JP2556025B2 - Wafer surface inspection device calibration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In a wafer surface inspection apparatus that detects particulate foreign matter adhering to the surface of a wafer, detection accuracy is improved by using a calibrated wafer provided with a pseudo foreign matter that serves as a reference for the size of the particulate foreign matter. When calibrating, the use of a calibration wafer with an anti-reflection film on the surface prevents the calibration accuracy from deteriorating due to foreign matter adhering to the calibration wafer.

[Industrial applications]

The present invention, in a wafer surface inspection apparatus for detecting the particulate foreign matter adhered to the surface of the wafer, the detection accuracy is calibrated using a calibration wafer provided with a pseudo foreign matter serving as a reference for the size of the particulate foreign matter, the wafer surface The present invention relates to an inspection apparatus calibration method, and more particularly, to improvement of a calibration wafer.

The above-mentioned wafer surface inspection apparatus performs the above-mentioned inspection on semiconductor wafers before processing, which are used for semiconductor devices, for example, and accepts wafers and determines the degree of contamination of wafer handling equipment (transport equipment, processing equipment, etc.). It is used for the judgment of. The degree of contamination can be determined by passing a clean or unprocessed wafer, to which foreign matter is known to adhere, through the apparatus, and detecting the foreign matter that adheres between the wafers by the inspection apparatus.

This wafer surface inspection apparatus has, for example, the configuration shown in the side view of FIG. 3 and detects particulate foreign matter as follows.

That is, in the figure, 1 is a wafer to be inspected, 2 is a particulate foreign substance adhered on the wafer 1, 3 is incident light from a laser which obliquely irradiates and scans the wafer 1 with a spot, 4
Is the reflected light, 5 is the scattered reflected light emitted when the foreign substance 2 exists in the spot area of the incident light 3, and 6 is a photodetector for detecting the intensity of the scattered reflected light 5.

When the surface of the wafer 1 is a mirror surface like a wafer before processing, when the foreign matter 2 does not exist in the spot area of the incident light 3, the scattered reflected light 5 is not emitted, and the foreign matter 2 enters the spot area by scanning. Sometimes scattered reflected light 5 is emitted.
The intensity of the scattered / reflected light 5 depends on the size of the foreign matter 2, and becomes stronger as the size becomes larger.

On the other hand, the foreign matter 2 that adheres to the wafer 1 during handling of the wafer 1 is generally a few μm or less in size and not so many in number, and the adhesion is sparse.

For this reason, the size of the spot is set to, for example, 1 to 0.1 mmφ so that multiple foreign substances do not enter the spot of the incident light 3 at the same time.
By monitoring the scattered / reflected light 5 with the photodetector 6 to some extent, the size and number of the foreign matter 2 attached to the surface of the wafer 1 can be detected.

However, since the detection of the size of the foreign matter 2 is particularly the detection of the intensity of the scattered reflected light 5, the detection value is likely to deviate due to the influence of drift or the like, and therefore it is necessary to calibrate at any time. The calibration is performed by inspecting the calibrated wafer as a wafer to be inspected and correcting the detected value.

Therefore, it is desired that the calibration wafer does not deteriorate the calibration accuracy.

[Conventional technology]

FIG. 4 is a side sectional view of a calibration wafer used in a conventional method in the above calibration.

In this figure, this calibration wafer is a sparsely dispersed pseudo foreign substance 12 made of polystyrene latex particles (PSL particles) of a predetermined size on a substrate 11 made of a clean unprocessed silicon wafer.

The size of the pseudo foreign matter 12 is equal to a reference size selected from the sizes of the foreign matter that adheres to the wafer to be inspected and is to be detected, and is, for example, 0.5, 1 or 2 μmφ.

Further, since the pseudo foreign material 12 is PSL particles, it is fixed to the extent that it cannot be moved by normal handling due to the adhesion force due to static electricity and intermolecular force.

Therefore, in this calibration wafer, the size of the pseudo-foreign matter 12 becomes the reference size for calibration as it is.

[Problems to be solved by the invention]

However, in this calibration wafer, since the size of the pseudo foreign matter 12 is close to the size of the adhered foreign matter adhered during the handling, the adhered foreign matter is confused with the pseudo foreign matter 12 during the calibration, and there is a problem that the calibration accuracy is deteriorated.

In order to avoid this problem, the adhered foreign matter may be removed before the calibration, but it is difficult to selectively remove the adhered foreign matter because the pseudo foreign matter 12 is PSL particles.

Therefore, conventionally, a product in which a pseudo foreign substance is formed by patterning a silicon dioxide (SiO ₂ ) film provided on the substrate 1 is commercially available, but even in that case, it is difficult to sufficiently remove the attached foreign substance. there were.

[Means for solving problems]

The above problem is that in the calibration method of the wafer surface inspection apparatus that detects the particulate foreign matter adhered to the surface of the wafer, a pseudo foreign matter having a size larger than that of the reference foreign matter is formed on the upper surface of the antireflection film formed to cover the surface. Wafer surface inspection device calibrating method for calibrating detection accuracy using the formed calibration wafer, and using a calibration wafer in which a pseudo foreign substance having a concave shape is formed on the upper surface of the antireflection film formed to cover the surface And a wafer surface inspection apparatus calibration method for calibrating detection accuracy.

[Action]

The scattered reflected light 5 described in FIG. 3 includes reflected light reflected on the surface of the foreign substance 2 and reflected light transmitted through the foreign substance 2 and reflected on the surface of the substrate 1. It has been found that the reflected light that is reflected occupies most of the scattered reflected light 5.

Therefore, if the reflected light reflected by the substrate 1 is removed, the intensity of the scattered reflected light 5 becomes weak and the size of the foreign matter 2 is detected as being much smaller than it actually is.

 The present invention utilizes this principle.

That is, by providing the antireflection film on the surface of the substrate of the calibration wafer, the adhered foreign matter is detected as being much smaller than the actual size and is not confused with the pseudo foreign matter provided on the calibration wafer.

Therefore, if such a calibration wafer is used in the calibration, deterioration of the calibration accuracy can be prevented even if foreign matter adheres to the calibration wafer.

〔Example〕

Two embodiments of the method of the present invention will be described below with reference to side sectional views of FIGS. 1 and 2 showing a calibration wafer used in each embodiment.

In one embodiment, calibration is performed using the calibration wafer shown in the side sectional view of FIG. 1, and the method of using the calibration wafer is the same as the conventional method.

The calibration wafer shown in FIG. 1 is made of silicon dioxide or silicon nitride (SiN) on a substrate 21 made of a clean silicon wafer.
An antireflection film 23 which is antireflection for the wavelength of 3) in the figure is formed, and further a silicon nitride film or a silicon dioxide film formed thereon (the material is different from the antireflection film 23).
Is patterned to form a plurality of pseudo foreign particles 22 sparsely distributed in a matrix with, for example, 1 mm intervals.

The thickness of the antireflection film 23 is about 1000Å for silicon dioxide and about 800Å for silicon nitride when the wavelength of incident light is 6330Å (the light source is helium / neon laser).
This thickness t is obtained by t = λ / 4n, where λ is the wavelength of incident light and n is the refractive index of the antireflection film 23, and t = (1 + 2N) λ / 4n (N is an integer) Should be satisfied.

The size of the pseudo foreign material 22 is five times as large as the reference size described above, for example, 2.5, 5 or 10 μm square, and the thickness is about 1 μm. The reason why this size is made larger than the reference size is to compensate for the fact that the pseudo foreign substance 22 is also detected as being smaller than the actual size according to the principle described above. It is a thing.

When this calibrated wafer is used for the calibration of the wafer inspection apparatus, even if the adhered foreign matter adhered on the antireflection film 23 is as large as 2 μm due to the principle described above,
Since it is detected as much smaller than the actual size, such as being detected as 4 μm, it is almost never confused with the pseudo foreign material 22, and deterioration of the calibration accuracy is prevented even if the foreign material adheres to the calibration wafer. . Furthermore, if the adhered foreign matter is removed by cleaning or the like prior to the calibration, it is possible to ensure the reliability even if the removal is insufficient.

Incidentally, the coefficient of compensation for the size of the pseudo foreign matter 22 may vary depending on the wafer inspection apparatus, in which case, the size of the pseudo foreign matter 22 is left as it is to correct the size as a reference, or, The size of the pseudo foreign material 22 may be determined according to the compensation coefficient of the device.

In another embodiment described below, calibration is performed using the calibration wafer shown in the side sectional view of FIG. 2, and the method of using the calibration wafer is the same as the conventional method.

The calibration wafer shown in FIG. 2 is a pseudo foreign material composed of etch pits formed by selectively etching the antireflection film 23 from the pseudo foreign material 22 of the calibration wafer used in the previous embodiment.
It is replaced with 22a.

The size of the etch pid serving as the pseudo foreign matter 22a is equal to the reference size described above, for example, 0.5, 1 or 2 μm square, and the depth is about 300Å. To make this size equal to the reference size,
Since the condition of the antireflection film collapses at the bottom of the etch pit,
This is because the scattered reflected light 5 described with reference to FIG.

When this calibration wafer is used for the calibration of the wafer inspection apparatus, the adhered foreign matter adhered on the antireflection film 23 is detected to be much smaller than the actual size, as in the case of the previous embodiment, and the foreign matter of the previous embodiment is detected. Similar results are obtained. The same applies to the removal of adhered foreign matter prior to calibration.

〔The invention's effect〕

As described above, according to the configuration of the present invention, in the wafer surface inspection device for detecting the particulate foreign matter adhered to the surface of the wafer, the calibration wafer provided with the pseudo foreign matter serving as the reference of the size of the particulate foreign matter is provided on the surface. When the detection accuracy is calibrated, the foreign matter adhering to the calibration wafer can be prevented from being confused with the pseudo foreign matter, and it is possible to prevent the deterioration of the calibration accuracy due to the foreign matter adhering to the calibration wafer.

[Brief description of drawings]

1 is a side sectional view of a calibration wafer used in an embodiment, FIG. 2 is a side sectional view of a calibration wafer used in another embodiment, FIG. 3 is a side view illustrating a wafer surface inspection apparatus, and FIG. The figure is a cross-sectional side view of a calibration wafer used in a conventional method. In the figure, 1 is a wafer to be inspected, 2 is a particulate foreign material, 3 is incident light, 4 is reflected light, 5 is scattered reflected light, 6 is a photodetector, 11 and 21 are substrates, 12, 22 and 22a are pseudo foreign materials. , 23 is an antireflection film.

Claims (2)

(57) [Claims] 1. A method for calibrating a wafer surface inspection apparatus for detecting particulate foreign matter adhered to a wafer surface, wherein a pseudo foreign matter having a size larger than a reference foreign matter is present on an upper surface of an antireflection film formed to cover the surface. A method for calibrating a wafer surface inspection apparatus, which comprises calibrating detection accuracy using a formed calibration wafer. 2. A calibration method for a wafer surface inspection apparatus for detecting particulate foreign matter adhered to a surface of a wafer, wherein a pseudo foreign matter having a concave shape is formed on an upper surface of an antireflection film formed so as to cover the surface. A method for calibrating a wafer surface inspection apparatus, which comprises calibrating detection accuracy using a wafer.