Tin Oxide Mandrels for Precise Spacer Patterning
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Solution Overview
Problem
Current semiconductor manufacturing methods face challenges in achieving precise control over spacer and mandrel geometry and efficiency during patterning processes, particularly in using spacers formed on semiconductor substrates, where existing materials and etching techniques lack sufficient selectivity and control.
Innovation Solution
The use of tin oxide as a mandrel material in semiconductor substrate processing, where a method involves forming tin oxide protruding features, depositing a spacer material, selectively etching to expose underlying tin oxide, and removing the mandrels while preserving spacer material at sidewalls, utilizing various etch chemistries like hydrogen, chlorine, and fluorine-based processes to achieve high selectivity and control over geometry and material removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional spacer formation methods are used, then spacers can be formed on semiconductor substrates, but control over spacer and mandrel geometry is insufficient
Solution Approach 1:
The patterning process is divided into multiple sequential steps: forming mandrels, depositing spacer material, selectively removing mandrels, and performing controlled etching. This segmentation allows independent optimization of each step to achieve precise geometry control while managing overall process complexity
Solution Approach 2:
Mandrels are formed in advance as sacrificial structures that define the eventual spacer positions and geometries. The spacer material is deposited conformally on these pre-formed mandrels, ensuring precise geometry control before the mandrels are removed
2Reliability
If existing etching techniques are used, then material removal can be achieved, but etch selectivity is insufficient
Solution Approach 1:
Different etching parameters are optimized for different materials: fluorine-based chemistry for silicon-containing spacers, chlorine-based for titanium dioxide, and hydrogen-based for tin oxide mandrels. This parameter optimization achieves high etch selectivity (greater than 10:1) while maintaining process feasibility
Solution Approach 2:
An etch stop layer is introduced as an intermediary between the mandrels and the substrate. This layer provides additional selectivity control and protects the substrate during etching operations, enabling reliable material removal without compromising process simplicity
3Manufacturing precision
If spacers are formed using traditional mandrel methods, then patterning can be achieved, but critical dimension control is insufficient
Solution Approach 1:
Traditional mechanical lithographic patterning is replaced with a self-aligned chemical deposition and etching process. The conformal deposition of spacer material followed by selective mandrel removal automatically defines precise critical dimensions based on spacer thickness, achieving superior CD control while maintaining productivity through streamlined process steps
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 enables high-level control over spacer and mandrel geometry, achieving efficient integration of tin oxide films with diverse materials, meeting stringent critical dimension and selectivity requirements in applications like DRAM and finFETs, with enhanced etch selectivity and reduced material loss.
Implementation Method 1
The tin oxide protruding features are removed using a hydrogen-based etch chemistry that results in a formation of a tin hydride
Implementation Method 2
removing the spacer material from horizontal surfaces in (c) comprises etching the spacer material using fluorine-based etch chemistry
Implementation Method 3
removing the spacer material from horizontal surfaces in (c) comprises etching the spacer material using chlorine-based etch chemistry
Data Source
AI summary
Tin oxide films are used as mandrels in semiconductor device manufacturing. In one implementation the process starts by patterning a tin oxide layer using at least one of a hydrogen-based etch chemistry and a chlorine-based etch chemistry, and using patterned photoresist as a mask, thereby providing a substrate having a plurality of protruding tin oxide features (mandrels). Next, a conformal layer of spacer material is formed both on the horizontal surfaces and on the sidewalls of the mandrels. The spacer material is then removed from the horizontal surfaces exposing the tin oxide material of the mandrels, without fully removing the spacer material residing at the sidewalls of the mandrels. Next, mandrels are selectively removed (e.g., using hydrogen-based etch chemistry), while leaving the spacer material that resided at the sidewalls of the mandrels. The resulting spacers can be used for patterning underlying layers on the substrate.