Symbolism, Imagery, Allegory
Images of tombs and burials pop up a lot in the Oedipus plays. In Antigone, Creon causes all kinds of problems by bungling issues of burial. The prideful king has committed a double blasphemy by letting Polyneices's body go unburied, while entombing Antigone when she's still alive. At points we feel like saying, "No, no, Creon. It's the dead ones that go in the ground." The symbolic paradox of Creon's double blasphemy, shows just how far from sensible Creon's hubris has taken him.
Also, Antigone's fearless march to her own entombment and talk of being a bride to death suggests that she feels closer to her dead family members than to the living. She seems to have no problem at all leaving behind her sister Ismene and her fiancé Haemon, but talks of how swell it will be to reunite with Oedipus and her brothers in death. When Antigone takes her own life inside her tomb, it could be seen as symbolic of the fact that she's found the tragic fate she always knew awaited her.