Articles

Year Materials Info Company Author Tags View
2019
On-line measurement of total active ions at sub-PPB levels using advanced resistivity algorithms
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.
CT Associates; GF Signet Gary van Schooneveld; John Yates; Kelvin Frazier; Steven Wells Chemicals; Ultrapure Water View
2019
Profiling nanoparticles down to 10 nm in a UPW polishing system by two different particle counters
Nanoparticle contamination of ultrapure water (UPW) for microelectronics fabrication is expected to significantly decrease the yield and reliability of semiconductor devices. Tight nanoparticles control poses a technical and analytical challenge, especially in the particle size range down to a few nanometres. Most state-of-the-art online particle counters do not address the needs of advanced microelectronics manufacturing with critical particle sizes below 20 nm. Therefore, understanding of sources of nanoparticle contamination and strategies for control is limited. This study aims to profile nanoparticles ≥10 nm in a full-scale UPW polishing system after each process step using two novel particle measurement systems: an optical particle counter and an acoustic particle counter. For the first time, the performance of a whole UPW polishing system, including a reverse osmosis unit in terms of particle rejection, was investigated. Both particle counter instruments were evaluated with positive results. A statistical analysis was carried out to compare the significance of the particle counts achieved by the two different detection principles. Profiling throughout the UPW polishing system revealed that both instruments measure particle concentrations in the same range. The data is consistent and shows a clear trend: ion exchange mixed bed, reverse osmosis and ultrafiltration remove particles and represent sinks for nanoparticles ≥20 nm. The removal of nanoparticles between 10 nm and 20 nm is limited in this case however, especially for the final ultrafiltration. Scanning electron microscopy (SEM) with elemental analysis demonstrated that the particle chemistry was diverse. This indicates that different particle chemistries and particle properties might have influenced the particle counts. The results contribute to the advanced understanding of nanoparticle behaviour in UPW and provides more confidence in terms of monitoring at the lower particle range. This article was originally published in the Ultrapure Micro Journal in March 2019.
Ovivo; Micron; Philippe Rychen; Deena Starkel; Pia Herrling; Keanan Cassidy Ultrapure Water; Particles; Monitoring & Metrology View
2019
Industry Collaboration and SEMI Standards to enable IC manufacturing for advanced nodes
The complexity of integrated circuit (IC) manufacturing for advanced nodes, paired with the growing demand for higher yields and lower defectivity, requires close alignment among industry stakeholders. New systematic improvements of system design, material choice and quality assurance methodologies are needed to minimise every possible source of contamination and variation in the manufacturing process. An extensive collaborative effort between SEMI Standards Task Forces and IRDS roadmap teams, representing the IC manufacturing supply chain, is focused on developing industry best practices to enable proactive yield management. As a result, relevant SEMI Standards are being revised to focus on the quality of UPW and liquid chemicals, design and operation of related systems, qualification of polymer assemblies and process critical materials and components. This article was originally published in the Ultrapure Micro Journal in March 2019.
SEMI Bob McIntosh; Inna Skvortsova Yield; Process Control; Standards; Ultrapure Water; Chemicals View
2018
Development of H₂O₂ monitor most suitable for UPW polishing system
A newly developed H2O2 monitoring method is capable of continuous measurement without using chemical reagents but catalase-resin instead. This technology also makes it possible to measure H2O2 that is generated in a UV-ox (ultraviolet oxidizer) without interference. This study was conducted to support an ultrapure water (UPW) polishing system, and to compare existing H2O2 monitoring procedures with the new technology. This article was originally published in the Ultrapure Micro Journal in February 2018.
Nomura Micro Science; Yukio Noguchi Monitoring & Metrology; Cleaning & Polishing; Ultrapure Water View
2018
Simulation of metal contamination in wet cleaning of doped silicon wafer
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.
Sumco USA Drew Sinha Cleaning & Polishing; Ultrapure Water View
2017
Investigation of the behaviour of 10 nm particles and systems for reducing particles to produce ultrapure water
In recent years, with the development of the semiconductor manufacturing process, ultrapure water (UPW) used to wash semiconductor devices have required high purity. In particular, particles in UPW are strictly controlled. Our 10 nm SEM analysis can measure 10 nm particles, which was previously impossible. This article presents the results of measuring 10 nm particles in the existing ultrapure water system. We clarified the behaviour (including generation sources and compositions) of 10 nm particles in ultrapure water systems in order to optimize and enhance. This article was originally published in the Ultrapure Micro Journal in November 2017.
Organo; Fumitaka Ichihara; Hiroshi Sugawara; Masami Murayama; Kyohei Tsutano; Ultrapure Water View
2017
Using Particle Scout™ for testing filters
This article deliberates how it has become possible to test any microfine filter in real time, and in its actual conditions of use. For such testing to be possible it is vital to be able to obtain two particle-counting instruments matched for particle detection over a range of particle sizes. This attribute of matched detection appears to be possible with the acoustic method of detecting particles, and not commonly available with optical particle counters. This article was originally published in the Ultrapure Micro Journal in November 2017.
Unicopiers Sameer Madanshetty Particles; Ultrapure Water; Monitoring & Metrology View
2017
Characterizing the retention of UPW filters using enhanced SEMI C79 testing
Particles in ultrapure water (UPW), used during the manufacture of microcircuits on semiconductor wafers, can deposit onto the wafer surface thereby causing decreased yield and reliability of the microcircuits. As microcircuit future sizes continue to decrease, understanding the ability of a filter to capture and retain these particles becomes increasingly important and challenging. In 2013, SEMI C79-0113, “Guide to Evaluate the Efficacy of Sub-15 nm Filters used in Ultrapure Water (UPW) Distribution System” was published. This document provides a SEMI recommended method for evaluating the efficacy of filter elements used to remove particles in UPW fluid streams. Since the release of this guide, the method has been enhanced to allow quantification of particle retention over a broad size range. This was accomplished by adding larger silica particles to the Ludox® SM30 silica specified by SEMI C79 resulting in a poly-dispersed silica challenge. A particle size distribution (PSD) slope of -2 (log-log) was selected so the challenge would more closely mimic a PSD typically found in UPW, yet still have sufficient large particles to measure a log retention value of 2 or 99% retention. This silica challenge has been designated as an “area-weighted challenge”. The use of this enhanced method has resulted in some interesting observations including indication of a most penetrating particle size similar to what is observed in gas filtration. The presence of a most penetrating particle size would indicate that retention mechanisms other than sieving are active, particularly for particles smaller than 30 nm. This paper will review the enhancements made to the test method, review the retention data from a number of filter types and manufacturers, and discuss the implications for filters used in UPW. This article was originally published in the Ultrapure Micro Journal in November 2017.
CT Associates; W L Gore & Associates; Gary van Schooneveld; Don Grant; Kevin Cresswell; Mark Litchy; Uwe Beuscher Ultrapure Water; Particles View
2017
Challenges and opportunities for particle control in advanced semiconductor manufacturing
This article provides an overview of the biggest challenge of UPW technology – particle control. The latest semiconductor technologies require near particle-free water, where the “killer” particle size is far below the size that UPW metrology can effectively detect. Also, current advanced treatment methods cannot guarantee reliable removal of killer-sized particles. The quality of the high-purity materials used downstream of the final filters has not typically been tested for shedding of the “killer” particles. Consequently, the semiconductor industry requires a comprehensive approach for the particle control. A new approach should include mitigating particle occurrence and continuously improving the technologies used in UPW polish and distribution systems. Such an approach should also include extensive use of SEMI standards to improve the quality of the materials used; a new way to engineer solutions related to system-configuration and system design; improved process control; and a careful review of critical operational decisions. Collaboration throughout the industry via IRDS and SEMI Standards is key to enabling such systematic improvement, and overcoming the metrology and other constraints. This article was originally published in the Ultrapure Micro Journal in November 2017.
Kanomax FMT; FTD Solutions; Samsung Austin Semiconductor; Slava Libman; Dan Wilcox; David Blackford Ultrapure Water; Particles View
2017
Review of Nanoparticles in Ultrapure Water
Ultrapure water (UPW) is one of the main materials for electronics fabrication and therefore, it needs to be monitored for critical parameters such as nanoparticles (NP). The state-of-the-art online measurement techniques are challenged by particles at the killer particle sizes smaller than 10 nm. Due to the uncertainties in NP detection, the identification of NP sources and sinks in UPW system is limited nowadays. This review article aims to give an overview on the current developments and perspectives in metrologies for detection and control. The following topics will be discussed: transferability of general definition of NP to UPW, state-of-the-art particle analytics, sources and sinks of NP in UPW systems as well as dominant particle interactions responsible for NP contamination. This article was originally published in the Ultrapure Micro Journal in November 2017.
Ovivo; Philippe Rychen; Pia Herrling; Monitoring & Metrology; Particles; Ultrapure Water View