Light-Shielded Camera Wafer Stack Opaque Coating
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Solution Overview
Problem
Wafer-level CMOS manufacturing of cameras lacks effective light-shielding solutions for side walls, leading to image contrast degradation due to light entry through the lens or cover glass, especially in compact devices like medical endoscopes where space constraints are challenging.
Innovation Solution
A method for manufacturing light-shielded cameras involves pre-cutting and depositing an opaque material on the camera wafer stack before dicing, followed by applying an opaque coating to the second-side surfaces of the camera dies, forming planar side walls that prevent light from entering the camera through sides and backside, ensuring effective light-shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If wafer-level CMOS manufacturing is used to create compact cameras, then manufacturing cost is reduced and device size is minimized, but light-shielding capability is insufficient leading to image contrast degradation
Solution Approach 1:
The camera wafer stack is divided into multiple camera dies through dicing, and light-shielding opaque material is deposited into the pre-cuts and gaps between individual camera dies. This segmentation approach allows light-shielding treatment to be applied to each discrete unit while maintaining the compact wafer-level structure.
Solution Approach 2:
Pre-cuts are formed in the camera wafer stack before dicing to create spaces for light-shielding material. This preliminary action enables the deposition of opaque material in the gaps between camera dies before the final dicing process, ensuring light-shielding is integrated into the manufacturing flow rather than added as a separate post-processing step.
2Object-affected harmful factors
If light baffle is added to prevent light from entering the camera, then image contrast is improved, but device complexity and space requirements increase
Solution Approach 1:
The light-shielding opaque material is merged with the manufacturing process of the camera wafer stack itself, rather than being a separate light baffle component. The opaque material is deposited directly into the pre-cuts and gaps during wafer-level processing, combining the light-shielding function with the structural fabrication of the camera array.
Solution Approach 2:
The camera wafer stack structure itself provides the light-shielding function through the opaque material deposited in its gaps and pre-cuts. The manufacturing process creates the necessary features (pre-cuts, gaps between dies) that are then filled with light-shielding material, allowing the structure to serve both mechanical and optical functions without requiring external light baffles.
3Object-affected harmful factors
If opaque material is deposited in pre-cuts before dicing, then light-shielding is achieved, but manufacturing process steps are increased
Solution Approach 1:
Pre-cuts are formed and opaque material is deposited before the final dicing step, allowing light-shielding to be integrated into the wafer-level manufacturing process. This preliminary action enables batch processing of light-shielding treatment across multiple camera dies simultaneously, rather than treating individual cameras separately after dicing.
Solution Approach 2:
The pre-cut formation and opaque material deposition steps serve multiple functions: they create the structural separation between camera dies, provide light-shielding, and prepare the surfaces for subsequent dicing. This multi-functionality reduces the need for separate dedicated light-shielding steps for each individual camera.
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
The method significantly reduces light entry through side walls and backside, enhancing image contrast and preventing light flare, as demonstrated by improved image quality compared to cameras without adequate light-shielding measures.
Implementation Method 1
depositing an opaque material in the pre-cuts... applying an opaque coating to second-side surfaces of the camera dies... forms four sidewalls parallel to an optical axis... Each of the four sidewalls are coated by an opaque coating
Data Source
AI summary
A method for manufacturing light-shielded cameras includes forming a plurality of camera dies by dicing a camera wafer stack including (a) an image sensor wafer having a plurality of image sensors, (b) a cover glass bonded to the image sensor wafer, and (c) a lens wafer bonded to the cover glass and having a plurality of lenses, to form a plurality of camera dies. The method further includes, prior to the step of dicing, (i) from a first side of the image sensor wafer facing away from the cover glass and at least partly covered by an opaque layer, pre-cutting a sensor-cover wafer stack that includes the image sensor wafer and the cover glass, and (ii) depositing an opaque material in the pre-cuts. The method also includes, after the step of dicing, applying an opaque coating to second-side surfaces, of the camera dies, formed by the step of dicing.