Patent Publication Number: US-2012032284-A1

Title: Film for resin spacer, light-receiving device and method for manufacturing same, and mems device and method for manufacturing same

Description:
TECHNICAL FIELD 
     The present invention relates to a film for a resin spacer, a light-receiving device, a method for manufacturing the light-receiving device, a MEMS device, and a method for manufacturing the MEMS device. More particularly, the present invention relates to a film for a resin spacer used in the manufacture of a light-receiving device and a MEMS device, a light-receiving device using the film, a method for manufacturing the light-receiving device, a MEMS device, and a method for manufacturing the MEMS device. 
     BACKGROUND ART 
     In recent years, a light-receiving device equipped with a light-receiving element, such as a CCD or a CMOS, is widely used in the field of optical equipment, including mobile phones and digital still cameras. 
     Such a light-receiving device is required to have a structure in which the light-receiving element is hermetically housed, in order to prevent such foreign matter as dust or contamination, which can be a cause for imaging failure, from getting inside the light-receiving device. Accordingly, a commonly-used light-receiving device has a hollow package structure in which a base substrate including a light-receiving element formed therein and a transparent substrate disposed oppositely to the base substrate are bonded to each other through a spacer. 
     Spacers made of various materials have been proposed as spacers used to form a hollow package structure. Among these spacers, a resin spacer is a focus of attention since a light-receiving device having a hollow package structure can be manufactured at low costs. 
     For example, Patent Literature 1 discloses a method for manufacturing a light-receiving device having a hollow package structure by using an adhesive film in which a photosensitive resin composition is covered with a cover film. In this method, the adhesive film is laminated on a wafer in which a photoelectric conversion part including a CCD circuit or a CMOS circuit is formed. Thereafter, the adhesive film is exposed and developed, thereby forming a resin spacer surrounding the photoelectric conversion part of the wafer. Then, a transparent substrate is bonded to the resin spacer formed on the wafer, thereby obtaining a light-receiving device having a hollow package structure in which the photoelectric conversion part is hermetically sealed with the wafer, the resin spacer and the transparent substrate. 
     In addition, a resin spacer has the advantage of being inexpensive, lightweight, and so on. Accordingly, the resin spacer not only is used when manufacturing a light-receiving device having a hollow package structure, but also is taking the place of spacers made of a variety of other materials in various applications. 
     For example, Patent Literature 2 discloses a method for manufacturing a MEMS (Micro Electro Mechanical Systems) device by using a photosensitive resin film (film for a resin spacer). In this method, the photosensitive resin film is laminated on a wafer in which a MEMS element is formed. Thereafter, the photosensitive resin film is exposed and developed, thereby manufacturing a MEMS device having a structure in which the MEMS element is surrounded by the resin spacer. 
     CITATION LIST 
     Patent Literature 
     
         
         {PTL 1}: Japanese Patent Application Laid-Open No. 2008-42186 
         {PTL 2}: Japanese Patent Application Laid-Open No. 2007-189032 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     When a light-receiving device or a MEMS device is manufactured using a film for a resin spacer, as in the methods disclosed in Patent Literatures 1 and 2, the film for a resin spacer is, in some cases, previously cut in conformity to the shape of a wafer before the film is laminated thereon. 
       FIG. 12A  is a plan view illustrating one example of a cutting table used to cut a film for a resin spacer, whereas  FIG. 12B  is a cross-sectional view taken along the line I-I of the cutting table illustrated in  FIG. 12A . In addition,  FIG. 13  is a cross-sectional view illustrating the way the film for a resin spacer is cut using the cutting table illustrated in  FIGS. 12A and 12B . 
     As illustrated in  FIGS. 12A and 12B , a cutting table  100  comprises a stage section  100   a  in the central portion of which an opening is provided, and a film contact part  100   b  provided on the stage section  100   a  so as to surround the opening. As illustrated in  FIG. 13 , a film for a resin spacer  102  is placed on the film contact part  100   b  of the cutting table  100  at the time of film cutting. Then, the film is cut by a cutter  104  provided in the opening of the cutting table  100 . 
     In cases where the film for a resin spacer is cut in this way, the inventors of the present application have recognized the following problems. 
     That is, the inventors have recognized that in some cases, part of a resin composition of the film for a resin spacer adheres to the film contact part of the cutting table at the time of the above-described film cutting, thus adversely affecting the accuracy of subsequent film cutting. 
     In addition, a keen examination made by the inventors has revealed that the adherence of the resin composition to the cutting table at the time of film cutting can occur even if a silicone resin excellent in mold releasability is used as the film contact part. 
     The present invention has been accomplished in view of such circumstances as described above. Accordingly, an object of the present invention is to provide a film for a resin spacer capable of reducing the adherence of a resin composition to a cutting table at the time of film cutting, a light-receiving device using the film, a method for manufacturing the light-receiving device, a MEMS device, and a method for manufacturing the MEMS device. 
     Solution to Problem 
     One aspect of the present invention relates to a film for a resin spacer, the film including an adhesive layer made of a resin composition; and a cover film covering a surface of the adhesive layer, wherein an adhesion force C 1  between the adhesive layer and the cover film and an adhesion force D between the adhesive layer and a silicone resin satisfy the condition C 1 &gt;D. 
     In this aspect, the adhesion force C 1  between the adhesive layer of the film for a resin spacer and the cover film and the adhesion force D between the adhesive layer of the film for a resin spacer and the silicone resin, which is a typical material of the film contact part of the cutting table, are set so as to satisfy the condition C 1 &gt;D. An examination made by the inventors of the present application has revealed that according to the above-described aspect, it is possible to reduce adherence of the resin composition to the film contact part for various materials thereof, without limitation to cases in which a material constituting the film contact part of the cutting table is a silicone resin. 
     Here, the phrase “adhesion force” refers to a force per unit width necessary to vertically separate two dissimilar substances at the boundary face thereof and, specifically, refers to a peel strength at 25° C. In addition, the “silicone resin” used to measure the adhesion force D is specifically a composite silicone sheet (made by Nippa Co., Ltd.). 
     In the film for a resin spacer according to the above-described aspect, an adhesion force E 1  between the adhesive layer and a silicon wafer preferably satisfies the condition E 1 &gt;0.01 N/m. 
     If the adhesion force E 1  between the adhesive layer of the film for a resin spacer and a silicon wafer, which is a typical example of a substrate to be laminated with the film for a resin spacer, satisfies the condition E 1 &gt;0.01 N/m, as described above, the film for a resin spacer can be reliably fixed onto the substrate to be laminated. 
     Here, the “silicon wafer” used to measure the adhesion force E 1  is specifically a polished wafer (made by SUMCO Corporation; Part No. PW, 725 μm in thickness). 
     In the film for a resin spacer according to the above-described aspect, an adhesion force C 2  between the adhesive layer and the cover film after exposure on the i-line based cumulative light exposure condition of 700 mJ/cm 2  and an adhesion force E 2  between the adhesive layer and the silicon wafer after exposure on the i-line based cumulative light exposure condition of 700 mJ/cm 2  preferably satisfy the condition C 2 &lt;E 2 . 
     Here, the “silicon wafer” used to measure the adhesion force E 2  is specifically a polished wafer (made by SUMCO Corporation; Part No. PW, 725 μm in thickness). 
     If the adhesion force C 2  between the adhesive layer and the cover film after exposure and the adhesion force E 2  between the adhesive layer and the silicon wafer after exposure, which is a typical example of the substrate to be laminated, satisfy the condition C 2 &lt;E 2 , as described above, it is possible to reduce adherence of the resin composition to the cover film when peeling off the cover film after the exposure of the film for a resin spacer on the substrate to be laminated. 
     Here, the phrase “i-line based cumulative light exposure” refers to a value obtained by integrating the luminance of i-line light (near a wavelength of 365 nm) used for exposure by exposure time. 
     In addition, the phrase “i-line based cumulative light exposure of 700 mJ/cm 2 ” assumes common exposure conditions applied when a resin spacer of a light-receiving device or a MEMS device is formed. 
     In the film for a resin spacer according to the above-described aspect, the elastic modulus of the adhesive layer after exposure on the i-line based cumulative light exposure condition of 700 mJ/cm 2  is preferably 100 Pa or higher at a measurement temperature of 80° C. 
     Using such a film for a resin spacer as described above, it is possible to form a resin spacer less susceptible to resin spacer deformation and superior in shape retainability when a cover substrate and the silicon wafer are bonded to each other through the resin spacer, since the elastic modulus of the adhesive layer after exposure is sufficiently high. 
     In the film for a resin spacer according to the above-described aspect, the moisture permeation rate of the adhesive layer after exposure on the i-line based cumulative light exposure condition of 700 mJ/cm 2  and heat curing on the condition of 180° C. and 2 hours measured by a JIS Z0208 B method is preferably 12 g/m 2 /24 h or higher. 
     Using such a film for a resin spacer as described above, it is possible to release moisture within a hollow package of a light-receiving device or a MEMS device to the outside since the moisture permeation rate of the adhesive layer after exposure and heat curing is sufficiently high. Thus, it is possible to form a resin spacer capable of reducing dew condensation in the light-receiving device or the MEMS device. 
     In the film for a resin spacer according to the above-described aspect, the resin composition preferably contains an alkali-soluble resin and a photopolymerizable resin. 
     If the resin composition constituting the adhesive layer of the film for a resin spacer contains a photopolymerizable resin, as described above, it is possible to precisely form a resin spacer by a photolithographic technique. In addition, if the resin composition contains an alkali-soluble resin, it is possible to perform the development treatment of the film for a resin spacer by using an alkaline water solution having a small environmental load. 
     The resin composition may further contain a thermosetting resin. 
     If the resin composition contains a thermosetting resin, in addition to an alkali-soluble resin and a photopolymerizable resin, it is possible to not only form a resin spacer superior in heat resistance but also reliably bond the resin spacer and the substrate to each other by means of thermocompression bonding after the formation of the resin spacer. 
     The alkali-soluble resin may contain a (meth)acrylic modified novolac resin. 
     If the alkali-soluble resin contains a (meth)acrylic modified novolac resin, as described above, it is possible to improve the compatibility of the photopolymerizable resin and the thermosetting resin with each other. 
     The alkali-soluble resin may contain a carboxyl group-containing polymer selected from the group consisting of a carboxyl group-containing epoxy acrylate, a carboxyl group-containing acrylic polymer, and polyamide acid. 
     The photopolymerizable resin may contain an acrylic monomer. 
     If an acrylic monomer is used as the photopolymerizable resin, it is possible to suitably use a trifunctional (meth)acrylate compound, a tetrafunctional (meth)acrylate compound, or the like, superior in photopolymerizability. 
     The photopolymerizable resin may contain a (meth)acrylic acid adduct of an epoxy compound. 
     Another aspect of the present invention relates to a light-receiving device including: a base substrate in which a photoelectric conversion part is formed; a transparent substrate disposed so as to face the base substrate; and a resin spacer disposed between the base substrate and the transparent substrate so as to surround the photoelectric conversion part, wherein the resin spacer is formed of a film for a resin spacer according to the above-described aspect. 
     Yet another aspect of the present invention relates to a MEMS device including: a base substrate in which a functional part including a MEMS element is formed; a cover substrate disposed so as to face the base substrate; and a resin spacer disposed between the base substrate and the cover substrate so as to surround the functional part, wherein the resin spacer is formed of a film for a resin spacer according to the above-described aspect. 
     Still another aspect of the present invention relates to a method for manufacturing a light-receiving device, the method including: a film cutting step of cutting a film for a resin spacer according to the above-described aspect; a laminating step of laminating the film for a resin spacer cut in the film cutting step on a surface of a wafer in which a plurality of photoelectric conversion parts is formed; an exposure/development step of exposing and developing the film for a resin spacer laminated on the wafer, so that a resin spacer surrounding the plurality of photoelectric conversion parts is formed; a bonding step of bonding the wafer and the transparent substrate through the resin spacer formed in the exposure/development step; and a dividing step of dividing the wafer and the transparent substrate bonded through the resin spacer in units of photoelectric conversion parts. 
     Still another aspect of the present invention relates to a method for manufacturing a light-receiving device, the method including: a film cutting step of cutting a film for a resin spacer according to the above-described aspect; a laminating step of laminating the film for a resin spacer cut in the film cutting step on a surface of a transparent substrate; an exposure/development step of exposing and developing the film for a resin spacer laminated on the transparent substrate, so that a resin spacer is formed on the transparent substrate; a bonding step of bonding a wafer in which a plurality of photoelectric conversion parts is formed and the transparent substrate through the resin spacer formed in the exposure/development step, so that the plurality of photoelectric conversion parts is surrounded by the resin spacer; and a dividing step of dividing the wafer and the transparent substrate bonded through the resin spacer in units of photoelectric conversion parts. 
     Still another aspect of the present invention relates to a method for manufacturing a MEMS device, the method including: a film cutting step of cutting a film for a resin spacer according to the above-described aspect; a laminating step of laminating the film for a resin spacer cut in the film cutting step on a surface of a wafer in which a functional part including a MEMS element is formed; an exposure/development step of exposing and developing the film for a resin spacer laminated on the wafer, so that a resin spacer surrounding the functional part is formed; and a bonding step of bonding the wafer and a cover substrate through the resin spacer formed in the exposure/development step. 
     Still another aspect of the present invention relates to a method for manufacturing a MEMS device, the method including: a film cutting step of cutting a film for a resin spacer according to the above-described aspect; a laminating step of laminating the film for a resin spacer cut in the film cutting step on a surface of a cover substrate; an exposure/development step of exposing and developing the film for a resin spacer laminated on the cover substrate, so that a resin spacer is formed on the cover substrate; and a bonding step of bonding a wafer in which a functional part including a MEMS element is formed and the cover substrate through the resin spacer formed in the exposure/development step, so that the functional part is surrounded by the resin spacer. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to prevent the adherence of a resin composition to a cutting table at the time of film cutting by setting an adhesion force C 1  between an adhesive layer of a film for a resin spacer and a cover film and an adhesion force D between the adhesive layer of the film for a resin spacer and a silicone resin so as to satisfy the condition C 1 &gt;D. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating a structural example of a film for a resin spacer according to the present invention. 
         FIG. 2  is a cross-sectional view illustrating a structural example of a light-receiving device according to the present invention. 
         FIG. 3  is a cross-sectional view illustrating another structural example of the light-receiving device according to the present invention. 
         FIG. 4  is a process drawing illustrating one example of a method for manufacturing a light-receiving device according to the present invention. 
         FIG. 5A  is a drawing illustrating the way a film for a resin spacer is cut. 
         FIG. 5B  is a drawing illustrating the way the film for a resin spacer is conveyed after being cut. 
         FIG. 6  is a plan view illustrating one example of a resin spacer formed by an exposure/development treatment. 
         FIG. 7  is a cross-sectional view illustrating a structural example of a MEMS device according to the present invention. 
         FIG. 8  is a process drawing illustrating one example of a method for manufacturing a MEMS device according to the present invention. 
         FIG. 9  is a table showing ingredient amounts of a film for a resin spacer in Practical Examples 1 to 5 and Comparative Example 1. 
         FIG. 10  is a table showing measurement results in Practical Examples 1 to 5 and Comparative Example 1. 
         FIG. 11  is another table showing measurement results in Practical Examples 1 to 5 and Comparative Example 1. 
         FIG. 12A  is a plan view illustrating a structural example of a cutting table. 
         FIG. 12B  is a cross-sectional view taken along the line of the cutting table illustrated in  FIG. 12A . 
         FIG. 13  is a drawing illustrating the way a film for a resin spacer is cut using the cutting table illustrated in  FIGS. 12A and 12B . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 
     First, a description will be given of a configuration of a film for a resin spacer according to the present invention. Then, a description will be given of a resin composition constituting an adhesive layer of this film for a resin spacer. Thereafter, a description will be given of a light-receiving device using the film for a resin spacer, a method for manufacturing the light-receiving device, a MEMS device, and a method for manufacturing the MEMS device. 
     (Film for Resin Spacer) 
       FIG. 1  is a cross-sectional view illustrating a structural example of a film for a resin spacer according to the present invention. 
     As illustrated in the figure, a film for a resin spacer  10  comprises an adhesive layer  12  made of a resin composition, and a cover film  14  covering one surface of the adhesive layer  12 . 
     The resin composition constituting the adhesive layer  12  preferably has alkali developability, photosensitivity and thermosettability by containing an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin, as will be described later. 
     A film thickness t 1  of the adhesive layer  12  is preferably set to an appropriate range, according to the purpose of use of a light-receiving device or a MEMS device. For example, if the film for a resin spacer  10  is used in the manufacture of a light-receiving device, the film thickness t 1  of the adhesive layer  12  can be set to 5 μm or larger but not larger than 100 μm. 
     A material constituting the cover film  14  is not limited in particular, as long as the material has film characteristics (for example, rupture strength and flexibility) capable of maintaining a film state of the adhesive layer  12 . As the material, it is possible to use, for example, polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), or polyester. 
     In addition, a film thickness t 2  of the cover film  14  is preferably adjusted as appropriate, to the extent that the strength and handleability of the film for a resin spacer  10  are compatible with each other. 
     In the film for a resin spacer  10  having the above-described configuration, an adhesion force C 1  between the adhesive layer  12  and the cover film  14  before exposure and an adhesion force D between the adhesive layer  12  and a silicone resin before exposure are set so as to satisfy the condition C 1 &gt;D (preferably, C 1 &gt;3D). Here, the reason for setting the condition including the adhesion force D between the adhesive layer  12  and the silicone resin as an element of the condition is that a silicone resin is assumed as a typical material used as the film contact part of the cutting table. 
     If the adhesion force C 1  and the adhesion force D satisfy the condition C 1 &gt;D, it is possible to reduce adherence of the resin composition to the film contact part for various materials thereof, without limitation to cases in which a material constituting the film contact part of the cutting table is a silicone resin. In particular, if the adhesion force C 1  and the adhesion force D satisfy the condition C 1 &gt;3D, it is possible to more reliably reduce adherence of the resin composition to the film contact part. 
     Examples of a method for adjusting the adhesion force C 1  and the adhesion force D so as to satisfy the condition C 1 &gt;D (preferably, C 1 &gt;3D) also include appropriately adjusting the structures, the compounding ratio and the like of an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin, in addition to appropriately selecting a material of the cover film and a mold-releasing agent on a surface of the cover film. 
     An adhesion force E 1  between the adhesive layer  12  and a silicon wafer before exposure as a typical example of a substrate to be laminated with the film for a resin spacer  10  preferably satisfies the condition E 1 &gt;0.01 N/m and, more preferably, satisfies the condition E 1 &gt;200 N/m. 
     If the adhesion force E 1  between the adhesive layer  12  and the silicon wafer as a typical example of a substrate to be laminated satisfies the above-described condition, the film for a resin spacer  10  can be reliably fixed onto the substrate to be laminated (for example, a silicon wafer). 
     Examples of a method for adjusting the adhesion force E 1  so as to satisfy the condition E 1 &gt;0.01 N/m include appropriately adjusting the structures, the compounding ratio and the like of an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin. 
     In addition, the adhesion force C 2  between the adhesive layer  12  on the i-line based cumulative light exposure condition of 700 mJ/cm 2  and the cover film  14  after exposure and the adhesion force E 2  between the adhesive layer  12  on the i-line based cumulative light exposure condition of 700 mJ/cm 2  and a silicon wafer after exposure, which is a typical example of the substrate to be laminated, preferably satisfy the condition C 2 &lt;E 2 . 
     If the adhesion force C 2  and the adhesion force E 2  satisfy the above-described condition, it is possible to reduce adherence of the resin composition to the cover film  14  when exposing the film for a resin spacer  10  laminated on the substrate to be laminated (for example, a silicon wafer) and peeling off the cover film  14  from the adhesive layer  12 . 
     Examples of a method for adjusting the adhesion forces C 2  and E 2  so as to satisfy the condition C 2 &lt;E 2  include appropriately adjusting the structures of a photopolymerization initiator and a photopolymerizable resin and the compounding ratio of an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin. 
     In addition, the elastic modulus of the adhesive layer  12  after exposure on the i-line based cumulative light exposure condition of 700 mJ/cm 2  is preferably 100 Pa or higher at a measurement temperature of 80° C. 
     If the elastic modulus of the adhesive layer  12  after exposure is as sufficiently high as described above, it is possible to form a resin spacer superior in shape retainability. 
     Examples of a method for adjusting the elastic modulus of the adhesive layer  12  to 100 Pa or higher include appropriately adjusting the structure of a photopolymerizable resin and the structures of and the compounding ratio of an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin. 
     In addition, the moisture permeation rate of the adhesive layer  12  measured by a JIS Z0208 B method after exposure on the i-line based cumulative light exposure condition of 700 mJ/cm 2  and heat curing on the condition of 180° C. and 2 hours is preferably 12 g/m 2 /24 h or higher. 
     If the moisture permeation rate of the adhesive layer after exposure and heat curing is as sufficiently high as described above, it is possible to form a resin spacer capable of reducing dew condensation within a hollow package of a light-receiving device or a MEMS device. 
     Examples of a method for adjusting the above-described moisture permeation rate of the adhesive layer  12  to 12 g/m 2 /24 h or higher include appropriately adjusting the structure of a thermosetting resin and the structures and the compounding ratio of an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin. 
     (Resin Composition Constituting Adhesive Layer) 
     Next, a description will be given of a resin composition constituting the adhesive layer  12  of the film for a resin spacer  10 . 
     The resin composition of the adhesive layer  12  preferably has alkali developability, photosensitivity and thermosettability by containing an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin. 
     If the resin composition constituting the adhesive layer  12  contains a photopolymerizable resin as described above, it is possible to precisely form a resin spacer by a photolithographic technique. In addition, if the resin composition constituting the adhesive layer  12  contains an alkali-soluble resin, it is possible to perform a development treatment by using an alkaline water solution having a small environmental load. Yet additionally, if the resin composition constituting the adhesive layer  12  contains a thermosetting resin, it is possible to not only form a resin spacer superior in heat resistance but also reliably bond the resin spacer and a substrate to each other by means of thermocompression bonding after the formation of the resin spacer. 
     Hereinafter, a description will be given of details on resin compositions constituting the adhesive layer  12 , in the order of an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin. 
     Examples of an alkali-soluble resin that can be contained in the resin composition of the adhesive layer  12  may include a carboxyl group-containing polymer selected from the group consisting of a carboxyl group-containing epoxy acrylate, a carboxyl group-containing acrylic polymer, and polyamide acid, novolac resins of cresol type, phenol type, bisphenol-A type, bisphenol-F type, catechol type, resorcinol type, pyrogallol type and the like, (meth)acrylic modified novolac resins such as a (meth)acrylic modified bisphenol-A type novolac resin, a copolymer of styrene and acrylic acid, a polymer of hydroxystyrene, polyvinyl phenol, poly alpha-methylvinyl phenol, a phenol aralkyl resin, a (meth)acrylic acid resin, an acrylic resin such as a (meth)acrylic acid ester resin, a cyclic olefin-based resin containing a hydroxyl group, a carboxyl group or the like, and polyamide resins (specifically, a resin having at least one of a polybenzoxazole structure and a polyimide structure and including a hydroxyl group, a carboxyl group, an ether group or an ester group in a main chain or side chain, a resin having a polybenzoxazole precursor structure, a resin having a polyimide precursor structure, a resin having a polyamide acid ester structure, and the like). 
     Among these examples, a (meth)acrylic modified novolac resin is preferable in that the resin can be development-treated by using an alkaline water solution having a small environmental load and that the heat resistance of a resin spacer can be improved. 
     As the alkali-soluble resin to be contained in the resin composition of the adhesive layer  12 , alkali-soluble resins of a plurality of types may be used in combination. 
     In addition, the content ratio of the alkali-soluble resin in the resin composition is not limited in particular, but is preferably 50 to 95 wt. % of the resin composition constituting the adhesive layer  12 . If the content ratio of the alkali-soluble resin is lower than the above-described lower limit, it may not be possible to fully attain the effect of improving compatibility between a photocurable resin and a thermosetting resin. On the other hand, if the content ratio of the alkali-soluble resin is higher than the above-described upper limit, the developability or pattern resolution of the adhesive layer  12  may not be sufficient. 
     Examples of a photopolymerizable resin that can be contained in the resin composition of the adhesive layer  12  may include a (meth)acrylic acid adduct of an epoxy compound and an acrylic monomer of a (meth)acrylate compound or the like. 
     Among these examples, a polyfunctional acrylic monomer having a trifunctional or higher functional group is preferable, and a trifunctional (meth)acrylate compound or a tetrafunctional (meth)acrylate compound is more preferable. If a polyfunctional acrylic monomer is used, it is possible to improve the mechanical strength of a resin spacer after exposure and development. 
     As the polyfunctional acrylic monomer, it is possible to use, for example, a trifunctional (meth)acrylate such as a trimethylolpropane tri(meth)acrylate or a pentaerythritol tri(meth)acrylate, a tetrafunctional (meth)acrylate such as a pentaerythritol tetra(meth)acrylate or a ditrimethylolpropane tetra(meth)acrylate, or a hexafunctional (meth)acrylate such as a dipentaerythritol hexa(meth)acrylate. 
     If a polyfunctional acrylic monomer is used as the photopolymerizable resin, the content ratio of the polyfunctional acrylic monomer in the resin composition is not limited in particular, but is preferably 1 to 50 wt. %, and particularly preferably, 5% to 25 wt. % of the resin composition constituting the adhesive layer  12 . If the content ratio of the polyfunctional acrylic monomer is lower than the above-described lower limit, the strength of the resin spacer after exposure and development may not be sufficient. On the other hand, if the content ratio of the polyfunctional acrylic monomer exceeds the above-described upper limit, it may be difficult to thermocompression-bond a substrate through the resin spacer. 
     As the photopolymerizable resin, the above-described acrylic monomer may be used in combination with an epoxy vinyl ester resin. Consequently, the epoxy vinyl ester resin radical-polymerizes with the acrylic monomer at the time of exposure. Thus, it is possible to further improve the strength of the resin spacer. In addition, use of the epoxy vinyl ester resin improves the resolvability of unexposed portions of the adhesive layer  12  into an alkaline water solution. Thus, it is possible to reduce residues after development. 
     As the epoxy vinyl ester resin, it is possible to use a 2-hydroxy-3-phenoxypropyl acrylate, an EPOLIGHT 40E methacryl adduct, an EPOLIGHT 70P acrylic acid adduct, an EPOLIGHT 200P acrylic acid adduct, an EPOLIGHT 80MF acrylic acid adduct, an EPOLIGHT 3002 methacrylic acid adduct, an EPOLIGHT 3002 acrylic acid adduct, an EPOLIGHT 1600 acrylic acid adduct, a bisphenol-A diglycidyl ether methacrylic acid adduct, bisphenol-A diglycidyl ether acrylic acid adduct, an EPOLIGHT 200E acrylic acid adduct, an EPOLIGHT 400E acrylic acid adduct, or the like. 
     The content ratio of the epoxy vinyl ester resin in the resin composition is not limited in particular, but is preferably 3 to 30 wt. %, and more preferably, 5 to 15 wt. % of the resin composition constituting the adhesive layer  12 . If the content ratio of the epoxy vinyl ester resin is lower than the above-described lower limit, the water absorbency of the resin spacer may degrade, thus causing dew condensation within a hollow package. On the other hand, if the content ratio of the epoxy vinyl ester resin is higher than the above-described upper limit, the resolvability of unexposed portions of the adhesive layer  12  into an alkaline water solution may not be sufficient. Thus, residues may be produced after development. It is possible, however, to prevent residues from being produced after development, while still maintaining the water absorbency of the resin spacer, by setting the content ratio of the epoxy vinyl ester resin to within the range of 5 to 15 wt. % in particular. 
     Examples of a thermosetting resin that can be contained in the resin composition of the adhesive layer  12  include novolac-type phenol resins such as a phenol novolac resin, a cresol novolac resin and a bisphenol-A novolac resin, phenol resins such a resole phenol resin, bisphenol-type epoxy resins such as a bisphenol-A epoxy resin and a bisphenol-F epoxy resin, novolac-type epoxy resins such as a novolac epoxy resin and a cresol novolac epoxy resin, epoxy resins such as a biphenyl-type epoxy resin, a stilbene-type epoxy resin, a triphenolmethane-type epoxy resin, an alkyl modified triphenolmethane-type epoxy resin, a triazine nucleus-containing epoxy resin, a dicyclopentadiene modified phenol-type epoxy resin and a silicone modified epoxy resin, a urea resin, resins having a triazine ring such as a melamine resin, an unsaturated polyester resin, a bismaleimide resin, a polyurethane resin, a diallyl phthalate resin, a silicone resin, resins having a benzoxazine ring, and a cyanate ester resin. Among these examples, it is preferable to use an epoxy resin superior in heat resistance and adhesiveness. 
     Here, in a case where an epoxy resin is used as the thermosetting resin, an epoxy resin in a solid state at room temperature (for example, a bisphenol-type epoxy resin) and an epoxy resin in a liquid state at room temperature (for example, a silicone modified epoxy resin) may be used concomitantly. Consequently, it is possible to realize characteristics required of the adhesive layer  12  (flexibility, pattern resolution, adhesiveness, and the like) in a balanced manner, while still maintaining the heat resistance of the resin spacer. 
     The content ratio of the thermosetting resin in the resin composition is not limited in particular, but is preferably 10 to 40 wt. %, and more preferably, 15 to 35 wt. % of the entire resin composition constituting the adhesive layer  12 . If the content ratio of the thermosetting resin is lower than the above-described lower limit, the heat resistance of the resin spacer may not be sufficient. On the other hand, if the content ratio of the thermosetting resin is higher than the above-described upper limit, the toughness of the adhesive layer  12  may not be sufficient. 
     While an alkali-soluble resin, a photopolymerizable resin and a thermosetting resin have been described heretofore as main ingredients constituting the resin composition of the adhesive layer  12 , the resin composition of the adhesive layer  12  may contain various other types of additives, in addition to these ingredients. 
     For example, a photopolymerization initiator may be added to the resin composition for the purpose of improving the pattern resolution of the adhesive layer  12 . 
     Examples of the photopolymerization initiator include benzophenone, acetophenone, benzoin, benzoin isobutyl ether, benzoin methyl benzoate, benzoin benzoic acid, benzoin methyl ether, benzylphenyl sulfide, benzyl, dibenzyl, and diacetyl. 
     The content ratio of the photopolymerization initiator in the resin composition is not limited in particular, but is preferably 0.5 to 5 wt. %, and more preferably, 1 to 3 wt. % of the entire photosensitive resin composition. If the content ratio of the photopolymerization initiator is lower than the above-described lower limit, the effect of initiating a photopolymerization reaction may not be sufficient. If the content ratio of the photopolymerization initiator is higher than the above-described upper limit, the storage stability of the film for a resin spacer  10  may degrade or the pattern resolution of the adhesive layer  12  may decrease. 
     In addition, an auxiliary alkaline developing agent may be added to the resin composition for the purpose of improving the alkali developability of the adhesive layer  12 . 
     Examples of the auxiliary alkaline developing agent include a phenol novolac resin, phenol aralkyl resins having a phenylene skeleton, and phenol resins such as a trisphenylmethane-type phenol resin, a biphenyl aralkyl-type phenol resin, an α-naphthol aralkyl-type phenol resin, and a β-naphthol aralkyl-type phenol resin. Among these examples, a phenol novolac resin is preferable. Consequently, it is possible to perform a development treatment using an alkaline water solution without producing residues. 
     The content ratio of the auxiliary alkaline developing agent in the resin composition is not limited in particular, but is preferably 1 to 20 wt. %, and more preferably, 2 to 10 wt. % of the entire resin composition of the adhesive layer  12 . By setting the content ratio of the auxiliary alkaline developing agent to within the above-described range, it is possible improve alkali developability without impairing other characteristics. 
     In addition, an inorganic filler may be added to the resin composition for the purpose of improving characteristics, such as heat resistance, dimensional stability, and moisture resistance. 
     Examples of such an inorganic filler may include talc, fired clay, unfired clay, mica, silicates such as glass, a titanium oxide, alumina, oxides of silica powder such as molten silica (molten spherical silica and molten crushed silica) and crystalline silica, carbonates such as calcium carbonate, magnesium carbonate and hydrotalcite, hydroxides such as an aluminum hydroxide, a magnesium hydroxide and a calcium hydroxide, hydrosulfates or subsulfates such as a barium sulfate, a calcium sulfate and a calcium sulfite, borates such as a zinc borate, a barium metaborate, an aluminum borate, a calcium borate and a sodium borate, and nitrides such as an aluminum nitride, a boron nitride and a silicon nitride. These inorganic fillers may be used either independently or in combination. Among these examples, silica powder, such as molten silica and crystalline silica, is preferable and molten spherical silica is particularly preferable. 
     The content ratio of the inorganic filler in the resin composition is preferably 5 wt. % or lower from the viewpoint of reducing residues after patterning treatment. 
     Note that the shape of the inorganic filler is not limited in particular, but is preferably spherical. Consequently, it is possible to obtain a film for a resin spacer  10  free of anisotropy in characteristics. 
     The average particle diameter of the inorganic filler is not limited in particular, either, but is preferably 5 to 50 nm, and particularly preferably, 10 to 30 nm. If the average particle diameter of the inorganic filler is smaller than the above-described lower limit, the strength of the resin spacer may not be sufficient due to the presence of aggregates of the inorganic filler in the resin spacer. On the other hand, if the average particle diameter of the inorganic filler is larger than the above-described upper limit, radiant rays irradiated to the adhesive layer  12  at the time of exposure are scattered by the inorganic filler. As a result, the pattern resolution of the adhesive layer  12  may not be sufficient. 
     In addition to the additives described above, a plastic resin, a leveling agent, an antifoam agent, a coupling agent and the like may be added, as necessary, to the resin composition of the adhesive layer  12 . 
     (Light-Receiving Device) 
     Next, a description will be given of a light-receiving device manufactured using the above-described film for a resin spacer. 
       FIG. 2  is a cross-sectional view illustrating a structural example of a light-receiving device according to the present invention. 
     As illustrated in the figure, a light-receiving device  20  is comprised mainly of a base substrate  22  in which a photoelectric conversion part  22   a  is formed; a transparent substrate  24  disposed so as to face the base substrate  22 ; and a resin spacer  26  disposed between the base substrate  22  and the transparent substrate  24  so as to surround the photoelectric conversion part  22   a.    
     The base substrate  22  is made of monocrystalline silicon or the like and, on a surface of the base substrate  22 , the photoelectric conversion part  22   a  is formed. This photoelectric conversion part  22   a  is formed of a CCD (Charge Coupled Device) circuit or a CMOS (Complementary Metal Oxide Semiconductor) circuit. 
     A light-receiving part  28  made of a microlens array is formed on the photoelectric conversion part  22   a  of the base substrate  22 . 
     The resin spacer  26  surrounding the photoelectric conversion part  22   a  of the base substrate  22  is a spacer made of a resin formed using the above-described film for a resin spacer  10  (see  FIG. 1 ). 
     In addition, the transparent substrate  24  disposed opposite to the base substrate  22  is made of, for example, an acrylic resin, a polyethylene terephthalate resin (PET), or glass. 
     The light-receiving device  20  having such a configuration as described above can be used as a solid-state image pickup device. In this case, light entering the light-receiving device  20  through the transparent substrate  24  is received by the light-receiving part  28  and converted into an electrical signal at the photoelectric conversion part  22   a  of the base substrate  22 . Then, the electrical signal converted from the light at the photoelectric conversion part  22   a  is converted into image data by means of predetermined signal processing. 
     For the reasons described below, the above-described light-receiving device  20  is less liable to imaging failure resulting from dew condensation due to the characteristics of the film for a resin spacer  10  used to form the resin spacer  26 . 
     As has been already described, the film for a resin spacer  10  is adapted so that the moisture permeation rate of the film&#39;s adhesive layer after exposure and heat curing is 12 g/m 2 /24 h or higher. Accordingly, if humidity is higher inside the hollow package of the light-receiving device  20  than outside the hollow package, moisture within the hollow package is drained through the resin spacer  26 . Thus, dew condensation is prevented from occurring within the hollow package of the light-receiving device  20 . 
     Although an example is shown in  FIG. 2  in which the light-receiving part  28  made of a microlens array is formed only on the photoelectric conversion part  22   a  of the base substrate  22 , the present invention is not limited to this configuration. Alternatively, the microlens array may be formed across the entire surface of the base substrate  22 . 
       FIG. 3  is a cross-sectional view illustrating a structural example a light-receiving device in which a microlens array is formed across the entire surface of the base substrate. As illustrated in the figure, a microlens array  29  is formed across the entire surface of the base substrate  22 . Only a region of the microlens array  29  surrounded by the resin spacer  26  functions as a light-receiving part. Note that the rest of the configuration is the same as the structural example of the light-receiving device illustrated in  FIG. 2  and, therefore, will not be described again here. 
     (Method for Manufacturing Light-receiving Device) 
     Next, a description will be given of a method for manufacturing a light-receiving device having the above-described configuration. 
       FIG. 4  is a process drawing illustrating one example of a method for manufacturing a light-receiving device according to the present invention. 
     First, as illustrated in  FIG. 4(   a ), a microlens array  29  is formed on a surface of a silicon wafer  30  in which a plurality of photoelectric conversion parts  22   a  is formed. 
     In the figure, an example is shown in which the microlens array  29  is formed across the entire surface of the silicon wafer  30 . Alternatively, the microlens array  29  may be selectively formed only on the photoelectric conversion part  22   a  of the silicon wafer  30 . 
     In addition to the formation of the microlens array  29 , the above-described film for a resin spacer  10  is previously cut in conformity to the shape of silicon wafer  30 . 
     The film for a resin spacer  10  can be cut by an optional method. For example, as illustrated in  FIG. 5A , the film for a resin spacer  10  may be placed on a film contact part  100   b  of a cutting table  100 , and then cut by a cutter  104  provided in an opening of the cutting table  100 . At this time, the film for a resin spacer  10  may be cut with the film held down from the cover film  14  side by using a cutting aid member  106 , from the viewpoint of preventing flexure in the film for a resin spacer  10  when the film is cut. 
     Here, the film for a resin spacer  10  is preferably kept to a half-cut state, i.e., a state in which the film is cut to a depth approximately half the thickness of the cover film  14  by adjusting the amount of stab by the cutter  104 . Consequently, by conveying the film for a resin spacer  10  as a whole in a direction shown by an arrow A, as illustrated in  FIG. 5B , it is possible to easily move a half-cut portion of the film for a resin spacer  10  to the position of a silicon wafer  30  which is a substrate to be laminated. The film for a resin spacer  10  is conveyed with the film separated from the film contact part  100   b  by moving the cutting aid member  106  upwardly (in a direction shown by an arrow B in  FIG. 5B ). After the film for a resin spacer  10  is conveyed, the cutting aid member  106  is moved downwardly (in a direction opposite to the direction of the arrow B) to revert to the condition illustrated in  FIG. 5A  and repeat the cutting of the film for a resin spacer  10 . 
     Note that the film for a resin spacer  10  is such that an adhesion force C 1  between an adhesive layer  12  and the cover film  14  and an adhesion force D between the adhesive layer  12  and a silicone resin are set so as to satisfy the condition C 1 &gt;D. Consequently, it is possible to reduce adherence of a resin composition to the film contact part  100   b  at the time of the above-described film cutting. 
     Next, as illustrated in  FIG. 4(   b ), the film for a resin spacer  10  cut in conformity to the shape of the silicon wafer  30  is laminated on the microlens array  29  formed on the silicon wafer  30 . 
     Then, the adhesive layer  12  of the film for a resin spacer  10  is exposed and developed to form a resin spacer  26  surrounding the photoelectric conversion part  22   a  on the microlens  29 , as illustrated in  FIG. 4(   c ). The exposure and development treatments of the adhesive layer  12  are specifically performed in the following manner. 
     First, radiant rays (for example, ultraviolet light) are selectively irradiated to the adhesive layer  12  of the film for a resin spacer  10  through a photomask. Consequently, only a portion of the adhesive layer  12  irradiated with radiant rays is light-cured. Thereafter, the cover film  14  is peeled off from the adhesive layer  12 . The adhesive layer  12  is developed using a developing fluid, such as an alkaline water solution, to remove unexposed portions (portions not irradiated with radiant rays) of the adhesive layer  12 . In this way, the resin spacer  26  surrounding the photoelectric conversion parts  22   a  is formed as illustrated in, for example,  FIG. 6 . 
     Next, as illustrated in  FIG. 4(   d ), a transparent substrate  24  is bonded to the silicon wafer  30  through the resin spacer  26 . The transparent substrate  24  and the silicon wafer  30  may be bonded to each other only by heating or pressurization or by both heating and pressurization. 
     Thereafter, the silicon wafer  30  is diced from a side opposite to the transparent substrate  24  side, as illustrated in  FIG. 4(   e ), to form a groove  32  in a position corresponding to each resin spacer  26 . 
     Note that while the silicon wafer  30  is being diced, heat is generated due to friction between a dicing saw and the silicon wafer  30 . Accordingly, dicing is preferably performed while feeding water. 
     Finally, incisions are made by the dicing saw from the transparent substrate  24  side to divide the silicon wafer  30  and the transparent substrate  24  in units of photoelectric conversion parts  22   a . Thus, there are obtained light-receiving devices  20  illustrated in  FIG. 4(   f ). 
     Note that though not illustrated, an electrical insulating layer, such as a silicon oxide film, is formed and a metal film is formed by means of sputtering or the like on side surfaces of each groove  32  and on a bottom face of the silicon wafer  30  after the dicing of the silicon wafer  30 . This metal film functions as a signal transmission path for transferring an electrical signal output from each photoelectric conversion part  22   a  to the external substrate side when each light-receiving device  20  is mounted on an external substrate through solder bumps or the like. 
     Also note that though an example is shown in  FIG. 4  in which the resin spacer  26  is formed on the silicon wafer  30  side, the present invention is not limited to this configuration. Alternatively, the resin spacer  26  may be formed on the transparent substrate  24  side. In this case, the film for a resin spacer  10  is first laminated on the transparent substrate  24 , and is then subjected to exposure and development treatments, thereby forming the resin spacer  26  on the transparent substrate  24 . Then, the transparent substrate  24  and the silicon wafer  30  are bonded to each other through the resin spacer  26 , with the transparent substrate  24  and the silicon wafer  30  aligned with each other so that the photoelectric conversion parts  22   a  of the silicon wafer  30  are surrounded by the resin spacer  26 . Finally, the transparent substrate  24  and the silicon wafer  30  bonded to each other through the resin spacer  26  are divided in units of photoelectric conversion parts  22   a  by the same methods as those illustrated in  FIGS. 4(   e ) and  4 ( f ). 
     (MEMS Device) 
     Next, a description will be given of a MEMS device manufactured using the above-described film for a resin spacer. 
       FIG. 7  is a cross-sectional view illustrating a structural example of a MEMS device according to the present invention. 
     As illustrated in the figure, a MEMS device  40  is comprised mainly of a base substrate  44  in which a functional part  42  is formed; a cover substrate  46  disposed so as to face the base substrate  44 ; and a resin spacer  26  disposed between the base substrate  44  and the cover substrate  46 , so as to surround the functional part  42 . 
     The base substrate  44  is made of monocrystalline silicon or the like, and a functional part  42  including MEMS elements, such as a pressure sensor and an acceleration sensor, is formed on the base substrate  44 . 
     The resin spacer  26  surrounding the functional part  42  on the base substrate  44  is a spacer made of a resin formed using the above-described film for a resin spacer  10  (see  FIG. 1 ). 
     In addition, the cover substrate  46  facing the base substrate  44  is made of, for example, an acrylic resin, a polyethylene terephthalate resin (PET), glass, or monocrystalline silicon. 
     Note that in the example illustrated in  FIG. 7 , a description has been given of a MEMS device having a hollow package structure in which the functional part  42  including MEMS elements is surrounded by the resin spacer  26 . The present invention is not limited to this MEMS device, however. Alternatively, the present invention may be applied to various other MEMS devices including a resin spacers, such as a printer head, an optical scanner, and a flow path module. 
     (Method for Manufacturing MEMS Device) 
     Next, a description will be given of a method for manufacturing a MEMS device having the above-described configuration. 
       FIG. 8  is a process drawing illustrating one example of a method for manufacturing a MEMS device according to the present invention. 
     First, there is prepared a silicon wafer  50  in which a plurality of functional parts  42  including a MEMS element is formed, as illustrated in  FIG. 8(   a ). In addition, the above-described film for a resin spacer  10  is previously cut in conformity to the shape of the silicon wafer  50 . The film for a resin spacer  10  may be cut using the same method as used in the already-described method for manufacturing a light-receiving device. 
     Next, as illustrated in  FIG. 8(   b ), the film for a resin spacer  10  cut in conformity to the shape of the silicon wafer  50  is laminated thereon. 
     Then, the adhesive layer  12  of the film for a resin spacer  10  is exposed and developed to form the resin spacer  26  surrounding the functional part  42  on the silicon wafer  50 , as illustrated in  FIG. 8(   c ). The exposure and development treatments of the adhesive layer  12  may be performed using the same method as used in the already-described method for manufacturing a light-receiving device. 
     Next, as illustrated in  FIG. 8(   d ), a cover substrate  46  is bonded to the silicon wafer  50  through the resin spacer  26 . The cover substrate  46  and the silicon wafer  50  may be bonded to each other only by heating or pressurization or by both heating and pressurization. 
     Thereafter, the silicon wafer  50  is diced from a side opposite to the cover substrate  46  side, as illustrated in  FIG. 8(   e ), to form a groove  52  in a position corresponding to each resin spacer  26 . 
     Note that while the silicon wafer  50  is being diced, heat is generated due to friction between a dicing saw and the silicon wafer  50 . Accordingly, dicing is preferably performed while feeding water. 
     Finally, incisions are made by the dicing saw from the cover substrate  46  side to divide the silicon wafer  50  and the cover substrate  46  in units of functional parts  42 . Thus, there are obtained MEMS devices  40  illustrated in  FIG. 8(   f ). 
     Note that though an example is shown in  FIG. 8  in which the resin spacer  26  is formed on the silicon wafer  50  side, the present invention is not limited to this configuration. Alternatively, the resin spacer  26  may be formed on the cover substrate  46  side. In this case, the film for a resin spacer  10  is first laminated on the cover substrate  46 , and is then subjected to exposure and development treatments, thereby forming the resin spacer  26  on the cover substrate  46 . Then, the cover substrate  46  and the silicon wafer  50  are bonded to each other through the resin spacer  26 , with the cover substrate  46  and the silicon wafer  50  aligned with each other so that the functional part  42  on the silicon wafer  50  is surrounded by the resin spacer  26 . Finally, the cover substrate  46  and the silicon wafer  50  bonded to each other through the resin spacer  26  are divided in units of functional parts  42  by the same methods as those illustrated in  FIGS. 8(   e ) and  8 ( f ). 
     EXAMPLES 
     Hereinafter, the present invention will be described in detail according to practical and comparative examples, though the invention is not limited to these examples. 
     Practical Example 1 
     1. Synthesis of Alkali-soluble Resin (Methacryloyl Modified Novolac-type Bisphenol-A Resin) 
     500 g of a MEK (methyl ethyl ketone) solution with a 60% solid content of a novolac-type bisphenol-A resin (PHENOLITE LF-4871 made by Dainippon Ink and Chemicals, Incorporated) was poured into a 2 L flask. 1.5 g of tributylamine and 0.15 g of hydroquinone were added to this solution as a catalyst and a polymerization inhibitor, respectively. The solution was warmed to 100° C. 180.9 g of glycidyl methacrylate was dropped into the solution in 30 minutes, and the solution was agitated and reacted at 100° C. for 5 hours. Thus, there was obtained a methacryloyl modified novolac-type bisphenol-A resin MPN001 (methacryloyl modification ratio of 50%) with a 74% solid content. 
     2. Preparation of Resin Varnish 
     There were weighed 60 wt. % of the above-described methacryloyl modified novolac-type bisphenol-A resin MPN001 (MPN001) as an alkali-soluble resin, 10 wt. % of a bisphenol-A type epoxy resin (EP-1001 made by Japan Epoxy Resin Co., Ltd.) and 5 wt. % of a cresol novolac-type epoxy resin (EOCN-1020-70 made by Nippon Kayaku Co., Ltd.) as a thermosetting resin and an epoxy resin, 5 wt. % of epoxy ester (Epoxy Ester 3002M made by KYOEISHA CHEMICAL Co., LTD.) as a photopolymerizable resin, 15 wt. % of trimethylolpropane trimethacrylate (LIGHT-ESTER TMP made by KYOEISHA CHEMICAL Co., LTD.), 2 wt. % of a photopolymerization initiator (IRGACURE 651 made by Ciba Specialty Chemicals Corporation), and 3 wt. % of a phenol novolac resin (PR53647 made by Sumitomo Bakelite Company, Limited). Using a disperser, these materials were agitated at a revolution speed of 3000 rpm for one hour, thereby preparing resin varnish. 
     3. Fabrication of Film for Resin Spacer The resin varnish was coated on a polyester film (MRX50, 50 μm in thickness, made by Mitsubishi Plastics, Inc.) serving as a supporting base material by using a comma coater, and dried at 80° C. for 20 minutes. Thus, there was obtained a film for a resin spacer having a 50 μm-thick adhesive layer. 
     Practical Example 2 
     Practical Example 2 was the same as Practical Example 1, except that the composition of the resin varnish in Practical Example 1 was set as described below. The ingredient amount of trimethylolpropane trimethacrylate was set to 20 wt. %, the ingredient amount of bisphenol-A type epoxy resin was set to 20 wt. %, and the ingredient amount of (meth)acrylic modified bis-A novolac resin was set to 45 wt. %. 
     Practical Example 3 
     Practical Example 3 was the same as Practical Example 1, except that the composition of the resin varnish in Practical Example 1 was set as described below. The ingredient amount of trimethylolpropane trimethacrylate was set to 20 wt. %, the ingredient amount of bisphenol-A type epoxy resin was set to 25 wt. %, and the ingredient amount of (meth)acrylic modified bis-A novolac resin was set to 40 wt. %. 
     Practical Example 4 
     Practical Example 4 was the same as Practical Example 1, except that the composition of the resin varnish in Practical Example 1 was set as described below. The ingredient amount of trimethylolpropane trimethacrylate was set to 20 wt. %, the ingredient amount of bisphenol-A type epoxy resin was set to 5 wt. %, the ingredient amount of cresol novolac-type epoxy resin (EOCN-1020-70 made by Nippon Kayaku Co., Ltd.) was set to 20 wt. %, and the ingredient amount of (meth)acrylic modified bis-A novolac resin was set to 45 wt. %. 
     Practical Example 5 
     Practical Example 5 was the same as Practical Example 1, except that the composition of the resin varnish in Practical Example 1 was set as described below. The ingredient amount of epoxy ester (Epoxy Ester 3002M made by KYOEISHA CHEMICAL Co., LTD.) was set to 1 wt. %, the ingredient amount of trimethylolpropane trimethacrylate was set to 5 wt. %, the ingredient amount of bisphenol-A type epoxy resin was set to 8 wt. %, the ingredient amount of cresol novolac-type epoxy resin (EOCN-1020-70 made by Nippon Kayaku Co., Ltd.) was set to 25 wt. %, and the ingredient amount of (meth)acrylic modified bis-A novolac resin was set to 56 wt. %. 
     Comparative Example 1 
     Comparative Example 1 in which the ingredient amount of resin varnish was varied was set, in addition to the practical examples described above. 
     The table of  FIG. 9  shows the ingredient amounts of films for a resin spacer in Practical Examples 1 to 5 and Comparative Example 1. 
     (Evaluation of Films for Resin Spacer) 
     Using the films for a resin spacer obtained as described above, evaluations were made on resin adherability at the time of film cutting, provisional fixability to a substrate to be laminated, and the detachability of a cover film. 
     (1) Measurement of Adhesion Forces 
     The films for a resin spacer obtained in Practical Examples 1 to 5 and Comparative Example 1 were cut to a width of 18 mm. The cover film side of each film was fixed to a glass epoxy substrate with a double-sided adhesive tape. In addition, Sellotape® (18 mm-wide tape made by Mitsubishi Uni) was tightly laminated on the adhesive layer of each film by using a rubber roller, so as not to let in air bubbles. The Sellotape® was pulled with a tensile testing machine in a 180° direction under the pulling rate condition of 1000 mm/min to measure an adhesion force C 1  (N/m). The table of  FIG. 10  shows measurement results. 
     Likewise, the films for a resin spacer obtained in Practical Examples 1 to 5 and Comparative Example 1 were cut to a width of 18 mm. The cover film side of each film was fixed to a glass epoxy substrate with a double-sided adhesive tape. Thereafter, each film was exposed on the cumulative light exposure condition of 700 mJ/cm 2  by using light of a 365 nm wavelength. In addition, Sellotape® (18 mm-wide tape made by Mitsubishi Uni) was tightly laminated on the adhesive layer of each film by using a rubber roller, so as not to let in air bubbles. The Sellotape® was pulled with a tensile testing machine in a 180° direction under the pulling rate condition of 1000 mm/min to measure an adhesion force C 2  (N/m). The table of  FIG. 10  shows measurement results. 
     In addition, the films for a resin spacer obtained in Practical Examples 1 to 5 and Comparative Example 1 were cut to a width of 36 mm. The adhesive layer side of each film was overlapped on a silicone resin sheet (composite functional silicone sheet made by Nippa Co., Ltd.). Under this condition, the adhesive layer side of each film for a resin spacer was laminated on the silicone resin sheet by taking advantage of the self weight of a rubber roller (roll weight: 400 g, roll width: 16.5 cm). A silicone resin sheet with an adhesive layer obtained in this way was specified as an evaluation sample used to measure an adhesion force D between an adhesive layer and a silicone resin before exposure. The base material of the evaluation sample thus prepared was pulled with a tensile testing machine in a 180° direction under the pulling rate condition of 1000 mm/min to measure the adhesion force D (N/m). The table of  FIG. 10  shows measurement results. 
     The films for a resin spacer obtained in Practical Examples 1 to 5 and Comparative Example 1 were respectively laminated on an 8-inch silicon wafer (part number: PW, 725 μm in thickness, made by SUMCO Corporation) by using a roll laminator (roll temperature: 60° C., rolling rate: 0.3 m/min, syringe pressure: 2.0 kgf/cm 2 ). A silicon wafer with an adhesive layer obtained in this way was specified as an evaluation sample used to measure an adhesion force E 1  between the adhesive layer and the silicon wafer before exposure. 
     In addition, a sample obtained by exposing the above-described silicon wafer with an adhesive layer on the cumulative light exposure condition of 700 mJ/cm 2  by using light of a 365 nm wavelength was specified as an evaluation sample used to measure an adhesion force E 2  between the adhesive layer and the silicon wafer after exposure. 
     Then, Sellotape® (18 mm-wide tape made by Mitsubishi Uni) was tightly attached to the adhesive layer of the above-described prepared evaluation sample by using a rubber roller, so as not to let in air bubbles. An 18 mm-wide incision was made in the adhesive layer. The Sellotape® was pulled with a tensile testing machine in a 180° direction under the pulling rate condition of 1000 mm/min to measure the adhesion forces E 1  (N/m) and E 2  (N/m). The table of  FIG. 10  shows measurement results. 
     (2) Resin Adherability at the Time of Film Cutting 
     The films for a resin spacer obtained in Practical Examples 1 to 5 and Comparative Example 1 were cut to a shape 1 mm smaller than the diameter of the silicon wafer by using a film laminator (Team  100  made by Takatori Corporation). After film cutting, a cutting stage was visually observed to evaluate resin adherability to the cutting stage according to the below-described criteria. The table of  FIG. 10  shows evaluation results. 
     Acceptable: No visually observable resin deposits are present on the cutting stage. 
     Defective: Visually observable resin deposits are present on the cutting stage. 
     (3) Provisional Fixability to Substrate to be Laminated 
     The films for a resin spacer obtained in Practical Examples 1 to 5 and Comparative Example 1 were respectively laminated on an 8-inch silicon wafer (part number: PW, 725 μm in thickness, made by SUMCO Corporation) by using a roll laminator (roll temperature: 60° C., rolling rate: 0.3 m/min, syringe pressure: 2.0 kgf/cm 2 ). 
     The silicon wafer on which a film for a resin spacer was laminated was visually observed to evaluate provisional fixability to a substrate to be laminated according to the below-described criteria. The table of  FIG. 10  shows evaluation results. 
     Acceptable: The film is not peeled off across the entire surface of the silicon wafer. 
     Defective: The film is partially peeled off at an end face of the silicon wafer. 
     (4) Detachability of Cover Film 
     The films for a resin spacer obtained in Practical Examples 1 to 5 and Comparative Example 1 were respectively laminated on a silicon wafer (part number: PW, 725 μm in thickness, made by SUMCO Corporation) by using a roll laminator (roll temperature: 60° C., rolling rate: 0.3 m/min, syringe pressure: 2.0 kgf/cm 2 ). Subsequently, exposure using light of a 365 nm wavelength was performed on the film for a resin spacer on the silicon wafer on the cumulative light exposure condition of 700 mJ/cm 2 . Thereafter, the cover film was peeled off from the adhesive layer. 
     The cover film peeled off from the adhesive layer was visually observed to evaluate the detachability of the cover film according to the below-described criteria. The table of  FIG. 10  shows evaluation results. 
     Acceptable: No visually observable resin deposits are present on the cover film, and neither lift nor delamination is observed in the adhesive layer on the silicon wafer. 
     Defective: Visually observable resin deposits are present on the cover film, and either lift or delamination is observed in the adhesive layer on the silicon wafer. 
     As is understood from the table of  FIG. 10 , resin adherence to the cutting stage did not occur in Practical Examples 1 to 5 in which the adhesion forces C 1  and D satisfied the condition C 1 &gt;D. In addition, if the adhesion force E 1  satisfied the condition E 1 &gt;200 N/m, it was possible to provisionally fix each film for a resin spacer onto the silicon wafer in a reliable manner. In addition, if the adhesion forces C 2  and E 2  satisfied the condition C 2 &lt;E 2 , resin adherence to the cover film did not occur when the cover film was peeled off. 
     In contrast, resin adherence to the cutting stage occurred in Comparative Example 1 in which the adhesion forces C 1  and D did not satisfy the condition C 1 &gt;D. 
     (Evaluation of Resin Spacer Characteristics) 
     For the above-described films for a resin spacer, resin spacer characteristics were evaluated as described below. 
     (1) Elastic Modulus 
     Exposure using light of a 365 nm wavelength was performed on the films for a resin spacer obtained in Practical Examples 1 to 5 and Comparative Example 1 on the cumulative light exposure condition of 700 mJ/cm 2 . Subsequently, a cover film was peeled off from the adhesive layer of each film for a resin spacer. Three adhesive layers were stacked to measure a storage elastic modulus G′ with a dynamic viscoelasticity measuring apparatus Rheo Stress RS150 (made by HAAKE; measuring frequency: 1 Hz, gap pitch: 100 μm, measurement temperature range: 25 to 200° C., rate of temperature rise: 10° C./min), thereby determining an elastic modulus at 80° C. The table of  FIG. 11  shows measurement results. 
     (2) Moisture Permeation Rate 
     Using a laminator set at 60° C., films for a resin spacer were bonded to fabricate a 100 μm-thick adhesive layer. The adhesive layer was exposed on the cumulative light exposure condition of 700 mJ/cm 2  by using light of a 365 nm wavelength. Thereafter, the adhesive layer was heat-cured on the condition of 180° C./2 hours. The exposed and heat-cured adhesive layer thus obtained was evaluated in compliance with the water vapor permeability cup method (JIS Z0208) under the ambient condition of 40° C./90%, thereby measuring a moisture permeation rate. The table of  FIG. 11  shows measurement results. 
     (3) Resin Spacer Characteristics 
     An evaluation sample for evaluating resin spacer characteristics was fabricated according to the following procedure. 
     A film for a resin spacer was laminated on an 8-inch silicon wafer (base substrate) (part number: PW, 725 μm in thickness, made by SUMCO Corporation) by using a roll laminator (roll temperature: 60° C., rolling rate: 0.3 m/min, syringe pressure: 2.0 kgf/cm 2 ), thereby obtaining a silicon wafer with a film for a resin spacer. Next, a mask of an exposure apparatus and the above-described silicon wafer were aligned with each other by using light of a 600 nm wavelength. Next, the film was exposed on the cumulative light exposure condition of 700 mJ/cm 2  by using light of a 365 nm wavelength. Thereafter, the cover film was peeled off from the adhesive layer. In addition, the adhesive layer was subjected to a development treatment (pressure: 0.3 MPa, time: 90 sec) using a 2.38% TMAH (tetramethylammonium hydroxide) to form a 0.6 mm-wide resin spacer having a 5 mm square opening. 
     Next, the above-described silicon wafer in which the resin spacer was formed and an 8-inch transparent substrate were set on a substrate bonder (SB8e made by SÜSS MicroTec AG.) to pressure-bond the silicon wafer and the 8-inch transparent substrate. In addition, the bonded wafer and substrate were post-cured on the condition of 150° C., 90 minutes. A bonded product of the silicon wafer and the 8-inch transparent substrate thus obtained was diced to a predetermined size by using a dicing saw to obtain a light-receiving device as an evaluation sample. 
     The resin spacer of the above-described evaluation sample was visually observed to evaluate the flowability (degree of collapse) of the resin spacer according to the below-described criteria. The table of  FIG. 11  shows evaluation results. 
     Acceptable: No changes are observed in the dimensions of the resin spacer before and after thermocompression bonding. 
     Defective: The resin spacer after thermocompression bonding flows to a large degree, thus resulting in significant variations in both dimensions and shape. 
     Next, the above-described evaluation sample was allowed to stand for 168 hours under the temperature and humidity conditions of 85° C. and 85%, and then exposed to the ambient temperature and humidity conditions of 25° C. and 50%. The inside of a hollow package of the evaluation sample was observed with a microscope. Then, evaluations were made, according to the below-described criteria, as to whether or not dew condensation was present inside the hollow package. The table of  FIG. 11  shows evaluation results. 
     Acceptable: No dew condensation is present inside the hollow package. 
     Defective: Dew condensation is present inside the hollow package. 
     In addition, the above-described evaluation sample was allowed to stand for 168 hours under the temperature and humidity conditions of 85° C. and 85%, and then subjected to a 260° C. solder reflow process three times. Thereafter, the evaluation sample was observed with a microscope. Then, evaluations were made, according to the below-described criteria, on the reliability of the evaluation sample as a light-receiving device. 
     Acceptable: Neither delamination nor chip cracks are present. 
     Defective: Either delamination or chip cracks are present. 
     As is understood from the table of  FIG. 11 , any shape variations in the resin spacer did not occur at the time of pressure-bonding the transparent substrate, if the elastic modulus of the adhesive layer after exposure was 100 Pa or higher. In addition, any dew condensation did not occur inside the hollow package if the moisture permeation rate of the adhesive layer after exposure and heat curing was 12 g/m 2 /24 h or higher. Yet additionally, it has been found that a light-receiving device superior in reliability can be obtained using the films for a resin spacer of Practical Examples 1 to 5. 
     In contrast, shape variations in the resin spacer occurred at the time of pressure-bonding the transparent substrate in Comparative Example 1 in which the elastic modulus of the adhesive layer after exposure was 80 Pa. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10 : Film for a resin spacer,  12 : Adhesive layer,  14 : Cover film,  20 : Light-receiving device,  22 : Base substrate,  22   a : Photoelectric conversion part,  24 : Transparent substrate,  26 : Resin spacer,  28 : Light-receiving part,  29 : Microlens array,  30 : Silicon wafer,  32 : Groove,  40 : MEMS device,  42 : Functional part,  44 : Base substrate,  46 : Cover substrate,  50 : Silicon wafer,  52 : Groove,  100 : Cutting table,  100   a : Stage section,  100   b : Film contact part,  102 : Film for a resin spacer,  104 : Cutter,  106 : Cutting aid member