Spacer Etch Process for Sidewall Spacer Slimming Reduction

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Solution Overview

Problem

Conventional spacer etch processes in semiconductor manufacturing produce unacceptable results in terms of sidewall spacer footing, substrate recess, spacer recess, and capping material consumption, leading to excessive CD slimming and recess formation.

Innovation Solution

A method involving a spacer etch process sequence that includes oxidizing the spacer material to form an oxidation layer, followed by anisotropic removal of the oxidation layer and selective removal of the spacer material, using specific etching processes with controlled plasma compositions and conditions to retain a sidewall spacer with minimal recess and CD reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional spacer etch processes are used to remove spacer material, then the spacer material is removed from the gate top and substrate, but excessive CD slimming and recess formation occur

Engineering Contradiction:

Improvespacer critical dimension controlVSAvoidCD slimming and recess formation

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The spacer etch process is divided into multiple sequential steps: (1) oxidizing the spacer material to form an oxidation layer, (2) anisotropically removing the oxidation layer, and (3) selectively removing the remaining spacer material. This segmentation allows each step to be optimized independently, preventing excessive CD slimming and recess formation while achieving complete spacer removal where needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The oxidation step is performed as a preliminary action before etching. By oxidizing the spacer material surface first, a protective oxidation layer is formed that can be anisotropically removed to define the spacer footprint, preventing unwanted lateral etching and CD slimming during subsequent spacer removal steps.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If aggressive etching is used to remove spacer material quickly, then productivity increases, but sidewall spacer footing and substrate recess worsen

Engineering Contradiction:

Improvespacer etch rateVSAvoidsidewall spacer footing and recess control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The etch process is segmented into an oxidation step followed by selective removal steps. The oxidation layer removal is performed anisotropically at a controlled rate, while the subsequent spacer material removal is performed selectively. This segmentation enables high overall productivity while maintaining precise control over sidewall spacer footing and substrate recess.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The process changes the chemical state of the spacer material by oxidizing it, creating a composition gradient. The oxidation layer has different etch selectivity compared to the unoxidized spacer material, allowing differential removal rates that achieve both high productivity and precise footing control.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If selective removal processes are used to preserve sidewall spacers, then manufacturing precision improves, but process complexity increases

Engineering Contradiction:

Improvesidewall spacer retentionVSAvoidetch process sequence

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The oxidation layer serves as an intermediary that facilitates selective removal. By converting the spacer material surface to an oxidation layer with different etch properties, the process enables selective removal of spacer material while preserving sidewall spacers. This intermediary step simplifies the overall selectivity control compared to attempting direct selective etching.

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

The method achieves reduced CD slimming, minimal sidewall spacer footing, and decreased substrate and spacer recess, resulting in improved precision and control during transistor gate fabrication.

Implementation Method 1

oxidizing an exposed surface of the spacer material to form a spacer oxidation layer

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

performing a first etching process to anisotropically remove the spacer oxidation layer... and performing a second etching process to selectively remove the spacer material

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentUS8664125B2Highly selective spacer etch process with reduced sidewall spacer slimming

Publication Date: 2014.03.04 TOKYO ELECTRON LTD

AI summary

A method for performing a spacer etch process is described. The method includes conformally applying a spacer material over a gate structure on a substrate, and performing a spacer etch process sequence to partially remove the spacer material from a capping region of the gate structure and a substrate region on the substrate adjacent a base of the gate structure, while retaining a spacer sidewall positioned along a sidewall of the gate structure.