Method for manufacturing a Bi-CMOS device

Claim 1

In a process for the simultaneous production of vertical NPN and PNP bipolar transistors and complementary field effect transistors on a common P-doped epitaxial layer wherein said substrate has an epi layer grown on its surface and said substrate has formed at selected locations N+ subcollector areas which subcollectors are oxidized to a different height for alignment of subsequent masks and said substrate has also formed therein P+ subcollectors at selected locations for providing a low resistance path to the substrate, the improvement to the process comprising the steps of: (a) growing/depositing a thin oxide and nitride layer on the surface of said wafer and depositing an oxide layer onto said nitride layer, (b) patterning said oxide/nitride/oxide layer to locate the surface isolation areas, (c) masking said n well regions, (d) implanting n type dopant at the exposed regions to form a device guard ring, (e) removing the exposed oxide layer and implanting n type dopant to adjust the threshold voltage, (f) removing the n well resist mask and repeating steps c-e for the P well for the n/FET and PNP substituting P type dopant for the n-type dopant, and then removing the P well resist, (g) oxidizing the field, removing the nitride/pad oxide layer and growing a gate oxide, (h) blanket depositing a layer of LPCVD polysilicon, (i) masking said polysilicon with resist and selectively etching said polysilicon down to the gate oxide in the bipolar emitter region and collector reach-through region, (j) implanting an n-type pedestal collector in said opened locations, (k) etching back the photoresist, (1) implanting P type dopant into the bipolar base well, (m) removing the photoresist mask, (n) repeating steps g-m for the opposite type of bipolar device substituting P type dopant for the n type dopant, (o) removing the gate oxide layer, (p) depositing a second layer of polysilicon on the surface, (q) doping the polysilicon, (r) patterning the polysilicon to form the gate electrodes and polysilicon emitter contacts whereby a recess is produced at the surface adjacent to the emitter contact, and (s) forming the respective p type and n type reach-through, extrinsic base, and source and drain using photoresist masks and implanting the respective dopant in the predetermined regions.