Self-Aligned CuSiN Barrier for Copper Diffusion Control
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Solution Overview
Problem
Existing self-aligned barriers in microelectronics, such as silicon nitride barriers, cause partial refraction of light rays in imager applications due to their higher optical index and do not effectively retain copper atoms under high current conditions, leading to unsatisfactory ageing resistance.
Innovation Solution
A semiconductor product with a self-aligned barrier comprising two copper silicide layers, where the second layer has a higher silicon concentration than the first, providing enhanced retention of copper atoms and improved ageing resistance, formed through a process involving deoxidation, silicidation, and nitrogen plasma treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon nitride barriers are deposited over the entire surface of the wafer, then diffusion of copper atoms into the dielectric is prevented, but light refraction occurs and the process requires additional etching operations and initial copper deoxidation
Solution Approach 1:
The patent extracts the barrier function from a full-surface silicon nitride layer and applies it selectively only where needed (at copper-dielectric interfaces). This is achieved through self-aligned barrier formation where the barrier material is deposited only on copper surfaces, eliminating the need for etching operations to create openings in a full-surface barrier layer.
Solution Approach 2:
The patent implements local quality by providing barrier protection only at specific locations (copper-dielectric interfaces) rather than uniformly across the entire wafer surface. The self-aligned barrier forms selectively on copper regions, giving different areas of the wafer different properties: barrier protection where copper contacts dielectric, and no barrier where only dielectric exists.
2Reliability
If silicon nitride barriers are deposited over the entire surface of the wafer, then diffusion of copper atoms into the dielectric is prevented, but light refraction occurs due to higher optical index
Solution Approach 1:
The patent removes the harmful optical effect by extracting the barrier function from the full-surface silicon nitride layer. The self-aligned barrier formation ensures that barrier material is present only at copper-dielectric interfaces, leaving dielectric regions transparent and free from refraction issues while maintaining diffusion prevention where needed.
Solution Approach 2:
The patent applies local quality by creating barrier properties only where copper-dielectric interfaces exist, leaving other dielectric regions optically uniform and free from refraction. The self-aligned approach ensures that barrier material is localized to specific areas, eliminating the global optical distortion caused by full-surface deposition.
3Ease of manufacture
If copper oxide is not deoxidized before barrier formation, then the process is simpler, but copper atom retention under high current is poor leading to unsatisfactory ageing resistance
Solution Approach 1:
The patent applies self-service by using the copper surface itself to catalyze the decomposition of silane, forming the barrier layer automatically where copper is present. The self-aligned barrier formation process eliminates the need for separate deoxidation steps because the barrier material deposits selectively on copper surfaces through catalytic decomposition, and the resulting copper silicide layer provides effective copper atom retention.
4Ease of manufacture
If a single-layer copper silicide barrier is formed, then the process is simpler, but copper atom retention under high current is insufficient
Solution Approach 1:
The patent segments the barrier into multiple copper silicide layers with different silicon concentrations. The first layer has lower silicon concentration and the second layer has higher silicon concentration, creating a graded structure that provides superior copper atom retention compared to a single-layer barrier. This segmentation allows optimization of both processability and retention performance.
Solution Approach 2:
The patent uses composite materials by forming a multi-layer copper silicide structure with varying compositions. The first copper silicide layer and second copper silicide layer have different silicon concentrations, creating a composite barrier system that combines the benefits of different compositions for optimal copper atom retention and processability.
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 two-layer self-aligned barrier effectively retains copper atoms and improves the ageing resistance of microelectronic circuits, reducing light refraction issues in imager applications while maintaining stability and hardness.
Implementation Method 1
Copper acts as a catalyst in the reaction of decomposing silane to silicon, so that silicon is formed on the copper surface.
Implementation Method 2
treating using a nitrogen-containing plasma
Data Source
AI summary
A semiconductor product includes a portion made of copper, a portion made of a dielectric and a self-aligned barrier between the copper portion and the dielectric portion. The self-aligned barrier includes a first copper silicide layer comprising predominantly first copper silicide molecules, and a second copper silicide layer comprising predominantly second copper silicide molecules. The proportion of the number of silicon atoms is higher in the second silicide molecules than in the first silicide molecules. The second copper silicide layer is positioned between the copper portion and the first copper silicide layer. A nitride layer may overlie at least part of the first copper silicide layer.