Zhongxin Wafer: Successfully produced 12-inch silicon ingots weighing 450 kg in consecutive runs—mass production is within reach!

On August 17, 2021, Zhongxin Wafer successfully produced its first 12-inch ingot weighing 450 kilograms with a feedstock charge! This ingot had a net weight of 437.7 kg, a length of 2,900 mm, and a body length of 2,400 mm, with a yield rate reaching 87.6%. This represents an improvement of 4.6 percentage points compared to the yield rate achieved when using a 300-kilogram feedstock charge previously. On September 5, the company successfully drew a second 12-inch ingot weighing 450 kilograms with a feedstock charge. The parameter specifications of this second ingot were virtually identical to those of the first one. It can be said that the company has now attained the technical and process capabilities necessary for standardized mass production of 12-inch ingots with a 450-kilogram feedstock charge.

According to sources from the raw material ingot R&D team at Zhongxin Wafer, the successful pulling of this “overweight” ingot represents a milestone for the company. Its advantages include:

1. Achieve process improvement

During the crystal rod pulling process, the greater the amount of feed material used, the higher the requirements for both the process itself and the precision of control in the single-crystal furnace. Since a 32-inch quartz crucible can hold up to 340 kilograms of polysilicon material in a single charge, increasing the feed amount to 450 kilograms necessitates the adoption of a two-stage feeding technique. Since the inception of the Zhongxin Wafer’s 12-inch 450-kilogram feed crystal rod R&D project, the R&D team has built upon the earlier 8-inch two-stage feeding technology and, based on the structural design of the 12-inch single-crystal furnace, developed matching two-stage feeding tooling. After successfully completing the assembly of all components, the R&D team conducted trial runs using an empty furnace and ultimately achieved the successful continuous pulling of two 12-inch 450-kilogram feed crystal rods, thereby driving significant improvements in the process. In the future, the 12-inch 450-kilogram feed crystal rods produced by Zhongxin Wafer will be standardized for mass production.

2. Effectively improve yield and product quality.

The successful growth of large-diameter silicon ingots has enabled Zhongxin Wafer to increase its monthly production capacity. Meanwhile, the increased length of these large-diameter ingots has improved the utilization rate of each individual ingot, thereby helping to enhance the yield and stability of 12-inch silicon wafers.

3. Achieve cost reduction and efficiency improvement

Under the condition of identical diameter, a larger-diameter crystal ingot implies an increase in length, while the amounts of head and tail material correspondingly decrease, thereby enhancing the utilization rate of the ingot and achieving cost reduction with increased efficiency. On the other hand, as the charge amount increases, the same crucible and auxiliary materials can produce more output, reducing the consumption of crucibles and auxiliary materials and further lowering costs.

Zhongxin Wafer boasts a domestically advanced semiconductor silicon wafer production line and is one of the few Chinese companies capable of mass-producing 12-inch large silicon wafers. Currently, its monthly production capacity stands at 400,000 6-inch and smaller wafers, 450,000 8-inch wafers, and 100,000 12-inch wafers. By December 2022, Zhongxin Wafer will have a monthly production capacity of 200,000 12-inch wafers. Its products include polished wafers (highly doped/lowly doped/Cop-free) and epitaxial wafers, primarily used in logic chips, flash memory chips (3D NAND & Nor Flash), dynamic random-access memory chips (DRAM), image sensors (CIS), and display driver ICs. Through dedicated and intensive technological research, Zhongxin Wafer has achieved breakthroughs in 12-inch heavily doped arsenic wafers with low resistivity ranging from 2.3 to 3 milliohms, as well as heavily doped red phosphorus wafers with low resistivity of just 1.3 milliohms, and has begun supplying these high-quality wafers to customers both domestically and internationally!

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