Strain measurements in large diameter InP and GaAs wafers

Abstract

By using a scanning infrared polariscope (SIRP), the residual strain components such as |S/sub yy/-S/sub zz/|, 2|S/sub yz/| and |S/sub r/-S/sub t/| are quantitatively measured in commercially-available large-diameter wafers of 4/spl phi/ Fe-doped InP crystals grown by the VGF and VCZ methods and of 6/spl phi/ SI GaAs crystals grown by the LEC and VB methods. The |S/sub r/-S/sub t/| map of 4/spl phi/ VCZ-grown InP wafers exhibits a clear four-fold symmetry with the maximum value at the wafer periphery while that of the 4/spl phi/ 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/sub r/-S/sub t/| is also found in 6/spl phi/ VB-grown GaAs wafers. Slip-lines are sometimes observed in 6/spl phi/ 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.