Scratchiness could be a sign that your voice is tired. It depends on the type of scratchy that you mean.
If you mean it sounds scratchy and it tickles or makes you cough then it could be that your false vocal folds are closing over your airway. You have two sets of vocal folds - true folds and false folds. The true folds have underlying muscles and a covering of mucus and they collide to make voiced sounds (like mmmmm zzzz d g ). The false folds are pads of fat and tissue and are part of the mechanism in your throat that closes up (constricts) when you swallow so you won't get liquids or food in your lungs.
Swallowing is the main job of the larynx. Singing is its hobby. When you swallow you want the entire airway to close tight. When you sing you certainly don't want this to happen. But there are triggers in music that cause the larynx to rise (changes in pitch, belting, yelling sounds) and this rising movement tricks your larynx into thinking (if it could think at all!)that it should be closing. The main consequence of this is that the false folds move to close over your airway, and this causes scratching, buzzing or scraping in the throat.
I do not happen to think that the cure for this is to ensure that the larynx doesn't rise by holding it down. I think you can hold the false folds in a retracted (open) position by imagining a loud, hard laugh in your throat. Try it out. If you imagine that you are on stage and something hilarious happens, something the audience must not know about, and you are laughing just inside not on your face and not holding your breath. There is an open feeling in your throat. That is the feeling of retracted false folds. The idea is to establish this feeling as part of your technique at a very basic level so that you always sing with the false folds retracted. Then you shouldn't get any buzzing or scratching.