PPC Plasma Etching Gas for Low-GWP High-Aspect-Ratio Structures

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Solution Overview

Problem

Conventional plasma etching methods using perfluorocarbon (PFC) gases have high global warming potential (GWP), leading to environmental concerns and inefficiencies in achieving high aspect ratio etched structures.

Innovation Solution

A plasma etching method utilizing perfluoropropyl carbinol (PPC) as a discharge gas with a low GWP, which involves vaporizing PPC and combining it with argon and optional oxygen gases to generate plasma for etching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If perfluorocarbon (PFC) gas is used for plasma etching, then etching selectivity and mask protection are improved, but global warming potential increases significantly

Engineering Contradiction:

Improveetching selectivityVSAvoidglobal warming potential

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameter of the etching gas from conventional PFC gases (CF4, C2F6, C3F6, C3F8, C4F8) to perfluoropropyl carbinol (PPC), which has similar etching performance but significantly lower GWP (16 vs 6500+ for PFC gases), thereby resolving the contradiction between etching selectivity and environmental harm

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs PPC gas that decomposes more readily than PFC gases, creating a short-lived etching agent that achieves the required etching function without persistent environmental accumulation, thus reducing long-term harmful effects while maintaining process effectiveness

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If fluorocarbon thin film deposition is increased for mask protection, then mask selectivity is improved, but etch rate decreases due to interference with reactive ion diffusion

Engineering Contradiction:

Improvemask protectionVSAvoidetch rate

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent modifies the gas composition from PFC to PPC, which changes the deposition characteristics of the fluorocarbon thin film. PPC generates a fluorocarbon film with optimal thickness and composition that protects the mask while allowing sufficient ion diffusion, thus balancing mask protection and etch rate

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent controls the fluorocarbon film deposition to be partially sufficient rather than excessive, achieving just enough mask protection without over-deposition that would block ion diffusion and reduce etch rate, optimizing the balance between protection and productivity

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If excessive fluorocarbon thin film is deposited on etched structure walls, then mask protection is enhanced, but etching stop occurs preventing target depth achievement

Engineering Contradiction:

Improvemask protectionVSAvoidetched depth control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent changes the etching gas from PFC to PPC, which alters the fluorocarbon film deposition rate and composition. This parameter change results in controlled film thickness that provides mask protection without causing excessive wall deposition that would lead to etching stop and depth control issues

Inventive Principle:

Principle #35Parameter changes

4Object-affected harmful factors

If perfluoropropyl carbinol (PPC) is used as discharge gas, then global warming potential is reduced, but vaporization and supply control complexity increases

Engineering Contradiction:

Improvegreenhouse gas emissionVSAvoidvaporization control system

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent utilizes the phase transition of PPC from liquid to vapor form for delivery to the plasma chamber. By controlling the vaporization process through temperature and pressure parameters, the system achieves precise gas flow control while using an environmentally friendly etchant, resolving the contradiction between reduced GWP and increased system complexity

Inventive Principle:

Principle #36Phase transitions

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 method reduces greenhouse gas emissions and achieves optimal high aspect ratio etched structures by controlling the etch rate and preventing excessive fluorocarbon deposition, thus enhancing etching efficiency and environmental sustainability.

Implementation Method 1

a first step of vaporizing liquid perfluoropropyl carbinol (PPC)

Methodology Applied

Scientific EffectVaporization: Evaporation

Implementation Method 2

a third step of discharging the discharge gas to generate plasma and of performing plasma etching on the etching target using the generated plasma

Methodology Applied

Scientific EffectPlasma generation: Plasma

Implementation Method 3

performing plasma etching on the etching target using the generated plasma

Methodology Applied

Scientific EffectPlasma etching:

Data Source

PatentUS12217970B2Plasma etching method using perfluoropropyl carbinol

Publication Date: 2025.02.04 AJOU UNIV IND ACADEMIC COOP FOUND

AI summary

Disclosed is a plasma etching method. The plasma etching method comprises: a first step for evaporating liquid perfluoropropyl carbinol (PPC); a second step for supplying a discharge gas including the evaporated PPC and argon gas to a plasma chamber in which an object to be etched is arranged; and a third step for discharging the discharge gas to generate plasma, and using the plasma to plasma-etch the object to be etched.