Phosphonic Acid Monolayer Adhesion on Titanium Hardmasks

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Solution Overview

Problem

Existing surface treatments for titanium-containing hardmasks in semiconductor manufacturing face challenges with adhesion failure and lift-off issues when applying organic layers, particularly with titanium oxide surfaces treated using hexamethyldisilazane, and the use of bottom antireflective coatings complicates stack patterning.

Innovation Solution

A self-assembled monolayer of a blend of alkyl phosphonic acids, specifically X(CH2)nPO(OH)2, with a ratio of methyl terminated to carboxyl terminated acids ranging from 25:75 to 75:25, is applied to the titanium-containing hardmask to improve adhesion and facilitate the deposition of an organic layer, which can be subsequently patterned and wet stripped without adhesion failure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hexamethyldisilazane (HMDS) is used to treat titanium oxide surfaces, then adhesion of organic layers is improved, but lift-off and adhesion failure occur

Engineering Contradiction:

Improveadhesion of organic layerVSAvoidlift-off and adhesion failure

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the chemical parameters of the surface treatment by using a blend of phosphonic acids with specific chain lengths (n=6 to 16) and terminal groups (methyl or carboxyl) in controlled ratios, rather than using HMDS. This parameter change in the treatment composition eliminates lift-off and adhesion failure while maintaining reliable adhesion of organic layers to titanium-containing hardmasks.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention applies a composite surface treatment using a blend of multiple phosphonic acid components with different chain lengths and terminal groups. This composite approach, where phosphonic acids with n=6 to 16 are combined in specific ratios (25:75 to 75:25 methyl to carboxyl terminated), creates a synergistic effect that improves adhesion reliability and prevents lift-off compared to single-component treatments.

Inventive Principle:

Principle #40Composite materials

2Reliability

If bottom antireflective coatings (BARC) are used as adhesion promoter, then adhesion is improved, but stack patterning becomes complicated

Engineering Contradiction:

Improveadhesion promotionVSAvoidstack patterning process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the need for separate BARC layers by integrating adhesion promotion functionality directly into the phosphonic acid surface treatment on titanium-containing hardmasks. This removal of the BARC step simplifies the stack patterning process while maintaining effective adhesion, as the phosphonic acid blend provides both adhesion promotion and pattern definition capabilities in a single treatment.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The phosphonic acid blend treatment serves multiple functions simultaneously: it acts as an adhesion promoter, a surface preparation layer, and a pattern definition interface. This multi-functionality replaces the separate BARC layer that would otherwise be needed for adhesion promotion, thereby simplifying the overall stack patterning process while maintaining reliable adhesion of subsequent organic layers.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If self-assembled monolayer of phosphonic acid blend is applied, then adhesion and patterning are improved, but additional process step is added

Engineering Contradiction:

Improveadhesion and patterning successVSAvoidnumber of process steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention merges the surface treatment and adhesion promotion steps into a single phosphonic acid blend application process. By combining multiple phosphonic acid components with different chain lengths and terminal groups into one treatment solution, the process achieves reliable adhesion and successful patterning without requiring multiple separate process steps, thereby minimizing added complexity while maximizing effectiveness.

Inventive Principle:

Principle #5Merging (Combining)

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 self-assembled monolayer enhances the adhesion of organic layers to titanium-containing hardmasks, allowing for successful patterning and wet stripping without lift-off, simplifying the semiconductor fabrication process and improving the compatibility of the hardmask surface with organic layers.

Implementation Method 1

applying a self-assembled monolayer to a titanium containing hardmask layer overlaying a substrate

Methodology Applied

Scientific EffectChemisorption: Chemisorption

Implementation Method 2

depositing an organic layer onto the self-assembled monolayer

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentUS11556057B2Surface treatment of titanium containing hardmasks

Publication Date: 2023.01.17 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A surface treatment composition and methods for improving adhesion of an organic layer on a titanium-containing hardmask includes forming a self-assembled monolayer on a surface of the titanium-containing hardmask prior to depositing the organic layer. The self-assembled monolayer is formed from a blend of alkyl phosphonic acids of formula (I): X(CH2)nPOOH2 (I), wherein n is 6 to 16 and X is either CH3 or COOH, wherein a ratio of the methyl terminated (CH3) alkyl phosphonic acid to the carboxyl terminated (COOH) alkyl phosphonic acid ranges from 25:75 to 75:25.