Local Purging Tool for Wafer Surface Contamination Control
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Solution Overview
Problem
Atmospheric molecular contamination (AMC) accumulation on semiconductor wafers impairs the accuracy of optical metrology systems used in semiconductor manufacturing, as existing methods for removing AMC are incomplete and allow re-accumulation before measurement.
Innovation Solution
A system and method for local purging of a wafer surface with purging gas, such as nitrogen, using a local purging tool with a permeable surface to diffuse gas and prevent AMC accumulation, combined with a humidity sensor to determine thickness corrections based on relative humidity changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a cleanroom is sealed and maintained at positive pressure to prevent contamination, then molecular contamination control is improved, but water condensation and delamination of optically sensitive surfaces can occur
Solution Approach 1:
The cleanroom environment is segmented into multiple isolated chambers (first cleanroom chamber, second cleanroom chamber, third cleanroom chamber) with separate temperature and pressure control systems. This allows different temperature conditions in different chambers without causing condensation, as each chamber can be independently controlled and sealed during purging operations.
Solution Approach 2:
Temperature and humidity are controlled in advance before optically sensitive surfaces are exposed. The system pre-cools or pre-heats chambers and pre-dries surfaces before introducing or removing purging gas, preventing temperature-induced condensation and delamination during the purging process.
2Object-affected harmful factors
If purging gas is introduced into a cleanroom to remove molecular contamination, then contamination control is improved, but particle contamination can be generated
Solution Approach 1:
Purging gas is introduced locally at specific positions (first purging gas introduction position, second purging gas introduction position) rather than uniformly throughout the cleanroom. This localized approach targets specific contamination sources while minimizing disturbance to other areas, reducing particle generation from turbulent flow.
Solution Approach 2:
A laminar flow hood serves as an intermediary structure that guides purging gas flow in a controlled manner. The hood creates a laminar flow pattern that efficiently removes molecular contamination while minimizing turbulence and particle generation compared to uncontrolled gas introduction.
3Temperature
If temperature is lowered to prevent water condensation during purging, then condensation control is improved, but purging effectiveness may be reduced
Solution Approach 1:
The purging process operates continuously with constant purging gas flow and maintained positive pressure throughout the cleanroom. This continuous action ensures effective molecular contamination removal without interruption, while temperature is simultaneously controlled to prevent condensation, achieving both goals without compromise.
Solution Approach 2:
The system dynamically adjusts multiple parameters including temperature, humidity, and purging gas flow rate to optimize both purging effectiveness and condensation prevention. By changing these parameters in coordination rather than fixing temperature alone, the system maintains high purging efficiency while preventing water condensation on optically sensitive surfaces.
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
Effectively inhibits AMC re-accumulation on the wafer surface during measurements, enhancing the accuracy of optical metrology by maintaining a controlled environment and allowing for precise thickness corrections.
Implementation Method 1
molecular contamination control
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A local purging tool for purging a portion of a surface of a wafer with purging gas is disclosed. The purging tool includes a purging chamber configured to contain purging gas within a cavity of the purging chamber, a permeable portion of a surface of the purging chamber configured to diffuse purging gas from the cavity of the chamber to a portion of a surface of a wafer, and an aperture configured to transmit illumination received from an illumination source to a measurement location of the portion of the surface of the wafer and further configured to transmit illumination reflected from the measurement location to a detector.