Multi-Resonant Eddy Current Detection for CMP Film Thickness
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Solution Overview
Problem
Existing eddy current detection methods for CMP end-point detection in integrated circuit chips face challenges in balancing high frequency and high quality factor, leading to inadequate detection intensity and frequency limitations.
Innovation Solution
An eddy current end-point detection device and method utilizing multiple resonant circuits connected in series, with inductors wound around a magnetic core, allowing selection of target frequencies based on metal film thickness, and integrating a detection and processing unit to calculate film thickness from voltage signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frequency of the detection magnetic field is increased, then the detection capability for thin metal films is improved, but the quality factor of the circuit decreases
Solution Approach 1:
The patent divides the detection system into multiple resonant circuits operating at different frequencies (first resonant circuit at higher frequency, second resonant circuit at lower frequency). This segmentation allows the system to select appropriate frequency ranges for different metal film thicknesses, resolving the contradiction between high frequency (for thin film detection) and high quality factor (for stable operation).
Solution Approach 2:
The system dynamically switches between different resonant circuits based on the detected metal film thickness. When processing thin films, the higher frequency first resonant circuit is activated; when processing thicker films, the lower frequency second resonant circuit is used. This dynamic adaptation resolves the fixed contradiction between frequency and quality factor requirements.
2Reliability
If the quality factor is increased, then the stability of the circuit is improved, but the detection frequency is reduced
Solution Approach 1:
The patent segments the frequency spectrum into two operational ranges using separate resonant circuits: a first resonant circuit for high-frequency operation (when high detection frequency is needed) and a second resonant circuit for lower-frequency operation (when high quality factor is prioritized). This segmentation eliminates the need to compromise between the two conflicting requirements in a single circuit.
Solution Approach 2:
The system changes the operating frequency parameter by switching between different resonant circuits based on the metal film thickness being detected. For thin films requiring high frequency, the first resonant circuit is selected; for thicker films where stability is more important, the second resonant circuit is selected. This parameter change strategy resolves the contradiction between frequency and quality factor.
3Device complexity
If a single resonant circuit is used, then the device complexity is reduced, but the adaptability to different metal film thicknesses decreases
Solution Approach 1:
The patent implements multi-functionality by designing a detection system that can operate in two distinct frequency modes using two resonant circuits. The first resonant circuit handles thin metal film detection, while the second resonant circuit handles thicker metal film detection. This universal design allows a single device to adapt to various detection scenarios without requiring completely different hardware configurations.
Solution Approach 2:
The system dynamically selects which resonant circuit to use based on the metal film thickness characteristics. This dynamic switching capability provides adaptability to different detection scenarios while maintaining a relatively compact device structure, resolving the contradiction between simplicity and versatility.
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 high frequency and quality factor, enabling flexible and accurate detection of varying metal film thicknesses with real-time output, suitable for both thick and thin films, and adaptable frequency switching.
Implementation Method 1
an exciting coil and a detecting coil are often used together, wherein the exciting coil is used to generate a magnetic field at a certain frequency on the surface of a metal film
Implementation Method 2
an eddy current method is often used for online CMP end-point detection of metal films
Implementation Method 3
the detecting coil is used to detect the change of the magnetic field
Data Source
AI summary
The invention discloses an eddy current end-point detection device comprises multiple resonant circuits connected in series, each resonant circuit generating a set frequency; a magnetic core, inductors of all the resonant circuits being wound around the magnetic core; according to a thickness threshold of a metal film, the corresponding resonant circuit being selected to generate a target frequency, which is applied to a surface of the metal film; a detection unit, configured to acquire first voltage signals of two terminals all the resonant circuits connected in series and second voltage signals of two terminals of any resonant circuits; and a processing unit, configured to calculate the thickness of the metal film according to the detection voltage signals acquired by the detection unit. The invention further discloses an eddy current end-point detection method.