Semiconductor Patterning With Carbon-Capped Self-Aligned Spacers
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Solution Overview
Problem
As semiconductor devices continue to shrink, traditional photolithography equipment struggles to achieve the desired pitch between elements, approaching the limits of its capabilities, making it challenging to manufacture devices with increasingly smaller dimensions and tighter spacings.
Innovation Solution
A self-aligned double patterning process is employed, where mandrels and spacers are patterned and selectively removed to achieve features at half the pitch of what is achievable with photolithography, using a carbon-rich capping layer to reduce etching damage and improve critical dimension control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional photolithography equipment is used, then manufacturing process is simple, but manufacturing precision deteriorates due to inability to achieve desired pitch between elements
Solution Approach 1:
The patterning process is divided into multiple discrete steps: forming mandrels, depositing spacers, selective removal of mandrels and spacers, and capping layer formation. Each step creates intermediate patterns that are progressively refined to achieve the final sub-photolithography pitch features, breaking down the complex task of achieving half-pitch features into manageable sequential operations
Solution Approach 2:
The patent transitions from planar 2D photolithography patterning to 3D self-aligned double patterning by forming vertical mandrels and spacers. This dimensional transition enables pitch multiplication where the horizontal spacing between final features is determined by vertical spacer thickness rather than direct optical projection, achieving sub-photolithography pitch through vertical dimension control
2Length of moving object
If photolithography is used, then device dimensions can be manufactured, but spacing between elements cannot be reduced below theoretical limits
Solution Approach 1:
The spacer structures are self-aligned to the mandrels through conformal deposition, automatically positioning themselves with precise thickness control determined by deposition parameters rather than alignment processes. This self-alignment mechanism eliminates alignment errors and provides inherent critical dimension control, with spacer thickness directly controlling the final feature pitch without requiring additional alignment steps
Solution Approach 2:
The patent controls critical dimensions by changing the thickness parameter of spacers through controlled deposition processes. By precisely controlling spacer deposition thickness, the final feature pitch is determined by a single controllable parameter (spacer thickness) rather than multiple alignment parameters, enabling sub-photolithography pitch with improved dimensional control
3Manufacturing precision
If mandrels and spacers are selectively removed, then features at half pitch are achieved, but material loss increases
Solution Approach 1:
The mandrels are selectively removed after serving their purpose as templates for spacer formation, while the spacers are retained as the final pattern-defining structures. This selective discarding approach eliminates the need to remove all temporary structures, recovering the valuable spacer material that defines the final sub-photolithography pitch features while only removing the sacrificial mandrel material
4Manufacturing precision
If etching is performed to remove mandrels and spacers, then patterning is achieved, but etching damage occurs
Solution Approach 1:
A capping layer is introduced as an intermediary protective structure deposited over the spacers before selective removal processes. This capping layer acts as a protective barrier during etching operations, preventing direct etchant exposure to the spacer surfaces and reducing etching damage while still allowing selective removal of mandrels and uncap'ed spacer regions to proceed
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 process allows for precise patterning of semiconductor features with reduced spacing and increased gate density, overcoming the limitations of traditional photolithography by enabling the creation of smaller semiconductor devices with improved precision and reduced material loss.
Implementation Method 1
using a carbon-rich capping layer to reduce etching damage
Implementation Method 2
forming a plurality of spacers on sidewalls of the plurality of mandrels
Data Source
AI summary
A method includes depositing a first mask over a target layer; forming a first mandrel and a second mandrel over the first mask; forming first spacers on the first mandrel and second spacers on the second mandrel; and selectively removing the second spacers while masking the first spacers. Masking the first spacers comprising covering the first spacers with a second mask and a capping layer over the second mask, and the capping layer comprises carbon. The method further includes patterning the first mask and transferring a pattern of the first mask to the target layer. Patterning the first mask comprises masking the first mask with the second mandrel, the first mandrel, and the first spacers.