Optical integrated circuit sensor package with sensor / transmitter die stack configuration

Abstract

This disclosure relates to an optical integrated circuit sensor package with a sensor / emitter die stack configuration. For example, the optical sensor package includes an emitter die mounted to the upper surface of a package substrate. The sensor die is mounted to the upper surface of the package substrate using a die-on-film (FOD) adhesive layer that extends and encapsulates the emitter die on the upper surface of the package substrate. The sensor die is positioned in a stacked relationship relative to the emitter die such that an optical channel region extending through the sensor die is optically aligned with the emitter die. Light emitted by the emitter die passes through the optical channel region of the sensor die. Both the emitter die and the sensor die are electrically coupled to the package substrate.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 187,473, filed May 12, 2021, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The embodiments relate to optical integrated circuit sensor packages that include both a sensor die and a transmitter die. Background Technology

[0004] refer to Figure 1 The diagram shows a cross-section of an optical integrated circuit sensor package 10. The package includes, for example, a package substrate 12 in the form of a lead frame, having an upper surface on which a sensor die 14 and an emitter die 16 are mounted. The sensor die 14 and emitter die 16 can be mounted to the package substrate 12 using any suitable die attachment mechanism known to those skilled in the art. Bonding wires 18 are used to electrically connect pads (not explicitly shown) on the front side of the die to conductive portions of the package substrate 12 (e.g., leads of the lead frame). The sensor die 14 includes a first photosensitive region 20 and a second photosensitive region 22 located on the front side of the die. Photosensitive regions 20 and 22 can, for example, each be formed from one or more single-photon avalanche diode (SPAD) devices. The emitter die 16 includes a light-emitting region 24 on the front side of the die. The emitter die 16 can, for example, include a vertical-cavity surface-emitting laser (VCSEL) diode configured to emit light perpendicularly from the front side of the die. In one embodiment, the light can have any suitable wavelength for the desired sensing application, but is preferably emitted in the infrared or near-infrared range.

[0005] A cover 30 is mounted on a package substrate 12. The cover 30 includes a peripheral outer wall 32 defining a cavity and a front wall (or top wall) 34, and an inner wall 36 extending between opposite sides of the peripheral outer wall 32, dividing the cavity into a first cavity region 38 and a second cavity region 40. The end edges of the peripheral outer wall 32 are mounted to the upper surface of the package substrate 12 using a suitable adhesive to enclose the sensor die 14 and the transmitter die 16 within the cavity of the cover 30 (more specifically, the sensor die 14 is partially located within each of the first and second cavity regions, while the transmitter die 16 is only located within the first cavity region). The inner wall 36 is positioned between a first photosensitive region 20 and a second photosensitive region 22 and is sealed to the front surface of the sensor die 14 by an adhesive to form a light barrier that prevents light emitted by the light-emitting region 24 of the transmitter die 16 within the first cavity region 38 from passing through the cavity of the cover 30 to the second photosensitive region 22 within the second region 40. However, the light barrier does not prevent such emitted light from reaching the first photosensitive region 20 within the first cavity region 38.

[0006] The front wall (or top wall) 34 of the cover 30 includes a first opening 42, which is optically aligned with the position of the light-emitting region 24 for the emitter die 16. An optical element 44 is mounted at (or possibly within) the first opening 42. The front wall (or top wall) 34 of the cover 30 further includes a second opening 46, which is optically aligned with the position of the second photosensitive region 22 for the sensor die 14. An optical element 48 is mounted at (or possibly within) the second opening 44. Optical elements 44 and 48 may be designed to include lens and / or filter structures required for optical sensing applications.

[0007] The optical integrated circuit sensor package 10 is particularly suitable for proximity sensing or distance measurement applications using time-of-flight (ToF) technology. A light pulse 4 is emitted from the light-emitting region 24 of the transmitter die 16, and this emission event is detected by the first photosensitive region 20 of the sensor die 14 (using the reflected light path 6) to provide an emission pulse time reference. The emitted light pulse 4 exits the package 10 through the optical element 44 and the first opening 42, and is reflected back to the package from a target object (not explicitly shown). The reflected light pulse 8 passes through the optical element 48 and the second opening 46, and is detected by the second photosensitive region 22 of the sensor die 14 to provide a reflected pulse time reference. The time taken for the light pulse to propagate to the object and be reflected back and sensed (i.e., the difference between the reflected pulse time reference and the emitted pulse time reference) can be used to determine the distance between the object and the package 10 based on the known speed of light.

[0008] and Figure 1Similarly, package 10, which includes multiple integrated circuit dies and must be designed according to specific design spacing rules, and must further include optical elements, is an optical integrated circuit sensor package. The focus is on the overall size of the package (both in terms of the area occupied in the XY plane and the total volume taking into account the thickness in the Z direction). It would be particularly advantageous if the optical integrated circuit sensor package could support a reduced footprint and a simpler structure. Summary of the Invention

[0009] In one embodiment, an optical sensor package includes: a package substrate; an emitter die mounted to an upper surface of the package substrate; an adhesive layer extending over the upper surface and encapsulating the emitter die; a sensor die mounted in a stacked relationship to the upper surface of the adhesive layer, wherein the sensor die is positioned to cover the emitter die; the sensor die includes an optical channel region extending through the sensor die and optically aligned with the emitter die such that light emitted by the emitter die passes through the optical channel region of the sensor die; and an electrical connection between each of the emitter die and the sensor die and the package substrate.

[0010] The sensor die may further include an integrated diffractive optical element for the optical channel region, the integrated diffractive optical element being configured to diffract the light passing through the optical channel. The integrated diffractive optical element may include, for example, a passive element formed of a plurality of metal structures associated with one or more metallization layers of the sensor die. Alternatively, the integrated diffractive optical element may include, for example, an active element formed of a plasmonic device or a liquid crystal on silicon (LCOS) device.

[0011] In embodiments of active elements, one or more of the following may be provided: selectively configurable diffraction effects, selectively configurable on / off switches, selectively controllable diffraction patterns, selectively controllable polarization filters, and selectively controllable lenses.

[0012] In one embodiment, the adhesive layer may be provided by a die-on-film (FOD) structure.

[0013] In one embodiment, an apparatus includes: a substrate; a first integrated circuit die mounted to an upper surface of the substrate; an adhesive film extending over the upper surface and encapsulating the first integrated circuit die; a second integrated circuit die mounted in a stacked relationship to the upper surface of the adhesive film, wherein the second integrated circuit die is positioned to cover the first integrated circuit die; and an electrical connection between each of the first and second integrated circuit dies and the substrate. Attached Figure Description

[0014] To better understand the embodiments, reference will now be made to the accompanying drawings by way of example only, in which:

[0015] Figure 1 This is a cross-section of an optical integrated circuit sensor package;

[0016] Figure 2 It is a cross-section of an optical integrated circuit sensor package; and

[0017] Figures 3 to 5 It shows integration in Figure 2 Details of the optical diffraction element in the sensor die of the optical integrated circuit sensor package are shown in the figure. Detailed Implementation

[0018] refer to Figure 2The diagram shows a cross-section of an optical integrated circuit sensor package 50. The package includes, for example, a package substrate 52 in the form of a lead frame, having an upper surface on which an emitter die 56 is mounted. The emitter die 56 can be mounted to the package substrate 52 using any suitable die attachment mechanism known to those skilled in the art. The emitter die 56 includes a light-emitting region 64 on the front side of the die. The emitter die 56 may, for example, include a vertical-cavity surface-emitting laser (VCSEL) diode configured to emit light perpendicularly from the front side of the die. In one embodiment, the light can have any suitable wavelength, but is preferably emitted in the infrared or near-infrared range. One or more bonding lines 58 are used to electrically connect pads (not explicitly shown) on the front side of the emitter die 56 to a conductive portion of the package substrate 52 (e.g., leads of the lead frame). A thick die attachment film layer 53 extends in contact with the upper surface of the package substrate 52 and further encapsulates the emitter die 56 and its bonding lines 58. This is known in the art as a “die-on-film” (FOD) structure. A sensor die 54 is mounted to the upper surface of a package substrate 52 using a thick die-attachment film layer 53. The sensor die 54 is positioned in a stacked relationship relative to the emitter die 56 in the Z direction, such that in the XY plane, the sensor die 54 covers (i.e., completely covers) the emitter die 56. With this stacked die arrangement, light emitted by the light-emitting region 64 of the emitter die 56 (in the Z direction perpendicular to the upper surface of the package substrate 52) will pass through the covered portion of the film layer 53 and completely through the thickness of the sensor die 54 in the light channel region 55, which extends from the rear surface to the front surface of the sensor die. This is possible because many materials used in the manufacture of the sensor die (silicon, oxides, etc.) are transparent to the preferred infrared or near-infrared light emitted by the emitter die 56. The light channel region 55 is optically aligned with the light-emitting region 64 of the emitter die 56. In one embodiment, the optical channel region 55 may be partially defined by a region of the semiconductor substrate of the sensor die 54 having a lower intrinsic doping concentration, for example, different from the remainder of the semiconductor substrate in which active semiconductor devices (such as analog and / or digital circuits) are fabricated. In one embodiment, the optical channel region 55 may also be partially defined by a region of an overlying interconnect layer that does not have metal electrical interconnects and vias for electrically interconnecting the integrated circuit of the sensor die. Bonding lines 59 are used to electrically connect pads (not explicitly shown) on the front side of the die 54 to conductive portions (e.g., leads of a lead frame) of the package substrate 52. The integrated circuit of the sensor die 54 includes a first photosensitive region 60 and a second photosensitive region 62 on the front side of the die. Each photosensitive region 60 and 62 may be formed, for example, by one or more single-photon avalanche diode (SPAD) devices integrated on and / or within the semiconductor substrate.

[0019] A cover 70 is mounted on a package substrate 52. The cover 70 includes a peripheral outer wall 72 defining a cavity and a front wall (or top wall) 74, and an inner wall 76 extending between opposite sides of the peripheral outer wall 72, dividing the cavity into a first cavity region 78 and a second cavity region 80. The end edges of the peripheral outer wall 72 are mounted to the upper surface of the package substrate 52 using a suitable adhesive to enclose the sensor die 54 and the transmitter die 56 within the cavity of the cover 70 (more specifically, the sensor die 54 is partially within each of the first and second cavity regions, while the transmitter die 56 is only within the first cavity region). The inner wall 76 is positioned between the first photosensitive region 60 and the second photosensitive region 62 and is sealed to the front surface of the sensor die 54 by an adhesive to form a light barrier that prevents light emitted by the light emitting region 64 of the transmitter die 56 (which passes through the channel region 55 and enters the first cavity region 78) from reaching the second photosensitive region 62 within the second region 80 through the cavity of the cover 70. However, this light barrier does not prevent such emitted light within the first cavity region 78 from reaching the first photosensitive region 60.

[0020] The front wall (or top wall) 74 of the cover 70 includes a first opening 82, which is optically aligned with the positions of both the channel region 55 and the light-emitting region 64 for the transmitter die 56. An optical element 84 is mounted within the first opening 82. The front wall (or top wall) 74 of the cover 70 further includes a second opening 86, which is optically aligned with the position of the second photosensitive region 62 for the sensor die 54. An optical element 88 is mounted within the second opening 84. Optical elements 84 and 88 are typically transparent glass structures, but may also be designed to include lens and / or filter structures required for optical sensing applications.

[0021] In addition to the first photosensitive region 60 and the second photosensitive region 62 integrated in the sensor die 54 on the front side, the sensor die further includes an integrated diffractive optical element (DOE) 90, which is located, for example, on or near the front side of the die and is provided in a manner connected to (e.g., as part of) the light channel region 55. The integrated diffractive optical element 90 is optically aligned in the Z direction with the light emitting region 64 of the emitter die 56 in the channel region 55 and is configured to diffract light emitted from the light emitting region 64 of the emitter die 56 and passing through the channel region 55. In one embodiment, the integrated diffractive optical element 90 is a passive element provided in the form of a pattern of a metal structure 92 (e.g., forming a grating). The metal structure 92 is formed by one or more metallization layers 94 of an interconnect layer 96 and is located within the one or more metallization layers 94 of the interconnect layer 96, which extends on the top surface of the semiconductor substrate 98 of the sensor die 54 (see [link to documentation]). Figure 3– Those skilled in the art will understand that the interconnect layer, in the region outside the channel region 55, also includes metal lines and vias (typically reference numeral 9) in the metallization layer 94 for electrical connection of integrated circuit devices. In another embodiment, the integrated diffractive optical element 90 is a passive element provided in the form of a pattern of transparent structures 100, 102 with different refractive indices within the interconnect 96 (see…). Figure 4 In yet another embodiment, the integrated diffractive optical element 90 is an active element provided in the form of a plasmonic diffraction element or a liquid crystal on silicon (LCOS) diffraction element (see [link to relevant documentation]). Figure 5 The active integrated diffractive optics element can be controlled by control circuitry located on (or externally provided and electrically coupled to) sensor die 54 to actively control the type of diffraction effect to be provided. For example, the active integrated diffractive optics element can be configured to provide a controllable on / off function to selectively block / pass through light emitted by emitter die 56. As another example, the active integrated diffractive optics element can be configured to provide a controllable diffraction pattern (e.g., through appropriate control of one or more of the following: the number of openings, the size of the openings, and the spacing between the openings). In another example, the active integrated diffractive optics element can be configured to provide a controllable polarization filter (e.g., switching between polarization modes). In yet another example, the active integrated diffractive optics element can be configured to provide a controllable lens (e.g., for controlling the beam shape, focus, field of view, etc., of the emitted light pulse 4).

[0022] The optical integrated circuit sensor package 50 is particularly suitable for proximity sensing or distance measurement applications using time-of-flight (ToF) technology. A light pulse 4 is emitted from the light-emitting region 64 of the emitter die 56, passes through the channel region 55, and enters the first cavity region 78. The emitted light pulse 4 is further diffracted (actively or passively) by the integrated diffractive optics element 90. This light emission event is detected by the first photosensitive region 60 of the sensor die 54 (using the reflected light path 6) to provide an emission pulse time reference. The emitted and diffracted light pulse 4 exits the package 50 through the optics element 84 and the first opening 82, and is reflected back to the package from a target object (not explicitly shown). The reflected light pulse 8 passes through the optics element 88 and the second opening 86, and is detected by the second photosensitive region 62 of the sensor die 54 to provide a reflected pulse time reference. The time taken for the light pulse to propagate to the object and be reflected back and sensed (i.e., the difference between the reflected pulse time reference and the emitted pulse time reference) can be used to determine the distance between the object and the package 50 based on the known speed of light.

[0023] Figure 2 The package 50 relative to Figure 1The advantage of the package 10 is that it reduces the footprint in the XY plane at the cost of a relatively small increase in thickness in the Z direction. Another advantage is that the functionality of the optical diffraction element 90, whether passive or active, is provided by the sensor die 54. This simplifies the structure and further reduces the number of parts in the overall device.

[0024] The preceding description has provided a complete and informative description of exemplary embodiments of the invention through exemplary and non-limiting examples. However, various modifications and adaptations will become apparent to those skilled in the art when read in conjunction with the accompanying drawings and appended claims, given the preceding description. Nevertheless, all such and similar modifications taught in this invention will still fall within the scope of the invention as defined in the appended claims.

Claims

1. An optical sensor package, comprising: Package substrate; The transmitter die, the rear surface of which is mounted to the upper surface of the package substrate; An adhesive layer extends over the upper surface and encapsulates the transmitter die on its side and front surfaces, wherein the adhesive layer includes a portion covering the transmitter die; A sensor die is mounted to the upper surface of the adhesive layer in a stacked relationship, wherein the sensor die is positioned to cover the portion of the adhesive layer that covers the transmitter die; The sensor die includes an optical channel region that extends through the thickness of the sensor die and is optically aligned with the transmitter die, such that light emitted by the transmitter die passes through the optical channel region of the sensor die. as well as Electrical connection between each of the transmitter die and the sensor die and the package substrate.

2. The optical sensor package according to claim 1, wherein the package substrate includes a lead frame.

3. The optical sensor package of claim 1, wherein the transmitter die is a vertical cavity surface-emitting laser (VCSEL) diode, and wherein the sensor die includes at least one photosensitive region.

4. The optical sensor package of claim 3, wherein the at least one photosensitive region comprises one or more single-photon avalanche diode (SPAD) devices.

5. The optical sensor package of claim 1, wherein the sensor die includes an integrated diffractive optical element for the optical channel region, the integrated diffractive optical element being configured to diffract the light passing through the optical channel.

6. The optical sensor package of claim 5, wherein the integrated diffractive optical element is a passive element formed by a transparent structural pattern with different refractive indices.

7. The optical sensor package of claim 5, wherein the integrated diffractive optical element is a passive element formed of a plurality of metal structures, the plurality of metal structures being formed by one or more metallization layers of the sensor die and located within one or more metallization layers of the sensor die.

8. The optical sensor package according to claim 5, wherein the integrated diffractive optical element is an active element.

9. The optical sensor package of claim 8, wherein the active element is selected from the group consisting of: plasmonic devices and liquid crystal on silicon (LCOS) devices.

10. The optical sensor package of claim 8, wherein the operating features of the active element are selected from the group consisting of: selectively configurable diffraction effects, selectively configurable on / off switches, selectively controllable diffraction patterns, selectively controllable polarization filters, and selectively controllable lenses.

11. The optical sensor package of claim 1, further comprising a cover including a peripheral wall and a front wall, the cover being mounted to the package substrate, and wherein the front wall includes a first opening optically aligned with the optical channel region of the sensor die and optically aligned with the transmitter die.

12. The optical sensor package of claim 11, wherein the front wall of the cover further includes a second opening optically aligned with the photosensitive region of the sensor die.

13. The optical sensor package of claim 1, wherein the adhesive layer is a thin-film FOD structure on the die.

14. The optical sensor package of claim 1, wherein the sensor die comprises a semiconductor substrate, and wherein the optical channel region is at least partially defined by a region of the semiconductor substrate having an intrinsic doping concentration level different from that of another region in which an active integrated circuit is fabricated.

15. The optical sensor package of claim 1, wherein the sensor die comprises: Semiconductor substrate; as well as An interconnect layer extends over the semiconductor substrate; as well as The optical channel region extends from the back side of the sensor die through a first portion of the semiconductor substrate and a first portion of the interconnect layer to the front side of the sensor die.

16. The optical sensor package of claim 15, wherein the semiconductor substrate further includes a second portion in which a photosensitive circuit is formed, and wherein the first portion and the second portion of the semiconductor substrate have different intrinsic doping concentration levels.

17. The optical sensor package of claim 16, wherein the interconnect layer includes a second portion in which electrical interconnects and vias are formed, and further includes an integrated diffractive optical element within the first portion of the interconnect layer.

18. The optical sensor package of claim 17, wherein the integrated diffractive optical element is a passive element selected from the group consisting of: transparent structural patterns with different refractive indices, and a plurality of metal structures forming a grating.

19. The optical sensor package of claim 17, wherein the integrated diffractive optical element is an active element selected from the group consisting of: plasmonic devices and liquid crystal on silicon (LCOS) devices.

20. An apparatus comprising: Substrate; A first integrated circuit die is mounted on the upper surface of the substrate; A thin-film FOD structure on a die provides a die with a bonding film layer that extends over the upper surface and completely encapsulates the first integrated circuit die. A second integrated circuit die is mounted on the upper surface of the FOD structure in a stacked relationship, wherein the second integrated circuit die is positioned to cover the first integrated circuit die. as well as Electrical connection between each of the first integrated circuit die and the second integrated circuit die and the substrate.

21. The apparatus of claim 20, wherein the first integrated circuit die includes a light emitter configured to emit a light beam passing through an optical channel region extending through the thickness of the second integrated circuit die, and wherein the second integrated circuit die includes a light sensor configured to sense the emitted light beam.

22. The apparatus of claim 21, wherein the second integrated circuit die includes an integrated diffractive optical element for the optical channel region, the integrated diffractive optical element being configured to diffract the light beam passing through the optical channel region.

23. The apparatus of claim 21, wherein the second integrated circuit die comprises: Semiconductor substrate; as well as An interconnect layer extends over the semiconductor substrate; as well as The optical channel region extends from the back side of the second integrated circuit die through a first portion of the semiconductor substrate and a first portion of the interconnect layer to the front side of the second integrated circuit die.

24. The apparatus of claim 23, wherein the second integrated circuit die includes an integrated diffractive optical element for the optical channel region, the integrated diffractive optical element being configured to diffract the light beam passing through the optical channel region.

25. The apparatus of claim 20, wherein the first integrated circuit die includes a light-emitting region, and wherein the FOD structure covers the light-emitting region.

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