Capacity and yield will be important factors affecting LED costs

“There are many LED manufacturing plants in the south of Tokyo, Japan. This time, Japan experienced a major earthquake. Let us all pray for Japanese friends!” at the “LED Illuminating the Future” International Seminar at SEMICON China 2011 on March 16th. Thomas Morrow, SEMI Executive Vice President and Chief Market Officer of Emerging Markets, expressed his sincere condolences to the earthquake-stricken area in Japan when the meeting officially began.

Then, on behalf of SEMI, he announced the current global LED situation. In the high-brightness LED market, global revenue in 2010 was US$10.8 billion, a year-on-year increase of 93%. Among them, Japan ranks first in the world with 33%, South Korea 28%, and China only 2%. In the first quarter of 2011, the top four rankings for monthly production capacity of 4-inch wafers were 345,188 in Taiwan, 320,344 in Japan, 290,125 in South Korea, and 202,375 in mainland China.

Industry development, standards first
By the end of 2010, the price of LED lights in the market was basically 10-25 US dollars, and this downward trend will continue in 2011.

Morrow pointed out that at present, the decrease in the cost of white LED devices is mainly due to the improvement of luminous efficiency, and it will shift to increase productivity and yield in the future.

Research results from the National Institute of Standards and Technology (NIST) showed that from 1996 to 2011, standards for software, calibration, and test methods generated nearly $10 billion in revenue. The study by the Department of Trade and Industry of the United Kingdom shows that the official standard contributes about 2.5 billion pounds to the economic growth of the UK each year. The German Institute for Standardization also believes that standardization can greatly reduce the R&D risks and costs of companies.

Morrow believes that the industry standards for solid-state lighting end products are critical to the industry's growth and market adoption rates. However, only a few standard development organizations (SDOs) are currently working on standards for product performance and testing, and manufacturing standards for materials, equipment, and automation are still blank.

Morrow said that the development of LED manufacturing standards will enable suppliers to compete more fully and focus on innovation and price, performance improvements. Therefore, LED manufacturers can purchase from different suppliers at the lowest cost, thereby reducing costs, improving quality, and accelerating time to market.

In 2010, the market for 6-inch sapphire substrates was 1%. It will grow to 5% in 2011. Therefore, the task of the wafer manufacturing standards working group should mainly focus on the following aspects: Define the physical dimensions of 6-inch sapphire wafers for manufacturing high-brightness LEDs, including wafer benchmarks (scratches and flatness); wafer ID markings (locations And content); center point thickness/TTV, warpage, bending, and other flatness parameters. At present, the working group has more than 10 manufacturers such as Osram, Veeco and Chongqing Silian.

The tasks of the equipment automation and interface working group should focus on: defining the backplane carrier physical interface for manufacturing high-brightness LEDs; and wafer and backplane carrier processing and measurement tools. At present, the working group has more than 10 manufacturers such as Brooks Automation, Osram, Veeco and Applied Materials.

The task of the assembly task group is mainly to define the physical and package characteristics of the die-level conductor elements optimized by general-purpose assembly equipment. Currently, members of the working group include Kulicke & Soffa, Amkor, TSMC, Chongqing Silian, Veeco, Brooks Automation, and Entegris.

Process control and yield are key to lowering the cost of high-brightness LEDs
Morrow's view that the increase in production capacity and yield is the main factor in the future decline in the cost of white LED devices has been agreed by all speakers present at the conference.

Srini Vedula, Director of Global Marketing at KLA Tencor, stressed that reducing high-brightness LED costs must focus on manufacturing process control and yield management, which can also increase the return on investment. He said that by 2015, 50% of all cost savings will depend on online testing.

Vedula uses excursion detection as an example. The automated method can detect key defect drift problems and provide feedback in time, but manual methods cannot.

In addition, process defects can lead to deterioration of product performance and reduced reliability. Various steps in production will have a cumulative effect on yield loss. The effect of majority and minority shifts (1σ, 3.6σ, and 10σ) on cost.

Based on the above analysis, Vedula proposes the following inspection strategies: Strict defect inspection specifications for improving yield; SPC control during MOCVD (Metal Organic Chemical Vapor Deposition).

Zhou Xuejun, Asia Pacific marketing director for Philips Lumileds, also stated that luminous efficiency will continue to affect LED cost reduction, but manufacturing and packaging will play a greater role in the future.

He also introduced the Lumileds Film Flip Chip (TFFC) process and Lumiramic fluorescence technology, which provide optimized white spot accuracy and color temperature consistency.

The surge in MOCVD market
MOCVD has been growing for six consecutive quarters, but it will be stable in 2011. However, oversupply may still occur in 2011-2012. In 2010, MOCVD shipped 786 units worldwide, of which China accounted for 34%, South Korea 31%, and Taiwan 27%. In 2009, these figures were 13%, 40% and 35% respectively. Only China's mainland has soared while South Korea and Taiwan have fallen sharply, and South Korea’s willingness to invest in 2011 will no longer be as enthusiastic as it was in previous years. This seems to indicate that the focus of the MOCVD market will shift from South Korea to mainland China.

Xu Yujuan, Director of Display and LED Department of Taiwan in IMS Research Institute in the United Kingdom, said that China's MOCVD stimulus plan has enabled more manufacturers to enter the field, and South Korea and Taiwan are also actively building capacity in the mainland. Since the third quarter of 2010, China has taken the lead in installing MOCVD for the first time, and it will continue to maintain this trend in 2011.

Since MOCVD in China is mainly concentrated on 2-inch wafers, this has caused the supply of 2-inch sapphire to be tight in 2010 and prices have increased by 50%.

However, Wang Keyang, president of Veeco Greater China, said that with Qingdao Jiaxing Jingdian, Jiangsu Xiexin Optoelectronics Technology, Eurasian Sapphire Optoelectronics, Zhejiang Crystal Optoelectronics, Tiantong, HIT Optoelectronics, Chongqing Silian, Yunnan Blue Crystal and Guiyang Engineering. The investment of sapphire substrates from mainland manufacturers and other manufacturers has been basically solved.

Wang Keyang pointed out that once the general lighting market demand, the adoption rate of 4-inch sapphire substrate will accelerate, and may increase from the current 27% to about 50%.

However, people in the industry are divided on the timing of the rapid development of the general lighting market. Some people think that it will appear in 2012, while others believe that this situation will not be seen until at least 2015.

MOCVD reaction chamber design

The design of the MOCVD reaction chamber is critical to film thickness consistency and material quality. In theory, all MOCVD processes use deposition mode, but the coating must ensure the stability of the process.

The spacing determines the cavity volume and surface area. Poor spacing control can cause particle problems and waste of molybdenum. Although the narrow spacing allows better gas distribution and reduces the consumption of molybdenum, it causes frequent clogging of the nozzles; while the wide spacing uses more molybdenum, but it can ensure the stability of the processing and avoid particle problems.

Good MOCVD reaction chamber design must ensure the uniformity of the gas supply; heating problem; reduce the pre-reaction; there can be no residual reaction of the cavity.

In addition, Wang Keyang said that pallet optimization and temperature control improvements can increase the production capacity of the machine (see Figure 6). In order to effectively control the cost of the epitaxy, high-capacity MOCVD requires a versatile production method. MaxBright applies multiple high-flow MOCVD reactors to modular two- or four-group reactors to implement FlowFlange and automation technology in the MaxBright GaN MOCVD multireactor system used by Veeco to produce high-brightness LEDs. . The advantage is that it is 25% more than the standard K465i, with good consistency, repeatability and material quality.