Lithography Wafer Stage Segmented Support for Measurement Isolation
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Solution Overview
Problem
Existing stage devices in lithography processes face challenges in maintaining high precision positional control and throughput due to the degradation of measurement accuracy caused by reaction forces and deformations in integrated support systems.
Innovation Solution
A stage device design that includes a movable body, a guide surface forming member, a drive system, and separate support members with independent measurement systems. This configuration allows for precise measurement of the movable body's position within a two-dimensional plane while minimizing the impact of reaction forces and deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the encoder head is placed inside the surface plate to measure wafer stage position, then measurement capability is provided, but measurement accuracy is degraded due to reaction forces acting on the surface plate during wafer stage drive
Solution Approach 1:
The support structure is divided into a first support member (surface plate) and a second support member (reference member) that are spatially separated. The encoder head is positioned on the first support member while the measurement target is on the second support member, isolating the measurement system from reaction forces acting on the first support member during wafer stage acceleration.
Solution Approach 2:
The guide surface forming member acts as an intermediary element between the movable body and the support members. It provides a stable reference interface that allows the encoder head to measure position without being directly subjected to the harmful reaction forces from the drive system.
2Productivity
If the wafer stage is driven at high speed and high acceleration to improve throughput, then productivity increases, but measurement accuracy is degraded due to deformation and vibration
Solution Approach 1:
By separating the first support member (surface plate) from the second support member (reference member), the system allows the wafer stage to be driven at high speed and acceleration on the first member while the measurement is performed on the isolated second member, preventing deformation and vibration from affecting measurement accuracy.
3Device complexity
If the first support member and second support member are integrated to simplify structure, then device complexity decreases, but measurement accuracy is degraded due to transmission of vibration and deformation
Solution Approach 1:
The support system is segmented into distinct first and second support members rather than being integrated. This segmentation, while increasing structural complexity, prevents the transmission of vibration and deformation from the driven first member to the measurement system on the second member, thereby maintaining measurement accuracy.
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 proposed solution enhances the measurement accuracy and positional control of the stage device, thereby improving the precision and throughput of the lithography process. It achieves this by isolating the measurement systems from the reaction forces and deformations, ensuring high-precision positioning even under high-speed and high-acceleration conditions.
Implementation Method 1
a first 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
a stage device that controls the position of a wafer within a two-dimensional plane using a planar motor by an electromagnetic force drive method
Data Source
Figure 1
Figure 2
Figure 3(A)~3(B)
AI summary
Positional information of each of wafer stages (WST1 and WST2) during exposure and during alignment is measured directly under a projection optical system (PL) and directly under a primary alignment system (AL1), respectively, by a plurality of encoder heads, Z heads and the like, which a measurement bar (71) placed below surface plates (14A and 14B) has, using gratings placed on the lower surfaces of fine movement stages (WFS1 and WFS2) . Since a main frame (BD) that supports the projection optical system (PL) and the measurement bar (71) are separated, deformation of the measurement bar caused by inner stress (including thermal stress) and transmission of vibration or the like from the main frame to the measurement bar, and the like do not occur, which is different from the case where the main frame and the measurement bar are integrated. Consequently, high-precision measurement of the positional information of the wafer stages can be performed.