Plasma Head Thermal Control via Segmented Cooling
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Solution Overview
Problem
Existing plasma sources for wafer-to-wafer bonding at low temperatures face challenges in maintaining the plasma head temperature below 60°C, as the plasma gas temperature is around 120°C, exceeding safety specifications and requiring inefficient warm-up times to achieve equilibrium.
Innovation Solution
An atmospheric pressure plasma system with a plasma head featuring a heating element and an active cooling element, including a resistive heater and a liquid cooling system, controls the plasma head temperature to a set-point independent of plasma power variations, ensuring the outer surface remains below 60°C and maintaining temperature consistency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plasma is generated to activate wafer surfaces, then wafer bonding strength is improved, but plasma head temperature exceeds safety specifications
Solution Approach 1:
The plasma head is segmented into distinct functional zones: a cooling channel system separate from the plasma generation zone, allowing independent temperature control of the head structure while maintaining plasma discharge for surface activation and bonding
Solution Approach 2:
A cooling fluid intermediary is introduced through channels in the plasma head, acting as a heat transfer medium that absorbs excess thermal energy from the plasma generation process and carries it away, maintaining the plasma head temperature below 60°C while plasma gas activates wafer surfaces
2Reliability
If plasma power is increased to improve activation, then wafer surface activation is enhanced, but plasma head temperature increases beyond safety limits
Solution Approach 1:
A temperature sensing system provides real-time feedback on plasma head temperature, which is fed back to the power controller to dynamically adjust plasma generating power, ensuring the plasma head temperature remains below 60°C while maintaining effective wafer surface activation
Solution Approach 2:
The system dynamically changes operational parameters including plasma generating power and cooling fluid flow rate to maintain the plasma head temperature within safety limits while optimizing wafer surface activation effectiveness
3Stability of the object's composition
If plasma head is allowed to warm up to equilibrium temperature, then stable plasma operation is achieved, but warm-up time and gas waste increase
Solution Approach 1:
The cooling system is activated in advance and maintains the plasma head at the desired temperature range before plasma generation begins, eliminating the need for warm-up time and associated gas waste while ensuring stable plasma operation from the start
Solution Approach 2:
The active cooling system operates continuously to maintain the plasma head temperature at the optimal set-point throughout operation, allowing the plasma head to remain ready for immediate plasma generation without periodic warm-up cycles, thus eliminating warm-up time and gas waste
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 solution eliminates plasma head warm-up time, minimizes gas waste, and maintains process temperature consistency within safety limits, achieving precise temperature control regardless of plasma ON/OFF status or power settings, thus optimizing process efficiency and safety.
Implementation Method 1
a liquid cooling system, featuring a coolant supply line and a coolant exhaust line
Implementation Method 2
a heating element and an active cooling element, including a resistive heater and a liquid cooling system
Data Source
AI summary
An atmospheric pressure plasma system includes an atmospheric pressure plasma source that generates a glow discharge-type plasma. The atmospheric pressure plasma source comprises a plasma head, a heating element and an active cooling element and the heating element and active cooling element control the plasma head temperature to a set-point temperature independent of variations in plasma generating power or plasma power ON/OFF status.