Cap Layer Sidewall Protection During Via Patterning
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Solution Overview
Problem
In the fabrication of advanced integrated circuits, the reduced cross-sectional area of interconnect structures leads to high current densities, causing electromigration issues such as void formation and premature device failure, particularly at the interface between copper and dielectric cap layers, which is exacerbated by the challenges of patterning cobalt/tungsten/phosphorous cap layers during the damascene process.
Innovation Solution
A protective material is locally applied to the sidewall portions of the conductive cap layer during the patterning of via openings, allowing for efficient wet chemical cleaning without significant material removal, and material redistribution at the via bottom is used to cover exposed cap layer surfaces, enhancing the integrity of the copper-based interconnects and reducing electromigration effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cross-sectional area of interconnect structures is reduced to increase circuit density, then the number of circuit elements per unit area increases, but current density increases causing electromigration and void formation
Solution Approach 1:
The patent uses a composite cap layer structure consisting of a first cap layer material (e.g., tungsten) and a second cap layer material (e.g., cobalt or platinum) deposited sequentially. This composite structure provides both the electrical conductivity needed for high current density operation and the mechanical properties to resist electromigration, thereby resolving the contradiction between increased circuit density and maintained reliability.
Solution Approach 2:
The patent changes the material composition parameters of the cap layer by introducing a second material with different properties than the first cap layer material. This parameter change allows the cap layer to maintain structural integrity under high current density conditions while enabling reduced interconnect dimensions for higher circuit density.
2Reliability
If cobalt/tungsten/phosphorous cap layers are used to improve electromigration performance, then the integrity of copper interconnects is enhanced, but the cap layers are prone to erosion during via patterning
Solution Approach 1:
The patent applies a protective material to the sidewall portions of the cap layer before performing the etching process to form via openings. This preliminary protective action prevents erosion of the cobalt/tungsten/phosphorous cap layer during patterning, allowing the use of these materials for improved electromigration performance without suffering from manufacturing difficulties.
Solution Approach 2:
The patent introduces a protective material as an intermediary substance between the cap layer and the etching environment. This protective material acts as a mediator that shields the cap layer from etchant exposure during via patterning, thereby enabling the use of high-performance cap layer materials while simplifying the manufacturing process.
3Ease of manufacture
If wet chemical cleaning is performed to remove residues during via patterning, then cleaning efficiency is improved, but significant material removal from the cap layer occurs
Solution Approach 1:
The patent applies a protective material to the cap layer sidewalls before performing wet chemical cleaning. This preliminary protection allows efficient cleaning of residues while preventing significant material removal from the cap layer, thereby resolving the contradiction between cleaning efficiency and manufacturing precision.
Solution Approach 2:
The protective material serves as an intermediary barrier between the wet chemical cleaner and the cap layer. This intermediary allows the cleaning process to remove residues effectively while the protective material prevents the cleaner from attacking and removing cap layer material, thus maintaining manufacturing precision.
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
This approach significantly reduces the creation of voids and defects in the conductive cap material, maintaining the electromigration performance of the metal lines while ensuring compatibility with conventional process techniques and improving device reliability.
Implementation Method 1
A protective material is locally applied to the sidewall portions of the conductive cap layer during the patterning of via openings
Implementation Method 2
performing a wet chemical cleaning process
Implementation Method 3
material redistribution at the via bottom is used to cover exposed cap layer surfaces
Implementation Method 4
enhancing the integrity of the copper-based interconnects and reducing electromigration effects
Data Source
AI summary
During the patterning of via openings in sophisticated metallization systems of semiconductor devices, the opening may extend through a conductive cap layer and an appropriate ion bombardment may be established to redistribute material of the underlying metal region to exposed sidewall portions of the conductive cap layer, thereby establishing a protective material. Consequently, in a subsequent wet chemical etch process, the probability for undue material removal of the conductive cap layer may be greatly reduced.