JP2848874B2 - Contact hole opening inspection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for determining whether or not a contact hole of a semiconductor device is open.

(Prior Art) Conventionally, as a technique in such a field, for example, “Nikkei Micro Device No. 46”, published by Nikkei BP, May.
Some were described on page 61.

Hereinafter, the contact hole opening inspection direction will be described.

In other words, according to the level of secondary electron intensity obtained by irradiating the sample with an electron beam, a submicron contact hole is observed using an electron beam length measuring machine that performs pattern length measurement. It is determined whether there is a resist residue at the bottom.

However, in the contact hole opening inspection method described above, the diameter of the contact hole is small, for example, 4M.
When applied to highly integrated semiconductor devices typified by bDRAM, etc., secondary electrons from the bottom of the contact hole cannot be obtained sufficiently, so the S / N ratio of the signal decreases, and the state of the bottom of the contact hole is not necessarily There was a problem that it could not be grasped accurately.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above problems and to provide a contact hole opening inspection method capable of accurately inspecting the state of the contact hole bottom even if the diameter of the contact hole becomes small.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for inspecting a contact hole opening of a semiconductor device, the method comprising: irradiating a contact hole with X-rays of a first wavelength; Comparing the intensity of each of the X-rays transmitted through the contact hole with the step of irradiating the contact hole with the X-ray of the second wavelength, in which the mass absorption coefficient of the material to be etched in the etching is different from the X-ray. Thus, the determination of the opening of the contact hole is performed.

(Operation) According to the present invention, as described above, in the method for inspecting the opening of a contact hole in a semiconductor element, X-rays having wavelengths whose oxygen (O) mass absorption coefficients are significantly different, for example, 22 ° and 24 °.
The opening of the contact hole is determined by monitoring the intensity of the transmitted X-ray obtained when each of the X-rays is applied to the contact hole by the X-ray detector (7).

Therefore, even if the diameter of the contact hole is small, it is possible to reliably determine the contact hole opening.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 is an overall configuration diagram of a contact hole opening inspection apparatus for a semiconductor device showing an embodiment of the present invention, FIG. 2 is a wavelength characteristic diagram of a mass absorption coefficient, and FIG. FIG. 4 is a view showing an example of a microscope, and FIG. 4 is a view showing an example of application of the present invention to a submicron contact hole.

As shown in FIG. 1, X-rays emitted from an X-ray source 1 such as an X-ray tube are separated by an X-ray spectral crystal 2 such as potassium hydrogen phthalate.

As shown in FIG. 2, the X-ray spectral crystal 2 has, for example,
The mass absorption coefficients of oxygen (O), such as {} and [24], are set so that X-rays having wavelengths greatly different from each other can be separated. In FIG. 2, the mass absorption coefficient of X-rays having a wavelength of 22 ° is
While it is on the order of 10 ⁴ cm ² / g, the mass absorption coefficient of X-rays with a wavelength of 24 ° is on the order of 10 ³ cm ² / g, which varies by one digit.

The split X-rays are collimated by a collimator 3 and incident on a wafer 4 mounted on a stage 5 having a hollow portion for transmitting X-rays. Here, the position of the wafer 4 is previously adjusted by the stage controller 6 and, for example, the optical microscope system shown in FIG. 3 so that the X-rays can irradiate the contact hole to be observed.

Next, the optical microscope system will be described with reference to FIG.

In this figure, a wafer 15 (corresponding to the wafer 4 in FIG. 1) on a stage 16 (corresponding to the stage 5 in FIG. 1) is aligned by a stage controller 17 (corresponding to the stage controller 6 in FIG. 1). , Eyepiece 11, light source 13, mirror II19, mirror III20, beam splitter 21, mirror IV22, objective lens 14, mirror I1
By using the beam splitter 8 and the alignment by the optical microscope system including the image display unit 12 together, the contact hole to be moved and to be inspected is focused on the objective lens 14.

Hereinafter, the contact hole opening inspection method will be described.

Here, a part of the X-rays incident on the wafer 4
And reaches an X-ray detector 7 (for example, an X-ray detector composed of a CCD camera and an image processing device) which is most sensitive to the wavelength to be used. In the present embodiment, for example,
To separate X-rays having two wavelengths of
The value of θ must be changed based on the following relational expression.

2d sin θ = nλ d: lattice constant of X-ray spectral crystal θ: incident angle of X-ray to X-ray spectral crystal n: order λ: wavelength accordingly, light of collimator 3, wafer 4, and X-ray detector 7 The optical system controller 8 and the stage controller 6 are linked and adjusted so that the axes do not shift.

If an oxide film remains at the bottom of the contact hole, the X-ray having a wavelength of 22 ° differs from the X-ray having a wavelength of 24 ° because the mass absorption coefficient due to oxygen (O) is one digit different. The intensity of the X-rays reaching 7 differs.

On the other hand, when the oxide film does not remain at the bottom of the contact hole, the difference in the mass absorption coefficient due to oxygen (O) does not matter. There is no difference in the X-ray intensity reaching the X-ray detector 7 between when the X-ray is irradiated.

Therefore, when irradiating X-rays having two different wavelengths, for example, 22 ° and 24 °, a contact hole is opened by comparing the respective signal intensities obtained by the X-ray detector 7. Can be determined.

At the present time, the collimator 3 can irradiate a parallel light beam having a diameter of about 1 μm to the contact hole. However, as shown in FIG. Some will enter the resist.

In FIG. 4, 30 is a silicon substrate, 31 is SiO ₂
Reference numeral 32 denotes a resist film, and reference numeral 33 denotes a contact hole.

However, as shown in FIG.
The mass absorption coefficients of H and N, and the mass absorption coefficient of Si constituting the oxide film are almost the same between the X-rays having a wavelength of 22 ° and the X-rays having a wavelength of 24 ° described in the examples. Considering that the thickness of the resist and the underlying oxide film is about two orders of magnitude larger than the thickness of the oxide film that is problematic in contact hole opening inspection, the X-rays of different wavelengths incident on the resist are:
Mostly absorbed by the resist and the oxide film under the resist.
Therefore, an accurate inspection that reflects only the information on the bottom of the contact hole can be performed.

In the above embodiment, an oxide film has been described as an example of a material to be etched in contact hole etching. However, in the case of a nitride film, as shown in FIG. 2, X-rays having wavelengths of 29 ° and 32 ° are used. By using the method described above, the inspection of the opening of the contact hole can be performed in the same manner as described above.

Further, the present invention is not limited to the above embodiments, and various modifications are possible based on the gist of the present invention.
They are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, in the method for inspecting the contact hole opening of a semiconductor device, the first method is used.
Irradiating the contact hole with X-rotation having a second wavelength, and irradiating the contact hole with an X-ray having a second wavelength, which has a different mass absorption coefficient of the material to be etched in the etching of the contact hole from the X-ray. By comparing the process and the intensity of each of the X-rays transmitted through the contact hole, the determination of the contact hole opening is performed. Therefore, even if the diameter of the contact hole is small, the determination of the contact hole opening can be reliably performed. It can be carried out.

[Brief description of the drawings]

1 is an overall configuration diagram of a contact hole opening inspection apparatus for a semiconductor device showing an embodiment of the present invention, FIG. 2 is a wavelength characteristic diagram of a mass absorption coefficient, and FIG. FIG. 4 is a view showing an example of a microscope, and FIG. 4 is a view showing an example of application of the present invention to a submicron contact. DESCRIPTION OF SYMBOLS 1 ... X-ray source, 2 ... X-ray spectral crystal, 3 ... Collimator, 4 ... Wafer, 5 ... Stage, 6 ... Stage controller, 7 ... X-ray detector, 8 ... Optical system controller.

Claims (1)

(57) [Claims] 1. A method for inspecting a contact hole opening of a semiconductor device, comprising: (a) irradiating a contact hole with X-rays of a first wavelength; and (b) mass absorption coefficient of a material to be etched in etching the contact hole. Irradiating the contact hole with an X-ray having a second wavelength different from the X-ray, and (c) comparing the intensity of each of the X-rays transmitted through the contact hole to obtain the contact hole. Determining the opening; and a contact hole opening inspection method comprising: