A new technique enables the conversion of an ordinary camera into a light-field camera capable of recording high-resolution, multiperspective images.
A commentary by Jesus A. del Alamo, MIT Professor of Electrical Engineering and Computer Science
The Microelectronics WebLab is an on-line laboratory that allows remote testing of transistors and other microelectronics devices through the web from anywhere at anytime.
The Microelectronics WebLab is a research project at MIT that is developing a remote web-accessible microelectronics test station for microelectronics education. The MIT Microelectronics WebLab 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.
Development of the Microelectronics WebLab at MIT started in the Spring of 1988 by Prof. Jesus del Alamo of the Department of Electrical Engineering and Computer Science. The first version of the Microelectronics WebLab was deployed in the Fall of 1988. Improved versions have been used several times since then in graduate and undergraduate microelectronics subjects at MIT. In the Fall of 2000, the system was accessed by students from Singapore as part of a graduate microelectronics subject of the Singapore-MIT Alliance.
The success of the Microelectronics Weblab project has spawned the iLab initiative at MIT to explore the compliance of the weblab concept to other engineering disciplines. The Microelectronics WebLab is currently funded by iCampus, the MIT-Microsoft alliance. Significant equipment donations have been received from Hewlett Packard, Agilent Technologies, and Advanced Micro Devices.
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.
The MIT Microelectronics WebLab enables real microelectronic device characterization to be carried out by large number of students in the context of a device physics class. In this approach, students measure the current-voltage characteristics of transistors and other microelectronics devices that are placed in a laboratory at MIT. Unlike a regular laboratory experience, students access the device characterization instrumentation through the web simply using a Java-enabled web browser.
There are several advantages to this approach:
- 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.
The basic architecture of the MIT Microelectronics WebLab 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
The computer that runs the Microelectronics WebLab system is a standard PC running Windows NT Server. Very soon, it will be upgraded to an Athlon-class PC running Windows 2000 Server.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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 WebLab 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ WebLab 4.0
WebLab 4.0 was released in June 2000. This is the latest version of the system that is currently deployed in
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".
The extensive use of WebLab in the Fall of 2000 allowed us to estimate the capacity of the system.
In the Fall 2000 semester, at its busiest hour, WebLab handled 13 users running a total of 99 experiments. This extrapolates to a minimum capacity of over 2000 users per week and over 15,000 experiments per week.
Even at its busiest hour, the average total execution time for each job was less than 15 seconds. Over 70% of all test requests were executed immediately after being received by the server, about 25% had to wait for one job to be finished, and only 3% had two jobs ahead of them.
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.
There have now been several educational experiments that have been carried using the MIT Microelectronics WebLab.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
Testimonials from two 6.012 students:
"I thought this was a very useful experience. It's often tough to go through a course like this where we deal with such microscopic elements and not be able to see any real data. This problem set allowed us to get some real data and do some real calculations on it."
"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."
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 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.
Two graduate students at National University of Singapore were hired in Singapore to carry out a detailed MOSFET device characterization exercise, similar to the one envisioned for SMA5104. Tutoring was remotely available from MIT. The only manual to the system was the one available on-line.
The experiment was a great success. The feedback from the students was very positive:
"We are confident that this system can definitely be used for SMA5104 this coming Fall."
"It is REALLY a GOOD experience to participate in this excercise."
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).
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Fall 2000
In the Fall of 2000, two exciting educational experiments were carried out.
>>Simultaneous use of the MIT Microelectronics WebLab in three subjects, including one from Singapore
In the Fall of 2000, the MIT Microelectronics WebLab was used in a simultaneous fashion in three different subjects, including one involving students in Singapore.
This unprecedented educational experiment was possible through the introduction to the system of the Switching Matrix. This allows up to eight transistors or other devices to be available for testing at any one time. Through a "Device" menu, a remote user simply selects the proper device to test. This new capability allows the Microelectronis WebLab to be deployed in different subjects simultaneously and it also provides redundancy against device blowup.
The three subjects, involving a total of about 120 students, were:
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 6.012 "Microelectronics Devices and Circuits", (about 80 undergrads)
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ 6.720J/3.43J "Integrated Microelectronics Devices" (about 20 grads)
ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ SMA5104 "Fundamentals of Semiconductor Device Physics" (about 20 graduate students in Singapore as part of the Singapore-MIT Alliance)
Each subject used different devices at different times throughout the semester. Thanks to the device redundancy enabled by the Switching Matrix, there was not a single device blackout event.
The use of the Microelectronics WebLab 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."
"I think this is a great exercise. It allows us to compare real data with the modelled one. In doing so, I realize that the model is in fact quite simplified."
Remote characterization of Compaq's 0.18 um CMOS
In the Fall of 2000, for the first time, students in 6.720J/3.43J "Integrated Microelectronic Devices" (a graduate subject taught by Prof. del Alamo at MIT) characterized state-of-the-art 0.18 um CMOS hardware. This is the latest and fastest CMOS technology generation that has recently been deployed in the real world. This technology has enabled microprocessors with clock speeds exceeding 1 GHz.
0.18 um technology Si wafers are "too hot to handle" and are closely guarded. Having a wafer on campus to enable transistor characterization by our students was clearly out of question due to IP concerns.
Thanks to the initiative of Ted Equi of Compaq and with the help of Larry Bair and Norm Leland (also of Compaq) and MIT student Lane Brooks (the creator of the microelectronics weblab), earlier in the year we installed a copy of the MIT Microelectronics WebLab at Compaq's Alpha Development Group center in Shrewsbury, MA. Through this system, 6.720J/3.43J students accessed the latest 0.18 um CMOS hardware that Compaq's designers are currently working with. Students were able to take remote measurements in real time and download the data. They were also able to compare the performance of the 0.18 um technology with 10-year old 1.5 um hardware that was made available through the on-campus Microelectronics WebLab.
In this exercise, students not only were able to learn about the manifestation of a number of short-channel effects that appear in modern deep-submicron CMOS, but they could also appreciate the staggering progress that has taken place in microelectronics technology in the last 10 years.
In this educational experiment, an interesting technical issue also emerged. For security reasons, networking of the system was not allowed behind Compaq's firewall. To get around this, the system was accessed through a phone line and a local ISP at 56 Kb/s rate. In spite of this, the initial downloading of the Applet was reasonably fast and device characterization was confortably responsive.
The MIT Microelectronics WebLab project was launched in the Spring of 1988 thanks to a seed grant from Microsoft of $3.5K, a software donation from Microsoft with a value of $8K, and a Windows NT server donation from Intel with a value of $6K.
In the Spring of 1999 the MIT Microelectronics WebLab received a donation of a HP4155B Semiconductor Parameter Analyzer and a HPE5250A Switching Matrix from Hewlett Packard. This donation was valued at $76K.
Further development of the system over the academic year 1999-2000 was funded by three MIT Alumni Funds: the Class of '51 Fund for Excellence in Education, the Class of '55 Fund for Excellence in Teaching, and the Class of '72 Fund for Educational Innovation. Total support received from these funds was about $20K.
In the Summer of 2000, the iLab project was launched under sponsorship of the iCampus alliance between Microsoft and MIT. The MIT Microelectronics WebLab received funding of $78K for the first year and $73K for the second year.
In the Fall of 2000, the MIT Microelectronics WebLab received a donation from Agilent Technologies of seven device test fixtures valued at $37K. This allowed us to exploit all the capabilities built into WebLab 4.0 that incorporates the switching matrix.
In the Summer of 2000, we received a grant of $65K from the Singapore-MIT Alliance to develop a second system to be used in the SMA program.
In the Winter of 2000, we also received a donation from Advanced Micro Devices of two Athlon-class servers valued at $11K. This will allow us to achieve a significant enhancement in system reliability and performance.