Implementation of a system for metal contamination control based onclassification criteria

摘要

Recent years have seen a diversification of materials that are used in micro-electronic devicefabrication. Initially, the materials were limited to silicon, silicon oxide and silicon nitride.ormetallization, aluminum was used. Metal silicides were introduced to lower contact resistance.Later, TiN barriers and W plugs were used, followed by copper metallization and low-x dielectrics.Currently the very heart of the memory cell and the transistor are being replaced by metallic oxidesand metal gate electrodes.While these materials improve device performance, they may also be detrimental contaminants ifthey are unintentionally present in sensitive device regions. Consequently, contamination controlhas become increasingly complex. Both substrate cleaning and contamination metrology face anexpanding range of contaminants and substrate materials. In addition, the specifications forallowable contaminant concentrations are being decreased continuously. In order to makecontamination control more manageable, common practice is to distinguish between groups ofcontaminants. The most common classification system for contaminants is based on the detection methods that areused. The following types of contamination are discerned: metallic contamination (usually detectedusing Total Reflection X-Ray Fluorescence, Inductively Coupled Plasma – Mass Spectrometry etc.),particle contamination (detected by light scatter tools), airborne molecular contamination (Ion MassSpectrometry, Capillary Electrophoresis), and organic contamination (Thermal Desorption – MassSpectrometry). Obviously, some contaminants may fall in more than one category. Therefore itshould be realized that a classification system is always artificial and a simplification of reality.For the control of metallic contamination in IMEC's pilot line, a dedicated classification system wasdeveloped. It allows the controlled introduction of new materials in an advanced researchenvironment, while minimizing the possible impact of contaminants.