Atomic Layer Deposition Recipes

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Atomic Layer Deposition (Oxford FlexAL)

Atomic Layer Deposition (aka ALD) - what is it?

Atomic layer deposition (ALD) utilizes sequential exposure cycles of 2 gaseous precursors to a substrate surface. Each half-cycle exposes one of the precursors to the substrate (and in the absence of the other) to ensure a "saturated" coverage on the surface. The saturation in exposure within each half-cycle leads to the self-limiting reaction behavior which defines an ALD process from other deposition techniques. With this in place, the deposition can proceed layer-by-layer with cycling and will result in uniform conformal growth over different substrate topographies.

In most standard process, one half-cycle utilizes an organometallic precursor to deposit the metal of interest. The other half-cycle utilizes a counter-reactant to either oxidize or nitridize this metal to form the oxide or nitride film required.

By nature of the deposition process, the reactions are slow. Hence, users are restricted to 30 nm maximum thickness for all films when using the tool. Any deviations from this requirement needs special permission (contact Tool Supervisor if needed).

Process Options

Thermal ALD

In all ALD processes used in our lab, the organometallic half-cycle is always thermal, i.e., the precursor is exposed to the substrate as a vapor. In a fully thermal ALD process, the counter reactant half-cycle also utilizes gas exposure to the substrate. Because the intact molecules are less reactive than activated gases from a plasma, thermal ALD can be on the slower side. One advantage however is this lower reactivity means that the substrate itself can remain inert to the deposition process.

Activated ALD

Plasma

O* or N* in the recipe title means Oxygen or Nitrogen plasma, derived from flowing O2 or N2 gases through the ICP tube at the top of the chamber, respectively.

The plasma processes on this tool will run considerably faster than purely thermal processes, because the ions/radicals formed are significantly more reactive (which can be a drawback if depositing on a sensitive substrate). Note that the O* plasma can also reduce carbon contaminants from the organic precursors when forming oxide films. When growing nitride films, H2 is often added to the nitride-plasma gases to generate H* ions/radicals which can assist with the removal of C within the film.

Ozone

O3 in the recipe title refers to an oxidation reaction that uses an external Ozone generator for oxide growth (InUSA, Series 5000). Ozone is a more reactive form of oxygen than O2 that can be used to generate oxide films in a more thermal manner than plasma.

Note that the generator must first be turned on prior to running any ozone-based recipe. Clicking on the O3 Generator icon on the tool desktop will open the control window. Both the O2 flow and the O3 concentration should be set to the defaults of 250 sccm and 19 wt% in the field settings. Clicking on the "Start Generator" button will start the ozone generator running. Wait for about 5 minutes for the system to stabilize. When done, always be sure to click on the "Stop Generator" button to turn off the generator and stop the O2 flow - it is very important not to forget to do this as the source could be burned out and/or the O2 bottle supplying the generator could be depleted if it runs too long! O2 will remain flowing for an additional minute to flush out any residual O3. Once that is completed, you can close the window. Check with supervisor for further details.

Chamber #1: Conductive Films

Chamber 1 utilizes a dual manometer system that allows higher pressures during deposition than chamber 3.  For example, chamber 1 has an upper limit of 2000 mTorr whereas chamber 3 has an upper limit of only 240 mTorr.  The higher pressures allow the use of less reactive organo-metallic precursors to effect ALD growth in a reasonable time-frame.

Maximum 30nm deposition thickness for all processes in chamber 1! Any depositions outside this maximum are prohibited unless discussed first with the Tool Supervisor.

Al₂O₃ deposition (ALD CHAMBER 1)

• Recipe name: CH3-TMA+H2O-300C ("Thermal")
  • 300°C Dep., Thermal Water reaction
  • This is considered the standard recipe for ALD
  • Al₂O₃ deposition rate ~ 1 A/cyc
  • Recipe variations: TBD

Pt deposition (ALD CHAMBER 1)

• Recipe name: Ch1_TMCpPt+O3-300C
  • Pt deposition rate ~ 0.5-0.6 A/cyc
  • Conductivity data: (to be added)
  • recipe utilizes the ozone generator which must be first set to the following conditions:
    • O₂ flow = 250sccm
    • O₃ concentration = 15 wt%
  • 300°C deposition
• Recipe name: CH1-TMCpPt+250W/O*-300C
  • Uses Oxygen plasma
  • 300°C deposition

Ru deposition (ALD CHAMBER 1)

• Recipe name: Ch1_Ex03Ru[HPbub]+O2-300C
• Ru deposition rate ~ 0.6-0.7A/cyc.
• Conductivity data: (to be added)
• 300°C, O2 gas reaction

SiO₂ deposition (ALD CHAMBER 1)

• Recipe name: CH3-TDMAS+250W/O*-300C ("Plasma")
  • SiO₂ deposition rate ~ 0.7-0.8A/cyc
  • Recipe utilizes an O* plasma @ 250W, 5mTorr pressure, 300°C Temp.
  • Temperature variations: 300*C (std.), 250°C, 200°C, 120°C
• Recipe name: CH1-BDEAS-O*/300W-300C
  • SiO₂ deposition rate ~ 1.008 A/cyc
  • Similar to above TDMAS recipes, with different precursor gas.
  • Temperature variations: To Be Added
  • Etch rate (BHF:DI=1:100)~7.46nm/min

ZnO Deposition (ALD Chamber 1)

Conductive film.

• Recipe name: Ch1_DEZ+H2O-200C
• ZnO deposition rate ≈ 1.6 A/cycle
• resistivity ≈ TBA
• 200°C Deposition, Water reaction

ZnO:Al deposition (ALD CHAMBER 1)

Al-Doped ZnO for variable resisitivity.

• Recipe name: Ch1_DEZ/TMA+H2O-200C
  • The recipe has TWO loops. The Outer loop determines final thickness. The Inner loop determines how much AlOx is doped into the film. Note that each full (outer-loop) cycle takes a long time due to this double-loop structure.
• Al dose fraction = 5% for lowest resistivity
• ZnO deposition rate ~ 1.7A/cyc
• resistivity ~ 4200uOhm.cm (390A film)

Oxford FlexAL Chamber #3: Dielectrics

Maximum 30nm deposition thickness! (ask Tool Supervisor if needed.)

Al₂O₃ deposition (ALD CHAMBER 3)

• Recipe name: CH3-TMA+H2O-300C ("Thermal")
  • 300°C Dep., Thermal Water reaction
  • This is considered the standard recipe for ALD
  • Al₂O₃ deposition rate ~ 1.192 A/cyc
• Recipe name: CH3-TMA+H2O-250C ("Thermal")
  • Al₂O₃ deposition rate ~ 1.214 A/cyc
• Recipe name: CH3-TMA+H2O-200C ("Thermal")
  • Al₂O₃ deposition rate ~ 1.184 A/cyc
  • Temperature variations: 300°C (std.), 250°C, 200°C, 150°C, 120°C
• Recipe Name: CH3-TMA+250W/O*-300C ("Plasma")
  • Oxygen Plasma reaction instead of H2O
  • Lower carbon content
  • Approx. 1.5–2x faster deposition rate than thermal.
  • Temperature variations: 300°C (std.), 200°C, 120°C
• Recipe Name: CH3-TMA+O3/200mT-300C ("Ozone")
  • Similar dep. rate
  • Ozone (O₃) reactant, experimental
  • Requires Ozone generator to be turned on - ask supervisor

AlN deposition (ALD CHAMBER 3)

• Recipe name: CH3-TMA+100W/N*-300C
  • AlN deposition rate ~ t.b.d.
  • Recipe utilizes a N* plasma @ 100W, 20mTorr pressure.
  • Temperature Variations: 300°C Dep. (std.), 200*C, 120°C
  • Power variations: 300W, 400W (at 300°C)
  • Nitrogen/Hydrogen variations: "30N*/30H*" at 200*C and 300°C

HfO₂ deposition (ALD CHAMBER 3)

• Recipe name: CH3-TEMAH+H2O-300C ("Thermal")
  • HfO₂ deposition rate ~ 0.9-1.0A/cyc
  • Note: deposition shows significant parasitic growth (via CVD channel) if H₂O purge/pump times are not sufficient.
  • Temperature variations: 300°C (std.), 250°C, 200°C, 150°C, 120°C
• Recipe name: CH3-TEMAH+250W/O*-300C ("Plasma")
  • Uses Oxygen plasma reactant instead of H₂O
• Recipe name: CH3-TEMAH+O3/100mT-300C ("Ozone")
  • Uses Ozone (O₃) for reactant instead of H₂O
  • Requires Ozone generator to be turned on - ask supervisor

SiO₂ deposition (ALD CHAMBER 3)

• Recipe name: CH3-TDMAS+250W/O*-300C ("Plasma")
  • SiO₂ deposition rate ~ 0.7-0.8A/cyc
  • Recipe utilizes an O* plasma @ 250W, 5mTorr pressure, 300°C Temp.
  • Temperature variations: 300°C (std.), 250°C, 230°C, 220°C, 200°C, 175°C, 150°C, 120°C
• Recipe name: CH3-TDMAS+O3/200mT-300C ("Ozone")
  • Uses Ozone (O₃) for reactant instead of H₂O
  • Requires Ozone generator to be turned on - ask supervisor

ZrO₂ deposition (ALD CHAMBER 3)

• Recipe name: CH3-TEMAZ+H2O-300C ("Thermal")
  • ZrO₂ deposition rate ~ 0.9-1.0A/cyc
  • Not directly characterized since results are basically the same as the HfO₂ process above.
  • Temperature variations: 300°C (std.), 200°C
• Recipe name: CH3-TEMAZ+250W/O*-300C ("Plasma")
  • Uses Oxygen plasma reactant instead of H₂O
• Recipe name: CH3-TEMAZ+O3/100mT-300C ("Ozone")
  • Uses Ozone (O₃) for reactant instead of H₂O
  • Requires Ozone generator to be turned on - ask supervisor

TiO₂ deposition (ALD CHAMBER 3)

• Recipe name: CH3-TDMAT+H2O-300C ("Thermal")
  • TiO₂ deposition rate ~ 0.6A/cyc
  • Note: deposition shows parasitic growth (via CVD channel) if H₂O purge/pump times are not sufficient.
  • Temperature variations: 300°C (std.), 200°C, 120*C
• Recipe name: CH3-TDMAT+250W/O*-300C ("Plasma")
  • Uses Oxygen plasma reactant instead of H₂O

TiN deposition (ALD CHAMBER 3)

• Recipe name: CH3-TDMAT+400W/12N*/4H*-300C
  • TiN deposition rate ~ 0.7A/cyc
  • Conductivity data: (to be added)
  • Uses Plasma of N2 & H2 gases.
  • Temperatures: 300°C (std.), 200°C
• Recipe name: CH3-TDMAT+100W/N*-300C
  • Uses Plasma of N2 only
  • Temperatures: 300°C (std.), 200°C
• Recipe name: CH3-TDMAT+100W/NH3*-300C
  • Uses Plasma of NH₃ only
  • Temperatures: 300°C (std.), 200°C

Historical Data (ALD Chamber 3)

• 2021 ALD Al2O3 (H2O, 300°C) Historical Data