Uniformity Testing Procedure for TylanBPSG LTO
Purpose: To provide a standard procedure to monitor oxide thickness and uniformity both wafer-to-wafer over a 52 wafer load and within-a-wafer.
Frequency of test; to be completed after major maintenance such as a tube change or on a set schedule to be determined or as needed based on user feedback.
Documentation of results; to be posted in hardcopy in the Uniformity Test Book located in the lab, posted in the email archive for TylanBPSG and keep in process/maintenance group internal spreadsheet.
††††††††††† Use six new 'L' test wafers; <100>, P-type (boron), 10-20 ohm-cm.
Clean at wbdiff in the following sequence;† 4:1 H2SO4:H2O2 ten minutes, rinse, 5:1:1 DI;HCl:H2O2 ten minutes, rinse, 50:1 DI:HF 30 sec, rinse, spin dry.
††††††††††† Load program LTO400 into TylanBPSG.† Time variable is 00:20:00.
The boats must be loaded with dummies (26 wafers in each) at all times to ensure uniform wafer to wafer deposition.
Using very clean tweezers or vacuum wand replace the dummy wafers with a cleaned test wafers the following positions:
1st boat (Front) in the third slot.
1st boat in the 13th.†
1st boat in the 25 slot.†
2nd boat (Back) in the third slot.
2nd boat in the 13th.†
2nd boat in the 25 slot.†
Use Nanospec to measure oxide thickness across each wafer in five locations.† Test sites should be no more than about 15mm from the edge of the wafer.
Record results on the Uniformity Testing Form and post to appropriate email and spreadsheets. If testís values arenít not within 10% of plotted test average, contact the Diffusion Process/Maintenance team.
††††††††††† Save wafers in a box with the date, furnace number, program name and growth time.† They may be re-tested sometime in the future.