We report on the printability, mitigation and actinic mask level review of programmed substrate blank pit and bump defects in a EUV lithography test mask. We show the wafer printing behavior of these defects exposed with an NXE:3300 EUV lithography scanner and the corresponding mask level actinic review using the AIMS (TM) tool. We will show which categories of these blank substrate defects print on wafer and how they can be mitigated by hiding these defects under absorber lines. Furthermore we show that actinic AIMS (TM) mask review images of these defects, in combination with a simple thresholded resist transfer model, can accurately predict their wafer printing profiles. We also compare mask level actinic AIMS (TM) to top down mask SEM review in their ability to detect these defects.

The EUV mask infrastructure is of key importance for the successful introduction of EUV lithography into volume production. In particular, for the production of defect free masks an actinic review of potential defect sites is required. ZEISS and the SUNY POLY SEMATECH EUVL Mask Infrastructure consortium have developed such an EUV aerial image metrology system, the AIMS (TM) EUV, with the prototype tool regularly being used for customer measurement campaigns and the first system shipped to customer end of last year. In this paper, we provide an update on the system performance and present quantitative measurements of the impact of mask surface roughness on the aerial image. We show that an increasing amount of effects is only visible in actinic aerial imaging and discuss potential benefits of aerial image based mask qualification.

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Key enabler of the successful introduction of EUV lithography into volume production is the EUV mask infrastructure. For the production of defect free masks, actinic review of potential defect sites to decide on the need for repair or compensation is required. Also, the repair or compensation with the ZEISS MERiT electron beam repair tool needs actinic verification in a closed loop mask repair solution. For the realization of actinic mask review, ZEISS and the SEMATECH EUVL Mask Infrastructure consortium started a development program for an EUV aerial image metrology system, the AIMS (TM) EUV, with realization of a prototype tool.The development and prototype realization of the AIMS (TM) EUV has entered the tool calibration and qualification phase utilizing the achieved capabilities of EUV aerial image acquisition and EUV mask handling. In this paper, we discuss the current status of the prototype qualification and show recent measurement results.

This PDF file contains the front matter associated with SPIE Proceedings Volume 9422 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

The EUV mask infrastructure is of key importance for a successful introduction of EUV lithography into volume production. In particular, for the production of defect free masks, actinic review of potential defect sites is required. To realize such an actinic review tool, Zeiss and the SEMATECH EUVL Mask Infrastructure consortium started a development programme for an EUV aerial image metrology system (AIMS™ EUV). In this paper, we discuss the status of the on-going system integration and show first results from the first light tests of the prototype tool.

Overcoming the challenges associated with photomask defectivity is one of the key aspects associated with EUV mask infrastructure. In addition to establishing specific EUV mask repair approaches, the ability to identify printable mask defects that require repair as well as to verify if a repair was successful are absolutely necessary. Such verification can only be performed by studying the repaired region using actinic light at an exact emulation of the scanner illumination conditions of the mask as can be done by the AIMS T EUV. ZEISS, in collaboration with the SEMATECH EUVL Mask Infrastructure (EMI) consortium are currently developing the AIMS T EUV system and have recently achieved First Light on the prototype system, a major achievement. First light results will be presented in addition to the current development status of the system.

In previous conferences the status of the AIMS™ EUV project has been presented in which the basic layout scheme and preliminary design have been shown along with the targeted performance specification levels to be met. Presently the final design milestone of the project has been successfully completed and assembly of the prototype tool is underway. The final design concept will be presented along with the current status of the tool and simulated performance data.

The EUV mask infrastructure is of key importance for a successful introduction of EUV lithography into volume production. In particular, for the production of defect free masks an actinic review of potential defect sites is required. With such a review it can be decided if a defect needs to be repaired or compensated. It also serves as verification whether the respective absorber or compensational repair with e.g. the MeRiT® tool has been successful, i.e. it closes the control loop in mask repair. To realize such an actinic review tool, Carl Zeiss and the SEMATECH EUVL Mask Infrastructure consortium started a development programme for an EUV aerial image metrology system (AIMS™ EUV). In this paper, we discuss the application of the AIMS™ EUV in the compensational repair process of multilayer and blank defects and present the status of the AIMS™ EUV project.

The high volume device manufacturing infrastructure for the 22nm node and below based on EUVL technology requires defect-free EUV mask manufacturing as one of its foundations. The EUV Mask Infrastructure program (EMI) initiated by SEMATECH has identified an actinic measurement system for the printability analysis of EUV mask defects to ensure defect free mask manufacturing and cost-effective high-volume EUV production as an infrastructural prerequisite for the EUVL roadmap ([1], [2]).The Concept and Feasibility study for the AIMS (TM) EUV resulted in a feasible tool concept for 16nm defect printability review. The main development program for the AIMS (TM) EUV has been started at Carl Zeiss leading to a commercialized tool available in 2014.In this paper we will present the status of the progress of the design phase of this development and an infrastructure progress update of the EUV Mask defect printability review.

On the road to and beyond the 22nm half-pitch on chip patterning technology, 13.5nm EUVL is widely considered the best next technology generation following deep ultraviolet lithography. The availability of an actinic measurement system for the printability analysis of mask defects to ensure defect-free mask manufacturing and cost-effective high-volume EUV production is an infrastructural prerequisite for the EUVL roadmap and represents a significant step toward readiness for commercialization of EUV for high-volume-manufacturing [1].Carl Zeiss and SEMATECH's EUVL Mask Infrastructure (EMI) program started a concept study and feasibility plan for a tool that emulates the aerial image formed by a EUV lithography scanner supporting the 22 nm half-pitch node requirements with extendibility to the 16nm half-pitch node. The study is targeting a feasible concept for the AIMS T EUV platform, bridging a significant gap for EUV mask metrology.In this paper we will present the concepts and feasibility results of this study and give an outlook on the next steps in this project.

EUV mask infrastructure is of key importance for the introduction of the 13.5nm extreme ultraviolet (EUV) wavelength into volume production. In particular, the manufacturing of defect free masks is essential and requires a printability analysis ("review") of potential defect sites. For this purpose, Carl Zeiss and the SEMATECH EUVL Mask Infrastructure consortium have performed a concept and feasibility study for an actinic aerial image metrology system (AIMS™). In this paper, we discuss the main results of this study. We explain the system concept, discuss the expected performance and show simulations of the capability to find minimum sized defects. We demonstrate that our EUV AIMS concept is technically feasible and supports the defect review requirements for the 22nm and 16nm half-pitch (hp) node.

In microelectronic industry, mainly from the 65nm node, phase shift photomasks (PSM) are increasingly used for critical layers, optical properties of the shifter (MoSi) giving a better control of critical dimensions (CD) in photoresist. Fab-users and maskshops have committed on specifications that restrict phase and transmission variations within certain limits. The goal of this study is to validate and/or update these previously admitted limits. A specific test reticle has been jointly designed with several structures representative of 65nm and 45nm nodes and then manufactured with a specific process in order to voluntarily degrade the phase and transmission uniformity within the mask. Knowing all CD and their related phase and transmission on mask, CD variations seen on wafers have been directly linked to phase and transmission variations. In parallel, rigorous simulations have been performed using Panoramic software in order to predict effects of phase and transmission variations on wafer. This reticle has been also used for early studies to evaluate the impact of phase and transmission variations on optical proximity correction (OPC) model.

Immersion lithography has moved into 45nm node and will soon go into 32nm node. Alternating Phase Shifting Masks (alt. PSM's) are one of the most effective methods to enhance resolution and process window. . However there are two major challenges: intensity balancing and quartz dry etch process. The dry etch process requires not only an uniform quartz etch but also a good linearity over a wide range of feature sizes to ensure a 180° phase shift through pitch and duty cycle. Phase errors lead to an image placement error during printing becoming even worse through focus. As feature sizes shrink imaging effects and 3D mask effects impact the phase shift and accurate phase shift measurement becomes extremely important. In this paper we report on phase shift measurements through pitch and duty cycle on alt. PSM taken on the newly developed phase metrology system Phame® and compare them to rigorous 3D simulations. Furthermore we correlate the phase shift measurements to process window data such as maximum exposure latitude. Through pitch investigations on alt. PSM show that for print pitches below 200nm (wafer level) the phase shift drops significantly below 180° which will lead to an image placement error during printing and a shrinking process window. Furthermore a strong correlation between phase shift and maximum exposure latitude is shown. Largest maximum exposure latitude is achieved for phase shift close to 180°. Phame® enables optical phase shift measurement in critical production features down to 120nm half pitch providing the opportunity to optimize the quartz dry etch process in terms of signature and linearity. This will help to optimize the phase shift of critical features on alt. PSM for largest process window and hence increase end of line yields for reducing overall chip manufacturing costs.

As lithography mask processes move toward 45nm and 32nm node, mask complexity increases steadily, mask specifications tighten and process control becomes extremely important. Driven by this fact the requirements for metrology tools increase as well. Efforts in metrology have been focused on accurately measuring CD linearity and uniformity across the mask, and accurately measuring phase variation on Alternating/Attenuated PSM and transmission for Attenuated PSM. CD control on photo masks is usually done through the following processes: exposure dose/focus change, resist develop and dry etch. The key requirement is to maintain correct CD linearity and uniformity across the mask. For PSM specifically, the effect of CD uniformity for both Alternating PSM and Attenuated PSM and etch depth for Alternating PSM becomes also important. So far phase measurement has been limited to either measuring large-feature phase using interferometer-based metrology tools or measuring etch depth using AFM and converting etch depth into phase under the assumption that trench profile and optical properties of the layers remain constant. However recent investigations show that the trench profile and optical property of layers impact the phase. This effect is getting larger for smaller CD's. The currently used phase measurement methods run into limitations because they are not able to capture 3D mask effects, diffraction limitations or polarization effects. The new phase metrology system - Phame(R) developed by Carl Zeiss SMS overcomes those limitations and enables laterally resolved phase measurement in any kind of production feature on the mask. The resolution of the system goes down to 120nm half pitch at mask level. We will report on tool performance data with respect to static and dynamic phase repeatability focusing on Alternating PSM. Furthermore the phase metrology system was used to investigate mask process signatures on Alternating PSM in order to further improve the overall PSM process performance. Especially global loading effects caused by the pattern density and micro loading effects caused by the feature size itself have been evaluated using the capability of measuring phase in the small production features. The results of this study will be reported in this paper.

The extension of optical lithography to 45nm and beyond goes along with an increased mask complexity and tighter specifications. Both attenuated and alternating phase shift masks (PSMs) require precise control of the phase shift as a function of both pitch and target sizes. Simulations show that the phase shift in the image plane of a microlithography scanner is strongly impacted by numerical aperture (NA), mask pitch, 3D mask effects, and polarization, especially if the feature sizes come close to the imaging wavelength. Carl Zeiss SMS has developed a new phase metrology system that overcomes the limitations of currently existing tools.The new optical metrology tool - Phame (R) - enables the industry to perform in-die phase measurements on alternating PSM (altPSM), attenuated PSM (attPSM), and CPL (chromeless phase lithography) masks down to 120nm half pitch at the mask.The optical beam path of the new metrology system allows actinic phase measurements of 193nm photomasks with a mask side NA up to 0.4, which is 1.6NA scanner equivalent at the wafer. This enables full compatibility to future 193nm immersion scanners down to the 32nm node.Off-axis phase measurement is realized by applying consecutive measurements of single source points according to the scanner relevant illumination settings. Phame (R) measures the scanner equivalent phase and amplitude in the image plane for each coherent source point. For off-axis phase shift extraction Zeiss has developed a new concept called high resolution phase. This high resolution phase is sensitive to the diffraction spectrum and to mask phase errors. In this paper we will explain the off-axis high resolution concept in detail.First measurements have been performed on attPSM with 45nm node test features. The results show strong deviations of the high resolution phase shift depending on the pitch. Isolated features combined with dense features have been investigated. The measurement results will be presented in the paper.

As PSM (Phase Shift Mask) process moves toward 45nm and 32nm node, phase control is becoming more important than ever. Both attenuated and alternating PSM need precise control of phase as a function of both pitch and target sizes. However conventional interferometer-based phase shift measurements are limited to large CD targets and requires custom designed target in order to function properly, which limits clear understanding and control of small target PSM features. New type of Phase metrology tool created by Zeiss, in collaboration with Intel has been introduced and Intel's 45nm node PSM targets have been measured. In this paper we present test results from AAPSM/EAPSM targets with space CDs down to 45nm a wafer-level. Smallest pitch was 300nm print pitch, 150nm CD at mask (75nm pitch at wafer). In addition to this, phase and transmission matching between conventional phase metrology tool and new tool has been investigated and shown.

As the lithography process moves toward the 45nm and 32nm nodes, phase control on the mask is becoming more important than ever. To ensure an accurate printing, both attenuated and alternating phase shift masks (PSMs) need precise control of the phase shift as a function of both pitch and target sizes. Simulations show that the phase shift in the image plane of a microlithography scanner is strongly affected by numerical aperture (NA), makes pitch, 3D mask effects, and polarization, especially if the feature sizes come close to the imaging wavelength. A new phase metrology system that overcomes the limitation of currently existing tools has been developed.

The extension of optical lithography to the 45nm node and beyond goes along with increased mask complexity and tightening of specifications. The proper use of PSM becomes more and more important and the phase shift needs to be quantified exactly in order to achieve accurate CD printing results during wafer processing. The methods currently available run into limitations because they are not able to consider diffraction limitations caused by scanner NA and mask pitch, as well as 3D mask effects. In the transition to the 45nm node and beyond, these effects play an important role and need to be considered. Zeiss' new phase metrology system Phame (R) captures diffraction limitations, rigorous effects (i.e., a failure of the Kirchhoff approximation), and polarization effects. The new phase metrology system measures the phase shift in any in-die feature of the active mask area for on- and off-axis applications with high spatial resolution.This paper is focused on through pitch and through duty cycle measurements on an alternating PSM. Phame (R) measurements will be compared to AFM measurements. Additionally rigorous 3D simulations have been performed for different CD, varying pitch and varying duty cycle using coherent illumination with polarization. The simulation results will be compared to Pham (R) measurement results.