Performance studies on inversion channels of nMOSFETs under extreme mechanical load

Test chips containing nMOSFET with different gate orientations were processed on a (100) silicon wafer using a 0.65 /spl mu/m CMOS technology. The wafer was diced into strips. The strips were thinned down to a thickness t of 65 /spl mu/m and bent parallel to the [110]-direction through a four-point bending fixture. For the first time uniaxial mechanical stress up to 350 MPa was applied externally to the strips. In order to get reference values thick strips of 300 /spl mu/m thickness were also investigated. The drain current I/sub D/ was measured for different bending stress values. The relative current change /spl Delta/I/sub D//I/sub D/ shows a linear behavior with respect to the applied stress. No other effect than piezoresistance plays a major role in changing the current in stressed thin chips.