Long Term Stability of Polysilicon Microelectromechanical Structures

这项工作将研究多晶硅微机电结构（MEMS）的失效模式和长期结构稳定性。鉴于许多MEMS被设计为在不利条件下长时间使用，我们发现目前缺乏对MEMS可靠性的研究是惊人的。具体而言，我们打算实现以下目标。1. 确定多晶硅微机电结构的失效模式。在了解可能的失效模式之前，MEMS的长期性能无法实现。2. 提供MEMS加速测试的协议。虽然MEMS的预期寿命是几十年，但在投入使用之前，它们无法在这段时间内进行测试。必须开发加速测试技术来评估设备的长期性能。3. 描述多晶硅结构的可靠性作为加工和几何的函数。我们已经证明了单晶硅微机电结构中由于环境影响而裂纹扩展的可能性。考虑到晶界等额外的微观结构特征，我们可以预期多晶硅中会有额外的失效模式。4. 设计测试结构以指示初期或可能出现的故障。这些结构意味着与运行的MEMS设备一起放置，以检测裂纹萌生、永久变形、冲击或结构响应的变化。这项工作对于确保可靠的MEMS应用至关重要。＊＊＊

9410989 Brown This effort will examine failure modes and long term structural stability of polysilicon microelectromechnical structures(MEMS). We find the current absence of research on MEMS reliability striking given that many MEMS are designed to last long periods of time under adverse conditions. Specifically, we intend to address the following goals. 1. Identify failure modes for polysilicon microelectromechanical structures. Long term performance of MEMS cannot be achieved until possible failure modes are understood. 2. Provide a protocol for accelerated testing of MEMS. Although MEMS are meant to operate for decades, they cannot be tested for that period before being put to use. Accelerated testing techniques must be developed to assess the long term performance of the devices. 3. Characterize the reliability of polysilicon structures as a function of processing and geometry. We have shown the possibility of crack growth in a single crystal silicon microelectromechanical structure due to environmental effects. In light of additional microstructural features s such as grain boundaries, we may expect additional failure modes in polysilicon. 4. Design test structures to indicate incipient or possible failure. These structures are meant to be placed with operating MEMS devices to detect crack initiation, permanent deformation, shock, or changes in structural response. This work is essential to ensure reliable MEMS applications. ***