The Art of Sapphire – Ensuring High Quality Sapphire Wafers

You might think from the title of this post that we’re talking about gems or jewelry, but we’re not. We’re talking about commercial sapphire – the type that is used to make LEDs. Not all commercial sapphire is high quality. In fact, the quality of the sapphire crystal impacts the quality of the sapphire wafer and the resulting LED. Sapphire producers must go through a qualification process in order for LED manufacturers to select the vendor. What are they looking for? Raja Parvez, President and CEO of Rubicon Technology shared information about what LED manufacturers look for when they come to Rubicon.

Rubicon Technology shared information about what LED manufacturers look for when they come to Rubicon.

Flatness: When a sapphire wafer is not flat it will become like a potato chip during processing. This prevents the wafer from being processed properly. The key tolerance for 6-inch and 8-inch is the flatness across the wafer. Thickness is not standardized yet and can range anywhere from 1-2 mm. The greater thickness also uses a larger amount of sapphire, but we’ll get to that in a later post.

Cleanliness: Surface morphology of the wafer needs to be clean and presents a uniform surface before depositing the epitaxial layer. The particulate count on the polished surface is very important too. A dirty wafer will cause issues when depositing the epitaxial layer. In addition, if impurities have been introduced in crystal development, colorization will be introduced rendering a colored crystal. This has a negative effect on commercial sapphire quality in contrast to gem quality sapphire that depend on impurities for their color such as red (with chromium impurities) for rubies and blue (with titanium and iron impurities) for sapphire. For example, commercial sapphire crystals with impurities result in pink wafers that interfere with LED performance.

Stress: LED manufacturers need stress-free wafers. Sapphire crystals go through temperature cycles of up to 1200ºC. That causes stress that can create cracks in the wafers and reduce yield. Rubicon’s ES2 technology produces almost stress-free crystals. During the crystal growth cycle, 50 percent of the time is taken to grow our crystal, and 50 percent is taken to cool down the crystal. During cooling, stresses are automatically released. Other wafer technologies introduce significant stress, so it’s common to put those wafers through an annealing furnace to reduce stress. This adds operational costs and time to production.

LED Lighting Drives Growth in Global Lighting Market

A new research report from IMS Research in July 2011 states that LED lighting is driving growth in the global lighting market. Previously stagnant, the lighting market is experiencing new growth. IMS Research Lighting Market Analyst, Philip Smallwood, states that “Growth is stemming from advancements in LEDs which are increasing their efficiency, while decreasing their overall price. Currently, LEDs make up 10% of the total lighting market ($US), but by 2015, this is expected to increase to 46%.”

According to IMS, the new LED market is bringing new entrants to a rather stagnant lighting market that was dominated by the same global lighting suppliers for decades. Innovations in LED technologies have opened the door for these new suppliers to develop different niches within the lamp (light bulb) and luminaire (lighting fixture) markets. This creates a great growth environment.

The Rise of the LED

With EISA of 2007, Congress set forth the rise of the LED. The new standards launched a paradigm shift within the residential lighting market. The incandescent technology in the U.S. will be phased out, and, as per the standards, there are only three alternatives to fill the empty sockets in every American home and business: CFLs, halogen and LEDs.

Each alternative has its good and bad points. CFLs, while more energy efficient than incandescents, also contain harmful mercury. Not many people want to take out an EPA certified disposal kit to clean up a light bulb (yes, you actually have to and can pick up the kits at many home and hardware stores). Then, halogen bulbs tend to cost the same as CFLs, but don’t last any longer. LEDs have improved over the years. LEDs last about 50,000 hours (compared to 1,000 for an incandescent) and are about 30% more energy efficient. They still cost a pretty penny, but the costs are expected to come down to more reasonable levels. Home Depot now offers a proprietary brand of LEDs under the EcoSmart name, including a bulb that retails for $19.97 and is a 40W equivalent.

By 2015, IMS analyst Phillip Smallwood “expects LED lamp replacement installations will greatly increase. Technological breakthroughs will make these lamps look more like general incandescent lamps, all while being cost competitive with CFLs. At the same time, concerns over the mercury contained in CFL lamps and their shorter life will make them less and less appealing to consumers. More rebate programs will be established for LEDs leading to even more replacements being installed.” Here’s what he thinks the market will look like.

Incandescent Bulbs Days are Numbered

In order to figure out the impact of the LED on the general lighting market, IMS Research created a global installed base model of incandescent, CFL, linear fluorescent HID and halogen lamps, divided by region in 2010. The graphic below shows that there are approximately; 3.9 billion incandescent, 1.75 billion CFL, 1.75 billion linear fluorescent, 50 million HID and 550 million Halogen lamps installed in the United States alone.

Incandescent bulbs have enjoyed long dominance since the days of Thomas Edison. According to IMS analyst Phillip Smallwood, “the main reason behind this is that incandescent lamps are extremely cheap with an average selling price of approximately $0.43 cents. Add an average cost of electricity of $0.11/kWh to the equation, and you get a large group of consumers that base their lamp purchasing decision solely on the initial cost of the lamp.”

Unfortunately for consumers, Congress enacted The Energy Independence and Security Act (EISA) of 2007. That act created higher efficiency standards targeting 40–100W incandescent and halogen general-service lamps. Starting in 2012, 100W lamps will be required to be 28% more efficient, 75W lamps in 2013 and 40-60W lamps in 2014. According to Smallwood, the new efficiency standards effectively ban most current incandescent technologies from being purchased after the block out date.

Source: IMS Research