Feedforward Thermal Control for Imprint Lithography Frames
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Solution Overview
Problem
Conventional nanoimprint lithography faces limitations in thermal control performance due to high time constants in feedback-based methods, leading to low closed-loop control bandwidth, which affects overlay control accuracy and stability.
Innovation Solution
A thermal frame with a motor and cooling element, thermally isolated from a metrology frame, uses digital controllers to apply control signals based on thermal sensor data to maintain thermal balance, employing feedforward design to enhance thermal control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback-based thermal control methods are used, then thermal control is provided, but the high time constant results in very low closed-loop control bandwidth, limiting thermal control performance
Solution Approach 1:
The patent applies feedforward control that anticipates thermal disturbances before they affect the metrology frame. By calculating the thermal impact of motor operation in advance and pre-applying compensating cooling, the system avoids the slow response inherent in feedback control, achieving high-speed thermal compensation without waiting for temperature changes to occur
Solution Approach 2:
The patent introduces a thermal model as an intermediary that mathematically represents the thermal system's behavior. This model allows the controller to predict future thermal states and calculate optimal cooling signals without directly measuring temperature changes in real-time, effectively decoupling the control speed from the thermal time constant
2Ease of operation
If the motor is thermally coupled to the metrology frame, then the motor drives the metrology frame, but thermal drift occurs affecting overlay control accuracy
Solution Approach 1:
The patent segments the thermal management function from the mechanical driving function by introducing a separate thermal frame that houses both the motor and cooling elements. This thermal frame is thermally isolated from the metrology frame, allowing the motor to operate independently thermally while still mechanically driving the metrology frame through a coupling mechanism
Solution Approach 2:
The patent extracts the thermal management components (motor and cooling elements) into a dedicated thermal frame that is thermally isolated from the metrology frame. This separation removes the source of thermal drift from the precision measurement system while preserving the mechanical drive function through a thermal barrier
3Manufacturing precision
If thermal isolation is provided between the motor and metrology frame, then thermal drift is reduced, but the motor cannot effectively drive the metrology frame
Solution Approach 1:
The patent introduces a mechanical coupling mechanism as an intermediary between the thermal frame and metrology frame. This coupling allows mechanical force and motion to be transmitted while blocking thermal energy transfer, effectively decoupling the thermal and mechanical functions
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
The solution significantly improves thermal control performance by minimizing thermal drift and maintaining thermal equilibrium, thereby enhancing overlay control accuracy and stability in nanoimprint lithography.
Implementation Method 1
A digital controller applies a control signal for controlling a driving signal (e.g. driving current or driving voltage) of the cooling element to maintain a thermal balance, such as thermal equilibrium, of heat flow between the frames
Implementation Method 2
Thermal sensors are disposed at locations of the frames
Data Source
AI summary
A thermal frame of an imprinting apparatus has an motor and a cooling element. A metrology frame of the imprinting apparatus is coupled to an output end of the motor and receives an imprinting mold. Thermal isolation is provided between the motor and the metrology frame. Thermal sensors are disposed at locations of the frames. A digital controller applies a control signal for controlling a driving signal of the cooling element to maintain a thermal balance, such as thermal equilibrium, of heat flow between the frames. The digital controller uses output of the thermal sensors to identify transfer functions of heat flow used to calculate the control signal. The feedforward design avoids the very low control bandwidth that limits the performance of typical feedback designs.