Veeco (Cambridge NanoTech) Savannah thermal ALD system

Where the Savannah fits

The Savannah was developed by Cambridge NanoTech, which passed to Ultratech and then to Veeco, so older units carry the Cambridge NanoTech name. It is a compact thermal ALD reactor that became one of the most widespread ALD tools in academic cleanrooms. A used Savannah suits a research group or shared facility that needs conformal oxides for gate dielectrics, passivation, encapsulation or nanostructure coating, on pieces or wafers.

The tool has a small heated reactor, fast pneumatic pulse valves and precursor cylinders mounted on the frame. Most labs run Al2O3 from trimethylaluminium and water first, then add a second or third chemistry. For an overview of other film tools, see our deposition equipment page.

Thermal ALD and its limits

Thermal ALD gives excellent conformality with a simple, robust tool, but the chemistry range is narrower than in plasma ALD and some films need higher temperatures. If you are weighing a used Savannah against a plasma system, our post on thermal vs plasma ALD for research labs sets out where each one wins.

What we inspect

• Pulse valves. Response, leak-by and seat condition; ALD valves are the highest-cycle part on the tool.
• Heaters. Reactor, lid, precursor lines and cylinder jackets checked against setpoint with independent thermocouples.
• Vacuum. Base pressure, pump condition and the foreline trap, which collects reaction products.
• Flow. Carrier gas mass flow controller zero and span.
• Process. For Certified systems, an Al2O3 test run with thickness and uniformity measured by ellipsometry.

The common wear points are ALD valve diaphragms, O-rings exposed to precursor, heater tape and controller channels, and powder build-up in the exhaust line and trap. Precursor cylinders are never sold with the tool unless empty, purged and documented.

Precursor handling and safety

Trimethylaluminium and diethylzinc ignite in air, and metal amide precursors for HfO2 or ZrO2 react with moisture, so line and cylinder work is a safety task, not routine maintenance. Before any line is opened we purge it with inert gas and confirm it is free of precursor. On installation we fit cylinders with your site's procedure, leak test every connection under vacuum and check the over-temperature limits on the cylinder heaters. Exact requirements depend on your precursors and your site's safety rules.

Refurbishment and upgrades

We decontaminate the reactor, lines and trap, replace valves and seals as needed, verify every heater zone and service the pump. See decontamination for how we handle tools that ran pyrophoric or toxic precursors. Upgrades include extra heated lines, an ozone source, a dry pump conversion and a controller or software update. We can also supply valves, heaters and seals as spare parts for systems you already run.

Facilities you will need

• Single-phase power for the tool; pump power depending on pump type
• Nitrogen or argon carrier gas of high purity
• Clean dry air for the pneumatic valves
• Ventilated enclosure or extraction for precursor cylinders
• Exhaust for the pump outlet
• Ozone destruct and monitoring, if an ozone generator is fitted

Buying advice

List the films you need and check them against lines, heaters and temperature range of the system on offer. Ask what precursors the tool has run, since that sets the decontamination effort and whether lines should be replaced. Plan a safety review for pyrophoric precursors early; it often takes longer than the installation.