Silicon Nitride Etching Composition for High SiO2 Selectivity
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Solution Overview
Problem
Existing etching processes for semiconductor devices suffer from low selectivity in removing silicon nitride (Si3N4) relative to silicon oxide (SiO2), leading to potential damage and deformation of semiconductor layers, especially in highly integrated 3D NAND memory devices, necessitating higher selectivity and reduced byproduct generation.
Innovation Solution
An etching solution comprising water, phosphoric acid, and a hydroxyl group-containing water-miscible solvent, such as saturated aliphatic monohydric alcohols, is used to enhance the selectivity of Si3N4 etching over SiO2, with optional additives like organosilicon compounds and silicic acid to protect SiO2 and increase selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hot phosphoric acid at 160°C is used to etch Si3N4, then the etching process can be accomplished, but the selectivity relative to silicon or silicon oxide material is low
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by adding specific organic additives (ammonium bifluoride, hydrofluoric acid, and organosilicon compounds) to the phosphoric acid system. This changes the chemical reactivity parameters to achieve differential etching rates, resulting in Si3N4 to SiO2 selectivity exceeding 1000:1 while maintaining effective etching of silicon nitride
Solution Approach 2:
The patent creates a composite etching solution system that combines inorganic phosphoric acid with organic additives (ammonium bifluoride, hydrofluoric acid, and organosilicon compounds). This composite formulation synergistically enhances both the etching capability for Si3N4 and the selectivity against SiO2, achieving over 1000:1 selectivity ratio
2Productivity
If higher integration is achieved in semiconductor devices, then device capacity increases, but the material selectivity requirement becomes more critical and SiO2 layer must be left unchanged
Solution Approach 1:
The patent adjusts the chemical parameters of the etching solution by incorporating ammonium bifluoride and hydrofluoric acid in specific concentrations, which fundamentally changes the etching mechanism to be highly selective for Si3N4 while being virtually inert to SiO2, achieving over 1000:1 selectivity and protecting the SiO2 core structure in highly integrated devices
3Productivity
If traditional Si3N4 etch is performed, then Si3N4 can be removed, but byproduct generation occurs and process defects increase
Solution Approach 1:
The patent converts the potentially harmful aggressive etching action into a beneficial selective process by adding organosilicon compounds that form protective complexes. The ammonium bifluoride and hydrofluoric acid components, which could cause unwanted etching, are transformed into selective etching agents that produce minimal byproducts and reduce process defects through controlled chemical reactions
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 achieves a selectivity of over 1000:1 for Si3N4 etching over SiO2, minimizing SiO2 etch rate and reducing process defects, suitable for devices with over 30 alternating layers.
Implementation Method 1
an etching process employing the etching composition... Si3N4 is removed, leaving the SiO2 core with SiO2 fins unchanged
Implementation Method 2
a hydroxyl group-containing water-miscible solvent... optional additives like organosilicon compounds and silicic acid to protect SiO2
Data Source
AI summary
Described herein is an etching solution and the method of using the etching solution comprising water, phosphoric acid solution (aqueous), an organosilicon compound as disclosed herein, and a hydroxyl group-containing water-miscible solvent. Such compositions are useful for the selective removal of silicon nitride over silicon oxide