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Browse Prior Art Database

One Mask Level Complementary Poly Emitter

IP.com Disclosure Number: IPCOM000121174D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Antipov, I: AUTHOR

Abstract

Disclosed is a process for making a complementary doped polysilicon layer, in which one rather than two photo masking levels are required, thereby reducing process complexity.

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This is the abbreviated version, containing approximately 100% of the total text.

One Mask Level Complementary Poly Emitter

      Disclosed is a process for making a complementary doped
polysilicon layer, in which one rather than two photo masking levels
are required, thereby reducing process complexity.

      Two masking levels are generally required when defining
impurity type emitters for complementary vertical bipolar devices
(NPN-PNP).  By using polysilicon as a source emitter doping in single
crystal, however, the number of masking levels may be reduced to one
as here disclosed.  Referring to Fig. 1, after defining bases and
opening emitters of complementary devices, a layer of polysilicon (1)
is applied by chemical vapor deposition (CVD).  This is followed by a
blanket ion implant (very shallow) (2) of one of the impurity types,
for example, p+ poly.  With a photoresist (P/R) mask operating to
define areas for the other type of impurity, the oxide (3) and
polysilicon (1) are reactive ion etched (RIE) to the depth necessary
to remove the shallow implant (2), as illustrated in Fig. 2.  The P/R
mask is then stripped and the second impurity type (n+ poly) (4) is
ion implanted.  The oxide (3) is then stripped and the process
completed by conventional procedures.  An equal reduction in mask
levels and process complexity through use of the disclosed technique
would be expected with its application to CMOS or bi-CMOS
technologies.

      Disclosed anonymously.