MICROSENS

Product S ecific Data Sheet

Ion Sensitive Field-Effect Transistor - ISFET

• MSFET 3310 Si3N4 gate

• MSFET 3320 AI203 gate

• The ISFET devices are realized with

microelectronic technology compatible

with CMOS processes.

• Si3N4 and AI203 insulating gate

ISFET base devices are measuring the

pH value in a wide range from basic toacidic solutions

ISFET principle

• The measurement of ion concentra­

tions such as K+, Ca2+ is realized with

an additional organic ion-selective

membrane photopolymerized on the

insulating gate of the sensor.

ISFET device

Legend:

1. drain

2. source

3. substrate

4. Si02 insulator

5. Si3N4 or AI203insulator

6. meta 1contacts

7. reference electrode

8. ion selective mem­

brane (option)

9. encapsulant

ISFET encapsulated on a ceramic based Printed

Circuit Board (PCB)

s e n S 0 r s p e c i f c a t.1 o n S

pH

K+, Ca2+, Mg2+,with additional ion selective membrane

Measured chemical

speCies

MSFET3310 MSFET3320

• Sensor construction (3310)(3320)

Base structure

• Sensor base materials

Silicon, polysilicon, Si3N4,AI203

• Technology used

4" planar CM OS process

Sensitive membrane• pH-sensitive material

Si3N4AI203

• ion selective membrane

lonophores doped polysiloxane

Sensor dimensions.Chip dimensions

0.6 x 4.5 x 0.3 mm

• Packaged sensor: - DIL

20 x 8 x 2 mm (pins not included)

- PCB (typical)

50 x 4 x 1 mm

• Sensor SpecificationsSensitivity:

• pH:

50 mV/pH unit

• K+:

58 mV/pK

• Ca2+30 mV/pCa

Concentration range:

• pH:

1 - 12

• K+:

10-7 - 1 (M)

• Ca2+

10-6 -1 (M)

Accuracy

0.01 pH (or 0.1 %)

Stability

0.1 pH/day (or 1%)

Operating temperature

-450 C + 1200 C

Response time

< 1 sec. (90%)

• Reference-electrode

Ami n iaturized Ag/Ag C 1 Reference

Electrode is realized together with the

packaged ISFET chip acting as metal

gate electrode and providing a stable

reference potential. For specific applica­

tions, an Integrated Reference

Electrode (IRE)* has been developedwhich is manufactured on the same

chip together with the ISFET.

The Ag/AgCI electrode is then deposi­

ted on the reversed side of the ISFET

device and a silicon-structured cavity is

containing the KCI Electrolyte. The

liquid junction of the IRE is obtained by

a porous silicon membrane manufactu­

red on the ISFET front-si de chip.

* Patent US 06/7757669.

Typical Sensor Character stics

15

_ 1.3

LU"'"--~-=/2:. ~. ~-_.-

<n

en> 97+/

>270

..s<D

210<n c0~ 150t;:; ~ 90.0+"'"

30.0

.5

K+ ion selective membranes on planarCMOS ISFET

Photopolymerised ion-selective membranes

Highly selective organic membranes for differention-concentration measurements such as K+,

Ca2+, Mg2+ are deposited and structured with a

wafer-scale photolithographie technique. Thanks

the very good adhesion and stability of these

membranes the specifie ion selective FETcan be

used for ion-concentration monitoring with a good

sensitivity and a linearity within a wide range ofconcentration down to 10-6 M.

o 1 2 3 4 5 6 7 8 9 10 11 1213 14

pH

AI20J gate ISFET pH sensitivitySaturated calomel reference electrode

buffer solutions pH 2 ta 11

Siope = 53.7 mV/pH

Vds = 1 V Ids = 50 ~A

Potassium membrane ISFET

DlL packaged ISFET multi-sensor devicefor flow through measurement

Flow through cell measurement configura­tion

The ISFETsingle or multi-sensor chip is mounted,

on a standard DIL package. The disposable sensor

can be used for single or multiple use in a flow

through cell measurement system.

3.000 , ,500>2.900

400.s>

m.""

- CQJ

2.800 300El

:>0c-mQJ

."" 200>

c 2.700 .~QJ a Qjc-

a:::

y..C

2.600 100-QJQJ :>a:::

2.500

03

456789

pH

ISFET pH sensitivityAI203 gate device referenced towards satura­

ted calomel electrode (SCE) and Ag/AgCI

integrated reference electrode (IRE)

Vds = 1.5 V Ids = 100 ~A

Calcium membrane ISFET

>180

3Slope: 30.0 mV / pCa

..s<D

<n 140c 0sriO'

100>- LW~+

50.0

NroU 20.0

-5.00 -4.00 -3.00 -2.00

LOG a (K)

-1.00 -5.00 -4.00 -3.00 -2.00

LOG a (Ca)

-100

ISFET K+ ion concentration sensitivity ISFET Ca2+ ion concentration sensitivity

lmMICROSENS

Packaging

• ISFET-chips are mounted, micro­

bounded and sealed in hermetic encap­

sulant to be used as sensor devices for

different applications. Application spe­

cifie packages, such as hermetically

sealed PCB (Printed Circuit Board) as

weil as OIL (Oual ln Line) standard

package, are available.

ISFET encapsulated in a catheter for

medical "in vivo" pH monitoring

PCB or Kapton based circuits boards are used

for the packaging of pH sensors in

2 mm diameter catheters.

Dil Packaged ISFET for flow through

cel! measurement system.

Specifie OIL packaged ISFET are manufactu­

red with silicone encapsulant providing on

hermetic interface with the tubing of a flow

through cell system.

1

1

1

1 1

L ~ J

Ids = 100 ~A

rel

0

c::=::Jflcr---..L + Vds = 1.0V 1~ substrate

G

---r-- Vd > Vs

S

Vgs> 0

Electrical connections of ISFET devices

Legend:0: Drain

S: Source

Su b : Su bstrate

G : Reference electrode

Schematic electronic circuit diagram

This circuit configuration is used for a

constant drain current operation of the ISFET

device.

MICROS ENS SA

Rue Jaquet-Droz 1. CH-ZOO? Neuchâtel/Switzerland

Tél.:+41327205161 • Fax: +41 327205744

www.micrasens.ch • info@microsens.ch