High frequency piezoelectric crystal composites, devices, and methods for manufacturing the same
The present invention generally relates to high frequency piezoelectric crystal composites, devices, and method for manufacturing the same. In adaptive embodiments an improved imaging device, particularly a medical imaging device or a distance imaging device, for high frequency (>20 MHz) applications involving an imaging transducer assembly is coupled to a signal imagery processor. Additionally, the proposed invention presents a system for photolithography based micro-machined piezoelectric crystal composites and their uses resulting in improved performance parameters.
1. A method for fabricating a high frequency imagery transducer for an imagery device, said imagery transducer including one or more composite crystal elements, comprising the steps of:
providing an oriented single crystal plate of a piezoelectric material having a thickness electromechanical coupling factor k t in the range of approximately 0.65-0.90;
etching said oriented single crystal plate with photolithography based micromachining to form a plurality of hybrid piezoelectric structures separated by a plurality of kerfs;
wherein said photolithography based micromachining further includes the steps of:
(a) forming a hard metal mask over portions of said plate where said plurality of hybrid piezoelectric structures are to be formed separated by said plurality of kerfs;
(b) said kerfs including at least one kerf direction having a range of approximately 30 to 35° degrees from a noted orientation direction for said single crystal plate operative to minimize a clamping effect according to the following formula: d′ 31 =d 31 *Cos(θ)*Cos(θ)+d 32 *Sin(θ)*Sin(θ);
(c) conducting at least one of a step of reactive-ion etching (RIE) and deep reactive ion etching (DRIE);
(i) said hybrid piezoelectric structures having a vertical etching profile of at least 85°;
filling said kerfs with a polymeric material to form a unitary assembly;
conducting a fine mechanical finishing step of said unitary assembly;
coating electrodes on said unitary assembly; and
assembling said unitary assembly with a backing operative to form said imagery transducer for said imagery device.
2. The method of claim 1 , wherein:
said imagery transducer is in a hexagonal hybrid 1-3 configuration.
3. The method of claim 2 , wherein:
said composite crystal elements are (001) cut and <001> poled.
4. The method of claim 2 , wherein:
said composite crystal elements are (011) cut and <011> poled.
5. The method of claim 4 , wherein:
said at least one kerf direction is +/−32.5° (+/−2.5°) away from a <10 1 > direction for said composite crystal elements, whereby said at least one kerf direction is strain free under a clamping effect.
6. The method of claim 1 , wherein:
said imagery transducer is in a parallelogram hybrid 1-3 configuration.
7. The method of claim 6 , wherein:
said composite crystal elements are (011) cut and <011> poled.
8. The method of claim 7 , wherein:
said at least one kerf direction is +/−32.5° (+/−2.5°) away from a <10 1 > direction for said composite crystal elements, whereby said at least one kerf direction is transverse strain free under a clamping effect.
9. The method of claim 1 , wherein:
said imagery transducer is in a hybrid 2-2/1-3 configuration.
10. The method of claim 9 , wherein:
said composite crystal elements are (011) cut and <011> poled.
11. The method of claim 10 , wherein:
said at least one kerf direction is +/−32.5° (+/−2.5°) away from a <10 1 > direction for said composite crystal elements, whereby said at least one kerf direction is transverse strain free under a clamping effect.
12. The method of claim 1 , wherein:
said imagery transducer is operative at a frequency of at least 20 MHz.
13. The method of claim 12 , wherein:
said imagery transducer is operative at a frequency of at least 100 MHz.
14. The method of claim 1 , wherein:
each respective said kerf of said plurality of kerfs has width in the range of approximately 1 to 10 μm.
15. The method of claim 14 , wherein:
said hybrid piezoelectric structures are at least one of a configuration selected from a group consisting of a
a hexagonal hybrid 1-3 configuration and a parallelogram hybrid 1-3 configuration;
each said hybrid piezoelectric structure having a post height and an average post width; and
an aspect ratio of said post height (H) to said average post width (W) is at least 0.50.
16. The method of claim 15 , wherein:
said aspect ratio is at least said 0.50 and less than 2.0.
17. The method of claim 2 , wherein:
said in a hexagonal hybrid 1-3 configuration includes said hybrid piezoelectric structures having a hexagon cross section bounded by said plurality of kerfs, wherein said kerfs are discontinuous and said hybrid piezoelectric structure is interrupted.
18. The method of claim 6 , wherein:
said in a parallelogram hybrid 1-3 configuration includes said hybrid piezoelectric structures having a parallelogram cross section bounded by said plurality of kerfs, wherein said kerfs extend in a continuously through said configuration.
19. The method of claim 9 , wherein:
said imagery transducer is in a hybrid 2-2/1-3 configuration and further comprises:
at least one elongate web bar member spanning between a first end and a second end;
at least two bridge members on opposing sides of said web bar member forming respectively four bridge member parts, two on opposing sides of said elongate web bar;
a leg bar member extending from each said bridge member parts parallel to said elongate web bar member and separated by respective ones of said kerfs; and
said elongate web bar member parallel to said clamping direction.
20. An imaging device configured to operatively include a high frequency transducer assembly; said imaging device comprising:
at least one said transducer assembly coupled to an imaging array and operative to generate an image signal;
at least one communication pathway from said transducer assembly to an operative processer and imaging system effective to receive said image signal;
said transducer assembly includes one or more composite crystal elements, in an oriented single crystal plate of a piezoelectric material having a thickness electromechanical coupling factor k t in the range of approximately 0.65-0.90, wherein each transducer assembly is in a configuration selected from a group of configurations consisting of:
a hexagonal hybrid 1-3 configuration, a parallelogram hybrid 1-3 configuration and a hybrid 2-2/1-3 configuration.
21. The imaging device of claim 20 , wherein:
said configuration is said hexagonal hybrid 1-3 configuration and contains at least one composite crystal element being (001) cut and <001> poled.
22. The imaging device of claim 20 , wherein:
said configuration is said hexagonal hybrid 1-3 configuration and contains at least one composite crystal element being (011) cut and <011> poled.
23. The imaging device of claim 20 , wherein:
said configuration is said parallelogram hybrid 1-3 configuration and contains at least one composite crystal element being (011) cut and <011> poled.
24. The imaging device of claim 20 , wherein:
said configuration is said hybrid 2-2/1-3 configuration.