Four key technologies for the production of high-purity ammonia

High-purity ammonia products are indispensable supporting materials for optoelectronics and microelectronics technology. It is widely used in semiconductor lighting, flat panel displays, solar cells and large-scale integrated circuit manufacturing. The quality of high-purity ammonia directly affects the optical and electrical properties of the material and even the service life of the device. There are huge potential markets both at home and abroad. With the development of the domestic semiconductor industry, the demand for high-purity ammonia is growing rapidly, and the localization of high-purity electronic gas is an inevitable trend of development.

Ultra-high purity ammonia is also a key support material for the production of third-generation compound semiconductor material gallium nitride (GaN) by metal organic chemical vapor deposition (MOCVD) technology. The MOCVD technology to prepare gallium nitride (GaN) requires that the ammonia used must be high-purity and ultra-clean, and its purity level is 7N (99.99999%). Due to technical bottlenecks and technical barriers, the purity of domestic high-purity ammonia has been up to 6.0N, which is difficult to meet the requirements of GaN growth technology. With the start of my country's "National Semiconductor Lighting Project", the need for key support materials for GaN has become more urgent. Therefore, it is imperative to break through the purification technology of ultra-pure white ammonia for GaN and realize the large-scale production of ultra-high-purity ammonia to replace imported products.

High-purity and ultra-clean ammonia is the most fundamental film-forming source for thin film formation. Oxygen molecules (O2), water (H2O) and CO2 are very harmful impurities, which will cause the quality of the deposited metal and metal compound active film to decrease. Metal impurities in high-purity and ultra-clean ammonia are extremely harmful to the preparation of compound semiconductor materials, and are one of the key factors that affect their photoelectric performance indicators. Remove oxygen molecules (O2), water (H2O) and metal impurities in high-purity ammonia. The reduction of the total impurity content below 0.1ppm is currently a problem for gas purification in the world. During the implementation of the project, the key technologies to be solved include:

1、Purification technology: Corresponding to the high purity gas used in the semiconductor field, the purity requirements are extremely high, especially the content of oxygen, water and other impurities that affect the growth of semiconductor materials must reach the ppm-ppb level. Aiming at the impurity content and physical and chemical properties of the raw gas, the main purification methods are high-efficiency adsorption and high-efficiency rectification. The focus is on the research and development of new adsorbents and high-performance catalysts with good selectivity, large adsorption capacity and high purification depth, which have adsorption and catalysis Two functions meet the requirements of impurity removal, and this process is particularly suitable for large-scale production.

2、Purification technology: In order to achieve the expected purity and cleanliness of high-purity ultra-clean ammonia, the materials of all equipment, containers, and pipelines in contact with the gas are pretreated to achieve no surface adsorption, no surface chemical reactions, no particle shedding, and no Dead volume and good sealing performance. In the purification system, choose a high-efficiency filter with high trapping efficiency and small pore size to greatly reduce the dust particles in the product and achieve ultra-pure product cleanliness.

3、Analysis and detection technology: ppb level or ppt (10-9~10-12) level gas impurities, metal ions and dust particles detection is the key technology that must be resolved in the development of high-purity ammonia. The detection of trace impurities is based on establishing reliable analysis Methods and advanced testing equipment. Based on the introduction of foreign advanced analytical instruments, a ppb-ppt level impurity analysis method has been established. Especially for the analysis of water and metal impurities, data repeatability and accuracy are achieved regardless of online or random inspection. Provide technical guarantee to ensure product quality.

4、Industrialized production technology: Adopting the combined purification technology of adsorption, rectification, and ultrafiltration, it is easier to purify high-purity ammonia at a large flow rate; using innovative processes and operating conditions to improve the adsorbent regeneration technology. After the regeneration of the adsorbent is completed, a special backflushing technology is adopted as a transition of the next adsorption cycle to restore the adsorbent to the highest activity, which can continuously and stably produce high-purity ammonia products.