Product Description
Toho Technology
Stress Calculation The FLX-2320-S determines stress by measuring the curvature change of pre- and post-deposition of the film. This difference in curvature is used to calculate stress by way of Stoney's equation, which relates the biaxial modulus of the substrate, thickness of the film and substrate, and the radius of curvatures of pre- and post-process. Curvature is measured by directing a laser at a surface with a known spatial angle. The reflected beam strikes a position sensitive photodiode. The geometry of the film is recorded by scanning the surface.
Thermal Process Development A key FLX-2320-S feature is it's ability to produce stress temperature correlations. In-situ stress measurements can be made from -65 o C to 500 o C at heating rates up to 30 o C per minute (the cooling unit to -65 o C is optional). An understanding of stress variations with temperature is essential for characterizing material properties such as stress relaxation, moisture evolution, and phase changes. In turn, this helps monitor and control process parameters such as sputtering power, furnace temperature, and gas flow rate.
Advanced Laser Technology The FLX-2320-S features KLA- Tencor's patented dual wavelength technology, which enables the system to slect the wavelength most suitable for the particular application. Pre-selecting the optimal wavelength minimizes destructive interference patterns from transparent films such as silicon nitride. In addition, the laser assembly has only a single moving component ensuring low vibration and high accuracy.
Comprehensive Data Analysis The intuitive, Windows-based analysis software displays any combination of stress, time,surface deflection, or reflected light intensity measurements.
Data analysis features includes
- Calculation of biaxial modulus of elasticity, linear expansion coefficient, stress uniformity, and file subtraction
- Trend plotting for Statistical Process Control (SPC)
- Calculation of water diffusion coefficient in dielectric films
- Automatic recalculation of stress when film or substrate thickness is corrected
- Two- and three-dimensional views of wafer topography
- Plotting of the measured stress-temperature curve
In general stress is induced when materials of dissimilar coefficients of thermal expansion are bonded together. Films may behave similarly at high temperatures but as films are cooled, materials may contract/expand differently, thus causing stress in the film. With a stressed film, defects such as dislocations, voids, and cracking may occur. The FLX stress measurement system helps troubleshoot applications listed below
- Aluminium stress-induced voids
- Passivation cracking (nitride, oxide)
- Stress-induced dislocations in silicon
- Electrical test yeild degradation
- Tungsten silicide cracking
- Stress increase in oxides during temperature cycling
- Constant current stress test (CCST) degradation
- Matching metallization expansion on GaAs
- Silicon cracking due to high film stress
