Specific Process Knowledge/Thin film deposition/Deposition of NiV/Sputtering of NiV in Lesker

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All contents by DTU Nanolab staff. See further attribution below.

NiV is used as a seed layer before Ni electroplating. To start the plating process the surface has to be conducting, and it should be made of nickel since it is the plating material. Sputtering is the technique that allows improved step coverage and this means that it is an obvious choice for seed layer preparation. Ni in its pure form will quickly develop a native oxide, which will degrade the plating performance. To avoid oxidation, the nikel is replaced by NiV alloy were the small amount of vanadium (7 At.%) stabilizes Ni.

The NiV sputter deposition is highly dependent on the process parameters (Power and Pressure)

by Patama Pholprasit @ dtu nanolab in December 2016

Power [W]	Pressure [mtorr]	NiV deposition rate [Å/s]	Roughness Ra by AFM [nm]	AFM image	SEM image	Comments
157	5	0.833	0.546	AFM image of the NiV film surface on the Si substrate/ Dec 2016	SEM image of the cross section of NiV on the Si substrate/ Dec 2016	With 10 Watts RF Substrate bias Pressure: 5 mtorr = 0.0067 mbar

X-Ray Reflectivity analysis of ultrathin NiV films

by Evgeniy Shkondin @ dtu nanolab in August 2022

In some cases, very thin layers (down to a few nm) of NiV need to be deposited. It is very challenging to measure the thickness since the Dektak profilometer is not sensitive in that range. Alternative methods include AFM or, as in this case, non-destructive X-ray reflectivity measurement (XRR).

This section describes the deposition of a very thin NiV layer, where aimed thickness is 5 nm.

NiV has been sputtered (Source 2 DC) from gun 2 (HSM) in Sputter System (Lesker) with the following parameters: 157W, 3mTorr, and the 60s deposition time. The measured DC bias was 375V

X-ray reflectivity (XRR) profiles for NiV films at two different positions (center and edge) on a 150 mm wafer have 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 an IPS (incident parallel slit) adaptor with a 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. The fitting procedure was performed using commercial GlobalFit software assuming the model is based on Si substrate with native oxide followed by the deposited NiV film with thin oxides and moisture surfaces. NiV density is assumed to be linearly dependent as a function of depth. The results are summarized in the table below.

Sample model used in XRR analysis.
Sample considers to have NiV layer with oxide top / moisture deposited on natively oxidized silicon.

Layer parameter list (center point)
Layer name	Thickness (nm)	Density (g/cm³)	Depth distribution	Bottom Density (g/cm³)	Rougness (nm)	Delta	Beta
NiVO_x (top layer/moisture)	1.64	2.22	No distribution		0.35	7.2251e-6	1.6778e-7
NiV (sputtered)	5.95	9.00	Linear	7.13	1.16	2.4961e-5	5.0462e-7
SiO₂ (native oxide)	0.98	1.88	No distribution		0.33	6.0936e-6	7.9412e-8
Si (wafer)	$\infty$	2.328	No distribution		0.00	7.5626e-6	1.7561e-7

Layer parameter list (edge point)
Layer name	Thickness (nm)	Density (g/cm³)	Depth distribution	Bottom Density (g/cm³)	Rougness (nm)	Delta	Beta
NiVO_x (top layer/moisture)	1.65	2.28	No distribution		0.37	7.4468e-6	1.7293e-7
NiV (sputtered)	5.00	8.20	Linear	6.41	0.97	2.2744e-5	4.5979e-7
SiO₂ (native oxide)	0.98	1.87	No distribution		0.33	6.0936e-6	7.9411e-8
Si (wafer)	$\infty$	2.328	No distribution		0.00	7.5626e-6	1.7561e-7

XRR analysis of thin NiV.
X-ray reflectivity. Measurement and Fit. Center point.
X-ray reflectivity. Measurement and Fit. Edge point.