JPH079909B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION [Outline] In a gettering technique using polysilicon, a polysilicon layer is formed between two single crystal silicon wafers in order to reduce warpage that occurs during an element formation process. A method of manufacturing a semiconductor device, comprising integrating two wafers and forming a semiconductor device on the wafer.

[Industrial application field]

The present invention relates to a gettering technique carried out for the purpose of removing defects and heavy metals mixed therein during a semiconductor element manufacturing process, and more particularly to a method for preventing deformation of a single crystal silicon wafer.

2. Description of the Related Art In recent years, semiconductor elements have been highly integrated and miniaturized, and accordingly, semiconductor substrates, which are used as materials, are required to have higher quality without defects.

However, a semiconductor substrate such as a silicon substrate manufactured by the CZ method contains oxygen and carbon at the ppm level or iron (Fe) and copper (Cu) which are heavy metals at the ppt level.

Of these, oxygen, which has the highest concentration, is solid-soluted in a supersaturated state and precipitates when subjected to heat treatment in the element manufacturing process, causing dislocations, stacking faults, and the like.

Further, although the element manufacturing process is carried out in a clean atmosphere, there are relatively many impurities mixed in from the equipment, gas, water and the like. And if these defects and impurities exist in the active region of the device,
It has been confirmed by experiments that the electrical characteristics of the device are deteriorated.

Therefore, in order to manufacture a high quality semiconductor device with a high yield, it is necessary to control or remove the above defects and impurities and clean the active region of the device.

Under the circumstances as described above, there is a demand for a method of manufacturing a semiconductor device that can be applied with a gettering technique without any side effects in implementation.

[Conventional technology]

Although there are various conventional gettering techniques, the gettering technique by forming a polysilicon layer, which is simple and highly effective for a single crystal silicon wafer, is generally widely used. Those having a polysilicon layer are already on the market.

The formation of the polysilicon layer in the conventional gettering technique will be described with reference to FIG.

In the figure, a polysilicon layer 3 is formed on the whole or a part of the back surface of the single crystal silicon wafer 1 by CVD. In this case, a polysilicon grain and an interface between the single crystal silicon wafer 1 and the polysilicon layer 3 are formed. It is considered that the strained layer 2 thus formed functions as a getter sink for capturing impurities.

[Problems to be solved by the invention]

The problem with the conventional gettering technology described above is that
Since the polysilicon layer is formed only on the back surface of the single crystal silicon wafer or on a part of the back surface and the front surface, the single crystal silicon wafer will be formed due to the difference in coefficient of thermal expansion between the single crystal silicon and the polysilicon after the element formation process. The problem of warping occurs.

The warp of the single crystal silicon wafer is desired to be further reduced with the miniaturization of the element and the increase in the diameter of the wafer.

The present invention has an object to provide a method for manufacturing a semiconductor device which can be easily and easily implemented from the above situation.

[Means for solving problems]

The above problem is that a polysilicon layer is formed between two single crystal silicon wafers to integrate the two wafers,
This is solved by the method for manufacturing a semiconductor device according to the present invention, in which a semiconductor device is formed on this single crystal silicon wafer.

[Action]

That is, in the present invention, since a polysilicon layer is formed between two single crystal silicon wafers to form a single wafer, since the polysilicon layer is formed in the central portion of the wafer, during the device formation process. The warp of the wafer is reduced because the stresses generated in the wafers work symmetrically and cancel each other out.

Further, when the polysilicon layer is formed on the back surface, the polysilicon layer is thinned in the element forming process. However, according to the present invention, the polysilicon layer remains as it is until the end of the process, so that there is an advantage that the getter ability is maintained.

〔Example〕

An embodiment of the present invention will be described in the order of steps with reference to FIG. 1 in the case where a polysilicon layer 3 is formed on each single crystal silicon wafer 1 and bonded.

As shown in FIG. 1 (a), two single crystal silicon wafers 1 whose both surfaces are mirror-polished with a polysilicon layer 3 formed on one surface are manufactured.

Next, in order to improve the adhesiveness of the polysilicon layers 3 formed on the two single crystal silicon wafers 1, a hydrophilic treatment is performed and then drying is performed to bring the polysilicon layers 3 into close contact with each other. ) As shown in FIG.

High temperature treatment in this state, for example, in a nitrogen atmosphere for 30 minutes,
When heat-treated at 1,000 ° C., the surfaces of the polysilicon layer 3 are bonded to each other, and the two single crystal silicon wafers 1 are integrated as shown in FIG. 1 (c).

A semiconductor element is formed on the single crystal silicon wafer 1 integrated in this way.

In this way, since the wafer having the polysilicon layer 3 inside is formed, the structure becomes symmetrical with the polysilicon layer 3 as the center, so that the stress generated during the element forming process acts symmetrically. Wafer warpage is reduced.

Although the polysilicon layer 3 is formed on both of the single crystal silicon wafers 1 in the above embodiment, a manufacturing method in which the polysilicon layer 3 is formed only on one of the single crystal silicon wafers 1 is also possible. . Also, the polysilicon layer 3
The number is not limited to one and may be two or more layers.

〔The invention's effect〕

As described above, according to the present invention, the two single crystal silicon wafers can be formed into symmetrical wafers by an extremely simple process, so that the warp of the wafer is reduced, and the polysilicon layer is formed in the center of the wafer. Since it is located, there is an advantage that the getter ability is not deteriorated, and it can be expected to have a remarkable economic and reliability improving effect, which is extremely useful industrially.

[Brief description of drawings]

1 is a side sectional view showing an embodiment of the present invention in the order of steps, and FIG. 2 is a side sectional view showing the formation of a conventional polysilicon layer. In the figure, 1 is a single crystal silicon wafer, 2 is a strained layer, and 3 is a polysilicon layer.

Claims (1)

[Claims] 1. In a gettering technique using polysilicon, a polysilicon layer (3) is formed between two single crystal silicon wafers (1) and the two wafers are integrated to form the single crystal silicon wafer. (1) A method of manufacturing a semiconductor device, which comprises forming a semiconductor device on the semiconductor device.