EpiTT VCSEL and EpiCurve® TT VCSEL

Combined power of spectral sensing and industry proven EpiTT / EpiCurve® performance

Four measured features of EpiTT/VCSEL: wafer temperature, growth rate, wafer bow, spectral reflectance在砷化镓上生长的VCSEL是快速发展市场,如手势识别、3D成像、数据通信等其他市场中的一项新兴技术。LayTec可根据客户要求,充分利用Gen3原位平台的模块化概念定制并拓展VCSEL外延的原位测量性能。今年5年,我们在欧洲的一位领先用户已首先认购了第一套EpiTT/VCSEL系统。该工具将于2017年初出货。EpiTT/VCSEL包括两个光纤测量头:一个用于标准EpiTT,另一个用于光谱反射率传感(R-VCSEL). 两个光纤测量头均可通过EpiCurve®测量头上的转接法兰进行连接 EpiCurve®/VCSEL系统如图1所示。该项设置可同时集成完整的EpiCurve®TT性能和DBR(分布式布拉格反射镜)阻带和腔倾角位置的频谱监测功能。在图1中,该四合一计量工具安装于Aixtron G3行星式反应器顶部。EpiTT/VCSEL和EpiCurve®TT/VCSEL由新型软件模块供电,实现单阱和多阱运行。更多详情 (See "EpiNet software performance for VCSEL" below.)

High performance of EpiTT in industrial VCSEL applications

EpiTT in industrial VCSEL applicationsFor industrial VCSEL processes, EpiTT has a Return-on-Investment (RoI) of only a few months. The standard EpiTT offers all features necessary for GaAs/InP based epitaxy:

  • Wafer temperature with ±1K accuracy
  • 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 

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. Fig. 2 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.

Simulated in-situ data of 980 nm InGaAs/GaAs VCSEL growth Fig. 2: Simulated in-situ data of 980 nm InGaAs/GaAs VCSEL growth (x=12%/90%DBRs) based on A.Mutig, PhD thesis (Technical University of Berlin).

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.

LayTec’s EpiNet software performance for EpiTT VCSEL

EpiNet is LayTec’s control and analysis software for EpiTT, EpiCurve® TT and Pyro 400 products. EpiNet converts in-situ data into profitable information. For VCSEL applications, EpiNet offers:

  • 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-waveleght reflectance transients to EpiNet
  • Automated feed-forward of these additional data lines to the customer's MES/SPC systems 

For further information please contact info@laytec.de or call +49-30-89 00 55-0.