JPS6251220A - Formation of pattern - Google Patents

Abstract

PURPOSE:To restrain varied pattern dimension, by providing a second absorption layer which absorbs radiation and weakens it on a radiation sensitive resist, by controlling the film thickness of the absorption layer, and then by adjusting exposure energy given to the resist layer. CONSTITUTION:A negative photoresist 2 having 1mum of thickness is coated on a base 1 having 1mum of a step with a wafer rotated and then it is baked. At this time, approximate 4,000Angstrom of film thickness difference is generated between the top and the bottom of the step. Next, the coating surface becomes almost flat by coating absorption layer 3 having 5,000Angstrom of thickness with the wafer being rotated. Absorption layer 3 is formed and adjusted by using novolak resin as a base resin, coumarin as an absorption coloring matter, and xylene as a solvent. After a baking is performed for 15min at 80 deg.C the same dimension of pattern exposure is conducted so that latent images 5 and 6 are formed in the resist. Then an absorption layer is removed by using trichloroethane and, in addition, resist patterns 7 and 8 are formed through development.

Description

[Detailed Description of the Invention] [Technical background of the invention and its problems] When a positive photoresist, such as a novolak-based radiation-sensitive resist, is spun onto a substrate, the resin is radially spread during rotation. Due to the balance between the flow and the drying speed of the solvent at that time, the number of waves radiating from the center of the recirculation is 1.
A change in resist film thickness of 00X occurs. This is generally referred to as striation, and when pattern exposure is applied to a resist in this state, the dimensions increase in the thicker areas, and become smaller in the thinner areas. There was a problem. .

1. Although the above-mentioned striations occur in negative-type photoresists, for example,
When there is a step on the substrate, there is a problem that the resist thickness is thinner at the top of the step, resulting in a narrower dimension, and the resist is thicker at the bottom of the step, resulting in a larger dimension. .

[Object of the Invention] The present invention has been made in view of the above points, and it is an object of the present invention to provide a pattern forming method that reduces variations in pattern dimensions caused by variations in resist film thickness above and below striage and steps. It is in.

[Summary of the invention]

The gist of the present invention is to provide a second absorption layer on a radiation-sensitive resist that absorbs and attenuates the radiation, and to control the thickness of the absorption layer to adjust the exposure energy applied to the resist layer to form a pattern. This suppresses variations in dimensions. Immediately, when applying a large amount of exposure energy,
When reducing the thickness of the absorbing layer and applying less exposure energy, the thickness of the absorbing layer is increased to adjust the exposure amount. Furthermore, the thickness of the absorbing layer is automatically controlled in accordance with the variation in the thickness of the resist so as to suppress the dimensional variation.

〔Effect of the invention〕

According to the present invention, dimensional variations due to striation,
We were able to suppress dimensional fluctuations above and below the step.

[Embodiments of the invention]

The present invention will be described in detail below using Examples.

(Example 1) As shown in FIG. 1(a), a 1 μm thick negative photoresist 0MR83 (Tokyo Ohka Co., Ltd. ml 2) was spin coated on a substrate 1 having a 1 μm step and baked. At this time, a film thickness difference of about 4000λ was generated between the top and bottom of the step.Next, as shown in (bl), the absorption layer 3 was spin-coated to a thickness of 50001.At this time, the coating surface became almost flat. ,
The thin portion of the resist above the step was automatically coated thinly, and the thick portion of the resist below the step was automatically coated thickly. The absorption layer 3 was prepared by using, for example, borac resin as a base resin, coumarin as an absorption pigment, and osylene as a solvent. The transmittance of the absorption layer is 500
It was approximately IoLs at a thickness of 0λ. Next, 80℃, 1
After 5 minutes of baking, pattern exposure of the dimensions is carried out;
Latent images 5 and 6 were formed in the resist. At this time, the exposure 5 at the top of the step is sufficient because the absorption layer is thin, and the exposure 6 at the bottom of the step is low in intensity because the absorption layer is thick, and the exposure amount is relatively small compared to exposure 5. became. Then (d
), after removing the absorption layer with trichloroethane, development was performed to form a resist pattern 7.8. In a normal process that does not use an absorption layer, pattern 7 tends to be overdeveloped due to the thin resist, resulting in a smaller dimension Wl and, conversely, a larger W3, but the exposure amount is adjusted to offset this. Therefore, W, , W, could be set to almost equal values.

(Example 2) As shown in Shin), positive photoresist 0FPR80
09 was spin-coated to a thickness of 1^m. At this time, the thickness is about 2
Periodic unevenness (striation) with a positive photoresist percentage of 0.00% occurred. An absorbent layer 10 was spin-coated thereon as shown in (b). The surface became almost flat, and the absorption layer could be applied thinly in the thicker portions of the photoresist, and thicker in the thinner portions of the photoresist. Therefore, as in Example 1, it was possible to self-compensate by giving excessive exposure to thick parts of the resist and giving less exposure to thin parts of the resist. Therefore, as shown in (C), in the normal process, periodic thickening and thinning occur in the resist pattern width, but with the method of the present invention, a pattern with good dimensional accuracy can be obtained as shown in (d). did it.

Note that the absorbing layer used in the present invention is not limited to this example, and may be any layer as long as it has absorption and can be coated on the water resist.

[Brief explanation of drawings]

Fig. m1 and Fig. 2 are process cross-sectional views showing each embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Negative resist, 3... Absorption layer, 4... Bright light, 5.6... Latent image forming part, 7, 8
...Resist pattern. Agent Patent attorney Nori Chika Ken Copper quantity Bamboo flower Honor Kyuriki (a) 1'j (b) 1 ↓ ↓ I I 1-4 (C) Otsu (d) W2 (a) (b) (C) (d) Figure 2 Figure 1

Claims (3)

[Claims] (1) A pattern forming method characterized by forming a second layer that absorbs and attenuates radiation on a radiation-sensitive resist and then exposing the resist to light. (2) A patent claim characterized in that, using a positive radiation-sensitive resist, the second layer is formed to be thin in a portion where the resist film is thick and thick in a portion where the resist film thickness is small. The pattern forming method according to item 1. (3) A patent claim characterized in that, using a negative radiation-sensitive resist, the second genus is formed to be thicker in a portion of the resist where the film is thicker and thinner in a portion where the resist is thinner. The pattern forming method according to scope 1.