JPS635203A - Method and apparatus for detecting pattern - Google Patents

Abstract

PURPOSE:To enhance the detection accuracy of the pattern formed on an article to be inspected, by comparing the quantity of a normal (S) polarized beam component and that of a parallel (P) polarized beam component with a predetermined threshold value. CONSTITUTION:Polarized beams S emitted from beam sources 3, 4 are allowed to irradiate an aligning mark 2a and, further, an XY table 1 is appropriately moved to scan the aligning mark 2a by the polarized beams S. At this time, scattering or reflected beams 11 obtained from the part irradiated with the polarized beams S of the aligning mark 2a are incident on a polarizing beam splitter 13 and indivisually split into a P polarized beam component 11P and an S polarized beam component 11S to be converted to electric signals corresponding to the quantities of both beam components by detectors 14, 15. Next, the ratio R of the quantity of the components 11S and that of the component 11P is calculated in an operation part 16 and compared with a predetermined threshold value Th in a comparing part 17 and, when R>Th is formed, the edge part of the aligning mark 2a is judged to make it possible to accurately detect the position of the mark 2a on an article 2 to be inspected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pattern detection technique, and particularly to a technique that is effective when applied to the detection of alignment marks during exposure of a semiconductor wafer in the manufacture of semiconductor devices.

[Prior Art] Regarding the detection technology of alignment marks during exposure of semiconductor wafers in the manufacture of semiconductor devices, please refer to "Electronic Materials J 19" published by Kogyo Kenkyukai Co., Ltd., November 15, 1981.
It is described in the November 1983 special edition, pages 97 to 104.

The outline of this method is to irradiate a laser or other beam onto an alignment mark formed near the exposure area of a semiconductor wafer and detect scattered or reflected light. Alternatively, the position of the alignment mark is determined by utilizing the fact that the reflected light becomes the strongest.

[Problems to be Solved by the Invention] However, as described above, in the method of simply detecting the scattered light or reflected light generated when laser is irradiated on the alignment mark, the surface of the alignment mark or the semiconductor wafer cannot be detected. If there are irregularities caused by crystal grains etc. in the underlying part, the scattered light from the edge part of the alignment mark will be buried in the scattered light from the underlying part, resulting in a decrease in the detection accuracy of the alignment mark. , repeating photolithography causes a reduction in the mutual overlay accuracy of integrated circuit patterns formed in multiple layers on the surface of a semiconductor wafer.

This is because, as semiconductor devices become smaller and more highly integrated, the patterns to be formed on semiconductor wafers become finer, and it is required to superimpose patterns formed in multiple layers with higher precision. The inventors of the present invention have found that this poses an important problem in consideration of the current situation.

An object of the present invention is to provide a pattern detection technique that can improve the detection accuracy of a pattern formed on an object to be inspected.

The above and other objects and novel features of the present invention include:
It will become clear from the description herein and the accompanying drawings.

[Means for Solving the Problems] A brief summary of typical inventions disclosed in this application is as follows.

That is, the light intensity of the P (parallel) polarized light component and the S polarized light component of the scattered light or reflected light obtained by irradiating S (senkrecht = 5 enkrecht = 5 enkrecht) polarized light onto the surface of the inspected object on which a predetermined pattern is formed is calculated. The pattern formed on the surface of the object to be inspected is detected by individually detecting the light quantity and comparing the ratio of the light quantity of the S-polarized light component and the light quantity of the P-polarized light component with a predetermined threshold value.

[Function] According to the above-mentioned means, for example, a pattern is generated from a relatively regularly shaped pattern formed on the surface of the object to be inspected,
The S-polarized light component is larger than the P-polarized light component, and the scattered or reflected light is generated from the underlying part, which has unevenness due to crystal grains and has a relatively disordered surface state, and the S-polarized light component and the P-polarized light component are almost equal. The scattered light or reflected light from the mold is detected with a large contrast, and the detection accuracy of the pattern formed on the surface of the object to be inspected can be improved.

[Embodiment 1] FIG. 1 is an explanatory diagram showing a state in which a pattern detection apparatus according to an embodiment of the present invention is installed in a reduction projection exposure apparatus.

That is, in this embodiment, the pattern detection device is used as an alignment mark detection device of a reduction projection exposure apparatus.

On the XY child table, which is movable within a predetermined plane, there is placed, for example, a semiconductor wafer to be inspected whose surface is coated with photoresist and a predetermined positioning mark 2a (pattern) is formed at a predetermined location. '31IJ
2 is removably positioned, and above the XY child table are a reduction lens 3 and a condenser lens 4, as well as an original 5 such as a reticle interposed between the reduction lens 3 and the condenser lens 4. By irradiating exposure light 6 obtained from a light source (not shown) onto a predetermined part of the object to be inspected 2 through a condenser lens 4, an original 5, and a reduction lens 3, the transparent substrate of the original 5 is exposed. A figure 5a made of a light-shielding film or the like formed in a predetermined shape is reduced to a predetermined magnification by a reduction lens 3, transferred to a predetermined part of the object 2 to be inspected, and applied to the surface of the object 2 to be inspected. A photoresist or the like is configured to be exposed to a predetermined pattern 5b.

In this case, a plurality of light sources 7 and 8, such as lasers, which emit only S-polarized light (S) are disposed around the XY child table, facing each other via the XY child table, and the light a7 and S polarized light (S) emitted from 8 is XY
It is structured so that the light is irradiated almost horizontally toward an alignment mark 2a formed on an object to be inspected 2 placed on a sub-table.

Further, a mirror pattern 9 such as a laser mirror capable of reflecting polarized light without disturbing the polarization state of the polarized light is provided near the figure 5a on the lower surface of the original 5.
A reflecting mirror 10 also made of a laser mirror or the like is provided near the bottom of the
is generated from the alignment mark 2a etc. that is irradiated,
Scattered light or reflected light 11 transmitted through the reduction lens 3 is configured to be extracted laterally through a mirror pattern 9 and a reflecting mirror 10.

Furthermore, the optical path of the scattered light or reflected light 11 that has passed through the reflecting mirror 10 includes a polarizing beam splinter 13 via a lens 12.
(branch) is provided.

This polarizing beam splitter 13 is configured to divide the P-polarized light component 1 out of the P-polarized light component lIP and the S-polarized light component 113 contained in the scattered light or reflected light 11 incident through the lens 12.
1P goes straight in the same direction as the incident direction of the scattered light or reflected light 11, and reflects the S polarized light component 113 in a direction intersecting the optical path of the scattered light or reflected light 11. The components 113 are configured to be separated and taken out individually.

In addition, P split at the polarization beam splitter 13
A plurality of detectors 14 and a plurality of detectors 15 are provided in the optical paths of the polarized light component 11P and the S polarized light component 113, respectively, and the light amounts of the P polarized light component LIP and the S polarized light component 113 are adjusted according to their respective light amounts, for example. The structure is such that it is converted into a strong electrical signal and can be detected individually.

Further, the plurality of detectors 14 and 15 are connected to a calculation unit 16, and the calculation unit 16 calculates, for example, the value of the light amount of the S polarization component 11S obtained from the detector 15. It is configured to calculate a ratio R between the light amount of the S-polarized light component Its and the light amount of the P-polarized light component 11P, which is obtained by dividing the value of the light amount of the P-polarized light component 11P obtained.

Further, a comparator 17 is connected to the arithmetic unit 16, and the ratio R between the amount of light of the S-polarized light component 11S and the amount of light of the P-polarized light component LIP obtained in the arithmetic unit 16 is calculated by a reference voltage generator 18, etc. By comparing with a predetermined threshold value Th given by , the edge portion of the alignment mark za formed at a predetermined portion of the inspection object 2 can be determined from the underlying portion.

The operation of this embodiment will be explained below.

First, an object 2 to be inspected, such as a semiconductor wafer, which has an alignment mark 2a formed together with an integrated circuit pattern in a previous photolithography process or the like in a predetermined part of its surface, and is coated with photoresist or the like is placed on an XY child table. is fixed on top.

Next, by moving the XY child table appropriately, positioning marks 2a are formed on a predetermined portion of the object 2.
By irradiating S polarized light (S) emitted from light sources 3 and 4 and further moving the XY child table appropriately,
The region of the alignment mark 2a formed on the object to be inspected 2 is scanned by the S-polarized light (S).

At this time, the S polarized light (S) of the alignment mark 2a'
Scattered light or reflected light 11 obtained from the irradiation site is transmitted through the reduction lens 3. The P-polarized light component 11P and the S-polarized light component 113 included in the scattered light or reflected light 11 are incident on the polarizing beam splitter 13 through the mirror pattern 9 and the reflecting mirror 10, and are then separately split into the detector 1.
4 and 15, and are converted into electrical signals with intensities corresponding to the respective amounts of light.

Furthermore, a calculation unit 16 to which the detectors 14 and 15 are connected
For example, the light amount of the S-polarized component 115 is obtained by dividing the value of the light amount of the S-polarized component Its obtained from the detector 15 by the optical cover Φ value of the P-polarized component LIP obtained from the detector 14. A ratio R to the light amount of the P-polarized light component 11P is calculated, and the comparison unit 17 compares the ratio R with a predetermined threshold Th. If R>Th, the alignment mark 2a is
By determining that the edge portion is the edge portion, the position of the alignment mark 2a on the object to be inspected 2 is accurately detected.

That is, as shown in FIG. 2, the scattered light or reflected light 11 from the substantially regularly shaped alignment mark 2a formed on the object to be inspected 2 has a reflecting surface that has a substantially regular shape. Therefore, the polarization state of S-polarized light (S) is preserved, and most of it is composed of S-polarized light component IIs, and P-polarized light component LIP
On the other hand, in the scattered light or reflected light 11 from the underlying portion of the object to be inspected 2, which is relatively disordered due to unevenness such as crystal grains, the amount of S-polarized light component 113 included and the P-polarized light component 11P are small. The amount of light becomes almost equal.

Therefore, the ratio R of the light amount of the S-polarized light component 113 in the scattered light or reflected light 11 from the alignment mark 2a and the light amount of the P-polarized light component 11P, and the S-polarized light component 113 in the scattered light or reflected light 11 from the underlying portion are determined. The difference in the ratio R between the amount of light and the amount of light of the P-polarized component 11P is extremely large. Scattered light or reflected light 11 is clearly distinguished from scattered light or reflected light 11 from the underlying portion, which is relatively disordered, and the position of alignment mark 2a formed on object 2 to be inspected can be accurately grasped. be done.

Thereafter, by finely moving the XY child table based on the accurately detected position of the alignment mark 2a, the axes of the reduction lens 3 and original 5 are aligned with respect to the object 2 to be inspected. inspection'! The integrated circuit pattern already formed on J2 is superimposed on a predetermined figure 5b formed on the original plate 5 as a figure 5a such as a light-shielding film and transferred to the object 2 to be inspected via the reduction lens 3. done accurately.

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

(1) P-polarized light component 11P and S-polarized light contained in scattered light or reflected light 11 generated when S-polarized light (S) is irradiated to a predetermined portion of the inspection object 2 where the alignment mark 2a is formed. component 113 is individually detected by the polarization beam splinter 13 and a plurality of detectors 2314.15, and furthermore, the calculation unit 16 calculates the ratio R between the light amount of the S-polarized light component 115 and the light amount of the P-polarized light component 11P, and calculates the liquid ratio. By comparing R with a predetermined threshold Th in the comparing section 18, the scattered light or reflected light 11 from the alignment mark 2a formed on the inspection object 2 and the scattered light or reflected light 11 from the underlying portion are determined. Since the structure is such that the alignment mark 2a formed on the object 2 to be inspected is detected by determining the Detection accuracy of alignment marks 2a and the like formed on the inspection object 2 is improved.

(2) As a result of (1) above, by using the pattern detection device of this embodiment for detecting alignment marks during exposure of semiconductor wafers in the manufacture of semiconductor devices, it is possible to form multiple layers by repeating photolithography. The mutual overlay accuracy of integrated circuit patterns is improved, and the yield in manufacturing semiconductor devices is improved.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the method of splitting the S-polarized light and the P-polarized light contained in the scattered light or reflected light and extracting them individually is not limited to using a beam splitter. Alternatively, a polarizing plate that transmits only S-polarized light or P-polarized light may be interposed in each branched optical path, and the S-polarized light component and the P-polarized light component may be detected separately.

In the above explanation, the invention made by the present inventor was mainly applied to the technology for detecting alignment marks during exposure of semiconductor wafers, which is the field of application in which the invention was made, but the invention is not limited thereto. For example, the present invention can be widely applied to pattern detection in integrated circuit pattern size inspection equipment.

[Effects of the Invention] The effects obtained by typical inventions disclosed in this application are briefly described below.

That is, a plurality of light sources irradiate S-polarized light onto the surface of an object to be inspected on which a predetermined pattern is formed, and a P-polarized light component and an S-polarized light component contained in scattered light or reflected light from the object to be inspected are separated. a branching section, a plurality of detection sections that individually detect the amount of light of each of the P-polarized light component and the S-polarized light component branched at the branching section, and the amount of light of the S-polarized light component detected in the plurality of detection sections and the The structure has a calculation section that calculates the ratio of the light amount of the P-polarized light component and a comparison section that compares the ratio obtained in the calculation section with a predetermined threshold. Scattered light or reflected light is generated from the formed pattern with a relatively regular shape, and the S-polarized light component is larger than the P-polarized light component, and the underlying part has unevenness due to crystal grains and has a relatively disordered surface state. Scattered light or reflected light that is generated from a light source and has an S-polarized light component and a P-polarized light component that are almost equal in size is detected with a large contrast, and a pattern is detected based solely on changes in the amount of scattered light or reflected light. It is possible to improve the detection accuracy of a pattern formed on the surface of an object to be inspected.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a state in which a pattern detection device according to an embodiment of the present invention is installed in a reduction projection exposure apparatus, and FIG. 2 is an explanatory diagram illustrating its operation. 1...XY child table 2...Object to be inspected, 2a...
Positioning mark (pattern), 3... reduction lens,
4... Condenser lens, 5... Original plate, 5a... Figure formed on the original plate, 5. b...Figure to be transferred to the inspected object, 6...Exposure light, 7.8...Light source, 9...Mirror pattern, lO...Reflector, 11...Scattered light or reflection Light, 115... S polarized light component, zp... P polarized light component, 12... Lens, 13... Polarized beam splitter, 14.15... Detector, 16...・
Arithmetic unit, 17... Comparison unit, 18... Reference voltage generator, S... S polarized light, R... Ratio of light amount of S polarized light component and light amount of P polarized light component of scattered light or reflected light. , Th...Threshold value. Fig. 2 δ violent poor child 1 F, ゛1-pa-,''-1゛5'.

Claims (1)

[Claims] 1. P contained in scattered light or reflected light obtained by irradiating S-polarized light onto the surface of an object to be inspected on which a predetermined pattern is formed.
The amount of light of the polarized light component and the S polarized light component is detected individually, and the amount of light of the S polarized light component is detected individually.
A pattern detection method comprising: detecting a pattern formed on the surface of the object to be inspected by comparing a ratio of the amount of light of the polarized light component and the amount of light of the P-polarized light component with a predetermined threshold value. 2. The surface of the object to be inspected is scanned by the S-polarized light by relatively moving the object to be inspected irradiated with the S-polarized light in parallel. pattern detection method. 3. The pattern detection method according to claim 1, wherein the object to be inspected is a semiconductor wafer, and the pattern is an alignment mark formed on the semiconductor wafer during exposure. 4. A plurality of light sources that irradiate S-polarized light onto the surface of the object to be inspected on which a predetermined pattern is formed, and branch the P-polarized light component and the S-polarized light component contained in the scattered light or reflected light from the object to be inspected. a branching section, a plurality of detection sections that individually detect the amount of light of each of the P-polarized light component and the S-polarized light component branched at the branching section, and the amount of light of the S-polarized light component detected in the plurality of detection sections and the A pattern detection device comprising: a calculation unit that calculates a ratio between the amount of light of a P-polarized component; and a comparison unit that compares the ratio obtained in the calculation unit with a predetermined threshold value. 5. By moving the object to be inspected in parallel relative to the plurality of light sources, the object to be inspected is scanned with S-polarized light irradiated from the plurality of light sources onto the surface of the object to be inspected. 5. The pattern detection device according to claim 4, characterized in that: 6. The pattern detection device according to claim 4, wherein the plurality of light sources are arranged to face each other with the object to be inspected interposed therebetween. 7. The pattern detection device according to claim 4, wherein the object to be inspected is a semiconductor wafer, and the pattern is an alignment mark formed on the semiconductor wafer during exposure.