PRECISION FREQUENCY TRIMMING OF SAW AND STW RESONATORS USING XE-ION BOMBARDMENT( HEAVY)

A method for precision frequency trimming of surface acoustic wave (SA W) and surface transverse wave (STW) based resonant devices using a Xe + heavy ion bombardment technique is described. The devices are downtr immed in frequency in an in-situ monitoring process by means of a Kauf mann type ion source that allows first a rough and then a fine frequen cy trimming with an accuracy of 1 ppm in a single continuous in-situ m onitoring process. An improvement of the device insertion loss and unl oaded Q as a result of the trimming process is achieved. Single mode 7 76 MHz STW resonators can be downtrimmed by more than 5000 ppm without deteriorating their parameters while SAW resonators allow a much lowe r frequency downshift. The method is simple and can cost effectively b e applied to SAW and STW device fabrication.