The outstanding material properties of single crystal diamond have been at the origin of the long-standing interest in its exploitation for engineering of high-performance micro- and nanosystems. In particular, the extreme mechanical hardness, the highest elastic modulus of any bulk material, low density, and the promise for low friction have spurred interest most notably for micro-mechanical and MEMS applications. While reactive ion etching of diamond has been reported previously, precision structuring of freestanding micro-mechanical components in single crystal diamond by deep reactive ion etching has hitherto remained elusive, related to limitations in the etch processes, such as the need of thick hard masks, micromasking effects, and limited etch rates. In this work, we report on an optimized reactive ion etching process of single crystal diamond overcoming several of these shortcomings at the same time, and present a robust and reliable method to produce fully released micro-mechanical components in single crystal diamond. Using an optimized Al/SiO₂ hard mask and a high-intensity oxygen plasma etch process, we obtain etch rates exceeding 30 µm/h and hard mask selectivity better than 1:50. We demonstrate fully freestanding micro-mechanical components for mechanical watches made of pure single crystal diamond. The components with a thickness of 150 µm are defined by lithography and deep reactive ion etching, and exhibit sidewall angles of 82°–93° with surface roughness better than 200 nm rms, demonstrating the potential of this powerful technique for precision microstructuring of single crystal diamond.

单晶金刚石出色的材料特性一直是人们对其用于高性能微米和纳米系统工程开发的长期兴趣的根源。特别是，极高的机械硬度、任何散装材料中最高的弹性模量、低密度以及低摩擦的前景，激发了人们对微机械和 MEMS 应用的兴趣。虽然以前已经报道了金刚石的反应离子蚀刻，但迄今为止，通过深反应离子蚀刻在单晶金刚石中精确构造独立式微机械部件仍然难以捉摸，这与蚀刻工艺的限制有关，例如需要厚硬掩模，微掩模效应和有限的蚀刻速率。在这项工作中，我们报告了一种优化的单晶金刚石反应离子蚀刻工艺，同时克服了其中的几个缺点，并提出了一种稳健可靠的方法来生产单晶金刚石中完全释放的微机械部件。使用优化的Al/SiO ₂硬掩模和高强度氧等离子体蚀刻工艺，我们获得了超过30 µm/h的蚀刻速率和优于1:50的硬掩模选择性。我们展示了由纯单晶金刚石制成的机械手表的完全独立式微型机械部件。厚度为 150 µm 的组件通过光刻和深反应离子蚀刻定义，侧壁角度为 82°–93°，表面粗糙度优于 200 nm rms，展示了这种强大技术在单晶精密微结构方面的潜力钻石。