Electrostatic Chuck Wafer De-chucking Voltage Control
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Solution Overview
Problem
Existing methods for de-chucking wafers from electrostatic chucks often result in damage due to residual electrostatic forces, as charges take time to neutralize, leading to over-bending or breakage during physical separation.
Innovation Solution
A method involving the application of a first de-chucking voltage with a different polarity or zero value, followed by a second de-chucking voltage that varies periodically, such as alternating voltages, to efficiently neutralize electrostatic charges, accompanied by the use of a de-chucking gas to facilitate safe separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electric power is interrupted to eliminate electrostatic force, then the wafer can be unloaded from the electrostatic chuck, but residual charges remain causing over-bending or breakage during physical separation
Solution Approach 1:
A de-chucking voltage with opposite polarity is applied in advance to neutralize residual charges before physical separation occurs. This preliminary counter-action eliminates the harmful electrostatic force that would otherwise cause wafer damage during unloading.
Solution Approach 2:
The de-chucking voltage is applied before the wafer is physically separated from the electrostatic chuck. By preparing the charge neutralization process in advance, the system ensures that no residual electrostatic force remains when separation occurs, preventing wafer damage.
2Reliability
If a voltage with different polarity is applied to neutralize charges, then electrostatic power is weakened, but new charges with opposite polarity are generated preventing complete extinction
Solution Approach 1:
An alternating voltage is applied instead of a constant opposite polarity voltage. The periodic nature of the alternating voltage allows charges to be continuously neutralized without generating persistent opposite polarity charges, as the voltage polarity switches periodically to prevent charge accumulation.
Solution Approach 2:
The voltage parameters are changed from a constant opposite polarity to an alternating voltage with specific frequency and amplitude. This parameter change enables effective charge neutralization while avoiding the generation of stable opposite polarity charges that would persist and complicate the de-chucking process.
3Reliability
If charges are allowed to flow out through grounded chamber after interruption, then some neutralization occurs, but the process takes predetermined time causing delays
Solution Approach 1:
The de-chucking voltage is applied in advance before the wafer is physically removed, actively neutralizing charges during the unloading process itself rather than allowing passive dissipation after separation. This eliminates the time delay associated with waiting for charges to naturally flow out through the grounded chamber.
Solution Approach 2:
Instead of allowing charges to slowly dissipate through the grounded chamber over a predetermined period, the alternating de-chucking voltage rapidly neutralizes charges in real-time during the unloading process, effectively skipping the time-consuming passive dissipation phase.
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 electrostatic forces between the wafer and the chuck, preventing damage during de-chucking and improving semiconductor device manufacturing yield by ensuring safe and reliable separation.
Implementation Method 1
The electrostatic chuck may attract the wafer using an electrostatic force
Implementation Method 2
a voltage having a different polarity from the polarity applied to the electrodes during the process may be applied to the electrostatic chuck. Consequently, the charges remaining in the electrodes may be neutralized
Implementation Method 3
the second de-chucking voltage varies periodically in polarity... the electrostatic power between the electrostatic chuck and the wafer may not be completely extinguished, but may only be weakened gradually
Data Source
AI summary
Example embodiments provide a method of de-chucking a wafer by alternating between using a direct voltage and an alternating voltage, and an apparatus for fabricating a semiconductor device using the same. The method of de-chucking a wafer comprises interrupting a chucking voltage applied to an electrostatic chuck, applying a first de-chucking voltage to the electrostatic chuck, and applying a second de-chucking voltage to the electrostatic chuck.