Passivation of Metal-Plated Through Glass Vias
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Solution Overview
Problem
Conventional techniques struggle to establish a complete barrier layer on the large-dimension hourglass-shaped through-glass vias (TGVs) in glass substrates, leading to incomplete sealing and metal diffusion, which degrades the performance and reliability of high-frequency devices by allowing metal-oxide byproducts to form.
Innovation Solution
The implementation of oxide-based and nitride-based thin films, such as silicon dioxide (SiO2) and titanium nitride (TiN), deposited using conventional methods like CVD, PVD, and ALD, serves as a diffusion barrier layer to prevent metal diffusion and oxygen interaction, ensuring complete coverage of the 3D topology of TGVs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition techniques (PVD, CVD) are used to form a barrier layer on large-dimension hourglass-shaped TGVs, then the manufacturing process is simple and equipment requirements are low, but the barrier layer is incomplete and metal diffusion occurs
Solution Approach 1:
The deposition process is divided into multiple sequential steps: first depositing a preliminary barrier layer, then performing a first reflow treatment, followed by depositing a second barrier layer, and finally performing a second reflow treatment. This segmentation allows each layer to be optimized independently, ensuring complete coverage of the hourglass-shaped TGV geometry while maintaining manufacturing feasibility
Solution Approach 2:
The preliminary barrier layer is deposited first to provide initial protection and prepare the surface for subsequent layers. This preliminary action ensures that even if later layers have defects, the underlying metal plating layer remains protected, thereby improving overall barrier reliability without requiring perfectly complex deposition equipment
2Ease of manufacture
If the barrier layer is made thinner to reduce processing steps, then manufacturing is easier, but metal diffusion increases and reliability decreases
Solution Approach 1:
Instead of using a single thin barrier layer, the solution segments the barrier function into multiple layers of moderate thickness. Each layer provides partial protection, and together they form a robust barrier system that prevents metal diffusion while keeping individual layer thicknesses at manageable levels for conventional deposition equipment
Solution Approach 2:
The barrier structure uses composite material architecture with multiple layers of different compositions (e.g., tungsten, platinum, or other barrier materials) deposited at different stages. This composite approach provides superior diffusion blocking capability compared to a single thin layer, maintaining reliability while simplifying manufacturing control
3Reliability
If multiple barrier layers are deposited to ensure complete coverage, then metal diffusion is prevented, but the fabrication process becomes more complex and time-consuming
Solution Approach 1:
The preliminary barrier layer is deposited in advance to establish initial protection before subsequent processing steps. This preliminary action reduces the stringency requirements for later deposition steps, allowing faster deposition rates and shorter processing times while maintaining overall barrier integrity
Solution Approach 2:
The reflow treatment parameters (temperature, time, atmosphere) are optimized to achieve the desired barrier layer morphology and adhesion. By carefully controlling these parameters, the process achieves complete coverage and reliable diffusion prevention without requiring excessive deposition time or multiple redundant layers, thereby maintaining productivity
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
This solution effectively reduces the formation of parasitic metal-oxides, enhancing the reliability and longevity of high-frequency devices by preventing metal diffusion and ensuring a clean substrate surface, suitable for applications in 2.5D, 3D ICs, and MEMS with superior electrical isolation and thermal stability.
Implementation Method 1
Some of the atoms of the metal plating layer 124 may diffuse along the grain boundaries of the patterned metallization layer disposed upon the metal plating layer 124 and encounter O2
Implementation Method 2
deposited using conventional methods like CVD, PVD, and ALD
Implementation Method 3
deposited using conventional methods like CVD, PVD, and ALD
Data Source
AI summary
A through-glass via (TGV) formed in a glass substrate may comprise a metal plating layer formed in the TGV. The TGV may have a three-dimensional (3D) topology through the glass substrate and the metal plating layer conformally covering the 3D topology. The TGV may further comprise a barrier layer disposed over the metal plating layer, and a metallization layer disposed over the barrier layer. The metallization layer may be electrically coupled to the metal plating layer through the barrier layer. The barrier layer may comprise a metal-nitride film disposed on the metal plating layer that is electrically coupled to the metallization layer. The barrier layer may comprise a metal film disposed over the metal plating layer and over a portion of glass surrounding the TGV, and an electrically-insulating film disposed upon the metal film, the electrically-insulating film completely overlapping the metal plating layer and partially overlapping the metal film.