Multi-Layer Etch Stop Structure for Hydrogen-Stable Copper Interconnects
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Solution Overview
Problem
The semiconductor industry faces challenges in forming reliable copper-based interconnect structures due to issues like copper pits and hillocks, which lead to yield loss and reduced performance, particularly in multilayer interconnect features as IC feature sizes shrink.
Innovation Solution
A method is introduced that involves forming a multi-layer etch stop structure using a combination of metal-containing and silicon-containing dielectric layers over copper conductive features, with specific deposition processes to prevent hydrogen diffusion and mitigate hillock formation, thereby enhancing the reliability of interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper-based interconnect structures are formed in multilayer interconnect features, then interconnect functionality is achieved, but copper pits and hillocks occur leading to yield loss
Solution Approach 1:
A multi-layer etch stop structure is introduced as an intermediary layer between the copper interconnect and the overlying dielectric layers. This etch stop structure includes a first etch stop layer and a second etch stop layer that acts as a barrier to prevent hydrogen diffusion into the copper, thereby preventing pit formation while also serving as an etch stop during subsequent processing
Solution Approach 2:
The etch stop structure employs composite material layers with different properties - the first etch stop layer provides hydrogen barrier functionality, while the second etch stop layer provides etch selectivity and structural support. This composite approach addresses multiple requirements simultaneously to prevent copper degradation
2Reliability
If fabrication processes are performed to form passivation layer over interconnect structures, then device protection is achieved, but copper hillock formation occurs
Solution Approach 1:
The etch stop structure is formed preliminarily before the passivation layer fabrication process. This preliminary structure prevents copper atoms from diffusing outward during subsequent high-temperature annealing processes, thereby preventing hillock formation before it can occur
Solution Approach 2:
The etch stop structure serves as an intermediary barrier between the copper interconnect and the passivation layer processing environment, blocking the pathways that would otherwise allow copper diffusion and hillock formation during device fabrication
3Productivity
If IC feature size is scaled down, then production efficiency increases and costs decrease, but processing complexity increases
Solution Approach 1:
The etch stop structure is segmented into multiple functional layers - a first etch stop layer for hydrogen barrier functionality and a second etch stop layer for etch selectivity. This segmentation allows each layer to be optimized for its specific function, managing the complexity of scaled-down interconnect processing
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 effectively reduces the occurrence of pits and hillocks, improving the reliability and performance of interconnect structures, and increasing yield by protecting copper features from damage during annealing in hydrogen gas environments.
Implementation Method 1
a silicon-containing dielectric layer formed over the first metal-containing dielectric layer to prevent the first metal-containing dielectric layer from becoming damaged due to moisture
Implementation Method 2
with specific deposition processes to prevent hydrogen diffusion and mitigate hillock formation
Data Source
AI summary
A method for forming a semiconductor device structure is provided. The method includes successively forming a first multi-layer etch stop structure and an insulating layer over a first conductive feature. The insulating layer and the first multi-layer etch stop structure are successively etched to form an opening substantially aligned to the first conductive feature. A second conductive feature is formed in the opening. The formation of the first multi-layer etch stop structure and the second multi-layer etch stop structure includes forming a first metal-containing dielectric layer, forming a silicon-containing dielectric layer over the first metal-containing dielectric layer, and forming a second metal-containing dielectric layer over the silicon-containing dielectric layer. The second metal-containing dielectric layer has a material that is different from the material of the first metal-containing dielectric layer.