A new approach for improving the silicon texturing process using gas-lift effect

Abstract

A new cost-effective and efficient approach is proposed for texturing the crystalline silicon using the gas-lift effect (GLE). The advantages of this approach over the conventional ones are that significantly lower amounts of IPA is used and much shorter etching time is required to achieve the same reflectivity. GLE is generated by taking advantage of the hydrogen bubbles evolved between the silicon wafer being etched and a glass plate, placed in parallel, creating a gap of 1–2 mm. This effect then acts as a pumping mechanism detaching more bubbles from the silicon surface, accelerating them to the top and out of the system, as quickly as they are generated. Experiments were carried out with various combinations of TMAH/IPA concentrations for two different GLE conditions to analyse and determine their influence on etching time, etching rate, surface morphology and reflectivity of the textured silicon surface. The use of this new approach in surface texturing, allowed the reduction of the required IPA by 50% and etching time by more than 60% to achieve the same reflectivity. This can ultimately lead to a significant reduction in cost by increasing the efficiency of the texturing process. A combination of 3.5% IPA and 2 mm GLE resulted in a textured silicon surface having a low specular solar-weighted reflectivity of 0.15%.