Saghir Munir

Internet-based teleoperation using wave variables with prediction

Wave-based teleoperation has been previously attempted over the Internet, however, performance rapidly deteriorates with increasing delay. This paper focuses on the use of a modified Smith predictor, a Kalman filter and an energy regulator to improve the performance of a wave-based teleoperator. This technique is further extended for use over the Internet, where the time delay is varying and unpredictable. It is shown that the resulting system is stable even if there are large uncertainties in the model of the remote system (used in prediction). Successful experimental results using this technique for teleoperation in a master-slave arrangement over the Internet, where the control signal is streamed between Atlanta (Georgia) and Tokyo (Japan), are also given.

Control Techniques and Programming Issues for Time Delayed Internet Based Teleoperation

This article focuses on Internet-based real time control, such as remote bilateral teleoperation. In such applications, it is required that the control loop be closed through a time delayed network. This paper focuses on two control strategies (based on wave variables and a time forward observer), bandwidth issues, and some related programming details. Experimental results of bilateral teleoperation via the Internet between Atlanta and Tokyo are given. The system used is a two-degree-of-freedom haptic interface, bilaterally coupled to a simulation (implemented on a windows NT based computer) of a similar system.

Wave-based teleoperation with prediction

Wave variables based on passivity and scattering theory provide a good tool for establishing bilateral teleoperation in the presence of a constant time delay. Recently, these techniques have been extended to be used for a varying time delay, as in the case of Internet-based teleoperation. Although stability is guaranteed for virtually any time delay, performance rapidly degrades for larger delays. In this paper, a predictor derived from a modified Smith predictor along with a Kalman estimator and an energy regulator is used to enhance the performance of a wave-based teleoperator in the presence of a constant delay. Also, the current wave transformation equations are extended to a more general case (better suited for systems with multiple degrees of freedom).

Experimental evaluation of a new braking system for use in passive haptic displays

Passive haptic displays have several advantages when compared to active devices. Safety elements associated with active haptic displays may make them undesirable for certain applications. One method of actuation for passive haptic robots is through the use of brakes and clutches. Traditionally, friction brakes have undesirable behaviour, such as stiction and delay in response time due to mechanical motion. In this study a new brake concept is proposed. The performance of this brake is evaluated and quantified through a series of controlled experiments. Particular attention is given to the phenomenon of stiction in Delrin, dynamic response of the new brake, and effectiveness of feedback control for braking torque.

Internet based teleoperation using wave variables with prediction

Wave-based teleoperation has been previously attempted over the Internet, however performance rapidly deteriorates with increasing delay. The paper focuses on the use of a modified Smith predictor, a Kalman filter and an energy regulator to improve the performance of a wave-based teleoperator. This technique is further extended for use over the Internet, where the time delay is varying and unpredictable. It is shown that the resulting system is stable even if there are large uncertainties in the model of the remote system (used in prediction). Successful experimental results using this technique for teleoperation in a master-slave arrangement over the Internet, where the control signal is streamed between Atlanta (Georgia) and Tokyo (Japan), are also given.

Image-based metrology software for analysis of features on masks and wafers

Tebaldi is a software tool developed at Intel Mask Operation (IMO) for quantitatively analyzing patterns in 2D. Its initial scope was to analyze aerial images taken with a microscope. However the software has recently been enhanced to support aerial images obtained through simulation, bitmap, jpeg and tiff files saved from the mask inspection systems and the scanning electron microscope (SEM). This article primarily focuses on the SEM module of the software. Tebaldi supports simulated aerial images generated through IMO’s simulation based defect disposition system. This allows engineers to directly correlate 2D structures in an experimental aerial image, with those in a simulated image. To analyze SEM images, the software features scaling, alignment and calibration functions. Several linear and non-linear filtration techniques to reduce noise and charging exist. Custom convolution kernels can be user defined. Ability to segment features and extract contours also exist. Further, these contours can be overlayed and shortest distances between corresponding points can be computed in a user friendly manner with a high degree of confidence. Tebaldi is currently used in production to disposition defects in repaired sites on masks shipped from IMO as well as to compare SEM images to determine the pattern fidelity across mask writers and processes within IMO.

PRIMADONNA: a system for automated defect disposition of production masks using wafer lithography simulation

Todays reticle inspection tools can provide a wealth of information about defects. We introduce here a system called DIVAS: Defect Inspection Viewing, Archiving, and Simulation that fully uses and efficiently manages this wealth of defect information. In this paper, we summarize the features of DIVAS and describe in more detail PRIMADONNA, one of its components. Current reticle defect specifications are based, primarily, on defect size. Shrinking design rules, increasing MEEF and use of Optical Enhancement Techniques cause size to be an inadequate criterion for disposition. Furthermore, visual disposition of defects is not automated, strictly reproducible, or directly tied to wafer lithography. To compensate for these inadequacies, reticle specifications are set conservatively adding direct and hidden costs to the manufacturing process. PRIMADONNA, utilizing Prolith as the simulation engine, retrieves all defect and reference images saved from a KLA SLF77 inspection tool and processes them through a series of increasingly rigorous simulation stages. These include pre-filtering, aerial image formation, and post filtration. Difference metrics are used to quantify a defects wafer impact. We will report results comparing PRIMADONNA decisions to manual classifications for a significant volume of inspections. Correlation between PRIMADONNA results and AIMS metrology will be presented.

Lithography-based automation in the design of program defect masks

In this work, we are reporting on a lithography-based methodology and automation in the design of Program Defect masks (PDM’s). Leading edge technology masks have ever-shrinking primary features and more pronounced model-based secondary features such as optical proximity corrections (OPC), sub-resolution assist features (SRAF’s) and phase-shifted mask (PSM) structures. In order to define defect disposition specifications for critical layers of a technology node, experience alone in deciding worst-case scenarios for the placement of program defects is necessary but may not be sufficient. MEEF calculations initiated from layout pattern data and their integration in a PDM layout flow provide a natural approach for improvements, relevance and accuracy in the placement of programmed defects. This methodology provides closed-loop feedback between layout and hard defect disposition specifications, thereby minimizing engineering test restarts, improving quality and reducing cost of high-end masks. Apart from SEMI and industry standards, best-known methods (BKM’s) in integrated lithographically-based layout methodologies and automation specific to PDM’s are scarce. The contribution of this paper lies in the implementation of Design-For-Test (DFT) principles to a synergistic interaction of CAD Layout and Aerial Image Simulator to drive layout improvements, highlight layout-to-fracture interactions and output accurate program defect placement coordinates to be used by tools in the mask shop.

DIVAS: fully automated simulation based mask defect dispositioning and defect management system

This article presents the evolution of the first fully automated simulation based mask defect dispositioning and defect management system used since late 2002 in a production environment at Intel Mask Operation (IMO). Given that inspection tools flag defects which may or may not have any lithographic significance, it makes sense to repair only those defects that resolve on the wafer. The system described here is a fully automated defect dispositioning system, where the lithographic impact of a defect is determined through computer simulation of the mask level image. From the simulated aerial images, combined with image processing techniques, the system can automatically determine the actual critical dimension (CD) impact (in nanometers). Then, using the product specification as a criteria, can pass or fail the defect. Furthermore, this system allows engineers and technicians in the factory to track defects as they are repaired, compare defects at various inspection steps and annotate repair history. Trends such as yield and defect commonality can also be determined. The article concludes with performance results, indicating the speed and accuracy of the system, as well as the savings in the number of defects needing repair.