Recently, LayTec launched EpiCurveTT AR (advanced resolution) for measurements of the aspherical curvature component during epitaxial growth. The tool is the perfect solution for Planetary and other gas-foil rotation MOCVD systems where the azimuth of the rotating wafers is unknown.
The standard EpiCurveTT without AR measures randomly either along the major axis (larger bow - blue arrow in Fig. 2) or along the minor axis (smaller bow - red arrow). In a Planetary reactor the phase of rotation is unknown. As a result, the signal looks "noisy" (red line on graph): it oscilates between the maximum and the minimum of the azimuthal aspherical bow.
Measurement principle with a 1-dimensional detection system (EpiCurve®TT without advanced resolution) and curvature measurements with conventional EpiCurve®TT (red) and EpiCurve®TT AR (black). The new tool eliminates the aspherical distortion in the signal.
The new AR tool measures curvature along two perpendicular perpendicular axes and eliminates 2nd order azimuthal bowing effects.
In the figure, the black line shows the curvature signal of the new EpiCurveTT AR sensor. The signal-to-noise ratio of the tool with advanced resolution improves the curvature signal from ±8 km-1 (red line) to ± 0.2 km-1 (black line) and measures only the main curvature component by eliminating the aspherical contribution.
Even the quantity of asphericity can be extracted by analysis of the advanced resolution signal. For further information please ask us for the new application note about EpiCurveTT AR.