WO2019022054A1

WO2019022054A1 - Production method for sic mono-crystals, production method for ingot sic, production method for sic wafer, and sic mono-crystals

Info

Publication number: WO2019022054A1
Application number: PCT/JP2018/027634
Authority: WO
Inventors: 紀人矢吹; 悠介須藤; 純久阿部; 暁野上; 北畠　真; 忠昭金子; 晃嗣芦田
Original assignee: 東洋炭素株式会社; 学校法人関西学院
Priority date: 2017-07-28
Filing date: 2018-07-24
Publication date: 2019-01-31
Also published as: JP2019026500A; JP6949358B2

Abstract

This production method for SiC mono-crystals (41) comprises a TSD visualization step, a recessed portion formation step, and a crystal growth step. In the TSD visualization step, TSDs (51) are visualized by dry etching a SiC substrate (40). In the recessed portion formation step, portions in which the TSDs (51) visualized by the TSD visualization step are present are removed, leaving portions surrounding the portions in which the TSDs (51) are present, to form recessed portions (53). In the crystal growth step, crystal growth is promoted on the SiC substrate (40) in the a-axis direction and in the c-axis direction so that SiC mono-crystals (41) grown from the portions surrounding the recessed portions are joined together on the recessed portions (53).

Description

Method of manufacturing single crystal SiC, method of manufacturing SiC ingot, method of manufacturing SiC wafer, and single crystal SiC

The present invention mainly relates to a method for producing single crystal SiC by removing TSD (penetrating screw dislocation) occurring in a SiC substrate.

Conventionally, in order to manufacture high quality semiconductor devices, methods of manufacturing single crystal SiC with few defects have been sought. Patent documents 1 to 5 disclose this type of technology.

In the method of manufacturing single crystal SiC of Patent Document 1, first, the surface of the SiC substrate is removed in a lattice shape by a laser to form a plurality of convex portions. Thereafter, crystal growth is performed on the SiC substrate by the MSE method (metastable solvent epitaxy method). At this time, since the growth rate in the c-axis direction is faster than that in the case where the TSD is included, the height in the c-axis direction is increased. After the convex portion having a high height in the c-axis direction is removed by laser, the MSE method is performed again. Thereby, single crystal SiC grown from a plurality of convex portions is connected, and large area single crystal SiC is manufactured.

In the method for producing single crystal SiC of Patent Document 2, first, macro step bunching is formed in the SiC seed crystal to form a second seed crystal. Next, step bunching is formed on the TSD of this second seed crystal. By forming step bunching on the TSD, the TSD is converted into a stacking fault, so that single crystal SiC with a small TSD is manufactured.

In the method of manufacturing single crystal SiC of Patent Document 3, first, single crystal SiC is formed on a SiC substrate by the MSE method. Next, sublimation is performed to grow crystals on this single crystal SiC.

In

Patent Documents

4 and 5, thin plate-like single crystal SiC is cut out from single crystal SiC manufactured by crystal growth on a SiC substrate. Then, crystal growth is performed again on the thin plate-like single crystal SiC. By repeating the above process, single crystal SiC with a small TSD is manufactured.

JP, 2017-88444, A JP 2014-43369 JP, 2010-89983, A JP 2003-119097 A JP, 2015-54814, A

Here, TSD contained in single crystal SiC plays an important role in stably inheriting the crystal polymorphism of the seed crystal when crystal growth is performed using the single crystal as a seed crystal. However, in the methods described in Patent Documents 1 to 5, it is difficult to perform processing such as removing TSDs generated at other positions while leaving TSDs generated at predetermined positions. For example, in patent document 1, at the stage of forming a convex part, TSD currently formed other than a convex part will be removed.

In addition, in the method of patent document 1, since it is necessary to perform the MSE method for visualizing TSD, and the MSE method for obtaining single crystal SiC, a manufacturing process becomes complicated. In the methods of Patent Documents 2 and 3, since crystal growth of two steps is required, the manufacturing process becomes complicated. In the methods of

Patent Documents

4 and 5, since it is necessary to perform crystal growth and cutting out a plurality of times, the manufacturing process becomes complicated.

The present invention has been made in view of the above circumstances, and the main object of the present invention is to remove the unnecessary TSD while leaving the necessary TSD when the necessary TSD is generated, and to perform the single crystal in a simple process. It is to provide a method of manufacturing.

Means and effect for solving the problem

The problem to be solved by the present invention is as described above, and next, means for solving the problem and its effect will be described.

According to an aspect of the present invention, the following method for producing single crystal SiC is provided. That is, the method of manufacturing single crystal SiC performs processing including a TSD visualization step, a recess formation step, and a crystal growth step. In the TSD visualization step, dry etching is performed on the SiC substrate to visualize TSD (penetrating screw dislocation). In the recess forming step, the recess is formed by leaving the periphery of the portion in which the TSD is generated while removing the portion in which the TSD visualized in the TSD visualizing step is generated. In the crystal growth step, single crystal SiC grown from the periphery of the concave portion is connected on the concave portion by performing crystal growth in the a-axis direction and the c-axis direction on the SiC substrate.

Thereby, since TSD contained in a SiC substrate can be removed, high quality single crystal SiC can be manufactured. In addition, since the TSD can be visualized without forming a convex portion or the like in advance, unnecessary TSD can be removed while leaving necessary TSD. In addition, when necessary TSD has not arisen, all TSD can also be removed. In addition, single crystal SiC can be manufactured by a simple process as compared with the conventional method.

In the method of manufacturing single crystal SiC described above, it is preferable that pits are formed in the portion where the TSD is generated in the TSD visualization step.

When the TSD is visualized using the MSE method as in Patent Document 1, the portion where the TSD is present grows largely, so when the TSDs are densely packed, the growth portions overlap, and the TSD can not be identified accurately. there is a possibility. On the other hand, in the above method, small pits of about 1 μm are formed in the portion where the TSD occurs, so that the TSD can be specified more accurately, so unnecessary TSD can be obtained while leaving necessary TSD. It can be removed.

In the method of manufacturing single-crystal SiC described above, in the recess forming step, a plurality of portions where the visualized TSD is generated are present, and it is preferable to remove only a portion of the portions.

Thus, since TSD can be selectively left, crystal polymorphism and the like can be stably controlled when crystal growth is performed using a seed crystal.

In the method of manufacturing single crystal SiC, it is preferable that the TSD be unevenly distributed on the surface of the SiC substrate as a result of removing the TSD in the recess forming step.

Thereby, desired crystal polymorph (for example, 4H-SiC) can be easily taken over from the seed crystal in the crystal growth step.

In the method of manufacturing single-crystal SiC, in the recess forming step, the TSD is preferably removed so that the TSD density on the surface is 1000 pieces / cm ² or less with respect to the visualized TSD.

As a result, it is possible to make it easy for the desired crystal polymorph (for example, 4H-SiC) to be handed over from the seed crystal in the high quality and crystal growth step.

In the method of manufacturing single crystal SiC, in the TSD visualization step, it is preferable to visualize the TSD by performing etching by heating under a Si vapor pressure.

Thereby, the surface of the SiC substrate can be planarized with high accuracy and the TSD can be visualized.

In the method of manufacturing single crystal SiC, in the recess forming step, it is preferable to form the recess by irradiating a portion where the TSD is generated with a laser.

As a result, it is possible to accurately form the recess in the portion where the TSD occurs in a simple and highly accurate method.

In the method of manufacturing single crystal SiC, the beam diameter of the laser is preferably 1 μm or more.

Thereby, when forming the said recessed part, the distortion area | region of the vicinity of the dislocation core of TSD can be removed.

In the method of manufacturing single-crystal SiC, the SiC substrate is etched after the recess formation step and before the crystal growth step, thereby removing the damage caused to the SiC substrate in the recess formation step. It is preferable to perform the damage removal process.

Thereby, since the damage which arose in the recessed part formation process can be removed, higher quality single crystal SiC can be manufactured.

In the method of manufacturing single crystal SiC, in the crystal growth step, Si melt is present between the SiC substrate and a feed material having a higher free energy than the SiC substrate and supplying at least C. It is preferable to perform a metastable solvent epitaxy method of growing the single crystal SiC on the surface of the SiC substrate by heating in a state.

Thereby, since the growth rate in the a-axis direction is high in the metastable solvent epitaxy method, the upper part of the recess can be closed with single crystal SiC in a short time.

In the method of manufacturing single crystal SiC described above, it is preferable to do as follows. That is, in the TSD visualization step, the TSD is visualized by performing etching by heating under a Si vapor pressure. In the recess forming step, the recess is formed by irradiating a laser on a portion where the TSD is generated. After the recess formation step, etching is performed by heating under a Si vapor pressure to perform a damage removal step of removing damage caused to the SiC substrate. In the crystal growth step, heating is performed in a state in which the Si melt is present between the SiC substrate and a feed material having a free energy higher than that of the SiC substrate and supplying at least C; A metastable solvent epitaxy method is performed to grow the single crystal SiC on the surface.

Thereby, high purity single crystal SiC can be manufactured in a short time. Moreover, since both etchings are Si vapor pressure etching, the manufacturing process can be simplified.

Further, according to another aspect of the present invention, it is preferable to manufacture a SiC ingot using the single crystal SiC manufactured using the above-described manufacturing method. For example, in the case of producing an ingot by a solution growth method, it is preferable to form the recess such that the TSD density of the outer edge portion of the surface of the SiC substrate is higher than the TSD density of other than the outer edge portion. In the case of producing an ingot by vapor phase growth, the recess may be formed such that the TSD density at the central portion in the radial direction of the surface of the SiC substrate is higher than the TSD density other than the central portion. preferable.

This makes it possible to obtain a SiC ingot having high quality and a desired crystal polymorph.

Further, according to another aspect of the present invention, it is preferable to manufacture a SiC wafer using the single crystal SiC manufactured using the above manufacturing method. In the case of producing a SiC wafer having an off angle, the TSD density on the upstream side with respect to the center of the step flow growth in the epitaxial layer forming step is higher than the TSD density on the downstream side with respect to the center. Preferably, the recess is formed. Further, the single crystal SiC may be used as it is as a SiC wafer.

Thereby, it is possible to suppress the mixing of the upstream heterocrystal polymorph in the epitaxial layer forming step.

BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining the outline | summary of the high temperature vacuum furnace used with the manufacturing method of single crystal SiC of this invention, etc. FIG. The schematic diagram which shows the manufacturing process (TSD visualization process, recessed part formation process, and damage removal process) of single crystal SiC. The schematic diagram which shows the manufacturing process (crystal growth process) of single crystal SiC. The microphotograph of TSD which has arisen on the surface of a SiC substrate, and a figure showing the stress analysis result. The schematic diagram which shows the crystal growth process by MSE method. The schematic diagram which shows the process of producing a SiC wafer from a SiC seed crystal via a SiC ingot. The graph which shows the relationship between the beam diameter of the laser used at the recessed part formation process, and the TSD propagation rate. The figure which shows distribution of the location where TSD propagation did not occur, and the location which TSD propagation produced, when crystal growth was performed after removing TSD using a laser with a beam diameter of 40 micrometers. The figure which shows distribution of the location where propagation of TSD did not occur, and the location which propagation of TSD produced, when crystal growth was performed after removing TSD using a laser with a beam diameter of 60 micrometers. The figure which shows distribution of the location where TSD propagation did not occur, and the location which TSD propagation produced, when crystal growth was performed after removing TSD using a laser with a beam diameter of 100 micrometers. The schematic diagram which shows that distribution of TSD of removal object for producing a SiC ingot, and TSD of remaining object differs according to the growth method. The schematic diagram which shows distribution of TSD of removal object for producing a SiC wafer, and TSD of remaining object.

Next, embodiments of the present invention will be described with reference to the drawings. First, with reference to FIG. 1, a high temperature vacuum furnace 10 used in the method of manufacturing single crystal SiC of the present embodiment and the like will be described.

As shown in FIG. 1, the high temperature vacuum furnace 10 includes a main heating chamber 21 and a preheating chamber 22. The main heating chamber 21 can heat a single crystal SiC substrate (hereinafter, the SiC substrate 40) whose surface is at least a single crystal SiC to a temperature of 1000 ° C. or more and 2300 ° C. or less. The preheating chamber 22 is a space for performing preheating before the SiC substrate 40 is heated in the main heating chamber 21.

The main heating chamber 21 is connected to a vacuum forming valve 23, an inert gas injection valve 24, and a vacuum gauge 25. The vacuum forming valve 23 can adjust the degree of vacuum of the main heating chamber 21. The inert gas injection valve 24 can adjust the pressure of the inert gas in the main heating chamber 21. In the present embodiment, the inert gas is, for example, a gas of a Group 18 element (a rare gas element) such as Ar, that is, a gas having poor reactivity to solid SiC and excluding nitrogen gas. . The vacuum gauge 25 can measure the degree of vacuum in the main heating chamber 21.

A heater 26 is provided inside the main heating chamber 21. Further, a heat reflecting metal plate (not shown) is fixed to the side wall and ceiling of the main heating chamber 21, and this heat reflecting metal plate reflects the heat of the heater 26 toward the central portion of the main heating chamber 21. Is configured. Thereby, the SiC substrate 40 can be heated strongly and uniformly, and the temperature can be raised to a temperature of 1000 ° C. or more and 2300 ° C. or less. In addition, as the heater 26, for example, a resistance heating heater or a high frequency induction heating heater can be used.

The high temperature vacuum furnace 10 heats the SiC substrate 40 stored in the crucible (storage container) 30. The storage container 30 is placed on a suitable support or the like, and is configured to be movable from at least the preheating chamber to the main heating chamber by moving the support. The storage container 30 includes an upper container 31 and a lower container 32 which can be fitted to each other. The SiC substrate 40 is supported by a support 33 placed on the lower container 32 of the container 30.

Containment container 30 includes a tantalum layer (Ta) and a tantalum carbide layer (TaC and TaC) in the order from the outer side to the inner space side in a portion constituting the wall surface (upper surface, side surface, bottom surface) of inner space Ta ₂ C), and is composed of tantalum silicide layer (TaSi ₂ or Ta ₅ Si _3, etc.).

The tantalum silicide layer supplies Si to the internal space of the storage container 30 by heating. Further, since the container 30 includes the tantalum layer and the tantalum carbide layer, it is possible to take in the surrounding C vapor. Thereby, the inside of the internal space can be made into a high purity Si atmosphere at the time of heating. Note that instead of providing a tantalum silicide layer, a Si source such as solid Si may be disposed in the internal space. In this case, the inside of the internal space can be made to have a high purity Si vapor pressure by sublimation of solid Si during heating.

When heating the SiC substrate 40, first, the storage container 30 is disposed in the preheating chamber 22 of the high-temperature vacuum furnace 10 as shown by the chain line in FIG. 1 and spared at an appropriate temperature (for example, about 800.degree. C.). Heat up. Next, the storage container 30 is moved to the main heating chamber 21 which has been heated to a set temperature (for example, about 1800 ° C.) in advance. Thereafter, the SiC substrate 40 is heated while adjusting the pressure and the like. Preheating may be omitted.

Next, the manufacturing process of single crystal SiC 41 performed in the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 and FIG. 3 are schematic views showing the manufacturing process of single crystal SiC 41.

As shown in FIG. 2, a plurality of TSDs (TSD: threading screw dislocation, threading screw dislocation) are generated in the SiC substrate 40. TSD is a crystal defect in which the displacement direction (Burgers vector) of the crystal and the dislocation line are parallel. Further, FIG. 4 shows a photomicrograph of TSD and a stress analysis result. The analysis of stress is the result of using EBSD (Electron Backscatter Pattern). According to the stress analysis result, the size of the TSD (a strained area near the dislocation core) is about 1 μm. TSD reduces the quality of single crystal SiC 41 by propagating to single crystal SiC 41 at the time of crystal growth. On the other hand, by intentionally leaving a part of the TSD generated in the SiC substrate 40, it is possible to control the crystal polymorphism. Therefore, in the present embodiment, the remaining TSDs are removed (while the TSDs are selectively removed) while intentionally leaving some of the TSDs. The details will be described below. Further, in the following description, when the TSD generated in the SiC substrate 40 is described, the reference numeral 51 is attached and described.

The SiC substrate 40 used in the present embodiment is a substrate (on substrate) having an off angle of 0 °, but the off angle may be larger than 0 °. The crystal polymorphism of the SiC substrate 40 is 4H-SiC, but may be another crystal polymorphism (6H-SiC, 3C-SiC, etc.). The main surface (surface to be processed) of the SiC substrate 40 is a Si surface (ie, (0001) surface), but may be a C surface (ie, (000-1) surface). Moreover, the convex part etc. are not formed in the SiC substrate 40, but the surface (specifically, the main surface, the same applies to the following) is flat.

First, a TSD visualization process is performed on the SiC substrate 40. The TSD 51 produced on the SiC substrate 40 can not be detected (or is difficult) even if the surface is observed with a microscope or the like. The TSD visualization step is a step of changing the TSD 51 generated on the SiC substrate 40 into a viewable state. Note that the TSD visualization step also includes a step of emphasizing the TSD 51 which is difficult but not impossible to make observation easier. In the present embodiment, the Si vapor pressure etching is performed on the SiC substrate 40, but another dry etching (for example, hydrogen etching) may be performed. By performing dry etching on the SiC substrate 40, pits 52 are formed in the portion where the TSD 51 is generated, as shown in the SiC substrate 40 after the TSD visualization step of FIG. The pits 52 are slight depressions formed on the surface of the SiC substrate 40. This makes it possible to visualize the portion where the TSD 51 is generated.

Here, Si vapor pressure etching will be described in detail. In Si vapor pressure etching, the SiC substrate 40 is accommodated in the container 30, and the above-described Si source is present in the container 30 (and in a state in which elements other than Si and an inert gas are not positively supplied) Heating is performed using the high-temperature vacuum furnace 10 in a temperature range of 1500 ° C. or more and 2200 ° C. or less, desirably 1600 ° C. or more and 2000 ° C. or less. As a result, the inside of the storage container 30 has a high-purity Si vapor pressure, and the SiC substrate 40 is heated in this state. Thereby, the surface of the SiC substrate 40 is etched and the surface is planarized. During the Si vapor pressure etching, the following reaction is performed. Briefly described, the SiC substrate 40 is heated under the Si vapor pressure, whereby the SiC of the SiC substrate 40 is thermally decomposed and chemically reacted with Si to become Si ₂ C or SiC ₂ or the like and sublimated, and the Si atmosphere The lower Si bonds to C at the surface of the SiC substrate 40 to cause self-organization and planarization.
(1) SiC (s) → Si (v) I + C (s) I
(2) 2SiC (s) → Si (v) II + SiC ₂ (v)
(3) SiC (s) + Si (v) I + II → Si ₂ C (v)

Since Si vapor pressure etching is not chemical mechanical processing but thermochemical etching, it does not cause processing damage. Rather, the processing damage (for example, the processing damage which arose during cutting and polishing etc.) which arose, for example at the time of preparation of SiC substrate 40 can be removed. That is, in the TSD visualization step of the present embodiment, not only the TSD 51 is visualized, but also the removal of processing damage caused to the SiC substrate 40 can be performed simultaneously. In the TSD visualization step, the etching rate by Si vapor pressure etching is preferably, for example, 1 μm / min or more, and may be less than 1 μm / min except in the TSD visualization step.

Next, a recess forming process is performed on the SiC substrate 40. The recess forming step is a process of forming the recess 53 by leaving the periphery of the portion where the TSD 51 is generated while removing the portion where the TSD 51 visualized in the TSD visualization step is generated. In the present embodiment, the portion where the TSD 51 is generated is removed by irradiating the laser. As a matter of course, the portion where the TSD 51 is not generated is not irradiated with the laser. Thereby, as shown in the SiC substrate 40 after the recess forming step of FIG. 2, the recess 53 can be formed in the portion where the TSD 51 is generated.

The recess 53 has a longer length in the radial direction (horizontal direction, a-axis direction, direction perpendicular to c-axis, the same applies hereinafter) than the pit 52, and further has a length in the depth direction (substrate thickness direction, c-axis direction). That's the long part. The recess 53 is a non-through hole having a circular cross section and a constant diameter, but the shape may be different from that of the present embodiment. For example, the cross section may have a trapezoidal shape (conical concave portion), that is, a shape in which the length in the radial direction becomes shorter as it proceeds in the depth direction. In addition, when the laser is irradiated, damage occurs in the vicinity of the recess 53.

As described above, in the present embodiment, the TSD 51 generated on the SiC substrate 40 is intentionally left. The distribution of TSD 51 is involved in the control of crystal polymorphism. Therefore, in the present embodiment, a part of the TSDs 51 among the plurality of TSDs 51 visualized in the TSD visualization process is irradiated with a laser. That is, a plurality of TSDs 51 visualized in the TSD visualization step are classified into TSDs 51 to be removed and TSDs 51 to be remaining.

In addition, although the recessed part 53 is formed using a laser in this embodiment, as long as the recessed part 53 can be formed, another method can also be used. For example, a mask having an opening formed only in a portion where TSD 51 to be removed is formed is mounted on the surface of SiC substrate 40, and etching (dry etching such as hydrogen etching or wet etching such as KOH etching) Do. Thereby, the recessed part 53 can be formed in the part in which TSD51 of removal object has arisen.

Next, a damage removal process is performed on the SiC substrate 40. The damage removing step is a step of removing the damage caused in the vicinity of the recess 53 in the recess forming step. In the present embodiment, the damage removal step is performed by the above-described Si vapor pressure etching. By performing the Si vapor pressure etching, the damage of the recess 53 is removed. In addition, the recess 53 has a trapezoidal cross section (conical recess), that is, a shape in which the length in the radial direction becomes shorter as it proceeds in the depth direction. In addition, the shape of the recess 53 after the damage removal may be different from that of the present embodiment.

In the present embodiment, the damage removal step is performed using Si vapor pressure etching, but the damage of the recess 53 may be removed by another method (for example, dry etching such as hydrogen etching). Further, in the present embodiment, not only the recess 53 but the entire surface of the SiC substrate 40 is removed, but the configuration may be such that etching (removal of damage) is performed only around the recess 53.

Next, a crystal growth step is performed on the SiC substrate 40. In the crystal growth step, crystal growth is performed from the periphery of the recess 53 by performing crystal growth in the a-axis direction (horizontal direction, direction perpendicular to the substrate thickness direction) and c-axis direction (substrate thickness direction) with respect to the SiC substrate 40. The single crystal SiC 41 is connected on the recess 53. In this embodiment, single crystal SiC (epitaxial layer) is grown using MSE (metastable solvent epitaxy) which is one of solution growth methods.

Hereinafter, the MSE method will be described with reference to FIG. FIG. 5 is a schematic view showing a crystal growth step by the MSE method. As shown in FIG. 5, in the present embodiment, the SiC substrate 40 is accommodated in the accommodation container 30. In addition to the SiC substrate 40, a Si plate 61 and a feed material 62 are disposed inside the storage container 30. These are supported by a support 33.

The SiC substrate 40 is used as a substrate (seed side) for liquid phase epitaxial growth. A Si plate 61 is disposed on one side (upper side) of the SiC substrate 40. The Si plate 61 is a plate-like member made of Si. Since the melting point of Si is about 1400 ° C., the Si plate 61 is melted by heating in the high temperature vacuum furnace 10 described above. A feed material 62 is disposed on one side (upper side) of the Si plate 61. The feed material 62 is made of, for example, polycrystalline 3 C—SiC, and is a substrate having a higher free energy than the SiC substrate 40.

When the SiC substrate 40, the Si plate 61, and the feed material 62 are disposed and heated as described above, the Si plate 61 disposed between the SiC substrate 40 and the feed material 62 is melted, and the silicon melt is used as carbon. Act as a solvent for transfer. The heating temperature is preferably, for example, 1500 ° C. or more and 2300 ° C. or less. This heating generates a concentration gradient in the Si melt based on the difference in free energy between the SiC substrate 40 and the feed material 62, and this concentration gradient becomes a driving force to transfer Si from the feed material 62 to the Si melt. C elutes. C taken into the Si melt bonds with Si of the Si melt and precipitates on the SiC substrate 40 as single crystal SiC. As described above, single crystal SiC 41 can be grown on the surface of SiC substrate 40. In addition, in the MSE method, crystal growth can be performed even when the off-angle is not formed in the SiC substrate 40.

In the MSE method, crystal growth is performed in the a-axis direction and the c-axis direction. Therefore, single crystal SiC 41 is precipitated on the SiC substrate 40 (specifically, the portion excluding the recess 53) by performing crystal growth by performing the MSE method on the SiC substrate 40 in which the recess 53 is formed. By growing the single crystal SiC 41 in the a-axis direction, as shown in the SiC substrate 40 after the crystal growth step of FIG. 3, the single crystal SiC 41 grows so as to close the upper part of the recess 53. Thereafter, by further growing single crystal SiC 41, the upper portion of the recess 53 is completely closed.

Here, since the distance to the feed material 62 is long at the bottom of the recess 53, the growth rate is slow or crystals do not grow. Therefore, the TSD 51 at the bottom of the recess 53 does not propagate to the single crystal SiC 41. On the other hand, since only a few pits 52 are formed in the remaining target TSD 51, single crystal SiC 41 grows. As described above, among the TSDs 51 formed (visualized) on the SiC substrate 40, the TSD 51 to be removed can not be propagated to the single crystal SiC 41, and the TSD 51 to be remaining can be propagated to the single crystal SiC 41. . Thereby, single crystal SiC 41 in which TSD 51 is formed in a desired position can be manufactured. The TSD density of the surface of the single crystal SiC 41 is, for example, 0 / cm ² or more and 1000 / cm ² or less by manufacturing the method according to the present embodiment.

In this embodiment, the crystal growth step is performed using the MSE method, but another method (for example, vapor phase growth method such as CVD method, solution growth in which C in solution is moved by providing a temperature gradient) You may use a law etc.). When using the CVD method, it is necessary to form an off angle in the SiC substrate 40.

Next, applications of the single crystal SiC 41 manufactured as described above will be described with reference to FIG. FIG. 6 is a schematic view showing a process of forming SiC wafer 73 from SiC seed crystal 71 through SiC ingot 72. In the following description, the SiC seed crystal made of single crystal SiC 41 manufactured as described above will be described with reference numeral 71.

By performing the bulk growth process on the SiC seed crystal 71, as shown in FIG. 6, the SiC ingot 72 can be manufactured. The bulk growth step is performed by, for example, a solution growth method such as MSE, or a vapor phase growth method such as sublimation or HTCVD. As described above, the SiC seed crystal 71 has high quality because the TSD 51 to be removed is removed. Furthermore, since the remaining TSD 51 is intentionally left, it is possible to grow a predetermined crystal polymorph (for example, 4H-SiC) regardless of the crystal growth method and various conditions (for example, the overheat temperature). .

Further, as shown in FIG. 6, a wafer manufacturing process is performed on this SiC ingot 72, whereby a plurality of SiC wafers 73 are manufactured. In the wafer manufacturing process, a plurality of SiC wafers 73 are manufactured by cutting the SiC ingot 72 at predetermined intervals by a cutting means such as a diamond wire, for example. The SiC wafer 73 can also be manufactured from the SiC ingot 72 by another method. For example, after providing a damaged layer on the SiC ingot 72 by laser irradiation or the like, it can be formed into a wafer and taken out as the SiC wafer 73.

Similar to the SiC seed crystal 71 and the SiC ingot 72, the SiC wafer 73 manufactured in this manner has a low TSD density on the surface, and is formed of a predetermined crystal polymorphism. Further, on this SiC wafer 73, an epitaxial layer forming step of forming an epitaxial layer made of single crystal SiC is performed. Thereby, the SiC wafer 73 having the epitaxial layer 74 is manufactured. The SiC wafer 73 is used to manufacture a semiconductor device.

In the present embodiment, single crystal SiC 41 is used as SiC seed crystal 71 for producing SiC ingot 72 etc. However, instead of producing SiC ingot 72 from SiC substrate 40 with single crystal SiC 41, single crystal SiC 41 is used. It can also be used as a SiC wafer 73.

Next, with reference to FIGS. 7 to 10, an experiment conducted to confirm the relationship between the beam diameter of the laser irradiated in the recess forming step and the TSD propagation rate will be described. The beam diameter of the laser is the beam diameter set in the laser processing machine, and the diameter of the recess 53 is larger than that. In this experiment, a laser device (MD-T1000) made by Keyence was used. The medium of the laser is Nd: YVO ₄ , and the wavelength of the laser is 532 nm.

First, the SiC substrate 40 was divided into three regions, and the TSD 51 was removed by irradiating each region with a laser of different beam diameter (40 μm, 60 μm, and 100 μm). In this experiment, all of the visualized TSDs 51 were irradiated with a laser. Thereafter, crystal growth of the SiC substrate 40 was performed by the MSE method.

In FIGS. 8 to 10, when crystal growth is performed after removing TSD 51 using lasers with beam diameters of 40 μm, 60 μm, and 100 μm, propagation of TSD 51 occurs where TSD 51 did not occur and propagation of TSD 51 occurred. It is a figure showing distribution of a part. In FIG. 8 to FIG. 10, the area where the propagation of the TSD 51 can be prevented by irradiating the laser to the TSD 51 to form the recess 53 is indicated by a black circle, and the area to which the TSD 51 is propagated is grayed even when the laser is irradiated. It is indicated by a circle. As shown in FIG. 8 to FIG. 10, it was confirmed that the propagation of most of the TSD 51 can be prevented by irradiating the laser to form the recess 53.

Further, FIG. 7 shows a graph showing the relationship between the beam diameter of the laser used in the recess forming step and the TSD propagation rate. The TSD propagation rate is (the number of TSDs 51 propagated) / (the number of TSDs 51 irradiated with a laser). As shown in the graph of FIG. 7, similar propagation rates are realized in the beam diameter range of 40 μm to 100 μm. Specifically, the transmission rate is 15% to 25% (about 20%) in all cases. In other words, the rate at which the TSD 51 can be removed is 75% to 85% (about 80%). In this experiment, a laser device having a beam diameter of 40 μm to 100 μm was used. However, as described above, since the size of the TSD 51 is about 1 μm, the beam diameter may be 1 μm or more. Although the upper limit of the beam diameter is not particularly defined, it takes 40 minutes or less, or preferably 100 μm or less, for example, because it takes time to close the recess 53 as the beam diameter increases.

Next, an example of selectively removing the TSD 51 will be briefly described with reference to FIGS. 11 and 12. FIG. 11 is a schematic view showing the distribution of the TSD 51 to be removed of the SiC substrate 40 for manufacturing the SiC ingot 72 and the TSD 51 to be removed. FIG. 12 is a schematic view showing the distribution of the TSD to be removed and the TSD to be left for producing the SiC wafer 73. As shown in FIG.

In the above-described embodiment, part of the TSD 51 is intentionally left to control (to grow a desired crystal polymorph) in order to control the crystal polymorph of single crystal SiC 41 generated when performing crystal growth, The TSD 51 is left only in the necessary part (as a result, the distribution of the TSD 51 becomes uneven). The selection of the TSD 51 to be removed and the TSD 51 to be remaining is not uniformly determined according to the desired crystal polymorphism and various conditions, and an example will be described below.

The upper part of FIG. 11 is a schematic view showing the distribution of TSD of the SiC substrate 40 (SiC seed crystal 71) for producing the SiC ingot 72 by the solution growth method. When the solution growth method is performed, first, two-dimensional nucleation is performed on the outer edge portion of the SiC substrate 40, and then crystals are grown so as to perform step-flow growth toward the radial center. Therefore, when the SiC substrate 40 is 4H-SiC, the crystalline polymorphism can be taken over to the SiC ingot 72 by the TSD 51 remaining in the outer edge portion. Therefore, in the SiC substrate 40 for producing the SiC ingot 72 by the solution growth method, the recess 53 is formed so that the TSD density of the outer edge portion of the surface of the SiC substrate 40 is higher than the TSD density of other than the outer edge portion. It is preferable to form (forming the recess 53 so that the removal rate of the TSD 51 at the outer edge is lower than the removal rate of the TSD 51 other than the outer edge when the TSD distribution is uniform). The outer edge portion is preferably defined within 10 mm (L1 = 10 mm in FIG. 11) from the outer peripheral surface, for example, when the SiC substrate 40 is viewed in the thickness direction (c axis direction). It is further preferred to define within 5 mm.

The lower part of FIG. 11 is a schematic view showing distribution of TSD of the SiC substrate 40 (SiC seed crystal 71) for producing the SiC ingot 72 by the vapor phase growth method. When the vapor phase growth method is performed, two-dimensional nucleation is first performed in the central portion of the SiC substrate 40, and then the crystal is grown such that step flow growth is performed outward in the radial direction. Therefore, when the SiC substrate 40 is 4H—SiC, the crystalline polymorph can be taken over to the SiC ingot 72 by the TSD 51 remaining in the central portion in the radial direction. Therefore, in the SiC substrate 40 for producing the SiC ingot 72 by the vapor phase growth method, the concave portion 53 is formed such that the TSD density in the central portion of the surface of the SiC substrate 40 is higher than the TSD density in the other portions. (If the distribution of TSDs is uniform, it is preferable to form the recess 53 so that the removal rate of the TSD 51 at the central portion is lower than the removal rate of the TSD 51 other than the central portion). Further, it is more preferable to form the recess 53 so that the TSD density becomes higher toward the radial center. The central portion is preferably defined as, for example, a region within 40% of the diameter from the center in the radial direction when the SiC substrate 40 is viewed in the thickness direction (c-axis direction).

FIG. 12 is a schematic view showing a TSD distribution of the SiC substrate 40 (or the SiC wafer 73 formed via the SiC ingot 72) for forming the epitaxial layer 74 by the step flow growth by CVD or the like. When performing step flow growth by CVD or the like, as shown in the lower part of FIG. 12, the growth is performed so as to take over the crystal polymorph on the upstream side of the step flow growth. Therefore, when the SiC substrate 40 is 4H-SiC, the TSD 51 remains on the upstream side of the step flow growth (upstream from the center of the step flow growth direction, hereinafter the same) to epitaxially crystallize this crystal polymorph. Layer 74 can take over. Therefore, in the SiC substrate 40 for growing the epitaxial layer 74 by step flow growth by CVD or the like, the recessed portion is such that the TSD density on the upstream side of the step flow growth of the SiC substrate 40 is higher than the TSD density on the downstream side. 53 is preferably formed (if the distribution of TSDs is uniform, the recess 53 is formed so that the removal rate of the TSD 51 on the upstream side is lower than the removal rate of the TSD 51 on the downstream side).

As explained above, the manufacturing method of single crystal SiC 41 of this embodiment performs processing including a TSD visualization step, a recess formation step, and a crystal growth step. In the TSD visualization step, dry etching is performed on the SiC substrate 40 to visualize the TSD 51 (penetrating screw dislocation). In the recess formation step, the recess 53 is formed by leaving the periphery of the portion in which the TSD 51 is generated while removing the portion in which the TSD 51 visualized in the TSD visualization step is generated. In the crystal growth step, single crystal SiC 41 grown from the periphery of the recess 53 is connected on the recess 53 by performing crystal growth in the a-axis direction and the c-axis direction on the SiC substrate 40.

Thereby, since TSD 51 contained in SiC substrate 40 can be removed, high quality single crystal SiC 41 can be manufactured. In addition, since the TSD 51 can be visualized without forming a convex portion or the like in advance, the unnecessary TSD 51 can be removed while leaving the necessary TSD 51. In addition, when required TSD51 has not arisen, all TSD51 can also be removed.

Further, in the method of manufacturing single crystal SiC 41 of the present embodiment, in the TSD visualization step, pits 52 are formed in the portion where TSD 51 is generated.

When the TSD 51 is visualized using the MSE method as in Patent Document 1, the portion where the TSD 51 exists grows largely, so the growth portions overlap when the TSD 51 is densely packed, etc., and the TSD 51 can not be identified accurately. there is a possibility. On the other hand, according to the above method, since small pits of about 1 μm are formed in the portion where the TSD 51 is generated, the TSD 51 can be specified more accurately. Therefore, the unnecessary TSD 51 can be identified while leaving the necessary TSD 51 It can be removed.

Further, in the method of manufacturing single crystal SiC 41 of the present embodiment, in the recess forming step, there are a plurality of portions where the visualized TSD 51 is generated, and only a part of the portions is removed.

Thus, since the TSD 51 can be selectively left, crystal polymorphism and the like can be stably controlled when crystal growth is performed using a seed crystal.

Further, in the method of manufacturing single crystal SiC 41 of the present embodiment, it is preferable that TSD 51 be unevenly distributed on the surface of SiC substrate 40 as a result of removing TSD 51 in the recess forming step.

In the method for producing a single crystal SiC41 of this embodiment, the recess forming step, against TSD51 visualized, the TSD51 as TSD51 density of the surface becomes 0 / cm ² or more 1000 / cm ² or less Remove.

Moreover, in the manufacturing method of single crystal SiC41 of this embodiment, TSD51 is visualized by performing the etching by heating by Si vapor pressure in a TSD visualization process.

Thereby, the surface of the SiC substrate 40 can be planarized with high accuracy and the TSD 51 can be visualized.

Further, in the method of manufacturing single crystal SiC 41 according to the present embodiment, in the recess forming step, the recess 53 is formed by irradiating the portion where the TSD 51 is generated with a laser.

Thereby, the recessed part 53 can be correctly formed in the part which TSD51 has produced by the simple and highly accurate method.

Further, in the method of manufacturing single crystal SiC 41 of the present embodiment, the beam diameter of the laser is 1 μm or more.

Thereby, when the recess 53 is formed, the strained area near the dislocation core of the TSD 51 can be removed.

Further, in the method of manufacturing single crystal SiC 41 according to the present embodiment, damage is caused to SiC substrate 40 in the recess forming step by etching SiC substrate 40 after the recess forming step and before the crystal growth step. Perform a damage removal process to remove

Thereby, since the damage which arose in the recessed part formation process can be removed, higher quality single crystal SiC41 can be manufactured.

Further, in the method of manufacturing single crystal SiC 41 of the present embodiment, in the crystal growth step, Si is interposed between SiC substrate 40 and feed material 62 having a higher free energy and supplying at least C than SiC substrate 40. By heating in the presence of the melt, the MSE method of growing single crystal SiC 41 on the surface of the SiC substrate 40 is performed.

Thus, since the growth rate in the a-axis direction is high in the MSE method, the upper part of the recess 53 can be closed with the single crystal SiC 41 in a short time.

Moreover, in the manufacturing method of single crystal SiC 41 of the present embodiment, in the TSD visualizing step, the TSD 51 is visualized by performing etching by heating under Si vapor pressure. In the recess formation step, the recess 53 is formed by irradiating a laser on a portion where the TSD 51 is generated. After the recess formation step, the damage removal step of removing the damage caused to the SiC substrate 40 is performed by performing the etching by heating under the Si vapor pressure. In the crystal growth step, heating is performed in a state in which the Si melt is present between the SiC substrate 40 and a feed material having a free energy higher than that of the SiC substrate 40 and supplying at least C, A metastable solvent epitaxy method for growing single crystal SiC 41 on the surface is performed.

Thereby, high purity single crystal SiC 41 can be manufactured in a short time. Moreover, since both etchings are Si vapor pressure etching, the manufacturing process can be simplified.

The preferred embodiment of the present invention has been described above, but the above-described configuration can be modified, for example, as follows.

The manufacturing process described in FIGS. 2 and 3 is an example, and the order of the processes can be changed, some processes can be omitted, and other processes can be added. For example, the damage removal step can be omitted.

The temperature conditions and pressure conditions described above are examples and can be changed as appropriate. In addition, a heating device other than the high temperature vacuum furnace 10 described above (for example, a high temperature vacuum furnace having a plurality of internal spaces), a polycrystalline substrate as a SiC substrate, or a container having a different shape or material from the storage container 30 is used. You may

10 high temperature vacuum furnace 40 SiC substrate 41 single crystal SiC
51 TSD
52 pit 53 recess 71 SiC seed crystal 72 SiC ingot 73 SiC wafer

Claims

TSD visualization step of performing dry etching on the SiC substrate to visualize TSD (penetration screw dislocation);
A recess forming step of forming a recess by leaving the periphery of the portion where the TSD is generated while removing the portion where the TSD is visualized in the TSD visualization step;
A crystal growth step of connecting single crystal SiC grown from the periphery of the recess on the recess by performing crystal growth in the a-axis direction and c-axis direction on the SiC substrate;
A process for producing single crystal SiC characterized in that the process includes
A method of producing single crystal SiC according to claim 1, wherein
In the TSD visualization step, a pit is formed in a portion where the TSD is generated.
A method of producing single crystal SiC according to claim 1, wherein
In the concave portion forming step, there are a plurality of portions where the visualized TSD is generated, and only a part of the portions is removed.
A method of producing single crystal SiC according to claim 3, wherein
In the recess formation step, as a result of removing the TSD, the TSD is unevenly distributed on the surface of the SiC substrate, and the method for manufacturing single crystal SiC is provided.
A method of producing single crystal SiC according to claim 3, wherein
In the recess forming step, the TSD is removed so that the TSD density on the surface is 1000 pieces / cm 2 or less with respect to the visualized TSD.
A method of producing single crystal SiC according to claim 1, wherein
In the TSD visualization step, the TSD is visualized by performing etching by heating under a Si vapor pressure, thereby producing a single crystal SiC.
A method of producing single crystal SiC according to claim 1, wherein
In the concave portion forming step, the concave portion is formed by irradiating the portion where the TSD is generated with a laser, thereby forming a single crystal SiC.
8. A method of manufacturing single crystal SiC according to claim 7, wherein
A method of manufacturing single crystal SiC, wherein a beam diameter of the laser is 1 μm or more.
A method of producing single crystal SiC according to claim 1, wherein
After the recess forming step and before the crystal growth step, a damage removing step of removing the damage caused to the SiC substrate in the recess forming step by etching the SiC substrate is performed. Method of manufacturing single crystal SiC.
A method of producing single crystal SiC according to claim 1, wherein
In the crystal growth step, heating is performed in a state in which the Si melt is present between the SiC substrate and a feed material having a free energy higher than that of the SiC substrate and supplying at least C; A method for producing single crystal SiC comprising performing metastable solvent epitaxy method for growing the single crystal SiC on the surface.
A method of producing single crystal SiC according to claim 1, wherein
In the TSD visualization step, the TSD is visualized by performing etching by heating under Si vapor pressure,
In the recess forming step, the recess is formed by irradiating a laser on a portion where the TSD is generated;
After the recess formation step, a damage removal step of removing damage caused to the SiC substrate is performed by performing etching by heating under Si vapor pressure,
In the crystal growth step, heating is performed in a state in which the Si melt is present between the SiC substrate and a feed material having a free energy higher than that of the SiC substrate and supplying at least C; A method for producing single crystal SiC comprising performing metastable solvent epitaxy method for growing the single crystal SiC on the surface.
A SiC ingot is manufactured by performing a bulk growth step of performing crystal growth using the single crystal SiC manufactured using the method of manufacturing single crystal SiC according to claim 1 as a seed crystal. Method of manufacturing ingots.
A method of manufacturing a SiC ingot according to claim 12, wherein
In the bulk growth step, a single crystal SiC of the predetermined crystal polymorphism is grown by using the seed crystal according to the predetermined crystal polymorphism.
A method of manufacturing a SiC ingot according to claim 12, wherein
In the recess forming step, the recess is formed such that the TSD density of the outer edge portion of the surface of the SiC substrate is higher than the TSD density of other than the outer edge portion,
In the said bulk growth process, crystal growth is performed by the solution growth method, The manufacturing method of the SiC ingot characterized by the above-mentioned.
A method of manufacturing a SiC ingot according to claim 12, wherein
In the recess forming step, the recess is formed such that the TSD density at the central portion in the radial direction of the surface of the SiC substrate is higher than the TSD density other than the central portion,
In the said bulk growth process, crystal growth is performed by a vapor phase growth method, The manufacturing method of the SiC ingot characterized by the above-mentioned.
A method for producing a SiC wafer, comprising producing a SiC wafer using the SiC ingot produced by using the method for producing a SiC ingot according to claim 12.
A SiC wafer is manufactured by performing an epitaxial layer forming step of forming an epitaxial layer using the single crystal SiC manufactured using the method of manufacturing single crystal SiC according to claim 1. Wafer manufacturing method.
The method of manufacturing a SiC wafer according to claim 17, wherein
In the recess forming step, the recess is formed such that the TSD density on the upstream side with respect to the center of the step flow growth in the epitaxial layer forming step is higher than the TSD density on the downstream side with respect to the center. A method of manufacturing a characterized SiC wafer.
The surface TSD density is 1000 pcs / cm 2 or less,
Single crystal SiC characterized in that it is possible to grow single crystal SiC of the predetermined crystal polymorphism by having a TSD distribution according to a predetermined crystal polymorphism.
21. Single crystal SiC according to claim 19, wherein
Single crystal SiC characterized in that it has an off angle, and the TSD density on the upstream side with respect to the center of step-flow growth in crystal growth is larger than the TSD density on the downstream side with respect to the center.