US 2016/0117541 A1 Lu Et Al
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US 201601 17541A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2016/0117541 A1 Lu et al. (43) Pub. Date: Apr. 28, 2016 (54) MUT FINGERPRINT ID SYSTEM Related U.S. Application Data (71) Applicant: THE REGENTS OF THE (60) Provisional application No. 61/846,925, filed on Jul. UNIVERSITY OF CALIFORNLA, 16, 2013. Oakland, CA (US) Publication Classification (72) Inventors: Yipeng Lu, Davis, CA (US); David (51) Int. Cl Horsley, Albany, CA (US); Hao-Yen we Tang, Berkeley, CA (US); Bernhard G06K9/00 (2006.01) Boser, Berkeley, CA (US) (52) U.S. Cl. CPC .................................... G06K9/0002 (2013.01) (21) Appl. No.: 14/896,150 (57) ABSTRACT (22) PCT Filed: Jul. 14, 2014 MEMS ultrasound fingerprint ID systems are provided. (86). PCT No.: PCT/US1.4/46557 Aspects of the systems include the capability of detecting both epidermis and dermis fingerprint patterns in three S371 (c)(1), dimensions. Also provided are methods of making and using (2) Date: Dec. 4, 2015 the systems, as well as devices that include the systems. Patent Application Publication Apr. 28, 2016 Sheet 1 of 12 US 2016/0117541 A1 - - - - - - - -3 a. s. sers c s re X------------ - - - - - - - - - - - - - - - - - - - - - Patent Application Publication Apr. 28, 2016 Sheet 2 of 12 US 2016/0117541 A1 re a was w w m w w m me we ree mere w .C. N s Y. r & r - a "a w Patent Application Publication Apr. 28, 2016 Sheet 3 of 12 US 2016/0117541 A1 Saw, w, . Patent Application Publication Apr. 28, 2016 Sheet 4 of 12 US 2016/0117541 A1 Patent Application Publication Apr. 28, 2016 Sheet 5 of 12 US 2016/0117541 A1 Ø×2 *******zºz-*zzzzzz|91-¿¿ ?ŽŽŽŽŽŽŽŽŽŽŽŽŽŽŽ Patent Application Publication Apr. 28, 2016 Sheet 6 of 12 US 2016/0117541 A1 Patent Application Publication Apr. 28, 2016 Sheet 7 of 12 US 2016/0117541 A1 S. 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Patent Application Publication Apr. 28, 2016 Sheet 12 of 12 US 2016/0117541 A1 15 elements, 8 charrels, 140 am Pitch kPa, O 65 6 S S 4. O S (5 3 O 4. 35 13-a- - laterai distance (in) Figure 3.2 US 2016/01 17541 A1 Apr. 28, 2016 MUT FINGERPRINT ID SYSTEM SUMMARY 0008. The micromachined ultrasonic transducer finger CROSS-REFERENCE TO RELATED print identification system (MUT fingerprint ID system) of APPLICATIONS the present invention is a revolutionary advancement in the 0001 Pursuant to 35 U.S.C. S 119 (e), this application field of personal authentication. The unprecedented small claims priority to the filing date of the U.S. Provisional Patent size, robust solid-state construction, and orders of magnitude Application Ser. No. 61/846,925, filed Jul. 16, 2013; the lower cost per unit than current systems opens a new era in disclosure of which is herein incorporated by reference. personal identification capabilities, with transformational impact on personal electronic devices, many other consumer INTRODUCTION goods, and entry enablement devices. 0009. The MUT fingerprint ID system is a novel finger 0002. Two dimensional fingerprint analysis has been used print sensor based on an array of ultrasonic transducers. Com for centuries for personal identification in criminal justice pared with existing ultrasonic fingerprint sensors based on cases. More recently, the applications for fingerprint identi bulk piezoelectric material, the MUT fingerprint ID system fication have been extended to use in the broader commercial has advantages of a small size, easy fabrication, easy integra sphere, and have been effectively deployed in niche applica tion with electronics, and fast electronic scanning. These tions, such as security-critical applications such as banking. features represent a game-changing advancement over cur 0003. However, automated optical fingerprint scanning rently available bulky, failure prone mechanical scanners. techniques have a number of limitations that block their use in This novel ultrasonic fingerprint sensor avoids the mechani broader applications. For example, automated optical finger cal scanning needed by earlier ultrasonic fingerprint sensors. print Scanning techniques sense only the epidermal layer of a 0010 Conventional fingerprint sensors used in consumer fingerprint. As a result, they are prone to errors created by electronics applications are capacitive sensors and are finger contamination. extremely prone to errors due to wet, dry or oily fingers. 0004. The marketplace has reflected the limitations of Optical sensors are sensitive to dirt on fingers. Unlike both optical fingerprint identification features for broad market capacitive and optical sensors, which measure the fingerprint needs, such as personal electronic devices. While initially on the epidermis (skin Surface), the ultrasonic sensor at the provided as features for identification in many personal elec core of the MUT fingerprint ID system can detect the finger tronic devices, optical fingerprint Scanners have been print on both the epidermis and dermis (subcutaneous) layers. removed from most later models due to these limitations. 0011 Since both dermis and epidermis detection are used They lacked the necessary robustness to perform predictably by MUT fingerprint ID system to obtain the correct finger in Such everyday environments. print pattern, the sensor is insensitive to both contamination 0005 Ultrasonic fingerprint scanners have been devel and moist conditions of fingers. By contrast, optical and oped in an effort to minimize the limitations of currently capacitive sensors are sensitive to contamination. The MUT available automated optical fingerprint Scanning, and avoid fingerprint ID system is able to electronically scan the Some of the resulting errors, by analyzing the dermal finger focused acoustic beam over a large distance (from several mm print. For example, such a system is described by Schneider, to several cm) with small step size (~50 um). et al. U.S. Pat. No. 5,224,174 issued Jun. 29, 1993. However, 0012 Ultrasonic fingerprint sensors have high fidelity and currently available ultrasonic fingerprint Scanners devices are are used in security-critical applications such as banking. limited in their applications because of large size, the require However, existing ultrasonic sensors use a single bulk ultra ment of a physically moving scanning device, and cost. Sound transducer that is mechanically scanned, making these 0006 Recently, initial experimental work has been con sensors too large, slow, and expensive for use in consumer ducted on the development of micromachined ultrasonic electronics (e.g. laptops and Smartphones). transducers (MUTs). This research includes capacitive (0013 The novel MUT fingerprint ID system is provided micromachined ultrasonic transducers (CMUTs), such as that with a micromachined ultrasonic transducer array and a new described at the website produced by placing “http://before electronic scanning method that is digital, has a fast response, and “.pdf after “publications.lib.chalmers.se/records/full and can work in a live scan mode. text/166084' (Chalmers University of Technology, Göte borg, Sweden, 2012); and University of Salerno, Italy, 2011 BRIEF DESCRIPTION OF THE DRAWINGS further described at the website produced by placing “http:// (0014 FIG. 1 shows a generalized view of the MUT fin www.” before “sciencedirect.com/science/article/pii/ gerprint ID system detecting both epidermis and dermis fin S092442471 1005528. In an additional line of research, gerprint patterns, piezoelectric micromachined ultrasonic transducers (PMUTs) have been investigated at the University of Califor (0015 FIG.2 shows the MUT fingerprintID system phased nia, Davis (Thesis, Christine Dempster January, 2013 as fur array embodiment with transducers subgroup Scanning, ther described at the website produced by placing "http:// 0016 FIG. 3 shows a non-beam forming system employ before and “.html after gradworks.umi.com/15/30/ ing acoustic waveguides to detect both the epidermis and 1530021.) dermis layers, 0007. It would be a transformative advancement in finger (0017 FIG. 4 shows a cross-section PMUT array embodi print identification (fingerprint ID) if micromachined ultra ment of the MUT fingerprint ID system, Sonic transducers (MUTs). Such as capacitive micromachined 0018 FIG. 5 is a flow diagram showing the fabrication of ultrasonic transducers (CMUTs) and piezoelectric microma the MUT fingerprint ID system, chined ultrasonic transducers (PMUTs) could be utilized to 0019 FIG. 6 is the system architecture that is particularly accomplish three dimensional fingerprint ID. useful with CMOS, US 2016/01 17541 A1 Apr. 28, 2016 0020 FIG. 7 shows the basic ASIC structure of the MUT 0031 Certain ranges are presented herein with numerical fingerprint ID system, values being preceded by the term “about.” The term “about 0021 FIG.8 shows the simulated vibration mode-shape of is used herein to provide literal support for the exact number a single PMUT, that it precedes, as well as a number that is near to or approxi 0022 FIG. 9 shows the first resonant frequency of a mately the number that the term precedes.