A method that uses Fourier Transform Infrared (FTIR) Reflectance spectroscopy to determine the depths of poly silicon filled trenches is described. These trenches, which form the cells for trench DRAM, are arranged in arrays that are periodic in both directions. The method is non-contact and non-destructive. Large number of points per wafer can be easily measured to determine etch uniformity performance. Unlike cross section SEM based metrology, the wafer does not need to be cleaved, and thereby destroyed. The technique is thus suited for in-line metrology of product wafers. The FTIR technique was found t be very robust and provided excellent correlations with SEMs have been observed for 110 nm trenches and are reported in the paper. The method is a viable manufacturing solution for inline, non-destructive, rapid metrology on product wafers.
Non-destructive uniformity and defect control is an essential requirement for yield performance improvement and cost reduction of Silicon-on-Insulator (SOI) 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 SOI 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 On-Line 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.
The perception of FTIR spectroscopy as an expensive, non- compact and vibration sensitive analytical technique, is rapidly changing with the recent introduction of small, robust and fast FTIR spectrometers dedicated to in-line and in-situ process control. FTIR Reflectance Spectroscopy has become a powerful in-line characterization technique delivering information on epi-thickness, doping concentration, dielectric film composition, molecular bond density, thickness of thick semiconductor films, deep trenches, etc., inaccessible in the visible range. The metrology capabilities of the technique will be outlined, including a discussion of process integration and semiconductor yield enchantment issues. The new instrument employs a vibrationally isolated FTIR interferometer and a high-speed digitizer. This combination allows a significantly faster scan rate, and a subsequently superior signal-to-noise ratio. The sensor is designed to be mounted on a process chamber equipped with normal or oblique ports, and provides normal or oblique incidence measuring modes. Outstanding vibration suppression, thermal stability, and high S/N makes it possible to achieve process control with monolayer thickness resolution. Particular examples on ULSI thin film/wafer-state FTIR metrology is presented.
We have developed in-situ infrared sensors for on-line measurements of particle size distributions and temperatures during the manufacture of metal powders produced by the supersonic inert gas molten atomization technique. The sensors are based on novel applications of Fourier transform infrared spectroscopy and advanced numerical analysis techniques based on sound physical models. We have demonstrated the ability to measure the infrared transmission and emission of a hot molten particle stream. We have also identified a promising mathematical approach which deconvolves particle size distributions from extinction spectra.