Varian 350D medium-current ion implanter

Where the Varian 350D fits

The Varian 350D is one of the medium-current implanters that taught a generation of process engineers how to dope silicon. A used 350D is a practical choice for a university cleanroom or small fab that needs boron and phosphorus implants on 100 or 150 mm wafers, controlled doses and repeatable energies, without the footprint and service load of a production tool. Typical work is well and source/drain doping for teaching CMOS runs, resistor and diode test structures, and dopant studies for MEMS and sensor devices.

It sits in the ion implantation range alongside newer medium-current tools. Its age means the decision is less about process capability and more about how well a particular unit has been kept: the beamline physics have not changed, but control electronics and vacuum hardware from this era need attention.

What we inspect on a used 350D

We power the tool up, pump down and, where gas and site conditions allow, strike a beam. The inspection report covers:

• Ion source. Filament and arc chamber condition, source magnet, extraction electrodes and the insulators around them. Deposits of phosphorus and arsenic compounds tell us how the source was run and how it must be cleaned.
• High-voltage section. Insulator surfaces for tracking, corona rings, the acceleration column and the terminal supplies. A tool that cannot hold voltage without arcing is the most common reason an older implanter fails acceptance.
• Beamline and analyser. Magnet supply stability, beam steering, apertures and the condition of graphite liners.
• Vacuum. Base pressure, cryopump regeneration behaviour, roughing pumps, valves and gauges.
• End station and dosimetry. Wafer handling, clamping, Faraday cup and dose integrator, interlocks and the X-ray survey points.

Each finding is graded so you can see what is wear, what is a defect and what is a risk.

Refurbishment scope

A typical refurbishment starts with decontamination of source and beamline parts, because dopant residues are hazardous and must be handled before anyone works on the tool. We then replace source consumables and worn insulators, rebuild or replace cryopumps, and service valves and gauges as part of vacuum system refurbishment. High-voltage supplies are tested under load. Dosimetry is checked against a known beam current before the tool is graded.

Lead time depends mainly on the vacuum hardware and on whether boards need repair. We give you the scope in writing before we start, and you approve it.

Upgrades and spare parts

The upgrade that most often extends a 350D's life is a control system retrofit: replacing hard-to-source boards with modern controllers and adding recipe and dose logging that research groups need for their records. Dry roughing pumps, refurbished or replacement cryopumps and updated gas cabinets follow closely. Consumables such as filaments, arc chambers and graphite parts are the steady cost of ownership, and we keep track of where they can still be sourced.

Facilities

Exact figures depend on configuration; we confirm them for your unit.

• Power: three-phase supply sized for the high-voltage and magnet supplies
• Cooling water for the source, magnet and pumps
• Compressed dry air for valves; nitrogen for venting and purging
• Exhaust and toxic gas handling for dopant sources
• Floor space with service access on all sides, and room shielding as your radiation safety officer requires

Buying advice

Ask for the hours on the high-voltage supplies, the last cryopump service and which species were run, because arsenic use changes the decontamination scope. A unit that was cleanly decommissioned with its gas lines purged is worth more than one that was switched off and left. Our article on keeping legacy tools running covers the spare-parts planning that an implanter of this age needs.