[Source: "High-tech LED - Technology and Applications" September issue]
The rapid development of the sapphire industry has benefited from the demand of the LED industry. At present, there are many manufacturers investing in sapphire crystals, and the application of LED has slowed down. The sapphire flat substrate has been oversupplied, and its price has dropped from the highest of $30 in 2010 to the present. 8~9 dollars. At the same time, sapphire substrates are also facing competition from silicon substrates. The silicon substrate LED chips jointly developed by Toshiba and Bridgelux are expected to be mass-produced in October this year. Since silicon substrates are low in cost and easy to obtain large sizes, once silicon substrate LEDs The yield and performance are comparable to those of sapphire substrate LEDs, and sapphire substrates will face even more severe challenges.
LED sapphire traditional crystal growth method
At present, the sapphire crystal growth method for LED mainly includes a pulling method, a heat exchange method, a bubble generation method, a vertical horizontal gradient crystallization method (VHGF), and an advanced thermal control method. Kyocera in Japan, Sino-US Silicon Crystal Products Co., Ltd. in Taiwan, and Chongqing Silian Sapphire Co., Ltd. have all achieved the growth of 4-inch sapphire, but it is more difficult to obtain larger size, long crystal growth time and C-direction. Growth is its main advantage; the heat exchange method was developed by the original Crystal System Company, which has a strong advantage in growing large-size sapphire but has a low yield (45%). The one-time molybdenum crucible also increases the production cost while growing the sapphire. It is pink and affects the light transmittance of LED. The bubble method is the most widely used method. It can grow large-sized ingots and has a long crystal growth time. However, as the size of the ingot increases, the yield also follows. Reduced. South Korea's STC company uses the VHGF method, A-direction growing cuboid sapphire and then C-clamping rods, currently only 6 inches, because the method is more special for the thermal field, the thermal field design is the bottleneck for growing larger sapphire.
Crystal growth requirements for sapphire substrates
At present, sapphire substrate manufacturers need to further reduce production costs due to increased investment and competition from silicon substrates. LED chip manufacturers will gradually adopt large-size substrates for reasons of cost reduction. Silicon substrates have obvious advantages in large size. Therefore, in order to win in the market competition, sapphire substrates must meet the LED size requirements and reduce production costs. . Due to lattice matching, the core material GaN film of LED is most suitable for epitaxial growth on C-plane sapphire substrate, but C-axis crystal is more difficult than A-axis crystal growth. Therefore, the traditional sapphire crystal growth method adopts A-axis. Long crystals, but the ingots grown from the A-axis crystals need to be smashed from the side to obtain a C-to-sapphire ingot and processed into a C-direction sapphire substrate. This will greatly reduce the material utilization of the ingot, such as the bubble method. The material utilization rate is about 35%. The use of C-axis crystals can increase the material utilization rate to 80%, thereby greatly reducing the production cost of sapphire. In addition, the growth time of each part of the substrate is different by the A-axis crystal growth method, so the uniformity is better. Poor, and the C-axis crystal growth method is used at the same time, and the uniformity is high, as shown in Fig. 1. At the same time, the C-axis crystal growth is easier to obtain the large-size C-direction sapphire substrate than the A-axis crystal.
Figure 1 Comparison of A-axis growth and C-axis growth
Unfinished
For more information, please refer to: "High-tech LED - Technology and Applications" September issue
The rapid development of the sapphire industry has benefited from the demand of the LED industry. At present, there are many manufacturers investing in sapphire crystals, and the application of LED has slowed down. The sapphire flat substrate has been oversupplied, and its price has dropped from the highest of $30 in 2010 to the present. 8~9 dollars. At the same time, sapphire substrates are also facing competition from silicon substrates. The silicon substrate LED chips jointly developed by Toshiba and Bridgelux are expected to be mass-produced in October this year. Since silicon substrates are low in cost and easy to obtain large sizes, once silicon substrate LEDs The yield and performance are comparable to those of sapphire substrate LEDs, and sapphire substrates will face even more severe challenges.
LED sapphire traditional crystal growth method
At present, the sapphire crystal growth method for LED mainly includes a pulling method, a heat exchange method, a bubble generation method, a vertical horizontal gradient crystallization method (VHGF), and an advanced thermal control method. Kyocera in Japan, Sino-US Silicon Crystal Products Co., Ltd. in Taiwan, and Chongqing Silian Sapphire Co., Ltd. have all achieved the growth of 4-inch sapphire, but it is more difficult to obtain larger size, long crystal growth time and C-direction. Growth is its main advantage; the heat exchange method was developed by the original Crystal System Company, which has a strong advantage in growing large-size sapphire but has a low yield (45%). The one-time molybdenum crucible also increases the production cost while growing the sapphire. It is pink and affects the light transmittance of LED. The bubble method is the most widely used method. It can grow large-sized ingots and has a long crystal growth time. However, as the size of the ingot increases, the yield also follows. Reduced. South Korea's STC company uses the VHGF method, A-direction growing cuboid sapphire and then C-clamping rods, currently only 6 inches, because the method is more special for the thermal field, the thermal field design is the bottleneck for growing larger sapphire.
Crystal growth requirements for sapphire substrates
At present, sapphire substrate manufacturers need to further reduce production costs due to increased investment and competition from silicon substrates. LED chip manufacturers will gradually adopt large-size substrates for reasons of cost reduction. Silicon substrates have obvious advantages in large size. Therefore, in order to win in the market competition, sapphire substrates must meet the LED size requirements and reduce production costs. . Due to lattice matching, the core material GaN film of LED is most suitable for epitaxial growth on C-plane sapphire substrate, but C-axis crystal is more difficult than A-axis crystal growth. Therefore, the traditional sapphire crystal growth method adopts A-axis. Long crystals, but the ingots grown from the A-axis crystals need to be smashed from the side to obtain a C-to-sapphire ingot and processed into a C-direction sapphire substrate. This will greatly reduce the material utilization of the ingot, such as the bubble method. The material utilization rate is about 35%. The use of C-axis crystals can increase the material utilization rate to 80%, thereby greatly reducing the production cost of sapphire. In addition, the growth time of each part of the substrate is different by the A-axis crystal growth method, so the uniformity is better. Poor, and the C-axis crystal growth method is used at the same time, and the uniformity is high, as shown in Fig. 1. At the same time, the C-axis crystal growth is easier to obtain the large-size C-direction sapphire substrate than the A-axis crystal.
Figure 1 Comparison of A-axis growth and C-axis growth
Unfinished
For more information, please refer to: "High-tech LED - Technology and Applications" September issue
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