Low temperature dry etching of chromium towards control at sub-5 nm dimensions

Abstract

Patterned chromium and its compounds are crucial materials for nanoscale patterning and chromium based devices. Here we investigate how temperature can be used to control chromium etching using chlorine/oxygen gas mixtures. Oxygen/chlorine ratios between 0% and 100% and temperatures between -100 °C and +40 °C are studied. Spectroscopic ellipsometry is used to precisely measure rates, chlorination, and the thickness dependence of n and k. Working in the extremes of oxygen content (very high or very low) and lower temperatures, we find rates can be controlled to nanometers per minute. Activation energies are measured and show that etch mechanisms are both temperature and oxygen level dependent. Furthermore, we find that etching temperature can manipulate the surface chemistry. One surprising consequence is that at low oxygen levels, Etching rates increase with decreasing temperature. Preliminary feature-profile studies show the extremes of temperature and oxygen provide advantages over commonly used room temperature processing conditions. One example is with higher ion energies at -100 °C, where etching products deposit.

Atomic layer deposition for spacer defined double patterning of sub-10 nm titanium dioxide features

“…We are currently tuning the carbon etching to reduce this effect. The TiO 2 structures in figure 5(c) could be used directly as the structural template material, or alternatively transferred to the underlying chromium layer using chlorine and oxygen gas mixture plasma [30].…”

“…Here we use PS-b-PMMA with 30 nm starting pitch. From previous research, we demonstrated nanoscale etching of relevant materials for imprint template fabrication at sub-10 nm dimensions [29][30][31][32][33]. We build on this experience to identify a material stack with coordinated selectivities for high resolution pattern transfer in the SDDP process.…”

Etching of iron and iron–chromium alloys using ICP-RIE chlorine plasma

“…Curtis et al [44] studied the evolution of Cr etching by varying the percentage of O 2 in CCl 4 /O 2 mixtures and observed a maximum of chromium etch rate for 50 %O 2 . Staaks et al [45,46] performed etching of Cr by using Cl 2 /O 2 plasma, observing a maximum of etch rate for 20-40 %O 2 . By studying the substrate temperature impact, they showed a strong increase in etch rate, from 5 to 40 nm/min when the substrate temperature increased from -80 o C to 40 o C. This evolution can be due to chemical etching of Cr.…”

Cr and CrOx etching using SF6 and O2 plasma

“…The plasma etching of Cr is currently almost exclusively reserved for chlorine-oxygen-based chemistry by forming chromyl chloride (CrO 2 Cl 2 ) as the final etch product. [29][30][31][32][33][34][35][36][37][38][39][40][41] The consensus is that both chlorine (e.g., Cl 2 plasma) and oxygen radicals (e.g., O 2 plasma) are needed to create the volatile chromyl chloride product. It was demonstrated by Abe et al 29 roughly 45 years ago and a few years later explained by Nakata et al 30 As both O and Cl radicals are needed to remove a Cr atom, possibly allowing any intermediate CrO x Cl y reaction path, the etch rate (ER) shows an optimum for a specific ratio between the supplied Cl 2 and O 2 gas.…”

“…This ratio is typically around 30% O 2 in the Cl 2 + O 2 mixture, but depends on the temperature and other plasma parameters. 33,40 Indeed, at low O 2 content, the formed CrCl x species have a very high melting temperature (CrCl 2 and CrCl 3 ) or simply decompose (CrCl 4 ). At high O 2 concentrations, the CrO x species are difficult to evaporate as well.…”