Trench storage capacitor for high density DRAM(s) - uses rectangular trench with (100) walls and bottom plane to improve oxide thickness and threshold control with die oriented parallel to (110) planes

摘要

Semiconductor die, pref. single crystalline Si, has a surface orientation of (100) and 4 side planes consisting of (110) planes. The edges of the die are inside (111) planes. The die contains trenches which have a rectangular cross section with 4 (100) planes as walls and a (100) plane as bottom. This makes the angle between the trench edges and a (110) die-edge plane 45 degrees. The trench has an outer conductive layer, pref. a diffusion layer pref. inside the substrate, along the trench-periphery, an inner conductive layer, pref. polycrystalline Si, and an insulating layer, pref. an oxide layer, between them. The outer conductive layer pref. forms one of the diffusions in an MOS transistor and the insulating layer is pref. also the gate dielectric of the MOS transistor. Also claimed is the use of substrtes of GaAs, InP and Si-Ge. The die is pref. cut from a wafer of the substrate material which has a (110) plane as registration edge. USE/ADVANTAGE - The orientation of the trench walls ensures that the oxide thickness, grown as dielectric layer of the embedded capactor, has an even thickness along the entire periphery and that the threshold under the inner electrode is controlled. This improves the yield and reliability of the trench capacitors and of the devices using them.