A Vertically Integrated Approach to Sapphire Production

One of the things we take pride in at Rubicon Technology is our end-to-end manufacturing capabilities.

By having state-of-the-art facilities that support vertical integration, starting with the raw material aluminum oxide, we’re able to eliminate excess costs for our customers, and provide greater quality control to ensure the delivery of defect-free sapphire with diameters of 2, 4, 6, and soon, 8 inches.

This ultimately benefits LED chip manufacturers since high-quality, large-diameter wafers provide a higher yield and reduce costs of LEDs for commercial and residential use. Improved cost and luminous efficiency are fundamental to the acceleration of LED adoption in the marketplace — and continue to be strategic priorities for Rubicon.

The infographic below explains the basics of the six-step process of transforming sapphire into an LED module. Rubicon carries out steps 1 through 4 of the process — from crystal growth to wafer processing — before turning over to LED chip manufacturers.

We should also note that Rubicon recently started providing patterned sapphire substrates (PSS) to increase the LEDs’ light output by up to 30 percent. PSS is added directly prior to the epitaxial growth process.

The latter part of the process, after drilling, is primarily carried out in Rubicon’s facility in Malaysia. This facility enables Rubicon to reduce costs associated with making a 6-inch wafer.

For more info on the benefits of a vertically integrated approach, check out pages 50-55 of Compound Semiconductor’s March 2013 edition.

Rubicon Announces Large Diameter Patterned Sapphire Substrates

PSS with dome shape

PSS with dome shape

 

This week, Rubicon Technology announced the launch of the first commercial line of large diameter patterned sapphire substrates (PSS) in four-inch through eight-inch diameters.  The new product line provides LED chip manufacturers with a ready-made source of large diameter PSS to serve the needs of the rapidly growing LED general lighting industry.

This is doubly important since patterning helps improve both epitaxial growth and light extraction for each chip and enhances a chipmaker’s throughput and efficiency.  Rubicon announced that they have fully customizable sub-micron patterning capability with tight dimensional tolerances, within ±0.1 µm.  Rubicon offers LED chip manufacturers more usable area to maximize the number of chips per wafer due to an edge exclusion zone as small as 1 mm.  Rubicon’s patterning is available in a range of shapes including cone, dome and pyramid, and in a range of orientations.  Further customization of geometry, pattern and orientation is available too.  You can find a brochure about it on Rubicon’s web site here.

Rubicon’s president and CEO Raja Parvez pointed out the importance of large diameter patterned sapphire substrates in a news release.  “As LED-based general lighting gains worldwide adoption, large-diameter patterned sapphire substrates will become necessary to meet the demands of the rapidly growing lighting market.”

Parvez added that the company developed an unmatched technology platform that is vertically integrated from raw material through crystal growth, large diameter polished wafers, and now custom PSS in 4”, 6” and 8” diameters.  According to Parvez, vertical integration enables Rubicon to produce progressively larger sapphire products while providing customers with exceptional quality, cost control, reliability, and consistency.

For Further Reading

Rubicon Technology, Rubicon Technology Launches First Commercial Line of Large Diameter Patterned Sapphire Substrates for the LED Industry, http://bit.ly/1itVMHq

Clearlysapphire.com, LED Lighting Spotlight: Patterned Sapphire Substrates, http://blog.clearlysapphire.com/?p=390

 

LED Lighting Spotlight: Patterned Sapphire Substrates

In the ongoing quest to make LEDs more efficient, LED chip manufacturers have developed patterned sapphire substrates (PSS).  In fact, most high-brightness LEDs are made using PSS. There are very few resources online that explain patterned sapphire substrates. Here’s a brief explanation.

PSS helps extract more light from LEDs.  A lot of light bounces back into the LED when using a polished sapphire substrate.  Researchers discovered that patterning the surface of the substrate by etching nano-scale patterns helps more light, in the form of photons, escape, improving the light generated or extracted by the LED.  It is reported that patterning can improve the extraction of light by as much as 30%.

A second important point is that patterning also improves the epitaxial growth process.  The nano-patterned surface can have a positive effect on the nitride semiconductor growth process by promoting growth of the GaN in parallel to the substrate surface, called lateral growth.  This also helps reduce the number of dislocations, the dislocation density, that can degrade performance.

LED chip manufacturers originally developed PSS.  The patterns are quite proprietary and helped the LED chip companies differentiate themselves.  Today, the sapphire industry has joined in and sapphire wafer manufacturers have begun to put patterns on sapphire wafers in partnership with the LED chip manufacturers. The patterning work is concentrated with smaller wafers in the 2 to 4-inch diameter range, but manufacturers of large diameter wafers like Rubicon Technology are beginning to develop PSS for larger wafers.

Most patterning is based on a proprietary design from the LED chip manufacturer.  The patterns can vary from cones, pyramids and flat tops and can be organized in hexagonal or trigonal patterns.  Some basic design rules based on height and height/pitch ratio have emerged, but so far, no standards exist.  Currently the most popular pattern is a cone shape, but these patterns change frequently.  Here are some sample patterns.

Sample patterns:

Sample patterns for PSS

 

 

 

 

 

 

 

Sample Pattern for PSS

 

 

 

 

 

 

For Further Reading

Semiconductor Today, Patterned sapphire for nitride enhancements, http://www.semiconductor-today.com/features/SemiconductorToday_SeptOct_PatternedSapphire.pdf

Compound Semiconductor, New Wet Process For LEDs On Patterned Sapphire Boosts Efficiency, http://www.compoundsemiconductor.net/csc/news-details.php?cat=news&id=19734296

Compound Semiconductor, Rubicon Orders Multiple Profilers For Sapphire Production, http://www.compoundsemiconductor.net/csc/news-details.php?cat=news&id=19735318