Polysilicon Trench Fill via Plasma Oxidation
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Solution Overview
Problem
Conventional shallow trench isolation techniques face challenges in precisely controlling planarity and trench fill, leading to variations in charge buildup and semiconductor gate performance due to non-uniformity in passivation layer thicknesses and aspect ratios.
Innovation Solution
A method involving plasma oxidation to form a conformal polysilicon layer within the trench, followed by a wet clean process to remove excess oxide, ensuring a substantial reduction in void space and improving the polysilicon layer profile, which includes forming a first conductive layer with varying thicknesses and a second conductive layer to fill the trench completely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional shallow trench isolation techniques are used to fill trenches, then the trench can be filled with dielectric material, but void space remains and planarity control is imprecise leading to non-uniform passivation layer thickness
Solution Approach 1:
The patent changes the physical state and properties of the filling material by using polysilicon that can be oxidized. By controlling the oxidation parameters (temperature, time, atmosphere), the patent achieves precise planarity control and eliminates void space while maintaining uniform passivation layer thickness, directly resolving the contradiction between manufacturing precision and reliability
Solution Approach 2:
The patent applies plasma oxidation or chemical oxidation to convert the conformal polysilicon layer into silicon oxide. This accelerated oxidation process completely fills the trench void space and creates a uniform, planar surface that improves both planarity control and passivation layer uniformity, addressing the technical contradiction
2Reliability
If multiple masking, ion implantation, and deposition steps are used to form shallow trench structures, then the trench isolation can be achieved, but the process complexity increases and variability in STI sizes leads to charge buildup issues
Solution Approach 1:
The patent performs preliminary actions by forming a conformal polysilicon layer before trench filling, which serves as a foundation for subsequent oxidation. This preliminary conformal deposition simplifies the overall process by eliminating the need for multiple masking and ion implantation steps while ensuring reliable trench isolation performance
Solution Approach 2:
The patent changes the material parameter from conventional dielectric materials to oxidizable polysilicon, which can be transformed into silicon oxide through controlled oxidation. This parameter change simplifies the fabrication process while maintaining reliable trench isolation, reducing both process complexity and variability
3Manufacturing precision
If oxide liner is applied across trench surfaces to form continuous layer, then the trench isolation structure is formed, but the oxide liner does not substantially fill the trench leaving void space
Solution Approach 1:
The patent changes the volume and density parameters of the filling material through oxidation. The conformal polysilicon layer, when oxidized to silicon oxide, increases in volume and completely fills the trench void space, achieving both precise trench fill control and eliminating voids for reliable device operation
Solution Approach 2:
The patent uses plasma oxidation or chemical oxidation to rapidly convert the polysilicon layer into silicon oxide that completely fills the trench. This accelerated oxidation process ensures substantial void space reduction while maintaining precise control over the trench fill, resolving the contradiction between manufacturing precision and reliability
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 void space in the trench fill, enhancing the uniformity and performance of semiconductor gates by minimizing variations in sidewall liners and dielectric fill, resulting in improved control over peak electric fields and consistent semiconductor operation.
Implementation Method 1
forming an oxide layer on a top region of the first conductive layer
Implementation Method 2
the oxide layer may be removed using, for example, a wet clean process
Data Source
AI summary
A semiconductor gate structure is provided having a trench, the trench assembled by a dielectric structure and a stack structure. A first conductive layer may be conformally applied to the dielectric structure and the stack structure. An oxide layer is formed along the first conductive layer and may then be substantially removed from the first conductive layer. In certain gate structures, a conductive fill structure having the first conductive layer and a second conductive layer may be disposed on the stack structure and the dielectric structure.