U.S. patent application number 13/808391 was filed with the patent office on 2013-05-02 for nano-precision photo/electrochemical planarization and polishing methods and apparatus therefor.
The applicant listed for this patent is Lianhuan Han, Kang Shi, Jing Tang, Zhaowu Tian, Zhongqun Tian, Dongping Zhan, Jianzhang Zhou. Invention is credited to Lianhuan Han, Kang Shi, Jing Tang, Zhaowu Tian, Zhongqun Tian, Dongping Zhan, Jianzhang Zhou.
Application Number | 20130105331 13/808391 |
Document ID | / |
Family ID | 43053041 |
Filed Date | 2013-05-02 |
United States Patent
Application |
20130105331 |
Kind Code |
A1 |
Zhan; Dongping ; et
al. |
May 2, 2013 |
NANO-PRECISION PHOTO/ELECTROCHEMICAL PLANARIZATION AND POLISHING
METHODS AND APPARATUS THEREFOR
Abstract
The present invention provides a nano-presion
photo/electrochemical planarization and polishing method and an
apparatus therefor. The method comprises through electrochemical,
photochemical or photoelectrochemical means, an etchant being
generated on a surface of a tool electrode which has a
nanometer-sized planeness; the generated etchant reacting with a
scavenger contained in an working electrolyte solution, or decaying
itself in the working electrolyte solution, such that a confined
etchant liquid layer is generated on the tool electrode surface and
having a confined thickness of nanoscale; and by a chemical
reaction between the etchant contained in the confined etchant
liquid layer and a surface of a workpiece, the surface of the
workpiece being polished or planarized to a nanometer scaled
profile precision and surface roughness, thereby, realizing the
planarization and polishing in nano-precision for the
workpiece.
Inventors: |
Zhan; Dongping; (Fujian,
CN) ; Shi; Kang; (Fujian, CN) ; Tian;
Zhongqun; (Fujian, CN) ; Zhou; Jianzhang;
(Fujian, CN) ; Tian; Zhaowu; (Fujian, CN) ;
Han; Lianhuan; (Fujian, CN) ; Tang; Jing;
(Fujian, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zhan; Dongping
Shi; Kang
Tian; Zhongqun
Zhou; Jianzhang
Tian; Zhaowu
Han; Lianhuan
Tang; Jing |
Fujian
Fujian
Fujian
Fujian
Fujian
Fujian
Fujian |
|
CN
CN
CN
CN
CN
CN
CN |
|
|
Family ID: |
43053041 |
Appl. No.: |
13/808391 |
Filed: |
June 30, 2011 |
PCT Filed: |
June 30, 2011 |
PCT NO: |
PCT/CN11/76700 |
371 Date: |
January 4, 2013 |
Current U.S.
Class: |
205/668 ;
204/239 |
Current CPC
Class: |
C25F 3/00 20130101; C25F
3/12 20130101; C03C 15/02 20130101; H01L 21/30604 20130101; C25F
7/00 20130101; H01L 21/02024 20130101; H01L 21/7684 20130101; H01L
21/30612 20130101; C25F 3/14 20130101; H01L 21/32115 20130101 |
Class at
Publication: |
205/668 ;
204/239 |
International
Class: |
C25F 3/14 20060101
C25F003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 7, 2010 |
CN |
201010219037.5 |
Claims
1. A photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision,
comprising: through electrochemical, photochemical or
photoelectrochemical means, an etchant being generated on a surface
of a tool electrode which has a nanometer-sized planeness; the
generated etchant reacting with a scavenger contained in an working
electrolyte solution, or decaying itself in the working electrolyte
solution, such that a confined etchant liquid layer is generated on
the tool electrode surface and has a confined thickness of
nanoscale; and by a chemical reaction between the etchant contained
in the confined etchant liquid layer and a surface of a workpiece,
the surface of the workpiece being polished or planarized to a
nanometer scaled profile precision and surface roughness, thereby,
realizing the planarization and polishing in nano-precision for the
workpiece.
2. The photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision
according to claim 1, wherein a concentration ratio of precursor
which generates the etchant or leveling agent to the scavenger
usually is in a range of from 10:1 to 1:100 if the scavenger is
existed.
3. The photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision
according to claim 1, wherein the chemical reaction between the
etchant and the workpiece are at least one selected from the group
consisting of means of controlling the pH of the confined etchant
liquid layer to promote the concentration of strong acidic species
in the confined etchant liquid layer such that the workpiece is
reacted to produce soluble salt; means of generating a strong
oxidative etchant which reacts directly with the workpiece to
produce a soluble compound; means of forming an oxidative material
which oxidizes the workpiece surface to an oxide, and then the
oxide is dissolved by acidic or alkali species in the working
electrolyte solution; means of adding an additive or surfactant to
the working electrolyte solution, which is complex with metal ions
of the workpiece through complex reaction; and means of generating
strong oxidants in the confined etchant liquid layer, together
adding complexing agents to the confined etchant liquid layer so as
to promote solubility of the resultant product.
4. The photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision
according to claim 3, wherein the scavenger is selected from the
group of consisting of disulfide bond compounds, ferrocene and its
derivatives, persulfate salts, nitrites, sulfites, thiosulfates,
ascorbic acid, cystine and sorbitols.
5. The photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision
according to claim 1, wherein the working electrolyte solution
further contains at least one selected from the group consisting of
surfactants, supporting electrolytes, pH buffers and the mixtures
thereof.
6. The photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision
according to claim 1, wherein the tool electrode with nanometer
planeness is manufactured by at least one selected from the group
consisting of: a method of fabricating a tool electrode with
nano-planeness of platinum, gold, iridium, tungsten or other metal
though the ultra-precision machining; a method of depositing a
metal or semiconductor on a substrate with an atomic planeness
through various processes for forming film, or growing a metal or
semiconductor on the substrate through crystal epitaxial growth
technology to make the substrate conductive; a method of
fabricating a single-crystal electrode having a surface of
nano-planeness formed of platinum, gold, iridium and other metals
through accurately cooling or drawing of the corresponding metal
melt; a method of fabricating a electrode having a
nanometer-precise surface planeness by polishing and planishing
polycrystal or single crystal metal electrode through CMP
technology together with an electrolytic process; a method of using
a nanometer planeness surface formed by liquid metal or alloys
spontaneously; and a method for photocatalytical or
photoelectrocatalytical tool electrode, which comprising a step of
using an insulating quartz optical material or conductive ITO or
FTO optical glass as a substrate, and a step of covering the
substrate with a layer of TiO.sub.2, ZnO, WO.sub.3,
Fe.sub.2O.sub.3, CdSe or the composite photocatalysts thereof
through surface modification, electrochemical deposition in situ or
chemical vapor deposition.
7. The photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision
according to claim 1, further comprising: controlling the distance
between the tool electrode and the workpiece less than the
thickness of the confined etchant layer, and/or controlling the
relative motion between the tool electrode and the workpiece so as
to improve the profile precision the workpiece surface and lower
the surface roughness of the workpiece surface.
8. The photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision
according to in claim 7, wherein in the case of the tool electrode
being a planar tool electrode, the profile precision the workpiece
surface can be improved and the surface roughness the workpiece
surface can be lowered by means of making the tool electrode or the
workpiece rotate in a plane while being parallel swing.
9. The photo/electrochemically-induced confined chemical etching
method for a surface planarization and polishing in nano-precision
according to claim 1, wherein the method further includes a step of
adjusting the distance and parallelity between the tool electrode
and the workpiece.
10. An apparatus for the photo/electrochemically-induced confined
chemical etching method for a surface planarization and polishing
in nano-precision, wherein the apparatus comprises a tool
electrode, a photo/electrochemical reaction control system, a
working electrolyte solution recycling system, a working
electrolyte solution temperature control system, and an automated
control system; and wherein the tool electrode is a tool electrode
having a surface of nano-planeness; the photo/electrochemical
reaction control system is provided with a potentiostat, an optic
control system, a photo/electrochemical working electrode, an
auxiliary electrode, a reference electrode, a working electrolyte
solution and a container for the working electrolyte solution, and
the tool electrode functions as the photo/electrochemical working
electrode and connects with the potentiostat and/or the optic
control system, and the photo/electrochemical working electrode,
the auxiliary electrode and reference electrode are immersed in the
container in which the working electrolyte solution is contained,
and the workpiece is further contained; the working electrolyte
solution recycling system is used to recycle the working
electrolyte solution in the electrochemical reaction system and its
instrumental control system; the working electrolyte solution
temperature control system is used to keep the temperature of the
working electrolyte solution in the electrochemical reaction system
and its instrumental control system at a constant temperature; the
automated computer-controlled system is provided with a fixed
mount, a multi-dimension micro manipulator, a video monitor, a
force sensor, a parallel laser ranging device, an electrolytic
current feedback device and an information processing computer,
wherein a lower part of the fixed mount is used to fix the tool
electrode, and an upper part of the fixed mount is connected to the
Z-axial micro motor of the multi-dimension micro manipulator in the
automated computer-controlled system which connects with the
information processing computer; the X-Y-axial micro motors of the
multi-dimension micro-manipulator are employed as a workbench to
support the container; the video monitor is used to monitor an
approaching process of the tool electrode to the workpiece; the
current feedback device is used to monitor or measure the
electrical current flowing through the tool electrode surface; the
force sensor is used to detect whether the tool electrode touches
the workpiece or not; the parallel laser ranging device is used to
detect the distance between the tool electrode surface and the
workpiece surface; according to the collected parameters such as
the feedback current provided by the electrical current feedback
device, the contact force provided by the force sensor, and the
distance between the two surfaces provide by the parallel laser
ranging device, the information processing computer sends commands
to the Z-axial micro motor and the X-Y-axial micro motors of the
multi-dimension micro-manipulator to adjust the distance and
parallelity between the tool electrode surface and the workpiece
surface; the working electrolyte solution contains precursors of
the etchant and/or leveling agent, and the precursors of the
etchant and/or leveling agent can produce the etchant and leveling
agents on the surface of the tool electrode through
photo/electrochemical reaction, wherein if the produced etchant and
leveling agents cannot decay spontaneously, the working electrolyte
solution needs to further contain scavenger which reacts with the
etchant and/or leveling agent contained in the etchant liquid layer
and compacts the etchant liquid layer to a nanometer-scaled
thickness.
11. The apparatus for the photo/electrochemically-induced confined
chemical etching method for a surface planarization and polishing
in nano-precision according to claim 10, wherein the apparatus
adjusts the thickness of the confined etchant and/or leveling agent
liquid layer by tuning the potential of the photo/electrochemical
reaction system, wavelength and intensity of incident light,
photocatalytical layer parameter, and the formulation, temperature
and circulation of the working electrolyte solution.
Description
TECHNICAL FIELD
[0001] The present invention concerns a photo/electrochemical
inducing planarization and polishing technology based on confined
chemical etching, especially the planarization and polishing
methods and apparatus based on confined chemical etching on the
surfaces of metals, semiconductors or insulates for the large-area
and mass production.
STATE OF THE ART
[0002] Nowadays, in semiconductor industry, the feature linewidth
of ultra-large scale integrate circuit (ULSI) has been down to 120
nm and the diameter of wafer has been up to 300 mm. Feature
linewidth lower than 100 nm is coming into market. The number of
transistors on a single chip has broken through 10.sup.8. According
to the development blueprint of the Semiconductor Industry
Association of USA, the feature linewidth of microelectronics will
be down to 50 nm, the wafer diameter will be up to 450 mm by 2011,
and the metal layers of ULSI will be developed from 5-6 toward
larger than 5-6. At present, the International Semiconductor
Industry Association considers that the globe planarization of the
wafer has to be performed when the feature size is down to 350 nm
or less in order to ensure the precision and resolution of
lithography. Planarization and polishing will become a key
technique and play a crucial role in the development of the ULSI
manufacture.
[0003] The precondition of USLI manufacture is that a substrate
such as silicon wafer has to subject to the planarization and
polishing of the surface and then is used. With the feature size of
a device decreasing down to nanometer size, the requirements of
surface quality, especially the surface planeness and mechanical
damage of the silicon wafer become higher and higher while the
resolution and the focusing depth of lithography have more and more
limitation. Thus, the wafer with large size surface should have a
surface with a profile precision of nanometer and a surface
roughness of sub-nanometer. Meantime, the wafer should have a
surface and subsurface without stresses and damages. Furthermore,
each layer has to be planarized globally during the construction of
the multi-layer wiring of ULSI. With the development of ULSI in the
miniaturization of feature linewidth, three-dimensional
constructions and multi-layer wiring, RC delay affects the
performance of devices. In order to eliminate the RC delay,
multi-layer high frequency metal interconnection structures have to
be constructed. During the construction, if any layer constructing
the device is too high in surface roughness, the device will have
an increasing noise and poor uniformity of the electrical property,
which will reduce frequency characteristic of the device and
thereby reduce the integrated level, reliability and high quality
product of ULSI. Thus, each layer for the device must be globally
planarized, i.e., it is required to provide the removement and
planarization of the excess deposition of copper (Cu)
interconnectors of multiple wirings and of the dielectric layer
such as SiO.sub.2, SiOF and other layer with superlow k having
concavo and convex, which is a key step to achieve three
dimensional structure of the ULSI. Moreover, as the feature size is
further down, the adverse effect caused by diffusion of metal Cu
into the SiO.sub.2 insulating layer will tend to be severe. It is
an efficient way to provide a diffusion barrier layer or a porous
delectric material with superlow k (insulator) in order to solve
above technical problem. Moreover, Ta or TaN are considered a
desirable metal material for the barrier layer due to their
excellent adhesiveness to Cu and thermostability. However, the
deposition of Ta or TaN onto the microcircuit board is
non-selective. That means the insulator SiO.sub.2 layer will be
covered totally. Thus, the unwanted Ta or TaN depositions have to
be removed out of the Cu wire casing. Since Ta is a hard metal and
is harder when oxidized, how to remove and planarize the unwanted
Ta or TaN depositions will be another key technique for the globe
planarization for the future ULSI manufacture. Moreover, how to
planarize the fragile or flexible porous low-k dielectric material
still remains great challenge. In summary, developing a
multifunctional planarization and polishing method in
nano-precision applied to metal, semiconductor and insulator at the
same time is a common and key technique for the industrial
manufacture of ULSI, which is recognized by all the countries all
over the world.
[0004] Currently, chemical mechanical polishing (CMP) is the most
effective technology and the only way to achieve the submicron size
global planarization. CMP is a process of smoothing surfaces with
the combination of chemical and mechanical forces, i.e., the
oxidizers, catalysts and the like existed in the polishing slurry
react with the surface atoms of the workpiece to form an oxide film
on the workpiece surface, which is removed through mechanical
friction by the abrasive grains suspended in the polishing slurry;
the resulted fresh surface of the workpiece continues to be
oxidized; thus, with the alternative oxidization and polishing, the
workpiece surface is polished and planarized. However, due to the
nonuniformity of mechanical friction and external force, the
roughness after polishing still remains high, which will affect
directly on the subsequent processes and also the finished product
ratio. The most frequently used abrasive grains, e.g.,
Al.sub.2O.sub.3 particles, are hard and dispersed in the viscous
slurry, which is easy to cause surface damages, even deep surface
damages. Furthermore, there exist many other problems such as metal
ion contaminations to workpiece surface, poor dispersion of
abrasive grains in the slurry, and low removal rate in alkaline
environment. During application of the CPM technology, another
important issue is to determine and control the end points for the
planishing-polishing method, i.e. it is difficult to determine when
the desired amount of material has been removed or the desired
degree of planarization has been obtained. If the oxide layer has
been overly thinned and/or the desired degree of planarity has not
been obtained during this process, the sequence process would be
further done. More importantly, the future ULSI manufacture
requires the wafer of having a profile precision of nanometer and a
surface roughness of sub-nanometer, which is beyond the limit of
CMP (in a 20 mm.times.20 mm area Ra<20 nm). Although, in recent
years, assistant means of electrochemistry has be applied to CMP,
where anodic dissolution is employed so as to improve the effects
on polishing and planarization of copper or other semiconductor
material. Unfortunately, the above mentioned disadvantages for CMP
are not completely eliminated.
[0005] On the other hand, there are two development tendencies for
the manufacture of modern precision optical devices: the
micro-optical elements (MOC) and large dimensional ultra-precise
optical devices. MOC is the optical element constructed by freeform
optical surface with microstructure which has a profile precision
of micrometer and a surface roughness of sub-nanometer, typically
it includes the holographic lens, diffractive optical elements,
GRIN-rod lens and so forth. With the tendency of miniaturization,
MOC has prospective application into the science and technology of
both national defense and civil industrial domains. Large
dimensional ultra-precise optical devices are also important. For
example, it may use as the huge lens and reflecting mirrors of
space telescopes and the large dimensional high precise optical
glass elements in laser fusion devices, which should have a surface
roughness Ra of less than 1 nm in the high-frequency section. The
polishing method for the ultra-precision optical devices is also
dependent on CMP. Thus, it is necessary to develop a new
planarization and polishing method which may avoid the
disadvantages of CMP and, at meantime time, may achieve a profile
precision of nanometer and a surface roughness of
sub-nanometer.
[0006] The applicants, in their Chinese patent ZL03101271.X,
disclose a fabrication method and its apparatus for 3D complex
microstructures on metal surface. The method comprises: fixing a
molded tool electrode with micro structure on a fixing mount;
pouring the working electrolyte solution into an electrochemical
cell; immersing the molded tool electrode into the working
electrolyte solution; starting an electrochemical workstation to
produce etchant on the surface of the molded tool electrode;
confining a layer of the etchant into a micro/nano-meter thickness
through a scavenger existed in the electrolyte solution; starting a
manipulator to carry out a etching process for a workpiece by an
etchant layer such that material of a surface of the workpiece is
removed and separated from the etchant layer until the etching
process is completed. The manufacturing apparatus includes a molded
tool electrode, a fixed mount, a manipulator, an electrochemical
workstation, and a computer control system. This method and its
apparatus disclosed in the Chinese patent ZL03101271.X can perform
the mass production of the duplication of various 3D complex
microstructures. It is a one-step forming technique without
coating, exposuring, developing and decoating. Consequently, the
cost is lowered and the precision as well as the planarization are
promoted dramatically. Since this technique is indeed distance
sensitive, the removal amount for the workpiece can be well
controlled by accurately controlling feeding distance of a
template.
DISCLOSURE OF THE INVENTION
[0007] The first object of the present invention is to provide a
photo/electrochemically-induced confined chemical etching method
for the surface planarization and polishing in profile precision
and surface roughness of nanometer scale. This method comprises the
following steps: generating an etchant on the surface of a tool
electrode having a nanometer-sized planeness through
electrochemical, photochemical or photoelectrochemical means; the
generated etchant reacting with a scavenger contained in a working
electrolyte solution, or the etchant itself decaying such that an
etchant liquid layer with a thickness of nanometer-scale is
produced on the surface of the tool electrode; and the etchant in
the etchant liquid layer reacting with a workpiece such that the
surface of the workpiece is provided with nanometer-scale profile
precision and roughness, so as to realize planishing and polishing
in nano-precision for the workpiece.
[0008] The another object of the present invention is to provide an
apparatus for the photo/electrochemically-induced confined chemical
etching method for the surface planarization and polishing in
profile precision and surface roughness of nanometer scale. The
apparatus includes a tool electrode, a photo/electrochemical
reaction control system, an optic control system, a working
electrolyte solution recycling system, a working electrolyte
solution temperature controlled system, and an automated
computer-controlled system.
[0009] The tool electrode is a tool electrode having a planeness of
nanometer-scale;
[0010] The photo/electrochemical reaction control system includes:
a potentiostat, an optic control system, a photo/electrochemical
working electrode, an auxiliary electrode, a reference electrode, a
working electrolyte solution and a container. The tool electrode
functions as the photo/electrochemical working electrode and
connects with the potentiostat and/or the optic control system. The
photo/electrochemical working electrode, the auxiliary electrode
and reference electrode are immersed in the container which
contains the working electrolyte solution and also contains the
workpiece.
[0011] The working electrolyte solution recycling system is used to
recycle the working electrolyte solution in the
photo/electrochemical reaction control system;
[0012] The working electrolyte solution temperature controlled
system is used to make the working electrolyte solution in the
photo/electrochemical reaction control system at constant
temperature;
[0013] The automated computer-controlled system includes: a fixed
mount, a multi-dimension (>3D) micro-manipulator, a video
monitor, a force sensor, a parallel laser ranging device, an
electrical current feedback device and an information processing
computer. The lower part of the fixed mount functions to fix the
tool electrode, and the upper part of the fixed mount functions to
connect with the Z-axial micro motor of the multi-dimension
micro-manipulator in the automated computer-controlled system,
wherein the Z-axial micro motor connects with the information
processing computer. The container is provided on the X-Y-axial
micro motors of the multi-dimension micro manipulator. The video
monitor is used to monitor the approaching process of the tool
electrode to the workpiece. The electrical current feedback device
is used to monitor or measure the electrical current flowing
through the surface of the tool electrode. The force sensor is used
to detect whether the tool electrode touches the workpiece or not.
The parallel laser ranging device is used to detect the distance
between the tool electrode and the workpiece. According to the
collected parameters such as the feedback current provided by the
electrical current feedback device, the contact force provided by
the force sensor, and the distance between the two surfaces provide
by the parallel laser ranging device, the information processing
computer send commands to the Z-axial micro motor and the X-Y-axial
micro motors of the multi-dimension micro manipulator to adjust the
distance and parallelity between the tool electrode surface and the
workpiece surface.
[0014] The working electrolyte solution contains precursors of the
etchant and/or leveling agent. The precursors of the etchant and/or
leveling agent can generate the etchant and leveling agents on the
surface of the tool electrode through photo/electrochemical
reaction. If the generated etchant and leveling agents cannot decay
spontaneously, the electrolyte solution further contains scavengers
which can confine the etchant liquid layer on the tool electrode
surface to a nanometer-scaled thickness.
[0015] The polishing and planishing method and apparatus disclosed
by the present invention can realize a nanometer-scaled profile
precision and surface roughness (i.e. nano-precision) on the
surface of the workpiece. Comparing to CMP, the distinct advantages
of the present invention lie in that: there is no surface and
sub-surface mechanical damages for a workpiece; there is no
residual stress; and the endpoint of polishing and planarization is
easily controllable.
DESCRIPTION OF FIGURE
[0016] FIG. 1 is schematic diagram of an example of the apparatus
of the present invention for the photo/electrochemically-induced
confined chemical etching method for a surface planarization and
polishing in nano-precision.
[0017] FIG. 2 is schematic diagram of another example of the
apparatus of the present invention for the
photo/electrochemically-induced confined chemical etching method
for a surface planarization and polishing in nano-precision.
[0018] FIG. 3 is schematic flow chart of the
photo/electrochemically-induced confined chemical etching method
for a surface planarization and polishing in nano-precision
according to the present invention.
[0019] FIG. 4 is the schematic diagrams of a nano-planeness planar
tool electrode and its technical process for polishing and
planishing the surface of a workpiece used in the present invention
wherein it is described that the tool electrode having a large size
in X-Y dimensions approaches the workpiece. During polishing and
planarization, the workbench is rotating while the tool electrode
or the workpiece is swaying on the plane of workbench. Through the
relative movement between the tool electrode and the workpiece, the
profile precision on the surface of the workpiece is further
improved and the surface roughness is lowered.
[0020] FIG. 5 is the schematic diagrams of a nano-planeness linear
tool electrode and its technical process used in the present
invention. The linear tool electrode has a larger size in X
dimension but smaller size in Y dimension, and the tool electrode
or the workpiece is subjected to a relative movement (translation
movement or rotary motion) in X-Y direction to realize the
large-area polishing and planarization of a plane surface in mass
production.
[0021] FIG. 6 is the schematic diagrams of a nano-planeness linear
tool electrode and its technical process used in the present
invention. The tool electrode has a larger size in X dimensions but
smaller size in Y dimension. The tool electrode approaches to a
rotating workpiece to realize the large-area polishing and
planarization of a cylindrical surface.
[0022] FIG. 7 is the schematic diagram of a milling cutter like
tool electrode with nano-planeness, which moves according to a
programmed track to perform large-area polishing and planarization
of an irregular surface.
[0023] FIG. 8 is the SEM images of a copper (Cu) surface before (a)
and after (b) polishing and planarization according to example 1 of
the present invention.
[0024] FIG. 9 is the SEM images of a silicon (Si) surface before
(a) and after (b) polishing and planarization according to example
2 of the present invention.
[0025] FIG. 10 is the SEM images of gallium arsenic (GaAs) surface
before (a) and after (b) polishing and planarization according to
example 3 of the present invention.
[0026] FIG. 11 is the SEM images of a SiO.sub.2 glass surface
before (a) and after (b) polishing and planarization according to
example 4 of the present invention.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
Definitions
[0027] In the present invention, the term "photo/electrochemical"
includes photochemical, electrochemical and/or photoelectrochemical
means which are employed to produce etchant at a surface of the
tool electrode.
[0028] In the present invention, the terms "etchant" or "etchant
and/or leveling agent" refer to chemicals which can react with and
etch the surface of the workpiece, or catalysts which can promote
the etching and polishing rate of the etchant and/or leveling agent
contained in the working electrolyte solution. The terms
"precursors of the etchant" refer to materials which can produce an
etchant through inducing of the photo/electrochemical reaction.
[0029] In the present invention, the term "confined etchant layer"
refers to a liquid layer with a nanometer-sized thickness
containing etchant and/or leveling agent which is generated through
photo/electrochemical means and compacted by the scavengers in the
working electrolyte solution. In general, the thickness of confined
etchant layer is controlled no more than 100 nm. In the more
accurate polishing and planarization process, it can be controlled
less than 20 nm. The term "confined" means the thickness of the
etchant liquid layer always keeps a thickness at nanometer scale
during the processes of polishing and planarization of the
workpiece.
[0030] In the present invention, the term "scavenger" is the
chemical in the working electrolyte solution which can react with
the etchant and/or leveling agent produced on the surface of the
tool electrode and, consequently, compact the etchant liquid layer
into a thickness of nanometer scale.
[0031] In the present invention, the terms "confined etching
system" and "working electrolyte solution" refer to the solution
system containing a precursors of etchant, a scavenger and
optionally, a surfactant, a supporting electrolyte, a pH buffer,
and the like according to special object to be etched, or, the
solution system containing a precursors of etchant, and optionally,
a surfactant, a supporting electrolyte, a pH a buffer, and the like
according to special object to be etched. The term "mass balance of
the confined etching system" means to keep a ratio of the
components of the confined etching system in a reasonable
range.
[0032] The present invention provides a
photo/electrochemically-induced chemical etching method for surface
planarization and polishing in a nanometer scale precision,
characterized by use of the confined etchant layer technique
(CELT). That is, through the photo/electrochemical means, a
confined etchant and/or leveling agent layer having a thickness of
nanometer scale is formed on the surface of the tool electrode with
nano-planeness; the etchant reacts with and remove a workpiece
material until the profile precision and surface roughness of the
workpiece surface reach a precision of nanometer scale; thereby the
workpiece achieves the desirable polishing and planishing
treatment. The basic principle of CELT is described as
followed:
[0033] (1) Through the electrochemical, photochemical or
photoelectrochemical means, i.e. the suitable parameters such as
potential or/and light wavelength and intensity is choosed based on
chemical characteristics of the confined etching system, the
precursors of etchant will be reacted to form etchant on the
surface of tool electrode through the photo/electrochemical means.
The etchant can be either a conventional chemicals or chemical
radicals. The etchant generation reaction presented on the surface
of the tool electrode can be expressed as:
R.fwdarw.O+ne or R+h.nu..fwdarw.O (+ne) (1)
where, R is the precursor of etchant and O is the generated
etchant.
[0034] (2) The scavenger contained in the working electrolyte
solution will react with the etchant in the vicinity of tool
electrode surface to compact the etchant layer to a thickness of
nanometer scale. If the generated etchant is a chemical radical,
the thickness of the etchant layer can be compact through either
the scavenger or spontaneous decay of the radical itself. The
scavenging reaction can be expressed as:
O+S.fwdarw.R+Y or O.fwdarw.Y (2)
where, S is the scavenger and Y is product by a reaction between
the etchant O and the scavenger or by the decay of the etchant O
itself. The thickness of confined etchant layer depends on the
reaction rate of reaction (1) and (2), and the concentration ratio
of between the etchant precursor and the scavenger. If the
concentration of the scavenger is pretty higher than that of the
etchant precursor, a limited thickness of the confined etchant
layer can be estimated by the following equation:
.mu.=(k.sub.2/D.sub.R).sup.1/2 (3)
where, k.sub.2 is the quasi-first order reaction rate of scavenging
reaction (2), D.sub.R is diffusion coefficient of etchant precursor
in the working electrolyte solution. In the practical etching
process, the thickness of confined etchant layer can be adjusted by
changing the concentration ratio of between the etchant precursor
and the scavenger, i.e., the precision of polishing and
polarization can be tunable. Although the thickness of a confined
etchant layer is at nanometer scale, the concentration distribution
of etchant keeps constant inside the confined etchant layer.
[0035] (3) Through the automated computer-controlled system, let
the confined etchant layer contacts with the workpiece and start
the process of polishing and planarization for the workpiece. The
etching reaction can be expressed as:
O+M.fwdarw.R+P (3)
where, M is the material of workpiece, and P is the product of a
reaction between the workpiece and the etchant. The removal rate of
the workpiece surface is determined by a rate of the etching
reaction (3). Once the surface parts of workpiece contacting with
the confined etchant layer are removed, the workpiece will separate
from the confined etchant layer. Consequently, the polishing and
planarization process stops. Then, the automated
computer-controlled system will feed the tool electrode and
continue the etching process until the workpiece is well polished
and planarized.
[0036] Concretely, the photo/electrochemically-induced, chemical
etching method for surface planarization and polishing in a
nanometer scale precision described in the present invention
includes the following steps:
[0037] (1) Fabricating a tool electrodes with nano-precision
planeness surface as the working electrode for the
photo/electrochemical reaction to produce an etchant through
photo/electrochemical means;
[0038] (2) Fixing the tool electrode with nano-precision planeness
surface on a fixed mount and a workpiece in the bottom of a
container; or fixing the workpiece on a fixed mount (or the
workbench), and fixing the tool electrode with nano-precision
planeness surface in the bottom of a container;
[0039] (3) Pouring a working electrolyte solution into the
container, which containing the etchant precursor, a scavenger, a
solvent and at least one selected from the group consisting of a
surfactant, a supporting electrolyte, a pH buffer and so on;
[0040] (4) Immersing the tool electrode (or the workpiece) into the
working electrolyte solution as the working electrode for the
photo/electrochemical reaction. In the container, the reference and
auxiliary electrodes are also implanted. The photo/electrochemical
reaction system starts and produces an etchant on the surface of
tool electrode. The produced etchant reacts with the scavenger, or
spontaneously decays if the etchant is free radical, and forms the
confined etchant layer with a thickness of nanometer scale on the
surface of tool electrode;
[0041] (5) Through the multi-dimension micro-manipulator driven by
the automated computer-controlled system, feeding the tool
electrode (or workpiece) and approaching it to the workpiece (the
tool electrode); adjusting the distance and parallelity between the
tool electrode surface and the workpiece with the help of in-situ
observation from the video monitor and parallel laser ranging
device. Furthermore, through controlling the distance between the
tool electrode and the workpiece less than the thickness of the
etchant layer or/and the relative motion (comprising translation
movement and rotary movement) between the tool electrode and the
workpiece to improve the mass balance of the working electrolyte
solution. In this way, the uniformity of polishing and
planarization is promoted, i.e., the profile precision of the
working piece surface is improved and the surface roughness of the
working piece surface is lowered;
[0042] (6) Feeding the tool electrode (or the workpiece) in
vertical direction to the workpiece (or the tool electrode) such
that the confined etchant layer on the tool electrolyte surface
contacts with the workpiece surface, and thereby keeps the etching
process advance. Also, the tool electrode or workpiece to be
processed is fed in X-Y dimensions until the whole surface of
workpiece to be processed is well polished and planarized.
[0043] In the step (4), the thickness of the confined etchant
liquid layer can be tuned through controlling the potential of a
tool electrode, a wavelength and intensity of a light-wave, and a
formulation, temperature and recycle of the working electrolyte
solution. The described confined etchant layer can be controlled at
a thickness of 100 nm or less, preferably less than 20 nm. In
practice, an amount of etchant is controlled by selection of the
parameters such as the limiting diffusion potential of the
generation reaction of the etchant as well as the wavelength and
intensity of the excised light, and the selection of these
parameters directly affect on the thickness of confined etchant
layer, and the removal rate of the workpiece surface. The described
"limiting diffusion potential" means under this potential the
photo/electrochemical current keeps a constant maximum. For
example, when etching Si under acidic condition, the "limiting
diffusion potential" for oxidizing a bromide ion (Br.sup.-) to an
etchant bromine (Br.sub.2) should be 0.9 V or more. The term
"surface removal rate" refers the removal mass of workpiece surface
material in a unit time by the chemical etching (g/min), or the
removal thickness of the workpiece surface in a unit time
(.mu.m/min) For example, in the case of etching GaAs by Br.sub.2,
the surface removal rate can be achieved 0.2 .mu.m/min.
[0044] In the step (5), the distance and parallelity between the
tool electrode and the workpiece can be controlled based on the
feedback parameters provided by the current feedback device, the
force sensor and the parallel laser ranging device.
[0045] The tool electrode (a working electrode in the
photo/electrochemical system) used in the present invention has a
nanometer-precise surface planeness, which can be planar and have a
large size in X-Y dimensions, or be linear and have a large size in
one dimension. The tool electrode may be fabricated by the method
for preparing the tool electrode having a nanometer-precise surface
planeness in the prior art, or may be fabricated by some new
methods provided by the present inventor for preparing the tool
electrode having a nanometer-precise surface planeness. These
methods are listed as followed:
[0046] (1) Fabricating a tool electrode with nano-planeness of
platinum, gold, iridium, tungsten or other metal though the
ultra-precision machining (e.g., nano-cutting).
[0047] (2) Depositing a metal or semiconductor on a substrate with
an atomic planeness through various processes for forming film
(such as electron beam evaporation, magnetron sputtering,
electroplating and chemical plating), or growing a metal or
semiconductor on the substrate through crystal epitaxial growth
technology to make the substrate conductive.
[0048] (3) Fabricating a single-crystal tool electrode having a
surface of nano-planeness formed of platinum, gold, iridium or
other metal through accurate cooling or drawing of the
corresponding melt metal;
[0049] (4) Fabricating a electrode surface having a
nanometer-planeness by polishing and planarizing polycrystal or
single crystal metal electrodes through CMP technology together
with an electrolytic process;
[0050] (5) Using a nanometer planeness surface formed by liquid
metal or alloy spontaneously; and
[0051] (6) A process for photocatalytical or
photoelectrocatalytical tool electrode, that is, the insulating
quartz optical material or conductive ITO or FTO optical glass is
used as a substrate, and is covered with a layer of TiO.sub.2, ZnO,
WO.sub.3, Fe.sub.2O.sub.3, CdSe or the composite photocatalysts
thereof through surface modification, electrochemical deposition in
situ or chemical vapor deposition.
[0052] During the polishing and planarization process, the species
produced in the vicinity of tool electrode surface through
photo/electrochemical means may be either the etchant and leveling
agent which can directly react with the material of workpiece
surface, or be one of catalysts which can accelerate the chemical
etching rate of the etchant and leveling agent contained in the
electrolyte solution, or the both.
[0053] In the photo/electrochemically-induced confined chemical
etching method for surface planarization and polishing in nanometer
scale precision according to the present invention, the etchant and
leveling agent can be widely chosen according to different
workpieces. In general, etchants are determined by the material of
workpiece, and suitable precursors of etchants and corresponding
scavengers are determined by the etchants. Moreover, the selected
precursors of the etchant and leveling agent and the selected
scavengers are added to the working electrolyte solution,
respectively.
[0054] The workpiece to be processed in the present invention can
be a workpiese formed of metals (e.g., Cu in the USLI board),
semiconductors (e.g., Si substrate), or insulators (e.g., SiO.sub.2
glass). Furthermore, the present invention can realize polishing
and planarization in nano-precision of the surface of metals,
semiconductors or insulators in mass production.
[0055] For example, when the workpieces to be processed are metals,
the concentration of strong acids such as HNO.sub.3,
H.sub.2SO.sub.4 and the like contained in the confined etchant
layer is increased by a control of pH of the confined etchant
layer, and thereby the metal is reacted with the acid to form
soluble salts; or an etchant with strong oxidizability such as
oxygen, fluorine, chlorine, bromine, ferrocene, iron cyanides,
metal complex and the like is generated and can directly react with
the objective metal to form soluble salt; or a strong oxidant such
as hydrogen peroxide, oxygen, ozone, oxygen-containing radicals is
generated and can react with the metal surface to form oxide, then,
the formed oxide can be dissolved and removed by acid material
contained in the electrolyte solution such as sulfuric acid, nitric
acid, hydrochloric acid, oxalic acid and the like. The examples of
the used scavengers are compounds containing disulfide bond such as
cystine and the like, ferrocene and its derivatives, persulfates,
nitrites, sulfites, thiosulfates, ascorbic acid, sorbitol, and
mixtures thereof. In order to improve the solubility of metal ions
in the working electrolyte solution, additives or surfactants may
be added to the working electrolyte solution and complex with the
metal cations. The examples of the additives and surfactants
include halide ions, ammonia, cyanide ion, thiocyanide ion,
crownether based supermolecular compounds, sodium alkylsulfonate,
polyethers (preferably oxyethylene), nitrogen-containing azole
based compound and so forth.
[0056] For example, when the objective workpieces are
semiconductors such as Si, Ge, GaAs, or transition metals and their
binary/ternary alloys thereof, or insulators such as quartz, glass,
sapphire, MgO, TeCdHg, and KH.sub.2PO.sub.4, the strong oxidants
such as oxygen, fluorine, chlorine, bromine, permanganate ion,
bichromate ion, perchlorate ion, nitrate ion, or oxygen-containing
free radicals are generated in the confined etchant layer, and
meanwhile, complexing agents such as halide ions, ammonia, cyanide
ion, thiocyanide ion, crownether based supermolecular compounds,
sodium alkylsulfonate, polyethers (preferably polyoxyethylene), or
nitrogen-containing azole based compound are added to the working
electrolyte solution to improve the solubility of etching products
and thereby achieve the object of polishing and planishing surface
of the workpiece. The used scavengers are the reductive compounds
such as cystine and the other compounds containing disulfide bond,
ferrocene and its derivatives, persulfates, nitrites, sulfite,
thiosulfates, ascorbic acid, sorbitol, or mixtures thereof. The
used solvent may be water, acetonitrile, tetrahydrofuran,
dimethylsulfoxide, N,N'-dimethylformamide, and ionic liquids
including quarternary ammonium ion, quarternary phosphorus ion,
imidazolium ion, or pyrrolium ion as a cation.
[0057] Moreover, as described above, the thickness of the confined
etchant layer according to the present invention also depends on
concentration ratio of etchant over scavenger. In general, the
ratio is from 10:1 to 1:100, preferable 1:1 to 1:20. For example,
when at least one selected from the group consisting of ferrocene
and its derivatives, persulfate, dissolved oxygen, bromide,
fluoride, and alkylamine is used as etchant precursor, the
concentration of etchant precursor is usually controlled in a range
from 0.001 to 1.0 mol/dm.sup.3. The etchant precursors generate
etchants and/or leveling agents which can etch the surface of the
workpiece through electrochemical reaction, and the generated
etchants and/or leveling agents may rapidly react with at least
scavenger selected from the group consisting of disulfide bond
compounds, ferrocene and its derivatives, persulfates, nitrites,
sulfites and thiosulfates. Consequently, the lifetime of the
etchant and/or leveling agent will be shortened due to the fast
scavenging reaction. Since their lifetime is very short, the
etchant and/or leveling agents can't diffuse too far away from the
tool electrode surface and would form a confined etchant liquid
layer having a thickness of nanometer scale. That means the
polishing and planarization can be processed with an extremely high
resolution. Moreover, due to the existence of confined etchant
liquid layer between the tool electrode and the workpiece, the tool
electrode does not actually contact the surface of the workpiece
and thereby keeps its surface retaining the nano-precise
planeness.
[0058] When the etchant precursors used in the present invention
are at least one selected from the group consisting of dissolved
oxygen, ozone, peroxides, superoxides, oxynitrides, hypochlorites,
nitrites, persulfates and alkyl peroxides, the concentrations of
the etchant precursors are in range of from 0.001 to 1.0
mol/dm.sup.3. The free radical etchant is produced through
photo/electrochemical reaction on the surface of tool electrode and
etches the workpiece surface. Since the free radicals etchant in
these cases are chemical radicals with very short lifetime, they
only diffuse in the solution in very short diffusion distance from
the surface of tool electrode. Thus, a confined etchant liquid
layer having a thickness of nanometer scale may be formed on the
surface of tool electrode. Thus, a chemical etching on the surface
of the workpiece may be performed at extremely high resolution.
[0059] Moreover, due to the existence of confined etchant liquid
layer between the tool electrode and the workpiece, the tool
electrode does not actually contact the surface of the workpiece
and thereby keeps its surface retaining the nano-precise
planeness.
[0060] According, it can be concluded that the formulation of the
working electrolyte solution used in the present invention meets
the following requirements:
[0061] (1) The working electrolyte solution contains precursors of
the etchants and/or leveling agents. The etchants and leveling
agents can be produced through photo/electrochemical reaction and
etch the workpiece surface. The reaction rate is sufficiently high,
and the etching rate is not less than 10 nm/min.
[0062] (2) The chemical etching reaction between the etchant and
the workpiece should be isotropic.
[0063] (3) There should be no indissolvable or poor dissolubility
compounds formed during the process of polishing and
planarization.
[0064] (4) The scavengers (confining agents) can react fast with
the etchants and/or leveling agents and confine the etchant and/or
leveling agent layer in a thickness of nanometer scale.
[0065] (5) The whole solution system should be stable.
[0066] Comparing to CMP, prominent advantages of the present
invention are listed as followed:
[0067] (1) Since the tool electrode doesn't contact with the
workpiece, there are no surface and subsurface mechanical damages
and no residual stress on the workpiece surface.
[0068] (2) Since there are no other metal ions formed during the
polishing and planarization process, which are easily precipitated,
the metal ions contaminations can be avoided.
[0069] (3) Since the occurrence of a chemical etching and/or
leveling reaction depends on whether the confined etchant liquid
layer contacts with the workpiece surface or not, the polishing and
planarization is typically a self-ended process. That means, with
the chemical etching and/or leveling reaction going on, the surface
material of workpiece is gradually dissolved and finally separates
from the confined etchant layer. Then, the chemical etching
reaction is stopped. Therefore, the end-point of polishing and
planarization process is controllable.
[0070] The second object of the present invention is to provide an
apparatus for the photo/electrochemically-induced confined chemical
etching method which provides a workpiece with profile precision
and surface roughness of nanometer scale. The apparatus includes a
tool electrode, a photo/electrochemical reaction control system, a
working electrolyte solution recycling system, a working
electrolyte solution temperature control system, and an automated
computer-controlled system.
[0071] The tool electrodes have a nano-precise planeness. The
materials of the tool electrodes can be metals such as platinum,
gold, iridium, tungsten, titanium and the like, and alloys thereof;
or semiconductors such as TiO.sub.2, ZnO, WO.sub.3,
Fe.sub.2O.sub.3, CdSe, and the like, and photocatalytic composites
thereof; or non-metal materials such as glass carbon, high
temperature pyrolysis graphite, boron doped diamond and so on.
[0072] There are no special limitation on the shape of tool
electrode, which can be a milling cutter like shape, a linear
scraper like shape, a planar disk like shape or a groove based on
the principle of hydrodynamic design. However, reasonable designs
of the shape of the tool electrode, relative motion between the
tool electrode and the workpiece and feeding means of the tool
electrode are selected such that the processed shape of the
workpiece may be plane, cylinder, cone, sphere, and non-sphere. In
this way, the profile precision of workpiece is improved, and the
surface roughness of workpiece is lowered. For example, in the case
of a disk tool electrode, the profile precision can be improved and
the surface roughness can be lowered by means of keeping the tool
electrode or workpiece rotating while lateral swing in a plane.
[0073] The photo/electrochemical reaction control system can
precisely control the thickness of the etchant and/or leveling
agent layer at nanometer scale. In general, the thickness of the
confined etchant layer can be controlled no more than 100 nm. In
the more precise process of polishing and planarization, the
thickness of the confined etchant layer can be controlled no more
than 20 nm. Herein, the photo/electrochemical reaction system
includes: a potentiostat or/and an optic control system, a
photo/electrochemical working electrode, an auxiliary electrode, a
reference electrode, a working electrolyte solution and a
container.
[0074] The working electrolyte solution recycling system includes a
circulating pump, a flow controller and a fluid bath.
[0075] The working electrolyte solution temperature controlled
system includes a thermoscope, a heater, a cooler and a fluid
bath.
[0076] The automated computer-controlled system includes: a fixed
mount, a multi-dimension (.gtoreq.3D) micro manipulator, a video
monitor, a force sensor, a parallel laser ranging device, an
electric current feedback device and an information processing
computer.
[0077] The tool electrode is fixed on the lower part of the fixed
mount. The upper part of the fixed mount is connected with the
Z-axial micro motor of the multi-dimension micro-manipulator in the
automated computer-controlled system, wherein the Z-axial micro
motor is controlled by the information processing computer. The
tool electrode functions as the photo/electrochemical working
electrode, which is connected with potentiostat and/or optical
control system via the fixed mount. The auxiliary and reference
electrodes are implanted into the working electrolyte solution in
the container. The working electrolyte solution is heated to a
constant temperature by the working electrolyte solution
temperature controlled system, then pumped into the container, and
circulated between the container and the fluid bath at constant
temperature by the working electrolyte solution recycling system.
The container is provided on the X-Y-axis micro motors of the
multi-dimension micro-manipulator. The workpiece is placed in the
container. The video monitor is used to control the procedure of
the tool electrode approaching to the workpiece. The electrical
current feedback device is used to detect the electrical current
flowing through the surface of tool electrode. The force sensor is
used to detect whether the tool electrode contacts with the
workpiece or not. The parallel laser ranging device is used to
detect the distance between the tool electrode surface and the
workpiece surface. According to the collected parameters (such as a
feedback electrical current provided by the electrical current
feedback device, a contact force provided by the force sensor, and
a distance between the two surfaces provided by the parallel laser
ranging device), the information processing computer will send
commands to the Z-axial micro motor and X,Y-axis micro motors of
the multi-dimension micro-manipulator to adjust the distance and
parallelity between the tool electrode surface and the workpiece
surface. At the meantime, the multi-dimension micro-manipulator is
also used to control the feeding means of tool electrode, and the
relative motion means between the tool electrode and the
workpiece.
[0078] The working electrolyte solution contains precursor of an
etchant and leveling agent or/and a scavenger and a solvent, and
optionally, a surfactant, a supporting electrolyte, a pH buffer and
so on.
[0079] The solvent may be water, organic solvents, or ionic
liquids. The organic solvent may be at least one selected form the
group consisting of acetonitrile (CH.sub.3CN), dimethyl sulphoxide
(DMSO), N,N'-dimethylformamide (DMF) and so on, and mixtures
thereof. The ionic liquids include quarternary ammonium ion,
quarternary phosphorus ion, imidazolium ion, pyrrolium ion or the
like as a cation. The additives contained in the ionic liquids may
be at least one selected from the group consisting of urea,
acetamide, thiourea, trichloroacetic acid, phenylacetic acid,
malonic acid, oxalic acid, p-toluene sulfonic acid, m-cresol,
p-cresol, o-cresol, (-)fructose, and the like, and mixtures
thereof. The additives have a concentration in a range of from 5%
to 95% by mass based on the total mass of the working electrolyte
solution.
[0080] The precursor of the etchant and/or leveling agent used in
the present invention may be at least one selected from the group
consisting of ferrocene and its derivates, persulphate, dissolved
oxygen, bromide, fluid, alkyl amine compound and the like. In
general, the precursor of the etchant and/or leveling agent has a
concentration in a range of from 0.001 to 1.0 mol/dm.sup.3,
preferably from 0.01 to 0.1 mol/dm.sup.3. The scavenger may be at
least one selected from the group consisting of mercapto compound,
ferrocene and its derivatives, persulfates, nitrites, sulfites,
thiosulfates, and the like, and has a concentration in a range of
from 0.05 to 10.0 mol/dm.sup.3, preferably 0.1.about.1.0
mol/dm.sup.3. The surfactant may be at least one selected from the
group consisting of alkylsulfonate, quarternary ammonium salts,
polyethers, benzotriazole compound and the like. In general, the
surfactant has a concentration in a range of from 0.001 to 1.0
mol/dm.sup.3, preferably 0.01.about.0.1 mol/dm.sup.3.
[0081] The supporting electrolytes used in the working electrolyte
solution function to ensure conductivity of the working electrolyte
solution. The concentration of the supporting electrolyte is varied
depending on the concrete material of the workpiece to be
processed, and is usually 0.01 to 1 mol/L. A pH buffer added in the
working electrolyte solution may be either acid or alkali.
[0082] The micro manipulator, the information processing computer,
and the electrochemical reaction control system used in the
apparatus for the photo/electrochemically-induced confined chemical
etching method which provides a workpiece with profile precision
and surface roughness of nanometer scale according to the present
invention have been explained in the former Chinese patent
ZL03101271.X of the present applicant, respectively. Based on the
mentioned former patent, the micro manipulator extends from
3-dimensions to multi-dimensions (.gtoreq.3D), which is suitable
for the polishing and planarization of complex surface types.
Meantime, an optical control system is added in the apparatus of
the present invention so as to modulate the process of polishing
and planarization in photo- and electrochemical means. Since a
confined etchant layer technique is adopted and a thickness of the
confined etchant layer formed by photo/electrochemical reaction on
the surface of tool electrode is at nanometer scale, the
parallelity between the tool electrode and the workpiece is very
crucial, especially, in the process of polishing and planishing a
workpiece with large area. In the former patent, a force sensor is
adopted to adjust the distance between the tool electrode and the
workpiece. In the present invention, a parallel laser ranging
device is further incorporated into the apparatus of the present
invention so as to adjust the distance and parallelity between the
tool electrode and the workpiece together with the force sensor. In
addition, the automated control system is incorporated into the
apparatus of the present invention for fine tuning the
multi-dimensional micro-manipulator, and, for feeding the tool
electrode toward the workpiece until the confined etchant layer
contacts the surface of workpiece to start the etching process
through the feedback information from the current feedback device,
the force sensor and the parallel laser ranging device. With the
etching and leveling process going on, the surface material of
workpiece is gradually dissolved and removed, and the automated
control system keeps feeding the tool electrode through the
multi-dimensional micro manipulator until the polishing and
planarization well-done. The polishing and planarization process
may be monitored through the video monitor. In order to ensure
complement of scavenger and the mass balance during the polishing
and planarization process, and in order to adjust etching reaction
rate, the working electrolyte solution recycling system and the
temperature control system are added in the present invention.
[0083] There is no mechanical stress, surface and subsurface
damage, and metal ion contamination on the workpiece surface during
the polishing and planarization process. The processing end-point
of the polishing and planarization process is very easily
controlled. Meanwhile, the method according to the present
invention may apply to the mass production of large scale surfaces
of various materials such as metals, semiconductors and
insulators.
[0084] FIG. 1 shows a schematic diagram of an example of the
apparatus for performing the photo/electrochemically induced,
confined chemical etching method for nano-precise polishing and
planarization according to the present invention. The tool
electrode 5 is a disk platinum electrode with a surface planeness
of nanometer precision. The tool electrode 5 is fixed on the lower
part of the fixed mount 4. The fiber optical probe 16 of the
parallel laser ranging device 17 fixed on the outside of the tool
electrode 5 is also fixed on the lower part of the metal fixed
mount 4. The parallel laser ranging device 17 is connected to the
information processing computer 3. The metal fixed mount 4 is
composed by two cylinders with different diameter. The Z-axial
micro motor 2 of the micro manipulator is equipped on the upper
part of the fixed mount 4 and connected to the information
processing computer 3. The electrochemical control system comprises
a potentiostat 1, an auxiliary electrode 8, a reference electrode
9, a container 10, a working electrolyte solution 11 and so on. The
disk platinum tool electrode 5 connects with the potentiostat 1 via
the fixed mount 4, and thereby acts as the electrochemistry working
electrode. The auxiliary electrode 8 and the reference electrode 9
are immersed into the working electrolyte solution 11. The working
electrolyte solution 11 is heated and kept at a constant
temperature through the fluid bath at constant temperature 13, and
then injected into the container 10. Under the help of the working
electrolyte solution recycling system 12, the working electrolyte
solution is circulated between the container 10 and the fluid bath
at constant temperature 13. The container 10 is provided on the
force sensor 15 which is connected with the information processing
computer 3. Moreover, both the container 10 and the force sensor 15
are equipped on the X-Y-axial (i.e. horizontal axis) micro motor 7
(not shown in FIG. 1) of the manipulator. The workpiece 6 is placed
in the container 10. The video monitor 14 is used to detect whether
the tool electrode contacts with the workpiece or not.
[0085] FIG. 2 shows another schematic diagram of the apparatus for
performing the photo/electrochemically induced, confined chemical
etching method for nano-precise polishing and planarization
according to the present invention. Here, the apparatus also
includes a tool electrode, a photo/electrochemical reaction control
system, a working electrolyte solution recycling system, a working
electrolyte solution temperature controlled system, and an
automated control system. As shown in FIG. 2, the
photo/electrochemical reaction control system includes an optical
control system 3, and/or an electrochemical workstation 9. The
automated control system includes an information processing
computer 1, a multi-dimensional micro motor, a workbench (similar
to the fixed mount in FIG. 1), and a video monitor 14. The
information processing computer 1 is a maincenter of the apparatus
and connects with the multi-dimensional micro motor (including a
tool electrode motion controller 2 and a workpiece motion
controller 8, an optical control system 3, an electrochemical
workstation 9, a working electrolyte solution recycling system 12,
a working electrolyte solution temperature control system 13, and a
video monitor 14. The information processing computer 1 is in
charge of sending out commands, collecting feedback information of
technical parameters, and monitoring the polishing and
planarization processes. The tool electrode motion controller 2 is
a super-stable rotating stage and used to fix the tool electrode 4.
The working parameters of tool electrode motion controller 2 are
adjustable and controlled by the information processing computer 1.
The workpiece 6 is fixed on the workpiece stage 7. The workpiece
stage 7 is connected with the workpiece motion controller 8, which
moves vertically and/or laterally according to the commands sent
out by the information processing computer 1. For an
electrochemically-induced confined etching reaction, the
electrochemical workstation 9, reference electrode 15, auxiliary
electrode 16, the tool electrode 4 (acting as working electrode)
are needed. The working electrolyte solution 10 is injected into
the container 11, which is connected with the working electrolyte
solution recycling system 12 and the working electrolyte solution
temperature control system 13. The potential of the working
electrode (i.e. the tool electrode) is controlled such that a
confined etchant layer 5 is formed by the electrochemical reaction.
In the case of photochemically or photoelectrochemically-induced
confined chemical etching, a photocatalytic layer has to be coated
on the tool electrode surface. Starting the optical control system,
the exiting light irradiates on the surface of the photocatalytic
layer to generate the photochemical and photoelectrochemical
reaction and thereby form the radical etchant layer 5. The
workpiece motion controller 8 will be activated to keep the
workpiece surface contacting with the confined etchant layer until
the polishing and planarization is well done. The force sensor 17
and the laser ranging probe 18 (which are not shown in FIG. 2) are
implanted in the workpiece stage 7 and, together with
photo/electrochemical control system, are used to adjust the
distance and parallelity between the tool electrode and the
workpiece through the feedback parameters such as force, distant
and electric current.
[0086] In the apparatus shown in FIGS. 1 and 2 for performing the
photo/electrochemically induced, confined chemical etching method
for nano-precise polishing and planarization according to the
present invention, the principle of the polishing and planarization
method are as follows: in the working electrolyte solution, a
liquid layer containing etchant and/or leveling agent 22 is formed
on the tool electrode (i.e. the working electrode) surface with
nano-precise planeness through photo/electrochemical reaction (as
shown in FIG. 3a). Due to the scavenger which is added to the
solution in advance can react quickly with the etchant and/or
leveling agent, the life time of the etchant and/or leveling agent
is dramatically shortened. That means the etchant and/or leveling
agent cannot diffuse far away from the surface of tool electrode
21. The thickness of the formed "confined etchant layer" can be
confined to nanometer scale (as shown in FIG. 3b, where the
reference number 24 is the plating layer, and the reference number
25 is the dielectric layer). The polishing and planarization will
be in process once the confined etchant and leveling layer on the
tool electrode surface contacts with the workpiece surface. With
the etching reaction going on, the workpiece surface will separated
from the confined etchant layer. So, in order to ensure that the
confined etchant and leveling layer may sequentially contact with
the workpiece surface and achieve the desirable etching degree, the
automated control system will keep feeding the tool electrode
toward the workpiece until the polishing and planarization is
finished (as shown in FIG. 3c). Since the confined etchant layer is
very thin, i.e. has a thickness of no more than 20 nm, and has a
stable concentration distribution, it keeps the planeness of the
surface of tool electrode. When the etching process is done, the
workpiece surface will have the same nano-precise planeness as that
of the tool electrode (as shown in FIG. 3d).
[0087] The photo/electrochemically-induced, confined chemical
etching method for surface planarization and polishing in profile
precision and surface roughness of nanometer scale as described in
the present invention, can not only perform the operation of
polishing and planarization on the large-scale area, but also work
on the workpieces with 2-D planar, cylindrical or irregular
surface.
[0088] As shown in FIG. 4, the planar tool electrode 31 has a
nano-precise planeness and large sizes in X-Y dimensions. The tool
electrode 31 is gradually fed toward the workpiece 32 so as to
perform the polishing and planarization process on the workpiece
surface. The automated control system drives the tool electrode
motion controller 2 to make the nanometer-thick confined etchant
layer coated on the tool electrode surface approach to the
workpiece surface. When the highest points on the workpiece surface
touch the confined etchant layer on the workpiece surface, the
chemical etching reaction occurs and the polishing and
planarization process on the workpiece surface is going on. When
the highest points are dissolved and separated from the etchant
layer, the automated control system feeds the tool electrode to the
workpiece surface. These procedures repeat until the precision
requirement for the polishing and planarization is met. The
reference number 33 is a planar tool electrode fabricated through
ultra-precise mechanical machining.
[0089] As shown in FIG. 5, the linear tool electrode 41 has a
nano-precise planeness and large sizes in one dimension. Through
the relative motion in X-Y directions between the tool electrode
and the workpiece, the polishing and planarization process is
performed on the workpiece. The automated control system drives the
tool electrode motion controller 2 to make the nanometer-thick
confined etchant layer approach to the surface of workpiece 42
gradually. When the highest points on the workpiece surface touch
the confined etchant layer on the tool electrode, the chemical
etching reaction occurs and the polishing and planarization process
is going on. When the highest points are dissolved and separated
from the confined etchant layer, the tool electrode or the
workpiece is relatively moved in X-Y dimensions plane direction
until the tool electrode has gone through the whole surface of the
workpiece. These procedure repeat until the precision requirement
for the polishing and planarization is met.
[0090] As shown in FIG. 6, the linear tool electrode 53 has a
nano-precise planeness and works on a workpiece with a cylindrical
surface. Herein, the automated control system drives the tool
electrode motion controller 2 to make the tool electrode having a
surface coated with the nanometers-thick confined etchant layer 52
approach gradually to the surface of a rotating workpiece 51 which
is rotated around the central axis. When the highest points on the
workpiece surface touch the confined etchant layer, the chemical
etching reaction occurs and the polishing process is going on. When
the highest points are dissolved and separated from the confined
etchant layer, the automated control system controls an amount of
the tool electrode feeding to the workpiece until the tool
electrode has gone through the whole surface of the workpiece.
These procedures are repeated until the precision requirement for
the polishing and planarization is met.
[0091] As shown in FIG. 7, a milling-cutter-like tool electrode 62
with a nano-precise planeness is adopted to polish and planarize an
irregular surface of a workpiece. First, the irregular surface of a
workpiece is numeralizationed to program the motion trial of the
tool electrode. Second, the automated control system is employed to
make the confined etchant layer on the tool electrode surface
contact with the workpiece surface, and then drive the tool
electrode to move on the irregular surface of the workpiece
according to the programmed motion trail set beforehand. In this
way, the irregular surface of the workpiece is polished and
smoothed. The reference number 61 is the programmed motion trail of
the tool electrode. The reference number 63 is the auxiliary
electrode for controlling the potential of the tool electrode. The
reference number 64 is the workpiece with an irregular surface.
[0092] Next, the present invention will be more fully understood by
reference to the following Examples together with other Figures.
However, the Examples are only illustrative, and should not be
construed as limited the scope of the invention.
EXAMPLES
Example 1
[0093] The surface of a Cu workpiece was planarized and polished
using the apparatus shown in FIG. 2. Processing conditions were as
follows: a working electrolyte solution for circulating contained
acetic acid (0.1 mol/dm.sup.3, pH 5.5), benzotriazole (2
mg/dm.sup.3), sodium thiosulfate (Na.sub.2S.sub.2O.sub.8, 10
mmol/dm.sup.3), and N-acetylcysteine (0.1 mol/dm.sup.3); the
processing temperature was maintained at 25.degree. C. during the
whole polishing and planarization process; when the electrochemical
etching system was started, radical etchants SO.sub.4.sup.-.cndot.
were generated by electrolysis of Na.sub.2S.sub.2O.sub.8 at surface
of Pt disk electrode as a tool electrode; N-acetylcysteine was
added to the solution as a scavenger; using potentiostatic method,
the potential of the tool electrode (Pt disk electrode) was kept at
-0.5V vs. saturated calomel electrode (SCE) during the whole
polishing and planarization process. The Pt disk tool electrode
which had subjected to CMP had a surface planeness of 60 nm or
more, and was fixed on the top of the tool electrode motion
controller 2 as shown in FIG. 2. Upon the automated control system
starting, according to the parameters such as feedback current,
contact force and parallelity provided by the corresponding devices
such as the electric current feedback device, the force sensor and
the parallel laser ranging device, the automatic operation system
drove automatically the workpiece motion controller 8 and thereby
make the workpiece move precisely to the Cu workpiece fixed on top
of the tool electrode motion controller 2 until the confined
etching layer contacted with the surface of the Cu workpiece. Thus,
the process of polishing and planarization was started and the
surface of the Cu workpiece was gradually removed with time going
on. The automatic operation system constantly made the tool
electrode feed and thereby made the chemical reaction for the
polishing and planishing be continued. During the process, the
workpiece was rotating at low speed (1 rmp) in a ultra-steady
state, and the confined etchant Layer (thickness.ltoreq.50 nm) was
inside the laminar layer. Therefore, the relative motion between
the tool electrode and the workpiece has no impact on the planeness
of the confined etchant layer surface. Processing time depended on
the removal rate which was relevant to both the workpiece material
and confined etching system. In the case of planarization and
polishing process of Cu workpiece, feeding time of the tool
electrode lasted 15 min. After that, the automatic operation system
was cut off and the feeding of the tool electrode was stopped. 5
minutes later, the electrochemical system was turned off and the
tool electrode is withdrawn. As shown in FIG. 8, the obtained
workpiece surface was characterized by an optical microscope
(Olympus BX-51, manufactured by Olympus Co.) and an atomic force
microscope (Tapping Mode Nanoscope IIIa, manufactured by Digital
Instrument Co.), which indicated that the surface roughness of the
polished workpiece surface was 12.0 nm.
Example 2
[0094] The surface of a Si workpiece was planarized and polished
using the apparatus shown in FIG. 2. Processing conditions were as
follows: a working electrolyte solution for circulating contained
ammonium fluoride (NH.sub.4F, 0.1 mol/dm.sup.3), tetramethyl
ammonium bromide ((CH.sub.4).sub.4NBr, 1 mmol/dm.sup.3), L-cystine
(0.01 mol/dm.sup.3) and sulfuric acid (H.sub.2SO.sub.4, 0.5
mol/dm.sup.3); the processing temperature was maintained at
30.degree. C. during the whole polishing and planishing process;
when the electrochemical etching system was started, the etchants
Br.sub.2 were generated by electrolyzing bromide ions Br.sup.- at
the surface of the Pt disk tool electrode; L-cystine was used as
the scavenger; by using potentiostatic method, the electrode
potential of the Pt disk tool electrode was held at 0.9 V vs. SCE.
The Pt disk tool electrode which had been subjected to CMP process,
had a surface planeness of larger than 60 nm, and was fixed on the
top of tool electrode motion controller 2 as shown in FIG. 2. Upon
the automated control system starting, according to the parameters
such as feedback current, contact force and parallelity provided by
the corresponding devices such as the electric current feedback
device, the force sensor and the parallel laser ranging device, the
automatic operation system automatically drove the workpiece motion
controller 8 such that the workpiece was precisely move to the tool
electrode which was fixed on the top of the tool electrode motion
controller 2 until the confined etching layer (having a confined
thickness of <20 nm) coated on the tool electrode surface
contacted with the Si surface. Thus, the process of polishing and
planarization was started and the Si surface would be gradually
removed with time going on. The automatic operation system kept
feeding the tool electrode so as to ensure the polishing and
planarization processing to be continued. In the case of
planarization and polishing process of Si workpiece, the time of
feeding the tool electrode lasted 10 min. After that, the automatic
operation system was cut off, and further 3 minutes later, the
electrochemical system was turned off and the tool electrode was
withdrawn. As shown in FIG. 9, the obtained workpiece surface was
characterized by scanning electron microscope (FESEM LEO 1530,
manufactured by LEO Co.) and atomic microscope (Tapping Mode
Nanoscope IIIa, manufactured by Digital Instrument Co.), which
indicated the surface roughness of the polished workpiece surface
was 0.6 nm.
Example 3
[0095] The surface of a gallium arsenide (GaAs) workpiece was
planarized and polished using the apparatus shown in FIG. 2.
Processing conditions are as follows: a working electrolyte
solution for circulating contained hydrogen bromide HBr (10
mol/dm.sup.3), L-cystine (10 mmol/dm.sup.3) and H.sub.2SO.sub.4
(0.5 mol/dm.sup.3); the processing temperature was maintained at
20.degree. C. during the whole polishing process; when the
electrochemical etching system was started, the etchants Br.sub.2
were generated by electrolyzing bromide ion Br.sup.- at the surface
of the Pt disk tool electrode; L-cystine was used as the scavenger;
In the process of polishing and planishing, by using potentiostatic
method, the electrode potential of the Pt disk tool electrode was
held at 0.9 V vs. SCE. The Pt disk tool electrode which had
subjected to CMP had a surface planeness of larger than 60 nm, and
was fixed on the top of tool electrode motion controller 2 as shown
in FIG. 2. Upon the automated control system starting, according to
the parameters such as feedback current, contact force and
parallelity provided by the corresponding devices such as the
electric current feedback device, the force sensor and the laser
ranging device, the automatic operation system drove automatically
the workpiece motion controller 8 and thereby make the workpiece
move precisely to the tool electrode fixed on the top of the tool
electrode motion controller 2 until the confined etching layer on
the tool electrode surface contacted with the Si surface. Thus, the
process of polishing and planarization was started and the Si
surface would be gradually removed with time going on. The
automatic operation system kept feeding the tool electrode so as to
ensure the chemical reaction for the polishing and planarization
processing to be continued. In the case of planarization and
polishing process in this example, the time of feeding the tool
electrode lasted 8 min. After that, the automatic operation system
was cut off and the feeding of tool electrode was stopped. Further
2 minutes later, the electrochemical system was turned off and the
tool electrode was withdrawn. As shown in FIG. 10, the obtained
workpiece surface was characterized by scanning electron microscope
(FESEM LEO 1530, manufactured by LEO Co.) and atomic microscope
(Tapping Mode Nanoscope IIIa, manufactured by Digital Instrument
Co.), which indicated that the surface roughness of the polished
surface was 1.0 nm.
Example 4
[0096] The SiO.sub.2 glass surface of a workpiece was planarized
and polished using the apparatus shown in FIG. 2. Processing
conditions were as follows: a working electrolyte solution for
circulating contained ammonium fluoride NH.sub.4F (0.1
mol/dm.sup.3), ammonia (NH.sub.4OH, pH 12), sodium nitrite
(NaNO.sub.2, 10 mmol/dm.sup.3); the processing temperature was
maintained at 30.degree. C. during the whole polishing and
planishing process; when the electrochemical etching system was
started, the etchants H.sup.+ were generated by electrolyzing
NaNO.sub.2.sup.- at the surface of the Pt disk tool electrode,
thus, a strong acidic etching layer was formed on the surface of
the Pt disk tool electrode; in the strong acidic environment,
SiO.sub.2 formed a complex with F.sup.- and thereby was removed;
OH.sup.- in the etching solution which is provided by NH.sub.4OH
was used as the scavenger, and make a thickness of the confined
etchant layer be confined to a thickness of 20 nm or less; during
the process for polishing and planishing, by using potentiostatic
method, the electrode potential of the tool electrode (i.e. the Pt
disk tool electrode) was held at 0.9 V vs. SCE. The Pt disk tool
electrode which had been subjected to CMP process, had a surface
planeness of larger than 60 nm, and was fixed on the top of tool
electrode motion controller 2 as shown in FIG. 2. Upon the
automated control system starting, according to the parameters such
as feedback current, contact force and parallelity provided by the
corresponding devices such as the electric current feedback device,
the force sensor and the parallel laser ranging device, the
automatic operation system automatically drove the workpiece motion
controller 8 such that the workpiece was precisely move to the tool
electrode which was fixed on the top of the tool electrode motion
controller 2. Thus, the process of polishing and planarization was
started and the surface of the SiO.sub.2 glass workpiece would be
gradually removed with time going on. The automated control system
kept feeding the tool electrode so as to ensure the polishing and
planarization processing to be continued. In the case of
planarization and polishing process, the time of feeding the tool
electrode lasted 30 min. After that, the automatic operation system
was cut off and the feeding of tool electrode was stopped. Further
10 minutes later, the electrochemical system was turned off and the
tool electrode was withdrawn. As shown in FIG. 11, the obtained
workpiece surface was characterized by optical microscope (Olympus
BX-51, manufactured by Olympus Co.) and atomic microscope (Tapping
Mode Nanoscope IIIa, manufactured by Digital Instrument Co.), which
indicated that the surface roughness of the polished surface was
0.6 nm.
Examples 5 to 32
[0097] Processing steps in examples 5 to 13 were similar to those
in example 2, processing steps in examples 14 to 22 were similar to
those in example 1, and processing steps in examples 23 to 31 were
similar to those in example 4, except that the components of the
workinging electrolyte solutions, of the scavengers, and contents
thereof. The specific components and contents thereof may be seen
in tables 1 to 3. Etching results can be characterized using
high-powered optical microscope (Olympus BX-51, manufactured by
Olympus Co.) and atomic microscope (Tapping Mode Nanoscope IIIa,
manufactured by Digital Instrument Co). The surface roughness Ra
was obtained by analysis the scanning results from atomic force
microscope (Tapping Mode Nanoscope IIIa, manufactured by Digital
Instrument Co).
TABLE-US-00001 TABLE 1 Polishing solution for Si etching Scavenger
surface Example (CH.sub.4).sub.4NBr H.sub.2SO.sub.4 NH.sub.4F
L-Cystine roughness No. (mol/dm.sup.3) (mol/dm.sup.3)
(mol/dm.sup.3) (mol/dm.sup.3) Ra(nm) 5 0.001 0.5 1 0.001 1.9 6
0.001 0.5 1 0.01 1.2 7 0.001 0.5 1 0.1 0.6 8 0.005 0.1 0.1 0.1 1.3
9 0.005 0.1 0.1 0.3 0.7 10 0.005 0.1 0.1 0.5 0.5 11 0.005 0.5 1 0.1
1.1 12 0.005 0.5 1 0.3 0.6 13 0.005 0.5 1 0.5 0.5
[0098] As shown in Table 1, the nano-precision
photo/electrochemical planarization and polishing methods according
to the present invention can be applied in the polishing of Si, and
result in remarkable effect. Moreover, surface roughness Ra of the
resulted workpiece was 2.0 nm or less.
TABLE-US-00002 TABLE 2 Polishing solution for Cu etching
CH.sub.3CO.sub.2H Scavenger --CH.sub.3CO.sub.2 Benzo- N-acetyl-
surface Exam- K.sub.2S.sub.2O.sub.8 Na (pH 5.5, triazole cysteine
roughness ple No. (mol/dm.sup.3) mol/dm.sup.3) (mol/dm.sup.3)
(mol/dm.sup.3) Ra(nm) 14 0.01 0.1 0.1 0.01 24.3 15 0.01 0.1 0.1 0.1
15.4 16 0.01 0.1 0.1 0.5 8.3 17 0.001 0.5 1 0.1 14.7 18 0.001 0.5
0.1 0.3 11.6 19 0.001 0.1 2 0.1 8.5 20 0.005 0.1 1 0.3 15.3 21
0.005 0.1 0.1 0.3 9.8 22 0.005 0.5 1 0.1 7.2
[0099] As seen in Table 2, the nano-precision photo/electrochemical
planarization and polishing methods according to the present
invention can be applied in the polishing of Cu workpiece, and
result in remarkable effect. Moreover, surface roughness Ra of the
resulted workpiece was 25 nm or less.
TABLE-US-00003 TABLE 3 Polishing solution for SiO.sub.2 etching
Dodecyl sulphonic Scavenger surface Example KNO.sub.2 acid
NH.sub.4F NH.sub.4OH roughness No. (mol/dm.sup.3) (mol/dm.sup.3)
(mol/dm.sup.3) (mol/dm.sup.3) Ra(nm) 23 0.005 0.005 1 0.01 1.1 24
0.005 0.005 0.1 0.01 0.8 25 0.005 0.005 0.01 0.01 1.3 26 0.01 0.001
1 1 0.9 27 0.01 0.001 0.1 1 1.2 28 0.01 0.001 0.01 1 1.3 29 0.01
0.001 1 0.5 0.9 30 0.01 0.001 0.1 0.5 0.9 31 0.01 0.001 0.01 0.5
1.1
[0100] As seen in Table 3, the nano-precision photo/electrochemical
planarization and polishing methods according to the present
invention can be applied in the polishing of SiO.sub.2 workpiece,
and result in more remarkable effect. Moreover, surface roughness
Ra of the resulted workpiece was 1.5 nm or less.
TABLE-US-00004 TABLE 4 Working condition for photochemical
planarization and polishing Cu surface Example Catalyst Thickness
of Light roughness No. TiO.sub.2 TiO.sub.2 film (nm) source pH
Ra(nm) 32 Nanotube 100 500 W 4 10.7 (on the tool Xenon lamp
electrode) Remark: pH was adjustable by using 0.01 mol/L HClO.sub.4
and 0.01 mol/L NaOH, and 0.01 mol/L NaClO.sub.4 was used as the
supporting electrolyte.
INDUSTRIAL APPLICABILITY
[0101] The planarization and polishing method and an apparatus
therefor the same according to the present invention may provide a
surface of the workpiece with profile precision and surface
roughness of nanometer scale (i.e nano-precision). In addition, the
present invention has more advantages over CMP technology due to no
surface and subsurface mechanical damage, no residual stress, no
metal ion contaminations, and having controllable end-point of the
polishing and planarization process. Therefore, the present
invention is especially suitable to be applied in the field of the
industrial semiconductor materials, ultra large scale integrated
circuit, Micro Electromechanical System (MEMS), Micro
Opto-Electro-Mechanical Systems, modern precision optical device,
aerospace engine blades, and etc..
* * * * *