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The purposes of multivariate statistical process control (MSPC) are to improve process operations by quickly detecting when process abnormalities have occurred and diagnosing the sources of the process abnormalities. In the area of semi-conductor manufacturing, increased yield and improved product quality result from reducing the amount of wafers produced under suboptimal operating conditions. This paper presents a complete MSPC application method that combines recent contributions to the field, including multiway principal component analysis (PCA), recursive PCA, fault detection using a combined index, and fault contributions from Hotelling's T2 statistic. In addition, a method for determining multiblock fault contributions to the combined index is introduced. The effectiveness of the system is demonstrated using postlithography metrology data and plasma stripper processing tool data. [ABSTRACT FROM AUTHOR]

As production requirements in semiconductor manufacturing continue to escalate, it is rarely possible to perform quality measurements on a product before subsequent process operations are performed. This delay between manufacturing and metrology coupled with inaccurate process models can lead to closed-loop instabilities. This paper investigates the effect of metrology delay on the closed-loop stability of a multiple input-multiple output exponentially weighted moving average run-to-run controller. The generalized Routh-Hurwitz stability criteria are used to derive the necessary and sufficient conditions for stability. A sufficient condition for stability is then derived for systems with any length of metrology delay. This condition states that if all of the eigenvalues of a model-mismatch matrix fall inside a circle with unit radius and centered at {1,0} on the complex plane, then the closed-loop system is stable. [ABSTRACT FROM AUTHOR]

A new thermal model is developed to predict wafer temperatures within a hot-wall low pressure chemical vapor deposition furnace based on the furnace wall temperatures as measured by thermocouples. Based on an energy balance of the furnace system, this model is a transformed linear model which captures the nonlinear relationship between the furnace wall temperature distribution and the wafer temperature distribution. The model can be solved with a direct algorithm instead of iterative algorithms which are used in all existing thermal models. Since the direct algorithm is noniterative, there is no convergence problem, nor local minima problem, related to nonlinear optimization. In addition, the direct algorithm greatly reduces the computation effort. Configuration factors are calculated by a finite area to finite area method. This avoids numerical integration methods which are much more difficult to implement and require more computation. The simplicity of the model form and the fast algorithm make the model useful for real-time updating and control. Model predictions show excellent agreement with experimental data. [ABSTRACT FROM AUTHOR]

Investigates the suitability of using optical emission spectroscopy in fault detection and classification of plasma etchers. Collection of spectra at different wavelengths; Extraction of multiple scans of the spectra from a semiconductor wafer; Proposal of a multiway principal component analysis to analyze the sensitivity of multiple scans within a wafer.

Run-toe run (RtR) control technology has received tremendous interest in semiconductor manufacturing. Exponentially weighted moving average (EWMA), double-EWMA, and internal model control (IMC) filters are recognized methods for online RtR estimation. In this paper, we consider recursive least squares (RLS) as an alternative for online estimation and RtR control. The relationship between EWMA-type and RLS-type estimates is analyzed and verified with simulations. Because measurement delay is almost inevitable in semiconductor manufacturing, we discuss and compare the performance of EWIVIA, RtR-IMC, and RLS controllers in handling measurement delay and measurement noise for processes with a deterministic drift. An ad hoc solution is proposed to handle measurement delay for processes with time-varying drifts. The results are illustrated through several simulations and a shallow trench isolation (S TI) etch process as an industrial example. [ABSTRACT FROM AUTHOR]