This paper will examine an approach for automatically identifying endpoint (the completion in etch of a thin film) during plasma etching of low open area wafers. Since many endpointing techniques use a few manually selected wavelengths or simply time the etch, the resulting endpoint detection determination may only be valid for a very short number of runs before process drift and noise render them ineffective. Only recently have researchers begun to examine methods to automatically select and weight spectral channels for estimation and diagnosis of process behavior. This paper will explore the use of principal component analysis (PCA) based T 2 formulation to filter out noisy spectral channels and characterize spectral variation of optical emission spectroscopy (OES) correlated with endpoint. This approach is applied and demonstrated for patterned contact and via etching using Digital Semiconductor's CMOS6 (0.35µm) production process.

No abstract

Semiconductor fabrication requires an increasingly expensive and integrated set of tightly controlled processes, driving the need for a fabrication facility with fully computerized, networked processing equipment. We describe an integrated, open system architecture enabling distributed experimentation and process control for plasma etching. The system was developed at MIT's Microsystems Technology Laboratories and employs in-situ CCD interferometry based analysis in the sensor-feedback control of an Applied Materials Precision 5000 Plasma Etcher (AME5000). Our system supports accelerated, advanced research involving feedback control algorithms, and includes a distributed interface that utilizes the internet to make these fabrication capabilities available to remote users.The system architecture is both distributed and modular: specific implementation of any one task does not restrict the implementation of another. The low level architectural components include a host controller that communicates with the AME5000 equipment via SECS-Il, and a host controller for the acquisition and analysis of the CCD sensor images. A Cell Controller (CC) manages communications between these equipment and sensor controllers. The CC is also responsible for process control decisions; algorithmic controllers may be integrated locally or via remote communications. Finally, a System Server manages connections from internet/intranet (web) based clients and uses a direct link with the CC to access the system. Each component communicates via a predefined set of TCP/ IP socket based messages. This flexible architecture makes integration easier and more robust, and enables separate software components to run on the same or different computers independent of hardware or software platform.

SUMMARYThe lack of platform-independent numerical toolsets presents a barrier to the development of distributed scientific and engineering applications. Unlike self-contained applications, which can utilize specialized interfaces to numerical algorithms, distributed applications require a computing environment with cohesive data structures and method interfaces. These features are essential in providing consistency between independently developed parts of distributed applications. We describe a Java-based framework that provides a set of consistent data structures and standard interfaces for numerical methods which operate on these data structures. The data structures we utilize are double precision real and complex matrices in Java. Our method interfaces are designed to model those of MATLAB. Since many engineering toolsets rely heavily on core numerical linear algebra algorithms, our current work is focused on implementing a computational foundation of fundamental numerical algorithms operating within our matrix framework. The matrix framework and numerical algorithm libraries are extremely useful for a wide range of applications and should prove to be easily extendable for developing various applications and toolsets beyond their current implementations.

Fourier transform infrared (FTIR) spectroscopy has emerged as an attractive sensor for in-situ monitoring and control of semiconductor fabrication processes. New applications are being enabled by advances in FTIR hardware and software that provide for: compact size, fast measurements with exceptional stability and signal to noise, and intelligent model based algorithms for thin film and gas analysis. In previously reported work, FTIR instrumentation with automated spectral analysis software was demonstrated as a novel sensor for monitoring layer properties such as thickness, composition and temperature. Recent work has emphasized applications to practical problems in modem semiconductor manufacturing. In this paper we will report pioneering results on: 1) Run-to-run closed loop control of a single wafer epitaxial silicon process using integrated infrared thickness and doping profiling metrology, 2) Fault detection during cluster tool plasma etching using real-time infrared exhaust gas analysis, and 3) oxygen implantation process monitoring during the formation of silicon on insulator (SOI) wafers using infrared reflectometry.