SiCN Film Stack for Semiconductor Copper Wiring Reliability
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Solution Overview
Problem
The miniaturization of copper wiring in semiconductor devices leads to deteriorating electromigration resistance due to the thinning of the SiCN copper diffusion prevention film, resulting in reduced water penetration resistance and increased parasitic capacitance, which affects the reliability of the semiconductor device.
Innovation Solution
Forming a SiCN film with a reduced tetramethylsilane gas flow rate to densify the film and improve water penetration resistance, while using a stacked structure of SiCN films with different methyl group contents to balance water penetration resistance and permittivity, and incorporating a SiCO film to prevent resist poisoning and copper diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the SiCN film is thinned to reduce parasitic capacitance, then the parasitic capacitance between wirings is reduced, but the water penetration resistance of the SiCN film lowers
Solution Approach 1:
The SiCN film is divided into multiple layers with different methyl group contents. The first SiCN film layer has a lower methyl group content for water penetration resistance, while the second SiCN film layer has a higher methyl group content for low permittivity. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between protection and signal speed.
Solution Approach 2:
Different regions of the SiCN film structure are assigned different properties. The lower SiCN film layer is designed with water penetration resistance as the primary quality, while the upper SiCN film layer is designed with low permittivity as the primary quality. This local differentiation of film properties enables simultaneous achievement of both water penetration resistance and reduced parasitic capacitance.
2Speed
If the SiCN film is thinned to reduce parasitic capacitance, then the parasitic capacitance between wirings is reduced, but the electromigration resistance of copper wiring deteriorates
Solution Approach 1:
The copper diffusion prevention function is segmented between multiple SiCN film layers. The first SiCN film layer provides the primary barrier against copper diffusion and maintains water penetration resistance, while the second SiCN film layer contributes to overall diffusion prevention and maintains structural integrity. This segmentation allows the total film thickness to be reduced for lower parasitic capacitance while maintaining sufficient electromigration resistance.
Solution Approach 2:
The SiCN film structure is designed as a composite of layers with different compositions (different methyl group contents). This composite structure combines the advantages of each layer: the lower methyl group content layer provides water penetration resistance and copper diffusion prevention, while the higher methyl group content layer provides low permittivity. The composite nature enables simultaneous optimization of electromigration resistance and parasitic capacitance.
3Speed
If the methyl group content in SiCN film is increased to reduce permittivity, then the parasitic capacitance is reduced, but the water penetration resistance lowers
Solution Approach 1:
The methyl group content is locally optimized in different SiCN film layers. The first SiCN film layer has lower methyl group content specifically for water penetration resistance, while the second SiCN film layer has higher methyl group content specifically for low permittivity. This local quality differentiation resolves the contradiction by assigning different compositional properties to different regions of the film structure based on their primary functions.
Solution Approach 2:
The SiCN film structure is segmented into layers with different methyl group contents. This segmentation allows the system to achieve both low permittivity (through the higher methyl group content layer) and water penetration resistance (through the lower methyl group content layer) simultaneously, avoiding the need to compromise one property for the other.
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
Enhances the electromigration properties and inter-wire time-dependent dielectric breakdown of copper wiring by maintaining water penetration resistance and reducing parasitic capacitance, thereby improving the overall reliability of the semiconductor device.
Implementation Method 1
the SiCN film is a copper diffusion prevention film having a function of preventing the diffusion of copper from the copper wiring
Implementation Method 2
the SiCO film is a film of preventing the diffusion of amine generated in the SiCN film to thereby suppress the resist poisoning
Data Source
AI summary
A barrier insulating film is constituted from a first SiCN film formed with a tetramethylsilane gas flow rate lower than usual, a second SiCN film formed over the first SiCN film and formed with a usual tetramethylsilane gas flow rate, and a SiCO film formed over the second SiCN film.