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Using MTL » Fabrication » Standard Operating Procedures

ALD

STANDARD OPERATING PROCEDURE

CORAL Name:

aald

Model Number:

--

Location:

ICL

What it does:

Atomic Layer Deposition (ALD) tool

Introduction:

The Cambridge Nanotech Atomic Layer Deposition (ALD) tool allows deposition of various materials at the atomic scale by sequential pulsing of special precursor vapors.

Safety:

Due to the toxic nature of the process gases, the supply cylinders are turned on and off by qualified technical staff only. All tank changes are performed by qualified technical staff only. Do not try to defeat any interlock on the system. Keep your hands away from all moving parts and be sure that all covers are in place when you are processing. If you encounter any equipment problems while operating the system, contact the technical staff in charge of the system. Do not try repairs on your own.

Procedure:

It is mandatory to reserve the system prior to use and to ENGAGE MACHINE prior to starting your process in CORAL.

Starting an ALD Process:

Before beginning a process, the chamber and precursor temperatures should be set to the temperatures required for deposition and the system allowed to come up to temperature. The correct chamber temperatures are as follow:

Film	Inner Heater (#9)	Outer Heater (#8)
Hafnium Oxide	200°C	200°C
Aluminum (TMA)	200°C	200°C
Aluminum (TDMAA)	200°C	200°C
Tungsten Nitride	350°C	250°C

The precursor temperatures are:

Precursor	TC#	Setpoint
Hafnium	11	95°C
Tungsten	12	90°C
Aluminum (TMA)	13	n/a
Aluminum (TDMAA)	13	108°C

ALD 1

The process chamber is kept under vacuum and must be vented to load your sample.

Make sure all ALD valves on the precursor cylinders are shut.
Set the Nitrogen flow to 100 sccm.
Press the Vent button.

ald 2

When the chamber pressure reaches atmosphere (7.60E+02)

Set the Nitrogen flow to 5 sccm.
Open the process chamber lid.

Pieces and wafers should be processed on top of the dummy wafer that should always be present in the chamber.

Be careful not to come into contact with the chamber surface – the chamber temperature is kept at 150°C and this may melt gloves and result in a serious injury.
Do not load samples using composite or plastic tweezers as they may melt.

Close the chamber lid and ensure it is centered on the chamber body. Press the Pump button.

ald 3

Recipes are loaded and edited from the text box in the center of the screen.

right click anywhere in the recipe area and select ‘Load Recipe’
Choose the desired recipe from the ‘MASTER_09’ folder.
Simple edits may be made to change the number of cycles or the chamber temperature only. Do not change purge times, carrier flow rates or precursor pulse times. Never change the precursor operating temperature , as overheating will result in the premature degradation of the precursor.
With the sample loaded, and the chamber under vacuum, the process is almost ready to start. The estimated run time is indicated on the screen.

Before starting a recipe, the required precursor/gas valves must be opened on the manifold. Open the door to the ALD cabinet – the precursor manifold is on the left side. The precursors are installed as follows:

Port	Precursor	Chemical Name
0	Hafnium	Tetrakis(dimethylamido)-Hafnium (IV)
1	Tungsten	Bis(tert-butylimino)bis(dimethylamino)-Tungsten
2	Aluminum	Tris(dimethylamido)-Aluminum (III) or Trimethyl Aluminum
3	Water/Ozone	H2O or O3
4	Ammonia	NH3

Each precursor cylinder has a black quarter turn valve installed inline – these valves should remain in the closed position (perpendicular to the cylinder) when not in use.

Open the valve for the required precursor by turning the valve 90° counter-clockwise.
When depositing Tungsten Nitride, click on the Advanced tab and set the Overpressure Threshold to 500 torr – when the Ammonia ALD valve is pulsed, the resulting pressure increase can cause an error if this valve is not increased from the default value of 250 torr.

Press the Start button to being processing. As the recipe progresses you should observe pressure spikes as each ALD valve opens and closes. Absence of a spike during each pulse may indicate a problem with the ALD valve or the exhaustion of the precursor. If you have made an error in the recipe or something does not appear to be functioning correctly, press the Abort button to end the recipe.

When the recipe has ended, close the precursor valves and Vent the chamber to recover your samples.

If no further samples are being processed, load the recipe “DEGAS” and press Start. This recipe will purge the headspace of excess precursor vapor, helping to maintain purity and increasing the lifetime of the ALD valves.

When processing is complete, return the system to idle state temperature using the following values:

Item	TC #	Setpoint
Foreline	6	100°C
Isolation Valve	7	100°C
Outer Heater	8	100°C
Inner Heater	9	150°C
Manifold	10	115°C

All precursor temperatures should be set to 0°C.

ALD 4

Author:

Donal Jamieson, 9/10