With the next technology nodes 193nm lithography is pushed to its utmost limits. The industry is forced to print at low k1 factor which goes along with a high MEEF. Additionally, new blank materials are being introduced for smaller nodes. From 4x node and beyond, global CD uniformity on wafer is getting more critical and becomes key factor to ensure a high yield in chip production. Advanced process control is required and correction strategies are applied to maintain tight wafer CD uniformity. Beside other parameters, like scanner and etch process, mask CD uniformity is one main contributor to the intra-field CD on wafer. To enable effective CDU correction strategies it is necessary to establish a mask CD uniformity metrology which shows a good correlation to wafer prints. Especially for logic pattern mask uniformity measurements to control intra-field CD uniformity becomes challenging.In this paper we will focus on mask CD uniformity measurement for logic application utilizing WLCD, which is based on aerial image technology. We will investigate 40nm node and 28nm node gate masks using 6% MoSi phase shifting mask and MoSi binary mask respectively. Furthermore, we will correlate the mask CD uniformity data to wafer data to evaluate the capability of WLCD to predict the intra-field wafer CD uniformity correctly in order to support feed-forward correction strategies. We will show that WLCD shows an excellent correlation to wafer data. Additionally, we will provide an outlook on logic contact-hole masks showing first CD uniformity data and wafer correlation data.

For the next years optical lithography stays at 193nm with a numerical aperture of 1.35. Mask design becomes more complex, mask and lithography specifications tighten. The k1 factor comes close to 0.25 which leads to a tremendously increased Mask Error Enhancement Factor (MEEF). This means that CD errors on mask are getting highly amplified on wafer. Process control becomes more important than ever. Accurate process control is a key factor to success to maintain a high yield in chip production.One key parameter to ensure a high and reliable functionality for any integrated circuit is the critical dimension uniformity (CDU). There are different contributors which impact the intra-field CD performance at wafer such as mask CD uniformity, scanner fingerprint, resist process etc. In the present work we focus on improvement of mask CD signature which is one of the main contributors to intra-field CD uniformity. The mask CD uniformity has been measured by WLCD32 which measures the CD based on proven aerial image technology. Based on this CD input the CD uniformity was corrected by CDC200 (TM) and afterwards verified by WLCD32 measurement. The CDC200 (TM) tool utilizes an ultrafast femto-second laser to write intra-volume shading elements (Shade-In Elements T) inside the bulk material of the mask. By adjusting the density of the shading elements, the light transmission through the mask is locally changed in a manner that improves wafer CDU when the corrected mask is printed.Additionally, the impact of the improved CD uniformity on the lithography process window was investigated. Goal of the work is to establish a process flow for mask CD uniformity improvement based on mask CD metrology by WLCD32 and mask CD uniformity control by CDC200 (TM) and to verify its impact on the lithography process window. The proposed process flow will be validated by wafer prints. It was shown that the WLCD32 has an excellent correlation to wafer data and an outstanding CD repeatability. It provides a reliable input for CD uniformity correction and is the tool of choice to verify the CD uniformity improvement after CDC200 (TM) treatment.Furthermore, it was shown that the CDC200 (TM) improves the CD uniformity significantly. The intra-filed CD uniformity was reduced by 50% down to the noise level of the wafer process. The final validation by wafer-prints confirms the viability of the closed loop solution WLCD32/CDC200 (TM). This solution is optimally suited to be used in captive and merchant mask shops to control the mask CD performance without the need of wafer-prints. Additionally, the impact of CD uniformity improvement on the lithography process window was investigated. It was worked out that the CD uniformity correction yields to an improved CD behavior through focus. Moreover, the CD uniformity improvement enlarges the exposure latitude by 20% and increases the overall process window.

For the next years optical lithography stays at 193nm with a numerical aperture of 1.35. Mask design becomes more complex, mask and lithography specification tighten and process control becomes more important than ever. Accurate process control is a key factor to success to maintain a high yield in chip production.One of the key parameters necessary to assure a good and reliable functionality of any integrated circuit is the Critical Dimension Uniformity (CDU). There are different contributors which impact the total wafer CDU: mask CD uniformity, scanner repeatability, resist process, lens fingerprint, wafer topography etc.In this work we focus on improvement of intra-field CDU at wafer level by improving the mask CD signature using a CDC200 (TM) tool from Carl Zeiss SMS. The mask layout used is a line and space dark level of a 45nm node Non Volatile Memory (NVM). A prerequisite to improve intra-field CDU at wafer level is to characterize the mask CD signature precisely. For CD measurement on mask the newly developed wafer level CD metrology tool WLCD32 of Carl Zeiss SMS was used. The WLCD32 measures CD based on proven aerial imaging technology. The WLCD32 measurement data show an excellent correlation to wafer CD data. For CDU correction the CDC200 (TM) tool is used which utilizes an ultrafast femto-second laser to write intra-volume shading elements (Shade-In Elements (TM)) inside the bulk material of the mask. By adjusting the density of the shading elements, the light transmission through the mask is locally changed in a manner that improves wafer CDU when the corrected mask is printed.In the present work we will demonstrate a closed loop process of WLCD32 and CDC200 (TM) to improve mask CD signature as one of the main contributors to intra-field wafer CDU. Furthermore we will show that the process window will be significantly enlarged by improvement of intra-field CDU. An increase of 20% in exposure latitude was observed.

Since 2008, we have been presenting some papers regarding CMOS 45nm logic gate patterning activity to reduce CD dispersion. After a global CD budget evaluation at SPIE08, we have been focusing on Intrafield CD corrections using Dose MapperTM. The story continues and since then we have pursued our intrafield characterisation and focus on ways to get Dose MapperTM dose recipe created before the first silicon is coming. In fact 40nm technology is already more demanding and we must be ready with integrated solutions for 32/28nm node. Global CD budget can be divided in Lot to Lot, Wafer to Wafer, Intra wafer and Intra field component. We won't talk here about run to run solutions which are put in place for Lot to Lot and Wafer to Wafer. We will emphasize on the intrafield / intrawafer process corrections and outline process compensation control and strategy. A lot of papers regarding intrafield CD compensation are available in the litterature but they do not necesserally fit logic manufacturing needs or possibilities. We need to put similar solutions in place which are comprehensive and flexible. How can we correct upfront an Etch chamber CD profile combined with a mask and scanner CD signature? How can we get intrafield map from random logic devices? This is what we will develop in this paper.

For many critical lithography applications the main contributor to wafer intra-field CD variation is the reticle CD variation. Current practice is that the input data needed to correct the effect of the reticle on the wafer CD is gathered using wafer exposures and SEM or scatterometry analysis. This approach consumes valuable scanner time and adds wafer costs. In this work we evaluate the potential for Intra-Field CD non-uniformity (CDU) correction based on aerial image reticle measurements for a complex 2D structure, including peripheral structures. The application selected is a 45nm rotated brick wall structure (active area DRAM). A total of 10 line / space structures (both horizontal and vertical) through pitch represent the periphery. Mask qualification has been performed using the newly developed Zeiss WLCD32 metrology tool, which measures wafer level CD on masks using aerial imaging technology. Excellent correlation is shown between intra-field wafer data and WLCD32 data. Furthermore, a comparison is made between the correction potential of ASML DoseMapper recipes based on wafer data and on WLCD32 mask data, indicating that the potential CDU improvement via both approaches is similar. Exposures with the resulting dose recipes have been used to confirm this predicted correction potential in a realistic setting.

One of the key parameters necessary to assure a good and reliable functionality of any integrated circuit is the Critical Dimension Uniformity (CDU). There are different contributors which impact the total CDU: mask CD uniformity, scanner and lens fingerprint, resist process, wafer topography, mask error enhancement factor (MEEF) etc. In this work we focus on improvement of intra-field CDU at wafer level by improving the mask CD signature using a CDC200TM tool from Carl Zeiss SMS. The mask layout used is a line and space dark level of a 45nm node Non Volatile Memory (NVM). A prerequisite to improve intra-field CDU at wafer level is to characterize the mask CD signature precisely. For CD measurement on mask the newly developed wafer level CD metrology tool WLCD32 of Carl Zeiss SMS was used. The WLCD32 measures CD based on aerial imaging technology. The WLCD32 measurement data show an excellent correlation to wafer CD data. For CDU correction the CDC200TM tool is used. By utilizing an ultrafast femto-second laser the CDC200TM writes intra-volume shading elements (Shade-In ElementsTM) inside the bulk of the mask. By adjusting the density of the shading elements, the light transmission through the mask is locally changed in a manner that improves wafer CDU when the corrected mask is printed. In the present work we will demonstrate a closed loop process of WLCD32 and CDC200TM to improve mask CD signature as one of the main contributors to intra-field wafer CDU.

With the transition of lithography into 45nm node and beyond the industry faces the challenge that mask complexity increases steadily, mask specifications tighten and process control becomes extremely important. The use of Phase Shifting Masks (PSM), combined with off-axis illumination schemes, is essential to print feature sizes going beyond the lithographic wavelength. In conjunction with the shrinking feature size the tolerable defect size shrinks as well. This goes along with rising mask costs and therefore a high first pass yield becomes more important than ever. Repair strategies are required which have the potential to support the trend of decreasing tolerable defect sizes for both clear and opaque defects. In case of PSM it is not only important to remove material, of special interest is the capability to repair phase defects. This requires material deposition and etching accounting for transmission and phase as well. The ebeam repair system MeRiT(R) MG 45 is based on the GEMINI(R) column and allows etching and deposition to repair both clear and opaque defects with high resolution and edge placement precision. In this paper we focus on repair of phase defects on 6% att. PSM. We concentrate on 45nm lines/spaces looking into different defect dimensions. At feature sizes of 45nm CD, corresponding to 180nm CD at mask, feature topography already impacts the phase shift. Therefore a base line investigation is performed evaluating the correlation between deposited PSM layer height and phase shift covering also the impact of 3D mask effects on phase shift. The deposited layer height is measured using AFM. For phase evaluation the newly developed phase metrology system Phame(R) was used. Phame(R) enables optical phase shift measurement with high spatial resolution down to 120nm half pitch on mask. On-axis and off-axis illumination can be applied according to the required scanner settings during wafer printing. Phame(R) captures imaging effects as well as 3D mask eff- - ects which are of special importance for further shrinking feature sizes.

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.

Flash memory is an important driver of the lithography roadmap, with its dramatic acceleration in dimensional shrink, pushing for ever smaller feature sizes. The introduction of hyper-NA immersion lithography has brought the 45nm node and below within reach for memory makers using single exposure. At these feature sizes mask topology and the material properties of the film stack on the mask play an important role on imaging performance. Furthermore, the break up of the array pitch regularity in the NAND-type flash memory cell by two thick wordlines and a central space, leads to feature-center placement (overlay) errors, that are inherent to the design. An integral optimization approach is needed to mitigate these effects and to control both the CD and placement errors tightly. In this paper we will show that aerial image measurements at mask-level are useful for characterizing the gate layer of a NAND-Flash design before exposure. The aerial image measurements are performed with the AIMSTM 45-193i. and compared to CD measurements on the wafer obtained with an XT:1900Gi hyper-NA immersion system. An excellent correlation is demonstrated for feature-center placement errors and CD variations across the mask (see Figure 1) for several features in the gate layer down to 40nm half pitch. This shows the potential to use aerial image measurements at mask-level in combination with correction techniques on the photomask, like the CDC200 tool in combination with exposure tool correction techniques, such as DoseMapperTM, to improve both across field and across wafer CD uniformity of critical layers.

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.

The AIMTM45-193i is the established tool for mask performance qualification and defect printing analysis in the mask shop under scanner conditions. Vector effects are taken into account by the proprietary Zeiss vector effect emulator. In several studies an excellent correlation to wafer prints has been reported. However, a systematic offset to wafer prints in terms of mask error enhancement factor (MEEF) and exposure latitude has been observed which is attributed to well known resist effects. The AIMSTM measures the aerial image in resist whereas in a real lithography process further image blur of the latent image is caused by photo acid diffusion during wafer processing and resist development. To explain the gap between the AIMTM and wafer prints we have investigated aerial images in combination with an easy to use resist model. It does take resist effects into account with sufficient accuracy to explain printing behavior of photo masks but without the need to calibrate lots of parameters of the actually used resist which usually are not known to a mask shop. The resist effects predominantly reduce the image contrast and thus increase the MEEF and the sensitivity to mask defects. This somewhat counterintuitive behavior is labeled "contrast enhancement by contrast reduction". Additionally application of the resist model improves the agreement of e.g. the exposure latitude or MEEF measured by the AIMSTM compared to wafer prints.

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.

With the introduction of the TWINSCAN XT:1900Gi the limit of the water based hyper-NA immersion lithography has been reached in terms of resolution. With a numerical aperture of 1.35 a single expose resolution of 36.5nm half pitch has been demonstrated. However the practical resolution limit in production will be closer to 40nm half pitch, without having to go to double patterning alike strategies. In the relentless Flash memory market the performance of the exposure tool is stretched to the limit for a competitive advantage and cost-effective product.In this paper we will present the results of an experimental study of the resolution limit of the NAND-Flash Memory Gate layer for a production-worthy process on the TWINSCAN XT:1900Gi. The entire gate layer will be qualified in terms of full wafer CD uniformity, aberration sensitivities for the different wordlines and feature-center placement errors for 38, 39, 40 and 43nm half pitch design rule. In this study we will also compare the performance of a binary intensity mask to a 6% attenuated phase shift mask and look at strategies to maximize Depth of Focus, and to desensitize the gate layer for lens aberrations and placement errors. The mask is one of the dominant contributors to the CD uniformity budget of the flash gate layer. Therefore the wafer measurements are compared to aerial image measurements of the mask using AIMS (TM) 45-1931 to separate the mask contribution from the scanner contribution to the final imaging performance.

Flash memory has become one of the most important segments of the semiconductor industry in recent years. Flash memory is also an important driver of the lithography roadmap, with its dramatic acceleration in dimensional shrink, pushing for ever smaller feature sizes. The introduction of the XT: 1700Fi and XT: 1900Gi have brought the 45nm node and below within reach for memory makers. At these feature sizes mask topology and the material properties of the film stack on the mask play an important role on imaging performance. Furthermore, the break up of the array pitch regularity in the NAND-type flash memory cell by two thick wordlines and a central space, leads to feature-center placement (overlay) errors, that are inherent to the design. An integral optimization approach is needed to mitigate these effects and to control both the CD and placement errors tightly. In this paper we will present the results of aerial image measurements on mask level of a NAND-Flash Memory Gate layer using AIMS(TM) 45-193i. Various imaging relevant parameters, such as MEEF, EL, DoF and placement errors are measured for different mask absorber materials for features sizes ranging from 39nm half pitch to 41nm half pitch design rule on wafer level. The AIMS(TM) measurements are compared to experimental results obtained with a XT: 1900Gi hyper-NA immersion system. Mask optimization strategies are sought to increase Depth of Focus and minimize feature-center placement errors.

Recently more and more mask designs for critical layers involve strong OPC which increases the complexity for standard CID SEM mask measurements and conclusive interpretation of results. For wafer printing the wafer level CID is the crucial measure if the mask can be successfully used in production. Recent developments in the AIMS (TM) software have enabled the user to use the tool for wafer level CD metrology under scanner conditions. The advantage of this methodology is that AIMS (TM) does see the CD with scanner eyes. All lithographic relevant effects like OPC imaging which can not be measured by other tools like mask CID SEM will be captured optically by the AIMS (TM) principle. Therefore, measuring the CD uniformity of the mask by using AIMS (TM) Will lead to added value in mask metrology. With decreasing feature sizes the requirements for CD metrology do increase. In this feasibility study a new prototype algorithm for measuring the lithographically relevant AIMS (TM) CD with sub pixel accuracy has been tested. It will be demonstrated that by using this algorithm line edge and line width roughness can be measured accurately by an AIMS (TM) image. Furthermore, CID repeatability and tool matching results will be shown.

It has been previously demonstrated that wafer CD uniformity can be improved via an ultrafast laser system. The system provides local CD Control (CDC) by writing inside the bulk of photomasks. Intra-field CD variation correction has been implemented effectively in mask-shops and fabs based on CD-SEM and Scatterometry (Optical CD or OCD) as the CD data source. Using wafer CD data allows correction of all wafer field CD contributors at once, but does not allow correcting for mask CD signature alone. For mask shops attempting to improve CDU of the mask regardless of the exposure tool, it is a better practice to use only mask CD data as the CD data source. In this study, we investigate the use of an aerial imaging system AIMSTM45-193i (AIMS45) as the mask CD data source for the CDC process. In order to determine the predictive value of the AIMS45 as input to the CDC process, we have created a programmed CD mask with both 45nm and 65nm node L/S and hole patterns. The programmed CD mask has CD errors of up to 20nm in 2.5nm steps (4X). The programmed CD mask was measured by AIMS45, defining the CDU map of the programmed CD mask. The CDU data was then used by Pixer CDC200TM to correct the CDU and bring it back to a flat, almost ideal CDU. In order to confirm that real CDU improvement on wafer had been achieved, the mask was printed before and after CDC on an immersion scanner at IMEC and results of pre and post CD data were compared.

We have tested the validity of the so-called 'vector-effect emulation mode' of the newest member of the AIMS (TM)(1) family, the AIMS (TM) 45-193i, that was recently developed for Hyper-NA applications. This vector-effect emulation mode (also called 'scanner mode') converts the measured signals into a prediction of what the image-in-resist of a Hyper-NA scanner would be (so including vector- and polarization effects). We've done a number of experiments that directly test the validity of this vector-effect emulation, by comparing them to rigorous lithographic simulations and to CD-measurements from printed NA=1.20 scanner wafers, and found that the AIMS (TM) 45-193i results are in fact quite accurate. Afterwards we looked at a number of potential Hyper-NA imaging applications for the AIMS (TM) 45-193i, again comparing it to rigorous simulations and wafer CD-measurements. These results indicate that, next to its traditional use as reticle-inspection tool, the AIMS (TM) 45-193i has potential use also in the wafer fab as an 'imaging-inspection' or 'OPC-defect inspection' tool, especially when applied to 2D patterns.

CD uniformity control by ultrafast laser system writing inside the bulk of photomasks has previously been shown to be an effective method for local CD Control (CDC) [1].Intra-field CD variations correction has been implemented effectively in mask-shops and fabs based on CDC SEM [2, 3] and OCD as the CD data source. Using wafer CD data allows correction of all wafer field CD contributors at once, but does not allow correcting for mask CD signature alone. In case of a mask shop attempting to improve CDU of the mask regardless of a particular exposure tool, it is a better practice to use mask CD data by itself as the CD data source.We propose using an aerial imaging system AIMS(TM)45-193i as the mask CD data source for the CDC process.In this study we created a programmed CD mask (65nm dense L/S) with relatively large CD errors. The programmed CD mask was then measured by AIMS(TM)45-193i (AIMS45) which defined the CDU map of the programmed CD mask. The CDU data from AIMS(TM)45-193i was then used by Pixer CDC101 to correct the CDU and bring it back to a flat almost ideal CDU.Results1. AIMS (TM) 45-193i managed to map the full mask CDU with a resolution of 0.5 nm.2. The CDC101 managed to correct the CDU based on the AIMS (TM) 45-193i data from Range 5nm and 3S 4nm down to Range<1.5nm and 3S< 1.0nmConclusionsBy using AIMS (TM) 45-193i and CDC101 alone, without any wafer CD data, the mask CDU can be improved >70% and mask contribution to wafer CDU can be brought down to <1.0 run 3S.

Hyper-NA lithography with polarized light illumination is introduced as the solution of 45nm or 32nm node technology. In that case, consideration of new characteristics of mask materials and pellicle films has been required. In order to analyze the influence of mask material's optical characteristics, we have proposed to use the AIMS (TM) system measuring diffraction intensity balance in previous work *(4). That was enabled by acquiring pupil plane images using the Bertrand lens in the AIMS (TM) system to measure selected area's diffracted light.In this study of mask material evaluation, we used same functionality of AIMS (TM) system, MonoPole illumination and Bertrand lens, as previous work but other direction's pole is also used on the illumination aperture to cover total diffraction orders of Cross-quad illumination because this illumination is more flexible for x and y patterns. In order to get diffracted light of 45nm half-pitch, hyper-NA e.g. NA=1.35 was applied and the AIMS (TM) 45-193i Alpha system was used for this evaluation. The examinations were performed with binary and half tone PSM with half pitch 40 to 150nm on a 1x scale and fixed half pitch 45nm with various mask bias. We confirmed the relation between diffractions' intensity balance and wafer printing performance for each material and we compared them to 3D simulation results.Moreover, by using the same functionality of AIMS (TM) system, the transmission change by pellicle film was also examined. We have prepared two different thickness pellicles to compare transmission change and printed CD on the wafer. Intensity profile at pupil plane on the clear region of the mask was acquired with Bertrand lens and conventional large sigma setting for both with and without pellicle film on the mask. By comparing transmission distribution change between with and without pellicle, we could calculate transmission loss by pellicle at large incident angles. For this experiment, NA=1.40 was applied and the AIMS (TM) 45-193i Alpha system was also used. The examinations were performed with half tone PSM at half pitch 45nm and 65nm on a 1x scale on linear polarized DiPole illumination.As a result, we have confirmed good agreement between AIMS (TM) measurement data and optical 3D simulations. In conclusion, the AIMS (TM) system is a valuable tool for analyzing diffraction efficiency or intensity distribution on the pupil plane and comparison to wafer printing performance.

The lithographic performance of current state-of-the-art resolution enhancement techniques (RET) will become critical at hyper numerical aperture (NA>1) due to mask 3D effects. We have studied the impact of the mask material on the lithographic performance at NA 1.2 and above. The assessment, both by rigorous simulations and experiments, involves the standard mask stacks, Cr binary mask (BIM) and MoSi 6% attenuated phase shift mask (attPSM), as well as alternatives such as thick Cr BIM, Ta/SiO2 1% and 6% attenuated PSM, and Ta/SiON 1% attenuated PSM.Using the rigorous electro-magnetic field (EMF) and lithographic process simulations (IISB DrLiTHO) the mask structure is optimized taking into account the trade-off with mask error enhancement factor (MEEF). Next, a through-pitch evaluation of the 45nm half-pitch (HP) node at NA1.2-1.35 is carried out examining maximum exposure latitude (EL), depth-of-focus (DOF), best focus shifts, and MEEF behavior for the various mask stacks.For the validation of the simulation methodology a correlation is made between scanner (ASML XT:1700Fi), AIMS (Zeiss AIMS(TM)45-193i), and simulation results indicating the importance of the mask quality and mask properties. Based on the lithographic performance and the mask manufacturability we put together a ranking of the commercially available mask stacks for the 45nm HP node at NA 1.2 and 1.35.