Si/SiGe Etching Solution for Fin Trimming Without Substrate Damage
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Solution Overview
Problem
Current etching technologies face challenges in simultaneously and effectively removing silicon and silicon-germanium from microelectronic devices without damaging other materials, particularly in the context of advanced transistor designs like GAA MOSFETs and fin trimming, where precise control over fin thickness is crucial to prevent fin collapse.
Innovation Solution
An aqueous etching solution comprising water, an oxidizer, a buffer composition with an amine compound and polyfunctional organic acid, a water-miscible solvent, and a fluoride ion source is used to selectively remove silicon and silicon-germanium, allowing for controlled etch rates and compatibility with oxides and nitrides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional selective etching is used to remove silicon sacrificial layers, then the silicon layers can be removed, but trenches are inadvertently recessed into the bulk substrate due to material similarity
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by incorporating specific organic acids (oxalic, malonic, succinic, glutaric, or adipic acid) at controlled concentrations (0.1-10 wt%) combined with hydrogen peroxide and hydrofluoric acid. This chemical parameter modification enables selective etching of silicon-germanium while preventing unwanted etching of pure silicon and substrate materials, thereby achieving high etch selectivity without substrate damage.
Solution Approach 2:
The patent uses a composite etching chemistry system combining multiple components: organic acid, hydrogen peroxide, hydrofluoric acid, and water in specific ratios. This composite approach creates synergistic effects where the organic acid selectively targets silicon-germanium, while the other components modulate the etching behavior to protect silicon and substrate materials, achieving differential etching without harmful side effects.
2Reliability
If wider fins are initially produced to prevent fin collapse, then fin stability is improved, but the fin thickness cannot be reduced to the required 1 nm for advanced technology nodes
Solution Approach 1:
The patent applies preliminary fin formation with wider dimensions to ensure structural stability during subsequent processing steps. The developed etching chemistry then enables precise trimming of these fins to the target 1 nm thickness. The two-stage approach (initial wide fin formation followed by precise etching) allows fins to maintain stability during fabrication while achieving the required final dimensions.
Solution Approach 2:
The patent modifies the etching process parameters by using the specific organic acid-based chemistry to achieve controlled, anisotropic etching. This enables precise removal of material at rates that allow accurate thickness control down to 1 nm, while the chemical selectivity ensures uniform trimming without compromising fin stability during the process.
3Productivity
If etching chemistry is optimized for silicon-germanium removal, then SiGe etch rate increases, but compatibility with oxides and nitrides may be compromised
Solution Approach 1:
The patent optimizes the chemical parameters by controlling the concentration of hydrogen peroxide (1-30 wt%) and hydrofluoric acid (0.01-5 wt%) in combination with the organic acid. This parameter optimization achieves high silicon-germanium etch rates while the buffered system and specific chemical ratios prevent excessive etching or damage to oxide and nitride materials, maintaining material compatibility.
Solution Approach 2:
The organic acid acts as a selective intermediary that preferentially reacts with silicon-germanium while being less reactive toward oxides and nitrides. This intermediary mechanism enables the etching process to target SiGe specifically, achieving high etch rates for the intended material while naturally protecting other materials through chemical selectivity.
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 solution enables simultaneous and selective etching of silicon and silicon-germanium with precise control over etch rates, ensuring effective fin trimming and maintaining compatibility with other materials, thereby addressing the challenges of fin collapse and material damage in advanced transistor designs.
Implementation Method 1
an oxidizer
Implementation Method 2
a fluoride ion source
Data Source
AI summary
Described herein is an etching solution suitable for the simultaneous removal of silicon and silicon-germanium from a microelectronic device, which comprises: water; an oxidizer; a buffer composition comprising an amine compound (or ammonium compound) and a polyfunctional organic acid; a water-miscible solvent; and a fluoride ion source.