Flip-Chip Photodiode
A photodiode is provided according to various embodiments. In some embodiments, the photodiode includes a substrate and an active region. The active region is configured to receive light through the substrate. In such a configuration, the substrate not only participates in the photodiode operation acts as a light filter depending on the substrate material. In some embodiments, the active region may include solder balls that may be used to couple the photodiode to a printed circuit board. In some embodiments, the active region is coupled face-to-face with the printed circuit board.
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This application is a non-provisional, and claims the benefit, of commonly assigned U.S. Provisional Patent Application No. 60/949,200, filed Jul. 11, 2007, entitled “Flip Chip Photo-Diode,” the entirety of which is herein incorporated by reference for all purposes.
This application is a non-provisional, and claims the benefit, of commonly assigned U.S. Provisional Patent Application No. 60/949,229, filed Jul. 11, 2007, entitled “Flip Chip Quantum Well Modulator,” the entirety of which is herein incorporated by reference for all purposes.
This application is a non-provisional, and claims the benefit, of commonly assigned U.S. Provisional Patent Application No. 60/949,230, filed Jul. 11, 2007, entitled “Integrated Modulating Retro-Reflector,” the entirety of which is herein incorporated by reference for all purposes.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTThe U.S. Government may have rights in this invention pursuant to Special Operations Command under Contract No. H92222-04-C-0004.
BACKGROUNDThis disclosure relates in general to photodiodes. Photodiodes are constructed with an active layer placed upon a substrate that may then be coupled, for example, with a printed circuit board. In some applications, an optical filter may also be included to block unwanted bands of light. The inclusion of the filter often adds weight and complexity, increases costs, and decreases the photodiode field of view.
BRIEF SUMMARYA flip-chip photo diode is provided according to various embodiments. The flip-chip photodiode may include an active layer, a substrate, and a plurality of solder balls. The active layer comprises a top and a bottom surface such that the top surface of the active layer is coupled with the substrate. In some embodiments, the active layer is coupled with the substrate with an intervening layer, for example, an intrinsic layer, or a gap. The plurality of solder balls may be coupled with the bottom of the active layer and may be configured to couple with a circuit board. In other embodiments a plurality of solder balls may be coupled with the bottom of the substrate and configured to couple with a circuit board. The substrate may include an antireflective coating on the top surface thereof.
A flip-chip photo diode stack is provided according to another embodiment, that includes a substrate, an active area and a printed circuit board. The substrate includes a top surface and a bottom surface. The top surface may be configured to receive light. The active layer includes a top surface and a bottom surface. The top surface of the active area may be coupled with the bottom surface of the substrate. The printed circuit board includes at least a top surface coupled with the active layer. Solder balls, according to another embodiment, may be used to couple the active array to the printed circuit board. An intrinsic layer may, in some embodiments, be included between the active layer and the substrate.
A photodiode is provided according to some embodiments that includes a substrate and an active region. The substrate includes a top surface and a bottom surface. The active region comprises a top surface and a bottom surface. The top surface of the active region may be aligned below the bottom surface of the substrate. The photodiode may be configured to receive light through the top surface of the substrate. At least a portion of the light received through the top surface of the substrate may be incident on the active region. In one embodiment, the substrate may be substantially transparent to light with wavelengths between about 1530 nm and about 1560 nm. In another embodiment, the substrate may be substantially transparent to infrared light.
Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating various embodiments, are intended for purposes of illustration only and do not limit the scope of the disclosure.
In the appended figures, similar components and/or features may have the same reference label. Where the reference label is used in the specification, the description is applicable to any one of the similar components having the same reference label.
DETAILED DESCRIPTIONThe ensuing description provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment. It should be understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims.
In one embodiment, the present disclosure provides for a flip-chip photodiode. In some embodiments, a flip-chip photodiode may use the substrate as a light filter. In other embodiments, a flip-chip diode may include an active layer and a substrate. The active layer may be coupled with the substrate. The coupling of the active layer with the substrate may include direct coupling, indirect coupling, coupling with a gap between, and/or coupling with an intrinsic layer between the two. In embodiments described herein, the photodiode may be constructed from a plurality of semiconductor materials. In other embodiments, the photodiode may be a surface mount device.
Referring first to
The active area 105 may be coupled with solder balls 120 or other connectors used to couple the active area to a circuit board, such as, for example, conductive epoxy bumps. In some embodiments, the active area 105 may include various surface-mount interconnects. These interconnects may include, for example, J-leads, solder balls, pins, fine pitch balls, leads, epoxy bumps, stencil printed polymer bumps, conductive adhesives, stud bumps, etc. Accordingly, the photodiode may be used as a surface-mount device with any type of grid array and/or packaging. In the embodiment shown in
The substrate 110 may include any semiconductor material. For example, the substrate may comprise indium phosphide, silicon, silicon germanium, and/or indium gallium arsenide. As another example, the active area 105 may include silicon, gallium, indium gallium arsenide, gallium phosphide, silicon carbide, titanium dioxide, germanium, gallium nitride, aluminum gallium nitride, and/or lead sulfide. In some embodiments, the active area 105 comprise a p-type semiconductor material and the substrate 110 comprises an n-type semiconductor material.
The photodiode may comprise any type of photodiode. For example, the photodiode may include a PN photodiode, a PNN photodiode, a PIN photodiode, a Schottky type photodiode, and/or an avalanche type photodiode.
Various embodiments use the substrate as a sunlight filter. Such a filter may eliminate the need for added filter components, which may reduce the photodiode stack height and dimension. Moreover, using the substrate as a sunlight filter reduces the complexity and cost of the photodiode. The sunlight filter also reduces photocurrent within the photodiode according to some embodiments. In other embodiments, the sunlight filter may also reduce power consumption from the photocurrent when the photodiode is reverse biased.
In various embodiments, the inventive photodiode may be included in the optical tag 320 as part of optical receiver 330. As such, the photodiode detects the information bearing signal and may be exposed to significant solar radiation. An optical tag employing a flip-chip photodiodes, for example, may provide a large field of view (e.g., 120 degrees). Moreover, such photodiodes may be inexpensive to construct and have a small size, a low weight, and modest power requirements.
In operation in a solar environment, photodiodes may undergo solar loading. Under the influence of solar loading, conventional photodiodes generate significant sun current, which can increase “shot noise” in the optical receiver, which reduces the signal to noise ratio and the effective optical range. Optical receivers including a flip-chip photodiode, in some embodiments, may exhibit significantly reduced solar current, higher signal-to-noise ratios, and improved optical range improvements. In addition, unlike conventional photodiodes, in some embodiments, flip-chip photodiodes can eliminate the need for an additional narrow-band filter attachment. Narrow-band filters used with conventional photodiodes often limit the field of view, whereas flip-chip photodiodes may avoid such limitations through use of the filtering substrate.
Specific details are given in the above description to provide a thorough understanding of the embodiments. However, it is understood that the embodiments may be practiced without these specific details. For example, circuits, structures, and/or components may be shown in block diagrams in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, components, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.
While the principles of the disclosure have been described above in connection with specific apparatuses and methods this description is made only by way of example and not as limitation on the scope of the disclosure.
Claims
1. A flip-chip photo diode, comprising:
- a substrate;
- an active layer comprising a top and a bottom, wherein the top of the active layer is coupled with the substrate; and
- a plurality of interconnects coupled with the bottom of the active layer and configured to couple with a circuit board.
2. The flip-chip photodiode according to claim 1, wherein the plurality of interconnects comprise at least one solder ball or at least one epoxy bump.
3. The flip-chip photodiode according to claim 1, further comprising a plurality of interconnects coupled with the bottom of the substrate and configured to couple with a circuit board.
4. The flip-chip photodiode according to claim 3, wherein the plurality of interconnects coupled with the bottom of the substrate comprise at least one solder ball or at least one epoxy bump.
5. The flip-chip photodiode according to claim 1, wherein the substrate layer comprises indium phosphide.
6. The flip-chip photodiode according to claim 1, wherein the active layer comprises a material selected from the group consisting of indium gallium arsenide, gallium arsenide, aluminum gallium arsenide, silicon, germanium, and lead sulfide.
7. The flip-chip photodiode according to claim 1, wherein the substrate comprises silicon.
8. The flip-chip photodiode according to claim 1, further comprising a gap between the substrate and the active layer.
9. The flip-chip photodiode according to claim 1, further comprising an antireflective coating on the top surface of the substrate.
10. The flip-chip photodiode according to claim 1, further comprising an intrinsic layer between the substrate and the active layer.
11. The flip-chip photodiode according to claim 1, wherein the substrate is used as a sunlight filter that eliminates the need for an added filter component.
12. The flip-chip photodiode according to claim 1, wherein the substrate reduces photocurrent.
13. The flip-chip photodiode according to claim 1, wherein the substrate reduces power consumption when reverse biased.
14. A flip-chip photo diode stack, comprising:
- a substrate with a top surface and a bottom surface, wherein the top surface is configured to receive light;
- an active layer with a top surface and a bottom surface, wherein the top surface of the active area is coupled with the bottom surface of the substrate; and
- a printed circuit board with at least a top surface, wherein the bottom surface of the active layer is coupled with the printed circuit board.
15. The flip-chip photodiode according to claim 14, further comprising at least one solder ball coupled with the bottom surface of the active layer and the printed circuit board.
16. The flip-chip photodiode according to claim 14, further comprising at least one connector coupled with the substrate and the printed circuit board.
17. The flip-chip photodiode according to claim 14, wherein the substrate layer comprises indium phosphide.
18. The flip-chip photodiode according to claim 14, further comprising an intrinsic semiconductor layer between the substrate and the active layer.
19. The flip-chip photodiode according to claim 14, wherein the active layer comprises a material selected from the group consisting of indium gallium arsenide; silicon, germanium, and lead sulfide.
20. The flip-chip photodiode according to claim 14, further comprising a gap between the substrate and the active layer.
21. The flip-chip photodiode according to claim 14, further comprising an antireflective coating on the top surface of the substrate.
22. A photodiode comprising:
- a substrate comprising a top surface and a bottom surface;
- an active region comprising a top surface and a bottom surface, wherein the top surface of the active region is aligned below the bottom surface of the substrate,
- wherein the photodiode is configured to receive light through the top surface of the substrate, and wherein at least a portion of the light is incident on the active region.
23. The photodiode according to claim 22, further comprising an intrinsic semiconductor layer between the substrate and the active region.
24. The photodiode according to claim 22, wherein the active region comprises a material selected from the group consisting of indium gallium arsenide, silicon, germanium, and lead sulfide.
25. The photodiode according to claim 22, further comprising at least one connector coupled with the bottom surface of the active region.
26. The photodiode according to claim 22, wherein the substrate is substantially transparent to light with a wavelength of 1550 nm.
27. The photodiode according to claim 22, wherein the substrate is substantially transparent to infrared light.
28. The photodiode according to claim 22, wherein the field of view of the photodiode is at least ±60°.
29. The photodiode according to claim 22, wherein the substrate is used as a sunlight filter that eliminates the need for an added filter component.
30. The photodiode according to claim 22, wherein the substrate reduces photocurrent.
31. The photodiode according to claim 22, wherein the substrate reduces power consumption when reverse biased.
Type: Application
Filed: Jul 11, 2008
Publication Date: Feb 5, 2009
Applicant: Cubic Corporation (San Diego, CA)
Inventors: Tony Maryfield (Poway, CA), Mahyar Dadkhah (San Diego, CA), Thomas Davidson (Santee, CA)
Application Number: 12/171,944
International Classification: H01L 31/00 (20060101);