Preheat oven to 350. Prepare a 1 1/2-quart casserole dish with cooking spray; set aside. In a mixing bowl, combine chicken, celery, cheese, onions, lemon juice, salt, black pepper, and mayonnaise. Mix lightly. Spoon into prepared dish. Sprinkle chips on top. Bake for 35 minutes, or until lightly browned on top.