Copper Extrusion Protection in Integrated Circuit Metallization
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Solution Overview
Problem
In integrated circuits (ICs) with DRAM capacitors, copper extrusions from metal lines can cause failures and short circuits due to reactions with barrier layers, especially at advanced fabrication technologies like 32 nm where spacing between copper lines is reduced.
Innovation Solution
Incorporating an electrical link made of a conductive material different from copper, which passes through a barrier layer and is in direct contact with copper lines, to prevent copper extrusion and reduce the risk of short circuits by spacing the capacitor away from copper lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If copper metallization levels with reduced spacing are used to increase density, then productivity and device density are improved, but the risk of short circuits between capacitors and copper lines increases
Solution Approach 1:
A titanium nitride layer is introduced as an intermediary between the copper metallization level and the capacitor electrodes. This intermediate layer prevents direct contact and potential short circuits between copper lines and capacitors, while still allowing electrical connection through the barrier layer, thus resolving the contradiction between high density and short circuit risk
Solution Approach 2:
The barrier layer structure is made non-uniform: it is present in some regions (between copper lines and capacitors) and absent in others (where electrical connection is needed). This localized variation allows the system to simultaneously achieve electrical connectivity where required and insulation where required, enabling high density without short circuits
2Reliability
If barrier layers are placed between metallization levels and insulating regions to prevent copper diffusion, then reliability is improved, but copper extrusion toward capacitors occurs during high-temperature processing
Solution Approach 1:
The titanium nitride layer serves as a mediator between the copper metallization and the silicon nitride barrier layer. During high-temperature atomic layer deposition, this intermediate titanium nitride layer prevents direct reaction between copper and silicon nitride, thereby preventing copper extrusion while maintaining the barrier layer's copper diffusion prevention function
Solution Approach 2:
The barrier structure is made composite by combining titanium nitride and silicon nitride layers. This composite barrier layer structure leverages the complementary properties of both materials: titanium nitride provides thermal stability and prevents copper extrusion during processing, while silicon nitride provides copper diffusion barrier functionality, thus resolving the contradiction between copper diffusion prevention and copper extrusion
3Productivity
If capacitors are placed close to copper lines to increase density, then productivity is improved, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The barrier layer thickness is optimized to a specific range (5-20 nm) that allows capacitors to be placed close to copper lines for high density, while still providing sufficient insulation to prevent short circuits. This parameter optimization resolves the contradiction between high density and manufacturing precision by finding the optimal spacing that enables both goals
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 copper extrusion and short circuit risks, allowing for the production of larger capacitors with higher capacitive value, even in advanced technologies, while maintaining high density and reducing the footprint of logic signals.
Implementation Method 1
barrier layers, for example, made of silicon nitride (SiN) or SiCN, placed between the metallization levels and the various insulating regions. The aim of these barrier layers is to prevent copper from diffusing into the insulating regions
Implementation Method 2
the electrical link enables the copper line to be spaced away from the element connected to this line, thereby, on the one hand, making it easier to place a material different from copper in direct contact with the copper line, despite the presence of the barrier layer, and, on the other hand, reducing the risk of short circuits
Implementation Method 3
During the atomic layer deposition step for forming the titanium nitride layers, very high temperatures (above 400° C.) are reached. These temperatures promote a reaction between the copper of the metal lines and the silicon nitride barriers
Data Source
AI summary
An integrated circuit may include an element placed in an insulating region adjacent to a copper metallization level and including a barrier layer in contact with a metallization level. The element may be electrically connected to and spaced away from a copper line of the metallization level by way of an electrical link passing through the barrier layer and including an electrically conductive material different from copper in direct contact with the copper line.