NOVELTY - A substrate or deposited layer is provided on a movable carrier, preheated, and moved for etching from an external ambient environment through a purge gas containment curtain, and into an open atmospheric reactor. The substrate is continuously moved into or through an etchant delivering feature inside the reactor. Etchant(s) in gas form is applied to create the desired texture on the substrate. The substrate or deposited layer is moved for etching. The etchant(s) gas is fluoride-containing gas and/or chlorine-based compound gas.    USE - Modification of surface structure of silicon substrate or deposited silicon layer to desired texture, suitable for making photovoltaic devices e.g. solar cell (claimed).    ADVANTAGE - The method uses a high-throughput dry etching method which can be carried out at atmospheric pressure. The apparatus does not require plasma to aid the etching process using fluoride-containing gases and chlorine-based compounds. The use of elemental fluorine, which has a significantly lower bonding energy than any of the other etchants used to date, allows for the use of much lower power energy source to crack the elemental fluorine in to its etching radicals. The apparatus enables the delivery of preset texture finish by controlling the flow rate of the gases which are bombarded on the surface of the substrate.    DETAILED DESCRIPTION - A substrate or deposited layer is provided on a movable carrier and preheated. The substrate or deposited layer is continuously moved for etching from an external ambient environment through a purge gas containment curtain, and into an open atmospheric reactor. The substrate is continuously moved into or through an etchant delivering feature inside the reactor. Etchant(s) in gas form is applied to the substrate or deposited layer in the reactor, to create the desired texture on the substrate by controlling the flow rate and angle of the applied etchant gas. The substrate or deposited layer is continuously moved for etching out from the open atmospheric reactor and through a further or same set of purge gas containment curtains to the external ambient environment. The etchant(s) gas is fluoride-containing gas and/or chlorine-based compound gas. INDEPENDENT CLAIMS are included for the following:    (1) apparatus for modifying surface structure of silicon substrate or deposited silicon layer; and    (2) device comprising etched substrate.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow diagram of the dry etching process.