U.S. patent application number 17/012146 was filed with the patent office on 2020-12-24 for features for improving process uniformity in a millisecond anneal system.
The applicant listed for this patent is Beijing E-Town Semiconductor Technology Co., Ltd., Mattson Technology, Inc.. Invention is credited to Alexandr Cosceev, Markus Hagedorn, Christian Pfahler.
Application Number | 20200402811 17/012146 |
Document ID | / |
Family ID | 1000005073696 |
Filed Date | 2020-12-24 |
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United States Patent
Application |
20200402811 |
Kind Code |
A1 |
Cosceev; Alexandr ; et
al. |
December 24, 2020 |
Features for Improving Process Uniformity in a Millisecond Anneal
System
Abstract
Systems and methods for improving process uniformity in a
millisecond anneal system are provided. In some implementations, a
process for thermally treating a substrate in a millisecond anneal
system can include obtaining data indicative of a temperature
profile associated with one or more substrates during processing in
a millisecond anneal system. The process can include one or more of
(1) changing the pressure inside the processing chamber of the
millisecond anneal system; (2) manipulating the irradiation
distribution by way of the refracting effect of a water window in
the millisecond anneal system; (3) adjusting the angular
positioning of the substrate; and/or (4) configuring the shape of
the reflectors used in the millisecond anneal system.
Inventors: |
Cosceev; Alexandr; (Lonsee,
DE) ; Hagedorn; Markus; (Ulm, DE) ; Pfahler;
Christian; (Ulm, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mattson Technology, Inc.
Beijing E-Town Semiconductor Technology Co., Ltd. |
Fremont
Beijing |
CA |
US
CN |
|
|
Family ID: |
1000005073696 |
Appl. No.: |
17/012146 |
Filed: |
September 4, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15378580 |
Dec 14, 2016 |
10770309 |
|
|
17012146 |
|
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62272817 |
Dec 30, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/324 20130101;
H01L 21/6719 20130101; F27B 5/16 20130101; F27B 17/0025 20130101;
H01L 21/68785 20130101; H01L 21/67115 20130101; H05B 3/0047
20130101; H01L 21/67109 20130101; H01L 21/2686 20130101; F27B 5/04
20130101 |
International
Class: |
H01L 21/324 20060101
H01L021/324; H01L 21/67 20060101 H01L021/67; H01L 21/687 20060101
H01L021/687; H01L 21/268 20060101 H01L021/268; H05B 3/00 20060101
H05B003/00 |
Claims
1-11. (canceled)
12. A process for thermally treating a substrate in a millisecond
anneal system, comprising: obtaining data indicative of a
temperature profile associated with one or more substrates during
processing in a millisecond anneal system, the millisecond anneal
system having a wafer plane plate dividing the processing chamber
into a top chamber and a bottom chamber; adjusting a shape,
configuration, or position of one or more of an edge reflector or a
wedge reflector in the millisecond anneal system based at least in
part on the temperature profile.
13. The process of claim 12, wherein the wedge reflector is located
on a chamber wall proximate the wafer plane plate.
14. The process of claim 13, wherein adjusting a shape,
configuration, or position of one or more of an edge reflector or a
wedge reflector in the millisecond anneal system comprises
adjusting a wedge angle for the wedge reflector.
15. The process of claim 13, wherein adjusting a shape,
configuration, or position of one or more of an edge reflector or a
wedge reflector in the millisecond anneal system comprises
adjusting a height for the wedge reflector.
16. The process of claim 13, wherein the edge reflector is located
in the wafer plane plate.
17. The process of claim 12, wherein adjusting a shape,
configuration, or position of one or more of an edge reflector or a
wedge reflector in the millisecond anneal system comprises
adjusting a surface profile for the edge reflector.
18. The process of claim 12, wherein adjusting a shape,
configuration, or position of one or more of an edge reflector or a
wedge reflector in the millisecond anneal system comprises
adjusting, with one or more controllers, a position of wedge
reflector relative to the substrate during processing of the
substrate.
19. A process for thermally treating a substrate in a millisecond
anneal system, comprising: obtaining data indicative of a
temperature profile associated with one or more substrates during
processing in a millisecond anneal system, the millisecond anneal
system having a wafer plane plate dividing the processing chamber
into a top chamber and a bottom chamber, the wafer plane plate
comprising a non-rotating substrate support; determining an angular
location for placement of a device substrate in a processing
chamber of the millisecond anneal system, the angular position
determined based at least in part on the temperature profile.
20. The process of claim 19, wherein the angular position is
determined based at least in part on a location of one or more
support pins in the millisecond anneal system.
Description
PRIORITY CLAIM
[0001] The present application claims the benefit of priority of
U.S. Provisional Patent Application Ser. No. 62/272,817, filed Dec.
30, 2015, entitled "Features for Improving Process Uniformity in a
Millisecond Anneal System," which is incorporated herein by
reference.
FIELD
[0002] The present disclosure relates generally to thermal
processing chambers and more particularly to millisecond anneal
thermal processing chambers used for processing, for instance,
semiconductor substrates.
BACKGROUND
[0003] Millisecond anneal systems can be used for semiconductor
processing for the ultra-fast heat treatment of substrates, such as
silicon wafers. In semiconductor processing, fast heat treatment
can be used as an anneal step to repair implant damage, improve the
quality of deposited layers, improve the quality of layer
interfaces, to activate dopants, and to achieve other purposes,
while at the same time controlling the diffusion of dopant
species.
[0004] Millisecond, or ultra-fast, temperature treatment of
semiconductor substrates can be achieved using an intense and brief
exposure of light to heat the entire top surface of the substrate
at rates that can exceed 10.sup.4.degree. C. per second. The rapid
heating of just one surface of the substrate can produce a large
temperature gradient through the thickness of the substrate, while
the bulk of the substrate maintains the temperature before the
light exposure. The bulk of the substrate therefore acts as a heat
sink resulting in fast cooling rates of the top surface.
SUMMARY
[0005] Aspects and advantages of embodiments of the present
disclosure will be set forth in part in the following description,
or may be learned from the description, or may be learned through
practice of the embodiments.
[0006] One example aspect of the present disclosure is directed to
a process for thermally treating a substrate in a millisecond
anneal system. The process can include obtaining data indicative of
a temperature profile associated with one or more substrates during
processing in a millisecond anneal system. The millisecond anneal
system can have a wafer plane plate dividing the processing chamber
into a top chamber and a bottom chamber. The process can include
adjusting a pressure in the processing chamber to affect a
temperature uniformity across one or more substrates.
[0007] Another example aspect of the present disclosure is directed
to a process for thermally treating a substrate in a millisecond
anneal system. The process can include obtaining data indicative of
a temperature profile associated with one or more substrates during
processing in a millisecond anneal system. The millisecond anneal
system can have a wafer plane plate dividing the processing chamber
into a top chamber and a bottom chamber. The process can include
determining a shape and configuration of one or more of an edge
reflector or a wedge reflector in the millisecond anneal system
based at least in part on the temperature profile.
[0008] Yet another example aspect of the present disclosure is
directed to a process for thermally treating a substrate in a
millisecond anneal system. The process can include obtaining data
indicative of a temperature profile associated with one or more
substrates during processing in a millisecond anneal system. The
millisecond anneal system can have a wafer plane plate dividing the
processing chamber into a top chamber and a bottom chamber. The
wafer plane plate can include a non-rotating substrate support. The
process can include determining an angular location for placement
of a device substrate in a processing chamber of the millisecond
anneal system. The angular position can be determined based at
least in part on the data indicative of the temperature
profile.
[0009] Variations and modification can be made to the example
aspects of the present disclosure. Other example aspects of the
present disclosure are directed to systems, methods, devices, and
processes for thermally treating a semiconductor substrate.
[0010] These and other features, aspects and advantages of various
embodiments will become better understood with reference to the
following description and appended claims. The accompanying
drawings, which are incorporated in and constitute a part of this
specification, illustrate embodiments of the present disclosure
and, together with the description, serve to explain the related
principles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Detailed discussion of embodiments directed to one of
ordinary skill in the art are set forth in the specification, which
makes reference to the appended figures, in which:
[0012] FIG. 1 depicts an example millisecond anneal heating profile
according to example embodiments of the present disclosure;
[0013] FIG. 2 depicts an example perspective view of a portion of
an example millisecond anneal system according to example
embodiments of the present disclosure;
[0014] FIG. 3 depicts an exploded view of an example millisecond
anneal system according to example embodiments of the present
disclosure;
[0015] FIG. 4 depicts a cross-sectional view of an example
millisecond anneal system according to example embodiments of the
present disclosure;
[0016] FIG. 5 depicts a perspective view of example lamps used in a
millisecond anneal system according to example embodiments of the
present disclosure;
[0017] FIG. 6 depicts example edge reflectors used in a wafer plane
plate of a millisecond anneal system according to example
embodiments of the present disclosure;
[0018] FIG. 7 depicts example reflectors that can be used in a
millisecond anneal system according to example embodiments of the
present disclosure;
[0019] FIG. 8 depicts an example arc lamp that can be used in a
millisecond anneal system according to example embodiments of the
present disclosure;
[0020] FIGS. 9-10 depict the operation of an example arc lamp
according to example embodiments of the present disclosure;
[0021] FIG. 11 depicts a cross-sectional view of an example
electrode according to example embodiments of the present
disclosure;
[0022] FIG. 12 depicts an example closed loop system for supplying
water and gas (e.g., Argon gas) to example arc lamps used in a
millisecond anneal system according to example embodiments of the
present disclosure;
[0023] FIG. 13 depicts an example temperature measurement system
for a millisecond anneal system according to example embodiments of
the present disclosure;
[0024] FIG. 14 depicts an example gas flow system for adjusting
pressure in the processing chamber of a millisecond anneal system
according to example embodiments of the present disclosure;
[0025] FIG. 15 depicts a changing shape of a water window in a
millisecond anneal system according to example embodiments of the
present disclosure;
[0026] FIG. 16 depicts a changing shape of a water window in a
millisecond anneal system according to example embodiments of the
present disclosure;
[0027] FIG. 17 depicts an example product wafer with devices in an
array arrangement;
[0028] FIG. 18 depicts an example residual non-uniformity of the
irradiation of a wafer in a millisecond anneal system;
[0029] FIG. 19 depicts a product wafer located inside a processing
chamber at a different angular orientation according to example
embodiments of the present disclosure;
[0030] FIG. 20 depicts a product wafer located inside a processing
chamber at different angular orientations relative to support pins
according to example embodiments of the present disclosure;
[0031] FIG. 21 depicts a cross sectional view showing the locations
of top wedge reflectors and edge reflectors in a processing chamber
in a millisecond anneal system according to example
embodiments.
[0032] FIGS. 22(a) and 22(b) depicts example top wedges with
varying wedge angles according to example embodiments of the
present disclosure.
[0033] FIGS. 23(a) and 23(b) depicts the example improvement of
irradiation distribution by adjusting the wedge angle of the top
wedge according to example embodiments of the present
disclosure;
[0034] FIG. 24 depicts edge reflectors used in a millisecond anneal
processing chamber according to example embodiments of the present
disclosure;
[0035] FIG. 25 depicts an example edge reflector with a linear
profile;
[0036] FIGS. 26(a), 26(b) and 26(c) depicts various heated zones on
a wafer by edge reflectors of varying shapes and positions
according to example embodiments of the present disclosure.
DETAILED DESCRIPTION
[0037] Reference now will be made in detail to embodiments, one or
more examples of which are illustrated in the drawings. Each
example is provided by way of explanation of the embodiments, not
limitation of the present disclosure. In fact, it will be apparent
to those skilled in the art that various modifications and
variations can be made to the embodiments without departing from
the scope or spirit of the present disclosure. For instance,
features illustrated or described as part of one embodiment can be
used with another embodiment to yield a still further embodiment.
Thus, it is intended that aspects of the present disclosure cover
such modifications and variations.
Overview
[0038] Example aspects of the present disclosure are directed to
features for improving temperature uniformity across a substrate
(e.g., a semiconductor wafer) during processing in a millisecond
anneal system. Aspects of the present disclosure are discussed with
reference to a "wafer" or semiconductor wafer for purposes of
illustration and discussion. Those of ordinary skill in the art,
using the disclosures provided herein, will understand that the
example aspects of the present disclosure can be used in
association with any workpiece, semiconductor substrate or other
suitable substrate. The use of the term "about" in conjunction with
a numerical value is intended to refer to within 10% of the stated
numerical value.
[0039] Millisecond, or ultra-fast, temperature treatment of
semiconductor substrates can be achieved using an intense and brief
exposure of light to heat the entire top surface of the
semiconductor substrate at rates that can exceed about
10.sup.4.degree. C./sec. The flash of light is typically applied to
a semiconductor substrate, which was previously heated to an
intermediate temperature Ti at ramp rates of up to 150.degree.
C./sec. After the heating process step, the semiconductor substrate
is left inside the chamber for cool down. Both the low heating
processes and the cool down can cause lateral temperature
differences resulting in a non-uniform temperature distribution
across the substrate. In many cases, the heat treatment
applications can be temperature sensitive. In addition, wafer
stress can be driven by thermal gradients in the wafer material.
Large lateral thermal gradients can therefore result in wafer
warping, slip, and even wafer breakage.
[0040] The main cause for temperature differences during the heat
treatment lies in the non-uniform irradiation of the wafer surface
by the light source. The main cause for temperature differences
during the cool down phase can result from the geometry of the
wafer itself. For instance, a wafer can be disk-shaped and for
geometric reasons, the edges of the wafer can cool off faster than
the center of the wafer. Another cause for temperature differences
can result from the convective cooling effects by the gas
ambient.
[0041] The non-uniformity can be mitigated by the use of highly
reflective mirrors. For instance, the irradiation non-uniformity
can be mitigated by the integrating effect of a cube with mirror
walls. The cool down non-uniformity can be mitigated by redirecting
light emitted from the wafer center to be re-absorbed by the wafer
edge. Again, this can be achieved by way of the integrating effect
of a cube with mirror walls.
[0042] Even though processing chambers in millisecond anneal
systems can make use of the integrating effect of mirror walls,
there can still be a residual non-uniformity, which needs to be
further compensated. A prime influencing factor for compensating
the residual non-uniformity can be by manipulating the irradiation
distribution.
[0043] According to example embodiments of the present disclosure,
various features are disclosed for improving the temperature
uniformity of the semiconductor substrate during processing in a
millisecond anneal system. These features can include, for
instance: (1) changing the pressure inside the processing chamber
of the millisecond anneal system; (2) manipulating the irradiation
distribution by way of the refracting effect of a water window in
the millisecond anneal system; (3) angular positioning of the
wafer; and/or (4) configuring the shape and/or position of the
reflectors used in the millisecond anneal system.
[0044] One example embodiment of the present disclosure is directed
to a process for thermally treating a substrate in a millisecond
anneal system. The process includes obtaining data indicative of a
temperature profile associated with one or more substrates during
processing in a millisecond anneal system. The millisecond anneal
system includes a wafer plane plate dividing the processing chamber
into a top chamber and a bottom chamber. The process includes
adjusting a pressure in the processing chamber to affect a
temperature uniformity across one or more substrates based at least
in part on the data indicative of the temperature profile. For
instance, in some embodiments, adjusting a pressure includes
adjusting the pressure in the processing chamber during processing
of at least one of the one or more substrates to adjust a
temperature profile of the at least one of the one or more
substrates. The pressure can be adjusted, for instance, within the
range of +2 kPA to -2 kPA relative to atmospheric pressure.
[0045] In some embodiments, adjusting the pressure in the
processing chamber includes adjusting a pressure differential
between the processing chamber and a downstream line in a gas flow
system configured to glow process gas through the processing
chamber. The downstream line can be located downstream of one or
more vent openings in the process chamber. Adjusting the pressure
differential can include adjusting a valve disposed in the
downstream line. The valve can be adjusted by one or more
controllers based on one or more signals from a pressure sensor
configured to measure pressure inside the processing chamber. The
pressure can be adjusted to influence a flow pattern of process gas
in the processing chamber.
[0046] In some embodiments, adjusting a pressure in the process
chamber includes warping a water window based on the pressure in
the processing chamber. The water window can include an inner plate
and an outer plate with water flowing between the inner plate and
the outer plate. The inner plate is disposed closer to the
processing chamber relative to the outer plate. In some
implementations, the water window can be warped such that the inner
plate of the water window bends away from the processing chamber to
provide a defocusing effect on the lamp light. In some
implementations, the water window can be warped such that the inner
plate of the water window bends toward the processing chamber to
provide a focusing effect on the lamp light.
[0047] Another example embodiment of the present disclosure is
directed to a process for thermally treating a substrate in a
millisecond anneal system. The process includes obtaining data
indicative of a temperature profile associated with one or more
substrates during processing in a millisecond anneal system. The
millisecond anneal system can include a wafer plane plate dividing
the processing chamber into a top chamber and a bottom chamber. The
process can include adjusting a shape, configuration, or position
of one or more of an edge reflector or a wedge reflector in the
millisecond anneal system based at least in part on the temperature
profile.
[0048] In some embodiments, the wedge reflector can be located on a
chamber wall proximate the wafer plane plate. Adjusting a shape,
configuration, or position of one or more of an edge reflector or a
wedge reflector in the millisecond anneal system includes adjusting
a wedge angle and/or a height for the wedge reflector.
[0049] In some embodiments, the edge reflector is located in the
wafer plane plate. Adjusting a shape, configuration, or position of
one or more of an edge reflector or a wedge reflector in the
millisecond anneal system includes adjusting a surface profile for
the edge reflector. In some embodiments, adjusting a shape,
configuration, or position of one or more of an edge reflector or a
wedge reflector in the millisecond anneal system comprises
adjusting, with one or more controllers, a position of wedge
reflector relative to the substrate during processing of the
substrate.
[0050] Another example embodiment of the present disclosure is
directed to a process for thermally treating a substrate in a
millisecond anneal system. The process includes obtaining data
indicative of a temperature profile associated with one or more
substrates during processing in a millisecond anneal system. The
millisecond anneal system can include a wafer plane plate dividing
the processing chamber into a top chamber and a bottom chamber. The
process can include determining an angular location for placement
of a device substrate in a processing chamber of the millisecond
anneal system. The angular position can be determined based at
least in part on the temperature profile. In some embodiments, the
angular position can be determined based at least in part on a
location of one or more support pins in the millisecond anneal
system.
Example Millisecond Anneal Systems
[0051] An example millisecond anneal system can be configured to
provide an intense and brief exposure of light to heat the top
surface of a wafer at rates that can exceed, for instance, about
10.sup.4.degree. C./s. FIG. 1 depicts an example temperature
profile 100 of a semiconductor substrate achieved using a
millisecond anneal system. As shown in FIG. 1, the bulk of the
semiconductor substrate (e.g., a silicon wafer) is heated to an
intermediate temperature T.sub.i during a ramp phase 102. The
intermediate temperature can be in the range of about 450.degree.
C. to about 900.degree. C. When the intermediate temperature
T.sub.i is reached, the top side of the semiconductor substrate can
be exposed to a very short, intense flash of light resulting in
heating rates of up to about 10.sup.4.degree. C./s. Window 110
illustrates the temperature profile of the semiconductor substrate
during the short, intense flash of light. Curve 112 represents the
rapid heating of the top surface of the semiconductor substrate
during the flash exposure. Curve 116 depicts the temperature of the
remainder or bulk of the semiconductor substrate during the flash
exposure. Curve 114 represents the rapid cool down by conductive of
cooling of the top surface of the semiconductor substrate by the
bulk of the semiconductor substrate acting as a heat sink. The bulk
of the semiconductor substrate acts as a heat sink generating high
top side cooling rates for the substrate. Curve 104 represents the
slow cool down of the bulk of the semiconductor substrate by
thermal radiation and convection, with a process gas as a cooling
agent. As used herein, the term "about" when used in reference to a
numerical value refers to within 30% of the stated numerical
value.
[0052] An example millisecond anneal system can include a plurality
of arc lamps (e.g., four Argon arc lamps) as light sources for
intense millisecond long exposure of the top surface of the
semiconductor substrate--the so called "flash." The flash can be
applied to the semiconductor substrate when the substrate has been
heated to an intermediate temperature (e.g., about 450.degree. C.
to about 900.degree. C.). A plurality of continuous mode arc lamps
(e.g., two Argon arc lamps) can be used to heat the semiconductor
substrate to the intermediate temperature. In some embodiments, the
heating of the semiconductor substrate to the intermediate
temperature is accomplished through the bottom surface of the
semiconductor substrate at a ramp rate which heats the entire bulk
of the wafer.
[0053] FIGS. 2 to 5 depict various aspects of an example
millisecond anneal system 80 according to example embodiments of
the present disclosure. As shown in FIGS. 2-4, a millisecond anneal
system 80 can include a process chamber 200. The process chamber
200 can be divided by a wafer plane plate 210 into a top chamber
202 and a bottom chamber 204. A semiconductor substrate 60 (e.g., a
silicon wafer) can be supported by support pins 212 (e.g., quartz
support pins) mounted to a wafer support plate 214 (e.g., quartz
glass plate inserted into the wafer plane plate 210).
[0054] As shown in FIGS. 2 and 4, the millisecond anneal system 80
can include a plurality of arc lamps 220 (e.g., four Argon arc
lamps) arranged proximate the top chamber 202 as light sources for
intense millisecond long exposure of the top surface of the
semiconductor substrate 60--the so called "flash." The flash can be
applied to the semiconductor substrate when the substrate has been
heated to an intermediate temperature (e.g., about 450.degree. C.
to about 900.degree. C.).
[0055] A plurality of continuous mode arc lamps 240 (e.g., two
Argon arc lamps) located proximate the bottom chamber 204 can be
used to heat the semiconductor substrate 60 to the intermediate
temperature. In some embodiments, the heating of the semiconductor
substrate 60 to the intermediate temperature is accomplished from
the bottom chamber 204 through the bottom surface of the
semiconductor substrate at a ramp rate which heats the entire bulk
of the semiconductor substrate 60.
[0056] As shown in FIG. 3, the light to heat the semiconductor
substrate 60 from the bottom arc lamps 240 (e.g., for use in
heating the semiconductor substrate to an intermediate temperature)
and from the top arc lamps 220 (e.g., for use in providing
millisecond heating by flash) can enter the processing chamber 200
through water windows 260 (e.g., water cooled quartz glass
windows). In some embodiments, the water windows 260 can include a
sandwich of two quartz glass panes between which an about a 4 mm
thick layer of water is circulating to cool the quartz panes and to
provide an optical filter for wavelengths, for instance, above
about 1400 nm.
[0057] As further illustrated in FIG. 3, process chamber walls 250
can include reflective mirrors 270 for reflecting the heating
light. The reflective mirrors 270 can be, for instance, water
cooled, polished aluminum panels. In some embodiments, the main
body of the arc lamps used in the millisecond anneal system can
include reflectors for lamp radiation. For instance, FIG. 5 depicts
a perspective view of both a top lamp array 220 and a bottom lamp
array 240 that can be used in the millisecond anneal system 200. As
shown, the main body of each lamp array 220 and 240 can include a
reflector 262 for reflecting the heating light. These reflectors
262 can form a part of the reflecting surfaces of the process
chamber 200 of the millisecond anneal system 80.
[0058] The temperature uniformity of the semiconductor substrate
can be controlled by manipulating the light density falling onto
different regions of the semiconductor substrate. In some
embodiments, uniformity tuning can be accomplished by altering the
reflection grade of small size reflectors to the main reflectors
and/or by use of edge reflectors mounted on the wafer support plane
surrounding the wafer.
[0059] For instance, edge reflectors can be used to redirect light
from the bottom lamps 240 to an edge of the semiconductor substrate
60. As an example, FIG. 6 depicts example edge reflectors 264 that
form a part of the wafer plane plate 210 that can be used to direct
light from the bottom lamps 240 to the edge of the semiconductor
substrate 60. The edge reflectors 264 can be mounted to the wafer
plane plate 210 and can surround or at least partially surround the
semiconductor substrate 60.
[0060] In some embodiments, additional reflectors can also be
mounted on chamber walls near the wafer plane plate 210. For
example, FIG. 7 depicts example reflectors that can be mounted to
the process chamber walls that can act as reflector mirrors for the
heating light. More particularly, FIG. 7 shows an example wedge
reflector 272 mounted to lower chamber wall 254. FIG. 7 also
illustrates a reflective element 274 mounted to reflector 270 of an
upper chamber wall 252. Uniformity of processing of the
semiconductor substrate 60 can be tuned by changing the reflection
grade of the wedge reflectors 272 and/or other reflective elements
(e.g., reflective element 274) in the processing chamber 200.
[0061] FIGS. 8-11 depict aspects of example upper arc lamps 220
that can be used as light sources for intense millisecond long
exposure of the top surface of the semiconductor substrate 60
(e.g., the "flash"). For instance, FIG. 8 depicts a cross-sectional
view of an example arc lamp 220. The arc lamp 220 can be, for
instance, an open flow arc lamp, where pressurized Argon gas (or
other suitable gas) is converted into a high pressure plasma during
an arc discharge. The arc discharge takes place in a quartz tube
225 between a negatively charged cathode 222 and a spaced apart
positively charged anode 230 (e.g., spaced about 300 mm apart). As
soon as the voltage between the cathode 222 and the anode 230
reaches a breakdown voltage of Argon (e.g., about 30 kV) or other
suitable gas, a stable, low inductive plasma is formed which emits
light in the visible and UV range of the electromagnetic spectrum.
As shown in FIG. 9, the lamp can include a lamp reflector 262 that
can be used to reflect light provided by the lamp for processing of
the semiconductor substrate 60.
[0062] FIGS. 10 and 11 depict aspects of example operation of an
arc lamp 220 in millisecond anneal system 80 according to example
embodiments of the present disclosure. More particularly, a plasma
226 is contained within a quartz tube 225 which is water cooled
from the inside by a water wall 228. The water wall 228 is injected
at high flow rates on the cathode end of the lamp 200 and exhausted
at the anode end. The same is true for the Argon gas 229, which is
also entering the lamp 220 at the cathode end and exhausted from
the anode end. The water forming the water wall 228 is injected
perpendicular to the lamp axis such that the centrifugal action
generates a water vortex. Hence, along the center line of the lamp
a channel is formed for the Argon gas 229. The Argon gas column 229
is rotating in the same direction as the water wall 228. Once a
plasma 226 has formed, the water wall 228 is protecting the quartz
tube 225 and confining the plasma 226 to the center axis. Only the
water wall 228 and the electrodes (cathode 230 and anode 222) are
in direct contact with the high energy plasma 226.
[0063] FIG. 11 depicts a cross sectional view of an example
electrode (e.g., cathode 230) used in conjunction with an arc lamp
according to example embodiments of the present disclosure. FIG. 11
depicts a cathode 230. However, a similar construction can be used
for the anode 222.
[0064] In some embodiments, as the electrodes experience a high
heat load, one or more of the electrodes can each include a tip
232. The tip can be made from tungsten. The tip can be coupled to
and/or fused to a water cooled copper heat sink 234. The copper
heat sink 234 can include at least a portion the internal cooling
system of the electrodes (e.g., one or more water cooling channels
236. The electrodes can further include a brass base 235 with water
cooling channels 236 to provide for the circulation of water or
other fluid and the cooling of the electrodes.
[0065] The arc lamps used in example millisecond anneal systems
according to aspects of the present disclosure can be an open flow
system for water and Argon gas. However, for conservation reasons,
both media can be circulated in a close loop system in some
embodiments.
[0066] FIG. 12 depicts an example closed loop system 300 for
supplying water and Argon gas needed to operate the open flow Argon
arc lamps used in millisecond anneal systems according to example
embodiments of the present disclosure.
[0067] More particularly, high purity water 302 and Argon 304 is
fed to the lamp 220. The high purity water 302 is used for the
water wall and the cooling of the electrodes. Leaving the lamp is a
gas/water mixture 306. This water/gas mixture 306 is separated into
gas free water 302 and dry Argon 304 by separator 310 before it can
be re-fed to the inlets of the lamp 220. To generate the required
pressure drop across the lamp 220, the gas/water mixture 306 is
pumped by means of a water driven jet pump 320.
[0068] A high power electric pump 330 supplies the water pressure
to drive the water wall in the lamp 220, the cooling water for the
lamp electrodes, and the motive flow for the jet pump 320. The
separator 310 downstream to the jet pump 320 can be used extracting
the liquid and the gaseous phase from the mixture (Argon). Argon is
further dried in a coalescing filter 340 before it re-enters the
lamp 220. Additional Argon can be supplied from Argon source 350 if
needed.
[0069] The water is passing through one or more particle filters
350 to remove particles sputtered into the water by the arc. Ionic
contaminations are removed by ion exchange resins. A portion of
water is run through mixed bed ion exchange filters 370. The inlet
valve 372 to the ion exchange bypass 370 can be controlled by the
water resistivity. If the water resistivity drops below a lower
value the valve 372 is opened, when it reaches an upper value the
valve 372 is closed. The system can contain an activated carbon
filter bypass loop 380 where a portion of the water can be
additionally filtered to remove organic contaminations. To maintain
the water temperature, the water can pass through a heat exchanger
390.
[0070] Millisecond anneal systems according to example embodiments
of the present disclosure can include the ability to independently
measure temperature of both surfaces (e.g., the top and bottom
surfaces) of the semiconductor substrate. FIG. 13 depicts an
example temperature measurement system 150 for millisecond anneal
system 200.
[0071] A simplified representation of the millisecond anneal system
200 is shown in FIG. 13. The temperature of both sides of a
semiconductor substrate 60 can be measured independently by
temperature sensors, such as temperature sensor 152 and temperature
sensor 154. Temperature sensor 152 can measure a temperature of a
top surface of the semiconductor substrate 60. Temperature sensor
154 can measure a bottom surface of the semiconductor substrate 60.
In some embodiments, narrow band pyrometric sensors with a
measurement wavelength of about 1400 nm can be used as temperature
sensors 152 and/or 154 to measure the temperature of, for instance,
a center region of the semiconductor substrate 60. In some
embodiments, the temperature sensors 152 and 154 can be ultra-fast
radiometers (UFR) that have a sampling rate that is high enough to
resolve the millisecond temperature spike cause by the flash
heating.
[0072] The readings of the temperature sensors 152 and 154 can be
emissivity compensated. As shown in FIG. 13, the emissivity
compensation scheme can include a diagnostic flash 156, a reference
temperature sensor 158, and the temperature sensors 152 and 154
configured to measure the top and bottom surface of the
semiconductor wafers. Diagnostic heating and measurements can be
used with the diagnostic flash 156 (e.g., a test flash).
Measurements from reference temperature sensor 158 can be used for
emissivity compensation of temperature sensors 152 and 154
[0073] In some embodiments, the millisecond anneal system 200 can
include water windows. The water windows can provide an optical
filter that suppresses lamp radiation in the measurement band of
the temperature sensors 152 and 154 so that the temperature sensors
152 and 154 only measure radiation from the semiconductor
substrate.
[0074] The readings of the temperature sensors 152 and 154 can be
provided to a processor circuit 160. The processor circuit 160 can
be located within a housing of the millisecond anneal system 200,
although alternatively, the processor circuit 160 may be located
remotely from the millisecond anneal system 200. The various
functions described herein may be performed by a single processor
circuit if desired, or by other combinations of local and/or remote
processor circuits.
[0075] The readings of the temperature sensors 152 and 154 can be
used by the processor circuit 160 to determine a temperature
profile across the substrate. The temperature profile can provide a
measure of the temperature of the substrate at various locations
across the surface of the substrate. The temperature profile can
provide a measure of thermal uniformity of the substrate during
processing. As discussed in detail below, data indicative of a
temperature profile can be used for improving thermal uniformity by
(1) changing the pressure inside the processing chamber of the
millisecond anneal system; (2) manipulating the irradiation
distribution by way of the refracting effect of a water window in
the millisecond anneal system; (3) angular positioning of the
wafer; and/or (4) configuring the shape of the reflectors used in
the millisecond anneal system.
Example Uniformity Improvement Through Chamber Pressure Control
[0076] According to example aspects of the present disclosure, the
temperature uniformity of a semiconductor substrate can be improved
during processing in a millisecond anneal system by changing the
pressure inside the process chamber. The pressure inside the
process chamber can influence a flow pattern of process gas inside
the chamber, changing the convective cooling contribution on
different regions of the wafer.
[0077] The processing chamber in a millisecond anneal system can be
operated at atmospheric pressure. The processing chamber can be
sealed against the surrounding air to realize an ultra-pure gas
ambient inside the chamber. The pressure inside the chamber can be
modified within the limits given by the mechanical stability of the
quartz plates of the water window. The allowable pressure range can
be, for instance, about +2 kPa to about -2 kPa pressure over
atmosphere.
[0078] For instance, in some embodiments, a process for thermally
treating a substrate in a millisecond anneal system can include
obtaining data indicative of a temperature profile associated with
one or more substrates during processing in a millisecond anneal
system. A temperature profile can provide a measure of thermal
uniformity of the substrate during processing. The temperature
profile can provide a temperature at various points on the
substrate. The data indicative of the temperature profile for one
or more substrates can be analyzed to determine any
non-uniformities in the temperature profile during process. To
address the non-uniformities, a pressure in the processing chamber
can be adjusted to affect the temperature uniformity across one or
more substrates.
[0079] In some embodiments, the data indicative of the temperature
profile can be obtained for a substrate during processing.
Non-uniformities identified in the temperature profile can trigger
the adjustment of the pressure during processing of the
semiconductor substrate. In this way, a closed loop control of
pressure based on the measured temperature profile can be used to
adjust the temperature uniformity of a wafer during processing.
[0080] FIG. 14 depicts an example gas flow system for adjusting
pressure in the processing chamber 200 of a millisecond anneal
system according to example embodiments of the present disclosure.
The process chamber 200 can be an open flow system, where process
gas is constantly entering the chamber from gas inlet 302 through
gas inlet ports located in the top corners of the process chamber
200. The process gas can leave the process chamber 200 chamber
through vent ports located in the bottom corners of the process
chambers. Downstream of the vent ports, the four vent lines can be
combined to a single downstream line 304. The downstream line 304
can be connected to a downstream exhaust duct 340. The downstream
duct 340 can provide a pressure differential PA relative to the
process chamber 200 necessary to vent the process gas from the
chamber 200. By changing this pressure differential PA, the
pressure in the processing chamber can be adjusted.
[0081] In some embodiments, the pressure differential PA can be
adjusted by a controller 320. The controller 320 can be any
suitable control device, such as one or more processor circuits
executing computer-readable instructions stored in one or more
memory devices. A control variable for the controller 320 can be a
pressure sensor 315 mounted to the chamber. The pressure sensor 315
can measure the pressure inside the chamber 200 and can send
signals indicative of the pressure to the controller 320 over a
suitable communication medium.
[0082] The actuator of the controller 320 can be a valve 325 (e.g.
a butterfly valve) in the vent manifold, changing the flow
resistance and thus the pressure differential of the downstream
line 304. Low flow resistance can lower the chamber pressure. High
flow resistance can increase the chamber pressure. The pressure
set-point for the controller 320 can be defined by a user, for
instance, based on a temperature profile across the substrate. The
controller 320 can be configured to control the pressure based on
signals from the pressure sensor to achieve the pressure-set point.
In some embodiments, the pressure differential can be adjusted by
passive mechanical restrictions (e.g. orifices, dampers, or
baffles) inside the vent line, or by setting the external exhaust
duct pressure.
[0083] The pressure inside the process chamber can influence a flow
pattern of process gas inside the chamber. Thus, the convective
cooling contribution on different regions of the wafer can be
adjusted by adjusting the pressure inside the process chamber
according to example embodiments of the present disclosure.
[0084] Adjusting the pressure can also affect the irradiation
distribution of lamp light provided through water windows in the
millisecond anneal system. For instance, in some embodiments, the
temperature uniformity of a semiconductor substrate can be improved
during processing in a millisecond anneal system by adjusting the
irradiance distribution based on the refracting effect of a water
window used in the millisecond anneal system. A water window in its
normal state is a plane-parallel plate with a stack sequence of:
(1) quartz; (2) water; (3) quartz. Water can flow through a
sandwich of two quartz plates. Warping the stack can cause the
water window to act as a lens for the lamp light passing through
the window, adjusting the irradiation distribution through the
water window.
[0085] In some embodiments, the warping of the water window can be
accomplished by increasing or decreasing the pressure inside the
chamber. As discussed above, the pressure inside the chamber can be
modified within the limits given by the mechanical stability of the
quartz plates of the water window. The allowable pressure range can
be, for instance, about +2 kPa to about -2 kPa pressure over
atmosphere. As the cooling water flowing inside the water window is
at constant pressure very close to the atmospheric pressure, a
pressure change inside the chamber an affect the inner quartz plate
of the water window. This can results in a thickness change of the
water layer center to edge.
[0086] More particularly, FIGS. 15 and 16 illustrate a water window
260 having an inner plate 282 and an outer plate 284. The inner
plate 282 and the outer plate 284 can be formed from, for instance,
quartz. Water can flow between the inner plate 282 and the outer
plate 284. The inner plate 282 can be disposed closer to the
processing chamber of a millisecond anneal system relative to the
outer plate 284.
[0087] As shown in FIG. 15, with a positive chamber pressure
relative to atmosphere, the inner 282 of the water window 260 is
bending outwards (e.g., away from the process chamber), resulting
in a convex layer of water with a defocusing effect on light. As
shown in FIG. 16, with a negative chamber pressure relative to
atmosphere, the inner plate 282 of the water window 260 is bending
inwards (e.g. toward the processing chamber), resulting in a convex
layer of water with a focusing effect on light.
Example Uniformity Improvement Through Angular Positioning of
Wafer
[0088] According to example aspects of the present disclosure, the
temperature uniformity of a patterned device wafer (e.g., a product
wafer) during processing in a millisecond anneal system can be
improved by angular wafer positioning. A product wafer can
sometimes contain several hundreds of dies arranged in form of an
array on the front surface of the wafer.
[0089] For instance, FIG. 17 depicts an example product wafer 500
with devices in an array arrangement. As silicon is a crystal, the
dies can be oriented along the main axis of the crystal lattice.
Most commonly, the wafer surface is cut along the [100] plane of
the silicon lattice. The wafer has a notch 502 marking the
<110> crystal lattice orientation. The die arrangement
results in a laterally varying absorption ability of light. Hence
the array of dies imposes a non-uniform light absorption property
onto the wafer surface.
[0090] FIG. 18 depicts a representation 510 of example residual
non-uniformity of the irradiation of a wafer in a millisecond
anneal system. As shown in FIG. 18, the chamber can have a
residual, inherent irradiation non-uniformity giving rise to a
lateral wafer-temperature non-uniformity. This inherent irradiation
non-uniformity can result, for instance, from the orientation of
lamps, location of reflectors, and other components of the
millisecond anneal system.
[0091] Millisecond anneal systems according to example aspects of
the present disclosure can use a stationary, non-rotating wafer
support arrangement. Therefore, the angular wafer orientation can
be used to optimize or improve the temperature uniformity by
aligning based at least in part on the irradiation pattern inherent
to the chamber.
[0092] More particularly, in some embodiments, a process for
thermally treating a substrate in a millisecond anneal system can
include obtaining data indicative of a temperature profile
associated with one or more substrates during processing in a
millisecond anneal system. The data indicative of the temperature
profile for one or more substrates can be analyzed to determine any
non-uniformities in the temperature profile during processing. To
address the non-uniformities, the angular positioning of one or
more wafers in the processing chamber can be adjusted to affect the
temperature uniformity across the one or more substrates.
[0093] FIG. 19 depicts a product wafer 500 located inside a
processing chamber 200. As shown, the wafer 500 can be placed at
different angular orientations relative to the chamber and to the
lamps. In the example, of FIG. 19, the wafer 500 is placed so that
notch 502 is at notch alignment angle .theta.. Accordingly,
interaction between absorption pattern and irradiation pattern can
be enhanced by adjusting the angular orientation of the wafer
500.
[0094] In some embodiments, product wafers can be notch aligned
before being loaded onto the handling system of the millisecond
anneal system. The notch alignment angle .theta. can determine the
angular orientation inside the chamber. Wafer orientation can be
measured based on the notch position relative to the chamber main
axis (e.g., given by the walls). In other embodiments, the notch
alignment can be performed inside the processing chamber, for
instance, by a notch alignment station or by a notch aligner
integrated to a robot.
[0095] In some implementations, wafers can be supported by quartz
pins mounted to a wafer support plate. The number of pins used for
supporting the wafer can vary between three up to six or more. A
common wafer support scheme uses four pins arranged as a square
with equal distance to the wafer center. Typically the pins can
cause a localized cold spot. Also the pins can induce a mechanical
stress pattern. By angular orientation of the wafer relative to the
pins, the negative impacts of the pins can be moved to more
favorable regions of the wafer. Also, by off-setting the points of
contact from the main lattice axis, wafer stress can be
mitigated.
[0096] For instance, FIG. 20 depicts a wafer 500 inside a
processing chamber 200 with the location of support pins 212
relative the wafer 500 shown. Angular orientation of the wafer 500
relative to the pins 212 can reduce the influence of the pins 212
by positioning the pins 212 at different locations relative to the
wafer 500.
Uniformity Improvement Through Shape and Position of Reflectors
[0097] According to example embodiments of the present disclosure,
the temperature uniformity of a semiconductor substrate can be
improved during processing in a millisecond anneal system based at
least in part the shape of one or more reflectors in the processing
chamber of the millisecond anneal system. For instance, a top wedge
reflector and/or one or more edge reflectors can have a shape
and/or configuration designed to improve thermal uniformity.
Small-sized reflectors can be used to reduce the residual
non-uniformity of the processing chambers in millisecond anneal
system.
[0098] In some embodiments, a process for thermally treating a
substrate in a millisecond anneal system can include obtaining data
indicative of a temperature profile associated with one or more
substrates during processing in a millisecond anneal system. The
data indicative of the temperature profile for one or more
substrates can be analyzed to determine any non-uniformities in the
temperature profile during process. To address the
non-uniformities, the shape, configuration, and/or position of one
or more reflectors in the processing chamber can be adjusted to
affect the temperature uniformity across the one or more
substrates.
[0099] FIG. 21 depicts a cross sectional view of a millisecond
anneal system showing the locations of top wedge reflectors 274 and
edge reflectors 264 in a processing chamber in a millisecond anneal
system. The top wedge reflectors 274 can be located on process
chamber walls proximate the wafer plane plate. The top wedge
reflectors 264 can be wedge shaped. The edge reflectors 264 can be
located on the wafer plane plate and can surround a substrate
during processing.
[0100] In some embodiments, there can be two top wedge reflectors
264 located on chamber walls in the top chamber portion of a
processing chamber of a millisecond anneal system. The top edge
reflectors 264 can be used to control the irradiation distribution
perpendicular to the main axis of the lamps. In some embodiments,
the wedge reflectors 264 can be mounted in the top half of the
chamber along the bottom edge of the mirror panels facing the door
and facing the rear of the chamber.
[0101] Typically, the wafer-temperature distribution has cold
regions at the wafer edge, perpendicular to the lamp orientation.
The size and magnitude of these cold spots can be impacted by the
wedge reflectors 264. Millisecond anneal systems can have the
ability to trigger the flash discharge of each top lamp
individually. The main application of this ability is to shape the
time-temperature profile of the flash event. A side effect of this
ability is that the irradiation pattern changes locally with time,
as the top lamps are at different positions relative to the wafer.
This can have impact on the size of the cold spot on the wafer
edge, depending on the trigger sequence of the lamps. Using wedges
with optimized angles can compensate for these effects.
[0102] FIG. 22 depicts example top wedge reflectors 264 with
varying wedge angles. More particularly, FIG. 22(a) depicts a top
wedge reflector 264 with a 0.degree. wedge angle. FIG. 22(b)
depicts atop wedge reflector with a 100 wedge angle. By changing
the wedge angle, the amount of light incident to the edge region
can be controlled. In some embodiments, the wedge reflectors 264
can be mounted to a motor or other mechanical apparatus that can be
configured to adjust the position and/or wedge angle of the wedge
reflectors 264. For instance, a controller can adjust the wedge
angle of the wedge reflectors in real time in response to
temperature measurements of the substrate to provide for more
uniform processing.
[0103] In some embodiments, the wedge angle can be pre-set by
machining the parts. Optimization of the uniformity can be
performed by mounting a suitable wedge with a selected wedge angle
to the processing chamber. In another embodiment, the wedge angle
can be set by inclining the wedge with shims, or by set screws. In
some embodiments, the irradiation distribution is manipulated by
additionally changing the wedge height and the wedge
reflectivity.
[0104] FIG. 23 depicts the example improvement of irradiation
distribution by adjusting the wedge angle of the top wedge from a
5.degree. wedge angle to a 1.degree. wedge angle. More
particularly, FIG. 23(a) depicts a temperature profile of a wafer
processed in a processing chamber having top wedge reflectors with
a 5.degree. wedge angle. As shown, the wafer can have cold spots
520 at the wafer edges due to reduced irradiance. FIG. 23(b)
depicts a temperature profile of a wafer processed in a processing
chamber having top wedge reflectors with a 1.degree. wedge angle.
As shown, the temperature at the wafer edges 525 is more uniform
and the presence of cold spots have been reduced.
[0105] Another way to manipulate the amount of irradiation at the
wafer edge is by location, shape, and reflectivity of the edge
reflectors 274. FIG. 24 depicts a perspective view of four edge
reflectors 274 used in the processing chamber. The edge reflectors
274 can redirect light from the bottom lamps to the edge of the
wafer. The reflectivity of the edge reflectors 274 can be modified
by cutting slots 276 into the reflecting surface. The ratio of slot
area to remaining reflector area determines the amount of
reflectivity.
[0106] FIG. 25 depicts a linear profile of a standard edge
reflector 274 used in a millisecond anneal system. According to
example embodiments of the present disclosure, the temperature
uniformity of a wafer can be modified by converting the profile
shape from linear to parabolic, or a combination hereof, and/or by
the relative position to the wafer. This determines the size and
location of the heated zone on the wafer edge.
[0107] More particularly, FIG. 26(a) depicts the reflection of
light onto a substrate 60 by an edge reflector 274 with a linear
profile 274.2. FIG. 26(b) depicts the reflection of light onto a
substrate 60 by an edge reflector 274 with a combination of a
parabolic and linear profile 274.4. FIG. 26(c) depicts the
reflection of light onto substrate 60 by an edge reflector 274 with
a combination of a parabolic and linear profile 274.4 but with an
adjusted position relative to the substrate.
[0108] In some embodiments, the edge reflectors 274 can be mounted
to a motor or other mechanical apparatus that can be configured to
adjust the position and/or surface profile of the edge reflectors.
For instance, a controller can adjust the position of one or more
edge reflectors in real time in response to temperature
measurements of the substrate to provide for more uniform
processing.
[0109] While the present subject matter has been described in
detail with respect to specific example embodiments thereof, it
will be appreciated that those skilled in the art, upon attaining
an understanding of the foregoing may readily produce alterations
to, variations of, and equivalents to such embodiments.
Accordingly, the scope of the present disclosure is by way of
example rather than by way of limitation, and the subject
disclosure does not preclude inclusion of such modifications,
variations and/or additions to the present subject matter as would
be readily apparent to one of ordinary skill in the art.
* * * * *