Specific Process Knowledge/Thin film deposition/Deposition of Aluminium/Al Sputtering in Cluster Lesker PC3

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This page is written by Evgeniy Shkondin @DTU Nanolab if nothing else is stated.
All images and photos on this page belongs to DTU Nanolab.
The fabrication and characterization described below were conducted in 2022 by Evgeniy Shkondin, DTU Nanolab.


This page presents the results of Al deposition using DC sputtering in Sputter-system Metal-Nitride (PC3), now commonly known as "Cluster Lesker". The deposition target is Al 3-inch. Source #2 (DC/p-DC) was used.

The focus of the study was the deposition conditions.

The prepared samples were investigated by the X-ray Reflectivity method. The process recipe is following:

  • Power unit: Power Supply 5 (DC)
  • Deposition type: DC
  • Gas: Ar
  • Power used: 100-500W
  • Pressure: 3 mTorr and 8 mTorr
  • Temperature: 20°C (no heating) and 300°C
  • Deposition time: variable

Scanning Electron Microscopy (SEM) was used to visualize surface morphology at different powers and different temperatures. The initial test was performed to roughly estimate the deposition rate so assuming the linear dependence of the rate as a function of power the deposition time was calculated for each power setpoint to achieve the same layer thickness. The deposition rate dependencies with pressure were not considered. This is how the time scales were calculated (183, 228, 304, 456, and 913). Since they were calculated based on a rough estimate, the achieved thicknesses were not the same but were deviating (89.9-94.2nm at 3 mTorr and 58.39-78.54 nm at 8 mTorr). The deviations however a quite small so the surface morphology could easily be compared.

One of the critical questions about this study was the possibility of depositing Al at elevated temperatures (in this case 300°C). This could potentially allow combining deposition of Al with other high-temperature processes (TiN, α-Ta, anatase or rutile TiO2, etc). The tests with 300°C proved it to be impossible since Al creates big droplets and discontinues structure on a wafer. The sample appeared to be rough with a texture similar to the white paper, with no reflection.


Results summary

  • Deposition rate as a function of power.

  • Al thin film deposited at 100-500 W, 3 and 8 mTorr. Room temperature (20°C).

Al Deposition conditions
Deposition conditions at 3 mTorr Pressure
Power (W) Pressure (mTorr) Time (s) Total Thickness (nm) Deposition rate (nm/s)
500 3 183 94.2

0.51

400 3 228 94.1

0.41

300 3 304 93.53

0.31

200 3 456 92.61

0.2

100 3 913 89.99

0.1
Deposition conditions at 8 mTorr Pressure
Power (W) Pressure (mTorr) Time (s) Total Thickness (nm) Deposition rate (nm/s)
500 8 183 94.2

0.43

400 8 228 94.1

0.33

300 8 304 93.53

0.24

200 8 456 92.61

0.15

100 8 913 89.99

0.06


X-ray reflectivity analysis

X-ray Reflectivity analysis of Al samples have been performed to investigate the thicknesses, roughness, and density profiles.

The scans has been obtained using Rigaku XRD SmartLab equipment. The voltage and current settings for the Cu X-ray tube were standard 40kV and 30mA. The incident optics contained a IPS (incident parallel slit) adaptor with 5 ° Soller slit. Other slits: IS=0.03mm RS1=0.03mm and RS2=0.075mm. Step size: 0.01 and measurement time - 5s for each point. Fitting procesure was performed using commercial GlobalFit software assuming the model based on Si substrates with native oxide followed by the deposited Al film with thin oxides and moisture surfaces. The results are summarized in a tables below.


  • X-ray reflectivity results.

  • Al thin film deposited at 100-500 W, 3 mTorr and 20°C. Variable deposition time.

  • Al thin film deposited at 100-500 W, 8 mTorr and 20°C. Variable deposition time.



Extracted values

XRR results for Al layers deposited at 3 mTorr
Top layer (moisture) Main layer Si native oxide Si substrate
Deposition name Al2O3/Moisture thickness (nm) Al2O3/Moisture density (g/cm3) Al2O3/Moisture roughness (nm) Al thickness (nm) Al density (g/cm3) Al roughness (nm) SiO2 thickness (nm) SiO2 density (g/cm3) SiO2 roughness (nm) Si thickness (nm) Si density (g/cm3) Si roughness (nm)
500W, 3mTorr, 183s 3.85 1.90 2.00

90.35

2.68

2.00

 2.21 2.19 0.26 2.33 0.00
400W, 3mTorr, 228s 4.95 1.84 1.98

89.11

2.72

2.11

 2.01 2.32 1.3 2.33 0.00
300W, 3mTorr, 304s 5.13 1.75 2.00

88.40

2.71

2.19

 2.15 2.39 1.36 2.33 0.00
200W, 3mTorr, 456s 5.05 1.36 2.00

87.56

2.72

3.16

 2.22 2.36 2.00 2.33 0.00
100W, 3mTorr, 913s 5.07 1.037 2.00

84.92

2.67

3.9

 0.17 2.26 2.73 2.33 0.00


XRR results for Al layers deposted at 8 mTorr
Top layer (moisture) Main layer Si native oxide Si substrate
Deposition name Al2O3/Moisture thickness (nm) Al2O3/Moisture density (g/cm3) Al2O3/Moisture roughness (nm) Al thickness (nm) Al density (g/cm3) Al roughness (nm) SiO2 thickness (nm) SiO2 density (g/cm3) SiO2 roughness (nm) Si thickness (nm) Si density (g/cm3) Si roughness (nm)
500W, 8mTorr, 183s 4.34 1.87 2.00

74.20

2.71

2.23

 1.76 2.37 0.01 2.33 0.00
400W, 8mTorr, 228s 4.89 1.87 1.99

69.86

2.71

2.02

 2.48 2.49 0.03 2.33 0.00
300W, 8mTorr, 304s 5.07 1.76 1.92

66.85

2.68

2.12

 3.11 2.46 0.00 2.33 0.00
200W, 8mTorr, 456s 5.17 1.47 2.00

62.32

2.67

2.90

 3.95 2.45 0.03 2.33 0.00
100W, 8mTorr, 913s 4.90 1.05 2.00

53.49

2.67

4.06

 5.52 2.42 0.06 2.33 0.00



Fitting parameters
Sample Al2O3/Moisture Al Si native oxide Si substrate Fitting parameters
Delta Beta Delta Beta Delta Beta Delta Beta Intensity Background Fitting area () R
500W, 3mTorr, 183s 6.1989E-6 1.4395E-7 8.4401E-6 1.5722E-7 7.1509E-6 1.6605E-7 7.5860E-6 1.7616E-7 8.23366E-001 1.23806E-006 0.3521 - 2.9423 0.01161 0.00295
400W, 3mTorr, 228s 5.9925E-6 1.3916E-7 8.5759E-6 1.5975E-7 7.5624E-6 1.7561E-7 7.5860E-6 1.7616E-7 8.93948E-001 1.00352E-005 0.3521 - 1.9973 0.01627 0.00458
300W, 3mTorr, 304s 5.7180E-6 1.3278E-7 8.5216E-6 1.5874E-7 7.7964E-6 1.8104E-7 7.5860E-6 1.7616E-7 8.11574E-001 8.94119E-006 0.3521 - 1.9973 0.01832 0.00607
200W, 3mTorr, 456s 4.4169E-6 1.0257E-7 8.5388E-6 1.5906E-7 7.6838E-6 1.7843E-7 7.5860E-6 1.7616E-7 8.58394E-001 1.56839E-005 0.3521 - 1.5000 0.01755 0.00463
100W, 3mTorr, 913s 3.3778E-6 7.8438E-7 8.4137E-6 1.5673E-7 7.3732E-6 1.7122E-7 7.5860E-6 1.7616E-7 9.47129E-001 1.60808E-005 0.3521 - 1.5000 0.01370 0.00293
500W, 8mTorr, 183s 6.0906E-6 1.4143E-7 8.5314E-6 1.5892E-7 7.7172E-6 1.7920E-7 7.5860E-6 1.7616E-7 9.09415E-001 8.93730E-006 0.3521 - 1.9993 0.01571 0.00420
400W, 8mTorr, 228s 6.0839E-6 1.4128E-7 8.5219E-6 1.5875E-7 8.1208E-6 1.8858E-7 7.5860E-6 1.7616E-7 9.16616E-001 1.04849E-005 0.3521 - 1.9973 0.01705 0.00501
300W, 8mTorr, 304s 5.7189E-6 1.3280E-7 8.4424E-6 1.5726E-7 8.0221E-6 1.8629E-7 7.5860E-6 1.7616E-7 8.99112E-001 1.15761E-005 0.3521 - 1.9973 0.01674 0.00480
200W, 8mTorr, 456s 4.7867E-6 1.1115E-7 8.4042E-6 1.5655E-7 7.9812E-6 1.8533E-7 7.5860E-6 1.7616E-7 9.24743E-001 1.78133E-005 0.3521 - 1.5020 0.01661 0.00401
100W, 8mTorr, 913s 3.4163E-6 7.9332E-7 8.3829E-6 1.5616E-7 7.9093E-6 1.8367E-7 7.5860E-6 1.7616E-7 1.09148E+000 4.50203E-005 0.4138 - 1.2275 0.02364 0.00722






SEM images

  • Al thin film deposited at 500 W, 3 mTorr and 300°C. Deposition time 183 s.

  • Al thin film deposited at 500 W, 3 mTorr and 300°C. Deposition time 183 s.

  • Al thin film deposited at 500 W, 3 mTorr and 20°C. Deposition time 183 s. Thickness: 94.2 nm

  • Al thin film deposited at 500 W, 3 mTorr and 20°C. Deposition time 183 s. Thickness: 94.2 nm

  • Al thin film deposited at 400 W, 3 mTorr and 300°C. Deposition time 228 s.

  • Al thin film deposited at 400 W, 3 mTorr and 300°C. Deposition time 228 s.

  • Al thin film deposited at 400 W, 3 mTorr and 20°C. Deposition time 228 s. Thickness: 94.06 nm

  • Al thin film deposited at 400 W, 3 mTorr and 20°C. Deposition time 228 s. Thickness: 94.06 nm

  • Al thin film deposited at 300 W, 3 mTorr and 300°C. Deposition time 304 s.

  • Al thin film deposited at 300 W, 3 mTorr and 300°C. Deposition time 304 s.

  • Al thin film deposited at 300 W, 3 mTorr and 20°C. Deposition time 304 s. Thickness: 93.53 nm

  • Al thin film deposited at 300 W, 3 mTorr and 20°C. Deposition time 304 s. Thickness: 93.53 nm

  • Al thin film deposited at 200 W, 3 mTorr and 300°C. Deposition time 456 s.

  • Al thin film deposited at 200 W, 3 mTorr and 300°C. Deposition time 456 s.

  • Al thin film deposited at 200 W, 3 mTorr and 20°C. Deposition time 456 s. Thickness: 92.61 nm

  • Al thin film deposited at 200 W, 3 mTorr and 20°C. Deposition time 456 s. Thickness: 92.61 nm

  • Al thin film deposited at 100 W, 3 mTorr and 300°C. Deposition time 913 s.

  • Al thin film deposited at 100 W, 3 mTorr and 300°C. Deposition time 913 s.

  • Al thin film deposited at 100 W, 3 mTorr and 20°C. Deposition time 913 s. Thickness: 89.99 nm

  • Al thin film deposited at 100 W, 3 mTorr and 20°C. Deposition time 913 s. Thickness: 89.99 nm

  • Al thin film deposited at 500 W, 8 mTorr and 300°C. Deposition time 183 s.

  • Al thin film deposited at 500 W, 8 mTorr and 300°C. Deposition time 183 s.

  • Al thin film deposited at 500 W, 8 mTorr and 20°C. Deposition time 183 s. Thickness: 78.55 nm

  • Al thin film deposited at 500 W, 8 mTorr and 20°C. Deposition time 183 s. Thickness: 78.55 nm

  • Al thin film deposited at 400 W, 8 mTorr and 300°C. Deposition time 228 s.

  • Al thin film deposited at 400 W, 8 mTorr and 300°C. Deposition time 228 s.

  • Al thin film deposited at 400 W, 8 mTorr and 20°C. Deposition time 228 s. Thickness: 74.74 nm

  • Al thin film deposited at 400 W, 8 mTorr and 20°C. Deposition time 228 s. Thickness: 74.74 nm

  • Al thin film deposited at 300 W, 8 mTorr and 300°C. Deposition time 304 s.

  • Al thin film deposited at 300 W, 8 mTorr and 300°C. Deposition time 304 s.

  • Al thin film deposited at 300 W, 8 mTorr and 20°C. Deposition time 304 s. Thickness: 71.91 nm

  • Al thin film deposited at 300 W, 8 mTorr and 20°C. Deposition time 304 s. Thickness: 71.91 nm

  • Al thin film deposited at 200 W, 8 mTorr and 300°C. Deposition time 456 s.

  • Al thin film deposited at 200 W, 8 mTorr and 300°C. Deposition time 456 s.

  • Al thin film deposited at 200 W, 8 mTorr and 20°C. Deposition time 456 s. Thickness: 69.47 nm

  • Al thin film deposited at 200 W, 8 mTorr and 20°C. Deposition time 456 s. Thickness: 69.47 nm

  • Al thin film deposited at 100 W, 8 mTorr and 300°C. Deposition time 913 s.

  • Al thin film deposited at 100 W, 8 mTorr and 300°C. Deposition time 913 s.

  • Al thin film deposited at 100 W, 8 mTorr and 20°C. Deposition time 913 s. Thickness: 61.71 nm

  • Al thin film deposited at 100 W, 8 mTorr and 20°C. Deposition time 913 s. Thickness: 61.71 nm


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