Cobalt Etch Surface Roughness Reduction
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Solution Overview
Problem
Dry etch processes for metal etching on semiconductor substrates, particularly for metals like cobalt and nickel, face challenges due to non-volatility of halogenated and organometallic compounds at conventional temperatures, leading to surface roughness and uneven etching rates.
Innovation Solution
A two-stage etching sequence involving pre-treatment with a hydrogen-containing plasma to reduce cobalt oxide and disorder crystalline regions, followed by exposure to halogen-containing and carbon-nitrogen-containing precursors to form volatile etch products, with optional additional plasma treatments after multiple etching sequences to enhance etch rate and smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etch processes are used to etch cobalt and nickel, then the etching process can be performed with precise control and low impact on patterned features, but the halogenated and organometallic compounds formed are non-volatile at conventional temperatures, leading to surface roughness and uneven etching rates
Solution Approach 1:
The patent changes the temperature parameter during the etching process to above the decomposition temperature of the halogenated and organometallic compounds. This allows the compounds to decompose and volatilize, removing them from the substrate surface and preventing surface roughness while maintaining etching uniformity
Solution Approach 2:
The patent employs a multi-step etching sequence with periodic plasma treatments. Between etching steps, plasma is used to clear residual non-volatile compounds from the surface, creating a periodic cycle of etching and cleaning that maintains surface smoothness throughout the process
2Productivity
If the substrate is exposed to remote plasma by-products from halogenated and carbon-nitrogen-containing precursors, then volatile etch products are formed and removed, but residual liquid etchants remain on exposed substrate surfaces, causing over-etching
Solution Approach 1:
The patent replaces wet etching (liquid etchants) with dry plasma etching. The plasma process allows for precise control of the etching reaction and immediate termination by stopping plasma generation and evacuating or purging the chamber, eliminating the over-etching problem associated with liquid etchants that require manual removal
Solution Approach 2:
The patent maintains continuous plasma exposure during the etching process to ensure complete removal of etch products and prevent residue formation. The plasma continues to act on the surface throughout the etching cycle, ensuring clean surfaces and precise etch stops without the interruption needed for liquid etchant removal
3Temperature
If cobalt is etched using conventional dry etch processes, then the etching can be performed at conventional temperatures, but the non-volatilized cobalt etch products remain on the substrate surface, increasing surface roughness
Solution Approach 1:
The patent increases the temperature parameter during etching to above the decomposition temperature of cobalt halides and organometallic compounds. This temperature change enables the non-volatile etch products to decompose and volatilize, completely removing them from the substrate surface and eliminating surface roughness
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 method achieves a more uniform and faster etching of metal layers with reduced surface roughness, effectively addressing the difficulties in etching cobalt and nickel using conventional dry etch processes.
Implementation Method 1
The treatment of the metal layer with the plasma formed from the hydrogen-containing precursor includes reducing metal oxide formed on the metal layer to additional metal
Implementation Method 2
The chemical reduction of the cobalt oxide to cobalt metal is complemented by a physical bombardment of the etchable surface by ionically charged species in the plasma
Implementation Method 3
The metal layer is reacted with a halogen-containing precursor to form a halogenated metal layer that includes a halogenated etch product
Implementation Method 4
The carbon-and-nitrogen-containing precursor further reacts with the cobalt and cobalt halide etch products to create volatile organometallic cobalt complexes that desorb from the cobalt layer
Data Source
AI summary
Methods are described for etching metal layers that are difficult to volatize, such as cobalt, nickel, and platinum to form an etched metal layer with reduced surface roughness. The methods include pretreating the metal layer with a local plasma formed from a hydrogen-containing precursor. The pretreated metal layer is then reacted with a halogen-containing precursor to form a halogenated metal layer having a halogenated etch product. A carbon-and-nitrogen-containing precursor reacts with the halogenated etch product to form a volatile etch product that can be removed in the gas phase from the etched surface of the metal layer. The surface roughness may be reduced by performing one or more plasma treatments on the etching metal layer after a plurality of etching sequences. Surface roughness is also reduced by controlling the temperature and length of time the metal layer is reacting with the etchant precursors.