Text and required materials:
Instructor:
D.W. Greve
HH B204, X8-3707
dg07@andrew.cmu.edu
Schedule:
Lectures: presently MWF 12:30-1:20, DH 1211
Course Secretary:
Lydia Corrado
HH B205
Course file cabinet:
in front of HH B205
About this course:
This course is a companion to 18-311, which provides an introduction to the physics of semiconductor devices. 18-312 addresses in detail the physics of semiconductor devices which work on the field effect principle. These devices include the MOSFET, junction field effect devices (JFET and MESFETs), thin film field effect transistors (TFTs), and related devices. The course material is specifically motivated by current applications in which portable and low power operation is required. Particular applications which are discussed in detail include scaled MOSFETs for logic and memory; CCD imagers; active matrix flat panel displays; and MESFETs for digital and RF applications.
Prerequisites for this course are successful completion of 18-311 or an introductory course in semiconductor devices; a sophomore level physics course including electromagnetic fields; and a general acquaintance with electronic circuits.
Text and required materials:
The text for this course will be my recently published textbook, Field Effect Devices and Applications, published by Prentice Hall in 1998. Homework assignments and solutions will be distributed via the course website. My intention is that many homework assignments will be completed using Mathcad, a program which integrates text, graphics, and calculation.
Use of Mathcad is required in this course. Mathcad is a program which makes it easy to perform symbolic and numerical calculations, graph the results, and to use text to annotate the resulting worksheet. Mathcad is not a programming language (so you don't need to learn another). The Mathcad interface uses equations which look very similar to those in a textbook or on a blackboard. In some cases, your assignment will involve modification of a pre-existing Mathcad worksheet.
Mathcad is available on PC, Macintosh, and other platforms. Mathcad is installed on PCs in HH A104. Access to A104 can be obtained by signout of a key from Tech Electronics. Mathcad is also available at a number of university clusters.
You may want to purchase the student version for the PC or a professional (and more expensive!) version for the Macintosh. Alternatively, it may be possible to do many of the assignments using the Mathbrower program. This program is available only for the PC and has "limited" capabilities to edit equations and parameters in pre-existing Mathcad worksheets. All Mathcad worksheets which appear in the textbook (and more besides) are available on the course website; if you have network access, these can be downloaded and run similarly to using Netscape.
Suggestions of other textbooks which may be helpful as supplementary reading are found at the end of each chapter of the text.
Course Objectives:
1. To develop an understanding of the basic physical principles which underlie the operation of field effect devices.
2. To derive the basic device equations which describe the current-voltage and capacitance-voltage characteristics of field effect devices.
3. To develop the small-signal and large-signal circuit models and explore the applications of field effect devices in simple circuits, including study of the limits of performance imposed by the device itself. There will be particular emphasis on the consequences of scaling and the demands for low power operation.
4. To acquire the ability to manipulate the basic equations of semiconductor physics to obtain useful results, and also to acquire facility in obtaining numerical answers.
5. To gain an appreciation of the magnitude of quantities of engineering importance (such as dimensions, current and voltage levels, switching speeds, etc.) and also an appreciation of practical and fundamental limits encountered in semiconductor device fabrication.
Course Outline
1. Review. The basic concepts of semiconductor physics and the essential equations will be briefly reviewed.
2. Introduction. The field effect principle; early field effect devices; examples and classification of present field effect transistors; brief outline of fabrication technology, especially techniques for device isolation; enhancement and depletion devices and application to basic logic circuits; outline of the remainder of the course.
3. The MOS capacitor. Construction of band diagrams and definitions of accumulation, depletion and inversion; review of carrier statistics; capacitance, bandbending, and charges in the depletion approximation; exact formulation and solutions; MOS nonidealities; review of recombination and generation; nonequilibrium MOS behavior; the MOS capacitor as a characterization tool.
4. Applications of the MOS capacitor. The gated diode and the CCD; image sensors.
5. The MOSFET. Qualitative behavior; definitions of the threshold voltage; bulk-charge theory and simplification to the square-law theory; capacitances and cutoff frequency; second-order effects, including subthreshold current, short-channel effects and narrow-channel effects; application and limitations of the MOSFET in basic logic circuits.
6.* MOS memory. Classification of memory types; the memory array; memory cells for SRAM, DRAM, EPROM, EEPROM, and "flash" memory.
7.* The TFT. Application in active matrix high density displays; properties of amorphous and polycrystalline materials; various TFT process technologies; effects of traps in TFTs and trends in effective mobility, leakage current, and threshold voltage; various drift phenomena, including insulator instability and the Staebler-Wronski effect.
8.* The MESFET. Construction of the MESFET and potential advantages of GaAs; the Schottky barrier junction and evaluation of its current-voltage characteristic; velocity saturation and pinchoff; cutoff frequency of the MESFET; high-speed logic families; relation to the JFET.
* Choice of topics will depend on student interest.
Policies
Students are expected to attend all lectures, to complete all assigned homework assignments, and to take exams as scheduled. Attendance at lectures and participation in discussions will be considered when final grades are assigned. The emphasis of the lectures, homework assignments, and reading assignments will be a good indication of the material to be covered on exams.
Regular homework will be assigned. Late homework will be accepted for a limited time (typically up until the beginning of the class after the official due date) although with a 10%/ day penalty. Any questions about grading of tests or homework assignments should be addressed promptly (within one week after return of the paper).
Three tests are anticipated. There will be either a final exam (default option) or a final oral report on a journal article (only if all students agree in written balloting). As noted above, you are expected to take these as scheduled unless you have a truly unavoidable and compelling excuse. If such a situation arises, contact me in advance if at all possible. Tests will be scheduled in the near future. Nominations for undesired dates will be accepted during the first week of classes.
Students are reminded of the university policy on cheating and plagiarism. In fairness to all students, I will take measures to discourage cheating including spacing of students during exams, use of alternate versions of tests, careful proctoring, etc.
Note that according to university policy each instructor may set policy concerning acceptable collaboration on homework assignments. I regard it allowable (and even desirable) for students to discuss the general approach to be taken for homework problems. However, work handed in for grading must be a product of your own individual effort, and thus solutions which are nearly exact copies of another are evidence of an unacceptable collaboration.
Homework assignments will be issued only via the course website. I intend to design most assigments so that they can be completed using Mathcad.
I do not believe in grading on a curve. Your grade is determined by your performance relative to an absolute standard, that is, mastery of the material presented. A good to very good understanding of the material (as demonstrated by the ability to correctly answer most of the questions on exams and homework assignments) will merit a grade of B. I am prepared to give the entire class grades of A (or R) if such is warranted.
The weighting for calculation of the final grade will be approximately 25% homework, 35% final exam, and 40% tests. Performance in class, attendance, etc. will be considered as a factor in borderline or near-borderline grades.