The emitter diffusion depth of wider emitters was found to be shallower than that of narrower emitters for transistors with a TiSi 2 -formed in-situ phosphorus doped polysilicon (IDP) emitter. This dependence of emitter diffusion depth on emitter width W E resulted in a large dependence of h FE on W E . We found that the emitter diffusion in emitters with TiSi 2 formation was shallower than that in emitters without TiSi 2 formation. We conclude that the dependence of emitter diffusion depth on W E is due to variation in phosphorus diffusivity caused by the TiSi 2 formation. We found by X-ray diffraction measurements that TiSi 2 formation reduced the crystal lattice volume of the IDP emitter layers by 0.2-0.3%. We attribute this reduction to a reduction in packing density due to a supersaturation of vacancies caused by the TiSi 2 formation. We believe that the vacancy supersaturation decreases the density of interstitials in the emitter regions, which decreases the emitter diffusion depth, and that the dependence of emitter diffusion depth on W E is due to variations in the density of vacancies depending on W E .
- Bipolar transistor
- Titanium compounds
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering