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Self-Aligned Subcollector/Isolation Using Polysilicon Masking

IP.com Disclosure Number: IPCOM000041286D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Dockerty, RC: AUTHOR

Abstract

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.

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Self-Aligned Subcollector/Isolation Using Polysilicon Masking

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. area oxidizes approximately 3X faster than P-isolation areas). Grow 2500 oxide in S.C. (all of N+ poly is oxidized and N800 oxide is grown in isolation windows). The resultant structure is shown in Fig. 2. 12. RIE 800 oxide from isolation windows and do BBr3 diffusion reox - or implant boron through 800 oxide and drive in. 13. Strip all oxides. 14. Deposit epi. The process can use - diffused or implanted S.C., diffused or implanted isolation, wet or dry S.C. oxide etch, wet or dry isolation oxide etch. The subcollector and isolation are self- aligned with no extra masks; polysilicon is used instead of nitride masking...