Hexamethyldisilazid

Hexamethyldisilazide, often abbreviated as HMDS or (Me3Si)2NH, is an organosilicon compound with the chemical formula ((CH3)3Si)2NH. It is a colorless liquid with a pungent ammonia-like odor. HMDS is a derivative of ammonia where the three hydrogen atoms have been replaced by trimethylsilyl groups (Me3Si). This structure makes it a strong base and a silylating agent.

HMDS is widely used in organic synthesis as a silylating agent to protect hydroxyl and amine groups. Silylation involves replacing a hydrogen atom attached to an oxygen or nitrogen with a trimethylsilyl group. This protection strategy is valuable because it can render sensitive functional groups inert to certain reaction conditions and can also increase the solubility of molecules in organic solvents. After the desired reaction is complete, the silyl protecting group can typically be removed under mild acidic or basic conditions.

Another significant application of HMDS is in the semiconductor industry. It is used as an adhesion promoter for photoresist materials on silicon wafers. HMDS modifies the surface of the silicon wafer, making it more hydrophobic, which improves the adhesion of the organic photoresist layer. This is crucial for achieving high-resolution patterns during photolithography.

HMDS is also employed as a precursor in the synthesis of various silicon-containing materials, including silicon nitride and silicon carbide. Its reactivity and the presence of silicon-carbon and silicon-nitrogen bonds make it a versatile building block for advanced materials. It is typically handled under an inert atmosphere due to its sensitivity to moisture.