Composition for surface treatment and method of producing the same, surface treatment method, and method of producing semiconductor substrate

Abstract

The purpose of the present invention is to provide means for sufficiently removing residues on a surface of an object which has been polished including silicon nitride, silicon oxide, or polysilicon. Provided is a composition for surface treatment including an anionic surfactant having a molecular weight of 1,000 or less and water, the composition having a pH of less than 7, wherein a ratio of a molecular weight of a hydrophilic moiety to a molecular weight of a hydrophobic moiety (the molecular weight of the hydrophilic moiety/the molecular weight of the hydrophobic moiety) of the anionic surfactant is 0.4 or more (in which the hydrophobic moiety is a hydrocarbon group having 4 or more carbon atoms and the hydrophilic moiety is a part excluding the hydrophobic moiety and a counterion), and the composition for surface treatment is used for surface treatment of an object which has been polished including at least one selected from the group consisting of silicon nitride, silicon oxide, and polysilicon.

Claims

1. A composition for surface treatment comprising an anionic surfactant having a molecular weight of 1,000 or less and water, the composition for surface treatment having a pH of less than 7, wherein the anionic surfactant comprises at least one selected from the group consisting of polyoxyalkylene styrenated phenyl ether sulfuric acid (salt) and polyoxyalkylene alkyl sulfosuccinic acid (salt), wherein a ratio of a molecular weight of a hydrophilic moiety to a molecular weight of a hydrophobic moiety (the molecular weight of the hydrophilic moiety/the molecular weight of the hydrophobic moiety) of the anionic surfactant is 0.4 or more (in which the hydrophobic moiety is a hydrocarbon group having 4 or more carbon atoms and the hydrophilic moiety is a part excluding the hydrophobic moiety and a counterion), and the composition for surface treatment is used for surface treatment of an object which has been polished including at least one selected from the group consisting of silicon nitride, silicon oxide, and polysilicon.

2. The composition for surface treatment according to claim 1, wherein the anionic surfactant has a sulfonic acid (salt) group or a sulfuric acid (salt) group.

3. The composition for surface treatment according to claim 1, further comprising a polymer compound of a molecular weight of 10,000 or more, having a sulfonic acid (salt) group.

4. The composition for surface treatment according to claim 3, wherein the polymer compound comprises at least one selected from the group consisting of sulfonic acid group-containing polyvinyl alcohol, sulfonic acid group-containing polystyrene, sulfonic acid group-containing polyvinyl acetate, sulfonic acid group-containing polyester, a copolymer of (meth)acryl group-containing monomer-sulfonic acid group-containing monomer, and salts thereof.

5. The composition for surface treatment according to claim 3, wherein a ratio of a content (mass) of the anionic surfactant to a content (mass) of the polymer compound is 1 to 100.

6. The composition for surface treatment according to claim 3, wherein a content of the polymer compound is 0.001% by mass or more and 1.0% by mass or less, and a content of the anionic surfactant is 0.01% by mass or more and 1.0% by mass or less.

7. The composition for surface treatment according to claim 1, wherein the anionic surfactant comprises at least one selected from the group consisting of polyoxyethylene styrenated phenyl ether ammonium sulfate, sodium polyoxyethylene alkyl(12-14) sulfosuccinate, and disodium polyoxyethylene lauryl sulfosuccinate.

8. The composition for surface treatment according to claim 1, further comprising a phosphonic acid compound having 2 or more nitrogen atoms.

9. The composition for surface treatment according to claim 1, which includes substantially no abrasive grains.

10. A method of producing the composition for surface treatment set forth in claim 1, comprising a step of mixing an anionic surfactant having a molecular weight of 1,000 or less and water, the composition for surface treatment having a pH of less than 7, wherein the anionic surfactant comprises at least one selected from the group consisting of polyoxyalkylene styrenated phenyl ether sulfuric acid (salt) and polyoxyalkylene alkyl sulfosuccinic acid (salt), wherein a ratio of a molecular weight of a hydrophilic moiety to a molecular weight of a hydrophobic moiety (the molecular weight of the hydrophilic moiety/the molecular weight of the hydrophobic moiety) of the anionic surfactant is 0.4 or more (in which the hydrophobic moiety is a hydrocarbon group having 4 or more carbon atoms and the hydrophilic moiety is a part excluding the hydrophobic moiety and a counterion).

11. A surface treatment method comprising a step of surface-treating an object which has been polished including at least one selected from the group consisting of silicon nitride, silicon oxide, and polysilicon, using the composition for surface treatment set forth in claim 1.

12. The surface treatment method according to claim 11, wherein the surface treatment is rinse polishing and/or cleaning.

13. A method of producing a semiconductor substrate, comprising a step of reducing residues on a surface of a semiconductor substrate which has been polished including at least one selected from the group consisting of silicon nitride, silicon oxide, and polysilicon, by the surface treatment method set forth in claim 11.

14. The composition for surface treatment according to claim 1, wherein the anionic surfactant has a polyoxyethylene (POE) group having a number of repeating units n of 3 to 10.

15. The composition for surface treatment according to claim 1, wherein the anionic surfactant comprises alkyl sulfosuccinic acid (salt) containing an alkyl group having 8 or more carbon atoms.

16. The composition for surface treatment according to claim 1, wherein the ratio of a molecular weight of a hydrophilic moiety to a molecular weight of a hydrophobic moiety of the anionic surfactant is 2.2 or more.

Description

EXAMPLES

(1) The present invention will be further described in detail using the following Examples and Comparative Examples. However, the technical scope of the present invention is not limited to the following Examples. In addition, unless otherwise stated, “%” and “parts” refer to “% by mass” and “parts by mass”, respectively.

(2) <Preparation of Composition for Surface Treatment>

Example 1

(3) (Preparation of Composition for Surface Treatment A-1)

(4) 0.5 parts by mass of an aqueous maleic acid solution at a concentration of 30% by mass (0.18 parts by mass of maleic acid) as an organic acid, 0.05 parts by mass of sodium polystyrene sulfonate (manufactured by Tosoh Organic Chemical Co., Ltd., Product name: Poly NaSS (registered trademark) PS-1, weight average molecular weight: 20,000, pKa value: 1.0) (0.01 parts by mass of sodium polystyrene sulfonate) as a polymer compound, 0.02 parts by mass of sodium polyoxyethylene (POE) alkyl ether phosphate (n=1) (C.sub.18H.sub.37O(POE)).sub.2—PO.sub.2Na) as an anionic surfactant, and an amount to be 100 parts by mass in total of water (deionized water) were mixed, thereby preparing composition for surface treatment A-1. When the pH of composition for surface treatment A-1 (liquid temperature: 25° C.) was confirmed by a pH meter (manufactured by HORIBA, Ltd., product name: LAQUA (registered trademark)), pH was 2.1.

Examples 2 to 9 and Comparative Examples 2 and 3

(5) (Preparation of Compositions for Surface Treatment A-2 to A-9 and a-1 to a-2)

(6) Each composition for surface treatment was prepared in the same manner as in the preparation of the composition for surface treatment A-1 in Example 1, except that the type of the anionic surfactant was changed as shown in the following Table 1. In addition, “-” in the table shows that the component was not used. Also, the pH of each composition for surface treatment is shown in the following Table 1.

(7) <Measurement of Weight Average Molecular Weight>

(8) As the weight average molecular weight of the polymer compound, a value of the weight average molecular weight measured by gel permeation chromatography (GPC) (in terms of polyethylene glycol) was used. The weight average molecular weight was measured by the following apparatus and conditions.

(9) GPC apparatus: manufactured by Shimadzu Corporation

(10) Model: Prominence+ELSD detector (ELSD-LTII)

(11) Column: VP-ODS (manufactured by Shimadzu Corporation)

(12) Mobile phase A: MeOH B: 1% aqueous acetic acid solution

(13) Flow rate: 1 mL/min

(14) Detector: ELSD temp. 40° C., Gain 8, N.sub.2 GAS 350 kPa

(15) Oven temperature: 40° C.

(16) Injection amount: 40 μL.

(17) <Evaluation of the Number of Residues (Defects)>

(18) [Preparation of Object which has been Polished]

(19) A silicon nitride substrate which has been polished, after being polished by the following chemical mechanical polishing (CMP) step was prepared as an object which has been polished (also referred to as a substrate which has been polished).

(20) (CMP Step)

(21) For a silicon nitride substrate which is a semiconductor substrate, a polishing composition M (composition; 4% by mass of sulfonic acid-modified colloidal silica (manufactured by a method described in “Sulfonic acid-functionalized silica through quantitative oxidation of thiol groups”, Chem. Commun. 246-247 (2003), a primary particle size of 30 nm, a secondary particle size of 60 nm), 1% by mass of ammonium sulfate, 0.018% by mass of an aqueous maleic acid solution at a concentration of 30% by mass, solvent: water) was used to perform polishing under the following conditions. Here, as the silicon nitride substrate, a 300 mm wafer was used.

(22) (Polishing Apparatus and Polishing Conditions)

(23) Polishing apparatus: FREX300E manufactured by Ebara Corporation

(24) Polishing pad: rigid polyurethane pad IC 1400 manufactured by Nitta Haas Incorporated

(25) Polishing pressure: 2.0 psi (1 psi=6894.76 Pa, the same applies hereinafter)

(26) Rotation number of polishing table: 60 rpm

(27) Rotation number of head: 60 rpm

(28) Supply of polishing composition: constant flowing

(29) Supply amount of polishing composition: 300 mL/min

(30) Polishing time: 60 seconds.

(31) [Cleaning Step]

(32) After the surface of the silicon nitride substrate was polished in the CMP step, the silicon nitride substrate was removed from the polishing table (platen). Subsequently, in the same polishing apparatus, the thus-prepared composition for surface treatment (A-1 to A-9 and a-1 to a-2) or water (deionized water; described as Comparative Example 1 in Table 1 below) was used to clean each silicon nitride substrate which has been polished, by a cleaning method in which the silicon nitride substrate which has been polished is rubbed under the following conditions while the silicon nitride substrate which has been polished is sandwiched from above and below between a sponge made of polyvinyl alcohol (PVA) which is a cleaning brush and pressure is applied.

(33) (Cleaning Apparatus and Cleaning Conditions)

(34) Apparatus: FREX300E manufactured by Ebara Corporation

(35) Rotation number of cleaning brush: 100 rpm

(36) Rotation number of object which has been polished (substrate which has been polished): 100 rpm

(37) Flow rate of cleaning solution (composition for surface treatment or water): 1000 mL/min

(38) Cleaning time: 30 seconds

(39) [Measurement of the Number of Residues (Defects)]

(40) For each cleaned substrate after being cleaned by the above cleaning step, the number of residues were measured by the following procedure. The evaluation results are shown together in Table 1.

(41) The number of residues (defects) of 0.09 μm or more was measured after cleaning the silicon nitride substrate which has been polished using each composition for surface treatment under the above cleaning conditions. SP-2 manufactured by KLA Corporation was used for measurement of the number of residues. The measurement was performed on the remaining portion excluding a 5 mm wide portion from the outer peripheral end of the one surface of the cleaned substrate.

(42) [Evaluation of the Number of Organic Residues]

(43) Each composition for surface treatment was used to clean the silicon nitride substrate which has been polished, under the above-described cleaning conditions, and then the number of organic residues was measured by SEM observation using Review SEM RS6000 manufactured by Hitachi, Ltd. First, 100 defects present in the remaining portion excluding a 5 mm wide portion from the outer peripheral end of one surface of the silicon nitride substrate which has been polished were sampled in the SEM observation. Next, out of the 100 sampled defects, the organic residues were visually determined by SEM observation and the number of the organic residues was confirmed to calculate a ratio (%) of the organic residues in the defects. Then, a product of the number of defects of 0.09 μm or more measured using SP-2 manufactured by KLA corporation in the evaluation of the number of defects described above and the ratio (%) of the organic residues in the defects calculated from the SEM observation result was calculated as the number of organic residues. The evaluation results are shown together in Table 1.

(44) TABLE-US-00001 TABLE 1 Composition for surface Polymer Anionic surfactant treatment compound Product name Structure Comparative Water — — — Example 1 Comparative a-1 Present — — Example 2 Comparative a-2 Present Sodium straight chain C.sub.18H.sub.37—C.sub.6H.sub.4—SO.sub.3Na Example 3 alkylbenzene sulfonate Example 1 A-1 Present Sodium POE alkyl ether (C.sub.18H.sub.37O(POE)).sub.2—PO.sub.2Na phosphate (n = 1) Example 2 A-2 Present Sodium alkyl naphthalene (C.sub.3H.sub.7)—C.sub.10H.sub.4—SO.sub.3Na sulfonate Example 3 A-3 Present Sodium alkylbenzene C.sub.2H.sub.5—C.sub.6H.sub.4—SO.sub.3Na sulfonate Example 4 A-4 Present POE styrenated phenyl ether (C.sub.6H.sub.5—CH—CH.sub.3).sub.3—C.sub.6H.sub.4O(POE)SO.sub.3NH.sub.4 ammonium sulfate (n = 10) Example 5 A-5 Present POE styrenated phenyl ether (C.sub.6H.sub.5—CH—CH.sub.3)—C.sub.6H.sub.4O(POE)SO.sub.3NH.sub.4 ammonium sulfate (n = 4) Example 6 A-6 Present Disodium POE lauryl C.sub.12H.sub.25O(POE)COCH.sub.2CHCOONa(—SO.sub.3Na) sulfosuccinate (n = 3) Example 7 A-7 Present POE isodecyl ether C.sub.10H.sub.21O(POE)SO.sub.3NH.sub.4 ammonium sulfate (n = 6) Example 8 A-8 Present POE alkyl(10-12) ether C.sub.12H.sub.25O(POE)PO.sub.3 phosphate ester (n = 8) Example 9 A-9 Present Sodium POE alkyl (12-14) C.sub.12H.sub.25O(POE)COCH.sub.2CHCOONa(—SO.sub.3Na) sulfosuccinate (n = 7) Anionic surfactant Molecular weight*.sup.1 Molecular weight ratio The number of Hydrophilic Hydrophobic Hydrophilic moiety/ The number organic Total moiety moiety hydrophobic moiety pH of residues residues Comparative — — — 2.1 400000 216840 Example 1 Comparative — — — 2.1 43 23 Example 2 Comparative 432 103 329 0.31 2.1 47 22 Example 3 Example 1 712 206 506 0.41 2.1 39 13 Example 2 270 103 167 0.62 2.1 30 12 Example 3 208 103 105 0.98 2.1 25 9 Example 4 946 554 392 1.41 2.1 26 8 Example 5 471 290 181 1.60 2.1 27 11 Example 6 542 373 169 2.21 2.1 19 8 Example 7 519 378 141 2.68 2.1 17 9 Example 8 638 469 169 2.78 2.1 19 2 Example 9 718 549 169 3.25 2.1 10 4 *.sup.1In the table, the molecular weight of the anionic surfactant is a value calculated from the sum of the atomic weight.

(45) As shown in Table 1, according to the composition for surface treatment of the present invention (Examples 1 to 9), it was confirmed that the residues on the surface of the object which has been polished including silicon nitride can be sufficiently removed. Among the residues on the surface of the object which has been polished including silicon nitride, silicon oxide, or polysilicon, in particular, the surface of the organic residues having high hydrophobicity such as pad waste is difficult to be removed, but from the above results, it is considered that the organic residues of the surface of the object which has been polished can be also sufficiently removed. Also, according to the composition for surface treatment of the present invention, since the surface of the object which has been polished including polysilicon which has high hydrophobicity can be hydrophilized, it is considered that the composition can be appropriately used for removal of, in particular, the residues on the surface of the object which has been polished including polysilicon.

(46) Meanwhile, it was shown that the composition for surface treatment of Comparative Example 3 using the anionic surfactant having the molecular weight of the hydrophilic moiety/the molecular weight of the hydrophobic moiety of less than 0.4 had the effect of removing the residues which is inferior even to that of Comparative Example 2 which does not include the anionic surfactant.

(47) Also, from a comparison of Example 1 and Example 2, it was shown that by using the anionic surfactant having the molecular weight of the hydrophilic moiety/the molecular weight of the hydrophobic moiety of 0.6 or more, the effect of removing the residues is more improved.

(48) Also, from a comparison of Example 5 and Example 6, it was shown that by using the anionic surfactant having the molecular weight of the hydrophilic moiety/the molecular weight of the hydrophobic moiety of 2.2 or more, the effect of removing the residues is further improved.

(49) Also, from a comparison of Example 8 and Example 9, it was shown that by using the anionic surfactant having the molecular weight of the hydrophilic moiety/the molecular weight of the hydrophobic moiety of 3.2 or more, the effect of removing the residues is further improved.

(50) The present application is based on the Japanese patent application No. 2017-044133 filed on Mar. 8, 2017, and a disclosed content thereof is incorporated herein as a whole by reference.