Abstract: A process for fabricating high-capacitance trench capacitors in a lightly doped, shallow well of a semiconductor substrate. The process involves a two-step doped glass deposition/diffusion routine. After trench formation into a shallow, lightly doped well, a first doped glass is deposited inside the trench and the dopant is diffused from the glass through the trench interior surface to form a region or halo of extra doping around and below each trench. A second doped glass deposition and diffusion of an impurity of the opposite conductivity type to a shallow depth on the trench wall surfaces provides a p/n junction with the first diffusion region to increase the capacitance of the subsequent capacitor. In addition, the trench devices are better isolated from each other, the substrate and any adjacent devices.

Abstract: An isolation formation process that minimizes bird's beak encroachment and preserves gate oxide integrity in the active region. Future active areas are protected by a structure having a central protective material layer, such as a thermal oxide, surrounded by a ring of thermal nitride. The thermal nitride and central protective material are coated by active region protection masking covers. In one embodiment, the masking covers include sidewalls over the thermal nitride ring. In another embodiment, the central protective material layer is overetched beneath an undercut covering layer to provide an undercut filled by the sidewall. All of these features contribute to bird's beak encroachment prevention which may be narrowed to as little as 0.07 microns per side.

Abstract: A process having three steps to etch a vertical trench with rounded top corners and rounded bottom corners. The first step involves anisotropically etching a vertical trench through an opening in a masking layer to approximately 85 to 90% of the final trench depth to give a trench with sharp or abrupt top corners and sharp bottom corners. The second step rounds the top corners and the third step extends the trench depth and provides rounded bottom corners. Using CHF.sub.3 as an etch species and adjusting the DC bias differently for each step gives better profile control and better critical dimension (CD) control.

Abstract: A method for determining the etch bias of a particular semiconductor device feature layer material in a given etch process employing a hard mask reference material that changes very little or not at all during the etch under examination, and using a cross-sectional examination of the critical dimensions to determine the bias. Silicon dioxide would be a suitable hard mask material for a plasma etch bias study, for example. Preferably, a scanning electron microscope would determine the etch bias in one microphotograph. The need for optically taking two or more separate measurements to optically determine the etch bias, and the possiblility for incorporating error between measurements, is eliminated. In addition, the contribution of photoresist erosion to the etch bias of the device feature layer may be independently determined.

Abstract: A process is disclosed for fabricating a semiconductor device which includes a trench formed at the surface of the device substrate. The surface of the device substrate is oxidized and the oxide is patterned to form an opening which exposes a portion of the underlying surface. Ions are implanted through the opening and into the surface to form a damaged surface region which is coincident with the opening and extends under the edge of the oxide. A trench is etched by reactive ion etching using the opening in the oxide as an etch mask. The substrate, including the walls of the trench and the ion implant damaged surface portion under the edge of the oxide, is thermally oxidized. The oxidation rate is enhanced by the damage and causes a thicker oxide to grow in the damaged region which forms a collar around the intersection of the trench with the surface.