Difference between revisions of "Lesker PVD75 DC/RF Sputterer"
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| imagecaption = | | imagecaption = | ||
| Instrument_Type = Deposition | | Instrument_Type = Deposition | ||
− | | Staff_Manager = David Barth | + | | Staff_Manager = [[David Barth | David Barth]] |
| Lab_Location = Bay 2 | | Lab_Location = Bay 2 | ||
| Tool_Manufacturer = Kurt J. Lesker | | Tool_Manufacturer = Kurt J. Lesker | ||
| Tool_Model = PVD75 | | Tool_Model = PVD75 | ||
− | | | + | | NEMO_Designation = PVD-03 |
− | | Lab_Phone = | + | | Lab_Phone = 215-898-9748 |
| SOP Link = [https://www.seas.upenn.edu/~nanosop/PVD75_Sputtering_SOP.htm SOP] | | SOP Link = [https://www.seas.upenn.edu/~nanosop/PVD75_Sputtering_SOP.htm SOP] | ||
}} | }} | ||
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== Tool description == | == Tool description == | ||
The Kurt J. Lesker PVD75 Sputter system is configured with 4 sputter guns in the following configuration: | The Kurt J. Lesker PVD75 Sputter system is configured with 4 sputter guns in the following configuration: | ||
− | Target 1: RF power, insulating/conductive target <br> | + | '''Target 1:''' RF power, insulating/conductive target <br> |
− | Target 2: DC power, magnetic/non-magnetic conductive target <br> | + | '''Target 2:''' DC power, magnetic/non-magnetic conductive target <br> |
− | Target 3: DC power, non-magnetic conductive target <br> | + | '''Target 3:''' DC power, non-magnetic conductive target <br> |
− | Target 4: DC power, magnetic/non-magnetic conductive target <br> | + | '''Target 4:''' DC power, magnetic/non-magnetic conductive target <br> |
The system is cryo-pumped process chamber with an automated interface, wafer platen rotation and heating up to 550°C, accepting sample sized from pieces to 150 mm diameter wafers. | The system is cryo-pumped process chamber with an automated interface, wafer platen rotation and heating up to 550°C, accepting sample sized from pieces to 150 mm diameter wafers. | ||
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* PVD-03 is in a sputter up configuration, which means the guns point up and the sample must be attached upside down. This is usually considered cleaner, but requires greater consideration for sample mounting. PVD-05 is in sputter down configuration, so samples can just be placed on the platen. | * PVD-03 is in a sputter up configuration, which means the guns point up and the sample must be attached upside down. This is usually considered cleaner, but requires greater consideration for sample mounting. PVD-05 is in sputter down configuration, so samples can just be placed on the platen. | ||
* Magnetic materials can only be sputtered from PVD-03. PVD-05 does not have the necessary high mag sources | * Magnetic materials can only be sputtered from PVD-03. PVD-05 does not have the necessary high mag sources | ||
+ | |||
+ | '''For more information on PVD Equipment capabilities click [[PVD Equipment Overview|here]].''' | ||
== Deposition sources == | == Deposition sources == | ||
+ | |||
+ | Below is a list of our sputtering materials along with links to materials specs (coming soon!). | ||
===== Metals ===== | ===== Metals ===== | ||
− | * Ag ('''Warning!''' Ag target must be cooled down for more than 15 min after deposition) | + | * Ag - Silver ('''Warning!''' Ag target must be cooled down for more than 15 min after deposition) |
− | * Al | + | * Al - Aluminum |
− | * Au | + | * [[Au (gold)|Au - Gold]] |
− | * Co | + | * Co - Cobalt |
− | * Cr | + | * Cr - Chromium |
− | * Cu | + | * Cu - Copper |
− | * Fe | + | * Fe - Iron |
− | * Mn | + | * Mn - Manganese |
− | * Mo | + | * Mo - Molybdenum |
− | * Nb | + | * Nb - Niobium |
− | * Ni | + | * Ni - Nickel |
− | * Pd | + | * Pd - Palladium |
− | * Pt | + | * Pt - Platinum |
− | * Ti | + | * [[Ti (titanium)|Ti - Titanium]] |
− | * W | + | * W - Tungsten |
===== Semiconductors & metalloids ===== | ===== Semiconductors & metalloids ===== | ||
− | * Ge | + | * Ge - Germanium |
− | * | + | * Si - Silicon |
− | * Si | + | * n-Si - n-type silicon (doped) |
− | * p-Si ( | + | * p-Si - p-type silicon (doped) |
===== Oxides, fluorides & nitrides ===== | ===== Oxides, fluorides & nitrides ===== | ||
Line 73: | Line 69: | ||
* NbN | * NbN | ||
* Si<sub>3</sub>N<sub>4</sub> | * Si<sub>3</sub>N<sub>4</sub> | ||
− | * SiO<sub>2</sub> | + | * [[SiO2 (silicon dioxide)| SiO<sub>2</sub>]] |
* Ta<sub>2</sub>O<sub>5</sub> | * Ta<sub>2</sub>O<sub>5</sub> | ||
* TiO<sub>2</sub> | * TiO<sub>2</sub> | ||
* TiN | * TiN | ||
+ | * ZnO | ||
===== Alloys & ceramics ===== | ===== Alloys & ceramics ===== | ||
Line 95: | Line 92: | ||
===== SOPs & troubleshooting ===== | ===== SOPs & troubleshooting ===== | ||
− | * [https:// | + | * [https://nemo.nano.upenn.edu/media/tool_documents/pvd-03-pvd75-sputterer/PVD03_SOP_v02.docx_1.pdf SOP] |
* [https://upenn.box.com/s/duex4o7xnhoq4dbqoo51aaij1o1b44mk PVD-03 Open Load SOP] | * [https://upenn.box.com/s/duex4o7xnhoq4dbqoo51aaij1o1b44mk PVD-03 Open Load SOP] | ||
− | ===== Process | + | <pdf height="800">File:PVD03 SOP v02.pdf</pdf> |
+ | |||
+ | == DC & RF sputtering process data == | ||
+ | |||
+ | ===== DC deposition ===== | ||
+ | |||
+ | {| class="wikitable" | ||
+ | ! rowspan=2 | Material Name | ||
+ | ! colspan=3 | Cathode 2 (DC; high mag) | ||
+ | ! rowspan=2 | Recorded | ||
+ | ! colspan=3 | Cathode 3 (DC) | ||
+ | ! rowspan=2 | Recorded | ||
+ | ! colspan=3 | Cathode 4 (DC; high mag) | ||
+ | ! rowspan=2 | Recorded | ||
+ | |- | ||
+ | ! Pressure || Power || Rate || Pressure || Power || Rate || Pressure || Power || Rate | ||
+ | |- | ||
+ | | Ag (silver) || 3 mTorr || 400 W || 22 Å s<sup>-1</sup> || 08/08/24 || 3 mTorr || 400 W || 7.6 Å s<sup>-1</sup> || || 3 mTorr || 400 W || 8 Å s<sup>-1</sup> || | ||
+ | |- | ||
+ | | Al (aluminum) || - || - || - || || - || - || - || || 5 mTorr || 350 W || 1.2 Å s<sup>-1</sup> || 06/27/23 | ||
+ | |- | ||
+ | | Cr (chromium) || 4 mTorr || 240 W || 2.1 Å s<sup>-1</sup> || || 4 mTorr || 240 W || 1.6 Å s<sup>-1</sup> || 04/05/23 || 4 mTorr || 240 W || 1.7 Å s<sup>-1</sup> || Kyle Skelil: 09/27/23 | ||
+ | |- | ||
+ | | Cu (copper) || 4 mTorr || 400 W || 6.2 Å s<sup>-1</sup> || || 3 mTorr || 400 W || 3.8 Å s<sup>-1</sup> || || 5 mTorr || 400 W || 4.0 Å s<sup>-1</sup> || 03/06/23 | ||
+ | |- | ||
+ | | ITO (indium tin oxide)|| - || - || - || || 3 mTorr || 120 W || 1 Å s<sup>-1</sup> || || - || - || || | ||
+ | |- | ||
+ | | Permalloy || 4 mTorr || 300 W || 2.7 Å s<sup>-1</sup> || || - || - || - || || - || - || - || | ||
+ | |- | ||
+ | | [[Ti (titanium)|Ti (titanium)]] || 6 mTorr || 300 W || 3.7 Å s<sup>-1</sup> || 08/12/24 || 5 mTorr || 300 W || 0.98 Å s<sup>-1</sup> || 03/06/23 || 6 mTorr || 300 W || 0.8 Å s<sup>-1</sup> || | ||
+ | |- | ||
+ | | TiN (titanium nitride) || - || - || - || || 4 mTorr || 120 W || 0.18 Å s<sup>-1</sup> || 08/08/24 || - || - || - || | ||
+ | |- | ||
+ | | W (tungsten) || 3 mTorr || 140 W || 2.5 Å s<sup>-1</sup> || 10/18/24 || 5 mTorr || 400 W || 2.3 Å s<sup>-1</sup> || 07/31/24 || - || - || - || | ||
+ | |- | ||
+ | | Ni (nickel) || 3 mTorr || 350 W || 2.5 Å s<sup>-1</sup> || || - || - || - || || 4 mTorr || 350 W || 2.0 Å s<sup>-1</sup> || 07/31/24 | ||
+ | |- | ||
+ | | Mo (molybdenum) || 4 mTorr || 350 W|| 2.8 Å s<sup>-1</sup> || || - || - || - || || 5 mTorr || 350 W|| 2.9 Å s<sup>-1</sup> || | ||
+ | |- | ||
+ | | FeGa (galfenol) || 3 mTorr || 140 W || 1 Å s<sup>-1</sup> || || - || - || - || || - || - || - || | ||
+ | |- | ||
+ | | Ge (germanium) || 4 mTorr || 120 W || 2 Å s<sup>-1</sup> || || 4 mTorr || 120 W || 1.1 Å s<sup>-1</sup> || || - || - || - || | ||
+ | |- | ||
+ | | [[Au (gold)|Au (gold)]] || 4 mTorr || 140 W || 3.1 Å s<sup>-1</sup> || 02/24/23 || 3 mTorr || 140 W || 2.5 Å s<sup>-1</sup> || || 5 mTorr || 140 W || 3.1 Å s<sup>-1</sup> || 03/01/24 | ||
+ | |- | ||
+ | | i-Si (intrinsic silicon) || - || - || - || || - || - || - || || - || - || - || | ||
+ | |- | ||
+ | | n-Si (n-type silicon) || - || - || - || || 4 mTorr || 280 W || 1.3 Å s<sup>-1</sup> || || - || - || - || | ||
+ | |- | ||
+ | | p-Si (p-type silicon) || - || - || - || || 3 mTorr || 280 W || 0.8 Å s<sup>-1</sup> || || - || - || - || | ||
+ | |- | ||
+ | | Pt (platinum) || 4 mTorr || 140 W || 1.7 Å s<sup>-1</sup> || || - || - || - || || 4 mTorr || 140 W || 1.5 Å s<sup>-1</sup> || 08/12/24 | ||
+ | |- | ||
+ | | CoFeB || 2 mTorr || 100 W || 1.07 Å s<sup>-1</sup> || 10/28/24 || - || - || - || || - || - || - || | ||
+ | |- | ||
+ | |} | ||
+ | |||
+ | ===== RF deposition ===== | ||
+ | {| class="wikitable" | ||
+ | ! rowspan=2 |Material Name | ||
+ | ! colspan=3 | Cathode 1 (RF) | ||
+ | ! rowspan=2 | Recorded | ||
+ | |- | ||
+ | ! Pressure || Power || Rate | ||
+ | |- | ||
+ | | [[SiO2 (silicon dioxide)| SiO<sub>2</sub>]] || 5 mTorr || 120 W || 0.043 Å s<sup>-1</sup> || 10/03/24 | ||
+ | |- | ||
+ | | MgO || 5 mTorr || 120 W || 0.028 Å s<sup>-1</sup> || 10/10/24 | ||
+ | |- | ||
+ | | TiO<sub>2</sub> || 3 mTorr || 120 W || 0.067 Å s<sup>-1</sup> || - | ||
+ | |- | ||
+ | | Al<sub>2</sub>O<sub>3</sub> || - || - || - || - | ||
+ | |- | ||
+ | | ZnO || 3 mTorr || 120 W || 0.2 Å s<sup>-1</sup> || - | ||
+ | |- | ||
+ | | Si<sub>3</sub>N<sub>4</sub> || 3 mTorr || 120 W || 0.014 Å s<sup>-1</sup> || 01/03/22 | ||
+ | |- | ||
+ | | i-Ge || 3 mTorr || 120 W || 0.35 Å s<sup>-1</sup> || 6/24/24 | ||
+ | |- | ||
+ | |} | ||
+ | |||
+ | ===== Independent Deposition Rate Characterization ===== | ||
+ | * [[Simple Rate Characterization Process | Simple Rate Characterization Process]] | ||
+ | |||
+ | ===== Additional resources ===== | ||
+ | |||
* [https://upenn.box.com/s/lujbua3msga3313fntajkw3bcwh0d63w PVD-03 Recipes] | * [https://upenn.box.com/s/lujbua3msga3313fntajkw3bcwh0d63w PVD-03 Recipes] | ||
* [https://www.angstromsciences.com/sputtering-yields Sputter Yield Chart] | * [https://www.angstromsciences.com/sputtering-yields Sputter Yield Chart] | ||
− | + | ||
+ | |||
+ | |||
+ | Note: The sputter yield chart can be useful for estimating approximately what rate to expect from materials, but the rate given is highly dependent on tool configuration and is not directly relevant | ||
+ | |||
+ | ===== Maintenance ===== | ||
+ | * [https://upenn.box.com/s/14f01uv8o6ol2dwmzzx7uhliobf822lw Maintenance Docs] | ||
+ | |||
+ | == The basics of magnetron sputtering == | ||
+ | |||
+ | ''Magnetron sputtering'', also simply called ''sputtering'', is a PVD method that involves a gaseous plasma (often consisting of high-energy Ar ions) which is generated within the chamber and bombarded onto the material to be deposited, known as the ''target''. During the bombardment, the surface of the target is eroded by the plasma and the ejected atoms travel from the surface of the target, through the vacuum environment, and deposit onto a ''substrate'' (such as a Si or quartz wafer) to form a thin film. Materials ranging from metals to dielectrics can be deposited via sputtering, and the technique is widely used within both academia and industry, with a variety of applications ranging from electronics to food packaging. | ||
+ | |||
+ | During a typical sputtering process, the chamber is evacuated to high vacuum (~ 5 x 10<sup>-8</sup> Torr) to minimize the partial pressures of background gases (oxygen, nitrogen, water vapor, etc.) along with potential volatile contaminants (such as solvents). After high vacuum is reached, the sputtering gas that is used to form the plasma is injected into the chamber. The total pressure is subsequently regulated to the mTorr range (typically 3 to 10 mTorr). To strike the plasma, a high voltage is applied between the cathode (often located directly behind the sputtering target) and the anode (often connected to the chamber as electrical ground). | ||
+ | |||
+ | As a high voltage is applied, electrons are accelerated away from the cathode towards the anode, colliding with the nearby injected gas atoms. These collisions knock electrons off the sputtering gas atoms, causing positive ionization, hence forming the plasma. The ionized sputter gas atoms are now accelerated towards the negatively charged cathode, resulting in high energy collisions with the target. Each of these collisions can cause atoms at the surface of the target to be ejected into the vacuum environment with enough kinetic energy to reach the surface of the substrate. The overall gas pressure is typically reduced to around 3 mTorr to ensure fewer collisions between the ejected atoms and the gas atoms, as these collisions increase the diffusivity of the ejected atom stream. These collisions can give rise to a quasi-conformal coating, which can be both beneficial or detrimental for the overall application. | ||
+ | |||
+ | While sputtering is typically a slower process than evaporation, sputtering results in smoother thin-films. |
Latest revision as of 10:05, 19 November 2024
Tool Name | Lesker PVD75 DC/RF Sputterer |
---|---|
Instrument Type | Deposition |
Staff Manager | David Barth |
Lab Location | Bay 2 |
Tool Manufacturer | Kurt J. Lesker |
Tool Model | PVD75 |
NEMO Designation | PVD-03 |
Lab Phone | 215-898-9748 |
SOP Link | SOP |
Tool description
The Kurt J. Lesker PVD75 Sputter system is configured with 4 sputter guns in the following configuration:
Target 1: RF power, insulating/conductive target
Target 2: DC power, magnetic/non-magnetic conductive target
Target 3: DC power, non-magnetic conductive target
Target 4: DC power, magnetic/non-magnetic conductive target
The system is cryo-pumped process chamber with an automated interface, wafer platen rotation and heating up to 550°C, accepting sample sized from pieces to 150 mm diameter wafers.
When choosing between PVD-03 and PVD-05, consider the following:
- PVD-03 is a load-locked system so base pressure will be better (~5e-8 torr vs. ~5e-6 torr) and pumpdown times will be much faster compared with PVD-05, which is an open load system.
- PVD-03 can handle one 6" wafer or one 4" wafer (or several smaller pieces) per run. PVD-05 has a large platen and can accept about four 4" wafers with good uniformity.
- PVD-03 is in a sputter up configuration, which means the guns point up and the sample must be attached upside down. This is usually considered cleaner, but requires greater consideration for sample mounting. PVD-05 is in sputter down configuration, so samples can just be placed on the platen.
- Magnetic materials can only be sputtered from PVD-03. PVD-05 does not have the necessary high mag sources
For more information on PVD Equipment capabilities click here.
Deposition sources
Below is a list of our sputtering materials along with links to materials specs (coming soon!).
Metals
- Ag - Silver (Warning! Ag target must be cooled down for more than 15 min after deposition)
- Al - Aluminum
- Au - Gold
- Co - Cobalt
- Cr - Chromium
- Cu - Copper
- Fe - Iron
- Mn - Manganese
- Mo - Molybdenum
- Nb - Niobium
- Ni - Nickel
- Pd - Palladium
- Pt - Platinum
- Ti - Titanium
- W - Tungsten
Semiconductors & metalloids
- Ge - Germanium
- Si - Silicon
- n-Si - n-type silicon (doped)
- p-Si - p-type silicon (doped)
Oxides, fluorides & nitrides
- Al2O3
- AZO (ZnO2/Al2O3; transparent conductive oxide)
- ITO (indium-doped tin oxide; transparent conductive oxide)
- MgF2
- MgO
- NbN
- Si3N4
- SiO2
- Ta2O5
- TiO2
- TiN
- ZnO
Alloys & ceramics
- Al/Si (99/1)
- Fe/Ge (81/19 & 83/17)
- Ni/Fe
- Ni/Cr (80/20)
- YSZ (Yttria-stabilized zirconia)
Other targets
- Please consult with staff
Important resources
Target request form
SOPs & troubleshooting
DC & RF sputtering process data
DC deposition
Material Name | Cathode 2 (DC; high mag) | Recorded | Cathode 3 (DC) | Recorded | Cathode 4 (DC; high mag) | Recorded | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Pressure | Power | Rate | Pressure | Power | Rate | Pressure | Power | Rate | ||||
Ag (silver) | 3 mTorr | 400 W | 22 Å s-1 | 08/08/24 | 3 mTorr | 400 W | 7.6 Å s-1 | 3 mTorr | 400 W | 8 Å s-1 | ||
Al (aluminum) | - | - | - | - | - | - | 5 mTorr | 350 W | 1.2 Å s-1 | 06/27/23 | ||
Cr (chromium) | 4 mTorr | 240 W | 2.1 Å s-1 | 4 mTorr | 240 W | 1.6 Å s-1 | 04/05/23 | 4 mTorr | 240 W | 1.7 Å s-1 | Kyle Skelil: 09/27/23 | |
Cu (copper) | 4 mTorr | 400 W | 6.2 Å s-1 | 3 mTorr | 400 W | 3.8 Å s-1 | 5 mTorr | 400 W | 4.0 Å s-1 | 03/06/23 | ||
ITO (indium tin oxide) | - | - | - | 3 mTorr | 120 W | 1 Å s-1 | - | - | ||||
Permalloy | 4 mTorr | 300 W | 2.7 Å s-1 | - | - | - | - | - | - | |||
Ti (titanium) | 6 mTorr | 300 W | 3.7 Å s-1 | 08/12/24 | 5 mTorr | 300 W | 0.98 Å s-1 | 03/06/23 | 6 mTorr | 300 W | 0.8 Å s-1 | |
TiN (titanium nitride) | - | - | - | 4 mTorr | 120 W | 0.18 Å s-1 | 08/08/24 | - | - | - | ||
W (tungsten) | 3 mTorr | 140 W | 2.5 Å s-1 | 10/18/24 | 5 mTorr | 400 W | 2.3 Å s-1 | 07/31/24 | - | - | - | |
Ni (nickel) | 3 mTorr | 350 W | 2.5 Å s-1 | - | - | - | 4 mTorr | 350 W | 2.0 Å s-1 | 07/31/24 | ||
Mo (molybdenum) | 4 mTorr | 350 W | 2.8 Å s-1 | - | - | - | 5 mTorr | 350 W | 2.9 Å s-1 | |||
FeGa (galfenol) | 3 mTorr | 140 W | 1 Å s-1 | - | - | - | - | - | - | |||
Ge (germanium) | 4 mTorr | 120 W | 2 Å s-1 | 4 mTorr | 120 W | 1.1 Å s-1 | - | - | - | |||
Au (gold) | 4 mTorr | 140 W | 3.1 Å s-1 | 02/24/23 | 3 mTorr | 140 W | 2.5 Å s-1 | 5 mTorr | 140 W | 3.1 Å s-1 | 03/01/24 | |
i-Si (intrinsic silicon) | - | - | - | - | - | - | - | - | - | |||
n-Si (n-type silicon) | - | - | - | 4 mTorr | 280 W | 1.3 Å s-1 | - | - | - | |||
p-Si (p-type silicon) | - | - | - | 3 mTorr | 280 W | 0.8 Å s-1 | - | - | - | |||
Pt (platinum) | 4 mTorr | 140 W | 1.7 Å s-1 | - | - | - | 4 mTorr | 140 W | 1.5 Å s-1 | 08/12/24 | ||
CoFeB | 2 mTorr | 100 W | 1.07 Å s-1 | 10/28/24 | - | - | - | - | - | - |
RF deposition
Material Name | Cathode 1 (RF) | Recorded | ||
---|---|---|---|---|
Pressure | Power | Rate | ||
SiO2 | 5 mTorr | 120 W | 0.043 Å s-1 | 10/03/24 |
MgO | 5 mTorr | 120 W | 0.028 Å s-1 | 10/10/24 |
TiO2 | 3 mTorr | 120 W | 0.067 Å s-1 | - |
Al2O3 | - | - | - | - |
ZnO | 3 mTorr | 120 W | 0.2 Å s-1 | - |
Si3N4 | 3 mTorr | 120 W | 0.014 Å s-1 | 01/03/22 |
i-Ge | 3 mTorr | 120 W | 0.35 Å s-1 | 6/24/24 |
Independent Deposition Rate Characterization
Additional resources
Note: The sputter yield chart can be useful for estimating approximately what rate to expect from materials, but the rate given is highly dependent on tool configuration and is not directly relevant
Maintenance
The basics of magnetron sputtering
Magnetron sputtering, also simply called sputtering, is a PVD method that involves a gaseous plasma (often consisting of high-energy Ar ions) which is generated within the chamber and bombarded onto the material to be deposited, known as the target. During the bombardment, the surface of the target is eroded by the plasma and the ejected atoms travel from the surface of the target, through the vacuum environment, and deposit onto a substrate (such as a Si or quartz wafer) to form a thin film. Materials ranging from metals to dielectrics can be deposited via sputtering, and the technique is widely used within both academia and industry, with a variety of applications ranging from electronics to food packaging.
During a typical sputtering process, the chamber is evacuated to high vacuum (~ 5 x 10-8 Torr) to minimize the partial pressures of background gases (oxygen, nitrogen, water vapor, etc.) along with potential volatile contaminants (such as solvents). After high vacuum is reached, the sputtering gas that is used to form the plasma is injected into the chamber. The total pressure is subsequently regulated to the mTorr range (typically 3 to 10 mTorr). To strike the plasma, a high voltage is applied between the cathode (often located directly behind the sputtering target) and the anode (often connected to the chamber as electrical ground).
As a high voltage is applied, electrons are accelerated away from the cathode towards the anode, colliding with the nearby injected gas atoms. These collisions knock electrons off the sputtering gas atoms, causing positive ionization, hence forming the plasma. The ionized sputter gas atoms are now accelerated towards the negatively charged cathode, resulting in high energy collisions with the target. Each of these collisions can cause atoms at the surface of the target to be ejected into the vacuum environment with enough kinetic energy to reach the surface of the substrate. The overall gas pressure is typically reduced to around 3 mTorr to ensure fewer collisions between the ejected atoms and the gas atoms, as these collisions increase the diffusivity of the ejected atom stream. These collisions can give rise to a quasi-conformal coating, which can be both beneficial or detrimental for the overall application.
While sputtering is typically a slower process than evaporation, sputtering results in smoother thin-films.