JP2764466B2 - Manufacturing method of semiconductor laminated substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor laminated substrate, and is particularly suitable for application to a method for manufacturing an SOI substrate using a bonding method.

[Conventional technology]

SOI (Silicon On Insulator) using the bonding method
Conventionally, a method for manufacturing a substrate has been performed as follows.

First, as shown in FIG. 2A, an SiO ₂ film 2 is formed on a main surface of a first silicon substrate 1 by a thermal oxidation method.

Next, as shown in FIG. 2 (b), the main surface of the second silicon substrate 3 is bonded to the main surface of the first silicon substrate 1, and the silicon substrates are bonded to each other by heat treatment.

Next, as shown in FIG. 2 (c), the second silicon substrate 3 is polished from its back side, leaving a thin silicon film 3 as an active region on the SiO ₂ film 2 to remove the SOI substrate. Form.

However, in this method, it is difficult to monitor the polishing amount in the last polishing step, and therefore, it is difficult to precisely control the thickness of the remaining silicon film 3.

In order to solve this problem, the following method has been adopted.

First, as shown in FIG. 3A, an SiO ₂ film 2 is formed on the entire main surface of the first silicon substrate 1 by a thermal oxidation method.
On the other hand, a part of the main surface of the second silicon substrate 3 is thermally oxidized to locally form SiO ₂ 4. The surface of the SiO ₂ 4 protrudes from the surface of the main surface of the silicon substrate 3 in a convex shape, and the boundary surface between the SiO ₂ 4 and the silicon substrate 3 is deeper than the surface of the main surface of the silicon substrate 3. There.

Next, as shown in FIG. 3 (b), the main surfaces of the first silicon substrate 1 and the second silicon substrate 3 are bonded to each other and bonded by heat treatment.

Next, as shown in FIG. 3 (c), the second silicon substrate 3 is polished from the back surface side. At this time, since the polishing rate of SiO ₂ is much smaller than that of silicon, the SiO ₂ 4 formed on the silicon substrate 3 functions as a stopper, and the SiO ₂ film 2
The thickness of the silicon film 3 left as an active region on the top can be made constant.

[Problems to be solved by the invention]

However, in the method shown in FIG. 3, since the projection of SiO ₂ 4 exists on the main surface of the second silicon substrate 3, when the substrates are bonded to each other as shown in FIG.
There have been problems such as the formation of voids around the protrusions, resulting in poor adhesion, and the main surface of the silicon substrate 3 around the protrusions being bent without maintaining a flat surface, resulting in poor crystallinity of silicon.

The present invention has been made in view of the above-described problems, and can control a film thickness of a silicon film serving as an active region to be constant, and can manufacture an SOI substrate without impairing crystallinity or adhesiveness. It seeks to provide a way in which it can be done.

[Means for solving the problem]

In order to solve the above-mentioned problems, a method of manufacturing a semiconductor laminated substrate according to the present invention comprises the steps of: forming an oxide film on a main surface of a first semiconductor substrate; Forming a convex portion relative to the film; forming a concave portion at a position corresponding to the convex portion of the first semiconductor substrate on the main surface of the second semiconductor substrate; Bonding the main surfaces of the first and second semiconductor substrates to each other by heat treatment so that the convex portions of the first and second semiconductor substrates fit into the concave portions of the second semiconductor substrate; and exposing the oxide film. Polishing the second semiconductor substrate from the back surface side.

[Action]

In the present invention, since the concave portion is formed at the position of the main surface of the second semiconductor substrate corresponding to the protrusion existing on the main surface of the first semiconductor substrate, the first and second semiconductor substrates are bonded to each other. When combined, the respective main planes are in close contact with each other. Therefore, no void is formed near the protrusion and no bending of the main surface of the second silicon substrate occurs.

Since the protrusion of the oxide film provided on the main surface of the first semiconductor substrate functions as a stopper when polishing the second semiconductor substrate, the thickness of the second semiconductor substrate left as an active region is controlled to be constant. can do.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

First, as shown in FIG. 1A, a 2.5 μm thick SiO ₂ film 2 is formed on a main surface of a silicon substrate 1 by a thermal oxidation method.

Next, a photoresist pattern is formed on the SiO ₂ film 2, and using the mask as a mask, the SiO ₂ film 2 is selectively etched to a depth of 5000 ° in a buffered hydrofluoric acid solution, and then the photoresist is removed. 1 As shown in FIG.
A plurality of convex portions 6 are formed relatively to the O ₂ film 2.

On the other hand, a photoresist pattern is formed on the main surface of the second silicon substrate 3, and using this as a mask, the surface of the silicon substrate 3 is selectively etched to a depth of 5000 ° by a plasma etching method, and then the photoresist is removed. Then, as shown in FIG. 1C, a recess 7 is formed on the surface of the silicon substrate 3. Here, the position of the concave portion 7 formed on the surface of the silicon substrate 3 is different from that of the first and second silicon substrates 1.
When the principal surfaces of the first and third substrates are bonded to each other, they correspond to the positions of the convex portions 6 formed on the SiO ₂ film 2 on the first silicon substrate 1.

Next, as shown in FIG. 1 (d), the main surfaces of the first silicon substrate 1 and the second silicon substrate 3 are bonded to each other, and heat treatment is performed to bond them. At this time, the protrusions 6 of the SiO ₂ film 2 formed on the first silicon substrate 1 fit into the recesses 7 formed on the second silicon substrate 3, so that the protrusions of the first silicon substrate 1 The flat portions excluding the concave portions 6 and the flat portions excluding the concave portions 7 of the second silicon substrate 3 are sufficiently adhered to each other. Further, the second silicon substrate 3 does not bend, and therefore, does not lose its crystallinity.

Next, as shown in FIG. 1 (e), the second silicon substrate 3 is polished from the back surface side until a part of the convex portion 6 of the SiO ₂ film 2 is exposed, so that the second silicon substrate 3 is polished on the SiO ₂ film 2. A silicon film 3 having a thickness of about 5000 mm is formed as an active region.

〔The invention's effect〕

As described above, according to the present invention, when a semiconductor laminated substrate is manufactured by a bonding method, an oxide film formed on a first semiconductor substrate and a second semiconductor bonded on the oxide film are formed on the first semiconductor substrate. The adhesiveness between the substrate and the substrate is high, and the crystallinity of the second semiconductor substrate as an active region is not impaired.

[Brief description of the drawings]

1 (a) to 1 (e) are sectional views showing a method of manufacturing a semiconductor laminated substrate according to an embodiment of the present invention in the order of steps, and FIGS. 2 (a) to 2 (c) are conventional methods of manufacturing a semiconductor laminated substrate. 3 (a) to 3 (c) are cross-sectional views showing another conventional method for manufacturing a semiconductor laminated substrate in the order of steps. Note that in the code used in the drawings, 1 ...... first silicon substrate 2 ...... SiO ₂ film 3 ...... second silicon substrate 6 ...... protrusions 7 ...... recess.

Claims (1)

(57) [Claims] A step of forming an oxide film on a main surface of a first semiconductor substrate; a step of forming a protrusion relative to the oxide film by removing a part of the oxide film; Forming a concave portion at a position corresponding to the convex portion of the first semiconductor substrate on the main surface of the second semiconductor substrate; and fitting the convex portion of the first semiconductor substrate into the concave portion of the second semiconductor substrate. Bonding the main surfaces of the first and second semiconductor substrates to each other and bonding them together by heat treatment, and polishing the second semiconductor substrate from the back surface side until an oxide film is exposed. And a method for manufacturing a semiconductor laminated substrate.