AN A-SI-H VACUUM-COMPATIBLE PHOTORESIST PROCESS FOR FABRICATING DEVICE STRUCTURES IN HGCDTE

A process for transferring patterns into HgCdTe epilayers using a hydr ogenated amorphous silicon (a-Si:H) photomask has been demonstrated, a -Si:H films were grown using plasma enhanced chemical vapor deposition (PECVD). A latent image of a projected mask pattern was created at th e a-Si:H surface by ultraviolet enhanced oxidation in the load lock of the PECVD vacuum chamber. This image was transformed into a mask by h ydrogen plasma removal of the unexposed areas. A hydrogen plasma etch selectivity value greater than 500:1 for oxide and a-Si:H allows patte rns as thick as 700 nm to be generated. a-Si:H masks were used to crea te arrays of mesas in planar HgCdTe epilayers by etching in an electro n cyclotron resonance (ECR) plasma reactor. Etch selectivity between a -Si:H and HgCdTe during an ECR hydrogen plasma etch was measured to be greater than 18:1. RP values > 10(3) were obtained for midwavelength infrared diodes made from HgCdTe heterojunctions using a-Si:H masks.