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Possibility to test/measure small FET's Ron even in presence of high series contact resistances

IP.com Disclosure Number: IPCOM000194461D
Publication Date: 2010-Mar-25
Document File: 2 page(s) / 21K

Publishing Venue

The IP.com Prior Art Database

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Possibility to test/measure small FET's Ron even in presence of high series contact resistances

Summary

Testing the ON Resistance (RON) of an integrated Field Effect Transistor (FET) is always a tough stage in the testing of an integrated circuit since the contact resistances (Rc) of the prober can be higher than the Device Under Test (DUT) preventing an accurate measure of the RON.

This paper presents a method to evaluate the RON resistance of an integrated FET without implementing additional probe pads/pins for the test.

Description of the invention

Assuming a FET is to be tested. The DUT is split in 2 FETs (DUT_A and DUT_B) having ON resistance values called Ra and Rb.

During regular functioning of the device the 2 FETs are always driven in parallel so that the global ON resistance will be equal to Ra // Rb. The contact resistance of the prober will be noted Rc.

During the test phase:
• a first resistance measurement will be done with just DUT_A turned ON, so the resistance seen by the tester will be R1 = Ra + Rc

• a second resistance measurement will be done with just DUT_B turned ON, so the resistance seen by the tester will be R2 = Rb + Rc

• a third resistance measurement will be done with both DUT_A and DUT_B turned ON, so the resistance seen by the tester will be R3 = Ra // Rb + Rc

Starting from the measured resistances (R1, R2 and R3) the values of Ra and Rb can be calculated with the following formulas:

Ra

=

R

1

R

3

+

R

3

2 R

R

R

R

R

R

( )

1

3

+

2

3

1

2

Rb

=

and if necessary,

R

2

R

3

+

R

3

...