U.S. patent application number 14/955251 was filed with the patent office on 2017-06-01 for thermal sensor combination.
This patent application is currently assigned to Texas Instruments Incorporated. The applicant listed for this patent is Texas Instruments Incorporated. Invention is credited to HENRY LITZMANN EDWARDS.
Application Number | 20170153146 14/955251 |
Document ID | / |
Family ID | 58708951 |
Filed Date | 2017-06-01 |
United States Patent
Application |
20170153146 |
Kind Code |
A1 |
EDWARDS; HENRY LITZMANN |
June 1, 2017 |
THERMAL SENSOR COMBINATION
Abstract
A thermal sensor device using a combination of thermopile and
pyroelectric sensors is disclosed. The combination is achieved in a
process flow that includes ferroelectric materials, which may be
used as a pyroelectric sensor, and p-poly/n-poly for thermopiles.
The combination retains the sensitivity and accuracy of the
thermopile sensor and speed of pyroelectric sensors. The
combination provides lower noise than individual thermopile sensors
and results in a higher signal-to-noise ratio.
Inventors: |
EDWARDS; HENRY LITZMANN;
(GARLAND, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Texas Instruments Incorporated |
Dallas |
TX |
US |
|
|
Assignee: |
Texas Instruments
Incorporated
Dallas
TX
|
Family ID: |
58708951 |
Appl. No.: |
14/955251 |
Filed: |
December 1, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01J 2005/123 20130101;
G01J 5/12 20130101; G01J 2005/345 20130101; G01J 5/34 20130101 |
International
Class: |
G01J 5/12 20060101
G01J005/12; G01J 5/34 20060101 G01J005/34 |
Claims
1: A microelectronic device comprising: a heat sensing layer formed
in a semiconductor substrate, the heat sensing layer comprising an
array of thermopile elements arranged around an array of
pyroelectric elements; a thermal isolation membrane formed
underneath the heat sensing layer; a heat absorbing layer formed
over the heat sensing layer; and a heat sink coupled to the
semiconductor substrate, wherein a first end of each one of the
thermopile elements is thermally coupled to the heat absorbing
layer and thermally isolated from the heat sink by the thermal
isolation membrane, and a second end of each one of the thermopile
elements is thermally coupled to the heat sink and thermally
isolated from the heat absorbing layer by the thermal isolation
membrane.
2: The micro electric device of claim 1, wherein the pyroelectric
array is thermally coupled to the heat absorbing layer and
thermally isolated from the heat sink by the thermal isolation
membrane.
3: The microelectronic device of claim 1, wherein the thermal
isolation membrane is formed on the semiconductor substrate using
one or more of hydrofluoric acid (HF) vapor etching and
reactive-ion etching.
4: The microelectronic device of claim 1, wherein the pyroelectric
elements are ferroelectric isolation capacitors.
5: A microelectronic device comprising: a heat sensing layer formed
in a semiconductor substrate, the heat sensing layer comprising an
array of thermopile elements and an array of pyroelectric elements;
a thermal isolation membrane formed underneath the heat sensing
layer; a heat absorbing layer formed over the heat sensing layer;
and a heat sink coupled to the semiconductor substrate, wherein a
first end of each one of the thermopile elements is thermally
coupled to the heat absorbing layer and thermally isolated from the
heat sink by the thermal isolation membrane, and a second end of
each one of the thermopile elements is thermally coupled to the
heat sink and thermally isolated from the heat absorbing layer by
the thermal isolation membrane, wherein a temperature response
coefficient of the thermopile array is substantially similar to a
temperature response coefficient of the pyroelectric array.
6: The microelectronic device of claim 1, wherein the thermopile
array and the pyroelectric array are electrically coupled in
parallel.
7: The microelectronic device of claim 1, wherein the thermopile
array is selected from a group of materials consisting of
polysilicon, poly silicon germanium, and a combination thereof.
8: A radiant energy sensing device formed on a semiconductor
substrate, comprising: a heat absorber; a heat sensor thermally
coupled to the heat absorber and comprising an array of thermopile
elements and an array of pyroelectric elements wherein thermopiles
of the array of thermopiles each extend from an edge of the
semiconductor substrate to an interior region adjacent the array of
pyroelectric elements; a thermal isolation element coupled to the
heat sensor; and a heat sink coupled to the semiconductor
substrate, wherein a first end of each one of the thermopile
elements is thermally coupled to the heat absorber and thermally
isolated from the heat sink by the thermal isolation element, and a
second end of each one of the thermopile elements is thermally
coupled to the heat sink and thermally isolated from the heat
absorber by the thermal isolation element.
9: The radiant energy sensing device of claim 8, wherein the
thermopile array and the pyroelectric array are electrically
coupled in parallel.
10: The radiant energy sensing device of claim 8, wherein the
pyroelectric array is thermally coupled to the heat absorber and
thermally isolated from the heat sink by the thermal isolation
element.
12: The radiant energy sensing device of claim 8, wherein the
thermopile array is selected from a group of materials consisting
of polysilicon, poly silicon germanium, and combination
thereof.
13: The radiant energy sensing device of claim 8, wherein the
thermal isolation element is formed on the semiconductor substrate
using one or more of hydrofluoric acid (HF) vapor etching and
reactive-ion etching.
14: The radiant energy sensing device of claim 8, wherein the
pyroelectric elements are ferroelectric isolation capacitors.
15: The radiant energy sensing device of claim 8, wherein the
thermopiles elements are electrically connected in series.
16: The radiant energy sensing device of claim 8, wherein the
pyroelectric elements arranged electrically in a series-parallel
combination.
17: The radiant energy sensing device of claim 8, wherein a
temperature response coefficient of the thermopile array is
substantially similar to a temperature response coefficient of the
pyroelectric array.
18: A semiconductor thermal sensor, comprising: a heat absorber; a
heat sensor thermally coupled to the heat absorber and comprising
an array of thermopile elements and an array of pyroelectric
elements; a thermal isolation element coupled to the heat sensor;
and a heat sink coupled to the thermal sensor, wherein a first end
of each one of the thermopile elements is thermally coupled to the
heat absorber and thermally isolated from the heat sink by the
thermal isolation element, a second end of each one of the
thermopile elements is thermally coupled to the heat sink and
thermally isolated from the heat absorber by the thermal isolation
element, and a temperature response coefficient of the thermopile
array is substantially similar to a temperature response
coefficient of the pyroelectric array.
19: The semiconductor thermal sensor of claim 18, wherein the
pyroelectric array is thermally coupled to the heat absorber and
thermally isolated from the heat sink by the thermal isolation
element.
20: The semiconductor thermal sensor of claim 18, wherein the
thermopile array is selected from a group of materials consisting
of polysilicon, poly silicon germanium, and combination thereof,
and the pyroelectric elements are ferroelectric isolation
capacitors.
Description
BACKGROUND
[0001] Thermal sensors operate by absorbing radiation, such as
infrared energy emitted by a hot object, and converting that heat
into an electric signal. These sensors are also known as
bolometers. Thermal sensors can be used as single pixel detectors
or may be built as a linear or rectangular array for radiation
imaging. Thermal imaging arrays can detect hot objects with high
pixel resolution and video frame rates. Thermal sensors such as
those used to sense thermal infrared radiation for thermal imaging
or thermometry typically fall into three categories: thermistors,
thermopiles, and pyroelectric.
[0002] Thermistors are a type of resistors whose resistance changes
with temperature significantly more than standard resistors.
Thermistors are generally used as temperature sensors,
self-regulating heating elements, and for other applications.
Thermistor sensors are mostly accurate but have a low sensitivity
and require a current bias. Thermopiles are composed of
thermocouples that convert thermal energy into electrical energy.
The Seebeck effect causes a voltage proportional to the temperature
difference to appear across thermopiles. The temperature of
thermopile thermal sensors can be read by measuring this voltage.
Thermopile sensors are generally accurate and more sensitive than
thermistor sensors but often are very slow due to high series
resistance which combines with gate input capacitance of a
measurement circuit to form a low-pass filter. Pyroelectric sensors
based on pyro-electricity concept. Certain pyroelectric minerals
and crystals create electric charge when they are subject to
temperature change. Pyroelectric sensors are fast and sensitive but
generally inaccurate because the pyroelectric crystals exhibit
leakage and hysteresis which corrupts their stored charge.
Pyroelectric sensors cannot be used for thermal imaging due to
image fade and ghosting effects.
SUMMARY
[0003] In accordance with an embodiment a microelectronic device is
provided. The microelectronic device comprises a heat sensing layer
formed in a semiconductor substrate, the heat sensing layer
includes an array of thermopile elements and an array of
pyroelectric elements. A thermal isolation membrane formed
underneath the heat sensing layer, a heat absorbing layer formed
over the heat sensing layer, and a heat sink coupled to the
semiconductor substrate. A first end of each one of the thermopile
elements is thermally coupled to the heat absorbing layer and
thermally isolated from the heat sink by the thermal isolation
membrane, and a second end of each one of the thermopile elements
is thermally coupled to the heat sink and thermally isolated from
the heat absorbing layer by the thermal isolation membrane.
[0004] In accordance with some embodiment, a radiant energy sensing
device is provided. The radiant energy sensing device is formed on
a semiconductor substrate and includes a heat absorber, a heat
sensor thermally coupled to the heat absorber and comprising an
array of thermopile elements and an array of pyroelectric elements,
a thermal isolation element coupled to the heat sensor, and a heat
sink coupled to the semiconductor substrate. A first end of each
one of the thermopile elements is thermally coupled to the heat
absorber and thermally isolated from the heat sink by the thermal
isolation element, and a second end of each one of the thermopile
elements is thermally coupled to the heat sink and thermally
isolated from the heat absorber by the thermal isolation
element.
[0005] In accordance with some embodiment, a semiconductor thermal
sensor is provided. The thermal sensor includes a heat absorber, a
heat sensor thermally coupled to the heat absorber and comprising
an array of thermopile elements and an array of pyroelectric
elements, a thermal isolation element coupled to the heat sensor,
and a heat sink coupled to the thermal sensor. A first end of each
one of the thermopile elements is thermally coupled to the heat
absorber and thermally isolated from the heat sink by the thermal
isolation element, a second end of each one of the thermopile
elements is thermally coupled to the heat sink and thermally
isolated from the heat absorber by the thermal isolation element,
and a temperature response coefficient of the thermopile array is
substantially same as a temperature response coefficient of the
pyroelectric array.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is an exemplary schematic 100 for a combination of
thermopile and pyroelectric sensors according to some
embodiment.
[0007] FIG. 2 illustrates an exemplary cavity sensor type
semiconductor configuration 200 according to some embodiment.
[0008] FIG. 3 illustrates an exemplary block diagram of a sensor
device according to some embodiment.
DETAILED DESCRIPTION
[0009] The following description provides many different
embodiments, or examples, for implementing different features of
the subject matter. These descriptions are merely for illustrative
purposes and do not limit the scope of the invention.
[0010] According to some embodiments, a combination of thermopile
and pyroelectric sensors is disclosed. Such a combination can be
achieved in a process flow that includes ferroelectric materials,
which may be used as a pyroelectric sensor, and p-poly/n-poly for
thermopiles. These sensors can be combined in various different
combinations such as parallel, series, or a combination
thereof.
[0011] Referring to FIG. 1, an exemplary circuit schematic 100 for
a combination of thermopile and pyroelectric sensors is shown
according to some embodiment. In the present example, a parallel
combination is shown; however, other combinations can be used to
achieve similar results. Circuit 100 includes a combination of
resistors R.sub.TP 110 representing reflecting the resistance of a
thermopile array including a number of thermopiles (N.sub.TP). The
amount of resistance depends upon the number N.sub.TP of
thermopiles used, in series or parallel. In the present example,
N.sub.TP thermopiles are used in series thus the total resistance
of thermopiles will be N.sub.TP*R.sub.TP. Based on the temperature
exposure, a voltage .DELTA.V.sub.TP 120 is developed across
thermopiles. An array of pyroelectric sensor elements R.sub.PYRO
130 is electrically connected to thermopile array 110 in parallel.
In the exemplary embodiment, Pyroelectric sensors perform similar
functions as capacitors. When pyroelectric sensors are subject to a
temperature change then over a period of time, a charge Q.sub.PYRO
is stored across each end of the pyroelectric capacitor 140 with a
capacitance of C.sub.PYRO and leakage resistance of R.sub.LEAK 160.
Pyroelectric capacitors generate leakage current I.sub.PYRO 150.
I.sub.PYRO=(d/dt) Q.sub.PYRO and related to pyroelectric
coefficient. An Op Amp 170 with appropriate feedback loop 180 is
connected to the sensor combination. The voltage V.sub.OUT
generated across sensors can be measured using the Op Amp 170. This
voltage reflects the temperature change across sensors.
[0012] Pyroelectric sensors are faster than thermoelectric sensors
and more sensitive to changes. A pyroelectric sensor is a
self-charging capacitor. An open-circuit ideal pyroelectric sensor
behaves like a battery as the pyroelectric current charges its
capacitance. There are two resistors--resistance in the
pyroelectric capacitor electrodes R.sub.PYRO 130 and a leakage
resistance R.sub.LEAK 160 through the pyroelectric film. The
pyroelectric sensor can exhibit low-pass behavior and signal
fading. The pyroelectric crystal of sensors also exhibits a memory
cell; however, the amount of charge on the pyroelectric sensor
capacitor is not determined by the equivalent circuit. So the
pyroelectric sensor can also exhibit hysteresis. The feedback
mechanism V.sub.NOISE 180 provided by the thermopiles 120
stabilizes the voltage across the pyroelectric sensor capacitor to
near its ideal value and the speed and change sensitivity of the
pyroelectric sensors can be preserved while the stability and image
accuracy can be recovered.
[0013] The circuit analysis of the circuit combination of FIG. 1 is
shown as follows:
For Pyroelectric:
[0014] I.sub.PYRO=C.sub.PYRO*(.alpha..sub.PYRO*h/.di-elect
cons.*.di-elect cons..sub.0)*(d.DELTA.T.sub.PYRO/dt)
Where .di-elect cons. is relative permittivity, .di-elect
cons..sub.0 is permittivity of free space, and `h` is thickness of
pyroelectric layer in a given semiconductor arrangement.
Pyroelectric coefficient B.sub.PYRO=(.alpha..sub.PYRO*h/.di-elect
cons.*.di-elect cons..sub.0)
Thus,
I.sub.PYRO=B.sub.PYRO*C.sub.PYRO*(d.DELTA.T.sub.PYRO/dt)
For Thermopile:
[0015] .DELTA.V.sub.TP=N.sub.TP*.alpha..sub.pn*.DELTA.T.sub.TP
Where .alpha..sub.pn is Seebeck coefficient of thermopile and
.DELTA.T.sub.TP is change in temperature across thermopile.
Thermopile coefficient is given as
B.sub.TP=N.sub.TP*.alpha..sub.pn
Thus,
.DELTA.V.sub.TP=B.sub.TP*.DELTA.T.sub.TP
[0016] Analyzing the equivalent circuit combination further, it can
be shown that coefficient of thermopile B.sub.TP and of
pyroelectric B.sub.PYRO can be made equal by choosing the
appropriate number of thermopiles stacked in series. The number of
thermopiles for achieving this can be determined as follows:
The objective is to have a design choice with
.DELTA.V.sub.TP=.DELTA.V.sub.PYRO
Where:
[0017] .DELTA.V.sub.PYRO=(.alpha..sub.PYRO*h/.di-elect
cons.*.di-elect cons..sub.0).DELTA.T.sub.PYRO; and
.DELTA.V.sub.TP=N.sub.TP*.alpha..sub.pn*.DELTA.T.sub.TP*.xi.,
where .xi. is thermal coupling efficiency of thermopiles.
Therefore:
[0018] (.alpha..sub.PYRO*h/.di-elect cons.*.di-elect
cons..sub.0).DELTA.T.sub.PYRO=N.sub.TP*.alpha..sub.pn*.DELTA.T.sub.TP*.xi-
.
Per the design objective, .DELTA.V.sub.TP=.DELTA.V.sub.PYRO, which
means .DELTA.T.sub.TP=.DELTA.T.sub.PYRO
=>(.alpha..sub.PYRO*h/.di-elect cons.*.di-elect
cons..sub.0)=N.sub.TP*.alpha..sub.pn*.xi.
=>N.sub.TP=(.alpha..sub.PYRO*h/.di-elect cons.*.di-elect
cons..sub.0)*(1/.alpha..sub.pn*.xi.)
[0019] As shown above, by selecting the appropriate thickness of
pyroelectric layer on a given semiconductor arrangement, the number
of thermopiles in the combination can be determined. The number of
thermopile N.sub.TP calculated by
.DELTA.V.sub.TP=.DELTA.V.sub.PYRO, results in similar or
substantially similar temperature response coefficients of
thermopile array .DELTA.V.sub.TP and Pyroelectric
.DELTA.V.sub.PYRO. In some cases, it may be desirable to stack the
pyroelectric elements in series to multiply the pyroelectric
voltage, using a similar matching criterion to that described above
for thermopile stacking. Thus a combination of series and parallel
stacking may be used in the array of pyroelectric elements just as
it is used in the thermopile array. This may be helpful in matching
thermal responsivity of the thermopile array to that of the
pyroelectric array. It also provides the ability to adjust the
overall responsivity of the sensor to a desired value. This results
in pyroelectric and the thermopile exhibiting the same voltage
response to temperature. This is because the thermopile acts as a
voltage source through the Seebeck effect and a pyroelectric can be
viewed as a self-charging capacitor. The parallel combination of
thermopile and pyroelectric of FIG. 1 can provided many advantages.
First, it retains the sensitivity and accuracy of the thermopile
sensor. Second, it retains the speed of pyroelectric sensors and
finally, the sensor combination has much lower noise than
individual thermopile sensors and results in a higher
signal-to-noise ratio. The large capacitance of the pyroelectric
sensors averages out the Johnson noise fluctuations, which can be
generated by the thermal agitation of the charge carriers in these
sensors. In an embodiment, the combination of sensors is combined
spatially in a cavity sensor type of semiconductor
configuration.
[0020] Referring to FIG. 2, the top view of an exemplary cavity
sensor type semiconductor configuration 200 is illustrated
according to an embodiment. The sensor configuration 200 includes a
substrate 210, a poly thermopiles sensor array 220, and a
pyroelectric sensor capacitor array 230. A dielectric isolation
membrane (not shown) is formed by etching the silicon substrate 200
underneath sensors 220 and 230, allowing thermal isolation of
elements fabricated within it. This improves the thermal isolation.
Typically the membrane dimensions can be 100 um or more.
Alternatively thermal isolation may be achieved in various
different ways, such as using a release etch to release the
structure, minimizing conductive heat loss effects in the
semiconductor. According to an embodiment, Poly thermopile sensor
array 220 and pyroelectric sensors 230 are electrically connected
in a configuration similar to illustrated in FIG. 1. A
semiconductor thermal absorption layer (not shown) made of thermal
absorptive material may be deposited over the sensor
arrangement
[0021] In the present example, the poly thermopiles 220 are arrayed
at the edge of the semiconductor substrate 200 such that they
capture the maximum temperature gradient. Infrared energy is
absorbed in the semiconductor thermal absorption membrane, causing
the center of the membrane to become hotter than the edges. The
thermopile array 220 can be configured such that each has one end
at the cavity edge, which can be used as the `cold junction` and an
edge in the interior of the semiconductor membrane over the cavity,
which can be used as the `hot junction`. The array can be
configured using size depending on the number of thermopiles
needed. In an embodiment, thermopiles can be of 0.2 um allowing to
use the maximum number of thermopile sensors in a given
configuration. The dielectric thermal isolation membrane layer can
also be configured such to preserve thermal isolation of these
sensors. Thermopile array 220 can be configured using polysilicon
or poly silicon germanium, which can be deposited as SiGe or
Ge-implanted polysilicon on the semiconductor substrate 210.
[0022] As illustrated in FIG. 2, thermopiles 220 run substantially
radially from the edge towards the middle of the membrane so that
they can experience the most temperature difference along their
length. Depending on the size and shape of silicon substrate, poly
thermopile array 220 can be structured in many different forms to
capture maximum temperature gradient. Further, these thermopile can
be arranged in parallel or series combination and may comprise
series-connected pairs of n-type and p-type polysilicon.
Electrically, the pyroelectric and thermoelectric sensors can be in
a parallel combination. According to some embodiment, the
pyroelectric sensors 230 are configured using ferroelectric
isolation capacitors based on an embedded ferroelectric random
access memory cell structure for example, using the process
described in U.S. Pat. Nos. 6,225,655; 6,362,499; and 6,548,343
assigned to the assignee of the present application and their
description is incorporated herein by reference in its entirety for
all purposes. The ferroelectric capacitors can be arranged mostly
in the middle region of the semiconductor substrate membrane 210 so
they can be sensitive to the strongest temperature deviations of
the semiconductor membrane. The pyroelectric capacitors can be
arranged in individual series or parallel combination or a
series-parallel combination. The series configurations increase the
sensitivity and the parallel configuration increases the current
drive capability of sensors. An optional metal or similar heat
absorption grating can be placed on top the pyroelectric sensors
230 to increase the heat absorption capability of sensors. Further,
a series/parallel combination of thermopiles and a series/parallel
combination of pyroelectric elements may be used if needed to match
the temperature coefficients while maximizing the use of membrane
area for sensor elements.
[0023] When a temperature gradient .DELTA.T develops, pyroelectric
crystals of pyroelectric sensors 230 undergo a thermal expansion,
and through its piezoelectric coefficient, each unit cell's
polarization changes. This results in charge being deposited on the
capacitor plates, which forms a voltage across the pyroelectric
element. As stated hereinabove, the temperature gradient .DELTA.T
across the poly thermopiles 220 causes a voltage difference
.DELTA.V to develop through the Seebeck effect
.DELTA.V=.alpha..DELTA.T, where .alpha. is the Seebeck coefficient
of poly thermopiles. Thermopiles 220 respond to .DELTA.T and
pyroelectric sensors 230 respond to dT/dt. Pyroelectric sensors 230
charge their capacitance to .DELTA.V voltage. A change in infrared
signal causes a current spike in pyroelectric sensors 230 as it
tries to adjust its capacitance. Thermopile sensors on the other
hand provide a "battery" at the same voltage to pyroelectric
sensors 230. This reduces the charge drift in pyroelectric
capacitors due to the leakage. Pyroelectric capacitors provide a
"hold" function similar to a sample-and-hold circuit of an
analog-to-digital converter by capturing the .DELTA.V voltage in
response to dT/dt.
[0024] The number of thermopiles N.sub.TP can be chosen such that
the pyroelectric sensors and thermoelectric sensors produce the
same voltage response to the temperature change .DELTA.T. In that
case, the output voltages of these sensors increase together and
the charge produces is not exchanged among sensors. The combination
of thermopile and pyroelectric sensors produces same sensitivity as
each of the individual sensor. The circuit combination of FIG. 1
can be realized by using appropriate number N.sub.TP of thermopile
sensors connected in parallel to match pyro sensitivity of
pyroelectric sensors with a feedback mechanism to stabilize the
pyroelectric sensors as described hereinabove. In an exemplary
embodiment, considering the signal expressions of both thermopile
and pyroelectric sensors and making certain assumptions about
materials parameters, the optimal number of thermopile sensors per
pyroelectric element were calculated in the range 20-200.
[0025] Referring to FIG. 3, an exemplary cross-sectional
illustration of semiconductor configuration of sensor 200 according
to some embodiment. System 300 includes an object 310 and a Sensor
device 200. Object 310 can be any object emitting heat and/or
infrared radiation (IR) (thermal emission) such as human body,
electronic circuit, or any other similar object capable of
generating heat and IR radiation with a thermal temperature of
T.sub.object. The Sensor device 200 can be fabricated on a
semiconductor substrate using the ferroelectric memory cell
described hereinabove. Sensor device 200 includes an Absorber 320,
Sensors 330, an Isolation layer 340 and a Heat sink 350. The
thermal emission from Object 310 is absorbed by Absorber 320.
Absorber 320 can be any material capable of absorbing heat such as
metals with high thermal absorption coefficient such as silicon
dioxide, silicon nitride, polysilicon, ferroelectric material, and
packaging related materials such as polyimide, PBO, epoxy or mold
compound and the like that are well known in the art. Small metal
structures (dimensions smaller than the wavelength of the IR of
interest) can also be used as absorbers even though large sheets of
metal make good IR mirrors. Absorber 320 also emits heats and
reflects some of the heat that impinges upon its surface from
Object 310. Absorber 320 is thermally connected to Sensors 330.
Poly thermopiles absorb IR radiation; however, optionally
additional absorbing layer can be added to improve the heat
absorption. In an embodiment, the nitride PO or a SiO.sub.2 layer
above (and encasing) the thermopile and pyro sensor elements is
used to improve heat absorption of the Absorber 320.
[0026] In an embodiment, Sensors 330 are thermally isolated from
Heat sink 350 by Isolation layer 340. Isolation layer 340 thermally
can be configure using various etching processes such as
release-etch process, reflective ion etch (RIE) process and the
like known in the art. Release-etch process uses an aqueous etching
mechanism utilizing hydrofluoric acid (HF) vapor etching to remove
silicon dioxide from the semiconductor substrate. RIE process uses
chemically reactive plasma to remove material deposited on
semiconductor wafers. Typically, the plasma is generated under low
pressure (vacuum) by an electromagnetic field and high-energy ions
from the plasma attack the wafer surface and react with it for
etching.
[0027] In an embodiment, the Isolation 340 is configured using a
bulk Silicon (Si) etch where dielectrics above the Si substrate are
left as a membrane with poly thermopile gates, metal traces, thin
film resistors, vias, and other elements remain trapped inside. In
an embodiment, Sensor 330 unit is configured similar to the
configuration 200 illustrated in FIG. 2 with arrays of thermopile
sensors 220 and pyroelectric sensor grid 230 where the a `hot end`
of each of the thermopile array is thermally connected to Absorber
320 and thermally isolated from Heat sink 350 by Isolation 340 and
a `cold end` of thermopile array is connected to Heat sink 350 and
thermally isolated from Absorber 320 by Isolation 340.
[0028] When Absorber 320 is subject to IR emission form hot Object
310, Absorber 320 absorbs net heat minus Absorber's emissions and
reflection losses and develops a temperature T.sub.absorber.
Absorber 320's temperature increases, activating a response in
Sensor 330 and Sensors 330 "Sees" the temperature T.sub.object of
Object 310. Sensors 330 develop a temperature T.sub.top at the `hot
end` connected to Absorber 320, which will be different from
temperature T.sub.bot of its "cold end" that is connected to Heat
sink 350. Ideally, for poly thermopile sensors .DELTA.T,
T.sub.top=T.sub.object; and T.sub.bot=T.sub.sink and the absolute
temperature T for both types of sensors will be
T.sub.top=T.sub.bot=T.sub.object. The sensor 200 can be configured
to measure temperature in various different applications including
but not limited to environmental control electronics, automotive,
electronic devices and the like.
[0029] The foregoing outlines features of several embodiments so
that those of ordinary skill in the art may better understand
various aspects of the present disclosure. Those of ordinary skill
in the art should appreciate that they may readily use the present
disclosure as a basis for designing or modifying other processes
and structures for carrying out the same purposes and/or achieving
the same advantages of various embodiments introduced herein. Those
of ordinary skill in the art should also realize that such
equivalent constructions do not depart from the spirit and scope of
the present disclosure, and that they may make various changes,
substitutions, and alterations herein without departing from the
spirit and scope of the present disclosure.
[0030] Although the subject matter has been described in language
specific to structural features or methodological acts, it is to be
understood that the subject matter of the appended claims is not
necessarily limited to the specific features or acts described
above. Rather, the specific features and acts described above are
disclosed as example forms of implementing at least some of the
claims. Various operations of embodiments are provided herein. The
order in which some or all of the operations are described should
not be construed to imply that these operations are necessarily
order dependent. Alternative ordering will be appreciated having
the benefit of this description. Further, it will be understood
that not all operations are necessarily present in each embodiment
provided herein. Also, it will be understood that not all
operations are necessary in some embodiments.
[0031] Moreover, "exemplary" is used herein to mean serving as an
example, instance, illustration, etc., and not necessarily as
advantageous. Also, although the disclosure has been shown and
described with respect to one or more implementations, equivalent
alterations and modifications will occur to others of ordinary
skill in the art based upon a reading and understanding of this
specification and the annexed drawings. The disclosure comprises
all such modifications and alterations and is limited only by the
scope of the following claims. In particular regard to the various
functions performed by the above described components (e.g.,
elements, resources, etc.), the terms used to describe such
components are intended to correspond, unless otherwise indicated,
to any component which performs the specified function of the
described component (e.g., that is functionally equivalent), even
though not structurally equivalent to the disclosed structure. In
addition, while a particular feature of the disclosure may have
been disclosed with respect to only one of several implementations,
such feature may be combined with one or more other features of the
other implementations as may be desired and advantageous for any
given or particular application.
* * * * *