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Fabrication Technique For an Ion Beam Lithography Mask in Tensile Stress

IP.com Disclosure Number: IPCOM000051752D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 90K

Publishing Venue

IBM

Related People

Keller, JH: AUTHOR [+2]

Abstract

An arrangement is provided which eliminates the thermal expansion and bowing of a mask up to a given power density of an ion beam. In known fabrication techniques for ion beam lithography masks, it is advantageous to have the mask under tension so that the mask will not expand and distort when subjected to the heat flux of the ion beam during exposure. Rather, the temperature rise will act to relieve some of the tensile stress.

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Fabrication Technique For an Ion Beam Lithography Mask in Tensile Stress

An arrangement is provided which eliminates the thermal expansion and bowing of a mask up to a given power density of an ion beam. In known fabrication techniques for ion beam lithography masks, it is advantageous to have the mask under tension so that the mask will not expand and distort when subjected to the heat flux of the ion beam during exposure. Rather, the temperature rise will act to relieve some of the tensile stress.

Described here are two processes which may be employed to achieve the tensile stress in the mask. In the first process, before the "deep dielectric" etch technique is used for etching the silicon, a thick layer of silicon nitride 1 is placed on the doped region of wafer 3, and the desired mask pattern is etched into the silicon nitride, as shown in Fig. 1. Then silicon etching and wafer thinning are carried out by known techniques. Layers of silicon nitride 5 and photoresist 7 are then applied to the silicon side of the mask, as shown in Fig. 2. The photoresist is exposed through the silicon mask (using the mask to transfer the pattern to the photoresist and through the silicon nitride). For this purpose, a wavelength, which is weakly absorbed by silicon and for which silicon nitride is transparent, is used, relying on the differential silicon thickness to provide the patterning. The photoresist is then developed, and the silicon nitride is etched using either wet etching, dry etching, or a combination.

An alternative approach to achieving the nitride layers involves use...