PMGI SF6 process recipe

Spin coating

PMGI SF6 is spin-coated to 0.3–0.5 µm. The curve below is redrawn from the manufacturer's published data — read your target thickness off the vertical axis and take the matching spin speed as a starting point.

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.

Soft bake

Soft bake

Not published — characterize on-tool

Notes

Recommended bake TEMPERATURE RANGE is 150-200°C (some PMGI products may be baked up to 250°C) - a range, not a single value, so temp_c is left null. Pre-bake (soft-bake) temperature is stated as having the single greatest influence on undercut rate, more so than pre-bake time, the patterning resist's exposure dose, developer choice, develop mode, or develop time. Hot plates are preferred; convection ovens are also compatible. No single recommended temperature or time is stated for SF6 specifically - the document instead recommends a matrix design varying pre-bake temperature and time for process fine-tuning per grade. Separately, Table 1's optical-constant (n/k) measurements for the SF family (which includes SF6) were taken on samples soft-baked at 180°C for 3 minutes, but this is stated as the optical-measurement condition, not a general process recommendation, so it is not used to populate temp_c/time_s either.Show more

SOURCE: 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). General text elsewhere states the line is "optimized for use with various metal ion free and metal ion containing developers," a broader claim than the SF-specific selection-guide row.Show more

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.Show more

Developer family

TMAH-based

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. Removal rate of LOR/PMGI is dependent upon soft-bake temperature of the LOR/PMGI product and remover bath temperature. As a baseline process, use Remover PG in two tanks: at 60°C for 30 minutes in the first tank and rinse at 60°C in the second tank. Ultrasonic action will improve the resist removal efficiency." (Lift-Off Process, p.4). A separate category-level chart (Figure 9, p.4, labeled "SF Series" - not SF6 individually) shows removal rate in Remover PG rising with bath temperature (40°C bath removes faster than 25°C) and falling as the PMGI's own soft-bake temperature increases (150 -> 180 -> 200°C); exact rates were not extracted here since the chart is not SF6-specific and its bar-scale precision is limited.Show more

Storage

"Store upright in original sealed containers in a dry area between 4 and 27°C (40-80°F). Keep away from sources of ignition, light, heat, oxidants, acids, and reducers. Do not use after the expiration date (1 year from date of manufacture)." (LOR/PMGI Storage, p.7)Show more

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

Where it's used

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.

Sources & disclaimer

• MicroChem — PMGI SF6 datasheet (Rev. A (printed bottom-right of p.7)) · accessed 2026-07-10

1. Cord et al.. Robust shadow-mask evaporation via lithographically controlled undercut. Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena (2006). doi:10.1116/1.2375090
   The Dolan-bridge PMMA/PMGI undercut process used worldwide for superconducting-qubit Josephson junctions.

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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