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Improved X-Ray Mask Structure

IP.com Disclosure Number: IPCOM000059713D
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 21K

Publishing Venue

IBM

Related People

Acosta, R: AUTHOR [+6]

Abstract

An improved X-ray mask structure is described in which one or more windows 12 are used to form an X-ray exposure pattern, and separate windows 14 are used for alignment. The exposure-forming windows are covered with a thin X-ray transparent membrane 10 carrying an X-ray absorbing pattern 16. In the separate windows, used only for alignment, the X-ray transparent membrane has been removed, leaving one or more free-standing alignment bars 18 bridging the alignment windows. The free-standing bars form holes 20 in an alignment area. The holes provide means for detecting the alignment marks on the wafer (not shown) without any loss of the signal received from the marks on the wafer. The X-ray transparent area can be boron-doped silicon, BN or any other appropriate substrate. The alignment areas consist of a metallic film (i.e.

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Improved X-Ray Mask Structure

An improved X-ray mask structure is described in which one or more windows 12 are used to form an X-ray exposure pattern, and separate windows 14 are used for alignment. The exposure-forming windows are covered with a thin X-ray transparent membrane 10 carrying an X-ray absorbing pattern 16. In the separate windows, used only for alignment, the X-ray transparent membrane has been removed, leaving one or more free-standing alignment bars 18 bridging the alignment windows. The free-standing bars form holes 20 in an alignment area. The holes provide means for detecting the alignment marks on the wafer (not shown) without any loss of the signal received from the marks on the wafer. The X-ray transparent area can be boron-doped silicon, BN or any other appropriate substrate. The alignment areas consist of a metallic film (i.e., Cr, Au or W) or a non-metallic film coated with metal (i.e., Si, BN, etc. coated with Cr, Au, etc.) containing the alignment features in a self-supporting structure (holes). The films should be chosen to be under tensile stress and thick enough to stop the aligning radiation (light, E-beam, etc). For a B-doped Si substrate (X-ray transparent area), the processing steps could be as follows: (1) B dope the front of the wafer and define a hole pattern in the back of the wafer. (2) Etch back the wafer, producing an X-ray transparent area 12 and alignment areas 14. (3) Deposit a plating base on the Si wafer. (4) The alignment window areas are wet etched or reactive ion etched (RIE) to remove the thin Si film and leave a free standing Au- Cr film...