ClearlySapphire.com


 

Clearly Brilliant, Clearly Powerful, Clearly Sapphire

Quality

As manufacturers of LEDs and electronic devices become increasingly dependent upon reliable supplies of larger diameter sapphire wafers, the need for consistently high quality sapphire grows as well.  Because manufacturers need to ensure maximum yield from each wafer, the flatness and uniformity of the wafer surface is a key measure.  The purity of the crystal, along with transmission properties and etch pit density (EPD – a measure of the quality of semiconductor wafers), are all core metrics of sapphire quality.

 

Before the epitaxial layer is deposited for LED growth, a wafer’s surface morphology must be uniform.  Wafer uniformity and flatness are paramount qualities – particularly in larger diameter (six- and eight-inch) sapphire wafers that are rapidly becoming the industry standard for substrates used to produce LEDs and silicon-on-sapphire.

 

Aside from particulate and bubble flaws, sapphire crystals and wafers are subject to tiny cracks, which are typically the result of the crystal growth process.  Crystal growth techniques vary, but include temperature cycles up to 1200 degrees Celsius.  This intense heat, and the subsequent cooling process, cause stress that can result in cracks.   To reduce these flaws, sapphire suppliers are adopting growth techniques that employ a stable thermal gradient in a low stress environment.

 

The absence of flaws and defects begins with crystal growth process, but continues through fabrication - coring, slicing, polishing.