Fast bipolar transistor for integrated circuit structure and method for forming same

DETAILED DESCRIPTION It is therefore an object of this invention to provide an improved bipolar device characterized by fast operation and low capacitance and a method of making same.
It is another object of this invention to provide an improved high gain bipolar device having an emitter made using polysilicon with self-aligned contacts.
It is yet another object of this invention to provide an improved bipolar device having improved speed by providing a metal silicide layer over a portion of the base to lower the resistance between the intrinsic base and the base contact.
It is a further object of this invention to provide an improved bipolar device having oxide spacers formed adjacent the sidewall of the emitter to separate the emitter from the metal silicide base contact.
It is yet a further object of this invention to provide an improved bipolar device using planarization techniques to provide separate contacts to the emitter and the metal silicide base region.
It is a still further object of this invention to provide an improved bipolar device having a raised polysilicon base contact which may be opened simultaneously with the opening of the emitter and collector contacts to eliminate a step to the base contact.
These and other objects of the invention will become apparent from the following description and accompanying drawings.
In accordance with the invention, an improved bipolar device is provided having a polysilicon emitter formed over a base region of a silicon substrate with oxide spacer portions formed on the sides of the emitter and metal silicide portions formed over the base region adjacent the oxide spacers whereby the use of polysilicon for the emitter results in high gain as well as vertical shrinking of the device because of the shallow diffusion of the emitter into the base and the elimination of the extrinsic base.
The use of oxide spacers and metal silicide adjacent the spacers results in a shrinkage of the horizontal spacing of the device to lower the base-emitter resistance without raising the capacitance to thereby increase the speed of the device