JP2996239B1 - Method and apparatus for inspecting contact opening in semiconductor device - Google Patents

Abstract

An object of the present invention is to provide a method and an apparatus for inspecting a contact opening in a semiconductor device which can be inspected stably at a low cost without destruction of a sample, with a short inspection time. A step of supplying an electrolytic solution to a surface of an interlayer insulating film in which a contact hole is formed;
Is electrically connected to the electrolytic solution 2, and the negative electrode plate 7 is electrically connected to the semiconductor substrate 1 underlying the interlayer insulating film 9 so that the electrode plate 6
Energizing between the electrode and the electrode plate, irradiating the contact hole with light while scanning spot-like light on the surface of the interlayer insulating film 9 through the electrolytic solution 2, and generating by the irradiation of the light. And detecting the generated electric charge as a current through the electrolytic solution 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for inspecting a contact opening in a semiconductor device, and more particularly to a method and an apparatus for inspecting a contact opening in a semiconductor device which can be easily and quickly inspected.

[0002]

2. Description of the Related Art Conventionally, a contact hole (hereinafter referred to as a contact) formed in an interlayer insulating film on a semiconductor substrate.
Because of their small diameter and high aspect ratio (the ratio of depth to contact diameter is large), the contact is completely open in optical microscope inspection and scanning electron microscope inspection, which are usually performed as nondestructive inspections. You can't check if you're doing it. For this reason, the cross section of the semiconductor device is usually exposed by cleavage or the like, and the opening inspection is performed by observing the cross section.

However, since the above-described inspection method is a destructive inspection, it is necessary to evaluate many points and to obtain a distribution in a substrate surface, which requires a lot of time for the evaluation. For this reason, usually, only a few points are inspected.

In order to solve the problem of the above-described inspection method, an inspection method using a defect inspection apparatus using a scanning electron microscope has been proposed by Pr.
receiveds of the sixth In
international Symposium on
SemiconductorManufacturin
g P-99, (1997). FIG. 4 is a schematic view showing a contact opening inspection method in a semiconductor device by a conventional defect inspection apparatus using a scanning electron microscope.

As shown in FIG. 4, a semiconductor device 118 includes a substrate 101 and an interlayer insulating film 109 formed on the surface thereof. In this interlayer insulating film 109, an opening contact 116 which is completely opened and the substrate 101 is exposed.
In addition, an unopened contact 117 that is not opened and the substrate 101 is not exposed is formed.

The inspection method described in this paper scans a semiconductor device 118 with a primary electron beam and generates secondary electrons 115 generated from a contact opening (when electrons irradiated from an electron microscope collide with a solid surface). , Low-energy electrons newly generated from the substance). When the contact is not open, the amount of secondary electrons generated increases. Therefore, by mapping this amount of secondary electrons, the opening state of the contact can be identified as an image.

[0007]

However, the conventional method for inspecting a contact opening in a semiconductor device by a destructive inspection has a disadvantage that the semiconductor device needs to be destroyed as a sample and the inspection requires a lot of time. is there.

In a conventional contact opening inspection method for a semiconductor device using a defect inspection apparatus using a scanning electron microscope, a primary electron beam is scanned at a high speed to detect the amount of secondary electrons generated thereby. The need for a high-luminance and stable electron source necessitates a complicated structure of the inspection apparatus, which causes a problem that the inspection apparatus is expensive.

Further, the contact is charged up by the irradiation of the primary electron beam (a phenomenon that charges are accumulated in the insulator), and the amount of the charge-up changes depending on the surface condition of the sample and the irradiation condition of the primary electron beam. There is a problem that inspection stability is poor.

The present invention has been made in view of the above problems, and does not destroy a sample, shortens an inspection time,
It is an object of the present invention to provide a method and an apparatus for inspecting a contact opening in a semiconductor device which can be inspected stably at low cost.

[0011]

According to a method for inspecting a contact opening in a semiconductor device according to the present invention, a contact hole of a semiconductor device is irradiated with spot-like light, and charges generated by the light irradiation are passed through an electrolyte. The opening state of the contact hole is inspected by detecting the current as a current and measuring the magnitude of the current.

A method for inspecting a contact opening in a semiconductor device according to the present invention includes a step of supplying an electrolytic solution to a surface of an interlayer insulating film in which a contact hole is formed, a step of applying an electric current to the electrolytic solution, and Irradiating the contact hole with light while scanning spot-like light on the surface of the interlayer insulating film; and detecting a charge generated by the irradiation of the light as a current through the electrolytic solution. It is characterized by.

Further, the step of energizing the electrolytic solution includes electrically connecting a positive electrode to the electrolytic solution, electrically connecting a negative electrode to a semiconductor substrate underlying the interlayer insulating film, and connecting the positive electrode to the negative electrode. Electric current may be applied between the electrodes.

In the present invention, when spot-shaped light is incident on the opened contact hole, a charge is generated because the semiconductor substrate underlying the interlayer insulating film serves as a light irradiation surface. On the other hand, when light enters a contact hole that has not been opened, the interlayer insulating film serves as a light irradiation surface, and thus charge-up (accumulation of charges due to the incident light).
Almost no charge is generated. Therefore, when this charge is detected as a current through the electrolytic solution and the magnitude of this current is measured, light is incident on the open contact hole and light is incident on the unopened contact hole. The measured current value differs between the two cases. Therefore, by determining this current value, the opening state of the contact hole can be easily and quickly inspected.

Further, the electrolytic solution is partitioned by a partition member into a first electrolytic solution and a second electrolytic solution, and the step of energizing the electrolytic solution includes electrically connecting a first electrode to the first electrolytic solution. And the second electrode may be electrically connected to the second electrolyte, and the polarity of the first electrode and the second electrode may be switched by a changeover switch. In this case, since the first and second electrodes are not brought into contact with the peripheral portion of the semiconductor substrate, it is possible to prevent occurrence of metal contamination during inspection.

A contact opening inspecting apparatus in a semiconductor device according to the present invention comprises: an electrolytic solution supply means for supplying an electrolytic solution to a surface of an interlayer insulating film in which a contact hole is formed; a DC power supply; A first electrode connected to a positive electrode of the DC power supply; a second electrode electrically connected to a semiconductor substrate underlying the interlayer insulating film and connected to a negative electrode of the DC power supply; And a current measuring means for measuring a current flowing between the second electrodes, and a light irradiation device for irradiating the contact hole with spot light.

Further, the contact opening inspecting apparatus in the semiconductor device according to the present invention comprises: an electrolytic solution supply means for supplying an electrolytic solution to the surface of the interlayer insulating film in which the contact hole is formed; A partition member that separates into an electrolyte solution, a first electrode immersed in the first electrolyte solution,
A second electrode immersed in the second electrolyte;
A DC power supply for applying a DC voltage between the first and second electrodes, a changeover switch for switching the polarity of the first and second electrodes, and a current measurement for measuring a current between the first and second electrodes Means, and a light irradiation device for irradiating the contact hole with spot light.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method and an apparatus for inspecting a contact opening in a semiconductor device according to a first embodiment of the present invention will be specifically described with reference to the accompanying drawings.
FIG. 1 is a longitudinal sectional view showing a contact opening inspection method and apparatus according to a first embodiment of the present invention.

As shown in FIG. 1, a semiconductor device 18 is provided with a substrate 1 and an interlayer insulating film 9 formed on the surface thereof. In this interlayer insulating film 9, an opening contact 16 which is completely opened and the substrate 1 is exposed, and an unopened contact 17 which is not opened and the substrate 1 is not exposed are formed by etching.

The frame-shaped member 4 is provided on the surface of the interlayer insulating film 9 in the semiconductor device 18 having the above-described structure, and the frame-shaped member 4 is provided upright through the seal 12. This frame-shaped member 4
Has a cylindrical shape, and a space S surrounded by the semiconductor device 18 and the frame-shaped member 4 has, for example, 1%
The electrolyte 2 made of an acetic acid solution is filled. On the inner wall of the frame-shaped member 4, a cylindrical electrode plate 6 provided so as to be inscribed in the inner wall is provided soaked in the electrolytic solution 2.
An electrode plate 7 is electrically connected to the ohmic electrode on the lower surface of the substrate 1. The electrode plate 6 is connected to a positive electrode of the DC power supply 5 via a DC meter 10, and the electrode plate 7 is connected to a negative electrode of the DC power supply 5.

A window member 3 made of a light transmitting material is provided so as to cover the opening of the frame member 4. Therefore, when the inspection apparatus of the present embodiment is tilted, the electrolytic solution 2 is prevented from spilling from the upper end of the window frame member 4. Further, the frame-shaped member 4 is provided with a supply pipe (not shown) for supplying the electrolytic solution 2 into the space S by a pump (not shown).

Further, a light irradiating device 8 which is separately supported above the frame-shaped member 4 and irradiates the semiconductor device 18 with scanning a small spot-like light passing through the window member 3 and the electrolytic solution 2 while scanning is arranged. ing. The light irradiation device 8 includes, for example, a light irradiation head including a white lamp, a condenser lens, and a relay lens, and scans light in one direction on the semiconductor device 18 by reflecting light collected from the light irradiation head. And a polygon mirror (both not shown). The semiconductor device 18 is mounted on a carriage (not shown) movable in a direction perpendicular to the scanning direction of the light irradiation device 8. Therefore, light can be scanned over the entire semiconductor device 18 by the light scanning of the light irradiation device 8 and the movement of the carriage.

When scanning with white light, a photoexcitation current can be obtained efficiently, but the light irradiation head is expensive because a light-collecting mechanism is required. Therefore, an inexpensive commercially available helium-neon gas laser oscillator may be used.

An inspection method using the contact opening inspection apparatus according to the first embodiment of the present invention will be described below. First, the semiconductor device 18 is mounted on a carriage (not shown). Then, the frame member 4, the window member 3, the electrode plates 6 and 7, and the like are arranged so as to have the above-described configuration. Thereafter, the pump is driven to supply the electrolyte 2 from the supply pipe.
To fill the space S.

Next, a DC voltage is applied between the electrode plate 6 and the electrode plate 7 so that the electrode plate 6 becomes a positive electrode. That is, a DC voltage is applied between the substrate 1 and the electrolyte 2. At this time, the ammeter 10 measures a constant current value.

Thereafter, the carriage and the light irradiating device 8 are driven, and the semiconductor device 18 is irradiated with the spot-like light while scanning through the window member 3 and the electrolytic solution 2. When the irradiation light is incident on the opening contact 16, the irradiation light is irradiated on the substrate 1 which is a semiconductor, and electric charges are generated. Since this charge moves to the electrode plate 6 which is a positive electrode through the electrolyte solution 2,
The current value measured by the ammeter 10 increases. When the irradiation light is incident on the unopened contact 17,
Since the irradiation light is applied to the interlayer insulating film 9 which is an insulator,
Charge-up (a state where electric charge is accumulated in the insulator)
Since almost no electric charge is generated, the current value measured by the ammeter 10 is smaller than when the irradiation light is incident on the opening contact 16. The magnitude of the current value when the irradiation light is incident on the aperture contact 16 can be viewed as a pulse-like current waveform by observing with an oscilloscope.

As described above, in this embodiment, the light beam is applied to the semiconductor device 18 through the window member 3 and the electrolytic solution 2 so as to generate photo-excited charges on the substrate 1 underlying the interlayer insulating film 9. Is scanned, and the charge generated from the contact formed in the interlayer insulating film 9 is detected as the magnitude of the current using an ammeter, so that the presence or absence of the opening of the contact can be easily inspected.

Since the substance which comes into contact with the interlayer insulating film 9 and the semiconductor layer is the electrolytic solution 2 and the irradiation light, the inspection can be performed without contaminating and damaging the interlayer insulating film 9 and the semiconductor layer.

Further, since the charge generated from the contact can be immediately measured by the ammeter 10 as the magnitude of the current, the inspection can be performed very quickly.

Next, a method and an apparatus for inspecting a contact opening in a semiconductor device according to a second embodiment of the present invention will be described. FIGS. 2 and 3 show a contact opening inspection method and apparatus according to a second embodiment of the present invention.
2 is a longitudinal sectional view, and FIG. 3 is a transverse sectional view.

As shown in FIGS. 2 and 3, the inspection apparatus according to the second embodiment is different from the inspection apparatus according to the first embodiment in that:
A partition plate 11 in the form of a rectangular plate having the same height as the frame member 4 is water-tightly mounted on the surface of the interlayer insulating film 9 via a seal 20 so as to divide the space S and the electrode plate 6 (see FIG. 1) into two. Has been established. As described above, the partition S divides the space S into two such that one is the space T ₁ and the other is the space T ₂ . Further, the electrolyte solution 13a in the space T _1, the electrolyte in the space T ₂ 13
b is satisfied.

The semi-cylindrical electrode plates 19a electrolytic solution as the inner wall of the frame-shaped member 4 in the space T ₁ is inscribed in the inner wall 1
Provided is immersed in 3a, and the electrode plates 19b of the semi-cylindrical is provided is dipped in the electrolyte solution 13b to the inner wall of the frame-shaped member 4 in the space T ₂ is inscribed in the inside wall. The electrode plate 19a is connected to the DC power supply 5 via the DC meter 10, and the electrode plate 19b is directly connected to the DC power supply 5. In the electrode plates 19a and 19b, the polarity of the voltage applied from the DC power supply 5 is inverted by an automatic changeover switch (not shown). Also, the first
Unlike the embodiment, no electrode plate is provided on the lower surface of the substrate 1. The other configuration is the same as that of the first embodiment, and the description is omitted.

An inspection method using the contact opening inspection apparatus according to the second embodiment of the present invention will be described below. First, the semiconductor device 1 is placed on the carriage.
8 is placed. Then, the frame member 4 is placed on the interlayer insulating film 9 via the seal 12, and the partition plate 11 is placed via the seal 20. Thereafter, meet each electrolyte 13a and 13b in the space T ₁ and space T _2, it is placed by dipping the electrode plate 19a and the electrode plate 19b, respectively electrolyte 13a and 13b. Further, the window member 3, the ammeter 10, the DC power supply 5, and the like are arranged so as to have the above-described configuration.

Next, a DC voltage is applied to the electrolytes 13a and 13b. Then, the carriage and the light irradiating device 8 are driven to irradiate the semiconductor device 18 with the spot-like light while scanning through the window member 3 and the electrolytic solution 13a or 13b. When the electrolyte 13a is irradiated with light,
When a positive voltage is applied to the electrode plate 19a, a negative voltage is applied to the electrode plate 19b, and the electrolyte 13b is irradiated with light, a positive voltage is applied to the electrode plate 19b, and a negative voltage is applied to the electrode plate 19a. The polarity of the applied voltage is inverted by the automatic changeover switch. Therefore, the electrode plate immersed in the electrolyte irradiated with light is a positive electrode.

For this reason, when the irradiation light is incident on the opening contact 16, the irradiation light is irradiated on the semiconductor substrate 1 to generate electric charge. This charge is stored in the electrolyte 13a or 13
Since the electrode moves to the electrode plate 19a or 19b, which is the positive electrode, through b, the current value measured by the ammeter 10 increases. When the irradiation light is incident on the unopened contact 17, the irradiation light is applied to the interlayer insulating film 9 as an insulator, so that the charge is increased (a state in which charges are accumulated in the insulator) and almost no charge is generated. Not to use the ammeter 10
The current value measured by means of
6 is smaller than that in the case where the light is incident on. The magnitude of the current value when the irradiation light is incident on the aperture contact 16 can be viewed as a pulse-like current waveform by observing with an oscilloscope.

As described above, in the second embodiment according to the present invention, since the metal electrode is not brought into contact with the peripheral portion of the substrate 1, it is possible to prevent the occurrence of metal contamination at the time of inspection.

[0037]

EXAMPLES The results of tests performed to demonstrate the effects of the present invention will be specifically described below.

First, the contact opening was inspected using the inspection apparatus shown in FIG. In this semiconductor device 18, after depositing an interlayer insulating film 9 having a thickness of 500 nm on the semiconductor substrate 1, a contact having a diameter of 300 nm was opened, and a 1% acetic acid solution was used as the electrolytic solution 2. The electrolyte 2
The voltage of 5 V was applied from the DC power supply 5 via the DC meter 10 with the electrode plate 6 immersed in the battery positive and the electrode plate 7 negative. Irradiation was performed while scanning a laser beam having a spot diameter of 1 mm and a wavelength of 670 nm by the light irradiation device 8. Then, the current flowing in the electrolyte solution 2 was measured by the ammeter 10 while scanning with light, and the amount of current was simultaneously observed as the luminance of the display using a display such as an oscillograph.

When the semiconductor device in which the contact was actually formed according to the present embodiment was inspected, a current value of 204 μA was measured at the contact opening and a current value of 20 μA was measured at the unopened portion. This makes it possible to detect the presence of the unopened portion.

Next, the contact openings were inspected using the inspection apparatus shown in FIGS. Electrolytes 13a and 13b
Uses a 1% acetic acid solution, corrects the electrolytic plate 19a immersed in the electrolytic solution 13a, corrects the electrolytic plate 19a immersed in the electrolytic solution 13b.
A voltage of 5 V was applied from the DC power supply 5 through the DC meter 10 with b being negative. In addition, a laser beam having a spot diameter of 1 mm and a wavelength of 670 nm is applied by the light irradiation device 8 to the electrolyte 1.
Irradiation was performed on the 3a side, and scanning was performed. The current flowing through the electrolyte 13a was measured by the ammeter 10 while scanning with light. When irradiating the electrolytic solution 13b side, the electrolytic plate 19a is switched to the negative electrode and the electrolytic plate 19b by an automatic changeover switch.
The polarity was switched so that became a positive electrode, and the measurement was performed similarly.

According to the present embodiment, when the opening state of the semiconductor device having the contact formed thereon was evaluated, the same measurement results as in the first embodiment were obtained. Further, in the first embodiment, the amount of heavy metal contamination of the substrate 1 is 10 ¹¹ atoms / c.
whereas a m ² approximately, in the second embodiment, the heavy metal contamination of the substrate 1 is 10 ¹⁰ atoms / cm ² or less, were found to be heavy metal contamination amount is small.

[0042]

As described in detail above, according to the present invention,
The current value measured when light is incident on the open contact hole and the current value measured when the light is incident on the unopened contact hole are different. Therefore, by determining this current value, the contact hole is measured. Can be easily and quickly inspected.

Further, the electrolytic solution is partitioned by a partition member into first and second electrolytic solutions, and the step of applying a current to the electrolytic solution comprises electrically connecting a first electrode to the first electrolytic solution. And the second electrode is electrically connected to the second electrolytic solution, and the polarity of the first electrode and the second electrode is switched by a changeover switch. Since the first and second electrodes are not brought into contact with each other, the occurrence of metal contamination during inspection can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a contact opening inspection method and apparatus according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a contact opening inspection method and apparatus according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a contact opening inspection method and apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic view showing a contact opening inspection method in a semiconductor device by a conventional defect inspection apparatus using a scanning electron microscope.

[Explanation of symbols]

 1, 101; substrate 2, 13a, 13b; electrolyte 3, window member 4, frame member 5, DC power supply 6, 7, 19a, 19b; electrode plate 8, light irradiation device 9, 109; Ammeter 11; Partition plates 12, 20; Seals 16, 116; Open contacts 17, 117; Non-open contacts 18, 118; Semiconductor device 114; Primary electron beam 115; Secondary electron beam

Claims (6)

(57) [Claims] 1. A method according to claim 1, further comprising irradiating a contact hole of the semiconductor device with spot-shaped light, detecting a charge generated by the irradiation of the light as a current through an electrolytic solution, and measuring a magnitude of the current. A method for inspecting a contact opening in a semiconductor device, comprising: inspecting an opening state of a contact hole. A step of supplying an electrolytic solution to the surface of the interlayer insulating film in which the contact hole is formed; a step of applying an electric current to the electrolytic solution; and a step of applying spot-like light to the interlayer insulating film via the electrolytic solution. A method of irradiating the contact hole with light while scanning the surface, and a step of detecting a charge generated by the light irradiation as a current through the electrolytic solution, wherein the method includes the steps of: . 3. The step of applying a current to the electrolytic solution includes electrically connecting a positive electrode to the electrolytic solution, electrically connecting a negative electrode to a semiconductor substrate underlying the interlayer insulating film, and connecting the positive electrode to the negative electrode. 3. An electric current is supplied between the electrode and the electrode.
3. A contact opening inspection method in a semiconductor device according to claim 1. 4. The method according to claim 1, wherein the electrolytic solution is partitioned into a first and a second electrolytic solution by a partition member, and the step of energizing the electrolytic solution includes electrically connecting a first electrode to the first electrolytic solution. The second electrode is electrically connected to the second electrolyte, and the polarity of the first electrode and the second electrode is switched by a changeover switch. 3. A method for inspecting a contact opening in a semiconductor device according to item 2. 5. An electrolytic solution supply means for supplying an electrolytic solution to a surface of an interlayer insulating film in which a contact hole is formed, a DC power supply, and a first electrode immersed in the electrolytic solution and connected to a positive electrode of the DC power supply. A current flowing between the first electrode and the second electrode, and a second electrode electrically connected to the semiconductor substrate underlying the interlayer insulating film and connected to the negative electrode of the DC power supply are measured. A contact opening inspection device for a semiconductor device, comprising: a current measuring means; and a light irradiation device for irradiating the contact hole with spot light. 6. An electrolytic solution supply means for supplying an electrolytic solution to a surface of an interlayer insulating film having a contact hole formed therein, a partition member for separating the electrolytic solution into first and second electrolytic solutions, A first electrode immersed in the electrolyte, a second electrode immersed in the second electrolyte, a DC power supply for applying a DC voltage between the first and second electrodes, A changeover switch that switches the polarity of the first electrode and the second electrode,
A contact opening inspection device for a semiconductor device, comprising: a current measuring means for measuring a current between the first and second electrodes; and a light irradiation device for irradiating the contact hole with spot light.