Cyclic Dry Etch Selectivity for Silicon and Organic Layers

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Solution Overview

Problem

Conventional pattern transfer processes using dry methods for silicon-containing layers under a patterned organic layer suffer from poor selectivity, leading to issues like critical dimension enlargement, distortion, and complete loss of photoresist due to the inability to anisotropically etch the silicon-containing layer with high precision.

Innovation Solution

A cyclic dry process involving multiple plasma processing steps, including a deposition step, an etch step with pulsed plasma, and a purge step, is employed to anisotropically etch the silicon-containing layer with high selectivity, reducing lateral damage and improving pattern transfer performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a dry process comprising a single plasma is used to remove exposed portions of the silicon-containing layer, then the pattern transfer is simplified, but poor etch selectivity between the organic layer and silicon-containing layer causes CD enlargement, CD distortion and complete loss of photoresist

Engineering Contradiction:

Improveprocess complexityVSAvoidpattern transfer precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The single plasma process is segmented into multiple distinct plasma steps with different chemistries and parameters. The first plasma step (e.g., CF4-based) selectively etches the silicon-containing layer, while the second plasma step (e.g., NF3-based) removes deposited fluorocarbon polymer and completes the etch. This segmentation allows each step to be optimized for its specific function, achieving high selectivity and precision without compromising process simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs periodic alternation between deposition and etching phases within the plasma process. Fluorocarbon polymer is periodically deposited onto the organic layer to protect it during silicon etching, then removed in subsequent steps. This periodic action maintains high etch selectivity throughout the process while preventing photoresist loss and CD distortion.

Inventive Principle:

Principle #19Periodic action

2Productivity

If a dry process is used to transfer the pattern, then the process is faster and more controlled, but poor selectivity causes the organic layer to be etched along with the silicon-containing layer

Engineering Contradiction:

Improvepattern transfer efficiencyVSAvoidlayer selectivity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A fluorocarbon polymer layer is introduced as an intermediary protective layer between the organic photoresist layer and the plasma etching environment. This polymer deposits during the etch process and selectively protects the organic layer from etching while allowing the silicon-containing layer to be etched underneath. The polymer is then removed in a subsequent plasma step, completing the selective pattern transfer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes multiple plasma process parameters between steps including gas chemistry (CF4 to NF3), power levels, pressure, and temperature. These parameter changes optimize each plasma step for its specific function - the first step for selective silicon etching with organic layer protection, and the second step for polymer removal and pattern completion - thereby achieving both high productivity and reliability.

Inventive Principle:

Principle #35Parameter changes

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 cyclic dry process effectively transfers patterns from a patterned organic layer to a silicon-containing layer, preventing CD enlargement and distortion, and ensuring complete removal of exposed portions without losing the photoresist, thereby enhancing pattern transfer performance.

Implementation Method 1

depositing a polymer layer onto a surface of the substrate by exposing the substrate to a first plasma while the substrate is disposed within a processing chamber

Methodology Applied

Scientific EffectPlasma deposition: Chemical Vapour Deposition

Implementation Method 2

etching the polymer layer and the exposed portions of the silicon-containing layer by exposing the substrate to a second plasma while the substrate is disposed within a processing chamber, wherein the second plasma utilizes the pulsed plasma

Methodology Applied

Scientific EffectPlasma etching: Plasma

Data Source

PatentUS11342195B1Methods for anisotropic etch of silicon-based materials with selectivity to organic materials

Publication Date: 2022.05.24 TOKYO ELECTRON LTD

AI summary

Improved process flows and methods are provided that use a cyclic dry process to transfer a pattern from a patterned organic layer to an underlying silicon-containing layer. The cyclic dry process disclosed herein includes a deposition step, an etch step and a purge step, which may be repeated a number of cycles to progressively etch the exposed portions of the silicon-containing layer. Unlike conventional pattern transfer processes, the cyclic dry process described herein anisotropically etches the silicon-containing layer with high selectivity to the patterned organic layer. In doing so, the disclosed process improves pattern transfer performance and avoids problems typically seen in conventional pattern transfer processes such as, e.g., CD enlargement, CD distortion and/or complete loss of photoresist.