Hexamethyldisilazane

CAS: 999-97-3

Overview

Hexamethyldisilazane (CAS 999-97-3 ), commonly abbreviated as HMDS, is a silylating agent used across semiconductor fabrication, surface chemistry, and specialty coatings.

Bis(trimethylsilyl)amine is a recognized alternative name in chemical procurement. It functions by converting surface hydroxyl groups into trimethylsilyl groups, rendering substrates hydrophobic.

This process improves adhesion or compatibility with downstream processes. In semiconductor manufacturing, HMDS is applied as a photoresist adhesion promoter for silicon wafer surfaces.

Treating surfaces before lithography helps to prevent delamination and improve pattern resolution. Pharmaceutical and analytical laboratories use it to silylate active compounds.

It is also used for chromatography column packings, improving compound stability and peak symmetry in GC analysis. In specialty coatings, it modifies the surface of silica and titanium dioxide.

This improves dispersion in hydrophobic resin systems. Personal care formulators apply HMDS-treated powders in cosmetic products where improved skin feel and moisture resistance are required.

HMDS is supplied as a colorless liquid in standard packaging ranging from small reagent quantities up to bulk drums. Technical and reagent grades are the most commonly available.

Purity specifications are typically at 97% or higher depending on application requirements. Semiconductor-grade material is available under tighter purity controls for microelectronics.

Physical Properties

Melting Point	-78 °C
Boiling Point	125 °C
Density	0.7741 g/cm³ @ Temp: 25 °C
Flash Point	57.2 °F
Appearance	Colorless liquid
Color	Colorless
Odor	Ammonia odour
Form	Liquid
Water Solubility	REACTS
Vapor Pressure	20 hPa (20 °C)
Refractive Index	n 20/D 1.407(lit.)
Log P	0.23-1.19 at 20-25℃

Safety & Handling

Danger GHS02 GHS05 GHS06 GHS07 GHS08 Hazard Statements H225 Highly Flammable liquid and vapor H302 Harmful if swallowed H311 Toxic in contact with skin H314 Causes severe skin burns and eye damage H320 Causes eye irritation H331 Toxic if inhaled H332 Harmful if inhaled H335 May cause respiratory irritation H336 May cause drowsiness or dizziness H370 Causes damage to organs H402 Harmful to aquatic life H412 Harmful to aquatic life with long lasting effects H302+H332 Harmful if swallowed or if inhaled Precautionary Statements P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking. P233 Keep container tightly closed. P240 Ground and bond container and receiving equipment. P241 Use explosion-proof [electrical/ventilating/lighting/…] equipment. P242 Use non-sparking tools. P243 Take action to prevent static discharges. P260 Do not breathe dust/fume/gas/mist/vapours/spray. P261 Avoid breathing dust/fume/gas/mist/vapours/spray. P262 Do not get in eyes, on skin, or on clothing. P264 Wash … thoroughly after handling. P270 Do not eat, drink or smoke when using this product. P271 Use only outdoors or in a well-ventilated area. P273 Avoid release to the environment. P280 Wear protective gloves/protective clothing/eye protection/face protection. P316 Get emergency medical help immediately. P317 Get emergency medical help. P319 Get medical advice/attention if you feel unwell. P321 Specific treatment (see … on this label). P330 Rinse mouth. P363 Wash contaminated clothing before reuse. P405 Store locked up. P501 Dispose of contents/container in accordance with local regulations. P264+P265 Wash … thoroughly after handling. P301+P317 Get emergency medical help. P302+P352 IF ON SKIN: Wash with plenty of water. P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing. P308+P316 Get emergency medical help immediately. P337+P317 If eye irritation persists: Get medical advice/attention. Get emergency medical help. P361+P364 Take off immediately all contaminated clothing and wash it before reuse. P370+P378 Use … for extinction. P403+P233 Store in a well-ventilated place. Keep container tightly closed. P403+P235 Store in a well-ventilated place. Keep cool. P301+P330+P331 Rinse mouth. Do NOT induce vomiting. P302+P361+P354 IF ON SKIN: Take off immediately all contaminated clothing. Rinse skin with water/shower. P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water/shower. P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. P305+P354+P338 IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.

Trade & Regulatory

HS Code	29319099
UN Number	3286
ADR Class	3
Packing Group	II
Storage Class	3 - Flammable liquids
WGK (Germany)	2

Other Names

Industries

Personal Care & Cosmetics