Specific Process Knowledge/Lithography/Coaters/Spin Coater: Gamma DUV processing

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General Process Information

Processing using Spin Coater: Süss stepper is divided into two parts:

  • Spin coating
  • Soft baking

Spin coating

The process of spin coating on Spin Coater: GSüss stepper consists of a selection of the following steps:

  • Acceleration to a low spin speed if dynamic dispense is used
  • Resist dispense
  • Spin-off

The wafer is first centered on the spindle chuck and held in place by vacuum. If static dispense is specified in the process, the spindle remains static during the ensuing resist dispense. In the case of dynamic dispense, the spindle is accelerated to a low spin speed before the resist is dispensed. Using too high spin speed during dispense can cause surface wetting issues, while a too low spin speed causes the resist to flow onto the backside of the wafer. The resist is dispensed through the dispense arm, positioned over the center of the wafer. The resist pump administers a volume of resist which depends on the substrate size.

The spin-off cycle determines the thickness of the resist coating. The thickness is primarily a function of the spin-off speed and the spin-off time, both following an inverse power-law. The acceleration to the spin-off speed also influences the thickness, but the effect is dependent on previous steps. The spin-off is usually a simple spin at one speed, but it may be comprised of several steps at different spin speeds. After spin-off, the wafer is decelerated.

Dependent on the spin speeds used in the various steps of the spin coating, resist may creep over the edge of the wafer and onto the backside. Also, some resists tend to leave fine strings of resist protruding from the edge of the wafer, or folded onto the backside, an effect sometimes referred to as "cotton candy". This resist will contaminate the soft bake hotplate, and thus subsequent wafers with resist.

Soft baking

After spin coating, the solvent in the resist formulation must be evaporated in a baking step in order to solidify the resist. This soft bake can be carried out as a contact bake or a proximity bake. In a contact bake, the wafer is held in close contact to the hotplate surface while resting on shallow bumps only 150µm above the hotplate. In a proximity bake, the wafer is first moved into proximity, e.g. 1mm, of the hotplate surface, then held there (on the lift pins) for the duration of the bake. The hotplate temperatures of the baking modules of Spin Coater: Süss stepper are set at temperatures relevant to the resist used, typically 130-175°C. After baking, the wafer is cooled on the cool plate.

Quality Control (QC)

Quality Control (QC) for Spin coater: Süss Stepper - BARC DUV42S-6
QC Recipe: (1201) DCH 150mm BARC 65nm
Substrate size 6"
Resist volume 3 ml
Spin-off speed 4700 rpm
Spin-off time 30 s
Soft bake temperature 175°C, contact
Soft bake time 60 s
QC limits Spin coater: Süss Stepper - BARC DUV42S-6
Nominal film thickness 65 nm
Film thickness deviation from nominal <15%
Film thickness non-uniformity <5%

Spin-off speed will be adjusted if film thickness is outside the limit.


Quality Control (QC) for Spin coater: Süss Stepper - BARC DUV42S-6
QC Recipe: (1202) DCH 100mm BARC 65nm
Substrate size 4"
Resist volume 1.6 ml
Spin-off speed 3000 rpm
Spin-off time 30 s
Soft bake temperature 175°C, contact
Soft bake time 60 s
QC limits Spin coater: Süss Stepper - BARC DUV42S-6
Nominal film thickness 65 nm
Film thickness deviation from nominal <15%
Film thickness non-uniformity <5%

Spin-off speed will be adjusted if film thickness is outside the limit.

Standard Processes

BARC DUV42S-6 coating sequences:

  • (1201) DCH 150mm BARC 65nm Dispense 3ml@1000rpm; spin-off 30s@4700rpm; softbake 60s@175°C
  • (1202) DCH 100mm BARC 65nm Dispense 1.6ml@1000rpm; spin-off 30s@3000rpm; softbake 60s@175°C

KRF M230Y coating sequences:

  • (1301) DCH 150mm M230Y 360nm Dispense 3ml@1000rpm; spin-off 30s@2500rpm; softbake 90s@130°C
  • (1302) DCH 100mm M230Y 360nm Dispense 1ml@1000rpm; spin-off 30s@2500rpm; softbake 90s@130°C

KRF M35G coating sequences:

  • (1401) DCH 150mm M35G 750nm Dispense 3ml@1000rpm; spin-off 60s@5000rpm; softbake 90s@130°C
  • (1402) DCH 100mm M35G 750nm Dispense 1ml@1000rpm; spin-off 60s@5000rpm; softbake 90s@130°C
  • (1403) DCH 150mm M35G 1000nm Dispense 3ml@1000rpm; spin-off 60s@2630rpm; softbake 90s@130°C
  • (1404) DCH 100mm M35G 1000nm Dispense 1ml@1000rpm; spin-off 60s@2630rpm; softbake 90s@130°C
  • (1405) DCH 150mm M35G 1400nm Dispense 3ml@1000rpm; spin-off 60s@1310rpm; softbake 90s@130°C
  • (1406) DCH 100mm M35G 1400nm Dispense 1ml@1000rpm; spin-off 60s@1310rpm; softbake 90s@130°C
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