JP6949358B2 - Method for manufacturing single crystal SiC, method for manufacturing SiC ingot, and method for manufacturing SiC wafer - Google Patents

Description

The present invention mainly relates to a method for producing single crystal SiC by removing TSD (through spiral dislocation) generated on a SiC substrate.

Conventionally, in order to manufacture a high-quality semiconductor device, a method for manufacturing a single crystal SiC having few defects has been sought. Patent Documents 1 to 5 disclose this type of technology.

In the method for producing a single crystal SiC of Patent Document 1, first, a plurality of convex portions are formed by removing the surface of the SiC substrate in a grid pattern with a laser. Then, crystal growth is carried out on the SiC substrate by the MSE method (semi-stable solvent epitaxy method). At this time, the convex portion containing the TSD has a higher growth rate in the c-axis direction than the convex portion not containing the TSD, so that the height in the c-axis direction is higher. After removing the convex portion having a high height in the c-axis direction with a laser, the MSE method is performed again. As a result, the single crystal SiC grown from the plurality of convex portions is connected, and a large-area single crystal SiC is produced.

In the method for producing a single crystal SiC of Patent Document 2, first, a second seed crystal is formed by forming macrostep bunching on the SiC 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 defect, so that a single crystal SiC having a small amount of TSD is produced.

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

In Patent Documents 4 and 5, a thin plate-shaped single crystal SiC is cut out from a single crystal SiC produced by performing crystal growth on a SiC substrate. Then, crystal growth is performed again on this thin plate-shaped single crystal SiC. By repeating the above process, a single crystal SiC having a small amount of TSD is produced.

Japanese Unexamined Patent Publication No. 2017-88444 Japanese Unexamined Patent Publication No. 2014-43369 Japanese Unexamined Patent Publication No. 2010-89983 Japanese Unexamined Patent Publication No. 2003-119097 Japanese Unexamined Patent Publication No. 2015-54814

Here, the TSD contained in the single crystal SiC plays an important role in stably inheriting the crystal polymorphism of the seed crystal when the single crystal is used as the seed crystal to grow the crystal. However, in the methods described in Patent Documents 1 to 5, it is difficult to remove the TSD generated at another position while leaving the TSD generated at a predetermined position. For example, in Patent Document 1, at the stage of forming the convex portion, the TSD formed other than the convex portion is removed.

In the method of Patent Document 1, it is necessary to perform the MSE method for visualizing TSD and the MSE method for obtaining single crystal SiC, which complicates the manufacturing process. In the methods of Patent Documents 2 and 3, the manufacturing process becomes complicated because two-step crystal growth is required. In the methods of Patent Documents 4 and 5, the manufacturing process becomes complicated because it is necessary to perform crystal growth and cutting out a plurality of times.

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

Means and effects to solve problems

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

From the viewpoint of the present invention, the following method for producing single crystal SiC is provided. That is, this method for producing single crystal SiC includes a TSD visualization step, a recess forming step, and a crystal growth step. In the TSD visualization step, TSD (through spiral dislocation) is visualized by performing dry etching on the SiC substrate. In the recess forming step, the recess is formed by removing the portion where the TSD is generated, which is visualized in the TSD visualization step, and leaving the periphery of the portion where the TSD is generated. In the crystal growth step, single crystal SiC grown from the periphery of the recess is connected on the recess by performing crystal growth in the a-axis direction and the c-axis direction with respect to the SiC substrate.

As a result, the TSD contained in the SiC substrate can be removed, so that high-quality single crystal SiC can be produced. Further, since the TSD can be visualized without forming a convex portion or the like in advance, it is possible to remove the unnecessary TSD while leaving the necessary TSD. If the required TSD has not been generated, all the TSDs can be removed. In addition, single crystal SiC can be produced by a simple process as compared with the conventional method.

In the method for producing single crystal SiC, 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 by using the MSE method as in Patent Document 1, the portion where the TSD exists grows large. Therefore, when the TSDs are densely packed, the growing portions overlap and the TSD cannot be specified accurately. there is a possibility. On the other hand, in the above method, a small pit of about 1 μm is formed in the portion where the TSD is generated, so that the TSD can be specified more accurately. Can be removed.

In the method for producing single crystal SiC, it is preferable that in the recess forming step, there are a plurality of parts where the visualized TSD is generated, and only a part thereof is removed.

As a result, since TSD can be selectively left, crystal polymorphs and the like can be stably controlled when crystal growth is performed by using the seed crystal.

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

This makes it possible for the desired polymorph (for example, 4H-SiC) to be easily inherited from the seed crystal in the crystal growth step.

In the method for producing single crystal SiC, in the recess forming step, it is preferable to remove the TSD so ^{that the surface TSD density is 1000 pieces / cm 2 or less with respect to the visualized TSD.}

This makes it possible to facilitate high quality and desired crystal polymorphism (for example, 4H-SiC) from the seed crystal in the crystal growth step.

In the method for producing single crystal SiC, it is preferable that the TSD is visualized by etching by heating under Si vapor pressure in the TSD visualization step.

As a result, the surface of the SiC substrate can be flattened with high accuracy and the TSD can be visualized.

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

Thereby, the recess can be accurately formed in the portion where the TSD is generated by a simple and highly accurate method.

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

Thereby, when the recess is formed, the strain region in the vicinity of the dislocation core of the TSD can be removed.

In the method for producing single crystal SiC, damage caused to the SiC substrate in the recess forming step is removed by etching the SiC substrate after the recess forming step and before the crystal growth step. It is preferable to carry out a damage removing step.

As a result, the damage generated in the recess forming step can be removed, so that higher quality single crystal SiC can be produced.

In the method for producing single crystal SiC, in the crystal growth step, a 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 carry out a semi-stable solvent epitaxy method for growing the single crystal SiC on the surface of the SiC substrate by heating in this state.

As a result, since the semi-stable solvent epitaxy method has a high growth rate in the a-axis direction, the upper part of the recess can be closed with single crystal SiC in a short time.

In the method for producing single crystal SiC described above, it is preferable to carry out as follows. That is, in the TSD visualization step, the TSD is visualized by performing etching by heating under Si steam pressure. In the recess forming step, the recess is formed by irradiating the portion where the TSD is generated with a laser. After the recess forming step, a damage removing step of removing damage generated on the SiC substrate is performed by performing etching by heating under Si steam pressure. In the crystal growth step, the SiC substrate is heated by heating in a state where a 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. A semi-stable solvent epitaxy method is performed in which the single crystal SiC is grown on the surface.

As a result, high-purity single crystal SiC can be produced in a short time. Further, since the two etchings are both Si vapor pressure etchings, the manufacturing process can be simplified.

Further, from another viewpoint of the present invention, it is preferable to produce a SiC ingot using the single crystal SiC produced by the above production method. For example, when an ingot is produced by a solution growth method, it is preferable to form the recess so that the TSD density of the outer edge portion of the surface of the SiC substrate is higher than the TSD density of the other outer edge portion. Further, when the ingot is produced by the vapor phase growth method, the recess may be formed so that the TSD density of the radial central portion of the surface of the SiC substrate is higher than the TSD density of the non-central portion. preferable.

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

Further, from another viewpoint of the present invention, it is preferable to manufacture a SiC wafer by using the single crystal SiC manufactured by the above-mentioned manufacturing method. When 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. It is preferable to form a recess. Further, the single crystal SiC may be used as it is as a SiC wafer.

As a result, it is possible to suppress the mixing of heterogeneous crystal polymorphs on the upstream side in the epitaxial layer forming step.

The figure explaining the outline of the high temperature vacuum furnace used in the manufacturing method of the single crystal SiC of this invention. The schematic diagram which shows the manufacturing process (TSD visualization process, recess 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 figure which shows the micrograph and the stress analysis result of TSD generated on the surface of a SiC substrate. The schematic diagram which shows the crystal growth process by the MSE method. The schematic diagram which shows the process of making a SiC wafer from a SiC seed crystal through a SiC ingot. The graph which shows the relationship between the beam diameter of the laser used in the recess formation process, and the TSD propagation rate. The figure which shows the distribution of the part where the TSD propagation did not occur, and the part where the TSD propagation occurred when crystal growth was performed after removing TSD using a laser having a beam diameter of 40 μm. The figure which shows the distribution of the part where the TSD propagation did not occur, and the part where the TSD propagation occurred when crystal growth was performed after removing TSD using a laser having a beam diameter of 60 μm. The figure which shows the distribution of the part where the TSD propagation did not occur, and the part where the TSD propagation occurred when crystal growth was performed after removing TSD using a laser having a beam diameter of 100 μm. The schematic diagram which shows the distribution of the TSD of the removal target and the TSD of the residual target for making a SiC ingot. The schematic diagram which shows the distribution of the TSD of the removal target and the TSD of the residual target for manufacturing a SiC wafer.

Next, an embodiment of the present invention will be described with reference to the drawings. First, the high-temperature vacuum furnace 10 used in the method for producing single crystal SiC of the present embodiment will be described with reference to FIG.

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

The vacuum forming valve 23, the inert gas injection valve 24, and the vacuum gauge 25 are connected to the heating chamber 21. 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 a gas of a Group 18 element (noble gas element) such as Ar, that is, a gas having poor reactivity with 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 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 the heat-reflecting metal plate reflects the heat of the heater 26 toward the central portion of the main heating chamber 21. It is configured in. As a result, the SiC substrate 40 can be heated strongly and evenly, and the temperature can be raised to a temperature of 1000 ° C. or higher and 2300 ° C. or lower. As the heater 26, for example, a resistance heating type heater or a high frequency induction heating type heater can be used.

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

In the storage container 30, the tantalum layer (Ta), the tantalum carbide layer (TaC, and the tantalum carbide layer) (TaC and the tantalum carbide layer) are arranged in this order from the outside side to the inside space side in the portion constituting the wall surface (upper surface, side surface, bottom surface) of the internal space in which the SiC substrate 40 is accommodated. It is composed of Ta ₂ C) and a tantalum silicide layer (Ta Si ₂ or Ta _{5 Si 3, etc.).}

This tantalum silicide layer supplies Si to the internal space of the storage container 30 by heating. Further, since the storage container 30 contains the tantalum layer and the tantalum carbide layer, the surrounding C vapor can be taken in. This makes it possible to create a high-purity Si atmosphere in the internal space during heating. Instead of providing the tantalum silicide layer, a Si source such as solid Si may be arranged in the internal space. In this case, the solid Si sublimates during heating, so that the inside of the internal space can be reduced to a high-purity Si vapor pressure.

When heating the SiC substrate 40, first, as shown by the chain line in FIG. 1, the storage container 30 is arranged in the preheating chamber 22 of the high-temperature vacuum furnace 10 and preliminarily at an appropriate temperature (for example, about 800 ° C.). Heat. 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. After that, the SiC substrate 40 is heated while adjusting the pressure and the like. Preheating may be omitted.

Next, the manufacturing process of the single crystal SiC41 performed in the present embodiment will be described with reference to FIGS. 2 and 3. 2 and 3 are schematic views showing a manufacturing process of the single crystal SiC41.

As shown in FIG. 2A, a plurality of TSDs (TSD: threading screw dislocations) are generated on 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 micrograph of TSD and the result of stress analysis. The stress analysis is the result of using EBSD (Electron Backscatter Pattern). According to this stress analysis result, the size of TSD (strain region near the dislocation core) is about 1 μm. TSD propagates to the single crystal SiC41 during crystal growth, thereby degrading the quality of the single crystal SiC41. On the other hand, the polymorphism can be controlled by intentionally leaving a part of the TSD generated on the SiC substrate 40. Therefore, in the present embodiment, the remaining TSD is removed (the TSD is selectively removed) while a part of the TSD is intentionally left. Hereinafter, a specific description will be given. Further, in the following description, when the TSD generated on the SiC substrate 40 will be described, reference numeral 51 will be attached.

The SiC substrate 40 used in the present embodiment is an on-board board that does not have an off-angle, but may have an off-angle. The polymorph of the SiC substrate 40 is 4H-SiC, but other polymorphs of crystals (6H-SiC, 3C-SiC, etc.) may be used. The main surface (the surface to be processed) of the SiC substrate 40 is the Si surface (0001) surface, but it may be the C surface (000-1) surface. Further, the surface of the SiC substrate 40 is flat because no convex portions or the like are formed.

First, a TSD visualization step is performed on the SiC substrate 40. The TSD51 formed on the SiC substrate 40 cannot 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 an observable state. The TSD visualization step also includes a step of emphasizing the TSD 51, which is difficult to observe but not impossible, to facilitate observation. In the present embodiment, Si vapor pressure etching is performed on the SiC substrate 40, but other dry etching (for example, hydrogen etching) may be performed. By performing dry etching on the SiC substrate 40, as shown in FIG. 2B, a pit 52 is generated in the portion where the TSD 51 is generated. The pit 52 is a slight depression formed on the surface of the SiC substrate 40. As a result, the location where the TSD51 is generated can be visualized.

Here, Si vapor pressure etching will be described in detail. In the Si vapor pressure etching, the SiC substrate 40 is housed in the storage container 30, and the above-mentioned Si source is present in the storage container 30 (and 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 higher and 2200 ° C. or lower, preferably 1600 ° C. or higher and 2000 ° C. or lower. As a result, the inside of the storage container 30 becomes a high-purity Si steam pressure, and the SiC substrate 40 is heated in this state. As a result, the surface of the outer peripheral surface of the SiC substrate 40 is etched and the surface is flattened. During this Si vapor pressure etching, the following reactions are carried out. Briefly, that SiC substrate 40 is heated by the Si vapor pressure, with SiC of the SiC substrate 40 to sublimate becomes Si ₂ C or SiC ₂ and the like by a chemical reaction between the pyrolysis and Si, Si Atmosphere The lower Si combines with C on the surface of the outer peripheral surface of the SiC substrate 40 to cause self-assembly and flattening.
(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 thermochemical etching rather than machining, it does not cause processing damage. Rather, it is possible to remove, for example, processing damage (for example, processing damage generated during cutting, polishing, etc.) during the production of the SiC substrate 40. That is, in the TSD visualization step of the present embodiment, not only the TSD 51 can be visualized, but also the processing damage generated on the SiC substrate 40 can be removed at the same time. Further, in the TSD visualization step, the etching rate by Si vapor pressure etching is preferably 1 μm / min or more, and may be less than 1 μm / min except in the TSD visualization step.

Next, a recess forming step is performed on the SiC substrate 40. The recess forming step is a process of forming the recess 53 by removing the portion where the TSD 51 visualized in the TSD visualization step is generated and leaving the periphery of the portion where the TSD 51 is generated. In the present embodiment, the portion where the TSD51 is generated is removed by irradiating the laser. As a matter of course, the laser is not applied to the portion where TSD51 is not generated. As a result, as shown in FIG. 2C, the recess 53 can be formed in the portion where the TSD 51 is generated.

The recess 53 has a larger radial length (horizontal direction, a-axis direction, direction perpendicular to the 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). It is a long part. In FIG. 2C, the recess 53 is a non-penetrating 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 trapezoidal concave portion), that is, a shape in which the length in the radial direction becomes shorter as the cross section advances in the depth direction. Further, by irradiating the laser, 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 TSD51 is involved in the control of polymorphism. Therefore, in the present embodiment, among the plurality of TSD51s visualized in the TSD visualization step, some TSD51s are irradiated with the laser. That is, the plurality of TSDs 51 visualized in the TSD visualization step are classified into a TSD51 to be removed and a TSD51 to remain.

In the present embodiment, the recess 53 is formed by using a laser, but other methods can be used as long as the recess 53 can be formed. For example, a mask having an opening formed only in the portion where the TSD51 to be removed is generated is placed on the surface of the SiC substrate 40 and etched (dry etching such as hydrogen etching or wet etching such as KOH etching). conduct. As a result, the recess 53 can be formed in the portion where the TSD 51 to be removed is generated.

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

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

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

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

When the SiC substrate 40, the Si plate 61, and the feed material 62 are arranged and heated as described above, the Si plate 61 arranged between the SiC substrate 40 and the feed material 62 is melted, and the silicon melt melts carbon. It acts as a solvent for transfer. The heating temperature is preferably 1500 ° C. or higher and 2300 ° C. or lower, for example. By this heating, a concentration gradient is generated 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 serves as a driving force to transfer Si from the feed material 62 to the Si melt. C elutes. C incorporated in the Si melt is combined with Si in the Si melt and precipitated as single crystal SiC on the SiC substrate 40. As described above, the single crystal SiC 41 can be grown on the surface of the SiC substrate 40. Further, in the MSE method, crystal growth can be performed even when the off-angle is not formed on the SiC substrate 40.

In the MSE method, crystal growth is carried out in the a-axis direction and the c-axis direction. Therefore, as shown in FIG. 3E, the single crystal SiC 41 is formed on the SiC substrate 40 (specifically, the portion excluding the recess 53) by performing the MSE method on the SiC substrate 40 on which the recess 53 is formed to grow crystals. Precipitate. As the single crystal SiC 41 grows in the a-axis direction, as shown in FIG. 3 (f), the single crystal SiC 41 grows so as to close the upper part of the recess 53. After that, by further growing the single crystal SiC 41, the upper part 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 the crystal does 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, the single crystal SiC 41 grows. As described above, among the (visualized) TSD51 formed on the SiC substrate 40, the TSD51 to be removed can not be propagated to the single crystal SiC41, and the remaining target TSD51 can be propagated to the single crystal SiC41. .. This makes it possible to produce a single crystal SiC41 in which the TSD51 is formed at a desired position. By producing by the method of this embodiment, the TSD density on the surface of the single crystal SiC 41 is, for example, 0 pieces / cm ² or more and 1000 pieces / cm ² or less.

In this embodiment, the crystal growth step is performed using the MSE method, but other methods (for example, a vapor phase growth method such as the CVD method, or solution growth in which C or the like in the solution is moved by providing a temperature gradient). Law, etc.) may be used. When the CVD method is used, it is necessary to form an off-angle on the SiC substrate 40.

Next, the use of the single crystal SiC41 produced as described above will be described with reference to FIG. FIG. 6 is a schematic view showing a process of producing a SiC wafer 73 from a SiC seed crystal 71 via a SiC ingot 72. In the following description, the SiC seed crystal made of the single crystal SiC 41 produced as described above will be described with reference to reference numeral 71.

By performing a bulk growth step on the SiC seed crystal 71, the SiC ingot 72 can be produced as shown in FIG. The bulk growth step is carried out by, for example, a solution growth method such as the MSE method, or a vapor phase growth method such as a sublimation method or HTCVD. As described above, the SiC seed crystal 71 is of high quality because the TSD51 to be removed has been removed. Further, since the TSD51 to be retained is intentionally left, a predetermined crystal polymorph (for example, 4H-SiC) can be grown regardless of the crystal growth method and various conditions (for example, superheat temperature). ..

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

Like the SiC seed crystal 71 and the SiC ingot 72, the SiC wafer 73 produced in this manner has a low surface TSD density and is composed of predetermined polymorphs of crystals. Further, the SiC wafer 73 is subjected to an epitaxial layer forming step of forming an epitaxial layer made of single crystal SiC. As a result, the SiC wafer 73 having the epitaxial layer 74 is manufactured. The SiC wafer 73 is used for manufacturing a semiconductor device.

In the present embodiment, the single crystal SiC 41 is used as the SiC seed crystal 71 for producing the SiC ingot 72 and the like, but instead, the SiC ingot 72 is not produced from the SiC substrate 40 with the single crystal SiC 41. It can also be used as a SiC wafer 73.

Next, with reference to FIGS. 7 to 10, an experiment performed to confirm the relationship between the beam diameter of the laser irradiated in the recess forming step and the TSD propagation coefficient will be described. The laser beam diameter is a 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) manufactured by KEYENCE was used. The medium of the laser was Nd: YVO ₄ , and the wavelength of the laser was 532 nm.

First, the SiC substrate 40 was divided into three regions, and the TSD 51 was removed by irradiating each region with lasers having different beam diameters (40 μm, 60 μm, and 100 μm). In this experiment, all of the visualized TSD51 was irradiated with a laser. Then, the SiC substrate 40 was crystal-grown by the MSE method.

8 to 10 show a portion where TSD51 did not propagate and a portion where TSD51 propagated when crystal growth was performed after removing TSD51 using lasers having beam diameters of 40 μm, 60 μm, and 100 μm, respectively. It is a figure which shows the distribution of a place. In FIGS. 8 to 10, the area where the propagation of the TSD 51 can be prevented by irradiating the TSD 51 with the laser to form the recess 53 is indicated by a black circle (none), and the portion where the TSD 51 is propagated even when the laser is irradiated is displayed. Is indicated by a gray circle (TSD). As shown in FIGS. 8 to 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 coefficient. The TSD propagation rate is (the number of TSD51 propagated) / (the number of laser irradiations on the TSD51). As shown in the graph of FIG. 7, in the range of the beam diameter of 40 μm to 100 μm, the same propagation rate is realized. Specifically, the propagation rates are all 15% to 25% (about 20%). In other words, the rate at which TSD51 could be removed was 75% to 85% (about 80%). In this experiment, a laser device having a beam diameter of 40 μm or more and 100 μm or less was used. However, since the size of the TSD 51 is about 1 μm as described above, the beam diameter may be 1 μm or more. The upper limit of the beam diameter is not particularly specified, but as the beam diameter increases, it takes time to close the recess 53, so that it is preferably 40 μm or less, or 100 μm or less, for example.

Next, an example of selectively removing the TSD51 will be briefly described with reference to FIGS. 11 and 12. FIG. 11 is a schematic view showing the distribution of the TSD51 to be removed and the remaining TSD51 of the SiC substrate 40 for manufacturing the SiC ingot 72. FIG. 12 is a schematic view showing the distribution of the TSD to be removed and the TSD to be retained for producing the SiC wafer 73.

In the above-described embodiment, in order to control the crystal polymorphism of the single crystal SiC41 generated when the crystal growth is performed (to grow the desired crystal polymorphism), a part of TSD51 is intentionally left. The TSD51 remains only in the necessary portion (as a result, the distribution of the TSD51 becomes non-uniform). Since the selection of the TSD51 to be removed and the TSD51 to be retained is not uniformly determined according to the desired polymorphism and various conditions, an example will be described below.

FIG. 11A 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 of the SiC substrate 40, and then the crystal grows by performing step flow growth toward the center in the radial direction. Therefore, when the SiC substrate 40 is 4H-SiC, the TSD51 remains at the outer edge portion, so that this polymorph can be taken over by the SiC ingot 72. Therefore, in the SiC substrate 40 for producing the SiC ingot 72 by the solution growth method, the recess 53 is provided so that the TSD density of the outer edge portion of the surface of the SiC substrate 40 is higher than the TSD density other than the outer edge portion. It is preferably formed (when the distribution of TSD is uniform, the recess 53 is formed so that the removal rate of TSD51 at the outer edge portion is lower than the removal rate of TSD51 other than the outer edge portion). Further, it is preferable that the outer edge portion is defined as, for example, within 10 mm (L1 = 10 mm in FIG. 11A) from the outer peripheral surface when the SiC substrate 40 is viewed in the thickness direction (c-axis direction). It is more preferable to specify that it is within 5 mm from the outer peripheral surface.

FIG. 11B 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 vapor phase growth method. When the vapor phase growth method is performed, first, two-dimensional nucleation is performed in the central portion of the SiC substrate 40, and then the crystal grows by performing step flow growth toward the outside in the radial direction. Therefore, when the SiC substrate 40 is 4H-SiC, the TSD51 remains in the central portion in the radial direction, so that this polymorph can be taken over by the SiC ingot 72. Therefore, in the SiC substrate 40 for producing the SiC ingot 72 by the vapor phase growth method, the recess 53 is provided so that the TSD density in the central portion of the surface of the SiC substrate 40 is higher than the TSD density in the non-central portion. (When the distribution of TSD is uniform, the recess 53 is formed so that the removal rate of the TSD 51 in 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 increases as it approaches the center in the radial direction. Further, the central portion is preferably defined as a region within 40% of the diameter from the center in the radial direction when, for example, the SiC substrate 40 is viewed in the thickness direction (c-axis direction).

FIG. 12 is a schematic view showing the distribution of TSD of the SiC substrate 40 (or the SiC wafer 73 created via the SiC ingot 72) for forming the epitaxial layer 74 by step flow growth by CVD or the like. When step flow growth is carried out by CVD or the like, as shown in FIG. 12 (b), the growth is carried out so as to inherit the crystal polymorph on the upstream side of the step flow growth. Therefore, when the SiC substrate 40 is 4H-SiC, the TSD51 remains on the upstream side of the step flow growth (upstream side from the center of the step flow growth direction, and the same applies hereinafter), so that this crystal polymorph is epitaxialized. It can be taken over by layer 74. Therefore, in the SiC substrate 40 for growing the epitaxial layer 74 by step flow growth by CVD or the like, the recess is provided so 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. It is preferable to form 53 (when the distribution of TSD is uniform, the recess 53 is formed so that the removal rate of TSD 51 on the upstream side is lower than the removal rate of TSD 51 on the downstream side).

As described above, the method for producing a single crystal SiC41 of the present embodiment performs a process including a TSD visualization step, a recess forming step, and a crystal growth step. In the TSD visualization step, the SiC substrate 40 is dry-etched to visualize the TSD 51 (through spiral dislocation). In the recess forming step, the recess 53 is formed by removing the portion where the TSD 51 visualized in the TSD visualization step is generated and leaving the periphery of the portion where the TSD 51 is generated. In the crystal growth step, the 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 with respect to the SiC substrate 40.

As a result, the TSD 51 contained in the SiC substrate 40 can be removed, so that a high-quality single crystal SiC 41 can be manufactured. Further, since the TSD51 can be visualized without forming a convex portion or the like in advance, it is possible to remove the unnecessary TSD51 while leaving the necessary TSD51. If the required TSD51 is not generated, all TSD51 can be removed.

Further, in the method for producing a single crystal SiC 41 of the present embodiment, in the TSD visualization step, a pit 52 is formed in a portion where the TSD 51 is generated.

When the TSD51 is visualized by using the MSE method as in Patent Document 1, the portion where the TSD51 exists grows large. Therefore, when the TSD51 is densely packed, the growing portions overlap and the TSD51 cannot be specified accurately. there is a possibility. On the other hand, in the above method, since a small pit of about 1 μm is formed in the portion where the TSD51 is generated, the TSD51 can be specified more accurately, so that the unnecessary TSD51 can be retained while the necessary TSD51 remains. Can be removed.

Further, in the method for producing the single crystal SiC41 of the present embodiment, in the recess forming step, there are a plurality of portions where the visualized TSD51 is generated, and only a part thereof is removed.

As a result, the TSD51 can be selectively left, so that the polymorphism and the like can be stably controlled when the crystal is grown by using it as a seed crystal.

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

This makes it possible for the desired polymorph (for example, 4H-SiC) to be easily inherited from the seed crystal in the crystal growth step.

Further, in the method for producing the single crystal SiC41 of the present embodiment, in the recess forming step, the TSD51 is formed so that the surface TSD51 density is 0 pieces / cm ² or more and 1000 pieces / cm ² or less with respect to the visualized TSD51. Remove.

This makes it possible to facilitate high quality and desired crystal polymorphism (for example, 4H-SiC) from the seed crystal in the crystal growth step.

Further, in the method for producing a single crystal SiC41 of the present embodiment, in the TSD visualization step, the TSD51 is visualized by etching by heating under Si vapor pressure.

As a result, the surface of the SiC substrate 40 can be flattened with high accuracy and the TSD 51 can be visualized.

Further, in the method for producing the single crystal SiC 41 of 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 recess 53 can be accurately formed in the portion where the TSD 51 is generated by a simple and highly accurate method.

Further, in the method for producing a single crystal SiC41 of the present embodiment, the beam diameter of the laser is 1 μm or more.

As a result, when the recess 53 is formed, the strain region near the dislocation core of the TSD 51 can be removed.

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

As a result, the damage generated in the recess forming step can be removed, so that a higher quality single crystal SiC41 can be produced.

Further, in the method for producing a single crystal SiC 41 of the present embodiment, in the crystal growth step, Si is placed between the SiC substrate 40 and the feed material 62 which has higher free energy than the SiC substrate 40 and supplies at least C. The MSE method is performed in which the single crystal SiC 41 is grown on the surface of the SiC substrate 40 by heating in the presence of the melt.

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

Further, in the method for producing a single crystal SiC41 of the present embodiment, in the TSD visualization step, the TSD51 is visualized by performing etching by heating under Si vapor pressure. In the recess forming step, the recess 53 is formed by irradiating the portion where the TSD 51 is generated with a laser. After the recess forming step, a damage removing step of removing damage generated on the SiC substrate 40 is performed by performing etching by heating under Si steam pressure. In the crystal growth step, the SiC substrate 40 is heated by heating in a state where a Si melt is present between the SiC substrate 40 and a feed material having a higher free energy than the SiC substrate 40 and supplying at least C. A semi-stable solvent epitaxy method is performed in which single crystal SiC41 is grown on the surface.

As a result, a single crystal SiC41 having high purity can be produced in a short time. Further, since the two etchings are both Si vapor pressure etchings, the manufacturing process can be simplified.

Although the preferred embodiment of the present invention has been described above, the above configuration can be changed as follows, for example.

The manufacturing processes described in FIGS. 2 and 3 and the like are examples, 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, pressure conditions, etc. described above are examples and can be changed as appropriate. Further, a heating device other than the above-mentioned high-temperature vacuum furnace 10 (for example, a high-temperature vacuum furnace having a plurality of internal spaces) is used, a polycrystalline substrate is used as the SiC substrate, or a container having a shape or material different from that of the storage container 30 is used. You may do it.

10 High temperature vacuum furnace 40 SiC substrate 41 Single crystal SiC
51 TSD
52 Pit 53 Recessed 71 SiC seed crystal 72 SiC ingot 73 SiC wafer

Claims (18)

A TSD visualization process that visualizes TSD (through spiral dislocation) by performing dry etching on a SiC substrate.
A recess forming step of forming a recess by removing the portion where the TSD is generated, which is visualized in the TSD visualization step, and leaving the periphery of the portion where the TSD is generated.
A crystal growth step in which single crystal SiC grown from the periphery of the recess is connected on the recess by performing crystal growth in the a-axis direction and the c-axis direction on the SiC substrate.
A method for producing single crystal SiC, which comprises performing a treatment including. The method for producing single crystal SiC according to claim 1.
A method for producing single crystal SiC, which comprises forming pits in a portion where the TSD is generated in the TSD visualization step. The method for producing single crystal SiC according to claim 1 or 2.
A method for producing single crystal SiC, which comprises a plurality of visualized portions where the TSD is generated in the recess forming step, and removing only a portion thereof. The method for producing single crystal SiC according to claim 3.
A method for producing a single crystal SiC, which comprises removing the TSD in the recess forming step, and as a result, the TSD is unevenly distributed on the surface of the SiC substrate. The method for producing single crystal SiC according to claim 3 or 4.
A method for producing single crystal SiC, which comprises removing the TSD so that the surface TSD density is 1000 pieces / cm ^{2 or less with respect to the visualized TSD in the recess forming step.} The method for producing single crystal SiC according to any one of claims 1 to 5.
The TSD visualization step is a method for producing a single crystal SiC, which visualizes the TSD by performing etching by heating under Si vapor pressure. The method for producing single crystal SiC according to any one of claims 1 to 6.
A method for producing single crystal SiC, which comprises forming the recess by irradiating a portion where the TSD is generated with a laser in the recess forming step. The method for producing single crystal SiC according to claim 7.
A method for producing single crystal SiC, wherein the beam diameter of the laser is 1 μm or more. The method for producing single crystal SiC according to any one of claims 1 to 8.
It is characterized in that a damage removing step of removing damage generated in the SiC substrate in the recess forming step is performed by etching the SiC substrate after the recess forming step and before the crystal growth step. A method for producing single crystal SiC. The method for producing single crystal SiC according to any one of claims 1 to 9.
In the crystal growth step, the SiC substrate is heated by heating in a state where a 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. A method for producing single crystal SiC, which comprises performing a semi-stable solvent epitaxy method for growing the single crystal SiC on the surface. The method for producing single crystal SiC according to claim 1.
In the TSD visualization step, the TSD is visualized by performing etching by heating under Si steam pressure.
In the recess forming step, the recess is formed by irradiating the portion where the TSD is generated with a laser.
After the recess forming step, a damage removing step of removing damage generated on the SiC substrate is performed by performing etching by heating under Si steam pressure.
In the crystal growth step, the SiC substrate is heated by heating in a state where a 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. A method for producing single crystal SiC, which comprises performing a semi-stable solvent epitaxy method for growing the single crystal SiC on the surface. A SiC ingot is obtained by performing a bulk growth step of performing crystal growth using the single crystal SiC produced by the method for producing single crystal SiC according to any one of claims 1 to 11 as a seed crystal. A method for manufacturing a SiC ingot, which comprises manufacturing. The method for manufacturing a SiC ingot according to claim 12.
A method for producing a SiC ingot, which comprises growing a predetermined polymorphic single crystal SiC by using the seed crystal corresponding to a predetermined polymorph in the bulk in the bulk growth step. The method for manufacturing a SiC ingot according to claim 12 or 13.
In the recess forming step, the recess is formed so that the TSD density of the outer edge portion of the surface of the SiC substrate is higher than the TSD density other than the outer edge portion.
A method for producing a SiC ingot, which comprises performing crystal growth by a solution growth method in the bulk growth step. The method for manufacturing a SiC ingot according to claim 12 or 13.
In the recess forming step, the recess is formed so that the TSD density of the radial central portion of the surface of the SiC substrate is higher than the TSD density of the non-central portion.
A method for producing a SiC ingot, which comprises performing crystal growth by a vapor phase growth method in the bulk growth step. A method for producing a SiC wafer, which comprises producing a SiC wafer using the SiC ingot produced by using the method for producing a SiC ingot according to claim 12 or 13. A SiC wafer is obtained by performing an epitaxial layer forming step of forming an epitaxial layer using the single crystal SiC produced by the method for producing single crystal SiC according to any one of claims 1 to 11. A method for producing a SiC wafer, which comprises producing a SiC wafer. The method for manufacturing a SiC wafer according to claim 17.
In the recess forming step, the recess is formed so 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 characteristic method for manufacturing a SiC wafer.

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