(19) United States
`(12) Patent Application Publication
`Amemiya et al.
`
`(10) Pub. No.: US 2001/0025017 Al
`Sep. 27, 2001
`(43) Pub. Date:
`
`1111111111111111 IIIIII IIIII 11111 1111111111 11111 1111111111 11111 11111111111111
`US 20010025017 Al
`
`(54) CLEANING AGENT COMPOSITION,
`METHOD FOR CLEANING AND USE
`THEREOF
`
`(76)
`
`Inventors: Masahiro Amemiya, Fukushima (JP);
`Satoshi Saito, Fukushima (JP); Katsuji
`Yano, Fukushima (JP); Kunio Matsuki,
`Kanagawa (JP)
`
`Correspondence Address:
`SUGHRUE, MION, ZINN, MACPEAK &
`SEAS, PLLC
`2100 Pennsylvania Avenue, N.W.
`Washington, DC 20037-3213 (US)
`
`(21)
`
`Appl. No.:
`
`09/794,620
`
`(22)
`
`Filed:
`
`Feb.28,2001
`
`Related U.S. Application Data
`
`(63)
`
`Non-provisional of provisional application No.
`60/241,839, filed on Oct. 20, 2000.
`
`(30)
`
`Foreign Application Priority Data
`
`Feb. 29, 2000
`Aug. 22, 2000
`
`(JP) ...................................... P2000-54670
`(JP) .................................... P2000-250540
`
`Publication Classification
`
`Int. Cl.7 ................................ B08B 3/04; C11D 1/00
`(51)
`(52) U.S. Cl. ................................. 510/175; 134/2; 134/26
`
`(57)
`
`ABSTRACT
`
`An object of the present invention is to provide a new
`cleaning agent composition having excellent cleaning power
`for the surface contamination of a semiconductor wafer or
`various precisely worked instruments made of glass or
`ceramic, which is used in the manufacture of wafer; a
`method for cleaning a wafer; a semiconductor wafer having
`a surface cleaned by a cleaning method; and a method for
`manufacturing a semiconductor wafer. A semiconductor
`wafer is cleaned using a cleaning agent composition includ(cid:173)
`ing a specific fluorine-containing anionic surfactant, a qua(cid:173)
`ternary ammonium hydroxide and/or an alkanolamine.
`
`TOK Ex. 1019
`PGR Petition
`
`

`

`US 2001/0025017 Al
`
`Sep.27,2001
`
`1
`
`CLEANING AGENT COMPOSITION, METHOD
`FOR CLEANING AND USE THEREOF
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`[0001] This application is an application filed under 35
`U.S.C. lll(a) claiming benefit pursuant to 35 U.S.C.
`§119(e)(l) of the filing date of Provisional Application
`60/241,839 filed Oct. 20, 2000 pursuant to 35 U.S.C.
`§lll(b).
`
`FIELD OF THE INVENTION
`
`[0002] The present invention relates to a cleaning agent
`composition for use in removing contamination on the
`surface of a semiconductor wafer or a precisely worked
`instrument made of glass, ceramic or the like, which is used
`in the manufacture of a wafer. In addition, the present
`invention also relates to a method for cleaning a semicon(cid:173)
`ductor wafer, a semiconductor wafer and a method for
`manufacturing a semiconductor wafer.
`
`BACKGROUND OF THE INVENTION
`
`[0003] Semiconductor devices such as transistor, diode,
`IC, LSI and rectifying element are manufactured by apply(cid:173)
`ing steps such as growth in vapor phase, formation of oxide
`film, diffusion of impurities and vapor deposition of elec(cid:173)
`trode metal film, to a silicon wafer or a compound semi(cid:173)
`conductor wafer.
`
`[0004] The electric properties of a semiconductor device
`are conspicuously affected by impurities, and therefore, the
`semiconductor wafer surface is thoroughly cleaned to
`remove contamination with impurities before applying the
`respective steps described above. As industrial means there(cid:173)
`for, a large number of methods using a treating solution
`mainly comprising an organic alkali or a treating solution
`obtained by adding a complexing agent, a surfactant, a
`hydrogen peroxide and the like to an organic alkali have
`been proposed.
`
`[0005]
`JP-A-50-147287 (the term "JP-A" as used herein
`means an "unexamined published Japanese patent applica(cid:173)
`tion") describes the fact that sole use of, for example,
`tetramethylammonium hydroxide (hereinafter referred to as
`"TMAH") out of tetraalkylammonium hydroxides is effec(cid:173)
`tive in the degreasing, removal of contamination with inor(cid:173)
`ganic substances and removal of ultra-thin oxide layer.
`However, (1) due to poor wettability to the surface to be
`treated, the cleaning power is not sufficiently high, and (2)
`etching activity depends on the orientation of silicon crystal
`(that is, the (100) plane is readily etched, whereas the (111)
`plane has resistance against the etching activity and in the
`case of a (100) mirror face wafer, this plane is roughened
`due to etching). Thus, improvement is still needed.
`
`[0006]
`JP-A-50-158281 describes a solution obtained by
`adding a complexing agent to TMAH. In this case, the
`cleaning power may be improved as compared with the sole
`use of TMAH; however, the wettability to the surface to be
`treated is poor and the cleaning power is still insufficient.
`
`[0007] With respect to the etching of silicone crystal, the
`addition of only a surfactant to an aqueous alkali solution
`may have an effect of preventing etching of silicone crystal.
`However, the effectiveness varies depending on the kind of
`
`surfactant, the alkali concentration, the temperature or the
`like. Therefore, a sufficiently high effect is not always
`ensured in all possible conditions. To cope with this, a case
`of using a hydrogen peroxide in addition to an alkali and a
`surfactant has been reported. For example, JP-A-63-274149
`describes a case where etching can be satisfactorily con(cid:173)
`trolled when a hydrogen peroxide is used in addition to a
`tetraalkylammonium hydroxide and a nonionic surfactant.
`This technique, however, has a problem in that the capability
`of removing particles is not sufficiently high.
`
`[0008] As described in Japanese Patent 2,579,401, a case
`of adding an alkanolamine to a tetraalkylammonium hydrox(cid:173)
`ide and a nonionic surfactant is known. By adding an
`alkanolamine, the cleaning power increases; however, this
`technique has a problem that the capability of removing
`particles is not sufficiently high.
`
`[0009] With recent tends toward higher integration of
`semiconductors, the requirement for removing impurities is
`further increasing and a new cleaning solution having high
`effects of removing impurities, preventing re-adsorption of
`desorbed impurities and ensuring satisfactorily controlled
`etching property is being demanded.
`
`SUMMARY OF THE INVENTION
`
`[0010] The present invention has been made under these
`circumstances and an object of the present invention is to
`provide a cleaning agent composition having excellent
`cleaning power for contamination on the surface of a semi(cid:173)
`conductor wafer or various precisely worked instruments
`made of glass, ceramic or the like, which are used in the
`manufacture of semiconductor wafer. Another object of the
`present invention includes providing a method for cleaning
`a wafer, a method for manufacturing a semiconductor wafer,
`and a semiconductor wafer having a surface cleaned by a
`cleaning method.
`
`[0011] As a result of extensive investigations to solve the
`above-described problems, the present inventors have found
`that these problems can be solved by using a cleaning agent
`composition comprising a specific fluorine-containing
`anionic surfactant, a quaternary ammonium hydroxide and/
`or an alkanolamine. The present invention has been accom(cid:173)
`plished based on this finding.
`
`[0012] More specifically, an embodiment of the present
`invention is a cleaning agent composition comprising from
`0.0001 to 5 mass % of a fluorine-containing anionic surfac(cid:173)
`tant, from 0.001 to 30 mass % of a quaternary ammonium
`hydroxide and/or from 0.01 to 20 mass % of an alkanola(cid:173)
`mine. In a preferred embodiment of the present invention,
`the fluorine-containing anionic surfactant is at least one
`compound selected from the group consisting of carboxylic
`acids represented by the following formula (1):
`
`R 1COOM
`(1)
`[0013] wherein R1 represents a linear or branched alkyl
`group or alkenyl group having from 2 to 20 carbon atoms,
`with a part or all of hydrogen atoms being substituted by
`fluorine atom, and M represents a hydrogen atom, an alkali
`metal atom, an ammonium group, an alkylammonium group
`or an alkanolammonium group, salts thereof, sulfonic acids
`represented by the following formula (2):
`
`(2)
`
`

`

`US 2001/0025017 Al
`
`Sep.27,2001
`
`2
`
`[0014] wherein R2 represents a linear or branched alkyl
`group or alkenyl group having from 2 to 20 carbon atoms,
`with a part or all of hydrogen atoms being substituted by
`fluorine atom, and M has the same meaning as defined
`above, and salts thereof, and in a more preferred embodi(cid:173)
`ment, the fluorine-containing anionic surfactant is at least
`one compound selected from the group consisting of per(cid:173)
`fluorocaprylic acid, perfluorocapric acid, perfluorooctane
`sulfonic acid and salts thereof.
`[0015] Also, in a preferred embodiment, the quaternary
`ammonium hydroxide is at least one compound selected
`from the group consisting of compounds represented by the
`following formula (3):
`
`(3)
`
`, R5 and R 6
`, R4
`[0016] wherein R3
`, which may be the same
`or different, each independently represents an alkyl group
`having from 1 to 6 carbon atoms or a hydroxyalkyl group,
`and in a more preferred embodiment, the quaternary ammo(cid:173)
`nium hydroxide is tetramethylammonium hydroxide.
`[0017] Also, in a preferred embodiment, the alkanolamine
`is at least one compound selected from the group consisting
`of compounds represented by the following formula (4):
`
`(4)
`
`[0018] wherein R 7 represents a hydroxy alkyl group having
`from 1 to 4 carbon atoms, Rs and R9
`, which may be the same
`or different, each independently represents a hydrogen atom,
`an alkyl group having from 1 to 4 carbon atoms, a hydroxy(cid:173)
`alkyl group having from 1 to 4 carbon atoms or an ami(cid:173)
`noalkyl group having from 1 to 4 carbon atoms, and Rs and
`R9 may combine to represent an alkylene group having from
`3 to 6 carbon atoms, which may be interrupted by an oxygen
`atom or a nitrogen atom, and in a more preferred embodi(cid:173)
`ment, the alkanolamine is at least one compound selected
`from the group consisting of monoethanolamine, diethano(cid:173)
`lamine and triethanolamine.
`[0019]
`In a preferred embodiment of the present invention,
`the composition contains from 0.0001 to 5 mass % of a
`nonionic surfactant, and in a more preferred embodiment,
`the nonionic surfactant is at least one compound selected
`from the group consisting of polyoxyalkylene alkyl ether
`compounds represented by the following formula (5):
`R10-0-(R11-0)p-H
`(5)
`[0020] wherein R10 represents an alkyl group having from
`6 to 20 carbon atoms, R11 represents an alkylene group
`having from 2 to 4 carbon atoms, and p represents an integer
`of 3 to 20, polyoxyalkylene aryl ether compounds repre(cid:173)
`sented by the following formula (6):
`
`[0021] wherein R12 represents an alkyl group having from
`6 to 20 carbon atoms, R13 represents an alkylene group
`having from 2 to 4 carbon atoms, and q represents an integer
`of 3 to 20, and polyoxyalkylene alkyl ester compounds
`represented by the following formula (7):
`
`R14-COO-(R15-0),-H
`(7)
`[0022] wherein R14 represents an alkyl group having from
`9 to 16 carbon atoms, R15 represents an alkylene group
`having from 2 to 4 carbon atoms, and r represents an integer
`of 6 to 16, and in another preferred embodiment of the
`present invention, the composition contains from 0.01 to 20
`mass % of hydrogen peroxide.
`
`[0023] Another embodiment of the present invention is a
`method for cleaning a semiconductor wafer, comprising (1)
`a cleaning step using the above-described cleaning agent
`composition and (2) a cleaning step using a cleaning agent
`containing an ammonia and a hydrogen peroxide. In a
`preferred embodiment, the cleaning step (1) performs
`degreasing of the semiconductor wafer surface and removal
`of particles thereon, and the cleaning step (2) performs
`removal of particles on the semiconductor wafer surface.
`
`[0024] Another embodiment of the present invention is a
`semiconductor wafer having a surface cleaned by the above(cid:173)
`described cleaning method. In a preferred embodiment, the
`number of particles of 0.2 µm or more adhering to the
`semiconductor wafer surface is 100 or less, and the semi(cid:173)
`conductor wafer is a silicon wafer, a gallium phosphide
`wafer, a gallium arsenide wafer or an indium phosphide
`wafer. In a more preferred embodiment, the semiconductor
`wafer is a silicon wafer and the surface roughness (Ra)
`thereof is 0.2 µm or less, or the semiconductor wafer is a
`gallium arsenide wafer and the surface roughness (Ra)
`thereof is 0.4 nm or less.
`
`[0025] Another embodiment of the present invention is a
`method for manufacturing a semiconductor wafer, compris(cid:173)
`ing (1) a lapping step of lapping the wafer surface, (2) a
`polishing step of specularly polishing the wafer surface and
`(3) a cleaning step using the above-described cleaning agent
`composition and a cleaning step using a cleaning agent
`containing an ammonia and a hydrogen peroxide.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`[0026] The present invention is described in detail below.
`
`[0027] At first, a cleaning agent composition of the present
`invention is described.
`
`[0028] The cleaning agent composition of the present
`invention comprises a fluorine-containing anionic surfac(cid:173)
`tant, a quaternary ammonium hydroxide and/or an alkano(cid:173)
`lamine.
`
`[0029] The fluorine-containing anionic surfactant includes
`a fluorine-containing anionic surfactant which is at least one
`compound selected from the group consisting of carboxylic
`acids represented by the following formula (1):
`
`(1)
`R 1COOM
`(wherein R1 and M have the same meanings as
`[0030]
`defined above), salts thereof, sulfonic acids represented by
`the following formula (2):
`
`(6)
`
`(2)
`
`

`

`US 2001/0025017 Al
`
`Sep.27,2001
`
`3
`
`(wherein R2 and M have the same meanings as
`[0031]
`defined above), and salts thereof.
`
`[0032] The fluorine-containing anionic surfactant is pref(cid:173)
`erably at least one compound selected from the group
`consisting of carboxylic acids represented by formula (1)
`wherein R1 is a linear or branched perfluoroalkyl, hydrof(cid:173)
`luoroalkyl, perfluoroalkenyl or hydrofluoroalkenyl group
`having from 6 to 16 carbon atoms, salts thereof, sulfonic
`acids represented by formula (2) wherein R2 is a linear or
`branched perfluoroalkyl, hydrofluoroalkyl, perfluoroalkenyl
`or hydrofluoroalkenyl group having from 6 to 12 carbon
`atoms, and salts thereof. Specific examples thereof include
`perfluoroheptanoic acid (C 6F 3 COOH), perfluorocaprylic
`acid (C7F15COOH), perfluorononanoic acid (C8 F17COOH),
`5,5,6,6,7,7,8,8,9,9,9-undecafluorononanoic
`acid
`(C5F1i(CH2 ) 3 COOH), perfluorocapric acid (C9 F19COOH),
`perfluorododecanoic acid (C 11F23COOH), 6,6,7,7,8,8,9,9,
`10,10,11,11,12,12,12-pentadecafluoro-4-dodecenoic
`acid
`(CFiCF2 ) 6 CH=CH(CH2 ) 2 COOH),
`perfluorotetra-de(cid:173)
`canoic acid (C 13F27COOH), 12-trifluoromethyl-12,13,13,
`14,14,15,15,16,16,16-decafluorohexadecanoic
`acid
`(CFiCF2 ) 3 CF(CF3)(CH2 ) 10COOH),
`perfluorooctane(cid:173)
`sulfonic acid (C8 F17S0 3H), and ammonium salts and tet(cid:173)
`ramethylammonium salts thereof. Among these, preferred
`are perfluorocaprylic acid, perfluorocapric acid, perfluo(cid:173)
`rooctanesulfonic acid and salts thereof. These compounds
`may be used individually or two or more thereof may be
`used in combination at an arbitrary ratio.
`
`[0033]
`In the cleaning agent composition of the present
`invention, this fluorine-containing anionic surfactant is an
`essential component and contained in an amount of 0.0001
`to 5 mass %, preferably from 0.0001 to 1 mass %, more
`preferably from 0.0001 to 0.5 mass %, based on the entire
`cleaning agent. If the content exceeds 5 mass %, bubbling or
`problem
`in
`the rinsing may disadvantageously arise,
`whereas if the content is less than 0.0001 mass %, the
`activity of improving the cleaning power cannot be suffi(cid:173)
`ciently brought out.
`
`[0034] The quaternary ammonium hydroxide is a com(cid:173)
`pound represented by the following formula (3):
`
`(3)
`
`, R5 and R 6 have the same meanings
`[0035] wherein R3 , R4
`as defined above. Specific examples thereof include tetram(cid:173)
`ethylammonium hydroxide (TMAH), trimethylhydroxy(cid:173)
`ethylammonium hydroxide (choline), methyltrihydroxy(cid:173)
`ethylammonium
`hydroxide,
`dimethyldihydroxyethylammonium hydroxide,
`tetraethy(cid:173)
`lammonium hydroxide
`and
`trimethylethylammonium
`hydroxide. Among these, tetramethylammonium hydroxide
`and trimethylhydroxyethylammonium hydroxide are pre(cid:173)
`ferred. These quaternary ammonium hydroxides may be
`used individually, or two or more thereof may be used in
`combination at an arbitrary ratio. The quaternary ammonium
`hydroxide is contained in an amount of 0.001 to 30 mass %,
`
`preferably from 0.05 to 20 mass %, based on the entire
`cleaning agent. If the concentration exceeds 30 mass %, the
`wafer is excessively etched and this cannot be controlled,
`giving rise to problems such as roughening of the waver
`surface.
`
`[0036] The alkanolamine
`least one compound
`is at
`selected from the group consisting of compounds repre(cid:173)
`sented by the following formula (4):
`
`(4)
`
`, R8 and R9 have the same meanings as
`[0037] wherein R7
`defined above. Specific examples of the alkanolamine
`include monoethanolamine, diethanolamine and triethano(cid:173)
`lamine. Only one alkanolamine may be used alone or two or
`more thereof may be used in combination at an arbitrary
`ratio.
`
`[0038] The cleaning agent composition of the present
`invention can be used as a cleaning agent containing two
`components of a fluorine-containing anionic surfactant and
`a quaternary ammonium hydroxide or as a cleaning agent
`containing two components of a fluorine-containing anionic
`surfactant and an alkanolamine, but is preferably used as a
`cleaning agent containing three components of a fluorine(cid:173)
`containing anionic surfactant, a quaternary ammonium
`hydroxide and an alkanolamine, which is improved in the
`cleaning property and life. In the case of using an alkano(cid:173)
`lamine, the alkanolamine may be added in an amount of 0.01
`to 20 mass %, preferably from 0.1 to 10 mass %, more
`preferably from 0.1 to 5 mass %, based on the entire
`cleaning agent. If the concentration thereof exceeds 20 mass
`%, a problem of reduction in the cleaning performance is
`caused and also,
`the profitability disadvantageously
`decreases.
`
`[0039] For the purpose of preventing etching of the wafer
`surface, the cleaning agent composition of the present inven(cid:173)
`tion may further contain a nonionic surfactant, in addition to
`a fluorine-containing anionic surfactant, a quaternary ammo(cid:173)
`nium hydroxide and an alkanolamine. The nonionic surfac(cid:173)
`tant is suitably at least one compound selected from the
`group consisting of polyoxyalkylene alkyl ether compounds
`represented by the following formula (5):
`
`R10-0-(R11-0)p-H
`(5)
`, R 11 and p have the same meanings as
`[0040] wherein R 10
`defined above, polyoxyalkylene aryl ether compounds rep(cid:173)
`resented by the following formula (6):
`
`(6)
`R12-C6H4 -0-(R13-0)q-H
`[0041] wherein R12
`, R13 and q have the same meanings as
`defined above, and polyoxyalkylene alkyl ester compounds
`represented by the following formula (7):
`
`R 14-COO-(R15-0),-H
`(7)
`[0042] wherein R14
`, R15 and r have the same meanings as
`defined above.
`
`[0043] The alkylene group in the above-described non-
`10mc
`surfactant
`1s
`preferably
`or
`-CH2 CH2 -
`
`

`

`US 2001/0025017 Al
`
`Sep.27,2001
`
`4
`
`-CH2 CH2 CH2- , more preferably -CH2 CH2- . Specific
`examples of the polyoxyalkylene alkyl ether compound
`include polyoxyethylene decanyl ether, polyoxyethylene
`undecanyl ether, polyoxyethylene dodecanyl ether and poly(cid:173)
`oxyethylene tetradecanyl ether. Specific examples of the
`polyoxyalkylene aryl ether compound include polyoxyeth(cid:173)
`ylene nonylphenyl ether, polyoxyethylene octylphenyl ether
`and polyoxyethylene dodecylphenyl
`ether. Specific
`examples of the polyoxyalkylene alkyl ester compound
`include polyoxyethyleneoleic acid ester. However, the non(cid:173)
`ionic surfactant is not limited thereto.
`
`[0044] This nonionic surfactant can be added in the range
`from 0.0001 to 5 mass %, preferably from 0.0001 to 1 mass
`%, more preferably from 0.0001 to 0.5 mass%, based on the
`entire cleaning agent. If the nonionic surfactant is used in
`excess of 5 mass %, bubbling or a problem in the rinsing
`may disadvantageously arise.
`
`[0045] The cleaning agent composition of the present
`invention may further contain a hydrogen peroxide. In the
`cleaning of a silicon wafer, the wafer can be prevented from
`etching by the addition of only a surfactant to an alkali.
`However, the effect is greatly affected by the kind of the
`surfactant, the alkali concentration and the temperature, and
`a sufficiently high effect is not always obtained in all
`possible conditions. By using a hydrogen peroxide, the
`etching can be appropriately controlled even at high tem(cid:173)
`peratures and the cleaning agent composition of the present
`invention can be broadened in the range of use.
`
`[0046]
`In the case of adding a hydrogen peroxide, the
`hydrogen peroxide may be added in the range from 0.01 to
`20 mass %, preferably from 0.05 to 10 mass %, based on the
`entire cleaning agent. If the hydrogen peroxide concentra(cid:173)
`tion exceeds 20 mass %, the amount of hydrogen peroxide
`decomposed increases and this is not profitable, although the
`cleaning power itself is not particularly affected.
`
`[0047] The components constituting the cleaning agent of
`the present invention are fundamentally a fluorine-contain(cid:173)
`ing anionic surfactant, a quaternary ammonium hydroxide
`and/or an alkanolamine. By using the cleaning agent in
`which these fundamental components are combined accord(cid:173)
`ing to the use conditions, the removal of contamination on
`the wafer surface and the prevention of re-adhesion of the
`contaminant can be performed with good efficiency.
`Depending on the use conditions, the nonionic surfactant or
`hydrogen peroxide is added at an appropriate time to prevent
`etching on the wafer surface by an alkali. For example, in the
`cleaning of a silicon wafer, when the cleaning agent is used
`at a high temperature, for example at 60 to 80° C., the
`etching of the wafer by an alkali excessively proceeds.
`Therefore, a hydrogen peroxide is preferably added. On the
`other hand, when the cleaning agent of the present invention
`is used at an ordinary temperature, a nonionic surfactant may
`be added in place of a hydrogen peroxide, or both a
`hydrogen peroxide and a nonionic surfactant may be added.
`The etching of a wafer varies in degree depending on the
`kind of the wafer. For example, in the cleaning of a gallium
`arsenide wafer, the etching activity of an alkali on the wafer
`surface is extremely small, and therefore, a nonionic sur(cid:173)
`factant or a hydrogen peroxide may not be added depending
`on the use conditions. The cleaning agent composition of the
`present invention exhibits excellent cleaning effect, needless
`to say, at an ordinary temperature, but can also be suitably
`
`used in the cleaning under appropriate heating or cleaning
`using ultrasonic waves. In addition, the cleaning agent
`composition of the present invention can remove the surface
`contamination not only of a semiconductor wafer, but also of
`a precisely worked instrument made of glass, ceramic or the
`like, which is used in the manufacture of a wafer.
`[0048] A method for cleaning a semiconductor wafer of
`the present invention is described below.
`[0049] The method for cleaning a semiconductor wafer of
`the present invention comprises (1) a cleaning step of using
`the above-described cleaning agent composition and (2) a
`cleaning step of using a cleaning agent containing an ammo(cid:173)
`nia and a hydrogen peroxide. The cleaning step (1) has a
`purpose mainly of degreasing the semiconductor wafer
`surface and removing particles thereon, and the cleaning
`step (2) has a purpose mainly of removing particles on the
`semiconductor wafer surface.
`[0050] A representative example of the step of performing
`the degreasing of the semiconductor wafer surface and
`removal of particles thereon includes a wax cleaning after
`the specular polishing of wafer. The specular polishing of a
`semiconductor wafer is performed by adhering and fixing
`the wafer to a plate Qig) with wax. Therefore, a large amount
`of wax used as an adhesive remains adhered to the wafer
`when the wafer is stripped off from the plate after the
`completion of polishing. The cleaning agent composition of
`the present invention is particularly effective in cleaning to
`remove these wax and particles adhering to the wafer.
`[0051] The cleaning agent composition of the present
`invention has both a wax-removing effect and a particle(cid:173)
`removing effect even if the composition is used alone;
`however, it may be used in combination with other cleaning
`agents. A cleaning method of performing a cleaning step for
`removing wax and particles on a semiconductor wafer using
`the cleaning agent composition of the present invention and
`further performing a cleaning step for removing particles
`using a cleaning agent having other compositions, is
`described below. At first, a cleaning step for removing wax
`and particles is performed using a cleaning agent of the
`present invention obtained by adding perfluorocaprylic acid
`to an aqueous tetramethylammonium hydroxide solution. To
`this cleaning agent, a hydrogen peroxide can be added, if
`desired. Thereafter, a cleaning step for removing particles is
`performed using a cleaning agent containing an ammonia
`and a hydrogen peroxide. Each cleaning step may be per(cid:173)
`formed multiple times. A rinsing step using, for example,
`water may also be performed. After the completion of all
`cleaning steps, the wafer is dried using an organic solvent
`such as isopropyl alcohol. The thus-cleaned semiconductor
`wafer is not only free of wax, but also is reduced in the
`particle level as compared with the case of using conven(cid:173)
`tional cleaning solutions.
`[0052]
`In the above-described two cleaning steps, the
`cleaning temperature, the cleaning conditions and the like
`are not particularly limited and appropriate conditions can
`be properly selected depending on the wafer to be cleaned.
`Examples of the semiconductor wafer which can be cleaned
`using the cleaning method of the present invention include
`one-element semiconductors such as silicon and germanium,
`and compound semiconductors such as gallium phosphide,
`gallium arsenide and indium phosphide.
`[0053] Another embodiment of the present invention is a
`semiconductor wafer cleaned by the above-described clean-
`
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`5
`
`ing method, reduced in the number of particles adhering to
`the wafer surface and having a small surface roughness (Ra).
`The number of particles adhering to the wafer surface is 100
`or less in terms of particles having a particle size of 0.2 µm
`or more. This number of particles is not limited by the size
`of wafer. The surface roughness (Ra) varies depending on
`the kind of wafer and it is 0.2 nm or less in the case of a
`silicon wafer and 0.4 nm or less in the case of a gallium
`arsenide wafer.
`
`[0054] A method for manufacturing a semiconductor
`wafer of the present invention is described below. Although
`a method for manufacturing a silicon wafer is described
`here, the present invention is not limited to the manufactur(cid:173)
`ing method of silicon wafer.
`
`[0055] The method for manufacturing a semiconductor
`wafer of the present invention is comprises a lapping step of
`lapping the wafer surface, a polishing step of specularly
`polishing the wafer surface, and a cleaning step. First, a
`silicon single crystal is drawn up and the ingot drawn up is
`cut into a wafer through grinding of outer periphery and
`working of orientation flatting. The thus-obtained wafer is
`transferred to a beveling (side polishing), to a lapping
`(surface polishing) step and then a to polishing (specular
`polishing) step. In the specular polishing, the wafer is
`bonded and fixed to a plate Qig) made of glass or ceramic
`using a wax (adhesive) and the wafer surface is polished
`with an abrasive and an abrasive cloth. After the completion
`of specular polishing, the wafer is stripped off from the plate
`and transferred to a cleaning step to remove wax or particles
`adhering to the wafer surface or remove contamination such
`as metal impurities. This cleaning step comprises (1) a
`cleaning step of using the above-described cleaning agent
`composition and (2) a cleaning step of using a cleaning agent
`containing an ammonia and a hydrogen peroxide. After the
`completion of cleaning, the wafer surface is inspected and
`the wafer is used as a product.
`
`EXAMPLES
`
`[0056] The present invention is described in greater detail
`below by referring to the Examples and Comparative
`Examples, however, the present invention should not be
`construed as being limited thereto. Unless otherwise indi(cid:173)
`cated herein, all parts, percents, ratios and the like are by
`weight.
`
`Example 1
`
`[0057] Wettability
`
`[0058] A contact angle of an aqueous solution of a clean(cid:173)
`ing agent containing 0.35 mass % of TMAH and 100 ppm
`of perfluorocaprylic acid to a silicon wafer or a gallium
`arsenide wafer was measured. The results are shown in Table
`1.
`
`Comparative Example 1
`
`[0059] A contact angle of an aqueous solution of a clean(cid:173)
`ing agent containing 0.35 mass % of TMAH to a silicon
`wafer or a gallium arsenide wafer was measured. The results
`are shown in Table 1.
`
`TABLE 1
`
`TMAH
`
`Example 1
`0.35 mass %
`
`Comparative
`Example 1
`0.35 mass %
`
`Additive
`Contact
`Angle
`
`Perfluorocaprylic acid
`Silicon wafer
`Gallium arsenide wafer
`
`100 ppm
`48°
`7°
`
`60°
`14 °
`
`[0060] From the measurement results of the contact angle
`shown in Table 1, it can be seen that by adding perfluoro(cid:173)
`caprylic acid to an aqueous solution of a cleaning agent
`containing TMAH, the cleaning agent was improved in the
`wettability to a silicon wafer and a gallium arsenide wafer.
`
`Example 2
`
`[0061] Wax Removability
`
`[0062] A commercially available wax (Alpha Liquid
`TR-100, trade name (produced by Ink Tech Co.)) was coated
`on the surface of a 4-inch gallium arsenide wafer to a film
`thickness of 1.7 µm, and this wafer was baked at 80° C. for
`5 minutes to manufacture a test wafer.
`
`[0063] The test wafer was dipped in a cleaning agent
`composition shown in Table 2 at 25° C. for 6 minutes, rinsed
`with ultrapure water for 6 minutes, and then dried. After the
`treatment, a condensing lamp was irradiated on the wafer
`surface and the wax removability was examined with a
`naked eye. The results are shown in Table 2. The evaluation
`was performed according to three-stage criteria, that is, 0:
`wax was completely removed, li.: wax partially remained,
`and X: wax remained throughout the wafer surface.
`
`Comparative Examples 2 and 3
`
`[0064] Test wafers manufactured in the same manner as in
`Example 2 each was dipped in a cleaning agent composition
`shown in Table 2. Then, the wafers were treated in the same
`manner as in Example 2 and then examined on the wax
`removability. The results are shown in Table 2.
`
`TABLE 2
`
`TMAH
`
`Comparative Comparative
`Example 2
`Example 3
`Example 2
`0.16 mass % 0.16 mass % 0.16 mass %
`
`Additives Polyoxyethylene
`nonylphenyl ether
`Perfluorocaprylic 100 ppm
`acid
`Test Results
`
`100 ppm
`
`[0065] From the test results shown in Table 2, it can be
`seen that the cleaning agent obtained by adding perfluoro(cid:173)
`caprylic acid to an aqueous TMAH solution is more
`improved in wax removability than the cleaning agent
`obtained by adding polyoxyethylene nonylphenyl ether,
`which is used in many cases for cleaning semiconductors.
`
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`US 2001/0025017 Al
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`Sep.27,2001
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`
`Example 3
`[0066] Particle Removability (1) (Gallium Arsenide
`Wafer Cleaning Test)
`
`specularly polished with an abrasive and an abrasive cloth.
`After the completion of specular polishing, the wafer was
`stripped off from the plate and used as a test wafer.
`
`[0067]
`In the process of manufacturing a 4-inch gallium
`arsenide wafer, a wafer passed through a lapping step and an
`etching step was bonded and fixed to a glass plate using a
`commercially available wax (Alpha Liquid TR-100, trade
`name, (produced by Ink Tech Co.)), and the wafer surface
`was specularly polished with an abrasive and an abrasive