Plasma etch properties of organic BARCs

Abstract

Plasma etching is an integral part of semiconductor integrated circuit (IC) processing and is widely used to produce high-resolution patterns and to remove sacrificial layers. Bottom anti-reflective coatings (BARCs) under the resist absorb light to minimize reflectivity during lithography and are typically opened during pattern transfer using plasma etching. High etch selectivity is required in the BARC opening process to minimize resist loss to allow further substrate etching. Because the plasma etch process combines physical bombardment and chemical reaction, the factors affecting etch rate and selectivity are complex. The results are related to etch conditions and the chemical nature of polymer. This paper addresses plasma etch properties as they relate to polymer type and etch gas composition. Polyacrylate, polyester, and polymers containing nitrogen and halogens have been investigated. The research was carried out by a series of designs of experiments (DOEs), which varied the flow rate of Ar, CF 4 , and O 2 in plasma gas. The selectivity of BARC to resist depends not only on the carbon content but also on the different ways polymer compositions and structures respond to an oxidizing gas, a reducing gas, and plasma bombardment. Based on a polymer decomposition mechanism, we discuss what could happen physically and chemically during the polymer's exposure to the high-energy reactive plasmas. We also modified the Ohnishi parameter for the polymers containing nitrogen and halogen using our polymer decomposition theory. The contribution of nitrogen and halogen in the etch equation can be positive or negative depending on the chemical properties of the plasma.

Electron Beam Lithography Using Highly Sensitive Negative Type of Plant-Based Resist Material Derived from Biomass on Hardmask Layer

“…The Ohnishi parameter is a popular empirical correlation that relates the atomic composition of the polymer, in particular, the number of carbon and oxygen atoms. 9,10) The Ohnishi parameter was calculated according to…”

Understanding etch properties of advanced chemically amplified EUV resist

“…In earlier studies, incorporation of halogen atoms, specifically fluorine and bromine into polymers was found to induce slower etch rate under O2 oxidizing gas and faster etch rate under CF4 reducing gas. 3,4 However, a literature review revealed that there is very limited work done to understand the effect of iodine elements on etch properties of advanced EUV resist. Figure 2 shows the etch rate results of 3 different formulations (Resist-1, Resist-2, and Resist-3) under O2 (Figure 2-A) and CF4 (Figure 2-B) plasma etch conditions plotted with adjusted Ohnishi Parameter (OP) on the x-axis.…”

“…The surface fluorine content change before and after CF4 plasma etching is in an agreement with the earlier result reported by Huang and Weigand. 3 It is believed that during CF4 etching, fluorine replaces hydrogen or substitutes other groups to form a protective film on the organic (resist) surface. 3,6 It is important to note that XPS results confirm that Resist-3 contains the highest iodine content, followed by Resist-2 and Resist-1 at 0 sec etching time (Figure 7-D).…”

“…3 It is believed that during CF4 etching, fluorine replaces hydrogen or substitutes other groups to form a protective film on the organic (resist) surface. 3,6 It is important to note that XPS results confirm that Resist-3 contains the highest iodine content, followed by Resist-2 and Resist-1 at 0 sec etching time (Figure 7-D). At longer CF4 etching time, iodine % appeared to behave differently for each resist.…”

Optimization of Etch Process for Ultra-Narrow Via in 3D NAND Flash Memory by DOE Method

“…It is so-called ultra-narrow via in 3D NAND flash. In the industry, anti-reflective coating (ARC) etching of ultra-narrow via usually uses CF 4 , Ar, O 2 , CHF 3 , CO, Cl 2 [5][6][7] etc. CO 2 , COS, O 2 , C 4 F 8 , SF 6 , Ar etc., are usually used during hard mask etching.…”