Polyimides are finding increased use in integrated circuits as a dielectric and protective layer. Its low dielectric constant, ease of application, and ability to planarize the surfaces, permit their incorporation into very large scale integrated and ultra‐large scale integrated circuit processing. However, there is no single polyimide available which possesses high‐temperature stability at temperature>300 °C. A newer class of polymers called polyimidesiloxane (SIM‐2000), resulting from the modification of polyimides by special equilibrated silicone blocks, has been found superior to commercial polyimides especially with respect to their high‐temperature stability. In this paper, we present the results of our investigation of the high‐temperature stability of a few polyimidesiloxane materials spun on various substrates including Si, SiO2, and Al.