Titanium Nitride Hardmask Removal Using Remote Plasma
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Solution Overview
Problem
Current methods for removing titanium nitride hardmasks from semiconductor substrates are inefficient, particularly in dual-damascene structures, as they can damage underlying copper layers and increase the dielectric constant of low-k dielectric layers, and existing dry etch processes lack selectivity and control.
Innovation Solution
A method involving the deposition of a non-porous carbon layer to protect the low-k dielectric layer and copper, followed by a gas-phase etch using plasma effluents from a remote plasma reactor with chlorine and carbon-hydrogen precursors, which selectively removes the titanium nitride hardmask without reacting with the underlying materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dry etch processes are used to remove titanium nitride hardmask, then etching capability is achieved, but selectivity is insufficient causing damage to underlying copper layers and low-k dielectric layers
Solution Approach 1:
A carbon-containing layer is deposited as an intermediary protective layer between the titanium nitride hardmask and the underlying copper/low-k dielectric structures. This carbon layer selectively reacts with the chlorine-containing etch precursor to form volatile products, while the remaining carbon layer continues to protect the underlying sensitive materials from etch damage, enabling selective removal of the hardmask without harming the copper interconnects or low-k dielectric properties
Solution Approach 2:
The etch process utilizes plasma effluents from a remote plasma source with specifically controlled chemistry (chlorine-containing precursors) and physical parameters (electron temperature below 0.5 eV). These parameter changes create highly selective etching conditions where the carbon-containing layer and titanium nitride react preferentially, while the underlying copper and low-k dielectric materials remain unaffected due to their different chemical reactivity under these controlled conditions
2Productivity
If aggressive etching is used to ensure complete hardmask removal, then removal efficiency is improved, but physical disturbance to miniature structures increases
Solution Approach 1:
The process replaces aggressive mechanical/physical sputtering etching with a chemical etching mechanism using plasma effluents. The chemical reactions between chlorine-containing species and the carbon-containing layer/titanium nitride enable efficient material removal through volatile product formation, eliminating the need for high-energy ion bombardment that would cause physical disturbance to the miniature dual-damascene structures
Solution Approach 2:
By controlling the electron temperature to remain below 0.5 eV in the substrate processing region, the process ensures that ions arrive at the substrate with minimal kinetic energy. This parameter control allows chemical etching to proceed at effective rates while preventing physical sputtering and mechanical damage to the delicate copper fills and low-k dielectric walls
3Reliability
If remote plasma with chlorine-containing precursor is used, then etch selectivity is improved, but process complexity increases
Solution Approach 1:
The process is divided into distinct stages: first, deposition of the carbon-containing layer to provide selective protection; second, remote plasma etching with chlorine-containing precursors to selectively remove the titanium nitride hardmask while leaving the carbon layer intact; third, removal of the remaining carbon layer. This segmentation allows each step to be optimized independently, achieving high selectivity without requiring overly complex integrated processes
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 effectively removes titanium nitride hardmasks with high selectivity, maintaining the integrity of the low-k dielectric layer and preventing damage to the copper layer, while maintaining a low dielectric constant and minimizing physical disturbance to the substrate.
Implementation Method 1
gas-phase etch using plasma effluents formed in a remote plasma from a chlorine-containing precursor
Implementation Method 2
plasma effluents within the remote plasma are flowed into a substrate processing region where the plasma effluents react with the non-porous carbon layer and the titanium nitride
Implementation Method 3
The radical-chlorine precursor and the radical-carbon-hydrogen precursor are prevented from reacting with the underlying copper layer by the remainder of the carbon-containing layer
Implementation Method 4
the plasma effluents react with the non-porous carbon layer and the titanium nitride
Implementation Method 5
flowing a radical-chlorine precursor and a radical-carbon-hydrogen precursor into the substrate processing region
Data Source
AI summary
A method of removing titanium nitride hardmask is described. The hardmask resides above a low-k dielectric layer prior to removal and the low-k dielectric layer retains a relatively low net dielectric constant after the removal process. The low-k dielectric layer may be part of a dual damascene structure having copper at the bottom of the vias. A non-porous carbon layer is deposited prior to the titanium nitride hardmask removal to protect the low-k dielectric layer and the copper. The titanium nitride hardmask and the non-porous carbon layer are removed with a gas-phase etch using plasma effluents formed in a remote plasma from a chlorine-containing precursor. Plasma effluents within the remote plasma are flowed into a substrate processing region where the plasma effluents react with the non-porous carbon layer and the titanium nitride.