Fourier transform infrared (FTIR) reflectance emerges as a powerful, versatile tool for process characterization and control. Here, the thickness, free carrier concentration and optical properties of GaN-based, single-and multi-layer structures are extracted.
Non-destructive uniformity and defect control is an essential requirement for yield performance improvement and cost reduction of Silicon-on-Insulator (SOl) materials. To maximize performance and minimize production costs, it is critical to maintain a tight control over the oxygen implant dose. This has proven to be particularly true for the most advanced low dose SIMOX processes. Advanced FTIR reflectance spectroscopy and scatterometry have been used to characterize the buried layers of SO! materials and to relate unambiguously the process dose variations and corresponding changes of IR reflectance spectra.
The technique of implanting silicon wafers with sufficient oxygen to form a continuous buried oxide (BOX) layer is known as SIMOX (Separation by Implanting Oxygen). SIMOX wafers present leading-edge semiconductor technology with a great need for on-line process control. Development of thin (80 to 200 nm) BOX is a primary step toward improved device performance and cost reduction. Tight control of the BOX properties, such as the implant dose, thickness, refractive index, and composition, is required in the production. A method to characterize non-destructively BOX layer by means of FTIR normal incidence reflectance spectroscopy has been developed with a particular orientation to in-situ applications. A data reduction procedure based on multi-layer model delivers thickness and dielectric function of a thin BOX layer, and enables one to measure the implant dose with a precision of a tenth of a percent. A compact and robust FTIR spectrometer from OnLine Technologies, combined with sampling optics and sensitive detection, provides excellent signal-to-noise ratio and is well suited for a coupling with oxygen implantation machines for in-situ process control.
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