JP3141378B2 - Semiconductor substrate manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for a method of manufacturing a semiconductor substrate, and particularly, an SO in which a silicon semiconductor single crystal layer is provided on an insulator layer.
The present invention relates to a method of manufacturing an I (Silicon-on-insulator) substrate.

〔Overview〕

The present invention relates to a method for manufacturing a semiconductor substrate having a silicon single crystal layer on an insulator layer, wherein a recess is provided with a predetermined size and arrangement on one main surface of the silicon single crystal substrate, and a silicon oxide film is formed on the entire surface by thermal oxidation. By forming and polishing a silicon single crystal layer constituting the bottom surface of the concave portion to a predetermined thickness to form a silicon single crystal layer serving as an element region, an SOI substrate having excellent crystallinity can be obtained. is there.

[Conventional technology]

Various improvements have been made to today's large-scale integrated circuits in response to demands for higher operating speeds. However, in order to realize a large-scale integrated circuit that can operate at higher speed, it is essential to significantly reduce parasitic capacitance. SOI technology, in which a single-crystal Si (silicon) thin film is formed on an insulator layer and an element is formed on the single-crystal Si thin film, is considered promising for such a drastic reduction in parasitic capacitance. Also, various SOI substrate manufacturing methods have been proposed.

One of them is SIMOX (Separation by Im-planted
Oxygen) method. (For example, Izumi et al., Electron Letter "K. Izumi et al. Elect-ron Lett." Volume 14,
(P593, 1978) FIGS. 4 (a) and 4 (b) are schematic longitudinal sectional views showing an example of a manufacturing process of an SOI substrate by the SIMOX method. 4th
As shown in FIG. 1A, a predetermined amount of oxygen ions 24 are implanted at a high acceleration from a surface of a Si single crystal substrate (hereinafter, referred to as a Si substrate) 21, that is, an element formation surface, to form an ion implantation damaged layer 22. I do. Next, as shown in FIG. 4 (b), a high-temperature heat treatment is performed to chemically crystallize the implanted oxygen and the Si of the substrate to form a buried Si oxide film layer 23, and an upper part of the buried Si oxide film 23. Is provided as a thin Si single crystal layer 25 to the element formation region.

SIMOX method uses polycrystalline Si (or amorphous S
i) depositing and growing this into large-diameter grains,
The ability to form a Si single crystal layer on an insulating film with a large area and relatively excellent crystallinity compared to the method of growing a Si single crystal on an insulating film from an underlying Si substrate by applying selective epitaxial growth Therefore, it is considered to be the most promising SOI substrate manufacturing method.

[Problems to be solved by the invention]

In the above-described method for manufacturing an SOI substrate by the SIMOX method, since high-capacity oxygen is ion-implanted at high acceleration through the substrate surface on which an element is to be formed later, the crystallinity recovery of the Si layer serving as the element formation region is insufficient. In addition, as shown in FIG. 4 (b), there is a problem that a crystal defect 26 is easily induced at the interface between the buried Si oxide film 23 and the Si single crystal layer 25. Such recovery of the crystallinity of the Si layer and elimination of crystal defects at the interface can be improved to some extent by raising the temperature of the heat treatment after the ion implantation to 1200 ° C. or higher.

However, a method for completely erasing crystal defects 26 at the interface between the buried Si oxide film 23 and the Si single crystal layer 25 serving as an element formation region has not yet been established (for example, Akira Yoshino et al., IEICE). , Technical Research Report, SDM87-39, P73, 1987). These crystal defects 26 cause deterioration of leak characteristics of an element to be formed later, and have been conventionally proposed.
This is the biggest drawback of the SOI substrate manufacturing method by the SIMOX method.

The drawbacks described above are a manufacturing procedure for recrystallizing the surface Si layer which has been made amorphous by ion implantation of oxygen at the same time as the formation of the buried Si oxide film 23, that is, a single Si step on the buried Si oxide film 23. It is inevitable that a manufacturing procedure for forming the crystal layer 25 is taken. The same applies to the case where solid-phase epitaxial growth or selective Si growth of a Si layer (amorphous or polycrystalline Si layer) on the above-mentioned insulating film is applied.

The object of the present invention is to eliminate the disadvantages mentioned above,
An SOI substrate having excellent crystallinity can be manufactured by preventing generation of crystal defects. An object of the present invention is to provide a method for manufacturing a semiconductor substrate.

[Means for solving the problem]

The present invention relates to a method for manufacturing a semiconductor substrate having a silicon single crystal layer on an insulating film formed on a silicon single crystal substrate, wherein a plurality of recesses are formed with a predetermined size and arrangement on one main surface of the silicon single crystal substrate. Forming a silicon oxide film having a predetermined thickness by thermally oxidizing the entire surface of the silicon single crystal substrate having the concave portions formed thereon, and polishing the main surface on the side where the concave portions are not formed by polishing. A step of thinning the silicon single crystal layer forming the bottom of the recess to a predetermined thickness to form a silicon single crystal layer to be an element formation region, and selecting only a predetermined width of both corners of the recess in which the silicon oxide film is formed Forming a projection of a silicon oxide film of a predetermined size on both ends of the silicon oxide film on the bottom surface of the concave portion, and forming a silicon single crystal layer forming the bottom surface of the concave portion on the bottom portion of the concave portion. Characterized in that it comprises a step of polishing until.

Further, the present invention can be implemented by adding a step of filling the recess with a coated and baked silicon oxide film after the completion of the thermal oxidation step of the recess.

[Action]

In contrast to the above-described conventional method of manufacturing a SOI substrate, the present invention provides that the element formation region is always maintained in a single crystal state,
Since the buried Si oxide film is formed by thermally oxidizing the back surface of the Si substrate, no crystal blood vessels are generated at the interface between the Si single crystal layer on which the element is formed and the buried Si oxide film, and excellent crystallization is achieved. Thus, an SOI substrate having properties can be obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1A is a schematic longitudinal sectional view of an SOI substrate showing an outline of an initial step in an embodiment of the present invention, and FIG. 1B is a plan view thereof, and FIG. (B)
It is AA 'sectional drawing.

Conductive P-type, specific resistance 10Ω-cm, plane orientation <100>, mirror-polished on both sides, 100 mm diameter, 400 μm thick Si substrate 1 with one main surface, 15 mm long, 15 mm wide, 350 μm deep recess 2 for 10m
Formed at m intervals.

2 (a) and 2 (b) are schematic longitudinal sectional views of an SOI substrate in a main manufacturing process according to a reference example of the present invention. In the initial process shown in FIGS. 1 (a) and 1 (b), a concave portion is shown. 2
Are shown focusing on one recess 2. In addition, for convenience of explanation, the drawing is drawn upside down.

The Si substrate 1 on which the recesses 2 are formed as shown in FIG. 1A is oxidized at 1000 ° C. by hydrogen combustion oxidation, and as shown in FIG. 2A, a 1.1 μm thick Si oxide film is formed. Form 3 Next, the concave / convex oxide film 4 is buried in the concave portion 2 to flatten the irregularity.

Thereafter, as shown in FIG. 2 (b), the Si oxide film 3 on the side where the recess 2 is not formed is removed, exposing the Si single crystal plane. Subsequently, the Si single crystal surface is polished with a polishing allowance of about 45 μm using fine abrasive grains such as alumina, and the Si single crystal layer 5 on the Si oxide film 3 is formed to a thickness of 0.3 μm by mirror polishing. This is an element formation region.

A Si oxide film 3 as a base of the SOI substrate manufactured in this reference example,
As a result of observing the interface with the Si single crystal layer 5 as the element formation region using a transmission electron microscope, there was no crystal defect at the interface. On the other hand, the conventional SIMOX method (oxygen injection conditions 180 KeV, 1.5
In the SOI substrate under the conditions of × 10 ¹⁸ / cm ² and heat treatment at 1280 ° C. for 3 hours, a large number of stacking faults and twins are observed at the interface between the buried Si oxide film and the upper Si single crystal layer. Was confirmed.

3 (a) to 3 (d) are schematic vertical sectional views of an SOI substrate in a main manufacturing process according to an embodiment of the present invention, in the same manner as in the reference example.

As shown in FIG. 3A, the Si substrate 11 is 15 mm long and 15 mm wide.
The concave portion 12 having a depth of 350 μm was formed. This Si substrate 11 is oxidized in a dry oxygen atmosphere at 1000 ° C. to form a 0.04 μm-thick Si oxide film 13 as shown in FIG. 3 (b). A μm Si nitride film 16 was deposited.

Thereafter, as shown in FIG. 3C, the Si nitride film 16 is removed from the wall surface of the concave portion 12 with a width of 500 μm, and further subjected to hydrogen combustion oxidation at 1000 ° C. to remove the Si oxide film 13 in the Si nitride film removed portion. The projections 17 were formed with a thickness of 0.7 μm, and the recesses 12 were filled with a coated and baked oxide film 14 and planarized.

Subsequently, as shown in FIG. 3D, the Si nitride film 16 and the Si oxide film 13 on the side where the concave portion 12 is not formed are removed,
Approximately 45 μm rough polishing with fine abrasive grains such as alumina, and further, Si selective polishing technology using piperazine (NH (CH ₂ ) ₄ NH) (Hamaguchi et al., IEICE, Technical Report, SSD86-13, P3
7, 1986). In the selective polishing using piperazine, only Si is polished and Si oxide is not polished. Therefore, as shown in FIG. 3D, the 0.7 μm Si oxide film formed near the wall surface of the concave portion 12 It protrudes toward the Si single crystal as a projection 17 of a 0.3 μm Si oxide, and serves as a stopper for selective polishing of Si. Therefore, the thickness of the thin Si single crystal layer 15 that is to be an element formation region is controlled to have a value equal to the step of the projection 17 of the Si oxide.

In this embodiment, a thin Si single crystal layer serving as an element formation region is used.
Since the step of controlling the thickness of the thin 15 is added, there is an advantage that the uniformity of the thickness of the thin Si single crystal layer 15 can be greatly improved. In the reference example, when the silicon single crystal layer 5 is manufactured to have a thickness of 0.3 μm, the variation is ± (0.1 to 0.2) μm.
On the other hand, in the second embodiment, the Si single crystal layer 15
Was ± (0.005 to 0.015) μm.

In addition, in both the reference example and the example, when forming the concave portion on the Si substrate, the length was 15 mm, the width was 15 mm, and the depth was 350 μm.However, in the manufacturing process of the present invention and the subsequent device manufacturing process, the mechanical strength can be maintained. It can be arbitrarily changed as long as it is a thing.

Further, in the embodiment, the step of the projection 17 of the Si oxide is set to 0.3
μm, the thickness of the thick oxide film near the wall surface of the recess is set to 0.
The thickness is set to 7 μm, but this can be arbitrarily changed in order to set the thickness of the Si single crystal layer to be an element formation region, and is not limited to the value described in the embodiment.

〔The invention's effect〕

As described above, the present invention forms a thermal oxide film of Si on the back surface side of the element formation region of the Si substrate, and completes the SOI structure using this as a base insulating film. This has the effect of completely suppressing crystal defects occurring at the interface with the Si single crystal layer that is to be an element formation region.

Therefore, according to the present invention, excellent crystallinity, large area
The SOI substrate can be easily manufactured, and the effect is great.

[Brief description of the drawings]

FIGS. 1A and 1B are a schematic longitudinal sectional view and a plan view of an SOI substrate showing an outline of an initial step in an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of an SOI substrate in a main manufacturing process according to a reference example of the present invention.

FIG. 3 is a schematic longitudinal sectional view of an SOI substrate in a main manufacturing process according to an embodiment of the present invention. 4 (a) and 4 (b) are schematic longitudinal sectional views of an SOI substrate in a main manufacturing process of a conventional example. 1, 11, 21 ... Si substrate, 2, 12 ... recess, 3, 13 ... Si
Oxide film, 4, 14… Coated and baked oxide film, 5, 15, 25… Si
Single crystal layer, 16 ... Si nitride film, 17 ... Protrusion, 22 ... Implantation damaged layer, 23 ... Buried Si oxide film, 24 ... Oxygen ion implantation, 26 ... Crystal defect.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/70 H01L 21/74-21/764 H01L 21/768 H01L 21/78 H01L 21/3205 H01L 21 / 3213

Claims (2)

(57) [Claims] 1. A method of manufacturing a semiconductor substrate having a silicon single crystal layer on an insulating film, comprising the steps of: forming a plurality of recesses with a predetermined size and arrangement on one main surface of a silicon single crystal substrate; Forming a silicon oxide film of a predetermined thickness by thermally oxidizing the entire surface of the silicon single crystal substrate on which is formed, and polishing the main surface on the side where the recess is not formed to form the bottom of the recess A step of thinning the silicon single crystal layer to a predetermined thickness to form a silicon single crystal layer to be an element formation region; and selectively oxidizing only two corners of the concave portion in which the silicon oxide film is formed with a predetermined width. Forming a silicon oxide film on the bottom surface of the concave portion and a protrusion of a silicon oxide film of a predetermined size on both end portions; polishing the silicon single crystal layer constituting the bottom surface of the concave portion to the surface of the protrusion portion; Including The method of manufacturing a semiconductor substrate according to claim. 2. The method of manufacturing a semiconductor substrate according to claim 1, further comprising the step of filling the concave portion with a coated and baked silicon oxide film after the completion of the thermal oxidation step of the concave portion.