Rugged surface polycrystalline silicon film deposition and its application in a stacked dynamic random access memory capacitor electrode

Abstract

Rugged surface polycrystalline silicon (poly-Si) films deposited by low-pressure chemical vapor deposition have been studied and the films have been applied to a storage electrode for stacked dynamic random access memory capacitors. The surface morphology of the films was drastically affected by growth conditions and by the film thickness. However, the rugged surface poly-Si was characterized by the growth of grains that have 〈311〉 preferred orientation. The grains had grown on the amorphous Si surface just after deposition in the low-pressure chemical vapor deposition furnace. It was observed that the amorphous Si films deposited at the transition temperature between amorphous and polycrystalline Si have small crystalline particles in the films. We surmise that the nucleation sites of rugged surface poly-Si grains are small crystalline particles in amorphous Si near the surface, because the amorphous Si films deposited at high SiH4 pressure and low temperature (less than 540 °C) that have no crystalline particles in the film show no grain growth of rugged surface poly-Si. Stacked capacitors were fabricated using rugged surface poly-Si films and thin silicon nitride dielectric films. It was found that the thin poly-Si film electrode about 100 nm thick deposited at 570 °C shows 2.5 times more surface area than that of the conventional poly-Si film electrode. A rugged surface poly-Si electrode deposited under optimized growth conditions is promising for high density dynamic random access memory with stacked capacitor cells.