This paper reports an improved CMOS compatible low temperature sacrificial layer fabrication process for Capacitive Micromachined Ultrasonic Transducers (CMUTs). The process adds the fabrication step of silicon oxide evaporation which is followed by a lift-off step to define the membrane support area without a need for an extra mask. This simple addition improves reliability by reducing the electric field between the top and bottom electrodes everywhere except the moving membrane without affecting the vacuum gap thickness. Furthermore, the parasitic capacitance which degrades the CMUT receive performance is reduced. A 1-D CMUT array suitable for Intracardiac Echocardiography (ICE) imaging with 9MHz center frequency is fabricated using this method. Detailed electrical and acoustic testing indicates adequate performance of the devices for ICE in agreement with simulations. Long term output pressure testing with more than 2×1011 pulsing cycles and environmental testing demonstrate the efficacy of the approach for improved reliability as compared to devices without the additional membrane support layer.

中文翻译：

---

具有电介质剥离膜支撑的低温 CMUT 制造工艺以提高可靠性

本文报告了一种用于电容微机械超声换能器 (CMUT) 的改进的 CMOS 兼容低温牺牲层制造工艺。该工艺增加了氧化硅蒸发的制造步骤，随后是剥离步骤以定义膜支撑区域，而无需额外的掩模。这种简单的添加通过在不影响真空间隙厚度的情况下减少除移动膜外各处的顶部和底部电极之间的电场来提高可靠性。此外，降低了降低 CMUT 接收性能的寄生电容。使用这种方法制造了适用于具有 9MHz 中心频率的心内超声心动图 (ICE) 成像的一维 CMUT 阵列。详细的电气和声学测试表明，ICE 设备的性能与模拟相符。具有超过 2×1011 个脉冲循环的长期输出压力测试和环境测试证明了与没有额外膜支撑层的设备相比，该方法提高可靠性的有效性。