Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
1998-12-09
2001-05-29
Mills, Gregory (Department: 1763)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C216S089000
Reexamination Certificate
active
06239032
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polishing method using chemical mechanical polishing (CMP), and more particularly to a polishing method suitable for use in the manufacture of semiconductor devices.
In association with the recent trend toward the high integration and miniaturization of semiconductor devices, various kinds of fine structure working technology are being researched and developed in the field of the manufacture of semiconductor devices. Among the various kinds of technology, the CMP technology can be used for many purposes, such as the flattening of the interlayer insulation film, the formation of plugs, the formation of buried metal wiring, and buried isolation of elements. The CMP technology, required for executing these, is now essential technology.
In the manufacture of semiconductor devices, there is a demand for a reliable process in which a silicon nitride film is polished using CMP, with a silicon oxide film used as a stopper. If such a process is available, it can be applied to the buried isolation of elements, the formation of a self-aligned contact, etc., thus enabling the fabrication of devices that are reliable and have high performance. However, in the case where conventional slurry is used, the ratio (selection ratio) of the polishing rate of a silicon nitride film to that of a silicon oxide film is smaller than 1. In this case, the process described above cannot be put to use.
As a method for realizing the above-described process, it is thought to prepare slurry by dispersing silica particles (polishing particles) in water and adding phosphoric acid to the water. The use of such slurry is proposed in Jpn. Pat. Appln. KOKAI Publication No. 6-124932. According to the method shown in this publication, it may be able to set the selection ratio to be larger than 1.
However, even when the method of KOKAI publication No. 6-124932 is used, it is hard to set the selection ratio to be sufficiently large. In particular, in the case of a fine pattern of 0.2 &mgr;m or less, the substantial selection ratio is inevitably small.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above problems, and is intended to provide a polishing method that can provide a sufficiently large selection ratio even in the case of a fine pattern.
According to one polishing method provided by the present invention, a silicon nitride film formed on a silicon oxide film is selectively polished with reference to the silicon oxide film in a chemical mechanical polishing process, the chemical mechanical polishing process using slurry containing a phosphoric acid and silica whose particle diameter is less than 10 nm, or slurry containing a phosphoric acid derivative and silica whose particle diameter is less than 10 nm.
Another polishing method provided by the present invention comprises the steps of: forming a silicon nitride film on a base layer, which has a silicon oxide film and a depression, such that the depression of the base layer is filled with the silicon nitride film; and selectively polishing the silicon nitride film with reference to the silicon oxide film, using the silicon oxide film as a stopper, so as to selectively remain the silicon nitride film inside the depression, the silicon nitride film being polished in a chemical mechanical polishing process that uses slurry containing a phosphoric acid and silica whose particle diameter is less than 10 nm, or uses slurry containing a phosphoric acid derivative and silica whose particle diameter is less than 10 nm.
The ratio (selection ratio) of the polishing rate of a silicon nitride film to that of a silicon oxide film can be set to be larger than 1 by using slurry containing both a phosphoric acid (or its derivative) and silica (which is mainly formed of SiO
2
and serves as polishing powder). In actuality, however, a sufficiently large selection ratio cannot be easily attained, as described above. According to the present invention, silica whose particle diameter is less than 10 nm is used, and use of such silica enables the selection ratio to be sufficiently large in practice.
In particular, in the case of a highly-integrated fine pattern wherein the width of a depression (such as a trench) is 0.2 &mgr;m or less, the effect to make the selection ratio large is remarkably available according to the present invention. In the case of such a fine pattern, therefore, the silicon nitride film is polished, with the silicon oxide film as a stopper. With the polishing executed in this manner, the depression can be reliably filled with the silicon nitride film.
As described above, according to the present invention, the silicon nitride film can be polished with a sufficiently large selection ratio even in the case of a fine pattern. By applying the present invention to a semiconductor device-manufacturing process, it is possible to provide high-performance and reliable semiconductor devices.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5770095 (1998-06-01), Sasaki et al.
patent: 5783489 (1998-07-01), Kaufman et al.
patent: 6077773 (2000-06-01), Lin
patent: 6-124932 (1994-05-01), None
Nakamura Kenro
Yano Hiroyuki
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Mills Gregory
Powell Alva C
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