제조 is an engineering term (to manufacture) 제작 is an artistic term (movie, music, etc) or when only very few or a single unit is created (prototype) 생산 is an economic term (국민총생산 = GDP)

제조 Manufacturing. 농업/제조업/서비스업, (공장에서) 비행기나 자동차를 제조하다 제작 To produce something new with materials. 공구, 영화, 음반, 예술 작품을 제작하다 생산 To produce something necessary for human. The broadest meaning. 상품, 쌀, 석유, 농업 생산.