Abstract:
An optical detection sensor functions as a proximity detection sensor that includes an optical system and a selectively transmissive structure. Electromagnetic radiation such as laser light can be emitted through a transmissive portion of the selectively transmissive structure. A reflected beam can be detected to determine the presence of an object. The sensor is formed by encapsulating the transmissive structure in a first encapsulant body and encapsulating the optical system in a second encapsulant body. The first and second encapsulant bodies are then joined together. In a wafer scale assembling the structure resulting from the joined encapsulant bodies is diced to form optical detection sensors.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of United States Application for U.S. patent application Ser. No. 13/670,766 filed Nov. 7, 2012, which claims priority to U.S. Provisional Application No. 61/559,532, filed Nov. 14, 2011, the disclosure of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The techniques described herein relate to an optical detection sensor, a wafer level package and a technique for forming the same. 
         [0004]    2. Discussion of the Related Art 
         [0005]    A proximity detector is an optical detection sensor that is capable of detecting the presence of a nearby object. An optical detection sensor may emit a beam of electromagnetic radiation (e.g., infrared radiation) and detect a reflected beam from a target object. 
       SUMMARY 
       [0006]    Some embodiments relate to an optical detection apparatus. The optical detection apparatus includes a device configured to emit electromagnetic radiation, a structure including a first region of transmissive material to allow a first portion of the electromagnetic radiation to pass through the first region to an exterior of the optical detection apparatus. The structure is configured to reflect a second portion of the electromagnetic radiation. The optical detection apparatus also includes a sensor configured to detect the second portion of the electromagnetic radiation. 
         [0007]    Some embodiments relate to a method of forming at least a selectively transmissive structure. The method includes forming a first region of transmissive material, forming a second region of transmissive material. The second region of transmissive material having a shape different from that of the first region of transmissive material. The method also includes contacting the first and second regions of transmissive material to an adhesive, and encapsulating the first and second regions of transmissive material. 
         [0008]    Some embodiments relate to a method of forming at least an optical system. The method includes contacting a device for emitting electromagnetic radiation and a sensor chip to an adhesive material, the sensor chip having a plurality of optical sensors, and encapsulating the device for emitting electromagnetic radiation and the sensor chip. 
         [0009]    In an embodiment, a method comprises: forming a transmissive structure, comprising: placing a first region of transmissive material and a second region of transmissive material on a first support; and encapsulating the first and second regions of transmissive material with an encapsulant to form a first encapsulating body for said transmissive structure; forming an optical system, comprising: placing an electromagnetic emitter circuit and an electromagnetic sensor circuit on a second support; and encapsulating the electromagnetic emitter circuit and electromagnetic sensor circuit with an encapsulant to form a second encapsulating body for said optical system; and joining the first encapsulating body to the second encapsulating body such that said first region of transmissive material is aligned with the electromagnetic emitter circuit and said second region of transmissive material is aligned with said electromagnetic sensor circuit. 
         [0010]    In an embodiment, a method comprises: forming a first encapsulating body including a plurality of transmissive structures, comprising: placing for each transmissive structure a first region of transmissive material and a second region of transmissive material on a first support; and encapsulating the first and second regions of transmissive material for each of the plurality of transmissive structures with an encapsulant to form said first encapsulating body; forming a second encapsulating body including a plurality of optical systems, comprising: placing for each optical system an electromagnetic emitter circuit and an electromagnetic sensor circuit on a second support; and encapsulating the electromagnetic emitter circuit and electromagnetic sensor circuit for each of the optical systems with an encapsulant to form said second encapsulating body; joining the first encapsulating body to the second encapsulating body such that each first region of transmissive material is aligned one of the electromagnetic emitter circuits and each second region of transmissive material is aligned with one of the electromagnetic sensor circuits to produce a combined structure; and dicing the combined structure to form a plurality of optical detection sensors, wherein each optical detection sensor includes one transmissive structure and one optical system. 
         [0011]    The foregoing summary is provided by way of illustration and is not intended to be limiting. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]    In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like reference character. For purposes of clarity, not every component may be labeled in every drawing. The drawings are not necessarily drawn to scale, with emphasis instead being placed on illustrating various aspects of at least one embodiment. 
           [0013]      FIGS. 1A and 1B  show cross sections of optical detection sensors, according to some embodiments. 
           [0014]      FIG. 2  shows a bottom view of an optical detection sensor. 
           [0015]      FIG. 3  schematically shows a top view of an optical system of the optical detection sensor. 
           [0016]      FIG. 4  shows an example of a glass panel from which transmissive glass regions may be formed. 
           [0017]      FIG. 5  shows a cross section of the glass panel having trenches formed therein. 
           [0018]      FIGS. 6 a -6 d    show a process of forming a selectively transmissive structure, according to some embodiments. 
           [0019]      FIGS. 7 a -7 e   - 2  show a process of forming an optical system of an optical detection sensor, according to some embodiments. The optical system may be formed on the wafer level, e.g., with a 200 mm or 300 mm wafer size. 
           [0020]      FIGS. 8 a -8 b    show a step of applying a bonding material to the optical system, according to some embodiments. 
           [0021]      FIG. 9  shows a step of bonding the optical system to the selectively transmissive structure, according to some embodiments. 
           [0022]      FIG. 10  shows a step of forming solder ball(s) on metal plugs on the bottom of the optical detection sensor, according to some embodiments. 
           [0023]      FIG. 11  shows a step of separating a plurality of optical detection sensors formed in the same structure, according to some embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Described herein is an optical detection sensor and method of forming the same. 
         [0025]      FIG. 1A  shows a cross-section of an optical detection sensor  1  that may include an optical system  100  bonded to a selectively transmissive structure  300  using a bonding material  200 , according to some embodiments. 
         [0026]    As shown in  FIG. 1A , the optical system  100  may include a device  101  configured to emit an electromagnetic signal and a detection sensor chip  102  that includes a first sensor  311  for detecting an electromagnetic signal and a second sensor  312  for detecting an electromagnetic signal. Sensor chip  102  may include electronics such as amplification circuitry and/or circuitry for determining whether an object has been detected. Device  101  may include a laser or other device for emitting electromagnetic radiation. The optical system  100  may also include one or more metal plugs  103 , a metal interconnect  107  contacting the metal plug(s)  103 , and a passivation layer  108 . The metal plugs  103  and metal interconnect  107  may be electrically coupled to the sensor chip  102 . At least a portion of the optical system  100  may be embedded in an encapsulant material  104 , which may be a polymer material such as epoxy. 
         [0027]    The selectively transmissive structure  300  may include regions  301 ,  302  of transmissive material embedded in an encapsulant material  303 , which may be a polymer material such as epoxy. In some embodiments, encapsulant material  303  may be formed of the same material as that of encapsulant material  104 . Regions  301  and  302  of transmissive material may be formed of glass, or any other suitable transmissive material. For example, regions  301  and  302  may be formed of a material capable of allowing electromagnetic radiation having a wavelength of the electromagnetic radiation emitted by device  101  to pass therethrough. The encapsulant material  303  may be opaque to electromagnetic radiation having the wavelength of the electromagnetic radiation emitted by device  101 . Thus, regions  301  and  302  may operate as windows enabling electromagnetic radiation to selectively pass through structure  300 . In some embodiments, selectively transmissive structure  300  and optical device  100  may be formed on a 200 mm or 300 mm diameter wafer with multiple devices according to the same pattern. 
         [0028]    A bonding material  200  may be disposed between the optical system  100  and the selectively transmissive structure  300  to bond the optical system  100  to the selectively transmissive structure  300 . Any suitable bonding material  200  may be used, such as a double sided glue, for example. In addition, an opaque region  202  may be disposed between the optical system  100  and structure  300  in a region between the sensors  311  and  312 . Opaque region  202  may prevent the direct passage of light between the device  101  and cavity  201 , thereby preventing direct passage of light from device  101  to sensor  312 . 
         [0029]    In operation, optical detection sensor  1  may detect a nearby object by transmitting, through transmissive region  302 , the electromagnetic radiation produced by device  101 . If a nearby object is present, the transmitted electromagnetic radiation may be reflected by the object and then pass back into the interior of the optical detection sensor  1  through transmissive region  301 . The reflected electromagnetic radiation passing through transmissive region  301  may then be detected by sensor  312 . The optical detection sensor  1  may determine that a nearby object is present based upon the reflected signal detected by sensor  312 . 
         [0030]    A portion of the electromagnetic radiation generated by device  101  may be detected by sensor  311 . By detecting the electromagnetic radiation generated by device  101 , the optical detection sensor may determine whether device  101  is functioning properly. 
         [0031]    In some embodiments, optical detection sensor  1  may include a reflective region that reflects a portion of the electromagnetic radiation generated by device  101  to sensor  311 . For example, as shown in  FIG. 1A , transmissive region  302  may be formed in a shape that enables a portion of the electromagnetic radiation generated by device  101  to be transmitted therethrough, and a portion of the electromagnetic radiation to be reflected to sensor  311 .  FIG. 1A  shows in example in which the transmissive region  302  has L-shape. In this example, the right side of the transmissive region  302  extends only partially through the encapsulant  303 . Electromagnetic radiation incident upon the right side of transmissive region  302  is reflected by the uppermost edge of the transmissive region  302 , causing a portion of the electromagnetic radiation produced by device  101  to be detected by sensor  311 . 
         [0032]    Transmissive region  302  may have an L-shape or any other suitable shape. For example, transmissive region  302  may have a shape suitable for reflecting a portion of the electromagnetic radiation incident theron while transmitting a portion of the electromagnetic radiation therethrough. The transmissive region  302  may include a reflective portion different from the uppermost and lowermost surfaces of region  302 . 
         [0033]      FIG. 1B  shows that solder balls  105  may be optionally formed on the lower surface of the optical detection sensor  1 . For example, one or more solder balls  105  may be formed on the metal plug(s)  103 . 
         [0034]      FIG. 2  shows a bottom view of the optical detection sensor  1 , according to some embodiments. As shown in  FIG. 2 , contact regions of the metal plugs  103  may be exposed at the bottom surface of the encapsulant  104 . 
         [0035]      FIG. 3  schematically shows a top view of the optical system  100 , illustrating device  101  for producing electromagnetic radiation as well as sensor chip  102 . 
         [0036]    A technique for forming the optical detection sensor  1  will be described. The method of forming optical detection sensor  1  may include a method for producing a selectively transmissive structure  300 , as illustrated in  FIGS. 4-6   d.    
         [0037]      FIGS. 4 and 5  illustrate a technique for forming a transmissive region  302  having an L-shape, according to some embodiments. As shown in  FIG. 4 , the transmissive region  302  may be formed from a glass panel  400 . Any suitable shape of glass panel  400  may be used. The glass panel  400  may be cut in a cross-hatched pattern, as shown in  FIG. 4 , to produce trenches  302 (a) in the glass panel, as shown in  FIG. 5 . The glass panel  400  may then be cut along the dashed lines shown in  FIG. 5  to produce an L-shaped transmissive region  302 . Transmissive regions  301  having a rectangular cross section may be formed by cutting portions of a glass panel that do not include trenches  302 ( a ). 
         [0038]      FIG. 6 a    shows that the transmissive regions  301  and  302  may be affixed to an adhesive  601 , which may be an adhesive tape. The adhesive  601  may be disposed on a solid handle substrate  602 , which may be formed of a metal, a semiconductor, or another solid material (e.g., a rigid material). 
         [0039]    As shown in  FIG. 6 b   , the transmissive regions  301  and  302  may be encapsulated in encapsulant  303 . Regions  301  and  303  may be encapsulated in an epoxy material which may be heated to a temperature of 120° C. to 150° C. and cured for ten minutes, for example. However, the techniques described herein are not limited to a particular encapsulant material or curing technique, as any suitable encapsulant materials or curing techniques may be used. 
         [0040]    As shown in  FIG. 6 c   , the adhesive  601  may be removed. For example, the adhesive  601  may be removed by removing the handle substrate  602 . 
         [0041]    As shown in  FIG. 6 d   , the encapsulant  303  may be subjected to a thinning process to expose the surfaces of transmissive regions  301  and  302  to enable light to pass therethrough. 
         [0042]    Any suitable thinning process may be used to reduce the thickness of the encapsulant  303 , such as a grinding process, for example. 
         [0043]    The selectively transmissive structure  300  can thereby be produced using the process illustrated in  FIGS. 4-6   d.    
         [0044]    An optical system  100  may be formed using a process such as that illustrated in  FIGS. 7 a  to 7 e   - 2 . 
         [0045]    As shown in  FIG. 7 a   , elements of optical system  100  may be placed on an adhesive  701 , such as adhesive tape. For example, a device  101  for emitting electromagnetic radiation, sensor chip  102  and one or more one or more metal plugs  103  may be placed on adhesive  701 . Adhesive  701  may be formed on a carrier substrate (not shown). 
         [0046]    As shown in  FIG. 7 b   , device  101 , sensor chip  102  and one or more one or more metal plugs  103  may be encapsulated in an encapsulant  104  such as an epoxy. Any suitable curing process may be used for encapsulant  104 , such as the process discussed above. 
         [0047]    As shown in  FIG. 7 c   , the adhesive  701  may then be removed from the encapsulant  104 . 
         [0048]    As shown in  FIGS. 7 d   - 1  and  7   d - 2 , the optical system  100  may be thinned. Any suitable thinning process may be used to reduce the thickness of the encapsulant  104 , such as a grinding process, for example. The thinning process may expose the surface of metal plugs  103  to enable contact to be made thereto. The thinning process may reduce the thickness of the encapsulant  104  to expose the surface of the sensor chip  102 , as shown in  FIG. 7 d   - 1 , or may not expose the surface of the sensor chip  102 , as shown in  FIG. 7 d   - 2 . Thinning the encapsulant in a manner that exposes the surface of the sensor chip  102  may reduce warping of the optical system  100 . If sensor chip  102  is formed of silicon, exposing the surface of the sensor chip  102  may allow infrared radiation to penetrate the optical detection sensor through the sensor chip  102 , which may be undesirable. Infrared radiation may be prevented from penetrating the sensor chip  102  by forming a protective layer  109  opaque to the infrared radiation on the bottom of the exposed sensor chip  102 , as shown in  FIG. 7 e   - 1 . As further shown in  FIG. 7 e   - 1 , an isolation layer  106 , metal interconnect  107  and passivation layer  108  may be formed on top of the structure. Alternatively, if the thinning process does not expose the surface of the sensor chip  102 , the resulting structure with isolation layer  106 , metal interconnect  107  and passivation layer  108  is shown in  FIG. 7 d   - 2 , according to some embodiments. 
         [0049]    As shown in  FIG. 8 a   , a bonding material  200  may be applied to the upper surface of optical system  100 . For example, bonding material  200  may be printed on optical system  100 . Bonding material  200  may be a two-sided glue or any other suitable bonding material. In some embodiments, opaque region  202  may be formed of bonding material  200 .  FIG. 8 b    shows the same step as illustrated in  FIG. 8 a    for the case where the encapsulant is not thinned all the way to sensor chip  200 . 
         [0050]      FIG. 9  shows the bonding of the optical system  100  and the selectively transmissive structure  300 . The optical system  100  may be brought into contact with the selectively transmissive structure  300  such that bonding material  200  holds the structures together. 
         [0051]      FIG. 10  shows that optionally, one or more solder balls  105  may be formed on the one or more metal plugs  103 . 
         [0052]    In some embodiments, multiple optical detection sensors may be formed using the process described above. For example, multiple structures  100  may be formed in the same layer of encapsulant material, and multiple structures  300  may be formed in another layer of encapsulant material, and then the two structures may be bonded together. A singulation step may be performed to separate the individual optical detection sensors by dicing or otherwise cutting the combined structure, as illustrated in  FIG. 11 . 
         [0053]    The apparatus and techniques described herein are not limited in application to the details of construction and the arrangement of components set forth in the foregoing description or illustrated in the drawings. The apparatus and techniques described herein are capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
         [0054]    Having thus described several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Accordingly, the foregoing description and drawings are by way of example only.