Patterning Assist Feature for RIE Microloading Mitigation
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Solution Overview
Problem
The microloading effect in semiconductor fabrication during reactive ion etching (RIE) causes local variations in etch rate due to pattern density, leading to inconsistent etching results.
Innovation Solution
The method involves forming masking layers with patterning assist features on semiconductor substrates to create isolated and sacrificial fins, which reduces the microloading effect by controlling the etching process and maintaining the integrity of isolated fins during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reactive ion etching is performed on isolated fins, then the etching process can be completed, but the microloading effect causes local variations in etch rate due to pattern density
Solution Approach 1:
Sacrificial fins are introduced as intermediary structures between isolated fins during the etching process. These sacrificial fins act as mediators that modify the local pattern density environment, allowing reactive species to distribute more uniformly across the substrate surface. The sacrificial fins are temporarily present during etching to mitigate the microloading effect, then removed afterward to leave the desired isolated fin structure.
Solution Approach 2:
The sacrificial fins are formed in advance before the etching process begins. This preliminary action creates a modified pattern density distribution that compensates for the upcoming etching of isolated fins. By pre-positioning these sacrificial structures, the etching process experiences more uniform reactive species distribution from the start, preventing the microloading effect before it occurs.
2Manufacturing precision
If patterning assist features are added to mitigate microloading, then etch rate uniformity improves, but the fabrication process complexity increases
Solution Approach 1:
The formation of sacrificial fins is merged with the existing fin formation process. Both isolated fins and sacrificial fins are created using the same masking layer and etching process, combining multiple functions into a single process step. This reduces the overall fabrication complexity compared to adding entirely separate process steps for patterning assist features.
Solution Approach 2:
The sacrificial fins are formed as temporary structures that are discarded after serving their purpose of mitigating the microloading effect during etching. This approach allows the use of complex patterning assist features without permanently increasing device complexity, as the sacrificial elements are removed in a subsequent cleaning step after having fulfilled their function.
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 ensures consistent etching by reducing the microloading effect, resulting in more precise and uniform semiconductor fin structures with improved critical dimension control.
Implementation Method 1
The etch rate of silicon during reactive ion etching (RIE) can be affected by local variations in the pattern density
Implementation Method 2
The local depletion of reactive species that cause the local variations in the pattern density and is typically referred to as the RIE microloading effect
Data Source
AI summary
A method of fabricating a semiconductor device includes forming a masking layer on an upper surface of a semiconductor substrate. The masking layer is patterned to form at least one masking element that designates an active region of the semiconductor substrate and at least one patterning assist feature adjacent the at least one masking element. An etching process is performed to form a plurality of semiconductor fins on the semiconductor substrate. The plurality of semiconductor fins include at least one isolated fin formed on the active region according to the at least one masking element and at least one sacrificial fin formed according to the patterning assist feature that reduces a loading effect that occurs during the etching process.