Trilayer Block Mask for High Aspect Ratio Lithography

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Solution Overview

Problem

Conventional block masks used in FinFET manufacturing are difficult to completely remove, leading to substrate damage during reactive ion etching, which negatively impacts the characteristics of FinFETs.

Innovation Solution

A trilayer stack comprising an organic planarization layer, a titanium-containing antireflective coating layer, and a photoresist layer is employed as a block mask, allowing for easy removal by wet chemical etching to minimize substrate damage and prevent residue formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional block masks are used for FinFET patterning, then the masking function is achieved, but the block masks are difficult to completely remove and cause substrate damage during reactive ion etching

Engineering Contradiction:

Improvesubstrate integrityVSAvoidblock mask removal

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The block mask is segmented into three distinct layers: an organic planarization layer (OPL), a titanium-containing antireflective coating layer (TiARC), and a photoresist layer. Each layer serves a specific function and can be selectively removed. The OPL is designed to be etched away first, followed by TiARC removal, allowing complete mask removal without substrate damage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the material parameters of the block mask by using an organic planarization layer with specific etch selectivity and a TiARC layer with controlled thickness and composition. These parameter changes enable the mask to be easily removed by wet chemical etchants while maintaining its masking function during patterning.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If reactive ion etching is performed to remove block mask residue, then complete mask removal is achieved, but surface damage is caused to the substrate

Engineering Contradiction:

Improveblock mask removalVSAvoidsubstrate surface damage

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The invention replaces the mechanical/physical process of reactive ion etching with a chemical dissolution process using wet chemical etchants. The TiARC layer is designed to be soluble in mild chemical etchants, allowing residue removal through chemical dissolution rather than physical sputtering, thereby eliminating substrate surface damage.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The TiARC layer acts as a sacrificial layer that is easily dissolved by wet chemical etchants. This disposable layer protects the underlying substrate during the removal process, allowing complete mask removal without requiring damaging RIE steps.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Object-affected harmful factors

If a trilayer stack with high etch rate OPL and easily removable TiARC is used, then substrate damage is minimized, but the device complexity increases

Engineering Contradiction:

Improvesubstrate damageVSAvoidblock mask structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The trilayer stack structure serves multiple functions: the OPL provides planarization and initial etch resistance, the TiARC layer provides antireflective properties and serves as a sacrificial removal layer, and the photoresist layer provides the patterning function. This multi-functional design achieves substrate protection while maintaining process efficiency.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 trilayer stack effectively reduces substrate damage and residue during lithographic patterning, maintaining the integrity of FinFET components by utilizing a high etch rate organic planarization layer and a TiARC layer that can be easily removed with mild chemical etchants, thereby enhancing the focus and exposure process window.

Implementation Method 1

a titanium-containing antireflective coating (TiARC) layer that can be easily removed by a mild chemical etchant solution

Methodology Applied

Scientific EffectChemical etching: Chemical Bonding

Data Source

PatentUS9425053B2Block mask litho on high aspect ratio topography with minimal semiconductor material damage

Publication Date: 2016.08.23 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A trilayer stack that can be used as a block mask for forming patterning features in semiconductor structures with high aspect ratio topography is provided. The trilayer stack includes an organic planarization (OPL) layer, a titanium-containing antireflective coating (TiARC) layer on the OPL layer and a photoresist layer on the TiARC layer. Employing a combination of an OPL having a high etch rate and a TiARC layer that can be easily removed by a mild chemical etchant solution in the trilayer stack can significantly minimize substrate damage during lithographic patterning processes.