Laser-Reflowed Fin Trench Filling to Eliminate Gate Stack Voids
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Solution Overview
Problem
Conventional methods for filling narrow trenches with high aspect ratios in integrated circuit fabrication, such as forming amorphous silicon layers, result in voids due to the inability of reaction vapor to penetrate deeply, leading to issues in subsequent processes like post-gate-cut and spacer-deposition.
Innovation Solution
A trench-filling process involving the deposition of a trench-filling material followed by an annealing process to reflow the material, reducing or eliminating voids through local heating techniques like laser or UV radiation, ensuring complete or partial filling of voids without damaging the surrounding structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical vapor deposition is used to form amorphous silicon layers, then the deposition process can be completed, but voids are formed in the amorphous silicon extending into the trenches due to inability of reaction vapor to penetrate deeply
Solution Approach 1:
The patent utilizes phase transition by melting the amorphous silicon layer through laser annealing and then allowing it to resolidify. This phase change enables the material to flow and fill voids, then solidify into a dense, void-free structure upon cooling, directly resolving the void formation problem while maintaining layer integrity
Solution Approach 2:
The patent employs periodic action through multiple deposition and annealing cycles. Each cycle deposits a thin amorphous silicon layer followed by laser annealing to eliminate voids. This repeated sequence progressively builds up the complete layer while ensuring each sub-layer is void-free, achieving both precision and reliability
2Manufacturing precision
If bottom-up gap filling methods are used, then void formation can be avoided, but very high selectivity reactants are required
Solution Approach 1:
The patent replaces the complex chemical selectivity mechanism with a physical thermal field approach. Instead of relying on highly selective reactants that require precise chemical control, the invention uses laser-induced thermal fields to melt and flow the deposited material, physically filling voids through thermal energy rather than chemical selectivity, thereby simplifying the process
3Manufacturing precision
If annealing process is used to eliminate voids, then voids can be reduced, but temperatures higher than the original thermal budget are required
Solution Approach 1:
The patent applies local quality by concentrating thermal energy only in the trench regions containing voids through focused laser beams. Instead of uniformly heating the entire wafer, the laser selectively targets and melts only the amorphous silicon in the trench areas, eliminating voids locally while keeping the rest of the structure at lower temperatures, thus maintaining the overall thermal budget
Solution Approach 2:
The patent segments the annealing process into localized laser heating zones rather than uniform bulk heating. Each trench region is independently treated with focused laser energy, allowing precise thermal control in specific areas without subjecting the entire device structure to high temperatures, thereby resolving the thermal budget constraint
4Manufacturing precision
If deposition-and-etching cycles are used, then void and seam width and length can be reduced, but the process becomes costly and time consuming
Solution Approach 1:
The patent extracts and eliminates the etching step from the conventional deposition-etching cycle. By using laser annealing to melt and flow the amorphous silicon material to fill voids, the process achieves void elimination and seam reduction without requiring subsequent etching operations to remove excess material, thereby significantly reducing process time and cost while maintaining precision
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 effectively reduces or eliminates voids in high aspect ratio trenches, ensuring high-quality, void-free amorphous silicon layers, thereby improving the integrity and reliability of integrated circuits.
Implementation Method 1
performing a laser reflow process on the trench-filling material, wherein in the laser reflow process, the trench-filling material has a temperature higher than a first melting point of the trench-filling material
Implementation Method 2
the trench-filling material has a temperature higher than a first melting point of the trench-filling material, and lower than a second melting point of the first protruding fin and the second protruding fin
Implementation Method 3
performing an annealing process to reflow the material, reducing or eliminating voids through local heating techniques like laser or UV radiation
Data Source
AI summary
A method includes forming a first protruding fin and a second protruding fin over a base structure, with a trench located between the first protruding fin and the second protruding fin, depositing a trench-filling material extending into the trench, and performing a laser reflow process on the trench-filling material. In the reflow process, the trench-filling material has a temperature higher than a first melting point of the trench-filling material, and lower than a second melting point of the first protruding fin and the second protruding fin. After the laser reflow process, the trench-filling material is solidified. The method further includes patterning the trench-filling material, with a remaining portion of the trench-filling material forming a part of a gate stack, and forming a source/drain region on a side of the gate stack.