Abstract:
An integrated circuit includes a first plate-shaped part and at least a plate-shaped second part separate from the first part and attached to the first part by deformable mechanical connection defining a non-zero angle with the first part. A method of producing the integrated circuit includes depositing deformable connecting means in contact with a first portion of the structure and a second portion of the structure, etching the structure to separate the first portion and the second portion, relatively moving the first and second portions to deform the connecting means and fastening together the first portion and the second portion.

Description:
PRIORITY CLAIM 
       [0001]    This application is a U.S. nationalization of PCT Application No. PCT/FR2007/001188, filed Jul. 11, 2007, and claiming priority to French Patent Application No. 0652966, filed Jul. 13, 2006. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention concerns an integrated circuit distributed over at least two non-parallel planes, including for example an electrical circuit, a magnetic circuit or an electronic circuit, or of MEMS (MicroElectroMechanical System) type, and a method of production of such integrated circuits. It can in particular be a question of a microelectronic component or a component produced using techniques from the field of micro- or nano-technologies. 
       BACKGROUND 
       [0003]    Components are frequently used having a portion consisting of at least one plate-shaped structure one face of which carries an electrical circuit. In the context of microelectronics, for example, a substrate can carry electronic circuits such as magnetic field sensors. 
         [0004]    It is sometimes required to dispose at least a portion of the circuit in a plane inclined, or even perpendicular, to the plane defined by the plate. 
         [0005]    This is the case in particular when it is required to measure a magnetic field in three dimensions, for example as described in U.S. Pat. No. 5,446,307. 
         [0006]    In that document, magnetic sensors are placed so that each measures the component of the magnetic field perpendicular to one of the inclined faces of a pyramidal structure, which is a simple way to provide access to the three components of the magnetic field. 
         [0007]    The front face etching technology used to obtain the pyramidal structure limits the height that can be envisaged for that structure to a few micrometers, however, and means that this solution cannot be applied to magnetic sensors of larger size (for example with dimensions of the order of 1000 μm), the use of which on the inclined faces of the structure would result in much too low an inclination of the latter (less than 1% inclination) to be able to measure efficiently the magnetic field in a direction other than perpendicular to the substrate. 
         [0008]    PCT Patent Publication No. WO 2006/001978 proposes a solution of the same type. 
         [0009]    The above two inventions also have the major drawback that the electrical or microelectronic circuits must be produced on inclined planes, which gives rise to numerous difficulties. 
       SUMMARY 
       [0010]    The invention therefore aims in particular to propose an alternative solution for producing a component having faces inclined to each other, possibly with a significant inclination, and in particular, starting with a plate-shaped structure, a plane inclined to the rest of that structure. This inclined plane could advantageously include, before or after inclination, a magnetic sensor in the context of microelectronics or any other microelectronic device. 
         [0011]    In this context, the invention proposes an integrated circuit including a plate-shaped first portion (carrying in a general manner a circuit), characterized in that it includes at least one second plate-shaped portion separate from the first portion, attached to the first portion, connected to the first portion by deformable mechanical connecting means and forming a non-zero angle with the first portion. 
         [0012]    Because the two portions are separate, they are independent (at least during part of the process of producing the integrated circuit) and can be moved freely relative to each other to their reciprocal final position, whilst nevertheless being retained by the deformable connecting means. 
         [0013]    Thus all of the elements (such as electrical circuits) can be produced on the two portions in the same plane, after which one portion is moved relative to the other to obtain elements distributed over two non-parallel faces. 
         [0014]    The connecting means are at least in part of metal, for example, enabling them to be used also as electrical conductors, where appropriate. 
         [0015]    In practice, the connecting means can include at least one metal wire fastened to the first portion at one end and to the second portion at the opposite end. In another embodiment, the connecting means can include at least one metal trellis connected to the first portion and to the second portion. 
         [0016]    The connecting means can be produced in copper or in gold, particularly suitable because of their flexibility. 
         [0017]    For example, the first portion includes a silicon plate. 
         [0018]    For example, according to the invention, the angle between the first and second portions is greater than 60°, or even equal to approximately 90°, for example to within 10°. 
         [0019]    When the second portion carries an electrical element the connecting means can contribute to an electrical connection between an electrical circuit carried by the first portion and the electrical element carried by the second portion. 
         [0020]    For example, the electrical circuit carried by the first portion includes at least one sensor adapted to measure a magnetic component in a direction parallel to a main surface of the first portion and the second portion can carry a sensor adapted to measure a component of the magnetic field in a direction parallel to a main surface of the second portion. 
         [0021]    For example, the sensors are micro-fluxgate sensors, magnetoresistive sensors, magneto-impedance sensors or Hall-effect sensors. 
         [0022]    When the first portion carries a plurality of first connection studs, another integrated circuit having second connection studs can be mounted in contact with the first portion, with electrical connection between at least one of said second connection studs and one of said first connection studs (for example thanks to the interposition of conductive balls, by means of anisotropic conductors or by thermocompression). This produces a particularly compact structure. 
         [0023]    The second portion can then be near a flank of the other integrated circuit, which makes the assembly even more compact. 
         [0024]    In an embodiment described hereinafter, the plates are obtained from substrates conventionally used in microtechnology, for example in semiconductor material, such as silicon, germanium (or III-V or II-VI materials); the plates are then essentially rigid (in particular, essentially incapable of being curved) given the dimensions characteristic of such substrates. 
         [0025]    The invention also proposes a method of producing an integrated circuit from a plate-shaped structure (which generally carries a circuit), including the following steps: 
         [0026]    depositing deformable connecting means in contact in particular with a first portion of the structure and a second portion of the structure; 
         [0027]    etching the structure to separate the first portion and the second portion; 
         [0028]    relatively moving the first and second portions, leading to deformation of the connecting means; 
         [0029]    fastening together the first portion and the second portion. 
         [0030]    This method can also include a step, after the movement step, of fastening together the first and second portions (directly or via another portion), a non-zero angle then existing between their respective main surfaces. 
         [0031]    For example, the movement is a rotation of the second portion relative to a hinge formed by the connecting means. 
         [0032]    The connecting means can be deposited during at least one of the technology steps of producing the circuit carried by the plate-shaped structure. 
         [0033]    The method can also include a step of thinning the structure before etching it and/or a step of partial grinding of an area subjected to said etching before the etching step. 
         [0034]    When the connecting means are produced in an electrically conductive material, there can be a step of depositing a conductor between at least one circuit carried by the first portion or the second portion of the structure and the connecting means, in order to make the electrical connection to these various elements. 
         [0035]    When the conductor is deposited between a circuit of the second portion and the connecting means, the method can further include a step of depositing a conductor between the connecting means and a circuit element on the first portion, in order to extend the connection previously produced. 
         [0036]    The etching can be precisely localized anisotropic etching. 
         [0037]    The face of the second portion that has been subjected to etching (rear face) can be assembled to the edge of the first portion (in particular, a lateral face of the first portion, different from the main faces of the plate). 
         [0038]    In another embodiment, the etching step can form an inclined profile on a face of each of the first and second portions receiving the etching. The movement step can then move the inclined profile of the second portion near (or even into contact with) the inclined profile face of the second portion, and there can then be a further step, after the movement step, of assembling the inclined profile of the second portion against the inclined profile face of the second portion, which produces a particularly compact and robust structure. The assembly process can include sticking the two portions together (for example by depositing a bead of glue that can further make good any interstice between the two portions). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0039]    Other features and advantages of the invention will become more clearly apparent in the light of the following description, given with reference to the appended drawings, in which: 
           [0040]      FIGS. 1 and 2  represent two of the steps of producing an integrated circuit conforming to the teachings of the invention; 
           [0041]      FIG. 3  represents in perspective an integrated circuit obtained by such a method, before bending one of its portions; 
           [0042]      FIG. 4  represents the assembly of the integrated circuit from  FIG. 3  and another integrated circuit; 
           [0043]      FIG. 5  is a diagram of a second embodiment of the invention; 
           [0044]      FIGS. 6 and 7  are diagrams of a third embodiment of the invention; and 
           [0045]      FIGS. 8 and 9  show alternatives to the deformable connecting means provided in the previous embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]      FIG. 1  represents a substrate  10 , here in silicon, onto the front face of which have been deposited elements of an electrical circuit, including three magnetic field sensors  12 ,  14 ,  16 . 
         [0047]    Each sensor  12 ,  14 ,  16  is adapted to measure the magnetic field in a given direction and three magnetic field sensors  12 ,  14 ,  16  are therefore provided to obtain measurements of the local magnetic field projected in the three directions in space (X, Y, Z), i.e. the three components of this magnetic field. 
         [0048]    A first sensor  12  and a second sensor  14  are situated in a first region  2  of the substrate  10  and are disposed perpendicularly to each other in order to measure the respective components of the magnetic field in the direction Y and in the direction X. (These latter two directions X, Y are essentially parallel to the front face of the substrate  10 .) 
         [0049]    A second region  4  of the substrate  10  carries the third sensor  16 . In this example this sensor is parallel to the second sensor  14 , but is intended to measure the component of the magnetic field in the direction Z normal (i.e. perpendicular) to the front face of the substrate  10  (which carries the aforementioned elements), in the manner described hereinafter. 
         [0050]    Each magnetic sensor is produced using the micro-fluxgate technology, for example. Alternatively, these could be magneto-resistive sensors (in particular AMR, GMR or TMR sensors), magneto-impedance (MI) sensors, or Hall-effect sensors. 
         [0051]    The front face of the substrate  10  also carries connection studs  18  some of which are connected to a corresponding sensor by means of conductors  20  (for example conductive tracks, possibly separated from the substrate by a layer of insulative material). 
         [0052]    A plurality of metal (here copper) tracks (or wires)  22  have equally been deposited on the front face of the substrate  10 , at the boundary between the first region  2  and the second region  4 , encroaching of each of those two regions, and here with an interposed insulator  24  (for example silicon oxide). 
         [0053]    In practice, the insulative layer  24  could extend over the whole surface of the substrate  10  in order to insulate the elements described above. 
         [0054]    Some of the metal tracks  22  are electrically connected to the magnetic sensor  16  in the second region  4 , for example by a conductor  26 . These same metal tracks  22  are also electrically connected to one of the connection studs  18  in the first region  2 , by a conductor  28 . 
         [0055]    Thus the magnetic sensor  16  in the second region  4  of the substrate  10  is electrically connected to connection studs  18  in the first region  2  of the substrate  10  via at least one of the metallic tracks  22  in particular. 
         [0056]    The various conductors  20 ,  26 ,  28  are, for example, copper or gold tracks deposited during the production of the other elements carried by the substrate  10  (for example by the same technique as the metal tracks  22 , possibly during the same technology step). Alternatively, the conductors could be formed by gold wires produced after construction of the other elements carried by the substrate. 
         [0057]    It may be noted here that a plurality of components (integrated circuits) can be obtained from the same substrate  10  using collective integrated circuit production technology. There can therefore be seen in  FIG. 1  a magnetic field sensor  16 ′ located near the first sensor  12  and a magnetic field sensor  12 ′ located near the third sensor  16 , these sensors  16 ′,  12 ′ being each intended for a component of the same type as that described above and obtained in parallel. 
         [0058]    Once the various elements referred to above and visible in  FIG. 1  have been deposited on the front face of the substrate  10 , the rear face of the substrate  10  is etched to eliminate the entire thickness of the substrate over a portion of limited extent situated at the boundary between the first region  2  and the second region  4 . There is produced for example in this step, by protecting the portion of the substrate to be retained (in practice virtually all of the substrate) by means of photolithography and applying anisotropic etching to the rear face, for example deep reactive ion etching (DRIE), or by chemical etching (for example using KOH when the substrate  10  is of silicon). 
         [0059]    In one embodiment that can be envisaged, this rear face etching step can separate the various components formed from the same substrate. Alternatively, the different components produced from the same substrate could naturally be separated in a later step. 
         [0060]    Moreover, another etching step could be used (for example appropriate reactive ionic etching or ionic machining) to eliminate the layer  24  of insulation located under the metal tracks  22  in the portion that has been etched. 
         [0061]    This produces the integrated circuit represented in  FIG. 2 , which therefore includes a first substrate portion  30  that corresponds to the first region  2  of the substrate described above and a second substrate portion  32  that corresponds to the second region  4  referred to above. 
         [0062]    Because of the total elimination of the substrate (and of the layer  24  of insulation) at the boundary  3  between the regions  2 ,  4 , in particular by means of the etching previously referred to, the first portion  30  is separated from the second portion  32  by a gap  31 , the two portions  30 ,  32  now being mechanically connected to each other only by the metal tracks  22 . 
         [0063]    The integrated circuit obtained is also shown in perspective in  FIG. 3 . 
         [0064]    Thanks to the possibility of bending the integrated circuit (i.e. of rotating the second portion  32  relative to the first portion  30  as indicated by the arrow R in  FIG. 3 ) offered by the hinge consisting of the metal tracks  22  thanks to their deformability perpendicularly to their surface, the second portion  32  can be inclined relative to the first portion  30  as described hereinafter, for example at an angle of up to 90°, which here enables the sensor  16  to be oriented so that it can measure efficiently the component of the magnetic field in the direction Z. 
         [0065]    The first portion and the second portion can then be fastened together (i.e. the second portion can be immobilized relative to the first portion), either directly (for example by gluing), or via another portion as described hereinafter. 
         [0066]      FIG. 4  represents the same component on which another integrated circuit  34  (for example an application-specific integrated circuit (ASIC)) has been mounted using the flip-chip technique. 
         [0067]    Using this technique, the face of the integrated circuit  34  carrying the contacts is placed in contact with the front face of the component, which carries the magnetic field sensors  12 ,  14 ,  16  and the connection studs  18 , with conductive balls  36  between them that make the electrical connection of each of the connection studs  18  to corresponding contacts (or studs) of the microcircuit  34  using the ball bonding technique. 
         [0068]    The integrated circuit  34  further includes means  38  for connecting it to an external device and/or remote power feed and/or transmission antennas. 
         [0069]    Thus the integrated circuit  34  can provide signal shaping, power supply and signal processing functions for the electrical signals transmitted to the magnetic sensors  12 ,  14 ,  16  and received therefrom in order to generate, for example in its connection means  38 , processed signals representing (for example in digital form) the components of the magnetic field measured by the sensors  12 ,  14 ,  16 . 
         [0070]    As explained above, the sensors  12 ,  14  respectively measure the components of the magnetic field in the directions Y and X. 
         [0071]    In order to obtain by means of the sensor  16  the component of the magnetic field in the direction Z (perpendicular to the main face of the substrate  10  as already mentioned), the second portion  32  is bent relative to the first portion  30  at the hinge formed by the metal tracks  22  whose flexibility (resulting, for example, from the fact that they are produced in a plastic metal, here copper, or alternatively gold) enables deformation without risk of breakage. 
         [0072]    In the embodiment shown in  FIG. 4 , the bending corresponds to rotation about one of the axes forming the plane of the substrate (here the Y axis) as indicated by the arrow R in  FIG. 4 , which enables positioning of the second portion  32  above the plane formed by the substrate and that contains the first and second sensors  12 ,  14 , near one edge of the integrated circuit  34  (here a flank of the integrated circuit  34 ), which can moreover provide a mechanical stop for the second portion  32 . The second portion  32  can thus be fastened to the first portion  30  via the integrated circuit  34 , for example by gluing the second portion  32  to the integrated circuit  34 . 
         [0073]    This produces a particularly compact magnetic field measuring device in which the third magnetic sensor  16  is placed in a plane inclined to (here even perpendicular to) that which contains the other two sensors  12 ,  14 , which ensures efficient measurement of the three components of the magnetic field. 
         [0074]    As already indicated above, it will be noted that the electrical connection between this third magnetic sensor  16  located in a plane perpendicular to that of the main substrate (first portion  30 ) is provided in particular by some of the deformed metal tracks  22 , themselves electrically connected to the main portion of the connection studs  18  and therefore to the integrated circuit  34  via the conductive balls  36 . 
         [0075]    Flexible deformation of the metal tracks  22  therefore provides not only for ensuring relative mechanical retention of the two substrate portions to each other, but also ensures electrical continuity of the connection between these two portions, despite the strong inclination of one portion relative to the other. 
         [0076]      FIG. 5  is a diagram of a component conforming to a second embodiment of the invention. 
         [0077]    In this second embodiment, the component includes a first substrate portion  102  (which can carry elements of electrical and/or electronic circuits, not shown) and a second portion  104  that is thinner compared to the thickness of the substrate  102  (which also carries circuits, not shown, that it is required to dispose in a plane inclined relative to that of the substrate). The first portion  102  and the second portion  104  are separated by a gap  103  and are mechanically connected by a plurality of metal tracks (or strips)  105  analogous to the metal tracks described above with reference to the first embodiment. 
         [0078]    The  FIG. 5  component is obtained from a plate-shaped silicon substrate, for example, as represented in dashed line in  FIG. 5 ), in which etching has removed only a portion of the thickness in the second portion  104  and the whole of the thickness in the gap  103 . 
         [0079]    To do this, a first etching step is effected, for example, using a mask that covers only the first portion  102 , to eliminate a portion of the thickness of the substrate, leaving only the thickness of the second portion  104 , then a second etching step with a mask that covers all of the first and second portions  102 ,  104 , except in the boundary area between these two portions, which enables the substrate to be eliminated throughout its thickness only in this boundary area of limited extent, and thus to obtain the gap  103 . 
         [0080]    Alternatively, mechanical pregrinding of the boundary area intended to receive the gap  103  (for example with a grinding tool or a string of grinding tools) so that, during a subsequent step of etching this area and the second portion  104 , the boundary area is etched throughout the thickness of the substrate whereas the second portion  104  retains the required remanent thickness. 
         [0081]    There can naturally be provided, prior to the etching step that had just been mentioned, a grinding step to thin the entire substrate. This possibility can also be envisaged for the other embodiments. 
         [0082]    In this second embodiment, in particular in the case of bending in the rotation direction R′ indicated below, the thickness of the second portion  104  is of the order of (and preferably slightly less than) the width of the gap  103  (in particular, the distance between the first portion  102  and the second portion  104 ). 
         [0083]    Thus the second portion  104  cannot be moved by bending about the hinge formed by the metal tracks  105 , either in the rotation direction R identical to that referred to in connection with the first embodiment or in the opposite direction R′, whereby the second portion  104 , once inclined, remains under the plane of the first portion  102  that carries metal tracks  105 . 
         [0084]    In the latter case, the thinness of the second portion  104  avoids the overall size problems that could prevent significant inclination of the second portion  104 . 
         [0085]      FIG. 6  represents another embodiment in which such problems are also avoided. 
         [0086]    To this end, the gap  203  between a first portion  202  of the substrate and a second portion  204  of the substrate with a beveled etching profile, for example by means of a KOH type silicon etching medium, so that, when the second portion  204  is bent around the hinge formed by metal tracks  205  analogous to those already described, the beveled face at an angle close to 45° to the second portion  204  faces the beveled face of the first portion  202  at an angle close to 45°: thus an angle of bending of the second portion  204  can be obtained, running for example up to 90° (as represented in dashed line under the reference  204 ′ in  FIG. 6 ) with no mutual mechanical impediment of the portions during rotation (in the direction R′) of the second portion  204  relative to the first portion  202 . Rotation in the direction R (opposite to the direction R′) is also possible in this context. 
         [0087]      FIG. 7  represents a variant in which the extent of the second portion  204  in the plane of the substrate before bending and gluing is limited to the thickness of the substrate, enabling production, after bending, and then deposition of a bead  206  of glue, of the particularly compact arrangement shown in  FIG. 7 . When the angles of the beveled surfaces are close to 45°, the glue joint  206  can also slightly compensate the bending angle to approximate or even achieve an angle of 90°. 
         [0088]      FIG. 8  represents a plan view of another embodiment of the invention. 
         [0089]    In this embodiment, a plate-shaped first portion  302  is separated from a plate-shaped second portion  304  and connected to the latter by metal elements  305  adapted to be deformed. Note that the metal elements  305  are produced in the form of strips and that some of these include one or more holes  306 , for example to reinforce (thanks to the braiding which forms angular points generating mechanical stresses in the metal strips) or more generally to adapt the mechanical resistance to bending of each of the strips to the requirements of the application. 
         [0090]    The first portion  302  includes connecting lands  308  and a circuit (for example a first integrated circuit) diagrammatically represented by the reference number  310 . The second portion  304  carries a second integrated circuit  311 , including, for example, in the  FIG. 8  illustration, an inductive component  312  and a magnetoresistive serpentine  314 . 
         [0091]    As can be seen in  FIG. 8 , some connection studs  308  are electrically connected to the first integrated circuit  310 , while the circuits  312  and  314  of the second integrated circuit  311  are connected to other connection studs  308 , in particular via deformable metal tracks  305 . There could equally be provision for at least some of the circuits  312  and  314  of the second integrated circuit  311  to be connected to the first integrated circuit  310  (and not to the connection studs  308 ) via the metal tracks  305 . 
         [0092]    The component is obtained by bending the device represented in  FIG. 8  about the hinge formed by the deformable metal tracks  305 , that is to say by moving (here in rotation) the second portion  304  relative to the first portion  302 . 
         [0093]    The circuits  312 ,  314  in the second portion  304  can therefore be situated there in a plane inclined (for example at an angle of 90°) to the first portion  302 , the metal tracks  305  deformed during this movement continuing to provide the electrical connections referred to above between the elements  312  and  314  of the second portion  304  and the studs and circuits  308 ,  310  of the first portion  302 . 
         [0094]      FIG. 9  represents a variant in which the deformable connecting means do not take the form of a plurality of tracks or strips (partial trellis), but instead the form of a trellis that covers a significant proportion of (or even all of) the hinge, which in some cases ensures a better mechanical connection between the first portion  402  and the second portion  404  joined by that trellis. 
         [0095]    The embodiments that have just been described merely constitute possible examples of the use of the invention.