Microscale Patterning of Single Crystal Diamond Using Sidero-Metal/Diamond Thermochemical Reaction
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1222-DD05-05
Microscale Patterning of Single Crystal Diamond Using Sidero-Metal/Diamond Thermochemical Reaction Yuko Morofushi,1 Hajime Matsushita1 and Norihisa Miki1 1 Mechanical Engineering, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, Japan.
ABSTRACT Single crystal diamond is expected to be a new material for not only micro machining tools but also innovative micro devices. In this paper, we demonstrate the micro-patterning of bulk diamond by exploiting thermochemical reaction between diamond and sidero-metals. We demonstrate micro-patterning of single crystal diamond by annealing at ~1073 K after either micro-patterning nickel on the diamond or placing the diamond on a silicon substrate with a micro-patterned nickel layer. Etching rates ~0.2µm/min were successfully achieved. We also experimentally elucidated the etching mechanisms and identified the dominant factors in the etching processes. INTRODUCTION Single crystal diamond possesses a variety of excellent characteristics, such as hardness and wear resistance, and hence, is expected to be a new material for not only micro machining tools but also innovative micro devices. It is mandatory to develop a patterning process of diamond with high precision and at ｑ low cost. Laser processing is currently widely used [1-2], but it is a serial process and costly. Film deposition and plasma etching are also effective, but they are time consuming [3-5]. Thermochemical reaction between diamond and sidero-metals is well known in the field of mechanical machining [6-7]. Diamond tools cannot machine sidero-metals, such as iron, nickel, and cobalt, when the diamond tools wear instead of the sidero-metals. We used this reaction to micro pattern single crystal diamond [8]. We used nickel as the sidero-metal that was patterned either directly on bulk of single crystal diamond or on a silicon substrate as shown in Figure 1. We term the former and the latter processes as direct and indirect patterning processes, respectively. In the indirect patterning a bulk of single crystal diamond was placed on the substrate. The pattern was negatively transferred to the diamond after thermal treatment in air at ~1000 K in both processes as shown in Figure 1(iii). The sidero-metal layer can be patterned by photolithography, which enables precise manufacturing and mass production. In this research, we elucidate the processing principle via experiments under various conditions. THEORY Thermochemical reaction between diamond and sidero-metal at high temperatures are caused by; diffusion of carbon from diamond into the sidero metal [9], oxidation-reduction reaction between diamond and the metal [10], combustion of diamond [11], and carbide formation [10]. We detail these reactions.
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(iii) Figure 1. Schematic diagrams of micromachining process by thermochemical reaction. (i) Direct patterning process, (ii) indirect patterning process and (iii) photos of micro-patterned bulk single crystal diamond (direct patterning). Diffusion of carbon atom When a diamond is in c
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