JP2017168710A - Wafer cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer cleaning method by which a stable water-repellent property can be imparted to a wafer surface without causing the degradation of a vinyl chloride resin even in the case of using a chemical solution for water-repellent protection film formation which has been stored over a long time in wafer cleaning by using a wafer cleaning apparatus including the vinyl chloride resin as a liquid-contact member.SOLUTION: A wafer cleaning method comprises: a preparation step for mixing a first liquid containing a sililation reagent, and a second liquid containing tertiary alcohol to prepare a chemical solution for water-repellent protection film formation; and a water-repellent protection film formation step for holding the chemical solution for water-repellent protection film formation at least in a concave portion of a convex-concave pattern to form a water-repellent protection film on the surface of the concave portion after the preparation step. The amount of the tertiary alcohol is 80-100 mass% to a total amount of nonaqueous solvent, including an aprotic solvent included in the first liquid and the tertiary alcohol in the second liquid. The content of the sililation reagent is 1-20 mass% to a total amount of the first liquid and the second liquid.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wafer cleaning method using a wafer cleaning apparatus including a vinyl chloride resin as a liquid contact member.

  As described in Patent Documents 1 to 8, some wafer cleaning apparatuses use a vinyl chloride resin as a member that comes into contact with a cleaning liquid or a processing liquid (a liquid contact member). There is a need to not degrade the vinyl resin.

In the patent document 9, the present applicant
As a water-repellent cleaning solution for improving a cleaning process that easily induces pattern collapse in a method of manufacturing a silicon wafer having a fine uneven pattern on the surface,
A silicon wafer comprising a water-repellent compound containing a reactive site capable of chemically bonding to Si and a hydrophobic group, or 0.1% by weight or more of the water-repellent cleaning liquid with respect to 100% by weight in total. It discloses a mixture containing an aqueous compound and an organic solvent, and discloses a wafer cleaning method using the water-repellent cleaning liquid.
Moreover, it discloses that the following compounds are used as the water repellent compound.
R ³ Si (CH ₃ ) ₂ Y
Here, R ³ is a monovalent organic group containing a hydrocarbon group having 1 to 18 carbon atoms or a monovalent organic group containing a perfluoroalkyl chain having 1 to 8 carbon atoms. Y represents a monovalent organic group in which the element bonded to Si is nitrogen.

JP 05-259136 A JP 07-245283 A JP-A-10-189527 Japanese Patent Laid-Open No. 10-229062 JP 11-283949 A JP 2001-087725 A JP 2008-098440 A JP 2010-003739 A JP 2010-192878 A

In a method for cleaning a wafer having a fine concavo-convex pattern on the surface with a wafer cleaning apparatus containing a vinyl chloride resin as a liquid contact member and at least a part of the concavo-convex pattern containing silicon
Even in the chemical solution for forming a water repellent protective film described in Patent Document 9, as a solvent contained in the chemical solution, for example, glycol acetates such as propylene glycol monomethyl ether acetate (PGMEA) and ketones such as cyclohexanone are used. In some cases, the chemical solution deteriorates the vinyl chloride resin.
In addition, since the water-repellent compound contained in the chemical solution for forming a water-repellent protective film described in Patent Document 9 easily reacts with a protic solvent, the water-repellent compound and, for example, a protic property such as a primary alcohol or a secondary alcohol The water-repellent protective film-forming chemical after mixing with a solvent and storing for a long time has a water repellency-imparting effect that suddenly changes (decreases) over time and becomes unstable. There was a case.

Therefore, the present invention is a wafer cleaning apparatus containing a vinyl chloride resin as a liquid contact member, and a wafer having a fine concavo-convex pattern on the surface and at least a part of the concavo-convex pattern containing silicon element (hereinafter simply referred to as “wafer”). In the method of cleaning)
Even when using a chemical solution for forming a water-repellent protective film that has been stored for a long time (hereinafter sometimes simply referred to as “chemical solution for forming a protective film” or “chemical solution”)
It is an object of the present invention to provide a wafer cleaning method capable of imparting stable water repellency to the wafer surface without deteriorating the vinyl chloride resin.

The present invention provides a method for cleaning a wafer having a fine concavo-convex pattern on a surface thereof and having at least a part of the concavo-convex pattern containing silicon element by a wafer cleaning apparatus containing a vinyl chloride resin as a liquid contact member.
A first step containing a silylating agent represented by the following general formula [1] and a second solution containing a tertiary alcohol to prepare a chemical solution for forming a water-repellent protective film, a preparation step,
After the preparation step, the water-repellent protective film-forming chemical solution is retained in at least the concave portion of the concave-convex pattern to form a water-repellent protective film (hereinafter sometimes simply referred to as “protective film”) on the concave surface. A water repellent protective film forming step,
An aprotic solvent that may be contained in the first liquid, and
The amount of the tertiary alcohol is 80 to 100% by mass relative to 100% by mass of the total amount of the nonaqueous solvent including the tertiary alcohol in the second liquid,
The amount of the silylating agent (silylating agent content) with respect to 100% by mass of the total amount of the first liquid and the second liquid is 1 to 20% by mass.
A wafer cleaning method.
(R ¹ ) _a (H) _3-a Si—N (R ² ) ₂ [1]
[In the formula [1], R ^{1 s} are independently of each other from the group consisting of monovalent hydrocarbon groups having 1 to 18 carbon atoms in which some or all of the hydrogen elements may be replaced by fluorine elements. At least one group selected, and each R ² is independently selected from the group consisting of monovalent hydrocarbon groups having 1 to 8 carbon atoms. a is 2 or 3. ]
In the present invention, the time during which the chemical solution is stored after the preparation step and before the water-repellent protective film forming step is referred to as “standing time”.

The silylating agent is preferably a silylating agent represented by the following general formula [2].
(R ³ ) (CH ₃ ) ₂ Si—N (R ⁴ ) ₂ [2]
[In the formula [2], R ³ is a monovalent hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen elements may be replaced by fluorine elements, and R ⁴ is independent of each other. And a methyl group or an ethyl group. ]

  The tertiary alcohol is at least one selected from the group consisting of tert-butyl alcohol, tert-amyl alcohol, 2-methyl-2-pentanol, 3-methyl-3-pentanol, and 3-ethyl-3-pentanol. It is preferable that In the present invention, when a tertiary alcohol is used as a solvent for a cleaning liquid or a chemical solution for forming a water repellent protective film, it is desirable to control the liquid temperature so that the tertiary alcohol does not coagulate in the cleaning liquid or the chemical liquid. More preferably, the temperature of the cleaning liquid or chemical liquid using a tertiary alcohol is set to a temperature equal to or higher than the melting point of the tertiary alcohol.

  The silylating agent content is preferably 1 to 5% by mass.

  It is preferable to perform the said preparation process and the said water-repellent protective film formation process continuously.

  After the water repellent protective film forming step, it is preferable to remove the water repellent protective film forming chemical from the recesses by drying.

  After the water repellent protective film forming step, it is preferable to replace the chemical liquid for forming the water repellent protective film in the concave portion with a cleaning liquid different from the chemical liquid, and remove the cleaning liquid from the concave portion by drying.

  Further, the water-repellent protective film is removed by performing at least one treatment selected from the group consisting of heat treatment, light irradiation treatment, ozone exposure treatment, plasma irradiation treatment, and corona discharge treatment on the wafer surface after the drying. May be.

  Even when the wafer cleaning method of the present invention is performed, the liquid contact member made of vinyl chloride resin in the wafer cleaning apparatus does not deteriorate. In addition, according to the wafer cleaning method of the present invention, even when a chemical solution for forming a water-repellent protective film stored for a long time is used, it is possible to impart stable water repellency to the wafer surface. Capillary force on the surface of the pattern is reduced, and as a result, a stable pattern collapse preventing effect is exhibited. When the cleaning method is carried out, the cleaning step in the method for manufacturing a wafer having a fine uneven pattern on the surface is improved without lowering the throughput. Therefore, the wafer manufacturing method using the wafer cleaning method of the present invention has high productivity.

  The wafer cleaning method of the present invention can cope with a concavo-convex pattern having an aspect ratio of, for example, 7 or more which is expected to become higher in the future, and can reduce the cost of production of higher-density semiconductor devices. In addition, the conventional apparatus can be applied without major changes such as a wetted member, and as a result, can be applied to the manufacture of various semiconductor devices.

The figure which shows a schematic diagram when the wafer 1 made into the surface which has the fine uneven | corrugated pattern 2 on the surface is perspective. FIG. 2 shows a part of a cross section a-a ′ in FIG. 1. The flowchart showing an example of the washing | cleaning method of this invention. The schematic diagram of the state in which the recessed part 4 hold | maintained the chemical | medical solution 8 for protective film formation. The schematic diagram of the state by which the liquid was hold | maintained at the recessed part 4 in which the protective film was formed. The graph which plotted the relationship between the stationary time of Tables 2-6, and a contact angle. The graph which plotted the relationship between the stationary time of Table 7, and a contact angle. The graph which plotted the relationship between the standing time and contact angle of Examples 4-1, 4-2, 4-5, and Tables 8 and 9.

  As a wafer to be subjected to the cleaning method of the present invention, a wafer in which a film containing a silicon element such as silicon, silicon oxide, or silicon nitride is formed on the wafer surface, or when the above uneven pattern is formed, the uneven pattern is formed. In which at least a part of the surface thereof contains silicon element such as silicon, silicon oxide, or silicon nitride. In addition, a protective film can be formed on the surface of a component containing a silicon element even for a wafer composed of a plurality of components containing at least a silicon element. As the wafer composed of the plurality of components, silicon, silicon oxide, silicon nitride and other components containing silicon elements are formed on the wafer surface, or when the concavo-convex pattern is formed, at least the concavo-convex pattern A part of which includes a silicon element such as silicon, silicon oxide, and silicon nitride is also included. In addition, it is the surface of the part containing the silicon element in the said uneven | corrugated pattern that can form a protective film with the said chemical | medical solution.

  In general, in order to obtain a wafer having a fine uneven pattern on the surface, first, a resist is applied to a smooth wafer surface, and then the resist is exposed through a resist mask, and the exposed resist or the exposed resist is exposed. A resist having a desired concavo-convex pattern is produced by etching away the resist that was not present. Moreover, the resist which has an uneven | corrugated pattern can be obtained also by pressing the mold which has a pattern to a resist. Next, the wafer is etched. At this time, the wafer surface corresponding to the concave portion of the resist pattern is selectively etched. Finally, when the resist is removed, a wafer having a fine uneven pattern is obtained.

  After the surface of the wafer has a fine uneven pattern, the surface is cleaned with an aqueous cleaning solution, and the aqueous cleaning solution is removed by drying or the like. Is likely to occur. The concavo-convex pattern is defined as shown in FIGS. FIG. 1 is a schematic view when a wafer 1 whose surface is a surface having a fine concavo-convex pattern 2 is viewed from the perspective, and FIG. . As shown in FIG. 2, the width 5 of the concave portion is indicated by the interval between the convex portion 3 and the convex portion 3, and the aspect ratio of the convex portion is expressed by dividing the height 6 of the convex portion by the width 7 of the convex portion. Is done. Pattern collapse in the cleaning process tends to occur when the width of the recess is 70 nm or less, particularly 45 nm or less, and the aspect ratio is 4 or more, particularly 6 or more.

  Prior to the cleaning method of the present invention, the wafer obtained by etching as described above and having a fine uneven pattern may be cleaned with an aqueous cleaning solution in order to remove etching residues and the like. After the cleaning, the aqueous cleaning liquid held in the recess may be replaced with a cleaning liquid different from the aqueous cleaning liquid (hereinafter referred to as “cleaning liquid A”), and further cleaning may be performed.

  Examples of the aqueous cleaning liquid include water or an aqueous solution in which at least one of organic solvents, hydrogen peroxide, ozone, acid, alkali, and surfactant is mixed in water (for example, the water content is 10 mass). % Or more).

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

  In the present invention, the cleaning method of the wafer is not particularly limited as long as the chemical solution or the cleaning solution can be held in at least the concave portion of the concave / convex pattern of the wafer. As a wafer cleaning method, a wafer cleaning method represented by spin cleaning in which a wafer is cleaned one by one by supplying liquid to the vicinity of the rotation center while rotating the wafer while holding the wafer substantially horizontal, or a plurality of cleaning methods in the cleaning tank. One example is a batch system in which a single wafer is immersed and washed. The form of the chemical solution or the cleaning liquid when supplying the chemical solution or the cleaning liquid to at least the concave portion of the concave / convex pattern of the wafer is not particularly limited as long as it becomes liquid when held in the concave portion. And steam.

  Examples of the organic solvent that is one of the preferred examples of the cleaning liquid A include hydrocarbons, esters, ethers, ketones, halogen-containing solvents, sulfoxide solvents, lactone solvents, carbonate solvents, alcohols, Examples include a derivative of a polyhydric alcohol having an OH group, a derivative of a polyhydric alcohol having no OH group, and a nitrogen element-containing solvent. Of these, hydrocarbons, ethers, alcohols, and polyhydric alcohol derivatives having no OH group and acetate group are preferable because the vinyl chloride resin is hardly deteriorated. When an organic solvent is used as the cleaning liquid A, hydrocarbons, ethers, alcohols, polyhydric alcohol derivatives having no OH group and acetate group, which are preferable solvents, are 80% by mass of the total amount of the organic solvent. It is desirable to occupy the above.

  The chemical solution for forming a protective film of the present invention is used by replacing the above-mentioned aqueous cleaning solution or cleaning solution A with the chemical solution. In addition, the replaced chemical liquid may be replaced with a cleaning liquid different from the chemical liquid (hereinafter referred to as “cleaning liquid B”).

The chemical solution for forming a water-repellent protective film of the present invention is a mixture of a first liquid containing a silylating agent represented by the following general formula [1] and a second liquid containing a tertiary alcohol in the preparation step. can get.
(R ¹ ) _a (H) _3-a Si—N (R ² ) ₂ [1]
[In the formula [1], R ^{1 s} are independently of each other from the group consisting of monovalent hydrocarbon groups having 1 to 18 carbon atoms in which some or all of the hydrogen elements may be replaced by fluorine elements. At least one group selected, and each R ² is independently selected from the group consisting of monovalent hydrocarbon groups having 1 to 8 carbon atoms. a is 2 or 3. ]
An aprotic solvent that may be contained in the first liquid, and
The amount of the tertiary alcohol is 80 to 100% by mass with respect to 100% by mass of the total amount of the nonaqueous solvent including the tertiary alcohol in the second liquid.
Moreover, the quantity (silylation agent content) of the said silylating agent with respect to 100 mass% of total amounts of a 1st liquid and a 2nd liquid is 1-20 mass%.

(About the first liquid)
When the silylating agent reacts with the silanol group on the wafer surface, a water-repellent protective film is formed on the wafer surface.

The silylating agent is preferably a silylating agent represented by the following general formula [2].
(R ³ ) (CH ₃ ) ₂ Si—N (R ⁴ ) ₂ [2]
[In the formula [2], R ³ is a monovalent hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen elements may be replaced by fluorine elements, and R ⁴ is independent of each other. And a methyl group or an ethyl group. ]

  Specific examples of the silylating agent include trimethylsilyldimethylamine, trimethylsilyldiethylamine, ethyldimethylsilyldimethylamine, butyldimethylsilyldimethylamine, hexyldimethylsilyldimethylamine, octyldimethylsilyldimethylamine and the like. From the viewpoint, trimethylsilyldimethylamine, trimethylsilyldiethylamine, butyldimethylsilyldimethylamine, octyldimethylsilyldimethylamine and the like are preferable.

When the silylating agent is in a liquid state, the first liquid may not contain a solvent for dilution. Specifically, the first liquid may consist only of a liquid silylating agent.
On the other hand, when the silylating agent is in a solid state, the first liquid contains a solvent in order to dissolve the silylating agent into a liquid. Further, even if the silylating agent is in a liquid state, a solvent may be included in the first liquid in order to dilute the silylating agent. At this time, the solvent that may be contained in the first liquid is an aprotic solvent that does not react with the silylating agent. Examples of the aprotic solvent include hydrocarbons, esters, ethers, ketones, halogen-containing solvents, polyhydric alcohol derivatives having no OH group, and the like.

(About the second liquid)
The tertiary alcohol is one of the solvents contained in the water repellent protective film forming chemical solution. When primary alcohol or secondary alcohol is used instead of tertiary alcohol, when mixed with the silylating agent, the silylating agent reacts quickly with the primary alcohol or secondary alcohol, and the concentration of the silylating agent in the chemical solution increases rapidly. Therefore, the effect of imparting water repellency becomes insufficient. This is probably because primary alcohol and secondary alcohol have a small steric hindrance in the reaction with the silylating agent, whereas tertiary alcohol has a large steric hindrance. Therefore, it is important to use a tertiary alcohol. Specific examples of the tertiary alcohol include tert-butyl alcohol, tert-amyl alcohol, 2-methyl-2-pentanol, 3-methyl-3-pentanol, 3-ethyl-3-pentanol and the like. From the viewpoint of the freezing point, tert-amyl alcohol, 2-methyl-2-pentanol, 3-methyl-3-pentanol, and 3-ethyl-3-pentanol are preferable.
The second liquid may contain a nonaqueous solvent other than the tertiary alcohol. Further, the second liquid may be only a tertiary alcohol.

(About water-repellent protective film forming chemical and its preparation)
The chemical solution of the present invention may contain a nonaqueous solvent other than the tertiary alcohol. However, from the viewpoint of preventing the deterioration of the vinyl chloride resin, all the solvents contained in the chemical solution raw material (that is, the first solution) The total amount of the tertiary alcohol in the non-aqueous solvent including the aprotic solvent which may be contained therein and the tertiary alcohol in the second liquid is 100 to 100% by mass. More preferably, it is 90-100 mass%.

  The amount of the silylating agent (silylating agent content) is 1 to 20% by mass with respect to 100% by mass of the total amount of the first and second liquids. If it is less than 1% by mass, the effect of imparting water repellency will be insufficient. Further, even if a silylating agent exceeding 20% by mass is used, there is almost no further improvement in the water repellency imparting effect. Therefore, the upper limit of the silylating agent content is desirably 20% by mass from the viewpoint of cost. Furthermore, from the viewpoint of preventing deterioration of the vinyl chloride resin, it is more preferably 1 to 15% by mass, and still more preferably 1 to 10% by mass.

  Moreover, it is preferable that the total amount of water in the starting material of the chemical solution is 5000 ppm by mass or less with respect to the total amount of the material. When the total amount of moisture exceeds 5000 ppm by mass, the effect of the silylating agent is reduced, and it is difficult to form the protective film in a short time. For this reason, it is preferable that the total amount of water in the chemical solution raw material is as small as possible, particularly 1000 ppm by mass or less, more preferably 500 ppm by mass or less.

  Moreover, it is preferable that the number of particles larger than 0.2 μm is 100 or less per 1 mL of the chemical liquid in the particle measurement by the light scattering type in-liquid particle detector in the liquid phase of the chemical liquid. If the number of particles larger than 0.2 μm is more than 100 per 1 mL of the chemical solution, pattern damage due to the particles may be induced, which causes a decrease in device yield and reliability. Further, it is preferable that the number of particles larger than 0.2 μm is 100 or less per mL of the chemical solution because washing with a solvent or water after forming the protective film can be omitted or reduced. Although the number of particles larger than 0.2 μm is preferably as small as possible, there may be one or more per 1 mL of the chemical solution. The particle measurement in the liquid phase in the chemical solution in the present invention is performed by using a commercially available measuring device in the light scattering liquid particle measurement method using a laser as a light source. , PSL (polystyrene latex) standard particle-based light scattering equivalent diameter.

  Here, the particles are particles such as dust, dust, organic solids and inorganic solids contained as impurities in the raw materials, and dust, dust, organic solids and inorganic solids brought in as contaminants during the preparation of chemicals. It is a particle such as an object, and finally exists as a particle without being dissolved in a chemical solution.

  Further, the metal impurity content of each element (metal impurity) of Na, Mg, K, Ca, Mn, Fe, Cu, Li, Al, Cr, Ni, Zn, and Ag in the chemical solution is the chemical solution. It is preferable that it is each 0.1 mass ppb or less with respect to the total amount. If the metal impurity content is more than 0.1 mass ppb with respect to the total amount of the chemical solution, it is likely to increase the junction leakage current of the device, which causes a decrease in device yield and reliability. Absent. Further, when the metal impurity content is 0.1 mass ppb or less with respect to the total amount of the chemical solution, the surface of the wafer (protective film surface) with the solvent or water after the protective film is formed on the wafer surface. This is preferable because cleaning can be omitted or reduced. For this reason, the content of the metal impurities is preferably as small as possible, but may be 0.001 mass ppb or more for each element with respect to the total amount of the chemical solution as long as it is within the above content range.

  In the preparation step, since heat may be generated when the first liquid and the second liquid are mixed, it is preferable to mix while maintaining the liquid temperature near room temperature.

(About formation of water-repellent protective film)
Then, as shown in FIG. 3, a water-repellent protective film forming step is performed in which the chemical solution is held in at least the concave portion of the concave-convex pattern after the preparation step to form a water-repellent protective film on the concave surface.

  You may perform a water-repellent protective film formation process continuously from said preparation process. For example, a flow path in which the flow path through which the first liquid flows and the flow path in which the second liquid flows are formed in the middle, and the water repellent protective film is formed by merging the first liquid and the second liquid at the merging portion. The water-repellent protective film forming step may be continuously performed from the above preparation step by preparing the chemical solution and supplying the water-repellent protective film-forming chemical solution to the wafer from the end of the flow path. Thus, the method of continuously performing the water-repellent protective film forming step from the preparation step can suppress the reaction between the silylating agent and the tertiary alcohol to the minimum, and has the effect of imparting water repellency with little variation between lots. It is preferable because it is easy to achieve.

  After the cleaning with the aqueous cleaning liquid or the cleaning liquid A as described above, the cleaning liquid is replaced with a protective film-forming chemical solution, and at least the surface of the concave and convex pattern has at least the surface of the concave and convex pattern while the chemical liquid is held in at least the concave portion. Then, the protective film is formed. The protective film of the present invention does not necessarily have to be formed continuously, and does not necessarily have to be formed uniformly. However, since it can impart better water repellency, it can be applied continuously and uniformly. More preferably, it is formed.

  In the present invention, the water-repellent protective film is a film that is formed on the wafer surface to reduce the wettability of the wafer surface, that is, a film that imparts water repellency. In the present invention, the water repellency means that the surface energy of the article surface is reduced and the interaction (for example, hydrogen bond, intermolecular force) between water or other liquid and the article surface is reduced. It is. In particular, the effect of reducing the interaction with water is great, but it has the effect of reducing the interaction with a mixed liquid of water and a liquid other than water or a liquid other than water. By reducing the interaction, the contact angle of the liquid with the article surface can be increased. The water repellent protective film may be formed from the above silylating agent or may contain a reaction product containing the silylating agent as a main component.

  FIG. 4 is a schematic view showing a state in which the recess 4 holds the chemical solution 8 for forming the protective film. The wafer in the schematic diagram of FIG. 4 shows a part of the a-a ′ cross section of FIG. 1. At this time, a protective film is formed on the surface of the recess 4 to make the surface water repellent.

  When the temperature of the protective film-forming chemical is increased, the protective film is easily formed in a shorter time. The temperature at which a homogeneous protective film is easily formed is preferably 10 ° C. or higher and lower than the boiling point of the chemical solution, and particularly preferably 15 ° C. or higher and 10 ° C. lower than the boiling point of the chemical solution. The temperature of the chemical solution is preferably maintained at the temperature even when held in at least the concave portion of the concavo-convex pattern. The boiling point of the chemical solution means the boiling point of the component having the largest amount by mass ratio among the components contained in the protective film forming chemical solution.

(About the process after the water repellent protective film forming process)
After forming the protective film as described above, the chemical solution remaining in at least the concave portion of the concave / convex pattern may be replaced with the cleaning liquid B, and then the drying process may be performed. Examples of the cleaning liquid B include an aqueous cleaning liquid, an organic solvent, a mixture of an aqueous cleaning liquid and an organic solvent, a mixture of at least one of an acid, an alkali, and a surfactant, and a protective film with them. Examples include a mixture of chemicals for forming. 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 that is one of the preferred examples of the cleaning liquid B include hydrocarbons, esters, ethers, ketones, halogen-containing solvents, sulfoxide solvents, alcohols, polyhydric alcohol derivatives, nitrogen elements Examples thereof include a solvent. Of these, hydrocarbons, ethers, alcohols, and polyhydric alcohol derivatives having no OH group and acetate group are preferable because the vinyl chloride resin is hardly deteriorated. When an organic solvent is used as the cleaning liquid B, hydrocarbons, ethers, alcohols, polyhydric alcohol derivatives having no OH group and acetate group, which are preferable solvents, are 80% by mass of the total amount of the organic solvent. It is desirable to occupy the above.

  In addition, when an organic solvent is used as the cleaning liquid B, the protective film formed on the wafer surface with the chemical liquid of the present invention tends to be less likely to have reduced water repellency due to the cleaning of the cleaning liquid B.

  FIG. 5 shows a schematic diagram in the case where the liquid is held in the recess 4 that has been made water-repellent by the protective film forming chemical. The wafer in the schematic diagram of FIG. 5 shows a part of the a-a ′ cross section of FIG. 1. The surface of the concavo-convex pattern is made water-repellent by forming a protective film 10 with the chemical solution. The protective film 10 is held on the wafer surface even when the liquid 9 is removed from the concavo-convex pattern.

  When the protective film 10 is formed on at least the concave surface of the concave / convex pattern of the wafer by the chemical solution for forming the protective film, the pattern collapses when the contact angle is assumed to be 50 to 130 ° when water is held on the surface. Is preferable because it is difficult to occur. When the contact angle is large, the water repellency is excellent, so 60 to 130 ° is more preferable, and 65 to 130 ° is particularly preferable.

  Next, the liquid held in the recess 4 in which the protective film is formed by the chemical solution is removed from the uneven pattern by drying. At this time, the liquid held in the recess may be the chemical solution, the cleaning solution B, or a mixture thereof. The mixed liquid is contained so that each component contained in the protective film forming chemical solution is at a lower concentration than the chemical liquid, and the mixed liquid is in a state of being replaced with the cleaning liquid B. The liquid may be sufficient, and the liquid mixture obtained by mixing each said component with the washing | cleaning liquid B previously may be sufficient. From the viewpoint of wafer cleanliness, water, an organic solvent, or a mixture of water and an organic solvent is preferable. Moreover, after the liquid is once removed from the surface of the concave / convex pattern, the cleaning liquid B may be held on the surface of the concave / convex pattern and then dried.

  In the case of cleaning with the cleaning liquid B after the formation of the protective film, the cleaning time, that is, the time for which the cleaning liquid B is held is 10 seconds or more, more preferably 20 from the viewpoint of removing particles and impurities on the uneven pattern surface. It is preferable to carry out for 2 seconds or more. From the viewpoint of the effect of maintaining the water repellency of the protective film formed on the surface of the uneven pattern, when an organic solvent is used as the cleaning liquid B, the water repellency of the wafer surface tends to be easily maintained even after the cleaning. On the other hand, if the washing time is too long, productivity is deteriorated.

  By the drying, the liquid held in the uneven pattern is removed. The drying is preferably performed by a known drying method such as a spin drying method, IPA (2-propanol) vapor drying, Marangoni drying, heat drying, hot air drying, air drying, or vacuum drying.

  The protective film 10 may be further removed after the drying. When removing the water repellent protective film, it is effective to cut the C—C bond and C—F bond in the water repellent protective film. The method is not particularly limited as long as it can cut the bond, for example, light irradiation of the wafer surface, heating of the wafer, exposure of the wafer to ozone, irradiation of the wafer surface with plasma, For example, corona discharge on the wafer surface may be mentioned.

When removing the protective film 10 by light irradiation, shorter than 340 nm and 240 nm which are energy corresponding to 83 kcal / mol and 116 kcal / mol which are binding energies of C—C bonds and C—F bonds in the protective film 10. It is preferable to irradiate ultraviolet rays including wavelengths. As this light source, a metal halide lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an excimer lamp, a carbon arc, or the like is used. If the ultraviolet irradiation intensity is a metal halide lamp, for example, measurement with an illuminometer (irradiance intensity meter UM-10 manufactured by Konica Minolta Sensing, light receiving unit UM-360 [peak sensitivity wavelength: 365 nm, measurement wavelength range: 310 to 400 nm]) 100 mW / cm ² or more is preferable in value, 200 mW / cm ² or more is particularly preferable. When the irradiation intensity is less than 100 mW / cm ² , it takes a long time to remove the protective film 10. Further, a low-pressure mercury lamp is preferable because it can irradiate ultraviolet rays having a shorter wavelength, and thus the protective film 10 can be removed in a short time even if the irradiation intensity is low.

  Further, when the protective film 10 is removed by light irradiation, if the constituent components of the protective film 10 are decomposed by ultraviolet rays and ozone is generated at the same time, and the constituent components of the protective film 10 are oxidized and volatilized by the ozone, the processing time is shortened. Therefore, it is particularly preferable. As this light source, a low-pressure mercury lamp, an excimer lamp, or the like is used. Further, the wafer may be heated while irradiating light.

  When heating the wafer, it is preferable to heat the wafer at 400 to 1000 ° C., preferably 500 to 900 ° C. The heating time is preferably 10 seconds to 60 minutes, preferably 30 seconds to 10 minutes. In this process, ozone exposure, plasma irradiation, corona discharge, etc. may be used in combination. Further, light irradiation may be performed while heating the wafer.

  Methods for removing the protective film 10 by heating include a method of bringing a wafer into contact with a heat source and a method of placing the wafer in a heated atmosphere such as a heat treatment furnace. Note that the method of placing the wafer in a heated atmosphere is easy to operate because it is easy to uniformly apply energy for removing the protective film 10 to the wafer surface even when processing a plurality of wafers. This is an industrially advantageous method that requires a short processing time and a high processing capacity.

  When the wafer is exposed to ozone, it is preferable that ozone generated by ultraviolet irradiation with a low-pressure mercury lamp or the like or low-temperature discharge with a high voltage is provided on the wafer surface. The wafer may be irradiated with light while being exposed to ozone, or may be heated.

  By combining the light irradiation, heating, ozone exposure, plasma irradiation, and corona discharge, the protective film on the wafer surface can be efficiently removed.

  Examples that specifically disclose the embodiments of the present invention will be described below. In addition, this invention is not limited only to these Examples.

  Making the surface of the wafer a surface having a concavo-convex pattern, replacing the cleaning liquid held at least in the concave portion of the concavo-convex pattern with another cleaning liquid, various studies have been made in other literatures, etc. and already established techniques Therefore, in the present invention, the water repellency imparting effect of the chemical solution for forming the protective film and the resistance of the vinyl chloride resin to the chemical solution were evaluated. In the examples, water, which is a typical water-based cleaning liquid, was used as the liquid to be brought into contact with the wafer surface when the contact angle was evaluated.

  However, in the case of a wafer having an uneven pattern on the surface, the contact angle of the protective film 10 itself formed on the uneven pattern surface cannot be accurately evaluated.

  The contact angle of water droplets is evaluated by dropping several μl of water droplets on the sample (base material) surface as in JIS R 3257 “Test method for wettability of substrate glass surface”, and the angle between the water droplet and the substrate surface. It is made by measuring. However, in the case of a wafer having a pattern, the contact angle becomes very large. This is because a Wenzel effect and a Cassie effect occur, and the contact angle is affected by the surface shape (roughness) of the substrate, and the apparent contact angle of water droplets increases.

Therefore, in this embodiment, the above chemical solution is applied to a wafer having a smooth surface, a protective film is formed on the wafer surface, and the protective film is formed on the surface of the wafer having a concavo-convex pattern formed on the surface. Various evaluations were made. In this example, a “wafer with SiO ₂ film” (indicated as SiO _{2 in the} table) having a SiO ₂ layer on a silicon wafer having a smooth surface was used as the wafer having a smooth surface.

  Details are described below. Hereinafter, an evaluation method, preparation of a protective film forming chemical solution, a wafer cleaning method using the protective film forming chemical solution, and evaluation results will be described.

〔Evaluation method〕
The following (1) to (2) were evaluated.

(1) Contact angle evaluation of the protective film formed on the wafer surface About 2 μl of pure water is placed on the surface of the wafer on which the protective film is formed, and the angle (contact angle) formed between the water droplet and the wafer surface is measured by a contact angle meter (Kyowa). When the contact angle was 50 ° or more, it was determined to be acceptable.

(2) Resistance of the vinyl chloride resin to the chemical solution In the embodiment of the present invention, instead of evaluating whether or not the liquid contact member is deteriorated when the wafer is cleaned by a wafer cleaning apparatus containing a vinyl chloride resin as the liquid contact member. Furthermore, the presence or absence of deterioration of the vinyl chloride resin was evaluated by immersing the vinyl chloride resin in a chemical solution for forming a protective film. Specifically, after immersing a vinyl chloride resin (the surface is glossy) in a chemical solution for forming a protective film and immersing it at 40 ° C. for 4 weeks, the deterioration of the vinyl chloride resin is visually observed, and discoloration, swelling, etc. The presence or absence of deterioration was confirmed. Those with no deterioration were accepted and those with no deterioration were rejected.

[Preparation of chemical for forming water-repellent protective film]
As shown in Table 1, the first liquid and the second liquid were prepared, and the water-repellent protective film-forming chemicals were prepared by mixing them while maintaining them at 20 ° C. (preparation step). However, when t-butyl alcohol which is a tertiary alcohol is used, the first liquid and the second liquid were mixed while being maintained at 27 ° C.
In the table,
“TMSDMA” means trimethylsilyldimethylamine,
“TAA” means tertiary alcohol, t-amyl alcohol,
“TBA” means tertiary alcohol t-butyl alcohol,
“IPA” means secondary alcohol, isopropyl alcohol,
“2E1HA” means 2-ethyl-1-hexanol, which is a primary alcohol,
“EA” means ethanol, a primary alcohol,
“NOA” means n-octanol, which is a primary alcohol;
“3M1BA” means 3-methyl-1-butanol, which is a primary alcohol;
“PGMEA” means propylene glycol monomethyl ether acetate.

[Examples 1-1 to 1-6]
A silicon wafer with a smooth thermal oxide film (Si wafer having a 1 μm thick thermal oxide film layer on the surface) is immersed in a 1% by mass hydrofluoric acid aqueous solution at room temperature for 10 minutes, and then immersed in pure water at room temperature for 1 minute. It was immersed in propanol (iPA) for 1 minute at room temperature.
The above silicon wafer is immersed at 20 ° C. for 1 minute in the chemical solution prepared in the above-mentioned [Preparation of water repellent protective film forming chemical solution] at 20 ° C. for a period of time as indicated by “Standing time” in Table 2. (Water repellent protective film forming step). Subsequently, it was immersed in iPA at room temperature for 1 minute and in pure water at room temperature for 1 minute. Finally, the silicon wafer was taken out from the pure water and air was blown to remove the pure water on the surface.
“Standing time” in Table 2 means the time during which the chemical solution was allowed to stand after the preparation step and before the water repellent protective film forming step.
Evaluation was carried out in the manner described in (1) to (2) above. The results are shown in Table 2.

[Examples 2-1 to 2-6]
Except that the chemical solution 2 was used instead of the chemical solution 1, the wafer was subjected to surface treatment in the same manner as in Examples 1-1 to 1-6, and the evaluation was further performed. The results are shown in Table 3.

[Examples 3-1 to 3-6]
Except that the chemical solution 3 was used instead of the chemical solution 1, the wafer was subjected to surface treatment in the same manner as in Examples 1-1 to 1-6, and the evaluation was further performed. The results are shown in Table 4.

[Examples 4-1 to 4-6]
Except that the chemical solution 4 was used instead of the chemical solution 1, the wafer surface treatment was performed in the same manner as in Examples 1-1 to 1-6, and the evaluation was further performed. The results are shown in Table 5.

[Comparative Examples 5-1 to 5-6]
Except that the chemical solution 5 was used instead of the chemical solution 1, the wafer surface treatment was performed in the same manner as in Examples 1-1 to 1-6, and the evaluation was further performed. As a result, the contact angle was less than 50 ° and the effect of imparting water repellency was insufficient. The results are shown in Table 6.

  The graph which plotted the relationship between the stationary time of Tables 2-6 and a contact angle is shown in FIG. When only tertiary alcohol (t-amyl alcohol) was used as the solvent in the chemical solution, the contact angle hardly changed with respect to the standing time of about 24 hours. It was confirmed that when a chemical solution having a silylating agent content of 1.0% by mass or more is used, stable water repellency can be imparted to the wafer surface. On the other hand, when a chemical solution having a silylating agent content of less than 1.0% by mass was used, the effect of imparting water repellency was insufficient although the change in the contact angle was small with respect to the standing time.

[Examples 6-1 to 6-7]
The surface treatment of the wafer was carried out in the same manner as in Example 1-1, except that the chemical solution 6 was used instead of the chemical solution 1, the temperature of standing and the temperature of the chemical solution in the water repellent protective film forming step were set to 27 ° C., and the standing time was changed. And further evaluated. The results are shown in Table 7.

  A graph plotting the relationship between the standing time and the contact angle in Table 7 is shown in FIG. Even when only tertiary alcohol (t-butyl alcohol) is used as the solvent in the chemical solution, the contact angle hardly changes with respect to the standing time of about 24 hours, and further, the standing for about 30 days longer. The contact angle hardly changed over time. This also confirmed that stable water repellency can be imparted to the wafer surface even when a chemical solution for forming a water repellent protective film stored for a long time is used.

[Comparative Examples 7-1 to 7-3]
Except that the chemical solution 7 was used instead of the chemical solution 1, the wafer surface treatment was performed in the same manner as in Examples 1-1, 1-2, and 1-5, and the evaluation was further performed. The results are shown in Table 8.

[Comparative Examples 8-1 to 8-3]
Except that the chemical solution 8 was used instead of the chemical solution 1, the wafer surface treatment was performed in the same manner as in Examples 1-1, 1-2, and 1-5, and the evaluation was further performed. The results are shown in Table 9.

FIG. 8 shows a graph plotting the relationship between the standing time and the contact angle in Examples 4-1, 4-2, 4-5, and Tables 8 and 9. In Examples 4-1, 4-2, and 4-5 using only tertiary alcohol (t-amyl alcohol) as a solvent in the chemical solution, the contact angle hardly changed with respect to the standing time.
On the other hand, in Comparative Examples 7-1 to 7-3 using only the secondary alcohol (isopropyl alcohol) as the solvent in the chemical solution, the contact angle rapidly decreases with respect to the standing time, and after 30 minutes, 5 ° repellent. No more water.
In Comparative Examples 8-1 to 8-3 using only a primary alcohol (2-ethyl-1-hexanol) as a solvent in the chemical solution, the contact angle is 40 ° and the water repellency imparting effect is 10 minutes after standing. Further, the contact angle rapidly decreased with respect to the standing time, and after 30 minutes, the water repellency was not exhibited at 6 °.
Therefore, when tertiary alcohol is used as a solvent instead of primary alcohol or secondary alcohol, a stable water repellency is imparted to the wafer surface even when a chemical solution for forming a water-repellent protective film stored for a long time is used. It was confirmed that it was possible.

[Comparative Examples 9-1 to 11-1]
Except that the chemical solutions 9 to 11 were used in place of the chemical solution 1, wafer surface treatment was performed in the same manner as in Example 1-1, and the evaluation was further performed. As a result, the contact angle was about 5 ° and did not show water repellency. In this comparative example, since the water repellency was not shown in the standing time of 10 minutes, the contact angle was not evaluated in the standing time thereafter. The results are shown in Table 10.

[Comparative Examples 12-1, 12-2]
Except that the chemical solution 12 was used instead of the chemical solution 1, the wafer surface treatment was performed in the same manner as in Examples 1-1 and 1-6, and the evaluation was further performed. As a result, although the contact angle hardly changed with respect to the standing time of about 24 hours, the resistance of the vinyl chloride resin was insufficient because swelling occurred. The results are shown in Table 11.

[Comparative Examples 13-1 and 13-2]
Except that the chemical solution 13 was used instead of the chemical solution 1, the wafer surface treatment was performed in the same manner as in Examples 1-1 and 1-6, and the evaluation was further performed. As a result, although the contact angle hardly changed with respect to the standing time of about 24 hours, the resistance of the vinyl chloride resin was insufficient because swelling occurred. The results are shown in Table 12.

[Comparative Examples 14-1 and 14-2]
Except that the chemical solution 14 was used instead of the chemical solution 1, the wafer was surface-treated in the same manner as in Examples 1-1 and 1-6, and the evaluation was further performed. As a result, although the contact angle hardly changed with respect to the standing time of about 24 hours, the resistance of the vinyl chloride resin was insufficient because swelling occurred. The results are shown in Table 13.

In the wafer cleaning method of the present invention,
The amount of tertiary alcohol in the total solvent is 80-100% by mass,
In Examples where the content of the silylating agent represented by the general formula [1] is 1 to 20% by mass, a vinyl chloride resin is used even when a chemical solution for forming a water-repellent protective film stored for a long time is used. It was confirmed that stable water repellency can be imparted to the wafer surface without deterioration.

On the other hand, in Comparative Examples 5-1 to 5-6 in which the silylating agent content was less than 1.0% by mass, the contact angle was less than 50 °, and the water repellency imparting effect was insufficient.
Further, in Comparative Examples 7-1 to 7-3 using a secondary alcohol instead of a tertiary alcohol, the contact angle rapidly decreased with respect to the standing time, and the water repellency was not exhibited as 5 ° after 30 minutes. It was. Therefore, when the chemical solution for forming a water-repellent protective film stored for a long time was used, stable water repellency could not be imparted to the wafer surface.
Moreover, in Comparative Examples 8-1 to 8-3 and Comparative Examples 9-1 to 11-1 using a primary alcohol instead of a tertiary alcohol, the contact angle is less than 50 ° and the water repellency imparting effect is insufficient. there were.
In addition, Comparative Examples 12-1 to 12-2, 13-1 to 13-2, and 14-1 to 13-2, in which the amount of the tertiary alcohol in the total solvent is less than 80% by mass and the other solvents are glycol acetates. In 14-2, the contact angle hardly changed with respect to the standing time, and although stable water repellency could be imparted to the wafer surface, the resistance of the vinyl chloride resin was insufficient.

[Example 15]
A silicon wafer with a smooth thermal oxide film (Si wafer having a 1 μm thick thermal oxide film layer on the surface) is immersed in a 1% by mass hydrofluoric acid aqueous solution at room temperature for 10 minutes, and then immersed in pure water at room temperature for 1 minute. It was immersed in propanol (iPA) for 1 minute at room temperature.
TMSDMA and tAA are separately fed through two tubes while being maintained at 20 ° C., and the two liquids are joined together in the middle of the Y-tube to prepare a chemical solution for forming a water-repellent protective film. 20 ° C.) was discharged from the tube tip.
At this time, since the silicon wafer was placed so that the chemical liquid discharged from the tube tip hits, the chemical liquid was held on the surface of the silicon wafer by the discharge. The chemical solution holding state was continued for 1 minute. Next, the silicon wafer was immersed in iPA at room temperature for 1 minute and in pure water at room temperature for 1 minute. Finally, the silicon wafer was taken out from the pure water and air was blown to remove the pure water on the surface.
This operation was performed on three separate silicon wafers.

That is, in this embodiment, the first liquid and the second liquid are supplied from separate pipes, mixed and supplied to the silicon wafer immediately.
The results are shown in Table 14. There was almost no difference in the contact angles of the three wafers obtained in this example. From this, it is confirmed that when the preparation step of mixing the first liquid and the second liquid and the water-repellent protective film forming step are continuously performed, the wafer surface can be given water repellency with little variation between lots. It was.

DESCRIPTION OF SYMBOLS 1 Wafer 2 Fine uneven | corrugated pattern on the wafer surface 3 Pattern convex part 4 Pattern concave part 5 Concave width 6 Convex height 7 Convex width 8 The protective film forming chemical 9 held in the concave part 4 In the concave part 4 Retained liquid 10 protective film

Claims (8)

In a method for cleaning a wafer having a fine concavo-convex pattern on the surface with a wafer cleaning apparatus containing a vinyl chloride resin as a liquid contact member and at least a part of the concavo-convex pattern containing silicon
A first step containing a silylating agent represented by the following general formula [1] and a second solution containing a tertiary alcohol to prepare a chemical solution for forming a water-repellent protective film, a preparation step,
Holding the water-repellent protective film-forming chemical solution in at least the concave portion of the concave-convex pattern after the preparation step, and forming a water-repellent protective film on the concave surface;
An aprotic solvent that may be contained in the first liquid; and
The amount of the tertiary alcohol is 80 to 100% by mass relative to 100% by mass of the total amount of the nonaqueous solvent including the tertiary alcohol in the second liquid,
The amount of the silylating agent (silylating agent content) with respect to 100% by mass of the total amount of the first liquid and the second liquid is 1 to 20% by mass.
Wafer cleaning method.
(R ¹ ) _a (H) _3-a Si—N (R ² ) ₂ [1]
[In the formula [1], R ^{1 s} are independently of each other from the group consisting of monovalent hydrocarbon groups having 1 to 18 carbon atoms in which some or all of the hydrogen elements may be replaced by fluorine elements. At least one group selected, and each R ² is independently selected from the group consisting of monovalent hydrocarbon groups having 1 to 8 carbon atoms. a is 2 or 3. ] The wafer cleaning method according to claim 1, wherein the silylating agent is a silylating agent represented by the following general formula [2].
(R ³ ) (CH ₃ ) ₂ Si—N (R ⁴ ) ₂ [2]
[In the formula [2], R ³ is a monovalent hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen elements may be replaced by fluorine elements, and R ⁴ is independent of each other. And a methyl group or an ethyl group. ] The tertiary alcohol is at least one selected from the group consisting of tert-butyl alcohol, tert-amyl alcohol, 2-methyl-2-pentanol, 3-methyl-3-pentanol, and 3-ethyl-3-pentanol. The wafer cleaning method according to claim 1, wherein the wafer is cleaned. The wafer cleaning method according to claim 1, wherein the silylating agent content is 1 to 5 mass%. The wafer cleaning method according to claim 1, wherein the preparation step and the water-repellent protective film forming step are continuously performed. The method for cleaning a wafer according to claim 1, wherein the chemical solution for forming the water repellent protective film is removed from the recesses by drying after the water repellent protective film forming step. 6. The water repellent protective film forming chemical solution in the recess is replaced with a cleaning solution different from the chemical solution after the water repellent protective film forming step, and the cleaning solution is removed from the recess by drying. A method for cleaning a wafer according to claim 1. The wafer surface after the drying is subjected to at least one treatment selected from the group consisting of heat treatment, light irradiation treatment, ozone exposure treatment, plasma irradiation treatment, and corona discharge treatment to remove the water-repellent protective film. Item 8. The wafer cleaning method according to Item 6 or 7.

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