Specific Process Knowledge/Thermal Process/Oxidation/Standard oxidation recipes

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The oxidation furnaces in the cleanroom are being used for dry and wet oxidation of silicon wafers.

On this page the steps in the standard oxidation recipes on the furnaces will be listed.


Dry oxidation can be done in the these furnaces:

  • A1 Boron Drive-in and Pre-dep furnace
  • A2 Gate Oxide furnace
  • A3 Phosphorus Pre-dep furnace
  • C1 Anneal-Oxide furnace
  • C3 Anneal-Bond furnace
  • Multipurpose Anneal furnace

The dry oxidation recipes in the A- and C-stack furnaces are very similar and will be described on this page.

There are no standard recipes on the Multipurpose Anneal furnace, so no oxidation recipes will be described here.


Wet oxidation can be done in these furnaces:

  • A1 Boron Drive-in and Pre-dep furnace
  • A3 Phosphorus Pre-dep furnace
  • C1 Anneal-Oxide furnace
  • C2 III-V Oxidation furnace
  • C3 Anneal-Bond furnace

The wet oxidation recipes in the A-stack, C1 and C3 furnaces are very similar.

However, there are a few differences in recipes, because water vapour can be generated by either a torch, a steamer or a bubbler. More information can be found on each furnace page.

Wet oxidation of III-V sample in the C2 furnace is described here:

http://labadviser.nanolab.dtu.dk/index.php/Specific_Process_Knowledge/Thermal_Process/Oxidation/Oxidation_on_III-V_oxidation_furnace_(C2)

General recipe remarks:

The oxidation temperature is fixed in each recipe. The temperature can be seen in the recipe name, e.g. "DRY1000" for dry oxidation at 1000 C and "WET1100" for wet oxidation at 1100 C.

The oxidation and annealing times are variable commands in oxidation recipe. It means that these can be changed by the users.

The oxid thickness is defined by the oxidation time. Wet oxidation is much faster then dry oxidation. It is maximum allowed to grow 300 nm of dry oxide and 3 um of wet oxidation.

The annealing improves... The standard annealing time is 20 minutes, but it is possible to change the time.





Dry oxidation recipe steps

00 STANDBY

Message: "Standby"

This will be the active step, when the furnace is not in use, and when a recipe is selected.

If a recipe is aborted, it will also jump to the STANDBY step.

In the standby step, the furnace is closed and kept clean by an N2 flow.

  • Standby temperature: 700 oC
  • N2 flow: 3 SLM
  • O2 flow: 0 SLM

The user has to press "Start" (on the touch screen or furnace computer) to start the recipe.


01 LM-LOCK

The recipe can only continue, if a user is logged on in LabManager, otherwise the furnace will shown an alarm (digital input 6) after 1 minute.


02 OPEN

Message: "Boat moving"

The furnace opens


03 LOAD WAFERS

Message: "Load wafers

When the furnace is open, the user can load wafers in the furnace.

The quartz boat for the wafers is located in furnace, so it has to be liftet down on the quartz plate, before the wafers are loaded.

After the wafers are loaded, the user has to press "Start" (on the touch screen) or "Continue" (on the furnace computer) to close the furnace.


04 CLOSE

Message: "Boat moving"

The furnace closes.


05 HEAT UP

Message: "Heat-up"

The furnace heats up to the temperature defined in the recipe (usually 800-1150 oC).

The recipe will continue to the next step, when the temperature of center heating zone (zone 2) reaches the right temperature.


06 OXIDATION

Message: "Oxidation"

The dry oxidation is started by flowing O2 through the furnace instead of N2</sub.

  • O2 flow: 5 SLM
  • N2 flow: 0 SLM

The oxidation time is a variable command, so it can be set by the user.

The oxidation time can be changed, until the oxidation step is started.


07 ANNEAL

Message: "Anneal/Dens"

The O2 gas is purged out of the furnace by an N2 flow, so that the oxidation stop.

The wafers are annealed in N2 at the same temperature as the oxidation temperature. The annealing will improve the oxide quality by making it more dense.

  • N2 flow: 6 SLM
  • O2 flow: 0 SLM

Normally the annealing time is 20 minutes, but it is a variable command, so it can be set by the user.

The annealing time can be changed, until the annealing step is started.


08 COOL DOWN

Message: "Cool-down"

The furnace is cooling down to 700 oC (the standby temperature)


09 UNLOAD WAFERS

Message: "Unload wafers"

The recipe is paused, until the user presses "Start" (on the touch screen) or "Continue" (on the furnace computer).


10 OPEN

Message: "Open"

The furnace opens.


11 UNLOAD

Message: "Unload wafers"

When the furnace is open, the wafers can be unloaded.

Place the boat on the quartz plate in front of the furnace to unload the wafers. And be aware of, that the wafers are very hot, so they have to cool down for a few minutes, before they are removed from the boat.

When the wafers are unloaded, the user has to press "Start" (on the touch screen) or "Continue" (on the furnace computer) to close the furnace. The recipe then jumps to the STANDBY step, and the user can leave the furnace, after it has closed.

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