U.S. patent application number 13/441134 was filed with the patent office on 2013-10-10 for temperature stabilitized mems.
This patent application is currently assigned to TAIWAN SEMICONDUCTOR MANUFACTURING CO., LTD.. The applicant listed for this patent is Tung-Tsun CHEN, Chia-Hua CHU, Jui-Cheng HUANG, Chung-Hsien LIN. Invention is credited to Tung-Tsun CHEN, Chia-Hua CHU, Jui-Cheng HUANG, Chung-Hsien LIN.
Application Number | 20130264610 13/441134 |
Document ID | / |
Family ID | 49291607 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130264610 |
Kind Code |
A1 |
CHEN; Tung-Tsun ; et
al. |
October 10, 2013 |
TEMPERATURE STABILITIZED MEMS
Abstract
A semiconductor device with temperature control system.
Embodiments of the device may include a MEMS chip including a first
heater with a dedicated first temperature control loop and a CMOS
chip including a second heater with a dedicated second temperature
control loop. Each control loop may have a dedicated temperature
sensor for controlling the thermal output of each heater. The first
heater and sensor are disposed proximate to a MEMS device in the
MEMS chip for direct heating thereof. The temperature of the MEMS
chip and CMOS chip are independently controllable of each other via
the temperature control loops.
Inventors: |
CHEN; Tung-Tsun; (Hsinchu
City, TW) ; CHU; Chia-Hua; (Zhubei City, TW) ;
LIN; Chung-Hsien; (Hsinchu City, TW) ; HUANG;
Jui-Cheng; (Hsinchu City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CHEN; Tung-Tsun
CHU; Chia-Hua
LIN; Chung-Hsien
HUANG; Jui-Cheng |
Hsinchu City
Zhubei City
Hsinchu City
Hsinchu City |
|
TW
TW
TW
TW |
|
|
Assignee: |
TAIWAN SEMICONDUCTOR MANUFACTURING
CO., LTD.
Hsin-Chu
TW
|
Family ID: |
49291607 |
Appl. No.: |
13/441134 |
Filed: |
April 6, 2012 |
Current U.S.
Class: |
257/252 ;
257/467; 257/E27.014; 257/E29.347 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 23/34 20130101; H01L 23/345 20130101; B81C 1/0023 20130101;
B81B 2201/0278 20130101; H01L 27/0629 20130101; B81B 7/0096
20130101; H01L 2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
257/252 ;
257/467; 257/E29.347; 257/E27.014 |
International
Class: |
H01L 29/66 20060101
H01L029/66; H01L 27/06 20060101 H01L027/06 |
Claims
1.-9. (canceled)
10. A semiconductor package comprising: a substrate; a MEMS device
provided on the substrate, the MEMS device comprising: a body; a
first heating element integrated with the body, and a dedicated
first temperature control loop operable to control operation of the
first heating element, the first heating element being operable to
generate heat when a current flows through the element and transfer
the heat directly to the body of the MEMS device; and a CMOS chip
provided on the substrate, the CMOS chip including a second heating
element and a dedicated second temperature control loop operable to
control operation of the second heating element; wherein the
temperature of the MEMS device and CMOS chip are independently
controllable; wherein the first temperature control loop comprises
a first power controller comprising circuitry operable to control
power supply to the first heating element and a first temperature
sensor operable to measure an operating temperature of the MEMS
device, operation of the first power controller being controlled at
least in part by the first temperature sensor; wherein the first
temperature sensor and first heating element are physically
disposed in the MEMS chip; and wherein the first power controller
is disposed in the CMOS chip.
11. (canceled)
12. (canceled)
13. (canceled)
14. The semiconductor package of claim 10, wherein the first
temperature control loop further comprises a temperature
independent reference circuit that operably functions in
cooperation with the first temperature sensor to compare an actual
measured operating temperature of the MEMS device with a setpoint
temperature provided by the temperature independent reference
circuit.
15. The semiconductor package of claim 10, wherein the second
temperature control loop comprises a second power controller
comprising circuitry operable to control power supply to the second
heater and a second temperature sensor operable to measure an
operating temperature of the CMOS chip.
16. The semiconductor package of claim 10, wherein the MEMS device
and CMOS chip are disposed in a semiconductor package, the package
being sealed and under a vacuum.
17. The semiconductor package of claim 10, wherein the CMOS chip is
disposed on the substrate and the MEMS device is stacked above the
CMOS chip.
18. The semiconductor package of claim 10, wherein the CMOS chip
and MEMS device are disposed side-by-side on a common
substrate.
19.-20. (canceled)
21. The semiconductor package of claim 10, wherein the first
heating element comprises a current input terminal and a current
output terminal, the terminals being in electrical communication
with the heating element.
22. The semiconductor package of claim 10, wherein the first
heating element is formed by the body of the MEMS device, the body
being made of an electrically conductive metallic or non-metallic
containing material having an electrical resistance and being
operable to generate heat via current flowing through the body.
23. The semiconductor package of claim 10, wherein the first
heating element is a thin film resistive heating element provided
onto the body of the MEMS device.
24. The semiconductor package of claim 10, wherein the first
heating element is also provided on the substrate adjacent to and
in conductive direct contact with the body of the MEMS device by a
thermally conductive block.
25. The semiconductor package of claim 10, wherein the first
heating element is electrically isolated from the substrate.
26. The semiconductor package of claim 10, wherein the body of the
MEMS device is suspended and spaced above the substrate by
isolation pedestals.
27. The semiconductor package of claim 26, wherein the isolation
pedestals include insulating spacers in contact with the substrate
and conductive blocks in contact with the first heating element.
Description
FIELD
[0001] The present invention generally relates to semiconductors
structures, and more particularly to semiconductor structures
including micro-electro-mechanical systems (MEMS) and methods for
forming the same.
BACKGROUND
[0002] Semiconductor device packages are comprised of different
types of active devices incorporated within the package that serve
various functions. Semiconductor packages include CMOS
(complementary metal oxide semiconductor) devices such as chips
built on a silicon substrate or wafer. In some instances, the CMOS
chip may be an application-specific integrated circuit (ASIC) chip
which is generally classified as a chip having an integrated
circuit (IC) that is custom built for a specific end use or
purpose. Some ASIC chips may be a system-on-chip (SoC) which
includes a processor, memory devices, and other ancillary
components that are built on an application specific chip.
[0003] MEMS devices of various types are sometime incorporated into
the semiconductor package to augment and support the functionality
of the ASIC chips in the package. MEMS devices are micro-sized
devices or machines that may have stationary and/or movable
elements that provide some type of electro-mechanical functionality
desired for a particular application and system. Some type MEMS
devices which may be found in a semiconductor chip package may
include, for example without limitation, micro-timing devices (i.e.
resonators, oscillators, real-time clocks, clock generators, etc.),
micro-sensors (e.g. pressure and temperature transducers that
convert mechanical movement or displacement into electrical
signals), micro-actuators, accelerometers, micro-switches,
micro-pumps and valves, and others that support and assist with
controlling the functionality of the chip(s) in the package and/or
system-level integrated circuit (IC).
[0004] MEMS devices have dimensions that may fall in a range from
less than 1 micron to several millimeters in size. MEMS devices may
be constructed on a silicon substrate or wafer similarly to CMOS
chips by using various fabrication techniques including without
limitation bulk micromachining of the silicon substrate itself
and/or surface micromachining involving building microstructures on
the surface of the substrate using various semiconductor IC
fabrication technologies such as material deposition, patterned
photolithography, and etching. The foregoing manufacturing
techniques may be used to construct many different types of MEMS
devices from simple structures with no moving elements to complex
electromechanical systems having a plurality of moving elements
that may be controlled by integrated microelectronics. The MEMS
chip is mounted in the semiconductor package at the wafer level
with the ASIC chip.
[0005] MEMS devices and their performance are sensitive to
operating temperature and temperature fluctuations which may be
caused by swings in ambient temperatures and cause differential
thermal expansion problems of the elements used to construct the
MEMS device since different types of materials used may each have
different coefficients of thermal expansion. Thermal excursions due
to ambient temperature excursions may also cause temperature
induced voltage drift and other similar electrical problems
adversely affecting the performance of the MEMS. Accordingly, it is
desirable to regulate and control the operating temperature of the
MEMS device independent of the ambient operating environment
temperature in which the device may be located. Optimally, it is
beneficial that the operating temperature of the MEMS device remain
relatively uniform or stable during its operation irrespective of
changing ambient conditions or operating environments to avoid
operating temperature swings and potential performance
problems.
[0006] An improved temperature control system for MEMS devices is
desired.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The features of the preferred embodiments will be described
with reference to the following drawings where like elements are
labeled similarly, and in which:
[0008] FIG. 1 is a schematic system block diagram showing one
embodiment of temperature control system for regulating the
temperature of devices in a semiconductor package;
[0009] FIGS. 2 and 3 are a schematic diagram top view and
cross-sectional side/elevation view respectively of one possible
embodiment of a MEMS heater;
[0010] FIGS. 4 and 5 are a schematic diagram top view and
cross-sectional side/elevation view respectively of a second
possible embodiment of a MEMS heater;
[0011] FIGS. 6 and 7 are a schematic diagram top view and
cross-sectional side/elevation view respectively of a third
possible embodiment of a MEMS heater;
[0012] FIG. 8 is a schematic diagram showing one possible
embodiment and arrangement of a combination MEMS--CMOS device
semiconductor package;
[0013] FIG. 9 is a schematic diagram showing another possible
embodiment and arrangement of a combination MEMS--CMOS device
semiconductor package;
[0014] FIG. 10 is a schematic block diagram of a semiconductor
package temperature control system applicable to FIGS. 8 and 9;
[0015] FIG. 11A is a schematic diagram showing a CMOS chip
temperature control loop;
[0016] FIG. 11B is a schematic circuit diagram of one embodiment of
a temperature sensor useable with the temperature control system
disclosed herein;
[0017] FIG. 11C is a schematic circuit diagram of one embodiment of
temperature sensing circuitry for a temperature sensor useable with
the temperature control system disclosed herein;
[0018] FIG. 12 is a cross-sectional side/elevation view of a CMOS
chip showing the physical layout of components in one embodiment of
a temperature control loop;
[0019] FIG. 13 is a cross-sectional side/elevation view of a CMOS
chip showing the physical layout of components in an alternative
embodiment of a temperature control loop;
[0020] FIG. 14 is a schematic diagram of a constant voltage power
control scheme;
[0021] FIG. 15 is a schematic diagram of a constant current power
control scheme;
[0022] FIGS. 16-18 are schematic diagrams of exemplary embodiments
of temperature sensors; and
[0023] FIG. 19 is a schematic diagram of a thermocouple temperature
sensor.
[0024] All drawings are schematic and are not drawn to scale.
DETAILED DESCRIPTION
[0025] This description of illustrative embodiments is intended to
be read in connection with the accompanying drawings, which are to
be considered part of the entire written description. In the
description of embodiments disclosed herein, any reference to
direction or orientation is merely intended for convenience of
description and is not intended in any way to limit the scope of
the present invention. Relative terms such as "lower," "upper,"
"horizontal," "vertical,", "above," "below," "up," "down," "top"
and "bottom" as well as derivative thereof (e.g., "horizontally,"
"downwardly," "upwardly," etc.) should be construed to refer to the
orientation as then described or as shown in the drawing under
discussion. These relative terms are for convenience of description
only and do not require that the apparatus be constructed or
operated in a particular orientation. Terms such as "attached,"
"affixed," "connected" and "interconnected," refer to a
relationship wherein structures are secured or attached to one
another either directly or indirectly through intervening
structures, as well as both movable or rigid attachments or
relationships, unless expressly described otherwise. The term
"adjacent" as used herein to describe the relationship between
structures/components includes both direct contact between the
respective structures/components referenced and the presence of
other intervening structures/components between respective
structures/components. Moreover, the features and benefits of the
invention are illustrated by reference to the preferred
embodiments. Accordingly, the invention expressly should not be
limited to such preferred embodiments illustrating some possible
non-limiting combination of features that may exist alone or in
other combinations of features; the scope of the invention being
defined by the claims appended hereto. The term signal as used
herein means any voltage, current, charge, data, or other
signal.
[0026] One approach to controlling and regulating MEMS temperatures
is to heat the entire semiconductor package that houses the MEMS
device and CMOS chip which may include an ASIC using a single
heater that is integrated into the package for heating both the
MEMS device and CMOS chip. It is desirable to control and maintain
a uniform temperature for the CMOS chip for the same reasons as
maintaining a steady MEMS temperature as already described herein
to protect chip performance by minimizing differential thermal
expansion and operating temperature swings. In this semiconductor
package-level heating approach, the MEMS device and chip are heated
together using a single heater and temperature sensor disposed
somewhere in the package (sometimes nearest the chip). This may
make it difficult to control the temperature of and efficiently
heat both the MEMS device and chip uniformly due to the temperature
sensor and heater being remote from the MEMS device. In addition,
heating the entire package and cavity formed inside the package
increases power consumption and correspondingly lower heating
efficiency. The accuracy of the temperature sensor and capability
of the chip to accurately control the temperature of the MEMS
device to eliminate operating temperature swings may further be
problematic in this embodiment.
[0027] FIG. 1 is a schematic system block diagram showing one
embodiment of temperature control system for regulating the
temperature of devices in a semiconductor package. The
semiconductor package 50 may include a CMOS chip 100 and a MEMS
chip 200 as shown. In some embodiments, the chip 100 may be may be
an ASIC chip including an ASIC 102. MEMS chip 200 includes a MEMS
element or device 202. CMOS chip 100 and MEMS chip 200 are mounted
and bonded in semiconductor package 50 which may be sealed from the
environment. In some embodiments, semiconductor package may be a
chip-scale-package (CSP). Semiconductor package 50 may be made of a
plastic, ceramic, or other suitable materials.
[0028] The temperature control system of FIG. 1 includes a separate
and dedicated heater and temperature sensor for both the chip 100
and MEMS device 202 to accurately regulate both the chip and MEMS
device operating temperatures. Accordingly, in this embodiment, the
MEMS heater is packaged with the MEMS chip 200 instead of utilizing
the single heater packaged with the CMOS chip as in the prior
example above. The temperatures of the chip 100 and MEMS device in
semiconductor package 50 may therefore advantageously be
independently controlled and adjusted in the embodiment shown.
[0029] Referring to FIG. 1, the semiconductor package 50 includes a
chip temperature control subsystem or loop 110 and a MEMS
temperature control subsystem or loop 210. The chip temperature
control loop 110 includes temperature sensor 120, power controller
130, and heater 140, all of which may be mounted on or in the CMOS
chip 200. Similarly, MEMS temperature control loop 210 in one
embodiment includes a separate or discrete temperature sensor 220,
power controller 230, and heater 240, all of which may be mounted
on or in the MEMS chip 200 so as to be in close proximity to the
MEMS device 202 for improving heating performance.
[0030] The foregoing temperature control loop components, MEMS
device 202, and ASIC 102 are electrically coupled together by
conductive interconnects 201 as represented by the double-head
arrows shown in FIG. 1. The interconnects 201 may be in the form of
conductive traces, lines, pad, wires, vias, or other electrically
conductive structures used for interconnects in semiconductor and
MEMS fabrication. The interconnects 201 form a two way electrical
and signal communication pathways between the components in FIG. 1
as shown. In some embodiments, the interconnects may be made of a
material or combination/alloys of materials including without
limitation metals (e.g. copper, aluminum, gold, titanium, tungsten,
platinum, etc.), polysilicon, or other electrically conductive
materials.
[0031] Referring to FIG. 1, temperature sensor 120 operably
measures actual operating temperatures of temperature sensitive
ASIC 102 in CMOS chip 100 and generates temperature signals
representing the measured temperature to ASIC 102. Similarly,
temperature sensor 220 operably measures actual operating
temperatures of temperature sensitive MEMS device 202 in MEMS chip
200 and generates temperature signals representing the measured
temperature to ASIC 102. ASIC 102 is operative to control the
heating and temperature of CMOS chip 100 and MEMS chip 200. In some
embodiments, ASIC 102 may generate an output data signals as shown
containing information representing temperatures measured for CMOS
chip 100 and MEMS chip 200, as well as other operating parameters
for the temperature control loops.
[0032] Temperature sensors 120, 220 may be any type of temperature
measurement device suitable for incorporation into a semiconductor
package 50. In some embodiments, temperature sensors 120 and 220
may be a semiconductor or IC temperature sensor which is an
electronic device fabricated in a similar way to other
semiconductor components using semiconductor and MEMS fabrication
processes. Such devices may include, without limitation, voltage
output, current output, resistance output, digital output, and
diode type semiconductor temperature sensors built upon a silicon
substrate or wafer and embedded in the chip as will be well known
in the art. The digital temperature sensor integrates a sensor and
an analog to digital converter (ADC) on a silicon chip and may be
configured for thermal management of microprocessor chips. In some
embodiments, resistor output silicon-based temperature sensors may
include varying constructions including diffused resistors, ion
implanted resistors, and thin film resistors having resistive
elements made of a thin film layer of polysilicon, metal or metal
alloys, or other suitable electrically conductive materials having
a bulk resistance.
[0033] The foregoing resistor-type silicon-based temperature
sensors are used to measure temperature by correlating the bulk
resistance or resistivity of the resistive element used in the
sensor with temperature. The temperature is proportional to and
varies with the resistance. The resistive element has predictable
variations in resistance at different temperatures such that a
measured change in resistance (R) as electrical current (I) and
voltage (V) is applied can be correlated to and may be used to
determine temperature such as by using Ohms Law (I=V/R). The
operation and use of such resistors to measure and determine
temperature by converting resistance (based on measured current or
voltage from the resistive element) into a representative
temperature is well known to those skilled in the art without
further elaboration.
[0034] In some embodiments, temperature sensor 120, 220 is a
semiconductor thermal diode temperature sensor having a silicon
diode and utilizing proportional to absolute temperature (PTAT)
temperature sensing which outputs a signal proportional to absolute
temperature. The absolute temperature can be calculated from the
equation: T=(V1-V2)/(8.7248.times.10-5 ln(I1/ I2)). Such
temperature sensors and determination of temperature are well known
to those skilled in the art without further elaboration.
[0035] Referring to FIG. 1, heaters 140, 240 may be any type of
heater suitable for incorporation into a semiconductor package 50.
Heater 140, 240 may be a semiconductor heater having a heating
element which generates heat when an electric current flows through
the element. In one possible embodiments, the heating element may
be a resistive-type heating element built on or in a silicon-based
wafer substrate and containing a resistive heating layer or element
142, 242 of any suitable configuration which generates heat by
resistance when a voltage and current is applied across the
resistive element. In some embodiments, such semiconductor
resistance heaters may be structured similarly to the resistor
output silicon-based temperature sensors 120, 220 (e.g. diffused
resistors, ion implanted resistors, and thin film resistors
temperature sensors) already described herein having the resistive
element embedded in the silicon substrate, suspended above and
spaced apart from the substrate, or isolated by at least one
dielectric layer from the substrate. The resistive elements formed
in a semiconductor sensor or heater function in the similar manner,
and therefore may be used for both temperature sensing and heating
applications. Semiconductor resistance type heaters are well known
in the art.
[0036] The resistive heating elements 142, 242 in heaters 140, 240
may be formed of any suitable conductive material having bulk
resistance and which will generate heat when a voltage and current
is applied across the element. In some embodiments, without
limitation, the resistive heating elements may be made of
polysilicon, metals and/or meal alloys, minimally conductive oxide
resistive materials, metal nitride, metal silicide materials, and
others. Resistive heating elements 142, 242 may have any suitable
configuration and cross-sectional shape as desired for the intended
application. The resistive heating elements typically have a
generally square or rectangular cross-sectional shape (to current
flow), and in some embodiments the vertical thickness of the
resistive layer or elements may be relatively thin in comparison
with the width of the elements particularly if a thinly deposited
but wide layer of the resistive material is used. Since the
resistance varies with the cross-sectional area to current flow
through the resistor, for a fixed resistance desired for generating
a given amount of heating when current and voltage is applied, the
width of the resistive element gets larger as the thickness gets
thinner, and vice-versa.
[0037] FIGS. 2-3, 4-5, and 6-7 are schematic diagram top views and
cross-sectional views respectively of three possible embodiments
and arrangements of MEMS heater 240. Heater 240 may be located
proximate to and in conductive direct contact with body 207 of MEMS
device 202 as shown. Heater 240 is in conductive thermal
communication with the MEMS device 202, and the heater is operative
to generate and transfer heat directly to the body of the MEMS
device by conductive contact with the body 207 thereby minimizing
heat loss to the semiconductor package 50 or other components such
as CMOS chip 100 located in the package.
[0038] FIGS. 2 and 3 shows one embodiment of heater 240 which may
be built adjacent to but proximate MEMS device 202 and anchored on
the same substrate 204 as the MEMS device. The heater 240 in this
embodiment is proximate to and conductively coupled directly to the
MEMS device 202 via physical contact as shown to transfer heat by
means of conduction to the body 207 of MEMS device 202. This direct
coupling/contact and proximity of the heater 240 advantageously and
efficiently heats the MEMS device 202. The current input "Iin" and
current output "Iout," as well as the current flow "If "through
resistive heating element 242 are shown. Current input In and
output lout may be reversed or arranged in any other suitable
manner.
[0039] Both the body 207 of MEMS device 202 and resistive element
242 may be thermally and electrically isolated from and suspended
above substrate by isolation pedestals 201 as shown in FIGS. 2-7,
which in some embodiments may include insulating spacers 203,
conductive blocks 205, and bond pads 206. In some embodiments,
insulating spacers 203 may be made of an electrically and thermally
insulating layer of silicon dioxide (SiO2) or similar insulating
material. The spacers 203 may also serve to anchor the MEMS device
202 and/or resistive heating 202 element to the substrate 204.
Electrically and thermally conductive blocks 205 may be formed on
the isolation spacers 203 as shown in FIGS. 2 and 3 by any suitable
manner used in the semiconductor art. In some embodiments,
conductive blocks 205 may be made of polysilicon, silicon, silicon
germanium (SiGe), metal, or other suitable electrically conductive
materials. Conductive blocks 205 are operable to receive and
transmit electrical current, and to further receive and transmit
heat generated by resistive heating element 202 to body 207 of MEMS
device 202. In some embodiments, the conductive blocks 205 may be
capped by bond pads 206 formed of a suitable metal conductor for
electrical bonding and interconnection to the CMOS chip 100 or
other device or component used in the semiconductor package 50. The
bond pads 206 on either end of resistive element 242 are coupled to
the power supply to the element which is controlled by power
controller 230.
[0040] The substrate 204 may be of any suitable type and material
used in the semiconductor art including without limitation silicon,
SOI (silicon-on-insulator), SGOI (silicon germanium-on-insulator),
or other thermal isolation substrates in some possible
embodiments.
[0041] FIGS. 4 and 5 show another possible embodiment of heater 240
in which the body 207 of MEMS device 202 itself is used as the
resistive heating element 242. In one embodiment, the MEMS body 207
may be made of polysilicon which will conduct electrical current
and generate heat. The current may be applied via the bond pad 206
as shown. The isolation spacers 203 and conductive blocks 205
structures may be arranged similarly to that shown in FIGS. 2 and
3.
[0042] FIGS. 6 and 7 show another possible embodiment of heater 240
which is a semiconductor "on-chip" heater which is embedded within
or built on the body 207 of MEMS device 202. Such thin film heaters
are well known in the art. The resistive heating element 242 is in
the form of a layer formed above, on, or embedded in body 207 but
in thermal conductive communication therewith. In some embodiments,
resistive element 242 may be formed on a first dielectric layer 244
and surrounded by a second dielectric 244 or other passivation
layer as shown. Heat generated by resistive heater element 242 is
conducted through dielectric layer 244 below to heat the body 207
of MEMS device 202. Conductive leads 243 may be provided to
electrically connect the bond pads 206 to resistive heating element
242 as shown. The current may be applied via the bond pad 206 as
shown to the resistive element. The isolation spacers 203 and
conductive blocks 205 structures may be arranged similarly to that
shown in FIGS. 2 and 3.
[0043] It should be recognized that although the embodiment shown
in FIGS. 6-7 places the resistive heating element 242 above MEMS
body 207, the heating element may also be built beneath but in
thermal communication with the body. On-chip semiconductor resistor
heaters and their construction are well known in the art; the
heater shown in FIGS. 6-7 representing only one possible
arrangement.
[0044] Heater 140 may be configured similarly to heater 240 as in
any of the foregoing embodiments in FIGS. 2-7.
[0045] With continuing reference to FIG. 1, power controllers 130
and 230 each include circuitry that is operative to regulate the
current or voltage to heaters 140 and 240 thereby controlling the
amount of heat generated by the heaters. Power controllers 130, 230
are connected to a power supply 70 (see FIG. 10), which in some
embodiments may be a DC power supply of suitable voltage generated
by any suitable source.
[0046] In any of the above described possible embodiments of MEMS
heater 240 shown in FIGS. 2-7, either a constant voltage or
constant current scheme may be used to generate heat. This is also
applicable to CMOS heater 140. In the constant voltage scheme, heat
is generated by P=V.sup.2/R (where P=power, V=voltage,
R=resistance). In the constant current scheme, heat is generated by
P=I.sup.2R. The same applied to CMOS heater 140. The power P
dissipated by resistive element 202 is equated with the heat
generated by heater 240 which is available for heating MEMS device
202. Depending on the scheme selected, the power controllers 130,
230 will be configured to vary either the current (for constant
voltage scheme) or the voltage (for constant current scheme) for
controlling the power input to heaters 140, 240 and corresponding
heat output from the heaters for heating CMOS chip 100 and MEMS
chip 200. It is well within the knowledge of those skilled in the
art to design such circuits for power controllers 130, 230.
[0047] FIGS. 14 and 15 are exemplary schematic diagrams
representing a constant voltage and constant current power control
scheme for power controllers 130, 230, respectively.
[0048] With continuing reference to FIG. 1, ASIC 102 may include
temperature control circuitry configured to control operation of
heaters 140, 240 via temperature control loops 110 and 210
respectively. In operation, ASIC 102 receives electrical signals
from temperature sensor 220 (e.g. current or voltage) which are
indicative of the temperatures measured for MEMS device 202. ASIC
102 processes the signals and converts the signals into a measured
temperature based on the known resistance of the resistive elements
in the temperature sensors. The actual or measured temperature
(e.g. Tm) is compared to a desired predetermined setpoint
temperature (e.g. Tset) preprogrammed or input into ASIC 102. If Tm
is above or below the desired setpoint temperature Tset either
absolutely or within a predefined tolerance range, ASIC 102 adjusts
(i.e. increases or decreases) the power supply to the heater 240
via circuitry in power controller 230 to adjust the temperature of
MEMS device 202 as required to bring the temperature Tm back within
range. Since the heater 240 and temperature sensor 220 are located
proximate to or on MEMS device 202, the response to a temperature
change is rapid and lag time to bring the temperature of the MEMS
device back into compliance is minimized. ASIC 102 may control its
own temperature in a similar manner using temperature sensor 120,
power controller 130, and heater 140.
[0049] In some embodiments, the MEMS temperature control loop 210
may be configured to maintain the temperature of MEMS chip 200 at
or higher than the ambient operating environment in which
semiconductor package 50 may be located. For example, without
limitation, if the ambient operating environment temperature is
approximately 40 degrees C., ASIC 102 may be configured with a
higher setpoint temperature Tset of about 75 degrees C. at which
the MEMS chip 200 is desired to be maintained. Accordingly, no
cooling is needed for the MEMS device. In some situations, it is
useful to maintain the setpoint temperature Tset higher enough to
account for anticipated variations in ambient temperature so that
the actual measured temperature Tm of MEMS chip 200 is maintained
above the highest anticipated ambient temperature swing. It is
helpful to maintain a constant MEMS chip temperature to maintain a
stable MEMS temperature and preserve performance of the MEMS device
202 regardless of the fact that the setpoint temperature Tset is
set higher than the ambient conditions. Certain design
considerations and limitations will apply such as such as
minimizing the power consumed by the MEMS heater 240 by not setting
the setpoint temperature Tset too high.
[0050] FIGS. 8 and 9 show two possible schematic arrangements and
embodiments of a combination MEMS--CMOS semiconductor package 50.
FIG. 9 is a side/elevation cross-sectional view through the
semiconductor package and shows an arrangement in which the MEMS
chip 200 is stacked above and supported by the CMOS chip 100 below.
This arrangement minimizes the amount of wafer or substrate spaced
consumed by the semiconductor package and is consistent with
2.5D/3D IC chip stacking methodology.
[0051] Referring to FIG. 8, the MEMS chip 200 may house temperature
sensor 220 and heater 240 in addition to MEMS device 202. The power
controller 230 for MEMS heater 240 may be contained in CMOS chip
100, which in some embodiments may also contain temperature sensing
circuitry 222 for temperature sensor 220 and a temperature
independent reference circuit 224 for regulating the temperature of
MEMS device 202 as further described herein. This arrangement
beneficially minimizes the size of the MEMS chip. In one
embodiment, as shown, temperature sensing circuitry 222 for
temperature sensor 220 and a temperature independent reference
circuit 224 may be located in ASIC 102. The MEMS chip 200 may be
structured and configured similarly to any of the embodiments shown
in FIGS. 2-7. Insulating isolation spacers 203 may therefore be
provided to space and support MEMS chip 200 on CMOS chip 100. The
CMOS chip 100 is built on and bonded to a suitable wafer substrate
60, which in some embodiments may be silicon, SOI
(silicon-on-insulator), SGOI (silicon germanium-on-insulator), or
other thermal isolation substrates in some possible embodiments. It
should be noted that MEMS chip 200 including heater 240 are
represented schematically, and not physically in FIG. 8. Therefore,
this figure should not be construed as a physical representation of
the MEMS chip.
[0052] FIG. 9 is a side/elevation cross-sectional view through the
semiconductor package and shows an arrangement in which the MEMS
chip 200 and CMOS chip 100 are bonded separately to substrate 60.
In both FIGS. 8 and 9, the MEMS chip 200 may be isolated in a
confined environment in the chip package 50 as shown, and may be
sealed in a vacuum environment. In addition, the MEMS chip 200 may
be thermally isolated from the substrate 60 as shown. The sealed
and thermally isolated environment advantageously minimizes
convective and conductive heat loss from MEMS chip 200 thereby
improving temperature control and reducing power requirements for
MEMS heater 240. This further enhances the creation of a stable
MEMS temperature which translates into improved performance
characteristics.
[0053] FIG. 10 is a schematic diagram of the semiconductor package
temperature control system applicable to both embodiments of FIGS.
8 and 9. In this embodiment, temperature sensing circuitry 222 for
temperature sensor 220 and a temperature independent reference
circuit 224 are contained in the CMOS chip 100. FIG. 11C shows
temperature sensing circuitry 222 for temperature sensor 220 in
greater detail. Temperature sensing circuitry 222 links signal
outputs from the temperature independent reference circuit 224 and
temperature sensor 220 together to control operation of heater 240
via power control circuitry 230. The temperature sensing circuitry
222 is used to sense and amplify the signal of MEMS chip 200
temperature sensor 220, and includes an amplifier 300 and loop
filter 302. The CMOS chip 100 temperature sensor 120 shown in FIG.
11B already contains the circuitry of an amplifier 300 and loop
filter 302 to sense and amplify the signal. The temperature
independent reference circuit 224 provides a constant voltage or
current signal which does not vary while the temperature is
changing. The temperature sensors 120, 220 provide a current or
voltage signal based on temperature, but do not provide a reference
voltage.
[0054] FIGS. 16-18 are exemplary schematic diagrams of possible
temperature sensing circuitry 222 configurations that can be used,
which is shown in FIG. 10 and discussed above. R(T) shown in FIGS.
16-18 represents the temperature sensing resistance element or
resistor. These temperature sensing devices and circuits shown,
including determination of the corresponding measured/sensed
temperature are well known to those skilled in the art without
further elaboration.
[0055] FIGS. 11A and 11B are schematic diagrams showing the CMOS
chip temperature control loop 110 and the circuit configuration of
temperature sensor 120 in greater detail, respectively. Referring
to FIG. 11B specifically, the operation of temperature sensor 120
is to give a constant current "Iref" to drive the diode 400
operation in forward biasing. It results in diode 400 having a
forward biasing voltage Vbe(T) which is a temperature dependent
signal because diode is a temperature dependent device. This
forward biasing voltage Vbe(T) signal is then compared to a
temperature independent reference voltage Vref from reference
circuit 224 and the difference is amplified by amplifier 300 and
loop filter 302 to enhance the SNR (signal to noise ratio).
[0056] FIG. 12 is a cross-sectional side/elevation view of CMOS
chip 100 showing the physical layout of the temperature control
loop 110 components of FIG. 11. FIG. 13 is a cross-sectional
side/elevation view of an alternative embodiment of CMOS chip 100
showing the physical layout of an alternative arrangement of
temperature control loop 110 of FIG. 11 configured as a
differential type temperature sensor arrangement. This latter
arrangement utilizes two temperature sensing diodes and provides
more accurate temperature control of the CMOS chip. Two heaters 140
and diodes 400 are used in FIG. 13 to implement the differential
sensing and amplification configuration to enhance the SNR
further.
[0057] According to one aspect of the present disclosure, an
embodiment of a MEMS chip with integrated temperature control
system includes a MEMS device having a body, and a heater
positioned proximate to and in conductive thermal communication
with the MEMS device, the heater including a resistive heating
element operable to generate heat when a current flows through the
element. The heater is operable to transfer heat directly to the
body of the MEMS device by conductive contact between the resistive
heating element and the body of the MEMS device.
[0058] According to another aspect of the present disclosure, an
embodiment of a semiconductor device includes a MEMS chip including
a MEMS device having a first heater with resistive heating element
and a dedicated first temperature control loop operable to control
operation of the first heater, the first heater being disposed
proximate to and in conductive thermal communication with the MEMS
device, and a CMOS chip including a second heater and a dedicated
second temperature control loop operable to control operation of
the second heater. The temperature of the MEMS chip and CMOS chip
are independently controllable via the first and second temperature
control loops, respectively.
[0059] According to yet another aspect of the present disclosure,
an embodiment of a semiconductor temperature control circuit for
heating a MEMS device includes a MEMS temperature control loop
including a heater disposed proximate to the MEMS device in a
semiconductor package, a power controller controlling operation of
the heater, a temperature independent reference circuit, a
temperature sensor, and temperature sensing circuitry associated
with the first temperature sensor. The first temperature sensing
circuitry operably receiving a temperature signal generated by the
temperature sensor representing an actual measured operating
temperature of the MEMS device and further operably comparing the
temperature signal to a reference temperature generated by the
temperature independent reference circuit. The temperature sensing
circuitry operably generating an output signal to the power
controller, the power controller controlling a supply of power to
the heater using the output signal generated by the temperature
sensing circuitry.
[0060] While the foregoing description and drawings represent
exemplary embodiments of the present disclosure, it will be
understood that various additions, modifications and substitutions
may be made therein without departing from the spirit and scope and
range of equivalents of the accompanying claims. In particular, it
will be clear to those skilled in the art that embodiments
according to the present disclosure may be include other forms,
structures, arrangements, proportions, sizes, and with other
elements, materials, and components, without departing from the
spirit or essential characteristics thereof. One skilled in the art
will further appreciate that the embodiments may be used with many
modifications of structure, arrangement, proportions, sizes,
materials, and components and otherwise, used in the practice of
the invention, which are particularly adapted to specific
environments and operative requirements without departing from the
principles of the present invention. In addition, numerous
variations in the exemplary methods and processes described herein
may be made without departing from the spirit of the present
disclosure. The presently disclosed embodiments are therefore to be
considered in all respects as illustrative and not restrictive, the
scope of the invention being defined by the appended claims and
equivalents thereof, and not limited to the foregoing description
or embodiments.
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