High density substrates and packaging

Summary form only given. The ideal package for direct chip attachment, from a thermal and mechanical viewpoint is silicon. Unfortunately, this material is produced in formats no larger than 300 mm in diameter. A research program is currently under way to look at alternative substrate materials that are well suited to MCM-D/L processing. Ideally, the candidate would be of a low cost, off-the-shelf large format (400 mm square) variety, able to withstand the high temperatures and chemicals commonly used in thin-film processing. This paper details a program developed by a consortium of large area processing vendors to evaluate materials as a base for RF and high frequency applications. Specifics on the materials chosen and methods used to test them are provided. The first task is to identify possible candidate base materials that could be used given certain requirements. Second is to evaluate their resistance to various chemicals. Third is to determine the materials' dimensional stability. This is accomplished by running test specimens through thin film processing and determining if warpage occurs after steps involving extreme temperature cycles such as dielectric curing. One of the most sensitive indicators of dimensional instability occurs during photolithography, when the metal or dielectric pattern is being transferred. If a material were to shrink or expand, evidence of this occurs when trying to position alignment markers correctly. Should the materials pass these preliminary tests, actual test vehicles may be built to determine the material viability under electrical and reliability testing.