Power supply switching device and inspection system

Abstract

To provide an inspection system capable of inspecting a defective part of a semiconductor sample by an OBIRCH analysis technique and other analysis techniques with high efficiency and low noise.SOLUTION: The inspection system 1B includes a power source switching unit 10B, an OBIRCH analyzer 21, a power source 22 for light emission analysis, a power source 23 for heat generation analysis, and a system controller 24. The power source switching apparatus 10B includes a switch 1112, a switching control circuit 13B, an insulated power source 14B, and an insulated signal transmitter 15. The switch 11,12 selects one of the OBIRCH analyzer 21, the power supply for emission analysis 22 and the power supply for heating analysis 23 and connects the selected one to the semiconductor sample 2. The insulated power source 14B is provided on a path for supplying power from the system control device 24 to the switching control circuit 13B, and electrically insulates the system control device 24 and the switching control circuit 13B from each other.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a system for inspecting semiconductor samples for defects, and to a power supply switching device for switching power supply devices connected to the semiconductor samples in the system. [Background technology]

[0002] OBIRCH (Optical Beam Induced Resistance Change) analysis technology is known as a technology for inspecting defective portions of semiconductor samples (Patent Document 1). In the OBIRCH analysis technology, a current is passed through a semiconductor integrated circuit sample, and the semiconductor sample is irradiated with and scanned by a laser beam, and changes in the current flowing through the semiconductor sample are detected, thereby inspecting defective portions of the semiconductor sample.

[0003] Furthermore, optical emission analysis and heat generation analysis are also known as techniques for inspecting defects in semiconductor samples. These analysis techniques inspect defects in semiconductor samples by observing the optical emission and heat generation in the semiconductor sample when a voltage is applied to the semiconductor sample.

[0004] In each of the OBIRCH analysis technology, optical emission analysis technology, and heat generation analysis technology, a dedicated power supply is connected to the semiconductor sample. In the OBIRCH analysis technology, a constant voltage or current is applied to the semiconductor sample from the power supply, and changes in the output electrical signal associated with the laser beam scanning are detected. In the optical emission analysis technology, a constant voltage is applied to the semiconductor sample from the power supply, and the light emission state of the semiconductor sample is observed. In the heat generation analysis technology, a voltage whose value changes periodically over time is applied to the semiconductor sample from the power supply, and the heat generation state of the semiconductor sample is observed in synchronization with this periodic change in voltage value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-300824 Summary of the Invention [Problem to be solved by the invention]

[0006] However, there is a demand for applying other analytical techniques (emission analysis technique, heat generation analysis technique) to semiconductor samples in addition to OBIRCH analytical technique to efficiently inspect defective locations in semiconductor samples using these analytical techniques. However, the inventors have found that simply combining these analytical techniques into a system configuration can result in noise that is thought to be caused by the combination appearing in the OBIRCH analytical results.

[0007] The present invention has been made to solve the above problems, and aims to provide an inspection system that can inspect semiconductor samples for defects using OBIRCH analysis technology and other analysis technologies with high efficiency and low noise, and also aims to provide a power supply switching device for use in such an inspection system. [Means for solving the problem]

[0008] The power supply switching device of the present invention is a device that selects one device from a plurality of devices including an OBIRCH analysis device and one or more power supply devices, and connects the first terminal and second terminal of the selected device to a semiconductor sample.

[0009] A first aspect of the power supply switching device of the present invention comprises: (1) a first switch that selects one of the first terminals of each of a plurality of devices and electrically connects it to a semiconductor sample; (2) a second switch that selects one of the second terminals of each of the plurality of devices and electrically connects it to the semiconductor sample; (3) a switching control circuit that simultaneously selects the first terminal by the first switch and the second terminal by the second switch for a common device; and (4) an isolated power supply that is provided on a path that supplies power from the outside to the switching control circuit and electrically isolates the outside from the switching control circuit.

[0010] A second aspect of the power supply switching device of the present invention, in addition to the first aspect, further comprises an isolated signal transmission unit that is provided on a signal path for providing switching control signals that control the operation of each of the first switch and the second switch from the outside to the switching control circuit, and that electrically isolates the outside from the switching control circuit.

[0011] The inspection system of the present invention is a system for inspecting defective portions of a semiconductor sample. A first aspect of the inspection system of the present invention comprises: (1) a plurality of devices including an OBIRCH analysis device and one or more power supply devices; (2) the above-mentioned power supply switching device of the present invention that selects one of the plurality of devices and connects the first and second terminals of the selected device to a semiconductor sample; (3) a laser light irradiation device that irradiates and scans a laser beam onto the semiconductor sample when the OBIRCH analysis device is selected by the power supply switching device and connected to the semiconductor sample; and (4) an observation device that observes the semiconductor sample when the power supply device is selected by the power supply switching device and connected to the semiconductor sample.

[0012] A second aspect of the inspection system of the present invention, in addition to the first aspect, includes (1) a power supply for optical emission analysis as a power supply device, and (2) an optical emission analysis camera as an observation device that observes the optical emission status of the semiconductor sample when the optical emission analysis power supply is selected by the power supply switching device and connected to the semiconductor sample.

[0013] A third aspect of the inspection system of the present invention, in addition to the first or second aspect, includes (1) a power supply for heat generation analysis as a power supply device, and (2) a camera for heat generation analysis as an observation device, which observes the heat generation status in the semiconductor sample when the power supply for heat generation analysis is selected by the power supply switching device and connected to the semiconductor sample.

[0014] A fourth aspect of the inspection system of the present invention is, in addition to any one of the first to third aspects, further comprising a system control device that provides a switching control signal to the switching control circuit to control the operation of each of the first switch and the second switch, and supplies power to the switching control circuit via an isolated power supply.

[0015] In a fifth aspect of the inspection system of the present invention, in addition to any one of the first to fourth aspects, the ground potentials of the plurality of devices are connected to each other by a common ground line. [Effects of the Invention]

[0016] According to the present invention, inspection of defective portions of semiconductor samples can be performed with high efficiency and low noise using the OBIRCH analysis technique and other analysis techniques. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing the configuration of an inspection system 1A of the comparative example. [Figure 2] FIG. 2 is a diagram showing the configuration of an inspection system 1B of this embodiment. [Figure 3] FIG. 3 is a diagram showing an example of the configuration of an insulated power supply 14B of the power supply switching device 10B. [Figure 4] FIG. 4 is a diagram showing an example of the configuration of the isolated signal transfer unit 15 of the power supply switching device 10B. [Figure 5] FIG. 5 is an image showing the result of OBIRCH analysis when the inspection system 1A shown in FIG. 1 is used. [Figure 6] FIG. 6 is an image showing the result of OBIRCH analysis when the inspection system 1B shown in FIG. 2 (however, the insulated signal transmission unit 15 is not provided) is used. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0019] First, the configuration of a comparative example will be described. In order to apply other analysis techniques (emission analysis technique, heat generation analysis technique) in addition to the OBIRCH analysis technique to a semiconductor sample and efficiently inspect defective portions of the semiconductor sample using these analysis techniques, it is possible to configure an inspection system 1A as shown in Figure 1.

[0020] 1 is a diagram showing the configuration of an inspection system 1A of a comparative example. The inspection system 1A is a system that inspects defective portions of a semiconductor sample 2, and includes a power supply switching device 10A, an OBIRCH analysis device 21, an optical emission analysis power supply 22, a heat generation analysis power supply 23, a system control device 24, a laser light irradiation device 31, an optical emission analysis camera 32, and a heat generation analysis camera 33. The power supply switching device 10A includes a switch 11, a switching control circuit 13A, and an apparatus power supply 14A.

[0021] The power supply switching device 10A is electrically connected to the OBIRCH analysis device 21 via a cable 41, to the optical emission analysis power supply 22 via a cable 42, to the heat generation analysis power supply 23 via a cable 43, to the system control device 24 via cables 44 and 45, and to the semiconductor sample 2 via a cable 46. The cables 41 to 46 may be of any type, but in the following description they are assumed to be coaxial cables having an inner conductor (core wire) and an outer conductor.

[0022] The outer conductors of the coaxial cables 41 to 46 are connected to a common ground potential (device GND) within the power supply switching device 10A. The outer conductor of the coaxial cable 41 is connected to a second end of the OBIRCH analysis device 21. The outer conductor of the coaxial cable 42 is connected to a second end of the optical emission analysis power supply 22. The outer conductor of the coaxial cable 43 is connected to a second end of the heat generation analysis power supply 23. The second ends of the OBIRCH analysis device 21, the optical emission analysis power supply 22, and the heat generation analysis power supply 23 are connected to the ground potential of each device. The outer conductor of the coaxial cable 46 is connected to the semiconductor sample 2.

[0023] Switch 11 of power supply switching device 10A is connected to a first end of OBIRCH analyzer 21 via the inner conductor of coaxial cable 41, to a first end of optical emission analysis power supply 22 via the inner conductor of coaxial cable 42, to a first end of heat generation analysis power supply 23 via the inner conductor of coaxial cable 43, and to semiconductor sample 2 via the inner conductor of coaxial cable 46. Switch 11 can select any one of OBIRCH analyzer 21, optical emission analysis power supply 22, and heat generation analysis power supply 23 to connect to semiconductor sample 2.

[0024] The switching control circuit 13A of the power supply switching device 10A receives a switching control signal from the system control device 24 via the coaxial cable 44, and controls the operation of the switch 11 based on this switching control signal to connect one of the OBIRCH analysis device 21, the light emission analysis power supply 22, and the heat generation analysis power supply 23 to the semiconductor sample 2 via the switch 11.

[0025] The device power supply 14A of the power supply switching device 10A receives power from the system control device 24 via a coaxial cable 45, and supplies the power to the switching control circuit 13A to operate the switching control circuit 13A.

[0026] The laser light irradiation device 31 is used when the OBIRCH analysis device 21 is selected by the switch 11 and connected to the semiconductor sample 2. The laser light irradiation device 31 irradiates and scans the semiconductor sample 2 with a laser beam. At points on the semiconductor sample 2 irradiated with the laser beam, the temperature rises and the resistance changes. The OBIRCH analysis device 21 applies a constant voltage or current to the semiconductor sample 2 and detects changes in the output electrical signal that accompany the scanning of the laser beam, thereby inspecting for defects.

[0027] The optical emission analysis camera 32 is used when the optical emission analysis power supply 22 is selected by the switch 11 and connected to the semiconductor sample 2. The optical emission analysis camera 32 is an observation device that observes the optical emission state of the semiconductor sample 2 when the optical emission analysis power supply 22 applies a constant voltage to the semiconductor sample 2. As the optical emission analysis camera 32, for example, a cooled CCD camera or SI (Si Intensified)-CCD camera that has sensitivity in the visible range, or an InGaAs camera that has sensitivity in the near-infrared range can be used.

[0028] The heat generation analysis camera 33 is used when the heat generation analysis power supply 23 is selected by the switch 11 and connected to the semiconductor sample 2. The heat generation analysis camera 33 is an observation device that observes the heat generation state of the semiconductor sample 2 in synchronization with the periodic change in voltage value when the heat generation analysis power supply 23 applies a voltage whose value changes periodically over time to the semiconductor sample 2. As the heat generation analysis camera 33, for example, a Thermo Dynamic camera having sensitivity in the mid-infrared range is used.

[0029] By using such an inspection system 1A, OBIRCH analysis, optical emission analysis, and heat generation analysis can be applied in sequence by switching the switch 11, and defective portions of a semiconductor sample can be efficiently inspected.

[0030] The present inventors constructed an inspection system 1A as shown in FIG. 1 and attempted to inspect defects on a semiconductor sample. They found that significant noise appeared in the OBIRCH analysis results (images showing changes in the output electrical signal at each position of the laser beam irradiation) (as will be described later with reference to FIG. 5). This significant noise did not appear when the OBIRCH analysis device 21 was directly connected to the semiconductor sample without using the power supply switching device 10A. Furthermore, the present inventors found that when the ground potentials of the devices in the inspection system 1A as shown in FIG. 1 were made common, the noise was somewhat reduced but still significant. It is believed that this significant noise was caused by the configuration in which the power supply switching device 10A was used to switch between the OBIRCH analysis device 21, the optical emission analysis power supply 22, and the heat generation analysis power supply 23.

[0031] The configuration of the inspection system 1B of this embodiment, which will be explained next with reference to Figures 2 to 4, is an improvement of the inspection system 1A based on the findings of the inventors described above, and is capable of inspecting defective areas in semiconductor samples using OBIRCH analysis technology and other analysis technologies with high efficiency and low noise.

[0032] 2 is a diagram showing the configuration of an inspection system 1B of this embodiment. Compared to the configuration of inspection system 1A (FIG. 1), inspection system 1B (FIG. 2) differs in that it includes a power supply switching device 10B instead of power supply switching device 10A. Power supply switching device 10B includes a first switch 11, a second switch 12, a switching control circuit 13B, an isolated power supply 14B, and an isolated signal transmission unit 15.

[0033] Similar to the switch 11 of the power supply switching device 10A, the first switch 11 of the power supply switching device 10B is connected to a first end of the OBIRCH analyzer 21 via the inner conductor of the coaxial cable 41, to a first end of the optical emission analysis power supply 22 via the inner conductor of the coaxial cable 42, to a first end of the heat generation analysis power supply 23 via the inner conductor of the coaxial cable 43, and to the semiconductor sample 2 via the inner conductor of the coaxial cable 46. The first switch 11 can select any one of the first ends of the OBIRCH analyzer 21, the optical emission analysis power supply 22, and the heat generation analysis power supply 23 to connect to the semiconductor sample 2.

[0034] The second switch 12 of the power supply switching device 10B is connected to a second end of the OBIRCH analyzer 21 via the outer conductor of the coaxial cable 41, to a first end of the optical emission analysis power supply 22 via the outer conductor of the coaxial cable 42, to a first end of the heat generation analysis power supply 23 via the outer conductor of the coaxial cable 43, and to the semiconductor sample 2 via the outer conductor of the coaxial cable 46. The second switch 12 can select one of the second ends of the OBIRCH analyzer 21, the optical emission analysis power supply 22, and the heat generation analysis power supply 23 and connect it to the semiconductor sample 2. The second ends of the OBIRCH analyzer 21, the optical emission analysis power supply 22, and the heat generation analysis power supply 23 are connected to the ground potential of each device. The outer conductors of the coaxial cables 41 to 46 do not need to be connected to a common ground potential within the power supply switching device 10B.

[0035] The switching control circuit 13B of the power supply switching device 10B receives a switching control signal from the system control device 24 via the coaxial cable 44, the insulated signal transmission unit 15, and the coaxial cable 47, and controls the operation of the first switch 11 and the second switch 12 based on this switching control signal to connect any one of the OBIRCH analysis device 21, the optical emission analysis power supply 22, and the heat generation analysis power supply 23 to the semiconductor sample 2 via the first switch 11 and the second switch 12. The switching control circuit 13B simultaneously selects the first end by the first switch 11 and the second end by the second switch 12 for a common device.

[0036] The isolated power supply 14B of the power supply switching device 10B is provided on a path that supplies power from the system control device 24 to the switching control circuit 13B, and electrically isolates the system control device 24 from the switching control circuit 13B. The isolated power supply 14B receives power from the system control device 24 via a coaxial cable 45, and supplies the power to the switching control circuit 13B to operate the switching control circuit 13B.

[0037] The isolated signal transmission unit 15 of the power supply switching device 10B is provided on a signal path for transmitting a switching control signal from the system control device 24 to the switching control circuit 13B, and electrically insulates the system control device 24 from the switching control circuit 13B. The isolated signal transmission unit 15 receives the switching control signal from the system control device 24 via a coaxial cable 44, and transmits the switching control signal to the switching control circuit 13B via a coaxial cable 47.

[0038] The laser light irradiation device 31 is used when the OBIRCH analysis device 21 is selected by the switches 11 and 12 and connected to the semiconductor sample 2. The optical emission analysis camera 32 is used when the optical emission analysis power supply 22 is selected by the switches 11 and 12 and connected to the semiconductor sample 2. The heat generation analysis camera 33 is used when the heat generation analysis power supply 23 is selected by the switches 11 and 12 and connected to the semiconductor sample 2.

[0039] In addition, in the inspection system 1B, it is preferable that the ground potentials of the power supply switching device 10B, the OBIRCH analysis device 21, the light emission analysis power supply 22, the heat generation analysis power supply 23, and the system control device 24 are strongly connected to each other so that the difference between them is as small as possible.

[0040] FIG. 3 is a diagram showing an example of the configuration of an isolated power supply 14B of the power supply switching device 10B. The isolated power supply 14B shown in this figure includes a power transformer 140, a primary-side conversion circuit 141, and a secondary-side conversion circuit 142. The primary-side conversion circuit 141 converts a DC voltage input from the system control device 24 via a coaxial cable 45 into an AC voltage and outputs the AC voltage to the primary coil of the power transformer 140. The secondary-side conversion circuit 142 converts an AC voltage induced in the secondary coil of the power transformer 140 into a DC voltage and outputs the DC voltage to the switching control circuit 13B. The isolated power supply 14B having such a configuration can electrically insulate the system control device 24 and the switching control circuit 13B from each other in the power supply path. Other configurations of the isolated power supply 14B are also possible.

[0041] FIG. 4 illustrates an example of the configuration of the isolated signal transmission unit 15 of the power supply switching device 10B. The isolated signal transmission unit 15 shown in this figure includes a coupled inductor 150, a modulation circuit 151, and a demodulation circuit 152. The modulation circuit 151 modulates the switching control signal received from the system control device 24 via the coaxial cable 44 and outputs the modulated signal to the primary coil of the coupled inductor 150. The demodulation circuit 152 demodulates the modulated signal induced in the secondary coil of the coupled inductor 150 to generate a switching control signal, which is then provided to the switching control circuit 13B. The isolated signal transmission unit 15 having such a configuration can electrically isolate the system control device 24 and the switching control circuit 13B from each other along the transmission path of the switching control signal. The isolated signal transmission unit 15 may have other configurations, such as a configuration in which the switching control signal is temporarily converted into an optical signal before being transmitted. More specifically, the insulated signal transmission section 15 may be configured using a photocoupler, or may be configured with an optical waveguide such as an optical fiber provided between a laser diode and a photodiode.

[0042] 5 and 6 are diagrams showing examples of images showing the results of OBIRCH analysis. These images show changes in the output electrical signal at each position of the laser beam irradiation on the semiconductor sample. FIG. 5 is an image showing the results of OBIRCH analysis when the inspection system 1A shown in FIG. 1 is used. FIG. 6 is an image showing the results of OBIRCH analysis when the inspection system 1B shown in FIG. 2 (however, the insulated signal transmission unit 15 is not provided) is used. These two images show the results of OBIRCH analysis of the same location on the same semiconductor sample. In addition, in each of these two images, the black linear region extending from the lower left to the upper right within the region surrounded by the dashed ellipse indicates the path of the wiring through which current flows in the semiconductor sample.

[0043] In the OBIRCH analysis results shown in Figure 5, significant noise appears throughout the image, such as the black area near the upper left corner of the image, the black area below the dashed ellipse, and stripes extending horizontally across the entire image, and the signal representing the wiring route within the area surrounded by the dashed ellipse is weak.In contrast, in the OBIRCH analysis results shown in Figure 6, the noise that appeared in the OBIRCH analysis results image shown in Figure 5 is suppressed, and the signal representing the wiring route within the area surrounded by the dashed ellipse is strong.

[0044] 2, the power supply switching device 10B is equipped with the second switch 12 in addition to the first switch 11, and is also equipped with an insulated power supply 14B, thereby enabling inspection of defective portions of a semiconductor sample using the OBIRCH analysis technique and other analysis techniques (emission analysis technique, heat generation analysis technique) with high efficiency and low noise. Furthermore, the power supply switching device 10B in the inspection system 1B of the present embodiment shown in FIG. 2 is further equipped with an insulated signal transmission unit 15, thereby enabling inspection of defective portions of a semiconductor sample using the OBIRCH analysis technique and other analysis techniques with even lower noise.

[0045] It is believed that this low-noise effect is achieved for the following reason: Namely, during OBIRCH analysis, the signal path between the OBIRCH analysis device 21 and the semiconductor sample 2 is isolated from the ground potential of other devices. As a result, even if there is a fluctuation in the ground potential difference between the power supply switching device 10B, the OBIRCH analysis device 21, the light emission analysis power supply 22, the heat generation analysis power supply 23, and the system control device 24, it is believed that this can prevent the fluctuation in the ground potential difference from adversely affecting the OBIRCH analysis as noise.

[0046] The present invention is not limited to the above embodiment, and various modifications are possible. For example, the power supply switching device 10B may select only one of the optical emission analysis power supply 22 and the heat generation analysis power supply 23 as the power supply other than the OBIRCH analysis device 21. In this case, only one of the optical emission analysis camera 32 and the heat generation analysis camera 33 needs to be provided correspondingly. Furthermore, a power supply device for semiconductor sample inspection other than the optical emission analysis power supply 22 and the heat generation analysis power supply 23 may be connected to the power supply switching device 10B. [Explanation of symbols]

[0047] 1A, 1B... Inspection system, 2... Semiconductor sample, 10A, 10B... Power supply switching device, 11... First switch, 12... Second switch, 13A, 13B... Switching control circuit, 14A... Device power supply, 14B... Isolated power supply, 15... Isolated signal transmission unit, 21... OBIRCH analysis device, 22... Power supply for optical emission analysis, 23... Power supply for heat generation analysis, 24... System control device, 31... Laser light irradiation device, 32... Optical emission analysis camera, 33... Heat generation analysis camera, 41 to 47... Coaxial cables.

Claims

1. An apparatus for selecting one of a plurality of apparatuses including an OBIRCH analysis apparatus and one or more power supply apparatuses, and connecting a first terminal and a second terminal of the selected apparatus to a semiconductor sample, a first switch for selecting one of the first terminals of each of the plurality of devices and electrically connecting the selected one to the semiconductor sample; a second switch for selecting one of the second terminals of each of the plurality of devices and electrically connecting the selected one to the semiconductor sample; a switching control circuit that simultaneously selects the first end by the first switch and the second end by the second switch for a common device; an isolated power supply provided on a path for supplying power from the outside to the switching control circuit, electrically insulating the outside from the switching control circuit; A power supply switching device comprising:

2. an isolated signal transmission unit that is provided on a signal path for supplying a switching control signal that controls the operation of each of the first switch and the second switch from an external device to the switching control circuit, and electrically insulates the external device from the switching control circuit; The power supply switching device according to claim 1 .

3. A system for inspecting a semiconductor sample for defects, comprising: a plurality of devices including an OBIRCH analysis device and one or more power supplies; a power supply switching device according to claim 1 or 2, which selects one of the plurality of devices and connects a first terminal and a second terminal of the selected device to the semiconductor sample; a laser light irradiation device that irradiates and scans a laser beam onto the semiconductor sample when the OBIRCH analysis device is selected by the power supply switching device and connected to the semiconductor sample; an observation device that observes the semiconductor sample when the power supply device is selected by the power supply switching device and connected to the semiconductor sample; An inspection system comprising:

4. a power supply for optical emission analysis is provided as the power supply device; the observation device is an optical emission analysis camera that observes an optical emission state in the semiconductor sample when the optical emission analysis power supply is selected by the power supply switching device and connected to the semiconductor sample; The inspection system of claim 3 .

5. a power supply for heat generation analysis as the power supply device; a heat generation analysis camera as the observation device for observing a heat generation state in the semiconductor sample when the heat generation analysis power supply is selected by the power supply switching device and connected to the semiconductor sample; The inspection system of claim 3 .

6. a system control device that supplies a switching control signal to the switching control circuit to control operations of the first switch and the second switch, and that supplies power to the switching control circuit via the isolated power supply; The inspection system of claim 3 .

7. the ground potentials of the plurality of devices are connected by a common ground line; The inspection system of claim 3 .

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