Substrate Processing RF Voltage Pulse Control
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Solution Overview
Problem
The increasing trend towards larger substrate diameters and higher plasma densities in parallel-plate substrate processing leads to a significant variation in the incident energy of ions due to the cancellation of negative voltage applied to the lower electrode, resulting in poor processing precision.
Innovation Solution
A substrate processing apparatus and method that applies a RF voltage with a frequency of 40 MHz or higher, combined with a pulse voltage that decreases over time, to reduce the voltage change on the substrate, thereby stabilizing the incident energy of ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the negative voltage is applied to the lower electrode to control ion energy, then the ion incident energy can be controlled, but the voltage of the substrate changes due to ion accumulation, leading to large variation in ion incident energy
Solution Approach 1:
The patent applies periodic pulse negative voltage to the lower electrode instead of continuous negative voltage. By using pulsed voltage with controlled width and cycle, the system can control ion incident energy while allowing the substrate voltage to recover between pulses, preventing excessive voltage accumulation and reducing variation in ion incident energy.
Solution Approach 2:
The patent dynamically adjusts the pulse voltage parameters (width, cycle, amplitude) based on processing conditions to optimize both ion energy control and voltage stability. The dynamic pulse modulation allows the system to adapt to changing plasma conditions and maintain stable ion incident energy throughout the processing cycle.
2Productivity
If larger diameter substrates and higher plasma density are used to increase productivity, then more ions enter the substrate per unit time, but the negative voltage applied to the lower electrode is cancelled, causing large variation in ion incident energy
Solution Approach 1:
The periodic pulse negative voltage compensates for the increased ion flux from higher plasma density and larger substrate area. The pulsed application allows charge accumulation to be controlled in discrete steps, preventing complete cancellation of the negative voltage even with increased ion bombardment, thereby maintaining ion energy uniformity across the substrate surface.
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 effectively reduces the voltage change on the substrate to 50 V or less, minimizing the variation in ion energy and improving processing precision, particularly for low-K materials.
Implementation Method 1
a RF power source applying to the first electrode a RF voltage whose frequency is equal to or higher than 40 MHz
Implementation Method 2
a pulse voltage applying unit applying to the first electrode a pulse voltage decreasing in accordance with a lapse of time, by superimposing the pulse voltage on the RF voltage
Implementation Method 3
generates plasma by applying RF (radio frequency voltage) to the upper electrode or the lower electrode to process a substrate (wafer) placed on the lower electrode by the plasma
Implementation Method 4
controls plasma density and energy of ions entering the substrate from the plasma
Data Source
AI summary
There are provided a substrate processing apparatus and a substrate processing method realizing an effective reduction of a voltage change of a substrate on an electrode to reduce the variation of incident energy of ions entering the substrate. The substrate processing apparatus includes: a first electrode holding a substrate on a main surface of the first electrode; a second electrode facing the first electrode; a RF power source applying to the first electrode a RF voltage whose frequency is equal to or higher than 40 MHz; and a pulse voltage applying unit applying to the first electrode a pulse voltage decreasing in accordance with a lapse of time, by superimposing the pulse voltage on the RF voltage.