Semiconductor Via Etch Stop Using Rear-Side Metal Structure
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Solution Overview
Problem
Existing methods for producing metal structures in semiconductor substrates with electrically insulated vias are sensitive to mechanical forces, prone to notching effects, and difficult to handle due to superficially sealed isolation trenches, limiting the use of filling methods and planarization of the rear side substrate.
Innovation Solution
The method involves producing the metal structure from the rear side of the semiconductor substrate to the front side layer structure, using it as a lateral etch stop, and applying a sealing layer after the trench process, allowing for more robust handling and reduced notching, enabling the use of various filling methods and planarization techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circumferential isolation trench with superficial sealing is used to electrically insulate the via, then electrical insulation is achieved, but the structure becomes sensitive to mechanical forces and difficult to handle
Solution Approach 1:
The patent applies preliminary action by forming the isolation trench and applying the sealing layer BEFORE filling the via with metal. This sequence allows the sealing layer to be properly formed and cured while the structure is still accessible, avoiding damage that would occur if the via were filled first. The trench is etched, sealed, and only then is the via filled, which resolves the handling difficulty while maintaining electrical insulation.
2Reliability
If a circumferential isolation trench is used to electrically insulate the via, then electrical insulation is achieved, but the structure is sensitive to mechanical forces during filling
Solution Approach 1:
The sealing layer is applied and cured before the via filling process. This preliminary sealing creates a robust, mechanically strong barrier that can withstand the forces applied during subsequent via filling operations. The sealing layer is formed while the trench is still open and accessible, allowing for proper adhesion and curing, which then provides mechanical strength during the filling step.
3Length of stationary object
If no lateral etch stop is provided during trench production, then the trench can be etched deeply, but notching effects appear at high aspect ratios
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary etch stop during the trench formation process. This dielectric layer is deposited on the substrate before trench etching and serves as a lateral barrier that prevents over-etching and notching effects. The trench is etched through the substrate and stops at this dielectric layer, which provides the necessary lateral etch stop while allowing deep trench formation without notching.
Data Source
AI summary
A method for producing a metal structure in a semiconductor substrate includes: producing an opening in the rear side of the semiconductor substrate in the area of the metal structure to be produced, which extends to the front side layer structure; filling the opening at least partially with a metal so that a metal structure is created which extends from the rear side of the semiconductor substrate to the front side layer structure; masking the rear side of the semiconductor substrate for a trench process for exposing the metal structure in such a way that the trench mask includes a lattice structure in an area adjacent to the metal structure; producing an isolation trench adjacent to the metal structure, the metal structure acting as a lateral etch stop and the lattice structure being laterally undercut in the trench mask; and applying a sealing layer to the mask.