TSV Pad Opening Align Key for Stacked Image Sensor Alignment
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Solution Overview
Problem
The challenge in manufacturing stacked type image sensors with a through-silicon via (TSV) structure is the difficulty in accurately aligning and monitoring the connection between the lower and upper devices, leading to potential connection failures that increase resistance and affect the sensor's functionality.
Innovation Solution
Incorporating a TSV pad with an opening as an align key to facilitate precise alignment and connection of the TSV structure, ensuring proper electrical contact between the upper and lower devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TSV structure is formed to electrically connect lower and upper devices, then electrical connection is achieved, but alignment accuracy and connection reliability deteriorate due to lack of align key
Solution Approach 1:
The patent introduces a TSV pad as an intermediary element between the lower and upper devices. This TSV pad includes a pad opening that serves as an align key, enabling accurate alignment during bonding. The pad opening provides a visual reference that facilitates precise positioning of the upper device relative to the lower device, thereby resolving the alignment accuracy issue while maintaining connection reliability.
2Device complexity
If no align key is used in TSV structure, then device complexity is reduced, but monitoring connection failure becomes difficult
Solution Approach 1:
The patent utilizes the pad opening in the TSV pad as a visual indicator (align key) that can be monitored during and after the bonding process. The presence and position of this opening provide visual feedback that helps detect alignment issues and connection failures without adding complex monitoring systems, thus maintaining structural simplicity while improving detectability.
3Productivity
If TSV connection fails and is not fixed, then manufacturing time is saved by not reworking, but resistance increases and sensor functionality deteriorates
Solution Approach 1:
The patent implements preliminary alignment using the TSV pad opening as an align key before bonding. This preliminary action ensures correct positioning and prevents connection failures, eliminating the need for rework and maintaining both manufacturing efficiency and electrical reliability. The align key allows operators to verify alignment before final bonding, preventing defective connections from occurring in the first place.
Data Source
AI summary
An image sensor having a lower device, an upper devise, and a TSV structure is provides. The lower device may include a lower substrate, a lower TSV pad, and a lower interlayer insulating layer. The lower TSV pad may be formed over the lower substrate. The lower interlayer insulating layer may cover the lower TSV pad. The upper device may include an upper substrate, an upper TSV pad, and an upper interlayer insulating layer. The upper TSV pad may be formed over the upper substrate. The upper interlayer insulating layer may cover the upper TSV pad. The TSV structure may vertically pass through the upper device and electrically connect the upper TSV pad to the lower TSV pad. The upper TSV pad may include an upper opening. The lower TSV pad may include a unit pad and a lower opening. The unit pad may be exposed through the upper opening and contacts the TSV structure in a top view.