Procedure – n-type pocl

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Procedure – N-type POCl3 Dopant and Diffusion @ 9500C

The N-type dopant is POCl3 which runs during the diffusion. Depth of the diffusion is determined by time alone since the temperature is fixed at 9500C.

  1. Furnace #6 is used for N-type dopants (phosphorus)

  2. Verify furnace #6 is available for use

Furnace #6 for phosphorus doping only.

Use only wafer tweezers for Furnace #6

  1. Verify the center zone of furnace is 9500C +/- 20C. Temperature controller is under gas panels.

  2. Adjust temperature if needed.

Verify or set all zones for 9500C

Contact lab manager if all zones do not read 950oC +/- 2O

  1. Using the high temperature gloves, carefully remove the end cap and place on the lowest loader area.

  1. Using only the tweezers designated for phosphorus diffusion load one wafer into the quartz boat.

Shiny side (polished side) faces the furnace. Backside has SiO2 from previous processing. Run only one wafer at a time wafer

  1. Load polished side (shiny side) facing the back of the furnace. Do not remove or adjust the quartz boat from the loader.

  1. Verify/set the main nitrogen flow for 150 - stainless steel ball on the flowmeter. The flowmeters are located in the back of the furnace.

Main nitrogen with SS ball at 150

  1. Verify POCl3 bubbler temperature is 20oC +/- 2oC

POCL3 bubbler showing temperature at 20.4oC

  1. With the robot loader in the manual mode, switch to “load” and the wafers should begin to enter the furnace

Load/unload switch

Switch in manual mode

  1. Allow the loader to load the wafers into the furnace tube. The loader will stop automatically in the center zone of the furnace.

Place the stainless steel plate across the furnace opening. Store the plate on the track above this furnace

  1. Once the wafers have stopped moving place the stainless steel plate to cover the furnace opening as shown in the photo. The plate can be found and stored on the loader track above the loader for furnace #6

  2. Allow the temperature to stabilize for 10 minutes.

  3. Adjust the oxygen flow to a reading of 100 on the flow meter using the stainless steel ball. Adjust the nitrogen source reading to 30 on the flowmeter using the stainless steel ball.

Set the main oxygen to 100 using the stainless steel ball.

Set the source nitrogen to 30 using the stainless steel ball.

Main nitrogen flow remains at 150 SS ball

Furnace #6 gas flow meters

Pressing the black button will illuminate the view port. You should see bubbles when the source nitrogen is flowing

POCL3 inside bubbler

  1. At the end of the diffusion time specified (typically 30 minutes) on the traveler, turn off the source nitrogen. Verify source nitrogen is completely off by verifying no bubbles can be seen in the bubbler.

  2. Allow 5 minutes with the wafers inside the tube to stabilize.

  3. Remove the stainless steel plate covering the furnace opening

  4. Change the load/unload switch on the Robot Load to unload and allow the wafers to come out of the furnace. Verify Robot loader arm is moving.

  5. Once wafer is completely out, turn off the main oxygen flowmeter. Leave the main nitrogen flowmeter at 150 SS ball.

  6. Allow the wafer to cool.

Wafer will have a uniform color on the FRONT side. Notify lab manager if color is not uniform

  1. Once cool, unload the wafer with the phosphorus tweezers. Do not touch or remove the quartz boat from the robot load arm.

File: Procedure – N-Type Spin-on or Paint-on dopant diffusion @ 9500C 7/6/2015

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