November_EDFA

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ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 18 NO. 4

(a)

signal and the noise are higher. (In fact, themeasurement

noise increases with voltage because some light from

the neighboring FETs is collected as well.) The resulting

signal-to-noise ratio (SNR) is shown in Fig. 5(b). The sec-

ond-generation SSPD yields a better SNR at high voltage

due to its improved detection efficiency, but it also has

worse performance at low voltage due to its higher DCR.

It should be noted that the switching emission peak

amplitude strongly depends on the temporal response

(i.e., jitter) of the system(detector

electronics): the lower

the jitter, the narrower and taller the peak. Therefore, it is

crucial to optimize the SSPD front‑end electronics. With

careful tuning of themain systemknobs that are available

to the user,

[11]

it is possible to acquire TRE waveforms in

just a few seconds at a nominal supply voltage of 0.9 V

and in approximately 20min at aworld record low-supply

voltage of only 0.4 V

[10]

(Fig. 6).

APPLICATION TO SCALED

TECHNOLOGY NODES

The capabilities of TRE have been demonstrated on

scaled technology nodes such as a ring oscillator fabri-

cated in 14 nm FinFET technology. The TRE waveform

acquired fromone of the inverter stages is shown in Fig. 7.

Eachminimum-sized transistor has five fins, and the sepa-

ration between

FET and

FET of each inverter is 86 nm.

Fig. 5

(a) Switching emission signal and noise as a function of chip supply voltage for two different generations of SSPD.

[10]

The noise at low voltage is limited by the detector noise, while at high voltage it is limited by the background (i.e., light

coming from neighboring devices). (b) Signal-to-noise ratio (SNR) as a function of supply voltage for the two detec-

tors.

[10]

SDE, system detection efficiency; DCR, dark-count rate

Fig. 6

Ultra‑low-voltage TRE measurement acquired from an inverter chain fabricated in IBM SOI 32 nm technology.

[10]

The

leakage emission can be distinguished from the noise level, and the switching emission peak can be easily identified.

(b)