Over the years of developing the high-speed abrasive wafer polishing system, many advancements have been made due to discoveries that occurred during testing. These discoveries led to improvements to the lapper and disc grinder machines, the wafer polishing process procedures, production of the abrasive particle filled beads and coating of the beads on the island disc substrates. This work has also led to new patents and more proprietary/trade secret information.
3rd Generation Wafer Head
Continued development of the wafer head will provide improved flatness of the polished wafers. When built, the 3rd generation wafer head will offer increased wafer flatness and improve the ability to quickly attach wafers to the head with vacuum. Also, the new head will accommodate larger wafers and workpieces to be used with both 12” and 18” diameter abrasive island discs.
Abrasive Bead Development
Because of the very large 0.016” (406um) diameters beads used here, the encapsulation of corresponding large abrasive particles of 100um or more in the individual beads will be explored. Further development will be focused on many of the bead characteristics including strength, durability, erodibility, sizes of the abrasive particles, types of abrasive materials, bead fillers, and the bead process conditions. Large quantities of the abrasive bead coated disc islands will require bead production to be scaled-up. Further development of the Keltech existing patented and proprietary manufacturing techniques will allow beads to be produced by continuous process systems.
Improve Bead Coating On Disc Islands
Different coating techniques are being explored to assure that a controlled amount of the very large equal-sized abrasive beads is coated on each island disc substrate for consistent abrading performance of individual discs. Also, a bead coating system is being developed to provide controlled spacing between individual beads to promote full utilization of all the individual abrasive particles encapsulated in the beads.
High-Speed Lapping, Polishing Tests
A wide variety of abrasive materials and abrasive particle sizes will be tested over a range of abrading speeds and abrading pressures to obtain material removal rate (MRR) data for different wafer materials. Also, testing will be made for both 12” and 18” diameter abrasive island discs when used with small and large wafers or workpieces. Abrading procedures will be developed and optimized for selected wafer geometries and materials including sapphire, silicon, silicon carbide, glass, ceramics and hard metals.
Abrasive Island Discs
The size, shape and location patterns of islands in annular bands on flexible polymer substrates will be explored. The island annular band width corresponds to the width-size of the individual wafers or groups of smaller wafers where the “effective diameter” of the wafers slightly overhang both the inner and outer diameter of the annular band. Optimizing the overhang will provide uniform wear-down of the disc abrasive over the abrading life of the disc. Also, different disc substrate materials and different substrate manufacturing techniques will be explored.
Large Diameter Discs and Lapping Machines
Production of large diameter island discs having 36” diameters, or much larger, will be explored for use with large groups of wafers or for very large sapphire display screens wafers. These large island discs can be produced using industry-standard materials. Large diameter lapping and polishing high speed machines for these large diameter discs can be readily produced using air bearing platen technology.
Continuing Performance Improvements
The success and performance advantages of the high-speed abrading system has already been demonstrated with the existing system. Continuing advancements with the abrasive beads, island discs, machines, and processes will provide even better productivity advances.
Demo Polishing of Your Wafers
You are invited to send us samples of your sapphire or silicon carbide wafers to be lapped and polished using our diamond abrasive at high speeds. We will provide you with the removal rate data for your appraisal.