Substrate treating method and substrate manufacturing method

Abstract

A substrate treating method according to the present invention comprises: a preparation step for preparing a substrate having a first surface having silicon nitride; and a surface modification step for forming a protective film for protecting the first surface, wherein the surface modification step includes a gas exposure treatment for bringing a reforming gas including a gas of a surface modifier into contact with the first surface in a heated state in a substrate holding space, and the surface modifier has a predetermined carboxylic acid silyl ester.

Description

Method for treating substrate and method for manufacturing substrate

[0001] The present invention relates to a method for treating a substrate and a method for manufacturing a substrate.

[0002] Conventionally, fine patterning has been achieved by multiple lithography and etching processes to obtain semiconductor devices. However, in recent years, semiconductor devices have tended to become more highly integrated and miniaturized, and in order to meet these demands, lithography processes have become more complex and costly, creating a need for alternative technologies to lithography.

[0003] As an alternative to lithography, a technology using a self-assembled monolayer (SAM) is being considered. Specifically, this technology involves selectively depositing a self-assembled monolayer (hereinafter simply referred to as a "monolayer") as a masking material or protective material on regions of a substrate that are not to be processed, and then forming or depositing a desired film material on the remaining regions of the substrate (i.e., regions that are to be processed), or performing an etching process.

[0004] A method has been studied for selectively etching only the silicon oxide surface of a wafer having a silicon nitride surface and a silicon oxide surface using the monomolecular film. One such technique is described in Patent Document 1.

[0005] U.S. Patent No. 5,999,623 describes a dry process in which a substrate containing a silicon oxide film and a silicon nitride film is exposed to a plasma-excited passivation gas containing carbon, sulfur, or both, to form a thicker passivation layer on the silicon nitride film than on the silicon oxide film.

[0006] Special Publication No. 2022-527552

[0007] However, as a result of research by the present inventors, it was found that the dry processing technique of forming a protective film on a surface having silicon nitride using a gas containing a surface modifier has not yet been fully investigated.

[0008] As a result of extensive research, the inventors discovered that the protective properties of a silicon nitride surface can be enhanced by heating the surface during dry processing to form a protective film, and by using a specific silicon compound, a carboxylic acid silyl ester, as a surface modifier, which led to the completion of the present invention. Although the detailed mechanism is unknown, it is presumed that heating the surface increases the reactivity of the surface, and basic sites resulting from the N element of the silicon nitride contained on the surface act as reaction catalysts, improving the reactivity with the carboxylic acid silyl ester and improving the protective properties.

[0009] According to one aspect of the present invention, there is provided the following method for treating a substrate and method for manufacturing a substrate.

[0010] Examples of reference embodiments are given below. 1. A method for treating a substrate, comprising: a preparation step of preparing a substrate having a first surface made of silicon nitride; and a surface modification step of forming a protective film to protect the first surface, wherein the surface modification step includes a gas exposure treatment of contacting the heated first surface in a substrate holding space with a modifying gas containing a gas of a surface modifier, and wherein the surface modifier has at least one silicon compound represented by the following general formula (1): (X-COO) ａ -Si-R ｂ(1) (In the above general formula (1), X's each independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms, R's each independently represent a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms, and a and b each represent an integer from 1 to 3, with the proviso that a+b=4.) 2. A method for treating a substrate according to 1., wherein the preparation step prepares the substrate having the first surface and a second surface having silicon oxide, and the surface modification step forms a protective film on at least the first surface that selectively protects the first surface against the second surface by the gas exposure treatment of bringing the modifying gas into contact with the first surface and the second surface in a heated state in the substrate holding space. 3. 1. or 2. 4. The method for treating a substrate according to 2., wherein in the surface modification step, the water contact angle at 25°C of the first surface after the gas exposure treatment is 55° or more. 4. The method for treating a substrate according to 2., wherein in the surface modification step, the water contact angle at 25°C of the first surface after the gas exposure treatment is CA １ , the water contact angle of the second surface at 25°C is CA ２ When this is done, CA １ and C.A. ２ However, 1<CA １ / CA ２≦5. 5. A method for treating a substrate according to any one of 1. to 4., wherein the surface temperature of the substrate during the gas exposure treatment is 50°C or higher and 400°C or lower. 6. A method for treating a substrate according to any one of 1. to 5., wherein the temperature of the modifying gas introduced into the substrate holding space is 0°C or higher and 400°C or lower. 7. A method for treating a substrate according to any one of 1. to 6., wherein the concentration of the silicon compound in the modifying gas is 1% by volume or higher and 100% by volume or lower. 8. A method for treating a substrate according to any one of 1. to 7., wherein the boiling point of the silicon compound in the modifying gas is 40°C or higher and 400°C or lower. 9. A method for treating a substrate according to any one of 1. to 8., wherein the modifying gas contains 0% by volume or higher and 99% by volume or lower of an inert gas. 10. A method for treating a substrate according to any one of 1. to 9. The method for treating a substrate according to any one of the above, wherein the pressure in the substrate holding space during the gas exposure treatment is 1 Pa or more and 10 ６ A method for treating a substrate, wherein the pressure is 0.1 Pa or less. 11. A method for treating a substrate as set forth in any one of 1. to 10., wherein the surface modification step includes a gas replacement treatment of introducing an inert gas into the substrate holding space at least either before or after the gas exposure treatment. 12. A method for treating a substrate as set forth in any one of 1. to 11., wherein the surface modification step includes a pretreatment of removing a native oxide film on the first surface before the gas exposure treatment. 13. A method for treating a substrate as set forth in any one of 1. to 12., wherein after the surface modification step, a processing step including one or more selected from the group consisting of an etching treatment and a film formation treatment. 14. A method for treating a substrate as set forth in any one of 1. to 13., wherein the silicon compound includes trimethylsilyl trifluoroacetate and / or trimethylsilyl acetate. 15. A method for treating a substrate as set forth in any one of 1. to 14. A method for producing a substrate, comprising a step of obtaining a substrate that has been subjected to each step in the method for treating a substrate described in any one of the above items.

[0011] According to the present invention, a method for treating a substrate and a method for manufacturing a substrate are provided that are capable of forming an excellent protective film on a surface having silicon nitride using a dry processing technique.

[0012] 1A to 1C are cross-sectional views schematically illustrating the steps of a method for treating a substrate according to an embodiment of the present invention.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by similar reference numerals, and descriptions thereof will be omitted where appropriate. Furthermore, the drawings are schematic diagrams and do not correspond to actual dimensional proportions.

[0014] An outline of the substrate processing method of this embodiment will be described.

[0015] The method for treating a substrate of the first embodiment includes a preparation step of preparing a substrate having a first surface made of silicon nitride, and a surface modification step of forming a protective film to protect the first surface, wherein the surface modification step includes a gas exposure treatment of contacting a modification gas containing a gas of a surface modifier with the first surface in a heated state in a substrate holding space.

[0016] The method for treating a substrate of the second embodiment includes a preparation step of preparing a substrate having a first surface having silicon nitride and a second surface having silicon oxide, and a surface modification step of forming a protective film on at least the first surface that selectively protects the first surface relative to the second surface by a gas exposure treatment in which a modifying gas containing a surface modifier gas is brought into contact with the first surface and the second surface in a heated state in a substrate holding space.

[0017] In both the first and second embodiments, the surface modifier contains at least one silicon compound (hereinafter sometimes referred to as a carboxylic acid silyl ester) represented by the general formula (1) described below.

[0018] According to the findings of the inventors, in the first embodiment, it has been found that the dry treatment increases the frequency of contact with the surface modifier, the heated first surface increases the diffusibility of the surface modifier, and the use of a carboxylic acid silyl ester as a surface modifier causes basic sites, probably due to the N element, to act as a reaction catalyst, increasing reactivity, thereby improving the protection of the first surface having silicon nitride.

[0019] Furthermore, dry treatment increases the frequency of contact between both the first and second surfaces and the surface modifier, which reduces the selective protection of the first surface. However, in the second embodiment, when the second surface having silicon oxide is heated, even if the carboxylic acid silyl ester used as the surface modifier contacts or adsorbs onto the second surface, the adsorption state is difficult to maintain. Furthermore, unlike the first surface, there are almost no basic sites resulting from N elements that can act as a reaction catalyst for the carboxylic acid silyl ester, so the protection of the second surface is reduced compared to the first surface. In other words, it has been found that the selective protection of the first surface relative to the second surface can be improved.

[0020] Although the detailed mechanism of wet processing using a chemical solution containing a surface modifier and a solvent is unclear, it is speculated that the surface modifier and the solvent compete with each other when they come into contact with the surface, which may lead to the solvent inhibiting the adsorption of the surface modifier. Furthermore, the reaction catalytic effect of carboxylic acid silyl esters has not been observed in wet processing. According to the results of preliminary experiments conducted by the inventors, wet processing using a chemical solution containing a carboxylic acid silyl ester and a solvent has been found to preferentially protect the silicon oxide surface over the silicon nitride surface. It is likely that the reaction catalytic effect in dry processing is a relatively weak effect that is exerted in an environment without inhibitions such as solvation.

[0021] Each component of the substrate treatment method according to an embodiment of the present disclosure will be described in detail below. An example of the substrate treatment method will be described using FIG. 1. FIGS. 1(A) to 1(C) are cross-sectional views that schematically illustrate each process of the substrate treatment method. FIG. 1(A) shows a preparation step, and FIGS. 1(B) and 1(C) show a surface treatment step. This embodiment is not limited to the following.

[0022] (Preparation Step) In the preparation step, a substrate 1 having at least a first surface 11 containing silicon nitride is prepared. The substrate 1 in Fig. 1(A) has the first surface 11 and a second surface 12 containing silicon oxide.

[0023] The material of the substrate 1 is not particularly limited as long as it is a substrate used in a semiconductor manufacturing process, and may be made of, for example, silicon, silicon carbide, a plurality of components containing silicon element, sapphire, various compound semiconductors, etc. Furthermore, the substrate 1 may be, for example, a wafer.

[0024] The substrate 1 may have a relief structure (not shown) formed on the substrate surface. The relief structure may be, for example, a three-dimensional structure having one or more structures arranged along the vertical direction of the substrate surface and / or one or more structures arranged along a horizontal direction perpendicular to the vertical direction. Examples of such three-dimensional structures may constitute at least a part of a logic device, a memory device, a gate electrode, etc., such as a FinFET, a nanowire FET, a nanosheet FET, or other multi-gate FET, a three-dimensional memory cell, etc.

[0025] The first surface 11 and the second surface 12 may be disposed along the planar direction of the substrate surface, or along a direction perpendicular to the substrate surface. According to this embodiment, not only two-dimensional selective processing on a plane but also three-dimensional selective processing on a three-dimensional structure (three-dimensional film formation, three-dimensional etching, etc.) is possible.

[0026] The first surface 11 and the second surface 12 may be formed adjacent to each other or may be formed spaced apart from each other. Each of the first surface 11 and the second surface 12 may be composed of one region or two or more regions. The multiple regions in each surface may be formed spaced apart from each other, and the materials of the surfaces constituting the multiple regions may be the same or different from each other.

[0027] The first surface 11 is a surface containing silicon nitride. The surface containing silicon nitride is not particularly limited as long as it contains Si and N elements. The stoichiometric ratio of Si and N elements in silicon nitride is not limited to 1:1, and does not have to be an integer ratio. For example, ３ N ４As shown, the stoichiometric ratio is 1:1.33. Similarly, when a compound is referred to as "SiN" or the like in this specification, the stoichiometric ratio is not limited to 1:1 and does not have to be an integer ratio. Specific examples of surfaces containing silicon nitride include SiN, SiON, SiCN, SiOCN, etc., with SiN being preferred. The first surface 11 may have a total content of Si atoms and N atoms of 80 mol % or more. The first surface 11 may also contain elements other than Si and N (H, P, B, etc.) as long as the water repellency is not significantly impaired. Furthermore, the Si element of the first surface 11 may be naturally oxidized to form a natural oxide film when left in the atmosphere, but such a natural oxide film can be removed by a pretreatment for removing the natural oxide film, as described below. Therefore, even if a surface has a natural oxide film in the preparation stage, it may be used as the first surface 11 as long as it originally contains silicon nitride. However, if oxidation occurs for reasons other than natural oxidation, it is not included in the above-mentioned first surface 11, except for surfaces that were originally prepared as SiON, SiOCN, or the like as described above.

[0028] The second surface 12 is a surface containing silicon oxide. The surface containing silicon oxide is not particularly limited as long as it contains Si and O elements. In addition, it is preferable that the content of N atoms in the second surface is 1 mol % or less. The stoichiometric ratio of Si and O elements in silicon oxide is not limited to 1:1, as in the case of silicon nitride described above, and does not have to be an integer ratio. For example, SiO ２ As shown in the figure, the ratio is 1:2. Specific examples of surfaces containing silicon oxide include SiO, SiCO, and SiCOH, with SiO being preferred. The second surface 12 may have a total of 80 mol % or more of Si atoms and O atoms. The second surface 12 may also contain other elements (O, C, H, P, B, etc.) within a range that does not adversely affect the processes subsequent to the surface treatment process.

[0029] First surface 11 and second surface 12 may be the surfaces of components made of the above materials, or may be the surfaces of films formed from the above materials. Also, both the surfaces of components made of the above materials and the surfaces of films formed from the above materials may exist.

[0030] (Surface modification process) The surface modification process includes a gas exposure treatment in which a modifying gas 20 is brought into contact with the first surface 11 in a heated state or the first surface 11 and the second surface 12 in a heated state in the substrate holding space 30, as shown in FIG. 1(B).

[0031] As an example of the surface modification step, the following procedure may be performed: First, the substrate 1 is placed in a substrate holding space 30 such as a chamber. In the substrate holding space 30, the substrate 1 may be held by a substrate holding part (not shown).

[0032] An example of the chamber configuration may include an enclosed space that forms the substrate-holding space 30, a substrate-holding section that holds the substrate within the substrate-holding space 30, and may further include gas supply pipes that connect the chamber to a gas supply device for each type of gas to be supplied, and a gas exhaust pipe that exhausts the gas within the substrate-holding space 30. Heaters that can heat the gases supplied to the substrate 1 and the substrate-holding space 30 may be installed inside and / or outside the chamber. Each pipe may be provided with a valve or a mechanism for adjusting the temperature inside the pipe. The chamber may also include various instruments, such as a temperature gauge that measures the internal temperature and / or the surface temperature of the substrate 1 and a pressure gauge that measures the pressure in the substrate-holding space 30, and may also include a control device (computer) that controls these temperatures and pressures.

[0033] Next, in order to replace the inside of the substrate-holding space 30 with gas, the space is filled with an inert gas such as nitrogen gas (gas purging). The inert gas may be introduced into the substrate-holding space 30 from an inert gas supply device via a supply pipe (gas replacement process).

[0034] Next, the first surface 11 and the second surface 12 are heated. Known heating methods can be used to achieve the heated state. For example, the entire or part of the chamber may be heated with a heater to indirectly heat the substrate 1, or the substrate 1 may be directly heated with a heater installed in the substrate holder. Furthermore, as long as surface modification of the first surface 11 is possible, heating may be performed using a modifying gas or by spraying any inert gas or the like. As long as the first surface 11 and the second surface 12 are in a heated state during the gas exposure treatment, the timing of heating and the timing of stopping heating are not particularly limited. For example, heating may be started before or simultaneously with the gas exposure treatment. Furthermore, as long as the heated state can be maintained, heating may be stopped before the end of the gas exposure treatment. Starting heating of the substrate 1 before the gas exposure treatment is preferable because it enables efficient surface modification. In this specification, the term "heated state" refers to a state in which the above-mentioned surface is at a temperature higher than room temperature (5 to 35°C).

[0035] The lower limit of the surface temperature of the substrate 1 is preferably 50° C. or higher, more preferably 75° C. or higher, and even more preferably 100° C. or higher. The upper limit of the surface temperature of the substrate 1 is, for example, 400° C. or lower, preferably 250° C. or lower. When the substrate 1 is heated directly, the value measured by a non-contact method on the surface of the substrate 1 may be used as the surface temperature of the substrate 1. When the substrate is heated indirectly, the value measured by a contact method on the temperature of the internal space of the substrate-holding space 30 may be used.

[0036] Next, the gasified surface modifier is introduced into the substrate holding space 30 via a supply pipe using a modifying gas supply device. This brings the modifying gas into contact with the heated first surface 11 and second surface 12. The substrate 1 is then surface-treated with the modifying gas at a predetermined temperature, time, and pressure (gas exposure treatment). Thereafter, the modifying gas is discharged outside the substrate holding space 30, completing the surface treatment process.

[0037] 1C , a protective film 21 can be formed on the first surface 11. Depending on the conditions of the gas exposure treatment and the type of surface modifier used, a protective film (not shown) with low protective properties may also be formed on the second surface 12.

[0038] In this specification, the term "protective film" refers to both a compound having a protective group derived from a surface modifier chemically bonded to the first surface and a group of such compounds, regardless of whether or not the compounds interact with each other or whether or not they are bonded. The above bond does not necessarily have to be direct, but also includes bonding via other elements, substituents, etc. Even if a protective film is formed, depending on the amount and density of the compound having the above protective group, the protective property may be high enough to exhibit the desired performance, or low enough to not exhibit the desired performance. In this specification, even a protective film with low protective property will be referred to as a "protective film."

[0039] (Protectiveness) In this specification, protectiveness can be expressed using water repellency, which will be described later. Specifically, when the water repellency of the surface after the gas exposure treatment is improved compared to the water repellency of the surface before the treatment and the water repellency of the surface after the treatment is higher than a predetermined value, protectiveness is considered high, and when it is low, protectiveness is considered low. Furthermore, when the improvement in water repellency after the gas exposure treatment is small or there is no change, it is considered that no protectiveness is exhibited or that a protective film is not formed. Furthermore, in the second embodiment, selective protectiveness refers to a case where a protective film is present on a first surface and the water repellency of the first surface is higher than the water repellency of the second surface.

[0040] (Water repellency) In this specification, water repellency will be explained using the water contact angle obtained by the following measurement. Details of cleaning and drying before each measurement will be described later. First, a smooth substrate is placed horizontally with each surface facing up, and a 2 μl droplet of pure water is placed on the surface. Next, in accordance with JIS R 3257:1999 "Test method for wettability of substrate glass surfaces," the angle between the water droplet and the substrate is measured using a contact angle meter (CA-X model, manufactured by Kyowa Interface Science Co., Ltd.), and the obtained value is taken as the water contact angle.

[0041] The water contact angle of first surface 11 at 25° C. after the gas exposure treatment is, for example, 50° or more, preferably 55° or more, and more preferably 60° or more. When the water contact angle of the first surface is equal to or more than the above-mentioned lower limit, preferably 55° or more, this is suitable because the first surface can be protected, for example, when an etching treatment is performed after forming a protective film.

[0042] The water contact angle of the first surface 11 at 25°C after the gas exposure treatment was measured as CA １ , the water contact angle of the second surface 12 at 25°C is CA ２ Let's say. CA １ and C.A. ２ For example, 1<CA １ / CA ２ ≦5. １ / CA ２ The lower limit of CA is, for example, more than 1, preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 1.9 or more. １ / CA ２ The upper limit of CA is not particularly limited, but may be 5 or less. １ / CA ２ In this case, a protective film is selectively formed on the first surface 11 relative to the second surface 12, which is advantageous because, for example, when an etching process is performed after the protective film is formed, it becomes possible to selectively etch the second surface 12.

[0043] The lower limit of the surface treatment time with the modifying gas is, for example, 0.1 minutes or more, preferably 0.2 minutes or more, and more preferably 0.5 minutes or more, and the upper limit of the surface treatment time is, for example, 100 minutes or less, preferably 10 minutes or less, and more preferably 5 minutes or less.

[0044] When the modifying gas is introduced into the substrate-holding space 30, the inert gas filled in the substrate-holding space 30 may be discharged to the outside via a gas discharge pipe, if necessary.

[0045] The lower limit of the pressure in the substrate holding space 30 during the surface treatment is, for example, 1 Pa or more, preferably 10 ２ Pa or more, more preferably 10 ３ The upper limit of the pressure is, for example, 10６ Pa or less, preferably 5.0 × 10 ４ Pa or less, more preferably 2.0 × 10 ４ Pa or less.

[0046] The lower limit of the temperature of the reforming gas introduced into the substrate holding space 30 is, for example, 0° C. or higher, preferably 10° C. or higher, and more preferably 15° C. or higher. The upper limit of the temperature of the reforming gas is, for example, 400° C. or lower, preferably 300° C. or lower, and more preferably 250° C. or lower.

[0047] After the gas exposure treatment, the substrate holding space 30 may be purged with an inert gas, and the subsequent treatment of the substrate 1 may be carried out in the substrate holding space 30, or the subsequent treatment may be carried out on the substrate 1 removed from the substrate holding space 30.

[0048] (Modifying Gas) The modifying gas used in the gas exposure treatment will now be described. The modifying gas contains at least a gas of a surface modifying agent.

[0049] The surface modifier is an agent that modifies the surface of at least the first surface, and contains at least one silicon compound represented by the following general formula (1): In a preferred embodiment of the present disclosure, the surface modifier can improve the water repellency of at least the first surface by using the silicon compound shown below: Furthermore, the surface modifier may consist solely of one or more silicon compounds shown below, or may further contain other compounds that impart properties other than water repellency to the first surface.

[0050] The lower limit of the concentration of the silicon compound in the modified gas is, for example, 1% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more. The upper limit of the concentration of the silicon compound is not particularly limited, but may be, for example, 100% by volume or less. When two or more silicon compounds are contained, the total value thereof is taken as the concentration of the silicon compound.

[0051] The lower limit of the boiling point of the silicon compound used as a surface modifier is, for example, 40°C or higher, preferably 50°C or higher, more preferably 60°C or higher. The upper limit of the boiling point of the silicon compound is, for example, 400°C or lower, preferably 300°C or lower, more preferably 250°C or lower. By setting it to the above upper limit or lower, the thermal stability of the silicon compound in the modified gas can be improved. In addition, by setting it to the above lower limit or higher, the silicon compound becomes liquid at room temperature (25°C), which is preferable because it is easy to handle during storage and transportation.

[0052] (Silicon Compound) The silicon compound used is a carboxylic acid silyl ester represented by the following formula (1): (X-COO) ａ -Si-R ｂ (1) In the above general formula (1), each X independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms, each R independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms, and a and b independently represent an integer of 1 to 3, provided that a+b=4.

[0053] The group represented by (X-COO) in the general formula (1) is a leaving group that leaves when the protective film is formed, and is not particularly limited as long as it is removable from the substrate. Furthermore, it is more preferable that it is volatilizable as a leaving group during gas exposure treatment. While X may be a hydrogen atom, it is preferable that X be a hydrocarbon group having 1 to 8 carbon atoms, in which some or all of the hydrogen atoms may be substituted with halogen atoms, due to its high chemical stability and volatility. Furthermore, when X is a hydrocarbon group, a smaller carbon number is more preferable. Furthermore, the halogen atoms substituting the hydrogen atoms may all be the same atom, or two or more types of atoms. The number of hydrogen atoms substituted by halogen atoms is not particularly limited as long as the desired protective properties can be exhibited. Furthermore, the type of halogen atom is not particularly limited as long as it does not impair protective properties, and examples include chlorine and fluorine.

[0054] (Si—R ｂ) is a group that remains on the substrate as a protecting group. The above R may be a hydrogen atom. Furthermore, when the above R is a hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms, a smaller carbon number tends to increase the reactivity with the substrate surface. Furthermore, a larger carbon number tends to increase the water contact angle value described above. Therefore, the number of carbon atoms may be appropriately selected to obtain the desired protective properties. Furthermore, when the above R is a hydrocarbon group, it may contain a branched structure or a ring structure. Furthermore, the halogen atoms substituting the above hydrogen atoms may all be the same atom, or two or more types of atoms. The number of hydrogen atoms substituted by halogen atoms is not particularly limited as long as the desired protective properties can be obtained. Furthermore, fluorine and chlorine are preferably used as the type of halogen atom in order to improve water repellency.

[0055] Examples of the silicon compound include trimethylsilyl trifluoroacetate, trimethylsilyl acetate, hydroxydimethylsilyl trifluoroacetate, hydroxydimethylsilyl acetate, butyldimethylsilyl trifluoroacetate, butyldimethylsilyl acetate, octyldimethylsilyl trifluoroacetate, octyldimethylsilyl acetate, tert-butyldimethylsilyl trifluoroacetate, tert-butyldimethylsilyl acetate, etc. Of the above, it is preferable to use trimethylsilyl trifluoroacetate and / or trimethylsilyl acetate as the silicon compound.

[0056] The modifying gas may not contain an inert gas, but may contain an inert gas. The content of the inert gas in the modifying gas is, for example, 0% by volume or more and 99% by volume or less, preferably 0% by volume or more and 80% by volume or less, and more preferably 0% by volume or more and 50% by volume or less. By containing an inert gas, it becomes easier to suppress temperature changes in the supply path of the gasified silicon compound. Furthermore, when two or more types of inert gas are contained, the total amount thereof is taken as the content of the inert gas.

[0057] The inert gas may include, for example, one or more gases selected from the group consisting of nitrogen gas and rare gases such as helium gas, argon gas, and xenon gas.

[0058] Here, a modified example of the surface modification step of this embodiment will be described.

[0059] The surface modification step may include a gas replacement treatment in which an inert gas is introduced into the substrate holding space 30 at least either before or after the gas exposure treatment.

[0060] The surface modification step may include, before the gas exposure treatment, a pretreatment for removing a native oxide film on first surface 11. The pretreatment may be performed inside or outside the chamber.

[0061] Specific methods of pretreatment include, for example, contacting first surface 11 and second surface 12 with hydrogen fluoride (HF) or contacting first surface 11 and second surface 12 with a diluted aqueous hydrogen fluoride solution, i.e., hydrofluoric acid (DHF). Known methods can be used for the specific contact method, but when hydrogen fluoride is supplied as a gas or vapor and becomes a liquid after contact with first surface 11 and second surface 12, known steam injection methods can be used. Alternatively, a mixed gas of hydrogen fluoride and ammonia may be brought into contact with first surface 11 and second surface 12. After pretreatment, a cleaning treatment may be performed using a cleaning agent described below before the gas exposure treatment.

[0062] Between the surface modification step and the processing step described below, a cleaning treatment may be carried out once or twice or more times to clean at least a part of the substrate surface using a cleaning agent.

[0063] The cleaning agent is not particularly limited as long as it does not oxidize at least the first surface 11. Examples thereof include aqueous cleaning solutions such as water and alcohol. These may be used alone or in combination of two or more.

[0064] A rinse solution may also be used as the cleaning agent. Similar to the aqueous cleaning solution, the rinse solution is not particularly limited as long as it does not oxidize at least the first surface 11. A cleaning agent different from the aqueous cleaning solution may be used as the rinse solution. Examples of the rinse solution include water, an organic solvent, a mixture thereof, or a mixture of these with at least one of an acid, an alkali, and a surfactant. Examples of organic solvents used in the rinse solution include hydrocarbons, esters, ethers, ketones, halogen-containing solvents, sulfoxide-based solvents, alcohols, polyhydric alcohol derivatives, and nitrogen-containing solvents. Among these, it is preferable to use at least one organic solvent selected from alcohols having 3 or fewer carbon atoms, such as methanol, 1-propanol, and 2-propanol (isopropanol).

[0065] In this embodiment, the method of contacting the cleaning agent is not particularly limited, but examples thereof include immersion, application methods such as spin coating and spray coating, and vapor contact.

[0066] Between the surface modification step and the processing step described below, a drying treatment for drying at least a part of the surface of the substrate may be carried out once or twice or more times. In addition, the drying treatment and the cleaning treatment may be repeated alternately.

[0067] The drying process may be carried out by known means such as spin drying, IPA (2-propanol) vapor drying, Marangoni drying, heat drying, air drying, hot air drying, vacuum drying, or the like.

[0068] (Processing Step) The method for treating a substrate according to this embodiment may, after the surface modification step, optionally include a processing step including one or more steps selected from the group consisting of an etching treatment and a film formation treatment.

[0069] When the processing step is an etching process, the etching process is not particularly limited as long as it can etch the second surface 12, and a known dry etching method or wet etching method can be selected. It is also preferable to perform various etching processes using an etching agent. In the case of a gas, for example, HF gas, HCl gas, Cl ２Gas, F ２ gas, interhalogen gas (e.g., ClF ３ Gas, IF ７ In the case of liquids, HF, NH ４ F, N.H. ４ HF ２ , H ３ P.O. ４ , and H ２ SO ４ The etching agent may be heated or may be in the form of plasma or radicals.

[0070] If the protective film 21 remaining on the first surface 11 after the etching step is unnecessary, a removal process may be performed to remove at least a portion of the protective film 21. The removal method is not particularly limited as long as it is a known method capable of removing the protective film. Examples include light (ultraviolet) irradiation, heat treatment, ozone exposure, plasma irradiation, and corona discharge. Removal by a wet process is also possible, such as contact with an ammonium hydroxide aqueous solution, a tetramethylammonium aqueous solution, a hydrochloric acid aqueous solution, or a sulfuric acid aqueous solution. By appropriately controlling the etching conditions, the etchant used in the etching step may be reused in the removal process. This simplifies the process. Furthermore, selecting a non-plasma method as the removal method can reduce defects on the substrate surface.

[0071] When the processing step is a film formation process, known methods such as CVD and atomic layer deposition can be used as the film formation method. Atomic layer deposition is particularly preferred because of its excellent film thickness control, uniformity, and conformability to the surface shape of the film formation target. A known ALD apparatus can be used as a film formation method using atomic layer deposition. For example, a thin film formation method based on adsorption of a first gas-phase reactant (film material) and a desired second gas-phase reactant (thermal ALD) or a thin film formation method similar to the above, in which a first gas-phase reactant (film material) is adsorbed on a surface and then reacted with a plasma such as oxygen (plasma ALD) can be used. The film formation temperature and film formation time can be appropriately selected depending on the film thickness and film material.

[0072] The method for manufacturing a substrate of this embodiment includes a step of obtaining a substrate that has been subjected to each step in the above-described method for treating a substrate. By the method for manufacturing a substrate, a desired semiconductor wafer or semiconductor device can be obtained.

[0073] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.

[0074] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0075] (1) Substrate Preparation Step A silicon substrate with a smooth surface measuring 30 mm × 40 mm × 1 mm was used as the substrate. A silicon oxide film or a silicon nitride film was formed on the surface of this substrate, and the substrate with the silicon nitride film formed thereon was regarded as the first surface, and the substrate with the silicon oxide film formed thereon was regarded as the second surface. The following is a simulation test using the above substrate.

[0076] (2) Removal of native oxide film from substrate (pretreatment) Each substrate was immersed in 1 wt % hydrofluoric acid at room temperature for 1 minute, and then in a rinse solution (ultrapure water) for 1 minute. In the etching treatment described below, the thickness of the silicon oxide or silicon nitride film was measured with an ellipsometer after immersion in order to calculate the amount of etching after treatment.

[0077] (3) Surface modification process A tubular furnace was used as the chamber, and the substrate after the pretreatment described above was set in the chamber, and the internal gas was replaced with nitrogen gas. Next, the temperature of the tubular furnace was increased to heat the substrate, and the substrate was heated to a predetermined temperature and placed in a heated state. At this time, the substrate temperature was measured using a thermometer (thermocouple) previously placed in contact with the substrate. The substrate temperature was set to each temperature listed in Table 1.

[0078] Next, the surface modifier was supplied to the vaporization chamber connected to the chamber via a pipe, and gasified to form a modified gas. The composition of the surface modifier used was 100 mass% of the silicon compound listed in Table 1, and the modified gas supplied to the chamber also contained 100 volume% of substantially the same silicon compound gas. Each reference example was an example (blank) in which no surface modifier was used, and no modified gas was prepared in each reference example.

[0079] Next, the chamber was evacuated, and the pressure in the chamber was reduced to be lower than the pressure in the vaporization chamber, so that the modified gas was introduced into the chamber and contacted with the surface of the substrate (gas exposure treatment). At this time, the pressure in the chamber was 6.7 kPa, and the treatment time was 10 minutes. In each reference example, no modified gas was supplied, and the pressure was set to 6.7 kPa with nitrogen gas filled in the chamber, and this state was maintained for 10 minutes. Next, heating was stopped, and the gas in the chamber was evacuated, and the chamber was replaced with air. After the temperature of the substrate was lowered to about room temperature, the substrate was removed, and a measurement sample was obtained.

[0080] (4) Various Evaluations (Evaluation of Water Repellency of Substrate) The water contact angle of the substrate surface of the obtained measurement sample was measured by the following method, and the results are shown in Table 1. The water contact angle of the first surface was measured by CA １, the water contact angle of the second surface is CA ２ First, the substrate was placed horizontally with the treated surface of the measurement sample facing up, and a 2 μl droplet of pure water was placed on the surface. Next, in accordance with JIS R 3257:1999 "Test method for wettability of substrate glass surfaces," the angle between the water droplet and the substrate was measured using a contact angle meter (CA-X model, manufactured by Kyowa Interface Science Co., Ltd.), and the obtained value was taken as the water contact angle.

[0081]

[0082] (Evaluation of Protective Properties of Protective Film) Of the obtained measurement samples, the substrates of Example 1-1, Comparative Example 3-2, and Reference Example 1-2 were immersed in hydrofluoric acid (HF) for 60 seconds, and then immersed in ultrapure water as a rinse solution and thoroughly washed. The concentrations of hydrofluoric acid were 0.1 mass % and 0.5 mass %, as shown in Table 2. Next, the thickness of the silicon oxide or silicon nitride film after etching was measured with an ellipsometer, and the amount of reduction from the thickness measured in step (2) was calculated as the amount of etching.

[0083]

[0084] It was found that the surface treatment method of the substrate in Examples 1 and 2 can increase the water contact angle of the first surface to 55° or more by dry-treating the heated first surface (silicon nitride film surface) with a carboxylic acid silyl ester. Furthermore, the substrate in Example 1-1, which actually had a water contact angle of 60°, was shown to have protective properties against etching treatment. On the other hand, in Comparative Examples 1 and 2, in which the surface was not heated, both water contact angles were lower than those of the Examples. Furthermore, it was found that Comparative Example 3, in which a silicon compound other than a carboxylic acid silyl ester was used as the surface modifier, had a water contact angle of less than 50° and was unable to provide protective properties against etching treatment. From the above, it was shown that the protective properties of the first surface having silicon nitride can be improved by using a carboxylic acid silyl ester as a surface modifier and dry-treating the surface in a heated state.

[0085] Furthermore, in each example, it was shown that dry treatment of the heated first and second surfaces (silicon oxide film surfaces) with a carboxylic acid silyl ester selectively improved the protection of the silicon nitride film (first surface) compared to Comparative Examples 1 and 2. On the other hand, in Comparative Example 1, in which the surfaces were not heated, the water contact angle of the second surface was higher than that of the first surface, and it could not be said that the first surface was selectively protected. Furthermore, in Comparative Example 2, the water contact angles were similar, indicating that selective protection was not achieved, as in Comparative Example 1. Furthermore, in each Comparative Example 3, the water contact angle of the first surface was higher than that of the second surface, but because the water contact angle of the first surface was low as described above, only a protective film with low protective properties was formed.

[0086] This application claims priority based on Japanese Patent Application No. 2023-145315, filed September 7, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0087] REFERENCE SIGNS LIST 1 substrate 11 first surface 12 second surface 20 reforming gas 21 protective film 30 substrate holding space

Claims

1. A method for treating a substrate, comprising: a preparation step of preparing a substrate having a first surface having silicon nitride; and a surface modification step of forming a protective film for protecting the first surface, the surface modification step including a gas exposure treatment in which a modifying gas containing a gas of a surface modifier is brought into contact with the first surface in a heated state in a substrate holding space, the surface modifier comprising at least one silicon compound represented by the following general formula (1): (X-COO) ａ -Si-R ｂ (1) (In the above general formula (1), each X is independently a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms, each R is independently a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms in which some or all of the hydrogen atoms may be substituted with halogen atoms, and each a and b is an integer of 1 to 3, with the proviso that a+b=4.) 2. A method for treating a substrate as described in claim 1, wherein the preparation step includes preparing the substrate having the first surface and a second surface having silicon oxide, and the surface modification step includes forming a protective film on at least the first surface, which selectively protects the first surface against the second surface, by the gas exposure treatment in which the modifying gas is brought into contact with the first surface and the second surface in a heated state in the substrate holding space.

3. A method for treating a substrate according to claim 1, wherein in the surface modification step, the first surface after the gas exposure treatment has a water contact angle of 55° or more at 25°C.

4. The method for treating a substrate according to claim 2, wherein in the surface modification step, the water contact angle of the first surface at 25° C. after the gas exposure treatment is measured by CA １ , the water contact angle of the second surface at 25° C. is CA ２ When this is done, CA １ and C.A. ２ However, 1<CA １ / CA ２ A method for treating a substrate, which satisfies ≦5.

5. A method for treating a substrate according to claim 1 or 2, wherein the surface temperature of the substrate during the gas exposure treatment is 50°C or higher and 400°C or lower.

6. A method for treating a substrate according to claim 1 or 2, wherein the temperature of the reformed gas introduced into the substrate holding space is 0°C or higher and 400°C or lower.

7. A method for treating a substrate according to claim 1 or 2, wherein the concentration of the silicon compound in the reformed gas is 1% by volume or more and 100% by volume or less.

8. A method for treating a substrate according to claim 1 or 2, wherein the boiling point of the silicon compound in the reforming gas is 40°C or higher and 400°C or lower.

9. A method for treating a substrate according to claim 1 or 2, wherein the modifying gas contains from 0 vol % to 99 vol % of an inert gas.

10. The method for treating a substrate according to claim 1 or 2, wherein the pressure in the substrate holding space during the gas exposure treatment is 1 Pa or more and 10 ６ A method for treating a substrate, wherein the thermal expansion coefficient is 0.01 Pa or less.

11. A method for treating a substrate according to claim 1 or 2, wherein the surface modification step includes a gas replacement treatment for introducing an inert gas into the substrate holding space at least either before or after the gas exposure treatment.

12. A method for treating a substrate according to claim 1 or 2, wherein the surface modification step includes a pretreatment for removing a native oxide film on the first surface prior to the gas exposure treatment.

13. A method for treating a substrate according to claim 1 or 2, comprising, after the surface modification step, a processing step including one or more treatments selected from the group consisting of an etching treatment and a film formation treatment.

14. A method for treating a substrate according to claim 1 or 2, wherein the silicon compound is trimethylsilyl trifluoroacetate and / or trimethylsilyl acetate.

15. A method for producing a substrate, comprising the steps of obtaining a substrate that has been subjected to each step in the method for treating a substrate according to claim 1 or 2.

Images