WO1998047181A1 - Electromagnetic radiation sensor with high local contrast - Google Patents
Electromagnetic radiation sensor with high local contrast Download PDFInfo
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- WO1998047181A1 WO1998047181A1 PCT/EP1998/002130 EP9802130W WO9847181A1 WO 1998047181 A1 WO1998047181 A1 WO 1998047181A1 EP 9802130 W EP9802130 W EP 9802130W WO 9847181 A1 WO9847181 A1 WO 9847181A1
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- layer
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- radiation
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- detector
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- 230000005670 electromagnetic radiation Effects 0.000 title claims abstract description 9
- 229910021417 amorphous silicon Inorganic materials 0.000 claims abstract description 22
- 230000005855 radiation Effects 0.000 claims abstract description 9
- 238000002955 isolation Methods 0.000 claims description 12
- 239000012212 insulator Substances 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 7
- 229910045601 alloy Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 4
- 239000012774 insulation material Substances 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 230000001419 dependent effect Effects 0.000 claims description 2
- 230000005693 optoelectronics Effects 0.000 claims 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 2
- 239000011810 insulating material Substances 0.000 abstract description 2
- 238000004886 process control Methods 0.000 abstract 1
- 238000009413 insulation Methods 0.000 description 17
- 238000000034 method Methods 0.000 description 14
- 230000003287 optical effect Effects 0.000 description 14
- 238000000151 deposition Methods 0.000 description 8
- 230000008021 deposition Effects 0.000 description 8
- 239000010409 thin film Substances 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000001465 metallisation Methods 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 239000002800 charge carrier Substances 0.000 description 3
- 238000005530 etching Methods 0.000 description 3
- 230000010354 integration Effects 0.000 description 3
- 238000001312 dry etching Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229920000052 poly(p-xylylene) Polymers 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000012369 In process control Methods 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 239000000539 dimer Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
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- 238000010438 heat treatment Methods 0.000 description 1
- 238000010965 in-process control Methods 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000003079 width control Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14643—Photodiode arrays; MOS imagers
- H01L27/14645—Colour imagers
- H01L27/14647—Multicolour imagers having a stacked pixel-element structure, e.g. npn, npnpn or MQW elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14601—Structural or functional details thereof
- H01L27/1463—Pixel isolation structures
Definitions
- the invention relates to a sensor for electromagnetic radiation formed by a structure from an integrated circuit, in particular an ASIC, on the surface of which a layer sequence sensitive to the electromagnetic radiation containing amorphous silicon (a-Si: H) and / or its alloys is applied, wherein Pixel units which are spatially adjacent to one another are formed within the structure and are separated from one another by at least one boundary region with a conductivity which is lower than the conductivity of the layers of the layer sequence, each pixel unit having a radiation converter for converting the incident radiation into an intensity-dependent measured value and means for recording and storing of the measured value and wherein a readout control device is provided for reading out the measured values in each case related to a pixel unit such that the measured values related to the pixel unit refer to the d en sensor irradiated image can be assembled.
- a-Si: H amorphous silicon
- Electromagnetic radiation sensors are from “J. Schulte, J. Giehl, M. Böhm, JPM Schmitt, Thin Film on ASIC - A Novel Concept for Intelligent Image Sensors, Mat. Res. Soc. Symp. Proc, Vol. 285, pp. 1139ff. (1992) ".
- Such a component designed as an optical sensor is known in what is known as thin film on ASIC technology is formed and consists of an optically active detector layer in the form of a thin layer structure, which is vertically integrated on an integrated circuit, for example an ASIC (Application Specific Integrated Circuit).
- the ASIC contains the matrix-organized pixel unit structure (pixel structure) including the necessary pixel circuits for integrating the photocurrent, for storing the measured values and for reading them out.
- the optical detector consists of a layer or a multilayer system based on amorphous silicon or its alloys, which converts the incident photons into charge carriers, which are recorded as measured values.
- the measured values can be given by the instantaneous value of the photocurrent or by the voltage signal which is established on an integrator means after time integration.
- the integrator means can in turn consist of a capacity which is integrated in the ASIC, or be given by the intrinsic capacity of the detector.
- the two functional components, optical detector and ASIC are separated by an electrically insulating layer, which is only open at the points provided for signal transmission. The detector is contacted via contact layers on both sides.
- the mode of operation of an integrating sensor two different modes are distinguished, which are given by the type of integration of the photocurrent within the pixels. If the intrinsic capacity of the detector is used to integrate the photoelectrically generated charges, the electrical voltage across the detector varies during the integration. The change in voltage is a measure of the number of generated charge carriers and therefore for the intensity of the illumination of the pixel. In this case, one speaks of the charge storage mode. In contrast, in the so-called constant voltage mode, the voltage across the detector is kept constant with the aid of a control circuit implemented for each pixel in the ASIC. In this case, the photocurrent is integrated on a capacitance in the ASIC. Both operating modes can be regarded as known, they are described in H. Fischer, J. Schulte, P. Rieve, M. Böhm, Technology and Performance of TFA (Thin Film on ASIC) sensors, Mat. Res. Soc. Sy p. Proc, Vol. 336, pp. 867ff. (1994) and compared them.
- the optical detector of a TFA sensor consists of a layer or a layer system composed of several layers of amorphous silicon or its alloys stacked perpendicular to the direction of light propagation.
- the layer system can comprise a pin photodiode, i. H. the sequence of an n-doped, an intrinsically conductive (intrinsic) and a p-doped amorphous silicon layer, which is applied to an ASIC, for example using the known PECVD method.
- detectors with spectrally controllable sensitivity are known, which, for. B. consist of multilayer systems of the type piiin, nipiin or other layer sequences, which emerge from the patent applications DE P 44 41 444, 196 37 126.0, and 197 10 134.8.
- the layer system of a TFA sensor forming the optical detector is generally not for each individual pixel of the one- or two-dimensional pixel arrangement executed separately; rather, the manufacturing process in its simplest form provides that the multilayer system extends across the entire pixel arrangement and is only removed at the edge of the optically active surface of the sensor.
- the optical converters of two adjacent pixels are therefore not electrically separated from one another, but are coupled to one another by the conductive a-Si: H layers. This means that charge carriers that are generated between the pixels can be assigned to one of the two pixels.
- compensating currents can occur in the a-Si: H layer system, the magnitude of which depends on the size of the potential difference and the conductivity, especially the lowest, directly above the
- Detector back electrodes lying layer aligns. If this is a layer with sufficient conductivity, for example a p- or n-doped layer, then lateral compensation currents can flow which are superimposed on the photocurrents. The level of the equalizing currents, if it reaches the magnitude of the photocurrents, falsifies the actual measurement signals, especially at low ones
- the front electrodes are generally at a common potential for all pixels, so that no equalizing currents can occur at this point. Since in the above-mentioned layer systems the lowest layer is formed by a highly doped n- or p-layer, the equalizing currents between neighboring pixels can define the local contrast, defined as the maximum difference between the Reduce measurement signals of neighboring pixels to a not inconsiderable degree.
- a sensor manufactured using this method is unsatisfactory since equalizing currents can occur across the illuminated intrinsically conductive layer.
- the invention is based on the object of further developing a sensor of the type mentioned at the outset such that greater flexibility can be achieved in its manufacture, at the same time compensating currents which result as a result of different sensor voltages due to sufficiently conductive layers of the detector being suppressed, in order to increase the local contrast and to reduce the fixed pattern noise.
- the problem specified above is solved according to the invention in that the at least one boundary region has an insulator material applied to the surface of the integrated circuit, the layer thickness of which is dimensioned such that the insulation region extends at least through the layer of the layer sequence of the radiation converter which is closest to the integrated circuit extends.
- the invention is characterized in that the boundary regions between the individual picture elements are formed by insulation materials introduced.
- this design of the insulation areas results in considerably greater flexibility in process control.
- the layer thickness of the insulation layer and its lateral extension can be variably adjusted. The variability allows both the overlap width control the insulation layer as well as the extent of the insulation effect.
- the thin-film detectors of the TFA image sensor are thus partially or completely isolated from one another.
- this measure requires more effort in the technological processing of the sensors, however, allows the complete elimination of crosstalk described and consequently ⁇ the realization of fixed pattern noise-free sensors with a high local contrast.
- Show 1 Schematic cross section through the optically active area of a known sensor
- Fig. 4 Schematic cross section through the optically active area of a sensor according to a second embodiment of the invention.
- FIG. 1 shows a schematic cross section of a known sensor, the optical detector being formed by a pin photodiode.
- the figure shows an ASIC (01), which is shortened to the representation of the top metallization level (02), on which an insulating layer (03) and a further metallization layer are applied.
- the insulation layer is interrupted at the points at which the photocurrents from the detector are transferred to the ASIC.
- the metallization layer is structured in such a way that it forms detector back contacts (04). If necessary, the application of an insulation and metal layer can also be dispensed with if the uppermost metal level of the ASIC is used for the detector back electrodes.
- the optical detector shown as an example as a pin photodiode (05-07), is flat, ie unstructured, applied to the ASIC provided with the back electrodes. It is contacted on the front by a transparent and conductive oxide (TCO) (08).
- TCO transparent and conductive oxide
- This standard structure of a TFA sensor has the disadvantage that compensating currents can arise in the lowest, generally highly doped and therefore conductive layer (05) between the back electrodes of adjacent pixels, which overlap the photocurrents and falsify the information of the pixels.
- Fig. 2 shows a TFA sensor with self-structuring, which is known from J. Schulte et.al., SPIE Proc, Vol.2247, p.292 ff. (1994).
- trenches (11) are etched into the insulation layer underneath, which cause the bottom, doped layer (05) of the detector to tear off.
- FIG. 3 A first exemplary embodiment of a TFA sensor with pixel structuring according to the invention is shown in FIG. 3.
- the detector layers of adjacent pixels are completely separated from one another by an insulation layer (09).
- Pixel isolation can be done in two different ways. Firstly, after the deposition of the optical detector, trenches are etched into the a-Si: H structure (05-07) between the pixels, which trenches are then filled with an insulator (09). After removing excess insulator material from the optically active surfaces, the front contact (08) can be applied. On the other hand, an insulation layer is applied before the a-Si: H deposition and structured in such a way that a web structure (09) is created between the pixels, into which the optical detector (05-07) is then deposited.
- One possible implementation relates to the complete removal of the optical detector layers in the areas between the pixels immediately after the a-Si: H detector has been applied.
- the resulting trenches must then be filled up again with an insulator to ensure contacting of the sensor elements on the front.
- the manufacturing process provides for the multilayer system of amorphous silicon deposited on the ASIC to be structured in a photolithographic process in accordance with the pixel arrangement in such a way that the spaces between adjacent pixels are exposed. This can be done, for example, as part of a dry etching process.
- the trenches thus created are then filled again with an insulating material. In this context, it is usually necessary to coat the entire substrate with the insulator.
- the insulation material located above the active pixels must then be removed again by photolithography in order to cover the thin film detector with the aid of a transparent and conductive oxide (TCO - Transparent Conductive Oxide). or to be able to make electrical contact with an alternative material.
- TCO - Transparent Conductive Oxide
- the requirements for the insulation materials in the described type of pixel insulation relate to a low electrical conductivity and the possibility of photolithographic structuring. Furthermore, the temperatures required for processing the insulator material are relevant, which must not impair the functionality of the optical a-Si: H detectors produced in a low-temperature process. The maximum permissible temperature load can be specified at approx. 150 ° C.
- suitable insulators for example, special polymers (e.g. parylenes) can be used, which can be applied to a substrate in thin, non-planarizing layers or layers which are not very planar.
- the starting material a dimer
- a heating chamber Parylene has a high insulation resistance and a low susceptibility to water absorption.
- the layers can be structured using dry etching processes.
- Organically modified ceramics, so-called ORMOCERs, can be considered as alternative materials, which can be applied in a spin-on process and structured using dry or wet chemical methods.
- pixel isolation is the application of insulating webs, which are generated on the sensor substrate provided with the detector back electrodes before the deposition of the a-Si: H detector become. After applying and structuring the detector back contacts, another insulation layer is applied. This insulator is then structured in such a way that narrow webs remain only in the spaces between the detector back electrodes, which later separate the detector system from neighboring pixels. The a-Si: H detector is then deposited into these webs, which is completed by the front contact. In order to ensure continuous contact on the front of the sensor, the amorphous silicon deposited on the webs may have to be removed again by an etching process.
- the height of the isolation webs can either be the same as the height of the a-Si: H detector layer stack, so that adjacent detector elements are completely separated from one another, or the web height is less than the total Height of the detector. In the latter case, however, at least the lowest doped and thus conductive layer must be interrupted.
- a low-temperature process materials that require higher process temperatures can also be used.
- materials that require higher process temperatures can also be used.
- cyclotenes a polymer applied using the spin-on method, polyimide or CVD dielectrics (silicon nitride, silicon oxynitride, etc.) are suitable.
- the insulation layers are first applied over the entire surface and then structured so that the insulation webs exist between the pixels stay.
- the width of the isolation webs is not necessarily tied to the pixel spacing, it can also be larger or smaller if necessary.
Abstract
An electromagnetic radiation sensor comprises a structure composed of an integrated circuit (01), in particular an ASIC, and of an electromagnetic radiation-sensitive sequence of layers (05, 06, 07, 08) which contains amorphous silicium (a-Si:H) and is applied on the surface of the integrated circuit. Image point units (B) are spatially separated within the structure by at least one border region with a lower conductivity than the layers of the sequence of layers. In order to improve the process control flexibility of such a sensor, the at least one border region has an insulating material (09, 10) applied on the surface of the integrated circuit and having such a thickness that the insulating region extends at least through the layer (05) of the sequence of layers of the radiation transducer nearest to the integrated circuit (01).
Description
Elektromagnetischer Strahlungssensor mit hohem Electromagnetic radiation sensor with high
LokalkontrastLocal contrast
Die Erfindung betrifft einen Sensor für elektromagnetische Strahlung gebildet durch eine Struktur aus einem integrierten Schaltkreis, insbesondere einem ASIC, auf dessen Oberfläche eine für die elektromagnetische Strahlung sensitive Schichtenfolge enthaltend amorphes Silizium (a-Si:H) und/oder dessen Legierungen aufgebracht ist, wobei innerhalb der Struktur räumlich aneinander angrenzende Bildpunkteinheiten ausgebildet sind, die durch mindestens einen Grenzbereich mit einer gegenüber der Leitfähigkeit der Schichten der Schichtenfolge herabgesetzten Leitfähigkeit voneinander getrennt sind, wobei jede Bildpunkteinheit einen Strahlungswandler zum Umwandeln der einfallenden Strahlung in einen intensitätsabhängigen Meßwert und Mittel zum Erfassen und Abspeichern des Meßwertes aufweist und wobei eine Auslesesteuereinrichtung für das jeweils auf eine Bildpunkteinheit bezogene Auslesen der Meßwerte vorgesehen ist derart, daß aus den bildpunkteinheitsbezogenen Meßwerten das auf den Sensor eingestrahlte Bild zusammensetzbar ist.The invention relates to a sensor for electromagnetic radiation formed by a structure from an integrated circuit, in particular an ASIC, on the surface of which a layer sequence sensitive to the electromagnetic radiation containing amorphous silicon (a-Si: H) and / or its alloys is applied, wherein Pixel units which are spatially adjacent to one another are formed within the structure and are separated from one another by at least one boundary region with a conductivity which is lower than the conductivity of the layers of the layer sequence, each pixel unit having a radiation converter for converting the incident radiation into an intensity-dependent measured value and means for recording and storing of the measured value and wherein a readout control device is provided for reading out the measured values in each case related to a pixel unit such that the measured values related to the pixel unit refer to the d en sensor irradiated image can be assembled.
Elektromagnetische Strahlungssensoren sind aus „J. Schulte, J. Giehl, M. Böhm, J. P. M. Schmitt, Thin Film on ASIC - A Novel Concept for Intelligent Image Sensors, Mat. Res. Soc. Symp. Proc, Vol. 285, S. 1139ff. (1992)" bekannt. Ein solches als optischer Sensor ausgeführtes Bauelement ist in sogenannter Thin Film on
ASIC-Technologie ausgebildet und besteht aus einer optisch aktiven Detektorschicht in Form einer Dünnschichtstruktur, welche vertikal auf einem integrierten Schaltkreis, beispielsweise einem ASIC (Application Specific Integrated Circuit) integriert ist. Der ASIC enthält hierbei die matrixorganisierte Bildpunkteinheitstruktur (Pixelstruktur) einschließlich der erforderlichen Pixelschaltkreise zur Integration des Photostromes, zur Speicherung der Meßwerte und zu deren Auslese. Der optische Detektor besteht aus einer Schicht oder einem Mehrschichtsystem auf der Basis amorphen Siliziums oder dessen Legierungen, welches die einfallenden Photonen in Ladungsträger umwandelt, die als Meßwerte erfaßt werden. Die Meßwerte können dabei durch den Momentanwert des Photostromes oder durch das Spannungssignal gegeben sein, welches sich nach zeitlicher Integration auf einem Integratormittel einstellt. Das Integratormittel wiederum kann aus einer Kapazität bestehen, welche im ASIC integriert ist, oder durch die Eigenkapazität des Detektors gegeben sein. Die beiden funktionalen Komponenten optischer Detektor und ASIC sind durch eine elektrisch isolierende Schicht getrennt, die lediglich an den für die Signalübergabe vorgesehenen Stellen geöffnet ist. Die Kontaktierung des Detektors erfolgt über Kontaktschichten auf beiden Seiten.Electromagnetic radiation sensors are from “J. Schulte, J. Giehl, M. Böhm, JPM Schmitt, Thin Film on ASIC - A Novel Concept for Intelligent Image Sensors, Mat. Res. Soc. Symp. Proc, Vol. 285, pp. 1139ff. (1992) ". Such a component designed as an optical sensor is known in what is known as thin film on ASIC technology is formed and consists of an optically active detector layer in the form of a thin layer structure, which is vertically integrated on an integrated circuit, for example an ASIC (Application Specific Integrated Circuit). The ASIC contains the matrix-organized pixel unit structure (pixel structure) including the necessary pixel circuits for integrating the photocurrent, for storing the measured values and for reading them out. The optical detector consists of a layer or a multilayer system based on amorphous silicon or its alloys, which converts the incident photons into charge carriers, which are recorded as measured values. The measured values can be given by the instantaneous value of the photocurrent or by the voltage signal which is established on an integrator means after time integration. The integrator means can in turn consist of a capacity which is integrated in the ASIC, or be given by the intrinsic capacity of the detector. The two functional components, optical detector and ASIC, are separated by an electrically insulating layer, which is only open at the points provided for signal transmission. The detector is contacted via contact layers on both sides.
Hinsichtlich der Betriebsweise eines integrierenden Sensors werden zwei verschiedene Modi unterschieden, die durch die Art der Integration des Photostromes innerhalb der Bildpunkte gegeben sind. Wird die Eigenkapazität des Detektors zur Integration der photoelektrisch erzeugten Ladungen benutzt, so variiert die elektrische Spannung über dem Detektor während der Integration. Die Änderung der Spannung ist dabei ein Maß für die Zahl der
generierten Ladungsträger und mithin für die Intensität der Beleuchtung des Bildpunktes. Man spricht in diesem Fall vom Ladungsspeicherungsmodus (Charge Storage Mode) . Im Gegensatz dazu wird beim sog. Konstantspannungsmodus (Constant Voltage Mode) die Spannung über dem Detektor mit Hilfe einer für jeden Bildpunkt im ASIC ausgeführten Regelschaltung konstant gehalten. Die Integration des Photostromes erfolgt in diesem Fall auf einer Kapazität im ASIC. Beide Betriebsmodi können als bekannt angesehen werden, sie sind in H. Fischer, J. Schulte, P. Rieve, M. Böhm, Technology and Performance of TFA (Thin Film on ASIC) -Sensors, Mat . Res. Soc. Sy p. Proc, Vol. 336, S. 867ff. (1994) beschrieben und einander gegenübergestellt.With regard to the mode of operation of an integrating sensor, two different modes are distinguished, which are given by the type of integration of the photocurrent within the pixels. If the intrinsic capacity of the detector is used to integrate the photoelectrically generated charges, the electrical voltage across the detector varies during the integration. The change in voltage is a measure of the number of generated charge carriers and therefore for the intensity of the illumination of the pixel. In this case, one speaks of the charge storage mode. In contrast, in the so-called constant voltage mode, the voltage across the detector is kept constant with the aid of a control circuit implemented for each pixel in the ASIC. In this case, the photocurrent is integrated on a capacitance in the ASIC. Both operating modes can be regarded as known, they are described in H. Fischer, J. Schulte, P. Rieve, M. Böhm, Technology and Performance of TFA (Thin Film on ASIC) sensors, Mat. Res. Soc. Sy p. Proc, Vol. 336, pp. 867ff. (1994) and compared them.
Der optische Detektor eines TFA-Sensors besteht aus einer Schicht oder einem Schichtsystem aus mehreren senkrecht zur Lichtausbreitungsrichtung gestapelten Schichten aus amorphem Silizium oder dessen Legierungen. Beispielsweise kann das Schichtsystem eine pin-Photodiode umfassen, d. h. die Abfolge einer n-dotierten, einer eigenleitenden (intrinsischen) und einer p-dotierten amorphen Siliziumschicht, welche beispielsweise mit Hilfe des bekannten PECVD-Verfahrens auf einem ASIC aufgebracht wird.The optical detector of a TFA sensor consists of a layer or a layer system composed of several layers of amorphous silicon or its alloys stacked perpendicular to the direction of light propagation. For example, the layer system can comprise a pin photodiode, i. H. the sequence of an n-doped, an intrinsically conductive (intrinsic) and a p-doped amorphous silicon layer, which is applied to an ASIC, for example using the known PECVD method.
Des weiteren sind Detektoren mit spektral steuerbarer Empfindlichkeit bekannt, welche z. B. aus Mehrschichtsystemen vom Typ piiin, nipiin oder weiteren Schichtenfolgen bestehen, die aus den Patentanmeldungen DE P 44 41 444, 196 37 126.0, und 197 10 134.8 hervorgehen.Furthermore, detectors with spectrally controllable sensitivity are known, which, for. B. consist of multilayer systems of the type piiin, nipiin or other layer sequences, which emerge from the patent applications DE P 44 41 444, 196 37 126.0, and 197 10 134.8.
Das den optischen Detektor bildende Schichtsystem eines TFA-Sensors ist in der Regel nicht für jeden einzelnen Bildpunkt der ein- oder zweidimensionalen Pixelanordnung
separat ausgeführt; vielmehr sieht der Herstellungsprozeß in seiner einfachsten Form vor, daß sich das Mehrschichtsystem flächig über die komplette Bildpunktanordnung erstreckt und lediglich am Rand der optisch aktiven Fläche des Sensors entfernt wird. Die optischen Wandler zweier benachbarter Bildpunkte sind mithin nicht elektrisch voneinander getrennt, sondern durch die leitfähigen a-Si :H-Schichten miteinander gekoppelt. Dies bedeutet, daß Ladungsträger, welche zwischen den Bildpunkten generiert werden, einem der beiden Bildpunkte zugerechnet werden können. Darüber hinaus kann es bei unterschiedlichen Spannungen an benachbarten Bildpunkten, d. h. bei Vorliegen einer Potentialdifferenz zwischen benachbarten Detektorrückkontakten zu Ausgleichsströmen im a-Si:H- Schichtsystem kommen, deren Höhe sich nach der Größe der Potentialdifferenz und nach der Leitfähigkeit vor allem der untersten, unmittelbar über denThe layer system of a TFA sensor forming the optical detector is generally not for each individual pixel of the one- or two-dimensional pixel arrangement executed separately; rather, the manufacturing process in its simplest form provides that the multilayer system extends across the entire pixel arrangement and is only removed at the edge of the optically active surface of the sensor. The optical converters of two adjacent pixels are therefore not electrically separated from one another, but are coupled to one another by the conductive a-Si: H layers. This means that charge carriers that are generated between the pixels can be assigned to one of the two pixels. In addition, with different voltages at adjacent pixels, i.e. when there is a potential difference between adjacent detector back contacts, compensating currents can occur in the a-Si: H layer system, the magnitude of which depends on the size of the potential difference and the conductivity, especially the lowest, directly above the
Detektorrückelektroden liegenden Schicht richtet. Handelt es sich bei dieser um eine Schicht mit ausreichender Leitfähigkeit, beispielsweise eine p- oder n-dotierte Schicht, so können laterale Ausgleichsströme fließen, die sich den Photoströmen überlagern. Die Höhe der Ausgleichsströme, wenn sie in die Größenordnung der Photoströme vordringt, verfälscht die eigentlichen Meßsignale speziell bei niedrigenDetector back electrodes lying layer aligns. If this is a layer with sufficient conductivity, for example a p- or n-doped layer, then lateral compensation currents can flow which are superimposed on the photocurrents. The level of the equalizing currents, if it reaches the magnitude of the photocurrents, falsifies the actual measurement signals, especially at low ones
Beleuchtungsintensitäten. Die Frontelektroden liegen in der Regel für alle Bildpunkte auf gemeinsamem Potential, so daß an dieser Stelle keine Ausgleichsströme auftreten können. Da bei den oben genannten Schichtsystemen die unterste Schicht durch eine hoch dotierte n- oder p- Schicht gebildet wird, können die Ausgleichsströme zwischen benachbarten Bildpunkten den lokalen Kontrast, definiert als maximaler Unterschied zwischen den
Meßsignalen benachbarer Bildpunkte, in nicht unerheblichem Maße herabsetzen.Lighting intensities. The front electrodes are generally at a common potential for all pixels, so that no equalizing currents can occur at this point. Since in the above-mentioned layer systems the lowest layer is formed by a highly doped n- or p-layer, the equalizing currents between neighboring pixels can define the local contrast, defined as the maximum difference between the Reduce measurement signals of neighboring pixels to a not inconsiderable degree.
Das erläuterte Problem haftet in besonderer Weise Sensoren an, die nach dem Ladungsspeicherungsmodus arbeiten, da es hierbei, bedingt durch das Sensorprinzip, zu signifikanten Abweichungen der Sensorspannungen bei unterschiedlich beleuchteten Bildpunkten kommen kann. Jedoch auch bei der Betriebsart des Konstantspannungsmodus, bei denen sämtliche Rückelektroden auf einem festen und konstanten Potential gehalten werden, können geringfügige Variationen der Detektorpotentiale auftreten, welche beispielsweise die Folge prozeßbedingter lokaler Schwankungen der Schaltungs- und Transistorparameter sind. Als Konsequenz weist ein Bild, das mit einem derartigen Sensor aufgezeichnet wird, ein festes, dem eigentlichen Bildinhalt überlagertes Muster auf (Fixed Pattern Noise) , wobei dieses Muster wiederum vom Beleuchtungszustand des Sensors abhängen kann. Der lokale Kontrast, d. h. der zwischen zwei benachbarten Pixel detektierbare Signalunterschied, wird ebenfalls durch dieses Muster beschränkt.The problem explained is particularly associated with sensors that operate according to the charge storage mode, since, due to the sensor principle, there may be significant deviations in the sensor voltages in the case of differently illuminated pixels. However, even in the operating mode of the constant voltage mode, in which all the back electrodes are kept at a fixed and constant potential, slight variations in the detector potentials can occur, which are, for example, the result of process-related local fluctuations in the circuit and transistor parameters. As a consequence, an image that is recorded with such a sensor has a fixed pattern that is superimposed on the actual image content (fixed pattern noise), which in turn can depend on the illumination state of the sensor. The local contrast, i.e. H. the signal difference detectable between two neighboring pixels is also limited by this pattern.
Aus: J. Schulte, H. Fischer, M. Böhm, Intelligent Image Sensor for On-Chip Contour Extraction, SPIE Proc, Vol. 2247, S. 292ff. (1994) ist ein Sensor der eingangs genannten Art bekannt. Dort wird offenbart, zur Pixelisolation einen Graben zu verwenden, welcher vor der Deposition des Dünnschichtdetektors in die Isolationsschicht zwischen ASIC und a-Si :H-Detektor im Bereich zwischen den Detektorrückelektroden geätzt wird, wobei beispielsweise die Metallisierungen der Detektorrückelektroden als Ätzstopmaske verwendet werden können. Bei der anschließenden Deposition des Detektors
reißt die unterste, in der Regel hoch dotierte Detektorschicht an diesen Stellen ab, so daß Ausgleichsströme zwischen benachbarten Pixeln gemindert werden.From: J. Schulte, H. Fischer, M. Böhm, Intelligent Image Sensor for On-Chip Contour Extraction, SPIE Proc, Vol. 2247, pp. 292ff. (1994) a sensor of the type mentioned is known. There it is disclosed to use a trench for pixel isolation, which is etched before the deposition of the thin-film detector into the insulation layer between ASIC and a-Si: H detector in the area between the detector back electrodes, wherein the metallizations of the detector back electrodes can be used as an etching stop mask, for example. During the subsequent deposition of the detector tears off the bottom, usually highly doped detector layer at these points, so that equalizing currents between neighboring pixels are reduced.
Ein nach diesem Verfahren hergestellter Sensor ist jedoch nicht zufriedenstellend, da hierbei Ausgleichsströme über die beleuchtete eigenleitfähige Schicht auftreten können. Weitere Nachteile ergeben sich, insbesondere bei Verwendung farbauflösender Schichtstrukturen, durch dotierte Schichten im Innern der Struktur sowie durch durch Schichtenfolgen, die mehrere unmittelbar aneinander angrenzende eigenleitende Schichten enthalten. Hierbei kann es bei unterschiedlichen Beleuchtungssituationen in benachbarten Bildpunkteinheiten zu unterschiedlichen Potentialverteilungen in den Detektorschichten kommen, welche infolge des Fehlens einer kompletten Pixelisolation ebenfalls Ausgleichsströme verursachen können. Darüber hinaus besteht ein Nachteil bei der Ausbildung eines solchen durch einen Ätzprozeß gebildeten Grabens darin, daß die Tiefe des Grabens und damit die Dicke der halbleitenden Schicht technologisch durch den Abstand zum integrierten Schaltkreis gegeben ist.However, a sensor manufactured using this method is unsatisfactory since equalizing currents can occur across the illuminated intrinsically conductive layer. Further disadvantages arise, in particular when using color-resolving layer structures, from doped layers in the interior of the structure and from layer sequences which contain a plurality of intrinsically conductive layers directly adjacent to one another. Different lighting situations in neighboring pixel units can lead to different potential distributions in the detector layers, which can also cause equalizing currents due to the lack of complete pixel isolation. In addition, there is a disadvantage with the formation of such a trench formed by an etching process that the depth of the trench and thus the thickness of the semiconducting layer is given technologically by the distance from the integrated circuit.
Der Erfindung liegt die Aufgabe zugrunde, einen Sensor der eingangs genannten Art dahingehend weiter zu entwickeln, daß eine höhere Flexibilität bei seiner Herstellung erreichbar ist, wobei gleichzeitig Ausgleichsströme, welche sich als Folge unterschiedlicher Sensorspannungen aufgrund ausreichend leitfähiger Schichten des Detektors ergeben, unterdrückt werden sollen, um auf diese Weise eine Steigerung des lokalen Kontrastes zu erzielen und das Fixed Pattern Noise zu reduzieren.
Das vorstehend spezifizierte Problem wird erfindungsgemäß dadurch gelöst, daß der mindestens eine Grenzbereich ein auf die Oberfläche des integrierten Schaltkreises aufgebrachtes Isolatormaterial aufweist, dessen Schichtdicke so bemessen ist, daß sich der Isolationsbereich mindestens durch die dem integrierten Schaltkreis am nächsten liegende Schicht der Schichtenfolge des Strahlungwandlers hindurch erstreckt.The invention is based on the object of further developing a sensor of the type mentioned at the outset such that greater flexibility can be achieved in its manufacture, at the same time compensating currents which result as a result of different sensor voltages due to sufficiently conductive layers of the detector being suppressed, in order to increase the local contrast and to reduce the fixed pattern noise. The problem specified above is solved according to the invention in that the at least one boundary region has an insulator material applied to the surface of the integrated circuit, the layer thickness of which is dimensioned such that the insulation region extends at least through the layer of the layer sequence of the radiation converter which is closest to the integrated circuit extends.
Die Erfindung zeichnet sich dadurch aus, daß die Grenzbereiche zwischen den einzelnen Bildelementen durch eingebrachte Isolationsmaterialen gebildet werden. Durch diese Gestaltung der Isolationsbereiche ergibt sich im Gegensatz zur der bekannten Lösung in Form der „Grabenstruktur" eine erheblich größere Flexibilität in der Prozeßsteuerung. Die Schichtdicke der Isolationsschicht kann dabei ebenso wie deren laterale Erstreckung variabel eingestellt werden. Durch die Variabilität läßt sich sowohl die Überlappungsweite der Isolationsschicht als auch der Umfang der Isolationswirkung steuern.The invention is characterized in that the boundary regions between the individual picture elements are formed by insulation materials introduced. In contrast to the known solution in the form of the "trench structure", this design of the insulation areas results in considerably greater flexibility in process control. The layer thickness of the insulation layer and its lateral extension can be variably adjusted. The variability allows both the overlap width control the insulation layer as well as the extent of the insulation effect.
Erfindungsgemäß werden somit die Dünnschicht-Detektoren des TFA-Bildsensors teilweise oder vollständig voneinander isoliert. Diese Maßnahme bedingt zwar einen höheren Aufwand bei der technologischen Prozessierung der Sensoren, erlaubt jedoch die vollständige Unterbindung des beschriebenen Übersprechens und mithin^die Realisierung Fixed Pattern Noise-freier Sensoren mit einem hohen Lokalkontrast.According to the invention, the thin-film detectors of the TFA image sensor are thus partially or completely isolated from one another. Although this measure requires more effort in the technological processing of the sensors, however, allows the complete elimination of crosstalk described and consequently ^ the realization of fixed pattern noise-free sensors with a high local contrast.
Die Erfindung wird im Folgenden anhand einer Ausführungsbeispiele darstellenden Zeichnung näher erläutert. Dabei zeigen
Fig. 1: Schematischer Querschnitt durch den optisch aktiven Bereich eines bekannten Sensors,The invention is explained in more detail below with reference to a drawing showing exemplary embodiments. Show 1: Schematic cross section through the optically active area of a known sensor,
Fig. 2: Schematischer Querschnitt durch den optisch aktiven Bereich eines weiteren bekannten Sensors,2: Schematic cross section through the optically active area of a further known sensor,
Fig. 3: Schematischer Querschnitt durch den optisch aktiven Bereich eines Sensors gemäß einem ersten Ausführungsbeispiel der Erfindung,3: Schematic cross section through the optically active area of a sensor according to a first embodiment of the invention,
Fig. 4: Schematischer Querschnitt durch den optisch aktiven Bereich eines Sensors gemäß einem zweiten Ausführungsbeispiel der Erfindung.Fig. 4: Schematic cross section through the optically active area of a sensor according to a second embodiment of the invention.
In Fig. 1 ist ein schematischer Querschnitt eines bekannten Sensors dargestellt, wobei der optische Detektor durch eine pin-Photodiode gebildet wird. Die Abbildung zeigt einen ASIC (01), welcher auf die Darstellung der obersten Metallisierungsebene (02) verkürzt ist, auf den eine isolierende Schicht (03) sowie eine weitere Metallisierungsschicht aufgebracht sind. Die Isolationsschicht ist an den Stellen unterbrochen, an denen die Photoströme des Detektors an den ASIC übergeben werden. Die Metallisierungsschicht ist derart strukturiert, daß sie Detektorrückkontakte (04) bildet. Auf das Aufbringen einer Isolations- und Metallschicht kann gegebenenfalls auch verzichtet werden, falls die oberste Metallebene des ASIC für die Detektorrückelektroden verwendet wird. Der optische Detektor, exemplarisch als pin-Photodiode (05-07) dargestellt, ist flächig, d. h. unstrukturiert auf dem mit den Rückelektroden versehenen ASIC aufgebracht. Er wird auf der Frontseite von einem transparenten und leitfähigem Oxid (TCO) (08) kontaktiert.
Diese Standardstruktur eines TFA-Sensors besitzt den Nachteil, daß in der untersten, in der Regel hoch dotierten und damit leitfähigen Schicht (05) Ausgleichsströme zwischen den Rückelektroden benachbarter Bildpunkte entstehen können, die sich den Photoströmen überlagern und die Information der Bildpunkte verfälschen.1 shows a schematic cross section of a known sensor, the optical detector being formed by a pin photodiode. The figure shows an ASIC (01), which is shortened to the representation of the top metallization level (02), on which an insulating layer (03) and a further metallization layer are applied. The insulation layer is interrupted at the points at which the photocurrents from the detector are transferred to the ASIC. The metallization layer is structured in such a way that it forms detector back contacts (04). If necessary, the application of an insulation and metal layer can also be dispensed with if the uppermost metal level of the ASIC is used for the detector back electrodes. The optical detector, shown as an example as a pin photodiode (05-07), is flat, ie unstructured, applied to the ASIC provided with the back electrodes. It is contacted on the front by a transparent and conductive oxide (TCO) (08). This standard structure of a TFA sensor has the disadvantage that compensating currents can arise in the lowest, generally highly doped and therefore conductive layer (05) between the back electrodes of adjacent pixels, which overlap the photocurrents and falsify the information of the pixels.
Fig. 2 zeigt einen TFA-Sensor mit Selbststrukturierung, der aus J. Schulte et.al., SPIE Proc, Vol.2247, S.292 ff. (1994) , bekannt ist. Hierbei werden vor der Deposition des optischen Detektors Gräben (11) in die darunter liegende Isolationsschicht geätzt, die ein Abreißen der untersten, dotierten Schicht (05) des Detektors bewirken.Fig. 2 shows a TFA sensor with self-structuring, which is known from J. Schulte et.al., SPIE Proc, Vol.2247, p.292 ff. (1994). Before the deposition of the optical detector, trenches (11) are etched into the insulation layer underneath, which cause the bottom, doped layer (05) of the detector to tear off.
Ein erstes erfindungsgemäßes Auführungsbeispiel eines TFA-Sensors mit Pixelstrukturierung ist in Fig. 3 dargestellt. Hierbei sind die Detektorschichten benachbarter Bildpunkte vollständig durch eine Isolationsschicht (09) voneinander getrennt. Die Pixelisolation kann auf zwei verschidene Arten erfolgen. Zum einen werden nach der Deposition des optischen Detektors zwischen den Bildpunkten Gräben in die a-Si:H- Struktur (05-07) geätzt, welche dann mit einem Isolator (09) aufgefüllt werden. Nach dem Entfernen überschüssigen Isolatormaterials auf den optisch aktiven Flächen kann der Frontkontakt (08) aufgebracht werden. Zum anderen wird vor der a-Si :H-Deposition eine Isolationsschicht aufgetragen und derart strukturiert, daß eine Stegstruktur (09) zwischen den Bildpunkten entsteht, in die dann die Deposition des optischen Detektors (05-07) erfolgt. Den Frontkontakt bildet auch in diesem Fall ein TCO (08) . Im Ergebnis führen beide Varianten zu einer vollständigen Pixelisolation, welche Ausgleichsströme zwischen benachbarten Pixeln unterdrückt.
In der Regel ist eine dergestaltige komplette Pixelisolation nicht unbedingt erforderlich, sondern es ist ausreichend, die unterste, dotierte Schicht (05) zwischen den Bildpunkten zu unterbrechen. Eine schematische Darstellung eines solchen, gemäß einem zweiten Ausführungsbeispiel der Erfindung gestalteten TFA-Sensors mit teilweiser Pixelisolation (10) enthält Fig. 4. In diesem Fall muß die Pixelisolation vor der Deposition des a-Si :H-Detektors erfolgen. Die Pixelstrukturierung kann durch verschiedene technologische Maßnahmen realisiert werden, die im folgenden beschrieben sind:A first exemplary embodiment of a TFA sensor with pixel structuring according to the invention is shown in FIG. 3. The detector layers of adjacent pixels are completely separated from one another by an insulation layer (09). Pixel isolation can be done in two different ways. Firstly, after the deposition of the optical detector, trenches are etched into the a-Si: H structure (05-07) between the pixels, which trenches are then filled with an insulator (09). After removing excess insulator material from the optically active surfaces, the front contact (08) can be applied. On the other hand, an insulation layer is applied before the a-Si: H deposition and structured in such a way that a web structure (09) is created between the pixels, into which the optical detector (05-07) is then deposited. In this case, too, the front contact is formed by a TCO (08). As a result, both variants lead to complete pixel isolation, which suppresses equalizing currents between neighboring pixels. As a rule, complete pixel isolation of this type is not absolutely necessary, but it is sufficient to interrupt the lowest, doped layer (05) between the pixels. A schematic representation of such a TFA sensor designed in accordance with a second exemplary embodiment of the invention with partial pixel isolation (10) is shown in FIG. 4. In this case, the pixel isolation must take place before the deposition of the a-Si: H detector. Pixel structuring can be implemented using various technological measures, which are described below:
Eine mögliche Realisation bezieht sich auf die komplette Entfernung der optischen Detektorschichten in den zwischen den Pixeln liegenden Bereichen unmittelbar nach dem Aufbringen des a-Si :H-Detektors. Die dabei entstehenden Gräben müssen anschließend mit einem Isolator wieder aufgefüllt werden, um die Kontaktierung der Sensorelemente auf der Frontseite zu gewährleisten. Das Herstellungsverfahren sieht vor, das auf dem ASIC deponierte Mehrschichtsystem aus amorphem Silizium in einem photolithographischen Prozeß entsprechend der Pixelanordnung derart zu strukturieren, daß die Zwischenräume zwischen benachbarten Bildpunkten offengelegt werden. Dies kann beispielsweise im Rahmen eines Trockenätzprozesses geschehen. Anschließend werden die so entstandenen Gräben mit einem isolierenden Material wieder aufgefüllt. In der Regel ist es in diesem Zusammenhang erforderlich, das komplette Substrat mit dem Isolator zu beschichten. Das über den aktiven Bildpunkten befindliche Isolationsmaterial muß anschließend auf photolithographischem Wege wieder entfernt werden, um den Dünnfilmdetektor mit Hilfe eines transparenten und leitfähigen Oxides (TCO - Transparent Conductive Oxide)
oder eines alternativen Materials elektrisch kontaktieren zu können.One possible implementation relates to the complete removal of the optical detector layers in the areas between the pixels immediately after the a-Si: H detector has been applied. The resulting trenches must then be filled up again with an insulator to ensure contacting of the sensor elements on the front. The manufacturing process provides for the multilayer system of amorphous silicon deposited on the ASIC to be structured in a photolithographic process in accordance with the pixel arrangement in such a way that the spaces between adjacent pixels are exposed. This can be done, for example, as part of a dry etching process. The trenches thus created are then filled again with an insulating material. In this context, it is usually necessary to coat the entire substrate with the insulator. The insulation material located above the active pixels must then be removed again by photolithography in order to cover the thin film detector with the aid of a transparent and conductive oxide (TCO - Transparent Conductive Oxide). or to be able to make electrical contact with an alternative material.
Die Anforderungen an die Isolationsmaterialien bei der beschriebenen Art der Isolierung von Pixeln betreffen eine geringe elektrische Leitfähigkeit sowie die Möglichkeit der photolithographischen Strukturierbarkeit . Des weiteren sind die zur Prozessierung des Isolatormaterials erforderlichen Temperaturen relevant, die die in einem Niedertemperatureprozeß hergestellten optischen a-Si :H-Detektoren nicht in ihrer Funktionsfähigkeit beeinträchtigen dürfen. Die maximal zulässige Temperaturbelastung kann mit ca. 150°C angegeben werden. Als geeignete Isolatoren können beispielsweise spezielle Polymere (z. B. Parylene) verwendet werden, welche in dünnen, nicht bzw. wenig planarisierenden Schichten bei Raumtemperatur auf ein Substrat aufgebracht werden können. Das Ausgangsmaterial, ein Dimer, wird dabei zunächst verdampft und anschließend in einer Heizkammer in einer chemischen Reaktion in ein Monomer umgewandelt, welches sich dann in der evakuierten Depositionskammer als polymerer Film auf dem Substrat niederschlägt. Parylene weist einen hohen Isolationswiderstand sowie eine geringe Anfälligkeit gegen Wasseraufnahme auf. Die Schichten können mit Hilfe von Trockenätzprozessen strukturiert werden. Als alternative Materialien kommen organisch modifizierte Keramiken, sog. ORMOCERe, in Frage, die in einem Spin-On- Verfahren aufgebracht und auf trocken- oder naßchemischem Wege strukturiert werden können.The requirements for the insulation materials in the described type of pixel insulation relate to a low electrical conductivity and the possibility of photolithographic structuring. Furthermore, the temperatures required for processing the insulator material are relevant, which must not impair the functionality of the optical a-Si: H detectors produced in a low-temperature process. The maximum permissible temperature load can be specified at approx. 150 ° C. As suitable insulators, for example, special polymers (e.g. parylenes) can be used, which can be applied to a substrate in thin, non-planarizing layers or layers which are not very planar. The starting material, a dimer, is first evaporated and then converted in a chemical reaction in a heating chamber into a monomer, which is then deposited in the evacuated deposition chamber as a polymer film on the substrate. Parylene has a high insulation resistance and a low susceptibility to water absorption. The layers can be structured using dry etching processes. Organically modified ceramics, so-called ORMOCERs, can be considered as alternative materials, which can be applied in a spin-on process and structured using dry or wet chemical methods.
Eine weitere Möglichkeit zur Pixelisolation stellt das Aufbringen von isolierenden Stegen dar, welche vor der Deposition des a-Si :H-Detektors auf dem mit den Detektorrückelektroden versehenen Sensorsubstrat erzeugt
werden. Hierbei wird nach Aufbringen und Strukturierung der Detektorrückkontakte eine weitere Isolationsschicht aufgetragen. Dieser Isolator wird anschließend derart strukturiert, daß nur in den Zwischenräumen zwischen den Detektorrückelektroden schmale Stege zurückbleiben, die später das Detektorsystem benachbarter Pixel voneinander trennen. In diese Stege hinein erfolgt anschließend die Deposition des a-Si :H-Detektors, welcher durch den Frontkontakt komplettiert wird. Um eine kontinuierliche Kontaktierung auf der Frontseite des Sensors zu gewährleisten, muß gegebenenfalls das auf den Stegen abgeschiedene amorphe Silizium durch einen Ätzprozeß wieder entfernt werden. Im Zusammenhang mit dieser Art der Pixelisolation sind zwei Varianten möglich: Die Höhe der Isolationsstege kann entweder gleich der Höhe des a- Si :H-Detektor-Schichtstapels sein, so daß benachbarte Detektorelemente komplett voneinander getrennt sind, oder die Steghöhe ist geringer als die gesamte Höhe des Detektors. Im letzteren Fall muß jedoch zumindest die unterste dotierte und damit leitfähige Schicht unterbrochen werden.Another possibility for pixel isolation is the application of insulating webs, which are generated on the sensor substrate provided with the detector back electrodes before the deposition of the a-Si: H detector become. After applying and structuring the detector back contacts, another insulation layer is applied. This insulator is then structured in such a way that narrow webs remain only in the spaces between the detector back electrodes, which later separate the detector system from neighboring pixels. The a-Si: H detector is then deposited into these webs, which is completed by the front contact. In order to ensure continuous contact on the front of the sensor, the amorphous silicon deposited on the webs may have to be removed again by an etching process. In connection with this type of pixel isolation, two variants are possible: The height of the isolation webs can either be the same as the height of the a-Si: H detector layer stack, so that adjacent detector elements are completely separated from one another, or the web height is less than the total Height of the detector. In the latter case, however, at least the lowest doped and thus conductive layer must be interrupted.
Da bei der zuletzt dargestellten Möglichkeit die Temperaturbeaufschlagung während der Herstellung der Isolationsstege unkritisch ist, weil der optische a-Si.H- Detektor erst anschließend in einemSince the temperature exposure during the manufacture of the insulation webs is not critical in the last option presented, because the optical a-Si.H detector only then in one
Niedertemperaturprozeß aufgebracht wird, kommen hierbei auch Materialien in Frage, die höhere Prozeßtemperaturen erfordern. Es eignen sich in diesem Zusammenhang beispielsweise Cyclotene, ein im Spin-On-Verfahren aufgetragenes Polymer, Polyimid oder CVD-Dielektrika (Siliziumnitrid, Siliziumoxinitrid, etc.). Die Isolationsschichten werden zunächst ganzflächig aufgetragen und anschließend strukturiert, so daß die Isolationsstege zwischen den Bildpunkten bestehen
bleiben. Die Breite der Isolationsstege ist nicht notwendigerweise an den Pixelabstand gebunden, sie kann gegebenenfalls auch größer oder kleiner sein.
If a low-temperature process is applied, materials that require higher process temperatures can also be used. In this context, for example, cyclotenes, a polymer applied using the spin-on method, polyimide or CVD dielectrics (silicon nitride, silicon oxynitride, etc.) are suitable. The insulation layers are first applied over the entire surface and then structured so that the insulation webs exist between the pixels stay. The width of the isolation webs is not necessarily tied to the pixel spacing, it can also be larger or smaller if necessary.
Claims
1. Sensor für elektromagnetische Strahlung gebildet durch eine Struktur aus einem integrierten Schaltkreis (01), insbesondere einem ASIC, auf dessen Oberfläche eine für die elektromagnetische Strahlung sensitive Schichtenfolge (05, 06, 07, 08) enthaltend amorphes Silizium (a-Si.H) und/oder dessen Legierungen aufgebracht ist, wobei innerhalb der Struktur räumlich aneinander angrenzende Bildpunkteinheiten (B) ausgebildet sind, die durch mindestens einen Grenzbereich mit einer gegenüber der Leitfähigkeit der Schichten der Schichtenfolge herabgesetzten Leitfähigkeit voneinander getrennt sind, wobei jede Bildpunkteinheit einen Strahlungswandler zum Umwandeln der einfallenden Strahlung in einen intensitätsabhängigen Meßwert und Mittel zum Erfassen und Abspeichern des Meßwertes aufweist und wobei eine Auslesesteuereinrichtung für das jeweils auf eine Bildpunkteinheit bezogene Auslesen der Meßwerte vorgesehen ist derart, daß aus den bildpunkteinheitsbezogenen Meßwerten das auf den Sensor eingestrahlte Bild zusammensetzbar ist, dadurch gekennzeichnet, daß der mindestens eine Grenzbereich ein auf die Oberfläche des integrierten Schaltkreises aufgebrachtes Isolatormaterial (09, 10) aufweist, dessen Schichtdicke so bemessen ist, daß sich der Isolationsbereich mindestens durch die dem integrierten Schaltkreis (01) am nächsten liegende Schicht (05) der Schichtenfolge des Strahlungwandlers hindurch erstreckt.
1. Sensor for electromagnetic radiation formed by a structure of an integrated circuit (01), in particular an ASIC, on the surface of which a layer sequence sensitive to the electromagnetic radiation (05, 06, 07, 08) containing amorphous silicon (a-Si.H ) and / or its alloys, whereby pixel units (B) spatially adjacent to one another are formed within the structure, which are separated from one another by at least one border region with a conductivity that is lower than the conductivity of the layers of the layer sequence, each pixel unit being a radiation converter for conversion of the incident radiation in an intensity-dependent measured value and means for recording and storing the measured value and wherein a read-out control device is provided for reading out the measured values related to a pixel unit in such a way that from the pixel unit-related measured values that on d The sensor irradiated image can be put together, characterized in that the at least one border area has an insulator material (09, 10) applied to the surface of the integrated circuit, the layer thickness of which is dimensioned such that the isolation area extends at least through the integrated circuit (01). closest layer (05) of the layer sequence of the radiation converter extends through it.
2. Bauelement nach Anspruch 1, dadurch gekennzeichnet, daß das Isolationsmaterial in einer der Gesamtdicke der strahlungssensitiven Schichtenfolge entsprechenden Schichtdicke aufgebracht ist.2. Component according to claim 1, characterized in that the insulation material is applied in a layer thickness corresponding to the total thickness of the radiation-sensitive layer sequence.
3. Bauelement nach einem der vorgenannten Ansprüche, dadurch gekennzeichnet, daß der Strahlungssensor ein optolektronischer Wandler ist.
3. Component according to one of the preceding claims, characterized in that the radiation sensor is an optoelectronic converter.
Applications Claiming Priority (2)
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DE19715432.8 | 1997-04-14 | ||
DE19715432 | 1997-04-14 |
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WO1998047181A1 true WO1998047181A1 (en) | 1998-10-22 |
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PCT/EP1998/002130 WO1998047181A1 (en) | 1997-04-14 | 1998-04-11 | Electromagnetic radiation sensor with high local contrast |
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EP1045450A2 (en) * | 1999-04-13 | 2000-10-18 | Agilent Technologies Inc. | Image sensor array device |
DE19944731A1 (en) * | 1999-09-17 | 2001-04-12 | Siemens Ag | Image detector for electromagnetic radiation is structured in such a way that insulating regions are formed between individual metal electrodes in a photodiode layer |
EP1326278A2 (en) * | 2002-01-07 | 2003-07-09 | Xerox Corporation | Image sensor with performance enhancing structures |
EP1482558A2 (en) * | 2003-05-26 | 2004-12-01 | STMicroelectronics S.A. | Photo detector array |
WO2009083920A1 (en) * | 2007-12-28 | 2009-07-09 | Koninklijke Philips Electronics N.V. | Electrical isolation of x-ray semiconductor imager pixels |
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Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1045450A2 (en) * | 1999-04-13 | 2000-10-18 | Agilent Technologies Inc. | Image sensor array device |
EP1045450A3 (en) * | 1999-04-13 | 2002-05-29 | Agilent Technologies, Inc. (a Delaware corporation) | Image sensor array device |
DE19944731A1 (en) * | 1999-09-17 | 2001-04-12 | Siemens Ag | Image detector for electromagnetic radiation is structured in such a way that insulating regions are formed between individual metal electrodes in a photodiode layer |
EP1326278A2 (en) * | 2002-01-07 | 2003-07-09 | Xerox Corporation | Image sensor with performance enhancing structures |
EP1326278A3 (en) * | 2002-01-07 | 2004-03-10 | Xerox Corporation | Image sensor with performance enhancing structures |
EP1482558A2 (en) * | 2003-05-26 | 2004-12-01 | STMicroelectronics S.A. | Photo detector array |
EP1482558A3 (en) * | 2003-05-26 | 2005-02-23 | STMicroelectronics S.A. | Photo detector array |
US7279729B2 (en) | 2003-05-26 | 2007-10-09 | Stmicroelectronics S.A. | Photodetector array |
WO2009083920A1 (en) * | 2007-12-28 | 2009-07-09 | Koninklijke Philips Electronics N.V. | Electrical isolation of x-ray semiconductor imager pixels |
US8373134B2 (en) | 2007-12-28 | 2013-02-12 | Koninklijke Philips Electronics N.V. | Electrical isolation of X-ray semiconductor imager pixels |
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