Immersion Lithography Edge Bead Removal Process
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Solution Overview
Problem
Immersion lithography processes face contamination issues due to resist residue interacting with immersion exposure fluids and lenses, leading to defects on semiconductor wafers, primarily because conventional edge-bead removal processes do not effectively remove solvent from the resist edges, causing particles to form and contaminate the fluid and lens.
Innovation Solution
An enhanced edge-bead removal (EBR) process involving multiple spinning speeds and solvent dispensing positions to increase centrifugal force and prevent resist edge bead contamination, including spinning the wafer at speeds greater than 1000 rpm and positioning nozzles closer to the edge to remove solvent effectively, followed by slower speed steps to ensure thorough cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional edge-bead removal process is used, then the process is simple, but resist residue contaminates the immersion fluid and lens causing defects
Solution Approach 1:
The EBR process is divided into multiple sequential steps with different spinning speeds (e.g., first step at higher speed to remove bulk edge bead, second step at lower speed for thorough cleaning). This segmentation allows each step to target specific contamination levels, improving overall reliability while managing complexity through structured progression
Solution Approach 2:
The EBR process is performed before immersion lithography exposure to pre-remove resist edge beads and prevent their formation during subsequent processing. This preliminary action eliminates the source of contamination before it can affect the immersion fluid and lens, thereby improving defect reduction without requiring complex post-processing steps
2Loss of substance
If wafer spinning speed is increased to improve solvent removal, then solvent removal effectiveness increases, but centrifugal force may cause other issues
Solution Approach 1:
The wafer spinning speed is dynamically adjusted during the EBR process, transitioning from higher speeds in initial steps to lower speeds in subsequent steps. This dynamic adjustment optimizes solvent removal efficiency at each stage while preventing excessive centrifugal force from causing resist distortion or other processing issues
Solution Approach 2:
The EBR process uses periodic spinning cycles with alternating speed levels rather than continuous high-speed spinning. Each cycle removes progressively less solvent, allowing effective substance removal while distributing centrifugal force application over time, preventing cumulative harmful effects
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 improved EBR process significantly reduces resist residue particles in the immersion fluid and lens, thereby minimizing defects on the wafer by enhancing solvent removal and preventing contamination, resulting in a more reliable and defect-free immersion lithography process.
Implementation Method 1
spinning the wafer at speeds greater than 1000 rpm to increase centrifugal force
Data Source
AI summary
A method of performing immersion lithography on a semiconductor wafer is provided. The method includes providing a layer of resist onto a surface of the semiconductor wafer. Next, an edge-bead removal process spins the wafer at a speed greater than 1000 revolutions per minute and dispenses solvent through a nozzle while the wafer is spinning. Then, the resist layer is exposed using an immersion lithography exposure system.