Etch Process for Producing Positively-Sloped Via Hole Edges in Silicon Nitride
Original Publication Date: 1988-Jul-01
Included in the Prior Art Database: 2005-Feb-15
Isotropic reactive ion etching (RIE) of over half the thickness of a silicon nitride (Si3N4) film followed by anisotropic RIE through the remainder of the Si3N4 film is used to create acceptable, positive via hole edge slopes. Changes in isotropy of the etch are made by changing power dissipated in the plasma, system gas pressure, and flow rate of CF4 gas. Some portions of edges of via holes through a nitride film which are allowed to overlap underlying metal lands may become undercut or too steep when a single isotropic or anisotropic etch is used to cut through the total nitride film thickness. By first etching through half of the nitride film thickness with an isotropic etch process and completing the etching with anisotropic conditions, acceptable edge slope is achieved everywhere.