Selective Reactive Ion Etch for Silicon Nitride Over Silicon Dioxide
Original Publication Date: 1988-Jan-01
Included in the Prior Art Database: 2005-Feb-14
A specific set of reactive ion etching (RIE) process parameters provides a very high etch rate ratio (ERR) of silicon nitride (Si3N4) to silicon dioxide (SiO2), high etch anisotropy (steep etched edges), and uniform etching over all wafers in a hexode system. The following conditions used in a hexode RIE system result in a 14:1 ERR of Si3N4:SiO2, anisotropic etching, and better than 5% uniformity of etch rate (ER) of Si3N4 (ER = 70 nm/minute) over all wafers in the system: Etch gas, CO2/CHF3 = 85.7% Pressure = 30 mTorr Power = 200-400 watts DC Bias = -290 volts Since silicon (Si) etch rate is also high under these RIE system conditions, a thin layer of SiO2 is used as an etch stop on Si under Si3N4 .