JPH0248663A - Light exposure method - Google Patents

Abstract

PURPOSE:To form a pattern of high sensitivity and resolution for which the developing time is short by using a positive resist, which contains a sensitizer, a base resin, and a photochemical reaction product of the sensitizer, for light exposure. CONSTITUTION:The positive resist preliminarily containing the sensitizer, the base resin, and the photochemical reaction product of the sensitizer is used to transfer a mask pattern. Thus, the sensitivity is increased while keeping the resolution. A resist pattern having a sharper sectional form is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light exposure method used in manufacturing a semiconductor device, and particularly to shortening and increasing resolution of a light exposure process.

[Conventional technology]

In recent years, as LSIs have become more highly integrated, there has been an increasing demand for fine pattern formation. Currently, the mainstay of this fine pattern formation technology (lithography technology) is optical exposure technology, and along with improvements in the performance of optical exposure equipment (larger diameter lenses, higher NA, improved eye metal precision, etc.), resist Resolution is being improved.

In particular, positive resists composed of diazonaphthoquinone photosensitizers and novolac resins exhibit high resolution, and it is becoming possible to form patterns at the submicron level.

The principle is that (1) during development, the photosensitive agent in the unexposed area significantly reduces the dissolution rate of the resin, and (2) on the other hand, photoproducts generated in the exposed area increase the dissolution rate of the resin. It is based on letting.

Therefore, in recent high-resolution resists, in order to achieve high resolution, there is a tendency to study the resin structure and to increase the concentration of the photosensitizer in order to increase the difference in dissolution rate between exposed and unexposed areas.

[Problem to be solved by the invention]

The conventional high-resolution resist mentioned above has a high concentration of photosensitizer,
Therefore, the required exposure amount increases, resulting in a decrease in sensitivity. Therefore, it is necessary to increase sensitivity while maintaining resolution as much as possible.

[Means to solve the problem]

According to the present invention, there is obtained a light exposure method that includes a step of transferring a mask pattern using a positive resist that previously contains a photosensitive agent, a base resin, and a photochemical reaction product of the photosensitive agent. By adding a photoreaction product to a positive resist in this way, sensitivity can be increased while maintaining resolution.

In addition, on the lower resist formed of a positive resist having photochemical reaction products in advance, a layer is formed that is made of the same photosensitizer and the same base resin as the positive resist, and that the concentration of the photosensitizer is such that the photochemical reaction products are not present. By applying a positive resist whose concentration is higher than the sum of the photosensitizer and the photochemical reaction product contained in the positive resist and transferring the mask pattern, a resist pattern with a steeper cross-sectional shape can be created. is obtained.

The light exposure method of the present invention is a method in which a positive resist is exposed to light using a resist containing a photosensitizer, a resin, and a photochemical reaction product of the photosensitizer.The principle thereof will be described next.

FIG. 1 shows the relationship between the dissolution rate constant and the amount of absorbed light when various resists made of novolac resin and diazonaphthoquinone photosensitizer were exposed. At the point where the solid line or broken line ends, the photosensitizer has completely changed into a photoreaction product (in the case of diazonaphthoquinone photosensitizer, it has changed into a carboxylic acid compound). In the figure, (A) is a normal resist, (B)
is a high resolution resist.

High-resolution resist (B) compared to normal resist (A)
The difference in dissolution rate constant before and after exposure is large, and the rise is steep. Furthermore, the achieved dissolution rate constant is also large. This is because when the concentration of photochemical reaction products is small, a large amount of unreacted photosensitizer suppresses the increase in speed caused by the reaction products. The amount of absorbed light increases and the reaction product ratio increases to 50%.
At a certain level, the contribution of reaction products becomes obvious and the dissolution rate rises sharply. Therefore, both resolution and dissolution rate are increased. However, since the region where the dissolution rate is extremely low is long, the amount of absorbed light required for exposure increases significantly.

On the other hand, (C) shows the dissolution rate constant of the positive resist of the present invention in which a part of the photosensitizer in the high-resolution resist of (B) is converted into a photoreaction product. The rising exposure dose decreases, the steepness of the curve, and the reached dissolution rate constant are equivalent to Regis) (B). Hence the resolution.

Sensitivity can be increased with the same development time.

Further, the dissolution rate constant of a positive resist of the present invention containing a photosensitizer at the same concentration as the photosensitizer (C) and containing no reaction product is shown in (D). Positive resist (C)
The sensitivity is the same, but the resolution is inferior and the development time is longer.

Furthermore, high-resolution resist) (Resist) (C
) and transfer the pattern to CEL (Cont
Last Enhancement Layer) effect can be expected, and a more rectangular pattern can be formed. Also, unlike ordinary CEL dyes, it has two layers of the same type of resist, so steps such as pre-treatment during coating of CEL dyes and removal after exposure can be omitted, simplifying the process.

However, a positive type resist having a photosensitizer concentration below (B) will have a small CEL effect and will have a smaller final solubility constant than the underlying resist. In this case, pattern abnormalities may appear after development, which is not effective.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

Figures 2 to 4 show an example of the present invention using a positive resist consisting of the above-mentioned novolak resin and diazonaphthoquinone photosensitizer, in which a positive resist containing a photoreaction product (C), The characteristics of a single layer are described above (resis) (
This is a comparison with A), (B), and (D). Second
The figure shows the results at the development time at which the maximum gamma value (the slope of the curve at the point of residual film O) is obtained in the residual film characteristics (resist film thickness vs. exposure amount).

Generally, it is considered that the larger the gamma value, the higher the resolution.

Furthermore, the faster the dissolution rate, the shorter the development time.

The positive resist (C) has a higher gamma value than the normal resist (A), and has a resolution of 2.5% higher than the regular resist (D).
Developing time is also short. Also, high-resolution resist (B) has the same development time as resist (C), has a slightly higher gamma value, but has lower sensitivity.

FIG. 3 is a practical sensitivity curve showing the variation of mask dimensions with respect to exposure time. It can be seen that resist (C) requires a short exposure time and also has a small dimensional variation.

FIG. 4 shows general pattern shapes for each resist. Regis) CC”) is resist (B)
Next, it shows a good rectangular shape.

FIG. 5 shows the resist pattern fidelity of the gate width of a field effect transistor formed using the above resist. Similar to the pattern shape, resist (C) is resist)
It shows almost the same fidelity as (B).

Furthermore, by pre-baking resist (C) containing a photoreaction product, and then applying a resist containing a photosensitizer concentration equal to or higher than (B), the resist shape can be further improved to a rectangular shape due to the CEL effect. FIG. 6 schematically shows the shape of the resist when exposed to light using the above two-layer resist structure. It can be seen that the resist shape is further improved.

〔Effect of the invention〕

As explained above, the present invention achieves excellent sensitivity and resolution by performing light exposure using a positive resist in which a photosensitive agent and a base resin further contain a photochemical reaction product of the photosensitive agent. This has the effect of allowing pattern formation to take less time.

[Brief explanation of the drawing]

Figure 1 shows resist (regular resist) (A), high-resolution resist (B), resist (C) in which a part of the photosensitizer of resist (b) is converted into a photoreaction product. Figure 2 is a graph showing the relationship between the dissolution rate constant and the amount of absorbed light when resist (D)) containing the same concentration of photosensitizer as (D)) and no reaction products is exposed to light. Figure 3 shows the practical sensitivity curve, that is, a graph showing the mask dimension variation with respect to exposure time. Figure 4 is a schematic diagram of the pattern shape for each resist single layer. The figure is a graph showing resist pattern fidelity, and Figure 6 shows two-layer resist and single-layer resist) (C
) is a schematic diagram comparing pattern shapes. Agent Susumu Uchihara, Patent Attorney Figure 7 Damage K Light Amount (Log Pattern width Figure 5

Claims (1)

[Claims] A light exposure method comprising a step of transferring a mask pattern using a positive resist having a photosensitizer, a base resin, and a photochemical reaction product of the photosensitizer.