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MOSFET Hot Electron Effect Characterization

IP.com Disclosure Number: IPCOM000087235D
Original Publication Date: 1976-Nov-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Kriese, E: AUTHOR [+2]

Abstract

The proposed VDSOFF measurement is a new hot electron effect (HEE) characterization method for field-effect transistor (FET) production. It measures the most important hot plot parameter VDSmax independently of other mobile charge effects, and it is capable of predicting three Khrs HEE stress results.

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MOSFET Hot Electron Effect Characterization

The proposed VDSOFF measurement is a new hot electron effect (HEE) characterization method for field-effect transistor (FET) production. It measures the most important hot plot parameter VDSmax independently of other mobile charge effects, and it is capable of predicting three Khrs HEE stress results.

VDSOFF, as an equivalent HEE parameter, is defined as the highest VDS (drain-to-source voltage) stress value at which, with VGR and VGN being, respectively, the reserve and normal gate voltages, Alpha = (VGR - VGN)(ID = 4 mu A, VDS - 8 V). It does not increase further after having reached a particular value, e.g., 30 to 50 mV, with the stress being, e.g., VDS > VDSOFF and VC = 10 V + VT (threshold voltage).

The main feature of the VDSOFF measurement is to develop an Alpha value in a few minutes by means of a high VDS stress, then to reduce this stress to as low a value as is necessary to stop the hot electron effect developing further. "Stop" in this context means that the HEE development becomes as slow as the hot plot definition for VDSmax requires, e.g., 10 mV in 3 Khrs. The 1-to-1 correlation of VDSOFF and life test values coincide with what is obtainable in practice.

The measurement procedure and set-up in general are as follows: An adjusted time control unit subjects the FET to stress for 5 sec., then VGN is measured for 0.5 sec. After another stress period of 5 sec., VGR is measured for 0.5 sec. The VGN value is stored in a low-leakage capacitor. A fast digital voltage meter (DVM) is triggered to measure the difference between the capacitor voltage and the VGR amplifier output. Thus the DVM shows a zero value for 5 sec. during the first stress period and an Alpha value equaling VGR - VGN during the second stress period.

The following step sequence is suggested, although it is understood that other time and voltage values, etc., are possible:
1) Adjust all measurement voltages and currents.
2) Set VG stress and VDS stress to zero volts.
3) Measure VGN and VGR.
4) Measure Alpha.
5) Set VG stress to 11 V.
6) Monitor Alpha for 10 min.
7) If Alpha remains stable go ahead; if no...