L09 Wires

L09 Wires - Wires 6.371 Fall 2002 L09 Wires 1 Modern...

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L09 – Wires 1 6.371 – Fall 2002 10/2/02 Wires
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L09 – Wires 2 6.371 – Fall 2002 10/2/02 Modern Interconnect Stack IBM CMOS7 process 6 layers of copper wiring 1 layer of tungsten local interconnect © IBM © IBM Metal 1 Metal 6 Metal 5 Metal 4 Metal 2 Metal 3 Via 5-6 Via 1-2 Tungsten local interconnect
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L09 – Wires 3 6.371 – Fall 2002 10/2/02 Interconnect Problems ± A lot of circuit designers are very worried about what’s happening with wires ± Device technology has been scaling well, with gate performance increasing linearly with decreasing feature size ± Wires scale differently, and long wires have been getting relatively slower over time ± Wire delay is a function of wire resistance and capacitance
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L09 – Wires 4 6.371 – Fall 2002 10/2/02 Wire Resistance ± bulk aluminum 2.8x10 -8 -m ± bulk copper 1.7x10 -8 -m ± bulk silver 1.6x10 -8 -m Width Length Height ( ) () width height y resistivit length resistance × × = ± Thickness fixed in given manufacturing process ± Resistances quoted as /square ± TSMC 0.18 µ m 6 Aluminum metal layers M1-5 0.08 /square (0.5 µ m x 1mm wire = 160 ) M6 0.03 /square (0.5 µ m x 1mm wire = 60 )
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L09 – Wires 5 6.371 – Fall 2002 10/2/02 Local Interconnect ± Use contact material (tungsten) to provide extra layer of connectivity below metal 1 ± Can also play same trick with silicided poly to connect gates to diffusion directly in RAMs ± Typically used to shrink memory cells or standard cells ± Contacts directly to poly gate or diffusion Contact plug Local Wire
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6 6.371 – Fall 2002 10/2/02 Contact Resistance ± Contact resistance significant ± TSMC 0.18 µ m 6-Al Diff-M1 11.0 Poly-M1 10.4 M2-M1 4.5 M3-M1 9.5 M4-M1 15.0 M5-M1 19.6 M6-M1 21.8 ± Resistance of two via stacks at each end of M1 wire equivalent to about 0.1 mm wire (~20 ) ± Resistance of two via stacks at each end of M6 wire about the same as 1 mm narrow M6 wire (~60 )!!! ± Use more vias in parallel to reduce effective contact resistance ± Copper processes have lower via resistance Vias made from Tungsten in Aluminum processes. Vias are Copper in Copper
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This note was uploaded on 08/23/2009 for the course EECS 6.371 taught by Professor Krsteasanovic during the Fall '02 term at MIT.

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L09 Wires - Wires 6.371 Fall 2002 L09 Wires 1 Modern...

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