Microchip and film forming method for metal thin film of microchip

Abstract

Disclosed herein are a microchip provided with a titanium oxide film between a glass substrate and a metal thin film; and a method for forming the metal thin film and the titanium oxide film on the glass substrate of the microchip. The microchip has a second microchip substrate that has the metal thin film inside a channel, and the titanium oxide film, which has a low extinction coefficient, is provided as a buffer layer between the substrate and the metal thin film such as a gold film.

Claims

1. A method of forming a metal thin film in a microchip including a substrate made of glass on which the metal thin film is formed, and a channel formed in a space including the metal thin film, the method comprising: irradiating a surface of the substrate with light including vacuum ultraviolet light with a wavelength equal to or less than 200 nm under an ambient atmosphere containing oxygen and moisture; immersing the substrate in titanium ion solution and forming a titanium oxide film having a rutile type structure and an anatase type structure being mixed on a vacuum ultraviolet light irradiated face of the substrate; and depositing the metal thin film on the surface of the substrate on which the titanium oxide film is formed.

2. The method for forming a metal thin film in a microchip according to claim 1, wherein the metal thin film is composed of any of gold (Au), platinum (Pt), rhodium (Rh), palladium (Pd), or palladium-platinum alloy (PdPt alloy).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A shows an exemplary configuration of a microchip according to one embodiment of the present invention;

(2) FIG. 1B shows an exemplary configuration of a metal thin film 4 of FIG. 1A;

(3) FIG. 2 is a schematic diagram showing an outline of processes for forming a titanium oxide film on a base material made of, for example, glass according to one embodiment of the present invention;

(4) FIG. 3 is a schematic diagram showing processes in which the metal thin film having the titanium oxide film is formed as shown in FIG. 2, a first and second microchip substrates are joined together to constitute the microchip according to one embodiment of the present invention;

(5) FIG. 4A is a view showing an initial state of the glass substrate in the process 0 of FIG. 2;

(6) FIG. 4B is a view showing the cleavage of an olefin ring of the glass substrate in the process 0 of FIG. 2;

(7) FIG. 4C is a view showing oxygen being introduced into an olefin ring of the glass substrate in the process 0 of FIG. 2;

(8) FIG. 5 is a view (1) showing the titanium oxide film being formed in the process 1 of FIG. 2;

(9) FIG. 6 is a view (2) showing the titanium oxide film being formed in the process 1 of FIG. 2;

(10) FIG. 7 is a view (3) showing the titanium oxide film being formed in the process 1 of FIG. 2;

(11) FIG. 8 is a view (4) showing the titanium oxide film being formed in the process 1 of FIG. 2;

(12) FIG. 9 is a view (5) showing the titanium oxide film being formed in the process 1 of FIG. 2;

(13) FIG. 10 is a view (6) showing the titanium oxide film being formed in the process 1 of FIG. 2;

(14) FIG. 11 is a view (7) showing the titanium oxide film being formed in the process 1 of FIG. 2;

(15) FIG. 12 is a view (8) showing the titanium oxide film being formed in the process 1 of FIG. 2;

(16) FIG. 13A is a view showing the light being irradiated onto a joining face of the first microchip substrate in the process for joining the first and second microchip substrates;

(17) FIG. 13B is a view showing the process for joining the first and second microchip substrates;

(18) FIG. 13C is a view showing the configuration of the microchip obtained by the joining process of FIGS. 13A and 13B;

(19) FIG. 14 shows an exemplary configuration of an excimer lamp;

(20) FIG. 15 is a view showing a distribution of the emission wavelength of the excimer lamp;

(21) FIG. 16 is a schematic diagram showing an experimental system for irradiating the vacuum ultraviolet light onto the base material from the excimer lamp;

(22) FIG. 17 is a view showing the wetting property (wettability) being improved by irradiation the ultraviolet light onto the glass;

(23) FIG. 18 is a view showing the XPS measurement results regarding the titanium oxide for the specimen to which the processes 0 to 3 of FIG. 2 are performed by use of three kinds of mixed solution;

(24) FIG. 19A is a side view showing another exemplary configuration of a noble (inert) gas fluorescent lamp;

(25) FIG. 19B is an enlarged sectional view taken from 19A-19A line of FIG. 19A;

(26) FIG. 20 is a view showing one example of the extinction coefficient with respect to the incident light wavelength of the titanium film and the titanium oxide film;

(27) FIG. 21 is a view showing one example of a variance in the SPR signals with respect to the film thickness of the titanium oxide film;

(28) FIG. 22 is a view showing one example of a variance in the SPR signals with respect to the film thickness of the titanium film;

(29) FIG. 23 is a schematic diagram showing a SPR sensor;

(30) FIG. 24 is a view showing an exemplary configuration of the microchip and the SPR sensor employing the microchip;

(31) FIG. 25 is a view showing an exemplary configuration of the metal thin film having the titanium film; and

(32) FIG. 26 is a schematic diagram showing a case in which the titanium oxide film immobilized onto the surface of the glass base material becomes in a shape of particles.

DETAILED DESCRIPTION OF THE INVENTION

(33) 1. Processes 1 to 3 and Actions Thereof

(34) Hereinafter, first, each of treatments in processes according to one embodiment of the present invention will be in turn described in detail.

(35) In the present embodiment, as mentioned above, the following processes 0 to 3 are in turn performed with respect to a second microchip substrate 2 made of glass so as to form a titanium oxide film on a portion of the second microchip substrate 2 made of the glass.

(36) (Process 0)

(37) A shielding member 5 is provided on one face of the second microchip substrate 2, the shielding member 5 has an aperture 5a of which dimension corresponds to a region on which a titanium oxide film is to be formed, as shown in FIG. 2. Then, a surface of the second microchip substrate 2 made of the glass to immobilize titanium oxide is irradiated with ultraviolet light in an ambient atmosphere containing oxygen and moisture.

(38) (Process 1)

(39) The second microchip substrate 2 is immersed in mixed solution of titanium chloride aqueous solution and nitrite ion contained aqueous solution (for example, sodium nitrite aqueous solution).

(40) (Process 2)

(41) After the prescribed time elapses, the second microchip substrate is pull out from the above mentioned mixed solution and washed (cleaned) with purified water. (By doing this, the reaction is stopped).

(42) (Process 3)

(43) The substrate after washing is air dried (dried) at an ambient temperature.

(44) As mentioned above, in the Process 1, the second microchip substrate 2 is irradiated with the ultraviolet light under an air atmosphere containing oxygen through the shielding member having the aperture of which dimension corresponds to the region on which the titanium oxide film is to be formed.

(45) The above mentioned shielding member may be a stencil having the aperture which is made of, for example, silicone or stainless. The shielding member is arranged and immobilized on one face of the second microchip substrate 2 with a holder or the like, which is not shown.

(46) It has been confirmed that the Process 0 employed in the present embodiment performs a following action with respect to the second microchip substrate 2 made of glass (hereinafter also referred to as glass molding or glass compact).

(47) (i) A surface of the molding is activated with the surface of the second microchip substrate 2 made of the glass (the glass molding) being irradiated with the ultraviolet light. More particularly, the cleavage of the binding portion between the metallic atom or the like and oxygen occurs on the surface of the molding. For example, in the case of common silicate glass, the cleavage occurs in a portion of a siloxane bond (linkage).

(48) In order to allow the cleavage in the portion of the siloxane bond to be generated, certain light is required to irradiate that is absorbed in the glass and that has the wavelength exceeding the activation energy of the glass. More particularly, when the surface of the molding made of the glass (silicate glass) is irradiated with the vacuum ultraviolet light having the wavelength equal to or less than 200 nm, the cleavage of the portion of the siloxane bond occurs on the surface of the molding.

(49) More particularly, according to the experiment conducted by the inventors of the present invention, it is turned out that the surface of the molding is preferably irradiated with the light having the wavelength equal to or less than 180 nm in order to assure the cleavage in the portion of the siloxane bond.

(50) (ii) Subsequently, the above mentioned activated molding surface and hydrogen in the air bind, and the glass surface becomes the hydroxyl group terminated (the terminal of the hydroxyl group). In other words, oxygen (O) is exposed on the glass surface by the above mentioned cleavage.

(51) The exposed oxygen binds to hydrogen (H) in moisture contained in the atmosphere to form the hydroxyl group. Thus, it is assumed that the terminal of the glass substrate ultimately becomes the hydroxyl group.

(52) Subsequently, by applying the following Processes 1, 2 and 3, it has been confirmed that the titanium oxide film having a uniform film thickness is formed on the above mentioned molding surface. It should be noted that the Process 1, in which the base material is immersed in the mixed solution of the titanium chloride aqueous solution and nitride ion contained aqueous solution, can be performed at an ambient temperature without requiring a heating process.

(53) It should be also noted that, when irradiating the vacuum ultraviolet light having the wavelength equal to or less than 180 nm, an incidental effect can also be significantly achieved that a contamination of an organic substance or the like adhered to the glass surface can be decomposed. The contamination of the organic substance or the like may constitute a reaction inhibition (inhibiting) substance against the reaction for forming the titanium oxide film in the Process 1, which will be described below. Thus, in the Process 0, it is particularly preferable to irradiate the vacuum ultraviolet light having the wavelength equal to or less than 180 nm.

(54) It is assumed that a mechanism is approximately as the followings in which the titanium oxide is immobilized on the second microchip substrate 2 made of the glass (the glass molding) according to the method of the present embodiment for forming the titanium oxide film on the base material.

(55) Referring now to FIGS. 4A, 4B and 4C, the cleavage of the binding portion between the metallic atoms or the like and oxygen and the formation of the hydroxyl group terminal in the Process 0 will be explained. Although an example of the silicate glass, which has a skeleton of silicon dioxide, will be explained below, the glass in the present embodiment is not limited to those explained below.

(56) In the Process 0, the glass molding is irradiated with the light including the ultraviolet light having the wavelength equal to or less than 200 nm (in particular, the vacuum ultraviolet light (hereinafter referred to as VUV) having the wavelength equal to or less than 180 nm) (FIG. 4A to FIG. 4B). Thus, as shown in FIG. 4B, the cleavage in the binding portion of the metallic atoms or the like (silicon (Si) in the example of FIGS. 4A, 4B and 4C) and oxygen (O) occurs. Subsequently, as shown in FIG. 4C, hydrogen is introduced into the cleavage (cleaved) portion from moisture in the atmospheric air, and it is assumed that the terminal of the glass surface ultimately becomes hydroxyl group (hydroxyl group terminated).

(57) Next, referring now to FIG. 5 to FIG. 12, forming the titanium oxide film in the Process 1 will be explained.

(58) In the Process 1 in FIG. 2, as shown in the Process (a) in FIG. 5, the glass molding irradiated with the VUV is immersed in the mixed solution of the titanium chloride (III) aqueous solution (TiCl.sub.3 aqueous solution) and sodium nitrite aqueous solution (NaNO.sub.2 aqueous solution). The above mentioned mixed solution contains titanium ions (Ti.sup.3+) and nitrite ions (NO.sup.2).

(59) As a result of the immersion, as shown in the Process (b) in FIG. 5, hydrogen is disengaged from the hydroxyl group terminal of the glass molding, and oxygen binds to a titanium ion in the mixed solution.

(60) Here, for facilitating understanding, it is assumed that silicon dioxide forming the glass (silicate glass) has a crystal structure such as a quartz crystal.

(61) The schematic diagram is shown in (m-0) and (m-1) in FIG. 5 that oxygen and titanium ion bind together in the crystal structure. A circle with hatched lines in FIG. 5 denotes titanium atom (ion).

(62) According to the experimental result, which will be described below, a transparent (i.e., a rutile type) titanium oxide film has been formed by applying the Processes 0 to 3. From the experimental result, as shown in the schematic diagram in (m-1) in FIG. 5, it is assumed that the titanium molecules bound (combined) to oxygen distribute such that four titanium molecules are arranged in a square shape.

(63) In other words, the VUV irradiation allows the binding portion of silicon (Si) and oxygen (O) to be cleaved. The distribution of the hydroxyl group terminal exposed on the glass surface corresponds to the distribution of oxygen atoms in the mixed solution to be exposed on the glass surface. As the titanium ion binds to the exposed oxygen atom, the arrangement of the titanium ions depends on the above mentioned distribution of the oxygen atoms.

(64) Furthermore, the distribution of the titanium ions bound (combined) to oxygen is the distribution that corresponds to the bond (binding) distance of the titanium oxide. As such, the arrangement of titanium has the distribution demonstrating the rutile type tetragonal system.

(65) In other words, the rutile type becomes dominant in the molecule structure of the titanium oxide film which is formed according to the method of the present embodiment for forming the titanium oxide film.

(66) As apparent from the schematic diagram in (m-1) in FIG. 5, a first tier of the cubical crystal is formed with four titanium atoms on the surface of the glass (silicate glass) molding in a state that the binding portion of silicon (Si) and oxygen (O) is cleaved by being irradiated with the vacuum ultraviolet light in the atmospheric air containing oxygen and moisture. It should be noted that two oxygen atoms are distributed in the square composed of four titanium atoms.

(67) By the above mentioned immersion, as the time elapses, the titanium oxide film are grown, as shown in FIGS. 6 to 12. In other words, as shown the Process (c) in FIG. 6, [(titanium oxidation)->(binding of titanium and oxygen)] is repeatedly performed.

(68) First, as shown in the Process (c-1) in FIG. 6, titanium ion, which binds to oxygen in the glass molding is oxidized with nitrite ions, which is coexistent with the titanium ions in the mixed solution, and Ti.sup.3+ is transformed to Ti.sup.4+ (as shown in the schematic diagram in (m-2) in FIG. 6.)

(69) The above oxidized titanium ion binds, as shown in the Process (c-2) in FIG. 7, oxygen supplied from the moisture in the mixed solution. For the sake of simplicity, the first tier of the cubical crystal, which is composed of the square constituted with four titanium atoms (titanium ions) and two oxygen atoms distributed in the square, as shown in the schematic diagram in (m-3) in FIG. 7, is referred to as a first layer.

(70) The binding of the titanium ion and the oxygen atom in the Process (c-2) in FIG. 7 is performed by binding one oxygen atom to two titanium ions in the first layer. As the first layer contains four titanium ions, the number of oxygen atoms to be bound (combined) is (counts) two. For the sake of simplicity, a region in which two oxygen atoms are located is, as shown in (m-3) in FIG. 7, referred to as a second layer.

(71) Subsequently, as shown in the Process (c-3) in FIG. 8, the oxygen atom binds to the titanium ion in the mixed solution. As shown in the schematic diagram in (m-4) FIG. 8, two oxygen atoms located in the first layer bind to one titanium ion.

(72) Then, as shown in the Process (c-1) in FIG. 9 and the schematic diagram in (m-5) in FIG. 9, one titanium ion, which is introduced as above described, is oxidized with the nitrite ions, and Ti.sup.3+ is transformed to Ti.sup.4+.

(73) The oxidized titanium ion binds, as shown in the Process (c-2) in FIG. 10, to oxygen supplied from the moisture in the mixed solution.

(74) More particularly, as shown in the schematic diagram (m-6) in FIG. 10, two oxygen atoms bind to one titanium ion in the second layer. For the sake of simplicity, a region in which two oxygen atoms are located is referred to as a third layer.

(75) Yet subsequently, as shown in the Process (c-3) in FIG. 11, the oxygen atom binds to the titanium ion in the mixed solution. More particularly, as shown in the schematic diagram (m-7) in FIG. 11, two oxygen atoms in the third layer bind to four titanium ions.

(76) Yet subsequently, as shown in the Process (c-1) in FIG. 11 and the schematic diagram (m-8) in FIG. 11, four titanium ions are oxidized with the nitrite ions.

(77) After then, the above mentioned processes, i.e., [(c-2): the binding of the oxidized titanium ion to oxygen], [(c-3): the binding of the bound (combined) oxygen to the titanium ion], and then [(c-1): the oxidization of the titanium ion with the nitrite ion], are repeatedly performed.

(78) In the titanium oxide film, which has grown by laminating (accumulating) in the order of the first layer, the second layer, and the third layer, as shown in the schematic diagram (m-9) in FIG. 12, the rutile type (structure) becomes dominant as shown in FIGS. 12A and 12B.

(79) For this reason, the titanium oxide film formed according to the present invention demonstrates a higher transparency. In other words, as the light is hardly absorbed at the wavelength region 300 to 700 nm, the titanium oxide film can demonstrate an extremely higher transparency.

(80) As described above, in the process 1, at the terminal of a glass molding at which the siloxane binding is cleaved, (c-1) the oxidization of the titanium ions with the nitrite ions; (c-2) the binding of the oxidized titanium ion to oxygen; and (c-3) the binding of the bound (combined) oxygen to the titanium ions, are repeatedly performed. As a result, it is assumed that the titanium oxide film is grown on the VUV irradiated surface of the glass molding.

(81) In other words, in the VUV irradiated region on the glass molding surface, which is immersed in the mixed solution of titanium chloride (III) aqueous solution (TiCl.sub.3 aqueous solution) and sodium nitrite aqueous solution (NaNO.sub.2 aqueous solution), the titanium oxide is formed according to the following reaction formula:
3Ti.sup.+3+6H.sub.2O->3TiO.sub.2+12H.sup.++3e.sup.

(82) It should be noted that in forming the titanium oxide film in the Process 1, which has been explained referring to FIGS. 5 to 12, it is presumed that, as mentioned above, silicon dioxide, which forms the glass (silicate glass), has a crystal structure such as a quartz crystal. In fact, as shown in FIGS. 1A and 1B, the glass may have an amorphous structure, and silicon and oxygen may be irregularly arranged.

(83) As mentioned above, it is assumed that the crystal structure of the titanium oxide, which is formed on the glass molding, is defined by the location of oxygen existing on the surface of the glass molding. For this reason, when silicon dioxide forming the glass (silicate glass) has the crystal structure such as the quartz crystal, the distribution of the titanium ions to be bound (combined) to the oxygen atom exposed on the surface demonstrates the distribution that the crystal structure of the growing titanium oxide film is such that it becomes the rutile type tetragonal system. On the other hand, in the glass with the amorphous structure, the arrangement of the oxygen atoms exposed on the glass surface in the Process 0 (that is, the distribution of the titanium ions to be bound to oxygen) does not necessarily become the distribution that the crystal structure of the glowing titanium oxide film is such that it becomes the rutile type tetragonal system.

(84) With respect to the arrangement of the oxygen atoms exposed on the surface, in a region in which the arrangement (distance) of the titanium ions to be bound to the oxygen atoms substantially corresponds to the lattice constant of the anatase type titanium oxide, it is assumed that the anatase type titanium oxide is formed.

(85) In other words, in the titanium oxide film formed on the surface of the glass molding with the amorphous structure, the rutile type titanium oxide and the anatase type titanium oxide are intermingled (are mixed).

(86) As mentioned above, after the glass molding is immersed in the above mentioned mixed solution for a prescribed time, in the Process 2, the class compact is pulled out from the mixed solution and washed (cleaned) with the purified water or the like to stop the above mentioned reaction.

(87) As the immersion (immersing) time into the above mentioned mixed solution elapses, the film thickness of the titanium oxide on the base material becomes thicker. However, by pulling out the base material from the mixed solution and washing the base material, the reaction for forming the titanium oxide film can be stopped. As such, it is assumed that the film thickness of the titanium oxide film can be controlled by controlling the immersion time.

(88) In the Process 3, the above mentioned base material after washing is dried (air dried) at an ambient temperature.

(89) 2. Process 4 to Process 5

(90) Next, according to the present embodiment, the following Process 4 and Process 5 is applied to the second microchip substrate 2 to which the above mentioned Processes 0 to 3 has been applied, as shown in FIG. 3. Accordingly, the metal foil film such as gold (Au) or the like is formed on the titanium oxide film formed on a portion of the second microchip substrate 2 made of glass.

(91) (Process 4)

(92) The second microchip substrate (glass molding) made of glass, to which the process 3 has been applied, is provided (installed) in a film forming (deposition) equipment that performs the film forming by way of the vapor deposition method or the sputtering method or the like. A metal thin film such as gold (Au) or the like is formed on the glass molding at the shielding member side.

(93) (Process 5)

(94) The shielding member is exfoliated from the second microchip substrate. As a result of the exfoliation, the Au film is, except for those formed on the titanium oxide film, removed from the second microchip substrate along with the shielding member.

(95) In the Process 4, the metal thin film 4 is formed on the glass molding at the shielding member side, to which the process 3 has been applied.

(96) As mentioned above, as a metal material for forming the metal thin film, gold, silver, copper, and aluminum may be used. Nevertheless, in general, the gold (Au) may be in particular used as a metal material that corresponds to the visible light or the near-infrared light and that is chemically stable. It should be noted that the metal material other than gold that has a similar efficacy as the gold may include, for example, platinum (Pt), and rhodium (Rh) and the like.

(97) In the Process 5, with the shielding member being exfoliated from the second microchip substrate, the metal thin film such as Au or the like is, except for those formed on the titanium oxide film, removed from the second microchip substrate along with the shielding member.

(98) Removing the shielding member can be performed by detaching a holder, which is not shown, and then detaching the shielding member from the second microchip substrate 2.

(99) 3. Process 6

(100) Next, according to the present embodiment, the following Process 6 is applied to the second microchip substrate to which the above mentioned Processes 0 to 5 have been applied. Accordingly, a microchip is formed that is composed of the second microchip substrate and the first microchip substrate.

(101) (Process 6)

(102) The first microchip substrate is laminated onto the second microchip substrate to be joined together.

(103) The joining of the microchip substrates can be performed by bonding the second microchip substrate 2 to the first microchip substrate 1, after the surface of the first microchip substrate 1 is irradiated with the vacuum ultraviolet light and the surface thereof is activated, as disclosed in, for example, the Patent Literature 5 (Japanese Patent Application Laid-open Publication No. 2006-187730A) and the Patent Literature 6 (Japanese Patent Publication No. 3714338B).

(104) More particularly, as shown in FIG. 13A, the first microchip substrate 1 is irradiated with the light emitted from an excimer lamp and having a bright line at the wavelength of 172 nm so as to applying a reforming (modification) treatment (i.e., the oxidization treatment) onto the surface thereof.

(105) Subsequently, as shown in FIG. 13B, a side of the first microchip substrate 1 to which the reforming treatment is applied is faced to a face of the second microchip substrate 2 on which the metal thin film 4 is applied, and both substrates are laminated, and adhered to be joined together. Accordingly, the microchip as shown in FIG. 13C can be obtained.

(106) By forming the microchip for the SPR sensor as explained above, the following effect can be achieved.

(107) (1) According to the microchip of the present embodiment, the titanium oxide film having the smaller extinction coefficient is employed as the buffer film for the metal thin film to be applied the second microchip substrate 2. Thus, the deviation in the film thickness of the buffer film is less likely to affect the SPR signals. As a result, the film thickness of the titanium oxide film is not required to accomplish the higher uniformity of approximately 1 nm as in the case of the titanium film.

(108) (2) Also, the titanium oxide film has the hydrophilic surface and the better adhesiveness to the metal thin film such as gold or the like. Thus, it is useful as an adhesive layer for improving the adhesiveness between the second microchip substrate 2 of the glass substrate and the metal thin film 4. In other words, as the titanium oxide film formed according to the titanium oxide film of the present invention has the hydrophilic surface, when the gold film 4a is formed on thus formed titanium oxide by way of the vapor deposition method or the sputtering method, the binding state between the titanium oxide film and the gold film 4a becomes stronger. In addition, the thickness of the gold film 4a can become relatively uniform.

(109) (3) As already explained referring to FIGS. 4 to 12, it is assumed that the titanium oxide film is formed on the second microchip substrate 2 according to the present embodiment by repeatedly performing (c-1) the oxidization of titanium, (c-2) the binding of the oxidized titanium to oxygen, and (c-3) the binding of the bound oxygen to the titanium. In other words, as the immersion time elapses, the film thickness of the titanium oxide on the base material becomes thicker. Thus, the film thickness of the titanium oxide film can be easily controlled by controlling the immersion time. In other words, the film thickness of the titanium oxide film can be controlled by washing the surface with water as in the Process 2 to stop the reaction for forming the titanium oxide film.

(110) (4) Also, because the titanium oxide is formed without using the hydrolysis reaction, the solution temperature is not required to be set at the higher temperature than an ambient temperature.

(111) (5) The titanium oxide film formed according to the present embodiment is grown in the covalent binding between oxygen on the glass surface and titanium ion. Thus, even if the film thickness of the titanium oxide formed is relatively thick, still the titanium oxide film is immobilized firmly on the glass surface, unlike in the case that the titanium oxide is immobilized on the glass surface by the physical absorption by use of the conventional Wet Process.

(112) (6) Furthermore, during the processes forming the titanium oxide film, a burning process is not required that heats the titanium oxide up to several hundred degree Celsius for crystallizing the titanium oxide on the base material. Thus, the granulation (particles) of the titanium oxide due to the heating process is not likely to occur. For this reason, any defect can be avoided which may be caused due to the titanium oxide film being unintentionally exposed from the metal thin film 4 such as the gold film 4a or the like.

(113) 4. Specific (Working) Examples of the Present Embodiments

(114) Hereinafter, specific (working) examples of the present embodiment will be described in detail. Nevertheless, the present invention is not limited to the following examples, and can be embodied by adding appropriate modification within the scope of the purpose of the present invention. It should be noted that, in a part of which description may be duplicated, the duplicated description may be appropriately omitted, but it is not to intend to limit the scope of the present invention.

(115) Hereinafter, the working examples of the present embodiment will be described below, in turn, first (a) the Process 0 in which the shielding member having the aperture of which dimension corresponds to a location of the metal thin film 4 being provided on the second microchip substrate 2 (glass molding), and then a surface of the glass molding at the shielding member side is irradiated with the ultraviolet light to activate the surface of the molding; then (b) the Processes 1 to 3 in which the base material to which surface finishing applied in the Process 0 is immersed in the mixed solution of titanium chloride aqueous solution and sodium nitrite aqueous solution that is nitrite ion contained aqueous solution, the base material is pulled out and washed after the prescribed time elapses, and the base material after the washing is dried (air dried) at the ambient temperature.

(116) [Process 0]

(117) In the Process 0, as shown in FIG. 2, the shielding member 5 is provided that has an aperture 5a on the surface of the glass molding (i.e., the base material W), and a surface of the glass molding at the shielding member side is irradiated with the ultraviolet light.

(118) The above mentioned shielding member 5 is, for example, a stencil having the aperture 5a composed of, for example, silicone, or stainless steel. The shielding member 5 is arranged and fixed on one face of the second microchip substrate 2 with a holder or the like, which is not shown.

(119) Then, by irradiating the surface of the glass molding (the base material W) at the shielding member side with ultraviolet light, the surface is activated.

(120) As the light source L, for example, the excimer lamp emitting the vacuum ultraviolet light with the central wavelength of 172 nm can be employed.

(121) FIG. 14 is a view showing an exemplary configuration of the excimer lamp. The excimer lamp has a tubular structure, and FIG. 14 shows a sectional view taken from a plane containing the tube axis. The excimer lamp 10 has a bulb (arc tube) 11 with a substantially double tube structure in which an inner tube 111 and an outer tube 112 are approximately coaxially arranged. A discharge space S with a cylindrical shape is formed inside the bulb 11 with both ends 11A, 11B of the bulb 11 being sealed. A noble gas such as xenon, argon, krypton or the like is enclosed in the discharge space S. The bulb 11 is made of quartz glass. An inner electrode 12 is disposed on an inner peripheral surface of the inner tube 111, and an outer electrode 13 with a reticular (net) shape is disposed on an outer peripheral surface of the outer tube 112. As such, those electrode 12, 13 are supposed to be arranged with the discharge space S intervening. The electrodes 12, 13 are connected to the power supply 16 through a lead wires W11, W12. When high frequency voltage is applied from the power supply 16, discharge (so called dielectric barrier discharge) is formed between the electrodes 12, 13 with dielectric substances (111, 112) intervening. In the case of xenon gas, the vacuum ultraviolet light with the central wavelength of 172 nm is generated and emitted to the exterior.

(122) FIG. 15 shows an exemplary distribution of an emission wavelength (radiation wavelength) when the excimer lamp 10 shown in FIG. 14 is lighted with the frequency of 20 KHz and the bulb wall loading of 0.1 W/cm.sup.2. The horizontal axis shows the emission wavelength, and the vertical axis shows relative values with respect to the light intensity of the light with the wavelength of 170 nm.

(123) FIG. 16 is a schematic view of the experimental system. As shown in FIG. 16, the base material W on a work stage WS has been irradiated with the vacuum ultraviolet light from the excimer lamp 10. The excimer lamp 10 emitting the vacuum ultraviolet light with the central wavelength of 172 nm as mentioned above is employed, and the irradiance (radiation illuminance) on a surface of the specimen was 20 mW/cm.sup.2.

(124) The specimen is a molding molded with silicate glass, and is a square substrate having the dimension of 10 mm in thickness, 100 mm in height, and 100 mm in width.

(125) FIG. 17 is a view showing an exemplary state demonstrating improved wettability when the glass is irradiated with the ultraviolet light. In FIG. 17, the horizontal axis shows the ultraviolet light irradiation time (sec), and the vertical axis shows the contact angle of water with respect to the glass (degree). FIG. 17 demonstrates data when alkali-free glass is irradiated with the ultraviolet light of 172 nm from the standard output excimer lamp (10 mW/cm.sup.2) at an irradiation distance of 2 mm.

(126) As shown in FIG. 17, with the glass being irradiated with the ultraviolet light, the contact angle (degree) of water with respect to the glass becomes smaller so that the wettability is improved. The reason why the wettability is proved to be improved is assumed that irradiating the glass with the ultraviolet light allows the glass surface to be active so that the terminal of the activated surface becomes the hydroxyl group (OH group).

(127) To summarize, in the glass compact surface treatment process during the Process 0 in which the surface of the glass molding is irradiated with the ultraviolet light (vacuum ultraviolet light), the surface thereof is activated and the terminal of the activated surface becomes the hydroxyl group (hydroxyl group terminated). As long as determined from the above mentioned data, during the Process 0, more particularly, it is assumed that the binding portion between metallic atom or the like on the surface and oxygen is cleaved (cleavage occurs) as the activation of the surface, hydrogen is introduced from moisture in the atmospheric air into the cleaved portion, and the terminal of the glass surface ultimately becomes the hydroxyl group (terminated).

(128) [Process 1], [Process 2] and [Process 3]

(129) Next, hereinafter the Process 1, the Process 2, and the Process 3 will be explained.

(130) The Process 1 is the process that the base material of the glass compact having a surface irradiated with the ultraviolet light (vacuum ultraviolet light) in the Process 0 is immersed in the mixed solution of titanium chloride aqueous solution and nitrite ion contained aqueous solution. The Process 2 is the process that the base material is pulled out from the mixed solution after the prescribed time elapses, and the base material is then washed. The Process 3 is a process that the base material after the washing is air dried at an ambient temperature.

(131) The base material employed is a molding molded with silicate glass, and is a squared substrate with 2 mm in thickness, 8 mm in height, and 8 mm in width.

(132) The base material was irradiated with the vacuum ultraviolet light from an excimer lamp emitting the vacuum ultraviolet light with the central wavelength of 172 nm for 1 to 2 minutes. The irradiance (radiant illumination) was equal to or less than 4 to 5 mW/cm.sup.2.

(133) Subsequently, during the Process 1, the Process 2, and the Process 3, the above mentioned base material was immersed in the mixed solution of titanium chloride (III) aqueous solution, with the concentration of titanium chloride (III) being 20% to 10 mM, and sodium nitrite aqueous solution, with the concentration of sodium nitrite being 0.1 M. Three kinds of mixed solution was employed that were regulated with hydrogen ion exponents of pH=7, pH=8.5, and pH=10, respectively, for the mixed solution in which the base material was immersed. It should be noted that to regulate to pH=8.5, calcium acetate was introduced into the mixed solution. Likewise, to regulate to pH-10, calcium acetate and sodium hydroxide were introduced into the mixed solution. After 30 minutes since the immersion started, the base material was pulled out from each of the mixed solution and then washed with purified water, and then air dried at an ambient temperature.

(134) In order to observe the state of the surface of the specimen after the Process 1, the Process 2, and the Process 3, XPS-7000 type X-ray Electron Spectroscopic (XPS) Equipment, manufactured by Rigaku Co., Ltd., was used to perform the XPS measurement for the surface.

(135) FIG. 18 shows the result of the XPS measurement. In any of the base material immersed in the mixed solution with each pH value, although a peak in the vicinity of 453 eV, attribute to titanium (Ti), was not confirmed, a peak in the vicinity of 458 eV, attribute to titanium oxide (TiO.sub.2) was confirmed.

(136) In other words, by applying the treatment in the Process 1, the Process 2, and the Process 3, the titanium oxide film was formed on the surface of the molding made of silicate glass to which the treatment in the Process 0 was applied.

(137) [Crystal Structure]

(138) Glass (silicate glass) has an amorphous structure, and silicon and oxygen are irregularly arranged. As mentioned above, it is assumed that the crystal structure of the titanium oxide formed on the glass molding is defined by the location of oxygen existing on the surface of the glass molding. For this reason, it is considered that the arrangement of oxygen atoms exposed on the glass surface in the Process 0 (that is, the distribution of titanium ions to be bound to oxygen) is partially distributed such that the crystal structure of the growing titanium oxide film becomes the rutile type, while it is partially distributed such that the anatase type titanium oxide film is formed.

(139) In other words, in the titanium oxide film formed on the surface of the glass molding with the amorphous structure, it is assumed that the rutile type titanium oxide and the anatase type titanium oxide are intermingled (mixed).

(140) [Hydrophilic Property]

(141) Subsequently, by applying the treatment in the Processes 0 to 3 using the above mentioned three kinds of mixed solution, a contact angle was measured on the surface of each molding on which the titanium oxide film was formed, with respect to the three kinds of glass moldings having the glass compact surfaces to which the titanium oxide films were applied. As a comparative example, a contact angle was measured on the surface of each molding before the titanium oxide film was formed on the surface. Water was employed as liquid for measuring the contact angle.

(142) The contact angle of the glass molding surface before the titanium oxide was formed on the surface was approximately 60 degree. On the other hand, any of contact angles of the above mentioned three kinds of glass moldings on the surface on which the titanium oxide was formed was less than 10 degree. It is observed that when the titanium oxide is formed on the glass molding surface using the method for forming the titanium oxide film according to the present invention, the surface on which the titanium oxide was formed becomes the hydrophilic surface.

(143) [Light Absorbance]

(144) By applying the treatment in the Processes 0 to 3 using the above mentioned three kinds of mixed solution, the wavelength characteristic in the light absorbance was measured, for the three kinds of glass moldings having the glass molding surface to which the titanium oxide film were applied. As a comparative example, the wavelength characteristic of the light absorbance was also measured in the glass molding before the titanium oxide was formed on the surface. The Absorption Spectrophotometer (model U-3310), manufactured by Hitachi High Technologies Co., Ltd., was used for the measurement.

(145) As a result, in the wavelength region of 300 to 700 nm, no variance was observed between the light absorption characteristic of the glass molding before the titanium oxide film was formed and the light absorption characteristic of the glass molding after the titanium oxide film was formed. Accordingly, it is turned out in the formed titanium oxide film, light absorption hardly occurs in the wavelength region of 300 to 700 nm.

(146) In general, it is known that the titanium oxide demonstrates higher transparency with respect to the visible light region, when the particle size of the titanium oxide becomes of nano-sized. Thus, it is assumed that the film thickness of the titanium oxide formed on the glass molding surface this time is in the order of nm.

(147) It should be noted that as the immersing time in the mixed solution of titanium chloride aqueous solution and nitrite ion contained aqueous solution becomes longer, the film thickness of the titanium oxide film formed on the glass molding surface also becomes thicker. According to the experimental result conducted by the inventors of the present invention, it is turned out that the immersing time is preferably equal to or less than 30 minutes in order to maintain the transparency in the wavelength region of 300 to 700 nm.

(148) The titanium oxide film formed on the glass molding (i.e., the second microchip substrate 2) according to the present embodiment is crystallized such that the rutile type and anatase type are mixed (intermingled). Thus, it make it possible to obtain stable adhesiveness.

(149) In general, the rutile type titanium oxide film has higher transparency with respect to the light with the wavelength equal to or less than 300 nm compared to the anatase type titanium oxide film.

(150) As the rutile type and the anatase type are mixed in the titanium oxide film according to the present embodiment, the titanium oxide film according to the present embodiment has the photocatalytic function with the anatase type titanium oxide film as well as the higher transparency with the rutile type titanium oxide film so that it has a smaller extinction coefficient.

(151) Here, in the above mentioned examples, although the excimer lamp was used as the light source emitting the vacuum ultraviolet light, the present invention is not limited to those. For example, the noble (rare) gas fluorescent lamp may be used.

(152) FIGS. 19A and 19B shows another exemplary configuration of the noble gas fluorescent lamp. FIG. 19A is a cross sectional view taken by a plane including the tube axis, and FIG. 19B is a cross sectional view with 19B-19B line in FIG. 19A. In FIGS. 19A and 19B, a lamp 20 has a pair of electrodes 22, 23. The Electrodes 22, 23 is disposed on an outer peripheral surface of a bulb (arc tube) 21, and a protective film 24 is provided outside the electrodes 22, 23. An ultraviolet reflective film (coating) 25 is provided on an opposite inner surface with respect to a light emission direction side of an inner peripheral surface of the bulb 21 (as shown in FIG. 19B). A low softening point glass layer 26 is provided on its periphery (circumference), and a phosphor layer 27 is provided on an inner periphery surface of the low softening point glass layer 26. Other configuration is similar to those shown in FIG. 14. Likewise, gas enclosed in the discharge space S in the bulb 21 and a phosphor used for the phosphor layer 25 are also similar.

(153) When high frequency voltage is applied to the electrodes 22, 23, dielectric barrier discharge is formed between the electrodes 22, 23 so that the ultraviolet light is generated, as mentioned above. It allows the phosphor to be excited, and the light emits from the phosphor layer. With the phosphor being appropriately selected, the ultraviolet light with the wavelength, for example, in the vicinity of 190 nm is emitted (generated) from the phosphor layer. This light is reflected with the ultraviolet reflective film (coating) 25 and then emitted outward from a portion of an aperture in which the ultraviolet reflective film 25 is not provided.

(154) Also, when the irradiation region of the vacuum ultraviolet light on the molding surface is small, it is possible to employ a deuterium lamp emitting the light having the wavelength region including the vacuum ultraviolet light wavelength.

(155) It should be noted that in the above mentioned examples, in the Process 0, the hydroxyl group (OH group) was introduced into the glass surface, and also the glass surface was irradiated by the light including the vacuum ultraviolet light with the wavelength equal to or less than 200 nm under an ambient atmosphere containing oxygen and moisture in order to remove contaminant such as an organic substance or the like, which may act as a reaction inhibition substance for forming the titanium oxide film. Nevertheless, other method can achieve the similar effect.

(156) For example, the similar effect can be also achieved in the case that the glass is immersed in acidic solution such as hydrofluoric acid (HF), hydrogen peroxide water, or mixed acid (for example, mixed liquid of sulfuric acid and nitric acid in the volume ratio of 3:1) or the like, or alkaline solution such as sodium hydroxide aqueous solution or the like.

(157) Furthermore, the similar effect can be also achieved in the case that the plasma discharge treatment (for example, atmospheric pressure plasma treatment) is applied to the glass surface under an atmosphere of the atmospheric pressure.

(158) However, in the case that the immersing process in the acidic solution or the alkaline solution or the atmospheric pressure plasma treatment process is employed, the destructive action on the glass surface occurs, as well as the OH group introducing action on the glass surface and the removing action of the reaction inhibiting substance. Thus, the glass surface undergoes a damage so that the surface status becomes roughen. Accordingly, as the process to be employed in the Process 0, it is preferable to employ the process in which the glass surface is irradiated with the light including the vacuum ultraviolet light with the wavelength equal to or less than 200 nm.

(159) Next hereinafter, (c) the Process 4 and (d) the Process 5 will be in turn explained. In (c) the Process 4, the second microchip substrate 2 (the glass molding) having the titanium oxide film in the aperture portion (section) of the shielding member 5 through the Process 0 to the Process 2, and the metal thin film 4 such as gold (Au) or the like is formed on the glass molding at the shield member side. In the Process 5, the shielding member 5 is exfoliated from the second microchip substrate 2, and the metal thin film 4 such as gold or the like is, except for those formed on the titanium oxide film, removed from the second microchip substrate 2 as well as the shielding member 5.

(160) In the process forming the metal thin film 4 in the Process 4, as shown in FIG. 3, the gold film 4a was this time configured on the second microchip substrate 2 (the glass molding). The sputtering equipment was employed as a film forming equipment, and the gold film 4a was formed with the film thickness of 50 nm on the second microchip substrate 2.

(161) In the process 5, the shielding member 5 made of the stencil is removed (detached) from the second microchip substrate 2 by, for example, detaching the holder, which is not shown.

(162) Lastly, (e) the Process 6 in which the first microchip substrate 1 is laminated on the second microchip substrate 2 and both are joined together will be explained below.

(163) Here, an exemplary joining procedure will be explained below in the case that the material of the first microchip substrate 1 is polydimethylsiloxane (PDMS), and the second microchip substrate 2 is the glass molding.

(164) (a) First, with the configuration shown in FIG. 13A, a joining surface (to be joined) of the first microchip substrate 1 was irradiated with the light emitted from an excimer lamp with the central wavelength of 172 nm. The distance between an irradiation (irradiated) surface of the first microchip substrate 1 and a lower surface of the lamp is 3 mm. the irradiance (radiation illuminance) on the surface of the first microchip substrate 1 was 10 mW/cm.sup.2, and the irradiation time was 120 seconds.

(165) (b) Next, the light irradiated side of the first microchip substrate 1 is faced to the surface of the second microchip substrate 2 on which the metal thin film 4 is applied, and both substrates are laminated to be adhered each other.

(166) (c) Subsequently, the laminated first and second microchip substrates 1, 2 were pressurized under the pressure of 1 kg/cm.sup.2. The pressurizing time was 10 seconds, and after then the pressurized status was released.

(167) (d) After then, the laminated first and second microchip substrates 1, 2 were placed on a heating stage, which is not shown and was preheated at 150 degree Celsius. After 5 seconds elapsed, the laminated first and second microchip substrates 1, 2 was pulled out from the heating stage.

(168) By performing the above mentioned procedure, the microchip as shown in FIG. 13C was obtained.

(169) Next, FIG. 20 is a graph showing the extinction coefficient of the titanium oxide with respect to the incident light wavelength. In FIG. 20, the horizontal axis shown the wavelength (nm), and the vertical axis show the extinction coefficient. As apparent from the graph, the extinction coefficient of the titanium oxide is 0 at the wavelength of 670 nm. For this reason, in the case that the titanium oxide film is the buffer film, the film thickness of the titanium oxide is not likely to affect the SPR signals.

(170) Taking the above mentioned observation into consideration, the SPR signal sensitivities were obtained by the simulation and then compared each other in the case that the buffer film of the metal thin film is the conventional titanium film and in the case that the buffer film of the metal thin film is the titanium oxide film according to the present invention.

(171) The simulation condition was set such that the incident light wavelength is 670 nm, the metal thin film 4 has the film thickness of 40 to 50 nm, and the SPR resonance angle 71 of degrees (fixed angle condition).

(172) Then, within the rage of the film thickness of the titanium film or the titanium oxide film being 0 to 50 nm, it was observed how the SPR signals varied. FIG. 21 shows the case of the titanium oxide film, while the FIG. 22 show the case of the titanium film. In FIGS. 21 and 22, the horizontal axis shows the incident light angle, and the vertical axis shown the SPF signal intensity.

(173) As apparent from FIG. 22, in the case of the titanium film, it is observed that the intensity of the reflected light of the light irradiated onto a rear face of the metal thin film 4 considerably (largely) varies depending on the film thickness within the range of the film thickness of 0 to 50 nm. In contrast, as apparent from FIG. 21, in the case of the titanium oxide film, it is observed that the intensity of the reflected of the light irradiated onto the rear face of the metal thin film 3 hardly differs depending on the film thickness with the rage of the film thickness of 0 to 50 nm.

(174) As a result, it is turned out the titanium oxide film is preferable to be employed as the buffer film of the metal thin film 4 for the fixed angle type SPR sensor.

(175) It should be noted that although particular embodiments have been explained above, the above mentioned embodiments are only for the illustrative purpose, and not intended to limit the scope of the present invention. The apparatus and the method described in the specification may be reduced to practice in various embodiments other than the above disclosed ones. Also, any omission, replacement, and modification may be appropriately made to the above mentioned embodiments without departing from the scope of the present invention. It should be noted that those embodiments with omission, replacement, and modification is also within the scope of what is claimed in the claims and the equivalents thereof so that those embodiments also fall into the technical scope of the present invention.

(176) The present application is based on Japanese Patent Application No. 2013-117836 (filed on Jul. 4, 2013) and claims the priority based on the above Japanese Patent Application. All those disclosed in the above Japanese Patent Application and Japan Patent Application No. 2013-35578 (filed on Feb. 26, 2013) are hereby incorporated into the present application by reference.

REFERENCE SIGNS LIST

(177) 1 First Microchip Substrate 2 Second Microchip Substrate 3 Channel 3a Inlet Port 3b Outlet Port 4 Metal Thin Film 4a Gold Film 4b Titanium Oxide Film (Buffer Layer) 5 Shielding Member 5a Aperture 10 Excimer Lamp 11 Bulb (Arc Tube) 12 Internal Electrode 13 External Electrode 16 Power Supply 21 Bulb (Arc Tube) 22, 23 Electrodes 24 Protective Layer 25 Ultraviolet Reflective Film 26 Glass Layer 27 Fluorescent Layer L Lamp W Base Material WS Work Stage