by Debra Vogler, Senior Technical Editor, and James Montgomery, News Editor,Solid State Technology
Tiger Optics says its latest analyzer, based on cavity ring-down spectroscopy (CRDS), called Tiger-i, targets ambient molecular contaminants (AMCs). Trace amounts of such molecules, in particular HF and HCl, in the presence of ammonia or amines lead to the formation of ammonium chloride and ammonium fluoride microcrystals, the origin of “haze” on wafer surfaces and reticles.
“HF and HCl lead to etching of boron silicate fibers in HEPA filters,” explained Matt Lyons, US sales director of UHP and semiconductor applications at Tiger Optics, in an interview with SST. “This etching process then releases boron, which has an affinity for silicon surfaces.” He also noted that boron contamination can lead to unintentional p-type doping of lightly doped n-type layers due to this reaction.
The company says the capability to measure to parts-per-trillion stems from its patented “continuous wave cavity ring-down spectroscopy” technology. A beam of light energy from a diode laser is directed through a mirror into the absorption cell and then bounced back and forth between two ultrahigh-reflective mirrors; once a preset energy level is achieved the source is shuttered or diverted away from the cavity. On each pass, a small amount of light or ring-down signal emits through the second mirror and is sensed by a light detector. Once the light “rings down,” the detector achieves a point of zero light energy in milliseconds, completing the measurement process.
The specificity of this technology executed with precise lasers and mirrors is key to reaching those ppt measurements with the company’s products, and in the case of the new Tiger-i that applies to HF and HCl, the company told SST.
The Tiger-i analyzer comes in two platforms: a 1000 model with a split architecture to place sensor modules up to 50m away from the central analyzer, and a compact smaller-footprint 2000 version. — D.V., J.M.