https://nanyte.com/photoresists/pmgi-sf-6 · last updated 2026-07-26
- Manufacturer
- MicroChem
- Tone
- Not photoimageable (underlayer)
- Chemistry
- Ancillary (not photoimageable)
- Thickness
- 0.3–0.5 µm
- Exposure dose
- Not exposed — dissolves in developer
- Developer
- Metal-ion-free (MIF) developers, specifically 0.26N and 0.24N MIF per the Product Selection Guide's "SF" column (SF6's category); the SF category is NOT starred for metal-ion-bearing (MIB) compatibility in that same guide (only LOR B is).
- Applications
- Lift-off · MEMS structural
Cross-checked — two independent extractions agree on the spin curve and the single-value figures.
- Substrate
- Underlayer
- Resist
- Exposed
Spin coating
Data points
| Series | rpm | µm |
|---|---|---|
| PMGI SF6 | 1000 | 0.48 |
| 1500 | 0.39 | |
| 2000 | 0.34 | |
| 2500 | 0.30 | |
| 3000 | 0.28 | |
| 3500 | 0.27 | |
| 4000 | 0.26 |
Values are the manufacturer’s starting points, not a guarantee — characterize on your own tool. Series digitized from a published figure are approximate (±10 %).
read from figure ("Spin Speed vs Thickness - Intermediate Films"), p.5 of the "LOR and PMGI Resists" Technical Data section. Five traces share this chart (legend: LOR 7B - open square; LOR 5A - open circle; LOR 5B - x; "LOR 3A, LOR 3B" combined - open diamond; SF6 - open triangle). The SF6 trace was identified unambiguously by its own dedicated triangle-marker legend entry, distinct from the explicitly-combined 'LOR 3A, LOR 3B' diamond series (which was NOT used for this recipe per the no-combined-trace rule) and from the other individually-named LOR grades. SF6 is the bottommost (thinnest) of the five traces at every plotted speed and is also the only one of the five sampled at 500 rpm intervals (1000-4000 rpm, 7 points) rather than 1000 rpm intervals (4 points) used for the other four traces on the same chart.
- General coating guidance (p.2, applies to the LOR/PMGI line as a whole, not SF6-specific numbers): spin speeds between 2,500 and 4,500 rpm give maximum coating uniformity
- higher speeds for smaller substrates, lower for larger or topographically irregular substrates.
- Recommended Coating Parameters box (p.5, generic to the line): dispense volume 5 ml (150 mm Si wafer), dispense mode dynamic 3-5 s, dispense spin speed 300-500 rpm, acceleration 10,000 rpm/second, terminal spin speed 3,000 rpm, spin time 45 seconds, edge-bead remover MicroChem EBR PG (acetone and conventional-resist edge-bead removers are explicitly NOT recommended with LOR/PMGI).
- None of this coating-parameter box is stated as SF6-specific - it is a line-wide recommendation.
- Adhesion
- HMDS not required — "Primers such as HMDS (hexamethyldisilazane) are typically NOT required to promote adhesion with PMGI/LOR products when used as recommended." (Substrate preparation, p.2).
Soft bake
- Soft bake
- 150–200 °C · hotplate
- Notes
- Recommended bake range is 150-200°C; some PMGI grades take up to 250°C. Pre-bake temperature has the single largest influence on undercut rate — more than pre-bake time, the imaging resist's exposure dose, developer choice, develop mode or develop time.
SOURCE: Soft-bake/Prebake Process section, p.3 ("The recommended bake…
Soft-bake/Prebake Process section, p.3 ("The recommended bake temperature range is 150°C - 200°C..."); Table 1 footnote, p.5 ("Products were soft-baked at 180°C for 3 min")
Exposure
PMGI SF6 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
- Developer
- Metal-ion-free (MIF) developers, specifically 0.26N and 0.24N MIF per the Product Selection Guide's "SF" column (SF6's category); the SF category is NOT starred for metal-ion-bearing (MIB) compatibility in that same guide (only LOR B is).
- Dilution
- 0.26N MIF (2.38% TMAH) and 0.24N MIF (2.2% TMAH w/surfactant) are both marked compatible for the "SF" category in the Product Selection Guide (p.6); no single dilution is singled out as SF6's own specific recommendation.
- Developer family
- TMAH or buffered alkaline
Not published for this resist: Time, Method, Rinse — characterize on-tool.
SOURCE: Development Process section, p.4; Product Selection Guide ("Developer Compatibility" rows, "SF" column), p.6
Hard bake, etch & strip
- Stripper
- MicroChem Remover PG. "Use MicroChem's Remover PG to remove the bi-layer resist stack.
- Storage
- "Store upright in original sealed containers in a dry area between 4 and 27°C (40-80°F).
Not published for this resist: Hard bake, Descum, Etch resistance — characterize on-tool.
Where it's used
Practical notes from the datasheet
PMGI SF6 belongs to MicroChem's PMGI SF series (SF2/SF3/SF5/SF6/SF9/SF11, plus a slower-dissolving 'SF Slow' variant), a polydimethylglutarimide-based ancillary layer that is never itself exposed for patterning: in the standard bi-layer lift-off flow it is coated and soft-baked first, then a conventional imaging resist is coated, exposed and developed on top, and the same develop step dissolves an undercut into the PMGI beneath the imaging-resist pattern. Its dissolution rate - and therefore the achievable undercut geometry - is controlled primarily by SOFT-BAKE TEMPERATURE rather than by exposure or develop time; this datasheet's own quantified bake-temperature-vs-undercut-rate curves (Figures 5a/5b) are published only for LOR 10B, not for SF6, so no grade-specific undercut-rate number is reported here - a matrix design varying pre-bake temperature and time is explicitly recommended instead for fine-tuning any given grade. HMDS priming is explicitly NOT required for PMGI/LOR adhesion, and the document notes the overlying imaging resist can be applied directly over PMGI without barrier layers or a plasma descum step. As a PMGI-branded (not LOR-branded) product, SF6 is also compatible with an optional 'Cap-On' process in which the PMGI layer is separately deep-UV (240-290 nm) flood exposed to obtain straighter sidewall profiles - the document ties this option to PMGI generically rather than to SF6 specifically, so it is noted here as available but not confirmed SF6-specific. Stripping uses MicroChem Remover PG (baseline two-tank 60°C/30 min process); actual removal rate depends on the layer's own soft-bake temperature and the remover bath temperature.
Troubleshooting
Common failure modes for PMGI SF6, answered from the manufacturer's datasheet and application notes. These are starting points — your substrate, tooling and environment shift the specifics, so calibrate on-tool.
Is PMGI SF6 exposed like a normal photoresist?
No. PMGI SF6 is a non-photoimageable, polydimethylglutarimide-based underlayer — it is never exposed for patterning. In the standard bilayer lift-off flow it is coated and soft-baked first; a conventional imaging resist is then coated, exposed and developed on top, and the same develop step dissolves an undercut into the PMGI beneath the imaging-resist pattern. The datasheet notes LOR/PMGI does not require post-exposure baking.
SOURCE: MicroChem 'LOR and PMGI Resists' datasheet Rev. A, Post-Exposure (PEB) Process section, p.4
How do I control the undercut of PMGI SF6?
Its dissolution rate — and therefore the achievable undercut — is controlled primarily by soft-bake temperature, stated to have the single greatest influence (more than pre-bake time, the imaging resist's dose, developer choice, develop mode or develop time). Recommended bake range is 150–200 °C (some PMGI grades to 250 °C); a matrix varying pre-bake temperature and time is recommended for tuning. The datasheet's quantified undercut-rate curves are published only for LOR 10B, not SF6, so characterize SF6's rate on-tool.
SOURCE: MicroChem 'LOR and PMGI Resists' datasheet Rev. A, Soft-bake/Prebake Process, p.3
Which developer does PMGI SF6 use?
The Product Selection Guide marks the SF category compatible with metal-ion-free (MIF) developers — 0.26N (2.38% TMAH) and 0.24N (2.2% TMAH with surfactant); the SF category is not starred for metal-ion-bearing compatibility (only LOR B is). No SF6-specific develop time, method or rinse is published — develop time depends on the combined thickness of the PMGI and overlying imaging-resist layers and must be set experimentally.
SOURCE: MicroChem 'LOR and PMGI Resists' datasheet Rev. A, Development Process p.4 + Product Selection Guide p.6
Does PMGI SF6 need HMDS or a descum/barrier layer under the imaging resist?
No. HMDS priming is explicitly not required for PMGI/LOR adhesion, and the overlying imaging resist can be applied directly over the PMGI without barrier layers or a plasma descum step (no intermixing occurs). Recommended substrate prep is a solvent clean or dilute-acid rinse, a DI water rinse, then a dehydration bake at 200 °C (5 min on a contact hotplate or 30 min in a convection oven).
SOURCE: MicroChem 'LOR and PMGI Resists' datasheet Rev. A, Substrate preparation, p.2
Can PMGI SF6 sidewalls be made straighter?
Yes — as a PMGI-branded product, SF6 is compatible with an optional 'Cap-On' process in which the PMGI layer is separately deep-UV (240–290 nm) flood exposed to obtain straighter sidewall profiles. The datasheet ties this option to PMGI generically rather than to SF6 specifically, so treat it as available but characterize on-tool.
SOURCE: MicroChem 'LOR and PMGI Resists' datasheet Rev. A (PMGI 'Cap-On' deep-UV flood option)
Sources & disclaimer
- MicroChem — PMGI SF6 datasheet (Rev. A (printed bottom-right of p.7)) · accessed 2026-07-10
- Cord et al.. Robust shadow-mask evaporation via lithographically controlled undercut. Journal of Vacuum Science & Technology B (2006). doi:10.1116/1.2375090The Dolan-bridge PMMA/PMGI undercut process for evaporated Josephson junctions; PMGI develops in aqueous base, enabling a controlled undercut independent of the PMMA imaging layer.
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 2026-07-26.