HMDS (Hexamethyldisilazane) process recipe

Spin coating

The manufacturer does not publish a spin curve for HMDS (Hexamethyldisilazane). HMDS must not be spin-coated as a liquid — the only correct application is vapor-phase, via a nitrogen-carrier 'bubbler' held at room temperature feeding a heated (75-120°C) substrate, where HMDS bonds chemically as a monolayer ("Correct Use of HMDS", Fig. 47-48, p.2). If liquid HMDS is spun on instead, the resulting layer is only physically (not chemically) bound; ammonia released from it during the resist softbake diffuses into and cross-links the resist near the substrate, suppressing development and degrading resolution and profile ("Incorrect Application of HMDS", Fig. 49, p.2-3) — this failure mode is explicitly documented, not inferred. For the same reason, the note advises against applying HMDS in the same spin coater used for resist coating (slow HMDS evaporation can contaminate later coating runs); if spin-application is unavoidable, it recommends a 100-120°C water-desorption bake beforehand, a 100-120°C thermal-activation bake afterward, and strict spatial separation from resist-coating equipment (p.3). Because there is no legitimate spin-speed-vs-thickness relationship for a vapor-deposited chemisorbed monolayer, spinCurves is empty by design, not because data is missing.

Soft bake

Soft bake

Not published — characterize on-tool

Notes

This field is repurposed to record the bake/process temperatures this note actually publishes for HMDS, since the schema has no dedicated vapor-prime field. Correct (vapor-phase) HMDS application: HMDS vapor is carried by dry nitrogen from a room-temperature bubbler to a substrate heated to 75-120°C, where it bonds chemically as a monolayer (p.2). No dwell time is stated for this step, and temperature is given only as a range (75-120°C), so both temp_c and time_s are left null here rather than fabricated as a single value; the range is recorded in this note instead. If HMDS can only be applied by spin-coating (the note's documented 'incorrect' fallback), it separately recommends a 100-120°C bake to desorb water before HMDS application and a further 100-120°C activation bake afterward (p.3) — again stated as ranges. A general, non-HMDS-specific substrate dehydration bake of 'approx. 120°C for a few minutes' (optionally above 140°C on oxidized surfaces, to maximize adhesion) is described as a preceding step independent of which adhesion promoter is used ("Adsorbed Water", p.1).Show more

SOURCE: Correct Use of HMDS / Incorrect Application of HMDS, p.2-3; Adsorbed Water, p.1

Exposure

HMDS (Hexamethyldisilazane) is not photoimageable. It is not exposed at all — it is coated beneath an imaged top resist and undercut laterally during development. See the development step below.

Development

Not published for this resist: Developer, Dilution, Time, Method, Rinse — characterize on-tool.

Hard bake, etch & strip

Not published for this resist: Hard bake, Descum, Etch resistance, Stripper, Storage — characterize on-tool.

Where it's used

HMDS (hexamethyldisilazane) is a vapor-phase adhesion promoter, not a photoimageable resist: it converts a hydrophilic, OH-terminated oxide surface (native or thermal SiO2, quartz, glass, most base metals) into a hydrophobic, resist-wetting surface by chemically bonding a monolayer of non-polar trimethylsilyl groups, releasing ammonia as a byproduct (p.2). The only correct application is vapor-phase, via a nitrogen-carrier bubbler at room temperature feeding a substrate heated to 75-120°C; spin-coating liquid HMDS instead yields only a physically bound layer whose ammonia, released during the subsequent resist softbake, diffuses into and cross-links the resist near the substrate, suppressing development and degrading resolution — a failure mode this note documents explicitly as 'Incorrect Application' (p.2-3). On noble metals without native oxide (gold, platinum), HMDS and other organic adhesion promoters show little to no adhesion benefit because they cannot chemically bond to the surface; base metals such as Al, Cr and especially Ti already adhere well without a promoter (p.3-4). This document is a general MicroChemicals application-note chapter ('01 Chapter — Basics of Microstructuring: Substrate Preparation'), not a manufacturer technical datasheet for a specific HMDS product or grade — HMDS itself is a commodity chemical sold by many suppliers, and this note is the correct place to attribute process guidance about it rather than any single vendor's TDS.

Sources & disclaimer

• MicroChemicals GmbH (application-note publisher; HMDS itself is a commodity chemical sold by many suppliers, not a single manufacturer's proprietary product) — HMDS (Hexamethyldisilazane) datasheet · accessed 2026-07-10

Manufacturer datasheet values are starting points; optimal parameters depend on your substrate, equipment and environment. Product names and trademarks belong to their respective owners. NANYTE is not affiliated with the manufacturers listed. Last updated 2026-07-10.

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