NOVELTY - The method involves spraying clean deionized water and freshly mixed and gradually aged reaction solutions with solution pipes (107), spray nozzles (105), and spray pumps (106) or compressed air nozzles. The freshly mixed reaction solution is sprayed continuously onto surfaces of a series of vertically traveling plane substrates (100). The sprayed and gradually aged solution is collected and sprayed back onto the traveling substrate surfaces continuously until a predicted film thickness is obtained. The residue solution is washed away from the deposited surface using minimum rinsed water.    USE - Chemical bath deposition (CBD) method for forming thin films on surfaces of a plane substrate utilized to deposit cadmium sulfide/ zinc sulfide semiconductor films to fabricate thin film solar cells. Uses include but are not limited to glass substrate, silicon crystalline substrate, ceramic substrate, polymer substrate, plastic substrate and metallic substrate.    ADVANTAGE - The method enables making the plane substrates to be continuously delivered side by side through a CBD reactor by a conveyor belt, so that a backside of the substrate can remain dry and clean, thus reducing amount of waste solutions for chemical treatments and making deposition easier, and hence reducing waste amount and amount of the rinsing water by separating a waste compartment from the rinsing sections. The method enables washing the residue solution away from the deposited surface using minimum rinsed water so as to reduce volumes of the waste to be treated and the deionized rinsing water, thus facilitating generation of minimum amount of waste solutions for chemical treatments.    DETAILED DESCRIPTION - The plane substrates are made from glass, silicon crystalline, ceramic, polymer, plastic material and metallic material.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of an apparatus for performing a CBD deposition on plane substrates transported continuously by a stainless steel conveyor belt.    Vertically traveling plane substrates (100)    Heating device (103)    Spray nozzles (105)    Spray pump (106)    Solution pipe (107)    Groove (108)    Separation board (116)