JP2003224082A - Silicon ring for holding silicon wafer in light irradiation thermal treatment equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon ring for holding a silicon wafer wherein uniform thermal treatment can be performed to the whole surface of the silicon wafer while holding the wafer horizontally without generating thermal distortion, in a silicon ring for holding a wafer which is used when a silicon wafer is thermally treated by light irradiation thermal treatment equipment. <P>SOLUTION: This silicon ring 6 for holding a silicon wafer which is composed of silicon is used as a holding ring for holding an outer periphery of a silicon wafer when a disk-shaped silicon wafer is thermally treated by the light irradiation thermal treatment equipment. Slits 8a, 8b in centripetal direction are arranged in the silicon ring 6, and the ring is cut and opened. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a silicon ring for supporting a silicon wafer in a light irradiation heat treatment apparatus for rapidly heating and heat-treating a silicon wafer. [0002] A silicon wafer is heat-treated by rapid heating and rapid cooling using a light irradiation type heat treatment apparatus for heating by light irradiation for forming a surface thin film, oxidizing, diffusing or annealing. In this heat treatment, the heat dissipation from the outer peripheral edge of the silicon wafer becomes larger than the heat dissipation from the central portion, and a temperature difference is generated between the outer peripheral edge and the central portion of the silicon wafer. But the temperature decreases.
When the temperature distribution becomes non-uniform in this way, a defect called a slip occurs in the silicon wafer. [0003] As an improvement for eliminating the drawbacks in the heat treatment using the light irradiation type heat treatment apparatus, Japanese Patent Application Laid-Open No.
Japanese Patent Application Laid-Open No. 22879 discloses a thin plate body having a thin plate shape, an inner peripheral edge of which is formed in a shape facing the outer peripheral edge of the substrate with a gap provided outside thereof, and extending from the thin plate main body in the centripetal direction. There has been proposed a light irradiation type heat treatment apparatus configured to support a substrate via a substrate pseudo-complementary plate composed of a support portion that horizontally supports the substrate. Silicon carbide, which is excellent in heat resistance and thermal conductivity, is used as the substrate pseudo-complementary plate. Japanese Patent Application Laid-Open No. 2000-58471 discloses a light irradiation type in which a substrate to be heat-treated by light irradiation is held by a guard ring, and the outer peripheral edge of the substrate is radiatively heated by the guard ring. In the heating apparatus, there is described an apparatus in which an annular auxiliary ring having a heat capacity per unit area equivalent to that of the guard ring is interposed between the guard ring and the guard ring support. Again, the ring is made of silicon carbide. Further, in this method, the number of components increases and the structure is complicated, so that processing is troublesome and economically disadvantageous. [0005] Further, as a means for alleviating thermal shock due to a rapid change in temperature, although not for a wafer, a circle on the outer peripheral surface of a ring body is cut off with a chord, or a slit is formed by cutting off a part of the chord. Heat treatment jig is disclosed in JP-A-10-287473.
No., published in US Pat. However, even if a silicon ring for lamp annealing a silicon wafer is made by this method, the ring is extremely thin and is often broken during handling such as processing and mounting to a device, and the string is used during use. Cracks appear to be caused by stress concentration on the extension of the slit, which is partially cut off, so that it cannot be used. Conventionally, ceramics such as silicon carbide have been mainly used for a wafer support ring used for heat treatment of a silicon wafer by a light irradiation type heating device. Conventionally, ceramics such as silicon carbide have been used for the following reasons. In heat treatment of a silicon wafer by a light irradiation type heating device, a support ring made of silicon
When used by heating to a high temperature range of 1C to 1100C, silicon has a lower melting point than ceramics and is thermally weak. Therefore, as the number of heating increases, the plate surface is distorted due to the temperature difference between the inside and outside of the ring. There was a problem. In the heat treatment of a silicon wafer by a light irradiation type heating apparatus, deformation such as waveform deformation is generated by heating a support ring to compensate for heat radiation from a peripheral portion of the wafer and keeping a uniform temperature distribution over the entire surface of the wafer. Can be prevented. Therefore, ceramics having high heat resistance have been adopted as the material of the support ring. However, silicon wafers have recently been increasing in size and are shifting to silicon wafers having an outer diameter of 300 mm (12 inches). Further, as the degree of semiconductor integration increases along with the increase in size, improvement in quality, such as in-plane uniformity during heat treatment, for silicon wafers has been strongly demanded. Therefore, in a recent light irradiation type heating apparatus for a silicon wafer having an outer diameter of 300 mm, it has become necessary to use a silicon ring instead of a conventional ceramic ring for the following reasons. A wafer having an outer diameter of 300 mm has an outer diameter of 200 mm.
Not only is the diameter larger than the wafer, but also the area and weight are large, making it difficult to raise the temperature uniformly during heating. When supporting a 200 mm outer diameter wafer with a ceramic ring and performing heat treatment, the center and outer periphery of the wafer Although there was no problem of a temperature difference between the wafer and the outer portion, it was found that a wafer having an outer diameter of 300 mm had a high temperature difference between the central portion and the outer peripheral portion of the wafer, and was more likely to generate crystal defects such as slip. [0011] The reason for this is that when ceramics are used, even if materials having physical properties such as specific heat, heat transfer coefficient, and emissivity close to those of a silicon wafer are selected, their physical property values are not equal to those of silicon. However, it turned out that it had a big influence. As described above, when a ceramic ring is used in the heat treatment of a wafer having an outer diameter of 300 mm, the problem may be caused by the thermal expansion coefficients and specific heats of silicon carbide and silicon which could be ignored in the heat treatment of a wafer having an outer diameter of 200 mm. And the difference in thermal properties cannot be ignored. It is desirable that the support ring for supporting the wafer in the light irradiation type heating device be in a state where it can be regarded as an extension of the wafer. Therefore, it is necessary to make the material of the support ring the same silicon as the wafer, and to further reduce the temperature difference between the center and the outer periphery of the wafer. The use of a silicon ring is also effective to avoid contamination of impurities. However, according to an experiment conducted by the inventor, when the heat treatment was repeatedly performed using the silicon ring, the ring gradually deformed due to minute undulation. In particular, it was found that when rapid heating was repeatedly performed by lamp heating at the time of a CVD reaction or the like, deformation was remarkable. [0014] This is because the light of the lamp annealing irradiates the wafer and the silicon ring, but the heat radiation from the ring to the ring holding portion (member supporting the outer portion of the ring) affects the inner side (inner diameter side) of the silicon ring. Is higher than the outside (outer diameter side). It is considered that the temperature difference causes the inside of the ring to expand significantly. Also, silicon is different from silicon carbide in that the lamp annealing temperature is 1000 to 1
It is considered that since plastic deformation occurred at around 100 ° C., deformation based on plastic deformation that did not occur in silicon carbide occurred. Deformation of the silicon ring does not cause a problem when processing about several wafers, but starts to deform while processing several tens or more wafers. In a specific state after the deformation, the inner peripheral portion is elongated and deformed, so that the inner peripheral portion has a shape slightly waving up and down. However, even with this slight deformation, the silicon ring could not be used for supporting the silicon wafer for lamp annealing because the wafer could not be held properly horizontally. Further, the present inventor thought that if the width {(outer diameter−inner diameter) / 2} of the silicon ring in the centripetal direction is reduced, stress generation during heating is reduced. However, if the distance between the wafer and the supporting member that holds the holding portion of the silicon ring is too narrow, the temperature distribution of the wafer cannot be kept uniform due to heat radiation from the supporting member. for that reason,
Various tests were also conducted on the minimum interval at which the temperature distribution of the wafer could be kept uniform. The present invention, based on the above considerations, provides a silicon ring for directly supporting a silicon wafer in a heat treatment of the silicon wafer by a light irradiation type heating device. The silicon ring for supporting the silicon wafer in the light irradiation heat treatment apparatus according to the present invention is a silicon wafer used for heat treatment of a disk-shaped silicon wafer by the light irradiation heat treatment apparatus. The support ring for supporting the portion is made of silicon, and the silicon ring is cut open by providing a slit in the centripetal direction in the silicon ring. The slit in the centripetal direction includes not only the direction on the diameter line passing through the center of the silicon ring but also the inclination direction off the center. Accordingly, the fracture surface caused by the slit can be an inclined fracture surface inclined at an arbitrary angle with respect to the tangent line, in addition to the fracture surface perpendicular to the tangent to the silicon ring outer peripheral surface. DESCRIPTION OF THE PREFERRED EMBODIMENTS A silicon ring for supporting a silicon wafer in a light irradiation heat treatment apparatus according to the present invention supports an outer peripheral portion of a silicon wafer when a disk-shaped silicon wafer is heat treated by the light irradiation heat treatment apparatus. This is a silicon ring in which a support ring is formed of silicon. Then, the silicon ring is provided with a slit in the centripetal direction and the ring is cut open. Regardless of the size of the silicon wafer, a sufficient effect can be obtained simply by providing the slit at one location on the ring. However, the slit is not limited to one, and for example, the effect of the present invention can be obtained even if the ring is divided into two by providing slits in the centripetal direction at two positions facing each other on the diameter line of the silicon ring, Since the surface accuracy of the wafer support may be a problem, it is more preferable to provide a slit at one place of the ring than to divide the ring into two parts. Also, the slit width can be made wider on the inside of the ring. As described above, when slits are provided at two places on the ring, the divided ring pieces maintain a circular shape,
It is necessary to ensure that the silicon wafer can be held horizontally and that the silicon ring does not fall off the ring support when the silicon wafer is taken out. Since the silicon ring is heated by lamp irradiation together with the silicon wafer, it is desirable that the thickness of the silicon ring be equal to or close to the thickness of the silicon wafer. The inner peripheral surface of the silicon ring that supports the silicon wafer is formed so as to be stepped or tapered so that the silicon wafer can be placed and held on the stepped or tapered surface. Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a light irradiation type heating device for rapidly heating and heat-treating a semiconductor silicon wafer supported by a silicon ring. A plurality of arc-shaped reflectors 4 are arranged on the inner surface of the ceiling of the furnace body 1, and each of the arc-shaped reflectors 4 is provided.
And a silicon ring support 5 made of silicon carbide is installed on the floor in the furnace. The silicon ring support 5 has a structure capable of horizontally holding a silicon ring 6 capable of supporting a silicon wafer 7 having a diameter of, for example, 300 mm. The plurality of halogen lamps 2 provided on the ceiling are connected to a lighting power source (not shown) installed outside the furnace, and are configured to be turned on by a lighting control signal from a controller. A radiation thermometer 3 for measuring the temperature of the silicon wafer 7 is provided in a non-contact manner with the lower surface of the silicon wafer 7 through a hole penetrating the center of the furnace bottom. And in the controller,
The lighting output is controlled so that the silicon wafer can be heat-treated at a predetermined heating / cooling rate, holding temperature, and holding time. The silicon ring support 5 is configured to rotate in a horizontal plane by a rotation mechanism (not shown) so that the entire surface of the silicon wafer 7 can be uniformly heated. In addition,
In FIG. 1, an apparatus for loading / unloading a semiconductor silicon wafer into / out of the furnace and equipment related thereto are omitted. Next, the silicon wafer 7
An embodiment of the present invention will be described with reference to FIGS. 3 and 4 as a silicon ring for horizontally supporting. FIG. 3 shows a case where a slit is provided at one position of the silicon ring 6. FIG. 3A shows a case where the slit 8a is cut open toward the center of the ring, and FIG. 3B shows a case where the slit is cut and opened using the slit 8b inclined off the center of the ring. FIG. 4 shows a case where the silicon ring 6 is divided into two parts by providing slits 9 at two opposing positions on the diameter line of the silicon ring 6. In the silicon ring divided into two, the ring shape is maintained when the silicon wafer is attached and detached, and the silicon ring is fixed at a fixed position so as not to be disassembled. The silicon wafer to be subjected to the heat treatment is inserted into the space inside the silicon ring and incorporated.
As shown in FIG. 2, the inside of the silicon ring 6 is provided with a locking side 6a having a projecting cross section, and the outer peripheral edge of the wafer is placed thereon and supported thereon, or the inner peripheral edge of the ring is formed as an upwardly inclined surface 6b. The outer peripheral edge of the wafer is placed and supported on the inclined surface. It is desirable to provide a small horizontal gap between the support and the ring in order to escape the difference in thermal expansion between the wafer and the ring. As a specific example of the dimensions of the silicon wafer and the silicon ring, if a silicon wafer having an outer diameter of 300 mm is shown, the silicon ring has an outer diameter of 365 mm, an inner diameter of 295 mm, and a thickness of 0.8 mm.
A silicon ring was made by cutting a part of the ring with a 2 mm slit. In this case, a support side 6a having a length of 1 mm and a thickness of 0.4 mm is formed on the inner peripheral edge of the ring,
The outer peripheral portion of the wafer was placed. The silicon ring 6 is formed by cutting the same single-crystal or polycrystalline silicon as the silicon wafer 7 into a desired shape. Both are made of the same silicon and have similar properties, and exhibit similar temperature rise characteristics. Therefore, since the silicon wafer 7 and the silicon ring 6 are heated and heated under the same conditions, heat radiation from the outer peripheral edge of the wafer is hardly observed.
The entire surface of the silicon wafer 7 is uniformly heated. But,
The heat of the outer peripheral portion of the silicon ring 6 supported in contact with the silicon ring support 5 is transferred to the support by heat conduction from the contact portion, and the heat is transferred between the outer peripheral portion and the inner peripheral portion of the silicon ring 6. There is a large temperature difference between them. For this reason, the inner peripheral portion is elongated by thermal expansion, but the expansion of the slit width absorbs the elongated portion, does not cause distortion due to thermal stress, and keeps the silicon wafer horizontally supported.
Uniform heat treatment can be continued. As a result, no slip is observed on the silicon wafer, and there is no risk of impurity contamination on the wafer. According to the present invention, when a silicon wafer is supported and heat-treated by the silicon ring according to the embodiment of the present invention, thermal stress caused by a temperature difference between an outer peripheral portion and an inner peripheral portion of the silicon ring is provided on the ring. Since the slit width is not absorbed and deformed due to the widened slit width, uniform heat treatment can be performed on the entire surface of the silicon wafer, no crystal defects such as slips are generated, and contamination by impurities can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view schematically showing a cross section of an example of a light irradiation type heating device used for carrying out the present invention. FIG. 2 is an explanatory view showing details of a support portion for supporting a silicon wafer with a silicon ring according to the embodiment of the present invention in the apparatus of FIG. 1; 3 is a plan view of a silicon ring in which a slit is provided in one place of the ring according to an embodiment of the present invention. FIG. 3a shows a case where the ring is cut open by a slit directed to the center of the ring, and FIG. This is the case where the ring is cut open by the inclined slit directed to the vertical direction. FIG. 4 is a plan view showing a case where a ring is divided into two by providing slits at two opposing positions on a diameter line of the ring according to another embodiment of the present invention. [Description of Signs] 1 Furnace body 2 Halogen lamp 3 Radiation thermometer 4 Arc-shaped reflector 5 Silicon ring support 6 Silicon ring 6a Support side 6b Upward inclined surface 7 Silicon wafer 8a, 8b Slit 9 Slit

Claims (1)

Claims: 1. A silicon ring formed of silicon, wherein a support ring for supporting an outer peripheral portion of a silicon wafer used when heat-treating a disk-shaped silicon wafer by a light irradiation heat treatment apparatus is provided. A silicon ring for supporting a silicon wafer in a light irradiation heat treatment apparatus, wherein the silicon ring is provided with a slit in a centripetal direction and the ring is cut open.