As a doctoral researcher, it is also possible for you to receive funding for a student or researcher exchange. The different options for these depend on whether you are employed by the university or not.
If you are doing your dissertation in an employment relationship with the University of Helsinki, the student exchange instructions and agreements do not primarily apply to you. As an employed doctoral researcher, you can instead go on a teacher exchange, which lasts a maximum of 1 week. If you are doing a dissertation with or without a grant, the same instructions and rules apply to you as for exchange undergraduate students. However, a large part of the exchange agreements at the University of Helsinki are only aimed at bachelor's and master's level students, so if you find an exchange destination that suits you, read the instructions carefully and make sure that you are eligible to apply for that destination.
Most of the international visits of doctoral researchers take place with other funding mechanisms than funding from the International Exchange Services and Education Cooperation unit, i.e. for example, travel grants from the doctoral school or with funding from scholarship foundations.
Your supervisor can help you find a suitable exchange destination and a possible supervisor/mentor at the target university. So discuss your plans well in advance with your instructor.