Metal Lift-Off System

Metal lift-off on the C&D P9000 and P8000

Lift-off patterns a metal film by dissolving the resist beneath it, and the unwanted metal has to come away cleanly without settling back on the wafer. C&D’s lift-off module does the whole job in one chamber. A low-pressure spray soaks the wafer in heated solvent for a programmed time, then a fine high-pressure needle spray sweeps across it and lifts the metal away. The robot only ever handles dry wafers, while the wafer stays wet from the start of processing to the final dry, so lifted metal can’t dry back onto it.

The module runs on the P9000 cluster tool and the P8000 linear track, cassette to cassette, for 50mm to 300mm wafers. The same module strips photoresist after etch. SiSTEM is C&D’s distributor for the UK and Ireland: we specify and quote the system with you, and our after-sales team installs and supports it.

How the module works

• A programmable sweep arm with adjustable speed spreads the spray evenly across the wafer
• Z-axis control of nozzle height sets the force of the high-pressure spray
• A raster scan function matches solvent volume to nozzle position, for even lift-off from centre to edge
• Four independent dispense lines let one recipe combine spray, puddle and high-pressure spray
• A backwash stops metal settling on the underside, and an air ring keeps the back of the wafer and the chuck dry
• The chamber is shaped to cut misting and splashback, with fume extraction built in

Solvents and metal recovery

The module takes acetone, IPA, NMP and other lift-off chemistries, heated. A dual drain keeps the solvent apart from the IPA and DI water rinse, and a diverting valve can send different solvents to separate waste streams, so the stripped metal collects in one place. C&D has several options for capturing precious metals.

Results

C&D has shown clean lift-off of metal stacks at high and low pattern density and of indium bump metal. It has also lifted off hafnium oxide, and features down to 300nm wide.

System

Brushless spindle motor with a digital controller, C&D’s smartPro Windows software with unlimited recipes, and SECS/GEM capability. Throughput is 8 to 20 wafers an hour, depending on the process. CE marked.

To quote lift-off we’ll ask about

• The metal stack and its thickness
• Resist type and pattern density
• Wafer sizes and the solvents you use now
• Throughput, and whether you want metal recovery