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High performance bipolar transistors, characterized by a heavily doped emitter and small emitter-base spacing, are fabricated in accordance with the present laser-annealing method.
English (United States)
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Laser Annealing Method For Making Heavily Doped Emitter Transistor
High performance bipolar transistors, characterized by a heavily doped
emitter and small emitter-base spacing, are fabricated in accordance with the
present laser-annealing method.
N+ subcollector 1 of Fig. 1 is placed in P- substrate 2 and covered by N- epi 3. Deep (4) and shallow (5) oxide-filled isolation trenches are formed, and base
regions 6 and N+ collector reach-through (RT) region 7 are made in the usual
The wafer is metallized using Al or a refractory metal, such as Ta, Ti or Ti-W,
and is patterned (8), as shown in Fig. 2. The metal 8 over base region 6
provides good ohmic contact to the base.
Pyrolytic oxide 9 is deposited and patterned to cover metal 8 to a thickness of
3000-5000 angstroms using a low temperature. If a refractory metal is used, the
deposition temperature can be 600 degrees C. Arsenic is implanted to form N+
emitter region 10 and collector reach-through region 11 (Fig. 3). The implanted
regions are then annealed using a laser beam to convert the polycrystalline
silicon (caused by implantation) to single crystal.
A base contact region is opened over the oxide isolated region 4 (Fig. 4), and
the wafer is metallized to provide the usual base, emitter and collector contacts
12, 13 and 14, respectively.
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