HBM Underfill Recess Structure for Fillet-Free Die Stacking
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Solution Overview
Problem
The formation of fillets during thermal compression bonding in high bandwidth memory (HBM) manufacturing leads to irregular interfaces and structural instability, which are difficult to address with conventional mechanical cutting methods.
Innovation Solution
The use of plasma etching to recess the sides of underfill members between memory dies, allowing for efficient removal of fillets and enhancing structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermal compression bonding is performed to bond memory dies, then the memory dies are successfully bonded together, but underfill members overflow and form fillets that create irregular interfaces
Solution Approach 1:
The patent introduces a recess structure in the underfill member before bonding occurs. This preliminary geometric feature prevents the underfill material from overflowing during thermal compression bonding, thereby avoiding fillet formation and ensuring a flat, uniform interface with the molding material from the outset.
2Ease of manufacture
If mechanical cutting methods are used to remove fillets, then some fillet removal is achieved, but the process is inefficient and cannot adequately address the irregular interfaces
Solution Approach 1:
The patent replaces mechanical cutting methods with plasma etching technology. This substitution enables precise, uniform removal of fillets and creates perfectly flat interfaces between the underfill member and molding material, significantly improving both manufacturing precision and process efficiency compared to conventional mechanical methods.
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
Plasma etching effectively removes fillets, ensuring uniformity and precision, reducing production time, and improving the structural stability and productivity of high bandwidth memory devices.
Implementation Method 1
performing plasma etching such that each of first sides of the plurality of underfill members is recessed from a corresponding second side of the plurality of memory dies
Data Source
AI summary
In an embodiment of the present inventive concept, a high bandwidth memory includes a base die, and a semiconductor stack disposed on the base die, the semiconductor stack comprising a plurality of underfill members and a plurality of memory dies that are alternately stacked. Each of the plurality of underfill members includes first sides, each of the plurality of memory dies includes second sides, and each of the first sides is recessed from a corresponding second side.