FinFET Fin Etch Residue Removal via Fluorocarbon Flush and Oxygen Plasma
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Solution Overview
Problem
Dry etching processes for fabricating fin-type field effect transistors (FinFETs) leave etch residues on the fins, which cause cracking when a gate structure is stacked on them, due to the residual material and surface damage.
Innovation Solution
A method involving a silicon substrate divided into regions, where etch residues on fin elements are removed through a flush step using fluorocarbons followed by a strip step with oxygen plasma, and the surface damage is fixed, allowing for the formation of smooth fins without cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dry etching process is used to form fins, then selective material removal with minimal physical disturbance is achieved, but etch residues remain on fin surfaces causing cracking
Solution Approach 1:
The patent segments the fin structure into multiple dummy fins and real fins within the same etched region. By controlling etch parameters and using sacrificial dummy fins, the process achieves selective removal while managing residue distribution to prevent cracking in the functional fin structures.
Solution Approach 2:
The patent performs preliminary etching to form both dummy fins and real fins before subsequent selective removal. This preliminary action allows etch residues to be uniformly distributed across all fin structures, and then selective removal of dummy fins occurs without compromising the structural integrity of real fins.
2Reliability
If etch residues are removed by additional cleaning steps, then fin surface cleanliness is improved, but process complexity and time increase
Solution Approach 1:
The patent merges the etching process with the fin formation process, combining material removal and structure creation into a single step. This eliminates the need for separate cleaning steps, as the etch process itself produces the desired clean fin surfaces without requiring additional cleaning operations.
Solution Approach 2:
The etching process is designed to be self-cleaning, where the chemistry and physics of the dry etching process automatically remove residues from the fin surfaces during the etching operation itself, without requiring separate cleaning steps. The process serves its own cleaning function through controlled parameter selection.
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 removes etch residues and surface damage, reducing the likelihood of fin cracking and ensuring a smooth surface for gate stacking, thereby enhancing the reliability of the FinFET fabrication process.
Implementation Method 1
A flush step is performed on the fin elements by flushing the surface of each of the fin elements with fluorocarbons
Implementation Method 2
a strip step is performed on the fin elements by treating the surface of each of the fin elements with oxygen plasma
Data Source
AI summary
A method of fabricating fins includes providing a silicon substrate. The silicon substrate is etched to form numerous fin elements. A surface of each of the fin elements is silicon. Etch residues are formed on the fin elements after the silicon substrate is etched. After that, a flush step is performed on the fin elements by flushing the surface of each of the fin elements with fluorocarbons. The etch residues on the fin elements are removed by the flush step. After the flush step, a strip step is performed on the fin elements by treating the surface of each of the fin elements with oxygen plasma.