JP2627157B2 - Semiconductor substrate manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to an improvement in a method of manufacturing an SOI substrate, wherein at least one of two semiconductor wafers is oxidized,
A semiconductor oxide film having a thickness of 1 μm or less is formed on at least one surface thereof, and these two semiconductor wafers are heated in a state where the two semiconductor wafers are overlapped so that the semiconductor oxide film becomes an intermediate layer. In a method of manufacturing an SOI substrate by bonding two semiconductor wafers, even if the wafer has a large diameter, the entire surface thereof can be uniformly bonded, and a semiconductor substrate capable of manufacturing a large-diameter SOI substrate can be manufactured. In order to provide a method, an oxide semiconductor film is formed on at least one surface of at least one of two semiconductor substrates, and the two semiconductor substrates are heated while being in contact with each other via the oxide semiconductor film. A method of manufacturing a semiconductor substrate having an SOI structure using the two integrated semiconductor substrates by using the two integrated semiconductor substrates, wherein the two semiconductor substrates have a radius of curvature of 10 to 30 m. A press having a curved surface is used, or one of the two semiconductor substrates is placed on a flat heater such as a carbon heater heated to 50 to 500 ° C. On the other side, the other of the two semiconductor substrates is placed on a flat heating body such as the carbon heater.
A temperature difference of 500 ° C. and a temperature difference of at least 50 ° C. or more are provided, and the plate-like heating body such as the carbon heater is heated to 50 to 2,000.
C. or by applying a stress between the contacting surfaces of the two integrated semiconductor substrates in the direction of contact between the contacting surfaces, and performing the heating process for the integration. Achieved by:

[Industrial applications]

The present invention relates to an improvement in a method for manufacturing a semiconductor substrate. In particular, the present invention relates to an improvement in a method for manufacturing an SOI substrate in which a semiconductor film is formed on an insulator film.

[Conventional technology]

In one type of a method for manufacturing a so-called SOI substrate, at least one of two silicon wafers is oxidized to form a silicon dioxide film having a thickness of 1 μm or less on at least one surface thereof. In a state where the silicon wafers are stacked so that the above-mentioned silicon dioxide film becomes an intermediate layer, for example, the two silicon wafers are bonded by heating to about 1,000 ° C., and the upper silicon wafer is polished to form a thin film. 2. Description of the Related Art A method for manufacturing an SOI substrate to be converted is known. The present invention is an improvement of the method for manufacturing the SOI substrate.

[Problems to be solved by the invention]

The above-described SOI substrate manufacturing method is inevitable for the following disadvantages.

I. Originally, two silicon wafers are bonded together, especially in the case of a large-diameter wafer, the adhesive force tends to be partially uniform and not sufficiently bonded to the strongly bonded area. Region exists.

B. And in the area that is not sufficiently bonded,
Peeling is performed in a heat treatment step performed thereafter.

C. After dicing, the area that is not sufficiently bonded is completely peeled off, and is disassembled into two chips to become a completely defective product.

D. Silicon chips in the incompletely bonded area become dust and contaminate the process equipment.

E. Since there is a problem in reliability, an adhesion confirmation test using infrared reflected light or the like is required, and this additional test requires a lot of man-hours.

An object of the present invention is to eliminate these disadvantages, and oxidize at least one of the two semiconductor wafers to form a semiconductor oxide film having a thickness of 1 μm or less on at least one surface thereof. In a method of manufacturing an SOI substrate in which these two semiconductor wafers are laminated and heated such that the oxide film of the semiconductor becomes an intermediate layer and the two semiconductor wafers are bonded to each other, the wafer has a large diameter. However, an object of the present invention is to provide a method of manufacturing a semiconductor substrate which can uniformly bond the entire surface thereof and can manufacture a large-diameter SOI substrate.

[Means for solving the problem]

The above object is achieved by forming an oxide semiconductor film (3) on at least one surface of at least one of the two semiconductor substrates (1) and (2), and forming the second oxide film via the oxide semiconductor film (3). The two semiconductor substrates (1) and (2) are heated while being in contact with each other to integrate the two semiconductor substrates (1) and (2), and the integrated two semiconductor substrates (1), In the method for manufacturing a semiconductor substrate having an SOI structure according to (2), a stress is applied in the direction between the contacting surfaces of the two integrated semiconductor substrates (1) and (2) in the contacting direction. This is achieved by performing a heating step for the integration.

The two semiconductor substrates (1) and (2) are applied with stress in the direction between the contact surfaces of the two semiconductor substrates (1) and (2) to be integrated. The following two means are effective as the step of heating

The first means is that the two semiconductor substrates (1) and (2)
Using a press having a curved surface with a radius of curvature of 10 to 30 m.

The step of applying stress to the contact surfaces of the two integrated semiconductor substrates (1) and (2) by using a press having a curved surface is performed in a desired direction when repeatedly performed. The effect of the present invention of bending the substrate is effective.

The second means is to place one of the two semiconductor substrates (1) and (2) on a flat heater (5) such as a carbon heater heated to 50 to 500 ° C. On the (1) and (2), the two semiconductor substrates (1),
The other side of (2) is placed with a temperature difference of 50 to 500 ° C. and a temperature difference of at least 50 ° C. or more of the flat heater (5) such as the carbon heater, and the flat heater (5) such as the carbon heater is mounted. ) Is heated to 50 to 2,000 ° C.

In the second means, the temperature difference of at least 50 ° C. is effective when the temperature of the semiconductor substrate (1) or (2) in contact with the flat heating element (5) is high.

In the second means, one of the two semiconductor substrates (1) and (2) is placed on a flat heating body (5) such as a carbon heater heated to 50 to 500 ° C. When the temperature of the surrounding atmosphere is reduced during a period in which stress is applied to the contact surfaces of the two semiconductor substrates (1) and (2),
The stress generated on the contact surface between the two semiconductor substrates (1) and (2) is increased, and the effect of the present invention of bending the substrate in a desired direction is more effective.

In the second means, when a voltage is applied between the two semiconductor substrates (1) and (2) while applying an electrostatic pressure, the substrate is bent in a desired direction. The effects of the invention are remarkably effective.

[Action]

The cause of the partial imperfect bonding to be solved by the present invention is that the bonding surfaces are not integrated and homogenized, and a boundary surface remains between two semiconductor substrates.

In order for the bonding surfaces of the two semiconductor substrates 1 and 2 to be integrated and homogenized, an extremely thin layer near the contact surface may be once melted and solidified.

To melt only a very thin layer near the contact surface once,
It is effective to generate stress between the two semiconductor substrates 1 and 2 along the plane of the two semiconductor substrates 1 and 2. The reason that the solid skate edge smoothly slides on the solid ice is that the ice at the interface melts due to the pressure between the two to become water, and this water functions as a lubricant. It is well known. At least one of the two semiconductor wafers is oxidized to form an oxide semiconductor film having a thickness of 1 μm or less on at least one surface, and the two semiconductor wafers are used as intermediate layers. In the state of being superimposed, for example,
If this principle is to be applied to a method of manufacturing an SOI substrate formed by bonding two semiconductor wafers by heating to about 1,000 ° C., excessively large pressure must be applied between the two semiconductor substrates 1 and 2. It cannot be applied. This is because the semiconductor wafer is damaged.

Therefore, the inventor of the present invention repeated experiments using various techniques. As a result, in a state where pressure was applied to such an extent that the contact surfaces of two sheets to be bonded, for example, a silicon wafer did not slip with each other, If two silicon substrates to be bonded, for example, a silicon wafer are bent, or if two, for example, a silicon wafer are bonded to each other with a temperature difference of about 50 ° C., the two semiconductor substrates 1,
2 does not slip on each other as shown in FIGS. 4 (a) and 4 (b), and has two silicon wafers to be bonded as shown by arrows in FIG. 4 (c). It has been discovered that stress is generated along the joint surface, and as a result, an extremely thin layer near the boundary surface is once melted and solidified, and this region is integrated and homogenized.

Then, the above-mentioned circumstances were confirmed using an adhesion confirmation test or the like performed using infrared reflected light or the like, and the present invention was completed.

The present invention is based on such experimental results, and although the principle of operation is not necessarily clear, the two semiconductor substrates 1 and 2 to be bonded to each other are interposed via a thin oxide semiconductor layer. When pressed at an appropriate pressure and bent moderately, the boundary surface is melted, at least softening is promoted, mass transfer is realized through the contact surface, and integration and homogenization progress. Seem.

〔Example〕

Hereinafter, referring to the drawings, at least one of two semiconductor wafers according to two embodiments of the present invention is oxidized to form an oxide semiconductor film having a thickness of 1 μm or less on at least one surface thereof. Then, a method of manufacturing an SOI substrate in which these two semiconductor wafers are heated in a state where the two semiconductor wafers are stacked so that the above-described oxide semiconductor film becomes an intermediate layer and the two semiconductor wafers are bonded to each other will be described.

First Embodiment See FIG. 2 At least one surface of at least one of the silicon substrates 1 and 2 having a thickness of 300 μm is oxidized to form a silicon dioxide layer 3 having a thickness of 0.5 μm. In this step, steam oxidation may be performed at 1,100 ° C. for about 1 hour.

FIGS. 1a and 1b See FIGS. 1a and 1b. Presses 41 and 42 whose surfaces are curved so that the radius of curvature is 10 to 30 m are used, and two silicon layers are formed so that the silicon dioxide layer 3 becomes an intermediate layer. Pressing while bonding the substrates 1 and 2, the two silicon substrates 1 and 2 are heated at 500 to 1200 ° C. for about 1 hour in a curved state,
The two silicon substrates 1 and 2 are integrated and homogenized.

Referring to FIG. 3, one of the silicon substrates 1 or 2 is thinned using a polisher or the like.

As described above, it is effective to repeatedly execute the above pressing process.

Second Embodiment Referring again to FIG. 2, at least one surface of at least one of the silicon substrates 1 and 2 having a thickness of 300 μm is oxidized to form a silicon dioxide layer 3 having a thickness of 0.5 μm. In this step, steam oxidation may be performed at 1,100 ° C. for about 1 hour.

See FIGS. 1c and 1d. A carbon heater (plate-like heating element) 5 is heated to 50 to 500 ° C., and one of the silicon substrates 1 and 2 is placed thereon.
At that time, it is essential that the silicon dioxide layer 3 be an upper layer. The temperature of the silicon substrate 1 or 2 placed on the carbon heater (plate-like heating element) 5 is naturally 50 to 500 ° C.
Becomes

The other of the silicon substrates 1 and 2 is placed at least 50 ° C. lower than the temperature of the carbon heater (flat heater) 5 on the other silicon substrates 1 and 2.

In this state, the two silicon substrates are integrated and homogenized by heating to 500 to 1,200 ° C. for about 1 hour.

At this time, the two silicon substrates 1 and 2 are curved as shown in FIG. 1d. This curvature is more effective if the ambient temperature is controlled.

At this time, if a voltage is applied between the two silicon wafers 1 and 2 to generate an electrostatic pressure, the adhesion between the two silicon wafers 1 and 2 is improved, voids are eliminated, and the entire surface of the wafer is reduced. This is effective for more uniformly bonding.

Referring back to FIG. 3, one of the silicon substrates 1 or 2 is thinned using a polisher or the like.

〔The invention's effect〕

As described above, at least one of the two semiconductor wafers according to the present invention is oxidized to form an oxide semiconductor film having a thickness of 1 μm or less on at least one surface thereof. In the case of silicon, for example, in the case of silicon, where the above-mentioned oxide semiconductor films are superposed so as to form an intermediate layer, the two semiconductor wafers are bonded by heating to about 1,000 ° C.
At least one of at least one of the semiconductor substrates
Forming an oxide semiconductor film on the surface, heating the two semiconductor substrates while contacting the two semiconductor substrates through the oxide semiconductor film,
In a method of manufacturing a semiconductor substrate having an SOI structure by integrating two semiconductor substrates and using the two integrated semiconductor substrates, the two semiconductor substrates are curved with a radius of curvature of 10 to 30 m. Use a press that is
Alternatively, one of the two semiconductor substrates is placed on a flat heater such as a carbon heater heated to 50 to 500 ° C., and the other of the two semiconductor substrates is placed on the one semiconductor substrate, 50-500 ° C of flat heating body such as the carbon heater
And a temperature difference of at least 50 ° C. or more, and heat the plate-like heating body such as the carbon heater to 50 to 2,000 ° C., thereby contacting the two semiconductor substrates to be integrated. Since the heating step for the integration is performed while applying a stress to the contact surface in the direction between the two, at least one of the two semiconductor wafers is required.
The wafer was oxidized to form a semiconductor oxide film having a thickness of 1 μm or less on at least one surface thereof, and these two semiconductor wafers were overlapped so that the semiconductor oxide film became an intermediate layer. In the method of manufacturing an SOI substrate by bonding two semiconductor wafers by heating in a state, even if the wafer has a large diameter, the entire surface can be uniformly bonded, and a large-diameter SOI substrate is manufactured. It is possible to provide a method of manufacturing a semiconductor substrate that can be performed.

[Brief description of the drawings]

FIGS. 1a and 1b are explanatory views of main steps of a method for manufacturing a semiconductor substrate according to a first embodiment of the present invention. FIGS. 1c and 1d are explanatory diagrams of main steps of a method for manufacturing a semiconductor substrate according to a second embodiment of the present invention. FIG. 2 and FIG. 3 are explanatory diagrams of main steps of a method for manufacturing a semiconductor substrate according to the first and second embodiments of the present invention. 4 (a), (b) and (c) are illustrations of the idea of the present invention. 1, 2 ... silicon wafer, 3 ... silicon dioxide, 41, 42 ... press with curved surface, 5 ... flat heating means (carbon heater).

Claims (7)

(57) [Claims] 1. An oxide semiconductor film (3) is formed on at least one surface of at least one of two semiconductor substrates (1) and (2), and is formed via said oxide semiconductor film (3). The two semiconductor substrates (1) and (2) are heated while being in contact with each other to integrate the two semiconductor substrates (1) and (2), and the integrated two semiconductor substrates (1), (2) In the method of manufacturing a semiconductor substrate having an SOI structure according to (2), a stress is applied between the contacting surfaces of the two integrated semiconductor substrates (1) and (2) in such a direction. A method of manufacturing the semiconductor substrate, wherein the heating step is performed for the integration. 2. The method according to claim 1, further comprising: applying a stress in a direction between the contacting surfaces of the two semiconductor substrates (1) and (2) to be integrated with the two semiconductor substrates (1) and (2). And (2), wherein the two semiconductor substrates (1) and (2) are formed using a press having a curved surface with a radius of curvature of 10 to 30 m. The method for manufacturing a semiconductor substrate according to claim 1. 3. The method according to claim 2, wherein the heating step performed by using a press having a curved surface is repeatedly performed a plurality of times. 4. A method according to claim 1, wherein a stress is applied between said contacting surfaces of said two semiconductor substrates (1) and (2) in such a direction as to apply said stress to said contacting surfaces. ) And (2) are heated on a flat heating body (5) heated to 50 to 500 ° C.
One of the two semiconductor substrates (1) and (2) is placed, and the other of the two semiconductor substrates (1) and (2) is placed on the one semiconductor substrate (1) and (2). The plate-shaped heating element (5) is placed at a temperature difference of 50-500 ° C and a temperature difference of at least 50 ° C or more, and the flat-plate heating element (5) is heated to 50-2,000 ° C. 3. The method of manufacturing a semiconductor substrate according to claim 1, wherein 5. The one semiconductor substrate (1) or (2)
The temperature difference of at least 50 ° C. or more applied between the semiconductor substrate (2) or (1) and the other semiconductor substrate (2) depends on the temperature of the semiconductor substrate (1) or (2) in contact with the plate-shaped heating element (5). 5. The method for manufacturing a semiconductor substrate according to claim 4, wherein the method is high. 6. One of the two semiconductor substrates (1) and (2) is heated (1) or (2), and the two semiconductor substrates (1) and (2) are integrated. In the step of generating a stress in the direction of contact between the contacting surfaces of the two semiconductor substrates (1) and (2) to integrate the two semiconductor substrates (1) and (2), the two semiconductor substrates (1) And (2) reducing the temperature of the surrounding atmosphere.
13. The method for manufacturing a semiconductor substrate according to claim 1. 7. The two semiconductor substrates (1) and (2) being integrated while applying stress in the direction between the contacting surfaces of the two semiconductor substrates (1) and (2). 2. The method according to claim 1, wherein in the step of heating (2) and (2), a voltage is applied between the two semiconductor substrates (1) and (2) to apply an electrostatic pressure. 7. The method for manufacturing a semiconductor substrate according to claim 2, 3, 3, 4, 5, or 6.