Device application and structure observation for hemispherical-grained Si

A polycrystalline-silicon surface with hemispherical grains (HSG) is deposited by low-pressure chemical vapor deposition at 590 °C. At the temperature, 590 °C, the structure of the Si film just after deposition is amorphous, but crystallization of the amorphous Si occurs to produce HSG-Si during annealing after deposition. The HSG-Si is formed by the nuclei generation on the clean amorphous-Si surface and by the crystalline growth during annealing. The surface area of the HSG-Si film is about twice as large as Si films deposited at other temperatures. By applying the HSG-Si film as the storage electrode for a 64-M-bit dynamic random access memories (DRAM) stacked-capacitor with a SiO2/Si3N4 dielectric film, a capacitance of twice the value is obtained. The increase of the capacitance makes it possible to reduce the DRAM cell area, even by using a relatively thick dielectric film for higher reliability.