ISICL: In Situ Coherent Lidar for Submicron Particle Detection
Particles in plasma etch chambers are a major source of yield loss in semiconductor manufacturing. Particles condensing from the plasma or spalling out of films on the chamber walls are levitated in the edges of the plasma sheath for long periods, and then (too often) drop on the wafer when the plasma excitation is turned off.
Process control and tool utilization can both be improved by knowing what’s happening inside the chamber while the process is going on—but how? The plasmas are usually too bright to look at, and there’s only one (poor quality) window in the typical chamber, so an optical particle detector would have to work in backscatter, with a huge background.
ISICL is capable of seeing and mapping individual particles of less than 0.2 μm diameter, as they float around in the plasma, a unique capability.