International Business Machines Corporation

Eric Seung Lee

Chung H Lam

Francis Roger White

Terence B Hook

Robert C Wong

Richard Quimby Williams

James Spiros Nakos

Nivo Rovedo

A method for reactive ion etching of SiO and an etch stop barrier for use in such an etching is provided. A silicon nitride (Si N ) barrier having a Si to N ratio (x:y) of less than about 0.8 and preferably the stoichiometric amount of 0.75 provides excellent resilience to positive mobile ion contamination, but poor etch selectivity. However, a silicon nitride barrier having a ratio of Si to N (x:y) of 1.0 or greater has excellent etch selectivity with respect to SiO but a poor barrier to positive mobile ion contamination. A barrier of silicon nitride is formed on a doped silicon substrate which barrier has two sections. One section has a greater etch selectivity with respect to silicon dioxide than the second section and the second section has a greater resistance to transmission of positive mobile ions than the first section. One section adjacent the silicon substrate has a silicon to nitrogen ratio of less than about 0.8. The second section, formed on top of the first section is formed with the ratio of the silicon to nitrogen of greater than about 0.8. Preferably the two sections together are from about 50 to about 100 nanometers thick.

Dual layer etch stop barrier

An apparatus and method for detecting a defective array of NVRAM cells. A counter is provided which times an erase time interval for the NVRAM cells during a regular erase function. The computed erase interval is compared with a maximum erase interval to determine at least a first characteristic which indicates the block of NVRAMs is at the end of its useful life. A second characteristic is determined by computing the slope in the erase time function versus the number of simulated erase functions. When the slope of the erase function exceeds a maximum slope, the NVRAM array is determined to be at the end of its useful life.

Apparatus and method for detecting defective NVRAM cells

Growing community of inventors

Essex Junction, VT, United States of America

Eric Seung Lee