JPH0739993B2 - Inspection method and device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inspection technique, and particularly to a technique effective when applied to a wafer visual inspection in the manufacture of a semiconductor device.

[Prior Art] The appearance inspection of wafers in the manufacture of semiconductors is described in Kogyo Kogyo Kaisha, Ltd., November 15, 1983, "Electronic Materials", November 1983, Supplement, P204-209. .

By the way, the present inventor examined the appearance inspection of a wafer, which detects foreign matters and the like attached to the surface of a wafer by irradiating polarized light. The following is a technology which has not been publicly known but has been studied by the present inventor, and the outline thereof is as follows.

That is, a predetermined part of the wafer plane rotated in a predetermined plane is scanned while irradiating with P-polarized light (primary Primary polarized light) and S-polarized light (secondary polarized light) to form a regular shape on the wafer surface. When P-polarized light and S-polarized light are reflected by the pattern of
By utilizing the fact that the reflected light is S-polarized in both cases of P-polarized light and S-polarized light, the amount of P-polarized light included only in the reflected light from the irregularly shaped foreign matter adhering to the regular pattern By detecting a change or the like, a foreign substance or the like attached to a predetermined portion of the wafer is detected.

[Problems to be Solved by the Invention] However, as described above, in an inspection in which the presence or absence of foreign matter is determined by simply detecting the change in the amount of P-polarized light, for example, a pattern is formed in a multi-layered pattern and a wafer is formed. If the amount of P-polarized light contained in the reflected light from the base portion where there is no foreign substance is relatively large due to the complicated surface shape of the item or the change in step size becomes large, it is included in the reflected light from the substrate. There is a drawback that the contrast between the P-polarized light and the P-polarized light from the foreign matter is reduced, the minimum size of the detectable foreign matter becomes relatively large, and the detection sensitivity and detection accuracy are reduced.

This means that with the miniaturization and high integration of the semiconductor device, the pattern formed on the wafer is miniaturized, and it is required to detect the foreign matter adhering to the pattern with higher sensitivity and accuracy. Considering that, the inventor has found that it is an important issue.

An object of the present invention is to provide an inspection technique capable of improving the detection sensitivity and the detection accuracy of a foreign substance or the like attached to an inspection object.

The above and other objects and novel characteristics of the present invention are
It will be apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, the reflected light obtained by irradiating the S-polarized light with different wavelengths from two sets of light sources arranged around the object to be inspected in two directions orthogonal to each other is branched for each wavelength. The amount of light of the P-polarized component and the amount of S-polarized component contained in each of the reflected light is detected individually, and the ratio of the amount of light of the P-polarized component and the amount of S-polarized component for each wavelength is compared with a predetermined threshold value. By doing so, a predetermined inspection is performed on the surface of the inspection object.

[Operation] According to the above-described means, for example, reflected light reflected from a foreign substance having a disordered shape attached to the surface of the inspection object and containing substantially equal amounts of the S-polarized component and the P-polarized component, and the base of the inspection object. Reflected light that is reflected from a portion and has a relatively small amount of light of the S-polarized component with respect to the amount of P-polarized component is detected with a large contrast, and a blind spot due to a step or the like on the surface of the inspection object does not occur. In addition, a sufficient amount of reflected light can be obtained, and it becomes possible to improve the detection sensitivity and detection accuracy of foreign matter or the like attached to the inspection object.

[Embodiment 1] FIG. 1 is a schematic view showing a main part of an inspection apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory view for explaining its operation.

An object to be inspected 2 such as a wafer is removably placed on an XY table 1 which is movable in a predetermined plane.

Further, S-polarized light (S1) (first S-polarized light) and S-polarized light (S2) (second S-polarized light) having different wavelengths are provided around the XY table 1 on which the inspection object 2 is placed. A pair of radiating light sources 3a, 3b (first light source) and 4a, 4b
The (second light source) is arranged around the object to be inspected 2 in a direction orthogonal to each other, and the light sources 3a and 3b and the light source 4 are arranged.
S-polarized light (S1) and S-polarized light (S2) emitted from a and 4b are
The structure is such that a predetermined portion of the inspection object 2 placed on the XY table 1 is irradiated substantially horizontally.

Then, the inspection object 2 placed on the XY table 1
The surface of the object 2 to be inspected is scanned by S-polarized light (S1) and S-polarized light (S2) by moving in parallel with respect to 3a, 3b and the light sources 4a, 4b.

Further, immediately above the XY table 1, the S of the inspection object 2 is
An objective lens 6 for converging the reflected light 5 generated from a portion irradiated with polarized light (S1) and S-polarized light (S2) is provided with its optical axis substantially vertical.

In this case, a dichroic mirror D (first branch portion) having the same optical axis as the objective lens 6 is provided above the objective lens 6, and the reflected light 5 is reflected light having different wavelengths.
It is configured to be split into 51 and reflected light 52.

Further, a polarization beam splitter 7a and a polarization beam splitter 7b (second branch portion) are arranged in the optical paths of the branched reflected lights 51 and 52, respectively.

The polarization beam splitters 7a and 7b are used for the objective lens 6
Of the P-polarized component 51P, P-polarized component 52P and S-polarized component 51S, S-polarized component 52S contained in the reflected lights 51 and 52 branched via the dichroic mirror D, respectively.
By making the polarized components 51P and 52P go straight in the same direction as the reflected lights 51 and 52 and reflecting the S polarized components 51S and 52S in the direction intersecting the optical paths of the reflected lights 51 and 52, P polarization components 51P and 52P included in 52
And S-polarized components 51S and 52S are branched and taken out.

In addition, a plurality of detectors 8a, detectors 8b and detectors 9a, 9b are provided in the optical paths of the P-polarized components 51P, 52P and the S-polarized components 51S, 52S respectively branched by the polarization beam splitters 7a, 7b. It is provided with P polarization components 51P, 52P
The light amounts of the S-polarized components 51S and 52S are converted into electric signals having intensities corresponding to the respective light amounts and detected.

Further, the plurality of detectors 8a, 8b and the detectors 9a, 9b are connected to the calculation unit 10a and the calculation unit 10b, respectively. Then, in the arithmetic unit 10a (10b), for example, a detector
The value of the electric signal corresponding to the light quantity of the P-polarized component 51P (52P) obtained from 8a (9a) is the value of the electric signal corresponding to the light quantity of the S-polarized component 51S (52S) obtained from the detector 8b (9b). The amount of light of the P-polarized component 51P (52P) and the S-polarized component 51 obtained by dividing by
The ratio R1 (R2) to the light intensity of S (52S) is reflected light with different wavelengths.
51 and the reflected light 52 are configured to be calculated individually.

In addition, the comparison units 11a and 1 are included in the arithmetic units 10a and 10b.
1b is connected, and the light quantity of the P-polarized component 51P (52P) and the S-polarized component 51S (52P) obtained by the arithmetic unit 10a (10b) are connected.
S1) light intensity ratio R1 (R2) and a predetermined threshold T1 (T2)
And are configured to be compared.

Further, the comparison units 11a and 11b are connected to the determination unit 12, and in the determination unit 12, the comparison unit 11a and the comparison unit 1 are connected.
Based on the comparison result in 1b, the presence or absence of foreign matter in a predetermined portion of the inspection object 2 is determined. In the figure, 14 indicates a reference voltage generator.

The operation of this embodiment will be described below.

First, the inspected object 2 such as a wafer has a pattern 2a formed on the surface of the inspected object 2 that is substantially aligned with the optical axes of the light sources 3a and 3b and the light sources 4a and 4b provided opposite to each other. It is fixed on the XY table 1 in a vertical posture.

Next, the light sources 3a and 3b and the light source 4 are provided at predetermined portions of the inspection object 2.
S-polarized light (S1) and S with different wavelengths emitted from a and 4b
Polarized light (S2) is emitted from four orthogonal directions,
The XY table 1 is zigzag translated in directions orthogonal to each other, and the surface of the inspection object 2 is scanned by S-polarized light (S1) and S-polarized light (S2) with which the inspection object 2 is irradiated.

Then, S-polarized light (S1) and S-polarized light (S2) of the inspection object 2
The reflected light 5 generated from the irradiation portion of (1) enters the dichroic mirror D through the objective lens 6 and is branched into reflected lights 51 and 52 having different wavelengths. Then, the reflected light 51
(52) are incident on the polarization beam splitters 7a (7b) and are included in the reflected light 51 (52).
2P) and the S-polarized component 51S (52S) are separately branched and reach the detector 8a (9a) and the detector 8b (9b),
It is converted into an electric signal having an intensity corresponding to each light quantity.

Further, in the arithmetic unit 10a (10b) to which the detector 8a (9a) and the detector 8b (9b) are connected, for example, the detector 8a
The value of the electric signal corresponding to the light quantity of the P-polarized component 51P (52P) obtained from (9a) is the value of the electric signal corresponding to the light quantity of the S-polarized component 51S (52S) obtained from the detector 8b (9b). The amount of light of the P-polarized component 51P (52P) and the S-polarized component 51S obtained by dividing
The ratio R1 (R2) to the light intensity of (52S) is calculated, and the comparison unit 11a
In (11b), the ratio R is compared with a predetermined threshold value T.

Then, in the determination unit 12, in either one of the comparison units 11a and 11b, for example, when R1 (R2)> T1 (T2), it is determined that the foreign matter 13 is present in a predetermined portion of the inspection object. However, the information is output to a predetermined storage unit (not shown) or display unit together with information such as coordinate values at that time.

That is, as shown in FIG. 2, reflected light 51 (52) from the regularly shaped pattern 2a formed on the inspection object 2
Since the shape of the reflection surface is almost regular, most of it is composed of the S-polarized component 51S (52S) and the P-polarized component 51P (5S).
2P) is small, while S is contained in the reflected light 5 from the foreign matter 13 having an irregular outer shape.
The amount of light of the polarization component 51S (52S) and the amount of light of the P polarization component 51P (52P) are substantially equal.

Therefore, P in the reflected light 51 (52) from the pattern 2a
The ratio R1 (R2) of the light quantity of the polarization component 51P (52P) and the light quantity of the S polarization component 51S (52S), and P in the reflected light 5 from the foreign matter 13
The difference between the ratio R1 (R2) of the light quantity of the polarization component 51P (52P) and the light quantity of the S polarization component 51S (52S) becomes extremely large, and by setting a predetermined threshold value T1 (T2) between them. , Foreign matter 13
Pattern 5 formed on the object 2 and the reflected light 5 from the
The reflected light 51 (52) from the base portion such as 2a is clearly distinguished.

Further, since the S-polarized light (S1) and the S-polarized light (S2) having different wavelengths are irradiated onto a predetermined portion of the inspection object 2 from four directions which are orthogonal to each other, the amount of the S-polarized light irradiated on the inspection object 2 is increased. Along with the increase, the blind spots due to the steps of the pattern 2a are eliminated, and the detection sensitivity and accuracy of the foreign matter 13 adhering to the inspection object 2 are improved.

In the above description, the detection of the foreign matter 13 adhering to the pattern 2a formed on the inspection object 2 has been mainly described, but defects such as irregular protrusions and defects of relatively large size in the pattern 2a are also usually described above. Needless to say, the foreign matter 13 has an irregular surface shape like the foreign matter 13, and the inspection apparatus of this embodiment can be used for detecting these defects.

As described above, according to this embodiment, the following effects can be obtained.

(1). The dichroic mirror D reflects the reflected light 5 generated when the S-polarized light (S1) and the S-polarized light (S2) having different wavelengths are applied to a predetermined portion of the inspection object 2 from four directions orthogonal to each other.
Split the reflected light 51 and 52 for different wavelengths by
The P-polarized component 51P (52P) and the S-polarized component 51S (52S) included in the reflected light 51 (52) are converted into the polarization beam splitter 7a (7b).
And a plurality of detectors 8a (9a) and a plurality of detectors 8b (9b) individually detect, and P in the arithmetic unit 10a (10b).
The ratio R1 (R2) between the light quantity of the polarization component 51P (52P) and the light quantity of the S polarization component 51S (52S) is calculated, and the ratio R1 (R2) is compared to the comparison unit 11a.
By comparing with the predetermined threshold value T1 (T2) in (11b), reflected light 51 (52) with different wavelengths from the foreign matter 13 adhering to the inspection object 2 and the rule formed on the inspection object 2 Reflected light from the underlying part such as the pattern 2a with a unique shape 51
By determining (52), the foreign matter 13 or the like attached to the surface of the inspection object 2 can be detected. Therefore, for example, a change in the light amount of the P-polarized component contained in the reflected light of a single wavelength is detected. Compared with the case where the pattern 2a is formed on the surface of the object 2 to be inspected, the foreign matter 13 and the like are clearly distinguished from the base, and the amount of S-polarized light with which the object 2 to be inspected is further increased. The blind spot due to the stepped portion or the like is eliminated, and the detection sensitivity and accuracy of the foreign matter 13 adhering to the inspection object 2 are improved.

(2). A plurality of light sources 3a and 3b and light sources 4a and 4b are provided for the inspection object 2.
S-polarized light (S
1) Since the surface of the inspection object 2 is scanned by (S2), the irradiation angle of the S-polarized light S1 (S2) with respect to the pattern 2a regularly formed on the inspection object 2 becomes constant, and the pattern 2a
It is possible to stably maintain the light amount of the P-polarized component 51P (52P) included in the reflected light 51 (52) from the base portion such as a P-polarized component included in the reflected light 51 (52). 51P
Ratio R1 between the light intensity of (52P) and the light intensity of S-polarized component 51S (52S)
The detection of the foreign matter 13 based on (R2) is performed with stable sensitivity.

(3). As a result of the above (2), foreign matter is
It is possible to easily set a non-inspection area where 13 is not detected, and the inspection process can be simplified.

(4). As a result of the above (1) to (3), the productivity in the appearance inspection of the wafer in the manufacture of the semiconductor device is improved.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Nor.

For example, by rotating the inspection object, the surface of the inspection object may be scanned with S-polarized light having different wavelengths.

In the above description, the case where the invention made by the present inventor is mainly applied to the wafer appearance inspection technology which is the field of application which is the background has been described, but the invention is not limited thereto, and, for example, a photomask, a diffraction It can be widely applied to inspection of regular patterns such as lattices.

[Effects of the Invention] The effects obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, a pair of first light sources that are arranged so as to face the object to be inspected and irradiate the surface of the object to be inspected with the first S-polarized light, and are orthogonal to the direction in which the first light sources are arranged. A pair of second light sources that face each other and irradiate the surface of the inspection object with the second S-polarized light having a wavelength different from that of the first S-polarized light; P included in each of the one branching portion and the reflected light branched for each different wavelength.
A plurality of second branch portions for branching the polarized light component and the S polarized light component, a plurality of detection portions for detecting the respective light amounts of the P polarized light component and the S polarized light component branched in the second branched portion, A plurality of calculation units for calculating the ratio of the light amount of the P-polarized component and the light amount of the S-polarized component detected by the detection unit for each different wavelength, and the calculation unit for each different wavelength obtained by the plurality of calculation units. Since the structure has a plurality of comparison parts for comparing the ratios with a predetermined threshold value respectively, even if the amount of the P-polarized component contained in the reflected light from the base part of the inspection object is relatively large, the base part It is possible to clearly distinguish the reflected light from the object and the reflected light from the foreign matter, eliminate the blind spot due to the stepped portion on the surface of the inspection object, and increase the amount of S-polarized light irradiated on the inspection object. It is possible to In order to improve the detection sensitivity and the detection accuracy of the foreign matter adhering to the object to be inspected, compared with, for example, the case of detecting the foreign matter based on only the change of the light quantity of the P-polarized component contained in the reflected light. You can

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of an inspection device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram for explaining its operation. 1 ... XY table, 2 ... inspection object, 2a ... pattern,
3a, 3b, 4a, 4b …… Light source, 5,51,52 …… Reflected light, 51P, 52P…
... P-polarized component, 51S, 52S ... S-polarized component, 6 ... Objective lens, 7a, 7b ... Polarizing beam splitter (second branching part), 8,8a, 9,9a ... Detector, 10a, 10b ... Calculation unit, 11a,
11b …… Comparison part, 12 …… Judgment part, 13 …… Foreign matter, S1, S2 ……
S-polarized light, R1, R2 ... Ratio of light quantity of P-polarized light component in reflected light to light quantity of S-polarized light component, T, T2 ... Threshold value, D ... Dichroic mirror (first branch portion).

Claims (8)

[Claims] 1. The amount of light of the P-polarized component and the amount of S-polarized component in the reflected light obtained by irradiating the surface of the inspection object with S-polarized light is individually detected, and the amount of light of the P-polarized component and the amount of light of the S-polarized component are detected. The inspection method is characterized in that a predetermined inspection is performed on the surface of the object to be inspected by comparing the ratio of the ratio with the predetermined threshold value. 2. Perpendicular to each other around the surface of the object to be inspected
Reflected light obtained by irradiating S-polarized light having different wavelengths from two sets of light sources arranged facing each other in each direction is branched for each wavelength, and a P-polarized component and an S-polarized light component included in each of the branched reflected light are included. A predetermined inspection on the surface of the object to be inspected is performed by individually detecting the light amount of the polarized component and comparing the ratio of the light amount of the P polarized component and the light amount of the S polarized component for each wavelength with a predetermined threshold value. An inspection method characterized by performing. 3. The inspection method according to claim 2, wherein the surface of the inspection object is scanned by S-polarized light having different wavelengths by relatively moving the inspection object in parallel. . 4. The inspection method according to claim 2, wherein the object to be inspected is a wafer, and the inspection is performed for the presence or absence of foreign matter on the surface of the wafer. 5. A plurality of light sources for irradiating the surface of an object to be inspected with S-polarized light, a branch portion for branching a P-polarized component and an S-polarized component contained in reflected light from the object, and the branch portion. A plurality of detectors that detect the respective light amounts of the branched P-polarized component and S-polarized component, and a ratio between the light amount of the P-polarized component and the light amount of the S-polarized component detected by the plurality of detectors is calculated. An inspection apparatus, comprising: a calculation unit that performs: and a comparison unit that compares the ratio obtained by the calculation unit with a predetermined threshold value. 6. A pair of first light sources, which are arranged so as to face each other around the object to be inspected and irradiate the surface of the object to be inspected with a first S-polarized light, and a direction in which the first light source is arranged. A pair of second light sources, which are orthogonally opposed to each other and irradiate the surface of the object to be inspected with a second S polarized light having a wavelength different from that of the first S polarized light, and reflected light from the object to be inspected for each different wavelength. P included in each of the first branching portion for branching and the reflected light branched for each different wavelength.
A plurality of second branch portions for branching the polarized light component and the S polarized light component, a plurality of detection portions for detecting the respective light amounts of the P polarized light component and the S polarized light component branched in the second branched portion, A plurality of calculation units for calculating the ratio of the light amount of the P-polarized component and the light amount of the S-polarized component detected by the detection unit for each different wavelength, and the calculation unit for each different wavelength obtained by the plurality of calculation units. An inspection apparatus comprising: a plurality of comparison units that compare the ratio with a predetermined threshold value. 7. The surface of the object to be inspected is irradiated from the first and second light sources by parallel movement of the object to be inspected relative to the first and second light sources. The inspection apparatus according to claim 6, wherein scanning of the polarized light is performed on the inspection object. 8. The inspection apparatus according to claim 6, wherein the object to be inspected is a wafer, and inspecting for the presence or absence of foreign matter on the surface of the wafer.