Sapphire technology is diversifying, and the Czochralski method is gradually becoming the market mainstream.

1. Overview of the Sapphire Industry

The chemical properties of sapphire crystals are very stable, characterized by a high melting point (2050℃), high hardness (Mohs hardness of 9, second only to diamond), good light transmission, thermal conductivity, electrical insulation, as well as excellent mechanical properties, wear resistance, and wind erosion resistance.

Therefore, sapphire is an extremely important basic material in the microelectronics and optoelectronics industries, widely used in semiconductor, microelectronics, optoelectronics, information display, optical communication, lasers, precision machinery, national defense, and military fields. With the development of science and technology, new requirements for the size and quality of sapphire crystal materials are constantly being proposed. Now, with the rapid development of semiconductor lighting and other emerging applications, the market demand for low-cost, high-quality, large-sized sapphire crystals is rapidly expanding.

Since 1885, when Fremy, Feil, and Wyse used a hydrogen-oxygen flame to melt natural ruby powder with potassium dichromate to create the sensational "Geneva Ruby," research on artificially grown sapphire has a history of over 100 years. Over the past century, in order to adapt to the development of science and technology and the special requirements of industrial production for the quality, size, and shape of sapphire crystals, efforts to improve the yield, utilization, and reduce costs of sapphire crystals have never ceased. Research on sapphire growth methods and related theories has continued, and equipment and technology have rapidly developed since the end of the last century. To date, the sapphire industry has achieved a high level of technology and large production capacity, with crystal rod sizes expanding from 2 inches to the current 12 inches, and supporting equipment and materials have also developed rapidly.

2. Comparison of Sapphire Crystal Growth Technologies

Currently, various crystal growth technologies are applied in the market, and the purity of the crystals can reach 99.99%. However, due to different growth mechanisms, there are certain drawbacks and limitations, making it difficult to simultaneously meet the future development needs of large size, high quality, and low cost for sapphire crystals. For example, the quality and size of crystals grown by methods such as the flame melting method and the pulling method are limited; methods like the heat exchange method, temperature gradient method, and floating zone method require a large amount of helium as a coolant; sapphire crystal blanks grown by the temperature gradient method and floating zone method require high-temperature annealing treatment, and the subsequent processing of the blanks is relatively complex and costly.

However, from the perspective of market share, the floating zone method currently holds an advantageous position. The world's largest sapphire production companies, American Rubicon and Russian Monocrystal, both use this technology to produce sapphire crystals. Additionally, several Chinese sapphire production companies, including Jingjing Optoelectronics, also use this method. The sapphire crystals produced by this method account for over 50% of global output, with over 70% of sapphire substrates used for semiconductor lighting produced by this method. The temperature gradient method is the main technology used by South Korean manufacturers, which can produce high-quality crystal rods with low electrical density, allowing for relatively less restriction on the size (diameter and height) and shape of the crystals, and it currently holds a certain market share. The guided method is mainly mastered and used by Japanese companies, with products primarily supplied to the Japanese market. Additionally, Ukraine also produces guided method crystal growth furnaces.

Table 2: Comparison of Advantages and Disadvantages of Main Sapphire Crystal Growth Technologies