Abstract:We have studied the mechanisms underpinning effective surface passivation of silicon with hafnium oxide (HfO 2 ) thin films grown via atomic layer deposition (ALD). Plasma-enhanced ALD with O 2 plasma and a tetrakis(dimethylamido)hafnium precursor was used to deposit 12 nm thick HfO 2 films at 200 °C on high-lifetime 5 Ωcm n-type Czochralski silicon wafers. The passivation was activated by postdeposition annealing, with 30 min in air at 475 °C found to be the most effective. High-resolution grazing incidence X… Show more
“…Earlier studies into HfO 2 passivation stated that for HfO 2 -based layers to be incorporated into photovoltaic processing schemes, the temperatures they were exposed to could not exceed 400 °C. 16 We have since shown that HfO 2 -based films perform well up to ∼500 °C, 30 but, nevertheless 400–500 °C temperature range provides a useful benchmark for testing thermal stability.…”
Section: Resultsmentioning
confidence: 99%
“…The passivation quality of both HfO 2 and Al 2 O 3 are known to be dependent on annealing temperature, with optimal passivation achieved in both cases on annealing at 450-500 °C. 11,30 Photoconductance decay lifetime curves for the three structures activated at 450 °C are shown in Fig. 1(a).…”
“…The average passivation quality of HF-dipped stacks exceeds that of untreated Si/HfO 2 / Al 2 O 3 at all temperatures studied. Higher temperature ranges could not be studied, as above ∼500 °C, HfO 2 -based passivation quality is known to degrade, 30 and hence it would not be possible to separate contributions from the dielectric layers and the chemical treatment at these annealing temperatures.…”
Section: Stability Of Enhanced Passivationmentioning
confidence: 99%
“…Thus, the observed improvement seems related to properties of the complete stack, not the individual layers. Changes in CPD could also be due to changes in the dielectric constant, 30 but this does not seem likely for a simple room temperature chemical treatment.…”
Section: Electronic Origins Of Improved Passivationmentioning
confidence: 99%
“…The difference in behaviour for ≥30 s of HF immersion for 1 nm and 10 nm interlayers is likely because of differences in crystallisation level between the HfO 2 films of different thicknesses. 10 nm thick films are known to crystallise upon annealing at 450 °C, 30 becoming highly resistant to etching in HF. 65 ∼1 nm HfO 2 films are unlikely to crystallise fully without being annealed at 700-800 °C, 66 and thus have not developed resistance to etching in HF.…”
Section: Chemical Analysis Of Hf-treated Stacks and Correlation With ...mentioning
Production of a temporally stable chemically enhanced ultra-thin HfO2 interlayer with excellent passivation for use in photovoltaic passivating contacts.
“…Earlier studies into HfO 2 passivation stated that for HfO 2 -based layers to be incorporated into photovoltaic processing schemes, the temperatures they were exposed to could not exceed 400 °C. 16 We have since shown that HfO 2 -based films perform well up to ∼500 °C, 30 but, nevertheless 400–500 °C temperature range provides a useful benchmark for testing thermal stability.…”
Section: Resultsmentioning
confidence: 99%
“…The passivation quality of both HfO 2 and Al 2 O 3 are known to be dependent on annealing temperature, with optimal passivation achieved in both cases on annealing at 450-500 °C. 11,30 Photoconductance decay lifetime curves for the three structures activated at 450 °C are shown in Fig. 1(a).…”
“…The average passivation quality of HF-dipped stacks exceeds that of untreated Si/HfO 2 / Al 2 O 3 at all temperatures studied. Higher temperature ranges could not be studied, as above ∼500 °C, HfO 2 -based passivation quality is known to degrade, 30 and hence it would not be possible to separate contributions from the dielectric layers and the chemical treatment at these annealing temperatures.…”
Section: Stability Of Enhanced Passivationmentioning
confidence: 99%
“…Thus, the observed improvement seems related to properties of the complete stack, not the individual layers. Changes in CPD could also be due to changes in the dielectric constant, 30 but this does not seem likely for a simple room temperature chemical treatment.…”
Section: Electronic Origins Of Improved Passivationmentioning
confidence: 99%
“…The difference in behaviour for ≥30 s of HF immersion for 1 nm and 10 nm interlayers is likely because of differences in crystallisation level between the HfO 2 films of different thicknesses. 10 nm thick films are known to crystallise upon annealing at 450 °C, 30 becoming highly resistant to etching in HF. 65 ∼1 nm HfO 2 films are unlikely to crystallise fully without being annealed at 700-800 °C, 66 and thus have not developed resistance to etching in HF.…”
Section: Chemical Analysis Of Hf-treated Stacks and Correlation With ...mentioning
Production of a temporally stable chemically enhanced ultra-thin HfO2 interlayer with excellent passivation for use in photovoltaic passivating contacts.
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