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Anti-reflective nano- and micro-structures on 4H-SiC for photodiodes.

Kang MS, Joo SJ, Bahng W, Lee JH, Kim NK, Koo SM - Nanoscale Res Lett (2011)

Bottom Line: In this study, nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC.We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55% compared with the reference devices.As a result, the optical response Iillumination/Idark of the 4H-SiC photodiodes were enhanced up to 178%, which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Electronics and Information, Kwangwoon University, Seoul 139-701, Korea. smkoo@kw.ac.kr.

ABSTRACT
In this study, nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC. The surface of 4H-SiC wafer after a conventional photolithography process was etched by inductively coupled plasma. We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55% compared with the reference devices. As a result, the optical response Iillumination/Idark of the 4H-SiC photodiodes were enhanced up to 178%, which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing.

No MeSH data available.


SEM images of representative "as-manufactured" structures. (a) The image shows the nano-honeycomb structures created by the photolithographic process. The detailed images show the rough surface on the bottom side (b) and the top side (c) of the nano-honeycomb structures created by the ICP-etching process using the gaseous mixture of SF6 + O2.
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Figure 2: SEM images of representative "as-manufactured" structures. (a) The image shows the nano-honeycomb structures created by the photolithographic process. The detailed images show the rough surface on the bottom side (b) and the top side (c) of the nano-honeycomb structures created by the ICP-etching process using the gaseous mixture of SF6 + O2.

Mentions: Figure 1 shows the three different surface types of samples on 4H-SiC wafers that were prepared. In order to form nano-scale-textured honeycomb structures on the 4H-SiC surface, we first fabricated nano-structure patterns of the SiC surface. The samples were first cleaned in H2SO4:H2O2 = 4:1, followed by a BOE dip to remove the native oxide. The so-called nano-honeycomb etching process was performed in the following steps. First, to prepare a dry etching mask, a 100-nm Ni layer was sputtered and patterned by a conventional photolithographic process. A plasma-etching process was performed using SF6 plasma (15% O2 by flowing in a total gas load of 14 sccm) with ICP discharges at 550 W and RF chuck powers that created the dc self-bias from 117 V. The chamber pressure was 50 mTorr, and the sample was placed on the chuck that was cooled by He. Then, the remaining Ni was removed from the SiC surface by the Ni etchant (HF:H2O2:H2O = 1:1:8). The honeycomb structures were created with a width and spacing, both of 3 μm, and a height of 100 nm as shown in Figure 2a. This method is used for forming the honeycomb structures of SiC surfaces which are referred to hereafter as micro-honeycomb structures [7,8]. The substrate for SiO2/4H-SiC was oxidized at 1150°C in O2 for 5 h, and then a Si layer was deposited by electron-beam evaporation to be used as a masking layer for etching. The thicknesses of the SiO2 and Si layers were 100 nm and 1 μm, respectively. Nano-scale texturing was performed using SF6 plasma (17% O2 by flowing in a total gas load of 24 sccm), with an ICP discharge power and a chamber pressure of 550 W and 30 mTorr, respectively, and a RF chuck power that created dc self-biases starting from 49 V. The nano-scale textures on the honeycomb structures were made by ICP etching as shown in Figure 2b, c[9]. This method is used for forming nano-scale-textured structures of SiC surfaces, referred to hereafter as nano-honeycomb structures, utilized the naturally roughened SiC surface morphology when the overlying Si turns into the so-called black Si by the ICP etching. After the black Si layer was consumed completely, the morphology was transferred to the underlying SiC, resulting in a roughened SiC surface.


Anti-reflective nano- and micro-structures on 4H-SiC for photodiodes.

Kang MS, Joo SJ, Bahng W, Lee JH, Kim NK, Koo SM - Nanoscale Res Lett (2011)

SEM images of representative "as-manufactured" structures. (a) The image shows the nano-honeycomb structures created by the photolithographic process. The detailed images show the rough surface on the bottom side (b) and the top side (c) of the nano-honeycomb structures created by the ICP-etching process using the gaseous mixture of SF6 + O2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211295&req=5

Figure 2: SEM images of representative "as-manufactured" structures. (a) The image shows the nano-honeycomb structures created by the photolithographic process. The detailed images show the rough surface on the bottom side (b) and the top side (c) of the nano-honeycomb structures created by the ICP-etching process using the gaseous mixture of SF6 + O2.
Mentions: Figure 1 shows the three different surface types of samples on 4H-SiC wafers that were prepared. In order to form nano-scale-textured honeycomb structures on the 4H-SiC surface, we first fabricated nano-structure patterns of the SiC surface. The samples were first cleaned in H2SO4:H2O2 = 4:1, followed by a BOE dip to remove the native oxide. The so-called nano-honeycomb etching process was performed in the following steps. First, to prepare a dry etching mask, a 100-nm Ni layer was sputtered and patterned by a conventional photolithographic process. A plasma-etching process was performed using SF6 plasma (15% O2 by flowing in a total gas load of 14 sccm) with ICP discharges at 550 W and RF chuck powers that created the dc self-bias from 117 V. The chamber pressure was 50 mTorr, and the sample was placed on the chuck that was cooled by He. Then, the remaining Ni was removed from the SiC surface by the Ni etchant (HF:H2O2:H2O = 1:1:8). The honeycomb structures were created with a width and spacing, both of 3 μm, and a height of 100 nm as shown in Figure 2a. This method is used for forming the honeycomb structures of SiC surfaces which are referred to hereafter as micro-honeycomb structures [7,8]. The substrate for SiO2/4H-SiC was oxidized at 1150°C in O2 for 5 h, and then a Si layer was deposited by electron-beam evaporation to be used as a masking layer for etching. The thicknesses of the SiO2 and Si layers were 100 nm and 1 μm, respectively. Nano-scale texturing was performed using SF6 plasma (17% O2 by flowing in a total gas load of 24 sccm), with an ICP discharge power and a chamber pressure of 550 W and 30 mTorr, respectively, and a RF chuck power that created dc self-biases starting from 49 V. The nano-scale textures on the honeycomb structures were made by ICP etching as shown in Figure 2b, c[9]. This method is used for forming nano-scale-textured structures of SiC surfaces, referred to hereafter as nano-honeycomb structures, utilized the naturally roughened SiC surface morphology when the overlying Si turns into the so-called black Si by the ICP etching. After the black Si layer was consumed completely, the morphology was transferred to the underlying SiC, resulting in a roughened SiC surface.

Bottom Line: In this study, nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC.We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55% compared with the reference devices.As a result, the optical response Iillumination/Idark of the 4H-SiC photodiodes were enhanced up to 178%, which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Electronics and Information, Kwangwoon University, Seoul 139-701, Korea. smkoo@kw.ac.kr.

ABSTRACT
In this study, nano-scale honeycomb-shaped structures with anti-reflection properties were successfully formed on SiC. The surface of 4H-SiC wafer after a conventional photolithography process was etched by inductively coupled plasma. We demonstrate that the reflection characteristic of the fabricated photodiodes has significantly reduced by 55% compared with the reference devices. As a result, the optical response Iillumination/Idark of the 4H-SiC photodiodes were enhanced up to 178%, which can be ascribed primarily to the improved light trapping in the proposed nano-scale texturing.

No MeSH data available.