JPH0427684B2 - - Google Patents

Description

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

Masks for X-ray lithography have conventionally been made using any of the three methods described below or a combination thereof. 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 on this resist film is drawn 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 heat of the resist film required for ion beam etching is thicker than the heat of the gold film, so the required aspect ratio of the resist pattern is extremely large, and it takes a long time to process the gold film by ion beam etching. It has a serious drawback that it takes a lot of time. In order 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, an electron beam resist film is first 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 on pp.1949-1952 (1979),
This lift-off method is often used in combination with the first method as a method for processing intermediate metal resist films.

Japanese by Ono and A.Ozawa
Journal 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, a predetermined pattern is drawn using an electron beam drawing device, the irradiated resist film is developed with a solvent, and the gold film is applied to the etched portion of the resist film using the thin gold film deposited first as an electrode. Electrodeposit. Since in this method the electrodeposited gold pattern only fills the grooves of the defined 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 dependent on various factors, and it is therefore difficult to obtain a uniform film thickness across the front surface of the mask. 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 to 10 wavelength range, gold is the best X-ray absorber, and 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 direction for 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), in the paper "Colored Polymer Coatings by Plasma Polymerization". Experiments have shown that up to 42% of colloidal gold particles can be dispersed in plasma-polymerized methyl methacrylate.

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

Various combinations of the above-described methods of preparing a polymeric metal particle composite material and methods of electron beam phosphorography for microfabrication of patterns on this composite material are contemplated.

Therefore, an object of the present invention is to use the above-mentioned polymer gold particle composite material instead of bulk gold, which has been conventionally used as an X-ray absorbing material, to effectively utilize gold resources and to improve the efficiency of all lithography processes. An object of the present invention is to provide a novel method for manufacturing a mask for X-ray lithography using a drying process.

For this purpose, in the method according to the invention:
First, a layer of polymeric gold particle composite material is formed on a substrate by plasma polymerization metal evaporation diffusion method, an electron beam resist layer is formed on the composite material layer thus formed by plasma polymerization method, and It is characterized in that a resist relief pattern formed by dry development after electron beam writing is transferred to a polymer gold particle composite material layer by a reactive ion etching method.

Hereinafter, one embodiment of the method of the present invention will be described with reference to the accompanying drawings.

First, as shown in FIG. 1, a polymer gold particle composite material layer 2 is formed on a boronide substrate 1 having a thickness of 10 μm by a plasma polymerization metal evaporation diffusion method. This process is carried out as follows. In other words, substrate 1 flows at a flow rate of 30 c.c.stp/cm ²
MMA (methyl methacrylate) placed downstream of a high frequency discharge of 5W/ ^cm2 of 0.2Torr argon gas
3 c.c.stp/cm ² of vapor between the discharge excitation and the substrate
is introduced at a flow rate of PPMMA is deposited onto the substrate 1 at a rate of 0.1 μm/min. On the other hand, the evaporated gold is injected towards the substrate 1 at a rate of 6×10 ^-5 gr/cm ^{2 .}
Dispersed in PPMMA, giving a colloidal particle density of 30% by volume. On the composite material layer 2 formed in this way, PP (MMA + sty) with a thickness of 1.5 μm is
(plasma copolymerized MMA styrene)
Resist layer 3 and PP (MMA+sty+TMT)
A second resist with a thickness of 0.3 μm consisting of six alternating layers of low-molecular PP (sty) (plasma polymerized styrene) containing the monomers DPVS (dimethyltin-doped plasma copolymerized MMA styrene) and DPVS (defhenyl vinyl silane) Layer 4 is plasma cast. after that,
These first and second resist layers 3, 4 are irradiated with a patterned electron beam 5.

Next, in the step shown in FIG. 2, the unirradiated portions of the second resist layer 4 are etched away by high frequency H ₂ plasma, generally indicated by reference numeral 6. In the irradiated part of the second resist layer 4, DPVS molecules are grafted to the polymer that bridges the broken bonds of the polymer created by the electron beam, and the entire six resist layers are plasma resistant. It becomes a layer.

In the step shown in FIG. 3, the developed relief pattern of the second resist layer 4 (see FIG. 2) is etched by a first O ₂ reactive ion etching process, indicated schematically at 7.
It is transferred to the resist layer 3.

The final step is shown in FIG. 4, and the relief pattern transferred to the first resist layer 3 is O ₂ indicated by reference numeral 8.
It is transferred again to the polymer gold particle composite layer 2 by reactive ion etching.

Thickness containing 30% gold thus obtained
A patterned layer of 2.5 μm polymeric gold particle composite material transmits only 8% of the incident X-rays (4.4〓).

As explained above, in the method according to the present invention, a polymer gold particle composite material is used instead of bulk gold as the X-ray absorbing layer, so a thick X-ray absorbing layer can be easily microfabricated. Dry etching, lift-off or electrodeposition of metals can be avoided. In addition, this invention
By using the polymer gold particle composite material, the entire mask forming process can be made dry.

[Brief explanation of drawings]

1 to 4 are schematic diagrams showing each step of an embodiment of the method according to the present invention. In the figure, 1... substrate, 2... composite material layer, 3...
1st resist layer, 4...2nd resist layer.

Claims (1)

[Claims] 1. A layer of an X-ray absorbing composite material containing fine particles of high atomic number metal is placed on a substrate, and fine particles of high atomic number metal are placed in the layer while forming a film of polymeric binder material by plasma polymerization treatment. A resist relief pattern is formed by vacuum evaporation, an electron beam resist layer is formed by plasma polymerization on the thus formed composite material layer, and a resist relief pattern is formed by electron beam drawing and dry development on the resist layer. X characterized in that it is transferred onto the composite material layer by a reactive ion etching method.
A method for manufacturing a mask for line lithography.