Through Silicon Via Buffer Layer Mitigates Thermal Stress
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Solution Overview
Problem
The existing Through Silicon Via (TSV) technology faces issues due to the significant differences in thermal expansion coefficients and tensile modulus between copper conductive electrodes and silicon substrates, leading to problems such as silicon cracking and contamination.
Innovation Solution
A TSV structure is developed with a buffer layer made of tungsten, which is placed between the conductive electrode and the substrate, along with a barrier layer, to provide a buffer environment and improve adhesion, while maintaining high conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper conductive electrode is used in TSV, then high conductivity is achieved, but silicon cracking occurs due to mismatch in thermal expansion coefficient and tensile modulus with the silicon substrate
Solution Approach 1:
A buffer layer made of tungsten is introduced between the copper conductive electrode and the silicon substrate. This intermediary layer has thermal expansion and mechanical properties that are intermediate between copper and silicon, thereby reducing the stress concentration and preventing silicon cracking while maintaining the high conductivity of the copper electrode.
Solution Approach 2:
The TSV structure employs a composite material system consisting of multiple layers (insulation layer, barrier layer, buffer layer, and conductive electrode) with different material properties. The buffer layer (tungsten) and barrier layer are combined to create a composite structure that simultaneously addresses thermal expansion mismatch, adhesion, and conductivity requirements.
2Object-affected harmful factors
If a buffer layer is added between the conductive electrode and substrate, then silicon cracking is mitigated, but device complexity increases
Solution Approach 1:
The TSV structure is segmented into distinct functional layers: insulation layer, barrier layer, buffer layer, and conductive electrode. Each layer serves a specific function (insulation, adhesion, stress buffering, and conductivity), which allows the complex problem of material mismatch to be solved through modular design while maintaining manufacturing feasibility.
3Strength
If a barrier layer is added to enhance adhesion, then bonding strength is improved, but manufacturing complexity increases
Solution Approach 1:
The barrier layer is formed prior to depositing the conductive electrode, establishing strong adhesion between the buffer layer and the subsequent copper layer before the copper is deposited. This preliminary action ensures that the adhesion problem is resolved in advance, preventing potential delamination issues during subsequent manufacturing steps.
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 layer effectively mitigates silicon cracking and contamination, while the barrier layer enhances adhesion, resulting in improved reliability and performance of the TSV by matching the thermal expansion and mechanical properties of the materials.
Implementation Method 1
since TSV is usually made of copper, which coefficient of thermal expansion (CTE) and the tensile modulus are very different from those of the silicon substrate, a lot of problems arise
Implementation Method 2
the barrier layer enhances adhesion
Data Source
AI summary
The present invention relates to a through silicon via (TSV). The TSV is disposed in a substrate including a via opening penetrating through a first surface and a second surface of the substrate. The TSV includes an insulation layer, a barrier layer, a buffer layer and a conductive electrode. The insulation layer is disposed on a surface of the via opening. The barrier layer is disposed on a surface of the insulation layer. The buffer layer is disposed on a surface of the barrier layer. The conductive electrode is disposed on a surface of the buffer layer and a remainder of the via opening is completely filled with the conductive electrode. A portion of the buffer layer further covers a surface of the conductive electrode at a side of the second surface and said portion is level with the second surface.