Specific Process Knowledge/Thermal Process/Dope with Phosphorus: Difference between revisions

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-==Phosphorous doping test after change of hardware==
+==Phosphorous doping test after hardware and software upgrades==
-In 2022, the POCl has line lines on the furnace were modified. At the same time some software changed were also made, and the recipes on the furncewere updated.
+In 2022, the POCl<sub>3</sub> line on the furnace was modified to make the setup more safe. At the same time some software changes were also made, and the recipes on the furnace were updated.
-Afterwards, a phosphorus doping test was made with a test wafer and four dummy wafers (two dummy wafers on each side of the test wafers) in the furnace.
+Afterwards, a phosphorus doping test was made to see, if the modification had affected the phosphorus doping process. The test was done with a test wafer and four dummy wafers (two dummy wafers on each side of the test wafers) in the furnace.
 ====Process:====
-* RCA cleaning of test wafer (p-type, 1-20 Ωcm) and dummy wafers
+* RCA cleaning of the test wafer (p-type, 1-20 Ωcm) and the dummy wafers
-* Phosphorus pre-dep in the A4 furnace. Recipe: "POCLNEW", 900 °C, 15 min phosphorus pre-dep and 20 min annealing
+* Phosphorus pre-deposition in the Phosphorus Pre-dep furnace (A4).
+** Recipe: "POCLNEW"
+** Temperature: 900 °C
+** Time: 15 min phosphorus pre-dep and 20 min annealing/N<sub>2</sub> post purge
 * BHF dip in the RCA cleaning bench to remove phosphorus glass from the test wafer
 * Measure sheet resistance using the 4-point proble
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 After the process describe above, the sheet resistance on the test wafer was measured.
-The sheet resistance was 54 Ωsq in the center of the wafer and 45-48 Ωsq in the edge of the wafer. This correspond quite quite good to results that have been obtained previously for the furnace as can be seen on this LabAdviser page.
+The sheet resistance was 54 Ωsq in the center of the wafer and 45-48 Ωsq in the edge of the wafer. This correspond quite good to the results that previously had been obtained for the furnace as can be seen on this LabAdviser page.
+====Notes about the "POCLNEW" recipe====
+A new recipe called "POCLNEW" was made, after the POCl<sub>3</sub> line was modified. The N<sub>2</sub> high flow (3 SLM) is on all the time through the recipe. There is a 2 min pre-purge with first N2 low (150 sccm) through the POCl3 bubbler, i.e. with the valves v4a and v4b closed, and then with O2 (0.50 SLM), before the pre-deposition time starts. After the pre-deposition, an N2 low post-purge (500 sccm) is done for 2 minutes with v4a and v4b closed.
+For safety reasons it is important that the POCl<sub>3</sub> is completely removed from the furnace, before it is opened to load or unload wafers.
+With 150 sccm N2 low through 25°C POCl<sub>3</sub> liquid + 3 slm N<sub>2</sub> high + 0.5 slm O<sub>2</sub>, 3300 ppm Cl<sub>2</sub> is created in the tube. These 3300 ppm Cl<sub>2</sub> must be diluted to less than 0.5 ppm (the TLV value).
+The tube diameter is 16 cm and the length without ball valve is about 125 cm, and thus the volume is about 25 L. After the phosphorus pre-deposition step, the N<sub>2</sub> high flow (3 SLM) is on during the annealing/N<sub>2</sub> post purge, the cooling and a waiting step. The time for the waiting step is 30 minutes, so even if the annealing time is set to 0 minutes, and the furnace does not have to cool down, there will still be an N<sub>2</sub> high flow for 30 minutes to remove the POCl<sub>3</sub> from the furnace. The waiting time is the same in the abort recipe that is activated, if the "POCLNEW" recipe is aborted.
+The "POCLNEW" recipe can just be modified with other temperatures an names.