In-situ Optical Monitor for Plasma Etch Control
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Solution Overview
Problem
Current etch process control methods for stepped structures in semiconductor manufacturing are inadequate, leading to low device yield due to insufficient lateral and vertical control, with existing methods requiring post-processing measurement and resulting in a significant percentage of devices being out-of-spec or discarded.
Innovation Solution
The implementation of an in-situ optical monitor (ISOM) with a reflectometer that measures the intensity of reflected light beams to control plasma etching processes, allowing for real-time monitoring and feedback to achieve precise lateral and vertical etch control by correlating etched thickness and lateral recess measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If post-processing measurement methods are used to control etch processes, then device yield is reduced due to large percentage of out-of-spec devices, but implementing in-situ measurement systems increases device yield
Solution Approach 1:
The patent implements real-time feedback control by measuring reflected light intensity during the etch process and using this information to dynamically adjust etch parameters. The system continuously monitors the etch process and provides feedback to the control system, which then adjusts process parameters to maintain etch features within specified tolerances, thereby improving device yield while managing system complexity through automated closed-loop control.
Solution Approach 2:
The patent replaces mechanical post-processing measurement systems with an optical measurement system that uses reflected light intensity to monitor etch progress in real-time. This substitution eliminates the need for physical intervention and post-processing measurements, enabling continuous monitoring and control during the etch process itself, which improves yield without proportionally increasing mechanical system complexity.
2Manufacturing precision
If in-situ optical monitoring is implemented for real-time etch control, then etch process precision is improved, but system cost and complexity increase
Solution Approach 1:
The patent introduces an optical intermediary (reflected light) as a mediator between the etch process and the measurement system. By measuring the intensity of reflected light, the system indirectly monitors etch progress without requiring direct physical contact or complex internal sensors within the plasma chamber. This intermediary approach enables precise etch monitoring while keeping the measurement system relatively simple and non-invasive.
Solution Approach 2:
The patent substitutes mechanical measurement approaches with optical measurement methods. Instead of using physical probes or post-process mechanical measurements, the system uses optical properties (reflected light intensity) to monitor etch progress in real-time. This substitution improves measurement precision while avoiding the complexity and contamination risks associated with mechanical systems in the plasma environment.
3Manufacturing precision
If lateral etch control is maintained during stepped structure formation, then structural accuracy is improved, but process control complexity increases
Solution Approach 1:
The patent segments the etch process into distinct phases (first plasma etch process for lateral trimming, second plasma etch process for vertical etching) and applies different control strategies to each phase. By dividing the complex stepped structure formation into manageable segments with specific control objectives for each, the system achieves high lateral and vertical precision without requiring all control mechanisms to operate simultaneously, thereby managing overall process control complexity.
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 significantly enhances the accuracy of etch process control, reducing the number of out-of-spec devices and increasing yield by enabling real-time adjustments during the etching process, thus improving the production of stepped structures in semiconductor manufacturing.
Implementation Method 1
illuminating the structure on the substrate with an incident light beam, the reflection of the incident light beam from the structure forming a reflected light beam; measuring a first intensity of the reflected light beam
Data Source
AI summary
Disclosed is an in-situ optical monitor (ISOM) system and associated method for controlling plasma etching processes during the forming of stepped structures in semiconductor manufacturing. The in-situ optical monitor (ISOM) can be optionally configured for coupling to a surface-wave plasma source (SWP), for example a radial line slotted antenna (RLSA) plasma source. A method is described to correlate the lateral recess of the steps and the etched thickness of a photoresist layer for use with the in-situ optical monitor (ISOM) during control of plasma etching processes in the forming of stepped structures.