Electron tube

Electric lamp and discharge devices – Photosensitive

Reexamination Certificate

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Details

C313S530000, C313S542000, C313S544000

Reexamination Certificate

active

06586877

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a highly sensitive electron tube for quantitatively measuring an extremely weak light.
BACKGROUND ART
This field of technology is described in Japanese Patent Publication No. HEI-7-95434, for example. An electron tube described in this publication has a package, in which a charge coupled device (CCD) of a back-illuminated type is provided. In this type of electron tube, electron emitted from a photocathode in response to an incidence of light is directed into a back side of a device formation surface to detect a signal. This electron tube is widely used because of its high sensitivity and its high imaging quality.
An imaging device employing a back-illuminated type semiconductor device is described in Japanese unexamined patent application publication No. HEI-6-29506. The semiconductor device is fixed on a substrate whose thermal expansion coefficient is equal to that of the semiconductor device. A plurality of metal bumps are formed on the semiconductor device, each bump being connected to a metal wiring formed on the substrate (silicon wafer). The space between the semiconductor device and the substrate is filled with a nonconductive resin to prevent silicon etchant from entering therein. Since the space is filled prior to thinning of the semiconductor device, the resin has to not include alkali metal, has to have a suitable contraction stress during curing to maintain sufficient contact of the bonding part of the bumps, and has to be able to withstand heat up to about 150° C. during die-bonding and wire-bonding.
However, conventional electron tubes and imaging devices have the following problems due to the construction described above.
In the electron tube described in Japanese patent publication No. HEI-7-95434, the semiconductor device is fixed to the stem by bonding metal pads to contacts. However, the metal pads have a tendency to slip off the contacts to lose a sufficient connection when the electron tube is assembled under a high-temperature environment.
In the imaging device described in Japanese unexamined patent application publication No. HEI-6-29506, the semiconductor device is thinned with etchant after the semiconductor device is fixed to the substrate. Accordingly, the space between the semiconductor device and the substrate is completely filled with resin in order to prevent any etchant from entering therein. Since the resin is attached directly on the electron incidence part of the semiconductor device, stress is generated in the electron incidence part when the resin cures or hardens. The electron incidence part runs the risk of becoming deformed, resulting in poor images, or in some cases broken.
In view of the foregoing, it is an object of the present invention to solve the above-described problems and to provide an electron tube which is capable of avoiding poor connections that can occur during the assembly process, as well as deformation or damage to the.semiconductor device that can also occur during this process.
DISCLOSURE OF THE INVENTION
These objects and others will be attained by an electron tube, comprising: a side tube; a faceplate provided at one end of the side tube and having a photocathode that emits electrons in response to incident light; a stem provided at the other end of the side tube, the stem and the faceplate defining a vacuum region, the stem having a bump connection portion on its surface; and a semiconductor device fixed to the stem at its vacuum side, the semiconductor device having a front surface positioned on the stem side and a back surface positioned on the faceplate side, the semiconductor device including an electron incidence part, for receiving electrons emitted from the photocathode, and a periphery part provided at an outer periphery of the electron incidence part, the electron incidence part having a thin plate shape whose thickness is smaller than that of the periphery part, the periphery part having a bump which protrudes from the front surface thereof the bump being fixed to the bump connection portion, the bump forming a space between the front surface of the semiconductor device and the surface of the stem, a filling material with insulation property being filled partially in the space at the periphery part, thereby partially closing the space at the periphery part.
Hence, the electron tube of the present invention includes: a side tube; a faceplate provided at one end of the side tube and having a photocathode that emits electrons in response to incident light; a stem provided at the other end of the side tube, the stem and the faceplate defining a vacuum region; and a semiconductor device fixed to the evacuated side of the stem and having an electron incidence part for receiving electrons emitted from the photocathode. The semiconductor device is configured as a back-illuminated type semiconductor device. That is, the semiconductor device has a front surface positioned on the stem side and a back surface positioned on the faceplate side. The semiconductor device has a plate-shaped electron incidence part that is formed thinner than the periphery part which is formed around the electron incidence part. A bump is formed to protrude from the front surface of the periphery part. The bump is fixed to a bump connection portion provided on the surface of the stem. The bump forms a space between the front surface of the semiconductor device and the surface of the stem. The space at the periphery part is partially filled with a filling material with insulating properties. Accordingly, the space at the periphery part is partially closed with the filling material having insulating properties.
Accordingly, in the electron tube of the present invention, insulating filling material is filled partially in the space between the periphery part of the semiconductor device and the stem, while the bump formed on the semiconductor device is connected to the bump connection portion provided on the surface of the stem. Hence, the filling material functions as a reinforcing member to prevent the bump from separating from the bump connection portion even when the electron tube is assembled under a high-temperature environment.
The space defined at the periphery of the semiconductor device is filled with insulating filling material, while the space defined at the electron incidence part is not filled with the insulating filling material. Accordingly, there is no danger of the electron incidence part becoming deformed or damaged due to stress generated when the insulating filling material is hardened.
Further, ventilation between the semiconductor device and the stem is ensured because the space between the semiconductor device and stem is only partially closed by the filling material. If the entire circumference of the periphery part of the semiconductor device were completely closed by the filling material, an air reservoir would be formed between the electron incidence part and the surface of the stem. During the process of assembling the electron tube in a vacuum, this air would expand and could cause damage to the electron incidence part which is formed as a thin plate on the back-illuminated semiconductor device. Contrarily, the present invention enables air to flow between the semiconductor device and the stem, ensuring that air can be evacuated in the vacuum environment when the electron tube is assembled.
Thus, according to the present invention, the bump protruding from the front surface of the periphery part of the semiconductor device is fixed to the bump connection portion which is provided on the surface of the stem. This bump forms the space between the front surface of the semiconductor device and the surface of the stem. The space along the periphery part of the semiconductor device is partially filled with a filling material with insulation properties. Accordingly, the space is closed only partially with the insulating filling material. As a result, it is possible to prevent poor bump connection that can possibly arise when the electron tube is assembled and to prevent

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