Tri-layer Plasma Etch Resist Rework for Sub-45nm Nodes

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Solution Overview

Problem

Conventional resist reworking methods for semiconductor devices, such as solvent and ash rework, are inefficient as they can only remove a portion of the tri-layer resist stack in a single process, requiring multiple steps and often leaving residues or altering the SOG layer, which complicates the photolithographic process.

Innovation Solution

A single plasma etch process is used to remove and re-form one or more layers of the tri-layer resist stack, including the resist layer, intermediate layer, and under-layer, allowing for complete removal and reformation of the stack in a single process, enabling flexible resist reworking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If solvent rework is used to remove the resist layer, then the PR layer can be removed, but residues are left and SOG layer properties are altered

Engineering Contradiction:

Improveresist layer removalVSAvoidresidues and SOG layer changes

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent changes the removal mechanism from chemical dissolution (solvent) to physical sputtering (plasma). By using oxygen plasma, the resist layer is removed through ion bombardment and oxidation rather than chemical dissolution, eliminating solvent residues and preventing alterations to the SOG layer's refractive index and thickness

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the chemical mechanism (solvent dissolution) with a physical mechanism (plasma sputtering). The oxygen plasma uses ion bombardment and oxidative reactions to remove the resist layer physically, avoiding the chemical residues and unwanted side effects of solvent-based removal

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Quantity of substance

If ash rework is used to remove the PR layer and under-layer, then these layers can be removed, but the SOG layer cannot be removed

Engineering Contradiction:

ImprovePR layer and under-layer removalVSAvoidremoval capability for different layers

Core Design Contradiction:

Quantity of substanceVSAdaptability or versatility

Solution Approach 1:

The patent makes the plasma etch process universal by adjusting plasma parameters (power, pressure, gas composition, etch time) to remove any combination of layers in the tri-layer stack. The same oxygen plasma process can remove PR layer alone, PR+SOG layers, or all three layers (PR+SOG+under-layer), providing flexible, multi-functional rework capability

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent introduces dynamic control of plasma etching parameters to adapt the removal depth and selectivity. By varying etch time, power levels, and gas flow rates, the process can be tuned to remove specific layer combinations, making the rework process versatile and adaptable to different rework scenarios

Inventive Principle:

Principle #15Dynamics

3Quantity of substance

If multiple processing steps on multiple tools are used to remove the full TLR stack, then complete removal is achieved, but process complexity and time increase

Engineering Contradiction:

Improvecomplete TLR stack removalVSAvoidnumber of processing steps and tools

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent merges multiple separate removal steps into a single plasma etch process. Instead of using different tools and processes for PR layer removal, SOG layer removal, and under-layer removal, the invention uses one oxygen plasma etch process that can remove all layers sequentially in a single step, dramatically simplifying the rework workflow

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent enables continuous removal of all tri-layer stack components in an uninterrupted plasma etching process. The oxygen plasma maintains continuous action throughout the etch, removing PR, SOG, and under-layer materials in sequence without interrupting the process or transferring the substrate between tools, improving efficiency and reducing complexity

Inventive Principle:

Principle #20Continuity of useful action

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 allows for efficient and complete removal of the tri-layer resist stack in a single process, reducing the need for multiple steps and minimizing residues, thereby improving the accuracy and reliability of the photolithographic process, particularly for sub 45-nm node semiconductor structures.

Implementation Method 1

A single plasma etch process can then be performed to remove one or more layers of the resist layer, the intermediate layer, and the under-layer

Methodology Applied

Scientific EffectPlasma etching: Plasma

Data Source

PatentUS7811942B2Tri-layer plasma etch resist rework

Publication Date: 2010.10.12 TEXAS INSTRUMENTS INC

AI summary

Exemplary embodiments provide a tri-layer resist (TLR) stack used in a photolithographic process, and methods for resist reworking by a single plasma etch process. The single plasma etch process can be used to remove one or more portions/layers of the TLR stack that needs to be reworked in a single process. The removed portions/layers can then be re-formed and resulting in a reworked TLR stack for subsequent photo-resist (PR) processing. The disclosed plasma-etch resist rework method can be a fast, simple, and cost effective process used in either single or dual damascene tri-layer patterning processes for the fabrication of, for example, sub 45-nm node semiconductor structures.