2 - Clean Rooms Chemicals and Vacuum Science Himanshu J...

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Clean Rooms, Chemicals, and Vacuum Science Himanshu J. Sant Fundamentals of Microfabrication Learning Objectives • Identify the clean room requirements and practices • Understand the need of good laboratory practices – Safety – Clean environment • Understand the processes used to maintain clean environment • Familiarize with common chemicals and related safety measures/precautions
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IC Processing Requirements 0.01 0.1 1 5 50 100 500 1,000 Utility Purity (ppb) 0.1 0.1 0.1 0.1 1 10 100 1,000 Cleanroom Class ~ 800 600 500 400 300 200 150 100 Process Steps 0.2-0.1 0.25 0.35 0.5 0.8 1 1.5 2 Feature Size (μm) 4.5 3 2 1.4 0.9 0.5 0.4 0.3 Chip Size (cm2) 1G 256M 64M 16M 4M 1M 256K 64K DRAM Technology 300 200 200 200 150 125 100 75 Wafer Size (mm) 2004 1999 1996 1993 1990 1987 1984 1980 Mass Production Started Data from Chang and Sze, ULSI Technology . How Big of a Particle is Tolerable? • Example: 0.5 μm CMOS technology – Lateral Features: • pattern size = 0.5 μm • pattern tolerance = 0.15 μm • level-level registration = 0.15 μm – Vertical Features: • gate oxide thickness = 10 nm • field oxide thickness = 20 nm • film thicknesses = 250-500 nm • junction depths = 50-150 nm
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Size Ranges of Suspended Particles • Macro Particle Range – > 25 μm, visible to the naked eye • Micro Particle Range – 1 - 15 μm, visible with an optical microscope • Macro Molecular Range – 0.1 - 1 μm, visible with a high power optical microscope • Molecular Range – 1 - 100 nm, visible with a scanning electron microscope • Ionic Range – 0.1 - 1 nm, not visible with current technology Size Range of Common Particles Atomic Radii 1-6 Å Metal Ions 2-7 Å Aqueous Salts 2-20 Å Sugars 7-25 Å Pyrogens 20-250 Å Collodial Silica 6-250 nm Albumin Protein 8-100 nm Viruses 9-100 nm
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2 - Clean Rooms Chemicals and Vacuum Science Himanshu J...

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