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<center><span style="background:#87CEEB">4th Level - Comparison</span></center>
{{cc-nanolab}}
'''Feedback to this page''': '''[mailto:labadviser@danchip.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.danchip.dtu.dk/index.php/Specific_Process_Knowledge/Etch/RIE_(Reactive_Ion_Etch) click here]'''


Gold can be deposited by e-beam evaporation or sputtering. In the chart below you can compare the different deposition equipment.
'''Feedback to this page''': '''[mailto:labadviser@nanolab.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.nanolab.dtu.dk/index.php/Specific_Process_Knowledge/Thin_film_deposition/Deposition_of_Gold click here]'''


Gold can be deposited by e-beam evaporation or sputtering. In the chart below you can compare the different deposition equipment. We also describe the temperature rise on the wafer during gold deposition, the adhesion layers that can be used for gold deposition, the roughness of gold deposited in the Wordentec, and issues with particulates on the gold films in the Temescal and the Wordentec.


== Adhesion of Au on Si ==
== Au deposition ==
The adhesion of gold on Silicon or Silicon with native oxide is not very good. The Si substrate is often deposited an adhesion layer before the gold deposition. A few nm of Chromium or Titanium works well and they react with the Oxygen of Silicon oxide and present a metallic bond with gold. 5 nm to 10 nm thick of Cr or Ti is commonly used and it is important to deposit Cr or Ti and then immediately Au. If the vacuum chamber is opened in between, the surface of Cr or Ti will get oxidized and that will give a poor adhesion. If a gold layer needs to be deposited directly on Silicon, then native oxide has to be removed by deep in diluted HF and immediately load the evaporation chamber. And after the deposition, the wafer has to be heated op to get some Au-Si diffusion which improves the adhesion.
Below you can compare the different equipment that allows Au deposition.
 


{| border="1" cellspacing="0" cellpadding="4"  
{| border="1" cellspacing="0" cellpadding="4"  
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|-style="background:silver; color:black"
|-style="background:silver; color:black"
!  
!  
! E-beam evaporation ([[Specific Process Knowledge/Thin film deposition/Alcatel|Alcatel]])
! E-beam evaporation ([[Specific Process Knowledge/Thin film deposition/Temescal|E-beam evaporator (Temescal)]] and [[Specific Process Knowledge/Thin film deposition/10-pocket e-beam evaporator|E-beam evaporator (10-pockets)]])
! E-beam evaporation ([[Specific Process Knowledge/Thin film deposition/Wordentec|Wordentec]])
! Resistive thermal evaporation ([[Specific Process Knowledge/Thin film deposition/thermalevaporator|Thermal Evaporator]])
! Sputter ([[Specific Process Knowledge/Thin film deposition/Lesker|Lesker]])
! Sputter ([[Specific Process Knowledge/Thin film deposition/Lesker|Lesker]])
! E-beam evaporation ([[Specific Process Knowledge/Thin film deposition/Physimeca|Physimeca]])
! Sputter ([[Specific Process Knowledge/Thin film deposition/Cluster-based multi-chamber high vacuum sputtering deposition system|Sputter-system Metal-Oxide (PC1) and Sputter-system Metal-Nitride (PC3)]])
! Sputter coater [[Specific Process Knowledge/Thin film deposition/Sputter coater#Sputter coater 03|(Sputter coater 03)]]
! Sputter coater [[Specific Process Knowledge/Thin film deposition/Sputter coater#Sputter coater 03|(Sputter coater 03)]]
! Sputter coater [[Specific Process Knowledge/Thin film deposition/Sputter coater#Sputter coater 04|(Sputter coater 04)]]
! Sputter coater [[Specific Process Knowledge/Thin film deposition/Sputter coater#Sputter coater 04|(Sputter coater 04)]]
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! General description
! General description
| E-beam deposition of Au
| E-beam deposition of Au
| E-beam deposition of Au
| Resistive thermal deposition of Au
| Sputter deposition of Au
| Sputter deposition of Au
| Sputter deposition of Au
| E-beam deposition of Au
| Sputter deposition of Au
| Sputter deposition of Au
| Sputter deposition of Au
| Sputter deposition of Au
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|-style="background:LightGrey; color:black"
|-style="background:LightGrey; color:black"
! Pre-clean
! Pre-clean
|Ar ion etch (only in E-beam evaporator Temescal)
|
|
|RF Ar clean
|RF Ar clean
|RF Ar clean
|RF Ar clean
|
|
|
|
|
|-style="background:WhiteSmoke; color:black"
|-style="background:WhiteSmoke; color:black"
! Layer thickness
! Layer thickness
|10 Å to 5000Å*  
|10 Å to 600 nm *
|10 Å to 5000Å*
|10 Å to 200 nm
|10 Å to
|10 Å to 500 nm *
|10Å to about 3000Å*
|10 Å to 500 nm *
|
| very thin, few nm range
|
| very thin, few nm range


|-
|-
|-style="background:LightGrey; color:black"
|-style="background:LightGrey; color:black"
! Deposition rate
! Deposition rate
|2 Å/s to 10 Å/s
|1-5 Å/s
|1 Å/s to 10 Å/s
|1 Å/s (can be adjusted to around 5 Å/s)
|
|Depends on process parameters, 1-10 Å/s  
|From 5 Å/s up to 10Å/s
|Depends on process parameters
|Not measured
|Not measured
|Not measured
|Not measured
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! Batch size
! Batch size
|
|
*Up to 1x4" wafers
*Up to 4x6" wafers or
*smaller pieces
*Up to 3x8" wafers (ask for special holder)
*many smaller pieces
|
|
*24x2" wafers or  
*4x2" wafers or  
*6x4" wafers or
*3x4" wafers or
*6x6" wafers
*1x6" wafer
*1x8" wafer
*many smaller pieces
|
|
*Pieces or
*Pieces or
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*1x6" wafer
*1x6" wafer
|
|
*1x 2" wafer or
*Up to 10x6" or 4" wafers
*1x 4" wafers or
*Many small pieces  
*Several smaller pieces  
|
|
*Several smaller samples
*Several smaller samples
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|-style="background:LightGrey; color:black"
|-style="background:LightGrey; color:black"
!Heating
|to 250 C (in 10-pocket evaporator)
|no
|no
|to 600 C
|no
|no
|-style="background:WhiteSmoke; color:black"
!Allowed materials
!Allowed materials


|
|
* Silicon oxide
*See the [http://labmanager.dtu.dk/function.php?module=XcMachineaction&view=edit&MachID=429 cross-contamination sheet]
* Silicon (oxy)nitride
* Photoresist
* PMMA
* Mylar
* SU-8
* Metals
|
|
* Silicon oxide
* Almost any as long as it does not outgas - see cross-contamination sheets in Labmanager
* Silicon (oxy)nitride
* Photoresist
* PMMA
* Mylar
* SU-8
* Metals
|
|
* Silicon
* Silicon
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* Carbon
* Carbon
|
|
* III-V materials
* Almost any as long as it does not outgas - see cross-contamination sheets in Labmanager
* Silicon wafers
* Quartz wafers
* Pyrex wafers
|
|
* All samples allowed in the SEM Supra 1
* All samples allowed in the SEM Supra 1
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* All samples allowed in the SEM Supra 2 or 3
* All samples allowed in the SEM Supra 2 or 3


|-style="background:WhiteSmoke; color:black"
|-style="background:LightGrey; color:black"
! Comment
! Comment
|
|
* For thicknesses above 200 nm permission is required
* Pumpdown approx 20 min.
* An adhesion layer (of Cr or Ti) is recommended under Au.
|
|
* For thicknesses above 200 nm permission is required
*Make sure that all pellets are melted beforehand
* An adhesion layer (of Cr or Ti) is recommended under Au.
*Pumpdown approx. 20 min
|
|
*Takes approx. 10 minutes to load and transfer sample
|
|
 
* Takes approx. 12 minutes to load and transfer samples
|
|
* Used for gold sputter coating of samples before SEM inspection
* Used for gold sputter coating of samples before SEM inspection
* Very fast.
|
|
* Used for gold sputter coating of samples before SEM inspection
* Used for gold sputter coating of samples before SEM inspection
*Very fast.
|-
|-
|}
|}




'''*'''  ''For thicknesses above 200 nm permission from ThinFilm group (thinfilm@danchip.dtu.dk) is required.''
'''*'''  ''For thicknesses above 200 nm write to metal@nanolab.dtu.dk as extra deposition costs a higher fee.''


== Studies of Au deposition processes in the Wordentec==
== Resistive thermal evaporation of Au ==
[[/Roughness of Au|Roughness of Au layers]] - ''Roughness of Au layers deposited with different equipment and settings''
 
* [[Specific Process Knowledge/Thin film deposition/Deposition of Gold/Resistive thermal evaporation of Au in Thermal Evaporator|Resistive thermal evaporation of Au in Thermal Evaporator]]
 
== Adhesion of Au on Si ==
The adhesion of gold on Silicon or Silicon with native oxide is not very good. The Si substrate is often deposited an adhesion layer before the gold deposition. A few nm of Chromium or Titanium works well and they react with the Oxygen of Silicon oxide and present a metallic bond with gold. You can also use polymer or organosilane adhesion layers as exemplified by the work in the next section.


===Wafer temperature===
For Cr and Ti adhesion layers, a 5 nm to 10 nm thick layer is commonly used and it is important to deposit Cr or Ti and then immediately Au. If the vacuum chamber is opened in between, the surface of Cr or Ti will get oxidized and that will give a poor adhesion. If a gold layer needs to be deposited directly on Silicon, then native oxide has to be removed by a dip in diluted HF and wafer must be immediately loaded into the evaporation chamber. And after the deposition, the wafer has to be heated up to get some Au-Si diffusion which improves the adhesion.
The wafer temperature during e-beam deposition of 200 nm Au on six wafers has been measured using thermal labels on the backside of the wafers. The following results were obtained:
{| border="1" cellspacing="0" cellpadding="2"
! Wafer
! Temperature [C]
|-
|1
|48
|-
|2
|60
|-
|3
|65
|-
|4
|71
|-
|5
|71
|-
|6
|77
|-
|}
The temperatures are accurate within approximately +/- 3C and probably underestimating the actual wafer temperature slightly. It is observed that the wafer temperature increases with each wafer, thus if wafer temperature is of concern it is advised to reduce the number of wafers per run.


*[[/Adhesion layers|Read more about Ti and Cr adhesion layers]].


[[Image:section under construction.jpg|70px]]
== Thin Au layer using APTMS adhesion layer and sputter system Lesker ==
== Thin Au layer deposition using Lesker==
For depositing very thin, down to 6nm continuous Au layers on Si/SiO<sub>2</sub> substrates. Works also with ALD deposited Al<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> as substrate.
For depositing very thin, down to 6nm continuous Au layers on Si/SiO<sub>2</sub> substrates. Works also with ALD deposited Al<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> as substrate.


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Adhesion promoter deposition: 3h immersion in 95%IPA, 2.5% H<sub>2</sub>O, 2.5% APTMS.
Adhesion promoter deposition: 3h immersion in 95%IPA, 2.5% H<sub>2</sub>O, 2.5% APTMS.


''NOTE: the APTMS is time sensitive, so deposit it as close to the Au deposition as possible.''
''NOTE: the APTMS layer is degrading quickly in atmosphere, so deposit it as close to the Au deposition as possible.''


Lesker deposition parameters:
Lesker deposition parameters:
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|}
|}


''NOTE: As a general rule, the lower the pressure and higher the power, the better.''  
''NOTE: As a general rule, the lower the pressure and higher the power (i.e. higher the deposition rate), the better.''  


Film characteristics:
Film characteristics (5-10 wafers for each thickness):
{| border="1" cellspacing="0" cellpadding="2"
{| border="1" cellspacing="0" cellpadding="2"
! Thickness [nm]
! Thickness [nm]
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|}
|}


''NOTE: After depositing 10layers of 10nm each, the roughness increased to 0.8nm RMS''
''NOTE: After depositing 10 layers of 10nm each, one on top of each other, the roughness increased to 0.8nm RMS''
 
Work done by Johneph Sukham (@ DTU Fotonik) and Radu Malureanu (@ DTU Fotonik and DTU Nanolab) in 2016-2017.
 
==Particulates in e-beam evaporated films==
[[File:particulates au film.png|right|thumb|upright=2|Alt=SEM image of a film with droplets ranging in size from a few hundred nanometers to about 1.5 microns.|Au droplets on an Au film (image by Evgeniy Shkondin, Au identified by EDX).]]
 
We have found that the amount of particulates on the e-beam evaporated films depends on the deposition parameters. Specifically for gold it is hard to avoid tiny gold droplets on the films, but they can be minimized with careful attention to the sweep parameters, cleanliness of the target, etc.
 
The droplets appear to be inconsequential for many users, for instance if the Au layer is simply used as an electrical contact. However, for some users it is very important, for instance when the exact resistivity of the Au layer is critical.
 
 
You can read more about this issue [[Specific_Process_Knowledge/Thin_film deposition/Temescal/Particulates_in_Temescal_Au_films|here]].


Work done by Johneph Sukham ([mailto:johsu@fotonik.dtu.dk?Subject=Thin Au deposition using Lesker click to email]) and Radu Malureanu ([mailto:rmal@dtu.dk?Subject=Thin Au deposition using Lesker click to email])
<br clear="all" />
 
==Quality control of e-beam evaporated TiAu films==
 
{| border="1" cellspacing="2" cellpadding="2" colspan="3"
|bgcolor="#98FB98" |'''Quality control (QC) for the E-beam Evaporator (Temescal) and the E-beam Evaporator (10-pockets)'''
|-
|
TiAu or CrAu is tested approximately once a month on both of Nanolab's e-beam evaporators.
 
'''You can find the QC procedures and data in LabManager here''' (requires login):
 
*[http://labmanager.dtu.dk/d4Show.php?id=5862&mach=429 QC procedure, E-beam Evaporator (Temescal)]<br>
*[https://labmanager.dtu.dk/view_binary.php?type=data&mach=429 Newest QC data, E-beam Evaporator (Temescal)]<br>
 
*[http://labmanager.dtu.dk/d4Show.php?id=5862&mach=511 QC procedure, E-beam Evaporator (10-pockets)]<br>
*[https://labmanager.dtu.dk/view_binary.php?type=data&mach=511 Newest QC data, E-beam Evaporator (10-pockets)]<br>
 
 
 
{| {{table}}
| align="left" valign="top"|
{| border="2" cellspacing="1" cellpadding="2" align="left" style="width:400px"
! QC Recipe:
! Standard recipes/TiAu or Cr/Au
|-
|Deposition rate
|2 Å/s
|-
|Thickness
|10 nm / 90 nm
|-
|Pressure
|Below 1*10<sup>-6</sup> mbar
|-
|}
|-
|}
 
 
{| {{table}}
| align="left" valign="top"|
{| border="2" cellspacing="1" cellpadding="2" align="left" style="width:400px"
!QC limits
!Both e-beam evaporators
|-
|Deposition rate deviation
|± 20 %
|-
|Measured average thickness
|± 10 %
|-
|Thickness deviation across a 4" wafer
|± 5 %
|-
|}
|-
|}
 
Thickness is measured in 5 points with a stylus profiler. <br>
Additionally we examine the newly deposited films for particles using the particle scanner (if available, otherwise we use the Jenatech microscope in darkfield mode) and we monitor the sheet resistance of the Ti/Au or Cr/Au films.
|}
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