Al Interconnection Etching to Eliminate Chloride Corrosion
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Solution Overview
Problem
Existing etching processes for aluminum interconnection lines in integrated circuits fail to completely remove chloride ions (Cl−) remaining on the surface, leading to corrosion issues, especially in high aspect ratio and densely spaced lines.
Innovation Solution
A method involving a main etch process with chlorine-containing gas, followed by a gradient over etch process using increasing proportions of fluorine-containing gas to exchange AlCl3 for AlF3, and subsequent soaking in ammonium fluoride (NH4F) solution to remove residual AlF3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chlorine-containing gas is used for main etch to remove Al2O3 layer and etch Al, then etching efficiency is improved, but chloride ions remain on the Al surface causing corrosion
Solution Approach 1:
The patent converts the harmful chloride ions remaining on the Al surface after chlorine-based etching into beneficial aluminum fluoride by introducing fluorine-containing gas. The fluorine reacts with the adsorbed chlorine to form volatile AlF3, which is then removed by NF3 plasma, transforming the corrosion-causing residues into removable byproducts and achieving complete elimination of chloride contamination.
Solution Approach 2:
The patent systematically removes and discards the harmful chloride ions through a multi-step process: first converting them to AlF3 using fluorine-containing gas, then removing AlF3 with NF3 plasma, and finally performing chemical cleaning with NH4F solution. This complete removal sequence ensures no chloride ions remain to cause corrosion, while recovering the etching benefits of chlorine.
2Manufacturing precision
If gaseous CH4 is introduced to form protective polymer layer against lateral etching, then void defects are prevented, but chloride-containing polymers lead to corrosion defects
Solution Approach 1:
The patent addresses the corrosion problem caused by chloride-containing polymers by introducing fluorine-containing gas that reacts with and removes the chloride from the polymer layer. The fluorine converts the harmful chloride-containing polymers into removable fluoride compounds, which are then eliminated by NF3 plasma and chemical cleaning, transforming the corrosion source into a removable substance while maintaining the protective polymer function.
Solution Approach 2:
The patent completely removes chloride-containing polymers through a systematic process: fluorine-containing gas converts the chloride to fluoride form, NF3 plasma removes the fluoride compounds, and NH4F solution performs final chemical cleaning. This multi-stage removal ensures no corrosion-causing polymers remain, while the protective polymer layer continues to prevent void defects during etching.
3Reliability
If water and oxygen plasma is used to remove chlorides and form Al2O3 protective layer, then corrosion protection is improved, but it cannot completely remove adsorbed Cl− ions in high aspect ratio structures
Solution Approach 1:
The patent introduces fluorine-containing gas as an intermediary substance that effectively removes adsorbed chloride ions from Al surfaces, particularly in high aspect ratio structures where water and oxygen plasma fail. The fluorine acts as a mediator that can access and react with trapped chloride ions, converting them to removable AlF3, which is then eliminated by NF3 plasma and chemical cleaning, achieving complete chloride removal.
Solution Approach 2:
The patent changes the chemical parameter of the cleaning process by switching from water/oxygen-based cleaning to fluorine-based cleaning. This parameter change enables effective removal of adsorbed chloride ions in difficult-to-reach areas of high aspect ratio structures, as fluorine has different chemical properties that allow it to access and react with trapped chlorides that water and oxygen cannot reach.
4Reliability
If SiO2 layer is deposited to isolate Al lines from moisture, then corrosion resistance is improved, but step coverage is limited and cracks develop at corners under stress
Solution Approach 1:
The patent eliminates the need for SiO2 protective layers by completely removing chloride ions through fluorine-based cleaning. By converting and removing all chloride contaminants that cause corrosion, the patent makes the SiO2 isolation layer unnecessary, thereby avoiding its step coverage limitations and crack formation problems while still achieving complete corrosion protection.
Solution Approach 2:
The patent extracts and removes the harmful chloride ions that necessitate the use of SiO2 protective layers. By completely eliminating the corrosion source through fluorine-based cleaning and NF3 plasma treatment, the patent removes the need for the problematic SiO2 layer, achieving corrosion protection without the associated manufacturing complexities.
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 Cl− ions, preventing corrosion of aluminum interconnection lines and ensuring their integrity in high aspect ratio and densely spaced configurations.
Implementation Method 1
a proportion of the fluorine-containing gas is increased stepwise to exchange the AlCl3 for aluminum fluoride (AlF3)
Implementation Method 2
soaking the wafer in an ammonium fluoride (NH4F) solution to remove the AlF3
Implementation Method 3
Cl2 chemically reacts with Al to produce volatile aluminum chloride (AlCl3), which is then blown away from the reactor chamber by a stream of gas
Implementation Method 4
the supply of power is continued to maintain the plasma for a short additional period of time after the etching reactions are complete
Data Source
AI summary
The present invention provides a metal interconnection line and a method of manufacturing the same. The method includes: providing a wafer on which a metal layer comprising an Al layer is formed; performing an ME process on the Al layer using a chlorine-containing gas, thereby removing a partial thickness of the Al layer and producing AlCl3; performing a gradient OE process on the remainder of the Al layer using the chlorine-containing gas and a fluorine-containing gas, thereby removing an undesired part of the remainder of the Al layer and forming an Al interconnection line, wherein in the gradient OE process, a proportion of the fluorine-containing gas is increased stepwise to exchange the AlCl3 for AlF3; and soaking the wafer in an NH4F solution to remove the AlF3. According to the present invention, Cl− ions remaining on the surface of the Al interconnection line from the etching processes for forming the line can be completely removed, preventing corrosion of the Al interconnection line.