Silicon-Germanium Etching with Fluorine Passivation Selectivity
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Solution Overview
Problem
As device sizes shrink, conventional etching technologies struggle with maintaining selectivity during the removal of silicon-and-germanium-containing materials, leading to decreased etch selectivity and damage to underlying structures like gate structures due to pitting.
Innovation Solution
A method involving specific fluorine-containing precursors, such as nitrogen trifluoride, silicon tetrafluoride, and hydrogen fluoride, is used to etch silicon-and-germanium-containing materials with high selectivity and form a passivation material to protect underlying materials, employing controlled plasma conditions and precursor flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to remove silicon-and-germanium-containing materials, then the etching process can proceed, but etch selectivity decreases and damage to underlying structures occurs
Solution Approach 1:
The etching process is segmented into multiple sequential steps using different fluorine-containing precursors. The first precursor (NF3) performs initial etching, followed by a second precursor (SiF4) that provides selective etching with passivation, and optionally a third precursor (HF) for final selective removal. This segmentation allows each step to be optimized for specific functions, achieving high overall selectivity while protecting underlying structures.
Solution Approach 2:
The first fluorine-containing precursor (NF3) performs preliminary etching of the silicon-and-germanium-containing material before the selective etching step. This preliminary action removes the bulk material, reducing the workload for subsequent selective etching steps and enabling better control over the final selective removal process.
Solution Approach 3:
The second fluorine-containing precursor (SiF4) acts as an intermediary that provides both etching and passivation functions. It selectively etches silicon-and-germanium-containing materials while simultaneously forming protective fluorinated layers that prevent damage to underlying structures, serving as a bridge between aggressive etching and protective passivation.
2Productivity
If the etch rate is increased to improve productivity, then material removal is faster, but selectivity decreases and underlying structures are damaged
Solution Approach 1:
The etching process is divided into multiple steps with different precursors, each optimized for specific rates and selectivity requirements. The first precursor provides high etch rate for productivity, while subsequent precursors provide selective etching with lower rates to preserve underlying structures, achieving both high overall productivity and maintained selectivity.
Solution Approach 2:
The process uses periodic alternation between different precursor exposures, with each precursor providing specific functions at different stages. This periodic action allows the system to switch between high-rate etching modes and selective/passivation modes, achieving both high productivity and high selectivity throughout the overall process.
3Productivity
If device sizes are reduced to increase integration density, then more devices fit on a substrate, but maintaining selectivity during material removal becomes more difficult
Solution Approach 1:
The multi-precursor process provides locally optimized chemistry for different regions and materials. Each precursor is tuned to interact specifically with certain materials (silicon-and-germanium-containing layers) while being selective against others (silicon-containing layers, underlying structures). This local quality control through chemical specificity enables high selectivity even in densely integrated devices with minimal spacing.
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 achieves a high etch rate of silicon-and-germanium-containing materials while minimizing etching of underlying materials, enhancing selectivity and preventing damage to structures like gate structures.
Implementation Method 1
generating plasma effluents of the first fluorine-containing precursor in the remote plasma system
Implementation Method 2
contacting the substrate with the plasma effluents of the first fluorine-containing precursor and with the second fluorine-containing precursor. The methods may include etching the silicon-and-germanium-containing material
Implementation Method 3
The methods may include forming a passivation material on the substrate. The passivation material may include a silicon-fluorine-and-hydrogen-containing material
Data Source
AI summary
Exemplary methods of semiconductor processing may include providing a first fluorine-containing precursor to a remote plasma system of a semiconductor processing chamber. The methods may include generating plasma effluents of the first fluorine-containing precursor in the remote plasma system. The methods may include providing plasma effluents of the first fluorine-containing precursor to a processing region of the semiconductor processing chamber. The methods may include providing a second fluorine-containing precursor to the processing region of the semiconductor processing chamber. A substrate including alternating layers of material may be disposed within the processing region. The alternating layers of material may include a silicon-and-germanium-containing material. The methods may include contacting the substrate with the plasma effluents of the first fluorine-containing precursor and with the second fluorine-containing precursor. The methods may include etching the silicon-and-germanium-containing material of the alternating layers of material on the substrate.