U.S. patent application number 11/558270 was filed with the patent office on 2008-05-15 for system and method for control of electromagnetic radiation in pecvd discharge processes.
Invention is credited to Jose Manuel Dieguez-Campo, Michael Liehr, Michael W. Stowell.
Application Number | 20080113108 11/558270 |
Document ID | / |
Family ID | 39047929 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080113108 |
Kind Code |
A1 |
Stowell; Michael W. ; et
al. |
May 15, 2008 |
SYSTEM AND METHOD FOR CONTROL OF ELECTROMAGNETIC RADIATION IN PECVD
DISCHARGE PROCESSES
Abstract
A system and method for coating a substrate with a film is
described. One embodiment includes a process that provides a
substrate on which to deposit a film; generates a plasma to produce
radicals from a support gas; produces the radicals from the support
gas; disassociates a precursor gas using the radicals; deposits
material from the disassociated precursor gas on the substrate; and
controls the amount of electromagnetic radiation to which the
deposited material is exposed.
Inventors: |
Stowell; Michael W.;
(Loveland, CO) ; Liehr; Michael; (Feldatal,
DE) ; Dieguez-Campo; Jose Manuel; (Hanan,
DE) |
Correspondence
Address: |
COOLEY GODWARD KRONISH LLP;ATTN: Patent Group
Suite 1100, 777 - 6th Street, NW
WASHINGTON
DC
20001
US
|
Family ID: |
39047929 |
Appl. No.: |
11/558270 |
Filed: |
November 9, 2006 |
Current U.S.
Class: |
427/569 ;
118/690 |
Current CPC
Class: |
H01J 37/32357 20130101;
C23C 16/52 20130101; H01J 37/32623 20130101; C23C 16/517 20130101;
C23C 16/452 20130101; C23C 16/482 20130101; H01J 37/32339
20130101 |
Class at
Publication: |
427/569 ;
118/690 |
International
Class: |
C23C 4/00 20060101
C23C004/00 |
Claims
1. A method for coating a substrate with a film, the method
comprising: providing a substrate on which to deposit a film;
generating a plasma to produce radicals from a support gas;
producing the radicals from the support gas; disassociating a
precursor gas using the radicals; depositing material from the
disassociated precursor gas on the substrate; and controlling the
amount of electromagnetic radiation to which the deposited material
is exposed.
2. The method of claim 1, wherein controlling the amount of
electromagnetic radiation to which the deposited material is
exposed comprises: blocking ultraviolet radiation emitted by the
plasma.
3. The method of claim 1, wherein controlling the amount of
electromagnetic radiation to which the deposited material is
exposed comprises: reducing an aperture opening between the plasma
and the deposited material.
4. The method of claim 1, wherein controlling the amount of
electromagnetic radiation to which the deposited material is
exposed comprises: increasing ultraviolet radiation generated.
5. The method of claim 1, wherein generating a plasma to produce
radicals from a support gas comprises: providing a power signal to
generate the plasma.
6. The method of claim 5, wherein providing a power signal to
generate the plasma comprises: spiking the power signal to thereby
increase the amount of ultraviolet radiation.
7. The method of claim 6, wherein spiking the power signal to
thereby increase the amount of ultraviolet radiation comprises:
controlling the timing of spiking the power signal to thereby
control the increase in the amount of ultraviolet radiation.
8. The method of claim 1, wherein providing a power signal to
generate the plasma comprises: varying the power signal to thereby
increase the amount of ultraviolet radiation.
9. The method of claim 1, wherein providing a power signal to
generate the plasma comprises: varying the power signal to thereby
vary the wavelength of the ultraviolet radiation.
10. The method of claim 1, wherein controlling the amount of
electromagnetic radiation to which the deposited material is
exposed comprises: varying the amount of ultraviolet radiation to
which the deposited material is exposed in accordance with the
density of radicals.
11. The method of claim 10, wherein varying the amount of
ultraviolet radiation to which the deposited material is exposed
comprises: increasing the amount of ultraviolet radiation to which
the deposited material is exposed when the density of radicals is
reduced.
12. The method of claim 10, wherein varying the amount of
ultraviolet radiation to which the deposited material is exposed
comprises: decreasing the amount of ultraviolet radiation to which
the deposited material is exposed when the density of radicals is
increased.
13. The method of claim 8, wherein controlling the amount of
electromagnetic radiation to which the deposited material is
exposed comprises: varying the amount of ultraviolet radiation to
which the deposited material is exposed in accordance with
variations to a power signal used to produce the plasma.
14. A PECVD system comprising: a plasma chamber; an antenna; a
substrate support; a electromagnetic radiation restrictor
positioned between the antenna and the substrate support, the
restrictor having a controllable aperture; and a controller
configured to control the controllable aperture.
15. The PECVD system of claim 14, wherein the controller comprises:
a computer configured to vary the size of the aperture according to
at least one PECVD process parameter.
16. The PECVD system of claim 14, wherein the controller comprises:
a computer configured to vary the size of the aperture according to
a density of radicals produced in the plasma chamber.
17. The PECVD system of claim 14, wherein the controller comprises:
a computer configured to vary the size of the aperture according to
variations in a power signal applied to the antenna.
18. A method of producing a film, the method comprising: initiating
a PECVD process to deposit a film on a substrate; and varying the
amount of ultraviolet radiation to which the film is exposed during
growth.
19. The method of claim 18, wherein varying the amount of
ultraviolet radiation to which the film is exposed during growth
comprises: mechanically varying the amount of ultraviolet radiation
to which the film is exposed during growth.
20. The method of claim 18, wherein varying the amount of
ultraviolet radiation to which the film is exposed during growth
comprises and wherein a plasma used during the PECVD process
generates a first amount ultraviolet radiation comprises: blocking
a first portion of the first amount of ultraviolet radiation from
reaching the film.
21. The method of claim 20, wherein varying the amount of
ultraviolet radiation to which the film is exposed during growth
comprises and wherein a plasma used during the PECVD process
generates a first amount ultraviolet radiation: blocking less than
the first portion of the first amount of ultraviolet radiation
blocked from reaching the film.
22. The method of claim 18, wherein varying the amount of
ultraviolet radiation to which the film is exposed during growth
comprises: varying the amount of ultraviolet radiation to which the
film is exposed during growth by contouring a power waveform used
to drive the PECVD process.
23. A method of producing a film, the method comprising: initiating
a PECVD process to deposit a film on a substrate; generating
ultraviolet radiation, wherein the film is exposed to the
ultraviolet radiation; varying the wavelength of the ultraviolet
radiation.
24. The method of claim 23, wherein varying the wavelength of the
ultraviolet radiation comprises: contouring a power waveform used
to drive the PECVD process.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to plasma enhanced chemical
vapor deposition (PECVD) processes. In particular, but not by way
of limitation, the present invention relates to systems and methods
for controlling electromagnetic radiation during the PECVD
process.
BACKGROUND OF THE INVENTION
[0002] The process of depositing films using PECVD is well known
and has been employed for many years. PECVD is used in several
industries to deposit non-conductive and conductive films on a
variety of substrates, including glass, semiconductor wafers, and
plasma display panels.
[0003] These films vary widely in quality and chemistry. With
regard to quality, films made of the same material can vary widely
in density and purity. That is, depending upon the PECVD
parameters, the type of PECVD system, and the system inputs, films
can increase or decrease in quality.
[0004] In some cases, variations in film quality and chemistry are
unintentional. But in other cases, film chemistry can deliberately
be altered to create films with particular properties and
characteristics. For example, PECVD process parameters such as
radical density, pulsing frequency, duty cycle, gas pressure, and
temperature can be varied to change film chemistry.
[0005] As the control over these process parameters improves, new
applications become available for films and film quality for
existing applications increases. Despite current process controls,
the PECVD industry continues to search for new and better ways to
control film chemistry. Accordingly, systems and methods are needed
to more finely control film chemistry. Similarly, new films are
needed that can be produced as a result of finely controlled film
chemistry.
SUMMARY OF THE INVENTION
[0006] Exemplary embodiments of the present invention that are
shown in the drawings are summarized below. These and other
embodiments are more fully described in the Detailed Description
section. It is to be understood, however, that there is no
intention to limit the invention to the forms described in this
Summary of the Invention or in the Detailed Description. One
skilled in the art can recognize that there are numerous
modifications, equivalents and alternative constructions that fall
within the spirit and scope of the invention as expressed in the
claims.
[0007] A system and method for coating a substrate with a film is
described. One embodiment includes a process that provides a
substrate on which to deposit a film; generates a plasma to produce
radicals from a support gas; produces the radicals from the support
gas; disassociates a precursor gas using the radicals; deposits
material from the disassociated precursor gas on the substrate; and
controls the amount of electromagnetic radiation to which the
deposited material is exposed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Various objects and advantages and a more complete
understanding of the present invention are apparent and more
readily appreciated by reference to the following Detailed
Description and to the appended claims when taken in conjunction
with the accompanying Drawings wherein:
[0009] FIG. 1 is a block diagram of a remote plasma source in
accordance with conventional technology;
[0010] FIG. 2 is a diagram of a remote plasma source in accordance
with conventional technology in operation;
[0011] FIG. 3 is an illustration of a dielectric film constructed
in accordance with conventional processes;
[0012] FIG. 4 is an illustration of a direct plasma source in
accordance with conventional technology;
[0013] FIG. 5 is an illustration of a dielectric film constructed
in accordance with principles of one embodiment of the present
invention;
[0014] FIG. 6 is an illustration of a remote plasma source with an
electromagnetic radiation assist device;
[0015] FIG. 7 is an illustration of a direct plasma source that
includes a radiation assist device;
[0016] FIG. 8 is an illustration of a direct plasma source in
accordance with one embodiment of the present invention;
[0017] FIG. 9 is an illustration of a thin film constructed in
accordance with one embodiment of the present invention;
[0018] FIG. 10 is an illustration of a thin film constructed in
accordance with another embodiment of the present invention;
[0019] FIG. 11A illustrates a power waveform that can be used to
generate additional ultraviolet radiation;
[0020] FIG. 11B illustrates the ultraviolet radiation that results
from the power waveform of FIG. 11A;
[0021] FIG. 12A illustrates a power wave form that can be used to
generate additional ultraviolet radiation; and
[0022] FIG. 12B illustrates the ultraviolet radiation that results
from the wave form of FIG. 12A.
DETAILED DESCRIPTION
[0023] Referring now to the drawings, where like or similar
elements are generally designated with identical reference numerals
throughout the several views, and referring in particular to FIG.
1, it is a remote PECVD system 100 in accordance with conventional
technology. This system includes a process chamber 105, a substrate
support 110, a substrate 115 on which a film will be deposited, a
precursor gas source 120, a gas pump 125, a plasma chamber 130, an
antenna 135, a protective sheath 140, a supporting gas source 145,
and a connecting neck 150 that connects the plasma chamber 130 with
the process chamber 105. Remote plasma systems of this type are
generally known in the art and not described in full detail
herein.
[0024] Referring now to FIG. 2, it shows the remote PECVD system
100 of FIG. 1 in operation. This PECVD system 100 is configured to
deposit a dielectric layer of SiO.sub.2 onto the substrate 115. To
deposit this dielectric layer, the precursor gas, HMDSO, is
disassociated using O.sub.3 and O.sub.1 ions. These O.sub.3 and
O.sub.1 ions are created by exposing the supporting gas, O.sub.2,
to electrons emitted by the antenna 135 and to ion collisions.
Generally, the antenna 135 is powered by an RF source, but it could
also be driven by other power sources.
[0025] The electrons emitted from the antenna 135 causes the
O.sub.2 gas to ionize and form a plasma 155. This plasma 155 causes
a cascade reaction, thereby forming more ions and fractionalized
O.sub.2 gas (radicals). These radicals then travel through the neck
150 connecting the remote plasma chamber 130 to the plasma chamber
105. Once in the plasma chamber 105, the radicals collide with the
HMDSO molecules, breaking them into SiOx, H, OH, etc.
[0026] For this embodiment, a perfect film would include only
SiO.sub.2. However, waste particles such as OH, H.sub.2O and SiOH
form during the disassociation and deposition process. And these
particles also deposit upon the substrate and growing film. When
the growing film is SiO.sub.2, these impurities reduce its
dielectric properties but may also introduce flexibility into the
film. Similar changes result in other types of films.
[0027] Most of the impurities produced during the PECVD process are
actually pumped out of the process chamber rather than deposited
upon the substrate. However, in most processes, enough impurities
deposit upon the substrate to significantly change the film
chemistry.
[0028] Those of skill in the art will understand that a remote
plasma source can be used for other thin films besides the
dielectric SiO.sub.2 layer. This process is shown for illustration
purposes only.
[0029] Referring now to FIG. 3, it illustrates a SiO.sub.2 film 160
produced by the remote PECVD system described in FIG. 2. This
figure illustrates a substrate layer and the film deposited
thereon. Most of the thin film is formed of SiO.sub.2. However, the
film also includes certain impurities such as OH, H.sub.2O and
SiOH. These impurities tend to slowly combine in the matrix with
un-decomposed materials from the precursor, fractionalization
processes materials and also unsatisfied bonds in the matrix
increasing the films density, this results in increased film stress
that lead to cracking and delamination as the film ages. Moreover,
the film does not have a uniform density. That is, the deposited
material is not deposited evenly and leaves gaps. Moreover, as the
film cools, some of the H.sub.2O molecules eventually escape,
leaving gaps where the H.sub.2O molecules were originally
located.
[0030] These types of flaws in thin films are found in nearly all
film chemistries and are not limited to SiO.sub.2 dielectrics. And
although these films are functional for some purposes, these flaws
limit the film's ability and life span in many instances. For
example, these impurities and gaps cause thin films to crack and
reduce their desired electrical properties.
[0031] In some instances, films may actually benefit from a
carefully added amount of impurities. But this process of adding
impurities must be carefully controlled or the film quality will
suffer significantly.
[0032] Referring now to FIG. 4, it illustrates a direct PECVD
system 170 in accordance with conventional technology. In this type
of PECVD system, the plasma chamber and process chambers are
combined. Otherwise, the direct PECVD system works similarly to the
remote PECVD system.
[0033] This embodiment of a conventional PECVD system includes a
process chamber 175, an antenna 180, a dielectric sheath 185, a
supporting gas supply 190, a precursor gas supply 195, and a
substrate 200. Although not shown, this system could also include a
substrate support. Again, this type of PECVD system is well known
in the art and not described in great detail herein.
[0034] Although this PECVD system should work almost identically to
the remote PECVD system shown in FIG. 1, it has been discovered
that, for certain film chemistries, the direct PECVD system
produces a somewhat higher quality film than does the remote PECVD
system. For example, FIG. 5 illustrates a dielectric film 205
produced by a direct PECVD system. While this film still includes
impurities and gaps that reduce the overall quality of the film,
the number of impurities and gaps is decreased.
[0035] It was recently discovered that part of the reason for this
increase in film quality was due to electromagnetic radiation, and
in particular ultraviolet radiation, radiated outward from the
plasma formed around the antenna. In a remote PECVD system, the
electromagnetic radiation was blocked from reaching the substrate
and the growing film. But in the direct PECVD system, the radiation
from the plasma could directly bombard the substrate and the
growing film. This bombardment was discovered to significantly
affect the chemistry of the growing film. In some instances, the
electromagnetic radiation bombardment enhanced the quality of the
film. However, in other cases, the electromagnetic radiation
bombardment could actually disrupt the growth of the film.
[0036] As previously discussed, the PECVD industry is always
searching for new and better ways to control the PECVD process and
more finely tune the chemistry of the deposited films. And
conventionally, the PECVD industry controlled process parameters
such as radical density, pulsing frequency, duty cycle, gas
pressure and temperature. In accordance with embodiments of the
present invention, the additional process parameter of
electromagnetic radiation can also be controlled.
[0037] By controlling the amount of electromagnetic radiation,
including UV radiation, to which the growing film is exposed, film
chemistry can be more finely controlled. Moreover, the substrate
can be preconditioned by controlling the amount of electromagnetic
radiation to which the substrate is exposed prior to depositing the
film. In both instances, the amount of electromagnetic radiation
can be significantly and quickly varied during the course of film
production. Alternatively, the amount of electromagnetic radiation
can be set for a desired film chemistry. This ability to vary
electromagnetic radiation during the film production allows film
chemistry to be finely controlled and changed as the film is
grown.
[0038] Referring now to FIG. 6, this is one embodiment of a PECVD
system 210 that includes electromagnetic radiation control. This
system is a remote plasma system similar to the system shown in
FIG. 1. This system includes the plasma chamber 130 and the process
chamber 105 separated by a connecting neck 150. Typically, this
type of system blocks electromagnetic radiation produced by the
plasma from reaching the substrate. But this system uses a
radiation assist device 215 added to the process chamber to
introduce radiation to the growing film.
[0039] In one embodiment, this radiation assist device 215 is an
ultraviolet source that is controlled by a computer or manually by
a user. The UV source output could be linked to any of the process
parameters commonly used to control film quality. For example, the
UV source could be linked to radical density so that the UV source
is at a high output level when radical density is at its lowest
point and UV could be at its lowest point when radical density is
at its highest point. Those of skill in the art could determine how
to adjust the process parameters and the UV output to achieve their
unique, desired film chemistries.
[0040] FIG. 7 illustrates a direct plasma source that includes a
radiation assist device 225. This direct plasma system is similar
to the system shown in FIG. 4. It includes the process chamber 230,
the antenna 235, the dielectric sheath 240 protecting the antenna,
the substrate support 245, the substrate 250, a supporting gas
supply 255, a precursor gas supply 260, and an exhaust pump
270.
[0041] In this embodiment it is assumed that the electromagnetic
radiation radiated from the plasma around the antenna 235 is not
sufficient to achieve the film properties desired. Accordingly, an
assist device 225 is added to provide extra electromagnetic
radiation as needed. This electromagnetic radiation assist device
225 could also be manually controlled or computer controlled and
timed to operate with other conventional process parameters.
[0042] FIG. 8 illustrates a portion of a direct PECVD system 275 in
accordance with the present invention. This diagram illustrates a
cutaway of the process chamber 280. In particular, it illustrates
the process chamber walls 280, the antenna 285, the dielectric
sheath 290 protecting the antenna, the substrate support 295, and
the substrate 300. This embodiment also illustrates a radiation
shield 305 with variable shutters 310 to restrict apertures in the
shield. The general operation of a process chamber and a PECVD
systems--not including the radiation shield--is known in the art
and not described further.
[0043] This embodiment assumes that the electromagnetic radiation
produced by the plasma surrounding the antenna 285 is sufficient to
sufficiently alter film chemistry. In fact, this embodiment assumes
that at times the electromagnetic radiation produced by the plasma
may be more than is needed to adequately alter film chemistry.
Accordingly, the shutters 310 in this embodiment can be opened,
restricted, or closed as the process parameters demand. The
shutters 310 are designed to block the passage of electromagnetic
radiation. As with the previously described radiation sources, the
shutters can be linked to other process parameter controls to
finally control film chemistry. Shutters can include any device
that restricts electromagnetic radiation, including UV
radiations.
[0044] FIGS. 9 and 10 illustrate two film chemistries that can be
produced by controlling the amount of electromagnetic radiation
that bombards the growing film. In FIG. 9, the electromagnetic
radiation is increased as the film 315 is grown. For example, the
shutters shown in FIG. 8 could be slowly opened as the film 315 is
grown. The resulting film chemistry becomes more dense as the film
grows outward. For a dielectric layer formed of SiO.sub.2, this
type of increasing density film results in an organo-silicon layer
nearest the substrate and a dense SiO.sub.2 layer on the outer
portions of the film. This type of film chemistry is desirable in
some cases so that the film adheres to the underlying substrate
adequately.
[0045] FIG. 10 illustrates another type of Film 320 that can be
generated by controlling the amount of radiation that bombards the
film. In this film 320, the film density varies from less dense to
dense, back to less dense. This type of chemistry produces
desirable electrical properties in certain instances.
[0046] In some instances, control of electromagnetic radiation
alone can produce the desired film chemistries. But as previously
described, in other instances, the electromagnetic radiation is
controlled in conjunction with other process parameters such as
radical density, power modulation, duty cycle, pulsing frequency,
pulse shape, gas pressure, and radical density. In particular, as
previously described, one novel method of using UV control involves
linking the amount of UV at the film to the radical density.
[0047] For example, if a SiO.sub.2 dielectric layer is being
deposited, the UV could be linked to the density of O.sub.1 and
O.sub.3 radicals at a particular point in time. As the radical
density decreases, the amount of UV could be increased to prepare
the surface of the film as the deposition rate lowers, and as the
radical density increases, the UV could be reduced to allow more
material to be deposited unencumbered by added energy sources.
[0048] Referring now to FIGS. 11A and 11B, they illustrates a power
waveform that can be used to generate additional ultraviolet
radiation. Generally, the PECVD process is driven by applying
microwave or RF frequency power signals to the antenna within the
process chamber. In accordance with one embodiment of the present
invention, the power signal can be modified to generate more or
less ultraviolet radiation. In this embodiment, the power applied
to the PECVD process is initially spiked. Although the spike adds
little to the overall power delivered to the PECVD process, the
power spike generates significant amounts of additional ultraviolet
radiation. This additional ultraviolet radiation is illustrated in
FIG. 11B.
[0049] Notably, embodiments that use power waveform contouring to
control the amount of ultraviolet radiation need not include any
type of radiation shield. Although some embodiments of the present
invention can also include a radiation shield.
[0050] FIGS. 12A and 12B, they illustrate alternate waveforms used
to generate additional ultraviolet radiation. In this embodiment,
the power is spiked twice during a single pulse. These spikes do
little to the overall power delivered to the PECVD process, but
significantly increase the amount of ultraviolet radiation
produced.
[0051] Additionally, controlling the contour of the pulse shape
also enables control over the wavelength of the produced
ultraviolet radiation. And in some embodiments, the wavelength is
controlled independently of the amount of ultraviolet radiation
produced.
[0052] In conclusion, the present invention provides, among other
things, a system and method for PECVD and controlling the PECVD
process. Those skilled in the art can readily recognize that
numerous variations and substitutions may be made in the invention,
its use and its configuration to achieve substantially the same
results as achieved by the embodiments described herein.
Accordingly, there is no intention to limit the invention to the
disclosed exemplary forms. Many variations, modifications and
alternative constructions fall within the scope and spirit of the
disclosed invention as expressed in the claims.
* * * * *