The features of optical proximity correction are becoming very aggressive as production technology migrates into 90nm/130 nm regime. The complicated optical proximity correction (OPC) patterns often result in un-repairable defects, a major yield loss mechanisms in a mask production line. Defect control is increasingly important.
A methodology for identifying defect sources and reduction is demonstrated in this paper. The mechanisms and causes of defect formation could be determined with corresponding process step on the strength of sequence inspections. The cause of half-etched opaque defect on negative CAR process was found from PR fragment contamination of e-beam exposure step. After clean-up of e-beam chamber, yield was increased over 20%. Big pinhole defect and contact of AttPSM positive process was found on ADI step. The possible cause was poor CAR adhesion. These two type defects were decreased by modification of developing recipe, special on rinse step. Design experiment with Taguchi method was used to optimize the interactive recipe of plasma descum and rinse step on developing step of implanted layer. Average defect density was decreased from 0.99 to 0.27, and percentage of zero defect rate has been increased from 29.5 to 63.3%.
AlSi-based films could be formed by a combination of transparent chemical compositions and absorbing elements. When the oxide structure increased with the increasing of atomic percentage of oxygen, the n of AlSixOy appeared to increase while k appeared to decrease in 193 nm. The saturation of formation of AlN and Si3N4 in AlSixNy was observed about 4.8 sccm N2 flow rate. The correlation between optical properties and chemical compositions of AlSi-based films has been described, therefore, the chemical stability of embedded material could be approached. Top layer film with saturation of AlN, Si3N4 or Al2O3, SiO2 could provide better chemical stability. Bottom layer with suitable mount of Al and Si chemical structure could provide enough light absorption. With proper combination of top and bottom layer AlSixOy and AlSixNy embedded material, the optical properties of bi-layer attenuated phase-shifting mask could kept in the range of high transmittance. The 0.18-micrometers -line/space NEB-22 resist pattern exposed by e-beam writer on AlSixOy embedded layer has good resolution. Due to good resist profile, the 0.3-micrometers -line/space etched pattern of bi-layer AlSixOy was also successfully carried out.
Compared to normal transmittance attenuated phase-shifting mask (AttPSM), the higher transmittance AttPSM in clear-field masks has higher electric field amplitude with 180 degrees phase-shift for 0.1 micrometers isolated line. Due to the stronger interference with the higher electric field amplitude under the edge of line pattern with 180 degrees phase-shifting, the resolution of aerial image of 0.1 micrometers isolated line increased with the increasing of transmittance. Under dipole illumination (sigma) c 0.6 and (sigma) r 0.3, and NA 0.75, the T percent of AttPSM about 22 percent could provide the better normalized image log-slope of 0.1 micrometers isolated and semi-dense line pattern at focus -0.10 micrometers . When the layout of the 0.1 micrometers pitch and isolated contact pattern is designed as a dark-tone mask, the contrast of the aerial image increased with increasing T percent of AttPSM. The side-lobe could be avoided under the design of dark-tone mask. However, if the contact pattern is designed as a dark-tone mask, a negative resist is necessary. The combination of dark-tone mask, high-transmittance AttPSM and negative resist could provide better contrast of the aerial image and resolution of the 0.1 micrometers contact-hole pattern in 193 nm lithography.
Abstract-Five materials which are PdSixOy, CrAlxOy, SiNx, TiSixNy, and TiSixOyNz as absorptive shifters for attenuated phase-shifting mask in 193 nm wavelength lithography are presented. PdSixOy films were deposited by dual e-gun evaporation. CrAlxOy, TiSixNy and TiSixOyNz films were formed by plasma sputtering and SiNx films were formed with LPCVD. All of these materials are shown to be capable of achieving 4 percent - 15 percent transmittance in 193 nm with thickness that produce a 180 degrees phase shift. Under BCl3:Cl2 equals 14:70 sccm; chamber pressure 5 mtorr and RF power 1900W, the dry etching selectivity of TiSixNy over DQN positive resist and fused silica, were found to be 2:1 and 4,8:1 respectively. An embedded layer TiSixNy with 0.5 micrometers line/space was successfully patterned.
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