Depending on what camera took it, a medium format square negative (120, 620, 6x6cm) can have enough picture detail for a 14 inch square print. Maybe even more. All negatives should be scanned at 3000 dpi more or less (2400 dpi absolute minimum) and in the case of the medium format negative, you can expect it will take at least as long as scanning an 8x10 inch or 8-1/2x11 print at 300 dpi.
You can scan the negative itself at 200 to 500 dpi to make pictures to put on web sites and this will scan quite fast, except that these pictures are not suitable for archive purposes.
There are a lot of combination regular and film scanners with a lift top (flatbed scanners) but you need the film scanning portion down the middle to be a little over 2 inches wide to do the square negatives. Check the instructions and specifications before buying.