Varying Porosity Metallization Layer for Semiconductor Stress Management
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Solution Overview
Problem
Thick metallization layers in semiconductor devices face delamination and cracking due to thermal expansion coefficient mismatches, leading to mechanical stress and reduced processing feasibility, while porous layers offer reduced stress but compromised thermal and electrical conductivity.
Innovation Solution
A metallization layer with varying porosity, higher near the base element and lower further away, and incorporating a conductive filling material with a higher ratio at the latter region, enhancing mechanical stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the metallization layer is increased to improve electrical and thermal conductivity, then the conductivity is improved, but mechanical stress increases leading to delamination and cracking
Solution Approach 1:
The metallization layer is designed with spatially varying porosity: the first portion (adjacent to base element) has higher porosity to reduce mechanical stress and prevent delamination, while the second portion (remote from base element) has lower porosity to maintain high electrical and thermal conductivity. This local differentiation resolves the contradiction between conductivity and mechanical stress resistance.
Solution Approach 2:
The metallization layer is structured as a composite system with two distinct regions having different porosity characteristics. The first portion acts as a stress-relief zone with higher porosity, while the second portion functions as a high-conductivity zone with lower porosity, creating a composite structure that simultaneously achieves both mechanical stability and high conductivity.
2Strength
If a porous metallization layer is used to reduce mechanical stress, then mechanical stress is reduced, but thermal and electrical conductivity decreases
Solution Approach 1:
Instead of using a uniformly porous structure, the invention applies porosity selectively: the first portion adjacent to the base element has higher porosity for stress reduction, while the second portion remote from the base element has lower porosity to maintain high conductivity. This resolves the contradiction by localizing the porous structure only where mechanical stress relief is needed.
3Reliability
If a thick metallization layer is processed, then conductivity requirements are met, but the wafer bows making further processing difficult
Solution Approach 1:
The varying porosity structure reduces mechanical stress at the interface between the metallization layer and base element, preventing wafer bowing during processing. The first portion with higher porosity acts as a stress-compensation zone, allowing the thick metallization layer to maintain flatness and processability while still achieving the required conductivity through the low-porosity second portion.
Data Source
AI summary
A device comprises a base element and a metallization layer over the base element. The metallization layer comprises pores and has a varying degree of porosity, the degree of porosity being higher in a portion adjacent to the base element than in a portion remote from the base element.