Model-based design improvements for the 100-nm lithography generation

Abstract

Due to the challenging design rule and CD control requirements of the lOOnm device generation, a large number of complex patterning techniques are likely to be used for random logic devices [ 1] . The complexity of these techniques places considerable strain upon model-based OPC software to identify and compensate for a wide range of printing non-idealities [2]. Additionally, the rapidly increasing cost of advanced reticles has increased the urgency of obtaining reticles devoid of process limiting design or OPC errors. We have evaluated the capability of leading edge model-based OPC software to meet the challenging lithography needs of the lOOnm device generation. Specifically, we have implemented and verified model usefulness to correct for pattern deformation in complex binary gate, contact and via processes utilizing highly optimized illumination. Additionally, we present results showing the abilities of model-based methods to accurately find design related printing problems in complementary phase shift gate designs before they are committed to an expensive reticle. ii. IntroductionCurrently in early 2002, leading semiconductor manufacturers are starting pilot-line production of test circuits for the lOOnm technology generation and actively planning development for the 7Onm technology generation. Both of these generations will be accomplished with high numerical aperture (NA) 193nm lithography as the main patterning strategy. The main lithographic challenges of these generations are the lack of linearity (low ki processes); the low depth of focus (DOF) which accompanies high-NA illumination use; the complexity of reticle erthancement technology (RET) or scanner illumination which improves DOF & linearity; and the extremely high cost of ownership (COO) for the leading edge tools necessary to handle these challenges. Other difficult challenges include the relative immaturity of 193nm photoresists, the rising cost (& cycletime) of sophisticated high-end reticles, and the need for complex postprocessing techniques to alter final etched CD values [1,2]. These are difficult problems to overcome before these technologies can be made into working and cost-effective manufacturing processes. The main strategy for overcoming or reducing these problems is the use of optical proximity correction (OPC) methods. The goal of this work is to evaluate the effectiveness of model-based OPC (MBOPC) methods for solving critical patterning problems of the lOOnm technology generation.

Implementation of adaptive site optimization in model-based OPC for minimizing ripples

“…The contours are recomputed post-OPC for verification of the correction accuracy. Practically, the conventional OPC tools are depending mainly on sparse sampling for the aerial image intensity and not dense simulation [3]. This approximation is saving a lot of computation runtime, but it may lead to disregard of critical spots by the OPC solution.…”

“…In conventional Model-based OPC techniques, the computation of intensity and printing threshold are derived from simulation, while the fragmentation and the placement of simulation sites are typically specified by static rules based on geometrical relationships in the layout [3][4]. Problems with this methodology can arise whenever the location of the fragments and simulation points are non-optimal and not tracking the ripples locations.…”

“…The authors are primarily exploring more automated software methods to detect the location of the ripple peaks as well as implementing a simplified implementation strategy that is less costly. We define this to be an adaptive site placement methodology based on aerial image ripples.Recently, the phenomenon of aerial image ripples was considered within the analysis of the lithography process for cutting-edge technologies such as chromeless phase shifting masks and strong off-axis illumination approaches [3,4]. Effort is spent during the process development of conventional model-based OPC with the mere goal of locating these troublesome points.…”

“…Recently, the phenomenon of aerial image ripples was considered within the analysis of the lithography process for cutting-edge technologies such as chromeless phase shifting masks and strong off-axis illumination approaches [3,4]. Effort is spent during the process development of conventional model-based OPC with the mere goal of locating these troublesome points.…”

Enhanced model-based OPC for 65 nm and below

“…In recent years, the impact of aerial image ripples on pattern fidelity has been highlighted [1] [2]. The ripple phenomenon is highly pattern and illumination dependent, with the worst effects seen under the following conditions:…”