JP5452083B2 - Device and method for detecting defect of object to be measured - Google Patents

Description

  The present invention relates to a defect detection apparatus for an object to be measured, and relates to detection of an insulation defect position of a semiconductor device, particularly a high voltage device such as a power module.

  In recent years, the demand for power modules has increased as a device for efficient use of electrical energy. Since a high voltage is applied to the electrode portion, the power module is required to have high insulation reliability. However, an insulation defect may occur due to the influence of heat generated during the manufacturing process or driving. In order to suppress the occurrence of defects, it is necessary to first identify the location and cause, and an insulation defect detection method for that purpose is required. However, inspecting by disassembling the apparatus is very time consuming and it is difficult to identify defects, so a non-destructive inspection method is required. Further, in the inspection by X-ray transmission, even if a defect is found in the transmission image, it cannot be determined whether it is a discharge location. Therefore, confirmation by partial discharge measurement is also required.

  As a conventional insulation defect detection method, there is a method utilizing the fact that a partial discharge start voltage is lowered when initial electrons are induced in a defect portion by X-ray irradiation. This is a method of controlling the X-ray irradiation direction to irradiate a part of the sample, and comparing the partial discharge characteristics thereby to identify the defect position by comparing the X-ray irradiation direction and the sample structure (for example, Patent Documents). 1).

JP-A-9-105766

  However, due to the influence of measurement errors depending on the X-ray irradiation diameter and irradiation position deviation, it is difficult to accurately identify the defect occurrence location in the case of measuring a small and high-density module. In addition, in order to identify the cause of the defect, it is necessary to determine the shape and state of the defect (peeling or void), and to determine in what position the defect exists and in what state. .

  The present invention is intended to solve such a problem, and an object of the present invention is to provide a defect detection apparatus and method for an object to be measured that specifies a defect generation factor by measuring an accurate generation position, shape, and state of an insulation defect. It is to provide.

  A defect detection apparatus for an object to be measured according to the present invention is an apparatus for detecting a defect of an object to be measured, which detects a defect position and state by observation of a transmission image by X-ray irradiation and partial discharge measurement on the object to be measured. X-ray irradiation means having an X-ray generator to generate, an X-ray shielding plate for limiting an X-ray irradiation range for irradiating the object to be measured from the X-ray generator, and X-rays irradiated to the object to be measured X-ray irradiation position on the object to be measured by operating a transmission stage for observing a transmission image of the object to be measured by means of, and operating a movable stage on which the object to be measured is placed when observing the transmission image by the transmission imaging means Irradiating position moving means for controlling the X-ray shielding plate, X-ray irradiation range control to the object to be measured by controlling the X-ray shielding plate, and transmission image observation at the time of whole irradiation by X-ray irradiation to the whole object to be measured And partial illumination by X-ray irradiation Test for the object to be measured and irradiation position confirmation means for confirming the X-ray irradiation position by switching the image acquisition with transmission image observation at the time and comparing the transmission images acquired during whole irradiation and partial irradiation Partial discharge measuring means for applying a voltage and measuring partial discharge generated in the object to be measured is provided.

  Further, the defect detection method of the object to be measured according to the present invention confirms the X-ray irradiation position by the irradiation position confirmation means for confirming the X-ray irradiation position, and observes the transmission image to correct the deviation of the irradiation position. While moving to a reference position, applying a test voltage to the object to be measured by the voltage applying means, and operating the movable stage for placing the object to be measured by the irradiation position moving means to the object to be measured. The partial discharge generated on the object to be measured is measured by the partial discharge measuring means while moving the X-ray irradiation position, and the defect is visualized by observing the transmission image of the object to be measured by the transmission photographing means when the partial discharge occurs. It is characterized by comprising.

  According to the present invention, the X-ray irradiation range on the object to be measured can be controlled, and the irradiation position can be confirmed by comparing the entire transmission image with a partial X-ray transmission image in the form of a beam. The irradiation position can be easily controlled even in the constructed structure. Further, the irradiation position can be controlled without considering the coordinates, dimensions of the internal structure, and the like, so that the measurement accuracy can be improved and the measurement time can be shortened. In addition, it is possible to detect defects by partial discharge measurement, and at the same time to identify the detailed occurrence position of defects by visualizing the defects, so that from where the defect is located while the parts are dense like inside the power module. It is possible to accurately determine whether it has occurred. Furthermore, by combining with the defect state determination result by waveform observation, it becomes easy to specify the cause of the insulation defect.

It is a figure which shows the structure of the defect detection apparatus of the to-be-measured object which concerns on Embodiment 1 of this invention. It is a flowchart which shows the procedure at the time of confirming an irradiation position. It is a figure which shows the example which confirms an irradiation position by the response | compatibility of the transmission image at the time of whole irradiation and the time of partial irradiation. It is a figure which shows the relationship between the partial discharge start voltage at the time of X-ray irradiation and the time of non-irradiation, and a test voltage. It is a figure which shows that the irradiation range of X-ray changes with distance. It is a figure which concerns on Embodiment 2 of this invention, and shows an example of a measurement of an applied voltage and a partial discharge waveform. It is a flowchart which concerns on Embodiment 3 of this invention, and shows the implementation procedure of this invention.

Embodiment 1 FIG.
1 is a diagram showing a configuration of a defect detection apparatus for an object to be measured according to Embodiment 1 of the present invention. The defect detection apparatus for an object to be measured shown in FIG. 1 is an apparatus for detecting a defect of an object to be measured that detects a defect position and state by observation of a transmission image by X-ray irradiation and partial discharge measurement on the object to be measured 1. X-ray generator 3 for generating X-rays, an X-ray irradiation means having an X-ray shielding plate 4 for limiting the irradiation range of X-rays irradiated from the X-ray generator 3 to the DUT 1, and the DUT 1 A transmission imaging means consisting of a transmission imaging camera 6 and a transmission image monitor 7 for observing a transmission image of the object to be measured 1 by X-rays, and a movable stage on which the object to be measured 1 is placed when observing the transmission image by the transmission imaging means 2 for controlling the X-ray irradiation position on the measurement object 1 by controlling the X-ray shielding plate 4 and a stage control unit 12 as an irradiation position moving means for controlling the X-ray irradiation position on the measurement object 1 by operating 2. And X-ray irradiation on the entire DUT 1 X-ray irradiation position by switching image acquisition between transmission image observation at the time of irradiation and transmission image observation at the time of partial irradiation by X-ray irradiation to a part, and comparison of transmission images acquired at the time of full irradiation and partial irradiation The irradiation position confirmation control unit 16 as an irradiation position confirmation means for confirming the above and a part as a partial discharge measurement means for applying a test voltage to the device under test 1 and measuring the partial discharge generated in the device under test 1 A discharge measuring unit 18 is provided as a main configuration.

  Here, the partial discharge measurement unit 18 includes a high voltage power supply 8, a partial discharge measurement device 9, a coupling capacitor 10, a detection impedance 11, and a discharge waveform monitor 15, and the X-ray irradiation control unit 19 includes a transmission image monitor 7, It has a stage control unit 12, an X-ray control unit 13, and an X-ray shielding plate control unit 14, and includes a high voltage power supply 8, a stage control unit 12, an X-ray control unit 13, an X-ray shielding plate control unit 14, and an irradiation position confirmation control. The unit 16 is connected to the measurement control unit 17 and is configured to be controlled by the measurement control unit 17.

  In FIG. 1, an object to be measured 1 is placed on a movable stage 2 as an irradiation position moving means, and X-rays generated from an X-ray generator 3 are holes on the object 1 to be measured. A beam is formed by the shielding plate 4 and irradiated as an X-ray beam 5. At this time, a transmission image of X-rays irradiated on the DUT 1 is observed by the transmission imaging camera 6 and the transmission image monitor 7. Further, a test voltage is applied to the device under test 1 by a high voltage power supply 8, and the generated partial discharge is measured by a partial discharge measuring device 9 through a coupling capacitor 10 and a detection impedance 11.

  Further, the X-ray shielding plate 4 can be arbitrarily installed / not installed on the X-ray irradiation port, and can be switched between irradiating the entire object to be measured 1 and irradiating a part thereof. it can. When the current irradiation position cannot be determined by making the X-ray beam, the irradiation position confirmation control unit 16 switches to the whole irradiation at the same position and measures the transmission image, returns to the partial irradiation, and measures the transmission image again. To do. At this time, the X-ray irradiation position can be confirmed by superimposing the display range at the time of partial irradiation with the entire image at the time of the entire irradiation and controlling to display the image.

  FIG. 2 is a flowchart showing the flow of irradiation range control, image acquisition, comparison, and display by the irradiation position confirmation control unit 16. That is, when the current irradiation position becomes unknown by making the X-ray beam (S1), the irradiation range is switched to the entire irradiation by the X-ray shielding plate control unit 14 at the same position (S2), A transmission image is acquired by the transmission image monitor 7 (S3), the irradiation range is partially returned to the irradiation range by the X-ray shielding plate control unit 14 (S4), and the transmission image is acquired by the transmission image monitor 7 again (S5). At this time, the X-ray irradiation position can be confirmed by controlling the display range at the time of partial irradiation to be superimposed on the entire image at the time of the entire irradiation and displaying the irradiation position with respect to the entire image. As described above, the irradiation position can be easily confirmed by the automatic control by the irradiation position confirmation control unit 16.

  When moving the irradiation position, the stage control unit 12 operates the movable stage 2 based on a command from the measurement control unit 17 to control the X-ray irradiation position with respect to the DUT 1 and always perform transmission image observation. Do. At this time, an entire transmission image of the object to be measured is first acquired by the entire irradiation, and the irradiation position is confirmed during the movement of the irradiation position by corresponding to the entire image. For example, if the entire image is taken as shown in FIG. 3 (a), when the X-ray is formed into a beam, it becomes as shown in FIGS. 3 (b) and (c), and is obtained from (b) and (c). The current irradiation position is determined by comparing / corresponding the characteristics of the obtained image with those in the image of (a). If the moving distance is unknown and the feature cannot be determined from the image, or the feature is not known even if there is a feature, the irradiation position confirmation control unit 16 reconfirms the position.

  Here, the overall measurement flow is shown below. First, the X-ray shielding plate 4 is controlled by the X-ray shielding plate control unit 14 so as to irradiate the entire object to be measured 1 with X-rays. Subsequently, the partial discharge start voltage is measured by the partial discharge measuring unit 18 in order to determine the test voltage. When the defective part is irradiated with X-rays, initial electrons are induced, so that the partial discharge start voltage decreases. When the partial discharge start voltage in the state where X-rays are not irradiated to the defective portion is Vi and the partial discharge start voltage in the irradiated state is Vi ′, a defect exists if Vi ′ <Vi as shown in FIG. You can confirm that The test voltage Vp is set such that Vi ′ <Vp <Vi, and is a voltage that is discharged only when X-rays are irradiated.

  Next, the X-ray shielding plate 4 is controlled and set to irradiate an X-ray beam. At this time, the irradiation position is confirmed by the irradiation position confirmation control unit 16, and the movable stage 2 is operated and moved to an arbitrary irradiation position by the stage control unit 12 that operates based on a command from the measurement control unit 17.

  Then, the test voltage Vp is applied to the DUT 1 by the high voltage power supply 8 and it is confirmed by the partial discharge measuring device 9 whether partial discharge has occurred. If it is not discharged, the movable stage 2 is operated to move the irradiation position. As for the movement method, only an arbitrary region may be moved while viewing the transmission image, or may be moved in order from the end so as to irradiate the entire region of the object to be measured. When partial discharge occurs, the movement of the movable stage 2 is stopped, the defect is observed by the transmission image, and the defect shape and the detailed position are specified.

  In addition to using the X-ray shielding plate 4 with holes as described above as a method for forming the X-ray beam, the irradiation range can be arbitrarily changed by using a shielding plate capable of controlling the slit width, and the entire irradiation is performed. Switching to can also be performed.

  Since the X-rays are irradiated radially as shown in FIG. 5, the irradiation range D varies depending on the distance from the X-ray generator 3 and the X-ray shielding plate 4. Therefore, in the case of beam formation using the X-ray shielding plate 4 with a hole, the object to be measured 1 is irradiated by moving the X-ray generator 3 and the X-ray shielding plate 4 or the vertical position of the movable stage 2. The X-ray irradiation range can be controlled. When a shielding plate capable of controlling the slit width is used, the irradiation range can be increased by widening the slit width. After measuring the approximate position of the defect by increasing the X-ray irradiation range, the measurement time can be shortened by measuring with the irradiation range being reduced.

  The same effect can be obtained by adopting a configuration in which the X-ray generator 3 and the camera 6 are moved in conjunction with each other instead of the control by the movable stage 2 as the X-ray irradiation position moving means. It is necessary to prevent the irradiation axis from shifting with respect to the camera. The X-ray generator 3 and the camera 6 can have the same effect even if they are arranged in a positional relationship opposite to the position shown in FIG. 1 or the object to be measured 1 is sandwiched from the side. It is done.

  Therefore, according to the first embodiment, when the X-ray beam 5 is irradiated onto the DUT 1, the irradiation position is obtained by matching the entire image with the image in the irradiation range by switching the irradiation range and controlling the transmission image observation. By simultaneously observing the transmission image even when the irradiation position is moved and making it correspond to the image during the entire irradiation, it is possible to control the irradiation position without considering the coordinates and dimensions. On the other hand, since it is possible to irradiate an accurate position, the accuracy can be improved and the measurement time can be shortened. In addition, the defect visualization makes it possible to accurately measure the position of an insulation defect even in a power module in which components are arranged at high density, and can be applied as an insulation defect detection device for a semiconductor device.

Embodiment 2. FIG.
In the first embodiment, the partial discharge waveform can be observed from the discharge waveform monitor 15 when the defect position is measured by the partial discharge detection. A measurement example of the partial discharge waveform is shown in FIG. In the partial discharge, the phase and frequency of occurrence vary depending on the state of the defect, so the state of the defect can be determined from the observation result. For example, in the case of voids, there is not much difference in the discharge generation phase due to the polarity of the applied voltage, but in the peeled state where the metal electrode is exposed in the discharge part, discharge occurs due to the effect of electrons being easily emitted when negative voltage is applied The frequency is biased by the applied voltage polarity.

  Therefore, according to the second embodiment, the discharge waveform monitor 15 provided in the partial discharge measurement unit 18 observes the partial discharge waveform and discriminates the defect state (void, peeling, etc.), thereby determining the cause of the defect. Can be identified.

Embodiment 3 FIG.
By identifying the exact occurrence position of the insulation defect according to the first embodiment and determining the state of the defect according to the second embodiment, the cause of the defect can be identified. A flowchart of this measurement procedure is shown in FIG. The measurement flow can be controlled by the measurement control unit 17. That is, as shown in FIG. 7, it sets so that X-rays may be irradiated to the to-be-measured object 1 whole (S11), and the transmission image of the to-be-measured object 1 whole is acquired (S12). And the partial discharge start voltage at the time of X-ray irradiation and non-irradiation is measured (S13), and a test voltage is determined (S14). Next, X-rays are set to be irradiated in a beam shape (S15), X-ray beams are irradiated (S16), the irradiation position confirmation control unit 16 confirms the irradiation position, and the irradiation position deviation is corrected. The irradiation position is moved to a reference position while observing the transmission image as much as possible (S17).

  Thereafter, a test voltage is applied (S18), and it is determined whether or not a partial discharge has occurred (S19). When the partial discharge does not occur, the X-ray irradiation position is moved by operating the movable stage 2 (S20), the transmission image is observed, and the irradiation position is confirmed by correspondence with the entire transmission image (S21). In step S19, when a partial discharge occurs, the position and shape of the defect are observed from the transmission image (S22), the partial discharge waveform is observed (S23), and the cause of the defect is specified (S24).

  That is, in the defect detection method according to the third embodiment, the irradiation position confirmation control unit 16 that confirms the X-ray irradiation position confirms the X-ray irradiation position and observes the transmission image to correct the deviation of the irradiation position. Move to the reference position, apply a test voltage to the DUT 1 and operate the movable stage 2 on which the DUT 1 is placed to move the X-ray irradiation position on the DUT 1 However, the partial discharge measuring unit 18 measures the partial discharge generated in the DUT 1 and visualizes the defect by observing the transmission image of the DUT 1 when the partial discharge occurs.

  Thereby, when a test voltage is applied to the DUT 1 and a beam-like X-ray is irradiated to measure a partial discharge to detect a defect position, a transmission image of the irradiation range can be observed, By confirming the X-ray irradiation position in correspondence with the entire transmission image, the irradiation position can be accurately controlled, and by visualizing the defect at the time of defect detection, the exact position of the defect can be specified. Further, the cause of the defect is specified together with the determination result of the defect state by measuring the partial discharge waveform.

  Therefore, according to the third embodiment, it is possible to improve the insulation reliability of a device such as a power module by specifying a defect occurrence factor inside the device and taking a countermeasure against it by using this defect detection method. . The power module here is applicable to all modules such as silicone gel-sealed high-voltage models equipped with all chips such as Si and SiC chips, and mold-type modules by transfer molding of epoxy resin. There is no.

  1 object to be measured, 2 movable stage, 3 X-ray generator, 4 X-ray shielding plate, 5 X-ray beam, 6 X-ray transmission camera, 7 X-ray transmission image monitor, 8 high voltage power supply, 9 partial discharge measuring instrument DESCRIPTION OF SYMBOLS 10 Coupling capacitor, 11 Detection impedance, 12 Movable stage control part, 13 X-ray control part, 14 X-ray shielding board control part, 15 Discharge waveform monitor, 16 Irradiation position confirmation control part, 17 Measurement control part, 18 Partial discharge measurement Part, 19 X-ray irradiation control part.

Claims (2)

A device for detecting a defect of an object to be measured that detects a defect position and state by observation of a transmission image by X-ray irradiation and partial discharge measurement on the object to be measured,
An X-ray irradiation means having an X-ray generator for generating X-rays and an X-ray shielding plate for limiting an irradiation range of X-rays irradiated from the X-ray generator to the object to be measured;
Transmission imaging means for observing a transmission image of the measurement object by X-rays irradiated to the measurement object;
An irradiation position moving means for controlling an X-ray irradiation position on the object to be measured by operating a movable stage on which the object to be measured is placed during transmission image observation by the transmission imaging means;
Control of the X-ray irradiation range to the object to be measured by controlling the X-ray shielding plate, observation of a transmission image at the time of whole irradiation by X-ray irradiation to the entire object to be measured, and a part by X-ray irradiation to a part Irradiation position confirmation means for confirming the X-ray irradiation position by switching image acquisition with transmission image observation at the time of irradiation, and comparing transmission images acquired at the time of whole irradiation and partial irradiation,
A defect detection apparatus for a measured object, comprising: a partial discharge measuring means for applying a test voltage to the measured object and measuring a partial discharge generated in the measured object. In the to-be-measured object defect detection apparatus according to claim 1,
The apparatus for detecting a defect of an object to be measured, wherein the partial discharge measuring means includes a monitor for observing a partial discharge waveform.

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