JP7600898B2 - Semiconductor device inspection device and inspection method - Google Patents

Description

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

Conventionally, defect analysis of semiconductor devices is performed, for example, in the following way. First, a voltage is applied to cause defective areas on a semiconductor substrate to emit light, and the light-emitting points are detected by observing the back side of the substrate with an emission microscope. Next, etching is performed with a focused ion beam from the front side of the substrate, and the light-emitting points are roughly marked.

Then, the semiconductor device is observed again 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 is performed using a focused ion beam, and a marking is made at a position closer to the light emitting point. Based on this marking, the defective area is cut out, and the cross section is observed, etc.

In this conventional method, observation with an emission microscope and etching with a focused ion beam are performed in separate devices. This means that there is a tendency for the position of the light-emitting point and the marking to be misaligned, making it difficult to isolate defective areas with high precision.

For example, Patent Document 1 proposes the following inspection method for semiconductor devices such as power devices that have a characteristic pattern on the periphery. First, an electron beam and a laser beam are irradiated onto the front and back surfaces of the sample, 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 using a deflector to align the optical axis of the electron beam with the optical axis of the laser beam. Then, defective areas are detected, and the amount of shift of the detected defective areas from the optical axis of the laser beam is calculated. After that, the electron beam is scanned according to this amount of shift, and a mark is made near the defective areas.

JP 2014-143348 A

In the method described in Patent Document 1, the misalignment between the optical axis of the electron beam and the optical axis of the laser beam is corrected by deflecting the electron beam. However, there are cases where the optical axis of the laser beam and the optical axis of the electron beam are so greatly misaligned that it cannot be corrected by deflecting the electron beam alone. In such cases, it is difficult to detect the position of the defective area with high accuracy.

In view of the above, the present invention aims to provide an inspection device and inspection method for semiconductor devices that can detect the location of defects with high accuracy.

In order to achieve the above object, the invention described in claim 1 is an inspection device for semiconductor devices, comprising a light source (6) that forms an irradiation mark on a sample (30) by irradiating the sample with light, a voltage application unit (7) that causes the irradiation mark to emit light by applying a voltage to the sample and causes defective parts of the inspection object to emit light by applying a voltage to the inspection object (20), a first movement unit (7) that moves the inspection object, a light detection unit (9) that detects the emission from the irradiation mark, and a second movement unit (10) that moves the light detection unit , wherein the second movement unit moves the light detection unit so as to align the optical axis of the light detection unit with the emitted irradiation mark, and the first movement unit moves the inspection object so as to align the emitted defective part with the optical axis of the light detection unit .

By moving the light detection unit to align its optical axis with the irradiation mark on the sample, and by moving the inspection object to align the emitting part with the optical axis of the light detection unit, it is possible to align the defective part with the optical axis of the light source with high precision. Therefore, the position of the defective part can be detected with high precision.

In addition, the invention described in claim 4 is a method for inspecting a semiconductor device, 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 optical detection unit (9) with the emitted part by moving the optical detection unit; causing a defective part to emit light by applying a voltage to an object to be inspected (20); and aligning the emitted part with the optical axis of the optical detection unit by moving the object to be inspected.

By moving the light detection unit to align its optical axis with the irradiation mark on the sample, and by moving the inspection object to align the emitting part with the optical axis of the light detection unit, it is possible to align the defective part with the optical axis of the light source with high precision. Therefore, the position of the defective part can be detected with high precision.

The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below.

1 is a diagram showing a configuration of an inspection device according to a first embodiment; FIG. 1 is a cross-sectional view of a semiconductor device. FIG. FIG. 13 is a diagram showing how irradiation marks are formed on a sample. 13 is a diagram showing how the optical axis of the light detection unit is aligned with the irradiation mark. FIG. 1 is a diagram showing a state in which light from a defective portion of a semiconductor device is incident on a light detection unit;

The following describes embodiments of the present invention with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals.

First Embodiment
A first embodiment will be described. An inspection device 1 shown in Fig. 1 is an inspection device for a semiconductor device in which a power device or the like is formed, and is used for defect analysis of the semiconductor device. As shown in Fig. 1, the inspection device 1 includes a chamber 2. The internal space of the chamber 2 is divided into two by a partition wall 3. The 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. In other words, the first chamber 4 is reduced in pressure compared to the second chamber 5 by vacuuming. The first chamber 4 is equipped with a light source 6 and a stage 7.

The light source 6 irradiates the sample 30 (described later) with light, thereby forming an irradiation mark on the sample 30. The light source 6 includes an ion source that generates a Ga ion beam, an aperture, a focusing lens, an objective lens, etc., and is configured to irradiate the sample 30 with a focused ion beam in a spot.

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

The stage 7 has the 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 marks formed by the irradiation of light from the light source 6 to emit light. In addition, the stage 7 applies a voltage to the object to be inspected to cause defective parts of the object to emit light. The stage 7 corresponds to the voltage application unit.

The stage 7 also has a function of moving the inspection object held by it. Specifically, the direction perpendicular to the optical axis of the light source 6 is defined as the x direction, and the direction perpendicular to both the optical axis of the light source 6 and the x direction is defined as the y direction, and the stage 7 moves the inspection object held by it in the x direction and y direction. The stage 7 corresponds to a first moving unit.

The stage 7 is configured so that, when a voltage is applied, light generated from the sample 30 and the object to be inspected is transmitted to the second chamber 5. An opening is formed in the partition 3, and a vacuum window 8 is fitted into this opening. The light generated from the sample 30 and the object to be inspected is transmitted through the vacuum window 8 and enters the second chamber 5.

The second chamber 5 is equipped with a light detection unit 9. The light detection unit 9 detects light emission from irradiation marks formed on the sample 30 and light emission from defective parts of the inspection target. The light detection unit 9 is composed of, for example, an emission microscope.

The second chamber 5 is provided with a moving unit 10 that moves the light detection unit 9. The moving unit 10 is configured to slightly move the light detection unit 9 in the x and y directions. The moving unit 10 corresponds to the second moving unit.

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

The following describes the object to be inspected by the inspection device 1. Here, the inspection object is a power device such as a vertical MOS transistor with a trench electrode, and the case where deformation of the trench electrode is detected is described.

As shown in FIG. 2, the 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 electrode 23 formed on the back surface of the substrate 21.

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

The following describes a sample used to align the optical axis of the light detection unit 9 with the optical axis of the light source 6. 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 front electrode 32, and the back electrode 33 have the same configuration as the substrate 21, the front 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 removed except for a part so that the substrate 31 is irradiated with light from the light source 6 to form an irradiation mark, and light emitted from the irradiation mark is incident on the light detection unit 9, exposing the front and back surfaces of the substrate 31. For example, the inner periphery of the surface electrode 32 and the back electrode 33 is removed, and the outer periphery is left untouched, and a voltage is applied to this outer periphery from the stage 7.

The method of inspecting the semiconductor device 20 using the inspection device 1 will be described with reference to Figures 4 to 6. Note that the stage 7 and control unit 11 are not shown in Figures 4 to 6.

First, as shown in FIG. 4, the sample 30 is placed on the stage 7. Then, the control unit 11 controls the light source 6 to irradiate the sample 30 with a focused ion beam as shown by the arrow A1, thereby forming an irradiation mark on the sample 30. The diameter of the irradiation mark is set to, for example, less than 0.1 μm. In many cases, at this point, the optical axis of the light detection unit 9 shown by the arrow A2 is misaligned with the optical axis of the light source 6.

As shown in FIG. 5, the control unit 11 then controls the stage 7 to apply a voltage to the sample 30, causing the irradiation mark formed on the sample 30 to emit light, and the emitted light is detected by the light detection unit 9. The control unit 11 then controls the movement unit 10 to move the light detection unit 9 as shown by arrow A3, thereby aligning the optical axis of the light detection unit 9 with the emitted part. Specifically, the control unit 11 causes the movement unit 10 to slightly move the light detection unit 9 so that the emitted part is detected at the center of the angle of view of the light detection unit 9, thereby reducing the deviation between the emitted part and the optical axis of the light detection unit 9 to about ±0.1 μm.

Next, as shown in FIG. 6, the semiconductor device 20 is placed on the stage 7. The control unit 11 then controls the stage 7 to apply a voltage to the semiconductor device 20, causing the defective portion of the semiconductor device 20 to emit light. Note that in order to detect the emitted light, a portion of the back electrode 23 is removed, exposing a portion of the back surface of the substrate 21.

Then, the control unit 11 controls the stage 7 to move the semiconductor device 20, thereby aligning the light-emitting portion with the optical axis of the light detection unit 9. Specifically, the control unit 11 causes the stage 7 to slightly move the semiconductor device 20 so that the light-emitting portion is detected at the center of the angle of view of the light detection unit 9, thereby reducing the misalignment between the light-emitting portion and the optical axis of the light detection unit 9 to about ±0.1 μm.

By aligning the light-emitting portion of the semiconductor device 20 with the optical axis of the light detection unit 9 in this way, the defective portion of the semiconductor device 20 is aligned with the optical axis of the light source 6. Then, the portion of the semiconductor device 20 that corresponds to the optical axis of the light source 6 is cut out, and a cross section of the cut out portion is observed using an observation device (not shown) provided inside or outside the inspection device 1. Note that since the light detection unit 9 moves slightly due to thermal vibration, expansion, etc., the optical axis of the light detection unit 9 is adjusted using the sample 30 every time an inspection is performed.

As described above, in this embodiment, the light detection unit 9 is moved to align the optical axis of the light detection unit 9 with the irradiation mark on the sample 30, and the semiconductor device 20 is moved to align the emitting part with the optical axis of the light detection unit 9. This allows the defective part to be aligned with the optical axis of the light source 6 with high precision, and the position of the defective part can be detected with high precision. This makes it possible to precisely cut out and observe the defective part.

In addition, since no irradiation marks are formed by the focused ion beam on the semiconductor device 20 to be inspected, changes in characteristics due to the formation of irradiation marks can be suppressed. Furthermore, even if the semiconductor device 20 does not have a distinctive pattern, defective parts can be detected.

Other Embodiments
The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the claims. In addition, in the above-described embodiment, it goes without saying that the elements constituting the embodiment are not necessarily essential, except when they are specifically stated as essential or when they are clearly considered essential in principle. In addition, in the above-described embodiment, when the numbers, values, amounts, ranges, etc. of the components of the embodiment are mentioned, they are not limited to the specific numbers, except when they are specifically stated as essential or when they are clearly limited to a specific number in principle.

A scanning transmission electron microscope may be placed in the first chamber 4, and defects may be observed using this electron microscope.

The light detection unit 9 may be configured with a laser microscope. In the captured image of the semiconductor device 20, defective areas such as deformed trenches scatter light and appear black, so a color pattern corresponding to the type of defect may be created, and the type of defect may be estimated by comparing the captured image with this color pattern.

6 Light source 7 Stage 9 Light detection unit 10 Moving unit 20 Semiconductor device 30 Sample

Claims (4)

An inspection apparatus for a semiconductor device,
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 applies a voltage to the sample to cause the irradiation mark to emit light, and applies a voltage to an inspection object (20) to cause a defective portion of the inspection object to emit light;
A first moving unit (7) that moves the inspection object;
A light detection unit (9) for detecting light emitted from the irradiation mark;
A second moving unit (10) that moves the light detection unit ,
The second moving unit moves the light detection unit so as to align an optical axis of the light detection unit with the emitted irradiation mark,
The first moving unit moves the inspection object so as to align the emitted defective portion with the optical axis of the light detection unit . A control unit (11) for controlling the light source, the voltage application unit, the first movement unit, and the second movement unit,
The control unit is
forming an irradiation mark on the sample by irradiating the sample with light by controlling the light source;
The voltage application unit is controlled to apply a voltage to the sample, thereby causing the irradiation mark to emit light;
By controlling the second moving unit to move the light detection unit, the optical axis of the light detection unit is aligned with the light-emitting portion;
controlling the voltage application unit to apply a voltage to the inspection object to cause a defective portion to emit light;
2. The semiconductor device inspection apparatus according to claim 1, wherein the first moving unit is controlled to move the inspection object, thereby aligning the light-emitting portion with the optical axis of the light detection unit. An inspection apparatus for a semiconductor device,
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 applies a voltage to the sample to cause the irradiation mark to emit light, and applies a voltage to an inspection object (20) to cause a defective portion of the inspection object to emit light;
A first moving unit (7) that moves the inspection object;
A light detection unit (9) for detecting light emitted from the irradiation mark;
A second moving unit (10) that moves the light detection unit;
a control unit (11) that controls the light source, the voltage application unit, the first movement unit, and the second movement unit,
The control unit is
forming an irradiation mark on the sample by irradiating the sample with light by controlling the light source;
The voltage application unit is controlled to apply a voltage to the sample, thereby causing the irradiation mark to emit light;
By controlling the second moving unit to move the light detection unit, the optical axis of the light detection unit is aligned with the light-emitting portion;
controlling the voltage application unit to apply a voltage to the inspection object to cause a defective portion to emit light;
An inspection apparatus for semiconductor devices , which controls the first moving unit to move the inspection object, thereby aligning the light-emitting portion with the optical axis of the light detection unit . A method for inspecting a semiconductor device, comprising the steps of:
forming an irradiation mark on a sample (30) by irradiating the sample with light;
applying a voltage to the sample to cause the irradiation mark to emit light;
moving the light detection unit (9) so that the optical axis of the light detection unit is aligned with the part that emits light;
Applying a voltage to the inspection object (20) to cause a defective portion to emit light;
and moving the inspection object to align the emitted light portion with the optical axis of the light detection unit.

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