1. The Field of the Invention
The present invention relates to the manufacture of semiconductor devices. More particularly, the present invention is directed to a method for forming a spacer with a prograde profile useful for preventing stringers at the respective base of adjacent spacers, where the spacers are manufactured in the process of manufacturing semiconductor devices.
2. The Relevant Technology
Spacers are widely used in the manufacture of semiconductor devices to isolate laterally adjacent circuit elements. In DRAM devices, for example, spacers are employed to isolate wordlines and define source/drain regions. Spacers in DRAM devices are generally formed by deposition of a dielectric material over gate stacks. An anisotropic etch to remove the dielectric material from horizontal surfaces may follow. The resulting spacers laterally isolate the gate stacks from adjacent source/drain regions. The spacers also isolate the gate stacks from contact plugs that are subsequently formed. The contact plugs make contact with the source/drain regions and should be isolated from the gate stacks.
A problem often arises, however, due to sheer vertical or even slightly concave vertical spacer surfaces near the bottom of the spacers. The space between adjacent gate stacks after the spacer is formed is deposited with conductive material. Portions of the conductive material are then removed by etching, resulting remaining portions of conductive material. The sheer vertical or even concave vertical spacer surfaces can prevent the etch from removing all of the conductive material, resulting in "stringers" of conductive material along the base of the spacers. These stringers can cause a short between the remaining portions of conductive material, causing circuit and device failure.
A reliable, easily performed method of preventing such stringers along the base of spacers is thus needed.