JP2004193625A - Method of heat treatment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of heat treatment, which can eliminate crystal defects in a semiconductor substrate when the semiconductor substrate is heat-treated at a high temperature. <P>SOLUTION: In the method of the heat treatment, a semiconductor substrate 1 is mounted on the top surface of a film body 9 which is convexly warped upwards, to perform the heat treatment. The warp by the weight of the semiconductor substrate 1 is offset by the warp of the film body 9, so that the semiconductor substrate 1 becomes a flat surface. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a heat treatment method for performing heat treatment while holding a semiconductor substrate or the like in a horizontal direction.

  2. Description of the Related Art Conventionally, heat treatment for heating a semiconductor substrate has been performed in order to form a thin film such as an oxide film on a semiconductor substrate or to diffuse impurities into the semiconductor substrate. At this time, for example, a heat treatment apparatus as shown in FIG. 6 is used.

  The heat treatment apparatus shown in FIG. 6A is called a batch type hot wall type diffusion furnace, and processes a boat 2 holding a plurality of semiconductor substrates 1 and a semiconductor substrate 1 held by the boat 2. And a heater 4 for heating the semiconductor substrate 1. The housing 3 is provided with an inlet 5 for introducing, for example, a reaction gas into the reaction chamber, and an outlet 6 for discharging the reaction gas from the reaction chamber.

  Here, the semiconductor substrate 1 is held horizontally so that its edge is placed on a protruding portion provided on the boat 2. The semiconductor substrate 1 is held at, for example, four holding points 7 on its edge, as shown in FIG. 6B, for example. This is because by minimizing the contact area between the semiconductor substrate 1 and the boat 2, the amount of heat radiation absorbed by the boat 2 is reduced, and the semiconductor substrate 1 is uniformly heated. Further, when the semiconductor substrate 1 is mounted on the boat 2 or taken out of the boat 2, the semiconductor substrate 1 has such a structure that the semiconductor substrate 1 can be easily handled. Such a member that holds the semiconductor substrate 1 horizontally is generally called a susceptor.

  However, due to the weight of the semiconductor substrate 1, stress is generated inside the semiconductor substrate 1 and at the holding points 7 in the semiconductor substrate 1. In particular, since the holding point 7 is point-like, stress concentrates on this point.

  The stress σ generated inside the semiconductor substrate 1 can be calculated based on the following equation.

σ = (3 × (3 + ν) × q × a ² ) / (8 × h ² ) (1)
Here, ν is Poisson's ratio, q is the load per unit area, a is the radius of the semiconductor substrate, and h is the thickness of the semiconductor substrate.

  FIG. 7 shows the relationship between the stress generated inside the semiconductor substrate and the diameter of the semiconductor substrate, calculated by the equation (1). The thickness of the semiconductor substrate is changed as a parameter. As the diameter of the semiconductor substrate increases, the weight of the semiconductor substrate increases, so that the stress increases. Further, when the thickness of the semiconductor substrate is increased, the rigidity of the semiconductor substrate is reduced, so that the stress is increased.

When a high-temperature heat treatment is performed in a state where such a stress exists inside the semiconductor substrate, crystal defects called so-called slips occur inside the semiconductor substrate. For example, when the diameter of the semiconductor substrate is 200 mm, the stress inside the semiconductor substrate is about 5 × 10 ^6, and a heat treatment at about 1200 ° C. is performed in a state where such stress exists inside the semiconductor substrate. It is known that slip occurs due to its own weight.

  Further, as the diameter of the semiconductor substrate increases, as shown in FIG. 7, the stress generated inside the semiconductor substrate increases. In general, the higher the stress, the more slip will occur at lower temperatures.

  FIG. 8 shows the relationship between the temperature region where the slip occurs and the diameter of the semiconductor substrate. In the drawing, the region shown as the boundary region indicates that the temperature region where the slip occurs varies because the occurrence of the slip is affected by not only the stress but also other factors. As shown in this figure, when the diameter of the semiconductor substrate increases, the stress generated by its own weight increases, so that the critical temperature at which slip occurs decreases. That is, the occurrence of crystal defects due to the stress due to its own weight becomes a more and more serious problem as the diameter of the semiconductor substrate increases.

  As described above, in the conventional heat treatment apparatus and the conventional heat treatment method, a stress is generated inside the semiconductor substrate due to the weight of the semiconductor substrate, and the heat treatment is performed in a state where the stress is present, thereby causing a crystal defect. was there. In addition, as the diameter of the semiconductor substrate increases, the weight of the semiconductor substrate increases, which causes a problem that crystal defects are generated by heat treatment at a lower temperature.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to suppress generation of crystal defects in a semiconductor substrate when the semiconductor substrate is horizontally held and subjected to heat treatment. It is to provide a heat treatment method which can be performed.

  In order to solve the above problems and achieve the object, a susceptor according to an embodiment of the present invention holds the semiconductor substrate horizontally when heat-treating the semiconductor substrate, and the susceptor has the semiconductor substrate mounted thereon. The semiconductor substrate is configured to be flat at least at a heat treatment temperature in a state where the semiconductor substrate is placed.

  In addition, the susceptor according to an embodiment of the present invention holds the semiconductor substrate horizontally when heat-treating the semiconductor substrate, and the susceptor is mounted on the semiconductor substrate at least at the heat treatment temperature while the semiconductor substrate is mounted. Means for preventing deformation of the semiconductor substrate due to its own weight so that the surface becomes a plane.

  Further, the susceptor according to an embodiment of the present invention holds the semiconductor substrate horizontally when heat-treating the semiconductor substrate, and the susceptor is mounted on the semiconductor substrate at least at the heat treatment temperature while the semiconductor substrate is mounted. It is characterized by having a means for preventing the occurrence of stress inside.

  In addition, the susceptor according to an embodiment of the present invention holds the semiconductor substrate horizontally when heat-treating the semiconductor substrate, and the susceptor is mounted on the semiconductor substrate at least at the heat treatment temperature while the semiconductor substrate is mounted. Are constituted by means for supporting the semiconductor substrate at a plurality of locations including the central portion of the semiconductor substrate so that the surface becomes a plane.

  Further, the susceptor according to an embodiment of the present invention holds the semiconductor substrate horizontally when the semiconductor substrate is subjected to heat treatment, and the susceptor is an elastic body, and is formed of a film-like body that is convex upward with respect to gravity. It is characterized by comprising.

  In the susceptor, the susceptor may have a height difference between a peripheral portion and a center of the susceptor, which is set by the rigidity, thickness, and diameter of the susceptor.

  In the above-mentioned susceptor, the susceptor is formed of the same material as the semiconductor substrate, and can have a thickness greater than that of the semiconductor substrate.

  Further, in the above-described susceptor, the susceptor may be formed of a material having higher rigidity than the semiconductor substrate.

  In the above-mentioned susceptor, the susceptor may have a non-uniform thickness in the susceptor plane.

  In the susceptor described above, the susceptor may have a hole.

  In the above-mentioned susceptor, the susceptor can be constituted by a plurality of susceptor portions.

  In the above-described susceptor, the susceptor has a first susceptor portion that forms an outer peripheral portion of the susceptor, and a thermal expansion coefficient that is provided inside the first susceptor portion and has a larger coefficient of thermal expansion than the first susceptor portion. And a second susceptor portion made of a material.

  Further, the heat treatment apparatus according to one embodiment of the present invention includes a holding unit for holding the semiconductor substrate, and a heater for heating the semiconductor substrate mounted on the holding unit, wherein the holding unit holds the semiconductor substrate. A susceptor for holding the semiconductor substrate horizontally, wherein the susceptor is configured such that the semiconductor substrate is flat at least at a heat treatment temperature in a state where the semiconductor substrate is mounted thereon.

  Further, a heat treatment apparatus according to one embodiment of the present invention is a heat treatment apparatus comprising: a holding unit for holding a semiconductor substrate; and a heater for heating the semiconductor substrate mounted on the holding unit. A susceptor for horizontally holding the semiconductor substrate is provided, and the susceptor is an elastic body, and is formed of a film-like body that is convex upward with respect to gravity.

  In the heat treatment method according to one embodiment of the present invention, a step of forming a film on one surface of a semiconductor substrate that generates a tensile stress between the semiconductor substrate and the film is formed. Holding the semiconductor substrate so that the surface of the semiconductor substrate faces downward with respect to gravity and keeping the semiconductor substrate horizontal, and performing a heat treatment.

  Further, in the heat treatment method according to one embodiment of the present invention, a step of forming a film on one surface of the semiconductor substrate to generate a compressive stress between the semiconductor substrate and the film is formed. Holding the semiconductor substrate so that the surface of the semiconductor substrate faces upward with respect to gravity and keeping the semiconductor substrate horizontal, and performing a heat treatment.

  Further, in the heat treatment method described above, the film thickness of the film-shaped body is set such that the stress generated in the semiconductor substrate by the formation of the film-shaped body is equal to the stress generated by the weight of the semiconductor substrate. Is also possible.

In the heat treatment method according to an embodiment of the present invention, a film-like body that generates a compressive stress between the semiconductor substrate and one surface of the semiconductor substrate is formed of one of SiO ₂ , polycrystalline Si, and SiC. A heat treatment is performed by holding the semiconductor substrate so that the surface of the semiconductor substrate on which the film is formed is directed upward with respect to gravity and the semiconductor substrate is flat. Canceling the stress generated by the weight of the semiconductor substrate by the compressive stress generated in the step (c).

  Further, in the heat treatment method according to an embodiment of the present invention, a semiconductor substrate is mounted on the upper surface of a film-like body that is warped upwardly and heat-treated, and the weight of the semiconductor substrate is reduced so that the semiconductor substrate becomes flat. And the warpage of the film-like body are canceled out.

  As described above, the susceptor according to the embodiment of the present invention is configured so that the semiconductor substrate is flat at least at the heat treatment temperature in a state where the semiconductor substrate is mounted on the susceptor. can do. Therefore, it is possible to prevent the semiconductor substrate from being deformed downward by its own weight and generating stress inside the semiconductor substrate. Therefore, by performing the heat treatment in a state where the stress is reduced as described above, it is possible to prevent a crystal defect from being generated inside the semiconductor substrate.

  In addition, the susceptor according to an embodiment of the present invention has a means for preventing deformation of the semiconductor substrate due to its own weight so that the semiconductor substrate becomes flat at least at a heat treatment temperature in a state where the semiconductor substrate is mounted on the susceptor. It is possible to prevent the substrate from being deformed downward by its own weight and generating stress inside the semiconductor substrate. Therefore, by performing the heat treatment in a state where the stress is reduced as described above, it is possible to prevent a crystal defect from being generated inside the semiconductor substrate.

  Furthermore, the susceptor according to one embodiment of the present invention has a means for preventing stress from being generated inside the semiconductor substrate at least at the heat treatment temperature in a state where the semiconductor substrate is mounted on the susceptor. By performing the heat treatment in, generation of crystal defects inside the semiconductor substrate can be prevented.

  In addition, the susceptor according to an embodiment of the present invention supports the semiconductor substrate at a plurality of locations including the central portion of the semiconductor substrate so that the semiconductor substrate is flat at least at the heat treatment temperature with the semiconductor substrate mounted thereon. Since the semiconductor substrate is constituted by the means, the semiconductor substrate can be supported by using the supporting means so that the semiconductor substrate becomes flat. For this reason, it is possible to prevent the occurrence of stress inside the semiconductor substrate, and to prevent the occurrence of crystal defects in the semiconductor substrate by performing the heat treatment in such a state where the stress is reduced. Can be.

  In addition, the susceptor according to the embodiment of the present invention is an elastic body, and is formed of a film-shaped body that is convex upward with respect to gravity. Therefore, when the semiconductor substrate is mounted on the susceptor, The susceptor is deformed downward by its own weight, and the upwardly convex shape is made flat, so that the semiconductor substrate can be held flat. For this reason, it is possible to prevent the occurrence of stress inside the semiconductor substrate, and to prevent the occurrence of crystal defects in the semiconductor substrate by performing the heat treatment in such a state where the stress is reduced. Can be.

  In the susceptor, the amount of deformation of the susceptor when the semiconductor substrate is mounted on the susceptor is affected by the rigidity, thickness, and diameter of the susceptor. The height difference between the susceptor and the center is set by the stiffness, thickness, and diameter of the susceptor, so that the semiconductor substrate can be held flat when the semiconductor substrate is mounted on the susceptor.

  In the susceptor described above, the susceptor according to an embodiment of the present invention, which is formed of the same material as the semiconductor substrate and is thicker than the semiconductor substrate, can reduce the amount of deformation of the susceptor when the semiconductor substrate is mounted on the susceptor. Therefore, the stress generated inside the susceptor when the semiconductor substrate is placed can be reduced. Thereby, the reliability of the susceptor can be improved.

  Further, in the above-described susceptor, the susceptor according to an embodiment of the present invention, which is formed of a material having higher rigidity than the semiconductor substrate, is hardly deformed when the semiconductor substrate is mounted on the susceptor. Need to be thinner. Thus, the heat capacity of the susceptor can be reduced, and adverse effects such as the semiconductor substrate being less likely to be heated due to being in contact with the susceptor when the semiconductor substrate is heat-treated can be reduced.

  In the susceptor described above, the susceptor according to an embodiment of the present invention, in which the thickness is non-uniform in the susceptor surface, can change the heat capacity of the susceptor by the difference in the thickness of the susceptor. The temperature distribution in the plane of the semiconductor substrate which may occur can be corrected, and the semiconductor substrate can be uniformly heated.

  In the above-described susceptor, the susceptor having a hole according to the embodiment of the present invention can easily mount the semiconductor substrate on the susceptor or remove the semiconductor substrate from the susceptor.

  In the susceptor described above, the susceptor according to one embodiment of the present invention, which includes a plurality of susceptor portions, can change its rigidity depending on the shape of each susceptor portion. The susceptor can be configured to have a uniform distribution. For this reason, finer adjustment can be performed so that the semiconductor substrate becomes flat when the semiconductor substrate is mounted on the susceptor. In addition, since each susceptor portion can be manufactured individually, a convex shape can be easily formed. Further, since the thickness can be changed for each susceptor portion, such a susceptor can be easily formed when the thickness of the susceptor is changed in a plane.

  Further, in the above-described susceptor, a first susceptor portion forming an outer peripheral portion of the susceptor, and a second susceptor formed of a material provided inside the first susceptor portion and having a larger thermal expansion coefficient than the first susceptor portion. The susceptor according to an embodiment of the present invention, which is composed of the second susceptor portion and the second susceptor portion, is configured such that the second susceptor portion expands more than the first susceptor portion when the temperature is increased by the heat treatment. Becomes convex. Such deformation due to thermal expansion cancels the deformation of the semiconductor substrate due to its own weight, so that the semiconductor substrate can be held flat during heat treatment.

  Further, in the heat treatment apparatus according to one embodiment of the present invention, the holding means for holding the semiconductor substrate includes a susceptor for holding the semiconductor substrate horizontally, and the susceptor is at least when the semiconductor substrate is mounted thereon. Since the interface between the susceptor and the semiconductor substrate is flat at the heat treatment temperature, the heat treatment can be performed in a state where no stress is generated inside the semiconductor substrate. Thus, it is possible to prevent crystal defects from occurring inside the semiconductor substrate.

  Further, in the heat treatment apparatus according to one embodiment of the present invention, the holding means for holding the semiconductor substrate includes a susceptor for holding the semiconductor substrate horizontally, and the susceptor is an elastic body, and projects upward with respect to gravity. When the semiconductor substrate is placed on the susceptor, the susceptor is deformed downward by the weight of the semiconductor substrate, and the semiconductor substrate can be held in a planar shape. For this reason, it is possible to prevent the occurrence of stress inside the semiconductor substrate, and to prevent the occurrence of crystal defects in the semiconductor substrate by performing the heat treatment in such a state where the stress is reduced. Can be.

  Further, in the heat treatment method according to one embodiment of the present invention, since a film-like material that generates tensile stress between the semiconductor substrate and one surface of the semiconductor substrate is formed, the surface on which the film-like material is formed is formed. The semiconductor substrate is deformed so that is concave. For this reason, by directing the surface on which the film is formed downward with respect to gravity, the deformation due to the film cancels the deformation due to the weight of the semiconductor substrate, and the semiconductor substrate becomes planar. Accordingly, generation of stress in the semiconductor substrate is prevented, and by performing heat treatment while holding the semiconductor substrate in such a state, generation of crystal defects in the semiconductor substrate can be prevented.

  Further, in the heat treatment method according to one embodiment of the present invention, since a film-like body that generates a compressive stress between the semiconductor substrate and one surface of the semiconductor substrate is formed, the surface on which the film-like body is formed is formed. The semiconductor substrate is deformed so that is convex. Therefore, by turning the surface on which the film is formed upward with respect to gravity, the deformation due to the film cancels the deformation due to the weight of the semiconductor substrate, and the semiconductor substrate becomes planar. Accordingly, generation of stress in the semiconductor substrate is prevented, and by performing heat treatment while holding the semiconductor substrate in such a state, generation of crystal defects in the semiconductor substrate can be prevented.

  Further, in the heat treatment method according to one embodiment of the present invention, in the heat treatment method, the stress generated in the semiconductor substrate by the formation of the film is equal to the stress generated by the weight of the semiconductor substrate. Is set, the stress due to the formation of the film can completely cancel the stress due to its own weight. For this reason, a state can be obtained in which no stress is present in the semiconductor substrate, and by performing heat treatment in such a state, generation of crystal defects can be prevented.

  According to the present invention, since the generation of stress due to the weight of the semiconductor substrate can be suppressed, it is possible to provide a heat treatment method capable of suppressing the occurrence of crystal defects in the semiconductor substrate when performing heat treatment on the semiconductor substrate. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows only a portion for holding a semiconductor substrate 1 of a heat treatment apparatus according to a first embodiment of the present invention. For example, a structure or a structure as shown in FIG. 6A can be used for other parts of the heat treatment apparatus such as a housing or a heater. FIG. 1A shows a state before the semiconductor substrate 1 is mounted, and FIG. 1B shows a state where the semiconductor substrate 1 is mounted.

  As shown in FIG. 1A, the heat treatment apparatus according to the present embodiment includes a film body 8 as a susceptor mounted on a boat 2, and the film body 8 is warped upward in a convex shape. It is characteristic. Further, as shown in FIG. 1B, when the semiconductor substrate 1 is placed on the film body 8, the film body 8 is pressed by the weight of the semiconductor substrate 1 placed thereon, and It becomes a plane. The amount of warpage a of the film body 8 is adjusted as follows so that the semiconductor substrate 1 is horizontal.

  The warpage W of the semiconductor substrate 1 due to its own weight depends on the diameter and thickness of the semiconductor substrate 1, but can be calculated using the following equation.

W = (3 × (5 + ν) × q × a ⁴ ) / (16 × (E / (1-ν)) × h ³ ) (2)
Here, ν is Poisson's ratio, q is the load per unit area, a is the radius of the semiconductor substrate, h is the thickness of the semiconductor substrate, and E is the Young's modulus.

  FIG. 2 shows the relationship between the warpage of the semiconductor substrate calculated using this equation and the diameter of the semiconductor substrate. The thickness of the semiconductor substrate is changed as a parameter. As shown in this figure, for example, when the diameter of the semiconductor substrate is 200 mm and the thickness of the semiconductor substrate is 725 mm, the warp W is about 25 μm. When the diameter of the semiconductor substrate is 300 mm and the thickness of the semiconductor substrate is 725 mm, the warp W is about 120 μm.

  Thus, when the film body 8 is formed of, for example, Si, the diameter is, for example, 300 mm, and the thickness is, for example, 725 μm, only the film body 8 is placed on the boat 2 as shown in FIG. The film-like body 8 is formed such that the film-like body 8 is warped upward by 120 μm as the amount of warpage a in the mounted state.

  This can be configured by forming a 725 μm thick Si film by, for example, a CVD (chemical vapor deposition) method on a mold having a diameter of, for example, 300 mm and a warp of, for example, 240 μm. When the Si film 8 is placed on the boat 2 so as to project upward, the warp of the film 8 is reduced to 120 μm due to the weight of the film 8.

  As shown in FIG. 1B, when the Si substrate 1 having a diameter of, for example, 300 mm and a thickness of, for example, 725 μm is placed on the film body 8, the Si substrate 1 divides the film body 8 by its own weight. Since the Si substrate 1 is pushed down by 120 μm, the warpage of the Si substrate 1 due to its own weight and the amount of warpage a of the film body 8 cancel each other, and the Si substrate 1 becomes flat.

  In such a state, a large stress is generated inside the film-like body 8, but since the semiconductor substrate 1 on the film-like body 8 is held almost horizontally without warpage, the inside of the semiconductor substrate 1 Almost no stress occurs. Therefore, when a high-temperature heat treatment is performed in such a state, crystal defects such as slip do not occur.

  In the above embodiment, the film 8 having the same thickness as the semiconductor substrate 1 is made of the same material as the semiconductor substrate 1, but the film 8 having a thickness different from that of the semiconductor substrate 1 is formed. It is possible. For example, when the film body 8 having a thickness of 1450 μm, that is, twice the thickness of the semiconductor substrate 1 is used, the warpage amount a of the film body 8 when the film body 8 is placed on the boat 2 is as described above. By setting the thickness to half that of the embodiment, that is, 60 μm, the semiconductor substrate 1 can be made flat when the semiconductor substrate 1 is placed on the film-like body 8. In this case, the amount of deformation of the film body 8 when the semiconductor substrate 1 is mounted is halved as compared with the above-described embodiment, so that the stress generated in the film body 8 is also reduced by half. For this reason, the possibility that crystal defects are generated inside the film body 8 can be reduced, and the reliability of the film body 8 can be improved.

  Further, as the material forming the film-like body 8, it is not always necessary to use the same material as the semiconductor substrate 1 such as Si, and other materials may be used as long as they are rigid at the heat treatment temperature and do not contaminate the semiconductor substrate. It is also possible to use. For example, SiC has stiffness at high temperature and is stiffer than Si, so that the thickness of the film body 8 can be reduced. For example, when a film having a diameter of 300 mm is formed using SiC, a film thickness of 362 μm is required to cancel the warpage of 120 μm due to the weight of the Si substrate 1. It can be reduced to about half as compared with the above-described first embodiment constituting the body 8.

  As described above, when the film thickness of the film body 8 can be reduced, the heat capacity of the film body 8 can be reduced, so that the temperature of the semiconductor substrate 1 to be heat-treated can be rapidly increased or decreased. it can.

  As described above, the semiconductor substrate 1 is placed on the film 8 by appropriately setting the thickness of the film 8 and the amount of warpage a in accordance with the properties of the material forming the film 8 such as the elastic modulus. The semiconductor substrate 1 can be made flat.

  Further, the thickness of the film 8 does not need to be uniform in the plane of the film 8, and the film 8 may have a thick portion and a thin portion in the surface. In general, the thick portion of the film body 8 has a large heat capacity and absorbs more heat radiation. Therefore, by changing the film thickness in the plane of the film-like body 8, the temperature distribution generated in the plane of the semiconductor substrate 1 on which the heat treatment is performed is corrected, and the semiconductor substrate 1 is uniformly heated in the plane. Becomes possible.

  For example, as shown in FIG. 6, in a heat treatment apparatus in which a heater 4 is provided around the semiconductor substrate 1, the peripheral portion of the semiconductor substrate 1 is generally easily heated. Therefore, by increasing the thickness of the peripheral portion of the film body 8, the heat capacity of this portion can be increased, and the temperature of the peripheral portion of the semiconductor substrate 1 can be prevented from rising rapidly. On the other hand, in a heat treatment apparatus in which a heater is installed so as to face the upper and lower surfaces of the semiconductor substrate 1, since heat is released from the peripheral portion of the semiconductor substrate, the peripheral portion is not easily heated. Therefore, by reducing the thickness of the peripheral portion of the film body 8, the heat capacity of this portion can be reduced, and the temperature of the peripheral portion of the semiconductor substrate 1 can be easily increased.

  Further, the film body 8 does not need to be configured to cover the entire lower surface of the semiconductor substrate 1. FIG. 3 shows a top view of the film body 8 of the heat treatment apparatus according to the second embodiment of the present invention. As shown in FIG. 3, the film-shaped body 8 is formed by combining the film-shaped bodies in a radial (a) or concentric (b) manner so as to have a hole, or in a spiral shape. Parts can be configured. In this case, it is possible to integrally form all the film-like portions. However, after forming a plurality of film-like portions, these film-like portions are bonded to form the film-like body 8. It is also possible.

  Here, the elastic modulus can be changed in the plane by changing the shape such as the width of each of the film-like portions. In this way, it is possible to appropriately adjust the elastic modulus in the plane of the film-shaped body 8 so that the semiconductor substrate 1 becomes flatter when the semiconductor substrate 1 is mounted.

  Such adjustment of the in-plane elastic modulus can also be performed by changing the film thickness in the surface. However, when the film-shaped body 8 is formed by integral molding, the film thickness is changed in the surface. It is difficult to do so. On the other hand, in the present embodiment, by changing the shape of the film-like body portion, the elastic modulus can be changed while the film thickness in the plane of the film-like body 8 is made uniform. As described above, since each of the film-like portions can be formed with a uniform thickness, the film-like body 8 that can be finely adjusted so that the semiconductor substrate 1 becomes flat is easily formed. be able to.

  When the film body 8 is formed by being divided into a plurality of film bodies, the film thickness can be set for each component. Therefore, even when the film thickness is changed in the plane as described above, the film body 8 can be easily formed. In this manner, the in-plane elastic modulus can be optimized so that the semiconductor substrate 1 is held more planar. Further, since the film thickness of the film body 8 can be easily changed in the plane, the temperature distribution in the plane of the semiconductor substrate 1 during the heat treatment can be made more uniform during the heat treatment as described above. It can be made to be.

  Further, since the amount of heat radiation absorbed by the film body 8 during the heat treatment can be reduced as compared with the case where the entire lower surface of the semiconductor substrate 1 is covered, the radiation energy can be used more efficiently. 1 can be quickly raised.

  In addition, by forming the film body 8 by combining a plurality of film bodies, it is possible to easily adjust the amount of warpage or the shape of the film body 8.

  Further, in the present embodiment, when the semiconductor substrate 1 is placed on the film body 8 and when the semiconductor substrate 1 is removed from the film body 8, since the film body 8 has an opening, for example, a push-up pin The semiconductor substrate 1 can be easily attached and detached using

  Further, when the film body 8 is composed of a plurality of film parts as in the above embodiment, it is not necessary that all the film parts are made of the same material. As a third embodiment, a case where a film-like body 8 is formed by combining film-like bodies formed from different substances will be described with reference to FIG. 4A and 4B show a top view of the film body 8, FIGS. 4C and 4D show side views of the film body 8, and FIG. FIG. 4D shows a case where only the film body 8 is placed on the boat 2 and a case where the semiconductor substrate 1 is placed on the film body 8.

  The film-shaped body 8 according to the present embodiment has an annular portion 8a formed of a material having a low thermal expansion coefficient such as quartz, and a material having a higher thermal expansion coefficient such as SiC than the material used for the annular portion 8a. And a central portion 8b formed by Here, since the thermal expansion coefficient of the annular portion 8a is small, it does not expand even at the heat treatment temperature. However, since the central portion 8b has a larger thermal expansion coefficient than the annular portion 8a, it expands at, for example, a heat treatment temperature. However, since the outer periphery of the central portion 8b is defined by the annular portion 8a, the expanded central portion 8b has a convexly warped shape as shown in FIG.

  Further, by forming the film body 8 so that the upper surface side expands from the lower surface side, for example, by forming the upper surface side of the film body 8 from a material having a higher thermal expansion coefficient than the lower surface side, the film body 8 is formed. It can be made to warp upward.

  By appropriately setting the material, film thickness, shape, and the like of the film-shaped portion constituting the central portion 8b so that the warpage a 'at the heat treatment temperature and the warpage due to the weight of the semiconductor substrate 1 are offset. As shown in FIG. 4D, when the semiconductor substrate 1 is placed on the film body 8, the semiconductor substrate 1 can be made horizontal.

  As described above, in the present embodiment, by forming the film body 8 from, for example, two portions formed of materials having different thermal expansion coefficients, the film body 8 has a desired amount of warpage a at the heat treatment temperature. It is a feature to do so. By doing so, it is not necessary to form the film-like body 8 that is warped at room temperature. At room temperature, for example, the film-shaped body 8 having a flat shape can be used, so that the film-shaped body 8 can be easily formed as compared with the case of forming the film-shaped body 8 having a warped shape at normal temperature. Can be. In addition, handling such as storage of the film body 8 becomes easy.

  The case where the film body 8 is provided in the heat treatment apparatus has been described above. Next, as a fourth embodiment, the film body 8 is formed on the semiconductor substrate 1 so that the inside of the semiconductor substrate is formed. A method for reducing the stress of the above will be described with reference to FIG.

  FIG. 5 is a cross-sectional view showing a state in which, for example, a nitride film or the like is provided as the film body 9 on the semiconductor substrate 1. As shown in this figure, for example, a Si nitride film 9 is formed on one surface of the semiconductor substrate 1 by using, for example, a CVD method. At this time, the Si nitride film 9 is formed on the semiconductor substrate 1 so that the surface of the semiconductor substrate 1 on which the Si nitride film 9 is formed is concave as shown in FIG. It has a warped shape. Therefore, by placing the semiconductor substrate 1 on the boat 2 with the surface on which the nitride film 9 is formed facing downward, the tensile stress due to the nitride film 9 and the stress due to the weight of the semiconductor substrate 1 cancel each other. As shown in FIG. 5B, the semiconductor substrate 1 can be in a horizontal state.

Generally, as the thickness of the nitride film 9 increases, the tensile stress increases. By utilizing this, the thickness of the nitride film 9 can be appropriately set so that a stress that cancels the stress generated inside the semiconductor substrate 1 by the weight of the semiconductor substrate 1 is generated. For example, when the diameter of the semiconductor substrate 1 is 300 mm and the thickness is 725 μm, the stress generated inside the semiconductor substrate 1 by its own weight is about 9 × 10 ⁷ dyn / cm ^2. In order to cancel out, it is necessary to make the thickness of the Si nitride film about 0.725 μm.

  When the stress due to the weight of the semiconductor substrate 1 and the stress due to the nitride film 9 cancel each other, a large stress is localized at the interface between the semiconductor substrate 1 and the Si nitride film 9. There is almost no stress. Therefore, by performing heat treatment in such a state, generation of crystal defects can be suppressed.

  As shown in FIG. 5A, for example, in a state where the nitride film 9 is formed and the semiconductor substrate 1 is warped, a tensile stress is generated inside the semiconductor substrate 1, but the temperature is not high. Therefore, no crystal defects occur inside the semiconductor substrate 1.

Further, as another example of the present embodiment, the thickness of Si nitride film 9 can be changed in a plane. By changing the thickness of the nitride film 9 in this way, it is possible to adjust the stress distribution or the temperature distribution in the plane of the semiconductor substrate 1. For example, using a low-pressure CVD apparatus, the temperature is set to 850 ° C., the pressure is set to 0.5 Torr, 100 sccm of SiH ₂ Cl ₂ and 1000 sccm of NH ₃ are introduced as source gases, and the semiconductor substrate 1 having a diameter of 200 mm is placed at intervals of 3 mm. When the Si nitride films 9 are formed side by side, the thickness of the Si nitride film in the peripheral portion of the semiconductor substrate 1 is about 30% larger than the thickness in the central portion of the semiconductor substrate 1. Thereby, the correction of the stress in the peripheral portion can be made larger than that in the central portion of the semiconductor substrate 1. In addition, by appropriately changing the thickness of the nitride film 9 in the plane according to the in-plane distribution of the stress generated by the weight of the semiconductor substrate 1, the internal stress of the semiconductor substrate 1 is further reduced, and the crystal by the heat treatment is reduced. Generation of defects can be further suppressed.

Further, in the above-described embodiment, the Si nitride film 9 is formed on the semiconductor substrate 1, but the film body 9 formed on the semiconductor substrate 1 is not limited to this, and is made of a material that generates a tensile stress or a compressive stress. If so, it is possible to form the film body 9 from another substance. Here, when a compressive stress is generated, the surface of the semiconductor substrate 1 on which the film-shaped body 9 is formed has a convexly warped shape, and the semiconductor substrate 1 is placed on a boat with this surface facing upward. The same effect as in the case of the tensile stress described above can be obtained. As a substance that generates such a compressive stress, for example, SiO ₂ , polycrystalline silicon, SiC, or the like can be used. However, the characteristics of SiO ₂ change depending on the formation method. Further, since SiC has stable characteristics up to a high temperature, it is desirable to use SiC particularly when performing a high-temperature heat treatment.

  As described above, in the present embodiment, the film body 9 is formed on one surface of the semiconductor substrate 1, and the stress generated by the film body 9 cancels the stress due to the weight of the semiconductor substrate 1. Is the feature. Thus, the stress inside the semiconductor substrate 1 can be reduced, and the generation of crystal defects due to the heat treatment can be suppressed.

FIG. 2 is a side view showing the structure of the film according to the first embodiment of the heat treatment apparatus of the present invention. FIG. 4 is a diagram illustrating a relationship between warpage of a semiconductor substrate due to its own weight and a diameter of the semiconductor substrate. FIG. 6 is a top view showing a structure of a film-like body according to a second embodiment of the heat treatment apparatus of the present invention. The top view and side view which show the structure of the film-like body by 3rd Embodiment of the heat processing apparatus of this invention. The side view showing the structure of the film object by a 4th embodiment of the present invention. 2A and 2B are a cross-sectional view illustrating a structure of a conventional heat treatment apparatus and a top view of a semiconductor substrate. FIG. 4 is a diagram illustrating a relationship between stress generated inside the semiconductor substrate due to the weight of the semiconductor substrate and the diameter of the semiconductor substrate. FIG. 4 is a diagram showing a relationship between a temperature region where a slip occurs inside a semiconductor substrate and a diameter of the semiconductor substrate.

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor board, 2 ... Boat, 3 ... Case, 4 ... Heater, 5 ... Gas inlet, 6 ... Gas outlet, 7 ... Holding point, 8, 9 ... Film-like body.

Claims (17)

Forming, on one surface of the semiconductor substrate, a film-like body that generates a compressive stress between the semiconductor substrate and the semiconductor substrate using any of SiO ₂ , polycrystalline Si, and SiC;
The heat treatment is performed by holding the semiconductor substrate so that the surface of the semiconductor substrate on which the film is formed is directed upward with respect to gravity, so that the semiconductor substrate is flat, and the heat is generated on the film. Offsetting the stress generated by the weight of the semiconductor substrate by compressive stress. On one surface of the semiconductor substrate, a film-like body that generates a compressive stress between the semiconductor substrate and the film-like body at a peripheral portion of the semiconductor substrate is formed at a central portion of the semiconductor substrate. Forming a film to be thicker than the film thickness of
The heat treatment is performed by holding the semiconductor substrate so that the surface of the semiconductor substrate on which the film is formed is directed upward with respect to gravity, so that the semiconductor substrate is flat, and the heat is generated on the film. Offsetting the stress generated by the weight of the semiconductor substrate by compressive stress. On one surface of the semiconductor substrate, a film-like body that generates a compressive stress between the semiconductor substrate and the film-like body at a peripheral portion of the semiconductor substrate is formed at a central portion of the semiconductor substrate. Forming a film to be 30% thicker than the film thickness of
The heat treatment is performed by holding the semiconductor substrate so that the surface of the semiconductor substrate on which the film is formed is directed upward with respect to gravity, so that the semiconductor substrate is flat, and the heat is generated on the film. Offsetting the stress generated by the weight of the semiconductor substrate by compressive stress. Forming a film on one surface of the semiconductor substrate to generate a compressive stress between the semiconductor substrate and
By holding the semiconductor substrate at a plurality of locations including the center portion of the semiconductor substrate so that the surface of the semiconductor substrate on which the film is formed is directed upward with respect to gravity so that the semiconductor substrate is flat. Performing a heat treatment to offset a stress generated by the weight of the semiconductor substrate by a compressive stress generated in the film-shaped body. Forming a film on one surface of the semiconductor substrate to generate a compressive stress between the semiconductor substrate and a void portion,
The heat treatment is performed by holding the semiconductor substrate so that the surface of the semiconductor substrate on which the film is formed is directed upward with respect to gravity, so that the semiconductor substrate is flat, and the heat is generated on the film. Offsetting the stress generated by the weight of the semiconductor substrate by compressive stress. A first film-like body that generates a compressive stress between the semiconductor film and one surface of the semiconductor substrate is formed on one surface of the semiconductor film, and the outer periphery of the first film-like body expands more thermally than the first film-like body. Forming a second film made of a material having a high rate;
The heat treatment is performed by holding the semiconductor substrate such that the surface of the semiconductor substrate on which the first film-shaped body is formed is directed upward with respect to gravity so that the semiconductor substrate is flat, and the first heat treatment is performed. Canceling the stress generated by the weight of the semiconductor substrate by the compressive stress generated in the film-like body.   A semiconductor substrate is mounted on the upper surface of the film-like body that has been warped upward and subjected to a heat treatment to cancel the warpage due to the weight of the semiconductor substrate and the warpage of the film-like body so that the semiconductor substrate becomes flat. A heat treatment method comprising:   The heat treatment according to claim 7, wherein the film has a height difference between a peripheral portion and a center of the film which is set by rigidity, thickness and diameter of the film. Method.   The heat treatment method according to claim 7, wherein the film-like body is formed of a material similar to the semiconductor substrate, and has a thickness greater than that of the semiconductor substrate.   8. The heat treatment method according to claim 7, wherein the film is formed of a material having a higher rigidity than the semiconductor substrate.   The heat treatment method according to claim 7, wherein the thickness of the film is non-uniform in the plane of the film.   8. The heat treatment method according to claim 7, wherein the film has a hole.   The heat treatment method according to claim 7, wherein the film-like body is constituted by a plurality of film-like body portions. The film-like body,
A first film-shaped part constituting an outer peripheral part of the film-shaped body;
And a second film-shaped portion provided inside the first film-shaped portion and made of a material having a higher thermal expansion coefficient than that of the first film-shaped portion. The heat treatment method according to claim 13.   The method according to claim 7, wherein the film is an elastic body.   The method according to claim 7, wherein the film-like body holds the semiconductor substrate at a plurality of locations including a central portion of the semiconductor substrate. The film-like body,
A first film-shaped part constituting a lower surface part of the film-shaped body;
And a second film-shaped part comprising a material having a higher thermal expansion coefficient than the first film-shaped part constituting the upper surface part of the film-shaped body. The heat treatment method described.

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