Ryoji Hagiwara

Application of vector scanning in focused ion beam photomask repair system

With continuous reduction in linewidth of the VLSI devices, the pattern integrity of photomasks becomes considerably more important than ever. Consequently, requirement for the defect repair technology on photomasks is more severe and strict. Focused ion beam (FIB) technology has been widely used for defect repairing in photomask industry. Therefore, the performance of the FIB mask repair tool has to be improved especially in repair accuracy and precision. The FIB repair processes are classified into two kinds; one is additive repair using FIB induced deposition for missing patterns, the other is subtractive repair using gas assisted FIB etching for extra patterns. In both processes, precursor gas is applied onto the processing area through a small nozzle. Thus, the repair processes are controlled by the FIB irradiation and the precursor gas supply. Important characteristics of the repairs, such as size, shape, and placement of the repair area, are defined by the FIB scanning control. As conventional FIB ...

Advanced FIB mask repair technology for 100 nm/ArF lithography

The satisfactory data have been confirmed on the photomask repairing performance for 100nm-node/ArF-generation lithography with the model SIR5000 photomask repair system. In this report, the repairing ability is presented with transmittance and edge placement data. The edge placement was almost 15nm(3sigma) on binary and MoSi-HT masks, and there isn’t any transmittance loss in the AIMS193 data.

Damage analysis of EUV mask under Ga focused ion beam irradiation

EUV mask damage caused by Ga focused ion beam irradiation during the mask defect repair was studied. The concentration of Ga atom implanted in the multilayer through the buffer layer was calculated by SRIM. The reflectivity of the multilayer was calculated from the Ga distribution below the capping layer surface. To validate the calculation, a multilayer sample was irradiated with Ga FIB, and then EUV reflectivity was measured. The measured reflectivity change was in good agreement with the calculated value. An aerial image of patterns with Ga implanted region was simulated. The impact of the estimated Ga absorption on the linewidth of 32 nm hp line pattern was found to be less than 1 nm.

FIB mask repair technology for electron projection lithography

We have studied stencil mask repair technology with focused ion beam and developed an advanced mask repair tool for electron projection lithography. There were some challenges in the stencil mask repair, which were mainly due to its 3-dimensional structure with aspect ratio more than 10. In order to solve them, we developed some key technologies with focused ion beam (FIB). The transmitted FIB detection technique is a reliable imaging method for a 3-dimensional stencil mask. This technique makes it easy to observe deep patterns of the stencil mask and to detect the process endpoint. High-aspect processing can be achieved using gas-assisted etching (GAE) for a stencil mask. GAE enables us to repair mask patterns with aspect ratio more than 50 and very steep sidewall angle within 90±1°precisely. Edge placement accuracy of the developed tool is about 14nm by manual operation. This tool is capable to achieve less than 10nm by advanced software. It was found that FIB technology had capability to satisfy required specifications for EPL mask repair.

Evaluation of defect repair of EUVL mask pattern using FIB-GAE method

We utilized a newly developed low acceleration voltage FIB (Focused Ion Beam) system and evaluated the process for repairing the absorber layer on EUVL mask. During the etching of the absorber layer, which is a step in conventional repair technique, a phenomenon of side-etching of Ta-nitride layer with XeF2 gas was observed. This phenomenon was considered to be caused by the isotropic etching of the Ta-nitride layer with XeF2 gas. We then added another gas for etching and evaluated the new process to prevent the side-etching of Ta-nitride layer. In this paper, we will report four evaluation results of EUVL mask pattern defect repair using FIB-GAE (Gas Assisted Etching). The first one is the problem of pattern topography after conventional repairing process and the reaction mechanism of gas assisted etching of Ta based absorber. The second evaluation result is addressed in two parts. One is the evaluation of a new gas assisted etching process that employs an additional gas that has an ability to control the etching rate of absorber layer. The second part addresses the repairing accuracy of EUVL mask pattern. The third is the basic etching performance e.g. etching rate of Ta based absorber, Cr based buffer, and Si based capping layer. The fourth and the last evaluation is the application of the newly developed gas assisted etching process on programmed bridge defect in narrow pitched L/S patterns.

Ga implantation and interlayer mixing during FIB repair of EUV mask defects

EUV mask damage caused by Ga focused ion beam irradiation during the mask defect repair was studied. The concentration of Ga atom implanted in the multilayer through the buffer layer and distributions of recoil atoms were calculated by SRIM. The reflectivity of the multilayer was calculated from the Ga distribution below the capping layer surface. To validate the calculation, Ga focused ion beam was irradiated on the buffer layer. The EUV reflectivity was measured after the buffer layer etching process. The measured reflectivity change was considerably larger than the one predicted from the absorption of light by the implanted Ga. The large reflectivity loss was primarily due to the absorption of light by chromium silicide residue which was generated by the intermixing of the buffer and the capping layer. Both lowering of the acceleration voltage and using thicker buffer layer were found to be effective in reducing this intermixing. The reduction of the reflectivity loss by using thicker buffer layer was confirmed by our experiments. An aerial image of patterns with etching residue formed by the intermixing was simulated. When the thickness of the intermixed layer happened to be 8 nm and the size of the resulting residue was larger than 100 nm, then the impact of the estimated absorption by the residue on the linewidth of 32 nm hp line pattern became more than 5 %.

Image quality improvement in focused ion beam photomask repair system

Focused ion beam (FIB) technology has widely been adopted as a defect repair tool on photomasks for semiconductor manufacturing. In the FIB mask repair process, scanning ion image (FIB image) is used for the defect area recognition. Quality of the FIB images is one of the most important factors in order to improve the repair accuracy. Precise imaging of the small features on the photomasks, however, is a challenging subject due to the surface charge buildup induced by FIB scanning, even though simultaneous electron beam irradiation is used for the charge compensation. The authors have developed new method of the FIB scanning for better image quality. This method utilizes software accumulation of multiple images with different scan directions and results in higher peak-to-background ratio and higher contrast images with isolated mask patterns on the quartz substrate, compared to the images acquired from conventional single scanning. The images also show better uniformity and symmetry of the secondary elect...

Advanced photomask repair technology for 65-nm lithography (1)

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.

A semi-automated AFM photomask repair process for manufacturing application using SPR6300

For almost a decade Nanomachining application has been studied and developed to repair next generation of photomasks. This technique, based on Atomic Force Microscopy (AFM), applies a mechanical removing of the defects with almost negligible quartz-damage, high accuracy of the edge-placement and without spurious depositions (stain, implanted elements, etc.) that may affect the optical transmission. SII NanoTechnology Inc. (SIINT) is carrying out a joint-development project with DNP Photomask Europe S.p.A. (DPE) that has allowed the installation in DPE of the next generation state-of-the-art AFM based system SPR6300 to meet the repair specifications for the 65 nm Node. Drift phenomena of the AFM probe represent one of the major obstacles for whichever kind of nano-manipulation (imaging and material or pattern modification). AFM drift undermines the repeatability and accuracy performances of the process. The repair methodology, called NewDLock, implemented on SPR6300, is a semi-automated procedure by which the drift amount, regardless of its origin, is estimated in advance and compensated during the process. Now AFM Nanomachining approach is going to reveal properties of repeatability and user-friendly utilization that make it suitable for the production environment.

Advanced photomask repair technology for 65nm lithography (4)

Yasutoshi Itou, Yoshiyuki Tanaka, Osamu Suga *Yasuhiko Sugiyama, *Ryoji Hagiwara, *Haruo Takahashi, *Osamu Takaoka, *Tomokazu Kozakai, *Osamu Matsuda, *Katsumi Suzuki, *Mamoru Okabe, *Syuichi Kikuchi, *Atsushi Uemoto, *Anto Yasaka, *Tatsuya Adachi, **Naoki Nishida Semiconductor Leading Edge Technologies, Inc. 16-1, Onogawa, Tsukuba-shi, Ibaraki, 305-8569, Japan *SII NanoTechnorogy Inc. 36-1 Takenoshita, Oyama-cho, Sunto-gun, Shizuoka, 410-1393, Japan **HOYA Co. 1375 Kawaguchi-cho, Hachioji-shi, Tokyo, 193-8525, Japan