Lithographic Dose Characterization Using Oblique Light Scanning
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Solution Overview
Problem
Current lithography technologies face challenges in accurately characterizing and controlling unintended exposure doses due to flare and out-of-band radiation, leading to non-uniformity and inefficiencies in the exposure process.
Innovation Solution
A method involving open frame exposures with a lithography tool to create controlled exposure dose blocks and secondary blocks of alternative dosages, followed by oblique light scanning to generate haze maps, which are converted into graphical image files for analysis, allowing for the characterization of unintended exposure doses from flare and out-of-band radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional exposure dose measurement methods are used, then the exposure process can be performed, but the measurement precision and accuracy of unintended exposure doses from flare and out-of-band radiation are insufficient
Solution Approach 1:
The exposure field is segmented into multiple regions including a central region with first exposure dose and surrounding regions with second exposure dose. This spatial segmentation allows separate characterization of intended exposure versus unintended flare and out-of-band radiation contributions, enabling precise measurement of otherwise indistinguishable dose components.
Solution Approach 2:
A haze map is introduced as an intermediary measurement medium that captures the cumulative effect of all radiation components (intended exposure, flare, and out-of-band radiation). By measuring haze in different spatial regions and mathematically analyzing the differences, the unintended radiation components can be isolated and quantified with high precision.
2Measurement precision
If comprehensive exposure characterization is performed, then measurement precision improves, but the productivity and scanner time are reduced
Solution Approach 1:
The exposure dose characterization is performed as a preliminary action during routine maintenance or setup phases, using dedicated test substrates with specific patterns. This allows comprehensive measurement to be completed beforehand, so that during actual production scanning, the characterization data is already available and no additional time is required, thus maintaining high productivity.
Solution Approach 2:
The exposure characterization method serves multiple functions: it characterizes intended exposure dose, measures flare radiation, quantifies out-of-band radiation, and validates scanner performance all in a single process. This multi-functionality reduces the need for separate measurement procedures, thereby maintaining scanner productivity while achieving comprehensive exposure characterization.
3Manufacturing precision
If uniform exposure dose is maintained across the substrate, then manufacturing precision improves, but the ability to characterize and control unintended radiation effects is limited
Solution Approach 1:
The test substrate is designed with local variations in exposure dose: a central region receives first exposure dose while surrounding regions receive second exposure dose. These localized dose differences create corresponding haze variations that can be measured and analyzed. The local quality variation in the test structure enables detection and quantification of unintended radiation effects that would be invisible in uniformly exposed production substrates.
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 enables quick and accurate measurement of unintended exposure doses, improving the uniformity and consistency of the exposure process, reducing characterization time, and minimizing the impact on productive scanner time.
Implementation Method 1
Lithography includes an exposure process in which a layer of resist (also known as photoresist) on a substrate is exposed to radiation
Implementation Method 2
The resultant open frame images are scanned with oblique light and the light scattered from the substrate surface is captured using an oblique light inspection device
Data Source
AI summary
Methods for determining unintentional exposure dose such as flare or out-of-band radiation of a lithography tool are provided. The methods generally include performing a series of open frame exposures with the lithography tool on a substrate having a photoresist therein to produce a primary array of controlled exposure dose blocks in the photoresist. Secondary exposure blocks are embedded within the primary array. The resultant open frame images are scanned with oblique light and the light scattered from the substrate surface captured. A haze map is created from a background signal of the captured scattered light data and converted to a graphical image file. Analyzing the graphical image file can be used to correlate any localized changes in the effective dose of the primary exposure array to the impact of secondary exposure blocks to characterize flare or out-of-band radiation associated with the exposure dose.