JPH04132257A - Preparation of semiconductor laminated substrate - Google Patents

Abstract

PURPOSE:To make it possible to sufficiently bond the main surfaces of laminated semiconductor substrates to one another and to control a silicon film that becomes an active domain to have a constant thickness by preparing sunken sections on the main surface of a first semiconductor substrate corresponding to the protrusions that are present on the main surface of a second semiconductor substrate. CONSTITUTION:SiO2 film 2 is prepared on the main surface of silicon substrate 1, followed by selectively etching the SiO2 film 2 taking a photoresist pattern as mask to prepare a plurality of sunken sections 6 relative to the SiO2 film 2. On the other hand, on the main surface of the second silicon substrate 3 a plurality of SiO2 films 7 are prepared by heat oxidation method, followed by preparing Si3N4 films 8 thereon, further followed by patterning the main surface. Next, SiO2 4 is prepared in only the opening sections of Si3N4 films 8, followed by applying plasma etching to removing Si3N4 films 8 and SiO2 films 7, respectively. Next, the main surface of a first silicon substrate 1 and the main surface of a second silicon substrate 3 are put together and heated to bond them together, further followed by grinding the back surface of the second silicon substrate 3 until SiO2 4 is partly exposed to prepare silicon film 3 as an active domain on the SiO2 film 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor multilayer substrate, and is particularly suitable for application to a method for manufacturing a Sol substrate using a bonding method.

[Conventional technology]

SOI (Silicon O
Conventionally, a method for manufacturing a substrate (In5lator) has been carried out as follows.

First, as shown in FIG. 2(a), 5iOzl12 is formed on the main surface of a first silicon substrate l by thermal oxidation.

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 the back side, leaving a thin silicon film 3 as an active region on the Sing film 2 to form a Sol substrate. do.

However, with this method, it is difficult to monitor the amount of polishing in the final polishing step, and therefore it is difficult to accurately control the thickness of the silicon film 3 to remain.

In order to solve this problem, the following methods have been taken.

First, as shown in FIG. 3(a), a SiO□ film 2 is formed on the entire main surface of a first silicon substrate 1 by thermal oxidation. On the other hand, a part of the main surface of the second silicon substrate 3 is thermally oxidized to locally form SiO□4.

The surface of this Stow 4 protrudes convexly from the main surface of the silicon substrate 3, and the interface between the SiO□4 and the silicon substrate 3 is deeper than the main surface of the silicon substrate 3. It is in.

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 side. At this time, since the polishing rate of SiO2 is much lower than that of silicon, the SiO□4 formed on the silicon substrate 3 acts as a stopper, and the S
a silicon film 3 left on the ing film 2 as an active region;
The film thickness can be kept constant.

[Problem to be solved by the invention]

However, in the method shown in FIG. 3, since there are protrusions 5i (h4) on the main surface of the second silicon substrate 3,
As shown in FIG. 3(b), when the substrates are bonded together, voids may occur around the protrusions, resulting in poor adhesion, or the main surface of the silicon substrate 3 around the protrusions may not be able to maintain a flat surface. There were problems such as deterioration of silicon crystallinity due to bending.

The present invention has been made in view of the above-mentioned problems, and includes:
The present invention aims to provide a method in which the thickness of a silicon film serving as an active region can be controlled to be constant, and an SOI substrate can be manufactured without impairing crystallinity or adhesiveness.

[Means to solve the problem]

In order to solve the above problems, the method for manufacturing a semiconductor multilayer substrate of the present invention includes the steps of: forming an oxide film on the main surface of a first semiconductor substrate; forming a recess on the surface of the oxide film; forming a convex part using an oxide film at a position corresponding to the concave part of the first semiconductor substrate on the principal surface of the semiconductor substrate; a step of bonding the main surfaces of the first and second semiconductor substrates to each other and bonding them to each other by heat treatment so that they fit together; and a step of attaching the second semiconductor substrate from the back side until the oxide film is exposed. It has a step of polishing.

[Effect]

In the present invention, since the recess is formed at the position of the main surface of the first semiconductor substrate corresponding to the protrusion existing on the main surface of the second semiconductor substrate, the first and second semiconductor substrates can be attached to each other. When put together, each main plane hermit will be in close contact with each other. Therefore, no voids are formed near the protrusions, and no deflection of the main surface of the second silicon substrate occurs.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

First, as shown in FIG. 1(a), a 5ift film 2 having a thickness of 2 pm is formed on the main surface of a silicon substrate 1 by thermal oxidation.

Next, a photoresist pattern is formed on the 5iOz film 2, and using this as a mask, the Sing film 2 is selectively etched to a depth of 5000 mm in a buffered hydrofluoric acid solution.Then, the photoresist is removed and the first As shown in Figure (b), a plurality of recesses 6 are formed in the SiO□ film 2.

On the other hand, as shown in FIG. 1(c), a 200-layer thick O5ing film 7 is formed on the main surface of the second silicon substrate 3 by thermal oxidation.

Next, as shown in FIG. 1(d), this SiO□ film 7
After forming a SiJ4 film 8 with a thickness of 1500 mm (7) on top by the CVD method, this 5i2N film 8 is patterned by a well-known method. Here, the position of the opening formed in the Si3N4 film 8 is determined by the position of the opening formed in the Si3N4 film 8 when the main surfaces of the first and second silicon substrates l and 3 are bonded together.
, corresponds to the position of the recess 6 formed in the membrane 2.

Next, as shown in FIG. 1(e), Si was heated by thermal oxidation.
, SiO□4 is formed to a thickness of lam only in the opening portion of the N4 film 8.

Next, the 5iJa film 8 is formed by plasma etching.
Further, each SiO2 film 7 is removed using buffered hydrofluoric acid. As a result, protruding Si0g4 is formed on the main surface of the second silicon substrate 3, as shown in FIG. 1(f).

At this time, the top of the protrusion 5i (h4) rises by about 4,500 degrees from the silicon surface of the main surface of the second silicon substrate 3.

Next, as shown in FIG. 1(g), the main surfaces of the first silicon substrate 1 and the second silicon substrate 3 are bonded together and heat treated to bond them together. At this time,
The protruding SiO 4 of the second silicon substrate 3 fits within the recess 6 of the SiO2 film 2 on the first silicon substrate 1.
The planar portions of the silicon substrate 3 other than the protruding portions are in sufficient contact with each other.

Further, the second silicon substrate 3 is not bent, and therefore its crystallinity is not impaired.

Next, as shown in FIG. 1(h), by polishing the second silicon substrate 3 from the back side until a part of the 5iOz4 is exposed, about 4,500 layers of active area are formed on the 550z film 2. A silicon film 3 is formed.

〔Effect of the invention〕

As explained above, according to the present invention, when manufacturing a semiconductor multilayer substrate by a bonding method, an oxide film formed on a first semiconductor substrate and a second semiconductor bonded thereon are bonded together. It has high adhesion to the substrate, and does not impair the crystallinity of the second semiconductor substrate as an active region.

[Brief explanation of drawings]

1(a) to 1(h) are cross-sectional views showing the manufacturing method of a semiconductor multilayer substrate according to an embodiment of the present invention in the order of steps, and FIG. 2(a)
) to (c) are cross-sectional views showing a conventional method for manufacturing a semiconductor multilayer substrate in order of steps, and FIGS. 3(a) to (C) are cross-sectional views showing another conventional method for manufacturing a semiconductor multilayer substrate in order of steps. . In addition, in the symbols used in the drawings, l...... First silicon substrate 2...
...... SiO□ film 3 ...... Second silicon substrate 4 ...
・・・・・・・・・ SiO□ 6 ・・・・・・・・・ Concavity 7 ・・・・・・・・・ SiO□ film 8 ・・・・・・・・・ 5i3N41! It is.

Claims (1)

[Claims] A step of forming an oxide film on the main surface of a first semiconductor substrate; a step of forming a recess on the surface of the oxide film; and a step of forming a recess on the main surface of the second semiconductor substrate. forming a convex portion using an oxide film at a position corresponding to the concave portion of the second semiconductor substrate; A method for manufacturing a semiconductor multilayer substrate, comprising the steps of: bonding the main surfaces of the second semiconductor substrates together and bonding them to each other by heat treatment; and polishing the second semiconductor substrate from the back side until the oxide film is exposed.