Process-induced strain dependence of impact ionization efficiency (IIE) in nMOSFETs with a tensile contact etch stop layer (CESL) is presented for the first time. From the universal relationship between the IIE and the electric field in the pinch-off region, a difference in the IIE of nMOSFETs between without and with the tensile CESL is found. This result can be mainly attributed to the narrowing effect of the bandgap energy caused by the tensile CESL-induced strain into the channel, i.e., the reduced threshold energy for impact ionization. In addition, the wafer-bending experiments can further provide strong evidence for the bandgap energy narrowing. It means that the IIE measurement could serve as a reliable monitor of the process-induced strain into the channel.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Safety, Risk, Reliability and Quality
- Condensed Matter Physics
- Surfaces, Coatings and Films
- Electrical and Electronic Engineering