JP5087983B2 - Silicon carbide semiconductor crystal film forming apparatus and silicon carbide semiconductor crystal film forming method - Google Patents

Description

  The present invention relates to a semiconductor crystal film forming apparatus and a semiconductor crystal film forming method for forming a semiconductor crystal film, and more particularly to a silicon carbide semiconductor crystal film forming apparatus and a silicon carbide semiconductor crystal film for forming a silicon carbide (SiC) single crystal film. The present invention relates to a forming apparatus.

  Conventionally, an epitaxial growth method by chemical vapor deposition (CVD) is known as a method for forming a silicon carbide single crystal film. FIG. 8 is an explanatory view showing the structure of a semiconductor crystal film forming apparatus according to the prior art. FIG. 9 is a cross-sectional view showing a cross section along the line D-D ′ of the semiconductor crystal film forming apparatus shown in FIG. 8.

  A semiconductor crystal film forming apparatus 100 shown in FIG. 8 is a horizontal hot wall induction heating type semiconductor crystal film forming apparatus. The semiconductor crystal film forming apparatus 100 has a hot wall 102 inside a quartz tube 104 via a heat insulating material 103. The hot wall 102 is made of graphite (graphite). The inner wall surface of the hot wall 102 may be coated with silicon carbide. The heat insulating material 103 is made of carbon felt. A coil 101 is provided outside the quartz tube 104.

  When forming a silicon carbide crystal film with the semiconductor crystal film forming apparatus 100, first, a wafer 106 is placed on the hot wall 102. Next, current is passed through the coil 101 to inductively heat the hot wall 102. Then, a reaction gas 105 is injected into the quartz tube 104. The reaction gas 105 is a gas in which a precursor gas such as monosilane or propane and a carrier gas such as hydrogen are mixed. The wafer 106 and the reaction gas 105 are heated by heat transfer and heat radiation from the hot wall 102. As a result, the reaction gas 105 causes a thermochemical reaction, and a silicon carbide crystal film grows on the front surface of the wafer 106.

  As such a semiconductor crystal film forming apparatus, a semiconductor crystal in which the entire inner wall surface of a susceptor (a member corresponding to the hot wall in FIG. 8) or the surface facing the wafer is coated with a metal carbide such as tantalum carbide (TaC). A film forming apparatus is known (see Patent Documents 1 to 3 below).

JP 2005-508097 gazette JP 2006-028625 A JP 2005-109408 A

  However, the above-described prior art has a problem that the temperature of the wafer in the semiconductor crystal film forming apparatus is uneven and the thickness of the semiconductor crystal film is uneven. In designing a semiconductor crystal film forming apparatus, the temperature distribution of the wafer during heating is important. For example, silicon carbide has many crystal polymorphs (polytypes) depending on the crystal stack structure, and among these crystal polymorphs, the 4H type having a large band gap is used for manufacturing power devices. SiC (hereinafter referred to as “4H—SiC”). When 4H—SiC is grown at a low temperature, a stacking fault occurs on the surface of the crystal film. Therefore, when a 4H—SiC crystal film is formed, the temperature in the semiconductor crystal film forming apparatus must be relatively high, such as 1500 ° C. or higher.

  The wafer in the semiconductor crystal film forming apparatus is heated by the upper surface of the inner wall of the hot wall (surface on which the wafer front surface faces), the lower surface (surface on which the wafer back surface contacts), heat radiation from the side surface, and heat conduction from the lower surface. Is done. In the central portion of the hot wall, the wafer is heated by heat radiation from the upper and lower surfaces of the hot wall and heat conduction from the lower surface. On the other hand, in the region close to the side surface of the hot wall, the wafer is heated by heat radiation from the upper and lower surfaces of the hot wall and heat conduction from the lower surface, and by heat radiation from the side surface of the hot wall. Therefore, the wafer located in the region close to the side surface of the hot wall has a higher temperature than the central portion of the hot wall. The temperature of the wafer has a great influence on the growth of the semiconductor crystal film. For this reason, when unevenness occurs in the temperature of the wafer in the semiconductor crystal film forming apparatus, the thickness of the semiconductor crystal film is biased.

  In order to avoid the occurrence of unevenness in the temperature of the wafer, a method of arranging the wafer in a region away from the side surface of the hot wall can be considered. However, when the diameter of the wafer is large or when processing a plurality of wafers at the same time, the wafer cannot be disposed in a region away from the side surface unless the hot wall size is increased. Moreover, when the size of the hot wall is increased, there is a problem that the semiconductor crystal film forming apparatus main body is enlarged. Furthermore, when the size of the hot wall is increased, the heat capacity of the hot wall is increased, so that there is a problem that the temperature raising / lowering rate of the hot wall is lowered.

  Further, when the entire surface of the hot wall or the surface facing the wafer is coated with metal carbide as in the semiconductor crystal film forming apparatus according to Patent Documents 1 to 3 described above, the amount of heat radiation from the surface coated with the metal carbide is increased. Get smaller. For this reason, the back surface of the wafer is heated by heat conduction from the bottom surface, whereas the front surface of the wafer is cooled by the cold reaction gas, and a large temperature difference is generated between the wafer and the hot wall. Due to this temperature difference, there is a problem that the coating material of the hot wall is deposited on the back surface of the wafer, and the coating of the hot wall is peeled off or the back surface of the wafer is contaminated.

  In order to solve the above-described problems caused by the prior art, the present invention can heat a wafer so that the temperature of the wafer is uniform to form a semiconductor crystal film having a uniform thickness. An object is to provide a forming apparatus and a silicon carbide semiconductor crystal film forming apparatus.

In order to solve the above-described problems and achieve the object, a silicon carbide semiconductor crystal film forming apparatus according to a first invention supplies a gas into a gas flow path surrounded by a hot wall that is induction-heated by a coil. A silicon carbide semiconductor crystal film forming apparatus for forming a silicon carbide semiconductor crystal film on a surface of a wafer placed in a gas flow path, wherein the hot wall is made of graphite, , a surface other than the front surface and the opposite faces of the surface and the wafer the wafer is placed is covered with tantalum carbide, the front surface facing a surface and the wafer the wafer is placed The surface to be covered is not covered with the tantalum carbide .

The silicon carbide semiconductor crystal film forming apparatus according to the second aspect of the present invention provides a surface of a wafer placed in a gas flow path by supplying a gas into a gas flow path surrounded by a hot wall that is induction-heated by a coil. A silicon carbide semiconductor crystal film forming apparatus for forming a silicon carbide semiconductor crystal film on the surface, wherein the hot wall is made of graphite, and the wafer is disposed on the inner wall surface of the hot wall and the wafer A plate-like member formed of graphite and coated with tantalum carbide is installed on a surface other than the surface facing the front surface, and the surface on which the wafer is installed and the front surface of the wafer are opposed. The surface to be formed is characterized in that the plate-like member is not installed .

A silicon carbide semiconductor crystal film forming apparatus according to a third aspect of the present invention is the first or second aspect of the invention, wherein the wafer is installed on the inner wall surface of the hot wall and the front surface of the wafer. The surface facing is provided with a plate-like member made of graphite and covered with silicon carbide or a plate-like member made of silicon carbide.

According to a fourth aspect of the present invention, there is provided a silicon carbide semiconductor crystal film forming apparatus, comprising: supplying a gas into a gas flow path surrounded by a hot wall that is induction-heated by a coil; A silicon carbide semiconductor crystal film forming apparatus for forming a silicon carbide semiconductor crystal film, comprising a plate-like member for placing the wafer formed of graphite and covered with silicon carbide, wherein the hot wall is formed of graphite A plate-like member made of graphite and covered with silicon carbide or a plate-like member made of silicon carbide on the inner wall surface of the hot wall parallel to the plate-like member on which the wafer is installed The surface of the inner wall of the hot wall other than the surface parallel to the plate member on which the wafer is installed is graphite. Is formed, characterized in that coated plate-like member with tantalum carbide is provided.

The fifth silicon carbide semiconductor crystal film forming apparatus according to the invention of the fourth aspect, the plate-like member for mounting the wafer is characterized in that provided in plural.

According to a sixth aspect of the present invention, there is provided a silicon carbide semiconductor crystal film forming method, comprising: supplying a gas into a gas channel surrounded by a hot wall that is induction-heated by a coil; A method for forming a silicon carbide semiconductor crystal film comprising: forming a silicon carbide semiconductor crystal film, wherein the hot wall is formed of graphite, and a surface on which the wafer is placed among the inner wall surfaces of the hot wall and the wafer front surface facing the surface other than the surface of the are overturned be in tantalum carbide, front and opposite sides of plane and the wafer the wafer is placed is coated with the tantalum carbide and yet not, characterized in that by supplying a gas to form a silicon carbide semiconductor crystal film on a surface of the wafer in the hot wall.

According to the first to sixth invention, among the inner wall surface of the hot wall, the front surface or back surface contact or face-to-face non-oriented surfaces of the wafer, i.e., the side surface of the hot wall is coated with tantalum carbide Or a plate-like member coated with tantalum carbide. The thermal emissivity of tantalum carbide is lower than that of graphite or silicon carbide. For this reason, the heat radiated from the side surface of the hot wall can be suppressed, and the temperature distribution in the width direction in the gas channel can be made uniform.

According to the fourth or fifth invention, the plate-like member can be exchanged every time the film forming process is performed on the wafer. Thereby, the influence of peeling of particles and coatings can be reduced, and a semiconductor crystal film of stable quality can be formed. In addition, if the whole plate-shaped member on which the wafers are arranged is taken out from the apparatus after the formation of the semiconductor crystal film, the heat capacity of the plate-shaped member is small, so that it can be cooled in a short time and the film forming process can be performed in a short time. It can be finished with. Furthermore, according to the fifth invention, since a plurality of plate-like members for installing the wafer are provided, the semiconductor crystal film can be formed on the plurality of wafers by one process.

  According to the silicon carbide semiconductor crystal film forming apparatus and the silicon carbide semiconductor crystal film forming method according to the present invention, the wafer is heated so that the temperature of the wafer is uniform, and the semiconductor crystal film having a uniform film thickness is formed. Can do.

  Exemplary embodiments of a silicon carbide semiconductor crystal film forming apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is an explanatory diagram of the structure of the semiconductor crystal film forming apparatus according to the first embodiment. FIG. 2 is a cross-sectional view showing a cross section taken along line AA ′ of the semiconductor crystal film forming apparatus shown in FIG. A semiconductor crystal film forming apparatus 10 shown in FIG. 1 includes a coil 1, a hot wall 2, a heat insulating material 3, and a quartz tube 4. When the semiconductor crystal film is formed by the semiconductor crystal film forming apparatus 10, the wafer 6 is placed on the hot wall 2, current is passed through the coil 1, and the hot wall 2 is induction heated. In this case, the hot wall also serves as a susceptor. A susceptor may be provided separately from the hot wall. Then, a reaction gas 5 is introduced into the quartz tube 4 to epitaxially grow a semiconductor crystal film on the front surface of the wafer 6.

  Here, of the inner wall surface of the hot wall 2, the side surfaces (the surface other than the surface on which the wafer 6 is installed and the surface facing the front surface of the wafer 6) are coated with tantalum carbide (TaC) ( Tantalum carbide coating 7). The tantalum carbide coat 7 can suppress the heat radiation from the side surface of the hot wall 2 and suppress the occurrence of unevenness in the temperature of the wafer 6.

  Tantalum carbide has a lower thermal emissivity than silicon carbide coating the entire hot wall 2. For example, the thermal emissivity of silicon carbide at 1500 ° C. is 0.82, and the thermal emissivity of graphite is 0.72. On the other hand, the thermal emissivity of tantalum carbide at 1500 ° C. is 0.08. Further, tantalum carbide is stable even at a high temperature of 1500 ° C. or higher and has resistance to high-temperature hydrogen. Thus, tantalum carbide is a material suitable for coating the side surface of the hot wall 2.

  FIG. 3 is a graph showing the temperature distribution of the wafer heated by the semiconductor crystal film forming apparatus. In FIG. 3, the vertical axis represents the wafer temperature (° C.), and the horizontal axis represents the relative position (mm) from the center of the hot wall width direction (direction along the line segment AA ′ or line DD ′). It is. Also, the black circles (●) in FIG. 3 indicate the temperature of the wafer heated by the semiconductor crystal film forming apparatus 10 according to the first embodiment, and the white squares (□) in FIG. 3 indicate the semiconductor crystal according to the prior art shown in FIG. The temperature of the wafer heated by the film forming apparatus is shown.

  As shown in FIG. 3, the temperature of the wafer heated by the semiconductor crystal film forming apparatus according to the prior art is uniform near the center of the hot wall. However, as the temperature approaches the side of the hot wall, the temperature of the wafer rises due to the influence of radiant heating from the side. On the other hand, the wafer heated by the semiconductor crystal film forming apparatus 10 according to the first embodiment has a region having a uniform temperature increased by 60% or more as compared with the wafer heated by the semiconductor crystal film forming apparatus according to the prior art. Yes. Therefore, the semiconductor crystal film forming apparatus 10 according to the first embodiment can form a semiconductor crystal film on a wafer having a large diameter as compared with the semiconductor crystal film forming apparatus according to the prior art.

  Next, the film thickness distribution of the semiconductor crystal film formed by the semiconductor crystal film forming apparatus 10 according to the first embodiment and the film thickness distribution of the semiconductor crystal film formed by the semiconductor crystal film forming apparatus according to the prior art shown in FIG. The result of comparing with will be described. Note that the hot walls of both semiconductor crystal film forming apparatuses have gas flow paths having a width of 10 mm and a height of 40 mm. Further, the inner wall of the hot wall of the semiconductor crystal film forming apparatus according to the prior art is coated entirely with silicon carbide.

  A semiconductor crystal film was formed as follows. First, a wafer having a diameter of 3 inches is placed in the gas flow path. Next, hydrogen gas with a flow rate of 20 sml is flowed as a carrier gas. Subsequently, it is heated to 1600 ° C. in a reduced-pressure atmosphere of 80 Torr. Then, a monosilane gas with a flow rate of 6.3 sccm and a propane gas with a flow rate of 1.8 sccm are each flowed for 1 hour.

  A silicon carbide semiconductor crystal film was formed on the surface of the wafer 6 by such treatment. Then, a value obtained by dividing the standard deviation of the film thickness distribution by the average value of the film thickness (standard deviation / average value) was calculated. In the semiconductor crystal film forming apparatus according to the prior art, the standard deviation / average value of the semiconductor crystal film was 30%. In contrast, in the semiconductor crystal film forming apparatus according to the first embodiment, the standard deviation / average value of the semiconductor crystal film was improved to 10%.

  Further, in the semiconductor crystal film forming apparatus 10 according to the first exemplary embodiment, the tantalum carbide coat 7 is not formed on the surface on which the wafer 6 is installed and the surface facing the front surface of the wafer 6. For this reason, the wafer 6 is heated by heat radiation to the front surface in addition to heat conduction and heat radiation to the back surface. For this reason, the temperature difference between the wafer 6 and the hot wall 2 can be reduced, and the peeling of the coating material on the hot wall and the contamination of the back surface of the wafer 6 due to the temperature difference between the wafer 6 and the hot wall 2 are reduced. be able to.

  Tantalum carbide does not have high adhesion with silicon carbide particles. For this reason, when the upper surface of the inner wall of the hot wall 2 (the surface opposite to the front surface of the wafer 6) is coated with tantalum carbide, the silicon carbide particles easily fall onto the front surface of the wafer 6. Therefore, it is desirable that the upper surface of the inner wall of the hot wall 2 is not coated with tantalum carbide.

  As shown in FIG. 4, instead of the tantalum carbide coat 7, the side surface of the hot wall may be covered with a graphite plate (hereinafter referred to as “TaC graphite plate”) 8 coated with tantalum carbide. FIG. 4 is an explanatory diagram of a modification of the semiconductor crystal film forming apparatus according to the first embodiment. Since the TaC graphite plate 8 can be removed, the TaC graphite plate 8 can be exchanged when particles adhere or the tantalum carbide coating is peeled off. Thereby, since the state in the semiconductor crystal film forming apparatus can be kept uniform, a semiconductor crystal film of stable quality can be formed.

(Embodiment 2)
FIG. 5 is an explanatory diagram of the structure of the semiconductor crystal film forming apparatus according to the second embodiment. 6 is a cross-sectional view showing a cross section taken along line BB ′ of the semiconductor crystal film forming apparatus shown in FIG. Moreover, FIG. 7 is explanatory drawing to which the area | region C of sectional drawing shown in FIG. 6 was expanded. A semiconductor crystal film forming apparatus 20 shown in FIG. 5 includes a coil 1, a hot wall 2, a heat insulating material 3, and a quartz tube 4 similarly to the semiconductor crystal film forming apparatus 10 shown in FIG. The side surface of the hot wall 2 is covered with a TaC graphite plate 8 coated with tantalum carbide.

  The upper and lower surfaces of the hot wall 2 are covered with an SiC graphite plate 9, and a plurality of SiC graphite plates 9 are parallel to the SiC graphite plate 9 covering the upper and lower surfaces (longitudinal direction). Are lined up. The SiC graphite plate 9 is obtained by coating the surface of the graphite plate with silicon carbide. The SiC graphite plate 9 is supported by unevenness formed on the surface of the TaC graphite plate 8, for example, as shown in FIG.

  When the semiconductor crystal film is formed by the semiconductor crystal film forming apparatus 20, the wafer 6 is placed on each SiC graphite plate 9 (excluding the plate covering the upper and lower surfaces of the hot wall 2), and a current is passed through the coil 1. The hot wall 2 is induction heated. Then, a reaction gas 5 is injected into the quartz tube 4 to epitaxially grow a semiconductor crystal film on the front surface of the wafer 6. As described above, the semiconductor crystal film forming apparatus 20 can form the semiconductor crystal films on the plurality of wafers 6 in one process, as compared with the semiconductor crystal film forming apparatus 10 according to the first embodiment.

  The reason why the SiC graphite plate 9 is used as a plate on which the wafers 6 are arranged is because the thermal radiation rate of silicon carbide is high first, and secondly, the adhesion with silicon carbide particles is high. 5 and 6 show a configuration in which wafers 6 are arranged on three SiC graphite plates 9 and processing is performed at the same time. By adjusting the number of SiC graphite plates 9, the number of wafers that can be processed simultaneously is as follows. It can be adjusted appropriately.

  As described above, in the semiconductor crystal film forming apparatus 20 according to the second embodiment, the side surface of the hot wall 2 is covered with the TaC graphite plate 8 and the upper and lower surfaces of the hot wall 2 are covered with the SiC graphite plate 9. This makes it possible to make uniform the temperature distribution of the wafer by effectively using the heat radiation from the upper and lower surfaces of the hot wall while avoiding the heat radiation from the side surface of the hot wall.

  Further, since the graphite plate covering each surface of the hot wall 2 is removable, it can be exchanged every time a film is formed. Thereby, the influence of peeling of particles and coatings can be reduced, and a semiconductor crystal film of stable quality can be formed. Further, if the SiC graphite plate 9 on which the wafers 6 are arranged is taken out from the apparatus after the semiconductor crystal film is formed, the SiC graphite plate 9 can be cooled in a short time because the heat capacity of the SiC graphite plate 9 is small. Can be completed in a short time. In this embodiment, the SiC graphite plate is used, but the same effect can be obtained even if a plate made of silicon carbide is substituted.

  As described above, the silicon carbide semiconductor crystal film forming apparatus and the silicon carbide semiconductor crystal film forming method according to the present invention are useful for forming a semiconductor crystal film having a uniform film thickness, particularly for the manufacture of power devices. It is suitable for forming a 4H—SiC crystal film to be used.

1 is an explanatory diagram showing a structure of a semiconductor crystal film forming apparatus according to a first embodiment; It is sectional drawing which shows the cross section along line segment A-A 'of the semiconductor crystal film forming apparatus shown in FIG. It is a graph which shows the temperature distribution of the wafer heated with the semiconductor crystal film forming apparatus. FIG. 6 is an explanatory view showing a modification of the semiconductor crystal film forming apparatus according to the first embodiment. FIG. 6 is an explanatory diagram showing a structure of a semiconductor crystal film forming apparatus according to a second embodiment. It is sectional drawing which shows the cross section along line segment B-B 'of the semiconductor crystal film forming apparatus shown in FIG. It is explanatory drawing which expanded the area | region C of sectional drawing shown in FIG. It is explanatory drawing which shows the structure of the semiconductor crystal film forming apparatus by a prior art. It is sectional drawing which shows the cross section along line segment D-D 'of the semiconductor crystal film forming apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coil 2 Hot wall 3 Heat insulating material 4 Quartz tube 5 Reaction gas 6 Wafer 7 Tantalum carbide coating 8 TaC graphite plate 9 SiC graphite plate 10,20 Semiconductor crystal film formation apparatus

Claims (6)

A silicon carbide semiconductor crystal film forming apparatus that supplies a gas into a gas flow path surrounded by a hot wall that is induction-heated by a coil and forms a silicon carbide semiconductor crystal film on a surface of a wafer placed in the gas flow path. There,
The hot wall is made of graphite,
Of the inner wall surface of the hot wall, surfaces other than the surface on which the wafer is installed and the surface facing the front surface of the wafer are coated with tantalum carbide, and the surface on which the wafer is installed and the surface A silicon carbide semiconductor crystal film forming apparatus , wherein a surface facing a front surface of a wafer is not covered with the tantalum carbide. A silicon carbide semiconductor crystal film forming apparatus that supplies a gas into a gas flow path surrounded by a hot wall that is induction-heated by a coil and forms a silicon carbide semiconductor crystal film on a surface of a wafer placed in the gas flow path. There,
The hot wall is made of graphite,
Of the inner wall surface of the hot wall, the surface other than the surface on which the wafer is installed and the surface facing the front surface of the wafer is provided with a plate-like member formed of graphite and coated with tantalum carbide. A silicon carbide semiconductor crystal film forming apparatus , wherein the plate-like member is not installed on a surface on which the wafer is installed and a surface opposite to the front surface of the wafer . Of the inner wall surface of the hot wall, the surface on which the wafer is placed and the surface facing the front surface of the wafer are plate members made of graphite and covered with silicon carbide, or plate shapes made of silicon carbide The member is installed, The silicon carbide semiconductor crystal film forming apparatus of Claim 1 or 2 characterized by the above-mentioned. A silicon carbide semiconductor crystal film forming apparatus that supplies a gas into a gas flow path surrounded by a hot wall that is induction-heated by a coil and forms a silicon carbide semiconductor crystal film on a surface of a wafer placed in the gas flow path. There,
A plate-like member for installing the wafer formed of graphite and covered with silicon carbide;
The hot wall is made of graphite,
A plate-like member made of graphite and covered with silicon carbide or a plate-like member made of silicon carbide is placed on the inner wall surface of the hot wall parallel to the plate-like member on which the wafer is placed. And
Of the inner wall surface of the hot wall, a plate-like member formed of graphite and coated with tantalum carbide is provided on a surface other than a surface parallel to the plate-like member on which the wafer is installed. An apparatus for forming a silicon carbide semiconductor crystal film.   The silicon carbide semiconductor crystal film forming apparatus according to claim 4, wherein a plurality of plate-like members for installing the wafer are provided. A silicon carbide semiconductor crystal film forming method for forming a silicon carbide semiconductor crystal film on a surface of a wafer placed in a gas flow path surrounded by a hot wall induction-heated by a coil and placed in the gas flow path There,
The hot wall is made of graphite,
Of the inner wall surface of the hot wall, front surface which faces the other surface side and the wafer the wafer is placed is overturned be in tantalum carbide, the surface wherein the wafer is placed and The surface facing the front surface of the wafer is not coated with the tantalum carbide,
A method for forming a silicon carbide semiconductor crystal film, comprising: supplying a gas into the hot wall to form a silicon carbide semiconductor crystal film on a surface of the wafer.

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