Toshihiko Ishihara

XLA 300 : the fourth-generation ArF MOPA light source for immersion lithography

The XLA 300 is Cymers fourth-generation MOPA-based Argon Fluoride light source built on the production-proven XLA platform. The system is designed to support very high numerical aperture dioptric and catadioptric lens immersion lithography scanners targeted for volume production of semiconductor devices at the 45nm node and beyond. The light source delivers up to 90 W of power with ultra-line narrowed bandwidth as low as 0.12 pm FWHM and 0.25 pm 95% energy integral. The high output power is achieved by advancements in pulse power technology, which allow a 50% increase in repetition rate to 6 kHz. The increased repetition rate, along with pulse stretching, minimizes damage to the scanner system optics at this high power level. New developments in the laser optical systems maintain industry-leading performance for bandwidth stability and high level of polarization despite the increased thermal load generated at the higher repetition rate. The system also features state-of-the-art on-board E95% bandwidth metrology and improved bandwidth stability to provide enhanced CD control. The E95% metrology will move bandwidth monitoring from a quality safeguard flag to a tool that can be used for system feedback and optimization. The proven high power optics technology extends the lifetime of key laser optics modules including the line-narrowing module, and the cost of consumables (CoC) is further reduced by longer chamber lifetimes.

Dual-chamber ultra line-narrowed excimer light source for 193 nm lithography

Since the announcement in March 2002 of plans to develop an advanced light source to meet the future spectral power and cost requirements of photolithography, we have made significant progress in the development and productization of the core technology for an ultra line-narrowed, excimer light source based on a master oscillator-power amplifier (MOPA) approach. In this paper, we will focus on the architecture and performance of the first generation of production-ready, MOPA-based ArF light sources developed at Cymer, Inc. This first generation of MOPA-based ArF light sources is referred to as the XLA 100 product series.

Long-term reliable operation of a MOPA-based ArF light source for microlithography

Since the introduction of the XLA-100 in January 2003, we have built, tested, and shipped a large number of XLA-100 MOPA lasers to microlithography scanner manufacturers. Some systems have already been installed at chip fabrication lines. To ensure product design robustness, we have been performing a long-term system performance test of an XLA-100 laser at Cymer. In this paper, we will report optical performance of the XLA-100 we see during manufacturing final tests, and a summary of the long term testing.

ArF lasers for production of semiconductor devices with CD < 0.15 μm

The present day notion of the extensibility of KrF laser technology to ArF is revisited. We show that a robust solution to ArF requirements can be met by significantly altering the lasers core technology-discharge chamber, pulsed power and optics. With these changes, a practical ArF tool can be developed. Some of the laser specifications are: Bandwidth: 0.6 pm (FWHM) 1.75 pm (95% Included Energy); Average Power: 5 W; Repetition Rate: 1000 Hz; Energy Stability (3(sigma) ): 20% (burst mode) 8% (continuous); Pulse Width: 25 ns.

Parametric studies and the operating latitude of a spectrally narrowed KrF excimer laser for the deep-UV stepper

With the near certainty that the excimer stepper will become one of the lithography tools for printing sub -0.4 micrometers design rule features, it has now become imperative to better understand the performance characteristics of the excimer laser in the context of the total lithography process. It is no longer possible to treat the laser in isolation from the stepper or the resist. The cost of operation for the laser is integrally tied with the stepper specifications, design rule requirements, and resist characteristics. This paper discusses the dependence of laser parameters on stepper performance, and the relationship between various laser operating parameters and specification. In addition, it analyzes the combination of the laser to the lithography process cost per wafer level in terms of design rule requirements and resist characteristics. 15

Enabling high volume manufacturing of double patterning immersion lithography with the XLR 600ix ArF light source

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 XLRs long pulse duration, this allows for long life scanner optics while operating at 15mJ.

6 kHz MOPA light source for 193 nm immersion lithography

Volume production immersion lithography scanners will require new light sources offering increased output power while delivering improved dose stability over a shorter exposure window. Scaling the light source repetition rate from 4 to 6 kHz is the logical step toward meeting those combined requirements. We will present the results of the latest progress towards developing a 193 nm, 6 kHz light-source using Cymer’s proprietary MOPA technology. We will discuss how the design of critical core technology elements, such as the discharge chamber, the solid-state-pulsed-power modules and opto-electronic detectors within the system are modified to handle the higher average power, thermal demands, and speed to support reliable operation up to 6kHz. The XLA platform, which is already used on three generations of 193 nm MOPA light source, allows seamless integration of these improved technology elements into a reliable, proven product platform. We will also report results of the characterization of the optical parameters critical to the lithography process, such as spectral bandwidth and its stability, energy stability and dose stability, up to 6 kHz.

Parametric studies of a spectrally narrowed KrF excimer laser for the deep UV stepper

Abstract This paper, in view of excimer stepper requirements, discusses the dependence of one laser performance specification on other specifications and their relationship to operating conditions. It shows that there is a correlation between laser specifications, stepper performance, resist sensitivity and total cost of the process.