Fine-Pitch IC Die Interconnect Structure for Overlay Alignment
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Solution Overview
Problem
The existing technologies for wafer-level packaging of semiconductor devices face challenges in maintaining the alignment and reliability of IC dies due to non-uniform stress and improper alignment, especially as the demand for finer pitch die connectors increases, leading to potential shifts and misalignment issues during the encapsulation process.
Innovation Solution
The process involves forming conductive bumps with specific layer structures and pitches to compensate for expected shifts during encapsulation, using a seed material layer with sublayers like titanium and copper, and applying a diffusion barrier layer to prevent intermetallic compound formation, along with a reflow process to shape the bumps, and subsequent underfill and insulating encapsulation to secure the IC dies and connectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional wafer-level packaging is used, then manufacturing simplicity is maintained, but alignment precision and reliability deteriorate due to non-uniform stress and improper alignment
Solution Approach 1:
The patent applies preliminary action by forming conductive bumps with specific layer structures (seed material layer, diffusion barrier layer, reflective layer) and predetermined pitches before the encapsulation process. This pre-configuration compensates for expected shifts during encapsulation, ensuring alignment precision is maintained without requiring complex real-time adjustment mechanisms during the actual packaging process.
Solution Approach 2:
The patent employs parameter changes by carefully controlling the pitch, layer thickness, and material composition of the conductive bumps. By optimizing these parameters, the structure compensates for stress-induced shifts during encapsulation, achieving high alignment precision while maintaining a relatively simple manufacturing process that doesn't require advanced equipment or complex procedures.
2Reliability
If finer pitch die connectors are used, then electrical performance is improved, but alignment reliability worsens due to increased sensitivity to misalignment and shifts
Solution Approach 1:
The patent applies local quality by creating a specialized multi-layer structure at the conductive bump locations with specific materials and thicknesses. The seed material layer (titanium/copper), diffusion barrier layer, and reflective layer are locally configured to provide both mechanical stability and electrical conductivity, compensating for stress-induced shifts and maintaining alignment reliability for fine-pitch connectors without requiring overall package redesign.
Solution Approach 2:
The conductive bumps are formed with predetermined dimensions, layer compositions, and pitch configurations before encapsulation. This preliminary configuration anticipates and compensates for expected stress-induced shifts, ensuring that even with fine-pitch connectors that are highly sensitive to misalignment, the final alignment reliability is maintained with minimal overlay offset.
3Reliability
If conductive bumps with complex layer structures are formed, then electrical performance and reliability are improved, but manufacturing complexity increases
Solution Approach 1:
The conductive bump structure is segmented into distinct functional layers: seed material layer (titanium and copper sublayers), diffusion barrier layer, and reflective layer. Each layer serves a specific purpose (adhesion, conductivity, protection, reflection) and can be deposited using standard sequential sputtering or evaporation processes. This segmentation allows for optimized electrical performance and reliability while maintaining manufacturing ease through conventional multi-step deposition techniques.
Solution Approach 2:
The patent optimizes manufacturing ease by controlling the thickness and material composition parameters of each layer within specific ranges. The seed material layer thickness, diffusion barrier layer composition, and reflective layer properties are all parameterized to achieve desired electrical performance while remaining compatible with standard semiconductor fabrication equipment and processes, avoiding the need for specialized or complex manufacturing steps.
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
This approach enhances the alignment and reliability of the semiconductor package by reducing overlay offsets and misalignment, achieving better electrical performance and maintaining the fine-pitched configuration, thereby improving the overall manufacturing yield and device performance.
Implementation Method 1
a seed material layer with sublayers like titanium and copper
Implementation Method 2
applying a diffusion barrier layer to prevent intermetallic compound formation
Implementation Method 3
a reflow process to shape the bumps
Data Source
AI summary
A semiconductor device includes first IC dies disposed side-by-side, a second IC die overlapping and electrically coupled to the first IC dies, and first conductive features. Each first IC die includes first and second die connectors. A first pitch of the first die connectors is less than a second pitch of the second die connectors and is substantially equal to a third pitch of the third die connectors of the second IC die. The first conductive features are interposed between and electrically coupled to the first and third die connectors. Each first conductive feature includes at least a first conductive bump and at least a first conductive joint.