U.S. patent application number 14/324907 was filed with the patent office on 2016-01-07 for method and apparatus for depositing a monolayer on a three dimensional structure.
The applicant listed for this patent is Varian Semiconductor Equipment Associates, Inc.. Invention is credited to Thomas R. Omstead.
Application Number | 20160002784 14/324907 |
Document ID | / |
Family ID | 55016608 |
Filed Date | 2016-01-07 |
United States Patent
Application |
20160002784 |
Kind Code |
A1 |
Omstead; Thomas R. |
January 7, 2016 |
METHOD AND APPARATUS FOR DEPOSITING A MONOLAYER ON A THREE
DIMENSIONAL STRUCTURE
Abstract
In one embodiment, a processing apparatus may include a plasma
chamber configured to generate a plasma; a process chamber adjacent
the plasma chamber and configured to house a substrate that defines
a substrate plane; an extraction system adjacent the plasma chamber
and configured to direct an ion beam from the plasma to the
substrate, the ion beam forming a non-zero angle with respect to a
perpendicular to the substrate plane; and a molecular chamber
adjacent the process chamber, isolated from the plasma chamber and
configured to deliver a molecular beam to the substrate, wherein
the ion beam and molecular beam are alternately delivered to the
substrate to form a monolayer comprising species from the ion beam
and molecular beam.
Inventors: |
Omstead; Thomas R.;
(Gloucester, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Varian Semiconductor Equipment Associates, Inc. |
Gloucester |
MA |
US |
|
|
Family ID: |
55016608 |
Appl. No.: |
14/324907 |
Filed: |
July 7, 2014 |
Current U.S.
Class: |
427/523 ;
118/719; 118/723MP |
Current CPC
Class: |
H01L 21/02274 20130101;
H01L 21/02636 20130101; H01L 21/02219 20130101; C23C 16/486
20130101; H01L 21/31116 20130101; H01J 37/32357 20130101; H01L
21/02167 20130101; H01L 21/225 20130101; C23C 16/50 20130101; H01L
21/02164 20130101; H01L 21/0228 20130101; H01L 21/2253 20130101;
C23C 16/52 20130101; H01L 21/0217 20130101; H01L 21/02112 20130101;
H01L 29/66803 20130101; H01L 21/02057 20130101; H01L 21/02211
20130101; H01L 21/324 20130101; H01L 21/2252 20130101; C23C
16/45551 20130101; C23C 16/45536 20130101; H01L 21/0226 20130101;
H01L 21/2225 20130101 |
International
Class: |
C23C 16/455 20060101
C23C016/455; C23C 16/48 20060101 C23C016/48 |
Claims
1. A processing apparatus, comprising: a plasma chamber configured
to generate a plasma; a process chamber adjacent the plasma chamber
and configured to house a substrate that defines a substrate plane;
an extraction system adjacent the plasma chamber and configured to
direct an ion beam from the plasma to the substrate, the ion beam
comprising ions that form a non-zero angle with respect to a
perpendicular to the substrate plane; and a molecular chamber
adjacent the process chamber, isolated from the plasma chamber and
configured to deliver a molecular beam to the substrate, wherein
the ion beam and molecular beam are alternately delivered to the
substrate to form a monolayer comprising species from the ion beam
and molecular beam.
2. The processing apparatus of claim 1, wherein the substrate is
moved back and forth to alternately expose the substrate to the ion
beam and to a molecular beam composed of silane (SiH.sub.4), arsine
(AsH.sub.3), phosphine (PH.sub.3), or diborane B.sub.2H.sub.6.
3. The processing apparatus of claim 1, further comprising a gas
source configured to deliver a reactive gas to the plasma chamber,
the reactive gas comprising at least one of: oxygen, nitrogen,
nitrous oxide.
4. The processing apparatus of claim 3 further comprising a bypass
to deliver the reactive gas from the gas source directly to the
process chamber without entering the plasma chamber.
5. The processing apparatus of claim 4 further comprising a heater
configured to heat the substrate to at least 300.degree. C. when
the reactive gas is delivered directly to the process chamber.
6. The processing apparatus of claim 1, wherein the process chamber
comprises a first sub-chamber adjacent the plasma chamber, and a
second sub-chamber adjacent the molecular chamber.
7. The processing apparatus of claim 6 further comprising a
substrate stage, wherein the substrate stage is configured to
transport the substrate between the first sub-chamber and second
sub-chamber through a seal that restricts gas communication first
sub-chamber and second sub-chamber.
8. The processing apparatus of claim 1 further comprising a rotary
substrate stage wherein the rotary substrate stage is disposed
within the process chamber and configured to move the substrate
from a first position adjacent the plasma chamber to a second
position adjacent the molecular chamber.
9. The processing apparatus of claim 8 wherein the extraction
system comprises an extraction aperture having a wedge shape,
wherein the molecular chamber comprises a set of injectors that
define a wedge shape.
10. The processing apparatus of claim 8 wherein the plasma chamber
defines a wedge shape and molecular chamber defines a wedge shaped
chamber.
11. The processing apparatus of claim 8 wherein the substrate stage
is configured to hold a plurality of substrates.
12. The processing apparatus of claim 1 further comprising a second
plasma chamber configured to deliver second ion species and a
second molecular chamber configured to deliver second molecular
species.
13. The processing apparatus of claim 1, wherein the plasma
chamber, molecular chamber and process chamber are arranged in a
rotary chamber assembly, wherein the substrate is configured to
rotate between a first position adjacent the plasma chamber and a
second position adjacent the molecular chamber.
14. The processing apparatus of claim 13, further comprising a
rotary substrate stage comprising a plurality of substrate holders
and a plurality of pumping slots, wherein the rotary substrate
stage is disposed within the process chamber.
15. The processing apparatus of claim 13, wherein the ion beam is a
first ion beam, the plasma chamber is a first plasma chamber, and
the molecular chamber is a first molecular chamber, wherein the
rotary chamber assembly comprises: a second plasma chamber; a
second molecular chamber; and an extraction system adjacent the
first plasma chamber and the second plasma chamber, the extraction
system comprising a first extraction aperture that is coupled to
the first plasma chamber to direct the first ion beam to the
substrate, and a second extraction aperture that is coupled to the
second plasma chamber to direct a second ion beam to the
substrate.
16. The processing apparatus of claim 1, wherein the extraction
system comprises an extraction aperture that generates the ion
beam, the extraction aperture configured to modify a shape of a
plasma sheath boundary adjacent the extraction aperture, wherein
the ions exit the plasma sheath boundary at the non-zero angle.
17. A method, comprising: providing a substrate in a first
position, the substrate having a surface that defines a substrate
plane and a substrate feature that extends from the substrate
plane, the substrate feature having at least one surface that
extends at a non-zero angle with respect to the substrate plane;
directing an ion beam through an extraction system adjacent the
substrate while in the first position, the ion beam comprising
angled ions that are incident on the substrate at a non-zero angle
with respect to a perpendicular to the substrate plane, the ion
beam effective to form a first sub-monolayer comprising a first
species on the substrate feature including the at least one
surface; and directing a molecular beam to the substrate when the
substrate is in a second position when the first sub-monolayer is
disposed on the substrate feature, the molecular beam being
effective to form a second sub-monolayer of a second species that
is configured to react with the first sub-monolayer of the first
species to form a monolayer of a product material on the substrate
feature including the at least one surface.
18. The method of claim 17, further comprising transporting the
substrate from the first position, wherein the substrate is in a
first sub-chamber of a process chamber in the first position and
the substrate is in a second sub-chamber of the process chamber in
the second position that is isolated from the first sub-chamber.
Description
FIELD
[0001] The present embodiments relate to substrate processing, and
more particularly, to processing apparatus and methods for
depositing layers by atomic beam or molecular beam deposition.
BACKGROUND
[0002] Many devices including electronic transistors may have three
dimensional shapes that are difficult to process using conventional
techniques. The topology of such devices may be up-side down,
re-entrant, over-hanging, or vertical with respect to a substrate
plane of a substrate in which such devices are formed. In order to
process such devices such as to grow layers on such topology,
improved techniques may be useful that overcome limitations of
conventional processing. For example, doping of substrates is often
performed by ion implantation in which substrate surfaces that may
be effectively exposed to dopant ions are limited by line-of-site
trajectories of the ions. Accordingly, vertical surfaces,
re-entrant surfaces, or over-hanging surfaces may be inaccessible
to such dopant ions. It is with respect to these and other
considerations that the present improvements have been needed.
SUMMARY
[0003] This Summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the Detailed Description. This Summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended as an aid in determining the scope of the
claimed subject matter.
[0004] In one embodiment a processing apparatus may include a
plasma chamber configured to generate a plasma; a process chamber
adjacent the plasma chamber and configured to house a substrate
that defines a substrate plane; an extraction system adjacent the
plasma chamber and configured to direct an ion beam from the plasma
to the substrate, the ion beam comprising ions that form a non-zero
angle with respect to a perpendicular to the substrate plane; and a
molecular chamber adjacent the process chamber, isolated from the
plasma chamber and configured to deliver a molecular beam to the
substrate, wherein the ion beam and molecular beam are alternately
delivered to the substrate to form a monolayer comprising species
from the ion beam and molecular beam.
[0005] In a further embodiment a method may include providing a
substrate in a first position, the substrate having a surface that
defines a substrate plane and a substrate feature that extends from
the substrate plane, the substrate feature having at least one
surface that extends at a non-zero angle with respect to the
substrate plane; directing an ion beam through an extraction system
adjacent the substrate while in the first position, the ion beam
comprising angled ions that are incident on the substrate at a
non-zero angle with respect to a perpendicular to the substrate
plane, the ion beam effective to form a first sub-monolayer
comprising a first species on the substrate feature including the
at least one surface; and directing a molecular beam to the
substrate when the substrate is in a second position when the first
sub-monolayer is disposed on the substrate feature, the molecular
beam being effective to form a second sub-monolayer of a second
species that is configured to react with the first sub-monolayer of
the first species to form a monolayer of a product material on the
substrate feature including the at least one surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A depicts a side view of a processing apparatus in one
mode of operation for delivering ion beams to a substrate according
to embodiments of the disclosure;
[0007] FIG. 1B depicts the processing apparatus of FIG. 1A in
another operation mode for delivering a molecular beam to a
substrate;
[0008] FIG. 1C depicts a close-up of the operation of FIG. 1A;
[0009] FIG. 1D depicts a close-up of the operation of FIG. 1B;
[0010] FIG. 2A depicts a top plan view of a processing system
according to additional embodiments of the present disclosure;
[0011] FIG. 2B depicts a top plan view of an exemplary substrate
stage that may be implemented in the processing system of FIG.
2A;
[0012] FIG. 3 depicts an exploded isometric view of a processing
apparatus according to embodiments of the disclosure;
[0013] FIG. 4A to FIG. 4F depict an embodiment of the disclosure
that details exemplary operations involved in a method for forming
a multi-layer stack on three dimensional features using
monolayer-by-monolayer growth;
[0014] FIG. 5A to FIG. 5D depict details of a method for performing
monolayer doping on a three dimensional structure according to
embodiments of the disclosure; and
[0015] FIG. 6 provides a summary of representative conformal
layers, ion beam constituents, and molecular beam constituents
consistent with different embodiments of the disclosure.
DETAILED DESCRIPTION
[0016] The present embodiments are related to apparatus and
techniques for processing a substrate including forming thin layers
on surface features of a substrate. The surface features of the
substrate may extend from a substrate plane, and may form such
structures as three dimensional lines, fins, pads, pillars, walls,
trenches, holes, domes, bridges, cantilevers, other suspended
structures, and the like. The embodiments are not limited in this
context. Moreover, these features may be collectively or
individually referred to herein as a "three dimensional" feature or
features. A thin layer that is formed on a substrate feature may be
a layer provided for doping, insulation, for encapsulation, or for
other purposes.
[0017] In various embodiments, novel apparatus and systems are
presented that facilitate growth and etching of thin layers on
three dimensional features of a substrate. The apparatus of the
present embodiments may apply multiple processes to carry out
doping of a three dimensional feature. Included among these
processes are a modified atomic layer deposition or by modified
molecular layer deposition process, which techniques may share
characteristics common to conventional atomic layer deposition
(ALD) or conventional molecular layer deposition (MLD) except where
otherwise noted. The present embodiments provide novel improvements
over conventional ALD and MLD that facilitate formation on three
dimensional surface features in which surface topography may be
severe, such as that described above.
[0018] In some embodiments, processes that involve formation of a
doping layer using ALD or MLD, may include a series of operations
that form multiple layers on substrates that may include three
dimensional features. In addition, the formation of each layer may
involve multiple operations such as those characteristic of an ALD
or MLD process. In one implementation for doping a substrate using
a deposited layer formed by ALD or MLD, a surface of the substrate
feature may first be cleaned to remove native oxide, which may
involve providing a plasma using such species as hydrogen, oxygen,
and/or ammonia radicals and molecular hydrides such nitrogen
triflouride, arsine, and phosphine.
[0019] Secondly, a conformal plasma enhanced atomic layer
deposition of dopant oxides may be performed to form a dopant oxide
layer on a surface feature. This ALD process may involve deposition
of species that include arsenic, boron, phosphorus, arsenic oxide,
phosphorus oxide, boron oxides and/or doped silicon oxides such as
silicon arsenic oxide, silicon phosphorus oxide, and silicon boron
oxides. In particular, these oxides may be deposited using
molecular precursors such as arsine, phosphine, and diborane
together with plasma-generated atomic beams that contain a reactive
gas such as hydrogen, oxygen, nitrogen, and/or ammonia.
[0020] In a subsequent operation, a sealing or encapsulating layer
such as silicon nitride may be deposited using a combination of a
molecular beam containing silane, for example, and another beam
containing nitrogen, hydrogen, and/or ammonia. Once the native
oxide is removed from a substrate feature to be doped and the dual
layer of dopant oxide and sealing nitride is deposited dopants from
the dopant oxide layer may be driven into the substrate feature
using a known technique such as rapid thermal annealing.
[0021] In various embodiments of the disclosure, a layer or
plurality of layers may be deposited on a substrate or etched from
a substrate using a combination of angled ions and molecular beams,
where the molecular beams may comprise undissociated molecules in
some implementations. The directing of angled ions may be used in
conjunction with other operations to create novel ALD or MLD
processes that grow a layer or plurality of layers on a three
dimensional substrate feature without the use of a mask. As used
herein, unless otherwise noted or qualified by the context, the
term "layer" may refer to a sub-monolayer, a monolayer of a
material, or may refer to a thin coating or film that has the
thickness of many monolayers. Thus, in some instances, a grown
"layer" may be composed of a single monolayer that is formed over
target portions of a substrate or may be composed of multiple
monolayers. Moreover, consistent with various embodiments of the
disclosure, a layer that has the thickness of many monolayers may
be formed in a monolayer-by-monolayer-by-monolayer fashion as in
conventional ALD or MLD processes. However, the present embodiments
also cover growth of layers having the thickness of multiple
monolayers in which a layer is not grown in a
monolayer-by-monolayer fashion.
[0022] In various embodiments, novel multichamber apparatus and
systems are disclosed that facilitate rapid processing of
substrates using a combination of angled ions and molecular beams.
These apparatus may in particular minimize cross-contamination
between different sources of ions or molecules used to process a
substrate.
[0023] Formation of a layer comprising a product material by an ALD
or MLD process may involve deposition of one monolayer at a time of
the product material. Each monolayer of the product material may
include two or more different elements that together form a
compound material, an alloy, or other multielement material such as
silicon oxide, silicion nitride, doped oxides, or other material.
The formation of a given monolayer may be accomplished by
deposition of a sub-monolayer of a first species or component
followed by providing a second sub-monolayer of a second species
that reacts with the first sub-monolayer to form a monolayer of the
compound. Thus, as used herein the term "sub-monolayer" may denote
a layer of a first element that may react with a layer of a second
element to form a monolayer of the compound. For example, during
deposition of a binary compound such as silicon oxide the layer to
be formed is deposited by the repetition of two different
half-cycles. After each half-cycle, a fixed amount of reactive
species supplied by a first precursor remains on the substrate
surface. Ideally, though not necessarily, a single monolayer of a
first species may be produced after a first half cycle. In the
present context, this single monolayer of a first species of a
compound to be formed is referred to as a "sub-monolayer" because
the full monolayer of the compound requires the addition of second
species to react with the first species. Thus, atoms of the
sub-monolayer of first species may be reacted with atoms or
molecules of the second species supplied in the next half cycle. In
each half-cycle, subsequent to supplying a given species, a purge
can be performed to remove any unreacted species of the depositing
material. The total amount of material reacted in a cycle may thus
be equivalent to a sub-monolayer of each of the first species or
second species.
[0024] The present embodiments provide novel apparatus that are
effective to fabricate layers, films or coatings in a
monolayer-by-monolayer fashion, including on three dimensional
structures, in a manner that may provide more uniform layer
thickness over different surfaces of a three dimensional structure
as compared to that achieved by conventional ALD processes.
[0025] FIG. 1A depicts a processing apparatus 100 arranged
according to various embodiments of the disclosure. The processing
apparatus 100 may be employed in particular to grow or etch a layer
employed to etch and deposit multiple different materials on a
three dimensional structure. As detailed below, this capability may
be particularly suitable to perform a novel doping process for
doping of a three dimensional structure that may entail deposition
of multiple materials as well as etching of at least one layer. In
turn, the deposition of each material may entail multiple
operations that are performed using a combination of ion beams
containing angled ions as well as molecular beams.
[0026] As shown in FIG. 1A the processing apparatus 100 may include
a plasma chamber 102 that may be used to generate angled ions to be
provided to a substrate 124, which is held or supported by the
substrate stage 111 as shown. As further shown in FIG. 1A, the
processing apparatus 100 includes a process chamber 106 that is
adjacent the plasma chamber 102 and in communication with the
plasma chamber 102. In operation, the plasma chamber 102 may
deliver angled ions to the substrate 124 in the form of an ion beam
122 when the substrate 124 is disposed adjacent the plasma chamber
102. The use of angled ions is discussed in more detail below.
However, in brief, the term "angled ions" as used herein refers to
an assemblage of ions such as ions in an ion beam, at least some of
which are characterized by trajectories that have a non-zero angle
of incidence with respect to a perpendicular to a plane P of
substrate 124, as illustrated in FIG. 1C. For example, with
reference to the Cartesian coordinate system shown, angled ions may
have trajectories that form a non-zero angle with respect to the
Z-axis.
[0027] The processing apparatus 100 also includes a plasma source
114, which may include a power supply and applicator or electrode
to generate a plasma according to known techniques. For example,
the plasma source 114, in various embodiments, may be an in situ
source or remote source, an inductively coupled plasma source,
capacitively coupled plasma source, helicon source, microwave
source, arc source, or any other type of plasma source. The
embodiments are not limited in this context. When gas is supplied
by gas source 116 to the plasma chamber 102 the plasma source 114
may ignite a plasma that provides angled ions to the substrate 124
as discussed below. In some embodiments, such as apparatus that
uses an inductively coupled source, the angled ions may be formed
from molecular species such as oxygen or nitrogen, and may be
highly fractionated such that the angled ions are predominantly
atomic ions. However, the embodiments are not limited in this
context. The processing apparatus also may include a bypass 119 so
that gas from the gas source 116 is fed directly to the process
chamber 106. This may be used when the substrate 124 is heated by a
heater 125 to a higher temperature such as 400-700.degree. C. Under
such circumstances gas such as nitrogen, ammonia, or oxygen may
react with a substrate without being ionized.
[0028] In various embodiments, the gas pressure in a process
chamber such as the process chamber 106 may be maintained below 50
mTorr in order to minimize or eliminate gas phase collisions of
ions in the ion beam 122 before the ions strike the substrate 124.
This allows the angle of ions that are extracted from the plasma
chamber to be controlled and maintained so that angle(s) of
incidence of ions in an ion beam directed to the substrate 124 may
be tailored for a desired result. As discussed in more detail, in
various embodiments the substrate 124 may be scanned parallel to
Y-axis with respect to the plasma chamber 102 either in a single
direction, or back and forth, in order to provide uniform
deposition of a layer or etching of a layer over an entire
substrate, such as substrate 124.
[0029] As further shown in FIG. 1A, the processing apparatus 100
includes a molecular chamber 104. The molecular chamber 104 may
transport, for example, molecular gas that is received from a
molecular source 118. The molecular chamber 104 may provide the
molecular gas to the substrate 124 in the form of a molecular beam
128 for reaction with species such as angled ions provided by the
plasma chamber 102. As further illustrated in FIG. 1B, the
substrate stage 111 may be movable in a manner that transports the
substrate 124 from a first position adjacent the plasma chamber 102
(FIG. 1A) to a second position adjacent the molecular chamber
104.
[0030] In some embodiments, and as illustrated in FIG. 1A, a baffle
or wall 112 may be provided in the process chamber 106, which may
divide the process chamber 106 into a sub-chamber 108 adjacent the
plasma chamber 102 and sub-chamber 110 adjacent the molecular
chamber 104. The substrate stage 111 may be configured to engage
the wall 112 such that the substrate stage 111 and wall 112 isolate
sub-chamber 110 from the sub-chamber 108. In some implementations a
small gap may remain between the wall 112 and the substrate stage
111. However, the wall 112 may be hollow such that the wall 112 may
be differentially pumped by a pump (not shown) to evacuate gas 115
as illustrated. This gas may be either species from the plasma
chamber 102 that are present in sub-chamber 108 when the substrate
124 is exposed to the ion beam 122, or species that are present in
the sub-chamber 110 when the substrate is exposed to the molecular
beam 128. The wall 112 may accordingly prevent unwanted deposition
by blocking flow of molecular species such as SiH.sub.4, AsH.sub.3,
and the like, from sub-chamber 110 into sub-chamber 108. The wall
112 may also prevent plasma formed by the plasma chamber 102 from
extending into the sub-chamber 110,
[0031] In one implementation the substrate stage 111 may be movable
back and forth between the positions shown in FIGS. 1A and 1B such
that the substrate 124 may be exposed multiple times to the ion
beam 122 and molecular beam 128. This provides an efficient manner
to deposit a monolayer or plurality of monolayers of a desired
material on a three dimensional substrate.
[0032] FIG. 1C depicts a close-up of certain components shown
during the operation in FIG. 1A in which an ion beam 122 is
directed to the substrate 124, while FIG. 1D depicts a close-up of
the operation of FIG. 1B in which the molecular beam 128 is
provided to the substrate 124. As shown in FIG. 1B, the processing
apparatus 100 includes an extraction plate 120 containing an
extraction aperture 126 that provides a path for ions in the plasma
chamber 102 to traverse to the sub-chamber 108. In the instance
shown in FIG. 1C, a plasma 130 is present in the plasma chamber
102. When a voltage supply 148 (shown in FIG. 1A) provides an
extraction voltage between the plasma chamber 102 and substrate
stage 111, the ion beam 122 may be extracted from the plasma 130
and accelerated to the substrate 124. In some instances an
extraction voltage between 0 and 500 V may be applied to impart
energy to ions of the ion beam 122 sufficient to generate surface
reactions including attachment of ion species on a substrate
surface, but below an energy in which significant sub-surface ion
implantation takes place.
[0033] As shown in FIG. 1C, the substrate 124 may be provided with
three dimensional features such as substrate features 132. Notably,
the various components may not be drawn to scale, particularly in
the illustration of FIG. 1C. For example, features such as the
extraction aperture 126 may have dimensions on the order of
millimeters or centimeters, while the substrate features 132 may
have dimensions on the order of micrometers or nanometers in some
cases. As further shown in FIG. 1C, the extraction aperture 126 may
cause the plasma sheath boundary 140 to assume a curved shape
adjacent the extraction aperture, which may result in ions of the
ion beam 122 exiting the plasma 130 with trajectories that are
spread over a range of angles of incidence. The ion beam 122 may in
particular include angled ions that are effective to treat the
different surfaces of the substrate features 132, including
sidewalls of the substrate features 132, which may extend at an
angle relative the substrate plane P. Such sidewalls may not be
effectively treated by ions that are directed along the
perpendicular to the substrate plane P.
[0034] It is to be noted that although the ion beam 122 is shown in
FIG. 1C as having three trajectories the ion beam may be
characterized by an ion angular distribution. The term "ion angular
distribution" refers to the mean angle of incidence of ions in an
ion beam with respect to a reference direction such as a
perpendicular to a substrate, as well as to the width of
distribution or range of angles of incidence centered on the mean
angle, termed "angular spread" for short. In some examples, the ion
angular distribution may be a single mode in which the peak in
number of ions as a function of incidence angle is centered on a
perpendicular to the plane P. In other examples, the ion angular
distribution may involve a mean angle that forms a non-zero angle
with respect to a perpendicular to the plane P of the substrate
124. In particular examples, the ion angular distribution of ion
beam 122 may be a bimodal distribution of angles of incidence. For
example, the ion beam 122 may have trajectories where the greatest
number of trajectories are centered at two angular modes. In
various embodiments, by controlling apparatus settings such as
plasma power, plasma chamber pressure, and so forth, the separation
between peaks of a bimodal distribution may be varied. For example,
the peak angles may set at angles between +/-15 degrees with
respect to perpendicular to +/-45 degrees with respect to
perpendicular in various embodiments, and in one particular
embodiment at +/-30 degrees with respect to perpendicular to the
plane P. In some implementations a beam blocker (not shown) may be
positioned inside a plasma chamber adjacent an extraction aperture,
which may have the effect of creating a pair of angled ion beams
that may constitute a bimodal distribution of ions.
[0035] Referring also to FIGS. 1A and 1B it is further to be noted
that the extraction aperture 126 may be elongated in the
X-direction to cover an entire substrate, such as substrate 124, in
that direction. Accordingly, the ion beam 122 may be directed over
the entire substrate to provide uniform ion flux to the substrate
by scanning the substrate stage 111, for example, in a continuous
manner along the Y-direction while the substrate 124 is adjacent
the extraction aperture 126. Moreover, once the substrate 124 is
located in the sub-chamber 110 and adjacent the molecular chamber
104, the molecular beam 128 may in some implementations be
sufficiently large that the entire substrate 124 may remain
stationary and still be exposed to uniform molecular flux.
[0036] In some examples, the ion beam 122 may be composed of
reactive ions such as atomic oxygen or atomic nitrogen ions. In
other examples, the ion beam 122 may be composed molecular oxygen
ions or molecular nitrogen ions, or may be composed of mixtures of
atomic oxygen ions and molecular oxygen ions, or mixtures or
molecular nitrogen ions and atomic nitrogen ions. The embodiments
are not limited in this context.
[0037] As shown in FIG. 1C the ion beam 122 may be effective to
generate a sub-monolayer 134 that covers the three dimensional
surfaces of the substrate 124 including the substrate features 132.
In various implementations the exact ion angular distribution of
the ion beam 122 may be adjusted by adjusting any combination of
the aforementioned parameters such as plasma power, gas pressure,
extraction voltage, aperture size, or other parameters. This may be
useful to tailor the treatment of surfaces such as sidewalls 144,
trench bottoms 142, or other parts of a three dimensional feature
in order to ensure proper exposure of those surface to ions of the
ion beam 122. This may result in deposition of a uniform
sub-monolayer, shown as the sub-monolayer 134.
[0038] Turning now to FIG. 1D there are shown details of a gas
plate 129 that is disposed between the molecular chamber 104 and
sub-chamber 110. The gas plate 129 may include multiple apertures
136 that allow gas to stream out of the molecular chamber 104 and
form the molecular beam 128. The molecular beam 128 may include
molecular species that are effective to react with the
sub-monolayer 134 to form a product monolayer, shown as the
monolayer 138 as shown. Together, the sequence of operations shown
in FIGS. 1B and 1D may constitute a process cycle that is used to
form a layer of a material, such as a conformal monolayer of a
nitride or a dopant oxide on a three dimensional feature. In
implementations for doping of a substrate, for example, this
sequence of operations may be repeated a desired number of times to
deposit multiple monolayers according to the target level of doping
and depth of dopants. However, in some embodiments a single
monolayer of dopant oxide may be sufficient to generate a target
doping profile in a substrate.
[0039] FIG. 2A depicts a processing system 200 arranged according
to further embodiments of the disclosure. The processing system 200
may be employed for high throughput processing of substrates having
three dimensional features including ALD or MLD type processes. The
processing system 200 includes a load station 210, which may be
used to load substrates 224 for processing in various stations or
apparatus within the processing system 200, which may take place
under vacuum conditions. After loading in the load station 210, the
substrates 224 may be transferred by a robot 222 in a transfer
chamber 220 to a preclean station 230. The preclean station 230 may
include at least one plasma chamber, shown as plasma chamber 232,
which may be configured similarly to the plasma chamber 102. In
particular, the plasma chamber 232 may direct angled ions such as
nitrogen ions to clean surfaces of a substrate 224 including three
dimensional features. In the case in which the substrate is a
semiconductor material, this may be effective in removing oxide
from the surface. In addition, substrates 224 may be heated to
drive off other impurities.
[0040] The processing system 200 further includes a rotary chamber
assembly 240 which may process the substrates 224 through multiple
operations. The rotary chamber assembly 240 may perform a combined
molecular and atomic beam deposition (MABD) processes that entails
exposure to both angled ions from an ion beam and a molecular beam.
The angled ions and molecular beam may be provided to a substrate
in a manner similarly to that depicted in FIGS. 1A to 1D except as
otherwise noted. As illustrated in FIG. 2, the rotary chamber
assembly 240 may include a plurality of plasma chambers, shown as
plasma chambers 242 that may be disposed around an axis A that lies
parallel to the Z-axis as shown. The plasma chambers 242 may be
configured to generate the same type of ions as one another or
different ions according to alternative implementations.
[0041] From the perspective of FIG. 2A, ions that form in the
plasma chambers 242 may be extracted through extraction apertures
244 and directed toward substrates that lie below the extraction
apertures 244 (into the page). The extraction apertures 244 may be
elongated and may additionally be aligned such that their long axes
lie along the radii R that extend from the center of the rotary
chamber assembly 240. As noted previously, the gas pressure in a
chamber or region that houses substrates may be maintained below 50
mTorr to avoid gas phase collisions of ions that are directed
through the extraction apertures 244 to a substrate, which allows
the ion angular distribution generated by the extraction aperture
244 to be maintained when the ions impact a substrate.
[0042] FIG. 2B depicts a top plan view of an exemplary substrate
stage, shown as substrate stage 260, that may be implemented in the
processing system 200 of FIG. 2A. The substrate stage 260 may
include a plurality of recesses 262 configured to hold a plurality
of substrates 224. As also shown in FIG. 2B, the substrate stage
260 may be configured to rotate around the axis A such that a
substrate 224 may be rotatably scanned under an extraction aperture
244. In this manner, an entire substrate may be sequentially
exposed to angled ions from a narrow ion beam that is received from
a plasma chamber 242, even though the extraction aperture 244 (see
FIG. 2A) and ion beam may be much narrower than a diameter of the
substrate 224 in the direction perpendicular to R.
[0043] As further shown in FIG. 2A, the rotary chamber assembly 240
may include a plurality of injectors or gas apertures 246 that may
also extend radially from a center of the rotary chamber assembly.
These gas apertures 246 may provide narrow molecular beams to a
substrate 224 as the substrate is scanned under a given gas
aperture 246. In various embodiments, the molecular beams may
include such materials as beam composed of silane (SiH.sub.4),
arsine (AsH.sub.3), phosphine (PH.sub.3), or diborane
(B.sub.2H.sub.6), which are configured to cover a surface of the
substrates 224 and react with species provided by the plasma
chamber(s) 242.
[0044] FIG. 2A additionally illustrates an embodiment in which the
gas apertures 246 and extraction apertures 244 are wedge shaped
such that a gas aperture 246 or extraction aperture 244 is wider at
larger radial distances from a center of the rotary chamber
assembly 240. This allows the rotary chamber assembly 240 to
deliver a more uniform flux of molecules or angled ions across
different portions of a substrate 224 regardless of their radial
position when the substrate 224 is rotated under a given extraction
aperture 244 or gas aperture 246.
[0045] As further depicted in FIG. 2A, the processing system 200
includes an annealing station 250 which may perform annealing of
substrates 224 after the substrates 224 are coated with one or more
desired layers.
[0046] FIG. 3 depicts a variant of a rotary chamber assembly 302
according to various additional embodiments of the disclosure. The
rotary chamber assembly 302 includes a source assembly 304 that
contains a plurality of different sources. For simplicity, the
sources are shown as simple three dimensional wedge shapes. The
sources of source assembly 304 may represent at least one plasma
chamber and molecular chamber. In some embodiments, a plasma
chamber may be disposed adjacent a molecular chamber. For example,
source 306 may be a plasma chamber and source 308 may be a
molecular chamber, and so forth.
[0047] As further shown in FIG. 3, the rotary chamber assembly 302
includes a top plate 310, which may support the source assembly
304, and may include a plurality of apertures 312 that provide
communication from a given source to a substrate below. Apertures
in the top plate 310 that are coupled to a plasma chamber may be
configured to generate angled ions as described above.
[0048] As also shown in FIG. 3, the top plate 310 is configured to
engage a bottom plate 330. When assembled the top plate 310 and
bottom plate 330 may define a process chamber. A rotary substrate
stage 320 is provided that is configured to rotate around the
Z-axis with respect to the top plate 310 and source assembly 304.
The rotary substrate stage 320 may include a plurality of
individual substrate holders, shown as the substrate holders 322,
which may be used to hold substrates 326. In this manner, when the
rotary substrate stage rotates, the substrates 326 may be scanned
under plasma chamber(s) and molecular chamber(s) to generate a
monolayer-by-monolayer deposition, in one example. The substrate
holders 322 may be clamping chucks or electrostatic chucks, and may
additionally be equipped with heating capability in some
embodiments. For example, the substrate holders 322 may be heated
to at least 300.degree. C. in some instances. These substrate
holders 322 may be slightly recessed below other portions of the
rotary substrate stage 320.
[0049] The rotary substrate stage 320 may also be equipped with
pumping slots 324, which may be disposed adjacent to substrate
holders 322 as shown. The pumping slots 324 may provide a pumping
path for pumping apparatus (not shown) to evacuate gas species
received at an individual substrate holder 322 to provide isolation
between substrates receiving plasma (ion) treatment and those
receiving molecular gas exposure. This may be aided by the recessed
position of the substrate holders 322. In particular, the entrance
of pumping slots 324 may be raised with respect to a plane of the
substrate holders 322, which may form a differentially pumped wall
that is adjacent a given substrate holder 322.
[0050] As noted above, the apparatus of the present embodiments may
generate novel deposition techniques that provide improved
processing of substrates having three dimensional structures to be
processed. Although atomic layer deposition processes have been
employed previously, the present embodiments provide advantages
over conventional apparatus, which may not be ideally suited for
treating substrates having surfaces features that include vertical
or reentrant sidewalls, deep trenches, or other severe topology. By
maintaining low pressure adjacent a substrate that is below, for
example, 50 mTorr, angled ions may be extracted and delivered in a
collisionless ion beam to a substrate over a desired angular ion
distribution. For applications that entail ALD/MLD to deposit films
for doping three dimensional features, various embodiments employ
at least one operation that is configured to tailor the angle(s) of
incidence of ions provided to a substrate to be coated. This allows
a three dimensional substrate feature to be more uniformly coated
with a sub-monolayer of a given species using angled ions to
provide the given species to the substrate feature.
[0051] FIG. 4A to FIG. 4F depict an embodiment of the disclosure
that details exemplary operations involved in a method for forming
a multi-layer stack on three dimensional features using
monolayer-by-monolayer growth.
[0052] In FIG. 4A there is shown a substrate 402 that includes a
plurality of substrate features 404 that extend above a plane P of
the substrate 402. In one example, the substrate features 404 may
be fins of a finFET device to be fabricated. The substrate features
404 may have a surface layer 406, which may be a native oxide or
chemical oxide composed predominantly of silicon oxide, which is to
be removed before substrate doping is performed.
[0053] In a subsequent set of operations shown in FIG. 4B, the
substrate 402 is treated to remove the surface layer 406. In
particular, the substrate 402 may be scanned back and forth to
receive alternate exposure from an ion beam 416 that may be
extracted from the plasma chamber 102, and a molecular beam 418
that may be provided by the molecular chamber 104. In particular
implementations, the ion beam 416 may contain atomic nitrogen and
hydrogen ions that are created when from ammonia gas (NH.sub.3) is
provided to the plasma chamber 102. The molecular beam 418 may
comprise a beam of nitrogen triflouride (NF.sub.3) which is
activated to remove the native oxide layer, surface layer 406, by
the presence of a sub-monolayer (not shown) of atomic hydrogen
received in the ion beam 416.
[0054] Turning now to FIG. 4C there is shown a further instance in
which the substrate 402 is treated to form a dopant layer or dopant
oxide layer, shown as layer 420. In particular, the substrate 402
may be scanned back and forth to receive alternate exposure from an
ion beam 422 that may be extracted from the plasma chamber 102, and
a molecular beam 424 that may be provided by the molecular chamber
104. In a first operation, a hydrogen, ammonia, or
nitrogen/hydrogen plasma may be generated in the plasma chamber
102, which is used to form the ion beam 422. In particular, the ion
beam 422 supplies atomic hydrogen angled ions to the substrate 402.
The substrate 402 is moved back and forth to alternately expose it
to the ion beam 422 and molecular beam 424, which may be composed
of silane (SiH.sub.4), arsine (AsH.sub.3), phosphine (PH.sub.3),
diborane B.sub.2H.sub.6, or other molecular gases, depending upon
the type of dopant oxide layer to be formed. The molecular gase(s)
may be effective to react with the atomic hydrogen to form a
monolayer of a given material such as a semiconductor dopant.
[0055] In one particular example, the alternate exposures to the
ion beam 416 and molecular beam 418 deposit a layer of arsenic
material that is formed in a monolayer-by-monolayer fashion, and is
highly conformal on the substrate features 404. This may be
represented by the layer 420 shown in FIG. 4C. Depending upon
whether oxygen is supplied in addition to or instead of hydrogen in
the plasma chamber 102 to form the ion beam 416, the layer 420 may
be a dopant oxide layer. As noted above, the operations outlined in
FIG. 4C may be accelerated and modified by the use of a pulsed DC
or continuous substrate bias.
[0056] Moreover, by adjusting the gas flows, movement rate of
substrate 402, beam angle, gas pressure, substrate temperature, and
other parameters, a wide range of composition may be imparted into
a doped oxide film represented by the layer 420. The composition of
the layer 420 may range, for example, from pure arsenic oxide, to
silicon oxide doped with arsenic, to pure silicon oxide. In
addition multi-layers and gradients of doped nitrides oxides may be
deposited in a similar fashion. Because angled ions may be tailored
according to the geometry of the substrate features 404, such
dopant layers can be deposited with a high degree of uniformity and
control on different surfaces of the substrate features 404.
[0057] Turning now to FIG. 4D, there is shown a further instance in
which the substrate 402 is treated to form a silicon nitride layer
that may act as a sealing layer on top of the layer 420. This is
shown as the sealing layer 426. This layer may help drive dopants
from the layer 420 into the substrate 402. A nitrogen, ammonia, or
nitrogen/hydrogen plasma may be created in the plasma chamber 102
to form an ion beam 422 that contains nitrogen ions including
atomic nitrogen, which impinges on the substrate 402. Silane or a
similar gas may be introduced without plasma power in the molecular
chamber 104, to generate a molecular beam 430. The substrate 402
may then be moved back and forth under the atomic nitrogen beam,
that is, ion beam 428, and the molecular beam 430 to form the
sealing layer 426. In particular, the substrate 402 may be scanned
back and forth to receive alternate exposure from the ion beam 428
that may be extracted from the plasma chamber 102, and a molecular
beam 430 that may be provided by the molecular chamber 104. As with
the formation of a dopant oxide layer in FIG. 4C, the uniformity of
the deposition of the sealing layer 426 may be enhanced by
adjusting the angle(s) of incidence of the ion beam 428 so as to
enhance the deposition rate on the sidewalls 429 (see FIG. 4B).
[0058] In a subsequent operation, the substrate 402 may be exposed
to a heat source 440 that provides heat 442 to the substrate. The
heat source 440 may be a lamp system or other system that is
effective to anneal the substrate to a desired temperature. The
heat source 440 acts to drive in dopants from the layer 420 into
the substrate features 404. Subsequently the layer 420 and the
sealing layer 426 may be removed, for example, by known wet
chemical processing using HF, buffered oxide etch (BOE), hot
phosphoric acid, or other chemistries. This results in a doped
three dimensional structure composed of the substrate features 404
in which a three dimensional dopant layer 444 is formed, which may
be of uniform thickness on different surfaces of the substrate
features 404 as shown.
[0059] FIG. 5A to FIG. 5D depict details of a method for performing
monolayer doping on a three dimensional structure according to
embodiments of the disclosure. In FIG. 5A there is shown an example
of a substrate 500 that includes a layer stack that can be
conformally deposited over severe and/or reentrant topology that
may be presented by substrate features to be coated. In one
example, a base layer 510 may represent a silicon substrate upon
which a three dimensional transistor or other structure is to be
formed. A layer stack may be formed on the silicon substrate, base
layer 510, where the layer stack is composed of a lightly doped p-
silicon boron oxide layer 508, an undoped silicon oxide layer 506,
a heavily doped n.sup.+ silicon arsenic oxide layer 504, and a
silicon nitride capping layer 502. Instead of the oxide layers, in
other embodiments it is also possible to deposit layers of pure
boron, phosphorus, and arsenic.
[0060] Turning now to FIG. 5B, there is shown the structure of a
layer stack 520 formed after a Rapid Thermal Anneal (RTA) process
is performed on the substrate 500 of FIG. 5A. An n.sup.+ layer 522
is formed with arsenic doping at the top region of the original
base layer, base layer 510, and a graded lightly boron doped
region, p.sup.- layer 524, is created underneath the n.sup.+ layer
522. Separation of arsenic from a boron layer may be aided by the
slower solid state diffusion rate of arsenic within the base layer
510. In a subsequent operation shown in FIG. 5C, the oxide and
nitride layers are removed, such that a n.sup.+/p junction is
retained in the substrate at the interface of the n.sup.+ layer 522
and p.sup.- layer 524. This junction can be uniformly created over
difficult topology as shown in FIG. 5D, including the sidewalls 532
and trench bottom 534 of the substrate structure 530. This is not
possible using other conventional techniques such as conventional
ion implantation.
[0061] FIG. 6 provides a summary of representative conformal layers
602, ion beam constituents 604, and molecular beam constituents 606
that may be used to deposit the conformal layers consistent with
different embodiments of the disclosure.
[0062] The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are intended to fall within the scope of the present
disclosure. Furthermore, although the present disclosure has been
described herein in the context of a particular implementation in a
particular environment for a particular purpose, those of ordinary
skill in the art will recognize that its usefulness is not limited
thereto and that the present disclosure may be beneficially
implemented in any number of environments for any number of
purposes. Accordingly, the claims set forth below should be
construed in view of the full breadth and spirit of the present
disclosure as described herein.
* * * * *