AIXTRON has the key technology enablers in place to address the most stringent MOCVD requirements for Micro LED production

Excitement about microLED display technology was already palpable in 2014 after Apple acquired MicroLED display startup Luxvue. Since then, many large consumer electronics and semiconductor companies have committed to the technology, including Facebook-Oculus, Google, Sharp, ELUX, Samsung, LG etc. In total, a thorough analysis conducted in collaboration with Knowmade, Yole Développement’s partner, shows that more than 120 companies or research organizations have already filed about 1500 patents in more than 500 families,  as analysed in the report MicroLED Displays : Intellectual Property Landscape.

MicroLED displays could potentially match or exceed OLED performance in all critical attributes such as brightness, contrast, color gamut, refresh rate, viewing angle, ruggedness and durability, resolution and pixel density, lifetime, power consumption etc.
So how long will we have to wait until we see the first consumer applications? The science is here, but as discussed extensively in our MicroLED Displays : Intellectual Property Landscape report this is an inherently complex technology with cost drivers very different from those of incumbents OLED and LCD.
Eric Virey spoke with Arthur Beckers, Senior Product Manager at AIXTRON SE about the specific challenges associated with the epitaxy of high quality structures required for microLED displays.

R&D Center of Aixtron

Eric Virey: Can you briefly introduce AIXTRON and the different markets you serve?
Arthur Beckers: AIXTRON SE is a leading provider of deposition equipment to the semiconductor industry. The Company was founded in 1983 and is headquartered in Herzogenrath, in North West Germany, with subsidiaries and sales offices in Asia, United States and Europe. AIXTRON´s technology solutions are used by a wide range of customers across the world in a broad range of innovative applications, technologies and industries. These include latest display technologies, data storage, data transmission, power management and conversion, communication, and obviously the lighting and sensing markets as well.

EV: For how long has AIXTRON been involved in Micro LED developments?
AB: Through our global network of research and academic partners, AIXTRON has been involved in this area for a long time. Our focus has always been on innovating through new material and applications development, whether it be with our academic customers or funded projects or through collaboration with industrial partners. Through this work, we recognized maybe three years ago, a potential pathway for Micro LED technology into high volume applications in consumer electronic products, and we now see a tremendous growth opportunity for this emerging technology. We see strong possibilities that Micro LEDs become the standard technology used for next generation displays, but that said we are still at an early stage in terms of the commercialization of this technology.

EV: Could you please expand on this?
AB: Conventional Display Technologies are being challenged by the emergence of Micro LED Display Technology, due to their superior qualities in nearly all aspects of the customer experience. But unless we can bring the cost down to competitive levels, Micro LED Displays may stay a niche market product for the ‘Happy Few’. This is a shared industry responsibility as a complex processing chain has to be put in place to achieve the necessary yields. Additionally, there are others challenges to master besides the MOCVD processing step.

EV: What are the major differences between traditional LEDs and Micro LEDs in term of epiwafer requirements?
AB: Game changing technologies are required here. Equipment currently used for conventional products like BLU or general lighting are likely to be unable to deliver the necessary yields. There are quite specific differences between the MOCVD processing of traditional LEDs and Micro LEDs and work is needed to meet the most stringent Micro LED requirements in terms of defect density, uniformities of the epitaxial layers and run-to-run repeatability. And to meet cost targets these requirements have to be met at a very high productivity level, which means wafer throughput of the MOCVD equipment is crucial.

EV: What do they imply in terms of epitaxy, reactor requirement and infrastructure?
AB: The basic MOCVD processing specifications for Micro LED applications can be derived from the display requirements. To achieve a high MOCVD processing yield both a low defect density as well as a very high uniformity form the baseline. More precisely, a defect density of 0.1 defects/cm2 and a wavelength range of 4 nm needs to be achieved for all wafer areas being produced (based on Six Sigma processing). Achieving a good wafer utilization requires a wafer size of 6 inch or larger while the MOCVD reactor should be equipped with suitable technology to enable this. We strongly believe that without a cassette–to-cassette automation and clean reactor conditions, which ensure absolute stability run after run for very long campaigns, the above specifications cannot be achieved consistently. AIXTRON’s core strength in uniformity control, enabled by our Planetary® technology, is perfectly suiting the tight wavelength range requirements for Micro LEDs.

EV: Will this have an impact on epiwafer cost compared to traditional LEDs?
AB: The impact we achieve with highly efficient particle and uniformity control is significant. Today’s traditional LED systems don’t achieve the required defect density and are in the range of 0.5 defects/cm2 and worse. The same implies for uniformity control where traditional systems target a yield of >90 % in a 6 to 8 nm bin. In contrast, the basic requirements for Micro LED applications are to achieve > 99% in a 4 nm wavelength range. Note here that micro led chip sorting is not commercially viable when for example a total of 24-28 million subpixels are required for a 4K TV display product. So all in all, I would say that the price of a Micro LED wafer will likely be in the range of a premium LED wafer.

EV: How much progress has AIXTRON made in terms of adjusting its tools and recipes for those specific Micro LED requirement?
AB: The benefit of our system solution is that we have two platforms equipped with the same Planetary® technology: the AIX 2800 G4-TM serves the RED, ORANGE, YELLOW color range, while the AIX G5+C serves BLUE and GREEN LEDs. By close collaboration with our partners we can bring in our substantial knowhow grown over many years to meet specific customer requirements with our solutions. Our planetary® technology offers unmatched yield levels off the shelf, but we can support particular requirements, e.g. for substrates used, by dedicated carrier designs. Furthermore, AIXTRON has developed best known method (BKM) recipes for both 6-inch substrates as well as for 8-inch silicon wafers. Overall, AIXTRON’s Planetary® technology has always been perfectly positioned for advanced applications such as GaN on Si Power HEMT which also require wafer level control and defect controllability. This has given us a strong head start for the Micro LED application development.

AIX G5+C

EV: How difficult was it to achieve those performances? Did it involve some system design changes?
AB: The uniformity control is the result of years of development. We have introduced our specific technology and hardware, such as UV Pyrometry or Advanced Bow Management to enable a very tight control of uniformity. It is our objective to enable our customers to focus on the device development itself. The same applies to the low defect density level which is currently unmatched. Our Planetary® systems are equipped with a cassette-to-cassette automation and in-situ cleaning to enable this level of particle and defect control.

AIX G5+C

EV: In the future, will the MOCVD reactor design for Micro LED applications be different from those used in traditional LED manufacturing?
AB: Considering the tightened specifications, we can only conclude that traditional MOCVD manufacturing systems used for SSL (Solid State Lighting) are not suitable for Micro LED applications. We can envision a certain stretch being made for the mass production of the ‘intermediate’ Mini LEDs (>100 micron) but not for the smaller Micro LEDs (< 30 micron).

EV: In your opinion, what is the best substrate platform for Micro LED? Does silicon offer some benefits?
AB: The G5+C is the tool of reference in the market and because it was mainly developed for 6-inch and 8-inch wafer sizes, it can be applied to both sapphire as well as silicon substrates. A significant cost decrease can be enabled with silicon since 8-inch substrates allow for an improved wafer utilization and existing lines can be used for back end processing.

EV: How much interest are you seeing on Micro LED currently? What is the time horizon and when do you expect to see MOCVD sales specifically related to Micro LED?
AB: We are fully engaged with the key players in the field of Micro LED, and what we are seeing is increasing interest and those players preparing themselves for bringing their products to market. Timing will be different for Mini as opposed to Micro LED applications. We are already seeing the Mini LED finding its way into various Display products but it will probably take until 2021-2022 before we see the significant adoption of micro LEDs in commercial products. At the end, market adoption will determine how good the micro LED industry is capable of bringing down cost, and vice versa.

EV: Thanks for the interview, final question – where can we see AIXTRON presenting about Micro LED?
AB: We have had several talks at relevant conferences already, which allowed us to engage with various potential stakeholders. The next planned talk will be at the Display Week in L.A. (May 24th, Session 45: Micro-LED Epitaxial Semiconductor Materials & Manufacturing) where I will disclose more details and information. The title of the Invited Paper is ‘Enabling the Next Era of Display Technologies by Micro-LED MOCVD Processing’.

INTERVIEWEE

Ing. Arthur Beckers, AIXTRON SE

Arthur Beckers is Senior Product Marketing Manager of AIXTRON SE and is specialized in bringing new products to market. He joined AIXTRON SE in the year 2014 and is responsible for AIXTRON’s display and lighting business. He has held different positions within the high tech industry varying from solar, printing and semiconductor. He is a business manager with expertise in the area of engineering, sales, marketing and product management. Arthur Beckers holds an engineering degree in Applied Physics, as well as a degree in Technical Business Administration.

 

 Sources:  – 

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MicroLED Displays : Intellectual Property Landscape
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RELATED EVENT:

Yole Développement will participate to Display Week that will happen in Los Angeles from 20th to 25th February. Do not miss the presentations on “Are MicroLEDs a Credible Alternative to LCD and OLED?” and “Status and Prospects of MicroLED Displays“. More details here.