Cyclic Deposition for Near-Vertical Sidewall Spacers
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Solution Overview
Problem
The challenge in semiconductor device fabrication lies in forming nanostructures with accurate dimensions and precisely controlled structural features across a wide wafer, particularly in achieving near-vertical sidewalls for high-fidelity image transfer in double-patterning processes, where existing techniques struggle to maintain verticality due to tapered mandrel sidewalls.
Innovation Solution
The method employs a depth-dependent deposition (DDD) process, where a cap layer is formed with a thickness that decreases from top to bottom along the sidewalls, using a cyclic atomic layer deposition process with controlled precursor gas exposure, adjusting the sidewall slope by varying the rotational speed and precursor concentration, resulting in near-vertical sidewall spacers after mandrel removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional deposition processes are used to form cap layers on mandrels, then the deposition process is simple and fast, but the sidewalls remain tapered and cannot achieve near-vertical profiles
Solution Approach 1:
The deposition process is divided into multiple cyclic passes, where the substrate is repeatedly exposed to precursor gases in alternating reaction and isolation zones. Each cycle deposits a thin layer, and after multiple cycles, the cumulative effect creates near-vertical sidewalls through controlled depth-dependent deposition, transforming a simple continuous process into a periodic multi-stage process that achieves superior shape control.
Solution Approach 2:
The deposition chamber is segmented into distinct reaction zones and isolation zones along the substrate traversal path. This spatial segmentation allows different regions of the substrate to experience different precursor exposures during each cycle, enabling precise control over deposition thickness at different locations and achieving vertical sidewall profiles.
2Manufacturing precision
If the substrate is moved slowly through deposition modules to ensure uniform coating, then coating uniformity is improved, but the deposition time increases and productivity decreases
Solution Approach 1:
Instead of maintaining slow continuous movement for uniform coating, the process uses periodic cyclic exposure where the substrate moves through reaction and isolation zones repeatedly. This allows faster overall throughput while achieving uniform and controlled deposition thickness through the cumulative effect of multiple short exposure cycles.
Solution Approach 2:
The substrate motion is made dynamic and variable rather than static or uniformly slow. By controlling the substrate traversal speed through the cyclic zones and adjusting the number of cycles, the process optimizes both coating uniformity and deposition rate, allowing faster processing while maintaining precision.
3Productivity
If high precursor gas concentration is used to increase deposition rate, then productivity improves, but the sidewall slope control precision decreases
Solution Approach 1:
The cyclic alternation between high-concentration precursor exposure in reaction zones and isolation in inert zones allows controlled deposition at high rates. The periodic nature limits the diffusion distance of precursor gases during each exposure cycle, maintaining precise sidewall slope control even with high precursor concentrations, while the cumulative effect of multiple cycles achieves high overall deposition rates.
Solution Approach 2:
The precursor gas concentration is segmented in space and time, with high concentrations confined to specific reaction zones during specific cycles. This spatial and temporal segmentation allows high deposition rates in controlled regions while maintaining precision through limited exposure duration and targeted precursor delivery.
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 effectively adjusts the sidewall slope to near-vertical, enhancing the fidelity of image transfer during masked etching and improving pattern quality by maintaining vertical edges of spacers, even when starting with tapered mandrel lines, thus overcoming the limitations of existing techniques.
Implementation Method 1
executing an atomic layer deposition process that deposits a first material on the mandrels. The atomic layer deposition process includes cyclically moving the substrate through a set of atomic layer deposition modules
Data Source
AI summary
A method of patterning a substrate includes receiving a substrate having microfabricated structures, including mandrels; executing a deposition process that deposits a first material on the mandrels, the deposition process including cyclically moving the substrate through a set of deposition modules. The substrate is moved through the set of deposition modules so that the first material is deposited at a first thickness at top portions of the mandrels and at a second thickness at bottom portions of mandrels, the first thickness being greater than the second thickness. The method includes executing a spacer deposition process that conformally deposits a second material on the substrate; executing a spacer open etch that removes depositions of the second material from over a top surface of the mandrels; removing the first material and the mandrels from the substrate, leaving sidewall spacers; and transferring a pattern defined by the sidewall spacers into an underlying layer.