Real-Time Plasma Etch Rate Prediction for Wafer Uniformity
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Solution Overview
Problem
Current methods for qualifying etch rate and uniformity in plasma etch chambers are inefficient and prone to producing scrap material due to varying chamber conditions, often requiring time-consuming post-processing metrology and expensive equipment like laser interferometers and CCD arrays.
Innovation Solution
A real-time method involving depositing a film on a wafer, patterning with photoresist, and performing a series of etch and ash processes to determine etch rates for both center and edge regions, allowing for immediate qualification of the plasma etch chamber without separate metrology equipment, using automatic feedback loops and mask-less photolithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple wafer processes are combined in a single plasma chamber to improve efficiency, then productivity increases, but chamber condition variation worsens leading to scrap material
Solution Approach 1:
The patent performs preliminary qualification tests before production runs to establish baseline etch rate uniformity. By pre-characterizing the chamber with test wafers that map etch rates across different chamber positions, the system can predict and compensate for uniformity issues before they affect production wafers, thus maintaining reliability while enabling multiple processes
2Measurement precision
If traditional post-measuring metrology equipment is used to verify etch rate uniformity, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent makes the plasma etch chamber itself perform the measurement function by monitoring endpoint detection signals during the etch process. The chamber's own process control systems detect when etching reaches the underlying layer, providing real-time etch rate data without requiring external metrology equipment. This self-measuring approach eliminates complex post-process measurement devices while maintaining precision
Solution Approach 2:
The patent replaces mechanical/optical metrology equipment with electrical signal-based endpoint detection. Instead of using physical measurement tools like laser interferometers or CCD arrays to measure etch rates after processing, the system uses electrical signals from the plasma discharge and circuit responses to detect etch endpoints and calculate rates in real-time, substituting complex mechanical systems with simpler electrical sensing
3Manufacturing precision
If real-time endpoint detection is implemented to improve process control, then manufacturing precision improves, but process time increases due to additional monitoring steps
Solution Approach 1:
The patent implements continuous real-time monitoring of etch rate during the process rather than stopping to measure. Endpoint detection signals are continuously tracked throughout the etch, allowing the system to monitor precision without interrupting the useful etching action. This continuous measurement approach eliminates idle measurement time while maintaining manufacturing precision
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 method reduces scrap material by enabling real-time qualification of plasma etch chambers, eliminating the need for expensive metrology tools and reducing qualification time, ensuring efficient and cost-effective process control.
Implementation Method 1
Plasma etching is typically used to fabricate integrated circuits and involves bombarding a sample with pulses of a high-speed plasma discharge
Implementation Method 2
the gas etch chemistry forms volatile chemical compounds with the material being etched
Implementation Method 3
depositing photoresist on top of the film in a pattern that isolates the center region from the edge region of the wafer
Implementation Method 4
performing an in-situ ash to remove any photoresist
Data Source
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AI summary
The present disclosure relates to semiconductor manufacturing, in particular to a real-time method for qualifying the etch rate for plasma etch processes. A method for testing a semiconductor plasma etch chamber may include: depositing a film on a substrate of a wafer, the wafer including a center region and an edge region; depositing photoresist on top of the film in a pattern that isolates the center region from the edge region of the wafer; and performing an etch process on the wafer that includes at least three process steps. The three process steps may include: etching the film in any areas without photoresist covering the areas until a first clear endpoint signal is achieved; performing an in-situ ash to remove any photoresist; and etching the film in any areas exposed by the removal of the photoresist until a second clear endpoint is achieved. The method may further include determining whether both endpoints are achieved within respective previously set tolerances, and, if both endpoints are achieved within the previously set tolerance, qualifying the plasma etch chamber as verified.