Leveraging Advanced Analytical Techniques and Productive Data Processing Tools to Address UPW Challenges

In water treatment history, the problem of increased concentration of disinfection byproducts (DBPs) started to emerge in the early 1900s. This is when chlorine (and ozone) started to be applied as primary disinfection agents for drinking water. A reaction of the disinfection agent with organic compounds present in water often leads to the formation of various types of DBPs. Throughout the years, with a growth in awareness around the negative impacts of DBPs on human health, previously underutilized DBP removal technologies gained importance while new ones have also been developed.

Roundtable handout from February Community Event

This presentation was given as part of the Ultrapure Micro 2021 annual conference. It was given as part of the ultrapure water strand.

This presentation was given as part of the Ultrapure Micro 2021 annual conference. It was given as part of the ultra high purity chemicals strand.

This presentation was given as part of the Ultrapure Micro 2021 annual conference. It was given as part of the ultrapure water strand.

The main objective of wet cleaning a silicon wafer is to achieve a wafer surface free from contaminants such as particles, heavy metals, organic residues, mobile ions and oxides. Furthermore, wafer surface roughness and surface termination are becoming critical as semiconductor device geometry continues to shrink. A large amount of high-purity DI or ultrapure water (UPW) with chemicals is used during wet cleaning of a silicon wafer to remove contaminants from wafer. The wet cleaning process includes a number of individual process steps operating in sequence to remove these impurities. The primary objective of this paper is to develop an understanding of the adsorption of metallic impurities from each of these process steps and their removal by the subsequent step. Experimental simulation of metal deposition during post CMP cleaning of a silicon wafer is carried out by measuring the amount of deposited metal from a metal-contaminated chemical bath. In a similar manner metal removal by a clean chemical bath is determined by measurement of the surface metals on a wafer, following the processing in a metal-contaminated bath. This investigation provides information on the behavior of metal adsorption and metal desorption from chemical baths containing multiple metals. Both P-type and N-type wafers with different doping levels were used in order to evaluate the effect of doping on adsorption and desorption process. The metal adsorption and desorption are discussed in relation to solution pH and the nature of metal ions involved. This simulation was performed to gain a better understanding of the adsorption/desorption behaviour of metal ions in a multi-metal environment and can be used for the determination of acceptable contamination tolerance for the incoming wafer and permissible contamination levels for each cleaning step of a front-end line (FEOL) wet cleaning process. This article was originally published in the Ultrapure Micro Journal in February 2018.

The ability to conduct current through a liquid is measured by conductivity and can be related to the concentrations of ions in the solution. In this work, a patented analytical technique is used to quantify the contaminant level of specific chemicals in an on-line ultrapure water (UPW) system. The method uses a resistivity system with additional mathematical techniques to exploit the physical relationship between temperature and resistivity. This method utilises the slope between resistivity/temperature curves and not the absolute resistivity. The theoretical conductance of chemicals is compared with experimentally-measured values from 1 parts-per-trillion (ppt) to 10 parts-per-billion (ppb). This work helps establish the characteristics of compounds that can be measured with this technique and determines the limits of detection, and therefore has a potential commercial application. High conductance compounds like sodium chloride and potassium hydrogen phthalate are measurable at the 100 ppt level while low conductance compounds like boric acid cannot be discerned from the background. As the method matures into a product the limits of detection should be lowered. This article was originally published in the Ultrapure Micro Journal in March 2019.

This Q&A session took place at the 2020 Ultrapure Micro annual conference. It was a part of the Ultrapure Water Production track, and included speakers from the UPW Process Optimization session.

This presentation was given at the Ultrapure Micro 2020 annual conference. It was presented in the Ultrapure Water Production track, as part of the Wafer Contamination Control - Particles Monitoring session.

This presentation was given at the Ultrapure Micro 2019 annual conference. It was presented during the Learning Series, as part of the Ultrapure Water Production track.