Thin-film heterostructures experience structural relaxation when subjected to post-deposition thermal heat treatment. The rate of relaxation, elastic effects, and inelastic effects on the stress and deformation of the structure are determined by the physical properties of the materials, in particular, the solid-phase viscosity. During relaxation, movement of defects causes an increase of viscosity with time at a constant rate as these defects are annihilated. Experimental anneals have been performed on structures with polycrystalline silicon films on (111) germanium substrates, in which the substrate relaxes during thermal annealing. A numerical analysis of the experimental results has determined values for the viscosity and viscosity rate of (111) germanium wafers. In addition, four zones of the relaxation process have been identified, and results indicate that the increasing viscosity with time has a larger effect at lower furnace ramp-up rates.

Temperature measurements and processing uniformity continue to be major issues in Rapid Thermal Processing. Spatial and temporal variations in thermal radiative properties of the wafer surface are sources of non-uniformities and dynamic variations. These effects are due to changes in spectral distribution (wafer or heat source), oxidation, epitaxy, silicidation, and other microstructural transformations. Additionally, other variations are induced by the underlying (before processing) and developing (during processing) patterns on the wafer. Numerical simulations of Co silicidation that account for these factors are conducted to determine the radiative properties, heat transfer dynamics, and resultant processing uniformity.

Temperature measurements and processing uniformity continue to be major issues in Rapid Thermal Processing. Spatial and temporal variations in thermal radiative properties of the wafer surface are sources of non-uniformities and dynamic variations. These effects are due to changes in spectral distribution (wafer or heat source), oxidation, epitaxy, silicidation, and other microstructural transformations. Additionally, other variations are induced by the underlying (before processing) and developing (during processing) patterns on the wafer. Numerical simulations of Co silicidation that account for these factors are conducted to determine the radiative properties, heat transfer dynamics, and resultant processing uniformity.

This study investigates methods of predicting the deformation and stress distribution in multilayer optical thin film structures. The thin film layers include materials of various thermal expansion coefficients, elastic moduli, and melting temperatures. Each layer is deposited at a different temperature, causing complex thermal and deposition stresses throughout the structure. In addition, since the deposition temperatures of some of the layers are high (>600°C), stress relaxation and plastic flow may occur in materials with low melting temperatures. A combination of theoretical predictions and experimental measurements is used to measure and quantify the deformation caused by residual and thermal stresses in the films as well as any plastic deformation that may have occurred. Results from a model using multilayer plate bending theory to determine the elastic deformation of the device due to thermal stresses are reported. These predictions, as well as a more common method of predicting film stress and curvature, are compared to experimentally measured curvature changes as a function of temperature in the samples. However, when plastic deformation begins to occur at high temperatures, the residual stress and degree of deformation are no longer predictable based on elastic theory alone, and have to be measured experimentally. Plastic deformation in the substrate is discussed as a cause of a high observed curvature following sample heating.

Amorphous and polycrystalline silicon films are commonly used in a wide range of microelectronic and optical devices. Polycrystalline silicon is conventionally deposited by chemical vapor deposition (CVD) at temperatures in excess of 600°C. At these high deposition temperatures, thermal diffusion of dopants and thermally induced chemical reactions may occur within the substrate or device. Also, substrates with low melting temperatures such as germanium, may undergo irreversible deformation. In the present study, ion beam sputtering has been shown to enable the deposition of a stable polycrystalline silicon film on germanium as well as on silicon and glass substrates at temperatures as low as 350-400°C. The crystallization properties of silicon on the different substrate surfaces is reported. Crystallinity of the ion beam sputtered silicon films as a function of deposition temperature and substrate type is measured by X-Ray diffraction. These polysilicon films are shown to be thermally stable, have randomly oriented crystals, and have good adhesion to the substrates despite high compressive deposition stresses ranging from 700MPa to 1000MPa. Magnetron sputtered silicon films deposited on substrates in the same temperature range produced only completely amorphous films, with lower stresses and which are also thermally stable. This study demonstrated the feasibility of depositing extremely hard polycrystalline silicon films on germanium and other substrates by means of physical vapor deposition at temperatures as low as 350°C.