The curing process window and properties of both nitrogen (N-2) and ammonia (NH3) cured porous methyl silsesquioxane (MSQ) based low-dielectric-constant (low-k) spin-on dielectric (SOD) films are comprehensively explored and compared in this research. Higher curing temperatures, longer curing time, and an NH3 atmosphere provide more complete poragen removal and H-OR/H-OH hydration, and thus achieve higher degrees of cross-linking and volume shrinkage of these films. The desorption of water and ethylic organics confirms the release of hydrated ROH/H2O and is dominated by the curing temperatures. Smaller refractive indexes, better electrical properties, and stronger mechanical properties are obtained with NH3 curing and increased curing temperatures and time because of more complete hydration. With consideration of total thermal budget, the appropriate curing process window locates at 350degreesC for only 10 min or 300degreesC for 20-30 min with N-2/NH3 flows of 10/0.1-10/2.0 slm. All the properties do not degrade with extended thermal-cycle treatments, exhibiting good thermal stability. (C) 2004 The Electrochemical Society.