Composite Filled Through-Silicon Via Reducing Thermal Stress
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Solution Overview
Problem
Through-silicon vias (TSVs) face challenges with thermo-mechanical reliability due to differences in thermal expansion coefficients between filling materials and silicon substrates, leading to stress-induced deformation, voiding, and electrical conductivity issues.
Innovation Solution
A through-silicon via structure using a composite conductive material comprising copper and particles with a lower coefficient of thermal expansion, such as silicon carbide, diamond, beryllium oxide, aluminum nitride, or aluminum oxide, is introduced to fill the via holes, which are covered with an insulation layer to reduce mechanical stress and enhance electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used as filling material for TSVs, then electrical conductivity is improved, but thermo-mechanical reliability deteriorates due to CTE mismatch with silicon substrate
Solution Approach 1:
The patent uses a composite filling material consisting of copper particles combined with ceramic particles (such as alumina, silica, or boron nitride) having low CTE. This composite structure maintains the high electrical conductivity of copper while the ceramic particles with lower CTE reduce the overall CTE mismatch with the silicon substrate, thereby reducing internal stress and improving thermo-mechanical reliability.
Solution Approach 2:
The patent modifies the CTE parameter of the filling material by combining copper with ceramic particles having different CTE characteristics. By carefully selecting the type and proportion of ceramic particles, the overall CTE of the composite material is adjusted to be closer to that of the silicon substrate, reducing thermal expansion mismatch and associated stress.
2Reliability
If copper is used as filling material for TSVs, then electrical conductivity is improved, but structural stability deteriorates due to stress-induced deformation and voiding
Solution Approach 1:
The composite filling material combines soft copper particles with hard ceramic particles. The copper provides ductility and electrical conductivity, while the ceramic particles provide structural rigidity and resistance to deformation. This combination enhances the overall mechanical strength and resistance to stress-induced deformation and voiding.
Solution Approach 2:
The composite material creates local quality differentiation within the filling material. The copper regions provide electrical conductivity and ductility, while the ceramic particles provide local structural support and stress distribution, creating a material with spatially varying properties that address multiple requirements simultaneously.
3Reliability
If copper is used as filling material for TSVs, then electrical conductivity is improved, but interface reliability deteriorates due to peeling and popping up
Solution Approach 1:
The composite filling material with ceramic particles distributed throughout the copper matrix reduces the overall CTE mismatch at the interface between the TSV filling and the silicon substrate. This reduces the thermal stress concentrated at the interface, preventing peeling and popping up phenomena that occur with pure copper filling.
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 composite material-filled TSVs exhibit reduced warpage, lower Von Mise stress, and improved thermal mechanical reliability, maintaining superior electrical conductivity while addressing thermal mechanical issues, thus enhancing the overall reliability of the TSVs.
Implementation Method 1
Due to the differences in the coefficients of thermal expansion (CTE) of a filling material in the TSVs and of the silicon substrate, the internal stress of the TSVs usually leads to plastic deformation, stress-induced voiding, and stress migration.
Implementation Method 2
electrical conductivity of the TSVs should also be taken into consideration
Data Source
AI summary
By adding particles of high thermal conductivity and low thermal expansion coefficient into the copper as a composite material and filling with the composite material into the through-via hole, the mismatch of the coefficient of thermal expansion and the stress of the through-silicon via are lowered and the thermal conductivity of the through-silicon via is increased.