Spacer Etching with Selective Mandrel Passivation in SADP
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Solution Overview
Problem
The challenge in semiconductor processing is the poor etch selectivity during spacer etching in self-aligned double patterning (SADP) processes, which leads to mandrel damage, pitch walking, critical dimension variations, and line edge roughness, due to insufficient etch selectivity and resulting pattern irregularities.
Innovation Solution
A plasma etch process with selective deposition of a passivating layer over mandrels using a halogen-containing gas and a hydrocarbon passivating agent, allowing for anisotropic etching of spacer materials while protecting the mandrel, thereby improving etch selectivity and preventing mandrel damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used for spacer material removal, then etching speed is maintained, but mandrel damage occurs due to poor etch selectivity
Solution Approach 1:
A passivating layer is deposited as an intermediary protective coating on the mandrel surface before spacer etching. This passivating layer acts as a mediator that prevents direct interaction between the plasma etch chemistry and the mandrel material, thereby protecting the mandrel from damage while allowing selective removal of the spacer material.
Solution Approach 2:
The passivating layer is formed in advance before the spacer etching process begins. This preliminary protective action ensures that the mandrel is pre-protected against the harmful effects of plasma etching, enabling subsequent selective spacer removal without mandrel damage.
2Object-affected harmful factors
If etch selectivity is increased to protect mandrel, then mandrel damage is reduced, but pattern fidelity deteriorates due to pitch walking and line edge roughness
Solution Approach 1:
The passivating layer serves as a controlled intermediary that enables high etch selectivity while maintaining pattern fidelity. By providing uniform protection on the mandrel surface, it allows aggressive etch chemistry to be used for spacer removal without causing pitch walking or line edge roughness, as the passivating layer prevents unwanted lateral etching.
Solution Approach 2:
The introduction of the passivating layer changes the surface chemistry parameters of the mandrel, creating a distinct interface that enhances etch selectivity. This parameter change enables the plasma process to differentiate between the passivated mandrel surface and the unprotected spacer material, achieving both mandrel protection and precise pattern transfer.
3Manufacturing precision
If passivating layer is deposited during spacer etching, then etch selectivity is enhanced and mandrel protection is improved, but process complexity increases
Solution Approach 1:
The passivating layer deposition and spacer etching processes are merged into a single integrated plasma process. By combining these two steps, the need for separate deposition and etching chambers is eliminated, reducing overall process complexity while maintaining the benefits of mandrel protection and high etch selectivity.
Solution Approach 2:
The plasma processing system is designed to perform multiple functions: it can deposit the passivating layer, protect the mandrel during etching, and remove the spacer material, all within a single process step. This multi-functionality reduces the number of process steps and equipment requirements, thereby reducing process complexity.
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 approach enhances etch selectivity, reduces mandrel damage, and improves pattern fidelity by maintaining the integrity of the mandrel and spacer structures, leading to more precise feature formation and reduced line edge roughness.
Implementation Method 1
exposing the substrate to a plasma generated in the plasma processing chamber from a first halogen-containing process gas, a second halogen-containing process gas, and a carbon-containing passivating agent
Implementation Method 2
the exposing anisotropically etching the spacer material
Implementation Method 3
a polymeric layer including carbon is selectively deposited over the top surface of the mandrel
Implementation Method 4
the polymeric layer protecting the mandrel from etching
Data Source
AI summary
A method for processing a substrate includes: forming a mandrel over the substrate including an underlying layer, the mandrel having a top surface and sidewalls, the substrate including an exposed surface including a portion of the underlying layer; conformally depositing a spacer material over the substrate, the spacer material covering the top surface and the sidewalls of the mandrel and the portion of the underlying layer; in a plasma processing chamber, exposing the substrate to a plasma generated in the plasma processing chamber from a first halogen-containing process gas, a second halogen-containing process gas, and a carbon-containing passivating agent, the exposing anisotropically etching the spacer material; and removing the mandrel to form free-standing spacers from sidewall portions of the spacer material covering the sidewalls of the mandrel.