Winson Taam

A note on multivariate capability indices

In manufacturing industry, there is growing interest in quantitative measures of process variation under multivariate setting. This paper introduces a multivariate capability index and focuses its applications in geometric dimensioning and tolerancing. This index incorporates both the process variation and the process deviation from target. Two existing multivariate indices are compared with the proposed index.

Detecting Spatial Effects From Factorial Experiments: An Application From Integrated-Circuit Manufacturing

In addition to the number of functional chips on a silicon wafer, spatial patterns of the nonfunctional chips can provide important information for improving integrated-circuit fabrication processes. In this article, we consider a binary (functional/nonfunctional) response for each chip and propose a method to detect spatial effects in such processes through factorial experimentation. By using a measure of spatial dependence, process factors (parameters) that influence the spatial clustering of functional or nonfunctional chips can be identified. The proposed method, which assumes that a wafer contains a moderately large number of chips and that at least one wafer is produced for each experimental setting, is demonstrated with data from an actual experiment.

SOME APPLICATIONS OF A MULTIVARIATE CAPABILITY INDEX IN GEOMETRIC DIMENSIONING AND TOLERANCING

This article illustrates applications of a multivariate capability index for several concepts of engineering design. The focus is on three typical cases, each using geometric dimensioning and tolerancing to specify the design intent of a product. A mult..

Inference on the capability index: Cpm

In this paper properties of two estimators of Cpm are investigated in terms of changes in the process mean and variance. The bias and mean squared error of these estimators are derived. It can be shown that the estimate of Cpm proposed by Chan, Cheng and Spiring (1988) has smaller bias than the one proposed by Boyles (1991) and also has a smaller mean squared error under certain conditions. Various approximate confidence intervals for Cpm are obtained and are compared in terms of coverage probabilities, missed rate and average interval width.

Process monitoring in integrated circuit fabrication using both yield and spatial statistics

This paper presents the charting of spatial statistics in addition to yield information from the integrated circuits fabrication processes to detect systematic patterns. Early detection of process anomalies is critical for the manufacturing of integrated circuits because of its long cycle time. Charting spatial statistics provides opportunities to detect special causes that go undetected using only yield statistics. Examples from IC manufacturing processes are used to demonstrate this method.

USE OF DESIRABILITY FUNCTIONS TO DETERMINE OPERATING WINDOWS FOR NEW PRODUCT DESIGNS

A method is introduced to determine product design parameters using statistical techniques like design of experiments with multiresponse and simultaneous optimization of these responses with desirability functions. A desirable product design incorporate..

An Autologistic Model for Integrated Circuit Manufacturing

Spatial dependence is common among data from integrated circuit manufacturing. The assumption of nearest neighbor dependence among binary responses gives rise to an autologistic model, which enables the estimation of yield and spatial dependence simultaneously. A two stage estimation procedure is proposed for probe data from designed experiments. This method is compared with several recent approaches, and two examples from IC industry are used to illustrate this two stage methodology.

On Generalized Linear Model Method for Detecting Dispersion Effects in Unreplicated Factorial Designs

There are numerous approaches to screen location effects for unreplicated experiments, but only a handful to screen dispersion effects. Generalized linear models, popular in analyses of non-normal data, were recently proposed to screen both location and dispersion effects simultaneously. This paper illustrates and explains the impact of unidentified location effects on dispersion effects identification for such procedures. A remedy is proposed to recover the loss of power of the GLM method due to such impact.

A split-plot experiment in an automobile windshield fracture resistance test

The resistance of laminated glass to small projectile impact is examined with a design of experiments technique. The analysis follows a split-plot design, but other closely related approaches such as repeated measure analysis and multivariate analysis are also discussed and compared.

The value of unranked items in the analysis of incomplete ranking survey

In many market research studies, it is cost effective to ask the respondents to select and rank a small fixed number of the most preferred items from a list. There are several analyses available but they are not equally efficient.A simulation study is carried out to compare six intuitive approaches and a market research study is used throughout this article to illustrate the idea.