Copy of Pressure Sensor Lecture

8/9/2019 Copy of Pressure Sensor Lecture

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Pressure Sensor Lecture

ECE544

Prepared by D.J. Tegtmeier


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Presentation Overview1. Pressure Sensor Theory Overview

. Pressure Sensor Pro!ess Overview

and "abri!ation Theory #eview

$. E%press Sa&ety Con!erns &or Parti!u'ar

Pro!esses


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Pressure Sensor Theory Two Main Types of Pressure Sensors

Capacitive Sensors

( )or* based on measurement o&!apa!itan!e &rom two para''e'p'ates.

( C + ,-d / - + area o& p'ates d +distan!e between.

( This imp'ies that the response o& a!apa!itive sensor is inherent'ynon0'inear. )orsened bydiaphragm de&'e!tion.

( ust use e%terna' pro!essor to!ompensate &or non0'inearity


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Pressure Sensor TheoryPie2oresistive Sensors

)or* based on thepie2oresistive properties o&si'i!on and other materia's.

Pie2oresistivity is a response tostress.

Some pie2oresistive materia'sare Si/ 3e/ meta's.

n semi!ondu!tors/pie2oresistivity is !aused by

&a!tors geometry de&ormationand resistivity !hanges.

#e&eren!e httpen.wi*ipedia.orgwi*iPie2oresistan!e6E&&e!t


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Pressure Sensor Theory Our Sensor is a

Pie2oresistive

Sensor based on a

)heatstone 7ridge

Con&iguration.

#esistors are made

with 7oron Di&&usion.


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Pressure Sensor Process

Overview nitia' )a&er is 55

>m thi!*/ n0type/

?1@@A doub'e0side

po'ished BDSP.

)hy use a ?1@@A

DSP wa&er;

)hy use an n0typesubstrate;


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Overview Step 1 )hat shou'd -


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Overview Step 2-ny guesses; Therma' O%idation

)et O%idation"o''owed by DryO%idation

)hy do )et O%idation&o''owed by Dry;

Si + O2 SiO2 (Dry Oxiation!

Si + 2"2O2 SiO2 (#et Oxiation!


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Overview Step 3 Photo'ithography &or

Pie2oresistive E'ements Conta!t


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Overview Step 3 Cont. D=K ethod using

er!ury


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Overview Step 4 - Diffusion Creates #esistors in

Substrate Three ethods

1. So'id Evap. BTetramethy'7orate/ 7oron =itride 0 #are

. 3aseous M Diborane B7N MDangerous 1N@ ppm &or 15min 'i&e threatening

$.


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Pressure Sensor Process Overview

Step 4 Diffusion Continue )hat is a !onstant sour!e di&&usion;

)hat is a 'imited sour!e di&&usion;

)hat is drive0in;

ow !an you get rid o& boron o%ide

and borosi'i!ate g'ass;

)hat additiona' step does this

!reate;

Sur

&a!e

Con

!entration

Jun!tion Depth


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Step ! "ac#sie Phot$itho%raphy )indows ust 7e

Opened in =ew O%ide

"or 7a!*side Et!h.

Ise "ront to 7a!*side-'ignment

Et!h Si'i!on Dio%ide

w7OE B" N1

"inished when wa&er ishydrophobi! Bwater ro''s

o&&


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Step ! "ac#sie Phot$ith. Cont. ust -'ign ar*s

&rom 1stas* on

"ront o& )a&er to

Those on 7a!*

)hat is Sp'it "ie'd

-'ignment;

)hat is a !riti!a'dimension;

Photo

httpwww.ee.byu.edu!'eanrooma'ignment.phtm'


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Step & "ac#sie 'tch =eed @ >m Thi!*

Diaphragm/ there&oremust et!h appro%. 5@@>m.

)hy use T- insteado& QO i& QO is &aster;

TMAH/IPA KOH

25% wt.TMAH

45% wt KOH

17% vol IPA

70o 75o

!100" 12 #/$r 21 #/$r

!111" 0.7 #/$r 0.05 #/$r

S&O2 0.01#/$r 0.20 #/$r

#e& Crain/ ar*. RPowerpoint Thesis De&ense


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Step ( Pho$ith. )or Contact

*inows Topside -'ignment

Ise Ship'ey 11$

Postive #esist

#e& Crain/ ar*. RPowerpoint Thesis De&ense


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Step + ,eta$ Deposition an Pattern

Severa' ethods/ we

use Sputtering

Types Bagnetron

0#" Sputter

0DC Sputter

)hen do you use #"

sputter;

)hat is a sputter et!h;

)hat is argon used; httpen.wi*ipedia.orgwi*iSputtering


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Photo$itho%raphy an $uinu 'tch

"irst Photoresist isdeposited on meta' andpatterned &or desired tra!es

Ises -'uminum Et!h/ 50

5H Phosphori! -!id/ 0H=itri! -!id/ and )ater

)hy in the pi!ture is there aho'e in the meta';

)hat is the di&&eren!e

between 'i&t0o&& and meta'et!h;

ust Therma' -nnea' -&terEt!h/ )hy;


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Overview *afer Testin%

5 Squares

1 Square

3

Squar

es

'(lw/)*

's(/)*'(+squares,/)*

o-tats qu&vale-t 's(0.5 squares'es&st&ve le#e-t .3 squares


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Overview *afer Testin%

Testing Stru!tures

8an Der Pauw

0Conta!ts on Stru!ture

Edge/ Symmetri!a'

#s + BU'n 8!dab Qe'vin Stru!tures

0Ised &or E&&e!tive


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Overview noic "onin%

=egative Po'arity

)hy;

Positive Po'arity is &aster.

igh Temperature/ igh8o'tage

=aV ions moved &rom

inter&a!e/ 'eaving

O%ygen and &ormingSiO.


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*ire "onin% an Pac#a%in%

Severa' Types M 7a''/

)edge/ et!.

eated go'd wire is

pressed onto sur&a!e/me'ted/ and then

!oo'ed.


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Process Safety

ydro&'uori! -!id

0 @05@H So'utions

ay Produ!e =o

mmediate Symptoms 0 .5H Produ!e

ypo!a'!emia

0"ata' -!!idents 7e'ow

1@H

httpwww0sa&ety.deas.harvard.eduadvisea!!ident.htm'


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Process Safety

Prote!t our ands

-void P'a!ing ands

=ear )a&er 7e -ware o& Those

)or*ing =ear ou

Communi!ate

httpwww emedi!ine !omemergtopi!@4 htm

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