Electrostatic Chuck Wafer Declamping via Segmented Lifting
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Solution Overview
Problem
Existing methods for declamping semiconductor wafers from electrostatic chucks often result in the wafer 'popping' off with excessive force, leading to damage or defects due to inadequate removal techniques.
Innovation Solution
A method where only a portion of the wafer is initially lifted from the chuck while monitoring a predetermined condition, such as capacitance or time, before complete removal to minimize 'popping' force and ensure safe wafer extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wafer lifting mechanism lifts the wafer from the surface in one fell swoop, then the wafer is freed from the chuck quickly, but the wafer pops from the surface with excessive force causing damage or defects
Solution Approach 1:
The wafer removal process is segmented into multiple stages: initially lifting only a first region (edge portion) of the wafer while a second region (central portion) remains adhered, then monitoring a predetermined condition (capacitance change), and finally lifting the second region when the condition is met. This segmentation prevents sudden complete detachment and excessive popping force.
Solution Approach 2:
The method performs preliminary action by first lifting only the edge portion of the wafer before complete removal. This preliminary partial lifting allows the system to monitor capacitance changes and prepare for the final detachment phase, preventing sudden excessive force application.
2Ease of operation
If the clamping voltage is turned off completely, then the wafer should be released from the chuck, but the wafer sticks to the chuck surface for a considerable amount of time
Solution Approach 1:
The system continuously monitors a predetermined condition (capacitance change) during the wafer lifting process. This feedback mechanism detects when the wafer has sufficiently detached from the chuck surface, allowing the system to know when complete removal is safe to proceed, thus reducing unnecessary waiting time.
Solution Approach 2:
The lifting process is made dynamic by adjusting the lifting sequence based on real-time capacitance monitoring. The system transitions from lifting only the first region to lifting the second region based on the monitored condition, optimizing the removal timing rather than using fixed time delays.
3Reliability
If the wafer is lifted gradually in regions, then wafer damage is reduced, but the declamping process takes more time
Solution Approach 1:
The capacitance monitoring provides real-time feedback that accelerates the gradual lifting process. By detecting capacitance changes, the system knows when the wafer has sufficiently detached, allowing it to proceed to the next lifting phase without unnecessary delays, thus maintaining reliability while improving speed.
Solution Approach 2:
The lifting process uses periodic monitoring of the predetermined condition (capacitance) to determine when to transition between lifting phases. This periodic check optimizes the timing of each lifting stage, ensuring wafer integrity while minimizing total process time.
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 reduces wafer damage and maintains system throughput by gradually releasing the wafer from the chuck, minimizing dropped wafers and defects.
Implementation Method 1
a clamping voltage is typically applied between the wafer and the electrode, resulting in electrostatic forces that adhere the wafer to the surface of the electrostatic chuck
Implementation Method 2
the capacitance between the wafer and the chuck changes as the wafer is lifted from the chuck surface
Data Source
AI summary
One embodiment of the present invention relates to a method for declamping a semiconductor wafer that is electrically adhered to a surface of an electrostatic chuck by a clamping voltage. In this method, the clamping voltage is deactivated. For a time following the deactivation, a first region of the wafer is lifted an first distance from the surface of the electrostatic chuck while a second region of the wafer remains adhered to the surface of the electrostatic chuck. A predetermined condition is monitored during the time. The second region is lifted from the surface of the electrostatic chuck when the predetermined condition is met.