Oxide Spacer Smoothing via Chemical Oxide Removal
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Solution Overview
Problem
As semiconductor device feature sizes shrink, line edge roughness (LER) and line width roughness (LWR) defects become significant, causing variations in channel and line dimensions, impacting device performance and function, with existing methods failing to effectively eliminate these defects without undesirable effects like vertical height reduction or protrusion removal.
Innovation Solution
A method involving a chemical oxide removal (COR) process using a mixture of ammonia and hydrogen fluoride gases to etch and smooth the oxide spacers, followed by a post-heat treatment to remove reaction byproducts, effectively reducing or eliminating peak-to-valley amplitudes and whiskers along the edges and sidewalls of the spacers, thereby smoothing the line features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etch (HF wet chemistry) is used to trim oxide features, then overall trimming (thinning) of the feature is achieved, but undesirable curves and protrusions are not eliminated and line roughness is not reduced
Solution Approach 1:
The patent changes the etching parameters by using a vapor-phase HF etch process instead of wet etch, controlling temperature (20-80°C) and HF concentration (1-10%) to achieve selective removal of protrusions while maintaining overall feature dimensions. This parameter change enables both trimming and roughness reduction simultaneously
Solution Approach 2:
The patent replaces the liquid-phase wet etch mechanism with a vapor-phase etch mechanism. The vapor-phase HF provides more uniform exposure and controlled reaction kinetics, eliminating the inability to remove surface irregularities that plagues wet etch processes
2Object-generated harmful factors
If polymer deposition followed by plasma etch back is used to smooth line features, then line roughness is reduced, but the vertical height or thickness of the line is reduced which is undesirable in a mask structure
Solution Approach 1:
The patent converts the harmful protrusions and irregularities directly into removable material through controlled vapor-phase etching. By etching at controlled rates and temperatures, the protrusions are removed while the main feature body is preserved, transforming the roughness problem into a selective material removal opportunity without adding or removing bulk material
Solution Approach 2:
The vapor-phase HF etch process provides locally selective removal of material. The etching occurs preferentially at protruding regions and surface irregularities while leaving the main feature body intact, achieving local smoothing without global dimension changes that would affect vertical height
3Manufacturing precision
If conventional patterning methods are used to define small width lines, then high-resolution photolithography is required, but line edge roughness and line width roughness variations become problematic
Solution Approach 1:
The patent applies vapor-phase HF etching as a preliminary treatment step before final mask formation. This pre-smoothing step removes surface irregularities and protrusions from the deposited oxide layer, creating a cleaner template for subsequent patterning steps and reducing the propagation of roughness into final line features
Solution Approach 2:
The vapor-phase HF etch process acts as an intermediary treatment between oxide deposition and final patterning. It mediates the transition by selectively removing surface irregularities while preserving the overall feature geometry, creating an optimized intermediate state that reduces roughness without requiring extreme photolithography resolution
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 controlled reduction of line width roughness and edge roughness, resulting in more uniform and consistent critical dimensions, improving device performance by reducing leakage and enhancing overlay control, while maintaining the desired vertical height of the line features.
Implementation Method 1
A method involving a chemical oxide removal (COR) process using a mixture of ammonia and hydrogen fluoride gases to etch and smooth the oxide spacers
Implementation Method 2
followed by a post-heat treatment to remove reaction byproducts
Data Source
AI summary
Methods for reducing line roughness of spacers and other features utilizing a non-plasma and non-wet etch fluoride processing technology are provided. Embodiments of the methods can be used for spacer or line reduction and/or smoothing the surfaces along the edges of such features through the reaction and subsequent removal of material.