EE 330 Lecture 13 evices in Semiconductor Processes iodes
Exam 1 Friday Sept 22 Students may bring 1 page of notes Next weeks HW assignment due on Wed Sept 20 at beginning of class No 5:00 p.m extension so solutions can be posted Those with special accommodation needs, please send me an email message or contact me so arrangements can be made Review session 6:30 Rm 1011 Coover
Special Accommodations for Exam 1 Those in the class that have emailed me about special accommodations for Exam 1 should have now received notice from Lori Mickle, the Exam Accommodations Coordinator. f for any reason you have requested exam accommodations and have not received notice from Lori, please see me after class.
TA Office Hours Exam 1 Friday Sept 22 Locations: George: TLA Robert: HKN Help Room - Rm 1213 Coover Joseph: Rm 3011 Coover Pallavi: Rm 3102 Coover
Review from Last Lecture http://www.dayah.com/periodic/mages/periodic%20table.png
Basic evices and evice Models Resistor iode Capacitor MOSFET BJT
http://www.dayah.com/periodic/mages/periodic%20table.png
group (or family) 4 valence-band Electrons All elements in group have 4 valence-band electrons
Serves as an acceptor of electrons Acts as a p-type impurity when used as a silicon dopant All elements in group have 3 valence-band electrons Only 3 alenceband Electrons
http://www.oftc.usyd.edu.au/edweb/devices/semicdev/doping4.html
Serves as an donor of electrons Acts as an n-type impurity when used as a silicon dopant All elements in group have 5 valence-band electrons Five alenceband Electrons
Silicon opants in Semiconductor Processes B (Boron) widely used a dopant for creating p-type regions P (Phosphorus) widely used a dopant for creating n-type regions (bulk doping, diffuses fast) As (Arsenic) widely used a dopant for creating n-type regions (Active region doping, diffuses slower)
iodes (pn junctions) epletion region created that is ionized but void of carriers
pn Junctions Physical Boundary Separating n-type and p-type regions f doping levels identical, depletion region extends equally into n-type and p-type regions
pn Junctions Physical Boundary Separating n-type and p-type regions Extends farther into p-type region if p-doping lower than n-doping
pn Junctions Physical Boundary Separating n-type and p-type regions Extends farther into n-type region if n-doping lower than p-doping
pn Junctions Positive voltages across the p to n junction are referred to forward bias Negative voltages across the p to n junction are referred to reverse bias As forward bias increases, depletion region thins and current starts to flow Current grows very rapidly as forward bias increases Current is very small under revere bias
pn Junctions Anode Anode Cathode Cathode Circuit Symbol
pn Junctions As forward bias increases, depletion region thins and current starts to flow Current grows very rapidly as forward bias increases Anode Cathode Simple iode Model: =0 >0 =0 <0 Simple model often referred to as the deal diode model
pn Junctions Simple iode Model: pn junction serves as a rectifier passing current in one direction and blocking it n the other direction
Rectifier Application: 1 OUT Simple iode Model: N 1K N = M sinωt M N t OUT M t
- characteristics of pn junction mproved iode Model: (signal or rectifier diode) d S in the 10fA to 100fA range d kt = t q iode Equation d t e 1 S What is t at room temp? t is about 26m at room temp k= 1.380 6504(24) 10 23 JK -1 q = 1.602176487(40) 10 19 C k/q=8.62 10 5 K -1 iode equation due to William Schockley, inventor of BJT n 1919, William Henry Eccles coined the term diode n 1940, Russell Ohl stumbled upon the p-n junction diode
- characteristics of pn junction mproved iode Model: (signal or rectifier diode) iode Characteristics 0.01 d d d (amps) 0.008 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) iode Equation Under reverse bias ( d <0), Under forward bias ( d >0), d t e 1 S Simplification of iode Equation: S Se d t S in the 10fA to 100fA range kt = t q k= 1.380 6504(24) 10 23 JK -1 q = 1.602176487(40) 10 19 C k/q=8.62 10 5 K -1 t is about 26m at room temp Simplification essentially identical model except for d very close to 0 iode Equation or forward bias simplification is unwieldy to work with analytically
- characteristics of pn junction mproved iode Model: iode Equation Simplification of iode Equation: Under reverse bias, Under forward bias, (signal or rectifier diode) d t e 1 S S S e d t S often in the 10fA to 100fA range S proportional to junction area t is about 26m at room temp How much error is introduced using the simplification for d > 0.5? d t S e 1 Se d t e 1 S d t 1 05. 4. 4 10. 026 e How much error is introduced using the simplification for d < - 0.5? 05. 026 e. 4. 4 10 Simplification almost never introduces any significant error 9 9
Will you impress your colleagues or your boss if you use the more exact diode equation when d < -0.5 or d > +0.5? Will your colleagues or your boss be unimpressed if you use the more exact diode equation when d < -0.5 or d > +0.5?
pn Junctions Anode Cathode iode Equation: (good enough for most applications) JSAe 0 n T 0 0 Note: S =J s A J S = Sat Current ensity (in the 1aA/u 2 to 1fA/u 2 range) A= Junction Cross Section Area T =kt/q (k/q=1.381x10-23 C/ K/1.6x10-19 C=8.62x10-5 / K) n is approximately 1
pn Junctions iode Equation: J 0 S Ae n T 0 0 Anode J S is strongly temperature dependent With n=1, for >0, Cathode - G0 (T) J T m e Ae t t SX Typical values for key parameters: J SX =0.5A/μ 2, G0 =1.17, m=2.3
Example: pn Junctions - G0 (T) J m t T e Ae SX t What percent change in S will occur for a 1 C change in temperature at room temperature? - -G0 - - - G0 G0 G0 G0 (T ) t T1 (T ) (T ) m m m m t T1 t 2 t t 2 t 2 J T e Ae - J T e Ae T e - T e SX T SX T T T @ 1 2 1 S S -G0 - - G0 G0 m t T1 (T ) m t T1 t 2 J T e Ae T e SX T T 1 1 15 15 1 240x10 1 025x10 15 1. 025x10 S. -. 100% 21% S
pn Junctions Anode Cathode iode Equation: (good enough for most applications) JSAe 0 n T 0 0 S =J s A Simple iode Model: Often termed the conducting or ON state Often termed the nonconducting or OFF state
Consider again the basic rectifier circuit OUT N R Previously considered sinusoidal excitation Previously gave qualitative analysis Rigorous analysis method is essential? O U T
Analysis of Nonlinear Circuits (Circuits with one or more nonlinear devices) What analysis tools or methods can be used? KCL? KL? Superposition? Nodal Analysis Mesh Analysis Two-Port Subcircuits oltage ivider? Current ivider? Thevenin and Norton Equivalent Circuits?
Consider again the basic rectifier circuit OUT N R N OUT R R d t e 1 S OUT S R e N t O U T 1 Even the simplest diode circuit does not have a closed-form solution when diode equation is used to model the diode!! ue to the nonlinear nature of the diode equation Simplifications are essential if analytical results are to be obtained
Lets study the diode equation a little further d t d S e 1 iode Characteristics 10000 8000 d (amps) 6000 4000 2000 0 0 0.2 0.4 0.6 0.8 1 Linear-Linear Axis d (volts) Power issipation Becomes estructive if d > 0.85 (actually less)
Lets study the diode equation a little further d t e 1 d S iode Characteristics d (amps) 10000 100 1 0.01 0.0001 1E-06 1E-08 1E-10 1E-12 Linear-Log Axis 0 0.2 0.4 0.6 0.8 1 d (volts) For two decades of current change, d is close to 0.6 This is the most useful current range for many applications
Lets study the diode equation a little further d t e 1 d S iode Characteristics 0.01 d (amps) 0.008 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) For two decades of current change, d is close to 0.6 This is the most useful current range when conducting for many applications
Lets study the diode equation a little further d d t e 1 S iode Characteristics d 0 d 0.6 d d 0.6 0 0.01 0.008 d (amps) 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) Widely Used Piecewise Linear Model
Lets study the diode equation a little further d d t e 1 S iode Characteristics 0.01 0.008 d (amps) 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) Better model in ON state though often not needed ncludes iode ON resistance
Lets study the diode equation a little further d t e 1 d S Piecewise Linear Model with iode Resistance d d 0 if 0.6 d R d d 0.6 0 (R is rather small: often in the 20Ώ to 100Ώ range): if Equivalent Circuit A d C A C Off State d d A C d 0.6 R On State
The deal iode 0 if 0 0 if 0
The deal iode 0 if 0 0 if 0 OFF ON ON OFF alid for >0 0
iode Models d (amps) iode Characteristics 0.01 0.008 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) d (amps) iode Characteristics 0.01 0.008 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) iode Characteristics d (amps) 0.01 0.008 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) Which model should be used? The simplest model that will give acceptable results in the analysis of a circuit
iode Models iode Characteristics iode Equation d t e 1 S d (amps) 0.01 0.008 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) iode Characteristics d 0 d 0.6 if d if d 0.6 0 d (amps) 0.01 0.008 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) iode Characteristics Piecewise Linear Models d d 0 0.6 d R d if if d d 0.6 0 d (amps) 0.01 0.008 0.006 0.004 0.002 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 d (volts) 0 if 0 0 if 0
End of Lecture 13