CMOS Latch-Up Prevention via N-Well Contact Zone
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Solution Overview
Problem
CMOS ICs face latch-up issues due to the formation of a PNPN path, which can cause high current flow and damage, and existing solutions are not applicable to 1P1M process CMOS manufacturing as they cannot form a conductor to connect the P+ region externally.
Innovation Solution
A CMOS structure with a PMOS and NMOS portion isolated by a P-well and N-well region, an insulation layer, and a pad structure with contact plugs penetrating through the insulation layer to interface with the N-well region, where P-type dopants are implanted to create a contact zone that breaks the PNPN path, preventing latch-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a P+ region is added above the P-well region to drain high current, then latch-up protection is improved, but the manufacturing process becomes incompatible with 1P1M process since no conductor can be formed to connect the P+ region externally
Solution Approach 1:
The patent introduces an N-well region as an intermediary structure between the P-well and the external pad. This N-well acts as a mediator that can be externally connected through standard 1P1M process conductors, while still providing the necessary current drainage path to protect against latch-up. The N-well region with P-type dopants creates a controlled PN junction that diverts harmful currents without requiring direct external connection to P+ regions.
Solution Approach 2:
The patent modifies the electrical parameters of the N-well region by introducing P-type dopants to create a contact zone with specific electrical characteristics. This parameter change transforms the N-well from a simple isolation structure into an active protection mechanism that can drain high currents while maintaining compatibility with the 1P1M manufacturing process.
2Ease of operation
If the PNPN path is left intact for normal circuit operation, then device functionality is maintained, but latch-up can occur causing high current flow and potential damage
Solution Approach 1:
The patent applies local quality modification by introducing P-type dopants specifically in the contact zone of the N-well region. This localized doping creates a specific electrical property in one area (the contact zone) while leaving the rest of the N-well and P-well structures intact for normal circuit operation. The local modification provides protection against latch-up without disrupting the overall circuit functionality.
Solution Approach 2:
The patent implements preliminary anti-action by pre-configuring the N-well region with P-type dopants to create a protective mechanism before latch-up can occur. This preliminary structural arrangement ensures that when high current threatens to flow through the PNPN path, the pre-established N-well contact zone is already in place to drain the current and prevent latch-up damage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively minimizes latch-up by isolating the PNPN path with P-type dopants, preventing high current flow and reducing the risk of damage to the CMOS IC.
Implementation Method 1
performing an implantation process to provide P-type dopants as an outer area of a contact zone for interfacing an inner area of the contact zone with the N-well region
Data Source
AI summary
A CMOS structure includes a PMOS portion and an NMOS portion isolated from each other via a P-well region disposed next to the PMOS portion and an N-well region disposed between the P-well region and the NMOS portion, an insulation layer overlying at least the N-well region, and a pad structure disposed over the N-well region. The pad structure further includes: a pad body disposed on the insulation layer; and at least one contact plug penetrating through the insulation layer, having one end coupled to the pad body and the other end coupled to a contact zone in the N-well region; wherein the contact zone is interfaced with the N-well region with P-type dopants.