New Method of Purification of HF Chemicals for Very Large Scale Integration Manufacturing

Abstract

Metallic impurities having a lower ionization tendency than Si, such as Cu, are adsorbed onto the surface of the silicon substrate in hydrofluoric acid (HF) chemicals and buffered hycirofluoric acid (BHF) and then degrade device characteristics. A new purification method using a granular polysilicon (poly-Si) as an adsorbent was designed to remove the metallic impurities. As an adsorbent, Au deposited poly-Si (Au-poly-Si) was developed to improve the Cu removal efficiency of the poly-Si, and Au removed Au-poly-Si (Au-R-poly-Si) was also developed to prevent Au contamination from the Au-poly-Si. These poly-Si were more promising for HF than for BHF because of the difference in the etching rate of the silicon. The purification system using the Au-R-poly-Si was investigated using a 36 day running test. This system shows sufficient performance and reliability for reprocessing HF in a wet station at point-of-use. This purification method makes it possible to lengthen HF lifetimes and decrease the amount of HF used in very large scale integration manufacturing.

Point of Use HF Purification for Silicon Surface Preparation by Ion Exchange

“…7: a cumulative amount of 300 ppb corresponds to a bath concentration of 1.5 ppb). Equation 11can also be written as C [12] eq bSa where n,,10 is the total amount of impurity poured into the bath. This equation presents the advantage of highlighting the parameters affecting the impurity concentration in solution after purification.…”

“…Several purification techniques have already been applied to HF such as ion exchange,°1 reverse osmosis,1' and metal displacement. 12 Interesting results have been obtained with all of these techniques. However, there is still a lack of quantitative data to compare them.…”

Purification of dilute hydrofluoric acid by commercial ion exchange resins

“…Yamamoto et al [11] showed that Cu impurities contained in spent VLSI HF solutions can be adsorbed in gold deposited granular poly-silicon adsorbents. Laboratory data show that working with 4.9% HF Cu level can be reduced from 50 ppb to less than 0.01 ppb (g/L).…”

Metal Ions Removal from Organic Solvents using MXene-Based Membranes

“…12 Among these, PGMEA and PGME are predominantly used as solvents for photoresists and antireflective coatings. To purify these solvents, technologies such as ion exchange, 13 reactive distillation, 14 liquid−liquid extraction, 15 adsorption, 16 and membrane separation 17 are presently employed. Among these technologies, membrane-based separation was found to present fewer operational challenges.…”