3성분계 위상 반전 블랭크마스크용 박막 특성 연구

Abstract

According to the shrinkage of critical dimension (CD), high resolution is acquired by the exposure wavelength of optical lithography has been decreasing down to 193 nm. Therefore, the semiconductor industry has been studied the novel technology to increase the degree of integration in circuits. Phase shift masks (PSMs) are one of the resolution enhancement techniques (RET) used extensively in the semiconductor processing to improve the resolution, process latitude and pattern fidelity of optical lithography. In particular, single layer half-tone phase shift masks (HT-PSMs) are a very useful technology without restrictions in the manufacturing and patterning process and have been proved to be the most practical one among various types of PSMs, especially from the standpoint of mask manufacturing. Especially, molybdenum silicon nitride (MoSiN) seems to be the most practical material. Therefore, MoSiN has generally been used as PSM materials. However, transmittance variation and chemical durability problems have been reported and these changes in characteristics are an issue for yield drop in semiconductor device manufacturing. To manufacture PSM, sulfuric acid peroxide hydrogen mixture (SPM) and standard cleaning-1 (SC-1) cleaning processes are must be applied several times for the removal of the particles, so the PSM materials must have durability for SPM and SC-1 chemicals to keep the specification of the PSM such as phase shift and transmittance characteristics. on the other hand, MoSiN shows weak durability for cleaning chemicals such as SPM and SC-1 for removal of particles to meet the required criteria in the ArF lithography. For SPM and SC-1 chemicals, MoSiN PSM shows a 1.1 °, 8.4 ° of phase shift angle change and a 0.11 %, 1.02 % of transmittance change, respectively. Also, in order to embody high resolution at 32 nm and below, MoSiN PSM for ArF lithography is essential. It is also generally beneficial to use this material in the ArF lithography process. On the other hand, the second problem is that MoSiN shows weak exposure durability for ArF excimer laser irradiation. That is the oxidation phenomenon in the MoSiN thin film occurred by the diffusion of the oxygen by the ArF excimer laser exposure. This oxidation phenomenon makes change thin film materials change such as from the MoSiN thin film to MoSiON thin film by the O2 and H2O in the air during the ArF excimer laser irradiation. From the results, 0.36 % of the transmittance was changed by 193 nm irradiation with 12 kJ of exposure energy. Accordingly, MoSi thin film characteristics were degraded by the ArF laser irradiation. Finally, thirdly, the defect control of the PMSs became even more critical for semiconductor production. However, a new kind of defect called haze became an issue that is caused by photoreaction. This defect is caused by the photoreaction of chemical residues such as SO42-, NH4+ which are generated from the SPM and SC-1 in the photomask cleaning process and other chemicals by the 193 nm irradiation. The ion chromatography (IC) and gas chromatography-mass spectrometry (GC/MS) were used to confirm the ion and volatile organic compound (VOC) concentration on the surface of MoSiN PSM. Also, haze defects were inspected after exposure in order to evaluate the difference in the haze generation mechanism on the surface of MoSiN PSM through the microscopy. As a result, VOC concentration on MoSiN PSM surface was 227.5 ppbv and 2145.2 ppbv for SPM and SC-1 process. Also, number of haze defects on MoSiN PSM’s surface was 97 ea/cm2 at 12 kJ of exposure energy. In this work, Ta doped MoSiN (MoTaSiN) PSM has been investigated and its characteristics have been evaluated to solve out the unstable thermodynamic characteristic of the molybdenum silicide thin film. At first, MoTaSiN was chosen as ternary compound material and deposited on 152 x 152 x 6.35 mm synthetic fused silica substrate by DC reactive sputtering. Also, many kinds of materials are investigated such as W, Ti, Ge, Zr, Hf, In and Al to verify the superior characteristic of the Ta. Chemical and exposure durability properties in MoTaSiN were studied for SPM and SC-1 chemicals. Its characteristics had been evaluated number of haze defects for 193 nm irradiation with 12 kJ to investigate the relationship between the exposure energy and the durability. Transmittance and phase shift for MoTaSiN was 5.83 % and 178 ° at 193 nm of the exposure energy, respectively. MoTaSiN PSM showed superior chemical durability compared to MoSiN PSM under all other evaluation conditions. In the transmittance change after the ArF laser irradiation, MoTaSiN PSM shows 0.21 % of the transmittance change and this is 70 % of the improvement compared to MoSiN PSM. The result of exposure durability showed 0.24 % of transmittance change at 12 kJ. As a result, VOC concentration on MoTaSiN PSM’s surface was 43.1 ppbv and 309.1 ppbv for SPM and SC-1 process, respectively. Also, number of haze defects on MoSiN PSM surface was 20 ea/cm2 at 12 kJ of the exposure energy. Various analysis methods are applied such as X-ray diffractometer (XRD), Auger Electron Spectroscopy (AES), Field Emission Scanning Electron Microscopy (FE-SEM) to get conclusion. Density and contact angle of PSM using X-ray reflectometry (XRR) indicate that the MoSiN and MoTaSiN were obtained the various characteristics. Overall, the MoTaSiN PSM has considerable potential as excellent PSM blankmask and photomask in the manufacturing of the semiconductor circuit.