Matrix IC Fault Isolation for Large CMOS Sensors
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Solution Overview
Problem
Conventional semiconductor manufacturing processes result in high defect rates for very large area CMOS image sensors, leading to near zero yield due to fatal defects such as short circuits, which are unacceptable for sensors larger than 5x5 cm, as a single defect can render the entire wafer scrap.
Innovation Solution
A matrix type integrated circuit with a 2D array of cell elements, conductive traces, and switches, including fault detectors and an automatic fault isolator, which selectively disables defective columns to prevent contamination of the entire chip, allowing non-conforming chips to become conforming by isolating faults and improving yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional semiconductor manufacturing processes are used for very large area CMOS image sensors, then production capacity is maintained, but fatal defects such as short circuits occur frequently leading to near zero yield
Solution Approach 1:
The image sensor is divided into multiple independently controllable columns, each with its own switch that can disconnect defective columns from the communal module. This segmentation allows the sensor to function with only a portion of columns active, thereby maintaining productivity even when defects are present.
Solution Approach 2:
The patent introduces programmable switches that can change the operational state of columns based on detected defects. By dynamically adjusting which columns are active or inactive, the system adapts to defect conditions and maintains acceptable yield levels.
2Productivity
If a single fatal defect occurs in a very large area sensor, then the entire wafer is rendered scrap, but adding fault isolation capability increases device complexity
Solution Approach 1:
The sensor is segmented into columns with individual switches, allowing defective columns to be isolated. This segmentation adds some circuit elements but prevents entire wafers from being scrapped due to single defects, significantly improving yield.
Solution Approach 2:
The system includes automatic defect detection and isolation capabilities that operate without external intervention. The fault detection circuitry and programmable switches work autonomously to identify and isolate defective columns, reducing the need for complex external testing and repair processes.
3Ease of manufacture
If communal modules distribute signals to all cell elements, then signal distribution is efficient, but a defect in one trace can contaminate the entire chip
Solution Approach 1:
The communal module's signal distribution is segmented by column, with each column having its own switch. This allows the system to maintain efficient communal signal distribution while preventing defect propagation by isolating affected columns through their respective switches.
Solution Approach 2:
Programmable switches act as intermediaries between the communal module and individual columns. These switches control the flow of signals and can block defect propagation while allowing normal signal distribution to proceed efficiently through the communal infrastructure.
Data Source
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AI summary
Technology is described for selectively disconnecting a communal module (e.g., horizontal power and signal distribution network) from conductive traces (e.g., vertical columns) that are coupled to cell elements. In one example, a matrix type integrated circuit includes a two dimensional (2D) array of cell elements, a plurality of conductive traces, a communal module, and a plurality of switches. Each cell element in the 2D array provides a similar function. The plurality of conductive traces is substantially parallel to a first axis of the 2D array. Each conductive trace is coupled to a conductive interconnect of cell elements adjacent to the conductive trace. The communal module is configured to provide distribution of at least one electrical signal to the cell elements in the 2D array via at least two conductive traces that are substantially parallel to the first axis.