Selective Silicon Etching Using Nitrogen-Modified Acid Compositions
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Solution Overview
Problem
The increasing integration density and wafer diameter in IC devices require effective methods for selectively removing silicon films from structures that include epitaxial films, where the dopant concentrations differ, without damaging the epitaxial films.
Innovation Solution
An etchant composition comprising nitric acid, fluoric acid, phosphoric acid, acetic acid, and a nitrogen compound, including elements like fluorine, phosphorus, and carbon, is used to selectively etch silicon films while minimizing damage to epitaxial films with different dopant concentrations, maintaining a controlled etch rate and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to remove silicon film, then the silicon film can be removed, but the epitaxial film is damaged due to lack of selectivity
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by adding specific nitrogen compounds (ammonium fluoride, urea, or triazole) to conventional mixed acid etchants. This parameter change creates a chemical environment that selectively attacks silicon film while being inhibited by dopants in epitaxial films, achieving high selectivity without damaging the epitaxial structure
Solution Approach 2:
The etching solution is formulated as a composite chemical system combining multiple acids (nitric, fluororic, phosphoric, acetic) with nitrogen-containing compounds. This composite composition creates synergistic effects where the nitrogen compounds provide selective inhibition based on dopant concentration differences between silicon film and epitaxial film, enabling precise selective etching
2Productivity
If etching is performed to remove silicon film, then the silicon film is removed, but the etch rate is difficult to control
Solution Approach 1:
The etching process utilizes feedback mechanisms where the nitrogen compounds in the solution respond to the local chemical environment (dopant concentration) during etching. This creates self-regulating behavior where the etch rate automatically adjusts based on the material being etched, providing both high productivity and precise control without external intervention
Solution Approach 2:
The patent employs multiple acids with different etching characteristics (nitric, fluororic, phosphoric, acetic) in specific concentrations alongside nitrogen compounds. This multi-parameter chemical composition allows independent control of etch rate and selectivity, enabling fast etching of silicon film while maintaining precise control and preventing over-etching
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 etchant composition effectively removes silicon films from structures with varying dopant concentrations, ensuring minimal damage to epitaxial films, thereby improving the manufacturing process for IC devices by maintaining etch rate and selectivity.
Implementation Method 1
an etchant composition for etching a silicon film. The etchant composition includes nitric acid, fluoric acid, phosphoric acid, acetic acid, a nitrogen compound, and water
Implementation Method 2
The nitrogen compound includes atoms of at least one element selected from fluorine (F), phosphorus (P), and carbon (C)
Data Source
AI summary
Etchant compositions described herein include etchant compositions for etching a silicon film and may include nitric acid, fluoric acid, phosphoric acid, acetic acid, a nitrogen compound, and water. The nitrogen compound may include fluorine (F), phosphorus (P), and/or carbon (C). Also described are methods of manufacturing an integrated circuit (IC) device. The methods may include providing a structure in which a silicon film doped at a first dopant concentration and an epitaxial film doped at a second dopant concentration are stacked. The second dopant concentration may be different from the first dopant concentration. The silicon film may be selectively etched from the structure by using an etchant composition.