U.S. patent number RE37,546 [Application Number 09/672,842] was granted by the patent office on 2002-02-12 for reactor and method of processing a semiconductor substrate.
This patent grant is currently assigned to Micro C Technologies, Inc.. Invention is credited to Imad Mahawili.
United States Patent |
RE37,546 |
Mahawili |
February 12, 2002 |
**Please see images for:
( Certificate of Correction ) ** |
Reactor and method of processing a semiconductor substrate
Abstract
A reactor for processing a substrate includes a first housing
defining a processing chamber and supporting a light source and a
second housing rotatably supported in the first housing and adapted
to rotatably support the substrate in the processing chamber. A
heater for heating the substrate is supported by the first housing
and is enclosed in the second housing. The reactor further includes
at least one gas injector for injecting at least one gas into the
processing chamber onto a discrete area of the substrate and a
photon density sensor extending into the first housing for
measuring the temperature of the substrate. The photon density
sensor is adapted to move between a first position wherein the
photon density sensor is directed to the light source and a second
position wherein the photon density sensor is positioned for
directing toward the substrate. Preferably, the communication
cables comprise optical communication cables, for example sapphire
or quartz communication cables. A method of processing a
semiconductor substrate includes supporting the substrate in a
sealed processing chamber. The substrate is rotated and heated in
the processing chamber in which at least one reactant gas is
injected. A photon density sensor for measuring the temperature of
the substrate is positioned in the processing chamber and is first
directed to a light, which is provided in the chamber for measuring
the incident photon density from the light and then repositioned to
direct the photon density sensor to the substrate to measure the
reflection of the light off the substrate. The incident photon
density is compared to the reflected light to calculate the
substrate temperature.
Inventors: |
Mahawili; Imad (Grand Rapids,
MI) |
Assignee: |
Micro C Technologies, Inc.
(Kentwood, MI)
|
Family
ID: |
25430608 |
Appl.
No.: |
09/672,842 |
Filed: |
September 28, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
911638 |
Aug 15, 1997 |
05814365 |
Sep 29, 1998 |
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|
Current U.S.
Class: |
427/10; 118/666;
118/708; 118/712; 118/715; 118/725; 118/730; 374/131; 374/141;
427/248.1 |
Current CPC
Class: |
C23C
16/455 (20130101); C23C 16/45519 (20130101); H01L
21/67115 (20130101); C23C 16/481 (20130101); C23C
16/52 (20130101); C23C 16/45565 (20130101) |
Current International
Class: |
C23C
16/52 (20060101); C23C 16/48 (20060101); C23C
16/455 (20060101); H01L 21/00 (20060101); C23C
16/44 (20060101); C23C 016/00 () |
Field of
Search: |
;427/10,248.1
;118/666,708,712,715,725,730 ;374/131 ;324/141 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bueker; Richard
Attorney, Agent or Firm: Van Dyke, Gardner, Linn &
Burkhart, LLP
Claims
We claim:
1. A reactor for processing a substrate, said reactor
comprising:
a housing defining a processing chamber;
a light source supported in said housing;
a heater positioned in said housing, said heater being adapted to
heat the substrate;
at least one gas injector adapted to inject at least one gas into
said processing chamber onto a discrete area of the substrate;
and
a photon density sensor extending into said housing, said photon
density sensor being adapted to measure the emissivity of the
substrate and to move between a first position wherein said photon
density sensor is directed to said light source and a second
position wherein said photon density sensor is positioned for
directing toward the substrate.
2. The reactor according to claim 1, further comprising first and
second communication cables, said first communication cable
including said photon density sensor and being in communication
with said second cable and being adapted to send signals from said
photon density sensor to a processor.
3. The reactor according to claim 2, wherein said first and second
communications cable comprise optical communication cables.
4. The reactor according to claim 3, wherein said first
communication cable comprises a sapphire optical communication
cable.
5. The reactor according to claim 3, wherein said second
communication cable comprises a quartz optical communication
cable.
6. The reactor according to claim 3, wherein said first and second
communications cables are interconnected by a slip connection.
7. The reactor according to claim 6, wherein said first
communication cable is rotated between said first and second
positions by a driver.
8. The reactor according to claim 7, wherein said driver comprises
a motor.
9. The reactor according to claim 7, wherein at least a portion of
said first communication cable is housed in a rigid member, said
driver drivingly engaging said rigid member to rotate said
communication cable between said first position and said second
position.
10. The reactor according to claim 9, wherein said rigid member
comprises a cylindrical shaft.
11. The reactor according to claim 2, wherein said first
communications cable includes an angled portion, said photon
density sensor being defined on a distal end of said angle
portion.
12. The reactor according to claim 1, wherein said housing includes
a cover, said photon density sensor being supported by said
cover.
13. The reactor according to claim 12, wherein said photon density
sensor comprises an optic communication fiber.
14. The reactor according to claim 13, wherein said optic
communication fiber comprises a sapphire optic communication
fiber.
15. The reactor according to claim 1, further comprising a second
housing, said second housing being rotatably supported in said
housing defining a processing chamber and being adapted to
rotatably support the substrate in said processing chamber.
16. A reactor for processing a substrate, said reactor
comprising:
a housing defining a processing chamber;
a light source supported in said housing;
a heater adapted to heat the substrate, said heater being supported
in said housing;
a photon density sensor extending into said housing, said photon
density sensor being adapted to measure the emissivity of the
substrate and to move between a first position wherein said photon
density sensor is directed to said light source and a second
position wherein said photon density sensor is positioned for
directing toward the substrate; and
a plurality of gas injectors supported by said housing, said
plurality of gas injectors being adapted to inject at least one
reactant gas into said processing chamber.
17. The reactor according to claim 16, wherein said gas injectors
are arranged into at least two groups of gas injectors, each of
said groups of gas injectors being adapted to selectively deliver
at least one reactant gas and an inert gas into said processing
chamber.
18. The reactor according to claim 16, further including a manifold
supported by said housing said manifold being adapted to inject
inert gas into said processing chamber.
19. The reactor according to claim 18, wherein said manifold
comprises an injection ring, said injection ring being positioned
and adapted to align with the periphery of the substrate for at
least directing inert gas onto the periphery of the substrate.
20. The reactor according to claim 16, wherein each of said
injectors is adapted to be independently controlled whereby flow of
gas through each of said injectors can be independently
adjusted.
21. The reactor according to claim 16, wherein said gas injectors
are arranged in a uniform pattern adapted to direct a uniform flow
of a gas toward the substrate.
22. The reactor according to claim 16, wherein said gas injectors
are adapted to deliver the gas on a discrete area of the
substrate.
23. The reactor according to claim 22, further comprising an
exhaust manifold, said exhaust manifold adapted to remove unreacted
gas from the processing chamber and to substantially confine the
gas over the discrete area of the substrate.
24. The reactor according to claim 23, wherein said manifold
extends around said plurality of gas injectors to substantially
confine the gas in the processing chamber over the discrete area of
the substrate, said exhaust manifold interposed between said
injectors and said photon density sensor whereby said photon
density sensor is free from film depositions from the gas.
25. The reactor according to claim 16, wherein said gas injectors
are arranged in with a greater concentration of said gas injectors
positioned and adapted to align with a peripheral region of the
substrate and with a smaller concentration of gas injectors
positioned and adapted to align with a central region of the
substrate whereby the gas injected by the gas injectors produces a
uniform deposition on the substrate.
26. The reactor according to claim 16, wherein said housing
comprises a first housing, said reactor further comprising a second
housing rotatably supported in said first housing, said second
housing enclosing said heater and rotatably supporting the
substrate thereon.
27. The reactor according to claim 26, said second housing having a
removable platform, said removable platform being adapted to
support the substrate in said processing chamber.
28. A method of processing a semiconductor substrate comprising the
steps of:
providing a processing chamber;
supporting the substrate in the processing chamber;
directing light into the processing chamber toward the
substrate;
providing a photon density sensor;
directing the photon density sensor to the light;
measuring the incident photon density from the light with the
photon density sensor;
repositioning the photon density sensor to direct the photon
density sensor to the substrate;
measuring the reflection of the light off the substrate;
comparing the measured incident photon density to the reflected
light to calculate the substrate temperature;
heating the substrate; and
injecting at least one reactant gas into the chamber through at
least one injector.
29. A method of processing a semiconductor substrate according to
claim 28, wherein repositioning the photon density sensor includes
rotating the photon density sensor.
30. A method of processing a semiconductor substrate according to
claim 28, wherein rotating the photon density sensor includes
rotating the photon density sensor about one hundred eighty
degrees.
31. A method of processing a semiconductor substrate according to
claim 28, wherein comparing the measured incident photon density to
the reflected light includes:
providing a processor;
sending signals from the photon density sensor to the processor to
calculate the substrate emissivity and temperature; and
calculating the temperature with the processor from the signals
from the photon density sensor.
32. A method of processing a semiconductor substrate according to
claim .[.28.]. .Iadd.31.Iaddend., wherein sending signals
includes:
forming the photon density sensor on a first communications cable:
and
coupling the first communications cable to the processor.
33. A method of processing a semiconductor substrate according to
claim 32, wherein coupling includes coupling the first
communications cable to a second communications cable and coupling
the second communications cable to the processor.
34. A method of processing a semiconductor substrate according to
claim 33, wherein coupling the first communications cable to the
second communications cable includes providing a slip coupling
between the first communications cable and the second
communications cable.
35. A method of processing a semiconductor substrate according to
claim 28, further comprising adjusting the heating based on the
temperature of the substrate.
36. A method of processing a semiconductor substrate according to
claim 28, further comprising rotating the substrate in the
processing chamber, said injecting includes directing the reactant
gas to a discrete portion of the substrate while the substrate is
rotating.
37. A method of processing a semiconductor substrate according to
claim 36, wherein directing the reactant gas includes exhausting
unreacted gas from the processing chamber to isolate the reactant
gas over the discrete portion of the substrate whereby the photon
density sensor remains free of undesirable film depositions from
the reactant gas.
38. A method of processing a semiconductor substrate according to
claim 28, wherein injecting includes a first reactant gas through a
first group of the gas injectors and injecting a second reactant
gas through a second group of the gas injectors.
39. A method of processing a semiconductor substrate according to
claim 28, further comprising selectively varying the flow of the
reactant gas through the gas injectors.
40. A method of processing a semiconductor substrate according to
claim 28, further comprising arranging the gas injectors in a
uniform pattern to direct a uniform flow of gas into the processing
chamber.
41. A method of processing a semiconductor substrate according to
claim 28, wherein injecting includes injecting the gas into the
processing chamber with a non-uniform profile for uniformly
depositing film on the substrate.
42. A method of processing a semiconductor substrate according to
claim 41, wherein injecting the gas into the chamber with a
non-uniform profile includes arranging the gas injectors in a
non-uniform pattern to direct more gas to a peripheral region of
the substrate and less gas to the central region of the
substrate..Iadd.
43. A reactor for processing a substrate, said reactor
comprising:
a housing defining a processing chamber;
a light source positioned in said housing;
a heater positioned in said housing, said heater being adapted to
heat the substrate;
at least one gas injector adapted to inject at least one gas into
said processing chamber onto a surface of the substrate; and
a photon density sensor positioned in said housing, said photon
density sensor being adapted to measure the emissivity of the
substrate and to move between a first position wherein said photon
density sensor is directed to said light source and a second
position wherein said photon density sensor is positioned for
directing toward the substrate..Iaddend..Iadd.
44. The reactor according to claim 43, further comprising first and
second communication cables, said first communication cable
including said photon density sensor and being in communication
with said second cable and being adapted to send signals from said
photon density sensor to a processor..Iaddend..Iadd.
45. The reactor according to claim 43, wherein said first and
second communications cable comprise optical communication
cables..Iaddend..Iadd.
46. The reactor according to claim 45, wherein said first and
second communications cables are interconnected by a slip
connection..Iaddend..Iadd.
47. The reactor according to claim 46, wherein said first
communication cable is rotated between said first and second
positions by a driver..Iaddend..Iadd.
48. The reactor according to claim 44, wherein said first
communications cable includes an angled portion said photon density
sensor being defined on a distal end of said angle
portion..Iaddend..Iadd.
49. The reactor according to claim 43, further comprising a second
housing, said second housing being rotatably supported in said
housing defining a processing chamber and being adapted to
rotatably support the substrate in said processing
chamber..Iaddend..Iadd.
50. A reactor for processing a substrate said reactor
comprising:
a housing defining a processing chamber;
a light source positioned in said housing;
a heater adapted to heat the substrate said heater being supported
in said housing;
a photon density sensor positioned in said housing, said photon
density sensor being adapted to measure the emissivity of the
substrate and to move between a first position wherein said photon
density sensor is directed to said light source and a second
position wherein said photon density sensor is positioned for
directing toward the substrate; and
at least one gas injector supported by said housing, said gas
injector being adapted to inject at least one reactant gas into
said processing chamber..Iaddend..Iadd.
51. The reactor according to claim 50, wherein said gas injector
comprises a plurality of gas injectors said gas injectors are
arranged into at least two groups of gas injectors, each of said
groups of gas injectors being adapted to selectively deliver at
least one reactant gas and an inert gas into said processing
chamber..Iaddend..Iadd.
52. The reactor according to claim 50, further including a manifold
supported by said housing, said manifold including said at least
one gas injector, said manifold being adapted to inject inert gas
into said processing chamber..Iaddend..Iadd.
53. The reactor according to claim 52, wherein said manifold
comprises injection ring, said injection ring including a plurality
of said gas injector said injection ring being positioned and
adapted to align with the periphery of the substrate for at least
directing inert gas onto the periphery of the
substrate..Iaddend..Iadd.
54. The reactor according to claim 50, wherein said at least one
gas injector comprises a plurality of gas injectors, each of said
injectors is adapted to be independently controlled whereby flow of
gas through each of said injectors can be independently
adjusted..Iaddend..Iadd.
55. The reactor according to claim 50, wherein said at least one
gas injector comprises a plurality of gas injectors, said gas
injectors are arranged in a uniform pattern adapted to direct a
uniform flow of a gas toward the substrate..Iaddend..Iadd.
56. The reactor according to claim 50 wherein said gas injector is
adapted to deliver the gas on a discrete area of the
substrate..Iaddend..Iadd.
57. The reactor according to claim 56, further comprising an
exhaust manifold, said exhaust manifold adapted to remove unreacted
gas from the processing chamber and to substantially confine the
gas over the discrete area of the substrate..Iaddend..Iadd.
58. The reactor according to claim 57, wherein said at least one
gas injector comprising a plurality of gas injectors, said manifold
extending around said plurality of gas injectors to substantially
confine the gas in the processing chamber over the discrete area of
the substrate, said exhaust manifold interposed between said
injectors and said photon density sensor whereby said photon
density sensor is free from film depositions from the
gas..Iaddend..Iadd.
59. The reactor according to claim 50, wherein said at least one
gas injector comprises a plurality of gas injectors, said gas
injectors are arranged in with a greater concentration of said gas
injectors positioned and adapted to align with a peripheral region
of the substrate and with a smaller concentration of gas injectors
positioned and adapted to align with a central region of the
substrate whereby the gas injected by the gas injectors produces a
uniform deposition on the substrate..Iaddend..Iadd.
60. The reactor according to claim 50, wherein said housing
comprises a first housing, said reactor further comprising a second
housing rotatably supported in said first housing, said second
housing enclosing said heater and rotatably supporting the
substrate thereon..Iaddend..Iadd.
61. The reactor according to claim 60, said second housing having a
removable platform, said removable platform being adapted to
support the substrate in said processing chamber..Iaddend.
Description
BACKGROUND AND TECHNICAL FIELD OF THE INVENTION
The present invention relates to a processing reactor and, more
particularly to a processing reactor for the thermal processing and
chemical deposition of thin film applications on a substrate, such
as semiconductor wafer, in which the temperature of the substrate
can be accurately monitored and the injection of gas into the
chamber can be controlled to provide better control of the
substrate processing.
In semiconductor fabrication, semiconductor substrates are heated
during various temperature activated processes for example, during
film deposition, oxide growth, etching, and thermal annealing. The
control of deposition and annealing processes depends on the
control of the gas flow and pressure and the wafer temperature.
When heating a substrate, it is desirable to heat the substrate in
a uniform manner so that all the regions of the substrate are
heated to the same temperature. Uniform temperatures in the
substrate provide uniform process variables on the substrate; for
instance in film deposition, if the temperature in one region of
the substrate varies from another region, the thickness of the
deposition in these regions may not be equal. Moreover, the
adhesion of the deposition to the substrate may vary as well.
Furthermore, if the temperature in one region of the substrate is
higher or lower than the temperature in another region of the
substrate, a temperature gradient within the substrate material is
formed. This temperature gradient produces thermal moments in the
substrates which in turn induce radial local thermal stresses in
the substrate. These local thermal stresses can reduce the
substrate's strength and, furthermore, damage the substrate.
Therefore, knowing the temperature of the wafer is important in
determining the thermal diffusion depths of surface implanted
dopants, the deposited film thickness, and the material
constitution quality and annealed or reflowed characteristics.
Various methods have been developed for measuring the temperature
of a substrate during processing in order to improve the control of
the various processes. Direct methods, which include the use of
contact probes, such as thermocouples or resistance wire
thermometers, are generally not suitable for substrate processing
because direct contact between the probes and the substrate
contaminates the device structure. More typically, indirect
measuring methods are used, such as the use of preheated platforms
that are calibrated prior to processing. However, this method is
not typically accurate. In some applications, the temperature of
the back side of the substrate is calibrated or monitored, but such
methods also lead to significant errors due to the large variances
between the back side and device side surface characteristics that
lead to different substrate temperatures. The patterns of the
specific devices being processed, the type of material being
deposited or annealed, the degree of the roughness of the surface,
and the operating temperature all affect the characteristics of the
substrate surface and define what is known as the surface
emissivity of the substrate.
In U.S. Pat. No. 5,310,260 to Schietinger et al. a non-contact
temperature measuring device is disclosed. The device includes two
sapphire optical fibre probes, with one of the probes directed to
the lamp source providing the heat to the wafer and the other probe
directed to the wafer itself. Each fiber probe sends its respective
signal to a measuring instrument which converts the photon density
measured by the probe to an electrical current. The ratio of the
two signals provides a measure of the surface reflectivity, which
approximates the total hemispherical reflectivity. However, this
method can only be used with an AC source lamp and when the lamp
shines directly on the wafer. Since two optical fiber probes must
be used in order to implement this technique, the characteristics
of each probe must be accurately detailed in order to obtain
accurate emissivity measurements. In the event that one of the
probes must be replaced, a total system re-calibration is required.
Furthermore, this method cannot be used in chambers in which thin
films are deposited, etched, or sputtered since the thin films will
also deposit on the optical fiber photon density sensors and
drastically alter the results and render the measurement method
inoperative. Moreover, the optical fiber sensors are always
directed at one fixed area of the wafer. Since different parts of
the wafer may have different device patterns and, therefore, may
have different local emissivities, the temperature measurement and
control would be limited in value as it would represent the
emissivity information only for that specific area rather than the
average surface topology of the substrate.
In addition to temperature uniformity, the uniformity of film
deposition is affected by uniformity of the delivery of the process
gas. Good process uniformity usually requires adjustments and
optimizations for both the wafer temperature uniformity and the gas
flow pattern of the process gas. In most conventional chambers or
reactors, the reactant gas is delivered through a single port,
which injects gas into the chamber above the wafer. Due to the
geometry of the wafer, the resulting deposition of the gas onto the
wafer is not uniform.
More recently, shower-like gas injection systems have been
developed in which separate gases are injected in a shower-like
pattern over the entire substrate area. However, such gas delivery
systems fill the entire chamber volume and, thus, deposit films on
the substrate as well as the chamber walls. Consequently, these gas
delivery systems preclude the use of any optical instruments for
non-contact temperature measurement and in-situ film
methodology.
Consequently, there is a need for a processing reactor which can
deliver heat to a substrate in a uniform manner and can accurately
monitor the temperature of the substrate during processing and
adjust the profile of the applied heat as needed to achieve optimal
processing of the substrate. Furthermore, there is a need for a
processing reactor which can deliver and direct the flow of gas to
the substrate during processing so that the substrate receives a
uniform deposition of thin film of the process gas or gases in a
discrete area on the substrate.
SUMMARY OF THE INVENTION
One form of the invention provides a reactor having a processing
chamber with an emissivity measuring device and improved gas
injection system. The emissivity measuring device measures the
photon density from a light source, which is housed in the
processing chamber, and the reflected photon density off a
substrate, which is processed in the processing chamber. These
measurements are then used to determine the emissivity and,
ultimately, the temperature of the substrate with a high degree of
accuracy. The emissivity measuring device includes a communications
cable which includes a photon or emissivity sensor that is
positioned in the processing chamber. The photon density sensor is
adapted to move between a first position wherein the photon density
sensor is directed to the light source for measuring the incident
photon density of the light and a second position wherein the
photon density sensor is directed toward the substrate for
measuring the reflected photon density off the substrate. The gas
injection system is adapted to inject and direct at least one gas
onto a discrete area of the substrate. The reactor is, therefore,
particularly suitable for use in a semiconductor fabrication
environment where the control of heating and injection of gas must
be maintained in order to produce uniform process variables during
the fabrication of semiconductor devices.
In one aspect, the emissivity measuring device comprises first and
second communication cables. The first communication cable includes
the photon density sensor and is in communication with the second
cable for sending signals from the photon density sensor to a
processor. Preferably, the first and second communication cables
comprise optical communication cables. For example, the first
communication cable may comprise a sapphire optical communication
cable, and the second communication cable may comprise a quartz
optical communication cable. In further aspects, the first and
second communications cables are interconnected by a slip
connection so that the first communication cable can be rotated
between the first and second positions by a driver, for example a
motor.
In another form of the invention, a reactor for processing a
substrate includes a first housing, which defines a processing
chamber and supports a light source. A second housing is rotatably
supported in the first housing and is adapted to rotatably support
the substrate in the processing chamber. A heater for heating the
substrate is supported by the first housing and is enclosed in the
second housing. A photon density sensor extends into the first
housing for measuring the emissivity of the substrate, which is
adapted to move between a first position wherein the photon density
sensor is directed to the light source and a second position
wherein the photon density sensor is positioned for directing
toward the substrate. The reactor further includes a plurality of
gas injectors, the gas injectors being grouped into at least two
groups of gas injectors, with each group of gas injectors being
adapted to inject at least one gas into the processing chamber of
the reactor onto a discrete area of the substrate.
In one aspect, each group of injectors is adapted to selectively
deliver at least one reactant gas and an inert gas. In another
aspect, each group of gas injectors is adapted to be independently
controlled whereby flow of gas through each group of gas injectors
can be independently adjusted. In yet another aspect, the gas
injectors in each group of gas injectors may be arranged in a
uniform pattern for directing a uniform flow of a gas toward the
substrate. The reactor also preferably includes an exhaust manifold
for removing unreacted gas from the processing chamber.
In yet further aspects, the gas injectors are arranged in pattern
having a greater concentration of gas injectors in a peripheral
region and a smaller concentration of gas injectors in a central
region of the substrate whereby the gas injected by the gas
injectors produces a uniform deposition on the substrate.
In yet another form of the invention, a method of processing a
semiconductor substrate includes supporting the substrate in a
sealed processing chamber. The substrate is rotated and heated in
the processing chamber in which at least one reactant gas is
injected. A photon density sensor for measuring the emissivity of
the substrate is positioned in the processing chamber and is first
directed to a light, which is provided in the chamber, for
measuring the incident photon density from the light and then
repositioned to direct the photon density sensor to the substrate
to measure the reflected photon density off the substrate. The
incident photon density is compared to the reflected photon density
to calculate the substrate temperature.
As will be understood, the reactor of the present invention
provides numerous advantages over prior known reactors. The reactor
provides a single substrate photon density sensor which can be used
to accurately determine the temperature of the substrate during
processing. The single photon density sensor eliminates the need
for recalibration and complex calculations detailing the
characteristics of each sensor associated with temperature
measuring devices having two sensors. Moreover, the reactor
provides a gas injection system which directs one or more reactant
gases to the substrate during processing in a controlled manner and
directs the gas or gases to discrete regions of the substrate so
that emissivity measurements and temperature calculations can be
performed in the processing chamber during the injection of the gas
or gases without impairment from undesirable film depositions on
the emissivity measurement devices.
These and other objects, advantages, purposes and features of the
invention will be apparent to one skilled in the art from a study
of the following description taken in conjunction with the
drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a chemical vapor deposition chamber
of the present invention;
FIG. 2 is a schematic sectional view taken along line II--II of
FIG. 1;
FIG. 3 is an enlarged view taken along section lines III--III of
FIG. 2 illustrating the gas injection system;
FIG. 4 is a top plan view of the chamber cover;
FIG. 5 is a bottom plan view of the chamber cover; and
FIG. 6 is a schematic representation of an emissivity measurement
system cooperating with the chemical vapor deposition chamber of
FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings and particular to FIGS. 1 and 2, a
reactor for processing semiconductor substrates is generally
indicated by the numeral 10. In the illustrated embodiment, reactor
10 comprises a single wafer processing reactor that is suitable for
performing various fabrication processes on a semiconductor
substrate 12, such as a semi-conductor wafer. Reactor 10 is
particularly suitable for thermal processing of a semiconductor
wafer. Such thermal processes include thermal annealing of a
semiconductor wafer and thermal reflow of boro-phosphorous gasses,
and chemical vapor deposition of thin film applications, such as
high temperature oxide, low temperature oxide, high temperature
nitride, doped and undoped polysilicon, silicon epitaxial and
tungsten metal and tungsten silicide films, in the fabrication of a
semiconductor device. The control of these processes depends on the
control of gas flow, gas pressure, and wafer temperature. As will
be described in more detail, reactor 10 includes a heater assembly
14, which delivers heat to the substrate 12 in a uniform manner, a
gas injection assembly 34, which selectively delivers and directs
gas to a discrete region of the substrate in a uniform and
controlled manner, and an emissivity measurement assembly 60, which
permits continuous emissivity measurement of the average surface
area of the device side of the substrate during processing so that
the amount and/or the profile of the heat being delivered to the
substrate during processing may be adjusted.
As best seen in FIG. 2, reactor 10 includes a heater assembly 14,
which is enclosed in a heater housing 16. Heater assembly 14 is
designed to deliver radiant heat to substrate 12 in a manner such
that the temperature in the substrate is substantially uniform. In
a preferred form, heater assembly 14 includes an array of heating
elements such as linear tungsten-halogen lamps (not shown), which
emit peak radiation at 0.95 microns and are layered to form a
plurality of heating zones, which provide a concentrated heating
profile with a greater amount of heat being applied to the outer
perimeter of the substrate than the center of the substrate. For
further details of heater assembly 14, reference is made to pending
U.S. patent application entitled RAPID THERMAL PROCESSING HEATER
TECHNOLOGY AND METHOD OF USE, filed on Dec. 4, 1996. Ser. No.
08/759,559, which is incorporated herein by reference in its
entirety. It should be understood that other heaters may be used in
reactor 10, preferably heaters which deliver heat to substrate in a
substantially uniform manner.
Heater assembly 14 is enclosed in heater housing 16, which is
mounted on a rotatable base 18. Heater housing 16 is made from a
suitable material, such as a ceramic, graphite or, more preferably,
silicon graphite coated graphite, or the like. Heater assembly 14,
heater housing 16, and rotatable base 18 are enclosed and vacuum
sealed in an outer, reactor housing 20 and are supported on a base
wall 22 of reactor housing 20. Reactor housing 20 may be formed
from a variety of metal materials. For example, aluminum is
suitable in some applications, whereas stainless steel is more
suitable in others. The choice of material is driven by the type of
chemicals used during the deposition process and their reactivity
with respect to the metal of choice, as is understood by those
persons skilled in the art. The chamber walls are typically water
cooled to approximately 45-75 degrees Fahrenheit by a conventional
recirculating chilled water flow system, which is commonly known in
the art.
Referring to FIGS. 2 and 3, base 18 and housing 16 are rotatably
supported on base wall 22 of housing and are preferably rotated
using a conventional magnetically coupled drive mechanism 23, or
other suitable driving device which can impart rotation to base 18
through a vacuum seal. The revolutions per minute (rpm) of base 18
and housing 16 may be preset, for example preferably in a range of
5 to 60 rpm depending on the specific process, again as is
understood by those persons skilled in the art.
As best seen in FIG. 1, reactor housing 20 includes a cylindrical
outer wall 24 and a cover 26 which extends over cylindrical outer
wall 24. Substrate 12 is supported in reactor housing 20 on a
platform 28, which is made from a suitable material, such as
silicon carbide coated graphite, quartz, pure silicon carbide,
alumina, zirconia, aluminum, steel, or the like, and is oriented
with its device side 12a directed toward cover 26. For details of a
preferred embodiment of platform 28, reference is made to pending
U.S. patent application entitled A SUBSTRATE PLATFORM FOR A
SEMICONDUCTOR SUBSTRATE DURING RAPID HIGH TEMPERATURE PROCESSING
AND METHOD OF SUPPORTING A SUBSTRATE filed on Aug. 15, 1997, Ser.
No. 08/912,242, by Imad Mahawili, which is herein incorporated by
reference in its entirety. Platform 28 is seated and supported in a
recess or central opening 16a provided in a top wall 27 of housing
16 and spaced from cover 26 and substantially extends over and
completely cover opening 16a. Consequently, heater assembly 14 is
completely enclosed by heater housing 16 and platform 28, which
when placed on top of the housing 16, completes the enclosure of
heater assembly 14. Platform 28 can accommodate various substrate
sizes and, in particular, can accommodate substrates with 150, 200
and 300 mm diameters. The space between platform 28 and the lower
surface 26a of cover 26 defines an evacuated process chamber 30,
which is evacuated through the vacuum exhaust parts placed in a gas
injector assembly 34. Preferably, substrate 12 is introduced into
evacuated chamber 30 through a chamber valve 32 and is placed on
platform 28 by a conventional wafer transport device (not shown),
such as an automated transport robot.
Referring to FIGS. 4 and 5, reactor 10 further includes gas
injection manifold 34 which injects one or more gases onto a
localized or discrete region of the substrate surface wherein thin
film deposition takes place. Gas injection manifold 34 is
positioned in cover 26 and includes a plurality of reactive gas
injection segments 36, 38, and 40, an inert gas injection ring 41,
and an exhaust manifold 44. Injection ring 41 injects an inert gas,
preferably nitrogen or the like, into processing chamber 30 and
directs the inert gas to the perimeter of the substrate to form a
gas barrier so that the reactive gases injected through gas
injection segments 36, 38, and 40 are confined to the area of the
substrate directly below the respective segments 36, 38, and 40 due
to the placement of vacuum exhaust manifold 44 adjacent gas
injection segments 36, 38, and 40. As best seen in FIG. 5, gas
injection segments 36, 38, and 40 are aligned in a central region
of cover 26 to inject one or more gases, reactive and inert gases,
into chamber 30. Exhaust manifold 44 extends along and adjacent gas
injection segments 36, 38, and 40 so that gases directed onto
substrate 12 are confined to a discrete area across the substrate,
which preferably extends from one side or edge of the substrate to
an opposed side or edge of substrate 12. It should be understood
that gases injected by gas injection segments 36, 38, and 40 are
directed in the general direction substrate 12 and any stray gas
molecules which migrate near the region under exhaust manifold 44
will be exhausted from processing chamber 30. Therefore, the gases
introduced by gas injection segments 36, 38, and 40 are confined to
a discrete volume of processing chamber 30 and to a discrete area
of substrate 12.
Each gas injection segment 36, 38, 40 includes a plurality of
channels 36a, 36b, 36c, 36d, 38a, 38b, 38c, 38d, 40a, 40b, 40c, and
40d, respectively, which are arranged in a parallel adjacent
relationship. Each channel 36a, 36b, 36c, 36d, 38a, 38b, 38c, 38d
40a, 40b, 40c, and 40d includes a plurality of injectors or
orifices 42. Orifices 42 may be arranged in a uniform manner to
provide the same flow rate of gas across width of substrate 12.
Alternatively, one or more channels may include orifices 42 that
are arranged in a non-uniform pattern to vary the profile of the
gas flow across the substrate. Preferably, the profile of the flow
of the gas is adjusted to direct less gas to the center of the
substrate than to the regions toward the perimeter of the
substrate. For example, channels 38a-38d, which are generally
aligned with the central portion of the substrate, may include one
density or concentration of spaced orifices, and channels 36a-36d
and 40a-40d, which are generally aligned along the peripheral
portions of the substrate, may include a higher density or
concentration of orifices 42 than channels 38a-38d. In this manner,
the flow of gas from the various groups of orifices 42 has a flow
profile that varies across the substrate so that the regions over
the central region and the peripheral region of the substrate are
treated with the same density of gas to achieve a more uniform film
deposition on the substrate. It should be understood that the
number of orifices and the spacing between orifices 42 may be
individually adjusted to prove a more uniform flow or to direct
more gas to one area of the substrate than another where different
devices are being fabricated.
Furthermore, each orifice 42/ channel 36a, 36b, 36c, 36d, 38a, 38b,
38c, 38d 40a, 40b, 40c, and 40d and/or segments 36, 38, and 40 may
be coupled to a valve or regulator (not shown) which may be
adjusted using conventional controls to vary the flow of gas from
each orifice, channel, or gas injection segment or zone 36, 38, and
40 to adapt the gas flow profile. Furthermore, the controls may
adjust the sequence of gas flowing from the orifices, channels, or
segments. Moreover, each regulator may be adapted for connection
with one or more sources of reactant gases. Depending on the
application, the flow through each orifice/ channel/ segment/ may
be individually controlled so that they can all turn on together,
sequence one segment after another, or sequence the segments
randomly with various time intervals between each on/off cycle.
Furthermore, as reactive gases are turned off from one segment, an
inert gas may be injected into that segment to control the reaction
conditions at the surface of the wafer and to prevent any back flow
contamination of reactants. The design of a particular duty cycle
for each of the segments would, therefore, depend on the thin film
process that is being optimized and it would vary from one film to
another. Furthermore, each of the respective orifices, channels, or
gas injection segments 36, 38, 40 may be associated with an
injection of a specific gas. For example, gas injection zones 36
and 40 may be used to inject gas A while gas injection zone 38 may
be used to inject gas B. In this manner, two reactive gases (A and
B) may be injected that mix and react on the device side of the
substrate. It should be understood by those skilled in the art that
a wide variety of gasses can be employed and selectively introduced
through the orifices 42, for example, hydrogen, argon, tungsten
hexaflouride, or the like, to process substrate 12.
As best seen in FIG. 5, gas injection manifold 34 includes exhaust
manifold 44. As described above, exhaust manifold 44 extends around
segments 36, 38, and 40 to provide an additional boundary beyond
which the reactive gases can not extend. In addition to removing
unreacted gases from processing chamber 30, exhaust manifold also
assists in the prevention of back flow contamination of the
reactant gases. In combination with injection ring 41, exhaust
manifold 44 controls the film deposition on substrate 12 in a
manner which results in localized area of film deposition and,
therefore, permits the use of an emissivity measurement system,
described below.
Reactor 10 further includes a non-contact emissivity measurement
system 60 for measuring the emissivity and calculating the
temperature of substrate 12 during the various fabrication
processes. Emissivity measurement system 60 includes a central
processing unit 61 and a pair of fiber optic communication cables
62 and 64 which are coupled together and coupled to central
processing unit 61. Fiber optic cable 62 preferably comprises a
sapphire fiber optic communication cable and extends into cover 26
of reactor housing 20 through a rigid member 66, which provides a
vacuum feedthrough to reactor 10. Cable 62 extends through member
66 into a cavity 67 provided in cover 26, which is positioned above
platform 28 and substrate 12. Member 66 is preferably a cylindrical
drive shaft and, more preferably, a stainless steel cylindrical
drive shaft, and is rotatably mounted in cover 26. One end 68 of
fiber optic cable 62 is bent or oriented for directing at substrate
12 and light source 72, as will be more fully explained below, with
the photon sensing end of cable 62 forming a fiber optic photon
density sensor or probe 70. The second end portion of cable 62
extends through shaft 66 and into a fiber optic housing 76, which
is mounted to an exterior surface of cylindrical wall 24 of housing
20. Distal end 62a of cable 62 is slip attached to a distal end 64a
of cable 64, which preferably comprises a quartz fiber optic
communication cable, in fiber optic housing 76. The other end of
fiber optic communication cable 64 is then connected to processor
61. In this manner, when cable 62 is rotated, cable 62 remains in
communication with cable 64 and processing unit 61 through the slip
connection between the two communication cables. Processor 61
preferably comprises a measuring instrument, for example a Luxtron
Model 100, which converts the photon density measured by fiber
optic sensor 70 into an electrical current, which is displayed by
processor 61.
The position of fiber optic sensor 70 is changed by a driver 80,
preferably a motor, which is housed in fiber optic housing 76 and
which is drivingly coupled to shaft 66. Motor 80 includes a drive
shaft 81 and a drive wheel 82, which engages and rotates shaft 66
about its longitudinal axis 66a. Motor 80 rotates shaft 66, which
imparts rotation to fiber optic cable 62, so that the orientation
of fiber optic sensor 70 is moved between a first position wherein
the fiber optic sensor 70 is directed generally upward toward light
source 72 and a second position in which it is directed generally
downward to substrate 12. Therefore, end 68 of communication cable
62 is preferably oriented at a right angle with respect to the
horizontal axis 62a of communication cable 62. In this manner
sensor 70 can detect the photon density emitted from light source
72 and of the reflected light off substrate. Light source 72
preferably comprises a white light source, which emits light at a
wavelength so that the wafer optical transmission is minimized,
preferably, for example at a 0.95 micron wavelength. Emissivity
measurement system 60 determines the temperature of substrate 12 by
comparing of the radiation emitted by source 72 with that of the
radiation emitted by substrate 12. Source 72 preferably includes at
least one lamp which is a similar construction to the lamps used in
heater assembly 14, which are described in pending U.S. patent
application entitled RAPID THERMAL PROCESSING HEATER TECHNOLOGY AND
METHOD OF USE.
Preferably, photon density sensor 70 is spaced and, preferably,
located radially outward from gas injection system 34 and exhaust
manifold 44 so that the gas, which is injected into chamber 30 and
onto substrate 12, does not interfere with the temperature reading
of emissivity sensor 70. Since heater assembly 14 is completely
enclosed by the heater housing 16, there is no leakage of light
from heater assembly 14 into deposition chamber 30, which could
impact the readings taken by emissivity sensor 70. This eliminates
probe characteristics matching or corrections associated with the
conventional temperature measuring devices with two probes. After
substrate 12 is placed on platform 28, housing 16 and platform 28
are rotated during processing by drive mechanism 23. When the
emissivity of substrate 12 is to be measured, sensor 70 is rotated
to view light source 72 directly above substrate 12 and light
source 72 is turned on. Sensor 70 measures the incident photon
density from light source 72. While light source 72 is still on,
sensor 70 is rotated from its first position to its second position
to view substrate 12 directly below light source 72 while it is
rotating. In this position, sensor 70 measures the reflected photon
density off the device side 12a of substrate 12. Light source 72 is
then turned off. While still viewing substrate 12 directly, sensor
70 measures the emission of photons from heated substrate 12. This
last value is subtracted from the reflected radiation value.
According to Plank's law, the energy emitted off a given surface is
related to the temperature of the surface to the fourth power. The
proportionality constant consists of the product of the
Stephen-Boltzmann constant and the surface emissivity. Therefore,
the surface emissivity is preferably used when determining the
temperature of the surface in non-contact methods. The following
equations are used to calculate the total hemispherical
reflectivity of device side 12a of substrate 12 and, subsequently,
the emissivity, as given by Kirchoffs law:
Once the substrate emissivity is calculated, the substrate
temperature is then obtained from Plank's equations. This technique
is also used when the substrate is hot and, under such application,
the base thermal emission from the substrate is subtracted prior to
executing the above calculation. Preferably, sensor 70 is left in
the second position or wafer viewing position and, thus, constantly
yields emissivity data every time source lamp 72 is turned on.
Since substrate 12 is rotating, sensor 70 collects photon density
off the device side 12a of the substrate 12 during such rotation
and, therefore, measures the reflection from the averaged surface
topology of varied device structures that might be lithographed
onto the substrate. Furthermore, since the emissivity measurement
is performed during the process cycle including thin film
deposition process, the instantaneous changes of emissivity are
monitored and temperature corrections are performed dynamically and
continuously. Once the emissivity is calculated, it is sent into
the temperature control segment of the processor 21 where the
emissivity value is used in the application of the Plank
equation.
Reactor 10 further includes a plurality of optical fiber
temperature measurement probes 84, which are fixed to cover 26 and
constantly collect photon density emitted from device side 12a of
substrate device 12 during all processing conditions. The
temperatures measured by probes 84 are sent to the main control
computer to compare them to a set temperature and any deviation is
computed and transformed into a control current to drive a standard
off-the-shelf SCR current relay to deliver the proportional power
to each of the lamp zones within heater assembly 14. Preferably,
reactor 10 includes three probes (84) which are positioned to
measure the temperature of different parts of the wafer, which
assures temperature uniformity during the processing cycle.
Temperature readings of substrate 12 calculated by central
processing unit 21 are preferably used as input into a control
system (not shown) which monitors and controls the output of heater
assembly 14. The control system is coupled to heater assembly 14
through an electrical feedthrough 86 which extends to the base wall
22 of reactor housing 21. In order to maintain the vacuum in
reactor 10, feedthrough 86 is sealed by an O-ring or sealed using
other conventional sealing devices or methods.
After semiconductor substrate 12 has been processed, substrate 12
is raised off platform 28 by a plurality of lifter pins 88 which
protrude through and lift substrate 12 off platform 28 for
automatic loading and unloading of substrate 12 within reactor 10.
Lifter pins 88 are raised and lowered by magnetically coupled wafer
letters 90, which are conventionally known in the art. Pins 88 are
centrally located in housing 16 and project through a central
portion of the heater assembly 14 and through a central portion of
platform 28. Similarly, to maintain the vacuum in chamber 30.
Lifter pins 88 extend through O-ring seals provided in the base
wall 22 of housing 20.
In preferred form, at least three lifter pins 88 are provided. In
the most preferred form, four lifter pins 88 are provided, and
platform 28 includes a corresponding number of openings to enable
lifter pins 88 to protrude through and lift substrate 12 off
platform 28 for automatic loading and unloading of substrate 12. It
can be appreciated that lifter pins 88 can only be operated when
housing is positioned so that the openings in platform 28 are
aligned with lifter pins 88, for example in a "HOME" position.
For the purposes of the following description, the terms "up" or
"down" and derivatives or equivalents thereof shall relate to the
invention as oriented in FIGS. 1 to 6. It is understood that the
invention may assume various alternative orientations, except where
expressly specified to the contrary. It is also understood that the
specific devices and methods illustrated in the attached drawings,
and described in the following specification, are simply exemplary
embodiments of the inventive concepts defined in the appended
claims. Hence, specific dimensions and other physical
characteristics relating to the embodiments disclosed herein are
not to be considered Limiting unless the claims expressly state
otherwise.
Accordingly, the present invention provides a reactor chamber which
heats a substrate in a uniform manner and accurately measures the
emissivity and calculates the temperature of the substrate during
processing using a non-contact photon density measuring device and
adjusts the profile of the applied heat as needed to achieve
optimal processing of the substrate. Furthermore, the reactor
chamber delivers and controls the flow of gas to the substrate
during processing so that the substrate receives a uniform
deposition of thin film of the process gas or gases in a discrete
area on the substrate, which enables the use of a non-contact
emissivity measurement system.
While several forms of the invention have been shown and described,
other forms will now be apparent to those skilled in the art.
Therefore, it will be understood that the embodiments shown in the
drawings and described above are merely for illustrative purposes,
and are not intended to limit the scope of the invention which is
defined by the claims which follow.
* * * * *