Two-Step SOC Thermal Planarization for Pattern Density Variation
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Solution Overview
Problem
The increasing down-scaling of semiconductor devices leads to challenges in lithography patterning, where spin-on-coating (SOC) layer thickness variations across substrates with different pattern densities cause critical dimension enlargement and under-etch issues, affecting patterning integrity and yield.
Innovation Solution
A two-step thermal treatment process is applied to the SOC layer, first to modulate its viscosity and reduce thickness variations, and second to harden it, improving thickness uniformity by at least 50% across regions of varying pattern densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single thermal treatment process is used for the SOC layer, then the process is simple and fast, but the thickness uniformity across regions with different pattern densities cannot be improved
Solution Approach 1:
The thermal treatment process is segmented into two distinct steps: a first thermal treatment at a first temperature to planarize the SOC layer, and a second thermal treatment at a second temperature to harden the SOC layer. This segmentation allows each step to perform its specific function optimally, resolving the contradiction between achieving thickness uniformity and maintaining process simplicity.
Solution Approach 2:
The process utilizes parameter changes by applying different temperatures in sequence - a first temperature for planarization and a second temperature for hardening. This parameter variation enables the SOC layer to achieve both thickness uniformity and mechanical stability, addressing the manufacturing precision requirement without excessive complexity.
2Stability of the object's composition
If the SOC layer is heated to high temperature to harden it, then the layer becomes mechanically stable, but thickness variations increase due to differential expansion across pattern densities
Solution Approach 1:
The first thermal treatment at a lower temperature is performed as a preliminary action to planarize the SOC layer and eliminate thickness variations before the second thermal treatment at higher temperature hardens the layer. This preliminary planarization prevents differential expansion issues during the hardening step, maintaining both mechanical stability and thickness uniformity.
Solution Approach 2:
The thermal treatment is divided into two segments: the first segment performs planarization at a controlled temperature, and the second segment performs hardening at a higher temperature. This segmentation ensures that the SOC layer achieves mechanical stability without suffering from thickness variations caused by differential thermal expansion.
3Manufacturing precision
If the SOC layer viscosity is reduced to improve flow and planarization, then thickness uniformity improves, but the layer becomes too soft and mechanically unstable
Solution Approach 1:
The thermal treatment process is segmented into two distinct phases: the first phase reduces viscosity to enable flow and planarization for thickness uniformity, and the second phase increases viscosity through hardening to provide mechanical strength. This segmentation resolves the contradiction between achieving uniformity and maintaining strength.
Solution Approach 2:
The process utilizes parameter changes in temperature to dynamically adjust the viscosity of the SOC layer - a first temperature range to reduce viscosity for planarization, and a second temperature range to increase viscosity for hardening. This parameter control enables the layer to achieve both thickness uniformity and mechanical stability at different stages.
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
The process enhances patterning integrity by reducing etching defects and improving fabrication yield by smoothing topological variations and stabilizing the SOC layer, ensuring conformal trench formation according to design specifications.
Implementation Method 1
a first thermal treatment step in the two-step thermal treatment process is conducted at a first temperature below a glass transition temperature of the SOC layer to cause flow of the SOC layer
Implementation Method 2
a second thermal treatment step in the two-step thermal treatment process is conducted at a second temperature above the glass transition temperature of the SOC layer to increase viscosity of the SOC layer and cross-link the polymer
Data Source
AI summary
To reduce a thickness variation of a spin-on coating (SOC) layer that is applied over a plurality of first and second trenches with different pattern densities as a bottom layer in a photoresist stack, a two-step thermal treatment process is performed on the SOC layer. A first thermal treatment step in the two-step thermal treatment process is conducted at a first temperature below a cross-linking temperature of the SOC layer to cause flow of the SOC layer, and a second thermal treatment step in the two-step thermal treatment process is conducted at a second temperature to cause cross-linking of the SOC layer.