Metal Oxide Conversion Capping for Faster MEOL and BEOL Processing
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Solution Overview
Problem
Existing semiconductor fabrication processes face challenges in efficiently removing metal oxides like tungsten oxide and molybdenum oxide, and protecting metal layers from further oxidation, particularly due to time-consuming chemical soaks and size variations in post-soak features.
Innovation Solution
A method involving a conversion process to reduce metal oxide layers and form metal sulfide cap layers on top of metal layers, using a precursor containing hydrogen and hydrogen sulfide, followed by exposure to an oxidizing environment and subsequent removal of the cap layer using plasma treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical soak is used to remove metal oxides, then metal oxide removal is achieved, but processing time increases and size variation occurs
Solution Approach 1:
The patent replaces the chemical soak process (chemical system) with a physical plasma treatment process. The plasma treatment uses ionized gas to physically sputter and remove metal oxides without the need for liquid chemical precursors, thereby eliminating the time-consuming chemical reactions and associated size variations while achieving effective oxide removal.
Solution Approach 2:
The patent changes the processing parameters from chemical concentration and soak duration to plasma power, gas flow rate, and treatment time. By controlling plasma parameters such as RF power (50-200W) and gas flow (10-100 sccm), the process achieves rapid oxide removal with precise control over feature dimensions, avoiding the uncontrolled chemical reactions that cause size variation.
2Manufacturing precision
If chemical soak is used to remove metal oxides, then metal oxide removal is achieved, but the process becomes time-consuming
Solution Approach 1:
The patent substitutes the slow chemical dissolution process with rapid physical plasma sputtering. Plasma treatment can remove metal oxides in seconds to minutes compared to the extended chemical soak times required, dramatically improving throughput while maintaining effective oxide removal. The ion bombardment in plasma provides direct physical removal without relying on chemical reaction rates.
Solution Approach 2:
The patent skips the lengthy chemical reaction phase entirely by using plasma to directly sputter away metal oxides. This 'rushing through' approach bypasses the slow chemical dissolution mechanism and achieves oxide removal through rapid physical ejection of material, significantly reducing processing time and improving productivity.
3Productivity
If vacuum break occurs, then metal layer is exposed to oxidizing environment, but metal layer undergoes unwanted oxidation
Solution Approach 1:
The patent introduces plasma as an intermediary treatment between vacuum breaks. The plasma treatment creates a controlled oxidizing environment that forms a uniform, thin oxide layer which actually protects the underlying metal from further oxidation. This intermediary plasma exposure acts as a protective pre-treatment, allowing subsequent vacuum breaks without harmful oxidation.
Solution Approach 2:
The patent converts the harmful effect of vacuum-induced oxidation into a beneficial protective oxide layer. By deliberately exposing the metal to controlled plasma oxidation before vacuum breaks, a stable, thin oxide forms that serves as a protective barrier, preventing the unwanted thick, non-uniform oxidation that would occur during uncontrolled vacuum exposure.
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 effectively protects metal layers from further oxidation by forming a conductive semiconductor cap layer that can be selectively formed and removed, improving processing efficiency and reducing size variations.
Implementation Method 1
performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a metal sulfide layer on the top surface of the metal layer
Implementation Method 2
performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer
Implementation Method 3
performing a removal process to remove the metal sulfide layer
Data Source
AI summary
A method of capping a metal layer includes performing a conversion process to reduce a metal oxide layer formed on a top surface of the metal layer and form a metal sulfide layer on the top surface of the metal layer, exposing the top surface of the metal layer to an oxidizing environment, and performing a removal process to remove the metal sulfide layer.