Browse Prior Art Database

High Transmission X Ray Masks for Lithographic Applications

IP.com Disclosure Number: IPCOM000085751D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Bassous, E: AUTHOR [+4]

Abstract

A mask for X-ray lithography consists of a substrate, which should be transparent to X-rays, and a pattern on this substrate made from a material which absorbs X-rays. There is no material which is completely transparent to soft X-rays, therefore, in order to obtain reasonable transmission, the substrate for the mask has to be very thin.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 3

High Transmission X Ray Masks for Lithographic Applications

A mask for X-ray lithography consists of a substrate, which should be transparent to X-rays, and a pattern on this substrate made from a material which absorbs X-rays. There is no material which is completely transparent to soft X- rays, therefore, in order to obtain reasonable transmission, the substrate for the mask has to be very thin.

A new mask consisting of a Si(3)N(4) and SiO(2) substrate with a total thickness between 0.3 and 0.4mu is described here. This substrate has practically a transmission of 100%, such that the throughput of an X-ray system is increased by a factor of two compared to Si, MYLAR* or beryllium substrates used previously. The production of the mask is more reliable than the production of Si membranes.

The masks are fabricated by the following sequence of steps:.

1) A film of Si(3)N(4) (thickness approx. 1500-2000 Angstroms) and a film of SiO(2) is deposited by chemical vapor deposition on the front side of an (100) oriented single-crystal silicon wafer. The wafer is then thermally oxidized to grow an SiO(2) film approximately 4000 Angstroms thick on the back side.

2) Windows are etched into the SiO(2) on the back of the wafer in those regions where a pattern is required. This is carried out by conventional photolithographic techniques.

3) About 50 Angstroms of chromium and 200 Angstroms of gold is deposited on the front side of the wafer. This film will serve as the conducting layer for subsequent plating (Step 5).

4) An X-ray resist is spun on the wafer and exposed to X-rays through a mask which is fabricated using electron beam lithography. The required pattern is defined on the wafer after development.

5) Through the openings in the resist, gold up to a thickness of 1 mu is plated on the wafer. This gold layer will act as the X-ray absorbing region of the mask. With the present pattern, most of the area of the wafer is covered...