A polishing head for performing chemical-mechanical polishing on a linear polisher has a dual stage wafer carrier assembly that incorporates a removable subcarrier. When in use, a main pressure chamber exerts a downforce on the subcarrier housing, while a separate secondary pressure chamber residing between the subcarrier housing and the subcarrier exerts a slightly different downforce on the subcarrier. Since the second pressure chamber exerts the downforce pressure directly on the subcarrier, the direct pressure application, as well as a more uniform distribution of pressure ensures for an improvement to the uniformity of pressure distribution. Additionally, the easily removal subcarrier allows for faster and easier removal of the subcarrier for cleaning and maintenance, as well as for changing inserts and improving process repeatability.