Silicon nitride and silicon etching by CH3F/O2 and CH3F/CO2 plasma beams

Abstract

Silicon nitride (SiN, where Si:N ≠ 1:1) films low pressure-chemical vapor deposited on Si substrates, Si films on Ge on Si substrates, and p-Si samples were exposed to plasma beams emanating from CH3F/O2 or CH3F/CO2 inductively coupled plasmas. Conditions within the plasma beam source were maintained at power of 300 W (1.9 W/cm3), pressure of 10 mTorr, and total gas flow rate of 10 sccm. X-ray photoelectron spectroscopy was used to determine the thicknesses of Si/Ge in addition to hydrofluorocarbon polymer films formed at low %O2 or %CO2 addition on p-Si and SiN. Polymer film thickness decreased sharply as a function of increasing %O2 or %CO2 addition and dropped to monolayer thickness above the transition point (∼48% O2 or ∼75% CO2) at which the polymer etchants (O and F) number densities in the plasma increased abruptly. The C(1s) spectra for the polymer films deposited on p-Si substrates appeared similar to those on SiN. Spectroscopic ellipsometry was used to measure the thickness of SiN films etched using the CH3F/O2 and CH3F/CO2 plasma beams. SiN etching rates peaked near 50% O2 addition and 73% CO2 addition. Faster etching rates were measured in CH3F/CO2 than CH3F/O2 plasmas above 70% O2 or CO2 addition. The etching of Si stopped after a loss of ∼3 nm, regardless of beam exposure time and %O2 or %CO2 addition, apparently due to plasma assisted oxidation of Si. An additional GeOxFy peak was observed at 32.5 eV in the Ge(3d) region, suggesting deep penetration of F into Si, under the conditions investigated.

Atomic layer etching of silicon nitride using cyclic process with hydrofluorocarbon chemistry

“…In the conventional etch process using CH 3 F base chemistry, the HFC layer thickness on SiN is expected to be smaller than that on Si due to the suppression of HFC layer formation by the byproducts of HCN. [21][22][23][24] However, this is observed when nitrogen in SiN and carbon in the HFC layer on SiN are interacted with hydrogen. This means that the ion energy must be sufficiently high to initiate the reaction of SiN with a HFC layer.…”

Analysis of optical emission spectroscopy data during silicon etching in SF6/O2/Ar plasma

“…The characteristics of the resulting etch, such as wafer uniformity, etch rate, and profile, can be varied by the plasma state. Various researchers have investigated the optimization of etching characteristics by combining the various etching gas mixtures to improve it [1][2][3]. The development of the through-silicon-via technology for stacked dynamic random-access memory (DRAM) revolutionized the storage capacity limitations in a restricted form factor [4].…”

Gate spacers etching of Si3N4 using cyclic approach for 3D CMOS devices

“…32) and the doublet Si-Si bonds at 99.2 and 99.8 eV. 9 Intensity of Si-O bonds increases from 23.6% to 29.8%. For Si-Si bonds intensity, it decreases from 10.6% to 1% for 120 s time process.…”

“…[3][4][5][6] or hydrofluorocarbon C x H y F z (Refs. [7][8][9][10][11][12][13][14][15] chemistries. Fluorine-rich gases such as CF 4 , C 4 F 8 , or CHF 3 with a high Si 3 N 4 etch rate of about 30 nm min −1 were investigated.…”

“…6,9,10,13,17 Oxygen helps to reduce the concentration of fluorocarbon radicals like CF x by forming volatile species such as CO, CO 2 , or COF 2 and enhance Si 3 N 4 etching. 9,10,18 Hydrogen from incident hydrofluorocarbon tends to increase the etching rate of Si 3 N 4 compared to fluorocarbon without hydrogen by the possible reaction of volatile species, such as HCN. 18,19 Moreover, it scavenges fluorine from the deposited film, reducing its fluorine content.…”