Titanium Layer Etching with HF-Ozone Selectivity to Silicon
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Solution Overview
Problem
In semiconductor processing, achieving high selectivity in etching titanium and titanium nitride relative to other materials is challenging, particularly due to low selectivity with fluorine radicals when etching materials like silicon and silicon germanium.
Innovation Solution
A method involving a co-flow of hydrofluoric acid (HF) gas and ozone gas is used to selectively etch titanium and titanium nitride layers on semiconductor workpieces, with the HF gas and ozone gas being introduced simultaneously into a processing chamber, either directly or generated through a remote plasma source, to achieve a high etch rate and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine radicals are used to etch titanium and titanium nitride, then etching capability is achieved, but selectivity relative to other materials such as silicon and silicon germanium deteriorates
Solution Approach 1:
The patent combines fluorine radicals with ozone in a single etching process to achieve both etching capability and high selectivity. The fluorine radicals provide the etching action on titanium-containing layers while ozone suppresses etching of silicon and silicon germanium, resolving the selectivity problem without sacrificing etching performance.
Solution Approach 2:
The etching process uses a composite gas mixture containing fluorine-containing compounds and ozone. This composite approach creates a chemically selective environment where the combination of reactive species achieves differential etching rates between titanium nitride and underlying silicon layers, enabling high selectivity.
2Manufacturing precision
If high selectivity etching is pursued, then precision in material removal is improved, but processing time increases
Solution Approach 1:
By merging fluorine radical chemistry with ozone chemistry in one simultaneous process step, the patent achieves high selectivity without requiring multiple sequential etching steps. The fluorine radicals rapidly etch titanium-containing materials while ozone protects silicon, enabling fast processing with high precision.
Solution Approach 2:
The patent optimizes process parameters including gas flow rates, pressure, and temperature to maximize the selective etching rate. By adjusting these parameters, the process achieves both high selectivity and high etch rate, reducing processing time while maintaining 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
This approach enables a high etch rate of titanium nitride and titanium, with selectivity towards other materials such as silicon and silicon germanium, while maintaining an all-dry process, allowing for precise control and versatility in semiconductor fabrication equipment.
Implementation Method 1
exposing the first layer and the second layer on the workpiece to the process gas to at least partially etch the first layer at a greater etch rate relative to the second layer
Implementation Method 2
The process gas includes an ozone gas and a fluorine containing gas
Data Source
AI summary
Systems and methods for etching titanium containing layers on a workpiece are provided. In one example, a method includes placing the workpiece on a workpiece support in a processing chamber. The workpiece includes a first layer and a second layer. The first layer is a titanium containing layer. The method includes admitting a process gas into the processing chamber. The process gas includes an ozone gas and a fluorine containing gas. The method includes exposing the first layer and the second layer on the workpiece to the process gas to at least partially etch the first layer at a greater etch rate relative to the second layer.