Abstract:
An optocoupler has an organic light emitter and an inorganic photodetector with a detector area, the detector area being optically coupled to the organic light emitter. The organic light emitter converts an electrical input signal into a light signal and the inorganic photodetector converts the light signal into an electrical output signal, the organic light emitter and the inorganic photodetector being integrated in a component and galvanically separated.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from German Patent Application No. 10 2006 040 788.1, which was filed on Aug. 31, 2006, and is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention refers to an integrated optocoupler with an organic light emitter and an inorganic photodetector, and in particular to a monolithically integrated CMOS optocoupler with an OLED light source. 
         [0004]    2. Description of the Related Art 
         [0005]    Optocouplers have been widely spread as technical means for galvanic isolation and/or electrical potential separation. This includes applications in car industry, consumer electronics, medical and measuring technology, data communication and the like. Optocouplers are used for electrical isolation of an input signal from a corresponding output signal and can be used as a substitution for relays and Reed relays (protective glass relays). They are advantageous because of their fast switching speed, higher reliability, better electrical isolation and, compared to conventional relays, drawbacks due to mechanical bonding and/or switching (so-called bounce effects) are avoided. 
         [0006]    An optocoupler has a light emitter and a light receiver, which are optically coupled through a coupling medium and/or a light guide. Light-emitting diodes (LED), which emit e.g. infra-red light or red light, are often used as light emitters. Photodiodes, phototransistors, photothyristors, phototriacs, photo-Schmitt-triggers or photo-Darlington-transistors are e.g. used as light receivers. Light emitters and light receivers are connected to each other through an electrically non-conductive insulator. 
         [0007]    The electrical isolation of circuit parts is necessary for potential separation, but also in order to avoid parasitic reactions. Potential separation is inter alia advantageous as a protection against hazards in medical appliances, but also in data communication (network/interface card) or as over-voltage protection. Parasitic reactions, which one would like to suppress with optocouplers, are for example noise in small signals or transients in engine control. Binary or analogue signals are transmitted in optocouplers. 
         [0008]    An optocoupler is shown schematically in  FIG. 10 , a light emitter  20  converting an electrical signal, which is present at the input  10 , into an optical signal  40 . The optical signal  40  is transmitted from an optical outlet area  25 , by means of a light guide  30 , to an optical inlet area  55  of a light receiver  50 . The light receiver  50  re-converts the optical signal  40  into an electrical output signal, which is present at an output  60 . For potential separation, it is important that the light guide  30  electrically isolates the light emitter  20  from the light receiver  50 , i.e. that the light guide  30  has a transparent dielectric material. 
         [0009]    The market for optocouplers can be divided into two different main areas, on the one hand the simple optocoupler based on the classical photodiode and/or photo- (Darlington) transistor, on the other hand the fully integrated optocouplers with a CMOS read circuit (CMOS=Complementary Metal Oxide Semiconductor) for higher functions. 
         [0010]    Photodiodes as possible light receivers and/or photodetectors  50  can be reproduced during a standard CMOS process at different p-n interfaces and  FIG. 9  shows an example in an n-well CMOS process according to the state of the art. Formed in a p-doped substrate (p-type substrate)  910  is an n-doped well (n-well)  920 , which has a p + -doped layer  930  on the side opposite the p-type substrate  910 . As a final layer for the photodetector  50 , the p-type substrate  910  has an oxide layer  940 , which is followed by usual CMOS layers, such as e.g. an ILD layer  950  (ILD=Inter Layer Dielectric) and a IMD layer  960  (IMD=Inter Metal Dielectric). The oxide layer  940 , the ILD layer  950  and the IMD layer  960  have a dielectric material and are translucent. Several p-n junctions are designated in  FIG. 9  by diodes  925 ,  935  and  975 . 
         [0011]    Incident light beams  990  generate in the n-well  920  a pair of load carriers  985  of opposite loaded polarity, which is separated according to the polarity and causes an electrical signal. The photodetector  50  is comprised of the layers: p-type substrate  910 , n-well  920 , p + -doped layer  930 .  FIG. 9  shows furthermore a photodiode  975 , which is comprised of a p-n junction of p-type substrate  910  and an n + -doped surface layer  970 . The light signals  980  represent e.g. light reflected at the surface layer  970 . 
         [0012]    Known fully integrated optocouplers are based on a CMOS-based receiving and evaluating chip, as well as on an emitter (light emitter)  20  comprised of conventional (inorganic) light-emitting diodes (i.e. conventional LEDs), which have typically an optically close connection with the photodiode and/or with the photodetector  50 . These two technologies use materials and processes that differ from each other. The standard CMOS process is mostly based on single-crystal silicon material, while conventional light-emitting diodes mostly use single-crystal III-V semiconductors. Therefore, the elements photodetector  50  and light-emitting diode as light emitter  20  cannot be produced monolithically, but can exclusively be integrated in a hybrid way with each other. 
         [0013]    Conventional light-emitting diodes comprised of inorganic semiconductors, such as e.g. GaAs and related III-V semiconductors have been known for decades. The basic principle of such light-emitting diodes is that by applying an electric voltage electrons and holes are injected into a semiconductor and combine through radiation in a recombination zone during light emission. 
         [0014]    As an alternative to inorganic light-emitting diodes, light-emitting diodes based on organic semiconductors have in recent years achieved large progresses. For example, an organic electroluminescence presently experiences great attention as a medium suitable for displays. Organic light-emitting diodes have a series of organic layers with a thickness typically in the range of 100 nm, which is inserted between an anode and a cathode. Glass is often used as a substrate, on which a transparent electrically conductive oxide, such as e.g. indium-tin oxide (ITO=Indium-Tin Oxide), is applied. Then follows the series of organic layers, which has hole-transporting material, emitting material and electron-transporting material. A metallic cathode usually follows then. 
         [0015]      FIG. 8  shows organic light-emitting diodes (OLED) according to the state of the art, at the left being shown a so-called bottom emitter  810  and at the right a so-called top emitter  820 . 
         [0016]    In the case of the bottom emitter  810 , a transparent electrode  814 , a series of organic layers  816  and a second electrode  818  are deposited on a substrate  812 . The transparent electrode  814  is electrically connected through a first contact  815  and the second electrode  818  through a second contact  819 . In the series of organic layers  816 , an electric signal at the first contact  815  and the second contact  819  is converted into a light signal  40  which is radiated mainly downward in the representation shown here. 
         [0017]    As already mentioned above, the following materials can be used. For the transparent electrode  814 , e.g. ITO can be used, while for the second electrode  818  a metal is often used and the series of organic layers  816  has e.g. a hole-transporting material, an emitting material and an electron-transporting material. An upward radiation is prevented in the case of the bottom emitter  810  in that the second electrode  818  has an opaque material. In order for the substrate  812  not to prevent light propagation, glass is typically used as transparent material. 
         [0018]    The top emitter  820 , which is represented at the right side in  FIG. 8 , has an accordingly reversed series of layers. The second electrode  818  which has an opaque material is deposited on a substrate  822 . Then follows the series of organic layers  816 , followed by the transparent electrode  814 , which has a transparent material (e.g. ITO). The transparent electrode  814  is, in turn, electrically connected through the first contact  815  and the second electrode  818  through the second contact  819 . In this case too, an electrical signal at the first contact  815  and the second contact  819  is converted in the series of organic layers  816  into a light signal  40 , which because of the opacity of the second electrode  818  is mainly radiated upward in the representation shown. 
         [0019]    Irrespective of the selected representation, the bottom emitter  810  radiates the light signal  40  mainly through the substrate  812 , while the top emitter  820  radiates in a direction away from the substrate  822 . The light signal  40  in  FIG. 8  indicates a main radiation direction. The light generated in the series of organic layers  816  however also propagates along the series of organic layers  816  or along the transparent electrode  814  and, if no lateral protection is present, is also partly radiated sidewise. 
         [0020]    Optocouplers with an integration of both inorganic emitters (i.e. the light emitter  20 ), which are usually based on III-V semiconductors, and inorganic detectors (i.e. the photodetector  50 ), such as e.g. CMOS photodiodes are known. Optocouplers with the integration of both organic emitters and organic detectors are also known, which are described for example in DE 10061298 A1 or DE 10103022 A1. Furthermore, photodetectors for picture recorders are known, which are implemented in a silicon handle wafer of an SOI substrate (SOI=Silicon On Insulator) (inter alia U.S. Pat. No. 6,838,301 B2). 
         [0021]    Since conventional LEDS, as has been said, primarily use III-V semiconductors and the detector circuit (i.e. the photodetector  50  and the activating circuit) is mostly based on silicon, both elements cannot be produced on the same substrate and an integration therefore proves difficult. A possible hybrid integration in optocouplers, such as known for example from the state of the art, necessitates in principle a higher manufacturing cost and, as a matter of fact, does not allow a general price regression with large numbers of units. Furthermore, because of the hybrid structure, the necessary reliability for car applications can be achieved only at an extremely high cost. 
       SUMMARY OF THE INVENTION 
       [0022]    According to an embodiment, an optocoupler may have: an organic light emitter, and an inorganic photodetector having a detector area, the detector area being optically coupled with the organic light emitter, one or several shielding planes arranged above each other and separated by isolating layers arranged substantially parallel to a light-emitting surface of the organic light emitter between the photodetector and the OLED, the organic light emitter converting an electrical input signal into a light signal and the inorganic photodetector converting the light signal into an electrical output signal, and the organic light emitter and the inorganic photodetector being integrated in a component, wherein the shielding planes cause a light shielding and a focusing of the light signal and are electrically isolated from the light-emitting surface. 
         [0023]    Embodiments of the present invention are based on the finding that an integrated optocoupler can be created on a substrate by using an organic light emitter and an inorganic photodetector. An organic light emitter and an inorganic photodetector can have a conventional structure and are integrated in a component. For example, the monolithic integration of the light source and/or the light emitter and the photodetector on a chip becomes possible through integrating an OLED emitter as post-processing on a highly structured CMOS substrate. The structures of the CMOS construction can simultaneously serve as an electrical insulator and a light guide. Photodiodes forming at p-n stop layers and inherent to CMOS or similar elements can be used as a photodetector. 
         [0024]    OLEDs are in particular favourable, since they permit a high integration during a production of optocouplers and can, in addition, be deposited on almost any substrates and can thus, in particular, also be integrated directly on a silicon substrate. Furthermore, a deposition can occur at relatively low temperatures (for example below 100° C.). Thus, OLEDs can be deposited on a normal CMOS/BiCMOS circuit (BiCMOS=Bipolar Complementary Metal Oxide Semiconductor), without any risk of damages. An isolation oxide or an isolation layer present on an integrated circuit (CMOS structure) can simultaneously create an optical connection, i.e. serve as a light guide, whereby a desired electrical isolation value can be adjusted by means of a layer thickness of the isolation layer. Thus, this technology becomes very simple. 
         [0025]    The integration of OLEDs in CMOS structures can occur as follows. OLEDs as top emitters can use for example a usual CMOS metal layer as an electrode, on which the series of organic layers is deposited and a transparent electrode is applied. A concrete exemplary embodiment is described more in detail below. 
         [0026]    An OLED as bottom emitter can for example be applied on a usual CMOS oxide layer (e.g. an IMD layer), a transparent electrode being in this case deposited on the usual CMOS oxide layer, which serves as a substrate. A usual CMOS metal layer can, here too, serve as the second electrode, the series of organic layers being deposited as intermediate layer. The OLED as bottom emitter radiates directly on the photodetector under it, which can be made for example in the form of p-n stop layers inherent to CMOS. Typical transparent conductive materials for the transparent electrode are indium-tin oxide (ITO) or zinc oxide (ZnO) or other conductive oxides. A concrete embodiment is explained more in detail below. 
         [0027]    The light emitter and the light receiver have, according to an embodiment of the invention, an “optical proximity” and thus a necessary OLED area can be reduced and a current consumption can be kept low. The production is thus economical. Through an appropriate choice of a wavelength used of the light signal generated (which is substantially determined by the material used), can be achieved as low an absorption as possible of the light guide, which results in an optimized optical signal transmission. In order to maintain a necessary OLED voltage as low as possible, the series of organic layers can have a doped transport layer and a reduced input-voltage threshold can thus be achieved. 
         [0028]    The deposition of the OLED is thus technologically fully compatible with the CMOS/BiCMOS as well as the bipolar technology and thus allows manufacturing integrated OLED optocouplers. A production is even possible without any problem and at low cost on large substrates (e.g. up to 200×200 mm). 
         [0029]    With the OLED technology, i.e. using OLEDs as light emitters, there is provided for the first time the possibility of a monolithically integrated solution for optocouplers, i.e. of performing light generation and detection on one substrate (e.g. on a silicon substrate). They thus offer advantages as regards the size of the components as wells as regards the possibility of integrating new functions, i.e. they are can be easily and highly integrated. In addition, they exhibit high efficiency at varying insulation resistances and have low power consumption. 
         [0030]    Further advantages of the organic electroluminescence are that because of the chemical variability OLEDs can be produced in almost all colours and that because of the deposition at low temperatures OLEDs can be applied on the most diverse substrates. Therefore, multi-channel solutions, for example through the use of OLEDs emitting light of different colour or wavelength, can be integrated on a chip. 
         [0031]    The advantages of the optocouplers with integrated OLEDs, compared with well-known hybrid solutions, can be summarized as follows. The complexity of the construction and connection technique (CCT) for the integration is reduced and the costs are reduced. In addition, the monolithic integration of light source, electrical insulator, light guide and photodetector on a chip can easily be implemented. Furthermore, standard CMOS layers/structures can be used as electrical insulator and light guide. This results into an improvement of the isolation strength when using a SOI-CMOS substrate and a reduction of the chip area. Finally, the exemplary embodiments of the present invention provide the possibility of a complex integration of an activation circuit for the light emitter and electronic reading unit for the photodetector. 
         [0032]    Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    Exemplary embodiments of the present invention will now be described more in detail, with reference to the attached drawings, in which: 
           [0034]      FIG. 1  shows an OLED as a bottom emitter radiating directly onto a photodetector. 
           [0035]      FIG. 2  shows an OLED as a bottom emitter radiating directly onto a photodetector, with side shielding. 
           [0036]      FIG. 3  shows an OLED as a bottom emitter radiating directly onto a photodetector, with side shielding and additional light guiding. 
           [0037]      FIG. 4  shows an OLED as a bottom emitter radiating directly onto a photodetector, with a photodiode as photodetector. 
           [0038]      FIG. 5  shows an OLED as a bottom emitter radiating indirectly onto a photodetector. 
           [0039]      FIG. 6  shows an OLED as a top emitter radiating indirectly onto a photodetector. 
           [0040]      FIG. 7  shows an OLED as a micro-cavity OLED radiating indirectly onto a photodetector. 
           [0041]      FIG. 8  shows an OLED as a bottom emitter and an OLED as a top emitter. 
           [0042]      FIG. 9  shows photodiodes in the standard n-well CMOS process. 
           [0043]      FIG. 10  shows a schematic construction of an optocoupler. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0044]    Before describing the present invention more in detail hereafter with reference to the drawings, the attention is drawn on the fact that same elements in the figures are designated by same or similar reference numerals, and that a repeated description of these elements is omitted. 
         [0045]      FIG. 1  shows an OLED  100  as a bottom emitter, which has a light-emitting surface  102  and radiates directly onto the photodetector  104  located under it, which is for example part of a CMOS structure. The photodetector  104  is embedded in a substrate  110 , is connected through a contact  120  and shielded by an ILD layer  150  of the CMOS structure. An IMD layer  160  of the CMOS structure serves as a basis or substrate for the OLED  100 , i.e. on the IMD layer  160  are deposited a transparent electrode  170 , a series of organic layers  180  and a second electrode  190 . A passivation or protective layer  195  serves as finishing layer and a side passivation  197  isolates the transparent electrode  170  from the second electrode  190 . 
         [0046]    The OLED as bottom emitter  100  converts an electrical signal into a light signal  108  which passes, through the IMD layer  160  and then through the ILD layer  150 , to the photodetector  104  and is re-converted there into an electrical output signal. The photodetector  104  can be designed as an arbitrary photo-sensitive element present in CMOS structures, for example as a photodiode (see  FIG. 9 ) or as a phototransistor or the like. Further contacts necessary for the photodetector  104  are not shown in  FIG. 1 , for clarity reasons. 
         [0047]      FIG. 2  shows another exemplary embodiment of the present invention, which has an additional side shielding  210 . The shielding can be formed by a metal guiding plane of the CMOS structure and furthermore serve for the electrical connection of the transparent electrode  170 . 
         [0048]    Like in the exemplary embodiment of  FIG. 1 , the photodetector  104  is embedded in the substrate  110  and is electrically connected by the electrode  120 . The light emitter is, here too, an OLED  100  as bottom emitter with the transparent electrode  170 , the series of organic layers  180  and the second electrode  190  which is embedded in the passivation layer  195 . The side passivation layer  197  provides an isolation between the transparent electrode  170  and the second electrode  190 . Between the light emitter  100  and the photodetector  104 , the IMD layer is, here too, arranged on the side of the photodetector  104  and the ILD layer on the side of the light emitter  100 . 
         [0049]    The shielding layer  210 , which laterally surrounds the transparent electrode  170 , is advantageous for reducing parasitic effects due to light-guide effects in the transparent electrode  170 . It suppresses for example the above-mentioned side radiation. The shielding layer  210 , which has for example a metallic material, the ILD layer  150  and the IMD layer  160  can, here too, be possible inherent parts of the CMOS structure. 
         [0050]      FIG. 3  shows an exemplary embodiment in which, in addition to the layers which the structure of  FIG. 2  is comprised of, further shielding planes  310   a ,  310   b ,  310   c ,  310   d ,  310   e  are incorporated between the photodetector  104  and the OLED  100 . The shielding planes  310   a  and  310   d  are embedded in the IMD layer  150 , while the shielding planes  310   b  and  310   e  are embedded in the ILD layer  160 . Finally, the shielding plane  310   c  is deposited at an interface between the IMD layer  150  and the p-type substrate  110 . A new description of the elements already described in  FIG. 2  is omitted here. The shielding planes  310   a ,  310   b ,  310   c ,  310   d  and  310   e  in this exemplary embodiment can be e.g. additional metal guiding planes of the CMOS structure and serve as additional light shielding and focusing of the light signal  108  and, therefore, support a detection of the light signal  108  by the photodetector  104 . Besides their function as a shielding layer, some of the metal guiding planes can furthermore serve for the electrical connection of elements of the optocoupler according to the invention. 
         [0051]      FIG. 4  shows an exemplary embodiment in which a photodetector has a photodiode  400 , which can be formed e.g. by a p-n junction of a n-well to the substrate  405  or to a p + -doped surface layer (or also uses another existing p-n junction). The photodiode  400  is connected through the contact  120  and is embedded in the p-type substrate  405 . Further necessary contacts of the photodetector are not shown, for simplicity&#39;s reasons. Between the photodetector  400  and the OLED  100  are arranged, in this exemplary embodiment, the ILD layer  150 , followed by an IMD 1  layer  160   a  and an IMD 2  layer  160   b . The IMD 1  layer  160   a  has a shielding plane  310   a  and the IMD 2  layer  160   b  has a shielding plane  310   b . The OLED  100  has, here too, the transparent electrode  170 , which is deposited on the IMD 2  layer  160   b , the series of organic layers  180  and the second electrode  190  and is protected by the passivation layer  195 . The side passivation  197  provides, here too, an isolation between the transparent electrode  170  and the second electrode  190 . 
         [0052]    The contact  120  is connected to the shielding plane  310   a  through a bridge and/or a through-connection  410  which bridges the ILD layer  150 . The metal guiding plane, which provides the shielding plane  310   b , thus serves furthermore for electrically connecting the contact  120 . The ILD layer  150  serves, here too, as a protection for the photodiode  400  and the p-type substrate  910 . Like before also, the ILD layer  150 , the IMD 1  layer  160   a  and the IMD 2  layer  160   b  can also be part of a CMOS structure and the shielding planes  310   a  and  310   b  can for example be implemented by metal guiding planes of the CMOS structure. 
         [0053]    The OLED as a bottom emitter  100  generates from an electrical input signal the light signal  108  which passes through the IMD 2  layer  160   b , the IMD 1  layer  160   a  and finally the ILD layer  150 , before it enters into the photodiode  400  and generates an electrical output signal there. 
         [0054]      FIG. 5  shows an exemplary embodiment, in which the OLED  100  radiates indirectly onto a photodetector  515  using a buried dielectric transparent layer  510 , which serves as a light guide. The dielectric transparent layer  510  (which can be called buried layer) is deposited on a substrate  500  and serves as a basis for the photodetector  515  and an OLED driver transistor  540 . The photodetector  515  and the OLED driver transistor  540  are embedded in the ILD layer  150  and on the ILD layer  150  are deposited the IMD 1  layer  160   a  and the IMD 2  layer  160   b . The IMD 2  layer serves furthermore as a substrate for the following OLED  100  with the transparent electrode  170 , the series of organic layers  180  and the second electrode  190 , which are also embedded in a passivation layer  195  and the side passivation  197  provides isolation between the transparent electrode  170  and the second electrode  190 . 
         [0055]    The photodetector  515  is electrically connected through the contact  120  and a contact  520 . The contact  120  is connected through a first bridge  410   1  to a first portion  310   a   1  of the shielding plane  310   a . The contact  520  is connected through a second bridge  410   2  to a second portion  310   a   2  of the shielding plane  310   a  and the second portion  310   a   2  is, in turn, connected through a third bridge  530  to the shielding plane  310   b . An electrical connection of the OLED driver transistor  540  occurs through a first portion  310   c   1  and a second portion  310   c   2  of the shielding plane  310   c . The first portion  310   c   1  is connected through a fifth bridge  560   1  to a first portion  310   d   1  of the shielding plane  310   d . The second portion  310   c   2  is connected through a sixth bridge  560   2  to a second portion  310   d   2  of the shielding plane  310   d . The second portion  310   d   2  is, in turn, connected through a seventh bridge  570   2  to the shielding plane  310   e , which is, in turn, electrically connected through an eighth bridge  580   2  to the second electrode  190  of the OLED  100 . 
         [0056]    As described before, the shielding planes  310   b  and  310   e  are embedded in the IMD 2  layer  160   b  and the shielding planes  310   a  and  310   d  in the IMD 1  layer  160   a . On the other hand, the ILD layer  150  has the portions  310   c   1  and  310   c   2  of the shielding plane  310   c  as well as the contacts  120  and  520 . The structures designated as shielding planes are each implemented by sections of the metal guiding planes of a CMOS structure and serve furthermore, through respective bridges or through-connections, at least partly as connecting structures. 
         [0057]    In this exemplary embodiment, the light signal  108  which is emitted by the OLED  100  as bottom emitter, does not arrive directly on the photodetector  515 , but on the incorporated dielectric transparent layer  510 , which serves as light guide. The light signal  108  generates in the dielectric transparent layer  510  a light signal  590  which propagates toward the photodetector  515  and generates there an electrical signal which is output through the contacts  120  and  520 . As described above, the contact  120  is connected to the first portion  310   a   1  of the shielding plane  310   a   1  and the contact  520  is connected to the shielding plane  310   b , where the electrical signal is present as output signal. 
         [0058]    It is advantageous to use for the portions of the shielding planes  310   a   1 ,  310   a   2 ,  310   b ,  310   c   1 ,  310   c   2 ,  310   d   1 ,  310   d   2  and  310   e  metal guiding planes of the CMOS structure, which are for example schematically shown in  FIG. 3 . The exemplary embodiment of  FIG. 5  is therefore based on an SOI CMOS technology with a buried oxide layer, which corresponds to the dielectric transparent layer  510  and is at the same time used as electrical insulator and light guide. Hence, despite an eventually complex integration of the electronic emitter-activating and photodetector-reading unit, a high insulation voltage is obtained. Both circuit parts are fully isolated from each other on a chip. In order to achieve an as high as possible absorption by the photodetector  515 , the photodetector  515  should be selected accordingly large. An active layer, which has for example silicon and is provided on the dielectric transparent layer  510 , should be implemented thick enough to achieve a high probability of photon absorption. For example, a layer thickness, which is in the range from about 200 nm to about 3 μm could be selected. 
         [0059]    The structures designated in  FIG. 5  by the reference numerals  310   d   1 ,  310   d   2 ,  310   a   1  and  310   a   2  can each be a portion of a first metal guiding plane (MET 1 ) of a CMOS structure, the structures  310   b  and  310   e  can be portions of a second metal guiding plane (MET 2 ), and the structure  190  can be a portion of a third metal guiding plane (MET 3 ). 
         [0060]      FIG. 6  shows an exemplary embodiment in which an OLED  600  is used as top emitter, which radiates indirectly onto the photodetector  400 . Like in the exemplary embodiment that has been explained in the context of  FIG. 4 , the photodetector  400  has the photodiode (which is formed by an existing p-n junction), which is connected through the contact  120  and is embedded in the p-type substrate  405 . The contact  120  is connected through the bridge  410  with a metal guiding plane  612  of the CMOS structure. The metal guiding plane  612  is located in the IMD 1  layer  160   a , which follows the ILD layer  150 . 
         [0061]    The OLED  600  is applied on the IMD 1  layer  160   a , a metal guiding plane (MET 2 ) formed on the IMD 1  layer  160   a  serving as lower electrode  614 , on which are applied the series of organic layers  180  and the transparent electrode  170 . As a protection for the OLED as top emitter  600  follows finally the passivation layer  195 , which has a transparent material. The side passivation  197  provides, here too, isolation between the transparent electrode  170  and the second electrode  190 . The structures  612  and  614  serving for connecting can furthermore be, here too, inherent parts of the CMOS structure, be formed as metal guiding planes and in addition serve as shielding planes. 
         [0062]    In addition, this exemplary embodiment has a reflector  610  on an inner wall of a casing  620 . The reflector  610  is arranged so that a light signal  108  from the OLED  600 , which serves as top emitter, is reflected on the photodetector  400 , i.e. the light signal  108  is radiated toward the reflector  610 , reflected by the latter and arrives in the photodiode  400 , which is embedded in the p-type substrate  405 . In this reflection arrangement, the OLED  600  thus radiates upward, i.e. toward the passivation layer  195 . As can be seen in  FIG. 6 , in an embodiment, it should be made sure that the photodetector  400  is not covered by the shielding plane  310   e , in order for an as large as possible portion of the reflected light signal  108  to reach the photodetector  400 . 
         [0063]      FIG. 7  shows another exemplary embodiment, which has an OLED with two opaque electrodes  190  and  192 . The series of organic layers  180  is arranged between both opaque electrodes  190  and  192  and thus forms a so-called micro-cavity OLED  720 . Both opaque electrodes  190  and  192  can be formed, for example, by two metal layers, which are deposited on the CMOS structure located under them. The photodetector corresponds to photodetector described with reference to the exemplary embodiment of  FIG. 6 . 
         [0064]    The micro-cavity OLED  720  has an optical window  750 , at which protrudes the series of organic layers  180  between the two opaque electrodes  190  and  192  and which serves as an exit area  750  for the light signal  108  and is so arranged that it is in optical contact with the photodetector  400 . In addition, the micro-cavity OLED  720  is, here too, protected by a passivation layer  195  on the side opposite the optical window  750  and an outer casing  620  offers the advantage of a good shielding of the radiating micro-cavity OLED  720 . 
         [0065]    Since both electrodes  190  and  192  are opaque in this exemplary embodiment, light propagation can occur, after generation of the light signal  108  in the series of organic layers  180 , only along the series of organic layers  180 . Thus, the light signal  108  exits the micro-cavity OLED  720  through the optical window  750 , passes through the IMD layer  160  and the ILD layer  150 , before being converted in the photodiode  400  into an electrical output signal. 
         [0066]    The exemplary embodiments of the present invention described with reference to the figures can obviously also be combined or extended. For example, the exemplary embodiment, which has been described in the context of  FIG. 6 , can be changed in that the optocoupler has also further or other reflectors or a focusing of the light signal  108  occurs through an optical unit. Thus, instead of the reflector  610  on the inner side of the casing, a reflector can be placed on the passivation layer  195  or added as an additional reflector. The reflector  610  can also be designed as a reflecting surface or can also be designed so that the reflector  610  focuses the light signal  108  on the photodetector  400 . A focusing can for example be achieved in that the reflector  610  has an appropriate curvature or the optocoupler has a lens. A focusing reflector  610  or a lens would be advantageous in that the inlet area  55  of the photodetector  400  can be chosen accordingly smaller and nevertheless still receives a sufficient quantity of light. 
         [0067]    The highest insulation voltage is achieved in the exemplary embodiment of  FIG. 5 , since the organic light emitter  100  with its electronic activation unit is completely electrically isolated from the photodetector  400  and the isolation voltage can be adjusted through a layer thickness of the transparent layer  510  (buried layer) selected accordingly as well as through a side distance. In the exemplary embodiments of the remaining figures, the isolation voltage can be increased in that the electronic activation unit of the organic light emitters  100 ,  600  or  720  and the photodetector  400  are arranged in different substrate areas that are, in addition, isolated from each other, such as for example by means of trenches. The electronic activation unit can for example also be arranged in lower substrate areas. 
         [0068]    The optocoupler can transmit in operation both analogue and digitized signals. In order to be able to effectively suppress external parasitic effects or extraneous light influences, it can be advantageous to use a fixed timing or a modulation. Since OLEDs are available for a plurality of frequencies, a multi-channel solution can be achieved with a combination of various OLEDs (e.g. by depositing several OLEDs on a CMOS structure). Suitable activation circuits for adequately modulating the light source, i.e. the OLED, can be provided. 
         [0069]    The described exemplary embodiments of optocouplers with integrated OLED offer the advantages already mentioned above. These advantages include in particular a reduction of the complexity of the construction and connection technique (CCT) for the integration and the costs. In addition, the monolithic integration of light source, electrical isolator, light guide and photodetector on one chip is easy to carry out. Furthermore, standard CMOS layers/structures can be used as electrical isolator and light guide. This results in an improvement of the isolation strength when using an SOI-CMOS substrate as well as a reduction of the chip area. Finally, the exemplary embodiments of the present invention provide the possibility of a complex integration of an activation circuit for the light emitter and an electronic reading unit for the photodetector. Thus, a high isolation voltage is achieved, despite an eventually complex integration of the electronic emitter-activation and photodetector-reading unit. Both circuit parts are completely isolated from each other on one chip and the isolation voltage reached can be flexibly adjusted through an appropriate selection of the layer thicknesses or the layer materials. 
         [0070]    To conclude, different aspects of the present invention can thus be presented as follows:
       spatial co-integration of organic emitter and CMOS photodetector on a CMOS silicon chip in an arrangement as optocoupler;   using CMOS p-n junctions (e.g. well-substrate, well-contact, and the like) as photodetectors;   arrangement of the OLED emitter as a bottom emitter radiating directly onto the photodetector;   arrangement of the OLED emitter as a bottom emitter radiating indirectly onto the photodetector;   arrangement of the OLED emitter as a top emitter radiating indirectly, i.e. using a reflector, onto the photodetector;   arrangement of the OLED emitter as a top emitter radiating indirectly onto the photodetector, a reflection occurring at the passivation surface;   arrangement of the OLED emitter as a top emitter radiating indirectly onto the photodetector, an additional reflector being placed on the inner side of the casing;   arrangement of the OLED emitter as an OLED with two opaque electrodes radiating indirectly onto the photodetector, and;   using an SOI-CMOS substrate for an improved electrical isolation of the activation and reading circuit and using an SOI layer as light guide;   using the metallization planes of the CMOS structure in order to guarantee a light guiding to the detector;   modulation of the light source for the galvanic separated signal transmission; and   monolithic implementation in complex integrated circuits for—eventually multi-channel—galvanic uncoupling of switching blocks, e.g. for parasitic uncoupling, noise reduction or the like.       
 
         [0083]    While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention. 
         [0084]    While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.