ICLAB Lab12 Note

Week 15

LAB Description

Topic of this week

1. Power Verification
2. Bonding Pads Insertion Flow
3. Cell-Based Design Flow Review

Design

Artificial Neural Network APRII

Description

Finish the backend flow (APR) for the finished design and do the power verification.

GitHub

2021_Spring_NCTU_ICLAB/Lab12/

What did I learn?

1. How to do Power Analysis with Cadence Innovus.
2. More power stripes, less IR drop.

Lecture Note

Power Component

• Static Power : Leakage Power.
• Dynamic Power : Switching Power / Internal Power (Short Circuit Power).

Power Verification

Understanding Electromigration and IR Drop in Semiconductor Chip Design: Challenges and Techniques

• IR Drop : Average or Instantaneous Power Issue.
• Electro-Migration (EM) : Long Term Power Density Problem.

IR Drop (IRD)

• IR Drop : The voltage drop when current flows through a resistor.
• Cause chip failure due to :
  1. Performance : Circuit runs slower than specification.
  2. Functionality Problem : Setup/Hold violations.
  3. Unreliable Operation : Less noise margin.
• Prevention :
  1. Add power stripes : Avoid IR drop on cell’s power line.
  2. Change power pad positions : Avoid long power line.
  3. Use square-shaped Chip : Avoid long power line.
  4. Add decoupling cells.
• More advanced the process is, more serious the problem of IR drop is (1).
  1. Fabrication technologies smaller.
  2. The size of wires smaller.
  3. Physical chip dimensions roughly the same.
  4. Wires thinner but not shorter.
  5. An increase in resistance per unit length.
• More advanced the process is, more serious the problem of IR drop is (2).
  1. A reduction in operating voltage.
  2. Small changes in supply voltage means an increasing percentage of the digital swing.
  3. Potentially lead to incorrect logic values.

Electro-Migration, EM

Voids lead to open circuits. Hillocks lead to short circuit.

• A molecular displacement due to the momentum transfer between conducting electrons and ions over a period of time.
• Usually occurs after years of deployment of devices in the field.
• Black’s Equation : MTTF (Mean Time To Failure)
• Wire with length less than Blech-length will not suffer from electro-migration.

Bonding Pads

• Connect the circuit on a die to a pin on a packaged chip.
• Made from all the metal layers stacked on top of each other and connected through vias.

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