JAMES ARTHUR LAWSON
Pilots at Ellis Dr, Tempe, AZ

3954524, May 4, 1976

Jul 26, 1974

5/492090

James R. Lawson - Tempe AZ

Texas Instruments Incorporated - Dallas TX

H01L 21306

148187

This disclosure relates to a self-aligned photoresist process for use in removing silicon dioxide from the tops of silicon mesas or other semiconductor mesa structures. The specific application is in the production of an array of mesa P-N diodes on a semiconductor slice which have oxide passivation in the valleys between the mesas. In the production of such diodes, an early step in the overall processing of the devices is to thermally oxidize the entire mesa structure prior to diffusing the P-N junction therein. In order to prepare the slice for the junction diffusion, it is necessary to first remove the thermal oxide from only the tops of the mesas leaving the oxide in the valleys for the purpose of isolation. This oxide removal is provided herein without complicated alignment steps by depositing a photoresist over the oxide passivation layer in such a way that the photoresist thickness over the mesas is thinner than it is in the valleys between the mesas. The photoresist is then exposed to light for a predetermined amount of time so that the photoresist is completely exposed in the regions over the mesas but only exposed inwardly for a predetermined distance in the valleys.