A method for determining average damage depth of sawn crystalline silicon wafers.

The depth of surface damage (or simply, damage) in crystalline silicon wafers, caused by wire sawing of ingots, is determined by performing a series of minority carrier lifetime (MCLT) measurements. Samples are sequentially etched to remove thin layers from each surface and MCLT is measured after each etch step. The thickness-removed (δt) at which the lifetime reaches a peak value corresponds to the damage depth.

Use of optical scattering to characterize dislocations in semiconductors.

Optical scattering from a defect-etched semiconductor sample is used to characterize dislocations in the material. It is shown that when the sample is illuminated normally with a He-Ne (lambda = 6328-A) laser beam the reflection pattern can be used to identify the shapes of the etch pits and hence the directions of the dislocation propagation. The integrated light flux scattered by the illuminated sample, normalized by the incident flux, is shown to be proportional to the dislocation density.

Optical diffraction technique for determination of crystal orientations.

An optical technique for determination of crystal orientations is described. This technique uses texture etching to generate pseudoperiodic surface structures whose groove shape is characteristic of the surface orientation. When such a textured surface is illuminated with monochromatic light, a far-field diffraction pattern characteristic of the surface orientation is observed.

Efficient optical waveguide coupler.

A new method for high-efficiency interconnection of two planar optical waveguides is described. This technique is based on mode-matched coupling and is particularly useful when the difference between the refractive indices of the individual guides is large. The method consists of etching a deep vertical step in the highindex waveguide followed by the deposition of low-index waveguide on the etched section so that the two guides remain connected end to end.