JPH0272364A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To prevent the undercut of resist patterns and to improve the shape thereof by executing the full-surface exposing and developing of a resist layer plural times. CONSTITUTION:The full-surface exposing and developing of the resist layer 2 are executed plural times and the unexposed part 3 formed at the time of the 1st exposing is removed dividedly plural times. The 1st exposed part 4, therefore, acts as a mask to prevent the sufficient arrival of light at the part to be shadowed by the 1st exposed part 4 at the time of the full-surface exposing in order to remove the lower layer part of the unexposed part 3 and, therefore, this part remains insoluble and the part 8 eventually remains without being removed at the time of the development. The undercut of the resist pattern is prevented in this way and the shape thereof is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a method of forming a resist pattern by selectively exposing and developing a resist layer formed by coating a photoresist on a substrate. It is related to.

[Conventional technology]

In the manufacturing process of semiconductor devices, etc., a photoresist is applied onto a substrate to form a resist layer, a mask pattern is transferred by exposure, and this is developed to form a predetermined resist pattern. Etching is performed as a mask. An image reversal method is a method for forming such a resist pattern.

FIG. 3 is a flowchart showing the process of the conventional image reversal method, and the process will be explained below based on this diagram. First, a photoresist, for example, a positive photoresist containing naphthoquinone diazide as a photosensitizer in phenol novolac resin, to which triethanolamine or the like is added as a catalyst is applied onto the substrate, and this is pre-baked to make it volatile. A resist layer is formed by removing the organic solvent and drying.

Next, a first exposure (hereinafter referred to as "first exposure") is performed by selectively irradiating electron beams, ultraviolet rays, etc. through a mask with a desired pattern drawn thereon. At this time, the exposed portion of the resist layer (hereinafter referred to as the first exposed portion) undergoes a photoreaction and becomes soluble in the developer. After that, about 100°C ~
Reverse baking is performed at 130° C., and the first exposed portion is reacted and hardened by the action of the catalyst, and becomes insoluble in the developing solution.

Next, the entire surface of the resist layer including the first exposed area is exposed (hereinafter referred to as second exposure), and the unexposed area during the first exposure becomes soluble in the developer due to a photoreaction. Subsequently, by developing with an organic alkaline developer, for example, a 2.38% aqueous solution of trimethylammonium hydroxide, only the unexposed areas at the time of the first exposure are selectively removed, and the mask is completely removed. A resist pattern corresponding to an inverted image is obtained.

FIG. 4 is a cross-sectional view showing the resist layer in the above-mentioned bromo, and FIG. 4 (A) shows the state after reverse baking. In the figure, (1) is the substrate, (2) is the top (3) is the resist layer formed on the mask (3) during the first exposure.
The unexposed area that was in the shadow of the pattern (not shown),
) is cured by reverse baking in the first exposed area and becomes insoluble in the developer. Figure 4 (B) shows the state during the second exposure, in which light (5) is irradiated from above.
As a result, the unexposed area (3) during the first exposure reacts and becomes soluble in the developer.

FIG. 4(C) shows the developed state, in which the unexposed area (3) during the first exposure is removed, and the first exposed area (4) remains to form a pattern.

[Problem to be solved by the invention]

The conventional resist pattern forming method is performed as described above, so that as the light during the first exposure enters the resist layer, it is attenuated due to the light absorption of the resist layer.
Because sufficient photoreaction does not occur in the lower part of the resist layer near the substrate, the first
The reaction of curing the exposed area and making it insoluble in the developer is insufficient compared to the upper layer area. Therefore, during development, the dissolution rate of the lower layer of the first r&light area is faster than that of the upper layer, and the shape of the remaining resist pattern is changed to the shape of the first exposed area (4
), the lower layer becomes thinner and has an undercut shape, which poses a problem in that processing accuracy deteriorates in the subsequent etching step in the semiconductor manufacturing process.

This invention was made to solve the above-mentioned problems, and aims to prevent undercutting of a resist pattern and improve its shape.

[Means to solve the problem]

In the resist pattern forming method according to the present invention, a part of the resist layer is selectively exposed, the exposed part is cured, and then the entire resist layer is exposed to light and developed multiple times alternately. It is something.

[For production]

In the resist pattern forming method according to the present invention, the entire surface of the resist layer is exposed and developed multiple times, and the unexposed area at the time of the first exposure is removed in multiple steps, so that the lower layer of the unexposed area is removed. When exposing the entire surface for
The first exposed area acts as a mask and the light does not reach the shaded area of the exposed area, so it remains insoluble, and therefore this area remains without being removed during development.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a flowchart showing the process of a resist pattern forming method according to an embodiment of the present invention, and the following description will be made with reference to this figure. The steps from resist coating to inversion baking are the same as those in the conventional example shown in FIG. 3, so the explanation will be omitted. After inversion baking, the entire surface of the resist layer including the first exposed area is exposed (
(hereinafter referred to as second exposure). In this case the wavelength is 200
Light of about 300 nm to 300 nm, such as ultra-high pressure mercury lamp 2
Since the light is exposed with a relatively short wavelength such as 54 nm, and the light transmittance is low, about half the thickness of the surface side of the unexposed area during the first exposure undergoes photoreaction and development. Although it becomes soluble in the liquid, sufficient light does not reach about half the thickness of the unexposed area on the substrate side, so no photoreaction occurs and it remains insoluble. Subsequently, development (hereinafter referred to as first development) is carried out for 30 seconds with an organic alkaline developer, for example, a 2.38% aqueous solution of tetramethylammonium hydroxide.
When the film is developed (referred to as development) and washed with pure water, about half the thickness of the surface side of the unexposed area that has undergone the photoreaction is removed.
Approximately half of the substrate side remains without photoreaction. Furthermore, the entire surface is exposed once again in the same manner as above (hereinafter referred to as the third exposure).
and development (hereinafter referred to as second development) are repeated. As a result, the remaining approximately half of the unexposed portion on the substrate side is removed.

FIG. 2 is a cross-sectional view showing the resist layer during the above process, and FIG. 2(A) shows the time of reverse baking.
Since this is the same as the conventional example shown in FIG. 4(A), the explanation will be omitted. Figure 2 (B) shows the second exposure. In the figure, (6) is the upper layer on the surface side of the unexposed area (3) during the first exposure, and (7) is also on the substrate side. The upper layer (
6) reacts and becomes soluble in the developer. However, light (9
Due to its low transmittance, not enough light (5) reaches the lower layer (7), so no photoreaction occurs and it remains insoluble.

Figure 2 (C1 shows the state where the first development has been performed, and the upper layer (
6) has been removed, but the lower layer (7) remains. Figure 2 < DJ indicates the third exposure, and the lower layer (7) is exposed to light irradiated from above in the figure (it reacts with the town and becomes soluble, but it becomes a shadow of the first exposed area (2). The first exposure part (4) acts as a mask and the light (5) does not reach the part (8) sufficiently. In other words, the light (5) does not reach the part (8) while passing through the first exposure part (4). ) is attenuated, and the shaded area (8) remains insoluble. Figure 2 (E) shows the state after the second development, in which the lower layer (7) has been removed, but the shadowed area (8) remains insoluble. The shaded portion (8) of the exposed area (4) remains together with the first exposed area (A), forming a resist pattern (2).Therefore, undercutting of the resist pattern is prevented.

Note that in the above example, the second exposure and the third exposure were irradiated with light of the same wavelength (51), but it is also possible to use light of a different wavelength (9), and the first development and the second development are the same. Although the conditions were used, different types of developers or different lengths of time may be used.Furthermore, although we have shown an example in which full-surface exposure and development are performed twice each, the light used for full-surface exposure (5) By appropriately selecting the wavelength, irradiation time, etc. of
You can choose the number of times.

〔Effect of the invention〕

As described above, according to the present invention, the entire surface of the resist layer is exposed and developed multiple times, so that when the entire surface is exposed to remove the lower layer of the unexposed area during the first exposure, the 11th light section is The first exposed area serves as a mask in the shaded area, so it remains insoluble, and therefore, this area remains without being removed during development, preventing undercutting of the resist pattern and improving its shape. effective.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the process of a pattern forming method according to an embodiment of the present invention, FIG. 2 is a sectional view showing a resist layer during the process of FIG. 1, and FIG. 3 is a flow chart showing the process of a conventional pattern forming method. Flowchart, 4th
The figure is a cross-sectional view of the resist layer during the process of FIG. 3. In the figure, (1) is the substrate, (a is the resist layer, (4)
is the 1st B optical part, (51 is the light. The same reference numerals in each figure indicate the same or corresponding parts. /Substrate 2: b'; Strike layer 4: s! JIs Hikari JP J, Hikari agent Patent attorney Figure 3, Masuo Iwa, Figure 4

Claims (1)

[Claims] After forming a resist layer on the substrate and selectively exposing a part of this resist layer to light, the exposed part is cured,
Next, the pattern is formed by exposing and developing the entire surface of the resist layer including the exposed portion, characterized in that the entire surface of the resist layer is exposed and developed multiple times alternately. A resist pattern forming method.