JPH0370366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a soft X-ray transfer mask used in a soft X-ray lithography process during the manufacture of high-density integrated circuits such as LSI and VLSI.

[Prior art]

Conventionally, masks for soft X-ray lithography have been made by forming a soft X-ray absorbing image pattern of Au, Pt, etc. on a soft X-ray transparent support film fixed to a support frame. Ta. A silicon or glass substrate with a smooth surface is generally used as the support frame. Soft X-ray transparent support film materials include thin films of inorganic materials such as silicon nitride, boron nitride, silicon doped with boron, etc. at high concentrations, silicon carbide, titanium foil, etc., or polyethylene terephthalate, polyimide, polyparaxylylene, etc. Polymer membranes made of organic materials are known.

[Problem to be solved by the invention]

However, although support films made of inorganic materials such as silicon nitride and boron nitride have advantages such as thermal stability and chemical resistance, they are extremely thin and only a few μm thick because they allow soft X-rays to pass through. It has the disadvantage of being brittle and easily damaged. Furthermore, silicon nitride and boron nitride have higher coefficients of thermal expansion than silicon wafers used in lithography processes, so soft X-ray lithography masks made of support films made of these materials are difficult to expose to X-rays. Pitch deviation of the pattern is likely to occur during transfer, and the pitch deviation is particularly large when a large area mask is used.

Silicon dioxide SiO ₂ has a very small coefficient of thermal expansion (0.5X10 ^-6 /deg) and is a suitable material for masks, but silicon dioxide film alone has compressive stress, so it cannot be supported by silicon dioxide alone. In a soft X-ray mask composed of a membrane, the supporting membrane is warped, making it impossible to obtain a large-area mask.

On the other hand, polymer films such as polyethylene terephthalate and polyimide have the advantage of being relatively strong and transparent to visible light, but have the disadvantages of being susceptible to changes over time, low chemical resistance, and being easily affected by heat and humidity. There is.

[Means for solving problems]

The present inventor has conducted research in order to eliminate the drawbacks of the conventional methods as described above, and to develop a mask for soft X-ray transfer that has a large area and good flatness, with less mask deformation due to thermal expansion and less dimensional changes in the mask pattern. result,
A composite film of polyimide film and silicon dioxide film disposed through a Ti layer constitutes a support for the transferred pattern, and a quartz glass support frame is fixed on the silicon dioxide film, making it resistant to mechanical shock. strongly,
Not only is it possible to form a soft X-ray transfer mask that has less deflection and less pitch shift due to heat even when the area is large, but it is also possible to fabricate a support using a glass substrate with a smooth surface. The inventors have discovered that a large-area mask can be easily manufactured by a method in which the glass substrate is peeled off from the support after the glass substrate is formed, and the present invention has been completed based on this knowledge.

That is, the gist of the present invention is to provide a support made of a polyimide film and a silicon dioxide film bonded via a Ti layer, a soft X-ray absorbing pattern provided on the silicon dioxide film, and a support made of a polyimide film and a silicon dioxide film bonded together via a Ti layer, a soft X-ray absorbing pattern provided on the silicon dioxide film, and This is a soft X-ray transfer mask characterized by comprising a quartz glass support frame fixed to the top.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Figure 1 a to i are soft X produced by the manufacturing method of the present invention.
The manufacturing process of the ray transfer mask is shown, and FIG. 1i shows the completed soft X-ray transfer mask.

As shown in FIG. 1i, the soft X-ray transfer mask 14 of the present invention includes a support 4 made of a polyimide film 2 and a silicon dioxide film 3 bonded together via a Ti layer 9;
A soft X-ray absorbing pattern 5 made of a soft X-ray absorbing material such as AU or Pt provided on the silicon dioxide film 3, and quartz glass bonded onto the silicon dioxide film 3 via an adhesive layer 6. It consists of a support frame 7 made of steel.

[Effect]

Therefore, in the present invention, the support of the soft X-ray absorption pattern is a polyimide film 2 having tensile stress.
The two layers of silicon dioxide film 3 having compressive stress and Ti
Since the structure is such that they are brought into close contact with each other through the film, there is no deflection, there is little pitch shift due to heat, and the adhesion between the silicon dioxide film 3 and the polyimide film 2 is good.

Further, in the present invention, since the soft X-ray absorbing pattern is located on the X-ray source side, the pattern is less likely to be damaged.

Furthermore, in the present invention, the support is a polyimide film 2.
Since the two layers of the silicon dioxide film 3 and the silicon dioxide film 3 are adhered to each other by a Ti film, photoelectrons generated by the soft X-ray absorbing pattern on the mask and the X-rays passing through the silicon dioxide film during X-ray exposure are and Auger electrons can be absorbed by the polyimide film, resist fogging caused by X-rays can be reduced, and a high-resolution resist image can be formed.

Furthermore, in the present invention, since a support frame made of quartz glass having a coefficient of thermal expansion comparable to that of silicon dioxide is fixed on the silicon dioxide film, it is strong against mechanical shock and has good flatness.

As described above, the soft X-ray transfer mask according to the present invention has the advantage of being strong against mechanical shock, having little deflection even when it has a large area, and having little pitch shift due to heat.

The present invention will be explained below with reference to Examples.

Example 1 Optically polished size as shown in Figure 1a
A polyimide resin solution was applied using a spinner onto a 4x4 inch, 200 μm thick thin glass plate 1, and heated at 90°C and 250°C.
A polyimide film 2 with a thickness of 2 μm was formed by heating and curing at temperatures of 350° C. and 350° C. for 30 minutes. Next, in order to improve the peelability between the thin glass 1 and the polyimide film 2, ultraviolet light (365 nm, 10 mW/
cm ² ) was irradiated for 30 minutes.

Next, as shown in FIG. 1b, after forming a TI film 9 with a thickness of 20 to 50 Å on the polyimide film 2 by vapor deposition,
A silicon dioxide film 3 was formed to a thickness of 1 μm by high frequency sputtering using quartz as a target sample.
Here, the Ti film 9 is provided as an undercoat layer to improve the adhesion of the silicon dioxide film 3 to the polyimide film 2.

Next, as shown in FIG. 1C, on the silicon dioxide film 3,
Immediately after the Ti film 10 was deposited to a thickness of 0.02 μm by vapor deposition, the Au film 11 was deposited to a thickness of 0.6 μm. Here, Ti
The film 10 is provided to improve the adhesion of the Au film 11 to the silicon dioxide film 3.

Next, as shown in FIG. 1d, an electron beam positive resist PMMA is applied to a thickness of 0.5 μm on the Au film 11, exposed to electron beam, and developed with a predetermined developer.
An electron beam resist pattern 12 having lines and spaces of 1 μm was formed.

Next, as shown in FIG.
0.2 μm was deposited, and then, as shown in FIG. 1f, the electron beam resist pattern 12 was removed with acetone to form a lift-off pattern 13 of Ti.

Next, using the Ti lift-off pattern 13 as a mask during try etching, the Au film 11 was sputter etched under the conditions of Ar gas pressure of 2X10 ^-2 Torr and high frequency power of 70 W, and then the underlying Ti film 10 and Ti
Lift-off pattern 13 of CF ₄ gas pressure, 2Torr,
By plasma etching under the condition of high frequency power of 200W, Ti
A soft X-ray absorbing pattern 5 consisting of a base layer 10 and an Au layer 11 was formed.

Next, as shown in FIG. Light curing, 365nm,
8mW/cm ² )6.

Finally, the thin glass 1 and the polyimide film 2 are slowly peeled off by applying a minute force, and the
As shown in the figure, a soft X-ray transfer mask 14 of the present invention was obtained.

〔effect〕

With the above configuration, it is possible to provide a soft X-ray mask that is strong against mechanical shock, has little deflection even when it has a large area, and has the advantages of little pitch shift due to heat. be.

[Brief explanation of drawings]

FIGS. 1a to 1i are cross-sectional views showing the manufacturing process of the soft X-ray transfer mask 14 of the present invention. 1...Glass substrate, 2...Polyimide film, 3...
... silicon dioxide film, 4 ... support, 5 ... soft X-ray absorptive pattern, 6 ... adhesive layer, 7 ... quartz glass support frame.

Claims (1)

[Claims] 1 A support consisting of a polyimide film and a silicon dioxide film bonded via a Ti film, a soft X-absorbing pattern provided on the silicon dioxide film, and quartz fixed on the silicon dioxide film. A soft X-ray transfer mask characterized by comprising a glass support frame.