The one-piece UNI-Block® Indium-free Substrate Holder allows rapid mounting of full or partial substrates in the same holder ring with minimum particulate generation. The entire assembly procedure can be done in less than 30 seconds, reducing exposure of the substrate to the environment. There are no wires or clips to install and the substrate faces downward at all times, thereby reducing particulate contamination (see figure provided). A variety of configurations to accommodate partial wafers, diffuser plates and optical access to the backside of the wafer are available.
The UNI-Block Substrate Holder is fabricated from a single piece of molybdenum, increasing its ease of use and making it much more convenient to etch.
The face-down assembly method of the UNI-Block Substrate Holder results in low particulate defects (see figure provided). Excellent temperature uniformity can be achieved using a UNI-Block Substrate Holder for indium-free mounting of a 3" substrate. The PL emission spectra of the test structure (see figure provided) were measured at the center, middle, and edge of the wafer. The peaks for the 85Å well are exactly aligned, and only small PL shifts are observed for the thinner wells. This PL wavelength is indicative of a quantum well thickness variation of less than one monolayer across the wafer, and is undetectable by PL in the thickest of the four quantum wells. Since layer thickness in GaAs is strongly temperature dependent, the excellent thickness uniformity reflects high thermal uniformity across the substrate.
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