CMP Polishing Pad Light Path Cleaning for Film Thickness Measurement
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Solution Overview
Problem
The polishing liquid or debris adheres to the light passing portion of the polishing pad in CMP apparatuses, reducing the intensity of reflected light and affecting the accuracy of film thickness measurement in semiconductor manufacturing.
Innovation Solution
A polishing apparatus with a cleaning portion that forms a closed space over the light passing portion, supplying a cleaning fluid to remove debris and maintain light path integrity, using a cleaning nozzle, ultrasonic vibrator, and load measurement to ensure effective cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the polishing liquid is supplied onto the polishing pad during CMP processing, then the substrate surface can be polished effectively, but the polishing liquid and debris adhere to the light passing portion reducing light intensity
Solution Approach 1:
The polishing pad is divided into functionally distinct regions: a polishing region for substrate processing and a light passing portion for optical measurement. The cleaning portion further segments the light passing portion by enclosing it with a cleaning cover, isolating this critical measurement area from contamination by polishing liquid and debris, thereby maintaining measurement precision while preserving polishing productivity
Solution Approach 2:
A cleaning fluid is introduced as an intermediary substance to remove polishing liquid and debris from the light passing portion. The cleaning fluid acts as a mediator between the contaminated polishing surface and the optical measurement system, restoring light transmission without requiring interruption of the polishing process
2Measurement precision
If the light passing portion is used for film thickness measurement, then real-time monitoring is achieved, but the adhered debris reduces reflected light intensity affecting measurement
Solution Approach 1:
The cleaning cover is positioned to enclose the light passing portion before measurement occurs, and the cleaning fluid is supplied in advance to prevent debris accumulation. This preliminary cleaning action ensures that the light passing portion remains clear throughout the measurement process, maintaining both illumination intensity and measurement precision without interruption
Solution Approach 2:
The cleaning system operates continuously during the polishing process, with the cleaning cover enclosing the light passing portion and cleaning fluid continuously removing debris. This continuous cleaning action ensures uninterrupted optical measurement while maintaining the polishing process, preventing any degradation of light intensity or measurement capability
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
Prevents light intensity reduction, ensuring accurate film thickness measurement by effectively removing polishing liquid or debris from the light passing portion, thereby maintaining high precision in substrate polishing processes.
Implementation Method 1
a cleaning portion including an ultrasonic vibrator that generates ultrasonic waves and is configured to propagate the ultrasonic waves via the cleaning fluid
Implementation Method 2
an optical sensor disposed in the polishing table, irradiating light to the substrate through the light passing portion, and receiving reflected light from the substrate through the light passing portion
Data Source
AI summary
The disclosure provides a polishing apparatus capable of removing a polishing liquid or polishing debris from a light passing portion of a polishing pad. A polishing apparatus 1 includes a polishing table 3 supporting a polishing pad 2 that has a light passing portion 33; a polishing head 5 pressing a substrate W against a polishing surface 2a of the polishing pad 2; an optical sensor 21 disposed in the polishing table 3, irradiating light to the substrate W through the light passing portion 33, and receiving reflected light from the substrate W through the light passing portion 33; and a cleaning portion 12 forming a cleaning space CS that covers the light passing portion 33 above the light passing portion 33 and supplying a cleaning fluid to the light passing portion 33 through the cleaning space CS.