JPS6231139A - Method for filling insulating isolation groove - Google Patents

Abstract

PURPOSE:To reduce the cost and to improve the yield of wafers by omitting the mechanical polishing step by a method wherein a silicon-rich surface layer is formed on the surface of an oxide film on the bottom of an U-shaped groove and this U-shaped groove is filled by the preferential growth of silicon on said surface layer. CONSTITUTION:A substrate 1 on which an U-shaped groove 3 is to be formed is coated with an oxide film 4 and a resist film 6 on which the groove is to be opened is laminated. Silicon ions are projected to the bottom of the groove 3 by ion implantation. Consequently, a silicon-rich surface layer 7 is formed on the oxide film 4. After removing the resist film 6, gas-phase growth of silicon is made by hydrogen reduction technique using trichlorosilane. As a result, the groove 3 is filled with poly-silicon 8 and on the surface of other parts of the substrate 1, silicon does not grow. Thus, a mechanical polishing step can be omitted and the reduction of cost and the improvement in yield of wafers can be attained.

Description

[Detailed Description of the Invention] [Summary] The U-groove insulation isolation method is used as one of the methods for electrically isolating each element of a semiconductor integrated circuit. We used a selective silicon growth method to simplify the process.

[Industrial application field]

The present invention relates to an improved method for burying U-shaped isolation trenches.

2. Description of the Related Art In manufacturing semiconductor integrated circuits, methods such as a PN junction separation method and an insulating layer separation method are used to separate each element formed on a substrate.

Among these, the U-shaped insulation isolation method has good isolation characteristics and is often used to manufacture integrated circuits with a high degree of integration.
In order to fill the grooves with polysilicon, it is necessary to mechanically polish the entire surface of the substrate using a wet method, which has poor workability and requires improvement.

[Conventional technology]

The steps of a conventional U-shaped insulation separation method will be outlined with reference to drawings.

An insulating film 2 is laminated on a silicon substrate 1 (including an epitaxial growth layer, etc.), and a 0-shaped groove 3 is formed by the RIE method. The insulating film may be a single layer of SiO□ film, but SiO□
In some cases, two layers, a film and a Si 3 N m film, are laminated.

An oxide film 4 is also grown on the inner surface of the U-shaped groove by thermal oxidation. This is shown in FIG. 2(a).

Silicon is grown on the substrate in this state by vapor phase growth.

In this case, polysilicon grows on the insulating film, so
A polysilicon layer 5 is grown over the entire surface and fills the U-shaped groove. This is shown in FIG. 2(b).

Next, unnecessary polysilicon layers other than the polysilicon in the U-shaped trench are polished away, and a thermal oxidation process is further performed to complete the U-shaped isolation trench. This is shown in FIG. 2(C).

[Problem that the invention seeks to solve]

In the conventional method described above, the polysilicon layer deposited on the insulating film is planarized by mechanical polishing.

Since a silicon etching solution is used during polishing, it is a wet process, which not only increases the number of steps but also poses a risk of contamination, resulting in a decrease in wafer yield.

Further, depending on the conditions of silicon vapor phase growth, there are cases in which a recess is formed in the U-shaped groove region and the surface after polishing is not flattened.

[Means for solving problems]

The problem mentioned above is that after the substrate on which the U-shaped groove is formed is coated with an oxide film and the resist film that opens the U-shaped groove is laminated, silicon-rich material is formed on the surface of the oxide film at the bottom of the U-shaped groove. The problem is solved by the method of the invention, which consists of forming a surface layer and then performing selective growth of silicon on the surface layer to fill the U-shaped trench.

The above-mentioned silicon-rich surface layer can be formed by implanting silicon ions into the oxide film at the bottom of the U-shaped groove, or alternatively, by sputter etching with argon. You can.

[Effect]

The vapor phase growth of silicon is significantly influenced by the source gas and the surface condition of the growing surface.

By making the insulating film at the bottom of the U-shaped groove silicon-rich, the growth of silicon in this region is significantly promoted compared to other insulating films, filling the U-shaped groove. Polysilicon does not grow on other insulating films. Therefore, the polishing step can be omitted.

〔Example〕

The present invention applies the technique of selective vapor phase growth of silicon on an insulating film to the U-shaped groove insulation isolation method. A separate application has been filed.

An embodiment of the present invention will be explained in detail with reference to FIG. Descriptions of items that are the same as those will be omitted.

Using the above substrate, a resist film 6 is laminated except for the opening of the U-shaped groove. This is shown in FIG. 1(a).

Next, the bottom of the 0-shaped groove 3 is irradiated with silicon ions by an ion implantation method. Ion implantation is approximately 30KeV
, the dose amount is 5×10167 CII+2.

This forms a silicon-rich surface layer 7 on the oxidized top. This is shown in FIG. 1(b).

Next, vapor phase growth of silicon is performed by a hydrogen reduction method using trichlorosilane from which the resist film 6 has been removed.

Growth is performed under reduced pressure conditions and at a temperature of 800°C.

S i HC13+ Hz→Si↓+HCI ↑Thus, as shown in FIG. 1(C), the 0-shaped trench 3 is filled with polysilicon 8, and silicon does not grow on the other substrate surfaces.

In addition to the above-mentioned silicon ion implantation method, sputter etching using argon can also be applied to form a silicon-rich surface layer.

This method involves bombarding the bottom of the U-shaped groove with argon ions to expel (sputter) oxygen atoms on the surface of the oxide film to form a silicon-rich surface layer.

The steps after FIG. 1(C) are unchanged from the conventional method.

〔Effect of the invention〕

As explained above, by applying the method of the present invention, it is possible to omit the conventional mechanical polishing process, which greatly contributes to cost reduction and improvement of wafer yield.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(e) are step-by-step cross-sectional views illustrating the method of burying a U-shaped insulation isolation trench according to the present invention, and FIG. 2(a)
-[0] are process-sequential sectional views illustrating a conventional method for burying a U-shaped insulation isolation trench. In the drawings, 1 is a silicon substrate, 2 is an insulating film, 3 is a U-shaped groove, 4 is an oxide film, 5.8 is a polysilicon layer, 6 is a resist film, and 7 is a silicon-rich surface layer. @ 1 Figure 2m

Claims (3)

[Claims] (1) After covering the substrate on which the groove (3) is to be formed with an oxide film (4) and laminating the resist film (6) that opens the groove, a silicon-rich surface is formed on the surface of the oxide film at the bottom of the groove. layer (7
) and then selectively growing silicon on the surface layer. (2) The method for burying an insulation isolation trench according to claim (1), wherein the silicon-rich surface layer is formed by silicon ion implantation. (3) The method for burying an isolation trench according to claim (1), wherein the silicon-rich surface layer is formed by argon sputter etching.