JP4590567B2 - Method and apparatus for producing self-assembled monolayer - Google Patents

Description

  The present invention relates to a method for producing a self-assembled monolayer. Specifically, the present invention relates to a method for producing a higher quality self-assembled monolayer by a so-called gas phase method.

  Materials for forming a self-assembled monolayer (Self-Assembled Monolayer, hereinafter also referred to as “SAM”) on a substrate are known. As a main method of forming a SAM using such a material (hereinafter also referred to as “self-assembled monolayer film forming material” or “SAM forming material”), a method of bringing a solution containing the SAM forming material into contact with a substrate (Liquid phase method). Patent Documents 1 to 3 are cited as prior art documents relating to SAM formation by this type of method. Patent Documents 1 and 2 exemplify alcohols, aromatic hydrocarbons, aliphatic hydrocarbons and the like as the solvent constituting the solution containing the SAM-forming material. Patent Document 3 describes a technique using compressed carbon dioxide as a solvent constituting the solution.

JP 2001-152363 A JP 2004-315461 A JP 2002-327283 A

  On the other hand, as another method for forming a SAM on a base material, a method of chemical vapor deposition of a SAM forming material on the base material (sometimes referred to as a vapor phase method or a CVD method) has been proposed. This gas phase method has advantages such that the SAM forming material can be used efficiently, and the amount of waste liquid can be reduced as compared with the liquid phase method, so that the burden on the environment is small.

  However, it has been difficult to obtain a SAM having high orientation (which can be grasped as the degree of regularity of the arrangement of the SAM forming material on the substrate surface or the degree of crystallinity) by such a vapor phase method. In a SAM with low orientation (typically in an amorphous state), non-uniformity at the atomic level (roughness / density of the SAM forming material) tends to occur with respect to the surface direction (spreading direction) of the SAM. On the other hand, in a highly oriented SAM, since the SAM forming materials constituting the SAM are generally regularly arranged, the uniformity in the plane direction is high. Such a highly uniform SAM is useful because it can be of higher quality (for example, more appropriately exhibit the characteristics expected from the molecular structure of the SAM-forming material).

  Accordingly, one object of the present invention is to provide a method for producing a high quality (good orientation regularity) SAM by a vapor phase method. Another object of the present invention is to provide a SAM production apparatus suitable for producing such a high quality SAM.

According to the present invention, a method for producing a self-assembled monolayer on a substrate by chemical vapor deposition of a self-assembled monolayer forming material on the substrate is provided. In that method, the chemical vapor deposition is performed while cooling the base material so that the base material is maintained at a temperature lower than the ambient temperature.
According to such a method, a SAM with higher quality (for example, higher orientation) can be produced as compared with the case where chemical vapor deposition is performed in a state where the substrate temperature is equal to or higher than the ambient temperature. For example, the cooling may be performed so that the base material is maintained at a temperature approximately 60 ° C. or lower than the ambient temperature.

  In a preferred embodiment of the method disclosed herein, the chemical vapor deposition is performed at an ambient temperature of 100 ° C. to 200 ° C. Moreover, as a temperature which maintains the said base material, the temperature of about -10 degreeC-30 degreeC, for example can be employ | adopted preferably. This makes it possible to obtain a SAM with higher quality (higher orientation).

  The SAM production method disclosed herein can be applied particularly preferably when halosilane (such as trichlorosilane) is used as the SAM forming material. That is, it is preferably applied to the production of a SAM using a SAM forming material that is a compound capable of forming a SAM on the substrate surface and has at least one Si-X bond (where X is a halogen atom).

  In producing a SAM on a substrate by applying the method disclosed herein, a substrate that has been subjected to a predetermined pretreatment can be preferably used. The pretreatment can include, for example, a treatment for introducing a hydroxyl group into the substrate surface. By using a base material that has been subjected to such pretreatment, a high-quality (for example, highly oriented) SAM can be more appropriately produced on the base material.

As a suitable method for introducing the hydroxyl group, vacuum ultraviolet light (hereinafter also referred to as “VUV”) is applied to the surface of the substrate in an atmosphere containing oxygen (typically oxygen molecules (O ₂ )). The method of irradiating can be illustrated. For example, by irradiating the surface of the substrate with VUV in an atmosphere of reduced pressure (for example, about 1 Pa to 1500 Pa, preferably about 10 Pa to 1000 Pa), a hydroxyl group can be appropriately introduced onto the surface of the substrate. By this, the base material which has the surface suitable for vapor-depositing SAM formation material can be prepared.

The method disclosed herein can be preferably applied, for example, as a method for producing a SAM on the surface (for example, (111) plane) of a silicon substrate (base material). As the silicon substrate, a silicon substrate that has been pretreated by irradiating the surface with VUV under an atmosphere containing oxygen (typically oxygen molecules (O ₂ )) can be preferably used.

  According to the present invention, a SAM production apparatus suitable for carrying out any of the SAM production methods disclosed herein is also provided. The apparatus includes a reaction vessel with a substrate holder that holds the substrate. Further, it may include an atmospheric temperature control means for controlling the atmospheric temperature in the reaction vessel. Further, it may include a substrate holder cooling means for forcibly cooling at least the surface of the holder to a temperature lower than the atmospheric temperature in the reaction vessel. Further, it may include a raw material supply means for supplying a self-assembled monolayer forming material into the reaction vessel (for example, supplying a vapor of the self-assembled monolayer forming material in the gas phase).

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than those specifically mentioned in the present specification and matters necessary for the implementation of the present invention (for example, methods for obtaining or synthesizing various SAM forming materials, means for adjusting the atmospheric temperature, and Measurement methods, specific operation methods for vapor deposition, and the like) can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  The method of the present invention can be applied to the formation of self-assembled monolayers on various substrates using a so-called gas phase method. The material of the base material to be used is not particularly limited as long as it maintains a solid state at the atmospheric temperature when chemical vapor deposition is performed. For example, one or two selected from silicon (Si), glass, metal (copper, aluminum, germanium, etc.), ceramic (alumina, silica, silicon carbide, etc.), polymer material, carbon material (graphite, diamond, etc.) A base material mainly composed of the above materials can be used. The polymer material can be various thermoplastic resins or thermosetting resins. For example, acrylic resin such as polymethyl methacrylate, epoxy resin, polyamide, aramid (aromatic polyamide), polyimide, ABS resin, polyethylene, polypropylene, polystyrene, polycarbonate, polyethylene terephthalate (PET), phenol resin, urea resin, melamine resin, etc. Are mentioned as suitable polymer materials. As a particularly preferred substrate for the present invention, a substrate substantially composed of silicon (typically a silicon substrate) can be mentioned. At least the surface portion (surface portion on which the SAM is formed) may be a base material substantially made of silicon.

In the present invention, the term “self-assembled monolayer (SAM)” refers to a single molecule in which raw material molecules are assembled and autonomously assembled on the surface of a substrate (an interface between a solid and a liquid or an interface between a solid and a gas). A membrane (a membrane formed by a single molecule) However, even if a part of the resulting film is unexpectedly (unintentionally) not a monomolecular film (for example, a bilayer), at least mainly SAM. Applying the manufacturing method of the present invention with the intention of manufacturing can be included in the technical scope of the present invention.
In the present invention, the “self-assembled monolayer forming material” refers to a material capable of forming a self-assembled monolayer on the surface of a substrate. Such a material (SAM-forming material) typically has at least one functional group (head group) that can be adsorbed to the substrate by chemical bonding with the surface of the substrate, and conversely, on the outside of the substrate. It is a molecule (raw material molecule) having at least one tail group extending toward the surface.

As the SAM forming material, for example, a compound having a structure in which the head group and the tail group are bonded to a core atom such as silicon (Si) or titanium (Ti) can be used. A compound (organosilicon compound) in which the core atom is silicon is particularly preferable.
Preferable examples of the head group include halogen atoms such as fluorine (F), chlorine (Cl), bromine (Br) and iodine (I). Of these, Cl and Br are preferable, and Cl is particularly preferable. Another preferred example of the head group is an alkoxy group (alkoxysilyl group or the like). For example, an alkoxy group having 1 to 4 carbon atoms (more preferably 1 to 3 carbon atoms) is preferable. A methoxy group or an ethoxy group is more preferable, and a methoxy group is usually most preferable. In the SAM forming material having a plurality of head groups, these head groups may be the same or different, but usually a compound having a plurality of the same head groups is preferred. Examples of preferable SAM forming materials include compounds having a structure in which three halogen atoms (for example, Cl) and one tail group are bonded to a silicon atom as a core atom (trimethoxysilane, triethoxysilane, etc.).

  The tail group of the SAM-forming material is, for example, a substituted or unsubstituted aliphatic group or aromatic group (a group having a structural portion exhibiting aromaticity. Typically, the tail group includes at least one aromatic ring. Group). The aliphatic group may have, for example, 1 to 30 carbon atoms (more preferably 3 to 30 carbon atoms, still more preferably 5 to 30 carbon atoms). The aromatic group may have, for example, 5 to 30 (more preferably 6 to 30) carbon atoms. A part of carbon atoms constituting such an aliphatic group (typically, carbon atoms constituting the main chain of the aliphatic group) is replaced with a hetero atom (nitrogen atom, oxygen atom, sulfur atom, etc.). Or a part of carbon atoms constituting the aromatic group (typically carbon atoms constituting the aromatic ring) are replaced by heteroatoms (nitrogen atom, oxygen atom, sulfur atom, etc.) Also good.

  An example of a preferable tail group is an aliphatic group having 10 or more carbon atoms (typically 10 to 30). This aliphatic group may be saturated or unsaturated, and may be linear or branched. Further, the aliphatic group may be an open chain, and at least a part thereof may form a non-aromatic ring (for example, a cyclohexyl ring). For example, a linear aliphatic group having 10 to 30 carbon atoms (typically, a hydrocarbon group such as an alkyl group, an alkenyl group, or an alkynyl group) is preferable. A linear alkyl group having 10 to 30 carbon atoms is particularly preferred. Specific examples of such a SAM-forming material having a tail group include n-octadecyltrichlorosilane (hereinafter sometimes abbreviated as “OTS”), n-octadecyltrimethoxysilane, and the like. A tail group having a structure in which part or all of the hydrogen atoms constituting the aliphatic group are replaced with halogen atoms (fluorine atoms, chlorine atoms, etc.) is also preferable. For example, it is preferable that a majority of the hydrogen atoms constituting the aliphatic group (for example, 70% by number or more hydrogen atoms) are replaced with fluorine atoms. One specific example of such a SAM-forming material having a tail group is heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane.

  Another example of a preferable tail group is a saturated or unsaturated group having 2 or more carbon atoms (typically 2 to 9 carbon atoms, for example 3 to 6 carbon atoms) having a substituent at least at the terminal (opposite side to the core atom). Saturated aliphatic groups are mentioned. The substituent may be, for example, a substituted or unsubstituted amino group, mercapto group, hydroxyl group, carboxyl group, aldehyde group, sulfonic acid group, cyano group, halogen atom and the like. A specific example of such a SAM-forming material having a tail group is 3-mercaptopropyltrichlorosilane.

  Another example of a preferred tail group is an aromatic group containing at least one substituted or unsubstituted aromatic ring (typically a benzene ring). An aromatic group having 5 or more carbon atoms (typically 5 to 30) is preferable, and an aromatic group having 6 to 20 carbon atoms is more preferable. The tail group can be, for example, a substituted or unsubstituted aryl group or an alkylaryl group. A tail group having a structure in which part or all of the hydrogen atoms constituting such an aromatic group are replaced with halogen atoms (fluorine atoms, chlorine atoms, etc.) is also preferred. Moreover, this aromatic group may have a substituent other than a halogen atom. Such substituents include saturated or unsaturated substituted or unsubstituted hydrocarbon groups having about 1 to 12 carbon atoms (methyl group, ethyl group, chloromethyl group, etc.), unsubstituted amino groups, or substituted Illustrative examples include amino groups (mono- or dialkylamino groups such as dimethylamino group), fluoro groups and the like. Specific examples of the SAM-forming material having such a tail group include p-aminophenyltrichlorosilane and p-chloromethylphenyltrichlorosilane.

  The atmosphere temperature at the time of depositing such a SAM forming material (raw material molecule) on the substrate is not particularly limited as long as the vapor of the SAM forming material can be appropriately supplied to the substrate. For example, an atmospheric temperature comparable to that of SAM formation by a conventional vapor phase method can be employed. Here, the “atmosphere temperature” refers to the temperature of the gas phase (for example, the temperature in the reaction chamber of the CVD apparatus) when the SAM is produced by depositing raw material molecules on the surface of the substrate from the gas phase. Although the preferable atmospheric temperature may vary depending on the SAM forming material used, it is usually appropriate that the atmospheric temperature is at least about 60 ° C. or higher, preferably about 100 to 200 ° C., and about 100 to 200 ° C. More preferably, it is 180 ° C. (for example, about 120 to 150 ° C.). Moreover, the atmospheric pressure at the time of vapor-depositing a SAM formation material on a base material is not specifically limited, For example, the atmospheric pressure comparable as the SAM formation by the conventional vapor phase method is employable. From the viewpoints of ease of operation, simplification of the apparatus configuration, and the like, an atmospheric pressure of about atmospheric pressure can usually be preferably employed. From this point of view, the SAM forming material may be vapor-deposited on the substrate without specifically controlling the atmospheric pressure.

  In the SAM production method disclosed herein, the SAM forming material is vapor-deposited on the substrate while cooling the substrate so that the substrate is maintained at a temperature lower than the ambient temperature. Thus, by maintaining the substrate temperature lower than the ambient temperature, it is possible to obtain a SAM with better quality (for example, higher orientation). In general, the temperature of a substrate (for example, a substrate accommodated in a reaction vessel having a predetermined atmospheric temperature) disposed under a predetermined atmospheric temperature is intentional (forced). When cooling is not particularly performed, the temperature becomes substantially the same as the ambient temperature after being kept for a while (for example, 10 minutes or more) at least under the ambient temperature. On the other hand, in the SAM manufacturing method disclosed herein, the temperature of the substrate rises to a temperature similar to the ambient temperature by intentionally (forcefully) cooling the substrate. While avoiding, a SAM-forming material is deposited on the substrate.

  The vapor deposition of the SAM forming material can be performed while cooling the base material, for example, so that the base material temperature is maintained at about 40 ° C. or more (typically about 40 to 200 ° C.) lower than the ambient temperature. . That is, the substrate is cooled so that a relational expression of Tv−Tb ≧ 40 ° C. (typically 200 ° C ≧ Tv−Tb ≧ 40 ° C.) is established between the ambient temperature (Tv) and the substrate temperature (Tb). can do. Usually, Tv−Tb ≧ 60 ° C. (typically 200 ° C. ≧ Tv−Tb ≧ 60 ° C.) is preferable, and Tv−Tb ≧ 100 ° C. (typically 200 ° C. ≧ Tv−Tb ≧ 100 ° C.) ) Is more preferable. The base material is satisfied so that the above relational expression is satisfied and the temperature of the base material is maintained at a temperature of about −30 ° C. to 80 ° C. (typically −20 ° C. to 50 ° C., for example, about −10 to 30 ° C.). It is good to cool. Such a substrate temperature can be particularly preferably applied, for example, when the SAM forming material is a halosilane such as trichlorosilane.

  In one preferred embodiment of the SAM production method disclosed herein, the substrate temperature is kept lower than the ambient temperature continuously over the entire period during which at least the raw material molecules are deposited on the substrate surface. Here, the “period during which raw material molecules are vapor-deposited on the substrate surface” (hereinafter also referred to as “SAM growth period”) means that the formation of SAM is substantially from the start of vapor deposition of the SAM-forming material onto the substrate. Refers to the period until the end. The above “deposition start” means that the gaseous SAM forming material starts to be deposited on the surface of the substrate. For example, the SAM-forming material is heated in a state where a SAM-forming material (typically liquid or solid) and a substrate coexist in a predetermined vapor deposition space (in a sealed reaction vessel or the like) to form the SAM. The point in time when the material is volatilized and can be deposited on the substrate surface. Further, “SAM formation is substantially completed” means that the amount of the SAM forming material deposited on the substrate surface is substantially saturated. This can be grasped, for example, by the fact that the thickness of the SAM becomes substantially constant (the final film thickness is reached) over the vapor deposition time.

  The SAM manufacturing method disclosed herein can also be carried out in such a manner that the substrate temperature is maintained lower than the ambient temperature for at least a part of the SAM growth period. For example, the period during which the substrate temperature is maintained lower than the ambient temperature is the period from the start of vapor deposition of the SAM forming material until the SAM thickness reaches approximately 80% (or approximately 90%) of the final film thickness. Can do. Further, for example, it may be a period from when the SAM thickness reaches approximately 80% (or approximately 90%) of the final film thickness until the SAM formation is substantially completed. It is preferable to maintain the substrate temperature lower than the ambient temperature for at least about 50% or more of the SAM growth period (for example, about 30 minutes or more if the SAM growth period is 1 hour).

  A specific mode for maintaining the substrate temperature lower than the atmospheric temperature is not particularly limited. For example, a reaction vessel including a base material holder having a built-in refrigerant passage is used to hold a part of the base material in contact with the surface of the base material holder, and an appropriate refrigerant (for example, water) is circulated through the refrigerant passage. It is possible to adopt a mode in which the base material is cooled (heat is removed from the base material). Further, instead of incorporating the refrigerant passage in the base material holder or in addition to incorporating the refrigerant passage, a part of the base material holder may be drawn out of the reaction vessel to function as a heat radiating fin.

  The SAM production method disclosed herein is implemented in such a manner that the surface of the base material on which the SAM is to be formed is directed upward and the base material is disposed in the lower part of the predetermined vapor deposition space (for example, the bottom of the reaction vessel). can do. For example, it is preferable to arrange the substrate so that the surface on which the SAM is to be formed is substantially horizontally upward (for example, the angle formed with the horizontal plane is ± 5 ° or less). In the SAM manufacturing method, since the substrate temperature (Tb) is maintained lower than the ambient temperature (Tv), a downdraft toward the substrate surface can be generated by heat convection due to the temperature difference. According to the above aspect, it is advantageous because the vapor (raw material molecule) of the SAM forming material in the vapor deposition space can be efficiently supplied to the substrate surface using such a downdraft. In particular, when Tv−Tb ≧ 60 ° C. (typically 200 ° C. ≧ Tv−Tb ≧ 60 ° C.), the effect of adopting the above aspect can be better exhibited.

  In a preferred embodiment of the SAM production method disclosed herein, a SAM forming material (raw material molecules) is vapor-deposited on a substrate under an atmospheric gas having a predetermined humidity. Here, the “atmospheric gas” refers to a vapor deposition space (for example, in a reaction vessel) when source molecules are vapor-deposited on the substrate surface (that is, when gaseous source molecules are deposited from the gas phase to the substrate surface). ) Satisfies gas. As the main component of the atmospheric gas, it is preferable to use a gas having low reactivity with respect to the SAM forming material or the substrate surface. For example, an inert gas such as nitrogen gas or argon gas can be preferably used. This atmospheric gas may contain water molecules (water vapor) at a concentration corresponding to a predetermined humidity. The “predetermined humidity” is preferably about 30% or less (typically about 3 to 30%) of humidity in terms of relative humidity (RH) at 25 ° C. The predetermined humidity is more preferably about 5 to 25%, and further preferably about 5 to 20%. For example, in the case of an atmospheric gas containing nitrogen gas as a main component, the humidity can be adjusted by mixing water vapor alone into the dry nitrogen gas. Further, a gas having a humidity higher than the target value (for example, air) may be mixed in the dry nitrogen gas.

The suitable ranges of the atmospheric temperature and the atmospheric gas humidity during chemical vapor deposition may vary depending on the type of SAM forming material used. For example, when trichlorosilane having an unsubstituted alkyl group having 10 to 30 carbon atoms as a tail group is used as the SAM forming material, the ambient temperature is about 80 to 170 ° C. (more preferably about 90 to 160 ° C., for example, Particularly good results can be obtained by setting the substrate temperature to about −20 ° C. to 40 ° C. (more preferably about −10 ° C. to 30 ° C., for example, about 0 ° C. to 20 ° C.). . In one preferred embodiment, the humidity of the atmospheric gas is about 5 to 15% (for example, about 7 to 12%). Examples of the SAM forming material to which such deposition conditions are particularly preferably applied include compounds represented by the general formula: CH ₃ (CH ₂ ) _n SiX ₃ ; Here, n in the above general formula is an integer selected from 9 to 29, and X is the same or different halogen atom (preferably, each selected from Cl or Br).

In the SAM manufacturing method disclosed herein, a substrate mainly composed of various materials as described above (for example, silicon, aluminum, polymer material, etc.) can be used as it is (without performing pretreatment). In addition, it is preferable to use a substrate that has been appropriately pretreated as necessary (for example, depending on the material of the substrate, the surface state, the type of SAM forming material to be used, the quality of the target SAM, etc.). Can do. Such pretreatment includes a treatment for cleaning the surface of the substrate, a treatment for highly flattening the surface of the substrate (preferably at an atomic level), a treatment for forming fine irregularities on the surface of the substrate, and a surface of the substrate. A process for introducing a functional group (typically a functional group suitable for adsorption of the SAM-forming material, such as a hydroxyl group), a process for modifying the surface of the substrate (for example, a process for forming an oxide film on the substrate surface) 1 type or 2 types or more selected from etc. may be included.
The surface of the substrate can be washed by physical treatment such as immersing the substrate in an appropriate liquid and applying ultrasonic vibration, or by treating the substrate with an appropriate chemical (typically acid, alkali, peroxide) 1 type or 2 types selected from chemical processing such as treatment with one or more selected from materials, etc., high energy ray treatment that irradiates the substrate with high energy rays such as ultraviolet rays and electron beams, etc. The above can be adopted as appropriate. An example of a chemical that can be preferably used for the chemical treatment is Piranha solution (a mixture of 98% sulfuric acid and 30% hydrogen peroxide water in a volume ratio of 3: 1). Moreover, as a suitable example of a high energy ray process, the process which irradiates vacuum ultraviolet light (ultraviolet light with a wavelength in the range of 100-300 nm) among ultraviolet rays can be illustrated. Such vacuum ultraviolet light irradiation can be carried out using a conventionally known vacuum ultraviolet light irradiation apparatus equipped with a light source such as an excimer lamp or an H ₂ lamp.

The SAM manufacturing method disclosed herein can be applied to the case where the SAM is formed on any crystal plane of the silicon substrate. For example, by applying the method of the present invention, a SAM can be formed on the (111) plane, the (110) plane, etc. (particularly preferably the (111) plane) of the silicon substrate. Here, usually, a thin oxide film (silica layer) is formed on the surface of the silicon substrate by natural oxidation. Such an oxide film can preferably contribute to the adsorption of the SAM forming material (for example, alkoxysilane). In one preferred embodiment of the method disclosed herein, the oxide film on the surface of the silicon substrate is once completely removed (at least substantially completely). Such removal of the oxide film can be realized, for example, by performing a hydrogen termination process on the surface of the silicon substrate. Such a hydrogen termination treatment can be grasped as a suitable example of a treatment for highly flattening the surface of the substrate. The specific method for the hydrogen termination treatment is not particularly limited, and can be carried out in the same manner as the hydrogen termination method known in the semiconductor manufacturing field and the like. For example, the silicon substrate may be immersed in an aqueous solution of ammonium fluoride (NH ₄ F), hydrogen fluoride (HF), or the like.
Next, oxygen atoms are newly introduced into the surface of the silicon substrate terminated with hydrogen. As a preferable method for introducing such a functional group, a method of irradiating vacuum ultraviolet light in an atmosphere containing oxygen (for example, atmospheric pressure or reduced pressure) can be exemplified. Thereby, a functional group containing oxygen (for example, a hydroxyl group, that is, a silanol group) can be introduced into the surface of the silicon substrate.

  Such hydrogen termination is applied not only to silicon substrates, but also to pretreatment of substrates made of other materials to produce the desired effect (typically, higher quality SAMs by subsequent chemical vapor deposition). Effect). The material of the base material to which such treatment is applied is not particularly limited as long as it is a material capable of hydrogen termination. For example, it may be a base material mainly composed of materials such as silicon, silicon carbide, germanium, graphite and the like. The whole base material may be a base material made of such a material, or even a base material having a layer made of the above material on at least a surface portion (portion where SAM is to be formed) of the base material. Good.

FIG. 2 shows a schematic configuration example of an apparatus that can be preferably used in the SAM manufacturing method disclosed herein. This SAM production apparatus 1 roughly includes a reaction vessel 10, a base material holder 16 that holds a base material (here, a plate-like base material, ie, a substrate will be described as an example) 50, and a SAM forming material. A raw material container 18 as a raw material supply means for storing and supplying the vapor 60 of the SAM forming material into the reaction container 10, an atmospheric temperature control means 20 for controlling the temperature in the container, and a humidity in the container are controlled. The humidity control means 30 and the holder cooling means 40 for cooling the substrate holder 16 are configured.
The ambient temperature control means 20 includes a thermometer 22 arranged inside the container 10 and a heater 24 provided so as to surround the outer periphery of the container 10, and according to the temperature detection result by the thermometer 22, The temperature (atmosphere temperature) in the container 10 can be controlled by adjusting the output. The humidity control means 30 includes a hygrometer 32 disposed inside the container 10, and supplies moisture-containing gas or dry gas into the container 10 from a gas inlet (not shown) according to the humidity detection result by the hygrometer 32. Accordingly, the humidity in the container 10 (atmosphere gas humidity) can be controlled. The substrate holder 16 is disposed at the bottom of the reaction vessel 10, and the substrate 50 is in contact with the back surface of the substrate 50 (the surface opposite to the surface on which the SAM is to be formed) in contact with the upper surface thereof. 50 can be held substantially horizontally. The holder cooling means 40 is configured to allow a refrigerant to flow therein, and a refrigerant passage 42 partially disposed inside the base material holder 16, and a control unit that adjusts the temperature and / or flow rate of the refrigerant flowing through the passage. 44 and a thermometer 46 built in the base material holder 16, and the base material holder 16 is adjusted by adjusting the temperature and / or flow rate of the refrigerant flowing through the passage according to the temperature detection result by the thermometer. The temperature (degree of cooling) can be adjusted.

  Using the SAM production apparatus 1 having such a configuration, for example, the SAM can be formed on the upper surface of the substrate 50 as follows. That is, at room temperature, a SAM forming material (for example, OTS) is placed in a raw material container 18 having an opening 182 at the upper end and placed in the reaction container 10. Further, the base material 50 is set on the upper surface of the base material holder 16. The base material holder 16 is cooled to a predetermined temperature (for example, 10 ° C.) by circulating a coolant (for example, water) through the refrigerant passage 16, and the heater 24 is energized to cause the reaction vessel 10 to have a predetermined atmospheric temperature (for example, 150 ° C.). Heat to. Thereby, the SAM forming raw material in the raw material container 18 is volatilized. That is, the vapor (raw material molecule) 60 of the SAM forming raw material is supplied from the opening 182 of the raw material container 18 to the space in the reaction container 10. The raw material molecules 60 reach the surface of the substrate 50 to form a SAM. At this time, by maintaining the substrate holder 16 at the predetermined temperature (here, 10 ° C.), the substrate 50 fixed to the holder has a temperature lower than the ambient temperature (typically, the substrate holder 16 The base material 50 is cooled so that the temperature is substantially the same as that in FIG. As a result, a SAM having a regular orientation (high orientation) can be formed on the surface of the substrate 50. Further, the base material 50 (base material holder 16) is locally cooled with respect to the atmospheric temperature (150 ° C.) in the reaction vessel 10, so that heat convection in the reaction vessel 10 (towards the base material 50). The raw material molecules 60 can be efficiently supplied to the base material 50 using the downward air flow).

  For example, when the reaction vessel 10 is accommodated and heated in a heating device such as an electric furnace as in the examples described later, the temperature inside the heating device and the temperature of the reaction vessel 10 are approximately the same. Become. Therefore, the thermometer 22 for detecting the temperature in the reaction vessel 10 can be omitted, and a thermometer for detecting the temperature in the heating device can be provided instead. Or it is good also as a structure provided with the thermometer which detects the temperature in the said heating apparatus in addition to the thermometer 22 which detects the temperature in the reaction container 10. FIG. In addition, for example, the humidity in the reaction vessel 10 is in an appropriate range (for example, the relative humidity at 25 ° C. is about 5 to 15% from the start of vapor deposition of the SAM forming material to the base material until the SAM formation is substantially completed). ) May be formed by omitting the humidity control means 30 and heating the container while the reaction container 10 is sealed.

The reason why a highly oriented SAM is formed by the method disclosed herein is not necessarily clear, but can be considered as follows, for example. That is, in a typical mechanism when a SAM is formed by vapor-depositing a SAM forming material on the substrate surface, first, as shown in FIG. 6A, molecules 60 of a gaseous SAM forming material (for example, OTS) are used. Reaches the surface of the substrate 50 from the gas phase. In this figure, a SAM-forming material molecule (raw material molecule) 60 is a molecule having a core atom 62, three head groups 64 bonded to the core atom, and one tail group 66 bonded to the core atom. This is schematically shown.
As shown in FIG. 6B, the raw material molecules 60 that have reached the surface of the substrate 50 preferably move around the surface of the substrate 50 (surface migration), and find a position that is energetically advantageous over other locations. It physically adsorbs there. Next, a chemical bond is formed between the raw material molecules 60 and the substrate 50, and the raw material molecules 60 are fixed to the substrate 50. By repeating such an event, the SAM forming material is autonomously organized.

  Here, depending on the type (boiling point, etc.) of the SAM forming material, in order to efficiently supply the SAM forming material from the gas phase to the substrate surface, the temperature of the gas phase (atmospheric temperature) must be increased to some extent. Is effective. On the other hand, when the substrate is simply held under an atmospheric temperature suitable for supplying the SAM-forming material from the gas phase to the surface of the substrate (the temperature of the substrate is about the same as the ambient temperature), the temperature Since the raw material molecules 60 physically adsorbed on the substrate 50 have relatively high energy, they may be detached from the surface of the substrate 50 once adsorbed. The high frequency of such desorption is disadvantageous in forming a SAM having regular orientation.

  In the method disclosed herein, the substrate 50 is held at a temperature lower than the ambient temperature. This reduces the probability that the raw material molecules 60 physically adsorbed on the base material 50 have energy sufficient for the above desorption, as compared with the case where the base material 50 is at a temperature equal to or higher than the ambient temperature. (Reducing the frequency of desorption). That is, in the schematic diagram shown in FIG. 6 (b), the phenomenon that the raw material molecules 60 are desorbed from the base material 50 is suppressed, so that as shown in FIGS. 6 (c) and 6 (d), the raw material molecules 60 Regularly arranged (having regular orientation) SAMs can be formed.

  The fact that the SAM has regular orientation is, for example, a chart (longitudinal) showing the result of analyzing the surface having the SAM by an X-ray diffraction method (XRD method, typically, a grazing incidence X-ray diffraction method). It can be grasped by a peak being recognized at a position corresponding to the distance between the lattice planes of the SAM forming material molecules constituting the SAM in the axis: intensity (I) and the horizontal axis: diffraction vector (qxy). According to the method disclosed herein, a SAM that is highly oriented (the regularity of the arrangement of the SAM forming material) is high enough to allow the above peaks to be recognized. Therefore, the invention disclosed herein is a SAM formed by chemical vapor deposition of a SAM forming material (for example, OTS) on a base material, and the SAM is configured in an analysis chart by a small angle incident X-ray diffraction method. The SAM is characterized in that a peak is observed at a position corresponding to the distance between lattice planes of the SAM forming material molecules. The film material includes a base material (for example, a silicon substrate) and a SAM formed on the base material, and the SAM is formed by chemical vapor deposition of a SAM forming material (for example, OTS) on the base material. A peak is recognized at a position corresponding to the distance between lattice planes of the SAM forming material molecules constituting the SAM in the analysis chart of the surface of the substrate on which the SAM is formed by the small-angle incidence X-ray diffraction method. Membrane material is included.

  Since the SAM having such regular orientation or the film material including the SAM has high uniformity in the surface direction (spreading direction) of the SAM, the characteristics of the SAM (for example, from the molecular structure of the SAM forming material) (Expected characteristics) may be exhibited more appropriately. For example, compared to a SAM having a lower orientation (typically in an amorphous state), there is less variation in characteristics with respect to the surface direction of the SAM (there is less unevenness depending on the location), and the predetermined characteristics can be more reliably exhibited. At least one of the effects of exhibiting more advanced characteristics can be realized. Therefore, the SAM having the above-mentioned regular orientation has a more appropriate water repellency film (water repellent film) and a hydrophilic film (hydrophilic film) depending on the type of SAM forming material (particularly the type of tail group). Film) or a film exhibiting lubricity (lubricating film). The above-described film material having SAM exhibiting such characteristics includes, as other aspects, a water-repellent film material (for example, a film material exhibiting super-water repellency with a contact angle of 150 ° C. or higher), a hydrophilic film material, and a lubricating film material. And so on. In addition, such a highly uniform SAM is excellent in performance for protecting the substrate on which the SAM is formed (performance as a protective film). For example, the SAM imparts good antifouling properties, water resistance (a concept including water absorption resistance, moisture absorption resistance, etc.), chemical resistance (a concept including corrosion resistance) and the like to the substrate. can do.

  Moreover, since the SAM production method disclosed here produces the SAM by chemical vapor deposition of the SAM formation material, for example, the use efficiency of the SAM formation material is better than the case of using the liquid phase method. This is advantageous from the viewpoint of, for example, reducing the manufacturing cost of a SAM or a film material having the SAM. In addition, there is an advantage that the burden on the environment during the production of the SAM or the film material can be further reduced.

  According to the SAM manufacturing method disclosed herein, a SAM in which SAM forming materials are regularly arranged can be formed. According to such a regular arrangement, more (higher number of molecules) SAM-forming material can be deposited per unit area of the substrate. Therefore, the SAM produced by the method disclosed herein is more sensible than the SAM produced by chemical vapor deposition of the SAM forming material on the substrate under conditions where the substrate temperature is the same as or higher than the ambient temperature. The SAM-forming material may be arranged (filled) on the substrate surface in a more regular and denser manner. In particular, according to an embodiment in which the temperature of the substrate is maintained at a temperature around room temperature or lower (for example, approximately 30 ° C. or less, typically approximately −10 ° C. to 30 ° C.), the substrate is maintained at a higher temperature. In contrast, a SAM in which the SAM forming material is arranged at a higher density can be produced. The reason why such a high-density SAM is formed is not necessarily clear, but can be considered as follows, for example. That is, the raw material molecules on the substrate at a relatively low temperature (for example, at a temperature around room temperature or lower) are compared to the raw material molecules on the higher temperature substrate, the movement of each part of the molecule (head group and (Tail base vibration, rotation, etc.) are suppressed. For this reason, for example, when another raw material molecule B is newly placed in the vicinity of the raw material molecule A that has already been placed on the surface of the base material, the region is closer to the raw material molecule A than when the base material temperature is higher. Since the raw material molecule B is likely to undergo surface migration (approach), the raw material molecule B can be arranged at a position closer to the raw material molecule A. This is considered to facilitate the formation of a higher density SAM.

According to the SAM production method disclosed herein, a SAM that exhibits a contact angle (for example, a water droplet contact angle) approximate to a contact angle expected from the SAM formation material can be produced according to the type of the SAM formation material used. . Here, “expected contact angle” means (a) a SAM-forming material capable of forming SAM on a substrate in the same form as the SAM-forming material used in the production method of the present invention (a compound having at least a common tail group) , Preferably a compound having a common tail group and head group, typically the same compound as the SAM forming material used in the production method of the present invention, and the contact angle of the SAM formed by a general liquid phase method. (For example, a water droplet contact angle) or (b) a contact angle theoretically derived from the chemical structure of the SAM used in the production method of the present invention (the structure of the tail group of the SAM-forming material used). According to one preferred embodiment of the method disclosed herein, a SAM having a difference from an expected contact angle of ± 10 ° or less can be produced. According to a more preferred embodiment, a SAM having a difference from an expected contact angle of ± 5 ° or less can be produced.
The water droplet contact angle can be measured by various conventionally known means. For example, the static contact angle of distilled water can be measured using a contact angle measuring device (model “CA-X150”) manufactured by Kyowa Interface Science Co., Ltd.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Example 1>
Using n-octadecyltrichlorosilane (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter abbreviated as “OTS”) represented by CH ₃ (CH ₂ ) ₁₇ SiCl ₃ as a SAM-forming material, a silicon substrate is obtained by the following procedure. SAM was formed on the surface.

That is, an n-type low resistance (0.01-0.02 Ωcm) silicon substrate is subjected to ultrasonic cleaning with acetone for 10 minutes, then with ethanol for 10 minutes, and further with ultrasonic water for 10 minutes. went.
Vacuum ultraviolet light generated from an excimer lamp (Ushio Electric Co., Ltd., model “UER20-172V”, wavelength λ = 172 nm, irradiation energy density 10 mWcm ⁻² ) on the (111) surface of the silicon substrate at room temperature and atmospheric pressure. (VUV) was irradiated for 60 minutes. The distance from the lamp to the substrate was about 10 mm. By this VUV irradiation, the (111) surface of the silicon substrate was cleaned, and functional groups (mainly silanol groups) suitable for forming SAMs using SAM forming materials described later were introduced.

The VUV-irradiated silicon substrate was placed in a 65 mL Teflon (registered trademark) reaction vessel, introduced into an electric furnace, and heated at 150 ° C. for 10 minutes. This removed the adsorbed water on the reaction vessel and the substrate surface.
The silicon substrate and the reaction vessel that had undergone such heat treatment were transferred to a glove box maintained at a humidity of 7 to 12% (relative humidity at 25 ° C.). In the glove box, a silicon substrate was placed and fixed on a copper base holder provided at the bottom of the reaction vessel so that the (111) surface of the silicon substrate was on the top. Along with the silicon substrate, a SAM forming material (here OTS) placed in a glass cup was sealed in the reaction vessel. That is, the silicon substrate and the SAM forming material were accommodated in a reaction container, and the container was sealed (sealed).

  The sealed reaction vessel was kept in an electric furnace at 150 ° C. for 3 hours. At this time, a coolant (here, water) is circulated through a cooling pipe provided inside the substrate holder to cool the holder, whereby the temperature of the substrate holder (the temperature of the silicon substrate fixed to the holder) In general) was maintained at 10 ° C. That is, in this example, as shown in the temperature profile shown in FIG. 1, OTS was chemically vapor-deposited on the surface of the silicon substrate under the conditions of an atmospheric temperature of 150 ° C. and a substrate temperature of 10 ° C. to form a SAM on the surface of the substrate. Thereafter, the reaction vessel was removed from the electric furnace and cooled. In this way, a silicon substrate (sample 1) on which a SAM derived from OTS was formed was obtained.

<Example 2>
A SAM was formed in the same manner as in Example 1 except that the substrate holder was not cooled. That is, in this example, chemical vapor deposition was performed under conditions of an atmospheric temperature of 150 ° C. and a substrate temperature of 150 ° C., thereby obtaining a silicon substrate (sample 2) on which a SAM derived from OTS was formed.

About the said sample 1 and the sample 2, the orientation of SAM was evaluated by analyzing the SAM formation surface of each sample by a grazing incidence X-ray diffraction method. The above analysis was performed using an X-ray diffractometer apparatus (manufactured by Rigaku Corporation, model “ATX-G”) under the conditions of an acceleration voltage of 50 kV and a beam current of 300 mA. A chart obtained by the analysis is shown in FIG. The vertical axis of the chart shown in FIG. 3 is the diffraction intensity (relative value), and the horizontal axis is the wave number vector qxy. In this chart, the upper side shows the analysis results for sample 1 (atmosphere temperature 150 ° C., substrate temperature 10 ° C.), and the lower side shows sample 2 (atmosphere temperature 150 ° C., substrate temperature) It is an analysis result about 150 degreeC. As can be seen from this chart, no clear peak is observed in the analysis result of Sample 2. This is because, for example, as shown in the schematic diagram shown in the lower right in FIG. 3, the molecular arrangement of the SAM forming material (here OTS) constituting the SAM according to sample 2 does not have a clear regularity ( It is in an amorphous state). On the other hand, in the analysis result of sample 1, a clear peak is recognized in the vicinity of qxy = 15.1 nm ⁻¹ . This suggests that the molecular arrangement of the SAM forming material constituting the SAM according to Sample 1 has a regular orientation, as represented by the schematic diagram shown in the upper right in FIG. From the peak position, the interstitial distance in the molecular arrangement (molecular arrangement) can be calculated. The interstitial distance (the distance d between the straight lines shown in the schematic diagram shown in the upper right in FIG. 3) was 0.419 nm for the SAM according to Sample 1.

<Example 3>
The same procedure as in Example 1 was performed except that the time for holding the reaction vessel in the electric furnace (film formation time) was 0.25 hours, 0.5 hours, 1 hour, and 2 hours, respectively (ie, the atmospheric temperature was 150 ° C. Sample 3 having SAM on a silicon substrate was obtained under the conditions of a substrate temperature of 10 ° C. The thickness of the SAM of these samples was measured with an ellipsometer device (manufactured by PHILIPS, model “PZ-2000”). Moreover, about those SAM, the static contact angle of distilled water was measured by the droplet method (droplet diameter about 2 mm) in 25 degreeC atmosphere. For this contact angle measurement, a contact angle measuring device (model “CA-X150”) manufactured by Kyowa Interface Science Co., Ltd. was used. The obtained results are shown in FIG. 4 for the film thickness and in FIG. 5 for the contact angle. As can be seen from FIG. 4, when the film formation time was approximately 1.5 hours or longer, the film thickness became a substantially constant value. The film thickness of the SAM formed by the film formation for 2 hours was about 2.4 μm, and this value was substantially the same as the film thickness of the SAM obtained in Example 1. Further, as can be seen from FIG. 5, the static contact angle (water droplet contact angle) became a substantially constant value when the film formation time was about 1.5 hours or longer. The water droplet contact angle of the SAM formed by the film formation for 2 hours was about 109 °, and this value was substantially the same as the water droplet contact angle of the SAM obtained in Example 1 (film formation time: 3 hours). Note that it is theoretically said that the contact angle of SAM formed from OTS is about 110 °. In fact, the contact angle (that is, the expected contact angle) of the SAM formed almost ideally by a general liquid phase method using OTS is usually about 110 °.

<Example 4>
Except for the point that the substrate temperature was 20 ° C., in the same manner as in Example 3 (that is, under the conditions of an atmospheric temperature of 150 ° C. and a substrate temperature of 20 ° C.), OTS was chemically deposited on the surface of the silicon substrate for a predetermined film formation time. Thus, a sample in which the SAM was formed on the silicon substrate was obtained. About SAM which concerns on those samples, it carried out similarly to Example 3, and measured the film thickness and the water droplet contact angle. The obtained results are shown in FIG. 4 for the film thickness and in FIG. 5 for the contact angle. As can be seen from FIG. 4, when the film formation time was approximately 1 hour or longer, the film thickness became a substantially constant value. The film thickness of the SAM formed by the film formation for 2 hours was about 2.5 μm, and this value was almost the same as the SAM obtained by setting the film formation time to 3 hours. Further, as can be seen from FIG. 5, the static contact angle (water droplet contact angle) became a substantially constant value when the film formation time was about 1.5 hours or longer. The water droplet contact angle of the SAM formed by the film formation for 2 hours was about 109 °, and this value was almost the same as the SAM obtained by setting the film formation time to 3 hours.

<Example 5>
Except for the point that the substrate temperature was set to 0 ° C., in the same manner as in Example 3 (that is, under conditions of an atmospheric temperature of 150 ° C. and a substrate temperature of 0 ° C.), OTS was chemically deposited on the surface of the silicon substrate for a predetermined film formation time. Thus, a sample in which the SAM was formed on the silicon substrate was obtained. About SAM which concerns on those samples, it carried out similarly to Example 3, and measured the film thickness and the water droplet contact angle. The obtained results are shown in FIG. 4 for the film thickness and in FIG. 5 for the contact angle. As can be seen from FIG. 4, when the film formation time was approximately 1.5 hours or longer, the film thickness became a substantially constant value. The film thickness of the SAM formed by the film formation for 2 hours was about 2.6 μm, and this value was almost the same as the SAM obtained by setting the film formation time to 3 hours. Further, as can be seen from FIG. 5, the static contact angle (water droplet contact angle) became a substantially constant value when the film formation time was about 1.5 hours or longer. The water droplet contact angle of the SAM formed by the film formation for 2 hours was about 109 °, and this value was almost the same as the SAM obtained by setting the film formation time to 3 hours.

2 is a graph showing an atmospheric temperature and a substrate temperature when forming a SAM in Example 1. It is a schematic diagram which shows the outline of one structural example of a SAM production apparatus. It is a graph which shows the analysis result of the sample obtained by Example 1 and Example 2. FIG. It is a graph which shows the relationship between film forming time and the film thickness of SAM. It is a graph which shows the relationship between film-forming time and the water droplet contact angle of SAM. (A)-(d) is explanatory drawing which shows typically the process in which SAM is formed in the base-material surface.

Explanation of symbols

1: SAM production apparatus 10: Reaction vessel 16: Base material holder 18: Raw material container (raw material supply means)
20: Atmospheric temperature control means 30: Humidity control means 40: Holder cooling means 50: Substrate

Claims (8)

A method for producing a self-assembled monolayer on a substrate by chemical vapor deposition of a self-assembled monolayer forming material on the substrate,
A method for producing a self-assembled monolayer, wherein the chemical vapor deposition is performed while the base material is cooled so that the base material is maintained at a temperature lower than an ambient temperature.   The method of claim 1, wherein the substrate is maintained at a temperature 60 ° C. or more lower than the ambient temperature.   The method according to claim 2, wherein the chemical vapor deposition is performed while the atmospheric temperature is set to 100 ° C. to 200 ° C. and the base material is maintained at a temperature of −10 ° C. to 30 ° C.   The method according to claim 1, wherein halosilane is used as the film forming material.   The method according to claim 4, wherein a base material that has been subjected to a pretreatment for introducing a hydroxyl group onto the surface of the base material is used as the base material.   The method according to claim 5, wherein the introduction of the hydroxyl group is performed by irradiation with vacuum ultraviolet light in an atmosphere containing oxygen molecules.   The method of claim 6, wherein the substrate is a silicon substrate. An apparatus for carrying out the method according to any one of claims 1 to 7, comprising:
The following configuration:
A reaction vessel provided with a substrate holder for holding the substrate;
Atmosphere temperature control means for controlling the atmosphere temperature in the reaction vessel;
A substrate holder cooling means for forcibly cooling at least the surface of the holder to a temperature lower than the ambient temperature in the reaction vessel; and
Raw material supply means for supplying a self-assembled monolayer forming material into the reaction vessel;
A self-assembled monolayer production apparatus comprising:

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