Specific Process Knowledge/Lithography/Strip

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Strip Comparison Table

Equipment Plasma Asher 1 Plasma Asher 2 III-V Plasma Asher Acetone Strip Lift-off
Purpose

All purposes

Clean wafers only, no metal

III-V materials only

Resist strip, no metal

Resist strip or lift-off

Method

Plasma ashing

Plasma ashing

Plasma ashing

Solvent and ultra sound

Solvent and ultra sound

Process parameters Process gasses
  • O2 (0 - 400 sccm)
  • N2
  • CF4
  • O2 (0 - 400 sccm)
  • N2
  • O2 (flow unknown)
  • NA
  • NA
Max. process power
  • 1000 W
  • 1000 W
  • 100% (power unknown)
  • NA
  • NA
Solvent
  • NA
  • NA
  • NA
  • Acetone
  • Acetone
  • NMP (Remover 1165)
Substrates Batch size
  • 1 small sample
  • 1 50 mm wafer
  • 1 - 30 100 mm wafers
  • 1 - 25 150 mm wafers
  • 1 small sample
  • 1 50 mm wafer
  • 1 - 30 100 mm wafers
  • 1 - 25 150 mm wafers
  • 1 small sample
  • 1 50 mm wafer
  • 1 100 mm wafer
  • 1 - 25 100 mm wafers
  • 1 - 25 100 mm wafers
Allowed materials

Silicon, glass, and polymer substrates

Film or pattern of all but Type IV

No metal!

Silicon, glass, and polymer substrates

Film or pattern of photoresist/polymer

Silicon, III-V, and glass substrates

Film or pattern of all but Type IV

No metal!

Silicon, glass, and polymer substrates

Film or pattern of photoresist/polymer

Silicon and glass substrates

Film or pattern of all but Type IV


Plasma ashing

Photoresist stripping Descum after lithography Surface treatment of plastic, ceramic and metal Ashing of organic material
Process pressure 0.8- 1.0mbar 0.5- 1.0mbar 0.8-1.5mbar
Process gases
  • O2 (400 sccm)
  • N2 (0-70 sccm)
  • O2 (70-201 sccm)
  • N2 (0-70 sccm)
O2, CF4, N2 or their mixtures O2
Process power 600-1000W 150-300W 150-300W 1000W or less for heat- sensitive materials
Process time 5-60min, depending of photoresist thickness a few minutes a few seconds to a few minutes Between 0.5 and 20 hours, depending on the material
Batch size 1-30 1-10 1 wafer at a time 1 wafer at a time, use a container, e.g Petri dish


A typical process time for stripping of 1.5 µm AZ5214e resist is 15-25 min and for stripping of 9.5 µm AZ4562 resist is 20-35 min with the process parameters: 210ml O/min or mixture of 210ml O/min and 70ml N/min, power 1000W.

Plasma Asher 1

The PlasmaAsher1 is placed in C-1

The Plasma Asher1( 300 auto load model) can be used for the following process:

  • Photoresist stripping
  • Surface cleaning after storage
  • Surface cleaning after processes using oil pump or diffusion pump vacuum
  • Surface cleaning as part of photolithography after wet developing of lacquer structures prior to wet or plasma etching
  • Stripping of photoresist layers after etching, including after being exposed to high temperatures as after implantation, ion etching, sputter etching, RIE
  • Removal of organic passivating layers and masks
  • Etching of glass and ceramic
  • Etching of SiO, SiN, Si
  • Removal of polyimide layers

The machine can be used for almost every materials, but if you have any doubt about your materials are compatible with the plasma process it is better to ask photolithography group at Danchip.


Process Information


Plasma Asher 2

Plasma asher for removing AZ resist on 6" wafers: positioned in E-5

The Plasma Asher 2 is the same as Plasma Asher 1 but has another loading system which is more convenient for batch loading of 6inch substrates.

In this machine, only O2 and N2 gases are used for processes (in PlasmaAsher1, CF4 is used as well).

The typical process parameters when operating the equipment:

  • Photeresist stripping

Pressure: 0.8 - 1.0 mbar

Gas: O2

Power: 600 - 1000 watts

Time: 5 -30 min., depending on photoresist type and thickness

A typical process time for stripping of 1.5 um AZ5214e resist is 25 min for 6 wafers load in a boat, recipe 1.

A Descum process in manuel mode:O2:70, N2:70, power:150W, time:10min Be sure to wait for cooling if the mashine has been used at 1000W right before. At a load at 2 Fused silicawafers resist removed 0.01-01,5um

The other materials have not been tested yet.


III-V Plasma Asher

Plasma asher for removing resist on III-V samples: positioned in A-5


Acetone Strip

Acetone strip bench in D-3
Acetone bath "rough" for removing most of the resist
Acetone bath "fine" for removing the rest of the resist incl. ultrasound

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

There are two acetone bath: one rough for stripping the most of the resist from the surface and one fine with a ultrasound for cleaning the resists remains.


Here are the main rules for acetone strip use:

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


Overview of acetone benches

Acetone strip Lift-off
General description

wet stripping of resist

lift-off process

Chemical solution CH3COCH3 CH3COCH3
Process temperature 20 oC 20 oC
Batch size

1-25 wafers at a time

1-25 wafer at a time

Size of substrate

4" wafers

4" wafers

Allowed materials
  • Silicon
  • Silicon Oxide
  • Silicon Nitride
  • Silicon Oxynitride
  • All metals