JPS6048023B2 - positive resist - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive resist material whose main chain is cleaved by irradiation with deep ultraviolet light, electron beams, X-rays, etc.

Formation of thin film patterns on semiconductor substrates is primarily accomplished by etching in the presence of a photoresist layer.

Etching methods can be roughly divided into two processes.

These are wet processes that use various liquid chemicals, and dry processes that either do not use liquids or replace conventional liquid processes with liquid-free techniques. Wet processes are excellent, but as device densities increase and circuits become smaller, wet processes become impractical to obtain the fine resolution needed to finely define interconnects. It is becoming a stage.

By converting a wet process that uses liquid chemicals into a dry process, we can expect effects such as simplification of the manufacturing process, cleaning, improvement of the precision of processing dimensions of fine patterns, and stability of processing.

Although there are many types of dry etching processes, one of the problems associated with plasma etching, which is currently the most advanced in practical use, is temperature rise.

In other words, during etching, the substrate temperature rises to over 200°C due to reaction heat, radiation from plasma, etc., so most of the well-known photoresist materials and electron beam resist materials cannot withstand the process as they are. First, there was a problem in that the shape was distorted during plasma etching, and as a result, the wiring pattern was deformed, making it impossible to form a precise pattern. By the way, among positive electron beam resists,
Polymethyl methacrylate (PMMA) has the best resolution and is highly reliable and practical, but on the other hand, it has a slow exposure time, resulting in long exposure times and poor workability.

It is possible to increase the sensitivity of PMMA to some extent by adding an appropriate sensitizer, such as cinnamyl aldehyde, but in that case, the sensitizer tends to evaporate, so to prevent this, the pre-baking temperature must be set to a sufficient level. For example, if the pre-bake temperature is kept below 100°C, the adhesion of PMMA will decrease and the resolution will also deteriorate, making it impossible for PMMA to fully demonstrate its original excellent performance. Also, the thermal decomposition point of PMMA is 23
0.°C) Since the glass transition point was as low as 105°C, the dry etching resistance was low. The present invention was developed in view of these points. PMrlV4A containing an azide-type crosslinking agent containing a plurality of azide groups is applied as a resist to the surface of a thin film to be patterned, and ultraviolet rays are irradiated as a pretreatment. By heating to a temperature of 200°C, a crosslinking reaction is caused in PMrvA, and then a resist pattern is formed by irradiation with deep ultraviolet light, electron beams, X-rays, etc. The present invention provides a new resist material for thin film dry etching.

Examples of the resist of the present invention and the method of using the resist will be described below.

An example of the azide compound used as a crosslinking agent in the present invention is shown in the following formula.

4,4゛-diazidecalgon 2,6-bis-4゛azidobenzyl-cyclohexanone 2,6-bis-4゛azidostyrylacetone Does the above bisazide compound irradiate the skin with near-ultraviolet light with a wavelength of 0.3 to 0.4p? Alternatively, by heating to a temperature of 100-200°C, 2,6-bis-4'azidobenzyl-cyclohexanone is decomposed into highly active free radicals and nitrogen gas as shown in the formula below.

It is believed that the active free radicals generated by the above photo- or thermal reaction combine with PMMA to perform a cross-linking reaction as shown in the following formula.

Due to the crosslinking reaction as described above, the molecular weight of the resist increases, and the amount dissolved in the solvent decreases.

That is, PMMA contains 0.1 to 5% saliva, preferably 1
A resist material to which a bisazide crosslinking agent of ~2% by volume is added is applied onto the substrate to be patterned by a method such as a spin coating method, and the resist material is coated with a resist material containing a bisazide type crosslinking agent of 0.3 to 0 (without cutting the PMMA molecular chains). .4μm ultraviolet light or 100μm
By heating to temperatures of ~200<0>C, PMMA is crosslinked and its molecular weight increases. The resist has a wavelength of 0.
By patterning using deep ultraviolet light or electron beams of about 18 to 0.26 μm, the main chain of PMMA in the irradiated part is cut, and the molecular weight becomes low and soluble in the developer, making it difficult to develop. It becomes possible.

If a resist that crosslinks PMMA by adding the bisazide compound of the present invention is used, it is usually possible to
Pre-baking is carried out under the conditions of 170°C x 30-60n11n, but as in that case, the pre-bake temperature can be raised sufficiently, so P
The excellent performance of MMA can be fully demonstrated.

Furthermore, in the conventional method using only PMMA resist, P
There were problems such as unexposed areas of MrS/1A being dissolved by solvents with strong solubility or developing solutions, resulting in sagging of the pattern, but after crosslinking PMMA in advance using the method of the present invention In the method of deep ultraviolet exposure, the molecular weight of the resist increases and its solubility in solvents decreases, so the dissolution rate of unexposed areas becomes almost 0, making the pattern less likely to fade, and it is also possible to develop the resist for a longer time using a developer than before. This allows you to form beautiful patterns. Furthermore, by crosslinking, PMM
Since the molecular weight of A increases and it is bonded three-dimensionally, the heat resistance also improves.

Therefore, for example, the resist of the present invention to which about 10"1% of bisazide is added has the advantage that the dry etch resistance is about 6 times higher than that of a resist without additives. Also, at a wavelength of 0.4μ
Compared to the conventional method of exposing using ultraviolet light of about Conventionally, the distance between the two is about 3 μm, but when using far ultraviolet light, for example, it can be improved to about 2 μm.
The integration density of elements can be increased.

Claims (1)

[Claims] 1 0.1 to polymethyl methacrylate (PMMA)
A positive resist characterized by adding ~50% by weight of an azide crosslinking agent. 2. The positive resist according to claim 1, wherein an azide compound having a plurality of azide groups is used as the crosslinking agent.