JP2000114362A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation in shape due to wet etching during a device process, by filling element isolation trenches partway in the direction of the depth of the trenches by SOG, and filling the upper part of the trenches with an oxide film by CVD when the trenches are filled with an oxide film. SOLUTION: A SiO2 film 2 is formed on a Si substrate 1 by thermal oxidation, and a SiN film 3 is formed on the SiO2 film 2. The SiN film 3, SiO2 film 2, and Si substrate 1 are anisotropically etched, respectively, to form isolating trenches. An SiO2 film 4 is formed in the trenches, a SOG solution is then applied, and the trenches are filled by SOG partway in the direction of the depth of the trenches to form a SOG film 5. Subsequently, the upper part of the interior of the trenches is subjected to CVD at a high a temperature as 800 deg.C or so using silane gas, an HTO film 6 forming an oxide film is thereby formed, and the trenches are filled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device having a trench isolation step, and more particularly to a method of manufacturing a semiconductor device improved so as to obtain a good trench isolation shape.

[0002]

2. Description of the Related Art In a method of manufacturing a semiconductor device according to the present invention, obtaining a good trench isolation shape is one of the important factors.

[0003] For this purpose, there is a method using HDP-CVD as a method for obtaining a trench buried oxide film having a film quality close to that of a thermal oxide film, usually having a relatively good burying property. However, in this method, the trench isolation width 20
When a trench having a high aspect ratio of not less than 0 nm and an aspect ratio of 3 or more is buried, a sufficient burying property cannot be obtained as shown in FIG. 5, resulting in deterioration of element isolation characteristics.

As a method of forming an oxide film with good burying property, there is a method of forming an oxide film using SOG as a coating film. According to this method, a trench having a high aspect ratio as described above can be buried, but there is a drawback that a large step is generated between the trench and other portions as shown in FIG.

Further, Japanese Patent Publication No. 7-077231 discloses a trench isolation method for a semiconductor device.
In this known method, in order to bury a trench having a large aspect ratio without a gap, an underlying oxide film,
After the nitride films are grown, trench patterns are opened in those films, trenches are excavated using the nitride film as a mask, and after oxidizing the trench surface, SOG is applied and etched back, and SOG fills the trench to near the trench surface. Structure. Thereafter, an HTO film having good wet etching resistance is grown by CBD, an oxide film and a nitride film provided at an initial stage are removed, and the substrate surface is oxidized, whereby a substrate having a trench isolation and a small step is obtained.

[0006]

However, since the SOG film has poor wet etching resistance, the SOG film is largely etched as shown in FIG. 3 by a wet etching step in a device process, and the shape of the trench isolation deteriorates. Adversely affect The SOG film is a film containing a large amount of impurities such as metal, and if the SOG film is exposed on the trench surface, there is a possibility that the SOG film has a bad influence on a gate oxidation step and the like.

A main object of the present invention is to provide a method of manufacturing a semiconductor device for forming a trench isolation having good burying properties.

Another object of the present invention is to provide a method of manufacturing a semiconductor device having high process stability by forming a trench isolation having high etching resistance.

[0009]

A feature of the present invention is that in an embedding step of trench element isolation, an oxide film using SOG is formed halfway in the depth direction of the trench, and the upper portion of the trench is embedded by a CVD method. It is to be formed by an oxide film.

In other words, in the manufacturing method according to the present invention, when burying with an oxide film for separating the trench elements, burying with SOG is performed halfway in the depth direction of the trench.
The upper part of the trench is made of SiO ₂ as an oxide film by CVD.
The filling is performed by a film, for example, an HTO film.

By burying the upper part of the trench by using SOG in this way, it becomes easy to bury the trench having a high aspect ratio, and the burying of the upper part of the trench can be performed with a film quality, in particular, an HTO film or the like having good wet etching resistance. By using a CVD film, a role of preventing shape deterioration due to wet etching during a device process can be achieved.

Therefore, an effect is obtained that trench isolation having good burying property and high process stability can be realized even in a trench having a high aspect ratio.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings. 1 (a) to 4 (j) are cross-sectional views showing the steps in an embodiment of the present invention.

First, a Si substrate 1 is formed on a Si substrate 1 by thermal oxidation.
The O ₂ film 2 is formed with a thickness of, for example, 10 nm, and the SiN film 3 is formed with a thickness of, for example, 150 nm by a CVD method.
Then, using a lithography process, the SiN film 3, SiO 2
_{2 The} film 2 and the Si substrate 1 are respectively etched by anisotropic etching, and trenches for trench isolation are formed,
m and a depth of 500 nm (FIG. 1A).

In order to reduce etching damage,
SiO inside the trench by thermal oxidation _TwoForm the film 4
(FIG. 1 (b)).

Then, an SOG solution is applied, for example, 400
The baking is performed at a temperature of about 100 ° C. to form the SOG film 5 (FIG. 2).
(C)). Since the SOG film 5 is formed by applying the solution as described above, the SOG film 5 can be formed with a good burying property even in a trench having a high aspect ratio as in this example. Then S
The SOG film 5 is etched back by anisotropic dry etching to a depth of about 100 nm from the i-substrate surface (FIG. 2D).

Next, the upper 100 nm of the trench is
By performing CVD at a high temperature of about 800 ° C. using a silane-based gas to form an oxide film, a so-called HTO film 6 having a thickness of 200 nm is filled (FIG. 2E). .

The HTO film 6 is known to have high wet etching resistance and to be hardly mixed with metal impurities and the like. Then, extra HT on SiN is formed by CMP.
The O film 6 is removed (FIG. 3F).

Next, Si is wet-etched.
The N film 3 and the SiO ₂ film 2 are removed (FIG. 3G), and a SiO ₂ film 7 serving as a mask for ion implantation for forming a well or a channel is formed by thermal oxidation (FIG. 3H). Although it is omitted for simplicity, after forming a well and a channel by ion implantation, the SiO ₂ film 7 is removed by wet etching (FIG. 4 (i)), and a gate SiO ₂ film 8 is formed by thermal oxidation. A gate electrode 9 is formed of polysilicon by the method (FIG. 4 (j)).

Thereafter, patterning of the gate electrode is performed by a known method, source / drain is formed, and a MOS device is formed through a wiring process.

In such a manufacturing method, the lower portion of the trench is buried with SOG, and the upper portion is, for example, H
Since the trench is buried with the TO film, the trench having a high aspect ratio as in this example can be buried well, and the trench is reduced in the thickness of the trench oxide film during the process because it is covered with the HTO film having high wet etching resistance. Small, so that a good trench shape can be obtained. Furthermore, SOG
Is capped, so that the effect of preventing impurities in the SOG from affecting the gate oxidation step and the like can be prevented. Thereby, a film having high wet etching resistance can be formed.

In the above embodiment, a so-called LTO film having a lower growth temperature may be used in place of the HTO film, if high wet etching resistance can be obtained. In plasma CVD, HDP (High Density)
It is known that a film having high wet etching resistance can be obtained from an oxide film formed by plasma (CVD) CVD.
This may be used instead of O. Furthermore, the SOG film
Inorganic SOG or organic SOG may be used.
(Hydrogen-Silsesquioxane) may be used.

[0023]

As described above, in the method of manufacturing a semiconductor device according to the present invention, by burying the upper portion of the trench using SOG, it becomes easy to bury the trench having a high aspect ratio. In addition, by filling the upper portion of the trench with a film quality, particularly a CVD film such as an HTO film having good wet etching resistance, it plays a role of preventing shape deterioration due to wet etching in a device process.

Therefore, an effect is obtained that a trench isolation having a good filling property and a high process stability can be realized even in a trench having a high aspect ratio.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views illustrating a process according to an embodiment of the present invention.

2 (c) to 2 (e) are process cross-sectional views of a process performed after the process of FIG. 1 (a).

3 (f) to 3 (h) are process cross-sectional views of a process performed after the process of FIG. 2 (e).

FIGS. 4 (i) and (j) are process cross-sectional views of a process performed after the process of FIG. 3 (h).

FIG. 5 is a cross-sectional view showing a trench buried oxide film obtained by a conventional method.

FIG. 6 is a cross-sectional view showing a trench buried oxide film obtained by another conventional method.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Si substrate 2 SiO ₂ film 3 SiN film 4 SiO ₂ film 5 SOG 6 HTO film 7 SiO ₂ film 8 Gate SiO ₂ film 9 Gate electrode

Claims (3)

[Claims] In a method of manufacturing a semiconductor device having a trench isolation shape, when embedding with an oxide film for isolating a trench element, the SO is partially inserted in the depth direction of the trench.
A method of manufacturing a semiconductor device, comprising: burying with G, and burying an upper part of a trench with an oxide film. 2. The method according to claim 1, wherein the oxide film on the trench is HTO.
The method according to claim 1, which is a membrane or an LTO membrane. 3. The method according to claim 1, wherein the SOG film is an inorganic SOG film, an organic SOG film.
The method according to claim 1, which is an OG film or an HSQ (Hydrogen-Silsesquioxane) film.