Mask for ion, electron or X-ray lithography and method of making it

US4855197A · kind A · utility

Assignee

• International Business Machines Corporation · US

Inventors

• Werner Zapka · Gärtringen, DE
• Jurgen Kempf · Schönaich, DE
• Joachim Keyser · Wildberg, DE
• Karl Asch · Springe, DE

Key dates

• Filing date: May 1, 1987
• Grant date: Aug 8, 1989
• Expiry date: May 1, 2007

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S430/167
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

A mask for radiation beam lithography is formed from a semiconductor wafer by thinning a region into a membrane with a hole pattern defining the pattern of the mask. The membrane is doped with a tensile stress-generating material so that minimum doping exists at the periphery of the membrane with the maximum at its center. The difference in doping between the periphery and the center is chosen so that when the mask is irradiated with a given beam current intensity, the membrane is tension-free. To make a mask in the wafer, a hole pattern is formed by etching holes in the membrane or by depositing a layer on the membrane. The wafer is thinned from the opposite surface until the holes in the hole pattern are throughholes or until the desired thickness is reached. The membrane is doped with tensile-stress-generating material using ion implantation or diffusion proportionally to the temperature distribution existing in the membrane during irradiation with exposure beams.