JP2001023914A - Heat-treating method of semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the heat-treating method of a semiconductor substrate, which can make the substrate heat up uniformly trough a simple method and does not generate microslippage of the substrate. SOLUTION: Sintered bodies containing a gallim nitride, an aluminium nitride, a boron nitride and a silicon carbide are used as a holding stage 2 and a preventive plate 4, and when the sintered bodies are heat-treated, an infrared absorber is applied on the vicinity of the peripheral part of a semiconductor substrate 1 and a lamp annealing is performed on the absorber. These sintered bodies have a high thermal conductivity and rapidly transmit heat absorbed by the absorber 2, and the peripheral and center parts of the substrate 1 can be made to heat up uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment method for a semiconductor substrate and an epitaxial thin film, and more particularly to a lamp annealing method using an infrared lamp.

[0002]

2. Description of the Related Art When an impurity is added to a silicon semiconductor substrate or the like by ion implantation and is used as a conduction carrier, active impurities are used to restore crystal defects generated at the time of implantation and to move the added impurity atom to a desired lattice position. A heat treatment called "chemical treatment" is required. This heat treatment is performed by a method called a lamp annealing method in which a silicon semiconductor substrate or the like is irradiated with an infrared lamp to increase the substrate temperature in a short time.

Conventionally, no special holding table has been used when heat-treating a silicon semiconductor substrate by a lamp annealing method. When a holding table is not used, when a silicon semiconductor substrate is subjected to rapid thermal quenching such as a lamp annealing method, thermal deformation such as warpage occurs and the semiconductor substrate has surface defects such as microslip. there were.

In general, the lamp annealing apparatus is configured to control the output while monitoring the temperature of the semiconductor substrate surface with a pyrometer or the like. For that purpose, it is necessary to accurately grasp the emissivity of the substrate surface. There is. However, in the manufacturing process of the silicon semiconductor device, various materials such as an oxide film, a nitride film, and a polysilicon film are formed on the surface of the semiconductor substrate and have different thicknesses, so that it has been difficult to accurately measure the temperature. . Further, the silicon semiconductor substrate has a drawback that the absorptivity of infrared rays is low.

On the other hand, in the heat treatment of the compound semiconductor substrate by the lamp annealing method, it is necessary to use a holding table. An apparatus used for heat treatment of a compound semiconductor substrate has a structure in which a holding table is placed in a quartz tube, the compound semiconductor substrate is stacked thereon, and the substrate surface is irradiated with infrared rays vertically. The irradiated infrared rays are mainly absorbed by the holding table, and the compound semiconductor substrate is heated by heat conduction.

Conventionally, a silicon single crystal substrate, porous carbon, or the like has been used as a material for the holding table.
Among them, the silicon single crystal substrate is excellent in that it is chemically stable at a temperature of 1000 ° C. or more and can be processed with high flatness. And the like, there is a drawback that surface defects such as microslip occur on the compound semiconductor substrate. Furthermore, since silicon has almost no absorption band in the wavelength region of the infrared lamp, which is a heating source, there is a disadvantage that the heating efficiency is low. On the other hand, porous carbon is excellent in absorbing infrared rays in the wavelength region of an infrared lamp, but has a disadvantage that it has a large heat capacity and is not suitable for rapid heating and rapid cooling.

In the case of a gallium arsenide semiconductor, arsenic evaporates from the surface of the compound semiconductor substrate during the heat treatment. Specifically, in the case of a gallium arsenide semiconductor, the evaporated arsenic molecules are transferred to a holding base such as the silicon single crystal substrate. There is a problem that the crystallinity of the compound semiconductor substrate is further deteriorated due to absorption. In addition, after the arsenic evaporates, gallium remaining on the surface of the gallium arsenide semiconductor substrate causes a problem of deteriorating the characteristics of the electronic device, and cannot be used as a holding table.

In order to solve these drawbacks, the present applicant has prepared a flat plate member containing at least one of gallium nitride, aluminum nitride, and boron nitride which has excellent characteristics as a material for a holding table. A method of heat-treating a semiconductor substrate has been proposed (Japanese Patent Application No. 5-21).
490). Furthermore, in order to increase the infrared absorption efficiency,
A heat treatment method for a semiconductor substrate using a holder coated with an infrared absorber, specifically, tungsten carbide, molybdenum carbide, or the like, on the surface of the holder has been proposed (Japanese Patent Application No. Hei 7-187886).

However, even if such a holding table is used,
During the rapid temperature raising process, there is a difference in the rate of temperature rise between the central portion and the peripheral portion of the semiconductor substrate, so that microslip may occur in the peripheral portion of the semiconductor substrate.

Conventionally, as shown in FIG. 8, a method has been proposed in which a peripheral portion of a semiconductor substrate is heated in a state of being surrounded by an infrared absorber in order to eliminate a rate of temperature rise between a central portion and a peripheral portion of the semiconductor substrate. Have been. In the figure, 1 is a semiconductor substrate, 2
Is a holding table, and 3 is a ring-shaped infrared absorber made of carbon and configured to surround the peripheral portion of the semiconductor substrate 1.

In the method shown in FIG. 8, when infrared rays are irradiated from the upper surface and the lower surface of the semiconductor substrate, the temperature of the infrared absorber 3 rises faster than that of the holding table 2, and the temperature of the central portion and the peripheral portion of the semiconductor substrate becomes higher. This is a method of reducing the gradient. However, the holding table 2 conventionally used is transparent to infrared rays and does not have high thermal conductivity, so that only the temperature of the infrared absorber 3 rises and heat stays in this portion. As a result, the temperature rise in the central part and the peripheral part of the semiconductor substrate 1 was not constant, and the occurrence of microslip could not be completely suppressed.

Further, another method has been proposed in which the irradiation intensity of the infrared lamp is increased at the peripheral portion of the semiconductor substrate and the temperature rise in the peripheral portion is accelerated. However, adjusting the irradiation intensity of the infrared lamp is complicated. There was a problem that optimal conditions could not be obtained, resulting in microslip.

[0013]

As described above, in order to keep the temperature of the central portion and the peripheral portion of the semiconductor substrate constant, a method of heat-treating the semiconductor substrate in a state where the periphery of the semiconductor substrate is surrounded by an infrared absorber, and a method of irradiating an infrared lamp. The method in which the heat treatment is performed by partially adjusting the strength cannot completely suppress the occurrence of microslip. An object of the present invention is to provide a heat treatment method for a semiconductor substrate that can uniformly raise the temperature of the semiconductor substrate by a simple method and does not generate microslip.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for manufacturing a semiconductor substrate, comprising the steps of forming one of gallium nitride, aluminum nitride, boron nitride and silicon carbide on one main surface, another main surface and side surfaces. In a heat treatment method for a semiconductor substrate comprising a sintered body including one or two or more members, and heat-treating a member having an infrared absorber opposite thereto, a portion in contact with a peripheral portion of the semiconductor substrate to be processed is The heat treatment is performed with the members having the infrared absorbers facing each other.

Further, the absorber is made of any one of carbon, tantalum, tantalum carbide, tantalum boride, tungsten, tungsten carbide, tungsten boride, molybdenum, molybdenum carbide and molybdenum boride.

[0016]

Embodiments of the present invention will be described below. FIG. 1 shows a first embodiment of the present invention.
In FIG. 1, 1 is a semiconductor substrate made of a compound semiconductor such as gallium arsenide or a silicon semiconductor, and 2 is a holder made of a sintered body containing any one or two or more of gallium nitride, aluminum nitride, boron nitride and silicon carbide. Reference numeral 3 denotes an infrared absorber made of a carbon film or a carbon-containing film coated on the surface of the holding base 2 and the protective plate 4 in the vicinity of a portion where the peripheral portion of the semiconductor substrate 1 contacts, and 4 is made of the same material as the holding base 3 A protection plate made of a sintered body.

As shown in the figure, the surface of the semiconductor substrate 1 is brought into close contact with the holding table 2 or in parallel with a small gap, and heat treatment is performed by a lamp annealing apparatus using an infrared lamp (not shown) as a heating source. . The surface of the holding table 2 is flattened so that the surface of the holding table 2 can be in close contact with the surface of the semiconductor substrate 1 or in parallel with a small gap. In FIG. 1, the dimension between the semiconductor substrate 1 and the protective plate 4 is widely described for clarity of the configuration. However, in actual lamp annealing, contact with a close contact or a small gap is required. preferable. The holding table 2 is a semiconductor substrate 1
Is formed at a position facing the peripheral portion of the semiconductor substrate 1 so as to surround the peripheral portion. Further, the semiconductor substrate 1
The surfaces of the holding base 2 and the protection plate 4 are coated with an infrared absorber 3 so that the temperature of the holding base 2 and the protection plate 4 at the portion opposed to the peripheral portion increases.

The heat treatment process proceeds as follows. First, due to the irradiation of infrared rays, the infrared absorber 3 absorbs infrared rays, the temperature of the holding table 2 and the protection plate 4 in this portion rises, and the peripheral portion of the semiconductor substrate 1 is heated first. Holder 2
Further, since the protective plate 4 is formed of a sintered body having good thermal conductivity, heat is quickly conducted toward the center of the semiconductor substrate 1 to increase the temperature of the center of the semiconductor substrate 1. At the same time, the holding table 2 made of a sintered body and the protection plate 4 themselves also absorb infrared rays, and the temperature rises at a slower rate than that of the part coated with the infrared absorber 3. During the irradiation of infrared rays, the temperature of the infrared absorber 3 is increased, so that there is no decrease in temperature due to heat radiation around the semiconductor substrate. As a result, the temperature of the entire semiconductor substrate rises uniformly. Further, since the holding table and the protection plate have excellent thermal conductivity, heat does not stay in the peripheral portion.

Since the heat treatment process proceeds as described above, it is preferable that the holding table 2 and the protection plate 4 have a small infrared absorption coefficient. As shown in FIG. 2, when the binder material or the like at the time of formation is different, the infrared absorption coefficient is different. This infrared absorption coefficient is F
The linear transmittance of infrared light having a wavelength of 6 microns was measured by the T-IR method, and calculated from the result. In a holding table having a small infrared absorption coefficient (sintered body B in the figure), the infrared absorber absorbs infrared rays and rises in temperature. Fig. 2
As shown in (1), the heat conductivity is large, and the heat absorbed by the infrared absorber is quickly conducted toward the center of the semiconductor substrate.
As a result, the temperature of the peripheral portion of the semiconductor substrate rises first, and the temperature of the central portion also rises quickly, so that the temperature of the entire semiconductor substrate rises uniformly.

Since the holding table of the present invention is a sintered body,
The holder does not completely transmit the infrared rays, and the holder itself absorbs the infrared rays. If the infrared absorption coefficient of the holder is smaller than that of the infrared absorber, the effect of the present invention can be exerted. Therefore, the infrared absorption coefficient of the holding table is not limited.

As for the shape of the holding table, the shape of the holding table 2 and the protection plate 4 having the structure shown in FIG. is there. At this time, the height of the convex shape is equal to or slightly higher than the thickness of the semiconductor substrate 1 so that the convex shape of the holding table 2 is in close contact with the protective plate 4 and covers the entire surface of the semiconductor substrate 1. can do. Further, by making the thickness slightly lower than the thickness of the semiconductor substrate 1, the semiconductor substrate 1 can be brought into close contact with the protective plate 4.

FIG. 3 shows a second embodiment of the present invention.
As shown in the figure, it is also possible to form a convex shape on both the holding base 2 and the protection plate 4 so that the protruding shapes of the holding base 2 and the protection plate 4 adhere to each other to cover the peripheral portion of the semiconductor substrate 1. It is. Further, similarly to the first embodiment, the semiconductor substrate 1
The surfaces of the holding table 2 and the protection plate 4 are coated with an infrared absorber 3 so that the temperature of the holding table 2 at the portion where the peripheral portion faces is increased.

FIG. 4 shows a third embodiment of the present invention. As shown in the figure, both the holding table 2 and the protection plate 4 have a convex shape. By making the height of the convex shape of the holding table 2 equal to or slightly higher than the thickness of the semiconductor substrate 1, the holding table 2 and the protection plate 4 can be brought into close contact with each other, and the entire surface of the semiconductor substrate 1 can be covered. Also, as described above, the semiconductor substrate 1 can be brought into close contact with the protective plate 4 by reducing the height. Also in this embodiment, the surfaces of the holding table 2 and the protective plate 4 are coated with an infrared absorber 3 so that the temperature of the holding table 2 at the portion where the peripheral portion of the semiconductor substrate 1 faces is increased.

FIG. 5 shows a fourth embodiment of the present invention.
This is a combination of a flat holding table 2 and a protection plate 4 with a side member 5 formed of a ring or the like adapted to the shape of the semiconductor substrate 1 so as to face the periphery of the semiconductor substrate 1. In this case, as shown in the figure, by providing a gap between the side members by combining two rings and the like having different diameters, heat radiation from the peripheral portion of the semiconductor substrate is reduced,
More uniform heating can be realized. The height of the side member 5 can also be appropriately selected in relation to the thickness of the semiconductor substrate. The side member 5 is not limited to two rings, and may be a single ring or a divided member. The shape is not limited to a circular shape but may be a polygon.
In order to fix the position of the ring or the like, it is also possible to adopt a shape in which a groove is provided in the holding table. Also in this embodiment, the surfaces of the holding table 2 and the protection plate 4 are coated with the infrared absorber 3 so that the temperature of the holding table 2 and the protection plate 4 at the portion where the peripheral portion of the semiconductor substrate 1 faces is increased. .

Also in the second to fourth embodiments, the first
In the heat treatment step, as in the first embodiment, the infrared absorber 3 first absorbs infrared rays by irradiating the infrared rays, the temperature of the holder 2 and the protective plate 4 in this portion rises, and the peripheral portion of the semiconductor substrate 1 Heated. Since the holding table 2 and the protection plate 4 are formed of a sintered body having good thermal conductivity, heat is quickly conducted toward the center of the semiconductor substrate 1 to increase the temperature of the center of the semiconductor substrate. At the same time, the holding table 2 and the protection plate 4 made of a sintered body
The body itself also absorbs infrared rays, and the temperature rises at a slower rate than that of the part coated with the infrared absorber 3. During the irradiation of infrared rays, the temperature of the infrared absorber 3 is increased, so that there is no decrease in temperature due to heat radiation around the semiconductor substrate. As described above, the temperature rise in the peripheral portion of the semiconductor substrate 1 proceeds first, and the temperature rise in the central portion is delayed. As a result, the temperature of the entire semiconductor substrate is uniformly increased. Further, since the holding table 2 and the protection plate 4 are excellent in heat conductivity, heat does not stay in the peripheral portion.

The coated infrared absorber 3
The structure of the semiconductor device is not limited to those shown in FIGS. 1, 3 to 5, and can be variously changed as long as the structure can raise the temperature of the peripheral portion of the semiconductor substrate first. For example,
It is also possible to coat the side surfaces of the holding table and the protection plate with an infrared absorber, or to coat only one of them.

The dimension between the side surface of the semiconductor substrate 1 and the convex shape or the side surface member described in the first to fourth embodiments depends on the size of the semiconductor substrate, the size of the semiconductor substrate at the time of heating, or the size of the holder. It is set appropriately in consideration of the coefficient of thermal expansion.
It is preferable that the dimensions be such that they are in contact with each other or have a small gap during heating.

The infrared absorber may be a carbon film or the like, a metal which does not deform at the heat treatment temperature such as melting, for example, a high melting point metal such as tantalum, tungsten and molybdenum, and a carbide thereof such as tantalum carbide, tungsten carbide and molybdenum carbide. It is also possible to coat boride such as tantalum boride, tungsten boride and molybdenum boride in a state where the surface is porous and the reflected infrared rays do not occur. Here, when a metal is used as the infrared absorber, if there is a possibility that the surface of the semiconductor substrate to be processed is contaminated by these metals, another coating film, for example, a nitride film, an oxidized film, is formed on the infrared absorber. It is also possible to form a film, a polycrystalline silicon film, or the like. A nitride film, an oxide film, a polycrystalline silicon film, or the like allows infrared light to pass therethrough and allows an infrared absorber such as a carbon film to efficiently absorb infrared light.

The case where the infrared absorber is coated on the surface of the holder and the protective plate has been described above.
Since the holding table or the like of the present invention is made of a sintered body, it can be built inside. FIG. 6 shows a fifth embodiment. The figure shows a cross-sectional view of the holding table 2 on which the semiconductor substrate 1 according to the first embodiment is mounted, and the protection plate is omitted. In the figure, reference numeral 6 denotes raw material particles made of gallium nitride, aluminum nitride, boron nitride, and silicon carbide; 7, a binder; and 8, a particulate infrared absorber.

The holding table 2 having the structure shown in FIG.
And a binder 7, such as a particle-shaped infrared absorber 8 and yttrium oxide, and then molding, followed by sintering. The particulate infrared absorber 8 is mixed so as to be present in a portion that comes into contact with a peripheral portion of the semiconductor substrate 1 to be heat-treated. The amount of the infrared absorber to be included can be set as appropriate, such that the amount of the infrared absorber to be included is gradually increased from the center of the semiconductor substrate to the peripheral portion, or it is fixed only in the peripheral portion. It is also possible for the structure to have a quantity of infrared absorbers.

Needless to say, such a method can be applied to the holding table having the structure described in the second to fifth embodiments. Further, the present invention can be applied to a protection plate.

FIG. 7 shows a sixth embodiment. In the drawing, reference numeral 9 denotes a plate-like infrared absorber. The structure is such that a plate-like infrared absorber is provided in place of the particulate infrared absorber of the fifth embodiment described above. The sintered body having such a structure can also be formed by mixing the raw material particles 6 and the binder 7, forming a plate-like infrared absorber 9 therein, and then sintering. Also in this case, the present invention can be applied to the holding table having the structure described in the second to fifth embodiments, and can also be applied to the protective plate.

Also, after the raw material particles and the binder are once formed by sintering, they are immersed in a solution in which infrared absorbers, specifically, molybdenum particles, etc. are suspended, and impregnated to a desired concentration. Is also possible. Also in this case, the present invention can be applied to the holding table having the structure described in the second to fifth embodiments, and can also be applied to the protective plate.

In the above embodiment, the holding table and the protective film are preferably made of the same material in consideration of thermal expansion and the like, but are not necessarily the same.

The holding base and the protection plate thus formed have a low heat capacity and a high thermal conductivity.
As a result of performing the above heat treatment, thermal deformation was smaller, defects such as microslip could be prevented, and good results could be obtained as compared with the conventional holding table. In addition, even if these materials are compound semiconductors containing arsenic as a constituent element, they do not cause deterioration of the flatness of the semiconductor substrate due to evaporation of arsenic. Furthermore, instead of compound semiconductors,
Even when the silicon semiconductor substrate was heat-treated, surface defects such as microslip could be reduced.

The sintered body constituting the holding table and the protection plate of the present invention contains any one or more of gallium nitride, aluminum nitride, boron nitride and silicon carbide, but has a flat surface. It is preferable that the material contains any one or more of gallium nitride, aluminum nitride, and boron nitride.

[0037]

As described above, according to the present invention, a holding table used in a lamp annealing method particularly requiring rapid thermal quenching has a low heat capacity, a high thermal conductivity, and a center and a peripheral portion of a semiconductor substrate. Since the heat treatment can be performed without the temperature difference between the parts, the formation of crystal defects such as microslip can be prevented. In particular, when the semiconductor substrate to be processed is a compound semiconductor, it is advantageous in that a material such as a holding table does not absorb elements evaporated from the surface of the semiconductor substrate.

Further, the method of the present invention can provide a simple heat treatment method without requiring special adjustment or control for reducing the temperature difference between the peripheral portion and the central portion of the semiconductor substrate.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a material of a holding table of the present invention.

FIG. 3 is a diagram illustrating a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a third embodiment of the present invention.

FIG. 5 is a diagram illustrating a fourth embodiment of the present invention.

FIG. 6 is a diagram illustrating a fifth embodiment of the present invention.

FIG. 7 is a diagram illustrating a sixth embodiment of the present invention.

FIG. 8 is a diagram illustrating a conventional heat treatment method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Holder 3 Infrared absorber 4 Protective plate 5 Side member 6 Raw material particle 7 Binder 8 Particulate infrared absorber 9 Plate-shaped infrared absorber

Claims (2)

[Claims] 1. One or more of gallium nitride, aluminum nitride, boron nitride, and silicon carbide are provided on one main surface, another main surface, and side surfaces of a semiconductor substrate to be processed.
A heat treatment method for a semiconductor substrate, comprising a sintered body including the above, and heat-treating a member having an infrared absorber opposite thereto, wherein the infrared absorber is attached to a portion in contact with a peripheral portion of the semiconductor substrate to be processed. A heat treatment method for a semiconductor substrate, wherein a heat treatment is performed with the provided members facing each other. 2. The heat treatment method for a semiconductor substrate according to claim 1, wherein said absorber is carbon, tantalum, tantalum carbide, tantalum boride, tungsten, tungsten carbide, tungsten boride, molybdenum, molybdenum carbide, molybdenum boride. A heat treatment method for a semiconductor substrate.