Selective metal passivation by vapor-dosed phosphonic acid inhibitors for area-selective atomic layer deposition of SiO2 thin films

Abstract

Aiming for atomic-scale precision alignment for advanced semiconductor devices, area-selective atomic layer deposition (AS-ALD) has garnered substantial attention because of its bottom-up nature that allows precise control of material deposition exclusively on desired areas. In this study, we develop a surface treatment to hinder the adsorption of Si precursor on metal surfaces by using a vapor-phase functionalization of bulky phosphonic acid (PA) self-assembled monolayers (SAMs). Through the chemical vapor transport (CVT) method, the bulky solid PA inhibitor with a fluorocarbon terminal group was effectively vaporized, and the conditions for maximizing the blocking effect of the inhibitor were confirmed by optimizing the process temperature and dwelling time. The unintended PA inhibitors adsorbed on SiO₂ surfaces during the CVT process were selectively removed by post-HF treatment, thereby leading to selective deposition of SiO₂ thin films only on SiO₂ substrates. As a results, SiO₂ film growth on the PA SAM/HF-treated TiN surfaces was suppressed by up to 4 nm with just a single exposure to the long-chain inhibitor, even during the ALD process using highly reactive O₃ reactants. The proposed approach paves the way for highly selective deposition of dielectrics on dielectrics (DoD).

Keywords: Area-selective atomic layer deposition; Chemical vapor transport; Phosphonic acid; Selective removal; Silicon oxide.

Fig. 1

a, b Schematic illustration of (a) AS-ALD of SiO₂ thin films on SiO₂ (growth area) versus TiN and W (non-growth area) surfaces and b chemical vapor transport (CVT) process. c Water contact angle (WCA) values of SiO₂, TiN, and W substrates after PA SAMs solution treatment with toluene solvent after 24 h of dipping at RT. d, e WCA values after C12-PA vapor dosing on SiO₂, TiN, and W substrates as a function of substrate temperature with (d) 10 min and (e) 1 min of C12-PA dwelling time

Fig. 2

a WCA values after C12-PA vapor dosing on SiO₂, TiN, and W substrates as a function of C12-PA dwelling time with substrate temperature of 130 ℃. b–d WCA values for C12-PA treated SiO₂, TiN, and W substrates at 130 ℃ for different locations in the reactor with b 3 min, c 5 min, and d 10 min of dwelling time

Fig. 3

a XPS survey scan spectra, b F 1 s and c C 1 s core-level XPS spectra collected after C12-PA vapor dosing on TiN substrates with dwelling times of 1–5 min at 130 ℃. d XPS survey scan spectra, e F 1 s and f C 1 s core-level XPS spectra collected after C12-PA vapor dosing on SiO₂ substrates with dwelling times of 1–5 min at 130 ℃

Fig. 4

a, b WCA values before and after C12-PA vapor dosing on SiO₂ substrates with dwelling time of (a) 10 min and (b) 3 h (red). Thickness variation of SiO₂ thin films on untreated and C12-PA treated SiO₂ substrates as a function of C12-PA dwelling temperature (black). c Blocking capability of C12-PA treated for 3 h compared to that with 10 min plotted as a function of the dwelling temperature

Fig. 5

a–c XPS survey scan spectra before and after C12-PA vapor dosing on a SiO₂, b TiN, and c W substrates. d C 1 s, e F 1 s, and f P 2p core-level XPS spectra of C12-PA treated SiO₂, TiN, and W substrates with dwelling time of 3 h at 200 ℃

Fig. 6

a WCA values of C12-PA-treated SiO₂, TiN, and W substrates after wet-HF treatment as a function of HF concentration with treatment time of 1 s. b Thickness of ALD SiO₂ thin films plotted as a function of the number of ALD cycles on untreated and C12-PA/HF treated SiO₂, TiN, and W substrates. c Deposition selectivity plotted as a function of the number of ALD cycles. d–f TEM images of untreated and C12-PA/HF-treated TiN substrate after d 35 cycles, e 60 cycles, and f 70 cycles of SiO₂ ALD at 100 ℃. g–i TEM images of untreated and C12-PA/HF-treated W substrate after g 35 cycles, h 60 cycles, and i 70 cycles of SiO₂ ALD at 100 ℃