A method to modify a surface structure of a silicon substrate or deposited silicon layer to a desired texture, suitable for making photovoltaic devices, the method comprising the steps of: disposing the silicon substrate or deposited silicon layer on a moveable carrier; pre-heating the silicon substrate or deposited silicon layer in a pre-heating zone; continuously moving the silicon substrate or deposited silicon layer for etching from an external ambient environment through a purge gas containment curtain, and into an open, heat etching chamber at atmospheric pressure; continuously moving the silicon substrate or deposited silicon layer through the etching chamber comprising an etchant delivering feature, while applying and controlling a flow rate of Fluorine F2 gas at atmospheric pressure and a concentration between 5% and 100% to the silicon substrate or deposited silicon layer to lower surface reflectivity of the silicon surface of the silicon substrate or deposited silicon layer and increase light absorption; controlling an angle between 0 and 180 degrees of the Fluorine F2 etchant gas being applied at atmospheric pressure; and continuously moving the silicon substrate or deposited silicon layer out from the open, heated etching chamber at atmospheric pressure and through a further or same set of purge gas containment curtains to the external ambient environment, wherein the Fluorine F2 etchant gas is activated thermally without the need of any plasma; and wherein the Fluorine F2 etchant gas is directly applied to the silicon surface of the substrate or deposited silicon layer under atmospheric pressure to lower its surface reflectivity and increase the light absorbed by the silicon substrate or deposited silicon layer. disposing the silicon substrate or deposited silicon layer on a moveable carrier; pre-heating the silicon substrate or deposited silicon layer in a pre-heating zone; continuously moving the silicon substrate or deposited silicon layer for etching from an external ambient environment through a purge gas containment curtain, and into an open, heat etching chamber at atmospheric pressure; continuously moving the silicon substrate or deposited silicon layer through the etching chamber comprising an etchant delivering feature, while applying and controlling a flow rate of Fluorine F2 gas at atmospheric pressure and a concentration between 5% and 100% to the silicon substrate or deposited silicon layer to lower surface reflectivity of the silicon surface of the silicon substrate or deposited silicon layer and increase light absorption; controlling an angle between 0 and 180 degrees of the Fluorine F2 etchant gas being applied at atmospheric pressure; and continuously moving the silicon substrate or deposited silicon layer out from the open, heated etching chamber at atmospheric pressure and through a further or same set of purge gas containment curtains to the external ambient environment, wherein the Fluorine F2 etchant gas is activated thermally without the need of any plasma; and wherein the Fluorine F2 etchant gas is directly applied to the silicon surface of the substrate or deposited silicon layer under atmospheric pressure to lower its surface reflectivity and increase the light absorbed by the silicon substrate or deposited silicon layer.