October 2008 Issue

  October 2008
Journal of the IEST



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Peer-reviewed technical papers:
Optimal Utilization of Test Facilities to Replicate Operational Environments
Control of Time-Dependent Contamination during Bonding of Semiconductor and Optical Substrates
Health and Usage Monitoring Algorithm Based on Terrain Identification for Mechanical Components on an Army Ground Vehicle System
Accelerated Life Test Modeling of Outdoor Optical Products with Time-Varying Multi-Stresses
Higher Yield and Quality through Particle Identification

Complimentary
Tech Talk articles:
IEST Leads ISO 14644 Experts in Focus on Nanotechnology in Cleanrooms
Nanotech Facility Hosts ESTECH Tour

The following two Tech Talk articles are accessible free of charge (access Journal of the IEST).

IEST Leads ISO 14644 Experts in Focus on Nanotechnology in Cleanrooms
IEST has again taken a leadership role in ISO Technical Committee 209 Cleanrooms and associated controlled environments as the committee begins developing standards for the nanoscale.

Nanotech Facility Hosts ESTECH Tour
As part of a focus on nanotechnology, ESTECH 2008 offered attendees the opportunity to tour the state-of-the-art Birck Nanotechnology Center (BNC) at Purdue University. The tour group spent a day exploring cleanrooms and research laboratories in the $58-million,
186,000-square-foot facility.

The October 2008 issue also contains peer-reviewed technical papers related to the fields of contamination control; design, test, and evaluation; and product reliability. IEST members and Journal of the IEST subscribers have full access to technical papers in the current issue as well as a 23-year archive of technical papers. Others may obtain full-text abstracts of peer-reviewed technical papers and have the option to purchase individual papers (access Journal of the IEST).

Optimal Utilization of Test Facilities to Replicate Operational Environments
Timothy W. Hoy, U.S. Army Aberdeen Test Center
Jeffrey W. Herrmann, Department of Mechanical Engineering, University of Maryland

Useful system endurance tests require operating a system in settings similar to operational environments. However, existing test facilities may not be good replicas of the operational environment, especially for systems with long life cycles that are being used in new and unforeseen situations. Because constructing new test facilities can be expensive and time-consuming, it is desirable to use the existing test infrastructure to replicate the operational environment as closely as possible. This study presents an optimization model that determines the most appropriate amount of testing to conduct using each existing test facility. A multi-objective model is also presented, and the application of this work to two military vehicle tests is discussed.

Control of Time-Dependent Contamination during Bonding of Semiconductor and Optical Substrates
Iqbal (Izzy) Bansal, ASML Corporation

Microcontamination control is a key parameter for enhancing yield in terms of density of voids within the interface of a bonded wafer. One important cause of void density is time-dependent haze (TDH) or surface-particulate defect density. TDH on silicon surfaces is generated by the interaction of organic volatiles with moisture on the silicon surfaces. Sub-micrometer particle defect density, or haze level, is mainly affected by contamination arising from five factors: people, process, equipment, environment, and processing chemicals and gases.

Direct wafer bonding (DWB) is a three-step sequence consisting of ultra-clean surface preparation, contacting, and thermal annealing. Contacting is an operation of ultrafine alignment and face-to-face joining of two substrates. Prior to joining, each contacting substrate is chemically cleaned in order to minimize surface haze and particulate contamination. Both sub-micrometer particle density and surface haze can be greatly reduced by point-of-use (POU) microfiltration and purification of deionized (DI) water as well as application of ultra-dilute concentration of ultra-pure chemicals containing extremely low levels of liquid particle counts. Ultra-pure DI water is filtered with a high-efficiency membrane filter that removes particles down to 0.02 micrometer (µm), thus reducing metal ions to sub-parts-per-billion (ppb) levels. As a result, surface haze and sub-micrometer light-point defects density on a contacting surface are minimized to reduce the density of voided or disbonded regions. A 1-μm particle, for instance, can cause a void as large as 1 centimeter (cm) in diameter during the bonding operation. Data is presented in terms of fractional areas of the voided regions for direct silicon wafer-bonded substrates.

In addition to semiconductor wafer substrates, surface contamination is discussed for optical substrates such as fused silica. Minimizing microcontamination and TDH on the surface of optical substrates is important in maximizing ultraviolet (UV) transmission rates at wavelengths between 190 and 250 nanometers (nm). Methods and techniques are recommended for minimizing trace levels of surface contamination to improve UV transmission rates. No data for bonding of optical components is included in this study.

Health and Usage Monitoring Algorithm Based on Terrain Identification for Mechanical Components on an Army Ground Vehicle System
Richard Heine, United States Army Materiel Systems Analysis Activity
Donald Barker, University of Maryland

The desire for enhanced functionality of Army vehicle systems has resulted in increasingly complex systems. This drive is in direct contention with another Army goal of improved reliability. Health and usage monitoring systems (HUMS) and remaining-life prognostics are being developed to address these conflicting goals. One of the major challenges of applying a HUMS to an Army wheeled vehicle system is that the development and per unit cost of the HUMS needs to be relatively low in comparison with typical high-cost applications such as aircraft. Simplified algorithms that derive terrain exposure from a basic set of sensors and estimate fatigue damage accumulated on components where loading comes primarily from terrain have been developed to meet this need. Various inputs and statistical parameters are evaluated for this model based on accuracy of terrain identification and quality of fatigue prediction on an example component. The generalized process and recommendations for application of this model to military ground vehicle systems are discussed.

Accelerated Life Test Modeling of Outdoor Optical Products with Time-Varying Multi-Stresses
Chung F. Lam, Avanex Corporation
Huairui Guo, ReliaSoft Corporation

The long-term performance prediction of optical products deployed outdoors is important. The accuracy of the prediction directly affects warranty cost calculations. In indoor environments, products are generally operated under controlled temperature and humidity. However, products outdoors usually experience multiple stresses that continuously vary with time. An outdoor-use optical product, such as a fiber distribution hub cabinet with splitters, connectors, and fan-outs built in, will experience temperature cycling effects and varying humidity. Therefore, time-varying temperature and humidity are considered as major stresses acting on outdoor-use optical products. This study proposes a practical method that uses design of experiment (DOE) techniques and generalized log-linear (GLL) life-stress relationship to predict the life of outdoor optical products. The proposed method can consider the cumulative damage caused by time-varying temperature and humidity and was applied to predict the warranty return of an outdoor optical product.

Higher Yield and Quality through Particle Identification
O. Valet and M. Lankers, Rap.ID Particle Systems

The sources of particulate contamination are often not easy to identify. To control manufacturing processes, the measurement of particle concentration and size is necessary and has been routinely performed for many years. Technology has been developed to increase the information available for the immediate evaluation of particles. The method analyzes airborne particles or particles isolated from liquids automatically according to their number, size, and chemical composition. The analysis of thousands of particles enables users to locate the major sources of contamination in various manufacturing processes.

The analytical tool provides rapid determination of particulate contamination, thus allowing for a quick, efficient response. Over time, the ability to compare analytical result data sets assists in detecting trends and implementing the appropriate quality management. Routine use of the technology contributes to ongoing supervision and optimization of production processes. This study reports on the use of the technology to analyze foreign particles associated with oral, inhalable, and nasal drug products (OINDP), parenterals, and coronary stents. Applications for troubleshooting and identifying latent contamination sources are discussed through several examples.

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