In this paper, a simple fabrication process for SU-8 in-plane micro electro-mechanical systems (MEMS) structures, called “border-bulk micromachining”, is introduced. It aims to enhance the potential of SU-8 MEMS structures for applications such as low-cost/disposable microsystems and wearable MEMS. The fabrication process is robust and uses only four processing steps to fabricate SU-8 in-plane MEMS structures, simplifying the fabrication flow in comparison with other reported attempts. The whole fabrication process has been implemented on copper-polyimide composites. A new processing method enables the direct, laser-based micromachining of polyimide in a practical way, bringing in extra processing safety and simplicity. After forming the polymeric in-plane MEMS structures through SU-8 lithography, a copper wet etching masked by the SU-8 structure layers is carried out. After the wet etching, fabricated in-plane MEMS structures are suspended within an open window on the substrate, similar to the final status of in-plane MEMS devices made from industrial silicon micromachining methods (such as SOIMUMPS). The last step of the fabrication flow is a magnetron sputtering of aluminum. The border-bulk micromachining process has been experimentally evaluated through the fabrication and the characterization of simple in-plane electrically actuated MEMS test structures. The characterization results of these simple test structures have verified the following process qualities: controllability, reproducibility, predictability and general robustness.

中文翻译：

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SU-8 面内 MEMS 结构的简单而稳健的制造工艺

本文介绍了一种用于 SU-8 面内微机电系统 (MEMS) 结构的简单制造工艺，称为“边界体微加工”。它旨在增强 SU-8 MEMS 结构在低成本/一次性微系统和可穿戴 MEMS 等应用中的潜力。该制造工艺非常稳健，仅使用四个处理步骤来制造 SU-8 面内 MEMS 结构，与其他报道的尝试相比，简化了制造流程。整个制造过程已在铜-聚酰亚胺复合材料上实施。一种新的加工方法能够以实用的方式对聚酰亚胺进行直接、基于激光的微加工，从而带来额外的加工安全性和简单性。通过 SU-8 光刻形成聚合物面内 MEMS 结构后，进行由 SU-8 结构层掩蔽的铜湿法蚀刻。湿法蚀刻后，制造的面内 MEMS 结构悬挂在基板上的开窗内，类似于采用工业硅微加工方法（例如 SOIMUMPS）制造的面内 MEMS 器件的最终状态。制造流程的最后一步是磁控管溅射铝。通过简单面内电驱动 MEMS 测试结构的制造和表征，对边界体微加工工艺进行了实验评估。这些简单测试结构的表征结果验证了以下过程质量：可控性、再现性、可预测性和总体鲁棒性。