Abstract:
The present disclosure relates to a touch sensor and touch sensitive display having a plurality of first and second conductive lines arranged substantially orthogonally with a sensing material to sense a change in capacitance between them. The first and second conductive lines and the sensing material defining an array of sensitive transistors.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure relates to touch sensors and methods for making same. More particularly, the disclosure relates to a touch sensor that utilizes semiconductor and piezoelectric materials. 
       BACKGROUND 
       [0002]    Touch sensors are a component of touch-sensitive displays that are widely used in smart phones, tablet computers and portable game machines. Existing touch sensors may be based on resistive, capacitive, acoustic or optical touch sensing technologies. Each of these technologies have limitations such as, for example, no or limited multi-touch capabilities, limited sensitivity, complicated detection algorithms or a lack of user-friendliness. 
         [0003]    There is therefore a need in the art for touch sensors that do not suffer from some of these drawbacks. The embodiments of the present invention address this need. 
       SUMMARY 
       [0004]    A touch sensor includes first conductive lines, second conductive lines, and a sensing material between the first conductive lines and the second conductive lines to sense a change in capacitance between the first conductive lines and the second conductive lines and to sense a force applied to the sensing material. 
         [0005]    A method includes forming first conductive lines, forming second conductive lines, and forming a sensing material between the first conductive lines and the second conductive lines, the sensing material to sense a force applied to the sensing material and to sense a change in capacitance between the first conductive lines and the second conductive lines. 
         [0006]    In still another embodiment, a touch-sensitive display includes a display and a touch sensor in the display, the touch sensor including first conductive lines, second conductive lines, and a sensing material between the first conductive lines and the second conductive lines, the sensing material to sense a force applied to the sensing material and to sense a change in capacitance between the first conductive lines and the second conductive lines. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1A  is an oblique view of a touch sensor according to an example embodiment. 
           [0008]      FIG. 1B  is a front view of a portion of the example touch sensor of  FIG. 1A  according to an example embodiment. 
           [0009]      FIG. 2  is an exploded view of the example touch sensor of  FIG. 1A  according to an example embodiment. 
           [0010]      FIG. 3A  is an oblique view of a touch sensor according to an example embodiment. 
           [0011]      FIG. 3B  is a front view of a portion of the example touch sensor of  FIG. 3A  according to an example embodiment. 
           [0012]      FIG. 4  is an exploded view of the example touch sensor of  FIG. 3A  according to an example embodiment. 
           [0013]      FIG. 5A  is an oblique view of a touch sensor according to an example embodiment. 
           [0014]      FIG. 5B  is a front view of a portion of the example touch sensor of  FIG. 5A  according to an example embodiment. 
           [0015]      FIG. 6  is an exploded view of a touchscreen according to an example embodiment. 
           [0016]      FIG. 7  is an oblique view of a touch sensor and a pen according to an example embodiment. 
           [0017]      FIG. 8  is a flowchart illustrating a method of forming the example touch sensor of  FIG. 1A  according to an example embodiment. 
           [0018]      FIG. 9  is a top view of an electronic device with a touch-sensitive display according to an example embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims. 
         [0020]      FIG. 1A  is an oblique view of a touch sensor indicated generally at  100  according to an example embodiment. A number of first conductive traces or lines  106  may be formed on a substrate  108  in a first direction. A piezoelectric layer  120  may be formed on the first conductive lines  106  and a semiconductor layer  130  may be formed on the piezoelectric layer  120 . A number of second conductive traces or lines  140 ,  142 ,  144  and  146  may be formed over the semiconductor layer  130  in a second direction that is substantially orthogonal to the first direction. The first conductive lines  106  and the second conductive lines  140 ,  142 ,  144  and  146  can form a grid of conductive lines when viewed from the top of the touch sensor  100 . A dielectric layer  150  may be formed over the second conductive lines  140 ,  142 ,  144  and  146  and the semiconductor layer  130 . 
         [0021]    A location of a conductor (such as a human finger) near the first conductive lines  106  or the second conductive lines  140 ,  142 ,  144  and  146  may be sensed when current is flowing through the lines  106 ,  140 ,  142 ,  144  and  146 . The conductor changes a capacitance between one of the first conductive lines  106  and one of the second conductive lines  140 ,  142 ,  144  and  146  which may be sensed by sense circuitry (not shown). The grid of the first conductive lines  106  and the second conductive lines  140 ,  142 ,  144  and  146  defines an array of sensitive transistors. 
         [0022]    The piezoelectric layer  120  can sense an applied force. When stressed by a force applied to the touch sensor  100 , the piezoelectric layer  120  generates electric charge that modulates the current flowing through the semiconductor layer  130  and the second conductive lines  140 ,  142 ,  144  and  146 . The modulated current can be sensed by the sense circuitry (not shown). 
         [0023]      FIG. 1B  is a front view of a portion of the example touch sensor  100  of  FIG. 1A  illustrating one of the transistors according to an example embodiment. The front view of  FIG. 1B  includes one of the first conductive lines  106  that is a gate of a transistor. The second conductive line  142  is a source, the second conductive line  144  is a drain, and the semiconductor layer  130  is a channel of the transistor. 
         [0024]      FIG. 2  is an exploded view of the example touch sensor  100  of FIG. 
         [0025]      1 A according to an example embodiment to illustrate the formation of the touch sensor  100 . The first conductive lines  106  may be deposited on the substrate  108  which is transparent. The substrate  108  may comprise indium tin oxide over polyethylene terephthalate (ITOPET). The first conductive lines  106  may be obtained by patterning the indium tin oxide (ITO) in the ITOPET. 
         [0026]    The piezoelectric layer  120  may be transparent and comprise AN deposited by sputtering. The semiconductor layer  130  may be transparent and comprise ZnO, InGaZnO, Al(x)In(1−x)N or thin InN deposited by sputtering. The semiconductor layer  130  may also comprise carbon nanotubes or nanowires formed by printing. The second conductive lines  140 ,  142 ,  144  and  146  may be deposited on the semiconductor layer  130  and the dielectric layer  150  may be formed over the second conductive lines  140 ,  142 ,  144  and  146  and the semiconductor layer  130 . The second conductive lines  140 ,  142 ,  144  and  146  may comprise ITO and the dielectric layer  150  may comprise silicon dioxide. 
         [0027]      FIG. 3A  is an oblique view of a touch sensor indicated generally at  300  according to an example embodiment. A number of first conductive traces or lines  306  may be formed on a substrate  308  in a first direction. A number of blocks of piezoelectric material  320  may be formed on the first conductive lines  306  and a block of semiconductor material  330  may be formed on each respective block of piezoelectric material  320 . Two electrical contacts  336  may be formed on each of the blocks of semiconductor material  330 , one at each end of each block of semiconductor material  330 . A number of second conductive traces or lines  342 ,  344  and  346  may be formed over the blocks of semiconductor material  330  in a second direction that is substantially orthogonal to the first direction. The first conductive lines  306  and the second conductive lines  342 ,  344  and  346  can form a grid of conductive lines when viewed from the top of the touch sensor  300 . A dielectric layer  350  may be formed over the second conductive lines  342 ,  344  and  346  and the blocks of semiconductor material  330 . 
         [0028]    In a manner analogous to the operation of the touch sensor  100  described above, a location of a conductor (such as a human finger) near the first conductive lines  306  or the second conductive lines  342 ,  344  and  346  may be sensed. The conductor changes a capacitance between one of the first conductive lines  306  and one of the second conductive lines  342 ,  344  and  346  which may be sensed by sense circuitry (not shown) when current is flowing through the lines  306 ,  342 ,  344  and  346 . The grid of the first conductive lines  306  and the second conductive lines  342 ,  344  and  346  can define an array of sensitive transistors in the touch sensor  300 . 
         [0029]    The blocks of piezoelectric material  320  can sense an applied force. When stressed by a force applied to the touch sensor  300 , the closest block of piezoelectric material  320  generates electric charge that modulates the current flowing through the block of semiconductor material  330  above the block of piezoelectric material  320  and the nearby pair of second conductive lines  342 ,  344  and  346 . The modulated current can be sensed by the sense circuitry (not shown). 
         [0030]      FIG. 3B  is a front view of a portion of the example touch sensor  300  of  FIG. 3A  illustrating one of the transistors according to an example embodiment. The front view of  FIG. 3B  includes one of the first conductive lines  306  that is a gate of a transistor. The second conductive line  342  is a source that is electrically coupled to the block of semiconductor material  330  through a first one of the electrical contacts  336 . The second conductive line  344  is a drain that is electrically coupled to the block of semiconductor material  330  through a second one of the electrical contacts  336 . The block of semiconductor material  330  is a channel of the transistor. The transistors in the touch sensor  300  are physically separated from each other in contrast to the transistors in the example touch sensor  100  of  FIG. 1A . 
         [0031]      FIG. 4  is an exploded view of the example touch sensor  300  of  FIG. 3A  according to an example embodiment to illustrate the formation of the touch sensor  300 . The first conductive lines  306  may be deposited on the substrate  308  which is transparent. The substrate  308  may comprise ITOPET. The first conductive lines  306  may be obtained by patterning the ITO. 
         [0032]    The blocks of piezoelectric material  320  may be transparent and comprise MN. The blocks of semiconductor material  330  may be transparent and comprise ZnO, InGaZnO, Al(x)In(1−x)N or thin InN. The blocks of piezoelectric material  320  and the blocks of semiconductor material  330  may be deposited by sputtering on selected areas of the first conductive lines  306  using a mask. The blocks of semiconductor material  330  may also comprise carbon nanotubes or nanowires formed by printing. The electrical contacts  336  are deposited on either end of each block of semiconductor material  330  using a mask. 
         [0033]    The second conductive lines  342 ,  344  and  346  may be pre-patterned on the dielectric layer  350 , and the dielectric layer  350  with the second conductive lines  342 ,  344  and  346  may be bonded to the elements described above such that the second conductive lines  342 ,  344  and  346  are in contact with the electrical contacts  336 . The dielectric layer  350  is located over the second conductive lines  342 ,  344  and  346  and the blocks of semiconductor material  330 . The second conductive lines  342 ,  344  and  346  may comprise ITO and the dielectric layer  350  may comprise silicon dioxide. 
         [0034]      FIG. 5A  is an oblique view of a touch sensor indicated generally at  500  according to an example embodiment. A number of first conductive traces or lines  506  may be formed on a substrate  508  in a first direction. A combined layer  524  that has both piezoelectric and semiconductor properties may be formed on the first conductive lines  506 . A number of second conductive traces or lines  540 ,  542 ,  544  and  546  may be formed over the combined layer  524  in a second direction that is substantially orthogonal to the first direction. The first conductive lines  506  and the second conductive lines  540 ,  542 ,  544  and  546  can form a grid of conductive lines when viewed from the top of the touch sensor  500 . A dielectric layer  550  may be formed over the second conductive lines  540 ,  542 ,  544  and  546  and the combined layer  524 . 
         [0035]    A location of a conductor (such as a human finger) near the first conductive lines  506  or the second conductive lines  540 ,  542 ,  544  and  546  may be sensed when current is flowing through the lines  506 ,  540 ,  542 ,  544  and  546 . The conductor changes a capacitance between one of the first conductive lines  506  and one of the second conductive lines  540 ,  542 ,  544  and  546  which may be sensed by sense circuitry (not shown). The grid of the first conductive lines  506  and the second conductive lines  540 ,  542 ,  544  and  546  defines an array of sensitive transistors. 
         [0036]    The combined layer  524  can sense an applied force. When stressed by a force applied to the touch sensor  500 , the combined layer  524  generates electric charge that modulates the current flowing through the first conductive lines  506  and the second conductive lines  540 ,  542 ,  544  and  546 . The modulated current can be sensed by the sense circuitry (not shown). 
         [0037]      FIG. 5B  is a front view of a portion of the example touch sensor  500  of  FIG. 5A  illustrating one of the transistors according to an example embodiment. The front view of  FIG. 5B  includes one of the first conductive lines  506  that is a gate of a transistor. The second conductive line  542  is a source, the second conductive line  544  is a drain, and the combined layer  524  is a channel of the transistor. 
         [0038]    The touch sensor  500  may be formed in a manner analogous to the formation of the touch sensor  100  described above with reference to  FIG. 2 . Instead of forming the piezoelectric layer  120  and the semiconductor layer  130 , the combined layer  524  may be formed. The combined layer  524  may be transparent and may comprise ZnO, GaN, InN or AlInN that may be deposited by sputtering. The substrate  508  may comprise ITOPET. The first conductive lines  506  and the second conductive lines  540 ,  542 ,  544  and  546  may comprise ITO. The dielectric layer  150  may comprise silicon dioxide. 
         [0039]      FIG. 6  is an exploded view of a touch-sensitive display indicated generally at  600  according to an example embodiment. A touch sensor  602  is located on a display  610 . The touch sensor  602  may be any one of the touch sensors  100 ,  300  or  500  shown in the figures and described above. The display  610  may be a liquid-crystal display (LCD) or an organic light-emitting diode (OLED) display according to an example embodiment. 
         [0040]      FIG. 7  is an oblique view of a touch sensor  710  and a pen indicated generally at  720  according to an example embodiment. The touch sensor  710  may be any one of the touch sensors  100 ,  300  or  500  shown in the figures and described above that can detect two different control actions. The pen  720  may comprise a writing portion  730  and an erasing portion  740 . The writing portion  730  is electrically conductive and may be detected by capacitive sensing in the touch sensor  710 . The writing portion  730  may be used to write on a touch screen including the touch sensor  710 . The erasing portion  740  is an electrical insulator that may not be detected by capacitive sensing. The erasing portion  740  may be sharper and more rigid than the writing portion  730  and an application of the erasing portion  740  with force to the touch sensor  710  may be detected by piezoelectric sensing in the touch sensor  710 . The writing portion  730  may be used for writing, and the erasing portion  740  may be used for erasing. Alternatively, the writing portion  730  is an electrical insulator that may be used to write via the piezoelectric sensing and the erasing portion  740  is electrically conductive and may be used to erase via the capacitive sensing. Sense circuitry may distinguish between different levels of force applied to the touch sensor  710  by the pen  720  and trigger different functions in response. Alternatively, the pen  720  may be an electrical insulator that may be used to write via the piezoelectric sensing while an erase may be performed by a human finger or hand via the capacitive sensing. 
         [0041]      FIG. 8  is a flowchart illustrating a method  800  of forming the example touch sensor  100  of  FIG. 1A  according to an example embodiment. The method starts at  810 , and at  820  first conductive lines may be formed on a substrate in a first direction. The first conductive lines may be may be formed by patterning ITO. At  830 , a piezoelectric layer may be formed on the first conductive lines. The piezoelectric layer may comprise MN deposited by sputtering. At  840 , a semiconductor layer may be formed on the piezoelectric layer. The semiconductor layer may comprise ZnO, InGaZnO, Al(x)In(1−x)N or thin InN and may be deposited by sputtering. At  850 , second conductive lines may be formed on the semiconductor layer in a second direction that is substantially orthogonal to the first direction. The second conductive lines may comprise ITO deposited on the semiconductor layer. A dielectric layer may be formed over the second conductive lines and the semiconductor layer. The dielectric layer may comprise silicon dioxide. The method ends at  860 . 
         [0042]      FIG. 9  is a top view of an electronic device  900  with a touch-sensitive display  910  according to an example embodiment. The touch-sensitive display  910  may include any one of the touch sensors  100 ,  300  or  500  shown in the figures and described above. The touch-sensitive display  910  may display information including, but not limited to, text, images and videos. A hand  920  or a finger on the hand  920  may be sensed by the touch-sensitive display  910  near an image  930 . The electronic device  900  may be a smartphone or a tablet computer. 
         [0043]    Embodiments of the invention described and claimed herein are not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended as illustration of several aspects of the disclosure. 
         [0044]    Any equivalent embodiments are intended to be within the scope of this disclosure. Indeed, various modifications of the embodiments of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. 
         [0045]    All publications, including non-patent literature (e.g., scientific journal articles), patent application publications, and patents mentioned in this specification are incorporated by reference as if each were specifically and individually indicated to be incorporated by reference.