Sapphire Polishing: Superior SPH Oxide Solutions for The Optics, Electronics, Watchmaking & Semiconductor Sectors

With over 120 years of expertise, Baikowski® is a leading provider of advanced materials. We began by offering synthetic sapphire and then later expanded to powder solutions, including polishing solutions for the watchmaking, optics, electronics and semiconductor industries.

With our engineering and experience we are able to deliver customized alumina and colloidal silica solutions with optimized morphology, particle size distribution (PSD), and chemistry for applications requiring a superb finish produced with high efficiency.

In electronics and optics, where polished sapphire is crucial for high-performance devices, Baikowski’s® slurries help achieve surfaces free of micro-defects that can adversely impact light transmission and image clarity.

Sapphire Polishing Challenges

Polishing sapphire, one of the hardest materials known after diamond, demands meticulous, high-precision processing to achieve flawless, defect-free surfaces.

The primary challenges include surface defects, micro-scratches, and incomplete removal of grinding marks, all of which affect optical clarity and the final surface finish.

Achieving the perfect polish involves mastering three stages: rough grinding to remove initial material, intermediate polishing to refine surface irregularities, and final polishing for a mirror-like surface. Each step requires precise control to avoid introducing new imperfections.

C-axis & A-axis: The Impact of Crystal Orientation

The crystal orientation of sapphire is significantly related to polishing difficulty. The C-axis (0001 plane) is the hardest orientation to polish, presenting up to 20% more resistance, and requiring specially formulated slurries to achieve a fine, imperfection-free finish.

In contrast, the A-axis (11-20 plane) can be easier to polish but it still demands rigorous control. Slurries must be engineered to offer the proper abrasive particle size distribution, and pH to accommodate hardness variations and achieve uniform results across these orientations.

SPH Silica & Alumina-based Slurries for Enhanced Sapphire Polishing Productivity

Baikowski® has developed a unique CMP series in which chemicals play a major role to deliver smoother finishes with higher levels of precision on such hard substrates. This SPH specific range of patented alumina and silica-based slurries is tailored to improve productivity, especially on sensitive crystal planes such as that of the sapphire C-axis.

This range achieves remarkable efficiency, delivering 3 to 4 times faster material removal rates compared to traditional colloidal silica slurries. In addition, it achieves consistent material removal due to:

• The Controlled Morphology and Narrow PSD of Baikowski® milling optimized sapphire polishing slurries. They minimize the risk of introducing new scratches while balancing efficient material removal, making the series particularly effective in intermediate and final polishing.
• The stability of the suspension. It ensures uniform material removal and sustains good particle dispersion throughout the polishing process. The carefully balanced viscosity and pH enhance the slurry’s chemical activity on sapphire surfaces, accelerating the polishing process and making the SPH series ideal for applications where ease of use and high precision are priorities.

Baikowski’s® SPH series are available in both Silica and Alumina abrasive solutions

• SPH-51 is a silica solution, with specifications for D50 of 100 nm, and a pH of 10-11. It delivers high removal rates on sapphire’s C and A planes, achieving near-perfect surface finishes, especially when combined with Baikowski® polyurethane pad.

Performance of sph-51 Silica solution (A plane)
Polishing Conditions

This results in an ideal surface, ready for epitaxial layers, to ensure optimal light output and energy efficiency in the final LED application as one example.

• SPH-53 is also an optimized silica-based solution that provide an intermediate removal rate with proven performance over that of traditional silica. The specifications for D50 is 70 nm and it has a pH of 8-9.

Comparison of SPH-51 & SPH-53 Silica solutions (C PLANE 4’’)
Same polishing conditions as describe above

• The SPH-9D slurry is a very high removal rate alumina product, ideal for C-axis. It effectively removes surface irregularities and produces a best in class surface
  The specifications for D50 is 0.30 µm and it has a pH of 12.5–13.5. This slurry can also be utilized in dual face polishing operations.

ALUMINA-BASED SLURRIES COMPARISON
Surface Roughness 0.2 nm – 0.35 nm

Achieving optimal polishing results require the right combination of polishing speed, pressure, pad quality, and slurry formulation. Higher polishing pressures increase material removal rates but may induce scratches, while slower speeds often reduce scratch formation but can extend process time.

Learn more about SPH products

In summary, our SPH silica and alumina-based slurries offer a superior alternative by providing faster removal rates, reduced incidence of defects, improved surface finish, and enhanced process control over traditional silica products. The range, combined with the proper pads is ideal for high-precision applications in the optics, electronics, and semiconductor industries where surface quality and productivity are both critical.

Eager to learn more about Baikowski®’s polishing solution offering ?
Explore our dedicated White Paper titled Superior Intermediate & Final Polishing, Alumina, Silica, Ceria  & Diamond Solutions