U.S. patent application number 11/093578 was filed with the patent office on 2006-10-05 for polishing technique to minimize abrasive removal of material and composition therefor.
Invention is credited to Jennifer Cooper, Kevin E. Cooper, Janos Farkas, John C. Flake, Johannes Groschopf, Yuri Solomentsev.
Application Number | 20060223320 11/093578 |
Document ID | / |
Family ID | 37071132 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060223320 |
Kind Code |
A1 |
Cooper; Kevin E. ; et
al. |
October 5, 2006 |
Polishing technique to minimize abrasive removal of material and
composition therefor
Abstract
The present invention provides a composition and a method of
polishing a surface that minimizes abrasive removal of material
from the surface. To that end, the composition is formulated to
maximize dissolution of the material from the surface.
Inventors: |
Cooper; Kevin E.; (La
Terrasse, FR) ; Cooper; Jennifer; (La Terrasse,
FR) ; Farkas; Janos; (Saint Ismier, FR) ;
Flake; John C.; (Montbonnot, FR) ; Groschopf;
Johannes; (Wainsdorf, DE) ; Solomentsev; Yuri;
(Austin, TX) |
Correspondence
Address: |
FREESCALE SEMICONDUCTOR, INC.;LAW DEPARTMENT
7700 WEST PARMER LANE MD:TX32/PL02
AUSTIN
TX
78729
US
|
Family ID: |
37071132 |
Appl. No.: |
11/093578 |
Filed: |
March 30, 2005 |
Current U.S.
Class: |
438/693 ;
257/E21.304 |
Current CPC
Class: |
C09G 1/02 20130101; B24B
37/044 20130101; H01L 21/3212 20130101; C09G 1/04 20130101 |
Class at
Publication: |
438/693 |
International
Class: |
B24B 49/00 20060101
B24B049/00 |
Claims
1. A composition comprising: a carrier solution; a complexing agent
to dissolve a predetermined material; and a corrosion inhibitor to
minimize kinetic removal of said predetermined material, wherein
said carrier solution, said complexing agent and said corrosion
inhibitor being present in sufficient quantities to provide said
composition with a neutral pH; and wherein said composition has a
particle content no greater than approximately two hundred and
fifty parts per million.
2. The composition as recited in claim 1, wherein said neutral pH
is in a range of 5 to 8.
3. The composition as recited in claim 1, wherein said carrier
solution further includes hydrogen peroxide.
4. The composition as recited in claim 1, wherein said complexing
agent comprises ammonium salts of citric, oxalic, tartaric,
succinic, or actetic acids.
5. The composition as recited in claim 4 wherein said complexing
agent comprises dibasic ammonium citrate.
6. The composition as recited in claim 1, wherein said corrosion
inhibitor comprises triazole.
7. The composition as recited in claim 1, further comprising an
oxidizing agent, wherein said oxidizing agent includes
approximately 0.1% to 3% by weight of said composition of hydrogen
peroxide.
8. The composition as recited in claim 1, wherein said complexing
agent includes approximately 0.1% to 12% by weight of said
composition of dibasic ammonium citrate.
9. The composition as recited in claim 1, wherein said corrosion
inhibitor includes approximately 1% to 6% by weight of said
composition of an inhibitor selected from the group consisting of
triazole, imidazole, polyvinylimidazole, theophiline, bipyridyl,
mercapto benzothizole,phenyl marcapto tetrazole, and pyrazole.
10. The composition as recited in claim 1, wherein said corrosion
inhibitor includes benzotriazole.
11. The composition as recited in claim 1, wherein said corrosion
inhibitor includes 0.0001% to 1% by weight of the composition of
benzotriazole.
12. A composition comprising: a carrier solution including hydrogen
peroxide; a complexing agent; and a corrosion inhibitor, wherein
said carrier solution, said complexing agent and said corrosion
inhibitor are present in sufficient quantities to provide said
composition with a neutral pH, with a range of particles contained
therein in a range of zero to 250 parts per million.
13. The composition as recited in claim 12, wherein said complexing
agent comprises dibasic ammonium citrate.
14. The composition as recited in claim 13, wherein said corrosion
inhibitor includes benzotriazole.
15. The composition as recited in claim 13, wherein said corrosion
inhibitor comprises triazole.
16. The composition as recited in claim 12, wherein said hydrogen
peroxide is present in said composition in a quantity of
approximately 1% to 3% by weight.
17. The composition as recited in claim 16, wherein said complexing
agent includes approximately 0.1% to 12% by weight of said
composition of dibasic ammonium citrate.
18. The composition as recited in claim 17, wherein said corrosion
inhibitor includes approximately 1% to 6% by weight of said
composition of triazole.
19. The composition as recited in claim 17, wherein said corrosion
inhibitor includes 1% to 3% by weight of the composition of
benzotriazole.
20. A method for polishing a layer containing conductive material
and dielectric material, said method comprising: removing portions
of said layer by exposing said layer to a composition at a rate of
removal, with said rate of removal being principally controlled by
a dissolution of said layer with said composition, wherein said
composition includes a quantity of particles in a range of zero to
two hundred fifty parts per million.
21. The method as recited in claim 20, wherein said composition has
a neutral pH and kinetics of oxide formation do not control removal
rate.
22. The method as recited in claim 20, wherein said composition has
a pH in a range of 5-8.
23. The method as recited in claim 20, wherein said composition has
a pH of approximately 7.5.
24. A method for polishing a layer having conductive material and
dielectric material, said method comprising: removing portions of
said layer using a composition to generate a substantially smooth
surface including first and second regions, with said first region
including said conductive material and said second region including
said dielectric material, wherein kinetics of conductive oxide
formation do not principally control the removal of material from
one of said first and second regions.
25. The method as recited in claim 24, wherein removing further
includes principally controlling removal rate by dissolution with
the composition.
26. The method as recited in claim 24, wherein said composition has
a pH in a range of 5-8.
27. The method as recited in claim 26, wherein said composition has
a pH of approximately 7.5.
28. A method for making a semiconductor device comprising:
providing a slurry composition having a particle content no greater
than approximately two hundred and fifty parts per million and
comprising: a carrier solution; a complexing agent to dissolve a
predetermined material; and a corrosion inhibitor to minimize
kinetic removal of said predetermined material, wherein said
carrier solution, said complexing agent and said corrosion
inhibitor being present in sufficient quantities to provide said
composition with a neutral pH; providing a semiconductor substrate
having a trench formed within a dielectric layer, the trench having
a metal layer therein; providing a polishing apparatus having a
polishing pad; polishing a surface of the semiconductor substrate
using the polishing pad and the slurry composition.
29. The method as recited in claim 28 wherein wherein said neutral
pH is in a range of 5 to 8.
30. The method as recited in claim 28 wherein said carrier solution
comprises hydrogen peroxide.
31. The method as recited in claim 28 wherein said complexing agent
comprises dibasic ammonium citrate.
32. The method as recited in claim 28 wherein said corrosion
inhibitor comprises triazole.
33. The method as recited in claim 28 wherein said corrosion
inhibitor comprises benzotriazole.
Description
BACKGROUND OF THE INVENTION
[0001] The field of invention relates generally to the fabrication
of integrated circuits. More particularly, the invention relates to
compositions and methods for using polishing layers of material in
furtherance of fabricating semiconductor circuits.
[0002] The fabrication of modern semiconductor devices includes
forming multiple layers of conductive and dielectric materials on
substrates. To that end two various processes are employed to
deposit and to remove material associated with the layer. Exemplary
deposition techniques include electrochemical deposition, chemical
vapor deposition (CVD), plasma enhanced CVD (PECVD), atomic layer
deposition (ALD), physical vapor deposition (PVD) and the like.
Exemplary removal techniques include etching, such as chemical or
plasma etching, as well as polishing.
[0003] Chemical-mechanical polishing (CMP) methods and polishing
slurries are well known and widely used techniques for polishing
layers to provide the same with a smooth, if not planar, shape.
Often, however, the surface being polished has regions with
differing materials present, e.g., materials with differing
mechanical properties and chemical reactivity. As a result, the
removal rate over the surface is not uniform, which makes obtaining
the desired planarization of the surface difficult, while
minimizing roughness over the area thereof. For example when
polishing a surface having a metal region surrounded by dielectric,
minimization of dishing is difficult. Dishing results from one of
the regions, e.g., the metal region, being removed at a greater
rate than the rate at which the other regions of the surface are
removed. This results in a concave region in the metal area, which
is often undesirable when a planar shape is desired. To avoid the
deleterious effects of CMP of surfaces having regions of differing
material properties, various CMP slurries have been developed to
obtain desirable CMP characteristics: low polish induced damage,
high polishing rate, process predictability, high polished surface
uniformity, low polished surface roughness, and the use of
non-hazardous, low-cost polish materials.
[0004] Historically, polishing slurries for use in CMP contain
fine, suspended abrasive particles to facilitate mechanical
polishing of the surface, as well as acidic or basic chemical
components to facilitate chemical polishing of the surface. The
rate at which polishing occurs for a given material and operating
conditions is related to the quantity of abrasive particles in the
slurry. However, the damage to the surface being polished is also
related to the size of the particles in the slurry. Chemical
component selection may also dramatically affect polish rate and
quality for a given material and operating conditions.
[0005] Additionally, advanced integration schemes, e.g., stacks
with ultra low dielectric (ULK) and air gap integration schemes,
are often structurally compromised by CMP processes through
interfacial stress created during the CMP process, erosion, as well
as absorption of CMP slurry chemicals.
[0006] Therefore, a need exists to provide improved techniques for
polishing layers in furtherance of producing semiconductor
circuits.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a cross-sectional view of a chemical-mechanical
polishing machine known in the art but which can be used in
practicing the present invention;
[0008] FIG. 2 is a schematic cross-sectional view of a
chemical-mechanical polishing machine known in the art but which
can be used in practicing the present invention;
[0009] FIG. 3 is a cross-sectional view showing an exemplary
structure to undergo polishing in accordance with the present
invention;
[0010] FIG. 4 is a cross-sectional view showing a slurry
composition in accordance with the present invention, being
disposed between the exemplary structure of FIG. 3 and a polishing
pad of the polishing machine shown in FIG. 1 in accordance with the
present invention;
[0011] FIG. 5 is a cross-sectional view showing the exemplary
structure of FIG. 3 having a surface undergoing polishing;
[0012] FIG. 6 is a cross-sectional view showing the exemplary
structure of FIG. 3 after polishing in accordance with the present
invention; and
DETAILED DESCRIPTION OF THE INVENTION
[0013] Referring to FIGS. 1 and 2, a brief overview of a polishing
machine 10 is depicted that may be employed in accordance with the
present invention. Polishing machine 10 has a platen 12, a wafer
carrier 14, a polishing pad 16, and a slurry 18 on polishing pad
16. An under-pad 20 is typically attached to the upper surface 22
of platen 12, and polishing pad 16 is positioned on under-pad 20. A
drive assembly 24 rotates platen 12 as indicated by arrow A. In
addition, drive assembly 24 may cause platen 12 to reciprocate as
indicated by arrow B. The motion of platen 12 is imparted to
polishing pad 16 through under-pad 20 because polishing pad 16
frictionally engages under-pad 20. Wafer carrier 14 has a lower
surface 26 to which a wafer 28 may be attached, or wafer 28 may be
attached to a resilient pad 30 positioned between wafer 28 and
lower surface 26.
[0014] Wafer carrier 14 may be a weighted, free-floating wafer
carrier, or an actuator assembly 32 may be attached to wafer
carrier 14 to impart axial and rotational motion, as indicated by
arrows C and D, respectively. Polishing pad 16 may be embodied as a
conventional polishing pad, a web-type polishing pad, a belt-type
polishing pad, or any other polishing pad format known in the art.
Polishing pad 16 may also be employed as a fixed-abrasive polishing
pad. Such a fixed-abrasive polishing pad 16 may be impregnated with
particulate abrasives including, but not limited to, alumina,
titanium dioxide, silicon dioxide, and cerium dioxide. The
abrasives in a fixed-abrasive polishing pad 16 are typically
leached therefrom during polishing of wafer 28.
[0015] Referring to FIGS. 1 and 3, an exemplary wafer 28 that
undergoes polishing in accordance with the present invention
includes a substrate 40 having a recess 42 disposed within a
surface 44. In a preferred embodiment, substrate 40 includes a
dielectric layer and recess 42 is formed within the dielectric
layer. A metal layer 48, such as copper, is disposed on surface 44
and substantially fills recess 42. A liner 50 is disposed between
substrate 40 and metal layer 48, and is located on surface 44 and
surfaces 46 of recess 42. Wafer 28 may comprise various other
layers adjacent to recess 42, surface 44, liner 50, and/or metal
layer 48, but for the purposes of simplicity of discussion, no
other such structures are depicted.
[0016] Referring to FIGS. 4 and 5, to polish metal layer 48 in
accordance with the present invention, slurry 18 is disposed
between metal layer 48 and polishing pad 16. Polishing pad 16 is
placed in close proximity to metal layer 48. Subsequently,
polishing pad 16 is brought in frictional contact with metal layer
48 and, in combination with slurry 18, removes portions of metal
layer 48. To attenuate, if not prevent, "dishing," portions 52 of
metal layer 48 are removed before portions 54 of metal layer 48,
which are more distant from polishing pad 16. Once metal layer 48
is substantially removed outside the trench region, liner 50 is
subsequently removed from surface 44 outside the trench region by
continued polishing with slurry 18 and polishing pad 16.
[0017] Referring to FIG. 6, upon removal of metal layer 48 and
liner 50 from outside the trench region, a new surface 144 is
defined having first and second regions 146 and 148. First region
146 is comprised of metal from the remaining portions of metal
layer 48, with second region 148 comprising substrate 40 and liner
50. As a result, surface 144 has varying material properties across
an area thereof, with region 146 typically being harder than region
148, e.g. when region 148 is a dielectric material. As a result,
were polishing pad 16 to impart a uniform force against surface 144
for a given slurry composition, the polish rate of region 146 may
be greater than the polish rate of region 148. This may present as
"dishing" in which region 146 has a concave shape.
[0018] The present invention, however, significantly attenuates
dishing by changing the rate limiting step of the polishing
operation. In the present invention, metal removal is controlled
more by dissolution rather than kinetics during polishing of metal
layer 48. Specifically, it was recognized that by controlling or
limiting the removal rate by dissolution from surface 144, dishing
may be avoided while at the same time minimizing roughness. For
purposes of understanding the present invention, the polishing
operation can be understood to have two principle operating
mechanisms or steps, dissolution and kinetics. The kinetic step of
removal can be defined as the reaction to form soluble metal
oxides, while dissolution can be defined as the removal of the
metal oxide by dissolving the same in a solvent. In the context of
polishing copper, copper itself does not dissolve in solvents but
copper oxide does. Thus, to effectively remove copper using solvent
containing slurries, one has to first react the copper to form
copper oxide. In the present invention, the removal process is
principally governed or controlled by the removal of the oxides
from the surface by dissolution, and not by kinetics at the metal
interface.
[0019] Kinetic removal of material from surface 144 in accordance
with the invention has less of an influence in the polishing rate
in large part as a result of providing a neutral pH environment. In
a preferred embodiment, this is accomplished using a reactive
liquid (RL) slurry having a neutral pH. RL slurries are generally
characterized by containing little or no abrasives, i.e.,
particles. Removal of materials is achieved primarily through
chemical reaction of the material being polished with the RL slurry
components.
[0020] More specifically, a composition in accordance with an
embodiment of the present invention is provided with a pH that is
generally in the range of 5 to 8. Optimal results were achieved
using a pH of approximately 7.5. If present at all, particles in
the slurry are generally no greater than 250 parts per million of
the slurry composition or 0.0025 weight percent. Also included in
the composition is a corrosion inhibitor that further minimizes
kinetic removal of material from surface 144 during polishing.
Other components of the composition may include an oxidizing agent,
as well as a complexing agent that controls the rate of dissolution
of the material from surface 144. An exemplary material from which
region 146 is formed is copper. As a result, it is desired that the
RL composition facilitate removal of copper. An exemplary corrosion
inhibitor for the slurry composition may be a triazole-based
compound, such as 1,2,4-triazole, C.sub.2H.sub.3N.sub.3, and
benzotriazole. Other suitable inhibitors may include imidazole,
polyvinylimidazole, theophiline, bipyridyl, mercapto
benzothizole,phenyl marcapto tetrazole, or pyrazole compounds. An
exemplary oxidizing agent may be hydrogen peroxide, H.sub.2O.sub.2.
An exemplary complexing agent may be dibasic ammonium citrate,
(NH.sub.4).sub.2HC.sub.6H.sub.5O.sub.7, or more generally ammonium
salts of citric, oxalic, tartaric, succinic, or actetic acids.
[0021] A first embodiment of the present invention may be as
follows: TABLE-US-00001 COMPOSIITON 1 hydrogen peroxide dibasic
ammonium citrate 1,2,4-triazole water
Hydrogen peroxide consists of approximately 0.1% to 3%, and more
preferably 1% to 3%, by weight of COMPOSITION 1, and dibasic
ammonium citrate consists of approximately 0.1% to 12% by weight of
COMPOSITION 1. 1,2,4-Triazole consists of approximately 1% to 6% by
weight of COMPOSITION 1, with the remaining portion of the
COMPOSITION 1 consisting of a carrier including water.
[0022] A second embodiment of the present invention may be as
follows: TABLE-US-00002 COMPOSITION 2 hydrogen peroxide dibasic
ammonium citrate benzotriazole water
Hydrogen peroxide consists of approximately 0.1% to 3%, and more
preferably 1% to 3%, by weight of COMPOSITION 2, and dibasic
ammonium citrate consists of approximately 0.1% to 12% by weight of
COMPOSITION 2. Benzotriazole consists of approximately 0.0001% to
3% by weight of COMPOSITION 2, with the remaining portion of
COMPOSITION 2 consisting of a carrier including water.
[0023] A neutral pH RL slurry of the present invention offers many
advantages over conventional slurries, including improved
planarity. Specifically, copper is passivated when exposed to
neutral pH compositions. It is believed that the passivation of
copper during polishing provides improved planarization.
Additionally, the neutral pH slurry of the present invention
reduces the corrosion of the copper during polishing, thereby
minimizing the formation of micro-trenches and minimizing
roughness. As a result, the present neutral pH RL slurry provides
wider process windows, lower defects, and ease of integration into
present copper low-K dielectric layers.
[0024] The embodiments of the present invention described above are
exemplary. Many changes and modifications may be made to the
disclosure recited above, while remaining within the scope of the
invention. For example, the components of COMPOSITIONS 1 and 2 are
selected to facilitate planarization of surfaces having
copper-containing materials and dielectric-containing materials.
However, other components may be employed dependent upon the
materials contained in the layer being polished. Therefore, this
invention is not limited to the particular forms illustrated above.
Nor is the invention limited or restricted to the particular
theories, advantages, or perceived properties disclosed above.
Rather, the invention should be defined as set forth in the
appended claims and will cover all modifications that do not depart
from the scope of this invention.
* * * * *