JPH04244975A - Inspection apparatus and method for semiconductor device - Google Patents

Abstract

PURPOSE:To detect a spike current in a short time by computing a point at which a pulse width becomes zero based on a plurality of optional pulse widths to determine a peak value of the spike current. CONSTITUTION:A power 2 is connected to a comparison voltage input terminal of a comparator 5 which compares an amount of a spike current (voltage) with a comparison voltage equivalent to a comparison current value corresponding to the amount of the spike current through a resistance 4 for setting the comparison voltage while a constant current source 9 is connected thereto to obtain the comparison voltage with the constant current source 9 and the resistance 4 for setting the comparison voltage. To determine a peak value of the spike current, a computation by a linear approximation system based on a plurality of optional pulse widths obtained from an output of the comparator 5 varying a constant current source 9. This achieves inspection accurately solely depending on absolute accuracy of the resistance 3 for current detection, the resistance 4 for setting the comparison voltage and the constant power source 9 and in a short time by computation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spike current testing apparatus for semiconductor devices and a testing method thereof.

0002

2. Description of the Related Art During transient operation of semiconductor devices containing switching elements, a short-circuit phenomenon occurs in which the power supply current instantaneously increases due to circuit design, layout and wiring, or deviations in circuit timing. This current is generally called a spike current, and a semiconductor device with an abnormally large current has a short lifespan, so it must be removed by inspection during the manufacturing process.

Conventionally, a spike current testing device shown in FIG. 3 has been used to measure this spike current. In FIG. 3, the power supply 2 is connected to the power supply terminal of the semiconductor device under test 1 via the current detection resistor 3, and the amount of spike current flowing through the semiconductor device under test 1 is determined by the resistance value Rs of the current detection resistor 3. This causes a drop and appears as a change in voltage at the power supply terminals. Generally, the resistance value R of current detection resistor 3
A low resistance value is suitable for s in order to approximate the operation of an actual semiconductor device. The spike current amount (voltage) is applied to the negative input terminal 5b of the comparator 5, and the result of comparison with the voltage applied to the positive input terminal 5a is output as a pulse to the output terminal 5c.

The input terminal 5a of this comparator 5 has
A constant voltage source 10 that can be adjusted to any output is connected to the central processing unit 8 (which performs control, calculation, and judgment) that constitutes the semiconductor measuring device 6, and can freely adjust the comparison voltage corresponding to the spike current amount. Can be set. Further, a pulse measuring device 7 capable of reading measurement values is connected to the output terminal 5c of the comparator 5, and the output pulse width can be measured by the central processing unit 8.

[0005] In most cases, the shape of a typical spike current is wedge-shaped, showing the largest value very early in the timing of a transient phenomenon, and then gradually returning to a steady current value. To find the peak value of this spike current, change the comparison voltage from the constant voltage source 10 and measure the pulse width with the pulse measuring device 7 each time.
This is done by finding a point where the pulse width is exactly 0 (zero) and obtaining the peak value of the spike current from the set voltage v of the constant voltage source 10 at that time.

FIG. 4 shows input and output waveforms of the comparator 5. 5a is a comparison voltage corresponding to a comparison current value corresponding to the amount of spike current, 5b is the amount of spike current (voltage), and 5c is a pulse output of the comparison result. If Iref is the comparison current value corresponding to the spike current amount set by the constant voltage source 10, Vs is the voltage of the power supply 2, and v is the comparison voltage from the constant voltage source 10, Iref can be obtained from the following equation.

Iref = (Vs-v)/Rs Also, let Ipeak be the peak value of the spike current. Figure 4(a)
When Iref is within Ipeak, the time during which the spike current exceeds the Iref value appears as a pulse width at the output terminal 5c of the comparator 5. At this stage when the output pulse width can be measured, Iref = Ipea
Since this is not possible with k, set Iref to constant voltage source 1.
It is necessary to change it by changing the comparison voltage v of 0 and keep searching for the point where the output pulse width becomes 0 (zero).

In FIG. 4(b), Iref = Ipeak, and the output pulse width of the output terminal 5c is exactly 0 (zero).
Indicates the current state. At this point, the following equation holds true. Ipeak=Iref=(Vs-v)/Rs Therefore, the peak value (Ipeak) of the spike current can be determined from the set voltage (comparison voltage) v of the constant voltage source 10 at this point.

[0009]

[Problems to be Solved by the Invention] However, in the conventional spike current testing device described above, the accuracy of the resistance value Rs of the current detection resistor 3 is relatively easy to obtain;
It is difficult to accurately determine the relative accuracy of the comparison voltage v. In particular, the peak value of the spike current itself is usually very small, and the current detection resistance value Rs is preferably a low value as described above, so the change in voltage due to the amount of spike current input to the comparator 5 is at most a few at the peak value. It remains at 100 mV, which is 1/10 compared to the absolute voltage of the power supply voltage Vs.
The value will be around 0. Also, if the resolution for determining the peak value of the spike current is about 1/100 of the peak value, the relative accuracy of the voltage Vs of the power supply 2 and the comparison voltage v is 0.01%.
It requires a degree.

[0010] There is a drawback that maintaining such high accuracy is technically difficult, considering temporal changes in both power supply devices and especially instantaneous fluctuations in the voltage Vs of the power supply 2 due to load fluctuations. In addition, in the conventional method of determining the peak value of spike current, in order to find the point where the pulse width becomes 0 (zero), the pulse width is measured after changing the comparison voltage and the result is recognized. Since the process of changing the comparison voltage and measuring the pulse width is repeated, there is also the disadvantage that the higher the required resolution, the longer it takes to find the peak value.

[0011] The present invention solves the above problem by calculating the point at which the pulse width becomes 0 (zero) based on a plurality of arbitrary pulse widths, thereby accurately calculating the spike current in a short time. The object of the present invention is to provide an inspection device and an inspection method that can perform inspection.

0012

[Means for Solving the Problems] In order to solve the above-mentioned problems, an inspection device of the present invention has one power supply connected to one of a current detection resistor and a comparison voltage setting resistor, and the other power supply connected to one of a current detection resistor and a comparison voltage setting resistor. The other of the current detection resistors is connected to the power supply terminal of the semiconductor device under test and also connected to one input terminal of the comparator, and the other of the comparison voltage setting resistors is connected to the other input terminal of the comparator. and grounded via a constant current source, a comparison voltage is set at one terminal of the comparator by a current flowing from the power supply through the comparison voltage setting resistor to the constant current source, and further connected to the semiconductor to be tested. Compared to the spike current detected from the device's power terminal,
The spike current can be tested by detecting whether the result is output as a pulse to the comparator output terminal.

Furthermore, the inspection method of the present invention uses the above-mentioned inspection apparatus, sets the comparison voltage setting resistance value or constant current value to different arbitrary values multiple times, and checks each measured output pulse width. The depth of the spike current is calculated by a central processing unit based on .

[0014]

[Operation] According to the configuration of the present invention, the comparison voltage, which was conventionally obtained from a constant voltage source, is obtained from a constant current source and a comparison voltage setting resistor, so that the power supply voltage Vs and the set voltage v by the constant voltage source are increased. Even if relative accuracy is not required, by adjusting the current value of the constant current source or the resistance for setting the comparison voltage,
Any resolution can be easily set, and the measurement accuracy is determined only by the absolute accuracy of the current detection resistor, comparison voltage setting resistor, and constant current value, and it is only necessary to adjust each of them.

[0015] Conventionally, in order to find the peak value of the spike current, the point where the pulse width becomes 0 (zero) is found, so
However, according to the method of the present invention, the peak value is determined by calculation based on the pulse widths at a plurality of arbitrary points, so the process can be completed in a short time.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a spike current testing apparatus for semiconductor devices according to an embodiment of the present invention. In FIG. 1, a power supply 2 is connected to a power supply terminal of a semiconductor device under test 1 via a current detection resistor 3, and the amount of spike current flowing through the semiconductor device under test is reduced by a voltage drop due to the resistance value Rs of the current detection resistor 3. This occurs as a voltage change at the power supply terminals. Generally, a low resistance value Rs is suitable for the current detection resistor 3 in order to approximate the operation of an actual semiconductor device. The spike current amount (voltage) is applied to the negative input terminal 5b of the comparator 5, and the spike current amount (voltage) is applied to the negative input terminal 5b of the comparator 5.
The result of comparison with the voltage applied to the output terminal 5c is output as a pulse to the output terminal 5c.

A constant current source 9 is connected to the positive input terminal 5a of the comparator 5 and is adjustable to any output by a central processing unit 8 (performs control, calculation, and judgment) that constitutes the semiconductor measuring device 6. , the comparison voltage corresponding to the spike current amount can be freely set by the resistance value Rc of the comparison voltage setting resistor 4 interposed between the power supply 2 and the positive input terminal 5a of the comparator 5 and the set current value i of the constant current source 9. Can be set. Further, a pulse measuring device 7 capable of reading measured values is connected to the output terminal 5c of the comparator 5, and the output pulse width can be measured by the central processing unit 8.

As described in the conventional example, the shape of a spike current is generally wedge-shaped, so in order to obtain the peak value of this spike current, the comparison voltage from the constant current source 9 is divided into several times. Change it to an arbitrary different value, measure the pulse width each time with the pulse measuring device 7, and apply a linear approximation formula based on the comparison current value and pulse width corresponding to each spike current amount to find the pulse width. Exactly 0 (
The peak value of the spike current is obtained from the calculation result by calculating the point at which the spike current becomes zero.

FIG. 2 shows input and output waveforms of the comparator 5. 5a is a comparison voltage corresponding to a comparison current value corresponding to the amount of spike current, 5b is the amount of spike current (voltage), and 5c is a pulse output of the comparison result.

Letting Iref be the comparison current value corresponding to the spike current set by the constant current source 9, Iref is obtained from the following equation. Iref = (Vs-Rc·i)/Rs Also, let Ipeak be the peak value of the spike current.

First, when Iref 1 is set to an arbitrary Iref value as shown in FIG. 2(a), the time when the spike current exceeds the Iref 1 value is determined by
appears as a pulse width at the output terminal 5c. This is measured and set as d1. Next, for the second time, as shown in Figure 2(b), Ir
Let d2 be the pulse width when the ef value is changed to Iref 2 and measured in the same manner. These first and second comparison current values Iref 1 , Iref 2 and pulse width d
The point at which the pulse width becomes exactly 0 (zero) based on 1 and d2, that is, the peak value Ipeak of the spike current, can be determined from the following equation using a linear approximation equation.

Ipeak=Iref 1 + [(Ire
f 2 −Iref 1 )・d1/d1−d2] Figure 2
In the case of the example above, the measurement is performed only twice, but the measurement is performed three times, four times, and I
Ipeak by setting ref finely and linear approximation
It is also possible to obtain more accurately by searching for .

[0023]

As described above, according to the present invention, the current detection resistor, comparison voltage setting resistor, constant current source The spike current of a semiconductor device can be tested accurately only by the absolute accuracy of the constant current value, and in a short time by calculation based on a plurality of arbitrary pulse widths.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a spike current testing apparatus for semiconductor devices according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of signal waveforms of each part in the inspection apparatus of FIG. 1;

FIG. 3 is a block diagram showing a conventional spike current testing apparatus for semiconductor devices.

FIG. 4 is an explanatory diagram of signal waveforms of each part in the inspection apparatus of FIG. 3;

[Explanation of symbols]

1 Semiconductor device under test 2 Power supply 3 Current detection resistor 4 Comparison voltage setting resistor 5 Comparator 6 Semiconductor measurement equipment 7 Pulse measuring device 8 Central processing unit 9 Constant current source

Claims (2)

[Claims] 1. One of the power supplies is connected to one of a current detection resistor and a comparison voltage setting resistor, the other of the power supply is grounded, and the other of the current detection resistor is connected to a power supply terminal of a semiconductor device under test. and connected to one input terminal of the comparator; further, the other side of the comparison voltage setting resistor is connected to the other input terminal of the comparator and grounded via a constant current source; A comparison voltage is set by a current flowing from the power supply to the constant current source through the comparison voltage setting resistor, and is further compared with the spike current detected from the power supply terminal of the semiconductor device under test, and the result is sent to the comparator output terminal. A semiconductor device testing device that can test spike currents by detecting whether or not they are output as pulses. 2. Using the inspection device according to claim 1, the resistance value for setting the comparison voltage or the constant current value is set to different arbitrary values multiple times, and each measured output pulse width is used as a reference. A method for inspecting a semiconductor device, characterized in that the depth of the spike current is calculated by a central processing unit.