Ultrapure Water in Semiconductor

Semiconductors, integrated circuit chips and packages, liquid crystal displays, high-precision circuit boards, optoelectronic devices, various electronic devices, microelectronics industry, large-scale and ultra large-scale integrated circuits and other electronic industry fields need a large amount of pure water, ultra pure water to clean semi-finished products and finished products. The higher the integrated circuit is, the thinner the wire diameter between the components on the chip or the connecting components is, and the higher the requirements for water quality are (generally, the ultra pure water resistivity is 18.2M Ω. cm (25 ℃), TOC<5ppb, and bacterial endotoxin<0.03EU/ml). The quality of ultra pure water has become one of the important factors that affect the quality, yield and cost of electronic components.

In the production of electrolytic capacitors, ultrapure water is required for cleaning aluminum foil and working parts. If the water contains chloride ions, the capacitor will leak electricity. In the production of electronic tubes, the cathode of electronic tubes is coated with carbonate. If impurities are mixed in it, the emission of electrons will be affected, and then the amplification performance and life of electronic tubes will be affected. Therefore, ultrapure water will be used to prepare the liquid. In the production of picture tubes and cathode-ray tubes, the inner wall of the fluorescent screen is coated with a layer of fluorescent material by spraying or precipitation, which is made of phosphor particles composed of zinc or other metal sulfides and bonded with potassium silicate. Its preparation requires ultrapure water. If the copper content in the ultrapure water is more than 8 ppb, it will cause luminescence and discoloration; If the iron content is above 50ppb, the luminescence will change color, darken and flash jump; Containing organic colloids, particles, bacteria, etc., will reduce the intensity of the fluorescent layer and its adhesion to the glass shell, and will cause waste products such as bubbles, streaks, and light leaks. In the 12 processes of the production of black and white picture tube fluorescent screen, five processes, such as glass shell cleaning, precipitation, wetting, film washing, and neck cleaning, need to use ultrapure water. 80kg ultrapure water is required for each picture tube production. The LCD screen needs to be cleaned with ultrapure water and prepared with ultrapure water. If there are impurities such as metal ions, microorganisms and particles in the ultrapure water, the LCD circuit will malfunction, affect the quality of the LCD screen, and lead to waste and defective products.

In the production of transistors and integrated circuits, ultrapure water is mainly used to clean silicon wafers, and a small amount is used for liquid medicine preparation, water vapor source for silicon wafer oxidation, cooling water for some equipment, electroplating solution preparation, etc. 80% of the processes in the production process of integrated circuits need to use ultrapure water to clean silicon wafers. The quality of water is closely related to the product quality and production yield of integrated circuits. Alkali metals (K, Na, etc.) in water will cause poor withstand voltage of insulating film, heavy metals (Au, Ag, Cu, etc.) will reduce the withstand voltage of PN junction, Group III elements (B, Al, Ga, etc.) will worsen the characteristics of N-type semiconductor, Group V elements (P, As, Sb, etc.) will worsen the characteristics of P-type semiconductor, and phosphorus (about 20-50% of ash) after high-temperature carbonization of bacteria in water will change local areas on the P-type silicon chip into N-type silicon, resulting in device performance deterioration, If particles in water (including bacteria) are adsorbed on the surface of silicon wafer, they will cause short circuit or poor characteristics.