View source for Specific Process Knowledge/Thin film deposition/Deposition of Niobium Titanium Nitride



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== Deposition of Niobium Titanium Nitride ==
 
Deposition of NbTiN can be done by reactive sputtering using NbTi target.

The preferred tool for this application is the Cluster-based multi-chamber high vacuum sputtering deposition system, commonly referred to as the 'Cluster Lesker.' The operating process is thoroughly documented and described in detail.:

* [[Specific Process Knowledge/Thin film deposition/Deposition of Niobium Titanium Nitride/NbTiN Reactive p-DC Sputtering in Cluster Lesker PC3|Deposition of Niobium Titanium Nitride using reactive p-DC sputtering]] in Sputter-System Metal-Nitride(PC3) Source 1 (4-inch target)

At the moment (October 2023) we have a 4-inch NbTi target for PC3 Src1 and a 3-inch NbTi target for Sputter-System Lesker (Old Lesker).

==Comparison of LPCVD, PECVD, and sputter systems for silicon nitride deposition==

{|border="1" cellspacing="1" cellpadding="3" style="text-align:left;" 
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|-
|-style="background:silver; color:black"
!
![[Specific_Process_Knowledge/Thin_film_deposition/Cluster-based_multi-chamber_high_vacuum_sputtering_deposition_system|Sputter-System Metal-Nitride(PC3)]]
![[Specific Process Knowledge/Thin film deposition/Lesker|Lesker sputter system]]
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|-style="background:WhiteSmoke; color:black"
!Generel description
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*Pulsed DC reactive sputtering
*Reactive HIPIMS (high-power impulse magnetron sputtering) (require 3-inch target)
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*Reactive DC sputtering (not tested)
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|-
|-style="background:LightGrey; color:black"
!Stoichiometry
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*Nb<sub>x</sub>T<sub>y</sub>N (Sputter-System Metal-Nitride(PC3))
Tunable composition
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*Unknown
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|-
|-style="background:WhiteSmoke; color:black"
!Film thickness
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*Limited by process time. 
*Deposition rate (0.18 nm/s) likely faster than Sputter-System (Lesker)

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*Limited by process time. 
*Deposition rate unknown
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|-
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!Process temperature
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*Up to 600 °C
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*Up to 400 °C
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|-
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!Step coverage
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*Some step coverage possible
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*Some step coverage possible but amount unknown
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|-
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!Film quality
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*Deposition on one side of the substrate
*Properties including tunable stoichiometry (requires process development)
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*Deposition on one side of the substrate
*Unknown quality
*Likely O-contamination
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|-style="background:WhiteSmoke; color:black"
!Batch size
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*Many smaller samples
*Up to 10*100 mm or 150 mm wafers 
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*Several smaller samples
*1-several 50 mm wafers
*1*100 mm wafers
*1*150 mm wafer 
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!'''Allowed materials'''
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*Almost any as long as they do not outgas and are not very toxic, see cross-contamination sheets
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*Almost any as long as they do not outgas and are not very toxic, see cross-contamination sheets
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Deposition of Silicon Nitride can be done with either LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Enhanced Chemical Vapor Deposition).

==Deposition of Silicon Nitride using LPCVD==
LPCVD silicon nitride can be deposited in a [[Specific Process Knowledge/Thin film deposition/B2 Furnace LPCVD Nitride|LPCVD nitride furnace]]. DTU Nanolab has two LPCVD nitride furnaces: A new furnace (installed in 2008) for deposition of stoichiometric nitride on 4" or on 6" wafers and an older furnace (installed in 1995) for deposition of stoichiometric nitride and low stress nitride on 4" wafers.

The LPCVD nitride deposition is a batch process, meaning that nitride can be deposited on a batch of up to 15 wafers (in the old nitride furnace) or 25 wafers (in the new nitride furnace) at a time. The deposition takes place at temperatures of 780-845 degrees Celsius and at a pressure of 120-200 mTorr. The LPCVD silicon nitride has a good step coverage, and the film thickness is very uniform over the wafers. On the furnaces there are standard processes for deposition of stoichiometric nitride (Si<sub>3</sub>N<sub>4</sub>) and for deposition of low stress nitride (SRN) (only on the old nitride furnace).
*[[/Deposition of Silicon Nitride using LPCVD|Deposition of Silicon Nitride using LPCVD]]

==Deposition of Silicon Nitride using PECVD==
PECVD nitride and oxynitride can be deposited in one of the [[Specific Process Knowledge/Thin film deposition/PECVD|PECVD]] systems at DTU Nanolab. You can run 1-3 wafers on several smaller chips at a time depending on which one of the PECVD's you use. The deposition takes place at 300 degrees Celsius. This can be of importance for some applications, but it gives a less dense film compared to LPCVD nitride, and the stoichiometry is on the following form: Si<sub>x</sub>N<sub>y</sub>O<sub>z</sub>H<sub>v</sub>. The step coverage and the thickness uniformity of the film are not as good as for the LPCVD nitride. In one of our PECVD systems (PECVD3) we allow small amounts of metal on the wafers entering the system; this is not allowed in the LPCVD furnace and in the clean PECVD (PECVD1). We also have a PECVD for deposition on III-V materials (PECVD2).
*[[/Deposition of Silicon Nitride using PECVD|Deposition of Silicon Nitride using PECVD]] - ''or oxynitride''

==Comparison of LPCVD and PECVD for silicon nitride deposition==
{| border="1" cellspacing="0" cellpadding="3" align="center"
! 
! [[Specific Process Knowledge/Thin film deposition/Furnace LPCVD Nitride|LPCVD]]
! [[Specific Process Knowledge/Thin film deposition/PECVD|PECVD]]
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| Stoichiometry
|
*Si<sub>3</sub>N<sub>4</sub>
*SRN (only old nitride furnace, only 4" wafers)
Si<sub>3</sub>N<sub>4</sub>: Stoichiometric nitride

SRN: Silicon rich nitride (low stress nitride)
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*Si<sub>x</sub>N<sub>y</sub>H<sub>z</sub>
*Si<sub>x</sub>O<sub>y</sub>N<sub>z</sub>H<sub>v</sub>
Silicon nitride can be doped with boron, phosphorus or germanium
|-
|Film thickness
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*Si<sub>3</sub>N<sub>4</sub>: ~50 Å - ~1400 Å
*SRN: ~50 Å - ~2800 Å
Thicker nitride layers can be deposited over more runs
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*~40 nm - 10 µm
|-
|Process temperature
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*780 <sup>o</sup>C - 845 <sup>o</sup>C
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*300 <sup>o</sup>C
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|Step coverage
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*Good
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*Less good
|-
|Film quality
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*Deposition on both sides of the substrate
*Dense film
*Few defects
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*Deposition on one side of the substrate
*Less dense film
*Incorporation of hydrogen in the film
|-
|Batch size
|
Old nitride furnace:
*1-17 4" wafers per run 
New nitride furnace:
*1-25 4" or 6" wafers per run
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*1-3 4" wafers or one 6" wafer or many smaller chips per run
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| Substrate materials allowed
|
*Silicon wafers (new wafers or RCA cleaned wafers)
**with layers of silicon oxide or silicon (oxy)nitride (RCA cleaned)
**from furnaces in stack A or B in cleanroom 2
*Pure quartz (fused silica) wafers (RCA cleaned)
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*Silicon wafers
**with layers of silicon oxide or silicon (oxy)nitride
*Quartz wafers
*Small amounts of metal < 5% of the wafer coverage (ONLY in PECVD3!)
|- 
| Etch rate in 80 <sup>o</sup>C KOH
|Expected <1 Å/min
|Dependent on recipe: ~1-10 Å/min
|-
| Etch rate in BHF
|Very low
|Very high compared to the etch rate of LPCVD nitride
|-
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