Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
ELECTROSTATIC ULTRASONIC TRANSDUCER AND METHOD OF MAKING THE SAME
Document Type and Number:
WIPO Patent Application WO/2000/072631
Kind Code:
A2
Abstract:
The present invention provides a transducer and a method of making the same. The transducer is comprised of a plurality of transducer cells (200A, 200B, 200C), and conductive interconnects (220, 230) between the cells. Each transducer cell contains a bottom electrode (320A, 320B, 320C) formed on a layer of insulator material, a lower insulating film portion (320A) formed over the bottom electrode, a middle insulating film portion (320B) that includes an air/vacuum void region (340A, 340B, 340C), and an upper insulating film portion (320C) that includes a top electrode (350A, 350B, 350C) formed within a portion of the upper insulating film portion. A first layer of interconnects (230) electrically connect the bottom electrodes of each transducer cell and a second layer of interconnects (220) electrically connect the top electrodes of each transducer cell. The top and bottom layers of interconnects (220, 230) are patterned to avoid overlap between them, thus reducing the parasitic capacitance. Further, as noted, the top electrode (350A, 350B, 350C) is preferably formed within the upper insulating film portion, (320C), closer to the air/vacuum void than to the top surface of the insulating film, to increase the electric field for a given voltage. Still furthermore, the electrodes within each transducer cell are preferably formed to have dimensions that are smaller than the overall surface area of the membrane that they excite.

Inventors:
Ladabaum, Igal (121 Baytree Road San Carlos, CA, 94070, US)
Application Number:
PCT/US2000/013634
Publication Date:
November 30, 2000
Filing Date:
May 17, 2000
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
SENSANT CORPORATION (14470 Doolittle Drive San Leandro, CA, 94577, US)
International Classes:
B06B1/02; G01H11/06; H02N1/00; H04R19/00; H04R31/00; (IPC1-7): H04R19/00
Foreign References:
DE2444023A11975-03-20
US5619476A1997-04-08
Other References:
KENICHIRO SUZUKI ET AL: "A SILICON ELECTROSTATIC ULTRASONIC TRANSDUCER" IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS AND FREQUENCY CONTROL,US,IEEE INC. NEW.YORK, vol. 36, no. 6, 1 November 1989 (1989-11-01), pages 620-627, XP000099883 ISSN: 0885-3010
PATENT ABSTRACTS OF JAPAN vol. 014, no. 114 (P-1015), 2 March 1990 (1990-03-02) -& JP 01 312486 A (AGENCY OF IND SCIENCE & TECHNOL), 18 December 1989 (1989-12-18)
PATENT ABSTRACTS OF JAPAN vol. 013, no. 173 (E-748), 24 April 1989 (1989-04-24) -& JP 01 004199 A (NEC HOME ELECTRONICS LTD), 9 January 1989 (1989-01-09)
PATENT ABSTRACTS OF JAPAN vol. 014, no. 344 (E-0955), 25 July 1990 (1990-07-25) -& JP 02 117299 A (MAZDA MOTOR CORP), 1 May 1990 (1990-05-01)
Attorney, Agent or Firm:
Jakopin, David A. (Pillsbury, Madison & Sutro LLP 1100 New York Avenu, N.W. Washington DC, 20005, US)
Download PDF:
Claims:
I CLAIM:
1. A transducer comprising: a supporting substrate; at least two transducer cells formed on the substrate, each transducer cell including: a first electrode formed over the substrate; an insulating film formed over the first electrode and including a void region therein; and a second electrode disposed at least substantially parallel to the first electrode and formed over at least a portion of the insulating film such that the void region is disposed between the first electrode and the second electrode; a first interconnect that electrically connects the first electrodes of each of the at least two transducer cells; and a second interconnect that electrically connects the second electrodes of each of the at least two transducer cells, wherein the first and second interconnect do not substantially overlap.
2. The transducer of claim I further including an insulator material disposed between the substrate and the transducer cells.
3. The transducer of claim 2 wherein the substrate is silicon, the insulator material is silicon oxide and the insulating film is silicon nitride.
4. The transducer of claim 2 wherein there is no overlap of the first and second interconnects at areas which do not overlap the void regions.
5. The transducer of claim) wherein the second electrode is formed within the insulating film.
6. The transducer of claim 5 wherein the first and second interconnects are formed on the same conductor layer as the first and second electrodes, respectively.
7. The transducer of claim 6 wherein the first and second electrodes each have a surface area that is smaller than a surface area of the corresponding void region.
8. The transducer of claim 7 wherein the first and second interconnects are formed on the same conductor layer as the first and second electrodes, respectively.
9. The transducer of claim l wherein the first and second interconnects are formed on the same conductor layer as the first and second electrodes, respectively.
10. The transducer of claim 1 wherein the first and second electrodes each have a surface area that is smaller than a surface area of the corresponding void region.
11. The transducer of claim 1 wherein the first and second electrodes and the first and second interconnects are made of aluminum.
12. The transducer of claim I wherein the first and second electrodes and the first and second interconnects are made of copper.
13. The transducer of claim I wherein the first and second electrodes and the first and second interconnects are made of tungsten.
14. An transducer comprising: a supporting substrate; and a transducer cell formed on the substrate, said transducer cell including: a first electrode formed over the substrate; an insulating film formed over the first electrode and including a void region therein; and a second electrode disposed at least substantially parallel to the first electrode and formed within the insulating film such that the void region is disposed between the first electrode and the second electrode, and the thickness of the insulating film is greater than the spacing between the first and second electrode.
15. The transducer of claim 14 further including an insulator material disposed between the substrate and the transducer cell.
16. The transducer of claim 14 wherein the insulating film is silicon nitride.
17. The transducer of claim 14 wherein the first and second electrodes each have a surface area that is smaller than a surface area of the corresponding void region.
18. A method of manufacturing a transducer comprising: depositing a first conductive layer on a substrate; etching the first conductive layer to form at least two first electrodes and a first interconnect electrically connecting the at least two first electrodes; depositing a first insulating film layer of insulator material on the etched conductor; depositing a sacrificial layer over the first insulating film; etching the sacrificial layer to create at least two sacrificial portions, each in substantial alignment with and overlapping one of the two first electrodes; depositing a second insulating film layer of insulator material over the etched sacrificial layer; depositing a second conductive layer over the second insulating film layer; etching the second conductive layer to form at least two second electrode that overlap and substantially align with the first electrodes, and a second interconnect electrically connecting the two second electrodes, wherein the second interconnect does not overlap the first interconnect; and removing the sacrificial portions to form corresponding void areas.
19. The method of claim 18 wherein further comprising the step of depositing a third insulating film layer of insulator material over the etched second conductive layer.
20. The method of claim 19 wherein the step of removing takes place after the step of depositing the second insulating film layer.
21. The method of claim 18 wherein: the step of creating the sacrificial layer further creates a sacrificial pathway connected to the at least two sacrificial portions; and the step of removing the sacrificial portions includes the steps of : creating a via hole in the second insulating film layer to the sacrificial pathway; and etching the sacrificial pathway and the at least two sacrificial portions.
22. The method of claim 18 wherein the steps of depositing the first and second conductive layers deposit aluminum.
23. The method of claim 22 wherein the step of depositing the sacrificial layer deposits aluminum.
24. The method of claim 18 wherein the steps of depositing the first and second conductive layers deposit copper.
25. The method of claim 18 wherein the steps of depositing the first and second conductive layers deposit tungsten.
26. The method of claim 18 wherein the steps of depositing the first and second insulating film layers deposit silicon nitride using plasmaenhanced chemical vapor deposition.
27. The method of claim 18 wherein the step of depositing the sacrificial layer deposits a low temperature oxide.
28. The method of claim 19 wherein the step of depositing the sacrificial layer deposits aluminum.
29. The method of claim 18 wherein the step of etching the sacrificial layer creates the at least two sacrificial portions such that each sacrificial portion has a surface area that is larger than the corresponding first electrode.
30. The method of claim 18 wherein a plurality of transducers are simultaneously formed in an array.
Description:
INTERNATIONAL SEARCH REPORT In ational Application No ! n jtona! Apphcat! on No PCT/US00/13634 C. (Continuation) DOCUMENTS CONSIDERED TO BE RELEVANT Category Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. X PATENT ABSTRACTS OF JAPAN 14,15 vol. 014, no. 114 (P-1015), 2 March 1990 (1990-03-02) -& JP 01 312486 A (AGENCY OF IND SCIENCE & TECHNOL), 18 December 1989 (1989-12-18) A abstract 1,2,5 A US 5 619 476 A (HALLER MATTHEW I ET AL) 1,3,18 8 April 1997 (1997-04-08) cited in the application column 2, line 61-column 3, line 39 column 4, line 64-column 5, line 13 figures 1D, 3 A PATENT ABSTRACTS OF JAPAN 5,14 vol. 013, no. 173 (E-748), 24 April 1989 (1989-04-24) -& JP 01 004199 A (NEC HOME ELECTRONICS LTD), 9 January 1989 (1989-01-09) abstract; figure 3 A PATENT ABSTRACTS OF JAPAN 7,10,17 vol. 014, no. 344 (E-0955), 25 July 1990 (1990-07-25) -& JP 02 117299 A (MAZDA MOTOR CORP), 1 May 1990 (1990-05-01) abstract; figure 2 2 ,. nternational application No. INTERNATIONAL SEARCH REPORT PCT/US 00/13634 Box I Observations where certain claims were found unsearchable (Continuation of item 1 of first sheet) This International Search Report has not been established in respect of certain claims under Article 17 (2) (a) for the following reasons: 1. Claims Nos.: because they relate to subject matter not required to be searched by this Authority, namely : 2. Claims Nos. : because they relate to parts of the International Application that do not comply with the prescribed requirements to such an extent that no meaningful International Search can be carried out, specifically : 3. Claims Nos. : because they are dependent claims and are not drafted in accordance with the second and third sentences of Rule 6.4 (a). Box 11 Observations where unity of invention is lacking (Continuation of item 2 of first sheet) This International Searching Authority found multiple inventions in this international application, as follows : see additional sheet 1. As all required additional search fees were timely paid by the applicant, this International Search Report covers all searchable claims. 2. As ai) searchable claims could be searched without effort justifying an additional fee, this Authority did not invite payment of any additional fee. 3. As only some of the required additional search fees were timely paid by the applicant, this International Search Report covers only those claims for which fees were paid, specifically claims Nos.: 4. No required additional search fees were timely paid by the applicant. Consequently, this International Search Report is restricted to the invention first mentioned in the claims ; it is covered by claims Nos.: Remark on Protest 2 The additional search fees were accompanied by the applicant's protest. u ! Y No protest accompanied the payment of additional search fees. au FURTHER INFORMATION CONTINUED FROM PCT/fiSA/210 This International Searching Authority found multiple (groups of) inventions in this international application, as follows: 1. Claims: 1-13,18-30 Array of electrostatic transducers with interconnected electrodes and insulator material between substrate and transducers 2. Claims: 14-17 Electrostatic transducer with one electrode embedded in the insulating layer separating the electrodes INTERNATIONAL SEARCH _ Ir, ational Application No Informationon patent family members Patent document Publication Patent family Publication cited in search report date member (s) date DE 2444023 A 20-03-1975 BE 819975 A 16-01-1975 DK 484774 A 12-05-1975 FR 2246150 A 25-04-1975 IT 1021359 B 30-01-1978 JP 50089017 A 17-07-1975 NL 7412195 A 18-03-1975 SE 7411457 A 17-03-1975 JP 01312486 A 18-12-1989 NONE US 5619476 A 08-04-1997 US 5870351 A 09-02-1999 US 5894452 A 13-04-1999 US 6004832 A 21-12-1999 JP 01004199 A 09-01-1989 NONE JP 02117299 A 01-05-1990 NONE