DEVICE INSPECTION APPARATUS AND DEVICE INSPECTION METHOD

Abstract

A device inspection apparatus according to one aspect of the present disclosure includes a voltage source configured to apply a voltage to a device to be inspected, a plurality of resistors connected in series between the voltage source and the device, a detector configured to detect a potential difference across both ends of a resistor group that includes one or more resistors among the plurality of resistors, a switching device configured to switch the resistor group from which the detector detects the potential difference among the plurality of resistors, and a controller, wherein the controller is configured to control the detector and the switching device, so as to detect a potential difference across both ends of at least two or more different resistor groups, and is configured to control the detector and the switching device to detect the potential difference in an ascending order of a combined resistance value between both ends of the at least two or more resistor groups.

Claims

1. A device inspection apparatus comprising: a voltage source configured to apply a voltage to a device to be inspected; a plurality of resistors connected in series between the voltage source and the device; a detector configured to detect a potential difference across both ends of a resistor group that includes one or more resistors among the plurality of resistors; a switching device configured to switch the resistor group from which the detector detects the potential difference among the plurality of resistors; and a controller configured to control the detector and the switching device, so as to detect a potential difference across both ends of at least two or more different resistor groups, and control the detector and the switching device to detect the potential difference in an ascending order of a combined resistance value between both ends of the at least two or more resistor groups.

2. The device inspection apparatus as claimed in claim 1, wherein the detector includes an amplifier provided between the switching device and the controller or the at least two or more resistor groups.

3. The device inspection apparatus as claimed in claim 1, wherein the switching device is configured to switch only the device side of the at least two or more resistor groups.

4. The device inspection apparatus as claimed in claim 1, wherein the switching device is configured to switch the voltage source side and the device side of the at least two or more resistor groups.

5. The device inspection apparatus as claimed in claim 1, wherein the controller is configured to output a value according to one potential difference selected from a plurality of potential differences detected by the detector.

6. The device inspection apparatus as claimed in claim 1, wherein the controller is configured to compute a current supplied to the device based on the potential difference detected by the detector.

7. A device inspection method for inspecting a device to be inspected by applying a voltage to the device via a plurality of resistors connected in series, the device inspection method comprising: detecting a potential difference across both ends of a plurality of resistor groups including one or more resistors among the plurality of resistors, in an ascending order of a combined resistance value between both ends of the plurality of resistor groups.

8. The device inspection method as claimed in claim 7, further comprising: switching, by a switching device that switches a resistor group from which a detector detects the potential difference, only the device side of the resistor group from which the detector detects the potential difference.

9. The device inspection method as claimed in claim 7, further comprising: switching, by a switching device that switches a resistor group from which a detector detects the potential difference, a voltage source side of a voltage source that applies the voltage to the device, and the device side of the resistor group from which the detector detects the potential difference.

10. The device inspection method as claimed in claim 7, further comprising: outputting, by a controller, a value according to one potential difference selected from a plurality of potential differences detected by a detector that detects the potential difference.

11. The device inspection method as claimed in claim 7, further comprising: computing, by a controller, a current supplied to the device based on the potential difference detected by a detector that detects the potential difference.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0007] FIG. 1 is a diagram illustrating an example of an electric circuit of a device inspection apparatus according to a first embodiment;

[0008] FIG. 2 is a flow chart illustrating an example of an operation of the device inspection apparatus of FIG. 1;

[0009] FIG. 3 is a timing chart illustrating an example of the operation of the device inspection apparatus of FIG. 1;

[0010] FIG. 4 is a diagram illustrating an example of the electric circuit of the device inspection apparatus according to a second embodiment;

[0011] FIG. 5 is a diagram illustrating an example of the electric circuit of the device inspection apparatus according to a third embodiment; and

[0012] FIG. 6 is a diagram illustrating an example of the electric circuit of the device inspection apparatus according to a fourth embodiment.

MODE OF CARRYING OUT THE INVENTION

[0013] Non-limiting embodiments of the present disclosure will now be described with reference to the accompanying drawings. In all of the accompanying drawings, the same or corresponding members or components are designated by the same or corresponding reference numerals, and a redundant description thereof will be omitted.

First Embodiment

(Device Inspection Apparatus)

[0014] An example of a device inspection apparatus according to a first embodiment will be described, with reference to FIG. 1. The device testing apparatus according to the first embodiment inspects various electrical characteristics by applying a voltage to a semiconductor device that is to be inspected (DUT: Device Under Test).

[0015] A device inspection apparatus 10 includes a voltage source 11, resistors 12a.sub.1 and 12a.sub.2, a detector 13, a switching device 14, a controller 15, or the like.

[0016] The voltage source 11 applies a voltage set by a user (hereinafter referred to as a set voltage) to a DUT 19. Varying the set voltage, and switching the voltage source 11 between on and off states, are controlled by the controller 15. The voltage source 11 can be a programmable DC voltage source, for example.

[0017] The resistors 12a.sub.1 and 12a.sub.2 are connected in series with respect to the DUT 19. That is, the resistors 12a.sub.1 and 12a.sub.2 are connected in series between the voltage source 11 and the DUT 19. The resistor 12a.sub.1 is provided on the side of the voltage source 11, and the resistor 12a.sub.2 is provided on the side of the DUT 19. Resistance values of the two resistors 12a.sub.1 and 12a.sub.2 may be the same, or may be different.

[0018] The detector 13 detects a potential difference across both ends of the resistor 12a.sub.1, and a potential difference across both ends of the resistors 12a.sub.1 and 12a.sub.2. That is, the detector 13 detects the potential difference that is generated when a current supplied to the DUT 19 flows through the resistor 12a.sub.1, and a potential difference that is generated when the current supplied to the DUT 19 flows through the resistors 12a.sub.1 and 12a.sub.2. The detector 13 includes an amplifier 13a, an AD converter 13b, or the like.

[0019] The amplifier 13a is connected between the switching device 14 and the AD converter 13b. The amplifier 13a amplifies the potential difference between the voltage source 11 side of the resistor 12a, and the DUT 19 side of the resistor 12a.sub.1 or the potential difference between the voltage source 11 side of the resistor 12a.sub.1 and the DUT 19 side of the resistor 12a.sub.2, and outputs the amplified potential difference to the AD converter 13b. That is, the amplifier 13a amplifies the potential difference across both ends of the resistor 12a.sub.1, or the potential difference across both ends of the resistors 12a.sub.1 and 12a.sub.2, and outputs the amplified potential difference to the AD converter 13b. Hence, a small potential difference generated between both ends of the resistor 12a.sub.1 or between both ends of the resistors 12a.sub.1 and 12a.sub.2 is amplified and output to the AD converter 13b. As a result, a detection accuracy of the potential difference improves. The amplifier 13a may be a current sense amplifier, for example.

[0020] The AD converter 13b is connected between the amplifier 13a and the controller 15. The AD converter 13b converts the potential difference amplified by the amplifier 13a into a digital signal, and outputs the digital signal to the controller 15.

[0021] The switching device 14 switches a resistor group (the resistor 12a.sub.1, or the resistors 12a.sub.1 and 12a.sub.2) from which the potential difference is to be detected by the detector 13 that detects the potential difference from the two resistors 12a.sub.1 and 12a.sub.2. The switching device 14 includes two switches 14a.sub.1 and 14a.sub.2. The switch 14a.sub.1 switches a connection state between the DUT 19 side of the resistor 12a.sub.1 and the amplifier 13a. The switch 14a.sub.2 switches a connection state between the DUT 19 side of the resistor 12a.sub.2 and the amplifier 13a.

[0022] For example, in a case where the current supplied to the DUT 19 is relatively large, the switch 14a.sub.1 is switched on and the switch 14a.sub.2 is switched off. In this state, the amplifier 13a amplifies the potential difference across both ends of the resistor 12a.sub.1, that is, a potential difference generated by the current flowing through the resistor 12a.sub.1. In addition, in a case where the current supplied to the DUT 19 is relatively small, for example, the switch 14a.sub.1 is switched off and the switch 14a.sub.2 is switched on. In this state, the amplifier 13a amplifies the potential difference across both ends of the resistors 12a.sub.1 and 12a.sub.2, that is, a potential difference generated by the current flowing through the resistors 12a.sub.1 and 12a.sub.2. The switching of the on and off states the switches 14a.sub.1 and 14a.sub.2 is controlled by the controller 15.

[0023] The controller 15 is a computer, for example, and controls operations of the voltage source 11, the detector 13, the switching device 14, or the like. The controller 15 transmits a control signal for switching on and off states of the voltage source 11, and a control signal for varying the set voltage, to the voltage source 11. The control signals are generated according to a voltage value preset by the user. In addition, the controller 15 transmits a control signal for switching the on and off states of the switches 14a.sub.1 and 14a.sub.2 to the switching device 14. This control signal is generated according to a range of a current to be measured, preset by the user. In addition, the controller 15 transmits a control signal to the detector 13 and the switching device 14, so as to detect the potential difference of the resistor groups (the resistor 12a), and the resistors 12a.sub.1 and 12a.sub.2) in an ascending order of a combined resistance value between both ends of the resistor group. That is, after detecting the potential difference across both ends of the resistor 12a.sub.1, the controller 15 transmits the control signal to the detector 13 and the switching device 14 so as to detect the potential difference across both ends of the resistors 12a.sub.1 and 12a.sub.2.

(Device Inspection Method)

[0024] A device inspection method according to the first embodiment will be described for an example in which the DUT 19 is inspected by the device inspection apparatus 10 illustrated in FIG. 1, by referring to FIG. 2 and FIG. 3.

[0025] First, in step S1, the controller 15 switches on the voltage source 11, so that the set voltage is applied to the DUT 19. Hence, a current is supplied to the DUT 19 and the resistors 12a.sub.1 and 12a.sub.2.

[0026] Next, in step S2, the controller 15 controls the switching device 14 to switch a current range to a range B. The range B is the range that is selected in the case where the current supplied to the DUT 19 is relatively large. In the range B, the switch 14a.sub.1 is switched on and the switch 14a.sub.2 is switched off by the controller 15. Thus, the potentials between both ends of the resistor 12a.sub.1, that is, the potential on the voltage source 11 side of the resistor 12a.sub.1 and the potential on the DUT 19 side of the resistor 12a.sub.1, are input to the amplifier 13a.

[0027] Next, in step S3, the controller 15 stands by and waits until a predetermined time Ty elapses from a time when the current starts to flow through the resistor 12a.sub.1. Because the current starts to flow through the resistor 12a.sub.1 from the time when the voltage source 11 is switched on in step S1, the time when the current starts to flow through the resistor 12a.sub.1 is the time when the voltage source 11 is switched on in step S1. The predetermined time T.sub.B is a time from the time when the current starts to flow through the resistor 12a.sub.1 to the time when a potential difference generated across both ends of the resistor 12a.sub.1 stabilizes. This time until the potential difference stabilizes depends on the resistance value of the resistor 12a.sub.1, and becomes longer as the resistance value of the resistor 12a.sub.1 becomes higher, and becomes shorter as the resistance value of the resistor 12a.sub.1 becomes lower. This is because the DUT 19, a wiring connecting the voltage source 11 and the DUT 19, or the like have capacitance components to a certain extent, and an electric circuit included in the device inspection apparatus 10 can be regarded as an RC circuit. A time constant ? of the RC circuit can be computed from ?=RC (where R denotes a resistance value of the electric circuit, and C denotes a capacitance value of the electric circuit), and when the resistance value of the resistor 12a.sub.1 increases, the value of R in the formula described above increases, and the time constant ? increases. The predetermined time T.sub.B may be longer than a time from the time when the current starts to flow through the resistor 12a.sub.1 until the time when the potential difference generated across both ends of the resistor 12a.sub.1 stabilizes.

[0028] Next, in step S4, the controller 15 controls the detector 13, so that the amplifier 13a amplifies the potential difference across both ends of the resistor 12a.sub.1, and the AD converter 13b converts the potential difference amplified by the amplifier 13a into the digital signal. Further, the controller 15 computes the current value supplied to the DUT 19, based on the digital signal obtained by the conversion performed by the AD converter 13b.

[0029] Next, in step S5, the controller 15 controls the switching device 14 to switch the current range from the range B to a range A. The range A is selected in the case where the current supplied to the DUT 19 is relatively small. In the range A, the controller 15 switches the switch 14a.sub.1 off, and switches the switch 14a.sub.2 on. Hence, the potentials across both ends of the resistors 12a.sub.1 and 12a.sub.2, that is, the potential of the voltage source 11 side of the resistor 12a.sub.1 and the potential of the DUT 19 side of the resistor 12a.sub.2, are input to the amplifier 13a.

[0030] Next, in step S6, the controller 15 stands by until a predetermined time T.sub.A elapses from a time when the current starts to flow through the resistors 12a.sub.1 and 12a.sub.2. Because the current starts to flow through the resistors 12a.sub.1 and 12a.sub.2 from the time when the voltage source 11 is switched on in step S1, the time when the current starts to flow through the resistors 12a.sub.1 and 12a.sub.2 is the time when the voltage source 11 is switched on in step S1. In step S6, the predetermined time T.sub.B has already elapsed at the time when the process of step S6 starts, because the voltage source 11 is switched on in step S1. For this reason, in step S6, the controller 15 stands by and waits until a predetermined time T.sub.A-T.sub.B elapses. The predetermined time T.sub.A is a time from the time when the current starts to flow through the resistors 12a.sub.1 and 12a.sub.2 to the time when the potential difference generated across both ends of the resistors 12a.sub.1 and 12a.sub.2 stabilizes. This time until the potential difference stabilizes depends on the combined resistance value of the resistors 12a.sub.1 and 12a.sub.2, and becomes longer as the combined resistance value of the resistors 12a.sub.1 and 12a.sub.2 becomes higher, and becomes shorter as the combined resistance value of the resistors 12a.sub.1 and 12a.sub.2 becomes lower. The combined resistance value of the resistors 12a.sub.1 and 12a.sub.2 is higher than the resistance value of the resistor 12a.sub.1. For this reason, the predetermined time T.sub.A is longer than the predetermined time T.sub.B.

[0031] Next, in step S7, the controller 15 controls the detector 13, so that the amplifier 13a amplifies the potential difference across both ends of the resistors 12a.sub.1 and 12a.sub.2, and the AD converter 13b converts the potential difference amplified by the amplifier 13a into the digital signal. Further, the controller 15 computes the current value supplied to the DUT 19, based on the digital signal obtained by the conversion performed by the AD converter 13b.

[0032] Next, in step S8, the controller 15 selects a measurement result to be output, based on a measurement value measured in step S4 and a measurement value measured in step S7. The measurement value measured in step S4 may be the digital signal obtained by amplifying and converting the potential difference across both ends of the resistor 12a1, or may be the current value computed based on the digital signal, for example. The measurement value measured in step S7 may be the digital signal obtained by amplifying and converting the potential difference across both ends of the resistors 12a.sub.1 and 12a.sub.2, or may be the current value computed based on the digital signal, for example. For example, the controller 15 outputs the measurement result of the range A in a case where the measurement value in the range A is within a measurable range, and outputs the measurement result of the range B in a case where the measurement value in the range A is not within the measurable range. Thus, depending on a state of the DUT 19, even in a case where a large current flows to the DUT 19 and the measurement value in the range A is not within the measurable range, an accurate measurement value can be output because the measurement value in the range B selected in the case where the current supplied to the DUT 19 is relatively large is already obtained. An output mode of the measurement result is preferably a mode in which the user can confirm the measurement result, and may be a mode in which the measurement result is displayed on a display screen of the device inspection apparatus 10, for example.

[0033] As described above, according to the first embodiment, the controller 15 controls the detector 13 and the switching device 14, so as to detect the potential difference across both ends of the resistor groups in the ascending order of the combined resistance value across both ends of the resistor groups. That is, the controller 15 controls the detector 13 and the switching device 14, so as to detect the potential difference across both ends of the resistor 12a.sub.1, and thereafter detect the potential difference across both ends of the resistors 12a.sub.1 and 12a.sub.2. Accordingly, the measurement in the range B that is selected in the case where the current supplied to the DUT 19 is relatively large, can be performed within a measurement time in the range A that is selected in the case where the current supplied to the DUT 19 is relatively small. For this reason, the measurement results in the two current ranges (the range A and the range B) can be obtained within the measurement time in the range A. As a result, the device characteristics can be inspected in a short time, regardless of the state of the DUT 19.

Second Embodiment

(Device Inspection Apparatus)

[0034] An example of the device inspection apparatus according to a second embodiment will be described, with reference to FIG. 4. The device inspection apparatus according to the second embodiment differs from the device inspection apparatus 10 according to the first embodiment, in that the number of resistor groups is n (n is an integer greater than or equal to three). Hereinafter, differences from the device inspection apparatus 10 according to the first embodiment will mainly be described.

[0035] A device inspection apparatus 20 includes a voltage source 21, resistors 22a.sub.1 through 22a.sub.n, a detector 23, a switching device 24, a controller 25, or the like.

[0036] The voltage source 21 may have a configuration similar to configuration of the voltage source 11.

[0037] The resistors 22a; through 22a, are connected in series to a DUT 29. That is, the resistors 22a.sub.1 through 22a.sub.n are connected in series between the voltage source 21 and the DUT 29. The resistors 22a.sub.1 through 22a.sub.n are connected in an order of the resistors 22a.sub.1, 22a.sub.2, . . . , and 22a.sub.n from the voltage source 21 side. The resistors 22a.sub.1 through 22a.sub.n may have identical resistance values or different resistance values.

[0038] The detector 23 may have a configuration similar to the configuration of the detector 13, and includes an amplifier 23a, an AD converter 23b, or the like.

[0039] The switching device 24 switches a resistor group (the resistor 22a.sub.1, or the resistors 22a.sub.1, 22a.sub.2, . . . , or the resistors 22a.sub.1, 22a.sub.2, . . . , and 22a.sub.n) from which the potential difference is to be detected by the detector 23 that detects the potential difference from the n resistors 22a.sub.1 through 22a.sub.n. The switching device 24 includes n switches 24a.sub.1 through 24a.sub.n. The switches 24a.sub.1 through 24a.sub.n switch connection states between the DUT 29 side of the resistors 22a.sub.1, 22a.sub.2, and 22a.sub.n, and the amplifier 23a, respectively.

[0040] The controller 25 may have a configuration similar to the configuration of the controller 15, and controls operations of the voltage source 21, the detector 23, the switching device 24, or the like. The controller 25 transmits a control signal to the detector 23 and the switching device 24, so as to detect the potential difference across both ends of the resistor groups (the resistor 22a.sub.1, the resistors 22a.sub.1, 22a.sub.2, . . . , and the resistors 22a.sub.1, 22a.sub.2, . . . , and 22a.sub.n) in an ascending order of the combined resistance across both ends of the resistor groups.

(Device Inspection Method)

[0041] The device inspection method according to the second embodiment may be similar to the device inspection method according to the first embodiment. In the device inspection method according to the second embodiment, the controller 25 controls the detector 23 and the switching device 24 to detect the potential difference across both ends of at least two or more different resistor groups among the plurality of resistor groups. In addition, the controller 25 controls the detector 23 and the switching device 24, so as to detect the potential difference across both ends of the resistor groups in the ascending order of the combined resistance value between both ends of the resistor groups.

[0042] As described above, according to the second embodiment, the controller 25 controls the detector 23 and the switching device 24, so as to detect the potential difference across both ends of the resistor groups in the ascending order of the combined resistance value between both ends of the resistor groups. Hence, the measurement in a plurality of current ranges can be performed in a short time. As a result, the device characteristics can be inspected in a short time, regardless of the state of the DUT 29.

Third Embodiment

(Device Inspection Apparatus)

[0043] An example of the device inspection apparatus according to a third embodiment will be described, with reference to FIG. 5. The device inspection apparatus according to the third embodiment differs from the device inspection apparatus 20 according to the second embodiment, in that switching devices 34a and 34b for switching connection states between a DUT 39 side of the resistors 32a.sub.1 through 32a.sub.n and the amplifier 33a, and connection states between the voltage source 31 side of the resistors 32a.sub.1 through 32a.sub.n and the amplifier 33a, respectively, are provided. Hereinafter, differences from the device inspection apparatus 20 according to the second embodiment will mainly be described.

[0044] A device inspection apparatus 30 includes a voltage source 31, resistors 32a.sub.1 through 32a.sub.n, a detector 33, switching devices 34a and 34b, a controller 35, or the like.

[0045] The voltage source 31 may have a configuration similar to the configuration of the voltage source 21.

[0046] The resistors 32a.sub.1 through 32a.sub.n may have a configuration similar to the configuration of the resistors 22a.sub.1 through 22a.sub.n.

[0047] The detector 33 may have a configuration similar to the configuration of the detector 23, and includes an amplifier 33a, an AD converter 33b, or the like.

[0048] The switching device 34a may have a configuration similar to the configuration of the switching device 24, and includes n switches 34a.sub.1 through 34a.sub.n. The switches 34a.sub.1 through 34a.sub.n, switch the connection states between the DUT 39 side of the resistors 32a.sub.1, 32a.sub.2, . . . , and 32a.sub.n, and the amplifier 33a, respectively.

[0049] The switching device 34b includes n switches 34b.sub.1 through 34b.sub.n. The switches 34b.sub.1 through 34b.sub.n switch the connection states between the voltage source 31 side of the resistors 32a.sub.1, 32a.sub.2, . . . , and 32a.sub.n, and the amplifier 33a, respectively.

[0050] The controller 35 may have a configuration similar to the configuration of the controller 25, and controls operations of the voltage source 31, the detector 33, the switching devices 34a and 34b, or the like. The controller 35 transmits control signals to the detector 33 and the switching devices 34a and 34b, so as to detect the potential difference across both ends of the resistor groups in an ascending order of the combined resistance value between both ends of the resistor groups.

(Device Inspection Method)

[0051] The device inspection method according to the third embodiment may be similar to the device inspection method according to the second embodiment. In the device inspection method according to the third embodiment, the controller 35 controls the detector 33 and the switching devices 34a and 34b, so as to detect the potential difference across both ends of at least two or more different resistor groups among a plurality of resistor groups. In addition, the controller 35 controls the detector 33 and the switching devices 34a and 34b, so as to detect the potential difference across both ends of the resistor groups in the ascending order of the combined resistance value between both ends of the resistor groups.

[0052] As described above, according to the third embodiment, the controller 35 controls the detector 33 and the switching devices 34a and 34b, so as to detect the potential difference across both ends of the resistor groups in the ascending order of the combined resistance value between both ends of the resistor groups. Accordingly, the measurement can be performed in a plurality of current ranges in a short time. As a result, the device characteristics can be inspected in a short time, regardless of the state of the DUT 39.

[0053] In addition, according to the third embodiment, the connection states between the DUT 39 side of the plurality of resistors 32a.sub.1 through 32a.sub.n and the amplifier 33a, and the connection states between the voltage source 31 side of the plurality of resistors 32a.sub.1 through 32a.sub.n and the amplifier 33a, are switched by switching the on and off states of the switches 34a.sub.1 through 34a.sub.n and the switches 34b.sub.1 through 34b.sub.n, respectively. Thus, a resistor group, including one or more resistors among the plurality of resistors 32a.sub.1 through 32a.sub.n, is selected. As a result, because the number of resistor groups that is selected increases, the measurement in a large number of current ranges can be performed using a small number of components.

Fourth Embodiment

(Device Inspection Apparatus)

[0054] An example of the device inspection apparatus according to a fourth embodiment will be described, with reference to FIG. 6. The device inspection apparatus according to the fourth embodiment differs from the device inspection apparatus 20 according to the second embodiment, in that amplifiers 43a.sub.1 through 43a.sub.n are connected between the resistors 42a.sub.1 through 42a.sub.n and the switching device 44, respectively. Hereinafter, differences from the device inspection apparatus 20 according to the second embodiment will mainly be described.

[0055] A device inspection apparatus 40 includes a voltage source 41, resistors 42a.sub.1 through 42a.sub.n, a detector 43, a switching device 44, a controller 45, or the like.

[0056] The voltage source 41 may have a configuration similar to the configuration of the voltage source 21.

[0057] The resistors 42a.sub.1 through 42a.sub.n may have a configuration similar to the configuration of the resistors 22a.sub.1 through 22a.sub.n.

[0058] The detector 43 includes amplifiers 43a.sub.1 through 43a.sub.n, an AD converter 43b, or the like.

[0059] The amplifiers 43a.sub.1 through 43a.sub.n are connected between the switching device 44 and resistor groups (the resistor 42a.sub.1, the resistors 42a.sub.1, 42a.sub.2, . . . , and the resistors 42a.sub.1, 42a.sub.2, . . . , and 42a.sub.n). The amplifiers 43a.sub.1 through 43a.sub.n amplify potential differences between the voltage source 41 side of the resistor 42a.sub.1 and a DUT 49 side of the resistor 42a.sub.1 through 42a.sub.n, respectively, and output the amplified potential differences to the AD converter 43b via the switching device 44. Hence, small potential differences generated between both ends of the resistor groups (the resistor 42a.sub.1, the resistors 42a.sub.1, 42a.sub.2, . . . , and the resistors 42a.sub.1, 42a.sub.2, . . . , and 42a.sub.n) are amplified and output to the AD converter 43b. As a result, the detection accuracy of the potential differences improves. The amplifiers 43a.sub.1 through 43a.sub.n may be current sense amplifiers, for example.

[0060] The AD converter 43b may have a configuration similar to the configuration of the AD converter 23b.

[0061] The switching device 44 switches a resistor group (the resistor 42a.sub.1, the resistors 42a.sub.1, 42a.sub.2, . . . , or the resistors 42a.sub.1, 42a.sub.2, . . . , and 42a.sub.n) from which the potential difference is to be detected by the detector 43 that detects the potential difference from the n resistors 42a.sub.1 through 42a.sub.n. The switching device 44 includes n switches 44a.sub.1 through 44a.sub.n. The switches 44a.sub.1 through 44a.sub.n switch connection states between the amplifiers 43a.sub.1 through 43a.sub.n, and the AD converter 43b, respectively.

[0062] The controller 45 may have a configuration similar to the configuration of the controller 25, and controls operations of the voltage source 41, the detector 43, the switching device 44, or the like. The controller 45 transmits control signals to the detector 43 and the switching device 44, so as to detect the potential difference across both ends of the resistor groups (the resistor 42a.sub.1, the resistors 42a.sub.1, 42a.sub.2, . . . , and the resistors 42a.sub.1, 42a.sub.2, . . . , and 42a.sub.n) in an ascending order of the combined resistance value between both ends of the resistor groups.

(Device Inspection Method)

[0063] The device inspection method according to the fourth embodiment may be similar to the device inspection method according to the second embodiment. In the device inspection method according to the fourth embodiment, the controller 45 controls the detector 43 and the switching device 44 to detect the potential difference across both ends of at least two or more different resistor groups among a plurality of resistor groups. In addition, the controller 45 controls the detector 43 and the switching device 44, so as to detect the potential difference across both ends of the resistor groups in an ascending order of the combined resistance value between both ends of the resistor groups.

[0064] As described above, according to the fourth embodiment, the controller 45 controls the detector 43 and the switching device 44, so as to detect the potential difference across both ends of the resistor groups in the ascending order of the combined resistance value between both ends of the resistor groups. Hence, the measurement can be performed in a plurality of current ranges in a short time. As a result, the device characteristics can be inspected in a short time, regardless of the state of the DUT 49.

[0065] In the embodiments described above, the controllers 15, 25, 35, and 45 are an example of a controller.

[0066] It should be understood that the embodiments disclosed herein are illustrative in all respects and are non-limiting. The embodiments described above may include omissions, substitutions, and modifications in various forms, without departing from the scope and subject matter of the appended claims.

[0067] Although the cases where the switching device includes a plurality of switches are described in the embodiments above, the present disclosure is not limited to such cases. For example, the switching device may be configured to include a multiplexer.

[0068] The present international application is based upon and claims priority to Japanese Patent Application No. 2021-072503, filed on Apr. 22, 2021, the entire contents of which are incorporated herein by reference.

DESCRIPTION OF REFERENCE NUMERALS

[0069] 10, 20, 30, 40: Device inspection apparatus [0070] 11, 21, 31, 41: Voltage source [0071] 12a.sub.1 through 12a.sub.2, 22a.sub.1 through 22a.sub.n, 32a.sub.1 through 32a.sub.n, 42a.sub.1 through 42a.sub.n: Resistor [0072] 14, 24, 34a, 34b, 44: Switch [0073] 15, 25, 35, 45: Controller