Alternating Fluorocarbon Stripping for Low-K Dielectric Protection
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Solution Overview
Problem
In semiconductor processing, existing methods for etching and stripping ultra low-k dielectric layers suffer from significant damage, leading to yield loss and reliability failures, and existing stripping processes are either too slow or cause distortion in the etched features.
Innovation Solution
A method involving a plasma processing chamber that uses alternating cycles of fluorocarbon and reduced fluorocarbon stripping phases to efficiently strip the photoresist mask from the low-k dielectric layer, minimizing damage and distortion, with the fluorocarbon stripping phase forming a plasma to strip the mask and the reduced phase further removing sidewalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fluorocarbon stripping gas is used to strip the photoresist mask, then the stripping speed is fast, but the ultra low-k dielectric layer suffers significant damage
Solution Approach 1:
The stripping process alternates between fluorocarbon stripping phases (for fast mask removal) and reduced fluorocarbon stripping phases (for damage reduction). This periodic switching allows the process to achieve both fast stripping speed and minimal dielectric damage by resetting the sidewall deposition between phases
Solution Approach 2:
The continuous stripping process is divided into discrete cycles, where each cycle contains a fluorocarbon stripping phase followed by a reduced fluorocarbon stripping phase. This segmentation allows controlled deposition and removal of sidewalls, preventing cumulative damage to the dielectric layer
2Object-affected harmful factors
If the fluorocarbon flow rate is reduced to minimize dielectric damage, then the damage is reduced, but the stripping process becomes too slow
Solution Approach 1:
The process alternates between high flow rate fluorocarbon phases (fast stripping) and low flow rate reduced fluorocarbon phases (damage reduction). This periodic variation in flow rate allows the system to achieve both fast overall stripping and minimal dielectric damage
Solution Approach 2:
The fluorocarbon gas flow rate parameter is dynamically changed between phases - high during fluorocarbon stripping phases for speed, and low during reduced fluorocarbon stripping phases for damage reduction. This parameter modulation resolves the contradiction between speed and damage
3Productivity
If existing stripping processes are used to remove the photoresist mask, then the mask is stripped, but the etched features become distorted
Solution Approach 1:
The alternating fluorocarbon and reduced fluorocarbon stripping phases prevent feature distortion by periodically removing deposited sidewalls that would otherwise accumulate and distort the etched features. This periodic reset maintains shape accuracy throughout the stripping process
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 significantly reduces ultra low-k dielectric damage and ensures fast, complete stripping without distorting the etched features, as confirmed by reduced material loss and improved post-strip profiles.
Implementation Method 1
a plasma etcher is usually used to transfer an organic mask pattern
Implementation Method 2
This etching reaction is initiated by the chemically active species and electrically charged particles (ions) generated by exciting an electric discharge
Implementation Method 3
the ions are also accelerated towards the wafer materials through an electric field created between the gas mixture and the wafer materials
Implementation Method 4
generating a directional removal of the etching materials along the direction of the ion trajectory in a manner referred to as anisotropic etching
Implementation Method 5
flowing a fluorocarbon stripping gas into the plasma processing chamber, forming a plasma from the fluorocarbon stripping gas
Implementation Method 6
The organic mask is stripped from the etched low-k dielectric layer
Data Source
AI summary
A method for forming etched features in a low-k dielectric layer disposed below the photoresist mask in a plasma processing chamber is provided. Features are etched into the low-k dielectric layer through the photoresist mask. The photoresist mask is stripped, wherein the stripping comprising at least one cycle, wherein each cycle comprises a fluorocarbon stripping phase, comprising flowing a fluorocarbon stripping gas into the plasma processing chamber, forming a plasma from the fluorocarbon stripping gas, and stopping the flow of the fluorocarbon stripping gas into the plasma processing chamber and a reduced fluorocarbon stripping phase, comprising flowing a reduced fluorocarbon stripping gas that has a lower fluorocarbon flow rate than the fluorocarbon stripping gas into the plasma processing chamber, forming the plasma from the reduced fluorocarbon stripping gas, and stopping the flow of the reduced fluorocarbon stripping gas.