Microwave Plasma Oxide Layer Formation at Low Temperatures
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Solution Overview
Problem
Current methods for forming dielectric layers, particularly oxide layers, on semiconductor substrates face challenges such as high thermal budgets, uneven layer thicknesses, and insufficient electrical properties, especially when aiming for temperatures below 200°C, which is crucial for advanced semiconductor manufacturing like 3D chip structures and TSVs.
Innovation Solution
A method involving the generation of a plasma adjacent to the substrate using microwaves from an oxygen-containing gas, with specific process conditions like average microwave power density, plasma duration, and chamber pressure, to induce oxide growth at temperatures below 200°C, utilizing a microwave rod with an outer and inner conductor, and optionally a dielectric enveloping tube, to achieve high-quality, conformal oxide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal oxidation is used to form dielectric layers, then good electrical properties and reliable layer formation are achieved, but high temperatures are required which negatively affect underlying structures
Solution Approach 1:
The patent replaces thermal oxidation (heat-driven chemical reaction) with plasma oxidation (electron-driven chemical reaction). The plasma source generates reactive oxygen species through electromagnetic field excitation of oxygen-containing gas, which then oxidize the silicon substrate at low temperatures. This substitution of the oxidation mechanism allows dielectric layer formation with good electrical properties without requiring high temperatures that would damage underlying structures.
Solution Approach 2:
The patent changes the fundamental parameter of oxidation temperature from high (thermal oxidation) to low (plasma oxidation). By controlling plasma parameters such as power density, gas composition, and pressure, the oxidation process occurs at temperatures that do not adversely affect underlying semiconductor structures, while still achieving reliable dielectric layer formation with appropriate electrical properties.
2Temperature
If plasma oxidation is used to reduce thermal budget, then temperatures are reduced compared to thermal oxidation, but uneven oxide layers and insufficient electrical properties result
Solution Approach 1:
The patent employs a planar slot antenna configuration that creates a distributed plasma field across the substrate surface. The slot antenna geometry allows for uniform plasma generation over the entire wafer area, ensuring consistent oxide layer thickness and quality across different regions. This local uniformity of plasma distribution resolves the issue of uneven oxide layers while maintaining low temperature processing.
Solution Approach 2:
The planar slot antenna design creates a relatively uniform plasma potential distribution across the substrate surface. By maintaining equipotential conditions across the processing area, the oxidation rate becomes uniform, producing even oxide layers with consistent electrical properties throughout the wafer, thereby resolving the non-uniformity problem associated with conventional plasma oxidation.
3Temperature
If plasma oxidation is used to reduce thermal budget, then temperatures are reduced compared to thermal oxidation, but insufficient electrical properties of the formed layers result
Solution Approach 1:
The patent optimizes plasma process parameters including power density, oxygen partial pressure, and plasma duration to achieve high-quality dielectric layers at low temperatures. By carefully controlling these parameters, the oxidation process produces oxide layers with appropriate density, interface quality, and electrical properties, matching or exceeding thermal oxidation quality without the high temperature requirement.
Solution Approach 2:
The replacement of thermal oxidation with plasma oxidation using a planar slot antenna provides better control over the oxidation chemistry and kinetics. The plasma-generated reactive species enable oxidation at lower temperatures while maintaining or improving electrical properties through controlled reaction conditions, resolving the insufficiency of electrical properties in conventional low-temperature plasma oxidation.
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 method allows for the production of high-quality oxides with improved interface quality and reduced dopant redistribution, achieving electrical properties comparable to thermal oxides while maintaining low growth temperatures, suitable for complex semiconductor structures.
Implementation Method 1
the plasma is generated from an oxygen-containing gas or gas mixture using microwaves. The microwaves are coupled into the gas, which is located in a process chamber, by at least one magnetron via at least one microwave beam
Implementation Method 2
generating a plasma adjacent to at least one surface of the substrate, wherein the plasma is generated from an oxygen-containing gas or gas mixture using microwaves
Implementation Method 3
oxide growth is induced on the surface of the substrate facing the plasma
Data Source
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AI summary
A method for forming an oxide layer on a substrate is described, wherein a plasma is generated adjacent to at least one surface of the substrate by means of microwaves from a gas containing oxygen, wherein the microwaves are coupled into the gas by a magnetron via at least one microwave rod, which is arranged opposite to the substrate and comprises an outer conductor and an inner conductor. During the formation of the oxide layer, the mean microwave power density is set to P=0.8-10 W/cm2, the plasma duration is set to t=0.1 to 600 s, the pressure is set to p=2.67-266.64 Pa (20 to 2000 mTorr) and a distance between substrate surface and microwave rod is set to d=5-120 mm. The above and potentially further process conditions are matched to each other such that the substrate is held at a temperature below 200° C. and an oxide growth is induced on the surface of the substrate facing the plasma.