JPH09153543A - Method of manufacturing trench separation structured silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the dishing of silicon dioxide and wafer surface by clarifying the terminal of chemical-mechanical polishing step of a silicon dioxide film for performing the precise polishing step. SOLUTION: A trench 12 is formed on a silicon wafer 11 surface to be coated with an SiO2 film 13 while filling up the trench 12 with a silicon dioxide film 15. Next, the whole surface is chemical-mechanical polished using abrasives containing cerium for flattening the SiO2 film surface. Furthermore, the SiO2 film 13 is polished using another abrasives containing fumed silica until the silicon surface is exposed. When the hydrophobic surface is exposed, the polishing step is terminated. Next, the finish polishing step is performed using a silicon abrasives containing amine. Through these procedures, the silicon wafer 11 wherein flat silicon surface developing no dishing and the separating part of chamfered silicon dioxide are formed can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an element isolation technique for semiconductor devices, and more particularly to a method for manufacturing a silicon wafer having a trench isolation structure.

[0002]

2. Description of the Related Art As a method of manufacturing a silicon wafer having a trench isolation structure, the following methods have been conventionally known. That is, as shown in FIG. 3, first, a desired groove 32 is formed on the surface of the silicon wafer 31 by etching. Next, a silicon dioxide film 33 is laminated to a predetermined thickness on the entire surface of this silicon wafer.
As a result, the trench 32 is filled with the silicon dioxide 33.
Further, the surface of the silicon dioxide film is formed with predetermined irregularities by the grooves 32. Then, the surface of the silicon dioxide film is polished by chemical mechanical polishing using cerium oxide as an abrasive to expose the surface of the silicon wafer 31. Silicon dioxide 33 is embedded in the groove 32 to insulate the silicon wafer.

However, in this method, since cerium oxide was used as the polishing agent, a phenomenon called so-called dishing of an oxide film occurred on the polishing surface. That is, the surface of the silicon dioxide film 33 in the trench 32 was formed as a shallow dish-shaped recess. Then, this dishing causes a disadvantage in the subsequent device formation.

Further, as disclosed in Japanese Patent Laid-Open No. 7-263537, a method of polishing with a cerium oxide-based polishing agent and then with a silica-based polishing agent has been proposed. However, in this method, there is a large difference between the polishing rate in the chemical mechanical polishing between silicon dioxide and silicon, so that a phenomenon called dishing occurs on the polished surface of silicon. That is, as shown in FIGS. 4 and 5, the trench 4 in which the silicon dioxide 43 is embedded is formed.
Between the two, the surface of the silicon 41 was formed in a shallow dish shape. Even in the case of this silicon dishing, the edge forms an acute angle, which causes inconvenience in the subsequent device formation. Further, there is a drawback that the surface of the silicon wafer is easily scratched.

Therefore, a manufacturing method as shown in FIG. 6 was devised. That is, when the trench 62 is formed on the surface of the silicon wafer 61, the silicon nitride film Si ₃ N ₄ 64 is deposited on the surface of the silicon wafer 61 separated by the trench 62. Then, the silicon dioxide film 63 for insulation separation was deposited on the surface of the silicon wafer 61 in this state. Then, the silicon dioxide film 63 was chemically mechanically polished to expose the surface of the silicon nitride film 64. Then, the silicon nitride film 64 is selectively removed by etching. As a result, a silicon wafer having a trench isolation structure on the surface can be formed.

[0006]

However, even the conventional method of manufacturing a silicon wafer having a trench isolation structure has the following drawbacks. First
In addition, the silicon nitride film Si ₃ N ₄ must be deposited on the surface of the silicon wafer after the trench is formed, and the number of steps has been increased. Secondly, the silicon nitride film Si ₃ N ₄ does not function sufficiently as a stopper in chemical mechanical polishing. It was difficult to judge whether the nitride film was exposed on the surface, and the oxide film remained on the surface in some cases. It is difficult to judge whether SiO ₂ on silicon (on Si ₃ N ₄ ) could be completely removed on the entire surface of the silicon wafer. Third, silicon nitride film Si
_It takes time to remove (etch) ₃ N ₄ .

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to reduce the number of steps in manufacturing a silicon wafer having a trench isolation structure. Another object of the present invention is to clarify the end point in chemical mechanical polishing and perform accurate polishing. Another object of the present invention is to prevent the occurrence of dishing on the surfaces of the silicon dioxide film for separation and the silicon wafer. Still another object of the present invention is to easily determine the end of removal of the silicon dioxide film.

[0008]

The invention according to claim 1 is a method of manufacturing a silicon wafer having a trench isolation structure in which a trench is formed on the surface of the silicon wafer and an insulating film is buried in the trench. A step of forming a trench on the surface of the silicon wafer, a step of covering the surface of the silicon wafer with an insulating film, a step of covering the surface of the insulating film after covering with the insulating film, and a step of forming the silicon wafer Is a method for manufacturing a silicon wafer having a trench isolation structure, comprising: a step of polishing the surface of the insulating film until the surface of is exposed; and a step of finish polishing the surface of the insulating film and the surface of the exposed silicon wafer.

[0009]

According to the first aspect of the invention, in a silicon wafer having a trench formed on the surface thereof, the trench is filled with a silicon dioxide film (insulating film) and the surface of the silicon wafer is covered with the SiO ₂ film. Then, the surface of this SiO ₂ film is flattened. For example CeO
Chemical mechanical polishing is performed using an abrasive containing ₂ (cerium oxide). In addition, an SiO ₂ is used until the silicon surface is exposed, for example using an abrasive containing fumed silica.
Polish the film. In this case, the end point of polishing can be easily determined by exposing the hydrophobic silicon surface. Further, thereafter, finish polishing is performed using a silicon abrasive containing amine. As a result, a silicon wafer having a trench isolation structure in which a flat silicon surface and a silicon dioxide isolation portion with rounded corners are formed without dishing can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for manufacturing a silicon wafer having a trench isolation structure according to the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the flow of the manufacturing process. FIG. 2 is a diagram schematically showing the surface of the manufactured silicon wafer having a trench isolation structure by AFM measurement.

As shown in FIG. 1, first, a trench 12 having a predetermined width and a predetermined depth is formed at a predetermined position on a surface of a silicon wafer 11 by using a predetermined photolithography process (A). Next, the surface of the silicon wafer is covered with the silicon dioxide film 13. The trench 12 is filled with the silicon dioxide film 13, and the silicon wafer 11 is formed.
The entire surface of is covered with a silicon dioxide film 13 having a predetermined thickness (B). And this silicon dioxide film 1
The surface of 3 is processed flat (C). Chemical mechanical polishing is performed using an abrasive containing CeO ₂ (cerium oxide).

Further, thereafter, the flat silicon dioxide film 13 is polished by using a polishing agent containing fumed silica to expose the surface of the silicon wafer 11 (D). The end point of the chemical mechanical polishing in this case can be easily determined by the exposure of the hydrophobic silicon surface. Then, the surface of the wafer is subjected to final polishing using a silicon abrasive containing amine. As a result, a silicon wafer having a trench isolation structure in which a flat silicon surface without dishing and a silicon dioxide isolation portion with rounded corners are formed can be obtained (E).

Further, FIG. 2 schematically shows the surface structure of the silicon wafer having the trench isolation structure polished as described above. This figure shows the measurement results of the surface flatness with an AFM (atomic force microscope). As shown in this figure, the silicon dioxide portion (insulation isolation portion) embedded in each trench has rounded corners.

[0014]

According to the present invention, the number of steps can be reduced in manufacturing a silicon wafer having a trench isolation structure. In addition, the end point in chemical mechanical polishing can be clarified and accurate polishing can be performed. Further, it is possible to prevent the occurrence of dishing on the surface of the separating silicon dioxide film and the silicon wafer. further,
When removing the silicon dioxide film by polishing, it is possible to easily judge the end of polishing.

[Brief description of the drawings]

FIG. 1 is a process sectional view for explaining a method for manufacturing a silicon wafer having a trench isolation structure according to an embodiment of the present invention.

FIG. 2A is a view for explaining a method for manufacturing a silicon wafer having a trench isolation structure according to an embodiment of the present invention.
It is a schematic diagram which shows an FM measurement result.

FIG. 3 is a cross-sectional view for explaining a conventional method for manufacturing a silicon wafer having a trench isolation structure.

FIG. 4 is a cross-sectional view for explaining another method of manufacturing a silicon wafer having a conventional trench isolation structure.

FIG. 5 is a cross-sectional view showing a part of FIG. 4 in an enlarged manner.

FIG. 6 is a cross-sectional view for explaining still another method of manufacturing a silicon wafer having a conventional trench isolation structure.

[Explanation of symbols]

 11 silicon wafer, 12 trench, 13 silicon dioxide film (insulating film).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinsuke Sakai 1-5-1 Otemachi, Chiyoda-ku, Tokyo Sanryo Material Silicon Co., Ltd. (72) Inventor Keisuke Fujimoto 1-5 Otemachi, Chiyoda-ku, Tokyo No. 1 Sanritsu Material Silicon Co., Ltd. (72) Inventor Kei Komatsu 1-5-1, Otemachi, Chiyoda-ku, Tokyo Sanritsu Material Silicon Co., Ltd.

Claims (1)

[Claims] 1. A method of manufacturing a silicon wafer having a trench isolation structure in which a trench is formed on the surface of the silicon wafer and an insulating film is buried in the trench, the method comprising the step of forming a trench on the surface of the silicon wafer. The step of coating the surface of this silicon wafer with an insulating film, the step of planarizing the surface of this insulating film after coating with this insulating film, and the step of polishing the surface of the insulating film until the surface of this silicon wafer is exposed. And a step of finish polishing the surface of the insulating film and the exposed surface of the silicon wafer, and a method of manufacturing a silicon wafer having a trench isolation structure.