Microelectronic imagers with integrated optical devices and methods for manufacturing such microelectronic imagers

Abstract

Microelectronic imagers with integrated optical devices and methods for manufacturing imagers. The imagers, for example, typically have an imaging unit including a first substrate and an image sensor on and/or in the first substrate. An embodiment of an optical device includes a stand-off having a compartment configured to contain the image sensor. The stand-off has a coefficient of thermal expansion at least substantially the same as that of the first substrate. The optical device can further include an optics element in alignment with the compartment of the stand-off. The stand-off can be formed by etching a compartment into a silicon wafer or a wafer of another material having a coefficient of thermal expansion at least substantially the same as that of the substrate upon which the image sensor is formed. The optics elements can be formed integrally with the stand-offs or separately attached to a cover supported by the stand-offs.

1 . A method of fabricating an optical device for use in a microelectronic imager having an imaging unit including a first substrate and an image sensor on the first substrate, the first substrate being a semiconductive material, and the method comprising: forming a stand-off having a compartment configured to contain the image sensor and a coefficient of thermal expansion at least substantially the same as that of the first substrate; and fixedly positioning an optics element in alignment with the compartment of the stand-off.  
   
   
       2 . The method of  claim 1  wherein the stand-off comprises silicon, quartz, glass and/or a III-V silicon material.  
   
   
       3 . The method of  claim 1  wherein forming the stand-off comprises providing a second substrate composed of a material having a coefficient of thermal expansion at least approximately the same as that of the first substrate and etching a plurality of compartments into the second substrate.  
   
   
       4 . The method of  claim 1  wherein forming the stand-off comprises: providing a second substrate composed of a material having a coefficient of thermal expansion at least approximately the same as that of the first substrate and a cover stratum on the second substrate; and etching the second substrate to form a plurality of compartments with sidewalls.  
   
   
       5 . The method of  claim 4  wherein the cover stratum is a layer of material deposited onto the second substrate.  
   
   
       6 . The method of  claim 4  wherein the cover stratum is formed separately from the second substrate and attached to a surface of the second substrate.  
   
   
       7 . The method of  claim 4  wherein the cover stratum comprises glass.  
   
   
       8 . The method of  claim 4 , further comprising depositing a filter and/or an anti-reflective coating on the cover stratum.  
   
   
       9 . The method of  claim 4  wherein fixedly positioning an optics element in alignment with a compartment comprises forming optics elements by depositing an optics material layer on the cover stratum and etching the optics material layer to form lenses aligned with corresponding compartments, wherein individual lenses have a curved surface and define an individual optics element.  
   
   
       10 . The method of  claim 9  wherein the lenses are on a first surface of the cover stratum above the compartments.  
   
   
       11 . The method of  claim 9  wherein the lenses are on a second surface of the cover stratum within the compartments.  
   
   
       12 . The method of  claim 4  wherein fixedly positioning an optics element in alignment with a compartment comprises forming optics elements by depositing individual blocks of optics material on the cover stratum and curing the blocks to form lenses aligned with corresponding compartments, wherein individual lenses have a curved surface and define an individual optics element.  
   
   
       13 . The method of  claim 12  wherein the lenses are on a first surface of the cover stratum above the compartments.  
   
   
       14 . The method of  claim 12  wherein the lenses are on a second surface of the cover stratum within the compartments.  
   
   
       15 . The method of  claim 4  wherein fixedly positioning an optics element in alignment with a compartment comprises forming optics elements by constructing individual lenses separately from the cover stratum and adhering the individual lenses to the cover stratum in alignment with corresponding compartments, wherein individual lenses have a curved surface and define an individual optics element.  
   
   
       16 . The method of  claim 15  wherein the lenses are on a first surface of the cover stratum above the compartments.  
   
   
       17 . The method of  claim 15  wherein the lenses are on a second surface of the cover stratum within the compartments.  
   
   
       18 . The method of  claim 4 , further comprising: forming holes in the cover stratum, wherein individual holes are aligned with corresponding compartments; and fixedly positioning an optics element in alignment with a compartment by forming optics elements by constructing individual lenses separately from the cover stratum and mounting the lenses to the cover stratum, wherein individual lenses are at least partially received in a corresponding hole.  
   
   
       19 . The method of  claim 18  wherein the lenses have first reference elements and the holes have second reference elements, and the method further comprises engaging the first reference elements with corresponding second reference elements.  
   
   
       20 . The method of  claim 1  wherein (a) forming a stand-off further comprises constructing a plurality of stand-offs and (b) fixedly positioning an optics element in alignment with a compartment further comprises constructing a plurality of integrated optics elements by: providing a second substrate having a first side, a second side, and a coefficient of thermal expansion at least approximately the same as that of the first substrate; etching a plurality of depressions in the first side of the second substrate, wherein individual depressions have a contour defining a lens curvature; depositing an optics material layer onto the first side of the second substrate to fill the depressions; removing an upper portion of the optics material layer to form lenses defined by portions of the optics material layer remaining in the depressions; and etching compartments into the second side of the second substrate, wherein the compartments are aligned with corresponding lenses.  
   
   
       21 . The method of  claim 20  wherein the second substrate comprises silicon and the optics material layer comprises glass.  
   
   
       22 . The method of  claim 20  wherein the second substrate comprises silicon and the optics material layer comprises quartz.  
   
   
       23 . The method of  claim 20  wherein etching the compartments comprises etching the second substrate until the lenses are exposed within the compartments.  
   
   
       24 . The method of  claim 1  wherein fixedly positioning an optics elements in alignment with the compartment of the stand-off comprises providing a stacked optical device having a first optics element and a second optics element above the first optics element, and attaching the stand-off to the first substrate.  
   
   
       25 . The method of  claim 24  wherein the stacked optical device has a single stand-off with a first lens site where the first optics element is positioned and a second lens site where the second optics element is positioned.  
   
   
       26 . The method of  claim 24  wherein the stacked optical device has a first stand-off to which the first optics element is attached and a second stand-off to which the second optics element is attached, and wherein the second stand-off is stacked on top of the first stand-off.  
   
   
       27 - 62 . (canceled)  
   
   
       63 . A method for packaging a plurality of microelectronic imagers at the wafer level, comprising: providing a first substrate having a front side, a backside and a plurality of image sensors at the front side; mounting stand-offs to the front side of the first substrate, the stand-offs being formed from a second substrate having a coefficient of thermal expansion at least substantially the same as that of the first substrate, and the stand-offs having compartments aligned with corresponding image sensors; and fixedly positioning optics elements relative to the stand-offs so that individual optics elements are aligned with one of the compartments before or after mounting the stand-offs to the front side of the first substrate.  
   
   
       64 . The method of  claim 63  further comprising forming the stand-offs by etching the compartments into the second substrate.  
   
   
       65 . The method of  claim 63  further comprising forming the stand-offs by providing a cover stratum on the second substrate and etching the compartments into the second substrate to expose areas of the cover stratum.  
   
   
       66 . The method of  claim 65  wherein the cover stratum comprises a layer of material deposited onto the second substrate.  
   
   
       67 . The method of  claim 65  wherein the cover stratum comprises glass.  
   
   
       68 . The method of  claim 65 , further comprising depositing a filter and/or an anti-reflective coating on the cover stratum.  
   
   
       69 . The method of  claim 63  wherein the stand-offs are mounted to the front side of the first substrate and the optics elements are fixedly positioned relative to the stand-offs before cutting the first substrate to singulate the image sensors from each other.  
   
   
       70 . The method of  claim 63  wherein the optics elements are fixed relative to the stand-offs before mounting the stand-offs to the front side of the first substrate.  
   
   
       71 . The method of  claim 63:  further comprising forming the stand-offs by providing a cover stratum on the second substrate and etching the compartments into the second substrate to expose areas of the cover stratum; and wherein fixedly positioning the optics elements relative to the stand-offs comprises forming the optics elements by depositing an optics material layer on the cover stratum and etching the optics material layer to form lenses aligned with corresponding compartments, wherein individual lenses have a curved surface.  
   
   
       72 . The method of  claim 63  further comprising forming the stand-offs by providing a cover stratum on the second substrate and etching the compartments into the second substrate to expose areas of the cover stratum; and wherein fixedly positioning the optics elements relative to the stand-offs comprises forming the optics elements by depositing individual blocks of optics material on the cover stratum and curing the blocks to form lenses aligned with corresponding compartments, wherein individual lenses have a curved surface.  
   
   
       73 . The method of  claim 63  further comprising forming the stand-offs by providing a cover stratum on the second substrate and etching the compartments into the second substrate to expose areas of the cover stratum; and wherein fixedly positioning the optics elements relative to the stand-offs comprises forming the optics elements by constructing individual lenses separately from the cover stratum and adhering the individual lenses to the cover stratum in alignment with corresponding compartments, wherein individual lenses have a curved surface.  
   
   
       74 . The method of  claim 63  wherein forming the stand-offs and fixedly positioning the optics elements comprises: etching a plurality of depressions in a first side of the second substrate, wherein individual depressions have a contour defining a lens surface; depositing an optics material layer onto the first side of the second substrate to fill the depressions; removing an upper portion of the optics material layer to form lenses defined by portions of the optics material layer remaining in the depressions; and etching the compartments into a second side of the second substrate, wherein the compartments are aligned with corresponding lenses.  
   
   
       75 . The method of  claim 74  wherein etching the compartments comprises etching through the second substrate to expose portions of the lenses.  
   
   
       76 - 103 . (canceled)