Novel manufacturing route for scale up production of THz technology devices

The advances in the Terahertz (THz) technology drive the needs for the design and manufacture of waveguide devices that integrate complex 3D miniaturised components with meso- and micro- scale functional features and structures. Typical dimensions of the waveguide functional structures are in the range from 200 μm to 50 μm and dimensions decrease with the increase of the operating frequency of the waveguide devices. Technological requirements that are critical for achieving the desired filtering performance of the waveguides include geometrical accuracy, alignment between functional features and surface integrity. In this context, this paper presents a novel manufacturing route for the scaled-up production of THz components that integrate Computer Numerical Control (CNC) milling and laser micro-machining. A solution to overcome the resulting tapering of the laser machined structures while achieving a high accuracy and surface integrity of the machined features is applied in this research. In addition, an approach for two-side processing of waveguide structures within one laser machining setup is described. The capabilities of the proposed manufacturing process chain are demonstrated on two THz waveguide components that are functionally tested to assess the effects of the achieved machining results on devices’ performance. Experimental results show that the proposed process chain can address the manufacturing requirements of THz waveguide filters, in particular the process chain is capable of producing filters with geometrical accuracy better than 10 μm, side wall taper angle deviation of less than 1⁰ from vertical (90⁰), waveguide cavities corner radius better than 15 μm and surface roughness (Sa) better than 1.5 μm. The manufacturing efficiency demonstrated in this feasibility study also provides sufficient evidences to argue that the proposed hybrid manufacturing technique is a very promising solution for the serial production of small to medium batches of THz waveguide components. Finally, analyses of the manufacturing capabilities of the proposed process chain and the photo-resist based technologies were performed to clearly demonstrate the advantages of the proposed process chain over current waveguide fabrication solutions.