Substrate processing method and substrate processing apparatus

Abstract

Provided are a substrate processing method and a substrate processing apparatus capable of efficiently forming a self-assembled monomolecular film on the surface of a substrate in a short time, the self-assembled monomolecular film having excellent compactness and protection performance by suppressing or reducing the occurrence of film defects. This substrate treatment method comprises: a first contact step in which a first treatment liquid containing SAM molecules is brought into contact with the surface Wf of a substrate W and the SAM molecules are chemisorbed; a removal step for removing non-chemically adsorbed SAM molecules from the surface Wf of the substrate W; a surface modification step for surface-modifying a region in which no SAM molecules are present in the surface (Wf) after the removal step to a region capable of chemical adsorption of SAM molecules; and a second contact step in which a second treatment liquid containing SAM molecules and having the same kind or different kinds as the first treatment liquid is brought into contact with the surface-modified region, and the SAM molecules are chemisorbed.

Description

Technical Field

[0001] The present invention relates to a substrate processing method and a substrate processing apparatus, which can efficiently form a self-assembled monolayer with excellent densification and protective performance on a substrate surface in a short time. Background Art

[0002] In the manufacture of semiconductor devices, as a technique for selectively forming a film on a specific surface region of a substrate, a photolithographic technique is widely used. For example, after forming an underlying wiring, an insulating film is formed, and then a dual damascene structure having trenches and via holes is formed by photolithography and etching, and a conductive film such as copper (Cu) is buried in the trenches and via holes to form a wiring.

[0003] However, in recent years, semiconductor devices have become increasingly miniaturized, and in the photolithographic technique, there are also cases where the alignment accuracy is insufficient. Therefore, a method for selectively forming a film on a specific region of the substrate surface with high precision is sought to replace the photolithographic technique.

[0004] For example, Patent Document 1 discloses a method in which, in a substrate having a silicon nitride (SiN) film and a silicon oxide (SiO2) film provided in-plane, in order to selectively etch the silicon nitride film, a heat-resistant phosphoric acid material is pre-formed as a SAM on the surface of the silicon oxide film.

[0005] Here, in order to sufficiently protect the silicon oxide film from the etching solution, it is necessary to form a SAM with excellent densification. However, in the conventional SAM film formation method, it is difficult to form such a SAM with excellent densification in a short time, and there is a problem of poor production efficiency.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent No. 5490071. Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In view of the above problems, the present invention is proposed, and an object thereof is to provide a substrate processing method and a substrate processing apparatus that can efficiently form a self-assembled monolayer with excellent densification and protective performance on the substrate surface in a short time by suppressing or reducing the occurrence of film defects.

[0011] Means for Solving the Problems

[0012] In order to solve the problems described above, a substrate processing method of the present invention is used to form a self-assembled monolayer on the surface of a substrate, and is characterized by including: a first contact step of bringing a first treatment liquid containing molecules capable of forming the self-assembled monolayer into contact with the surface and causing the molecules to chemisorb; a removal step of removing the molecules that have not chemisorbed from the surface of the substrate; a surface modification step of modifying the surface of the region where the molecules do not exist after the removal step into a region capable of chemisorbing the molecules; and a second contact step of bringing a second treatment liquid containing the molecules and being of the same type or a different type from the first treatment liquid into contact with the region that has been surface-modified and causing the molecules to chemisorb.

[0013] In the configuration described above, in the first contact step, molecules capable of forming a self-assembled monolayer (hereinafter sometimes referred to as "SAM") (hereinafter sometimes referred to as "SAM molecules") are chemisorbed on the surface of the substrate, and then the unchemisorbed SAM molecules are removed by the removal step. Thereby, the surface modification of the region where SAM molecules cannot chemisorb is inhibited. Furthermore, the region capable of chemisorbing SAM molecules is surface-modified by the surface modification step, and then SAM molecules are chemisorbed on the surface-modified region by the second contact step. Thus, in the configuration described above, since the region where SAM molecules cannot be chemisorbed by the first contact step can be surface-modified so as to be capable of chemisorbing SAM molecules and then SAM molecules can be chemisorbed again, the situation where SAM molecules are brought into contact with the surface of the substrate for a long time to form a dense SAM as in the conventional substrate processing method can be reduced. As a result, the occurrence of film defects can be inhibited, and a dense SAM with excellent protective performance can be efficiently formed in a short time.

[0014] In the configuration described above, it may also be that the first contact step is the following step: bringing the first treatment liquid into contact with the surface of the substrate, thereby causing the molecules to chemisorb on the region capable of chemisorbing and self-assembling, thereby forming the self-assembled monolayer; and the second contact step is the following step: causing the molecules to chemisorb on the region surface-modified by the surface modification step and performing densification treatment on the self-assembled monolayer.

[0015] According to the configuration described above, after forming the SAM in the first contact step, the SAM molecules that are not chemisorbed on the surface of the substrate are removed by the removal step, and then surface modification is performed in such a way that the SAM molecules can be chemisorbed on the regions where the SAM molecules do not exist. After that, in the second contact step, the second treatment liquid containing the SAM molecules is brought into contact with the regions where the SAM molecules do not exist. Here, in the SAM formed by the first contact step, there are the following situations: the SAM molecules may not be chemisorbed on the surface of the substrate locally, etc., resulting in film defects. However, in the configuration described above, after forming the SAM by the first contact step, the unchemisorbed SAM molecules are removed from the regions where film defects occur and surface modification is performed, and the SAM molecules are chemisorbed on the regions where film defects occur, thereby improving and even enhancing the compactness of the SAM. As a result of this, it is not necessary to keep the SAM molecules in contact with the surface of the substrate for a long time as in the conventional SAM film formation method, and thus a SAM with excellent compactness and protective performance can be efficiently formed in a short time.

[0016] In the configuration described above, it may also be that at least the surface of the substrate is made of silicon dioxide; the molecule has a functional group capable of forming a siloxane bond with a hydroxyl group; the surface modification in the surface modification step generates hydroxyl groups in the regions where the molecule does not exist; the chemisorption of the molecule in the first contact step and the second contact step bonds the molecule to the surface via a siloxane bond with the hydroxyl groups on the surface of the substrate.

[0017] According to the configuration described above, for a substrate whose at least surface is made of silicon dioxide, the surface of the substrate is surface-modified in such a way that hydroxyl groups are formed on the surface, so that a molecule having a functional group capable of forming a siloxane bond with a hydroxyl group can be chemisorbed on the surface of the substrate via the siloxane bond.

[0018] In the configuration described above, it may also be that the surface modification step is the following step: bringing a surface modification liquid into contact with the regions where the molecule does not exist on the surface after the removal step; using a solution for generating hydroxyl groups on the surface made of silicon dioxide as the surface modification liquid.

[0019] In addition, in the configuration described above, it may also be that the surface modification step is at least one of the following steps: a step of bringing ozone gas into contact with the regions where the molecule does not exist on the surface; a step of irradiating ultraviolet light on the regions where the molecule does not exist on the surface; and a step of bringing a gas containing moisture into contact with the regions where the molecule does not exist on the surface.

[0020] Furthermore, in the configuration described above, preferably, the molecule contains octadecyltrichlorosilane (C 18 H 37 SiCl3).

[0021] In order to solve the problems described above, a substrate processing apparatus according to the present invention is configured to form a self-assembled monolayer on the surface of a substrate, and is characterized by including: a supply unit that supplies a processing liquid containing a molecule capable of forming the self-assembled monolayer to the surface; a removal liquid supply unit that supplies a removal liquid to the surface after the processing liquid has been supplied, thereby removing the molecules that have not been chemisorbed; and a surface modification unit that modifies the surface of a region where the molecules do not exist after the molecules have been removed by the removal liquid supply unit into a region capable of chemisorbing the molecules; the supply unit also supplies the processing liquid to the surface of the substrate surface-modified by the surface modification unit.

[0022] According to the configuration described above, a processing liquid containing SAM molecules is supplied to the surface of the substrate, whereby the SAM molecules can be chemisorbed onto the regions where the SAM molecules can be chemisorbed. In addition, the removal liquid supply unit removes the SAM molecules that have not been chemisorbed onto the surface of the substrate, whereby the regions where the SAM molecules have not been chemisorbed can be sufficiently exposed. Furthermore, the surface modification unit performs surface modification on the regions where the SAM molecules have not been chemisorbed, whereby the SAM molecules can be chemisorbed onto these regions. That is to say, in the case of the configuration described above, the supply unit supplies the processing liquid to the regions where surface modification has been performed again, whereby the SAM molecules can also be chemisorbed onto these regions. Therefore, compared with conventional substrate processing apparatuses, a substrate processing apparatus capable of efficiently forming a SAM with excellent denseness and protective performance in a short time can be provided.

[0023] In the configuration described above, it is also possible that at least the surface of the substrate is made of silicon dioxide; the molecule has a functional group capable of forming a siloxane bond with a hydroxyl group; the surface modification unit is a surface modification liquid supply unit configured to supply a surface modification liquid to the regions where the molecules do not exist; and a solution for generating hydroxyl groups on the surface made of silicon dioxide is used as the surface modification liquid.

[0024] In addition, in the configuration described above, it is also possible that at least the surface of the substrate is made of silica; the molecule has a functional group capable of forming a siloxane bond with a hydroxyl group; the surface modification unit is at least one of an ozone gas supply unit, an ultraviolet irradiation unit, and a gas supply unit, the ozone gas supply unit is used to supply ozone gas to the area of the surface where the molecule does not exist, the ultraviolet irradiation unit is used to irradiate ultraviolet rays to the area of the surface where the molecule does not exist, and the gas supply unit is used to supply a gas containing moisture to the area of the surface where the molecule does not exist.

[0025] Advantages of the Invention

[0026] According to the present invention, a substrate processing method and a substrate processing apparatus can be provided, which can efficiently form a self-assembled monolayer film on the surface of a substrate in a shorter time than the conventional film-forming method; the self-assembled monolayer film has a high film density, excellent denseness, can well suppress or reduce the occurrence of film defects, and has excellent protective performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. is a flowchart showing an example of the overall process of the substrate processing method according to the first embodiment of the present invention.

[0028] Figure 2A FIG. is a schematic diagram showing the state of supplying the first treatment liquid to the surface of the substrate in the first embodiment.

[0029] Figure 2B FIG. is a schematic diagram showing the state of chemical adsorption of SAM molecules on the surface of the substrate in the first embodiment.

[0030] Figure 2C FIG. is a schematic diagram showing the state of self-assembly of SAM molecules on the surface of the substrate and the formation of SAM in the first embodiment.

[0031] Figure 3A FIG. is a schematic diagram showing the state of the surface of the substrate after removing unadsorbed SAM molecules and reverse micelles in the first embodiment.

[0032] Figure 3B FIG. is a schematic diagram showing the state of performing surface modification on the area where SAM molecules do not exist and generating hydroxyl groups in the first embodiment.

[0033] Figure 3C FIG. is a schematic diagram showing the state of densification of SAM in the first embodiment.

[0034] Figure 4 FIG. is an explanatory diagram showing the schematic configuration of the substrate processing apparatus according to the first embodiment of the present invention.

[0035] Figure 5 Explanatory drawing showing a schematic configuration of a processing liquid reservoir provided in a supply unit in a substrate processing apparatus according to a first embodiment of the present invention.

[0036] Figure 6 Explanatory drawing showing a schematic configuration of another processing liquid reservoir provided in a supply unit in a substrate processing apparatus according to a first embodiment of the present invention.

[0037] Figure 7 Explanatory drawing showing a schematic configuration of a removal liquid reservoir provided in a removal liquid supply unit in a substrate processing apparatus according to a first embodiment of the present invention.

[0038] Figure 8 Explanatory drawing showing a schematic configuration of a surface modification liquid reservoir provided in a surface modification liquid supply unit in a substrate processing apparatus according to a first embodiment of the present invention.

[0039] Figure 9 Flowchart showing an example of an overall process of a substrate processing method according to a second embodiment of the present invention.

[0040] Figure 10 Explanatory drawing showing a schematic configuration of a substrate processing apparatus according to a second embodiment of the present invention.

[0041] Figure 11 Flowchart showing an example of an overall process of a substrate processing method according to a third embodiment of the present invention.

[0042] Figure 12 Explanatory drawing showing a schematic configuration in a substrate processing apparatus according to a third embodiment of the present invention. Detailed Embodiment

[0043] [First Embodiment]

[0044] The substrate processing method and substrate processing apparatus according to the first embodiment of the present invention will be described below.

[0045] [Substrate Processing Method]

[0046] First, the substrate processing method of the present embodiment will be described with reference to the accompanying drawings.

[0047] The substrate processing method of this embodiment provides the following technique: a self-assembled monolayer (hereinafter referred to as "SAM (self-assembled monolayer)") with excellent denseness and good protective performance is formed on the surface of the substrate. In this specification, the so-called "substrate" refers to various substrates such as semiconductor substrates at least whose surface is composed of metal oxides, glass substrates for photomasks, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for FEDs (Field Emission Displays), substrates for optical discs, substrates for magnetic discs, and substrates for magneto-optical discs. The metal oxide is not particularly limited, and preferably SiO2. The substrate of the present invention can include a substrate composed only of SiO2 (SiO2 substrate). In addition, the case where the substrate is an SiO2 substrate is taken as an example for explanation below.

[0048] The substrate processing method of this embodiment is as Figure 1 shown and at least includes a SAM formation step (first contact step) S101, a removal step S102, a surface modification step S103, a densification treatment step (second contact step) S104, and a rinse step S105. Figure 1 It is a flowchart showing an example of the overall process of the substrate processing method of the first embodiment of the present invention.

[0049] [SAM formation step (first contact step) S101]

[0050] The SAM formation step (first contact step) S101 is the following step: a first treatment liquid containing a material capable of forming a SAM (hereinafter sometimes referred to as "SAM formation material") is brought into contact with the surface Wf of the substrate W to form a SAM.

[0051] The method for bringing the first treatment liquid into contact with the substrate W is not particularly limited. For example, the following methods can be cited: a method for coating the first treatment liquid on the surface of the substrate W; a method for spraying the first treatment liquid on the surface of the substrate W; a method for immersing the substrate W in the first treatment liquid.

[0052] As a method for coating the first treatment liquid on the surface of the substrate W, for example, the following method can be used: while rotating the substrate W at a constant speed with the central part of the substrate W as the axis, the first treatment liquid is supplied to the central part of the surface of the substrate W. As a result, the first treatment liquid supplied to the surface of the substrate W flows from near the center of the surface of the substrate W toward the peripheral part of the substrate W due to the centrifugal force generated by the rotation of the substrate W, and spreads over the entire surface of the substrate W. As a result, the entire surface of the substrate W is covered with the first treatment liquid, thereby forming a liquid film of the first treatment liquid.

[0053] The first treatment liquid contains at least a SAM forming material. In addition, the SAM forming material in the first treatment liquid can be dissolved in the solvent or dispersed in the solvent. The SAM forming material is not particularly limited. For example, organosilane compounds such as octadecyltrichlorosilane can be cited. Octadecyltrichlorosilane is the following compound: having a trichlorosilyl group as a functional group capable of forming a siloxane bond with a hydroxyl group. In addition, the solvent is not particularly limited. For example, ether solvents, aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, fluorine-based solvents, etc. can be cited. The ether solvent is not particularly limited. For example, tetrahydrofuran (THF) can be cited. The aromatic hydrocarbon solvent is not particularly limited. Toluene, etc. can be cited. The aliphatic hydrocarbon solvent is not particularly limited. Decane, etc. can be cited. The fluorine-based solvent is not particularly limited. 1,3-bis(trifluoromethyl)benzene, etc. can be cited. These solvents can be used alone or in combination of two or more. From the viewpoint of dissolving octadecyltrichlorosilane in the exemplified solvents, an aliphatic hydrocarbon solvent is preferred, and decane is more preferred.

[0054] Relative to the total mass of the first treatment liquid, the content of the SAM forming material is preferably in the range of 0.005% by mass to 100% by mass, more preferably in the range of 0.05% by mass to 50% by mass, and still more preferably in the range of 1% by mass to 10% by mass.

[0055] In addition, within the range that does not hinder the effects of the present invention, known additives can also be contained in the first treatment liquid. The additive is not particularly limited. For example, stabilizers and surfactants can be cited.

[0056] The conditions for bringing the first treatment liquid into contact with the substrate W are not particularly limited. However, compared with the case of forming a SAM by a conventional method, the SAM forming step S101 of the present embodiment can shorten the contact time of the first treatment liquid. Specifically, depending on the type and concentration of the SAM forming material, the type of the solvent, etc., the time required for the SAM forming step S101 (the immersion time in the case of immersing the substrate W in the first treatment liquid) can be appropriately set within the following time range: within the range of 1 minute to 1440 minutes, preferably within the range of 1 minute to 60 minutes, and more preferably within the range of 1 minute to 10 minutes.

[0057] Next, the formation process of the SAM will be described more specifically by taking the case where the SAM-forming material is octadecyltrichlorosilane as an example.

[0058] As Figure 2A shown, when the first treatment liquid is supplied to the surface Wf of the substrate W, molecules capable of forming the SAM (octadecyltrichlorosilane, which will be referred to as "SAM molecules" in some cases hereinafter) 1 are dispersed or dissolved in the initially supplied first treatment liquid. Figure 2A It is a schematic diagram showing the state of supplying the first treatment liquid to the surface Wf of the substrate W.

[0059] Next, as Figure 2B shown, when there are hydroxyl groups (OH groups) 3 on the surface Wf of the substrate W, the SAM molecules 1 chemically adsorb to the surface Wf with the hydroxyl groups 3 as reaction sites. More specifically, the trichlorosilyl group of the SAM molecule 1 reacts with the hydroxyl group 3, thereby forming a siloxane bond, and thus the SAM molecule 1 chemically adsorbs to the surface Wf. In addition, in the case where water molecules 2 are present in the surface Wf of the substrate W and / or the first treatment liquid, the SAM molecules 1 aggregate around the water molecules 2. In particular, the SAM molecules 1 form reverse micelles 4 with respect to the water molecules 2 present in the first treatment liquid, and the reverse micelles 4 incorporate the water molecules 2 inside. In addition, Figure 2B It is a schematic diagram showing the state of the SAM molecules 1 chemically adsorbing to the surface Wf of the substrate W.

[0060] Next, when the SAM molecules 1 are chemically adsorbed to the surface Wf of the substrate W at a high density, an island structure of the SAM molecules 1 appears on the surface Wf. Furthermore, in these islands of the SAM molecules 1, self-assembly occurs through the hydrophobic interaction and / or electrostatic interaction between the SAM molecules 1 and grows (expands), and finally the SAM 5 is formed (refer to Figure 2C ). However, film defects 6 occur in the following parts of the SAM 5: the region where the reverse micelles 4 are attached to the surface Wf of the substrate W; the boundary between adjacent islands where the SAM molecules 1 do not enter; the region where the SAM molecules 1 are present on the surface Wf not by chemical adsorption but by attachment. In addition, Figure 2C It is a schematic diagram showing the state of the SAM molecules 1 self-assembling on the surface Wf of the substrate W and forming the SAM 5.

[0061] [Removal process S102]

[0062] The removal step S102 is the following step: removing the first treatment liquid remaining on the surface Wf of the substrate W after the SAM formation step S101. Thereby, the remaining SAM molecules 1 that do not contribute to the formation of SAM5 are removed from the surface Wf of the substrate W. More specifically, the SAM molecules 1 (including the reverse micelles 4) that are not chemisorbed on the surface Wf of the substrate W are removed from the surface Wf of the substrate W.

[0063] The method for removing the first treatment liquid from the substrate W is not particularly limited. For example, the following methods can be cited: a method for coating the removal liquid onto the surface Wf of the substrate W; a method for spraying the removal liquid onto the surface Wf of the substrate W; a method for immersing the substrate W in the removal liquid.

[0064] As a method for coating the removal liquid onto the surface Wf of the substrate W, for example, the following method can be used: while rotating the substrate W at a constant speed with the central portion of the substrate W as the axis, the removal liquid is supplied to the central portion of the surface Wf of the substrate W. Thereby, the removal liquid supplied to the surface Wf of the substrate W flows from the vicinity of the center of the surface Wf of the substrate W toward the peripheral portion of the substrate W by the centrifugal force generated by the rotation of the substrate W, and spreads over the entire surface of the surface Wf of the substrate W. As a result, the first treatment liquid on the surface Wf of the substrate W is replaced with the removal liquid, and the entire surface of the surface Wf of the substrate W is covered with the removal liquid to form a liquid film of the removal liquid.

[0065] In the case where the SAM forming material is octadecyltrichlorosilane, the surface Wf of the substrate W after the removal step S102 is as Figure 3A shown. As Figure 3A shown, the SAM molecules 1 and reverse micelles 4 that do not contribute to the film formation of SAM5 are removed from the surface Wf of the substrate W. Figure 3A It is a schematic diagram showing the appearance of the surface Wf after removing the unadsorbed SAM molecules 1 and reverse micelles 4.

[0066] As the removal liquid, an organic solvent is preferably used; the organic solvent dissolves the SAM forming material and has a low solubility in water, thereby suppressing the water content. When the removal liquid can dissolve the SAM forming material, the remaining SAM molecules 1 and reverse micelles 4 that do not contribute to the formation of SAM5 can be removed well from the surface Wf of the substrate W. The removal liquid preferably has a solubility in water at 25 °C of 0.033% (330 ppm) or less, for example. More specifically, the removal liquid can be cited as, for example, toluene, decane, 1,3-bis(trifluoromethyl)benzene, etc. These solvents can be used alone or in combination of two or more.

[0067] [Surface modification step S10_{3}]

[0068] The surface modification step S103 is the following step: the surface of the region where the film defect 6 occurs in the surface Wf of the substrate W is surface-modified into a region capable of chemisorbing the SAM molecule 1, that is, the region where the SAM5 is not formed is surface-modified into a region capable of chemisorbing the SAM molecule 1. Herein, the so-called "surface-modified into a region capable of chemisorbing..." in this specification means, for example, performing surface modification in such a manner that hydroxyl groups (OH groups) are generated on the surface Wf of the substrate W. For example, in the case where the substrate W is a SiO2 substrate, the so-called surface modification refers to a treatment for generating silanol groups (Si-OH groups) on the substrate W.

[0069] When performing surface modification on the surface Wf of the substrate W, as Figure 3B shown, hydroxyl groups 3 are generated in the film defect 6 of the SAM5 in a manner capable of chemisorbing the SAM molecule 1. Figure 3B It is a schematic diagram showing the appearance of performing surface modification on a region where the SAM molecule 1 does not exist and generating the hydroxyl groups 3.

[0070] In the present embodiment, the surface modification of the surface Wf of the substrate W is performed by a wet method. More specifically, it is performed by bringing the surface modification liquid into contact with the surface Wf of the substrate W after the removal step S102. The method for bringing the surface modification liquid into contact with the surface Wf of the substrate W is not particularly limited, and for example, the following methods can be cited: a method for coating the surface modification liquid onto the surface Wf of the substrate W; a method for spraying the surface modification liquid onto the surface Wf of the substrate W; a method for immersing the substrate W in the surface modification liquid.

[0071] Furthermore, as a method for coating the surface modification liquid onto the surface Wf of the substrate W, for example, the following method can be cited: while rotating the substrate W at a fixed speed with the central portion of the substrate W as the axis, the surface modification liquid is supplied to the central portion of the surface Wf of the substrate W. As a result, the surface modification liquid supplied to the surface Wf of the substrate W flows from the vicinity of the center of the surface Wf of the substrate W toward the peripheral portion of the substrate W due to the centrifugal force generated by the rotation of the substrate W, and spreads over the entire surface of the surface Wf of the substrate W. As a result, the entire surface of the surface Wf of the substrate W is covered with the surface modification liquid, thereby forming a liquid film of the surface modification liquid.

[0072] As the surface modification liquid, for example, SC-1 (standard clean-1; the first standard rinse liquid, namely an ammonia-hydrogen peroxide mixture) (in terms of volume ratio, ammonia (NH3 concentration of 28%): hydrogen peroxide (H2O2 concentration of 30%): DIW (deionized water) = 1:4:20), ammonium hydroxide (NH4OH), hydrogen peroxide (H2O2), ammonium fluoride (NH4F), diluted sulfuric acid-hydrogen peroxide mixture (SPM (sulfuric acid / hydrogen peroxide mixture)), diluted nitric acid, a mixed solution of hydrofluoric acid and ammonia, ozone water, ozone deionized water, water, etc. can be cited. From the viewpoint of being able to introduce hydroxyl groups well onto the surface Wf of the SiO2 substrate W, SC-1 is preferably used among these surface modification liquids.

[0073] In addition, in the case where the surface modification step S103 is performed by a wet method, it is preferable to sequentially perform a cleaning step for removing the surface modification liquid and a drying step immediately after the surface modification step S103 ends. The cleaning method in the cleaning step is not particularly limited, and for example, the following methods can be cited: a method for supplying a cleaning liquid to the surface Wf of the substrate W; a method for immersing the substrate W in the cleaning liquid. In addition, as the cleaning liquid, for example, toluene, decane, 1,3-bis(trifluoromethyl)benzene, etc. can be cited. These solvents can be used alone or in combination of two or more. The cleaning conditions such as the cleaning time and the temperature of the cleaning liquid are not particularly limited and can be appropriately set as needed. The purpose of the drying step is to remove the cleaning liquid remaining on the surface Wf of the substrate W. The drying method is not particularly limited, and for example, a method for blowing an inert gas such as nitrogen onto the surface Wf of the substrate W can be cited. The drying conditions such as the drying time and the drying temperature are not particularly limited and can be appropriately set as needed.

[0074] [Densification treatment step S104]

[0075] The densification treatment step (second contact step) S104 is the following step: bringing a second treatment liquid containing a SAM forming material into contact with the surface Wf of the substrate W after the surface modification step S103. In the region where the film defect 6 occurs, hydroxyl groups 3 are generated on the surface Wf by the surface modification step S103. Therefore, as Figure 3CAs shown, the second treatment liquid is brought into contact with the surface Wf of the substrate W, whereby the SAM molecules 1 can be chemically adsorbed onto the region where the film defect 6 occurs by forming a siloxane bond between the SAM molecules 1 and the hydroxyl groups 3. Thereby, the film defect 6 is repaired, and a densified SAM5' is formed. In addition, Figure 3C It is a schematic diagram showing the appearance of the densified SAM5' formed.

[0076] As a method of bringing the second treatment liquid into contact with the substrate W, it is the same as the method of contacting the first treatment liquid in the SAM formation step S101 described above. Therefore, the detailed description of this part is omitted.

[0077] Similar to the first treatment liquid in the SAM formation step S101, the second treatment liquid contains at least a SAM forming material and a solvent. The second treatment liquid may be of the same type as the first treatment liquid or a different type. In the case of using a second treatment liquid different from the first treatment liquid, the content of the SAM forming material and the type of the solvent are not particularly limited. However, the SAM forming material is preferably the same as the SAM forming material of the first treatment liquid.

[0078] As conditions for bringing the second treatment liquid into contact with the substrate W, they are not particularly limited. For example, the contact time of the second treatment liquid (the immersion time in the case of immersing the substrate W in the second treatment liquid) can be appropriately set within the following time range according to the type and concentration of the SAM forming material, the type of the solvent, and the occurrence frequency and the area of the occurrence region of the film defect 6 in the plane of the SAM5: within the range of 1 minute to 1440 minutes, preferably within the range of 1 minute to 60 minutes, more preferably within the range of 1 minute to 5 minutes.

[0079] [Rinsing step S105]

[0080] The rinsing step S105 is the following step: removing the second treatment liquid from the surface Wf of the substrate W. Specifically, the rinsing step S105 is performed in the following manner: supplying a rinsing liquid to the surface Wf of the substrate W to replace the remaining second treatment liquid with the rinsing liquid.

[0081] The method for bringing the rinsing liquid into contact with the surface Wf of the substrate W is not particularly limited. For example, the following methods can be cited: a method for directly supplying and coating the rinsing liquid onto the substrate W; a method for spraying the rinsing liquid onto the substrate W; a method for immersing the substrate W in the rinsing liquid. As a method for coating the rinsing liquid onto the surface Wf of the substrate W, for example, the following method can be used: while rotating the substrate W at a fixed speed with the central portion of the substrate W as the axis, the rinsing liquid is supplied to the central portion of the surface Wf of the substrate W. Thus, the rinsing liquid supplied to the surface Wf of the substrate W flows from the vicinity of the center of the surface Wf of the substrate W toward the peripheral portion of the substrate W due to the centrifugal force generated by the rotation of the substrate W, and spreads over the entire surface Wf of the substrate W. As a result, the entire surface Wf of the substrate W is covered with the rinsing liquid, so that a liquid film of the rinsing liquid can be formed and the treatment liquid can be replaced with the rinsing liquid. In addition, the time of the rinsing step S105 is not particularly limited and can be appropriately changed as needed.

[0082] As the rinsing liquid, for example, toluene, decane, 1,3-bis(trifluoromethyl)benzene, etc. can be cited. These solvents can be used alone or in combination of two or more. The rinsing conditions such as the rinsing time and the temperature of the rinsing liquid are not particularly limited and can be appropriately set as needed.

[0083] It is preferable to perform the drying step immediately after the rinsing step S105. The purpose of this drying step is to remove the rinsing liquid remaining on the surface Wf of the substrate W. The drying method is not particularly limited. For example, a method for blowing an inert gas such as nitrogen onto the surface Wf of the substrate W can be cited. The drying conditions such as the drying time and the drying temperature are not particularly limited and can be appropriately set as needed.

[0084] As described above, according to the substrate processing method of the present embodiment, in order to form a dense SAM, surface modification is performed on the region (film defect) of the substrate surface where SAM molecules cannot be chemisorbed. Furthermore, SAM molecules are chemisorbed onto the region where surface modification has been performed, thereby repairing the film defect. As a result, SAM can be formed in a shorter time than the conventional method; the SAM film has a high density and excellent denseness, can suppress or reduce the occurrence of film defects, and has excellent function as a protective film.

[0085] [Substrate Processing Apparatus]

[0086] Next, the substrate processing apparatus of the present embodiment will be described with reference to the accompanying drawings.

[0087] The substrate processing apparatus 100 of the present embodiment is a single-wafer type substrate processing apparatus for forming SAM on the surface Wf of the substrate W, and as Figure 4The following are provided at least: a substrate holding unit 10 that holds a substrate W; a supply unit 20 that supplies a first processing liquid and a second processing liquid to the surface Wf of the substrate W; a removal liquid supply unit 30 that supplies a removal liquid; a surface modification liquid supply unit (surface modification unit) 40; a chamber 50 that is a container for accommodating the substrate W; a splash prevention cover 60 that captures the processing liquid; a rotation drive unit 70 that rotationally drives the following-described arm portions of each part of the substrate processing apparatus 100 independently; and a control unit 80 that controls each part of the substrate processing apparatus 100. In addition, the substrate processing apparatus 100 can also include a loading / unloading mechanism (not shown) that loads or unloads the substrate W. In addition, Figure 4 FIG. is a schematic configuration explanatory diagram of the substrate processing apparatus 100 of the present embodiment. In Figure 4 it, in order to clarify the direction relationship of the illustration, the XYZ orthogonal coordinate axes are appropriately shown. Here, the XY plane represents a horizontal plane, and the +Z direction represents the vertically upward direction.

[0088] [Substrate holding unit 10]

[0089] The substrate holding unit 10 is a mechanism for holding the substrate W, and as Figure 4 shown, holds the substrate W in a substantially horizontal posture and rotates the substrate W in a state where the surface Wf of the substrate W faces upward. This substrate holding unit 10 includes a spin chuck 13, a spin base 11, and a spin support shaft 12 integrally combined. The spin base 11 has a substantially circular shape when viewed from above, and a hollow spin support shaft 12 is fixed to the central portion of the spin base 11, and the spin support shaft 12 extends in a substantially vertical direction. The spin support shaft 12 is connected to the rotation shaft of a chuck rotation mechanism 14 that includes a motor. The chuck rotation mechanism 14 is housed in a cylindrical casing 15, and the spin support shaft 12 is supported by the casing 15 so as to be rotatable about a vertical rotation axis.

[0090] The chuck rotation mechanism 14 can rotate the spin support shaft 12 about the rotation axis by driving from a chuck drive unit (not shown) of the control unit 80. Thereby, the spin base 11 mounted on the upper end portion of the spin support shaft 12 rotates about the rotation axis J. The control unit 80 can control the chuck rotation mechanism 14 via the chuck drive unit to adjust the rotation speed of the spin base 11.

[0091] A plurality of chuck pins 16 are erected near the peripheral portion of the rotary base 11, and the plurality of chuck pins 16 are used to hold the peripheral end portion of the substrate W. The number of the chuck pins 16 is not particularly limited, but in order to securely hold the circular substrate W, it is preferably at least three or more. In the present embodiment, three chuck pins 16 are arranged at equal intervals along the peripheral portion of the rotary base 11. Each chuck pin 16 includes: a substrate support pin that supports the peripheral portion of the substrate W from below; and a substrate holding pin that presses and holds the outer peripheral end surface of the substrate W supported by the substrate support pin.

[0092] [Supply unit 20]

[0093] The supply unit 20 of the present embodiment is a mechanism for supplying the first processing liquid and the second processing liquid to the surface Wf of the substrate W. As Figure 4 shown, the supply unit 20 has a processing liquid storage unit 21, a nozzle 22, and an arm unit 23.

[0094] In the case where the same type of processing liquid is used as the first processing liquid and the second processing liquid, the processing liquid storage unit 21, as Figure 5 shown, includes a pressurizing unit 24 and a processing liquid cylinder tank 25. In addition, Figure 5 FIG. is an explanatory diagram showing a schematic configuration of the processing liquid storage unit 21 in the supply unit 20.

[0095] The pressurizing unit 24 includes: a nitrogen supply source 24a, which is a gas supply source for pressurizing the inside of the processing liquid cylinder tank 25; a pump (not shown) that pressurizes nitrogen; a nitrogen supply pipe 24b; and a valve 24c provided in the middle of the path of the nitrogen supply pipe 24b.

[0096] The nitrogen supply pipe 24b is connected to the processing liquid cylinder tank 25 in a piping manner. Furthermore, a valve 24c is provided in the middle of the path of the nitrogen supply pipe 24b. The valve 24c is electrically connected to the control unit 80, and the opening and closing of the valve 24c can be controlled by an operation instruction of the control unit 80. When the valve 24c is opened by an operation instruction of the control unit 80, nitrogen can be supplied to the processing liquid cylinder tank 25.

[0097] The processing liquid cylinder tank 25 may also include: a stirring unit (not shown) that stirs the processing liquid in the processing liquid cylinder tank 25; and a temperature adjusting unit (not shown) that adjusts the temperature of the processing liquid. As the stirring unit, a stirring unit having a rotating unit and a stirring control unit can be cited. The rotating unit is used to stir the processing liquid, and the stirring control unit is used to control the rotation of the rotating unit. The stirring control unit is electrically connected to the control unit 80. The rotating unit, for example, has a propeller-shaped stirring blade at the lower end of the rotating shaft. The control unit 80 gives an operation instruction to the stirring control unit, thereby rotating the rotating unit, and thus the processing liquid can be stirred by the stirring blade. As a result, the concentration and temperature of the processing liquid can be set to be uniform inside the processing liquid cylinder tank 25.

[0098] Furthermore, a discharge pipe 25a is connected to the processing liquid cylinder tank 25 via a pipeline, and the discharge pipe 25a is used to supply the processing liquid to the nozzle 22. A discharge valve 25b is provided in the middle of the path of the discharge pipe 25a. In addition, the discharge valve 25b is electrically connected to the control unit 80. Thus, the opening and closing of these valves can be controlled by the operation instruction of the control unit 80. When the discharge valve 25b is opened by the operation instruction of the control unit 80, the processing liquid is pumped to the nozzle 22 via the discharge pipe 25a.

[0099] The nozzle 22 is installed at the top end of the horizontally extending arm 23 and is arranged above the rotating base 11 when spraying the processing liquid. The arm 23 is connected to the rotation driving unit 70 via a rotating shaft (not shown). The rotation driving unit 70 is electrically connected to the control unit 80 and rotates the arm 23 by the operation instruction from the control unit 80. Along with the rotation of the arm 23, the nozzle 22 also moves.

[0100] In addition, in the case where the supply unit 20 supplies the first processing liquid and the second processing liquid with different supply types, as Figure 6 shown, a processing liquid storage unit 21' can also be used. The processing liquid storage unit 21' includes a pair of first processing liquid cylinder tanks 26 and second processing liquid cylinder tanks 27. Thus, processing liquids of different types can be used respectively in the SAM formation process S101 and the densification process S104. Figure 6 It is an explanatory diagram showing the schematic configuration of the processing liquid storage unit 21' in the supply unit 20.

[0101] More specifically, the processing liquid storage unit 21' has the following configuration. That is, the first processing liquid cylinder tank 26 stores the first processing liquid, and the second processing liquid cylinder tank 27 stores the second processing liquid. In addition, the nitrogen supply pipe 24b branches into a first nitrogen supply pipe 24d and a second nitrogen supply pipe 24e. The first nitrogen supply pipe 24d is connected to the first processing liquid cylinder tank 26 via a pipeline, and the second nitrogen supply pipe 24e is connected to the second processing liquid cylinder tank 27 via a pipeline. Furthermore, a first valve 24f is provided in the middle of the path of the first nitrogen supply pipe 24d, and a second valve 24g is provided in the middle of the path of the second nitrogen supply pipe 24e. The valve 24c, the first valve 24f, and the second valve 24g are respectively electrically connected to the control unit 80, and the opening and closing of the valve 24c, the first valve 24f, and the second valve 24g are controlled by the operation instruction of the control unit 80. When the valve 24c, the first valve 24f, and the second valve 24g are opened by the operation instruction of the control unit 80, nitrogen can be supplied to the first processing liquid cylinder tank 26 and the second processing liquid cylinder tank 27 respectively.

[0102] The first processing liquid cylinder tank 26 and the second processing liquid cylinder tank 27 may also be respectively provided with: a stirring unit (not shown) that stirs the first processing liquid in the first processing liquid cylinder tank 26 and the second processing liquid in the second processing liquid cylinder tank 27; and a temperature adjustment unit (not shown) that adjusts the temperatures of the first processing liquid and the second processing liquid. As the stirring unit, a stirring unit having a rotating unit and a stirring control unit can be cited. The rotating unit is used to stir the first processing liquid or the second processing liquid, and the stirring control unit is used to control the rotation of the rotating unit. The stirring control unit is electrically connected to the control unit 80. The rotating unit, for example, has a propeller-shaped stirring blade at the lower end of the rotating shaft. The control unit 80 gives an operation command to the stirring control unit, thereby rotating the rotating unit, so that the first processing liquid or the second processing liquid can be stirred by the stirring blade. As a result, the concentrations and temperatures of the first processing liquid and the second processing liquid can be set to be uniform inside the first processing liquid cylinder tank 26 and the like.

[0103] Furthermore, a first discharge pipe 26a and a second discharge pipe 27a are respectively connected to the first processing liquid cylinder tank 26 and the second processing liquid cylinder tank 27 through pipelines. The first discharge pipe 26a and the second discharge pipe 27a are used to supply the first processing liquid or the second processing liquid to the nozzle 22. A first discharge valve 26b is provided in the middle of the path of the first discharge pipe 26a. In addition, a second discharge valve 27b is provided in the middle of the path of the second discharge pipe 27a. Furthermore, the first discharge pipe 26a and the second discharge pipe 27a are connected to a third discharge pipe 28 through pipelines in a manner that they converge on the downstream side of the first discharge valve 26b and the second discharge valve 27b. A third discharge valve 28a is provided in the middle of the path of the third discharge pipe 28. In addition, the first discharge valve 26b, the second discharge valve 27b, and the third discharge valve 28a are electrically connected to the control unit 80. Thus, the opening and closing of these valves are controlled by the operation command of the control unit 80. When the first discharge valve 26b and the third discharge valve 28a are opened by the operation command of the control unit 80, the first processing liquid is pumped to the nozzle 22 through the first discharge pipe 26a and the third discharge pipe 28. In addition, when the second discharge valve 27b and the third discharge valve 28a are opened by the operation command of the control unit 80, the second processing liquid is pumped to the nozzle 22 through the second discharge pipe 27a and the third discharge pipe 28.

[0104] [Removing liquid supply unit 30]

[0105] The removing liquid supply unit 30 of the present embodiment is a mechanism for supplying a removing liquid to the surface Wf of the substrate W. As Figure 4 shown, the removing liquid supply unit 30 has a removing liquid storage portion 31, a nozzle 32, and an arm portion 33.

[0106] As Figure 7As shown, the removal liquid reservoir portion 31 has a function of supplying the removal liquid to the nozzle 32, and includes a pressurizing portion 34 and a removal liquid cylinder tank 35. Figure 7 It is an explanatory diagram showing a schematic configuration of the removal liquid reservoir portion 31 in the removal liquid supply portion 30.

[0107] The pressurizing portion 34 includes: a nitrogen gas supply source 34a, which is a supply source of gas for pressurizing the inside of the removal liquid cylinder tank 35; a pump (not shown) for pressurizing nitrogen gas; a nitrogen gas supply pipe 34b; and a valve 34c provided in the middle of the path of the nitrogen gas supply pipe 34b.

[0108] The nitrogen gas supply pipe 34b is connected to the removal liquid cylinder tank 35 via a pipeline. Furthermore, a valve 34c is provided in the middle of the path of the nitrogen gas supply pipe 34b. The valve 34c is electrically connected to the control portion 80, and the opening and closing of the valve 34c can be controlled by an operation instruction of the control portion 80. When the valve 34c is opened by an operation instruction of the control portion 80, nitrogen gas can be supplied to the removal liquid cylinder tank 35.

[0109] The removal liquid cylinder tank 35 may also include: a stirring portion (not shown) for stirring the removal liquid in the removal liquid cylinder tank 35; and a temperature adjustment portion (not shown) for adjusting the temperature of the removal liquid. As the stirring portion, a stirring portion including a rotating portion and a stirring control portion can be cited. The rotating portion is used to stir the removal liquid in the removal liquid cylinder tank 35, and the stirring control portion is used to control the rotation of the rotating portion. The stirring control portion is electrically connected to the control portion 80. The rotating portion, for example, has a propeller-shaped stirring blade at the lower end of the rotating shaft. The control portion 80 gives an operation instruction to the stirring control portion, thereby causing the rotating portion to rotate, and thus the removal liquid can be stirred with the stirring blade. As a result, the concentration and temperature of the removal liquid can be set to be uniform inside the removal liquid cylinder tank 35.

[0110] Furthermore, a discharge pipe 35a is connected to the removal liquid cylinder tank 35 via a pipeline. The discharge pipe 35a is used to supply the removal liquid to the nozzle 32. A discharge valve 35b is provided in the middle of the path of the discharge pipe 35a. The discharge valve 35b is electrically connected to the control portion 80. Thus, the opening and closing of the discharge valve 35b can be controlled by an operation instruction of the control portion 80. When the discharge valve 35b is opened by an operation instruction of the control portion 80, the removal liquid is pumped to the nozzle 32 via the discharge pipe 35a.

[0111] The nozzle 32 is installed at the top end of an arm portion 33 that extends horizontally, and is disposed above the rotating base 11 when spraying the removal liquid. The arm portion 33 is connected to a rotation driving portion 70 via a rotation shaft (not shown). The rotation driving portion 70 is electrically connected to the control portion 80, and causes the arm portion 33 to rotate by an operation instruction from the control portion 80. Along with the rotation of the arm portion 33, the nozzle 32 also moves.

[0112] [Surface modification liquid supply portion 40]

[0113] The surface modification liquid supply unit 40 of the present embodiment is a mechanism for supplying a surface modification liquid to the surface Wf of the substrate W. As Figure 4 shown, the surface modification liquid supply unit 40 includes a surface modification liquid storage unit 41, a nozzle 42, and an arm unit 43.

[0114] As Figure 8 shown, the surface modification liquid storage unit 41 has a function of supplying the surface modification liquid to the nozzle 42, and includes a pressurizing unit 44 and a surface modification liquid cylinder tank 45. Figure 8 It is an explanatory diagram showing a schematic configuration of the surface modification liquid storage unit 41 in the surface modification liquid supply unit 40.

[0115] The pressurizing unit 44 includes: a nitrogen gas supply source 44a, which is a gas supply source for pressurizing the inside of the surface modification liquid cylinder tank 45; a pump (not shown) for pressurizing nitrogen gas; a nitrogen gas supply pipe 44b; and a valve 44c provided in the middle of the path of the nitrogen gas supply pipe 44b.

[0116] The nitrogen gas supply pipe 44b is connected to the surface modification liquid cylinder tank 45 through a pipeline. Furthermore, a valve 44c is provided in the middle of the path of the nitrogen gas supply pipe 44b. The valve 44c is electrically connected to the control unit 80, and the opening and closing of the valve 44c can be controlled by an operation instruction of the control unit 80. When the valve 44c is opened by an operation instruction of the control unit 80, nitrogen gas can be supplied to the surface modification liquid cylinder tank 45.

[0117] The surface modification liquid cylinder tank 45 may also include: a stirring unit (not shown) for stirring the surface modification liquid in the surface modification liquid cylinder tank 45; and a temperature adjustment unit (not shown) for adjusting the temperature of the surface modification liquid. As the stirring unit, a stirring unit having a rotating unit and a stirring control unit can be cited. The rotating unit is used to stir the surface modification liquid in the surface modification liquid cylinder tank 45, and the stirring control unit is used to control the rotation of the rotating unit. The stirring control unit is electrically connected to the control unit 80. The rotating unit, for example, has a propeller-shaped stirring blade at the lower end of the rotating shaft. The control unit 80 gives an operation instruction to the stirring control unit, thereby causing the rotating unit to rotate, and thus the surface modification liquid can be stirred by the stirring blade. As a result, the concentration and temperature of the surface modification liquid can be set uniformly inside the surface modification liquid cylinder tank 45.

[0118] Furthermore, a discharge pipe 45a is connected to the surface modification liquid cylinder tank 45 through a pipeline. The discharge pipe 45a is used to supply the surface modification liquid to the nozzle 42. A discharge valve 45b is provided in the middle of the path of the discharge pipe 45a. The discharge valve 45b is electrically connected to the control unit 80. Thus, the opening and closing of the discharge valve 45b can be controlled by an operation instruction of the control unit 80. When the discharge valve 45b is opened by an operation instruction of the control unit 80, the surface modification liquid is pumped to the nozzle 42 through the discharge pipe 45a.

[0119] The nozzle 42 is installed at the top of the horizontally extending arm 43 and is disposed above the rotary base 11 when ejecting the surface modification liquid. The arm 43 is connected to the rotation drive unit 70 via a rotation shaft (not shown). The rotation drive unit 70 is electrically connected to the control unit 80 and rotates the arm 43 by an operation instruction from the control unit 80. Along with the rotation of the arm 43, the nozzle 42 also moves.

[0120] [Scattering prevention cover 60]

[0121] The scattering prevention cover 60 is provided so as to surround the rotary base 11. The scattering prevention cover 60 is connected to a lifting drive mechanism (not shown) and can be lifted and lowered in the vertical direction. When supplying the first treatment liquid or the like to the surface Wf of the substrate W, the scattering prevention cover 60 is positioned at a predetermined position by the lifting drive mechanism and surrounds the substrate W held by the chuck pins 16 from the side position. Thereby, the first treatment liquid or the like scattered from the substrate W and the rotary base 11 can be trapped.

[0122] [Control unit 80]

[0123] The control unit 80 is electrically connected to each part of the substrate processing apparatus 100 and controls the operation of each part. The control unit 80 is constituted by a computer having an arithmetic unit and a storage unit. As the arithmetic unit, a CPU (Central Processing Unit) for performing various arithmetic processes is used. In addition, the storage unit includes: a ROM (Read Only Memory), which is a read-only memory for storing a substrate processing program; a RAM (Random Access Memory), which is a freely readable and writable memory for storing various information; and a magnetic disk, which pre-stores control software, data, etc. Substrate processing conditions are pre-stored in the magnetic disk, and the substrate processing conditions include: supply conditions of the first treatment liquid, the second treatment liquid, the removal liquid, and the surface modification liquid; rinsing conditions; film formation conditions of SAM, etc. The CPU reads the processing conditions into the RAM, and the CPU controls each part of the substrate processing apparatus 100 in accordance with the content of the processing conditions.

[0124] [Second Embodiment]

[0125] The substrate processing method and the substrate processing apparatus according to the second embodiment of the present invention will be described below.

[0126] Compared with the first embodiment, the difference in this embodiment is that the surface modification process is performed by a dry method using ultraviolet irradiation. With this configuration, reaction sites such as hydroxyl groups can also be formed in regions where SAM molecules cannot be chemically adsorbed, and the SAM molecules can be chemically adsorbed, thereby enabling the formation of a SAM with excellent denseness.

[0127] [Substrate Processing Method]

[0128] The following is a reference to Figure 9 Describe the substrate processing method of this embodiment. Figure 9 FIG. is a flowchart showing an example of the overall process of the substrate processing method of the second embodiment of the present invention. In addition, Figure 9 The SAM formation step S101, the removal step S102, the densification treatment step S104, and the rinsing step S105 shown are the same as those in the first embodiment. Therefore, the detailed description of these steps is omitted.

[0129] [1. Surface Modification Step S103']

[0130] The surface modification step S103' is the following step: modifying the surface of the region where the film defect 6 occurs in the SAM5 into a region where the SAM molecule 1 can be chemically adsorbed, that is, modifying the surface of the region where the SAM5 is not formed into a region where the SAM molecule 1 can be chemically adsorbed.

[0131] In this embodiment, the surface modification of the surface Wf of the substrate W is performed by a dry method of ultraviolet irradiation. In the case of ultraviolet irradiation, the irradiation conditions of ultraviolet rays such as the wavelength of the light source, the irradiation intensity, and the irradiation time only need to introduce the hydroxyl group 3 to the surface Wf of the substrate W to the extent that the SAM molecule 1 can be chemically adsorbed, and are not particularly limited.

[0132] In addition, as also described in the first embodiment, in the case of performing surface modification by a wet method, it is preferably to perform a cleaning step and a drying step for removing the surface modification liquid. However, in the dry method of ultraviolet irradiation in this embodiment, the implementation of these steps can be omitted. Therefore, compared with the substrate processing method of the first embodiment, the manufacturing efficiency can be improved.

[0133] [Substrate Processing Apparatus]

[0134] Next, the substrate processing apparatus of this embodiment will be described with reference to the drawings.

[0135] Compared with the substrate processing apparatus 100 of the first embodiment, the difference of the substrate processing apparatus 200 of this embodiment is that, as Figure 10 shown, it is provided with an ultraviolet irradiation unit 90 to replace the surface modification liquid supply unit 40. Figure 10 FIG. is an explanatory diagram showing the schematic configuration of the substrate processing unit 200 of the second embodiment. In Figure 10In order to clarify the directional relationship of the illustration, the XYZ orthogonal coordinate axes are also appropriately shown. Here, the XY plane represents the horizontal plane, and the +Z direction represents the vertically upward direction. In addition, components having the same functions as those of the substrate processing apparatus of the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0136] The ultraviolet irradiation unit 90 is disposed above the substrate holding unit 10 inside the substrate processing unit 200 ( Figure 10 in the direction indicated by the arrow Z in the figure), so that the surface Wf of the substrate W held by the substrate holding unit 10 can be irradiated with ultraviolet rays. The ultraviolet irradiation unit 90 includes at least a quartz glass 92 and a plurality of light source units 91.

[0137] Figure 10 The light source unit 91 shown in the figure is a linear light source, and is arranged such that the long side direction of the light source unit 91 is parallel to Figure 10 the direction indicated by the arrow Y in the figure. In addition, the respective light source units 91 are arranged at equal intervals in the direction indicated by the arrow X. However, the light source unit 91 of the present invention is not limited to this manner. For example, the following manner may also be adopted: a ring-shaped light source unit, and light source units having different diameters are arranged in concentric circles. In addition, the light source unit may also be a point light source. In this case, it is preferable that a plurality of light source units are arranged at equal intervals in the plane.

[0138] The type of the light source unit 91 is not particularly limited, and for example, a low-pressure mercury lamp, a high-pressure mercury lamp, a potassium lamp, a mercury xenon lamp, a flash lamp, an excimer lamp, a metal halide lamp, and a UV-LED (UltraViolet-Light Emitting Diode) can be used. In addition, the plurality of light source units 91 may be of the same type or different types. When a plurality of different types of light source units are used as the light source unit 91, they can be arranged such that the peak wavelength, the light intensity, etc. are different from each other.

[0139] The quartz glass 92 is disposed between the light source unit 91 and the substrate W. The quartz glass 92 is a plate-like body and is provided parallel to the horizontal direction. In addition, the quartz glass 92 has translucency, heat resistance, and corrosion resistance to ultraviolet rays, and can transmit the ultraviolet rays irradiated from the light source unit 91 and irradiate the surface Wf of the substrate W. Furthermore, the quartz glass 92 can protect the light source unit 91 from the atmosphere in the chamber 50.

[0140] [Third Embodiment]

[0141] The substrate processing method and the substrate processing apparatus according to the third embodiment of the present invention will be described below.

[0142] Compared with the first embodiment, the difference in this embodiment is that the surface modification process is carried out by a dry method of supplying ozone gas or gas containing moisture. With such a configuration, reaction sites such as hydroxyl groups can also be formed in regions where SAM molecules cannot be chemisorbed, enabling the chemisorption of the SAM molecules and the formation of a SAM with excellent compactness.

[0143] [Substrate processing method]

[0144] The following refers to Figure 11 to illustrate the substrate processing method of this embodiment. Figure 11 FIG. is a flowchart showing an example of the overall process of the substrate processing method according to the third embodiment of the present invention. In addition, since Figure 11 the SAM formation process S101, the removal process S102, the densification process S104, and the rinsing process S105 shown are the same as those in the first embodiment, detailed descriptions of these processes are omitted.

[0145] [1. Surface modification process S103”]

[0146] The surface modification process S103” is the following process: modifying the surface of the region where the film defect 6 occurs in the SAM5 into a region where the SAM molecule 1 can be chemisorbed, that is, modifying the surface of the region where the SAM5 is not formed into a region where the SAM molecule 1 can be chemisorbed.

[0147] In this embodiment, the surface modification of the surface Wf of the substrate W is carried out by a dry method of contacting with ozone gas or gas containing moisture. In the case of surface modification by these methods, ozone gas or gas containing moisture is blown onto the surface Wf of the substrate W, or the surface Wf of the substrate W is exposed to the atmosphere of ozone gas or gas containing moisture, whereby the hydroxyl group 3 can be introduced into the surface Wf. The concentration of ozone contained in the ozone gas or the amount of moisture contained in the gas containing moisture is not particularly limited as long as the hydroxyl group 3 can be introduced into the surface Wf of the substrate W to an extent that can chemisorb the SAM molecule 1. In addition, the contact time of the ozone gas or the gas containing moisture is not particularly limited as long as the hydroxyl group 3 can be introduced into the surface Wf of the substrate W to an extent that can chemisorb the SAM molecule 1.

[0148] [Substrate processing apparatus]

[0149] Next, the substrate processing apparatus of this embodiment will be described with reference to the accompanying drawings. In addition, in the following description, the case where the substrate processing apparatus includes an ozone gas supply unit for supplying ozone gas is taken as an example for explanation, but a gas supply unit for supplying gas containing moisture can also adopt the same configuration.

[0150] Compared with the substrate processing apparatus 100 of the first embodiment, the difference of the substrate processing apparatus 300 of this embodiment is that, as Figure 12 shown, it is provided with an ozone gas supply unit 93 to replace the surface modification liquid supply unit 40. In addition, Figure 12 FIG. is an explanatory diagram showing a schematic configuration of the substrate processing apparatus of the third embodiment. In Figure 12 , in order to clarify the direction relationship in the drawing, the XYZ orthogonal coordinate axes are also appropriately shown. Here, the XY plane represents the horizontal plane, and the +Z direction represents the vertically upward direction. In addition, components having the same functions as those of the substrate processing apparatus of the first embodiment are given the same reference numerals and detailed descriptions thereof are omitted.

[0151] The ozone gas supply unit 93 is a mechanism for supplying ozone gas to the surface Wf of the substrate W. As Figure 12 shown, the ozone gas supply unit 93 includes an ozone gas supply source 94, an ozone gas supply pipe 95, a valve 96, a nozzle 97, and an arm portion 98. The ozone gas supply pipe 95 supplies ozone gas from the ozone gas supply source 94 to the nozzle 97. A valve 96 is provided in the middle of the path of the ozone gas supply pipe 95. In addition, the valve 96 is electrically connected to the control unit 80. Thus, the opening and closing of the valve 96 can be controlled by an operation instruction from the control unit 80. When the valve 96 is opened by an operation instruction from the control unit 80, ozone gas is pumped to the nozzle 97 via the ozone gas supply pipe 95.

[0152] The nozzle 97 is installed at the top end of the horizontally extending arm portion 98 and is disposed above the rotating base 11 when spraying ozone gas. The arm portion 98 is connected to the rotation drive unit 70 via a rotation shaft (not shown). The rotation drive unit 70 is electrically connected to the control unit 80 and rotates the arm portion 98 by an operation instruction from the control unit 80. Along with the rotation of the arm portion 98, the nozzle 97 also moves.

[0153] [Other matters]

[0154] In the above description, the best embodiments of the present invention have been described. However, the present invention is not limited to such embodiments. Each of the components in the above-described embodiments and various variations can be changed, modified, replaced, added, deleted, and combined as long as they do not conflict with each other.

[0155] [Examples]

[0156] Hereinafter, exemplary preferred embodiments of the present invention will be described in detail. However, as long as the materials, blending amounts, conditions, etc. described in this embodiment are not particularly described in a limiting manner, the scope of the present invention is not limited to these ranges.

[0157] [Example 1]

[0158] Prepare a substrate with a SiO2 film (film thickness: 100 nm) formed on its surface, and immerse the substrate in an aqueous hydrofluoric acid solution for one minute. As the aqueous hydrofluoric acid solution, use an aqueous hydrofluoric acid solution with a volume ratio of hydrofluoric acid:DIW = 1:100.

[0159] Next, immerse the substrate lifted from the aqueous hydrofluoric acid solution in a first treatment liquid containing a SAM forming material for five minutes, so that SAM (thickness: approximately 1 nm) is formed on the surface of the SiO2 film of the substrate (first contact step (SAM forming step)). As the first treatment liquid, use a liquid in which octadecyltrichlorosilane belonging to the SAM forming material is dissolved in toluene belonging to the solvent. In addition, the content (concentration) of octadecyltrichlorosilane is 5% by mass relative to the total mass of the first treatment liquid.

[0160] Next, continuously supply a removal liquid to the substrate lifted from the first treatment liquid for one minute, thereby removing the unadsorbed SAM forming material remaining on the surface of the substrate (removal step). As the removal liquid, use decane.

[0161] Next, immerse the substrate lifted from the removal liquid in a surface modification liquid for one minute (surface modification step). As the surface modification liquid, use SC-1 (in terms of volume ratio, ammonia water (NH3 concentration: 28%): hydrogen peroxide water (H2O2 concentration: 30%): DIW = 1:4:20) surface modification liquid. After that, lift the substrate from the surface modification liquid, and blow nitrogen gas onto the surface where SAM is formed to dry the surface. The temperature of the nitrogen gas is set to normal temperature, and the drying time is set to 0.33 minutes.

[0162] Furthermore, immerse the dried substrate in a second treatment liquid containing a SAM forming material for five minutes, so that SAM is formed on the surface of the substrate (second contact step (densification treatment step)). As the second treatment liquid, use the same treatment liquid as the first treatment liquid in the first contact step.

[0163] Next, continuously supply toluene to the substrate lifted from the second treatment liquid for one minute to remove the second treatment liquid (rinsing step), and then blow nitrogen gas onto the surface where SAM is formed to dry the surface. The temperature of the nitrogen gas is set to normal temperature, and the drying time is set to 0.33 minutes. Thus, the sample of this example is produced.

[0164] Next, an etching process is performed on the obtained sample. Specifically, the substrate is immersed in an etching solution, and etching is performed on the area of the substrate surface that is not protected by the SAM. As the etching conditions, the immersion time (etching process time) in the etching solution is set to 195 seconds so that the etching amount of SiO2 is about 10 nm. In addition, as the etching solution, an aqueous hydrofluoric acid solution is used, and the volume ratio of hydrofluoric acid to DIW is set to hydrofluoric acid:DIW = 1:100.

[0165] Next, after immersing the substrate lifted from the etching solution in DIW for 0.5 minutes, the substrate is lifted from the DIW (DIW rinsing process), and nitrogen gas is blown onto the surface that has been subjected to the etching process to dry the surface (drying process). The temperature of the nitrogen gas is set to room temperature, and the drying time is set to 0.33 minutes.

[0166] [Comparative Example 1]

[0167] Compared with Example 1, the difference in this Comparative Example 1 is that after the SAM formation process using the first treatment solution, the removal process, the surface modification process, and the densification process (second contact process) are not performed. A more detailed description is as follows.

[0168] A substrate identical to that of Example 1 is prepared, and the substrate is immersed in an aqueous hydrofluoric acid solution for one minute. As the aqueous hydrofluoric acid solution, an aqueous hydrofluoric acid solution with a volume ratio of hydrofluoric acid to DIW of hydrofluoric acid:DIW = 1:100 is used.

[0169] Next, the substrate lifted from the aqueous hydrofluoric acid solution is immersed in the first treatment solution containing the SAM forming material for five minutes, so that a SAM (thickness of about 1 nm) is formed on the surface of the SiO2 film of the substrate. As the first treatment solution, a liquid in which octadecyltrichlorosilane belonging to the SAM forming material is dissolved in toluene belonging to the solvent is used. In addition, the content (concentration) of octadecyltrichlorosilane is 5% by mass relative to the total mass of the treatment solution.

[0170] Next, after continuously supplying toluene to the substrate lifted from the first treatment solution for one minute to remove the first treatment solution remaining on the surface of the substrate, nitrogen gas is blown onto the surface on which the SAM is formed to dry the surface. The temperature of the nitrogen gas is set to room temperature, and the drying time is set to 0.33 minutes. Thus, the sample of this comparative example is produced.

[0171] Next, an etching process is performed on the obtained sample. Specifically, the substrate is immersed in an etching solution, and etching is carried out on the area of the substrate surface that is not protected by the SAM. As the etching conditions, the immersion time (etching process time) in the etching solution is set to 195 seconds so that the etching amount of SiO2 is about 10 nm. In addition, as the etching solution, an aqueous hydrogen fluoride solution is used, and the volume ratio of hydrogen fluoride to DIW is set to hydrogen fluoride:DIW = 1:100.

[0172] Next, after immersing the substrate lifted from the etching solution in DIW for 0.5 minutes, the substrate is lifted from the DIW (rinsing process by DIW), and nitrogen gas is blown onto the surface that has been subjected to the etching process to dry the surface (drying process). The temperature of the nitrogen gas is set to room temperature, and the drying time is set to 0.33 minutes.

[0173] [Comparative Example 2]

[0174] Compared with Example 1, the difference in this Comparative Example 2 is that after the removal process using decane, the surface modification process is not performed. A more detailed description is as follows.

[0175] A substrate identical to that in Example 1 is prepared, and the substrate is immersed in an aqueous hydrogen fluoride solution for one minute. As the aqueous hydrogen fluoride solution, an aqueous hydrogen fluoride solution with a volume ratio of hydrogen fluoride to DIW of hydrogen fluoride:DIW = 1:100 is used.

[0176] Next, the substrate lifted from the aqueous hydrogen fluoride solution is immersed in a first treatment solution containing a SAM forming material for five minutes, so that a SAM (thickness of about 1 nm) is formed on the surface of the SiO2 film of the substrate. As the first treatment solution, a liquid in which octadecyltrichlorosilane belonging to the SAM forming material is dissolved in toluene belonging to the solvent is used. In addition, the content (concentration) of octadecyltrichlorosilane is 5% by mass relative to the total mass of the treatment solution.

[0177] Next, the substrate lifted from the first treatment solution is immersed in a removal solution for one minute to remove the unadsorbed SAM forming material remaining on the surface of the substrate. As the removal solution, decane is used.

[0178] Next, the substrate is lifted from the removal solution, and nitrogen gas is blown onto the surface on which the SAM is formed to dry the surface. The temperature of the nitrogen gas is set to room temperature, and the drying time is set to 0.33 minutes.

[0179] Furthermore, the dried substrate is immersed in a second treatment solution containing a SAM forming material for five minutes to form a SAM on the surface of the substrate. As the second treatment solution, the same treatment solution as the first treatment solution in the first contact process is used.

[0180] Next, toluene was continuously supplied to the substrate lifted from the second treatment liquid for one minute to remove the second treatment liquid, and then nitrogen gas was blown onto the surface on which the SAM was formed to dry the surface. The temperature of the nitrogen gas was set to room temperature, and the drying time was set to 0.33 minutes. Thus, the sample of this comparative example was produced.

[0181] Next, an etching treatment was performed on the obtained sample. Specifically, the substrate was immersed in an etching solution, and etching of the region in the substrate not protected by the SAM was performed (etching step). As the etching conditions, the immersion time (etching treatment time) in the etching solution was set to 195 seconds so that the etching amount of SiO2 would be about 10 nm. In addition, as the etching solution, an aqueous hydrogen fluoride solution was used, and the volume ratio of hydrogen fluoride to DIW was set to hydrogen fluoride:DIW = 1:100.

[0182] Next, after the substrate lifted from the etching solution was immersed in DIW for 0.5 minutes, the substrate was lifted from the DIW (DIW rinsing step), and nitrogen gas was blown onto the surface that had been subjected to the etching treatment to dry the surface (drying step). The temperature of the nitrogen gas was set to room temperature, and the drying time was set to 0.33 minutes.

[0183] [Evaluation of SAM Compactness]

[0184] For each of the samples of Example 1, Comparative Example 1, and Comparative Example 2, the area of the film defects of the SAM was calculated, and the compactness of the SAM was evaluated.

[0185] That is, the SAM of each sample was photographed using an atomic force microscope (AFM; Atomic Force Microscope) (trade name "Dimension Icon", manufactured by Bruker Japan Co., Ltd.) to obtain a 500 nm square observation image (AFM image). Next, after each of the obtained observation images was binarized, image processing was performed and then mapping of the film defects was carried out to specify the location (area) of the film defects of the SAM. In the specification of the mapping based on the location (area) of the film defects of the SAM, considering the case where the film thickness of the SAM is about 1 nm, image processing was performed such that defects located at a depth less than 1 nm from the SAM surface were mapped. Thus, it was set that the area at a depth exceeding 1 nm from the SAM surface was mapped as the area of the film defects of the SAM. More specifically, it was set that the etched area was mapped as the area of the film defects of the SAM, and the area not included in this area was not included. Next, the area of the region of the film defects of the SAM specified by the image processing was calculated, and the ratio to the area of the entire region in the observation image was calculated. The results are shown in Table 1.

[0186] As can be seen from Table 1, the area ratio of the film defects of the SAM in Example 1 was 25.4%, which was the smallest compared with the area ratios of the film defects of the SAMs in Comparative Example 1 and Comparative Example 2, and good denseness was confirmed.

[0187] [Evaluation of the protective performance of SAM]

[0188] For each of the samples of Example 1, Comparative Example 1, and Comparative Example 2, the protective performance of SAM was evaluated based on the film thickness of the SiO2 film and the water contact angle.

[0189] Specifically, an ellipsometer (trade name: "Flying MASE XI", manufactured by J.A. Woollam Co., Ltd.) was used to measure the film thickness d1 of the SiO2 film coated with SAM before the etching process was about to be performed and the film thickness d2 of the SiO2 film coated with SAM after all the processes were completed. The results are shown in Table 1.

[0190] In addition, a contact angle meter (trade name: "DMo-701", manufactured by Nippon Kyouwa Interface Science Co., Ltd.) was used to measure the water contact angle θ1 of the SiO2 film coated with SAM before the etching process was about to be performed and the water contact angle θ2 of the SiO2 film coated with SAM after all the processes were completed based on the droplet method. The results are shown in Table 1.

[0191] As can be seen from Table 1, in Example 1, the change in the film thickness of the SiO2 film before and after etching was from 99.6 nm to 98.8 nm, and the reduction was smaller compared with the cases of Comparative Example 1 and Comparative Example 2. In addition, the water contact angle of the surface of the SiO2 film after etching in Example 1 was larger than that in the cases of Comparative Example 1 and Comparative Example 2. From these results, it was confirmed that the protective performance of the SAM in Example 1 for the SiO2 film was superior to that of Comparative Example 1 and Comparative Example 2.

[0192] [Table 1]

[0193]

[0194]

Explanation of reference numerals

[0195] 1: SAM molecule

[0196] 2: Water molecule

[0197] 3: Hydroxyl group

[0198] 4: Reverse micelle

[0199] 5, 5': SAM

[0200] 6: Film defect

[0201] 10: Substrate holding part

[0202] 20: Supply part

[0203] 21, 21’: Processing liquid storage part

[0204] 24: Pressurizing part

[0205] 25: Processing liquid cylinder tank

[0206] 26: First processing liquid cylinder tank

[0207] 27: Second processing liquid cylinder tank

[0208] 30: Removing liquid supply part

[0209] 31: Removing liquid storage part

[0210] 35: Removing liquid cylinder tank

[0211] 40: Surface modification liquid supply part

[0212] 41: Surface modification liquid storage part

[0213] 44: Pressurizing part

[0214] 45: Surface modification liquid cylinder tank

[0215] 80: Control part

[0216] 90: Ultraviolet irradiation part

[0217] 93: Ozone gas supply part

[0218] 100, 200, 300: Substrate processing device

[0219] S101: SAM formation process (first contact process)

[0220] S102: Removal process

[0221] S103, S103’, S103”: Surface modification process

[0222] S104: Densification treatment process (second contact process)

[0223] S105: Rinsing process

[0224] W: Substrate

[0225] Wf: Surface of the substrate

Claims

1. A substrate processing method for forming a self-assembled monolayer on the surface of a substrate, wherein, Comprising: A first contact step of bringing a first treatment liquid containing molecules capable of forming the self-assembled monolayer into contact with the surface and causing the molecules to chemisorb; A removal step of removing the molecules that have not chemisorbed from the surface of the substrate; A surface modification step of modifying the surface of the region where the molecules do not exist after the removal step into a region capable of chemisorbing the molecules; And A second contact step of bringing a second treatment liquid containing the molecules and of the same or different type as the first treatment liquid into contact with the region surface-modified and causing the molecules to chemisorb.

2. The substrate treatment method according to claim 1, wherein The first contact step is the following step: bringing the first treatment liquid into contact with the surface of the substrate, thereby causing the molecules to chemisorb on the region capable of chemisorbing and self-assembling, thereby forming the self-assembled monolayer; The second contact step is the following step: causing the molecules to chemisorb on the region surface-modified by the surface modification step and performing a densification treatment on the self-assembled monolayer.

3. The substrate treatment method according to claim 1 or 2, wherein At least the surface of the substrate is composed of silicon dioxide; The molecules have functional groups capable of forming siloxane bonds with hydroxyl groups; The surface modification in the surface modification step generates hydroxyl groups in the region where the molecules do not exist; The chemisorption of the molecules in the first contact step and the second contact step bonds the molecules to the surface via siloxane bonds with the hydroxyl groups on the surface of the substrate.

4. The substrate treatment method according to claim 3, wherein The surface modification step is the following step: bringing a surface modification liquid into contact with the region where the molecules do not exist in the surface after the removal step; Using a solution for generating hydroxyl groups on the surface composed of silicon dioxide as the surface modification liquid.

5. The substrate treatment method according to claim 3, wherein The surface modification step is at least one of the following steps: A step of bringing ozone gas into contact with the region where the molecules do not exist in the surface; A step of irradiating ultraviolet rays on the region where the molecules do not exist in the surface; And A step of bringing a gas containing moisture into contact with the region where the molecules do not exist in the surface.

6. The substrate treatment method according to claim 3, wherein The molecules contain octadecyltrichlorosilane.

7. A substrate processing apparatus for forming a self-assembled monolayer on the surface of a substrate, wherein, Comprising: A supply unit for supplying a treatment liquid containing molecules capable of forming the self-assembled monolayer to the surface; A removal liquid supply unit for supplying a removal liquid to the surface after supplying the treatment liquid to remove the molecules that have not chemisorbed; And A surface modification unit for modifying the surface of the region where the molecules do not exist in the surface after the molecules are removed by the removal liquid supply unit into a region capable of chemisorbing the molecules; The supply unit also supplies the treatment liquid to the surface of the substrate surface-modified by the surface modification unit.

8. The substrate processing apparatus according to claim 7, wherein at least the surface of the substrate is made of silica; the molecule has a functional group capable of forming a siloxane bond with a hydroxyl group; the surface modification unit is a surface modification liquid supply unit for supplying a surface modification liquid to an area where the molecule does not exist; a solution for generating hydroxyl groups on the surface made of silica is used as the surface modification liquid.

9. The substrate processing apparatus according to claim 7, wherein at least the surface of the substrate is made of silica; the molecule has a functional group capable of forming a siloxane bond with a hydroxyl group; the surface modification unit is at least one of an ozone gas supply unit, an ultraviolet irradiation unit, and a gas supply unit. The ozone gas supply unit is used to supply ozone gas to an area where the molecule does not exist on the surface, the ultraviolet irradiation unit is used to irradiate ultraviolet rays to an area where the molecule does not exist on the surface, and the gas supply unit is used to supply a gas containing moisture to an area where the molecule does not exist on the surface.

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