This application is based on the Japanese Patent Application 2000-054551, filed on Feb. 29, 2000, all the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a solid-state image pickup device and a method of manufacturing the same, and in particular, to a solid-state image pickup device and a method of manufacturing the same in which a solid-state image pickup element is attached to a package with high precision.
2. Description of the Related Art
With an increasing need of higher picture quality for a digital video camera of integrated type and a digital still camera, research and development of a solid-state image pickup element for use with a solid-state image pickup device have been carried out for fine structure and high integration thereof. A need for an optical system is also highly increased, namely, an image must exactly focused on an image-pickup plane of the solid-state image pickup element.
FIG. 8 shows a general configuration of a solid-state image pickup device in a cross section.
In FIG. 8, a solid-state image pickup device X includes a package 101 in a contour of a box and a solid-state image pickup element 103 housed in the package 101.
As can be seen from FIG. 8, the package 101 includes a bottom plate 101a and a sidewall section 101b rising from a peripheral section of the bottom plate 101a. The configuration defines an opening section 101c formed in an upper section of the package 101 and a housing section 101d surrounded by the bottom plate 101a and the side wall section 101b to house the image pickup element 103.
The image pickup element 103 is installed in the housing section 101d. The image pickup element 103 is connected via bonding wires 107 to lead wires of the package 101.
The opening section 101c of the package 101 is covered with a transparent shield plate 111 placed on an upper surface 101e of the side wall section 101b. 
The solid-state image pickup device 103 ha a rear surface fixedly attached to the housing section 101d by adhesive 115.
FIG. 9 is a cross-sectional view to explain a method of manufacturing a solid-state image pickup device.
As shown in FIG. 9, a package 101 on a carrier 123 is transported (to a predetermined position). The carrier 123 has an opening below the package 101.
A package stage 121 made of iron-based material is moved upward through the opening to mount the package 101 on the stage 121. The stage 121 has a stage adsorbing hole 121a to fix the package 101 on the stage 121. The hole 121a produces a state like vacuum by sucking air to adsorb the rear surface of the package 101 on the package stage 121.
The housing section 101d of the package 101 is coated with adhesive 115. In the state, the solid-state image pickup element 103 is supported by a collet 125 and is placed at a predetermined position in the housing section 101d. 
The collet 125 has an adsorbing hole 125a which adsorbs the solid-state image pickup element 103 to fixedly support the element 103. The collet 125 with the element 103 is moved downward to be pressed against the adhesive 115 to install the solid-state image pickup element 103 on the housing section 101d of the package 101. The adhesive 115 between the element 103 and the package 101 is cured or hardened by heat to fix the element 103 in the package 101.
After a wire bonding process is conducted for the objective item, the upper opening section of the package 101 is covered by a shield plate to completely manufacture a solid-state image pickup device.
FIG. 10 shows in a schematic cross-sectional view a configuration of an image pickup device including a solid-state image pickup device and an optical system including a lens.
As shown in FIG. 10, an image pickup device Y includes a solid-state image pickup device X, a solid-state image pickup device fixing member 131, an image pickup lens body tube 133, and an image pickup lens 135.
The fixing member 131 supports a bottom surface of the package 101. The lens body tube 133 in a cylindrical shape is formed on a peripheral edge section of the fixing member 131. On an inner circumferential section 133a of the body tube 133, an upper engaging section 133b and a lower engaging section 133c are formed to support the image pickup lens 135. The upper and lower engaging section 133b and 133c fixedly support the lens 135.
As the adhesive to fix the solid-state image pickup element on the package, there has been used thermosetting adhesive such as silver paste or resin-based adhesive. The silver paste has a high reflection factor for light and is therefore not suitable as adhesive for a solid-state image pickup element. Consequently, resin-based adhesive has been increasingly used.
However, in a solid-state image pickup device including photo diodes in a fine structure, there arises a problem that resolution of the solid-state image pickup device deviates or fluctuates within a chip area of a solid-state image pickup device.
To increase picture quality of a digital video camera of integrated type and a digital still camera, only miniaturizing structure of photo diodes and the like is insufficient. To improve picture quality of a camera or the like, it is essential how to exactly adjust focus of an image pickup lens of a camera onto a light receiving plane of each photo diode formed in fine structure.
For this purpose, it is required to improve precision of tilt of image in a light receiving plane (parallelism of the light receiving plane with respect to the optical system).
It is therefore an object of the present invention to provide a technique to reduce fluctuation of the tilt angle of image in a solid-state image pickup element to increase picture quality of a camera or the like using the element.
According to one aspect of the present invention, there is provided a method of manufacturing a solid-state image pickup device comprising the steps of preparing a package including a housing section to house a solid-state image pickup element chip and an opening section in an upper section thereof, sporadically applying adhesive with a predetermined thickness on a bottom surface of the housing section, moving the solid-state image pickup element toward the housing section, an upper surface of the package and an upper surface of the element each having desired parallelism with respect to a predetermined reference surface with high precision, bringing a rear surface of the solid-state image pickup element into contact with the adhesive and stopping the movement of the element before the element comes into contact with the bottom surface of the housing section, and curing the adhesive while the solid-state image pickup element is floating on the adhesive and fixing the element in the housing section.
According to the present invention, there is provided a method of manufacturing a solid-state image pickup device, comprising the steps of preparing a package including a bottom plate and a side wall rising from the bottom plate to house a solid-state image pickup element chip, sporadically applying adhesive with a predetermined thickness on the bottom plate of the package, setting an upper surface of the side wall or an upper surface of the bottom plate as a reference plane, bringing a rear surface of the solid-state image pickup element into contact with the adhesive with parallelism adjusted with high precision between the upper surface of the element and the reference plane, moving the solid-state image pickup element, the rear surface of the element depressing the adhesive, the rear surface of the element not coming into contact with the upper surface of the bottom plate and curing the adhesive and fixing the solid-state image pickup element in the package.
According to the present invention, there is provided a package comprising a bottom plate, a side wall rising from said bottom plate, a housing section for hosing a solid-state image pickup element chip, an opening section in an upper section of the package, and a projection projecting outward from said side wall, said projection including a flat upper surface.
According to the present invention, there is provided a solid-state image pickup device comprising a package including a bottom plate, a side wall rising from said bottom plate, a housing section for hosing a solid-state image pickup element chip, and an opening section in an upper section thereof; adhesive with a predetermined width sporadically applied on said bottom plate, a solid-state image pickup element including a rear surface supported on the adhesive and being fixed thereon, said element being floating over a surface of said bottom plate; and a transparent shield plate for closing said opening section.
In the solid-state image pickup element, the fluctuation of resolution in the light receiving plane is reduced. This increases the picture quality of image pickup devices such as a camera using the element.