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EE105 - Fall 2006Microelectronic Devices and Circuits
Prof. Jan M. Rabaey (jan@eecs)
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What is this class all about?
Introduction to semiconductor devices and integrated circuits.– Circuit analysis and design techniques. Time and frequency
domain analysis. Modern semiconductor devices (PN juntions, MOSFETs). Integrated passives. Single stage amplifiers. Differential amplifiers. Introduction to feedback. Frequency response of amplifiers. Multistage Amps
What will you learn?– Understanding, designing, and optimizing analog integrated
circuits. Understanding the operation of semiconductor devices.
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Practical InformationInstructor– Prof. Jan M. Rabaey
511 Cory Hall, 666-3102, jan@eecsOffice hours: Tu 3:30-5:30pm
TAs:– Nate Pletcher, pletch@eecs– Gerald (Guoqiang) Wang, weraldw@eecs– Ryan Roberts, [email protected]– TBD
Reader– Chuo Liu, [email protected]
Web page: – http://www-inst.eecs.berkeley.edu/~ee105/fa06/
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Discussions and Labs (tentative)
Discussion sessions (293 Cory)– M 3-4 pm,
– We 9-10am
– Fr 11am-noon
Same material in all sessions!
Labs (353 Cory)– Tu 9am-noon,
– We 9am-noon
– We 3pm-6pm
– Fr 10am-1pm
Please choose one lab session and stick with it !
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Your EECS105 Week
6pm
5pm
4pmOffice Hours
Prof. Rabaey
511 Cory
Lab
353 Cory
Discussion
293 Cory
3pm
Lecture
203 McLaughlin
Lecture
203 McLaughlin
2pm
1pm
12pm
11am
Lab
353 Cory
10am Lab353 Cory
Lab353 Cory
9am
FrThWeTuMo
Discussion293 Cory
Discussion293 Cory
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Class Organization
~ 10 Assignments
~ 10 Labs
2 midterms, 1 final– Midterm 1: Thursday, September 28, 6:30-8:00 pm
– Midterm 2: Thursday, November 9, 6:30-8:00 pm
– Final: Wednesday December 13, 12:30-3:30 pm
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Some Important Announcements
Please use the newsgroup to ask questions (ucb.class.ee105)Labs done in pairs, individual measurements, individual reports
Homework should be done individually
The only way to learn things is to do them yourselves. Don’t even think about cheating!
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Grading Policy
Homeworks: 15%
Labs: 15%
Midterm-1: 15%
Midterm-2: 15%
Final: 40%
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Class Material
Textbook: – “Microelectronics: An Integrated Approach”, by R. Howe, C. Sodini
Class notes: Web page
Lab Reader:– Available on the web page!
– Selected material will be made available from Copy Central
Check web page for the availability of tools
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The Web Site
Class and lecture notes
Assignments and solutions
Lab manual
Past exams, earlier class web pages
Many other goodies …
The sole source of information
http://www-inst.eecs.berkeley.edu/~ee105/fa06
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Software
HSPICE – Industry standard
– Online tutorials
There are free versions of WinSpice and PSPICE that you can use at home
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Getting Started
Assignment 1: – Assigned next Tuesday, Due 9/12 (Tuesday), 5pm
NO discussion sessions or labs this week.
First discussion sessions in Week 2
First lab in Week 3
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EECS 105: Course Overview
Semiconductor physics (1 week)
PN Junction / BJT Physics/Model (1.5 weeks)
MOSFET Physics/Model (1 week)
Integrated Passives (R, C, L) (1 week)
Circuit analysis techniques (2 weeks)
Single Stage Amplifiers (2 weeks)
Feedback and Diff Amps (1 week)
Freq Resp of Single Stage Amps (1 week)
Multistage Amps (2.5 weeks)
Freq Resp of Multistage Amps (1 week)
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EECS 105 in the Grand Scheme
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EECS 105 in the Grand Scheme
Example: Cell Phone
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The First Integrated Circuits - 1958
R. N. NoyceFairchild Semiconductor
Co-Founder of both Fairchild and Intel(deceased 1990)
“Unitary Circuit” made of Si
Jack KilbyTexas Instruments
Invented IC during his first year at TI
(Nobel Prize 2000)
“Solid Circuit” made of Ge
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Intel Pentium 4 Microprocessor
90nm CMOS technology
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EECS 105: Emphasis in Analog
14-bit analog-to-digital converter– Y. Chiu, IEEE Int’l Solid-State Circuits Conference 2004.
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Transistors are Bricks
Transistors are the building blocks (bricks) of the modern electronic world:
Focus of course:– Understand device physics
– Build analog circuits
– Learn electronic prototyping and measurement
– Learn simulations tools such as SPICE
Analog “Amp”
DigitalGate
MOS Cap
PN Junction
VariableCapacitor
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SPICE
SPICE = Simulation Program with IC Emphasis
Invented at Berkeley (released in 1972)
.DC: Find the DC operating point of a circuit
.TRAN: Solve the transient response of a circuit (solve a system of generally non-linear ordinary differential equations via adaptive time-step solver)
.AC: Find steady-state response of circuit to a sinusoidal excitation
* Example netlistQ1 1 2 0 npnmodR1 1 3 1kVdd 3 0 3v.tran 1u 100u
SPICESPICE
stimulus netlist response
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BSIM
Transistors are complicated. Accurate sim requires 2D or 3D numerical sim (TCAD) to solve coupled PDEs (quantum effects, electromagnetics, etc)
This is slow … a circuit with one transistor will take hours to simulation
How do you simulate large circuits (100s-1000s of transistors)?
Use compact models. In EECS 105 we will derive the so called “level 1” model for a MOSFET.
The BSIM family of models are the industry standard models for circuit simulation of advanced process transistors.
BSIM = Berkeley Short Channel IGFET Model
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Some of the circuits we will explore
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An Essential Skill: Circuit Analysis
Please review your EE40 knowledge!– Mesh / Nodal analysis
– Equivalent Circuits
– Time versus frequency domain analysis
– Phasors / complex numbers
Some short recap is probably useful(the summer was long …)
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Basics of Circuit Analysis
Kirchoff’s Current Law (KCL)
Kirchoff’s Voltage Law (KVL)
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Nodal and Mesh Analysis
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A simplified case – the voltage divider
V2 = ?
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Equivalent Circuits
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Lecture Outline
Semiconductors
Si Diamond Structure
Bond Model
Intrinsic Carrier Concentration
Doping by Ion Implantation
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Resistivity for a Few Materials
Pure copper, 273K 1.56×10-6 ohm-cm
Pure copper, 373 K 2.24×10-6 ohm-cm
Pure germanium, 273 K 200 ohm-cm
Pure germanium, 500 K .12 ohm-cm
Pure water, 291 K 2.5×107 ohm-cm
Seawater 25 ohm-cm
What gives rise to this enormous range?
Why are some materials semi-conductive?
Why the strong temp dependence?
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Periodic Table of Elements
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Electronic Properties of Silicon
Silicon is in Group IV (atomic number 14)– Atom electronic structure: 1s22s22p63s23p2
– Crystal electronic structure: 1s22s22p63(sp)4
– Diamond lattice, with 0.235 nm bond length
Very poor conductor at room temperature: why?
(1s)2
(2s)2
(2p)6 (3sp)4
Hybridized State
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The Diamond Structure
3sp tetrahedral bond
o
A43.5
o
A35.2
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States of an Atom
Quantum Mechanics: The allowed energy levels for an atom are discrete (2 electrons with opposite spin can occupy a state)When atoms are brought into close contact, these energy levels splitIf there are a large number of atoms, the discrete energy levels form a “continuous” band
Ene
rgy
E1
E2
...E3
Forbidden Band Gap
AllowedEnergyLevels
Lattice ConstantAtomic Spacing
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Energy Band DiagramThe gap between the conduction and valence band determines the conductive properties of the material
Metal– negligible band gap or overlap
Insulator – large band gap, ~ 8 eV
Semiconductor– medium sized gap, ~ 1 eV
Valence Band
Conduction Band
Valence Band
Conduction Band
e-
Electrons can gain energy from lattice (phonon) or photon to become “free”
band gap
e-
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Model for Good Conductor
The atoms are all ionized and a “sea” of electrons can wander about crystal:
The electrons are the “glue” that holds the solid together
Since they are “free”, they respond to applied fields and give rise to conductions
+ + + + + + + +
+ + + + + + + +
+ + + + + + + +
On time scale of electrons, lattice looks stationary…
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Bond Model for Silicon (T=0K)Silicon Ion (+4 q)
Four Valence ElectronsContributed by each ion (-4 q)
2 electrons in each bond
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Bond Model for Silicon (T>0K)
Some bond are broken: free electron
Leave behind a positive ion or trap (a hole)
+
-
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Holes
Notice that the vacancy (hole) left behind can be filled by a neighboring electron
It looks like there is a positive charge traveling around!
Treat holes as legitimate particles.
+-
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More About Holes
When a conduction band electron encounters a hole, the process is called recombinationThe electron and hole annihilate one another thus depleting the supply of carriers
In thermal equilibrium, a generation process counterbalances to produce a steady stream of carriers
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Thermal Equilibrium (Pure Si)
Balance between generation and recombination determines no = po
Strong function of temperature: T = 300 oK
optth GTGG += )(
)( pnkR ×=
RG =)()( TGpnk th=×
)(/)( 2 TnkTGpn ith ==×
K300atcm10)( 310 −≅Tni
Mass-action law
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Doping with Group V Elements
P, As (group 5): extra bonding electron … lost to crystal at room temperature
+
ImmobileCharge
Left Behind
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Donor Accounting
Each ionized donor will contribute an extra “free”electronThe material is charge neutral, so the total charge concentration must sum to zero:
By Mass-Action Law:
000 =++−= dqNqpqnρ
Free Electrons
Free Holes
Ions(Immobile)
)(2 Tnpn i=×
00
2
0 =++− di qN
n
nqqn
0022
0 =++− nqNqnqn di
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Donor Accounting (cont)
Solve quadratic:
Only positive root is physically valid:
For most practical situations:
2
4
0
22
0
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idd
id
nNNn
nnNn
+±=
=−−
2
4 22
0idd nNN
n++
=
id nN >>
ddd
idd
NNNN
nNN
n =+≈⎟⎠⎞
⎜⎝⎛++
=222
412
0
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Doping with Group III ElementsBoron: 3 bonding electrons one bond is unsaturatedOnly free hole … negative ion is immobile!
- +
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Mass Action Law
Balance between generation and recombination:
2ioo nnp =⋅
• N-type case:
• P-type case:
)cm10,K300( 310 −== inT
dd NNn ≅= +0
aa NNp ≅= −0
d
i
N
np
2
0 ≅
a
i
N
nn
2
0 ≅
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Compensation
Dope with both donors and acceptors: – Create free electron and hole!
+
-
-
+
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Compensation (cont.)
More donors than acceptors: Nd > Na
iado nNNn >>−=ad
o NN
np i
−=
2
idao nNNp >>−=da
o NN
nn i
−=
2
More acceptors than donors: Na > Nd
