JPS6336545A - Manufacture of dielectric isolation type semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to form excellent island regions and to improve the integration degree and the characteristics of an element, in etching for forming the island regions having different depths, by using masks, in which two or more kinds of etching resisting films are combined, thereby improving the manufacturing yield rate and accuracy. CONSTITUTION:Masks 7a and 7b are selectively formed on the surface of a single crystal semiconductor substrate 1. The semiconductor substrate 1 is partially etched in different depths by using the masks 7a and 7b. A dielectric isolation film 4 and a supporting body layer 5 are deposited on the surface. Thereafter, the rear surface of the semiconductor substrate 1 is polished, and first and second single crystal semiconductor islands 6a and 6b, which are insulated and isolated from each other and have different depths, are formed. When the dielectric isolation type semiconductor device is manufactured in this way, the masks 7a and 7b, which are used in said etching, have the structure, in which two or more kinds of etching resisting films 2 and 3 are made to correspond to the island regions in different combinations. The process, in which the single crystal silicon substrate 1 is selectively etched by using the masks 7a and 7b, and a process, in which the etching resisting films 2 and 3 of the masks are sequentially removed, are laternately performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing an isolation type semiconductor device.

゛ [Conventional technology] A conventional isolation type semiconductor device is shown in FIG. 4(a).

As shown in (b), it is composed of a support layer 5 made of polycrystalline silicon or the like, an insulating separation film 4 such as a silicon dioxide film, and a single crystal silicon island 6 wrapped in the insulating separation film. Depending on the depth of the single crystal silicon island 6, for example,
1-160707, which has only a monocrystalline silicon island 6a with a uniform depth, or the one shown in FIG. ) with different depths of monocrystalline silicon islands 5a.
, 5b has been proposed.

Among these structures, especially the latter island structure, when manufacturing integrated circuit devices in which high-voltage elements and low-voltage elements coexist,
This is effective in improving the characteristics of low voltage elements and increasing the degree of integration.

FIGS. 5(a) to 5(e) show a method for manufacturing this latter island structure, in which a first single-crystal silicon island 6a with an island depth hl and a second single-crystal silicon island 6a with a smaller depth hl are shown in FIGS. It shows the process of forming a single crystal silicon island 6b.

First, as shown in FIG. 2A, a silicon dioxide film 2 is formed as an alkali-resistant coating on the surface of a single-crystal silicon substrate 1 by thermal oxidation. Next, a first photolithography process is performed to form a mask opening window 8 having an opening size W0 in the silicon dioxide film 2 in the second single crystal silicon island formation region.
form.

Then, by anisotropic etching with an aqueous potassium hydroxide solution, a recess 9a having a depth of do is formed in the single crystal silicon substrate 1.
form.

Next, a silicon dioxide film 2A is formed on the entire surface of the single crystal silicon substrate 1 as shown in FIG. Opening windows 8a and 8b having opening dimensions W, . . . W2 are opened in the silicon island 6b formation region, respectively. In this case, if the island depth is >h, the opening size is also W, >W2
Set to .

After that, as shown in the same figure (C), the silicon dioxide film 2A
Using this as a mask, the single crystal silicon substrate 1 is anisotropically etched to a depth d required to form the first single crystal silicon island 6-a, thereby forming VilOa. At this time, W=2
From the relationship of xd, in the formation region of the second single crystal silicon island 6b, V#10b of depth d2 according to the opening dimension W2.
is formed.

Furthermore, after removing the silicon dioxide film 2A as shown in FIG. 4(d), a silicon dioxide film with a thickness of about 2 μm is formed as an insulating separation film 4 on the entire surface, and a polycrystalline silicon film is formed on this as a support layer 5. 5 is formed to a required thickness by CVD method.

Thereafter, the single-crystal silicon substrate side is polished from the back side until a part of the insulating separation film 4 is exposed, as shown in the same figure.
First and second single crystal silicon islands 6a and 6b having different depths are completed as shown in e).

[Problem that the invention seeks to solve]

The conventional manufacturing method described above has the following problems.

(1) In the second photolithography step, since the single crystal silicon substrate 1 with the recessed portion 9a is handled, the substrate is likely to be broken, resulting in a decrease in yield.

(2) Since the second photolithography process is performed on the surface of the substrate 1 which has large irregularities due to the formation of the recessed portion 9a, the accuracy is lowered.

(3) In the second anisotropic etching, etching time is required to form the V-groove 10a with a large island depth, so the shallow V-groove 10b is etched extra.
The island shape formed here is likely to collapse, resulting in deterioration of the characteristics of the element.

(4) From the known anisotropic etching mask design method (for example, Japanese Patent Publication No. 45-17988), it is necessary to add a compensation pattern to the corners of the mask in order to uniformly form a silicon single crystal island shape. Although this is known, it is important to optimize the compensation pattern at the boundary portion of the recessed portion 9a, which is accompanied by difficulty in design.

[Means for solving problems]

In view of the above-mentioned problems, the method of manufacturing an isolation type semiconductor device of the present invention aims to improve manufacturing yield and precision, makes it possible to form a good island region, and improves the integration of elements formed here. This makes it possible to improve the characteristics and the characteristics, and also to facilitate the design.

In the method of manufacturing an isolation type semiconductor device of the present invention, when etching a single crystal semiconductor substrate to form island regions of various depths, two or more types of etching-resistant coatings are applied to each island region using a mask used for etching. The method is characterized in that the structures have different combinations in correspondence with each other, and the step of selectively etching a single crystal silicon substrate using these masks and the step of sequentially removing the etching-resistant coating of these masks from the upper layer are performed alternately. It is.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

(Example Work) FIGS. 1(a) to 1(e) are cross-sectional views showing the first embodiment of the present invention in the order of manufacturing steps, and here, a first single crystal silicon island 6a with a depth hl and a first single crystal silicon island 6a with a depth hl, hz second single crystal silicon island 5
b shows an example of forming single-crystal silicon islands with two different depths, where h+ >h,).

First, as shown in FIG. 2(a), a two-layer structure film consisting of a silicon dioxide film 2 and a silicon nitride film 3 having a thickness to be described later is formed on the surface of a single crystal silicon substrate 1 with a crystal plane (100). is patterned by photolithography, and a mask 7a consisting of a two-layer structure film is formed only in the region corresponding to the first single crystal silicon island 6a. Also,
A mask 7b made of only silicon dioxide film 2 is formed in a region corresponding to second single-crystal silicon island 6b.

At this time, the dimension W of the opening 8 in the mask is the width necessary to form the first single-crystal silicon island 6a, and the island depth hl
The etching depth is determined from d=h, +Δh, taking into consideration the polishing variation (Δh) in the subsequent process.

Next, as shown in FIG. 4B, the single crystal silicon substrate 1 is etched using an aqueous potassium hydroxide solution to form a trapezoidal groove 9 of a required depth do.

Next, as shown in the same figure (C), the second single crystal silicon island 6b
Silicon dioxide film 2 as mask 7b in jI region
The silicon dioxide film is removed using a silicon dioxide film etching solution such as Banfurd hydrofluoric acid (HF: NH4F). Note that since the surface of the mask 7a in the first single crystal silicon island 63 region is the silicon nitride film 3, it is not etched.

Then, etching is performed with an aqueous potassium hydroxide solution, and ■
A groove 10 is formed.

At this time, since the surface of the second single crystal silicon island 5beN region has exposed single crystal silicon in the crystal plane (100),
The substrate surface is etched by d-do as shown by the dotted line. On the other hand, since the side surfaces are crystal planes (111), the etching rate is extremely slow, resulting in the formation of grooves 10.

Next, as shown in FIG. 1D, a silicon dioxide film 4 is formed as an insulating separation film on the surface of the substrate 1, and polycrystalline silicon 5 is deposited thereon as a support layer by CVD. At this time, when forming a buried layer, it goes without saying that four impurities are added by thermal diffusion, ion implantation, etc. before forming the insulating separation film 4.

Thereafter, the single crystal silicon substrate 1 is polished from the back side to expose a part of the insulating separation film 4, as shown in FIG.
First and second single crystal silicon islands 6a and 6b are completed as shown in FIG.

Here, for example, the depth h+ of the first single crystal silicon island 6a
=45 μm, depth hz of second single crystal silicon island 6b”
20 μm, polishing variation Δh=5 μm, desired etching depth d#h, +Δh=50 crm, d
o = 25pm, mask opening size W = 21/
2×d″−10 μm.

Further, when etching a potassium hydroxide aqueous solution at 80° C., the etching rate of the crystal plane (100) of the single crystal silicon substrate 1 is about 1 μm/min.

The etching speed of the silicon dioxide film 2 is approximately 50 people/min.
The etching rate of the silicon nitride film 3 is about 5 people/min. Therefore, the etching time to obtain the desired depth d=50 μm is about 50 minutes, and the etching time for each silicon dioxide film 2 and silicon nitride film 3 is 1250 and 250, respectively.
Just do it to a person.

- According to this method, the photolithography process for forming the silicon dioxide film 2 and the silicon nitride film 3 as the masks 7a and 7b is performed on the flat single crystal silicon substrate 1, which causes cracks, etc. Moreover, since it can be done with high precision, the yield can be improved. Also, depending on the configuration of these masks 7a and 7b, two types of depths of islands 6a,
Since 6b can be etched at the same time, it is possible to form an island region whose shape does not collapse, thereby improving the degree of integration and device characteristics.

Here, a single layer film of silicon nitride film may be used as a mask for the first wheel crystal silicon island 6a. Also, the first and second
It is also possible to form the single crystal silicon film with the mask configuration reversed.

(Example 2) FIGS. 2(a) to 2(e) are cross-sectional views showing a second example of the present invention in the order of manufacturing steps, and here, the first to third different depths, hz, hz ( h+ >hz>h3)
An example of forming single crystal silicon islands 6a to 6c is shown.

First, as shown in FIG. 6(a), a first single crystal silicon island 6 a f is formed on the surface of a single crystal silicon substrate 1 having a crystal plane (100).
Silicon dioxide film 2 on the surface of the il region. Silicon nitride film 3
．． Mask 7 with a three-layer structure film consisting of silicon dioxide film 2
a, a mask 7b having a two-layer structure consisting of a silicon nitride film 3 and a silicon dioxide film 2 is provided on the surface of the second single-crystal silicon island 6bjl region, and a third single-crystal silicon island 6c8
Masks 7c made of only silicon dioxide film 2 are sequentially formed on the surface of region M by a photolithography process. At this time, the dimension W of the minimum mask opening 8 can be determined from the required etching depth d=h and Δh, as in the first embodiment.

Next, as shown in FIG. 2B, the substrate 1 is etched to a desired depth do using a potassium hydroxide aqueous solution to form a trapezoidal groove 9. This etching depth is determined by the depth of the third single crystal silicon island 6c.

Next, as shown in the same figure (c), third single crystal silicon, %6
c6J[[The silicon dioxide film 2 of the mask 7c on the surface is removed by etching with buffered hydrofluoric acid.

At this time, the first and second single crystal silicon islands 6a.

6bSN area mask? Since the silicon nitride film 3 is provided on the surfaces of a and 7b, the mask is not removed. In this state, when the etching of the trapezoidal groove 9 is progressed to a depth d using an aqueous potassium hydroxide solution, the etching progresses on the surface of the third single crystal silicon island 60 region, and the bottom surface of the single crystal silicon island is shown as a dotted line in the figure. The part becomes shallower by d, -do.

Next, as shown in FIG. 4(d), the silicon nitride film 3 on the surface of the second single crystal silicon island 6b region is removed by etching with phosphoric acid (H3P04). At this time, the first single crystal silicon island 6
The silicon dioxide film 2 is left as a mask on the surface of region a. Then, etching is performed to a depth d using a potassium hydroxide aqueous solution to form the grooves 10.
The surfaces of the single-crystal silicon islands 5b and 5c are etched by a depth dd as shown by the chain line in the figure. As a result, the bottom surface of the second single crystal silicon island 6b region becomes shallow to the position dd, and the bottom surface of the third single crystal silicon island 6c'6TI region becomes shallow to the position d-do.

Thereafter, as in the first embodiment, a silicon dioxide film 4 is formed as an insulating separation film, a polycrystalline silicon 5 is deposited as a support layer, and at least the single crystal silicon substrate 1 is polished. ), the first to third single crystal silicon islands 6a to 6c having three different depths can be completed.

FIG. 3 shows an example in which a semiconductor element is formed within the single crystal silicon island thus formed.

High-voltage elements, medium-voltage elements, and low-voltage elements can be easily formed depending on the depth of the single-crystal silicon island.

Here, the thyristor 11 is installed on the island 6a, and the NPN is installed on the island 6b.
A bipolar transistor 12 is formed on the island 6c, and a MOS transistor 13 is formed on the island 6c. In the figure, 14 is an insulating film, 15 is a metal wiring layer, and 16 is various diffusion layers.

In this embodiment as well, the same effects as in the first embodiment can be obtained.

Note that the first mask is used as a mask for the single-crystal silicon island formation region.
The single-crystal silicon island 6a is coated with a two-layer structure consisting of a silicon dioxide film and a silicon nitride film, the second single-crystal silicon island 6b is coated with only a silicon nitride film, and the third single-crystal silicon island 6c is coated with a film of only a silicon nitride film. Formation can be performed in the same manner even if a film made of only a silicon dioxide film is used as a mask. In this case, it goes without saying that the silicon dioxide film and the silicon nitride film are not limited, but other films can be used as long as they are a combination of two or more types of alkali-resistant films.

〔Effect of the invention〕

As explained above, the present invention enables etching of a single crystal semiconductor substrate to form island regions of various depths.
The mask used for etching has a structure with different combinations of two or more types of etching-resistant coatings corresponding to each island region, and the process of selectively etching a single crystal silicon substrate using these masks, and the etching-resistant coating of these masks. Since the method is characterized in that the steps of sequentially removing the upper layer are performed alternately, the following effects can be obtained.

(1) Since the photolithography process is performed on a flat single-crystal silicon substrate, there will be no decrease in strength or cracks during the process, and high-precision manufacturing can improve yields. .

(2) Since the mask is formed by a combination of alkali-resistant films, single-crystal silicon islands with two or more depths can be formed by simultaneous etching, and the island depth can be set according to the required characteristics of the semiconductor element. Therefore, it is possible to improve the degree of integration.

(3) Since single-crystal silicon islands with two or more depths can be formed by simultaneous etching, the shape of each single-crystal silicon island is less likely to be distorted, and the characteristics of the elements formed here are less likely to deteriorate. do not have.

(4) Since etching is performed using a continuous alkaline etching solution, manufacturing efficiency can be improved.

(5) It is not necessary to optimize the corner compensation pattern of the mask to match the depth of the single crystal silicon island, and the design can be simplified.

[Brief explanation of the drawing]

FIGS. 1(a) to (e) are cross-sectional views showing the first embodiment of the present invention in the order of manufacturing steps, and FIGS. 2(a) to (e) are cross-sectional views showing the second embodiment of the present invention.
3 is a sectional view of an example of a completed semiconductor device, FIGS. 4(a) and 4(b) are sectional views showing different conventional island structures, and FIG. )～(e
) is a sectional view showing the conventional manufacturing method in the order of steps. DESCRIPTION OF SYMBOLS 1... Single crystal silicon substrate, 2... Silicon dioxide film, 3... Silicon nitride film, 4... Insulating isolation film, 5
...Support layer, 6a...First single crystal silicon island, 6
b... Second single crystal silicon island, 6C... Third single crystal silicon island, 7a to 7c... Mask, 8... Opening,
9...Trapezoidal groove, 10...■groove, 11-13...Element. A-2

Claims (2)

[Claims] (1) After etching the semiconductor substrate to partially different depths using a mask selectively formed on the surface of the single crystal semiconductor substrate and depositing an insulating separation film and a support layer on the surface, the semiconductor substrate In the method for manufacturing an isolation type semiconductor device, in which monocrystalline semiconductor islands of different depths are formed and isolated from each other by polishing from the back side, when etching the monocrystalline semiconductor substrate, the mask is of two or more types. The etching-resistant coating is structured to have a different combination for each island region, and the process of selectively etching the single crystal silicon substrate using these masks and the process of sequentially removing the etching-resistant coating of these masks from the upper layer are alternately performed. 1. A method for manufacturing an insulation-separated semiconductor device, characterized in that the method comprises: (2) The method of manufacturing an isolation type semiconductor device according to claim 1, wherein an alkaline aqueous solution is used for etching, and a silicon dioxide film and a silicon nitride film are used as the etching-resistant film.