A spin on carbon composition, comprises: a carbon backbone polymer; a first crosslinker; and a second crosslinker. The first crosslinker reacts with the carbon backbone polymer to partially crosslink the carbon backbone polymer at a first temperature, and the second crosslinker reacts with the carbon backbone polymer to further crosslink the carbon backbone polymer at a second temperature higher than the first temperature. The first crosslinker is a monomer, oligomer, or polymer. The second crosslinker is a monomer, oligomer, or polymer. The first and second crosslinkers are different from each other. When either of the first crosslinker or the second crosslinker is a polymer, the polymer is a different polymer than the carbon backbone polymer.