Deep ultraviolet (DUV) lithography improvements have been focused on two paths:
further increases in the effective numerical aperture (NA) beyond 1.3, and double
patterning (DP). High-index solutions for increasing the effective NA have not gained
significant momentum due to several technical factors, and have been eclipsed by an
aggressive push to make DP a high-volume manufacturing solution. The challenge is to
develop a cost-effective solution using a process that effectively doubles the lithography
steps required for critical layers, while achieving a higher degree of overlay performance.
As a result, the light source requirements for DP fall into 3 main categories: (a) higher
power to enable higher throughput on the scanner, (b) lower operating costs to offset the
increased number of process steps, and (c) high stability of optical parameters to support
more stringent process requirements. The XLR 600i (6kHz, 90W @15mJ) was
introduced last year to enable DP by leveraging the higher performance and lower
operating costs of the ring architecture XLR 500i (6kHz, 60W @10mJ) platform
currently used for 45nm immersion lithography in production around the world. In
February 2009, the XLR 600ix was introduced as a 60/90W switchable product to
provide flexibility in the transition to higher power requirements as scanner capabilities
are enhanced. The XLR 600ix includes improved optics materials to meet reliability
requirements while operating at higher internal fluences. In this paper we will illustrate
the performance characteristics during extended testing. Examples of performance
include polarization stability, divergence and pointing stability, which enable consistent
pupil fill under extreme illumination conditions, as well as overall thermal stability which
maintains constant beam performance under large changes in laser operating modes.
Furthermore, the unique beam uniformity characteristics that the ring architecture
generates result in lower peak energy densities that are comparable to those of a typical
60W excimer laser. In combination with the XLR's long pulse duration, this allows for
long life scanner optics while operating at 15mJ.
Double patterning (DP) lithography is expected to be deployed at the 32nm node to enable the extension of high NA
(≥1.3) scanner systems currently used for 45nm technology. Increasing the light source power is one approach to address
the intrinsically lower throughput that DP imposes. Improved energy stability also provides a means to improve
throughput by enabling fewer pulses per exposure slit window, which in turn enables the use of higher scanner stage
speeds. Current excimer laser light sources for deep UV immersion lithography are operating with powers as high as
60W at 6 kHz repetition rates. In this paper, we describe the introduction of the XLR 600i, a 6 kHz excimer laser that
produces 90W power, based on a recirculating ring technology. Improved energy stability is inherent to the ring
technology. Key to the successful acceptance of such a higher power, or higher energy laser is the ability to reduce
operating costs. For this reason, the recirculating ring technology provides some unique advantages that cannot be
realized with conventional excimer lasers today. Longer intrinsic pulse durations that develop in the multi-pass ring
architecture reduce the peak power that the optics are subjected to, thereby improving lifetime. The ring architecture also
improves beam uniformity that results in a significantly reduced peak energy density, another key factor in preserving
optics lifetime within the laser as well as in the scanner. Furthermore, in a drive to reduce operating costs while
providing advanced technical capability, the XLR 600i includes an advanced gas control management system that
extends the time between gas refills by a factor of ten, offering a significant improvement in productive time. Finally, the
XLR 600i provides a novel bandwidth stability control system that reduces variability to provide better CD control,
which results in higher wafer yields.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.