Buffer Material Between Semiconductor Die and Underfill
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Solution Overview
Problem
As semiconductor devices are miniaturized and integrated into smaller volumes, challenges arise in bonding and operation due to differences in material properties such as Young's modulus and coefficient of thermal expansion, leading to issues like cracks and reduced reliability.
Innovation Solution
A buffer material with intermediate properties between the semiconductor die and underfill material is dispensed and cured to act as a buffer, reducing the negative effects of these differences and improving bonding and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor devices are miniaturized to improve integration density, then more components can be integrated into a given volume, but bonding reliability deteriorates due to differences in material properties
Solution Approach 1:
A buffer material layer is introduced between the semiconductor die and the underfill material. This intermediary layer has mechanical properties (Young's modulus and coefficient of thermal expansion) that are intermediate between those of the semiconductor die and the underfill material, thereby reducing stress concentration and improving bonding reliability during miniaturization.
Solution Approach 2:
The buffer material is designed with specific mechanical parameters (Young's modulus and coefficient of thermal expansion) that are tailored to be intermediate between the semiconductor die and underfill material. By changing and optimizing these material parameters, the stress mismatch is reduced, allowing reliable bonding at smaller device dimensions.
2Productivity
If device size is reduced to increase integration density, then more components fit in given volume, but cracks occur due to material property mismatches
Solution Approach 1:
The buffer material acts as a mediator between the semiconductor die and underfill material, preventing direct contact and the resulting stress concentration that leads to cracks. This intermediary layer absorbs and distributes thermal and mechanical stresses, eliminating the harmful cracking effect.
Solution Approach 2:
The buffer material is applied beforehand to the semiconductor die before the underfill material is applied. This pre-positioned cushioning layer anticipates and prevents the development of cracks by absorbing stress before it can propagate through the device structure.
3Reliability
If buffer material with intermediate properties is used to improve bonding reliability, then reliability window expands, but device structure becomes more complex
Solution Approach 1:
The bonding interface is segmented into multiple layers: the semiconductor die, the buffer material layer, and the underfill material. This segmentation allows each layer to be optimized independently for its specific function, with the buffer layer specifically designed to handle mechanical property mismatches, thereby improving reliability without requiring complete redesign of the entire device structure.
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
The buffer material enhances the yield and reliability of semiconductor devices by minimizing cracks and expanding the reliability window in chip on wafer on substrate configurations.
Implementation Method 1
A buffer material with intermediate properties between the semiconductor die and underfill material is dispensed and cured to act as a buffer, reducing the negative effects of these differences
Implementation Method 2
differences in material properties such as Young's modulus and coefficient of thermal expansion, leading to issues like cracks and reduced reliability
Data Source
AI summary
In order to prevent cracks from occurring at the corners of semiconductor dies after the semiconductor dies have been bonded to other substrates, an opening is formed adjacent to the corners of the semiconductor dies, and the openings are filled and overfilled with a buffer material that has physical properties that are between the physical properties of the semiconductor die and an underfill material that is placed adjacent to the buffer material.