JP2023005684A - Inspection equipment of semiconductor device and inspection method - Google Patents

Abstract

To provide an inspection equipment and an inspection method for semiconductor devices capable of detecting the location of defective parts with high accuracy.SOLUTION: An inspection equipment for a semiconductor device, comprises: a light source 6 that forms irradiation traces on a sample 30 by irradiating light onto the sample 30; a voltage application unit 7 that makes the irradiation traces emit light by applying voltage to the sample 30 and makes defective parts of the inspection target emit light by applying voltage to the inspection target; a first moving unit 7 that moves the inspection target; a light detection unit 9 that detects light emission from the irradiation traces; and a second moving unit 10 that moves the light detection unit 9.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inspection apparatus and an inspection method for semiconductor devices.

Conventionally, defect analysis of semiconductor devices is performed, for example, by the following method. First, a defective portion on a semiconductor substrate is caused to emit light by applying a voltage, and a light emitting point is detected by observing the substrate from the rear surface side with an emission microscope. Next, the substrate is etched from the front surface side with a focused ion beam to roughly mark light emitting points.

Then, the semiconductor device is again observed from the back side with an emission microscope to confirm the positional relationship between the light emitting point and the marking. After that, based on this positional relationship, etching with a focused ion beam is performed to mark a position closer to the light emitting point. Based on this marking, the defective portion is cut out, and the section is observed.

In such a conventional method, observation with an emission microscope and etching with a focused ion beam are performed in separate apparatuses. Therefore, the position of the light emitting point and the marking are likely to be misaligned, and it is difficult to cut out the defective portion with high accuracy.

Regarding this, for example, in Patent Document 1, the following inspection method is proposed for a semiconductor device such as a power device having a characteristic pattern on the outer periphery. First, the front and back surfaces of the sample are irradiated with an electron beam and a laser beam, and the amount of deviation between these optical axes and the above pattern is confirmed by a monitor.

Next, based on this amount of deviation, the deviation between the optical axis of the laser beam and the optical axis of the electron beam is corrected. Specifically, the deflection of the electron beam is corrected by a deflector, and the optical axis of the electron beam is aligned with the optical axis of the laser beam. Then, the defective portion is detected, and the shift amount of the detected defective portion from the optical axis of the laser beam is calculated. After that, the electron beam is scanned according to this shift amount to mark the vicinity of the defective portion.

JP 2014-143348 A

In the method described in Patent Document 1, the deviation between the optical axis of the electron beam and the optical axis of the laser beam is corrected by deflection of the electron beam. However, the optical axis of the laser beam and the optical axis of the electron beam may deviate so much that it cannot be corrected by electron beam deflection alone. is.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor device inspection apparatus and inspection method capable of detecting the position of a defective portion with high accuracy.

In order to achieve the above object, according to the first aspect of the invention, there is provided an inspection apparatus for a semiconductor device, comprising: a light source (6) for irradiating a sample (30) with light to form an irradiation mark on the sample; A voltage application unit (7) that emits light on the irradiation mark by applying a voltage to the inspection object (20), and a voltage application unit (7) that emits light on the defective portion of the inspection object by applying a voltage to the inspection object (20), and a first moving unit that moves the inspection object. (7), a photodetector (9) for detecting light emission from the irradiation mark, and a second moving unit (10) for moving the photodetector.

According to this, by moving the light detection unit to align the optical axis of the light detection unit with the irradiation mark of the sample, moving the inspection object and aligning the light emitting portion with the optical axis of the light detection unit, the light source can be detected. It is possible to align the defective portion with high accuracy with respect to the optical axis. Therefore, the position of the defective portion can be detected with high accuracy.

According to the third aspect of the invention, there is provided a method for inspecting a semiconductor device, comprising: forming an irradiation mark on a sample (30) by irradiating the sample (30) with light; By causing the mark to emit light, moving the photodetector (9) to align the optical axis of the photodetector with the portion that emits light, and applying a voltage to the inspection object (20), the defective portion is detected. and aligning the light-emitting portion with the optical axis of the photodetector by moving the inspection object.

According to this, by moving the light detection unit to align the optical axis of the light detection unit with the irradiation mark of the sample, moving the inspection object and aligning the light emitting portion with the optical axis of the light detection unit, the light source can be detected. It is possible to align the defective portion with high accuracy with respect to the optical axis. Therefore, the position of the defective portion can be detected with high accuracy.

It should be noted that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and specific components etc. described in the embodiments described later.

It is a figure which shows the structure of the inspection apparatus concerning 1st Embodiment. 1 is a cross-sectional view of a semiconductor device; FIG. It is a cross-sectional view of a sample. It is a figure which shows a mode that an irradiation trace is formed in a sample. It is a figure which shows a mode that the optical axis of a photon detection part is match|combined with an irradiation mark. FIG. 3 is a diagram showing how light from a defective portion of a semiconductor device is incident on a photodetector;

An embodiment of the present invention will be described below with reference to the drawings. In addition, in each of the following embodiments, portions that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment will be described. An inspection apparatus 1 shown in FIG. 1 is an inspection apparatus for semiconductor devices in which power devices and the like are formed, and is used for failure analysis of semiconductor devices. As shown in FIG. 1, the inspection device 1 has a chamber 2 . The internal space of the chamber 2 is divided into two by a partition wall 3 . Two spaces formed inside the chamber 2 are referred to as a first chamber 4 and a second chamber 5, respectively.

The first chamber 4 is a vacuum chamber, and the pressure in the second chamber 5 is, for example, approximately atmospheric pressure. That is, the pressure in the first chamber 4 is reduced compared to the second chamber 5 by vacuuming. A light source 6 and a stage 7 are provided in the first chamber 4 .

The light source 6 forms an irradiation mark on the sample 30 by irradiating the sample 30 to be described later with light. The light source 6 includes an ion source that generates a Ga ion beam, an aperture, a focusing lens, an objective lens, and the like, and is configured to spot-irradiate the sample 30 with the focused ion beam.

The stage 7 holds a sample 30 and a semiconductor device to be inspected. Note that FIG. 1 shows a state in which the sample 30 is placed on the stage 7 .

The stage 7 has a function of applying a voltage to the held sample 30 and the object to be inspected. By applying a voltage to the sample 30, the stage 7 causes the irradiation mark formed by the irradiation of the light from the light source 6 to emit light. In addition, the stage 7 applies a voltage to the inspection object, thereby causing the defective portion of the inspection object to emit light. The stage 7 corresponds to a voltage applying section.

Further, the stage 7 has a function of moving the held inspection object. Specifically, one direction perpendicular to the optical axis of the light source 6 is the x direction, and the direction perpendicular to both the optical axis of the light source 6 and the x direction is the y direction. and y-directions. The stage 7 corresponds to the first moving section.

The stage 7 is configured to transmit the light generated from the sample 30 and the inspection object to the second chamber 5 side by applying a voltage. An opening is formed in the partition wall 3, and a vacuum window 8 is fitted in the opening. Light generated from the sample 30 and the object to be inspected passes through the vacuum window 8 and enters the second chamber 5 .

A photodetector 9 is provided in the second chamber 5 . The photodetector 9 detects luminescence from irradiation traces formed on the sample 30 and luminescence from defective portions to be inspected. The photodetector 9 is composed of, for example, an emission microscope.

The second chamber 5 is provided with a moving section 10 for moving the light detecting section 9 . The moving section 10 is configured to slightly move the photodetecting section 9 in the x-direction and the y-direction. The moving section 10 corresponds to a second moving section.

The inspection device 1 includes a control section 11 . The control section 11 controls the light source 6, the stage 7, the light detection section 9, the moving section 10, and the like. The control unit 11 includes a CPU, memory such as ROM and RAM, I/O, etc., and executes predetermined processing according to a program stored in the built-in memory.

An object to be inspected by the inspection apparatus 1 will be described. Here, a case where a power device such as a vertical MOS transistor having a trench electrode is to be inspected and deformation of the trench electrode or the like is detected will be described.

As shown in FIG. 2, a semiconductor device 20 to be inspected includes a substrate 21 made of Si or the like, a surface electrode 22 formed on the surface of the substrate 21, and a back surface electrode 23 formed on the back surface of the substrate 21. and

The semiconductor device 20 also includes a trench electrode 24 formed on the surface layer of the substrate 21, an insulating film 25 formed on the trench electrode 24, and the like. The semiconductor device 20 is configured such that a channel is formed by applying a voltage to the trench electrode 24 and current flows between the surface electrode 22 and the back surface electrode 23 . A plurality of semiconductor devices 20 may be formed on a semiconductor wafer, or may be divided into chips.

A sample used to align the optical axis of the photodetector 9 with the optical axis of the light source 6 will be described. As shown in FIG. 3, the sample 30 includes a substrate 31 made of Si or the like, a surface electrode 32 formed on the surface of the substrate 31, and a back electrode 33 formed on the back surface of the substrate 31. .

The substrate 31 , the surface electrode 32 and the back electrode 33 have the same configuration as the substrate 21 , the surface electrode 22 and the back electrode 23 of the semiconductor device 20 . However, in the sample 30 , the surface electrode 32 and the back electrode 33 are partly formed in order to form an irradiation mark on the substrate 31 by irradiation with light from the light source 6 and allow light emission from the irradiation mark to enter the photodetector 9 . , and the front and back surfaces of the substrate 31 are exposed. For example, the surface electrode 32 and the back electrode 33 have their inner peripheral portions removed and their outer peripheral portions left unremoved, and a voltage is applied to the outer peripheral portions from the stage 7 .

A method of inspecting the semiconductor device 20 by the inspection apparatus 1 will be described with reference to FIGS. 4 to 6. FIG. 4 to 6, illustration of the stage 7 and the control unit 11 is omitted.

First, a sample 30 is placed on the stage 7 as shown in FIG. Then, the controller 11 controls the light source 6 to irradiate the sample 30 with the focused ion beam as indicated by an arrow A1, thereby forming an irradiation mark on the sample 30. FIG. The diameter of the irradiation trace is, for example, less than 0.1 μm. In many cases, the optical axis of the photodetector 9 indicated by the arrow A2 is shifted from the optical axis of the light source 6 at this point.

Subsequently, as shown in FIG. 5, the control unit 11 controls the stage 7 to apply a voltage to the sample 30 to cause the irradiation mark formed on the sample 30 to emit light, and the light emission is detected by the photodetector 9. detected by Then, the control unit 11 controls the moving unit 10 to move the light detection unit 9 as indicated by an arrow A3, thereby aligning the optical axis of the light detection unit 9 with the light-emitting portion. Specifically, the control unit 11 causes the moving unit 10 to slightly move the light detection unit 9 so that the light-emitted portion is detected at the center of the angle of view of the light detection unit 9, and the light-emitted portion and the light detection are detected. The deviation from the optical axis of the portion 9 is reduced to about ±0.1 μm.

Subsequently, the semiconductor device 20 is placed on the stage 7 as shown in FIG. Then, the control unit 11 controls the stage 7 to apply a voltage to the semiconductor device 20 so that the defective portion of the semiconductor device 20 emits light. In order to detect light emission, part of the back electrode 23 is removed, and part of the back surface of the substrate 21 is exposed.

After that, the control unit 11 controls the stage 7 to move the semiconductor device 20 so that the light-emitting portion is aligned with the optical axis of the light detection unit 9 . Specifically, the control unit 11 finely moves the semiconductor device 20 by the stage 7 so that the light-emitting portion is detected at the center of the angle of view of the light detecting unit 9, and the light-emitting portion and the light detecting unit 9 are detected. The deviation from the optical axis of is reduced to about ±0.1 μm.

By aligning the light-emitting portion of the semiconductor device 20 with the optical axis of the photodetector 9 in this manner, the defective portion of the semiconductor device 20 is aligned with the optical axis of the light source 6 . Then, a portion of the semiconductor device 20 corresponding to the optical axis of the light source 6 is cut out, and a section of the cut portion is observed by an observation device (not shown) provided inside or outside the inspection apparatus 1 . Since the photodetector 9 slightly moves due to thermal vibration, expansion, etc., the adjustment of the optical axis of the photodetector 9 using the sample 30 is performed for each inspection.

As described above, in the present embodiment, the light detection unit 9 is moved to align the optical axis of the light detection unit 9 with the irradiation mark of the sample 30, and the semiconductor device 20 is moved to detect the portion emitting light. Align with the optical axis of part 9. As a result, the defective portion can be aligned with high accuracy with respect to the optical axis of the light source 6, and the position of the defective portion can be detected with high accuracy. This makes it possible to accurately cut out and observe the defective portion.

In addition, since the semiconductor device 20 to be inspected is not irradiated with the focused ion beam, it is possible to suppress the characteristic change due to the formation of the irradiation mark. Moreover, even if the semiconductor device 20 does not have a characteristic pattern, the defective portion can be detected.

(Other embodiments)
It should be noted that the present invention is not limited to the above-described embodiments, and can be appropriately modified within the scope of the claims. Further, in the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except when explicitly stated as being essential or when they are considered to be clearly essential in principle. . In addition, in the above embodiments, when numerical values such as the number, numerical value, amount, range, etc. of the constituent elements of the embodiment are mentioned, when it is explicitly stated that they are essential, and when they are clearly limited to a specific number in principle It is not limited to that particular number, except when

A scanning transmission electron microscope may be placed in the first chamber 4 to observe the defective portion.

The photodetector 9 may be configured by a laser microscope. In the captured image of the semiconductor device 20, a defective portion such as a deformed trench appears black due to scattering of light. The type of defect may be estimated by

6 light source 7 stage 9 photodetector 10 moving unit 20 semiconductor device 30 sample

Claims (3)

An inspection device for a semiconductor device,
a light source (6) that irradiates a sample (30) with light to form an irradiation mark on the sample;
a voltage application unit (7) for causing the irradiation mark to emit light by applying a voltage to the sample, and for causing a defective portion of the inspection object to emit light by applying a voltage to the inspection object (20);
a first moving unit (7) for moving the inspection target;
a photodetector (9) for detecting light emission from the irradiation mark;
A semiconductor device inspection apparatus, comprising: a second moving part (10) for moving the photodetector. A control unit (11) that controls the light source, the voltage application unit, the first moving unit, and the second moving unit,
The control unit
forming an irradiation mark on the sample by controlling the light source to irradiate the sample with light;
causing the irradiation mark to emit light by controlling the voltage applying unit to apply a voltage to the sample;
aligning the optical axis of the light detection unit with the light-emitting portion by controlling the second moving unit to move the light detection unit;
causing the defective portion to emit light by controlling the voltage applying unit to apply a voltage to the inspection object;
2. The semiconductor device inspection apparatus according to claim 1, wherein the light-emitting portion is aligned with the optical axis of the photodetector by controlling the first moving unit to move the inspection object. A semiconductor device inspection method comprising:
forming an irradiation mark on a sample (30) by irradiating the sample with light;
causing the irradiation mark to emit light by applying a voltage to the sample;
Aligning the optical axis of the light detection unit with the light emitting portion by moving the light detection unit (9);
Applying a voltage to the inspection object (20) to cause the defective portion to emit light;
A method of inspecting a semiconductor device, comprising: aligning the light-emitting portion with the optical axis of the photodetector by moving the inspection object.

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