Characterization of residues formed by anhydrous hydrogen fluoride etching of doped oxides

Abstract

The byproducts in residue layers produced after etching doped oxide films with anhydrous hydrogen fluoride (HF) in a commercial gas phase wafer processing tool operated at atmospheric pressure and 55 °C have been characterized using transmission Fourier transform infrared (FTIR) spectroscopy. Approximately 4000 Å was etched from the borophosphosilicate glass (BPSG), borosilicate glass (BSG), and phosphosilicate glass (PSG) films, creating a condensed layer on the oxide surfaces during etching. The primary etching products in the condensed layer on BPSG were found to be a mixture of boric acid B(OH)3, phosphoric acid H3PO4, and water. The etching products in the residue on PSG were H3PO4 and water. The reaction of boric oxide (B2O3) crystallites with water to produce B(OH)3 is thermodynamically favorable and should react further to boron trifluoride BF3 in the presence of HF. The formation of B(OH)3 rather than BF3 in the etching residue on BPSG indicates that a kinetic limitation exists due to either the relatively low HF exposure used or the chemistry within the mixed acid film. The etching product in the residue on BSG, which was exposed to a higher HF flux, was primarily boron trifluoride dihydrate BF3⋅2H2O. The condensed layer supports the etching of the Si–O matrix by concentrating the HF and water reactants close to the surface, which explains the enhancement in the etching rate when a condensed layer is formed. The etching products identified by FTIR could also play a direct role in the etching reaction since hydroxyl groups on the acids can activate Si–O bonds similar to water and the Lewis acid BF3 can attach to Si–O via the pair of electrons on the O atom.

Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition of Borophosphosilicate Glass Films

“…The most significant features in these spectra are labeled in the figure, which include the O-Si-O symmetric bending band at $810 cm À1 , the Si-O asymmetric stretching band at $1080 cm À1 , the Si-O-Si stretching band at $1190 cm À1 that appears like a shoulder, the P=O vibration band at $1330 cm À1 , the B-O band at $1395 cm À1 , and the Si-O-B band at $930 cm À1 . All of these features show normal FTIR absorption spectra results for the BPSG film, which are similar to the FTIR result described previously [11][12][13]. FTIR showed the formation of BPSG, BSG, and PSG by the presence of their respective characteristic peaks.…”

“…All of these features show normal FTIR absorption spectra results for the BPSG film, which are similar to the FTIR result described previously. [11][12][13] FTIR showed the formation of BPSG, BSG, and PSG by the presence of their respective characteristic peaks. The B-O band ($1395 cm À1 ) and Si-O-B band ($930 cm À1 ) were found in the spectra of BSG, and the P=O band ($1330 cm À1 ) appeared in the spectra of PSG.…”

“…In addition, no obvious peaks were observed between 2500 and 3750 cm À1 , that is, those corresponding to moisture (H-O-H bond at 3300 -3500 cm À1 ) and relative OH (Si-OH at 3300 -3650 cm À1 , B-OH at 3200 -3300 cm À1 , P-OH at 2500 -3300 cm À1 ), indicating that OH content is low in the films under the deposition conditions. [10][11][12][13] Figure 4(a) shows the typical XPS wide scan spectra of the BPSG, BSG, and PSG films. The XPS survey plot of the as-deposited samples further confirmed the composition of the samples.…”

“…The B-O band ($1395 cm À1 ) and Si-O-B band ($930 cm À1 ) were found in the spectra of BSG, and the P=O band ($1330 cm À1 ) appeared in the spectra of PSG. In addition, no obvious peaks were observed between 2500 and 3750 cm À1 , that is, those corresponding to moisture (H-O-H bond at 3300 -3500 cm À1 ) and relative OH (Si-OH at 3300 -3650 cm À1 , B-OH at 3200 -3300 cm À1 , P-OH at 2500 -3300 cm À1 ), indicating that OH content is low in the films under the deposition conditions [10][11][12][13]. Figure4(a) shows the typical XPS wide scan spectra of the BPSG, BSG, and PSG films.…”

The effect of stochastic nano-scale surface roughness on microfluidic flow in computational microchannels

“…Modified from a paper to be submitted to Applied Physics Letters [8,9,10]. A byproduct of HF etching is an inherent, stochastic surface roughness [11].…”