JP6069545B2 - Evaluation method of SiC epitaxial wafer - Google Patents

Description

The present invention relates to a method for the evaluation of the SiC epitaxial web leaves.

  Silicon carbide (SiC) has characteristics such as a dielectric breakdown electric field that is an order of magnitude larger than silicon (Si), a band gap that is three times larger, and a thermal conductivity that is about three times higher. Application to high temperature operation devices is expected. As the SiC epitaxial wafer, a SiC single crystal wafer processed from a bulk single crystal of SiC produced by a sublimation method or the like is used as a substrate for forming an SiC epitaxial film. Usually, a chemical vapor deposition (Chemical Vapor Deposition: It is manufactured by growing a SiC epitaxial film that becomes an active region of a SiC semiconductor device by CVD.

As a cause of deteriorating the quality of the SiC epitaxial film, a triangular defect (hereinafter referred to as “triangular defect”) is known. This triangular defect is formed in the direction in which the apex of the triangle and its opposite side (base) are aligned in order along the step flow growth direction (Non-patent Document 3). That is, the opposite side (bottom side) of the triangular defect is arranged in a direction orthogonal to the <11-20> direction. There are a number of possible causes of this triangular defect. For example, damage such as polishing scratches remaining on the substrate (wafer) surface (Patent Document 1), two-dimensional nuclei formed on the terrace during step flow growth ( Patent Document 2), starting from a dissimilar polytype crystal nucleus (Non-Patent Document 1) formed at the interface between the substrate and the epitaxial film in the supersaturated state in the initial stage of growth, and a minute fragment of the SiC film described later There is. Triangular defects grow with the growth of the SiC epitaxial film. That is, along with step flow growth, the above starting point is used as the apex of a triangle, and the area grows while maintaining a similar triangular shape (see the schematic diagram in FIG. 2). Therefore, generally, the triangular defect that has occurred at the beginning of the growth of the SiC epitaxial film has a larger size, and the depth of the starting point in the film can be estimated from the size of the triangular defect.
In order to improve the yield in mass production of SiC epitaxial wafers, it is indispensable to reduce such triangular defects, and Patent Documents 1 and 2 propose measures according to the cause for the reduction.

In addition to the above-mentioned triangular defects, as a cause of deteriorating the quality of the SiC epitaxial film, an SiC film deposited on a ceiling (top plate) disposed above and facing the upper surface of the susceptor having a wafer mounting portion for mounting a wafer Is peeled off, and there is a fine fragment (hereinafter referred to as “downfall”) of the SiC film that has fallen onto the SiC single crystal wafer or the SiC epitaxial film. This downfall can also be a starting point for triangular defects.
Here, during the growth of the SiC epitaxial film, it is necessary to heat the SiC single crystal wafer as a substrate to a high temperature and maintain the temperature. This heating and holding method is mainly performed on the lower surface side of the susceptor and / or the sealing. The method of heating using the heating means arrange | positioned at the upper surface side of this is used (patent document 3, nonpatent literature 2, 3). In the case of heating the sealing, one that is heated by high-frequency induction heating by an induction coil is generally used, and one made of carbon suitable for high-frequency induction heating is usually used.

During the formation of the SiC epitaxial film, SiC deposition occurs not only on the SiC single crystal wafer but also on the ceiling. When the film formation is repeated, the amount of SiC deposited on the ceiling increases, so that the problem of downfall becomes apparent especially in mass production.
In order to improve the yield in mass production of SiC epitaxial wafers, it is indispensable to reduce downfall. In Patent Document 4, a cover plate that covers the wafer is disposed on the SiC single crystal wafer for the reduction, A configuration for preventing the downfall from falling on the SiC single crystal wafer or the SiC epitaxial film is disclosed.

Japanese Patent No. 4581081 JP 2009-256138 A JP-T-2004-507897 JP 2009-164162 A JP 2011-49496 A

Journal of Applied Physics 105 (2009) 074513 Materials Science Forum Vols. 483-485 (2005) pp141-146 Materials Science Forum Vols. 556-557 (2007) pp57-60

  However, with regard to triangular defects, the present situation is that the triangular defect density has not been sufficiently reduced even if the methods disclosed in Patent Documents 1 and 2 are employed. One of the reasons is the existence of triangular defects whose cause is not well understood.

  As for the downfall, the method disclosed in Patent Document 4 can prevent the downfall falling from the ceiling to the SiC epitaxial film grown on or above the SiC single crystal wafer. The cause of SiC deposition (or SiC film growth) on the sealing itself cannot be suppressed. Therefore, it is necessary to clean the ceiling. In this case, there is a problem that the operating rate of the apparatus is lowered. In addition, since SiC is deposited on the lower surface of the cover plate, there is a problem that if the film formation is repeated, a downfall from the cover plate occurs.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a SiC epitaxial wafer having a low surface density of triangular defects starting from a material piece of a member in a chamber and a method for evaluating the same.

  The present inventors first discovered a triangular defect starting from a material piece of a member in the chamber. That is, a new type of triangular defect has been found in which a material piece of a member in a chamber falls on a SiC single crystal wafer or a SiC epitaxial film in the middle of growth for some reason and a triangular defect grows from that. Conventionally, as described above, as a starting point of triangular defects, polishing scratches remaining on the surface of the substrate (wafer) or crystal nuclei of different polytypes generated on the step have been known. The defect originates from a piece of material of the member in the chamber. As a result of discovering this new type of triangular defect and intensive studies to reduce the triangular defect, the present inventors have completed the present invention.

FIG. 1A shows an optical microscope image of a triangular defect starting from a material piece of a member in a typical chamber. The optical microscope used was Olympus MX51.
The SiC epitaxial wafer shown in FIG. 1 (a) uses a hot wall SiC CVD (VP2400HW) manufactured by Ixtron, which is a mass production type multi-susceptor (automatic revolution) type epitaxial wafer manufacturing apparatus, without using a shielding plate. A SiC epitaxial wafer in which a SiC epitaxial film is formed on a 4H-SiC single crystal substrate with an off angle of 4 ° using a graphite as the sealing, and the 80th production lot (ie, in the chamber) And after the film formation corresponding to the SiC epitaxial film of 800 μm).

When observing a SiC epitaxial wafer using an optical microscope, the defects on the surface are usually observed while focusing on the surface of the epitaxial film. FIG. 1B is an optical microscope image obtained by observing the same triangular defect with the focus on the surface of the epitaxial film as usual.
On the other hand, the present inventors usually shift the focus on the surface and focus on the interface between the SiC single crystal substrate and the epitaxial film, thereby blackening the tip of the triangular defect (in the direction away from the opposite side). A visible foreign substance (a black spot ("triangular defect origin") visible in the center of the circle) is identified and analyzed in detail to identify the origin of the foreign substance (the material piece of the member in the chamber), and the chamber It was discovered that this was a new type of triangular defect that had not been known so far, starting from the piece of material of the inner member.

FIG. 2 is a transmission electron microscope (TEM) image obtained for the same SiC epitaxial wafer. A transmission electron microscope (HF-2200 manufactured by Hitachi High-Technologies Corporation) was used.
The diagram shown on the right side of the TEM image in FIG. 2 schematically shows the starting point of the triangular defect and the triangular defect grown therefrom. A portion surrounded by a square indicates the range indicated by the TEM image, and the TEM image is an observation image near the starting point of the triangular defect. Further, the figure shown below schematically shows a cross section near the triangular defect.
In the case of this triangular defect, the foreign substance serving as the starting point of the triangular defect exists at a distance of about 7 μm in the horizontal direction from the apex of the triangle, and the horizontal distance from the starting point to the opposite side of the triangle is about 143 μm.

FIG. 3 shows the origin of triangular defects in a SiC epitaxial wafer manufactured under the same conditions as in the above SiC epitaxial wafer except that a shielding plate in which a graphite base material is coated with a tantalum carbide (TaC) film is used on the lower surface of the sealing. A transmission electron microscope (TEM) image in the vicinity of (foreign matter) is shown.
The portion of the triangular defect starting from the foreign material is made of 3C—SiC single crystal, and the portion of the periphery of the triangular defect that is normally epitaxially grown is made of 4H—SiC single crystal.

FIG. 4A shows the result of composition analysis of the foreign matter that is the starting point of the triangular defect shown in FIG. 3 by energy dispersive X-ray spectroscopy (EDX).
The peaks at 1.711 keV and 8.150 keV in FIG. 4A indicate tantalum (Ta), and no member made of a material containing tantalum (Ta) exists in the chamber other than the shielding plate. It can be determined that it is tantalum (Ta) of tantalum carbide (TaC), which is a coating material.
FIG. 4B shows the EDX analysis result of the EDX sample holder. It can be seen that the peaks of Zn, Cu, etc. appearing in FIG. 4A are derived from the material of the EDX holder.

  As described above, the present inventors start from a foreign substance (material piece) made of a material of a member in the chamber (in the case of FIG. 3, a shielding plate in the case of FIG. 3) at the tip of the triangular defect (a direction away from the opposite side). A new type of triangular defect was found.

When a triangular defect is observed using an optical microscope or an optical surface inspection apparatus using a laser beam (for example, Candela manufactured by KLA-Tencor), a starting point of the triangular defect and a non-clear one are observed. Conventionally, the cause of triangular defects whose origin is not clear is that the growth conditions are not suitable (for example, the growth temperature is too low), and normal step flow growth is not possible, and crystal nuclei of different polytypes have started. It was often interpreted as a thing. In contrast, the inventors have found that among the triangular defects whose starting points are not clear, there are those caused by the material pieces of the members in the chamber. At present, it cannot be determined whether all the triangular defects whose origins are not clear are caused by the material pieces of the members in the chamber. However, as described later, the present invention for reducing the triangular defects caused by the material pieces of the members in the chamber will be described. By doing so, it has succeeded in almost eliminating the triangular defects whose starting point is not clear, so it is considered that most of the triangular defects whose starting point is not clear are caused by the material pieces of the members in the chamber.
As described above, whether or not a triangular defect whose origin is not clear is a triangular defect starting from a material piece of a member in the chamber is identified by, for example, a method of shifting the focal point from the surface in the depth direction using an optical microscope. It is possible to obtain the surface density of the triangular defect starting from the material piece of the member in the chamber.

  Also, as the film formation is repeated (the number of manufacturing lots increases), the deterioration of the members in the chamber progresses and the amount of the material pieces falling increases, so the material pieces of the members in the chamber start from the repetition of film formation. The surface density of triangular defects increases. Here, the deterioration of the members in the chamber is, for example, in the case of a sealing in which a graphite base material is coated with a tantalum carbide (TaC) film, since the thermal expansion coefficient differs between the tantalum carbide film and the graphite base material. Stress is applied to the tantalum carbide film above and below the temperature due to repetition, the film peels off, the tantalum carbide film cracks and the graphite substrate generates dust, and the gas in the chamber and the sealing surface interact with each other. It refers to the sublimation of the sealing material by the action. Further, SiC is deposited on the ceiling and a SiC film grows. The SiC film and the tantalum carbide film have different coefficients of thermal expansion, and this difference in coefficient of thermal expansion also causes deterioration of the tantalum carbide film. Thus, the surface density of the triangular defect starting from the material piece of the member in the chamber is highly dependent on the number of film formation (or the number of production lots). When the number of film formations exceeds a predetermined number (depending on manufacturing conditions), deterioration of the members in the chamber progresses at once, and the surface density of triangular defects starting from the material pieces of the members in the chamber increases rapidly.

In contrast, triangular defects starting from damage such as polishing scratches on the surface of the substrate (wafer), or triangular defects starting from different types of polytype crystal nuclei formed due to inappropriate growth conditions Does not depend on the number of film formations. That is, the triangular defect caused by the substrate and the triangular defect caused by the growth condition do not depend on the number of times of film formation.
On the other hand, the triangular defect starting from the downfall also depends on the number of film formations. Downfall falls from the ceiling when no shielding plate is used, and falls from the shielding plate when a shielding plate is used, but the SiC film formed on the sealing or shielding plate when film formation is repeated This is because the film becomes thicker and more easily peeled off. As will be described later, when a shielding plate is used, at least the lower surface of the shielding plate is made of a material having a higher adhesion of the SiC film than the sealing, thereby reducing downfall as compared with the case where no shielding plate is used. Can do.
Accordingly, the triangular defects that increase due to repeated film formation include those starting from the material pieces of the members in the chamber and those starting from downfall. However, the triangular defect starting from the material piece of the member in the chamber has a feature that the starting point is not clear in an optical microscope image or an image by an optical surface inspection apparatus using laser light (hereinafter referred to as a “candela image”). On the other hand, the triangular defect starting from the downfall often has a clear starting point, so that it can usually be identified from an optical microscope image or a candela image. Even if a triangular defect whose origin is not clear is caused by downfall or other causes, the surface density is considered to be the upper limit of the surface density of the triangular defect starting from the material piece of the member in the chamber. Therefore, by managing the surface density, the upper limit of the surface density of the triangular defect starting from the material piece of the member in the chamber can be managed. Thereby, an SiC epitaxial wafer having a low surface density of triangular defects starting from a material piece of a member in a chamber is manufactured by managing an increase in the surface density of triangular defects whose starting point is not clear due to repeated film formation. Is possible.
If you want to measure and manage the density of triangular defects starting from the material pieces of the members in the chamber more strictly, analyze the composition of the foreign matter ahead of the triangular defects using energy dispersive X-ray analysis etc. Can be performed.

The material piece of the member in the chamber that becomes the starting point of the triangular defect has a minute lump formed on the wafer or on the growing SiC epitaxial film due to the deterioration of the member due to repeated film formation and peeling from the surface. It is thought to have fallen. Then, the member in the chamber that generates the material piece that becomes the starting point of the triangular defect is a member that is mainly disposed above the wafer, and the material piece that falls on the wafer from the other wall surfaces of the chamber or other members in the chamber. Is estimated to be negligible.
Therefore, in order to reduce the triangular defect starting from the material piece of the member in the chamber, the inventors covered the member arranged facing the wafer above the wafer with a material that generates less dust and sublimation. Regularly (for each production lot, each production lot, etc.), or irregularly, measure the surface density of triangular defects starting from the material pieces of the members in the chamber and manage the values, If the surface density of the triangular defect is exceeded, the SiC epitaxial wafer having a low triangular density starting from the material piece of the member in the chamber is manufactured by exchanging the member and then manufacturing the next SiC epitaxial wafer. He came up with the idea of manufacturing a wafer.

  As described above, the inventors discovered the existence of a new type of triangular defect starting from the material piece of the member in the chamber, and as a result of earnestly researching the problem of reducing the triangular defect, the book having the following means: I came up with the invention.

The present invention provides the following means in order to solve the above problems.
(1) A SiC epitaxial wafer having a SiC epitaxial layer on a SiC single crystal substrate having an off angle, which is present in the SiC epitaxial layer and is focused using an optical surface inspection apparatus using an optical microscope image or laser light. Is determined by shifting the position of the substrate from the surface of the epitaxial film of the SiC epitaxial wafer toward the interface between the epitaxial film and the SiC single crystal substrate, and the starting point identified is identified as the apex, and the apex and the apex along the step flow growth direction. A SiC epitaxial wafer characterized in that the surface density of triangular defects, which are triangular defects formed so as to face in the direction in which the bottoms that are opposite to each other are arranged in order, is 0.5 piece / cm ² or less.
(2) The SiC epitaxial wafer according to (1), wherein the starting point is a material piece of a member in the chamber.
(3) The SiC epitaxial wafer according to (2), wherein the starting material piece is made of carbon or silicon carbide.
(4) A method for evaluating a SiC epitaxial wafer having a SiC epitaxial layer on a SiC single crystal substrate having an off angle, and in the measurement of an image by an optical microscope image or an optical surface inspection apparatus using laser light, the position of a focal point From the surface of the epitaxial film of the SiC epitaxial wafer by shifting it from the surface of the epitaxial film to the interface between the epitaxial film and the SiC single crystal substrate, the starting point that can be found and identified as the apex, the starting point as the apex, and the apex along the step flow growth direction A method for evaluating an SiC epitaxial wafer, comprising a step of detecting a triangular defect which is a triangular defect formed in a direction in which bottoms which are opposite sides of the apex are arranged in order.
(5) The method for evaluating an SiC epitaxial wafer according to (4), wherein composition analysis of the triangular defect having the origin as a vertex is performed using an energy dispersive X-ray analysis method.

According to the SiC epitaxial wafer of the present invention, the surface density of triangular defects starting from a piece of material of a member in a chamber that has not been known and could not be reduced so far is as low as 0.5 pieces / cm ² or less. Therefore, it is possible to take a larger number of devices from one SiC epitaxial wafer than before.

  According to the SiC epitaxial wafer manufacturing method of the present invention, using a SiC epitaxial wafer manufacturing apparatus provided with a shielding plate, a material piece of a member in a chamber is used as a starting point for a SiC epitaxial film of a previously manufactured SiC epitaxial wafer. After measuring the surface density of the triangular defects to be measured, the structure including the process of manufacturing the next SiC epitaxial wafer was adopted, so that the SiC epitaxial layer with few triangular defects starting from the material pieces of the members in the chamber is included in the SiC epitaxial layer. A wafer can be manufactured. In addition, since a configuration using a surface that is opposed to the susceptor as a shielding plate, which is made of silicon carbide film or pyrolytic carbon film, or made of silicon carbide is adopted, the degradation of the shielding plate is difficult to proceed (silicon carbide film In the case of using a material coated with silicon carbide or silicon carbide, since the SiC film deposited on the shielding plate and the coating film or the material thereof are the same material, there is no difference in the coefficient of thermal expansion, so that deterioration occurs. In addition, when using a material coated with a pyrolytic carbon film, the difference in thermal expansion coefficient between the base material and the pyrolytic carbon film is small by using a carbon material base material as the shielding plate. Deterioration is difficult to progress.) The material pieces falling on the wafer from the shielding plate are reduced, and the shielding plate can be used for a longer time.

  According to the SiC epitaxial wafer manufacturing method of the present invention, if the surface density of the triangular defect starting from the material piece of the member in the chamber exceeds a predetermined density as a result of the measurement, the shielding plate is replaced. By adopting a configuration for manufacturing the next SiC epitaxial wafer, it is possible to manufacture a SiC epitaxial wafer having triangular defects having a predetermined surface density or less starting from a material piece of a member in the chamber.

  According to the SiC epitaxial wafer manufacturing method of the present invention, after measuring the surface density of triangular defects starting from the material pieces of the members in the chamber of the SiC epitaxial film of the previously manufactured SiC epitaxial wafer, Since the structure including the process of manufacturing the epitaxial wafer is adopted, it is possible to manufacture a SiC epitaxial wafer having few triangular defects starting from the material pieces of the members in the chamber in the SiC epitaxial layer. In addition, since the structure using the surface facing the susceptor as the top plate is covered with a silicon carbide film or a pyrolytic carbon film, or made of silicon carbide, the top plate is hardly deteriorated (silicon carbide film) In the case of using a material coated with silicon carbide or silicon carbide, since the SiC film deposited on the top plate and the coating film or the material thereof are the same material, there is no difference in the coefficient of thermal expansion, so that deterioration occurs. In addition, when using a material coated with a pyrolytic carbon film, the difference in thermal expansion coefficient between the base material and the pyrolytic carbon film is small by using a carbon material base material as the top plate. Deterioration is difficult to proceed.) While the material pieces falling on the wafer from the top plate are reduced, the top plate can be used for a longer time.

  According to the SiC epitaxial wafer manufacturing method of the present invention, when the surface density of the triangular defect starting from the material piece of the member in the chamber exceeds a predetermined density as a result of the measurement, the top plate is replaced. By adopting a configuration for manufacturing the next SiC epitaxial wafer, it is possible to manufacture a SiC epitaxial wafer having triangular defects having a predetermined surface density or less starting from a material piece of a member in the chamber.

  According to the SiC epitaxial wafer manufacturing apparatus of the present invention, close to the lower surface of the top plate so as to prevent deposits from adhering to the lower surface of the top plate and receive dust generated from the lower surface of the top plate. Since the shielding plate is disposed and the surface of the shielding plate facing the susceptor is covered with a silicon carbide film or a pyrolytic carbon film, or made of silicon carbide, the shielding is adopted. Since the material pieces falling from the plate onto the wafer are reduced, it is possible to manufacture a SiC epitaxial wafer having a low surface density of triangular defects starting from the material pieces of the members in the chamber.

  According to the SiC epitaxial wafer manufacturing apparatus of the present invention, the surface of the top plate facing the susceptor is covered with a silicon carbide film or a pyrolytic carbon film, or made of silicon carbide. Since it has been adopted, the number of material pieces falling on the wafer from the top plate is reduced, so that it is possible to manufacture a SiC epitaxial wafer having a low surface density of triangular defects starting from the material pieces of the members in the chamber.

FIG. 2 is an optical microscope image of a triangular defect starting from a material piece of a member in a typical chamber, (a) focusing on a foreign substance, (b) focusing on the surface of an epitaxial film. . It is a transmission electron microscope (TEM) image of the same SiC epitaxial wafer as FIG. It is a transmission electron microscope (TEM) image of the SiC epitaxial wafer manufactured using the shielding board which consists of graphite coat | covered with the tantalum carbide film | membrane. It is the measurement result by the energy dispersive X-ray analysis method of the same SiC epitaxial wafer as FIG. 3, Comprising: (a) It is the result of measuring a foreign material, (b) It is the result of measuring a sample holder. It is a cross-sectional schematic diagram which shows the manufacturing apparatus of the epitaxial wafer used in embodiment of this invention. It is a perspective view which shows the lower part side of the manufacturing apparatus of the epitaxial wafer along the A-A 'line of FIG. It is an expansion schematic diagram of the periphery of the shielding board shown in FIG. It is a candela image of an Example. (A) A candela image of Comparative Example 1. (B) A candela image of Comparative Example 2.

Hereinafter, an SiC epitaxial wafer to which the present invention is applied, an SiC epitaxial wafer manufacturing method, and an epitaxial wafer manufacturing apparatus will be described in detail with reference to the drawings.
In addition, the drawings used in the following description may show the features that are enlarged for the sake of convenience in order to make the features easier to understand, and the dimensional ratios of the respective components may be different from the actual ones. . In addition, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately changed and implemented without changing the gist thereof.

[SiC epitaxial wafer]
The SiC epitaxial wafer to which the present invention is applied is a SiC epitaxial wafer having a SiC epitaxial layer on a SiC single crystal substrate having an off angle, and starts from a material piece of a member in the chamber existing in the SiC epitaxial layer. The surface density of the triangular defect is 0.5 piece / cm ² or less.

  Since the triangular defect starting from the material piece of the member in the chamber is not a triangular defect caused by the substrate, there is no particular limitation on the SiC single crystal substrate.

  Any polytype substrate can be used as the SiC single crystal substrate, and 4H—SiC which is mainly used for producing a practical SiC device can be used. A SiC single crystal substrate processed from a bulk crystal produced by a sublimation method or the like is used as the substrate of the SiC device, and an SiC epitaxial film that becomes an active region of the SiC device is usually formed thereon by chemical vapor deposition (CVD). Form.

Further, any off-angle of the SiC single crystal substrate can be used, and there is no limitation, but from the viewpoint of cost reduction, a small off-angle, for example, 0.4 ° to 5 ° Is preferred. 0.4 ° is the lower limit of the off-angle at which step flow growth is possible.
In the case where the SiC single crystal substrate has a size up to about 2 inches, the off angle of the SiC single crystal substrate has been mainly 8 °. At this off-angle, the terrace width of the wafer surface is small and step flow growth can be easily obtained, but the larger the off-angle, the smaller the number of wafers obtained from the SiC ingot. Those with an off angle of about 4 ° are mainly used.
The lower the off-angle, the larger the terrace width of the surface of the SiC single crystal substrate. Therefore, the migration rate of the migration atoms taken into the step end, that is, the growth rate of the step end tends to vary, resulting in a slower growth rate. Steps with a fast growth rate catch up with these steps, and step bunching is likely to occur. In addition, for example, a 0.4 ° off-angle substrate has a terrace width 10 times that of a 4 ° off-angle substrate, and the step flow growth length is an order of magnitude longer. It should be noted that it is necessary to adjust the conditions of the step flow growth that has been used in the substrate.

As the SiC single crystal substrate, a substrate obtained by processing the growth surface of the SiC epitaxial layer into a convex shape can be used.
During the manufacture of a SiC epitaxial wafer (formation (growth) of a SiC epitaxial layer), the back surface of the SiC single crystal substrate is directly heated from a heated susceptor, but the front surface (formation surface of the SiC epitaxial layer) is a vacuum. Exposed to the space and not heated directly. Furthermore, since the carrier gas hydrogen flows over the front surface, heat is taken away. For these reasons, the front surface during epitaxial growth is at a lower temperature than the back surface. Due to this temperature difference, the magnitude of thermal expansion is smaller on the front surface than on the rear surface, and the SiC single crystal substrate is deformed so that the front surface is recessed during epitaxial growth. Therefore, by using a SiC single crystal substrate with a growth surface of the SiC epitaxial layer processed into a convex shape, the SiC single crystal substrate can be epitaxially grown in a state in which the dent (warp) of the substrate during epitaxial growth is eliminated. It becomes possible.

  The thickness of the SiC epitaxial layer is not particularly limited. For example, if the film is formed for 2.5 hours at a typical growth rate of 4 μm / h, the thickness becomes 10 μm.

[SiC epitaxial wafer manufacturing apparatus (first embodiment)]
FIG. 5 is a schematic sectional view showing a part of an epitaxial wafer manufacturing apparatus to which the present invention is applied, and FIG. 6 is a perspective view showing a lower side of the epitaxial wafer manufacturing apparatus along the line AA ′ in FIG. FIG. 7 is an enlarged schematic view of the periphery of the shielding plate shown in FIG.

An epitaxial wafer manufacturing apparatus 100 according to this embodiment is a CVD apparatus 100 as shown in FIG. 5, for example, and forms an epitaxial layer on the wafer surface while supplying a source gas into the chamber 1. A reaction space 4 between the susceptor 2 and the susceptor 2 having the plurality of placement portions 2b on which the wafer is placed and the plurality of placement portions 2b arranged in the circumferential direction. So that the deposits from the gas phase are prevented from adhering to the bottom surface of the ceiling 3 and the bottom surface of the ceiling 3. A shielding plate 10 disposed close to the lower surface, the shielding plate 10 having a surface facing the susceptor 2 covered with a silicon carbide film or a pyrolytic carbon film, or made of silicon carbide. Characterized in that the at it.
As the source gas, for example, a gas containing silane (SiH ₄ ) as a Si source, propane (C ₃ H ₈ ) as a C source, and a gas containing hydrogen (H ₂ ) as a carrier gas can be used. Can be used.

  The epitaxial wafer manufacturing apparatus 100 of the present embodiment is further disposed on the lower surface side of the susceptor 2 and the upper surface side of the ceiling, and heating means 6 and 7 for heating the wafer placed on the placement portion 2b, and the sealing 3 A gas introduction pipe 5 having a gas introduction port for introducing a source gas into the reaction space 4 from the center of the upper surface of the gas, and supplying the source gas released from the gas introduction port from the inside to the outside of the reaction space 4 With.

The heating means 6 and 7 are induction coils, which heat the ceiling 3 by high-frequency induction heating by the induction coil, heat the shielding plate 10 by radiant heat from the heated ceiling 3, and heat the wafer by radiant heat from the shielding plate 10. can do.
In this embodiment, the wafer is heated using heating means disposed on the lower surface side of the susceptor 2 and the upper surface side of the ceiling. However, the wafer may be configured to have heating means only on the lower surface side of the susceptor 2. .
In addition, the heating means for the SiC single crystal substrate is not limited to the above-described high-frequency induction heating, but may be resistance heating.

  The sealing 3 is supported by a support member 13 fixed to the gas introduction pipe 5 via a projection 12 provided so as to be located inside the opening 10b of the shielding plate 10 at the center of the lower surface thereof. ing. The protrusion 12 makes it difficult for gas to flow from the inner peripheral side of the shielding plate 12 to the ceiling 3.

  The sealing 3 may be made of a carbon material such as graphite or silicon carbide, or a carbon material base material coated with a film of SiC, pyrolytic carbon, TaC, or the like. It is preferably made of a material that is unlikely to generate sublimation due to generation of dust at high temperatures or interaction with gas in the chamber.

The shielding plate 10 is configured to be detachably attached to the chamber. In this embodiment, the outer peripheral portion 10a is placed on a support portion 11 provided on the inner wall surface of the chamber.
By supporting only the outer peripheral portion of the shielding plate, the gas introduction pipe 5 which is cooled to introduce the raw material gas without being decomposed into the shielding plate heated to high temperature by the heating means, and the shielding The shielding plate can be detachably attached to the chamber while avoiding contact with the inner peripheral portion of the plate (the central portion where the opening is formed).

The shielding plate 10 is preferably divided into a plurality of parts. In the present embodiment, as shown in FIG. 6, the shielding plate 10 includes a pair of members 10A and 10B divided into two at the center line. In this case, the pair of members 10A and 10B can be placed on the support portion 11 one by one, and can be removed from the support portion 11 one by one at the time of replacement, so that workability is high and at the time of placement, replacement, and maintenance. The risk of breakage is reduced.
Moreover, if the shielding board 10 is divided | segmented into plurality, a thermal stress will be relieve | moderated and generation | occurrence | production of curvature and a deformation | transformation will be suppressed.

The shielding plate 10 normally prevents dust generated from the lower surface of the graphite sealing 3 (graphite) from falling on the wafer, thereby reducing the surface density of triangular defects starting from the sealing material piece. it can. However, when the material piece of the shielding plate 10 falls on the wafer, a triangular defect starting from the material piece of the shielding plate is formed. Therefore, in order to suppress this, dust generation at a higher temperature than the material of the sealing 3 is generated. In addition, it is necessary to be made of a material that hardly causes sublimation due to interaction with the gas in the chamber. For this reason, the shielding plate 10 is made of silicon carbide or a graphite base material coated with a silicon carbide film or a pyrolytic carbon film.
The film thickness of the silicon carbide film or the pyrolytic carbon film is preferably 20 μm or more from the viewpoint of suppressing deterioration. Moreover, it is preferable that it is 100 micrometers or less from a viewpoint of the stress reduction based on a thermal expansion coefficient difference with a graphite base material.

  Further, the shielding plate 10 has at least the surface of the lower surface in order to reduce the amount of downfall that occurs when the SiC film is deposited from the vapor phase and peels off and falls onto the SiC single crystal wafer or the SiC epitaxial film. Is preferably a material with high adhesion of SiC film. Examples of such a material include those made of silicon carbide and those coated with a silicon carbide film.

  In this embodiment, as the material of the shielding plate 10, the shielding plate 10 is heated by receiving heat radiation from the ceiling 3, and it is necessary to release the radiant heat to heat the wafer. Therefore, the shielding plate 10 has high thermal conductivity. Is preferred.

  When the shielding plate 10 is made of silicon carbide, it can be produced by a chemical vapor deposition (CVD) method, sintering, or the like, but a shielding plate with higher material purity can be produced by the CVD method. The surface of the shielding plate 10 on which silicon carbide is deposited is preferably roughened by polishing or the like in order to improve the adhesion of silicon carbide.

  The shielding plate 10 preferably has a thickness of 2 to 6 mm from the viewpoint of preventing cracks. This is because the shielding plate is easy to crack, and if it is thinner than 2 mm, it will bend too much, and will break even if it is thicker than 6 mm.

  In the case where the sealing is made of silicon carbide, by making the thickness of the member thinner than that of the sealing, even the same material can withstand thermal strain and is difficult to break.

  The plurality of placement portions 2b are arranged side by side in the circumferential direction on the disc-shaped susceptor 2 so as to surround the center portion thereof. A revolution rotating shaft 2 a is attached to the center of the lower surface of the susceptor 2. The revolving rotary shaft 2 a is arranged immediately below the gas introduction pipe 5. A rotating shaft (not shown) for rotation is attached to each mounting portion 2b.

  With this configuration, the SiC single crystal wafer is revolved by the susceptor 2 with the gas introduction tube 5 as the central axis, and the SiC single crystal wafer itself is rotated with the mounting portion 2b with the center of the SiC single crystal wafer as the axis. It has become.

  In this SiC epitaxial wafer manufacturing apparatus, since a cold gas is introduced from the gas introduction pipe 5 disposed at the center, and induction heating is difficult to be applied to the center of the susceptor 2, The temperature of the susceptor 2 becomes lower as it approaches the part. Under the influence, the temperature of the outer peripheral portion of the rotating mounting portion 2b, that is, the outer peripheral portion of the SiC single crystal wafer placed on the mounting portion 2b is lowered. For this reason, in a general susceptor type epitaxial growth apparatus, the SiC single crystal wafer to be installed has a temperature gradient in which the temperature is highest at the center of the wafer and decreases toward the outer periphery of the wafer. . This temperature gradient of the SiC single crystal wafer causes compressive stress in the central portion of the SiC single crystal wafer during the epitaxial growth process.

  Further, a flange portion 9 a that protrudes in the diameter increasing direction is provided at the distal end portion (lower end portion) of the gas introduction pipe 5. The flange portion 5a is for causing the raw material gas G released vertically downward from the lower end portion of the gas introduction pipe 9 to flow radially in the horizontal direction between the opposing susceptor 2.

  In this CVD apparatus 100, the source gas G discharged from the gas introduction tube 9 is caused to flow radially from the inside to the outside of the reaction space 4, so that the source gas is parallel to the plane of the SiC single crystal substrate. G can be supplied. Further, the gas that is no longer necessary in the chamber can be discharged out of the chamber through an exhaust port (not shown) provided on the wall of the chamber.

  Here, the sealing 3 is heated by the induction coil 7 at a high temperature, but its inner peripheral portion (center portion where the opening 10b is formed) has a low temperature for introducing the raw material gas G. 9 is not contacted. Further, the ceiling 3 is supported vertically upward by placing the inner peripheral portion thereof on a support member 11 attached to the outer peripheral portion of the gas introduction pipe 9. Further, the ceiling 3 can be moved in the vertical direction.

  Since the temperature gradient of the SiC single crystal wafer changes depending on the flow rate of the introduced gas, the position of the induction heating coil, etc., in this embodiment, the temperature is the lowest at the wafer central portion and the temperature goes toward the wafer outer peripheral portion. It is desirable to adjust the flow rate of the introduced gas and the position of the induction heating coil so that the temperature gradient becomes higher.

The distance d ₁ between the upper surface of the shielding plate 10 and the lower surface of the ceiling 3 is preferably set in the range of 0.5 to 1 mm. This is to prevent SiC deposits from being deposited on the lower surface of the ceiling 3 by the shielding plate 10.

Further, the shield plate 10 is spaced from the inner wall 1a of the chamber 1, the horizontal distance _{d 2} between the inner wall 1a of the outer circumferential side surface 10c and the chamber 1 of the shield plate 10 is a 1.0~3.0mm Preferably there is. This is to prevent the shielding plate 10 from contacting the wall surface 1a due to thermal expansion during heating.
For example, when the shielding plate is made of silicon carbide, the thickness is preferably 1.0 to 2.0 mm.

The distance d ₃ from the inner wall 10d of the opening 10b of the shielding plate 10 to the outer wall 5a of the gas introduction pipe 5 is preferably set in the range of 0.5 to 1 mm. This is to make it difficult for gas to flow from the inner peripheral side of the shielding plate 10 to the ceiling 3 while preventing the shielding plate 10 from coming into contact with the protrusions 12 due to thermal expansion during heating.

The distance d ₄ between the inner peripheral surface of the ceiling 3 and the outer peripheral surface of the gas introduction pipe 9 is preferably set to a range of 0.5 mm or less. This is to prevent the gas introduction pipe 5, which is at a low temperature for introducing the raw material gas G, from being affected as much as possible by the radiant heat from the ceiling 3 heated to the high temperature by the induction coil 7.

In the present embodiment, as shown in FIG. 7, the ceiling 3 has a protruding portion from the inner peripheral portion 3 d of the lower surface 3 c between the inner wall 10 d of the opening 10 b of the shielding plate 10 and the outer wall 5 a of the gas introduction pipe 5. 12 is provided. The protrusion 12 may be formed integrally with the ceiling 3 or may be a separate member from the ceiling 3. The protrusion 12 is preferably arranged along the inner wall 10d of the opening 10b of the shielding plate 10. 5 and 7 show only a part of the cross section.
The protrusion 12 can prevent the gas of the film material in the gas phase from entering the sealing from the gap between the inner wall 10 d of the opening 10 b of the shielding plate 10 and the outer wall 5 a of the gas introduction pipe 5.
In addition, although this embodiment is provided with the projection part 12, the structure which is not provided may be sufficient.

According to the epitaxial wafer manufacturing apparatus of this embodiment, since the shielding plate 10 is provided, even if a material piece of the ceiling 3 falls, it is received by the shielding plate 10 and prevented from falling on the wafer or the epitaxial film. Therefore, the surface density of the triangular defect starting from the material piece of the sealing 3 in the epitaxial film can be reduced. Further, since the shielding plate 10 uses at least the lower surface coated with a silicon carbide film or a pyrolytic carbon film, or is made of silicon carbide, the amount of the material piece falling from the shielding plate 10 is less than the ceiling. There are few.
Therefore, if the epitaxial wafer manufacturing apparatus is used, it is possible to manufacture a SiC epitaxial wafer in which the surface density of triangular defects starting from the material pieces of the members in the chamber is lower than when a conventional epitaxial wafer manufacturing apparatus is used. it can.

[SiC epitaxial wafer manufacturing apparatus (second embodiment)]
The epitaxial wafer manufacturing apparatus of this embodiment is an epitaxial wafer manufacturing apparatus that forms an epitaxial layer on the surface of a wafer while supplying a raw material gas into the chamber, and includes a wafer mounting portion for mounting the wafer. A sealing (top plate) disposed opposite to the upper surface of the susceptor so as to form a reaction space between the susceptor and the susceptor, and a surface facing the susceptor of the sealing is a silicon carbide film or a pyrolytic carbon film The epitaxial wafer manufacturing apparatus according to the first embodiment is different from the epitaxial wafer manufacturing apparatus according to the first embodiment in that there is no shielding plate.

  According to this epitaxial wafer manufacturing apparatus, the number of material pieces falling from the ceiling onto the wafer is reduced, so that it is possible to manufacture a SiC epitaxial wafer with a low surface density of triangular defects starting from the material pieces of the members in the chamber. it can.

  In the epitaxial wafer manufacturing apparatus of the present invention, the surface facing the susceptor is covered with a silicon carbide film or a pyrolytic carbon film as a member disposed above the wafer (a shielding plate if a shielding plate is provided, or a sealing if not). It is possible to reduce the triangular defects starting from the material pieces of the members in the chamber as those made of silicon carbide or silicon carbide, but other members in the chamber are also preferably made of those materials. .

[Method of Manufacturing SiC Epitaxial Wafer (First Embodiment)]
The epitaxial wafer manufacturing method of the present embodiment is a method of manufacturing an SiC epitaxial wafer using the epitaxial wafer manufacturing apparatus of the first embodiment, wherein the SiC epitaxial film of the previously manufactured SiC epitaxial wafer is in the chamber. After the surface density of the triangular defect starting from the material piece of the member is measured, a step of manufacturing the next SiC epitaxial wafer is included.
By having this process, it becomes possible to manage the surface density of the triangular defect starting from the material piece of the member in the chamber in the SiC epitaxial film.

<Polishing process>
In the polishing process, the 4H—SiC single crystal substrate remaining on the wafer surface in the slicing process is polished until the lattice disorder layer on the surface becomes 3 nm or less.
A “lattice disordered layer” is a TEM lattice image (an image in which a crystal lattice can be confirmed) in which a striped structure corresponding to an atomic layer (lattice) of a SiC single crystal substrate or a part of the stripe is not clear. It refers to a layer (see Patent Document 5).
The polishing process includes a plurality of polishing processes such as rough polishing usually called lapping, precision polishing called polishing, and chemical mechanical polishing (hereinafter referred to as CMP) which is ultra-precision polishing. In mechanical polishing before CMP, By using abrasive grains having a processing pressure of 350 g / cm ² or less and a diameter of 5 μm or less, not only damage that can be detected as a “lattice disorder layer” in the TEM, but also distortion of the lattice that cannot be detected by the TEM is deeper. In the CMP, the polishing slurry contains abrasive particles having an average particle diameter of 10 nm to 150 nm and an inorganic acid, and the pH at 20 ° C. is less than 2. Preferably, the abrasive particles are silica and more preferably contain 1% to 30% by weight. Ku, inorganic acids hydrochloric acid, nitric acid, phosphoric acid, and more preferably at least one of sulfuric acid.

<Cleaning (gas etching) process>
In the cleaning process, the surface of the substrate after the polishing and the convex processing is cleaned at 1400 to 1800 ° C. in a hydrogen atmosphere (gas etching).
The gas etching is performed for 5 to 30 minutes by holding the SiC single crystal substrate at 1400 to 1800 ° C., setting the flow rate of hydrogen gas to 40 to 120 slm, and the pressure to 100 to 250 mbar.

  After the polished SiC single crystal substrate is cleaned, the substrate is set in an epitaxial growth apparatus, for example, a mass production type multiple planetary CVD apparatus. After introducing hydrogen gas into the apparatus, the pressure is adjusted to 100 to 250 mbar. Thereafter, the temperature of the apparatus is raised, the substrate temperature is set to 1400 to 1600 ° C., preferably 1480 ° C. or higher, and gas etching of the substrate surface is performed with hydrogen gas for 1 to 30 minutes. When gas etching with hydrogen gas is performed under such conditions, the etching amount is about 0.05 to 0.4 μm.

SiH ₄ gas and / or C ₃ H ₈ gas may be added to the hydrogen gas. Although short step bunching may occur along with shallow pits caused by screw dislocation, SiH ₄ gas having a concentration of less than 0.009 mol% is added to hydrogen gas to make the environment in the reactor Si-rich. By performing gas etching, the depth of the shallow pit can be reduced, and the occurrence of short step bunching associated with the shallow pit can be suppressed.
When SiH ₄ gas and / or C ₃ H ₈ gas is added, it is preferable to evacuate once to form a hydrogen gas atmosphere before the film formation (epitaxial growth) step.

<Film formation (epitaxial growth) process>
In the film formation (epitaxial growth) step (after the temperature rise when the growth temperature of the epitaxial film is higher than the cleaning (gas etching) temperature), it is required for epitaxial growth of silicon carbide on the surface of the cleaned substrate. A SiC film is epitaxially grown by supplying a predetermined concentration ratio of carbon-containing gas and silicon-containing gas (for example, concentration ratio C / Si of SiH ₄ gas and C ₃ H ₈ gas is 0.7 to 1.2). Let

The carbon-containing gas and the silicon-containing gas are preferably supplied simultaneously. This is because step bunching is significantly reduced.
Here, “simultaneously supplying” means that it is not necessary to be completely the same time, but it is within several seconds.

Each flow rate, pressure, substrate temperature, and growth temperature of SiH ₄ gas and C ₃ H ₈ gas are 15 to 150 sccm, 3.5 to 60 sccm, 80 to 250 mbar, higher than 1600 ° C. and lower than 1800 ° C., and the growth rate is 1 per hour. Within a range of ˜20 μm, it is determined while controlling the off angle, film thickness, carrier concentration uniformity, and growth rate. By introducing nitrogen gas as a doping gas simultaneously with the start of film formation, the carrier concentration in the epitaxial layer can be controlled. As a method for suppressing step bunching during growth, in order to increase the migration of Si atoms on the growth surface, it is known to lower the concentration ratio C / Si of the source gas to be supplied. 0.7-1.2. The epitaxial layer to be grown is usually about 5 to 20 μm in thickness and about 2 to 15 × 10 ¹⁵ cm ⁻³ in carrier concentration.

Although the growth temperature is 1400 to 1800 ° C., it is preferably 1600 ° C. or higher in order to reduce stacking faults. Moreover, it is preferable to increase the growth rate as the growth temperature increases. For the same growth temperature, it is preferable to increase the growth rate as the off-angle of the SiC single crystal substrate increases.
For example,
(1) When a 4H—SiC single crystal substrate with an off angle of 0.4 ° to 2 ° is used, when the growth temperature for epitaxial growth of the silicon carbide film is 1600 to 1640 ° C., the growth rate is 1 to 3 μm / When the growth temperature is 1640 to 1700 ° C., the growth rate is 3 to 4 μm / h. When the growth temperature is 1700 to 1800 ° C., the growth rate is 4 to 10 μm / h.
(2) When a 4H—SiC single crystal substrate with an off angle of 2 ° to 5 ° is used, when the growth temperature for epitaxial growth of the silicon carbide film is 1600 to 1640 ° C., the growth rate is set to 2 to 4 μm / h. When the growth temperature is 1640 to 1700 ° C., the growth rate is 4 to 10 μm / h. When the growth temperature is 1700 to 1800 ° C., the growth rate is 10 to 20 μm / h. preferable.

<Cooling process>
In the temperature lowering step, it is preferable to simultaneously stop the supply of the carbon-containing gas and the silicon-containing gas (for example, SiH ₄ gas and C ₃ H ₈ gas). This is because it is effective in suppressing deterioration of morphology. After stopping, the substrate temperature is maintained until the carbon-containing gas and the silicon-containing gas are exhausted, and then the temperature is lowered.

<Measurement of surface density of triangular defects and member replacement process>
After measuring the surface density of triangular defects starting from a piece of material in the chamber of the SiC epitaxial film of the SiC epitaxial wafer periodically (for each manufacturing lot, for each of a plurality of manufacturing lots, etc.) or irregularly The next SiC epitaxial wafer is manufactured.

  The surface density of the triangular defect starting from the material piece of the member in the chamber is, for example, the position of the focal point using the optical microscope from the surface of the epitaxial film of the SiC epitaxial wafer to the interface between the epitaxial film and the SiC single crystal substrate ( The triangular defect starting from the material piece of the member in the chamber can be found by shifting to the depth direction of the film) and can be obtained by measuring it. Further, in the present embodiment, the types (types) of triangular defects that increase as the film formation is repeated are considered to be only triangular defects starting from a material piece of a member in the chamber and triangular defects starting from a downfall. be able to. Normally, a triangular defect starting from a downfall has a clear starting point, whereas a triangular defect starting from a material piece of a member in the chamber has a characteristic that the starting point is not clear. By identifying the triangular defects starting from the fall and managing the increase in the surface density, it is possible to manufacture a SiC epitaxial wafer having a low surface density of triangular defects starting from the material pieces of the members in the chamber. Become. If you want to measure and manage the density of triangular defects starting from the material pieces of the members in the chamber more strictly, analyze the composition of the foreign matter ahead of the triangular defects using energy dispersive X-ray analysis etc. Can be performed.

As a result of the above measurement, when the surface density of the triangular defect starting from the material piece of the member in the chamber exceeds a predetermined density, it is preferable to replace the shielding plate 10 to manufacture the next SiC epitaxial wafer. For example, when the surface density of the triangular defects of the SiC epitaxial wafer manufactured previously is about 0.25 / cm ² , the surface density is determined by replacing the shielding plate 10 and manufacturing the next SiC epitaxial wafer. It is possible to manufacture an SiC epitaxial wafer having a value of 0.5 / cm ² or less.

[SiC Epitaxial Wafer Manufacturing Method (Second Embodiment)]
The epitaxial wafer manufacturing method according to the present embodiment is a method for manufacturing a SiC epitaxial wafer using the epitaxial wafer manufacturing apparatus according to the second embodiment, wherein the SiC epitaxial film of the previously manufactured SiC epitaxial wafer is contained in the chamber. After the surface density of the triangular defect starting from the material piece of the member is measured, a step of manufacturing the next SiC epitaxial wafer is included.
By having this process, it becomes possible to manage the surface density of the triangular defect starting from the material piece of the member in the chamber in the SiC epitaxial film.

Also in the manufacturing method of the SiC epitaxial wafer of this embodiment, each SiC epitaxial wafer can be manufactured as in the first embodiment.
Moreover, the measurement process of the surface density of a triangular defect can also be performed similarly to 1st Embodiment.

As a result of the above measurement, when the surface density of the triangular defect starting from the material piece of the member in the chamber exceeds a predetermined density, it is preferable to replace the sealing 3 and manufacture the next SiC epitaxial wafer. For example, when the surface density of the triangular defects of the SiC epitaxial wafer manufactured previously is about 0.25 / cm ² , the surface density is determined by replacing the shielding plate 10 and manufacturing the next SiC epitaxial wafer. It is possible to manufacture an SiC epitaxial wafer having a value of 0.5 / cm ² or less.

The invention related to the present invention is shown below.
(1) A SiC epitaxial wafer having a SiC epitaxial layer on a SiC single crystal substrate having an off angle, wherein the surface density of triangular defects starting from a material piece of a member in a chamber existing in the SiC epitaxial layer is An SiC epitaxial wafer characterized by being 0.5 pieces / cm ² or less.
(2) The SiC epitaxial wafer according to (1), wherein the starting material piece is made of carbon or silicon carbide.
(3) a susceptor having a wafer placement unit for placing a wafer, and a top plate disposed to face the upper surface of the susceptor so as to form a reaction space between the susceptor; A shielding plate arranged close to the lower surface of the top plate to prevent deposits from adhering to the lower surface, and supplying a source gas into the chamber, on the surface of the SiC single crystal wafer A method for manufacturing a SiC epitaxial wafer using a SiC epitaxial wafer manufacturing apparatus having a SiC epitaxial layer, wherein the surface facing the susceptor is coated with a silicon carbide film or a pyrolytic carbon film as the shielding plate Or a triangle made from a material piece of a member in a chamber of a SiC epitaxial film of a SiC epitaxial wafer manufactured previously using a material made of silicon carbide The surface density of Recessed After measuring method of the SiC epitaxial wafer which comprises a step of producing the following SiC epitaxial wafer.
(4) As a result of the measurement, when the surface density of the triangular defect starting from the material piece of the member in the chamber exceeds a predetermined density, the next SiC epitaxial wafer is manufactured by replacing the shielding plate. (6) The method for producing an SiC epitaxial wafer according to (3).
(5) a susceptor having a wafer placement unit for placing a wafer, and a top plate disposed to face the upper surface of the susceptor so as to form a reaction space between the susceptor and A SiC epitaxial wafer is manufactured using a SiC epitaxial wafer manufacturing apparatus having a SiC epitaxial layer on the surface of a SiC single crystal wafer while supplying a raw material gas to the susceptor as the top plate. The surface to be covered is covered with a silicon carbide film or a pyrolytic carbon film, or is made of silicon carbide, and the material of the member in the chamber is used as the starting point for the SiC epitaxial film of the SiC epitaxial wafer manufactured previously. After measuring the surface density of the triangular defect, the method includes the step of manufacturing the next SiC epitaxial wafer Manufacturing method of iC epitaxial wafer.
(6) As a result of the measurement, when the surface density of the triangular defect starting from the material piece of the member in the chamber exceeds a predetermined density, the top plate is replaced and the next SiC epitaxial wafer is manufactured. (6) The method for producing an SiC epitaxial wafer according to (5).
(7) A SiC epitaxial wafer manufactured using the method for manufacturing a SiC epitaxial wafer according to any one of (3) to (6).
(8) An epitaxial wafer manufacturing apparatus for forming an epitaxial layer on a surface of a wafer while supplying a source gas into the chamber, the susceptor having a wafer mounting portion for mounting the wafer, and the susceptor So as to form a reaction space between the top surface of the susceptor and the bottom surface of the top plate so as to prevent deposits from adhering to the bottom surface of the top plate. A shielding plate disposed in proximity, the shielding plate having a surface facing the susceptor covered with a silicon carbide film or a pyrolytic carbon film, or made of silicon carbide. An epitaxial wafer manufacturing apparatus.
(9) An epitaxial wafer manufacturing apparatus for forming an epitaxial layer on a surface of a wafer while supplying a source gas into the chamber, the susceptor having a wafer mounting portion for mounting the wafer, and the susceptor The top plate disposed to face the upper surface of the susceptor and the surface of the top plate facing the susceptor are covered with a silicon carbide film or a pyrolytic carbon film so as to form a reaction space between An epitaxial wafer manufacturing apparatus characterized in that it is made of silicon carbide.
(10) The epitaxial wafer manufacturing apparatus according to any one of (8) and (9), wherein the silicon carbide film or the pyrolytic carbon film has a thickness of 20 to 100 μm.
(11) The epitaxial wafer manufacturing apparatus according to any one of (8) to (10), further comprising heating means disposed on a lower surface side of the susceptor and / or an upper surface side of the top plate. .

  Hereinafter, the effect of the present invention will be specifically described with reference to examples. The present invention is not limited to these examples.

(Example)
Examples are examples of the SiC epitaxial wafer manufacturing apparatus and the SiC epitaxial wafer manufacturing method according to the first embodiment.
In the SiC epitaxial wafer manufacturing apparatus shown in FIG. 5, the sealing is made of graphite, and the shielding plate is the two-part shown in FIG. 6 in which a graphite substrate is coated with a silicon carbide film (diameter: 371 mm, thickness: 4 mm). The shielding plate was arranged at a distance (d ₁ ) of 0.5 mm from the ceiling.
As a 4H-SiC single crystal wafer, the c-plane ((0001) plane) has an Si surface inclined 4 ° in the <11-20> direction as a main surface, a diameter of 3 inches (76.2 mm) and a thickness of 350 μm. A thing was used.
Next, the SiC single crystal wafer was subjected to organic solvent cleaning, acid / alkali cleaning, and sufficient water cleaning as pretreatment.

The SiC single crystal wafer was placed on the wafer mounting section, and after evacuation, hydrogen gas was introduced to adjust the pressure to 200 mbar. Thereafter, the temperature was raised to 1570 ° C., growth was performed at a growth rate of 5 μm / h for 1 hour, a SiC epitaxial film having a thickness of 5 μm was formed, and a SiC epitaxial wafer was manufactured.
Hydrogen was used as a carrier gas, a mixed gas of SiH ₄ and C ₃ H ₈ was used as a source gas, and N ₂ was supplied as a dopant.

Under the above conditions, the manufacture of the SiC epitaxial wafer was repeated without replacing the members in the chamber. 8A and 8B are a candela image of the second production lot and a candela image of the 80th production lot, respectively. What appears to be black spots are triangular defects.
The number of triangular defects of all types was measured from the candela image to obtain the surface density of all types of triangular defects. Further, the number of triangular defects starting from the material piece of the member in the chamber was measured by a method of observing by shifting the focus using an optical microscope, and the surface density of the triangular defect was obtained.
The area density of triangular defects of the SiC epitaxial wafer of the second production lot is 0.5 / cm ² , and the area density of triangular defects starting from the material piece of the member in the chamber is 0 / cm ^2. Met.
Further, the surface density of triangular defects of the SiC epitaxial wafer of the 80th production lot is 2 / cm ² , and the surface density of triangular defects starting from the material piece of the member in the chamber is 0.5 / cm ² .
Note that the surface density of triangular defects of the SiC epitaxial wafer of the 20th manufacturing lot is 1 piece / cm ² , of which the surface density of triangular defects starting from a piece of material of the member in the chamber is 0 piece / cm ^2. Met.

FIG. 8C shows a candela image of a production lot immediately after the production of the SiC epitaxial wafer after the 80th production, after the shielding plate is replaced with a new one. The surface density of the triangular defect was 0.5 / cm ² , and the surface density of the triangular defect starting from the material piece of the member in the chamber was 0 / cm ² .
From this result, it was confirmed that by replacing the shielding plate with a new one, the surface density of the triangular defect starting from the material piece of the member in the chamber can be reduced.

(Comparative Example 1)
Comparative Example 1 was different from the SiC epitaxial wafer manufacturing apparatus used in the Examples in that the shielding plate was a graphite base material coated with a tantalum carbide film, and the other manufacturing conditions were the same.
Under this condition, the manufacture of the SiC epitaxial wafer was repeated without replacing the members in the chamber. FIG. 9A is a candela image of the 20th manufacturing lot.
The surface density of all kinds of triangular defects of this SiC epitaxial wafer was 2 / cm ² , and among them, the surface density of triangular defects starting from the material piece of the member in the chamber was 1 / cm ² .
Even if the number of repetitions of the manufacture of the SiC epitaxial wafer is the same as in the embodiment, both the surface density of all types of triangular defects and the surface density of triangular defects starting from the material pieces of the members in the chamber are examples. It was higher than
As a result, it was found that using a graphite substrate coated with a silicon carbide film as a shielding plate, rather than a graphite substrate coated with a tantalum carbide film, the surface density of all types of triangular defects and in the chamber It was found that the surface density of the triangular defect starting from the material piece of the member can be reduced.

(Comparative Example 2)
Comparative Example 2 was different in that the shielding plate was not used in the SiC epitaxial wafer manufacturing apparatus used in the examples, and other manufacturing conditions were the same.
Under this condition, the manufacture of the SiC epitaxial wafer was repeated without replacing the members in the chamber. FIG. 9B is a candela image of the 20th manufacturing lot.
The surface density of all kinds of triangular defects of this SiC epitaxial wafer was 100 / cm ² , and among them, the surface density of triangular defects starting from the material piece of the member in the chamber was 90 / cm ² .
Even if the number of repetitions of the manufacture of the SiC epitaxial wafer is the same as in the embodiment, both the surface density of all types of triangular defects and the surface density of triangular defects starting from the material pieces of the members in the chamber are examples. It was significantly higher than
From this result, it was found that by using the shielding plate, the surface density of all kinds of triangular defects and the surface density of triangular defects starting from the material pieces of the members in the chamber can be greatly reduced.

  The SiC epitaxial wafer, the manufacturing method thereof, and the SiC epitaxial wafer manufacturing apparatus of the present invention can be used for manufacturing an SiC epitaxial wafer having a low surface density of triangular defects starting from a material piece of a member in a chamber.

DESCRIPTION OF SYMBOLS 1 Chamber 1a Inner wall 2 Susceptor 2b Mounting part 3 Sealing (top plate)
4 reaction space 6, 7 induction coil (heating means)
DESCRIPTION OF SYMBOLS 10 Shielding board 10a Outer peripheral part 10A, 10B Shielding board 11 Supporting part 100 CVD apparatus (Epitaxial wafer manufacturing apparatus)

Claims (2)

A method for evaluating a SiC epitaxial wafer having a SiC epitaxial layer on a SiC single crystal substrate having an off angle,
In the measurement of the image by the optical surface inspection apparatus using an optical microscopic image or a laser beam, the origin can be identified finding by Ras without the position of the focal point and the vertex, and the vertices of the standing point, according to the step flow growth direction have a step which is opposite side of the vertex and the vertex base detects the triangular defects is triangular defects formed by oriented as arranged in this order,
In the step of detecting the triangular defect, the starting point is found by shifting the position of the focal point from the surface of the SiC epitaxial film through the SiC epitaxial film toward the interface with the SiC single crystal substrate. A method for evaluating an SiC epitaxial wafer, characterized by identifying . 2. The method for evaluating an SiC epitaxial wafer according to claim 1, further comprising using an energy dispersive X-ray analysis method to compositionally analyze a foreign substance at the tip of the triangular defect having the starting point as a vertex.