Optical Metrology for Plasma Etch Process Control
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Solution Overview
Problem
Conventional measurement techniques for monitoring process parameters during semiconductor trench etching, such as wafer temperature and feature dimensions, are inadequate for next-generation IC fabrication requiring higher aspect ratios and critical dimensions, leading to a need for improved real-time metric acquisition.
Innovation Solution
A processing chamber equipped with a showerhead assembly and optical metrology system, utilizing a fiber optic cable bundle to direct and collect optical signals from the plasma, allowing for real-time monitoring and control of the etch process through spectral sensing and endpoint detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement techniques (thermocouples, probes, pyrometers) are used to monitor process parameters, then the measurement setup is simple, but the measurement precision and reliability are insufficient for next-generation IC fabrication with higher aspect ratios and critical dimensions
Solution Approach 1:
The patent replaces conventional mechanical measurement devices (thermocouples, probes, pyrometers) with an optical measurement system that uses light transmission through the plasma to monitor process parameters. This substitution enables non-contact, real-time measurements with higher precision suitable for next-generation IC fabrication, while avoiding the limitations of mechanical systems in harsh plasma environments
Solution Approach 2:
The patent introduces optical windows as intermediaries that allow light to pass through the chamber wall and plasma to reach the substrate. These windows enable the optical measurement system to penetrate the plasma and obtain real-time information about process parameters without direct mechanical contact, thereby improving measurement precision while maintaining system integrity
2Loss of information
If optical energy is introduced into the plasma to enable real-time monitoring, then real-time metric acquisition is achieved, but plasma interference with optical signals occurs
Solution Approach 1:
The patent converts the harmful plasma interference into a beneficial measurement mechanism by monitoring how the plasma absorbs and transmits optical energy. The plasma's effect on the optical signal (absorption, scattering) becomes the measurement mechanism itself, allowing real-time acquisition of process parameters such as plasma density, temperature, and composition while accounting for plasma interference
Solution Approach 2:
The patent implements feedback control by continuously monitoring the optical signal transmission through the plasma and using this information to adjust process parameters in real-time. The optical measurement system provides feedback about plasma conditions and etch process status, enabling dynamic control to maintain optimal processing conditions and compensate for plasma interference effects
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
Enables accurate and real-time monitoring of process parameters, enhancing trench uniformity and etch process control, thereby supporting the fabrication of next-generation ICs with higher aspect ratios and critical dimensions.
Implementation Method 1
collecting a first signal and a second signal from the plasma
Implementation Method 2
introducing optical energy into the plasma and directed towards the substrate
Data Source
AI summary
Embodiments described herein provide a method and apparatus for obtaining process information in a substrate manufacturing process using plasma. In one embodiment, a chamber is provided having one or more optical metrology modules that are positioned such that optical energy from the plasma process is detected at substantially orthogonal angles. Metrics derived from detected optical energy may be used for endpoint determination, substrate temperature, and monitoring of critical dimensions on the substrate.