JP3603216B2 - Thin film growth equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thin film growth apparatus and a vapor phase growth apparatus provided with a wafer holder for equalizing the temperature within a wafer surface. For example, a MOCVD (organic metal vapor phase) for growing a compound semiconductor crystal having a mechanism in which a wafer rotates or revolves. The present invention relates to a technique that is useful when applied to an apparatus used for the (growth) method.
[0002]
[Prior art]
FIG. 5 shows a conventional MOCVD apparatus for growing a compound semiconductor crystal of the thermal radiation type substrate heating method. The MOCVD apparatus includes a wafer tray 1 made of graphite or the like on which a wafer is placed, a susceptor 2 made of graphite or the like supporting the plurality of wafer trays 1, a plurality of concentric heaters 3 for heating the susceptor 2 from the back side, and a susceptor 2. Is supported rotatably. The wafer tray 1, the susceptor 2, and the heater 3 are housed in a reactor 6, and the periphery of the reactor 6 is water-cooled. In this apparatus, the wafer is heated by the radiant heat from the heater 3 while revolving around the support shaft 4 or rotating together with the revolution.
[0003]
As shown in FIG. 6, the wafer tray 1 has a circular and concave wafer mounting portion 5 on which a wafer is mounted, and has a projection 7 on the back side for fitting with the susceptor 2. ing. On the other hand, the susceptor 2 has a recess into which the projection 7 of the tray 1 is fitted.
[0004]
The source gas is introduced from a gas inlet above the center of the reactor 6 and undergoes a chemical reaction on the wafer to precipitate crystals. The gas generated by the reaction and the unreacted gas are discharged outside through a gas discharge port provided on the side of the reactor 6.
[0005]
In the MOCVD method, the composition and characteristics of the formed film are sensitive to the temperature of the wafer, so that in order to grow a uniform film over the entire surface of the wafer, it is necessary to maintain a uniform temperature distribution on the wafer surface during the film formation. There is.
[0006]
However, in the case of the apparatus having the above-described configuration, even if the output ratio of the concentric heater 3 is adjusted, the temperature distribution is such that the temperature in the central portion of the wafer is the highest and the temperature in the peripheral portion is the lowest. The composition and characteristics of the grown film become non-uniform.
[0007]
Therefore, various proposals have been made in the vapor phase growth method to keep the temperature distribution on the wafer surface uniform during film formation. In Japanese Patent Publication No. 55-28546, heat conduction from the susceptor to the support plate is suppressed by reducing the thickness of the susceptor near the support plate supporting the susceptor or by providing a groove in the susceptor. A CVD apparatus is disclosed. Japanese Unexamined Patent Publication (Kokai) No. 1-203291 discloses that a concave and convex groove for receiving a flow gas is formed on a surface of a substrate holder around a substrate receiving portion so that a temperature distribution of a semiconductor substrate is made uniform by the gas flow. The disclosed substrate holder is disclosed. Japanese Patent Application Laid-Open No. 1-291421 discloses a susceptor in which a groove is formed around a counterbore for holding a substrate, and a reaction product is dropped and collected in the groove so that the substrate and the susceptor are brought into close contact with each other. There is disclosed a vapor phase growth apparatus in which the temperature distribution of a substrate is made uniform. In Japanese Patent Publication No. 4-5000, a recess is formed in the substrate mounting portion of the susceptor so that the distance from the substrate center is larger than the distance from the substrate outer periphery. Discloses a vapor phase growth apparatus configured to prevent the temperature from becoming lower than the temperature. Japanese Patent Application Laid-Open No. 9-36049 discloses that a wafer holder corresponding to a susceptor has a convex portion formed on the entire back surface of a wafer pocket for receiving a wafer, and the thickness of the wafer pocket is increased to increase the temperature in the peripheral portion of the wafer. A vapor phase growth apparatus designed to prevent the above is disclosed. Japanese Patent Application Laid-Open No. Hei 7-277885 discloses that a cavity is formed inside a susceptor that expands in a tapered shape from the center of the substrate toward the outer periphery, thereby compensating for a temperature difference occurring in the radial direction of the susceptor, thereby reducing the temperature of the substrate surface. A vapor phase epitaxy apparatus designed to be uniform is disclosed.
[0008]
[Problems to be solved by the invention]
However, any of the techniques described in the above publications has a disadvantage that the susceptor must be processed or the susceptor must be designed and manufactured exclusively. Further, the effect of making the temperature distribution on the wafer surface uniform cannot be sufficiently obtained.
[0009]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a thin film growth apparatus capable of equalizing the temperature in a wafer surface by simple means.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have found that the reason why the temperature distribution on the wafer surface on the susceptor becomes non-uniform is that a large amount of heat is radiated radially outward from the center of the reactor. , Thought. Therefore, we thought that it was only necessary to limit the escape of heat to the susceptor, which is a good conductor of heat, from the periphery of the wafer mounting part of the wafer tray located outside the center of the reactor. Invented the invention.
[0011]
That is, the present invention provides a thin film growth apparatus including a wafer tray on which a thin wafer is placed, and a susceptor for holding the wafer tray at a predetermined position, wherein a wafer placement portion is provided on the front side of the wafer tray, and On the back side of the wafer tray, there is provided a heat insulating portion for blocking heat dissipation from the wafer tray, and the heat insulating portion is located inside a peripheral portion in contact with the susceptor and below a peripheral edge of the wafer mounting portion. It is provided so as to surround the vicinity .
[0012]
According to the present invention, since most of the heat from the wafer tray is considered to be radiated to the susceptor through the peripheral portion that comes into contact with the susceptor, the heat insulating portion is provided inside the susceptor. Since the amount of heat escaping from the portion to the susceptor decreases, the temperature at the peripheral portion of the wafer increases, and the temperature on the wafer surface can be made uniform.
[0013]
Further, according to the present invention, there is no need to modify the susceptor, so that an existing thin film growth apparatus can be used as it is. Since the temperature of the wafer can be made uniform by preparing a wafer tray appropriately designed in accordance with the type of the wafer, film forming conditions, and the like, the usefulness thereof is extremely high.
[0014]
When a heat insulating portion is provided inside the wafer mounting portion of the wafer tray, the temperature of the wafer periphery outside the heat insulating portion decreases, and the temperature profile on the wafer surface becomes M-shaped. It is not preferable. In addition, when the heat insulating portion is provided outside the protrusion of the wafer tray, the amount of heat escaping from the peripheral portion of the wafer mounting portion of the wafer tray to the susceptor cannot be reduced. The effect of uniformity cannot be obtained.
[0015]
In the above invention, the heat insulating portion may be formed by a groove. In this case, the effect of uniformizing the temperature on the wafer surface can be obtained most simply. Here, the depth, position, and the like of the groove are determined by preliminary experiments and the like according to the structure of each thin film growth apparatus.
[0016]
In addition, other than forming the groove, the heat insulating portion may be formed by forming a part of the wafer tray with a heat non-conductor.
[0017]
Also, providing a groove on the surface of the wafer tray is not preferable because it disturbs the flow of the source gas.
[0018]
Further, the present invention may be applied to an apparatus used in metal organic chemical vapor deposition. Then, an MOCVD apparatus capable of growing a thin film while keeping the temperature on the wafer surface uniform can be obtained.
[0019]
Japanese Patent Application Laid-Open No. 4-182386 discloses a susceptor in which a groove is formed at a position corresponding to the peripheral portion of a substrate so that the peripheral portion of the substrate does not contact the susceptor so as to prevent the occurrence of cracks. The disclosed invention is disclosed. However, in the present invention, the crystallinity of the peripheral portion of the substrate is deteriorated by making the temperature of the peripheral portion of the substrate more unstable than that of the central portion, and the technical idea is completely different from that of the present invention.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
An example of an embodiment of the present invention will be described.
[0021]
FIG. 1 shows an example of a MOCVD apparatus for growing a compound semiconductor crystal of the thermal radiation type substrate heating system to which the present invention is applied. The MOCVD apparatus includes a wafer tray 10 made of graphite or the like on which a wafer is placed, a susceptor 2 made of graphite or the like supporting the plurality of wafer trays 10, a plurality of concentric heaters 3 for heating the susceptor 2 from the back side, as in the prior art. And a support shaft 4 that rotatably supports the susceptor 2. The wafer tray 10, the susceptor 2, and the heater 3 are housed in a reactor 6 as in the related art, and the periphery of the reactor 6 is water-cooled. In this apparatus, the wafer is heated by the radiant heat from the heater 3 while revolving around the support shaft 4 or rotating together with the revolution.
[0022]
As shown in FIG. 2, the wafer tray 10 has a circular and concave wafer mounting portion 5 on which a wafer is mounted, and a projection portion 7 fitted to the susceptor 2 on the back side thereof. The heat insulating portion 8 is provided inside the projection 7, that is, inside the peripheral portion in contact with the susceptor and outside the periphery of the wafer mounting portion 5.
[0023]
The heat insulating part 8 is formed of, for example, a groove. This groove is formed, for example, so as to form a concentric circle with the periphery of the wafer mounting portion 5.
[0024]
The susceptor 2 is formed with a plurality of tray receiving portions 9 having a circular shape and a concave shape for accommodating the wafer tray 10 at a plurality of locations, for example, three locations so as to accommodate three wafer trays as shown in FIG. The susceptor 2 may have two tray receiving portions, or may have four or more tray receiving portions.
[0025]
As in the related art, the tray receiving portion 9 of the susceptor 2 has a recess into which the protrusion 7 of the tray 10 is fitted. The wafer tray 10 is positioned at a predetermined position on the susceptor by fitting the projection 7 of the wafer tray 10 into the recess. Then, a gap created by the heat insulating portion 8 of the wafer tray 10 exists between the susceptor 2 and the wafer tray 10. With this gap, heat is prevented from escaping from the peripheral portion of the wafer mounting portion 5 of the wafer tray 10 to the susceptor 2.
[0026]
The introduction and discharge of gas into and from the reactor 6 are the same as in the prior art. That is, the source gas is introduced from the gas inlet above the center of the reactor 6 and undergoes a chemical reaction on the wafer to precipitate crystals. The gas generated by the reaction and the unreacted gas are discharged outside through a gas discharge port provided on the side of the reactor 6.
[0027]
According to the above embodiment, since the groove-shaped heat insulating portion 8 is provided on the back side of the wafer tray 10 and between the peripheral portion in contact with the susceptor 2 and the periphery of the wafer mounting portion 5, the wafer tray 10 In the state of being accommodated in the susceptor 2, a gap created by the heat insulating portion 8 exists between the susceptor 2 and the wafer tray 10, and the amount of heat escaping from the peripheral portion of the wafer mounting portion 5 to the susceptor 2 decreases. Since the temperature around the wafer rises, the temperature on the wafer surface can be made uniform. Therefore, the uniformity of the composition and characteristics of the crystal such as the compound semiconductor in the wafer plane can be improved.
[0028]
The heat insulating portion 8 is not limited to the groove as described above, and if heat can be prevented from escaping from the peripheral portion of the wafer mounting portion 5 to the susceptor 2, a part of the wafer tray 10 may be made of non-conductive material. It may be constituted by forming.
[0029]
【Example】
Hereinafter, the results of measurement of the temperature profile on the wafer surface performed by the present inventors using an MOCVD apparatus will be described. As the MOCVD apparatus, a vertical MOCVD apparatus having the configuration shown in FIG. 1 was used. The susceptor 2 was made of graphite, and the wafer tray 10 was made of carbon having the configuration shown in FIG. The wafer mounting part 5 of the wafer tray 10 was formed so as to form a circular concave part having a diameter of 101 mm. The heat insulating portion 8 of the wafer tray 10 was formed of concentric grooves formed near the inside of the protrusions 7 of the wafer tray 10, the width of the grooves was 2 mm, and the depth was 4 mm. As the wafer, a silicon wafer in which a thermocouple was embedded was used, and was mounted on the wafer mounting portion 5 of the wafer tray 10.
[0030]
The measurement of the temperature profile was performed under a reduced pressure atmosphere of H _{2 at} 30 Torr while setting the temperature of the central portion of the wafer tray in two ways, about 700 ° C. and about 650 ° C. For comparison, a temperature profile was measured using the same apparatus and under the same conditions using a wafer tray having no groove in the heat insulating portion 8 (see FIG. 6).
[0031]
FIG. 4 shows the measurement results of the profile. In FIG. 4, the point at which the position of the horizontal axis is 0 (zero) corresponds to the center point of the wafer, and the points of −40 mm and +40 mm correspond to the wafer peripheral portions opposed to each other across the center point of the wafer. I have. In FIG. 4, the upper plot shows the set temperature of about 700 ° C., and the lower plot shows the set temperature of about 650 ° C. Further, in FIG. 4, the plot of black circles (●) is obtained by using the wafer tray 10 according to the present invention having the grooves of the heat insulating unit 8, and the plot of white circles (○) is the wafer tray without the heat insulating unit (FIG. 6) (Comparative Example).
[0032]
As is clear from FIG. 4, the temperature difference between the central portion (point 0) and the peripheral portion (points −40 mm and +40 mm) of the wafer tray 10 is 20 when the set temperature of the tray central portion is 700 ° C. When the set temperature at the center of the tray is 650 ° C, the temperature is between 14 ° C and 3 ° C. In each case, it is significantly improved as compared with the comparative example having no heat insulating part. It turned out that it was.
[0033]
【The invention's effect】
According to the present invention, in a thin film growth apparatus including a wafer tray on which a thin wafer is placed, and a susceptor for holding the wafer tray at a predetermined position, a wafer placement section is provided on a front side of the wafer tray, and On the back side of the wafer tray, there is provided a heat insulating portion for blocking heat dissipation from the wafer tray, and the heat insulating portion is located inside a peripheral portion in contact with the susceptor and below a peripheral edge of the wafer mounting portion. Since it is provided so as to surround the vicinity, the amount of heat escaping from the peripheral portion of the wafer mounting portion of the wafer tray to the susceptor decreases, and the temperature of the peripheral portion of the wafer rises, so that the temperature of the wafer surface can be made uniform. Therefore, the uniformity of the composition and characteristics of the crystal such as the compound semiconductor in the wafer surface can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view schematically showing an example of a thin film growth apparatus according to the present invention.
FIG. 2 is a sectional view showing an example of a wafer tray used in the thin film growth apparatus according to the present invention.
FIG. 3 is a schematic diagram illustrating a positional relationship among a susceptor, a wafer tray, and a heater.
FIG. 4 is a characteristic diagram showing temperature profiles of a thin film growth apparatus according to the present invention and a conventional thin film growth apparatus.
FIG. 5 is a sectional view schematically showing a conventional thin film growth apparatus.
FIG. 6 is a sectional view showing a conventional wafer tray.
[Explanation of symbols]
2 Susceptor 3 Heater 4 Support shaft 5 Wafer placing part 6 Reactor 7 Projecting part 8 Heat insulating part 9 Tray receiving part 10 Wafer tray

Claims (3)

In a thin film growth apparatus provided with a wafer tray on which a thin wafer is placed and a susceptor for holding the wafer tray at a predetermined position, a wafer placement portion is provided on the front side of the wafer tray, and on the back side of the wafer tray, A heat insulating portion for blocking heat dissipation from the wafer tray is provided, and the heat insulating portion is provided so as to surround the lower part of the peripheral edge of the wafer mounting portion inside the peripheral portion in contact with the susceptor. An apparatus for growing a thin film, comprising: 2. The thin film growth apparatus according to claim 1, wherein said heat insulating portion is formed by a groove. 3. The thin film growth apparatus according to claim 1, wherein the apparatus is used in a metal organic chemical vapor deposition method.

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