JPH0219970B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming fine rectangular patterns with high precision.

In a method for forming a rectangular pattern on a substrate to be etched, a positive photosensitive resin film is usually used for microfabrication in which the pattern width is 2 to 3 μm or less. As an exposure method for this positive photosensitive resin, a projection exposure method using a lens, such as a step-and-repeat method, which provides high resolution and high yield, is used.

In the projection exposure method, as shown in FIG. 1, light beams that have passed through a mask 1 are imaged through an X-ray lens 2 onto a photosensitive resin film 4 on a substrate 3 to be etched. However, since this method uses the lens 2, light is diffracted at the edge of the mask pattern, and as the pattern width becomes finer, the contrast between the light irradiated area and the thinner area deteriorates. In other words, the amount of light at the irradiated area is reduced, and the light also goes around the mask and the hidden area. In particular, in the case of a rectangular pattern, the defects occur from four sides, and the influence from the four sides causes a large deterioration in the irradiation amount. Therefore, it is necessary to increase the irradiation dose to form a fine rectangular pattern. However, as the irradiation amount increases, the amount of radiation that goes around the soles also increases.

These inconveniences will be explained with reference to FIG. When the irradiation amount is increased as described above, the photosensitive resin film 4a is formed in the fine pattern forming area 5 as shown in FIG. 2(A).
The amount of remaining film is reduced. When the substrate 3 to be etched is etched by a so-called dry etching method such as a sputtering method in such a state, the photosensitive resin 4a with a small residual amount and small pattern size is also etched, and the etched portion 8 becomes the desired shape. Mo4a
The shape of the etched portion 8 of the substrate to be etched, which is etched using the mask, also deteriorates. (Figure 2B). Also,
As is clear from FIG. 2(C), the accuracy at the corners of the etched portion 8, which should originally be a rectangular pattern, was not bad, and there was also a drawback that the corners were circular.

The present invention has been made in view of the above drawbacks.
The present invention provides a method for forming fine rectangular patterns with high precision using a projection exposure method.

That is, in the present invention, after forming a first layer having a first pattern on a film to be etched or a substrate to be etched, a photosensitive resin film is formed to be thicker than the first layer. After performing light irradiation using a mask having a second pattern that at least partially overlaps with the pattern, and removing the photosensitive resin film and the first layer in the overlapping portion of the first pattern and the second pattern,
This method is characterized by forming a rectangular pattern on the etched film.

Hereinafter, the present invention will be explained in detail using the drawings.

3, 4, and 5 are plan and sectional views of steps showing an embodiment of the present invention. Incidentally, predetermined cross sections corresponding to the plane of FIG. 3 are shown in FIGS. 4 and 5.

First, an insulating film 1 such as SiO ₂ is deposited on a semiconductor substrate 10.
A first pattern 12 of a first layer such as a polycrystalline silicon film or aluminum is formed on the substrate to be etched on which the pattern 1 has been formed (FIGS. 3, 4 and 5A). Next, an amount of positive photosensitive resin 13 is formed on the entire surface to be thicker than the first layer (FIGS. 3, 4, and 5B).
Next, the photosensitive resin film 13 is irradiated with light by a projection exposure method using a mask 16 shown in FIG. Do this. The amount of light irradiation is sufficient so that the first pattern 12 and the photosensitive resin film 13' on the intersections are removed in a subsequent development process. Next, by a development process, the resin films 13 and 13' located above the surface of the pattern 12 are removed to expose only the first layer 12 at the intersections, and the insulating film 11 of the substrate to be etched is covered with the resin films 13 and 13'. A part 13a of the resin film 13 is left on the pattern 12, leaving the photosensitive resin film 13.
(Figures 3, 4, and 5 C).

Thereafter, the exposed portion of the first pattern 12 is etched to form an opening 17 and expose a portion of the insulating film 11 (FIGS. 3, 4, and 5D). Next, the insulating film 11 of the substrate to be etched is etched using the remaining first pattern 12 and photosensitive resin film 13 as an etching mask, and then the first pattern 12 and photosensitive resin film 13 are removed. Then, a predetermined opening rectangular pattern 18 is formed (FIGS. 3, 4, and 5E).

According to the above method, two sides of the pattern for forming the rectangular pattern 19 are the first pattern 12 and the other two sides are the photosensitive resin film 13, so unlike the conventional method, the resin film is It is not necessary to form a rectangular pattern, and a rectangular pattern can be formed with high precision. Further, the photosensitive resin film pattern 13a on the first pattern 12 is a stripe pattern, and this pattern 13 may serve as a mask for selectively etching the first pattern 12, which serves as a mask for etching the insulating film 12. Therefore, even if the film thickness is thin and the cross-sectional shape is slightly deformed, the shape of the rectangular pattern 19 is hardly affected.

As described above, in the present invention, only the photosensitive resin film on the convex portions formed in the first layer is removed by exposure and development processing,
In addition, since a rectangular pattern is formed by the intersection of the first and second stripe patterns, the rectangular pattern can be formed with high precision.

Note that if the first layer is made of a metallic substance with high reflectance, the amount of radiation required for forming the second pattern is smaller, and the photosensitive resin film on the substrate to be etched other than the first pattern 12 is 13 can remain thickly. It goes without saying that the present invention can be applied to exposure methods other than projection exposure, and the first and second patterns may intersect at a right angle or at any other angle.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of a general projection exposure method, Figure 2
Figures A, B, and C are process diagrams of a conventional pattern forming method;
Figures A to E are process plan views of a pattern forming method according to an embodiment of the present invention, Figures 4A to E, and Figures 5A to E.
are - lines and - lines in FIGS. 3 A to E, respectively.
FIG. 6, which is a cross-sectional view of the process corresponding to the line, is a diagram showing a mask pattern for exposing a photosensitive resin film used in the present invention. 11... Insulating film, 12... First pattern, 1
3, 13a...Photosensitive resin film, 16...Mask having a second pattern, 19...Opening pattern.

Claims (1)

[Claims] 1. A first pattern having a first pattern on a substrate to be etched.
a step of forming a photosensitive resin film thicker than the first layer; and a step of forming a photosensitive resin film having a thickness greater than that of the first layer; irradiating the film with light and removing the photosensitive resin film in the area where the light irradiation parts of the first pattern and the second pattern overlap through a development process to expose the first layer and the overlapping area; a step of leaving the photosensitive resin film on other areas, etching the exposed first layer to expose the substrate to be etched, and etching two sides with the first pattern and the other two sides with the photosensitive resin film; A pattern forming method comprising the step of etching the substrate to be etched using a mask having openings formed in the second pattern. 2. The pattern forming method according to claim 1, characterized in that a metal layer with high reflectance is used as the first layer.