Laser micromachining of optical biochips

Abstract

Optical biochips may incorporate both optical and microfluidic components as well as integrated light emitting semiconductor devices. They make use of a wide range of materials including polymers, glasses and thin metal films which are particularly suitable if low cost devices are envisaged. Precision laser micromachining is an ideal flexible manufacturing technique for such materials with the ability to fabricate structures to sub-micron resolutions and a proven track record in manufacturing scale up.Described here is the manufacture of a range of optical biochip devices and components using laser micromachining techniques. The devices employ both microfluidics and electrokinetic processes for biological cell manipulation and characterization. Excimer laser micromachining has been used to create complex microelectrode arrays and microfluidic channels. Excimer lasers have also been employed to create on-chip optical components such as microlenses and waveguides to allow integrated vertical and edge emitting LEDs and lasers to deliver light to analysis sites within the biochips.Ultra short pulse lasers have been used to structure wafer level semiconductor light emitting devices. Both surface patterning and bulk machining of these active wafers while maintaining functionality has been demonstrated. Described here is the use of combinations of ultra short pulse and excimer lasers for the fabrication of structures to provide ring illumination of in-wafer reaction chambers.The laser micromachining processes employed in this work require minimal post-processing and so make them ideally suited to all stages of optical biochip production from development through to small and large volume production.

Thin wafer dicing using a high repetition rate femtosecond laser

“…However, it has greater effect on die strength which must be analyzed in depth for thin wafer dicing. INTRODUCTION femtosecond laser systems are becoming more established in industrial applications and have demonstrated high potential in thin wafer dicing [91][92][93]. Although much research have been carried out to push femtosecond laser into industrial application, the main obstacle of thermal damage and throughput still remain.…”

A simple three-dimensional computer simulation tool for predicting femtosecond laser micromachined structures

“…The etch profiles were characterized by machining test pieces of each material and measuring the etch profile using a surface profilometer (Tencor P10, KLA-Tencor Instruments, USA) to allow accurate depth measurements to be taken across the region irradiated by the beam. For each material, a total of 25 pulses were incident at each point, and because the machining process is cumulative [10,17,18], the depth at any given point of the etched channel was assumed to be a scaled version of the etch profile obtained after one pulse for simulation purposes.…”

“…Such steps have not been considered here as they could potentially damage or influence other fabrication steps that may be needed to produce microfluidic devices, e.g. damage polymer layers used to isolate multi-layer dielectrophoresis microelectrodes, or cause migration of contaminants into doped silicon substrates [17][18][19].…”

“…The work presented here focuses on accurately predicting and shortening the design iterations needed to generate lasermachined microfluidic structures that are commonly fabricated in glasses, such as borosilicate or sodalime. Silicon is also considered here, as it is used in such devices to allow the incorporation of active components, such as illumination sources and optical detectors [17,18]. Micro-patterned silicon can also be used as a micromould in replication processes, such as soft lithography or hot embossing [37,38].…”

“…Most laser microprocessing systems incorporate some sort of computer numerically controlled (CNC) system that allows synchronization of the various system components, and so accurate and repeatable micromachining [9,[11][12][13][14][15][16][17][18][19][20]. The CNC programs used to control laser micromachining workstations provide various parameters needed to simulate the resulting structure, such as all workpiece positioning information, the regions exposed to the laser beam and the workpiece motion speeds.…”