Selective Plasma Etching of Silicon-Oxygen Regions

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Solution Overview

Problem

Existing etching methods for regions containing silicon and oxygen atoms face challenges in selectively etching these regions without undesirably cutting or narrowing the openings in adjacent regions made of different materials, due to the trade-off between suppressing cutting and reducing opening width caused by fluorocarbon-containing films.

Innovation Solution

A method involving alternating sequences of forming a fluorocarbon-containing film without oxygen and etching with fluorocarbon radicals, followed by reducing the film thickness using nitrogen trifluoride or oxygen-containing plasmas, under controlled pressure and bias voltage conditions, to minimize cutting and width reduction of the second region.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a large amount of fluorocarbon is deposited on the second region to suppress cutting, then the cutting of the second region is suppressed, but the opening width is narrowed or blocked by the fluorocarbon-containing film

Engineering Contradiction:

Improvecutting of the second regionVSAvoidopening width

Core Design Contradiction:

Object-affected harmful factorsVSLength of moving object

Solution Approach 1:

The patent applies periodic action by alternating between fluorocarbon deposition steps and oxygen plasma treatment steps. The fluorocarbon deposition suppresses cutting during etching, while the periodic oxygen plasma steps remove excess fluorocarbon film to prevent opening narrowing. This cyclic process allows the system to benefit from both fluorocarbon protection and opening width maintenance.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes physical parameters by controlling the oxygen plasma conditions (power, pressure, gas flow rate) to selectively remove fluorocarbon film without damaging the underlying structure. By adjusting these parameters, the process optimizes the balance between maintaining opening width and preserving the protective fluorocarbon layer where needed.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If fluorocarbon-containing film is formed to protect the second region, then cutting is suppressed, but the opening becomes narrower due to film deposition

Engineering Contradiction:

Improveprotection of the second regionVSAvoidopening width

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent applies local quality by creating non-uniform fluorocarbon film thickness through controlled deposition conditions. The film is thicker on the second region providing protection, while being thinner or absent in the opening areas to maintain width. This spatial variation in film properties resolves the contradiction between protection and opening maintenance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent temporarily deposits fluorocarbon film for protection during etching, then selectively removes (discards) the excess film from opening areas using oxygen plasma. The film is recovered or maintained in protected areas, allowing cyclic protection and clearance to resolve the width versus protection contradiction.

Inventive Principle:

Principle #34Discarding and recovering

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 method effectively suppresses cutting of the second region and maintains the opening width by selectively forming and reducing the fluorocarbon-containing films, ensuring precise etching of the first region while protecting the second region.

Implementation Method 1

generating plasma of a processing gas containing a fluorocarbon gas

Methodology Applied

Scientific EffectPlasma: Plasma

Implementation Method 2

forming a fluorocarbon-containing film on the processing target object

Methodology Applied

Scientific EffectDeposition (physical): Deposition (physical)

Implementation Method 3

etching the first region with radicals of fluorocarbon contained in the fluorocarbon-containing film

Methodology Applied

Scientific EffectEtching:

Implementation Method 4

etching the first region with radicals of fluorocarbon

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 5

reducing a film thickness of the fluorocarbon-containing film

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 6

generating plasma of a processing gas containing nitrogen trifluoride gas

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentUS10090191B2Selective plasma etching method of a first region containing a silicon atom and an oxygen atom

Publication Date: 2018.10.02 TOKYO ELECTRON LTD

AI summary

A method includes performing one or more times of a sequence and reducing a film thickness of a fluorocarbon-containing film formed by performing one or more times of the sequence. Each of the one or more times of the sequence includes forming the fluorocarbon-containing film on a processing target object by generating plasma of a processing gas containing a fluorocarbon gas and not containing an oxygen gas; and etching a first region with radicals of fluorocarbon contained in the fluorocarbon-containing film. In the method, an alternating repetition in which the one or more times of the sequence and the reducing of the film thickness of the fluorocarbon-containing film are alternately repeated is performed.