Ee 434 lecture 12
Download
1 / 35

EE 434 Lecture 12 - PowerPoint PPT Presentation


  • 74 Views
  • Uploaded on

EE 434 Lecture 12. Devices in Semiconductor Processes Diodes Capacitors MOS Transistors. Quiz 10. A “10K” resistor has a temperature coefficient of +80ppm/ o C If the resistor was measured to be 9.83K at 20 o C, what would be the resistor value at 80 o C? . And the number is ….

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'EE 434 Lecture 12' - kaiyo


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Ee 434 lecture 12 l.jpg
EE 434Lecture 12

Devices in Semiconductor Processes

Diodes

Capacitors

MOS Transistors


Slide2 l.jpg

Quiz 10

A “10K” resistor has a temperature coefficient of +80ppm/oC If the resistor was measured to be 9.83K at 20oC, what would be the resistor value at 80oC?



Slide4 l.jpg

Quiz 10

A “10K” resistor has a temperature coefficient of +80ppm/oC If the resistor was measured to be 9.83K at 20oC, what would be the resistor value at 80oC?

Solution


Slide5 l.jpg

Review from Last Time

  • Process Flow is a “recipe” for the process

    • Shows what can and can not be made

    • Gives insight into performance capabilities and limitations

  • Back-End Processes

    • Die attach options (eutectic, preform,conductive epoxy)

      • Stresses the die

    • Bonding

      • Wire bonding

      • Bump bonding

    • Packaging

      • Many packaging options

      • Package Costs can be large so defective die should be eliminated before packaging


Basic devices and device models l.jpg
Basic Devices and Device Models

  • Resistor

  • Diode

  • Capacitor

  • MOSFET

  • BJT


Diodes pn junctions l.jpg
Diodes (pn junctions)

N

P

Depletion region created that is ionized but void of carriers


Pn junctions l.jpg
pn Junctions

N

P

Physical Boundary Separating n-type and p-type regions

If doping levels identical, depletion region extends equally into n-type and p-type regions


Pn junctions9 l.jpg
pn Junctions

N+

P-

Physical Boundary Separating n-type and p-type regions

Extends farther into p-type region if p-doping lower than n-doping


Pn junctions10 l.jpg
pn Junctions

N-

P+

Physical Boundary Separating n-type and p-type regions

Extends farther into n-type region if n-doping lower than p-doping


Pn junctions11 l.jpg
pn Junctions

N

P

I

V


Pn junctions12 l.jpg
pn Junctions

I

N

P

V

I

V

Diode Equation:

JS= Sat Current Density

A= Junction Cross Section Area

VT=kT/q

n is approximately 1


Basic devices and device models13 l.jpg
Basic Devices and Device Models

  • Resistor

  • Diode

  • Capacitor

  • MOSFET

  • BJT


Capacitors l.jpg
Capacitors

  • Types

    • Parallel Plate

    • Fringe

    • Junction


Parallel plate capacitors l.jpg
Parallel Plate Capacitors

A2

C

A1

cond1

cond2

d

insulator

A = area of intersection of A1 & A2

One (top) plate intentionally sized smaller to determine C

: Dielectric constant



Fringe capacitors l.jpg
Fringe Capacitors

C

d

A is the area where the two plates are parallel

Only a single layer is needed to make fringe capacitors



Capacitance l.jpg
Capacitance

Junction Capacitor

C

VD

p

d

d

n

depletion

region

  • Note: d is voltage dependent

  • capacitance is voltage dependent

  • usually parasitic caps

  • varicaps or varactor diodes exploit

  • voltage dep. of C

Cj0: junction capacitance at VD = 0V

B: barrier or built-in potential


Basic devices and device models20 l.jpg
Basic Devices and Device Models

  • Resistor

  • Diode

  • Capacitor

  • MOSFET

  • BJT


N channel mosfet l.jpg
n-Channel MOSFET

Poly

Gate oxide

n-active

p-sub


N channel mosfet22 l.jpg
n-Channel MOSFET

Gate

Drain

Source

L

W

LEFF

Bulk


N channel mosfet23 l.jpg
n-Channel MOSFET

Poly

Gate oxide

n-active

p-sub

depletion region (electrically induced)


N channel mosfet operation and model l.jpg
n-Channel MOSFET Operation and Model

VDS

ID

VGS

IG

VBS

IB

Apply small VGS

(VDS and VBS assumed to be small)

ID=0

IG=0

IB=0

Depletion region electrically induced in channel

Termed “cutoff” region of operation


N channel mosfet operation and model25 l.jpg
n-Channel MOSFET Operation and Model

VDS

ID

VGS

IG

VBS

IB

Increase VGS

(VDS and VBS assumed to be small)

ID=0

IG=0

IB=0

Depletion region in channel becomes larger


N channel mosfet operation and model26 l.jpg
n-Channel MOSFET Operation and Model

VDS

Critical value of VGS that creates inversion layer termed threshold voltage, VT)

ID

VGS

IG

VBS

IB

(VDS and VBS small)

Increase VGS more

IDRCH=VDS

IG=0

IB=0

Inversion layer forms in channel

Inversion layer will support current flow from D to S

Channel behaves as thin-film resistor


N channel mosfet operation and model27 l.jpg
n-Channel MOSFET Operation and Model

VDS

ID

VGS

IG

VBS

IB

(VDS and VBS small)

Increase VGS more

IDRCH=VDS

IG=0

IB=0

Inversion layer in channel thickens

RCH will decrease

Termed “ohmic” or “triode” region of operation



N channel mosfet operation and model29 l.jpg
n-Channel MOSFET Operation and Model

VDS

ID

VGS

IG

VBS

IB

(VBS small)

Increase VDS

ID=?

IG=0

IB=0

Inversion layer thins near drain

ID no longer linearly dependent upon VDS

Still termed “ohmic” or “triode” region of operation



N channel mosfet operation and model31 l.jpg
n-Channel MOSFET Operation and Model

VDS

ID

VGS

IG

VBS

IB

(VBS small)

Increase VDS even more

ID=?

IG=0

IB=0

Inversion layer disappears near drain

Termed “saturation”region of operation

Saturation first occurs when VDS=VGS-VT


Saturation region of operation l.jpg
Saturation Region of Operation

For VDS at saturation


N channel mosfet operation and model33 l.jpg
n-Channel MOSFET Operation and Model

VDS

ID

VGS

IG

VBS

IB

(VBS small)

Increase VDS even more (beyond VGS-VT)

ID=?

IG=0

IB=0

Nothing much changes !!

Termed “saturation”region of operation


Saturation region of operation34 l.jpg
Saturation Region of Operation

For VDS in Saturation


Model summary l.jpg
Model Summary

Note: This is the third model we have introduced for the MOSFET