Wafer Stage Guide Surface Segmentation for Exposure Apparatus
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Solution Overview
Problem
In exposure apparatuses for semiconductor device manufacturing, the integration of high-precision positional control and maintenance of large wafers is hindered by the degradation of measurement accuracy due to reaction forces and the complexity of maintaining large guide surfaces, especially when using planar motors with integrated encoder heads.
Innovation Solution
The exposure apparatus features a movable body with a guide surface formed by adjacent sections and a measurement system that irradiates a measurement beam parallel to the plane, allowing for high-precision positional measurement and improved maintenance by separating the measurement and guide surfaces, and using noncontact levitation mechanisms to reduce reaction forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If encoder heads are placed inside the surface plate to measure wafer stage position, then measurement precision is improved, but measurement accuracy degrades due to reaction forces from the planar motor
Solution Approach 1:
The patent divides the surface plate into multiple independent sections (first surface plate section, second surface plate section, third surface plate section) that can move independently. This segmentation allows the guide surface sections to move with the wafer stage, isolating the encoder measurement system from reaction forces and maintaining measurement accuracy.
Solution Approach 2:
The patent introduces an intermediary mechanism where guide surface sections act as mediators between the planar motor and the encoder measurement system. These guide surface sections absorb and isolate the reaction forces from the planar motor, preventing them from affecting the encoder heads and maintaining reliable measurements.
2Productivity
If the wafer stage and surface plate increase in size to accommodate larger wafers (e.g., 450mm), then productivity is improved, but maintenance difficulty increases
Solution Approach 1:
The patent segments the large surface plate into multiple smaller, independently movable sections. This allows maintenance personnel to access and service individual sections without having to handle the entire large surface plate, significantly reducing maintenance difficulty while supporting larger wafer sizes.
Solution Approach 2:
The patent makes the guide surface sections dynamically movable rather than fixed. This dynamic configuration allows sections to be repositioned or accessed independently during maintenance operations, making it easier to service large-scale systems without requiring complete system disassembly.
3Productivity
If a planar motor is used to drive the wafer stage for high-speed and high-acceleration movement, then productivity is improved, but measurement accuracy degrades due to reaction forces acting on the surface plate
Solution Approach 1:
The patent segments the guide surface into multiple independently movable sections that can follow the motion of the wafer stage. This allows the encoder measurement system to remain isolated from the reaction forces generated by the planar motor, maintaining high measurement precision even during high-speed and high-acceleration operations.
Solution Approach 2:
The guide surface sections serve as intermediary elements between the planar motor and the measurement system. These intermediaries absorb and isolate the reaction forces from rapid acceleration and deceleration, preventing them from corrupting the position measurements while allowing the planar motor to achieve high productivity.
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 configuration enhances the precision of positional measurement and facilitates easier maintenance by minimizing the impact of reaction forces and atmospheric fluctuations, enabling stable and precise operation of large wafers.
Implementation Method 1
a measurement member that irradiates a measurement surface parallel to the two-dimensional plane with a measurement beam and receives light from the measurement surface
Implementation Method 2
using noncontact levitation mechanisms to reduce reaction forces
Data Source
AI summary
Positional information of wafer stages is measured by a plurality of encoder heads, Z heads and the like that a measurement bar placed below surface has, using gratings placed on the lower surface of fine movement stages. Consequently, high-precision measurement of the positional information of the wafer stages can be performed. Further, since a guide surface of the wafer stages is formed by the two guide surface forming members placed side by side via a predetermined clearance, each guide surface forming member is easier to handle and also maintenance of the vicinity of the guide surface forming member is easier to perform, compared with the case where the guide surface forming members are integrated.