Evaluation of the Plasmaless Gaseous Etching Process

[1] US patent : US2004185670(A1) 0 1 2 3 4 5 6 7 8 9 01234 Process time （min） Etched amount (nm) Th- Ox LP- TEOS P- TEOS HDP The fThe firstirst treatment chamber treatment chamber Wafer Heater N2 H2 NH3 SiF4 NH3 SiF4 N2 SiF4 H2O The second treatment chamber The second treatment chamber � Surface Micro Etch � NH3/HF adsorption onto wafer surface � Wafer temp. 20～40℃ � Heat up to 100～200℃ � To Evaporate By-product from Wafer Surface ( w/ N2 Gas ) Wafer NH3 NH3 NH3 HF HF HFBy-product HF NH3 The fThe firstirst treatment chamber treatment chamber Wafer Heater N2 H2 NH3 SiF4 NH3 SiF4 N2 SiF4 H2O The second treatment chamber The second treatment chamber � Surface Micro Etch � NH3/HF adsorption onto wafer surface � Wafer temp. 20～40℃ � Heat up to 100～200℃ � To Evaporate By-product from Wafer Surface ( w/ N2 Gas ) Wafer NH3 NH3 NH3 HF HF HFBy-product HF NH3 Figure 1: Schematic of the COR Figure 3: The etched amount of various films treated by the COR as a function of process time No treatment COR DHF No treatment COR DHF 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 No treatment COR DHF Surface roughness Ra (nm) Figure 2: Surface roughness of silicon substrate after the COR or DHF processes-0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 500 1000 1500 2000 2500 3000 3500 4000 Frequency (cm-1) Absorbance Th- Ox PTEOS -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 700 750 800 850 Frequency (cm-1) Absorbance Th- Ox PTEOS -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 700 750 800 850 Frequency (cm-1) Absorbance Th- Ox PTEOS -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 500 1000 1500 2000 2500 3000 3500 4000 Frequency (cm-1) Absorbance Th- Ox PTEOS -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 700 750 800 850 Frequency (cm-1) Absorbance Th- Ox PTEOS -0.02 -0.01 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 700 750 800 850 Frequency (cm-1) Absorbance Th- Ox PTEOS Binding Energy (eV) Ratio (%) Binding Energy (eV) Ratio (%) N(1s) 402.0 21 402.1 20 (NH4)2SiF6 F(1s) 685.3 60 685.3 53 (NH4)2SiF6 Si(2p) 103.4 13 103.5 14 (NH4)2SiF6 Estimation Photoelectron Th-Ox PTEOS Th-Ox PTEOS sacrificed oxide for well implantations 1st Gate oxide 2nd Gate oxide Sacrificed oxide removal Gate oxide removal for multi oxides formation STI Si sub STI Si sub STI Si sub STI Si sub Figure 5: The ratios of nitrogen, fluorine, and silicon on the reacted layer of the thermal oxide and plasma-TEOS obtained with XPS measurements HF NH3 HF NH3 (NH4)2SiF6 layer ThOx，TEOS，HDP Surface reaction Diffusion Diffusion Adsorption HF NH3 HF NH3 (NH4)2SiF6 layer ThOx，TEOS，HDP Surface reaction Diffusion Diffusion Adsorption 42.6 31.2 0 10 20 30 40 50 DHF COR Etched amount (nm) Si substrate STI Etched amount Si substrate STI Etched amount 42.6 31.2 0 10 20 30 40 50 DHF COR Etched amount (nm) Si substrate STI Etched amount Si substrate STI Etched amount Figure 4: FT-IR Spectrum for the reacted layers on the thermal oxide and the plasma-TEOS measurements. The slight peak shift around 785cm -1 (expanded in the inset) may suggest a difference in the quality of by-products of the thermal oxide and those of plasma-TEOS. Figure 6: Schematic of the COR reaction model Figure 7: Schematic diagram of the divot formation Figure 8: The etched amount of STI Figure 9: AFM images of the STI shape COR DHF Figure 10: TEM images of the STI shape DHF COR

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