JP4963353B2 - Method for producing silicon carbide mixed crystal - Google Patents

Description

  The present invention relates to a method for producing a silicon carbide mixed crystal, and more particularly to a method for producing a silicon carbide mixed crystal suitable for producing a SiMC mixed crystal (M = Ge, Sn).

  A method is known in which vapor deposition of silicon carbide is performed in an atmosphere containing Si source gas and C source gas on the substrate surface, and the partial pressure of the C source gas is kept constant during vapor deposition using such a method. The partial pressure of the Si source gas is alternately changed between the high side and the low side, or the partial pressure of the C source gas is changed between the high side and the low side by keeping the partial pressure of the Si source gas constant. A technique is known in which an SiC crystal can be formed without causing crystal defects by alternately changing.

However, the above-described technique is limited to silicon carbide. Only the techniques known so far include silicon carbide-based mixed crystal semiconductors such as Si _1-x Ge _x C and Si _1-x Sn _x C. Composition control cannot be performed.

In relation to the above, there is a method in which a plurality of raw materials or raw material gases are alternately introduced into a crystal apparatus at predetermined time intervals, and epitaxial crystal growth of a monomolecular layer is alternately performed (see, for example, Patent Document 1). This method describes that GaAs is obtained by alternately repeating the introduction / stop of triethylgallium (TEG) and arsine (AsH ₃ ).
Japanese Patent No. 2987379

However, it is not easy to substitute other metal elements such as Ge and Sn by substitution for Si in the SiC crystal to form a mixed crystal. In the above-described method, a part of Si of silicon carbide (SiC) is not obtained. It is not possible to form a Si _1-x M _x C mixed crystal by substituting with metal M (Ge or Sn). That is, when a mixed crystal is prepared by adding Ge or Sn to a SiC crystal, the melting point of Ge or Sn is lower than the preparation temperature of the mixed crystal and the vapor pressure is high. It is difficult to make the ratio 0.1 or more, and it is difficult to easily control the composition.

From the viewpoint of realizing various semiconductor devices, since the band gap, refractive index, lattice constant, and the like can be controlled by changing the composition, silicon carbide based mixed crystal semiconductors (Si _1-x Ge _x C, Si _{1 -x} Sn _x C, etc.) is expected, but the manufacturing method has not yet been established in the conventional technology.

The present invention has been made in view of the above, and easily incorporates Ge or Sn into a SiC crystal to easily control the composition of the Si _1-x M _x C mixed crystal, has a high quality and desired composition with few crystal defects. is intended to provide a Si _1-x M _x C mixed crystal can be obtained a method of manufacturing a silicon carbide based mixed crystal consisting of, and aims to achieve the objective.

  In the present invention, the partial pressure of at least one source gas of the Si source gas and the C source gas as the main components and the Ge source gas or the Sn source gas as the additive component may be periodically changed over a predetermined time period. The inventors have obtained knowledge that it is useful for incorporating Ge or Sn by substituting Si into SiC crystals, and have been achieved based on such knowledge.

In order to achieve the above object, a method for producing a silicon carbide based mixed crystal according to the present invention supplies Si source gas, Si source gas, and M (Ge or Sn) source gas to the substrate surface to produce Si _1-x M. is intended to form, for example, a thin film of _{x C} mixed crystal, specifically, with at least while M source gas is supplied to supply the C source gas, the relative partial pressure p _M of the M source gas Si The source gas and the M source gas are supplied by alternately switching (preferably repeatedly) a condition in which the ratio of the source gas partial pressure p _Si (p _Si / p _M ) is large and small. is there.
When increasing the partial pressure of at least the M source gas, it is preferable to increase the partial pressure of the C source gas. The C source gas is preferably supplied at a constant partial pressure.

In the method for producing a silicon carbide mixed crystal according to the present invention, when supplying the Ge source gas or the Sn source gas, the C source gas is supplied at least while the M (Ge or Sn) source gas is supplied. A condition where the ratio (p _Si / p _M ) of the partial pressure p _Si of the Si source gas to the partial pressure p _M of the M source gas is large and small is alternately set in relation to the supply amount of the Si source gas. By switching, the ratio of p _Si / p _M becomes small during the manufacturing process, that is, by periodically forming a time zone in which an atmosphere with a large amount of M with respect to the amount of Si is formed, Ge or Sn can be incorporated into the SiC crystal. Since it can be promoted, the SiGeC mixed crystal or the SiSnC mixed crystal can be easily and controlled to have a desired composition. In addition, the growth of SiC crystals with little or no Ge or Sn content is not impaired, as well as the growth of mixed crystals.

  In the present invention, it is effective to use an organic metal compound gas as the M source gas. Of the Ge source gas or Sn source gas, in particular, an organometallic compound gas is selectively used, so that Ge—C bonds or Sn—C bonds are already present at the time of the raw material gas. Alternatively, Sn can be easily taken in, and a SiGeC mixed crystal or a SiSnC mixed crystal can be easily produced.

Also, when supplying M source gas, the partial pressure of the C source gas when high low comb the partial pressure of the C source gas, a partial pressure p _M of M source gas when to lower the partial pressure p _M of M source gas It is effective to be controlled to increase the value. In particular, when the partial pressure of the M source gas is high, by increasing the partial pressure of the C source gas, the formation of Ge—C bonds or Sn—C bonds can be further promoted, and the incorporation of Ge or Sn into the SiC crystal can be promoted. It can be done more easily.

According to the present invention, incorporating easily Ge or Sn in the SiC crystal Si _1-x M _x C mixed crystal composition control is easily performed, the crystal defects consisting of desired composition at least good quality Si _1-x M _A method for producing a silicon carbide based mixed crystal capable of obtaining an _x C mixed crystal can be provided.

  Hereinafter, an embodiment of a method for producing a silicon carbide mixed crystal of the present invention will be described in detail with reference to the drawings.

(First embodiment)
1st Embodiment of the manufacturing method of the silicon carbide type mixed crystal of this invention is described with reference to FIGS. In the method for producing a silicon carbide mixed crystal of the present embodiment, the C source gas, the Si source gas, and the Ge source gas have a constant partial pressure p _C of the _C source gas and a partial pressure p _{Si of the} Si source gas. And a condition (condition 1) in which the ratio p _Si / p _{Ge of the} partial pressure p _Ge of the Ge source gas is high and a condition (condition 2) in which the ratio is small are alternately supplied repeatedly.

In the present embodiment, the CVD apparatus shown in FIG. 1 is used to supply C ₂ H ₂ as the C source gas, SiH ₂ Cl ₂ as the Si source gas, and Ge source gas and Ge (C ₂ H ₅ ) _4. A description will be made mainly on the case of producing a Si _1-x Ge _x C mixed crystal (silicon carbide mixed crystal).

As shown in FIG. 1, the CVD apparatus is supplied with hydrogen gas from a hydrogen cylinder (not shown) and removes impurities in the gas, and a mass flow controller (MFC) 12 connected to the hydrogen purifier 11 and Hydrogen gas supply system comprising a supply pipe 30 provided with a pressure regulating valve V1, a supply pipe comprising a hydrogen diluted SiH ₂ Cl ₂ gas cylinder 15, a pressure regulating valve V2, a mass flow controller (MFC) 13 and a gas flow switching valve V3. 31, a Si source gas supply system composed of 31, a C ₂ H ₂ gas cylinder 16 diluted with hydrogen, a pressure adjustment valve V 4, a mass flow controller (MFC) 14, and a supply pipe 32 including a gas flow switching valve V 5. A source gas supply system, and a stainless bubbler container 18 filled with an M source gas [Ge (C ₂ H ₅ ) ₄ here], The supply pipe 30 and the bubbler container 18 communicate with each other, a supply pipe 33 having a mass flow controller (MFC) 17 for controlling the carrier gas to the bubbler container 18 is connected to the bubbler container 18 at one end, and the internal pressure of the bubbler container 18 is reduced. An M source gas supply system including a pressure adjusting valve V6 to be adjusted and a pipe 34 having a gas flow switching valve V7 is provided. The bubbler container 18 is covered with a thermostatic bath 19 so that the container temperature can be controlled.

The supply pipes 30, 31 and 32 and the pipe 34 are further communicated with each other at one end of the quartz reaction tube 20 for producing the Si _1-x Ge _x C mixed crystal via the pipe. Connected to the end is a valve V8 for adjusting the internal pressure of the quartz reaction tube 20 and a discharge tube 24 to which an exhaust pump 22 is attached.

  The quartz reaction tube 20 is an internal hollow tubular body composed of a quartz wall, and a graphite substrate holder (susceptor) (not shown) for holding the substrate is provided inside the tube. A high-frequency heating device 21 is provided outside the quartz reaction tube 20 so that the inside can be induction-heated through an outer wall of the tube. Heating can be suitably performed within a range of 1100 to 1800 ° C.

  The gas flow switching valves V3, V5, and V7 are connected to a branch end of a discharge pipe 25 having a discharge pump 23 attached to one end, and the gas flow is switched by automatic control by a PC (personal computer) (not shown). By automatically switching the valves, each gas supply system is switched to communicate with the discharge pipe 25 and can be discharged from the discharge pipe 25 to the outside.

When the CVD apparatus is started, as shown in FIG. 2, the condition 1 (the difference between the partial pressure p _Si and the partial pressure p _Ge is large, from the Si source gas supply system and the M source gas supply system including the bubbler container 18. Each gas is supplied under the condition that the ratio p _Si / p _Ge is large. Specifically, the supply of C ₂ H ₂ gas as a C source gas at a partial pressure p _Si and a constant partial pressure higher than the partial pressure p _Ge is started, and the partial pressure p _Si with respect to the partial pressure p _Ge is increased. Then, SiH ₂ Cl ₂ and Ge (C ₂ H ₅ ) ₄ are supplied simultaneously.

After the time of condition 1, the supply of C ₂ H ₂ gas is continued at a constant partial pressure as described above, and condition 2 where the difference between partial pressure p _Si and partial pressure p _Ge is small (ratio p _Si / p _Ge is Each gas is supplied by switching to a smaller condition. Specifically, when the partial pressure is in the range of p _Si > p _Ge , the partial pressure p _Si is lowered and the partial pressure p _Ge is increased, and the partial pressure difference between the partial pressure p _Ge and the partial pressure p _Si is reduced to reduce SiH. ₂ Cl ₂ and Ge (C ₂ H ₅ ) ₄ are supplied. By reducing the partial pressure p _Si , the Ge uptake efficiency can be improved.

  In this case, when the repetition interval of conditions 1 and 2 for performing alternate supply, that is, when the duration of each condition is increased, a layer having a small amount of Ge uptake and a layer having a large amount of Ge are alternately formed. By sufficiently shortening (duration time), it is possible to form a single layer having a uniform uptake by causing mutual diffusion.

  Then, after the time of condition 2 has elapsed, condition 1 and condition 2 are alternately repeated in the same manner as described above. The period in which the condition 1 and the condition 2 are alternately repeated can be appropriately selected according to the purpose and the properties of the film to be formed. In the above, the duration of condition 1 is preferably 0.1 to 60 seconds, and the duration of condition 2 is preferably 0.1 to 60 seconds. The duration of condition 1 and the duration of condition 2 may be the same time, or one of them may be longer than the other.

As the C source gas, gases such as CH ₄ , C ₃ H ₈ , C ₂ H ₄ , and CCl ₄ are suitable in addition to the C ₂ H ₂ gas.

As the Si source gas, gases such as SiH ₄ , Si ₂ H ₆ , SiH ₃ CH ₃ , and SiH (CH ₃ ) ₃ are suitable in addition to the SiH ₂ Cl ₂ gas.

As the Ge source gas, in addition to Ge (C ₂ H ₅ ) ₄ , gases such as GeH ₄ and GeH (CH ₃ ) ₃ are suitable, and among them, organometallic compounds (particularly Ge (C ₂ H ₅ ) ₄ , A gas such as GeH (CH ₃ ) ₃ is more preferable.

In the above, the partial pressure p _Ge in condition 1, each maintaining a certain degree of partial pressure p _Si under the condition 2, Ge in the SiC crystal, but to perform the control to supply as Si is contained none, It is not always necessary to maintain these partial pressures. In condition 1, the partial pressure p _Ge is substantially 0 (zero), and in condition 2, the partial pressure p _Si is substantially 0 (zero). You may do it. That is, by substantially alternately switching and supplying the Si source gas and the Ge source gas, the incorporation of Ge into the SiC crystal is further facilitated, and the total supply of the Si source gas and the Ge source gas is achieved. A Si _1-x Ge _x C mixed crystal having a composition ratio close to that can be obtained.

Further, as shown in FIG. 2, but to enhance the partial pressure p _Ge of the condition 2 Ge source gas, to increase the partial pressure p _Ge in condition 2, by increasing also the partial pressure p _C of C source gases, Formation of a Ge—C bond can be promoted, and incorporation of Ge into a SiC crystal can be performed more easily. When the partial pressure p _Ge is increased, it is effective that the degree (ratio) of increasing the partial pressure p _C of the C source gas is p _C (condition 2) / p _C (condition 1) = 2-4.

  In the present embodiment, the condition 1 and the condition 2 are alternately repeated. However, in addition to repeating the conditions 1 and 2, three or more conditions may be repeated depending on the purpose. Good.

(Second Embodiment)
2nd Embodiment of the manufacturing method of the silicon carbide type mixed crystal of this invention is described with reference to FIG. In the present embodiment, the M 1 source gas (Ge source gas) used in the first embodiment is supplied instead of the Sn source gas to produce a Si _1-x Sn _x C mixed crystal (silicon carbide based mixed crystal). It is a thing.

  The C source gas and the Si source gas can be the same as those used in the first embodiment, and the same reference numerals are given to the same components as those in the first embodiment, and detailed description thereof is omitted. .

In the present embodiment, Sn (CH ₃ ) ₄ is used as Sn source gas from the M source gas supply system provided with the bubbler container 18 using the CVD apparatus shown in FIG. 1, as shown in FIG. In the same manner as above, Condition 1 where the difference between the partial pressure p _Si and the partial pressure p _Sn is large (condition where the ratio p _Si / _psn is large) and Condition 2 where the difference between the partial pressure p _Si and the partial pressure p _Sn is small. (Conditions where the ratio p _Si / _psn is small) are repeatedly supplied.

Specifically, supply of C ₂ H ₂ gas as a C source gas at a constant partial pressure higher than the partial pressure p _Si and the partial pressure p _Sn is started, and the partial pressure p _Si with respect to the partial pressure p _Sn is increased. Then, SiH ₂ Cl ₂ and Sn (CH ₃ ) ₄ are supplied at the same time. After the time of Condition 1, the partial pressure is within the range of p _Si > p _{Sn and} the partial pressure p _Si is lowered and the partial pressure p _Sn enhanced, by reducing the partial pressure difference between the divided p _Sn and partial pressure p _Si to supply the SiH ₂ Cl ₂ and Sn (CH _{3) 4.}

  As in the case of the first embodiment, when the repetition interval (duration) of the condition 1 and condition 2 in which the alternate supply is performed is increased, a layer with a small amount of Sn uptake and a layer with a large amount of Sn are alternately formed. By making the repetition interval (duration) sufficiently short, interdiffusion can occur and a single layer with a uniform uptake can be formed. The duration of condition 1 and the duration of condition 2 may be the same time, or one of them may be longer than the other.

Similarly to the case where the Ge source gas is supplied as the M source gas in the first embodiment, in condition 2, the partial pressure p _Sn is increased, and the partial pressure p _C of the C source gas is also increased, whereby Sn—C Bond formation can be promoted, and Sn can be incorporated into the SiC crystal more easily. When the partial pressure p _Sn is increased, the degree (ratio) of increasing the partial pressure p _C of the C source gas with respect to the partial pressure p _Sn is set to p _C (condition 2) / p _C (condition 1) = 2-4. It is effective.

As the Sn source gas, gases such as SnH ₄ , Sn (CH ₃ ) ₄ , Sn (C ₂ H ₅ ) ₄ , SnH (CH ₃ ) ₃ are suitable, and among them, organometallic compounds (particularly Sn (CH ₃₎ ) ₄ , Sn (C ₂ H ₅ ) ₄ , SnH (CH ₃ ) _3, etc.) are more preferable.

In the above, the partial pressure p _Sn in condition 1, each maintaining a certain degree of partial pressure p _Si under the condition 2, Sn in the SiC crystal, but to perform the control to supply as Si is contained none, It is not always necessary to maintain these partial pressures. In condition 1, the partial pressure _pSn is substantially 0 (zero), and in condition 2, the partial pressure _pSi is substantially 0 (zero). You may do it. That is, by substantially alternately switching and supplying the Si source gas and the Sn source gas, the incorporation of Sn into the SiC crystal is further facilitated, and the total supply of the Si source gas and the Sn source gas is achieved. A Si _1-x Sn _x C mixed crystal having a composition ratio close to the above ratio can be obtained.

In the present embodiment, by performing repeated alternately ratio of the partial pressure p _Si and the partial pressure p _Sn as described above, Si _1-x Sn _x C mixed crystal incorporating easily Sn in the SiC crystal The composition of can be controlled.

In the above embodiments, the partial pressure p _C of C source gas constant, and the partial pressure p _Sn partial pressure p _Ge or Sn source gas partial pressure p _Si and Ge source gas of the Si source gas in this state However, instead of keeping the partial pressure p _C of the C source gas constant, the ratio of the partial pressure p _Si and the partial pressure p _Ge or the partial pressure p _Sn of the Sn source gas is changed. while changing alternately in aforementioned conditions 1 and 2, to lower the condition 1, the partial pressure p _C, forms for supplying repeated alternately so as to increase the condition 2, partial pressure p _C also suitable is there.

At this time, the partial pressure p _Ge or partial pressure p _Sn in condition 1, each maintaining a certain degree of partial pressure p _Si under the condition 2, be subjected to supply so that the Ge or Sn and Si contained in the SiC crystal In condition 1, the partial pressure p _Ge or the partial pressure p _Sn is substantially 0 (zero), and in condition 2, the partial pressure p _Si is substantially 0 (zero). May be. Thus, as already described, Sn or incorporation of Ge into the SiC crystal becomes easier, Si _1-x having a composition ratio close to the total feed ratio of Si source gas and the Sn source gas or Ge source gas A Sn _x C mixed crystal or a Si _1-x Ge _x C mixed crystal can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

(Example 1): Si _1-x Ge _x C mixed crystal-preparation of CVD apparatus-
First, a CVD apparatus configured similarly to the configuration shown in FIG. 1 was prepared.

−Preparation of Si _1-x Ge _x C mixed crystal−
A commercially available 8 ° off-Si surface 4H—SiC (0001) substrate (hereinafter referred to as SiC substrate) was prepared, cleaned, and placed inside the quartz reaction tube 20 of the CVD apparatus. The cleaning was performed by first cleaning with acetone or ethanol (organic solvent), followed by hydrofluoric acid etching and pure cleaning, and further sprayed with nitrogen gas and dried.

Next, the CVD apparatus is started and hydrogen gas is supplied from the hydrogen gas supply system to the quartz reaction tube 20 on which the SiC substrate is installed to form a hydrogen gas atmosphere, and the pressure is 1.33 × 10 ³ Pa in the hydrogen gas atmosphere. The temperature was raised to 1650 ° C. over 30 minutes at (10 torr).

Thereafter, while the quartz reaction tube 20 is maintained at 1650 ° C., C ₂ H ₂ gas is separated from the Si source gas supply system, the C source gas supply system, and the M source gas supply system as shown in FIG. While supplying at a pressure p _C , alternating supply of SiH ₂ Cl ₂ gas and Ge (C ₂ H ₅ ) ₄ gas under conditions 1 and 2 was continued for 2 hours to grow a SiGeC thin film on the SiC substrate. Details of conditions 1 and 2 are as follows. After completing the thin film growth, the temperature was lowered while the supply of H ₂ gas and C ₂ H ₂ gas was continued.

[Condition 1] H ₂ = 500 sccm, C ₂ H ₂ = 0.065 sccm, SiH ₂ Cl ₂ = 0.13 sccm, Ge (C ₂ H ₅ ) ₄ = 0.02 sccm for 5 seconds [Condition 2] H ₂ = 500 sccm, C ₂ H ₂ = 0.065 sccm, SiH ₂ Cl ₂ = 0 sccm, Ge (C ₂ H ₅ ) ₄ = 0.02 sccm for 5 seconds

-Evaluation 1
The obtained SiGeC thin film was evaluated for film properties and Ge composition ratio.
1. Film Properties The film surface of the SiGeC thin film was in a mirror state, and the film thickness measured by cross-sectional observation with a scanning electron microscope (SEM) was about 2 μm. When the diffraction pattern of the SiGeC thin film was evaluated by reflection high-energy electron diffraction (RHEED), the diffraction pattern was spot-like, and epitaxial growth was confirmed. Further, it was confirmed by a Raman spectroscopic measurement method that the 4H structure does not contain 3C structure crystals.

2. Ge composition ratio Quantitative analysis of Si and Ge of the crystalline thin film was performed by X-ray photoelectron spectroscopy (XPS). As a result, the Ge composition ratio was 1.8 atomic%. In the present embodiment, the Ge composition ratio (atomic) with respect to the change in the amount of carrier gas (the amount of C ₂ H ₂ gas) is changed by keeping the temperature of the Ge (C ₂ H ₅ ) ₄ gas constant. %) Is plotted. The plotted results are shown in FIG. As shown in FIG. 4, the Ge composition ratio increased linearly as the amount of carrier gas increased, and the Ge composition could be precisely controlled.

(Example 2): Si _1-x Sn _x C mixed crystal In Example 1, the M source gas (Ge (C ₂ H ₅ ) ₄ gas) was replaced with Sn (CH ₃ ) ₄ gas, and conditions 1 and A SiSnC thin film was grown on the SiC substrate in the same manner as in Example 1 except that 2 was changed to the conditions 3 and 4 shown below and the supply was performed as shown in FIG. Details of conditions 3 and 4 are as follows.

[Condition 3] 5 seconds under component conditions of H ₂ = 500 sccm, C ₂ H ₂ = 0.065 sccm, SiH ₂ Cl ₂ = 0.13 sccm, Sn (CH ₃ ) ₄ = 0 sccm [Condition 4] H ₂ = 500 sccm , C ₂ H ₂ = 0.065 sccm, SiH ₂ Cl ₂ = 0 sccm, Sn (CH ₃ ) ₄ = 0.04 sccm for 5 seconds

-Evaluation 2-
The obtained SiSnC thin film was evaluated for film properties and Sn composition ratio.
1. Film Properties The film surface of the SiSnC thin film was in a mirror state, and the film thickness measured in the same manner as in Example 1 was about 2 μm. When the diffraction pattern of the SiSnC thin film was evaluated by reflection high-energy electron diffraction (RHEED), the diffraction pattern was spot-like, and epitaxial growth was confirmed. Further, it was confirmed by a Raman spectroscopic measurement method that the 4H structure does not contain 3C structure crystals.

2. Sn composition ratio Quantitative analysis of Si and Sn of the crystal thin film was performed by X-ray photoelectron spectroscopy (XPS). As a result, the Sn composition ratio was 1.5 atomic%.

(Example 3): Si _1-x Ge _x C mixed crystal In Example 1, the ratio of the partial pressures p _Si and p _Ge is alternately changed at regular intervals while the partial pressure p _C is constant. In addition to changing the partial pressure p _C , the conditions 1 and 2 are changed to the conditions 5 and 6 shown below, respectively, and the supply is performed as shown in FIG. In the same manner as in Example 1, a SiGeC thin film was grown on the SiC substrate. Details of conditions 5 and 6 are as follows.

[Condition 5] 5 seconds under component conditions of H ₂ = 500 sccm, C ₂ H ₂ = 0.05 sccm, SiH ₂ Cl ₂ = 0.13 sccm, Ge (C ₂ H ₅ ) ₄ = 0.02 sccm [Condition 6] 5 seconds under component conditions of H ₂ = 500 sccm, C ₂ H ₂ = 0.10 sccm, SiH ₂ Cl ₂ = 0 sccm, Ge (C ₂ H ₅ ) ₄ = 0.02 sccm

-Evaluation 3-
The obtained SiGeC thin film was evaluated for film properties and Ge composition ratio.
1. Film Properties The film surface of the SiGeC thin film was in a mirror state, and the film thickness measured in the same manner as in Example 1 was about 2 μm. When the diffraction pattern of the SiGeC thin film was evaluated by reflection high-energy electron diffraction (RHEED), the diffraction pattern was spot-like, and epitaxial growth was confirmed. Further, it was confirmed by a Raman spectroscopic measurement method that the 4H structure does not contain 3C structure crystals.

2. Ge composition ratio Quantitative analysis of Si and Ge of the crystalline thin film was performed by X-ray photoelectron spectroscopy (XPS). As a result, the Ge composition ratio was 2.5 atomic%. Compared with Example 1 in which the supply amount (partial pressure p _Ge ) of Ge (C ₂ H ₅ ) ₄ that is a Ge source gas is the same as in Example 1, the Ge composition ratio was 1.8 atomic%. As a result of alternately changing the supply amount (partial pressure p _C ) of the C source gas C ₂ H ₂ at regular intervals, the incorporation of Ge into the SiC crystal can be increased by about 30%. It was.

It is a schematic block diagram which shows the CVD apparatus used in 1st Embodiment of this invention. It is explanatory drawing which shows the supply timing of C source gas, Si source gas, and Ge source gas in 1st and 2nd embodiment of this invention. It is explanatory drawing which shows the supply timing of C source gas in Example 1, Si source gas, and Ge source gas. It is a relationship figure which shows the relationship between carrier gas flow volume and Ge density | concentration. It is explanatory drawing which shows the supply timing of C source gas in Example 2, Si source gas, and Sn source gas. It is explanatory drawing which shows the supply timing of C source gas in Example 3, Si source gas, and Ge source gas.

Explanation of symbols

15 ... SiH ₂ Cl ₂ gas cylinder 16 ... C ₂ H ₂ gas cylinder 18 ... Bubbler container 20 filled with M source gas ... Quartz reaction tube

Claims (5)

A method for producing a silicon carbide-based mixed crystal in which a Si _1-x M _x C mixed crystal is formed by supplying a C source gas, a Si source gas, and an M (Ge or Sn) source gas to a substrate surface,
While supplying C source gas at least while M source gas is supplied,
The Si source gas and the M source gas are alternately switched between a condition in which the ratio (p _Si / p _M ) of the partial pressure p _Si of the Si source gas to the partial pressure p _M of the M source gas is large and small. A method for producing a silicon carbide-based mixed crystal characterized by comprising the steps of: 2. The method for producing a silicon carbide based mixed crystal according to claim 1, wherein at least the partial pressure of the M source gas is increased, the partial pressure of the C source gas is increased . 3. The method for producing a silicon carbide based mixed crystal according to claim 1, wherein the supplying is performed so that the small condition includes a period satisfying p _Si / p _M <1.   The method for producing a silicon carbide based mixed crystal according to any one of claims 1 to 3, wherein the C source gas is supplied at a constant partial pressure. Claim low comb the partial pressure of the C source gas when to lower the partial pressure p _M of the M source gas, when increasing the partial pressure p _M of the M source gas to increase the partial pressure of the C source gas 1 The manufacturing method of the silicon carbide type mixed crystal of any one of Claims 4-5.

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