https://nanyte.com/photoresists/az-125nxt · last updated 2026-09-28
- Manufacturer
- Merck
- Tone
- negative
- Chemistry
- Photopolymer
- Thickness
- 18–120 µm
- Developer
- AZ 300MIF
- Applications
- Etch mask · Electroplating / molding · High aspect ratio
Cross-checked — two independent extractions agree on the spin curve and the single-value figures.
- Substrate
- Resist
- Exposed
Spin coating
Data points
| Series | rpm | µm |
|---|---|---|
| AZ 125nXT-10B | 600 | 120 |
| 800 | 100 | |
| 1000 | 75 | |
| 1500 | 55 | |
| 1900 | 48 | |
| 2100 | 43 | |
| 2500 | 38 | |
| AZ 125nXT-7B | 600 | 57 |
| 1000 | 35 | |
| 1300 | 24 | |
| 1500 | 21 | |
| 1900 | 18 | |
| 2300 | 14 |
Values are the manufacturer’s starting points, not a guarantee — characterize on your own tool. Series digitized from a published figure are approximate (±10 %).
AZ 125nXT-10B: read from figure, p.10 of AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24), 'COATING GUIDELINES' spin-speed chart. Two-grade chart; traces identified by the chart's own legend (filled triangle = AZ 125nXT-10B, filled circle = AZ 125nXT-7B), not by color alone.
AZ 125nXT-7B: read from figure, p.10 of AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24), 'COATING GUIDELINES' spin-speed chart. Two-grade chart; traces identified by the chart's own legend (filled triangle = AZ 125nXT-10B, filled circle = AZ 125nXT-7B), not by color alone.
- The datasheet explicitly cautions (p.10) that, unlike thin-resist spin curves, 'films will continue to thin with extended spin times' for a resist this viscous, and that the plotted curves 'may be used as general guidelines for coating films of 30µm thickness and above' - i.e. the document itself flags the low-thickness end of its own chart as unreliable.
- That caveat is directly visible in the data: the AZ 125nXT-7B trace spans 14-57 µm (2300 rpm to 600 rpm), both outside the grade's own stated 18-35 µm range (p.2 THICKNESS GRADES table) — consistent with the datasheet's own guidance that the curves apply to films of 30 µm and above (p.10).
- A full example coating sequence with acceleration and function-per-step (dispense/spread/snap-spin/set-thickness/backside rinse-dry/edge-bead-flatten) is given on p.10 for building a real recipe, rather than a single spin-speed number.
- Adhesion
- HMDS recommended — 'Oxide forming substrates (Si, etc.) should be HMDS primed prior to coating AZ 125nXT. Contact your product representative for detailed information on pre-treating with HMDS.' (p.11, Substrate Preparation).
- Rehydration
- None required - the datasheet states explicitly, in both the Typical Process summary ('Rehydration Hold: None', p.1) and in bold in the Process Considerations section ('NO POST BAKE REHYDRATION DELAYS ARE REQUIRED', p.11), that no rehydration hold is needed, unlike thick DNQ resists.
Soft bake
- Soft bake
- 115–140 °C · 5–20 min
- Notes
- Soft-bake conditions are 115-140°C for 5-20 min, and the time scales with film thickness. The published examples span the whole window: 115°C stepping-proximity bake, up to 120 s at a 0.002 in gap, for 20 µm of the 7B grade; 130°C for 13 min on a hotplate for 50 µm of 10B; 120°C stepping-proximity, up to 400 s in contact, for 20 µm of 7B on a different tool; 135°C for 25 min for 120 µm of 10B.
SOURCE: p.1, p.11 (range); pp.3-6 (worked-example values)
Exposure dose
Sensitivity spans 365 to 435 nm with no single stated dose, and the tool matters as much as the film: one 20 µm coat took 1120 mJ/cm² on a Suss MA-200 and 2000 mJ/cm² on an Ultratech AP300; a 70 µm film took 1800 mJ/cm². Run a dose array on your own tool to land the working dose.
Not published for this resist: Dose at 365 nm, Dose at 405 nm — characterize on-tool.
Development
- Developer
- AZ 300MIF
- Dilution
- 0.26N (2.38%) TMAH, ready-to-use; puddle mode recommended
- Method
- puddle
- Developer family
- TMAH-based
Not published for this resist: Time, Rinse — characterize on-tool.
SOURCE: p.1, p.11 (developer/mode); pp.3-6 (worked-example times)
Hard bake, etch & strip
- Hard bake
- 130–140 °C (optional — generally not required)
- Etch resistance
- Described only qualitatively: 'etch resistance, chemical resistance, and thermal stability far superior to typical chemically amplified photoresists' (p.1) and 'RIE etch applications' (p.1). No etch rate or selectivity number is given anywhere.
- Stripper
- AZ 400T, 75°C, 20-25 min with agitation (p.11, Stripping); corroborated by worked electroplating examples: 'Strip: AZ 400T @ 75C' for Cu (p.7) and 'Photoresist Strip AZ 400T @ 75°C' for Au (p.8)
Not published for this resist: Descum, Storage — characterize on-tool.
SOURCE: p.11 (Hard Bake)
Where it's used
Practical notes from the datasheet
AZ 125nXT is a photopolymer (not conventional DNQ or the vendor's own 'typical' CAR) negative resist purpose-built for ultra-thick, high-aspect-ratio plating molds and RIE masks up to and beyond 100 µm in a single coat. Two properties make it distinct from thinner thick-film resists: no rehydration hold is needed after softbake, and a PEB is explicitly not required at all - both are called out in bold in the datasheet, in direct contrast to the classic DNQ rehydration wait needed by thick DNQ resists. Real electroplating results are documented for Cu, Ni-compatible, and Au processes with post-plate/post-strip micrographs (pp.7-8), and the stripped resist shows no reported underplating. Coating this resist is its own discipline: the vendor explicitly warns that, unlike thin-resist spin coating, films keep thinning with extended spin time, so both spin speed and spin time must be tuned together (p.10), and the datasheet's own coating-guideline curves are only endorsed for films of 30 µm and above even though they are plotted further down. HMDS priming is required on oxide-forming substrates such as Si.
Troubleshooting
Common failure modes for AZ 125nXT, 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.
Why is my AZ 125nXT film sticking to the mask or tearing when I separate it?
AZ 125nXT stays soft after spin and slightly tacky even after soft bake, and the datasheet says direct or vacuum contact lithography is not recommended. Its 50 µm example prints on a proximity aligner with a 60 µm gap, and its gap study covers 10–90 µm. If you cannot avoid contact, MicroChemicals' trouble shooter names AZ 125nXT as a resist where switching from hard to soft contact helps. It also notes that a cool or short soft bake leaves more solvent and makes sticking worse, and that particles or bubbles in the film can transfer to the mask.
SOURCE: AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) —…
AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) — Process Considerations: Coating, p.11; Example Process (50 µm on Cu), p.4; Top and Bottom CD Dependency on Proximity Gap, p.9; Photolithography Trouble Shooter (MicroChemicals) — Sticking Between Resist Film and Mask, p.6
My AZ 125nXT thickness keeps coming in thinner than the spin curve says — why?
With a resist this viscous the film does not spin to an equilibrium thickness. It dries slowly and keeps thinning the longer it spins, so the final-speed step time matters as much as the speed. The datasheet's coating sequence uses a 1.2 s snap spin at 1000 rpm followed by a 12 s thickness-setting step, and flags both as the parameters to adjust. Keep spin times as short as possible, and treat the curves as a guide only for films of 30 µm and above.
SOURCE: AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) —…
AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) — Coating Guidelines and Example Coating Sequence, p.10; Process Considerations: Coating, p.11
Do I need a rehydration hold or a PEB for AZ 125nXT, as with thick DNQ resists or CARs?
No to both. The datasheet states in bold that no post-bake rehydration delay is required, and that a PEB is not required; the front-page typical process lists the PEB as optional. Every worked example, from 20 µm to 120 µm, runs with no post-bake delay and no PEB. Develop in 0.26 N (2.38 %) TMAH; AZ 300MIF in puddle mode is recommended.
SOURCE: AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) —…
AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) — Typical Process, p.1; Example Processes, pp.3–6; Process Considerations: Soft Bake, Post Expose Bake, Developing, p.11
How much does the proximity gap change AZ 125nXT CDs in a 60 µm film?
Very little, across the 10–90 µm gaps tested. On 60 µm film, 100 µm nominal lines measured 100 µm (top) and 96.6 µm (bottom) at a 10 µm gap, against 97.1 µm and 93.3 µm at 90 µm. At 20 µm nominal the spread was 17.0–18.1 µm top and 14.8–15.9 µm bottom. The bottom CD runs 0.6–3.8 µm under the top across the table, even at a 10 µm gap, so size the mask for that taper rather than chasing it with the gap.
SOURCE: AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) — Top…
AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) — Top and Bottom CD Dependency on Proximity Gap for Projection Aligners (film thickness 60 µm), p.9
AZ 125nXT won't come off after plating or a hard bake — what should I strip it with?
The datasheet's remover is AZ 400T at 75 °C for 20–25 min with agitation, and all its Cu and Au plating examples strip in AZ 400T at 75 °C. Hard bake is generally not needed; if you use one for an aggressive dry etch, keep it at 130–140 °C. If the film has crosslinked heavily from high process temperatures, MicroChemicals recommends TechniStrip P1316 for AZ 125nXT. After a dry etch, MicroChemicals adds, redeposited material may have to be wet-etched off first, which ultrasonics can assist.
SOURCE: AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) —…
AZ 125nXT Series Technical Datasheet (Merck, Rev. 01/24) — Hard Bake and Stripping, p.11; plating results, pp.7–8; Photolithography Trouble Shooter (MicroChemicals) — Photoresist Removal: After Dry Etching, Crosslinked Negative Resists, p.20
Sources & disclaimer
- Merck — AZ 125nXT datasheet (Rev. (01/24)) · accessed 2026-07-10
- Staab et al.. Applications of Novel High-Aspect-Ratio Ultrathick UV Photoresist for Microelectroplating. Journal of Microelectromechanical Systems (2011). doi:10.1109/jmems.2011.2159098The acrylic resist AZ 125 nXT is demonstrated at 400, 800 and 1400 um film thickness with 20:1 aspect ratio for low-cost UV-LIGA, electroformed in acid copper at room temperature and near-neutral nickel at 50 C, then stripped in DMSO/acetone or plasma to release freestanding metal at 13:1 and 16:1.
- Knoll et al.. Fabrication of microfluidic chips using lithographic patterning and adhesive bonding of the thick negative photoresist AZ 125 nXT. Proceedings of SPIE (2015). doi:10.1117/12.2178812AZ 125 nXT was lithographically patterned into 90 um deep microfluidic channels and sealed by adhesive bonding, presented as an SU-8 alternative that fully cross-links during UV exposure without a post-exposure bake.
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.