Using environmentally friendly wet ozone instead of chemicals, we removed B-, P-, and As-ion-implanted positive-tone novolak photoresists with an implantation dose of 5 X 10(12)-1 X 10(16) atoms/cm(2) at an acceleration energy of 70 keV. Ion-implanted photoresists with an implantation dose exceeding 5 X 10(15) atoms/cm(2) could not be removed, but photoresists implanted at doses below 5 X 10(13) atoms/cm(2) could be removed. Photoresist implanted with B ions at 5 X 10(14) atoms/cm(2) was removed slowly, but photoresists implanted with P and As ions were not removed at all. The hardness of the photoresist with B ions implanted at 5 X 10(14) atoms/cm(2) was 1.8 times greater than that of the nonimplanted photoresist (AZ6112), that of the P-ion-implanted photoresist was eight times greater, and that of the As-ion-implanted photoresist was five times greater. The B-ion-implanted photoresist was softer than the P- and As-ion-implanted photoresists. We also obtained the calculation results in which the energy supplied from the B ions to the photoresist was lower than that from P and As ions. We assumed that the ion-implanted photoresists were hardened by cross-linkage due to the energies supplied to the photoresists from the ions. Therefore, we determined that the hardness threshold of the photoresist that could be removed by using wet ozone was twice the hardness of AZ6112. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3121583] All rights reserved.