JP2002299300A - Substrate treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate treatment method capable of completely removing contaminants stuck to the rear surface of a substrate without influencing the front surface of the substrate. SOLUTION: The method has a first step A of treating the substrate 1 with organic alkaline treatment liquid, a second step B of treating the substrate 1 with organic acid treatment liquid after being treated by the first step A, a third step C of supplying high oxidizing power treatment liquid on the rear surface of the substrate 1 to clean it during rotation while supplying pure water on the front surface of the substrate 1 to form a liquid film after being treated by the second step B, and a step D of ultrasonically cleaning and drying the substrate 1 after being treated by the third step C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a substrate processing method.

[0002]

2. Description of the Related Art In recent years, as electronic devices have been downsized, the number of wiring layers has been increased with the increase in the density of semiconductor devices, and the formation of metal wiring on a semiconductor substrate and the flattening of the interlayer insulating film of the multilayer wiring have been advanced. Chemical mechanical polishing (hereinafter, referred to as CMP) has been used as a technique for forming the surface.

In CMP, a semiconductor wafer as a substrate is pressed against a cloth called a buff while supplying a mixture of a polishing agent and a chemical (hereinafter, also referred to as a polishing liquid) called a slurry. Alternatively, this is a technique in which an interlayer insulating film or a metal material on a semiconductor wafer is polished by rotating a buff to flatten the film.

[0004] Particles such as used abrasives (alumina particles and silica particles), metal impurities contained in chemicals, and metal wiring on the semiconductor wafer are formed on the surface of the semiconductor wafer as a substrate after being processed by CMP. Large amount of metal ions and fine particles used in the process are attached. For example, metal ions such as copper diffuse into a semiconductor wafer, lowering insulation resistance and adversely affecting semiconductor devices. Therefore, the surface of the semiconductor wafer is cleaned with high cleanliness, and ions and fine particles of particles and metal impurities. Must be completely removed.

Therefore, as a method of cleaning a substrate after being processed by CMP, so-called RCA cleaning is conventionally performed. The RCA cleaning includes a first step of removing particles with an alkaline solution (ammonia-hydrogen peroxide solution), and cleaning of the substrate treated in the first step with an acid solution (DH
F (dilute hydrofluoric acid) or the like to remove metal impurities.

However, ammonia used in the first step of the RCA cleaning has a property that metal is easily etched, and ions of metal impurities contained in a solution easily adhere to the substrate surface in reverse. For example, if copper wiring is exposed as metal wiring on the surface of the substrate, copper forms a complex with ammonia and elutes, and fine pits are generated on the copper metal wiring film, and the planarity of the surface is reduced. May drop. Also,
When ions of metal impurities adhere to the pits, the second
It becomes difficult to sufficiently remove even if washing with an acid solution is performed in the step.

Further, DHF used in the second step
(Dilute hydrofluoric acid) and the like have a strong dissolving power for metals, and the metal wiring film and the like exposed on the surface of the substrate are easily etched.

As shown in FIG. 10, when metal wirings and the like are formed on a semiconductor wafer as a substrate by CMP, so-called dishing occurs. Dishing is a phenomenon in which a depression occurs in the central portion of a buried metal wiring film. FIG. 10 is a cross-sectional view schematically showing a state in which dishing has occurred on a semiconductor wafer as a substrate.

Metal wiring exposed on the surface of a semiconductor wafer as a substrate is formed by forming an interlayer insulating film 53 made of a silicon oxide (SiO ₂ ) film or the like on a semiconductor wafer 1 made of a silicon (Si) substrate or the like. A metal wiring 51 such as copper (Cu) is buried in a predetermined portion of the film 53 via a barrier film 52 made of titanium (Ti), titanium nitride (TiN) or the like. In this step, unnecessary portions of the metal wiring 51 and the barrier film 52 are polished and removed by CMP, but the metal wiring 51 (for example, copper (C
u)) is softer than the barrier film 52 and has a higher polishing rate. Therefore, the central portion of the surface of the metal wiring 51 is excessively polished, a dent is generated, and a dishing 55 is formed.

When the dishing 55 is formed, a step 56 is formed at the boundary between the metal wiring 51 and the barrier film 52.
Are generated, particles and metal impurities are adsorbed in the step portion 56 and the dishing 55, and a sufficient cleaning effect may not be obtained even when cleaning is performed in the first step and the second step. The barrier film 52 is formed of the metal wiring 5
This is to prevent the ions of the metal used in 1 from diffusing into the semiconductor wafer 54.

Therefore, the present applicant has filed Japanese Patent Application No. 2000-23.
No. 6082, it is possible to prevent a metal wiring or the like formed in a state where a metal material is exposed on the surface of a substrate from corroding, prevent adhesion of metal impurity ions to the surface of the substrate, and to form a dent or a step formed on the metal wiring. The present invention provides a substrate processing method capable of improving the cleanliness of a substrate by reliably removing particles and metal impurities attached to a portion.

[0012]

However, in the above-described substrate processing method (Japanese Patent Application No. 2000-236082), particles and metal impurities adhered to the surface of the substrate can be surely removed, but particles adhered to the back surface of the substrate can be removed. For metal impurities and the like, the response was insufficient. That is, when a metal material, such as copper (Cu), disposed on the surface of the substrate, is polished by CMP, the back surface of the substrate is naturally contaminated by metal ions such as copper (Cu). Then, when the back surface of the substrate is left in a contaminated state, a plurality of substrates are placed and placed, in a so-called wafer board, the back surface of one substrate arranged adjacent to each other comes into contact with the surface of another substrate. This contaminates the substrate, and consequently both the rear surface and the front surface of the substrate are contaminated.

In order to avoid such a situation, a substrate having a high oxidizing power (eg, hydrofluoric acid / hydrogen peroxide solution, sulfuric acid / hydrogen peroxide solution, hydrochloric acid / hydrogen peroxide solution, etc.) is used. It is necessary to remove the contaminants adhering to the back surface, but at this time, the high oxidizing treatment liquid should not adhere to the surface of the substrate.
Great care must be taken. Because, in the double-sided brush cleaning, which has been conventionally used as one cleaning means for a substrate, if a high oxidizing treatment liquid is applied to the back surface of the substrate, the brush is in contact with both the back surface and the front surface of the substrate. This is because, even if the high oxidizing treatment liquid is applied only to the back surface of the substrate, the etchant spills over to the surface of the substrate, causing a problem that the metal wiring on the surface of the substrate is also corroded.

The present invention has been made in view of the above points, and does not corrode a metal wiring or the like formed in a state where a metal material is exposed on a surface of a substrate, and has a method of forming a metal on a surface of a substrate. Prevents impurity ions from adhering, reliably removes particles and metal impurities adhering to dents and steps formed in metal wiring and improves the cleanliness of the substrate, and also adheres to the back surface of the substrate It is an object of the present invention to provide a substrate processing method capable of completely removing contaminants without affecting the surface of the substrate.

[0015]

The substrate processing method of the present invention performs a chemical mechanical polishing process by supplying a polishing liquid to a substrate having a metal wiring with a metal material exposed on the surface.
A substrate processing method for processing the substrate after the chemical mechanical polishing treatment, wherein an organic alkali that is non-reactive with the metal material, a complex with a metal contained in the metal material particles and the polishing liquid. A first step of washing the substrate with an organic alkaline treatment liquid containing a complexing agent that forms a metal material, an organic acid that is non-reactive with the metal material after the first step, A second step of cleaning the substrate with an organic acid treatment liquid containing particles of and a complexing agent that forms a complex with a metal contained in the polishing liquid; and after the second step, the metal wiring is provided. A third step of supplying a pure water to the front surface of the substrate to form a liquid film, and supplying a high oxidizing treatment liquid for removing contaminants to the back surface of the substrate and cleaning while rotating. .

After the third step, a fourth step of cleaning the substrate with an ultrasonic cleaning fluid excited by ultrasonic waves.
It has a process of.

Further, the ultrasonic cleaning fluid is pure water.

The fourth step includes a step of cleaning the substrate with an ultrasonic cleaning fluid and then rotating the substrate at a high speed to dry the substrate.

Further, the high oxidizing power treatment liquid includes hydrofluoric acid / hydrogen peroxide solution (FPM), sulfuric acid / hydrogen peroxide solution (SP
M), hydrochloric acid / hydrogen peroxide solution (HPM), buffered hydrofluoric acid / ammonium fluoride (BHF), hydrofluoric acid (HF)
/ HNO ₃ ) and at least one cleaning liquid selected from the group consisting of ozone hydrofluoric acid (HF / O ₃ ).

The metal material is copper, tungsten or aluminum.

The organic alkali is a quaternary ammonium salt and / or an organic amine.

Further, an alcohol was added to the organic alkali.

In addition, the alcohol is used in an amount of 0.005% to
10% isopropyl alcohol (IPA).

The quaternary ammonium salt is a group consisting of tetramethylammonium hydroxide (TMAH), trimethyl-2-hydroxyethylammonium hydroxide (TMAH), and trimethyl-2-hydroxyethylammonium hydroxide (choline). At least one compound selected from the group consisting of:

In addition, the organic amines are at least one compound selected from the group consisting of trimethylamine, triethanolamine, ethylenediamine, guanidine and toluidine.

The complexing agent contained in the organic alkaline treating solution is a fluoride ion, an OH group and / or an O ^- group having a cyclic skeleton in the molecular structure and bonded to a carbon atom constituting the ring. At least one substance selected from the group consisting of compounds having at least one.

Further, the organic alkaline treating solution contains a second complexing agent having a metal ligand, wherein the second complexing agent is a compound having a donor atom, sulfur or carbon,
At least one compound selected from the group consisting of compounds having a donor atom, nitrogen, compounds having a carboxyl group as a metal coordinating group, and compounds having a carbonyl group as a metal coordinating group.

The organic acid is a carboxylic acid that forms a complex with the oxide particles of the metal material, and the carboxylic acid is oxalic acid, citric acid, malic acid, maleic acid, succinic acid, tartaric acid, It is at least one compound selected from the group consisting of malonic acid and salts thereof.

Further, an additive such as a surfactant was added to the organic acid.

The additives are anionic and cationic.

Further, the complexing agent contained in the organic acid treatment solution is a polyaminocarboxylic acid and / or ammonium fluoride.

The polyaminocarboxylic acids are ethylenediaminetetraacetic acid (EDTA), trans-1,2
-Cyclohexanediaminetetraacetic acid (CyDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N- (2-hydroxyethyl) ethylenediamine-N, N ', N'-triacetic acid (EDTA-
OH) and at least one compound selected from the group consisting of salts thereof.

[0033]

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a flowchart showing steps of a substrate processing method according to the present invention.
FIG. 3 is a view showing a processing step of the substrate processing method according to the present invention, FIG. 3 is a perspective view showing a substrate cleaning apparatus used in the substrate processing method according to the present invention, and FIG. FIG. 5 is a cross-sectional view of the cleaning device viewed from the front,
FIG. 2 is a cross-sectional view of the ultrasonic cleaning apparatus used in the substrate processing method according to the present invention as viewed from the front.

As shown in FIGS. 1 and 2, the substrate processing method according to the present invention includes a first step A in which a substrate 1 is treated with an organic alkaline processing liquid, and a substrate treated in the first step A. A second step B of treating the substrate 1 with an organic acid treatment liquid, and supplying pure water to the surface of the substrate 1 treated in the second step B to form a liquid film, The method includes a third step C of supplying a high oxidizing treatment liquid and cleaning while rotating, and a fourth step D of performing ultrasonic cleaning and drying of the substrate 1 processed in the third step C. As the substrate 1, various substrates 1 such as a semiconductor wafer and a glass substrate can be applied.
A metal wiring or the like is formed on the surface of a metal material (for example, copper (Cu), tungsten (W), aluminum (Al)).
Chemical mechanical polishing (CM) of semiconductor wafer with exposed
P) It is suitable for the cleaning treatment after the treatment.

First, the first step A of the substrate processing method according to the present invention will be described. The first step A is a step of washing while supplying the organic alkaline treatment liquid to both the front and back surfaces of the substrate 1 to remove particles attached to the surface of the substrate 1. As shown in FIG. 3, the substrate cleaning apparatus 2 used in the first step A includes a pair of rotating brushes 3 a and 3 b arranged on the front and back surfaces of the substrate 1, respectively. A cleaning fluid supply nozzle 9 for supplying a cleaning fluid (in this case, an organic alkaline processing liquid) to both front and back surfaces, a driving roller 7 and a holding roller 6a as driving means for holding and rotating the substrate 1
And a holding roller 6e.

The driving roller 6 and the holding rollers 6a to 6e as driving means for rotating the substrate 1 are
A roller member 8a fitted to the shaft member 8c,
A large-diameter stepped portion 8b located below the roller member 8a
And The driving roller 7 has a shaft member 8c connected to driving force applying means (not shown) such as a motor, and is rotatable forward and backward in a direction indicated by an arrow R (or a reverse direction thereof). The holding roller 6e is rotatable about the shaft member 8c in the direction of arrow R and in the opposite direction. The driving roller 7 and the holding roller 6a
Or at least one of the holding rollers 6e.
The entirety of the holding roller 6a and the holding roller 6e can be moved in the directions of arrows P and Q by a moving mechanism (not shown). The substrate 1 is a substrate transfer device (FIG.
(Only 9 is shown), and moves in the direction of arrow Q to hold the substrate 1 at a predetermined position. In this state, the peripheral portion of the substrate 1 is engaged and held by the driving roller 7 and the holding rollers 6a to 6e, respectively.

The rotating brushes 3a and 3b extend in correspondence with the front and back surfaces of the substrate 1, and the shaft 5a is covered with a brush 5b made of PVA (polyvinyl alcohol) or the like. Are formed with a large number of protrusions 5c. Further, the rotating brushes 3a and 3b are respectively movable in the direction of arrow Z, and the substrate 1 is transferred to the substrate transport device (FIG. 4).
(Only the claw portion 19 is shown), the rotating brush 3a and the rotating brush 3b retract upward and downward, respectively, and when the substrate 1 is held at a predetermined position, each of the rotating brushes 3a and 3b moves in the opposite direction. To contact both sides of the substrate 1. Also,
The rotating brush 3a and the rotating brush 3b are connected to a driving mechanism (not shown), and are configured to be rotationally driven in mutually opposite directions (arrow S and arrow T directions).

Therefore, the driving roller 7 is moved by the driving force applying means (not shown) in the direction of arrow R (or in the opposite direction).
When the substrate 1 is rotated, the substrate 1 is rotationally driven in the direction of the arrow W (or the opposite direction), and in this state, the cleaning fluid (in this case, the organic alkaline processing liquid) is supplied from the cleaning fluid supply nozzle 9
Is dripped, and the rotating brushes 3a and 3b are rotationally driven in opposite directions (the directions of the arrow S and the arrow T), so that the front and back surfaces of the substrate 1 are washed by contacting the protrusions 5c of the rotating brushes 3a and 3b. . When the cleaning with the cleaning fluid (in this case, the organic alkaline processing liquid) is completed, pure water is supplied to both the front and back surfaces of the substrate 1, and the cleaning fluid remaining on the substrate 1 and the substrate 1 are separated from the substrate 1. The removed particles and the like are washed.

When the processing in the first step A is completed, the substrate 1
Is carried out by a substrate transfer device (only the claw portion 19 is shown in FIG. 4) and is transferred toward the second step B. The operation of the substrate cleaning apparatus 2 when unloading the substrate 1 is the reverse of the operation when loading the substrate 1, and the basic operation is the same.

Next, the organic alkaline treatment liquid used in the first step A will be described. This organic alkaline processing liquid is non-reactive with metal wiring (eg, copper (Cu), tungsten (W), aluminum (Al), etc.) formed in a state where the metal material is exposed on the surface of the substrate 1. It contains an organic alkali and a complexing agent such as a chelating agent capable of capturing metal impurities as a stable water-soluble complex.
The organic alkaline treatment liquid according to the present invention contains an organic alkali as a main component, preferably contains hydrogen peroxide and water, and has a pH value of more than 7. Since the particles of the metal material used for the metal wiring are generated on the substrate 1 by the CMP, the complexing agent to be added to the organic alkaline processing liquid is exposed to the metal material formed on the surface of the substrate 1. It is preferable to select a compound that easily forms a chelate complex with the particles of and the metal contained in the polishing liquid used.

As the organic alkali, quaternary ammonium salts such as quaternary ammonium hydroxide and organic amines can be used, and it is usually preferable to use 1 to 30% by weight aqueous solution. Representative examples of the quaternary ammonium hydroxide include, but are not limited to, tetramethylammonium hydroxide (TMAH) and trimethyl-2-hydroxyethylammonium hydroxide (choline). As organic amines, trimethylamine,
Tertiary amines such as triethanolamine, diamines such as ethylenediamine, guanidine, toluidine and the like can be used. Two or more of these organic alkalis may be added.

When hydrogen peroxide is mixed with the organic alkaline processing solution, it is usually used as an aqueous solution of 20 to 40% by weight, and the hydrogen peroxide concentration in the entire processing solution is usually 0.01 to 30% by weight. %.

Further, an alcohol solution, for example, isopropyl alcohol (IPA) having a concentration of, for example, 0.005% to 10% may be added to the organic alkaline treatment liquid.

Examples of complexing agents such as chelating agents to be added to the organic alkaline treating solution include a fluoride ion, an OH group having a cyclic skeleton in the molecular structure and bonded to a carbon atom constituting the ring. At least one or more substances selected from the group consisting of compounds having one or more O ^- groups are preferred.

When the fluoride ion is added to the organic alkaline treatment liquid, it may be added in any form, but usually, it is added as an organic alkali fluoride or ammonium fluoride. The fluoride ion concentration in all the processing solutions is 0.15 mol / l or more, preferably 0.1 mol / l.
At 20 mol / l or more, the upper limit is 2.0 mol / l.

[0046] Further, an annular skeleton in the molecular structure an organic alkaline processing liquid, and OH groups and / or O bonded to the carbon atom of the ring ^- adding an organic complexing agent having one or more groups In this case, the total addition amount in the organic alkaline treatment liquid is usually 10 ^{−7 to} 5% by weight, preferably 10 ⁻⁶ % by weight.
It is preferable to add in the range of 0.1 to 0.1% by weight, and the following can be used, but it is not particularly limited thereto. Further, the cyclic skeleton in the molecular structure may be any of an alicyclic compound, an aromatic compound, and a cyclic skeleton corresponding to a heterocyclic compound, and it is sufficient that at least one of these cyclic skeletons is present in the molecular structure. . In addition, although a specific example is illustrated as a compound having an OH group, a corresponding salt such as an ammonium salt is also included. Common names or abbreviations are shown in [] after the compound name.

(1) Phenols having only one OH group and derivatives thereof Phenol, cresol, ethylphenol, t-butylphenol, methoxyphenol, salicyl alcohol, chlorophenol, aminophenol, aminocresol, amidole, p- (2 -Aminoethyl) phenol, salicylic acid, o-salicylanilide, naphthol, naphtholsulfonic acid, 7-amino-4-hydroxy-2-naphthalenedisulfonic acid and the like.

(2) Phenols having two or more OH groups and derivatives thereof Catechol, resorcinol, hydroquinone, 4-methylpyrocatechol, 2-methylhydroquinone, pyrogallol, 1,2,5-benzenetriol, 1,3,3 5-
Benzenetriol, 2-methylphloroglucinol,
2,4,6-trimethylphloroglucinol, 1,2,2
3,5-benzenetetraol, benzenehexaol, tyrone, aminoresorcinol, 2,4-dihydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, dihydroxyacetophenone, 3,4-dihydroxybenzoic acid, gallic acid, 2,3 4-trihydroxybenzoic acid, 2,4-dihydroxy-6-methylbenzoic acid, naphthalene diol, naphthalene triol,
Nitronaphthol, naphthalenetetraol, binaphthyldiol, 4,5-dihydroxy-2,7-naphthalenedisulfonic acid, 1,8-dihydroxy-3,6-naphthalenedisulfonic acid, 1,2,3-anthracentriol, 1,3 , 5-Tris ((2,3-dihydroxybenzoyl) aminomethyl) benzene [MECAM],
1,5,10-tris (2,3-dihydroxybenzoyl) -1,5,10-triazadecane [3,4-LIC
AM], 1,5,9-tris (2,3-dihydroxybenzoyl) -1,5,9-cyclotriazatridecane [3,3,4-CYCAM], 1,3,5-tris ((2 , 3-Dihydroxybenzoyl) carbamide) benzene [3,3,4-CYCAM], 1,3,5-tris ((2,3-dihydroxybenzoyl) carbamide)
Benzene [TRIMCAM], enterobactin, enancycloenterobactin and the like.

(3) Hydroxybenzophenones Dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,6-dihydroxy-4-methoxybenzophenone, 2,2 ', 5,6'-tetrahydroxybenzophenone, 2,3 ', 4,4', 6-pentahydroxybenzophenone and the like.

(4) Hydroxybenzanilides O-hydroxybenzanilide and the like. (5) Hydroxyanil glyoxal bis (2-hydroxyanil) and the like. (6) hydroxybiphenyls biphenyltetraol and the like.

(7) Hydroxyquinones and derivatives thereof 2,3-hydroxy-1,4-naphthoquinone, 5-hydroxy-1,4-naphthoquinone, dihydroxyanthraquinone, 1,2-dihydroxy-3- (aminomethyl)
Anthraquinone-N, N'-2 acetic acid [alizarin complexan], trihydroxyanthraquinone and the like.

(8) Diphenyl or triphenylalkane derivatives diphenylmethane-2,2'-diol, 4,4 ',
4 "-triphenylmethanetriol, 4,4'-dihydroxyfuchsone, 4,4'-dihydroxyfuchsone,
4,4'-dihydroxy-3-methylfuchsone, pyrocatechol violet [PV] and the like.

(9) Phenol derivative of alkylamine Ethylenediaminediorthohydroxyphenylacetic acid [E
DDHA], N, N-bis (2-hydroxybenzyl)
Ethylenediamine-N, N-2acetic acid [HBED], ethylenediaminedihydroxymethylphenylacetic acid [EDD
HMA]. (10) Phenol derivatives of alkyl ethers 3,3'-ethylenedioxydiphenol and the like.

(11) Phenols having an azo group and derivatives thereof 4,4'bis (3,4-dihydroxyphenylazo)-
Diammonium 2,2'-stilbenedisulfonic acid [stilbazo], 2,8-dihydroxy-1- (8-hydroxy-3,6-disulfo-1-naphthylazo) -3,6
-Naphthalenedisulfonic acid, o, o'-dihydroxyazobenzene, 2-hydroxy-1- (2-hydroxy-
5-methylphenylazo) -4-naphthalenesulfonic acid [calmagite], chlorohydroxyphenylazonaphthol, 1 ′, 2-dihydroxy-6-nitro-1,
2'-azonaphthalene-4-sulfonic acid [Eriochrome Black T], 2-hydroxy-1- (2-hydroxy-4-sulfo-1-naphthylazo) -3,6-naphthalenedisulfonic acid, 5-chloro-2 -Hydroxy-3-
(2,4-dihydroxyphenylazo) benzenesulfonic acid [lumogallion], 2-hydroxy-1- (2-hydroxy-4-sulfo-1-naphthylazo) -3-naphthalene acid [NN], 1,8-dihydroxy- 2- (4-
Sulfophenylazo) -3,6-naphthalenedisulfonic acid, 1,8-dihydroxy-2,7-bis (2-sulfophenylazo) -3,6-naphthalenedisulfonic acid, 2
-[3- (2,4-dimethylphenylaminocarboxy) -2-hydroxy-1-naphthylazo] -3-hydroxybenzenesulfonic acid, 2- [3- (2,4-dimethylphenylaminocarboxy) -2-hydroxy -1
-Naphthylazo] phenol and the like.

(12) Heterocyclic compounds having an OH group and derivatives thereof 8-quinolinol, 2-methyl-8-quinolinol, quinolinediol, 1- (2-pyridineazo) -2-naphthol, 2-amino-4 , 6,7-pteridinetriol, 5,7,3 ', 4'-tetrahydroxyflavone [luteolin], 3,3'-bis [N, N-bis (carboxymethyl) aminomethyl] fluorescein [calcein], 2, , 3-hydroxypyridine and the like.

(13) Alicyclic compounds having an OH group and derivatives thereof Cyclopentanol, croconic acid, cyclohexanol, cyclohexanediol, dihydroxydiquinoyl, tropolone, 6-isopropyltropolone and the like.

The organic complexing agent selected from the group consisting of the above (1) to (13) is at least one type in consideration of the cost of the complexing agent and the chemical stability in the added organic alkaline processing solution. In terms of metal adhesion preventing effect, phenol derivatives of alkylamines such as ethylenediamine diorthohydroxyphenylacetic acid [EDDHA], phenols having two or more OH groups such as catechol and tyrone and derivatives thereof may be added. Are better.

Further, when a second complexing agent having a metal ligand is added in addition to the organic complexing agent selected from the group consisting of the above (1) to (13), the effect of preventing metal adhesion is improved. And
More preferred. Hereinafter, compounds added as the second complexing agent will be exemplified, but are not particularly limited thereto. In the following description, the donor atom is
An atom that can supply electrons required for coordination bond with a metal.

[0059] As [A] a complexing agent having sulfur or carbon as a donor atom (14) complexing agent coordinating groups having sulfur donor atoms, wherein _{^{HS -, S 2-, S 2}} O 3 2- , RS ^-, R-
COS ^- is selected from, or CS ₃ ^2-in has at least one of the groups represented, or RSH, R 'thiol represented by ₂ S or R ₂ C = S, sulfide or thiocarbonyl compounds ^-, R-CSS There is something. Here, R represents an alkyl group, R ′ represents an alkyl group or an alkenyl group, and may be further linked to each other to form a ring containing a sulfur atom.

Specifically, hydrogen sulfide or a salt thereof, or a sulfide such as ammonium sulfide as having an HS ^- group or a S ^2- group; thiosulfuric acid or a salt thereof, having an S ₂ O ₃ ^2- group A lower alkylthiol such as thiol, ethanethiol, 1-propanethiol or the like having a RSH or RS- group or a salt thereof; thioacetic acid, dithiooxalic acid or a salt thereof having an R-COS ^- group; R-CSS ⁻ Etanjibisu as having a group (dithio acid), dithio acid or its salts; as having a group having a CS ₃ ^2-group, trithiocarbonate carbonate or a salt thereof;
As the sulfide represented by R _'2 S, methyl sulfide, methyl thio ethane, diethyl sulfide, vinyl sulfide, benzothiophene, and the like; as thiocarbonyl compound represented by R ₂ C = S group professional punch on, 2,4-pentane dithio emissions such as Is raised.

[0061] (15) as a complexing agent coordinating groups having carbon as a donor ^atom, NC - those having a ^-, RNC, RCC. For example, cyanides such as hydrogen cyanide and ammonium cyanide, isocyanides such as ethyl isocyanide, allylene, metal acetylide and the like.

[B] Complexing agents having nitrogen as a donor atom include the following (16) to (29).

(16) Monoamines Ethylamine, isopropylamine, vinylamine, diethylamine, dipropylamine, N-methylethylamine, triethylamine, benzylamine, aniline,
Toluidine, ethylaniline, xylidine, thymilamine, 2,4,6-trimethylaniline, diphenylamine, N-methyldiphenylamine, biphenylylamine, benzidine, chloroaniline, nitrosoaniline,
Aminobenzenesulfonic acid, aminobenzoic acid and the like.

(17) Diamines and polyamines Ethylenediamine, propylenediamine, trimethylenediamine, hexamethylenediamine, diethylenetriamine, diaminobenzene, toluenediamine, N-methylphenylenediamine, triaminobenzene, aminodiphenylamine, diaminophenylamine and the like.

(18) Amino alcohols Ethanolamine, 2-amino-1-butanol, 2-
Amino-2-methyl-1-propanol, 2-amino-
2-ethyl-1,3-propanediol, 2- (ethylamino) ethanol, 2,2′-iminodiethanol,
Dimethylethanolamine, diethylethanolamine, ethyldiethanolamine, 3-diethylamino-
1,2-propanediol, triethanolamine and the like.

(19) Aminophenols Aminophenol, p-aminophenol sulfate, (methylamino) phenol, aminoresorcinol and the like.

(20) Amino acids glycine, glycine ethyl ester, sarcosine, alanine, aminobutyric acid, norvaline, valine, isovaline, norleucine, leucine, isoleucine, serine, L-threonine, cysteine, cystine, methionine, ornithine, lysine, arginine , Citrulline, aspartic acid, asparagine,
Glutamic acid, glutamine, β-hydroxyglutamic acid, N-acetylglycine, glycylglycine, diglycylglycine, phenylalanine, tyrosine, L-thyroxine, N-phenylglycine, N-benzoylglycine and the like.

(21) Iminocarboxylic acids Imino diacetic acid, nitrilotriacetic acid, nitrilotripropionic acid, ethylenediaminediacetic acid [EDDA], ethylenediaminetetraacetic acid [EDTA], hydroxyethylethylenediaminetetraacetic acid [EDTA-OH], trans-1 , 2
-Diaminocyclohexanetetraacetic acid [CyDTA], dihydroxyethylglycine [DHGE], diaminopropanoltetraacetic acid [DPTA-OH], diethylenetriaminepentaacetic acid [DTPA], ethylenediamine2propiondiacetic acid [EDDP], glycol etherdiaminetetraacetic acid [GEDTA] 1,6-hexamethylenediamine 4
Acetic acid [HDTA], hydroxyethyl imino diacetic acid [H
IDA], methyl EDTA (diaminopropane tetraacetic acid), triethylenetetramine hexaacetic acid [TTHA],
3,3'-dimethoxybenzidine-N, N, N ', N'
-4 acetic acid and the like.

(22) Iminophosphonic acids Ethylenediamine-N, N′-bis (methylenephosphonic acid) [EDDPO], ethylenediaminetetrakis (methylenephosphonic acid) [EDTPO], nitrilotris (methylenephosphonic acid) [NTPO], diethylenetriaminepenta ( Methylene phosphonic acid) [ETTPO],
Propylenediaminetetra (methylenephosphonic acid) [P
DTMP].

(23) Heterocyclic amines pyridine, coniline, lutidine, picoline, 3-pyridinol, isonicotinic acid, picolinic acid, acetylpyridine, nitropyridine, 4-pyridone, bipyridyl, 2,
4,6-tris (2-pyridyl) -1,3,5-triazine [TPTZ], 3- (2-pyridyl) -5,6-bis (4-sulfonyl) -1,2,4-triazine [P
Pyridines such as DTS], syn-phenyl-2-pyridylketoxime [PPKS], quinoline, quinaldine, lepidine, dimethylquinoline, 8-quinolinol,
Quinolines such as 2-methyl-8-quinolinol, methoxyquinoline, chloroquinoline, quinoline diol, quinaldic acid, quinic acid, nitroquinoline, quinulin, kynurenic acid, 8-acetoxyquinoline and bicinchoninic acid;
Isoquinolines, acridine, 9-acridone, phenanthridine, benzoquinoline, benzoquinolines such as benzoisoquinoline, naphthoquinolines such as naphthoquinoline, o-phenanthroline, 2,9-dimethyl-
1,10-phenanthroline, bathocuproine, bathocuproine sulfonic acid, bathophenanthroline, bathophenanthroline sulfonic acid, 2,9-dimethyl-4,7-
Phenanthrolines such as diphenyl-1,10-phenanthroline, pyrazoles such as pyrazole and 5-pyrrolozone, imidazoles such as imidazole and methylimidazole, imidazolines and imidazolidines such as 2-imidazoline, imidazolidine and ethyleneurea, benzimidazole Benzimidazoles, such as
Diazines such as diazine, pyrimidine and pyrazine, hydropyrimidines such as uracil and thymine, piperazines such as piperazine, benzodiazines and dibenzodiazines such as cinnoline and phenazine, triazines, purines, oxazole, 4-oxazolone, iso Oxazoles and isoxazoles such as oxazole and azoxime, oxazines such as 4H-1,4-oxazine and morpholine, thiazoles and benzothiazoles, isothiazoles, thiazines, pyrroles, pyrrolines and pyrrolidines, indoles, Indolines, isoindoles, carbazoles, indigo, porphyrins and the like.

(24) Amides and imides Carbamic acid, ammonium carbamate, oxamic acid, ethyl oxamate, ethyl N-nitrocarbamate, carbanilic acid, carbanilonitrile, oxanilic acid, formamide, diacetamide, hexaneamide,
Acrylamide, lactamide, cyanoacetamide, oxamide, succinamide, salicylamide, nitrobenzamide, succinimide, maleimide, phthalimide, and the like.

(25) Anilides Formanilide, acetanilide, hydroxyanilide, chloroanilide, methoxyacetanilide, oxanilide and the like.

(26) Urea, thiourea and derivatives thereof urea, N-methylurea, N, N'-ethylideneurea, allophanoic acid, glycolic acid, oxalic acid, biuret, N-nitrourea, azodicarbonamide, thiourea , Methylthiourea, dimethylthiourea and the like.

(27) Oximes Formaldoxime, p-benzoquinonedioxime, benzaldoxime, benzyldioxime and the like.

(28) Compounds having a coordination group in which nitrogen atoms are bonded to each other: hydrazines such as azobenzene, azotoluene, methyl red, azobenzenedicarboxylic acid, hydroxyazobenzene, and azoxybenzene; and hydrazides, such as phenylhydrazine and p-bromophenylhydrazine , P
Azo and azoxy compounds such as -nitrophenylhydrazine and N ',-phenylacetohydrazide; hydrazo compounds such as hydrazobenzene and hydrazodibenzoic acid; oxalic bis (salicylidenehydrazide); (Carboxyphenyl) hydrazones, hydrazones such as benzaldehyde hydrazone, acetaldehyde phenylhydrazone, azines such as benzylideneazine, azides such as benzoyl azide, diazonium salts such as benzenediazonium chloride, diazo compounds such as benzenediazohydroxide, semicarbazide and the like And thiosemicarbazides such as thiosemicarbazide.

(29) Others Azides such as ammonium azide and sodium azide, nitriles such as acetonitrile, amide sulfate, imide disulfate, nitride trisulfate, thiocyanic acid, ammonium thiocyanate and the like.

[C] Complexing agents having a carboxyl group as a metal coordinating group include the following (30) to (33).

(30) Monocarboxylic acids Formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid,
Decanoic acid, undecanoic acid, dodecanoic acid, stearic acid,
Acrylic acid, crotonic acid, oleic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, fluoroacetic acid, benzoic acid, methylbenzoic acid, chlorobenzoic acid, nitrobenzoic acid, sulfocarboxylic acid, phenylacetic acid and the like.

(31) Polycarboxylic acids: oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, 1,2,3-propanetricarboxylic acid, chlorosuccinic acid, phthalic acid, 1,3,5-benzenetricarboxylic acid, Dichlorophthalic acid, nitrophthalic acid, phenylsuccinic acid and the like.

(32) Hydroxy monocarboxylic acids having 4 or less hydroxyl groups As those having one hydroxyl group, glycolic acid, lactic acid,
As those having two hydroxyl groups such as 2-hydroxybutyric acid, hydroacrylic acid, hydroxybenzoic acid, salicylic acid, and sulfosalicylic acid, glyceric acid, 8,9-dihydroxystearic acid, 2,4-dihydroxybenzoic acid,
As having three hydroxyl groups, such as protocatechuic acid,
Gallic acid and the like.

(33) Hydroxy dicarboxylic acids having 4 or less hydroxyl groups As those having one hydroxyl group, two hydroxyl groups such as tartronic acid, malic acid, 2-hydroxybutane diacetic acid, 2-hydroxy dodecane diacetic acid, and hydroxyphthalic acid are used. Those having four hydroxyl groups, such as tartaric acid and 3,4-dihydroxyphthalic acid, and tetrahydroxysuccinic acid.

[D] Complexing agents having a carbonyl group as a metal coordinating group include the following (34) to (41).

(34) Aliphatic aldehydes Formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, acrylaldehyde,
Crotonaldehyde, chloroacetaldehyde, dichloroacetaldehyde, butylchloral, hydroxyacetaldehyde, lactaldehyde, D-glyceraldehyde, formal, acetal, dichloroacetal and the like.

(35) Aliphatic ketones Acetone, ethyl methyl ketone, 2-methylpentanone, 3-pentanone, 3-methyl-2-butanone, 4-
Methyl-2-pentanone, pinacolin, 2-heptanone, 3-heptanone, 4-heptanone, 6-methyl-heptanone, diisobutyl ketone, di-tert-butyl ketone, dihexyl ketone, methyl vinyl ketone, allyl acetone, 1-chloro- 2-propanone, 1,1-dichloro-2-propanone, hydroxyacetone, dihydroxyacetone and the like.

(36) Polyoxo compounds Di- and polyaldehydes such as glyoxal, malonaldehyde and succinaldehyde, di- and polyketones such as diacetyl, acetylacetone and acetonylacetone, and keto such as pyruvaldehyde and 4-oxopentanal. Aldehydes and the like.

(37) Ketene Ketene, dimethylketene and the like.

(38) Ketocarboxylic and aldehydecarboxylic acids 4,4,4-trifluoro-1-phenyl-1,3-butanedione, 2,2,6,6-tetramethyl-3,5-
Heptanedione, pyruvic acid, malonaldehyde acid, acetoacetic acid, glyoxylic acid, mesooxalic acid, oxaloacetic acid, oxalogultaric acid and the like.

(39) Aromatic aldehydes and aromatic ketones Benzaldehyde, tolualdehyde, phenylacetaldehyde, cinnamaldehyde, terephthalaldehyde, protocatechualdehyde, acetophenone, methylacetophenone, benzophenone, chloroacetophenone, dihydroxybenzophenone, phenylglyoxal and the like.

(40) Quinones o-benzoquinone, p-benzoquinone, naphthoquinone,
Quinhydrone, 2,6-dichloro-p-benzoquinone,
2,5-dihydroxy-p-benzoquinone, tetrahydroxy-p-benzoquinone, 2,3-hydroxy-1,
4-naphthoquinone and the like.

(41) Tropolones Tropolone, 6-isopropyltropolone and the like.

The organic alkaline processing liquid used in the first step A has no corrosiveness to metals (for example, copper (Cu), tungsten (W), aluminum (Al), etc.), and is a stable aqueous solution of metal impurities. Since it contains a complexing agent such as a chelating agent that can be trapped as an acidic complex, it is formed in a state where a metal material (for example, copper (Cu), tungsten (W), aluminum (Al), etc.) is exposed on the surface of the substrate 1. The surface of the metal wiring thus formed is not roughened, and the metal impurity ions are prevented from adhering to the surface of the substrate 1, thereby achieving a high cleaning effect on particles adhering to the substrate surface. The complexing agent and the second complexing agent contained in the organic alkaline treating solution according to the present invention effectively act on metal particles and ions to form a complex, but the substrate is strongly bonded to the metal. 1 does not easily form a complex with the metal wiring itself, and has no corrosiveness.

Next, the second step B of the substrate processing method according to the present invention will be described. As shown in FIGS. 1 and 2,
The second step B is a step of cleaning while supplying the organic acid treatment liquid to both the front and back surfaces of the substrate 1 to remove metal impurities attached to the surface of the substrate 1. Note that the second step B includes:
Only the cleaning fluid (in this case, the organic acid treatment liquid) used in the first step A is different, and the configuration and operation of the substrate cleaning apparatus 2 used in the second step B are the same. The detailed description of is omitted.

The substrate 1 processed in the first step A is carried into the substrate cleaning apparatus 2 in the second step B by a substrate transfer device (only the claws 19 are shown in FIG. 4). When the substrate 1 is held at a predetermined position of the substrate cleaning apparatus 2, a cleaning fluid (in this case, an organic acid treatment liquid) is dropped from the cleaning fluid supply nozzle 9, and the rotating brush 3 a Cleaning is performed by contact of the protrusion 5c of 3b. When the cleaning with the cleaning fluid (in this case, the organic acid treatment liquid) is completed, pure water is supplied to both the front and back surfaces of the substrate 1 and separated from the cleaning fluid remaining on the substrate 1 and the substrate 1. The removed metal impurities and the like are washed. When the processing in the second step B is completed, the substrate 1 is unloaded by the substrate transfer device (only the claw portions 19 are shown in FIG. 4) and is transferred toward the third step C.

The organic acid treatment liquid used in the second step B is formed in a state where a metal material (for example, copper (Cu), tungsten (W), aluminum (Al), etc.) is exposed on the surface of the substrate 1. And a complexing agent such as a chelating agent capable of capturing metal impurities as a stable water-soluble complex. The organic acid treatment liquid according to the present invention contains an organic acid as a main component and has a pH value of less than 7.

As the organic acid, carboxylic acids can be used, and at least one or more selected from the group consisting of oxalic acid, citric acid, malic acid, maleic acid, succinic acid, tartaric acid, malonic acid and salts thereof. Preferably, it is a compound. On the substrate 1, particles of the metal material used for the metal wiring may be oxidized by CMP to generate metal oxide particles, and the organic acid may be exposed on the surface of the substrate 1. It is preferable to select a compound that easily forms a chelate complex with the oxide particles. For example, when a copper metal wiring is exposed on the surface of the substrate 1, copper oxide particles (CuOx) and a chelate complex are used. Oxalic acid, which has a high forming effect, is preferred.

The carboxylic acids hardly form a complex with the metal wiring itself which is strongly bonded to the metal, and are not corrosive. Also, a barrier film 52 (titanium (Ti), titanium nitride (TiN), etc.) formed on the substrate 1
Does not form complexes with these carboxylic acids and is not corroded. The carboxylic acids are preferably used as a 0.01 to 5% by weight aqueous solution.

As a complexing agent such as a chelating agent to be added to the organic acid processing solution, metal impurities remaining as particles or ions on the substrate 1 after being processed by CMP (for example, used polishing liquid or (K), calcium (Ca), titanium (Ti), copper (C)
u), zinc (Zn), etc.), and polyaminocarboxylic acids and ammonium fluoride, which easily form a complex with zinc (Zn). Examples of polyaminocarboxylic acids include ethylenediaminetetraacetic acid (EDTA), trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA), nitrilotriacetic acid (NTA), and diethylenetriaminepentaacetic acid (DTP).
A), compounds such as N- (2-hydroxyethyl) ethylenediamine-N, N ', N'-triacetic acid (EDTA-OH) and salts thereof are preferable, and ammonium salts which do not adversely affect the properties of semiconductors are particularly preferable. Metal-free salts of are preferred. The concentration of the complexing agent is preferably 1 to 10000 ppm, more preferably 10 to 1000 ppm, based on the organic acid treatment solution. Note that an anionic or cationic additive such as a surfactant may be added to the organic acid treatment liquid.

The organic acid treatment solution used in the second step B includes a metal (for example, copper (Cu), tungsten (W),
(Aluminum (Al), etc.) is not corrosive, and contains a complexing agent such as a chelating agent capable of capturing metal impurities as a stable water-soluble complex. It does not corrode the surface of the metal wiring and has a high cleaning effect on metal impurities attached to the surface of the substrate 1. The complexing agent contained in the organic acid treatment solution according to the present invention effectively acts on metal particles and ions to form a complex. On the other hand, it does not easily form a complex and has no corrosiveness.

Next, the third step C of the substrate processing method according to the present invention will be described. As shown in FIG. 4, the substrates 1 processed in the second step B are gripped one by one by the claw portions 19 of the substrate transfer device, and are carried into the rotary cleaning device 12 in the third step C. The rotary cleaning device 12 used in the third step C of the substrate processing method according to the present invention includes a holding table 13 for fixing and holding the substrate 1 and a substrate 1 provided on the holding table 13.
, A plurality of needle-like holding pins 13b for supporting the same, a hook-like chuck member 14 that engages with the peripheral edge of the substrate 1, and a cleaning fluid (in this case, pure water) is supplied to the surface of the substrate 1. And a cleaning fluid supply nozzle 90. Holding table 13,
The holding pins 13b and the chuck member 14 constitute a means for fixing the substrate 1.

The holding table 13 is formed in a disk shape.
The peripheral portion is formed at least higher than the surface of the substrate 1, and the protrusion 13 prevents scattering of the cleaning fluid (in this case, pure water).
a. A discharge duct 2 for discharging a cleaning fluid during or after cleaning is provided on the inner peripheral side of the convex portion 13a.
3 are provided. In the present embodiment, the discharge duct 2
3 are provided at two places, but the discharge duct 23 may be provided at at least one place.

The holding pin 13b is formed of a needle-like member,
The back surface of the substrate 1 is supported at one point to prevent contamination on the back surface side of the substrate 1, and is disposed at, for example, four locations (only two locations are shown in FIG. 4) at equal intervals. In addition, the chuck members 14 are provided at four locations (only two locations are shown in FIG. 4) at equal intervals along the circumference of the substrate 1. The chuck member 14 can be opened and closed by an opening / closing mechanism (not shown) from a position indicated by a two-dot line to a position indicated by a solid line, and receives the substrate 1 from above in an open state (the position indicated by the two-dot line). Is closed on the holding pin 13b (at the position indicated by the solid line), the peripheral edge of the substrate 1 is engaged and held and fixed. Therefore, in this state, the substrate 1 processed in the second processing step B in the preceding stage is fixed by the holding table 13, the holding pins 13 b and the chuck member 14. The holding pin 13
b and the chuck member 14 may be provided in at least three places.

A shaft member 15 is connected at one end to the center of the back side of the holding table 13. The other end of the shaft member 15 is connected to rotation driving means (not shown),
Numeral 5 is rotatable forward and backward (for example, rotated in the direction of arrow V) by a rotation drive unit. A cleaning fluid supply path 24a for supplying a high oxidizing treatment liquid toward the back surface of the substrate 1 is formed at the center of rotation of the shaft member 15, and penetrates through the center of the holding table 13 to provide a back surface cleaning fluid. A spout 24b is provided. The rotation speed of the shaft member 15 is, for example, 400
~ 1200r. p. m (revolution per minute), and the holding table 13 can rotate at a high speed in the direction of the arrow V (or the opposite direction).

In the third step C, pure water is supplied to the surface of the substrate 1 having the metal wiring treated in the second step B to form a liquid film, and the back surface of the substrate 1 is contaminated with contaminants. A high oxidizing treatment liquid for removing a certain metal, for example, copper (Cu), tungsten (W), aluminum (Al), etc. is supplied to, for example, move the substrate 1 from 400 rpm to 1200 rpm.
Washing is performed while rotating at a high speed of about 1 minute or more at a rotation speed in the range of m. By rotating the substrate 1 at a high speed in this manner, the high oxidizing treatment liquid is prevented from flowing from the back surface to the front surface of the substrate 1. Further, even if the high oxidizing treatment liquid flows around the surface of the substrate 1, the surface of the substrate 1 is protected by the pure water film supplied to the surface of the substrate 1.

The high oxidizing treatment liquid supplied to the back surface of the substrate 1 is prepared from hydrofluoric acid / hydrogen peroxide solution (FPM), sulfuric acid / hydrogen peroxide solution (SPM), hydrochloric acid / hydrogen peroxide solution (HPM). At least one cleaning liquid selected from the group consisting of: The hydrofluoric acid-hydrogen peroxide solution (FPM) is hydrofluoric acid HF: 0.1% ~3%, hydrogen peroxide H ₂ O _2: 0.1
% To 10%.

The hydrofluoric acid / hydrogen peroxide solution (FPM) is, for example, 0.4 liter of a 50% solution of hydrofluoric acid, 0.8 liter of a 30% solution of hydrogen peroxide, and 8 liters of pure water. It is preferably a mixture. The sulfuric acid / hydrogen peroxide solution (SPM) is desirably a mixed liquid having a ratio of, for example, 4 liters of a 98% sulfuric acid solution and 1 liter of a 30% hydrogen peroxide solution. Further, the hydrochloric acid / hydrogen peroxide solution (HPM) is preferably a mixed solution of hydrochloric acid, hydrogen peroxide at 1, pure water at a ratio of 5.

The high oxidizing solution used in the third step C of the present invention includes hydrofluoric acid / hydrogen peroxide solution (FPM), sulfuric acid / hydrogen peroxide solution (SPM), and hydrochloric acid / hydrogen peroxide solution ( HP
The present invention is not limited to M). For example, all substances capable of removing contaminants attached to the back surface of the substrate 1, such as ozone hydrofluoric acid (HF / O ₃ ) and buffered hydrofluoric acid / ammonium fluoride (BHF). Is included. Also, hydrofluoric acid / hydrogen peroxide solution (FPM), sulfuric acid / hydrogen peroxide solution (SP
As for the mixing ratio of M), hydrochloric acid / hydrogen peroxide (HPM), and the ratio of the mixed liquid constituting itself, a preferable one is appropriately adopted.

Next, a fourth step D of the substrate processing method according to the present invention will be described. The fourth step D is a step in which the front and back surfaces of the substrate 1 treated in the third step C are finish-cleaned by ultrasonic waves and then dried, and the substrate 1 treated in the third step C is As shown in FIG. 5, the substrates are gripped one by one by the claws 19 of the substrate transfer device, and are carried into the ultrasonic cleaning device 12 in the fourth step D. Ultrasonic cleaning apparatus 12 used in fourth step D of the substrate processing method according to the present invention
A holding table 13 fixedly holding the substrate 1, and a plurality of needle-like holding pins 1 provided on the holding table 13 to support the substrate 1.
3b, a hook-shaped chuck member 14 that engages with the peripheral edge of the substrate 1, and a cleaning fluid jet that supplies an ultrasonic cleaning fluid (in this case, pure water) to the substrate 1 by exciting the ultrasonic cleaning fluid. And a nozzle (ultrasonic nozzle) 17. The holding means 13, the holding pins 13 b and the chuck member 14 constitute a fixing means for the substrate 1.

The holding table 13 is formed in a disk shape.
The peripheral portion is formed at least higher than the surface of the substrate 1, and serves as a convex portion 13a for preventing scattering of the ultrasonic cleaning fluid (in this case, pure water). A discharge duct 23 for discharging the ultrasonic cleaning fluid during or after cleaning is provided on the inner peripheral side of the convex portion 13a. In the present embodiment,
Although the discharge duct 23 is provided at two places, the discharge duct 23 may be provided at at least one place.

The holding pin 13b is made of a needle-like member.
The back surface of the substrate 1 is supported at one point to prevent contamination on the back surface side of the substrate 1. For example, the back surface of the substrate 1 is provided at four locations (only two locations are shown in FIG. 5) at equal intervals. Further, the chuck members 14 are provided at four locations (only two locations are shown in FIG. 5) at equal intervals along the circumference of the substrate 1. The chuck member 14 can be opened and closed by an opening / closing mechanism (not shown) from a position indicated by a two-dot line to a position indicated by a solid line, and receives the substrate 1 from above in an open state (the position indicated by the two-dot line). Is closed on the holding pin 13b (at the position indicated by the solid line), the peripheral edge of the substrate 1 is engaged and held and fixed. Therefore, in this state, the substrate 1 processed in the third processing step C of the preceding stage is fixed by the holding table 13, the holding pins 13 b and the chuck member 14. The holding pin 13
b and the chuck member 14 may be provided in at least three places.

A shaft member 15 is connected at one end to the center of the back side of the holding table 13. The other end of the shaft member 15 is connected to rotation driving means (not shown),
Numeral 5 is rotatable forward and backward (for example, rotated in the direction of arrow V) by a rotation drive unit. A cleaning fluid supply path 24a for supplying an ultrasonic cleaning fluid (pure water in this case) toward the back surface of the substrate 1 is formed at the center of rotation of the shaft member 15, and the center of the holding table 13 is formed. A cleaning fluid ejection port 24b for the back surface is provided therethrough. The rotation speed of the shaft member 15 is, for example, 1800 to 2000 r. p. m (revolution per minute), and the holding table 13 can rotate at a high speed in the direction of the arrow V (or the opposite direction).

Cleaning fluid jet nozzle (ultrasonic nozzle) 1
Reference numeral 7 includes an ultrasonic oscillator (not shown) connected to an oscillator. When an ultrasonic cleaning fluid (in this case, pure water) is supplied, the oscillator and the ultrasonic oscillator are connected. The ultrasonic cleaning fluid (in this case, pure water) driven at a predetermined frequency
And is ejected toward the substrate 1. Further, the cleaning fluid jet nozzle (ultrasonic nozzle) 17 can be moved in directions of arrows F and G by a moving mechanism (not shown),
By moving the cleaning fluid jet nozzle (ultrasonic nozzle) 17, the ultrasonic cleaning fluid excited by the ultrasonic vibration can be jetted evenly toward the entire surface of the substrate 1. The driving frequency of the ultrasonic transducer (not shown) is as follows.
A frequency of 500 kHz or more can be used, and in this embodiment, the driving frequency is 950 kHz, which is compatible with high megasonics.

Therefore, the holding table 1 to which the substrate 1 is fixed
3 is rotated in the direction of arrow V (or the opposite direction) by a rotary drive means (not shown), and the cleaning fluid jet nozzle (ultrasonic nozzle) 17 is supplied with an ultrasonic cleaning fluid (pure water in this case).
When the oscillator and the ultrasonic transducer (not shown) are driven, the surface of the substrate 1 can be precisely cleaned with the ultrasonic cleaning fluid excited by the ultrasonic wave. At this time, the cleaning fluid injection nozzle (ultrasonic nozzle)
By spraying the ultrasonic cleaning fluid while moving 17 in the direction of arrow F, the entire surface of the substrate 1 can be cleaned evenly. In addition, since the powerful ultrasonic wave applied to the front surface of the substrate 1 propagates also to the back surface of the substrate 1, the ultrasonic cleaning is performed through the cleaning fluid supply path 24a and the back surface cleaning fluid jet port 24b. If the working fluid (in this case, pure water) is supplied to the back surface of the substrate 1, the front and back surfaces of the substrate 1 can be simultaneously ultrasonically cleaned.

The dishing 55 generated on the metal wiring 51 on the substrate 1 such as a semiconductor wafer by the ultrasonic cleaning.
Particles, metal impurities, and the like adsorbed in the step portion 56 (see FIG. 10) can be reliably cleaned, and the front and back surfaces of the substrate 1 can be precisely cleaned to improve cleanliness.
When the cleaning with the ultrasonic cleaning fluid (pure water in this case) excited by the ultrasonic wave is completed, pure water is supplied to both the front and back surfaces of the substrate 1 while the rotation of the holding table 13 is maintained, The ultrasonic cleaning fluid remaining on the substrate 1 and particles and metal impurities separated from the substrate 1 are cleaned. In the present embodiment, a high cleaning effect is obtained by injecting the ultrasonic cleaning fluid (in this case, pure water) by exciting with ultrasonic waves. And a cleaning fluid such as pure water may be pressurized and ejected.

When the cleaning of the front and back surfaces of the substrate 1 is completed, the supply of pure water is stopped, and the holding table 13 is continuously rotated for a predetermined time, and the pure water remaining on the front and back surfaces of the substrate 1 is centrifuged by high-speed rotation. Disperse by force and dry. At this time, as shown in FIG. 2, if dry nitrogen (N ₂ ) gas or the like is sprayed on both the front and back surfaces of the substrate 1, metal wiring (eg, copper (Cu), tungsten (W)) formed on the surface of the substrate 1 is formed. (W), aluminum (Al) and the like can be prevented from being oxidized and the drying time can be shortened, which is preferable.

When the processing in the fourth step D is completed, the substrate 1
Is carried out by the claw portion 19 of the substrate transfer device and transferred to a subsequent process. Note that the operation of the ultrasonic cleaning device 12 when unloading the substrate 1 is the reverse of the operation when the substrate 1 is unloaded, and the basic operation is the same.

Next, the effects of the substrate processing method according to the present invention on metal impurities will be described with reference to FIGS. 6 (a) and 6 (b).
This will be described with reference to FIG. In the substrate processing method according to the present invention, the liquid film formed by the pure water supplied to the front surface of the substrate 1 in the third step C and the substrate 1 by the high oxidizing processing liquid supplied to the back surface of the substrate 1 The removal of metal impurities on the back surface and the centrifugal force generated when the substrate 1 is rotated at a high speed cooperate to completely eliminate metal contamination on the back surface of the substrate 1 without corroding metal wiring on the surface of the substrate 1. Cleaning to prevent contamination from being carried into the next process.
At this time, by rotating the substrate 1 at, for example, about 600 rpm, the high oxidizing processing liquid is prevented from flowing to the surface of the substrate 1, and the high oxidizing processing liquid is rotated around the surface of the substrate 1 by splashing. Even if it does, the surface of the substrate 1 is protected by the pure water film formed on the surface of the substrate 1.

The metal impurity concentration was measured by measuring an 8-inch substrate (a semiconductor wafer having copper (Cu) metal wiring formed on the surface of the substrate by CMP, also called Cu-CMP).
1 was prepared by attaching copper (Cu) or iron (Fe) to the specimens, and the cleaning times in the first to fourth processing steps were set to 20 seconds and 60 seconds, respectively. And the metal impurity concentration (a
toms / cm ² ) using a total reflection X-ray fluorescence spectrometer (TXR
It measured using F). Further, a first step A (treatment with an organic alkaline treatment liquid), a second step B (treatment with an organic acid treatment liquid), a third step C (treatment with a high oxidizing treatment liquid), and a fourth step D (Ultrasonic cleaning with pure water and drying) in this order.

The measurement results of the metal impurity concentration (vertical axis, atoms / cm ² ) remaining on the metal back surface after the treatment are shown in FIG.
In the case where a point (horizontal axis) of 10 mm from the edge part (horizontal axis) was measured at four points, that is, left, right, up and down, as shown in FIG. , Metal impurity concentration is acceptance standard (5.0E × 10)
Although present slightly, in the case of using the high oxidizing treatment liquid, as shown in FIG. 6B, the metal impurity concentration is clearly lower than the acceptance standard (5.0E × 10). .

Next, the processing effects of the substrate processing method according to the present invention will be described with reference to FIGS. 7 (a) and 7 (b). FIG. 7A is a diagram showing a processing effect on particles in the substrate processing method according to the present invention, wherein the horizontal axis indicates the cleaning time and the vertical axis indicates the number of particles. FIG.
(B) is a diagram showing a processing effect on metal impurities by the substrate processing method according to the present invention, in which the horizontal axis represents cleaning time and the vertical axis represents metal impurity concentration (atoms / cm ² ).

First, the effect of the substrate processing method according to the present invention on particles will be described with reference to FIG. The particles were measured by using at least 10,000 particles adhered to an 8-inch substrate (semiconductor wafer) as a sample, and the cleaning time in each of the first step A to the fourth processing step was measured. The treatment was carried out at 20 seconds and 60 seconds, and the number of particles of 0.2 μm or more in each cleaning time was measured using a laser reflection type surface foreign matter inspection device (SP1). FIG. 7A shows a first step A (treatment with an organic alkaline treatment liquid), a second step B (treatment with an organic acid treatment liquid), and a fourth step D (ultrasonic cleaning with pure water). (Drying) is sequentially processed in this order.

As shown in FIG. 7A, the initial value is 100
If the substrate to which 00 or more particles adhere is washed in each of the first step A to the fourth step D for at least 20 seconds, the number of particles is reduced to almost 0, and a high cleaning effect is obtained in a short time. Is obtained.

Next, the effect of the substrate processing method of the present invention on metal impurities will be described with reference to FIG. That is, the initial value is 1.0 × 10 ¹¹ (atom
s / cm ² ) or more, and copper (Cu) contamination having a concentration of 1.0 × 10 ¹² (atoms / cm ² ) or more, both in the first steps A to 4th
If washing is performed for at least 20 seconds in step D, it can be seen that the washing efficiency is reduced to the detection limit value (1.0 × 10 ¹⁰ (atoms / cm ² )) or less and a high washing effect can be obtained in a short time.

Comparative Example 1 Next, the organic alcohol according to the present invention was used.
For metal impurities when only potash solution is used alone
8 (a) and 8 (b) for the cleaning effect to be performed.
Will be explained. FIG. 8A shows an organic alcohol according to the present invention.
To prevent copper (Cu) contamination when the reconstituting solution is used alone
FIG. 8B is a diagram showing the processing effect of the present invention.
When the organic alkaline treatment solution is used alone
FIG. 3 is a view showing the effect of treatment on (Fe) contamination.
The horizontal axis represents the cleaning time, and the vertical axis represents the metal impurity concentration (atoms).
/ Cm ^Two).

The metal impurity concentration was measured with the substrate body (silicon (Si)) exposed (B in FIG. 8).
are described below) and two types of 8-inch substrates (semiconductor wafers) each having an oxide film (SiO ₂ ) formed on the substrate body (denoted as SiO _{2 in} FIG. 8).
u) (FIG. 8 (a)) or iron (Fe) (FIG. 8 (b)) is used as a sample, and the cleaning time is reduced to 20 seconds and 60 seconds using only an organic alkaline treatment solution. The processing is performed by setting, and the metal impurity concentration (a
toms / cm ² ) using a total reflection X-ray fluorescence spectrometer (TXR
It measured using F).

First, the treatment effect on copper (Cu) contamination when the organic alkaline treatment liquid according to the present invention is used alone will be described with reference to FIG. FIG.
As shown in (a), the initial value is 1.0 × 10 ¹² (ato
ms / cm ² ) or more,
Although the cleaning time tends to decrease as the cleaning time becomes longer, a sufficient cleaning effect is obtained particularly in the sample in which the substrate body (silicon (Si)) is exposed (denoted as Bare in FIG. 8). It turns out that it has not been obtained. In FIGS. 8A and 8B, the D.D. L indicates that the value was below the detection level (Detection Level).

On the other hand, the treatment effect on iron (Fe) contamination when the organic alkaline treatment liquid according to the present invention is used alone will be described with reference to FIG. FIG.
As shown in (b), the initial value is 1.0 × 10 ¹¹ (ato
ms / cm ² ) or more,
Although the cleaning time tends to decrease as the cleaning time becomes longer, it is particularly sufficient for a specimen in which an oxide film (SiO ₂ ) is formed on the substrate body (denoted as SiO _{2 in} FIG. 8). It can be seen that the cleaning effect was not obtained.

Therefore, it can be seen that the use of the organic alkaline treating solution according to the present invention alone alone does not provide a sufficient cleaning effect especially for metal impurities.

(Comparative Example 2) Next, regarding the treatment effect on particles when the organic acid treatment solution, organic alkaline treatment solution and pure water according to the present invention were used alone,
This will be described with reference to FIG. FIG. 9 is a diagram showing the processing effect on particles when the organic acidic processing liquid, organic alkaline processing liquid and pure water according to the present invention are used alone. The particles were measured by using an organic acid treatment solution, an organic alkali treatment solution, and pure water according to the present invention on a sample in which at least 10,000 particles were adhered to an 8-inch substrate (semiconductor wafer). After treating with the cleaning time set to 20 seconds, the number of particles of 0.2 μm or more was measured using a laser reflection type surface foreign matter inspection device (SP1).

As shown in FIG. 9, although the organic alkaline treatment liquid according to the present invention has a certain effect on particles even when used alone, the organic acid treatment liquid according to the present invention and pure water It can be seen that the use of only A alone does not provide a sufficient cleaning effect particularly on particles.

That is, (Comparative Example 1) and (Comparative Example 2)
As is evident from the above, the substrate 1 cannot be washed with a high degree of cleanliness by using only one of the organic alkaline treatment liquid and the organic acid treatment liquid according to the present invention alone,
First, in a first step A, the substrate 1 is treated using an organic alkaline treatment liquid (or an organic acid treatment liquid), and then in a second step B, the substrate 1 is treated with an organic acid treatment liquid (or an organic alkaline treatment liquid). It can be seen that the substrate processing method of the present invention in which processing is performed on the substrate 1 that has been processed in the first step A is effective in improving the cleaning effect of the substrate 1.

In particular, the organic alkaline treatment liquid and the organic acid treatment liquid according to the present invention have no corrosiveness to metals (eg, copper (Cu), tungsten (W), aluminum (Al), etc.) and stabilize metal impurities. Since a complexing agent such as a chelating agent that can be trapped as a water-soluble complex is contained, the metal wiring formed by being exposed on the surface of the substrate 1 is not corroded. Accordingly, particles and metal impurities attached to the surface of the substrate 1 can be removed with high efficiency.

Furthermore, in the substrate processing method according to the present invention, in the fourth step D, the substrate 1 is subjected to finish cleaning by ultrasonic waves, so that the dishing 55 or the step 56 generated in the metal wiring 51 of the substrate 1 is performed. A high cleaning effect can be obtained even for particles and metal impurities adsorbed in the substrate 1 (see FIG. 10). If the first step A to the fourth step D are performed consistently, the substrate 1 can be cleaned. The degree can be further improved.

[0133]

As described above, according to the present invention, the metal wiring or the like formed in a state where the metal material is exposed on the surface of the substrate 1 does not corrode, and the metal impurity ions adhere to the surface of the substrate 1. In addition to improving the cleanliness of the substrate 1 by reliably removing particles and metal impurities adhered to the dents and steps formed in the metal wiring, the contamination adhered to the back surface of the substrate 1 can be prevented. It is possible to provide a substrate processing method capable of completely removing a substance without affecting the surface of the substrate 1 at all.

[Brief description of the drawings]

FIG. 1 is a flowchart showing steps of a substrate processing method according to the present invention.

FIG. 2 is a diagram showing processing steps of a substrate processing method according to the present invention.

FIG. 3 is a perspective view showing a substrate cleaning apparatus used in the substrate processing method according to the present invention.

FIG. 4 is a cross-sectional view of a rotary cleaning apparatus used in the substrate processing method according to the present invention as viewed from the front.

FIG. 5 is a sectional view of the ultrasonic cleaning apparatus used in the substrate processing method according to the present invention as viewed from the front.

FIG. 6 (a) is a diagram showing a treatment effect on metal contamination when the high oxidizing solution according to the present invention is not used, and FIG. 6 (b) is a diagram when the high oxidizing solution according to the present invention is used. 5 is a diagram showing the effect of treatment on metal contamination, in which the horizontal axis represents the measurement position 10 mm from the edge, and the vertical axis represents the metal impurity concentration (atoms / cm ² ).

FIG. 7A is a diagram showing a processing effect on particles by the substrate processing method according to the present invention, in which the horizontal axis represents the cleaning time and the vertical axis represents the number of particles. (B) is a diagram showing a processing effect on metal impurities by the substrate processing method according to the present invention, in which the horizontal axis represents cleaning time and the vertical axis represents metal impurity concentration (atoms / cm ² ).

FIG. 8 (a) is a diagram showing a treatment effect on copper (Cu) contamination when the organic alkaline treatment liquid according to the present invention is used alone, and FIG. 8 (b) is a graph showing the organic alkaline treatment liquid according to the present invention alone. It is a figure which shows the processing effect with respect to iron (Fe) contamination at the time of using, a horizontal axis shows a cleaning time, and a vertical axis | shaft shows metal impurity concentration (atoms / cm <2>).

FIG. 9 is a diagram showing a treatment effect on particles when each of the organic acid treatment solution, the organic alkaline treatment solution and pure water according to the present invention is used alone.

FIG. 10 is a cross-sectional view schematically showing a state in which dishing has occurred on a semiconductor wafer as a substrate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate (semiconductor wafer) 2 Substrate cleaning device 3a, 3b Rotary brush 5a Shaft 5b Brush 5c Projection 6a-6e Holding roller 7 Drive roller 8a Roller member 8b Stepped portion 8c Shaft member 9 Cleaning fluid supply nozzle 12 Super Sonic cleaning device 13 Holder (fixing means) 13a Convex part (fixing means) 13b Holding pin (fixing means) 14 Chuck member (fixing means) 15 Shaft member 17 Cleaning fluid ejection nozzle (ultrasonic nozzle) 19 (substrate transfer device) ) Claw portion 23 discharge duct 24a cleaning fluid supply path 24b back surface cleaning fluid ejection port 51 metal wiring 52 barrier film 53 interlayer insulating film 55 dishing 56 step portion 90 cleaning fluid supply nozzle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/304 651 H01L 21/304 651B B08B 3/02 B08B 3/02 B 3/08 3/08 Z 3 / 12 3/12 A H01L 21/308 H01L 21/308 G (72) Inventor Osamu Takahashi 3-1-5 Sakaemachi, Hamura-shi, Tokyo F-term inside Kaijo Co., Ltd. 3B201 AA03 AB01 AB34 AB42 BA02 BA15 BB22 BB83 BB92 BB93 BB94 BB95 BB96 CC01 CC12 CC13 5F043 BB27 DD16 DD19 GG10

Claims (18)

[Claims] A substrate for performing a chemical mechanical polishing process by supplying a polishing liquid to a substrate having a metal wiring with a metal material exposed on the surface, and processing the substrate after the chemical mechanical polishing process A processing method, wherein an organic alkali that is non-reactive with respect to the metal material and a complexing agent that forms a complex with a metal contained in the polishing liquid and particles of the metal material are treated with an organic alkaline processing liquid. A first step of cleaning the substrate; and after the first step, a complex is formed with an organic acid that is non-reactive with the metal material and a metal contained in the metal material particles and the polishing liquid. A second step of cleaning the substrate with an organic acidic treatment liquid containing a complexing agent, and after the second step, forming a liquid film by supplying pure water to the surface of the substrate having the metal wiring. High oxidation to remove contaminants on the back of the substrate And a third step of supplying a force treatment liquid and performing cleaning while rotating. 2. The substrate processing method according to claim 1, further comprising a fourth step of cleaning the substrate with an ultrasonic cleaning fluid excited by ultrasonic waves after the third step. 3. The substrate processing method according to claim 2, wherein the ultrasonic cleaning fluid is pure water. 4. The substrate processing method according to claim 2, wherein the fourth step includes a step of cleaning the substrate with an ultrasonic cleaning fluid and then rotating the substrate at a high speed to dry the substrate. . 5. The high oxidizing treatment liquid includes hydrofluoric acid / hydrogen peroxide solution (FPM), sulfuric acid / hydrogen peroxide solution (SPM), hydrochloric acid / hydrogen peroxide solution (HPM), buffered hydrofluoric acid / hydrofluoric acid. Ammonium fluoride (BHF), hydrofluoric / nitric acid (HF / HNO)
₃₎ The substrate processing method as claimed in any one of claims 1 to 4, characterized in that at least one or more of the cleaning solution selected from the group consisting of hydrofluoric acid ozone (HF / O _3). 6. The substrate processing method according to claim 1, wherein said metal material is copper, tungsten, or aluminum. 7. The substrate processing method according to claim 1, wherein the organic alkali is a quaternary ammonium salt and / or an organic amine. 8. The substrate processing method according to claim 1, wherein an alcohol is added to the organic alkali. 9. The method according to claim 8, wherein the alcohol is present in an amount of 0.005% to 10%.
The substrate processing method according to claim 8, wherein the substrate is isopropyl alcohol (IPA) having a concentration of 100%. 10. The quaternary ammonium salt is a group consisting of tetramethylammonium hydroxide (TMAH), trimethyl-2-hydroxyethylammonium hydroxide (TMAH), and trimethyl-2-hydroxyethylammonium hydroxide (choline). The substrate processing method according to claim 7, wherein the compound is at least one compound selected from the group consisting of: 11. The method according to claim 7, wherein the organic amine is at least one compound selected from the group consisting of trimethylamine, triethanolamine, ethylenediamine, guanidine, and toluidine. 12. The complexing agent contained in the organic alkaline treatment liquid has a fluoride ion and a cyclic skeleton in its molecular structure.
And OH groups and / or O bonded to the carbon atom of the ring ^- of claims 1 to 11, characterized in that at least one or more substances selected from the group consisting of compounds having 1 or more groups The substrate processing method according to any one of the above. 13. The organic alkaline processing liquid contains a second complexing agent having a metal ligand, wherein the second complexing agent is a compound having a donor atom, sulfur or carbon, and a donor atom. The compound having at least one selected from the group consisting of a compound having a nitrogen, a compound having a carboxyl group as a metal coordinating group, and a compound having a carbonyl group as a metal coordinating group. Item 13. The substrate processing method according to any one of Items 12. 14. The organic acid is a carboxylic acid that forms a complex with the oxide particles of the metal material, wherein the carboxylic acid is oxalic acid, citric acid, malic acid, maleic acid, succinic acid, tartaric acid, The compound according to claim 1, wherein the compound is at least one compound selected from the group consisting of malonic acid and salts thereof.
The substrate processing method according. 15. The substrate processing method according to claim 1, wherein an additive such as a surfactant is added to the organic acid. 16. The substrate processing method according to claim 15, wherein the additive is an anionic or a cationic. 17. The complexing agent contained in the organic acid treatment solution,
17. The substrate processing method according to claim 1, wherein the substrate is a polyaminocarboxylic acid and / or ammonium fluoride. 18. The polyaminocarboxylic acids are ethylenediaminetetraacetic acid (EDTA), trans-1,2-
Cyclohexanediaminetetraacetic acid (CyDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), N- (2-hydroxyethyl) ethylenediamine-N, N ', N'-triacetic acid (EDTA-O
18. The method according to claim 17, wherein the method is at least one compound selected from the group consisting of H) and salts thereof.