Infinitely high selective inductively coupled plasma etching of an indium tin oxide binary mask structure for extreme ultraviolet lithography

Abstract

Currently, extreme ultraviolet lithography (EUVL) is being investigated for next generation lithography. Among the core EUVL technologies, mask fabrication is of considerable importance due to the use of new reflective optics with a completely different configuration than those of conventional photolithography. This study investigated the etching properties of indium tin oxide (ITO) binary mask materials for EUVL, such as ITO (absorber layer), Ru (capping/etch-stop layer), and a Mo–Si multilayer (reflective layer), by varying the Cl2/Ar gas flow ratio, dc self-bias voltage (Vdc), and etch time in inductively coupled plasmas. The ITO absorber layer needs to be etched with no loss in the Ru layer on the Mo–Si multilayer for fabrication of the EUVL ITO binary mask structure proposed here. The ITO layer could be etched with an infinitely high etch selectivity over the Ru etch-stop layer in Cl2/Ar plasma even with a very high overetch time.

Origin of defects on targets used to make extreme ultraviolet mask blanks

“…[1][2][3][4][5] A critical area in the production of these masks is the detection and reduction of defects on these masks 6 which can affect the whole production process. They have high normal incidence reflectivity in the EUV spectral range and are the focusing and imaging components in EUV lithography.…”

Effects of hydrogen-damaged layer on tin-doped indium oxide etching by H2/Ar plasma

“…Halogen-based species are generally used as source gases for the etching of conventional materials. [7][8][9][10][11] However, the halogen-containing reaction by-products of indium have boiling points of 700-800 °C, which cause difficulties during dry etching. 12) The other issue is the low etch selectivity to the photoresist mask on ITO pattern etching.…”