USE OF A SPUTTER ETCH PROCESS FOR ILD PLANARIZATION
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2002-Feb-21
Planarization of interlayer dielectrics is an increas- ingly important part of multilayer metal processing. At the same time, metal films are being deposited at higher temperatures to allow for better via filling and electromigration resistance. A lack of ILD planarity combined with a metal film deposited at an elevated temperature can result in significant var- iation in the thickness of the metal film over topog- raphy. This can lead to the potential for leakage paths (stringers) between metal lines in the lower topog- raphy areas on the die. A sputter etch process can be used to shape the edges ofthe steps ofa nonplanar ILD structure, The advantages of the sputter etch process for ILD planarization are listed below: 1) The process is simple, a 100 to 150 second Ar sputter etch is done in a Lam 4SOOi RIE sys- tem. No resist coating or other processing is required. 2) The sputter etch process does not thin the dielectric, the process only shapes the cor- ners. No redeposition ofdielectric is required. 3) The metal thickness variation over topogra- phy is reduced from 2 60% to 5 10%. 4) The leakage between minimum pitch features over topogrraphy is eliminated. 5) The overetch required during the metal etch process is minimized.