Through Vias in SOI Substrates Using Segmented Etching
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Solution Overview
Problem
The challenge in integrated circuits is to form reliable metallization in high-aspect-ratio through vias without voids or breaks, while maintaining a thick substrate to withstand mechanical and electrical stresses, which complicates via formation and filling.
Innovation Solution
The solution involves forming vias from opposite sides of a silicon-on-insulator (SOI) substrate, using deep reactive ion etching and electroplating to achieve uniform via depths and reduce the aspect ratio, allowing for precise control and reliable metallization, and depositing metal only part way through the substrate to minimize processing challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If via width is reduced to minimize package size, then package area is reduced, but via aspect ratio increases making metallization unreliable
Solution Approach 1:
The substrate is divided into two separate substrates with the insulating layer positioned between them. Vias are formed through each substrate separately, effectively segmenting the single high-aspect-ratio via into two lower-aspect-ratio vias. This segmentation allows reliable metallization in each via while maintaining narrow via width for compact package size.
Solution Approach 2:
The problem is solved by transitioning from a single-substrate vertical via structure to a dual-substrate structure with vias formed in separate layers. This dimensional reorganization allows each via to have reduced aspect ratio while the overall package remains compact through the layered architecture.
2Strength
If substrate thickness is increased to withstand mechanical and electrical stresses, then structural integrity is improved, but via aspect ratio increases complicating via formation and filling
Solution Approach 1:
The thick substrate is segmented into two separate substrates, each with manageable thickness. This allows each substrate to maintain sufficient structural integrity while the vias formed through each substrate have reduced aspect ratios, making via formation and metallization feasible.
3Manufacturing precision
If via aspect ratio is reduced to enable reliable metallization, then metallization quality is improved, but package size increases
Solution Approach 1:
By segmenting the via structure into two separate substrates, each via achieves lower aspect ratio for high-quality metallization while the overall package remains compact through the layered configuration of the two substrates with insulating layer between them.
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 approach enables reliable metallization in high-aspect-ratio vias, reducing the package size and maintaining mechanical and electrical integrity, while ensuring uniform via depths and efficient metal deposition, thus addressing the complexities of via formation and filling.
Implementation Method 1
using deep reactive ion etching
Implementation Method 2
and electroplating to achieve uniform via depths and reduce the aspect ratio
Data Source
AI summary
A through via contains a conductor (244, 262) passing through a substrate (140). The substrate can be SOI or some other substrate containing two semiconductor layers (140.1, 140.2) on opposite sides of an insulating layer (140B). The through via includes two constituent vias (144.1, 144.2) formed from respective different sides of the substrate by processes stopping on the insulating layer (140B). Due to the insulating layer acting as a stop layer, high control over the constituent vias' depths is achieved. Each constituent via is shorter than the through via, so via formation is facilitated. The conductor is formed by separate depositions of conductive material into the constituent vias from each side of the substrate. From each side, the conductor is deposited to a shallower depth than the through-via depth, so the deposition is facilitated. Other embodiments are also provided.