Microwave Oxidation Etching for Low-Resistance Interconnect Gap Fill
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Solution Overview
Problem
Current interconnect manufacturing processes face challenges in reducing via resistance and improving deposition selectivity, particularly in smaller features, due to the high resistivity of barrier layers and difficulties in gap fill processes with materials like tungsten and molybdenum.
Innovation Solution
A method involving physical vapor deposition of a metal film followed by exposure to oxygen gas and microwave energy to form a metal oxide layer, which is then etched using hydrogen gas and microwave energy, is repeated to fill gaps with dielectric sidewalls and epitaxial silicon bottoms, enhancing deposition selectivity and reducing via resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If barrier layer thickness is reduced to decrease via resistance, then via resistance decreases, but adhesion and diffusion prevention capabilities deteriorate
Solution Approach 1:
The patent applies local quality by creating different barrier layer thicknesses at different locations: a first thickness on the dielectric sidewalls and a second, smaller thickness on the metal surface at the bottom of the via. This allows the barrier layer to maintain adhesion and diffusion prevention capabilities on the sidewalls while reducing via resistance at the bottom where it contributes most to resistance.
2Reliability
If selective deposition is used to reduce barrier layer thickness on metal surface, then via resistance decreases, but process complexity increases
Solution Approach 1:
The patent uses parameter changes in the deposition process to achieve selective barrier layer thickness. By modifying deposition parameters such as precursor flow rates, pressure, and substrate temperature during atomic layer deposition, the process selectively deposits thinner barrier layer on the metal surface compared to the dielectric sidewalls, reducing via resistance while maintaining protective functionality.
3Strength
If tungsten is used as gap fill material, then melting point and conductivity are improved, but etchability deteriorates
Solution Approach 1:
The patent employs phase transitions by oxidizing tungsten to tungsten oxide, which has different etchability properties. The tungsten oxide can be selectively removed by etching processes that do not affect the dielectric sidewalls, enabling precise gap fill control while maintaining tungsten's superior melting point and conductivity in the final interconnect structure.
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 via resistance and improves deposition selectivity, addressing the limitations of conventional methods by utilizing microwave oxidation and etching techniques to enhance interconnect performance.
Implementation Method 1
exposed to an oxidizing condition comprises a flow of oxygen gas and microwave energy to form a metal oxide layer
Implementation Method 2
The metal oxide layer is etched by exposure to an etching condition comprising a flow of etching as and microwave energy
Implementation Method 3
A metal film is deposited by physical vapor deposition
Data Source
AI summary
Methods of manufacturing interconnect structures as part of a microelectronic device fabrication process are described. The methods include filling a gap in a surface of a substrate by depositing a metal film by physical vapor deposition followed by oxidizing the metal film using microwave energy and then etching the metal oxide layer formed. The deposition, oxidation and etching processes are repeated to fill the gap.