JP2007242972A - Manufacturing method for soi wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of obtaining an SOI wafer with an SOI layer having a uniform film thickness. <P>SOLUTION: The manufacturing method for the SOI wafer has a process in which at least the SOI wafer having the SOI layer on an insulator is oxidized and treated thermally, an oxide film is formed on the surface of the SOI layer and the film thickness of the SOI layer is reduced by removing the oxide film. In the manufacturing method for the SOI wafer, the in-plane film-thickness distribution of the SOI layer is measured before the SOI layer 2 is oxidized and treated thermally, and a thermal oxidation treatment is conducted so that the in-plane temperature of the SOI layer in a region having the thick film thickness of the SOI layer is made higher than that in the region having the thin film thickness of the SOI layer on the basis of a measured value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an SOI wafer, and more particularly to a method for thinning an SOI layer to improve the film thickness uniformity of the SOI layer.

  In recent years, SOI wafers having an SOI structure in which a silicon layer (SOI layer) is formed on an insulator are superior in device high speed, low power consumption, high pressure resistance, environmental resistance, etc. It is particularly attracting attention as a high-performance LSI wafer for devices.

  When a semiconductor device is manufactured using an SOI layer of an SOI wafer, a device with uniform characteristics can be manufactured when the variation in the thickness of the SOI layer is smaller. For this reason, it is necessary to improve the uniformity of the thickness of the SOI layer. However, the in-plane uniformity of the thickness of the SOI layer of an SOI wafer manufactured through many processes reflects the characteristics of each process. As a result, a locally thinned region or a locally thick region is formed.

  As a typical method for manufacturing SOI wafers, silicon wafers are bonded together via an insulating film, and one silicon wafer is thinned by mechanical processing such as grinding, or a high concentration inside the silicon wafer. An oxygen ion implantation layer is formed by implanting oxygen ions, and then an annealing process is performed at a high temperature of about 1300 ° C. to form a buried silicon oxide layer in the silicon wafer, and the surface side layer is used as an SOI layer. This is one of the SIMOX method and the bonding method used. After an ion implantation layer is formed by implanting hydrogen or rare gas ions into a silicon wafer, the ion implantation surface of this silicon wafer is used as a bonding surface through an oxide film. Pasted to a single crystal wafer or directly to an insulating wafer, and then heated to a temperature of about 500 ° C. By peeling at the ion implanted layer, the ion implantation separation method or the like to form an SOI layer on the surface of the wafer it has been proposed.

  Regardless of which method is used to fabricate the SOI wafer, the SOI layer is oxidized at the final stage by adjusting the SOI film thickness or performing heat treatment in an oxidizing atmosphere for the purpose of removing surface roughness and damage. After the film is formed, a step of performing so-called sacrificial oxidation in which the oxide film is removed is often performed (for example, refer to Patent Document 1 and Patent Document 2).

  Such sacrificial oxidation is basically performed in a batch-type heat treatment furnace that heat-treats a large number of wafers at once. However, sacrificial oxidation using an existing batch-type heat treatment furnace cannot improve the film thickness uniformity of the SOI layer, and an SOI wafer with little variation in the in-plane film thickness of the SOI layer cannot be obtained. It was.

Japanese Patent Application Laid-Open No. 2000-124092 JP 2004-55750 A

  The present invention has been made in view of such problems, and an object of the present invention is to provide an SOI wafer manufacturing method capable of obtaining an SOI wafer having an SOI layer with a uniform in-plane film thickness. .

  The present invention has been made to solve the above problems, and at least an SOI wafer having an SOI layer on an insulator is thermally oxidized to form an oxide film on the surface of the SOI layer. A method of manufacturing an SOI wafer having a step of reducing the film thickness of the SOI layer by removing the SOI layer, measuring an in-plane film thickness distribution of the SOI layer before thermally oxidizing the SOI layer, Provided is a method for manufacturing an SOI wafer characterized in that the thermal oxidation treatment is performed so that the in-plane temperature of the SOI layer is higher in a region where the SOI layer film thickness is thicker than in a thin region based on the measured value ( Claim 1).

  As described above, in the sacrificial oxidation process of the SOI wafer, before the SOI layer is thermally oxidized, the in-plane film thickness distribution of the SOI layer is measured, and an area where the SOI layer film thickness is thick is determined based on the measured value. When the thermal oxidation treatment is performed so that the in-plane temperature of the SOI layer is higher than that of the thin region, a thick oxide film is formed in the region where the SOI layer is thick. If the oxide film is removed thereafter, the allowance increases only in the region where the SOI layer is thick, and an SOI wafer having an SOI layer with a uniform thickness can be obtained.

  Also, a process of thermally oxidizing at least an SOI wafer having an SOI layer on an insulator, forming an oxide film on the surface of the SOI layer, and reducing the film thickness of the SOI layer by removing the oxide film An in-plane film thickness distribution of the SOI layer is measured before the SOI layer is thermally oxidized, and the in-plane temperature distribution of the SOI layer is changed based on the measured value. Then, the thermal oxidation treatment is performed, and an SOI wafer manufacturing method is provided (claim 2).

  As described above, in the sacrificial oxidation treatment of the SOI wafer, before the thermal oxidation treatment of the SOI layer, the in-plane film thickness distribution of the SOI layer is measured, and the in-plane temperature distribution of the SOI layer is calculated based on the measured value. If the thermal oxidation process is performed while changing the thickness, the thickness of the oxide film can be locally changed in the plane of the SOI layer. That is, a thick oxide film can be formed where the SOI layer is thick, and a thin oxide film can be formed where the SOI layer is thin. In this way, if oxide films having different thicknesses are locally formed in the plane of the SOI layer and then removed, only the allowance for the thick portion of the oxide film can be increased. Thus, by locally changing the removal allowance of the SOI layer, an SOI wafer having an SOI layer with a uniform film thickness can be obtained as a result.

  Further, the thermal oxidation treatment is performed using a lamp heating device, and the distribution of the in-plane temperature of the SOI layer during the thermal oxidation treatment is adjusted, and the output distribution of the lamps arranged in the plane of the lamp heating device is adjusted. It is preferable to carry out by adjusting (Claim 3).

  Thus, the thermal oxidation treatment is performed using a lamp heating device, and the distribution of the in-plane temperature distribution of the SOI layer during the thermal oxidation treatment is adjusted to output distribution of lamps arranged in the plane of the lamp heating device. Can be performed by finely changing the in-plane temperature distribution of the SOI layer in accordance with the in-plane film thickness distribution of the SOI layer, so that the SOI with a more uniform film thickness can be performed. An SOI wafer having a layer can be obtained.

  Further, the output distribution of the lamp heating device can be adjusted concentrically with respect to the SOI wafer.

  When an SOI wafer is manufactured by the bonding method, the in-plane film thickness distribution of the SOI layer is often concentric, such that the wafer peripheral part or the wafer central part becomes thick. Therefore, the in-plane temperature distribution of the SOI layer can be easily controlled by making the output distribution of the lamp heating device concentric so as to match the film thickness distribution shape.

  Moreover, it is preferable that the temperature of the thermal oxidation treatment is 1000 ° C. or less.

  As described above, when the temperature of the thermal oxidation treatment is set to 1000 ° C. or lower, the occurrence of slip dislocation due to the heat treatment can be reliably suppressed, and a higher quality SOI wafer can be manufactured.

  As described above, according to the present invention, the thickness of the oxide film can be locally changed according to the in-plane film thickness distribution of the SOI layer. In this way, if oxide films having different thicknesses are locally formed within the surface of the SOI layer and then removed, only the allowance for the thick portion of the oxide film can be increased. Thus, by locally changing the removal allowance of the SOI layer, an SOI wafer having an SOI layer with a uniform film thickness can be obtained.

  Hereinafter, although this invention is demonstrated in detail, this invention is not limited to these.

  As a result of intensive studies on the problem of variations in the thickness of the SOI layer, the present inventors have found that a region where the SOI layer thickness of the SOI wafer is relatively thick compared to other regions using a lamp heating device. The thickness of the SOI layer can be increased by thickening the oxide film by oxidizing with HF, and then performing HF cleaning to remove the oxide film. The inventors have conceived that the uniformity can be improved and completed the present invention.

  That is, according to the present invention, at least an SOI wafer having an SOI layer on an insulator is thermally oxidized to form an oxide film on the surface of the SOI layer, and the oxide film is removed to remove the film of the SOI layer. A method for manufacturing an SOI wafer including a step of reducing a thickness, wherein an in-plane film thickness distribution of the SOI layer is measured before the SOI layer is thermally oxidized, and the SOI layer film thickness is determined based on the measured value. A method for manufacturing an SOI wafer is provided in which the thermal oxidation treatment is performed such that the in-plane temperature of the SOI layer is higher in a thick region than in a thin region.

  The present invention also provides a film of the SOI layer by thermally oxidizing at least an SOI wafer having an SOI layer on an insulator, forming an oxide film on the surface of the SOI layer, and removing the oxide film. A method for manufacturing an SOI wafer having a step of reducing a thickness, wherein an in-plane film thickness distribution of the SOI layer is measured before the SOI layer is thermally oxidized, and an in-plane of the SOI layer is measured based on the measured value. There is provided a method for manufacturing an SOI wafer, wherein the thermal oxidation process is performed while changing a temperature distribution.

  As described above, in the sacrificial oxidation treatment of the SOI wafer, before the thermal oxidation treatment of the SOI layer, the in-plane film thickness distribution of the SOI layer is measured, and the in-plane temperature distribution of the SOI layer is calculated based on the measured value. If the thermal oxidation process is performed while changing the thickness, the thickness of the oxide film can be locally changed in the plane of the SOI layer. Specifically, a thick oxide film is formed at a thicker SOI layer so that the temperature is higher, and a thin oxide film is formed at a thinner SOI layer so that the temperature is lower than the thicker part. Like that. In this way, if oxide films having different thicknesses are locally formed in the plane of the SOI layer and then the oxide films are removed, only the allowance for the thick portions of the oxide films can be increased. Thus, by locally changing the removal allowance of the SOI layer, an SOI wafer having an SOI layer with a uniform film thickness after the oxide film is removed can be manufactured.

  An example of a method for manufacturing an SOI wafer according to the present invention will be described with reference to FIG. 1, but the present invention is not limited to this.

First, an SOI wafer 1 having an SOI layer 2 on an insulator 3 is prepared (FIG. 1A).
As shown in FIG. 1A, the SOI layer 2 has a locally thinned region or a locally thick region in the plane (however, the drawing is exaggerated for easy understanding). Is described).
In addition, the manufacturing method of SOI wafer 1 is not specifically limited, For example, it can manufacture using the ion implantation peeling method etc. which are a bonding method, a SIMOX method, and a kind of bonding method.

  Next, the in-plane film thickness distribution of the SOI layer 2 is measured (FIG. 1B). The method for measuring the in-plane film thickness distribution is not particularly limited, and any of the usual methods can be used. For example, it can be performed using an optical method such as reflection spectroscopy or polarization analysis.

  Next, the thermal oxidation process is performed by changing the in-plane temperature distribution of the SOI layer based on the measured value of the in-plane film thickness distribution of the SOI layer 2 thus obtained. For example, if the thermal oxidation treatment is performed so that the in-plane temperature of the SOI layer is higher in the region where the SOI layer thickness is thicker than that in the thin region, the oxide layer is thicker in the region where the SOI layer is thicker than the thin region. 4 is formed (FIG. 1C).

Although the method of this thermal oxidation treatment is not particularly limited, for example, it can be performed using a lamp heating device in an oxidizing atmosphere.
The lamp heating device can rapidly heat the substrate by light irradiation. A lamp heating apparatus generally uses a halogen lamp as a heating source, and irradiates light from the lamp in a predetermined oxidizing gas atmosphere such as oxygen gas, thereby bringing the substrate to a desired temperature (eg, 1,200 ° C. or lower) in a few seconds. It is an apparatus that can be rapidly cooled in a few seconds after being heated up to 1 second to several tens of minutes. Therefore, it is suitable for the present invention in which the film thickness is measured and processed one by one, and the productivity can be improved. The heat treatment time may be determined so that the desired SOI layer thickness is obtained after sacrificial oxidation.

The in-plane temperature distribution of the SOI layer during the thermal oxidation treatment can be adjusted by adjusting the output distribution of the lamps arranged in the plane of the lamp heating device.
For example, it is possible to adjust the in-plane temperature distribution of the SOI layer more finely by locally configuring each of the lamps arranged in the plane of the lamp heating device so that the output can be adjusted independently. The film thickness can be changed. The larger the number of array lamps, the more accurately the in-plane temperature distribution can be controlled. However, in consideration of cost, the number is set to several thousand or less, more preferably several hundred.

  Further, when an SOI wafer is manufactured by the bonding method, the in-plane film thickness distribution of the SOI layer is often concentric, such that the wafer peripheral part or the wafer central part becomes thick. Therefore, the in-plane temperature distribution of the SOI layer can be easily controlled by adjusting the arrangement and output distribution of the lamp heating device to be concentric with the SOI wafer so as to match the film thickness distribution shape.

  For example, as shown in FIG. 2, the lamps 12 arranged in the plane of the lamp heating apparatus are divided into four substantially concentric blocks a, b, c, and d so that the outputs in each block are the same. Can be set to For example, when an SOI wafer having an in-plane film thickness at the center and having a thick SOI layer is subjected to thermal oxidation, a, b, c, and d are set in descending order of output, toward the center of the wafer 11. The temperature can be adjusted to be high. When an SOI wafer having an in-plane film thickness at the center and a thin SOI layer is thermally oxidized, a, b, c, d are set in ascending order of output, and the temperature is increased toward the outer periphery of the wafer 11. Can be adjusted to be higher.

  In this case, if the temperature of the thermal oxidation treatment is set to 1000 ° C. or lower, the occurrence of slip dislocation due to the heat treatment can be surely suppressed, so that a higher quality SOI wafer can be manufactured.

Next, the thickness of the SOI layer is made uniform by removing the oxide film 4 formed by the thermal oxidation treatment (FIG. 1D).
The method for removing the oxide film 4 is not particularly limited. For example, the oxide film 4 can be removed by immersing the wafer in hydrofluoric acid having an HF concentration of 1 to 50%.

With the above manufacturing method, an SOI wafer having an improved SOI layer thickness distribution can be obtained.
The SOI wafer obtained by the above manufacturing method is a high-quality SOI wafer in which the locally thinned region and the locally thick region are corrected and the thickness uniformity of the SOI layer is very high. .

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
(Example)
As the SOI wafer 1, an SOI wafer X having a diameter of 300 mm and polished so that the central portion in the SOI layer surface is thicker than other regions, and a peripheral portion in the SOI layer surface having a diameter of 300 mm and thicker than other regions. Two kinds of SOI wafers Y polished were prepared (FIG. 1A).

Next, the in-plane film thickness distribution of the SOI layer 2 of the SOI wafer 1 was measured (FIG. 1B).
The in-plane film thickness range (the value obtained by subtracting the minimum film thickness from the in-plane maximum film thickness) for both SOI wafers X and Y was about 5 nm. Further, the SOI layer film thickness distributions of these two types of wafers were substantially concentric. FIG. 3A shows the cross-sectional thickness distribution of the SOI wafer X (perpendicular to the notch), and FIG. 3B shows the cross-sectional thickness distribution of the SOI wafer Y (perpendicular to the notch).

Next, based on the measured value of the in-plane film thickness distribution, thermal oxidation treatment was performed by changing the in-plane temperature distribution of the SOI layer as described below (FIG. 1C).
Oxygen gas was allowed to flow through the lamp heating apparatus for RTO treatment, and the thermal oxidation temperatures of SOI wafers X and Y were set to five conditions of 900 ° C., 950 ° C., 1000 ° C., 1050 ° C., and 1100 ° C., respectively. The thermal oxidation time was adjusted so that the maximum film thickness of the oxide film 4 formed by this thermal oxidation treatment was 10 nm under all conditions.

  At this time, the lamp arrangement of the lamp heating apparatus used as seen from above is as shown in FIG. 2, and the lamp 12 is divided into four substantially concentric blocks a, b, c and d in FIG. The output was set to be the same.

  When the SOI wafer X having a thick center portion in the SOI layer is thermally oxidized, a, b, c, and d in descending order of output, as shown in FIG. 3C, from the center portion of the SOI layer. The temperature was adjusted so as to decrease toward the outer periphery, and the temperature of the outer periphery of the SOI layer was set to the thermal oxidation temperature set above. Further, when the SOI wafer Y having a thin center portion in the SOI layer is thermally oxidized, the temperature decreases from the outer peripheral portion of the SOI layer toward the central portion as a, b, c, and d in the order of decreasing output. The temperature at the center of the SOI layer was adjusted to the thermal oxidation temperature set above. The difference between the highest temperature and the lowest temperature (the thermal oxidation temperature) in the SOI layer surface was about 10 ° C., respectively. The thermal oxidation treatment was performed in a state where the SOI wafer was rotated in the horizontal direction around the center of the SOI wafer.

Next, the SOI wafers X and Y are immersed in hydrofluoric acid having an HF concentration of 5%, and the oxide film 4 formed by the thermal oxidation treatment is removed to make the in-plane film thickness of the SOI layer uniform (FIG. 1). (D)).
Next, the in-plane film thickness distribution of the SOI layer was measured again, and compared with the film thickness range before thermal oxidation (a value obtained by subtracting the minimum film thickness from the maximum film thickness in the plane). The obtained results are shown in Table 1 below.

  As apparent from Table 1 above, the film thickness range in the SOI layer surface of both the SOI wafer X and the SOI wafer Y was reduced by about 2 nm by performing the thermal oxidation treatment of the present invention. Thus, it was confirmed that an SOI wafer having an SOI layer with a uniform film thickness can be manufactured by correcting the local unevenness of the SOI layer by the SOI wafer manufacturing method of the present invention.

  In addition, as a result of observing the occurrence of slip dislocations under these condensing lamps for these SOI wafers, slip dislocations were generated slightly on wafers having thermal oxidation temperatures of 1050 ° C. and 1100 ° C., although they were in an allowable range. However, no slip dislocation was observed on the wafer having a thermal oxidation temperature of 1000 ° C. or lower.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  That is, in the above example, the SOI layer film thickness distribution is substantially concentric, and thus the thermal oxidation process was performed while rotating the SOI wafer. However, when processing an SOI layer film thickness distribution that is not concentric, the lamp output distribution is adjusted to correspond to the SOI layer film thickness distribution, and thermal oxidation is performed without rotating the wafer. Good.

  In the above embodiment, the SOI layer thickness distribution measurement and the thermal oxidation treatment are performed by separate devices, but a multi-chamber device in which the film thickness distribution measurement device and the thermal oxidation treatment device are integrated is configured. By using a program that immediately feeds back the film thickness distribution measurement results to the lamp heating device and automatically adjusts the lamp output distribution, the SOI wafer can be continuously processed, which is suitable for mass production. .

It is explanatory drawing which shows an example of the manufacturing method of the SOI wafer which concerns on this invention. It is the schematic which shows an example of the lamp arrangement | sequence of the lamp heating apparatus used with the manufacturing method of the SOI wafer which concerns on this invention. In the embodiment of the present invention, (A) is the cross-sectional film thickness distribution of the SOI wafer X, (B) is the cross-sectional film thickness distribution of the SOI wafer Y, and (C) is the in-plane temperature distribution of the thermal oxidation treatment of the SOI wafer X. FIG. 4D is a schematic diagram illustrating an in-plane temperature distribution of the thermal oxidation process of the SOI wafer Y. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... SOI wafer, 2 ... SOI layer, 3 ... Insulator, 4 ... Oxide film,
11 ... wafer, 12 ... lamp.

Claims (5)

  At least a process of thermally oxidizing an SOI wafer having an SOI layer on an insulator to form an oxide film on the surface of the SOI layer and removing the oxide film to reduce the film thickness of the SOI layer. A method for manufacturing an SOI wafer, wherein an in-plane film thickness distribution of the SOI layer is measured before the SOI layer is thermally oxidized, and a region where the SOI layer is thick is changed to a thin region based on the measured value. A method for manufacturing an SOI wafer, wherein the thermal oxidation treatment is performed such that the in-plane temperature of the SOI layer is higher than that of the SOI layer.   At least a process of thermally oxidizing an SOI wafer having an SOI layer on an insulator to form an oxide film on the surface of the SOI layer and removing the oxide film to reduce the film thickness of the SOI layer. A method of manufacturing an SOI wafer, wherein an in-plane film thickness distribution of the SOI layer is measured before the SOI layer is thermally oxidized, and an in-plane temperature distribution of the SOI layer is changed based on the measured value. A method for manufacturing an SOI wafer, wherein the thermal oxidation treatment is performed.   The thermal oxidation treatment is performed using a lamp heating device, and the distribution of the in-plane temperature of the SOI layer during the thermal oxidation treatment is adjusted, and the output distribution of the lamps arranged in the plane of the lamp heating device is adjusted. The method for manufacturing an SOI wafer according to claim 1, wherein the method is performed.   4. The method for manufacturing an SOI wafer according to claim 3, wherein an output distribution of the lamp heating device is adjusted concentrically with respect to the SOI wafer.   5. The method for manufacturing an SOI wafer according to claim 1, wherein a temperature of the thermal oxidation treatment is set to 1000 ° C. or less.

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