What is Sapphire?
Sapphire is typically gemstone variety of the mineral Corundum and Aluminium Oxide. Due to their remarkable hardness they rate 9 on the Mohs scale, the third hardest mineral after diamond and moissanite.
Sapphire is particularly attractive to those working within the laser industry due to its uniform dielectric constant and high quality crystalline structure. This has led to an increase in the use of sapphire substrates for blue laser diodes whilst the sapphire has become the basis of today’s RF switch applications.
Sapphire Wafer Processing
The objective of Sapphire wafer polishing is to reduce the final thickness of the substrate to the required target vale, with a TTV of better than +/-2 microns and an improved surface roughness of less than 2nm. This full process can be achieved using Logitech precision systems from bonding using the Wafer Substrate Bonding Unit to polishing using one of our lapping and polishing systems such as the new PM6.
By using a Logitech polishing system it is possible to achieve ideal surface roughness in advance of further processing using traditional CMOS techniques. Each polished wafer will have a uniform amount of material removed during the process and a consistently flat surface finish. By varying pressure loads it is possible to achieve an optimal Material Removal Rates (MRR) of 1-2 microns per hour.
The following results are taken from a batch of 84 x 2” diameter Sapphire wafers processed on the Logitech DP4 precision polishing system.
- Diameter: 2”
- Material Removal Rate (MRR): 6 microns per hour
- Final Ra value: <1nm
- Flatness: +/- 2 microns