The source of flare in EUVL systems is mostly from the mid-spatial frequency roughness (1 /mum - 1 /mm spatial periods) of mirrors. Due to the challenges in polishing mirrors to a small. fraction of the wavelength, flare in EUV lithography tools is expected to be greater than flare in current DUV tools. Even though EUV flare is constant across the field, there can be within-die flare variations due to variations in layout density. Hence, it is expected that to meet the CD control requirements for the 32 nm node, Flare Variation Compensation (FVC), akin to Optical Proximity Correction (OPC) would be required. FVC needs the within-die flare level estimated by convolving the Point Spread Function due to scatter (PSFsc) with the mask layout. Thus, accurate knowledge of the system PSFsc is essential for FVC. Experimental results of the Modulation Transfer Function (MTF) technique to estimate flare and the PSFsc of the Engineering Test Stand (ETS) are presented. It was also determined that due to the nature of the PSFsc in EUVL tools a more accurate measure for flare would be to use the 0.5 mum line as opposed to the current 2 mum line standard for measuring flare on DUVL tools.

The minimum gate CD for the 32 nm node is 15 nm and the CD control requirement on the gate CD is < 2.5 nm 3σ. One of the major concerns for meeting these targets using EUV lithography is flare. Flare degrades the aerial image contrast which decreases the process window, and within-die chrome density variation results in local flare variation which worsens the CD control. Since mirror roughness contributes to flare, mirror polishing needs to be improved so that the Mid Spatial Frequency Roughness (MSFR) will be reduced to < 0.14 nm/mirror for 6 mirror imaging systems. In this paper, we will determine the minimum acceptable flare for the 32 nm node to meet the CD target and control requirements using modeling and present methods to meet them as demonstrated by experiments run on the Engineering Test Stand (ETS). Effectiveness of flare mitigation methods using chrome dummification and negative tone resists are quantified, and the capability of Flare Variation Compensation (FVC) to meet CD control targets are verified experimentally.

The success of extreme ultraviolet (EUV) lithography depends upon developing resists that meet the patterning requirements for the technology node in which EUV is inserted. This paper presents Intel's patterning requirements and development strategies for EUV resists. Two of the primary problems for EUV resists are meeting the linewidth roughness (LWR) requirement, and reducing resist absorbance to obtain good sidewall profiles. Benchmarking data shows that none of the current EUV photoresists meet LWR targets. Modeling results for EUV resists show the impact of resist absorbance on sidewall angle and resolution.

Static and scanned images of 100-nm dense features using a developmental set of lambda/14 projection optics, POB1, were successfully obtained in the Engineering Test Stand (ETS) with various laser produced plasma (LPP) source powers last year. The ETS with POB1 has been used to understand initial system performance and to provide lithographic learning. Since then, numerous system upgrades have been made to improve ETS lithographic performance to meet or exceed the original design objectives.The most important upgrade has been the replacement of POB1 with an improved projection optics system. POB2. having lower figure error (lambda/20 rms wavefront error) and lower flare. Both projection optics boxes are a four-mirror design with a 0.1 numerical aperture. Scanned 70-nm dense features have been successfully printed using POB2. Aerial image contrast measurements have been made using the resist clearing method. The results are in good agreement to previous POB2 aerial image contrast measurements at the subfield exposure station (SES) at Lawrence Berkley National Laboratory. For smaller features the results deviate from the modeling predictions due to the inherent resolution limit of the resist. The intrinsic flare of POB2 was also characterized. The experimental results were in excellent agreement with modeling predictions. As predicted, the flare in POB2 is less than 20% for 2 mum features, which is two times lower than the flare in POB1. EUV flare is much easier to compensate for than its DUV counterpart due to its greater degree of uniformity and predictability. The lithographic learning obtained from the ETS will be used in the development of EUV High Volume Manufacturing tools. This paper describes the ETS tool setup, both static and scanned, that was required after the installation of POB2. The paper will also describe the lithographic characterization of POB2 in the ETS and compare those results to the lithographic results obtained last year with POB1.

Early production EUV exposure tools may have difficulty achieving flare requirements in the 5-6% range for the 32nm technology node. In this case, flare compensation may be needed to achieve the necessary CD control budget for production. This paper explores both experimentally as well as computationally wafer CD compensation though mask CD resizing so that proper CD control across the exposure field can be maintained. Experimental resist data collected on POB#2 of the Engineering Test Stand (ETS) suggest that even a simple linear CD compensation model can signifantly improve CD contorl in the presence of flare variation. Extending a similar concpet to a hypothetical full-field 25×33 mm2 mask area containgin 20 nm gate CDs shwos taht CD compensation, while computationally demanding, can be realized through a convolution approach of a 1×1 mm2 mask area using a non-uniform adaptive grid.

Static and scanned images of 100 nm dense features were successfully obtained with a developmental set of projection optics (lambda/14 projection optics box or POB 1) and a 500W drive laser laser-produced-plasma (LPP) source in the Engineering Test Stand (ETS). The ETS, configured with POB 1, has been used to understand system performance and acquire lithographic learning which will be used in the development of EUV high volume manufacturing tools. The printed static images for dense features below 100 nm with the improved LPP source (500W drive laser) are comparable to those obtained with the low power LPP source (40W drive laser), while the exposure time was decreased by more than 30x. Image quality comparisons between the static and scanned images with the improved LPP source are also presented. Lithographic evaluation of the ETS includes flare and contrast measurements. By using a resist clearing method, the flare and aerial image contrast of POB1 have been measured, and the results have been compared to analytical calculations and computer simulations.

The extreme ultraviolet (EUV) Engineering Test Stand (ETS) is a step-and-scan lithography tool that operates at a wavelength of 13.4 nm. It has been developed to demonstrate full-field EUV imaging and acquire system learning for equipment manufacturers to develop commercial tools. The initial integration of the tool is being carried out using a developmental set of projection optics, while a second, higher-quality, projection optics is being assembled and characterized in a parallel effort. We present here the first lithographic results from the ETS, which include both static and scanned resist images of 100 nm dense and isolated features throughout the ring field of the projection optics. Accurate lithographic models have been developed and compared with the experimental results.

The Engineering Test Stand (ETS) is an EUV lithography tool designed to demonstrate full-field EUV imaging and provide data required to accelerate production-tool development. Early lithographic results and progress on continuing functional upgrades are presented and discussed. In the ETS a source of 13.4 nm radiation is provided by a laser plasma source in which a Nd:YAG laser beam is focused onto a xenon- cluster target. A condenser system, comprised of multilayer-coated and grazing incidence mirrors, collects the EUV radiation and directs it onto a reflecting reticle. The resulting EUV illumination at the reticle and pupil has been measured and meets requirements for acquisition of first images. Tool setup experiments have been completed using a developmental projection system with (lambda) /14 wavefront error (WFE), while the assembly and alignment of the final projection system with (lambda) /24 WFE progresses in parallel. These experiments included identification of best focus at the central field point and characterization of imaging performance in static imaging mode. A small amount of astigmatism was observed and corrected in situ, as is routinely done in advanced optical lithographic tools. Pitch and roll corrections were made to achieve focus throughout the arc-shaped field of view. Scan parameters were identified by printing dense features with varying amounts of magnification and skew correction. Through-focus scanned imaging results, showing 100 nm isolated and dense features, will be presented. Phase 2 implementation goals for the ETS will also be discussed.

157-nm lithography has gained significant momentum and worldwide support as the post-193 nm technology. Due to higher absorption at shorter wavelength, however, there are several critical issues including materials and reticle handling at 157-nm. These key technical areas are being studied at Intel in collaboration with worldwide industrial and academic partners. In this paper, we will report the progress on 157-nm specific mask technology development.

Intel is aggressively pursuing the use of 157 nm lithography for the 0.1 mm patterning node. Two areas of concentration have been in photoresist and reticle materials development. Over the six months, we have seen considerable progress in new materials development in both areas. In the photoresist area, the use of ultra-thin resists of currently used chemistries appear to be capable of providing short-term layer development and tool testing patterning capability. We have obtained imaging results using a 0.5 NA Schwartzchild optics system. Our best result to data show 70-80 nm lines printed on a pitch of 180 nm. While this small field system has considerably immature optics, it can be used effectively to do basic resist development. In the area of reticle materials development, we have seen considerable improvement in the reduction of OH in blank materials, resulting in higher transmission. We expect to see substrates with greater than 80 percent transmission within the next year at the current rate of accelerated progress. Furthermore, we are not seeing any major processing differences with these new blank materials. Overall, we have seen an accelerated pace of learning in materials development for both resist and new blank materials. Overall, we have seen an accelerated pace of learning in materials development for both resist and reticle materials for 157 nm lithography.