Hot Plate Emissivity Effect in Low Temperature Annealing

The effect of hot plate emissivity on wafer temperature was investigated using a stacked hot plate system in the temperature range of 100degC to 500degC. Aluminum was used as the hot plate material. The emissivity of the hot plates was modified by selecting appropriate machining precision, intentional surface roughening and surface oxidation (aging). As the emissivity of the hot plates increases from 0.06 (as machined aluminum) to ~0.8 (oxidized aluminum with rough surface), the wafer temperature stabilized at higher temperatures. The difference in stabilized wafer temperature increased as the hot plate temperature increased. The difference in stabilized wafer temperature between low emissivity and high emissivity hot plates, at hot plate temperatures of 200degC and 500degC, were ~20degC and ~80degC, respectively. The effect of hot plate emissivity on wafer stabilization temperature was also verified by inserting high emissivity (~0.9 in the infrared region) quartz plates between low emissivity, stacked aluminum hot plates. The emissivity enhancement of the hot plate system was effective in bringing the stabilized wafer temperature close to that of the surrounding hot plates, even at temperatures below 500degC