Robert A. Bergstedt

Laser produced plasma EUV sources for device development and HVM

Laser produced plasma (LPP) systems have been developed as the primary approach for the EUV scanner light source for optical imaging of circuit features at sub-22nm and beyond nodes on the ITRS roadmap. This paper provides a review of development progress and productization status for LPP extreme-ultra-violet (EUV) sources with performance goals targeted to meet specific requirements from leading scanner manufacturers. We present the latest results on exposure power generation, collection, and clean transmission of EUV through the intermediate focus. Semiconductor industry standards for reliability and source availability data are provided. We report on measurements taken using a 5sr normal incidence collector on a production system. The lifetime of the collector mirror is a critical parameter in the development of extreme ultra-violet LPP lithography sources. Deposition of target material as well as sputtering or implantation of incident particles can reduce the reflectivity of the mirror coating during exposure. Debris mitigation techniques are used to inhibit damage from occuring, the protection results of these techniques will be shown over multi-100s of hours.

Laser Digital Cinema

Electronic cinema projectors are being developed that use a digital micromirror device (DMDTM) to produce the image. Photera Technologies has developed a new architecture that produces truly digital imagery using discrete pulse trains of red, green, and blue light in combination with a DMDTM where in the number of pulses that are delivered to the screen during a given frame can be defined in a purely digital fashion. To achieve this, a pulsed RGB laser technology pioneered by Q-Peak is combined with a novel projection architecture that we refer to as Laser Digital CameraTM. This architecture provides imagery wherein, during the time interval of each frame, individual pixels on the screen receive between zero and 255 discrete pulses of each color; a circumstance which yields 24-bit color. Greater color depth, or increased frame rate is achievable by increasing the pulse rate of the laser. Additionally, in the context of multi-screen theaters, a similar architecture permits our synchronously pulsed RGB source to simultaneously power three screens in a color sequential manner; thereby providing an efficient use of photons, together with the simplifications which derive from using a single DMDTM chip in each projector.

Microlaser-based displays

Laser Power Corporation has developed a new type of projection display, based upon microlaser technology and a novel scan architecture, which provides the foundation for bright, extremely high resolution images. A review of projection technologies is presented along with the limitations of each and the difficulties they experience in trying to generate high resolution imagery. The design of the microlaser based projector is discussed along with the advantage of this technology. High power red, green, and blue microlasers have been designed and developed specifically for use in projection displays. These sources, in combination with high resolution, high contrast modulator, produce a 24 bit color gamut, capable of supporting the full range of real world colors. The new scan architecture, which reduces the modulation rate and scan speeds required, is described. This scan architecture, along with the inherent brightness of the laser provides the fundamentals necessary to produce a 5120 by 4096 resolution display. The brightness and color uniformity of the display is excellent, allowing for tiling of the displays with far fewer artifacts than those in a traditionally tiled display. Applications for the display include simulators, command and control centers, and electronic cinema.

XLR 600i: recirculating ring ArF light source for double patterning immersion lithography

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.

XLR 500i: recirculating ring ArF light source for immersion lithography

As Argon Fluoride (ArF) lithography moves into high volume production, ArF light sources need to meet performance requirements beyond the traditional drivers of power and bandwidth. The first key requirement is a continuous decrease in Cost of Ownership (CoO) where the industry requirement is for reduction in ArF CoO in line with the historical cost reduction demonstrated for Krypton Fluoride (KrF) light sources. A second requirement is improved light source performance stability. As CD control requirements shrink, following the ITRS roadmap, all process parameters which affect CD variation need tighter control. In the case of the light source, these include improved control of bandwidth, pulse energy stability and wavelength. In particular, CD sensitivity to exposure dose has become a serious challenge for device processing and improvements to laser pulse energy stability can contribute to significantly better dose control. To meet these performance challenges Cymer has designed a new dual chamber laser architecture. The Recirculating Ring design requires 10X less energy from the Master Oscillator (MO). This new configuration enables the MO chamber lifetime to reach that of the power amplifier chamber at around 30Bp. In addition, other optical modules in the system such as the line narrowing module experience lower light intensity, ensuring even longer optics lifetime. Furthermore, the Recirculating Ring configuration operates in much stronger saturation. MO energy instabilities are reduced by a factor of 9X when passed through the Ring. The output energy stability exhibits the characteristics of a fully saturated amplifier and pulse energy stability improvement of 1.5X is realized. This performance enables higher throughput scanner operation with enhanced dose control. The Recirculating Ring technology will be introduced on the XLR 500i, Cymers fifth-generation dual chamber-based light source built on the production-proven XLA platform. This paper will describe the design details and performance characteristics of the new laser architecture.

OPO-based compact laser projection display

In this paper we discuss our red, green, and blue (RGB) optical parametric oscillator (OPO) based laser projection display. The complete project display consists of two subsystems, the RGB-OPO laser head and the light modulation unit. The RGB lights from rack-mounted laser head are fibers coupled to the projection unit for independent placement. The light source consists of a diode-pumped pump laser and a LBO-based OPO. Based on our Nd:YLF gain module design, the pump laser is frequency doubled to serve as the pump source for the OPO. The unconverted pump power is recycled as the green light for projection. The singly resonant, non- critically phase-matched (NCPM) OPO has, to date, generated 13 W of 898-nm signal power and an estimated 9.3 W of intra- cavity idler power at 1256 nm. With approximately 76% of pump depletion, the power of the residual green light for projection is about 5.8 W. We have extra-cavity doubled the signal to produce approximately 3.5 W of 449-nm blue light and intra-cavity doubled the idler to produce approximately 6 W of 628-nm red light. The OPO-based RGB source generates about 4000 lumens of D65-balanced white light. The overall electrical power on a commercially available JVCs three- panel D-ILA (reflective LCD) projector with the arc-lamp removed and extensive modifications. The projector has a native resolution of 1365 x 1024 and the expected on screen lumens from our laser display is about 1200 lumens.

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.

CO2/Sn LPP EUV sources for device development and HVM

Laser produced plasma (LPP) systems have been developed as the primary approach for use in EUV scanner light sources for optical imaging of circuit features at 20nm nodes and beyond. This paper provides a review of development progress and productization status for LPP extreme-ultra-violet (EUV) sources with performance goals targeted to meet specific requirements from ASML. We present the latest results on power generation and collector protection for sources in the field operating at 10W nominal power and in San Diego operating in MOPA (Master Oscillator Power Amplifier) Prepulse mode at higher powers. Semiconductor industry standards for reliability and source availability data are provided. In these proceedings we show results demonstrating validation of MOPA Prepulse operation at high dose-controlled power: 40 W average power with closed-loop active dose control meeting the requirement for dose stability, 55 W average power with closed-loop active dose control, and early collector protection tests to 4 billion pulses without loss of reflectivity.

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.

Solid-State Laser-Based Displays

Recent advances in compact visible microlasers have enabled the development of portable laser display systems. The benefits of large color gamut, invariant color accuracy, image uniformity, high contrast, large depth of focus and reliability inherent in the microlaser design make them attractive for display applications. Lasers are under development for both “backlit” and “direct-write” displays. Advantages of the microlaser technology will enable applications such as command/control centers, simulators, HMDs/HUDs, CAD workstations, and electronic cinema.