U.S. patent application number 11/477267 was filed with the patent office on 2008-01-03 for integrated microelectronic package temperature sensor.
Invention is credited to Neha Patel, Nachiket R. Raravikar.
Application Number | 20080002755 11/477267 |
Document ID | / |
Family ID | 38876632 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080002755 |
Kind Code |
A1 |
Raravikar; Nachiket R. ; et
al. |
January 3, 2008 |
Integrated microelectronic package temperature sensor
Abstract
Temperatures in microelectronic integrated circuit packages and
components may be measured in situ using carbon nanotube networks.
An array of carbon nanotubes strung between upstanding structures
may be used to measure local temperature. Because of the carbon
nanotubes, a highly accurate temperature measurement may be
achieved. In some cases, the carbon nanotubes and the upstanding
structures may be secured to a substrate that is subsequently
attached to a microelectronic package.
Inventors: |
Raravikar; Nachiket R.;
(Chandler, AZ) ; Patel; Neha; (Chandler,
AZ) |
Correspondence
Address: |
TROP PRUNER & HU, PC
1616 S. VOSS ROAD, SUITE 750
HOUSTON
TX
77057-2631
US
|
Family ID: |
38876632 |
Appl. No.: |
11/477267 |
Filed: |
June 29, 2006 |
Current U.S.
Class: |
374/100 ;
374/E7.018; 428/367 |
Current CPC
Class: |
G01K 7/16 20130101; H01L
2224/73204 20130101; B82Y 15/00 20130101; H01L 2924/15311 20130101;
Y10T 428/2918 20150115; H01L 2924/00011 20130101; H01L 2224/73204
20130101; Y10S 977/955 20130101; H01L 2224/32225 20130101; G01K
2211/00 20130101; H01L 2924/00014 20130101; H01L 2924/00014
20130101; H01L 2224/16225 20130101; H01L 2224/73204 20130101; H01L
2224/16225 20130101; H01L 2224/0401 20130101; H01L 2224/32225
20130101; H01L 2924/00 20130101; H01L 2224/16225 20130101; H01L
2924/00 20130101; H01L 2924/00011 20130101; H01L 2924/15311
20130101; H01L 2224/32225 20130101; H01L 2224/0401 20130101 |
Class at
Publication: |
374/100 ;
428/367 |
International
Class: |
G01K 1/00 20060101
G01K001/00; B32B 9/00 20060101 B32B009/00 |
Claims
1. A method comprising: using carbon nanotubes to measure
temperature on a microelectronic integrated circuit.
2. The method of claim 1 including forming a pair of spaced apart
vertical structures on a substrate and growing carbon nanotubes
between said vertical structures.
3. The method of claim 2 including forming a unit by reducing the
thickness of said substrate.
4. The method of claim 3 including securing said unit to an
integrated circuit.
5. The method of claim 3 including securing said unit to a package
component of a microelectronic integrated circuit.
6. The method of claim 5 including securing said unit to a first
level interconnect.
7. The method of claim 5 including securing said unit to a second
level interconnect.
8. The method of claim 6 including providing current to said unit
in a first level interconnect through a second level
interconnect.
9. The method of claim 1 including providing a plurality of carbon
nanotubes extending across adjacent interconnects.
10. The method of claim 1 including providing at least two carbon
nanotubes on the back side of an integrated circuit die to measure
temperature on said die.
11. A microelectronic component comprising: a microelectronic
element; and a pair of carbon nanotubes supported on said element
to measure the temperature of said element.
12. The component of claim 11 wherein said component is a first
level interconnect.
13. The component of claim 11 wherein said component is a second
level interconnect.
14. The component of claim 11 wherein said component is part of an
integrated circuit package.
15. The component of claim 11 wherein said component is an
integrated circuit die.
16. The component of claim 15 including carbon nanotubes on
opposite sides of said die.
17. The component of claim 11 wherein said carbon nanotubes are
mounted on a substrate secured to said component.
18. The component of claim 17 wherein said carbon nanotubes are
glued to said component.
19. The component of claim 11 wherein said component is a first
level interconnect and is coupled to a second level
interconnect.
20. The component of claim 11 wherein said carbon nanotubes extend
between a pair of metallic structures.
21. A system comprising: a processor; a dynamic random access
memory coupled to said processor; and said processor including a
microelectronic element and a pair of carbon nanotubes supported on
said element to measure the temperature of said element.
22. The system of claim 21 wherein said processor is in the form of
a die having carbon nanotubes on two opposed sides of said die.
23. The system of claim 21 wherein said processor includes a
package and carbon nanotubes on said package.
24. The system of claim 21 wherein said processor includes a die
having carbon nanotubes formed on at least one side thereof.
25. The system of claim 21 wherein said carbon nanotubes are formed
on a substrate and secured to said die.
Description
BACKGROUND
[0001] This relates generally to measuring temperature in
connection with microelectronic packages and components.
[0002] The effects of temperature on microelectronic packages and
components may be various. Many packaging processes involve the
application of elevated temperatures. These elevated temperatures
may adversely affect components, including the integrated circuit
chip within the package. In addition, the packages may be exposed
to various other temperature effects which may have an impact on
the packaged components. Also, the integrated circuits themselves
can be exposed to various temperature conditions.
[0003] It is known how to integrate integrated circuit temperature
sensors within an overall integrated circuit. Temperature readings
can be obtained from serpentine, integrated temperature sensors.
However, the accuracy of these measurements may, in some cases, be
limited. Moreover, the temperature sensors may take up a relatively
significant percentage of the overall available integrated circuit
space. Also, in some cases, the places at which such temperature
sensors can be formed are limited. Namely, there are generally
limited to areas of sufficient size that can receive such an
integrated element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a greatly enlarged, partial, cross-sectional view
of one embodiment of the present invention;
[0005] FIG. 2 is a greatly enlarged, cross-sectional view of the
embodiment shown in FIG. 1 after further processing;
[0006] FIG. 3 is a top plan view of the embodiment of FIG. 2 in
position on an integrated circuit or other microelectronic package
component;
[0007] FIG. 4 is an enlarged, cross-sectional view of a package in
accordance with one embodiment of the present invention;
[0008] FIG. 5 is an enlarged, cross-sectional view of a package in
accordance with another embodiment of the present invention;
[0009] FIG. 6 is an enlarged, cross-sectional view of an integrated
circuit in accordance with one embodiment of the present
invention;
[0010] FIG. 7 is an enlarged, cross-sectional view of still another
embodiment of the present invention using two spaced metallic
lines; and
[0011] FIG. 8 is a system depiction in accordance with one
embodiment of the present invention.
DETAILED DESCRIPTION
[0012] Referring to FIG. 1, in accordance with some embodiments of
the present invention, a temperature sensor 10 may be formed on an
integrated circuit substrate 12. A plurality of metallic structures
16 may be formed which extend upwardly from the substrate 12. The
structures 16 may be made of a material suitable for the growth of
bridge-like carbon nanotubes 18. Those carbon nanotubes 18 may act
as temperature sensors. Namely, the conductivity of those nanotubes
is a function of temperature. By measuring the conductivity of the
nanotubes, by passing current through them, one can determine the
local temperature.
[0013] In some embodiments of the present invention, a large number
of upstanding structures 16 may be formed. They may be formed in
regular arrays, in some embodiments, using well known techniques.
The arrays may be composed of an inner pillar 14 which may be a
non-metallic material and a metallic coating that forms the
upstanding structure 16.
[0014] Carbon nanotubes 18 may bridge between adjacent structures
16. Thus, a plurality of carbon nanotubes 18 may be randomly
arranged in a generally horizontal configuration transverse to the
upstanding structures 16.
[0015] In some embodiments of the present invention, the structures
16 may be formed directly on the substrate 12. The structures 16
may include the pillars 14, in one embodiment of the present
invention, covered by a metal catalyst to form the metallic
structure 16. Suitable metal catalysts include iron, cobalt, and
nickel. As an example, the structure 16 may be of a height of about
a micron.
[0016] The structures may be formed, for example, by glancing
angled deposition methods. By controlling the substrate 12
rotational motion, including both its angle and velocity, the
structure 16 height can be controlled. Although different metal
catalysts may be utilized to form the structures 16, nickel may be
preferred because it may offer lower contact resistance with the
nanotubes 18 to be formed subsequently.
[0017] In some embodiments of the present invention, some number of
the upstanding structures 16 on the substrate 12 may be used to
make a separable unit 20, shown in FIG. 2. The separable unit 20
may be formed of a portion of the substrate 12 whose thickness has
been reduced so that the substrate thickness does not adversely
affect the temperature measurements. Thus, the substrate 12 may be
reduced in size and thickness to form the unit 20 with some lesser
number of upstanding structures 16 formed thereon.
[0018] The carbon nanotubes 18, shown in FIG. 1, may be grown so as
to bridge between structures 16. This is particularly useful when
large arrays of structures 16 are provided in regular rows and
columns. In one embodiment, gas phase chemical vapor deposition may
be used to grow the carbon nanotubes. In one embodiment of the
present invention, methane may be used as a source for carbon for
the growth of carbon nanotubes. As a result, nanotubes may extend
from one upstanding structure to another. Argon gas may be supplied
during the deposition of the carbon nanotubes to reduce oxidation.
A pressure of about 500 Torr and a furnace temperature in a range
including, but not limited to, 800 to 950 degrees Celsius in the
methane environment may be utilized in one embodiment.
[0019] Advantageously, adjacent structures 16 are spaced reasonably
proximately so that the carbon nanotubes (FIG. 3) of a given length
may span across them.
[0020] The structures 16 may be formed, in one embodiment, by
depositing a catalyst over the pillar 14, preformed on the
substrate 12. For example, the pillars 14 may be silicon or silicon
dioxide pillars. The pillars may be formed, for example, by growing
or depositing the pillar material, masking, and etching to form the
pillars in the desired arrangement. In some embodiments, at least
two of the pillars may be aligned with a crystallographic plane of
the substrate 12 in an embodiment where the substrate is a
crystalline semiconductor.
[0021] During catalyst film deposition, the substrate 12 may be
tilted twice about +/-45 degrees to spread the catalyst over the
pillars 14 to form the structures 16. The carbon nanotubes 18 later
form on the tops and sidewalls of the pillars 14 where the catalyst
is present. The catalyst may not completely cover the pillars in
some cases.
[0022] In some embodiments, an array of pillars (not shown) may be
grown, but only some of the pillars may be activated with the
catalyst. For example, only two pillars may be activated with
catalyst so carbon nanotubes bridge only the two catalyst activated
pillars. The selective activation may be accomplished using masks
or selective catalyst deposition. While cylindrically shaped
structures 16 are depicted, other shapes may also be used.
[0023] Generally, the nanotubes 18 grow generally or roughly
horizontally from the top to the bottom along the structures 16.
The nanotubes span like bridges over the substrate 12.
[0024] In some embodiments, the substrate 12 (FIG. 1) may
subsequently be thinned down to form the unit 20 (FIG. 2) so that
its own thickness does not contribute to changes in the temperature
of the die whose temperature is being measured. A thinned down unit
20 may then be glued onto any polymeric or ceramic surface.
[0025] Referring to FIG. 3, the nanotubes 18 may then be
electrically coupled to an external temperature sensor (not shown)
using metal lines 30. Particularly, the unit 20 may be adhesively
secured to a structure 32 whose temperature is to be measured.
Then, metal lines 30 may be deposited or otherwise formed to the
structures 16. The metal lines 30 may then connect each side of the
array of carbon nanotubes 18 to a suitable pad (not shown) to which
a temperature sensing circuit may be attached. The metal lines 30
and the pads may be printed using conventional processes such as
screen printing or plating.
[0026] In other embodiments, the nanotubes may be prepared on a
substrate using a tall pillar pattern such as one which uses
staples secured to a substrate. By "tall," it is intended to refer
to structures 16 having a height on the order of (but not limited
to) 0.7 centimeters. Subsequently, the nanotubes are grown and
metallizations are completed. Other structures 16 may be also be
utilized to grow bridge-like carbon nanotubes, including telephone
pole and soccer goal oriented office staples. Literally, upstanding
office staples may be utilized by securing them to silicon wafers
using an appropriate adhesive such as carbon tape. The staples may
have their points upstanding ("telephone poles") or inverted
("soccer goal") and extending into the substrate.
[0027] Then, carbon nanotubes may be grown using chemical vapor
deposition in a furnace at 1373 degrees Kelvin under about 100 m
Torr vacuum. To 0.02 g/ml solution of ferrocene and 10 ml of
hexane, two volume percent thiophene is added. The hexane may act
as a source of carbon and the ferrocene acts as a catalyst for gas
diffusion formation of carbon nanotubes. The solution may be heated
to 150.degree. C. and then introduced into a horizontal quartz tube
furnace at an average rate of 0.1 mls. per minute for ten minutes.
Other process parameters may also be used.
[0028] Thiophene is known to promote the formation of single walled
carbon nanotubes in a hydrogen gas atmosphere, whereas multi-walled
carbon nanotubes are found to grow predominantly in the absence of
a hydrogen gas atmosphere. Single walled carbon nanotubes or
multi-walled carbon nanotubes can be used by controlling the
nanotubes growth conditions by controlling the hydrogen gas
concentration in the furnace (no hydrogen gas atmosphere giving
multi-walled carbon nanotubes, whereas hydrogen gas atmosphere may
promote the single walled carbon nanotube growth).
[0029] Although the recipe and numbers recited above are
recommended to grow carbon nanotubes, the growth conditions are not
limited to this recipe or these numbers, but, rather, is inclusive
of them. In some temperature sensing applications, multi-walled
carbon nanotubes may be advantageous.
[0030] Referring to FIG. 4, in accordance with one embodiment of
the present invention, temperatures associated with surface mount
techniques may be measured by growing carbon nanotubes across
second level interconnects, such as solder ball or surface mount
pads 26a. The pads 26a may mount solder balls 34. The solder balls
34 may couple the package 37 to an external printed circuit board
(not shown) such as a motherboard.
[0031] The carbon nanotubes 18 may be grown so as to span between
sufficiently adjacent pads 26a. In some cases, only some of the
pads 26a may be used for the temperature measurement and other pads
may have no such function, but, instead, function conventionally as
second level interconnects. In some cases, the pads 26a may be
otherwise electrically non-functional and may only be used for
temperature measurement purposes.
[0032] The pads 26a may be formed on a suitable substrate 36, over
which is mounted the integrated circuit die 40. A housing 38 may
cover the die 40 and be secured to the substrate 36. First level
interconnects 44 may be positioned between the die 40 and the
substrate 36.
[0033] Referring to FIG. 5, basically the same package is shown.
However, in this case, the carbon nanotubes 18 are grown between
first level interconnects 44, instead of between second level
interconnects, as depicted in FIG. 4. In this way, carbon nanotubes
18 can be selectively grown between appropriately spaced elements
to make temperature measurements for first and/or second level
interconnects.
[0034] In some cases, the length of the carbon nanotubes may be
different for different applications in order to span the necessary
space. For example, in some cases, it may be desirable to have
carbon nanotubes on the order of 1 micron to span between metal
lines on a die, 10 to 50 microns to span between adjacent surface
mount pads, and all the way up to 1 millimeter for adjacent solder
bumps.
[0035] Generally, different techniques may be utilized to form the
carbon nanotubes in different applications. In one embodiment, some
interconnects, such as the solder ball pads 26, may be masked and
other interconnects, such as the solder balls 26a, may not be
masked so that the carbon nanotubes form only between the exposed
pads 26a. As another example, a unit 20 may be laminated into
position between adjacent pads 26a to achieve a comparable effect.
As still another possibility, nanotubes in a solvent solution may
be dispensed as a liquid at selected locations at room temperature
and allowed to dry. As still another option, electrodeposition may
be utilized.
[0036] For the first level interconnects, it may be desirable to
use the electrodeposition or liquid deposition techniques to avoid
exposing the substrate or die 40 to excessive temperatures that may
be required in some carbon nanotube fabrication processes.
[0037] In some embodiments, it may be desirable for the first level
interconnects, from the silicon to the substrate, to connect to
second level interconnects that are actually active
(non-temperature sensing) interconnects, even though the first
level interconnects with the carbon nanotubes between them may be
electrically non-functional for their normal interconnect
(non-temperature sensing) purposes. Thus, the first level
interconnects with the carbon nanotubes connected to them may be
only functional for sensing temperature, but may be connected to
second level interconnects that are effective, but are effective
really only to convey the signals to and from the carbon nanotubes
of the first level interconnects. Similarly, the second level
interconnects with carbon nanotubes may be functional only for
purposes of providing signals to and from the carbon nanotubes for
purposes of making temperature measurements and perform no other
interconnection function, in some embodiments.
[0038] In some embodiments, the nanotubes may be highly accurate
temperature indicators. Because they have anisotropic
characteristics in the length dimension and have very small
dimensions transversely to length dimensions, high temperature
resolutions may be obtained with carbon nanotubes. Carbon nanotubes
may tend to be atomically relatively perfect and chemically stable
and, therefore, may be more reliable as sensors than metallic
structures of similar dimensions. In addition, temperatures in hard
to reach locations may be measured in some cases.
[0039] Referring to FIG. 6, the units 20 may be secured to opposite
sides of an integrated circuit die 40 in another embodiment. In one
embodiment, a unit 20 may be secured to the front side 42 of the
die 40 and, in another embodiment, a unit 20 may be secured to the
back side 44 of the die 40, as shown. In some cases, temperature
sensing units 20 may be provided on both die sides, together with
suitable metallizations to an external temperature sensor. The
suitable metallizations may be provided to a current source which
provides current to the carbon nanotubes in the units 20 and
measures the resulting current therefrom to determine temperature
in accordance with known principles.
[0040] Referring to FIG. 7, in accordance with another embodiment
of the present invention, spaced metal lines 26 may be bridged by
carbon nanotubes 18. The carbon nanotubes 18 may span an
intermediate underlying trench 24 and a substrate 22. The metal
lines 26 may be dummy metal lines for temperature purposes only or,
in some cases, could be actual metal lines. Where the lines 26 are
actual metal lines, these metal lines may be subsequently used for
carrying signals, for example, by first destroying the carbon
nanotubes 18 after having used them, if desired, for temperature
measurements. Alternatively, the lines 26 may couple to a
temperature sensor that uses the varying resistance of the
nanotubes to develop a temperature indication.
[0041] Finally, referring to FIG. 8, in accordance with some
embodiments of the present invention, the integrated circuits or
packaged devices with the integrated temperature sensors may be
incorporated into a system including a processor 10. The processor
10 may be coupled by a bus 38 to a dynamic random access memory 40
and an input/output device 42. While a simple architecture is
shown, many other embodiments may be possible.
[0042] References throughout this specification to "one embodiment"
or "an embodiment" mean that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one implementation encompassed within the
present invention. Thus, appearances of the phrase "one embodiment"
or "in an embodiment" are not necessarily referring to the same
embodiment. Furthermore, the particular features, structures, or
characteristics may be instituted in other suitable forms other
than the particular embodiment illustrated and all such forms may
be encompassed within the claims of the present application.
[0043] While the present invention has been described with respect
to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is
intended that the appended claims cover all such modifications and
variations as fall within the true spirit and scope of this present
invention.
* * * * *