Crystal adjustment by laser chemical deposition

Maskless adjustment of quartz crystals has been developed using laser-induced deposition of material. The process uses an excimer laser operating in the UV, which dissociates volatile precursors and leaves a stable material. This material is deposited where the laser strikes the surface of the crystal and hence can be used to adjust it. A simple means of beam steering has been developed and the necessary process parameters such as laser fluence and precursor flow rate have been investigated. Problems such as window fouling and gas phase reactions have been solved. Up to 2000 p.p.m. of adjustment to crystal resonators of up to 125-MHz fundamental has been demonstrated. Initial aging of canned crystals look very promising.<>