AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
DMA Size-Selection and Electrostatic Deposition of Particle Size Standards down to 10nm
BENJAMIN HUNT, William Dick, Zeeshan Syedain, MSP Corporation
Abstract Number: 129 Working Group: Instrumentation and Methods
Abstract Particle deposition system (PDS) tools deposit particles of known size and count on substrates encountered in the semiconductor industry including silicon wafers and reticles (photomasks). Typically, particle size standards such as PSL spheres are deposited to create standards for calibrating inspection tools, such as the laser-based scanning surface inspection system (SSIS). Particle size standards are typically classified with a DMA before they are deposited to eliminate residue particles and minimize agglomerates of monomers. The DMA is also used for measuring the peak diameter and width of the size distribution of the particle size standard via mobility scanning. The operator can specify any particle size for selection by the DMA and subsequent electrostatic deposition, but the deposited size may not be accurately known if the selected size is substantially different than the measured peak diameter. With the next generation of PDS tools slated to achieve sizing accuracy of ±0.5nm and repeatability on the order of ±0.1nm for deposited particle size ranging from 10nm to 50nm, the need for accurate prediction of the size distribution entering the deposition chamber is evident. Such a prediction requires knowledge of the particle size distribution immediately after atomization and the DMA transfer function and therefore requires inversion of the mobility scan of the size standard. The methods of Twomey and Markowski are used to invert the mobility scan data. A means of predicting the diameter shift due to off-peak diameter selection is proposed. This allows the operator to determine the DMA voltage that would result in the desired peak diameter being deposited. The method is tested by deposition of particle size standards on silicon wafers and subsequent inspection with a commercial SSIS tool.