JP5030440B2 - Seed crystal fixing device and seed crystal fixing method - Google Patents

Description

  The present invention relates to a seed crystal fixing device and a seed crystal fixing method for fixing a seed crystal to a seed crystal arrangement part of a reaction vessel via an adhesive.

  Silicon carbide is attracting attention as a small and high-power electronic device material such as a semiconductor because it has a larger band gap and is superior in dielectric breakdown characteristics, heat resistance, radiation resistance, and the like. In addition, it has attracted attention as an optical device material because of its excellent optical characteristics. Among such silicon carbide crystals, a silicon carbide single crystal has an advantage that it is particularly excellent in uniformity of characteristics within a wafer when applied to a device such as a wafer, compared to a silicon carbide polycrystal.

  As one method for producing this silicon carbide single crystal, a sublimation raw material is accommodated in a first end portion in a reaction vessel (crucible), and a second end portion (seed) that substantially faces the sublimation raw material in the reaction vessel. There is an improved Rayleigh method in which a silicon carbide single crystal seed crystal is arranged in the crystal arrangement portion), and the sublimated raw material for sublimation is recrystallized on the seed crystal to grow a silicon carbide single crystal.

  In the modified Rayleigh method, when a seed crystal is grown in a state where the seed crystal is not completely adhered to the seed crystal arrangement portion, the crystal grown through the seed crystal from the seed crystal arrangement portion side of the portion not completely adhered There was a tendency for the macro defect (cavity defect) to occur inside and to deteriorate the quality of the wafer. Further, it has been considered that the adhesive is gasified at a high temperature and remains as bubbles in the adhesive layer as a cause of the deterioration of quality.

  Several techniques have been proposed as means for solving the above problems (see, for example, Patent Documents 1 and 2). For example, Patent Literature 1 discloses a fixing method in which a predetermined pressure is applied for fixing. Patent Document 2 discloses a fixing method in which a weight is placed on a seed crystal and pressure-bonded.

However, in the mechanical pressure bonding method, fine irregularities are generated on the surface of the seed crystal, so that it is difficult to press the entire surface of the seed crystal uniformly. In addition, it is difficult to uniformly press the weight using the weight.
JP 2001-139394 A Japanese Patent Laid-Open No. 2003-119098

  There has been a demand for a seed crystal fixing method and a seed crystal fixing device that uniformly press-bond the seed crystal surface to the seed crystal arrangement portion.

That is, the present invention relates to the following description items.
(1) A seed crystal fixing device for fixing a seed crystal to a seed crystal arrangement part of a reaction vessel via an adhesive, the chamber in which the seed crystal arrangement part can be arranged, and the inside of the chamber And a flexible bag body that expands and contracts by gas supply / exhaust and contacts the surface of the seed crystal when it expands and applies uniform pressure to the entire surface of the seed crystal. apparatus.
(2) The seed crystal fixing device according to (1), wherein the chamber can form a reduced-pressure atmosphere.
(3) The seed crystal fixing device according to (1) or (2), wherein the chamber has a guide for fixing the seed crystal arrangement portion and fixing the seed crystal.
(4) The seed crystal fixing device according to (3), wherein the guide contacts the side surface of the seed crystal at least at three points.
(5) The seed crystal fixing device according to any one of (1) to (4), wherein the flexible bag is made of rubber or resin.
(6) The seed crystal fixing device according to any one of (1) to (5), further including a heating body that heats and cures the adhesive.
(7) A seed crystal fixing method for disposing a seed crystal disposition portion provided with a seed crystal via an adhesive, wherein the seed crystal is expanded by inflating a flexible bag body that expands and contracts by gas supply and exhaust. A step of bringing a flexible bag into contact with the other side of the seed crystal arrangement surface to uniformly apply pressure to the entire surface of the seed crystal, and a step of curing the adhesive,
A seed crystal fixing method comprising:
(8) The seed crystal fixing method according to (6), wherein the heat curing is performed under reduced pressure.

  Provided is a reproducible seed crystal fixing method and seed crystal fixing apparatus that can uniformly press-bond a seed crystal surface to a seed crystal arrangement part.

  Hereinafter, the present invention will be described with reference to embodiments, but it goes without saying that the present invention is not limited to the following embodiments. In addition, about the thing which has the same function use in a figure, the same or similar code | symbol is attached | subjected and description is abbreviate | omitted.

(Seed crystal fixing device)
FIG. 1A shows a schematic cross-sectional view of a seed crystal fixing device 1 in which a seed crystal placement unit 3 in which a seed crystal 9 is placed via an adhesive 5 is housed, and FIG. 1B shows an upper surface of a lower chamber. The figure is shown. As shown in FIG. 1 (a), a seed crystal fixing device 1 according to the embodiment is a seed crystal fixing device for fixing a seed crystal 9 to a seed crystal placement portion 3 of a reaction vessel via an adhesive 5. The seed crystal placement portion 3 can be placed inside the chamber 10 to form a sealed atmosphere, and the seed crystal placement portion 3 is placed inside the chamber 10, expands and contracts by gas supply and exhaust, and contacts the surface of the seed crystal when expanded. And a flexible bag body 16 that applies pressure uniformly over the entire surface of the crystal. The seed crystal fixing device 1 further includes a heating body 20 that heats and cures the adhesive.

  The chamber 10 includes an upper chamber 11 and a lower chamber 13 that are detachably formed. When the chamber 10 is used, the upper chamber 11 is attached to the lower chamber 13 with an O-ring 15 disposed on the outer periphery of the lower chamber 13 interposed therebetween. Thus, a sealed atmosphere is formed. A suction exhaust port 12 is provided in the chamber 10, and a reduced pressure atmosphere is formed by sucking air from the chamber 10 in which a sealed atmosphere is formed. Moreover, the lower chamber 13 has a guide 17 for fixing the seed crystal 9 and fixing the seed crystal 9 as shown in FIGS. After the seed crystal placement unit 3 is stored in the lower chamber 13, the guide 17 is detachably fixed to the lower chamber 13, and the seed crystal 9 is placed on the seed crystal placement unit 3.

  The guide 17 is preferably in contact with the side surface of the seed crystal 9 at three or more points. This is to prevent the adhesive 5 protruding from the seed crystal 9 from adhering and solidifying to the guide 17 and preventing the seed crystal 9 from peeling off from the guide 17. Specifically, as shown in FIG. 5 (b), the guide 171 is provided with claws 171a to 171d, and the seed crystal 9 can be held at these four points. The shape of the pawls 171a to 171d is not limited to a semicircular shape as shown in the top view of FIG. Therefore, it may be a substantially equilateral triangle shape that tapers toward the contact point with the seed crystal 9. From the viewpoint of being easily pressed by the flexible bag body 16, the pawls 171a to 171d are preferably substantially equilateral triangles. The surface of the guide 17 is preferably coated with a fluororesin (Teflon (registered trademark)). The Teflon (registered trademark) coating may be applied only to the surfaces of the claws 171 a to 171 d of the guide 17, but may be applied to the entire surface of the guide 17.

  The flexible bag body 16 is made of rubber or resin. The method for fixing the seed crystal arrangement part 3 is not limited to the above, and it may be fixed in a digging manner in the chamber.

  As seed crystal arrangement part 3 accommodated in seed crystal fixing device 1, for example, seed crystal arrangement part 3 of silicon carbide single crystal manufacturing apparatus 30 shown in FIG. 3 described later can be used. The seed crystal 9 is appropriately determined depending on the purpose of use, but 6H Rayleigh crystal, 6H Atchison crystal, or the like can be used. Examples of the adhesive 5 include resins, carbohydrates, and heat-resistant fine particles. As the resin, a thermosetting resin such as a phenol resin, a novolac resin, a furfuryl alcohol resin, or the like can be used. It is also possible to use a phenol resin mixed with carbon powder. As the carbohydrate, saccharides such as monosaccharides such as glucose and polysaccharides such as cellulose and derivatives thereof can be used. As heat-resistant fine particles, in addition to graphite (carbon), heat-resistant materials such as silicon carbide (SiC) and boron nitride (BN), refractory metals such as tungsten and tantalum, and compounds thereof such as carbides and nitrides are used. be able to.

(Seed crystal fixation method)
A seed crystal fixing method according to the embodiment using the seed crystal fixing device of FIG. 1 will be described with reference to FIGS.

(A) First, the lower chamber 13 is prepared as shown in FIG.
(B) Next, as shown in FIG. 2 (b), the seed crystal arrangement part 3 of the reaction vessel is arranged in the lower chamber 13.
(C) Then, as shown in FIG. 2 (c), the seed crystal arrangement part 3 is fixed by the guide 17.

(D) As shown in FIG. 2 (d), the adhesive 5 is applied onto the seed crystal arrangement part 3. The coating amount is preferably from ^{1μl / cm 2 ~25μl / cm 2} .
(E) Next, as shown in FIG. 2 (e), the seed crystal 9 is arranged on the seed crystal arrangement part 3 through the adhesive 5. From the viewpoint of improving adhesiveness, it is preferable to polish the contact surface of the seed crystal 9 with the seed crystal arrangement portion 3 in advance. Specifically, the surface roughness (Ra) of the contact surface of the seed crystal 9 is preferably 0.1 μm or less. Further, it is preferable that the surface roughness (Ra) of the seed crystal 9 arrangement surface of the seed crystal arrangement part 3 is 1.4 μm or less from the viewpoint of improving the adhesiveness.

(F) As shown in FIG. 2F, the upper chamber 11 is attached to the lower chamber 13 to form a sealed atmosphere.
(G) As shown in FIG. 2G, gas is supplied to the flexible bag body 16 to inflate the flexible bag body 16. Then, the flexible bag 16 is brought into contact with the other side of the seed crystal placement surface of the seed crystal 9 to apply pressure uniformly to the entire surface of the seed crystal 9. It is preferable to apply a load at a pressure of about 0.01 to 1 MPa.
(H) The adhesive 5 is cured by heating with the heating body 20. The heating conditions depend on the properties of the adhesive (thermosetting resin) and the like, but are 100 ° C. to 1000 ° C., preferably 100 ° C. to 300 ° C., for about 5 minutes to 10 minutes.

  Here, if the gas generated when the adhesive 5 is cured remains as bubbles between the seed crystal 9 and the seed crystal disposition portion 3, it may cause adhesion unevenness. Therefore, it is preferable to heat and cure while forming a reduced-pressure atmosphere by sucking air or gas considered to cause uneven adhesion from the chamber 10 using a suction device (not shown) connected to the suction exhaust port 12. . In the case of forming this reduced pressure atmosphere, the reduced pressure atmosphere is formed prior to the above step (G), and then the uniformity of the pressure applied to the seed crystal 9 by performing the steps (G) and (H). The improvement effect can also be obtained. That is, the reproducibility of adhesiveness is improved by always bonding under the same conditions. The reduced pressure atmosphere is preferably 300 Torr or less. The seed crystal 9 is fixed on the seed crystal arrangement part 3 by the above.

(Method for producing silicon carbide single crystal)
Although the seed crystal fixing method and the like have been described above, a method for producing a silicon carbide single crystal is provided as another embodiment of the present invention. That is, the sublimation raw material is contained in a reaction vessel containing the sublimation raw material, a seed crystal is disposed substantially opposite to the sublimation raw material, and the sublimated sublimation raw material is recrystallized on the seed crystal to obtain a silicon carbide single substance. A method for manufacturing a silicon carbide single crystal for growing a crystal, the method for manufacturing a silicon carbide single crystal for growing a single crystal on a seed crystal fixed to a seed crystal arrangement portion by the seed crystal fixing method according to the above embodiment. Provided.

  As shown in FIG. 3, the reaction vessel includes a reaction vessel main body 31 that can accommodate the sublimation raw material 35, and a seed crystal placement unit that is detachably attached to the reaction vessel main body 31 and can place the seed crystal 9. 3 is used. A first induction heating coil 33a and a second induction heating coil 33b for forming a silicon carbide sublimation atmosphere are provided on the outer periphery of the reaction vessel. The reaction vessel body 31 is not particularly limited as long as it can form a silicon carbide sublimation atmosphere inside the reaction vessel body 31. For example, a crucible can be used as the reaction vessel main body 31, and the material thereof is preferably graphite, and further preferably has a thermal expansion coefficient substantially the same as that of the seed crystal. From the viewpoint of easy storage of the sublimation raw material 35, it is preferable that the reaction vessel main body 31 and the seed crystal arrangement portion 3 are integrally formed detachably. As the joining means, any joining means may be used as long as the airtightness inside the reaction vessel main body 31 is maintained. Examples of the joining means include screwing means.

  A conventionally known material can be used as the sublimation raw material 35. As the sublimation raw material 35, for example, a high purity tetraethoxysilane polymer is used as a silicon source, a resol type phenol resin is used as a carbon source, and a mixture obtained by uniformly mixing these is heated and fired in an argon atmosphere. The silicon carbide powder obtained can be used. A conventionally known single crystal can be used as the seed crystal of the silicon carbide single crystal.

  The heating conditions such as the heating temperature of the sublimation raw material 35 are not particularly limited, and can be appropriately set by those skilled in the art based on known techniques.

(Silicon carbide single crystal)
The silicon carbide single crystal is manufactured by the above-described method for manufacturing a silicon carbide single crystal. The silicon carbide single crystal has a crystal defect (pipe defect) evaluated by etching with molten alkali of preferably 50 pieces / cm ² or less, and more preferably 10 pieces / cm ² or less. The total content of metal impurity elements in the silicon carbide single crystal is preferably 10 ppm or less. The silicon carbide single crystal obtained by the present invention is free from crystal defects such as polycrystals, polymorphs, and micropipes, and is extremely high quality. Therefore, the silicon carbide single crystal is excellent in dielectric breakdown characteristics, heat resistance, radiation resistance, etc. It is particularly suitably used for electronic devices such as wafers and optical devices such as light emitting diodes.
As described above, according to the method for producing a silicon carbide single crystal of the present invention, a high-quality silicon carbide single crystal can be produced efficiently and easily without breakage such as cracks.

(Example)
The seed crystal 9 was fixed to the seed crystal arrangement part 3 in accordance with the seed crystal fixing method according to the embodiment using the seed crystal fixing device of FIG. At that time, phenol resin was applied as an adhesive 5 at 7.5 μl / cm ² . As the seed crystal 9, a 6H Rayleigh crystal having a seed crystal thickness of 0.4 mm and a diameter of 50 mm was used. Then, under reduced pressure (30 Torr), after heating to 90 ° C. over 15 minutes and further preheating at 90 ° C. for 2 minutes, heating to 160 ° C. over 25 minutes and then heating at 160 ° C. for 10 minutes. Curing was performed.
As a result, as shown in the surface observation photograph of the seed crystal of FIG. 4B, it was confirmed that the seed crystal 9 of the example was adhered without adhesion unevenness.

Furthermore, the seed crystal arrangement part 3 to which the seed crystal 9 was fixed was mounted on the silicon carbide single crystal manufacturing apparatus 30 of FIG. 3 to grow a silicon carbide single crystal. The sublimation raw material 35 was obtained by heating and firing a mixture obtained by uniformly mixing a high-purity tetraethoxysilane polymer as a silicon source and a resol type phenol resin as a carbon source in an argon atmosphere. Silicon carbide powder (6H (including part of 3C), average particle diameter of 200 μm) was used. In the silicon carbide single crystal manufacturing apparatus 30, a current was passed through the first induction heating coil 33a to heat it, and the sublimation raw material 35 was heated with the heat. At that time, after the bottom of the reaction vessel main body 31 was heated to 2350 ° C., the pressure was maintained at 50 Torr (6665 Pa) in an argon gas atmosphere. The sublimation raw material 35 was heated to a predetermined temperature (2540 ° C.) and sublimated. On the other hand, the seed crystal arrangement part 3 side was heated by the second induction heating coil 33b. The set temperature of the seed crystal arrangement part 3 by the second induction heating coil 33b was 2300 ° C.
When the wafer cross section of the obtained silicon carbide single crystal was observed (FIG. 4B), the number of macro defects on the entire surface immediately above the seed crystal was 10 or less, and the macro defects on the entire surface of the wafer 10 mm above the seed crystal. The number of was zero. Further, the size of the defect was smaller than that obtained by the conventional method.

(Comparative example)
As shown in FIG. 6, a seed crystal placement unit 103 was placed on the mounting table 101, and a seed crystal 109 was placed thereon via an adhesive (phenolic resin) 105. Then, the weight stone 107 was placed on the seed crystal 109, and the phenol resin was heat-cured at 300 ° C. for 0.5 hours under atmospheric pressure while applying a load to the seed crystal 109 with the weight stone 107. As a result, as shown in the surface observation photograph of the seed crystal in FIG. 4A, adhesion unevenness was confirmed on the surface of the seed crystal 109 of the comparative example.
Using the obtained seed crystal 109, a silicon carbide single crystal was grown in the same manner as in the example.
When the side sectional view of the obtained silicon carbide single crystal was observed (FIG. 4A), the number of macro defects on the entire surface immediately above the seed crystal was 100 or less, and the macro on the entire wafer surface 10 mm above the seed crystal. The number of defects was 10-20. The size of the macro defect was larger than that of the example.

FIG. 1 (a) shows a schematic cross-sectional view of a seed crystal fixing device containing a seed crystal placement portion in which a seed crystal is placed via an adhesive, and FIG. 1 (b) shows a top view of a lower chamber. 2A to 2G are process diagrams of the seed crystal fixing method. FIG. 3 is a schematic cross-sectional view of a silicon carbide single crystal production apparatus (crucible). FIG. 4A shows an enlarged surface photograph of the silicon carbide single crystal wafer obtained by the comparative example, and FIG. 4B shows an enlarged surface photograph of the silicon carbide single crystal wafer obtained by the example. FIG. 5A shows a schematic cross-sectional view of a modified example of the seed crystal fixing device that accommodates a seed crystal placement portion in which a seed crystal is placed via an adhesive, and FIG. 5B is a top view of the lower chamber. Indicates. FIG. 6 shows a schematic view of a conventional seed crystal fixing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 ... Seed crystal fixing device 3, 103 ... Seed crystal arrangement part 5, 105 ... Adhesive 9, 109 ... Seed crystal 10 ... Chamber 11 ... Upper chamber 13 ... Lower chamber 12 ... Suction exhaust port 15 ... O-ring 16 ... Flexible bag 17 ... guide 20 ... heater (heating body)
30 ... Silicon carbide single crystal manufacturing apparatus 31 ... Container 33a ... First induction heating coil 33b ... Second induction heating coil 35 ... Sublimation raw material 107 ... Clay stone

Claims (10)

A seed crystal fixing device for fixing a seed crystal to the seed crystal arrangement part of the reaction vessel via an adhesive,
A chamber in which the seed crystal arrangement part can be arranged;
A flexible bag body that is disposed inside the chamber, expands and contracts by gas supply and exhaust, and contacts the surface of the seed crystal when inflated to uniformly apply pressure to the entire surface of the seed crystal;
Equipped with a,
The chamber has a guide for fixing the seed crystal and fixing the seed crystal,
Wherein the guide, pawl earlier becomes narrower toward the contact point seed crystal fixing device characterized that you have provided the seed crystal.   The seed crystal fixing device according to claim 1, wherein the chamber is capable of forming a reduced-pressure atmosphere. The guide is seed crystal fixing device according to claim 1, wherein the contact with the side surface with at least three points of the seed crystal. It said flexible bag body, the seed crystal fixing device according to any one of claims 1 to 3, characterized in that it consists of rubber or resin. Seed crystal fixing device according to any one of claims 1 to 4, characterized in that a heating member for heating and curing the adhesive. A seed crystal fixing method in which a seed crystal placement portion provided with a seed crystal via an adhesive is placed inside a chamber ,
A step of sucking a gas from the chamber to form a reduced pressure atmosphere;
After forming the reduced pressure atmosphere, in the reduced pressure atmosphere, the flexible bag body that expands and contracts by gas supply / exhaust is inflated to be flexible on the other surface side of the seed crystal arrangement surface of the seed crystal. Applying a pressure uniformly to the entire surface of the seed crystal by contacting the bag,
A step of uniformly applying pressure to the entire surface of the seed crystal and then curing the adhesive in the reduced-pressure atmosphere ; and
A seed crystal fixing method comprising the steps of:   Fixing the seed crystal using a guide for fixing the seed crystal arrangement portion and fixing the seed crystal;
  The seed crystal fixing method according to claim 6, wherein the guide is provided with a claw that tapers toward a contact point with the seed crystal.   A seed crystal fixing method for arranging a seed crystal arrangement portion provided with a seed crystal via an adhesive,
  Fixing the seed crystal using a guide for fixing the seed crystal placement section and fixing the seed crystal;
  The flexible bag body that expands and contracts by gas supply and exhaust is inflated, and the flexible bag body is brought into contact with the other side of the seed crystal placement surface of the seed crystal so that pressure is uniformly applied to the entire surface of the seed crystal. The process of applying,
  Curing the adhesive;
Including
  A seed crystal fixing method, wherein the guide is provided with a claw that tapers toward a contact point with the seed crystal.   Including a step of sucking a gas from a chamber in which the seed crystal arrangement portion is arranged to form a reduced pressure atmosphere,
  After forming the reduced-pressure atmosphere, performing a step of uniformly applying pressure to the entire surface of the seed crystal under the reduced-pressure atmosphere,
  The seed crystal fixing method according to claim 8, wherein the step of curing the adhesive is performed in the reduced pressure atmosphere after uniformly applying pressure to the entire surface of the seed crystal. The seed crystal fixing method according to claim 6 , wherein the adhesive is cured by heating.