In this paper comparative analysis of MEMS (Micro-electro-mechanical System) based Micro-hotplate
using three different heating elements use as separately are presented. Three different materials (viz. DilverP1,
Polysilicon, and Platinum) are used as heating elements with same thickness of 0.2 m. Coventor-
WareTM simulator has been used for construction of 3D model and electro-thermo-mechanical analysis of
Micro-hotplate device. Power consumption, stress and displacement of Micro-hotplate are studied at operating
temperature (165 ºC). It is obtained that power consumption, stress and displacement of Dilverp1 heating element
are 13.06 mW, 190 MPa and 0.028 m which are less in comparison to those with Poly Silicon heater
and Platinum heater at moderate temperature (150-200 C) over the sensing material (ZnO).
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3581

Kantha, Bijoy

Sarkar, Subir Kumar

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 6 No 1, 01004(5pp) (2014) Том 6 № 1, 01004(5cc) (2014) 
 
 
2077-6772/2014/6(1)01004(5) 01004-1  2014 Sumy State University 
The Design of a Low Power MEMS Based Micro-hotplate Device Using a Novel Nickel Alloy 
for Gas Sensing Applications 
 
Bijoy Kantha*, Subir Kumar Sarkar 
 
Jadavpur University, 188, Raja S. C. Mullick Road, Kolkata – 700032 West Bengal, India 
 
(Received 01 October 2013; published online 06 April 2014) 
 
In this paper comparative analysis of MEMS (Micro-electro-mechanical System) based Micro-hotplate 
using three different heating elements use as separately are presented. Three different materials (viz. Dil-
verP1, Polysilicon, and Platinum) are used as heating elements with same thickness of 0.2 m. Coventor-
WareTM simulator has been used for construction of 3D model and electro-thermo-mechanical analysis of 
Micro-hotplate device. Power consumption, stress and displacement of Micro-hotplate are studied at operating 
temperature (165 ºC). It is obtained that power consumption, stress and displacement of Dilverp1 heating el-
ement are 13.06 mW, 190 MPa and 0.028 m which are less in comparison to those with Poly Silicon heat-
er and Platinum heater at moderate temperature (150-200 C) over the sensing material (ZnO). 
 
Keywords: MEMS, Micro-hotplate, CoventorWareTM, Electro-thermo-mechanical, ZnO. 
 
 PACS numbers: 44.10. + i, 73.50.Lw, 62.20. – x 
 
 
                                                          
*bijoyvlsi@gmail.com 
1. INTRODUCTION 
 
Metal oxide based Micro-hotplate devices are essen-
tial for their versatile applications in industrial and 
domestic activities [1]. Low power consumption is a 
basic requirement for a gas sensor with an acceptable 
battery life-time. Conventional type gas sensor had 
some properties like high power consumption (500 mW-
1 W) and high operating temperature (≥ 300 C) [2]. 
Several work on platinum and polysilicon heating ele-
ment based gas sensors with high operating tempera-
ture (400-700 C) [2] have been reported. The life time 
of the hotplate is reduced due to high power consump-
tion. The problems can be reduced with the application 
of MEMS technology [3]. Several nano-structured semi-
conducting oxide based gas sensor’s works have been 
recorded at relatively low temperature (150-300 C)  
[4, 5]. The advantages of semiconductor gas sensors are 
low power consumption and a real simplicity in func-
tion, good mechanical stability, CMOS compatibility 
and low cost [6-8].Very little similar type report has 
been published on metal oxide based micro-hotplate 
device [8]. The various micromachining processes of 
low power MEMS micro-hotplate structure have been 
demonstrated [9-13].  
Gas sensors based on the semiconducting metal-
oxides such as SnO2 and ZnO [14-18] have been found 
to be very useful for detecting ethanol vapor, oxygen 
[19] and H2 [20] gases. Electro-thermo-mechanical 
analysis of Micro-hotplate model is determined by 
CoventorWareTM software (A MEMS design and simu-
lation software). Software based simulator is used to 
save the cost of device fabrication. The Mem Mech 
solver of CoventorWareTM software is used to obtain 
the temperature, mechanical deflection and stress dis-
tribution of the MEMS based Micro-hotplate. The re-
sult is used to predict the temperature and displace-
ment as a function of the applied voltage across heating 
layer. The mechanical behavior of the micro-hotplate is 
analyzed using the displacement result of the micro-
hotplate. In this paper MEMS based Micro-hotplate 
device using different heating materials (DilverP1, Pol-
ysilicon, Platinum) is reported for the detection of suit-
able material as heating element which is consumed 
low power and ZnO is used as a sensing layer of the 
Micro-hotplate. It has shown that power consumption, 
stress and displacement of Dilverp1 material are less 
in comparison to those with Poly Silicon heater and 
Platinum heater at moderate temperature (150-200 C) 
over the sensing material. So Dilverp1 heater will pro-
vide good mechanical strength comparison to those 
with Pt heater, Poly Silicon heater.The structure of 
MEMS based Micro-hotplate device is presented in 
section 2. Mathematical Formulations are discussed in 
section 3. Results and Discussions are presented in 
section 4 and conclusion appears in section 5.  
 
2. DEVICE STRUCTURE 
 
The flow chart for the preparation of the Micro-
hotplate device is pictorially depicted in Fig. 1. The 
simulation based fabrication is initially started with 
deposition of glass wafer (0.5 m) and then heater layer 
(DilverP1) with a length of 18µm, width of 20 m and 
thickness of 5µm is deposited to glass wafer to form the 
anchor. After formation of the anchor, DilverP1 layer 
with a length of 100 m, width of 22 m and thickness 
of 0.2 m is deposited on the anchors to form the heater 
layer. Silicon Nitride (Si3N4) and Silicon-di-oxide (SiO2) 
are used as an isolation layer of Micro-hotplate device. 
In this design, the electrode and sensing elements are 
gold (Au) with the thickness of 0.3 m and zinc oxide 
(ZnO) with the thickness of 0.6 m. Gold electrodes are 
deposited on the ZnO layer of the Micro-hotplate de-
vice. The thicknesses of air-gap, isolation, electrode, 
and sensing layers are 4 m, 1 m respectively. The 
dimension of central beam is 12 m  14 m. The dif-
ferent simulation based fabrication steps for developing 
the Micro-hotplate in CoventorWareTM (A MEMS de-
sign and simulation software) are stack material depo- 
 BIJOY KANTHA, SUBIR KUMAR SARKAR J. NANO- ELECTRON. PHYS. 6, 01004 (2014) 
 
 
01004-2 
 
 
 
a b 
 
  
c d 
 
 
 
 
e f 
 
g 
 
Fig. 1 – The process flow chart of the device 
 
 
 
Fig. 2 – The structure of micro-hotplate device 
 
sition, planar fill process, wet etching process, sacri-
ficed process and photolithography.  
The extruded brick mesh with lateral element size 
of 10 m is selected for the solid model. The fine-
structure region is consisted of Si3N4, Au, ZnO layers. 
The fine-structure region is meshed with element size 
of 0.3 m. The structure of micro-hotplate device is 
shown in fig. 2. CoventorWareTM software has been 
used for the simulation of the device.  
 
3. MATHEMATICAL FORMULATIONS 
 
Heat is produced in Micro-hotplate and can be esti-
mated by Joule’s Law as follows 
 
 2q rI t    (1) 
 
Here heated-area resistance is denoted by r and Δt 
denotes the time in second. Thermal losses are mainly 
three types: conduction in the device, convection in the 
air and radiation. So, the generation of heat by the mi-
cro-hotplate is the combination of three heat losses 
(conduction qc, convection qcon, and radiation qr) 
 
 2 c con rq rI t q q q       (2) 
 
The power can be obtained from equation (2) by di-
viding with time (Δt) 
 
 2 c con r
q q q
rI
t t t
  
  
  
 (3) 
 
First, the power lose due to conduction in the sub-
strate is given by 
 
 c
q
KA
t x
 

 
 (4) 
 
Here thermal conductivity of the substrate is denot-
ed by K, A is the area of cross-section of the surface in 
the substrate and temperature gradient is denoted by 
Δθ / Δx. 
Second, the power lose due to convection in the air 
is defined as 
 
 .con conv conv
q
h A
t


 

 (5) 
 
hconv is the Heat transfer coefficient (assumed inde-
pendent of t here) Aconv is the surface area of the heat 
being transferred, Δθ is the time-dependent thermal 
gradient between environment and device.  
Third, the powers lose due to radiation is given by 
[21]: 
 
 4r r
q
S
t
 

 

 (6) 
 
Here the emissivity of the material is denoted by ε,  
is the Stefan-Boltzmann constant (5.67  10 – 8Wm – 2K – 4) 
and the radiation of the surface is denoted by Sr. So, the 
total power loses can be defined by replacing the values of 
three power losses into equation (3): 
 
 2 4conv conv rrI KA h A S
x

  

    

 (7) 
 
The displacement is evaluated from the stress and 
mechanical static equation using the input thermal 
strain obtained from the solved temperature distribu-
tion and thermal expansion coefficient [8]. 
 
 ( - )i     (8) 
 
 i T    (9) 
 
Where , , i, Y, , ∆θ are stress, strain, initial ther-
mal strain, young’s modulus matrix, thermal expansion 
coefficient and differential temperature respectively. 
 
4. RESULTS AND DISCUSSIONS 
 
The parameters are used in our simulation are giv-
en in Table 1. The simulation result of temperature 
 THE DESIGN OF A LOW POWER MEMS BASED… J. NANO- ELECTRON. PHYS. 6, 01004 (2014) 
 
 
01004-3 
distribution of Micro-hotplate with selected heater ma-
terial (DilverP1) is depicted in Fig. 3. It shows from 
Fig. 3 that the temperature of DilverP1 plate layer is 
438 K at the center of DilverP1 plate layer. Proper elec-
trical isolation is provided by using Silicon Nitride 
(Si3N4) and Silicon-di-oxide (SiO2) layers. SiO2 and 
Si3N4 are used to improve the temperature uniformity 
above the sensing layer (ZnO). The stress distribution 
and mechanical deflection of Micro-hotplate using Dil-
verP1 material are shown in Fig. 4 and in Fig. 5. The 
mechanical deflection of DilverP1 heating material is 
less than other two materials. Based on the simulation 
result, it is noted that maximum stress occurs at the 
edge regions of the Micro-hotplate. The Current 
Density distribution of DilverP1 is shown in Fig. 6. The 
stress distributions of Polysilicon and Platinum based 
Micro-hotplate are shown in Fig. 7 and in Fig. 8. 
 
Table 1 – Device Parameters used in the Simulation of Micro-
hotplate 
 
Parameter Value 
Length of DilverP1 material 100 m 
Width of DilverP1 material 22 m 
Thickness of DilverP1 material 0.2 m 
 
 
 
Fig. 3 – Electro-thermal simulation of 0.2 m thick beam of 
DilverP1 material using CoventorWareTM Software 
 
     
 
Fig. 4 – Stress distribution of 0.2 m thick beam of DilverP1 
material using CoventorWareTM Software 
 
  
 
Fig. 5 – Electro-mechanical simulation of 0.2 m thick beam 
of DilverP1 material using CoventorWareTM Software 
 
 
Fig. 6 – Current Density distribution of 0.2 m thick beam of 
DilverP1 material using CoventorWareTM Software 
 
 
 
Fig. 7 – Stress distribution of 0.2 m thick beam of Polysilicon 
material using CoventorWareTM Software 
 
  
 
Fig. 8 – Stress distribution of 0.2 m thick beam of Platinum 
material using CoventorWareTM Software 
 
Fig. 9 indicates Power Consumption-Voltage char-
acteristics plot of Micro-hotplate using different heat-
ing elements (DilverP1, Polysilicon, and Platinum). 
From Fig. 9, it has shown that power consumption of 
DilverP1 material is less in comparison to Poly Silicon 
plate and Platinum plate at moderate temperature 
(150-200 C) over the sensing material (ZnO). 
 
0.0 0.1 0.2 0.3 0.4 0.5
0
10
20
30
40
50
60
70
P
o
w
e
r 
C
o
n
s
u
m
p
ti
o
n
 (
m
W
)
Voltage (Volt)
 DilverP1
 Polysilicon
 Platinum
 
 
Fig. 9 – Applied voltage as a function of Power Consumption 
 
The heater temperature along the applied voltage is 
plotted for different heating materials in Fig. 10. It is 
revealed that the temperature profile becomes more 
significant as applied voltage increases. Also from the 
 BIJOY KANTHA, SUBIR KUMAR SARKAR J. NANO- ELECTRON. PHYS. 6, 01004 (2014) 
 
 
01004-4 
simulation results we conclude that out of the materi-
als considered here, DilverP1 material is the best for 
desired operating temperature. 
 
0.0 0.1 0.2 0.3 0.4 0.5
300
400
500
600
700
800
900
1000
T
e
m
p
e
ra
tu
re
 (
K
)
Voltage (V)
 DilverP1
 Polysilicon
 Platinum
 
 
Fig. 10 – Heater Temperature-Voltage characteristics plot of 
Micro-hotplate device 
 
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
0.00
0.02
0.04
0.06
0.08
0.10
0.12
D
is
p
la
c
e
m
e
n
t 
(
m
)
Voltage (V)
 DilverP1
 Polysilicon
 Platinum
 
 
Fig. 11 – Displacement-Voltage characteristics plot of Micro-
hotplate device 
 
Fig. 11 represents the variation of displacement as 
a function of voltage for different heating elements 
(DilverP1, Polysilicon, and Platinum). From the graph, 
it is seen that the displacement of DilverP1 material is 
less than other two materials (Polysilicon plate and 
Platinum plate) at moderate temperature (165 C) over 
the sensing material (ZnO). 
This paper presents Micro-hotplate device with se-
lected material as heating beam (DilverP1). The com-
position of DilverP1 is shown in Table 2 [22]. The ma-
terial properties of different heating elements are given 
in Table 3 [22]. 
 
DilverP1 Polysilicon Platinum
0
10
20
30
40
50
60
70
P
o
w
e
r 
C
o
n
s
u
m
p
ti
o
n
 (
m
W
)
Materials
 Power Consumption
 
 
(a) 
DilverP1 Polysilicon Platinum
0.00
0.02
0.04
0.06
0.08
0.10
0.12
D
is
p
la
c
e
m
e
n
t 
(
m
)
Materials
 Displacement 
 
 
(b) 
 
DilverP1 Polysilicon Platinum
0
50
100
150
200
250
300
S
tr
e
ss
 (
M
P
a
)
Materials
 Stress
 
 
(c) 
 
Fig. 12 – Comparison Chart (a) Power Consumption of differ-
ent materials (b) Displacement of different materials (c) Stress 
of different materials 
 
DilverP1 consumes low power due to high resistivity 
and the life time of the Micro-hotplate can be increased 
with the use of a low cost alloy (DilverP1) having low 
thermal expansion coefficient (4.2  10 – 6/C) and very 
high yield stress (680 MPa). In presence of Cobalt, Dil-
verP1 shows corrosion resistant property. Very low stress 
is induced above the micro-hotplate due to low thermal 
expansion coefficient of DilverP1material. So it can be 
used as an ideal material for the micro-hotplate. The com-
parison chart is shown in Fig. 12. The SEM image of sens-
ing layer is shown in Fig. 13. 
 
Table 2 – Composition (Weight %) 
 
Element Ni Co Mn Si C Fe 
Typical 
value  
29 17  0.35  0.15  0.02 Bal 
 
Table 3 – Material Properties used in the Simulation of Mi-
cro-hotplate 
 
Materials Electrical resistivi-
ty in     Ωm 
Young’s modu-
lus GPa 
Pt 10.6  10 – 8 168 
Au 2.2  10 – 8 78 
Polysilicon 3.22  10 – 7 169 
DilverP1 49  10 – 8 207 
 
 THE DESIGN OF A LOW POWER MEMS BASED… J. NANO- ELECTRON. PHYS. 6, 01004 (2014) 
 
 
01004-5 
 
 
Fig. 13 – SEM image of sensing layer 
 
5. CONCLUSION 
 
In this paper, the electro-thermo-mechanical analy-
sis of Micro-hotplate device has been reported at the 
operating temperature range of 150-200 ºC. The com-
parative analysis of Micro-hotplate using different 
heating elements ((DilverP1 micro- hotplate, Polysili-
con micro-hotplate, Platinum micro hot-plate) has been 
presented at the same temperature (165 ºC). Coven-
torWareTM software is used to get temperature, dis-
placement and stress distribution of micro-hotplate. 
Present simulation has shown that power consumption 
and displacement of Dilverp1 material are less in com-
parison to Poly Silicon plate and Platinum plate at 
moderate temperature (150-200C) above the sensing 
material (ZnO). The cost of DilverP1 is less compared 
to Platinum and Poly-Silicon, so it’s suitable for cost 
effective gas sensor fabrication.   
 
AKNOWLEDGEMENTS 
 
Authors are grateful to TEQIP PHASE-II for provid-
ing the necessary fund for carrying out this work. 
 
 
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English

The Design of a Low Power MEMS Based Micro-hotplate Device Using a Novel Nickel Alloy for Gas Sensing Applications

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 6 No 1, 01004(5pp) (2014) Том 6 № 1, 01004(5cc) (2014)   2077-6772/2014/6(1)01004(5) 01004-1  2014 Sumy State University The Design of a Low Power MEMS Based Micro-hotplate Device Using a Novel Nickel Alloy for Gas Sensing Applications  Bijoy Kantha*, Subir Kumar Sarkar  Jadavpur University, 188, Raja S. C. Mullick Road, Kolkata – 700032 West Bengal, India  (Received 01 October 2013; published online 06 April 2014)  In this paper comparative analysis of MEMS (Micro-electro-mechanical System) based Micro-hotplate using three different heating elements use as separately are presented. Three different materials (viz. Dil-verP1, Polysilicon, and Platinum) are used as heating elements with same thickness of 0.2 m. Coventor-WareTM simulator has been used for construction of 3D model and electro-thermo-mechanical analysis of Micro-hotplate device. Power consumption, stress and displacement of Micro-hotplate are studied at operating temperature (165 ºC). It is obtained that power consumption, stress and displacement of Dilverp1 heating el-ement are 13.06 mW, 190 MPa and 0.028 m which are less in comparison to those with Poly Silicon heat-er and Platinum heater at moderate temperature (150-200 C) over the sensing material (ZnO).  Keywords: MEMS, Micro-hotplate, CoventorWareTM, Electro-thermo-mechanical, ZnO.   PACS numbers: 44.10. + i, 73.50.Lw, 62.20. – x                                                             *bijoyvlsi@gmail.com 1. INTRODUCTION  Metal oxide based Micro-hotplate devices are essen-tial for their versatile applications in industrial and domestic activities [1]. Low power consumption is a basic requirement for a gas sensor with an acceptable battery life-time. Conventional type gas sensor had some properties like high power consumption (500 mW-1 W) and high operating temperature (≥ 300 C) [2]. Several work on platinum and polysilicon heating ele-ment based gas sensors with high operating tempera-ture (400-700 C) [2] have been reported. The life time of the hotplate is reduced due to high power consump-tion. The problems can be reduced with the application of MEMS technology [3]. Several nano-structured semi-conducting oxide based gas sensor’s works have been recorded at relatively low temperature (150-300 C)  [4, 5]. The advantages of semiconductor gas sensors are low power consumption and a real simplicity in func-tion, good mechanical stability, CMOS compatibility and low cost [6-8].Very little similar type report has been published on metal oxide based micro-hotplate device [8]. The various micromachining processes of low power MEMS micro-hotplate structure have been demonstrated [9-13].  Gas sensors based on the semiconducting metal-oxides such as SnO2 and ZnO [14-18] have been found to be very useful for detecting ethanol vapor, oxygen [19] and H2 [20] gases. Electro-thermo-mechanical analysis of Micro-hotplate model is determined by CoventorWareTM software (A MEMS design and simu-lation software). Software based simulator is used to save the cost of device fabrication. The Mem Mech solver of CoventorWareTM software is used to obtain the temperature, mechanical deflection and stress dis-tribution of the MEMS based Micro-hotplate. The re-sult is used to predict the temperature and displace-ment as a function of the applied voltage across heating layer. The mechanical behavior of the micro-hotplate is analyzed using the displacement result of the micro-hotplate. In this paper MEMS based Micro-hotplate device using different heating materials (DilverP1, Pol-ysilicon, Platinum) is reported for the detection of suit-able material as heating element which is consumed low power and ZnO is used as a sensing layer of the Micro-hotplate. It has shown that power consumption, stress and displacement of Dilverp1 material are less in comparison to those with Poly Silicon heater and Platinum heater at moderate temperature (150-200 C) over the sensing material. So Dilverp1 heater will pro-vide good mechanical strength comparison to those with Pt heater, Poly Silicon heater.The structure of MEMS based Micro-hotplate device is presented in section 2. Mathematical Formulations are discussed in section 3. Results and Discussions are presented in section 4 and conclusion appears in section 5.   2. DEVICE STRUCTURE  The flow chart for the preparation of the Micro-hotplate device is pictorially depicted in Fig. 1. The simulation based fabrication is initially started with deposition of glass wafer (0.5 m) and then heater layer (DilverP1) with a length of 18µm, width of 20 m and thickness of 5µm is deposited to glass wafer to form the anchor. After formation of the anchor, DilverP1 layer with a length of 100 m, width of 22 m and thickness of 0.2 m is deposited on the anchors to form the heater layer. Silicon Nitride (Si3N4) and Silicon-di-oxide (SiO2) are used as an isolation layer of Micro-hotplate device. In this design, the electrode and sensing elements are gold (Au) with the thickness of 0.3 m and zinc oxide (ZnO) with the thickness of 0.6 m. Gold electrodes are deposited on the ZnO layer of the Micro-hotplate de-vice. The thicknesses of air-gap, isolation, electrode, and sensing layers are 4 m, 1 m respectively. The dimension of central beam is 12 m  14 m. The dif-ferent simulation based fabrication steps for developing the Micro-hotplate in CoventorWareTM (A MEMS de-sign and simulation software) are stack material depo-  BIJOY KANTHA, SUBIR KUMAR SARKAR J. NANO- ELECTRON. PHYS. 6, 01004 (2014)   01004-2    a b    c d     e f  g  Fig. 1 – The process flow chart of the device    Fig. 2 – The structure of micro-hotplate device  sition, planar fill process, wet etching process, sacri-ficed process and photolithography.  The extruded brick mesh with lateral element size of 10 m is selected for the solid model. The fine-structure region is consisted of Si3N4, Au, ZnO layers. The fine-structure region is meshed with element size of 0.3 m. The structure of micro-hotplate device is shown in fig. 2. CoventorWareTM software has been used for the simulation of the device.   3. MATHEMATICAL FORMULATIONS  Heat is produced in Micro-hotplate and can be esti-mated by Joule’s Law as follows   2q rI t    (1)  Here heated-area resistance is denoted by r and Δt denotes the time in second. Thermal losses are mainly three types: conduction in the device, convection in the air and radiation. So, the generation of heat by the mi-cro-hotplate is the combination of three heat losses (conduction qc, convection qcon, and radiation qr)   2 c con rq rI t q q q       (2)  The power can be obtained from equation (2) by di-viding with time (Δt)   2 c con rq q qrIt t t       (3)  First, the power lose due to conduction in the sub-strate is given by   cqKAt x   (4)  Here thermal conductivity of the substrate is denot-ed by K, A is the area of cross-section of the surface in the substrate and temperature gradient is denoted by Δθ / Δx. Second, the power lose due to convection in the air is defined as   .con conv convqh At  (5)  hconv is the Heat transfer coefficient (assumed inde-pendent of t here) Aconv is the surface area of the heat being transferred, Δθ is the time-dependent thermal gradient between environment and device.  Third, the powers lose due to radiation is given by [21]:   4r rqSt   (6)  Here the emissivity of the material is denoted by ε,  is the Stefan-Boltzmann constant (5.67  10 – 8Wm – 2K – 4) and the radiation of the surface is denoted by Sr. So, the total power loses can be defined by replacing the values of three power losses into equation (3):   2 4conv conv rrI KA h A Sx       (7)  The displacement is evaluated from the stress and mechanical static equation using the input thermal strain obtained from the solved temperature distribu-tion and thermal expansion coefficient [8].   ( - )i     (8)   i T    (9)  Where , , i, Y, , ∆θ are stress, strain, initial ther-mal strain, young’s modulus matrix, thermal expansion coefficient and differential temperature respectively.  4. RESULTS AND DISCUSSIONS  The parameters are used in our simulation are giv-en in Table 1. The simulation result of temperature  THE DESIGN OF A LOW POWER MEMS BASED… J. NANO- ELECTRON. PHYS. 6, 01004 (2014)   01004-3 distribution of Micro-hotplate with selected heater ma-terial (DilverP1) is depicted in Fig. 3. It shows from Fig. 3 that the temperature of DilverP1 plate layer is 438 K at the center of DilverP1 plate layer. Proper elec-trical isolation is provided by using Silicon Nitride (Si3N4) and Silicon-di-oxide (SiO2) layers. SiO2 and Si3N4 are used to improve the temperature uniformity above the sensing layer (ZnO). The stress distribution and mechanical deflection of Micro-hotplate using Dil-verP1 material are shown in Fig. 4 and in Fig. 5. The mechanical deflection of DilverP1 heating material is less than other two materials. Based on the simulation result, it is noted that maximum stress occurs at the edge regions of the Micro-hotplate. The Current Density distribution of DilverP1 is shown in Fig. 6. The stress distributions of Polysilicon and Platinum based Micro-hotplate are shown in Fig. 7 and in Fig. 8.  Table 1 – Device Parameters used in the Simulation of Micro-hotplate  Parameter Value Length of DilverP1 material 100 m Width of DilverP1 material 22 m Thickness of DilverP1 material 0.2 m    Fig. 3 – Electro-thermal simulation of 0.2 m thick beam of DilverP1 material using CoventorWareTM Software        Fig. 4 – Stress distribution of 0.2 m thick beam of DilverP1 material using CoventorWareTM Software     Fig. 5 – Electro-mechanical simulation of 0.2 m thick beam of DilverP1 material using CoventorWareTM Software   Fig. 6 – Current Density distribution of 0.2 m thick beam of DilverP1 material using CoventorWareTM Software    Fig. 7 – Stress distribution of 0.2 m thick beam of Polysilicon material using CoventorWareTM Software     Fig. 8 – Stress distribution of 0.2 m thick beam of Platinum material using CoventorWareTM Software  Fig. 9 indicates Power Consumption-Voltage char-acteristics plot of Micro-hotplate using different heat-ing elements (DilverP1, Polysilicon, and Platinum). From Fig. 9, it has shown that power consumption of DilverP1 material is less in comparison to Poly Silicon plate and Platinum plate at moderate temperature (150-200 C) over the sensing material (ZnO).  0.0 0.1 0.2 0.3 0.4 0.5010203040506070Power Consumption (mW)Voltage (Volt) DilverP1 Polysilicon Platinum  Fig. 9 – Applied voltage as a function of Power Consumption  The heater temperature along the applied voltage is plotted for different heating materials in Fig. 10. It is revealed that the temperature profile becomes more significant as applied voltage increases. Also from the  BIJOY KANTHA, SUBIR KUMAR SARKAR J. NANO- ELECTRON. PHYS. 6, 01004 (2014)   01004-4 simulation results we conclude that out of the materi-als considered here, DilverP1 material is the best for desired operating temperature.  0.0 0.1 0.2 0.3 0.4 0.53004005006007008009001000Temperature (K)Voltage (V) DilverP1 Polysilicon Platinum  Fig. 10 – Heater Temperature-Voltage characteristics plot of Micro-hotplate device  0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.450.000.020.040.060.080.100.12Displacement (m)Voltage (V) DilverP1 Polysilicon Platinum  Fig. 11 – Displacement-Voltage characteristics plot of Micro-hotplate device  Fig. 11 represents the variation of displacement as a function of voltage for different heating elements (DilverP1, Polysilicon, and Platinum). From the graph, it is seen that the displacement of DilverP1 material is less than other two materials (Polysilicon plate and Platinum plate) at moderate temperature (165 C) over the sensing material (ZnO). This paper presents Micro-hotplate device with se-lected material as heating beam (DilverP1). The com-position of DilverP1 is shown in Table 2 [22]. The ma-terial properties of different heating elements are given in Table 3 [22].  DilverP1 Polysilicon Platinum010203040506070Power Consumption (mW)Materials Power Consumption  (a) DilverP1 Polysilicon Platinum0.000.020.040.060.080.100.12Displacement (m)Materials Displacement   (b)  DilverP1 Polysilicon Platinum050100150200250300Stress (MPa)Materials Stress  (c)  Fig. 12 – Comparison Chart (a) Power Consumption of differ-ent materials (b) Displacement of different materials (c) Stress of different materials  DilverP1 consumes low power due to high resistivity and the life time of the Micro-hotplate can be increased with the use of a low cost alloy (DilverP1) having low thermal expansion coefficient (4.2  10 – 6/C) and very high yield stress (680 MPa). In presence of Cobalt, Dil-verP1 shows corrosion resistant property. Very low stress is induced above the micro-hotplate due to low thermal expansion coefficient of DilverP1material. So it can be used as an ideal material for the micro-hotplate. The com-parison chart is shown in Fig. 12. The SEM image of sens-ing layer is shown in Fig. 13.  Table 2 – Composition (Weight %)  Element Ni Co Mn Si C Fe Typical value  29 17  0.35  0.15  0.02 Bal  Table 3 – Material Properties used in the Simulation of Mi-cro-hotplate  Materials Electrical resistivi-ty in     Ωm Young’s modu-lus GPa Pt 10.6  10 – 8 168 Au 2.2  10 – 8 78 Polysilicon 3.22  10 – 7 169 DilverP1 49  10 – 8 207   THE DESIGN OF A LOW POWER MEMS BASED… J. NANO- ELECTRON. PHYS. 6, 01004 (2014)   01004-5   Fig. 13 – SEM image of sensing layer  5. CONCLUSION  In this paper, the electro-thermo-mechanical analy-sis of Micro-hotplate device has been reported at the operating temperature range of 150-200 ºC. The com-parative analysis of Micro-hotplate using different heating elements ((DilverP1 micro- hotplate, Polysili-con micro-hotplate, Platinum micro hot-plate) has been presented at the same temperature (165 ºC). Coven-torWareTM software is used to get temperature, dis-placement and stress distribution of micro-hotplate. Present simulation has shown that power consumption and displacement of Dilverp1 material are less in com-parison to Poly Silicon plate and Platinum plate at moderate temperature (150-200C) above the sensing material (ZnO). The cost of DilverP1 is less compared to Platinum and Poly-Silicon, so it’s suitable for cost effective gas sensor fabrication.    AKNOWLEDGEMENTS  Authors are grateful to TEQIP PHASE-II for provid-ing the necessary fund for carrying out this work.   REFERENCES  1. I. Simon, N. Barsan, M. Bauer, U. Weimer, Sensor. Actuat. B 73, 1 (2001). 2. W. Chung, C. Shim, S. Choi, D. Lee, Sensor. Actuat. B 20, 139 (1994). 3. J.S. Suehle, R.E. Cavicchi, M. 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In this paper comparative analysis of MEMS (Micro-electro-mechanical System) based Micro-hotplate using three different heating elements use as separately are presented. Three different materials (viz. DilverP1, Polysilicon, and Platinum) are used as heating elements with same thickness of 0.2 µm. CoventorWareTM simulator has been used for construction of 3D model and electro-thermo-mechanical analysis of Micro-hotplate device. Power consumption, stress and displacement of Micro-hotplate are studied at operating temperature (165 ºC). It is obtained that power consumption, stress and displacement of Dilverp1 heating element are 13.06 mW, 190 MPa and 0.028 µm which are less in comparison to those with Poly Silicon heater and Platinum heater at moderate temperature (150-200 °C) over the sensing material (ZnO).
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The Design of a Low Power MEMS Based Micro-hotplate Device Using a Novel Nickel Alloy for Gas Sensing Applications

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