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The above drawings illustrate the processing stages utilizing oxidized polysilicon as the dielectric separating an emitter contact metal interconnection and doped polysilicon base contact interconnection.
English (United States)
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Polysilicon Base/Emitter Contact Process
The above drawings illustrate the processing stages utilizing oxidized
polysilicon as the dielectric separating an emitter contact metal interconnection
and doped polysilicon base contact interconnection.
The substrate, as shown in Fig. 1, is processed in accordance
with the following steps: 1. Polysilicon deposition (Poly I)
2. Polysilicon oxidation
3. Dopant implant
4. Si3N4 (chemical vapor deposition)
In the next step (Fig. 2), a polysilicon mask is formed by an RIE (reactive ion
etch) of the polysilicon followed by chemical vapor deposition (CVD) of SiO2 .
This is followed by a chemical vapor deposited Si3N4 layer, and an implanted
base (Fig. 3).
Fig. 4 shows a suceeding polysilicon deposition (Poly II), with (Fig. 5) a
blanket reactive ion etching of the silicon.
Following the RIE of the Poly II layer, the remaining polysilicon is oxidized
while all active device areas are protected with the Si3N4 to prevent oxidation of
any of the contact areas. The resultant structure is shown in Fig. 6.
The emitter contact is now opened by reactive ion etching of the thin Si3N4
and the CVD SiO2 film in all the contact areas, as shown in Fig. 7. Fabrication of
an ion-implanted emitter is then completed with anneal and P contacts opened to
complete the structure shown in Fig. 8.
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