JP2001040389A - Wafer cleaning liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a (poly)silicon-wafer cleaning liquid with a very low etching rate by using an aqueous alkali solution containing a surfactant. SOLUTION: Preferably, the etching rate is 1/2 of or lower than that in the case when the surfactant is not contained. Preferably, the surfactant is one represented by the formula: RCOOM, the formula: RSO3M, formula I, formula II or formula III or one represented by the formula: R' (CH2CH2O)qR", formula IV, the formula: R'O(CH2CH2O)qR" or formula V. In these formulas, R is (F-substituted) 8-30C alkyl; M is H, an alkali metal or ammonium; R' is (F- substituted) 6-30C alkyl; R" is H or R'; and q is 1-20. Preferably, an alkaline substance contained in the aqueous alkali solution is ammonia or amine represented by the formula: R1R2R3N or an ammonium hydroxide represented by the formula: [(R1)(R2)(R3)(R4)N]+OH-. In these formulas, R1 to R4 are each H or (OH-substituted) 1-6C alkyl.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cleaning liquid for a silicon wafer surface.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor integrated circuit device for forming an LSI on a semiconductor substrate (wafer) made of silicon single crystal, a wafer surface is cleaned to remove particles on the wafer. Ammonia water, an ammonia-hydrogen peroxide aqueous solution, or the like is used as the cleaning liquid. The portion where the oxide film is etched and the silicon (Si) surface and the polysilicon (polySi) surface are exposed is exposed to the cleaning solution simultaneously with the oxide film. When the above-described cleaning agent is used, Si and Si are removed. Corrosion of poly-Si surface,
Alternatively, there is a problem of being etched.

Japanese Patent Publication No. 55-40183 discloses that a semiconductor treatment agent obtained by adding a surfactant to trialkyl (hydroxyalkyl) ammonium hydroxide (THAH) suppresses an etching rate, and suppresses an etching rate. And 200Å / min. However, the suppression effect of the degree described in the publication is insufficient as a cleaning liquid in the manufacturing process of today's extremely miniaturized integrated circuits, and a cleaning liquid with a lower etching rate is required.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer cleaning liquid having an extremely low etching rate.

[0005]

Means for Solving the Problems The present inventor has found that a specific solution obtained by adding a surfactant to an aqueous alkali solution has an extremely low etching rate, and has completed the present invention.

That is, the present invention relates to the inventions described in the following items.

Item 1 A low etching rate silicon or polysilicon wafer cleaning liquid which is an aqueous alkaline solution containing a surfactant.

Item 2. The cleaning solution according to item 1, wherein the etching rate is one half or less of the case where no surfactant is contained.

Item 3. The cleaning solution according to item 2, wherein the etching rate is 1/10 or less of the case where no surfactant is contained.

Item 4 The surfactant is represented by the general formula (1): RCOOM wherein R represents an alkyl group having 8 to 30 carbon atoms which may be substituted by a fluorine atom, M represents a hydrogen atom, an alkali metal atom Or an ammonium group. General formula (2): RSO ₃ M [wherein, R and M are the same as described above.] ], General formula (3)

[0011]

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Wherein R and M are the same as above. ], General formula (4)

[0013]

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Wherein R and M are as defined above. ], General formula (5)

[0015]

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Wherein R and M are the same as above. Or a general formula (6): ROSO ₃ M wherein R and M are as defined above. ] The washing | cleaning liquid in any one of claim | item 1 -3 characterized by the above-mentioned.

Item 5 In the general formulas (1) to (6), R
Has 10 to 30 carbon atoms which may be substituted by a fluorine atom
Item 5. The cleaning solution according to Item 4, which is an alkyl group.

Item 6: The surfactant is represented by the general formula (7): R ′ (CH ₂ CH ₂ O) qR ″ wherein R ′ is an alkyl having 6 to 30 carbon atoms which may be substituted by a fluorine atom. R ″ represents an alkyl group having 6 to 30 carbon atoms or a hydrogen atom which may be substituted by a fluorine atom, and q represents an integer of 1 to 20. ], General formula (8)

[0019]

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Wherein R ′ and R ″ are as defined above. General formula (9) R′O (CH ₂ CH ₂ O) qR ″ wherein R ′ and R ″ are the same as above. ] Or general formula (10)

[0021]

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Wherein R ′ and R ″ are as defined above. ] The washing | cleaning liquid in any one of claim | item 1 -3 characterized by the above-mentioned.

Item 7 In the general formulas (7) to (10),
R 'has 8 to 3 carbon atoms which may be substituted by a fluorine atom.
Item 7. The cleaning liquid according to item 6, wherein the alkyl group is 0.

Item 8: When the concentration of the surfactant is 0.0000
Item 8. The cleaning liquid according to any one of Items 1 to 7, which is 1 to 5% by weight.

Item 9: The alkaline substance contained in the aqueous alkali solution is represented by the general formula (11): R ₁ R ₂ R ₃ N wherein R ₁ , R ₂ and R ₃ are the same or different and are substituted by a hydroxyl group. And represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. Ammonia or an amine and represented by the general _{formula] (12) [(R 1} ) (R 2) (R 3) (R 4) N] + OH - [ _{wherein, R 1, R 2, R} 3 and R ₄ is the same or different,
It represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom which may be substituted with a hydroxyl group. The cleaning solution according to any one of Items 1 to 8, which is at least one member selected from the group consisting of ammonium hydroxides represented by the formula:

Item 10: When the concentration of the alkaline substance is 0.0
Item 10. The cleaning liquid according to any one of Items 1 to 9, which is 1 to 30% by weight.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The cleaning solution of the present invention is obtained by adding a surfactant to an aqueous alkali solution and has a low etching rate.

The aqueous alkaline solution is prepared by dissolving an alkaline substance. Examples of the alkaline substance include R ₁ R ₂ R ₃ N [wherein R ₁ , R ₂ and R ₃
Represents the same or different and represents an alkyl group having 1 to 6 carbon atoms which may be substituted with a hydroxyl group, or a hydrogen atom. Ammonia or an amine represented by the general formula (12) [(R ₁ )
_{(R 2) (R 3)} (R 4) N] + OH - [ wherein, R _1, R _2, R ₃ and R ₄ are the same or different carbon atoms that may be substituted by a hydroxyl group 1 To 6 alkyl groups or hydrogen atoms. ] Ammonium hydroxide represented by the formula:

The alkyl group having 1 to 6 carbon atoms in the general formula (11) or (12) includes a linear or branched alkyl group such as methyl, ethyl, propyl, t-butyl, n-pentyl and n-hexyl. Alkyl group is exemplified.

Specific examples of the compound represented by the general formula (11) include ammonia; methylamine, ethylamine,
Propylamine, t-butylamine, pentylamine,
And aliphatic primary amines such as hexylamine.

Examples of the ammonium hydroxide represented by the general formula (12) include tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrahexylammonium hydroxide. Can be

The concentration of the alkaline solution is not particularly limited as long as the desired effect of the present invention can be achieved, but is usually about 0.01 to 30% by weight, preferably 0.1 to 1% by weight.
It is about 0% by weight, more preferably about 0.1 to 1% by weight.

The surfactant to be added to the cleaning solution of the present invention is not particularly limited as long as it can reduce the etching rate by being added to the above-mentioned alkaline solution. , A cationic surfactant, a nonionic surfactant and the like can be appropriately selected and added.

Specifically, RCOOM of the general formula (1) wherein R represents an alkyl group which may be substituted by a fluorine atom, M is a hydrogen atom,
Indicates an alkali metal atom or an ammonium group. A carboxylic acid type surfactant represented by the general formula (2): RSO ₃ M wherein R and M are as defined above. ], General formula (3)

[0035]

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Wherein R and M are as defined above. General formula (4)

[0037]

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Wherein R and M are as defined above. ], General formula (5)

[0039]

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A sulfonic acid type surfactant represented by the formula: ROSO ₃ M [wherein R and M are the same as those described above] And the like, and an anionic surfactant such as a sulfate ester type surfactant represented by the formula:

The number of carbon atoms of the alkyl group in the general formulas (1) to (6) is not particularly limited, but is preferably 8 or more, more preferably 10 or more, and further preferably 12 or more. The upper limit of the number of carbon atoms is not particularly limited.
It is about 0, preferably about 20. When the number of carbon atoms of the alkyl group in the general formulas (1) to (6) is 8 or more, it is preferable since the adsorptivity to the silicon or polysilicon surface is improved and the effect of lowering the etching rate is more excellent. 3 carbon atoms
It is preferable that it is within 0 because the solubility is excellent.

Examples of the alkyl group in formulas (1) to (6) include octyl, 1-methylheptyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, A linear or branched alkyl group such as a nonadecyl group is preferably exemplified.

The alkyl group in the general formulas (1) to (6) may have one, two or three fluorine atoms per carbon atom instead of a hydrogen atom. Examples of the alkyl group substituted with a fluorine atom include perfluorooctyl, perfluorononyl, perfluorodecyl, perfluoroundecyl, perfluorododecyl, perfluorotridecyl, perfluorotetradecyl, perfluoropentadecyl, and perfluorohexa. Examples include decyl, perfluoroheptadecyl, perfluorooctadecyl, and perfluorononadecyl groups.

Preferred examples of the alkali metal atom include lithium, sodium, potassium and the like.

Among the above general formulas (1) to (6), the surfactants of the present invention are preferably those represented by general formulas (5) and (6).

Examples of the surfactant further include R ′ (CH ₂ CH ₂ O) qR ″ [wherein R ′ represents an alkyl group which may be substituted with a fluorine atom; '' Represents a hydrogen atom or an alkyl group which may be substituted by a fluorine atom, and q represents an integer of 1 to 20. ), General formula (8)

[0047]

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Wherein R ′ and R ″ are as defined above. General formula (9) R′O (CH ₂ CH ₂ O) qR ″ [wherein,
R ′ and R ″ are the same as above. ], General formula (10)

[0049]

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Wherein R ′ and R ″ are as defined above. And the like, and a polyoxyethylene glycol type nonionic surfactant represented by the following formula:

The alkyl group or the alkyl group which may be substituted with a fluorine atom in the above general formulas (7) to (10) preferably has 6 or more carbon atoms, more preferably has 8 or more carbon atoms, and more preferably has 9 or more carbon atoms. preferable. Although the upper limit of the number of carbon atoms is not particularly limited, it is usually about 30 and preferably 2
It is about 0. When the number of carbon atoms of the alkyl group in the general formulas (7) to (10) is 6 or more, the adsorptivity to the silicon or polysilicon surface is improved, and the effect of lowering the etching rate is more excellent. It is preferable that the number of carbon atoms is 30 or less, since the solubility is excellent.

As the alkyl group or the alkyl group substituted by a fluorine atom in the general formulas (7) to (10), specifically, a linear or branched alkyl group exemplified in the anionic surfactants An alkyl group can be exemplified.
Further, examples of the alkyl group in the general formulas (7) to (10) include n-hexyl and n-heptyl, and examples of the alkyl group substituted with a fluorine atom include a perfluorohexyl group and a perfluoroheptyl group. It is preferably exemplified.

Q is an integer of 1 to 20, preferably 3 to 20, more preferably 5 to 20, and most preferably 10.

In the above general formulas (7) to (10),
R '' is preferably a hydrogen atom.

Among the above general formulas (7) to (10), the surfactants of the present invention include the general formulas (9) and (10)
The surfactant represented by is preferred.

As the surfactants represented by the general formulas (7) to (10), specifically, polyoxyethylene (4) butyl ether, polyoxyethylene (9) pentyl ether, polyoxyethylene (15) Dodecyl ether and the like are exemplified.

These surfactants can be added alone or in combination of two or more to an aqueous alkali solution.

The concentration of the surfactant is not particularly limited as long as the desired effect of the present invention can be achieved.
0.00001-5% by weight, preferably 0.0001-
About 0.5% by weight, more preferably 0.005 to 0.0
It is about 1% by weight.

The cleaning liquid of the present invention is a cleaning liquid having a low etching rate in which the etching rate is suppressed as compared with an alkaline solution to which no surfactant is added. In the present invention, “low etching rate” means (i) Compared to an alkaline aqueous solution without the addition of an activator, the etching rate is
Preferably at most about 1/2 or less, more preferably about 1/10 or less; and / or (ii) at 45 ° C., the etching rate of the silicon wafer is preferably about 6 ° / min or less;
It is more preferably about 1 ° / min or less, and further preferably about 0.2 ° / min or less.

[0060]

The cleaning liquid of the present invention has an extremely low etching rate, does not substantially etch silicon or polysilicon, and forms a LSI on a semiconductor substrate (wafer). It is useful as a cleaning solution.

[0061]

The present invention will be described below in more detail with reference to examples and comparative examples.

Examples 1 to 15 and Comparative Example 1 The etching rates of the cleaning liquids shown in Table 1 below with respect to polysilicon were measured. That is, the surfactants shown in Table 1 were added to 0.3% by weight of aqueous ammonia so as to have various concentrations shown in Table 1, and the obtained cleaning solution was adjusted to 45 ° C. Was immersed in the liquid, and the etching rate was measured. The etching rate (Å / min) was measured using an Auto EL-III ellipsometer manufactured by Rudolf Reseach before and after etching, and the difference between the film thickness before immersion and the film thickness after immersion was measured as the immersion time. Divided by.
Table 1 shows the results. Table 1 also shows a numerical value obtained by dividing the etching rate of each example by the etching rate of Comparative Example 1.

[0063]

[Table 1]

The cleaning liquid of the example had an extremely low etching rate.

Claims (10)

[Claims] 1. A low etching rate silicon or polysilicon wafer cleaning liquid which is an aqueous alkaline solution containing a surfactant. 2. The cleaning solution according to claim 1, wherein the etching rate is one half or less of the case where no surfactant is contained. 3. The cleaning solution according to claim 2, wherein the etching rate is 1/10 or less of the case where no surfactant is contained. 4. The surfactant is represented by the following general formula (1): RCOOM wherein R represents an alkyl group having 8 to 30 carbon atoms which may be substituted by a fluorine atom, M represents a hydrogen atom, an alkali metal atom Or an ammonium group. General formula (2): RSO ₃ M [wherein, R and M are the same as described above.] ], General formula (3) [Wherein, R and M are the same as above. ], General formula (4) [Wherein, R and M are the same as above. ], General formula (5) [Wherein, R and M are the same as above. Or a general formula (6): ROSO ₃ M wherein R and M are as defined above. The cleaning liquid according to any one of claims 1 to 3, which is a surfactant represented by the following formula: 5. The cleaning solution according to claim 4, wherein in formulas (1) to (6), R is an alkyl group having 10 to 30 carbon atoms which may be substituted by a fluorine atom. 6. A surfactant represented by the following general formula (7): R ′ (CH ₂ CH ₂ O) qR ″ wherein R ′ is an alkyl having 6 to 30 carbon atoms which may be substituted by a fluorine atom. R ″ represents an alkyl group having 6 to 30 carbon atoms or a hydrogen atom which may be substituted by a fluorine atom, and q represents an integer of 1 to 20. ], General formula (8) Wherein R ′ and R ″ are the same as above. General formula (9) R′O (CH ₂ CH ₂ O) qR ″ [wherein, R ′ and R ″ are as defined above. Or general formula (10) Wherein R ′ and R ″ are the same as above. The cleaning liquid according to any one of claims 1 to 3, which is a surfactant represented by the following formula: 7. The cleaning solution according to claim 6, wherein in formulas (7) to (10), R ′ is an alkyl group having 8 to 30 carbon atoms which may be substituted by a fluorine atom. 8. A surfactant having a concentration of 0.00001 to 0.00001.
The cleaning liquid according to any one of claims 1 to 7, which is 5% by weight. 9. An alkaline substance contained in an aqueous alkaline solution is represented by the following general formula (11): R ₁ R ₂ R ₃ N wherein R ₁ , R ₂ and R ₃ are the same or different and are substituted by a hydroxyl group. And represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. Ammonia or an amine and represented by the general _{formula] (12) [(R 1} ) (R 2) (R 3) (R 4) N] + OH - [ _{wherein, R 1, R 2, R} 3 and R ₄ is the same or different,
It represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom which may be substituted with a hydroxyl group. The cleaning solution according to any one of claims 1 to 8, wherein the cleaning solution is at least one selected from the group consisting of ammonium hydroxide represented by the following formula: 10. The concentration of the alkaline substance is from 0.01 to 10.
The cleaning liquid according to any one of claims 1 to 9, which is 30% by weight.