KR102612431B1 - Pattern forming material for semiconductor device manufacturing - Google Patents

Abstract

The present invention relates to a photosensitive polymer and resist composition containing a repeating unit derived from a styrene-vinylphosphonic acid copolymer compound as shown in the following formula (1).
[Formula 1]

Description

Pattern forming material for semiconductor device manufacturing}

The present invention relates to a pattern forming material for manufacturing semiconductor devices, and more specifically, to a photosensitive polymer having excellent adhesion properties to the underlying film and dry etching resistance during pattern formation, and a resist composition containing the photosensitive polymer. .

As semiconductor manufacturing processes become more complex and the degree of integration of semiconductor devices increases, fine pattern formation is required. As for resist materials, resist materials using ArF excimer lasers (193 nm), which use shorter wavelengths, have come to be used rather than resist materials using existing KrF excimer lasers (248 nm).

However, in semiconductor devices with a capacity of 16 gigabit or more, as the design rule requires a pattern size of 70 nm or less, the thickness of the resist film becomes increasingly smaller and the process margin in the process of etching the lower film material increases. As this decreases, limitations are increasingly emerging in the use of resist materials using ArF excimer lasers.

Resist materials used in lithography using ArF excimer lasers have many problems compared to existing resist materials for commercialization. The most representative problem is the resistance of photosensitive resin to dry etching.

As conventional ArF resists known so far, acrylic or methacrylic polymers have been mainly used. Among them, poly(methacrylate)-based polymer materials were most commonly used. A serious problem with these polymers is that their resistance to dry etching is very poor. In other words, the selectivity of these materials is too low in the dry etching process using plasma gas during the semiconductor device manufacturing process, making it difficult to proceed with the etching process.

Accordingly, in order to increase the resistance to dry etching, alicyclic compounds, which are materials with strong resistance to dry etching, such as isobornyl group, adamantyl group, and tricyclo A method of introducing a decanyl group (tricyclodecanyl group) as a substituent to the polymer was used. However, in order to satisfy the photosensitive resin requirements for satisfying the characteristics of the resist material, solubility in the developer and adhesion to the underlying film, the polymer form mainly has a structure higher than a triple copolymer (terpolymer), and among them, alicyclic Since the tableware occupies a small portion, the resistance to dry etching is still weak. Additionally, since alicyclic compounds are hydrophobic, if the triple copolymer structure as above contains a large amount of alicyclic compounds, the adhesion characteristics to the underlying layer of the resist film deteriorate.

As another conventional polymer, COMA (cycloolefin-maleic anhydride) alternating polymer has been proposed. In the production of COMA-type copolymers, the manufacturing cost of raw materials is low, but there are still problems in terms of synthesis yield and resolution during polymer production.

In addition, polymers synthesized with the above structure have a very hydrophobic alicyclic group as a backbone, and therefore have poor adhesion properties to membrane materials. In addition, above all, the COMA type photosensitive resin has a disadvantage in that it has a storage stability problem of the resist composition.

KR 10-2013-0004905

The present invention seeks to provide a photosensitive polymer using a styrene-vinyl phosphonic acid copolymer compound that is inexpensive to manufacture and has excellent dry etching resistance and adhesion properties to the underlying film.

The present invention also seeks to provide a resist composition that can provide excellent lithography performance even in lithography processes using light sources in extreme wavelength regions such as 248 nm, 193 nm, and EUV (13.5 nm) using the photosensitive polymer.

In addition, the present invention seeks to provide the photosensitive polymer and resist composition as a material for forming patterns for manufacturing semiconductor devices.

However, the technical problems to be achieved by the present invention are not limited to the problems mentioned above, and other technical problems will be clearly understood by those skilled in the art from the description below.

In order to achieve the above object, according to one embodiment of the present invention, a photosensitive polymer containing a repeating unit derived from a styrene-vinyl phosphonic acid copolymer is provided.

According to another embodiment of the present invention, a resist composition containing the photosensitive polymer is provided.

According to another embodiment of the present invention, a pattern forming material for manufacturing a semiconductor device including the photosensitive polymer and resist composition is provided.

Specific details of other embodiments of the present invention are included in the detailed description below.

Using the styrene-vinyl phosphonic acid copolymer according to the present invention, photosensitive polymer and chemically amplified resist compositions with excellent adhesion properties to film materials and dry etching resistance can be easily manufactured.

Therefore, the resist composition obtained from the photosensitive polymer according to the present invention has very excellent dry etching properties compared to existing resist materials for KrF and ArF, and can be very useful in manufacturing next-generation semiconductor devices in the future.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

Unless otherwise specified herein, “alkyl” refers to a C1 to C20 alkyl group, more preferably a C1 to C12 alkyl group, “lower alkyl” refers to a C1 to C4 alkyl group, and “alkoxy” refers to a C1 to C4 alkyl group. “Alkylene” refers to a C1 to C20 alkoxy group, more preferably a C1 to C12 alkoxy group, “alkylene” refers to a C1 to C20 alkylene group, more preferably a C1 to C12 alkylene group, and “aryl” refers to a C1 to C20 alkylene group. " means a C6 to C20 aryl group, more preferably a C6 to C12 aryl group, and "cycloalkyl" refers to a C3 to C14 cycloalkyl group.

The styrene-vinyl phosphonic acid copolymer according to one embodiment of the present invention has the structure of Formula 1 below.

[Formula 1]

In the above formula, R1 and R2 are hydrogen, hydroxy, alkoxy, halogen, nitrile, a C1~C20 alkyl group, or a C4~C20 cycloalkyl group. R1 and R2 may be the same or different from each other, and preferably include hydrogen, hydroxy group, fluorine, methyl group, methoxy, etc.

The styrene-vinyl phosphonic acid copolymer compound can be easily synthesized into a photosensitive copolymer by radical polymerization with (meth)acrylic monomers having various functional substituents.

Photosensitive copolymers prepared by the above method have etching resistance to dry etching, have excellent adhesion characteristics to the underlying film, and are very advantageous in forming resist patterns. As a result, it can overcome the shortcomings of existing KrF or ArF resist materials in terms of dry etching resistance and serve as a sufficient etch mask even in semiconductor devices that require higher resolution.

The photosensitive polymer further includes a repeating unit made of a styrene-vinylphosphonic acid copolymer and a repeating unit derived from the compounds of formulas 2 and 3 below.

[Formula 2] [Formula 3]

In the above formula, R3 and R5 are each independently hydrogen or a methyl group,

R4 is a C4 to C20 acid-labile group or a lactone derivative that decomposes in the presence of an acid catalyst.

The acid-decomposable group is preferably norbornyl, isobornyl, cyclodecanyl, adamantyl, norbornyl substituted with a lower alkyl group, isobornyl substituted with a lower alkyl group, cyclodecanyl substituted with a lower alkyl group, Substituted adamantyl, alkoxycarbonyl, alkoxycarbonylalkyl, amyloxycarbonyl, amyloxycarbonylalkyl, 2-tetrahydropyranyloxycarbonylalkyl, 2-tetrahydrofuranyloxycarbonylalkyl, tertiary It is selected from the group consisting of an alkyl group and an acetal group, more preferably 2-methyl-2-norbornyl, 2-ethyl-2-norbornyl, 2-methyl-2-isobornyl, and 2-ethyl-2-isobornyl. , 8-methyl-8-tricyclodecanyl, 8-ethyl-8-tricyclodecanyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, 2-propyl-2-ah Damantyl, t-butoxycarbonyl, t-butoxycarbonylmethyl, t-amyloxycarbonyl, t-amyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyranyloxy Selected from the group consisting of carbonylalkyl, 2-tetrahydrofuranyloxycarbonylalkyl, t-butyl group, triethylcarbyl group, 1-methyl cyclohexyl group, 1-ethylcyclopentyl group, t-amyl group, and acetal group. You can hear what happens.

In addition, the lactone derivative includes a lactone derivative group, preferably a substituent group having the structures of the following formulas 4 and 5.

[Formula 4] [Formula 5]

In Formula 4, two of X1 to am.

In the above formula (5), two of X5 to This is; All of X5 to

More preferably R4 is butyrolactonyl, valerolactonyl, 1,3-cyclohexanecarbolactonyl, 2,6-norbonanecarbolacton-5-yl, and 7-oxa-2,6-nor. is selected from the group consisting of bonancarbolactone-5-yl.

R6 is hydrogen; Or, it is an alkyl group or cycloalkyl group containing a polar group selected from the group consisting of a hydroxy group, a carboxyl group, and a combination thereof. The alkyl group is a C2 to C14 alkyl group, and the cycloalkyl group is a C3 to C14 cycloalkyl group. Preferred examples include 2-hydroxyethyl and 3-hydroxy-1-adamantyl.

That is, the photosensitive polymer has the form of a random copolymer of the compound of Formula 1 and the compounds of Formulas 2 and 3. Preferably, the photosensitive polymer has a weight average molecular weight (Mw) of 3,000 to 30,000. More preferably, it has a weight average molecular weight (Mw) of 5,000 to 20,000.

In addition, the photosensitive polymer preferably has a dispersion degree (Mw/Mn) of 1.5 to 2.5. Within the above range, excellent etching resistance and resolution can be achieved.

The photosensitive polymers according to the present invention are in the form of copolymers obtained from a styrene-vinyl phosphonic acid compound with a new functionality. It is possible to obtain a resist composition with excellent dry etching resistance and adhesion characteristics to the underlying film compared to existing resist materials. It has advantages.

When the resist composition obtained from this is applied to a photo lithography process, very excellent lithography performance can be obtained.

According to another embodiment of the present invention, a resist composition containing the photosensitive polymer is provided.

Specifically, the resist composition includes (a) the photosensitive polymer, (b) a photoacid generator (PAG), and (c) a solvent.

Hereinafter, each component included in the resist composition according to one embodiment of the present invention will be examined in detail.

(a) Photosensitive polymer

The photosensitive polymer is the same as previously described. Here, the photosensitive polymer is preferably included in an amount of 5 to 50 parts by weight based on 100 parts by weight of the resist composition.

When included in the resist composition in the above content range, excellent etching resistance and adhesion characteristics can be obtained.

(b) Photoacid generator (PAG)

The photoacid generator may be selected from the group consisting of inorganic onium salts, organic sulfonates, and mixtures thereof. Specifically, a sulfonium salt or iodonium salt selected from triarylsulfonium salts, diaryliodonium salts, sulfonates, or mixtures thereof may be used. More preferably, triarylsulfonium triflate, diaryliodonium triflate, triarylsulfonium nonaplate, diaryliodonium nonaplate, succinimidyl triflate, 2,6-dinitrobenzyl sulfonate. and mixtures thereof.

The photoacid generator is preferably included in an amount of 1 to 10 parts by weight based on 100 parts by weight of the photosensitive polymer. If the content of the photoacid generator is less than 1 part by weight, there is a risk that the exposure amount to the resist composition may be excessively increased, and if it exceeds 10 parts by weight, there may be a problem of insufficient transmittance of the resist composition.

(c) solvent

The solvents include propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), ethyl lactate (EL), cyclohexanone, 2-heptanone, and gamma-butyro. One or more types may be selected and used from the group consisting of lactones (GBL) and the like.

The solvent is included as a remaining component in the resist composition and its content is not particularly limited, but is preferably included in an amount of 50 to 95 parts by weight based on 100 parts by weight of the resist composition.

(d) acid quencher

In addition to the components (a) to (c), the resist composition may further include an organic base for the purpose of controlling exposure dose and forming a resist profile.

The organic base is mainly in the form of a trivalent amine, for example, an amine-based compound selected from triethylamine, triisobutylamine, trioctylamine, triisodecylamine, triethanolamine, or mixtures thereof may be used. You can.

The content of the organic base is preferably 0.01 to 1 part by weight based on 100 parts by weight of the photosensitive polymer. If the content of the organic base is less than 0.01 parts by weight, the desired effect cannot be expected, and if it exceeds 1 part by weight, the exposure amount may be excessively increased, and in severe cases, there may be a problem in which pattern formation is not possible.

The following process is used to form a desired pattern using a resist composition having the above composition.

Prepare a bare silicon wafer or a silicon wafer on which a lower layer such as a silicon oxide film, silicon nitride film, or silicon oxynitride film is formed on the upper surface, and the silicon wafer is treated with HMDS treatment or an organic anti-reflection film. Thereafter, the resist composition is coated on the silicon wafer to a thickness of approximately 100 to 500 nm to form a resist film.

The silicon wafer on which the resist film is formed is prebaked (SB) for about 60 to 120 seconds at a temperature range of about 90 to 150° C. to remove the solvent, and then exposed to various exposure light sources such as KrF, ArF, and extreme UV (EUV). ), or after exposure using an E-beam, etc., post-exposure baking (PEB) is performed for about 60 to 120 seconds at a temperature range of about 90 to 120°C to cause a chemical reaction in the exposed area of the resist film. do.

Then, the resist film is developed with a 2.38 wt% tetramethylammonium hydroxide (TMAH) solution. At this time, the exposed area shows very high solubility in a basic aqueous developer solution, so it is easily dissolved and removed during development. When the exposure source used is an ArF excimer laser, a line and space pattern of 80 to 100 nm can be formed at a dose of about 5 to 30 mJ/cm2.

The resist pattern obtained from the process described above is used as a mask, and the lower film material, such as a silicon oxide film, is etched using a specific etching gas, such as plasma such as halogen gas or CxFy gas. Subsequently, the resist pattern remaining on the wafer can be removed using a stripper to form a desired silicon oxide film pattern.

The present invention will be described in more detail with reference to examples below. However, the following examples are only preferred examples of the present invention and the present invention is not limited to the following examples.

Example-1) Synthesis of photosensitive polymer

Styrene (10 mmol), vinylphosphonic acid (10 mmol), t-butyl methacrylate (40 mmol), and γ-butyrolactonyl methacrylate (GBLMA) (40 mmol) were placed in a round flask and dissolved in dioxane solvent (monomer total). 3 times the weight), BPO (2% of monomer concentration) was added as a polymerization initiator, purged with nitrogen for about 20 minutes, and then polymerized at 80°C for about 20 hours.

After polymerization was completed, the reactant was slowly precipitated in an excess of methanol/water co-solvent, the resulting precipitate was filtered, and then the precipitate was dissolved in an appropriate amount of THF and reprecipitated in the methanol/water co-solvent. Afterwards, the obtained precipitate was dried in a vacuum oven at 80°C for about 24 hours to synthesize a polymer (yield: 80%).

The weight average molecular weight (Mw) of the synthesized polymer was 15,100, and the dispersion degree (Mw/Mn) was 1.7.

Example-2) Synthesis of photosensitive polymer

Styrene (20 mmol), vinylphosphonic acid (10 mmol), t-butyl methacrylate (40 mmol), and 3-hydroxy-1-adamantyl methacrylate (HAMA) (30 mmol) were prepared in Example-1) The polymer was synthesized by polymerization in the same manner as above (yield: 75%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 14,600, and the dispersion degree (Mw/Mn) was 1.7.

Example-3) Synthesis of photosensitive polymer

A polymer was synthesized by polymerizing styrene (20 mmol), vinylphosphonic acid (10 mmol), t-butyl methacrylate (40 mmol), and isobornyl acrylate (30 mmol) in the same manner as Example-1) (yield : 75%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 15,500, and the dispersion degree (Mw/Mn) was 1.7.

Example-4) Synthesis of photosensitive polymer

4-Fluorostyrene (20 mmol), vinylphosphonic acid (10 mmol), t-butyl methacrylate (40 mmol), and γ-butyrolactonyl methacrylate (30 mmol) were prepared in the same manner as in Example-1). The polymer was synthesized by polymerization (yield: 75%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 14,500, and the dispersion degree (Mw/Mn) was 1.8.

Example-5) Synthesis of photosensitive polymer

4-methylstyrene (20 mmol), vinylphosphonic acid (10 mmol), t-butyl methacrylate (40 mmol), and 3-hydroxy-1-adamantyl methacrylate (HAMA) (30 mmol) were used as examples. A polymer was synthesized by polymerization in the same manner as in -1) (yield: 75%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 14,800, and the dispersion degree (Mw/Mn) was 1.7.

Example-6) Synthesis of photosensitive polymer

4-hydroxystyrene (10 mmol), vinylphosphonic acid (10 mmol), γ-butyrolactonyl methacrylate (40 mmol), and 2-ethyl-2-adamantyl methacrylate (EAMA) (40 mmol) A polymer was synthesized by polymerization in the same manner as in Example-1) (yield: 70%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 14,600, and the dispersion degree (Mw/Mn) was 1.7.

Example-7) Synthesis of photosensitive polymer

4-methoxystyrene (10 mmol), vinylphosphonic acid (10 mmol), γ-butyrolactonyl methacrylate (40 mmol), and 2-methyl-2-adamantyl methacrylate (MAMA) (40 mmol) A polymer was synthesized by polymerization in the same manner as in Example-1) (yield: 75%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 14,800, and the dispersion degree (Mw/Mn) was 1.7.

Example-8) Synthesis of photosensitive polymer

Styrene (10 mmol), vinylphosphonic acid (10 mmol), γ-butyrolactonyl methacrylate (40 mmol), and 2-methyl-2-adamantyl methacrylate (40 mmol) were prepared in Example-1) and A polymer was synthesized by polymerization using the same method (yield: 70%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 16,100, and the dispersion degree (Mw/Mn) was 1.7.

Example-9) Synthesis of photosensitive polymer

Styrene (30 mmol), vinylphosphonic acid (5 mmol), 2-hydroxyethyl methacrylate (25 mmol), and 2-ethyl-2-adamantyl methacrylate (40 mmol) were prepared in Example-1) and A polymer was synthesized by polymerization using the same method (yield: 75%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 15,100, and the dispersion degree (Mw/Mn) was 1.7.

Comparative Example) Synthesis of photosensitive polymer

t-Butyl methacrylate (40 mmol), γ-butyrolactonyl methacrylate (GBLMA) (40 mmol), and 3-hydroxy-1-adamantyl methacrylate (HAMA) (20 mmol) were prepared in Example- A polymer was synthesized by polymerization in the same manner as in 1) (yield: 80%).

At this time, the weight average molecular weight (Mw) of the obtained polymer was 15,900, and the dispersion degree (Mw/Mn) was 1.7.

Example-10) Preparation and lithography performance of resist composition

Each photosensitive polymer (1 g) synthesized in Examples 1 to 9 and Comparative Examples was dissolved in PGMEA/EL (6/4) (17 g) together with triphenylsulfonium nonaplate (0.02 g), Triethanolamine (1 mg), an organic base, was added and completely dissolved to prepare each resist composition.

Example-11) Resist resolution evaluation

Each resist solution prepared in Example-10) was filtered using a 0.1㎛ membrane filter. The filtered resist solution was coated to a thickness of 140 nm on an organic BARC (AR46, Rhom & Hass Company) 600 Å thick treated silicon wafer, and then pre-baked (soft baking: SB) at a temperature of 130 degrees for 60 seconds.

After exposure at 20~50mj/cm2 using an ArF scanner (0.78NA, dipole), PEB (post-exposure bake) was performed at 110 degrees for 60 seconds, and then developed in a 2.38% by weight TMAH solution for 60 seconds. As a result, a clean 90~100nm L/S pattern result was obtained as shown in Table-1 below, and it was confirmed that the resolution was superior to that of the comparative example polymer.

polymer type Exposure energy (Eop) resolution Example 1 30mJ/cm2 90nm Example 2 30mJ/cm2 90nm Example 3 30mJ/cm2 90nm Example 4 30mJ/cm2 90 nm Example 5 30mJ/cm2 100nm Example 6 30mJ/cm2 100nm Example 7 30mJ/cm2 100nm Example 8 30mJ/cm2 100nm Example 9 30mJ/cm2 100nm Comparative Example 30mJ/cm2 120 nm

Example-12) Etch resistance evaluation

In order to evaluate the etching characteristics of each resist composition prepared in Example-10), bulk etching (composition; power 100W, pressure 5Pa, flow rate 30ml/min) was performed using RIE (reactive ion etching) under CF4 gas (composition; power 100W, pressure 5Pa, flow rate 30ml/min) bulk etch) evaluation was conducted. At this time, the reference used was normalized and evaluated based on the etching rate of polyhydroxystyrene (PHS) polymer, which is a resist for KrF. The measurement results are shown in Table-2, and the polymer of the present invention shows an etching rate of about 1.1 times (normalized) compared to the polymer for KrF, and the polymer of the comparative example shows an etching rate of about 1.5 times. It was confirmed that the polymers of the present invention have very strong etch resistance.

polymer type PHS (normalized) Etch rate (%) Example 1 100% 110 Example 2 100% 108 Example 3 100% 108 Example 4 100% 110 Example 5 100% 105 Example 6 100% 108 Example 7 100% 105 Example 8 100% 103 Example 9 100% 103 Comparative Example 100% 150

Above, the present invention has been described in detail with preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made by those skilled in the art within the scope of the technical idea of the present invention. possible.

Claims (11)

delete A photosensitive polymer comprising repeating units derived from compounds of Formula 1, Formula 2, and Formula 3 below.
[Formula 1] [Formula 2] [Formula 3]

In Formula 1, R1 and R2 are hydrogen, hydroxy, alkoxy, halogen, nitrile, a C1-C20 alkyl group, or a C4-C20 cycloalkyl group. R1 and R2 may be the same or different from each other.
In Formulas 2 and 3, R3 and R5 are hydrogen or a methyl group, R4 is an acid-labile group or a lactone derivative of C4 to C20 that decomposes in the presence of an acid catalyst, and R6 is hydrogen. ; It is an alkyl group or cycloalkyl group containing a polar group selected from the group consisting of a hydroxy group, a carboxyl group, and a combination thereof. R7 is hydrogen; Or, it is an alkyl group or cycloalkyl group containing a polar group selected from the group consisting of a hydroxy group, a carboxyl group, a sulphonyl group, and a combination thereof.
The method of claim 2, wherein the acid-decomposable group is norbornyl, isobornyl, cyclodecanyl, adamantyl, norbornyl substituted with a lower alkyl group, isobornyl substituted with a lower alkyl group, cyclodecanyl substituted with a lower alkyl group, or lower alkyl group. Adamantyl, alkoxycarbonyl, alkoxycarbonylalkyl, amyloxycarbonyl, amyloxycarbonylalkyl, 2-tetrahydropyranyloxycarbonylalkyl, 2-tetrahydrofuranyloxycarbonylalkyl, substituted with alkyl group, A photosensitive polymer, characterized in that it is selected from the group consisting of a tertiary alkyl group and an acetal group.
The photosensitive polymer according to claim 2, wherein the lactone derivative is a substituent having the structure of Formula 4 or 5 below.


[Formula 4] [Formula 5]

In the above formulas 4 and 5, two of X1 to is an alkylene), and two of X5 to Renim) or; All of X5 to
The photosensitive polymer of claim 2, wherein the photosensitive polymer has a weight average molecular weight (Mw) of 3,000 to 30,000.
(a) the photosensitive polymer according to any one of claims 2 to 5;
(b) photoacid generator (PAG); and
(c) A resist composition containing an organic solvent. The resist composition according to claim 6, wherein the photosensitive polymer is contained in an amount of 5 to 50 parts by weight based on 100 parts by weight of the resist composition.
The resist composition according to claim 6, wherein the photoacid generator is contained in an amount of 1 to 10 parts by weight based on 100 parts by weight of the photosensitive polymer.
The method of claim 6, wherein the photoacid generator is any one selected from the group consisting of triarylsulfonium salts, diaryliodonium salts, sulfonates, and mixtures thereof. Resist composition.
The resist composition according to claim 6, wherein the composition further contains an organic base in an amount of 0.01 to 1.0 parts by weight based on 100 parts by weight of the photosensitive polymer.
11. The resist composition of claim 10, wherein the organic base is selected from the group consisting of triethylamine, triisobutylamine, trioctylamine, triisodecylamine, triethanolamine, and mixtures thereof.