l SW_TSpecify the sidewall thickness of uniform layer. This definition is only allowed when the layer type is “UNIFORM”. As uniform layer, thickness, sw_t and tw_t can not be 0 at the same time. l TW_TSpecify the top thickness of uniform layer. This definition is only allowed when the layer type is “UNIFORM”. As uniform layer, thickness, sw_t and tw_t can not be 0 at the same time.