PVP-Assisted SiGe Etching Composition for Protecting Si Layers
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Solution Overview
Problem
Current methods for selectively etching silicon-germanium (SiGe) layers from microelectronic device substrates suffer from low SiGe/Si selectivity, slow etch rates, high etch rates for silicon-containing layers, and long incubation/ripening times, making them inadequate for precise nanowire or nanosheet structure fabrication.
Innovation Solution
A composition comprising an oxidizing agent, a fluoride etchant, an acid, polyvinylpyrrolidone (PVP), and water is used to selectively etch SiGe layers, enhancing SiGe/Si selectivity and etch rate while minimizing etching of silicon-containing layers like a-Si, SiOx, and SiN.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching compositions are used, then etching of SiGe layers can be achieved, but the SiGe/Si selectivity is too low causing unwanted attack on Si layers
Solution Approach 1:
The patent introduces PVP (polyvinylpyrrolidone) as an intermediary substance that selectively adsorbs onto Si surfaces, creating a protective layer that prevents the etching composition from attacking Si layers. This mediator allows the etch to proceed on SiGe while being blocked on Si, achieving high selectivity without requiring extreme conditions that might harm other structures.
Solution Approach 2:
The patent modifies the chemical parameters of the etching composition by adjusting the ratios of HF, H2O2, acetic acid, and adding PVP. These parameter changes create a chemical environment that preferentially reacts with SiGe while the PVP-Si complex resists etching, thereby achieving high SiGe/Si selectivity (greater than 10:1) while maintaining acceptable etch rates.
2Productivity
If conventional etching compositions are used, then etching can proceed, but the etch rate is too slow leading to long processing times
Solution Approach 1:
The patent optimizes the concentration parameters of the etching composition, specifically using HF in the range of 0.1-5% and H2O2 in the range of 1-10%, along with acetic acid 10-50% and PVP 0.1-5%. These parameter adjustments create a balanced chemical environment that maintains high reactivity toward SiGe (achievving etch rates greater than 10 nm/min) while ensuring selective protection of Si layers through PVP adsorption.
3Manufacturing precision
If conventional etching compositions are used, then etching can occur, but the etch rate for silicon-containing layers (SiO2, SiN, SiON) is too high
Solution Approach 1:
PVP acts as a selective intermediary that forms protective complexes with silicon-containing layers. The PVP-Si complex has significantly reduced etch susceptibility compared to unprotected Si, SiO2, SiN, or SiON layers. This intermediary mechanism allows the etching composition to selectively remove SiGe while preserving other silicon-containing structures that are coated or adjacent to PVP.
4Productivity
If conventional etching compositions are used, then etching can proceed, but a long incubation/ripening time is required before effective etching begins
Solution Approach 1:
The patent incorporates PVP in the etching composition itself, which performs the preliminary action of adsorbing onto Si surfaces and forming protective complexes before the etching reaction begins. This preliminary PVP adsorption eliminates the need for separate incubation or ripening steps, as the selective protection is established immediately upon contact with the substrate, allowing effective etching to begin right away.
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 composition allows for controlled and selective etching of SiGe layers, achieving etch rates at least 10 times faster for SiGe compared to silicon-containing layers, thereby improving the precision and efficiency of microelectronic device fabrication.
Implementation Method 1
an oxidizing agent
Implementation Method 2
an etchant comprising a source of fluoride ions
Data Source
AI summary
Described herein is a composition for selectively etching a layer including a silicon germanium alloy (SiGe) in the presence of a silicon-containing layer, particularly a layer comprising a-Si, SiOx, SiON, SiN, or a combination thereof, the composition including:(a) an oxidizing agent,(b) an acid selected from an inorganic acid and an organic acid,(c) an etchant including a source of fluoride ions,(d) a polyvinylpyrrolidone (PVP), and(e) water.