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On-line Monitoring of Metallic Contamination in Silicon


Future ULSI microelectronics technology will demand significant improvements in the purity of starting materials, quantification of contamination due to wafer handling systems and monitoring of impurities introduced during semiconductor fabrication process steps. Contamination in device manufacturing can be traced to a number of sources including foreign particles, trace metals, organic films and residues, hydrogen, halogens and other interfering substances. In particular, it is widely known that the presence of metallic contaminants such as sodium and aluminium, and heavy metals such as iron, copper, nickel and chromium are harmful to device yield, pertormance and reliability. A survey [1] by the JAPAN Electronics Industry Development Association (JEIDA) has stressed that the upper limits of trace metals acceptable in ULSI processing appears to be < 101 atoms/cm2 of heavy metals (Fe, Cr, Ni, Cu and Zn etc.) and 1011 atoms/cm2 of aluminium. These are extremely low levels - fewer than one part per trillion in the hulk. The recently published US Semiconductor Industry Association (SIA) roadmap, January 1995, has placed even more stringent conditions on allowable metallic contamination concentrations in silicon wafers for 0.18um geometry ULSI devices and beyond with Fe, Ni, Cu and Zn limited to below S E9 atoms/cm2. Traditionally, for analysis of metallic impurities, techniques such as atomic absorption spectroscopy (AAS) combined with vapour phase decomposition (VPD) have been employed. However, in order to monitor on-line metallic contamination in silicon, new analytical strategies are required and in particular the development of novel in-line monitoring tools. Recently.
research has focused on the development of photo-generated minority carrier electrical techniques and in particular the Flectrolytic Metal Tracing (ELYMAT), surface charge analyser (SCA) and microwave photoconductivity decay (#-PCD) instruments in response to this industrial prohlem.
The goal of this project is the development of a comprehensive measurement methodology tor the determination of extremely low levels (ppb or less) of impurities in silicon using novel analytical techniques. The specific project objectives are; to enhance the measurement capabilities of the ELYMAT, SCA and p-PCD measurement techniques on a wide range of sample types, calibrate these measurement tools vis a vis wafers with known amounts of contaminants with the aim of developing a comprehensive measurement methodology and finally propose this measurement methodology to CENELEC for adoption.
To achieve these objectives the project consortium comprises three partners from three member states of the E.U.; a silicon wafer manufacturer, an instrumentation manufacturer and analytical services laboratory and a microelectronics research centre.
This project is strategically important to enhance the competitive position of the European microelectronics industry and the analytical equipment sector. The successful completion of this project will result in the following three achievements; the t`abrication and characterisation of reference samples, the development and quantification of innovative measurement techniques for monitoring of metallic contamination and the elaboration of a new European standard for measurement of metallic contamination in silicon wafers. It is now recognised that high technology based European industries in automotive, aeronautics, consumer electronics, computers and bioengineering have all become critically dependent on silicon based microelectronics for their continued success on world markets. The OMMCOS project has therefore the potential to significantly enhance microelectronics competitiveness in European through ensuring access to and qualification of suitable starting silicon wafers. The direct multisectorial benefit to European industry is evident. Keywords: On-line Monitoring, Metallic Contamination, Non-destructive Analytical Techniques, Measurement Methodology


National University of Ireland, Cork
Prospect Row
30 Cork

Participants (2)

Gemetec Gesellschaft fuer Messtechnik und Technologie Mbh
10A,geretsrieder Strasse
81379 Muenchen
Viale Gherzi 31
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