Effects of photoresist polymer molecular weight on line-edge roughness and its metrology probed with Monte Carlo simulations
A fast 2D/3D resist dissolution algorithm based on the critical ionization model is used to quantify line-edge roughness and determine its relation to resist polymer molecular weight, the end-to-end distance and the radius of gyration, keeping acid effects off (i.e., minimal). The algorithm permits also simulations of line-edge roughness metrology by examining the effects of SEM measurement box length.
Generation mechanism of surface roughness in resists: free volume effect on surface roughness
To clarify the origin of the roughness generated on resist surface, we investigated the effects of molecular weight of resist, exposure dose, and developer molecular size on surface roughness by atomic force microscope observations of surface morphology of electron-beam exposed surface after development. Surface roughness is strongly influenced by the polymer aggregates appearing on the exposed resist surface after exposure and development. As the molecular weight becomes higher, surface roughness becomes larger because the aggregate size increases. On the other hand, at higher exposure doses, surface roughness gradually decreases because the number of aggregates on the surface decreases. This indicates that appearance of the aggregates due to aggregate extraction development is suppressed at higher doses. As the developer molecules become smaller, fewer aggregates appear on the surface and the surface roughness becomes small. This also indicates that the aggregate extraction development can be suppressed with small developer molecules. These results can be explained by considering the relationship between the size of free volume holes in the aggregates and the developer molecular size.
Phase formation during mechanical alloying in the Ti–Si system
Abstract Mechanical alloying of Ti–Si powder mixture or TiH 1.924 –Si powder mixture was performed by high-energy ball milling, in which the Ti to Si mole ratio was 1:2. The phase formations in both mixtures during milling were investigated by X-ray diffraction. Mechanical alloying a mixture of elemental powders led to the formation of TiSi 2 equilibrium compound, while when starting from Si + TiH 1.924 , a metastable phase was formed. The metastable phase completely transforms to TiSi 2 when the mechanically alloyed powder is annealed at temperatures above 800 °C. Two different pathways of phase transitions during mechanical alloying are attributed to the existence of hydrogen atoms, i.e., when starting from Si + TiH 1.924 compared to Si + Ti, the kinetics for the formation of the TiSi 2 intermetallic compound slows down. The kinetics related to the different phase transitions depending on the starting powder mixture are discussed.