SF₄ have Sp₃d hybridisation. SF₄ is not square planar. SF₄ has a seesaw geometry. Sulfur tetrafluoride has 10 electrons around the central sulfur atom. This means there are five electron pairs are present. The molecule has four S-F bonds and just one lone pair. Lone pair will occupy the place with least LP-bond repulsion. If LP occupies axial position in trigonal bipyramid, it will "feel" three S-F bonds nearby. If LP occupies equatorial position, it will "feel" only two S-F bonds, as other two will be pushed more away.