AZ 125nXT process recipe

AZ 125nXT is a photopolymer negative-tone photoresist for ultra-thick single-coat films (roughly 18-120 µm across its two viscosity grades), built for Cu/Au/solder electroplating and RIE etch masks in advanced packaging, with no rehydration hold and no PEB required.

https://nanyte.com/photoresists/az-125nxt · last updated 2026-07-10

At a glance

Manufacturer: Merck
Tone: negative
Chemistry: Photopolymer
Thickness: 18–120 µm
Developer: AZ 300MIF
Applications: Etch mask · Electroplating / molding · High aspect ratio

Etch maskSuitable for

Cross-checked — two independent extractions agree.

Coat18–120 µm

—01 / Coating

Spin coating

AZ 125nXT is spin-coated to 18–120 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.

AZ 125nXT-10B
AZ 125nXT-7B

Data points

AZ 125nXT — film thickness (µm) by spin speed (rpm)
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; verify on your own tool. Characterize on-tool. Series digitized from a published figure were independently cross-checked by a second blind read; treat those values as 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.

2 series redrawn from the manufacturer's published data — hover to read values between points, click to pin.

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: my read of the AZ 125nXT-7B trace extends from ~57 µm (600 rpm) down to ~14 µm (2300 rpm), both outside the grade's own stated 18-35 µm range (p.2 THICKNESS GRADES table) - an internal inconsistency a QC reviewer should note, not something I resolved. 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.

—02 / Bake

Soft bake

Soft bake: Not published — characterize on-tool
Notes: Stated only as a range: '115°-140°C/5-20min' (p.1 Typical Process; footnoted 'SB time is film thickness dependent'), and again '115°-140°C range' with no time in Process Considerations (p.11). Worked examples span the whole range by thickness/grade: 115°C stepping-proximity bake up to [email protected] for 20µm-7B (p.3); 130°C/13min hotplate for 50µm-10B (p.4); 120°C stepping-proximity bake up to 400s contact for 20µm-7B on a different tool (p.5); 135°C/25min for 120µm-10B (p.6). Left the scalar null per protocol rather than picking one of these.

SOURCE: p.1, p.11 (range); pp.3-6 (worked-example values)

—03 / Exposure

Exposure dose

The manufacturer does not publish a clearing dose for AZ 125nXT. Determine it with a dose array on your own tool.

As published: 'AZ 125nXT is sensitive in the 365-435nm wavelength range' (p.11, Exposure); Typical Process lists 'Expose: broadband sensitive' (p.1); worked-example exposures specify 'ghi mode' (combined g+h+i-line, i.e. broadband) or are captioned simply 'broadband exposure' (pp.2-3).

—04 / Development

Development

Developer: AZ 300MIF
Dilution: 0.26N (2.38%) TMAH, ready-to-use; puddle mode recommended
Method: puddle
Developer family: TMAH-based

SOURCE: p.1, p.11 (developer/mode); pp.3-6 (worked-example times)

—05 / Post-processing

Hard bake, etch & strip

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)

SOURCE: p.11 (Hard Bake)

—06 / Applications

Where it's used

Etch maskElectroplating / moldingHigh aspect ratio

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 this recipe library flags elsewhere. 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.

—07 / Sources

Sources & disclaimer

Merck — AZ 125nXT datasheet (Rev. (01/24)) · accessed 2026-07-10

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 2026-07-10.

Cite this recipe

NANYTE. "AZ 125nXT process recipe." NANYTE Photoresist Library. https://nanyte.com/photoresists/az-125nxt. Accessed 2026-07-10.

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