Dual-Damascene
The dual-Damascene process represents an advancement in semiconductor manufacturing, streamlining the fabrication of metallization layers and vias within a single deposition process. It offers greater efficiency compared to the traditional Damascene process. Here is an overview of the dual-Damascene process and its key steps, particularly for copper metallization:
First Insulating Oxide Layer: The process begins by depositing the first insulating oxide layer onto the wafer surface. This layer serves as a foundation for subsequent layers.
Nitride Layer Deposition: A nitride layer is deposited on top of the first insulating oxide layer.
Structuring Nitride Layer: The nitride layer is selectively structured to create a mask for etching the contacts/vias. This mask defines the locations where contacts/vias will be formed.
Second Insulating Oxide Layer: A second insulating oxide layer is deposited on top of the structured nitride layer.
Trench and Via Formation: Using selective etching, the top oxide layer is etched to create both the trenches for interconnects and the holes for contacts/vias. This step involves shaping the insulating layers to prepare for metal deposition.
Nitride Etching: Nitride etching is performed to remove the nitride layer that previously served as a mask for etching contacts/vias. This step exposes the underlying layers for further processing.
Barrier Layer and Seed Layer Deposition: A diffusion barrier layer and a seed layer for copper deposition are deposited onto the exposed surfaces. These layers prepare the surface for copper metalization.
Copper Deposition: Copper is deposited to fill both the contacts/vias and the trenches for interconnect structures. This is achieved in a single deposition process, streamlining the dual-Damascene approach.
Excess Copper Removal and Planarization: The excess copper on the wafer’s surface is removed, and the entire surface is planarized using a chemical-mechanical polishing (CMP) process. This step ensures that only the desired copper structures remain.
Nitride Layer as Barrier: Finally, a nitride layer is deposited as a barrier to prevent copper diffusion and oxidation. This protective layer ensures the long-term integrity of the metallization and via structures.
How does it differ from the traditional Damascene process?
The dual-Damascene process simplifies the fabrication of metallization layers and vias by combining the formation of both structures in a single deposition process. This approach reduces the number of CMP steps required and improves manufacturing efficiency. It is particularly well-suited for copper metallization, which can be challenging to etch using traditional methods. Different variations of the dual-Damascene process may exist, but they all share the fundamental goal of achieving integrated metallization via formation in a more streamlined manner.
What is the primary advantage of the dual-Damascene process?
The dual-Damascene process combines the filling of contact/via holes and interconnects trenches in a single deposition process, reducing complexity and requiring only one final CMP (chemical-mechanical polishing) step.
What is the purpose of depositing a nitride layer in the dual-damascene process?
The nitride layer is structured to serve as a mask for etching the locations of contacts/vias and plays a role in preventing copper diffusion and oxidation.
How does the dual-Damascene process streamline the fabrication of vias and interconnects?
It simultaneously etches the top oxide layer to create interconnect trenches while also etching holes for contacts/vias that were defined by the nitride mask.