Plasma cleaning, etching & surface treatment equipment · designed and built in CaliforniaVolume & academic pricing
+1-510-788-2439sales@piescientific.com
PIE Scientific logoPIE ScientificPlasma · Ion · Electron Request a Quote
Application note · Failure analysis & biomedical

Oxygen plasma ashing of polyimide

Polyimide is everywhere a device needs a tough, insulating polymer: die passivation and stress-buffer layers, flexible circuits, and the insulation of implantable electrodes and neural probes. Oxygen-based plasma removes it dry and evenly, exposing the metal and silicon underneath for inspection, probing or rework.

  • Ar + O₂ plasma
  • 25 µm film removed in ≈3 h
  • No solvents, no hot acids
Ask about your devicePlasma for failure analysis
Schematic of oxygen plasma ashing of polyimide: oxygen radicals, oxygen ions and UV from the plasma break the polymer chains, CO2, CO, H2O and nitrogen products are pumped away, and the film thins until the metal pad underneath is exposed
How it works: oxygen radicals turn polyimide into CO₂, CO, H₂O and N₂/NOₓ gas; oxygen ions and UV speed up the reaction. The substrate and metal are not attacked.
Test

Removing a 25 µm polyimide film

Sample: polyimide tape with a 1 mil (25 µm) polyimide film on a silicone adhesive, 2.7 mil (68 µm) total. Ashed with argon + oxygen plasma in a Tergeo plasma system.

Amber polyimide tape sample before plasma ashing
Initial: amber 25 µm polyimide on silicone adhesive
Polyimide tape after 1 hour of plasma ashing, lighter amber colour
1 h: color lighter — the polyimide is thinning
Polyimide tape after 3 hours of plasma ashing, amber layer mostly removed
3 h: most of the polyimide removed
Faint residue of silicone adhesive left after 3.5 hours of plasma ashing
3.5 h: only part of the silicone adhesive is left

Silicone (PDMS-type) adhesive ashes much more slowly than polyimide in oxygen: its silicon backbone converts to a silica-like skin. A fluorine-containing gas such as CF₄ added to the oxygen speeds up removal of silicone and silicon-containing residues.

Applications

Where polyimide removal is needed

Electronics failure analysis

Strip polyimide or PBO passivation and stress-buffer layers from die and wafer-level packages to inspect and probe the metal underneath. Oxygen plasma removes the layer evenly and does not etch aluminum or copper (copper surfaces may lightly oxidize).

Flexible circuits & packaging

Open polyimide coverlays, clean via and pad openings, and remove polyimide residue (desmear) before plating or bonding.

Biomedical devices

Polyimide insulates many implantable electrodes, neural probes and flexible sensors. Plasma ashing exposes electrode sites, removes insulation for failure analysis and cleans devices before coating.

Process tips

Faster, more controlled polyimide etching

  • Direct (immersion) mode for speed; downstream mode when the device underneath is delicate.
  • More power, more speed: Tergeo-Plus and Tergeo-Pro run up to 500 W for thick films.
  • Add CF₄ (a few percent in O₂) to increase the polyimide etch rate and clear silicon-containing residues.
  • Watch the end point: the plasma emission reading drops when the polyimide clears, provided the layer below resists oxygen plasma.
  • Mask what you want to keep: polyimide etching is isotropic; use a hard mask or aluminum foil for local openings.

Related application notes

Not sure which plasma cleaner fits your process?

Tell us your samples, size and process gas. Our engineers reply within one to two business days with a recommendation and a quote.

Request a quoteBrowse applications