WO2021106580A1

WO2021106580A1 - Chemical solution for forming protective film, and method for cleaning wafer

Info

Publication number: WO2021106580A1
Application number: PCT/JP2020/042146
Authority: WO
Inventors: 貴陽照井; 公文　創一
Original assignee: セントラル硝子株式会社
Priority date: 2019-11-29
Filing date: 2020-11-11
Publication date: 2021-06-03
Also published as: CN114762087A; KR20220106131A; JPWO2021106580A1; TW202130756A

Abstract

The present invention provides a chemical solution for forming a protective film, said chemical solution being used for a surface treatment of a wafer that has, in the surface, a recessed and projected pattern, at least a part of which contains at least one element selected from the group consisting of elemental silicon and metal elements, wherein: a protective film-forming agent and a solvent having a fluorine atom are contained therein; and the protective film-forming agent is a specific compound. The present invention also provides a method for cleaning a wafer.

Description

Cleaning method for protective film forming chemicals and wafers

The present disclosure relates to a method for manufacturing a wafer having a fine concavo-convex pattern, a method for preventing the concavo-convex pattern from collapsing during cleaning of the wafer, a chemical solution used in the method, and a method for cleaning the wafer.

In semiconductor devices for networks and digital home appliances, circuit patterns are being miniaturized in order to achieve higher performance, higher functionality, and lower power consumption. In the manufacturing process of semiconductor devices, a cleaning process for the purpose of removing particles and metal impurities occupies a large part, but in the cleaning process, unevenness constituting a circuit pattern accompanying miniaturization as described above (hereinafter, "" When the aspect ratio of (sometimes referred to as "concavo-convex pattern") is high, the phenomenon that the pattern collapses when the gas-liquid interface passes through the concavo-convex pattern after washing or rinsing (hereinafter referred to as pattern collapse) becomes remarkable. become. Since the design of the uneven pattern has to be changed in order to prevent the pattern from collapsing, and the yield at the time of production is lowered, a method for preventing the pattern from collapsing in the cleaning process is desired. ..

Since the pattern collapse occurs when the wafer on which the circuit pattern is formed is pulled up from the cleaning liquid or the rinsing liquid, it is considered that the capillary force of the cleaning liquid or the rinsing liquid in the pattern gap is the cause. The magnitude of the capillary force generated in the pattern gap is the absolute value of P obtained by the formula shown below, and it is expected that if γ or cosθ is reduced from this formula, the capillary force can be reduced and the pattern collapse can be suppressed. Will be done.
P = 2 × γ × cos θ / S (γ: surface tension, θ: contact angle, S: pattern size)

For example, Patent Document 1 proposes a pattern structure treatment method in which a treatment liquid containing a fluorine-based polymer having a repeating unit containing a fluorine atom is applied to a pattern structure composed of an inorganic material. The document discloses that the fluoropolymer is more likely to adhere to the pattern structure, especially when a cationic fluoropolymer is used. Further, in the examples of the document, it is disclosed that the treatment liquid containing a fluorine-based polymer can increase the contact angle between the wafer surface containing the Si element and isopropyl alcohol.

Further, Patent Document 2 proposes a method of forming a water-repellent protective film on the surface of a silicon-based wafer by using a silicon compound and an acid. The document discloses that by reacting a silicon compound with a silanol group on the wafer surface, the Si element on the wafer surface and the silicon compound are chemically bonded to impart water repellency to the wafer surface. .. Further, in the document, as a method for removing the protective film, irradiating the wafer surface with light, heating the wafer, exposing the wafer to ozone, and irradiating the wafer surface with plasma are exemplified. ..

International Publication WO2017 / 10321 Japanese Patent No. 5821844

For example, in the method of Patent Document 1 described above, the surface of the concave-convex pattern is made water-repellent, then washed with a rinsing liquid and dried to complete the treatment, and it is considered that organic substances derived from the treatment liquid are attached to the pattern surface. When removing organic substances derived from such a treatment liquid by a method as exemplified in Patent Document 2, it is desirable to remove them under less energy conditions in order to suppress oxidation of the wafer surface as much as possible, but it is sufficient. In some cases, it could not be removed, or it took a long time to remove it.

Therefore, in the surface treatment method for a wafer having a fine uneven pattern, an uneven pattern protective film that exhibits excellent liquid repellency, suppresses the collapse of the uneven pattern, and can be removed with less energy after the rinsing treatment is provided. An object of the present invention is to obtain a chemical solution for forming and a method for cleaning a wafer using the chemical solution.

The means for solving the above problems include the following aspects.

[1]
In a chemical solution for forming a protective film used for surface treatment of a wafer having a concavo-convex pattern on the surface and containing at least one selected from the group consisting of at least a Si element and a metal element in at least a part of the concavo-convex pattern.
The chemical solution for forming a protective film contains a protective film forming agent and a solvent having a fluorine atom.
A chemical solution for forming a protective film, wherein the protective film forming agent is a compound represented by the following formula (1).

(In the formula (1), R ¹ and R ² are each independently an organic group having a functional group having an affinity for at least one element contained in the uneven pattern, and w, x, and y are respectively. Independently, it is a mole fraction represented by a number from 0 to 1, and w + x + y = 1. Note that the order of existence of each repeating unit in parentheses with w, x, and y is arbitrary in the formula. .)

[2]
R ¹ and R ² are independently hydroxyl groups, carboxyl groups, phenol groups, phosphate groups, phosphite groups, sulfate groups, sulfite groups, nitrate groups, amino groups, and-(C = O) -NH-bonds. At least one selected from the group consisting of, aldehyde groups,-(C = O) -O- (C = O) -bonds,-(C = O) -CH _{2- (C = O) -bonds, and thiol groups.} The chemical solution for forming a protective film according to [1], which is an organic group having one functional group.

[3]
The chemical solution for forming a protective film according to [1] or [2], wherein the number average molecular weight of the protective film forming agent is 1000 or more and 20000 or less.

[4]
The chemical solution for forming a protective film according to any one of [1] to [3], wherein the solvent having a fluorine atom is compatible with water or alcohol.

[5]
In a method for cleaning a wafer having a concavo-convex pattern on the surface and containing at least one selected from the group consisting of at least a part of the concavo-convex pattern of Si element and a metal element.
The method for cleaning the wafer is a step 1 of forming a protective film on the surface of the uneven pattern using the chemical solution for forming a protective film according to any one of [1] to [4].
It has a step 2 of cleaning the surface of the wafer having the protective film with a rinsing liquid, and a step 3 of removing the protective film from the surface of the wafer after removing the rinsing liquid from the surface of the wafer.
The wafer cleaning method is a step of performing at least one process selected from the group consisting of a process of irradiating the wafer surface with light, a process of heating the wafer, and a process of exposing the wafer to ozone. ..

According to the present disclosure, in a surface treatment method for a wafer having a fine uneven pattern, the uneven pattern protection that exhibits excellent liquid repellency, suppresses the collapse of the uneven pattern, and can be removed with less energy after the rinsing treatment. It has become possible to obtain a chemical solution for forming a film and a method for cleaning a wafer using the chemical solution.

1: Chemical solution for forming a protective film The chemical solution for forming a protective film, which is one of the preferred embodiments of the present disclosure, has an uneven pattern on the surface, and at least a part of the uneven pattern is composed of a Si element and a metal element. Used for surface treatment of wafers containing at least one selected from the group.
The chemical solution for forming a protective film imparts liquid repellency by forming a protective film on an uneven pattern on the surface of the wafer, and makes it possible to remove the protective film with less energy. The above-mentioned chemical solution for forming a protective film contains a protective film-forming agent which is a compound represented by the formula (1) described later and a solvent having a fluorine atom (hereinafter, may be referred to as “fluorine-containing solvent”). It is a chemical solution containing.

(Protective film forming agent)
The protective film-forming agent used in the protective film-forming chemical solution is a compound represented by the following formula (1).

The chemical solution for forming a protective film, which is one of the preferred embodiments of the present disclosure, exhibits excellent liquid repellency in the surface treatment method of a wafer having a fine uneven pattern by adopting the above configuration, and the unevenness is exhibited. It is possible to form a concavo-convex pattern protective film that suppresses pattern collapse and can be removed with less energy after rinsing.
The reason is not clear, but it is presumed to be as follows.
The compound represented by the above formula (1) has a totally fluorinated polyether structure, and when used as a protective film forming agent, it gives low surface tension derived from fluorine atoms, and thus liquid repellency, to the surface of the pattern structure. Can be granted. Further, the totally fluorinated polyether structure is decomposed by volatilizing the repeating unit as gas molecules such as _{COF 2} and CF ₃ CFO when the ether bond is dissociated by the action of heat, ultraviolet rays, oxygen radicals and the like. Since the decomposition reaction occurs at a low temperature of, for example, about 200 ° C. under heating, it is considered that the unnecessary protective film can be removed from the surface of the uneven pattern with less energy than before.

The molecular weight of the protective film forming agent is not particularly limited, but a number average molecular weight of 300 or more is preferable because a protective film is easily formed, and a number average molecular weight of 500 or more causes unevenness in the formation of the protective film on the wafer. It is more preferable because it is difficult, and it is more preferable that the number average molecular weight is 1000 or more because it is easy to exhibit liquid repellency even in a small amount. Further, when the molecular weight of the protective film forming agent is 100,000 or less in terms of number average molecular weight, it is preferable because it is easily dissolved in a fluorine-containing solvent, and when it is 40,000 or less, it is more preferable because unevenness is less likely to occur in the protective film formation on the wafer. When it is 20,000 or less, it is more preferable because it is easy to remove the excess protective film forming agent in the rinsing step after forming the protective film described later.
The number average molecular weight of the protective film forming agent is preferably 300 or more and 100,000 or less, more preferably 500 or more and 40,000 or less, and further preferably 1000 or more and 20,000 or less.

In this specification, the above number average molecular weight is obtained by measuring using gel permeation chromatography (GPC). Specifically, for the above number average molecular weight, a model name EXTREMA (detector: refractive index difference detector RI-4030) manufactured by Nippon Spectroscopy Co., Ltd. was used as the GPC, and a column manufactured by Showa Denko Co., Ltd. (product name, GPC KF). -801 and product name, GPC KF-802 and product name, three GPC KF-802.5 connected in series), tetrahydrofuran was used as the developing solvent, and measurement was performed using the polystyrene molecular weight standard manufactured by Showa Denko Co., Ltd. as a reference. I got it.

^{Further, the compound represented by the above formula (1) has organic groups R 1} and R ² having a functional group having an affinity for at least one element contained in the above-mentioned unevenness pattern of the wafer, and the above-mentioned unevenness. Easy to adhere to the surface of the pattern. Further, the organic groups R ¹ and R ² may have a functional group having an affinity with at least one element selected from the group consisting of, for example, a Si element and a metal element.
Here, "having affinity" means that a van der Waals force, an electrostatic interaction, or the like acts between the surface of the uneven pattern containing the element and the functional group, so that the functional group and the functional group have the unevenness. It means that an interaction can be developed with the surface of the pattern.

R ¹ and R ² are independently hydroxyl groups, carboxyl groups, phenol groups, phosphate groups, phosphite groups, sulfate groups, sulfite groups, nitrate groups, amino groups, and-(C = O) -NH-bonds. At least one selected from the group consisting of, aldehyde groups,-(C = O) -O- (C = O) -bonds,-(C = O) -CH _{2- (C = O) -bonds, and thiol groups.} It is preferably an organic group having one functional group.
It is further further that R ¹ and R ² are each independently an organic group having at least one group selected from the group consisting of a hydroxyl group, a carboxyl group, a phosphoric acid group, a phosphite group, an amino group, and a thiol group. preferable. Further, from the viewpoint of the stability of the chemical solution, ^{it is particularly preferable that R 1} and R ² are organic groups each independently having a hydroxyl group or a carboxyl group.

The organic group containing a functional group having an affinity for at least one element contained in the above-mentioned uneven pattern of the wafer as ^{R 1} and R ^{2 is not particularly limited as long as it is a group containing one or more carbon atoms.} For example, one or more selected from the group consisting of a functional group having an affinity for at least one element contained in the uneven pattern of the wafer described above, a hydrocarbon group having 1 to 20 carbon atoms, an ester bond, and an ether bond. A combination of groups can be mentioned.
The hydrocarbon group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include an alkyl group having 1 to 20 carbon atoms and an aryl group having 6 to 20 carbon atoms.
The hydrocarbon group having 1 to 20 carbon atoms may be substituted with a halogen atom such as a fluorine atom or a chlorine atom.
The organic group having a functional group having an affinity with at least one element contained in the above-mentioned unevenness pattern of the wafer as ^{R 1} and R ^{2 has an affinity with at least one element contained in the above-mentioned unevenness pattern of the wafer.} It may be the functional group itself.

w, x, and y are mole fractions independently represented by numbers 0 to 1, and w + x + y = 1. w, x, and y are mole fractions of _{the repeating units (OCF 2} ), (OCF ₂ CF ₂ ), and (OCF (CF ₃ ) CF ₂ ) contained in the compound represented by the formula (1), respectively. Represents (molar ratio).
That is, w represents the content (molar ratio) of the repeating unit (OCF ₂ ) with respect to all the repeating units in the compound represented by the formula (1).
x represents the content (molar ratio) with respect to all the repeating units in the compound represented by the formula (1) of the repeating unit (OCF ₂ CF _2).
y represents the content (molar ratio) of the repeating unit (OCF (CF ₃ ) CF ₂ ) with respect to all the repeating units in the compound represented by the formula (1).

Although w, x, and y are not particularly limited, among the compounds represented by the formula (1), a _{protective film is formed on a compound containing a repeating unit of-(OCF 2} )-, that is, a compound in which w represents a number greater than 0. When used as an agent, it is preferable because it can form a protective film having excellent removability.
w is preferably 0 or more and 1 or less, more preferably greater than 0 and 0.9 or less, and further preferably 0.5 or more and 0.8 or less.
x is preferably 0 or more and 1 or less, more preferably greater than 0 and 0.9 or less, and further preferably 0.2 or more and 0.8 or less.
y is preferably 0 or more and 1 or less, more preferably 0 or more and 0.5 or less, and further preferably 0 or more and 0.3 or less.
In the present specification, the above w, x and y are calculated by obtaining the relative abundance ratio of each repeating unit from the nuclear magnetic resonance spectrum ( ¹⁹ ^{F-NMR) of the 19 F nucleus.} ^For the nuclear magnetic resonance spectrum of the 19 F nucleus, a product name ECZ 400S manufactured by JEOL Ltd. was used as a measuring device, and a deuterated chloroform solution was used as a deuterated solvent.

R ¹ constitutes one end of both ends of the compound represented by the formula (1), and —OR ² constitutes the other end.
The order of existence of each repeating unit is arbitrary in the equation. _{Specifically, (OCF 2} ), (OCF ₂ CF ₂ ), and (OCF (CF ₃ ) CF ₂ ) in the formula (1) may be combined in any order.
^{R 1} in formula (1) combines with O in (OCF ₂ ), O in (OCF ₂ CF ₂ ), or O in (OCF (CF ₃ ) CF _2).
O that binds to ^{R 2} in ^{-O-R 2} in the formula (1) binds C, and C in C in _(OCF 2 CF _2), or (OCF _(CF 3) CF ₂₎ in (OCF ₂₎ ..

The content of the fluorine atom of the compound represented by the formula (1) (hereinafter, may be referred to as “fluorine content”) is not particularly limited, but is preferably 40% by mass or more, more preferably 55% by mass. If it is the above, it is easy to exhibit liquid repellency even in a small amount. Further, if the fluorine content is preferably 90% by mass or less, more preferably 75% by mass or less, a protective film is likely to be formed.
In the present specification, the fluorine content was calculated from the number average molecular weight of the compound represented by the formula (1) and the values of w, x, and y. Specifically, the above number average molecular weight is M, the molecular weights of the organic groups R ¹ and R ² in the formula (1) are N ₁ and N ₂ , respectively, the fluorine content in the organic group R ¹ _{is f 1} , and the organic group. The fluorine content in R ^{2 was} _{defined as f 2,} _{and the fluorine content f T} of the compound represented by the formula (1) was calculated by the following formula.
_{The fluorine content of the repeating unit (OCF 2} ) in the formula (1) was 57.6% by mass, the fluorine content of (OCF ₂ CF ₂ ) was 65.5% by mass, and the fluorine content of (OCF (CF ₃ ) CF ₂ ) was The content was 68.7% by mass, and the molecular weight of O in the formula (1) was 16.
_{_{_{_{f T = {f 1 N 1}}}} + 57.6w (M-N 1 -N 2 -16) + 65.5x (M-N 1 -N 2 -16) + 68.7y (M-N 1 -N 2 -16) + F ₂ N ₂ } / M
Further, the protective film forming agent may be used alone or in combination of two or more.

The compound represented by the above-mentioned formula (1) can also be synthesized by, for example, the method described in US Pat. No. 3,214,478 or JP-A-38-25586, using perfluoroolefin epoxide as a raw material.
Further, a commercially available compound may be used, for example, Fomblin (registered trademark) D series (manufactured by Solvay Specialty Polymer Co., Ltd., w = 0.6, x = 0.4, R ¹ and R ² are −CH. _2- OH group), Fomblin® Z series (manufactured by Solvay Specialty Polymers, w = 0.8, x = 0.2, R ¹ and R ² are -CF ₂ COOH groups), Krytox® Examples thereof include a series (manufactured by DuPont, y = 1, R ¹ and R ² _{are -CF 2-} CF _2- COOH groups). The Fomblin (registered trademark) D series and the Fomblin (registered trademark) Z series are preferable because the protective film formed has good removability.
In a preferred embodiment, a compound having a fluorine content of 40 to 75% by mass, specifically, a Fomblin® D series (fluorine content 44 to 44 to 100,000) having a number average molecular weight in the range of 300 to 100,000. 61% by mass), Fomblin (registered trademark) Z series (fluorine content 44 to 59% by mass), Krytox (registered trademark) series (fluorine content 49 to 69% by mass) and the like.
Further, as a preferred embodiment, a compound having a fluorine content of 40 to 75% by mass, specifically, a Fomblin (registered trademark) D series having a number average molecular weight in the range of 1,000 to 20,000 (registered trademark). Fluorine content 56-61% by mass), Fomblin (registered trademark) Z series (fluorine content 54-59% by mass), Krytox (registered trademark) series (fluorine content 63-69% by mass) and the like.

The concentration of the protective film-forming agent contained in the protective film-forming chemical solution is preferably 0.001% by mass or more with respect to the total mass of the protective film-forming chemical solution because it tends to exhibit excellent liquid repellency. .. Further, although there is no particular upper limit, it is preferably 15% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less from the viewpoint of ease of coating on the wafer.

(Fluorine-containing solvent)
In the chemical solution for forming a protective film, a solvent containing a fluorine atom (fluorine-containing solvent) is used as a solvent in order to dissolve the protective film-forming agent. In particular, it is preferable to use a solvent having compatibility with the rinsing solution described later because it is possible to proceed with the cleaning step by directly replacing the protective film with the rinsing solution after forming the protective film with the chemical solution for forming the protective film. When a fluorine-containing solvent having compatibility with the rinsing solution is used as described above, it is preferably contained in the protective film-forming chemical solution in an amount of 40% by mass or more. In the present specification, "having compatibility" means that the amount of "rinse solution" that can be dissolved in 1 part by mass of the above-mentioned "fluorine-containing solvent" at 25 ° C. and 1 atm. It means that there are 0.05 parts by mass or more.

As the above-mentioned fluorine-containing solvent, a compound containing a fluorine atom is used, and for example, perfluorocarbons such as perfluorooctane, perfluorononane, perfluorocyclopentane, perfluorocyclohexane, and hexafluorobenzene, 1, 1, 1, 3 , 3-Pentafluorobutane, Octafluorocyclopentane, 2,3-dihydrodecafluoropentane, Hydrofluorocarbons such as Zeorora ™ H (manufactured by Nippon Zeon Co., Ltd.), Methylperfluoroisobutyl ether, Methylperfluorobutyl ether, Ethylperfluorobutyl ether, ethylperfluoroisobutyl ether, Asahiclin ™ AE-3000 (manufactured by AGC Co., Ltd.), Novec ™ 7100, Novec ™ 7200, Novec ™ 7300, Novec ™ 7600 ( Hydrofluoroethers such as (3M Japan Co., Ltd.), 1,1-dichloro-2,2,3,3,3-pentafluoropropane, 1,3-dichloro-1,1,2,2,3- Examples thereof include pentafluoropropane, CELEFIN ™ 1233Z (manufactured by Central Glass Co., Ltd.), and hydrochlorofluorocarbons such as 1,2-dichloro-3,3,3-trifluoropropene.

Further, as described above, it is preferable to use a fluorine-containing solvent compatible with the rinsing liquid. Since water or alcohol can be preferably used as the rinsing liquid as described later, it is more preferable that the fluorine-containing solvent as described above has compatibility with water or alcohol. For example, examples of the fluorine-containing solvent compatible with alcohol include 1,1,1,3,3-pentafluorobutane, octafluorocyclopentane, 2,3-dihydrodecafluoropentane, and Zeolola ™ H (Japan). Hydrofluorocarbons such as Zeon Co., Ltd., methylperfluoroisobutyl ether, methylperfluorobutyl ether, ethylperfluorobutyl ether, ethylperfluoroisobutyl ether, Asahiclean (trademark) AE-3000 (manufactured by AGC Co., Ltd.), Novec (trademark) ) 7100, Novec ™ 7200, Novec ™ 7300, Novec ™ 7600 (all manufactured by 3M Japan Co., Ltd.) and other hydrofluoroethers, 1,1-dichloro-2,2,3,3,3 -Pentafluoropropane, 1,3-dichloro-1,1,2,2,3-pentafluoropropane, CELEFIN ™ 1233Z (manufactured by Central Glass Co., Ltd.), 1,2-dichloro-3,3,3- Examples thereof include hydrochlorofluorocarbons such as trifluoropropene.

Examples of the fluorine-containing solvent compatible with water include 2-fluoroethanol, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2, Examples thereof include 2,2-trifluoro-1-propanol.

(Other solvents)
In addition to the protective film-forming agent and the fluorine-containing solvent, a solvent may be further added to the protective film-forming chemical solution for the purpose of adjusting the dissolving power. Examples thereof include hydrocarbons, esters, ethers, ketones, sulfoxide solvents, alcohols, derivatives of polyhydric alcohols, nitrogen-containing compounds and the like. Examples of the hydrocarbons include toluene, benzene, xylene, pentane, hexane, heptane, octane, nonane, decane and the like, and examples of the esters include ethyl acetate, propyl acetate, butyl acetate and ethyl lactate. Ethyl acetoacetate and the like, examples of the ethers include diethyl ether, dipropyl ether, dibutyl ether, tert-butyl methyl ether, tetrahydrofuran, dioxane and the like, and examples of the ketones include acetone, acetylacetone, etc. There are methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone and the like, examples of the sulfoxide-based solvent include dimethyl sulfoxide and the like, and examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, butanol, 4 -Methyl-2-pentanol, ethylene glycol, 1,3-propanediol and the like, and examples of the derivatives of the polyhydric alcohol include diethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether and propylene glycol monomethyl. Examples of the nitrogen-containing compound include ether, propylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate. , Formamide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, pyridine and the like.

2: Wafer cleaning method The wafer cleaning method, which is one of the preferred embodiments of the present disclosure, is
Step 1 of forming a protective film on the surface of the uneven pattern described above using the above-mentioned chemical solution for forming a protective film.
It has a step 2 of cleaning the surface of the wafer having the protective film with a rinsing liquid, and a step 3 of removing the protective film from the surface of the wafer after removing the rinsing liquid from the surface of the wafer.
The wafer cleaning method is a step of performing at least one process selected from the group consisting of a process of irradiating the wafer surface with light, a process of heating the wafer, and a process of exposing the wafer to ozone. Is. The cleaning method will be described below.

(Wafer)
As the above wafer, a wafer can be used in which at least a part of the uneven pattern contains at least one selected from the group consisting of Si element and metal element. Examples of the above elements include Si, Ge, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu. , Ag, Au, Zn, Al, Ga, In and the like, and alloys of the above elements, and may contain one kind or two or more kinds. Further, the oxides and nitrides of the above elements may be used, and those which are not particularly oxidized or nitrided such as silicon may be used. Further, the uneven pattern may have a film containing the element formed therein, or may contain the element in the composition of the surface of the uneven pattern.

(Rinse liquid)
As the rinsing liquid, any general rinsing liquid used for cleaning operations in the semiconductor manufacturing process is preferably used, but from the viewpoint of compatibility with the chemical solution for forming a protective film, water, the above-mentioned fluorine-containing solvent, etc. Examples thereof include hydrocarbons, esters, ethers, ketones, sulfoxide solvents, alcohols, derivatives of polyhydric alcohols, nitrogen-containing compounds and the like. Among them, water, primary alcohols, and secondary alcohols are preferable because they have excellent compatibility with the above-mentioned fluorine-containing solvent, and methanol, ethanol, 1-propanol, and 2-propanol are easy to dry. From the viewpoint, a particularly preferable example is given.

(Cleaning method, cleaning equipment)
The method for cleaning the wafer is a cleaning (surface treatment) method if a cleaning device capable of holding the chemical solution for forming the protective film in a liquid state or various cleaning solutions including the rinsing solution on the surface of the uneven pattern described above is used. Is not particularly limited. For example, a single-wafer represented by a cleaning method using a spin cleaning device in which a wafer on which the uneven pattern is formed is held substantially horizontally and rotated while a liquid is supplied near the center of rotation to clean the wafers one by one. Examples thereof include a method and a batch method using a cleaning device for immersing and cleaning a plurality of wafers in a cleaning tank.
The form of the protective film-forming chemical solution and the various cleaning solutions when the liquid state of the protective film-forming chemical solution and the various cleaning solutions is supplied to the surface of the uneven pattern is a liquid when the chemical solution is held on the surface of the uneven pattern. It is not particularly limited as long as it is. Examples include liquids and vapors if volatile during the desired process.

(Step 1)
In step 1, a protective film is formed on the surface of the uneven pattern using the above-mentioned chemical solution for forming a protective film. To form the protective film, the chemical solution for forming the protective film may be held on the surface of the uneven pattern for a predetermined time at a predetermined temperature. The protective film may not necessarily be formed continuously, and may not necessarily be formed uniformly, but since it can impart better liquid repellency, it may be continuously and uniformly formed. It is more preferable that it is formed. The time for holding the above-mentioned chemical solution for forming a protective film is not particularly limited, but may be, for example, 1 to 600 seconds.

The temperature at which a homogeneous protective film is likely to be formed is 5 ° C. or higher, which is lower than the boiling point of the protective film-forming chemical solution, and particularly, 10 ° C. or lower than the boiling point of the protective film-forming chemical solution. Is preferable. The boiling point of the protective film-forming chemical solution means the boiling point of the component having the largest amount in terms of mass ratio among the components contained in the protective film-forming chemical solution.

The wafer on which the protective film is formed is usually washed with an aqueous cleaning solution such as PM (sulfuric acid / hydrogen peroxide solution) or APM (ammonia / hydrogen peroxide solution) before step 1. Therefore, when the protective film is formed, the water-based cleaning liquid as described above may be retained on the surface of the uneven pattern. Therefore, in such a case, the protective film-forming chemical solution is supplied onto the aqueous cleaning solution held on the surface of the uneven pattern, the aqueous cleaning solution is replaced with the protective film-forming chemical solution, and then the protective film-forming chemical solution is used. Is held on the surface of the uneven pattern. When the compatibility between the water-based cleaning solution held on the uneven pattern and the protective film-forming chemical solution is insufficient, the above-mentioned aqueous cleaning solution is replaced with the cleaning solution A having compatibility with the protective film-forming chemical solution. It is desirable to add a step.
Further, further cleaning may be performed using the cleaning liquid A.

Examples of the cleaning liquid A include an organic solvent, a mixture of the organic solvent and an aqueous cleaning liquid, or a mixture in which at least one of an acid, an alkali, and a surfactant is mixed.

Examples of the above-mentioned organic solvent include the above-mentioned fluorine-containing solvent, hydrocarbons, esters, ethers, ketones, halogen-containing solvent, sulfoxide-based solvent, lactone-based solvent, carbonate-based solvent, alcohols, and polyhydric alcohol. From the viewpoint of compatibility with the protective film-forming chemical solution, the above-mentioned fluorine-containing solvent, hydrocarbons, esters, ethers, ketones, sulfoxide-based solvent, alcohols and the like can be mentioned. , Derivatives of polyhydric alcohols and nitrogen-containing compounds, among which primary alcohols and secondary alcohols are compatible with water used for cleaning before step 1 and water-based cleaning solutions such as water-containing cleaning solutions. It is preferable because it is excellent in solvent.

After the above step 1, the uneven pattern is made liquid-repellent by the protective film formed on the surface of the uneven pattern. Further, after the step 1, an excess chemical solution for forming a protective film remains on the surface of the uneven pattern. If the compatibility between the rinse solution used in the next step 2 and the above-mentioned chemical solution for forming a protective film is insufficient, an arbitrary cleaning solution B is used after step 1 to form the protective film on the uneven pattern. It is desirable to replace the drug solution. Further, as with the cleaning liquid A, cleaning may be performed using the cleaning liquid B. The protective film is retained on the surface of the uneven pattern even after the excess chemical for forming the protective film is removed from the surface of the uneven pattern.

Examples of the cleaning solution B include an aqueous cleaning solution, an organic solvent, a mixture of an aqueous cleaning solution and an organic solvent, a mixture thereof with at least one of an acid, an alkali, and a surfactant, and the above-mentioned cleaning solution B. Examples thereof include a mixture of chemicals for forming a protective film. The cleaning liquid B is more preferably water, an organic solvent, or a mixture of water and an organic solvent from the viewpoint of removing particles and metal impurities. Examples of the organic solvent include hydrocarbons, esters, ethers, ketones, halogen-containing solvents, sulfoxide solvents, alcohols, derivatives of polyhydric alcohols, nitrogen element-containing solvents and the like.

The better the liquid repellency of the protective film obtained in the above step 1, that is, the larger the contact angle of the protective film with the rinse liquid, the less the occurrence of pattern collapse when the rinse liquid is removed from the wafer surface in the later step 3. it can. Therefore, the larger the contact angle of the obtained protective film is, the more preferable it is.

(Step 2)
Step 2 is a step of cleaning the surface of the wafer having the protective film with a rinsing liquid. Specifically, by substituting the protective film-forming chemical solution or the cleaning solution B held in the uneven pattern with the above-mentioned rinsing solution, the protective film-forming chemical solution and the cleaning solution B can be removed from the wafer surface. This is the process of removing.

(Step 3)
Step 3 is a step of removing the protective film from the wafer surface after removing the rinsing liquid from the wafer surface. The rinse solution can be removed by a known drying method such as spin drying, IPA (2-propanol) steam drying, marangoni drying, heat drying, warm air drying, blast drying, vacuum drying, vacuum drying and the like. ..

(How to remove the protective film)
As a method for removing the protective film, a known method for removing organic substances from the semiconductor surface (wafer surface) can be applied, for example, a process of irradiating the wafer surface with light, a process of heating the wafer (heat treatment), or the wafer. The treatment of exposing the wafer to ozone can be exemplified.
Above all, at least one treatment selected from the group consisting of a treatment of irradiating the wafer surface with light, a treatment of heating the wafer, and a treatment of exposing the wafer to ozone is preferable. ..
Wherein as a process of light irradiation on the wafer surface is not particularly limited, for example, UV / O ₃ treatment can be exemplified.
The treatment for exposing the wafer to ozone is not particularly limited, and examples thereof include a plasma ashing treatment and an ion etching treatment.

In these methods, it is desirable to process under lower energy conditions where the wafer surface is less likely to be oxidized. Among these methods, heat treatment is preferable because it has a small effect on the surface forming the pattern structure. Since surface reactions such as oxidation proceed when the heating temperature is high, it is preferable that the heating temperature is low. For example, if the surface material of the pattern structure is silicon, the temperature is preferably 350 ° C. or lower. Further, if the heating temperature is excessively low, the removal of the protective film does not proceed or is delayed, so the temperature is preferably 160 ° C. or higher, more preferably 180 ° C. or higher.

Below, examples and comparative examples of the chemical solution for forming a protective film, which is one of the preferred embodiments of the present disclosure, are shown. In the following Examples and Comparative Examples, wafers in which various films were formed on a silicon wafer were used. A wafer having a smooth surface was used for the purpose of facilitating the evaluation of the liquid repellency of the protective film.

(1) Evaluation method of liquid repellency For each wafer on which the protective film was formed and each wafer for which the protective film was removed, the contact angle with respect to water or 2-propanol (IPA) was determined by Kyowa Interface Science. It was measured using a CA-X type contact angle meter. The liquid used for measuring the contact angle was the rinse liquid used in step 2 described later.

In addition, as a reference value, the contact angle of each wafer in the state where the protective film was not formed was measured.
Specifically, each wafer was immersed in an aqueous hydrogen fluoride solution, then dried, and the contact angle was measured and used as a reference value. The contact angles for IPA _{are 1 degree, 7 degrees, and 11 degrees for the SiO 2} film, SiN film, and TiN film, respectively, and the contact angles for water are 1 degree, 7 degrees, and 11 degrees for the SiN film, TiN film, W film, and Al ₂ O ₃ film, respectively. It was once, three times, once, and once.

If the contact angle with respect to the wafer on which the protective film was removed was significantly smaller than the contact angle with respect to the wafer on which the protective film was formed, it was determined that the protective film was removed by the above operation. It is more preferable that the smaller the contact angle with respect to the wafer subjected to the operation of removing the protective film, that is, the closer to the above reference value, the smaller the protective film remaining on the wafer.

(2) Chemical solution for forming a protective film (chemical solution A)
Fomblin ™ Z Diac 4000 manufactured by Solvay Specialty Polymer Co., Ltd. was mixed as a protective film-forming agent, and Novec7100 was mixed as a fluorine-containing solvent to obtain a chemical solution A having a protective film-forming agent concentration of 0.1% by mass.

Fomblin (trademark) Z Diac 4000 is a compound having a number average molecular weight of 1,300 represented by the following formula (2). When the fluorine content is calculated based on the above formula, it is 56% by mass.

(Chemical solutions B to D)
Similar to chemical solution A, except that the concentration of the protective film-forming agent in the chemical solution was 0.05% by mass (chemical solution B), 0.01% by mass (chemical solution C), and 0.001% by mass (chemical solution D). Each drug solution B to D was obtained by the method.

(Chemical solution E)
A chemical solution E having a protective film-forming agent concentration of 0.1% by mass was obtained in the same manner as the chemical solution A except that CELEFIN (trademark) 1233Z was used as the fluorine-containing solvent.

(Chemical solution F)
Chemical solution F was obtained in the same manner as in chemical solution A, except that 2,2,2-trifluoroethanol was used as the fluorine-containing solvent and the concentration of the protective film-forming agent in the chemical solution was 0.05% by mass.

(Chemical solution G)
With reference to Example 1 of Patent Document 1 described above, NK Guard S-750 manufactured by NICCA CHEMICAL CO., LTD. Was used as a protective film forming agent, ion-exchanged water was used as a solvent, and hydrochloric acid was further added and mixed to form a protective film. A chemical solution G having a drug concentration of 0.05% by mass and a hydrogen chloride concentration of 0.5% by mass was obtained.

NK Guard S-750 is a composition for forming a protective film, which comprises an acrylate polymer having a fluoroalkyl chain having 6 carbon atoms in a side chain, an emulsifier, a glycol-based organic solvent, and water.

(Chemical solution H)
With reference to Example 2 of Patent Document 1 described above, NK Guard S-750 manufactured by NICCA CHEMICAL CO., LTD. Was used as a protective film forming agent, ion-exchanged water was used as a solvent, and 2- (2-aminoethoxy) ethanol was further added. The mixture was mixed to obtain a chemical solution H having a protective film-forming agent concentration of 0.05% by mass and a 2- (2-aminoethoxy) ethanol concentration of 0.16% by mass.

(3) Formation and removal of protective film (Example 1)
Using the above-mentioned chemical solution A as the chemical solution for forming the protective film, a protective film was formed on the wafer by the following method. _{Further, as the wafer, a wafer in which a SiO 2} film was formed on a silicon wafer, a wafer in which a SiN film was formed, and a wafer in which a TiN film was formed were used.

First, each of the above-mentioned wafers was cut into a width of 1 cm and a length of 4 cm, immersed in an aqueous hydrogen fluoride solution to clean the surface, and then dried. Next, the dried wafer is immersed in a chemical solution A at room temperature (24 to 25 ° C.) for 5 minutes to form a protective film (step 1), and then immersed in a rinse solution at 40 ° C. for 30 seconds for rinsing (step 1). step 2), and finally the N ₂ gas is dried by blowing 60 seconds at room temperature. 2-Propanol (IPA) was used as the above-mentioned rinsing solution. Next, with respect to the obtained protective film, the contact angle with respect to IPA was measured according to the method described above.

Next, each wafer on which the protective film was formed was heated for 5 minutes on a hot plate preheated to 300 ° C. and returned to room temperature (24 to 25 ° C.) to attempt to remove the protective film (step 3). Next, the contact angle was measured as described in "(1) Evaluation method of liquid repellency" above to confirm whether or not the protective film could be removed, and the obtained results are shown in Table 1. Further, the contact angle with respect to the wafer on which the protective film is not formed is also described in “Before heat treatment” in Table 1 as a “reference value”.

(Comparative Examples 1 and 2)
The protective film was formed and removed, and the liquid repellent property was formed in the same manner as in Example 1 except that the above-mentioned chemical solution G (Comparative Example 1) and chemical solution H (Comparative Example 2) were used as the chemical solution for forming the protective film. Evaluation was performed. The results obtained are shown in Table 1.

From the above, it was confirmed that in Example 1 using the chemical solution A, the contact angle with respect to the IPA increased and the liquid repellency was confirmed. In Example 1 using the chemical solution A, it was found that the contact angle of the protective film with the rinse solution was large, the liquid repellency was increased, and the occurrence of pattern collapse when the rinse solution was removed from the wafer surface could be reduced. Further, as described above, as a result of heat treatment for the purpose of removing the protective film, the contact angle after heating at 300 ° C. is lowered to the same level as the value when the protective film is not formed, and is protected by heating. It was confirmed that the membrane had been removed. Further, _{the same tendency was observed in all of the SiO 2} film, the SiN film, and the TiN film. It was found that the protective film can be removed with less energy after the rinsing treatment.

Comparative Example 1 using the chemical solution G was _{able to make the SiO 2} film and the SiN film somewhat liquid-repellent, but had no effect on the TiN film. In addition, the contact angle after heating did not decrease significantly from that before heating, and the protective film could not be removed as in Example 1.

Comparative Example 2 using the chemical solution H had a somewhat liquid-repellent effect on the SiN film, but did not have a liquid-repellent effect on _{the SiO 2 film and the TiN film.} In addition, the contact angle after heating did not decrease significantly from that before heating, and the protective film could not be removed as in Example 1.

(Examples 2 to 7)
First, the above chemicals A to F are used as the chemicals for forming the protective film, and the wafer having the TiN film formed on the silicon wafer is used as the wafer, and the rinse liquid in step 2 is washed with IPA as the cleaning liquid B before the step 2. A protective film was formed and the liquid repellency (water repellency) of the protective film was evaluated in the same manner as in Example 1 except that water was used.

Next, for each wafer on which the protective film is formed, UV / _{O 3} treatment (center wavelength; 254 nm, ultraviolet light irradiation amount at the position of the substrate surface; 18mW / cm ²⁾ by performing 20 minutes, the protective film Attempted to remove (step 3). Next, the contact angle was measured as described in "(1) Evaluation method of liquid repellency" above to confirm whether or not the protective film could be removed, and the obtained results are shown in Table 2. The contact angle with respect to the wafer on which the protective film is not formed is also shown in “Before _{UV / O 3 treatment” in Table 2 as a “reference value”.}

From the above, it was confirmed that in Examples 2 to 7 using the chemical solutions A to F, the contact angle with water was increased and the liquid repellency (water repellency) was confirmed. In Examples 2 to 7 using the chemicals A to F, the contact angle of the protective film with the rinse liquid (water) was large, the liquid repellency (water repellency) was large, and the pattern collapsed when the rinse liquid was removed from the wafer surface. It was found that the occurrence of
_{Further, as a result of applying UV / O 3} treatment for the purpose of removing the protective film, the contact angle is remarkably reduced to a value similar to the value of the contact angle when the protective film is not formed, and the UV / O ₃ treatment protects the contact angle. It was confirmed that the membrane had been removed. It was found that the protective film can be removed with less energy after the rinsing treatment.

(Example 8)
The above solution A as liquid chemical for forming a protective film, the wafer W film on the silicon wafer is formed as a wafer, a wafer which SiN film is formed, and Al ₂ O ₃ except that the film was used as the wafer is formed is The formation and removal of the protective film and the evaluation of liquid repellency (water repellency) were carried out in the same manner as in Example 2. The results obtained are shown in Table 3. The contact angle with respect to the wafer on which the protective film is not formed is also shown in "Before _{UV / O 3 treatment" in Table 3 as a "reference value".}

(Example 9)
Additional chemical E as a protective film forming chemical, except for using wafer W film on the silicon wafer is formed, and Al ₂ O ₃ film wafers formed respectively as a wafer, the same method as in Example 2 The protective film was formed and removed, and the liquid repellency (water repellency) was evaluated. The results obtained are shown in Table 3.

From the above, it was confirmed that in Examples 8 and 9 using the chemical solutions A and E, the contact angle with water increased and the liquid repellency (water repellency) was confirmed even in the case _{of the W film and the Al 2} O _{3 film.} In Examples 8 and 9 using the chemicals A and E, the contact angle of the protective film with the rinse liquid (water) was large, the liquid repellency (water repellency) was large, and the pattern collapsed when the rinse liquid was removed from the wafer surface. It was found that the occurrence of
_{Further, as a result of applying UV / O 3} treatment for the purpose of removing the protective film, the contact angle is remarkably reduced to a value similar to the value of the contact angle when the protective film is not formed, and the UV / O ₃ treatment protects the contact angle. It was confirmed that the membrane had been removed. It was found that the protective film can be removed with less energy after the rinsing treatment.

According to the present disclosure, in a surface treatment method for a wafer having a fine uneven pattern, the uneven pattern protection that exhibits excellent liquid repellency, suppresses the collapse of the uneven pattern, and can be removed with less energy after the rinsing treatment. It becomes possible to obtain a chemical solution for forming a film and a method for cleaning a wafer using the chemical solution.

Although this disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of this disclosure.

This application is based on a Japanese patent application filed on November 29, 2019 (Japanese Patent Application No. 2019-217605), the contents of which are incorporated herein by reference.

Claims

In a chemical solution for forming a protective film used for surface treatment of a wafer having a concavo-convex pattern on the surface and containing at least one selected from the group consisting of at least a Si element and a metal element in at least a part of the concavo-convex pattern.
The chemical solution for forming a protective film contains a protective film forming agent and a solvent having a fluorine atom.
A chemical solution for forming a protective film, wherein the protective film forming agent is a compound represented by the following formula (1).

(In the formula (1), R 1 and R 2 are each independently an organic group having a functional group having an affinity for at least one element contained in the uneven pattern, and w, x, and y are respectively. Independently, it is a mole fraction represented by a number from 0 to 1, and w + x + y = 1. Note that the order of existence of each repeating unit in parentheses with w, x, and y is arbitrary in the formula. .)
R 1 and R 2 are independently hydroxyl groups, carboxyl groups, phenol groups, phosphate groups, phosphite groups, sulfate groups, sulfite groups, nitrate groups, amino groups, and-(C = O) -NH-bonds. At least one selected from the group consisting of, aldehyde groups,-(C = O) -O- (C = O) -bonds,-(C = O) -CH 2- (C = O) -bonds, and thiol groups. The chemical solution for forming a protective film according to claim 1, which is an organic group having one functional group.
The chemical solution for forming a protective film according to claim 1 or 2, wherein the number average molecular weight of the protective film forming agent is 1000 or more and 20000 or less.
The chemical solution for forming a protective film according to any one of claims 1 to 3, wherein the solvent having a fluorine atom is compatible with water or alcohol.
In a method for cleaning a wafer having a concavo-convex pattern on the surface and containing at least one selected from the group consisting of at least a part of the concavo-convex pattern of Si element and a metal element.
The method for cleaning the wafer is a step 1 of forming a protective film on the surface of the uneven pattern using the chemical solution for forming a protective film according to any one of claims 1 to 4.
It has a step 2 of cleaning the surface of the wafer having the protective film with a rinsing liquid, and a step 3 of removing the protective film from the surface of the wafer after removing the rinsing liquid from the surface of the wafer.
The wafer cleaning method is a step of performing at least one process selected from the group consisting of a process of irradiating the wafer surface with light, a process of heating the wafer, and a process of exposing the wafer to ozone. ..