The Laser Processing of Diamond and Sapphire

Transcription

1 The Laser Processing of Diamond and Sapphire Neil Sykes Micronanics Limited

2 Diamond Diamond has the highest hardness and thermal conductivity of any bulk material 10/10 on the Mohs hardness scale Diamond transmits light at wavelengths above 220nm so there are a limited range of laser wavelengths that offer suitable absorption for machining, generally these are Excimer lasers at 157nm (F2), 193nm(ArF) and Pico / femtosecond lasers

3 Ultra Short Pulse Lasers Diamond machining with femtosecond pulse lasers Advantages:- CAD file profiling Drilling Disadvantages:- Limited depth control 20mm/min 3 loops 0.3W

4 Diamond machining with 193nm Excimer laser Advantages:- -Depth control to ~0.1um -The ability to machine complex features using mask projection - Using mask dragging, workpiece manipulation and laser firing control, wall angles can be controlled allow ramps and slopes to be machined with high levels of repeatability. Disadvantages:- -High energy density required >5J cm Edge profiling of large areas slow

5 Diamond machining rate at 193nm At a fluence of 6J cm - 1 diamond machining rates are low, yielding approximately 25nm/shot, this allows depth to be accurately controlled. At a fluence of 9J cm - 1 diamond machining rates increase to approximately 50nm/shot. Machined depth in microns J Cm - 1 6J Cm Number of Shots

6 Polycrystalline Diamond Non machined polished diamond surface Diamond surface after 10 shots 6J cm - 1 Crystal lattice now visible

7 Sapphire Sapphire is highly transparent to wavelengths of light between 170 nm to 5.3 μm 9/10 on the Mohs hardness scale Melting point 2030 C Despite its high transmission Sapphire can be machined at 193nm and other laser wavelengths at high energy densities

8 Sapphire at 193nm Excimer lasers operating at 193nm allow relatively large areas to be machined at the same time, using mask projection a simple mask. In this case a circular aperture of 5.4mm diameter is projected onto the Sapphire surface using a X NA reduction lens). Resulting in a 0.54mm diameter well.

9 Sapphire Mask Projection at 193nm 193nm Mask projection More complicated masks can be manufactured, in this case a 40um gauze was projected using a X10 reduction lens giving 4um features. Further improvements could be made using Chrome on Quartz masks similar to those used for commercial lithography. 20 shots 4J 0.15NA

10 Sapphire Microfluidic device Microwave devices The inset shows a microwave sensing device. Shown here are the inner sampling ring and the fluid inlet. The entire sensing portion of the device is manufactured from Sapphire due to its low microwave absorption. The inner ring is 12mm diameter and approximately 150um wide and deep, the fluid inlet is 200um wide and deep to accept a micro bore tube. The device was capped with another sapphire disk. The sapphire was machined using a femtosecond laser. Sampling ring MetaFAB Cardiff University Fluidic inlet

11 Machines 193nm Macro Enables mask projection Large area machining Ideal for polymers, ceramics, glass, diamond, sapphire, peek, PTFE High resolution, micron level capability Structured side walls, trenches. Polycarbonate mask projection 7um laser machined features in glass

12 Machines 193nm Micro Mask projection system capable of individual site machining or repair using direct through lens alignment High NA lenses X15, X25 and X36 available High Fluence >20J cm - 1 Lambda Physik Compex 205i Areas up to 1mm diameter Sapphire 18um holes

13 Micronanics Limited New business venture based on strong background of Laser machining, Laser machine process, design and manufacture. The ability to machine almost any material High accuracy machining capability From experimental test samples to batch processing. Specialises in projects involving unusual methods and difficult to machine materials

14 Relocation Micronanics has been approved in principle to locate its laser machining facility to the Rutherford Appleton Laboratory. It is expected this will take place before the end of 2009 Exact location TBD

15 Summary 193nm laser :- Can machine many UV transmissive materials such as diamond, sapphire and other materials such as PTFE, Peek can produce a profiled surface with high degree of flatness is applicable where surface finish is critical or surface features are required e.g. Slopes, ramps. Fine depth control possible Can process relatively large areas >1mm 2 at a time at high energy densities, >5mm 2 at lower energy densities Femtosecond laser :- can be rapidly programmed & produce very complex, fine, detailed patterns is able to process virtually any material with little thermal damage.

16 Stainless steel PTFE Femtosecond laser machined model (MetaFAB) 130um hole machined into 1mm thick PTFE. Low thermal damage Virtually no debris 100um exit hole 193nm Excimer Laser