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Supercritical Fluid Technology

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JASCO's Supercritical CO2 Photo Resist Stripping and Wafer Cleaning System offers excellent performance as a cleaning solvent in the photoresist stripping/cleaning/drying processes due to unique properties such as low viscosity, high diffusivity, high permeability and no surface tension.

Features

System Description

The complexity of integrated circuits has been increasing as lithography technology improves. In order to achieve pattern widths in the sub-micrometer range, the method of photoresist stripping and cleaning of silicon wafers is critical.

In addition, the fluid becomes a gas when reducing the pressure to atmospheric at ambient temperature. A liquid solvent can often collapse microstructures with a high aspect ratio due to its high surface tension. On the other hand, supercritical CO2 has no liquid-gas phase boundary and no surface tension occurs, therefore, the fluid can penetrate into microstructures without damaging the lithography pattern.

Specifications

Perfluoropolyether lubricant preparative refinery system using the supercritical fluid extraction method

This preparative scale supercritical fluid extraction (SFE) system using carbon dioxide is equipped with a pump and back-pressure regulator to enable delivery of up to 150 ml/min of CO2, and is also equipped with a 1 liter extraction vessel.

confocal-diagram

1. CO2
2. Modifier or washing solution
3. CO2 Large volume solvent delivery pump (PU-2150; Max.150 mL/min)
4. Modifier delivery pump
5. Stop valve
6. Safety valve
7. Pre-heating coil
8. Extraction vessel (1000 mL)
9. Temperature control jacket
10. Temperature meter
11. Back pressure valve
12. 6-way switching valve
13. Pressure meter
14. Fraction vessel
15. Temperature controller

Perfluoropolyether (PFPE) is a lubricant widely used in many aerospace, vacuum, electronic and semiconductor applications due to its excellent chemical and tribological properties. It is typically used for friction reducing films on hard disks. In order to obtain a greater amount of functional PFPE, supercritical carbon dioxide extraction systems can refine and separate wide molecular weight distribution PFPE mixtures into a higher performance PFPE with a narrower molecular weight distribution.

GPC chromatograms of PFPE fractions (Z DOL-2000, Polydispersity: 1.78) extracted by this system

 

pfpe-chromatograms
 

Average molecular weight and polydispersity (Mw/Mn) of PFPE fractions extracted by this system.

 

Fractions Pressure
(MPa)
Extraction
Time (min)
Mw Mn d=Mw/Mn weight
(g)
%
Z DOL
2000
Starting
Material
  - 2128 1192 1.7844 203.95 -
  1 11.0MPa   90 767 638 1.2030 25.49 12.5
  2 12.0MPa   90 1141 888 1.2848 51.93 25.46
  3 12.5MPa   40 1502 1194 1.2573 21.61 10.59
  4 12.7MPa   40 1790 1459 1.2268 20.47 10.03
  5 13.0MPa   40 2191 1832 1.1960 18.25 8.94
  6 13.5MPa   40 2755 2321 1.1870 18.17 8.90
  7 14.0MPa   40 3469 2914 1.1904 17.14 8.40
 Residue   - 6714 5039 1.3324 27.48 12.47
 Total           200.54 98.32

 

The table outlines various PFPE fractions with narrow molecular weight distributions based on items such as polydispersity, 1.18 to 1.28.

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