Planar Inductor CMP Endpoint Detection via Skin Effect
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Solution Overview
Problem
Conventional methods for detecting the polishing end point in chemical mechanical polishing (CMP) processes face challenges such as excessive Joule heat loss due to strong magnetic fluxes, inaccurate film thickness measurement, and difficulty in determining the remaining film thickness, leading to potential wiring issues and element damage.
Innovation Solution
A method utilizing a planar inductor type sensor that monitors the change in magnetic flux induced in the conductive film by a skin effect, allowing for accurate forecasting of the polishing end point without exerting strong magnetic fluxes, thereby minimizing Joule heat loss and preventing element damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strong magnetic fluxes are applied to monitor film thickness during CMP, then detection capability is improved, but Joule heat loss increases and element damage occurs
Solution Approach 1:
The patent changes the operating frequency parameter of the eddy current sensor to 1 MHz or higher. This frequency change exploits the skin effect to concentrate eddy currents within the conductive film itself, improving thickness detection accuracy while preventing excessive heat generation in underlying elements. The high frequency enables precise measurement of remaining film thickness without the harmful effects of strong magnetic flux penetration.
Solution Approach 2:
The patent replaces conventional magnetic field-based thickness monitoring with an eddy current-based electromagnetic sensing system. This substitution allows for non-contact, real-time measurement of conductive film thickness during CMP by detecting changes in eddy current characteristics, thereby avoiding the need for strong magnetic fluxes that cause Joule heating and element damage.
2Measurement precision
If eddy current is induced in the conductive film for thickness monitoring, then film thickness can be detected, but excessive current causes Joule heat loss
Solution Approach 1:
The patent optimizes the eddy current frequency to 1 MHz or higher, which creates a skin effect that confines eddy currents to the conductive film layer. This parameter change enables accurate thickness measurement by monitoring eddy current distribution while minimizing energy loss as Joule heat in the underlying semiconductor elements.
Solution Approach 2:
The patent applies excessive frequency (1 MHz or higher) beyond conventional eddy current sensing frequencies. This excessive frequency action creates strong skin effect that concentrates eddy currents in the conductive film, providing sufficient signal for precise thickness measurement while the skin effect naturally limits current penetration and reduces Joule heat loss in deeper structures.
3Measurement precision
If magnetic flux penetrates the device wafer for eddy current generation, then eddy current can be formed, but element characteristics are altered
Solution Approach 1:
The patent increases the operating frequency to 1 MHz or higher, which creates a skin effect that prevents magnetic flux from penetrating deep into the device wafer. This parameter change allows eddy current detection at the conductive film level while protecting underlying semiconductor elements from magnetic flux-induced characteristic alterations.
Solution Approach 2:
The patent uses the skin effect as a preliminary protective mechanism that naturally blocks excessive magnetic flux penetration before it can reach and alter element characteristics. By operating at high frequency, the system creates this protective effect in advance, allowing eddy current monitoring without compromising element reliability.
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 precise detection of the polishing end point, reducing Joule heat loss and minimizing the risk of element damage, while accurately forecasting the completion of the polishing process.
Implementation Method 1
by the magnetic flux formed by the inductor, a change of magnetic flux induced in the predetermined conductive film is monitored
Implementation Method 2
based on a change of the magnetic flux by a skin effect decided by the film thickness
Implementation Method 3
suppressing a joule heat loss to the minimum due to the excess current
Data Source
AI summary
A method for forecasting a polishing end time or point, wherein an inductor 36 in a sensor is placed adjacent to the conductive film 28. The magnetic flux formed by the inductor 36 is monitored, and a change of magnetic flux induced in the conductive film 28 is detected. Based on the skin effect of the material of the conductive film 28 as a factor, a process is used in which an eddy current formed with the decrease of the film thickness by polishing increases and a process in which the eddy current formed with the decrease of the film thickness substantially decreases when the polishing is progressed. Based on the characteristic change of the magnetic flux induced in the conductive film 28, the polishing end point is forecasted, and at the same time, the magnetic flux induced in the conductive film 28 is alleviated or turned off.