Chip-Scale Image Sensor Thin Film Segmentation
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Solution Overview
Problem
The thin-film optical filters on image sensor wafers tend to warp and delaminate during the singulation process, leading to defects in high-volume products like cameras and motor vehicles, due to the lack of sufficient inter-film distances between adjacent filters.
Innovation Solution
Incorporating inter-film distances between thin films on the transparent wafer to prevent cracking and delamination, while aligning each thin film with a respective image sensor die and maintaining a portion of the transparent wafer surface uncovered to facilitate inspection, allowing for controlled dicing and reducing the risk of filter warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thin-film optical filters are placed close together on the transparent wafer, then the manufacturing density is improved, but the filters warp and delaminate during singulation
Solution Approach 1:
The patent introduces inter-film distances that segment the continuous thin-film optical filter layer into separate sections. Each thin film is isolated from adjacent films by defined spacing, preventing the propagation of warping and delamination forces between filters during the singulation process. This segmentation allows high manufacturing density while maintaining individual filter stability.
2Productivity
If the transparent wafer surface is fully covered with thin-film optical filters, then the manufacturing efficiency is improved, but the inspection difficulty increases
Solution Approach 1:
The patent applies local quality by leaving specific portions of the transparent wafer surface uncovered, creating inspection regions where the substrate is exposed. These localized uncovered areas allow optical inspection systems to access and detect defects in the thin-film optical filters and underlying structures without interference from adjacent filters, while the majority of the wafer remains covered for manufacturing efficiency.
3Manufacturing precision
If dicing is performed without inter-film distances, then the manufacturing precision is improved, but the filters crack and delaminate
Solution Approach 1:
The patent implements preliminary action by pre-establishing inter-film distances between thin-film optical filters before the dicing process. These predetermined spacing regions create stress relief zones that prevent crack propagation and delamination during subsequent dicing operations, allowing precise kerf formation without compromising filter integrity.
Data Source
AI summary
A chip-scale image sensor package includes a semiconductor substrate, a transparent substrate, a thin film, and a plurality of conductive pads. The semiconductor substrate has (i) a pixel array, and (ii) a peripheral region surrounding the pixel array. The transparent substrate covers the pixel array, has a bottom substrate surface proximate the pixel array, and a top substrate surface opposite the bottom substrate surface. The thin film is on a region of the top substrate surface directly above both (i) the entire pixel array and (ii) a portion of the peripheral region adjacent to the pixel array. Each of the plurality of conductive pads is located within the peripheral region, and is electrically connected to the pixel array. A portion of each of the plurality of conductive pads is not directly beneath the thin film.