PROCESS FLOW

Fabrication happens in sequence.

Each process step prepares the wafer for the next one.

1. Design Device layout

2. Cleanroom Entry Gown correctly

3. Wafer Cleaning Remove contaminants

4. Deposition Add material

5. Patterning Lithography

6. Etching Transfer pattern

7. Inspection Check the result

The order matters because later processes depend on structures created earlier.

PHOTOLITHOGRAPHY

How are patterns placed on a wafer?

Photolithography transfers a pattern from a photomask onto a wafer.

Photoresist Coat Light-sensitive polymer

Mask Alignment Position the pattern

UV Exposure Expose through mask

Development Create resist pattern

Precise mask alignment is critical because the pattern must appear in the correct location on the wafer.

ETCHING

▰ → ▱

Once the photoresist has been patterned, selected material can be removed from exposed regions.

Uses liquid chemical solutions to remove material.

Uses gas or plasma-based processes to remove material.

During etching, patterned photoresist can act as a protective mask over areas that should remain.

INSPECTION

Microfabrication is not just process, process, process.

Wafers should be inspected between important fabrication steps so defects can be identified before more processing is performed.

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Useful for routine inspection of patterns, particles, and visible defects.

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Scanning electron microscopy provides much higher magnification for examining small fabricated features.

Engineering mindset: If something looks wrong, investigate it before adding another process step.

UNIT 6 STUDY COMPLETE

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You've covered Process Flow & Inspection.