Overview

Molybdenum aperture etching produces the beam-defining discs, masks and pinhole arrays used in electron optics, electron- and ion-beam columns, X-ray systems, vacuum deposition tooling and semiconductor equipment. Molybdenum is chosen because its melting point of about 2623 °C, low thermal expansion near 4.8 × 10⁻⁶/K and high stiffness keep a beam aperture dimensionally stable under heat and in high vacuum, while the metal is non-magnetic and low-outgassing. Stock is typically pure Mo ≥ 99.95%, TZM alloy or molybdenum-copper from 0.02 mm to 0.50 mm, with hole diameters from 0.05 mm to 2.0 mm.

The process is less forgiving than stainless etching. Molybdenum is chemically resistant, so oxidative chemistries, careful activation and tightly held temperature are needed to cut a clean edge, and the rolled grain structure can show up as roughness on a 0.05 mm hole wall. With molybdenum aperture etching, roundness, wall taper and the absence of recast burrs are functional — a ragged edge scatters the beam and shifts the effective aperture — so qualified lines verify hole geometry optically rather than by a simple go/no-go gauge. Position tolerance of ±0.005 mm on multi-hole arrays is achievable when exposure is registered to the sheet edge and undercut is compensated from a measured coupon.

Parameter Window

• Available Materials: pure molybdenum Mo ≥ 99.95%, TZM molybdenum alloy, molybdenum-copper
• Material Thickness Range: 0.02–0.50 mm
• Tolerance: ±0.005 mm on hole position, ±0.01 mm on hole diameter at 0.10 mm stock
• Minimum Feature: 0.05 mm hole, 0.08 mm web, edge roundness within 0.01 mm
• Surface Options: stress-relief anneal, electropolish, vacuum bake, clean-room double pack, orientation mark
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Beam Requirement Review — Define aperture diameter, array pitch, beam energy, working vacuum and thermal load.
2. Material & Grain Selection — Choose pure Mo, TZM or Mo-Cu and specify grain direction for the hole wall finish.
3. Artwork Compensation — Apply a molybdenum-specific etch factor so the finished roundness matches the target.
4. Cleaning & Activation — Degrease and activate the resistant surface, then laminate dry-film resist on both faces.
5. Exposure & Development — Expose through registered high-resolution film, then develop and inspect every aperture.
6. Controlled Etching — Spray oxidative chemistry under logged temperature and time to hold wall taper and roundness.
7. Stripping & Finishing — Strip resist, stress-relieve, electropolish if specified, then vacuum bake for low outgassing.
8. Optical Verification — Measure diameter, roundness, taper and position by optical inspection, then clean-room pack.

Core Advantages

1. Thermal and vacuum stability: Low expansion and a high melting point keep the aperture on axis as the column heats.
2. Burr-free beam edge: Chemical cutting leaves no recast layer or rolled burr to scatter the beam.
3. Fine multi-hole arrays: 0.05 mm holes at ±0.005 mm position are possible on a single registered sheet.
4. Controlled wall geometry: Wall taper and roundness are measured and held, not assumed from the film.
5. Clean vacuum delivery: Vacuum baking and clean-room packing suit electron-optical assemblies.
6. Repeatable qualification: A disciplined molybdenum aperture etching line releases each lot against optical geometry data tied to an approved sample.

Typical Applications

• Electron microscope apertures: Beam-limiting discs and strip apertures for TEM and SEM columns.
• Ion-beam and lithography masks: Defining apertures in focused ion beam and e-beam tooling.
• X-ray collimators: Pinhole and slit arrays that shape diagnostic or inspection beams.
• Vacuum deposition masks: Shadow masks for thin-film and coating processes.
• Semiconductor equipment parts: Beam-defining and shielding apertures in process chambers.
• Optical and laser diaphragms: Heat-resistant stops and spatial filters in high-power systems.

Design Notes & Process Considerations

1. Web width versus thickness: Keep the web between holes at 1.2 × stock thickness or wider to avoid breakthrough.
2. Etch factor and roundness: Measure undercut on a coupon for each molybdenum grade; small holes round off as undercut grows.
3. Wall taper callout: State whether a straight or tapered wall is required, since taper changes the effective aperture at the exit face.
4. Grain and edge finish: Specify grain direction and an edge-roughness limit where beam scatter is critical.
5. Flatness in vacuum: Define flatness and the stress-relief condition, as a warped disc will not seat on the aperture holder.
6. Cleanliness and packaging: State particle and outgassing requirements and double-bag in a clean environment; a qualified molybdenum aperture etching supplier ships with optical geometry records for incoming verification.