Exposure Apparatus Controller Corrects Overlay Error via Thermal Deformation Model
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Solution Overview
Problem
The overlay accuracy of exposure apparatuses is compromised due to thermal deformation of substrates during repeated exposure processes, which existing compensation techniques struggle to predict and correct effectively, especially with the miniaturization and high integration of semiconductor devices.
Innovation Solution
An exposure apparatus with a controller that corrects overlay errors based on the relationship between elapsed time and substrate deformation, incorporating a heating model and cooling model to account for residual heat of the substrate holder, allowing for precise adjustment of the exposure process to maintain robust overlay accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If exposure is repeated to increase productivity, then more substrates are processed, but substrate thermal deformation increases causing overlay accuracy to deteriorate
Solution Approach 1:
The system performs preliminary measurement of substrate deformation using a moire shift measuring device before exposure, and pre-calculates correction values using a heating model that predicts thermal deformation based on elapsed time and residual heat. This preliminary action allows the overlay correction to be applied in advance, compensating for thermal deformation that will occur during repeated exposure processing.
Solution Approach 2:
The system implements a feedback mechanism where substrate deformation is measured during the exposure process, correction values are calculated based on the measured deformation and heating model predictions, and these corrections are applied to subsequent exposure operations. This closed-loop feedback ensures overlay accuracy is maintained even as productivity increases through repeated processing.
2Measurement precision
If existing compensation techniques are used to maintain overlay accuracy, then measurement precision is improved, but the complexity of the system increases due to multiple measurement and calculation components
Solution Approach 1:
The moire shift measuring device serves multiple functions: it measures substrate deformation directly, provides data for the heating model calibration, and enables correction value calculation. This multi-functionality reduces the need for separate dedicated measurement and correction systems, thereby limiting the increase in device complexity while maintaining high measurement precision.
3Manufacturing precision
If substrate deformation is measured and corrected in real-time to maintain overlay accuracy, then manufacturing precision is improved, but processing time increases due to additional measurement and calculation steps
Solution Approach 1:
Substrate deformation measurement and correction value calculation are performed as preliminary actions before the actual exposure process begins. The heating model predicts thermal deformation based on elapsed time and residual heat from previous substrates, allowing corrections to be prepared in advance rather than during exposure, thus minimizing additional processing time.
Solution Approach 2:
The system dynamically adjusts correction values based on the actual elapsed time and residual heat conditions of each substrate. Rather than using fixed correction values, the heating model continuously updates predictions based on changing thermal conditions, allowing efficient real-time adaptation without requiring exhaustive measurement and calculation for every parameter change.
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 effectively predicts and corrects thermal deformation-induced overlay errors, enhancing the accuracy of pattern transfer onto substrates by considering the initial deformation amount corresponding to residual heat, thereby improving overlay accuracy in exposure processes.
Implementation Method 1
a substrate or a substrate holder is heated by absorbing a part of the energy of exposure light
Implementation Method 2
the substrate is thermally expanded
Implementation Method 3
an initial deformation amount corresponding to residual heat of the substrate holder at the time of the substrate exchange
Data Source
AI summary
An exposure apparatus that performs a job process of exposing each of a plurality of substrates while exchanging the substrate is provided. The apparatus comprises a substrate holder configured to hold a substrate, and a controller configured to control the job process. The controller corrects, based on a relationship between an elapsed time of the job process and a substrate deformation amount, an overlay error generated due to deformation of the substrate, and exposes the substrate. In the relationship, the substrate conveyed to the substrate holder upon a substrate exchange is given an initial deformation amount corresponding to residual heat of the substrate holder at the time of the substrate exchange.