Surface characteristics and damage distributions of diamond wire sawn wafers for silicon solar cells

Sopori, Bhushan; Devayajanam, Srinivas; Basnyat, Prakash

doi:10.3934/matersci.2016.2.669

Cited by 15 publications

(8 citation statements)

References 12 publications

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“…Saw damage induces residual stresses, compressive in nature in the range from −20 to −85 MPa including stresses having a component in both the x‐ and y‐coordinate directions, namely, σ xx and σ yy . When those stresses exceed the Si critical shear stress, they cause plastic deformation and/or micro cleavage . However, the presence of this local strain remaining after the sawing step can only explain the formation of the morphology B dislocations.…”

Section: Discussionmentioning

confidence: 99%

In Situ Imaging of Dislocation Expansion in FZ‐Si Seeds During Temperature Ramp Heating Process

Tsoutsouva

Riberi-Béridot

Regula

et al. 2018

Physica Status Solidi (a)

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The impact of the thermal field in a directional solidification furnace on the generation and propagation of dislocations is investigated in intrinsic floating zone single crystal silicon.Seeds with different crystallographic orientations are wire-cut from mono-crystalline wafers and dislocation sources are solely left at the edges. Thermal annealing experiments are carried out in situ at the European synchrotron radiation facility and the evolution of the silicon crystalline quality is studied by X-ray diffraction imaging technique. At 1073 K, dislocations nucleate only at the edges and their strain field remains local. At higher temperature (1373 K), dislocations propagate throughout the entire width of the seed via the preferential activation of slip planes, related to the crystallographic orientation of the seed. These results confirm the high importance of seed preparation in mono -like silicon growth process. Both mechanical 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 and chemical polishing of all seed surfaces, including their edges, are mandatory to prevent dislocation expansion and multiplication. Revised Manuscript

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Section: Discussionmentioning

confidence: 99%

In Situ Imaging of Dislocation Expansion in FZ‐Si Seeds During Temperature Ramp Heating Process

Tsoutsouva

Riberi-Béridot

Regula

et al. 2018

Physica Status Solidi (a)

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“…These cracks observed in wafers under Conditions A and B are median cracks caused because the abrasive grains pushed into the wafer surface during machining, and the crack length increased with increasing cut depth; thus, the crack length was shorter in those under Condition A compared with those under Condition B. 33,37) Figure 6(c) shows a cross-sectional SEM image of typical subsurface damage of wafers sliced under Condition C. The observed cracks were the same median cracks as those observed in those under Conditions A and B, although they were larger, with a different shape, and may have had a greater impact on the mechanical strength of the wafer. A large feed rate increases the cut depth, which increases the depth of subsurface damage but also increases the size of the cracks.…”

Section: Sawing Damage Evaluationmentioning

confidence: 99%

“…33,34) Those under Condition A had the smoothest surface, attributed to the low feed rate and fine abrasive grains, effectively reducing the cut depth. [35][36][37] Figure 5 shows SEM images of the surfaces for each wafer. Those sliced under each condition had a smooth surface obtained by ductile mode machining and saw marks consisting of dents and parallel grooves due to brittle fracture, whereas those sliced under Conditions B and C had deep grooves and dents and were significantly more damaged than those under Condition A.…”

Section: Sawing Damage Evaluationmentioning

confidence: 99%

Effect of sawing damage on flexibility of crystalline silicon wafers for thin flexible silicon solar cells

Hara

Ide

Nishihara

et al. 2022

Jpn. J. Appl. Phys.

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The cost of solar cell production can be reduced by wafer thinning. A thinner wafer provides flexibility, and crystalline silicon solar cells are promising as flexible solar cells due to their flexibility. However, as wafers become thinner, production yield decreases due to wafer breakage caused by sawing damage; thus, to further reduce wafer thickness, it is necessary to suppress sawing damage. We investigated the flexibility of wafers under various slice conditions by conducting biaxial bending tests and clarified the dominant factor causing sawing damage to further reduce the wafer thickness for crystalline silicon solar cells. The results of damage observation by scanning electron microscopy and evaluation of the crystal structure by Raman spectroscopy confirm that the damage structure changes significantly depending on wire specifications. The results from the biaxial bending tests indicate that the three-dimensional flexibility of a wafer is determined by wire specifications.

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“…The scratching induces phase transformation, larger cracks, complex damage on a micron scale on the wafer surface, and forms periodic structures in the wire slicing direction. [17][18][19][20] The large cracks and surface damage are responsible for reducing the fracture strength of as-sawn wafers. In the past there were only few studies on fracture stress of c-Si wafers with thickness of 170-180 µm sawn from diamond and slurry wire technology.…”

Section: Introductionmentioning

confidence: 99%

The impact of subsurface damage on the fracture strength of diamond-wire-sawn monocrystalline silicon wafers

Sekhar

Fukuda

Tanahashi

et al. 2018

Jpn. J. Appl. Phys.

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We describe a multi-diamond-wire saw for cutting monocrystalline silicon bricks into thin (120 µm) and thick (200 µm) wafers and label as freshand worn-wire sides. While almost no difference was found in the fracture stress of the thick (200 µm) wafers cut from either side, the thin (120 µm) wafers showed a lower fracture stress in those from the fresh-wire side compared to the worn-wire side. This is a remarkable result when wafers are sawn with conventional diamond wire. On the contrary, wafers sawn with improved diamond wire (100d-M6/12) showed a higher fracture stress compared to those cut with conventional diamond wire (100d-M8/16), for both the fresh-and worn-wire sides. Observing the subsurface areas of wafers by micro-Raman spectroscopy, we succeeded in quantifying the defective silicon fraction as the Raman crystallinity factor (Φ c ). We found that wafers having a higher fracture strength had a larger Φ c .

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Surface characteristics and damage distributions of diamond wire sawn wafers for silicon solar cells

Cited by 15 publications

References 12 publications

In Situ Imaging of Dislocation Expansion in FZ‐Si Seeds During Temperature Ramp Heating Process

In Situ Imaging of Dislocation Expansion in FZ‐Si Seeds During Temperature Ramp Heating Process

Effect of sawing damage on flexibility of crystalline silicon wafers for thin flexible silicon solar cells

The impact of subsurface damage on the fracture strength of diamond-wire-sawn monocrystalline silicon wafers

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