It may be applied in vapor, liquid or solution form to reduce surface energy, provide excellent surface coverage, and reduce underetch and lifting of photoresists. Application is readily accomplished through batch or in-line track vapor prime systems. Solutions of HMDS are available for liquid applications where convenience or process and equipment mandates, as well as for backside rinse and EBR applications. It will chemically passivate a wide variety of substrates, promoting better photoresist coverage and reducing underetch. It is intended for use in vapor applications including vapor prime ovens and in-line track equipment.
Special packaging is available to meet equipment needs.
HMDS functions in the ASTM adhesive definition in that two surfaces are held together by interfacial forces which may consist of valence forces or interlocking forces, or both. The most salient feature in HMDS usage is its reduction in the substrate's surface tension. The reduction of surface tension occurs by means of a chemical reaction in which polar hydroxyl and oxide moieties on the surface of the substrate react with trimethylsilyl groups to produce a non- polar surface monolayer. The reaction will follow a two step sequence dependent on substrate condition. Water molecules adsorbed to the polar surface react first with HMDS to produce inert hexamethyldisiloxane and ammonia.