JP2011199295A - Semiconductor wafer rapid heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor wafer rapid heating apparatus which can rapidly heat a semiconductor wafer using flash lamps without subjecting the semiconductor wafer to breaking or hopping out.SOLUTION: The semiconductor wafer rapid heating apparatus includes a light source comprising a regularly arranged plurality of flash lamps and a reflection plate that reflects the light emitted from the flash lamps to the side of an object to be heated, and a heat treatment chamber in which a supporting pedestal that supports the semiconductor wafer is arranged. In the semiconductor wafer rapid heating apparatus that rapidly heat-treats a semiconductor wafer by the light from the flash lamps, the supporting pedestal has a recess thereon. The recess has horizontally a substantially circular shape with a slightly smaller diameter than that of the semiconductor wafer where the ratio of the diameter of the recess to that of the semiconductor wafer ranges between 40% and 90% while the vertical cross section thereof is substantially rectangular. When a semiconductor wafer is placed so as to cover the recess, a space is formed between the supporting pedestal and the semiconductor wafer.

Description

  The present invention relates to a rapid heating apparatus for semiconductor wafers. In particular, the present invention relates to a semiconductor wafer rapid heating apparatus using a flash lamp, which is characterized by the shape of the holding portion of the wafer.

  In recent years, semiconductor integrated circuits have been highly integrated and miniaturized, and a plurality of layers of circuits have been formed in the thickness direction of the semiconductor wafer. When such a semiconductor integrated circuit is formed, a method of forming a thin impurity diffusion layer on the surface layer portion of the semiconductor wafer is known. In this method, an impurity diffusion layer is formed in the surface layer portion by introducing impurities into the Si crystal in the surface layer portion of the semiconductor wafer, for example, by ion implantation, and performing heat treatment on the semiconductor wafer. When forming the impurity diffusion layer, it is important to heat the semiconductor wafer into which impurities have been introduced in as short a time as possible. If the semiconductor wafer into which the impurity is introduced is exposed to a high temperature for a long time, the distance in which the impurity is thermally diffused becomes long, the thickness of the impurity diffusion layer is increased, and a thin impurity diffusion layer cannot be formed. It is because it ends up.

  In order to form the impurity diffusion layer, it is necessary to raise the temperature of the semiconductor wafer to, for example, 1000 ° C. or more, and in order to reduce the thickness of the impurity diffusion layer, the temperature is increased to 1000 ° C. in as short a time as possible. The above temperature raising / lowering treatment is required. As described above, an RTP (Rapid Thermal Process) device is known as a device that realizes rapid temperature increase and decrease in a short time. As a heating source of the RTP apparatus, a halogen lamp is widely used, and the temperature of the semiconductor wafer is rapidly increased and decreased by lighting and blinking light emitted from the halogen lamp.

  However, it is necessary to make the impurity diffusion layer extremely thin in accordance with further higher integration and miniaturization of semiconductor integrated circuits in recent years, reduction of power consumption during circuit driving, and speeding up of the circuit itself. It has become. For example, when an impurity diffusion layer of 20 nm or less is formed, rapid heating with a halogen lamp has a problem that a thermal diffusion distance becomes long and a thin layer cannot be formed. In view of this, an apparatus has been proposed in which a flash lamp is used as a heating source of an RTP apparatus and a flash lamp is turned on so that very high energy is input to the semiconductor wafer in a short time and the temperature is raised and lowered instantaneously. An example of such a technique is disclosed in Japanese Patent Application Laid-Open No. 2004-31557.

  FIG. 5 shows an outline of a light heating apparatus using a conventional flash lamp. The light heating device 41 uses a semiconductor wafer W made of silicon or the like as an object to be processed, and includes a quartz glass chamber 44 having an atmospheric gas inlet 42A and an outlet 42B. And a support base 45 for supporting the semiconductor wafers arranged. A quartz flat plate 46 is provided on the ceiling surface (upper surface in FIG. 5) of the chamber 44 as an airtight translucent member.

  A flash lamp 48 is provided as a heating source above the flat plate 46, and a halogen heater lamp 49 is provided as a preheating means below the chamber 44. The halogen heater lamp 49 is embedded in the support base 45 and the temperature is controlled by the chamber control circuit 50. In the chamber control circuit 50, an elevating function of the support base 45, opening / closing control of the atmospheric gas inlet 42A and the outlet 42B are also performed.

  According to the light heating device 41, when the semiconductor wafer W made of silicon into which impurities are introduced is carried into the chamber 44, the halogen heater lamp 49 causes the semiconductor wafer W to reach a predetermined temperature at which the thermal diffusion of impurities does not become a problem. After preheating, the flash lamp 48 is caused to emit light so that the semiconductor wafer W is heat-treated by flash radiation. By such heat treatment, the semiconductor wafer W is heated so that the surface layer portion thereof is rapidly heated to high temperature, and then rapidly cooled and carried out of the chamber 44. The preheating is preferably performed for the purpose of reducing the temperature gradient in the thickness direction of the wafer and minimizing the energy injected into the lamp necessary for raising the temperature of the irradiated surface to a necessary level. A heating temperature is selected from the range of 300-500 degreeC, for example, is 350 degreeC. Further, the surface temperature of the semiconductor wafer W during the heat treatment by the halogen heater lamp 49 and the flash lamp 48 becomes 1000 ° C. or more, and specifically, the heat treatment is performed in the range of 1000 ° C. to 1300 ° C. Thus, by heating the maximum temperature of the semiconductor wafer W to 1000 ° C. or higher, the impurity diffusion layer can be reliably formed in the wafer surface layer portion.

The flash lamps 48 are arranged in parallel at equal intervals along the flat plate 46, and a common reflecting mirror 51 covers the flash lamps 48, and the reflecting mirror 51 is accommodated in the casing 52. The lighting operation of each flash lamp 48 is controlled by the power supply device 53.
JP 2004-31557 A

  However, when the semiconductor wafer is rapidly heated by the light heating apparatus using the flash lamp as described above, the semiconductor is gradually reduced as the pulse width which is a half-value half-width time with respect to the peak value of the pulse current for lighting the flash lamp is shortened. There was a problem that the wafer jumped by light irradiation. The reason for this jump is considered as follows. The surface of the semiconductor wafer that is irradiated with light undergoes rapid thermal expansion as the light is irradiated. At this time, due to the difference in thermal expansion caused by the temperature difference between the light-irradiated surface of the semiconductor wafer and the surface on the support base, the semiconductor wafer is instantaneously moved to the flash lamp side (hereinafter referred to as the upper side and the upper side). To a convex shape. Since this deformation occurs in a very short time, it is considered that a force that strikes the support table at the end face of the semiconductor wafer is generated, and as a result, the semiconductor wafer itself jumps. In addition, when the energy of light emitted from the flash lamp is 30 J / cm 2 or more and a single pulse width of pulse lighting is irradiated at 0.8 ms, the semiconductor wafer is broken by light irradiation. There was a problem.

  The problem to be solved by the present invention is that when a semiconductor wafer is rapidly heated using a flash lamp, the semiconductor wafer is not cracked and the semiconductor wafer is prevented from jumping. It is an object of the present invention to provide a semiconductor wafer rapid heating apparatus.

A semiconductor wafer rapid heating apparatus according to the present invention comprises a light source unit comprising a plurality of arranged flash lamps and a reflector that reflects light emitted from the flash lamps toward the object to be heated, and a support for supporting the semiconductor wafer. A semiconductor wafer rapid heating apparatus comprising: a heat treatment chamber having a table; and rapid heating treatment of the semiconductor wafer by the light of the flash lamp, wherein the support table is provided with a recess on the support table, The shape of the recess is a substantially circular shape that is slightly smaller than the diameter of the semiconductor wafer, the ratio of the diameter of the recess to the diameter of the semiconductor wafer is 40% to 90%, and the cross section is substantially rectangular. When the semiconductor wafer is disposed so as to cover the recess, a space is formed between the support base and the semiconductor wafer.

  According to the semiconductor wafer heating apparatus of the present invention, a sealed space is formed between the semiconductor wafer and the support table by being surrounded by the recess provided on the support table and the semiconductor wafer. Therefore, even if the semiconductor wafer is rapidly heated, the space does not cause the semiconductor wafer to jump or break. This effect is considered to be due to the following phenomenon. When the light from the flash lamp is irradiated onto the semiconductor wafer, the surface of the semiconductor wafer irradiated with the light is rapidly heated, and rapid thermal expansion is caused by this temperature increase. On the other hand, the surface on the support base side of the semiconductor wafer is not heated by light, so that the temperature does not increase rapidly and thermal expansion is small. With such a temperature difference, a difference occurs in elongation due to thermal expansion on the front and back surfaces of the semiconductor wafer. Due to the difference in elongation due to the thermal expansion, a tensile force is applied to the surface of the semiconductor wafer on the light irradiation side, and a compressive force is generated on the surface of the support table. For this reason, the semiconductor wafer is deformed in a convex shape toward the flash lamp side (upward). Since this deformation occurs in a very short time, a force that strikes the support table at the end face of the semiconductor wafer is generated, so that the semiconductor wafer itself jumps. On the other hand, the volume of the sealed space covered with the concave portion provided on the support table and the semiconductor wafer increases with the deformation of the semiconductor wafer. In the space, a gas having the same pressure as that in the heat treatment chamber is confined and kept airtight by placing the semiconductor wafer on the support base, and the volume of the space accompanying the deformation of the semiconductor wafer is kept. As the pressure increases, the pressure in the space rapidly decreases. This pressure drop generates a force that pulls the semiconductor wafer downward. Thereby, it is considered that the force that the semiconductor wafer tries to jump upward is suppressed.

  Furthermore, the shape of the recess formed directly on the support base is substantially circular with a gap slightly in the recess, slightly smaller than the diameter of the semiconductor wafer, and has a substantially rectangular cross section. Since the periphery of the recess and the periphery of the semiconductor wafer are in close contact with each other with high accuracy, it is easy to set the volume of the space formed by being surrounded by the recess and the semiconductor wafer without any gap, and the semiconductor wafer jumps or cracks. There is an effect that there is no.

  In addition, since the ratio of the diameter of the recess to the diameter of the semiconductor wafer disposed on the support table is 40% to 90%, the semiconductor wafer is cracked regardless of the diameter of the semiconductor wafer. There is no. Furthermore, even when the semiconductor wafer is preheated, there is an effect that a uniform heat treatment can be performed over the entire semiconductor wafer.

  The semiconductor wafer heating apparatus of the present invention has a light source unit in which a plurality of flash lamps are arranged in parallel, and includes a preheating mechanism unit for preheating the semiconductor wafer, and for supporting the semiconductor wafer when it is heat-treated. A semiconductor wafer heating apparatus provided with a table, wherein a thin gas layer is provided between the support table and a semiconductor wafer to be processed, thereby suppressing cracks that occur during rapid heating of the semiconductor wafer. .

  FIG. 1 shows a schematic cross-sectional view of a semiconductor wafer rapid heating apparatus 1 as a first embodiment of the present invention. The semiconductor wafer rapid heating apparatus 1 includes a light source unit 2, a heat treatment chamber unit 3, and a preheating mechanism unit 4. The light source unit 2 is provided with a tubular flash lamp 5 and a reflection mirror 6, and is provided with a light transmissive window unit 7 made of, for example, quartz glass. The heating chamber portion 3 includes a semiconductor wafer inlet / outlet 8, an atmospheric gas inlet 9, and a support table 10, and a semiconductor wafer W to be heat-treated is transferred onto the support table 10. A recess 20 is formed in the support table 10. When the semiconductor wafer W is placed on the support table 10, a space of a certain volume is provided on the support table side of the semiconductor wafer W. Provided. Further, the heating chamber portion 3 is provided with a window portion 11 for taking in light emitted from the light source portion 2, and is connected to the light transmitting window portion 7. In this embodiment, each of the light source unit 2 and the heating chamber unit 3 is partitioned by a plate material made of quartz glass or the like used for the light transmissive window unit 7. Alternatively, a light transmissive member made of, for example, quartz glass may be disposed. Further, the support base 10 and the preliminary heating mechanism unit 4 are partitioned by a heat transfer unit 12 to separate the heating chamber unit 3 and the preliminary heating mechanism unit 4. In this embodiment, the heat transfer section 12 uses a light transmissive plate member made of, for example, quartz glass. The preheating mechanism unit 4 is provided with a plurality of rod-shaped halogen lamps 13 and a reflector 14 that reflects light is provided on the heat transfer unit 12 side. In the present embodiment, the preliminary heating mechanism unit 4 is a light heating type in which the halogen lamp 13 is disposed. However, a heat transfer type heater such as a sheathed heater may be used. In the case of the heat transfer type, the heat transfer section 12 may be a heat transfer member such as metal, and a light transmissive member may not be used.

The semiconductor wafer W is transferred from the semiconductor wafer inlet / outlet 8 to the heat treatment chamber 3 of the semiconductor wafer rapid heating apparatus by a transfer robot arm or the like, and is placed on the support table 10. Thereafter, the gas inside the heat treatment chamber 3 is exhausted, and a gas necessary for the treatment, for example, a silane gas diluted with an inert gas such as argon, is introduced from the atmospheric gas inlet 9 by a specified amount. Is done. On the other hand, the semiconductor wafer W is preheated from about 150 ° C. to about 600 ° C. by the halogen lamp 14 provided in the preheating mechanism unit 4. Next, the flash lamp 5 is pulse-lit, for example, with an input power of 28 J / cm ² and a pulse width as a lighting time of 0.8 ms. At this time, heat treatment is performed so that the maximum surface temperature of the semiconductor wafer W (hereinafter referred to as peak temperature) is 1000 ° C. or higher, preferably 1000 ° C. to 1300 ° C.

  Next, FIG. 2 shows the shape of the recess 20 provided in the support base 10. FIG. 2A is a front view as seen from the surface side where the semiconductor wafer W is placed on the support base 10. The shape of the recess 20 is a circle that is slightly smaller than the diameter of the semiconductor wafer W. FIG. 2-b) shows an AA cross section cut along a one-dot chain line passing through the center of the support base 10 in FIG. 2-a). The shape of the recess 20 in the section AA is substantially rectangular. When the semiconductor wafer W is heat-treated, the recess 20 is confined with a gas having a pressure similar to that of the surrounding atmosphere by installing the semiconductor wafer W. Since the surface of the semiconductor wafer W becomes higher than the back surface due to the rapid heating process and a difference in thermal expansion occurs between the front and back surfaces, the semiconductor wafer W is deformed upward in a moment. With the convex deformation of the semiconductor wafer, the volume of the space formed by the recess 20 and the semiconductor wafer W substantially increases. At this time, the pressure of the gas confined in the recess 20 decreases with the amount of convex deformation of the semiconductor wafer, and the gas pressure in the recess 20 decreases, thereby lowering the semiconductor wafer W downward. Power works. By appropriately designing the volume of the recess 20, the downward pulling force due to the gas pressure drop accompanying the instantaneous deformation of the semiconductor wafer into a convex shape is controlled within a certain range, and the semiconductor wafer W There is no jump from the support table 20. In addition, by appropriately designing the volume in the recess 20, the force for pulling down the semiconductor wafer due to a drop in gas pressure accompanying the instantaneous deformation of the semiconductor wafer into a convex shape can be prevented from becoming excessively strong. The semiconductor wafer W itself is not destroyed. In the present embodiment, the shape of the recess 20 is a circle that is slightly smaller than the diameter of the semiconductor wafer W and is rectangular in the cross-sectional direction. However, the shape in the cross-sectional direction is not limited to this and is elliptical. Or an R shape or the like.

  FIG. 3 shows the semiconductor wafer W under various conditions when the depth of the recess 20 provided in the support table 10 is changed using the first embodiment of the present invention shown in FIG. The result of the comparative experiment of whether or not cracks are shown. In this comparative experiment, three types of wafers of 3 inches, 8 inches, and 12 inches were used as the semiconductor wafers W having different sizes. Further, the light emitted from the flash lamp 5 was verified for two types of pulse widths of 5 ms and 0.8 ms when the irradiation energy was changed between 10 to 65 J / cm 2. Here, when the pulse width is longer than 5 ms, current oscillation occurs and the charger is destroyed. Therefore, 5 ms is the longest pulse width substantially. Further, when energy of 30 J / cm 2 or more is input with a pulse width shorter than 0.8 ms, the instantaneous current density applied to the flash lamp is increased, and the lamp tube wall becomes cloudy in a short time. For this reason, it is not practical to drive the flash lamp with a pulse width of 0.8 ms or less. As an index indicating the size of the space formed between the semiconductor wafer W and the support base 10, the distance in the depth direction of the recess 20 is used, and 0 mm, 0.05 mm, 0.1 mm,. Comparison was made for each of 2 mm, 0.3 mm, and 0.4 mm. In this comparative experiment, the preheating temperature was 400 ° C., and the diameter of the recess 20 was 80% of the diameter of the semiconductor wafer W.

  In the conventional structure in which the depth of the recess 20 is 0 mm, that is, the semiconductor wafer W is arranged on a flat surface, the irradiation energy is 60 J / cm ^ 2 at a pulse width of 5 ms in each size of the semiconductor wafer W. When the pulse width was 0.8 ms, cracking occurred when the irradiation energy was 30 J / cm ^ 2. On the other hand, regardless of the light irradiation conditions such as the size, pulse width, and irradiation energy of the semiconductor wafer W, no cracks occurred when the depth of the recess 20 was 0.05 mm to 0.3 mm. However, when the depth of the recess 20 becomes 0.4 mm, the semiconductor wafer W is instantly deformed upwardly with light irradiation regardless of the size of the semiconductor wafer W and the light irradiation conditions. The phenomenon that the semiconductor wafer W itself jumped up and down occurred. Further, when the irradiation energy exceeds 60 J / cm 2, the jumping distance is increased, and a crack is generated due to collision with the wall or the like in the heat treatment chamber 3. Thus, in this comparative experiment, cracking of the semiconductor wafer W did not occur when the depth of the recess 20 was 0.05 to 0.3.

  As described above, the depth of the concave portion provided on the support base is desirably in the range of 0.05 mm to 0.3 mm. By setting the depth of the concave portion in this range, the depth is constant during light irradiation. When the pulse width and the irradiation energy are in the range, a special effect is produced that the semiconductor wafer does not jump or break from the support table.

  Next, FIG. 4 shows the result of the capture experiment for the comparative experiment. FIG. 4-1 is a result of the capture experiment performed for the case where the preheating temperature is changed. In the conventional shape, the semiconductor wafer W was cracked, and in the embodiment of the present invention, the heat treatment was performed by changing the preheating temperature under the condition that the crack did not occur. Specifically, a size of 3 inches was used as the semiconductor wafer W, and the light irradiation conditions were a pulse width of 5 ms, an irradiation energy of 60 J / cm ^ 2, and a depth of the recess 20 of 0 mm and 0.1 mm. As shown in FIG. 4A, when the preheating temperature is 150 ° C. to 550 ° C. and the depth of the recess 20 is 0 mm, cracking occurs at the preheating temperature of 350 ° C. On the other hand, when the depth of the recess 20 was 0.1 mm, no crack occurred at each preheating temperature. From this result, it is considered that there is no relationship between the occurrence of cracks and the preheating temperature.

  FIG. 4B shows experimental results when the ratio of the diameter of the recess 20 to the diameter of the semiconductor wafer W is changed. The size of the semiconductor wafer W is 3 inches, the light irradiation conditions are a pulse width of 5 ms, an irradiation energy of 60 J / cm ^ 2, a preheating temperature of 400 ° C., and the depth of the recess 20 is 0 mm, 0.05 mm, 0.1 mm. , 0.2 mm, 0.3 mm, and 0.4 mm, the ratio of the diameter of the concave portion 20 to the diameter of the semiconductor wafer W was changed for experiments. When the depth of the recess 20 was 0 mm and 0.4 mm, the semiconductor wafer W was cracked regardless of the diameter of the recess. On the other hand, when the depth of the recess 20 is between 0.05 mm and 0.3 mm, cracks occurred in all cases when the proportion of the diameter of the recess 20 was 30% or less, but cracks occurred at 40% or more. Did not occur. That is, if the diameter of the recess 20 is 40% or more with respect to the diameter of the semiconductor wafer W, cracks will not occur. When this ratio is 95% or more, there is a case where the heat treatment of the semiconductor wafer W cannot be uniformly performed. In practice, this ratio is desirably 90% or less. Further, a confirmation experiment was also conducted for the case where the size of the semiconductor wafer W was 12 inches. When the ratio of the diameter of the concave portion 20 to the diameter of the semiconductor wafer W was 40% or more, no crack was generated. The experimental conditions at 12 inches were such that the depth of the recess 20 was 0.2 mm, the preheating temperature was 400 ° C., the light irradiation condition was a pulse width of 5 ms, and the irradiation energy was 60 J / cm 2. As in the case of 3 inches, when the ratio of the diameter of the concave portion 20 to the diameter of the semiconductor wafer W is 95% or more, the semiconductor wafer W may not be uniformly heat-treated. Even in the case of inches, it is practically desirable that this ratio be 90% or less.

The schematic sectional drawing of the semiconductor wafer rapid heating apparatus in this invention. The figure which shows the trapezoid shape for support of the semiconductor wafer rapid heating apparatus in this invention. The figure which shows the experimental result in the structure of this invention The figure which shows the experimental result in the structure of this invention 1 is a schematic cross-sectional view of a conventional semiconductor wafer rapid heating apparatus.

DESCRIPTION OF SYMBOLS 1 Semiconductor wafer rapid heating apparatus 2 Light source part 3 Heat processing chamber part 4 Preheating mechanism part 5 Flash lamp 6 Reflection mirror 7 Light transmissive window part 8 Semiconductor wafer inlet / outlet 9 Atmospheric gas inlet 10 Support stand W Semiconductor wafer 11 Window part DESCRIPTION OF SYMBOLS 12 Heat transfer part 13 Halogen lamp 14 Reflector 20 Recessed part 41 Light heating apparatus 42A Atmospheric gas inlet 42B Outlet 44 Chamber 45 Supporting base 46 Flat plate 47 Translucent member 48 Flash lamp 49 Halogen heater lamp 50 Chamber control circuit 51 Reflector 52 Casing 53 Power feeding device

Claims (1)

A light source unit comprising a plurality of arranged flash lamps and a reflector that reflects the light emitted from the flash lamps to the object to be heated;
A heat treatment chamber in which a support table for supporting a semiconductor wafer is disposed;
Comprising
In a semiconductor wafer rapid heating apparatus for rapidly heating a semiconductor wafer by the light of the flash lamp,
The support table is provided with a recess on the support table, and the shape of the recess is a substantially circular shape slightly smaller than the diameter of the semiconductor wafer, and the ratio of the diameter of the recess to the diameter of the semiconductor wafer is When the semiconductor wafer is disposed so as to cover the recess, the space is formed between the support base and the semiconductor wafer. A semiconductor wafer rapid heating apparatus.

Images