A New Isolation Process for VLSI Devices
In this paper we present a new zero-bird's beak process which, with an additional photolithographic step, substitutes the thermal fully-recessed field oxide for a CVD oxide. With this process we have fabricated devices which present a very small narrow channel effect. Moreover, the use of a reference mask increases the process reproductivity and reduces the probability of the double-threshold voltage effect. The cross-section and electrical results are presented.
A new bird's-beak free field isolation technology for VLSI devices
A new field isolation technology ide-- al for VLSI devices has been developed incorporating a unique two step oxide-burying process. This technology is completely free from bird's beak formation which is particularly important for increasing the packing density. A near-perfect planar surface structure is also obtained. MOS devices fabricated by the new technology showed no thershold voltage increase due to the narrow channel effect for channel widths down to submicron region.
Thorium in monazite sand; separation and determination by precipitation from homogeneous solution
A new method is described which consists of three steps: (1) decomposition of the monazite sand with perchloric acid; (2) separation of thorium and the rare earths by hydrolysis of methyl-oxalate in acid solution; and (3) separation of thorium from the rare earths by hydrolysis of urea in the presence of formic acid. The authors consider the method to be accurate and rapid.