JP2007042899A - Vapor phase epitaxial growth apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a apparatus for manufacturing a semiconductor capable of improving material quality of an uniform heater plate, and growing a semiconductor crystal with little impurities mixed. <P>SOLUTION: The apparatus for vapor growth of a semiconductor crystal on a semiconductor substrate 4 by causing a material gas 15 to flow onto the heated semiconductor substrate 4 includes the uniform heater plate 7 located adjacent to the substrate 4, between the device and a heating source for uniformly heating the substrate 4. Silicon carbide or gas impermeable carbon is used as the material of the uniform plate 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vapor phase growth apparatus, and more particularly to a material for a soaking plate.

  One of the methods for growing semiconductor thin film crystals is a vapor phase growth method. In the vapor phase growth method, a gas is used as a raw material, a raw material gas is flowed over a heated semiconductor substrate, and a semiconductor crystal is grown on the surface of the semiconductor substrate. Since gas is used as a raw material, it has an advantage that an ultra-thin film having a thickness of several nm can be grown. In addition, since it does not require an ultra-high vacuum like molecular beam epitaxy (MBE), it has the feature of being excellent in mass productivity.

  Here, FIG. 10 shows a system for constituting a reaction furnace adopted by a conventional main MOVPE (metal organic chemical vapor deposition) apparatus. 10A is a barrel type in which the semiconductor substrate 4 is held on the pyramidal slope of the susceptor 31, and FIG. 10B is a diagram in which gas flows in one direction from one side of the reaction tube 2 to the other side, and the semiconductor substrate 4 is FIG. 10C shows a gas faced down from the center of the susceptor 33, and the semiconductor substrate 4 is opened in the susceptor 33. FIG. 10 (d) shows a gas that is face-up in the part (rotation and revolution type face-up). FIG. 10 (d) shows that the gas flowing from the bottom to the top flows radially outward from the center of the susceptor 34. The type provided by face down (spinning and revolution type face down) is shown.

  In these reactors, jigs such as carbon and quartz are mainly used around the portion where the semiconductor substrate 4 is set. Further, as shown in FIGS. 10B to 10D, in order to heat the semiconductor substrate 4 uniformly, a jig called a soaking plate 7 is set adjacent to the substrate.

  FIG. 5 shows a configuration of a conventional revolution / revolution type face-down reactor 1. This is provided with a plate-shaped revolution susceptor 3 that rotates so as to constitute a part of the upper wall of the gas flow path in a reaction tube 2 heated by a heating device and through which Group III and Group V source gases flow. A rotation susceptor 5 is inserted into an opening 13 provided in the susceptor 3, and the semiconductor substrate 4 is supported in the rotation susceptor 5 with its surface (growth surface) facing downward, and a heater serving as a heating source for heating the semiconductor substrate 12 is configured as an epitaxial device in which a soaking plate 7 is fitted in the rotating susceptor 5 so as to face 12.

  The rotation susceptor 5 has a cylindrical shape, and has an outward flange having a tooth shape formed on the outer periphery at the upper end, and three inward claws 6 as means for supporting the semiconductor substrate at the lower end. The semiconductor substrate 4 is housed in the rotating susceptor 5 with the surface facing downward, and is held by an inward claw 6 at the lower end. The rotation susceptor 5 is mounted on the revolution susceptor 3 via a bearing 14 at a portion of the outward flange, and is rotatably supported. Small gear teeth 8 are machined on the outer periphery of the outward flange of the rotation susceptor 5, and mesh with the teeth of an internal gear (large gear) 9 disposed on the outer periphery side of the revolution susceptor 3.

  The revolution susceptor 3 rotates by rotating a shaft 10 connected to the center by a motor 11. When the revolution susceptor 3 rotates, the rotation susceptor 5 also meshes with the internal gear 9 and thus rotates. That is, the semiconductor substrate 4 performs revolution and rotation.

  The source gas 15 is introduced from the lower side to the upper side through the source inlet 2a at the center of the revolution susceptor 3 as shown in FIG. 5, and radially outward from the center of the revolution susceptor 3 along the surface of the semiconductor substrate 4. It flows toward and exits from the gas outlet 2b. In the meantime, the semiconductor substrate 4 heated by the heater 12 is thermally decomposed and crystal growth is performed. Since the semiconductor substrate 4 revolves and rotates, a highly uniform semiconductor crystal can be grown on the semiconductor substrate 4.

  In the prior art, as shown in an enlarged view in FIG. 6, the semiconductor substrate 4 is held by an inward claw 6 provided at the lower end of the rotation susceptor 5. At that time, a play of about 1 mm is provided between the semiconductor substrate 4 and the rotation susceptor 5. The semiconductor substrate 4 is covered with a soaking plate 7 made of graphite in order to make the temperature in the semiconductor substrate uniform.

The purity of these jigs also affects the purity of the growing crystal. Therefore, conventionally, the surface of the jig around the part where the substrate is set, for example, the surface of the soaking plate 7, is coated with a III-V group compound semiconductor crystal thin film, and impurities remaining in the furnace and in the jig itself are removed. It has been proposed that the growth crystal is not affected (see, for example, Patent Document 1).
JP 2003-243318 A

  However, Patent Document 1 does not disclose the use of silicon carbide as the material for the soaking plate.

  The reactor of the prior art has an apparatus configuration as shown in FIG. 5, and high-purity graphite is used for the revolution susceptor 3, the rotation susceptor 5 and the soaking plate 7. Since semiconductor crystals are sensitive to the contamination of impurities and the characteristics deteriorate due to the contamination of impurities, the vapor phase growth apparatus uses high purity graphite having high purity and excellent durability.

  High-purity graphite contains almost no impurities such as heavy metals, but has a disadvantage that degassing is likely to occur due to its high porosity. Therefore, in the conventional vapor phase growth method, by repeating the growth, as shown in FIG. 7, the surface of the portion made of high-purity graphite, that is, the revolution susceptor 3, the rotation susceptor 5, and the lower surface of the internal gear 9, are made of semiconductor crystals. A high-quality semiconductor crystal is obtained which is covered with the deposit 16 and suppresses degassing from the surface of high-purity graphite and suppresses the contamination of impurities.

  However, in the prior art, semiconductor crystals are not deposited on the soaking plate 7 made of high-purity graphite. Therefore, as shown by arrows in FIGS. 8A and 8B, the degassing 17 from the soaking plate 7 is The rotation susceptor 5 and the semiconductor substrate 4 go around the surface of the semiconductor substrate 4 from the gap 18. For this reason, there exists a problem that the characteristic of the semiconductor crystal grown on the semiconductor substrate 4 will deteriorate.

In order to investigate the influence of impurities, an Al _0.3 Ga _0.7 As (aluminum gallium arsenide) crystal was grown in a vapor phase, and the photoluminescence intensity, which is an optical characteristic, was examined. Incidentally, photoluminescence is light emitted from a semiconductor crystal when the semiconductor crystal is irradiated with a laser beam. If there is an impurity that inhibits light emission, the photoluminescence intensity decreases. The diameter of the semiconductor substrate 4 is 76 mm. Use the Al (aluminum) as a raw material Al (CH _{3) 3} (trimethyl aluminum), Ga (gallium) as a raw material Ga (CH _{3) 3} (trimethylgallium), As (arsenic) AsH ₃ as a raw material (arsine) It was.

  The results are shown in FIG. The horizontal axis is the distance from the substrate center, and the unit is mm. The vertical axis represents photoluminescence intensity, and the unit is arbitrary. From the figure, it can be seen that the photoluminescence intensity is low in the peripheral portion of the semiconductor substrate 4 and impurities that inhibit photoluminescence are mixed. When impurities that impede photoluminescence are mixed, there is a problem that characteristics of a light emitting element such as a laser diode or a light emitting diode deteriorate.

  Accordingly, an object of the present invention is to provide a vapor phase growth apparatus capable of solving the above-described problems, improving the material of the soaking plate, and growing a semiconductor crystal with less impurities.

  In order to achieve the above object, the present invention is configured as follows.

  According to a first aspect of the present invention, there is provided a vapor phase growth apparatus for flowing a source gas over a heated substrate and vapor-phase-growing a semiconductor crystal on the substrate. It is characterized in that a soaking plate is set between the heating source and silicon carbide or gas-impermeable carbon is used as the material of the soaking plate.

  Here, the gas-impermeable carbon refers to, for example, a product name “Grassy Carbon” manufactured by Tokai Carbon Co., Ltd.

  A vapor phase growth apparatus according to a second aspect of the present invention supplies a group III and group V source gas, a doping source material and a carrier gas onto a heated substrate, and vapor phase grows a compound semiconductor crystal on the substrate. In order to heat the substrate uniformly, a soaking plate is set between the substrate and the heating source, and silicon carbide or gas-impermeable carbon is used as the material of the soaking plate. .

  The inventions of claims 1 and 2 are applicable to all reactors using soaking plates. That is, the present invention is not limited to whether the substrate rotates or revolves or remains stationary, regardless of whether the substrate is provided face-down or face-up. The present invention can be applied regardless of whether it flows in the diameter direction of the susceptor or in the radial direction. Therefore, the present invention can also be applied to a soaking plate, which is also used as a mounting table for a semiconductor substrate in a plasma CVD apparatus.

  As a typical reactor type to which the present invention can be applied, (1) a type in which gas flows in one direction from one side of the reaction tube to the other side and the substrate is provided face down (FIG. 10B). (2) A type in which the gas flowing from the top to the bottom flows radially outward from the center of the susceptor and the substrate is provided face-up (FIG. 10C) and (3) the gas from the bottom to the top There is a type (FIG. 10D) in which the substrate flows face down from the center of the susceptor in the radial direction.

  In addition, as the type of soaking plate, (1) a structure that enters into the opening of the susceptor and is supported by an inward flange at the bottom of the opening with the substrate, and (2) the sum of the thickness of the soaking plate and the substrate. Is made thicker than the susceptor, and a rib-like portion is formed on the surface side of the heat equalizing plate that does not contact the substrate, and the outer periphery is radially expanded, and the rib-like portion covers the gap between the substrate and the susceptor. Is also included.

  The vapor phase growth apparatus according to the invention of claim 3 is provided with a plate-like susceptor in a reaction tube through which a raw material gas flows or as a part of a wall of the reaction tube, and an object of vapor phase epitaxial growth in an opening provided in the susceptor. In the vapor phase growth apparatus in which the substrate is supported with its surface facing the inside of the reaction tube and a soaking plate is fitted between the back surface of the substrate and the heating source in the opening, the material of the soaking plate It is characterized by using silicon carbide or gas-impermeable carbon.

  The type of reactor in the invention of claim 3 is (1) a type in which gas flows in one direction from one side of the reaction tube to the other side and the substrate is provided face-down (FIG. 10B). In addition, (2) the type in which the gas from the top to the bottom flows radially outward from the center of the susceptor and the substrate is provided face up (FIG. 10 (c)) and (3) the gas from the bottom to the top is in the center of the susceptor And a type in which the substrate is provided face down (FIG. 10D).

  The vapor phase growth apparatus according to the invention of claim 4 is provided with a plate-shaped revolution susceptor that rotates in a reaction tube through which a source gas flows or as a part of a wall of the reaction tube, and rotates in an opening opened in the revolution susceptor. A gas phase in which a susceptor is inserted, a semiconductor substrate is supported in the rotation susceptor with its growth surface facing downward, and a soaking plate is fitted in the rotation susceptor so as to face a heating source for heating the semiconductor substrate. In the growth apparatus, silicon carbide or gas-impermeable carbon is used as a material for the soaking plate.

  According to a fifth aspect of the present invention, in the vapor phase growth apparatus according to any one of the first to fourth aspects, silicon carbide or gas-impermeable carbon is used as a material of the susceptor.

  According to a fifth aspect of the present invention, in the vapor phase growth apparatus according to any one of the first to fifth aspects, the substrate and the soaking plate are brought into contact with each other.

The present invention is a vapor phase growth apparatus according to any one of claims 2 to 6 and is configured as a vapor phase growth apparatus for epitaxially growing a group III-V compound semiconductor crystal, and GaAs (gallium arsenide) is used as a semiconductor substrate. AsH ₃ (arsine) and PH ₃ (phosphine) are used as group V materials, and Ga (CH ₃ ) ₃ (trimethylgallium), Al (CH ₃ ) ₃ (trimethylaluminum), In ( It can be configured as a vapor phase growth apparatus characterized by using CH ₃ ) ₃ (trimethylindium). As the semiconductor substrate, InP (indium phosphorus), GaN (gallium nitride), SiC (silicon carbide), or sapphire can also be used.

<Key points of the invention>
In the prior art, high-purity graphite having high porosity is used as the material of the soaking plate 7, so that degassing from the high-purity graphite is mixed as impurities into the semiconductor crystal, and the characteristics of the semiconductor crystal are deteriorated. There was a problem.

  In the present invention, the soaking plate is made of gas-impermeable SiC (silicon carbide) or gas-impermeable carbon (for example, “Grassy Carbon” manufactured by Tokai Carbon Co., Ltd.). As a result, degassing from the soaking plate can be suppressed, and a high-quality semiconductor crystal with few impurities can be grown.

  In addition, the distance between the soaking plate and the semiconductor substrate is preferably 0.7 mm or less, whereby the wraparound of the source gas can be suppressed and a high-purity semiconductor crystal can be obtained.

  The vapor phase growth method requires a chemically stable material because it uses a highly reactive gas. Moreover, since it is used at high temperature (about 600-800 degreeC), heat resistance is also important. Furthermore, in order to grow a high-quality semiconductor crystal, a high-purity material with less outgassing is required.

  SiC and gas impervious carbon (for example, “Glassy Carbon” manufactured by Tokai Carbon Co., Ltd.) used as the material for the soaking plate in the present invention are excellent in heat resistance, chemical resistance and gas impermeability. It is a high-purity material and is the most suitable material for use in vapor phase epitaxy. However, SiC and glassy carbon (trade name) have poor processability and are more expensive than high-purity graphite, and have not been used in the prior art.

  In the prior art, the soaking plate is made of high-purity graphite, and since there is much degassing, impurities are mixed in the semiconductor crystal and the characteristics of the semiconductor crystal are deteriorated.

  On the other hand, in the present invention, the soaking plate is made of SiC or made of gas-impermeable carbon, for example, “Grassy Carbon” manufactured by Tokai Carbon Co., Ltd., which can suppress degassing. Therefore, a semiconductor crystal with less impurities can be produced. For this reason, according to the vapor phase growth apparatus of the present invention, the characteristics of the semiconductor crystal are not deteriorated, the improvement of the yield can be expected, and the productivity can be greatly improved.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  FIG. 1 shows a configuration of a reaction furnace 1 of a vapor phase growth apparatus according to a first embodiment of the present invention.

In this case, a plate-shaped revolution susceptor 3 that rotates so as to constitute a part of the upper wall of the gas flow path is provided in a reaction tube 2 through which a group III and group V source gas flows, and the revolution susceptor 3 has a gas phase. An opening 13 is formed in substantially the same shape as the semiconductor substrate to be epitaxially grown, the rotation susceptor 5 is inserted into the opening 13, and the growth surface of the semiconductor substrate 4 is supported downward at the lower end of the rotation susceptor 5. At the same time, it is configured as a rotation / revolution type face-down reactor in which a soaking plate 70 made of SiC is fitted in the rotation susceptor 5 so as to face the heater 12 as a heating source for heating the semiconductor substrate 4. .
The distance between the soaking plate 70 and the semiconductor substrate 4 is 0.15 mm.

  In accordance with the present invention, SiC is used as the material of the soaking plate 70.

  The rotation susceptor 5 has a cylindrical shape, and has an outward flange having a tooth shape formed on the outer periphery at the upper end, and three inward claws 6 as means for supporting the semiconductor substrate at the lower end. The semiconductor substrate 4 is housed in the rotating susceptor 5 with the surface facing downward, and is held by an inward claw 6 at the lower end. The rotation susceptor 5 is mounted on the revolution susceptor 3 via a bearing 14 at a portion of the outward flange, and is rotatably supported. Small gear teeth 8 are machined on the outer periphery of the outward flange of the rotation susceptor 5, and mesh with the teeth of the internal gear 9 installed on the outer periphery side of the revolution susceptor 3.

  The revolution susceptor 3 rotates by rotating the shaft 10 connected to the center portion by a motor 11. When the revolution susceptor 3 rotates, the teeth 8 of the rotation susceptor 5 are also meshed with the internal gear 9 and thus rotate. That is, the semiconductor substrate 4 performs revolution and rotation. The shaft 10 and the motor 11 are driving mechanisms for revolving the susceptor, and the teeth 8 and the internal gear 9 of the rotating susceptor 5 are driving mechanisms for rotating the susceptor.

  The source gas 15 is introduced from the lower side to the upper side through the source inlet 2a at the center of the revolution susceptor 3 as shown in FIG. 1, and radially outward from the center of the revolution susceptor 3 along the surface of the semiconductor substrate 4. It flows toward and exits from the gas outlet 2b. In the meantime, the semiconductor substrate 4 heated by the heater 12 is thermally decomposed and crystal growth is performed. Since the semiconductor substrate 4 revolves and rotates, a highly uniform semiconductor crystal can be grown on the semiconductor substrate 4.

  In this embodiment, SiC (silicon carbide) with less degassing is used as the material of the soaking plate 70, so that a high-quality semiconductor crystal with less impurities can be grown.

  As the material of the soaking plate 70, in addition to SiC, gas-impermeable carbon (trade name: glassy carbon) can be used, which also suppresses degassing and has a good quality with less impurities. A simple semiconductor crystal can be grown.

  In the prior art, since high-purity graphite having high porosity and high degassing is used, degassing 17 from the soaking plate 7 wraps around the surface of the semiconductor substrate 4 as shown in FIG. There is a problem that the performance of the semiconductor deteriorates. The feature of the present invention is that SiC or glassy carbon (trade name) is used as the material of the soaking plate 7.

In order to investigate the influence of impurities, an Al _0.3 Ga _0.7 As crystal was vapor-phase grown and the photoluminescence intensity, which is an optical characteristic, was examined.

That is, an n-type GaAs substrate (carrier concentration: 1 to 5 × 10 ²⁴ m ⁻³ ) having a diameter of (100) as a surface is used as the semiconductor substrate 4, and Al _0.3 Ga _0.7 As is formed thereon by MOVPE. Crystals were vapor grown to a thickness of 1 μm. Al (CH ₃ ) ₃ (trimethylaluminum), Ga (CH ₃ ) ₃ (trimethylgallium), and AsH ₃ (arsine) were used as raw materials. The growth conditions were as follows: growth temperature: 650 ° C., Al (CH ₃ ) ₃ flow rate: 2.9 cc / min, Ga (CH ₃ ) ₃ flow rate: 7.2 cc / min, AsH ₃ flow rate: 1000 cc / min.

  The results are shown in FIG. The “measurement position” on the horizontal axis is the distance from the center of the substrate, and the unit is mm. The vertical axis represents “photoluminescence intensity”, and the unit is arbitrary. In the prior art (curve B in FIG. 2), a decrease in the photoluminescence intensity is observed at the periphery of the semiconductor substrate, but in the embodiment of the present invention (curve A in FIG. 2), the abrupt intensity at the periphery of the semiconductor substrate. There is no decline. That is, if the present invention is used, since there is little mixing of impurities that inhibit photoluminescence, the characteristics of light-emitting elements such as laser diodes and light-emitting diodes do not deteriorate. For this reason, a yield improves and productivity can be improved significantly.

<Modification 1>
FIG. 3 shows a modification of the present invention, which is an example using a revolution susceptor 30 made of SiC and a rotation susceptor 50 made of SiC. Since not only the soaking plate 70 but also the revolution susceptor 30 and the rotation susceptor 50 are made of SiC or gas-impermeable carbon (trade name glassy carbon), degassing can be further reduced.

<Modification 2>
FIG. 4 shows another modification of the present invention. This is characterized in that the soaking plate 70 and the semiconductor substrate 4 are brought into contact with each other.

  Also in this modified example, degassing from the soaking plate 70 itself is suppressed by making the soaking plate 70 made of SiC or the product name “Grassy Carbon”. However, if there is a gap between the soaking plate 70 and the semiconductor substrate 4, the source gas flows around, so that the source gas is adsorbed and desorbed. Therefore, by bringing the soaking plate 70 and the semiconductor substrate 4 into contact with each other, the wraparound of the source gas is suppressed, and the production of a higher purity semiconductor crystal is enabled.

It is sectional drawing of the reactor of the vapor phase growth apparatus which concerns on the Example of this invention. The substrate in-plane distribution of the photoluminescence intensity of Al _0.3 Ga _0.7 As crystal by vapor phase growth apparatus according to an embodiment of the present invention and shows as compared to the prior art. It is sectional drawing of the reaction furnace of the vapor phase growth apparatus which concerns on the modification of this invention. It is the fragmentary sectional view which showed the contact state of the semiconductor substrate and soaking plate in the reactor of the vapor phase growth apparatus which concerns on the other modification of this invention. It is sectional drawing of the vapor phase growth apparatus of a prior art. A part of the reactor of the vapor phase growth apparatus of the prior art is shown, (a) is a partial cross-sectional enlarged view of a semiconductor substrate and a soaking plate, and (b) is a plan view thereof. It is sectional drawing which showed the reactor of the vapor phase growth apparatus of a prior art. It is a figure for demonstrating the contamination by the degassing from the graphite soaking plate in a prior art, (a) is sectional drawing of the soaking plate vicinity, (b) is the top view. It is a diagram showing a substrate in-plane distribution of the photoluminescence intensity of Al _0.3 Ga _0.7 As crystal according to the prior art vapor phase growth apparatus. It is the figure which showed the main reactor systems of the vapor phase growth apparatus which can apply this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor 2 Reaction tube 3 Revolving susceptor 4 Semiconductor substrate 5 Rotation susceptor 6 Inward claw 7 Heat equalizing plate 8 Small gear teeth 9 Internal gear 10 Shaft 11 Motor 12 Heater 13 Opening 14 Bearing 15 Material gas 16 Semiconductor crystal deposit 17 Degassing 18 Clearance 30 Revolving susceptor 50 Rotating susceptor 70 Heat equalizing plate

Claims (6)

In a vapor phase growth apparatus for flowing a source gas over a heated substrate and vapor-depositing a semiconductor crystal on the substrate,
In order to heat the substrate uniformly, a soaking plate is set between the substrate and a heating source, and silicon carbide or gas-impermeable carbon is used as the material of the soaking plate. Growth equipment. In a vapor phase growth apparatus for supplying a group III and group V source gas, a doping source material and a carrier gas on a heated substrate, and vapor-phase-growing a compound semiconductor crystal on the substrate,
In order to heat the substrate uniformly, a soaking plate is set between the substrate and a heating source, and silicon carbide or gas-impermeable carbon is used as the material of the soaking plate. Growth equipment. A plate-shaped susceptor is provided in the reaction tube through which the source gas flows or as a part of the wall of the reaction tube, the substrate that is the target of vapor phase epitaxial growth is placed in the opening provided in the susceptor, and the surface thereof is placed inside the reaction tube. In the vapor phase growth apparatus in which a soaking plate is inserted between the back surface of the substrate and the heating source in the opening,
A vapor phase growth apparatus characterized in that silicon carbide or gas-impermeable carbon is used as a material for the soaking plate. A plate-shaped revolution susceptor that rotates in the reaction tube through which the source gas flows or as a part of the wall of the reaction tube is provided. The rotation susceptor is inserted into an opening opened in the revolution susceptor, and the semiconductor substrate is placed in the rotation susceptor. In the vapor phase growth apparatus in which a soaking plate is fitted in the rotation susceptor so as to face the heating source for heating the semiconductor substrate, while supporting the growth surface downward.
A vapor phase growth apparatus characterized in that silicon carbide or gas-impermeable carbon is used as a material for the soaking plate. In the semiconductor manufacturing apparatus according to any one of claims 1 to 4,
A vapor phase growth apparatus using silicon carbide or gas-impermeable carbon as a material of the susceptor. In the semiconductor manufacturing apparatus according to claim 1,
A vapor phase growth apparatus characterized in that the substrate and the soaking plate are brought into contact with each other.

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