JPH05226463A - Manufacture of joined dielectric isolation wafer - Google Patents

Abstract

PURPOSE:To eliminate level differences generated on the polished surface of a high temperature polysilicon film with a low temperature polysilicon film and to enhance a jointed surface in adhesive strength by a method wherein a polysilicon film is formed on a mirror-polished high temperature polysilicon layer through a low temperature CVD method. CONSTITUTION:An oxide film 12 is formed on the surface 11a of a silicon wafer 11 where a dielectric isolating groove has been formed, and a polysilicon layer 13 is successively provided thereon through a high temaperature CVD method and subjected to cutting work and mirror-polishing work. A polysilicon film 15 is formed on the high temperature polysilicon layer 14 through a low temperature CVD method and subjected to mirror-polishing work. The low temperature polysilicon film 16 is jointed on the surface 17a of a support silicon wafer 17 together. By this setup, level differences generated in a jointed surface between the silicon wafers 17 and 11 can be removed, and the wafers 11 and 17 can be enhanced in pasting strength. Therefore, air bubbles generated in a jointed surface can be lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bonded dielectric separated wafer which can reduce the step difference of the bonded surface and improve the bonding strength of the bonded surface.

[0002]

2. Description of the Related Art Conventionally, an oxide insulating film is formed after forming a dielectric isolation groove on a surface of a silicon wafer, and polysilicon is formed on this insulating film by high temperature CVD to a thickness corresponding to the thickness of the wafer. After depositing up to this point, an island-shaped silicon single crystal is made by grinding and polishing from the silicon wafer side.
So-called dielectric separated wafers are known.

This dielectric-divided wafer is usually manufactured by the method shown in FIG. First, FIG. 2 (a)
The surface 1a of the silicon wafer 1 shown in FIG. 2 is processed into a groove having a predetermined shape, and the thermal oxide film 3 is formed on the processed surface 2 (FIG. 2B). Next, high temperature CVD (Chemical Vapor)
Deposition: chemical vapor deposition), atmospheric pressure, 120
After thickly depositing the polysilicon layer 4 on the oxide film 3 under the condition of 0 ° C. ((c) in the same figure), the silicon wafer 1 was subjected to grinding processing and mirror polishing processing and embedded in the polysilicon 4. The island-shaped single crystal 7 is used (FIG. 7 (d)). The wafer having the island-shaped single crystal 7 obtained here is referred to as a dielectric isolation wafer 7.

[0004]

However, in the above-described dielectric-isolated wafer, high temperature CVD is performed for a long time, which further deteriorates the quality of the single crystal. A method of matching is proposed. However, also in this method, the thickness of the polysilicon layer 4 is set to be three times the groove depth, the irregularities of the polysilicon film are removed by grinding, and the polishing surface is used when mirror polishing is performed for bonding. In addition, there is a drawback that the surface is not smooth because the difference between the crystal grain size and the orientation is different in the CVD growth mode between the upper part of the groove and the silicon surface and the difference in polishing rate causes a step difference of about 20 to 100 nm. Therefore, when the polysilicon surface and the supporting wafer are bonded to each other, bubbles are likely to enter the bonding surface, the bonding strength of this bonding surface is weak, and the reliability of the bonded dielectric isolation wafer 7 is reduced. It was.

The present invention has been made in view of the above circumstances, and provides a method for manufacturing a dielectric-divided wafer, which can reduce the step of the bonding surface and improve the bonding strength of the bonding surface. To do.

[0006]

In order to solve the above problems, the present invention adopts the following method for manufacturing a bonded dielectric separated wafer. That is, a method for manufacturing a dielectric isolation wafer in which a silicon wafer having a dielectric isolation island is attached to a support wafer, the surface of the silicon wafer having a dielectric isolation groove of a predetermined shape, an oxide film,
A polysilicon layer is sequentially formed by the high temperature CVD method, and then the high temperature polysilicon layer is sequentially subjected to grinding processing and mirror polishing processing, and a polysilicon film is formed on the high temperature polysilicon layer by the low temperature CVD method. The low-temperature polysilicon film is mirror-polished, and then the low-temperature polysilicon film and the surface of the support silicon wafer are bonded to each other.

[0007]

In the method for manufacturing a bonded dielectric separated wafer according to the present invention, a low temperature polysilicon film is formed by forming a polysilicon film by a low temperature CVD method on a high temperature polysilicon layer that has been mirror-polished. The step generated on the polished surface of the high temperature polysilicon layer is eliminated, and the bonding strength of the bonding surface is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing a bonded dielectric separated wafer of the present invention will be described below with reference to FIG. First, the surface 1 of the silicon wafer 11 shown in FIG.
After performing a predetermined groove processing on 1a, a thermal oxide film 12 is formed on the processed surface (FIG. 2B). Next, high temperature CV
By the method D, a high temperature polysilicon layer 13 was deposited on the oxide film 12 at a depth of 3 times the groove depth under the conditions of trichlorosilane, atmospheric pressure and 1200 ° C. (FIG. 3C), and then this high temperature polysilicon layer was formed. Grinding and mirror polishing are sequentially performed on 13 to form a high temperature polysilicon film 14 having a thickness of 3 μm from a silicon single crystal (FIG. 3D).

Next, by a low temperature CVD method, 1 Torr, 6
Under the condition of 00 ° C., a low-temperature polysilicon film 15 having a thickness of 2 μm is formed on the high-temperature polysilicon film 14 (FIG. 8E).
Then, the low temperature polysilicon film 15 is subjected to mirror polishing to form a low temperature polysilicon film 16 having a thickness of 1 micron (FIG. 6 (f)).

Next, the surface 17a of the silicon wafer 17 shown in FIG. 1 (g) is washed with an alkali on the low-temperature polysilicon film 16 to make the surface hydrophilic, and then adhered thereto. For example, heat treatment at 1000 ° C. for 2 hours allows these silicon wafers 1
1, 17 are attached to each other ((h) in the figure). Thereafter, the silicon wafer 11 is sequentially subjected to grinding processing and mirror polishing processing to obtain a dielectric isolation wafer 18 having dielectric isolation islands of a predetermined shape ((i) in the figure).

In the method of manufacturing the dielectric-isolated wafer 18, the low-temperature polysilicon film 15 is formed on the high-temperature polysilicon layer 14 that has been mirror-polished, so that the low-temperature polysilicon film 15 becomes high-temperature polysilicon. The step generated on the surface of the film 14 is eliminated, and the bonding strength of the bonding surface is improved.

As described above, according to the method for manufacturing the dielectric separated wafer 18 of the above-described embodiment, the low temperature polysilicon film 15 is formed on the high temperature polysilicon layer 14 having a predetermined thickness which has been mirror-polished. Since the film is formed, the step on the bonding surface between the silicon wafer 17 and the silicon wafer 11 can be eliminated, and the bonding strength of this bonding surface can be improved. Therefore, it is possible to greatly reduce the bubbles on the bonding surface, which has been a problem in the past.

[0013]

As described above, the method for manufacturing a bonded dielectric separated wafer according to the present invention is a method for manufacturing a dielectric separated wafer in which a silicon wafer having dielectric separated islands is bonded to a supporting wafer. Then, an oxide film and a polysilicon layer by a high temperature CVD method are sequentially formed on the surface of the silicon wafer on which the dielectric isolation groove is formed, and then the high temperature polysilicon layer is sequentially subjected to grinding processing and mirror polishing processing. Forming a polysilicon film by the low temperature CVD method on the high temperature polysilicon layer, subjecting the low temperature polysilicon film to mirror polishing, and then bonding the low temperature polysilicon film and the surface of the support silicon wafer to each other. Therefore, it is possible to eliminate the step on the bonding surface of the silicon wafer with the low-temperature polysilicon film. It is possible to improve the strength. Therefore, it is possible to greatly reduce the air bubbles on the bonding surface, which has hitherto been a practical obstacle.

As described above, it is possible to provide a method for manufacturing a bonded dielectric separated wafer which can eliminate the step on the bonded surface and improve the bonding strength of the bonded surface.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a method for manufacturing a bonded dielectric separated wafer of the present invention.

FIG. 2 is a process diagram showing a conventional method for manufacturing a dielectric isolation wafer.

[Explanation of symbols]

 11 Silicon Wafer 11a Surface 12 Oxide Film 13 High Temperature Polysilicon Layer 14 High Temperature Polysilicon Layer 15 Low Temperature Polysilicon Film 16 Low Temperature Polysilicon Film 17 Silicon Wafer 18 Dielectric Separation Wafer

Claims (1)

[Claims] 1. A method for manufacturing a dielectric isolation wafer, which comprises bonding a silicon wafer having dielectric isolation islands to a support wafer, the method comprising: forming a dielectric isolation groove on a surface of the silicon wafer;
An oxide film and a polysilicon layer by a high temperature CVD method are sequentially formed, and then the high temperature polysilicon layer is sequentially subjected to grinding and mirror polishing, and a low temperature C is formed on the high temperature polysilicon layer.
A laminated dielectric characterized in that a polysilicon film is formed by the VD method, the low-temperature polysilicon film is mirror-polished, and then the low-temperature polysilicon film and the surface of a support silicon wafer are bonded to each other. Method for manufacturing separated wafer.