Dual Damascene Etching via Gap Fill Convexity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The dual damascene process faces issues with the rounding of trench corners and bridging of neighboring structures due to the shadowing effect of gap fill materials, leading to electrical damage and the formation of fence-shaped dielectric layers, which complicates the reliability and performance of semiconductor devices.
Innovation Solution
A method is introduced where a dielectric layer is formed with a liner, followed by a via opening and gap fill material deposition. A resistant layer is applied, and a photolithographic and etching process is used to create a trench with an etching selectivity that favors the gap fill material over the resistant and dielectric layers, ensuring a convex shape for the gap fill material and preventing rounding and bridging. This process includes using an etching gas like fluorohydrocarbon in an oxygen-free atmosphere to protect the dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gap fill material is filled in the via opening to prevent metal layer damage, then the metal layer is protected from etchant damage, but the shadowing effect of the gap fill material causes fence-shaped dielectric layer formation at the via opening corner
Solution Approach 1:
The patent applies a polymer light process before the trench etching process to prevent fence-shaped dielectric layer formation. The polymer is deposited in advance on the dielectric layer surface, creating a protective mask that prevents etchant from forming fences at the via opening corners during subsequent etching operations
Solution Approach 2:
The patent introduces a polymer layer as an intermediary substance between the gap fill material and the etchant. This polymer layer acts as a mediator that blocks the etchant from interacting with the dielectric layer at critical areas, preventing fence formation while allowing the etching process to proceed normally
2Manufacturing precision
If polymer light process is adopted in trench etching to prevent fence-shaped dielectric layer formation, then fence formation is prevented, but the dielectric layer corner is easily damaged by etchant causing trench corner rounding
Solution Approach 1:
The patent modifies the etching process to have different etching rates for different regions. The etching rate at the via opening corner region is controlled to be slower than in other areas, preventing the polymer from being completely removed and thus protecting the dielectric layer corner from damage while maintaining overall etching efficiency
3Ease of manufacture
If conventional photolithographic etching is used to form copper interconnects, then the process is simple, but copper patterning is difficult to achieve
Solution Approach 1:
The patent divides the single etching process into two separate etching steps: first forming the via opening, then forming the trench. This segmentation allows each etching step to be optimized independently, with the first etching creating precise via openings and the second etching creating the trench while using the via opening as a guide, thereby achieving better copper patterning precision
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 method effectively prevents the rounding of trench corners, avoids bridging between dual damascene structures, and eliminates the formation of fence-shaped dielectric layers, enhancing the reliability and performance of semiconductor devices by maintaining uniformity and preventing electrical issues.
Implementation Method 1
an etching process is performed to form a trench in the dielectric layer to remain the gap fill material having a top surface with a convex shape
Implementation Method 2
a photolithographic process and an etching process are performed to form a trench in the dielectric layer
Implementation Method 3
using an etching gas like fluorohydrocarbon in an oxygen-free atmosphere to protect the dielectric layer
Data Source
AI summary
A dual damascene process is provided. A dielectric layer is formed on a substrate and then a via opening is formed in the dielectric layer to expose a liner formed on the substrate. A gap fill (GF) layer is filled into the via opening and a resistant layer is formed on the substrate. A photolithographic process and an etching process are performed to form a trench in the dielectric layer and to remain the gap fill material having a top surface with a convex shape. In the etching process, an etching rate of the gap fill material layer is larger than that of the resistant layer. The gap fill material, the resistant layer, and the liner exposed by the via opening are removed. A conductive layer fills out the trench and the via opening. This invention is focusing on controlling etch-rate to avoid shielding effect when forming the composite opening.