U.S. patent application number 10/748629 was filed with the patent office on 2005-07-07 for method for monitoring surface treatment of copper containing devices.
Invention is credited to Barnes, Jeffrey A., Hollander, Orin, Walker, Elizabeth L..
Application Number | 20050145311 10/748629 |
Document ID | / |
Family ID | 34710957 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050145311 |
Kind Code |
A1 |
Walker, Elizabeth L. ; et
al. |
July 7, 2005 |
Method for monitoring surface treatment of copper containing
devices
Abstract
Determining the presence of a corrosion inhibitor on exposed
surfaces during manufacture of a microelectronic device subjected
to one or more cleaning operations using a cleaning solution
containing a corrosion inhibitor where a subsequent manufacturing
or handling step requires no corrosion inhibitor residue on the
device. A sacrificial copper test piece or coupon is subjected to
the cleaning operation along with the device is exposed to hydrogen
sulfide gas. The degree of color change in the surface of the
copper test piece is a qualitative means of indicating the presence
or absence of a corrosion inhibitor residue on exposed copper
surfaces of the microelectronic device.
Inventors: |
Walker, Elizabeth L.;
(Nazareth, PA) ; Barnes, Jeffrey A.; (Nazareth,
PA) ; Hollander, Orin; (Jamison, PA) |
Correspondence
Address: |
RATNERPRESTIA
P O BOX 980
VALLEY FORGE
PA
19482-0980
US
|
Family ID: |
34710957 |
Appl. No.: |
10/748629 |
Filed: |
December 30, 2003 |
Current U.S.
Class: |
148/687 ;
148/712 |
Current CPC
Class: |
B08B 3/00 20130101; C23G
5/00 20130101 |
Class at
Publication: |
148/687 ;
148/712 |
International
Class: |
C22F 001/08 |
Claims
Having thus described our invention what is desired to be secured
by Letters Patent of the United States is set forth in the appended
claims.
1. A method for detecting the presence of a residual amount of
corrosion inhibitor on a copper surface subjected to a cleaning
solution containing a corrosion inhibitor comprising exposing said
copper surface to a reactant that will attack said copper surface
causing a pronounced color change of said copper surface, said
color change indicating an absence of said corrosion inhibitor on
said copper surface.
2. A method according to claim 1 including using a gaseous
reactant.
3. A method according to claim 2 including exposing said copper
surface to hydrogen sulfide gas.
4. A method according to claim 2 including introducing acetic acid
into a solution of sodium sulfide in deionized water at room
temperature to generate hydrogen sulfide gas as said reactant.
5. A method for determining the presence of residual corrosion
inhibitor on copper surfaces or copper components of a
microelectronic device having been subjected to a cleaning prior to
a subsequent fabrication operation comprising: including a
sacrificial copper coupon or test piece in a group or batch of said
devices during said cleaning process; removing said test piece from
said batch and exposing said test piece to a gaseous reactant
selected to react with said test piece to produce a visible color
change of a surface said test piece in the absence of corrosion
inhibitor on said surface of said test piece.
6. A method according to claim 5 including using hydrogen sulfide
as said gaseous reactant.
7. A method according to claim 6 including producing said hydrogen
sulfide gas by reacting acetic acid with an aqueous solution of
sodium sulfide.
8. An apparatus for detecting the presence of a residual amount of
corrosion inhibitor on a copper surface subjected to a cleaning
solution containing a corrosion inhibitor comprising in
combination: a first receptacle adapted to receive a test piece or
pieces that have been exposed to cleaning solution, a second
receptacle placed inside said first receptacle proximate and said
test pieces, said second receptacle adapted to receive reactants to
produce a hydrogen sulfide gas; and means to cover said first
receptacle and direct said hydrogen sulfide gas at said test piece
or pieces.
9. An apparatus according to claim 1 including sodium sulfide
solution in said second receptacle.
10. An apparatus according to claim 9 including means to introduce
an acid into said second receptacle prior to covering said first
receptacle.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of
operations taking place during the manufacturing of
copper-containing microelectronic devices. In particular the
present invention relates to qualitative determination of the
effectiveness of removing certain residual components from cleaning
steps during manufacturing of microelectronic devices.
BACKGROUND OF THE INVENTION
[0002] The present day fabrication of semiconductor devices is a
complex, multi-step process. Such processes involve a multiplicity
of steps starting with a particular substrate and layering various
device configurations one on top of the other. In between each of
the successive layering steps the devices may be subject to a
cleaning step. In particular, when the surface to be cleaned
contains copper, copper surfaces or copper wire connects a cleaning
solution containing a corrosion inhibitor is generally used to
prevent corrosion of the copper during the cleaning step. When such
corrosion inhibitor is a beta triazole (BTA) which is commonly used
during the fabrication of microelectronic devices containing copper
connects or copper surfaces the corrosion inhibitor must be removed
prior to a subsequent manufacturing operation.
[0003] As part of normal cleaning step the cleaning solution is
usually rinsed from the surface of the microelectronic device using
the deionized water followed by a drying step. If the cleaning
solution is not removed from the surface subsequent manufacturing
steps may be effected and the device may not meet the required
specification, thus resulting in a high volume of rejected
devices.
SUMMARY OF THE INVENTION
[0004] The present invention is a method for detecting the presence
of a residual amount of corrosion inhibitor on a copper surface
subjected to a cleaning solution containing a corrosion inhibitor
by exposing the copper surface to a reactant that will react with
the copper surface causing a pronounced color change of the copper
surface, the color change indicating absence of corrosion inhibitor
on the cleaned copper surface. As a feature of the invention the
method can include using a sacrificial test piece or coupon that is
subjected to the cleaning operation along with the semi-conductor
device being fabricated. The test piece or coupon is then subjected
to contact with a gaseous reactant. If the test coupon surface is
devoid of residual corrosion inhibitor the surface will change
color, the color change indicative of the absence of corrosion
inhibitor on the devices being fabricated.
[0005] Therefore, the present invention is a method for determining
the presence of residual corrosion inhibitor on a copper surface or
copper components of a microelectronic device having been subjected
to a cleaning operation prior to a subsequent fabrication operation
comprising, including a sacrificial copper coupon or test piece in
a group or batch of the devices during the cleaning process,
removing the test piece from the batch after the cleaning step is
completed and exposing the test piece to a reactant selected to
react with the test piece to produce a visible color change on the
surface of the test piece, wherein the color change of the surface
indicates presence or absence of a residual corrosion inhibitor on
the test piece and the components being processed.
BRIEF DESCRIPTION OF THE DRAWING
[0006] FIG. 1 is a schematic representation of a test method
according to the present invention illustrating a first step in the
method of the present invention.
[0007] FIG. 2 is a schematic representation of the completion of
the method of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0008] Referring to FIG. 1 the apparatus of the invention 10
includes a first small beaker 12 (e.g. 100 milliliter capacity)
which contains a solution 14 consisting of 2% sodium sulfide and
deionized water. The solution 14 can be prepared by dissolving 1
gram of sodium sulfide and 49 grams of deionized water at room
temperature. The 100 milliliter beaker 12 is placed in the bottom
center of an upright two (2) liter beaker 16. Test pieces of copper
18 are placed on the bottom of the two (2) liter beaker 16
surrounding the 100 milliliter beaker 12. By means of a pipette or
other dropper device 20, one (1) milliliter of acetic acid 22 is
added to the sodium sulfide solution 14 in the small beaker 12. The
two (2) liter beaker is then covered by a four (4) liter beaker 24
as shown in FIG. 2 to contain hydrogen sulfide gas 26 which is
produced by the reaction of the acetic acid 22 and the sodium
sulfide solution 14. The test pieces 18 are treated for two (2)
minutes by hydrogen sulfide gas coming out of the small beaker 12
and falling to the floor of the two (2) liter beaker 16 thus
attacking the test pieces 18 uniformly. The entire experiment or
test must be carried out under suitable chemical evacuation hoods
so that the hydrogen sulfide gas does not enter the work space and
can be effectively scrubbed from the atmosphere. The reason for
using the large beaker inverted over the mid-size beaker is to
prevent the effect of hydrogen sulfide gas being evacuated from the
fume hood instead of attacking the test pieces 18, as would be the
problem with beaker 16 not being covered since the hydrogen sulfide
gas would be drawn into the fume hood and not fall onto the test
pieces 18.
[0009] According to the process of the invention adding the acetic
acid to the 2% sodium sulfide solution lowers the pH of the basic
solution to approximately 4.8. This reaction releases hydrogen
sulfide gas, which is heavier than air. By placing the test pieces
in an area surrounding the small beaker the gas will react with the
copper on the test pieces. The reaction is visible by a change in
the color of the copper on the test pieces. Areas of the wafer that
are still protected by the corrosion inhibitor (BTA or any other
copper protecting chemical) will not change color.
[0010] During the first 30 seconds, copper oxidation begins to
occur and continues throughout the treatment. A treatment time of
two (2) minutes was chosen to thoroughly expose to copper test
pieces while at the same time causing little or no color change to
any pieces that contain a surface covered with the corrosion
inhibitor. At longer treatment times hydrogen sulfide will begin to
react with the corrosion inhibitor, especially those pieces treated
with beta triazole (BTA).
[0011] Comparative tests were run to test the method of the present
invention. In one test a copper wafer was cleaned in a solution
containing 10 ppm of BTA. The test pieces were exposed to the
cleaning solution for two hours at 22.degree. C. and rinsed in for
30 seconds in deionized water followed by a drying treatment using
dry nitrogen gas. The test pieces thus prepared and test pieces
without exposure to the cleaning solution were subjected to the
process of the present invention. Those that were devoid of BTA
turned a deep blue color after exposure to the hydrogen sulfide
gas, indicating a complete removal of the BTA. In those instances
where the BTA was not completely removed the copper surface did not
change color and retained a reddish color throughout.
[0012] Experimental results also showed that in addition to acetic
acid other acids such as citric, ascorbic, hydrochloric and
sulfuric can be mixed with a sodium sulfide solution to generate
hydrogen sulfide gas. In any event in order to generate sufficient
hydrogen sulfide gas the acid must be added in sufficient quantity
to lower the pH of the acid/sulfide solution to below 8.
[0013] Prior to the present invention one way to determine whether
or not beta triazole (BTA) or some other corrosion inhibitor is
present on a copper surface was to submit samples or a test sample
suspected of having corrosion inhibitor on the surface to X-ray
Photon Spectroscopy (XPS) or Time Of Flight Scanning Ion Mass
Spectroscopy (TOF-SIMS).
[0014] The present invention provides a quick and inexpensive
qualitative method to determine whether or not any corrosion
inhibitor is left on exposed copper surfaces. The method of the
invention is used to determine if a cleaning regime has resulted in
the removal of corrosion inhibitor so that the microelectronic
devices can be moved to the next process step. Using a sacrificial
strip or test piece placed with the devices being cleaned it is
possible to determine whether or not the cleaning step is
effectively completed without sacrificing any of the devices being
processed, or subjecting any of the devices being processed to
complex analytical techniques.
[0015] The process of the present invention can also be used to
determine whether or not new cleaning formulations with corrosion
inhibitors are effective or can be effectively removed from the
microelectronic devices at the required stages during manufacture
of a device.
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