Invertable Pattern Loading Dry Etch Process
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Solution Overview
Problem
The Siconi™ etch process exhibits pattern loading effects where wide trenches etch slower than narrow trenches due to the greater amount of silicon oxide that needs to be consumed, limiting flexibility in pattern-related etching processes.
Innovation Solution
A method involving two dry etch cycles is employed, where a low-intensity sublimation step leaves solid residue in narrow trenches, inhibiting further etching during the second cycle, allowing the wide trench etch to progress further by partially removing by-products in the wide trench while leaving residual by-products in the narrow trench, which are then fully removed in a subsequent step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a standard Siconi etch process is used, then narrow trenches etch faster than wide trenches, but this creates pattern loading effects that limit process flexibility
Solution Approach 1:
The etch process is divided into multiple discrete cycles, each performing a specific function (etching, sublimation, residue removal). This segmentation allows independent optimization of each step to achieve overall pattern loading inversion without compromising total etch throughput
Solution Approach 2:
A preliminary sublimation step is performed before the main etch cycle to pre-condition the trench surfaces. This preliminary action removes initial by-products that would otherwise inhibit subsequent etching, particularly in narrow trenches, thereby enabling faster etch rates in narrow features before wide trenches catch up
2Productivity
If sublimation temperature is increased to remove solid by-products, then etch progress is improved, but narrow trenches etch even faster relative to wide trenches due to greater by-product accumulation
Solution Approach 1:
The process employs periodic alternation between etching cycles and sublimation cycles. During etching cycles, by-products accumulate and inhibit further etching in narrow trenches. During sublimation cycles, these by-products are selectively removed. This periodic action creates a dynamic balance that inverts the traditional pattern loading effect, allowing wide trenches to etch faster than narrow trenches while maintaining manufacturing precision
3Manufacturing precision
If the etch process is made selective to silicon oxide, then pattern transfer is improved, but pattern loading effects become more pronounced due to varying silicon oxide consumption
Solution Approach 1:
The etch process utilizes the by-products generated during silicon oxide etching as self-regulating elements. These by-products naturally accumulate in narrow trenches where etching is fastest, automatically inhibiting further etching in those regions. This self-service mechanism creates negative feedback that balances etch rates across different trench widths, improving etch rate uniformity while maintaining pattern transfer fidelity
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 inverts the typical etch rate pattern, allowing the wide trench to etch faster than the narrow trench, overcoming the natural limitations of the Siconi™ process and providing greater flexibility in pattern loading effects.
Implementation Method 1
flowing a fluorine-containing precursor and a hydrogen-containing precursor into a remote plasma region fluidly coupled to the substrate processing region while forming a plasma in the remote plasma region to produce plasma effluents
Implementation Method 2
The solid by-products are subsequently removed via sublimation when the temperature of the substrate is raised
Data Source
AI summary
A method of etching silicon oxide from a narrow trench and a wide trench (or open area) is described which allows the etch in the wide trench to progress further than the etch in the narrow trench. The method includes two dry etch cycles. The first dry etch cycle involves a low intensity or abbreviated sublimation step which leaves solid residue in the narrow trench. The remaining solid residue inhibits etch progress in the narrow trench during the second dry etch cycle allowing the etch in the wide trench to overtake the etch in the narrow trench.