Copper Etch Rate Control via Absorbance Spectroscopy
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Solution Overview
Problem
Current methods for monitoring and controlling copper etch rates in copper etching processes are inadequate due to their non-chemically specific nature, failing to accurately account for the complex chemical equilibrium of cupric chloride etch solutions, leading to unpredictable etch rates and difficulties in precise control.
Innovation Solution
The use of spectroscopy to detect and analyze the absorbance of copper etch solutions at specific wavelengths, allowing for the calculation and monitoring of etch rates, and subsequent adjustments to maintain desired etch rates through a system comprising a spectrophotometer, processing unit, and sensor devices like flow cells and attenuated total reflection probes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods (ORP, conductivity, density) are used to monitor etch rate, then measurement is simpler, but measurement precision and chemical specificity are insufficient
Solution Approach 1:
The patent replaces conventional mechanical/chemical measurement methods (ORP probes, conductivity meters, density measurements) with optical spectroscopy. The system uses a spectrophotometer to measure absorbance of the etch solution at specific wavelengths, substituting optical detection for the previously used electrochemical and gravimetric methods. This provides chemically specific measurements of Cu(II) concentration while maintaining practical system complexity.
2Productivity
If cupric chloride solution is regenerated and reused, then waste is reduced and efficiency increases, but chemical equilibrium changes causing unpredictable etch rates
Solution Approach 1:
The patent implements a feedback control system where the spectrophotometer continuously monitors the etch solution's absorbance, the processor calculates the Cu(II) concentration and predicts etch rate, and the system adjusts regeneration parameters based on this prediction. This closed-loop feedback maintains etch rate predictability throughout multiple regeneration cycles by allowing real-time observation and adjustment of chemical equilibrium changes.
Solution Approach 2:
The system performs preliminary measurement of absorbance and calculation of Cu(II) concentration before regeneration is complete, allowing prediction of the future etch rate. This preliminary action enables proactive adjustment of regeneration parameters to maintain desired etch rate performance across multiple uses.
3Volume of moving object
If feature sizes continue to shrink, then device density increases, but ability to precisely control copper etch becomes more critical and difficult
Solution Approach 1:
The patent utilizes changes in optical absorption parameters (absorbance at specific wavelengths) to monitor and control etch solution chemistry. By measuring absorbance at wavelengths specific to Cu(II) species and tracking changes in these optical parameters throughout the etch and regeneration process, the system achieves precise control over etch rate, which is critical for maintaining manufacturing precision as feature sizes shrink.
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 provides a chemically specific and accurate method for monitoring and controlling copper etch rates, improving precision and predictability by analyzing the chemical equilibrium changes in the etch solution, thereby ensuring consistent feature dimensions in microelectronics fabrication.
Implementation Method 1
detecting absorbance of the copper etch solution, wherein the absorbance is detected at one or more wavelength
Data Source
AI summary
Systems and methods for copper etch monitoring and control are described. Certain embodiments include utilizing thin-film cells to measure the absorbance of a copper etch solution to determine the etch rate of the solution. In another embodiment, a method of controlling etch rate of a copper etch solution includes detecting characteristics of the copper etch solution utilizing a sensor device, e.g., flow cell and/or attenuated total reflection probe, calculating, based on the detected characteristics of the copper etch solution, the etch rate of the copper etch solution, and adjusting the etch rate of the copper etch solution in response to the calculated etch rate deviating from a specified value.