THE INTERACTION OF STOICHIOMETRY, MECHANICAL-STRESS, AND INTERFACE-TRAP DENSITY IN LPCVD SI-RICH SINX-SI STRUCTURES

Mechanical and electrical properties were correlated in LPCVD SiN(x)-S i structures through the characterization of six wafers patterned with MNS capacitors whose insulator films were deposited rich in Si under various processing conditions. The samples were measured for mechanica l stress at the Si-SiN(x) interface with X-ray diffraction. The deposi ted SiN(x) films were measured for stoichiometry by Rutherford backsca ttering spectroscopy. Low-temperature C-V measurements were used for t he first time to estimate Si-SiN(x) interface trap densities in the ca pacitors. The interface trap densities were confirmed with the aid of a model based on a numerical analysis of the capacitor small-signal re sponse. The measurement results indicate that an increase in the Si/N ratio in the insulating films was accompanied by a decrease in the fil m tensile stress. Those SiN(x) films made sufficiently rich in Si were successfully deposited under compressive stress. Furthermore, a decre ase in the magnitude of the stress was accompanied by a decrease in in terface trap densities, suggesting that interfacial mechanical stress may be influential in the formation of Si-SiN(x) interface traps. Inte rface trap densities were lowest in those structures whose insulating films were deposited under compression.