Generally speaking, RAW photograph formats (including IIQ files from Phase One cameras), can be exported and saved to JPEG or TIFF formats in any digital photo editor with support of IIQ format.
The best choice would be the software provided or recommended by the manufacturer of your camera, but using any of the 3rd party alternatives (BatchPhoto, darktable etc.) should be viable option for iiq to tiff conversion. The resulting file will be just export picture without any of the metadata saved in the original raw file.