| 摘要 |
A reduced mask set, implant complexity process for manufacturing a (high frequency application) complementary bipolar transistor structure uses the fast lateral diffusion characteristic of a layer of material, that is at least an order of magnitude higher for emitter dopants than in single crystal semiconductor material. Separate base and emitter poly layers are formed undoped. Then, the emitter poly of one device and the edges of the base poly of the other device are exposed through a dopant mask and simultaneously doped. The emitter dopant goes directly into the surface of the emitter poly where it lies over and is in contact with the base. The base contact dopant goes into the edges of the base poly, including the layer of material having the high diffusion coefficient, rapidly diffuses laterally throughout that layer, and then diffuses down into the collector material (e.g. island) surface, to form the extrinsic base. A second mask is patterned to expose the emitter of the second device and the edges of the base poly of the first device. Each device is then doped with the second type impurity through the second mask. The use of the high diffusion coefficient layer in the base contact enables the base dopant to spread laterally from the edge contact to the region where the base poly is in contact with the collector, with the same diffusion cycle that is used for the emitter.
|
