https://nanyte.com/photoresists/k-pro · last updated 2026-09-28
- Manufacturer
- KemLab, Inc.
- Grades
- K-PRO 1 · K-PRO 2 · K-PRO 3 · K-PRO 5 · K-PRO 7 · K-PRO 151
- Tone
- positive
- Thickness
- 1–25 µm
- Developer
- 0.26N TMAH
- Applications
- Electroplating / molding · Etch mask · High aspect ratio
- Substrate
- Resist
- Exposed
Spin coating
For the K-PRO series spin curve, work from the manufacturer's datasheet and characterize film thickness on your own coater.
- Adhesion
- HMDS recommended — HMDS primer is recommended with oxide-forming substrates such as silicon (TDS p.2, Substrate Preparation); K-PRO adheres to silicon, copper, gold, glass, aluminum and chromium, and the datasheet claims excellent substrate adhesion for wet-etch work.
- Rehydration
- 3-30 minutes at 35-50% relative humidity, scaling with film thickness (TDS p.2, Rehydration Time: '3 – 30 minutes at 35 – 50% relative humidity is recommended'). The p.1 table pins it per process point: 3 min up to 3 µm, 5 min at 4 µm, 15 min at 7 µm, 30 min at 15 and 25 µm. A thick DNQ-type film that has not rehydrated will develop slowly and scum, so this step is recommended on the thicker grades.
Soft bake
- Soft bake
- 115 °C · 2–5 min · hotplate
- Rehydrate
- 3–30 min (recommended, 35–50 % RH)
- Notes
- Narrative Softbake section (p.2): 'Recommended softbake contact hotplate temperature is 115°C. Typical bake time is 2 – 5 minutes.' No single typical time is named, so the published 2-5 min window is recorded rather than a scalar. The p.1 Processing Guidelines table gives the per-thickness times at that same 115°C: 2 min at 1, 2 and 3 µm; 2.5 min at 4 µm; 3 min at 7 µm; 4 min at 15 µm; and 5.5 min at 25 µm — the 25 µm point sits above the narrative window.
SOURCE: Softbake section, p.2, and Processing Guidelines table, p.1, of the K-PRO TDS Rev 3-2021.
SOURCE: p.2: '3 – 30 minutes at 35 – 50% relative humidity is recommended'
Exposure dose
K-PRO series's dose is published against film thickness, not as a single number. Read the row for the film you coat and run a dose array around it.
- As published
- Broadband aligner dose climbs steeply with the coat — 65 mJ/cm² at 1 µm, 125 at 7 µm, 380 at 25 µm. No i-line or g-line number is published, so read the row for your film and bracket it with a dose array.
| Film thickness | Dose |
|---|---|
| 1 µm | 65 mJ/cm² |
| 2 µm | 72 mJ/cm² |
| 3 µm | 76 mJ/cm² |
| 4 µm | 80 mJ/cm² |
| 7 µm | 125 mJ/cm² |
| 15 µm | 210 mJ/cm² |
| 25 µm | 380 mJ/cm² |
SOURCE: 'Broadband Aligner Exposure' column of the Processing Guidelines table, p.1 of the K-PRO TDS Rev 3-2021.
Development
- Developer
- 0.26N TMAH
- Developer family
- TMAH or buffered alkaline
Not published for this resist: Dilution, Time, Method, Rinse — characterize on-tool.
SOURCE: Development section, p.3, and the Features block, p.1, of the K-PRO TDS Rev 3-2021.
Hard bake, etch & strip
- Etch resistance
- Wet chemical etchants for Au, Cu, Cr and Al do not degrade patterns made with K-PRO (TDS p.3, Etch Resist).
- Stripper
- Industry-standard removers such as NMP at 50-80°C (TDS p.3, Resist Removal). Thicker films may benefit from a two-bath process — the first bath takes off the bulk, the second cleans up.
- Storage
- Store upright in an airtight container at 4-21°C, away from light, oxidizers, acids, bases and ignition sources (TDS p.3, Storage).
Not published for this resist: Hard bake, Descum — characterize on-tool.
Where it's used
Practical notes from the datasheet
K-PRO is KemLab's advanced-packaging positive series — six grades sharing one process family, aimed at plating, bumping, TSV and other metal-deposition work rather than at general lithography. Two things set it apart from a conventional thick positive resist. First, no post-exposure bake is required at all, which removes a step and its associated stress from the flow. Second, rehydration is an explicit, thickness-dependent process step (3 min at 1-3 µm rising to 30 min at 15-25 µm, at 35-50% RH) rather than an afterthought — skip it on the thick grades and development slows and scums. Broadband dose climbs steeply with the coat, from 65 mJ/cm² at 1 µm to 380 at 25 µm, so a dose array around the tabulated row for your film is the practical starting point. The grade numbers are product names, not thicknesses: K-PRO 5 is tabulated at 4 µm and K-PRO 15 covers both the 15 and 25 µm process points. Compatibility with copper, pure tin and nickel plating chemistries is claimed by the manufacturer, as is wet-etch resistance to Au, Cu, Cr and Al etchants; both are worth confirming against your own bath.
Troubleshooting
Common failure modes for K-PRO series, 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 wait between softbake and exposure on a thick K-PRO coat?
Yes — KemLab builds a rehydration hold into the process, and it scales with thickness. The processing table sits it between the 115 °C softbake and the exposure: 3 min for the 1–3 µm points (K-PRO 1, 2, 3), 5 min at 4 µm (K-PRO 5), 15 min at 7 µm (K-PRO 7) and 30 min at 15 and 25 µm (K-PRO 15), all at 35–50 % relative humidity. What the flow does not have is a PEB: the datasheet says none is required, so the next step after exposure is develop.
SOURCE: K-PRO Positive Advanced Packaging Photoresist TDS (KemLab…
K-PRO Positive Advanced Packaging Photoresist TDS (KemLab Inc., Rev 3-2021) — Processing Guidelines table, p.1; Rehydration Time, p.2; Post-Exposure Bake, p.3
My 25 µm K-PRO 15 film is underexposed at the 7 µm dose — how much more does it need?
A lot more. The broadband aligner doses in KemLab's table climb from 65 mJ/cm² at 1 µm to 80 at 4 µm, 125 at 7 µm, 210 at 15 µm and 380 mJ/cm² at 25 µm. The softbake stretches too: 115 °C for 2 min at 1–3 µm, 3 min at 7 µm, 4 min at 15 µm and 5.5 min at 25 µm — longer than the 2–5 min the narrative softbake section calls typical, so do not cap the thickest coat at 5 min.
SOURCE: K-PRO Positive Advanced Packaging Photoresist TDS (KemLab…
K-PRO Positive Advanced Packaging Photoresist TDS (KemLab Inc., Rev 3-2021) — Processing Guidelines table, p.1; Softbake, p.2
The bottom of my K-PRO plating mould is not clearing in one develop — what does KemLab recommend?
Refresh the developer part-way through. The datasheet says these thick films benefit from it and gives two ways: two separate baths for immersion, or multiple puddles. K-PRO works in 0.26N TMAH, KOH-based or potassium-borate developers by immersion, puddle or spray puddle. No develop time is published for any grade, so set it on-tool against your own thickness.
SOURCE: K-PRO Positive Advanced Packaging Photoresist TDS (KemLab Inc., Rev 3-2021) — Development, p.3
How do I strip K-PRO from around plated copper posts without leaving residue?
KemLab specifies industry-standard removers such as NMP at 50–80 °C (DMSO is also listed on p.1), and says thicker films may benefit from a two-bath strip: the first bath removes the bulk of the resist and the second cleans it off thoroughly. The datasheet's own strip example is an array of 10 µm Cu posts on a copper substrate.
SOURCE: K-PRO Positive Advanced Packaging Photoresist TDS (KemLab…
K-PRO Positive Advanced Packaging Photoresist TDS (KemLab Inc., Rev 3-2021) — Figure 3 and Remover line, p.1; Resist Removal, p.3
What surface prep does K-PRO need so it survives a long wet etch or plating bath?
A clean, dry substrate, plus an HMDS prime on oxide-forming surfaces such as silicon — that is the whole of KemLab's preparation step. The datasheet names silicon, copper, gold, glass, aluminium and chromium as substrates K-PRO adheres to, claims excellent adhesion for wet-etch work, and states that wet etchants for Au, Cu, Cr and Al do not degrade K-PRO patterns.
SOURCE: K-PRO Positive Advanced Packaging Photoresist TDS (KemLab…
K-PRO Positive Advanced Packaging Photoresist TDS (KemLab Inc., Rev 3-2021) — Description, p.1; Substrate Preparation, p.2; Etch Resist, p.3
Sources & disclaimer
- KemLab, Inc. — K-PRO series datasheet (Rev 3-2021 (Copyright 2021 KemLab, Inc.; ISO 9001:2015 certified mark on every page)) · accessed 2026-08-04
- K-PRO TDS Rev 3-2021, 'PROCESSING GUIDELINES' table (p.1), Product column: K-PRO 1, K-PRO 2, K-PRO 3, K-PRO 5, K-PRO 7, K-PRO 15. The grade number does not track film thickness one-for-one — K-PRO 5 is tabulated at 4 µm, and K-PRO 15 carries two rows (15 µm and 25 µm) — so the numbers are product names, not thickness specifications.
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.