Dynamic testing of thin-film conductor

Claim 3

The method of claim 1 wherein the activation energy and the pre-exponential factor are calculated using a zeroth order rate expression wherein 1/R.sub.o.dR/dt=A exp(-Q/kT) Where: R o is the initial resistance of the thin-film conductor dR/dt is the variation in the conductor resistance produced by the electromigration process, Q is the activation energy for the process, A is the pre-exponential for the electromigration process, k is the Boltzmann's constant, and T is absolute temperature.

Claim 4

The method of claim 1 including the step of compensating the measured changes in resistance for changes in resistance due to temperature dependent components to determine the changes produced as a result of the electromigration process.

Claim 5

The method of claim 1 wherein said semiconductor wafer contains a plurality of like integrated circuits, and each of the latter contains a plurality of thin-film conductors, said method being carried out sequentially on a number of said thin-film conductors while said wafer remains in place on said test platform.

Claim 6

The method of claim 1, wherein said ramp current is supplied to said resistive heating element from a temperature controller device.

Claim 7

The method of claim 1 including the further step of determining the activation energy for the electromigration process by plotting 1n[T.sup.-2 (ΔR.sub.em /R.sub.o)] vs 1/T, where: ΔR em is the change in resistance of the conductor produced by the electromigration process.

Claim 8

The method of claim 6 wherein the activation energy of the process is determined from the plot according to the relationship Q=-ks, where s is the slope of the plotted line.

Claim 9

The method of claim 6 that further comprises the step of determining the pre-exponential factor from the relationship I=1n (Ak/βQ) so A=-S exp I where β is the heating rate.

Claim 10

Apparatus for testing a thin-film conductor that is contained in an integrated circuit on a semiconductor wafer, to determine the kinetic parameters of activation energy and pre-exponential factor leading to electromigration failure in the conductor, including a semiconductor wafer unit including a test platform on which said wafer is mounted, a plurality of probes which can be moved to contact with a thin-film conductor on said semiconductor wafer, and a resistive heating element mounted on said platform which is in thermal communication with said semiconductor wafer; electrical means coupled to one pair of said probes for supplying a constant current flow through said conductor as the same is being heated; heating current supply means supplying a ramp current to said resistive heating element for increasing the temperature of said wafer and the temperature of said conductor at a rate that is linear over time, including means for maintaining the linear rate of temperature increase at or below 1 degree K. per minute; first means coupled to another pair of said probes to measure the changes in resistance to said conductor as the temperature thereof increase at said linear rate over a predetermined period of time; and second means to measure the change in temperature of said wafer so that the change in conductor resistance due to the electromigration failure process can be calculated by relating such changes to said activation energy and pre-exponential factor, wherein a record of the changes in resistance over said predetermined period of time is obtained.

Claim 11

Apparatus for testing a thin-film conductor that is contained in an integrated circuit on a semiconductor wafer, to determine the kinetic parameters of activation energy and pre-exponential factor leading to electromigration failure in the conductor, including a semiconductor wafer unit including a test platform on which said wafer is mounted, a plurality of probes which can be moved to contact with a thin-film conductor on said semiconductor wafer, and a resistive heating element mounted on said platform which is in thermal communication with said semiconductor wafer; electrical means coupled to one pair of said probes for supplying a constant current flow through said conductor as the same is being heated; heating current supply means supplying a ramp current to said resistive heating element for increasing the temperature of said wafer and the temperature of said conductor at a rate that is linear over time, including means for maintaining the linear rate of temperature increase at or below 1 degree K. per minute; first means coupled to another pair of said probes to measure the changes in resistance to said conductor as the temperature thereof increase at said linear rate over a predetermined period of time; and second means to measure the change in temperature of said wafer so that the change in conductor resistance due to the electromigration failure process can be calculated by relating such changes to said activation energy and pre-exponential factor, wherein a record of the changes in resistance over said predetermined period of time is obtained.

Claim 12

The apparatus of claim 9 further comprising recording means for recording a record of changes in resistance and changes in temperature over said predetermined period of time.

Claim 13

The apparatus of claim 10 further comprising a plotter coupled to said recording means for producing a plot of the changes in resistance versus the changes in temperature.

Claim 14

The apparatus of claim 9, wherein said heating current supply means includes a programmable temperature controller for automatically increasing the current to said heating element to produce the desired increases in temperature for said wafer.

Claim 15

The apparatus of claim 9, wherein said test station device includes means for adjusting the positions of said probes while said semiconductor wafer remains positioned on said test platform so that similar thin-film conductors on a number of integrated circuits on said wafer can be tested sequentially to determine the kinetic parameters of activation energy and pre-exponential factor for each such conductor.

Claim 16

The method of claim 1 wherein said rate of increase of conductor temperature is on the order of 0.7 degrees per minute.