JP2014107483A - Obirch inspection method and obirch device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an OBIRCH inspection method and an OBIRCH device capable of detecting a point where a defect occurs with higher sensitivity than the conventional method.SOLUTION: At first, an inspected object 30 is mounted on the sample stage 11 of an OBIRCH device. A reflective plate 35 is arranged on the first side of the inspected object 30. Subsequently, a probe pin 12a is brought into contact with the inspected object 30. Thereafter, the second side of the inspected object 30 is irradiated with laser light, while applying a voltage via the probe pin 12a, and a current flowing through the probe pin 12a is detected.

Description

  The present invention relates to an OBIRCH inspection method and an OBIRCH apparatus.

  In recent years, semiconductor devices have been highly integrated, and the size of defects generated in the semiconductor devices has become extremely small. In addition, changes in voltage and current due to defects are extremely small.

  When evaluating defects in a semiconductor device, it is important to identify the location where the defect has occurred. Therefore, an inspection method that can detect a defective portion of a semiconductor device with high sensitivity is required. One such inspection method is the OBIRCH (Optical Beam Induced Resistance CHange) method.

  In the OBIRCH method, an infrared laser having a wavelength of about 1300 nm is used. Then, a laser beam is scanned on the surface of the semiconductor device while applying a voltage to the wiring formed in the semiconductor device.

  The temperature changes in the portion irradiated with the laser light, and the resistance value changes with the change in temperature. When this change in resistance value is detected and signal-processed at a timing synchronized with laser scanning, an OBIRCH image in which the resistance change of the wiring layer of the semiconductor device is represented by a two-dimensional image is obtained.

  Since the wiring material of a semiconductor device has an inherent resistance temperature dependency, if the wiring or the insulating layer has a defect, the change in the resistance value differs from that when there is no defect. This change in resistance value is a change in luminance in the OBIRCH image. Thereby, the location where the defect has occurred can be specified from the OBIRCH image.

JP 2004-264030 A JP 2009-272541 A

  It is an object of the present invention to provide an OBIRCH inspection method and an OBIRCH apparatus capable of detecting a location where a defect has occurred with higher sensitivity than a conventional method.

  According to one aspect of the disclosed technology, a step of disposing a reflector so as to face the first surface of the inspection object, and applying a voltage to the inspection object via a probe pin, the first of the inspection object OBIRCH inspection method comprising: irradiating laser beam onto the surface of 2 and detecting a current flowing through the probe pin.

  According to another aspect of the disclosed technique, a sample stage on which an inspection target is placed, a reflector disposed to face the first surface of the inspection target, and a voltage in contact with the inspection target. There is provided an OBIRCH device having a probe pin for applying a current, an optical device for irradiating the second surface to be inspected with laser light, and an amplifier for detecting a current flowing through the probe pin.

  According to the OBIRCH inspection method and the OBIRCH inspection apparatus according to the above aspect, even if there is a defect in a portion where the laser beam cannot be directly irradiated, the defective portion is irradiated with the laser beam reflected by the reflecting plate. This makes it possible to detect the location where the defect has occurred with higher sensitivity than in the conventional method.

FIG. 1 is a schematic diagram illustrating an example of an OBIRCH inspection apparatus used in the inspection method according to the first embodiment. FIG. 2 is a schematic diagram showing a semiconductor device placed on a sample stage. FIG. 3 is a diagram schematically showing a semiconductor device (without a reflector) during OBIRCH inspection. FIG. 4 is a diagram schematically showing a semiconductor device (with a reflector) during OBIRCH inspection. FIG. 5 is a schematic diagram illustrating an example of an OBIRCH inspection apparatus used in the inspection method according to the second embodiment. FIG. 6 is a schematic diagram showing a semiconductor device placed on a sample stage. FIG. 7 is a diagram schematically showing a semiconductor device (without a reflector) during OBIRCH inspection. FIG. 8 is a diagram schematically showing a semiconductor device (with a reflector) during OBIRCH inspection. FIG. 9A is a diagram showing an OBIRCH image obtained by irradiating a laser beam from the lower surface side of the semiconductor device without using the reflector, and FIG. 9B is a diagram illustrating the arrangement of the reflector on the upper side of the semiconductor device. It is a figure which shows the OBIRCH image acquired by irradiating a laser beam from the lower surface side of a semiconductor device. FIGS. 10A to 10E are cross-sectional views showing examples of reflectors having irregularities on the surface.

  Hereinafter, before describing the embodiment, a preliminary matter for facilitating understanding of the embodiment will be described.

  As described above, in the OBIRCH method, it is possible to detect a defective portion generated in the wiring layer of the semiconductor device with high sensitivity. In the OBIRCH method, since laser light having a wavelength that passes through the silicon substrate is used, the lower wiring layer can be irradiated with laser light from the lower surface side of the silicon substrate. Thereby, it is also possible to detect a defect that has occurred in a place that cannot be detected by laser irradiation from above.

  However, in the conventional OBIRCH method, when the defect is in a portion masked by the upper layer or lower layer wiring, the defect cannot be detected because the defect cannot be irradiated with the laser beam.

  Hereinafter, an OBIRCH inspection method and an OBIRCH apparatus capable of detecting a location where a defect has occurred with higher sensitivity than the conventional method will be described.

(First embodiment)
FIG. 1 is a schematic diagram illustrating an example of an OBIRCH inspection apparatus used in the inspection method according to the first embodiment.

  The OBIRCH inspection apparatus shown in FIG. 1 outputs an inspection apparatus main body 10 in which a semiconductor device 30 to be inspected is arranged, various control signals to the inspection apparatus main body 10 and various signals output from the inspection apparatus main body 10. And a console unit 20 for signal processing.

  The inspection apparatus main body 10 has a sample stage 11 on which a semiconductor device 30 is placed. A plurality of mechanical probers 12 are arranged on the sample stage 11, and probe pins 12 a that contact the electrodes of the semiconductor device 30 are attached to the tips of the mechanical probers 12. At the time of OBIRCH inspection, a voltage is applied from the OBIRCH amplifier 31 to the electrode of the semiconductor device 30 via the wiring 32 and the probe pin 12a, and a change in resistance value is detected by a change in the current flowing through the probe pin 12a.

  Above the sample stage 11, an optical system including the microscope tube 13 and the photodetector 15 is supported and disposed by the support column 16.

  A revolver 13b to which a plurality of objective lenses 13a are attached is disposed below the microscope tube 13. The revolver 13b is rotated by a control signal from the console unit 20, and a desired objective lens 13a is placed at a predetermined position.

  At the time of OBIRCH image acquisition, laser light generated by a laser light source 15b described later is emitted toward the semiconductor device 30 through the objective lens 13a disposed at the predetermined position. Further, at the time of acquiring a microscope image, an optical image of the semiconductor device 30 is input to the imaging element 15a described later via the objective lens 13a disposed at the predetermined position.

  Housed in the photodetector 15 are an image sensor 15a that detects an optical image of the semiconductor device 30 and converts it into an electrical signal (image signal), a laser light source 15b that generates laser light, and a laser light scanning unit 15c. Has been. The laser light source 15 b generates laser light having a wavelength of about 1300 nm in accordance with a signal from the laser driving device 17. The laser beam scanning unit 15 c scans (raster scan) the laser beam in accordance with a signal from the laser driving device 17.

  In the OBIRCH inspection apparatus shown in FIG. 1, a laser driving device 17 is disposed below the sample stage 11, and the laser driving device 17 and the photodetector 15 are connected via a cable 18.

  A light shielding cover 19 is disposed on the inspection stage 11, and the light shielding cover 19 forms a light shielding space where no external light enters. The semiconductor device 30, the mechanical prober 12, the microscope tube 13, and the photodetector 15 described above are arranged in a light shielding space covered with a light shielding cover 19.

  On the other hand, the console unit 20 is provided with an OBIRCH controller 21, a display device 23, and a power source 24.

  The power source 24 is connected to the OBIRCH amplifier 31 via the wiring 25 and supplies a predetermined voltage to the OBIRCH amplifier 31. Further, the power source 24 transmits information on the current acquired via the OBIRCH amplifier 31 to the OBIRCH controller 21.

  The OBIRCH controller 21 includes a computer. The OBIRCH controller 21 acquires an image signal from, for example, the image sensor 15 b in the photodetector 15, performs image processing, generates a microscopic image of the surface of the semiconductor device 30, and displays it on the display device 23. Further, the OBIRCH controller 21 acquires, for example, a change in the current flowing through the probe pin 12a via the OBIRCH amplifier 31, performs signal processing, generates an OBIRCH image, and displays the OBIRCH image on the display device 23. Further, the OBIRCH controller 21 also controls the laser driving device 17 and the optical system of the inspection unit 10.

  Hereinafter, the OBIRCH inspection method according to the present embodiment will be described.

  FIG. 2 is a schematic diagram showing the semiconductor device 30 placed on the sample stage 11. As shown in FIG. 2, in the OBIRCH inspection method according to this embodiment, a reflector 35 is disposed between the sample stage 11 and the semiconductor device 30. Further, the probe pin 12a is brought into contact with the electrode of the semiconductor device 30, and a predetermined voltage is applied from the OBIRCH amplifier 31 to the probe pin 12a.

  The reflection plate 35 may be any plate that reflects the laser light applied to the semiconductor device 30, and the material, shape, and the like are not limited. Here, a metal plate having a surface plated with gold (Au) is used as the reflection plate 35. In the present embodiment, the reflector 35 is disposed between the sample stage 11 and the semiconductor device 30, but a metal to be the reflector 35 is attached to the back side of the semiconductor device 30 by a method such as sputtering. May be.

  Next, laser light is irradiated from the upper side of the semiconductor device 30 through the objective lens 13a, and the current flowing through each probe pin 12a is monitored by the OBIRCH controller 21 while the laser light is raster-scanned. Is detected.

  FIG. 3 is a diagram schematically showing a semiconductor device under OBIRCH inspection. However, in the example of FIG. 3, the semiconductor device 30 is placed directly on the sample stage 11 and the reflecting plate 35 is not used.

  In FIG. 3, reference numeral 41 denotes a silicon substrate, 42 denotes a transistor, and 43 denotes a wiring formed of a metal such as aluminum or copper. Also, the portions indicated by arrows A and B in FIG. 3 indicate locations where defects have occurred, and the white arrows indicate laser light.

  When laser light is irradiated from the surface side of the semiconductor device 30, the laser light is irradiated to the portion indicated by the arrow A, so that the temperature rises and the resistance value changes. For this reason, the OBIRCH controller 21 can detect the defect in the portion indicated by the arrow A from the change in the current flowing through the probe pin 12a.

  However, the portion indicated by the arrow B is not irradiated with laser light because the upper portion is covered with the wiring 43. For this reason, the OBIRCH controller 21 cannot detect the defect in the portion indicated by the arrow B.

  FIG. 4 is a diagram schematically showing a semiconductor device under OBIRCH inspection. However, in the example of FIG. 4, the reflection plate 35 is disposed between the semiconductor device 30 and the sample stage 11.

  When the reflecting plate 35 is arranged between the semiconductor device 30 and the sample stage 11 as shown in FIG. 4, when the laser light is irradiated from the upper surface (front surface) side of the semiconductor device 30, as in the example shown in FIG. A portion indicated by A is irradiated with laser light. Thereby, the OBIRCH controller 21 can detect the defect of the part of the arrow A from the change of the current flowing through the probe pin 12a.

  On the other hand, the portion indicated by the arrow B has a wiring 43 above it, and therefore cannot be directly irradiated with laser light. However, since a part of the laser light that is transmitted through the silicon substrate 41 and reflected by the reflecting plate 35 irradiates the portion indicated by the arrow B, the temperature of the portion indicated by the arrow B rises. Thereby, the OBIRCH controller 21 can detect the defect of the part of arrow B from the change of the current flowing through the probe pin 12a.

  As described above, in this embodiment, the reflection plate 35 is disposed between the semiconductor device 30 and the sample stage 11, and the laser beam is irradiated from the upper surface side of the semiconductor device 30. Thereby, compared with the case where there is no reflecting plate 35 (in the case shown in FIG. 3), it is possible to detect the location where the defect has occurred with high sensitivity.

(Second Embodiment)
FIG. 5 is a schematic diagram illustrating an example of an OBIRCH inspection apparatus used in the inspection method according to the second embodiment. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and description of overlapping portions is omitted.

  In the OBIRCH inspection apparatus shown in FIG. 5, an optical system such as a microscope tube 13 and a photodetector 15 is arranged below the sample stage 11. That is, the photodetector 15 is disposed on the laser driving device 17, and the microscope tube 13 is disposed on the photodetector 15. A revolver 13b to which a plurality of objective lenses 13a are attached is arranged on the upper side of the microscope tube 13.

  Also in this embodiment, the revolver 13b is rotated by a control signal from the console unit 20 so that a desired objective lens 13a is disposed at a predetermined position, and laser light is transmitted through the objective lens 13a disposed at the predetermined position. The light is emitted toward the semiconductor device 30.

  In the present embodiment, it is important that at least a portion of the sample stage 11 where the sample device 30 is disposed is formed of a material that transmits laser light. In the present embodiment, it is assumed that the sample stage 11 is made of glass. Similarly to the first embodiment, the semiconductor device 30, the mechanical prober 12, the microscope tube 13, the photodetector 15, and the like are arranged in a light shielding space covered with a light shielding cover 19.

  FIG. 6 is a schematic diagram showing the semiconductor device 30 placed on the sample stage 11. As shown in FIG. 6, in the OBIRCH inspection method according to this embodiment, the reflector 35 is disposed on the semiconductor device 30. Here again, a metal plate whose surface is plated with gold is used as the reflecting plate 35.

  Next, a laser beam is irradiated from the lower side of the semiconductor device 30, and a current flowing through each probe pin 12a is monitored by the OBIRCH controller 21 while the laser beam is raster-scanned to detect a change in resistance value.

  FIG. 7 is a diagram schematically showing a semiconductor device under OBIRCH inspection. However, in the example of FIG. 7, the reflection plate 35 is not disposed on the semiconductor device 30.

  When laser light is irradiated from the lower surface (back surface) side of the semiconductor device 30, the portion indicated by arrow B is irradiated with laser light, so that the temperature rises and the resistance value changes. For this reason, the OBIRCH controller 21 can detect a defect in the portion indicated by the arrow B from the change in the current flowing through the probe pin 12a.

  However, the portion indicated by the arrow A is not irradiated with laser light because the lower portion is covered with the wiring 43. For this reason, the OBIRCH controller 21 cannot detect a defect indicated by the arrow A.

  FIG. 8 is a diagram schematically showing a semiconductor device under OBIRCH inspection. However, in the example of FIG. 8, the reflection plate 35 is disposed on the semiconductor device 30.

  As shown in FIG. 8, when the reflecting plate 35 is disposed on the semiconductor device 30, when the laser beam is irradiated from the lower surface side of the semiconductor device 30, the portion indicated by the arrow B is irradiated with the laser as in the example shown in FIG. Light is irradiated. Thereby, the OBIRCH controller 21 can detect the defect of the part of arrow B from the change of the current flowing through the probe pin 12a.

  On the other hand, since the wiring 43 is formed below the portion indicated by the arrow A, the laser beam cannot be directly irradiated. However, since part of the laser light that has been transmitted through the wiring layer and reflected by the reflecting plate 35 irradiates the portion indicated by the arrow A, the temperature of the portion indicated by the arrow A rises. Thereby, the OBIRCH controller 21 can detect the defect of the part of the arrow A from the change of the current flowing through the probe pin 12a.

  As described above, in this embodiment, the reflection plate 35 is disposed on the upper side of the semiconductor device 30 and the laser light is irradiated from the lower surface side of the semiconductor device 30. Thereby, compared with the case where there is no reflecting plate 35 (in the case shown in FIG. 7), it is possible to detect the location where the defect has occurred with high sensitivity.

(Experiment)
As an inspection target, a semiconductor device in which a short circuit occurred in the intermediate wiring layer was prepared, and an OBIRCH image was obtained using the OBIRCH apparatus shown in FIG.

  FIG. 9A is a diagram showing an OBIRCH image obtained by irradiating laser light from the lower surface side of the semiconductor device 30 without using a reflector as shown in FIG. FIG. 9B is a diagram showing an OBIRCH image obtained by arranging the reflecting plate 35 on the upper side of the semiconductor device as shown in FIG. 8 and irradiating laser light from the lower surface side of the semiconductor device 30.

  As can be seen from FIG. 9A, even in the case without the reflector, the luminance of the defective portion at the center on the right side in FIG. 9A is slightly higher than the other portions. This can be considered that a small amount of laser light reflected at the interface of the wiring 43 or the insulating layer reaches the defective portion even without the reflector. However, the difference in luminance between the defective portion and other portions is slight, and the defect detection accuracy is low.

  On the other hand, in the OBIRCH image of FIG. 9A obtained by arranging the reflector on the semiconductor device, it can be seen that the brightness of the defective portion is higher than that of FIG. 9A. Thus, in the OBIRCH inspection method according to this embodiment, the defect of the semiconductor device (inspection target) can be detected more reliably by reflecting the laser light with the reflector 35.

(Modification)
In both the first embodiment and the second embodiment described above, a plate having a flat surface is used as the reflector, but the reflector has irregularities on the surface as shown in FIGS. A member may be used.

  The reflective plate 35a in FIG. 10 (a) is provided with rectangular irregularities on the surface. In the reflecting plate 35b of FIG. 10B, trapezoidal irregularities are provided on the surface. In the reflection plate 35c of FIG. 10C, triangular irregularities are provided on the surface. In the reflecting plate 35d of FIG. 10D, convex-lens-like irregularities are provided on the surface. In the reflecting plate 35e of FIG. 10 (e), concave and convex portions having a concave lens shape are provided on the surface.

  When the reflection plates 35a to 35e having the unevenness on the surface are used, the laser light can be reflected in a wider range than the reflection plate 35 having a flat surface.

  The following additional notes are disclosed with respect to the above embodiments.

(Additional remark 1) The process of arrange | positioning a reflecting plate so as to oppose the 1st surface to be examined,
OBIRCH inspection, comprising: irradiating a laser beam onto the second surface of the inspection object while applying a voltage to the inspection object via a probe pin, and detecting a current flowing through the probe pin. Method.

  (Supplementary note 2) The OBIRCH inspection method according to supplementary note 1, wherein the inspection object is a semiconductor device having a silicon substrate.

  (Additional remark 3) The wavelength of the said laser beam is a wavelength which permeate | transmits the said silicon substrate, The OBIRCH inspection method of Additional remark 2 characterized by the above-mentioned.

  (Supplementary note 4) The OBIRCH inspection method according to supplementary note 3, wherein the first surface is a back surface of the silicon substrate, and the second surface is a surface on which wiring is formed.

  (Supplementary note 5) The OBIRCH inspection method according to supplementary note 3, wherein the second surface is a back surface of the silicon substrate, and the first surface is a surface on which wiring is formed.

  (Supplementary note 6) The OBIRCH inspection method according to any one of supplementary notes 1 to 5, wherein unevenness is provided on a surface of the reflection plate.

(Appendix 7) A sample stage on which an inspection object is placed;
A reflector disposed opposite the first surface to be inspected;
A probe pin for applying a voltage in contact with the inspection object;
An optical device for irradiating the second surface to be inspected with laser light;
An OBIRCH device comprising: an amplifier that detects a current flowing through the probe pin.

  (Supplementary note 8) The OBIRCH apparatus according to supplementary note 7, wherein the inspection target is a semiconductor device having a silicon substrate, and the wavelength of the laser beam is a wavelength that transmits the silicon substrate.

  DESCRIPTION OF SYMBOLS 10 ... Inspection apparatus main body, 11 ... Sample stage, 12 ... Mechanical prober, 12a ... Probe pin, 13 ... Microscope tube, 13a ... Objective lens, 13b ... Revolver, 15 ... Photo detector, 15a ... Imaging element, 15b ... Laser light source 15c ... Laser beam scanning unit, 16 ... support, 17 ... laser driving device, 19 ... light-shielding cover, 20 ... console unit, 21 ... OBIRC controller, 23 ... display device, 24 ... power supply, 30 ... semiconductor device, 31 ... OBIRC Amplifier, 35, 35a-35e ... reflector.

Claims (5)

Arranging the reflector so as to face the first surface to be inspected;
OBIRCH inspection, comprising: irradiating a laser beam onto the second surface of the inspection object while applying a voltage to the inspection object via a probe pin, and detecting a current flowing through the probe pin. Method.   The OBIRCH inspection method according to claim 1, wherein the inspection object is a semiconductor device having a silicon substrate.   The OBIRCH inspection method according to claim 2, wherein the wavelength of the laser beam is a wavelength that transmits the silicon substrate.   4. The OBIRCH inspection method according to claim 1, wherein unevenness is provided on a surface of the reflecting plate. 5. A sample stage on which the inspection object is placed;
A reflector disposed opposite the first surface to be inspected;
A probe pin for applying a voltage in contact with the inspection object;
An optical device for irradiating the second surface to be inspected with laser light;
An OBIRCH device comprising: an amplifier that detects a current flowing through the probe pin.

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