NOVELTY - A method of forming a multi-element layer that has a predetermined molar ratio range of elements involves depositing several films on a substrate in at least one deposition station (21), where the deposited films includes each of the elements for which the predetermined molar ratio range is desired; detecting an amount of each of the elements within the deposited films in at least one metrology station (22); and tuning the films based on the amount of each of the elements deposited to obtain the multi-element layer having predetermined molar ratio range.    USE - For forming multi-element layer having predetermined molar ratio of elements (claimed); for preparing thin films of compound semiconductor film for radiation detector and photovoltaic applications e.g. for fabricating solar cells.    ADVANTAGE - The molar ratio of the elements in the layers are detected so that tuning of the multi element layer can occur to obtain the multi-element layer having predetermined molar ratio range. The method is used for deposition of all sub-layers or only for sub-layers for which deposition thickness control is difficult, unstable or non-optimized.    DETAILED DESCRIPTION - A method of forming a multi-element layer that has a predetermined molar ratio range of elements involves depositing several films on a substrate in at least one deposition station (21), where the deposited films includes each of the elements for which the predetermined molar ratio range is desired; detecting an amount of each of the elements within the deposited films in at least one metrology station (22); and tuning the films based on the amount of each of the elements deposited to obtain the multi-element layer having predetermined molar ratio range. The step of tuning deposits another film that includes at least one element used for the predetermined molar ratio range. The steps of depositing, detecting and tuning are carried out on a flexible substrate in a roll-to-roll manner. An INDEPENDENT CLAIM is included for forming a layer formed of at least one of copper (Cu), indium (In) and gallium (Ga) having a pre-determined thickness involving depositing one of a Cu sub-layer, a In sub-layer and a Ga sub-layer on a substrate in at least one deposition station; detecting the thickness of the deposited sub-layer in a metrology station thus obtaining a measured thickness; and tuning the thickness of the sub-layer based upon the measured thickness to provide a tuned thickness that is same as the pre-determined thickness.    DESCRIPTION OF DRAWING(S) - The figure shows a cluster tool configuration with various chambers around a central handler.    cluster tool (20)    deposition station (21)    metrology station (22)    tuning station (23)    handler. (25)