Wear / Tooling Coatings · Stress fix

Thick CrN — Beat the Doming

Chromium nitride wear coating that has to go thick (> 3 µm) and stay down — no doming, no delamination off the part.

DEMO — generic parameters

The problem: Past about 3 µm the CrN domes up and peels off the edge. Built-in compressive stress stores elastic energy faster than the interface can hold it — the film lifts itself off.

🔍 Root Cause (why it domes)

MechanismHigh compressive intrinsic stress × thickness → stored energy exceeds adhesion → buckling/doming

DriverToo much ion bombardment (bias too hot / pressure too low) for a thick film

🛠️ The Fix — approach

Stress StagingStep the bias down as thickness builds — dense adherent base, lower-stress bulk on top

PressureRaise working pressure through the run to soften bombardment as it thickens

InterfaceGraded Cr → CrN interlayer so there's no sharp stress discontinuity to peel from

🔒 Locked

🎯 Dialed-in Stress Schedule

Bias Stage 1 (0–0.5 µm)−120V

Bias Stage 2 (0.5–2 µm)−70V

Bias Stage 3 (2 µm+)−40V

Pressure Ramp3 → 6 mTorr across the run

Target Net Stress≤ 1.0 GPa compressive at 5 µm

⚠️ Failure Mode Warnings

Still domes → drop stage-3 bias further or raise end pressure; stress still too high
Soft / porous top layer → over-corrected, bombardment now too low — tighten the bulk stage
Peels at the interface → strengthen the graded Cr base, recheck pre-etch

Stress is hardware-specific.

The bias steps depend on your geometry and target-to-substrate distance. LabForge schedules them for your setup.

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