Specific Process Knowledge/Lithography/Strip

The content on this page, including all images and pictures, was created by DTU Nanolab staff, unless otherwise stated.

Feedback to this page: click here

Strip Comparison Table

	Plasma Asher 3: Descum	Plasma Asher 4 (Clean)	Plasma Asher 5 (Dirty)	Resist strip	Lift-off
Purpose	Resist descum	Resist stripping Resist descum	Resist stripping Resist descum	Resist stripping	Metal lift-off
Method	Plasma ashing	Plasma ashing	Plasma ashing	Solvent & ultrasonication	Solvent & ultrasonication
Process gasses	O2 (50 sccm)	O2 (0-500 sccm) 2 (0-500 sccm)	O2 (0-500 sccm) N2 (0-500 sccm) CF4 (0-200 sccm)	NA	NA
Process power	10-100 W (10-100%)	150-1000 W	150-1000 W	NA	NA
Process solvent	NA	NA	NA	NMP (Remover 1165) IPA (rinsing agent)	NMP (Remover 1165) IPA (rinsing agent)
Substrate batch	Chips: several 50 mm wafer: several 100 mm wafer: 1	Chips: several 50 mm wafer: several 100 mm wafer: 1-25 150 mm wafer: 1-25 200 mm wafer: 1-25	Chips: several 50 mm wafer: several 100 mm wafer: 1-25 150 mm wafer: 1-25 200 mm wafer: 1-25	100 mm wafer: 1-25 150 mm wafer: 1-25	100 mm wafer: 1-25 150 mm wafer: 1-25
Substrate materials	No polymer substrates Silicon substrates III-V substrates Glass substrates Films, or patterned films, of any material except type IV (Pb, Te)	No metals No metal oxides No III-V materials Silicon substrates Glass substrates Polymer substrates Films, or patterned films, of resists/polymers	Silicon substrates III-V substrates Glass substrates Polymer substrates Films, or patterned films, of any material except type IV (Pb, Te)	No metals No metal oxides Silicon substrates III-V substrates Glass substrates Polymer substrates Films, or patterned films, of resists/polymers	Silicon substrates III-V substrates (only if clean) Glass substrates Films, or patterned films, of any material except type IV (Pb, Te)

Plasma Ashing process parameters

	Resist stripping (PA4 & PA5)	Descum (PA3)	Descum (PA4 & PA5)	Surface treatment	Other ashing of organic material
Process pressure	1.3 mbar	0.8 mbar	1.3 mbar	0.5-1.5 mbar	0.5-1.5 mbar
Process gasses	O2 (100 sccm) N2 (100 sccm)	O2 (45 sccm)	O2 (100 sccm) N2 (100 sccm)	O2 N2 CF4	O2
Process power	1000 W	100 W	200 W	150-1000 W	150-1000 W
Process time	20-90 minutes	1-10 minutes	5-15 minutes	Seconds to minutes	Many hours, material dependent
Substrate batch	1-25	1-2	1-25	1	1

Plasma Asher 1

Plasma asher 1 was decommissioned 2024-12-02.

Information about decommissioned tool can be found here.

Plasma Asher 2

Plasma asher 2 was decommissioned 2024-12-02.

Information about decommissioned tool can be found here.

Plasma Asher 3: Descum

Plasma Asher 3: Descum is a low power plasma asher dedicated for descumming on smaller substrates.

Product name: Diener Pico Plasma Asher
Year of purchase: 2014

The Plasma Asher 3: Descum is dedicated for resist descum, i.e. removal of remains resist traces after development. It has a small chamber, so you can only load a single 100 mm substrate, or a few smaller pieces.

In this machine, only Oxygen is used for processing.

Typical process parameters:
Process: Photoresist descumming
Pressure: 0.2-0.8 mbar
Gas: 45 sccm O₂
Power: 100 W (100%)
Time: 1 -10 minutes (depending on photoresist type and thickness)

Other materials have not been tested.

The user manual, user APV, and contact information can be found in LabManager - requires login

Process Information

Detailed information about descum processing on Plasma asher 3: Descum can be found here.

Plasma Asher 4

Plasma asher 4 in cleanroom E-5.

Product name: PVA Tepla Gigabatch 380M
Year of purchase: 2024

The Plasma Asher 4 can be used for the following processes:

• Photoresist stripping
• Descumming
• Surface cleaning
• Removal of organic passivation layers and masks

Plasma asher 4 has the following material restrictions:

• No metals allowed
• No metal oxides allowed
• No III-V materials allowed

The user manual, risk assessment, and contact information can be found in LabManager - requires login

Typical stripping parameters
Tested with 1.5 µm AZ 5214E on 100 mm silicon substrate.

• O₂: 100 sccm
• N₂: 100 sccm
• Pressure (DSC): 1.3 mbar
• Power: 1000 W
• Time (single wafer): 20-30 minutes
• Time (full boat): 90 minutes

Process gas ratio for plasma asher 4 & 5

Ashing rate as function of gas mix ratio when processing a single 100 mm wafer and when processing a full boat with 25 wafers. The green area (~50% N₂) covers the optimum range for both situations.

The ashing rate is related to the gas mix, usually expressed as percentage of nitrogen of the total amount of gas. Process development tests found that a gas mix of 50% nitrogen gives the highest ashing rate for both processing single substrates and when processing a full boat with 25 substrates.

Please note that the ashing rate for a full boat is approximately ten times slower, than the processing time for a single substrate.

	Single substrate	Full boat
Test results	Highest ashing rate at 30-80% Nitrogen	Highest ashing rate at 50-70% Nitrogen
Wafers	1	25
Wafer size	100 mm	100 mm
Boat position	Center of chamber	Center of chamber
Test wafer position	Center of boat	Center of boat
Total gas flow rate	500 sccm	200 sccm
Gas mix ratio	Tested parameter	Tested parameter
Chamber pressure	1.25 mbar	1.3 mbar
Power	1000 W	1000 W
Test processing time	2 minutes	10 minutes
Test average temperature	43°C	47°C

Process chamber pressure for plasma asher 4 & 5

Ashing rate as function of chamber pressure when processing a single substrate and when processing a full boat with 25 substrates. The green area covers the optimum range (~1.3 mbar) for both situations.

The ashing rate is related to the chamber pressure during processing. Process development tests found that 1.3 mbar gives the highest ashing rate for both processing single substrates and when processing a full boat with 25 substrates.

Please note that the ashing rate for a full boat is approximately ten times slower, than the processing time for a single substrate.

	Single substrate	Full boat
Test results	Highest ashing rate at 1.3 mbar	Highest ashing rate at 1.4 mbar
Wafers	1	25
Wafer size	100 mm	100 mm
Boat position	Center of chamber	Center of chamber
Test wafer position	Center of boat	Center of boat
Total gas flow rate	150 sccm	200 sccm
Gas mix ratio	30% N2	50% N2
Chamber pressure	Tested parameter	Tested parameter
Power	1000 W	1000 W
Test processing time	2 minutes	10 minutes
Test average temperature	43°C	55°C

Process gas flow rate for plasma asher 4 & 5

Ashing rate as function of total gas flow when processing a single substrate and when processing a full boat with 25 wafers. The green area covers the optimum range (~200 sccm) for both situations.

The ashing rate is related to the total gas flow rate during processing. Process development tests found that 200 sccm gives the highest ashing rate for both processing single substrates and when processing a full boat with 25 substrates. The experiments indicate that the gas flow rate has only a minor impact on the ashing rate.

Please note that the ashing rate for a full boat is approximately ten times slower, than the processing time for a single substrate.

	Single substrate	Full boat
Test results	Highest ashing rate at 200 sccm	Highest ashing rate at 200 sccm
Wafers	1	25
Wafer size	100 mm	100 mm
Boat position	Center of chamber	Center of chamber
Test wafer position	Center of boat	Center of boat
Total gas flow rate	Tested parameter	Tested parameter
Gas mix ratio	30% N2	30% N2
Chamber pressure	1.3 mbar	1.3 mbar
Power	1000 W	1000 W
Test processing time	2 minutes	10 minutes
Test average temperature	43°C	47°C

Process power for plasma asher 4 & 5

Ashing rate as function of microwave power.

The ashing rate is related to the power used during processing. Higher power increases ashing rate.

	Single substrate
Test results	Ashing rate follows Power
Wafers	1
Wafer size	100 mm
Boat position	Center of chamber
Test wafer position	Center of boat
Total gas flow rate	200 sccm
Gas mix ratio	30% N2
Chamber pressure	1.3 mbar
Power	Tested parameter
Test processing time	2 minutes
Test average temperature	40°C

Process temperature for plasma asher 4 & 5

Ashing rate as function of temperature.

The ashing rate is related to the temperature during processing. Higher temperature increases ashing rate.

	Single substrate
Test results	Ashing rate follows temperature
Wafers	1
Wafer size	100 mm
Boat position	Center of chamber
Test wafer position	Center of boat
Total gas flow rate	200 sccm
Gas mix ratio	30% N2
Chamber pressure	1.3 mbar
Power	1000 W
Test processing time	2 minutes
Test average temperature	Tested parameter

Comparison of ashing rate between substrate sizes for plasma asher 4 & 5

Comparison of ashing rate with different substrate sizes. Process was done using a single substrate placed in the middle of the glass boat, which was placed in the center of the chamber.

The ashing rate is highest for 100 mm substrates, lower for 150 mm substrates and even lower for 200 mm substrates.

All substrate sizes follows the same pattern:

• Ashing rate increases with a higher percentage nitrogen in the gas mix
• Ashing rate increases with a higher chamber pressure
• The total gas flow has only little influence on the ashing rate, but slightly favors the lower flow rate of 200 sccm, similar to previous experiment results

Process parameter impact on ashing rate
Investigating the ashing rate using linear regression models on the process parameters, indicates that the gas mix and the chamber pressure has a significant impact on the ashing rate, while the gas flow has only little effect:

• 
  100 mm parameter impact
• 
  150 mm parameter impact
• 
  200 mm parameter impact

Plasma Asher 5

Plasma asher 5 in cleanroom E-5.

Product name: PVA Tepla Gigabatch 380M
Year of purchase: 2024

The Plasma Asher 5 can be used for the following processes:

• Photoresist stripping
• Descumming
• Surface cleaning
• Removal of organic passivation layers and masks

Furthermore plasma processing using CF₄ in plasma asher 5 can be used for:

• Etching of glass and ceramic
• Etching of SiO₂, Si₃N₄, Si
• Removal of polyimide layers

Plasma asher 5 can be used for almost every material, but if you have any doubt if your materials are compatible/allowed in plasma asher 5, feel free to ask the lithography group at Nanolab.

The user manual, risk assessment, and contact information can be found in LabManager - requires login

Process Information

Plasma asher 5 is identical to plasma asher 4, see resist strip processing for plasma asher 4 here.

Processes specifically only for plasma asher 5:

• SiO₂ etch using Plasma Asher 1
• Descum using plasma asher 5

Resist Strip

Resist strip bench in D-3

This resist strip is only for wafers without metal and SU-8.

There are one Remover 1165 bath for stripping and one IPA bath for rinsing.

Here are the main rules for resist strip use:

• Place the wafers in a wafer holder and put them in the first bath for 10 min, this time is depending how much resist you have on the surface.
• After the strip rinse your wafers in the IPA bath for 2-3 min.
• Rinse your wafers for 4-5 min. in running water after stripping.

The user manual and contact information can be found in LabManager: Resist Strip - requires login

Overview of wet bench 06 and 07

	Resist Strip	Lift-off
Process	Wet resist strip	Metal lift-off process
Chemical	Remover 1165 (NMP)	Remover 1165 (NMP)
Process temperature	Up to 65°C	Up to 65°C
Substrate batch	1-25 wafers	1-25 wafers
Substrate size	100 mm wafers 150 mm wafers	100 mm wafers 150 mm wafers
Materials allowed	Silicon Silicon oxide Silicon nitride Silicon oxynitride	All metals except Type IV (Pb, Te)