Abstract:
A solid state image pickup device includes a light receiving area, a plurality of layers, and a light collecting unit disposed above the plurality of layers. The plurality of layers includes first and second layers, such that a pattern of the first layer is formed by a plurality of exposure shots each illuminating a different region, and a pattern of the second layer is formed by a one shot exposure. The patterns of the first and second layers have apertures corresponding to the light receiving area, and the light collecting unit and the aperture of the pattern of the second layer define a light path through which light is incident in the light receiving area, and the pattern of the first layer is disposed outside of the light path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional of U.S. patent application Ser. No. 10/991,396, filed Nov. 19, 2004 and claims benefit of the filing date of that application, and priority benefit of the filing dates of Japanese patent application no. 2003-404544, filed Dec. 3, 2003. The entire disclosure of the prior application is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a solid image pickup device having a plurality of solid image pickup elements comprising photoelectric conversion elements, a method for producing the same, and an image pickup system comprising the solid state image pickup device. 
   2. Related Background Art 
   A solid state image pickup device (hereinafter referred to simply as an image pickup device) having arranged one-dimensionally or two-dimensionally solid state image pickup elements (hereinafter referred to simply as image pickup elements) comprising light receiving areas having photoelectric conversion elements formed thereon is mounted as an area sensor on, for example, a digital camera, video camera, copier, facsimile or the like. Image pickup elements include, for example, CCD image pickup elements and amplification type image pickup elements. 
   An example of a circuit configuration of an amplification type image pickup device is shown in  FIG. 10 . The circuit of the image pickup device of  FIG. 10  has in a unit pixel at least a photodiode  501  and an amplification transistor  502  amplifying optical signals stored in the photodiode  501 . In each pixel, a plurality of drive lines  503  are arranged in a horizontal direction, and vertical output lines  504  and gland lines  505  are arranged in a vertical direction. 
   One pixel is comprised of an image pickup element as shown in  FIG. 11 . The image pickup element of  FIG. 11  has a light receiving area  2002  formed on a substrate  2001 , and a photoelectric conversion element (not shown) comprised of a photodiode  501  (see  FIG. 10 ) is formed on the light receiving area  2002 . The image pickup element of  FIG. 11  further has patterns  2003  and  2004  for operating the photoelectric conversion element on the light receiving area  2002 , an amplifier (not shown) amplifying charges generated in the light receiving area  2002 , and the like. Generally, the patterns  2003  and  2004  are comprised of metals, semiconductors and the like and have a light blocking effect, and therefore the layout thereof is desirably arranged, as shown, such that incident light to the light receiving area  2002  is not blocked. 
   For receiving incident light more efficiently in the image pickup element, a variety of techniques for arranging light collecting means on the light receiving area have been proposed (e.g. Japanese Patent Application Laid-Open No. 8-321595). 
   The pickup element shown in  FIG. 12  comprises a microlens  2210  as light collecting means. According to such a configuration, light incident to the microlens  2210  is collected toward the light receiving area  2202 . An optical path for incident light is narrowed as the light receiving area  2202  is approached, and an opening having a size not so great that the opening interferes with the optical path is formed in a pattern  2205 ′ arranged on the surface side. The patterns  2203  and  2204  are arranged with the optical path for incident light held therebetween. The arrangement position of the patterns  2203  and  2204  is not specifically limited but in the image pickup element shown in the figure, they are designed to be arranged in a position in which they interfere with the optical path for incident light and consequently, the optical path for incident light between the patterns  2203  and  2204  and the light receiving area  2202  has its shape regulated by the patterns  2203  and  2204 . 
   In recent years, the image pickup device (area sensor) has tended to have an increased number of pixels with a large number of image pickup elements arranged in high density. Particularly, in an image pickup device of 35 mm full size standard called a large size, an exposure device for use in production of the image pickup device should be capable of processing a fine line width and performing exposure over a wide area. However, as an area to be exposed increases, the exposure device becomes hard to ensure a uniform line width in the full area and cannot form a fine line width. 
   For this problem, a technique has been proposed in which a pattern designed when a fine pattern is formed on one chip is divided into several patterns, and the divided patterns are exposed in a joined fashion (hereinafter referred to as exposure in joined fashion) (e.g. U.S. Pat. Nos. 5,561,317 and 5,731,131). If a layer not required to have a fine pattern is exposed, exposure in a joined fashion is not required, but a large area may be exposed collectively by a normal exposure process. In this way, a method in which an exposure process is selectively used according to the accuracy of a pattern is called a mix and match. 
   Exposure in a joined fashion will be briefly described with reference to  FIG. 13 .  FIG. 13  is a top view showing an area in which the image pickup element is formed. As shown in  FIG. 13 , if a large size area  2101  exists, and an image pickup element (not shown) is formed in a two-dimensional form in an area  2102  in the area  2101 , for example, a desired pattern is exposed in the area  2102  by exposing two divided areas  2103 L and  2103 R in different steps. In this case, in an area  2105  in which the areas  2103 L and  2103 R overlap one another (joined area), patterns printed in the respective exposure steps are joined together, whereby a pattern with a fine line width is exposed in the area  2102  having a size equal to or greater than a size capable of being exposed with one exposure by the exposure device. 
   As described above, the image pickup device tends to have an increased number of pixels, and is desired to have a large number of image pickup elements arranged in high density over a wide area. Thus, a pattern exposed on a substrate becomes denser and finer. 
   In this way, however, there arises a problem of misalignment of a pattern formation position associated with alignment accuracy of the exposure device if a fined pattern is exposed. For example, in the image pickup element of  FIG. 12 , even if the position of a pattern  2203  shown in the figure is an ideal position in terms of design, the pattern is misaligned like, for example, a pattern  2203 ′ depending on misalignment of the exposure device exposing the pattern  2203 . 
   If the pattern and the optical path interfere with each other, and the optical path is substantially regulated by the pattern, or the pattern does not interfere with the optical path in design but a distance between the pattern and the optical path is very small, the optical path for incident light is deformed, resulting in variations in sensitivity of the image pickup element if the pattern is misaligned. Particularly, the image pickup element formed in the joined area of the image pickup device is significantly influenced by the misalignment described above because divided patterns are individually exposed with a divisional line therebetween in different steps. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a solid state image pickup element having fine patterns formed thereon without being influenced by alignment accuracy of an exposure device, a method for producing the same, and an image pickup system comprising the solid state image pickup element. 
   For achieving the above object, a method for producing a solid state image pickup device of the present invention is a method for producing a solid image pickup device comprising a light receiving area photoelectrically converting incident light, an insulation layer deposited on the light receiving area, a plurality of first patterns arranged with an optical path for the incident light incident to the light receiving area placed therebetween, comprising the steps of: 
   designing the first pattern so that the shortest distance between the each first pattern and the optical path is larger than alignment accuracy of an exposure device exposing the first pattern; 
   designing the first pattern; 
   dividing the first pattern into a plurality of patterns; and 
   exposing in different steps the divided patterns into of the first pattern. More preferably, the shortest distance between the first pattern and the optical path is equal to or greater than three times as large as the alignment accuracy of the exposure device. 
   According to the present invention, even if the first patterns arranged with the optical path for incident light placed therebetween are exposed by exposure in a joined fashion, the divided first patterns are designed to be at a predetermined distance, i.e. a distance longer than the alignment accuracy of the exposure device, from the optical path, and therefore there is no possibility that the first pattern is exposed in a position in which it interferes with the optical path even if misalignment occurs during exposure. 
   The production method according to the present invention may further comprise a step of collectively forming a second pattern having an opening regulating the optical path for incident light. The second pattern may be formed on the surface side from the above first pattern formed by exposure in a joined fashion. 
   The “second pattern” means a pattern formed by one-shot exposure. The “first pattern” described above means a pattern exposed by exposure in a joined fashion. Both patterns do not necessarily have an effect of blocking incident light, but include patterns being transparent to incident light but changing characteristics of a wavelength of the passed incident light. The “patterns changing characteristics of a wavelength of incident light” include, for example, color filters. 
   The production method according to the present invention may further comprise a step of depositing a first insulation layer on the light receiving area before the step of exposing the divided first patterns in different steps, and the step of exposing the divided first patterns in different steps may comprise exposing the first patterns on the first insulation layer, and the production method may further comprise a step of forming a second insulation layer having a reflection index smaller than that of the first insulation layer on the first insulation layer. 
   The solid state image pickup device according to the present invention is a solid state image pickup device comprising: 
   a light receiving area photoelectrically converting incident light; 
   a layer having formed thereon a first pattern formed on the light incidence side from the light receiving area by exposure in a plurality of steps; and 
   a layer having formed thereon a second pattern formed on the light incidence side from the light receiving area by one-shot exposure and having an opening regulating an optical path for the incident light 
   wherein the first pattern is arranged in a position in which the first pattern does not interfere with the optical path for the incident light passing through the opening. 
   The above solid state image pickup device may have further light collecting means for collecting incident light, formed on the light incidence side from the first pattern and the second pattern. The first pattern may be formed between the second pattern and the light receiving area. In this case, the first insulation layer may be formed between the light receiving area and the first pattern, and the second insulation layer having a refraction index smaller than that of the first insulation layer may be formed between the first pattern and the second pattern. The second pattern may be arranged between the first pattern and the light receiving area, or second light collecting means may be formed between the light collecting means and the light receiving area. 
   The image pickup system according to the present invention comprises: 
   a processing unit comprising the above solid state image pickup device according to the present invention or the solid state image pickup device produced by the production method according to the present invention; and processing means for processing output signals from the solid state image pickup apparatus to generate image data; 
   a recording unit storing the image data; 
   an optical unit forming a subject image on a screen surface of the solid state image pickup device; and 
   a control unit controlling the processing unit, the recording unit and the optical unit. With the image pickup system configured in this way, good image data having reduced variations among pixels is obtained. 
   According to the present invention, the first pattern is designed with a predetermined distance provided between the first pattern exposed in a joined fashion and the optical path for incident light, and divided patterns into which the first pattern is divided are exposed in a joined fashion, whereby the first pattern is prevented from being exposed in the optical path, and variations in sensitivity of the image pickup element formed in the joined area are reduced. Thus, the image pickup element of the solid state image pickup device has a uniform sensitivity. The image pickup system comprising the solid state image pickup device according to the present invention generates good image data having reduced variations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a top view showing wiring of an image pickup device according to the first embodiment, which is produced by a production method of the present invention; 
       FIG. 1B  is a sectional view showing an image pickup element of the image pickup device taken along a line  1 B- 1 B in  FIG. 1A ; 
       FIG. 2A  shows a schematic step until a pattern to be exposed by exposure in a joined fashion is exposed; 
       FIGS. 2B ,  2 C,  2 D and  2 E show steps of producing the image pickup device shown in  FIGS. 1A and 1B ; 
       FIG. 3  is a sectional view showing the image pickup element of the second embodiment according to the present invention; 
       FIG. 4  is a sectional view showing the image pickup element of the third embodiment according to the present invention; 
       FIG. 5  is a sectional view showing the image pickup element of the fourth embodiment according to the present invention; 
       FIG. 6  is a sectional view showing the image pickup element of the fifth embodiment according to the present invention; 
       FIG. 7  is a sectional view showing the image pickup element of the sixth embodiment according to the present invention; 
       FIG. 8  is a block diagram of one embodiment of an image pickup system comprising the image pickup device according to the present invention; 
       FIG. 9  is a sectional view of the image pickup element according to one example of the present invention; 
       FIG. 10  is a circuit diagram showing an example of a circuit configuration of an amplification type solid state image pickup element; 
       FIG. 11  is a sectional view showing an example of a configuration of the conventional image pickup element; 
       FIG. 12  is a sectional view showing one example of the image pickup element comprising collection means; and 
       FIG. 13  is a view for explaining exposure in a jointed fashion, which is a top view showing an area on which the image pickup element is formed. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will be described below with reference to drawings. 
   First Embodiment 
     FIG. 1A  is a top view showing wiring of an image pickup device according to the first embodiment, which is produced by a production method of the present invention.  FIG. 1B  is a sectional view showing an image pickup element of the image pickup device taken along a line  1 B- 1 B in  FIG. 1A . 
   As shown in  FIGS. 1A and 1B , an image pickup device  1  has a plurality of image pickup elements  11  arranged in a matrix form at predetermined spaces on a substrate  101 . 
   As shown in  FIG. 1B , the image pickup element  11  has a light receiving area  102  having a photoelectric conversion element (not shown) formed thereon, an insulation layer  104  deposited on a substrate  101  in such a manner as to cover the light receiving area  102 , and a microlens  106  placed on the surface of the insulation layer  104 . The materials of components and methods for forming them are almost same as those of a well known image pickup element, and therefore detailed descriptions thereof are not presented. The image pickup element  11  shown in  FIG. 1B  is an element exposed in a joined fashion with a divisional line between the elements shown in  FIG. 1A . 
   The substrate  101  is formed with, for example, a silicon substrate. For a photoelectric conversion element formed on the light receiving area  102  on the substrate  101 , a photodiode or phototransistor may be used. For example, the photoelectric conversion element may be provided as a photodiode obtained by forming the substrate  101  with a p type semiconductor, forming an N type semiconductor on the light receiving area  102  and jointing the former with the latter in a PN junction. 
   The shape of the light receiving area  102  when viewed from the top face side is not limited in any way, but it is formed as a rectangular area as shown in  FIG. 1A  in this embodiment. For transmitting electric signals generated in the light receiving area  102 , patterns  103 L and  103 R (first patterns) of vertical output lines are arranged in parallel to each other in both sides of the light receiving area  102 . Drive lines  107  extending in a direction orthogonal to patterns  103 L and  103 R and made of, for example, Al material are arranged with each light receiving area  102  held therebetween. On an area between adjacent light receiving areas  102 , metal wiring  105  (second pattern) made of, for example, Al material is arranged in a form of a lattice surrounding each light receiving area  102 . The image pickup device  1  having such a configuration functions as an area sensor having as pixels a plurality of image pickup elements  11  formed on the substrate  101 . 
   As shown in  FIG. 1B , the insulation layer  104  provides electrical insulation between the patterns  103 L and  103 R and metal wiring  105  and is provided as a layer for protecting them. The material of the insulation layer  104  is not specifically limited, but is preferably a material transparent to visible light or infrared light and for example, silicon oxides, silicon oxides doped with phosphor, boron, nitrogen, fluorine and the like, silicon nitrides and acrylic resins should be used. 
   The microlens  106  is placed on the insulation layer  104 , and its optical axis is positioned at the center of the light receiving area  102 . The microlens  106  is formed as a convex lens raised upward, i.e. toward the side of incidence of incident light (light incidence side), and the material thereof may be, for example, a resin. Light incident to the microlens  106  is collected in the light receiving area  102 . Color filter (not shown) may be formed just below the microlens  106 . 
   The metal wiring  105  may be formed on the surface side of the insulation layer  104 , and an opening  105   h  provided in a sufficient clearance so as not block the optical path for incident light passing through the microlens  106 . The metal wiring  105  does not require precise process accuracy compared with the patterns  103 L and  103 R, and is formed by one-shot exposure over an entire area (not shown) on which image pickup elements  11  are arranged. 
   The patterns  103 L and  103 R are formed between the metal wiring  105  and the light receiving area  102 , a distance between the patterns  103 L and  103 R is set so as not to block the optical path for incident light, and the patterns  103 L and  103 R are located symmetrically with respect to the optical axis of the microlens  106 . And the patterns  103  and  103 R are set so that the shortest distance (clearance) from the optical path for incident light is a distance L. 
   The “shortest distance from the optical path” means the shortest distance between the patterns  103 L and  103 R and the optical path in a horizontal direction, i.e. a direction in which the patterns  103 L and  103 R are misaligned on the exposure surface. The “distance L” is a distance set to a value greater than the alignment accuracy of the exposure device exposing the patterns  103 L and  103 R. The “alignment accuracy of the exposure device” means a standard deviation σ being an amount of variations in alignment of the exposure device. 
   In this embodiment, the distance L should have a value larger than the alignment accuracy of the exposure device, and is more preferably equal to or greater than three times as large as the alignment accuracy of the exposure device. 
   A method for producing the image pickup device  1  designed as described above will be described below. 
   A rough production step until the patterns  103 L and  103 R are exposed is as shown in a flowchart of  FIG. 2A , and has a step (S 1 ) of designing the patterns  103 L and  103 R so that the distance between the optical path for incident light and the patterns  103 L and  103 R equals the distance L described above, a step (S 2 ) of dividing designed patterns  103 L and  103 R into a plurality of patterns with a predetermined divisional line as a boundary, and a step (S 3 ) of individually exposing the divided patterns  103 L and  103 R by exposure in a joined fashion in different steps. 
   Thus, the image pickup device  11  is produced as described below based on data designed so that the distance from the optical path equals the distance L. 
   First, as shown in  FIG. 2B , the substrate  101  is prepared, and the light receiving area  102  comprising a photodiode and the like is formed on the substrate  101 . An active element such as an amplification transistor (not shown) for amplifying electric signals generated by photoelectric conversion by the light receiving area  102  is provided if necessary. 
   Then, as shown in  FIG. 2C , the insulation layer  104  covering the light receiving area  102  is deposited by thermal oxidation, the CVD (chemical vapor deposition) method, the sputtering method or the like. Patterns  103 L and  103 R are exposed on the surface of the insulation layer  104  by exposure in a joined fashion in different steps. Alignment of the exposure device may be performed on the basis of an alignment mark provided at a predetermined position. 
   After the patterns  103 L and  103 R are formed, the insulation layer  104  is further deposited on the patterns  103 L and  103 R as shown in  FIG. 2D . Patterns of metal wiring  105  are formed on the insulation layer  104  by one-shot exposure. 
   Thereafter, as shown in  FIG. 2E , the microlens  106  is collectively placed at a position corresponding to each light receiving area  102 . By the steps described above, the image pickup element  11  of this embodiment is formed. 
   According to the method for producing the image pickup device  1  of this embodiment described above, even if patterns  103 L and  103 R arranged in such a manner as to hold therebetween the optical path for incident light collected by the microlens  106  are exposed in a joined fashion in different exposure steps, the patterns  103 L and  103 R are never formed at positions in which the optical path for incident light is blocked even if the exposure device is misaligned because the patterns  103 L and  103 R are set to be arranged at a distance L from the optical path for incident light. Thus, the amount of light incident to the light receiving area  102  remains constant, and variations in sensitivity of the image pickup element  11  in the joined area are inhibited. 
   In this embodiment, the patterns  103 L and  103 R are each shown as one wire extending in a vertical direction (see  FIG. 1A ) for the sake of simplicity of explanation, but the shape of patterns is not limited thereto as a matter of course. For example, the shape of patterns may be such that a horizontal pattern element extending across a divisional line is provided, the horizontal pattern is divided near the divisional line, the divided patterns are exposed in a joined fashion and joined together. The arrangement of patterns  103 L and  103 R is not limited to an arrangement in which the distances between the patterns  103 L and  103 R and the optical path for incident light are the same as in the image pickup element  11  (see  FIG. 1B ) and for example, it may be an arrangement in which the distance between the pattern  103 L and the optical path equals L and the distance between the pattern  103 R and the optical path is  3 L. The image pickup element  11  (see  FIG. 1B ) has patterns  103 L and  103 R and metal wiring formed in one layer, but patterns (corresponding to patterns  103 L and  103 R) exposed by exposure in a joined fashion and patterns (corresponding to metal wiring  105 ) exposed by one-shot exposure may be formed on a plurality of layers. 
   The effect of the present invention can be obtained as long as the material of patterns  103 L and  103 R has an action of reducing incident light, and the material is not limited to a metal and the like, but may be a color filter, ITO (Indium-Tin-Oxide) or the like. The color filter and ITO are transparent to incident light, but have an action of selectively passing or attenuating only light of predetermined wavelengths in a predetermined band. This is because even in this pattern, wavelength characteristics of incident light are changed by blocking the optical path, and therefore the result of receiving light in the light receiving area  102  is influenced. 
   The image pickup element  11  (see  FIG. 1B ) has the microlens  106 , but the microlens  106  is not an absolutely necessary component for the invention, the invention described above can be applied to an image pickup element having no microlens as shown in  FIG. 9 , for example. 
   In the image pickup element of  FIG. 9 , the light receiving area  2202  is formed on the substrate  2201  and above the light receiving area  2202  (on the light incidence side), patterns  2203  and  2204  exposed by exposure in a joined fashion in different steps are formed in the same height. A pattern  2205  formed by one-shot exposure is arranged above the patterns  2203  and  2204 . The pattern  2205  has an opening for introducing incident light into the light receiving area  2202 . Even in the image pickup element having such a configuration, the clearances between the patterns  2203  and  2204  and the optical path for incident light each equal to the distance L described above, whereby patterns  2203  and  2204  are never formed in the optical path for incident light even if misalignment occurs during exposure. 
   In this embodiment, the image pickup device has been described taking an amplification type image pickup element as an example, but it may be charge coupled device (CCD) type one. 
   The method for producing the solid state image pickup device of the present invention is not exclusively applied to what has been described above but can be applied to a variety of image pickup devices. An example of the image pickup device produced according to the present invention will be described with reference to the drawings. 
   Second Embodiment 
   The opening  105   h  of the metal wiring  105  is formed with a sufficient clearance from the optical path for incident light as shown in  FIG. 1B  in the first embodiment, but the opening of metal wiring may be smaller so that the optical path for incident light is substantially regulated. 
   An image pickup element  12  shown in  FIG. 3  has a smaller opening of metal wiring  105 ′ compared with the image pickup element  11  of the first embodiment shown in  FIG. 1A , but is same as the image pickup element  11  for other configurations, and structural parts having same functions are given symbols identical to those of  FIG. 1B  and the descriptions thereof are not presented. 
   The metal wiring  105 ′ is designed so that the center of its opening is located on an optical axis of the microlens  106 . It is designed so that incident light collected by the microlens  106  passes through the opening to the light receiving area  102 . In this way, by reducing the opening of the metal wiring  105 ′, the area of an area on which the metal wiring  105 ′ can be increased, and therefore the degree of freedom in the design of the metal wiring  105 ′ is advantageously improved. The metal wiring  105 ′ is collectively exposed as in the case of the first embodiment. 
   Even in production of the image pickup element  12  having such a configuration, the patterns  103 L and  103 R are designed so that the clearance from the optical path for incident light equals the distance L, whereby the patterns  103 L and  103 R are never formed in the optical path even if they are exposed by exposure in a joined fashion, and an effect same as that of the first embodiment can be obtained. 
   Third Embodiment 
   An insulation layer may be composed of two or more layers having different refraction indexes. The image pickup element  13  shown in  FIG. 4  has an insulation layer  104  and an insulation layer  204  having a refraction index smaller than that of the insulation layer  104 . Other configurations are same as those of the image pickup element  12  of  FIG. 3 , and components having same functions are given symbols identical to those of  FIG. 3  and the descriptions thereof are not presented. 
   In the image pickup element  13 , the insulation layer  204  having a refraction index smaller than the insulation layer  104  is formed between the metal wiring  105 ′ and the patterns  103 L and  103 R. In this way, incident light collected by the microlens  106  passes through the insulation layer  104  and incidents into the insulation layer  204  and is then refracted toward the optical axis at the interface between the insulation layers  104  and  204 . Then, when the incident light enters the insulation layer  104  from the insulation layer  204 , it is refracted again and enters the light receiving area  102 . 
   In the image pickup element  13  having such a configuration, the patterns  103 L and  103 R are set so that the clearance from the optical path for incident light equals the distance L, and are exposed in a joined fashion, whereby an effect same as that of the above embodiment can be obtained. In the image pickup element  13 , the optical path at the lower end of the insulation layer  204 , i.e. at a position in which it is held between the patterns  103 L and  103 R is smaller than the optical path when the insulation layer  204  is not provided (shown by dotted lines in the figure), and therefore an area on which the patterns  103 L and  103 R are arranged relatively increases. As a result, the degree of freedom of arrangement of patterns is improved. For example, by increasing the distance between the pattern  103 L and an adjacent pattern  103 L′, improvement in yield can be expected. 
   Fourth Embodiment 
   Light collecting means may be provided in the insulation layer as means for refracting incident light in the insulation layer. 
   The image pickup element  14  shown in  FIG. 5  has a microlens  206  formed in the insulation layer  104  instead of the insulation layer  204  of the image pickup element  13  of  FIG. 4 . The microlens  206  is composed of a material having a refraction index larger than that of the insulation layer  104 , and has a convex shape raised toward the surface side. In this way, light incident from the microlens  106  is further collected by the microlens  206  and received by the light receiving area  102 . Even such an image pickup element  14  can provide an effect same as that of the third embodiment. 
   Fifth Embodiment 
   Metal wiring  105  and  105 ′ is arranged on the surface side in the embodiment described above, but the metal wiring  205  may be provided below patterns  203 L and  203 R formed by exposure in a joined fashion as in an image pickup element  15  shown in  FIG. 6 , for example. 
   In the image pickup element  15 , the patterns  203 L and  203 R are arranged on the insulation layer  104  on the surface side, and metal wiring  205  formed by one-shot exposure is arranged between the patterns  203 L and  203 R and the light receiving area  102 . Other configurations are same as those of the image pickup element  11  of  FIG. 1 , and components having same functions are given symbols identical to those of  FIG. 1  and descriptions thereof are not presented. 
   In the image pickup element  15 , an optical path for incident light passing through the microlens  106  is regulated by an opening of the metal wiring  205 , and only incident light passing through the opening reaches the light receiving area  102 . The patterns  203 L and  203 R formed above the metal wiring  205  are designed so that the clearance from the optical path regulated by the opening equals the distance L, whereby an effect same as that of the second embodiment can be obtained. In this way, if relative positions of the metal wiring  205  and the patterns  203 L and  203 R are the important factor in terms of optical design, it is desirable that their relative errors should be minimized. Thus, for example, an alignment mark may be provided on the metal wiring  205 , and the exposure device may be aligned on the basis of the alignment mark when the patterns  203 L and  203 R are exposed. In this way, misalignment in relative positions of the metal wiring  205  and the patterns  203 L and  203 R decrease. 
   Sixth Embodiment 
   A divisional line in exposure in a joined fashion is not necessarily located at an optical axis of a microlens, i.e. at almost the center of one image pickup element, but may be located between adjacent image pickup elements. 
     FIG. 7  shows a situation in which a divisional line is set at almost the center between adjacent image pickup elements  16 , and exposure in a joined fashion is performed with the divisional line therebetween. 
   Even in this case, patterns  303 L and  303 R and patterns  403 L and  403 R are set so that a clearance from each corresponding optical path for incident light equals the distance L, whereby the optical path for incident light is never influenced by alignment accuracy of an exposure device. 
   Seventh Embodiment 
     FIG. 8  is a block diagram of one embodiment of an image pickup system using the image pickup device according to the embodiment of the present invention described above. 
   The image pickup system  20  shown in  FIG. 8  is an image pickup system such as, for example, a still video camera, and is roughly comprised of an optical unit  20   a  for forming an image, a processing unit  20   b  photoelectrically converting the formed image and processing signals obtained thereby, a recording unit  20   c  in which data processed by the processing unit  20   b  is stored and so on, and a control unit  20   d  controlling drive of the units. 
   The optical unit  20   a  is comprised of a lens  22  forming an optical image of a subject, a barrier  21  protecting the lens  22  and also serving as a main switch and a diaphragm  23  making the light amount variable. 
   The processing unit  20   b  is comprised of an image pickup device  24  (e.g. image pickup device  1  described above) according to the present invention placed as an area sensor on the screen surface, an image pickup signal processing circuit  25  performing correction, clamp and the like of signals obtained by the image pickup device  24 , an A/D converter  26  performing analog-digital conversion of signals outputted from the image pickup signal processing circuit  25 , and a signal processing unit  27  correcting and compressing data outputted from the A/D converter  26 . 
   The recording unit  20   c  is comprised of a memory unit  30  temporarily storing final data obtained by processing the data by the signal processing unit  27 , an interface unit controlling recording medium  31 , to which a predetermined recording medium  32  such as a semiconductor memory is removably connected and which is for recording data in and reading data from the recording medium  32 , and an external interface unit  33  for communicating with an external computer and the like. 
   The control unit  20   d  controlling each unit comprises a timing generator  28  outputting timing signals to the image pickup device  24 , the image pickup signal processing circuit  25 , the A/D converter  26  and the signal processing unit  27 , and a unit controlling whole and arithmetic operation  29  controlling the timing generator  28 . The unit controlling whole and arithmetic operation  29  is configured to be capable of driving and controlling the lens  22 , the diaphragm  23 , the signal processing unit  27  and the recording unit  20   c.    
   Operations of the image pickup system  20  configured as described above will be described below. 
   When the barrier  21  is opened, a main power supply is turned on, a power supply of a control system is then turned on, and a power supply of an image pickup system circuit such as the A/D converter  6  is turned on. The unit controlling whole and arithmetic operation  29  opens the diaphragm  23 , and photoelectrically converts incident light incident through the lens  22 , whereby a signal outputted from the image pickup device  24  is outputted through the image pickup signal processing circuit  5  to the A/D converter  26 . The A/D converter  26  subjects the signal to A/D conversion and outputs the same to the signal processing unit  27 . The signal processing unit  27  performs an arithmetic operation of exposure based on the data at the unit controlling whole and arithmetic operation  29 . According to the result, the unit controlling whole and arithmetic operation  29  controls the diaphragm  23 . 
   Then, based on the signal outputted from the image pickup device  24 , high frequency components are taken out, and a distance from the subject image is calculated at the unit controlling whole and arithmetic operation  29 . The unit controlling whole and arithmetic operation  29  drives the lens  22  based on the distance obtained by the calculation, determines whether focus is achieved or not, and drives the lens  22  again and calculates the distance if it determines that focus is not achieved. 
   The steps are repeated, and when it is determined that focus is achieved, main exposure is started. When exposure is completed, an image signal outputted from the image pickup device  24  is subjected to correction and the like at the image pickup processing circuit  25  and further subjected to A/D conversion by the A/D converter  26 , passes through the signal processing unit  27  and is stored in the memory unit  30  by the unit controlling whole and arithmetic operation  29 . In this way, data stored in the memory unit  30  passes through the interface unit controlling recording medium  31  and is stored in the recording medium  32  under control by the unit controlling whole and arithmetic operation  29 . Alternatively, the stored data may be outputted through the external interface unit  33  directly to a computer or the like connected to the interface unit  33 . 
   In the image pickup system  20  comprising the image pickup device  24  according to the present invention described above, uniform photoelectric conversion is performed among pixels (image pickup elements), and good image data having reduced variations can be obtained. 
   Exemplary embodiments have been described above, but components described in the embodiments may be used in combination where possible. 
   This application claims priority from Japanese Patent Application No. 2003-404544 filed Dec. 3, 2003, which is hereby incorporated by reference herein.