Shuichiro Kanai

Development of a MoSi-based bilayer HT-PSM blank for ArF lithography

HT-PSM has been adopted for semiconductor industry since i-line lithography. We introduced MoSi-based HT-PSM blanks for i-line and KrF lithography. Today they have become popular material and been established mask process widely. Thus it will be convenience for many mask users that MoSi-based HT-PSM could expand to ArF lithography. We have been developing double-layer MoSi HT-PSM blanks, as same structure of KrF. We developed new sputtering method for this expansion to get smaller extinction coefficient with comparatively large refractive index at 193nm. We got following data for T6% MoSi ArF HT-PSM blanks. (1) Table 1 shows typical optical properties of T6% MoSi HT-PSM blanks for ArF. (2) Fig.1 shows a spectroscopic transmittance and reflectance properties of a sample with T=6%(at 193nm: air ref.). In this case, its transmittance of 365nm(that is a wavelength of pattern inspection) is under 40%. It shows that mask users do not need any special inspection systems. In fact, we confirmed our HT-PSM with 40% (at 365nm) was able to be inspected by a KLA-300 series UV. (3) Fig.2 shows chemical durability data. Basically MoSi film has good durability for acid (SPM: 80C H2SO4+H2O2 4:1), and slightly poor durability for alkaline (SC-1: RT. NH4OH+H2O2+H2O 1:1:4). However this 6% film has good enough durability for alkaline, as seen in Fig.2, it changed less than +/- 0.05% of transmittance (at 193nm) and -0.5 degree of phase value (at 365nm). It is evaluated same durability as our HT-PSM for KrF. (4) Table 2 shows ArF laser irradiation durability. In the air, after 10 kjoule/cm2 irradiation (estimated for one year exposure in an ArF stepper), transmittance changed less than -0.3% and phase value less than -2 degree. It seems good enough irradiation durability. (5) Fig.3 shows a typical pattern profile of the T6% MoSi ArF HT-PSM. It was processed by MERIE system (ULCOAT Dry Etcher: MEPS-6025) with CF4+O2 at 6.8Pa, 100W(0.11W/cm2), 80Gauss rotating magnetic field. The profile has more than 85 degree without

Quartz 9-inch size mask blanks for ArF PSM (Phase Shift Mask)

Semiconductor technology nodes are steadily miniaturizing. On the other hand, various efforts have been made to reduce costs, mass production lines have shifted from 200 mmφ of Si wafer to 300 mmφ, and technology development of Si wafer 450 mmφ is also in progress. As a photomask, 6-inch size binary Cr mask has been used for many years, but in recent years, the use of 9-inch binary Cr masks for Proximity Lithography Process in automotive applications, MEMS, packages, etc. has increased, and cost reduction has been taken. Since the miniaturization will progress in the above applications in the future, products corresponding to miniaturization are also desired in 9-inch photomasks. The high grade Cr - binary mask blanks used in proximity exposure process, there is a prospect of being able to use it by ULVAC COATING CORPORATIONs tireless research. As further demands for miniaturization, KrF and ArF Lithography Process, which are used for steppers and scanners , there are also a demand for 9-inch size Mask Blanks. In ULVAC COATING CORPORATION, we developed a 9 - inch size KrF PSM mask Blanks prototype in 2016 and proposed a new high grade 9 - inch photomask. This time, we have further investigated and developed 9-inch size ArF PSM Mask Blanks corresponding to ArF Lithography Process, so we report it.

New structure of ArF high-transmittance attenuated phase-shifting mask with dry etching process

ULVAC Coating Corporation proposes a new ArF high transmittance attenuated mask which consists of a thin MoSiON film and a quartz trench. We made an appropriate thickness MoSiON film and found a proper dry etching condition to dig a quartz trench by a NLD dry etcher. The etched quartz trench had very smooth bottom and correct depth. It is very difficult to make ArF high transmittance attenuated mask with perfectly satisfy the transmittance and phase shift angle because of characteristics of MoSiON film. PSM with MoSiON film has been used commercially under 248nm and 193nm wavelength. If it is possible to use the current MoSiON film also for ArF high transmittance attenuated mask making, it would be very convenient for mask makers. This report will show our investigation results in regards to the possibility of making ArF high transmittance attenuated mask by using current MoSiON film with setting the transmittance of 15% at 193nm wavelength and setting the phase shift angle of 180 degree by MoSiON film and quartz trench etching. NLD (Magnetic Neutral Loop Discharge) mask etcher was used for this investigation. At conventional conditions, a large side etch was observed on the MoSiON film as a result of the etching process. We checked correlation between gas pressure and side etch, and found lower pressure resulted in smaller side etch. As the further low pressure, appearance of sub-trench were observed. By adding a CxFy gas with CF4-base etching gas for the dry etching process, we are able to improve the side etching and also sub-trench.