Sapphire Substrate Advances Lead to Brighter LEDs at Lower Costs

As LED manufacturers relentlessly strive to produce greater light output at a lower cost, the most significant advance in cost per lumen in recent years has been the adoption of patterned sapphire substrates (PSS).

When a pattern is etched onto polished sapphire — the material used as a substrate in the vast majority of LED chips — total light extraction efficiency (LEE) can be increased by as much as 30 percent. This can happen in two different ways:

(1)    By encouraging lateral growth of the epitaxial layers, thereby reducing epitaxial defect density and increasing the light emission of the active quantum well layers

(2)    By reducing light loss, through creation of a photon scattering effect that allows more of the light generated to escape

Generally, the patterns consist of shapes — cones, domes, pyramids — created in a hexagonal pattern on the surface of the sapphire through dry plasma etching. Pattern features may be 0.65 to 2 microns in height, and the pitch (the distance between the centers of adjacent features) may be 1.5 to 3 microns.

SSL Design Blog Post Image

These pattern designs are developed independently by each of the LED manufacturers to meet the needs of their unique epitaxial recipes and are considered proprietary technology. Because of this, no standard library of patterns exists. The critical dimensions to increasing LEE include the shape and size of the pattern features and the aspect ratio — the ratio of height to width. Deeper patterns tend to be associated with greater LEE, but can be difficult to make if conditions are not well-controlled.

In addition to developing their PSS recipes in-house, LED manufacturers originally performed the patterning operations themselves. While most still conduct some of their patterning operations in-house, third-party patterning became more available in 2010 for two-inch wafers, and later four-inch wafers. It was then that LED companies had the option of outsourcing at least a portion of their patterning activity.

Concurrently with the development of patterned wafers, LED chip manufacturers have been slowly migrating to larger substrates for greater efficiency. Larger wafers provide several benefits, including:

  • Increased throughput for each reactor run, effectively increasing capacity without adding additional MOCVD reactors or additional floor space
  • Reduced edge loss
  • Reduced wafer handling

The yield for PSS at larger diameters is affected by the flatness of the wafer, and bowing of the wafer can cause inconsistent etching and lower yields.

So what’s next for PSS? Can we get even more luminous efficiency with this technology?

Nanoscale patterning has been extensively studied for its potential impact on light extraction efficiency due to both its significantly increased pattern density and its impact on internal quantum efficiency from the improvement of epitaxial quality. As we continue to test new patterns and sizes, like nanoscale patterning, it is clear that the industry hasn’t reached a wall in what is possible for light output. Further advances in PSS technology will provide improvements in light extraction efficiency, contributing to the continued market success of LED technology.

Sapphire Demystified

A look at Rubicon Technology's sapphire

A look at Rubicon Technology’s sapphire

There has been so much hype and misinformation about sapphire lately, particularly surrounding sapphire covers or faceplates for smartphones, that we thought we’d review some basic info about commercial sapphire.

  • “Sapphire glass”

There really isn’t any such thing as sapphire “glass.” Sapphire is not a kind of glass; it’s a very hard monocrystalline material. The proper way to reference the clear layer of stuff that may soon cover the screen of your smart phone is as a “sapphire cover” or “sapphire faceplate.” Glass is made of silica or sand, and sapphire is made from aluminum oxide. The two materials have very different physical properties. So, glass isn’t really the right descriptor.

  • Sapphire is unbreakable.

Well, no. That’s not really accurate. A thin piece of sapphire can shatter, similarly to glass or a piece of gorilla glass. Sapphire is the second hardest material on Earth (after the diamond). As such, a thin slice of sapphire will shatter. What is sapphire good at? Sapphire is scratch resistant. That’s one of the main reasons why smartphone vendors are interested in sapphire for applications in lenses and fingerprint scanners.

  • Sapphire is blue.
Sapphires come in a range of colors.

Sapphires come in a range of colors. The purest sapphires are clear.

Yes and No. Sapphire, also called corundum, comes in a range of colors. The purest form of sapphire is clear.  Sapphire is a crystal made from Aluminum Oxide (Al2O3). Natural sapphire forms over thousands of years in the earth, but comes in different colors due to impurities such as minerals or other conditions (like humidity or radiation). Rubies are made of aluminum oxide and are actually sapphires. They are red because the crystal contains impurities in the form of the mineral chromium, making the crystal red. Sapphire gemstones get their blue hue from iron and titanium. Yellow sapphires get their color from a combination of iron and radiation (interesting).  The commercial sapphire that’s now being used in consumer electronics is very pure, so it’s colorless.

  • Sapphire in LEDs and smart phones is from blue sapphire gemstones.

No. The sapphire that is used in LEDs and smartphones is grown in a commercial setting using one of few processes – the Verneuil Method, Kyropoulous Method, Heat Exchanger Method, Czochralski Method and Edge-Defined Film-Fed Growth Method. Each method has its differences, but they produce a single crystal of clear sapphire that is fabricated (cut and polished) into a sapphire substrate used in an LED or into a lens or faceplate for optical uses like smart phones.

 

Substrate Update: It’s All About Patterning & Large Diameter Wafers

yole_developpement_logoMarket research firm Yole Developpement recently published a new report on front-end manufacturing trends for LEDs. Their latest report gives us some very good news about the sapphire market. Semiconductor Today reported on Yole’s analysis. Here are some big take-aways:

  • There is increased demand for larger-diameter sapphire wafers, with big players (such as LG, Sharp or Osram) moving to 6” wafers and Taiwanese players moving to 4” wafers.
  • LED chip makers demand more patterned sapphire substrates (PSS). PSS are now mainstream in the market with an 87% share as of Q1 2014.
  • While some companies (such as Soraa and Toshiba) have begun mass production of gallium nitride-on-silicon (GaN-on-Si) and GaN-on-GaN LEDs, market penetration of these alternative substrates will depend on future improvements in terms of performance and cost.  Without these improvements, alternative substrates will not be able to fully compete with sapphire-based LEDs.

What does this mean for sapphire makers? LED chip manufacturers are looking to gain production efficiencies, lower costs, and increase performance for their LEDs.  As the adoption for LED lighting increases, they need to make more and better performing LEDs. Large diameter sapphire wafers enable more throughput for each run of the MOCVD reactor, making better use of the reactor “real estate” and decreasing the cost per unit of area processed. 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 as compared to two-inch wafers.

What does PSS offer? First, PSS helps improve epitaxial growth by promoting growth of the GaN in parallel to the substrate surface. This helps reduce the number of dislocations, called the dislocation density, which can degrade performance of an LED.  Secondly, patterning can help extract as much as 30 percent more light from an LED.  This is particularly advantageous for high brightness LEDs (HB LEDs) that are used in LED lighting applications.

LED chip manufacturers have been buying smaller 2-inch and 4-inch PSS from outside suppliers for years.  The next step in the evolution in the market is the migration to large diameter PSS. Already a pioneer in the development of large diameter sapphire substrates, Rubicon Technology has developed capabilities for large diameter PSS making it possible to manufacture 6-inch and even 8-inch PSS. Rubicon is already gaining traction in the PSS market.  The company recently reported in their Q1 2014 earnings call that they received their first order for PSS and have samples out to more than a dozen LED chip manufacturers.

For more information about the report from Yole, visit http://www.i-micronews.com/reports/LED-Front-End-Manufacturing-Trends-report/14/433

For Further Reading

Semiconductor Today, Substrates shaping trends in LED front-end manufacturing, http://www.semiconductor-today.com/news_items/2014/APR/YOLE_300414.shtml

Clearlysapphire.com, Larger Wafers, Larger Yield – The Numbers Behind Large Diameter Sapphire Wafers and Yield, http://blog.clearlysapphire.com/?p=435

Clearlysapphire.com, Large Diameter Patterned Sapphire Substrates Explained, http://blog.clearlysapphire.com/?p=582

Clearlysapphire.com, Sapphire Substrates for LED: The Big Move Toward 6″ Has Already Started, http://blog.clearlysapphire.com/?p=37

Large Diameter Patterned Sapphire Substrates Explained

Rubicon Technology offers large diameter PSS in a range range of shapes including cone, dome and pyramid as well as custom.

Rubicon Technology offers large diameter PSS in a range of shapes including cone, dome and pyramid and range of orientations.

While LED chip manufacturers have been using patterned sapphire substrates (PSS) for years, there’s growing interest in large diameter PSS.  Recently, Rubicon Technology announced the commercial availability of large diameter PSS.  During their latest earnings call, they indicated that they’ve received interest from 7 major LED chip manufacturers for 4- and 6-inch large diameter PSS.  Why the interest from LED chip manufacturers?

First, PSS helps improve epitaxial growth by promoting growth of the GaN in parallel to the substrate surface. This also helps reduce the number of dislocations, called the dislocation density, which can degrade performance of an LED.  Secondly, patterning can help extract as much as 30 percent more light from an LED.  This is particularly advantageous for high brightness LEDs (HB LEDs) that are used in LED lighting applications.

Second, the evolution of patterning large diameter substrates brings economical advantages to LED chip manufacturers, especially those anticipating demand from the LED lighting market.  Large diameter sapphire wafers help LED chip manufacturers cut costs by enabling more throughput for each run of the MOCVD reactor.  This helps chip manufacturers make better use of the reactor “real estate” and decreases the cost per unit of area processed because of the curvature of the larger wafer.  The outer curvature of a 6-inch wafer is less, enabling greater use of the surface area than the tighter curvature of a 2-inch wafer resulting in less edge loss.  Larger diameter wafers also provide post-MOCVD efficiencies.  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.  These efficiency gains become very compelling when manufacturers want to ramp up LED chip production to support greater volumes of LEDs for light bulbs.

Finally, LED chip manufacturers have been buying smaller 2-inch and 4-inch PSS from outside suppliers for years.  The next step in the evolution in the market is the migration to large diameter PSS for the reasons we mention above.  While some LED chip manufacturers will have specialized patterning needs and the resources to keep the work in-house, others will not.  Some LED chip manufacturers may not have the expertise and equipment to move to large diameter PSS, so having a ready, trusted supplier will prove handy.

For Further Reading

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

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

Clearlysapphire.com, Larger Wafers, Larger Yield – The Numbers Behind Large Diameter Sapphire Wafers and Yield, http://blog.clearlysapphire.com/?p=435

Sapphire Inside: Apple Builds Sapphire Lens into New Home Button, Touch ID

iPhone 5S with the Touch ID includes a sapphire lens

iPhone 5S with the Touch ID includes a sapphire lens on the home button

Today, Apple announced two new models of the iPhone, the iPhone 5S and  the iPhone 5C. One of the biggest news items at the Apple event is that the new iPhone 5S will sport a whole new home button with a fingerprint sensor with a sapphire lens, ringed in stainless steel.

Sapphire, the second hardest material on Earth after the diamond, is scratch resistant, so it should be very well suited for use as a lens. While this is great news for the sapphire community, this is not the only use for sapphire in a smart phone. Many smart phone OEMs already use sapphire for the camera lens cover because of its scratch resistance, but also is used for the LEDs in the backlighting for the screens as well as the silicon-on-sapphire (SOS)-based RFIC chips that power the RF antennas. There are more places for use of sapphire in a smart phone as well since OEMS are looking to use SOS chips for digitally tunable capacitors (DTCs) and power amplifiers. And, don’t forget sapphire’s largest overall market, LEDs, for lighting, displays and more.

Apple claims that Touch ID reads a fingerprint at an entirely new level by scanning sub-epidermal skin layers with 360 degree reading capabilities.  The sensor is part of the home button which is 170 microns thick with a 500 ppi resolution.  Touch ID stores the encrypted fingerprint info securely in a “secure enclave” inside the new A7 chip, the new processor for the iPhone 5S.  The neat thing is that it should be able to store multiple fingers.  The Touch ID will enable you to purchase items on iTunes, the AppStore or iBooks without a password.

You can see where the sapphire is in this photo of the home button from CNet’s live blog of the Apple event:

iPhone 5S graphic illustrates parts of the Touch ID (from CNet)

iPhone 5S graphic illustrates parts of the Touch ID (from CNet) with sapphire

 

 

 

 

 

 

 

The iPhone 5S (and the 5C) go on pre-sale on September 13th and will be on sale in stores on September 20th.

For Further Reading

Engadget, iPhone 5S fingerprint sensor called Touch ID, recognizes your thumb on the Home button: here’s how it works and what it does, http://www.engadget.com/2013/09/10/iphone-5s-fingerprint-sensor/

 

Alternative Substrates – Dimming the Hype

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

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

Today, more than 80% of LEDs are made based on sapphire wafers.   Recently, Lux Research published a report, Dimming the Hype: GaN-on-Si Fails to Outshine Sapphire by 2020, about the state of alternative substrates.  In LED production, sapphire is used as the substrate onto which the chemicals that will become the emitting layer of the LED are deposited as a vapor.  With the LED lighting market expected to grow to $80 billion, Lux Research expects the substrate market to grow to $4 billion in 2020 making it a highly attractive market.  Lux expects sapphire to continue to dominate the substrate market.

“Silicon is already widely used for electronics, and some LED die manufacturers are hoping to take advantage of silicon substrates,” said Pallavi Madakasira, Lux Research Analyst and lead author of the Lux report.  She explained that GaN-on-Si presents technical challenges such as cracking and a lattice mismatch that reduces the performance of LEDs based on the alternative substrate.

In an interview with Compound Semiconductor, Madakasira spoke about LEDs based on silicon substrates.  She doesn’t buy the argument that GaN-on-silicon makers can save on costs.  She says that even if they use fully depreciated CMOS equipment, the process of depositing complex buffer layers onto silicon prior to GaN deposition to overcome GaN and silicon lattice mismatches, adds time and cost to a manufacturing line.

Madakasira also shared performance data in her report with Compound Semiconductor. She notes that alternative substrates haven’t provided the performance of sapphire.  According to Lux, the luminance efficacy of GaN-on-SiC LEDs is 200 Lumens per Watt with GaN-on-sapphire devices coming in at between 150 to 180 Lumens per Watt.

What does this mean?  The Lux report concluded that sapphire will remain highly competitive for the rest of the decade.  GaN-on-silicon, will snare only 10% market share while GaN-on-silicon carbide will grow to 18% of the market.   Where do they fit? Here are Lux’s conclusions:

  • Choice and cost of LEDs will determine adoption. Where GaN-on-sapphire is suited to all applications, GaN-on-bulk GaN will be relegated to niche commercial lighting and GaN-on-Si, with unproven performance, will be better suited to cost-sensitive residential applications.
  • Four-inch wafers will rule (for now), though six-inch wafers start to come into vogue. Four-inch wafers will peak at 62% market share with $2.1 billion in 2017 sales. Later, the LED industry will move towards 6” epiwafers, which will take a 35% share, equivalent to $1.4 billion, in 2020.
  • Technology will advance sapphire substrates. Sapphire substrate manufacturing technology has advanced significantly with specialists such as Rubicon and Monocrystal demonstrating substrates up to 12” in diameter. New methods like hydride vapor phase epitaxy (HVPE) will further improve throughput and cut costs, keeping sapphire highly competitive for the rest of the decade.

For Further Reading

Lux Research, Epi-Wafer Market to Grow to $4 Billion in 2020 as LED Lighting Zooms to $80 Billion, http://www.luxresearchinc.com/news-and-events/press-releases/182.html

Compound Semiconductor, Sapphire Substrates to Lead Future LED Markets, http://www.compoundsemiconductor.net/csc/indepth-details/19736669/Sapphire-substrates-to-lead-future-LED-market.html

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: http://www.rubicontechnology.com/sites/default/files/From%20Sapphire%20to%20LED%20Infographic.pdf

Larger Wafers, Larger Yield – The Numbers Behind Large Diameter Sapphire Wafers and Yield

rubicon-waferyield-540x720-3Today, more than 80% of LEDs are based on sapphire substrates. For years, two-inch and four-inch diameter sapphire wafers have been the standard for LED production.  Now, LED chip manufacturers are looking to migrate to six-inch diameter wafers to increase the yield or the amount of LED chips they can make out of each wafer.  This is important as new market opportunities like LED-based general lighting take off, demanding more sapphire.

Rubicon put together an infographic, Larger Wafer, Larger Yield, about the yield from large diameter wafers. You can see it here on Rubicon’s new web site:  http://www.rubicontechnology.com/sites/default/files/Rubicon_WaferYield_v3.pdf

Rubicon Technology’s CEO Raja Parvez talked about the benefits of moving to large diameter sapphire wafers in an article, Vertical Integration Streamlines Sapphire Production, in Compound Semiconductor earlier this year.

According to Parvez, LED chip manufacturers look to large diameter sapphire wafers to cut costs.  Large diameter sapphire wafers enable more throughput for each run of the MOCVD reactor, making better use of the reactor “real estate” and decreasing the cost per unit of area processed.  The outer curvature of the 6 inch wafer is less, enabling greater use of the surface area than a 2 inch wafer resulting in less edge loss. In addition, large wafers provide post-MOCVD efficiencies.  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.  These efficiency gains become very compelling when LED chip production ramps up in large volumes to support a high growth market like general lighting.

For Further Reading

Compound Semiconductor, Vertical Integration Streamlines Sapphire Production http://www.compoundsemiconductor.net/csc/features-details.php?cat=features&id=19736275&key=rubicon%20technology&type=

Commercial Sapphire Spotlight – Vertical Integration in Sapphire

Rubicon Family of Sapphire Boules

Last month, Compound Semiconductor Magazine featured a contributed article about Vertical Integration in sapphire production by Raja M. Parvez, President and CEO of Rubicon Technology.  Rubicon has adopted vertical integration to set itself apart from other sapphire companies.  The article details Rubicon’s approach.

Vertical integration isn’t a new concept. It has been around since the 1800s when US Steel tycoon Andrew Carnegie introduced the vertical integration by owning virtually every part of the steel-making value chain from iron ore through steel mills to physically building the railroads.  Later, in the 1920s, Ford Motor Company decided to make the steel for their cars, popularizing the concept further.

According to Rubicon’s president and CEO Raja Parvez, vertical integration holds the key to Rubicon’s cost structure and reliable supply of high-quality products.  This integrated approach influences every step in the growth of sapphire crystals and their processing into wafers. The company’s end-to-end manufacturing capability, with strong intellectual property at each step of the manufacturing process, produces an advantageous cost structure and provides better control of product quality and delivery schedules. Vertical integration is also central to the company’s ability to grow larger and larger sapphire and be the first to market with large-diameter sapphire wafers for the LED and SoS/RFIC markets.  To date, Rubicon has shipped more than 400,000 6-inch wafers.

To read the full article, visit:   http://content.yudu.com/A2360p/CompSemMar13/resources/index.htm?referrerUrl=http%3A%2F%2Fwww.compoundsemiconductor.net%2Fcsc%2Fmagazine.php

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, http://bit.ly/1117AIk