U.S. patent application number 10/991693 was filed with the patent office on 2005-03-31 for cvd of ptrh with good adhesion and morphology.
Invention is credited to Li, Weimin, Visokay, Mark R..
Application Number | 20050066895 10/991693 |
Document ID | / |
Family ID | 25543630 |
Filed Date | 2005-03-31 |
United States Patent
Application |
20050066895 |
Kind Code |
A1 |
Li, Weimin ; et al. |
March 31, 2005 |
CVD of PtRh with good adhesion and morphology
Abstract
A method and system for performing metal-organic chemical vapor
deposition (MOCVD). The method introduces a metal-organic compound
into the CVD chamber in the presence of a first reactant selected
to have a reducing chemistry and then, subsequently, a second
reactant selected to have an oxidizing chemistry. The reducing
chemistry results in deposition of metal species having a reduced
surface mobility creating more uniform coverage and better
adhesion. The oxidizing species results in deposition of metal
species having a greater surface mobility leading to greater
surface agglomeration and faster growth. By alternating the two
reacts, faster growth is achieved and uniformity of the metal
structure is enhanced.
Inventors: |
Li, Weimin; (Boise, ID)
; Visokay, Mark R.; (Richardson, TX) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
25543630 |
Appl. No.: |
10/991693 |
Filed: |
November 18, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10991693 |
Nov 18, 2004 |
|
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09997073 |
Nov 28, 2001 |
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Current U.S.
Class: |
118/715 ;
257/E21.17 |
Current CPC
Class: |
H01L 21/28556 20130101;
C23C 16/18 20130101; C23C 16/0281 20130101; C23C 16/45523
20130101 |
Class at
Publication: |
118/715 |
International
Class: |
C23C 016/00 |
Claims
What is claimed is:
1. A system for forming a conductive element on a semiconductor
device, the system comprising: a CVD chamber that receives the
semiconductor device; a conductive precursor gas supply system that
provides a conductive precursor gas to the CVD chamber wherein the
conductive precursor gas has both conductive components that when
deposited on the semiconductor device form the conductive element
and organic components which facilitate step coverage of the
conductive element over the semiconductor device; and a reactant
gas supply system that provides both a first reactant and a second
reactant into the chamber so that conductive precursor gas is
deposited using both a first chemistry and a second chemistry such
that the first chemistry provides more uniform step coverage and
the second chemistry provides increased vertical growth of
conductive element and the semiconductor substrate.
2. The system of claim 1, wherein the conductive precursor gas
supply system provides a metal-organic gas to the CVD chamber.
3. The system of claim 2, wherein the conductive precursor gas
supply system provides a combination of Methylcyclopentadienyl
Trimethyl Platinum gas and a Dicarbonyl Cyclopentadienyl Rhodium
gas.
4. The system of claim 2, wherein the reactant gas supply system
provides a first reactant that is comprised of a reducing gas and a
second reactant that is comprised of a oxidizing gas.
5. The system of claim 4, wherein the reactant gas supply provides
a hydrogen-based reducing gas and an oxygen-based oxidizing gas.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 09/997,073 filed Nov. 18, 2001 and is hereby incorporated in
its entirety herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to semiconductor processing
and, in particular, concerns a chemical vapor deposition (CVD)
technique for forming conductive layers, such as platinum-rhodium
layers, in a manner that results in better adhesion of the
component layer on the surface of a semiconductor device and better
morphology of the layer.
[0004] 2. Description of the Related Art
[0005] Modern semiconductor chemical vapor deposition (CVD)
technology has provided fabrication procedures for the development
of VLSI (Very-Large-Scale Integration) and ULSI (Ultra-Large-Scale
Integration) circuitry. Even though the number of surface mounted
semiconductor devices has significantly increased, the surface
density is often limited by the finite quantity of real estate on
the semiconductor wafer surface. As a result, the finite surface
density limitation has induced growth in the vertical direction of
modern semiconductor devices. This often requires multiple levels
of the conductive interconnects that often, in turn, require
numerous metallic-based deposition layers.
[0006] As the size of the conductive elements has decreased to
accommodate higher density of components, many conventional
semiconductor processing techniques for forming conductive elements
are forming conductive elements that exhibit more gaps and pinholes
and poorer adhesion to the substrate. One particular CVD deposition
technique utilized for forming conductive elements is Metal-organic
Chemical Vapor Deposition (MOCVD). However, conventional MOCVD
techniques alone cannot always compensate for the relatively poor
adhesion and morphology that occurs in smaller devices.
[0007] For example, complex chemical reactions that occur during
the formation of semiconductor devices dictate the final
composition of the deposited layer, which may be different than the
intended composition. Specifically, the grain structure within the
deposited layer may vary depending on the growth rate and the
growth environment during the manufacturing and deposition process.
A variance in the grain size and grain structure within deposited
layers of similar composition and thickness may interfere with or
alter the conduction characteristics of electrical current flow
through the grain interfaces.
[0008] A typical MOCVD technique is as follows. A precursor gas,
comprising at least one conductive component or element, and other
reactants are introduced into a CVD chamber, and the conductive
element carried by the precursor gas is then deposited onto the
semiconductor surface of the semiconductor substrate through
thermal decomposition. The precursor gas may often be a
metal-organic compound, wherein conductive atoms may be bonded to
organic compounds, which allows the conductive atoms to be
transferred to the semiconductor surface in a gas phase. This
enables the conductive atoms, such as platinum and rhodium, to be
deposited over the surface of the semiconductor substrate surface
as the metal-organic compound facilitates conventional step
coverage.
[0009] In the prior art, there is generally only a single
deposition step such that the precursor gas is introduced into the
CVD chamber until enough conductive molecules have been deposited
on the exposed semiconductor surface to form a conductive element
of a desired thickness. However, as discussed above, conventional
MOCVD techniques can result in poor adhesion and poor morphology of
the deposited conductive element. This problem is exacerbated in
higher density applications requiring smaller conductive
components.
[0010] From the foregoing, it will be appreciated that there is a
need for an improved conductive layer processing technique for
depositing, in one embodiment, conductive materials onto a
semiconductor substrate surface such that improved substrate
adhesion and improved morphology may be obtained without a
significant increase in the cost of manufacturing the conductive
film layer. To this end, there is also a need for a more efficient
method of depositing conductive elements, such as platinum and
rhodium, in a manner that exhibits an improved grain interface
structure and greater compositional uniformity.
SUMMARY OF THE INVENTION
[0011] The aforementioned needs are satisfied by the present
invention which, in one aspect is comprised of a method of forming
a conductive layer on a substrate. In this aspect, the method
comprises positioning the substrate in a chemical vapor deposition
(CVD) chamber and then introducing at least one precursor gas,
having at least one conductive component and at least one organic
component, into the CVD chamber. A first reactant gas is then
introduced into the chamber so as to disassociate the at least one
conductive component from the at least one organic component at one
activation energy so as to result in a first layer of conductive
material being formed on the substrate. A second reactant gas is
then introduced into the chamber after introducing the first
reactant gas so as to disassociate the at least one conductive
component from the at least one organic component at another
activation energy greater than the first energy so as to result in
columnar growths of conductive material from the first layer of the
conductive material formed on the substrate. The method further
comprises re-introducing the first reactant gas into the chamber so
as to planarize the conductive film by filling in gaps between the
columnar growths of the conductive material.
[0012] In one embodiment, the first reactant gas is a reducing gas
and the second reactant gas is an oxidizing gas. The use of the
reducing gas results in reduced surface mobility of the atoms which
results in greater step coverage and promotes better adhesion. The
periodic use of the oxidizing gas results in greater surface
mobility causing the atoms to agglomerate together which promotes
faster columnar growths. The periodic reintroduction of the first
reactant gas, however, results in better filling in of the gaps and
pin holes resulting from the faster columnar growths. In one
specific embodiment, the at least one precursor gas is a mixture of
gases, which comprises platinum, rhodium, or a combination thereof.
In another specific embodiment, a plurality of precursor gases may
be used, wherein a first precursor gas comprises a platinum
component and a second precursor gas comprises a rhodium
component.
[0013] In another aspect of the invention, the invention comprises
a method of forming a conductive structure on a semiconductor
substrate. The method comprises (i) performing a first
metal-organic chemical vapor deposition step using a first
chemistry selected to provide more uniform coverage of the
semiconductor substrate and (ii) performing a second metal-organic
chemical vapor deposition step using a second chemistry selected to
provide for increased columnar growth. The method further comprises
alternating the acts (i) and (ii) until a conductive structure of a
pre-selected thickness is formed on the semiconductor substrate so
that the performance of the first metal-organic chemical vapor
deposition act decreased gaps and pin holes formed during the
performance of the second metal-organic chemical vapor deposition
act.
[0014] In yet another aspect of the invention, the invention
comprises a system for forming a conductive element on a
semiconductor device. The system comprises a CVD chamber that
receives the semiconductor device. The system also includes a
precursor gas supply system that provides at least one precursor
gas to the CVD chamber, wherein the at least one precursor gas
comprises conductive components that when deposited on the
semiconductor device form the conductive element and organic
components which facilitate step coverage of the conductive element
over the semiconductor device. The system also includes a reactant
gas supply system that provides both a first reactant and a second
reactant into the chamber so that the precursor gas is deposited
using both a first chemistry and a second chemistry such that the
first chemistry provides more uniform step coverage and the second
chemistry provides increased vertical growth of the conductive
element, which is comprised by the at least one precursor gas, on
the semiconductor substrate.
[0015] The aspects of the present invention result in a process or
system for forming conductive elements that is both efficient and
leads to improved morphology and adhesion. These and other objects
and advantages will become more apparent from the following
description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic illustration of a system block
diagram, which depicts one embodiment of a deposition system for
the formation of a conductive structure on a semiconductor
device;
[0017] FIGS. 2A-2E are cross-sectional views of a semiconductor
device illustrating one embodiment of a method, whereby a
conductive structure is formed on the semiconductor device;
[0018] FIG. 3A is a graphical illustration of a typical platinum
precursor gas molecule used in a CVD process;
[0019] FIG. 3B is a graphical illustration of a typical rhodium
precursor gas molecule used in a CVD process;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] Reference will now be made to the drawings wherein like
numerals refer to like parts throughout. FIG. 1 is a block diagram
of one embodiment of a deposition system 100 for the formation of a
conductive structure or element of the present invention. As is
illustrated in FIG. 1, a chemical vapor deposition (CVD) chamber
102, of a type known in the art, is supplied with precursor gases
104a, 104b that is utilized to deposit conductive layers and
structures on semiconductor devices positioned within the CVD
chamber 102. In particular, a carrier gas 106 from a carrier gas
source 116 is supplied to a bubbler 114, which, in this embodiment,
comprises a first metal-organic liquid precursor 108 and a second
metal-organic liquid precursor 110.
[0021] Additionally, the carrier gas 106 is utilized to carry the
vapor of the conductive metal-organic components comprised by the
liquid precursors 108 and 110. Furthermore, a first metal-organic
precursor gas 104a develops from the first metal-organic liquid
precursor 108, and a second metal-organic precursor gas 104b
develops from the second metal-organic liquid precursor 110. In one
embodiment, the precursor gases 104a, 104b may be introduced
separately, in either a simultaneous manner or at pre-determined
temporal intervals, to the CVD chamber 102 in a manner known in the
art. In another embodiment, the precursor gases 104a, 104b may be
mixed within the bubbler chamber 122 so as to form a precursor gas
mixture that may then be introduced to the CVD chamber 102 in a
manner known in the art.
[0022] In one preferred embodiment, the carrier gas 106 is a known
helium-based inert gas, which serves to carry the vapor of the
liquid precursors 108 and 110. The inert helium-based carrier gas
106 is supplied to the bubbler 114, which houses the first
metal-organic liquid precursor 108, such as, for example,
methylcyclopentadienyl trimethyl platinum (MeCpPtMe.sub.3) (See,
FIG. 3A), and the second metal-organic liquid precursor 110, such
as, for example, Dicarbonyl Cyclopenda Dienyl Rhodium (DCDR)(See,
FIG. 3B). The carrier gas 106 carries the vapor of the liquid
precursors 108 and 110, which may comprise the platinum-based
metal-organic components and the rhodium-based metal-organic
components. In one aspect, the platinum-based metal-organic vapor
and the rhodium-based metal-organic vapor may then be mixed in the
bubbler chamber 114 and subsequently introduced to the CVD chamber
102 for a pre-selected period of time so as to allow the conductive
metal-organic components to coat the semiconductor device via
chemical vapor deposition techniques. In another aspect, the first
precursor gas 104a, such as the platinum-based metal-organic vapor,
and the second precursor gas 104b, such as the rhodium-based
metal-organic vapor, may be separately introduced to the CVD
chamber 102 for a pre-selected period of time so as to allow the
conductive metal-organic components to coat the semiconductor
device via chemical vapor deposition techniques.
[0023] While in this particular embodiment, the metal-organic
precursor gases 104a, 104b have platinum-based and/or rhodium-based
components, it will be appreciated that any of a number of
different precursor gases and/or vapors may be used without
departing from the scope of the present invention. These
metal-organic gases and/or vapors include, but are not limited to,
gases and/or vapors that entrain conductive elements such as Pt,
Rh, Ir, Ni, Co, Cu, W, and the like or any combination thereof.
[0024] As is also illustrated in FIG. 1, the deposition system 100
includes a first reactant source 122 that provides a first reactant
vapor 126 and a second reactant source 124 that provides a second
reactant vapor 128 into the CVD chamber 102 that are alternatively
selected so as to interact with the conductive metal-organic
compounds of the precursor gases 104a, 104b to thereby facilitate
more a more uniform and efficient deposition of the conductive
metal-organic molecules comprised by the precursor gases 104a,
104b. Providing the reactant vapors, 126 and 128, into the CVD
chamber 102 allows the metal-organic molecules comprised by the
precursor gases 104a, 104b to deposit on the surface of the
semiconductor device that is positioned within the CVD chamber 102.
As is also illustrated in FIG. 1, the illustrated chemical vapor
deposition system 100 also includes a waste gas receptacle 130 that
receives waste gas 132, which may comprise unused precursor gases
104a, 104b, unused reactant vapors, 126, 128, and other reaction
by-products produced during the CVD process. In the preferred CVD
process, the first reactant vapor 126 is a reducing agent, such as
diatomic hydrogen or a hydrogen derivative (H.sub.2), and the
second reactant vapor is an oxidizing agent, such as diatomic
oxygen or an oxygen derivative (NO, N.sub.2O, O.sub.2, or
O.sub.3).
[0025] FIGS. 2A-2E are cross-sectional views of a semiconductor
device 200 depicting one embodiment of a deposition process and
method of the illustrated embodiment in greater detail, whereby a
conductive structure is formed on the semiconductor device 200. As
is illustrated in FIG. 2A, a semiconductor device 200, which may
comprise a semiconductor substrate 202 with a surface 204, is
positioned within the CVD chamber 102. The precursor gases 104a,
104b are introduced into the CVD chamber 102 such that a conductive
material, such as platinum-rhodium (PtRh), is deposited on the
exposed surface 204 of the semiconductor device 200. The deposition
process begins with a nucleation process, wherein nucleation sites
develop as the first few metal-organic molecules are deposited onto
the semiconductor substrate surface 204. The nucleation process
involves the first reactant vapor 126, which is simultaneously
introduced into the CVD chamber 102 along with the precursor gases
104a, 104b. The first reactant vapor 126 is preferably selected to
serve as a reducing agent that reacts with the precursor gases
104a, 104b. Additionally, the resulting reduction chemistry may
offer a more uniform nucleation on the semiconductor substrate
surface 204, which may possibly be due to its comparatively low
reaction energy and comparatively resulting low surface mobility.
In one particular embodiment, the first reactant vapor 126 includes
a hydrogen based gas, such as a gas selected from the group of
H.sub.2, NH.sub.3 or H.sub.2O.
[0026] The comparatively low reaction energy may provide for a
comparatively low surface mobility as the metal-organic molecules
adhere more readily to the semiconductor surface 204 with less
surface movement and less tendency to agglomerate together. The low
reaction energy, the low surface mobility, and the low deposition
rate of the reduction chemistry may provide increased uniformity
and less agglomeration, which may lead to better adhesion of the
conductive film layer during the nucleation process stage. Good
adhesion during the initial stage of the conductive film formation
process produces a semiconductor device film layer with less
internal defects, which serves to improve the functionality,
integrity, and reliability of the device. Also, residual hydrogen
bonding of conductive elements to the semiconductor substrate
surface may also contribute to the good nucleation adhesion.
[0027] FIG. 2B graphically illustrates the results of further
growth of the initial nucleation sites. After the nucleation
process is complete, the first reactant vapor 126 is no longer
introduced into the CVD chamber 102. Instead, the second reactant
vapor 128 is simultaneously introduced into the CVD chamber 102
along with the precursor gases 104a, 104b. The second reactant
vapor 128, in one embodiment, serves as an oxidizing agent that
reacts with the precursor gases 104a, 104b, and, due to its high
reaction energy, the applied oxidation chemistry results in rapid
columnar growths 208 above the initial nucleation sites that were
deposited with reduction chemistry on the semiconductor substrate
surface 204. The high reaction energy state may provide for an
increased surface mobility as the metal-organic molecules begin to
adhere to the semiconductor surface 204 which results in the metal
atoms agglomerating together into the columns. The fast columnar
growth tends to leave gaps 210 and pinholes 212 between the grain
structures of the conductive elements. These flaws may be corrected
with the application of another reduction chemistry process, which
will be further described herein below. In one embodiment, the
second reactant vapor 128 is comprised of an oxygen containing gas
such as N.sub.2O, O.sub.2, NO or O.sub.3.
[0028] FIG. 2C graphically illustrates the subsequent
processing--step of repeating the application of reduction
chemistry to the semiconductor device 200. After the oxidation
layer 208 is complete, the second reactant vapor 128 is no longer
introduced into the CVD chamber 102, but, instead, the first
reactant vapor 126 is introduced into the CVD chamber 102 along
with the introduction of the precursor gases 104a, 104b. Due to the
lower reaction energy and the resulting lower surface mobility of
depositing conductive elements with reduction chemistry, inserting
a conductive layer deposited with reduction chemistry interposed
between two conductive layers deposited with oxidation chemistry
may serve to disrupt the grain structure in the direction normal to
the semiconductor surface 204. In addition, the slow depositions
rates of reduction chemistry may tend to fill in the gaps and
pinholes left by the rapid growth rates of oxidation chemistry.
[0029] FIG. 2D graphically illustrates that the next layer of
oxidation chemistry will grow more uniformly. As is illustrated in
FIG. 2D, the use of the oxidation chemistry by the introduction of
the second reactant vapor 128, results in quicker growth of the
thin film layer, as discussed above. However, as is illustrated in
FIG. 2E, alternating reduction and oxidation chemistry processes
results in an improved grain structure as a result of the reducing
chemistry filling in more of the gaps and pin holes. The process of
alternating reduction and oxidation chemistries may be repeated
until the desired thickness of the conductive layer is
achieved.
[0030] The advantage of utilizing reduction chemistry for the
initial nucleation phase is the reduced surface mobility of the
metallic molecules, such as platinum, rhodium, and/or a combination
thereof. A reduced surface mobility of the metallic molecules
results in a more uniform coverage of the semiconductor surface
204, improved adhesion and improved morphology of the metallic
molecules onto the semiconductor surface 204. The uniform coverage
is the result of less agglomeration of the metallic molecule during
the reduction chemistry phase of the MOCVD process, which results
in a reduction of gaps and pinholes in the conductive film layer.
Additionally, there may also be some residual hydrogen bonding
between the substrate molecules and the metallic molecules, which
may also contribute to the improved adhesion of the metallic
molecules onto the semiconductor substrate surface.
[0031] Furthermore, the advantage of utilizing oxidation chemistry
after the reduction chemistry is that oxidation reactions involve
higher reaction energies, which result in an increased surface
mobility of the metallic molecules, such as platinum and rhodium.
The higher reaction energy of the metallic molecules increases the
agglomeration rate, which results in a rapid columnar growth rate.
Although the rapid growth rate may cause poorer adhesion and
morphology, such that gaps and pinholes in the film layer more
readily occur, the addition of another reduction film layer
interposed between two oxidation layers tends to reduce the
problems of poorer adhesion morphology.
[0032] Another advantage to alternating the reduction and oxidation
chemistries is that reduction contaminates, such as carbon, left
behind by the metal-organic reduction reactions may be burned out
of the conductive film layer during the oxidation process, which
improves the overall purity and cohesion of the metallic molecules
to each other and to the semiconductor surface. Additionally, the
process of alternating the reduction and oxidation chemistries
produces metal-organic deposition layers that exhibit the ability
to maintain a uniform topography, wherein the deposited layers have
a substantially flat and smooth surface. The improved morphology
results in the reduction of surface defects, such as step layer
thinning, cracks, and surface reflections.
[0033] In one particular example of the above process, a conductive
layer 220 is formed using an initial deposition step, wherein a
platinum-rhodium precursor carrier gas is provided from the
conductive carrier gas source 116 through the bubbler 114 at a rate
of between 5 to 300 sccm with the platinum-rhodium being
encapsulated within a helium carrier. The bubbler 114 contains a
liquid precursor at a temperature between 20.degree. C. and
200.degree. C., such that the resulting precursor gases 104a, 104b
emanating from the bubbler 114 has the chemical composition as
illustrated in FIGS. 3A and 3B. The resulting precursor gases 104a,
104b is provided from the bubbler 114 to the CVD chamber 102 along
with an initial simultaneous introduction of H.sub.2 reactant 126
at a rate of 50 to 1000 sccm from the reactant source 122. This
introduction of precursor gases 104a, 104b and reactant 126 is
provided to the CVD chamber 102 for approximately 50 seconds to
result in deposition of the nucleation sites 206. At the end of the
approximately 50 second nucleation period, the introduction of the
precursor gases 104a, 104b from the bubbler 114 is continued while
the introduction of the N.sub.2O reactant 128 from the reactant
source 124 is continued for approximately 50 seconds. The N.sub.2O
thus comprises the reactant 128, which reacts with the
metal-organic compounds comprised by the precursor gases 104a, 104b
in the deposited layer 160 to further grow the conductive layer
220. These two process steps are alternately repeated until a
conductive layer or element of a desired thickness is formed.
[0034] From the foregoing, it will be appreciated that the
above-described metal-organic chemical vapor deposition process
illustrates a method of forming a conductive film layer 220 or
structure on a semiconductor device 202 that results in a more
uniform conductive film structure with improved adhesion and
morphology. This results in a significantly efficient conductive
device that exhibits improved conduction and less resistivity
between grain interfaces. Moreover, the improved efficiencies may
also result in faster devices that exhibit improved reliability and
functionality overall.
[0035] Although the foregoing description of the preferred
embodiment of the present invention has shown, described and
pointed out the fundamental novel features of the invention, it
will be understood that various omissions, substitutions and
changes in the form of the detail of the apparatus as illustrated
as well as the uses thereof, may be made by those skilled in the
art without departing from the spirit of the present invention.
Consequently, the scope of the present invention should not be
limited to the foregoing discussions, but should be defined by the
appended claims.
* * * * *