Microelectronic imagers with curved image sensors and methods for manufacturing microelectronic imagers
Microelectronic imagers with curved image sensors and methods for manufacturing curved image sensors. In one embodiment, a microelectronic imager device comprises an imager die having a substrate, a curved microelectronic image sensor having a face with a convex and/or concave portion at one side of the substrate, and integrated circuitry in the substrate operatively coupled to the image sensor. The imager die can further include external contacts electrically coupled to the integrated circuitry and a cover over the curved image sensor.
The present invention generally relates to microelectronic imagers with curved image sensors and methods for forming curved image sensors for use in such microelectronic imagers.
BACKGROUNDMicroelectronic imagers are used in digital cameras, wireless devices with picture capabilities, and many other applications. Cell phones and Personal Digital Assistants (PDAs), for example, incorporate microelectronic imagers for capturing and sending pictures. The growth rate of microelectronic imagers has been steadily increasing as they become smaller and produce better images with more pixels.
Microelectronic imagers include image sensors that use Charged Coupled Device (CCD) systems, Complementary Metal-Oxide Semiconductor (CMOS) systems, or other solid-state systems. CCD image sensors have been widely used in digital cameras and other applications. CMOS image sensors are also quickly becoming very popular because they are expected to have low production costs, high yields, and small sizes. CMOS image sensors can provide these advantages because they are manufactured using technology and equipment developed for fabricating semiconductor devices. CMOS image sensors, as well as CCD image sensors, are accordingly “packaged” to protect delicate components and to provide external electrical contacts.
One problem with the microelectronic imaging unit 1 illustrated in
Another problem with conventional microelectronic imaging units is that they have relatively large footprints. For example, the footprint of the imaging unit 1 in
The imager 1 shown in
Another problem with conventional microelectronic imaging units that lens systems with multiple lenses or more complex aspherical lenses are relatively tall and complex. Conventional lens systems accordingly have high profiles, can be expensive to manufacture, and may be difficult to assemble. Therefore, it would be desirable to reduce the demands and complexity of lens systems in the manufacturing of microelectronic imagers.
The following disclosure describes several embodiments of microelectronic imagers having curved image sensors and methods for fabricating such microelectronic imagers at the wafer level and at the individual die level. In one embodiment, a microelectronic imager device comprises an imager die having a substrate, a curved microelectronic image sensor having a convex and/or concave face at one side of the substrate, and integrated circuitry in the substrate operatively coupled to the image sensor. The imager die can further include external contacts electrically coupled to the integrated circuitry and a cover over the curved image sensor.
The curved microelectronic image sensor can have a convex and/or concave face with a desired radius of curvature. For example, the curved image sensor can have a face with a single radius of curvature, a plurality of curves with different radii, and/or flat portions in combination with one or more curves. The curved face of the image sensor is expected to receive a generally spherical image field such that the lens assembly does not need to significantly flatten the field to compensate for a planar sensor array.
In an alternative embodiment, a microelectronic imager device includes an imager die having a substrate with a bowed portion, a microelectronic image sensor having a curved face at the bowed portion of the substrate, and integrated circuitry electrically coupled to the image sensor. The imager device can further include a flexor unit that exerts a force against the substrate to bend or otherwise flex the substrate to form the bowed portion under the image sensor. The flexor unit, for example, can include a first element attached to a first region of the substrate under an image sensor, a spacer attached to the substrate outwardly of the first element, and a plate attached to the first element and the spacer. The first element expands or contracts more or less than the spacer to flex the substrate. The flexor unit can alternatively comprise a compartment at the front side and/or the backside of the substrate and a fluid in the compartment at a pressure that causes the substrate to bow. Another embodiment of the flexor unit can comprise a material attached to the backside of the substrate that bends the substrate into a desired curvature. The flexor unit can alternatively comprise an actuator attached to the backside of the substrate to flex the substrate and bend the image sensor into a desired curvature.
Another aspect of the invention is a method for manufacturing microelectronic imager devices. In one embodiment, a such method includes constructing an imager die having a substrate, integrated circuitry in the substrate, and an image sensor having a curved face at one side of the substrate. This method can further include positioning a cover over the substrate and/or bending the substrate to flex the image sensor.
Several details of specific embodiments of the invention are described below with reference to CMOS imagers to provide a thorough understanding of these embodiments. CCD imagers or other types of sensors, however, can be used instead of CMOS imagers in other embodiments of the invention. Several details describing well known structures often associated with microelectronic devices may not be set forth in the following description for the purposes of brevity. Moreover, other embodiments of the invention can have different configurations or different components than those described and shown in this section. As such, other embodiments of the invention may have additional elements or may not include all the elements shown and described below with reference to
B. Microelectronic Imagers with Curved Image Sensors
The imager workpiece 210 includes a substrate 212 having a front side 214, a backside 216, and an initial thickness To to between the front side 214 and backside 216. The imager workpiece 210 further includes a plurality of imaging dies 220 formed on and/or in the substrate 212. Individual imaging dies 220 can include an image sensor 221, integrated circuitry 222 operatively coupled to the image sensor 221, and terminals 223 (e.g., bond-pads) electrically coupled to the integrated circuitry 222. The image sensors 221 can be CMOS devices, CCD image sensors, or other solid state devices for capturing pictures in the visible spectrum or sensing radiation in other spectrums (e.g., IR or UV ranges). As explained in more detail below, the terminals 223 can be connected to through-wafer interconnects formed according to the processes disclosed in U.S. patent application Ser. No. 10/713,878 entitled “Microelectronic Devices, Methods for Forming Vias in Microelectronic Devices, and Methods for Packaging Microelectronic Devices,” filed on Nov. 13, 2003, which is incorporated by reference herein in its entirety. Other embodiments of external contacts can include terminals that are at an intermediate depth within the first substrate 212 instead of being at the front side 214.
The embodiment of the imager unit assembly 200 illustrated in
The image sensors 221 flex as the curved portions 250 of the substrate 212 are formed such that the image sensors 221 have curved faces 260. The curvature of each curved face 260 is configured so that the array on the curved face 260 is at a desired focal distance for the image. In the embodiment illustrated in
The curved image sensors 221 with the curved faces 260 are expected to (a) reduce the complexity of fabricating lens systems and (b) increase the options of lens systems that can be used with the imagers. For example, because the image sensors 221 have curved faces 260, the image field does not need to be flattened using optics to the same extent as image fields need to be flattened for planar image sensors. This is expected to eliminate the need for field flattening lenses in the optics units that are attached to the cover 240, or at least reduce the complexity of fields flattening lenses. Therefore, the imaging dies 220 illustrated in
The curved image sensors 221 illustrated in
The flexor units 500 operate by expanding/contracting the first elements 510 either more or less than the spacers 520 to bend the substrate 212 in the local regions under corresponding image sensors 221. For example, the flexor units 500 can be attached to the substrate 212 at an elevated temperature, and then the assembly can be cooled such that the first elements 510 exert local forces (arrows F) that bend the substrate 212 into the concave curved portions 250 (shown in dashed lines) similar to those shown in
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. For example, the substrate 212 can have patterns of trenches or other voids etched on the front side 214 and/or the backside 216 to preferentially direct the flexure of the substrate 212 using any of the embodiments described above with respect to
Claims
1-32. (canceled)
33. A microelectronic imager die comprising:
- a substrate;
- a microelectronic image sensor at one side of the substrate, the microelectronic image sensor having a face for receiving radiation;
- integrated circuitry electronically coupled to the image sensor; and
- a flexor unit that bends a portion of the substrate and the image sensor.
34. The imager die of claim 33 wherein the flexor unit further comprises:
- a first element attached to a backside of the substrate under a central portion of the image sensor; and
- a spacer attached to the backside of the substrate outward of the first element.
35. The imager die of claim 34 -wherein the first element has a first coefficient of thermal expansion and the spacer has a different second coefficient of thermal expansion.
36. The imager die of claim 34 wherein the first element is a first compliant material and the spacer is a second compliant material.
37. The imager die of claim 33 wherein the flexor unit comprises a compartment attached to the backside of the substrate and a fluid in the compartment at a pressure that causes the substrate to bow.
38. The imager die of claim 33 wherein the flexor unit comprises a sealed compartment over the image sensor and fluid in the compartment at a pressure that causes the substrate to bow.
39. The imager die of claim 33 wherein the flexor unit comprises a material attached to the backside of the substrate that induces a force that bends the substrate.
40. The image die of claim 39 wherein the material comprises a bimetallic plate, a shape memory metal, and/or an epoxy.
41. The imager of claim 33 wherein the flexor unit comprises an actuator attached to the backside of the substrate, and wherein the actuator moves to flex the substrate and bend the image sensor.
42. A microelectronic workpiece, comprising:
- a substrate having a plurality of imager dies, wherein individual imager dies include an image sensor having a curved face and integrated circuitry operatively coupled to the image sensor; and
- a cover over the substrate.
43. The microelectronic workpiece of claim 42, further comprising a plurality of backside flexor units attached to a backside of the substrate under the image sensors, and wherein individual flexor units comprise:
- a first element, a spacer, and a plate, wherein at least the first element changes to bend the substrate under a corresponding image sensor.
44. The microelectronic workpiece of claim 43 wherein the first elements have a first coefficient of thermal expansion and the spacers have a different second coefficient of thermal expansion.
45. The microelectronic workpiece of claim 43 wherein the first elements are composed of a first compliant material and the spacers are composed of a second compliant material.
46. The microelectronic workpiece of claim 42, further comprising a plurality of compartments attached to the backside of the substrate at corresponding imager dies, and wherein the compartments contain a fluid at a pressure that causes the substrate to flex under the image sensors.
47. The microelectronic workpiece of claim 46 wherein the fluid in the compartments is at a lower pressure than an ambient pressure.
48. The microelectronic workpiece of claim 46 wherein the fluid in the compartments is at a higher pressure than an ambient pressure.
49. The microelectronic workpiece of claim 42, further comprising a material attached to the backside of the substrate under corresponding image sensors that bends the substrate locally under the image sensors.
50. The microelectronic workpiece of claim 49 wherein the material comprises an epoxy.
51. The microelectronic workpiece of claim 49 wherein the material comprises bimetallic plates and/or members made from a shape memory alloy.
52. The microelectronic workpiece of claim 42, further comprising a standoffs between the cover and the substrate, sealed compartments over the image sensors, and a fluid in the compartments at a pressure that causes the substrate to bow locally at the image sensors.
53. The microelectronic workpiece of claim 51 wherein the fluid in the compartments is at a lower pressure than an ambient pressure.
54. The microelectronic workpiece of claim 51 wherein the fluid in the compartments is at a higher pressure than an ambient pressure.
55. The microelectronic workpiece of claim 42, wherein the cover has a higher coefficient of thermal expansion from the substrate.
56. The microelectronic workpiece of claim 42, further comprising a plurality of actuators attached to the backside of the substrate at the imager dies, wherein the actuators move local regions of the substrate to bow the substrate locally and flex the image sensors.
57. The microelectronic workpiece of claim 42, further comprising a plurality of vacuum cups attached to the backside of the substrate, the individual vacuum cups having a curved interior surface adhered to the backside under a corresponding image sensor.
58-76. (canceled)
77. A microelectronic imager die comprising:
- a substrate having a front side and a back side;
- a microelectronic image sensor having a face for receiving radiation at the front side of the substrate;
- integrated circuitry in the substrate electrically connected to the image sensor; and
- a curved flexor unit having a curved surface, wherein the backside of the substrate in the region of the image sensor is attached to the curved surface of the flexor unit such that the substrate in the region of the image sensor at least generally conforms to the curved surface.
78. The die of claim 77, wherein the curved flexor unit comprises a vacuum cup having an opening through which a vacuum can be drawn.
79. The die of claim 77, wherein the curved flexor unit comprises a vacuum cup having an opening through which a vacuum can be drawn, and wherein the backside of the substrate is adhered to the curved surface of the vacuum cup.
80. The die of claim 77, wherein the curved flexor unit comprises a vacuum cup having the curved surface and interconnects, and wherein the substrate further comprises backside interconnects electrically coupled to interconnects of the curved flexor unit and the integrated circuitry.
Type: Application
Filed: Jun 6, 2008
Publication Date: Oct 2, 2008
Inventors: Steven D. Oliver (Boise, ID), Jin Li (Boise, ID), Ulrich C. Boettiger (Boise, ID)
Application Number: 12/155,645
International Classification: G01J 1/20 (20060101);