Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2001-01-31
2004-08-10
Versteeg, Steven (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298320, C204S298360
Reexamination Certificate
active
06773557
ABSTRACT:
BACKGROUND OF THE INVENTION
Frequency adjustment of piezoelectric resonators by ion etching has been known for decades. A summary is given in “A Survey of Ion Beam Techniques for Piezoelectric Device Fabrication” by R. N. Castellano et al, published in the “Proceeding of the 29
th
Annual Symposium on Frequency Control”, 1975, pp 128-134. However, inspite of this and other publications, the method has only recently been applied to the large-scale commercial frequency adjustment of electroded resonators.
In the adjustment process the electroded surface of the resonator is exposed to the beam of an ion gun in vacuum. The beam bombards and etches off a surface layer, thereby reducing the electrode mass and raising the resonator frequency toward a target value.
The process creates heat in the resonator that is proportional to the etch rate. Since the resonator frequency is affected by heat, it drifts as the resonator cools down after adjustment, thereby reducing the accuracy of the adjustment. The accuracy can be improved by lowering the etch rate, but this reduces the system throughput. Efficient and accurate large-scale processing therefore requires maximizing both the throughput and the accuracy of the adjustment system. This application describes such a system.
To our knowledge, the published reports of frequency adjustment by ion etching have used ion guns of the so-called “Kaufman” design. These guns include two heated filaments, one serving as a grid for controlling the ion beam, the other for neutralizing the ion beam. These filaments require relatively frequent maintenance.
The systems described in this application employ a so-called “Anode Layer” gun, which has no filaments and therefore requires little maintenance. However, it has the beam pattern of a closed, relatively narrow path rather than a contiguous area. The path can be circular or partially linear, but it must include curves for the path to be closed.
SUMMARY OF THE INVENTION
The invention relates to the frequency adjustment of piezoelectric resonators by ion etching in vacuum. It describes a novel system for maximizing both the throughput and accuracy of the adjustment. It is based on mounting the resonators on a tray in rows and columns and simultaneously exposing two rows at a time to an ion gun with a race-track-shaped beam pattern whose two straight tracks are spaced at a multiple of the inter-row distance d. The tray can be moved in steps of d such that each row is sequentially exposed to a “pre-etch” and “final-etch” stage, with time between the two exposures for the resonators to cool down after the “pre-etch” stage. The accuracy can be further enhanced by making the final-etch rate smaller than the pre-etch rate.
REFERENCES:
patent: 5662782 (1997-09-01), Gomi et al.
patent: 6368664 (2002-04-01), Veerasamy et al.
patent: 6564439 (2003-05-01), Takata et al.
Castellano et al., “A Survey of Ion Beam Milling Techniques for Piezoelectric Device Fabrication”, (1975).
Fay Sharpe Fagan Minnich & McKee LLP
Showa Shinku Co., Ltd.
Versteeg Steven
LandOfFree
System for frequency adjustment of piezoelectric resonators... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for frequency adjustment of piezoelectric resonators..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for frequency adjustment of piezoelectric resonators... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3278547