https://nanyte.com/photoresists/lor-7a · last updated 2026-09-28
- Manufacturer
- MicroChem (MCC) — now Kayaku Advanced Materials
- Tone
- Not photoimageable (underlayer)
- Chemistry
- Ancillary (not photoimageable)
- Thickness
- 0.4–1.1 µm
- Exposure dose
- Not exposed — dissolves in developer
- Developer
- 0.26N or 0.24N TMAH (no product named); metal-ion-bearing developers are not rated for LOR A (selection guide, p.7).
- Applications
- Lift-off
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 |
|---|---|---|
| LOR 7A | 1000 | 1.1 |
| 1500 | 0.71 | |
| 2000 | 0.66 | |
| 2500 | 0.56 | |
| 3000 | 0.50 | |
| 3500 | 0.46 | |
| 4000 | 0.44 |
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 — the red filled-square trace legended LOR 7A on the 'Thickness vs. Spin Speed - LOR A Thick Series' chart, p.5, second from the bottom of the four traces. Seven plotted markers at 500 rpm intervals; no numeric table accompanies the chart.
- The curve has a pronounced knee: 10,700 Å at 1000 rpm drops to about 7,100 Å by 1500 and then eases, reaching 4,400 Å at 4000 rpm.
- Almost half the available thickness range is spent in the first 500 rpm, so slow spins on this grade need tight speed control while anything above 2000 rpm is forgiving.
- It runs just above LOR 5A across the sweep and the two converge at the fast end.
- One published quirk is worth knowing before fitting anything to this curve: the 1500 rpm point sits slightly below a smooth fit through its neighbours, because the 1500-2000 rpm step is shallower than the 2000-2500 one.
- That is how the manufacturer plots it, so the trace is not perfectly monotonic in slope around the knee.
- Coating parameters are published for the product line rather than per grade: 5 ml dispensed dynamically over 3-5 s onto a 150 mm wafer at 300-500 rpm, 10,000 rpm/s acceleration to a 3,000 rpm terminal speed, 45 s spin, with EBR PG for edge-bead and whisker removal.
- Adhesion
- HMDS not required — "Primers, such as HMDS, are typically not required" when LOR/PMGI is used as recommended; the datasheet describes excellent adhesion across semiconductor substrates. To dehydrate the surface first, bake at 200 °C for 5 min. LOR/PMGI is virtually insoluble in typical photoresist solvents, so a properly baked underlayer does not intermix with the imaging resist above it.
Soft bake
- Soft bake
- 160–210 °C · hotplate
- Notes
- The prebake dries the film and fixes its dissolution and undercut rate, and no grade-specific temperature or time is published. The recommended prebake range for the product line is 160-210 °C, hotplate preferred, and some PMGI products bake as high as 280 °C. Prebake temperature has the greatest influence on undercut rate, with prebake time, developer choice, develop mode and especially develop time behind it. The published undercut-versus-bake curves (Figures 5a and 5b) are measured on LOR 10B — a B-series grade of comparable thickness but faster dissolution — so they give the shape of the relationship rather than numbers to copy onto an A grade.
SOURCE: Rev. D p.3: 'The recommended bake temperature range is 160°C –…
Rev. D p.3: 'The recommended bake temperature range is 160°C – 210°C'; 'Hot plates are the preferred tool for the prebake step.'
Exposure
LOR 7A 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
- 0.26N or 0.24N TMAH (no product named); metal-ion-bearing developers are not rated for LOR A (selection guide, p.7).
- Developer family
- TMAH or buffered alkaline
Not published for this resist: Dilution, Time, Method, Rinse — characterize on-tool.
SOURCE: Product description, the LOR/PMGI process-flow section and the…
Product description, the LOR/PMGI process-flow section and the product selection guide, Kayaku "LOR and PMGI Resists" technical data sheet, Rev. D (August 2023)
Hard bake, etch & strip
- Stripper
- Remover PG. EBR PG removes edge beads and whiskers and is also an effective spin-bowl cleaner and a rework solvent for unbaked wafers.
- Storage
- Store upright in original sealed containers in a dry area between 10 and 24 °C (50-76 °F), away from ignition sources, light, heat, oxidants, acids and reducers. Do not use after the expiration date, 13 months from manufacture.
Not published for this resist: Hard bake, Descum, Etch resistance — characterize on-tool.
Where it's used
Practical notes from the datasheet
LOR 7A is a PMGI-based sacrificial underlayer from the slow-dissolving A series, spun beneath a conventional photoresist and never exposed. It occupies the gap between LOR 5A and LOR 10A, and in practice that is exactly how it gets chosen: a target around 0.6-0.8 µm sits in the middle of this grade's usable band where its neighbours would each be working at the end of theirs. The underlayer is picked against the deposited film rather than the feature — it must be thicker than the metal so the deposit breaks cleanly at the edge — and the A series is the slower of the three dissolution families, so the undercut opens gradually and the process window is wider than a B or C grade would give. Nothing here is exposed, so prebake temperature and develop time are the only real controls.
Grades in this family
Other grades in the LOR A series line differ mainly in coating thickness:
Troubleshooting
Common failure modes for LOR 7A, 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.
Undercut under LOR 7A is too small for a clean lift-off. Do I need a B grade instead?
Depends how much ledge you need. The selection guide recommends LOR A for undercuts of 0.35-1.0 µm and gives it only some compatibility above 1 µm; beyond a micron, LOR B and LOR C are the recommended products. Inside that band, lower the prebake within the 160-210 °C range, since temperature is the strongest lever, then extend develop time. Develop time is set by both films together, so changing the imaging resist's thickness on top of 7A moves the ledge as well.
SOURCE: Kayaku Advanced Materials, "LOR and PMGI Resists" technical…
Kayaku Advanced Materials, "LOR and PMGI Resists" technical data sheet, Rev. D (August 2023) — Soft-Bake/Prebake Process, p.3; Development Process, p.4; Product Selection Guide (Undercut Geometry), p.7
LOR 7A coats unevenly or traps bubbles over topography. What's the fix?
The selection guide hatches out via fill and topography coating for both the A and B series, so 7A is not rated for it. The datasheet's advice is to spin substrates with deep topography or an irregular shape more slowly, and it recommends the LOR C products for coating into trenches or over topography without trapping bubbles. If you do slow down on 7A, the film thickens fast below 1500 rpm (0.71 µm at 1500 rpm, 1.07 µm at 1000 rpm), so re-check it against your deposit.
SOURCE: Kayaku Advanced Materials, "LOR and PMGI Resists" technical…
Kayaku Advanced Materials, "LOR and PMGI Resists" technical data sheet, Rev. D (August 2023) — Coating Process, p.2; Thickness vs. Spin Speed, LOR A Thick Series chart, p.5; Product Selection Guide (Coating), p.7
Can I develop an LOR 7A stack in a metal-ion-bearing developer?
Not by the selection guide's A-series row: it recommends 0.26N and 0.24N TMAH for LOR A and hatches out MIB (metal-ion-bearing) developers, which it rates only for the B series. The general text says LOR/PMGI works with both MIF and MIB chemistries, so go by the per-series row before swapping developers under 7A.
SOURCE: Kayaku Advanced Materials, "LOR and PMGI Resists" technical…
Kayaku Advanced Materials, "LOR and PMGI Resists" technical data sheet, Rev. D (August 2023) — Development Process, p.4; Product Selection Guide (Developer Compatibility), p.7
Sources & disclaimer
- MicroChem (MCC) — now Kayaku Advanced Materials — LOR 7A datasheet (Rev. D, August 2023 (printed in the footer of every page)) · accessed 2026-09-10
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 2026-09-28.