Anisotropic Etch Endpoint Detection Using Variable Gas Flow
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Solution Overview
Problem
Existing anisotropic etch processes face challenges in accurately detecting the end point due to weak optical emission spectrum signals from thick etch mask layers, leading to difficulties in controlling the depth of openings in semiconductor manufacturing.
Innovation Solution
The method involves alternating normal-flow and reduced-flow etch steps in an etch chamber, where optical emission spectroscopy (OES) data is collected during reduced-flow etch steps to determine the end point, and the etch gas flow rate is modulated to enhance signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If normal-flow etch steps are used to maintain etch rate, then productivity is improved, but measurement precision deteriorates due to weak OES signals
Solution Approach 1:
The patent implements periodic alternation between normal-flow etch steps and reduced-flow measurement steps. During reduced-flow steps, the etchant gas flow rate is decreased to enhance OES signal strength for accurate endpoint detection, while normal-flow steps maintain high etch rate for productivity. This periodic switching resolves the contradiction by separating the conflicting requirements of high etch rate and strong OES signals into different time periods.
Solution Approach 2:
The patent dynamically adjusts the etchant gas flow rate between two states: normal flow rate during etching phases and reduced flow rate during measurement phases. This dynamic adjustment allows the system to optimize for either etch rate or OES signal strength depending on the current process phase, thereby resolving the contradiction between productivity and measurement precision.
2Measurement precision
If reduced-flow etch steps are used to enhance OES signal strength, then measurement precision is improved, but productivity deteriorates due to lower etch rate
Solution Approach 1:
The patent uses periodic reduced-flow measurement steps interspersed among normal-flow etch steps. The reduced-flow steps are kept relatively short to minimize productivity loss while providing sufficient time for accurate OES measurement. This periodic approach ensures measurement precision is improved without sacrificing overall etch productivity.
Solution Approach 2:
The patent applies reduced flow rate only partially during specific measurement intervals rather than continuously. This partial application of reduced flow is sufficient to enhance OES signal strength for accurate endpoint detection, while the majority of the process time is spent in normal-flow high-productivity etching mode.
3Measurement precision
If continuous monitoring is performed during normal-flow etching, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent implements monitoring only during reduced-flow measurement steps rather than continuously during all etching. This periodic monitoring approach maintains adequate endpoint detection accuracy while significantly reducing the complexity of process control systems and data processing requirements compared to continuous monitoring.
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 allows for reliable endpoint detection even with weak OES signals, ensuring precise control of etch depth and improving the accuracy of semiconductor manufacturing processes.
Implementation Method 1
a plasma generator configured to generate a plasma of the etchant gas within the etch chamber
Implementation Method 2
a spectrometer having a light-receiving aperture located outside a transparent window located in a wall of the etch chamber, and configured to measure an optical emission spectrum intensity of the plasma
Data Source
AI summary
An etching method includes etching a material in an etch chamber by alternating normal-flow etch steps and reduced-flow etch steps, where an etchant gas is provided at a normal flow rate into the etch chamber during the normal-flow etch steps, and the etchant gas is provided at a reduced flow rate lower than the normal flow rate into the etch chamber during the reduced-flow etch steps, obtaining optical emission spectroscopy (OES) data during the reduced-flow etch steps, determining an end point for the etching based on the obtained OES data, and ending the etching at the determined end point.