U.S. patent application number 11/458984 was filed with the patent office on 2006-12-28 for laser assisted material deposition.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Philip H. Campbell, Craig M. Carpenter, Ross S. Dando, Dan Gealy, Allen P. Mardian.
Application Number | 20060288937 11/458984 |
Document ID | / |
Family ID | 34422835 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060288937 |
Kind Code |
A1 |
Dando; Ross S. ; et
al. |
December 28, 2006 |
LASER ASSISTED MATERIAL DEPOSITION
Abstract
Apparatus is provided for a method of forming a film on a
substrate that includes activating a gas precursor to deposit a
material on the substrate by irradiating the gas precursor with
electromagnetic energy at a frequency tuned to an absorption
frequency of the gas precursor. The electromagnetic energy may be
provided by an array of lasers. The frequency of the laser beam may
be selected by switching from one laser in the array to another
laser in the array. The laser array may include laser diodes, one
or more tunable lasers, solid state lasers, or gas lasers. The
frequency of the electromagnetic energy may be selected to impart
specific amounts of energy to a gas precursor at a specific
frequency that provides point of use activation of the gas
precursor.
Inventors: |
Dando; Ross S.; (Nampa,
ID) ; Gealy; Dan; (Kuna, ID) ; Carpenter;
Craig M.; (Boise, ID) ; Campbell; Philip H.;
(Meridian, ID) ; Mardian; Allen P.; (Boise,
ID) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Micron Technology, Inc.
|
Family ID: |
34422835 |
Appl. No.: |
11/458984 |
Filed: |
July 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10683806 |
Oct 10, 2003 |
|
|
|
11458984 |
Jul 20, 2006 |
|
|
|
Current U.S.
Class: |
118/722 ;
118/715; 257/E29.255 |
Current CPC
Class: |
C23C 16/483 20130101;
H01L 21/0228 20130101; H01L 21/3141 20130101; C23C 16/45523
20130101; H01L 29/78 20130101; H01L 21/02271 20130101 |
Class at
Publication: |
118/722 ;
118/715 |
International
Class: |
C23C 16/00 20060101
C23C016/00 |
Claims
1. A deposition system comprising: a reaction chamber; a source to
provide a precursor gas into the reaction chamber; a means for
providing electromagnetic energy to interact with the precursor gas
at selected locations in the reaction chamber; and a means for
controlling a frequency of the electromagnetic energy.
2. The deposition system of claim 1, wherein the means for
providing electromagnetic energy is configured to provide the
electromagnetic energy substantially perpendicular to a flow of the
precursor gas into the reaction chamber.
3. The deposition system of claim 1, wherein the means for
providing electromagnetic energy is configured to direct the
electromagnetic energy to a location to interact with the precursor
gas such that the location is at a distance from a substrate
mounted in the reaction chamber that is within a mean free path
from the substrate.
4. The deposition system of claim 1, wherein the means for
providing electromagnetic energy is configured to raster a location
of interaction of the electromagnetic energy with the precursor gas
along a surface of a substrate mounted in the reaction chamber.
5. The deposition system of claim 1, wherein the deposition system
includes a laser target mounted interior to the reaction chamber to
retain electromagnetic energy incident upon it.
6. The deposition system of claim 1, wherein the deposition system
includes control optics mounted inside the reaction chamber.
7. The deposition system of claim 1, wherein the means for
providing electromagnetic energy includes an array of sources of
electromagnetic energy, each source of the array at a different
operating frequency.
8. The deposition system of claim 1, wherein the means for
controlling a frequency of the electromagnetic energy includes a
switching circuit to select one of an array of sources of
electromagnetic energy.
9. The deposition system of claim 1, wherein the means for
controlling a frequency of the electromagnetic energy includes
circuitry to select an output frequency of a tunable laser.
10. A deposition system comprising: a reaction chamber; a source to
provide a gas into the reaction chamber; an array of lasers to
provide a laser beam to interact with the gas at a selected
location in the reaction chamber; and a switching circuit to select
one or more lasers of the array of laser to provide the laser beam
having a selected frequency.
11. The deposition system of claim 10, wherein the array of lasers
is configured to provide the laser beam substantially perpendicular
to a flow of the gas into the reaction chamber.
12. The deposition system of claim 10, wherein the selected
location is within a mean free path from a substrate mounted in the
reaction chamber.
13. The deposition system of claim 10, wherein the array of lasers
is configured to raster a location of interaction of the laser beam
with the gas along a surface of a substrate mounted in the reaction
chamber.
14. The deposition system of claim 10, wherein the array of lasers
is an array of diode lasers.
15. The deposition system of claim 10, wherein the array of lasers
includes a tunable laser.
16. The deposition system of claim 10, wherein the deposition
system includes multiple sources of gases and controls to operate
the deposition system as a atomic layer deposition system.
17. A deposition system comprising: a reaction chamber; a source to
provide a gas into the reaction chamber; an array of lasers to
provide a laser beam to interact with the gas at a selected
location in the reaction chamber; a switching circuit to select one
or more lasers of the array of laser to provide the laser beam
having a selected frequency; and optics to direct the laser
beam.
18. The deposition system of claim 17, wherein the optics include
optics mounted exterior to the reaction chamber.
19. The deposition system of claim 17, wherein the deposition
system includes a laser target to retain light incident upon it
from the laser beam substantially without reflection.
20. The deposition system of claim 17, wherein the deposition
system includes a laser target to manage redirection of light
incident upon it from the laser beam, laser target configured to
redirected the light to the gas.
21. The deposition system of claim 17, wherein the deposition
system includes a laser target configured such that light from the
laser beam incident on the laser target is directed out of the
reaction chamber.
22. The deposition system of claim 17, wherein the array of lasers
is an array of diode lasers.
23. The deposition system of claim 17, wherein the deposition
system includes an atomic layer deposition system.
24. The deposition system of claim 17, wherein the optics includes
optical filters correlated to an absorption frequency of the
gas.
25. The deposition system of claim 17, wherein the optics includes
optical attenuators correlated to the gas.
Description
RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. application Ser.
No. 10/683,806, filed Oct. 10, 2003, which is incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to electronic device
fabrication, in particular, semiconductor device fabrication.
BACKGROUND OF THE INVENTION
[0003] Fabrication of electronic devices such as integrated
circuits is performed through a series of processes, where each
process has its own thermal characteristics. Some processes require
high temperatures, while others not requiring high temperatures are
performed at temperatures elevated over ambient. The elevated
temperatures, whether small or large, provide an energic
environment in which reactants, or precursors, interact chemically
to form a desired material composition. This material composition
may be an intermediate composition or the final composition forming
an integral portion of the electronic device or system being
constructed.
[0004] A chemical reaction to form a desired material composition
is conducted by providing energy to reactant gases. This energy is
typically provided by heating the reactant gases, the reaction
environment, and/or a substrate on which the resultant composition
of the chemical reaction is to be formed. These heating processes
may place limitations on the fabrication process. For instance,
reactant gases that can provide the desired resultant composition
upon chemical reaction may be eliminated from being used because
the chemistries of these gases may be sensitive to heating, making
thermal control difficult. In other instances, conventional heating
methods may be inefficient for a wide variety of gases. As these
gases are heated, a significant percentage by mass volume may
decompose into unwanted gas compositions prior to undergoing the
intended chemical reaction with other materials or gases. Then,
only the non-decomposed portion of the volume of reactant gas
contributes to the fabrication process, limiting the reaction
efficiency. Thus, control of the thermal characteristics for
forming various materials to be used in electronic devices and
systems provides a significant challenge for fabrication
processes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 illustrates an embodiment of a process for point of
use activation in laser assisted deposition of a material onto a
substrate, according to the teachings of the present invention.
[0006] FIG. 2 depicts an embodiment of a deposition system
including a laser source, according to the teachings of the present
invention.
[0007] FIG. 3 depicts an embodiment of a laser source that can be
used with various deposition systems to provide a process for point
of use activation in laser assisted deposition of a material onto a
substrate, according to the teachings of the present invention.
[0008] FIG. 4 depicts an embodiment of a deposition system using a
laser source that can be applied to atomic layer deposition,
according to the teachings of the present invention.
[0009] FIG. 5 illustrates a flow diagram of elements for an
embodiment of a method to form a material on a substrate by point
of use activation in laser assisted deposition of the material,
according to the teachings of the present invention.
[0010] FIG. 6 illustrates a flow diagram of elements for an
embodiment of a method to form a material on a substrate by point
of use activation in laser assisted deposition of the material,
according to the teachings of the present invention.
[0011] FIG. 7 shows an embodiment of a transistor constructed using
point of use activation in laser assisted deposition of one or more
materials on a substrate, according to the teachings of the present
invention.
[0012] FIG. 8 is a simplified block diagram for an embodiment of a
memory device having one or more materials formed on a substrate
using point of use activation in laser assisted deposition of the
materials, according to the teachings of the present invention.
[0013] FIG. 9 illustrates a block diagram for an embodiment of an
electronic system having devices with one or more materials formed
on a substrate using point of use activation in laser assisted
deposition of the materials, according to the teachings of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The following detailed description refers to the
accompanying drawings that show, by way of illustration, specific
aspects and embodiments in which the present invention may be
practiced. These embodiments are described in sufficient detail to
enable those skilled in the art to practice the present invention.
Other embodiments may be utilized and structural, logical, and
electrical changes may be made without departing from the scope of
the present invention. The various embodiments disclosed herein are
not necessarily mutually exclusive, as some disclosed embodiments
can be combined with one or more other disclosed embodiments to
form new embodiments.
[0015] The terms wafer and substrate used in the following
description include any structure having an exposed surface with
which to form a material composition for an integrated circuit (IC)
and other electronic devices and systems. The term substrate is
understood to include semiconductor wafers. The term substrate is
also used to refer to semiconductor structures during processing,
and may include other layers that have been fabricated thereupon.
Both wafer and substrate include doped and undoped semiconductors,
epitaxial semiconductor layers supported by a base semiconductor or
insulator, as well as other semiconductor structures well known to
one skilled in the art.
[0016] The term "horizontal" as used in this application is defined
as a plane parallel to the conventional plane or surface of a wafer
or substrate, regardless of the orientation of the wafer or
substrate. The term "vertical" refers to a direction perpendicular
to the horizontal as defined above. Prepositions, such as "on",
"side" (as in "sidewall"), "higher", "lower", "over" and "under"
are defined with respect to the conventional plane or surface being
on the top surface of the wafer or substrate, regardless of the
orientation of the wafer or substrate. The following detailed
description is, therefore, not to be taken in a limiting sense, and
the scope of the present invention is defined only by the appended
claims, along with the full scope of equivalents to which such
claims are entitled.
[0017] In an embodiment, material is formed on a substrate by a
deposition process in which the energy of activation is controlled.
This embodiment includes activating a gas precursor by irradiating
the gas precursor with electromagnetic energy at a frequency tuned
to an absorption frequency of the gas precursor. The
electromagnetic energy may be from a source whose electromagnetic
output can be selectively filtered and attenuated to provide
electromagnetic energy at a select frequency. The select frequency
of the electromagnetic energy provided is the center frequency, or
peak frequency, of the electromagnetic energy. The electromagnetic
energy has energy components within a linewidth, or spectral
bandwidth, about the center frequency. In embodiments, the
linewidth about the center frequency is narrow providing
electromagnetic energy tuned to a frequency which can be targeted
for specific use. By controlling the frequency, or frequencies, of
the electromagnetic energy, the amount of energy applied to the gas
precursor can be regulated such that the gas precursor does not
decompose prior to undergoing the desired reaction for forming the
material on the substrate. Use of energy that can be tuned to
specific amounts correlated to specific absorption frequencies of a
gas precursor allows gas precursors with delicate chemistries to be
efficiently used in a variety of deposition processes.
[0018] In an embodiment, to provide control of the energy of
activation of a gas precursor, a laser source is provided to
generate electromagnetic energy having a frequency tuned to the
desired absorption frequency of the gas precursor. The laser source
provides packets of energy specifically tuned to a target bond
energy. Upon irradiation by the tuned electromagnetic energy,
specific bonds of a precursor are destabilization leading to a
chemical reaction with other precursors introduced into a reaction
chamber or with the surface of the substrate on which material is
being deposited. Providing control of the energy of activation can
be considered as providing point of use activation. In the various
embodiments, point of use activation provides heating essentially
at localized levels without the general heating of the gas
precursor and other gases, including carrier gases, in a gas
flow.
[0019] Activating a substance includes providing energy to that
substance to attain a necessary level of energy for the occurrence
of a chemical reaction. Supplying the energy can be realized by
heating or irradiating the substance with electromagnetic
radiation. The supplied energy is absorbed by the substance with
the excitation of the molecules within the substance to a higher
energy state relative to the state of the molecule at ambient
conditions without the external energy stimulus. An excited or
activated molecule may have electrons that have moved into higher
energy states breaking bonds existing before the activation energy
is supplied.
[0020] In an embodiment, point of use activation in laser assisted
deposition, i.e., laser assisted deposition in which the energy of
activation is controlled, provides an opportunity to supply a
specific amount of energy at a specific frequency to a sensitive
chemical at a predetermined level of activation for a desired use.
The predetermined level can be regulated by controlling the
intensity of the output light from one or more lasers. By
controlling the level of activation of the given chemical,
deterioration of the chemical before it provides a desired reaction
for a process can be prevented. Additionally, various embodiments
for point of use activation in laser assisted deposition allow use
of short time duration specie chemicals in a deposition
process.
[0021] In an embodiment, activation energy is supplied by a laser
beam at specific amounts to attain a desired activation state. In
an embodiment, the desired activation state is one in which
specific bonds are broken to prepare for a predetermined chemical
reaction leading to the deposition of a material onto a substance.
This deposition process may include illuminating a gas precursor in
a gas flow where the chemical reaction occurs downstream from the
illumination location. Alternately, this deposition process may
include illuminating a gas precursor at the surface of a substrate
with the chemical reaction occurring at this surface. In another
embodiment, the desired activation state is one in which specific
bonds are broken to provide for the decomposition of one or more
gases into one or more gas reactants to provide the chemical
reaction for depositing material on a substrate. This decomposition
can occur upstream from a substrate or at the substrate
surface.
[0022] An embodiment includes apparatus for a method of forming a
film on a substrate that includes activating a gas precursor to
deposit a material on the substrate by irradiating the gas
precursor with electromagnetic energy at a frequency tuned to an
absorption frequency of the gas precursor. The electromagnetic
energy can be provided by an array of lasers. The frequency of the
laser beam is selected by switching from one laser in the array to
another laser in the array. The laser array may include laser
diodes, one or more tunable lasers, solid state lasers, or gas
lasers. The frequency of the electromagnetic energy is selected to
impart specific amounts of energy to a gas precursor at a specific
frequency to activate the gas precursor.
[0023] FIG. 1 illustrates an embodiment of a process for point of
use activation in laser assisted deposition of a material onto a
substrate 110. Substrate 110 may include, but is not limited to,
substrate materials such as silicon, silicon-on insulator (SOI),
silicon-on sapphire (SOS), silica, ceramic, alumina, metals,
organic materials, silicon-germanium, germanium, or gallium
arsenide. A laser source 120 provides a laser beam 130 that
illuminates a gas flow 140 to provide an activated gas flow 150
having one or more activated gas precursors. The process includes
adjusting the laser beam to a select frequency correlated to a
specific absorption frequency of the gas precursor.
[0024] In an embodiment, laser beam 130 is adjusted to a select
frequency by switching laser beam 130 from an output of one laser
in a laser array to an output of another laser in the laser array
of source 120. Laser source 120 may include an array of diode
lasers. In an embodiment, the laser source 120 includes one or more
tunable lasers. In an embodiment, laser source 120 provides laser
beam 130 with a predetermined number of frequencies in order to
activate specific gases in gas flow 140, or to stimulate a number
of absorption frequencies for a given gas precursor in gas flow
140.
[0025] The location at which laser beam 130 interacts with one or
more gas precursors in gas flow 140 is controlled so that the
activated gas precursors are within a predetermined distance from
substrate 110. The distance from the region in which gas flow 140
is illuminated with laser beam 130 can be measured in terms of the
mean free path of an activated molecule defining a gas precursor,
where the mean free path of a molecule is the average distance
traveled by the molecule between collisions of the molecule with
other molecules. The illumination location relative to substrate
110 in terms of a number of mean free paths can be controlled by
regulating environmental parameters, such as pressure. In an
embodiment, a location, at which the laser beam illuminates gas
flow 140 to activate one or more precursors, occurs at a distance
from the substrate that is within a mean free path of an activated
gas precursor. In an embodiment, a location, at which the laser
beam illuminates gas flow 140 to activate one or more precursors,
occurs at a distance from the substrate that is within ten mean
free paths of an activated gas precursor. In an embodiment, a
location, at which the laser beam illuminates gas flow 140, is
within about two or three centimeters of the substrate surface. The
control of the relative illumination location can be realized with
laser source 130 fixed in a horizontal positive relative to gas
flow 140 with the substrate vertically adjusted. Alternately, the
control can be realized with laser source 130 rastered, or scanned,
across the surface of substrate 110.
[0026] In embodiment, activating a gas precursor includes breaking
specific bonds in a gas precursor. This activation places the gas
precursor in an excited state for chemically reacting with specific
reactants in gas flow or which specific compositions present at or
on the surface of substrate 110. Using laser beam 130 to activate a
gas precursor in gas flow 140 allows for precision in controlling
the activation process that is not as efficiently regulated by
conventional heating methods. In an embodiment, a laser is used to
provide point of use activation in an atomic layer deposition (ALD)
process.
[0027] ALD, also known as atomic layer epitaxy (ALE), was developed
in the early 1970's as a modification of chemical vapor deposition
(CVD) and is also called "alternatively pulsed-CVD." In ALD,
gaseous precursors are introduced one at a time to the substrate
surface mounted within a reaction chamber (or reactor). This
introduction of the gaseous precursors takes the form of pulses of
each gaseous precursor. Between the pulses, the reaction chamber is
purged with a gas, which in many cases is an inert gas, and/or
evacuated.
[0028] In a chemisorption-saturated ALD (CS-ALD) process, during
the first pulsing phase, reaction with the substrate occurs with
the precursor saturatively chemisorbed at the substrate surface.
The chemisorption process can be assisted using an embodiment for
point of use activation. Subsequent pulsing with a purging gas
removes precursor excess from the reaction chamber.
[0029] The second pulsing phase introduces another precursor on the
substrate where the growth reaction of the desired layer takes
place. Embodiments for point of use activation can provide a
controlled temperature increase for the growth reaction in both the
second precursor and the chemisorbed species. Subsequent to the
layer growth reaction, reaction by-products and precursor excess
are purged from the reaction chamber. With favourable precursor
chemistry where the precursors adsorb and react with each other on
the substrate aggressively, one ALD cycle may be performed in less
than one second in properly designed flow type reaction chambers.
Typically, precursor pulse times range from about 0.5 sec to about
2 to 3 seconds.
[0030] In ALD, the saturation of all the reaction and purging
phases makes the growth self-limiting. This self-limiting growth
results in large area uniformity and conformality, which has
important applications for such cases as planar substrates, deep
trenches, and in the processing of porous silicon and high surface
area silica and alumina powders. Thus, ALD provides for controlling
layer thickness in a straightforward manner by controlling the
number of growth cycles.
[0031] The precursors used in an ALD process may be gaseous, liquid
or solid. However, liquid or solid precursors must be volatile. The
vapor pressure must be high enough for effective mass
transportation. Also, solid and some liquid precursors need to be
heated inside the reaction chamber and introduced through heated
tubes to the substrates. The necessary vapor pressure must be
reached at a temperature below the substrate temperature to avoid
the condensation of the precursors on the substrate. Due to the
self-limiting growth mechanisms of ALD, relatively low vapor
pressure solid precursors may be used though evaporation rates may
somewhat vary during the process because of changes in their
surface area.
[0032] There are several other characteristics for precursors used
in ALD. The precursors must be thermally stable at the substrate
temperature because their decomposition would destroy the surface
control and accordingly the advantages of the ALD method that
relies on the reaction of the precursor at the substrate surface.
The control of the surface reaction is enhanced in various
embodiments by providing reaction energy by laser assisted point of
activation processes.
[0033] The precursors have to chemisorb on or react with the
surface, though the interaction between the precursor and the
surface as well as the mechanism for the adsorption is different
for different precursors. The molecules at the substrate surface
must react aggressively with the second precursor to form the
desired solid layer. Additionally, precursors should not react with
the layer to cause etching, and precursors should not dissolve in
the layer. In an embodiment, a laser beam rastered across the
substrate surface provides the energy for activation for the
molecules to react aggressively at the surface. Using highly
reactive precursors in ALD contrasts with the selection of
precursors for conventional CVD.
[0034] The by-products in the reaction must be gaseous in order to
allow their easy removal from the reaction chamber. Further, the
by-products should not react or adsorb on the surface.
[0035] In a reaction sequence ALD (RS-ALD) process, the
self-limiting process sequence involves sequential surface chemical
reactions. RS-ALD relies on chemistry between a reactive surface
and a reactive molecular precursor. In an RS-ALD process, molecular
precursors are pulsed into the ALD reaction chamber separately. The
precursor reaction at the substrate is typically followed by an
inert gas pulse to remove excess precursor and by-products from the
reaction chamber prior to pulsing the next precursor of the
fabrication sequence. Point of use activation can be applied to
enhance and control the surface reaction and can be terminated
while by-products are removed using the inert gas pulse.
[0036] By RS-ALD, layers can be layered in equal metered sequences
that are all identical in chemical kinetics, deposition per cycle,
composition, and thickness. RS-ALD sequences generally deposit less
than a full layer per cycle. Typically, a deposition or growth rate
of about 0.25 to about 2.00 .ANG. per RS-ALD cycle may be
realized.
[0037] The characteristics of RS-ALD include continuity at an
interface, conformality over a substrate, use of low temperature
and mildly oxidizing processes, freedom from first wafer effects
and chamber dependence, growth thickness dependent solely on the
number of cycles performed, and ability to engineer multilayer
laminate layers with resolution of one to two monolayers. RS-ALD
allows for deposition control on the order on monolayers and the
ability to deposit monolayers of amorphous layers.
[0038] In embodiment, activating a gas precursor includes breaking
specific bonds to decompose one or more gases into two or more
chemical vapors that act as gas reactants in a chemical reaction
leading to the deposition of material on substrate 110. Using laser
beam 130 to decompose gases in gas flow 140 allows conveniently
obtained complex molecules to be used to provide the gas reactants
for a deposition process. Illuminating the complex molecule with
the laser beam at specific frequencies may allow for regulating the
decomposition of the complex molecule into one or more desired
molecules in a manner that provides more control and efficiency
than other decomposition processes. In an embodiment, a laser is
used to provide point of use activation in a chemical vapor
deposition process.
[0039] In a CVD process using laser assisted point of use
activation, the activation energy for the vapor species used in a
desired deposition process is specifically supplied and regulated
by controlling a laser beam. The chemical reaction in the CVD
process may occur in gas flow 140 upstream from substrate 110, or
near the surface of substrate 110, or on the surface of substrate
110. The gases selected for gas flow 140 are chosen such that
by-products of a chemical reaction using the laser activated gases
of gas flow 150, other than the material being formed on substrate
110, do not interact to deposit on substrate. Point of use
activation using source 120 allows for maintaining the deposition
environment and substrate 110 at temperatures lower than needed for
deposition of unwanted by-products.
[0040] FIG. 2 depicts an embodiment of a deposition system 200
including a laser source 220. Deposition system 200 includes, in
addition to laser source 220, a reaction chamber 205, a substrate
holder 215 on which a substrate 220 can be mounted, a gas source
235 which provides a gas to reaction chamber 205, and laser control
circuitry 225. Laser control circuitry 225 controls laser 220 to
provide a laser beam 230 to illuminate gas flow 240 to provide an
activated gas flow 250 having one or more activated gas
reactants.
[0041] Control for locating laser beam 230 relative to gas flow 240
can be provided by control optics. External control optics 227 are
provided for an embodiment that places laser source 220 outside
reaction chamber 205. Internal control optics 229 is provided for
an embodiment that places control of laser beam 230 inside reaction
chamber 205. External control optics 227 and internal control
optics 229 provide one or more functions, including but not limited
to, steering laser beam 230 and focusing or expanding laser beam
230. Laser beam can be steered to raster across the surface of
substrate 210. In an embodiment, laser source 220 is mounted in
reaction chamber 205 with laser control circuitry mounted external
to reaction chamber 205. Alternately, laser control circuitry 225
can also be mounted in reaction chamber 205. In an embodiment,
laser source 220 can be positioned in reaction chamber 205 along
the portion of reaction chamber 205 where a gas enters reaction
chamber 205 from gas source 235.
[0042] Control optics 227 and 229 may also include optical filters
and attenuators. The spectral width of a laser beam about its laser
frequency may include frequencies correlated to absorption
frequencies for gases in gas flow 240 other than the desired gas
precursor, or precursors, or frequencies correlated to an
absorption frequency of the gas precursors at which stimulation is
unwanted. Optical filters and optical attenuators can be used to
eliminate or significantly reduce stimulation of unwanted energy
absorption at frequencies different from the targeted
frequencies.
[0043] Additionally, laser beam 230 can be constrained to interact
with gas flow 240 in a single pass without reflected light
interacting with gas flow 240 or activated gas flow 250 by steering
or directing laser beam 230 from its input through gas flow 240 to
a laser target 232. Laser target 232 is adapted to retain the light
incident upon it from laser beam 230 without significant
reflection. The light irradiating target 332 may be absorbed or
directed out of reaction chamber 205. In another embodiment, laser
target 232 includes optics to manage the redirection of incident
light back to gas flow 240 or activated gas flow 250 at specific
locations which can be regulated by controlling the optics and
circuitry of laser target 232.
[0044] In an embodiment, laser control circuitry 225 is configured
to select a frequency for laser beam 230 by switching an output of
one laser in a laser array of source 220 to an output of another
laser in the laser array of source 220. Laser source 220 may
include an array of diode lasers. Alternately, laser source 220
includes one or more tunable lasers. In an embodiment, laser source
220 provides laser beam 230 with a predetermined number of
frequencies in order to activate a number of gas precursors in gas
flow 240 or to activate a specific gas precursor at a number of
absorption frequencies of the gas precursor.
[0045] FIG. 3 depicts an embodiment of laser source 220 of FIG. 2
that can be used with various deposition systems to provide a
process for point of use activation in laser assisted deposition of
a material onto a substrate. In an embodiment, laser source 220
includes an array of lasers having individual lasers 222-1-222-N.
In an embodiment, each laser 222-1-222-N has an output laser
frequency different than the other lasers 222-1-222-N. In an
embodiment, each laser 222-1-222-N is a diode laser. Alternately,
laser source 220 may include one or more tunable lasers. In various
embodiments, lasers 222-1-222-N include other solid state lasers or
gas lasers. The laser array, lasers 222-1-222-N, are located
directly on a reaction chamber, in a delivery line for gases, or in
a small reservoir directly connected to a reaction chamber and
positioned in a precursor gas flow stream.
[0046] Laser source 220 having an array of lasers allows for
activating molecules at various frequencies specifically tuned to
an absorption frequency of the molecule. The output from laser
source 220 may be, but is not limited to, visible, infrared, or
ultraviolet radiation. Laser control circuitry 225 regulates the
intensity of the output of each laser 222-1-222-N, which controls
the amount of energy in the laser output at its given frequency.
Laser control circuitry 225 includes switching circuitry 224 to
regulate an output 231 of laser source 220. Switching circuitry 224
regulates which lasers of the 222-1-222-N lasers are on and which
are off. On demand, switching circuitry 224 can switch one or more
lasers on while switching the remaining lasers off, from control
signals provided from or to laser control circuitry 225. With the
output of two or more lasers 222-1-222-N provided in output 231 of
laser source 220, energy can be supplied to a gas flow at two or
more specific energies tuned to desired absorption frequencies
within the gas flow. The output of lasers may be steered from laser
source 220 using optics control 226 to provide output 231 of laser
source 220. When laser source 220 is used in a system such as
deposition system 200 of FIG. 2, output 231 becomes laser beam
230.
[0047] In an embodiment, laser source 220 is detachable from a
reactor chamber. For each deposition process involving a different
set of gas precursors to deposit different materials onto a
substrate at different stages of processing or in fabricating
different systems or devices, a different laser source 220 can be
mounted to or within the reaction chamber. The array of lasers of
the newly mounted laser source 220 is selected to have laser
frequencies correlated to the absorption frequencies of the new set
of gas precursors.
[0048] The elements depicted in FIGS. 2 and 3 are those elements
necessary for discussion of embodiments of the present invention
such that those skilled in the art may practice various embodiments
of the present invention without undue experimentation. Additional
gas sources and environmental controls can be used in a deposition
system in conjunction with the elements of FIGS. 2 and 3. Such a
deposition system can be used in different deposition processes
using various embodiments for laser assisted point of use
activation as discussed herein. An exemplary embodiment for a
deposition system having a laser source and control circuitry is an
atomic layer deposition system as depicted in FIG. 4.
[0049] In FIG. 4, a substrate 410 is located inside a reaction
chamber 405 of ALD system 400 including a laser source 420 and
laser control circuitry 425. ALD system may include optional
control optics 427 that may be located interior or exterior to
reaction chamber 405. Laser source 420 may be located directly on a
reaction chamber, in a delivery line for gases, or in a small
reservoir directly connected to a reaction chamber and positioned
in a precursor gas flow stream. Also located within reaction
chamber 420 is a substrate holder 415, which can be configured with
a temperature control to regulate the substrate temperature. A
gas-distribution fixture 445 introduces precursor gases to the
substrate 410. Each precursor gas originates from individual gas
sources 451-454 whose flow is controlled by mass-flow controllers
456-459, respectively. Each gas source, 451-454, provides a
precursor gas either by storing the precursor as a gas or by
providing a location and apparatus for evaporating a solid or
liquid material to form the selected precursor gas. Furthermore,
additional gas sources may be included, one for each precursor
employed.
[0050] Also included in ALD system 400 are purging gas sources 461,
462, each of which is coupled to mass-flow controllers 466, 467,
respectively. Furthermore, additional purging gas sources may be
constructed in ALD system 400, one purging gas source for each
precursor gas. For a process that uses the same purging gas for
multiple precursor gases less purging gas sources are used in ALD
system 400. Gas sources 451-454 and purging gas sources 461-462 are
coupled by their associated mass-flow controllers to a common gas
line or conduit 470, which is coupled to the gas-distribution
fixture 445 inside reaction chamber 420. Gas conduit 470 is also
coupled to vacuum pump, or exhaust pump, 281 by mass-flow
controller 486 to remove excess precursor gases, purging gases, and
by-product gases at the end of a purging sequence from gas conduit
270.
[0051] Vacuum pump, or exhaust pump, 482 is coupled by mass-flow
controller 487 to remove excess precursor gases, purging gases, and
by-product gases at the end of a purging sequence from reaction
chamber 420. Vacuum pumps 481, 482 may also be used in regulating
the pressure in reaction chamber 405. For convenience, control
displays, mounting apparatus, temperature sensing devices,
substrate maneuvering apparatus, and necessary electrical
connections as are known to those skilled in the art are not shown
in FIG. 4.
[0052] Gas-distribution fixture 445 provides a gas flow 440 that is
illuminated by a laser beam 430. Laser beam 430 may be rastered
across the surface of substrate 410 to provide specifically tuned
energy to gas flow 440 at or on the substrate surface. Alternately,
laser beam can provided substantially perpendicular to the gas flow
or at a selected angle with respect to gas flow 440. Laser source
may be mounted in reaction chamber 405. In an embodiment, laser
source 420 is mounted in reaction chamber such that laser beam 430
is provided in line with gas flow 440.
[0053] Various embodiments of a laser source 420 and laser control
circuitry 424 can be realized using embodiments as described with
respect to FIG. 3. In an embodiment, laser source 420 includes an
array of lasers having individual lasers, where the output
frequency for each laser is different than the other lasers in the
array. In an embodiment, each laser of laser source 420 is a diode
laser. Alternately, laser source 420 may include one or more
tunable lasers. In various embodiments, laser source 420 may
include other solid state lasers or gas lasers.
[0054] Laser source 420 having an array of lasers allows for
activating molecules at various frequencies specifically tuned to
an absorption frequency of a specifically selected molecule. Laser
control circuitry 425 regulates the intensity of the output of each
laser, which controls the amount of energy in the laser output at
its given frequency. Laser control circuitry 425 includes switching
circuitry to regulate the output of laser source 420. The switching
circuitry of laser control circuitry 425 regulates which lasers of
the laser array are on and which are off. On demand, the switching
circuitry of laser control circuitry 425 can switch one or more
lasers on while switching the remaining lasers off, from control
signals provided from or to laser control circuitry 425. With the
output of two or more lasers provided in the output of laser source
420, energy can be supplied to a gas flow at two or more specific
energies tuned to desired absorption frequencies within the gas
flow. In an embodiment, the frequencies to switch the laser beam
can be tuned includes at least one identified absorption frequency
for each of the gas precursors used in the ALD formation of a
material on a substrate. Since the purging gases are selected for
their non-reactive natural, laser source 420 is not required to
have an output frequency associated with the purging gases, though
it may, and can be placed in an off state during the gas purging
sequences of the ALD process.
[0055] Control optics 427 may also include optical filters and
attenuators. The spectral width of a laser beam 430 about its laser
frequency may include frequencies correlated to absorption
frequencies for gases in gas flow 440 other than the desired gas
precursor, or precursors, or frequencies correlated to an
absorption frequency of the gas precursors at which stimulation is
unwanted. Optical filters and optical attenuators can be used to
eliminate or significantly reduce stimulation of unwanted energy
absorption at frequencies different from the targeted
frequencies.
[0056] Those of ordinary skill in the art of semiconductor
fabrication understand the use, construction and fundamental
operation of reaction chambers for deposition of material layers.
Embodiments of the present invention may be practiced on a variety
of such reaction chambers without undue experimentation.
Furthermore, one of ordinary skill in the art will comprehend the
necessary detection, measurement, and control techniques in the art
of semiconductor fabrication upon reading and studying this
disclosure.
[0057] The elements of ALD system 400 of FIG. 4 and deposition
system 200 of FIG. 2 may be controlled by a computer. To focus on
the use of laser assisted point of activation processes and
apparatus in ALD system 400 and deposition system 200 in the
various embodiments of the present invention, the computer is not
shown. Those skilled in the art can appreciate that the individual
elements such as pressure control, temperature control, and gas
flow within these deposition systems may be under computer control
for management and regulation. Determination of the environmental
conditions, precursors used, purging gases employed, and pulse
periods for the precursors and purging gases may be made without
undue experimentation.
[0058] In an embodiment, a computerized method and the
computer-executable instructions for a method for laser assisted
point of use activation in the formation of materials on a
substrate includes controlling an environment of a reaction
chamber, a laser source, providing gas precursors, pulsing gas
precursors, and pulsing of purging gases, one for each precursor
gas and pulsing each purging gas after pulsing the associated
precursor gas. The computer-executable instructions may be provided
in any computer-readable medium. Such computer-readable medium may
include, but is not limited to, floppy disks, diskettes, hard
disks, CD-ROMS, flash ROMS, nonvolatile ROM, and RAM.
[0059] FIG. 5 illustrates a flow diagram of elements for an
embodiment of a method to form a material on a substrate by point
of use activation in laser assisted deposition of the material. In
this embodiment, the method includes selecting an absorption
frequency of a molecule of a gas reactant, at block 510, setting a
select frequency for a laser source correlated to the absorption
frequency, at block 520, and illuminating the gas reactant using
the laser source, at block 530.
[0060] In an embodiment, frequencies for a laser source are
selected to correspond to absorption frequencies for destabilizing
bonds in gas reactants used to form a material on a substrate. The
laser source is provided by using an array of lasers, where the
each laser is chosen such that its frequency corresponds to an
absorption frequency of one of the gas reactants used in the
deposition process. In an embodiment, for each precursor that is to
be activated, there corresponds at least one laser in a laser array
having a laser frequency correlated to an absorption frequency of
the given reactant. In an embodiment, a method includes using an
array of laser diodes. Alternately, the energy imparted to the gas
reactants can be applied using tunable lasers, other solid state
lasers, or gas lasers. In an alternate embodiment, a source
providing electromagnetic energy at a select target frequency, or
frequencies, with a narrow linewidths can used as a source to
irradiate the gas reactant, or reactants.
[0061] In an embodiment, the laser source is provided in a
configuration adapted to be attached and detachable from a reaction
chamber. For each deposition process involving a different set of
gas reactants to deposit different materials onto a substrate at
different stages of processing or in fabricating different systems
or devices, a different laser source is mounted to the reaction
chamber. Each newly attached laser source has an array of lasers
with frequencies correlated to the absorption frequencies to the
new set of gas reactants.
[0062] FIG. 6 illustrates a flow diagram of elements for an
embodiment of a method to form a material on a substrate by point
of use activation in laser assisted deposition of the material. In
this embodiment, the method includes measuring absorption
frequencies of one or more molecules of a gas flow, at block 610,
selecting an absorption frequency at which to activate a gas
precursor in the gas flow, at block 620, triggering a laser of a
laser array where the triggered laser has a frequency corresponding
to the selected absorption frequency, at block 630, and exposing
the gas flow with a laser beam from the triggered laser to deposit
a material on the substrate, at block 640.
[0063] In those embodiments in which the absorption frequencies of
the molecules used in a gas flow are known, measuring the
absorption frequencies of one or more molecules of a gas flow
includes looking up the absorption frequencies in a table for the
molecules used in the gas flow. Such a table can be realized in a
database when performed in a computerized manner. Specific energies
are imparted such that absorption of these energies is by
specifically targeted molecules in the gas flow in specific amounts
to activate the targeted molecules. In an alternate embodiment, the
gas flow is exposed to electromagnetic energy from a source having
filters and attenuators to provide the electromagnetic energy at a
select frequency and intensity to impart specifically targeted
amounts of energy.
[0064] An electronic device can be fabricated having a circuit
disposed on a substrate, where forming the circuit includes
depositing a material on the substrate by irradiating a gas
precursor with electromagnetic energy. The substrate may include,
but is not limited to, substrate materials such as silicon,
silicon-on insulator (SOI), silicon-on sapphire (SOS), silica,
ceramic, alumina, metals, organic materials, silicon-germanium,
germanium, or gallium arsenide. The electromagnetic energy at a
frequency tuned to an absorption frequency of the gas precursor
activates the targeted gas precursor to provide the necessary
energy to react with other gases in a reaction chamber or react
with a surface of the substrate to form the desired material.
Applying electromagnetic energy to different precursor gases
according to various embodiments in various process stages allows
for efficient construction of the structures for the electronic
device. Various electronic devices can be fabricated using
electromagnetic energy assisted deposition in accordance with
embodiments of the teachings of the present invention, such as
transistors, integrated circuits, memory devices, processors, and
electronic systems having a variety of electronic components.
[0065] FIG. 7 shows an embodiment of a transistor 700 constructed
using point of use activation in laser assisted deposition of one
or more materials on a substrate. Transistor 700 is constructed by
forming a source region 720 and a drain region 730 in a silicon
based substrate 710 where source and drain regions 720, 730 are
separated by a body region 732. Body region 732 defines a channel
having a channel length 734. A dielectric layer is disposed on
substrate 710 to form gate dielectric 740.
[0066] A gate 750 is formed over gate dielectric 740. Typically,
forming gate 750 may include forming a polysilicon layer, though a
metal gate may be formed in an alternative process. The sequencing
of the various elements of the process for forming a transistor,
including embodiments for point of use activation, is conducted
in-line with standard fabrication procedures, as known to those
skilled in the art. Other types of transistors including bipolar
transistors may be fabricated using various embodiments using point
of use activation in laser assisted deposition of one or more
materials on a substrate.
[0067] Transistors, capacitors, and other devices using methods
described herein may be implemented into memory devices and
electronic systems including information handling devices. Such
information devices may include wireless systems, telecommunication
systems, and computers. It will be recognized by one skilled in the
art that several types of memory devices and electronic systems
including information handling devices utilize embodiments of the
present invention.
[0068] FIG. 8 is a simplified block diagram for an embodiment of a
memory device 800 having one or more materials formed on a
substrate using point of use activation in laser assisted
deposition of the materials. Memory device 800 includes an array of
memory cells 802, address decoder 804, row access circuitry 806,
column access circuitry 808, control circuitry 810, and
input/output (I/O) circuit 812. The memory is operably coupled to
an external microprocessor 814, or memory controller for memory
accessing. Memory device 800 receives control signals from
processor 814, such as WE*, RAS* and CAS* signals, which can be
supplied on a system bus. Memory device 800 stores data that is
accessed via I/O lines. Each memory cell in a row of memory cell
array 802 is coupled to a common word line. The word line is
coupled to gates of individual transistors. At least one material
is deposited in the memory device structure using point of use
activation in laser assisted deposition of the material, in
accordance with the methods and apparatus previously described
herein. Additionally, each memory cell in a column is coupled to a
common bit line. Each cell in memory array 802 may include a
storage capacitor and an access transistor as is conventional in
the art. It will be appreciated by those skilled in the art that
additional circuitry and control signals can be provided, and that
the memory device of FIG. 8 has been simplified to focus on
embodiments of the present invention.
[0069] It will be understood that the above description of a memory
device is intended to provide a general understanding of the memory
and is not a complete description of all the elements and features
of a specific type of memory, such as DRAM (Dynamic Random Access
Memory). Further, embodiments are equally applicable to any size
and type of memory circuit and are not intended to be limited to
the DRAM described above. Other alternative types of devices
include SRAM (Static Random Access Memory) or Flash memories.
Additionally, the DRAM could be a synchronous DRAM commonly
referred to as SGRAM (Synchronous Graphics Random Access Memory),
SDRAM (Synchronous Dynamic Random Access Memory), SDRAM II, and DDR
SDRAM (Double Data Rate SDRAM), as well as Synchlink or Rambus
DRAMs and other emerging DRAM technologies.
[0070] FIG. 9 illustrates a block diagram for an embodiment of an
electronic system 900 having devices with one or more materials
formed on a substrate using point of use activation in laser
assisted deposition of the materials. Electronic system 900
includes a controller 905, a bus 915, and an electronic device 925,
where bus 915 provides electrical conductivity between controller
905 and electronic device 925. In various embodiments, controller
905 and/or electronic device 925 include an embodiment for one or
more materials formed on a substrate using point of use activation
in laser assisted deposition of the materials, as discussed herein.
In an embodiment, electronic system 900 includes a plurality of
electronic devices having one or more materials formed on a
substrate using point of use activation in laser assisted
deposition of the materials, according to the present invention.
Electronic system 900 may include, but is not limited to,
information handling devices, wireless systems, telecommunication
systems, fiber optic systems, electro-optic systems, and
computers.
[0071] Point of use activation in laser assisted deposition of
materials provides for specific control of energies imparted to
reacting chemical species providing enhanced control of the
temperature of the chemical species. In the various embodiments,
point of use activation provides heating essentially at localized
levels without the general heating of the gas precursor and other
gases, including carrier gases, in a gas flow. This specific
control provides for a reaction efficiency that may allow for
reduction in the consumption of source materials. This process may
also provide for faster control of reaction temperatures and may
provide for a significant reduction or elimination of by-products
associated with the chemical reactant that leads to the deposition
of a desired material on a substrate. Point of use activation also
allows for the use of chemistries that are sensitive to
conventional heating processes.
[0072] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement that is calculated to achieve the
same purpose may be substituted for the specific embodiments shown.
This application is intended to cover any adaptations or variations
of the present invention. It is to be understood that the above
description is intended to be illustrative, and not restrictive.
Combinations of the above embodiments, and other embodiments will
be apparent to those of skill in the art upon reviewing the above
description. The scope of the present invention includes any other
applications in which the above structures and fabrication methods
are used. The scope of the present invention should be determined
with reference to the appended claims, along with the full scope of
equivalents to which such claims are entitled.
* * * * *