Breakdown voltage

AN1228

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Breakdown voltage

a particular value of current with the drain biased and the gate, as well as the source,

multiple breaks in the curve which is indicative of non-uniformities in the stress within the

inter-digitated cell structure.

punch-through due to an improper body-doping profile. There are four significant areas on

this curve - the low, mid, high and breakdown drain-voltage regions which reflect leakage,

punch-through, space-charge-limited current and avalanche current respectively. Figure 1

also shows a curve with a very sharp break where the current suddenly increases. There

are two significant regions on this curve - pre-breakdown and post-breakdown. Prior to

breakdown, leakage current exists that could be from many sources, such as the normal p-

type, n-type (pn) junction leakage due to recombination and generation of carriers in the

quasi-neutral region of the junction. The breakdown-voltage regime is the avalanching of

carriers due to the electric field being greater than the critical electric field (approximately

Due to elastic and inelastic scattering this electron acceleration can generate more than one

carrier and thus a multiplication scheme transpires.

Figure 1.

Typical breakdown curves of a LDMOS transistor

Under these conditions the high-energy carriers can alter the device characteristics by

creating, filling and emptying interface traps. For an LDMOS device, if this avalanche

condition exists under or near the gate, the hot carriers can penetrate the gate oxide as well

as alter the on- and off-state characteristics. Typical problems due to this avalanching

include threshold-voltage drift and increased gate leakage. While evaluating devices for this

parameter, large variations are indicative of inconsistencies in device fabrication. For RF

operating voltage in order to support variations in RF voltage.