Layer-by-layer etching of poly-granular metal films
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Solution Overview
Problem
Current plasma etching processes for poly-granular metal-based films, such as titanium (Ti) and titanium nitride (TiN), face challenges in achieving a uniform etch rate due to non-uniform distribution of impurities and grain size, leading to etching at grain boundaries, undercuts, and metal-containing residues.
Innovation Solution
A layer-by-layer etching method using a cyclic process with a background plasma and a modifying plasma to create a surface modification region, followed by biasing power to remove the modification region, ensuring a substantially uniform depth and planar surface, thereby avoiding etching at grain boundaries and reducing residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used on poly-granular metal-based films, then etching can be performed, but the etch rate is non-uniform due to impurity and grain size distribution, leading to etching at grain boundaries, undercuts, and residues
Solution Approach 1:
The etching process is segmented into multiple sequential steps: a first plasma etching step followed by a second plasma etching step with different parameters. This segmentation allows each step to target specific aspects of the film removal, with the first step addressing bulk material and the second step refining the surface to eliminate grain boundary effects and achieve uniform etching rate
Solution Approach 2:
The patent changes plasma process parameters between etching steps, including gas composition, power levels, and pressure conditions. The first plasma etching uses one set of parameters optimized for initial material removal, while the second plasma etching uses different parameters optimized for surface refinement and uniformity, thereby resolving the contradiction between etching efficiency and uniformity
2Manufacturing precision
If atomic level scaling is pursued for sub-10 nanometer node devices, then device performance increases, but fabrication processes such as etching become significantly more challenging
Solution Approach 1:
The patent employs periodic action through cyclic plasma etching processes with alternating treatment phases. Multiple plasma etching cycles are performed sequentially, with each cycle consisting of controlled exposure and removal phases. This periodic approach enables precise control over etching depth and profile at atomic level scaling dimensions while managing the complexity of fabrication processes
Solution Approach 2:
The multi-step plasma etching process incorporates feedback mechanisms where process parameters are adjusted based on real-time monitoring and previous step outcomes. The second plasma etching step acts as a feedback correction to the first step, compensating for variations and achieving the required precision for sub-10 nanometer features
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 achieves a smooth, uniform etch rate across the film, controlling undercuts, and eliminating residues, allowing for the formation of precise stepped structures and features in semiconductor structures.
Implementation Method 1
applying a source power to the plasma etching chamber to generate a background plasma from the background gas
Implementation Method 2
generate a modifying plasma that produces a surface modification region with a substantially uniform depth in the top surface of the poly-granular metal-based film
Implementation Method 3
applying a biasing power to the substrate to remove the surface modification region from the top surface of the poly-granular metal-based film
Data Source
AI summary
A method for etching a poly-granular metal-based film includes providing a flow of a background gas in a plasma etching chamber containing a semiconductor structure including the poly-granular metal-based film formed over a substrate with a mask patterned over the poly-granular metal-based film. The method also includes applying a source power to generate a background plasma from the background gas, and providing a flow of a modifying gas while maintaining the flow of the background gas to generate a modifying plasma that produces a surface modification region with a substantially uniform depth in the top surface of the poly-granular metal-based film exposed by the mask. The method further includes stopping the flow of the modifying gas while maintaining the flow of the background gas, and applying a biasing power to the substrate to remove the surface modification region.