Strained silicon on wafer level by wafer bonding: materials processing, strain measurements and strain relaxation

Different methods to introduce strain in thin silicon device layers are presented. Uniaxial strain is introduced in CMOS devices by process-induced stressors allowing the local generation of tensile or compressive strain in the channel region of MOSFETs. Biaxial strain is introduced by growing thin silicon layer on SiGe buffer and transferring it to an oxidized silicon substrates. The latter forms strained silicon on insulator (SSOI) wafer characterized by tensile strain only. Future CMOS device technologies require the combination of the global strain of SSOI substrates with local stressors to increase the device performance.