RECIPROCAL SPACE MAPPING FOR SEMICONDUCTOR SUBSTRATES AND DEVICE HETEROSTRUCTURES

We produced wafer maps of triple-axis X-ray diffraction omega scans (o mega or omega-map) to determine the location of high and low crystalli ne perfection in both the substrate and the 15-20 nm channel region in device-quality GaAs and InP-based pseudomorphic high electron mobilit y transistors. The triple-axis maps are more sensitive to different ty pes of crystallographic defects than are double-axis measurements. A m ap showing full width at half-maximum variations provides information on variations in crystallographic tilt; a map showing full width at fi ve thousandths maximum shows polishing damage variations across the wa fer. Monitoring the detector position determines lattice parameter var iations across the wafer as well, although we did not observe signific ant lattice parameter variations in a given wafer. The crystallographi c perfection of the channel layer replicates that of the underlying su bstrate and electrical measurements taken at the different regions sho w that the lower crystalline quality conforms with reduced electrical performance. Omega maps are also used to assess the influence of diffe rent growth parameters and post-growth annealing treatments on substra te crystallographic perfection. The non-destructive nature of this tec hnique makes it ideal for studying structure/performance relationships in semiconductor heterostructures.