The successful development of Actinic Pattern Mask Inspection (APMI) has enabled the high-volume manufacturing of advanced chips, such as N5 and N3, due to the production of defect-free masks by tsmc's mask shop. This accomplishment can be attributed to the utilization of an innovative Extreme Ultraviolet (EUV) inspector and Graphics Processing Unit (GPU)-based defect detection with Artificial Intelligence (AI) assistance. The application of EUV inspector unleashed pellicle inspection to prolong mask operation periods in wafer foundries. Besides, the improving in the manufacturing efficiency via automation also boost the productivity in the mask shop. According to our previous report in BACUS 2023, the improvement by performing various approaches in the novel Laser-Produced Plasma (LPP) system enabled tsmc to capture EUV image with high stability. The continual improving in the system in later keep reducing the vibration of the crucible and hence improve the tin stability. Furthermore, tsmc developed a GPU-based inspection system, which allowed for flexible algorithm development compared to FPGA. The ML-based rendering model aligned features with tool images and reduced image residue. Therefore, the final inspected image could be possessed with high SNR in advanced node and aggressive OPC compared to DUV inspector. Additionally, the final inspection results will be processed via a Deep Learning (DL) based model, reducing false positives, and implementing auto-defect classification. By combining these contributions, the actinic tools were able to streamline the manufacturing flow and fulfill the requirements for massive production significantly.
High numerical aperture extreme ultraviolet (High NA EUV) lithography and the support of computational lithography are enabling the race towards smaller nodes. An important tool empowering this trend is the multi-beam mask writer (MBMW). Its most prominent component is the so-called BLC (blanking-chip): a MEMS processed CMOS chip determining writing speed and precision. This paper describes the innovative MEMS process on the post processing of such a BLC. Key features of the blanking-chip are 590k apertures and electrode pairs within an area of <15x15mm2. The strict requirement on performance and cleanness of the chip on the comparably large area makes the MEMS process challenging. Intensive analysis and optimized MEMS process make the 590k-BLC with >99.95% of all apertures and electrodes being clean and defect free. Additionally, other crucial performances such as crosstalk and blanking angle have met the required specification. The 590k-BLC was qualified in the MBMW-301 ALPHA. Comparing it to the latest MBMW-201 generation, optical performances of image plane curvature and aberration blur of the beams are decreased by 31% and 41%, respectively. The curvy pattern shows 30% improvement of the fidelity thanks to 15nm of spatial resolution and 20% reduction of line edge roughness (LER). The throughput improves 50% on the same writing mode. These results indicate that MBMW-301 with the core engine 590k-BLC is ready to be introduced into development and mass production of advanced nodes.
High numerical aperture extreme ultraviolet (High NA EUV) lithography and the support of computational lithography are enabling the race towards smaller nodes. An important tool empowering this trend is the multi-beam mask writer (MBMW). Its most prominent feature is the so-called BLC (blanking-chip): a MEMS processed CMOS chip determining writing speed and precision. This paper describes the innovative MEMS process on the post processing of such a BLC. Key features of the blanking-chip are its 590k apertures and electrode pairs within an area of <15x15mm^2. The strict requirement on performance and cleanness of the chip on the comparably large area makes the MEMS process challenging. Intensive analysis and MEMS process tuning made it possible to complete the first fully processed 590k-BLCs with >99.5% of all apertures and electrodes being clean and defect free. Additionally, other crucial parameters such as blanking angle and crosstalk have met the required specification. The 590k-BLC was qualified in the first prototype next generation MBMW-301 ALPHA. Comparing it to the latest MBMW-201 generation, optical performance as image plane curvature and aberration blur of the beams are decreased by 31% and 41%, respectively. These results indicate the upcoming potential of the 590k-BLC within the MBMW-301 enabling highly improved spatial resolution and pattern fidelity.
The high numerical aperture EUV exposure systems aim to target a 16-nm pitch to extend Moore's law throughout the next decade. However, thinner photoresist layers and worsened stochastic effects due to photons hitting the wafer at a shallower angle is a major concern. Furthermore, the projection optics utilize an anisotropic reduction factor, which remains an open issue, requiring a dual "half-field" mask exposure sequence or a 12-inch mask for each high-NA EUV layer. Therefore, the use of attenuated phase-shift masks (APSM) to extend 0.33NA to a 28-nm pitch becomes relevant. We will discuss the prospects on optical properties refractive index (n,k) optimization with material selection, feasibility of achieving a 28-nm pitch, 3D effect mitigation and the impact of mask tonality (dark tone vs clear tone). Finally, the challenges on the needs of new APSM materials that meet the requirements of high temp thermal stability, durability under mask clean solution, its dry etching characteristics, the corresponding repair process will be addressed and the experimental results on the Ru-based candidates will be shown.
Given the successful development in actinic pattern mask inspection (APMI), high-volume manufacturing of advanced chips including N5 and N3 was realized due to the defect-free masks provided by the TSMC mask shop. This achievement was attributed to the newly developed EUV source and GPU-based defect detection with machine learning (ML) assistance. Unlike conventional approaches which sustain less than two weeks, the rotated crucible fed by Sn fuel in the LPP (Laser-produced plasma) system provided one month of operating stability with ultra-low tin consumption. The newly developed LPP EUV light source has been moved towards double IR power to produce higher EUV photon counts, resulting in better throughput and inspection sensitivity. It enables captured images to possess an effective signalto-noise ratio (SNR) and reasonable inspection nuisance counts. The common technique challenges, Sn auto-refuel and debris mitigation, were overcome by auto-refuel and reuse, debris mitigation, and plasma position control. Moreover, the LPP system also showed its capability in performing pellicle inspection to prolong mask operation periods in wafer foundries. For the GPU-based inspection system, it provided the feasibility and flexibility in algorithm development compared to the FPGA approach. The TSMC developed machine-learning (ML) based rendering model played a key role in aligning features with tool images in D2D mode, as well as residue reduction of D2DB mode. All rendering models were implemented by CUDA coding and running on TSMC-customized GPU architecture to fulfill the goal of high-speed computation and defect capture rate that met production specifications. Combining with the ML model, proper detectors were designed for each specific feature, such as SRAF and curvy OPC design, and the performance of auto defect classification (ADC) with the model has been proven. By integrating all the work, it enabled the actinic tools to fulfill the requirement of massive production significantly.
In advanced optical lithography the requirements of focus control continues to tighten. Usable depth of focus (DoF) is already quite low due to typical sources of focus errors, such as topography, wafer warpage and the thickness of photoresist. And now the usable DoF is further decreased by hotspots (design and imaging hotspots). All these have put extra challenges to improve focus metrology, scanner focus stability calibrations and on-product correction mechanisms.
Asymmetric focus targets are developed to address robustness in focus measurements using diffraction-based focus (DBF and μDBF) metrology. A new layout specific calibration methodology is introduced for baseline focus setup and control in order to improve scanner focus uniformity and stability using the measurements of the above mentioned asymmetric targets. A similar metrology is also used for on product focus measurements. Moreover, a few novel alternative methods are also investigated for on-product focus measurements.
Data shows good correlation between DBF and process on record (POR) method using traditional FEM. The new focus calibration demonstrated robustness, stability and speed. This technical publication will report the data from all the above activities including results from various product layers.
A number of new technologies and processes have been developed for deep ultraviolet (DUV) wavelength
and femtosecond pulsed laser repair of photomasks. These advances have been shown to improve and extend the
repair of both pelliclized and non-pellicilized photomasks for both hard and soft (or nano-particle) in exhaustive
testing at the factory and the end-user site. However, even the best testing is only a simulation of what a repair
tool will see when brought into full production. The purpose of this work is to review some of the knowledge and
experience gained in bringing the repair processes defined with manufactured defects to the more variable defects
encountered in the real world. The impact of the repair technology on increases in mask house throughput and
decrease in costs will also be compared to other (another laser and an advanced FIB) repair tools.
As the lithography design rule of IC manufacturing continues to migrate toward more advanced technology nodes, the mask error enhancement factor (MEEF) increases and necessitates the use of aggressive OPC features. These aggressive OPC features pose challenges to reticle inspection due to high false detection, which is time-consuming for defect classification and impacts the throughput of mask manufacturing. Moreover, higher MEEF leads to stricter mask defect capture criteria so that new generation reticle inspection tool is equipped with better detection capability. Hence, mask process induced defects, which were once undetectable, are now detected and results in the increase of total defect count. Therefore, how to review and characterize reticle defects efficiently is becoming more significant.
A new defect review system called ReviewSmart has been developed based on the concept of defect grouping disposition. The review system intelligently bins repeating or similar defects into defect groups and thus allows operators to review massive defects more efficiently. Compared to the conventional defect review method, ReviewSmart not only reduces defect classification time and human judgment error, but also eliminates desensitization that is formerly inevitable. In this study, we attempt to explore the most efficient use of ReviewSmart by evaluating various defect binning conditions. The optimal binning conditions are obtained and have been verified for fidelity qualification through inspection reports (IRs) of production masks. The experiment results help to achieve the best defect classification efficiency when using ReviewSmart in the mask manufacturing and development.
As device technology shrinks beyond 0.13um, extensive resolution enhancement techniques such as PSM and OPC are employed in an attempt to gain usable photo process windows. Pattern fidelity on a mask measured in terms of corner rounding and line end shortening significantly influences the expected wafer performance. In this work, we report the effects of mask making parameters on the mask pattern fidelity and the resulting wafer pattern fidelity.
Process optimizations have been done to carried out xon '0.13micrometers ' reticle manufacturing with feature sizes of under 520nm. Micro-leading < 10nm and CD uniformity (3S) < 10nm process for binary Cr reticle can be achieved with dry etching process using chemical amplify resists blanks. HL-950 writer with resist films of 400nm and dy etching with Centura system were adopted for the purpose. It has shown that by optimizing selectivity window in Centura system without assistant gas addition, one could improve the process capability significantly. Design of experiment was applied to investigating the effects of source power, bias power and total pressure on CD uniformity, Micro-loading, Linearity and Process bias. With the DOE results, the process conditions could be fine-tuned to an optimal set of variables, which allow us to manufacture 0.13 micrometers masks.
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