Jennifer A. Sees

Copper Deposition on HF Etched Silicon Surfaces: Morphological and Kinetic Studies

The kinetics and morphologies of Cu deposition on HF-treated silicon surfaces were investigated by atomic force microscopy (AFM), inductively coupled plasma mass spectroscopy (ICP/MS), and graphite furnace atomic absorption spectroscopy (GFAAS). The early stage (<60 s) of Cu deposition, as characterized by AFM, was found to be dominated by the nucleation of nanometer-sized Cu nuclei on HF-treated silicon surfaces. After 60 s of Cu deposition, the total grain number of Cu deposits was leveled to a constant plateau. However, a significant grain size increase of deposition Cu nuclei was noticed. We employed an AFM volume-integration technique in conjunction with the ICP/MS and GFAAS measurements to demonstrate that the Cu deposition rate was limited by the diffusion of Cu 2+ ions across the stationary solution layer toward the silicon surface.

TXRF Analysis of SC‐1 Treated Silicon Wafers

Silicon wafer cleaning is the most frequently applied processing step in the integrated circuit manufacturing sequence. This process is intended to remove several different types of contaminants, among them particles, metallics, and organics. It has been estimated, however, that over fifty percent of yield losses in integrated circuit manufacturing are caused by contamination remaining on the surface of silicon wafers after cleaning. It is the object of this article to document the effects of using improved, ultrahigh purity chemicals on silicon wafer surfaces as measured by total reflection x-ray fluorescence, TURF. During this study, silicon samples were cleaned with standard grade chemicals and ultrahigh purity chemicals, and metallic impurities were then measured with TURF. It was found that the use of ultrahigh purity chemicals substantially reduced the amount of surface contamination present on wafer surfaces after cleaning

A New Potentiometric Sensor for the Detection of Trace Metallic Contaminants in Hydrofluoric Acid

Detection of ultratrace levels of metallic ion impurities in hydrofluoric acid solutions was demonstrated using a silicon-based sensing electrode. The sensors operation principle is based on direct measurements of the silicon open-circuit potential shift generated by the charge-transfer reaction between metallic ions and the silicon-based sensing surface. For instance, the silicon-based sensor is capable of detecting parts per-trillion to parts-per billion level of Ag + ions in HF solutions with a detection sensitivity of ca. +150 mV shift per decade change of [Ag + ]. The new sensor can have practical applications in the on-line monitoring of microelectronic chemical processing.

Ultrapure water quality monitoring by a silicon-based potentiometric sensor

A solid state silicon-based potentiometric sensor and a resistivity sensor were employed to monitor the water quality from an ultra-pure water production unit. A minute ionic impurity increase (at the low ppt level), which was not detectable by the conventional water resistivity sensor, can be sensitively detected by the silicon-based sensor. This slight degradation of water purity, independently confirmed by inductively coupled plasma mass spectrometry and atomic force microscopy, was attributed to early boil-off from the saturated water purification cartridge. The silicon-based sensor can potentially function as an ultra-sensitive monitoring sensor in conjunction with the conventional resistivity sensor to ensure water purity at parts per trillion level.