Lithography Stage Linear Motor Coil Control for Thermal Stability
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Solution Overview
Problem
Lithography apparatuses face challenges in managing temperature fluctuations caused by heat generated by linear motors during stage driving, which affects measurement accuracy and pattern formation on substrates.
Innovation Solution
A stage driving apparatus with a linear motor featuring a stator with alternately arrayed first and second phase coils, where the control unit manages the energization state to hold the stage position using the first phase coil during stopping periods and generates heat using the second phase coil without applying thrust, thereby reducing heat generation fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the linear motor is driven using conventional multi-phase excitation sine-wave driving method, then thrust uniformity is improved, but temperature fluctuation increases due to large heat generation difference between driving and stopping periods
Solution Approach 1:
The coil array is segmented into first phase coils and second phase coils that are alternately arrayed and operate independently. During stopping period, only the first phase coil is energized to hold position, while the second phase coil remains de-energized to minimize heat generation. This segmentation allows separate control of position holding and heat generation functions.
Solution Approach 2:
The control unit implements periodic switching between different coil energization states based on the driving cycle. During driving periods, both phase coils are energized to provide thrust; during stopping periods, only the first phase coil is energized to maintain position. This periodic action synchronizes heat generation with actual driving needs, reducing overall temperature fluctuation.
2Reliability
If both phase coils are energized during stopping period to maintain position, then position holding is achieved, but heat generation increases unnecessarily
Solution Approach 1:
The position holding function is extracted from the dual-coil system and assigned specifically to the first phase coil. The second phase coil is removed from the energization sequence during stopping periods, eliminating its contribution to heat generation while the first phase coil alone maintains sufficient magnetic field for position holding.
Solution Approach 2:
Different energization strategies are applied to different phases of the coil array based on local functional requirements. The first phase coil receives continuous energization during stopping periods for position holding, while the second phase coil receives no energization to minimize heat. This local differentiation optimizes the balance between position stability and heat generation.
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 heat generation fluctuations and unintended stress on the substrate stage, enabling more accurate temperature control and improved pattern formation on substrates.
Implementation Method 1
a linear motor including a stator which includes a coil array obtained by alternately arraying first phase coils and second phase coils, and a movable element placed on the stage
Implementation Method 2
generates heat by turning on the second phase coil arranged in a position where no thrust is given to the movable element among the coil array
Data Source
AI summary
The present invention provides a stage driving apparatus for driving a stage, comprising: a linear motor including a stator which includes a coil array obtained by alternately arraying first phase coils and second phase coils, and a movable element placed on the stage; and a control unit configured to control the linear motor by controlling an energization state of the coil array, wherein in a stopping period during which the stage is stopped in a predetermined position, the control unit holds a position of the stage in the predetermined position by turning on the first phase coil among the coil array, and generates heat by turning on the second phase coil arranged in a position where no thrust is given to the movable element among the coil array.