Piezoelectric devices for frequency control and selection in Japan

Abstract

A b s t r a c t P i e z o e l e c t r i c materials f o r SAW d e v i c e s w i l l be reviewed. A l l m a t e r i a l s have some d i s t r i b u t i o n o f m a t e r i a l c o n s t a n t s . The t y p i c a l r e s u l t s o f t h e d i s t r i b u t i o n of LSAW v e l o c i t y i n a s u b s t r a t e as measured by t h e Line-Focus-Beam u l t r a s o n i c microscope w i l l be r e p o r t e d . The d e s i g n s of o s c i l l a t o r c i r c u i t s u s i n g bulk wave and s u r f a c e a c o u s t i c wave r e s o n a t o r s a r e analyzed. Maximum i n p u t power f o r SAW d e v i c e s i s l i m i t e d by electrode m i g r a t i o n , which depends on t h e maximum stress a t I D T e l e c t r o d e s . S t r e s s d i s t r i b u t i o n i n a S A W s u b s t r a t e can be c a l c u l a t e d and shown g r a p h i c a l l y by t h e F i n i t e Element Method. The use of t h e o r i e n t e d A 1 e l e ct r o d e s , i n s t e a d of t h e o r d i n a r y amorphous A 1 e l e c t r o d e s , can i n c r e a s e t h e l i f e o f q u a r t z c r y s t a l S A W r e s o n a t o r s o v e r one thousand times. F i n a l l y , t h e r e l i a b i l i t y o f dipped r e s i n packages f o r TV VIF SAW f i l t e r s w i l l be r e p o r t e d . 1. I n t r o d u c t i o n S i n c e 1975, w e i n Japan have developed S A W d e v i c e s p r i m a r i l y f o r t h e consumer m a r k e t . [ l ] 2 . M a t e r i a l s I n J a p a n , p i e z o e l e c t r i c m a t e r i a l s f o r SAW r e s o n a t o r s and f i l t e r s a r e d i v i d e d i n t o c a t e g o r i e s o f s i n g l e c r y s t a l s , t h i n f i l m s and p i e z o e l e c t r i c ceramics. [ 31 Quartz c r y s t a l i s t h e b e s t m a t e r i a l f o r SAW r e s o n a t o r s , b u t LiTaOg and L&B407 a r e a l s o u s e f u l f o r v o l t a g e contro*d oscill a t o r s (VCO). Many kind o f t h i n f i l m m a t e r i a l s have been developed, b u t ZnO/IDT/glass i s t h e most popular f i l m f o r TV VIF i n mass p r o d u c t i o n o f more t h a n 30 m i l l i o n p i e c e s p e r y e a r . PZT modified by Sn and Sb i s developed t o have non p o r o s i t y , low d i e l e c t r i c cons t a n t s and low t e m p e r a t u r e c o e f f i c i e n t of SAW d e l a y time. Table 1 shows c o n s t a n t s o f each b a s i c m a t e r i a l f o r SAW d e v i c e s i n Japan. Fig.1 shows r e l a t i o n s of t h e SAW c o u p l i n g c o e f f i c i e n t t o t h e a b s o l u t e t e m p e r a t u r e c o e f f i c i e n t of d e l a y t i m e . A z e r o temper a t u r e c o e f f i c i e n t o f d e l a y t i m e and a h i g h c o u p l i n g c o e f f i c i e n t a r e i d e a l f o r SAW d e v i c e m a t e r i a l s , b u t s u c h m a t e r i a l s have n o t been d i s c o v e r e d y e t . I n p r a c t i c e , every s u b s t r a t e has some d i s t r i b u t i o n o f m a t e r i a l c o n s t a n t s . Fig.2 shows an example o f LSAW v e l o c i t y d i s t r i b u t i o n on a PZT 2 i n c h w a f e r poled i n t h e ...

Surface Acoustic Wave Devices in Telecommunications

“…40) and ( 4.41) and the object function of ( 4.42) as their input data. 40) and ( 4.41) and the object function of ( 4.42) as their input data.…”

“…ZnO has already been used for the development of TV-IF filters [39,40] and front-end filters in the 1.5 GHz range for mobile communications (41]. ZnO has already been used for the development of TV-IF filters [39,40] and front-end filters in the 1.5 GHz range for mobile communications (41].…”

“…A.4. (e14 + e36)-e16 40) where V = wj/3 is the phase velocity, and! Next let us assume that the solutions have an exp(-j/3x1) dependence.…”

Preparation of piezoelectric ZnO thin films by target-facing-type sputtering method

“…Piezoelectric zinc oxide (ZnO) thin films are used as surface acoustic wave (SAW) devices in the VHF and UHF bands [1] and as ultrasonic transducers [2]. They have also been studied in applications to thin-film bulk resonators [3] and sensors [4].…”

“…These high-quality characteristics are not obtained by ordinary RF magnetron sputtering, but are believed to be based on the following characteristics of ECR sputtering. (1) The sputter particles can migrate over a wide range after reaching the substrate because the gas pressure during sputtering is a conspicuously low 10 4 Torr and the sputter particles incident on the substrate have a large motion energy. (2) There is little irradiation of high-energy particles to the thin film because the high-density plasma generated by microwave irradiation is highly concentrated.…”