Wafer breakage at flash heating
Wafer breakage within the flash heating system:
The flash heating with the upper lamp created the gradient of the temperature of the air. The fast-changing of temperature results in the wind (tornado) formation that leads to the movement of the wafer. The moving of the wafer may result in a mechanical hit followed by the wafer breakage.
Wafer breakage occurs at flash heating
Run additional wafers to compensate for the broken wafers
3
A mechanical hit occurs
Redesign the pedestal or add a ring having no "walls" - no parts that the wafer can hit
2
Wafer moves due to air pressure difference appearing due to flash heating
Fixate the wafer - no movements at all (vacuum chuck?)
0
The pedestal has a special configuration: the wafer moves and can get a mechanical hit
Redesign the pedestal to exclude a mechanical hit
0
How wafer breakage occurs while the flash heating process:
Operational Effectiveness – OE
Effective
Ineffective
OE 0.59
Operational Perfectness - OP
Basic functions
Components
Supersystems
OP 0.39
Pedestal | 8 |
Low lamp | 6 |
Bumps | 4 |
Centering pins | 4 24 |
Upper light (flash) | 4 |
Atmosphere (N2) | 12 |
Air | 8 |
The main conclusion is that we need to exclude either movement of the wafer or vertical solid parts that the wafer can hit
If | Centering pins remains unchanged |
|---|---|
Then | Centering pins Hold Wafer |
But | Centering pins Stops Wafer |
If | we exclude the wafer movement |
|---|---|
Then | no breakage will occur due to a mechanical hit |
But | The thermal stress could appear and affect the parameters of the product or even result in breakage due to thermal stress |
Wafers break due to flash heating
Let's analyze the possibility of a mechanical hit during the flash heating process
Wafer got a mechanical hit during the flash heating process
Mechanical hit of the wafer with centring pins
Redesign centering pins with flexible, low-friction polymer coatings or spring-loaded tips that absorb minor impacts and allow self-centering without causing damage during wafer movement.
The wafer should move during the flash heating process
Keep the wafer against movement
Nitrogen gas moves and moves the wafer
Redesign the quartz pedestal with additional low-profile support ridges or pins positioned to provide lateral stability to the wafer, preventing displacement from gas flows while maintaining uniform light exposure.
Rapid thermal expansion of chamber gases inducing convective currents
Process in a vacuum or at least in low pressure
Different temperatures cause different pressures of nitrogen
Add the same flight on the bottom to get the same temperature
Flash heating is needed for implant ions activation
Integrate in-situ plasma-assisted activation during implantation to partially activate ions, reducing the reliance on subsequent high-temperature flash heating steps.
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