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LED

Sapphire in the LED Market

 


The LED market has been identified as a tremendous growth market. According to Yole Developpement, the LED industry grew by almost 75% in 2010 alone.  Growth will continue through 2015 thanks to widespread adoption in LCD TV and General Lighting applications.  There are three main segments in the LED market.

 

  • General Lighting – Increased efficiency standards, a growing interest in energy efficiency and breakthroughs in the efficiencies of LEDs have generated great interest in the use of LEDs for commercial, industrial and residential lighting.  According to IMS Research, the world lighting market was worth $83 billion, with lamps (the light bulb part of a light fixture) making up 24% of the total in 2010.  By 2015, the firm expects the value of the market will stand at $115 billion, with lamps making up 33%. 
  • Display -- Consumer electronic manufacturers became one of the first adopters of LEDs due to the energy efficiencies and small form factor of LEDs for backlighting screens. Today, LEDs are used to backlight everything from TVs, mobile phones, computers and tablets to large displays like those found in sports stadiums and on buildings for advertising signage.  LEDs are rapidly increasing in penetration in displays. According to iSupply, nearly half of flat-screen LCD TV and monitor panels shipped worldwide in 2011 will be illuminated by LEDs, a huge increase from 20% penetration in 2010.
  • Automotive – The automotive industry is also transitioning to LEDs. Auto manufacturers are using LEDs for everything from headlamps and brake lights to interior lighting and in-dash lighting.  According to Strategies Unlimited, the automotive portion of the LED market is about 8%.

 

Sapphire crystal and chip quality impacts LED yield and and performance.  LED manufacturers go through an extensive qualification process with sapphire manufacturers to ensure that the sapphire wafers are of desired quality for the intended application.  Quality is defined by these criteria:

 

  • Flatness:  The key tolerance for 6-inch and 8-inch is the flatness across the wafer.  Bowing of a wafer will impact performance of the wafer and yield.

  • Cleanliness: Surface morphology of the wafer needs to be clean and presents a uniform surface before depositing the epitaxial layer.  In addition, if impurities have been introduced in crystal development, colorization will be introduced rendering a colored crystal depending on the impurity.

  • Stress:  Sapphire crystals go through temperature cycles of up to 1200ºC. That causes stress that can create defects or cracks in the wafers that reduce yield.  During cooling, stresses are automatically released.

 

As the LED industry matures and LED lighting adoption accelerates, LED manufacturers will need greater numbers of LEDs and chips on which to grow the LEDs.  The transition to larger diameter wafers in LED production has begun.  Earlier in 2010, Rubicon Technology announced that the company entered into a $71 million agreement with a major LED chip manufacturer for which Rubicon will provide six-inch polished substrates.  Companies such as Philips Lumiled and Lextar Electronics have announced six inch production of LED wafers built on sapphire.