Porous SiOCH, SiCH and SiO₂ Etching in High Density Fluorocarbon Plasma with a Pulsed Bias

Abstract

The effect of radio frequency bias pulsing on porous SiOCH, SiCH and SiO2 etching using inductively coupled fluorocarbon plasmas was investigated. It was found that pulse frequency had only a small influence on material etch rates. However, pulse duty cycle, defined as the time during which a bias is applied over the total period, clearly modified etch rates and selectivities. Indeed, etch selectivities between porous SiOCH and SiCH or SiO2 were considerably improved when the duty cycle was decreased. This enhancement was associated with relatively high porous SiOCH etch rates, and pattern transfers under low duty cycle conditions proved to be successful. To better understand the pulse process, surface analysis was also realised. According to XPS analysis, the material surface structure was found to be similar after etching in continuous or in pulsed mode. However, fluorocarbon species on material surfaces were fluorine richer after etching in the pulsed mode.

Pulsed plasma etching for semiconductor manufacturing

“…It was concluded that pulsing the RF bias did not offer any selectivity advantages compared to CW plasma. Raballand et al [120] studied etching of SiOCH (a low-k dielectric), SiCH (an etch stop layer) and SiO 2 (a masking layer) in CHF 3 ICP with pulsed bias (1500 W source power, 40 sccm flow and 5 mTorr pressure). In accordance with Schaepkens et al [119], they observed that the etching rate of porous SiOCH was independent of PRF, in the range 1 Hz to 10 kHz investigated, but depended on duty ratio.…”

A global model for C4F8plasmas coupling gas phase and wall surface reaction kinetics

“…Plasmas of perfluorocyclobutane (c-C 4 F 8 , symbolized hereafter as C 4 F 8 ) and mixtures of C 4 F 8 with Ar, O 2 and H 2 have been widely used in the area of dielectric etching in microelectronics fabrication. In particular, they have been used for the etching of SiO 2 [1][2][3] and have been tested [4][5][6] for the etching of low-k and porous materials together with other fluorocarbon (fc) gases, such as CF 4 , CHF 3 and C 2 F 6 [7,8]. C 4 F 8 has been also used for plasma enhanced chemical vapour deposition of fc films [9][10][11], which are exploited either as low-k films or in bio-fluidic applications [12].…”

H atom surface loss kinetics in pulsed inductively coupled plasmas

“…The guard ring avoids edge effects and maintains a flat sheath above the disc. Figure 7 shows the biasing of the probe [17]. The disc and guard ring are biased at −60 V in order to repulse all electrons.…”