Bonding Pad Test Layout for Stacked Chip Misalignment Detection
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Solution Overview
Problem
Existing semiconductor devices face challenges in accurately detecting and measuring misalignment between stacked semiconductor structures, which affects electrical connectivity and reliability, particularly when using bonding pads for vertical stacking.
Innovation Solution
The semiconductor device incorporates lower and upper test pads and test terminals that are formed alongside bonding pads, allowing for precise alignment detection and measurement of misalignment extent by monitoring current flow between these test structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bonding pads are used for vertical stacking of semiconductor structures, then electrical connectivity between layers is achieved, but misalignment between layers cannot be accurately detected or measured
Solution Approach 1:
The bonding pad structure is segmented into multiple functional zones: a first bonding pad region for primary electrical connection, a second bonding pad region offset from the first, and test pad regions. This segmentation allows the same physical structure to serve both connectivity and measurement functions, enabling misalignment detection without compromising electrical connectivity.
Solution Approach 2:
Test pads are introduced as intermediary elements between the bonding pads and the measurement system. These test pads receive test signals and facilitate the detection of misalignment conditions by providing a controlled interface for measurement, separating the measurement function from the primary bonding function.
2Measurement precision
If additional test structures are added to detect misalignment, then measurement capability is improved, but device area increases
Solution Approach 1:
The bonding pad structure is designed to perform multiple functions simultaneously: the first and second bonding pad regions provide electrical connectivity while also serving as reference structures for misalignment measurement. The test pads integrated within the same structure enable measurement without requiring separate dedicated test areas, thus achieving multi-functionality that resolves the area contradiction.
Solution Approach 2:
The measurement function is merged with the bonding pad structure by integrating test pads and offset bonding pad regions into the same physical layout. This combination allows misalignment detection capabilities to be embedded within the existing bonding infrastructure, eliminating the need for separate measurement structures and preserving device area.
3Manufacturing precision
If bonding pads are designed for precise alignment, then manufacturing complexity increases, but alignment accuracy improves
Solution Approach 1:
The bonding pad structure is designed with predetermined geometric relationships before manufacturing: the second bonding pad region is intentionally offset from the first by a specific distance, and test pads are positioned at predetermined locations. These preliminary design decisions establish built-in reference frames that guide alignment during manufacturing, improving accuracy without requiring complex real-time adjustments.
Solution Approach 2:
The design utilizes controlled parameter variations, specifically the offset distance between bonding pad regions and the positioning of test pads, to create measurable reference structures. By carefully selecting and maintaining these geometric parameters, the structure provides inherent alignment references that improve manufacturing precision while keeping the overall design relatively simple.
Data Source
AI summary
A semiconductor device includes: a lower semiconductor structure including one or more first lower test pads, one or more second lower test pads that are alternately arranged with the one or more first lower test pads, and a lower test terminal that is electrically connected to the second lower test pad through a second lower test line; and an upper semiconductor structure positioned over the lower semiconductor structure and including an upper test pad and an upper test terminal that is electrically connected to the upper test pad through an upper test line, wherein, when the lower semiconductor structure and the upper semiconductor structure are aligned, the upper test pad overlaps with and contacts a corresponding first lower test pad among the one or more first lower test pads, and is spaced apart from the second lower test pad that is adjacent to the corresponding first lower test pad.