U.S. patent application number 13/178968 was filed with the patent office on 2012-06-28 for polishing method.
This patent application is currently assigned to Semiconductor Manufacturing International (Beijing) Corporation. Invention is credited to Li Jiang, Mingqi Li.
Application Number | 20120164923 13/178968 |
Document ID | / |
Family ID | 46317754 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120164923 |
Kind Code |
A1 |
Jiang; Li ; et al. |
June 28, 2012 |
POLISHING METHOD
Abstract
A polishing method is disclosed, which includes: conditioning a
polishing pad, after polishing metal material of a previous wafer;
spraying organic acid solution to the polishing pad; spraying
deionized water to the polishing pad; performing a water-removing
treatment on the polishing pad; and spraying polishing liquid to
the polishing pad and polishing metal material of a next wafer. The
method can prevent scratches on the surface of metal material of
wafers and improve yield rate.
Inventors: |
Jiang; Li; (Shanghai,
CN) ; Li; Mingqi; (Shanghai, CN) |
Assignee: |
Semiconductor Manufacturing
International (Beijing) Corporation
Beijing
CN
|
Family ID: |
46317754 |
Appl. No.: |
13/178968 |
Filed: |
July 8, 2011 |
Current U.S.
Class: |
451/56 |
Current CPC
Class: |
B24B 53/017
20130101 |
Class at
Publication: |
451/56 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 23, 2010 |
CN |
201010603419.8 |
Claims
1. A polishing method, comprising: conditioning a polishing pad,
after polishing metal material of a previous wafer; spraying
organic acid solution to the polishing pad; spraying deionized
water to the polishing pad; performing a water-removing treatment
on the polishing pad; and spraying polishing liquid to the
polishing pad and polishing metal material of a next wafer.
2. The polishing method of claim 1, wherein the conditioning of the
polishing pad is pad ex-situ condition.
3. The polishing method of claim 1, wherein the spraying organic
acid solution to the polishing pad has a flow rate of
100.about.1000 ml/min.
4. The polishing method of claim 3, wherein during the spraying
organic acid solution to the polishing pad, a platen has a rotation
speed of 10.about.150 RPM.
5. The polishing method of claim 1, wherein the spraying deionized
water to the polishing pad has a flow rate of 100.about.1000
ml/min.
6. The polishing method of claim 5, wherein during the spraying
deionized water to the polishing pad, a platen has a rotation speed
of 10.about.120 RPM.
7. The polishing method of claim 1, wherein the spraying polishing
liquid to the polishing pad includes: polishing liquid covering the
entire polishing pad.
8. The polishing method of claim 7, wherein the spraying polishing
liquid to the polishing pad has a flow rate of 100.about.1500
ml/min and a spraying time of 5.about.100 seconds.
9. The polishing method of claim 1, wherein the organic acid is
oxalic acid, malonic acid, succinic acid, maleic acid, phthalic
acid or amino acid.
10. The polishing method of claim 1, wherein the organic acid
solution has a concentration of 0.01.about.10 wt %.
11. The polishing method of claim 1, wherein the metal material is
aluminum or aluminum alloy.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the priority of Chinese
Patent Application No. 201010603419.8, entitled "Polishing Method",
and filed on Dec. 23, 2010, the entire disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the field of semiconductor
manufacturing, and particularly relates to a polishing method.
[0004] 2. Description of Prior Art
[0005] With the continuous development of the semiconductor
manufacturing process, the critical dimension (CD) of semiconductor
devices is getting smaller. Techniques of combining metal gate
electrode and gate dielectric layer of High-K material are
introduced into the manufacturing of the MOS transistor, to solve
the problems caused by small critical dimension devices. Currently,
High-K Metal Gate (HKMG) techniques have become the mainstream
techniques for 32 nm technology and below, in which chemical
mechanical polishing (CMP) on the metal gate electrode is one of
the most important step. For the mechanism of CMP, it is described
that: a surface layer which is relatively easy to remove is formed
by reaction of the surface material of a wafer and polishing
liquid, and the surface layer is then mechanically scraped off by
polishing pressure and by relative motion between polishing pad and
the wafer. Specifically, during the CMP of metal material,
polishing liquid is in contact with the surface of the metal
material, and metal oxide is generated which is then mechanically
scraped off to achieve the effect of polishing.
[0006] The most popular material for metal gate electrode is
aluminum and Cu--Al alloy (in which aluminum is the major
component). Large part of the by-product (i.e. metal oxide, which
is mainly alumina and aluminum hydroxide) of the CMP on aluminum is
left in the trench of the polishing pad. However, since aluminum
has a very low hardness compared with the by-product of the CMP,
during the CMP processes on aluminum of follow-up wafers, the
surface of the aluminum will be scratched, which affects the
functionality and reliability of semiconductor devices. Also the
by-product is not dissolved in deionized water; therefore, it is
difficult to be totally cleaned by conventional methods (such as
spraying deionized water).
SUMMARY OF THE INVENTION
[0007] The present invention is to solve the problem that during
the polishing process on metal material of a wafer, by-product left
on the polishing pad scratches the surface of the metal material
which has a very low hardness compared with the by-product.
[0008] To solve the above problem, there is provided a polishing
method in the present invention, which includes:
[0009] conditioning a polishing pad, after polishing metal material
of a previous wafer;
[0010] spraying organic acid solution to the polishing pad;
[0011] spraying deionized water to the polishing pad;
[0012] performing a water-removing treatment on the polishing
pad;
[0013] spraying polishing liquid to the polishing pad and polishing
metal material of a next wafer.
[0014] Optionally, the conditioning of the polishing pad is pad
ex-situ condition.
[0015] Optionally, the spraying organic acid solution to the
polishing pad has a flow rate of 100.about.1000 ml/min.
[0016] Optionally, during the spraying organic acid solution to the
polishing pad, a platen has a rotation speed of 10.about.150 RPM
(Revolutions per Minute).
[0017] Optionally, the spraying deionized water to the polishing
pad has a flow rate of 100.about.1000 ml/min.
[0018] Optionally, during the spraying deionized water to the
polishing pad, a platen has a rotation speed of 10.about.120
RPM.
[0019] Optionally, the spraying polishing liquid to the polishing
pad includes: polishing liquid covering the entire polishing
pad.
[0020] Optionally, the spraying polishing liquid to the polishing
pad has a flow rate of 100.about.1500 ml/min and a spraying time of
5.about.100 seconds.
[0021] Optionally, the organic acid is oxalic acid, malonic acid,
succinic acid, maleic acid, phthalic acid or amino acid.
[0022] Optionally, the organic acid solution has a concentration of
0.01.about.10 wt %.
[0023] Optionally, the metal material is aluminum or aluminum
alloy.
[0024] In comparison with the conventional technology, the present
invention has the following advantages:
[0025] By-product, which is generated during the polishing on a
previous wafer and is left on the polishing pad, will be dragged
out of the trench of the polishing pad during brushing of the
polishing pad. In addition, the by-product is dissolved in the
organic acid; the dissolved by-product and the organic acid are
then removed by spraying deionized water, which effectively removes
the by-product left in trenches of the polishing pad and prevents
the by-product from scratching the surface of the metal material of
a next wafer.
[0026] After performing a water-removing treatment on the polishing
pad, the spraying polishing liquid to the polishing pad makes the
polishing liquid cover the whole polishing pad, which further
avoids scratching to the surface of the metal material and improves
the yield rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a flow diagram of the polishing method in one
embodiment of the present invention;
[0028] FIG. 2 to FIG. 6 are schematic views of steps in the
polishing method in another embodiment of the present
invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0029] Hereunder, the present invention will be described in detail
with reference to embodiments, in conjunction with the accompanying
drawings.
[0030] Embodiments to which the present invention is applied are
described, in detail below. However, the invention is not
restricted to the embodiments described below.
[0031] As discussed in the background, in a conventional polishing
process, by-product of CMP of aluminum (i.e. metal oxide generated
in oxidation of aluminum by polishing agent, which is mainly
alumina and aluminum hydroxide) will be left in trenches of the
polishing pad. Since aluminum has a very low hardness compared with
the by-product, for example the hardness of aluminum is 160 Mpa
while the hardness of aluminum hydroxide is 20000 Mpa, the
by-product which is left in the trenches of the polishing pad will
scratches the surface of the aluminum during the CMP of a next
wafer. The by-product which is left in trenches of the polishing
pad can not be found by naked eyes, and is all over the trenches of
the polishing pad under a scanning electron microscope (SEM). It is
found that the scratches of different sizes on the surface of the
metal material are generated by the left by-product. If the metal
gate electrode is scratched, the functionality and reliability of
semiconductor devices will be affected. Since the by-product is not
dissolved in deionized water, it can not be cleaned well even with
large amount of deionized water.
[0032] To prevent by-product from scratching the surface of the
metal material, there is provided a polishing method in an
embodiment of the present invention.
[0033] FIG. 1 is a flow diagram of the polishing method in this
embodiment, which includes:
[0034] S101, conditioning a polishing pad, after polishing metal
material of a previous wafer;
[0035] S102, spraying organic acid solution to the polishing
pad;
[0036] S103, spraying deionized water to the polishing pad;
[0037] S104, performing a water-removing treatment on the polishing
pad; and
[0038] S105, spraying polishing liquid to the polishing pad and
polishing metal material of a next wafer.
[0039] The polishing method will be described in detail with
reference to another embodiment, in conjunction with FIG. 1 and
FIG. 2 to FIG. 6.
[0040] FIG. 2 illustrates the principle of a polishing apparatus.
As shown in FIG. 2, the polishing apparatus mainly includes a
platen 101, a polishing head (grinding head) 103, a polishing pad
102 positioned over the platen 101, and a polishing liquid nozzle
104. Before polishing, a wafer 100 is placed in the polishing
apparatus. Specifically in this embodiment, take polishing Al for
example, the polishing liquid nozzle 104 sprays polishing liquid
105 that contains polishing agent to the polishing pad 102; the
wafer 100, which is affixed to the polishing head by vacuum
suction, is placed in the polishing liquid 105 on the polishing pad
102. The polishing agent oxidizes the surface of the metal on the
wafer 100 into metal oxide (mainly alumina and aluminum hydroxide);
the polishing head 103 imposes downward pressure; the platen 101
rotates with the polishing pad 102 (the polishing head can rotate
in an opposite direction); the metal oxide on the surface of the
wafer 100 is then mechanically scraped off by pressure and by
relative motion between polishing pad 102 and the wafer. In
addition, during the polishing process, the polishing head 103 can
move back and forth in the horizontal direction with the wafer
100.
[0041] As discussed above, the metal oxide is the by-product during
the polishing of Al, and a large part of the by-product is left in
the trenches of the polishing pad 102. If not cleaned well, the
by-product in the trenches will scratch the surface of the Al of a
next wafer during polishing, which will affect the device
performance.
[0042] Referring to FIG. 1 and FIG. 3, in step S101, when the
polishing of metal material of a previous wafer is finished, the
polishing pad is conditioned. For a better conditioning result, in
this embodiment, the condition to the polishing pad 102 is a pad
ex-situ condition, which is conditioning the polishing pad 102
between wafer polishing cycles. Specifically, after the metal
material Al of the previous wafer is polished, the wafer is moved
off the polishing pad 102 (the platen 101 stops rotating before
moving the wafer off the polishing pad 102). The polishing pad 102
is then washed by deionized water and is scrubbed by the pad
conditioner 106, which achieves the condition of the polishing pad
102. Since a large part of the by-product is left in the trenches
of the polishing pad 102, which can not be cleaned completely only
by spraying deionized water, pad conditioner 106 is used to drag
the by-product out of the trenches of the polishing pad 102, for
the following cleaning steps. In other embodiments of the present
invention, the polishing pad 102 can be conditioned by pad in-situ
condition, which is to condition the polishing pad during a wafer
polishing cycle. Specifically, during the polishing cycle of the
previous wafer, the polishing pad 102 is scrubbed by the pad
conditioner 106.
[0043] Referring to FIG. 1 and FIG. 4, step 102 is performed as:
spraying organic acid solution to the polishing pad. Specifically,
the spraying of organic acid solution to the polishing pad 102 has
a flow rate of 100.about.1000 ml/min. Meanwhile, the platen 101 is
started (rotating); and the platen has a rotation speed of
10.about.150 RPM. The platen 101 rotates in a middle or low
rotation speed and the organic acid is sprayed with a high speed,
which makes the by-product (alumina, aluminum hydroxide, etc.)
dragged out by the pad conditioner 106 in S101 fully dissolved in
the organic acid. The organic acid can be oxalic acid, malonic
acid, succinic acid, maleic acid, phthalic acid or amino acid. The
concentration of the organic acid solution is 0.01.about.10 wt %
(weight %).
[0044] Still referring to FIG. 1 and FIG. 4, step S103 is performed
as: spraying deionized water to the polishing pad. Specifically,
spraying deionized water to the polishing pad has a flow rate of
100.about.1000 ml/min; meanwhile, the platen 101 is rotating and
has a rotation speed of 10.about.120 RPM. The platen 101 rotates in
a low speed and the deionized water is sprayed with a high speed,
which removes the organic acid and the by-product dissolved in the
organic acid in S102.
[0045] Referring to FIG. 1 and FIG. 5, step S104 is performed as:
performing a water-removing treatment on the polishing pad.
Specifically, the water-removing treatment is performed in a
conventional way, in which the platen 101 rotates in high speed to
remove the deionized water on the polishing pad 102. During the
rotation of the platen 101, desiccant can be used on the polishing
pad 102 for a drying process; the desiccant is nitrogen.
[0046] Referring to FIG. 1 and FIG. 6, step S105 is performed as:
spraying polishing liquid to the polishing pad and polishing metal
material of a next wafer. Specifically, the polishing liquid 105 is
sprayed through polishing liquid nozzle 104 to the polishing pad
102, and covers the entire polishing pad 102 (the polishing liquid
105 shown in FIG. 6 has not covered the entire polishing pad yet).
During the spraying of the polishing liquid, the spraying has a
flow rate of 100.about.1500 ml/min and a spraying time of
5.about.100 seconds, to make the polishing liquid 105 cover the
whole polishing pad 102. In this way, before polishing metal
material of a next wafer, the polishing pad 102 is covered with
polishing liquid 105 that is used for polishing aluminum, which can
ensure full contact between the polishing liquid 105 and the
aluminum. The aluminum will be oxidized by the polishing agent in
polishing liquid 105, which can further protect the surface of the
aluminum from the left by-product after the steps from S101 to S104
and further improves the yield rate. In other embodiments, the
polishing a next wafer and the spraying polishing liquid can be
performed at the same time.
[0047] In the above embodiments, the metal material is aluminum or
aluminum alloy. In other embodiments of the present invention, the
polishing method provided can also apply to polishing process in
which metal material has a low hardness.
[0048] In comparison with the conventional technology, the present
invention has the following advantages:
[0049] By-product, which is generated during the polishing on a
previous wafer and is left on the polishing pad, will be dragged
out of the trench of the polishing pad during brushing of the
polishing pad. In addition, the by-product is dissolved in the
organic acid; the dissolved by-product and the organic acid are
then removed by spraying deionized water, which effectively removes
the by-product left in trenches of the polishing pad and prevents
the by-product from scratching the surface of the metal material of
a next wafer.
[0050] After performing a water-removing treatment on the polishing
pad, the spraying polishing liquid to the polishing pad makes the
polishing liquid cover the whole polishing pad, which further
avoids scratching to the surface of the metal material and improves
the yield rate.
[0051] Although the present invention has been illustrated and
described with reference to the preferred embodiments of the
present invention, those ordinary skilled in the art shall
appreciate that various modifications in form and detail may be
made without departing from the spirit and scope of the
invention.
* * * * *