An Advanced Bipolar Transistor with Self-Aligned Ion-Implanted Base and W/Poly Emitter

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This paper presents the fabrication, device profile, and electrical characteristics of an advanced bipolar transistor with an LDD-like self-aligned lateral profile. An ion-implanted extrinsic base with a low sheet resistance of 55 Ω/square and a junction depth of 0.35 µm is obtained using rapid thermal annealing. The extrinsic base and emitter are separated by a temporary submicrometer sidewall spacer, which is subsequently removed to maintain a planar surface during the emitter-active base formation process. The emitter is contacted by a W-TiN-n+ polysilicon stack with a sheet resistance of 1 Ω/square. As a result of the planarity of the surface during the profile formation for the active region and the decoupling of the structural process from the thin base process, an active base width of 105 nm is obtained. © 1988 IEEE