Die Stack Matching Layer for Reduced NAND Die Warpage
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Solution Overview
Problem
The physical stacking of NAND dies in memory modules leads to manufacturing and production issues such as die warpage, causing non-stick problems during wire bonding and reducing manufacturing yield, due to mismatched coefficients of thermal expansion between different layers.
Innovation Solution
Incorporating a matching layer with a coefficient of thermal expansion that matches one or more of the existing layers within the die, significantly reducing warpage and ensuring successful wire bonding by balancing thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If NAND dies are physically stacked to increase storage capacity, then storage density is improved, but die warpage occurs due to mismatched coefficients of thermal expansion between layers
Solution Approach 1:
A matching layer is introduced between the polymer layer and semiconductor layer to act as a thermal expansion intermediary. This matching layer has a coefficient of thermal expansion that matches the polymer layer, creating a gradual transition and reducing the thermal stress mismatch that causes die warpage during the stacking process
Solution Approach 2:
The coefficient of thermal expansion parameter is modified by introducing the matching layer with specific thermal properties. By selecting a material whose thermal expansion coefficient matches the polymer layer, the overall thermal stress distribution in the stacked structure is optimized, preventing warpage while maintaining high storage capacity
2Quantity of substance
If multiple layers with different coefficients of thermal expansion are stacked, then storage density is improved, but wire bonding reliability deteriorates due to non-stick problems
Solution Approach 1:
The matching layer serves as a thermal stress intermediary that protects the wire bonding process. By matching the thermal expansion coefficient of the polymer layer, it prevents excessive stress transmission to the wire bonds during thermal cycling, ensuring reliable wire bonding attachment even in high-density stacked configurations
Solution Approach 2:
The matching layer provides beforehand cushioning against thermal stress by absorbing and distributing expansion forces before they reach critical components like wire bonds. This preventive cushioning effect ensures wire bonding reliability is maintained during subsequent manufacturing and operation
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 reduces die warpage by up to 50%, enhancing manufacturing yield, and allows for higher stacking density and increased storage capacity, improving the speed and reliability of memory modules.
Implementation Method 1
mismatched coefficients of thermal expansion between different layers
Data Source
AI summary
A microelectronic device can include a polymer, a semiconductor, and a matching layer. The polymer can include a first coefficient of thermal expansion. The semiconductor can be coupled to the polymer layer. The matching layer can be adjacent the semiconductor, and the matching layer can include a second coefficient of thermal expansion that is about the same as the first coefficient of thermal expansion.