How can I get my cat to stop scratching at the door?

Aside from double sticky tape (That tends to get dirty quickly and no longer stick) and pet deterrents (which technically need to be reapplied every 10-20 mins on most surfaces) you could adhere aluminum foil to the bottom portion of the doors or areas you do not want him to scratch or lay on. I use this for my infants crib when he’s not sleeping - works wonderfully. Additionally you could apply citronella on a cloth and wipe the doors. It doesn’t last forever but it’ll last longer than store bought pet deterrents. 

Good luck with your naughty kitty! 

You can search cat scratching boards find one if it could attach on your door. and you can try if some cat tree or cat scratching post could attract your cat's attention.

Ps: if you need cat tree cat cube cat scratching please have a look on cupets cat tree. 

Fit a cat flap, preferably a microchip operated one , and let it go out. It obviously wants to. 

Build or buy an enclosure (catio) where the cat can go outside but not roam off your property.  Here are examples :   https://www.catsofaustralia.com/cat-enclosures.htm

Get a tyoe of shock collar that shocks him when he goes near the door

Our son went through this. His cat scratched and scratched, and was quite sad. He meowed a LOT and made it nearly unbearable for them - I know because when we visited, we saw it first-hand. 

Because this cat had been out on occasion, the cat knew what he wanted. I suggested they let him out because it was unlikely the cat would stop. After a long while, they finally relented, and let Snuggie out. 

Yes, he loved it, yes he comes back at night, yes they are terribly relieved they have done this because life is much better for everyone. The cat is microchipped, and in the least a cat should have a collar and I.D. He now goes out every day, and is a happy cat.

Can I tell you this is best for you and your cat? Of course, I cannot. Each cat is different. Some have had the experience of being outsid!). Our cat used to sit at the door in the morning, just to go outside for potty purposes. Much easier on the litter box, too.

Some cats are smart about being outside, some aren't quite as smart. Some houses are too near busy roads, etc. 

If you can let the cat out, then try it and BE SURE he is inside before dark and not out again after that last meal. 

If you simply cannot let him outside, get a tall cat tree and place it near a window. Put a little catnip spray on it to make it more attractive. If you are especially creative, you can make the cat tree out of real branches, with little spots for him to sit. Some people even decorate them with what looks like leaves. Some build cat shelves which help occupy the cat and give spots for climbing. 

If you are especially devoted to your cat, try making a "catio" for him. You can look this up - it is a somewhat outside alternative but entirely safe for the cat. 

https://www.google.com/search?q=catio&rlz=1C1SQJL_...

After having experience with cats who INSIST on being outside, I can say, it is worth it for them to be happy and live a happy life. Our indoor-outdoor cats have all lived to be about 20 years. Most neutered cats will stay near the house. Our cat used to greet people walking by on the sidewalk, and had his special "friends", who loved petting him as much as he loved the greetings. 

Each cat is different, but I don't think any type of squirting, yelling or chasing from the door will cause your cat to stop trying, so if you are looking for the "perfect answer", unfortunately there may be none. 

If he does stop trying, he is likely to end up being sad or depressed which will be the reason he stops. He sounds like one of those cats who loves being outside.

Clip the claws weekly. Cut off the sharp tip. That would make the scratching harmless.

Try putting some double sided tape (sticky on both sides) on the areas he's scratching. Most cats do NOT like having something sticky on their paws. It will likely annoy him if he gets up to scratch and feels that tape. You can also spray the door with a safe deterrent.

I would suggest putting him in a crate when he does that and leave it near the door. Maybe he'll figure out that he's not supposed to do that after some time.