Patent Publication Number: US-2018035548-A1

Title: Patterned layer compound

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from German Patent Application No. 10 2016 213 878.2, which was filed on Jul. 28, 2016, and is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a method for manufacturing a microchip arranged on a patterned layer compound, comprising the features of claim  1 , and to a package for a microchip comprising the features of claim  23 . 
     Many sensors use an opening in the package in order to be able to measure a parameter of the environment, like air pressure, air humidity, gases, flow, particle measurement, radiation measurement, etc. For sensors based on semiconductor devices (“chips” or “microchips”), this means that the chip package (“package”) needs to have an opening to the surroundings/atmosphere. Since sensitive surfaces of a semiconductor sensor are frequently very small, i.e. &lt;1 mm 2 , realizing a precise opening above the sensor area is frequently very difficult or complicated. Frequently, the package results in the sensor housed to be bulky or big. However, for many applications, miniaturization or extreme flatness of the sensor device housed is an important requirement. 
     This applies, for example, for sensors which are to be integrated in portable electronics, like smartphones. Another critical problem results from the fact that an opening in the package results in the chip elements to fail when water or humidity penetrates, except when the contact regions (contact pads, wire bonds) are encapsulated completely. 
     Consequently, it would be desirable to realize a sensor package for chip elements which allows extremely small structural heights, like considerably below 1 mm, and which seals all electronic components, except for the sensitive area, from humidity and other influences hermetically. 
       FIGS. 13 and 14  show an example of a conventional pressure sensor package  1000 . An MEMS element  1001  which comprises the pressure-sensitive membrane and a respective ASIC  1002  which recalculates and communicates to the outside the measurement signal to form pressure values, are mounted on a small base plate  1003  and comprise wire bonds  1004  for contacting among one another and to the circuit board. As in shown in  FIG. 14 , the chips  1001 ,  1002  are covered on the mounting plate  1003  by a lid  1005  (like a metal sheet) comprising an opening  1006  in order for the surrounding pressure to be also measurable within the chamber of the MEMS element. 
     It is understandable that humidity/water can penetrate through the opening of the package  1006  with such structures, resulting in short circuits of the wiring within. The height of the wire bond also contributes to the structural height of the entire package. 
     Flip-chip mounting techniques for semiconductor devices on films or other substrates (PCB, printed circuit boards) are also known; see, for example, the publication: Rekha S. Pai, Kevin M. Walsh, “The viability of anisotropic conductive film as a flip chip interconnect technology for MEMS devices”, J. Micromech. Microeng. 15 (2005) 1131-1139. This publication describes how an ACA (anisotropic conductive adhesive) is used for flip-chip mounting a pressure sensor above an opening in a circuit board (circuit carrier). It becomes obvious from the description and the images that the ACA or ACF (anisotropic conductive film) material is applied on the side of the sensor chip and, after that, the chip is placed above the hole. In addition, only the chip area with the contact pads is covered by the ACA/ACF material. Applying the ACA/ACF material on the chip side is difficult and, with ever smaller chip sizes (below 1 mm), this entails a precise mechanical process. 
     U.S. Pat. No. 8,177,355 B2 describes cutting an ACF film by means of a laser. Column 4, line 55 mentions ACF laser cutting. What is described is that the ACF is patterned by means of the laser and, subsequently, the ACF patterned already is mounted on a substrate. 
     SUMMARY 
     According to an embodiment, a method may have the steps of: providing a layer compound having a substrate having an adhesive layer applied thereon at least in regions, introducing an opening extending through the substrate and the adhesive layer in order to obtain a patterned layer compound, providing a microchip having an active region arranged on the outside of the chip, wherein the active region is a sensor area or a radiation coupling-out area, and arranging the microchip on the adhesive layer of the patterned layer compound such that the active region is exposed through the opening. 
     According to another embodiment, a package for a microchip may have: a film substrate having a contact area for electrical chip contacting, an adhesive layer applied onto the film substrate and covering the contact area at least in portions, and a microchip having an active region arranged on the outside of the chip, wherein the microchip is in contact with the adhesive layer at least in portions, wherein the film substrate and the adhesive layer have a joint continuous opening, and wherein the microchip is arranged on the adhesive layer such that the active region is exposed through the opening. 
     In accordance with the inventive method, a layer compound comprising a substrate having an adhesive layer applied thereon at least in regions is provided. In the sense of the present disclosure, the substrate including the adhesive layer applied thereon is referred to as a layer compound. In accordance with the invention, an opening which extends through the substrate and the adhesive layer is introduced into this layer compound. The process of introducing the opening in the sense of the present disclosure is also referred to as patterning. The layer compound comprising the continuous opening thus is also referred to as a patterned layer compound. In addition, a microchip is provided in accordance with the invention. The microchip comprises an active region arranged on the outside of the chip. When, for example, the microchip is a sensor chip, the active region may be a sensor area. The microchip, however, may also comprise an emitter for emitting (for example electromagnetic) radiation, like an LED or the like, for example. In this case, the active area may be a radiation coupling-out area. The active area may also be referred to as effective area since the respective desired effect is achieved in the region of this area. In accordance with the invention, the microchip is arranged on the adhesive layer such that the active region of the microchip is exposed through the opening provided in the layer compound. Advantageously, the active region is not covered by the adhesive layer and thus is in contact with the surroundings by the opening. A medium to be measured (like gases, liquids, etc.) or radiation (like light) may, for example, propagate through the opening to the active region of the microchip and/or flow towards the active region. On the other hand, when the active region is a radiation coupling-out area, the radiation coupled out may be released to the surroundings through the opening. Advantageously, the entire area of the active region is arranged within the cross-section of the opening, i.e. the adhesive does not come into contact with the active region of the microchip. However, it would also be feasible for the adhesive to contact portions of the active region at least partly. This may, for example, occur when the adhesive is liquid and flows to a certain extent in the direction of the active region of the microchip. The adhesive can seal the microchip, except for the active region, and protect the same from humidity, dust, dirt, etc., for example. However, the active region will be freely accessible through the opening, at least with its part not covered by the adhesive, i.e. the medium to be measure or radiation to be measured or emitted may enter and exit through the opening. Advantageously, the microchip is arranged such that the active region is oriented to be symmetrical to the opening, i.e. the edge of the active area has the same distance to the edge of the opening. Among others, the inventive method offers the advantage that applying the adhesive or adhesive layer at the location of the future chip placement on the substrate may involve a great tolerance. Fewer process steps are used for manufacturing the microchip arranged on the patterned layer compound than with a conventional structure. This is cost and time-saving and the process security is increased. Additionally, the adhesive provides for the opening to be sealed from humidity and/or dirt penetrating. Patterning the layer compound, i.e. introducing a joint continuous opening in the substrate and the adhesive can take place relatively easily and at increased tolerance. In well-known chip manufacturing methods, like flip-chip bonding methods, for example, in contrast, the adhesive is patterned before and only applied on the substrate after that. With other known flip-chip bonding methods, the adhesive is applied on the chip and the chip has to be arranged precisely with the (usually conductive) adhesive applied on the electrical contacts of the substrate, such that a sensor area is at the same time oriented precisely above an opening in the substrate. The tolerances in known methods consequently are much smaller, which in turn entails precise processing, which in turn results in increased process costs. 
     In accordance with an embodiment, the microchip may be arranged on the adhesive layer of the patterned layer compound such that the active region, in a top view on the opening, is completely within the projection of the cross-sectional area of the opening. Thus, the entire active region at the outside of the chip remains completely accessible from outside, i.e. through the opening. Furthermore, it can be ensured that the entire active region is utilized, for example in order to provide the largest sensor area or radiation coupling-out area possible. 
     It is conceivable for patterning the substrate and the adhesive layer to be done in a joint process step. This is suitable when the adhesive layer has already been applied on the substrate. Thus, the opening is introduced into the substrate and into the adhesive layer jointly and/or at the same time. This saves time in manufacturing when compared to conventional methods where an ACF material is patterned separately from the substrate. In accordance with the invention, the positioning of the opening here may be done in dependence on the contact area for the chip contacting on the substrate or adjusting mark manufactured in relation with metal structures on the base substrate. Arranging the microchip may also be done in dependence on the contact areas or adjusting marks. In this way, the geometrical tolerances between the opening in the substrate and chip placement are kept at a minimum. 
     In accordance with an embodiment of the inventive method, the microchip may be arranged on the layer compound by means of an anisotropic conductive adhesive layer (ACA or ACF) using a flip-chip mounting technique. The anisotropic conductive adhesive layer here may be arranged on the substrate such that the anisotropic conductive adhesive layer contacts the substrate and a contact area, provided on the substrate, for electrically contacting the microchip. Such flip-chip mounting techniques including an ACA or ACF material are suitable for mass production and are able to shorten the clock times considerably when compared to conventional methods. 
     It is conceivable for the adhesive layer, after curing, to form a hermetic seal of the contact area between the microchip and the substrate. Hermetic sealing in particular means a water and dirt-tight sealing, or gas-tight sealing. This is of particular advantage when compared to conventionally packaged sensors where humidity can penetrate through the unprotected package opening and shorten electrical contacts. 
     It is conceivable for the adhesive layer to comprise a non-conductive adhesive, in particular an epoxide adhesive, wherein the electrical chip contacting is provided by means of thermo-compression bonding methods or by means of soldering. Non-conductive adhesives are cheaper and easier to handle than conducting adhesives, wherein the process costs can be reduced for mass production. 
     It is conceivable for the adhesive layer to be cured thermally after arranging the microchip on the adhesive layer. The thermo-activator adhesives employed here are highly suitable for being used in an inventive method, since these adhesives can be applied precisely on the substrate, without curing before being activated thermally. 
     In accordance with another embodiment, introducing the opening in the substrate and the adhesive layer may be done by means of laser patterning. Laser patterning or laser cutting is of advantage in that no shear forces are entailed for introducing the opening. This is of advantage when the substrate is a film, for example. 
     It is conceivable here for laser patterning to be done by means of short-pulse laser or by means of ultra-short-pulse lasers or by means of laser beams at wavelength of less than 400 nm, i.e. ultra-violet light. Short-pulse lasers are lasers emitting laser beams intermittently in the nanosecond range. Ultra-short-pulse lasers are lasers emitting laser beams intermittently in the piko or femtosecond ranges. Premature undesired thermo-activation of the adhesive can be avoided by such short-pulsed lasers. 
     In accordance with an embodiment of the inventive method, introducing the opening into the substrate and the adhesive layer may be done by means of a mechanical stamping process or by means of drilling. This is particularly suitable when using conventional PCBs (circuit boards) made of epoxide resin and the like. Drilling and stamping are very easy and quick methods for introducing the opening into the layer compound (substrate and adhesive). 
     It is feasible for the substrate to be a film having a thermo-stability of up to 300° C. Such films are of particular advantage when using thermally activatable glues, since these films keep their structures without any damages even when applying high temperatures. 
     In accordance with conceivable embodiments, the substrate may be a film made of polyimide (PI), polyethylene terephthalate (PET), polyethylene phtalate (PEN), polycarbonate, paper, polyether ether ketone (PEEK) or epoxide. With such film substrates, the structural height of a package (layer compound of film substrate and adhesives including the microchip) can be reduced considerably when compared to conventional PCBs made of epoxide resin and the like. 
     It would also be conceivable for the substrate to be a metal film which comprises an insulation layer arranged between the same and a contact area provided on the substrate. A metal film exhibits high stability and, at the same time, great flexibility. An insulation layer is arranged between the metal film and the contact area for electrically contacting the microchip in order to avoid short-circuiting. 
     It is conceivable for the substrate, the adhesive layer and the microchip connected thereto to exhibit an overall thickness between 50 μm and 500 μm. This is of particular advantage with electric sensorics to be mounted into mobile devices, like smartphones and the like. Such an overall thickness may be realized using the inventive method in a reproducible manner. Conventionally packaged sensors, in contrast, exhibit a thickness of 1 mm or more. 
     The adhesive layer may be applied on the substrate in a paste-like stated, wherein the adhesive layer is pre-dried before introducing the opening. Adhesives in a paste-like state are easy to handle and process. For example, an ACA film may be provided as a paste-like material which is applied onto the substrate and pre-dried subsequently. The joint opening in term is introduced into the ACA layer and the substrate, advantageously in a joint process step. 
     It is conceivable for the substrate to be a circuit board and to comprise at least one material from the group of glass, ceramics, plastics or epoxide. Such substrates are easy to produce and, in addition, relatively stable and heat-resistant so that processing and implementing the inventive method using these substrates may be done easily. 
     It is conceivable for the adhesive layer to be applied on the substrate such that the adhesive layer on the substrate covers an area which is larger by between 50 μm and 1 mm than the border of the contact area of the microchip which the microchip contacts the adhesive layer by. Consequently, applying the adhesive layer may be done at a relatively great tolerance, i.e. the adhesive area need not necessarily have the same size as the area of the microchip. In addition, this ensures that, on the one hand, the microchip is connected securely to the adhesive layer and, on the other hand, a good sealing effect relative to dirt and humidity is achieved. 
     In accordance with an embodiment, a window film having a recess can be provided, wherein the window film is arranged on the patterned layer compound such that the microchip is arranged within the recess, wherein the recess is filled at least partly by a potting compound. Thus, the window film forms a package where the microchip is arranged. Advantageously, the height of the window film exceeds that of the microchip. By means of the potting compound, the entire microchip packaged within the recess (window) of the window film in turn can be sealed hermetically, thereby protecting the entire microchip from dirt and humidity. 
     Another film or coating made of a polymer, glass or metal may, for example, be arranged on that side of the window film facing away from the substrate for covering the recess provided in the window film. 
     It is conceivable for the microchip to be a sensor chip configured to measure at least one of air pressure, temperature, humidity, gas, gas components, liquid flow or gaseous flow by means of the active region, or wherein the microchip is a sensor chip for a fluidic system, a biosensor chip or a capacitive sensor chip contactable by a liquid or gas. Furthermore, it is conceivable for the sensor chip to be useable also for measuring a pH value in a liquid, or as an amperometrical electrode or for measuring a potential in a fluidic surrounding. 
     In accordance with another embodiment, the microchip may be a sensor chip configured to measure radiation, particularly light, by means of the active region. The sensor chip may, for example, be a photo diode, wherein the photo sensor is arranged above the opening in the substrate and the adhesive layer so that light incident through the opening may be detected by the sensor area. 
     Additionally, the microchip may be configured to emit radiation, particularly light, by means of the active region. In this case, the active region is a radiation coupling-out area which is arranged above the opening in the substrate and the adhesive layer so that radiation can be emitted through the opening. Exemplarily, LEDs may be used here, the light exit area of which is placed above the opening so that LEDs can emit light to the outside through the opening. 
     A further aspect of the invention provides a package for a microchip, wherein the package comprises, among other things, a film substrate having a contact area for electrical chip contacting and an adhesive layer applied onto the substrate and covering the contact area at least in portions. In addition, the package comprises a microchip having an active region arranged on the outside of the chip, wherein the microchip contacts the adhesive layer at least in portions. In accordance with the invention, the substrate and the adhesive layer comprise a joint continuous opening and the active region of the microchip is arranged on the adhesive layer to be exposed through the opening. Such a package offers the advantage that the microchip, except for the active area which may, for example, be a sensor area or a radiation coupling-out area, is sealed hermetically and thus protected from humidity and/or dirt penetrating. Particularly, the electrical contacts are sealed by means of the adhesive layer so that short-circuiting can be avoided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are illustrated in the drawings and discussed below, in which: 
         FIG. 1A  shows a block diagram of an inventive method, 
         FIGS. 1B-1E  show cross-sectional views of a representational device for discussing method steps of the inventive method, 
         FIG. 1F  shows a top view on a device for discussing the projection area of the opening provided in the substrate, 
         FIGS. 2-6  show further cross-sectional views of a representational device for discussing method steps of the inventive method, 
         FIGS. 7-9  show side views on an inventive device, 
         FIG. 10  shows a top view on a layer structure having an adhesive applied and an opening extending through the layer structure, 
         FIG. 11  shows a view on the lower side of a layer structure with an opening extending through the layer structure, 
         FIG. 12  shows another cross-sectional view of a representational device for discussing a method step of the inventive method, 
         FIG. 13  shows a cross-sectional view of a well-known chip package, and 
         FIG. 14  shows a top view on a known sensor chip package covered by a cover having an opening. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1A  shows a block diagram for the progress of an inventive method which basically consists of four steps. The individual steps may also be executed in an order differing from that illustrated in  FIG. 1A . 
     In block  1 , a layer compound  11 ,  13  comprising a substrate  11  having an adhesive layer  13  applied at least in portions thereon is provided. 
     In block  2 , an opening  41  extending through the substrate  11  and the adhesive layer  13  is introduced in order to obtain a patterned layer compound  11 ,  13 . 
     In block  3 , a microchip comprising an active region arranged on the outside of the chip is provided. The active region may be a sensor area or a radiation coupling-out area. 
     In block  4 , the microchip is arranged on the adhesive layer. Thus, the microchip is arranged on that side of the adhesive layer facing away from the substrate. The microchip is arranged on the adhesive layer such that the active region is exposed through the opening. 
       FIGS. 1B to 1E  show a representational progress of the inventive method. 
     A substrate  11  is illustrated in  FIG. 1B . An adhesive layer  13  is applied on the substrate  11 . The adhesive layer  13  extends over the substrate  11  at least in portions. However, the adhesive layer  13  may also extend completely over the entire substrate  11 . The substrate  11  and the adhesive layer  13  applied thereon form a layer compound  11 ,  13 . 
     It is to be recognized in  FIG. 10  that an opening  41  is introduced into the layer compound  11 ,  13 . The layer compound  11 ,  13  is also patterned. The result is a patterned layer compound  11 ,  13 . The opening  41  extends completely through the substrate  11  and the adhesive layer  13 . 
     Advantageously, the opening  41  here extends perpendicularly to a direction of extension of the substrate  11 . 
     A microchip  14  is provided in  FIG. 1D . The microchip  14  comprises an active region  16  on its outside. The active regions  16  may be a sensor area. However, the active region  16  may also be a radiation coupling-out area. 
     It may be recognized from  FIG. 1E  how the microchip  14  is arranged on the layer compound  11 ,  13 . The microchip  14  is arranged on the adhesive layer  13  such that the active region  16  is exposed through the opening  41 . The active region  16  thus is in contact with the surroundings at least in portions. In the embodiment shown in  FIG. 1E , the active region  16  is exposed completely through the opening  41 , i.e. the entire active region  16  is in contact with the surroundings. 
     Expressed differently, the microchip  14  is arranged on the adhesive layer  13  of the patterned layer compound  11 ,  13  such that the active region  16 , in a top view on the opening  41 , is within the projection of the cross-sectional area of the opening  41 . This is to be discussed in greater detail referring to  FIG. 1F . 
       FIG. 1F  shows a top view on the patterned layer compound  11 ,  13  with the microchip  14  arranged thereon. The adhesive layer  13  may be recognized on the substrate  11 . The microchip  14  is arranged on the adhesive layer  13 . 
     In the top view shown, the microchip  14  hides the opening  41  and the active region  16  from being visible, which is why these two elements  41 ,  16  are illustrated in broken lines. However, it can be recognized that the active region  16  with its entire area (hatching from the top right to the bottom left) is arranged within the projection of the cross-sectional area of the opening  41  (hatching from the top left to the bottom right). As can be recognized in  FIG. 1F , the cross-sectional area of the opening  41  means a cross-section along the direction of extension or plane of the substrate  11 . 
     Another representational embodiment for visualizing an inventive method is shown in  FIGS. 2 to 6 . 
     A substrate  11  is shown in  FIG. 2 . The substrate  11  comprises a contact area  12  for electrical chip contacting. The contact area  12  in the embodiment illustrated is implemented to be a two-part area having a first area part  12   a  and a second area part  12   b.  These area halves  12   a,    12   b  of the contact area  12  not connected to each other electrically may, for example, be used as a plus pole and minus pole for contacting a microchip. 
     The substrate  11  may also comprise more than one contact area  12 . In addition, the one or several contact areas  12  in turn may comprise more than the two contacts  12   a,    12   b  mentioned above. 
     The contact area  12  may be pre-patterned. Exemplarily, there may be a distance of a certain size between the two area halves  12   a,    12   b  so that a gap  21  forms between the two area halves  12   a,    12   b.  The distance or clear width of this gap  21  may be adapted already to the size of an active area  16  of a microchip  14  to be arranged thereon later. This will be described below in greater detail referring to  FIGS. 5 and 6 . 
       FIG. 3  additionally shows an adhesive applied  13 . The adhesive layer  13  is applied onto the substrate  11  and the contact area  12  such that the adhesive layer  13  contacts the substrate  11  at least in portions and the contact area  12  at least in portions  12 . In the present embodiment, the adhesive layer  13  is applied at the position of the gap  21  mentioned before between the two contact area halves  12   a,    12   b.  Thus, the adhesive layer  13  advantageously covers the gap  21  completely. 
     As is shown in  FIG. 4 , the substrate  11  and the adhesive  13  are patterned together. Here, an opening  41  which extends through the substrate  11  and through the adhesive  13  is introduced into the layer compound  11 ,  13 . Advantageously, this is performed in a joint process step. 
     For further illustration of the opening  41  in the layer compound  11 ,  13 , reference here is made to  FIG. 10 .  FIG. 10  shows the layer compound  11 ,  13  in a top view. The adhesive layer  13  is applied on the substrate  11  with the two contact area halves  12   a,    12   b.  The opening  41  extends completely through the adhesive layer  13  and through the substrate  11 . 
     A microchip  14  is illustrated in  FIG. 5 . The microchip  14 , on the outside of the chip, comprises an active region  16 . The active region  16  may, for example, be implemented as an active area extending on the outside of the microchip  14 . The microchip  14  may, for example, be a sensor microchip and, in this case, the active area  16  would be a sensor area which may come into contact with the medium to be detected. However, the microchip may also be a radiation-emitting element. In this case, the active area  16  would be a radiation coupling-out area able to emit radiation towards the outside. Expressed more generally, the active region  16  is an effective region or effective area within which there is an effect, like detecting a medium, detecting radiation, in particular electromagnetic radiation, or emitting radiation, in particular electromagnetic radiation, like light, for example. 
     In this embodiment, the microchip  14  also comprises contacts  15  for electrically contacting the microchip  14  with the contact areas  12   a,    12   b  of the substrate  11 . The contacts  15  here may be contacted electrically with the contact areas  12   a,    12   b  of the substrate  11  directly or indirectly (like by means of ACA or ACF). 
     As can be seen in  FIG. 6 , the microchip  14  is arranged on the adhesive layer  13  such that the active region  16 , in a top view on the opening  41 , is within the projection of the cross-sectional area of the opening  41  at least in portions. 
       FIG. 11  shows a view on the substrate  11  from below for further illustration. What can be recognized is the opening  41  extending through the substrate  11  and the adhesive layer  13 . As can be seen, the opening  41  need not to be of a round shape. In the embodiment illustrated, for example, it is quadrangular. 
     When looking through the opening  41  from below, the microchip  14  and the active region  16  thereof can be recognized. In the embodiment illustrated, the active region  16  is completely within the projection of the cross-sectional area of the opening  41 . More precisely, the active region  16  is symmetrical within the opening  41 . This means that the active region  16 , which only exemplarily is illustrated to be quadrangular, comprises the same distance on all four sides to the four sides of the exemplarily quadrangular opening  41 . 
       FIG. 12  shows another embodiment where the active region  16  of the microchip  14  is exposed through the opening  41  at least in portions. The area of the active region  16  here is larger than the cross-sectional area or the diameter (or outer dimensions) of the opening  41 . Correspondingly, in a top view, the active region  16  overlaps the opening  41  at least in portions. It is also conceivable for the active region  16  to overlap the opening  41  only on one side. In accordance with the invention, in a top view on the opening  41 , the active region  16  is within the projection of the cross-sectional area of the opening  41  at least in portions. 
     Thus, it is conceivable for the active region to be arranged within the projection of the cross-sectional of the opening  41  by at least 80% of its overall area, advantageously to be arranged within the projection of the cross-sectional area of the opening  41  by at least 90%, and more advantageously at least 95% and, even more advantageously, completely. 
     In some embodiments, patterning the substrate  11  and the adhesive layer  13  takes place in a joint process step. This means that the opening  41  is introduced into the substrate  1  and the adhesive layer  13  in one and the same process step. 
     Introducing the opening  41  may, for example, be performed by means of etching methods, laser methods or by means of mechanical methods. Exemplarily, a wet or dry-etching method may be used in order to provide the opening  41  in the substrate  11  and the adhesive layer  13 . It would be conceivable here for the method steps shown in  FIGS. 5 and 6  to be interchanged. This means that the microchip  14  may be arranged on the adhesive layer  13  at first and then the opening  41  be etched. Advantageously, the active region  16  of the microchip  14  is resistant to the etchant used. 
     However, the opening  41  may also be introduced by means of mechanical methods, like stamping, cutting, sewing or drilling. Since, however, in this case large shear forces may act, this type of patterning is of particular advantage when the substrate  11  is formed from a material of little flexibility. Exemplarily, the substrate  11  may be implemented to be a circuit board made of epoxide resin and the like, or the substrate  11  comprises glass, ceramics or plastics. With this mechanical method, it is advantageous for the opening  41  to be patterned at first in the substrate  11  and the adhesive layer  13  and only then the microchip  14  to be placed on the adhesive layer  13 . 
     In some embodiments, providing the opening  41  may be done by means of laser patterning. In case a thermally activatable adhesive  13  is used, the adhesive  13  is in danger of curing prematurely due to the heat developed by the laser. In order to avoid this, it is of advantage for short-pulse lasers with laser durations in the nanosecond range to be used for laser patterning. It would also be conceivable to use ultra-short-pulse lasers with pulse durations in the piko or femtosecond ranges. Lasers emitting ultra violet laser radiation in a wave length range of 400 nm or less may also be used. 
     It would also be conceivable here for the method steps shown in  FIGS. 5 and 6  to be interchanged. This means that the microchip  14  may be arrange on the adhesive layer  13  at first and then the opening  41  be lasered. 
     Laser-patterning is of particular advantage when the substrate  11  is flexible and, for example, implemented as a film, since, in contrast to the mechanical processes discussed before, there are no shear forces in laser patterning. The film substrate  11  may, for example, be a film made of polyimide (PI), polyethylene terephthalate (PET), polyethylene phthalate (PEN), polycarbonate, paper, polyether ether ketone (PEEK) or epoxide. 
     In some embodiments, the film substrate  11  may also be implemented as a metal film. In contrast to plastic films, the metal film is of advantage in that it is more durable and able to withstand larger tensile forces, for example. In order to avoid short-circuiting, however, an insulation layer is arranged between the metal film and the contact areas thereof. 
     Film substrates  11  are of advantage in that the structural height of the layer compound  11 ,  13 , including the microchip  14  arranged thereon, can be kept very small, which is desirable in particular when being mounted in mobile devices. As is shown in  FIG. 6 , the layer compound, i.e. the substrate  11  and the adhesive layer  13 , including the microchip  14 , comprises an overall thickness h between 50 μm and 500 μm. 
     The adhesive layer  13  may comprise a thermally activatable adhesive. This means that the adhesive layer  13  cures only after introducing heat energy. Correspondingly, in accordance with the invention, the adhesive layer  13  may be applied on the substrate  11  and the contact areas  12   a,    12   b  without the same curing prematurely in air. After applying the adhesive layer  13  and introducing the opening  41 , the microchip  14  may be arranged on the adhesive layer  13  applied. Subsequently, the adhesive layer  13  is heated so that the adhesive layer  13  cures and connects the microchip  14  to the substrate  11 . 
     As has already been mentioned above, the adhesive layer  13  may comprise an ACA (anisotropic conductive adhesive) or ACF (anisotropic conductive film) adhesive. These adhesives  13  are usually used in flip-chip mounting, for example with RFID labels. 
     In accordance with embodiments of the invention, the microchip  14  may also be contacted electrically through the opening  41  in the base substrate  11  by means of an anisotropic conductive adhesive layer (ACA or ACF) in a so-called flip-chip technology. All the contact areas  15  of the microchip  14  are insulated among one another by the ACA/AFA layer and encapsulated in the epoxide matrix of the adhesive  13 . 
     After curing, the adhesive layer  13  forms a hermetic sealing of the contact areas  12   a,    12   b  between the microchip  14  and the substrate  11  around the opening  41 . Water penetrating through the opening  41  consequently does not reach to the contact areas  12   a,    12   b  embedded in the adhesive layer  13  and consequently no longer results in short circuits. When using a thin film for the substrate  11 , the thickness of the package (substrate  11  with optional contact area  12 , adhesive layer  13 , microchip  14 ) becomes considerably smaller than with the previous known technology (with a stable carrier plate and wire bond contacting). 
       FIGS. 7, 8, and 9  show further steps of the inventive method, wherein the microchip  14  may be packaged. 
     As is shown in  FIG. 7 , a window film  17  having a window  71  or recess  71  can be provided. The window film  17  is arranged on the layer compound  11 ,  13  such that the microchip  14  is arranged within the window  71  or recess  71 . In other words, the window film  71  is arranged such that the recess  71  surrounds the microchip  14 . In addition, the window film  17  exceeds the microchip  14  in height. As is illustrated in  FIG. 7 , the window film  17  may be arranged on the contact areas  12   a,    12   b  of the substrate  11 . The window film  17  may exemplarily be arranged directly on the substrate  11  or adhesive layer  13 . 
       FIG. 8  shows that the space between the microchip  14  and the recess  71  surrounding the microchip  14  may be filled by a potting compound  18 . Thus, a complete hermetic sealing of the microchip  14  may be realized. The potting compound  18  may be ridged or flexible, for example, made of silicone. 
     The window film  17  may be flexible. However, the stability of the window film  17  is increased considerably by means of filling by the potting compound. After curing of the potting compound, the window film  17  is comparable as regards stability to a package made of a rigid material. Additionally, the window film  17  here is connected fixedly to the microchip  14 . 
     As can be recognized in  FIG. 9 , another layer, like in the form of another film  19  or coating  19  made of a polymer, glass, ceramics, or metal may be arranged on that side of the window film  17  facing away from the substrate  11  for covering the recess  71  provided in the window film  17 . 
     Thus, using the inventive method, a packaged microchip  14  may be provided, wherein the microchip  14  is hermetically sealed from the outside, except for its active region  16 . The adhesive layer  13  arranged around the opening  41  seals the electrical contacts  12   a,    12   b,    15  from humidity and dirt entering, for example through the opening  41 , which may result in short-circuiting. The potting compound  18  filled into the recess  71  of the window film  17 , and maybe the additional film or layer  19 , seals the microchip  14  hermetically from humidity and dirt penetrating from outside or from above, for example. 
     Thus,  FIGS. 7, 8 and 9  also show an inventive package  70  for a microchip  14 . The package  70  comprises a film substrate  11  having contact areas  12   a,    12   b  for electrically contacting the microchip  14 . 
     In addition, the package  70  comprises an adhesive layer  13  applied on the substrate  11 . The adhesive layer  13  here covers the contact areas  12   a,    12   b  at least in portions. In particular, the adhesive layer  13  covers those portions of the contact areas  12   a,    12   b  adjacent to the opening  41 . 
     In addition, the package  70  comprises a microchip  14  having an active region  16  arranged on the outside of the chip. The active region  16  may be a sensor area or a radiation coupling-out area. 
     The microchip  14  is in contact with the adhesive layer  13  at least in portions. In particular, the microchip  14  is in contact with the adhesive layer  13  by at least nearly its entire lower side (i.e. that side facing the substrate  11  or adhesive layer  13 ), except for its active region  16 . 
     The film substrate  11  and the adhesive layer  13  comprise a joint continuous opening  41  which extends with basically no interruptions through both the film substrate  11  and through the adhesive layer  13 . 
     The microchip  14  is arranged on the adhesive layer  13  or the film substrate  11  such that its active region  16  is exposed through the opening  41 . For further details, reference here is made to the above discussions, in particular to  FIGS. 6, 11 and 12 . 
     The contact areas  12   a,    12   b  are hermetically sealed around the opening  41  by means of the adhesive layer  13 . Thus, humidity and/or dirt penetrating through the opening  41  is avoided from contacting the contact areas  12   a  and  12   b  and, possibly, causing a short circuit. 
     As can, for example, be seen in  FIGS. 10 to 1F, 4 to 9 and 12 , the joint continuous opening  41  may comprise a cross-section D continuous in the adhesive layer  13  and in the film substrate  11 . Alternatively or additionally, the cross-section D may be equal or constant as regards shape and dimension in both the adhesive layer  13  and the film substrate  11 . 
     As can be seen in the Figs, the cross-section d 1  of the opening  41  in the adhesive layer  13  may, for example, basically correspond to the cross-section d 2  of the opening  41  in the film substrate  11 . This may, for example, be achieved by the fact that the joint opening  41  is formed in the adhesive layer  13  and the film substrate  11  in a joint method step. 
     The shape of the joint continuous opening  41  may, for example, be cylindrical. However, it is also conceivable for the opening  41  to comprise a conical shape. In this case, the cross-section or diameter d 1  in the adhesive layer  13  would, for example, be smaller or greater than the cross-section or diameter d 2  in the film substrate  11 . The opening  41  may, for example, also be triangular, trapezoidal, conical, frustoconical, pyramidal and the like. Further or different geometrical shapes for the implementation of the opening  41  are also conceivable if these shapes are implemented to be continuous in the adhesive layer  13  and film substrate  11 . 
     The invention is to be summarized below in other words. 
     In accordance with embodiments of the invention, the microchip  14  (like sensor chip element) is contacted electrically through the opening  41  in the base substrate  11  by means of an isotropic conductive adhesive layer (ACA or ACF) in so-called flip-chip technique. By means of the ACA/ACF layer, all the contact areas  15  of the (for example, MEMS) microchip  14  are insulated among one another and encapsulated in the epoxide matrix of the adhesive  13 . Water penetrating no longer results in short circuits. When using a thin film as the substrate  11 , the thickness of the package  11 ,  12 ,  13 ,  14  becomes considerably smaller than according to the previous known technology (with a stable carrier plate and a wire bond contacting). The thickness of the chip package up to now has been at least 1 mm. 
     Previous known structural concepts exhibit the following technical challenges: the hole  41  in the film  11  needs to be adjusted very precisely above the sensitive area  16  of the microchip  14 . And: the mounting and contacting adhesive (ACA or ACF) must not cover the sensitive area  16  of the chip  14  (otherwise the sensor function would be impeded). 
     In order to solve these problems of known technology, an inventive method for manufacturing a microchip  14  arranged on a patterned layer compound  11 ,  13  is disclosed here. Referring to  FIGS. 1B to 9 , an exemplary embodiment including flip-chip bonding will be described below. 
       FIG. 2 : substrate  11  with circuit board patterns  12   
       FIG. 3 : ACF film  13  laminated at the position of the future chip placement 
       FIG. 4 : producing a hole  41  in the double layer made of ACF  13  and substrate  11   
       FIG. 5 : adjusting a semiconductor element  14  above the circuit board patterns  12 . The microchip  14  (like sensor element) comprises a sensitive or active area  16  and protruding contact pads  15 . 
       FIG. 6 : flip-chip bonding of the microchip  14  (like sensor element) on the patterned ACF  13  and substrate  11  including the hole  41   
       FIG. 7 : applying a window film  17  comprising an opening  71  for receiving the microchip  14  (like sensor element). This may take place with no precise adjusting and/or with increased tolerance when positioning. 
       FIG. 8 : (partly or completely) filling the space  71  between the microchip  14  (like sensor element) and the inner frame of the window film  17  by a polymer (potting compound)  18 . Thus, the chip package  11 ,  12 ,  13 ,  14 ,  17  is finished. It would also be possible to omit the step in  FIG. 7  and encapsulate the chip backside by a polymer. 
       FIG. 9 : optionally, another layer  19  (film or coating made of polymer, glass or metal) may be applied onto the chip package. In the case of semiconductor elements, light-proof packaging is of advantage. This may be done by sputtering a metal layer. 
     Embodiments of the inventive solution, among other things, provide for an anisotropic conductive film (ACF)  13  to be applied on the substrate  11  (at this time there is no hole  41 ) at first and to mechanically fix same by a slight pressure and then to form in a suitable patterning process the hole  41  through the ACF layer  13  and the substrate  11  (like film or thin plate) in only a single process step. In order to fulfill the adjusting requirements of chip placement and contacting, a laser which cuts the hole  41  through the substrate  11  and the ACF layer  13  in a single step is used advantageously. The laser cut here depends on the contact areas  12   a,    12   b  for the chip contacting on the substrate  11 , or adjusting marks produced on the base substrate  11  relative to metal structures. 
     Flip-chip mounting of the microchip  14  (like sensor chip) also depends on the contact areas  12   a,    12   b  or adjusting marks of the metal areas. In this way, the geometrical tolerances between the opening  41  in the substrate  11  and the chip placement are kept at a minimum. 
     An aspect of the invention is manufacturing a precisely adjusted hole  41  in a double layer of ACF  13  and substrate  11  in only a single method step, like by laser patterning. It is to be kept in mind here that the laser cut does not trigger thermal curing of the ACF material  13  along the laser cutting line. Thermal heating of the surrounding material may be achieved by using a short-pulse laser (pulse duration in the nanosecond range) or ultra-short pulse laser (picoseconds or femtoseconds). Using laser beams with short wavelengths in the ultraviolet range (smaller than 400 nm) reduces the thermal load of the layer to be cut. 
     Mounting the microchip  14  (like sensor element) by means of an ACF film  13  entails a short-term heat input and pressure. Thus, the ACF film  13  may partly also extend somewhat to towards the inside in the direction of the sensitive or active region  16  of the chip  14 . In order to avoid the ACF  13  becoming soft from flowing towards the inside too much, advantageously a certain lead is set between the hole opening  41  in the substrate  11  and the sensitive area  16  on the microchip  14  (like sensor element). How far the ACF  13  may flow towards the inside depends, among other things, on the film thickness thereof and the height of the bumps  15  on the chip  14  or metallization traces  12   a,    12   b  on the substrate  11 . 
     The bumps  15  here act as spacers; they define the minimum distance between the chip  14  and the substrate  11 . With higher bumps  15 , the ACF layer  13  will flow less towards the inside. Experiments by the inventors have shown that an equal and reproducible flow of the ACF layer  13  may be realized. Thus, this mounting technique is well suitable for encapsulating sensors having an opening to the surroundings. 
     An alternative to the method for simultaneously producing the opening  41  in the base substrate  11  and the ACF layer  13  may also be a mechanical stamping process. However, this should be implemented such that a good adjusting precision from the edge of the hole to the surrounding metal contact areas  12   a,    12   b  is ensured. 
     Another embodiment would be drilling a hole through the double layer of substrate  11  and ACF  13 . When mounting on a circuit board, this would be of advantage. When mounting on a thin film, however, laser cutting would be of advantage. Cutting using a laser is practically free of forces, which is of particular advantage with thin films and soft adhesive layers. The shear forces when mechanically drilling or stamping, however, may make precise adjusting difficult. 
     For flat chip packages, using films for the base substrate  11  is of advantage; for example a polyimide film exhibiting a good thermal resistance (up to around 300° C.); however, films made of PET, PEN, polycarbonate, paper, PEEK, epoxide and others may also be used. In addition, metal films provided with an insulating layer (and the metal contact areas  12   a,    12   b  thereon) at least on the side of chip mounting in the region of chip placement, may also be used. When using films as the base substrate  11 , the overall thickness of the chip package may be in the range of 50 μm to 500 μm; i.e. considerably thinner than according to known technology. 
     Furthermore, the base substrate  11  may also be a rigid material, like circuit board, glass, ceramics, plastics or epoxide, for example. 
     Instead of the ACF layer  13 , a layer of a non-conducting adhesive film  13  (like an epoxide adhesive film) may also be applied and subsequently the hole  41  in the adhesive layer  13  and the base substrate  11  manufactured. In this case, a different method may be used for electrical chip contacting. This may, for example, be thermal compression bonding (copper-copper or gold-gold). In addition, the electrical connections to the sensor element may be realized using a soldering process. 
     Another alternative would be applying an ACF film  13  as a paste-like material, followed by a step of pre-drying the ACA film  13  and then jointly producing a hole through the ACA layer  13  and the base substrate  11 . 
     Up to now, it has not been possible or known to place a microchip  14  (like sensor chip) above an opening  41  in a substrate  11  such that a small sensitive or active area  16  on the (conventionally also very small) chip  14  is placed very precisely below or adjacent to the opening  41  in the substrate  11 , wherein the somewhat outside chip contact pads  15  are encapsulated and insulated, and it is ensured at the same time that no mounting or encapsulating adhesive  13  covers the sensitive or active area  16  of the chip  14 . The solution approach suggested here (patterning by, for example, laser cutting of two layers  11 ,  13  in one step) is not obvious for a person skilled in the art since what would be expected is that the laser cut would influence the thermally activatable ACF material  13  along the cutting line thermally such that the epoxide matrix would cure here already. This would prevent future flip-chip bonding. In addition, a person skilled in the art would assume at first that the metal particles in the ACF material  13  impede the laser beam such that no clean cutting line is possible. 
     An advantage of the laser is the freedom in design for defining the shape of the opening  41 ; i.e., for example, round, quadrangular, or shaped differently. The opening  41  may in any case be adjusted optimally to the shape of the sensitive or active area  16  on the microchip  14  (like sensor element). 
     Applying the ACF layer  13  at the position of the future chip placement on the base substrate  11  may be done at great a tolerance. The AC film  13  here may be somewhat greater than the chip  14  itself, like 50 μm to 1 mm larger than the chip border. 
     Fewer process steps than in a conventional structure are used for manufacturing the package. This is cost and time-saving and increases the process security. 
     When using films, the package height may be in the range of 50 μm to 500 μm, i.e. considerably flatter than previous chip packages. The packages may even be implemented to be mechanically flexible. 
     The opening  41  in the package is sealed from humidity or dirt penetrating. 
     Fields of application are, for example, packages for sensors for air pressure, temperature, humidity, gas, gas components, flows (liquid or gaseous); sensors in fluidic systems, biosensors, capacitive sensors which are in contact with liquids or gases. Even for measuring pH values in liquids or amperometrical electrodes or measuring a potential in a fluid surrounding. 
     Also of interest for sensors for radiation, like light. In this case, photodiodes would be mounted above an opening in flip-chip technology; even mounting light-emitting elements, like LED elements, for example. Also of interest for electron radiation; any cover of the sensitive layer here would be a relatively strong absorber. 
     The package may of course contain more than a single chip element. A sensor and an ASIC for data evaluation or an additional element for data transmission, for example, would also be useful. 
     Although the embodiments described above have been described such that the substrate  11  comprises a planar shape, the substrate  11  may also exhibit different shapes. The substrate  11  may, for example, have a curved shape (like a dome structure) or a shape planar and/or folded in portions. 
     Although some aspects have been described in connection with a device, it is to be understood that these aspects also represent a description of the corresponding method so that a block or element of a device is to be understood to be also a corresponding method step or feature of a method step. In analogy, aspects having been described in connection with or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device. 
     The method steps described here may be executed in any different order than that stated in the claims. 
     While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents which will be apparent to others skilled in the art and 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.