Vapor-Phase Etching for Airgap Formation in High-Aspect-Ratio Trenches
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Solution Overview
Problem
Conventional etching processes face challenges in selectively removing materials from high-aspect-ratio structures without damaging surrounding features, particularly due to issues with wet etchants' inability to penetrate tightly constrained trenches and the potential for plasma-induced damage in dry etches.
Innovation Solution
The use of a vapor-phase etching method involving a fluorine-containing precursor and a hydrogen-containing precursor, such as anhydrous hydrogen fluoride and water vapor, in a semiconductor processing chamber, where a spacer with specific layer configurations is formed to selectively etch oxygen-containing materials relative to carbon-containing or nitrogen-containing materials, maintaining the plasma-free environment to protect delicate structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching is used to remove exposed material, then selectivity towards specific materials is improved, but penetration into constrained trenches deteriorates and material deformation occurs
Solution Approach 1:
The patent changes the physical state of the etchant from liquid (wet etching) to vapor phase (gas-phase HF), allowing the etchant to penetrate constrained trenches effectively while maintaining high selectivity for silicon oxide removal through controlled vapor-phase chemical reactions
Solution Approach 2:
The patent replaces the liquid-phase chemical etching mechanism with a vapor-phase etching mechanism using hydrogen fluoride gas, which can penetrate narrow trenches through vapor diffusion and condensation on substrate surfaces, avoiding the limitations of liquid etchant access while maintaining material selectivity
2Ease of operation
If dry etching with local plasma is used to penetrate constrained trenches, then trench penetration capability is improved, but substrate damage through electric arcs deteriorates
Solution Approach 1:
The patent changes the etching environment from plasma-based (dry etching) to vapor-phase chemical etching using hydrogen fluoride gas, eliminating ion bombardment and electric arc formation that cause substrate damage, while maintaining effective trench penetration through vapor-phase reaction mechanisms
Solution Approach 2:
The patent avoids the harmful effects of plasma (ion damage, electric arcs) by using a purely chemical vapor-phase etching process with hydrogen fluoride, which provides gentle yet effective material removal without the damaging side effects associated with plasma-based dry etching
3Productivity
If conventional etching processes are used on high-aspect-ratio structures, then etching speed is improved, but selectivity towards surrounding features deteriorates causing erosion
Solution Approach 1:
The patent uses vapor-phase hydrogen fluoride etching with controlled temperature and pressure parameters to achieve high etching rates for silicon oxide while maintaining exceptional selectivity, as the vapor-phase process allows precise control of reaction conditions to protect surrounding features
Solution Approach 2:
The patent achieves local selectivity by controlling the vapor-phase etching process to react preferentially with exposed silicon oxide surfaces while the spacer layers and other materials remain protected, allowing high-speed etching of specific regions without eroding surrounding structures
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 allows for the precise etching of high-aspect-ratio features without eroding other exposed materials, enabling the formation of airgaps while maintaining the integrity of carbon-containing or nitrogen-containing materials, and reduces the risk of plasma-induced damage.
Implementation Method 1
flowing a fluorine-containing precursor into a substrate processing region... flowing a hydrogen-containing precursor into the substrate processing region... contacting a substrate housed in the substrate processing region with the fluorine-containing precursor and the hydrogen-containing precursor... removing the oxygen-containing material
Data Source
AI summary
Exemplary etching methods may include flowing a fluorine-containing precursor into a substrate processing region of a semiconductor processing chamber. The methods may include flowing a hydrogen-containing precursor into the substrate processing region. The methods may include contacting a substrate housed in the substrate processing region with the fluorine-containing precursor and the hydrogen-containing precursor. The substrate may include a trench or recessed feature, and a spacer may be formed along a sidewall of the trench or feature. The spacer may include a plurality of layers including a first layer of a carbon-containing or nitrogen-containing material and a second layer of an oxygen-containing material. The methods may also include removing the oxygen-containing material.