We have reported the FIB repair system with low acceleration voltage is applicable to 65nm generation photomasks. Repair technology beyond 65nm generation photomasks requires higher edge placement accuracy and more accurate shape. We developed two new functions, "Two Step Process" and "CAD Data Copy". "Two Step Process" consists of primary process and finishing process. The primary process is conventional process, but the finishing process is precise process to control repaired edge position with sub-pixel order. "Two Step Process" achieved edge placement repeatability less than 3nm in 3sigma. At "CAD Data Copy", defects are recognized with comparison between shape captured from a SIM image and that imported from a CAD system. "CAD Data Copy" reproduced nanometer features with nanometer accuracy. Thus the FIB repair system with low acceleration voltage achieves high performance enough to repair photomasks beyond 65nm generation by using "Two Step Process" and "CAD Data Copy".
Repair technology for 65nm generation photomasks requires more accurate shape and transmittance. The objective of this study is to evaluate FIB repair process with low acceleration voltage. The evaluation items were imaging impact, defect visibility, repaired shape, through focus behavior, repeatability of edge placement and controllability of repair size. In conclusion, we confirmed that FIB repair process with low acceleration voltage is applicable to 65nm generation photomasks.
Since 2001, we have been improving the hp65nm generation photomask repairing systems, the SIR7000. FIB repair stains quartz substrate with Ga ions. We process the repaired area using two parameters: edge bias and over-etching depth to recover transmission loss. The simulation shows that smaller over-etching makes the lithography process window larger. The dependence of Ga density in quartz with on FIB acceleration voltages shows that the Ga-doped area is smaller according as acceleration voltage is lower. It is found that the over-etching depth should be below 15nm, and a new FIB repairing system should have a low acceleration column. In order to confirm the effect of low acceleration voltage, we investigated the transmittance and the over-etching depth as a feasibility study. As the result, lower acceleration voltage repair gives higher transmittance and lower over-etching depth. We confirmed that the FIB with low acceleration voltage is the most promising technology for the hp65nm generation photomask repairing.
The 65nm photomasks have to meet tight specifications and improve the production yield due to high production cost. The 65nm optical lithography was thought to have two candidates, 157nm and 193nm. However, at the advent of immersion lithography, it is certain that 193nm lithography will be adopted. Therefore, we decided to develop the FIB machine, SIR7000FIB, proior to the EB machine. We optimized repair conditions of FIB system, SIR7000FIB, and evaluated this system. First, we demonstrated minute defect repair using about 15nm defect mask. Then, we confirmed that the repeatability of repair accuracy was below 7nm on a MoSi HT mask patterned 360nm and 260nm L&S patterns with opaque and clear defects by AFM. Consequently, we have achieved the target specifications of this system.
The 65nm photomasks have to meet tight specifications and improve the production yield due to high production cost. The 65nm optical lithography has two candidates, 157nm and 193nm, and we are developing two types of experimental photomask repair systems, FIB and EB, for the 65nm generation. We designed and developed experimental EB and FIB system that are beta systems. The construction of these systems was the same design except the each column. The platforms of beta systems consist of anti-vibration design to reduce outer disturbance for repair accuracy. Furthermore, we developed a new CPU control system, especially the new beam-scanning control system that makes it possible to control the beam position below nanometer order. These developments will suppress transmission loss and improve repair accuracy of the systems. We also adopt the 6-inch mask SMIF pod system and the CAD data linkage system that matches the EB mask data image with the SED image to search defects in photomasks with sophisticated patterns such as OPC patterns. We evaluated the EB and FIB beta systems with AIMS, LWM and AFM. EB and FIB beta systems were able to deposit carbon film and etch chrome, quartz, and MoSi. Furthermore, We confirmed that repair accuracy is 3σ below 10nm and transmission is over 97%. We also confirmed that CAD linkage was able to repair sophisticated pattern completely. In this paper, we report the photomask defect repair experimental systems for the 65nm generation.
The technology node of semiconductor device production is progressing to 65nm generation. For the 65nm photomasks, the target specifications of defect size and repair accuracy are 52nm and 7nm, respectively. Especially, real defects on photomasks are not only simple two-dimensional patterns but also three-dimensional shapes such as phase shift defects and contamination, thus we need to recognize defect shapes accurately. Additionally, AAPSM's Cr patterns overhang, and we have to measure defects on three-dimensional shapes. To evaluate them, we use an AFM metrology system, Dimension X3D (Veeco), having both precise CD measurement repeatability (2nm) and high resolution for defects. In this report, we show the performance of the AFM metrology system. First, we evaluated CD metrology performance, CD repeatbility about four type photomasks: NEGA-BIM, POSI-BIM, KrF-HT and ArF-HT, and all masks met specifications. Next, we evaluated defect pattern shapes and AAPSM and CPL mask patterns. Consequently, we have confirmed that the AFM metrology system has high performance for 65nm photomasks.
The 65nm photomasks have to meet tight specifications and improve the production yield due to high production cost. The 65nm optical lithography has two candidates, 157nm and 193nm, and we are developing two types of experimental photomask repair systems, FIB and EB, for the 65nm generation. We designed and developed FIB and EB beta systems. The platforms of beta systems consist of anti-vibration design to reduce outer disturbance for repair accuracy. Furthermore, we developed a new CPU control system, especially the new beam-scanning control system that makes it possible to control the beam position below nanometer order. These developments will suppress transmission loss and improve repair accuracy of the systems. We also adopt the 6-inch mask SMIF pod system and the CAD data linkage system that matches the EB mask data image with the SED image to search defects in photomasks with sophisticated patterns such as OPC patterns. We evaluate the EB repair process, and confirm that it generates carbon film, which has possibility to generate the same quality as that of FIB. Furthermore, we confirmed that EB and FIB repair systems were able to deposit carbon film and etch chrome, quartz, and MoSi. In this paper, we report the photomask defect repair experimental systems and the feasibility study on photomask defect repair for the 65nm generation.
The SIR5000 mask repair system was developed with an FIB system featuring new ion optics, modified SED detectors, new platform software and optimized repair processes to repair 130nm/ArF generation masks. Thereafter we have continuously improved it for 90nm/ArF lithography and evaluated its performance such as edge placement repeatability, lithography simulation and printing tests.
The transmittance of FIB imaging area is more than 95% over 70 times scans, and the printing result data also shows that the imaging damage by FIB scans little affect CD until around 70 times. The ED windows of both repaired clear and opaque defects almost overlap non repaired reference ones, and they show that the printing performance of repaired mask does not have any printing issues. Consequently, we demonstrated that the improved SIR5000 capability has reached the 90nm node mask technology requirement.
Front-end semiconductor lithography demands smaller size of patterns for 90 nm node and beyond, on both Si wafers and photomasks. In dry etching for photomasks, it needs tighter CD uniformity and loading effect. For meeting these demands the advanced NLD (magnetic Neutral Loop Discharge) mask etcher has been developed, because it could operate at lower pressure for reducing loading effect than conventional ICP etchers, due to the magnetic confinement of electron in plasma generation. In the NLD mask etcher, the configuration of plasma source was investigated for better performance and the etching condition was re-optimized for improving selectivity. Consequently, the selectivity of Cr/resist (ZEP-7000) was more than 1.6, compared with 0.95 in the previous condition. And also, the CD uniformity in Cr etching was improved to meet our target 6 nm (3 sigma) around 0.68 Pa. However, in the view of reducing loading effect, other condition that is lower pressure than 0.68Pa and adding Helium (HE) showed smaller global loading. Therefore, making a balance of uniformity and loading is necessary to get better performance in mask process. We also propose a basic condition using the advanced NLD mask etcher for dry etching a MoSiON shifter of atenuated PSM in this paper.
The advanced photomask dry etching system using neutral loop discharge (NLD) has been thought as a promising candidate for the next generation technology, because the NLD plasma has a capability to control the plasma distribution and density. In previous work, we improved CD uniformity for 130nm node technology using the neutral loop modulation etching technique. However, 100nm node lithography requires tighter specification, thus we set a target to achieve CD accuracy of 6nm (3 sigma) by improving CD uniformity and loading effect of the NLD dry etching system. First, we changed the system configuration: exhaust place, reactor size, and electrode shape. Especially, by optimizing the antenna configuration, we improved the unevenly distributed plasma. Additionally, we introduced a new etching technique to reduce CD shift from resist profiles by enhancing Cr/Resist sensitivity. Consequently, the NLD dry etching system for 100nm node technology was confirmed the effectiveness to improve CD performance using the above techniques.