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Investigation on the passivated Si/Al2O3 interface fabricated by non-vacuum spatial atomic layer deposition system.

Lien SY, Yang CH, Wu KC, Kung CY - Nanoscale Res Lett (2015)

Bottom Line: Thin stoichiometric silicon dioxide films prepared on the Si surface prior to Al2O3 fabrication effectively reduce a considerable amount of blisters.Eventually, the entire PERC with the improved triple-layer SiO2/Al2O3/SiNx:H stacked passivation film has an obvious gain in open-circuit voltage (V oc) and short-circuit current (J sc) because of the increased minority carrier lifetime and internal rear-side reflectance, respectively.The electrical performance of the optimized PERC with the V oc of 0.647 V, J sc of 38.2 mA/cm(2), fill factor of 0.776, and the efficiency of 19.18% can be achieved.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, DaYeh University, No. 168, Xuefu Road, Changhua, 515 Taiwan.

ABSTRACT
Currently, aluminum oxide stacked with silicon nitride (Al2O3/SiNx:H) is a promising rear passivation material for high-efficiency P-type passivated emitter and rear cell (PERC). It has been indicated that atomic layer deposition system (ALD) is much more suitable to prepare high-quality Al2O3 films than plasma-enhanced chemical vapor deposition system and other process techniques. In this study, an ultrafast, non-vacuum spatial ALD with the deposition rate of around 10 nm/min, developed by our group, is hired to deposit Al2O3 films. Upon post-annealing for the Al2O3 films, the unwanted delamination, regarded as blisters, was found by an optical microscope. This may lead to a worse contact within the Si/Al2O3 interface, deteriorating the passivation quality. Thin stoichiometric silicon dioxide films prepared on the Si surface prior to Al2O3 fabrication effectively reduce a considerable amount of blisters. The residual blisters can be further out-gassed when the Al2O3 films are thinned to 8 nm and annealed above 650°C. Eventually, the entire PERC with the improved triple-layer SiO2/Al2O3/SiNx:H stacked passivation film has an obvious gain in open-circuit voltage (V oc) and short-circuit current (J sc) because of the increased minority carrier lifetime and internal rear-side reflectance, respectively. The electrical performance of the optimized PERC with the V oc of 0.647 V, J sc of 38.2 mA/cm(2), fill factor of 0.776, and the efficiency of 19.18% can be achieved.

No MeSH data available.


Related in: MedlinePlus

The blister-blocking effect of SiO2on silicon. (a) Minority carrier lifetime for 3 nm SiO2 films capped with various Al2O3 film thicknesses of 10 to 25 nm annealed at 450°C to 600°C in N2 ambient and (b) optical microscope image for 3 nm-SiO2/25 nm-Al2O3 stacked film annealed at 500°C N2 ambient.
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Fig5: The blister-blocking effect of SiO2on silicon. (a) Minority carrier lifetime for 3 nm SiO2 films capped with various Al2O3 film thicknesses of 10 to 25 nm annealed at 450°C to 600°C in N2 ambient and (b) optical microscope image for 3 nm-SiO2/25 nm-Al2O3 stacked film annealed at 500°C N2 ambient.

Mentions: The blister-blocking effect of SiO2 on silicon can be reflected in Figure 5. Figure 5a shows the minority carrier lifetime for 3 nm of the SiO2 films capped with various Al2O3 films thicknesses of 10 to 25 nm annealed at 450°C to 600°C in the N2 ambient. Compared to the trend of Figure 3, it almost maintains unchanged, but the average lifetime of all samples has a little increase. The peak value of 107.2 μs is obtained still when the thickness of the Al2O3 film is 25 nm, and the annealing temperature is 500°C. The increase of 21.7 μs between two peak lifetime values can be attributed to the enormous reduction of blisters, as shown in Figure 5b. The major reason to support SiO2 film to be our option is that the SiO2 film has more stoichiometric configuration compared to native oxide (SiOx). When the Al2O3 films deposited directly on the silicon substrate without SiO2 films as interlayers, the oxygen atom of reactant H2O tends to bond with SiOx to form the stable SiO2; thus, the released H2 and residual H2O may probably become the blisters after post-annealing process. The highly stoichiometric ICPCVD-SiO2 films inserted into the interface between the Al2O3 and silicon wafer effectively prevent the considerable amount of blisters from occurring. In addition, several studies have claimed that SiO2 film is a good candidate for chemical passivation to eliminate the dangling bonds on the surface of silicon wafer [15,16]. Also, it can help the Al2O3 films to rearrange their negative fixed charge distributed near the SiO2/Al2O3 interface [17,18].Figure 5


Investigation on the passivated Si/Al2O3 interface fabricated by non-vacuum spatial atomic layer deposition system.

Lien SY, Yang CH, Wu KC, Kung CY - Nanoscale Res Lett (2015)

The blister-blocking effect of SiO2on silicon. (a) Minority carrier lifetime for 3 nm SiO2 films capped with various Al2O3 film thicknesses of 10 to 25 nm annealed at 450°C to 600°C in N2 ambient and (b) optical microscope image for 3 nm-SiO2/25 nm-Al2O3 stacked film annealed at 500°C N2 ambient.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4385260&req=5

Fig5: The blister-blocking effect of SiO2on silicon. (a) Minority carrier lifetime for 3 nm SiO2 films capped with various Al2O3 film thicknesses of 10 to 25 nm annealed at 450°C to 600°C in N2 ambient and (b) optical microscope image for 3 nm-SiO2/25 nm-Al2O3 stacked film annealed at 500°C N2 ambient.
Mentions: The blister-blocking effect of SiO2 on silicon can be reflected in Figure 5. Figure 5a shows the minority carrier lifetime for 3 nm of the SiO2 films capped with various Al2O3 films thicknesses of 10 to 25 nm annealed at 450°C to 600°C in the N2 ambient. Compared to the trend of Figure 3, it almost maintains unchanged, but the average lifetime of all samples has a little increase. The peak value of 107.2 μs is obtained still when the thickness of the Al2O3 film is 25 nm, and the annealing temperature is 500°C. The increase of 21.7 μs between two peak lifetime values can be attributed to the enormous reduction of blisters, as shown in Figure 5b. The major reason to support SiO2 film to be our option is that the SiO2 film has more stoichiometric configuration compared to native oxide (SiOx). When the Al2O3 films deposited directly on the silicon substrate without SiO2 films as interlayers, the oxygen atom of reactant H2O tends to bond with SiOx to form the stable SiO2; thus, the released H2 and residual H2O may probably become the blisters after post-annealing process. The highly stoichiometric ICPCVD-SiO2 films inserted into the interface between the Al2O3 and silicon wafer effectively prevent the considerable amount of blisters from occurring. In addition, several studies have claimed that SiO2 film is a good candidate for chemical passivation to eliminate the dangling bonds on the surface of silicon wafer [15,16]. Also, it can help the Al2O3 films to rearrange their negative fixed charge distributed near the SiO2/Al2O3 interface [17,18].Figure 5

Bottom Line: Thin stoichiometric silicon dioxide films prepared on the Si surface prior to Al2O3 fabrication effectively reduce a considerable amount of blisters.Eventually, the entire PERC with the improved triple-layer SiO2/Al2O3/SiNx:H stacked passivation film has an obvious gain in open-circuit voltage (V oc) and short-circuit current (J sc) because of the increased minority carrier lifetime and internal rear-side reflectance, respectively.The electrical performance of the optimized PERC with the V oc of 0.647 V, J sc of 38.2 mA/cm(2), fill factor of 0.776, and the efficiency of 19.18% can be achieved.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, DaYeh University, No. 168, Xuefu Road, Changhua, 515 Taiwan.

ABSTRACT
Currently, aluminum oxide stacked with silicon nitride (Al2O3/SiNx:H) is a promising rear passivation material for high-efficiency P-type passivated emitter and rear cell (PERC). It has been indicated that atomic layer deposition system (ALD) is much more suitable to prepare high-quality Al2O3 films than plasma-enhanced chemical vapor deposition system and other process techniques. In this study, an ultrafast, non-vacuum spatial ALD with the deposition rate of around 10 nm/min, developed by our group, is hired to deposit Al2O3 films. Upon post-annealing for the Al2O3 films, the unwanted delamination, regarded as blisters, was found by an optical microscope. This may lead to a worse contact within the Si/Al2O3 interface, deteriorating the passivation quality. Thin stoichiometric silicon dioxide films prepared on the Si surface prior to Al2O3 fabrication effectively reduce a considerable amount of blisters. The residual blisters can be further out-gassed when the Al2O3 films are thinned to 8 nm and annealed above 650°C. Eventually, the entire PERC with the improved triple-layer SiO2/Al2O3/SiNx:H stacked passivation film has an obvious gain in open-circuit voltage (V oc) and short-circuit current (J sc) because of the increased minority carrier lifetime and internal rear-side reflectance, respectively. The electrical performance of the optimized PERC with the V oc of 0.647 V, J sc of 38.2 mA/cm(2), fill factor of 0.776, and the efficiency of 19.18% can be achieved.

No MeSH data available.


Related in: MedlinePlus