JPH04253351A - Method for measuring contact resistance - Google Patents

Abstract

PURPOSE:To enable contact resistance to a probe to be measured easily each time for each chip when measuring contact resistance between the probe which contacts an electrode pad and the pad. CONSTITUTION:A probe is allowed to contact an electrode pad where a diode is connected to, currents I1 and I2 with two different values are allowed to flow at a constant-voltage region of current-voltage static characteristic in forward or backward direction of the diode, voltages V1 an V2 which are applied to the diode corresponding to each current are measured, and then a contact resistance R between the electrode pad and the probe is calculated from R=(V2-V1)/(I2-I1). Also, the above electrode pad is constituted so that it can be used for I/O of signal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring contact resistance between a probe that contacts an electrode pad and a pad.

In the manufacturing process of semiconductor devices, after the wafer process is completed, a plurality of IC chips formed in the wafer are sequentially tested using a prober (probe testing device) to determine whether each IC chip is good or bad. ing. At this time, if the contact resistance of the probe becomes large,
There were times when measurement errors became large, making it impossible to accurately determine pass/fail.

The present invention can be used as a method for measuring contact resistance between a probe tip and a pad of a probe card having a plurality of probes that simultaneously contact electrode pads of an IC chip.

0004

2. Description of the Related Art FIGS. 4A and 4B are a plan view and a sectional view illustrating an example of a probe card. In the figure,
1 is a probe card board, 2 is a probe, 3 is an epoxy resin for fixing the probe, 4 is a wafer, and 5 is a prober stage.

FIGS. 5A and 5B are a cross-sectional view and an equivalent circuit diagram illustrating a conventional method for measuring contact resistance of a probe. A wafer with an aluminum (Al) film coated on its entire surface was used as the sample, probe 2 was brought into full contact with the Al film, and constant current source A was connected to the probe to be measured.
Ground all other probes that are not being measured.

In the equivalent circuit, R is the contact resistance of the probe to be measured, and R1 to Rn are the contact resistances of other probes that are not measured. Now, when current I is applied from current source A, voltage V on the voltmeter shows the following value.

V=I [R+ (combined resistance of R1 to Rn)]. Here, since a large number of combined resistances R1 to Rn are connected in parallel, the value becomes extremely small and can be ignored. Therefore, the above formula becomes as follows.

[0008]V=IR, R=V/R. The contact resistance of all probes was measured using the method described above.

[0009]

[Problem to be solved by the invention] In the conventional example, the IC wafer to be measured had to be replaced with a wafer whose entire surface was coated with Al, and it was impossible to measure each wafer every time. During the measurement process, the contact resistance of the probe increased, making it impossible to accurately measure the characteristics and sometimes determining good products as defective.

[0010] An object of the present invention is to make it possible to easily measure the contact resistance of a probe for each chip each time, and to perform probe tests accurately.

[0011]

[Means for solving the problem] The solution to the above problem is 1)
A probe is brought into contact with an electrode pad to which a diode is connected, and two different values of current I1,
Flow I2 through the probe and measure the voltages V1 and V2 applied to the diode corresponding to each current,
The contact resistance R between the electrode pad and the probe is expressed by the following formula, R=
(V2 - V1) / (I2 - I1), or 2) The electrode pad is achieved by the contact resistance measurement method described in 1) above, which is used for signal input/output of a semiconductor device. be done.

0012

[Operation] The present invention connects a diode in series to the contact resistance to be measured, and uses the forward or reverse rising characteristics of the diode to measure the contact resistance when two values of constant current are passed in the constant voltage region. The contact resistance is determined from the voltage at the series-connected end of the diode and the diode.

FIGS. 1A and 1B are diagrams explaining the principle of the present invention. FIG. 1A is a current-voltage characteristic diagram of a diode, and the rising region of S in the diagram is a constant voltage region where the voltage hardly changes even if the current varies greatly.

In the equivalent circuit shown in FIG. 1(B), R is a contact resistance, VD is a voltage applied to the diode, A is a constant current source, and V is a voltmeter. Currents I1 and I2 in constant voltage region
Measure the voltages V1 and V2 twice.

[0015] Voltage VD applied to the diode at this time
Assuming that VD1 and VD2 are VD1 and VD2, the following equation is obtained. V1 =I1 R+VD1,...■ V2 =I2 R+VD2. ...■Here, VD1
Since and VD2 are values in the constant voltage region of the diode, by setting VD1≒VD2≡VD, the equations ① and ② become as follows.

[0016]V1=I1 R+VD,...■V2
=I2R+VD. ...■■, ■VD from formula
By eliminating and finding R, we get the following formula.

R= (V2 −V1)/(I2 −I1). ...
■Now, if I2 = NI1, then R = (V2 - V1)/I1 (N-1). ...■ By measuring the voltage of the diode twice as described above, the contact resistance of the probe can be measured.

If an alarm is generated when this value exceeds the reference value, erroneous measurements can be prevented. In the above explanation, the constant voltage region uses forward characteristics, but reverse characteristics may also be used.

[0019]

[Example] Figures 2 and 3 show an IC used in an example of the present invention.
FIG. Figure 2 shows a positive NAN with 2 inputs.
One gate of the D gate is shown, and FIG. 3 shows one gate of the same open collector.

In the figure, the contact resistance is measured using a Schottky clamp diode (consisting of diode-connected transistors) connected to the input/output terminal, which is surrounded by a dotted line.

Next, numerical examples of equation (2) will be illustrated for when the contact resistance is normal and when it is abnormal. Now, measure V1 and V2 when I1 = 100 mA and I2 = 1000 mA flow through the diode. (1) Normal case (contact resistance 0.1 to 0.3 Ω
degree) V1 and V2 for the above I1 and I2 values
If the measured values of V1 = 920 mv and V2 = 1200 mV, then from equation (2), R = 0.31 Ω. In this case, the test results are good. (2) In case of abnormality (contact resistance is 1.5 to 5.0 Ω
degree) V1 and V2 for the above I1 and I2 values
If the measured values of V1 = 1100 mv and V2 = 2900 mV, then from equation (2), R = 2.0 Ω. In this case, the test result is negative.

In both cases (1) and (2) above, VD = 900 mV from equations (1) and (2).

[0023] The actual measured value of VD is when I1 = 100 mA flows through the diode, VD =
When flowing 830 mV, I2 = 1000 mA, VD = 920 mV, so VD =
900 mV is reasonable.

[0024]

[Effects of the Invention] The contact resistance of the probe can be easily measured for each chip without reducing the throughput of the probe test, and the probe test can now be performed accurately.

As a result, in an IC having a diode connected to an input/output terminal, it is possible to prevent the occurrence of apparently defective products due to erroneous judgment due to poor contact, and this can contribute to improving the reliability of measurement.

[Brief explanation of the drawing]

[Figure 1] Diagram explaining the principle of the present invention

[Figure 2] Partial equivalent circuit diagram of the IC used in the embodiment of the present invention (Part 1)

[Figure 3] Partial equivalent circuit diagram of the IC used in the embodiment of the present invention (Part 2)

[Figure 4] Plan view and cross-sectional view illustrating an example of a probe card

[Figure 5] Cross-sectional view and equivalent circuit diagram explaining a conventional method for measuring contact resistance of a probe

[Explanation of symbols]

1 Probe card board 2 Probe (tip) 3 Epoxy resin for probe fixation 4 Wafer 5 Prober stage

Claims (2)

[Claims] 1. A probe is brought into contact with an electrode pad to which a diode is connected, and currents I1 and I2 of two different values are applied from the probe in the constant voltage region of the forward or reverse current-voltage static characteristics of the diode. The voltages V1 and V applied to the diode correspond to the respective currents.
2, and calculates the contact resistance R between the electrode pad and the probe using the following formula: R=(V2-V1)/(I2-I1). 2. The contact resistance measuring method according to claim 1, wherein the electrode pad is used for inputting and outputting signals of a semiconductor device.