Practical use of an in-line vacuum metrology cluster in a minifactory environment

A single wafer metrology module capable of performing a variety of wafer property measurements under vacuum is presented. This metrology module was built by Texas Instruments for use in the Microelectronics Manufacturing Science and Technology program's 0.35 micrometers , single wafer processing factory. The primary measurement tools incorporated in our metrology module are a phase modulated spectral ellipsometer and a critical dimension sensor based on laser diffraction. The spectral ellipsometer was originally developed for real-time in situ film thickness measurements for process control. Using the speed of phase modulation, multichannel detection, and digital signal processing techniques, this ellipsometer is capable of measuring the thicknesses of dielectric films in multilayer stacks with a typical solution time of a few seconds. The critical dimension sensor is an in situ diffraction pattern measurement and analysis system capable of measuring sub-micron device dimensions down to 0.15 micrometers . Other sensors included on the machine are a microbalance, a scatter sensor for measuring surface roughness, and an optical microscope.