Toshiba: 2017 silicon substrate or become the mainstream of the market

Abstract Although the sapphire substrate material still sit tight in the leader, but with the continuous development of LED industry, based on technological development slows sapphire substrate, coupled with the problem of its high cost, patent barriers, many experts and engineers began to seek cost-effective Higher solution, and...
Although sapphire still sits firmly on the substrate material faucet, with the continuous development of the LED industry, the technology development based on sapphire substrate has slowed down, coupled with its high cost and patent barriers, many experts and engineers began to seek cost-effectiveness. High solutions, while silicon substrates are highly anticipated by the industry.

From the current use of substrate materials, most of the world's chip manufacturers use sapphire substrates. In recent years, more and more large manufacturers have begun to exert high-power LED chip technology on silicon substrates. Various market indications indicate that silicon substrates have become the focus of technology in the field of LEDs.
Gao Zhiwang, Senior Manager, Toshiba White LED Market & Technology Department

"We believe that silicon GaN may become the mainstream in 2017. Other companies will also put products using GaN-on-Si technology on the market." Toshiba White LED Market and Technology Senior manager Takahashi hopes to be full of hope for the silicon substrate. He told the reporter of "High-tech LED" that Toshiba has also used various materials to develop blue LEDs. Based on the 8-inch wafer technology of power semiconductor devices, many R&D personnel were gathered to carry out research and development on large-scale silicon substrates.

Talking about this, Gao Qiaowang introduced that compared to sapphire, silicon has a high thermal conductivity and is easier to design in terms of heat dissipation. The 8-inch wafer (non-silicon) case is very costly, and there are a lot of production difficulties when using 8-inch wafers for mass production of LEDs. “For silicon carbide (SiC) substrates and sapphire substrates, we think their maximum size is 6 inches.” He said: “The cost advantage of Toshiba’s silicon-based GaN technology is not only reflected in the material, but also On the process of using 8-inch wafers, and we can use the equipment that previously produced other 8-inch silicon wafer products for production. Therefore, we have the advantage of improved mass production control methods and high quality crystalline products. ”

The biggest technical difficulty compared to silicon substrates and other two substrates, silicon carbide and sapphire, is lattice mismatch and thermal mismatch. "It is difficult to grow a GaN layer on a silicon substrate, and it is difficult to obtain better crystallization. Therefore, mass production is still a challenge. However, Toshiba is leading other companies to establish a silicon-based GaN technology and mass production using a silicon substrate. Gaoqiao looked and smiled.

Specifically, silicon and gallium nitride have the largest lattice mismatch, which is several times that of silicon carbide. Large lattice mismatches lead to higher dislocation densities in gallium nitride materials, and it is for this reason that silicon substrates are considered to be an inaccessible technology route for a long time. At the same time, there is a large thermal mismatch between the silicon substrate and the gallium nitride. This problem leads to a certain match between the two at high temperature growth, but after falling to room temperature, the thermal expansion coefficient of the two is very different, Causes problems such as cracks.

Gao Qiaowang said that the conditions for GaN to grow on a silicon substrate are much more difficult than the conditions for GaN to grow on sapphire. Even so, Toshiba's use of GaN-on-Si has reached 170-180 lm/W, so he believes that silicon-based products can replace sapphire substrates in the near future.

It is reported that the current size of LED chips produced by Toshiba is: 1.1x1.1mm and 1.4x1.4mm. The chip size depends on the applied power. LED chips larger than 1.1x1.1mm and 1.4x1.4mm are suitable for 1~3W type products, which is basically the same size as sapphire chips. The current output power is around 700mW (under silicone package conditions).

From the point of view of the production process, the large size of the silicon substrate can be used to produce LEDs by the silicon integrated circuit production process developed by humans through years of technology accumulation, thereby greatly improving the degree of automation, and at the same time, minimizing the participation of personnel, the chip Reliability, consistency and yield will be greatly improved, and labor costs can be reduced, reducing the overall cost of LEDs by 20-30%, which is a revolutionary subversion for the entire LED industry.

In addition, GaN power devices on silicon substrates are also an important application area, and it is expected to open up a new application field beyond traditional power devices. A major feature of the third-generation semiconductor represented by gallium nitride is the wide band gap. This feature makes the device with high breakdown voltage, high current density, high operating temperature, etc., so the performance in high-power, high-temperature power electronic device applications is far superior to traditional silicon and gallium arsenide-based electronic devices. Its application range will include computers, mobile phones, digital cameras, power supplies, motors, UPS, electric vehicles, base stations, power plants, etc. The use of silicon as a substrate for gallium nitride electronic devices has been internationally recognized, primarily because of the unparalleled cost advantages of silicon for other substrate materials.

From the perspective of industrial structure, the current global LED industry has become the three pillars of the United States, Asia, and Europe. The five major manufacturers, such as CREE in the US, Osram in Europe, Philips Lumileds, Nichia Chemical in Japan, and Toyota Synthesizer, control the world. The LED market has monopolized the core technologies and patents of G aN-based Blu-ray LE D and white LED LE D. The patents applied by these manufacturers in order to maintain their competitive advantage and maintain their market share cover almost the entire industrial chain including raw materials, equipment, packaging and applications.

R&D and production between manufacturers through patent authorization and cross-licensing not only hinder the emergence of new entrants, but also increase the production costs of enterprises to a certain extent. Therefore, the development and establishment of a patent system with independent intellectual property rights can not only become the basis for the development of the enterprise, but also prepare for the future development of the enterprise. At this level, the development of silicon substrates is not only a simple technology research and development, but also paving the way for the future development of LED companies.

The silicon substrate LED technology avoids the international patent cofferdam formed by the sapphire substrate and the silicon carbide substrate technology route from the source of the substrate, and can form its own from low-power LED chip technology to high-difficult high-power LED chip technology. Patent system. “Silicon-based GaN technology is a fairly new technology, so in this new technology environment, we can discover new technologies more quickly. Toshiba will try to acquire more new patents.” Takahashi is like this. Say.

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