This page is based on a commentary by Jesus A. del Alamo, MIT Professor of Electrical Engineering and Computer Science at: http://web.mit.edu/newsoffice/2001/weblabcomment.html It needs to be edited to be shortened, and updated for the past five years of progress.
Microelectronics Device Characterization Lab
The Microelectronics Device Characterization Lab is an on-line laboratory that allows remote testing of transistors and other microelectronics devices through the web from anywhere at anytime.
Overview
The Microelectronics Lab is a research project at MIT that is developing a remote web-accessible microelectronics test station for microelectronics education. The MIT Microelectronics Device Characterization Lab project attempts to deal with the dearth of laboratory experiences in traditional microelectronics subjects. Through the microelectronics weblab, students can take measurements on transistors and other devices in real time from anywhere at any time. Currently, the system allows DC current-voltage characterization of multiterminal devices using an HP4155B Semiconductor Parameter Analyzer. The system is configured with a Switching Matrix that provides access to up to eight devices.
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The success of the Device Characterization Lab project has spawned the iLab initiative at MIT to explore the compliance of the weblab concept to other engineering disciplines. The Microelectronics Device Characterization Lab is currently funded by iCampus, the MIT-Microsoft alliance. Significant equipment donations have been received from Hewlett Packard, Agilent Technologies, and Advanced Micro Devices.
Purpose
Conventional courses in microelectronic device physics rarely include a laboratory experience that exposes students to the workings of real devices. This is because of equipment, space, training, safety and staffing constraints that become nearly insurmountable the moment there are more than a dozen students in the class. Actual device characterization, however, can substantially enhance the educational experience. Students can compare their measured data on real devices with the theoretical expectations and reflect on discrepancies, limitations, and design criteria. In addition, close contact with the real world is always a powerful motivator and students learn better.
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- The experimental setup is available over extended periods of time at any time of the day and night. This allows students to conduct their measurements whenever they wish.
- There are no special staffing requirements. Once the device is in place, no further staffing of the lab is required.
- The system is nearly as flexible as the instrumentation itself. This means that no new programming is required whenever a different device or measurement routine is required.
- There are no safety concerns. Students work from the safety of their homes or institutional computer clusters. No safety training is required to use the system.
- Scarce instrumentation and lab space can be effectively used by many students. The system queues requests and executes them in real time. Under most circumstances, students have the feeling of solely "owning" the entire measurement setup.
- Training is moderate since students need only learn those instrument functions that have been programmed in the software interface. A suitable manual is made available on line.
System Description
The basic architecture of the MIT Microelectronics Device Characterization Lab is shown in the figure. It basically consists of a device tester (an HP4155B Semiconductor Parameter Analyzer) and a computer that works double-duty as instrument controler and web server. The device under test is mounted on a test fixture that is connected to the tester. Communication between the instrument and the computer takes place through a GP-IB interface.
The latest release of WebLab (v. 4.0) includes an HPE5250A Switching Matrix. This is an instrument that multiplexes up to eight different devices into the system.
HP4155B Semiconductor Parameter Analyzer
The HP4155B Semiconductor Parameter Analyzer is a powerful professional engineering instrument that allows the measurement of current-voltage characteristics of microelectronics devices and small circuits with up to eight terminals. The HP4155B is standard issue in every state-of-ther-art microelectronics research and development organization.
Server
The computer that runs the Microelectronics Device Characterization Lab system is a standard PC running Windows NT Server. Very soon, it will be upgraded to an Athlon-class PC running Windows 2000 Server.
Java applet
Remote access to this set up is provided through a Java applet that is downloaded from the server to any remote user on an authorized list. The Java applet that we have constructed mimics the essential features of the front panel of the HP4155B. We have not attempted to capture the entire functionality of the HP4155B but just those elements that are useful to accomplish our educational goals. The ability to use a professional engineering instrument in an educational environment while drastically cutting down on its complexity is a unique and powerful feature of the iLabs concept.
The Java applet that is downloaded to the user is shown in the figure. Through this graphical interface, the user specifies a test vector that will be executed by the instrument. This Java applet is rather "smart" in the sense that it can pick up many kinds of errors in the test vector. In this way, traffic through the server is minimized and the instrument is only presented with testing requests that have a good chance of executing correctly.
Graphical data display
Once a successful test has been carried out, a new window automatically opens up on the client machine that graphs the measured data. The graphical format also mimics that of the HP4155B. The scales of the graphics can be manipulated with great flexibility.
Download function
There is also a download function that transfers the data to the client machine in several formats. This allows post-measurement manipulation, such as parameter extraction, comparison with theory, etc.
Switching Matrix
Version 4.0 of WebLab expanded the system by incorporating a HPE5250A Switching Matrix. This enables the user to remotely select one out of eight possible devices that are available in the system at any one time. The Switching Matrix then automatically connects this device to the HP4155B.
The Switching Matrix allows an exercise to involve several devices, it provides redundancy against device blow up (not a rare occurrence) and it also enables the system to be used in different subjects at the same time.
Job queueing
The system includes a queing function that queues job requests and transfers them for execution to the HP4155B in the order in which they are received by the server. Since typical microelectronics device characterization experiments are very fast, the queueing system allows multiple users in the system in what effectively is simultaneous basis.
System management
The system is password protected and allows access only to authorized users. The system records all logins, executed test vectors, and execution time. Device names and graphics describing terminal configurations can be specified remotely. System logins and test vectors can be also remotely monitored.
Set-up utility
The Java applet includes a tool to save and retrieve test vectors. This utility allows for successful test vectors to be saved for later use or for test vectors to be developed over different sessions. The server stores all these test vectors under each user name.
System Versions
WebLab 1.0
WebLab 1.0 was released in September 1998 and it was used in 6.720J/3.43J "Integrated Microelectronic Devices", a graduate subject taught by Prof. del Alamo. WebLab 1.0 included many of the basic capabilities that exist in today's system. In WebLab 1.0, only one device was connected to the system.
WebLab 2.0
WebLab 2.0 was released in February 1999 and was used in 6.012 "Microelectronics Devices and Circuits", a junior-level subject taught by Prof. del Alamo. Release 2.0 had a sharper looking Java GUI and corrected many bugs reported in version 1.0. Otherwise, no new functionality was added.
WebLab 3.0
WebLab 3.0 was released in September 1999 and was used in 6.720J/3.43J "Integrated Microelectronic Devices" by Prof. del Alamo. This version eliminated more bugs and made the graphical interface easier to use.
WebLab 3.1
WebLab 3.1 was released in April 2000 and made the system "firewall aware" so that it could be used by clients located behind corporate firewalls. Version 3.1 was used in the Spring of 2000 in an educational experiment involving students in Singapore.
WebLab 4.0
WebLab 4.0 was released in June 2000. This is the latest version of the system that is currently deployed in . This version incorporates for the first time a Switching Matrix which allows the user to select one out of eight possible devices.
Release 4.0 was simultaneously used in the Fall of 2000 by MIT students taking 6.720J/3.43J "Integrated Microelectronic Devices" and 6.012 "Microelectronics Devices and Circuits", as well as Singapore students in the Singapore-MIT Alliance taking SMA5104 "Fundamentals of Semiconductor Device Physics".
System Scalability
The extensive use of WebLab in the Fall of 2000 allowed us to estimate the capacity of the system.
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These data show the extraordinary capacity of the system as currently architectured. This capacity largely derives from judiciously limiting the maximum number of data points that each user can acquire in a single experiment and also by the "smarts" of the Java applet which does not pass bogus test vectors to the server. Out of the 99 jobs executed in that busiest hour referred to above, only one resulted in an HP4155B error message and could not be executed. All remaining 98 of them were legitimate experiments that got correctly performed.
Educational Experiments
There have now been several educational experiments that have been carried using the MIT Microelectronics Device Characterization Lab.
Fall 1998
The first "field-trial" of the Microelectronics WebLab was conducted in the Fall of 1998 in 6.720J/3.43J "Integrated Microelectronic Devices", a joint graduate-level subject between the Departments of Electrical Engineering and Computer Science and Material Science and Engineering. This subject was taught by Prof. del Alamo to about 30 students, half graduate and half undergraduates, from five different Departments.
In this first demonstration, two different homeworks using the setup were required of the students. In the first one, a Schottky diode was characterized. In the second one, a detailed characterization of a MOSFET (metal-oxide-semiconductor field-effect transistor) was carried out. In both cases, a number of different measurements were to be taken on the devices and the data was to be downloaded for further local processing and graphing using MATLAB or EXCEL. This typically took the form of calculating several figures of merit, extracting device parameters and comparing with theoretical models discussed in class.
Spring 1999
In the Spring semester of 1999, webLab was used in 6.012 "Microelectronic Devices and Circuits", a junior-level subject in the Department of Electrical Engineering and Computer Science at MIT that enrolled about 85 students and was taught by Prof. del Alamo. The web-based device characterization setup was used for real-time in-class demonstrations in which actual characteristics of devices were shown at lecture through a projection system. The set-up was also used in one homework in which students were asked to measure a MOSFET, compare the measurements with the models developed in class, and extract suitable parameters for a CAD description of the device. This experiment revealed the problem of device blow-up (particularly early morning the day the assignment is due) and its consequences.
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"I liked being able to work on this from the leisure of my room. I normally don't have time during the day to work on lab assignments and thus find myself going to labs late at night when being in the laboratory is the most unpleasant. Being able to sit at my computer and work on the problem made me much more apt to actually thinking about what was going on instead of just trying to get results so I could go home."
Fall 1999
In the Fall of 1999, the system was used in 6.720J/3.43J "Integrated Microelectronic Devices", a senior-level/graduate student subject taught by Prof. del Alamo. The system was used in one of the new web-ready classrooms at MIT for in-class demos while at lecture. The system was also used in an extensive homework in which students were asked to develop an equivalent circuit model for a metal-oxide-semiconductor field-effect transistor (MOSFET). This is the device of greatest importance in 6.720.
Spring 2000
In the Spring of 2000, the system was used in an experiment from Singapore in the context of the Singapore-MIT Alliance (SMA). The broad goal was to assess the extent to which the MIT Microelectronics WebLab could be used in the Fall of 2000 in SMA5104 "Fundamentals of Semiconductor Device Physics", a subject taught at a distance from MIT to students in Singapore.
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The students also provided excellent suggestions to improve several aspects of the system. A very useful outcome from this experiment was the upgrade of WebLab to be "proxy-aware" and to allow its use from behind a firewall (as is the case for NUS in Singapore).
Fall 2000
In the Fall of 2000, two exciting educational experiments were carried out.
Simultaneous use of the MIT Microelectronics Device Characterization Lab in three subjects, including one from Singapore
In the Fall of 2000, the MIT Microelectronics Device Characterization Lab was used in a simultaneous fashion in three different subjects, including one involving students in Singapore.
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The use of the Microelectronics Device Characterization Lab by students from Singapore was interesting in itself as the system, the instructor and the TA were all at MIT. No special problems were encountered in this experiment.
Testimonial from two students from Singapore:
"This assignment is quite an interesting and eye-opening experience because we actually obtained the experimental data from a lab in MIT through the internet. The advancement of technology in information transfer is really awesome."
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