JP5251720B2 - Chemical vapor deposition semiconductor film forming apparatus and chemical vapor deposition semiconductor film forming method - Google Patents

Description

  The present invention relates to a chemical vapor deposition semiconductor film forming apparatus for forming a semiconductor film on a substrate by chemical vapor deposition, and more particularly to an apparatus for forming a semiconductor film having a uniform impurity concentration.

  As a semiconductor film forming apparatus for forming a semiconductor film on a substrate, a lateral hot wall CVD (Chemical Vapor Deposition) apparatus is known. For example, a horizontal hot wall CVD apparatus 190 of Patent Document 1 shown in FIG. 7 includes a reaction vessel 170, a gas introduction nozzle 115, a gas discharge nozzle 116, a susceptor 113, an RF work coil 120, a heat insulating material 112, a reflection plate 131, and a cooling pipe. 132. The gas introduction nozzle 115 is formed on one of the opposing side surfaces of the reaction vessel 170. Further, the gas discharge nozzle 116 is formed on the other side surface opposite to the side surface on which the gas introduction nozzle 115 is formed. The susceptor 113 is a heating element and is located in the reaction container 170. The RF work coil 120 is for inductively heating the susceptor 113 from outside the reaction vessel 170. The heat insulating material 112 is located in the reaction vessel 170 and prevents heat radiation from the susceptor 113 to the outside. The reflection plate 131 is located outside the reaction container 170 and prevents heat radiation from the reaction container 170 to the outside. The cooling pipe 132 is located outside the reaction vessel 170 and serves to cool the reflection plate 131.

  For example, when a silicon carbide single crystal thin film is formed on a substrate using a horizontal hot wall CVD apparatus, first, a material gas such as silane or propane is introduced into the reaction vessel 170 from the gas introduction nozzle 15. Then, the substrate 114 is heated to a growth temperature of usually about 1500 ° C. on the susceptor 113 that is induction-heated by the RF work coil 120. Thereby, the introduced gas is reacted on substrate 114 to deposit a silicon carbide film on substrate 114.

JP 2002-252176 A

  However, in the technique of Patent Document 1, the material gas is not sufficiently heated on the gas introduction nozzle 115 side (upstream side) of the susceptor 113. For this reason, decomposition | disassembly of the propane used as the supply source of carbon (C) among material gas is not fully performed. On the other hand, the material gas is sufficiently heated on the gas discharge nozzle 116 side (downstream side) of the susceptor 113. For this reason, the C / Si ratio in the reaction vessel 170 obtained as a result of heating the material gas is not uniform on the upstream side and the downstream side of the susceptor 113 as shown in FIG. Usually, the C / Si ratio is low on the upstream side, and tends to stabilize at a predetermined value toward the downstream side.

  Thus, since the C / Si ratio is not uniform between the upstream side and the downstream side of the susceptor 113, the concentration of nitrogen as an impurity (impurity concentration) is not uniform even in the silicon carbide film formed on the substrate. Usually, when the impurity is nitrogen, nitrogen tends to enter the carbon site. Therefore, as shown in FIG. 8, the impurity concentration is high in the upstream portion of the susceptor 113 of the substrate 114, and the impurity concentration tends to stabilize at a predetermined value toward the downstream side.

In FIG. 8, the C / Si ratio of the material gas in the reaction chamber is set to 1.2 to 2.0. Further, the impurity concentration of the silicon carbide film is set to 2 × 10 ¹⁷ [/ cm ³ ]. In this case, the impurity concentration of the silicon carbide film on the upstream side of the substrate is 1 × 10 ¹⁸ [/ cm ³ ].

  In order to avoid such a non-uniform impurity concentration in the silicon carbide film based on the non-uniformity of the C / Si ratio on the upstream side and the downstream side of the susceptor 113, the flow rate of the carrier gas flowing along with the material gas is reduced. Or a method of raising the growth temperature as a whole.

  However, in the method of reducing the flow rate of the carrier gas, it takes a long time for the material gas to pass through the region heated by the susceptor. For this reason, the heating effect of the material gas is promoted, and the amount of N active species on the downstream side becomes higher than a predetermined value.

  Further, in the method of increasing the growth temperature as a whole, the growth rate of the silicon carbide film is lowered due to the effect of hydrogen etching.

  An object of the present invention is to provide a chemical vapor deposition semiconductor film forming apparatus for forming a semiconductor film having a uniform impurity concentration on a substrate by chemical vapor deposition.

Chemical vapor deposition semiconductor film forming apparatus of the present invention, have a convex particle disturbing the flow of the material gas on the upstream side of the material gas from the mounting position of the substrate, the convex particle, from the mounting position of the substrate This is a chemical vapor deposition semiconductor film forming apparatus that is disposed on the upstream side of a gas and generates heat . Since the convex material makes it easier for the gas to be heated on the upstream side of the material gas than the mounting position of the substrate, the concentration of the material gas on the substrate can be made uniform. Therefore, the impurity concentration of the semiconductor film formed over the substrate can be made uniform.

  By using a convex material that is disposed on the upstream side of the material gas from the mounting position of the substrate and generates heat, the material gas that is difficult to be thermally decomposed on the upstream side of the substrate can be thermally decomposed. Therefore, the component ratio after pyrolysis of the material gas can be made uniform on the upstream side and the downstream side of the substrate. Therefore, the impurity concentration of the semiconductor film formed over the substrate can be made uniform.

  In addition, by using a cylindrical shape, elliptical column shape, conical shape, polygonal pyramid shape, etc. as the shape of the convex object, an appropriate turbulent flow is generated without extremely impeding the flow of the material gas, Can be heated. Therefore, the concentration of the material gas on the substrate can be made uniform.

  Furthermore, by using a mushroom shape as the shape of the convex object, it is possible to generate an appropriate turbulent flow without extremely impeding the flow of the material gas. In addition, when the height of the mushroom-shaped umbrella portion is a, the height of the shaft portion is preferably (1/2) a to (3/2) a. Moreover, when the width | variety of an umbrella part is set to b, it is preferable that the width | variety of an axial part is (1/5) b- (1/2) b. In particular, it has been confirmed that an appropriate turbulent flow can be generated and the gas can be efficiently heated without extremely disturbing the flow of the mixed gas.

  By configuring the convex object with the same material as the susceptor, the convex object can be heated without adding any special components. Therefore, the manufacturing cost of the chemical vapor deposition semiconductor film forming apparatus can be suppressed.

  When the chemical vapor deposition semiconductor film forming apparatus of the present invention is used when forming a silicon carbide film on a substrate, a silicon carbide film having a uniform impurity concentration can be easily formed. Thereby, a high-quality silicon carbide film can be easily formed on the substrate.

  The chemical vapor deposition semiconductor film forming method of the present invention disturbs the flow of the material gas upstream of the material gas from the placement position of the substrate placed directly or indirectly on the susceptor, and upstream. This is a chemical vapor deposition semiconductor film forming method of forming a semiconductor film while heating a material gas on the side. Thereby, the flow of the material gas can be disturbed on the upstream side of the material gas with respect to the mounting position of the substrate, and the gas can be sufficiently heated, so that the concentration of the material gas on the substrate can be made uniform. Therefore, a semiconductor film with a uniform impurity concentration of the semiconductor film can be formed over the substrate.

  According to the semiconductor film forming apparatus of the present invention, the gas can be heated on the upstream side with respect to the substrate. Thereby, since the thermal decomposition of gas can be promoted on the upstream side, the constituent component ratio of the constituent elements of the semiconductor film during the formation of the semiconductor film can be made uniform. Therefore, the impurity concentration of the semiconductor film formed over the substrate can be made uniform, and local increase can be prevented. In addition, since heating is performed only on the upstream side of the substrate by the heating element, the temperature during the reaction is not increased. Therefore, the growth rate of the semiconductor is not reduced.

It is a perspective view of the principal part regarding the furnace part of the horizontal type hot wall CVD apparatus which concerns on Embodiment 1 of this invention. 3 is a cross-sectional view of a furnace part of the horizontal hot wall CVD apparatus according to Embodiment 1. FIG. 3 is a cross-sectional view of a furnace part of the horizontal hot wall CVD apparatus according to Embodiment 1. FIG. It is a figure which shows the heat generating body which concerns on other embodiment. It is a figure which shows the heat generating body which concerns on other embodiment. It is a figure which shows the heat generating body which concerns on other embodiment. It is a figure explaining the conventional horizontal type | mold hot wall CVD apparatus. It is a graph which shows the C / Si ratio in the reaction chamber of the conventional horizontal hot wall CVD apparatus, and the impurity concentration of a silicon carbide film.

(Embodiment 1)
-Structure of furnace section of horizontal hot wall CVD equipment-
FIG. 1 shows a perspective view of the main part of the furnace part of the horizontal hot wall CVD (Chemical Vapor Deposition) apparatus according to the present embodiment. The horizontal hot wall CVD apparatus is a semiconductor manufacturing apparatus that is widely used for the production of a silicon carbide film by epitaxial growth on a SiC wafer (SiC).

  The furnace unit 1 includes a quartz tube 11, a heat insulating material 13, a susceptor 15, a convex heating element 17, and a reaction chamber 25. The quartz tube 11 is an annular quartz furnace body. The heat insulating material 13 is disposed along the inner surface of the quartz tube 11. The susceptor 15 is disposed along the inner surface of the heat insulating material 13.

  The susceptor 15 is heated by high frequency induction heating. The susceptor 15 is made of high-purity carbon or SiC sintered body to enable high-frequency induction heating. Thereby, appropriate electrical conductivity and high temperature stability in the susceptor 15 are realized. An RF coil or the like for inductively heating the susceptor 15 is disposed outside the quartz tube 11, but is not shown in FIG.

  Note that the susceptor 15 may be composed of a SiC polycrystal or the like. Further, an appropriate coating such as SiC coating or TaC coating may be applied to the surface of the susceptor 15.

  The SiC wafer B1 is placed at a predetermined position of the susceptor 15. In the present embodiment, SiC wafer B1 is directly placed on susceptor 15, but it is indirectly placed on susceptor 15 using a member on which SiC wafer B1 is placed. It may be.

The reaction chamber 25 is heated to an epitaxial growth temperature of 1500 ° C. to 1600 ° C. by heating by the susceptor 15. In the present embodiment, a SiC wafer B1 having a diameter of 2 inches is used. A reaction gas composed of a carrier gas, a material gas, and a dopant gas flows in the reaction chamber 25. In this embodiment, hydrogen gas is used as the carrier gas. As a material gas, a mixed gas of silane (SiH ₄ ) and propane (C ₃ H ₈ ) is used. Further, nitrogen gas (N ₂ ) is used as the dopant gas.

  In the reaction chamber 25, the material gas and the dopant gas are thermally decomposed by heating by the susceptor 15, and an N-type silicon carbide film is epitaxially grown on the placed SiC wafer B1.

  Note that the inert gas, the material gas, and the reactive gas flow in the X-axis direction shown in FIG. The direction in which each gas flows is the upstream side, and the direction in which each gas flows is the downstream side.

  In the reaction chamber 25, a convex heating element 17 is arranged upstream of the position where the SiC wafer B1 is placed.

-Structure of heating element-
2 is a cross-sectional view taken along a plane P1 parallel to the XY plane in FIG. FIG. 3 is a cross-sectional view taken along the P3 plane parallel to the XZ plane in FIG.

  In the reaction chamber 25 in the present embodiment, the channel width W (see FIG. 2) is about 70 mm, and the channel length L (see FIG. 2) is about 120 mm. The height H (see FIG. 3) of the reaction chamber is about 10 mm.

  The convex heating element 17 is arranged on the upstream side with respect to the position where the SiC wafer B1 is placed. In the present embodiment, the convex heating element 17 has a circular shape with a cross section of a diameter of about 7 mm and a height of about 5 mm. In the convex heating element 17, the length L is preferably 1/10 to 1/5 of the channel width of the reaction chamber, and the height H is preferably 3/4 to 1/4 of the height of the reaction chamber. By disposing such a convex heating element 17 upstream of the SiC wafer B1, the gas is heated by the heating element. Thereby, it has been experimentally confirmed that the C / Si ratio, which is the component ratio of the material gas after pyrolysis, can be made uniform on the upstream side and the downstream side of the SiC wafer B1.

  The convex heating element 17 is arranged at a position where the distance from the end of the SiC heating element 17 on the convex heating element 17 side to the end of the convex heating element 17 on the SiC wafer B1 side is 30 mm to 35 mm. Yes. By disposing the convex heating element 17 at such a position, the material gas can be heated on the upstream side with respect to the SiC wafer B1. Thereby, since the thermal decomposition of the material gas can be promoted on the upstream side, the C / Si ratio in the reaction chamber 25 can be made uniform. Therefore, it is possible to make the impurity concentration of the silicon carbide film formed on SiC wafer B1 uniform and prevent it from being locally increased.

  Furthermore, since heating is performed by the convex heating element 17 only on the upstream side of the SiC wafer B1, the temperature of the reaction chamber 25 as a whole does not increase. Therefore, the epitaxial growth rate of the silicon carbide film is not reduced.

  In the present embodiment, the convex heating element 17 is integrally formed with the susceptor 15 by the same material as the susceptor 15. Thus, by forming the same material as that of the susceptor 15, similarly to the susceptor 15, heat can be generated by induction heating using an RF coil arranged outside. When forming a coating on the susceptor 15, the same coating may be formed on the convex heating element 17.

-Effects of the embodiment-
According to the horizontal hot wall CVD apparatus of the present embodiment, the following functions and effects can be obtained. The convex heating element 17 is arranged on the upstream side of the SiC wafer B1. By disposing the convex heating element 17 at such a position, an appropriate turbulent flow can be generated with respect to the flow of the mixed gas on the upstream side of the SiC wafer B1, and the gas can be heated. Thereby, the C / Si ratio which is the component ratio of the material gas after thermal decomposition can be made uniform on the upstream side and the downstream side of the SiC wafer B1 .

  Also, the material gas, particularly propane, which is a carbon supply source, can be heated upstream of the SiC wafer B1. Thereby, since the thermal decomposition of the material gas can be promoted on the upstream side, the C / Si ratio in the reaction chamber 25 can be made uniform on the upstream side and the downstream side. Therefore, the impurity concentration of the silicon carbide film formed on SiC wafer B1 can be made uniform, and the impurity concentration can be prevented from locally increasing.

  Further, the material gas can be thermally decomposed on the upstream side where the thermal decomposition has been insufficient. Therefore, the decomposition efficiency of the material gas can be increased. Therefore, in order to increase the thermal decomposition efficiency of the material gas, it is not necessary to reduce the flow rate of the carrier gas and lengthen the time for the material gas to pass through the region heated by the susceptor 15. That is, since the material gas is not thermally decomposed for a long time before reaching the downstream side, the amount of N active species is not increased on the downstream side. That is, since the C / Si ratio is increased on the upstream side and the amount of N active species is not increased on the downstream side, the C / Si ratio and the amount of N active species are made uniform for the entire reaction chamber 25. Can do.

  Furthermore, since the material gas is heated by the convex heating element 17 only on the upstream side with respect to the SiC wafer B1, the growth temperature of the reaction chamber 25 is not increased. Therefore, the epitaxial growth rate of the silicon carbide film is not reduced.

(Other embodiments)
In the above embodiment, the convex heating element 17 is configured to protrude in the positive direction of the Z axis from the lower surface of the reaction chamber 25 on which the SiC wafer B1 of the susceptor 15 is placed. You may comprise so that it may protrude in the negative direction of an axis | shaft. Further, the heating element may be supported from the side surface of the reaction chamber 25.

  In the above embodiment, the convex heating element 17 may be configured as a separate body from the susceptor 15. When configured as a separate body, the convex heating element 17 may be simply placed on the susceptor 15 or may be attached to the susceptor 15 by a predetermined method. For example, a convex portion may be provided on the lower surface of the convex heating element 17, a concave portion may be provided on the susceptor 15, and the convex portion of the convex heating element 17 may be inserted into the concave portion of the susceptor 15. Moreover, you may make it fix by screwing a convex part and a recessed part and screwing together.

  Further, an engaging portion may be provided on each of the convex heating element 17 and the susceptor 15 so as to be engaged with each other.

  In the above embodiment, the convex heating element 17 is formed in a cylindrical shape. However, for example, the convex heating element 17 may have an elliptic cylinder shape as shown in FIG. In this case, the elliptic cylinder is arranged so that the major axis of the ellipse is along the X axis in FIG. Thus, the material gas can be thermally decomposed on the upstream side while generating an appropriate turbulent flow without extremely impeding the flow of the mixed gas.

  Further, the convex heating element 17 may have a conical shape as shown in FIG. By adopting such a conical shape, the material gas can be thermally decomposed on the upstream side while generating an appropriate turbulent flow without extremely impeding the flow of the mixed gas.

  Furthermore, as shown in FIG. 5A, a passage hole through which the mixed gas can pass may be provided in the convex heating element 17. In this case, there may be one or more passage holes. Thus, the material gas can be thermally decomposed on the upstream side while generating an appropriate turbulent flow without extremely impeding the flow of the mixed gas. Further, as shown in FIG. 5B, the convex heating element 17 may be provided with one passage hole so that the convex heating element 17 has a gate shape.

  As another form, the convex heating element 17 may be a mushroom type as shown in FIG. In this case, the convex heating element 17 includes the umbrella portion 61 and the shaft portion 63. FIG. 6B shows a cross-sectional view of the mushroom-shaped convex heating element 17 shown in FIG. In this case, when the height of the umbrella portion 61 is a, the height of the shaft portion 63 is preferably (1/2) a to (3/2) a. Further, when the width of the umbrella portion 61 is b, the width of the shaft portion 63 is preferably (1/5) b to (1/2) b. Thus, the material gas can be thermally decomposed on the upstream side while generating an appropriate turbulent flow without extremely impeding the flow of the mixed gas.

  In the above-described embodiment, one SiC wafer B1 is placed on the susceptor 15, but a plurality of SiC wafers B1 may be placed on the susceptor 15. A plurality of SiC wafers B1 may be arranged in a predetermined form, for example, a circle. In this case, if a mounting member on which a plurality of SiC wafers B1 are mounted is used, the work of taking the SiC wafers B1 into and out of the reaction chamber 25 becomes easy. Further, if the mounting member is rotated, the effect that the silicon carbide film can be epitaxially grown uniformly without variation among the SiC wafers B1 can be exhibited. In addition, by rotating the SiC wafers B1 arranged in a circle, the effect that the uniform silicon carbide film can be epitaxially grown on each SiC wafer B1 can be exhibited.

In the above embodiment, nitrogen gas is used as the dopant gas. However, a gas such as TMA (trimethylaluminum) or NH ₃ (ammonia) may be used as the dopant gas. In these cases, the silicon carbide film formed on the SiC wafer B1 is N-type for TMA and P-type for NH ₃ .

  A gas such as Al (aluminum) may be used as the dopant gas. In this case, the silicon carbide film formed on SiC wafer B1 is P-type.

  In the above-described embodiment, the case where the silicon carbide film is formed on the SiC wafer B1 using the horizontal hot wall CVD apparatus has been described. However, the vertical hot wall CVD apparatus may be used.

  In the above-described embodiment, the silicon carbide film is formed on the SiC wafer B1, but another semiconductor film such as a gallium nitride film (GaN) may be formed on the SiC wafer B1.

  The semiconductor film forming apparatus according to the present invention can be used, for example, in a lateral hot wall CVD apparatus that forms a silicon carbide film on a SiC wafer by epitaxial growth.

DESCRIPTION OF SYMBOLS 1 ... Furnace part 11 ... Quartz tube 13 ... Heat insulating material 15 ... Susceptor 17 ... Convex-shaped heating element 21 ... Upper pipe line 23... Lower pipe line 25... Reaction chamber B 1... SiC wafer

Claims (5)

A chemical vapor deposition semiconductor film forming apparatus for forming a semiconductor film by chemical vapor deposition on a substrate placed at a predetermined position while flowing a predetermined gas from upstream to downstream,
A susceptor for heating the gas, wherein the substrate is directly or indirectly mounted;
A convex object that disturbs the flow of the gas on the upstream side of the gas from the mounting position of the substrate;
I have a,
The chemical vapor deposition semiconductor film forming apparatus , wherein the convex object is disposed upstream of the gas from the mounting position of the substrate and emits heat . The chemical vapor deposition semiconductor film forming apparatus according to claim 1 ,
The chemical vapor deposition semiconductor film forming apparatus, wherein the semiconductor film is a silicon carbide film. The chemical vapor deposition semiconductor film forming apparatus according to claim 1 or 2 ,
The convex-shaped object is a chemical vapor deposition semiconductor film forming apparatus having a mushroom shape. In the chemical vapor deposition semiconductor film forming apparatus according to any one of claims 1 to 3 ,
2. The chemical vapor deposition semiconductor film forming apparatus, wherein the convex is made of the same material as the susceptor. A chemical vapor deposition semiconductor film forming method for forming a semiconductor film using the chemical vapor deposition semiconductor film forming apparatus according to any one of claims 1 to 4 ,
From the mounting position of the substrate mounted directly or indirectly on the susceptor, the gas flow is disturbed on the upstream side of the gas, and the semiconductor film is heated while heating the gas on the upstream side. A method of forming a chemical vapor deposition semiconductor film.

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