As the design rule of the semiconductor devices approaches to 90nm node technology, the defect controllability of the photomask becomes critical success factor. The halftone defects generated in photomask cannot be easily judged because the results of Aerial Image Measurement System (AIMS) are flexible with the defect size and
transmission. Also, the printability of halftone defect on wafer is not clear because of low sensitivity of inspection system for pinholes. In this paper, halftone defects with programmed size were fabricated by Focused Ion Beam (FIB) repair tool. We evaluated the transmission correlation of the halftone defects between printability with 248nm simulation tool and inspection machine with 365nm light source. We could make the judgment criteria of halftone defects captured by inspection machine without AIMS result from this correlation result. Inspection machines such as KLA-Tencor and Lasertec are used to verify the detectability of halftone defects. Wafer printability was simulated using AIMS fab 248. Even though the transmission of halftone defects is same, the energy intensity of large size defects is higher than that of small size.
In Embedded Attenuated PSMs(Phase Shift Masks), chrome residues on MoSiON, especially at the edge of a pattern, should be decreasing the phase-shift effect and it must be also causing CD(critical dimension) variations in a wafer-process. Chrome residues on MoSiON are well known being generated at second level lithography or according to performance of cleaning process before it. In this paper, we investgated the influence of treatment on Cr surface during MoSiON etch process using CF4 plasma and proposed the optimum treatment procedure to reduce the Cr residues originated form re-deposition of carbon-contained polymers in CF4 plasma.
The semiconductor industry continuously shrink the linewidths and the smaller linewidths are easily affected by the defects. The defects have to be detected to prevent printed images on wafers. This paper will present the detection capability of current inspection machines for chrome defects on attenuated MoSiN layer and simulation results for the effect of chrome defect on attenuated layer. Two inspection machines based on i-line light source were used for comparison of detection capability for chrome defect on attenuated layer. The effect of chrome defect on attenuated MoSiN layer was evaluated with MSM 100 at 248 nm wavelength.
Increasing complexity, smaller design rule and development of PSM (Phase Shift Mask) are required more precise photomask repair technology. Recently, It is important unit process to enhance yield, production time and delivery in 130nm node below mass production. Furthermore, opaque defects are on the increase compare to clear defects using dry process. Therefore key issue of advanced repair technology is opaque defects removal and edge placement accuracy control. In this paper, we will discuss opaque repair technology of 90nm node EA-PSM to get improved edge placement using FIB (Focused Ion Beam) machine. Firstly, we started with a concept of low ion beam current at 30keV acceleration voltage. To optimize image quality in low beam current, we have changed suitable scan parameters in target FOV (Field Of View) and checked scan damage in these parameters with AIMS. Secondly, we have applied a reregistration function to enhance edge placement control and analyzed edge placement variation by CD-SEM and AIMS tool after pattern drift. Thirdly, transmission of repaired region was confirmed with AIMS and inspection tool.
A method of PSM cleaning has been developed and its cleaning performance was studied by changing H2SO4 / H2O2 mixture(SPM) and diluted standard cleaning-1 (SC-1) chemical ratio and controlling phase and transmittance of KrF HT PSM, within ±3° and ±0.3 percent respectively. The type of residue was scrutinized using KLA-Tencor SL3UV and scanning electron microscopy (SEM) during stepwise process and cleaning. X-ray photoelectron spectroscopy (XPS) was also employed to characterize the residues on the HT PSM surface. Diluted HF (DHF) and DHF/H2O2 mixture (FPM) were introduced to etch off the remaining defects on quartz after MoSiON dry etch process and also compared their results with the gas assisted etching (GAE) repair. It has turned out that DHF, FPM and GAE repair removed the remaining defects on quartz respectively. Our results demonstrate that approach of stepwise process inspection is very effective at identifying defects and their sources as they become evident at different process steps. Finally it was shown that diluted SC-1 with quick dump method followed by the direct displacement IPA dry is promising for the improvement of HT PSM cleaning efficiency and its residual impurities and causes no damage on the MoSiON surface. It is found that efficient and effective conventional chemical treatment, direct displacement IPA dry and GAE repair would be considered to be the integrated sequence to control the smallest particles for the HT PSM.
As photomask making procedures extend to more and more complex and difficult, the detected numbers of the quartz defects are increasing trend. These kinds of defects have been less detected frequently or not detected before. But, it can be found enough now because inspection machines are developed high resolution, short wavelength light source and low pixel size to find small size defects. Defect shapes and sizes detected by inspection machine are evaluated and classified to several types with SEM and then analyzed the wafer printing result with transmission data of the inspection and AIMS simulation result. By this analyzed result, the judge reference of the quartz defect was provided when the defect was detected by inspection machine during producing photomask. This will improve mask yield by reducing mask reject ratio classified blank mask defect problems.
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