Plasma Processing Magnetic Field Uniformity
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Solution Overview
Problem
In plasma processing for electronic device manufacturing, the miniaturization of devices leads to narrow recesses where thick deposit films on silicon oxide regions prevent etching, and non-uniform electric and plasma density distributions result in radial non-uniformity, necessitating a method to reduce ion energy and achieve uniform plasma density.
Innovation Solution
A plasma processing method using a plasma processing apparatus with a lower frequency second radio frequency power supply and an electromagnet to form a magnetic field with a horizontal component, increasing electron stay time and plasma density uniformly across the workpiece, especially during high-power second plasma processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high power is applied during plasma processing to increase etching speed, then productivity is improved, but ion energy increases causing unwanted etching of silicon nitride regions
Solution Approach 1:
The patent applies different radio frequency powers to different regions of the workpiece by utilizing the spatial distribution of electric fields. The center region receives higher power for faster etching, while edge regions receive lower power to prevent unwanted etching, achieving local optimization of processing conditions
Solution Approach 2:
The patent dynamically adjusts radio frequency power parameters during the plasma processing sequence. Power is increased during silicon oxide etching to maintain high productivity, then reduced during silicon nitride etching to prevent harmful effects,实现ing temporal control of processing conditions
2Reliability
If thick deposit films are formed on silicon oxide regions to protect them, then selectivity is improved, but the films prevent etching in narrow recesses where miniaturization has led to confined spaces
Solution Approach 1:
The patent employs periodic alternation between deposit formation and etching processes. Deposit films are formed temporarily to provide protection and selectivity, then removed when no longer needed to allow etching access in narrow recesses, achieving temporal separation of protective and etching functions
Solution Approach 2:
Deposit films are formed in advance before etching operations to pre-establish protective layers on silicon oxide regions. This preliminary protection enables selective etching of silicon nitride while preserving silicon oxide, with the understanding that deposits will be removed later
3Device complexity
If conventional radio frequency power supply is used, then device complexity is kept simple, but plasma density distribution becomes non-uniform across the workpiece surface
Solution Approach 1:
The patent introduces dynamic control of radio frequency power during the plasma processing sequence. Power levels are adjusted at different time points to compensate for spatial non-uniformities in plasma density, transforming a static system into a dynamically controlled one that maintains uniformity
Solution Approach 2:
The patent implements a control strategy where plasma processing conditions are monitored and power parameters are adjusted based on observed etching rates and plasma characteristics. This feedback mechanism compensates for non-uniform plasma density distribution without requiring complex hardware modifications
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 enables uniform plasma density distribution and improved in-plane uniformity during plasma processing, effectively reducing ion energy and preventing etching of silicon nitride regions while selectively etching silicon oxide regions, even in narrow recesses.
Implementation Method 1
an electromagnet configured to form a magnetic field in the inner space of the chamber body
Implementation Method 2
The first radio frequency power supply is configured to supply first radio frequency waves
Implementation Method 3
the second radio frequency waves are supplied to the lower electrode. Thus, ions in the plasma are accelerated toward the workpiece
Data Source
AI summary
A plasma processing method for a workpiece in a plasma processing apparatus includes (i) performing a first plasma processing on a workpiece, and (ii) performing a second plasma processing on the workpiece. Power of second radio frequency waves set in the second plasma processing is greater than the power of the second radio frequency waves set in the first plasma processing. In the second plasma processing, a magnetic field distribution having a horizontal component on an edge side of the workpiece greater than a horizontal component on a center of the workpiece is formed by an electromagnet.