18-312-1995
18-312
Semiconductor Devices II
Note: This is the 1995 syllabus, to be revised soon
Instructor:
D.W. Greve
HH
B204, X8-3707
Course Secretary: Annie Simpson
HH
B205
Course File Cabinet:in front of
HH B205
About this course:
This course is a
companion to 18-311, which focused
on the physics of semiconductor devices based on the injection
of carriers (that is, bipolar transistors and related devices). 18-312 addresses
the physics of the other broad class 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.
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 reference materials:
The primary text
for this course will be written notes, to be distributed as required. These
notes are essentially the first draft of a textbook and will be followed quite
closely. As the notes are a draft, errors may be found and some
sections may be incomplete. Corrections
and suggestions are welcome (and will be acknowledged).
As a
secondary text, I am recommending Field Effect Devices, by R.F. Pierret,
Volume IV from the Modular Series on Semiconductor Devices (Addison- Wesley).
This is a basic book and covers some, but not all, of the material of this
course. Students will also benefit from access to a basic book on semiconductor
devices. This could be the text from 18-311, Solid State Electronic
Devices, B. Streetman,
3rd edition. Other good basic references are volumes I-III of the Modular Series
(especially Semiconductor Fundamentals, Volume I). Some of the
material on CCDs is also covered in Advanced MOS Devices, D.K. Schroder,
from the Modular Series on Semiconductor Devices (Addison- Wesley).
This
course will include discussion of MESFETs and thin film field effect transistors.
My discussion of MESFETs will be similar to that in Physics
of Semiconductor Devices
by M. Shur (Prentice Hall). Thin film field effect transistors are not covered
well in any text I know of, so I can offer no reference beyond the
original literature (and my notes, of course).
MOSFETs are of enormous
importance, and I would be remiss if I did not mention the book Operation
and Modeling of the MOS Transistor, Y.P. Tsividis (McGraw- Hill, 1987).
This book is comprehensive, thorough, and next to impossible to read. For
fine points of MOSFET operation
and modeling it is the only source, however. The MOS capacitor has been the
object of extensive study in its own right and for details you may consult the
monumental book MOS Physics and Technology, E.H. Nicollian and J.R.
Brews, (John Wiley, 1982).
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.
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. 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.
2. 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.
3. Applications of the MOS capacitor. The gated diode and
the CCD; image sensors.
4. 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.
5. Applications
of the MOSFET. Basic logic circuits; the dynamic random access memory (DRAM).
6.* The MESFET. Construction of the MESFET and potential advantages
of GaAs; the Schottky barrier junction; evaluation of the current- voltage characteristic;
velocity saturation and pinchoff; cutoff frequency of the MESFET;
high- speed logic families; relation to the JFET.
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.
* If time
permits.
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).
Two tests and a final exam are anticipated.
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 will
be examined carefully.
Grading
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
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.