JPH0427685B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an X-ray lithography mask having a design width of 2 μm or less.

Masks for X-ray lithography have traditionally been made by any one or a combination of three methods described below. That is, in the first method, a film of a high atomic number metal, such as gold, having a thickness of 0.8 to 1.0 μm is vacuum deposited on a substrate, and an electron beam resist film is spin cast thereon. Then, a predetermined pattern is drawn on this resist film using an electron beam lithography device, the irradiated resist film is developed using a solvent, and the developed relief pattern is turned into a gold film by ion beam etching. transcribed. In this method, the thickness of the resist film required for ion beam etching is thicker than the thickness of the gold film, so the required aspect ratio of the resist pattern is extremely large. The major drawback is that it is time consuming. To eliminate these shortcomings, D. Mayden, GACouquin, HJ
Journal of Vacuum Science and
As published in Technology Vol. 16 PP. 1959-1961 (1979), an intermediate metal resist film has been used between the electron beam resist and the gold film.

In a second method called the lift-off method, first, an electron beam resist film is spin-cast onto a substrate, and a predetermined pattern is drawn on the formed resist film using an electron beam drawing device. The irradiated resist film is developed with a solvent, a gold film is vacuum deposited on the etched areas on the resist film, and the remaining resist film and unnecessary gold film deposited on it are removed. do. In this method, a gold film pattern with a high aspect ratio can be easily obtained by using a resist relief pattern having a narrow window at the top and a wide window at the bottom. However, unnecessary gold film fragments that must be removed often remain on the substrate and become a serious nuisance. Also DCFlanders, A.M.
Journal of Hawryluk and HISmith
Vacuum Science and Technology Vol.16,
As published in pp1949-1952 (1979),
This lift-off method is often used in combination with the first method as a method for processing intermediate metal resist films.

Japanese Journal by Ono and A.Ozawa
of Applied Physics, Vol.19, pp.2311−2312
(1980), first, a thin gold film is formed on a substrate by vacuum evaporation, and an electron beam resist film is formed on the formed thin gold film. Then, the desired pattern is drawn using an electron beam lithography system, the irradiated resist film is developed with a solvent, and the first deposited thin gold film is used as an electrode to apply the gold film to the etched portion of the resist film. Electrodeposit. Since in this method the gold pattern formed by electrodeposition only fills the grooves of the developed resist relief pattern, the aspect ratio of the developed resist film must be high. A major drawback of this method is that the growth rate of the electrodeposited gold film is sensitively influenced by various factors, and it is therefore difficult to obtain a uniform film thickness over the entire mask surface. be.

Common to the three methods described above is the use of bulk gold or tungsten as the X-ray absorbing material. In addition to the drawbacks mentioned above, the use of such bulk materials also has a significant cost impact.

Therefore, in the present invention, instead of such bulk gold, a composite material in which fine gold particles are dispersed in a polymeric material as a binder is used. Generally, in the 4 Å to 10 Å wavelength range, gold is the best X-ray absorber, and is more than twice as good as the next best absorber, tungsten. Therefore, composite materials containing 50% or more gold particles are as good as bulk tungsten as absorbers. It has been found that such a composite material is extremely easy to make and is much easier to process in microfabrication than bulk tungsten. Such composite materials can be easily spin cast like photoresists and can also be plasma etched as easily as photoresist films.

One way to make polymer metal particle composites is to
It consists of dissolving a polymer material in a good solvent and dispersing fine gold particles (average radius 0.02 μm) dispersed in vacuum into the solution. When this solution is spin-coated and prebaked, the solvent evaporates out of the film, giving a high metal density of 60% by volume or more. This metal density can theoretically approach 74%, which corresponds to the closest packing of uniform spheres. This method is similar to silver paste, where silver particles are dispersed in a solution of polymeric material.

Another method of making polymeric metal particle composites consists of vacuum evaporating gold onto a substrate where plasma polymerization of methyl methacrylate is in progress.
Similar methods include RFWielonski and HABeale
Thin Solid Film, Vol.84, pp.425−
426 (1981), published in the paper "Colored Polymer Coatings by Plasma Polymerization". According to experiments, a maximum of 42% of colloidal gold particles could be dispersed in plasma-polymerized methyl methacrylate.

Yet another method for producing a polymeric metal particle composite material is to disperse vacuum-dispersed fine gold particles in a dimethylacetone solution of polyimide acid made from pyromellitic anhydride and bis(4-aminophenol) ether, and to obtain a high It consists of spin-coating a molecular precursor solution onto a substrate and baking until the polyimide acid precursor becomes polyimide.

Various combinations of the above-described method of preparing a polymer metal particle composite material and the method of electron beam lithography for micromachining a pattern on this composite material are possible.

Therefore, an object of the present invention is to provide a method for manufacturing a self-sustaining mask for X-ray lithography without a substrate using such a method.

To this end, the method according to the invention involves dispersing fine particles of a high atomic number metal in a polyimide precursor solution and baking it to form a hard film of an X-ray absorbing composite material with polyimide as a binder. An electron beam resist layer is formed on the radiation absorbing composite material film, and a resist relief pattern formed by electron beam writing and development is transferred onto the X-ray absorbing composite material film, and the patterned X-ray It is characterized by forming a polyimide layer on the absorbent composite material membrane.

When transferring a registration relief pattern onto an X-ray absorbing composite film, preferably 5% of the composite may be left at the bottom of the pattern.

It has been found that the X-ray mask thus obtained has sufficient rigidity to be used without the use of a substrate.

An embodiment of the present invention will be described above with reference to the accompanying drawings.

In the illustrated embodiment, a polymer gold particle composite material using polyimide as a binder is microfabricated into a positive relief pattern, and polyimide is cast into the grooves of the pattern to form a self-sustaining mask.

As shown in Figure 1, in the first step, a temporary substrate 1
4.3 in a 10% dimethylacetone solution of a polyimide acid precursor obtained from pyromellitic anhydride and bis(4-aminophenol) ether.
% _H2- treated gold particles with a particle size of 0.02 μm were repeatedly spin-coated in an _N2 atmosphere.
Then, a polyimide precursor film 2 having a thickness of 2.7 μm is formed by drying with heat.

Next, as shown in FIG. 2, this polyimide precursor film 2 was heated at 150°C for 1 hour and at 200°C for 1 hour.
Heat treated at 300℃ for 1 hour as shown by code 3,
A polyimide gold particle composite film 4 is formed.

This polyimide gold particle composite film 4 is transferred onto another temporary substrate 5 as shown in FIG. 3, and a resist layer 6 made of pp (MMA+DPS+TMT) having a thickness of 0.4 μm is plasma cast thereon.

In the step shown in FIG. 4, the resist layer 6 is irradiated with a patterned electron beam 7. In the step shown in FIG.

In the next step, the irradiated resist layer 6 is developed with _H2 plasma 8, as shown in FIG.

The resist relief pattern 6' developed in this way is etched into the polyimide gold particle composite material 4 by reactive ion beam etching 9 as shown in FIG.
is transferred to a relief thickness of 2.5 μm.

Thereafter, as shown in FIG. 7, a polyimide precursor layer without gold particles is spin coated and heat treated at 350° C. for 1 hour as shown at 10 to form a polyimide layer 11, reducing the overall thickness.
Set to 5 μm.

In the final step shown in FIG.
The polyimide-gold particle composite membrane 4, which is an X-ray absorber reinforced with , is removed from the temporary substrate 5 and used as a self-sustaining mask.

As explained above, this invention enables thick X-ray absorbing films to be easily microfabricated by using a polymeric gold particle composite material instead of bulk gold, and allows for dry etching of thick metals. , lift-off method and electrodeposition can be avoided.
Also, according to the method according to the invention, by using a polymeric gold particle composite material, a self-sustaining mask that does not require a thin and strong X-ray absorbing mask support material can be obtained.

[Brief explanation of drawings]

Figures 1 to 8 show a method according to the present invention in which a polymer gold particle composite material using polyimide as a binder is microfabricated into a positive relief pattern, and polyimide is cast in the grooves of the pattern to construct a self-sustaining mask. FIG. 2 is a schematic diagram showing each step of an example. In the figure, 2... polyimide precursor film, 4...
...Polyimide gold particle composite material film, 6...Resist layer, 6'...Resist relief pattern, 11...
...Polyimide layer.

Claims (1)

[Claims] 1. Fine particles of high atomic number metal are dispersed in a polyimide precursor solution and baked to form a hard film of an X-ray absorbing composite material using polyimide as a binder, and an electron beam resist is applied on the formed X-ray absorbing composite material film. A resist relief pattern is transferred onto the X-ray absorbing composite film by electron beam writing and development on the resist layer, and a polyimide layer is deposited on the patterned X-ray absorbing composite film. 1. A method of manufacturing a mask for X-ray lithography, comprising: forming a mask for X-ray lithography.