Configurable Bias Supply with Bidirectional Switch for Plasma Etching
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Solution Overview
Problem
Current plasma processing technologies face challenges in achieving a narrow ion energy distribution, as sinusoidal waveforms induce broad distributions, limiting etch profile precision and increasing costs, inefficiencies, and affecting plasma density.
Innovation Solution
A bias supply system with a bidirectional switch and controller that applies a periodic voltage through a full current cycle, comprising positive and negative current flow phases, to control ion energy distribution and maintain plasma density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a sinusoidal waveform is applied to the substrate, then the substrate can be charged and ions can be attracted toward the substrate, but a broad distribution of ion energies is induced which limits etch profile precision
Solution Approach 1:
The patent applies periodic voltage pulses instead of continuous sinusoidal waveforms. The controller selectively activates switching elements during specific portions of the RF cycle to create tailored periodic voltage patterns that narrow the ion energy distribution while maintaining the periodic charging necessary for ion attraction and etching processes
Solution Approach 2:
The patent dynamically changes voltage parameters during the RF cycle by using multiple switching elements with different timing. The controller adjusts the magnitude and timing of voltage applied to the substrate throughout the cycle, creating a tailored voltage profile that controls ion acceleration and narrows the energy distribution at impact
2Manufacturing precision
If known techniques are used to achieve a narrow ion energy distribution, then etch profile precision may be improved, but the techniques are expensive, inefficient, difficult to control, and may adversely affect plasma density
Solution Approach 1:
The patent uses a single RF power source that serves multiple functions: it provides both the plasma sustaining power and the substrate bias voltage. The controller manages multiple switching elements that work together to create tailored voltage waveforms, eliminating the need for separate complex bias supply systems while achieving narrow ion energy distribution
Solution Approach 2:
The system incorporates sensors that monitor plasma conditions and provide feedback to the controller. The controller uses this feedback to dynamically adjust the switching element timing and voltage levels, automatically maintaining optimal ion energy distribution and plasma density without requiring complex manual control
3Reliability
If a non-varying voltage is applied to a dielectric substrate, then the voltage can be maintained across the substrate surface, but the voltage is ineffective to place a voltage across the surface of the substrate
Solution Approach 1:
The patent applies periodic voltage pulses during specific portions of the RF cycle rather than continuous DC voltage. This periodic application allows charge to accumulate on the dielectric substrate surface during the pulse duration, creating an effective voltage across the substrate that drives ion attraction while maintaining overall voltage stability through controlled repetition
Solution Approach 2:
The controller applies voltage pulses to the substrate before the main ion bombardment phase. This preliminary voltage application pre-charges the dielectric substrate surface, ensuring that when ions are attracted, there is already an established electric field across the substrate surface to guide and control the ion flux effectively
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 system achieves a tailored ion energy distribution, enhancing etch profile precision while maintaining plasma density, thus overcoming the limitations of existing technologies.
Implementation Method 1
a bidirectional switch configured to enable bidirectional control of current between a first node of the bidirectional switch and a second node of the bidirectional switch
Implementation Method 2
a plasma chamber including a volume to contain a plasma
Data Source
AI summary
Bias supplies, plasma processing systems, and associated methods are disclosed. One bias supply comprises a bidirectional switch configured to enable bidirectional control of current. A controller is configured to control a direction of current through the bidirectional switch over a full current cycle, the full current cycle comprising a first half current cycle and a second half current cycle, the first half current cycle comprising positive current flow, starting from zero current that increases to a positive peak value and then decreases back to zero. The second half current cycle comprises negative current flow, starting from zero current that increases to a negative peak value and then decreases back to zero current to cause an application of the periodic voltage between the output node and the return node.