Next-generation high performance MEMS ultrasonics

下一代高性能 MEMS 超声波

• 批准号: 567531-2021
• 负责人: Zemp, Roger
• 金额: $ 7.29万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Alliance Grants
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=722483
• 关键词: Next; generation; performance; MEMS; ultrasonics

It has long been hypothesized that capacitive micromachined ultrasound transducers (CMUTs) could potentially outperform piezoelectric technologies. However, challenges with dielectric charging, operational hysteresis, and transmit sensitivity have stood as obstacles to these performance outcomes. Typically, a CMUT element is designed with an ensemble of smaller membranes oscillating together to transmit or detect ultrasound waves. However, this approach can lead to unreliable behavior and suboptimal transmit performance if these smaller membranes oscillate out of phase, or collapse at different voltages. After nearly 15 years of work, we recently designed reliable CMUT elements composed of a single long rectangular membrane, that can outperform piezoelectrics. We explored various architectural modifications to the CMUT cavity in order to improve robustness to charging and minimize hysteresis without compromising performance. In order to fabricate CMUTs with these architectural modifications, we developed a double-SOI wafer bonded process with near-100% bonding yield, without the need for aligned bonding. The fabricated single-membrane CMUTs achieved electromechanical efficiency values as high as 0.95, higher than values reported with either piezoelectric transducers or CMUT elements. Moreover, these single-membrane CMUTs exhibited transmit efficiency 2-5 times greater than published CMUT or piezoelectric transducer elements in the 1.5-2.0 MHz range. Our devices demonstrated considerable charging robustness, demonstrating minimal charging over millions of collapse-snapback actuation cycles, while also mitigating hysteresis. In this proposal, we aim to further improve these devices for next-generation high-performance MEMS ultrasonics. Improvements will include high-K dielectrics enabling higher combined transmit and biasing voltages. We also propose an inverted CMUT architecture for piston-like motion, development of high-density through-silicon via technology, and development of prototype linear and 2D arrays. We aim to demonstrate the advantages of our technology using head-on comparisons against state-of-the art commercial probes.

长期以来，人们一直假设电容式微机械超声换能器（CMUT）可能优于压电技术。然而，电介质充电、操作滞后和发射灵敏度的挑战已经成为这些性能结果的障碍。通常，CMUT元件被设计为具有一起振荡以发射或检测超声波的较小膜的集合。然而，如果这些较小的膜异相振荡或在不同电压下崩溃，则这种方法可能导致不可靠的行为和次优的传输性能。经过近15年的努力，我们最近设计出了可靠的CMUT元件，该元件由一个长矩形膜组成，性能优于压电元件。我们探索了对CMUT腔体的各种架构修改，以提高对充电的鲁棒性并在不影响性能的情况下最小化滞后。为了制造CMUT与这些架构的修改，我们开发了一个双SOI晶片键合工艺，键合良率接近100%，而不需要对齐键合。所制造的单膜CMUT实现了高达0.95的机电效率值，高于压电换能器或CMUT元件所报告的值。此外，这些单膜CMUT在1.5-2.0 MHz范围内表现出比公开的CMUT或压电换能器元件大2-5倍的传输效率。我们的器件表现出相当的充电稳健性，在数百万次快速回跳致动循环中表现出最小的充电，同时还减轻了滞后。在这项提案中，我们的目标是进一步改进这些器件，以实现下一代高性能MEMS超声。改进将包括实现更高的组合发射和偏置电压的高K值。我们还提出了一个倒置CMUT架构的活塞式运动，高密度硅通孔技术的发展，原型线性和二维阵列的发展。我们的目标是通过与最先进的商业探头进行正面比较来展示我们技术的优势。