JPH05283518A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method for the manufacture of a highly reliable semiconductor device by which grooves varying in width in a silicon substrate is completely filled with silicon oxide films to form element isolation regions and thus characteristics of elements are not degraded. CONSTITUTION:A patterned acid-resistant coating 102 is formed on a silicon substrate 101. The silicon substrate 101 is selectively removed using the coating 102 as a mask. Then the silicon substrate 101 is oxidized to form a first silicon oxide film 103. The coating 102 is removed, and subsequently, a second silicon oxide film 103 is formed on the silicon substrate 101. Etching back is carried out to expose part of the surface of the silicon substrate 101.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] Involved in a method of manufacturing a semiconductor device,
The present invention relates to a method of manufacturing a semiconductor device in which a relatively thick insulating film is embedded in a region between elements in order to electrically insulate each element from each other on a semiconductor substrate.

[0002]

2. Description of the Related Art In a semiconductor device, particularly a MOS type semiconductor device, in order to eliminate insulation failure due to a parasitic channel and reduce the parasitic capacitance, a so-called field between elements is used.
A thick oxide film is formed in the field region.
Conventionally, a selective oxidation method is well known as an element isolation method using such an oxide film. This is to cover the element forming region with an oxidation resistant mask, typically a silicon nitride film, and perform high temperature oxidation to selectively form a thick oxide film in the field region. However, in such a selective oxidation method, the field oxide film bites like a bird's beak (hereinafter referred to as a bird's beak) from the end portion of the silicon nitride film during the above-described oxidation, so that a dimensional error in the element formation region is caused. As a result, the substantial device size is reduced, which hinders high integration of the integrated circuit.

On the other hand, there is trench filling separation (trench separation) in which a trench is formed in a semiconductor substrate and the trench is filled with an insulating material to form a separation region. Compared with the selective oxidation method, this groove filling separation does not require a high temperature treatment and does not generate a bird's beak. An example of this will be described with reference to FIGS.

First, as shown in FIG. 6, a silicon substrate 20 is used.
1 and mask material 2 using well-known lithographic techniques.
02 is formed into a predetermined pattern. The mask material 202
Is for forming a groove in a planned formation position of the element isolation region, and has a window portion 202a having a width corresponding to the element isolation region width,
It has 202b. On the other hand, in a semiconductor integrated circuit, active elements and passive elements are integrated on a single semiconductor substrate, so that the elements must be properly separated. The window portion is generally formed to form the groove portions 203a and 203b at the planned formation positions of the element isolation regions. A wide groove is formed because there is a margin between the elements having a small number of forming elements, and a narrow groove is formed because there is no margin between elements in a portion having a large number of forming elements, such as a memory cell. For the above reasons, groove portions of various widths are formed. Next in FIG.
As shown in FIG. 5, the mask material 202 is used to etch the silicon substrate 201 to a desired depth to form a plurality of grooves, for example, a narrow groove 203a and a wide groove 203b in the silicon substrate 201. Then, the mask material 20
Remove 2. Next, as shown in FIG. 8, for example, CVD
A silicon oxide film 204 is deposited by the method. On the surface of the silicon oxide film 204, recesses are formed because of the grooves 203a and 203b. The narrow groove 203a has a small recess, and the wide groove 203b has a large recess. Next, as shown in FIG. 9, in order to fill the recess and flatten the surface, a film such as a resist 206 having an etching rate equal to that of the silicon oxide film is formed.
In the narrow groove 203a, the concave portion almost disappears and becomes flat, but in the wide groove 203b, the concave portion is so large that it hardly becomes flat, and the concave portion inevitably remains. Next, FIG.
As shown in (3), the resist 206 and the silicon oxide film 204, which have the function of uniformly flattening the surface, are etched back to expose the silicon substrate 201 in the element formation region to form an element isolation region. Then, a desired element is formed in the element formation region by a usual method. This method is an excellent element isolation method that can substantially eliminate the bird's beak as compared with the selective oxidation method.

[0005]

As described above, in the conventional groove filling separation, there is no fear of bird's beak generated by the selective oxidation method, but there is a flattening action as shown in FIG. Due to the characteristics of the resist 206, the recesses in the narrow groove 203a almost disappear and become flat, but in the wide groove 203b, the recesses are so large that they are hardly flat, and the recesses inevitably remain. Therefore, as shown in FIG. 10, the narrow trench 203a serving as the element isolation region is formed in the silicon oxide film 2
The trench 203b which is filled with 04 but has a wide width is formed by the silicon oxide film 2
Element isolation is performed without being filled with 04. On the other hand, in the semiconductor integrated circuit, the active element and the passive element are integrated on one semiconductor substrate, so that the elements must be properly separated. If the groove is not completely filled, the elements cannot be properly separated.

Therefore, as shown in FIG. 9, after applying a resist 206 having a flattening action, as shown in FIG. 11, the resist 206 is patterned so as to remain on the wider groove 203b. To do. Then resist 2
06 and the silicon oxide film 204 are etched back. By etching back in this manner, the groove 203 is almost completely removed.
a, 203b can be filled, but resist 206
There is a problem that the number of steps for patterning is increased.

Therefore, the present invention eliminates the above drawbacks,
Provided is a method for manufacturing a highly reliable semiconductor device in which a silicon oxide film is completely embedded in a groove portion of various widths which becomes an element isolation region, and element characteristics are not deteriorated.

[0008]

In order to achieve the above object, according to the present invention, a step of forming an oxidation resistant coating having a predetermined pattern on the main surface of a silicon substrate, and the oxidation resistant coating. A step of selectively removing the silicon substrate by using the mask as a mask to form a predetermined groove; and a step of oxidizing the silicon substrate surface of the groove by using the oxidation resistant coating as a mask to form a first silicon oxide film, After removing the oxidation resistant film, a step of forming a second silicon oxide film on the silicon substrate, and a step of etching back the silicon oxide film to expose a surface of the silicon substrate between the grooves. It is characterized by doing.

[0009]

In the above-described invention, when the silicon substrate is oxidized by using the oxidation resistant film as a mask to form the first silicon oxide film, as shown in FIG. The silicon oxide film 103 is grown thin and the recess remains. In the wide groove 103b, the first silicon oxide film 103 grows thick and almost fills the recess. After that, the second silicon oxide film 104 is further formed on the entire surface of the silicon substrate.
Are deposited to fill the recesses in the narrow groove 103a, flatten the surface, and etch back the silicon substrate. Can be embedded.

[0010]

Embodiments of the present invention will be described in detail with reference to FIGS.

First, as shown in FIG. 1, a silicon substrate 10 is used.
1 thin, for example, about 1000 to 2000 angstroms
A silicon nitride film 102 having a thickness of about 100 μm is formed. Furthermore, an oxidation resistant coating is formed using a well-known lithographic technique,
For example, the silicon nitride film 102 is formed in a predetermined pattern. The silicon nitride film 102 is for forming a groove at a position where an element isolation region is to be formed, and has windows 102a and 102b having a width corresponding to the element isolation region width.
Next, as shown in FIG. 2, the silicon nitride film 102 is used to etch the silicon substrate 101 to a desired depth,
For example, sputter etching is performed to form a plurality of grooves, for example, a narrow groove 103a and a wide groove 103b. Specifically, after forming the silicon nitride film 102 on one surface, the silicon nitride film 102 and the silicon substrate 101 are subjected to reactive sputter etching using the resist as a mask to cut the grooves 103a and 103b. For example, using CF ₄ gas, gas pressure 5 × 10 ⁻⁵ torr, RF input 0.5 W / c
m ² Etching is performed under the conditions of. Since the reactive particles collide perpendicularly with the sample interface and the etching proceeds due to the sputtering and the chemical reaction, there is no side etching and there is almost no inclination angle of the etching wall surface, and the groove is almost vertical. Next, as shown in FIG. 3, for example, 1 atm, 100
The silicon substrate is oxidized in oxygen and water vapor atmosphere at 0 ° C. for 5 hours. On the other hand, in FIG. 12, the vertical axis represents the film thickness of the first oxide film (field oxide film), and the horizontal axis represents the pattern.
It is a figure showing the width between the silicon nitride films turned into silicon. According to this, the larger the width between the silicon nitride films, that is, the wider the groove, the larger the film thickness of the first oxide film, and the smaller the width between the silicon nitride films, that is, the narrower the groove, the first The oxide film has a small thickness. From this, it is understood that the diffusion of the oxidant in the vertical direction is more active in the wide groove than in the narrow groove. From the above, in FIG. 3, the narrow groove 10 is formed.
At 3a, the first silicon oxide film 103 grows thin and a recess remains. In the wide groove 103b, the first silicon oxide film 103 grows thick and almost fills the recess.
Next, as shown in FIG. 4, the silicon nitride film 102 on the silicon substrate 101 is peeled and removed, and a second silicon oxide film 104 is further deposited on the entire surface of the silicon substrate 101 by the CVD method to form the narrow groove 103a. Fill the recess of
Make the surface flat. Next, as shown in FIG.
The second silicon oxide films 103 and 104 are etched back to expose the silicon substrate 101 in the element formation region to form an element isolation region. Then, a desired element is formed in the element formation region by a usual method.

As described above, in this embodiment, the silicon nitride film is directly formed as the oxidation resistant film, but a thin silicon oxide film may be interposed between the silicon substrate and this silicon nitride film. If stricter planarization is required, a resist may be applied on the silicon oxide film and then etched back.

[0013]

As described above, according to the present invention, the silicon oxide film can be completely filled in the trenches of various widths which become the element isolation regions of the silicon substrate. Therefore, it is possible to manufacture a highly reliable semiconductor device in which element characteristics are not deteriorated.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a semiconductor device according to an embodiment of the invention.

FIG. 2 is a diagram showing a manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 3 is a diagram showing a manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 4 is a diagram showing a manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 5 is a diagram showing a manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 6 is a diagram showing a manufacturing process of a conventional semiconductor device.

FIG. 7 is a diagram showing a manufacturing process of a conventional semiconductor device.

FIG. 8 is a diagram showing a manufacturing process of a conventional semiconductor device.

FIG. 9 is a diagram showing a manufacturing process of a conventional semiconductor device.

FIG. 10 is a diagram showing a manufacturing process of a conventional semiconductor device.

FIG. 11 is a diagram showing a manufacturing process of a conventional semiconductor device.

FIG. 12 is a graph showing the relationship between the film thickness of the first oxide film (field oxide film) and the width between the patterned silicon nitride films.

[Explanation of symbols]

101, 201 Silicon substrate 102 Silicon nitride film (oxidation-resistant film) 202 Mask material 102a, 202a Narrow window portion 102b, 202b Wide window portion 103 First silicon oxide film 103a, 203a Narrow groove 103b, 203b wide groove 203
Silicon oxide film 104 Second silicon oxide film 204 Silicon oxide film 206 Resist

Claims (1)

[Claims] 1. A step of forming an oxidation resistant film having a predetermined pattern on a main surface of a silicon substrate; and a step of forming a predetermined groove by selectively removing the silicon substrate using the oxidation resistant film as a mask. A step of forming, a step of oxidizing the silicon substrate surface of the groove using the oxidation resistant film as a mask to form a first silicon oxide film, and a step of removing the oxidation resistant film and then forming a first silicon oxide film on the silicon substrate. A method of manufacturing a semiconductor device, comprising: a step of forming a second silicon oxide film; and a step of etching back the silicon oxide film to expose a surface of the silicon substrate between the trenches.