How Do They Do It? From Sapphire to LED Infographic

You’ve heard a lot about LEDs, but did you know that a tiny piece of sapphire – the pure, colorless industrial variety, not the blue gemstone – is in more than 80% of LEDs? Sapphire is the foundation for the LED chip, just as silicon is for a computer chip.  Rubicon Technology has put together an infographic that describes the sapphire manufacturing process and where sapphire is found in an LED. The bottom of the infographic features examples of products that feature LEDs for lighting. Click on the infographic below to see it larger.

Infographic for Post






Link to:

Rubicon Ships 400,000th Large Diameter Sapphire Wafer

Two-inch, Four-inch and Six-inch Sapphire Wafers

Today, Rubicon Technology, Inc. (NASDAQ:RBCN) announced that they shipped their 400,000th six-inch large sapphire wafer to the LED manufacturing and SoS/RFIC markets. Most of the world’s LED manufacturing takes place using sapphire – just as computer chip makers like Intel and AMD use silicon to make their microprocessors.

The most flashy, if you’ll pardon the pun, market for sapphire wafers is in LEDs, which are used for energy-efficient general lighting and as the source for backlighting in consumer products such as HDTVs, laptops, smart phones and tablets.  A second and significantly growing market for sapphire is its use in Silicon-on-Sapphire (SoS) Radio Frequency Integrated Circuits (RFICs).  SoS RFIC chips deliver high RF performance with low power consumption, a small form factor, and significantly reduced crosstalk in antenna applications that are pervasive in smart phones and other consumer devices.

Why large diameter wafers? Rubicon began developing large diameter sapphire wafers for SoS RFICs in the 2000s.  But the company soon tapped into the larger opportunity in the LED market, especially with LED-based general lighting. And, it’s all about the math.

The market has been dominated by two-inch wafers for years. The surface area of a six-inch wafer is nine times greater than that of a two-inch wafer, and its outer curvature is less, enabling greater use of the surface area, culminating in a reduction in edge loss.  In addition, use of larger wafers enables operational savings that offset the cost of the larger, thicker substrate and can help drive down the total cost of LEDs.  According to Rubicon, and depending on the type of MOCVD reactor used, LED chip manufacturers using six-inch wafer platforms may achieve up to 48% greater usable area per reactor run compared with two-inch wafers.

What does that mean? Larger diameter wafers will help LED manufacturers reduce costs throughout the manufacturing process in order to make LED-based lighting more affordable for consumers and encourage adoption worldwide.

Further Reading

Rubicon Technology, Rubicon Technology Ships 400,000th Large Diameter Sapphire Wafer; Company Continues Market Leadership Supplying Large Diameter Sapphire Wafers to LED and SoS/RFIC Markets,

Alternative Substrates for LEDs – Not Ready for Prime Time

Over the past several months, there has been some industry chatter about alternative substrates for the production of LEDs.  In fact, the dialog has been more heat than light until now if you think about it in terms of a filament in an incandescent light bulb.

Large Diameter Sapphire Wafer (source: Rubicon Technology)

Sapphire substrates have been established for quite some time as the base material for LED chips.  Today, more than 80% of LEDs are based on sapphire substrates with the remainder based on SiC and a few other materials.  But the big question is whether an alternative substrate like silicon or GaN can offer the performance and cost advantages of sapphire.

Last week, market research firm Yole Developpement held a webcast, Alternative Substrates for LED Manufacturing, to examine the alternatives, the technical challenges and the conditions for success.  You can access the archive here.

According to Yole analyst Eric Virey, the principal benefit of using Si as an LED substrate would be the ability to leverage larger 8” wafers and use fully depreciated and highly automated CMOS fabs.  But “the jury is still out,” he said, “regarding a massive industry transition from sapphire to silicon.  At the end of the day, this is a cost game; manufacturing yields are a major cost contributor to LED, and they pose specific challenges to the use of silicon.”

These challenges range from a lattice mismatch and thermal expansion coefficient mismatch, to melt back and blue light absorption. Sapphire outperforms silicon on all of these factors, and each is having a negative impact on LED chip yields from silicon.  Virey commented silicon and/or GaN must meet the performance of sapphire to be successful. To date, that hasn’t happened.

In the meantime, the sapphire substrate manufacturers have made great strides to making large diameter substrates that help LED manufacturers drive down costs and increase yields to support the aggressive cost targets of SSL.  For example, Rubicon Technology has shipped more than 230,000 large diameter sapphire wafers with this number growing.

Where are efforts now? Virey mentioned during the webinar that almost all LED manufacturers are exploring alternative substrates, although most are doing so only as a defensive strategy. Toshiba and Bridgelux have been working with silicon as a substrate. In July, the companies announced Toshiba would begin silicon-based LED production in October 2012, but there has been no further word. Plessey Semiconductors and Lattice Power also announced they would enter production in 2012.

LED Magazine reports that silicon-based substrates are “no sure thing” in their latest SSL Technology Update video blog.  Associate editor Nicole Pelletier said, “A number of companies plan to ride the incumbent sapphire technology. At The LED Show back in August, LED market leader Nichia said it had investigated and dismissed the possibility of using silicon.”

At the conclusion of the webcast, Virey agreed.  “If the technology hurdles are cleared, LED on silicon will be adopted by some LED manufacturers, but not necessarily become the standard.”

For Further Reading

LED Magazine, SSL Technology Update: October 22, 2012,

Yole Developpement Webinar, Alternative Substrates for LED Manufacturing,

Solid State Technology, Beyond sapphire: LED substrates from GaN to ZnO, SiC, and Si,

Solid State Technology, The demise of sapphire wafers?

Barriers to Entry 2: Yole Developpement Talks Sapphire, New Market Entrants Unlikely to Match Yields of Industry Leaders

In Part 2 in our Barriers to Entry posts (Part 1 is here), we’re focusing on a recent report from the industry experts at Yole Developpement.  Yole analysts have been keeping a keen eye on worldwide capacity for sapphire crystal growth.  According to Yole’s Eric Virey, more than 50 companies have announced their intention to enter the sapphire growth market, with more than 40 located in China.  While the capacity plans announced by all of the new companies collectively would add up to triple world demand, Yole believes it is “a situation unlikely to actually materialize.”

Why?  These new market players have little or no prior experience in sapphire crystal growth and wafer manufacturing.  And, while there are some “turn-key” solutions to lower the barrier to entry, “reaching and sustaining high quality and high yields in sapphire crystal growth still requires significant expertise.”  Indeed the learning curve is steep to reach yield levels on par with established Tier 1 manufacturers.

Yole’s report also said that margins in 2010 were favorable to new entrants allowing them to achieve comfortable margins “despite low yields and sub-par technology.”  However, with 2 inch pricing at historic lows, Yole calculates that they will lose money at the current market prices while “established vendors with higher yields, large volumes, and a more favorable product mix, including large-diameter wafers, can achieve production cost <$5 that will allow them to maintain positive margins and weather the storm.”

For Further Reading: Yole Developpement web site