Two-dimensional capacitive micromachined ultrasonic transducer (CMUT) arrays for a miniature integrated volumetric ultrasonic imaging system

被引:10
作者
Zhuang, X [1 ]
Wygant, IO [1 ]
Yeh, DT [1 ]
Nikoozadeh, A [1 ]
Oralkan, O [1 ]
Ergun, AS [1 ]
Cheng, CH [1 ]
Huang, Y [1 ]
Yaralioglu, GG [1 ]
Khuri-Yakub, BT [1 ]
机构
[1] Stanford Univ, E L Ginzton Lab, Stanford, CA 94305 USA
来源
MEDICAL IMAGING 2005: ULTRASONIC IMAGING AND SIGNAL PROCESSING | 2005年 / 5750卷
关键词
capacitive micromachined ultrasonic transducer; CMUT; two-dimensional array; ultrasonic imaging; through-wafer interconnect; integration; flip-chip bonding;
D O I
10.1117/12.594702
中图分类号
O42 [声学];
学科分类号
070206 ; 082403 ;
摘要
We have designed, fabricated, and characterized two-dimensional 16x16-element capacitive micromachined ultrasonic transducer (CMUT) arrays. The CMUT array elements have a 250-mu m pitch, and when tested in immersion, have a 5-MHz center frequency and 99% fractional bandwidth. The fabrication process is based on standard silicon micromachining techniques and therefore has the advantages of high yield, low cost, and ease of integration. The transducers have a Si3N4 membrane and are fabricated on a 400-mu m thick silicon substrate. A low parasitic capacitance through-wafer via connects each CMUT element to a flip-chip bond pad on the back side of the wafer. Each through-wafer via is 20 mu m in diameter and 400 mu m deep. The interconnects form metal-insulator-semiconductor (MIS) junctions with the surrounding high-resistivity silicon substrate to establish isolation and to reduce parasitic capacitance. Each through-wafer via has less than 0.06 pF of parasitic capacitance. We have investigated a Au-In flip-chip bonding process to connect the 2D CMUT array to a custom integrated circuit (IC) with transmit and receive electronics. To develop this process, we fabricated fanout structures on silicon, and flip-chip bonded these test dies to a flat surface coated with gold. The average series resistance per bump is about 3 Ohms, and 100% yield is obtained for a total of 30 bumps.
引用
收藏
页码:37 / 46
页数:10
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