A method of detecting developer endpoint. The method includes illuminating a device region of a substrate with a first optical beam prior to initiating a development stage of processing and detecting a baseline optical signal reflected from the device region of the substrate. The method also includes illuminating the device region of the substrate with a second optical beam during a development stage of processing and detecting an endpoint optical signal reflected from the device region of the substrate. The method further includes comparing the baseline optical signal to the endpoint optical signal and determining a developer endpoint based on the comparing step.