in step 130 after the precursor gas 18 has infiltrated spaces 12 14 16 the deposition chamber 2 is partially evacuated the partial evacuation of the deposition chamber 2 creates a gradient of precursor gas 18 within the spaces 12 14 16 as described above in step 140 the temperature of the substrate 4 is briefly increased above the threshold temperature or temperature range required for deposition of the precursor gas 18 onto the substrate 4 in particular for deposition to take place deep inside the high aspect ratio spaces because the thickness of the film deposited during each cycle is proportional to the local pressure of the precursor gas and further because the heating takes place when the chamber is beginning to be evacuated the deposited film thickness is always higher at the deeper end of individual high aspect ratio structures e g vias therefore by creating a pressure gradient the mechanism of keyhole formation is effectively reversed allowing for deep vias to be filled from the bottom to the top and no danger of the entrance being u201c pinched off u201d in a preferred embodiment the temperature of the substrate 4 is raised by use of one or more rtp heaters 10 in the process described above a single conformal thin film is deposited in the spaces 12 14 and 16 preferably the process e g steps 110 through 140 is repeated a plurality of times to completely fill the spaces 12 14 16 for example each cycle of the process may deposit a film having a thickness within the range of about 0 1 nm to about 3 nm the process may be repeated until the spaces 12 14 16 are completely filled for example the.