Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1998-06-18
2001-02-20
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S350000, C250S349000, C250S343000
Reexamination Certificate
active
06191420
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an infrared sensor for measuring temperatures of objects by means of measuring radiation temperatures without making physical contacts with the objects.
2. Description of the Related Art
An infrared sensor basically comprises an infrared sensitive element for capturing infrared rays and a compensating element for obtaining a signal that is used as a basis for calculating the quantity of infrared rays detected. Such an infrared sensor has the structure that prevents infrared rays from entering the compensating element. In order to measure the quantity of infrared rays detected by the infrared sensitive element accurately based on the signal output from the compensating element, it is preferable that the compensating element and the infrared sensitive element have identical characteristics. Therefore, it is common to use the same material and shape for both the compensating element and the infrared sensitive element to equalize their characteristics.
However, the characteristics of these elements may differ from each other minutely due to variations in manufacturing conditions. When a sensor is miniaturized, in particular, and delicate temperature changes have to be measured accurately, it may become impossible to compensate the measured values due to the difference of their characteristics. Therefore, it is necessary to evaluate with each sensor if it is necessary to match the characteristics of the infrared sensitive element and the compensating element.
Japanese Patent Unexamined Publication JP-A-08-159866 (1996) discloses an infrared sensor comprising an infrared sensitive element for infrared rays, a compensating element for compensating the measured values of the infrared sensitive element, and a processing circuit all formed on a single substrate. The elements are maintained in a vacuum environment.
The characteristics of the infrared sensitive element and the compensating element are easily equalized as they are both formed simultaneously on the identical substrate. In other words, there is no need for further matching the characteristics between the infrared sensitive element and the compensating element to improve the accuracy of the measured values.
Moreover, the infrared sensor has the infrared barrier layer for covering the entire internal surface of a package body (comprising top and bottom covers) hermetically sealed to maintain a vacuum inside, and an infrared transmission aperture provided on an area of the infrared sensitive element side of the top cover. In other words, the design allows infrared rays to enter an element that functions as the infrared sensitive element but prevents infrared rays from entering another element that functions as the compensating element.
However, in a design where an infrared transmission area is provided in one area of the package body and the rays are prevented from entering the sensor through any other parts of the package body, it is necessary to minimize the area of infrared transmission in order to block infrared rays from the compensating element completely. This causes a problem because it limits the view angle of the infrared sensitive element and the quantity of incident infrared rays, thus reducing the sensitivity of the sensor itself. Also, the infrared rays entered through the infrared transmission area makes random reflections inside the package body and may inadvertently enter the compensating element though the quantity may be small. Hence, there still remained a problem of not being able to detect delicate changes of infrared rays in the prior art.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide an infrared sensor with an improved sensitivity by preventing infrared rays from entering the compensating element.
In one aspect of this invention, areas through which infrared rays may enter the compensating element are covered with infrared protection layers via insulation layers to prevent infrared rays from entering the compensating element.
In another aspect of this invention, an infrared sensor having infrared protection layers on the front and back side of the compensating element can be easily manufactured.
Another aspect of the present invention is an infrared sensor comprising: an infrared sensitive element for detecting infrared rays; a compensating element for obtaining a signal to be used as a basis for calculating a quantity of infrared rays detected; and an infrared protection layer formed on a surface of said compensating element for protecting it from infrared rays.
Another aspect of the present invention is a method of manufacturing an infrared sensor comprising the steps of: (a) forming a pattern of first infrared protection layer on a first surface of a silicon substrate; (b) forming first insulation layers on the first surface and a second surface opposite to the first surface; (c) forming a pattern of temperature-sensing layer on the first insulation layer on the first surface; (d) forming a wiring pattern on the first insulation layer and the temperature-sensing pattern; (e) forming a pattern of second insulation layer on the first surface; (f) forming a wiring pattern on the temperature-sensing layer; (g) forming a third insulation layer on the first surface; and (h) forming a pattern of second infrared protection layer on the third insulation layer.
Another aspect of the present invention is a method of manufacturing an infrared sensor comprising the steps of: (a) forming first insulation layers on a first surface and a second surface opposite to the first surface of a silicon substrate; (b) forming a pattern of temperature-sensing layer on the first insulation layer on the first surface; (c) forming a wiring pattern on the first insulation layer and the temperature-sensing pattern; (d) forming a pattern of second insulation layer on the first surface; (e) forming a wiring pattern on the temperature-sensing layer; (f) forming a third insulation layer on the first surface; (g) forming a pattern of bridge structures from the first through third insulation layers on the first surface; (h) forming a window frame-shaped pattern from the first insulation layer on the second surface; (i) etching the second surface using the pattern of the first insulating layer as a mask to expose an inner surface of the first insulating layer on the first surface; (j) forming a pattern of infrared protection layer on the inner surface of the first insulating layer; and (k) forming a pattern of infrared protection layer on the third insulation layer.
Another aspect of the present invention is a method of manufacturing an infrared sensor comprising the steps of: (a) forming a pattern of first infrared protection layer on a first surface of a silicon substrate; (b) forming first insulation layers on the first surface and a second surface opposite to the first surface of the silicon substrate; (c) forming a pattern of temperature-sensing layer on the first insulation layer on the first surface; (d) forming a wiring pattern on the first insulation layer and the temperature-sensing pattern; (e) forming a pattern of second insulation layer on the first surface; (f) forming a wiring pattern on the temperature-sensing layer; (g) forming a third insulation layer on the first surface; (h) forming a pattern of bridge structures from the first through third insulation layers on the first surface; (i) forming a window frame-shaped pattern from the first insulation layer on the second surface; (j) etching the second surface using the pattern of the first insulating layer as a mask to expose an inner surface of the first insulating layer on the first surface; and (k) forming a pattern of second infrared protection layer on the third insulation layer.
The objects, features, and characteristics of this invention other than those set forth above will become apparent from the description given herein below with reference to preferred embodiments illustrated in the accompanying drawings.
REFERENCES:
patent: 3629585 (1971-12
Burns Doane , Swecker, Mathis LLP
Hannaher Constantine
Israel Andrew
Terumo Kabushiki Kaisha
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