The ESD Handbook

FGuard Ring Design Rules

F.1 Latchup Design Rule Checking (DRC) and Guard Rings

Latchup design rule checking (DRC) is important to avoid latchup concerns in semiconductor components. Guard rings are a key solution for latchup. In the 1980s, semiconductor corporations and foundries had few means of using electronic design automation (EDA) tools to check and verify latchup. The first latchup sections were being placed in technology design manuals in the mid-1980s

Today, latchup design rule checking are included within the design checking and verification. Latchup can occur in semiconductor devices in the following categories:

• Latchup between devices within a common circuit.
• Latchup between devices between different circuits.
• I/O circuit to I/O circuit latchup.
• I/O circuit to electrostatic discharge (ESD) circuit latchup.
• I/O circuit to core circuit latchup.
• Domain-to-domain latchup.

To address these issues, the solutions from a layout and design perspective can be achieved through physical spacing, separation of domains, and placement of guard rings to avoid formation of a parasitic pnpn that can lead to latchup. Latchup DRC check categories include the following:

• Placement of connections to power rails relative to devices.
• Device-to-device placement.
• Circuit-to-circuit placement.
• Existence of guard ring structures and spacing around devices.
• Existence of guard ring structures and spacing between devices.
• Existence of guard ring structures and spacing between circuits.
• Existence ...