Low-Temperature Plasma Etching of Si/SiGe Layers for Straighter Profiles
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Solution Overview
Problem
Conventional etching processes for semiconductor materials, particularly silicon and silicon germanium, face challenges in achieving high selectivity and uniformity, often leading to pattern deformation, sidewall passivation issues, and non-uniform etch profiles due to the use of wet etches and local plasmas that can damage substrates.
Innovation Solution
A single-step etching process using a halogen-containing precursor, optionally with a hydrogen-containing precursor, is performed at low temperatures and controlled power conditions to enhance directionality and reduce the need for polymeric passivation, thereby improving etch uniformity and minimizing sidewall deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet HF etch is used to preferentially remove silicon oxide, then selectivity towards silicon oxide is improved, but penetration into constrained trenches is poor and deformation of remaining material occurs
Solution Approach 1:
The patent changes the physical state parameter of the etching medium from liquid (wet etch) to gaseous plasma, enabling penetration into constrained trenches while maintaining material selectivity through chemical specificity of the plasma reactions
Solution Approach 2:
The patent replaces the chemical mechanism of wet etching with a plasma-based chemical reaction mechanism, where reactive species in the plasma provide both the chemical selectivity and the physical penetration capability needed for constrained geometries
2Ease of operation
If local plasma is used to penetrate constrained trenches, then trench penetration capability is improved, but substrate damage occurs through electric arcs
Solution Approach 1:
The patent changes the operational parameters of plasma etching by operating at low temperature (below 20°C) and controlled pressure conditions, which suppresses electric arc formation while maintaining plasma reactivity for effective trench penetration
Solution Approach 2:
The patent introduces a carefully controlled plasma environment as an intermediary between the etching process and the substrate, where controlled plasma parameters act as a mediator that enables trench penetration without direct harmful arc contact with the substrate
3Productivity
If conventional etching processes are used for silicon and silicon germanium, then etching capability is achieved, but etch profile uniformity and sidewall straightness deteriorate due to pattern loading and sidewall bending
Solution Approach 1:
The patent changes multiple process parameters simultaneously including temperature (below 20°C), pressure, and gas composition ratios, which collectively improve etch profile uniformity and reduce sidewall deformation while maintaining etching capability
Solution Approach 2:
The patent employs periodic pulsing of the plasma discharge and gas flow, creating cyclic periods of etching and passivation that maintain uniform etch profiles and prevent sidewall bending through controlled temporal variation of process conditions
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 process achieves a straighter etch profile without the need for intermediate passivation steps, reducing pattern loading and sidewall bending, and maintaining uniformity across alternating layers of silicon and silicon germanium.
Implementation Method 1
forming plasma effluents of the halogen-containing precursor
Data Source
AI summary
Exemplary semiconductor processing methods may include providing a halogen-containing precursor into a processing region of a semiconductor processing chamber. A substrate may be positioned within the processing region. The substrate may include alternating layers of silicon-containing material and silicon-and-germanium-containing material. The methods may include forming plasma effluents of the halogen-containing precursor. The methods may include contacting the alternating layers of silicon-containing material and silicon-and-germanium-containing material with the plasma effluents of the halogen-containing precursor. The contacting may etch a feature into the alternating layers of silicon-containing material and silicon-and-germanium-containing material. The contacting may be performed at a chamber operating temperature of less than or about 20° C.