JPH0658905B2 - Fine pattern forming method - Google Patents

Description

The present invention relates to a method for forming a fine pattern by etching a region not covered with a mask material in forming a semiconductor element.

[Prior art and its problems]

In recent years, with the high integration of semiconductor devices, fine pattern formation has made remarkable progress by improving lithography technology and dry etching technology. For example, Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.) Vol. 15, 1978.
On pages 319 to 326, it is reported that it is possible to form a silicon oxide winding pattern having a vertical cross-sectional shape that does not change the mask pattern width by reactive sputter etching with carbon tetrafluoride gas. Not only this example, but in reactive sputter etching, not only a silicon oxide film but also an insulator, a semiconductor, a metal, etc. can be processed in accordance with the mask size by appropriately selecting an etching gas and etching conditions. On the other hand, in the lithography technique, instead of the conventional light projection exposure method, the development of ultraviolet light reduction projection exposure, X-ray exposure, and electron beam exposure technology has made it possible to control the line width of submicron resolution.

However, even if the above-mentioned exposure technique is used, the shape of the pattern end is rounded, which causes a problem in forming a fine rectangular pattern.

For example, when the reticle pattern 21 as shown in FIG. 2A is transferred onto the substrate by the ultraviolet light reduction projection exposure method, it is transferred at the corner portion of the resist pattern 22 as shown in FIG. 2B. The corners of the resist pattern are rounded. Such a phenomenon is not limited to light exposure, and is an unavoidable problem to some extent in X-ray exposure and electron beam exposure, and is caused by the diffraction phenomenon of irradiation rays. If the resist pattern has a shape as shown in FIG. 2 (b), if anisotropic etching is used, the resist pattern is etched according to the resist pattern, which hinders the formation of a fine semiconductor element.

[Object of the Invention]

It is an object of the present invention to provide a method for forming a fine pattern having a rectangular shape by eliminating roundness at a pattern corner portion during fine pattern processing in forming a semiconductor element.

[Structure of Invention]

The present invention provides a fine pattern for anisotropically etching a substrate or a film deposited on a substrate by forming a mask pattern on the substrate or a film not deposited by the mask pattern using an exposure technique. In the pattern forming method, the mask material is anisotropically etched with a first resist pattern for forming two opposite sides of a rectangular mask pattern, and then a second side for forming two sides intersecting the two sides. The mask material is anisotropically etched with the resist pattern described in 1. above, and the rectangular mask pattern obtained is used to anisotropically etch an uncoated substrate or a film deposited on the substrate to form a rectangular pattern. I am trying.

[Detailed description of configuration]

The present invention has solved the problems of the prior art by adopting the above configuration. According to the present invention, when a mask pattern used for anisotropically etching a substrate or a film deposited on the substrate is formed, a first resist pattern for forming two opposing sides is used. Anisotropic etching is performed, and then second anisotropic etching is performed using a second resist pattern for forming two sides that intersect the two sides. By this procedure, it is possible to suppress a so-called corner drop phenomenon in which the mask pattern corner portion is rounded. By using the mask pattern obtained in this way to anisotropically etch the substrate or the film actually deposited on the substrate by reactive ion etching, it is possible to form a rectangular pattern without rounding at the pattern corners. Becomes Therefore, even if the pattern is miniaturized, the pattern corner portion can be formed while keeping the rectangular shape.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view showing a cross section or a front structure in a main manufacturing process for explaining an embodiment in which a fine groove type element isolation region is formed by using the method of the present invention.

In this embodiment, first, a 6000 Å silicon oxide film 2 is formed on a p-type silicon substrate 1 having a (100) plane orientation by thermal oxidation, and then a first resist pattern 3 is formed in a stripe shape. When the silicon oxide film 2 is subjected to reactive ion etching using as a mask, the structures shown in FIGS. 1 (a1) and (a2) are obtained. Next, after removing the first resist pattern 3, the second resist pattern 4 is formed in a stripe shape in a direction intersecting with the pattern of the silicon oxide film 2 to form the structure of FIGS. 1 (b1) and (b2). obtain. Next, the silicon oxide film 2 is reactively etched again using the second resist pattern 4 as a mask, and the second resist pattern 4 is removed.
A rectangular silicon oxide film pattern as shown in 2) is obtained. As described above, in the rectangular silicon oxide film pattern as the mask pattern obtained by the above procedure, the corner dropping phenomenon is suppressed, and therefore the pattern corner portion maintains the rectangular shape. Next, the silicon substrate 1 is reactively ion-etched using this silicon oxide film pattern as a mask to form a silicon groove 5 having a depth of 3 μm, and the silicon oxide film 2 is removed, as shown in FIGS. 1 (d1) and (d2). Get the structure. On the silicon substrate 1 having the groove obtained by the above procedure, a thermal oxide film 6 of about 1000Å is formed on the surface, and then a silicon nitride film 7 of about 500Å is deposited by the low pressure CVD method, and then the low pressure CVD method. By depositing the polycrystalline silicon film 8 until the trench is filled with, the structure shown in FIG. 1 (e) is obtained. Next, the polycrystal silicon film 8 is etched back so that it remains only in the region of the groove 5, and the surface of the polycrystal silicon embedded in the groove is oxidized to form the SiO ₂ layer 9, and the CVD silicon nitride on the surface of the silicon substrate is formed. When the film 7 and then the silicon oxide film 6 are removed, a substrate having the structure shown in FIG. 1 (f) is obtained. By such a procedure, an element isolation region that hardly changes the mask size was formed.

As described above, according to the present embodiment, since the fine groove type element isolation region can be formed while maintaining the rectangular shape, it is possible to avoid the reduction of the area of the device active region.

In the above examples, the mask pattern is formed on the silicon substrate. However, when a film such as an insulator or a conductor is deposited on the substrate, the method of the present invention is used for anisotropic etching of the film. Of course, it can be applied.

[Effects of the Invention] As described above, according to the present invention, when a mask pattern is formed, first anisotropic etching is performed using a first resist pattern for forming two opposite sides, Next, since the second anisotropic etching is performed by the second resist pattern for forming the two sides intersecting with the above two sides, a mask pattern without roundness at the corner portion is obtained, which results in a rectangular shape. It became possible to form a fine pattern having a shape.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view or front view showing a manufacturing method for forming a groove type element isolation region in an embodiment of the present invention, and FIG. 2 is a transfer of a reticle pattern and a resist pattern using a conventional method. It is a schematic diagram which shows change. 1 ... Silicon substrate 2, 6 ... Silicon oxide film 3 ... First resist pattern 4 ... Second resist pattern 5 ... Silicon groove 7 ... CVD silicon nitride film 8 ... CVD polycrystalline silicon film 9 ...... SiO ₂ layer obtained by oxidizing polycrystalline silicon 21 ...... Reticle pattern 22 ...... Resist pattern

Claims (1)

[Claims] 1. A mask pattern is formed on a substrate or a film deposited on the substrate by using an exposure technique, and the substrate not covered by the mask pattern or the film deposited on the substrate is anisotropically etched. In the fine pattern forming method, the mask material is anisotropically etched by a first resist pattern for forming two opposite sides of a rectangular mask pattern, and then a second side for forming two sides intersecting the two sides is formed. Anisotropic etching of the mask material with the resist pattern of No. 2 and anisotropic etching of the uncoated substrate or the film deposited on the substrate with the resulting rectangular mask pattern to form a rectangular pattern. A characteristic fine pattern forming method.