Abstract: The current invention relates to a semiconductor wafer heater assembly having a frosted clear quartz material for the wafer susceptor (6) that is placed between the heater (8) and the wafer (7) such that at certain wavelengths of the emitted radiant energy from the heater (8), the frosted clear quartz material is ‘thermally transmissive’ to the thermal radiation from the infrared region. The heater assembly is characterized in that the top quartz plate or susceptor (6) on which the wafer (7) is supported is made of a material that is not “optically transmissive” but is more than 90% “thermally transmissive” to infrared emission that is shorter than 3.5 micrometer wavelength and having higher tolerance and mechanical strength than conventional clear quartz material.