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1 GaAs MESFET Process Flow Wafer Cleaning Device Processing.

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Presentation on theme: "1 GaAs MESFET Process Flow Wafer Cleaning Device Processing."— Presentation transcript:

1 1 GaAs MESFET Process Flow Wafer Cleaning Device Processing

2 2 Wafer Cleaning Degreasing (grease) Degreasing (grease) Boil the substrate in Trichloroethane (TCE – 80 C) for 10 minutes (hard grease) Boil the substrate in Trichloroethane (TCE – 80 C) for 10 minutes (hard grease) Soak in warm Acetone (50 C) for 10 minutes (light grease and polymers) Soak in warm Acetone (50 C) for 10 minutes (light grease and polymers) Soak in IPA (2-propanol) for 10 minutes Soak in IPA (2-propanol) for 10 minutes Flush with cold IPA Flush with cold IPA Blow dry with N 2 Blow dry with N 2 RCA cleaning (oxides, metal contaminants) RCA cleaning (oxides, metal contaminants) Immerse GaAs in 1:1 solution of HCL:DI-water for 5 minutes Immerse GaAs in 1:1 solution of HCL:DI-water for 5 minutes Immerse GaAs in 1:1 solution of NH 4 OH:DI-water for 5 minutes Immerse GaAs in 1:1 solution of NH 4 OH:DI-water for 5 minutes Immerse GaAs in DI-water for 5 minutes Immerse GaAs in DI-water for 5 minutes Blow dry with N 2 Blow dry with N 2

3 3 SI-GaAs n-GaAs GaAs MESFET Process Flow Start with a n-GaAs / SI-GaAs wafer Apply positive-Photoresist (S-1813) Photoresist (positive)

4 4 GaAs MESFET Process Flow SI-GaAs n-GaAs Apply 1st mask to form the S/D ohmic contact pattern Apply UV-light Exposed PR will become softer Develop (MF sec.) the photoresist and remove soft parts soft PR hard PR

5 5 GaAs MESFET Process Flow SI-GaAs n-GaAs hard PR S/D ohmic contact deposition (AuGeNi) – deposit them first and then thermal annealing – thicknesses ??? Lift-off (with acetone and ultrosonic agitation) Apply PR to form the gate Apply the mask and expose the wafer to UV light AuGeNi

6 6 GaAs MESFET Process Flow SI-GaAs n-GaAs Develop the photoresist Evaporate TiPtAu Lift off AuGeNi TiPtAu

7 7 GaAs MESFET Process Flow SI-GaAs n-GaAs First metallization Develop the PR Evaporate TiAu Lift-off AuGeNi TiPtAu TiAu

8 8 GaAs MESFET Process Flow SI-GaAs n-GaAs Silicon-Nitride for electrical isolation AuGeNi TiPtAu TiAu

9 9 SI-GaAs n-GaAs AuGeNi TiPtAu TiAu SourceDrain Gate Final Device 2.5µm ~ 2.5µm TiAu AuGeNi TiPtAu 1-2 µm 1.5 µm * Optical lithography, feat.res. ~ µm * Ti( 250 A) / Au (1500 A)


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