JPS58153326A - Mask for x-ray lithography - Google Patents

Abstract

PURPOSE:To stabilize an organic polymer film and to obtain an organic polymer mask for highly accurate X-ray by implanting ions of light element such as H<+>, He<+> or Be<+> on the film. CONSTITUTION:When ions of light metal such as H<+>, He<+> or Be<+> or the like are implanted to an organic polymer film such as polyimide, the flying stroke of ions can be extended as compared by the implantation of relatively heavy element such as P<+>, B<+>, Ne<+>, Ar<+> or the like in the conventional method. In this manner, the entire film can be stabilized, mask dimensions can be stabilized at the X-ray emitting time or during retention, thereby obtaining an organic polymer mask having excellent positioning accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray lithography mask used for manufacturing semiconductor devices and the like.

Various lithography methods such as IJ lithography, electron beam lithography, and X-ray lithography are used to manufacture semiconductor devices, but in recent years, with the miniaturization of semiconductor devices, there has been a demand for so-called submicron pattern processing of 1 μm or less. has become expensive.

In photolithography, the practical resolution limit is 1 μm due to the diffraction effect of ultraviolet or far ultraviolet light used for exposure. On the other hand, in X,) phosphorography, the wavelength of the X-rays used for exposure is from several A to several 18, which is two to six orders of magnitude shorter than the wavelength of light, and the diffraction effect is small, so it is possible to create submicron patterns. It has the characteristic of being able to easily perform high-throughput resolution, and has recently been attracting attention in particular due to expectations for high throughput.

The basic configuration of X-ray phosphorography was developed by Spears and Smith (D, L, 5pears and H, I, S
m1th, “X-ray Lithography
-A New High Re5solution Re
pli.

cation Process” 5olid 5t
ate Technology, 15 (7) 21
(1972), an X-ray source, a mask with an X-ray absorber pattern formed on an X-ray transparent thin film, and a resist film placed in close contact with or close to the mask are coated. It consists of a semiconductor wafer.

In order to establish X-ray lithography in practice, in addition to a high-brightness X-ray source and a highly sensitive resist, a mask base with good X-ray transparency with excellent dimensional stability and positional accuracy, and a finely formed mask on this base are required. It is essential to develop a mask for X-ray lithography consisting of an X-ray absorber.

The base material for the X-ray phosphorography mask is 8i,
8i N 8i0 SiC, Ti h (
There are organic polymer materials such as D-free materials 341 2.1 materials, polyimide, and polyethylene tereftate, and composite film materials that are combinations of these materials. Among these, organic polymer materials have been praised because the process from film formation to mask creation is comparatively simple, but dimensional changes occur during X-ray irradiation or storage, resulting in the dimensional stability of the mask. There was a problem with accuracy.

The present invention was made in order to eliminate the above-mentioned drawbacks of this organic polymer mask, and is made by implanting light element ions such as )r', He++'Be+, etc. into an organic polymer film.

Conventionally, in order to stabilize organic polymer masks by ion implantation, relatively heavy elements such as P'', B+, Ne, Ar, etc. were implanted (for example, in Japanese Patent Application Laid-open No. 1983
-146625). In a normal ion accelerator, the accelerating voltage is at most 200 kV, so in this case, the range of ions in the organic polymer film is several thousand at most, so the organic polymer film with a film thickness of about 1 to 5 μm is usually used. Overall stabilization is difficult, and as a result, an organic polymer mask with sufficient positional accuracy has not been obtained. In contrast, in the present invention, B+.

By extending the range of ions by implanting light elements such as He+ and Be, the entire film is stabilized, making it possible to obtain an organic polymer mask with excellent positional accuracy.

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

Example After forming a Si3N4 film with a thickness of 200A on silicon wool by a conventional method (e.g., vapor phase deposition method), a polyimide film with a thickness of 2 μm was further formed thereon by a conventional method. . B+ ions were implanted into the entire surface of this polyimide film at an accelerating voltage of 200 kV.

The dose amount at this time was 10 cm. After this, a Ti film with a thickness of about 10A is applied to the entire surface of the polyimide film, and
An Au film having a thickness of 5000 Å was formed thereon by vapor deposition. Next, an electron beam resist was applied onto this Au film, a desired resist pattern was formed using an electron beam exposure device, and the Au film was etched using this as a mask to form a desired Au pattern. After that, the resist film was removed and the silicon wafer was exposed to HF-HNO from the back side.
Etching was performed using a 3-CH5C00H solution so as to leave an annular silicon layer on the periphery, thereby obtaining an X-ray lithography mask having a polyimide film as a base.

Furthermore, an X-ray phosphorography mask in which 10 cm of He and Be+ were each implanted was prepared in the same manner as above.

FIG. 1 shows the results of comparing the positional accuracy of the six types of ion-implanted masks obtained as described above with a polyimide mask without ion implantation.

The positional accuracy was expressed as the amount of deviation of the dimensional change when stored in air at room temperature from the reference mark placed on the annular silicon portion at the position of the mark placed on the circular mask with a diameter of 53 mm. As is clear from the results shown in the figure, the stability of the organic polymer mask is significantly improved by implanting light element ions.

Although the above embodiments were explained using polyimide as an example, similar effects were obtained with other organic polymers such as polyethylene terephthalate. However, the ion acceleration energy is not limited to 200, for example, H
In the case of 100, ■ or above gives a sufficiently effective result.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a chart showing the positional accuracy of masks with three types of ion implantation. Representative Patent Attorney Junnosuke Nakamura

Claims (1)

[Claims] (1) A mask for X-ray phosphorography, characterized in that it has an organic film as an X-ray transmitting substrate, the entire surface of which is irradiated with ions of at least one element selected from the group of H, He, and Be0.