Method and apparatus for protection of an anti-fuse element in a high-voltage integrated circuit

A soft clamp semiconductor device for preventing inadvertent programming of an unselected anti-fuse (AF) element of a high-voltage integrated circuit (HVIC), the unselected AF element having first and second capacitive plates, the soft clamp semiconductor device comprising:

• a substrate of a first conductivity type;
• a first well region of a second conductivity type disposed in the substrate;
• a source region of the first conductivity type disposed in the first well region, the source region being electrically coupled to the second capacitive plate;
• a drain region of the first conductivity type disposed in the first well region laterally separated from the source region by a channel area of the first well region, the drain region being electrically coupled to the first capacitive plate;
• an insulated gate disposed over the channel area, the drain region, source region, and the insulated gate comprising a MOSFET;
• wherein a gate capacitance of the MOSFET is substantially less than a capacitance of the unselected AF element such that when a programming voltage is applied to the first capacitive plate, a current flows through the MOSFET that charges the second capacitive plate, thereby reducing a voltage build-up across the unselected AF element.

A method for programming a selected anti-fuse (AF) element of a power integrated circuit (IC) device, comprising:

• turning on an isolation transistor element to couple a first pin of the power IC to a common node of an AF block that includes the selected AF element and an unselected AF element, the selected AF element and the unselected AF element each including first and second capacitive plates separated by a dielectric layer, the first capacitive plate being coupled to the common node;
• coupling the second capacitive plate of the selected AF element to ground;
• applying a pulsed voltage to the first pin such that a programming voltage is applied to the first capacitive plate of the selected AF element, the programming voltage being high enough to cause a first current to flow through the selected AF element sufficient to destroy at least a portion of the dielectric layer, thereby electrically programming the first and second capacitive plates;
• flowing a second current through a MOSFET having drain and source regions respectively coupled to the first and second capacitive plates of the unselected AF element, the second current charging the second capacitive plate, thereby reducing a voltage build-up across the unselected AF element.