10:30 AM - 10:45 AM
▲ [5a-A204-7] Measuring subsurface damage in diamond wire sawn mono-crystalline Silicon (120 µm) wafers using Raman spectroscopy
Keywords:Diamond wire sawing, Mono-crystalline Silicon, micro-Raman Spectroscopy
Crystalline Si (c-Si) solar cells with a thicknesses of 180μm have dominated in the present market. To reduce the production cost per watt has resulted thinning the wafer without sacrificing the surface quality, mechanical strength and to increase the efficiency of Si solar cell in the manufacturing. In slicing silicon bricks into 120 µm thick mono-crystalline silicon wafers, diamond abrasives with a diameter of 6 to 12 µm fixed on core steel wire with a diameter of 100 µm are employed [1]. When slicing with diamond abrasives fixed on a wire more seriously scratch front and backside surfaces of the wafer and damages the wafer subsurface and forms amorphous silicon. The diamond wire sliced wafers were labelled as a fresh wire side and worn-out wire side. After slicing fresh wafers undergone slight KOH etching (˜1µm).
Nondestructive, noncontact measurement such as micro-Raman spectroscopy employed to characterize as diamond wire sliced Si wafers and to detect the presence subsurface amorphous silicon. Surface profile of as a diamond sliced Si wafers are shown in Fig. 1(a), which contains terraces and craters. Miro-Raman spectrum measured using 100X microscope excited with 532nm laser. The penetration depth is almost 800nm. The Raman signal measured at terrace contains broad signal from 400-600 cm-1 region, the characteristics peaks in this region normally associated with crystalline, microcrystalline, and amorphous silicon. The sharp peak at approximately 520 cm-1 can be attributed to the crystalline silicon and broad peak at 470 cm-1 can be attributed to a-Si [2].
The Raman spectrum of as sliced and KOH etch wafers shown in Fig. 1(b) & (c). As fresh sliced wafers Raman signal measured at terrace point shows broad a-Si peak, from this results we confirm that subsurface layer transforms into amorphous. The Si-wafers are processed slight KOH etching and measured its Raman signal shown in Fig. 1 (c). An interesting double-peak feature was observed in micro-Raman spectra taken from terraces. The intensity of the amorphous phase reaches maximum near fresh wire side wafers and sharply decreases KOH etch worn-out side wafers. Raman signal measured at row of craters in all wafers shows sharp peak at 521 cm-1 appeared which indicates the absence of the amorphous phase. This work provides slight KOH etching completely remove a-Si from worn-out side wafers but cannot from fresh side wafers.
Nondestructive, noncontact measurement such as micro-Raman spectroscopy employed to characterize as diamond wire sliced Si wafers and to detect the presence subsurface amorphous silicon. Surface profile of as a diamond sliced Si wafers are shown in Fig. 1(a), which contains terraces and craters. Miro-Raman spectrum measured using 100X microscope excited with 532nm laser. The penetration depth is almost 800nm. The Raman signal measured at terrace contains broad signal from 400-600 cm-1 region, the characteristics peaks in this region normally associated with crystalline, microcrystalline, and amorphous silicon. The sharp peak at approximately 520 cm-1 can be attributed to the crystalline silicon and broad peak at 470 cm-1 can be attributed to a-Si [2].
The Raman spectrum of as sliced and KOH etch wafers shown in Fig. 1(b) & (c). As fresh sliced wafers Raman signal measured at terrace point shows broad a-Si peak, from this results we confirm that subsurface layer transforms into amorphous. The Si-wafers are processed slight KOH etching and measured its Raman signal shown in Fig. 1 (c). An interesting double-peak feature was observed in micro-Raman spectra taken from terraces. The intensity of the amorphous phase reaches maximum near fresh wire side wafers and sharply decreases KOH etch worn-out side wafers. Raman signal measured at row of craters in all wafers shows sharp peak at 521 cm-1 appeared which indicates the absence of the amorphous phase. This work provides slight KOH etching completely remove a-Si from worn-out side wafers but cannot from fresh side wafers.