Electrostatic Chuck Voltage Timing for Wafer Release After Plasma Etching
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Solution Overview
Problem
Existing plasma processing methods fail to effectively neutralize residual adsorption forces on wafers after plasma etching, leading to wafer deviation and potential damage due to unaddressed recharging by residual charged particles in the processing chamber, particularly with high resistive dielectric films.
Innovation Solution
A plasma processing apparatus and method that control the DC voltage applied to the electrostatic chuck electrode to nearly 0 V after a predetermined time following the cessation of radio frequency power, coinciding with the disappearance of charged particles and afterglow discharge, ensuring the wafer potential aligns with the electrode potential, thereby eliminating residual adsorption forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the voltage applied to the electrostatic chuck electrode is turned off immediately when plasma processing ends, then the neutralization process is simplified and faster, but residual adsorption force remains due to insufficient neutralization of charged particles
Solution Approach 1:
The patent applies preliminary action by continuing plasma discharge for a predetermined period after RF power cessation before turning off the electrode voltage. This preliminary continuation of plasma discharge ensures thorough neutralization of charged particles on the dielectric film surface, preventing residual adsorption force while maintaining a controlled and predictable neutralization timeline.
Solution Approach 2:
The patent maintains continuity of useful action by extending the plasma discharge state beyond RF power cessation. The plasma continues to neutralize charged particles on the dielectric film surface during this extended period, ensuring complete neutralization before voltage cutoff, thereby eliminating residual adsorption force without compromising process efficiency.
2Reliability
If the voltage applied to the electrostatic chuck electrode is delayed to be turned off after a predetermined time from RF power cessation, then residual adsorption force is eliminated through complete neutralization, but the neutralization process becomes more complex and time-consuming
Solution Approach 1:
The patent implements feedback control by using a control unit that automatically manages the electrode voltage cutoff timing based on RF power cessation. The system monitors the predetermined time interval and automatically cuts off the voltage after this interval elapses, eliminating the need for complex manual coordination and reducing control complexity while ensuring complete neutralization.
Solution Approach 2:
The patent applies self-service by designing a control system that autonomously manages the neutralization timing. The control unit automatically determines when to cutoff the electrode voltage based on the predetermined time from RF power cessation, without requiring external intervention or complex coordination, thereby simplifying the overall control mechanism.
3Stability of the object's composition
If high resistive dielectric films are used in the electrostatic chuck, then wafer adsorption stability is improved, but residual adsorption force persists longer due to insufficient charge neutralization
Solution Approach 1:
The patent applies preliminary action by extending plasma discharge before voltage cutoff to ensure complete neutralization of charged particles on high resistive dielectric films. This preliminary extension of plasma state compensates for the slow neutralization characteristics of high resistive materials, eliminating residual adsorption force while maintaining adsorption stability during processing.
Solution Approach 2:
The patent changes the timing parameter of voltage cutoff relative to RF power cessation. By setting the voltage cutoff to occur after a predetermined time from RF power cessation rather than simultaneously, the patent adjusts the neutralization process parameters to accommodate high resistive dielectric films, ensuring complete charge neutralization while maintaining adsorption stability.
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 ensures safe and precise release of wafers from the sample stage by eliminating residual adsorption forces, preventing wafer deviation and damage, thus enhancing manufacturing productivity by considering recharging effects post-plasma processing.
Implementation Method 1
the wafer is adsorbed by an electrostatic force generated in a dielectric film between the electrode and the wafer by applying a voltage to an electrode
Implementation Method 2
exposing plasma for neutralizing the adsorbed object
Data Source
AI summary
The invention provides a plasma processing apparatus which includes a processing chamber, a radio frequency power source to supply a radio frequency power for plasma generation, a sample stage equipped with an electrostatic chuck electrode of a sample, a DC power source to apply a DC voltage to the electrode, and a control unit to change the DC voltage from a predetermined value to almost 0 V when a predetermined time elapses since the supplying of the radio frequency power is stopped. The predetermined value is a predetermined value indicating that a potential of the sample when the DC voltage is almost 0 V becomes almost 0 V. The predetermined time is a time defined on the basis of a time when charged particles generated by the plasma processing disappear or a time when an afterglow discharge disappears.