Low-Temperature Plasma Pre-Clean for Selective Tungsten Gap Fill
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Solution Overview
Problem
Current methods for pre-cleaning semiconductor substrates face challenges in achieving defect-free and low resistivity metal gap fill due to impurities and unstable wafer temperatures during plasma cleaning, which affect selectivity and subsequent deposition processes.
Innovation Solution
A method involving a cooled pedestal with RF capability, maintaining a temperature below 100°C, and using a hydrogen and oxygen plasma treatment to remove chemical residues and impurities while minimizing metal oxidation, thereby improving dielectric selectivity and enabling stable selective metal deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heated plasma is used to clean surface contaminants, then cleaning effectiveness is improved, but wafer temperature becomes unstable and increases by 30°C to 100°C, causing metal oxidation and deposition challenges
Solution Approach 1:
The patent changes the temperature parameter by introducing a cooled pedestal that maintains wafer temperature below 100°C during plasma cleaning, preventing the temperature increase that occurs with conventional heated plasma processes while still achieving effective contaminant removal
Solution Approach 2:
The cooled pedestal acts as an intermediary thermal management system between the plasma source and the wafer, absorbing excess heat and maintaining stable wafer temperature during the plasma cleaning process
2Reliability
If heated plasma is used to remove impurities, then selectivity of metal growth on metal surface versus dielectric field is improved, but metal oxidation increases
Solution Approach 1:
By changing the temperature parameter to maintain wafer temperature below 100°C, the patent suppresses metal oxidation while preserving the selectivity of metal growth on metal surfaces versus dielectric fields during plasma cleaning
Solution Approach 2:
The cooled pedestal provides preliminary thermal protection to the wafer before plasma exposure, preventing the temperature conditions that would lead to metal oxidation while still allowing effective contaminant removal
3Manufacturing precision
If liner film is used for via/trench gap fill, then deposition coverage is improved, but defect free and low resistivity metal gap fill becomes difficult as feature size decreases
Solution Approach 1:
The patent applies preliminary plasma cleaning to remove impurities and repair surface defects in the dielectric, creating a cleaner surface that enables selective metal deposition without requiring a liner film, thereby simplifying the structure and improving gap fill quality
Solution Approach 2:
The patent extracts or removes the liner film from the gap fill process by enabling direct selective metal deposition on the cleaned dielectric surface, eliminating the additional layer and its associated complexity
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 cleans substrates, maintaining stable temperatures and enhancing selectivity for metal deposition, particularly for tungsten, by reducing incubation delays and preventing metal oxidation, thus improving the overall quality of gap fill processes.
Implementation Method 1
The substrate is exposed to a plasma treatment to remove chemical residual and/or impurities from the metal bottom, the dielectric sidewalls, and/or the field of the dielectric
Implementation Method 2
the plasma treatment comprises a hydrogen plasma and an oxygen plasma
Implementation Method 3
the plasma treatment comprises a hydrogen plasma and an oxygen plasma
Implementation Method 4
A substrate comprising a surface structure with a metal bottom, dielectric sidewalls, and a field of the dielectric is on a pedestal comprising a cooling feature. A temperature of the pedestal is set to less than or equal to 100° C.
Data Source
AI summary
Methods for pre-cleaning substrates having metal and dielectric surfaces are described. A temperature of a pedestal comprising a cooling feature on which a substrate is located is set to less than or equal to 100° C. The substrate is exposed to a plasma treatment to remove chemical residual and/or impurities from features of the substrate including a metal bottom, dielectric sidewalls, and/or a field of dielectric and/or repair surface defects in the dielectric sidewalls and/or the field of the dielectric. The plasma treatment may be an oxygen plasma, for example, a direct oxygen plasma. Processing tools and computer readable media for practicing the method are also described.