TWI405844B - Preparation method of protective film for wafer pattern and preparation method of liquid - Google Patents

Abstract

Disclosed is a chemical liquid relating to the washing of the surface of a wafer having an irregular pattern formed thereon and applicable to a method in which after a wafer is immersed in water, the wafer is pulled up from water and exposed to a gas atmosphere containing a vaporized "chemical liquid for forming a water-repellent protective film". The chemical liquid is used when washing a silicon wafer having a fine irregular pattern on a surface thereof for forming a water-repellent protective film on the surface having the irregular pattern, and the chemical liquid is supplied to the surface having the irregular pattern in the form of a vapor after introducing an OH group into the surface having the irregular pattern and contains: 93.5 to 97.499 % by mass of at least one fluorine-containing solvent selected from a group consisting of hydrofluorocarbon, hydrofluoroether, perfluorocarbon, and hydrochlorofluorocarbon; 2 to 5% by mass of at least one glycol ether acetate selected from a group consisting of ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate; 0.5 to 5% by mass of at least one silazane compound selected from a group consisting of hexamethyldisilazane and tetramethyldisilazane; and 0.001 to 0.25% by mass of at least one acid selected from a group consisting of trifluoroacetic acid, trifluoroacetic anhydride, trimethylsilyl trifluoroacetate, and dimethylsilyl trifluoroacetate.

Description

Method for preparing protective liquid for forming protective film of wafer pattern and chemical solution

The present invention relates to a water-repellent protective film forming liquid for preventing collapse of a concave-convex pattern caused by water (also referred to as damage) when cleaning a surface of a wafer on which a fine uneven pattern is formed. It is effective to reduce the capillary force of the pattern portion.

In the manufacture of a semiconductor wafer, fine concavo-convex patterns are formed on the surface of the germanium wafer by lithography or etching, and thereafter, the surface of the wafer is cleaned and washed with water (pure water). The components have a tendency to be finer, and the interval between the concave and convex patterns becomes narrower and narrower. Therefore, it is easy to cause a problem that capillary force generated when water (pure water) is used for washing and water is dried from the surface of the wafer causes the concave-convex pattern to collapse. This problem is particularly remarkable for a semiconductor wafer having a pattern size of 20 nm and a size of 10 nm which is narrower in the pattern of the unevenness.

As a method of washing the surface of the wafer while preventing the pattern from collapsing, Patent Document 1 discloses a method in which water remaining on the surface of the wafer is replaced with isopropyl alcohol or the like, followed by drying. Further, Patent Document 2 discloses a method in which a water-repellent protective film (which is finally removed) is formed in a concave-convex pattern portion after washing the surface of the wafer with water, followed by rinsing with water and then drying. This method is also effective for a pattern having an aspect ratio of 8 or more.

In addition, in addition to the prevention of pattern collapse, the method of cleaning a semiconductor wafer is disclosed in Patent Document 3, in which the wafer is immersed in a tank in which pure water is stored, and thereafter in the tank. A method of exposing a wafer to a gas containing a vapor of 1,1,1,3,3,3-hexafluoro-2-propanol for removing moisture.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-45843

[Patent Document 2] Japanese Patent No. 4403202

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2009-212445

It is known that a wafer cleaning method including a step of immersing a wafer in water, and then lifting a wafer from water and exposing the wafer to a vapor of the chemical liquid is performed by washing a plurality of wafers at a time. Further, in order to improve the efficiency of the semiconductor wafer cleaning process, it is necessary to solve the following two problems when it is applied to a cleaning method for forming a hydrophobic protective film to prevent collapse of the uneven pattern.

1) The liquid used to form the water-repellent protective film is easily vaporized

2) The vaporized chemical solution is compatible with water remaining on the surface of the wafer, and a water-repellent protective film can be formed in the concave-convex pattern portion.

An object of the present invention is to provide a chemical liquid applicable to the wafer cleaning method for cleaning the surface of a wafer on which a concave-convex pattern is formed.

The chemical solution for forming a protective film for a wafer pattern according to the present invention is characterized in that, when the silicon wafer having a fine uneven pattern on the surface is washed, a chemical liquid for forming a water-repellent protective film on the surface of the concave-convex pattern is formed, and And comprising: at least one fluorine-containing solvent selected from the group consisting of hydrofluorocarbon, hydrofluoroether, perfluorocarbon, and hydrochlorofluorocarbon, 93.5 to 97.499% by mass; selected from ethylene glycol monomethyl ether acetate At least one or more glycol ether acetates of the group consisting of esters and propylene glycol monomethyl ether acetate are 2 to 5% by mass; selected from the group consisting of hexamethyldiazepine and tetramethyldiazide At least one or more kinds of decazane compounds in the group of components are 0.5 to 5% by mass; and are selected from the group consisting of trifluoroacetic acid, trifluoroacetic anhydride, trimethyl decyl trifluoroacetate, and dimethyl decyl trifluoroacetate. At least one or more kinds of acids in the group are 0.001 to 0.25 mass%.

By forming the above-mentioned chemical liquid, it is a problem that is suitable for the above-mentioned two methods of solving the problem of "the object to be solved by the invention" and is suitable for the above-described wafer cleaning method:

1) Providing a liquid that is easy to vaporize to form a water-repellent protective film

2) The vaporized chemical solution is compatible with water remaining on the surface of the wafer, and a water-repellent protective film can be formed in the concave-convex pattern portion.

In particular, it is suitable for a wafer cleaning method including a step of immersing a wafer in water and then lifting the wafer from water and exposing the wafer to vapor of the chemical liquid. In the cleaning method, when the ruthenium wafer having the uneven pattern including the ruthenium oxide such as ruthenium oxide, tantalum nitride or ruthenium is immersed in water, the OH group is introduced on the surface of the concave-convex pattern including the layers or the like. . Further, the vapor of the chemical solution is dissolved in the water of the concave-convex pattern portion by lifting the wafer from the water and exposing it to the atmosphere of the vapor of the chemical liquid.

In this process, the above-described decazane compound reacts with the OH group on the surface of the concave-convex pattern to form a water-repellent protective film on the surface of the concave-convex pattern. Thereafter, the wafer is dried, and the water repellent protective film is removed from the wafer by UV irradiation, ozone treatment, heat treatment, or the like.

Since the chemical solution for forming a protective film for a wafer pattern of the present invention is easily vaporized and has excellent compatibility with water, the water-repellent protective film can be efficiently formed on the surface of the concave-convex pattern of the wafer by the wafer cleaning method.

The protective film forming chemical liquid for forming a wafer pattern according to the present invention is a method for forming a water-repellent protective film on the surface of the concave-convex pattern when cleaning a germanium wafer having a fine uneven pattern on the surface, comprising: selected from the group consisting of hydrofluorocarbon At least one or more fluorine-containing solvents of the group consisting of hydrofluoroether, perfluorocarbon and hydrochlorofluorocarbon 93.5 to 97.499% by mass; selected from ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether At least one or more glycol ether acetates of the group consisting of acid esters, 2 to 5% by mass; at least one selected from the group consisting of hexamethyldiazepine and tetramethyldiazepine And more than 0.5 to 5% by mass of the above sulfonium compound; and at least 1 selected from the group consisting of trifluoroacetic acid, trifluoroacetic anhydride, trimethyl decyl trifluoroacetate, and dimethyl decyl trifluoroacetate The above acid is 0.001~0.25% by mass.

When the concentration of the above decazane compound is lowered, the water repellency protective film cannot be sufficiently formed. On the other hand, since the above-mentioned decazane compound has flammability, if the concentration is increased, the risk of flammability increases. Since the chemical solution for forming a protective film of the present invention is vaporized, it is important to reduce the risk of flammability. According to the above, the concentration of the above guanidinium compound is from 0.5 to 5% by mass, more preferably from 0.7 to 4% by mass.

At least one or more acid groups selected from the group consisting of trifluoroacetic acid, trifluoroacetic anhydride, trimethyl decyl trifluoroacetate, and dimethyl decyl trifluoroacetate are used to promote the above-described decazane compound and embossing The reaction of the OH group on the surface of the pattern is effective. If the concentration of the above acid is small, the promoting effect becomes small. However, since the reaction of the above-mentioned acid with the above-mentioned decane compound lowers the reactivity of the decazane compound, when the concentration of the above-mentioned acid is large, the storage stability of the protective film-forming drug solution is lowered. Therefore, the concentration of the above acid is 0.001 to 0.25 mass%, particularly preferably 0.005 to 0.25 mass%.

The above glycol ether acetate is water-soluble and is effective for improving the compatibility of the protective film forming drug solution of the present invention with water. However, since the boiling point is high, if the concentration becomes high, vaporization of the chemical liquid becomes difficult. Therefore, the concentration of the above glycol ether acetate is 2 to 5% by mass, and more preferably 2.5 to 4% by mass.

The fluorine-based solvent has a low boiling point if the flammability is low (that is, the ignition point is high). Therefore, when the concentration is high, the flammability of the protective film forming chemical liquid becomes low (that is, the ignition point becomes high), and vaporization can be performed safely. However, when the concentration is too high, the concentration of the above-described decazane compound, the above acid, and the above glycol ether acetate becomes low. Therefore, the concentration is 93.5 to 97.499% by mass, more preferably 94.0 to 97.0% by mass.

The method for preparing a chemical solution for forming a protective film of the present invention comprises the step of mixing the fluorine-based solvent, the ether acetate, the aziridine compound, and the acid in a desired ratio.

Further, there is a possibility that the above-mentioned decazane compound reacts with the above acid to lower the reactivity of the decazane compound. Therefore, when the decane compound is mixed with the acid, if the fluorinated solvent or the ether acetate is used in advance to dilute at least one of the decazane compound and the acid, the reaction can be prevented from proceeding drastically. Therefore, it is better.

Further, the method for preparing a chemical solution of the present invention comprises the steps of mixing the fluorine-containing solvent, the glycol ether acetate, the aziridine compound, and the acid in a desired ratio, or before mixing. At least one of the fluorine-containing solvent, the glycol ether acetate, the decazane compound, the acid, and the mixed liquid mixture is purified by an adsorbent such as a molecular sieve or distillation or the like to remove water. Further, the aziridine compound and the acid before the mixing may be in a state of containing a solvent (a fluorine-containing solvent or a glycol ether acetate). The entire solution may be purified in advance before mixing, or the mixed solution may be purified.

In addition, the water content in the chemical solution forming solution is preferably 5,000 ppm by mass or less, more preferably 1,000 ppm by mass or less, and still more preferably 500 ppm by mass or less based on the total amount of the chemical solution. Further, the water content may be 50 ppm by mass or more.

Further, the chemical solution for forming a protective film of the present invention may contain other additives in addition to the fluorine-containing solvent, the glycol ether acetate, the above-described decazane compound, and the acid, without impairing the object of the present invention. Wait. Examples of the additive include an oxidizing agent such as hydrogen peroxide or ozone, a surfactant, and the like. Further, when a material which cannot form a protective film by the above-described aziridine compound exists in one of the concave-convex patterns of the wafer, a protective film may be added to the material.

As a method of cleaning a wafer having a fine uneven pattern on the surface, a method of using the chemical liquid of the present invention will be described below. The wafer W on which the surface of the concave-convex pattern is formed is introduced into the cleaning device 1 shown in FIG. Here, the surface of the uneven pattern is formed by various concave-convex pattern forming methods such as the RIE method, and it is preferable to use a groove having an interval of 45 nm or less and an aspect ratio of 5 or more. The surface of the concave-convex pattern includes tantalum, and the surface includes at least one of ruthenium oxide, tantalum nitride, polycrystalline germanium, and single crystal germanium.

The wafer W is held by the holder 4 by the holder 5 of the wafer W, and is immersed in the aqueous cleaning solution 2 of the water washing tank 3 together with the support member 4. Here, the water-based cleaning liquid 2 may be water or a mixture of an organic solvent, an acid, an alkali, or an oxidizing substance in water, and the water content is 50% by mass. Above). The aqueous cleaning solution 2 may also be plural. Further, in consideration of the degree of cleanliness, the aqueous cleaning solution is preferably water, or in the case of a plurality of species, the last is water.

After holding in the aqueous cleaning solution 2 for, for example, 0.5 to 10 minutes, the wafer W is lifted together with the support member 4. At this time, the concave-convex pattern concave portion is in a state in which the aqueous cleaning liquid is filled. After the wafer W is lifted from the aqueous cleaning solution, the groove 3 is preferably discharged to the outside of the apparatus 1, or is covered with a lid to be sealed in an environment in the apparatus 1.

Then, the protective film forming chemical liquid is vaporized by a device (not shown), and the protective film forming chemical liquid introducing device 1 is vaporized by a pipe or the like, and it is preferable to use a protective film forming chemical liquid in the device 1. The steam is full. By appropriately maintaining this state, replacement of the vapor of the protective film forming chemical liquid and the aqueous cleaning liquid filled with the concave-convex pattern concave portion is caused.

A hydroxyl group is generated on the surface of the concave-convex pattern by the previous aqueous cleaning solution, and the hydroxyl group reacts with the aziridine compound, thereby forming a water-repellent protective film. After the protective film is formed, the wafer W is dried in the apparatus 1 or in a state of being taken out of the apparatus 1 to remove the water-repellent protective film.

The removal of the water-repellent protective film may be performed by removing at least one of the treatments selected from the steps of light-irradiating the wafer surface, heating the wafer, and exposing the wafer to ozone. Further, in this step, plasma irradiation, corona discharge, or the like may be used in combination.

[Examples]

The degree of water repellency can be determined by the contact angle with respect to water. However, in the case of a wafer having a fine uneven pattern on the surface, since the pattern is very fine, the contact angle of the protective film itself formed on the surface of the concave-convex pattern cannot be accurately evaluated. The contact angle of water droplets is evaluated by adding a few microliters of water droplets to the surface of the sample (substrate) as described in JIS R 3257 "Test method for wettability of substrate glass surface", by measuring water droplets and the surface of the substrate. In terms of the angle. However, in the case of a patterned wafer, the contact angle becomes very large. The reason for this is that the contact angle is affected by the surface shape (roughness) of the substrate due to the effect of the Wenzel effect or the Cassie effect, and the contact angle of the water droplet is increased.

Therefore, in the present invention, the above-mentioned chemical liquid is supplied to a wafer having a smooth surface to form a protective film on the surface of the wafer, and the protective film is regarded as being formed on the surface of the wafer on which the fine uneven pattern is formed on the surface. Membrane, evaluated. Further, in the present invention, the wafer having a smooth surface is a tantalum wafer having a surface having a thermal oxide film layer and a smooth surface.

The details are as follows. Hereinafter, the evaluation method of the wafer to which the protective film forming chemical liquid is supplied, the preparation of the protective film forming chemical liquid, and the evaluation result after the supply of the protective film forming chemical liquid to the wafer will be described.

[Evaluation method of wafer supplied with protective film forming liquid]

As evaluation methods of the wafer to which the protective film formation liquid is supplied, the following evaluations (1) and (2) were performed.

(1) Evaluation of contact angle of protective film formed on the surface of the wafer

About 2 μl of pure water was placed on the surface of the wafer on which the protective film was formed, and the angle (contact angle) between the water droplet and the surface of the wafer was measured by a contact angle meter (manufactured by Kyowa Interface Science: CA-X type). Here, the contact angle of the protective film is in the range of 50 to 130° (it is indicated as ○ in the table).

(2) Evaluation of capillary force

P was calculated using the following formula, and the capillary force (absolute value of P) was obtained.

P=2×γ×cosθ/S

Here, γ represents a surface tension, θ represents a contact angle, and S represents a pattern size. Further, the pattern having a line width of 45 nm has a tendency that the pattern is liable to collapse when the cleaning liquid at the gas-liquid interface passes through the wafer, and the pattern is hard to collapse in the case of 2-propanol. When the pattern size is 45 nm and the surface of the wafer is yttrium oxide, if the cleaning solution is 2-propanol (the surface tension is 22 mN/m and the contact angle with yttrium oxide is 1°), the capillary force becomes 0.98 MN/m ² . On the other hand, if the cleaning liquid is water having the highest surface tension in a liquid other than mercury (surface tension is 72 mN/m, and the contact angle with cerium oxide is 2.5°), the capillary force becomes 3.2 MN/m ^{2 .} . Therefore, based on 2.1 MN/m ² in the middle, if the capillary force when water is maintained is 2.1 MN/m ² or less, it is qualified (indicated as ○ in the table), and it is more than 2.1 MN/m ² . It is unqualified (marked as × in the table).

Example 1

(1) Modulation of protective film forming liquid

95.4 g of hydrofluoroether (Novec HFE-7100) manufactured by 3M as a fluorine-containing solvent, and 3 g of propylene glycol monomethyl ether acetate (PGMEA, Propylene Glycol Monomethyl Ether Acetate) as a glycol ether acetate were mixed and used. Molecular sieve 4A (manufactured by Union Showa) removes water from the mixed solution and purifies it. Then, 1.5 g of hexamethyldiazepine [(H ₃ C) ₃ Si-NH-Si(CH ₃ ) ₃ ] as a decazane compound was mixed with the obtained mixture, and trifluoroacetic acid was used as the acid. Silane methyl ester _{[(CH 3) 3 Si-} OC (O) CF 3] 0.1 g, which was obtained by the water content of 10 ppm by mass or less, a concentration of the fluorine-containing solvent is 95.4% by mass, glycol ether acetate A chemical solution for forming a protective film having an ester concentration of 3% by mass, a decazane compound concentration of 1.5% by mass, and an acid concentration of 0.1% by mass. Further, the water content in the chemical solution was measured by a Karl Fischer moisture meter (manufactured by Kyoto Electronics, ADP-511 type).

(2) Wafer cleaning

A silicon wafer with a smooth thermal oxide film (Si wafer having a thermal oxide film layer having a thickness of 1 μm) was immersed in a 1% by mass aqueous solution of hydrofluoric acid for 2 min at room temperature, followed by pure water. Immerse for 1 min.

(3) Surface treatment of the surface of the wafer by the protective film forming solution

100 ml of the protective film forming chemical solution prepared in the above "(1) Preparation of protective film forming solution" was placed in a l l beaker, and the beaker was heated by a heater to boil the chemical solution. After the boiling stability, the wafer prepared in the "(2) Wafer Cleaning" is wetted in water, is not immersed in the chemical solution, and is placed in the beaker, and the vapor of the chemical liquid is placed in the beaker. Supply to the wafer. After maintaining this state for 3 minutes, the wafer was taken out and allowed to dry naturally.

The obtained wafer was evaluated based on the points described in the "Method for Evaluating Wafers Provided with Protective Film Forming Liquid", and as shown in Table 1, although the initial contact angle before surface treatment was less than 10°, The contact angle after the surface treatment was 80°, showing the water repellency imparting effect. Further, the capillary force when water was held was 0.6 MN/m ² , and the capillary force was small.

Example 2

All of the same procedures as in Example 1 were carried out except that trifluoroacetic acid was used as the acid. As a result, as shown in Table 1, although the initial contact angle before the surface treatment was less than 10°, the contact angle after the surface treatment was 78°, showing the water repellency imparting effect. Further, the capillary force when water was maintained was 0.7 MN/m ² , and the capillary force was small.

Example 3

All of the same procedures as in Example 1 were carried out except that trifluoroacetic anhydride was used as the acid. As a result, as shown in Table 1, although the initial contact angle before the surface treatment was less than 10°, the contact angle after the surface treatment was 80°, showing the water repellency imparting effect. Further, the capillary force when water was held was 0.6 MN/m ² , and the capillary force was small.

Example 4

All of the same procedures as in Example 1 were carried out except that 1,2-dichloro-3,3,3-trifluoropropene (DCTFP) was used as the fluorine-containing solvent. As a result, as shown in Table 1, although the initial contact angle before the surface treatment was less than 10°, the contact angle after the surface treatment was 82°, showing the water repellency imparting effect. Further, the capillary force when water was held was 0.4 MN/m ² , and the capillary force was small.

Example 5

All of the same procedures as in Example 1 were used except that the decazane compound was tetramethyldiazepine [(H ₃ C) ₂ Si(H)-NH-Si(H)(CH ₃ ) ₂ ]. As a result, as shown in Table 1, although the initial contact angle before the surface treatment was less than 10°, the contact angle after the surface treatment was 82°, showing the water repellency imparting effect. Further, the capillary force when water was held was 0.4 MN/m ² , and the capillary force was small.

Example 6

All of the same procedures as in Example 5 were carried out except that trifluoroacetic acid was used as the acid. As a result, as shown in Table 1, although the initial contact angle before the surface treatment was less than 10°, the contact angle after the surface treatment was 80°, showing the water repellency imparting effect. Further, the capillary force when water was held was 0.6 MN/m ² , and the capillary force was small.

Comparative example 1

The same as in the first embodiment except that the protective film forming solution liquid was not supplied to the wafer. That is, in this comparative example, the wafer in the surface state which was not dialed was evaluated. The evaluation results are shown in Table 1. The contact angle of the wafer was as low as 3°, and the capillary force when water was held was large, being 3.2 MN/m ² .

Comparative example 2

The same applies to Example 1 except that the concentration of the decazane compound was 0.1% by mass and the concentration of the fluorine-containing solvent was 96.8% by mass. The evaluation results are shown in Table 1. The contact angle after the surface treatment was as low as 30°, and the capillary force when water was held was large, being 2.8 MN/m ² .

Comparative example 3

All of them were the same as in Example 1 except that the acid concentration was 0.0001% by mass and the fluorine-containing solvent concentration was 95.4999% by mass. The evaluation results are shown in Table 1. The contact angle after surface treatment was as low as 36°, and the capillary force when water was retained was large, being 2.6 MN/m ² .

1. . . Device used when washing a wafer using the liquid of the present invention

2. . . Water cleaning solution

3. . . Washing tank

4. . . Wafer W support

5. . . Wafer W holder

W. . . Semiconductor wafer having a concave-convex pattern surface

Fig. 1 is a view schematically showing an example of a device used for washing a wafer using the chemical solution of the present invention.

1. . . Device used when washing a wafer using the liquid of the present invention

2. . . Water cleaning solution

3. . . Washing tank

4. . . Wafer W support

5. . . Wafer W holder

W. . . Semiconductor wafer having a concave-convex pattern surface

Claims (2)

A liquid medicine for forming a water-repellent protective film on a surface of the concave-convex pattern when the surface of the concave-convex pattern is cleaned on the surface of the concave-convex pattern; the chemical liquid is introduced into the surface of the concave-convex pattern After that, it is supplied as a vapor to the surface of the concave-convex pattern, and contains at least one or more fluorine-containing solvents selected from the group consisting of hydrofluorocarbon, hydrofluoroether, perfluorocarbon, and hydrochlorofluorocarbon, 93.5 to 97.499 mass%. a glycol ether acetate of at least one selected from the group consisting of ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate; 2 to 5% by mass; selected from hexamethyldiazine At least one or more kinds of decazane compounds of the group consisting of azaxane and tetramethyldiazepine are 0.5 to 5% by mass; and are selected from trifluoroacetic acid, trifluoroacetic anhydride, trimethylacetate trimethylacetate At least one or more acids selected from the group consisting of esters and dimethyl decyl trifluoroacetate are 0.001 to 0.25 mass%. A method for preparing a chemical solution for forming a water-repellent protective film on a surface of a concave-convex pattern, which is characterized in that it is prepared by the liquid medicine of claim 1 and by mixing the following components before mixing and the mixed liquid Purifying at least one of the water content in the chemical solution is 5000 mass ppm or less with respect to the total amount of the chemical liquid: a group selected from the group consisting of hydrofluorocarbon, hydrofluoroether, perfluorocarbon, and hydrochlorofluorocarbon At least one or more kinds of fluorine-containing solvents; at least one selected from the group consisting of ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate; At least one or more of a decazane compound of a group consisting of hexamethyldiazepine or tetramethyldiazepine; and a trimethyl decane selected from the group consisting of trifluoroacetic acid, trifluoroacetic anhydride, and trifluoroacetic acid trimethylacetate At least one or more acids selected from the group consisting of esters and dimethyl decyl trifluoroacetate.