The critical dimension (CD) of features formed during the fabrication of a semiconductor device may be controlled through the use of a dry develop chemistry comprising O2, SO2 and a hydrogen halide. For example, a dry develop chemistry comprising a gas comprising O2 and a gas comprising SO2 and a gas comprising HBr may be used to remove exposed areas of a carbon-based mask. The addition of HBr to the conventional O2 and SO2 dry develop chemistry enables a user to tune the critical dimension by growing, trimming and/or sloping the sidewalls and to enhance sidewall passivation and reduce sidewall bowing.