Optical waveguides – Optical waveguide sensor
Reexamination Certificate
2000-06-22
2004-03-09
Lee, John D. (Department: 2874)
Optical waveguides
Optical waveguide sensor
C250S227140, C385S014000
Reexamination Certificate
active
06704470
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optoelectronic gas sensor based on optodes as well as an electronic component for producing such an optoelectronic gas sensor.
BACKGROUND INFORMATION
An optoelectronic gas sensor is described in a technical article “A field hardened optical waveguide hybrid integrated-circuit, multi-sensor chemical probe and its chemistry” by Richard J. Polina et al. in SPIE, vol. 3105, pages 71-78. This known gas sensor based on optodes is diagramed schematically in
FIG. 6
, and its properties are described briefly below.
From an LED
33
, a light bundle is divided vertically by two mirrors
35
,
36
into two parts L
1
, L
2
and reflected laterally, so it goes to a measuring segment
38
made of optode material and a reference segment
39
. Light beam L
2
passing through optode segment
38
is in turn reflected down vertically on a mirror surface
37
, so it reaches the photosensitive surface of a first photodiode
32
, while light beam L
1
passing through reference segment
39
is reflected down vertically onto the photosensitive surface of another photodiode
31
at another mirror surface
34
. Optode segment
38
and reference segment
39
, mirror surfaces
34
-
37
and photodiodes
31
and
32
are arranged symmetrically about LED
33
which is arranged at the center. The optode material of measuring segment
38
is exposed opposite the gas to be measured (arrow), so this gas has access through an opening provided in the chip casing (not shown).
FIG. 7
shows schematically a gas measuring sensor
30
equipped with three successive sensor units
301
,
302
and
303
according to FIG.
6
.
Due to the method of coupling and reflection of light bundles L
1
and L
2
and mirror surfaces
34
-
37
, first from the vertical into the lateral direction and then from the lateral back into the vertical direction, the known gas sensor chip shown in FIG.
6
and described in the technical article cited above is relatively long and broad (e.g., 3 cm long and 0.35 cm broad), so a gas measuring sensor
30
according to
FIG. 7
constructed using multiple gas sensor chips
301
-
303
arranged in successive rows turns out to be rather long. In addition, such a known gas sensor chip and gas measuring sensor
30
implemented with it is relatively expensive. Furthermore, various aging phenomena on separate chips
301
-
303
can lead to unwanted measurement errors.
SUMMARY OF THE INVENTION
An object of the present invention is to make possible an improved optoelectronic gas sensor based on optodes, so that it will be less expensive and will have much smaller dimensions, and so that an electronic component according to the present invention can be made available for manufacturing an optoelectronic gas sensor without requiring additional optical components such as mirrors and prisms.
According to a first embodiment of the present invention, the object is achieved by providing an optoelectronic gas sensor based on optodes, where multiple separate photosensitive elements and an opto-transmitter located centrally between them are integrated into or onto a semiconductor substrate; this is characterized in that the photosensitive elements lie in one plane in the substrate, and together with a lateral emission area of the opto-transmitter emitting light laterally they are covered by sections of the optode material whose thickness and refractive index are selected so that light emitted laterally from the emission area is guided to the photosensitive elements by total reflection in the optode material in each transmission branch.
According to a second embodiment of the present invention, an optoelectronic gas sensor based on optodes achieving the above object is made available, where multiple separate photosensitive elements and an opto-transmitter located centrally between them are integrated into or onto a semiconductor substrate; this is characterized in that the photosensitive elements lie in one plane in the substrate and are each covered by a section of the optode material, the opto-transmitter is spaced a distance away from the sections of the optode material through an annular gap, and the thickness of the optode material is much smaller than the height of the opto-transmitter, so the light emitted by the opto-transmitter is emitted into air and then reaches the photosensitive elements through the optode material either directly or after being reflected on the inside walls of a casing surrounding the gas sensor chip.
One of the photosensitive elements and the layer covering it may form a reference segment. The optode material of the measuring segments is made of a gas-sensitive polymer carrier material to which is added at least one indicator substance from the group of compounds including, for example, azobenzenes, acetophenones, corrins, porphyrins, phthalocyanines, macrolides, porphyrinogens, nonactin, valinomycin and/or complexes thereof with transition metals of secondary groups I-II and V-VIII. However, the layer covering the reference segment may be made of a polymer carrier material without any added indicator substance.
In an embodiment of a layout according to the present invention, the photosensitive elements of the optoelectronic gas sensor with the sections of the optode material covering them or with the polymer carrier layer covering the reference segment may be arranged in sectors with central symmetry around the opto-transmitter. For example, in this way four symmetrical transmission branches may be formed, including three sensor segments and one reference segment.
The chip forming the optoelectronic gas sensor may be designed to be square, pentagonal, hexagonal, heptagonal or octagonal or even circular, for example. Of course, such an optoelectronic gas sensor may also include less than or more than four transmission branches.
With an optoelectronic gas sensor implemented according to the first embodiment, the individual transmission branches are separated by barriers, so that the individual transmission branches are not influenced optically by the stray light coming from the optode material. The height of these barriers may be selected to be approximately the same as the height of the central photosensor. In addition, all locations on the chip that are not photosensitive may be mirrorized if necessary, likewise the side walls of the barriers.
The substrate of the chip may be made of n-type silicon, and the photosensitive elements may be made of p-type regions of silicon integrated into the n-type silicon substrate. In this way, the photosensitive elements form photodiodes. The opto-transmitter is preferably an LED, but multiple LEDs may also be used to define the wavelength.
The thickness of the optode material over the photosensitive elements may be 200 &mgr;m to 300 &mgr;m and preferably in the range of 220 &mgr;m to 260 &mgr;m.
With an optoelectronic gas sensor constructed according to the second embodiment of the present invention, the thickness of the optode material is much less than the height of the LED and amounts to approx. 5 &mgr;m to 20 &mgr;m, preferably 5 &mgr;m to 10 &mgr;m, while the height of the opto-transmitter (LED) is much greater, and may amount to approx. 300 &mgr;m.
To produce an optoelectronic gas sensor, an electronic component provided for this purpose may be designed so that multiple separate photosensitive elements are integrated into or onto a semiconductor substrate in sectors with central symmetry while maintaining a certain mutual spacing; a thin dielectric insulation layer covers all the photosensitive semiconductor areas; contact openings are provided with contacts to the photosensitive semiconductor elements at defined peripheral locations on the photosensitive semiconductor elements; and metallized strips are provided in the spaces between the photosensitive elements leading to a central contact pad for connecting the LED functioning as the opto-transmitter.
In this way, four equally large photodiodes having a common cathode formed by the substrate and an area of the individual photosensitive
Hensel Andreas
Oppelt Ulrich
Pfefferseder Anton
Schneider Joachim
Kenyon & Kenyon
Lee John D.
Robert & Bosch GmbH
Song Sarah U
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