Micro-lithography Hierarchical Source and Mask Optimization using Abbe-PCA
Date Issued
2010
Date
2010
Author(s)
Chang, Hsih-Chie
Abstract
As the VLSI manufacture technology develops, the feature size of micro-electronic devices shrinks smaller than the wavelength of exposure light source and challenging the limit of micro-lithography image system. Consequently, optical diffraction significantly deviate the exposed image result from the original design pattern we expected.
Therefore, lots of resolution enhancement technologies (RETs) are so far widely proposed to minimize the difference between design pattern and image result. Conventional RETs such as phase shift mask (PSM), off-axis illumination (OAI), and optical proximity correction (OPC) are in favour of improving the printing quality.
The OPC method tried to take the behaviour of micro-lithography image system into consideration when optimizing the mask pattern with pre-correction. The mask pattern after correction is aimed to cancel non-ideal effects of micro-lithography process and have expect image result returned. However, the image quality using simply OPC is still not perfect due to limits such as mask cost and manufacturability.
In this work, we consider the latest method of source mask optimization (SMO), which take not only shapes on mask pattern but also the configuration of illuminator into consideration in broadening the solution space. In other words, the light source and mask are optimized simultaneously for an individual design given, which could provide finer image result and more flexibility using combined RETs than using simply conventional ones.
However, a detailed optimization may involve more variables, which cause a better result but costs longer runtime. In the other hand, a rough optimization in low resolution may involve fewer variables with shorter runtime but worse result. In this work, we propose to perform the source mask optimization in a hierarchical way, which could take both the advantage of faster runtime in lower resolution and detailed refinement in higher resolution.
Besides, micro-lithography image simulation is performed repetitively each time we change the source or mask to have a cost function evaluated in determining whether the image result is enhanced during optimization. Therefore, high speed micro-lithography simulator is in strong demand for growing computational complexity to state-of-art RETs
when handling modern industrial cases with millions of devices.
In this work, we utilize the principal component analysis on Abbe’s image formulation (Abbe-PCA) for high speed kernel compaction on the point spread functions produced during source optimization. Also, convolution lookup table is introduced to accelerate cost function evaluation defined using image intensity error (IIE) on sampled observation points instead of traditional edge placement error (EPE), which demands a time consuming full image simulation.
Subjects
projection optical micro-lithography
resist image simulation
Abbe-PCA (principal component analysis)
DFM (design for manufacturability)
RET (resolution enhancement technology)
OPC (optical proximity correction)
SMO (source mask optimization)
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-99-R97943124-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):4108e9d447d58851e7aecc81143d3e90