Remote plasma etching of silicon nitride and silicon dioxide using NF3/O2 gas mixtures

Abstract

The etching of silicon nitride (Si 3 N 4) and silicon dioxide (SiO 2) in the afterglow of NF 3 and NF 3 /O 2 microwave discharges has been characterized. The etch rates of both materials increase approximately linearly with the flow of NF 3 due to the increased availability of F atoms. The etch rate of Si 3 N 4 is enhanced significantly upon O 2 injection into the NF 3 discharge for O 2 /NF 3 ratios of 0.3 and higher, whereas the SiO 2 etch rate is less influenced for the same flow ratios. X-ray photoelectron spectroscopy of processed Si 3 N 4 samples shows that the fluorine content of the reactive layer, which forms on the Si 3 N 4 surface during etching, decreases with the flow of O 2 , and instead oxidation and nitrogen depletion of the surface occur. The oxidation of the reactive layer follows the same dependence on the flow of O 2 as the etch rate. Argon actinometry and quadrupole mass spectrometry are used to identify reactive species in the etching of both materials. The atomic fluorine density decreases due to dilution as O 2 is added to the discharge. The mass spectrometer did not detect NF x species (xϭ1-3) at any discharge parameter setting, which indicates the near complete dissociation of NF 3. Nitric oxide ͑NO͒ was detected by mass spectrometry, and the NO density shows the same dependence on O 2 flow as the Si 3 N 4 etch rate and the surface oxidation. Based on this observation, we propose that the etch rate enhancement for Si 3 N 4 is due to the adsorption of the NO on the Si 3 N 4 surface, followed by the formation of N 2 with a N atom from the surface. The O atom can then attach to the same surface site, contributing to the oxidation.

Cross Sections for Electron Collisions with NF3

“…NF 3 is widely used for semiconductor fabrication processes which include direct etching 2,3 , reactor cleaning 4 and remote plasma sources 5 , where use of pure NF 3 typically limits the reactants reaching the processing chamber to F x and NF x species only. NF 3 is also used in the production of thin films 6,7 and solar cells 8,9 ; it provides the initial gas for the HF chemical laser [10][11][12] .…”

A Study on the Fluorine Effect of Direct Contact Process in High-Doped Boron Phosphorus Silicate Glass (BPSG)

“…Also the n + contact resistance was gradually decreased according to the increase of Si treatment time because of the effective by-product and damaged Si surface removal and the contact area increase with the time [6]. The measured Si open sizes for n+ contacts are 80, 102 and 112nm for specimen (a), (b) and (c) in Fig.…”

Atmospheric‐Pressure Plasmas for Solar Cell Manufacturing

“…For precursor screening, a range of etching gases have been evaluated, among them those being widely used for low pressure plasma etching in microelectronics [9,10]. Table 3 summarizes the etching rates achieved under standard conditions (1 l/min (STP) etch gas + 1 l/min (STP) reactive gas).…”