containing 5% hydrogen and exposing the surface side of the semiconductor film to the plasma.

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