Abstract:
This present invention provides a novel sensing chip package and a manufacturing method thereof, and in particular provides a proximity sensing chip package and a manufacturing thereof, which is characterized by forming a light blocking layer surrounding the light emitting device of the sensor to block the lateral light emitted by the light emitting device to reduce the interference of the lateral light and enhance the sensitivity of the light sensing device.

Description:
[0001]    This application claims the benefit of U.S. provisional application No. 62/204,175, filed on Aug. 12, 2015, and the entirety of which is incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Field of the Invention 
         [0003]    The present invention relates to a sensing chip package and in particular relates to a proximity sensing chip package and a manufacturing method thereof. 
         [0004]    Description of the Related Art 
         [0005]    With the developments of technology, portable devices like PDA, smart phone or MP4 become more and more popular. Most of the portable devices are equipped with touch screens with proximity sensors to detect objects or obstacles in the front by an optical sensing way. The proximity sensor can be applied in smart phone or handset phone to judge if the user is close to telephone transmitter or the microphone, or be applied in a house-keeping robot to judge if there is any furniture or people in front of it. 
         [0006]      FIG. 1A  is a top view of a conventional proximity sensing chip package, and  FIG. 1B  is a cross-sectional view of a conventional proximity sensing chip package. As illustrated in  FIG. 1A , the proximity sensing chip package  1000  comprises a proximity sensor  100  having a first top surface  100   a  and a first bottom surface  100   b  opposite to each other, wherein a light emitting device  120  and a light sensing device  110  are formed the first top surface. Besides, as illustrated in  FIG. 1B , the first top surface  100   a  of the proximity sensor  100  is capped by a cap layer  130  having a first cavity  140  corresponding to the light emitting device  120  and a second cavity  150  corresponding to the light sensing device  110 . Owing to the demand of size shrinkage of the device, a point light source such as LED and in particular an IR LED is usually used as the light emitting device  120 . However, the emitting path of the point light source is non-directional, so the light angle of the point light source is usually greater than 180 degrees. In additional, the cap layer  130  is usually consisted of a material with a hardness greater than 8, such as glass, sapphire or silicon nitride, and these materials can&#39;t block the transmission of visible light. Therefore, the light sensing device  110  adjacent to the light emitting device  120  will be interfered by the lateral light emitted by the light emitting device  120  as the dashed arrows shown in the  FIGS. 1A ˜ 1 B. Consequently, the sensitivity of the proximity sensing chip package  1000  is reduced. 
         [0007]    In order to resolve above-mentioned problems, this invention provides a novel sensing chip package and a manufacturing method thereof, and in particular provides a proximity sensing chip package and a manufacturing thereof, which is characterized by forming a light blocking layer surrounding the light emitting device of the sensor to block the lateral light emitted by the light emitting device to reduce the interference of the lateral light and enhance the sensitivity of the light sensing device. 
       SUMMARY OF THE INVENTION 
       [0008]    A feature of this invention provides a sensing chip package, comprising: a sensor, having a first top surface and a first bottom surface opposite to each other, comprising a light emitting device and a light sensing device are depicted adjacent to the first top surface and spaced with a pre-determined distance, and a first conductive pad adjacent to the light emitting device and a second conductive pad adjacent to the light sensing device, whereby the light sensing device having a second top surface and a second bottom opposite to each other; and a light blocking layer formed on the first top surface of the sensor and surrounded the light emitting device, comprising a cap layer having a third top surface and a third bottom surface opposite to each other formed on the first top surface of the sensor, and the cap layer having a trench with an inner wall and a bottom wall not higher than the second bottom surface of the light sensing device; a adhesive layer sandwiched between the cap layer and the first top surface of the sensor to bound the cap layer to the first top surface of the sensor; and a light blocking material layer overlaid the inner wall of the trench or gap-filled in the trench. 
         [0009]    Another of this invention provides a sensing chip package as mentioned above, wherein the sensor is a proximity sensor. 
         [0010]    Another of this invention provides a sensing chip package as mentioned above, wherein the light blocking material layer is a black resistant which can absorb light. 
         [0011]    Another of this invention provides a sensing chip package as mentioned above, wherein the light blocking material layer is a metal with a high reflection coefficient or a distributed Bragg reflector. 
         [0012]    Another of this invention provides a sensing chip package as mentioned above, wherein the light emitting device is a LED. 
         [0013]    Another of this invention provides a sensing chip package as mentioned above, wherein the LED is a surface mounted LED selected from mesa-type LED, vertical-type LED and flip-chip LED mounted on the first top surface of the sensor by surface mounting technology. 
         [0014]    Another of this invention provides a sensing chip package as mentioned above, wherein the LED is a non-surface mounted LED buried in the wafer and adjacent to the first top surface. 
         [0015]    Another of this invention provides a sensing chip package as mentioned above, wherein the LED is an IR LED. 
         [0016]    Another of this invention provides a sensing chip package as mentioned above, wherein the light sensing device is an IR sensor. 
         [0017]    Another of this invention provides a sensing chip package as mentioned above, further comprising a first solder wire connecting to the first conductive pad and a second solder wire connecting to the second conductive pad. 
         [0018]    Another of this invention provides a sensing chip package as mentioned above, further comprising: an insulating layer formed on the first bottom surface of the sensor, having a first through hole exposing the first conductive pad and a second through hole exposing the second conductive pad; a re-distribution layer formed on the insulating layer and interconnected the first conductive pad and the second conductive pad via the first through hole and the second through hole respectively; a passivation layer overlaid the re-distribution layer, the first through hole, the second through hole, wherein the passivation layer has a first opening and a second opening exposing the re-distribution layer; and a first conductive structure formed in the first opening and a second conductive structure formed in the second opening and respectively interconnected to the re-distribution layer. 
         [0019]    Another of this invention provides a sensing chip package as mentioned above, wherein the first structure and the second structure comprise solder ball, solder bumps and conductive pillars. 
         [0020]    Another of this invention provides a sensing chip package as mentioned above, further comprising: an insulating layer formed on the first bottom surface of the sensor, having a first notch exposing an edge of the first conductive pad and a second notch exposing an edge of the second conductive pad, and part of the third bottom surface of the cap layer; a re-distribution layer formed on the insulating layer, the first notch and the second notch to interconnect the exposed edges of the first and the second conductive pads respectively; a passivation layer overlaid the re-distribution layer, the first notch and the second notch, wherein the passivation layer has a third opening and a fourth opening exposing the re-distribution layer; and a third conductive structure formed in the third opening and a fourth conductive structure formed in the fourth opening and respectively interconnected to the re-distribution layer. 
         [0021]    Another of this invention provides a sensing chip package as mentioned above, wherein the third structure and the fourth structure comprise solder ball, solder bumps and conductive pillars. 
         [0022]    Another feature of this invention provides a method of manufacturing a sensing chip package, comprising the steps of: providing a wafer having a plurality of sensing areas, each sensing area comprising a sensor having a first top surface and a first bottom surface opposite to each other comprising a light emitting device and a light sensing device are depicted adjacent to the first top surface and spaced with a pre-determined distance, and a first conductive pad adjacent to the light emitting device and a second conductive pad adjacent to the light sensing device, whereby the light sensing device having a second top surface and a second bottom opposite to each other; providing a cap layer having a third top surface and a third bottom surface opposite to each other, and the third bottom surface corresponding to each of the sensing areas including a first cavity corresponding to the light emitting device and a second cavity corresponding to the light sensing device; bonding the third bottom surface of the cap layer to the first top surface of the wafer by sandwiched an adhesive layer therebetween; forming a trench passing through the cap layer, the adhesive layer and part of the first top surface of the wafer and surrounding the light emitting device, wherein the trench has an inner wall and a bottom wall not higher than the light sensing device; formed on the first top surface of the sensor, and the cap layer having a trench with an inner wall and a bottom wall not higher than the second bottom surface of the light sensing device; forming a light blocking material layer to overlay the inner wall of the trench or gap-fill into the trench; removing the third top surface of the cap layer and the light blocking layer above the first cavity and the second cavity to form a light blocking layer surrounding the light emitting device. 
         [0023]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the sensor is a proximity sensor. 
         [0024]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the light blocking material layer is a black resistant which can absorb light. 
         [0025]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the light blocking material layer is a metal with a high reflection coefficient or a distributed Bragg reflector. 
         [0026]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the light emitting device is a LED. 
         [0027]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the LED is a surface mounted LED selected from mesa-type LED, vertical-type LED and flip-chip LED mounted on the first top surface of the sensor by surface mounting technology. 
         [0028]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the LED is a non-surface mounted LED buried in the wafer and adjacent to the first top surface. 
         [0029]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the LED is an IR LED. 
         [0030]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the light sensing device is an IR sensor. 
         [0031]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, further comprising a first solder wire connecting to the first conductive pad and a second solder wire connecting to the second conductive pad. 
         [0032]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, further comprising a step of scribing the sensing areas to generate a plurality of sensing chip packages. 
         [0033]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, further comprising the steps of: thinning the first bottom surface of the wafer; forming an insulating layer on the first bottom surface of the wafer, and the insulating having a first through hole exposing the first conductive pad and a second through hole exposing the second conductive pad; forming a re-distribution layer on the insulating layer to interconnect the first conductive pad and the second conductive pad via the first through hole and second through hole respectively; forming a passivation layer to overlay the re-distribution layer, the first through hole and the second through hole, and the passivation having a first opening and a second opening; and forming a first conductive structure in the first opening and a second conductive structure in the second opening to interconnect the re-distribution layer respectively. 
         [0034]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the first structure and the second structure comprise solder ball, solder bumps and conductive pillars. 
         [0035]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, further comprising a step of scribing the sensing areas to generate a plurality of sensing chip packages. 
         [0036]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, further comprising the steps of: thinning the first bottom surface of the wafer; forming a third cavity exposing the first conductive pad and a fourth cavity exposing the second conductive pad on the first bottom surface of the wafer; forming an insulating layer on the first bottom surface of the wafer and overlaying the third cavity and the fourth cavity; removing the insulating in the third and the fourth cavities and part of the first and the second conductive pads, part of the adhesive layer and part of the cap layer above the third and the fourth cavities by notching to respectively form a first notch exposing an edge of the first conductive pad and a second notch exposing an edge of the second conductive pad; forming a re-distribution layer on the insulating layer, the first notch and the second notch to interconnect the exposed edges of the first and the second conductive pads respectively; forming a passivation layer to overlay the re-distribution layer, the first notch and the second notch, and the passivation having a third opening and a fourth opening; and forming a third conductive structure in the third opening and a fourth conductive structure in the fourth opening to interconnect the re-distribution layer respectively. 
         [0037]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, wherein the third structure and the fourth structure comprise solder ball, solder bumps and conductive pillars. 
         [0038]    Another feature of this invention provides a method of manufacturing a sensing chip package as mentioned above, further comprising a steps of scribing the sensing areas to generate a plurality of sensing chip packages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]      FIG. 1A  is a top view of a conventional proximity sensing chip package. 
           [0040]      FIG. 1B  is a cross-sectional view of a conventional proximity sensing chip package as illustrated in  FIG. 1A . 
           [0041]      FIGS. 2A ˜ 2 E are cross-sectional views of a method of manufacturing a proximity sensing chip package according to the exemplary embodiment 1 of this present invention. 
           [0042]      FIG. 3  is a top view of a proximity sensing chip package as illustrated in  FIG. 2E . 
           [0043]      FIG. 4  is a cross-sectional view of a proximity sensing chip package according to the exemplary embodiment 2 of this present invention. 
           [0044]      FIG. 5  is a cross-sectional view of a proximity sensing chip package according to the exemplary embodiment 3 of this present invention. 
           [0045]      FIG. 6  is a cross-sectional view of a proximity sensing chip package according to the exemplary embodiment 4 of this present invention. 
           [0046]      FIG. 7  is a cross-sectional view of a proximity sensing chip package according to the exemplary embodiment 5 of this present invention. 
           [0047]      FIG. 8  is a cross-sectional view of a proximity sensing chip package according to the exemplary embodiment 6 of this present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0048]    The making and using of the embodiments of the present disclosure are discussed in detail below. However, it should be noted that the embodiments provide many applicable inventive concepts that can be embodied in a variety of specific methods. The specific exemplary embodiments discussed are merely illustrative of specific methods to make and use the embodiments, and do not limit the scope of the disclosure. 
       Exemplary Embodiment 1 
       [0049]    A detailed description of the proximity sensing chip package  2000  and a method of manufacturing the same according to embodiment 1 of this invention is given below with reference to the accompany  FIGS. 2A ˜ 2 E. 
         [0050]    First, please refer to  FIG. 2A . A wafer  200  having a plurality of sensing areas  205  is provided, wherein each sensing area  205  having a first top surface  200   a  and a first bottom surface  200   b  opposite to each other comprises a light emitting device  220  and a light sensing device  210  having a second top surface  210   a  and a second bottom surface  210   b  opposite to each other depicted adjacent to the first top surface  200   a  and spaced with a pre-determined distance, and each sensing area  205  further comprises a first conductive pad  225   a  adjacent to the light emitting device  220  and a second conductive pad  225   b  adjacent to the light sensing device  210 . Next, a cap layer having a third top surface  230   a  and a third bottom surface  230   b  opposite to each other is provided, wherein the third bottom surface  230   b  includes a first cavity  240  corresponding to the light emitting device  210   b  and a second cavity  250  corresponding to the light sensing device  210   a.  Then, the third bottom surface  230   b  of the cap layer  230  is bounded to the first top surface  200   a  by sandwiched an adhesive layer  260  therebetween. 
         [0051]    The light emitting device  220  can be a light emitting diode (LED), such as a surface mounted LED including mesa-type LED, vertical-type LED or flip-chip LED mounted on the first top surface  200   a  of the sensing chip area  205 , or a non-surface mounted LED buried in the wafer  200  adjacent to the first top surface  200   a  of the sensing chip area  205 . The light emitting device  220  of this embodiment is an IR LED, and the light sensing device  210  of this embodiment is an IR sensor. 
         [0052]    Next, please refers to  FIG. 2B . A trench  265  surrounding the light emitting device  220  is formed on the third top surface  230   a  of the cap layer  230  by the photolithography and etching. The trench  265  passes through the cap layer  230 , the adhesive layer and part of the first top surface  200   a  of the wafer  200 , and the trench  265  has an inner wall  265   a  and a bottom  265   b  not higher than the second bottom surface  210   b  of the light sensing device  210 . 
         [0053]    Next, please refers to  FIG. 2C , a light blocking material layer  270  is formed to overlay the third top surface  230   a,  and the inner wall  265   a  and the bottom wall  265   b  of the trench  265 . The light blocking material layer  270  of other embodiments according to this invention can also be gap-filled into the trench  265 . The light blocking material layer  270  is a black resistant which can absorb light, or a metal with a high reflection coefficient such as silver or aluminum or a distributed Bragg reflector. 
         [0054]    Next, please refer to  FIG. 2D , the third top surface  230   a  of the cap layer  230  and the light blocking material layer  270  above the first cavity  240  and the second cavity  250  is removed by polishing to make the first cavity  240  and the second cavity  250  pass through the cap layer  230  and form a light blocking layer  275  surrounding the light emitting device  220 . 
         [0055]    Next, please refer to  FIG. 2E , part of the adhesive layer  260  and cap layer  230  above the first conductive pad  225   a  and the second conductive pad  225   b  is removed to expose the first conductive pad  225   a  and the second conductive pad  225   b.  Then, each sensing area  205  of the wafer is scribed to form a plurality of sensors  200 ′. Finally, a first solder wire  278   a  and a second solder wire  278   b  are wired bounded to the first conductive pad  225   a  and the second conductive pad  225   b  of each sensor  200 ′ respectively to form a proximity sensing chip package  2000 . 
         [0056]    As the top view of the proximity sensing chip package  2000  illustrated in  FIG. 3 , the light emitting device  220  is surrounded by the blocking layer  275 , so the lateral light emitted by the light emitting device  220  will not reach the sensing device  210 . The light sensing device  210  will not be interfered by the later light emitted by the light emitting device  220 . Accordingly, the proximity sensing chip package  2000  according to the embodiment 1 of this invention is more sensitive than the conventional proximity sensing device  1000  illustrated in  FIGS. 1A ˜ 1 B. 
       Exemplary Embodiment 2 
       [0057]    A detailed description of the proximity sensing chip package  3000  and a method of manufacturing the same according to embodiment 2 of this invention is given below with reference to the accompany  FIG. 4 . 
         [0058]    The feature of this embodiment 2 is to treat the first bottom surface  200   b  of the wafer  200  of the structure as illustrated in  FIG. 2D  of the embodiment 1 by a so-called through silicon via process. The first bottom surface  200   b  of the wafer  200  is thinned first, then an insulating layer  280  is formed on the first bottom surface  200   b  of the wafer  200 . The insulating layer  280  has a first through hole (not shown) exposing the first conductive pad  225   a  and a second through hole (not shown) exposing the second conductive pad  225   b.  Next, a re-distribution layer  285  is formed on the insulating layer  280  to interconnect the first conductive pad  225   a  and the second conductive pad  225   b  via the first through hole (not shown) and second through hole (not shown) respectively. Next, a passivation layer  290  having a first opening (not shown) and a second opening (not shown) is formed to overlay the re-distribution layer  285  and the first through hole (not shown) and the second through hole (not shown), then a first conductive structure  295   a  and a second conductive structure  295   b  are formed in the first opening (not shown) and the second opening (not shown) to interconnect the re-distribution layer  285  respectively. 
         [0059]    Finally, each sensing area  205  of the wafer  200  is scribed to form a plurality of sensing chip package  3000  as illustrated in  FIG. 4 , wherein each sensing chip package  3000  has a sensor  200 ′ with TSV structures on its first bottom surface  200   a  comprising a light emitting device  220 , a light sensing device  210 , a first conductive pad  225   a,  a second conductive pad  225   b  and a light blocking layer  275  surrounding the light emitting device  220 . 
         [0060]    Similarly, the light sensing device  210  will not be interfered by the later light emitted by the light emitting device  220 . Accordingly, the proximity sensing chip package  3000  according to the embodiment 2 of this invention is more sensitive than the conventional proximity sensing device  1000  illustrated in  FIGS. 1A ˜ 1 B. 
       Exemplary Embodiment 3 
       [0061]    A detailed description of the proximity sensing chip package  4000  and a method of manufacturing the same according to embodiment 3 of this invention is given below with reference to the accompany  FIG. 5 . 
         [0062]    The feature of this embodiment 3 is to treat the first bottom surface  200   b  of the wafer  200  of the structure as illustrated in  FIG. 2D  of the embodiment 1 by a so-called T-contact process. The first bottom surface  200   b  of the wafer  200  is thinned to form a third cavity (not shown) and a fourth cavity (not shown) passing the first bottom surface  200   b  and exposing the first conductive pad  225   a  and the second conductive pad  225   b  respectively. Next, an insulating layer  280  is formed on the first bottom surface  200   b  of the wafer  200 . The insulating layer  280  is formed on the first bottom surface  200   b  of the wafer  200  and overlaid the third cavity (not shown) and the fourth cavity (not shown). Next, the insulating layer  280  in the third and the fourth cavities (not shown) and part of the first and the second conductive pads  225   a,    225   b,  part of the adhesive layer  260  and part of the cap layer  230  above the third and the fourth cavities (not shown) are removed by notching to respectively form a first notch  283   a  exposing an edge of the first conductive pad  225   a  and a second notch  283   b  exposing an edge of the second conductive pad  225   b.  Next, a re-distribution layer  285  is formed on the insulating layer  280  and overlaid the side-walls of the first notch  283   a  and the second notch  283   b  to interconnect the exposed edges of the first and the second conductive pads  225   a,    225   b  respectively. Next, a passivation layer  290  having a third opening (not shown) and a fourth opening (not shown) is formed to overlay the re-distribution layer  285  and the first notch  283   a  and the second notch  283   b.  Next, a third conductive structure  295   a  is formed in the third opening (not shown) and a fourth conductive structure  295   b  in the fourth opening (not shown) to interconnect the re-distribution layer  285  respectively. 
         [0063]    Finally, each sensing area  205  of the wafer  200  is scribed to form a plurality of sensing chip package  4000  as illustrated in  FIG. 5 , wherein each sensing chip package  4000  has a sensor  200 ′ with T-contact structures on its first bottom surface  200   a  comprising a light emitting device  220 , a light sensing device  210 , a first conductive pad  225   a,  a second conductive pad  225   b  and a light blocking layer surrounding the light emitting device  220 . 
         [0064]    Similarly, the light sensing device  210  will not be interfered by the later light emitted by the light emitting device  220 . Accordingly, the proximity sensing chip package  3000  according to the embodiment 2 of this invention is more sensitive than the conventional proximity sensing device  1000  illustrated in  FIGS. 1A ˜ 1 B. 
       Exemplary Embodiment 4 
       [0065]    A detailed description of the proximity sensing chip package  5000  and a method of manufacturing the same according to embodiment 4 of this invention is given below with reference to the accompany  FIG. 6 . 
         [0066]    As illustrated in  FIG. 6 , the proximity sensing chip package  5000  of the embodiment 4 according to this invention is manufactured by similar processes as that described in embodiment 1. The only one difference is that the light emitting device  220 ′ of the sensing device  200 ′ is replaced with a non-surface mounted LED which can be directly formed within the sensor  200 ′ by LED processes or finished by burying a LED chip in the sensing device  200 ′. 
         [0067]    Similarly, the light sensing device  210  will not be interfered by the later light emitted by the light emitting device  220 . Accordingly, the proximity sensing chip package  5000  according to the embodiment 4 of this invention is more sensitive than the conventional proximity sensing device  1000  illustrated in  FIGS. 1A ˜ 1 B. 
       Exemplary Embodiment 5 
       [0068]    A detailed description of the proximity sensing chip package  6000  and a method of manufacturing the same according to embodiment 5 of this invention is given below with reference to the accompany  FIG. 7 . 
         [0069]    As illustrated in  FIG. 7 , the proximity sensing chip package  6000  of the embodiment 5 according to this invention is manufactured by similar processes as that described in embodiment 2. The only one difference is that the light emitting device  220 ′ of the sensor  200 ′ is replaced with a non-surface mounted LED which can be directly formed within the sensing device  200 ′ by LED processes or finished by burying a LED chip in the sensing device  200 ′. 
         [0070]    Similarly, the light sensing device  210  will not be interfered by the later light emitted by the light emitting device  220 . Accordingly, the proximity sensing chip package  6000  according to the embodiment 5 of this invention is more sensitive than the conventional proximity sensing device  1000  illustrated in FIGS.  1 A˜ 1 B. 
       Exemplary Embodiment 6 
       [0071]    A detailed description of the proximity sensing chip package  6000  and a method of manufacturing the same according to embodiment 6 of this invention is given below with reference to the accompany  FIG. 8 . 
         [0072]    As illustrated in  FIG. 8 , the proximity sensing chip package  6000  of the embodiment 6 according to this invention is manufactured by similar processes as that described in embodiment 3. The only one difference is that the light emitting device  220 ′ of the sensor  200 ′ is replaced with a non-surface mounted LED which can be directly formed within the sensing device  200 ′ by LED processes or finished by burying a LED chip in the sensing device  200 ′. 
         [0073]    Similarly, the light sensing device  210  will not be interfered by the later light emitted by the light emitting device  220 . Accordingly, the proximity sensing chip package  5000  according to the embodiment 4 of this invention is more sensitive than the conventional proximity sensing device  1000  illustrated in  FIGS. 1A ˜ 1 B. 
         [0074]    While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.