An internship abroad is linked to a lot of expenses, e.g. travel, accomodation and living expenses, visa fees. It is possible that you might receive some compensation from your employer, but this is not alway the case. Hence, it is always worthwile to check for other financing options. These depend on region, study course, type, content and period of internship as well as other criteria.
Most scholarships are awarded through the DAAD (the German Academic Exchange Service). However, it is also a good idea to check with different assocations and companies, who might have programs as well.