Gas Phase Etching for Semiconductor Trench Oxide Removal
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Solution Overview
Problem
In integrated circuit fabrication, the natural oxidation of silicon surfaces leads to the formation of a dense silicon dioxide layer, which increases resistivity and decreases device performance, requiring removal before metal thin film deposition, while existing plasma etching processes are complex and require multiple chambers, increasing production costs and reducing yield.
Innovation Solution
A gas phase etching process using a reaction chamber with temperature and pressure control, employing a first etchant gas to form a solid-state by-product layer on the trench surfaces, followed by a second etchant gas to remove the oxide layer, and a heating process to thin and remove the by-product layer, eliminating the need for separate annealing and cooling chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching process is used to remove SiO2 layer, then oxide layer removal is achieved, but process complexity increases and multiple chambers are required
Solution Approach 1:
The patent combines multiple process steps (etching, annealing, cooling) into a single reaction chamber system. The reaction chamber can perform chemical etching of SiO2 layer using etchant gases, followed in-situ annealing by heating to sublimation temperature, and direct cooling within the same chamber, eliminating the need for separate process chambers and reducing overall process complexity.
Solution Approach 2:
The reaction chamber is designed as a multi-functional device that can perform multiple operations: chemical etching of oxide layers, thermal annealing through heating to sublimation points, and cooling. This universal chamber replaces multiple specialized chambers, simplifying the manufacturing system while maintaining etching quality.
2Manufacturing precision
If plasma etching process is used to remove SiO2 layer, then oxide layer removal is achieved, but production cost increases
Solution Approach 1:
By merging etching, annealing, and cooling steps into one reaction chamber, the patent reduces equipment investment costs and operational costs associated with multiple chambers. The integrated system requires fewer maintenance operations and reduces production time, thereby lowering overall manufacturing costs while maintaining etching precision.
3Manufacturing precision
If conventional etching process is used, then SiO2 layer is removed, but solid-state by-products block small trenches
Solution Approach 1:
The patent changes the physical state parameters of the etching by-products by controlling temperature and pressure conditions. By heating the reaction chamber to the sublimation temperature of the by-products, the solid-state residues are converted to gas phase and removed, preventing blockage in high-aspect-ratio trenches while maintaining effective SiO2 layer etching.
Solution Approach 2:
The patent utilizes phase transition of the etching by-products from solid to gas by heating to sublimation temperature. This phase change eliminates solid-state blockage problems in small and high-aspect-ratio trenches, as the by-products are vaporized and evacuated from the reaction chamber after serving their protective function during etching.
4Manufacturing precision
If separate annealing and cooling chambers are used, then complete process is achieved, but process time increases
Solution Approach 1:
The patent merges annealing and cooling operations into the same reaction chamber where etching occurs. The chamber can be heated to sublimation temperature for annealing, then cooled within the same chamber, eliminating transfer times and setup changes between separate chambers, thereby significantly improving process efficiency while maintaining complete process quality.
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 process simplifies the manufacturing process, reduces production costs, and improves the efficiency of SiO2 layer removal, especially in high-aspect-ratio trenches, by avoiding the production of solid-state by-products that block small trenches and allowing direct integration with subsequent processes.
Implementation Method 1
a solid-state by-product layer is formed on surfaces of a bottom and the sidewalls of the trench by introducing a first etchant gas to react with a naturally occurred oxide layer
Implementation Method 2
A second etchant gas is introduced into the trench to react with the solid-state by-product layer on the bottom and the sidewalls, thereby removing the naturally occurred oxide layer
Implementation Method 3
By a heating process, the thinned solid-state by-product layer is removed from the sidewalls of the trench, exposing the deposited oxide layer
Data Source
AI summary
A semiconductor manufacturing process is provided. A trench is formed in a semiconductor structure and an oxide layer is deposited on sidewalls of the trench. A solid-state by-product layer is formed on surfaces of the trench by introducing a first etchant gas to react with a naturally occurred oxide layer at the bottom of the trench and the deposited oxide layer. The solid-state by-product layer has a thickness on the bottom less than a thickness on the sidewalls. A second etchant gas is introduced into the trench to react with the solid-state by-product layer, thereby providing a thinned solid-state by-product layer on the sidewalls to protect the deposited oxide layer. By a heating process, the thinned solid-state by-product layer is removed from the sidewalls of the trench, exposing the deposited oxide layer and a surface portion of the semiconductor structure in the trench.