Key Property Q&A Is HMDS flammable? Yes - HMDS is classified as highly flammable (flash point 17°C). Store and handle away from all ignition sources in explosion-proof facilities.  |  Is HMDS soluble in water? No - HMDS reacts with water and moist air, hydrolyzing to hexamethyldisiloxane (HMDSO) and ammonia. All grades must be kept strictly anhydrous.  |  What is the HMDS formula? C₆H₁₉NSi₂, structural formula (CH₃)₃Si–NH–Si(CH₃)₃, MW 161.39 g/mol.  |  Is HMDS toxic? HMDS is harmful by inhalation, skin contact, and ingestion. It is classified as acutely toxic (Category 4 by GHS). Full SDS/MSDS available on request.  |  What is the HMDS pKa? The pKa of the conjugate acid (HMDS·H⁺) is approximately 30 in THF, making HMDS a moderately strong base widely used in organic synthesis for enolate formation and deprotonation reactions.

Specification	Industrial Grade Surface Treatment / Fillers	Pharmaceutical Grade Drug Synthesis (GMP)	Electronic Grade Semiconductor Lithography
Purity (GC)	≥ 98.0%	≥ 99.5%	≥ 99.999% (5N) up to 6N for advanced nodes
Water Content	≤ 0.1%	≤ 0.02%	≤ 0.005% (≤ 50 ppm)
Color (Pt-Co)	≤ 30	≤ 10	≤ 5
Boiling Point	125–127 °C	126.0–126.5 °C	126.2 ± 0.2 °C
Flash Point	17 °C (closed cup)	17 °C (closed cup)	17 °C (closed cup)
Metal Impurities	Not specified	Single ion ≤ 10 ppm	Single ion ≤ 1 ppb (ppt level for 14nm nodes)
Shelf Life	6 months (N₂-sealed)	12 months (N₂-sealed, dark)	18 months (ultra-clean N₂-sealed)
Packaging	180 kg steel drum 1000 kg IBC tote	20L HDPE drum 200L N₂-sealed steel drum	10L quartz-lined drum 200L ultra-clean steel drum

1. Semiconductor Lithography - Photoresist Adhesion Promoter

HMDS is the industry-standard adhesion promoter, primer, and hydrophobic coating agent in silicon wafer lithography, accounting for over 40% of total HMDS consumption. Applied as a vapor-phase primer (VPP) prior to photoresist coating, HMDS reacts with surface hydroxyl groups (Si–OH) on the wafer to form a dense hydrophobic trimethylsilyl layer. This dramatically improves photoresist adhesion, prevents resist peeling during development, and eliminates edge bead formation - ensuring accurate fine circuit patterning down to 28nm nodes and below.

As advanced semiconductor nodes progress to 14nm, 7nm, and beyond, purity requirements have escalated to 5N (99.999%) and 6N grades, with metal impurities controlled at the ppb–ppt level. Our electronic-grade HMDS products employ advanced trace metal removal technology, meeting the qualification standards of leading fabs including SMIC, Yangtze Memory, Changxin Memory, and UMC.

Reference: SEMI Standards - Semiconductor Materials Purity ↗

2. Pharmaceutical Industry - Silylating Agent for Drug Synthesis

In pharmaceutical synthesis, HMDS is widely used as a silylating agent to protect reactive protic functional groups (–OH, –NH₂, –COOH) in drug intermediates, preventing unwanted side reactions and significantly improving reaction selectivity and target product yield. It is a key reagent in the synthesis of anti-tumor, antiviral, and antiallergic active pharmaceutical ingredients (APIs).

Our pharmaceutical-grade HMDS (≥99.5% purity, GMP-compatible) has been validated by leading pharmaceutical CDMO enterprises and provides stable batch quality essential for drug R&D and large-scale manufacturing.

Reference: United States Pharmacopeia (USP) ↗

3. Materials & Surface Treatment - Hydrophobization Agent

HMDS is a highly effective hydrophobization agent for inorganic fillers such as fumed silica and titanium dioxide. Surface modification with HMDS significantly improves filler–matrix compatibility in silicone rubber and epoxy resin composites, enhancing mechanical properties (toughness, tensile strength) and weather resistance. It is widely used in OLED encapsulation materials and photovoltaic module glass treatment, where HMDS-modified surfaces show markedly improved moisture barrier performance, extending service life in harsh outdoor environments.

For glass, ceramic, and metal surface treatment, HMDS forms a dense, covalently bonded hydrophobic film that prevents moisture absorption and corrosion.

Reference: PubChem - Hexamethyldisilazane (NIH) ↗

4. Analytical Chemistry & Fine Chemicals

In analytical chemistry, HMDS is used as a derivatization reagent for GC analysis of protic compounds (alcohols, phenols, carboxylic acids). Silylated derivatives exhibit higher volatility and improved chromatographic separation, enabling precise quantitative analysis of trace substances in complex matrices.

In fine chemicals, HMDS serves as an intermediate for high-end silicone surfactants and silicone resins used in daily chemicals and textile printing. The electronic-grade HMDS market is projected to grow at a CAGR of 18.3% through 2026, driven by accelerating semiconductor localization and expansion of pharmaceutical CDMO capacity.

Reference: ECHA REACH Registration - HMDS ↗

5. HMDS as a Base - LiHMDS, NaHMDS & KHMDS

Beyond its role as a silylating agent, HMDS is a key precursor to the widely used metal amide bases: LiHMDS (lithium hexamethyldisilazide, lithium bis(trimethylsilyl)amide), NaHMDS (sodium hexamethyldisilazide), and KHMDS (potassium hexamethyldisilazide). These strong, hindered bases are essential reagents in pharmaceutical and fine chemical synthesis for selective enolate formation, directed deprotonation, and asymmetric reactions where steric bulk and chemoselectivity are critical.

LiHMDS (CAS 4039-32-1) is the most widely used, prized for its high basicity (pKa ~30 in THF) and excellent solubility in ethereal solvents. NaHMDS and KHMDS offer increasing reactivity and are used where LiHMDS is insufficiently reactive. All three are manufactured from HMDS as the key starting material, making high-purity HMDS supply critical to their production.

We supply high-purity HMDS suitable as feedstock for LiHMDS, NaHMDS, and KHMDS production. Contact us for bulk specifications.

⚠️ CRITICAL SAFETY NOTE: HMDS is highly flammable (flash point 17°C) and reacts violently with water, releasing ammonia. Store and handle exclusively in nitrogen-protected, explosion-proof environments. Do not use water to extinguish HMDS fires.

Bulk pricing tips: Orders above 50 MT typically qualify for a 5–10% discount; 200+ MT/year contracts can unlock 10–15% savings. Tank truck delivery reduces per-unit freight by 8–12% versus drum packaging. Long-term agreements (1–3 years) include priority supply allocation during peak semiconductor demand seasons. Request a custom HMDS price quote →

Q: What does HMDS stand for? What is HMDS full form?

HMDS stands for Hexamethyldisilazane - the full chemical name is 1,1,1,3,3,3-hexamethyldisilazane, also written as hexa methyl disilazane. In chemistry, HMDS specifically refers to this organosilicon compound (CAS 999-97-3) with the structure (CH₃)₃Si–NH–Si(CH₃)₃. Note: "HMDS" is also used as an abbreviation in unrelated fields (e.g., medical, military, or agricultural contexts), but in chemistry and semiconductor manufacturing contexts, HMDS invariably means hexamethyldisilazane.

Q: What is HMDS used for in semiconductor manufacturing?

HMDS is used as a vapor-phase adhesion promoter (primer) applied to silicon wafer surfaces before photoresist coating. It reacts with surface Si–OH groups to form a hydrophobic trimethylsilyl monolayer, which dramatically improves photoresist adhesion, prevents delamination during wet development, and ensures dimensional accuracy of fine circuit patterns. It is a standard process material at virtually every silicon wafer fab globally, from legacy 200mm to leading-edge 300mm EUV lithography lines.

Q: What is the difference between Industrial Grade and Electronic Grade HMDS?

Industrial Grade (≥98.0%) is suitable for surface treatment of fillers (fumed silica, TiO₂), coatings, and general silylation applications where trace metal content is not critical. Electronic Grade (≥99.999%, 5N) requires individual metal impurities below 1 ppb - mandatory for semiconductor lithography where sub-ppb metallic contamination would cause device failures. Electronic Grade is packaged under ultra-clean ISO 14644 conditions in quartz-lined or certified ultra-clean steel drums, with each batch accompanied by a full ICP-MS trace metals report.

Q: Why does HMDS react with water, and how should it be stored?

HMDS contains a Si–N–Si bond that is highly susceptible to hydrolysis: (CH₃)₃Si–NH–Si(CH₃)₃ + H₂O → 2 (CH₃)₃SiOH + NH₃. The released ammonia creates pressure buildup in sealed containers, and the resulting hexamethyldisiloxane (HMDSO) contaminates the product. All grades must therefore be stored under dry nitrogen in sealed containers, at 0–25°C, away from any moisture source. Open containers should be immediately re-sealed and blanketed with nitrogen after each use.

Q: What is HMDS and how does it differ from HMDSO?

HMDS (hexamethyldisilazane, CAS 999-97-3) contains a Si–N–Si linkage and is the active silylating reagent. HMDSO (hexamethyldisiloxane, CAS 107-46-0) contains a Si–O–Si linkage and is the hydrolysis by-product of HMDS - it is far less reactive. HMDS is used as a chemical surface modifier and silylation reagent; HMDSO is used mainly as a non-reactive silicone fluid and raw material for HMDS synthesis. The two should not be confused when specifying materials for lithography or pharmaceutical processes.

Q: What certifications should I require from an HMDS supplier?

For industrial applications: ISO 9001 (quality management) and ISO 14001 (environmental). For pharmaceutical grade: GMP compliance, ability to provide USP/EP-referenced COA, and third-party QC reports. For electronic grade: confirmation of downstream semiconductor fab qualification (e.g., SMIC, UMC certifications), SEMI F47 or equivalent materials standards compliance, full ICP-MS trace metals report per batch, and ISO 14644-certified clean packaging. All grades should carry current REACH and TSCA registrations for international export.

Q: What are the main alternatives to HMDS, and when is HMDS preferred?

Common silylating agent alternatives include trimethylchlorosilane (TMCS), N-methyl-N-trimethylsilylacetamide (MSA), and N,O-bis(trimethylsilyl)acetamide (BSA). HMDS is preferred when mild reaction conditions are required (no HCl by-product), when high silylation yield is critical, or when the process requires minimal contamination from acidic or corrosive by-products - making it the standard choice for semiconductor wafer treatment and pharmaceutical synthesis. For bulk industrial hydrophobization where cost is the primary driver, TMCS may be used as a lower-cost alternative.