Backside Defect Detector for Semiconductor Wafer Flatness
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Solution Overview
Problem
Minute amounts of materials remaining on the backside of semiconductor wafers after etching can distort the wafer's flatness, leading to non-uniform photoresist depths and improperly sized devices in sub-micron applications, necessitating a method to detect and remove unwanted materials before subsequent processing steps.
Innovation Solution
A backside defect detector using an IR light scan to determine the presence of unwanted materials on the backside of semiconductor wafers by comparing detected intensity values to stored values from known good wafers, generating error signals for areas requiring further cleaning, and utilizing IR sources and receivers to scan grid areas of the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etchant is used to remove materials from the backside of the wafer, then the backside should be clean and flat, but minute amounts of materials undesirably remain on the backside causing distortion
Solution Approach 1:
The patent applies preliminary action by performing an inspection of the backside of the wafer before subsequent processing steps. The system scans the backside to detect minute amounts of remaining materials that cause distortion, allowing for identification and correction of contamination issues before they affect photolithography and device fabrication.
2Manufacturing precision
If photoresist is deposited on the top surface of the wafer, then the photoresist should have uniform depth, but distorted backside causes non-uniform depth and focus spots
Solution Approach 1:
The system performs preliminary detection of backside contamination before photoresist deposition. By scanning the backside and identifying areas with minute materials that cause distortion, the system enables pre-processing or corrective actions to ensure the backside is properly prepared, thereby preventing photolithographic distortion and ensuring uniform photoresist depth.
Solution Approach 2:
The patent implements feedback by using the inspection system to detect backside conditions and providing information about minute materials present on the backside. This feedback mechanism allows process control systems to adjust or reprocess wafers with contamination issues, preventing defective photoresist deposition and ensuring manufacturing precision.
3Measurement precision
If IR light scan is performed to detect unwanted materials on the backside, then the presence of contaminants can be determined, but additional processing time is required
Solution Approach 1:
The patent replaces mechanical inspection methods with an optical detection system that uses IR light to scan the backside of the wafer. This substitution enables non-contact, rapid detection of minute materials causing distortion, achieving high measurement precision without the time-consuming manual inspection or physical sampling methods.
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
Ensures the backside of semiconductor wafers is clean and flat, preventing photolithographic distortion and ensuring uniformity in subsequent processing steps, thereby improving the accuracy of device fabrication.
Implementation Method 1
an IR source 110 and an IR receiver 112 that lie on opposite sides of a plane 114. IR source 110 outputs one or more wavelengths of IR light. IR receiver 112 detects the one or more wavelengths of IR light
Data Source
AI summary
Minute materials which can be undesirably left on the backside of a semiconductor wafer are detected by scanning the semiconductor wafer with an infra-red (IR) light following the completion of a process step that forms and then selectively removes a material from the top surface of the wafer. Any detected material can then be removed from the backside of the wafer to ensure that that backside of the wafer is clean and flat.