As the semiconductor manufacturing industry develops into the cutting-edge technology, the thick and high etch resistant material is required. Amorphous carbon layer (ACL), currently widely-used deposition-type film, can meet the requirement for etch resistance, but it has intrinsic problems such as darkness, defect control difficulty and low throughput which give limits to its further application. In order to overcome these problems, a novel thick spin-on carbon hardmask (SOH) is introduced in this paper. We designed the material from molecular level to achieve high etch resistance, good optical property, long shelf life and high thickness. Up to 3 micron-thick films with high transparency and etch resistance were successfully fabricated by spin-coating process. With long-enough shelf life for usage, we expect that this novel SOH can expand the possibility of spin-on material.