Selective Silicon Oxide Etching via Plasma Gas Ratios

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Solution Overview

Problem

In the etching process of silicon oxide with respect to silicon nitride, existing methods face challenges in selectively etching the silicon oxide while minimizing the etching of silicon nitride, leading to significant erosion of the nitride region.

Innovation Solution

A plasma etching method using a processing gas containing a fluorocarbon gas and a rare gas, with a self-bias potential of the lower electrode ranging from 4V to 350V and a rare gas flow rate 250 to 5000 times that of the fluorocarbon gas, is employed to selectively etch silicon oxide while suppressing the etching of silicon nitride.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a plasma of processing gas containing fluorocarbon gas, argon gas and oxygen gas is generated to etch silicon oxide, then the silicon oxide etching is achieved, but the silicon nitride region is considerably etched

Engineering Contradiction:

Improveselectivity of silicon oxide etchingVSAvoiderosion of silicon nitride region

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent changes the gas composition parameters by introducing rare gas (helium or neon) at specific flow rates (250-5000 times the fluorocarbon gas flow rate) and adjusts the self-bias potential (4-350V) to achieve selective etching of silicon oxide while protecting silicon nitride from erosion

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The rare gas acts as an intermediary that modifies the plasma characteristics and ion energy distribution, enabling selective etching of silicon oxide while minimizing damage to silicon nitride through controlled ion bombardment

Inventive Principle:

Principle #24Intermediary (Mediator)

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 etches the silicon oxide to the bottom of the recess formed by the silicon nitride while minimizing the erosion of the nitride region, ensuring precise control over the etching process.

Implementation Method 1

generating a plasma of a processing gas containing a fluorocarbon gas and a rare gas in the processing chamber

Methodology Applied

Scientific EffectPlasma: Plasma

Implementation Method 2

a self-bias potential of a lower electrode on which the target object is mounted is greater than or equal to 4V and smaller than or equal to 350V

Methodology Applied

Scientific EffectIon acceleration through self-bias potential: Electric Field

Implementation Method 3

a plasma of a processing gas containing a fluorocarbon gas and a rare gas

Methodology Applied

Scientific EffectChemical reactions between fluorocarbon gas and silicon oxide: Chemical Bonding

Data Source

PatentUS10541147B2Etching method

Publication Date: 2020.01.21 TOKYO ELECTRON LTD

AI summary

A method for selectively etching a first region of silicon oxide with respect to a second region of silicon nitride, includes: preparing a target object including the first region and the second region in a processing chamber of a plasma processing apparatus; and generating a plasma of a processing gas containing a fluorocarbon gas and a rare gas in the processing chamber. In the generating the plasma of the processing gas, a self-bias potential of a lower electrode on which the target object is mounted is greater than or equal to 4V and smaller than or equal to 350V and a flow rate of the rare gas in the processing gas is 250 to 5000 times of a flow rate of the fluorocarbon gas in the processing gas.