Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2000-07-26
2001-12-25
Christianson, Keith (Department: 2813)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
Reexamination Certificate
active
06333544
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of Japanese Patent Application No. 11-232972 filed on Aug. 19, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an integrated photo sensor provided by integrating a light-receiving element and elements for a signal processing circuit on a semiconductor substrate.
2. Description of the Related Art
JP-A-10-289994 proposes an integrated photo sensor. The photo sensor has a light-receiving element and signal processing circuit elements that are integrated on one chip, and a shading film for selectively determining a light-receiving region on the chip surface. It is considered that this structure reduces the chip size as small as possible for the integration, and prevents erroneous operations of the signal processing circuit elements ascribed to light incident on the elements. This kind of sensor is generally covered with a protective film made of resin such as silicone gel or the like for protection.
Specifically, the shading film covers a region other than the light-receiving element, and an insulating film (intermediate insulating film) such as a silicon oxide film underlies the shading film to assure electrical insulation from each of the signal processing circuit elements (each element for a digital circuit, an analog circuit, adjustment, or the like).
If the intermediate insulating film exists on the light-receiving element, however, optical characteristics vary due to interference of light in accordance with wavelength of light. To prevent this variation in optical characteristics, the intermediate insulating film is removed not to exist on the light-receiving element. The removal of the intermediate insulating film, however, increases the manufacturing cost. In addition, in this case, a protective film is disposed on the light-receiving element, which can vary sensor sensitivity.
JP-A-8-32045 discloses another integrated photo sensor. In the photo sensor, an intermediate insulating film remains on a light-receiving element. Further, a film (an oxide film formed by plasma CVD, and hereinafter referred to as a P—SiO
2
film) having a refractive index close to that of the intermediate insulating film is disposed on the intermediate insulating film provided on the light-receiving element so that light is restricted from being reflected at the interface between the P—SiO
2
film and the intermediate insulating film.
In this structure, since the thickness of the P—SiO
2
is thin, the reflection of light at the interface can be prevented effectively as compared to a case where a SiN film having a largely differing refractive index is left on the light-receiving element. However, since it is difficult to eliminate the effects by interference, the variation in optical characteristics is not prevented sufficiently.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is to provide an integrated photo sensor that is manufactured readily and can effectively restrict variation in optical characteristics produced due to interference of light.
According to the present invention, an integrated photo sensor has a light-receiving element and a signal processing circuit element that are provided on one chip. A shading film is provided on the chip to cover the signal processing element and not cover the light-receiving element. An intermediate insulating film is provided not only on the signal processing circuit through the shading film but also on the light-receiving element. Further, a light transmittable gel having a refractive index approximately equal to that of the intermediate insulating film is provided on the light-receiving element through the intermediate insulating film.
The light transmittable gel can be thickened sufficiently for preventing interference of light. Therefore, optical characteristics of the photo sensor are hardly affected by variation in thickness of the light transmittable gel. Further, since the intermediate insulating film can be thickened, the optical characteristics are hardly affected by variation in thickness of the intermediate insulating film. The intermediate insulating film needs not be removed from the surface of the light-receiving element.
REFERENCES:
patent: 8-32045 (1996-02-01), None
patent: 8-32545 (1996-02-01), None
patent: 10-289994 (1998-10-01), None
Gotoh Yoshitaka
Toyoda Inao
Christianson Keith
Denso Corporation
Law Office of David G. Posz
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