Graphite Apertures for Ion Implanation

In ion implant, graphite is the material-of-record for beam-line consumables—slits, liners, apertures, stops—because its combination of ultra-low atomic mass, refractory strength and chemical inertness delivers three performance levers simultaneously:

1. Minimal sputter yield and self-contamination: density ≥1.85 g cm⁻³, grain size <5 µm and total-metal purity ≤5 ppm keep Na/K/Fe pickup below 1×10¹⁰ cm⁻², a prerequisite for 3 nm node junctions.  

2. Thermal shock immunity: thermal conductivity ≈100 W m⁻¹ K⁻¹ diffuses 1–3 kW cm⁻² peak loads, while α <3 ppm K⁻¹ holds dimensional tolerance within 5 µm over 500 h of 180 keV–2 MeV operation.  

3. Particle suppression: glassy-carbon or SiC seal coats close surface pores, cutting ≥0.12 µm adders to <5 per 200 mm wafer pass and eliminating the post-implant wet clean, saving 5–7 % cycle time.

The outcome is a >3× extension in maintenance intervals (3 → 9 months) and a 60 % spare-part cost reduction versus SiC or refractory-metal equivalents, making high-purity, coated graphite the default for both sub-10 keV USJ and mega-electron-volt deep-well implants.