Passivation Layer Cavities to Prevent Thermal-Cycle Delamination
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Solution Overview
Problem
Semiconductor devices with passivation layers are prone to delamination due to non-uniform thermal cycling and differences in thermochemical properties of materials, leading to mechanical stress and potential electrical discharge.
Innovation Solution
The formation of a passivation layer with a plurality of cavities that extend through the layer, arranged in a staggered pattern relative to the circuitry, helps to relieve mechanical stress and improve durability by preventing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous passivation layer is formed over the semiconductor device, then electrical insulation and protection are improved, but mechanical stress during thermal cycling causes delamination
Solution Approach 1:
The passivation layer is segmented by introducing cavities that extend through the layer, dividing it into multiple sections. This segmentation allows the layer to accommodate thermal expansion and contraction stresses without continuous stress accumulation, preventing delamination while maintaining electrical insulation in the regions between cavities
Solution Approach 2:
The passivation layer is designed with a porous structure containing multiple cavities distributed throughout. This porous configuration provides stress relief pathways during thermal cycling, reducing mechanical stress on the layer while the remaining material maintains protective and insulating functions
2Strength
If the passivation layer is made thicker to improve durability, then protection is improved, but mechanical stress and risk of delamination increase
Solution Approach 1:
By segmenting the thick passivation layer with cavities, the layer can maintain its protective thickness while avoiding continuous stress accumulation. The cavities create discrete stress zones that prevent stress propagation across the entire layer, allowing durability without proportional stress increase
Solution Approach 2:
The cavities are pre-formed in the passivation layer to provide stress relief capacity before thermal cycling occurs. This beforehand cushioning allows the layer to accommodate future thermal stresses without exceeding delamination thresholds, enabling thicker design for durability
3Strength
If cavities are added to the passivation layer to relieve stress, then delamination is prevented, but electrical insulation may be compromised
Solution Approach 1:
The passivation layer exhibits local quality variations with solid material providing electrical insulation in regions between cavities, while cavity regions provide stress relief. This spatial differentiation allows simultaneous achievement of adhesion through stress relief and electrical insulation through continuous dielectric material in non-cavity zones
4Strength
If the passivation layer is made more rigid to improve durability, then protection is improved, but susceptibility to delamination during thermal cycling increases
Solution Approach 1:
The passivation layer transitions from a purely rigid static structure to a dynamic structure incorporating cavities that can deform and accommodate dimensional changes during thermal cycling. This dynamic capability allows the layer to maintain durability while adapting to thermal expansion and contraction, improving thermal stability
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 introduction of cavities in the passivation layer effectively reduces mechanical stress and enhances the durability of the passivation layer, preventing delamination and subsequent electrical discharge during thermal cycling.
Implementation Method 1
The plurality of cavities and the circuitry are non-overlapping along the third direction... helps to relieve mechanical stress and improve durability by preventing delamination
Data Source
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AI summary
Methods, systems, and devices for improving passivation layer durability are described. A device may include a semiconductor substrate elongated along a first direction and a second direction. The first direction may be parallel to a width of the semiconductor substrate and the second direction may be parallel to a depth of the semiconductor substrate. The device may include one or more layers formed above the semiconductor substrate with respect to a third direction parallel to a height of the semiconductor substrate. At least a region of the one or more layers may include circuitry. The device may include a passivation layer formed above the one or more layers with respect to the third direction. The passivation layer may include a plurality of cavities that each extend through the passivation layer. The plurality of cavities and the circuitry may be nonoverlapping with respect to the first direction and the second direction.