Focused Ion Beam Milling Simulator

Ion Beam

Incidence angle θ 45°

Beam dose (ion current) 5

Mill pattern

Live Readouts

Sputter yield Y(θ)

— at/ion

Mill rate

— nm/s

Deepest point milled

0.0 nm

How it works

A focused ion beam (FIB) fires ~10–30 keV gallium ions (Ga⁺) at a surface. Each ion strikes an atom, triggers a collision cascade in the lattice, and knocks out (sputters) a handful of surface atoms — material is removed one ion at a time, with no chemistry or resist involved, unlike lithography.

How many atoms leave per incident ion — the sputter yield Y — depends strongly on the incidence angle θ measured from the surface normal. This sim uses a Sigmund/Yamamura-type angular model:

Y(θ) = Y₀ · cos(θ)⁻ᶠ · exp[ −Σ·(sec θ − 1) ]
  Y₀ = 2.1 atoms/ion   (Si, Ga⁺, normal incidence)
  f = 1.7,  Σ = 0.9

Mill rate:  R(θ) = R₀ · Y(θ)/Y₀   [nm/s]
Depth removed at a cell:  Δz = R(θ) · Δt

θ small (near-normal) — ions penetrate straight in, most energy is deposited deep in the bulk, yield is near its baseline Y₀.
θ ≈ 60–70° — the cascade sits closer to the surface, so more struck atoms have a clear path out; yield peaks here, which is why real FIB tools tilt the stage for fast bulk milling.
θ → 90° (grazing) — ions increasingly reflect off the surface instead of embedding, and the exponential term wins out, so yield collapses back toward zero.

The beam raster-scans the selected pattern mask cell by cell (sped up for visualization); each pass removes another Δz of column height at the current tilt, exactly the mechanism used to prepare TEM lamellae, edit failed circuits, and mill nanostructures directly without a mask.

Ion beam Unmilled surface Milled (removed)

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