Stacked Optical Sensor Package with Diffractive Light Channel
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Solution Overview
Problem
Optical integrated circuit sensor packages face challenges in reducing overall size, particularly in occupied area and volume, while maintaining functionality for proximity sensing and distance measuring applications using time-of-flight techniques.
Innovation Solution
The sensor die is mounted in a stacked relationship over the emitter die with a light channel region that includes an integrated diffractive optical element, allowing light to pass through and being optically aligned with the emitter die, and featuring electrical connections between the substrate and both dies, with the diffractive optical element being either passive or active for controlling light effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the sensor die and emitter die are mounted side-by-side on the package substrate, then the package can accommodate both components, but the occupied area in the X-Y plane increases
Solution Approach 1:
The patent transitions from a planar side-by-side arrangement to a three-dimensional stacked configuration. The sensor die is mounted on the package substrate, and the emitter die is mounted on top of the sensor die, utilizing the vertical Z-dimension. This dimensional change reduces the X-Y plane footprint while maintaining all necessary functional connections through vertical interlayer vias and conductive structures.
Solution Approach 2:
The patent implements a nested hierarchical structure where the emitter die is positioned on top of the sensor die, creating a stacked configuration. The sensor die serves as the base layer with its photosensitive regions, and the emitter die with light emission region is nested above it. This nesting arrangement allows both dies to occupy overlapping X-Y projections, significantly reducing the overall package area.
2Reliability
If a light barrier is added to prevent light from reaching the second photosensitive region, then cross-talk is reduced, but the device complexity and construction difficulty increase
Solution Approach 1:
The patent extracts the light barrier function from a separate structural component and integrates it directly into the emitter die design. The emitter die includes a light emission region that is spatially separated from the second photosensitive region through vertical stacking, and the light barrier functionality is incorporated as an integral part of the emitter die structure rather than adding separate barrier elements.
Solution Approach 2:
The patent merges multiple functions into the stacked die configuration itself. The vertical stacking arrangement simultaneously achieves light emission, light detection, and cross-talk prevention without requiring separate dedicated structures for each function. The spatial separation in the Z-direction inherently provides light isolation while maintaining electrical and optical functionality.
3Volume of moving object
If multiple separate components are used for light emission and detection, then functionality is maintained, but the overall package volume increases
Solution Approach 1:
The patent combines light emission and light detection functionalities into a single integrated stacked die structure. The sensor die provides photosensitive regions for detection, while the emitter die mounted on top provides light emission capability. This merging of functions into a compact vertical stack reduces package volume compared to separate lateral components while maintaining full optical functionality for time-of-flight sensing applications.
Solution Approach 2:
The patent utilizes the vertical Z-dimension to accommodate multiple optical components that would otherwise require lateral separation. By stacking the emitter die above the sensor die, the design achieves three-dimensional integration that reduces the X-Y footprint and overall package volume while preserving all necessary optical paths for emission and detection functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces the occupied area in the X-Y plane with a minimal increase in thickness, simplifies construction, and enhances functionality by providing a diffraction element within the sensor die, improving the efficiency of proximity sensing and distance measurement applications.
Implementation Method 1
The sensor die may further include, for the light channel region, an integrated diffractive optical element configured to diffract the light passing through the light channel
Implementation Method 2
The emitter die 16 may, for example, comprise a vertical cavity surface emitting laser (VCSEL) diode which is configured to emit light perpendicularly from the front face of the die
Implementation Method 3
an adhesive layer extending over the upper surface and encapsulating the emitter die
Data Source
AI summary
An optical sensor package includes an emitter die mounted to an upper surface of a package substrate. A sensor die is mounted to the upper surface of the package substrate using a film on die (FOD) adhesive layer that extends over the upper surface and encapsulates the emitter die. The sensor die is positioned in a stacked relationship with respect to the emitter die such that a light channel region which extends through the sensor die is optically aligned with the emitter die. Light emitted by the emitter die passes through the light channel region of the sensor die. The emitter die and the sensor die are each electrically coupled to the package substrate.