JPS63295981A - Electrostatic breakage tester for semiconductor device - Google Patents

Abstract

PURPOSE:To enable a breakage judgment to be performed with a high accuracy by comparing a current value after the application of an electrostatic pulse and an initial current value with each other in a leakage current region and in a large current region. CONSTITUTION:A voltage value set in advance is applied to the pin P1 of an IC 10 to be tested via a current supply/current measuring circuit 5 from a personal computer 2. After measured by the circuit 5, a flowing current is A/D-converted 6 and set voltage-current values are stored in the personal computer 2 as initial characteristics. Then, after an electrostatic pulse is applied to the pin P1 from an electrostatic pulse generating circuit 9, a current value for the application of the set voltage is measured and voltage-current characteristics after the application of the electrostatic pulse are stored into the memory of the personal computer 2. Those processings are sequentially conducted on the pins. The stored characteristic values of the pins are classified to a leakage current region and a large current region. In the leakage current region, whether the current value after the application of the electrostatic pulse is increased from an initial current value up to a reference current value or above and, in the large current region, whether the current value after the application of the electrostatic pulse is changed at above a prescribed rate are judged and the pin whose current value exceeds a reference value is judged as a defective pin.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to an electrostatic breakdown testing device for semiconductor devices used for determining the quality of ICs, LSIs, and the like.

(b) Conventional technology Conventionally, to measure the electrostatic breakdown strength of ICs, LSIs, etc.
The measurement circuit shown in FIG. 3 is used.

In the figure, an electrostatic pulse applicator 11 and a curve tracer 12 are used as measuring instruments. Electrostatic pulse applicator 11
The GND terminals of the curve tracer 12 and the test object C13 are commonly connected, while the child terminals of the electrostatic/electric pulse applicator 11 and the child terminals of the curve tracer 12 are selectively connected by switching the switch S. Test terminal (pin) of test ICl3
P is connected to K. In this measurement circuit, first put the switch "S" into the curved tray, visually measure and memorize the V-I (voltage-current) characteristics before applying the electrostatic pulse as the initial characteristics, then switch "S" is applied to the electrostatic pulse applicator 11 side, and a pulse is applied to the terminal P+.

Then, set the switch S to the curve tracer 12 side again,
The V-1 characteristic is obtained and the memorized initial characteristic is compared with the characteristic after the current pulse application to determine destruction. In this case, the determination is visually compared with the initial characteristics over ranges a, b, and c.

In order to obtain the breakdown voltage of all terminals of the ICl3 under test, switch S is turned on to the curve tracer 12, and the test terminals are sequentially switched over ranges a, b, and c, and the initial characteristics of each terminal are determined. Next, switch S is turned on to the electrostatic pulse applicator 11, while the test terminals are sequentially switched and a pulse is applied to each test terminal. Thereafter, the switch S is again turned on to the curve tracer 12, the test terminals are sequentially switched, the V-1 characteristics of each terminal are obtained, and the results are visually compared with the initial characteristics over ranges a, b, and c.

In addition to the above-mentioned visual comparison, there is a method of determining electrostatic damage by calculating the percentage change in the V-I characteristics after the electrostatic pulse is applied to the V-I characteristics before the electrostatic pulse is applied. . This method focuses on the fact that the voltage-current characteristics between each terminal of an IC are as shown in FIGS. 4(a) and 4(b). For each breakdown region, current values are compared and the degree of variation is expressed as a percentage, and a predetermined percentage or more is determined to be defective.

(c) Problems to be Solved by the Invention The technique of visually determining destruction using the electrostatic pulse applicator and curve tracer described above requires that the human eye remember the initial characteristics of Vi. It is almost impossible to do this over a range. Although it is possible to record the initial characteristics using a photographic device, it is still impossible to do so over all terminals and all ranges of the IC in terms of work efficiency.

In addition, visual comparison does not provide quantitative values for subtle variations in characteristics or variations in measurement standards, so there is a problem in that highly accurate judgments cannot be expected and there is a high risk of erroneous judgments.

On the other hand, although it is possible to make a quantitative determination based on percentage comparison, the initial current value in the leakage current region is still around 101A, which is about three orders of magnitude lower than the forward current region. The reading error is large, and even when reading with an automatic tester, it is difficult to accurately determine failure.

In view of the above, it is an object of the present invention to provide an electrostatic breakdown testing device for semiconductor devices that is capable of making quantitative and highly accurate decisions.

(d) Means for Solving the Problems The electrostatic breakdown testing apparatus for semiconductor devices of the present invention includes a voltage setting means for setting in advance a voltage for measuring characteristics and a voltage for generating electrostatic pulses, and this voltage setting means. a voltage supply/current measuring means that applies a voltage set by the voltage between a predetermined terminal of the semiconductor device under test and a common reference potential terminal and obtains a corresponding current value; an electrostatic pulse generating means for generating an electrostatic pulse according to the characteristic measurement and applying it to a predetermined terminal of the semiconductor device under test in place of the voltage for measuring the characteristics; A characteristic storage means for storing the relationship between the voltage for characteristic measurement and the current value taken in by the voltage supply/current measurement means as an initial characteristic and a characteristic after application of an electrostatic pulse, respectively; and a characteristic stored in the characteristic storage means. current region classification means for classifying the current value into a leakage current region and a large current region equal to or higher than the leakage current region; a first defect determination means that determines the terminal as a defective terminal if the current value is large, and a first defect determination means that determines the terminal as a defective terminal if the current value after application of the electrostatic pulse fluctuates by more than a predetermined percentage with respect to the initial current value in the large current region; and a second defective determination means for determining a terminal as a defective terminal.

(E) Function In this electrostatic breakdown test apparatus, first, a set voltage is set between the terminal to be tested and the common reference potential (OND) terminal of the semiconductor device under test from the voltage setting means through the voltage supply/current measuring means. applied. The current flowing in response to the application of this set voltage is measured by the voltage supply/current measuring means. Current values corresponding to several points of the set voltage are measured, and these current values are stored in the characteristic storage means as initial characteristics. Next, instead of the voltage for measuring characteristics, a set voltage for electrostatic pulses is output from the voltage setting means, and in response to this, an electrostatic pulse is input from the electrostatic pulse generating means, and the An electrostatic pulse is applied to the terminal of the semiconductor device to be tested. After application of this electrostatic pulse, a set voltage is again applied from the voltage setting means to the test terminal via the voltage supply/current measuring means.

The current flowing in response to the application of this set voltage is measured by the voltage supply/current measuring means. Such measurements are performed at several points of the set voltage, and the corresponding current values are stored in the characteristic storage means as the characteristics after application of the electrostatic pulse. Subsequently, the characteristics stored in the characteristic storage means are classified by the current region classification means into a leak current region and a large current region. Then, in the leakage current region, the initial current value and the current value after applying the electrostatic pulse are compared, and if the current value after applying the electrostatic pulse is larger than the initial current value by a predetermined reference value or more, The terminal is determined to be a defective terminal. Furthermore, in the large current region, the rate of change in the current value after application of the electrostatic pulse with respect to the initial current value is calculated, and if the rate of change is equal to or greater than a predetermined value, the terminal is determined to be a defective terminal.

(f) Examples The present invention will now be explained in more detail with reference to Examples.

FIG. 1 shows an embodiment of the present invention, and is a measurement circuit diagram when performing an electrostatic discharge test on an IC using an automatic electrostatic discharge test apparatus. In the figure, an automatic electrostatic discharge test device 1 includes a personal computer (personal computer) 2 that performs test control and stores data, a digital interface 3 that outputs voltage values set by the personal computer 2,
D/A converter 4 that converts this voltage value into an analog value
, a voltage supply/current measurement circuit (■Form) that supplies an analog voltage to the ICl0 under test and measures the corresponding current.
5. An A/D converter 6 that converts the measured current value from an analog value to a digital value and provides it to the computer 2. A digital interface 7 that outputs the electrostatic pulse voltage value set for the computer 2. It is comprised of an electrostatic pulse generation circuit 9 consisting of a D/A converter 8 for converting into analog values, a bipolar power supply 9a, a charging resistor R, a capacitor C, and a switch S2.

The voltage supply/current measurement circuit 5 and the electrostatic pulse generation circuit 9 are connected to the test pin (terminal) P of the ICl0 under test via the switch Sl, and are connected to the GND terminal of the automatic electrostatic discharge test equipment 1 and the test pin (terminal) P of the ICl0 under test. The GND pins P6 of the test ICl0 are connected in common.

The automatic electrostatic discharge test device 1 is configured such that various setting voltages can be set in the memory of the personal computer 2, and a current value corresponding to the output setting voltage value is also stored, so that the so-called initial V
-I characteristics and V-1 characteristics after electrostatic pulse application are also stored. Furthermore, the electrostatic pulse generation circuit 9 can output electrostatic pulses of both polarities and arbitrary voltages. Although not shown, not only the test pins P of the ICl0 under test, but also P z , P 3 , . . . , Pl & . . .
... and gold pin terminals can be switched and connected using a pin conversion matrix (sequential switching circuit using relays).

Next, the operation when performing an electrostatic discharge test using the above measurement circuit will be explained with reference to the flowchart shown in FIG.

First, switch SI is put on the a side, that is, the voltage supply/current measurement circuit 5 side, and the voltage value preset from the personal computer 2 is outputted through the digital interface 3, and the D/
The A converter 4 converts it into an analog value, and the voltage supply/current measurement circuit 5 applies the set voltage to the pin p1 of the ICl0 under test.

Then, by applying this voltage, the flowing current is measured by the voltage supply/current measuring circuit 5, and this current value is taken into the personal computer h 2 via the A/D converter 6, and the set voltage - current value is calculated. Stored as an initial characteristic. The measurement memory of this initial characteristic is applied to other pins P,,P,,.

. . . are also sequentially switched over (step 5TI). Next, switch Sl is switched to the b side, that is, the electrostatic pulse generation circuit 9 side, and the applied voltage value initially set from the personal computer 2 is output through the digital interface 7, and switch S2 is switched to the b side to generate electrostatic pulses. An electrostatic pulse is applied from the circuit 9 to the pin Pl. Application of this electrostatic pulse is also performed sequentially to other pins P z and P z """ by switching the pins (step 5T2).
Subsequently, the switch S is again switched to the a side, the current value with respect to the application of the set voltage is measured, and the voltage-current characteristic after the application of the electrostatic pulse is stored in the memory of the personal computer 2.

These processes are also performed for each pin. Then, the stored characteristic values of each pin are classified into a leakage current region or a large current region greater than the leakage current region.

To determine the leakage current range, for example, ■ 1 μA or less or ■ 10 μA is used, but which one to use is
Set with initial parameters (step 5T3). If the classified data is in the leakage current region (step 5
T4), it is determined whether the current value after application of the electrostatic pulse has increased by a reference current value or more from the initial current value (Step 5T5).

This reference current value is set in advance as a parameter. If the current has increased by more than the reference current value in step ST5, that pin is determined to be defective. This defective pin will then be excluded from the application of electrostatic pulses (step 5).
T6).

If the data is in the large current region, it is determined whether the current value after application of the electrostatic pulse has varied by A% or more from the initial current value (step 5T7). The reference value A here is determined based on experience from previous failed ICs and is set as a parameter.

In step ST7, if it is determined that the current value has changed by A% or more from the initial current value, that pin is determined to be a defective bin.

Then, this defective bottle is also excluded from the application of the next electrostatic pulse (step 5T8). When the processing of steps ST4 to ST8 is completed for each pin, it is determined whether the electrostatic pulse is at the maximum set voltage or not (step 5T9),
If NO, a new electrostatic pulse with a voltage equal to the previously applied voltage plus a predetermined step voltage is applied to each pin other than the excluded defective pins (Step 5TIO). Then, the process returns to step ST3, and step ST3 is performed again.
3 to ST9 are executed. Thereafter, the above process is repeated while adding a predetermined step voltage until the applied pulse exceeds the maximum set voltage.

(G) Effects of the Invention According to the present invention, characteristics testing can be performed over a wide range, and is divided into a leakage current range and a large current range. Since the determination is based on the fluctuation of the value, the quality can be determined quantitatively and accurately, and there is no fear that it will be influenced by the subjectivity of the measurer.

In addition, for destructive measurements, it is possible to set parameters based on experience regarding the increase in leakage current and the fluctuation rate of current value, and by inputting data on the destructive state of the field, it is possible to obtain reasonable and appropriate detailed value data. Can be done.

In addition, a personal computer or the like can be used as a means for achieving the functions of the device of this invention, and by fully utilizing the storage and arithmetic functions of the personal computer, it is possible to obtain data on the electrostatic breakdown voltage of multiple pins with a single device. Compared to manual measurement, which generates one piece of data from one sample, this method has the advantage of being able to conduct a much more rational test, reducing the number of test samples, and making decisions in a shorter time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a measurement circuit for an electrostatic breakdown test showing an embodiment of the present invention, FIG. 2 is a flow diagram for explaining the measurement operation by the same measurement circuit, and FIG. A circuit diagram showing a measurement circuit for electrostatic discharge damage, FIG. 4(a)) is a diagram showing an example of voltage-current characteristics between terminals of a test IC. 2: Personal computer. 5: Voltage supply/current measurement circuit. 9: Electrostatic pulse generation circuit. 10: Tested IC0 Patent Applicant ROHM Co., Ltd. Agent Patent Attorney Shigeru Nakamura Figure 2 Figure 3

Claims (1)

[Claims] (1) Voltage setting means for setting the voltage for characteristic measurement and the voltage for electrostatic pulse generation in advance, and the voltage set by this voltage setting means between a predetermined terminal of the semiconductor device under test and a common reference potential terminal. a voltage supply/current measuring means for applying a voltage and taking a correspondingly flowing current value; An electrostatic pulse generation means applied to a predetermined terminal of a semiconductor device under test, and a current value taken in by the voltage for characteristic measurement and voltage supply/current measurement means before and after application of this electrostatic pulse. Characteristic storage means for storing the relationship as an initial characteristic and a characteristic after application of an electrostatic pulse, respectively, and a current value of the characteristic stored in this characteristic storage means is classified into a leakage current region and a large current region equal to or higher than the leakage current region. The current region classification means and the leakage current region include a first method for determining a terminal as a defective terminal if the current value after application of the electrostatic pulse is greater than the initial current value by a predetermined reference value or more.
and a second defect determining means that determines the terminal as a defective terminal if the current value after application of the electrostatic pulse fluctuates by more than a predetermined percentage with respect to the initial current value in a large current region. An electrostatic breakdown test device for semiconductor devices characterized by: