swing movement is sufficiently wide and fast as to promote an even temperature distribution of the treatment fluid across the wafer surface thereby to improve uniformity of treatment over a wafer surface as can be seen in fig2 the collector 14 may include multiple levels with the chuck 1 and collector 14 being movable relative to one another along the rotation axis of the chuck 1 so as to position the chuck at each of the levels as desired this positioning may be accomplished by moving the chuck or by moving the collector 14 for example by means of hydraulic jacks on which the collector is mounted in fig3 the apparatus includes two dispense arms 13 1 and 13 2 which are the same in construction but supplied with different process fluids and positioned at different locations about the periphery of the collector 14 each dispense arm is movable along an arcuate path as shown in broken line in fig3 from a standby position at the periphery of the collector 14 to a range of working positions in which the dispense nozzle 4 is positioned above the wafer w in the standby position each dispense arm 3 1 3 2 is received within a respective blow off block 12 1 12 2 in the detail of fig4 the dispense arm 3 1 is shown in its standby position.