Real Time Monitor and Control Of MBE Growth of HgCdTe by Spectroscopic Elliopso

Period of Performance: 05/19/1993 - 05/19/1995


Phase 2 SBIR

Recipient Firm

J.a. Woollam CO.
Lincoln, NE 68508
Principal Investigator


Hg1-xCdxTe is a II-VI semiconductor used extensively in infrared imaging and night vision electronics. These materials have soft surfaces, and growth of reproducible values is extremely important but difficult. Device yields are low and costs are high. Thus there is a great need for non-destructive, non-invasive process control. Spectroscopic ellipsometry is capable of measuring, and thus controlling, the x value to very high accuracy. Layer thickness control during etching is also possible by ellipsometry with atomic scale resolution. In Phase I we demonstrated the effectiveness of an ellipsometer which measures at 12 wavelengths simultaneously and with sufficient speeds that accurate control of x value during growth should be possible. In both growth and etching the surface roughness can be measured in real time. Our goals in Phase II are to build, install, and test an ellipsometer on the Army Night Vision Laboratory MBE chamber which will lead to accurate control of mercury content as well as monitor roughness during MCT growth. This technology will then also be available for other DoD MCT contractor laboratory use.