Process for Etching Self Aligned Concentric VIA Contract Holes
Original Publication Date: 1980-May-01
Included in the Prior Art Database: 2005-Feb-13
A method which eliminates a second masking step and associated overlay tolerance is given in the following steps: 1) A silicon nitride (Si(3) N(4)) layer 9 is deposited on the surface of a silicon water 10. 2) A polyimide layer 11 is formed over layer 9. 3) Resist coating 12 is applied to layer 11, exposed and developed to the desired pattern. 4) The polyimide layer is etched during the development of the resist pattern. 5) After sufficient undercutting of the polyimide layer 11, during the developing process, the photoresist is collapsed by solvent softening or elevated temperature treatment onto the underlying Si(3) N(4), as shown in Fig. 2. It is then used as the etching mask for Si(3)N(4). 6) Si(3)N(4) is etched (not shown). 7) The resist layer 12 is then removed.