PEALD SiN Film Conformality via Sequential Plasma Pretreatment
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Solution Overview
Problem
Silicon nitride films deposited by conventional Plasma-Enhanced Atomic Layer Deposition (PEALD) on three-dimensional structures with high aspect ratios suffer from low side-wall conformality and poor step coverage, leading to voids and seams in gap-fill processes due to non-uniform reactant exposure and re-sputtering during plasma treatment.
Innovation Solution
A sequential plasma pretreatment phase involving hydrogen and nitrogen plasma treatments is integrated into the PEALD process, where the substrate is exposed to hydrogen plasma followed by nitrogen plasma in the absence of hydrogen, modifying the surface to enhance conformal deposition of silicon nitride films by controlling silicon precursor adsorption, resulting in improved side-wall conformality and reduced voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional PEALD process is used to deposit silicon nitride films, then deposition can be achieved, but side-wall conformality is low and step coverage is poor
Solution Approach 1:
A plasma pretreatment phase is performed before the silicon nitride deposition phase to modify the substrate surface. This preliminary action prepares the surface by controlling precursor adsorption, ensuring uniform reactivity across different surface regions and enabling conformal deposition on high aspect ratio structures.
Solution Approach 2:
The plasma pretreatment creates different surface conditions at different locations on the substrate. By selectively modifying surface properties in different regions, the process achieves uniform precursor adsorption and reaction rates across planar regions, trench entrances, and trench interiors, resulting in consistent film quality throughout.
2Productivity
If conventional PEALD process is used, then deposition can proceed, but non-uniform reactant exposure causes slower growth inside trenches
Solution Approach 1:
The plasma pretreatment phase modifies the substrate surface before deposition to ensure uniform precursor adsorption. This preliminary action compensates for the non-uniform reactant exposure that would otherwise occur during deposition, enabling consistent growth rates across different trench locations.
3Reliability
If plasma treatment is performed during PEALD, then deposition is enabled, but re-sputtering at trench entrance occurs
Solution Approach 1:
The plasma treatment is segmented into a separate pretreatment phase performed before deposition, rather than being continuous during deposition. This segmentation allows the plasma to prepare the surface uniformly without causing localized re-sputtering at trench entrances during the deposition phase.
Solution Approach 2:
Plasma treatment is performed as a preliminary action before deposition begins. This timing separates the surface preparation function from the deposition function, allowing plasma to enhance surface reactivity uniformly without causing re-sputtering damage during film formation.
4Ease of manufacture
If conventional PEALD is used on high aspect ratio structures, then deposition can occur, but voids and seams form in gap-fill processes
Solution Approach 1:
The plasma pretreatment phase prepares the substrate surface before deposition to ensure uniform precursor adsorption and reaction. This preliminary action enables conformal deposition that completely fills high aspect ratio trenches without forming voids or seams, achieving continuous film formation throughout the gap-fill process.
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 high side-wall conformality, with silicon nitride films being thicker at the bottom than at the top of trenches, significantly reducing or eliminating voids and seams in gap-fill processes, and demonstrating enhanced resistance to wet etching.
Implementation Method 1
a plasma pretreatment phase comprising a first plasma treatment step and a second plasma treatment step is carried out as part of a PEALD deposition cycle
Implementation Method 2
modifying the surface to enhance conformal deposition of silicon nitride films by controlling silicon precursor adsorption
Implementation Method 3
silicon nitride can be deposited by atomic layer deposition (ALD), such as plasma enhanced ALD
Implementation Method 4
plasma enhanced ALD
Data Source
AI summary
Methods for forming silicon nitride films are provided. In some embodiments, silicon nitride can be deposited by atomic layer deposition (ALD), such as plasma enhanced ALD. One or more silicon nitride deposition cycle comprise a sequential plasma pretreatment phase in which the substrate is sequentially exposed to a hydrogen plasma and then to a nitrogen plasma in the absence of hydrogen plasma, and a deposition phase in which the substrate is exposed to a silicon precursor. In some embodiments a silicon hydrohalide precursors is used for depositing the silicon nitride. The silicon nitride films may have a high side-wall conformality and in some embodiments the silicon nitride film may be thicker at the bottom of the sidewall than at the top of the sidewall in a trench structure. In gap fill processes, the silicon nitride deposition processes can reduce or eliminate voids and seams.