150mm Wafer Transfer
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MIT Lincoln Laboratory 150mm Wafer Transfer Keith Warner, Andy Loomis April 7, 2000
description
150mm Wafer Transfer. Keith Warner, Andy Loomis April 7, 2000. Transfer Process Goals. Adhesive-based wafer-to-wafer bonding 2 – 5 µm bondline thickness, thermal limits on post-transfer processing, +/- 2 µm alignment accuracy with existing tools - PowerPoint PPT Presentation
Transcript of 150mm Wafer Transfer
MIT Lincoln Laboratory
150mm Wafer Transfer
Keith Warner, Andy Loomis
April 7, 2000
MIT Lincoln Laboratory
Transfer Process Goals
Adhesive-based wafer-to-wafer bonding
2 – 5 µm bondline thickness, thermal limits on post-transfer processing, +/- 2 µm alignment accuracy with existing tools
Complete transfer of NU processes, also useful for other device types
Oxide fusion bonding (Adopt existing process from CCD work)
< 1 µm bond layer, post-transfer processing ~400°C (Tungsten CVD plugs, “hot” Al), +/- 1 µm alignment with tool to be purchased
Determine technology limits on this program
Sub-micron via placement with oxide bonding
Build/specify tools using stepper technology techniques
MIT Lincoln Laboratory
Wafer Bonding - Voids
Voids are formed after the SOI handle wafer is removed
• Particulate - Cleaning, clean area, inspection, filtration
• Pinholes and oxide quality - Starting material
• Adhesion – Cleaning
• Bubbles – Vacuum outgassing of epoxy
MIT Lincoln Laboratory
Wafer Bonding - Voids
12/16/99 3/2/00
(After wafer thinning decorative etch)
Void – free wafer transfer achieved
MIT Lincoln Laboratory
Wafer Bonding - Alignment
• Alignment method – depends on type of tool
– Early work used Research Devices flip-chip bonder
– Limitations of optical system restricted accuracy to +/- 5 µm
MIT Lincoln Laboratory
Wafer Bonding - Alignment
– Karl Süss mask aligner with infrared optics
– Better than +/- 2 µm accuracy, repeatable
MIT Lincoln Laboratory
Wafer Bonding - Alignment
Accurate alignment achieved
(Same wafer without voids)
MIT Lincoln Laboratory
Wafer Bonding – Bondline Uniformity
• Wafer flatness – Double side polished ultra-flat wafers
• Adhesive curing cycle – Experiments started (Research Devices tool is not designed for wafer-to-wafer bonding; available pressure is inadequate)
• Spacers – Latex microspheres
• Particulate – Cleaning, inspection, filtration
(2-5 µm required across wafer)
Still working on optimization
MIT Lincoln Laboratory
Wafer Bonding Apparatus and Operation
MIT Lincoln Laboratory
Status
• Void-free transfer successful
• Alignment accuracy adequate for devices currently available (“North2”)
• Method identified to meet bondline requirements – experiments are underway
• Full-time effort has started
