Plasma Etching Endpoint Detection for 3D-NAND Multilayer Films
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Solution Overview
Problem
In semiconductor manufacturing, particularly for 3D-NAND flash memory, lateral etching of multilayer films with high aspect ratios and fine widths, such as tungsten films, requires precise control of etching amount at the atomic layer level, which is challenging due to the difficulty in accurately monitoring the etching process using existing techniques.
Innovation Solution
A plasma processing apparatus with a detection unit that monitors the change in amplitude of vibration in the wavelength direction of reflected light spectra during etching, allowing for precise determination of the etching end point and control of the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If time control is used for lateral etching of multilayer films, then the etching process is simple to control, but the etching precision at atomic layer level cannot be achieved
Solution Approach 1:
The patent implements real-time feedback monitoring of the etching process by detecting changes in reflected light characteristics. The system continuously measures the etching amount and provides feedback to control the etching end point, enabling precise control at atomic layer level while maintaining process simplicity through automated monitoring.
Solution Approach 2:
The patent replaces mechanical/time-based control with optical detection methods. By substituting time control with optical monitoring of reflected light characteristics, the system achieves higher precision without significantly increasing operational complexity, as the optical detection is performed automatically during the etching process.
2Measurement precision
If weight measurement is used to measure etching amount, then the measurement is simple, but it cannot provide real-time monitoring during the etching process
Solution Approach 1:
The patent enables continuous real-time monitoring of the etching process by performing measurements during etching rather than before and after. The optical detection system continuously tracks the etching amount throughout the process, eliminating idle measurement time and enabling dynamic control of the etching end point.
Solution Approach 2:
The patent replaces mechanical weight measurement with optical detection methods. By using reflected light characteristics to measure etching amount in real-time, the system eliminates the need for time-consuming weight measurements and enables continuous monitoring without interrupting the etching process.
3Adaptability or versatility
If conventional etching monitoring is used for planar films, then the method is well-established, but it cannot accurately monitor lateral etching of multilayer films with high aspect ratios
Solution Approach 1:
The patent applies local quality detection by analyzing specific characteristics of reflected light from different regions of the multilayer film structure. The system detects local changes in optical properties that occur during lateral etching, enabling precise monitoring tailored to the specific geometry and material composition of high aspect ratio structures.
Solution Approach 2:
The patent utilizes changes in optical parameters (reflected light characteristics) to monitor the etching process. By detecting changes in amplitude of vibration in wavelength direction and other optical parameters, the system adapts to different multilayer film structures and provides accurate monitoring across various film configurations and materials.
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 accurate monitoring of the etching amount and determination of the etching end point, improving the yield and precision of the etching process, especially for miniaturized semiconductor devices.
Implementation Method 1
a detection unit that detects reflected light obtained by the wafer reflecting light emitted to the wafer
Implementation Method 2
when the film structure is irradiated with light from plasma, the light is reflected at an inter-film boundary and a surface boundary portion to generate reflected light. Since an optical path difference occurs between the reflected light from the base film and the reflected light from the film to be processed, interference light is generated
Data Source
AI summary
A plasma processing apparatus 1 that performs, on a wafer 16 in which a multilayer film in which an insulating film and a film to be processed containing a metal are alternately laminated is formed on a substrate, plasma etching of the film to be processed, includes: a processing chamber 10 which is disposed inside a vacuum container; a sample stage 14 which is disposed inside the processing chamber and on which the wafer is placed; a detection unit 28 which detects reflected light obtained by the wafer reflecting light emitted to the wafer; a control unit 40 which controls plasma processing on the wafer; and an end point determination unit 30 which determines an etching end point of the film to be processed based on a change in an amplitude of vibration in a wavelength direction of a light spectrum of the reflected light, and the control unit receives determination of the end point made by the end point determination unit and stops the plasma processing on the wafer.