We suggested a solution and advised on methods of selecting spray nozzles to achieve it.
Study of the substrate products themselves will be required for a definitive assessment of whether better uniformity of application of the developer is being achieved. But if a nozzle manufacturer is willing to work with you, the right spray nozzle can be identified from data obtained by experimentation in the laboratory. There is very little difference between the density and viscosity of developer and that of water, so you can conduct various experiments using water at a manufacturer's facilities. For example, you can measure the flow distribution being achieved with present nozzle arrangements. Using these results, you can select nozzles that spray more uniformly and then review the new arrangements. Furthermore, you can measure the distribution of the sprayed material on impact and compare how various arrangements influence this. If you want to change the droplet size without changing the present flow rate, you should change the nozzle type or the pressure and measure the droplets using a PDPA (Phase Doppler Particle Analyzer). In this way you can obtain accurate data for your comparison. As you can see from this information, you can make a more efficient spray nozzle selection by making full use of various methods of measurement.