20 March 2013

LayTec launches version of EpiCurve TT with both blue laser and 405nm reflectance measurement

A major challenge of in-situ metrology on single-port reactors with small viewport geometries is the combination of curvature measurements (by blue laser) with reflectance measurement at a wavelength of 405nm, says LayTec AG of Berlin, Germany (which makes in-situ metrology systems for thin-film processes, focusing on compound semiconductor and photovoltaic applications).

Curvature measurement by blue laser is a must for patterned sapphire substrates (PSS) and double-side polished substrates, says the firm. Meanwhile, reflectance measurement at 405nm is indispensable for monitoring indium gallium nitride (InGaN) multi-quantum well (MQW) growth. Until now, it was impossible to have both features for reactors with only one small optical access because of the cross-talk effect, but the new optical and electronic design of EpiCurve TT eliminates this problem, says LayTec.

The latest version of the tool has been installed on an Aixtron 200-4 RF/S metal-organic chemical vapour deposition (MOCVD) reactor with just a 5mm hole in the ceiling at Otto-von-Guericke University in Magdeburg, Germany.

The team of professor Alois Krost and professor Armin Dadgar is using the tool in development projects for in-situ monitoring of various GaN-based optoelectronic and power electronic device structures on both silicon and sapphire substrates. The EpiCurve TT is equipped with a blue laser (emitting at 405nm) for wafer bow control and with triple-wavelength reflectance (405, 633 and 950nm) for precise monitoring of MQW layers, aluminium nitride (AlN) interlayers, aluminium gallium nitride (AlGaN) buffers, and further features.

After several years of experience with LayTec systems, Krost is convinced that “EpiCurve TT is the best in-situ tool available on the market to control strain, temperature uniformity, MQW formation and surface morphology during III-N device growth”. LayTec’s chief technology officer Dr Kolja Haberland thanks the team in Magdeburg for the year-long research cooperation and for testing the new product in the field.

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