U.S. patent application number 10/403269 was filed with the patent office on 2003-11-13 for etching composition and use thereof with feedback control of hf in beol clean.
This patent application is currently assigned to Infineon Technologies North America Corp.. Invention is credited to Krause, Holger, Nichterwitz, Marion, Nitschke, Christiane, Penner, Klaus, Ramachandran, Ravikumar.
Application Number | 20030209514 10/403269 |
Document ID | / |
Family ID | 29408030 |
Filed Date | 2003-11-13 |
United States Patent
Application |
20030209514 |
Kind Code |
A1 |
Ramachandran, Ravikumar ; et
al. |
November 13, 2003 |
Etching composition and use thereof with feedback control of HF in
BEOL clean
Abstract
A process for providing an aqueous back-end-of-line (BEOL) clean
with feed-back control to monitor the active component of HF in the
clean, for a wiring/interconnect of a reactive ion etched
semiconductor device, comprising: subjecting the reactive ion
etched semiconductor device to a post metal RIE clean using an
etchant composition comprising about 0.01 to about 15 percent by
weight of sulfuric acid; about 0.1 to about 100 ppm of a fluoride
containing compound; and a member selected from the group
consisting of about 0.01 to about 20 percent by weight of hydrogen
peroxide or about 1 to about 30 ppm of ozone, comprising: a) mixing
water, sulfuric acid and hydrogen peroxide in a mixing tank, b)
mixing HF directly into the mixing tank or adding HF into a
separate vessel for wafer processing, either before, during or
after the mixture water, sulfuric acid and hydrogen peroxide as a
mixture is transported to the separate tank for wafer processing;
c) taking a sample comprising HF from the mixing tank or HF from
the wafer processing tank and sending the sample through a feedback
loop; d) comparing the sample to a standard dilute solution of HF
to obtain a value of HF concentration in the sample; e) inputting
the value to a tank tool recipe control to cause any needed
adjustment in concentration of HF to a predetermined range, either
in the mixing tank or the wafer processing vessel; and f)
subjecting the wiring/interconnect of the semiconductor device to
etching by the etchant composition to remove sidewall polymer,
polymer rails and via residue without etching conductive materials
during removal of sidewall polymer, polymer rails, and via
residue.
Inventors: |
Ramachandran, Ravikumar;
(Pleasantville, NY) ; Penner, Klaus;
(Ottendorf-Okrilla, DE) ; Nichterwitz, Marion;
(Dresden, DE) ; Nitschke, Christiane; (Dresden,
DE) ; Krause, Holger; (Dresden, DE) |
Correspondence
Address: |
LERNER, DAVID, LITTENBERG,
KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
Infineon Technologies North America
Corp.
San Jose
CA
|
Family ID: |
29408030 |
Appl. No.: |
10/403269 |
Filed: |
March 31, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10403269 |
Mar 31, 2003 |
|
|
|
09627669 |
Jul 28, 2000 |
|
|
|
09627669 |
Jul 28, 2000 |
|
|
|
09137179 |
Aug 20, 1998 |
|
|
|
09137179 |
Aug 20, 1998 |
|
|
|
08975755 |
Nov 21, 1997 |
|
|
|
08975755 |
Nov 21, 1997 |
|
|
|
08832999 |
Apr 4, 1997 |
|
|
|
5780363 |
|
|
|
|
Current U.S.
Class: |
216/2 ;
257/E21.251; 257/E21.255; 257/E21.256 |
Current CPC
Class: |
C09D 9/00 20130101; G03F
7/426 20130101; C11D 7/08 20130101; H01L 21/31138 20130101; H01L
21/31111 20130101; C11D 11/0047 20130101; G03F 7/423 20130101; C11D
3/3947 20130101; H01L 21/31133 20130101; C09K 13/08 20130101 |
Class at
Publication: |
216/2 |
International
Class: |
C23F 001/00 |
Claims
1. A method for cleaning semiconductor devices using an etchant
composition, the method comprising: a) mixing water, sulfuric acid
and one of hydrogen peroxide or ozone in a mixing tank; b) mixing
HF directly into said mixing tank or adding HF into a separate tank
for wafer processing, either before, during or after said mixture
of said water, sulfuric acid and hydrogen peroxide is transported
to a tank for wafer processing; and c) subjecting said
semiconductor device to etching by said etchant composition to
remove sidewall polymer, polymer rails and via residue without
etching conductive materials during removal of sidewall polymer,
polymer rails, and via residue, said etchant composition
comprising: (i) about 0.01 to about 15 percent by weight of
sulfuric acid; (ii) about 0.1 to about 100 ppm of a fluoride
containing compound; and (iii) a member selected from the group
consisting of about 0.1 to about 20 percent by weight of hydrogen
peroxide or about 1 to about 30 ppm of ozone.
2. The process of claim 1 wherein said fluoride containing compound
comprises hydrofluoric acid.
3. The process of claim 1 wherein said etchant composition
comprises about 0.01 to about 20 percent by weight of hydrogen
peroxide.
4. The process of claim 1 wherein said etchant composition
comprises about 1 to about 30 ppm of ozone.
5. The process of claim 2 wherein said etchant composition
comprises about 1 to about 10 percent by weight of sulfuric acid,
about 1 to about 10 percent by weight hydrogen peroxide, and about
1 to about 50 ppm of hydrofluoric acid.
6. The process of claim 2 wherein said etchant composition
comprises about 5 percent by weight of sulfuric acid, about 12
percent by weight of hydrogen peroxide and about 10 ppm of
hydrofluoric acid.
7. The process of claim 1 wherein said etchant composition includes
deionized water.
8. A process for providing an aqueous back-end-of-line (BEOL) clean
with feedback control to monitor the active component of HF in said
clean, for a wiring/interconnect of a reactive ion etched
semiconductor device, comprising: subjecting said reactive ion
etched semiconductor device to a post metal RIE clean using the
etchant composition of claim 1, comprising: a) mixing water,
sulfuric acid and hydrogen peroxide in a mixing tank; b) mixing HF
directly into said mixing tank or adding HF into a separate vessel
for wafer processing, either before, during or after said mixture
water, sulfuric acid and hydrogen peroxide as a mixture is
transported to said separate tank for wafer processing; c) taking a
sample comprising HF from said mixing tank or HF from said wafer
processing tank and sending said sample through a feedback loop; d)
comparing said sample to a standard dilute solution of HF to obtain
a value of HF concentration in said sample; e) inputting said value
to a tank tool recipe control to cause any needed adjustment in
concentration of HF to a predetermined range, either in said mixing
tank or said wafer processing vessel; and f) subjecting said
wiring/interconnect of said semiconductor device to etching by said
etchant composition to remove sidewall polymer, polymer rails and
via residue without etching conductive materials during removal of
sidewall polymer, polymer rails, and via residue.
9 The process of claim 8, wherein said fluoride containing compound
comprises hydrofluoric acid.
10. The process of claim 8, wherein said etchant composition
comprises about 0.01 to about 2.0 percent by weight of hydrogen
peroxide.
11. The process of claim 8, wherein said etchant composition
comprises about 1 to about 30 ppm of ozone.
12. The process of claim 9, wherein said etchant composition
comprises about 1 to about 10 percent by weight of sulfuric acid,
about 1 to about 10 percent by weight of hydrogen peroxide, and
about 1 to about 100 ppm of hydrofluoric acid.
13. The process of claim 9, wherein said etchant composition
comprises about 5 percent by weight of sulfuric acid, about 12
percent by weight of hydrogen peroxide and about 10 ppm of
hydrofluoric acid.
14. The process of claim 8, wherein said etchant composition
includes deionized water.
15. The process of claim 8, wherein said separate vessel for wafer
processing is a spray processor.
16. The process of claim 12 when delivered to a spin-spray
processor, short times typically less than 1 minute, most
preferably 20 seconds could be used when HF concentration is close
to 100 ppm HF.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of copending U.S. patent
application Ser. No. 09/627,669, filed Jul. 28, 2000 entitled
"Etching Composition and Use Thereof with Feedback Control of HF in
BEOL Clean", which is a continuation in part of copending U.S.
patent application Ser. No. 09/137,179 filed Aug. 20, 1998, which
is a continuation in part of abandoned U.S. patent application Ser.
No. 08/975,755 filed on Nov. 21, 1997 entitled "Etching Composition
and Use thereof", assigned to the present assignee, which is a
continuation in part of U.S. patent application Ser. No. 08/832,999
filed on Apr. 4, 1997 entitled "Etching Composition and Use
Thereof", which issued as U.S. Pat. No. 5,780,363 assigned to
present assignee and all of which are incorporated by reference in
their entirety.
TECHNICAL FIELD
[0002] The present invention is concerned with an etchant
composition and especially with a composition that is capable of
removing inorganic polymer residue present on a substrate due to a
previous metal reactive ion etching process. In addition, the
present invention is directed to a method for removing such polymer
and via residue by employing the etchant compositions of the
present invention.
BACKGROUND OF THE INVENTION
[0003] Aluminum and aluminum alloys are frequently used for the
"metallizations" in large scale integrated circuits. The aluminum
alloys include those with small amounts of copper for reducing the
potential for electromigration effects, where current applied to
the device induces transport of the aluminum atoms. Small amounts
of silicon or titanium have been added to aluminum in order to
minimize the possibility of electrical spiking that can occur in
contact holes.
[0004] In order to form the patterned metallization, a series of
process steps are carried out. These include depositing a layer
containing aluminum, coating a photoresist film onto the aluminum
containing layer, creating in the photoresist film an image of the
predetermined required pattern, such as by exposing selected
portions of the photoresist film to light passing through a mask or
grating, and then removing either the exposed or unexposed portions
of the photoresist film, depending upon the type of resist
employed, and finally removing the aluminum or aluminum alloy layer
in the regions not masked by the remaining photoresist film. Next,
the remaining photoresist film can be removed.
[0005] More particularly, aluminum/copper metal line for BEOL
wiring/interconnect in semiconductor devices are currently
delineated by a reactive ion etching process. Such a process
involves patterning the aluminum/copper metal layer with a
photoresist and then reactive ion etching (RIE) in a chlorine
environment using boron trichloride, HCl gas, Cl.sub.2 or any other
chlorine containing reactive species in order to etch away the
exposed aluminum/copper layer. However, such etching process leaves
a residue around the metal lines which consist of complex polymeric
oxides of aluminum along with incorporating chlorine into the
inorganic matrix. This is typically referred to as sidewall polymer
residue, and its presence is a troublesome source of corrosion of
the Al/Cu lines when exposed to the environment such as atmospheric
air and/or humidity. Moreover, trace amounts of chlorine over time
break down the passivating layer of aluminum oxide and corrode the
underlying aluminum. Traditionally, the use of fluoride containing
compounds in general, and hydrofluoric acid in particular, has been
avoided because it has the tendency to degrade the quality of metal
lines in general, and aluminum in particular.
[0006] Additionally, after a RIE process, sidewall polymers remain
on the semiconductor wafer surface. These sidewall polymers known
as "polymer rails" are inorganic in nature and have various
chemical constituents, including aluminum, silicon, titanium,
oxygen, carbon and chlorine. Since each of their constituents tends
to react and/or interfere with the semiconductor wafer function,
removal of the sidewall polymers is therefore desirable. A post
metal RIE cleaning step is presently done using a
chromic/phosphoric acid etch, or solvent based chemistry methods.
However, one common chemical constituent with a solvent based
chemistry is an amine which can cause problems with certain types
of photoresists. Solutions which are based on diluted sulfuric acid
and hydrogen peroxide mixtures have been introduced in an attempt
to remove polymer rails. However, these methods have not been
successful in removing all types of polymer rails.
[0007] For example, as shown in FIG. 1, in regions where there is
an isolated metal pad which has a metal line density lower than the
array region of the semiconductor chip and a surrounding region
which is predominantly silicon oxide, current methods are less than
completely successful. FIG. 1 illustrates a situation where the use
solution of the present invention would be indicated. In FIG. 1, a
wafer is shown after it has undergone a RIE process. The direction
of the RIE process is shown by the arrow. The structure shown, 10,
can be comprised of multiple layers. For example, there can be an
oxide layer, 11, and a conductive layer, 12. The RIE process
selectively removed portions of the conductive layer to expose the
oxide layer. Accordingly, there is little to no residual left on
the surface, 5, of the oxide, 11. The RIE process was, in this
case, directed at the surface, 5, as shown by the arrow. However,
the structure, 10, may contain a solid film, 15, covering the
sidewalls, 13 and the top, 14, of the structure, 10.
[0008] Alternatively, as shown in FIG. 2, the etchant is useful for
processing steps not involving polymer etching. For example, there
could be regions in an oxide layer, where a via, 25, has been
previously formed and filled. Preferably the material filling the
via, 25, would be a conductive material. The via may provide
electrical communication between different levels of the wafer. The
etchant solution of the instant invention would also be useful for
cleaning the via, 20, which is opened to the via, 25, of many types
of residue material. Residue materials include, but are not limited
to oxygen, silicon, carbon and elements of an underlying conductive
layer.
[0009] Accordingly, methods are utilized for removing this sidewall
polymer residue, polymer rails, and via residue. One of the more
popular methods employs a chromic/phosphoric acid bath. However,
this procedure is only marginally effective. Moreover, the
chromic/phosphoric acid bath tends to cause some electrochemical
etching of aluminum, especially near a tungsten stud, which are
typically present, thereby causing degradation of the aluminum
metal layer.
[0010] Therefore, providing an etching process capable of removing
the sidewall polymer and via residue that does not etch conductive
materials, especially aluminum, to any undesired extent, while
removing the sidewall polymer, polymer rails, and via residue would
be desirable.
[0011] It would also be desirable to use the etchant composition of
the invention in a controlled manner for aqueous back-end-of-line
(BEOL) clean for interconnects, as the aqueous chemistry of an
aqueous mixture of sulfuric acid, hydrogen peroxide, and very small
amounts of HF introduces new challenges in the manufacturing
process. That is, it is especially important to control and monitor
the concentration of the active etching constituent, HF. Because of
the fact that the concentration level of HF in the mixture is in
the ppm range, it is necessary to incorporate a feedback control
mechanism to use this composition effectively for interconnect
cleaning in the BEOL.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] These and other features, aspects, and advantages will be
more readily apparent and better understood from the following
detailed description of the invention, in which:
[0013] FIG. 1 is a cross-sectional view of a portion of a
semiconductor device illustrating a problem the instant invention
is seeking to solve.
[0014] FIG. 2 is a cross-sectional view of a portion of a
semiconductor device illustrating a problem the instant invention
is seeking to solve.
[0015] FIG. 3 is a schematic of a flow diagram showing the method
of delivery of the chemistry to an open tank for an aqueous
back-end-of-line (BEOL) clean for interconnects.
[0016] FIG. 4 is a schematic of a flow diagram for on-line HF
monitoring of the aqueous clean for back-end-of-line (BEOL) clean
for interconnects.
[0017] FIG. 5 is a schematic of a flow diagram of a process control
for the aqueous back-end-of-line (BEOL) clean for interconnects
where the process implementation is extended to wafer processing in
a spray processor.
SUMMARY OF INVENTION
[0018] One object of the present invention is to provide an etchant
composition that is capable of removing via residue and not
adversely effect the aluminum lines or lines made of other
conductive materials. Moreover, the etching composition of the
present invention is quite acceptable from an environmental point
of view. Additionally, the etchant composition is particularly
useful in removing inorganic polymers attached to the metal lines
in isolated regions where there may be a higher silicon
concentration as compared to the array regions.
[0019] Another object of the present invention is to remove polymer
and via residue from a substrate which comprises contacting the
substrate with an aqueous solution containing about 0.01 to about
15 percent by weight of sulfuric acid, and about 0.01 to about 20
percent by weight of hydrogen peroxide, or about 1 to about 30 ppm
of ozone, and about 0.1 to about 100 ppm of a fluoride containing
compound.
[0020] A further object of the present invention is to provide a
process control methodology for the new aqueous clean for use in
back-end-of-line (BEOL) clean for interconnects, where the aqueous
chemistry is an aqueous mixture of sulfuric acid, hydrogen
peroxide, and very small amounts of HF, as the use of this
chemistry in manufacturing introduces new challenges, and it is
important to control and monitor the concentration of the active
etching constituents, HF.
[0021] The etchant composition of the present invention is an
aqueous solution containing about 0.01 to about 15 percent by
weight of sulfuric acid, about 0.01 to about 20 percent by weight
of hydrogen peroxide, or about 1 to about 30 ppm of ozone, and
about 0.1 to about 100 ppm of hydrofluoric acid.
[0022] Still other objects and advantages of the present invention
will become readily apparent to those skilled in this art from the
following detailed description, wherein it is shown and described
only the preferred embodiments of the invention, simply by way of
illustration of the best mode contemplated of carrying out the
invention. As will be realized, the invention is capable of other
and different embodiments, and its several details are capable of
modifications in various obvious respects, without departing from
the invention. Accordingly, the description is to be regarded as
illustrative in nature and not as restrictive.
BEST AND VARIOUS MODES FOR CARRYING OUT INVENTION
[0023] The etchant compositions of the present invention are
aqueous solutions containing about 0.01 to about 15 percent by
weight and preferably about 1 to about 10 percent by weight of
sulfuric acid and about 0.01 to about 20 percent by weight of
hydrogen peroxide, 0.1 to about 100 ppm of hydrofluoric acid and
preferably about 1 to about 10 percent by weight of hydrogen
peroxide or about 1 to about 30 ppm and preferably about 5 to about
20 ppm of ozone with the balance being substantially water, and
more preferably contain about 0.1 to about 100 ppm of a fluoride
containing compound, preferably hydrofluoric acid. It is not
necessary that the fluoride containing compound be hydrofluoric
acid. It is necessary that the fluoride containing compound
contribute free fluoride to the etchant composition. It is
preferred that the fluoride containing compound be able to
contribute the equivalent of at least about 8 and at most about 12
ppm of hydrofluoric acid to the etchant solution. A preferred
composition of the present invention is an aqueous solution of
about 8 percent by weight of sulfuric acid, and about 1.5 percent
by weight of hydrogen peroxide and the remainder being
substantially water, and more preferably contain about 10 ppm of a
fluoride containing compound, preferably hydrofluoric acid. This
composition is preferably employed at temperatures of about
35.degree. C. Another more preferred composition of the present
invention is an aqueous solution of about 9 percent by weight
sulfuric acid and about 4 percent by weight hydrogen peroxide and
the remainder being substantially water, and more preferably
contain about 10 ppm of a fluoride containing compound, preferably
hydrofluoric acid. This composition is preferably employed at
temperatures of about 35.degree. C. and is especially preferred for
removing thicker and more tenacious sidewall polymer. Yet another
more preferred composition of the present invention is an aqueous
solution of about 5% by weight of sulfuric acid, about 12% by
weight of hydrogen peroxide and about 10 ppm hydrogen fluoride. The
water employed is preferably deionized water.
[0024] These etchant compositions of the present invention can be
prepared by admixing an aqueous sulfuric acid such as a 98 percent
by weight solution with an aqueous solution of hydrogen peroxide
such as a 30 percent by weight solution and aqueous hydrofluoric
acid such as 49 percent by weight and adding these solutions to
water in an amount to provide the desired percentage of the
sulfuric acid, hydrogen peroxide, and hydrofluoric acid.
[0025] The compositions containing the ozone can be prepared by
bubbling ozone gas into the aqueous composition containing the
desired amounts of sulfuric acid and water, or diffusing ozone gas
through a membrane into water and then adding sulfuric acid to the
water, or by any other suitable method.
[0026] The etchant compositions of the present invention remove the
sidewall polymer residue remaining after the reactive ion etching
and with it removes any embedded chlorine. The etchant compositions
of the present invention also clean vias of other residues,
including, but not limited to, oxygen, carbon, silicon and elements
of an underlying conductive material. Furthermore, the etchant
compositions of the present invention, at most, only mildly etch
the aluminum/copper line. Since hydrofluoric acid is known to etch
aluminum/copper, the amounts in the etchant solution must be small.
When the amounts of hydrofluoric acid in the claimed etchant
solution are kept small (less than about 40 ppm) the potentially
detrimental effects of the hydrofluoric acid on aluminum/copper are
minimized. For HF concentration greater than 40 ppm and less than
100 ppm, the process times would be short, typically less than 1
minute. In most cases, no evidence of any local etching of the
aluminum, even aluminum in the vicinity of tungsten studs, has been
observed. The tungsten seems to act as a catalyst in etching
aluminum when using the prior art chromic/phosphoric acid bath.
They also can be used to remove and clean residues after
chemical-mechanical polishing and other `cleaning` processing
steps.
[0027] The etchant compositions of the present invention also
result in the formation of a pristine native oxide of aluminum
which acts as a passivating layer against subsequent corrosion. For
instance, an oxide thickness of about 30 angstroms as measured by
Auger Spectroscopy is obtained using an etchant composition at
about 35.degree. C. containing about 2.0 percent by weight of
sulfuric acid, about 1.0 percent by weight of hydrogen peroxide and
about 10 ppm of hydrofluoric acid.
[0028] The above disclosed relative amounts of components of the
composition tend to prevent redeposition of the polymer residue.
This occurs by having the pH of the etchant such that the charges
of the zeta potentials of the aluminum oxide species and the
silicon oxide surface of the substrate cause a repulsion
interaction between the surfaces. The desired pH is ensured by
observing the amounts of ingredients mentioned above. The zeta
potential reflects the charge induced on a surface caused by the
interactions of that surface with the ions in the solution,
primary, hydrogen and hydroxide. At a certain solution pH, the net
surface charge will be zero which occurs at about pH 2 to 3 for
silica and at about pH 9 to 10 for alumina. When the pH is less
than this point of zero charge, the charge on the surface would be
positive. For the case of a polymer residue removed in an acid
medium, the propensity of redeposition of the residue on either the
oxidized aluminum surface or on the silica dielectric material is
reduced because all surfaces would have a charge of the same sign
with zeta potentials also of the same sign. It should be noted that
HF acid in the concentrations employed in the present invention
(less than about 100 ppm) do not result in significant changes in
the pH of the resulting etchant solution.
[0029] The etchants of the present invention can be used to contact
the substrate where the polymer or via residue is to be removed by
any known technique, such as dipping in a bath or preferably
spraying the composition on the substrate or silicon wafer having
the aluminum copper lines thereon. Typically, the composition is
sprayed at a temperature of about 25 to about 95.degree. C. and
preferably at a temperature of about 30 to about 50.degree. C. for
about 1 to about 8 minutes, typical of which is about 2 minutes.
Following this, the wafer can be subjected to a deionized water
rinse followed by drying. For certain spin-spray processors, with
HF content close to 100 ppm, process times less than 1 minute can
be used.
[0030] The process of the present invention is also capable of
removing chlorine embedded material along with the aluminum/copper
sidewall polymer residue. The aluminum/copper profiles achieved by
the present invention can be smoother than those in the prior art
and are capable of being substantially free of electrochemical or
accelerated etching of Al/Cu lines near tungsten studs.
[0031] The following Table I illustrates various etch rates of the
Al/Cu with the etchant compositions of the present invention. The
percentages in Table I are volume percents for 98 percent by weight
H.sub.2SO.sub.4 and 30 percent by weight of H.sub.2O.sub.2
(remainder is H.sub.2O).
1TABLE 1 Etch rate of Al/Cu with sulfuric/peroxide Etch rate of
Al/Cu samples (Gravimetry) Sulfuric Peroxide Etch rate.sup.1
Temperature (percent) (percent) (Angstroms/min) .degree. C. 2.5 2.5
51/116 35/45 2.5 5.0 57/109 35/45 5.0 2.5 68/148 35/45 5.0 5.0
59/136 35/45 7.5 5.0 78 35 7.5 7.5 77 35 .sup.1Etch rate increases
with temperature
[0032] Table II illustrates various etch rates of the aluminum with
0.5% copper alloy with the etchant compositions of the present
invention. The percentages in Table II are volume percents for 98
percent by weight H.sub.2SO.sub.4 and 30 percent by weight of
H.sub.2O.sub.2 (remainder is H.sub.2O).
2TABLE II Etch rate of Al/Cu with sulfuric/peroxide/hydrofluoric
(gravimetry) HF Etch Rate (ppm) (Angstroms/min) 0 18 10 69 20 107
30 173
[0033] Etch rates were evaluated by measuring the total Al/Cu
etched (gravimetry) with 30 minute process time at about 35.degree.
C. The solution employed to develop Table II comprised about 9
percent by weight of sulfuric acid, 4 percent by weight of hydrogen
peroxide with hydrofluoric acid, with the addition of the amounts
of hydrofluoric acid shown in the first column and with the
remainder of the solution comprising water.
[0034] The percentages shown in the above in Table I and Table II
are exemplary only and others within the scope of the invention can
likewise be employed. The measured etch rates were evaluated by
averaging the total amount of Al--Cu etched over the process
time.
[0035] In the context of the invention, it is also contemplated to
provide process control for aqueous back-end-of-line (BEOL) clean
for interconnects for the new aqueous clean. The aqueous chemistry
is an aqueous mixture of sulfuric acid, hydrogen peroxide, and very
small amounts of HF, and use of this chemistry in manufacturing
introduces new challenges. Because of these new challenges, it is
especially important to control and monitor the concentration of
the active etching constituent, HF. This is so because, the
concentration level of HF in the mixture is in the ppm range,
thereby making it necessary to incorporate a feedback control
mechanism to use this composition effectively for interconnect
cleaning in the BEOL.
[0036] In the BEOL clean the methodology used to deliver the
chemistry to the open tank is first introduced, i.e. the tank is
used to deliver the main chemicals for the process: water, sulfuric
acid, and hydrogen peroxide, in the range already specified. The
active component, HF, is mixed directly with the above mixture in
the mixing tank or delivered directly to the bath separately.
Reference is now made to FIG. 3, which shows the schematic of the
methodology.
[0037] In FIG. 3, water, H.sub.2SO.sub.4 and H.sub.2O.sub.2 are
placed in a mixing tank 30 in amounts previously specified. The
active component HF, may be mixed directly into the mixing tank 30
or delivered separately from tank 31 by use of spiking pump 32,
into a tank for wafer processing 33 either before, during or after
the mixture of water, H.sub.2SO.sub.4 and H.sub.2O.sub.2 is mixed
in tank 30 and transported to the tank for wafer processing 33.
[0038] In order to use the chemistry of the aqueous composition
effectively in production, it is necessary to monitor the active
component, HF. Therefore, the control is set-up in an active mode
where the concentration information is sent to the two controls for
processing wafers in the chemistry tank 33 as follows:
[0039] a) a sample from the chemistry is taken for analysis;
[0040] b) the sample from the chemistry tank is sent to a HF
monitor;
[0041] c) the value of the measured amount of HF is input to the
tool recipe controls;
[0042] d) validation of the effective range within the process
recipe is made to enable processing of the wafer lot;
[0043] e) the sample used for analysis is then sent to a process
drain and is not used for processing wafers;
[0044] f) the foregoing steps a)-e) are repeated periodically, i.e.
about 30 minutes.
[0045] This online HF monitoring set-up is verified periodically,
and the value of the HF concentration is checked against the
standard. The standard may be an ion selective electrode, which is
well known in the art. Specifically, for the disclosure ranges, the
range of HF is preferably set between 5 and 15 ppm, more
preferably, between 7-12 ppm, and most preferably, in an operation
range of between 8-10 ppm.
[0046] A schematic with the HF process control methodology is shown
in FIG. 4, where a mixing tank 40 is employed to mix water,
sulfuric acid and hydrogen peroxide. The mixture from tank 40 is
then supplied to tank 41 for wafer processing, where a spiking pump
42 is used to supply a standard solution of dilute HF from tank 43.
The mixture of water, H.sub.2SO.sub.4 and H.sub.2O.sub.2 and dilute
solution of HF is sampled by a feedback loop for HF analysis to a
chemical analyzer for HF, 44. The value of the HF concentration is
sent to a tank tool recipe control 45. If the HF concentration is
too low, additional amounts of dilute HF is spiked from 43 into 41.
If the concentration of HF is too high, additional amounts of a
mixture of water, H.sub.2SO.sub.4 and H.sub.2O.sub.2 is supplied to
tank 41 to enable the correct amount of mixture of water,
H.sub.2SO.sub.4 and H.sub.2O.sub.2 to be mixed with the dilute
standard solution of HF and added to the chamber for wafer
processing, 46. The sample taken from tank 41 is discarded or
drained, as shown by the arrow leaving tank 44.
[0047] At the initial tank filling of tank 41, a sample is taken
for analysis to determine the amount of the active component, HF.
If the value is within the prescribed range as indicated by the
tank toll recipe control, the wafers are processed in chamber 46.
The control feedback schematic is as follows: 1
[0048] The process control feedback scheme shown above is for wafer
processing in a tank; however, the process implementation may also
be extended to wafer processing in a spray processor, where the
chamber is either opened or closed.
[0049] Wafer processing in a spray processor utilizing the etchant
composition of the invention is shown in FIG. 5. In FIG. 5, in
which a spray processor is used, the HF spiking from spiking pump
50 is done directly in the mixing tank 51 for the initial mixing of
water, sulfuric acid, and hydrogen peroxide after sample 52 taken
from 51 subsequent to supplying a standard solution of dilute HF
from tank 53, through a feedback loop 54 for chemical analysis of
HF value by chemical analyzer 55. If the amounts of HF is too low,
additional standard solution of dilute HF is spiked into tank 51.
If the amount of HF is too high a lesser amount of HF is supplied
from tank 53. When the correct ratio of the ingredients in the
invention etching composition is obtained, the mixture is sent to a
spray tool 56 and then sent of chamber 57 where the wafer is
processed. As in the case of FIG. 4, the value of the sample taken
for chemical analysis of HF at 55 is sent to a spray tool recipe
control 58, and this measured value of input to the spray tool
recipe control affects validation of the effective range of HF to
the chamber in which the wafer is processed. The actual sample
taken for comparison in the chemical analyzer for HF is discarded
or drained as shown by the arrow standing vertically downward from
chemical analyzer 55.
[0050] In the context of the invention, a similar process control
methodology is extendable to a single tank tool, where the
processing chamber and the post water rinse would be done in the
same tank.
[0051] In this disclosure there are shown and described only the
preferred embodiments of the invention, but, as aforementioned, it
is to be understood that the invention is capable of changes or
modifications within the scope of the inventive concept as
expressed.
* * * * *