Electrostatic Chuck Bias Compensation for Stable Plasma Clamping
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Solution Overview
Problem
Conventional substrate clamping systems in semiconductor manufacturing face challenges with maintaining consistent clamping voltage during plasma processing, leading to potential substrate damage due to fluctuations in plasma potential and inadequate adjustment mechanisms.
Innovation Solution
A plasma processing chamber system incorporating a substrate support assembly with a biasing electrode, a waveform generator, a power delivery line with a blocking capacitor, a clamping network, and a signal detection module, which delivers pulsed-voltage waveforms and adjusts the clamping voltage based on real-time signal characteristics to maintain a constant sheath voltage and ion energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed DC voltage is applied to the second electrode to clamp the substrate, then the substrate is securely held, but the electrostatic force fluctuates with RF bias power changes causing under or over clamping
Solution Approach 1:
The patent implements a feedback mechanism where the controller monitors the RF bias power level and automatically adjusts the DC voltage applied to the second electrode in real-time. This closed-loop control ensures that the electrostatic clamping force remains stable despite changes in RF bias power, preventing both under-clamping and over-clamping conditions.
Solution Approach 2:
The system transitions from a static fixed DC voltage approach to a dynamic adjustment mechanism. The DC voltage level is continuously modified based on the actual RF bias power being applied, allowing the clamping force to adapt dynamically to changing process conditions while maintaining optimal substrate contact.
2Power
If large bias voltage in the kilovolt range is applied for high bias power, then ion bombardment energy is sufficient for high aspect ratio etching, but voltage fluctuation increases the risk of arcing or sudden de-clamping
Solution Approach 1:
The controller continuously monitors the bias voltage and RF power levels, and automatically adjusts the DC voltage component to compensate for fluctuations. This feedback control stabilizes the total bias voltage in the kilovolt range, preventing dangerous voltage spikes that could cause arcing or sudden substrate de-clamping while maintaining sufficient ion bombardment energy for high aspect ratio etching.
Solution Approach 2:
The system proactively adjusts the DC voltage component in anticipation of or in response to RF power changes to prevent voltage excursions before they can cause harmful effects. By continuously modulating the DC bias to counteract potential fluctuations, the system cushions against arcing and de-clamping events before they occur.
3Power
If RF bias power is increased to achieve desired ion energy, then etching capability improves, but the electrostatic clamping force is affected leading to potential substrate damage
Solution Approach 1:
The system uses feedback control to monitor RF bias power levels and automatically compensates by adjusting the DC voltage component. This ensures that while high ion bombardment energy is delivered for effective etching, the electrostatic clamping force is simultaneously maintained at appropriate levels to prevent substrate damage from excessive or fluctuating clamping forces.
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 system reliably biases and clamps substrates, improving plasma processing results by maintaining a consistent ion energy distribution and preventing substrate damage from excessive clamping forces or voltage fluctuations.
Implementation Method 1
the first power delivery line comprises a blocking capacitor
Implementation Method 2
The ESC secures the substrate disposed thereon by applying a fixed DC voltage to a second electrode embedded in the ESC to establish an electric field between the ESC and the substrate. The electric field induces opposite polarity charges to accumulate on the substrate and the second electrode, respectively.
Implementation Method 3
The electrostatic attractive force between the oppositely polarized charges pulls the substrate toward the ESC to secure the substrate.
Implementation Method 4
Non-linear, diode-like nature of the plasma sheath results in rectification of the applied RF field, such that a direct-current (DC) voltage drop, or self-bias, appears between the substrate and the plasma.
Implementation Method 5
The RF source supplies an RF voltage to a first electrode embedded in an electrostatic chuck (ESC) or cathode. The first electrode is capacitively coupled to the plasma of a processing chamber through a layer of ceramic, which is a part of the ESC.
Data Source
AI summary
Embodiments of the present disclosure relate to a system for pulsed direct-current (DC) biasing and clamping a substrate. In one embodiment, the system includes a plasma chamber having an electrostatic chuck (ESC) for supporting a substrate. An electrode is embedded in the ESC and is electrically coupled to a biasing and clamping network. The biasing and clamping network includes at least a shaped DC pulse voltage source and a clamping network. The clamping network includes a DC source and a diode, and a resistor. The shaped DC pulse voltage source and the clamping network are connected in parallel. The biasing and clamping network automatically maintains a substantially constant clamping voltage, which is a voltage drop across the electrode and the substrate when the substrate is biased with pulsed DC voltage, leading to improved clamping of the substrate.