Abstract: A new and improved substrate holder assembly for supporting a substrate in a process chamber for the fabrication of semiconductor integrated circuits on the substrate. The substrate holder assembly comprises an annular shield which is fitted in the process chamber. A dish-shaped substrate holder extends through the center of the shield and includes a pair of outwardly-extending pin support flanges that are disposed beneath the shield. The substrate holder includes an annular substrate support shoulder for supporting the substrate. A substrate clamp of the substrate holder assembly includes a pair of downwardly-extending alignment pins which are inserted through respective pin openings in the shield and are supported by the respective pin support flanges. Accordingly, the alignment pins align and support the substrate clamp slightly above the substrate holder to prevent direct contact of the substrate clamp with the substrate holder thus, the formation of potential device-contaminating particles.