Edge Ring Voltage Timing for Wafer Edge Etching Uniformity
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Solution Overview
Problem
In plasma processing apparatuses, the etching shape of semiconductor wafers near the edge collapses in the radial direction, resulting in elliptical holes and tilting due to the consumption of the edge ring, which affects the uniformity and roundness of the etching process.
Innovation Solution
A plasma processing apparatus with a controller that applies a negative DC voltage to the edge ring, periodically alternating between two voltage states to control the sheath thickness and prevent tilting, ensuring a complete circular shape of the holes by synchronizing the DC voltage with the radio-frequency or pulse wave of the bias power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a DC voltage is applied to the edge ring to maintain sheath thickness, then the etching uniformity is improved, but the device complexity increases due to additional voltage control mechanisms
Solution Approach 1:
The DC voltage applied to the edge ring is periodically switched between a first voltage value (during plasma generation) and a second voltage value (during non-plasma periods). This periodic voltage application maintains appropriate sheath thickness at the wafer edge without requiring complex continuous control mechanisms, thereby improving etching uniformity while limiting device complexity increase
Solution Approach 2:
The edge ring voltage is dynamically adjusted based on the plasma generation state. The controller switches the DC voltage between two states in synchronization with the plasma generation cycles, allowing the sheath thickness to be maintained adaptively without complex real-time measurement and adjustment systems
2Stability of the object's composition
If the DC voltage is continuously applied to prevent edge ring consumption, then the tilting is prevented, but the energy consumption increases
Solution Approach 1:
The DC voltage to the edge ring is applied periodically only during plasma generation periods rather than continuously. The voltage switches between a first value during plasma generation and a second value during non-plasma periods, preventing tilting and maintaining vertical etching while significantly reducing energy consumption compared to continuous voltage application
Solution Approach 2:
The useful action of maintaining sheath thickness and preventing tilting is achieved by applying voltage during the critical plasma generation periods. This continuous useful action during active processing maintains vertical etching stability without the energy waste of continuous voltage application during idle periods
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
The solution effectively prevents tilting and maintains the roundness of the etching shape at the wafer edge, ensuring vertical etching and improved uniformity by dynamically controlling the sheath thickness in response to the wafer potential.
Implementation Method 1
a DC power supply configured to supply a DC voltage to the edge ring
Implementation Method 2
a plasma generation source configured to supply plasma into the processing container
Implementation Method 3
an etching process is performed with plasma generated from a gas by a radio-frequency power
Data Source
AI summary
A plasma processing apparatus includes: a processing container; an electrode that places a workpiece thereon; a plasma generation source that supplies plasma into the processing container; a bias power supply that supplies a bias power to the electrode; an edge ring disposed at a periphery of the workpiece; a DC power supply that supplies a DC voltage to the edge ring; a controller that executes a first control procedure in which the DC voltage periodically repeats a first state having a first voltage value and a second state having a second voltage value, the first voltage value is supplied in a partial time period within each period of a potential of the electrode, and the second voltage value is supplied such that the first and second states are continuous.