Investigation of SiO2 Etch Characteristics by C6F6/Ar/O2 Plasmas Generated Using Inductively Coupled Plasma and Capacitively Coupled Plasma

Abstract

The etching properties of C6F6/Ar/O2 in both an inductively coupled plasma (ICP) system and a capacitively coupled plasma (CCP) system were evaluated to investigate the effects of high C/F ratio of perfluorocarbon (PFC) gas on the etch characteristics of SiO2. When the SiO2 masked with ACL was etched with C6F6, for the CCP system, even though the etch selectivity was very high (20 ~ infinite), due to the heavy-ion bombardment possibly caused by the less dissociated high-mass ions from C6F6, tapered SiO2 etch profiles were observed. In the case of the ICP system, due to the higher dissociation of C6F6 and O2 compared to the CCP system, the etching of SiO2 required a much lower ratio of O2/C6F6 (~1.0) while showing a higher maximum SiO2 etch rate (~400 nm/min) and a lower etch selectivity (~6.5) compared with the CCP system. For the ICP etching, even though the etch selectivity was much lower than that by the CCP etching, due to less heavy-mass-ion bombardment in addition to an adequate fluorocarbon layer formation on the substrate caused by heavily dissociated species, highly anisotropic SiO2 etch profiles could be obtained at the optimized condition of the O2/C6F6 ratio (~1.0).

High‐aspect‐ratio oxide etching using CF4/C6F12O plasma in an inductively coupled plasma etching system with low‐frequency bias power

“…Meanwhile, O radicals formed in plasma are known to play a role in removing the CF x polymer layer. [4] As expected in Figure 5, as the C 6 F 12 O gas ratio increased, the density of the O radical seems to be increased. This indicates that there is a possibility of worsening etch selectivity with the ACL material.…”

“…Considering the fact that all HAR oxide etching processes have been performed with the RIE system and that the HAR oxide etching process cannot be successfully performed with the ICP system, the vertical etched profile extracted using the ICP system is notable. [4,[18][19][20] The vertical etched profiles of SiO 2 dielectrics confirm that HAR oxide etching processes can be performed in ICP etch systems using C 6 F 12 O liquid gas chemistry. Meanwhile, a slight necking phenomenon is observed in Figure 1c, compared with Figure 1d, which exhibits almost no necking.…”

“…This is because the ICP system of 13.56 MHz bias power has a lower DC bias voltage (V DC ) than that of the RIE system. [ 4 ] Owing to this low V DC , as the aspect ratio increases, a vertical etched profile is not formed in the HAR oxide etching process by ICP the etching system. This occurs despite the fact that the ICP processing pressure is lower than that of the RIE system and the mean free path of the ICP system is greater than that of the RIE system.…”

Effect of heavy inert ion strikes on cell density-dependent profile variation and distortion during the etching process for high-aspect ratio features

“…Nevertheless, most previous studies, especially in the computational area, have focused only on the problems induced by vertical scaling technology, not lateral scaling, especially in the HARC etching process. 8,9,[12][13][14][15] In this article, we address cell density-dependent feature-to-feature variation and distortion induced by lateral scaling, i.e., more holes between slots, during the HARC etching process for the first time. Moreover, the effects of heavy inert ions that incident into the feature of unpreferred etching profiles are investigated.…”

Analysis of formation mechanism of deposited film in a high-aspect-ratio hole during dry etching using fluorocarbon gas plasmas

“…4,5) In addition, to improve the selectivity and etch rate, research on etching using various FC gases with different compositions and structures such as CF 4 , C 2 F 6 , C 2 F 4 , C 3 F 6 , C 4 F 6 , C 4 F 8 , C 5 F 8 , and C 6 F 6 has been conducted. [6][7][8][9][10][11] In the RIE process with FC gas, a suitable thickness of amorphous-CF x (a-CF x ) film deposited on the mask or sidewalls of the hole by CF x radicals plays an important role in protecting the structures from ion bombardment, leading to high selectivity and reduction of side etching. Nevertheless, it has been reported that excessive or lack of a-CF x film deposition leads to various hole profile issues, such as bowing (increased hole diameter near the middle of a hole [12][13][14] ), distortion, 15,16) and striation (vertical scratches on the sidewall 17) ).…”