JPH01314246A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To make it possible to form a resist pattern, even in case that the wavelength having the sensitivity does not accord with the wavelength of a light source of a pattern exposing device, by exposing the whole surface of a resist layer with a 1st. light and then by exposing a prescribed pattern with a 2nd. light. CONSTITUTION:The resist pattern 28 is obtained by applying and forming a negative type resist layer 21 and then exposing the prescribed pattern, followed by developing it. And, the resist layer 21 is wholly exposed by a light 23 having a sensitive wavelength against the negative type resist of the resist layer 21 in an exposure which does not develop the resist layer, and then, the prescribed pattern exposure of the resist layer is effected by a light 25 having a few sensitive wavelength against a negative resist. Namely, as the wavelength of the light 25 is a low sensitive wavelength against the negative resist, and the resist has a less light absorption, the photosensitive region 26 of the resist layer generates over the whole thickness of the resist layer 21. Thus, the resist pattern is formed without increasing the exposure, even in case that the negative resist having a low sensitivity against the light coming from the exposure device is used in a pattern exposure.

Description

[Detailed Description of the Invention] [Summary] Regarding a resist pattern used for microfabrication of semiconductor devices such as LSI, more specifically, regarding a pattern forming method of a negative type photoresist, the sensitive wavelength of the negative type resist is the same as the pattern exposure. The purpose of the present invention is to provide a method for forming a resist pattern that can form a resist pattern even when the wavelength does not match the light source wavelength of the device and can improve the throughput of a stepper exposure device. , in a method of forming a resist pattern by exposing a predetermined pattern to light and developing it, the entire surface of the resist layer is exposed to a radiation dose that does not cause development by first light having a wavelength sensitive to the negative resist of the resist layer. Then, the predetermined pattern exposure is performed using second light having a wavelength that is slightly sensitive to the negative resist.

(Industrial Application Field) The present invention relates to a resist pattern used for microfabrication of semiconductor devices such as LSIs, and more specifically, to a method for forming a negative photoresist pattern.

[Conventional technology]

The step of forming a cyst pattern on the film to be etched using a photoresist is as shown in FIGS. 2(a) to 2(C). a)), the resist layer 1 is exposed by irradiating light 7 using a mask (reticle) 5 of a transparent substrate 4 having a light shielding layer 3 having a predetermined pattern shape, and the exposed portion 8 is shown with diagonal lines, FIG. 2(b) )) Then, a resist pattern 9 is formed by removing the resist in non-exposed areas using a developer. A wide variety of resists and exposure equipment exist for this type of photolithography.
They are used in combinations that are appropriately selected depending on the characteristics of the resist, the performance of the exposure equipment, etc.

[Problem to be solved by the invention]

In pattern exposure for forming a negative resist pattern, the resist must be completely exposed to the light (FIG. 2(b)). Since the resist layer absorbs light, the cross section of the resist pattern becomes an inverted trapezoid when developed (FIG. 2(C)).

Furthermore, the wavelength of light used in the exposure apparatus and the wavelength to which the resist is sensitive may not necessarily match. In that case, if the sensitivity is only marginal, it is necessary to increase the irradiation dose by lengthening the exposure time or increasing the energy of the light. Even in the case of complete exposure, a certain amount of irradiation is required, so the throughput decreases, especially in a stepper exposure apparatus.

An object of the present invention is to provide a method for forming a resist pattern even when the wavelength to which a negative resist is sensitive does not match the wavelength of the light source of a pattern exposure device.

Another problem to be solved by the present invention is to provide a method for forming a resist pattern in which the side surfaces of the resist pattern are formed more vertically.

Yet another object is to provide a resist pattern forming method that can improve the throughput of a stepper exposure apparatus.

[Means for Solving the Problem] The above-mentioned problem is solved by the method of coating a negative resist layer, exposing it to light in a predetermined pattern, and developing it to form a resist pattern. exposing the entire surface of the resist layer to a non-developing dose with first light having a wavelength to which the negative resist is sensitive, and then exposing the predetermined pattern to second light having a wavelength to which the negative resist is slightly sensitive. This problem is solved by a resist pattern forming method characterized by performing the following steps.

[Examples] Hereinafter, the present invention will be described in detail by way of embodiments of the present invention with reference to the accompanying drawings.

1A to 1D are schematic cross-sectional views of a resist layer for explaining the steps of the resist pattern forming method according to the present invention.

First, a negative resist layer 21 is applied by a spin code method onto a film to be etched 22 (a conductive film, an insulating film, etc.) formed on a predetermined substrate (for example, silicon wafer 1, not shown). (Figure 1A).

According to the method of the present invention, as shown in FIG. 1B, the entire surface of the resist layer 21 is exposed to the first light 23, and at this time, the wavelength of the light 23 is the wavelength at which the negative resist has high sensitivity. The amount of irradiation is desirably large enough to not cause development.

If the resist layer 21 is developed after the entire surface is exposed,
Everything will be dissolved. Furthermore, high sensitivity means that the resist absorbs light, and a photosensitive area 24 (FIG. 1B) is formed in the upper layer of the resist layer 21.

Next, the resist layer 21 is exposed in a pattern by irradiating the second light 25 using the same mask 5 as in the conventional method (FIG. 1C) consisting of the light-shielding layer 3 and the transparent substrate 4. At this time, the wavelength of the second light 25 is a wavelength to which the negative resist has low sensitivity, and the light absorption of the resist is small, so a photosensitive region 26 is generated throughout the thickness of the resist layer 21. The amount of irradiation is not so necessary as to enable development with the second light 25, but is sufficient to enable development in addition to the exposure already made with the first light 23.

After the pattern exposure, when the resist layer 21 is developed with a suitable developer, the resist pattern 2 is developed as shown in FIG. 1D.
8 is obtained. In this case, if the development conditions are set appropriately, a resist pattern 28 with almost vertical side surfaces (walls) can be formed.
It can be done.

According to the pattern forming method of the present invention, light with a wavelength of 365 nm (i-line) from a high-pressure mercury lamp is used as the first light for full-surface exposure, and then an excimer laser (e.g., krypton laser) is used as the second light for pattern exposure. Fluoride KrF wavelength 249
By using light with a shorter wavelength of 365 nm, it is possible to improve the resolution using an excimer laser in a negative resist that is sensitive to a wavelength of 365 nm and has low sensitivity to excimer lasers.

Furthermore, since the amount of second light irradiated for pattern exposure can be smaller than that of the conventional method, the throughput for hitting the sea urchin can be increased in an exposure apparatus such as a stepper.

A resist layer was formed by applying a negative resist (AZ5214, Tokyo Ohka Kogyo ■) having negative and positive effects sensitive to wavelengths around 400 nm. The entire surface of the resist layer was irradiated with light having a wavelength of 365 nm (i-line) from a mercury lamp using a contact exposure apparatus (PLA, manufactured by Canon Inc.) (irradiation amount: 4 mJ/c+fl). In addition, resist (AZ5214) t, Nikono exposure equipment Nite 15
If an irradiation amount of 11IJ/CTi1 or more is applied, development becomes impossible. Next, pattern exposure is performed using a stepper (DSW).

The measurement was carried out using light with a wavelength of 436 nm (g-line) passed through a filter from an ultra-high-pressure mercury lamp (manufactured by GC Corporation). The irradiation amount at this time was 60 mJ/cIi. Then, the resist layer was developed with a nonpolar organic solvent to form a resist pattern in which exposed portions of the pattern remained. If pattern exposure is performed using the stepper without the entire surface exposure step, the amount of radiation required for development is 120+sJ/c.
-, and the pattern forming method of the present invention requires only half of that.

〔Effect of the invention〕

According to the present invention, it is possible to form a resist pattern even with a negative resist that has low sensitivity to light from an exposure device during pattern exposure without increasing the amount of irradiation. Reducing the dose during pattern exposure shortens the exposure time and improves the throughput of the stepper exposure apparatus. Furthermore, the sides (walls) of the resist pattern can be made more vertical.

[Brief explanation of the drawing]

1A to 1D are schematic cross-sectional views of a resist layer for explaining the steps of the resist layer pattern forming method according to the present invention, and FIGS. 2A to 2C are schematic sectional views of the resist layer for explaining the steps of the conventional resist pattern forming method. FIG. 2 is a schematic cross-sectional view of a resist layer to be explained. 21...Resist layer, 23...Full surface exposure light, 2
5...Light of pattern exposure, 26...Exposure area, 28...Resist pattern. L I J G23 28...Resist pattern

Claims (1)

[Claims] 1. In the method of forming a negative resist layer by coating, exposing it to light in a predetermined pattern, and developing it to form a resist pattern, a first wavelength sensitive to the negative resist of the resist layer (21) is used. The entire surface of the resist layer is exposed to a non-developing dose of light (23), and then a second beam at a wavelength slightly sensitive to the negative resist is applied.
A resist pattern forming method characterized in that the predetermined pattern exposure is performed using light (25).