Residual stress gradients often negatively affect the performance of MEMS devices, causing film curvature and changing the designed gaps of released structures. In this work, we built folded beams designed to compensate for the film curvature and keep the actuator gaps of sensitive resonant switches constant. While the average stress gradient is cancelled by our designs, we find that random variations in the stress gradient (rather than random variations in device dimensions) cause the majority of the observed variation in actuator gap. To our knowledge, this has not previously been reported, and represents an important limitation on MEMS designs using sputtered films. The standard deviation of the 400 nm contact gap for a folded beam of total length 152 m and width 108 m was measured to be about 134 nm. Using parameters measured from test cantilevers, our simulations predict that about 98% of the variation in contact gap is due to stress gradient variation, rather than variations in device geometry.

残余应力梯度通常会对MEMS器件的性能产生负面影响，从而导致薄膜弯曲并改变释放结构的设计间隙。在这项工作中，我们构建了折叠梁，旨在补偿薄膜弯曲并保持敏感谐振开关的执行器间隙恒定。尽管我们的设计消除了平均应力梯度，但我们发现应力梯度的随机变化（而不是器件尺寸的随机变化）导致了执行器间隙中观察到的大部分变化。据我们所知，这以前没有被报道过，它代表了使用溅射膜的MEMS设计的重要限制。总长度为152的折叠光束的400 nm接触间隙的标准偏差m和宽度108 m被测量为约134nm。使用从测试悬臂梁测得的参数，我们的仿真预测，接触间隙的大约98％的变化是由于应力梯度的变化而不是器件几何形状的变化。