JPH0312452B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photomask for semiconductors. especially,
It is effective in X-ray exposure photomasks in X-ray photolithography.

Conventional X-ray exposure photomasks are used to reproduce the resist pattern formed by electron beam exposure into another thick film pattern when forming an X-ray absorbing layer with Au on an X-ray exposure mask substrate such as SiN, SiO ₂ or SiC. It was customary to form an X-ray absorbing layer by selective plating. However, when reproducing resist patterns on other thick films, there is a drawback that the patterning accuracy of the photomask deteriorates due to etching and lift-off processes, and this method does not fully satisfy the precision required for manufacturing submicron semiconductor devices. Nakatsuta.

In order to eliminate the drawbacks of the prior art, the present invention is characterized in that an impurity having an X-ray absorbing ability is implanted into the X-ray exposure mask substrate.
An object of the present invention is to provide an X-ray exposure photomask that does not include an etching or lift-off process in the manufacturing process in order to fully satisfy the precision required for manufacturing submicron semiconductors.

This will be explained in detail below using examples.

1 to 5 are cross-sectional views showing the manufacturing process of a conventional X-ray exposure photomask. 1 to 5 will be explained.

A Ti layer 3, an Au layer 2, and a polyimide layer 1 are formed on the membrane film 4 (FIG. 1). After forming a resist pattern on the resist 5 by electron beam exposure, the surface is covered with a Ti layer 6 (FIG. 2). After removing the resist 5 and the Ti layer on the resist, the polyimide layer is selectively etched by plasma ion milling (third step).
figure). Next, after forming an X-ray absorbing Au layer 2 by Au electroplating, the polyimide is removed by plasma etching (FIG. 4). Finally with Au
By etching Ti, a conventional X-ray exposure photomask as shown in FIG. 5 is obtained. Conventional manufacturing processes involve etching the lift-off polyimide layer of the Ti layer, etching the Au/
The etching process of the Ti layer degrades patterning accuracy, and the resist pattern formed by electron beam exposure is not converted into the Au pattern of the X-ray absorption layer with high precision and reproducibility. Conventional X-ray exposure photomasks have the above-mentioned drawbacks.

Further, FIG. 6 is a diagram for making it easier to understand the embodiment of the present invention. FIG. 6 shows an X-ray exposure photomask in which an X-ray absorbing layer 7 is formed by performing Au ion beam writing 11 directly on the membrane film 4 using Au as an impurity having X-ray absorbing ability. According to the method shown in FIG. 6, the patterning accuracy of the X-ray exposure photomask is determined only by the lateral spread of the implanted impurity Au having the ability to absorb X-rays, making it possible to perform highly accurate patterning.

However, in the method shown in Figure 6, the current and acceleration energy of the ion beam system are
It may not be possible to guarantee sufficient thickness and density to absorb the lines.

Therefore, as an embodiment of the present invention that solves the above-mentioned problems, a method for manufacturing an X-ray exposure photomask is shown in FIGS. 7 to 10.

FIG. 7 shows resist or
After forming a membrane thin film 9 of SiO ₂ or the like, direct Au ion beam writing is performed to form the X-ray absorption region 8 . Next, the same membrane thin film 10 as 9 is formed again (FIG. 8). The same pattern as in FIG. 7 is drawn again using an Au ion beam (FIG. 9). 8 and 9 so that the X-ray absorption region 8 has a sufficient thickness to perform the necessary X-ray attenuation.
By repeating the steps shown in the figure, the X-ray exposure photomask according to the present invention shown in FIG. 10 can be obtained. FIG. 10 shows the case where a resist is used for the membrane thin film 9 and 10, and the portions not irradiated with the Au ion beam have been developed. According to the present invention, the patterning accuracy of an X-ray exposure photomask is determined only by the lateral spread of the implanted impurity Au, which has X-ray absorption ability, and the alignment between multiple layers of ion beam lithography, making it possible to achieve high patterning accuracy. .

[Brief explanation of the drawing]

Fig. 1 to Fig. 5: Manufacturing process of conventional X-ray exposure mask. FIG. 6: A sectional view of an X-ray exposure mask to facilitate understanding of the embodiments of the present invention. FIGS. 7 to 10: sectional views showing the manufacturing process of the X-ray exposure mask according to the present invention. 1...Polyimide, 2...Au, 3...Ti, 4
...Membrane film, 5...PMMA, 6...Ti,
7... X-ray absorption layer by ion implantation, 8... Multilayer X-ray absorption region by ion implantation, 9, 10... Membrane thin film.

Claims (1)

[Scope of Claims] 1. A first X-ray absorbing layer formed by introducing an impurity having X-ray absorbing ability into a first membrane film serving as a substrate, the first membrane film having the first X-ray absorbing layer. a second membrane film formed on the second membrane film, the second membrane film being formed by introducing an impurity having an X-ray absorption ability into the second membrane film so as to have the same shape as the first X-ray absorption layer;
1. An X-ray exposure photomask comprising: a second X-ray absorption layer existing on the first X-ray absorption layer so as to be in contact with the first X-ray absorption layer. 2 A film formed by introducing an impurity with X-ray absorption ability into the membrane film that serves as the substrate.
1 X-ray absorption layer, a 2nd An X-ray exposure photomask comprising: a radiation absorption layer;