VCSEL
Combined power of spectral sensing and industry proven EpiTT and EpiCurve® TT performance.
VCSELs grown on GaAs are a leading technology in rapidly expanding markets like Gesture Recognition, 3D imaging, datacomm and others. Utilizing the modular concept of our in-situ platform, LayTec has customized and expanded the related in-situ metrology performance for VCSEL epitaxy. Our family of in-situ tools for VCSEL applications combines spectral reflectance measurements with the robust and industry proven EpiTT and EpiCurve® TT performance.
The concept of additional spectral sensing
The additional spectral reflectance module delivers real-time information about the evolving DBR (distributed Bragg reflector) and cavity structures already during epitaxy in a customer chosen spectral range. The figure below shows that the spectral reflectance during the growth of a VCSEL is shifted at growth temperature (Tg=650°C) to a longer wavelength as compared to the room temperature signatures.
For seamless integration of spectral sensing into EpiTT, it is of importance to adjust the wafer temperature measurement appropriately. The high reflectance of the growing VCSEL structure in the near infra-red range reduces the emissivity of the wafer. Hence, based on the specific requirements of our VCSEL customers, the EpiTT VCSEL optical set-up can be customized for minimizing trade-offs between wafer temperature measurement and spectral sensing.
Metrology solutions
EpiTT InspiRe
The standard EpiTT InspiRe offers all features necessary for VCSEL growth processes:
Wafer temperature with precision better than ±1K in a range of 600°C to 1400°C
High accuracy in-situ growth rate (film thickness) measurement with XRD accuracy by 405/633/950 nm low-noise 3-wavelength reflectance
24/7 performance with automated data analysis and integrated interfaces to the MES/SPC systems of our customers
Modular integration into EpiCurve®TT metrology for keeping lattice match of ternary and quaternary layers within narrow specification limits
Extension to spectral reflectance measurements in the VIS range
Automated spectral analysis regarding DBR (distributed Bragg reflector) signatures position, DBR shape and amplitude as well of VCSEL cavity resonance position
Transfer of selected multi-wavelenght reflectance transients to EpiNet®
Automated feed-forward of these additional data lines to the customer's MES/SPC systems systems
EpiX®
EpiX® mapping stations combine an XY-mapping stage with LayTec’s UV-VIS-NIR spectroscopic reflectance and photoluminescence metrology systems for a comprehensive 2D analysis of optical wafer properties by non-contact measurements. The fully automated version (EpiX® C2C) with cassette-to-cassette loading provides a high-throughput solution for industrial production lines. LayTec EpiX® mapping stations exhibit a superior measurement performance that stands out in absolute accuracy, signal-to-noise level and 2D-homogeneity over the wafer while maintaining short measurement times. For VCSEL wafers, the integrated software provides full automated data analysis, including the spectral analysis regarding DBR (distributed Bragg reflector) signatures position, DBR shape and amplitude as well of VCSEL cavity resonance position as well as a total stack thickness measurement.
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