Patternable Die Attach Film for Vertical Die Interconnections
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Solution Overview
Problem
Conventional die attach films (DAFs) are not patternable, making them unsuitable for vertical die-to-die connections and embedded through silicon via (TSV) approaches, as they require removal by wet chemistry or dry etching to expose backside copper pads, which complicates the manufacturing process and reduces product reliability.
Innovation Solution
Development of patternable die attach films that can be lithographically, laser drilled, or mask etched to create openings and channels, allowing for the exposure of backside pads for electrical testing and enabling vertical connections, thereby simplifying the manufacturing process and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional die attach film is used, then the mechanical stress from CTE mismatch is absorbed, but the material cannot be patterned and requires removal by wet chemistry or dry etch to expose backside copper pads
Solution Approach 1:
The die attach film material composition is changed to include photoresist components, enabling it to be patterned through lithography. This parameter change in material composition allows the film to maintain its stress-absorbing properties while gaining patternability, eliminating the need for wet chemistry or dry etch removal processes.
Solution Approach 2:
The die attach film is formulated as a composite material combining traditional stress-absorbing polymers with photoresist components. This composite structure enables dual functionality: maintaining mechanical stress absorption capabilities while adding lithographic patternability, thus resolving the contradiction between reliability and ease of manufacture.
2Ease of manufacture
If conventional DAF material is used, then the die can be attached to the package structure, but the backside copper pads cannot be accessed for vertical connections without complex removal processes
Solution Approach 1:
The material composition parameter is changed to include photoresist components, which enables direct lithographic patterning. This eliminates the need for complex wet chemistry or dry etch processes to expose backside copper pads, thereby reducing device complexity while maintaining ease of manufacture.
Solution Approach 2:
The harmful and complex removal processes (wet chemistry and dry etch) are extracted from the manufacturing flow. The invention replaces these complex extraction processes with a simpler lithographic patterning approach, directly exposing the backside copper pads without requiring additional removal steps.
3Ease of manufacture
If non-patternable DAF is used, then the manufacturing process is simpler, but vertical D2D and embedded die TSV approaches are not supported
Solution Approach 1:
The die attach film is designed with multi-functionality, serving both as a stress-absorbing attachment material and as a patternable layer for vertical connection access. This universal material enables both simple manufacturing and support for advanced vertical D2D and TSV approaches, resolving the contradiction between ease of manufacture and adaptability.
Solution Approach 2:
The composite material formulation combines the attachment and stress-absorption functions with lithographic patternability. This allows the single material to support multiple manufacturing approaches including vertical D2D and embedded die TSV, while maintaining process simplicity, thus achieving both ease of manufacture and versatility.
Data Source
AI summary
A die assembly is disclosed. The die assembly includes a die, one or more die pads on a first surface of the die and a die attach film on the die where the die attach film includes one or more openings that expose the one or more die pads and that extend to one or more edges of the die.