JP7593124B2 - Method and apparatus for manufacturing binary compound semiconductors - Google Patents

Description

The present invention relates to a method and apparatus for manufacturing binary compound semiconductors such as silicon carbide (hereinafter referred to as SiC) and gallium nitride (hereinafter referred to as GaN).

Conventionally, as one of the methods for manufacturing binary compound semiconductors, Patent Document 1 proposes a method for manufacturing a compound semiconductor device in which an epitaxial film is grown on a semiconductor substrate made of SiC or the like. In this manufacturing method, an epitaxial film is formed using a recipe having a step of a temperature rise period accompanied by pre-doping in which a dopant gas is introduced in advance, a step of a transition period in which the introduction of a raw material gas starts and gradually increases, and a step of a steady growth period in which the amount of the raw material gas introduced is kept constant. When forming an epitaxial film of SiC, silane (SiH ₄ ) and propane (C ₃ H ₈ ) are used as raw material gases, and a carrier gas such as hydrogen (H ₂ ) is introduced together with the raw material gas to stably supply the raw material gas to grow the epitaxial film.

JP 2017-152487 A

In general, raw gas cylinders that contain raw gas are diluted with dilution gas and have a certain gas concentration tolerance relative to the target gas concentration. For example, if the target gas concentration is one where the volume ratio of raw gas to the total volume of the mixed gas of raw gas and dilution gas is 10%, the allowable tolerance is ±5%. For this reason, even if the target concentration of raw gas is 10%, a raw gas cylinder with a gas concentration of 9.5 to 10.5% will be used to form the epitaxial film.

When forming epitaxial films on two-dimensional compound semiconductors such as SiC, it is known that the efficiency of dopant incorporation, such as aluminum (Al) or nitrogen (N), is highly dependent on the elemental ratio of Si and C contained in the Si-based material and the C-based material, but this changes every time the raw gas cylinder is replaced. For this reason, every time the raw gas cylinder is replaced, a semiconductor substrate is prepared as a reference sample, an epitaxial film is formed on it, and then the in-plane distribution of the epitaxial film thickness on the semiconductor substrate, an experiment to grasp the dopant incorporation efficiency, and concentration profile measurements are performed. Then, a calibration curve is obtained based on the results, and the raw gas concentration is controlled when forming the epitaxial film.

However, starting from the flow rate under the epitaxial film growth conditions before the raw gas cylinder was replaced, the flow rate is gradually changed and experiments are performed until the in-plane distribution of the epitaxial film thickness, the dopant incorporation efficiency, and the concentration profile reach the target values to obtain a calibration curve. This requires complicated experiments, and also makes it difficult to fix the epitaxial film formation recipe. Therefore, it is desirable to be able to easily fix the epitaxial film formation recipe without having to perform complicated experiments.

Here, we have explained not only the in-plane distribution of the epitaxial film thickness, but also the experiment to grasp the dopant incorporation efficiency and the concentration profile measurement. However, as mentioned above, the dopant incorporation efficiency and concentration profile are highly dependent on the element ratio of Si and C in the Si-based material and C-based material, and affect the in-plane distribution of the thickness of the obtained epitaxial film. Therefore, if it is possible to control at least the in-plane distribution of the epitaxial film thickness so that it is stable and reaches the target value, it will be possible to avoid the need for complicated experiments and to easily fix the epitaxial film formation recipe.

In view of the above, the present invention aims to provide a method and apparatus for manufacturing binary compound semiconductors that can easily fix the epitaxial film formation recipe without the need for complicated experiments.

In order to achieve the above object, the invention described in claim 1 is a method for manufacturing a binary compound semiconductor by supplying a first raw material gas containing a first raw material and a second raw material gas containing a second raw material to grow an epitaxial film (2) on a binary compound semiconductor substrate (1), and includes preparing a first raw material gas cylinder (41) containing a first raw material dilution gas obtained by diluting the first raw material gas with a dilution gas at a first gas concentration, and a second raw material gas cylinder (42) containing a second raw material dilution gas obtained by diluting the second raw material gas with a dilution gas that is the same as or different from the dilution gas, and preparing a reaction furnace (20) constituting a growth chamber for accommodating and heating the substrate. In addition, when replacing at least one of the first raw material gas cylinder and the second raw material gas cylinder, an inspection value of the gas concentration of the gas cylinder to be replaced, one of the first gas concentration and the second gas concentration, is obtained, and the inspection value is input to the device control unit (90). Then, the device control unit automatically corrects the gas flow rate of the first raw material dilution gas introduced from the first raw material gas cylinder into the reactor and the gas flow rate of the second raw material dilution gas introduced from the second raw material gas cylinder into the reactor based on the test values so that the number of atoms of the first raw material when the first gas concentration is the target value and the number of atoms of the second raw material when the second gas concentration is the target value are obtained, and creates a recipe for growing an epitaxial film. In accordance with the recipe, the first raw material dilution gas and the second raw material dilution gas are introduced into the reactor containing the substrate at the automatically corrected gas flow rates to grow an epitaxial film.

In this way, when replacing the cylinders, the gas flow rates of the first and second raw material dilution gases are automatically corrected to create a recipe so that the target number of atoms is maintained even for the first and second gas concentrations after replacement. For example, the gas concentration of the first raw material dilution gas in the first raw material gas cylinder after cylinder replacement and the gas concentration of the second raw material dilution gas in the second raw material gas cylinder are inspected, and the ratio of the inspection value to the target gas concentration is calculated. Then, based on the calculated ratio, the gas flow rates of the first and second raw material dilution gases are automatically corrected so that the number of atoms of the first and second raw materials are the same before and after replacement, and a recipe is created based on this.

By growing an epitaxial film according to the recipe obtained in this way, the atomic numbers of the first and second raw materials can be kept constant and stabilized before and after changing the cylinder, so that the in-plane distribution of the epitaxial film's thickness can be stably set to the target value. This makes it possible to easily fix the epitaxial film formation recipe without having to carry out complicated experiments.

In addition, the invention described in claim 8 is a manufacturing apparatus for a binary compound semiconductor that supplies a first raw material gas containing a first raw material and a second raw material gas containing a second raw material to grow an epitaxial film (2) on a substrate (1) of a binary compound semiconductor, and includes a first raw material gas cylinder (41) that contains a first raw material dilution gas obtained by diluting the first raw material gas with a dilution gas to a first gas concentration, a second raw material gas cylinder (42) that contains a second raw material dilution gas obtained by diluting the second raw material gas with a dilution gas that is the same as or different from the dilution gas, a reaction furnace (20) that constitutes a growth chamber that contains and heats the substrate, and a gas mixture containing the first raw material and the second raw material when the first gas concentration is a target value. The device control unit (90) stores the gas flow rate of the second raw material when the second gas concentration is a target value, and when replacing at least one of the first raw material gas cylinder and the second raw material gas cylinder, inputs an inspection value of the gas concentration of the gas cylinder to be replaced, out of the first gas concentration and the second gas concentration, and automatically corrects the gas flow rate of the first raw material dilution gas introduced from the first raw material gas cylinder to the reactor and the gas flow rate of the second raw material dilution gas introduced from the second raw material gas cylinder to the reactor based on the inspection value so that the number of atoms of the first raw material when the first gas concentration is the target value and the number of atoms of the second raw material when the second gas concentration is the target value are obtained, and creates a recipe for growing an epitaxial film.

In this way, it is possible to realize a manufacturing apparatus that realizes the epitaxial film manufacturing method described in claim 1. By using such a manufacturing apparatus, it is possible to easily fix the epitaxial film formation recipe without having to perform complicated experiments.

The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below.

1 is a diagram showing a schematic configuration of an epitaxial film manufacturing apparatus according to a first embodiment. FIG. 1 is a diagram showing a conventional manufacturing flow of an epitaxial film. FIG. 13 is a diagram showing the results of investigating the susceptor radius, which is the distance from the center of the susceptor portion, and the p-type impurity concentration of the epitaxial film at that location. FIG. 1 is a diagram showing the results of an investigation into the relationship between the depth in the thickness direction of an epitaxial film and the p-type impurity concentration. FIG. 2 is a diagram showing a manufacturing flow based on the manufacturing method according to the first embodiment. 4 is a table showing an example of a recipe created in the manufacturing method according to the first embodiment.

The following describes embodiments of the present invention with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals.

First Embodiment
A method and an apparatus for manufacturing a binary compound semiconductor according to a first embodiment of the present invention will be described. Here, an example will be described in which an epitaxial film of SiC is formed on a SiC substrate as a binary compound semiconductor, but this embodiment can also be applied to binary compound semiconductors other than SiC. This embodiment can also be applied to a case in which an epitaxial film is further formed on an epitaxial film or an ion-implanted layer formed on a SiC substrate.

First, the epitaxial film manufacturing apparatus, which is the binary compound semiconductor manufacturing apparatus of this embodiment, will be described with reference to FIG.

The epitaxial film growth apparatus 10 shown in FIG. 1 is an apparatus for growing an epitaxial film 2 on the surface of a substrate 1 made of SiC. As shown in FIG. 1, the epitaxial film growth apparatus 10 of this embodiment is configured to include a furnace body 20, a gas inlet 30, various gas cylinders 40, a gas inlet 50, a gas outlet 60, a susceptor section 70, a heating section 80, and an apparatus control section 90.

The furnace body 20 corresponds to a reaction furnace, and is configured with a heat insulating material 22 and a heated portion 23 arranged in that order inside a cover 21 made of quartz or the like, and is cylindrical with a hollow portion that constitutes a growth chamber 24 in which a substrate 1 for growing an epitaxial film 2 is placed. The heated portion 23 is a portion that is induction heated by a heating portion 80, which will be described later, and is arranged so as to substantially surround the growth chamber 24 in this embodiment. The heated portion 23 is also made of, for example, carbon or the like.

The gas inlet 30 is an inlet for introducing various gases for growing the epitaxial film 2 into the growth chamber 24 of the furnace body 20, and is provided on one end side of the cylindrical furnace body 20. Various gas cylinders 40 are connected to the gas inlet 30 through gas inlet paths 50. As a result, Si raw material gas containing Si raw material, C raw material gas containing C raw material, dopant raw material gas containing dopant raw material, etc. are introduced into the growth chamber 24 from the gas inlet 30.

The various gas cylinders 40 include a Si source gas cylinder 41, a C source gas cylinder 42, and a dopant gas cylinder 43. Each of the various gas cylinders 40 is individually replaceable, and when the gas runs out, it is replaced with a new one.

The Si raw material gas cylinder 41 contains the Si raw material gas, and contains the Si raw material diluted gas obtained by diluting the Si raw material gas with a dilution gas to a predetermined gas concentration. As the Si raw material gas contained in the Si raw material diluted gas, for example, _SiH4 (silane) gas is used, but a chlorine-based Si raw material gas (chloride-based raw material) containing Cl having an etching effect, such as _{SiH2Cl2 , SiHCl3} , or _SiCl4 , can also be used. In addition, as the Si raw material diluted gas, for example, a gas in which _H2 is added to silane can also be used.

The C raw material gas cylinder 42 contains the C raw material gas and contains a C raw material diluted gas obtained by diluting the C raw material gas with a dilution gas to a predetermined gas concentration. As the C raw material gas contained in the C raw material diluted gas, for example, C ₃ H ₈ (propane) gas or the like is used.

The dopant gas cylinder 43 contains a dopant source gas, and contains a dopant source diluted gas obtained by diluting the dopant source gas with a dilution gas to a predetermined gas concentration. The dopant source diluted gas is a gas for controlling the conductivity type of the epitaxial film 2, and contains a dopant source gas corresponding to the conductivity type of the epitaxial film 2 to be formed. When epitaxially growing N-type SiC, for example, a dopant source diluted gas containing N ₂ (nitrogen) is used as the dopant source gas. When epitaxially growing P-type SiC, for example, a dopant source diluted gas containing TMA (trimethylaluminum) is used as the dopant source gas.

As the dilution gas in the various gas cylinders 40, a gas that does not contain Si or C is used, such as _H2 gas or an inert gas (rare gas) such as Ar or He. By using such a gas that does not contain Si or C, it is possible to suppress the diffusion of the source gas and to suppress the formation of unnecessary Si, C, or SiC products, so that they do not become a particle source.

The gas concentration of the source gas in each gas cylinder 40, that is, the volume ratio of the source gas to the total volume of the mixed gas of the dilution gas and the source gas, is adjusted to a predetermined target value. However, the actual gas concentration has a predetermined gas concentration tolerance with respect to the target gas concentration. In the case of the Si source gas cylinder 41, for example, the target gas concentration is set to 10%, and the allowable tolerance is ±5%. Therefore, the actual gas concentration in the Si source gas cylinder 41 varies in the range of 9.5 to 10.5%. In the case of the C source gas cylinder 42, for example, the target gas concentration is set to 30%, and the allowable tolerance is ±5%. Therefore, the actual gas concentration in the C source gas cylinder 42 varies in the range of 28.5 to 31.5%. In the case of the dopant gas cylinder 43, if _N2 is used as the dopant source gas, for example, the target gas concentration is set to 1.0%, and the allowable tolerance is ±5%. Therefore, the actual gas concentration in the dopant gas cylinder 43 varies within the range of 0.95 to 1.05%.

The gas inlet passage 50 constitutes a gas flow path connecting the various gas cylinders 40 and the furnace body 20. The gas inlet passage 50 has a first passage 51 connected to the Si raw material gas cylinder 41, a second passage 52 connected to the C raw material gas cylinder 42, and a third passage 53 connected to the dopant gas cylinder 43, and the first to third passages 51 to 53 are each equipped with a flow control valve 54 to 56. The flow control valves 54 to 56 can adjust their opening based on a control signal from the device control unit 90, and the flow control valves 54 to 56 are individually controlled to adjust the flow rate of gas supplied from the various gas cylinders 40 to the first to third passages 51 to 53.

The gas exhaust port 60 is located on the opposite side of the furnace body 20 to the gas inlet port 30, and exhausts unreacted gases and the like that have passed through the growth chamber 24. The gas exhaust port 60 is also connected to a suction section (not shown) or the like so that the atmospheric pressure in the growth chamber 24 can be appropriately adjusted, and the growth chamber 24 can be evacuated.

The susceptor section 70 is disk-shaped and has a mounting section 71 that constitutes a mounting surface on which the substrate 1 is placed, and a support shaft 72 that extends downward from the center of the mounting section 71, with the mounting section 71 being disposed between the gas inlet 30 and the gas outlet 60. The susceptor section 70 is made rotatable by connecting the support shaft 72 to a rotation mechanism (not shown).

Note that, although the figure shows multiple substrates 1 arranged on the mounting surface of the susceptor section 70, the number of substrates 1 arranged on the mounting surface is arbitrary. For example, in the case of a single substrate, the substrate 1 is arranged so that the center of the susceptor section 70 coincides with the center of the substrate 1, and in the case of multiple substrates, the substrates 1 are arranged in a circumferential line around the center of the susceptor section 70.

The heating section 80 is composed of a coil arranged to surround the furnace body 20. The heating section 80 inductively heats the heated section 25 by applying an alternating current. This maintains the inside of the growth chamber 24 at a predetermined temperature.

The device control unit 90 controls the opening degree of each of the flow rate adjustment valves 54 to 56 to control the gas flow rate of the diluted Si raw material gas from the Si raw material gas cylinder 41, the diluted C raw material gas from the C raw material gas cylinder 42, and the diluted dopant raw material gas from the dopant gas cylinder 43. For example, the device control unit 90 controls each gas flow rate by transmitting a control signal for controlling the opening degree to each of the flow rate adjustment valves 54 to 56.

More specifically, when at least one of the Si raw material gas cylinder 41 and the C raw material gas cylinder 42 is replaced, the device control unit 90 controls the flow rate of each gas so that the epitaxial film 2 can be grown under the same conditions as when the gas concentration is the target value, even if the gas concentration is different from the predetermined target value. In other words, the device control unit 90 stores a recipe for each gas flow rate when the gas concentration is the target value, and automatically corrects the gas flow rate based on this and the test value of the actual gas concentration so that the number of gas molecules, in other words the number of Si and C atoms, is the same as when the gas concentration is the target value, even after the replacement. Also, when the dopant gas cylinder 43 is replaced, the gas flow rate is automatically corrected so that the gas molecular weight, in other words the number of dopant atoms, is the same as when the gas concentration of the dopant raw material dilution gas is the target value. Then, a recipe after the replacement is created based on the result of the automatic correction, and during the growth process of the epitaxial film 2, the opening degree of each flow rate control valve 54 to 56 is controlled according to the recipe to control the gas flow rate. The automatic correction and how to create recipes after replacement will be explained in detail later.

The above is the configuration of the epitaxial film growth apparatus 10 in this embodiment. Next, the method for manufacturing a SiC semiconductor in this embodiment will be explained with reference to a conventional manufacturing method.

In the conventional manufacturing method, an epitaxial film is grown according to the manufacturing flow shown in FIG. 2. First, in step S100, various gas cylinders are replaced, and then in step S110, an epitaxial film is grown on a SiC substrate that serves as a reference sample, and various parameters are measured. Specifically, experiments are performed to measure the in-plane distribution of the film thickness, the dopant incorporation efficiency, and the concentration profile.

At this time, the flow rate is first set to the epitaxial film growth conditions before the various gas cylinders were replaced, and the flow rate is gradually changed until the parameters of the in-plane distribution of the epitaxial film thickness, the dopant incorporation efficiency, and the concentration profile reach the target values. Then, in step S120, a calibration curve is obtained in which each parameter reaches the target value.

After that, in step S130, a recipe is created based on the calibration curve obtained earlier, so that each parameter reaches its target value. Then, in step S140, an epitaxial film is grown according to the created recipe, thereby obtaining an epitaxial film in which each parameter reaches its target value.

In this way, to ensure that each parameter of the epitaxial film reaches the target value, it is necessary to start with the flow rate that was in effect for the epitaxial film growth conditions before the various gas cylinders were replaced, and then conduct experiments by gradually changing the flow rate.

As mentioned above, for example, the target gas concentration of the Si raw material dilution gas is 10%, with an allowable tolerance of ±5%, so even if the target concentration of the Si raw material dilution gas is 10%, the gas concentration in the Si raw material gas cylinder is 9.5 to 10.5%. Because of this variation in gas concentration, there is variation in each parameter of the grown epitaxial film, and various experiments are conducted by changing the flow rate of each gas.

For example, the susceptor radius, which is the distance from the center of the susceptor part 70, and the p-type impurity concentration of the epitaxial film at that location were investigated for the case where the gas concentration of the C raw material dilution gas was the target value (ref.) and the case where there was a variation of +5% and -5% from the target value. In addition, the relationship between the depth in the thickness direction of the epitaxial film and the p-type impurity concentration was investigated. Figures 3 and 4 show these results.

As shown in Figure 3, the p-type impurity concentration relative to the susceptor radius is significantly different from the target value in both cases of +5% and -5%. Also, as shown in Figure 4, the p-type impurity concentration for each depth of the epitaxial film is significantly different from the target value in both cases of +5% and -5%. For this reason, every time the raw gas cylinder is replaced, it is necessary to prepare a SiC substrate as a reference sample, form an epitaxial film on it, and then repeatedly perform experiments to determine the in-plane distribution of the epitaxial film thickness, dopant incorporation efficiency, and concentration profile measurement. Therefore, experiments must be performed until each parameter reaches the target value to obtain a calibration curve, which not only requires complicated experiments but also makes it difficult to fix the epitaxial film formation recipe.

Therefore, in this embodiment, in order to eliminate the need for complicated experiments and to easily fix the epitaxial film formation recipe, the epitaxial film 2 is grown on the substrate 1 while controlling the concentrations of the source gas and dopant gas according to the manufacturing flow shown in Figure 5.

First, in step S200, the various gas cylinders 41 to 43 are prepared and the various gas cylinders 41 to 43 are replaced. At this time, only those of the various gas cylinders 41 to 43 that are empty or nearly empty of gas may be replaced.

Next, in step S210, the gas concentrations in the Si source gas cylinder 41, the C source gas cylinder 42, and the dopant gas cylinder 43 are inspected to obtain inspection values. Then, the inspected gas concentrations are input to the device control unit 90.

The gas concentration of the Si raw material diluted gas in the Si raw material gas cylinder 41 is, for example, set to a target value of 10%, and may vary in the range of 9.5 to 10.5%, but the gas concentration may be specified and distributed. In such cases, inspection is performed by confirming the specified gas concentration. Similarly, the gas concentration of the C raw material diluted gas in the C raw material gas cylinder 42 is, for example, set to a target value of 30%, and may vary in the range of 28.5 to 31.5%, but the gas concentration may be specified and distributed. In such cases, inspection is also performed by confirming the specified gas concentration. Furthermore, the gas concentration of the dopant gas in the dopant gas cylinder 43 is, for example, set to a target value of 1.0%, and may vary in the range of 0.95 to 1.05%, but the gas concentration may be specified and distributed. In such cases, inspection is also performed by confirming the specified gas concentration.

Next, in step S220, the device control unit 90 calculates the ratio of the test value to the target value. For example, in the case of the Si raw material gas cylinder 41, if the target value of the gas concentration of the Si raw material diluted gas is 10% and the actual test value of the gas concentration is 10.5%, the ratio of the test value to the target value is 1.05. Similarly, in the case of the C raw material gas cylinder 42, if the target value of the gas concentration of the C raw material diluted gas is 30% and the actual test value of the gas concentration is 29.0%, the ratio of the test value to the target value is 0.967.

Then, in step S230, the gas flow rate is automatically corrected based on the calculated ratio so that the number of gas molecules, in other words the number of Si and C atoms, is the same as the target value even after replacement, and a recipe for this is created and stored in the device control unit 90.

That is, a recipe is created in which corrections are made based on the test values calculated from the actual gas concentrations in response to the recipe when the gas concentration is the target value. As an example, a recipe as shown in FIG. 6 is created. FIG. 6 shows a case where the Si raw material gas cylinder 41 and the C raw material gas cylinder 42 are replaced, and when at least one of the Si raw material gas cylinder 41 and the C raw material gas cylinder 42 is replaced, the gas flow rate of the replaced side is automatically corrected. Also, FIG. 6 shows a case where the dopant gas cylinder 43 is not replaced, but when it is replaced, automatic correction can be made in the same way as the Si raw material dilution gas and the C raw material dilution gas described later. Note that this figure shows the flow rates when each gas is introduced into the furnace body 20 under standard conditions, for example, 27°C and 1 atmosphere, but when applied to the growth of the epitaxial film 2, the flow rates are converted to the temperature and atmospheric pressure during the growth of the epitaxial film 2.

Figure 6 shows two recipes: recipe 1, in which the epitaxial film 2 is grown at a relatively slow growth rate (hereafter referred to as slow growth), and recipe 2, in which the epitaxial film 2 is grown at a faster growth rate than recipe 1 (hereafter referred to as fast growth).

Recipe 1 includes step 1, in which epitaxial film 2 is grown at a slower growth rate than the slow growth rate during the initial growth, and step 2, in which epitaxial film 2 is grown at a faster growth rate than the initial growth rate.

For example, when the gas concentrations of the various gases are as targeted, the gas flow rate and gas introduction time of each step are set so that the number of Si and C atoms is the desired value based on the target value. When the gas concentration of the Si raw material dilution gas is 10%, the gas concentration of the C raw material dilution gas is 30%, and the gas concentration of the dopant gas is 1.0%, the flow rates and introduction times of the various gases in each of steps 1 and 2 are set to the values shown in the figure. At this time, the flow rates of the Si raw material dilution gas and the C raw material dilution gas are set so that the number of Si and C atoms introduced into the furnace body 20 is a predetermined number. In the case of step 1, the Si raw material dilution gas is 80.0 sccm and the C raw material dilution gas is 60.0 sccm. In addition, in the case of step 2, the Si raw material dilution gas is 240.0 sccm and the C raw material dilution gas is 180.0 sccm.

The number of Si and C atoms introduced into the furnace body 20 is a predetermined number determined by the gas concentration of the Si raw material dilution gas and the gas concentration of the C raw material dilution gas and the flow rate of each gas. That is, the number of Si atoms in _SiH4 is 1, and the number of C atoms in _C3H8 is 3. Since each gas concentration represents the content of _SiH4 or _C3H8 per unit volume, the number of Si and _C atoms introduced into the furnace body 20 per unit time is determined by each gas concentration _and gas flow rate.

For example, in step 1, the number of Si atoms introduced into the furnace body 20 per unit time is 1 [number of Si atoms] x 0.1 [gas concentration] x 80.0 [sccm: flow rate] x K, and the number of C atoms is 3 [number of C atoms] x 0.3 [gas concentration] x 60.0 [sccm: flow rate] x K. In step 2, the number of Si atoms per unit time is 1 [number of Si elements] x 0.1 [gas concentration] x 240.0 [sccm: flow rate] x K, and the number of C atoms is 3 [number of C elements] x 0.3 [gas concentration] x 180.0 [sccm: flow rate] x K. K is a coefficient equivalent to the number of molecules contained per unit volume.

In contrast, when the Si raw material gas cylinder 41 and the C raw material gas cylinder 42 are replaced, the gas concentration of the Si raw material dilution gas is 10.5% and the gas concentration of the C raw material dilution gas is 29.0% as shown in FIG. 6. In this case, too, the flow rates of the Si raw material dilution gas and the C raw material dilution gas are set so that the number of atoms is equal to the number of atoms when the gas concentration is the target value.

That is, in step 1, the number of Si atoms per unit time is 1 [number of Si elements] x 0.105 [gas concentration] x 76.2 [sccm: flow rate] x K, and the number of C atoms is 3 [number of C elements] x 0.29 [gas concentration] x 62.1 [sccm: flow rate] x K. The number of Si atoms is approximately equal to 1 [number of Si atoms] x 0.1 [gas concentration] x 80.0 [sccm: flow rate] x K before the replacement and 1 [number of Si elements] x 0.105 [gas concentration] x 76.2 [sccm: flow rate] x K after the replacement, and is maintained at the specified number. In addition, the number of C atoms is approximately equal to 3 [number of C atoms] x 0.3 [gas concentration] x 60.0 [sccm: flow rate] x K before the replacement, and 3 [number of C elements] x 0.29 [gas concentration] x 62.1 [sccm: flow rate] x K after the replacement, and is maintained at the specified number.

Also, in step 2, the number of Si atoms per unit time is 1 [number of Si elements] x 0.105 [gas concentration] x 228.6 [sccm: flow rate] x K, and the number of C atoms is 3 [number of C elements] x 0.29 [gas concentration] x 186.2 [sccm: flow rate] x K. The number of Si atoms is approximately equal to 1 [number of Si atoms] x 0.1 [gas concentration] x 240.0 [sccm: flow rate] x K before the replacement and 1 [number of Si elements] x 0.105 [gas concentration] x 228.6 [sccm: flow rate] x K after the replacement, and is maintained at the specified number. In addition, the number of C atoms is approximately equal to 3 [number of C atoms] x 0.3 [gas concentration] x 180 [sccm: flow rate] x K before the replacement, and 3 [number of C elements] x 0.29 [gas concentration] x 186.2 [sccm: flow rate] x K after the replacement, and is maintained at the specified number.

In this way, gas flow control is performed so that the number of Si and C atoms contained in each gas is maintained at a predetermined number before and after the gas cylinder is replaced. Furthermore, by performing such gas flow control, it is possible to ensure that the element ratios of Si and C after the gas cylinder is replaced also reach the target values.

That is, _one Si element is contained in _SiH4 , and three C elements are contained in _C3H8 . Therefore, in step 1, the element ratio of Si and C per unit time is 1 [number of Si elements] x 0.1 [gas concentration] x 80.0 [sccm: flow rate]: 3 [number of C elements] x 0.3 [gas concentration] x 60.0 [sccm: flow rate] = 8:54 = 4:27. Also, in step 2, the element ratio of Si and C per unit time is 1 [number of Si elements] x 0.1 [gas concentration] x 240.0 [sccm: flow rate]: 3 [number of C elements] x 0.3 [gas concentration] x 180.0 [sccm: flow rate] = 24:162 = 4:27.

On the other hand, even if the Si raw gas cylinder 41 and the C raw gas cylinder 42 are replaced, the flow rates of the Si raw gas dilution gas and the C raw gas dilution gas are set so that the element ratio is equal to the element ratio when the gas concentration is the target value. That is, in step 1, the element ratio of Si and C per unit time is set to 1 [number of Si elements] x 0.105 [gas concentration] x 76.2 [sccm: flow rate]: 3 [number of C elements] x 0.29 [gas concentration] x 62.1 [sccm: flow rate] ≒ 8:54 = 1:9. Also, in step 2, the element ratio of Si and C per unit time is set to 1 [number of Si elements] x 0.105 [gas concentration] x 228.6 [sccm: flow rate]: 3 [number of C elements] x 0.29 [gas concentration] x 186.2 [sccm: flow rate] ≒ 24:162 = 4:27.

In this way, the flow rates of the Si raw material dilution gas and the C raw material dilution gas are set and a recipe is created so that the number of Si and C atoms is maintained at a predetermined number even after replacing the Si raw material gas cylinder 41 or the C raw material gas cylinder 42.

Here, the method of creating recipe 1 has been described, but the same is true for recipe 2. Recipe 1 is applied, for example, when slow growth is desired, and recipe 2 is applied, for example, when fast growth is desired. An example of a case where slow growth is desired is when the epitaxial film 2 is grown on an ion-implanted layer in which the underlying SiC is ion-implanted with impurities. In such a case, if high-speed growth is performed, damage caused during ion implantation will be more significantly inherited, so slow growth that suppresses the inheritance of damage is desirable. An example of a case where high-speed growth is desired is when a drift layer is formed on a SiC substrate 1. In such a case, the epitaxial film 2 is grown on an underlying substrate with a good surface condition that is not damaged by ion implantation on the SiC substrate 1, so the possibility of crystal defects is relatively low. For this reason, high-speed growth that can increase the growth rate is desirable. In addition, recipes 1 and 2 have been given as examples, but these are merely given as examples of cases where low-speed growth and high-speed growth are performed, and other recipes can be created.

In addition, although _N2, which is an n-type dopant, is given as an example of the dopant gas, other dopant gases may be used. For example, _NH4 containing N, which is an n-type dopant, or TMA (trimethylaluminum) containing Al, which is a p-type dopant, may be used. In the case of _NH4 or TMA, these are diluted with a dilution gas such as _H2 and stored in the dopant gas cylinder 43. In this case, when the dopant gas cylinder 43 is replaced, if a recipe is created by performing automatic correction in the same manner as the above-mentioned Si raw material dilution gas and C raw material dilution gas, the dopant intake efficiency and concentration profile can be stably set to the target value.

Once the recipe is created in this manner, in step S240, the epitaxial film 2 is grown according to the recipe created in step S230. That is, an epitaxial film growth apparatus 10 having a furnace body 20 equivalent to a reactor as shown in FIG. 1 is prepared, and a substrate 1 made of SiC is placed in it. Then, the epitaxial film 2 is grown on the surface of the substrate 1 according to the created recipe.

As a result, the number of Si and C atoms, in other words the element ratio, can be kept constant and stabilized before and after replacement of the Si raw material gas cylinder 41 or the C raw material gas cylinder 42, making it possible to stably achieve the target value for the in-plane distribution of the film thickness of the epitaxial film 2. Furthermore, the dopant incorporation efficiency and concentration profile in the epitaxial film 2 can also be stably achieved at the target values.

The manufacturing flow shown in Figure 5 is performed every time the cylinder is replaced, and a recipe is created each time the deposition conditions for epitaxial film 2 are such that the number of Si and C atoms, in other words the element ratio, is approximately the same as the target value.

As explained above, when replacing the cylinders, the gas flow rates of the Si raw material dilution gas and the C raw material dilution gas are automatically corrected to create a recipe so that the target atomic number is maintained even for the gas concentrations of the Si raw material dilution gas and the C raw material dilution gas after the cylinder replacement. Specifically, the gas concentration of the Si raw material dilution gas in the Si raw material gas cylinder 41 after the cylinder replacement and the gas concentration of the C raw material dilution gas in the C raw material gas cylinder 42 are inspected, and the ratio of the inspection value to the target gas concentration is calculated. Then, based on the calculated ratio, the gas flow rates of the Si raw material dilution gas and the C raw material dilution gas are automatically corrected so that the number of Si and C atoms is the same before and after the replacement, and a recipe is created based on this.

By growing the epitaxial film 2 according to the recipe obtained in this manner, the number of Si and C atoms, in other words the element ratio, can be made constant and stabilized before and after replacement of the Si source gas cylinder 41 or the C source gas cylinder 42. This makes it possible to stably achieve the target value for the in-plane distribution of the film thickness of the epitaxial film 2. Furthermore, the dopant incorporation efficiency and concentration profile in the epitaxial film 2 can also be stably achieved at the target values.

In the example of FIG. 6, the dopant gas cylinder 43 is not replaced, but when the dopant gas cylinder 43 is replaced, a recipe can be created by automatically correcting the gas flow rate of the dopant gas so that the number of dopant atoms remains constant before and after replacement. This allows the dopant uptake efficiency and concentration profile in the epitaxial film 2 to be stable and reach the target values before and after replacement.

Other Embodiments
Although the present disclosure has been described based on the above-described embodiment, it is not limited to the embodiment, and includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

For example, in each of the above embodiments, as an example of a method for inspecting the gas concentration when a cylinder is replaced, a case where the gas concentration is specified and distributed is given. However, this is merely one example. For example, the Si raw material diluted gas or the C raw material diluted gas may be discharged from the replaced Si raw material gas cylinder 41 or the C raw material gas cylinder 42, and the gas concentration may be measured with a gas concentration measuring device such as an in-situ monitor to obtain the inspection value. In this way, by measuring the gas concentration during discharge to obtain the inspection value, it is possible to deal with cases where the gas concentration changes during flow into the furnace body 20.

Although the present invention has been described using SiC as an example of a binary compound semiconductor, the present invention can also be applied to other binary compound semiconductors, such as GaN, AsGa, and InP, when replacing the raw material gas cylinder or the dopant gas cylinder. That is, a first raw material gas cylinder containing a first raw material dilution gas obtained by diluting a first raw material gas with a dilution gas to a first gas concentration, and a second raw material gas cylinder containing a second raw material dilution gas obtained by diluting a second raw material gas with a dilution gas to a second gas concentration, are prepared. The present invention can be applied to setting the gas flow rate when replacing the gas cylinder when manufacturing a binary compound semiconductor using these first raw material gas cylinder and second raw material gas cylinder. In addition, for the dopant raw material, a dopant gas cylinder containing a dopant raw material dilution gas diluted with a dilution gas to a third gas concentration is prepared, and the present invention can be applied to setting the gas flow rate when replacing this gas cylinder. However, in the case of SiC, the cylinder needs to be replaced frequently, and the absolute value of the impurity concentration and the in-plane distribution are highly dependent on the C/Si ratio, so the effect of applying this invention is greater than in the case of other binary compound semiconductors.

In addition, although _H2 is used as an example of the dilution gas, a dilution gas other than _H2 , for example, a rare gas such as Ar or an etching gas such as HCl, may be used. In this case, the gas species of the dilution gas used in the various gas cylinders 41 to 43 may be the same or different.

In the above embodiment, the method used to make the number of Si and C atoms equal before and after gas cylinder replacement involves calculating the ratio of the test value to the target gas concentration value and automatically correcting the gas flow rate after the gas cylinder is replaced. This is not limiting, but it is also possible to obtain the number of atoms at the target value for the number of Si and C atoms supplied to the furnace body 20 per unit time, and set the gas flow rate so that the number of Si and C atoms in the test value is equal to the number of atoms at the target value.

In the above embodiment, the present invention has been described as a method and an apparatus for manufacturing a binary compound semiconductor. However, the present invention can also be understood as a program for manufacturing a binary compound semiconductor, including automatic correction of gas flow rates, which is applied to the manufacture of a binary compound semiconductor. In this case, (1) a step of storing the gas flow rates of the first raw material at the gas concentration of the first raw material dilution gas at the target value and the second raw material at the gas concentration of the second raw material dilution gas is performed. Then, when the cylinder is replaced, (2) a step of inputting that the cylinder has been replaced, and (3) a step of inputting the inspection value of the gas concentration are performed. After that, (4) a step of creating a recipe in which the gas flow rates of the first raw material dilution gas and the second raw material dilution gas are automatically corrected so that the atomic numbers of the first raw material and the second raw material at the inspection value are the atomic numbers at the target value are performed. Then, (5) a step of forming the epitaxial film 2 according to the created recipe is performed. A program for manufacturing a binary compound semiconductor having each of these steps can be created.

Reference Signs List 1 Substrate 2 Epitaxial film 10 Epitaxial film growth apparatus 20 Furnace body 41 Si source gas cylinder 42 C source gas cylinder 43 Dopant gas cylinder 70 Susceptor section

Claims (8)

A method for manufacturing a binary compound semiconductor, comprising the steps of: supplying a first source gas containing a first source and a second source gas containing a second source to grow an epitaxial film (2) on a substrate (1) of the binary compound semiconductor, the method comprising the steps of:
preparing a first raw material gas cylinder (41) for accommodating a first raw material dilution gas obtained by diluting the first raw material gas with a dilution gas to a first gas concentration, and a second raw material gas cylinder (42) for accommodating a second raw material dilution gas obtained by diluting the second raw material gas with a dilution gas that is the same as or different from the dilution gas,
Providing a reactor (20) constituting a growth chamber for containing and heating the substrate;
When replacing at least one of the first source gas cylinder and the second source gas cylinder, an inspection value of the gas concentration of the gas cylinder to be replaced is obtained, out of the first gas concentration and the second gas concentration;
inputting the test value into a device control unit (90);
the apparatus control unit automatically corrects a gas flow rate of the first raw material dilution gas introduced from the first raw material gas cylinder into the reactor and a gas flow rate of the second raw material dilution gas introduced from the second raw material gas cylinder into the reactor based on the test value so that the number of atoms of the first raw material when the first gas concentration is a target value and the number of atoms of the second raw material when the second gas concentration is a target value are obtained, and creates a recipe for growing the epitaxial film;
growing the epitaxial film by introducing the first dilution source gas and the second dilution source gas into the reactor containing the substrate at the automatically corrected gas flow rates according to the recipe;
A method for producing a binary compound semiconductor, comprising: The method for manufacturing a binary compound semiconductor according to claim 1, wherein the inspection values are obtained by discharging the first diluted raw gas from the first raw gas cylinder and discharging the second diluted raw gas from the second raw gas cylinder using a gas concentration measuring device to obtain the inspection values of the first gas concentration and the second gas concentration. A silicon carbide substrate (1) is used as the substrate,
3 . The method for producing a binary compound semiconductor according to claim 1 , wherein the first source gas containing Si is used as the first source material, and the second source gas containing C is used as the second source material. As the first dilution gas, the first dilution gas is prepared by diluting SiH ₄ as the first dilution gas with H ₂ as a dilution gas of the first dilution gas,
4. The method for producing a binary compound semiconductor according to claim 3, _wherein the second dilution gas is _C3H8 which serves as the second dilution gas, diluted with _H2 which serves as a dilution gas for the second dilution gas. preparing a dopant gas cylinder (43) for storing a diluted dopant source gas obtained by diluting a dopant source gas containing a dopant source with a third gas concentration;
obtaining a test value of the third gas concentration when replacing the dopant gas cylinder;
inputting the test value of the third gas concentration into the device controller;
and automatically correcting, by the apparatus control unit, a gas flow rate of the diluted dopant source gas introduced from the dopant gas cylinder into the reactor based on the inspection value of the third gas concentration so that the number of atoms of the dopant source is equal to a target value for the third gas concentration, and creating the recipe for growing the epitaxial film;
5. The method for manufacturing a binary compound semiconductor according to claim 1, wherein, in growing the epitaxial film, the dopant source gas is introduced in addition to the first dilution source gas and the second dilution source gas according to the recipe to grow the epitaxial film. 6. The method for producing a binary compound semiconductor according to claim 5, wherein the dopant source dilution gas is any one of _N2 , _NH3, and trimethylaluminum, which are the dopant source gases, diluted with _H2 , which is a dilution gas for the dopant source dilution gas. The method for manufacturing a binary compound semiconductor according to any one of claims 1 to 6, wherein the recipe is created by calculating a ratio of the gas concentration of the inspection value to a case where the first gas concentration and the second gas concentration are target values, and the automatic correction is performed based on the ratio. An apparatus for manufacturing a binary compound semiconductor, which supplies a first source gas containing a first source and a second source gas containing a second source to grow an epitaxial film (2) on a substrate (1) of the binary compound semiconductor, comprising:
a first raw material gas cylinder (41) for accommodating a first raw material diluted gas obtained by diluting the first raw material gas with a dilution gas to a first gas concentration;
a second raw material gas cylinder (42) for accommodating a second raw material diluted gas obtained by diluting the second raw material gas to a second gas concentration with a dilution gas that is the same as or different from the dilution gas;
a reactor (20) constituting a growth chamber for accommodating and heating the substrate;
an apparatus control unit (90) which stores gas flow rates of the first raw material when the first gas concentration is a target value and the second raw material when the second gas concentration is a target value, and when replacing at least one of the first raw material gas cylinder and the second raw material gas cylinder, inputs an inspection value of the gas concentration of the gas cylinder to be replaced, out of the first gas concentration and the second gas concentration, and automatically corrects the gas flow rate of the first raw material dilution gas introduced from the first raw material gas cylinder to the reactor and the gas flow rate of the second raw material dilution gas introduced from the second raw material gas cylinder to the reactor based on the inspection value so as to obtain the number of atoms of the first raw material when the first gas concentration is the target value and the number of atoms of the second raw material when the second gas concentration is the target value, and creates a recipe for growing the epitaxial film;
The manufacturing apparatus for binary compound semiconductors includes:

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