Silicon etching in NF3/O2 remote microwave plasmas

Abstract

A model for Si, SiCH, Si O 2 , SiOCH, and porous SiOCH etch rate calculation in inductively coupled fluorocarbon plasma with a pulsed bias: Importance of the fluorocarbon layer High density fluorocarbon etching of silicon in an inductively coupled plasma: Mechanism of etching through a thick steady state fluorocarbon layerThe etching of silicon in remote microwave discharges fed with NF 3 /O 2 has been investigated. In situ ellipsometry and x-ray photoelectron spectroscopy ͑XPS͒ were used to monitor surface effects, while mass spectrometry was used to monitor the gas phase dynamics. Varying the microwave power from 600 to 1400 W has little effect, due to the near complete dissociation of the NF 3 , even at lower powers. For discharges containing pure NF 3 , the poly-Si etch rate increases linearly with NF 3 flow. When a low proportion of O 2 (O 2 /NF 3 ϭ0.1) is added to the discharge, the etch rate increases quickly to its maximum of ϳ700 nm/min. With further O 2 addition, this etch rate decreases below that observed for pure NF 3 processing. The fluorine concentration in the processing region decreases for all O 2 additions by a dilution effect. For pure NF 3 discharges, XPS measurements reveal 1-2 nm thick, highly fluorinated reaction layers with a gradual loss of fluorine content as the NF 3 flow is increased. Specimens processed with both NF 3 and O 2 show much less surface fluorination that decreases with increasing O 2 content in the feed gas. At the etch rate maximum, the observed N (1s) signal is also maximized. The reaction layer thickness increases with added O 2 and continues to more than 10 nm at O 2 :NF 3 ratios greater than unity. We discuss the enhanced reactivity of the modified Si surface and compare our results with the role of admixed N 2 into the CF 4 /O 2 system. We also injected NO directly into the effluent of NF 3 and CF 4 /O 2 discharges. For fluorine rich discharges, NO removes the modified surface layer on Si and provides for an enhanced etch rate. In the oxygen rich regime, NO injection can increase both the etch rate and the reaction layer thickness. We will present a mechanism for the enhanced etching of Si in the presence of fluorine, oxygen and the NO molecule.

A novel silicon heterojunction IBC process flow using partial etching of doped a‐Si:H to switch from hole contact to electron contact in situ with efficiencies close to 23%

“…Therefore, we suggest that it could be the local presence of O 2 in these areas that could be hampering the etching reaction at the a‐Si:H surfaces in the open finger areas. The suppression of silicon etching because of the presence of O 2 by forming an oxide‐like layer on the reaction surface has been reported previously . Nevertheless, further investigation is needed to unravel the mechanisms leading to the observed etch rate differences.…”

“…The suppression of silicon etching because of the presence of O 2 by forming an oxide-like layer on the reaction surface has been reported previously. 36 Nevertheless, further investigation is needed to unravel the mechanisms leading to the observed etch rate differences. Importantly, it should be noted that the etch rate differences are not drastic and the spatial non-uniformity during the etching of approximately 22 nm of a-Si:H is only approximately 1 nm, ie, < 5% variation.…”

Role of N2 during chemical dry etching of silicon oxide layers using NF3/N2/Ar remote plasmas

“…The chemical dry etching of silicon nitride [1,2,4,9], silicon [3][4][5]7,8], and silicon oxide layers [1,2,7] has been investigated in downstream remote plasmas containing perfluorocarbons (PFCs) or nitrogen trifluoride (NF 3 …”

“…The chemical dry etching of thin film materials in semiconductor manufacturing has been widely used for removing the layers, while minimizing the ion-induced damage to the adjacent active layers and the erosion of the chamber materials [1][2][3][4][5][6][7][8][9]. The chemical dry etching of silicon nitride [1,2,4,9], silicon [3][4][5]7,8], and silicon oxide layers [1,2,7] has been investigated in downstream remote plasmas containing perfluorocarbons (PFCs) or nitrogen trifluoride (NF 3 …”

Comparison of Properties of Atmospheric-Pressure Radio Frequency He/SF6/O2and He/CF4/O2Discharges

“…Therefore, there have been extensive experimental and theoretical studies of lowpressure discharges containing such fluoride compounds. [1][2][3][4][5][6][7][8][9] In practice, fluoride compound gas discharges in a mixture with O 2 , rather than pure fluoride compound gas discharges, are commonly used in the semiconductor industry for etching SiO 2 and removing films deposited on a reactor surface, because O 2 addition is essential for controlling the production of radicals and for improving selectivity in etching. It is well known that the addition of O 2 to fluorocarbon gas plasmas can increase the density of fluorine atoms owing to the oxidation of CF x (x ¼ 1{ 3) radicals.…”