Browse Prior Art Database

X-Ray Lithography Mask With Visible Light Transmitting Areas

IP.com Disclosure Number: IPCOM000036537D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Dana, SS: AUTHOR [+3]

Abstract

Disclosed is a structure for a mask for X-ray Lithography which has areas transparent to visible light for mask wafer registration using visible light.

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X-Ray Lithography Mask With Visible Light Transmitting Areas

Disclosed is a structure for a mask for X-ray Lithography which has areas transparent to visible light for mask wafer registration using visible light.

A silicon wafer 1 shown in cross section in Fig. 1 is coated with a silicon dioxide coating 2 to make a boron diffusion mask. The front surface of the wafer 3 has oxide dots 4 laid down in the positions 7 where fiducial markers are desired. After boron is diffused approximately 3 microns deep into the silicon to form a doped silicon layer 9, and the oxide stripped off, a thin layer of silicon germanium boron alloy 8 is grown by low temperature ultra high vacuum chemical vapor deposition on surface 3 and the wafer is etched in an anisotropic etch such as KOH or pyrocatechol. Low temperature, ultra high vacuum CVD has been shown to grow boron doped silicon with etch rate ratios over undoped silicon of millions to one, and the low temperatures used ensure that the boron will not diffuse and change the doping profile attained by the previous boron diffusion step.

The mask 5 is delineated on the surface 3 of the wafer in precise relation to the alignment marks 6 aligned with areas 7 defined by the oxide dots 4 of the preceding steps to give the structure sketched in Fig. 2. The thin area carrying the fiducial marks can be lined up with normal optical means.

The thickness of the silicon germanium boron layer 8 can be controlled exactly to have a thickness such...