Precision frequency trimming of SAW and STW resonators using Xe+ heavy ion bombardment

A method for precision frequency trimming of surface acoustic wave (SAW) and surface transverse wave (STW) based resonant devices using an Xe⁺ heavy ion bombardment technique is described. The devices are down-trimmed in frequency in an in situ monitoring process by means of a Kaufmann-type ion source that first allows a rough frequency trimming and then a fine one with an accuracy of 1 ppm. An improvement of the device insertion loss and unloaded Q as a result of the trimming process is achieved. Single-mode 776-MHz STW resonators can be down trimmed by more than 5000 ppm without deteriorating their parameters while SAW resonators allow a much lower frequency downshift. The method is simple and can cost-effectively be applied to SAW and STW device fabrication