This is about an Information Note on the Laytec GmbH website that describes the technology they use in their TT products for semiconductor manufacturing and R&D processes. It is in the form of a PDF document, not easily read online like most web pages. It must be downloaded and then opened, usually in a seperate browser or reader window.

The rationale for using a thermal infrared approach in semiconductor wafer processing is explained at the outset of their note, as follows:

During epitaxial growth the wafer temperature is one of the key parameters. It influences
such elements as growth rate, composition of ternary and quaternary compounds and doping
levels. Wafer temperature also has an important impact on the quality of the grown layer and
its roughness and thereby on the performance of devices based on such epitaxial layers. Thus,careful monitoring and precise control of wafer temperature during the whole growth process are indispensable. Usually the temperature is controlled indirectly, either by thermocouples or by pyrometers.

The article goes on to describe how their pyrometry (radiation thermometry) method obtains the true temperature.

In brief, their technique works as follows:

Reflection of the thermal radiation at interfaces (of semiconductor layers) leads to interference and thus to an intensity modulation (of thermally emitted radiation), depending on the layer thickness in the pyrometry measurement. True wafer temperature is given by a correction according to an additional measurement of reflectance at the same wavelength (using a seperate source of illumination).

You can read the details by downloading the PDF file at the Laytec GmbH website or by downloading it from their website by clicking here.

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