Selective Silicon Etching Composition for High Si/SiGe Selectivity
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Solution Overview
Problem
Existing etching solutions for silicon (Si) in the presence of silicon-germanium (SiGe) alloys suffer from low selectivity and etch rate, failing to efficiently remove Si layers without attacking SiGe layers.
Innovation Solution
A composition comprising 4 to 15% by weight of a specific amine of formula E1 and water is used to selectively etch silicon layers, achieving a Si/SiGe selectivity of at least 100 times, particularly effective for amorphous silicon (aSi) or crystalline silicon, while minimizing etching of SiGe layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional alkaline etchants (TMAH, ammonium hydroxide) are used to etch silicon, then high selectivity between Si and SiO2 is achieved, but low horizontal etching power and low Si/SiGe selectivity result
Solution Approach 1:
The patent changes the chemical composition parameters of the etchant by introducing quaternary ammonium hydroxide compounds and amine compounds with specific molecular structures (formula E1) to achieve both high Si/SiO2 selectivity and enhanced horizontal etching power, resolving the contradiction between reliability and productivity
2Productivity
If conventional etchants are used to remove Si layers, then some Si removal is achieved, but low Si/SiGe selectivity causes simultaneous etching of SiGe layers
Solution Approach 1:
The patent modifies the etchant composition by incorporating quaternary ammonium hydroxide and amine compounds that selectively interact with Si while being inert to SiGe, achieving both high productivity in Si removal and high reliability in Si/SiGe selectivity
Solution Approach 2:
The quaternary ammonium hydroxide and amine compounds act as intermediary substances that facilitate selective Si etching by forming temporary complexes with Si atoms, enabling differential reactivity between Si and SiGe layers
3Loss of time
If etching time is extended to improve Si removal, then complete Si layer removal is achieved, but excessive SiGe etching occurs due to low selectivity
Solution Approach 1:
The patent optimizes etching time by changing the chemical composition of the etchant to achieve rapid Si removal with high selectivity, minimizing the required etching time and consequently reducing SiGe material loss
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 composition provides a controlled and selective etching of silicon layers, maintaining high etch rates for Si while significantly reducing etching of SiGe layers, thus enabling precise silicon structure formation in microelectronic devices.
Implementation Method 1
the use of specific amines significantly and selectively improve the Si/SiGe selectivity since the etching rate of silicon layers, particularly crystalline, poly-crystalline or amorphous silicon layers is much more reduced than the etching of the SiGe layer
Data Source
AI summary
Described herein is a method of using a composition for selectively etching a silicon layer in the presence of a layer including a silicon germanium alloy, the composition including: (a) 4 to 15% by weight of an amine of formula (E1), and (b) water, where XE1, XE2, and XE3 are independently selected from a chemical bond and C1-C6 alkanediyl; YE is selected from N, CRE1, and P; RE1 is selected from H and C1-C6 alkyl.