Abstract:
Disclosed is an image sensing microelectronic device with glass tilt control features, and various methods of make same. In one illustrative embodiment, an image sensor die is disclosed which includes a substrate comprising an active area formed therein, a window positioned above the active area and a plurality of window tilt alignment features formed above the substrate, the window tilt alignment features being positioned between the window and the substrate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention generally relates to the field of manufacturing microelectronic devices, and, more particularly, to an image sensing microelectronic device with glass tilt control features, and various methods of make same.  
         [0003]     2. Description of the Related Art  
         [0004]     Microelectronic devices generally have a die (i.e., a chip) that includes integrated circuitry having a high density of very small components. In a typical process, a large number of die are manufactured on a single wafer using many different processes that may be repeated at various stages (e.g., implanting, doping, photolithography, chemical vapor deposition, plasma vapor deposition, plating, planarizing, etching, etc.). The die typically include an array of very small bond pads electrically coupled to the integrated circuitry. The bond pads are the external electrical contacts on the die through which the supply voltage, signals, etc. are transmitted to and from the integrated circuitry. The die are then separated from one another (i.e., singulated) by backgrinding and cutting the wafer. After the wafer has been singulated, the individual die are typically “packaged” to couple the bond pads to a larger array of electrical terminals that can be more easily coupled to the various power supply lines, signal lines and ground lines.  
         [0005]     An individual die can be packaged by electrically coupling the bond pads on the die to arrays of pins, ball pads or other types of electrical terminals, and then encapsulating the die to protect it from environmental factors (e.g., moisture, particulates, static electricity and physical impact). For example, in one application, the bond pads can be electrically connected to contacts on an interposer substrate that has an array of ball pads. The die and a portion of the interposer substrate are then encapsulated with a covering.  
         [0006]     Electronic products require packaged microelectronic devices to have an extremely high density of components in a very limited space. For example, the space available for memory devices, processors, displays and other microelectronic components is quite limited in cell phones, PDAs, portable computers and many other products. As such, there is a strong drive to reduce the height of the packaged microelectronic device and the surface area or “footprint” of the microelectronic device on a printed circuit board. Reducing the size of the microelectronic device is difficult because high performance microelectronic devices generally have more bond pads, which result in larger ball grid arrays and thus larger footprints.  
         [0007]     Image sensor die present additional packaging problems. Image sensor die include an active area that is responsive to electromagnetic radiation. In packaging, it is important to cover and protect the active area without obstructing or distorting the passage of light or other electromagnetic radiation. Typically, an image sensor die is packaged by placing the die in a recess of a ceramic substrate and attaching a glass window to the die over the active area to hermetically seal the package.  
         [0008]      FIG. 1  is an illustrative example of a prior art image sensor die  10  formed in a semiconducting substrate  12 . The image sensor die  10  comprises a window or glass  14  that is positioned above an active area  18  formed in the substrate  12 . The active area  18  typically contains a plurality of sensor cells (not shown) that are responsive to electromagnetic radiation that passes through the window  14 . The image sensor die  10  further includes a plurality of bond pads  24  and a schematically depicted integrated circuit  20  that is electrically coupled to the bond pads  24  and the active area  18 .  
         [0009]     An adhesive or epoxy  16  is used to attach the window  14  to the substrate  12 . In forming the image sensor die  10  depicted in  FIG. 1 , an adhesive dispensing tool is used to place or “work” a line of adhesive material on the image sensor die  10 . Thereafter, using a vacuum tipped handling instrument, the window  14  is positioned slightly above the substrate  12  at the desired location above the active area  18 . Once the alignment is deemed proper, the window  14  is simply dropped onto the previously formed line of adhesive material on the image sensor die  10 .  
         [0010]     One problem with the above methodology is that the window  14  may have any excessive amount of tilt. Ideally, the window  14  will be positioned exactly parallel to the surface  13  of the substrate  12 . Any deviation from such a position is referred to as tilt. The window  14  may tilt in any direction, e.g., front-to-back, side-to-side, or a combination of both.  
         [0011]     Tilt of the window  14  can be problematic for many reasons. Tilt can distort the light passing through the window  14 , or even create dead spaces or areas within the active area  18  if the tilt is severe enough. In some cases, excessive tilt of the window  14  can necessitate removing the window  14  and reworking the process to try and produce an image sensor die  10  without an excessive amount of tilt. In other cases, the image sensor die  10  may simply be discarded.  
         [0012]     The present invention is directed to a device and various methods that may solve, or at least reduce, some or all of the aforementioned problems.  
       SUMMARY OF THE INVENTION  
       [0013]     The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.  
         [0014]     The present invention is generally directed to an image sensing microelectronic device with glass tilt control features, and various methods of make same. In one illustrative embodiment, an image sensor die comprises a substrate comprising an active area formed therein, a window positioned above the active area and a plurality of window tilt alignment features formed above the substrate, the window tilt alignment features being positioned between the window and the substrate.  
         [0015]     In another illustrative embodiment, an image sensor die comprises a substrate comprising an active area formed therein, a window positioned above the active area and two window tilt alignment features formed above the substrate, each of which are positioned on opposite sides of the active area, the window tilt alignment features being positioned between the window and the substrate, wherein the window contacts each of the window tilt alignment features.  
         [0016]     In yet another illustrative embodiment, an image sensor die comprises a substrate comprising an active area formed therein, a window positioned above the active area and four window tilt alignment features formed above the substrate, each of which is positioned proximate a side of the active area, the window tilt alignment features being positioned between the window and the substrate, wherein the window contacts each of the window tilt alignment features.  
         [0017]     In a further illustrative embodiment, an image sensor die comprises a substrate comprising an active area formed therein, a window positioned above the active area and four window tilt alignment features formed above the substrate, each of which is positioned proximate a corner of the active area, the window tilt alignment features being positioned between the window and the substrate, wherein the window contacts each of the window tilt alignment features.  
         [0018]     In still a further illustrative embodiment, an image sensor die comprises a substrate comprising an active area formed therein, a window positioned above the active area and three window tilt alignment features formed above the substrate, the three window tilt alignment features being arranged in a triangular pattern around the active area, the window tilt alignment features being positioned between the window and the substrate, wherein the window contacts each of the window tilt alignment features.  
         [0019]     In one illustrative embodiment, the method comprises forming a plurality of window tilt alignment features above a substrate of an image sensor die, the substrate comprising an active area. The method further comprises, after forming the plurality of window tilt alignment features, forming an adhesive material on the substrate, positioning a window above the active area and contacting the window with the adhesive material.  
         [0020]     In another illustrative embodiment, the method comprises forming a plurality of window tilt alignment features above a substrate of an image sensor die, the substrate comprising an active area, wherein the plurality of window tilt alignment features are formed from a first adhesive material and are allowed to at least partially cure. The method further comprises, after forming the plurality of window tilt alignment features, forming a second adhesive material on the substrate, positioning a window above the active area and contacting the window with the second adhesive material.  
         [0021]     In yet another illustrative embodiment, the method comprises forming a plurality of window tilt alignment features above a substrate of an image sensor die, the substrate comprising an active area, the forming of the plurality of window tilt control features comprising forming a layer of material above the substrate, forming a masking layer above the layer of material and performing an etching process to define the plurality of window tilt alignment features in the layer of material using the masking layer as an etch mask. The method further comprises, after forming the plurality of window tilt alignment features, forming an adhesive material on the substrate, positioning a window above the active area and contacting the window with the adhesive material.  
         [0022]     In a further illustrative embodiment, the method comprises forming a plurality of window tilt alignment features comprised of a conductive material above a substrate of an image sensor die, the substrate comprising an active area. The method further comprises, after forming the plurality of window tilt alignment features, forming an adhesive material on the substrate, positioning a window above the active area and contacting the window with the adhesive material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:  
         [0024]      FIG. 1  is an example of an illustrative prior art image sensor die;  
         [0025]      FIGS. 2A-2D  are examples of an image sensor die with illustrative window tilt control features in accordance with various aspects of the present invention;  
         [0026]      FIGS. 3A-3B  are enlarged views of one illustrative example of a window tilt control feature in accordance with the present invention;  
         [0027]      FIGS. 4A-4B  are enlarged views of yet another illustrative example of a window tilt control feature in accordance with the present invention;  
         [0028]      FIGS. 5A-5B  are side views depicting an image sensor die comprised of illustrative window tilt control features in accordance with one aspect of the present invention;  
         [0029]      FIGS. 6A-6B  depict one illustrative method for forming the window tilt control features depicted herein; and  
         [0030]      FIGS. 7A-7B  depict yet another illustrative method for forming the window tilt control features depicted herein. 
     
    
       [0031]     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0032]     Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.  
         [0033]     The present invention will now be described with reference to the attached figures. Although the various regions and structures of a semiconductor device are depicted in the drawings as having very precise, sharp configurations and profiles, those skilled in the art recognize that, in reality, these regions and structures are not as precise as indicated in the drawings. Additionally, the relative sizes of the various features depicted in the drawings may be exaggerated or reduced as compared to the size of those features or regions on fabricated devices. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present invention. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be explicitly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.  
         [0034]      FIGS. 2A-2C  are illustrative examples of an image sensor die  30  comprised of a plurality of window tilt control features  36 . In  FIG. 2A , the window tilt control features  36  are generally line-type features, whereas, in  FIGS. 2B-2C , the window tilt control features  36  are circular bump-type features. After a complete reading of the present application, those skilled in the art will understand that the window tilt control features  36  described herein may be of any desired shape or configuration as long as they are capable of performing the functions described herein. Thus, the illustrative configuration and size of the window tilt control features  36  described herein should not be considered a limitation of the present invention.  
         [0035]     As to more specifics, the image sensor die  30  in  FIGS. 2A-2C  comprises a substrate  32  having an active area  34  formed therein. The dashed lines  38  in  FIGS. 2A-2C  depict the line of adhesive that will ultimately be formed to secure the window  40  (see  FIGS. 5A-5B ) to the substrate  32 . In the depicted embodiment, the window tilt control features  36  are positioned between the active area  34  and the position of the line of adhesive.  
         [0036]     In  FIG. 2A , the window tilt control features  36  are line-type features that are positioned around the perimeter of the active area  34 . In the illustrative example depicted in  FIG. 2A , each of the window tilt control features  36  is proximate the middle of each side of the active area  34 . Of course, the end position of the window tilt control features  36  shown in  FIG. 2A  may vary depending on the particular application.  FIGS. 3A-3B  depict illustrative examples of the window tilt control features  36  shown in  FIG. 2A . As shown therein, the window tilt control features  36  may have a length  33  that ranges from approximately 60-80% of the side of the active area  34 , a width  35  that ranges from approximately 50-150 μm, and a height  37  that ranges from approximately 75-175 μm. Of course, such illustrative dimensions should not be considered as a limitation of the present invention.  
         [0037]      FIG. 2B  depicts yet another illustrative example of the present invention wherein the window tilt control features  36  have a generally rounded configuration, e.g., a circular or ball-shaped configuration. In  FIG. 2B , the image sensor die  30  comprises four of the window tilt control features  36  positioned proximate the corners of the active area  34 . In  FIG. 2C , the image sensor die  30  comprises three of the window tilt control features  36  that are positioned in a triangular shaped pattern around the active area  34 . The three window tilt control features  36  depicted in  FIG. 2C  define a plane that may be used to assist in positioning the window  40  on the image sensor die  30 .  
         [0038]      FIGS. 4A-4B  depict illustrative examples of the window tilt control features  36  shown in  FIG. 2B . As shown therein, the window tilt control features  36  may have a diameter  39  that ranges from approximately 30-70 μm and a height  41  that ranges from approximately 50-150 μm. Of course, such illustrative dimensions should not be considered as a limitation of the present invention.  
         [0039]      FIG. 2D  depicts yet another illustrative example of an image sensor die  30  comprised of a plurality of window tilt control features  36 . In this illustrative example, the image sensor die  30  comprises two window tilt control features  36  that are positioned on opposite sides of the active area  34 . As with the previous examples, the size of the window tilt control features  36  depicted in  FIG. 2D  may vary depending upon the particular application. For example, the relatively elongated window tilt control features  36  depicted in  FIG. 2D  may have a length of 60-80% of the side of the active area  34 .  
         [0040]      FIGS. 5A-5B  are side views showing how the illustrative window tilt control features  36  may be used in reducing or eliminating tilt of the window  40  of the image sensor die  30 .  FIG. 5A  depicts a plurality of illustrative line-type window tilt control features  36  (shown in dashed lines), whereas  FIG. 5B  depicts a plurality of illustrative rounded or ball shaped window tilt control features  36  (shown in dashed lines). After the window tilt control features  36  are formed, the line of adhesive  38  is positioned on the substrate  32 . Thereafter, the window  40  is moved to its proper position. At this time, the window  40  may simply be dropped onto the adhesive  38  and the window tilt control features  36 . Alternatively, if desired, a downward force, as indicated by the arrow  45 , may be applied to the window  40  to insure that it engages the window tilt control features  36 . The adhesive  38  is allowed to cure in accordance with normal practice, thereby securing the window  40  in position. Through use of the window tilt control features  36  described herein, the tilt of the window  40  may be reduced or eliminated.  
         [0041]     The window tilt control features  36  described herein may be comprised of a variety of different materials and they may be manufactured using a variety of techniques. For example, the window tilt control features  36  may be comprised of an adhesive or epoxy type material that is the same as or different from the adhesive  38  used to secure the window  40  to the substrate  32 . The epoxy or adhesive may be deposited (or “written”) in the desired shape (line-type feature as shown in  FIG. 2A  or  2 D, or rounded-type features as shown in  FIGS. 2B-2C ) using any of a variety of known epoxy distribution tools. Thereafter, the window tilt control features  36  may be allowed to partially cure, e.g., approximately 70-80% cured. At this stage of cure, the epoxy window tilt control features  36  have sufficient rigidity to perform the functions of the window tilt control features  36  described herein. Of course, if desired, the epoxy window tilt control features  36  may be allowed to fully cure. After the epoxy window tilt control features  36  are formed, the line of adhesive material  38  may be positioned on the substrate  32  and the window  40  may be attached as described above.  
         [0042]     In another illustrative example, the window tilt control features  36  may be formed using traditional deposition, photolithography and etching processes, as shown in  FIGS. 6A-6C . For example, the window tilt control features  36  may be formed by initially depositing a layer  42  of any desired material, e.g., silicon nitride, silicon dioxide, etc. If desired or necessary, the upper surface  43  of this deposited layer of material may be subjected to a planarization process, e.g., a chemical mechanical polishing process. Thereafter, a masking layer  44 , e.g., a patterned layer of photoresist material, may be formed above the layer of material  42  using known photolithography tools and techniques.  FIG. 6B  is a top view of the masking layer  44  comprised of a plurality of masking features  44 A. The masking features  44 A correspond to the tilt control features  36  that will ultimately be formed from the layer  42 . Thereafter, an anisotropic etching process may be performed to define the window tilt control features  36  (see  FIG. 6C ) from the deposited layer of material  42 .  
         [0043]     As yet another example, the window tilt control features  36  may be comprised of a non-functioning bond pad to which a non-functioning conductive member, e.g., ball, is attached. More specifically, as is well known to those skilled in the art, electrical connection between the image sensor die  10  (see  FIG. 1 ) and its packaging (not shown) is typically accomplished by forming a ball of conductive material on the bond pads  22 . In accordance with this illustrative aspect of the present invention, as shown in  FIGS. 7A-7B , a plurality of non-functioning bond pad structures  46 A may be formed on the substrate  32  during the process used to form functioning bond pads  46 B for the image sensor die  30 . Thereafter, a conductive ball of material  48 A may be formed on the non-functioning pads  46 A at the same time conductive balls of material  48 B are formed on the functioning bond pads  46 B for the image sensor die  30 . The non-functioning balls of material  48 A act as the window tilt control features  36  described herein.  
         [0044]     The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.