Trench Isolation Void Elimination via Polysilicon Oxidation
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Solution Overview
Problem
In semiconductor devices, the filling of high aspect ratio trench isolation regions often results in voids and seams due to non-conformal deposition of insulating materials, leading to reduced electrical isolation and potential short circuits, especially as device density increases and trench depths become more complex.
Innovation Solution
A method involving the growth of a thin thermal oxidation layer followed by alternating layers of polysilicon deposition and oxidation, which are then converted into silicon dioxide, is used to fill trenches, ensuring conformal filling and minimizing void formation, combined with conventional high-density plasma techniques for goal-post shaped trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high-density plasma oxide is used to fill isolation trenches, then good filling capability is achieved, but voids or seams exist in the isolation regions
Solution Approach 1:
The filling process is divided into multiple sequential steps: first forming a mandrel structure, then depositing insulating material, removing the mandrel, and filling the resulting cavity. This segmentation allows each step to be optimized independently, ensuring complete filling without voids or seams while maintaining good manufacturing capability.
2Productivity
If device packing density increases, then more devices are packed into small area, but electrical isolation between devices is reduced
Solution Approach 1:
The isolation structure is formed by nesting multiple layers: a mandrel structure is first formed, then insulating material is deposited around it, creating a nested configuration. This nested approach ensures complete isolation between densely packed devices while allowing maximum device density on the substrate.
3Ease of manufacture
If insulating layer is deposited on sidewalls at top of trench, then filling is initiated, but opening becomes closed-off before complete filling causing void region
Solution Approach 1:
A mandrel structure is formed in advance within the trench before any insulating material deposition. This preliminary action creates a permanent space-holder that prevents the trench opening from closing off during deposition, ensuring complete filling without void regions while maintaining process efficiency.
Solution Approach 2:
The mandrel structure serves as an intermediary element during the filling process. It temporarily occupies the trench space, allowing insulating material to be deposited conformally around it without closing the trench opening. After deposition, the mandrel is removed, leaving a completely filled trench without voids.
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 significantly reduces voids and seams, enhancing electrical isolation and preventing contamination traps, resulting in consistent film formation and improved reliability of semiconductor devices.
Implementation Method 1
a thin thermal oxidation layer is grown on the sidewall of each trench
Implementation Method 2
a layer of polysilicon is deposited above the oxidation layer
Implementation Method 3
polysilicon deposition and oxidation steps are performed until each trench has been completely filled
Data Source
AI summary
The invention relates to a method and resulting structure that can substantially minimize and/or eliminate void formation during an isolation trench isolation fill process for typical trench shaped and goal-post shaped isolation regions. First, a thin thermal oxidation layer is grown on the sidewall of each trench and then a layer of polysilicon is deposited above the oxidation layer and oxidized. In one embodiment, a repeating series of polysilicon deposition and polysilicon oxidation steps are performed until each trench has been completely filled. In another embodiment, within a goal-post shaped trench having a wider upper portion and a narrower lower portion, the remainder of the upper wider trench portion is filled using a conventional high density plasma technique.