John R. Sporre

Magnetic debris mitigation system for extreme ultraviolet sources

Abstract. In extreme ultraviolet (EUV) lithography, plasmas are used to generate EUV light. Unfortunately, these plasmas expel high-energy ions and neutrals which damage the collector optic used to collect and focus the EUV light. One of the main problems facing EUV source manufacturers is the necessity to mitigate this debris. A magnetic mitigation system to deflect ionic debris by use of a strong permanent magnet is proposed and investigated. A detailed computational model of magnetic mitigation is presented, and experimental results from an EUV source confirm both the correctness of the model and the viability of magnetic mitigation as a successful means of deflecting ionic debris.

FINFET technology featuring high mobility SiGe channel for 10nm and beyond

SiGe for channel material has been explored as a major technology element after the introduction of FINFET into CMOS technology [1-4]. Research on long channel FETs and discrete short channel FETs demonstrated benefits in mobility [1-4] and reliability [2]. Given the disruption that SiGe FIN brings, every aspect associated with SiGe FIN needs to be carefully studied towards technology insertion. In this paper, we report the latest SiGe-based FINFET CMOS technology development. CMOS FINFETs with Si-FIN nFET and SiGe-FIN pFET is demonstrated as a viable technology solution for both server and mobile applications at 10nm node and beyond.

In situ collector cleaning and extreme ultraviolet reflectivity restoration by hydrogen plasma for extreme ultraviolet sources

Laser-produced Sn plasmas used to generate extreme ultraviolet (EUV) light for lithography cause the release of Sn ions and neutrals in the EUV source chamber. These Sn atoms condense and deposit on the multilayer collector optic, which reduces its ability to reflect EUV light. This lowers the source throughput and eventually necessitates downtime for collector cleaning. In this paper, an in situ plasma-based collector cleaning technique is presented and experimentally demonstrated. First, the technique is shown to completely clean a 300 mm diameter stainless steel dummy collector. Second, simulations and secondary ion mass spectroscopy depth profiles show that the technique does not erode the real multilayer mirrors. Finally, EUV reflectivity measurements demonstrate the ability of the technique to restore EUV reflectivity to Sn-coated multilayer mirrors. This technique has the potential to be used in conjunction with source operation, eliminating cleaning-related source downtime.

Debris transport analysis at the intermediate focus of an extreme ultraviolet light source

As extreme ultraviolet light lithography matures, critical deficits in the technology are being resolved. Research has largely focused on solving the debris issue caused by using warm (Te ∼ 30  eV) and dense (ne ∼ 1020  cm−3) plasma to create 13.5-nm light. This research has been largely focused on the mitigation of the debris between the plasma and the collector optics. The next step of debris mitigation is investigated, namely the effect of debris mitigation on the transport of undesired contaminants to the intermediate focus (IF). In order to investigate emissions from the IF, the Center for Plasma-Material Interactions at the University of Illinois at Urbana-Champaign has developed the Sn intermediate focus flux emission detector. The effects of a secondary RF-plasma, buffer gas flow rate, chamber pressure, and charged plate deflection are investigated. By increasing the chamber pressure to 10 mTorr, flowing 1000 sccm Ar buffer gas, and utilizing charged particle deflection, it is possible to reduce the measured number of post-IF species by greater than 99%. Furthermore, it is shown that typical debris mitigation techniques lead to the development of a plasma near the IF that can be detrimental to post-IF optics.

In-situ Sn contamination removal by hydrogen plasma

One of the main challenges in extreme ultraviolet lithography (EUVL) is the development of a method for cleaning collector optics without inhibiting cost-effectiveness. Cost-effectiveness of EUV methods can be increased by in-situ processes for removing debris placed on the collector optic. This paper focuses on the use of a hydrogen plasma to remove Sn, a common EUV fuel, from Si surfaces. Sn was deposited on both large and small Si samples via magnetron sputtering, and optimized hydrogen plasma selectively etched the Sn. Deposition uniformity and thickness are measured, as are Sn etch rates and cleaning uniformity. Positive results indicate the potential of this method for use in cleaning EUV mirrors.

Ionic debris measurement of three extreme ultraviolet sources

Generation of debris in extreme ultraviolet (EUV) light sources is an inherent and real threat to the lifetime of collection optics. Debris measurement of these sources is useful to enable source suppliers to estimate collector lifetime. At the Center for Plasma Material Interactions (CPMI) at the University of Illinois, an Illinois calibrated spherical sector electrostatic energy analyzer (ICE) was built to measure the ion debris flux in absolute units. In addition to ion flux, the detector is also capable of identifying different ion species present in the plasma utilizing energy-to-charge ratio discrimination. The lifetime of the collector optics is calculated using the measured ion flux. In the current investigation we compare the measurement of ion debris production in three different EUV sources: the Energetiq EQ-10M, the AIXUV-100, and the XTREME XTS 13-35. In the EQ-10M source, three angular measurements are coupled with three variations in operating pressure to measure consequent effects on debri...

SiGe FinFET for practical logic libraries by mitigating local layout effect

SiGe FinFET has been explored for its benefit of high current drivability provided by channel strain [1-5]. We have demonstrated SiGe CMOS FinFET at 10nm technology ground rules including epitaxial defectivity control, DC performance and reliability benefit [6-8]. One concern of SiGe FinFET is channel strain relaxation by fin cut process [9] inducing local layout effect (LLE), which is crucial for product design. In this paper, we thoroughly examined LLE in SiGe pFinFET and explored its mitigation techniques. Two techniques are proposed and demonstrated successful LLE mitigation, which drives forward SiGe FinFET insertion to technology.

Collector optic in-situ Sn removal using hydrogen plasma

The presence of Sn on the collector optic of an extreme ultraviolet (EUV) light lithography tool continues to be a concern for source manufacturers. A mere nanometers deposition results in reduction of EUV light reflectivity to unacceptable levels. It has been shown previously that hydrogen radical etching of Sn provides a promising technique for in-situ cleaning of the collector optic. One concern in this technique is the redeposition by radicalized SnH4 breaking apart after making contact with a surface. To address this concern, large scale etching measurements were made using a metallic antenna as the substrate. Optimized etch rates approaching 7.5±1 nm/min have been achieved with a flow rate of 500 sccm at a pressure of 80 mTorr. The effect of variations in the Sn cleaning environment will be investigated with respect to temperature increases as well as air, oxygen, and methane contamination gasses. Furthermore, the effect of Sn located away from the cleaning location will also be presented.

Direct measurement and modeling of the redirected ion flux in a high-powered pulsed-plasma magnetron

Self-sputtering is a crucial feature in high-powered pulsed magnetron sputtering (HPPMS). A direct measurement of the recirculating ion fluxes to the target, however, has not been made until now using a specially designed magnetron system. A small orifice was drilled in the target, allowing plasma fluxes to penetrate and be diagnosed subsequently. Ion currents of the penetrating copper ions (Cu+) and argon ions (Ar+) were collected on biased grids, while Cu depositions were measured on witness Si wafers. Based on these measurements, fluxes of Cu+ ions and Ar+ ions were differentiated. For a tested condition, the ratio of Cu+ density to Ar+ density was determined to be 1.5 ± 0.3, indicating a strong self-sputtering effect during HPPMS. Using a semiempirical plasma model, this ratio was predicted to be 1.4 within plasma, matching well with the measurement. The model calculates the evolution of various plasma species in the strong ionization region and thus allows a quick estimation of some key HPPMS paramet...

Contamination concerns at the intermediate focus of an extreme ultraviolet light source

The emission of species that can chemically or physically alter the surface of post intermediate-focus optics will increase the cost of ownership of such an EUV lithography tool past the point of cost effectiveness. To address this concern, the Center for Plasma-Material Interactions has developed the Sn Intermediate Focus Flux Emission Detector (SNIFFED). The effects of increasing buffer gas, increasing pressure, and chosen buffer gas species will be presented. Furthermore the presence of a secondary plasma, generated by EUV light will be analyzed and exposed as a potential issue in the strive for a contaminant free intermediate focus.