Particle Society of Minnesota Fall/Spring 

Luncheon Speaker Series for 2004/2005

Over the Fall and Spring of 2004 / 2005, the Particle Society presented several talks on a broad range of particle science topics during the noon hour. All members of the Particle Society were invited to join us for lunch and an interesting particle science presentation.

Luncheon Speaker Series, June 8th, 2005.
Title: Particle Characterization Techniques for Submicron and Supermicron particle size ranges.
Speaker: Tim Johnson, of TSI Incorporated.

ABSTRACT:
To effectively measure aerosol size distributions in both the submicron and supermicron size ranges, different size characterization techniques are needed for detecting submicron and supermicron particles. This talk will discuss two high size resolution techniques that are commonly used.

For sizing submicron particle sizes electrical mobility techniques have been used for about 40 years. The first instrument to use this technique was the Whitby Aerosol Analyzer which was soon replaced by physically smaller version called the Electrical Aerosol Analyzer (EAA). Current systems use a component called a Differential Mobility Analyzer or DMA to select out a narrow size distribution from the sampled aerosol and a Condensation Particle Counter (CPC) to count the particles. This system is called a Scanning Mobility Particle Sizer™ (SMPS) spectrometer and the technique is to scan the voltage going to the DMA so that the size that gets out changes continuously and the counts measured by the CPC are correlated with the different sizes to create a size distribution.

For sizing supermicron particle size particles the aerodynamic particle size is the parameter that is measured. The instrument that will be described is the Aerodynamic Particle Sizer (APS). The technique used is a time-of-flight measurement where particles are accelerated and the time it takes to cross two laser beams is directly related to the particles aerodynamic size. The current version of this instrument can detect particle coincidence (multiple particles in the optical sensing volume at the same time) to prevent some of the errors that can occur with other optical sizing techniques.

Bio:
Tim has a Bachelors degree in Physics from Macalester College in St. Paul Minnesota. He has worked at TSI Incorporated for over 26 years and has worked with the Particle Instrument products for over 15 years where he is a Senior Application Engineer.

Luncheon Speaker Series, May 4th.
Title: Particle and Aerosol Technology In Semiconductor Integrated Circuit Device Manufacturing
Speaker: Benjamin Y. H. Liu
Regents' Professor Emeritus, University of Minnesota; President, MSP Corporation

Abstract:Aerosol particles are generally known for their harmful or detrimental effects on air quality, health, and loss of product yield or quality due to contamination. This seminar focuses on some beneficial use of aerosol particles in the semiconductor industry.

One aspect of the problem related to the need for an accurate particle size standard for wafer inspection. Wafer surface inspection by laser light scattering is itself used to detect particulate contamination of the wafer, which is the single largest cause of product yield loss in the $ 200 billion semiconductor industry. By providing a precise and accurate calibration tool for the laser scanning device, the industry is able to use the laser scanner as a precise tool to detect and measure contaminants on the wafer, therefore, improving the product yield. This seminar discusses wafer inspection and contamination control in semiconductor device manufacturing and the development of a NIST-traceable calibration standard for the semiconductor industry.

Another aspect of the talk relates to the challenge in making semiconductor device films with precursor chemicals that are mostly in liquid form. Films as thin as 30 Angstrom are now used in memory chip devices. Such films are now being made by the atomic layer deposition (ALD) process. In ALD, the films are formed one layer at a time. Since each atomic layer is about 1.0 ? in thickness, to make a 30 ? film, the ALD process must be repeated 30 times. Because the liquid chemical are easily damaged by heat, a gentle vaporization process must be developed to produce vapor on demand without thermal decomposition and material degradation. The approach to liquid vaporization involving an aerosol process is described and discussed in this seminar.

Luncheon Speaker Series, January 20th: Particle Measurement and Filtration in Liquids
By: Mark Litchy, CT Associates, Inc.

Abstract: This presentation will provide a broad overview of the factors affecting particle measurement and control in liquids. A brief discussion of particle measurement techniques in liquids and the factors that affect the measurements will be presented. Factors discussed will include particle and medium refractive indices, optical measurement techniques, sampling pressure, and coincidence.

Factors affecting the efficacy of particle removal from liquids such as filter pore size, filter type and material, particle loading, and the effect of flow stoppages will be covered. Particle capture mechanisms will be discussed and compared to removal mechanisms in aerosols.

Finally, particle control in liquid handling systems will be presented. The effects of stabilized distribution, particle shedding from components, and other factors affecting the cleanliness of process liquids will be addressed.

Speaker Bio: Mark Litchy works as an R&D engineer for CT Associates, Inc. in Bloomington, MN. He has several years of experience in particle measurement and control in high purity liquid chemicals and gases, surface contamination, and CMP slurry characterization. He has an MS in Mechanical Engineering from the University of Minnesota and a BA in Physics from St. John's University. He has authored or co-authored more than 15 publications and presentations.

Click here to see a copy of the presentation given by this speaker. Note, you must have Acrobat Reader installed on your computer to read this file. This is a large file, and will take some time to open.

Luncheon Speaker Series, November 9th: Size Segregated Aerosol Charge Measurement with Electrical Low Pressure Impactor (ELPI).
By: Tyler Beck, of Particle Instruments LLC.

Abstract: The charge state of aerosol particles is an important parameter to consider when calculating lung deposition, filter collection efficiency, transport efficiency and other aerosol behavior. Charge measurements are not often made however, in part due to a lack of suitable instrumentation for this purpose.

Recently, methods of using the Electrical Low Pressure Impactor (ELPI) for size segregated aerosol charge measurement have been developed. The ELPI combines inertial size separation with electrical detection to produce real-time aerosol size distributions from 0.007 to 10µm. By comparing measurements made with the instruments charger on and off the average net charge per particle can be determined for each of the ELPI's size channels.

A description of this measurement technique as well as examples of particle charge data will be presented.

Copyright 2006, Particle Society of Minnesota