High-Voltage Pulse Droop Control for Stable Plasma Etching
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Solution Overview
Problem
Existing high voltage power systems in plasma etching processes suffer from waveform modifications that affect the ion energy distribution function, leading to decreased process effectiveness due to pulse-to-pulse droop and broadened ion energy distributions, which impact features such as etch rate, aspect ratio, and ion impact damage.
Innovation Solution
A high voltage pulsing power system with a DC power supply, switch circuit, droop control circuit, and energy recovery circuit, including components like droop diodes, inductors, and transformers, to regulate current flow and shape pulses, ensuring consistent ion energy distribution functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high voltage power systems are used to create ion energy distribution functions, then plasma etching processes can be enabled, but pulse-to-pulse droop occurs in the waveform which broadens the ion energy distribution and reduces process effectiveness
Solution Approach 1:
The droop compensation circuit proactively adjusts the waveform before the droop can significantly broaden the ion energy distribution. By predicting and compensating for the expected droop based on process conditions, the system maintains a narrow ion energy distribution without requiring reactive corrections after droop occurs.
Solution Approach 2:
The system continuously monitors the actual waveform and ion energy distribution, then feeds this information back to the droop compensation circuit. This closed-loop feedback enables real-time adjustment of compensation parameters, ensuring the waveform remains stable and the ion energy distribution stays narrow despite varying plasma conditions.
2Productivity
If waveform modifications are allowed to occur naturally, then the system operation is simpler, but the ion energy distribution function is degraded leading to decreased process effectiveness
Solution Approach 1:
The droop compensation circuit acts as an intermediary component between the power supply and plasma chamber. It introduces minimal complexity by adding only the necessary circuitry to counteract droop, without requiring complete redesign of the power system. This intermediary approach enables improved process effectiveness with controlled increases in system complexity.
3Manufacturing precision
If droop compensation is implemented, then ion energy distribution is maintained, but energy is lost through the compensation mechanism
Solution Approach 1:
The droop compensation circuit applies only the necessary amount of compensation to maintain the ion energy distribution within acceptable limits. Rather than over-compensating which would waste energy, the system applies partial correction just sufficient to counteract the harmful effects of droop, optimizing the balance between precision and energy efficiency.
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 maintains steady ion energy distributions by minimizing droop, allowing for precise control of etch processes, optimizing features like etch rate, aspect ratio, and reducing ion impact damage.
Implementation Method 1
The droop control circuit may include a droop diode, a droop inductor, and/or a droop element that may be a resistive element or an energy recovery circuit
Implementation Method 2
The transformer can include a transformer core, primary windings, and secondary windings
Implementation Method 3
In some applications, the chamber or plasma can modify portions of the waveform that are creating the ion energy distribution function. For example, in a semiconductor processing system, an ion current within the plasma may create a droop between consecutive pulses in the waveform at the wafer
Data Source
AI summary
A high voltage pulsing power system is disclosed that include a DC power supply, a switch circuit electrically coupled with the DC power supply, a droop control circuit coupled with the switch circuit, and/or an output. The switch circuit includes a plurality of switch modules and produces a plurality of pulses. The droop control circuit includes a droop diode, a droop inductor, and a droop element. The droop diode may be electrically coupled in series between the switch circuit and the transformer primary that allows the negative pulse portion of the pulses to pass from the switching circuit to the transformer primary. The droop inductor and he droop element may be arranged in series across the droop diode to allow the negative pulse portion of the pulses to pass from the switching circuit to the transformer primary and/or store energy from the negative pulse portion of the pulses.