Wafer Bevel Polymer Removal via Plasma Cleaning
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Solution Overview
Problem
During semiconductor wafer processing, the etching of dielectric layers often results in polymer deposition on the wafer bevel, which is not effectively removed by conventional photoresist stripping processes, leading to incomplete cleaning and potential wafer damage.
Innovation Solution
A method and apparatus are provided where a wafer with a dielectric layer is placed in an etch chamber, and ceramic lifting pins are used to raise the wafer above a support, allowing a cleaning gas to form a plasma that effectively removes the polymer from the bevel, followed by quenching the plasma for thorough cleaning before removing the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photoresist stripping processes are used, then the photoresist mask is removed, but polymer deposition on the wafer bevel remains incomplete
Solution Approach 1:
The patent changes the parameters of the cleaning process by introducing a plasma cleaning step with specific gases (oxygen, nitrogen, or argon) and controlling plasma power (50-500 watts) and pressure (100-760 mTorr). This transforms the cleaning mechanism from conventional chemical stripping to plasma-based physical and chemical cleaning, effectively removing polymer deposits from the wafer bevel that conventional methods cannot eliminate
Solution Approach 2:
The patent replaces the mechanical/chemical photoresist stripping process with a plasma-based cleaning system. The plasma cleaner uses ionized gas to physically sputter and chemically react with polymer deposits, substituting the conventional stripping chemistry with a plasma physical-chemical cleaning mechanism that is more effective at removing adhered polymer from bevel surfaces
2Manufacturing precision
If plasma cleaning is applied to remove polymer, then cleaning effectiveness improves, but risk of wafer damage increases
Solution Approach 1:
The patent employs dynamic control of plasma parameters including adjustable power levels (50-500 watts), pressure ranges (100-760 mTorr), and gas flow rates. The process allows real-time optimization by adjusting these dynamic parameters to achieve effective polymer removal while maintaining wafer integrity. The lifting pin mechanism also provides dynamic positioning to optimize plasma exposure
Solution Approach 2:
The patent performs preliminary actions to protect the wafer before plasma cleaning: (1) lifting the wafer on ceramic pins to create spacing that protects the front surface while exposing the bevel, (2) using oxygen plasma to oxidize and loosen polymer deposits before the main cleaning step, and (3) establishing optimal pressure and gas flow conditions beforehand to ensure gentle yet effective cleaning
3Device complexity
If the wafer remains on the support during cleaning, then processing is simpler, but polymer on the bevel cannot be effectively accessed
Solution Approach 1:
The patent segments the wafer support system by introducing removable lifting pins that separate the wafer from the main support surface. This segmentation allows the bevel surface to be exposed and accessible to the plasma cleaning environment while the front surface remains protected, solving the accessibility problem without requiring complete redesign of the processing chamber
Solution Approach 2:
The patent introduces ceramic lifting pins as intermediary elements between the wafer and the support surface. These pins serve as mediators that mechanically support the wafer while positioning it to enable effective plasma access to the bevel. The ceramic material is chosen for its chemical inertness and ability to withstand plasma conditions without contaminating the wafer
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 ensures complete removal of polymer from the wafer bevel, minimizing damage and improving the efficiency of the cleaning process, allowing for precise feature definition in semiconductor devices.
Implementation Method 1
A plasma is formed from the cleaning gas. A polymer that has formed on the bevel of the wafer is removed using the plasma from the cleaning gas.
Data Source
AI summary
A method of forming a semiconductor device is provided. A wafer with a dielectric layer disposed under a photoresist mask is placed in an etch chamber. The dielectric layer is etched. The wafer is raised. A cleaning gas is provided. A plasma is formed from the cleaning gas. A polymer that has formed on the bevel of the wafer is removed using the plasma from the cleaning gas. The wafer is removed from the etch chamber.