Conductive Cap Layer Oxynitride Protection During Via Formation
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Solution Overview
Problem
The top portion of a metal layer used as a conductive cap layer in semiconductor devices is prone to oxidation during etching and soft ashing processes, leading to the formation of a fragile metal oxide layer that is easily stripped during wet cleaning, resulting in significant metal loss.
Innovation Solution
A soft ashing process using a gas mixture of nitrogen and hydrogen converts the metal oxide layer to a more stable metal oxynitride layer, which provides a protective barrier against further oxidation and damage during wet cleaning, thereby reducing metal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxygen-containing etchant gas is used in the etching process, then via opening formation is achieved, but metal oxide layer is formed on the conductive cap layer
Solution Approach 1:
The patent converts the harmful metal oxide layer into a beneficial protective barrier by applying a soft ashing process that transforms the oxide layer into a more stable and adherent form, which then protects the underlying metal during subsequent wet cleaning processes
Solution Approach 2:
The patent changes the chemical composition and physical properties of the metal oxide layer through soft ashing treatment, transforming it from a fragile, easily-stripped layer into a stable, protective barrier with enhanced bonding strength
2Ease of manufacture
If soft ashing process is conducted using oxygen gas, then organic material removal is achieved, but metal oxide layer is further oxidized and becomes more fragile
Solution Approach 1:
The patent modifies the chemical parameters of the soft ashing process by using nitrogen-containing chemicals instead of pure oxygen, which changes the oxidation mechanism to produce a more stable metal oxynitride layer rather than a fragile metal oxide layer
Solution Approach 2:
The patent creates a controlled atmosphere during soft ashing that limits excessive oxidation by using nitrogen as the primary atmosphere, preventing the formation of fragile metal oxide while still enabling organic material removal
3Ease of manufacture
If wet cleaning process is performed, then contamination removal is achieved, but metal oxide layer is stripped and metal loss occurs
Solution Approach 1:
The patent performs soft ashing treatment before wet cleaning to pre-protect the metal surface by forming a stable metal oxynitride layer that serves as a barrier during the subsequent wet cleaning process, preventing metal dissolution
Solution Approach 2:
The patent converts the potentially harmful wet cleaning process into a beneficial operation by first preparing a protective metal oxynitride layer that allows effective contamination removal while preventing metal loss
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 conversion to a metal oxynitride layer enhances the bonding strength, preventing further oxidation and damage during wet cleaning, thus significantly alleviating metal loss and ensuring better formation of via contacts.
Implementation Method 1
A soft ashing process using a gas mixture of nitrogen and hydrogen converts the metal oxide layer to a more stable metal oxynitride layer
Data Source
AI summary
A method for making a semiconductor device includes patterning at least one dielectric layer disposed over a conductive cap layer to form a via opening penetrating through the at least one dielectric layer to expose the conductive cap layer and to form a top portion of the conductive cap layer into a metal oxide layer; converting the metal oxide layer to a metal oxynitride layer by a soft ashing process using a processing gas containing nitrogen gas; removing the metal oxynitride layer from a remaining portion of the conductive cap layer; and forming a via contact in the via opening to electrically connect the remaining portion of the conductive cap layer.