Surface texturing method for silicon solar cell using reactive ion etching with metal mesh

Abstract

We have developed a new texturing method by forming a pyramidal black silicon structure using a metal mesh in the reactive ion etching (RIE) system in order to overcome the disadvantages of the texturing process using wet etching and the drawbacks of the needle(grass)-like black silicon. For the formation of a pyramidal black silicon on the silicon surface, the RIE system is modified to be equipped with a metal mesh on top of the head shower. The parameters for the RIE process are SF 6 /O 2 gas flow of 15/15 sccm, RF (radio frequency) power of 200 W, pressure of 50-200 mTorr, temperature of 5 8C, and process time of 5-20 min. An increase in the processing time increases the width of the pyramid; however, the height remains at 0.8 AE 0.1 mm for 15-20 min of processing. The crystalline wafer surface of the pyramidal black silicon of approximately 1.7 AE 0.2 mm width and at 0.8 AE 0.1 mm height in size is textured using the RIE system with 10.7% of reflectivity. Thus, the pyramidal black silicon and the RIE process using a metal mesh are superior to the conventional texturing structures and methods, respectively.

Effects on micropyramid and nanoneedle structures for superhydrophobicity on Si surface

“…Gas is injected into a process chamber via a showerhead gas inlet in the top electrode [21]. Negative self-bias forms on the lower electrode, and a single RF plasma source determines both ion density and energy [21,24]. The use of the metal mesh results in the formation of a remote plasma sheath boundary and causes ion trajectory bending.…”

“…As a result, a nanoneedle structure is formed on the silicon surface [21]. A metal mesh is placed inside the RIE system to function as a shadow mask and for ion trajectory bending [21,24]. The ions are accelerated and scattered through the holes on the metal mesh placed between the sample and the plasma.…”

“…The plasma ions collide with the sample. The RIE system is designed in this manner to enhance the scattering of the plasma ions [21,24]. The important parameters that enable the formation of nanoneedles are RF power, process pressure, and SF 6 /O 2 ratio.…”

“…The use of the metal mesh results in the formation of a remote plasma sheath boundary and causes ion trajectory bending. As a result, a nanoneedle structure is formed on the silicon surface [21]. A metal mesh is placed inside the RIE system to function as a shadow mask and for ion trajectory bending [21,24].…”

“…The substrate is usually placed on a quartz or graphite coverplate to avoid sputtering/ redepositioning of electrode material. Gas is injected into a process chamber via a showerhead gas inlet in the top electrode [21]. Negative self-bias forms on the lower electrode, and a single RF plasma source determines both ion density and energy [21,24].…”