https://nanyte.com/photoresists/lor-3a · last updated 2026-07-26
- Manufacturer
- Kayaku Advanced Materials
- Tone
- Not photoimageable (underlayer)
- Chemistry
- Ancillary (not photoimageable)
- Thickness
- 0.3–0.6 µm
- Exposure dose
- Not exposed — dissolves in developer
- Developer
- 0.26N (2.38%) TMAH metal-ion-free developer — e.g. Shipley/Rohm and Haas CD-26 or TOK NMD-3 — is the developer class the LOR-A series (including LOR 3A) is optimized for; the LOR-B series is instead optimized for lower-normality/metal-ion-bearing developers such as AZ 400K 1:4 or Shipley MF-319.
- 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 | 0.57 |
| 2000 | 0.40 | |
| 3000 | 0.34 | |
| 4000 | 0.28 |
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 the combined 'LOR 3A, LOR 3B' trace (black diamond markers) in the 'Spin Speed vs Thickness – Intermediate Films' chart, p.5 of the Kayaku/MicroChem 'LOR and PMGI Resists' datasheet (Rev. A). The chart plots exactly 4 markers for this trace (1000/2000/3000/4000 rpm) — there is no data at 500, 1500, 2500, 4500 or 5000 rpm. Neither this datasheet nor MicroChem's 2002 flyer publishes a numeric table isolating LOR 3A alone, so this is a figure read (±10% uncertainty). Treat as approximate; scrutinise before relying on it for a critical process.
- Recommended baseline coating parameters (Table 1, applies across the LOR/PMGI line, not LOR 3A-specific): dispense 5 mL for a 150 mm wafer, dynamic dispense 3-5 s at 300-500 rpm, acceleration 10,000 rpm/s, terminal spin speed 3,000 rpm held for 45 s, edge-bead removal with EBR PG.
- Spin speeds of 2,500-4,500 rpm give maximum coating uniformity (higher speeds for smaller substrates, lower for larger/topographic ones).
- Acetone and conventional resist edge-bead removers are explicitly NOT recommended with LOR (causes precipitation) — use EBR PG.
- Adhesion
- HMDS not required — HMDS priming is explicitly stated as typically NOT required to promote adhesion with LOR/PMGI products.
Soft bake
- Soft bake
- 180 °C · 3 min · hotplate
- Notes
- 180°C for 3 min is the specific bake condition the manufacturer states was used to generate its own published spin-curve/optical-constant data ('Products were soft-baked at 180°C for 3 min', Technical Data section).
SOURCE: Technical Data section note (p.5) and 'Soft-bake/Prebake…
Technical Data section note (p.5) and 'Soft-bake/Prebake Process' section (p.3), Kayaku/MicroChem 'LOR and PMGI Resists' datasheet Rev. A
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 (2.38%) TMAH metal-ion-free developer — e.g. Shipley/Rohm and Haas CD-26 or TOK NMD-3 — is the developer class the LOR-A series (including LOR 3A) is optimized for; the LOR-B series is instead optimized for lower-normality/metal-ion-bearing developers such as AZ 400K 1:4 or Shipley MF-319.
- Dilution
- ready-to-use (as supplied)
- Time
- Not published — characterize on-tool
- Method
- immersion (spray development is recommended instead for thick, >2 µm LOR/PMGI stacks, for straighter sidewalls)
- Rinse
- DI water
- Developer family
- TMAH or buffered alkaline
SOURCE: 'Development Process' section (p.4) and Product Selection…
'Development Process' section (p.4) and Product Selection Guide (p.6), Kayaku/MicroChem 'LOR and PMGI Resists' datasheet Rev. A. Develop time is explicitly not published as a single fixed number — the datasheet states it depends on the combined thickness of the LOR/PMGI layer and the patterning resist layer, and on the desired undercut (see undercut-rate figures); it must be set experimentally, not read off a table.
Hard bake, etch & strip
- Descum
- Not required.
- Stripper
- MicroChem/Kayaku Remover-PG is the recommended stripper; baseline two-tank process at 60°C for 30 min per tank, optionally ultrasonic-assisted to improve strip efficiency (actual time varies with prebake temperature, step coverage, and resist profile).
- Storage
- Store upright in original sealed containers in a dry area between 4-27°C (40-80°F), away from ignition sources, light, heat, oxidants, acids, and reducers.
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 amount is set primarily by LOR soft-bake temperature — higher bake temperature lowers the dissolution rate and reduces undercut for a given develop time; the manufacturer's own bar-chart data (0.26N TMAH/CD-26 developer) give LOR-A-class undercut rates of 42 Å/s at 190°C, 67 Å/s at 170°C, and 111 Å/s at 150°C (recommended bake range 150-200°C). This rate is published for the 'LOR A' class as a whole (which LOR 3A belongs to), not broken out for the 3A sub-grade specifically. Secondary levers are prebake time, developer choice/normality, develop mode, and develop time (increasing develop time increases undercut for otherwise fixed bake conditions). HMDS priming is explicitly not required. For clean lift-off, LOR film thickness should exceed the deposited metal thickness, by roughly 25-33% per the two primary datasheets (guidance differs slightly: 'typically 1.2 to 1.3 times' the metal thickness in the 2002 flyer vs. 'typically by 25%' in the later Rev. A datasheet).
Grades in this family
Other grades in the LOR A series line differ mainly in coating thickness:
| Grade | Thickness |
|---|---|
| LOR 3A (this page) | 0.3–0.6 µm |
| LOR 5A | 0.5–1.0 µm |
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.
Is LOR 3A photosensitive?
No. LOR 3A is a non-photoimageable PMGI-based lift-off underlayer — it is never itself exposed. It is spin-coated beneath a conventional imaging resist, and only that top resist is patterned by light. During development the LOR layer dissolves isotropically, undercutting laterally beneath the imaged resist to form the re-entrant profile a clean bilayer lift-off needs. Any PEB in the flow is for the top imaging resist, not for LOR.
SOURCE: Kayaku/MicroChem 'LOR and PMGI Resists' datasheet Rev. A, Post-Exposure (PEB) Process section, p.4
How do I control the undercut for lift-off with LOR 3A?
Undercut is set primarily by LOR soft-bake temperature: a higher bake lowers the dissolution rate and reduces undercut for a given develop time. The manufacturer's LOR-A-class data (0.26N TMAH / CD-26) give undercut rates of about 42 Å/s at 190 °C, 67 Å/s at 170 °C and 111 Å/s at 150 °C (recommended bake range 150–200 °C). Secondary levers are prebake time, developer choice, develop mode and develop time. These rates are published for the LOR-A class, not broken out for the 3A grade.
SOURCE: Kayaku/MicroChem 'LOR and PMGI Resists' datasheet Rev. A (LOR-A undercut-rate data, 0.26N TMAH developer)
Which developer does LOR 3A use?
The LOR-A series (including LOR 3A) is optimized for 0.26N (2.38%) TMAH metal-ion-free developer — e.g. CD-26 or TOK NMD-3 — used as supplied, with a DI water rinse. Immersion is standard; spray development is recommended for thick (>2 µm) LOR/PMGI stacks. Develop time is not published as a single number: it depends on the combined LOR + imaging-resist thickness and the desired undercut, and must be set experimentally.
SOURCE: Kayaku/MicroChem 'LOR and PMGI Resists' datasheet Rev. A, Development Process p.4 + Product Selection Guide p.6
Can I strip LOR 3A with acetone?
No. Acetone will not dissolve or remove LOR — use Kayaku/MicroChem Remover PG (baseline two-tank process, 60 °C for 30 min per tank, optionally ultrasonic-assisted). Keep acetone, PGMEA and ethyl-lactate waste streams separate, since LOR precipitates in these solvents and can clog lines.
SOURCE: Kayaku/MicroChem 'LOR and PMGI Resists' datasheet Rev. A (stripper: Remover PG; acetone incompatible)
Does LOR 3A need HMDS priming?
No. HMDS priming is explicitly stated as typically not required with LOR/PMGI. LOR has excellent inherent adhesion to Si, glass, NiFe, GaAs, InP and Au. 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) immediately before coating.
SOURCE: Kayaku/MicroChem 'LOR and PMGI Resists' datasheet Rev. A, Substrate preparation
Sources & disclaimer
- Kayaku Advanced Materials — LOR 3A datasheet (Kayaku/MicroChem 'LOR and PMGI Resists', Rev. A (undated on the document itself); cross-checked against the earlier MicroChem 'LOR™ Lift-Off Resists' flyer, © MicroChem Corp. 2002, mirrored at https://amolf.nl/wp-content/uploads/2016/09/datasheets_LOR_datasheet.pdf. The current kayakuam.com-hosted PDF (https://kayakuam.com/wp-content/uploads/2023/06/KAM-LOR-PMGI-Datasheet-4.30.24-final-1.pdf, dated 4/30/24 per its filename) returned HTTP 403 and could not be fetched directly; the two documents actually read are university-hosted mirrors of the same manufacturer-authored content.) · accessed 2026-07-10
- https://bionium.miami.edu/_assets/pdf/lor-3a-photoresist-process.pdf — University of Miami cleanroom process recipe for LOR 3A — used only to corroborate typical practical parameters (180°C/5min softbake, 3000rpm/35s spin, CD-26 60-90s or MF-319 45-60s develop), not as a primary numeric source
- https://cns1.rc.fas.harvard.edu/facilities/docs/SOP112_r1_1_%20LOR.pdf — Harvard CNS SOP112 lift-off processing procedure — used only to corroborate typical bake (180°C/4min) and CD-26 develop (75s) practice, and to confirm HMDS is not used with LOR; not a primary numeric source
- 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 2026-07-26.