Vapor-Phase MacEtch Using Titanium Nitride Catalyst
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Solution Overview
Problem
Metal-assisted chemical etching (MacEtch) methods, particularly those using noble metals like gold, introduce deep-level defects in silicon and are prone to inverse etching, limiting their application in CMOS fabrication and leading to ion-induced damage and sidewall scallops in semiconductor structures.
Innovation Solution
The development of vapor-phase MacEtch using a CMOS-compatible titanium nitride catalyst, which forms a vapor-phase etchant with an oxidant and acid to selectively etch semiconductor substrates, avoiding inverse etching and deep-level defects by diffusing through a patterned titanium nitride layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If noble metal catalysts (e.g., gold) are used in MacEtch, then the etching process can proceed effectively, but deep-level defects are introduced in silicon
Solution Approach 1:
The patent replaces expensive noble metal catalysts with a disposable patterned metal layer that serves its catalytic function during etching and is subsequently removed. This eliminates the introduction of deep-level defects while maintaining etching efficiency, as the catalyst does not remain in the final structure.
Solution Approach 2:
The patent extracts and removes the harmful noble metal catalyst from the final semiconductor structure after it has served its purpose. The patterned metal layer is etched away after facilitating the MacEtch process, leaving no residual defects in the silicon.
2Ease of manufacture
If conventional liquid-phase MacEtch is used, then the process is simple, but inverse etching occurs where regions not under the catalyst are etched
Solution Approach 1:
The patent introduces an intermediary patterned metal layer that mediates the etching process by providing localized catalytic activity only where needed. This layer controls the chemical reactions to occur precisely at the desired locations, preventing inverse etching while maintaining process simplicity.
Solution Approach 2:
The patent applies local quality by creating a patterned metal layer with spatially varying properties - metallic regions provide catalytic activity while non-metallic regions act as masks. This localized catalysis ensures etching occurs only in specific regions under the metal pattern, eliminating inverse etching.
3Shape
If conventional MacEtch is used, then high-aspect ratio structures can be formed, but ion-induced damage and sidewall scallops occur
Solution Approach 1:
The patent replaces mechanical ion bombardment (physical etching) with a chemical etching mechanism driven by catalytic reactions. The MacEtch process uses chemical oxidation and dissolution instead of ion impact, eliminating ion-induced damage while maintaining the ability to form high-aspect ratio structures.
Solution Approach 2:
The patent changes the etching mechanism from physical (ion-based) to chemical (catalyst-based), fundamentally altering the process parameters. This substitution of etching physics eliminates sidewall scallops and ion damage while preserving high-aspect ratio capability through controlled chemical reactions.
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
Vapor-phase MacEtch enables the production of high-aspect ratio semiconductor features without ion-induced damage or deep-level defects, enhancing the etching process by minimizing inverse etching and promoting forward etching, thus improving the fabrication of semiconductor structures for electronic and optoelectronic devices.
Implementation Method 1
an oxidant and an acid are evaporated to form a vapor-phase etchant comprising an oxidant vapor and an acid vapor
Implementation Method 2
The vapor-phase etchant diffuses through the patterned titanium nitride layer, and titanium nitride-covered regions of the semiconductor substrate are etched
Implementation Method 3
A method of catalyst-assisted chemical etching with a vapor-phase etchant has been developed. According to one embodiment of the method, a semiconductor substrate including a patterned titanium nitride layer thereon is heated
Data Source
AI summary
A method of catalyst-assisted chemical etching with a vapor-phase etchant has been developed. In one approach, a semiconductor substrate including a patterned titanium nitride layer thereon is heated, and an oxidant and an acid are evaporated to form a vapor-phase etchant comprising an oxidant vapor and an acid vapor. The semiconductor substrate and the patterned titanium nitride layer are exposed to the vapor-phase etchant during the heating of the semiconductor substrate. The vapor-phase etchant diffuses through the patterned titanium nitride layer, and titanium nitride-covered regions of the semiconductor substrate are etched. Thus, an etched semiconductor structure is formed.