Strain measurements in large diameter InP and GaAs wafers

By using a scanning infrared polariscope (SIRP), the residual strain components such as |S_yy-S_zz|, 2|S_yz| and |S_r-S_t| are quantitatively measured in commercially-available large-diameter wafers of 4"φ Fe-doped InP crystals grown by the VGF and VCZ methods and of 6"φ SI GaAs crystals grown by the LEC and VB methods. The |S_r-S_t| map of 4"φ VCZ-grown InP wafers exhibits a clear four-fold symmetry with the maximum value at the wafer periphery while that of the 4"φ VCZ-grown InP wafers reveals a weak four-fold symmetry indicating a relief of strain at the wafer periphery, which are caused by different thermal histories between the VGF and VCZ growth techniques. The clear four-fold symmetry of |S_r-S_t| is also found in 6"φ VB-grown GaAs wafers. Slip-lines are sometimes observed in 6"φ LEC-grown GaAs wafers. The SIRP measurements are very useful not only to characterize the large-diameter wafer but also to evaluate device-fabrication processes because the difference of thermal history during crystal growth and device-fabrication processes is sensitively reflected in the SIRP maps.