https://nanyte.com/photoresists/lor-3a · last updated 2026-09-28
- Manufacturer
- Kayaku Advanced Materials
- Tone
- Not photoimageable (underlayer)
- Chemistry
- Ancillary (not photoimageable)
- Thickness
- 0.2–0.4 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 3A | 1000 | 0.44 |
| 1500 | 0.32 | |
| 2000 | 0.27 | |
| 2500 | 0.24 | |
| 3000 | 0.23 | |
| 3500 | 0.21 | |
| 4000 | 0.20 |
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 green filled-triangle trace legended LOR 3A on the 'Thickness vs. Spin Speed - LOR A Thin Series' chart, p.5, the highest of the three traces. Seven plotted markers at 500 rpm intervals; no numeric table accompanies the chart.
- The thickest of the three traces on the A-thin chart, falling from 4,400 Å at 1000 rpm to 2,030 Å at 4000 rpm — a little over a factor of two across the sweep, with most of the drop before 2000 rpm and a near-flat tail after 3000.
- 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 — HMDS priming is explicitly stated as typically NOT required to promote adhesion with LOR/PMGI products. LOR exhibits excellent inherent adhesion to Si, glass, NiFe, GaAs, InP and other III-V/II-VI materials, and Au. Substrate prep: solvent clean or dilute-acid rinse followed by DI water rinse, then a dehydration bake at 200°C for 5 min (contact hotplate) or 30 min (convection oven) immediately before coating.
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. Hotter and longer both slow the dissolution and tighten the undercut. The published undercut-versus-bake curves (Figures 5a and 5b) are measured on LOR 10B, a faster B-series grade several times thicker, so they show the shape of the relationship rather than numbers to transfer here. Two cleanroom procedures cited below run this grade at 180 °C for 4-5 min, which is a fair starting point drawn from practice rather than from the manufacturer.
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 3A 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: 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; Thickness vs. Spin Speed, LOR A Thin Series chart, p.5; Product Selection Guide (Developer Compatibility), p.7
Hard bake, etch & strip
- Descum
- Not required. The datasheet states no intermixing occurs between LOR and the imaging resist above it, so the bilayer stack does not need a plasma descum step between coating the LOR layer and the patterning resist.
- Stripper
- Remover PG, or another NMP- or DMSO-based remover, strips the bi-layer stack. Baseline process: two Remover PG tanks, 30 min at 60 °C in the first, followed by a 60 °C rinse in the second; ultrasonic action improves removal. Removal rate depends on the LOR soft-bake temperature and the bath temperature, and actual times vary with prebake conditions, later processing and the pattern (Lift-Off Process, p.4). Acetone and conventional edge-bead removers are not recommended with LOR/PMGI; EBR PG handles edge beads, bowl clean-up and rework of unbaked wafers (Edge Bead Removal, p.3). Where conventional resist and LOR/PMGI share a coater, a dedicated coat bowl and drain are recommended, but not mandatory, to limit drain-line clogging (Coating Process, p.2).
- Storage
- Store upright in original sealed containers in a dry area between 10-24°C (50-76°F), away from ignition sources, light, heat, oxidants, acids, and reducers. Do not use past the expiration date (13 months from date of manufacture). Recommended processing environment: 20-25°C ± 1°C, 35-45% ± 2% relative humidity.
Not published for this resist: Hard bake, Etch resistance — characterize on-tool.
Where it's used
Practical notes from the datasheet
LOR 3A is not a photoresist in the imaging sense — it is a non-photoimageable PMGI underlayer that is coated and soft-baked beneath a conventional imaging resist, which alone is exposed and developed. During development the LOR layer dissolves isotropically (laterally undercutting beneath the imaged top resist), producing the re-entrant sidewall profile a clean bilayer lift-off requires. Undercut is set mainly by the LOR prebake: prebake temperature has the greatest influence on undercut rate, and a hotter bake slows dissolution, so it narrows the undercut for a given develop time. The recommended hotplate range is 160-210 °C. No undercut rate is published for LOR 3A itself; the bake-versus-rate curves are measured on LOR 10B. Prebake time, developer choice, develop mode and particularly develop time also matter, and the undercut-versus-develop-time bars grow as develop time goes from 2 to 3 min. HMDS priming is explicitly not required. For clean lift-off, LOR film thickness should exceed the deposited metal thickness, typically by 33% per the current datasheet.
Grades in this family
Other grades in the LOR A series line differ mainly in coating thickness:
Troubleshooting
Common failure modes for LOR 3A, 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.
Do I need to expose LOR 3A?
Not in the standard bilayer process. Kayaku's datasheet says LOR/PMGI do not require an exposure step: only the imaging resist on top is exposed, and the LOR then develops isotropically beneath it, undercutting the imaged resist to form the re-entrant profile a clean lift-off needs. Any PEB in the flow belongs to the imaging resist, not to LOR 3A.
SOURCE: Kayaku Advanced Materials, "LOR and PMGI Resists" technical…
Kayaku Advanced Materials, "LOR and PMGI Resists" technical data sheet, Rev. D (August 2023) — Figure 4 process flow, p.2; Application and Processing the Patterning Resist Layer, p.3; Post Exposure Bake (PEB) Process, p.4
How do I control the undercut for lift-off with LOR 3A?
Mostly with the prebake. The datasheet names prebake temperature as the strongest influence on undercut rate, ahead of prebake time, developer choice, develop mode and develop time, and recommends a hotplate bake at 160-210 °C. A hotter bake slows dissolution: on the one grade whose undercut rate it plots, LOR 10B, the rate drops about 1 nm/s per °C. No undercut rate is published for 3A, so run the matrix the datasheet asks for, prebake temperature against develop time, and measure the ledge you get.
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 and Figure 5a, p.3
Which developer does LOR 3A use?
No developer product is named. LOR/PMGI is optimized for metal-ion-free and metal-ion-bearing developers in general; LOR 3A is charted in the LOR A Thin Series, and the selection guide recommends LOR A with 0.26N and with 0.24N TMAH, leaving metal-ion-bearing developers unrated for it. Develop time is not published either, since the LOR and imaging-resist thicknesses together set it. Spray development for straighter sidewalls is advised only for LOR/PMGI layers over 2 µm, well above any 3A coat.
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; Thickness vs. Spin Speed, LOR A Thin Series chart, p.5; Product Selection Guide (Developer Compatibility), p.7
Can I strip LOR 3A with acetone?
No. The datasheet says acetone and conventional resist edge-bead removers are not recommended with LOR/PMGI, and gives EBR PG for edge beads, whiskers and rework of unbaked wafers. To strip the bi-layer stack, use Remover PG or another NMP- or DMSO-based remover. The baseline is two Remover PG tanks: 30 min at 60 °C in the first, then a 60 °C rinse in the second, with ultrasonics improving removal. Removal rate depends on the LOR soft-bake temperature and the bath temperature, so actual times vary.
SOURCE: Kayaku Advanced Materials, "LOR and PMGI Resists" technical…
Kayaku Advanced Materials, "LOR and PMGI Resists" technical data sheet, Rev. D (August 2023) — Edge Bead Removal, p.3; Lift-Off Process, p.4
Does LOR 3A need HMDS priming?
No. The datasheet says primers such as HMDS are typically not required with LOR/PMGI used as recommended. It lists excellent adhesion to Si, NiFe, GaAs, InP and other III-V and II-VI materials, and the selection guide also recommends LOR A on glass and Au. Start clean and dry: 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: Kayaku Advanced Materials, "LOR and PMGI Resists" technical…
Kayaku Advanced Materials, "LOR and PMGI Resists" technical data sheet, Rev. D (August 2023) — Features, p.1; Substrate Preparation, p.2; Product Selection Guide (Substrate Compatibility), p.7
Sources & disclaimer
- Kayaku Advanced Materials — LOR 3A datasheet (Rev. D, August 2023 (printed in the footer of every page)) · accessed 2026-09-10
- https://bionium.miami.edu/_assets/pdf/lor-3a-photoresist-process.pdf — University of Miami cleanroom process recipe for LOR 3A, showing typical practical parameters: 180°C/5min softbake, 3000rpm/35s spin, CD-26 60-90s or MF-319 45-60s develop
- https://cns1.rc.fas.harvard.edu/facilities/docs/SOP112_r1_1_%20LOR.pdf — Harvard CNS SOP112 lift-off processing procedure, showing a typical bake (180°C/4min) and CD-26 develop (75s), and confirming HMDS is not used with LOR
- Chen et al.. A lift-off process for high resolution patterns using PMMA/LOR resist stack. Microelectronic Engineering (2004). doi:10.1016/j.mee.2004.02.053Demonstrates sub-100 nm lift-off patterns using a PMMA/LOR bilayer resist stack, exploiting the controlled LOR undercut.
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.