I 1111111111111111 11111 1111111111 111111111111111 1111111111 lll111111111111111
`US007365045B2
`
`c12) United States Patent
`Walker et al.
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 7,365,045 B2
`Apr. 29, 2008
`
`(54) AQUEOUS CLEANER WITH LOW METAL
`ETCH RATE COMPRISING
`ALKANOLAMINE AND
`TETRAALKYLAMMONIUM HYDROXIDE
`
`(75)
`
`Inventors: Elizabeth L. Walker, Nazareth, PA
`(US); Jeffrey A. Barnes, Nazareth, PA
`(US); Shahriar Naghshineh,
`Allentown, PA (US); Kevin P. Yanders,
`Germansville, PA (US)
`
`(73) Assignee: Advanced Tehnology Materials, Inc.,
`Danbury, CT (US)
`
`5,143,648 A
`5,466,389 A
`5,563,119 A *
`5,597,420 A
`5,709,756 A
`5,863,344 A
`6,194,366 Bl*
`6,417,147 B2 *
`6,492,308 Bl *
`2004/0220065 Al *
`2006/0016785 Al*
`2006/0166847 Al *
`2007/0111912 Al*
`
`9/1992 Satoh et al.
`11/1995 Ilardi et al.
`10/1996 Ward .......................... 510/176
`1/1997 Ward
`1/1998 Ward
`1/1999 Nam
`2/2001 Naghshineh et al. ........ 510/175
`7/2002 Amemiya et al.
`.......... 510/175
`12/2002 Naghshineh et al. ........ 510/175
`11/2004 Hsu ........................... 510/175
`1/2006 Egbe et al.
`................... 216/83
`7/2006 Walker et al.
`.............. 510/175
`5/2007 Phenis et al. ............... 510/175
`
`FOREIGN PATENT DOCUMENTS
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 53 days.
`
`EP
`WO
`WO
`
`0 647 884 Al
`02/065538
`WO 02/065538
`
`4/1995
`* 8/2002
`8/2002
`
`(21) Appl. No.: 11/094,113
`
`(22) Filed:
`
`Mar. 30, 2005
`
`(65)
`
`(51)
`
`(52)
`
`(58)
`
`(56)
`
`Prior Publication Data
`
`US 2006/0229221 Al
`
`Oct. 12, 2006
`
`Int. Cl.
`CllD 3/30
`(2006.01)
`CllD 1162
`(2006.01)
`U.S. Cl. ...................... 510/178; 510/175; 510/176;
`510/181; 510/504
`Field of Classification Search ................ 510/175,
`510/176, 178,181,504; 134/1.2, 1.3
`See application file for complete search history.
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`OTHER PUBLICATIONS
`
`Int'! Search Report for PCT/US2006/007676 dated Jul. 12, 2006.
`
`* cited by examiner
`
`Primary Examiner----Charles I Boyer
`(74) Attorney, Agent, or Firm-Chih-Sheng (Jason) Lin;
`Tristan A. Fuierer; Moore & Van Allen, PLLC
`
`(57)
`
`ABSTRACT
`
`A cleaning solution is provided for cleaning metal-contain(cid:173)
`ing microelectronic substrates, particularly for post etch, via
`formation and post CMP cleaning. The cleaning solution
`consists of a quaternary ammonium hydroxide, an organic
`amine, and water. A preferred cleaning solution consists of
`tetramethylammonium hydroxide, monoethanolamine, and
`water. The pH of cleaning solution is greater than 10.
`
`4,808,513 A *
`
`2/1989 Lazarus et al .............. 430/331
`
`14 Claims, 7 Drawing Sheets
`
`TOK Ex. 1018
`PGR Petition
`
`

`

`U.S. Patent
`
`Apr. 29, 2008
`
`Sheet 1 of 7
`
`US 7,365,045 B2
`
`RUN NO. 1
`
`70° C/30 MINUTES
`
`FIG. 1
`
`Page i
`
`

`

`U.S. Patent
`
`Apr. 29, 2008
`
`Sheet 2 of 7
`
`US 7,365,045 B2
`
`RUN NO. 7
`
`40° C/5 MINUTES
`
`FIG. 2
`
`Page ii
`
`

`

`U.S. Patent
`
`Apr. 29, 2008
`
`Sheet 3 of 7
`
`US 7,365,045 B2
`
`RUN NO. 1
`
`70° C/60 MINUTES
`
`ATMI
`
`SEI
`
`6.0kV
`
`X6,000
`
`1µm
`
`WD9.4mm
`
`FIG. 3
`
`Page iii
`
`

`

`U.S. Patent
`
`Apr. 29, 2008
`
`Sheet 4 of 7
`
`US 7,365,045 B2
`
`RUN NO. 9
`
`50° C/15 MINUTES
`
`ATMI
`
`SEI
`
`6.0kV
`
`X6,000
`
`1µm
`
`WD 8.0mm
`
`FIG. 4
`
`Page iv
`
`

`

`UI = N
`UI = ~
`-....l w
`d r.,;_
`
`0--,
`
`FIG. 5
`
`6.0kV X60,000 100nm WD 10.3mm
`
`6.0kV X60,000 100nm WD 9.2mm
`
`Page v
`
`0 ....
`Ul
`.....
`rJJ =(cid:173)
`
`('D
`('D
`
`-....J
`
`QO
`0
`0
`N
`~\,Ci
`N
`:-:
`> "e
`
`~ = ~
`
`~
`~
`~
`•
`00
`
`e •
`
`CONTROL
`
`

`

`U.S. Patent
`
`Apr. 29, 2008
`
`Sheet 6 of 7
`
`US 7,365,045 B2
`
`ESC 7 4 50°C 10 min.
`
`Samsung ESC-74100% S0°C 10 min.
`
`100nm
`
`WD 10.1mm
`
`FIG. 6
`
`Page vi
`
`

`

`U.S. Patent
`
`Apr. 29, 2008
`
`Sheet 7 of 7
`
`US 7,365,045 B2
`
`ESC 74 50°C 10 min.
`
`100nm
`
`FIG. 7
`
`Page vii
`
`

`

`US 7,365,045 B2
`
`1
`AQUEOUS CLEANER WITH LOW METAL
`ETCH RATE COMPRISING
`ALKANOLAMINE AND
`TETRAALKYLAMMONIUM HYDROXIDE
`
`FIELD OF THE INVENTION
`
`The present invention relates to post etch and post chemi(cid:173)
`cal-mechanical polishing (post-CMP) cleaning operations,
`and more specifically to post etch and post-CMP cleaning
`solutions for metal-containing microelectronic substrates.
`
`BACKGROUND OF THE INVENTION
`
`2
`ammonium hydroxide, acetic acid, and water. The solution
`preferably contains a volumetric ratio of acetic acid to
`tetramethyl ammonium hydroxide ranging from about 1 to
`about 50.
`Ward, U.S. Pat. No. 5,597,420, discloses a post etch
`aqueous stripping composition useful for cleaning organic
`and inorganic compounds from a substrate that will not
`corrode or dissolve metal circuitry in the substrate. The
`disclosed aqueous composition contains preferably 70 to 95
`10 wt % monoethanolamine and a corrosion inhibitor at about
`5 wt % such as catechol, pyrogallol or gallic acid.
`Ward, U.S. Pat. No. 5,709,756, discloses a post etch
`cleaning composition containing about 25 to 48 wt %
`hydroxylamine, 1 to 20 wt% ammonium fluoride, and water.
`15 The pH of the solution is greater than 8. The solution may
`further contain a corrosion inhibitor such as gallic acid,
`catechol, or pyrogallol.
`Ilardi et al., U.S. Pat. No. 5,466,389, discloses an aqueous
`alkaline cleaning solution for cleaning microelectronic sub-
`20 strates. The cleaning solution contains a metal ion-free
`alkaline component such as a quaternary anmionium
`hydroxide (up to 25 wt%), a nonionic surfactant (up to 5 wt
`%), and a pH-adjusting component, such as acetic acid, to
`control the pH within the range of 8 to 10.
`Schwartzkopf et al., European Patent No. 0647884Al
`discloses photoresist strippers containing reducing agents to
`reduce metal corrosion. This patent teaches the use of
`ascorbic acid, gallic acid, and pyrogallol among others for
`the control of metal corrosion in alkali containing compo-
`30 nents.
`U.S. Pat. No. 5,143,648 to Satoh et al., which is herein
`incorporated by reference discloses novel ascorbic acid
`derivatives as antioxidants.
`35 Ward U.S. Pat. No. 5,563,119 discloses a post etch
`aqueous stripping composition consisting of an alkanola(cid:173)
`mine,
`tetraalkyammonium hydroxide, and a corrosion
`inhibitor for cleaning organic residue from aluminized inor(cid:173)
`ganic substrates.
`From the above noted prior art and general knowledge of
`workers skilled in the art cleaning compositions known prior
`to the invention described below required a corrosion inhibi(cid:173)
`tor. Furthermore, in view of the fact that since alkanolamine
`and a quaternary ammonium hydroxide in combination are
`45 each considered corrosive toward most metals, a combina(cid:173)
`tion of these two compounds would not be considered by a
`worker skilled in the art looking for new metal cleaning
`compositions.
`There is a need to further improve post-CMP cleaning
`50 compositions for copper-containing surfaces to not only
`clean residuals particles and contaminants from surfaces of
`devices but to further prevent or substantially lessen corro(cid:173)
`sion of the copper-containing substrate. Such a post-CMP
`cleaning composition must also refrain from attacking the
`55 process equipment used in the post-CMP process. Such a
`post-CMP cleaning composition should also be economical,
`work effectively through a wide temperature range, and
`preferably contain chemical components of comparatively
`lower toxicity. Such a post-CMP cleaning composition
`60 should also be useful in cleaning operations following CMP
`processes utilizing alumina or silica-based slurries.
`
`The present day fabrication of semiconductor devices is a
`complex, multi-step process. The CMP process and post etch
`processes are now well established enabling technology
`used by most advanced semiconductor operations for manu(cid:173)
`facturing of semi-conductor devices with design geometries
`less than 0.35 micron.
`The CMP processes involve holding and rotating a thin,
`flat substrate of the semiconductor material against a wetted
`polishing surface under controlled chemical, pressure and
`temperature conditions. A chemical slurry containing a
`polishing agent, such as alumina or silica, is used as the 25
`abrasive material. In addition, the chemical slurry contains
`selected chemicals which etch various surfaces of the sub(cid:173)
`strate during processing. The combination of mechanical
`and chemical removal of material during polishing results in
`superior planarization of the surface.
`The CMP process, however, leaves contamination on the
`surfaces of the semiconductor substrate. This contamination
`is comprised of abrasive particles from the polishing slurry
`which may consist of alumina or silica, with reactive chemi(cid:173)
`cals added to the polishing slurry. In addition, the contami(cid:173)
`nant layer may comprise reaction products of the polishing
`slurry and the polished surfaces. It is necessary to remove
`the contamination prior to subsequent processing of the
`semiconductor substrate in order to avoid degradation in
`device reliability and to avoid the introduction of defects 40
`which reduce the manufacturing process yield. Thus, post(cid:173)
`CMP cleaning solutions have been developed to cleanse the
`substrate surface of CMP residuum.
`Alkaline solutions based on ammonium hydroxide have
`been traditionally used in post-CMP cleaning applications. A
`majority of CMP applications have been directed to alumi(cid:173)
`num, tungsten, tantalum, and oxide-containing surfaces.
`Copper is increasingly becoming a material of choice in
`the production of interconnects in semiconductor fabrica(cid:173)
`tion. Copper is replacing aluminum as the metal of choice in
`such fabrication. There are several post-CMP processes for
`cleaning surfaces containing copper. Copper, copper oxide,
`and the slurry particles are the contaminants that exist on the
`copper-containing surface following this CMP process. The
`copper surface contamination diffuses quickly in silicon and
`silicon dioxide, and therefore, it must be removed from all
`wafer surfaces to prevent device failure.
`Effective post-CMP cleaning solutions are disclosed and
`claimed in U.S. Pat. No. 6,194,366 Bl now owned by the
`Assignee of the present application. Patentees disclose a
`cleaning composition containing tetramethyl-ammonium
`hydroxide (TMAH), monoethanol amine (MEA), a corro(cid:173)
`sion inhibitor being one of gallic acid ascorbic acid or
`mixtures thereof and water. The basic composition can be
`used in a dilute form for effective Post CMP cleaning.
`Nam, U.S. Pat. No. 5,863,344, discloses a cleaning solu(cid:173)
`tion for semiconductor devices containing tetramethyl
`
`65
`
`SUMMARY OF THE INVENTION
`
`In one aspect the present invention is a cleaning solution
`for cleaning metal-containing microelectronic substrates
`consisting of 0.09 to 22% by weight alkanolamine, 0.02 to
`
`

`

`US 7,365,045 B2
`
`3
`13.5% by weight quaternary ammonium hydroxide, balance
`deionized water. The pH of the solution should be greater
`than 10.
`In another aspect the present invention is a post-CMP
`cleaning solution for cleaning microelectronic substrates 5
`consisting of 0.09 to 22 wt % of an alkanolamine selected
`from the group consisting of monoethanolamine, 1, amino-
`2-propanol, 2-(methylamino) ethanol, triethanolamine and
`mixtures
`thereof, a quaternary ammonium hydroxide
`selected from the group consisting oftetramethylammonium 10
`hydroxide, tetrabutyl ammonium hydroxide and mixtures
`thereof in an amount in the range from about 0.02 wt % to
`about 13.5 wt%, balance deionized water.
`In yet another aspect the present invention is a cleaning
`composition containing 9.0 wt % to 22.0 wt % alkanola(cid:173)
`mine, 0.45 wt % to 12.2 wt % quaternary ammonium
`hydroxide, balance deionized water.
`In still another embodiment the present invention is a
`cleaning composition consisting essentially of 0.30 to 0.70
`wt% alkanolamine 0.02 to 0.7 wt% quaternary ammonium 20
`hydroxide, balance deionized water.
`In a further embodiment the present invention is a clean(cid:173)
`ing composition consisting essentially of 0.30 to 9.0 wt %
`alkanolamine, 0.06 to 13.5 wt % potassium hydroxide,
`balance deionized water.
`
`25
`
`4
`Generally, a copper-containing microelectronic substrate
`contains about 1-20% Cu, including the copper intercon(cid:173)
`nects.
`The cleaning solution of the invention may find applica-
`tion for any cleaning operation during the fabrication of
`microelectronic substrates, such as semiconductor wafers.
`Most notably, such cleaning applications include post-Via
`formations and post-CMP processes. The fabrication of
`conventional semiconductor wafers entails many steps
`requiring planarization, followed by the removal of residual
`product from the planarization process.
`The cleaning solution of the invention comprises quater(cid:173)
`nary ammonium hydroxide, an amine, and the balance
`15 deionized water.
`The pH of a cleaning solution of the invention is greater
`than 10.
`The constituents of the cleaning solutions of the invention
`may be mixed together in any order. The order of addition
`is exemplified with respect to the embodiment containing
`TMAH, MEA, and deionized water. In a preferred method
`of preparation, 100% of the water in the final solution is
`added to all of the MEA. The TMAH is then added and the
`composition mixed under low shear-stress conditions for
`about 10 minutes. The resulting mixture is then filtered
`through a 0.1 micron filter.
`The components of the preferred embodiment of a clean(cid:173)
`ing solution of the invention are commercially available.
`An important feature of the cleaning solutions of the
`invention is that only two non-aqueous constituents (the
`constituents other than water) are present in the solution.
`The compositions of invention consist of a quaternary
`35 ammonium hydroxide in an amount in the range from about
`0.02 to about 13.5 wt%, an alkanolamine in an amount in
`the range from about 0.3 to about 22.0 wt%, and the balance
`water (preferably deionized water).
`The compositions of the invention preferably use one or
`a mixture of tetramethylammonium hydroxide (TMAH) or
`tetrabutylammonium hydroxide (TBAH) as the quaternary
`ammonium hydroxide. The alkanolamine is preferably
`monoethanolamine (MEA)
`l-amino-2-propanol (1A2P),
`2-(methylamino) ethanol triethanolamine (TEA) and mix-
`45 tures thereof.
`The cleaning solutions of the invention may be employed
`for cleaning microelectronic substrates at temperatures rang(cid:173)
`ing from ambient conditions to about 70° C. It is generally
`recognized that cleaning improves as temperature increases.
`At temperatures greater than about 70° C., evaporation of
`constituent cleaning solution species may adversely alter the
`chemistry of the cleaning system over time in a process open
`to ambient conditions.
`The cleaning solutions of the invention, as noted, have a
`pH greater than 10. More preferably, the pH of cleaning
`solutions of the invention is maintained in the range from
`about 11.0 to about 12.2. A pH greater than 10 is necessary
`to obtain a negative zeta potential on the surface of the
`60 substrate and to avoid redeposition of the remaining par(cid:173)
`ticulates during the cleaning operation.
`The cleaning solutions of the invention meet generally
`accepted industry cleaning performance standards for post(cid:173)
`CMP applications. A common industrial cleaning target is a
`particle count on the substrate wafer of less than 20-particles
`greater than 0.2 microns in size for a 200 mm wafer, with a
`5 mm edge exclusion.
`
`55
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`FIG. 1 is a scanning electron microscope (SEM) photo- 30
`micrograph of a wafer prepared with an aggressive cleaning
`composition according to the invention.
`FIG. 2 is a scanning electron microscope (SEM) photo(cid:173)
`micrograph of a wafer cleaned in a less aggressive compo(cid:173)
`sition according to the present invention.
`FIG. 3 is a SEM photomicrograph of the device shown in
`FIG. 1 treated to strip photoresist with an aggressive com(cid:173)
`position according to the invention.
`FIG. 4 is a SEM photomicrograph of a device shown in
`FIG. 1 treated to strip photoresist with a less aggressive 40
`composition according to the invention.
`FIG. 5 is a pair of SEM photomicrographs of a patterned
`wafer before treatment with a composition according to the
`invention.
`FIG. 6 is a SEM photomicrograph of post etch short(cid:173)
`looped patterned wafer segments after treatment with a
`composition according to the present invention.
`FIG. 7 is a SEM photomicrograph of another portion of
`the device of FIG. 6 treated post etch with a composition 50
`according to the invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`Cleaning metal-containing substrates following CMP pro(cid:173)
`cessing are generally referred to as "post-Cu CMP" or
`"post-CMP copper clean". A "copper-containing microelec(cid:173)
`tronic substrate" is understood herein to refer to a substrate
`surface manufactured for use in microelectronic, integrated
`circuit, or computer chip applications, wherein the substrate
`contains copper-containing components. Copper-containing
`components may include, for example, metallic intercon(cid:173)
`nects that are predominately copper or a copper alloy. It is
`understood that the microelectronic surface may also be 65
`composed of semiconductor materials, such as AL, W, TiN,
`Ta, TiW (as copper diffusion barrier metals), and silica.
`
`

`

`US 7,365,045 B2
`
`6
`EXAMPLE 1
`
`5
`The cleaning solutions of the invention limit copper
`corrosion to smoothing of the surface and do not damage
`processing equipment.
`The cleaning solutions of the invention may be used with
`a large variety of conventional cleaning tools, including 5
`Verteq single wafer megasonic Goldfinger, OnTrak systems,
`DDS (double-sided scrubbers) and Megasonic batch wet
`bench systems.
`The cleaning solutions of the invention may be used
`successfully on surfaces containing copper, tungsten, and/or
`silica.
`Via cleaning is one application of the cleaning solution of
`the invention. Vias are holes etched in microelectronic
`substrates to provide a conduit for connecting metal layers.
`Vias are formed by etching the substrate surface with a
`gaseous etchant forms vias. The substrate is commonly a
`dielectric material, such as Fluorinated Silica Glass (FSG).
`The residue remaining on the substrate surface and via walls
`
`10
`
`Cleaning solutions were evaluated for the tendency to
`corrode copper. One hundred milliliter aqueous solutions of
`alkanolamines with and without added quaternary ammo(cid:173)
`nium hydroxides were prepared. Identical (4x0.02) inch
`copper wire samples were placed into these solutions for 10
`minutes at 22° C., the wire was removed, and the solutions
`analyzed for copper (in parts per billion) using graphite
`furnace atomic absorption spectroscopy. The results, set
`forth in Table 1, clearly show the ability of quaternary
`ammonium hydroxides to prevent or moderate the copper
`corrosion (as measured by copper uptake in the cleaning
`15 solutions) that accompanies exposure to alkanolamines.
`Relative copper corrosion rate=( copper content of formula(cid:173)
`tion with quaternary ammonium hydroxide)+(copper con(cid:173)
`tent of formulation without quaternary ammonium hydrox(cid:173)
`ide).
`
`TABLE 1
`
`Effect of Quaternary Ammonium Hydroxides on Alkanolamine Cleaners
`
`Comparative Alkanolamine
`Solutions without
`Quaternary Ammonium
`Hydroxides
`
`Alkanolamine Formulation
`Containing
`Quaternary Ammonium
`H droxide
`
`Alkanolamine
`
`wt.%
`
`Copper Quaternary
`Content Arnmoniwn
`(ppb) Hydroxide
`
`Copper Relative
`Content Corrosion
`(ppb)
`Rate
`
`wt.%
`
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`1-Amino-2-propanol
`1-Amino-2-propanol
`1-Amino-2-propanol
`1-Amino-2-propanol
`1-Amino-2-propanol
`2-(Metbylamino )etbanol
`2-(Metbylamino )etbanol
`2-(Metbylamino )etbanol
`2-(Metbylamino )etbanol
`2-(Metbylamino )etbanol
`2-(Metbylamino )etbanol
`Triethanolarnine
`Triethanolarnine
`Triethanolarnine
`Triethanolarnine
`Triethanolarnine
`
`9
`9
`9
`9
`11
`11
`11
`11
`11
`11
`11
`11
`11
`11
`11
`22
`22
`22
`22
`22
`
`505
`
`588
`
`344
`
`190
`
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrabutyl
`Tetrabutyl
`Tetrabutyl
`Tetrabutyl
`Tetrabutyl
`Tetrabutyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`Tetrametbyl
`
`0.45
`1.8
`5
`9
`1.1
`2.2
`3.7
`6.1
`11.0
`0.6
`1.1
`2.2
`3.7
`6.1
`11
`1.1
`2.2
`4.4
`7.3
`12.2
`
`455
`380
`290
`80
`613
`409
`480
`404
`287
`225
`212
`149
`133
`110
`28
`46
`0
`0
`0
`0
`
`0.9
`0.8
`0.6
`0.2
`1.0
`0.7
`0.8
`0.7
`0.5
`0.6
`0.6
`0.4
`0.4
`0.3
`0.08
`0.2
`0
`0
`0
`0
`
`EXAMPLE 2
`
`must be removed following the etching process. The residue 50
`is often referred to as "side wall polymer", as it is also found
`on the vertical walls of the via. Etching residue may also be
`located at the bottom of the via, on top of the metal. The
`cleaning solution of the invention does not react with or
`affect the exposed dielectric material.
`A series of tests were conducted to determine whether
`compositions according to the invention while being effec(cid:173)
`tive cleaning compositions could cause un-wanted and/or
`excessive corrosion of copper used in fabricating micro- 60
`electronic devices.
`The following examples summarize the data. In the data
`presented in Tables 1, 2 and 3 the left hand colunm lists the
`amine plus deionized water composition and the resulting
`copper concentration while the right hand colunm shows the 65
`data for the amine and water to which is added quaternary
`ammonium hydroxide.
`
`Cleaning solutions were evaluated for the tendency to
`55 corrode copper. Aqueous solutions of alkanolamines with
`and without added quaternary ammonium hydroxides were
`prepared. Identical blanket copper on silicon wafer pieces
`were submersed in these stirred solutions for 10 minutes at
`22° C. Four point probe measurements for sheet resistance
`were made on these pieces prior to and after treatment.
`Copper etch rates (in Angstroms per minute) for the solu(cid:173)
`tions were calculated. The results, set forth in Table 2,
`clearly show the ability of quaternary ammonium hydrox(cid:173)
`ides to prevent or moderate the copper corrosion (as mea(cid:173)
`sured by copper etch rate) that accompanies exposure to
`alkanolamines. Relative copper corrosion rate=( copper etch
`
`

`

`US 7,365,045 B2
`
`7
`rate of formulation with quaternary annnonium hydroxide)
`+( copper etch rate of formulation without quaternary ammo(cid:173)
`nium hydroxide).
`
`8
`water. These diluted solutions were used to clean pieces of
`the dirty wafers described above. A single wafer spray tool
`operating at 150 rpm at room temperature for 60 seconds
`
`TABLE 2
`
`Effect of Quaternary Ammonium Hydroxides on Alkanolamine Cleaners
`
`Comparative Alkanolamine
`Solutions without
`Quaternary Ammonium Hydroxides
`
`Alkanolamine Formulation
`Containing
`Quaternary Ammonium Hydroxide
`
`Alkanolamine
`
`wt.%
`
`Copper
`Etch rate
`(A/min.)
`
`Quaternary
`Arnmoniwn
`Hydroxide
`
`Relative
`Copper
`Etch rate Corrosion
`(A/min.)
`Rate
`
`wt.%
`
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`1-Arnino-2-propanol
`1-Arnino-2-propanol
`1-Arnino-2-propanol
`1-Arnino-2-propanol
`2-(Methylamino )ethanol
`2-(Methylamino )ethanol
`2-(Methylamino )ethanol
`2-(Methylamino )ethanol
`Triethanolarnine
`Triethanolarnine
`Triethanolarnine
`
`9
`9
`9
`9
`9
`9
`9
`9
`9
`9
`11
`11
`11
`11
`11
`11
`11
`11
`22
`22
`22
`
`9.8
`
`9.8
`
`7.7
`
`9.0
`
`5.1
`
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetrabutyl
`Tetrabutyl
`Tetrabutyl
`Tetrabutyl
`Tetrabutyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`
`0.45
`1.8
`5
`9
`13.5
`0.9
`5
`13.5
`23.3
`41.4
`1.1
`2.2
`6.1
`11.0
`1.1
`2.2
`6.1
`11
`2.2
`4.4
`12.2
`
`9.8
`8.9
`6.8
`5.2
`4.8
`10.0
`9.7
`5.7
`4.4
`4.2
`7.4
`7.5
`6.9
`5.1
`7.8
`7.0
`6.5
`6.8
`5.4
`4.7
`3.4
`
`1.0
`0.9
`0.7
`0.5
`0.5
`1.0
`1.0
`0.6
`0.4
`0.4
`1.0
`1.0
`0.9
`0.7
`0.9
`0.8
`0.7
`0.7
`1.0
`0.9
`0.7
`
`EXAMPLE 3
`
`Cleaning solutions were evaluated for the ability to
`remove particles from wafers patterned with copper into a
`low-K organosilicon dielectric. These received a final cop(cid:173)
`per chemical mechanical polish (CMP) using a Hitachi low
`pH barrier slurry followed by drying without post-CMP
`cleaning. Aqueous solutions of alkanolamines with and
`without added quaternary ammonium hydroxides similar to
`Examples 1 and 2 were prepared and diluted 30: 1 with
`
`35
`
`was used. Particle counts of 20x20 micron squares were
`obtained from scamiing electron microscope images using
`the Object Count routine of Sigma Scan Pro software. The
`results, set forth in Table 3, clearly show the ability of
`quaternary ammonium hydroxides to enhance the particle
`40 removing ability of the alkanolamine solutions. Relative
`particle count=(particle count of formulation with quater(cid:173)
`nary annnonium hydroxide )+(particle count of formulation
`without quaternary ammonium hydroxide).
`
`TABLE 3
`
`Effect of Quaternary Ammonium Hydroxides on Alkanolamine Cleaners
`
`Comparative Alkanolamine
`Solutions without
`Quaternary Arnmoniwn Hydroxides
`
`Alkanolamine Formulation
`Containing
`Quaternary Arnmoniwn Hydroxide
`
`Alkanolamine
`
`wt.%
`
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`Monoethanolarnine
`1-Arnino-2-propanol
`1-Arnino-2-propanol
`1-Arnino-2-propanol
`1-Arnino-2-propanol
`2-(Methylamino )ethanol
`2-(Methylamino )ethanol
`2-(Methylamino )ethanol
`2-(Methylamino )ethanol
`
`0.3
`0.3
`0.3
`0.3
`0.3
`0.4
`0.4
`0.4
`0.4
`0.4
`0.4
`0.4
`0.4
`
`Quaternary
`Particle Arnmoniwn
`Count Hydroxide
`
`14,400 Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`19,900 Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`3,800 Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`
`Relative
`Particle Particle
`Count
`Count
`
`5000
`860
`260
`260
`190
`3400
`1700
`1800
`660
`2400
`2200
`880
`100
`
`0.3
`0.06
`0.02
`0.02
`0.01
`0.2
`0.09
`0.09
`0.03
`0.6
`0.6
`0.2
`0.03
`
`wt.%
`
`0.02
`0.03
`0.1
`0.2
`0.3
`0.004
`0.01
`0.04
`0.07
`0.004
`0.01
`0.07
`0.2
`
`

`

`US 7,365,045 B2
`
`10
`
`9
`
`TABLE 3-continued
`
`Effect of Quaternary Ammonium Hydroxides on Alkanolamine Cleaners
`
`Comparative Alkanolamine
`Solutions without
`Quaternary Ammonium Hydroxides
`
`Alkanolamine Formulation
`Containing
`Quaternary Arnmoniwn Hydroxide
`
`Alkanolamine
`
`wt.%
`
`Quaternary
`Particle Arnmoniwn
`Count Hydroxide
`
`wt.%
`
`Particle
`Count
`
`Relative
`Particle
`Count
`
`Triethanolarnine
`Triethanolarnine
`Triethanolarnine
`Triethanolarnine
`
`0.7
`0.7
`0.7
`0.7
`
`28,000 Tetramethyl
`Tetramethyl
`Tetramethyl
`Tetramethyl
`
`0.04
`0.07
`0.1
`0.2
`
`8400
`6100
`5300
`5200
`
`0.3
`0.2
`0.2
`0.2
`
`EXAMPLE 4
`
`ethanolamine, 2% tetramethylammonium hydroxide, and
`6% water under the following process conditions.
`
`The usefulness of adding quaternary anmionium hydrox(cid:173)
`ides to alkanolamine cleaning solutions was further demon- 20
`strated by comparing a quaternary ammonium hydroxide
`containing formulation to aqueous alkanolamine with and
`without an added known copper corrosion inhibitor, 1,2,4-
`triazole. Aqueous cleaning solutions were prepared for com(cid:173)
`parison and are listed in Table 4. These were evaluated for
`the ability to remove particles from wafers patterned with
`copper into a low-K organosilicon dielectric using the
`method described in Example 3. Additional (unpatterned)
`blanket copper wafer pieces were cleaned using these solu(cid:173)
`tions under the same conditions, a single wafer spray tool
`operating at 150 rpm at room temperature for 60 seconds.
`After cleaning, surface roughness was evaluated using an
`atomic force microscope and the root mean square (Rms)
`roughness (in nanometers) of a 20x20 micron square deter(cid:173)
`mined. The results, set forth in Table 4, clearly show that 35
`quaternary ammonium hydroxide addition results
`in
`enhanced the particle removal and lower surface roughness
`than aqueous alkanolamine with or without the copper
`corrosion inhibitor.
`
`25
`
`30
`
`Run Number
`
`Temperature
`(" c.)
`
`Time
`(minutes)
`
`2
`3
`4
`5
`6
`7
`
`70
`70
`70
`55
`55
`40
`40
`
`30
`10
`5
`10
`5
`10
`5
`
`SEMs
`
`FIG. 1
`
`FIG. 2
`
`Scanning electron micrographs (SEM) were obtained for
`each wafer piece treated. These micrographs indicated that
`for every run listed above, the ARC and photoresist were
`completely removed without any damage to the underlying
`copper surface. FIG. 1 illustrates the absence of any damage
`to the copper surface using most aggressive treatment.
`Further evidence of copper compatibility was obtained by
`measuring the copper etch rate of the formulation prepared
`40 above using the sheet resistance method described in
`Example 2. A copper etch rate of 4.3 Angstroms/minute at
`70° C. was obtained which is similar to the improved etch
`rates reported for the formulations described in Example 2.
`FIG. 2 illustrates the complete removal of ARC and photo(cid:173)
`resist using the least aggressive treatment.
`
`45
`
`EXAMPLE 6
`
`The utility of quaternary ammonium hydroxide-contain(cid:173)
`ing alkanolamine cleaning solutions was further demon(cid:173)
`strated by stripping wafer pieces described in Example 5
`using a mixture of 92% 2-(2-dimethylaminoethoxy)ethanol,
`2% tetramethylanmionium hydroxide, and 6% water under
`the following process
`
`50
`
`55
`
`TABLE 4
`
`Comparison of Quaternary Ammonium Hydroxide and 1,2,4-Triazole
`
`Treatment Solution
`
`Particle
`Count
`
`Rms Roughness
`(nm)
`
`None
`Monoethanolamine (0.3%)
`Monoethanolamine (0.3%)
`1,2,4-Triazole (0.003%)
`Monoethanolamine (0.3%)
`Tetramethylammonium hydroxide (0.1%)
`
`27,300
`10,500
`380
`
`200
`
`2.8
`2.7
`2.9
`
`1.7
`
`EXAMPLE 5
`
`The utility of quaternary ammonium hydroxide-contain(cid:173)
`ing alkanolamine cleaning solutions was further demon-
`strated by using such a solution to strip a typical photoresist
`and anti-reflective coating (ARC) on a copper substrate. The
`test wafer was prepared by spin coating 0.2 micron of 60
`Brewer Science bottom-ARC #XL-20 onto a copper layer
`that had been deposited on a silicon wafer. The ARC was
`cured by baking at 190° C. followed by further spin coating
`with four microns of Shipley SPR-220 photoresist. The
`photoresist was then cured by baking at 140° C. followed by 65
`a one minute deep UV cure at the same temperature. Pieces
`of this wafer were stripped using a mixture of 92% mono-
`
`Run Number
`
`Temperature
`(" c.)
`
`Time
`(minutes)
`
`2
`3
`4
`5
`6
`7
`8
`
`70
`70
`70
`70
`60
`60
`60
`50
`
`60
`30
`15
`5
`30
`15
`5
`30
`
`SEMs
`
`FIG. 3
`
`

`

`US 7,365,045 B2
`
`11
`
`-continued
`
`Run Number
`
`Temperature
`(" c.)
`
`Time
`(minutes)
`
`9
`10
`
`50
`50
`
`15
`5
`
`SEMs
`
`FIG.4
`
`(SEMs) were
`Scanning electron photomicrographs
`obtained for each wafer piece treated. These micrographs 10
`indicated that for every run listed above, the ARC and
`photoresist were completely removed without any damage
`to the underlying copper surface. FIG. 3 illustrates the
`absence of any damage to the copper surface using the most
`aggressive treatment. Further evidence of copper compat- 15
`ibility was obtained by measuring the copper etch rate of the
`formulation prepared above using the sheet resistance
`method described in Example 2. A favorably low copper
`etch rate of 2.4 Angstroms/minute at 70° C. was obtained.
`FIG. 4 illustrates the complete removal of ARC and photo- 20
`resist using a much less aggressive treatment.
`It has also been discovered that potassium hydroxide is an
`effective alternate to the quaternary ammonium hydroxide
`for use in an effective cleaning solution. Examples 7 and 8
`set out below summarize data for compositions using an 25
`amine, ( e.g. MEA), potassium hydroxide (KOH) and deion(cid:173)
`ized water.
`
`EXAMPLE 7
`
`12
`in Example 3. The results, set forth in Table 8, clearly show
`that potassium hydroxide addition results in enhanced the
`particle removal.
`
`TABLE 8
`
`Treatment Solution
`
`None
`Monoetbanolamine (0.3%)
`Monoetbanolamine (0.3%)
`Potassium hydroxide (0.06%)
`Monoetbanolamine (0.1%)
`Potassium hydroxide (0.06%)
`
`Particle
`Count
`
`27,300
`10,500
`910
`
`80
`
`The foregoing examples illustrate the low corrosion rate
`and effective cleaning properties of compositions according
`to the invention.
`Additional short-loop patterned test wafers containing
`organosilicon glass (OSG) patterns on ECD copper and
`blan