Encoder Head Mounting on Coarse Stage for Wafer Position Detection
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Solution Overview
Problem
Existing exposure apparatuses face challenges in achieving high precision position detection for semiconductor devices due to wiring constraints between coarse and fine movement stages, which can cause mechanical obstruction and measurement inaccuracies.
Innovation Solution
An exposure apparatus with an encoder head mounted on the coarse movement stage that measures positional information of the fine movement stage using a diffraction grating system, allowing for precise measurement and operation without wiring-induced obstructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the encoder head is mounted on the fine movement stage, then the position detection accuracy is improved, but the wiring between coarse and fine movement stages causes mechanical obstruction and measurement inaccuracies
Solution Approach 1:
Instead of mounting the encoder head on the fine movement stage (conventional approach), the patent inverts the arrangement by mounting the encoder head on the coarse movement stage. This inversion eliminates the need for wiring between stages, as the encoder head remains stationary while still measuring the position of the fine movement stage through the diffraction grating system.
Solution Approach 2:
The patent introduces a diffraction grating as an intermediary element that enables position measurement without direct mechanical connection or wiring between the encoder head and the fine movement stage. The grating acts as a mediator that translates the position of the fine movement stage into measurable optical signals for the encoder head.
2Measurement precision
If multiple encoder heads are mounted on the fine movement stage, then the measurement capability is enhanced, but the drag of wiring causes significant operational problems
Solution Approach 1:
The patent inverts the conventional mounting approach by placing the encoder head on the coarse movement stage rather than the fine movement stage. This single stationary encoder head can measure the position of the fine movement stage without requiring any wiring connections, thereby enhancing measurement capability while completely eliminating wiring drag issues.
Solution Approach 2:
The patent extracts the encoder head from the fine movement stage and relocates it to the coarse movement stage. This extraction removes the harmful wiring connections entirely, as the encoder head no longer needs to move with the fine movement stage, thereby eliminating the drag problem while preserving measurement functionality.
3Ease of manufacture
If wiring is installed between coarse and fine movement stages, then power supply to the encoder head is enabled, but the tensile force on wiring prevents smooth operation of the fine movement stage
Solution Approach 1:
The patent extracts the encoder head from the fine movement stage and relocates it to the coarse movement stage. This extraction eliminates the need for wiring between stages entirely, as the encoder head remains stationary on the coarse stage. The fine movement stage can then operate smoothly without any tensile force from wiring, while the encoder head continues to receive power through its stationary mounting.
Solution Approach 2:
The diffraction grating serves as an intermediary that enables the stationary encoder head on the coarse movement stage to measure the position of the fine movement stage without requiring physical connection or power supply wiring to the moving fine stage, thus eliminating tensile force issues.
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
Enables high-precision driving of both the fine and coarse movement stages, improving positional accuracy and preventing measurement errors caused by wiring tensions, thereby enhancing the precision of pattern formation on semiconductor devices.
Implementation Method 1
measures first positional information by irradiating a first grating section placed external to the coarse/fine movement stage so as to be substantially parallel to the predetermined plane with a first measurement beam and receiving a diffracted light from the first grating section
Data Source
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AI summary
A stage device is equipped with: a wafer stage that has a coarse movement stage (91) that moves along an XY plane and a table (WTB) that is finely movable in at least a direction parallel to the XY plane; and an encoder system. A plurality of encoder heads (such as 60C) are arranged on the coarse movement stage. Each of the heads irradiates a first grating section (RG) placed parallel to the XY plane and a second grating section (RG2Y) arranged on the table with measurement beams (LB1, LB2), respectively, and receives diffracted lights from each of the first and second grating sections. The encoder system measures positional information of the table (wafer stage) within the XY plane based on an output of at least one encoder head that faces the first and second grating sections.