Plasma Etch Endpoint Detection Using Corrected Multi-Wavelength Reflection
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Solution Overview
Problem
Existing plasma processing technologies face challenges in accurately detecting film thickness and etching depth due to noise components from light source fluctuations, particularly pulse-shaped and step-shaped changes, which impair the accuracy of endpoint determination and yield in semiconductor wafer processing.
Innovation Solution
A plasma processing apparatus that uses a detector to measure the intensity of light at multiple wavelengths, with one range obtained from within the processing chamber and another range from outside, and a determination unit that corrects the light intensity using a change rate from the external light source to accurately determine the remaining film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external light source is used to measure film thickness during plasma etching, then the measurement can be performed without interference from plasma, but light source fluctuations introduce noise that reduces measurement precision
Solution Approach 1:
The system uses a feedback mechanism where the detector continuously monitors light intensity from the external light source, compares it against reference values, and automatically adjusts or corrects measurements in real-time to compensate for light source fluctuations, thereby maintaining measurement precision despite instability in the light source
Solution Approach 2:
The patent introduces an intermediary correction mechanism that acts between the light source and the measurement process. By using a detector to monitor light intensity changes and applying correction algorithms, the system mediates the effect of light source fluctuations on measurement accuracy, isolating the measurement from harmful variations
2Manufacturing precision
If plasma etching is performed with high precision requirements for advanced devices, then the processed shape accuracy improves, but the etching time increases and productivity decreases
Solution Approach 1:
The system performs preliminary action by continuously monitoring film thickness in real-time during the etching process using optical detection. This allows the system to identify the endpoint of etching early and accurately, preventing over-etching and eliminating the need for conservative timing margins, thereby maintaining high precision while reducing total processing time
Solution Approach 2:
The patent replaces mechanical or time-based endpoint determination methods with optical detection using an external light source and detector. This substitution enables non-contact, real-time measurement of film thickness, providing precise endpoint detection without the delays and inaccuracies of traditional methods, thus improving both precision and productivity
3Measurement precision
If the light detection system monitors multiple wavelengths to improve measurement accuracy, then the film thickness detection precision improves, but the device complexity increases
Solution Approach 1:
The detector is designed with multi-functionality to handle multiple wavelengths simultaneously. By using a single detector that can process a broad spectrum of light rather than multiple separate detectors for different wavelengths, the system achieves enhanced measurement precision through multi-wavelength analysis while avoiding the complexity of multiple detection devices
Solution Approach 2:
The system utilizes parameter changes in the light source, specifically varying the wavelength of emitted light, to extract multiple measurement parameters from a single detection system. By analyzing reflectance or interference patterns at different wavelengths, the system achieves precise film thickness measurement without requiring complex multi-detector arrangements
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 enables highly accurate film thickness and depth measurement, reducing noise interference and improving processing yield by effectively separating light changes due to etching from those caused by light source fluctuations.
Implementation Method 1
detecting a time point immediately before the film to be processed is completely removed by receiving a light reflected by the surface of the wafer that is being processed
Implementation Method 2
isotropy or anisotropy of the processing is different depending on sputtering of ions in the plasma
Implementation Method 3
a chemical reaction of a radical
Implementation Method 4
supplying radio frequency power from a radio frequency power source into the processing chamber, plasmaizing atoms and molecules of the gas
Data Source
AI summary
A plasma processing apparatus and method with an improved processing yield, the plasma processing apparatus including detector configured to detect an intensity of a first light of a plurality of wavelengths in a first wavelength range and an intensity of a second light of a plurality of wavelengths in a second wavelength range, the first light being obtained by receiving a light which is emitted into the processing chamber from a light source disposed outside the processing chamber and which is reflected by an upper surface of the wafer, and the second light being a light transmitted from the light source without passing through the processing chamber; and a determination unit configured to determine a remaining film thickness of the film layer by comparing the intensity of the first light corrected using a change rate of the intensity of the second light.