General Information

1kÅ Gate Oxide SOLID STATE DOSIMETER

The Technical Data Sheet is available in Postscript format here. 100nm gate oxide RADFET data sheet

The standard chip contains two types of PMOS dosimeter, each having different geometry,

Type 1 has a W/L value of 300/50. - PINS 1,2,3,4.

Type 2 has a W/L value of 868/11. - PINS 1,5,6,7.

(where PINS 1,2,3,4 refer to Bulk, Drain, Gate, Source , similarly for Type 2.)

Dosimeter operational specifcations are listed below, along with details of device biasing for radiation sensing and threshold voltage reading.

TECHNICAL SPECIFICATIONS

Typical values @ 27°C.

Oxide Thickness 1000Å

Note: These values refer to a 300/50 device.

Sensitivity of Vth to Radiation

Irradiation Field = 0.125 MV/cm : Sensitivity = 0.09mV/rad
Irradiation Field = 0 MV/cm : Sensitivity = 0.014mV/rad
(Sensitivity at 30 krad(H₂O) using a constant 10µA in Reader configuration below.)

Temperature Compensation:

TVTC 2.5mV/°C
(This figure taken from extrapolated Vtp value in linear mode @ temps from 27°C to 100°C.)

Z.T.C. value in Linear Mode ~ 3µA
(Vs=Vb=0, Vds=-0.1)

Z.T.C. value in Saturation Mode ~ 30µA
(Using Reader circuit configuration below)

Pre-irradiation Dosimeter Characteristics:

Threshold Voltage (Extrapolated) -2.15 +/- 0.1V
(Also see Reader circuit graph - Figure 2)

Vth drift with time (secs) 2.2mV/decade
(This value from Reader configuration forcing 40µA.)

Oxide Breakdown Voltage ~ 75V

Channel Leakage Current with Vd=-12, Vg=Vs=Vbulk=0 ~ 10 pA

Subthreshold Slope 100 +/- 20 mV/decade

Channel On Resistance with Vgs-Vth=5V, Vds=-0.1 ~ 0.3 Mohms

OPERATION IN RADIATION ENVIRONMENT

Vi = Irradiation Bias. The above biasing is used when sensing radiation.

For low field mode; Vi=0 (all pins tied together).
For high field mode; Vi=5V is used, giving a field of 0.5MV/cm, and Vth change with dose is measured with the Reader circuit.

THRESHOLD VOLTAGE READER CIRCUIT

To read the total absorbed dose at any time, connect the dosimeter in the Reader circuit above. Take Vth reading @ 20sec after power-up. Subtract Vth(zero dose) to give the Vth shift due to irradiation. Dose can be read from Delta Vth vs Dose graph, as in Fig 1.

Fig 1. Radiation response of the standard 1kÅ NMRC RADFET. The graph includes 0V and 5V irradiation bias responses.

Fig 2. Vth dependence on Ids, measured using the Vo of the Reader Circuit.

CAUTION: Devices are static sensitive. Use grounding straps when handling packages.