JP3585469B2 - Coverage inspection method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device inspection method, and more particularly to a coverage inspection of a metal film formed in a contact hole.
[0002]
[Prior art]
In semiconductor devices of the 130 nm generation or later, Cu having lower resistance than Al is used as a wiring material. An electrolytic plating method is used as a method for forming a Cu wiring.
When a contact portion made of Cu is formed using this electroplating method, it is strongly affected by the pattern shape and the coverage of the PVD-Cu film formed as a base. In particular, when the coverage of the PVD-Cu film is poor, even if the electrolytic plating is performed, Cu does not grow, and defects (vacancies) are generated in the Cu film.
Conventionally, the coverage of a PVD-Cu film has been inspected by cutting out a pattern cross section by a manual operation and observing the pattern cross section by SEM.
[0003]
[Problems to be solved by the invention]
However, in the above-described conventional inspection, there is a problem that the number of patterns to be inspected is limited because it is necessary to manually cut out the pattern cross sections for all the patterns to be inspected. In addition, there is a problem that it takes time (time) until an inspection result by the SEM is obtained.
Further, since the conventional coverage inspection using the SEM is a destructive inspection, it cannot be performed on a product wafer, and a test wafer must be separately prepared. For this reason, there has been a problem that the manufacturing cost increases.
[0004]
The present invention has been made in order to solve the above-mentioned conventional problems, and has as its object to provide an inspection method for non-destructively inspecting the coverage of a metal film formed on an inner wall of a contact hole.
[0005]
[Means for solving the problem]
The coverage inspection method according to the present invention is a method for inspecting the coverage of a metal film formed on an inner wall of a contact hole using a laser irradiation type film thickness measuring device ,
Irradiating a laser beam to a predetermined region in which a plurality of the contact holes are formed,
Measuring the intensity of the laser light reflected in the predetermined area, and inspecting the coverage of the metal film,
It is characterized by including.
[0006]
Oite the coverage test how according to the present invention,
The predetermined area, the opening ratio of the contact hole is suitably a region of 25% or more.
[0007]
Oite the coverage test how according to the present invention,
It is preferable that the diameter of the contact hole is 0.23 μm or more.
[0008]
Oite the coverage test how according to the present invention,
Wherein the predetermined region, it is preferable that a laser spot diameter 1.5Myuemu～2.5Myuemu.
[0010]
Oite the coverage test how according to the present invention,
The metal film is, PVD-Cu film, Ta film, Ti film, TaN film, it is preferable to include at least one of TiN film.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts have the same reference characters allotted, and description thereof may be simplified or omitted.
[0012]
Embodiment 1 FIG.
FIG. 1 is a conceptual diagram for explaining a laser irradiation type film thickness measuring device used for coverage measurement in the first embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a first laser light source, 2a to 2c denote beam splitters, 3 denotes a second laser light source, 4 denotes a detection unit, 5 denotes a display unit, 6 denotes an objective lens, and 7 denotes a wafer as a substrate. Is shown. A plurality of contact holes are formed in the wafer 7, and a PVD-Cu film as a metal film is formed on the inner wall of each contact hole.
[0013]
Here, the first laser light source 1 irradiates a laser beam to heat a metal film formed on the substrate 7. The second laser light source 2 irradiates the heated metal film with laser light for measurement. Further, the measuring section 4 measures the intensity of the laser light reflected by the metal film.
The first embodiment is characterized in that the laser irradiation type film thickness measuring device is used for coverage inspection of a metal film (PVD-Cu film) formed on the inner wall of a contact hole.
[0014]
FIG. 2 is a diagram showing a relationship between a laser spot and a contact hole in the first embodiment.
2, reference numeral 30 denotes a laser spot (laser irradiation area) irradiated with laser light from the second laser light source 3 (see FIG. 1), 70 denotes a contact hole formed on the wafer 7, and A denotes a laser spot. Reference numeral 30 denotes the diameter of the contact hole 70, and B denotes the diameter of the contact hole 70.
Here, the diameter A of the laser spot 30 is, for example, 1.5 μm to 2.5 μm.
In the first embodiment, the coverage measurement method of the present invention is applied to a contact hole 70 having a diameter B of 0.23 μm or more.
Although details will be described later, the present invention is effective when the ratio of the area of all contact holes 70 to the area of laser spot 30 irradiated with laser light (hereinafter, referred to as “hole opening ratio”) is 25% or more. is there.
[0015]
FIG. 3 is a micrograph showing a cross section of a sample in which the coverage of the PVD-Cu film is different in the first embodiment.
With reference to FIG. 3, three samples for performing a coverage inspection using the laser irradiation type film thickness measuring device will be described. The three samples are a sample with poor coverage of the PVD-Cu film formed on the inner wall of the contact hole, a sample with normal coverage, and a sample with good coverage.
[0016]
The sample having poor coverage was obtained by forming a Cu film by sputtering in a contact hole at a high temperature without performing Ar sputtering pretreatment (see “Slot 13” in the figure).
The sample having normal coverage is obtained by forming a Cu film by sputtering in a contact hole at a low temperature without performing Ar sputtering pretreatment (see “Slot 12” in the figure).
The sample having good coverage is a sample in which a Cu film is formed in the contact hole by sputtering at a low temperature by performing Ar sputtering pretreatment (see “Slot 14” in the figure).
Here, the Ar pre-sputtering process is a process in which the opening of the contact hole is widened using Ar plasma so that sputtered particles can easily enter the contact hole. The low temperature and high temperature during sputtering refer to the temperature of the stage that holds the wafer. The low temperature is, for example, -40C to -20C, and the high temperature is, for example, room temperature. In general, when the temperature of the stage is high, aggregation of the Cu film is likely to occur, resulting in poor coverage.
FIG. 3 shows a contact hole having a diameter B of 0.23 μm and a depth of 1.0 μm. Each sample is formed with contact holes having diameters of 0.30 μm and 0.35 μm in addition to the contact holes having a diameter B of 0.23 μm (not shown). Furthermore, metal films are formed on the inner walls of these contact holes.
[0017]
In the above-mentioned laser irradiation type film thickness measuring device, the coverage inspection of the metal film formed on the inner wall of the contact hole of the above-mentioned sample was performed. Specifically, the first laser light source 1 irradiates a predetermined position of the wafer 7 on which a plurality of contact holes are formed with laser light, and the second laser light source 3 applies laser light to a predetermined position heated by the laser light. Irradiation was performed, and the intensity of the reflected laser light was measured by the detection unit 4 (not shown).
[0018]
Hereinafter, the coverage inspection result by the laser irradiation type film thickness measuring device will be described.
FIG. 4 is a diagram showing a relationship between a hole aperture ratio and a measured signal intensity in a coverage inspection of a PVD-Cu film formed in a contact hole having a diameter of 0.23 μm. FIG. 5 is a diagram showing a relationship between a hole aperture ratio and a measured signal intensity in a coverage inspection of a PVD-Cu film formed in a contact hole having a diameter of 0.3 μm. FIG. 6 is a diagram showing a relationship between a hole opening ratio and a measured signal intensity in a coverage inspection of a PVD-Cu film formed in a contact hole having a diameter of 0.35 μm. 4 to 6, only a sample (Slot 13) having poor coverage and a sample (Slot 14) having good coverage are shown.
[0019]
As shown in FIG. 4, when the hole opening ratio is low, the difference in coverage does not appear in the intensity (laser intensity) of the measurement signal, but when the hole opening ratio is 25% or more, the difference in coverage was measured. Appears in signal strength. Therefore, the coverage inspection of the metal film formed on the inner wall of the contact hole having a hole opening ratio of 25% or more and a diameter of 0.23 μm can be performed by using a laser irradiation type film thickness measuring device.
[0020]
As shown in FIG. 5, similarly, for the contact hole having a diameter of 0.30 μm, the difference in coverage is shown in the measured signal intensity when the hole opening ratio is 25% or more. Also, as shown in FIG. 6, for a contact hole having a diameter of 0.35 μm, the hole aperture ratio is 25% or more, and the difference in coverage appears in the measured signal intensity. Therefore, the coverage inspection of the metal film formed on the inner wall of the contact hole having a hole opening ratio of 25% or more and a diameter of 0.30 μm or 0.35 μm can be performed by using a laser irradiation type film thickness measuring device. Furthermore, the inventor has confirmed that the coverage can be similarly measured for the metal film formed on the inner wall of the contact hole having a diameter exceeding 0.35 μm.
Therefore, it is possible to perform a coverage inspection of the metal film formed on the inner wall of the contact hole having a hole opening ratio of 25% or more and a diameter of 0.23 μm or more.
[0021]
As described above, in the first embodiment, the laser irradiation type film thickness measuring device is used for the coverage inspection of the PVD-Cu film formed on the inner wall of the contact hole. Specifically, a predetermined region in which a plurality of contact holes were formed was irradiated with laser light, the intensity of the reflected laser light was measured, and the coverage of the PVD-Cu film was inspected.
According to the first embodiment, the coverage inspection of the PVD-Cu film in the contact hole, which has been conventionally performed by the destructive inspection, can be performed by the non-destructive inspection. Therefore, it is not necessary to prepare a test wafer, and the manufacturing cost can be reduced. In addition, since the time until an inspection result is obtained can be significantly shortened as compared with the related art, the lot can be sent to the next process quickly.
[0022]
In the first embodiment, the coverage of the PVD-Cu film formed on the inner wall of the contact hole was measured by a laser irradiation type film thickness measuring device. However, the void in the Cu contact embedded in the contact hole by the electroplating method was used. The laser irradiation type film thickness measuring device can also be applied to the inspection for the presence or absence of a film. Also in this case, since the presence or absence of the void can be inspected nondestructively, it is not necessary to prepare a test wafer and the manufacturing cost can be reduced.
[0023]
Further, the laser irradiation type film thickness measuring device can be applied to the coverage inspection of a barrier metal film such as a TaN film or a TiN film formed on the inner wall of the contact hole, or a close contact film such as a Ta film or a Ti film. .
[0024]
【The invention's effect】
According to the present invention, it is possible to provide an inspection method for non-destructively inspecting the coverage of a metal film formed on an inner wall of a contact hole.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for explaining a laser irradiation type film thickness measuring device used for coverage measurement in Embodiment 1 of the present invention.
FIG. 2 is a diagram showing a relationship between a laser irradiation area and a contact diameter in the first embodiment of the present invention.
FIG. 3 is a micrograph showing a cross section of a sample in which the coverage of the PVD-Cu film is different in the first embodiment of the present invention.
FIG. 4 is a diagram showing a relationship between a hole aperture ratio and a measured signal intensity in a coverage inspection of a PVD-Cu film formed in a contact hole having a diameter of 0.23 μm.
FIG. 5 is a diagram showing a relationship between a hole opening ratio and a measured signal intensity in a coverage inspection of a PVD-Cu film formed in a contact hole having a diameter of 0.3 μm.
FIG. 6 is a diagram showing a relationship between a hole aperture ratio and a measured signal intensity in a coverage inspection of a PVD-Cu film formed in a contact hole having a diameter of 0.35 μm.
[Explanation of symbols]
Reference Signs List 1 First laser light source 2a, 2b, 2c Beam splitter 3 Second laser light source 4 Detector 5 Display 6 Objective lens 7 Substrate (wafer)
30 Laser irradiation area (laser spot)
70 Contact hole A Laser spot diameter B Contact hole diameter

Claims (5)

A method for inspecting the coverage of a metal film formed on an inner wall of a contact hole using a laser irradiation type film thickness measuring device ,
Irradiating a laser beam to a predetermined region in which a plurality of the contact holes are formed,
Measuring the intensity of the laser light reflected in the predetermined area, and inspecting the coverage of the metal film,
A coverage inspection method comprising: In the inspection method according to claim 1,
The coverage inspection method according to claim 1, wherein the predetermined area is an area where an opening ratio of the contact hole is 25% or more. In the inspection method according to claim 1 or 2,
A coverage inspection method, wherein the diameter of the contact hole is 0.23 μm or more. In the inspection method according to any one of claims 1 to 3,
A coverage inspection method, wherein the predetermined area is a laser spot having a diameter of 1.5 μm to 2.5 μm . In the inspection method according 請 Motomeko 1 to any one of 4,
A coverage inspection method, wherein the metal film includes at least one of a PVD-Cu film, a Ta film, a Ti film, a TaN film, and a TiN film.

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