Plasma Spacer Etching with C/F Ratio Control for Uniform Oxide Opening
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Solution Overview
Problem
The etching process in semiconductor manufacturing often results in nonuniform etching rates across different positions of a workpiece, leading to over-etching and excessive loss of the underlying substrate, which reduces yield and finished product ratio.
Innovation Solution
A plasma etching process is developed that modulates the volume ratio of carbon to fluorine in the etching gas to control the distribution of a carbon-based polymer layer on the spacer layer, allowing for simultaneous opening of top and bottom silicon oxide layers while minimizing over-etching time and substrate loss by adjusting the thickness of the polymer layer formed on different regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used, then etching process is simple, but etching rate is nonuniform across different positions of workpiece
Solution Approach 1:
The patent applies local quality by introducing a composition modulation gas (CHF3 or CF4) that selectively modifies the polymer layer formation at different spatial locations on the workpiece. The modulation gas creates location-dependent etching conditions: at the center region, higher carbon content promotes polymer layer formation that protects the substrate, while at peripheral regions, lower carbon content allows faster etching. This spatially varying etching behavior achieves uniform overall etching across the workpiece surface.
Solution Approach 2:
The patent changes chemical composition parameters of the etching gas by adding a modulation gas component (CHF3 or CF4) to the base etching gas (C4F8). This parameter change modifies the volume ratio of carbon to fluorine in the process gas, which directly controls the polymer layer thickness and etching rate. By adjusting the modulation gas flow rate, the process achieves precise control over etching uniformity without changing the fundamental etching chemistry.
2Manufacturing precision
If etching is performed to open both top and bottom oxide layers, then both layers are opened simultaneously, but over-etching occurs causing substrate loss
Solution Approach 1:
The patent uses local quality to create different etching protection levels at different locations. The composition modulation gas produces a nonuniform polymer layer distribution where the center region receives more carbon-containing species, forming a thicker protective polymer layer that prevents over-etching of the substrate. The peripheral regions receive less modulation gas, allowing the etching to proceed faster to open the oxide layers. This spatial differentiation enables simultaneous opening of top and bottom layers while protecting the substrate from excessive etching.
Solution Approach 2:
The composition modulation gas acts as an intermediary that mediates between the etching requirements of opening oxide layers and protecting the substrate. The modulation gas (CHF3 or CF4) introduces carbon species that form a polymer layer serving as a protective intermediary between the plasma etching process and the substrate. This polymer intermediary allows the etching to proceed controllably, opening the oxide layers while preventing direct excessive etching of the underlying substrate.
3Loss of substance
If polymer layer thickness is increased to protect substrate, then substrate loss is reduced, but etching time increases
Solution Approach 1:
The patent resolves this contradiction by making polymer layer thickness location-dependent through local quality. The composition modulation gas creates a gradient in carbon content across the workpiece surface, resulting in thicker polymer layers at the center (where substrate protection is critical) and thinner polymer layers at the periphery (where etching speed is needed). This spatial variation allows the process to reduce substrate loss at vulnerable locations without uniformly increasing etching time across the entire workpiece.
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 reduces over-etching height, improves etching precision, and enhances the yield and finished product ratio by optimizing the etching time difference between the top and bottom of the oxide spacer layer, laying a foundation for miniaturization.
Implementation Method 1
generating one or more species using one or more plasmas from a process gas to create a mixture
Implementation Method 2
exposing the workpiece to the mixture to form a polymer layer on at least a portion of the spacer layer
Implementation Method 3
exposing the workpiece to the mixture to etch at least a portion of the spacer layer of the workpiece
Data Source
AI summary
A method for processing a workpiece, a plasma processing apparatus and a semiconductor device are provided. The method includes placing a workpiece including a spacer layer on a workpiece support in a chamber; selecting a composition modulation gas to modulate a volume ratio of carbon and fluorine to process the workpiece, the composition modulation gas includes one or more molecules, the volume ratio of carbon and fluorine is indicative of a distribution of carbon-based polymer deposited on the spacer layer; generating one or more species using one or more plasmas from a process gas to create a mixture, the process gas includes an etching gas and the composition modulation gas; and exposing the workpiece to the mixture to form a polymer layer on at least a portion of the spacer layer and to etch at least a portion of the spacer layer.