Wafer-level packaged microelectronic imagers and processes for wafer-level packaging

Abstract

The following disclosure describes several embodiments of (1) methods for wafer-level packaging of microelectronic imagers, (2) methods of forming electrically conductive interconnects in microelectronic imagers, (3) methods for forming optical devices for microelectronic imagers, and (4) microelectronic imagers that have been packaged using wafer-level packaging processes. Wafer-level packaging of microelectronic imagers is expected to significantly enhance the efficiency of manufacturing microelectronic imagers because a plurality of imagers can be packaged simultaneously using highly accurate and efficient processes developed for packaging semiconductor devices. Moreover, wafer-level packaging of microelectronic imagers is expected to enhance the quality and performance of such imagers because the semiconductor fabrication processes can reliably align an optical device with an image sensor and space the optical device apart from the image sensor by a desired distance with a higher degree of precision.

1 . A method of packaging a microelectronic imager, comprising: 
 providing an imager workpiece comprising a first substrate and a plurality of imaging units formed on and/or in the first substrate, wherein individual imaging units comprise an image sensor, an integrated circuit formed in the first substrate and electrically coupled to the image sensor, and a plurality of external electrical contacts coupled to the integrated circuit and having contact pads arranged on the first substrate;    providing an optical device workpiece having a second substrate and a plurality of optical devices formed on and/or in the second substrate, wherein individual optical devices comprise an optics element; and    assembling the optical devices with corresponding imaging units so that an optics element of one optical device is positioned at a desired location with respect to an image sensor of a corresponding imaging unit before cutting the first substrate and/or the second substrate.    
     
     
         2 . The method of  claim 1  wherein the first substrate comprises a wafer having front side and a backside, the image sensors are at the front side of the wafer, and the contact pads are at the backside of the wafer, and wherein providing the imager workpiece comprises constructing through-wafer interconnects extending through at least a portion of the wafer to electrically couple contact pads to corresponding integrated circuits.  
     
     
         3 . The method of  claim 1  wherein providing the imager workpiece comprises forming the image sensors on a front side of the first substrate and forming the contact pads on a backside of the first substrate, and wherein the front side faces toward the optical device workpiece and the backside faces away from the optical device workpiece.  
     
     
         4 . The method of  claim 1  wherein the optics elements comprise lenses configured to direct radiation to corresponding image sensors, and providing the optical device workpiece comprises producing lenses on the second substrate in a pattern corresponding to a pattern of the image sensors on the first substrate.  
     
     
         5 . The method of  claim 4  wherein producing the lenses comprises molding the lenses on the second substrate, etching the lenses into the second substrate and/or attaching the lenses to the second substrate.  
     
     
         6 . The method of  claim 1  wherein the optics elements comprise lenses arranged in a pattern on the second substrate corresponding to a pattern of the image sensors on the first substrate, and wherein assembling the optical devices with corresponding imaging units comprises: 
 aligning the lenses with corresponding image sensors;    spacing the first substrate apart from the second substrate by a desired distance; and    fixing the first substrate relative to the second substrate.    
     
     
         7 . The method of  claim 1 , further comprising: 
 providing a spacer between the imager workpiece and the optical device workpiece; and    fixing the imager workpiece to one portion of the spacer and fixing the optical device workpiece to another portion of the spacer to fix the first substrate relative to the second substrate with the first and second substrates being separated by a desired distance, wherein the spacer has a plurality of openings arranged such that individual openings are aligned with a corresponding image sensor and a corresponding optics element.    
     
     
         8 . The method of  claim 1 , further comprising: 
 providing a spacer having a plurality of stand-offs, and wherein each stand-off has an opening; and    arranging the imager workpiece, the stand-offs and the optical device workpiece so that the imager workpiece is fixed to one portion of the stand-offs and the optical device workpiece is fixed to another portion of the stand-offs, wherein an individual image sensor and a corresponding optics element are aligned with an opening of one of the stand-offs.    
     
     
         9  The method of  claim 1  wherein: 
 the optical devices are assembled with corresponding imaging units before cutting either of the first substrate or the second substrate; and    the method further comprises cutting the first and second substrates to singulate individual imagers from each other.    
     
     
         10 . The method of  claim 1  wherein: 
 the second substrate is cut to singulate the optical devices from each other before assembling the optical devices with corresponding imaging units; and    the method further comprises (a) attaching separate optical devices to corresponding imaging units and (b) cutting the first substrate to singulate the imaging units from each other.    
     
     
         11 . The method of  claim 1  wherein: 
 the first substrate is cut to singulate the imaging units from each other before assembling the optical devices with corresponding imaging units; and    the method further comprises (a) attaching separate imaging units to corresponding optical devices and (b) cutting the second substrate to singulate the optical devices from each other.    
     
     
         12 . A method of packaging a microelectronic imager, comprising: 
 providing an imager workpiece comprising a first substrate, a plurality of microelectronic image sensors arranged in a pattern on the first substrate, and cutting lanes between adjacent image sensors;    providing an optical device workpiece comprising a second substrate and a plurality of optics elements arranged on the second substrate at least generally in the pattern of the image sensors on the first substrate;    fixing the imager workpiece relative to the optical device workpiece so that individual image sensors on the first substrate are aligned with corresponding optics elements on the second substrate; and    cutting the first and second substrates along the cutting lanes after fixing the imager workpiece relative to the optical device workpiece.    
     
     
         13 . The method of  claim 12  wherein the first substrate comprises a wafer having front side and a backside, the image sensors are at the front side of the wafer, and the imager workpiece further comprises a plurality of contact pads at the backside of the wafer, and wherein providing the imager workpiece comprises constructing through-wafer interconnects extending through at least a portion of the wafer to electrically couple the contact pads to corresponding integrated circuits.  
     
     
         14 . The method of  claim 12  wherein providing the imager workpiece comprises forming the image sensors on a front side of the first substrate and forming a plurality of contact pads on a backside of the first substrate, and wherein the front side faces toward the optical device workpiece and the backside faces away from the optical device workpiece.  
     
     
         15 . The method of  claim 12 , further comprising: 
 providing a spacer between the imager workpiece and the optical device workpiece; and    fixing the imager workpiece to one portion of the spacer, and fixing the optical device workpiece to another portion of the spacer to fix the first substrate relative to the second substrate with the first and second substrates being separated by a desired distance, wherein the spacer has a plurality of openings arranged such that individual openings are aligned with a corresponding image sensor and a corresponding optics element.    
     
     
         16 . The method of  claim 12 , further comprising: 
 providing a spacer having a plurality of stand-offs, and wherein each stand-off has an opening; and    arranging the imager workpiece, the stand-offs and the optical device workpiece so that the imager workpiece is fixed to one portion of the stand-offs and the optical device workpiece is fixed to another portion of the stand-offs, wherein an individual image sensor and a corresponding optics element are aligned with an opening of one of the stand-offs.    
     
     
         17 . A method of packaging a microelectronic imager, comprising: 
 forming a plurality of imaging units on and/or in a first substrate having a front side and a backside, each imaging unit having an image sensor at the front side of the first substrate and external contact pads at the backside of the first substrate operatively coupled to the image sensor;    fabricating a plurality of optical devices on and/or in a second substrate, each optical device having an optics element; and    fixing the imaging units relative to the optics elements in a spaced apart relationship before cutting the first substrate and/or the second substrate, wherein the image sensors are sealed in discrete compartments in alignment with a corresponding one of the optics elements.    
     
     
         18 . The method of  claim 17  wherein the optics elements comprise lenses configured to direct radiation to corresponding image sensors, and fabricating a plurality of optical devices comprises producing lenses on the second substrate in a pattern corresponding to a pattern of the image sensors on the first substrate.  
     
     
         19 . The method of  claim 18  wherein producing the lenses comprises molding the lenses on the second substrate, etching the lenses into the second substrate and/or attaching the lenses to the second substrate.  
     
     
         20 . The method of  claim 17  wherein the optics elements comprise lenses arranged in a pattern on the second substrate corresponding to a pattern of the image sensors on the first substrate, and wherein fixing the imaging units relative to the optics elements comprises: 
 aligning the lenses with corresponding image sensors;    spacing the first substrate apart from the second substrate by a desired distance; and    fixing the first substrate relative to the second substrate.    
     
     
         21 . The method of  claim 17 , further comprising: 
 providing a spacer between the first substrate and the second substrate; and    fixing the first substrate to one portion of the spacer and fixing the second substrate to another portion of the spacer to fix the first substrate relative to the second substrate with the first and second substrates being separated by a desired distance, wherein the spacer has a plurality of openings arranged such that individual openings are aligned with a corresponding image sensor and a corresponding optics element.    
     
     
         22  The method of  claim 17  wherein: 
 the imaging units are fixed relative to the optics elements before cutting either of the first substrate or the second substrate; and    the method further comprises cutting the first and second substrates to singulate individual imagers from each other.    
     
     
         23 . The method of  claim 17  wherein: 
 the second substrate is cut to singulate the optical devices from each other before the imaging units are fixed relative to the optics elements; and    the method further comprises (a) attaching separate optical devices to corresponding imaging units and (b) cutting the first substrate to singulate the imaging units from each other.    
     
     
         24 . The method of  claim 17  wherein, 
 the first substrate is cut to singulate the imaging units from each other before the imaging units are fixed relative to the optics elements; and    the method further comprises (a) attaching separate imaging units to corresponding optical devices and (b) cutting the second substrate to singulate the optical devices from each other.    
     
     
         25 . A method of packaging a microelectronic imager, comprising: 
 forming a plurality of imaging units on and/or in a first substrate, the imaging units being arranged in a die pattern, and individual imaging units having an image sensor and an array of external contact pads electrically coupled to the image sensor;    fabricating a plurality of optical devices on and/or in a second substrate, the optical devices being arranged in a device pattern at least generally corresponding to the die pattern of the imaging units, and individual optical devices having an optics element;    constructing a spacer having individual openings arranged to be aligned with the die pattern and the device pattern; and    fixing the first substrate relative to the second substrate with the spacer assembly between the first and second substrates, wherein individual imaging sensors on the first substrate are aligned with (a) a corresponding one the openings of the spacer assembly and (b) a corresponding one of the optics elements on the second substrate.    
     
     
         26 . The method of  claim 25  wherein the first substrate comprises a wafer having front side and a backside, the image sensors are at the front side of the wafer, and the contact pads are at the backside of the wafer, and wherein forming a plurality of imaging units comprises constructing through-wafer interconnects extending through at least a portion of the wafer to electrically couple contact pads to corresponding integrated circuits.  
     
     
         27 . The method of  claim 25  wherein forming a plurality imaging units comprises forming the image sensors on a front side of the first substrate and forming the contact pads on a backside of the first substrate, and wherein the front side faces toward the optical device workpiece and the backside faces away from the optical device workpiece.  
     
     
         28 . The method of  claim 25  wherein the optics elements comprise lenses configured to direct radiation to corresponding image sensors, and fabricating the optical devices comprises producing lenses on the second substrate arranged in the device pattern.  
     
     
         29 . The method of  claim 28  wherein producing the lenses comprises molding the lenses on the second substrate, etching the lenses into the second substrate and/or attaching the lenses to the second substrate in the device pattern.  
     
     
         30 . A microelectronic imager assembly, comprising: 
 an imager workpiece having a first substrate and a plurality of imaging units formed on and/or in the first substrate, the imaging units individually comprising an image sensor, an integrated circuit electrically coupled to the image sensor, and external electrical contacts having contact pads on the first substrate coupled to the integrated circuit; and    an optical device workpiece having a second substrate and a plurality of optical devices on and/or in the second substrate, the optical devices individually comprising an optics element, wherein the first and second substrates are fixed relative to each other in a spaced apart relationship so that the image sensors are aligned with corresponding optics elements.    
     
     
         31 . The imager assembly of  claim 30  wherein the first substrate comprises a semiconductor wafer and the second substrate comprises a glass wafer.  
     
     
         32 . The imager assembly of  claim 30  wherein the first substrate comprises a semiconductor wafer and the second substrate comprises a quartz wafer.  
     
     
         33 . The imager assembly of  claim 30  wherein: 
 the first substrate has a front side and a backside;    the image sensors are at the front side of the first substrate;    the contact pads are at the backside of the first substrate; and    the external electrical contacts further comprise through-wafer interconnects extending at least partially through the first substrate, the through-wafer interconnects operatively coupling contact pads at the backside to integrated circuits of corresponding image sensors at the front side.    
     
     
         34 . The imager assembly of  claim 30  wherein the first substrate has a front side and a backside, the image sensors are at the front side of the first substrate, and the contact pads are at the backside of the first substrate.  
     
     
         35 . The imager assembly of  claim 30  wherein: 
 the first substrate has a front side and a backside;    the image sensors are at the front side of the first substrate;    the contact pads are at the backside of the first substrate;    the imaging units further comprise a plurality of terminals at the front side of the first substrate, the terminals being electrically coupled to integrated circuits of corresponding image sensors; and    the external electrical contacts further comprise through-wafer interconnects extending through the first substrate, the through-wafer interconnects having first ends connected to the terminals and second ends connected to the contact pads.    
     
     
         36 . The imager assembly of  claim 30  wherein the optics elements comprise lenses in and/or on the second substrate.  
     
     
         37 . The imager assembly of  claim 30  wherein the second substrate comprises a glass wafer and the optics elements comprise lenses in and/or on the glass wafer.  
     
     
         38 . The imager assembly of  claim 30  wherein the second substrate comprises a glass wafer having a filtering film and the optics elements comprise lenses in and/or on the glass wafer.  
     
     
         39 . The imager assembly of  claim 38  wherein individual lenses comprise a focusing lens and/or a pin-hole lens.  
     
     
         40 . A microelectronic imager assembly, comprising: 
 a first substrate having a front side and a backside, a plurality of image sensors at the front side of the first substrate, a plurality of external electrical contacts having contact pads on the backside of the first substrate, and interconnects extending through at least a portion of the first substrate and electrically coupled to the contact pads on the backside of the first substrate;    a second substrate having a plurality of optics elements, wherein the optics elements are aligned with corresponding image sensors; and    a spacer having a first portion attached to the first substrate and a second portion attached to the second substrate, the spacer having openings arranged in a pattern such that individual openings are aligned with (a) a corresponding one of the image sensors and (b) a corresponding one of the optics elements.    
     
     
         41 . The imager assembly of  claim 40  wherein the optics elements comprise lenses in and/or on the second substrate.  
     
     
         42 . The imager assembly of  claim 40  wherein the second substrate comprises a glass wafer and the optics elements comprise lenses in and/or on the glass wafer.  
     
     
         43 . The imager assembly of  claim 40  wherein the second substrate comprises a glass wafer having a filtering film and the optics elements comprise lenses in and/or on the glass wafer.  
     
     
         44 . The imager assembly of  claim 43  wherein individual lenses comprise a focusing lens and/or a pin-hole lens.  
     
     
         45 . A microelectronic imager assembly, comprising: 
 a first substrate having (a) a first imaging unit including a first microelectronic image sensor and a first array of external contacts having contact pads operatively coupled to the first image sensor and (b) a second imaging unit including a second microelectronic image sensor and a second array of external contacts having contact pads operatively coupled to the second image sensor;    a first optics element fixed relative to the first imaging unit in alignment with the first microelectronic image sensor; and    a second optics element fixed relative to the second imaging unit in alignment with the second microelectronic image sensor.    
     
     
         46 . The imager assembly of  claim 45 , wherein the first substrate has a front side and a backside, the first and second image sensors are at the front side, and the contact pads are at the backside.  
     
     
         47 . The imager of  claim 46 , further comprising a plurality of through-wafer interconnects extending through at least a portion of the first substrate, the through-wafer interconnects being coupled to the contact pads.  
     
     
         48 . A microelectronic imager assembly, comprising: 
 a imager workpiece including a first substrate having a front side and a backside, a first imaging unit including a first microelectronic image sensor at the front side of the first substrate and a first array of external contacts having contact pads at the backside of the first substrate coupled to the first image sensor, and a second imaging unit including a second microelectronic image sensor at the front side of the first substrate and a second array of external contacts having contact pads at the backside of the first substrate coupled to the second image sensor;    a first optics element fixed relative to the first imaging unit in alignment with the first microelectronic image sensor; and    a second optics element fixed relative to the second imaging unit in alignment with the second microelectronic image sensor.    
     
     
         49 . A microelectronic imager assembly, comprising: 
 an imager workpiece having a first substrate and a plurality of microelectronic imaging means formed in and/or on the first substrate; and    an optical device workpiece having a second substrate fixedly coupled to the first substrate, the optical device workpiece having a plurality of optical device means in and/or on the second substrate in alignment with corresponding imaging means of the image workpiece.    
     
     
         50 . A microelectronic imager, comprising: 
 an imaging unit including a die having a front side and a backside, an image sensor at the front side of the die, and a plurality of contact pads at the backside of the die, the contacts being electrically coupled to the image sensor; and    an optical device having a substrate that is at least substantially non-transmissive to infrared radiation and an optics element integrated with the substrate, the optics element being aligned with the image sensor and configured to manipulate radiation for the image sensor.    
     
     
         51 . The microelectronic imager of  claim 50 , further comprising a stand-off between the imaging unit and the optical device, the stand-off having an opening aligned with the image sensor and the optics element, and the image sensor being exposed to the optics element without another transparent member therebetween.  
     
     
         52 . A microelectronic imager, comprising: 
 an imaging unit including a die having a front side and a backside, an image sensor at the front side of the die, an integrated circuit electrically coupled to the image sensor, a plurality of through-wafer interconnects electrically coupled to the integrated circuit and extending through the die to the backside, and a plurality of contact pads at the backside of the die and connected to the interconnects; and    an optical device fixed with respect to the imaging unit and having an optics element aligned with the image sensor.    
     
     
         53 . A microelectronic imager, comprising: 
 an imaging unit including a die having a front side and a backside, an image sensor at the front side of the die, an integrated circuit electrically coupled to the image sensor, a plurality of through-wafer interconnects electrically coupled to the integrated circuit and extending through the die to the backside, and a plurality of contact pads at the backside of the die and connected to the interconnects;    a stand-off projecting from the die and having an opening aligned with the image sensor; and    an optical device attached to the stand-off, the optical device having a substrate and an optics element on and/or in the substrate aligned with the image sensor.    
     
     
         54 . A microelectronic imager, comprising: 
 an imaging unit including a die having a front side and a backside, an image sensor at the front side of the die, and a plurality of contact pads at the backside of the die, the contact pads being operatively coupled to the image sensor for electrically attaching the imager to an external device; and    an optical device fixed with respect to the imaging unit and having an optics element aligned with the image sensor.