Deep Trench Isolation Tungsten Filling Cross-Talk Suppression
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Solution Overview
Problem
Conventional deep trench isolation structures in semiconductor manufacturing do not effectively provide electrical isolation and cross-talk suppression between electrical nodes in the substrate and deep buried layers, leading to undesired electrical coupling.
Innovation Solution
The conversion of deep trench isolation structures by removing the polysilicon filling and refilling with a conductive material like tungsten, or forming a contact to the polysilicon, to create electrical connections and improve isolation, involves etching techniques to access and modify the trench liner and fillings within the semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench isolation structures are used to provide electrical isolation between buried layers, then parasitic capacitance is reduced, but electrical isolation and cross-talk suppression between electrical nodes is insufficient
Solution Approach 1:
The patent changes the electrical parameter of the trench filling material from insulating (polysilicon) to conductive (tungsten) to transform the isolation mechanism. The conductive tungsten filling combined with liner connections creates an effective shield that suppresses cross-talk while maintaining electrical isolation between adjacent electrical nodes.
Solution Approach 2:
The liner layer acts as an intermediary between the conductive tungsten filling and the surrounding structures. By selectively connecting the liner to ground or other potentials, it mediates the interaction between adjacent trenches, enabling cross-talk suppression while maintaining isolation between electrical nodes.
2Ease of manufacture
If polysilicon filling is used in deep trench isolation structures, then trench filling is complete and thermal stress is mitigated, but electrical connection to deep buried layers is not achieved
Solution Approach 1:
The patent extracts the electrical connection function from the trench filling process by using a two-stage approach: first filling with polysilicon for manufacturing ease, then removing portions of the polysilicon and replacing with conductive tungsten to establish electrical connections to deep buried layers.
Solution Approach 2:
The patent employs a composite structure combining polysilicon and tungsten within the same trench. The polysilicon provides mechanical support and thermal matching, while the tungsten provides electrical conductivity and connection to buried layers, creating a multi-functional composite 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
This approach enhances electrical isolation and suppresses cross-talk between buried layers, allowing for improved electrical communication and reduced parasitic capacitance, as demonstrated by increased trans-admittance values and effective connection to deep buried layers.
Implementation Method 1
the deep trench is then re-filled with a conductive material such as tungsten
Implementation Method 2
the polysilicon filling is removed by isotropic etching
Data Source
AI summary
Electrically isolated, deep trench isolation (DTI) structures, are formed in a wafer, and a portion of the DTI structures are converted to electrically connected structures to provide a shielding function, or to provide connection to deep buried layers. In one aspect, DTI structures include a polysilicon filling over a liner layer disposed on the inner surface of a deep trench, the polysilicon is removed by isotropic etching, and the deep trench is re-filled with a conductive material. Alternatively, the polysilicon filling remains and a contact is formed to provide an electrical connection to the polysilicon. In another aspect, a deep trench is disposed in the wafer such that a lower portion thereof is located within a deep buried layer, and after the polysilicon is removed, an anisotropic etch removes a portion of the deep trench liner from the bottom of the deep trench, thereby allowing a tungsten deposition to make electrical contact with the deep buried layer.