WO2017163318A1

WO2017163318A1 - Inspection device

Info

Publication number: WO2017163318A1
Application number: PCT/JP2016/059074
Authority: WO
Inventors: 良光川越; 英利西山
Original assignee: 株式会社日立ハイテクノロジーズ
Priority date: 2016-03-23
Filing date: 2016-03-23
Publication date: 2017-09-28

Abstract

Patent Document 1 discloses the use of a beam splitter and detectors 51, 52 disposed on the optical axis of an image formation lens 22b to obtain a Fourier image. However, Patent Document 1 does not take into consideration the tendency of this type of optical system to be expensive. One characteristic of the present invention is obtaining Fourier plane data by obtaining Fourier plane information so as to be divided into a plurality of units and combining the plurality of units. One characteristic of the present invention is using a defect detection sensor for the Fourier plane data. One characteristic of the present invention is obtaining the Fourier plane data using the defect detection sensor and a light-blocking member that is movable in relation to a Fourier plane and has an opening formed therein. One effect of the present invention is making an expensive optical system for Fourier plane observation unnecessary.

Description

Inspection device

The present invention relates to the optical field. In particular, the present invention relates to an optical system for forming a Fourier plane and an inspection apparatus using the same.

In semiconductor manufacturing processes, defects exemplified by foreign matters and scratches on the surface of a semiconductor substrate (wafer) cause defects such as wiring insulation defects and short circuits, and also cause capacitor insulation defects and gate oxide film breakdown. . Therefore, it is important to detect the defect and manage the cause of the defect in managing the yield. A so-called inspection device is used for such defect detection.

The inspection apparatus may form a so-called Fourier plane when detecting light from the wafer. Patent document 1 is mentioned as an inspection apparatus which forms a Fourier surface.

JP 2012-073097

Patent Document 1 discloses using a beam splitter and detectors 51 and 52 arranged on the optical axis of the imaging lens 22b in order to obtain a Fourier image. However, in Patent Document 1, no consideration is given to the point that such an optical system tends to be expensive.

The present invention is characterized in that Fourier plane data is obtained by dividing and acquiring information on a Fourier plane as a plurality of units and combining the plurality of units.

One feature of the present invention is that a sensor for defect detection is used for Fourier plane data.

The present invention is characterized in that Fourier plane data is obtained by using a light shielding member having an opening formed therein and a sensor for detecting a defect, which is movable with respect to the Fourier plane.

According to the present invention, for example, an expensive optical system dedicated to Fourier plane observation becomes unnecessary.

FIG. 1 is a diagram for explaining the first embodiment (overall view of the apparatus). Mechanism of interference fringe generation on the Fourier plane (schematic diagram) The figure explaining interception of interference light by a slide board FIG. 6 is a diagram for explaining Example 2 (flexible slide corresponding to Fourier peak width). Diagram for explaining the third embodiment FIG. 4 is a diagram for explaining a fourth embodiment (application of a slide to oblique illumination and epi-illumination) Diagram for explaining Example 6 (continued) Diagram for explaining Example 5 (defect S / N improvement by Pattern Noise distribution analysis) Diagram for explaining Example 5 (continued) FIG. 6 is a diagram illustrating Example 6 (abnormality diagnosis of an optical system) Diagram for explaining Example 6 (continued)

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description is an example. Deletion of any part of the disclosure, substitution with another part, and combination are also within the scope of the disclosure of this specification.

FIG. 1 (a) is an overall view of the apparatus of this embodiment. The illumination system 100 supplies laser light to the wafer 102.

The wafer 102 is attracted and fixed to the stage 101. The stage 101 can move in the x and y directions.

The inspection apparatus of this embodiment has a plurality of optical systems for collecting scattered light. One of them can be expressed as Top Channel for detecting light scattered in a relatively narrow first angle range (narrow angle scattered light), and the other is a second angle range wider than the first angle range. It can be expressed as a Side-Channel for detecting light scattered by (a wide-angle scattered light). The Top channel includes an objective lens 103, a Fourier lens 104, an imaging lens 106, a line sensor 107, and an A / D converter 108. The Side-Channel includes an objective lens 109, a Fourier lens 110, an imaging lens 112, a line sensor 113, and an A / D converter 114.

The light scattered from the wafer 102 is collected by the objective lens 103. The condensed light becomes a Fourier plane 105 by the Fourier lens 104 and enters the imaging lens 106. The scattered light is combined with the line sensor 107 by the imaging lens 106. The scattered image obtained by the line sensor 107 is sent as an electrical signal to the A / D converter 108 and converted into digital data. A similar operation is performed for Side Channel. A comparison operation for defect detection is performed by the CPU 115 on at least one digital data of Top Channel,, and Side Channel, and as a result, a defect is detected.

Here, signal processing by the CPU 115 will be described. As shown in FIG. 1B, when the stage 101 moves in the direction of the arrow 116, the CPU 115 obtains an elongated image (swath image) from the left end to the right end of the wafer. A first swath image is obtained from the Top Channel, and a second swath image is obtained from the Side Channel.

The CPU 115 obtains a part of the A-Chip from the first swath. This portion can be referred to as a frame image 117. Further, the CPU 115 obtains an image (frame image 118) at substantially the same location as the frame image 117 from the adjacent B-Chip. The CPU 115 performs a comparison operation on the frame image 117 and the frame image 118 to obtain a first defect image 119. The CPU 115 performs the same process on the second swath image. More specifically, a comparison operation is performed on the frame image 120 from the A-chip and the frame image 121 from the B-chip to obtain a second defect image 122.

Defect determination is performed by integrating the first defect image 119 and the second defect image 122. An example of the integration process includes obtaining a logical sum and a logical product for the first defect image 119 and the second defect image 122.

FIG. 2 is a diagram illustrating that when the periodic pattern 201 is irradiated with laser light, interference fringes 204 are generated therefrom. The illumination system 100 forms a substantially linear illumination area on the wafer. When such an illumination region is formed in the periodic pattern 201 on the wafer, scattered light 203 is generated from individual patterns in the periodic pattern in the irradiation surface 202.

Here, when the optical path difference is the wavelength λ, the scattered light 203 is overlapped and strengthened at a point in a certain space, so that the interference light 204 is formed. The interference light 204 is formed at a hemispherical position from the irradiation surface 202, and as a result, interference fringes 205 are formed. The interference fringes 205 can be expressed as a circular arc with the irradiation surface 202 as a base point. A plurality of interference fringes 205 can be formed depending on the wavelength of the light to be irradiated, the period of the irradiated pattern, and the number of the patterns. The interference fringe 205 is imaged as a first interference fringe on the Fourier plane 105 by the objective lens 103 and the Fourier lens 104 of the Top Channel. Similarly, an image is formed as a second interference fringe on the Fourier plane 111 by the objective lens 109 and the Fourier lens 110 of the side channel.

FIG. 3 is an explanation of an example in which the interference light (or interference fringes) described above is blocked by a blocking plate (hereinafter referred to as “Rod”), and minute defects on the periodic pattern can be detected.

Suppose that the laser is irradiated to the periodic pattern 201 and the minute defect 312 on the periodic pattern 201. Interference light from the periodic pattern 201 and scattered light from the minute defect 312 pass through the objective lens 103, the Fourier lens 104, the Fourier plane 105, and the imaging lens 106, and the image is coupled to the line sensor 107.

At that time, the scattered light of the micro defect is swung by the interference light, and the signal of the micro defect becomes difficult to see.

Therefore, a flat plate (hereinafter referred to as a “slid plate”) 301 having an elongated groove (hereinafter referred to as a “slid”) 302 is moved substantially parallel to the Fourier plane 105. When the slit 302 comes to the position of the interference fringe 206 on the Fourier plane 105, the interference light passes through the slit plate and reaches the coupling lens 106 and the line sensor 107, and the image is formed on the line sensor 107 for defect detection. Will be. When the slide plate 301 is moved and the slit 302 is not present at the position of the interference fringe 206 or other interference fringes, the interference light is blocked by the slit plate 301 and the interference light is not observed on the line sensor 107. The information on the Fourier plane is divided (segmented) into a blocking portion and a transmitting portion by the sliding plate 301. Further, when the slide plate 301 is moved and the slit 302 comes to the position of the next interference fringe, the interference light image is formed again on the line sensor 107. In addition, a slide includes the meaning of a notch, for example, and may be called a slit.

In this embodiment, the slit 302 is formed so as to intersect with the pixel arrangement direction of the line sensor 107 when viewed from the z direction (the optical axis direction of the top channel), more specifically, substantially orthogonally. The slide plate 301 is moved along the projection 311 of the optical axis of the oblique illumination light onto the wafer, more specifically, parallel to the projection 311. This description can be made by replacing the projection 311 with a linear illumination region or the Y direction.

By such relative movement of the sliding plate 301 with respect to the Fourier plane 105, a profile 304 in which the moving distance of the sliding plate 301 and the observed interference light are plotted is obtained. The positions of

peaks

305, 306, and 307 in the profile represent the positions of interference fringes in the Fourier plane 105. It is possible to know at which position the interference fringe exists by the profile 304. These operations can also be expressed as obtaining Fourier plane data by dividing Fourier plane information into a plurality of units and combining the plurality of units.

Then,

Rods

308, 309, and 310 that block interference light are arranged at the positions of

peaks

305, 306, and 307, respectively. Then, the light that enters the coupling lens 105 is only scattered light of minute defects, and the scattered image combined by the line sensor 107 can clearly display the scattered light of minute defects.

FIG. 3 describes the Top channel, but the same description can be applied to the Side channel. Rod can be called a spatial filter or an optical filter. At least one of the first swath image and the second swath image in FIG. 1 is obtained by applying the method of FIG.

The movement of the sliding plate 301 is performed by a moving mechanism exemplified by a motor or the like. The movement distance of the sliding plate 301 is stored by the CPU 115 or another control device storing the output of the movement mechanism in its internal memory.

The position of the sliding plate 301 may not exactly coincide with the position of the Fourier plane 105. The slide 302 can be expressed as a hole or an opening. When the slide 302 captures a specific interference fringe, it is desirable that other portions be blocked. Therefore, it is desirable that the slide 301 includes a portion wider than the Fourier plane 105. The slide plate 301 can be expressed as an optical element that allows a specific component of the Fourier plane 105 to pass therethrough. As another expression, the slide plate 301 can be expressed by the slit 302 as information having Fourier plane information as a predetermined unit.

According to the present embodiment, since the signal of the Fourier plane is obtained by the slide plate and the defect detection sensor, a dedicated optical system for observing the Fourier plane becomes unnecessary. As a result, the apparatus can be configured at low cost.

Next, Example 2 will be described. The width of the interference light varies depending on the shape and number of periodic patterns and the laser wavelength to be irradiated. The present embodiment takes this point into consideration and is characterized in that the width of the slide is variable. FIG. 4 is a diagram for explaining this embodiment.

The sliding plate 401 of the present embodiment includes a plurality of stacked sliding plates, more specifically, two sliding

plates

402 and 403 that are close enough not to contact each other. A slit 404 is formed on each of the

slide plates

402 and 403. The slide of the slide plate 401 is expressed as a combination of two slides 404. By moving at least one of the

slides

402 and 403 with respect to the other by a moving mechanism such as a motor, the width of synthesis of the slide 404 can be changed. Even when the interference light 406 is changed from the interference light 406 to the interference light 407 by such a slide plate 401, only arbitrary interference light can be passed.

Next, Example 3 will be described. The kind of the slide is not limited to the first and second embodiments. FIG. 5 is a diagram for explaining this embodiment. FIG. 5A shows the slide (fixed slide) of the first embodiment, and FIG. 5B shows the slide (flexible slide) of the second embodiment. Furthermore, the slide of the present invention may include the slides of FIGS. 5 (c) and 5 (d).

The slide may be a set of a plurality of holes 502 (multi-spot slide) as shown in FIG. The holes 502 may be formed at equal intervals or may be formed at different intervals.

The saddle of the slide may include a spherical surface portion 503 as shown in FIG.

Next, a diagram for explaining the fourth embodiment. In this embodiment, more complex periodic patterns and illumination light directions are taken into consideration. FIG. 6 is a diagram for explaining this embodiment.

In an inspection apparatus, illumination light may be supplied so that a normal line of a wafer and its optical axis form a predetermined incident angle (>> 0 °). Such an illumination method is called oblique illumination. . In some inspection apparatuses, illumination light may be supplied so that the normal line of the wafer substantially coincides with its optical axis, and such an illumination method is called epi-illumination or vertical illumination. In FIG. 6, oblique illumination is represented by reference numeral 602, and epi-illumination is represented by reference numeral 603. The epi-illumination 603 is reflected by the mirror 604 and supplied to the wafer via the objective lens 103.

When oblique illumination 602 and epi-illumination 603 are supplied by the illumination system 100 to a periodic pattern 601 having a period of Δx width in the x direction and a period of Δy width in the y direction, Interference fringes (first interference fringes) according to the period in the x direction and interference fringes (second interference fringes) according to the period in the y direction are formed. As a result, the Fourier plane 105 includes a first portion 605 that is a combination of both the first interference fringe and the second interference fringe, a second portion 606 that includes only one component, and a second portion 606 that includes only the other component. 3 parts 607 will be included.

FIG. 7 is a diagram illustrating an example of shielding the interference pattern in the case of FIG. FIG. 7 can be described as an application of FIG. First, in order to observe the interference fringes in the x direction on the Fourier plane 105, the sliding plate 301 is moved relative to the Fourier plane 105 in the x direction on the Fourier plane by using a moving device such as a motor as in the first embodiment. The interference fringes in the x direction are imaged on the line sensor 107 for defect detection. The observed data is recorded in a memory inside the CPU 115 as a plot diagram 702.

Further, in this embodiment, the slide plate 701 having a slit orthogonal to the x direction on the wafer is moved using a moving device such as a motor along the y direction orthogonal to the x direction on the Fourier plane, The interference fringes in the y direction are imaged on the line sensor 107 for defect detection. The observed data is recorded in a memory inside the CPU 115 as a plot diagram 702. In this embodiment, the slits of the slit plate 701 are formed so as to extend toward the pixel arrangement direction of the line sensor 107 when viewed from the z direction, more specifically, to be substantially parallel.

The CPU 115 or other control device combines the plot diagrams 702 and 703 to create an intensity distribution 704 on the Fourier plane. An intensity distribution 704 represents the intensity distribution of light in the x and y directions on the Fourier plane. Therefore, if

Rods

308, 309, 310, 705, 706, 707, and 708 are arranged so as to shield the first portion 709, the second portion 710, and the third portion 711, a complicated pattern or a plurality of illumination lights can be obtained. Even in the case of supplying, it is possible to block unwanted interference light.

Next, Example 5 will be described. In addition to the memory pattern, a relatively complicated logic pattern 801 may be formed on the wafer as shown in FIG. As shown in FIG. 8A, in the logic pattern, pattern noise 803 due to the logic pattern is generated in addition to the scattered light 804 from the defect 802. This embodiment is an embodiment that takes this logic pattern into consideration.

In this embodiment, a slide plate 701 having a slide is used as shown in FIG. More specifically, the slide plate 701 is arranged so that the slide extends in the direction of the projection 805 on the wafer with oblique illumination. The direction in which the slide extends substantially coincides with the pixel arrangement direction of the line sensor 107. The sliding plate 701 moves in a direction intersecting with the projection 805 as viewed from the Z direction, more specifically, in a direction substantially orthogonal to the sliding plate 701. As a result, the combined scattered light of the scattered light 804 and the pattern noise 803 resulting from the logic pattern passes through the objective lens 103, the Fourier lens 104, and the coupling lens 106, and is imaged on the line sensor 107. An image obtained by moving the slide plate 701 is a two-dimensional image 805 shown in FIG. The distance in the x direction can be obtained from the size of the slide, and the size in the y direction can be obtained from the moving distance of the slide plate 701. Such a two-dimensional image 805 includes a stronger portion 806 than other portions. This portion 806 shows pattern noise 803. Therefore, by disposing Rod 309 in this portion 806, the signal from the defect is more emphasized, and the image quality is improved from the state of FIG. 9C to the state of FIG. 9D. The simple flow of this embodiment is expressed as FIG.

Next, Example 6 will be described. In this embodiment, a Fourier plane image is applied to abnormality diagnosis of an optical system.

In this embodiment, an alumina chip 901 whose surface is uniformly roughened is used. The illumination system 100 supplies oblique illumination to the alumina tip 901 to form a substantially linear illumination region extending in the Y direction. In this embodiment, illumination is supplied to the alumina chip 901 and the slide plate 701 is used. More specifically, the slide plate 701 is arranged so that the slide extends in the direction of the projection 807 onto the wafer with oblique illumination. The direction in which the slide extends substantially coincides with the pixel arrangement direction of the line sensor 107. The sliding plate 701 moves in a direction intersecting with the projection 805 as viewed from the Z direction, more specifically, in a direction substantially orthogonal to the sliding plate 701.

Scattered light from the alumina chip 901 will be scattered evenly. The scattered light evenly scattered is collected by the objective lens 103 and the Fourier lens 104, and the light that has passed through the slit 701 passes through the imaging lens 106 and forms an image on the line sensor 107. As a result, the CPU 115 obtains at least one of the digital data represented by FIGS. 11 (a) and 11 (b). For example, the data 902 indicates that both the illumination system 100 and the Top channel are normal. Data 903 indicates that at least one of the illumination system 100 and the Top Channel exists.

For example, if the peak of intensity existing at the center in the data 902 has moved to the position 904 in the data 903, it can be determined that there is distortion in the optical axis of the Top channel. When the brightness is reduced as indicated by reference numeral 905, it can be determined that the output of the illumination system 100 is reduced, for example, the laser light source is particularly deteriorated. When a geometric image exemplified by the dark line 906 is obtained, it can be determined that the pixel of the line sensor 107 is abnormal.

Accordingly, normal data such as data 902 is stored in the memory in the CPU 115, and the abnormality of the optical system is determined by comparing the data obtained by using the alumina 901 with the data 902. Can do. This comparison may be performed by at least one of a processor exemplified by the CPU 115 and an operator. This determination flow can also be expressed as the flow in FIG.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments. The disclosure of the present specification can be widely applied to optical devices that form a Fourier plane. Although the apparatus of the present embodiment is a dark field type optical apparatus that detects a scattered light image, the disclosure of the present specification can be applied to a so-called bright field type optical apparatus, a combination of a dark field type and a bright field type. .

The explanation of Top channel can also be applied to Side Channel. The positional relationship between the slide and the illumination area can be set arbitrarily. An arbitrary direction can be adopted as the moving direction of the slide plate. Arbitrary shapes can be set for the shape of the slide and the slide plate.

Slid board is only an example. For example, the present invention can be expressed as one feature of dividing a Fourier plane into a plurality of units (which can be referred to as sections or segments) and then synthesizing the segments to obtain Fourier plane data. it can. Thus, it is within the scope of this disclosure to use elements that do not move relative to the Fourier plane. As an example, there are a shutter array including a plurality of openings and a shutter capable of blocking any opening, and a liquid crystal shutter array capable of controlling the transmittance of any section.

The selective propagation of part of the light on the Fourier plane due to the movement of the slit plate relative to the Fourier plane can be expressed as a division of the Fourier plane. Further, the selectively transmitted information of the Fourier plane may be referred to as one unit for explanation. Further, this unit is detected, and data exemplified in at least one of the profile 304, the intensity distribution 704, FIG. 9 (a), FIG. 9 (b), FIG. 11 (a), and FIG. 11 (b) is obtained. This can be expressed as, for example, synthesis. This description can also be applied to opening / closing an arbitrary shutter and changing the transmittance of an arbitrary liquid crystal.

DESCRIPTION OF SYMBOLS 101 ... Stage 102 ... Wafer 103 ... Objective lens 104 ... Fourier lens 105 ... Fourier surface 106 ... Coupled lens 107 ... Line sensor 108 ... A / D converter 109 ... Objective lens 110 ... Fourier lens 111 ... Fourier surface 112 ... imaging lens 113 ... Line sensor 115 ... CPU

Claims

An illumination optical system for supplying light to the sample;
A detection optical system that collects light from the sample and forms a Fourier plane;
An optical element that divides the information of the Fourier plane into a plurality of units and propagates the plurality of units;
A defect detection sensor for detecting the unit;
A processor for obtaining Fourier plane data by synthesizing outputs from the sensors.
The inspection apparatus according to claim 1,
The sensor is a line sensor;
The optical element includes a first light shielding plate in which a first opening is formed,
The first opening is formed to intersect the pixel array direction of the line sensor,
And a first moving mechanism for moving the first light shielding plate with respect to the Fourier plane.
The inspection apparatus includes the data including first data obtained by moving the first light shielding plate.
The inspection apparatus according to claim 2,
The illumination optical system supplies oblique illumination to the sample, and epi-illumination through the detection optical system,
The optical element includes a second light shielding plate in which a second opening is formed,
The second opening is formed to extend in the pixel array direction of the line sensor,
And a second moving mechanism for moving the second light shielding plate with respect to the Fourier plane.
The inspection apparatus includes second data obtained by moving the second light shielding plate.
The inspection apparatus according to claim 3, wherein
The inspection apparatus, wherein the processor obtains third data using the first data and the second data, and obtains a light shielding position of the Fourier plane using the third data.
The inspection apparatus according to claim 4,
The second data includes scattered light data from an object with an evenly rough surface,
The processor compares the reference data with the second data to determine at least one abnormality of the illumination optical system and the detection optical system.
The inspection apparatus according to claim 5, wherein
An inspection apparatus in which at least one width of the first opening and the second opening is variable.
The inspection apparatus according to claim 5, wherein
An inspection apparatus in which at least one of the first opening and the second opening is a set of a plurality of holes.
The inspection apparatus according to claim 5, wherein
An inspection apparatus in which at least one ridge of the first opening and the second opening is spherically processed.
The inspection apparatus according to claim 1,
The sensor is a line sensor;
The optical element includes a light shielding plate in which an opening is formed,
Furthermore, it has a moving mechanism for moving the light shielding plate with respect to the Fourier plane,
The data is obtained by moving the shading plate,
The processor is an inspection apparatus that obtains a light shielding position of the Fourier plane using the data.
The inspection apparatus according to claim 9, wherein
The inspection apparatus is formed such that the opening intersects the pixel array direction of the line sensor.
The inspection apparatus according to claim 9, wherein
The inspection device is formed such that the opening extends in a pixel array direction of the line sensor.
The inspection apparatus according to claim 1,
The sensor is a line sensor;
The optical element includes a light shielding plate in which an opening is formed,
Furthermore, it has a moving mechanism for moving the light shielding plate with respect to the Fourier plane,
The data is obtained by moving the shading plate,
An inspection apparatus in which the width of the opening is variable.
The inspection apparatus according to claim 1,
The sensor is a line sensor;
The optical element includes a light shielding plate in which an opening is formed,
Furthermore, it has a moving mechanism for moving the light shielding plate with respect to the Fourier plane,
The data is obtained by moving the shading plate,
The inspection device is an assembly of a plurality of holes.
The inspection apparatus according to claim 1,
The sensor is a line sensor;
The optical element includes a light shielding plate in which an opening is formed,
Furthermore, it has a moving mechanism for moving the light shielding plate with respect to the Fourier plane,
The data is obtained by moving the shading plate,
The inspection device in which the eyelid of the first opening is spherically processed.
The inspection apparatus according to claim 1,
The data includes data of scattered light from an object with an evenly rough surface,
The processor compares the data as a reference with the data, and determines at least one abnormality of the illumination optical system and the detection optical system.