Self-Aligned Subcollector/Isolation Using Polysilicon Masking
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
The following process self-aligns subcollector and isolation regions using two masking operations. The first mask defines subcollector (A level) and isolation (B level) areas, while the second mask is a blockout mask. 1. Grow 1500 ˜ oxide on a P-substrate. 2. Deposit 1000 ˜ undoped polysilicon. 3. Photoresist (PR) (defines A and B patterns). 4. Reactive ion etch (RIE) poly. 5. Strip resist. 6. PR (resist covers isolation areas). 7. RIE oxide from subcollector (S.C.) windows (CHF3) or wet etch oxide. This provides the structure of Fig. 1. 8. Strip PR. 9. Arsenic (As) capsule diffusion or grow screen oxide and implant As (As dopes poly as well as P-substrate). 10. RIE oxide from isolation windows in CHF3 (preferred from ground rule standpoint) or wet etch. 11. Low temp reox (N+ poly and S.C.