KR100829658B1 - Wafer inspection system for irradiation at variable angles - Google Patents

Abstract

The present invention relates to a variable irradiation angle inspection system comprising a light source providing a light beam and a scanner for scanning deflecting the light beam to approach the scanning beam at a first angle to the substrate. A deflection element may be selectively inserted into the optical path of the scanning beam to deflect the scanning beam, thereby bringing the scanning beam close to the substrate at a second angle.

Description

Wafer inspection system which irradiates with variable angle {VARIABLE ANGLE ILLUMINATION WAFER INSPECTION SYSTEM}

The present invention relates to a wafer inspection system for irradiating at variable angles.

Wafer inspection systems are well known in the art. One conventional system described in US Pat. No. 5,699,447 uses a method of normal illumination and bright-field inspection (ie, the method of approaching the wafer at 90 degrees). Another type of conventional system described in US Pat. No. 5,825,482 uses oblique illumination and dark-field inspection (i.e., the method of irradiation is obliquely approaching the wafer). The third type of system described in US Pat. No. 5,982,921 uses a vertical irradiation and dark field inspection method. All of the above conventional methods have advantages and disadvantages, some of which relate to the particular application or situation in which the system is used.

Under normal irradiation, the surface of the observed object is perpendicular to the optical axis of the objective lens and light is used to irradiate the object. In bright field systems, light that is reflected back to the objective lens in a direction substantially parallel to the incident beam is used to form the image. Thus, reflective and perpendicular surfaces appear bright, and features that are non-reflective and obliquely reflect less light to the objective lens appear darker. The dark field system can be performed with vertical or oblique irradiation. In either case, light scattered from the optical axis is collected by a dark field detector placed at an angle on the observed surface for image formation. Thus, the inclined surfaces of features such as ridges, pits, scratches, and dirt appear bright, increasing the contrast of these features in indistinguishable topography features. Thus, reflective features that generally appear bright in brightfield irradiation are completely black in darkfield irradiation and fine features that cannot be detected using brightfield irradiation can be easily observed with darkfield irradiation.

In the laser-scanned wafer inspection method, it is often desirable to irradiate the wafer perpendicular to the wafer surface, while in other cases it is desirable to use a gradient irradiation method, depending on the wafer material, pattern and defects. The optical scattering properties of semiconductor wafers vary greatly as the wafer proceeds from one step of the IC manufacturing process to the next. Some layers (ie bare silicon) are very soft while some layers (ie deposited aluminum) are very rough.

The oblique illumination angle has a "Lloyd's mirror" effect (especially the interference of incident and reflected light on the surface where the height from the surface is much less than the wavelength of incident light on the metal surface and the scattering is substantially reduced from the grain). It is well known that it helps to reduce unwanted optical scattering of grain and roughness. However, the oblique irradiation angle has some limitations that make it less useful than the vertical irradiation of some layers. One disadvantage of the oblique irradiation angle is that light cannot penetrate between intensive lines, such as those used for poly-silicon or metal wiring. Another disadvantage of tilted irradiation is that the scattered signal depends on the direction of the substrate feature (ie there is a loss of symmetry in the vertical irradiation).

In practical inspection systems it is often desirable to have replaceable optical elements whose spot size can be determined. Thus, such a system can be optimized to scan at large spot sizes and obtain very high scanning speeds even at limited sensitivity, while on the other hand it can be optimized to achieve very high sensitivity at small spot sizes even at low scan speeds. For vertical irradiation this is extremely simple and limits how small the spot can be by conventional resolution only. However, in inclined irradiation, very small spots cannot be obtained due to the additional geometrical causes that the spots spread across the inclined substrate plane.

Accordingly, there is a need for an improved wafer inspection system that selectively and preferably uses vertical scattering radiation or oblique scattering radiation based on the specific optical scattering characteristics of the semiconductor wafer during inspection.

An advantage of the present invention is that a wafer inspection system is used which can optionally and preferably use vertical scanning radiation or oblique scanning radiation to optimize the inspection properties of the scanned layer.

According to the invention, the above and other advantages are achieved in part by a system for inspecting the substrate at varying irradiation angles. A substrate inspection system having a variable irradiation angle includes a light source for providing a light beam; A scanner for scanning deflecting the light beam to access the scanning beam at a first angle to the substrate; And a deflection element that can be selectively inserted into the optical path of the scanning beam and deflects the scanning beam to approach the substrate at a second angle.

Another aspect of the invention is a inspection system of varying irradiation angles for substrate inspection comprising a light source for providing a light beam and a scanning element provided for outputting the light beam along the first light path to the substrate. And a portion incident on the substrate to form a first angle with respect to the substrate. The deflection element is selectively introduced into the first light path to output the light beam along the second light path to the substrate, the second light path including a portion incident on the substrate to form a second angle with respect to the substrate, Wherein the first angle is different from the second angle.

Another aspect of the invention provides a deflection element for use in a substrate inspection system of varying irradiation angles. Such a deflection element includes a first deflection surface and a second deflection surface, and the first and second deflection surfaces each comprise a mirror surface. The first deflection surface is disposed at an angle with respect to the second deflection surface, so that the irradiation beam incident on the deflection element from the first direction is output from the deflection element in the second direction.

Thus, for the above reasons and the reasons discussed herein, the present invention can be optimized for the specific characteristics of the scanned layer.                 

Additional features and advantages of the invention will be readily understood by those skilled in the art from the following detailed description, in which only preferred embodiments of the invention are shown and described simply by way of explanation of the optimal method for carrying out the invention. . As will be realized, the invention is capable of different and different embodiments, and its several details are capable of modification in various obvious respects, all without departing from the scope of the invention. Accordingly, it should be appreciated that the drawings and specification are illustrative, but not restrictive.

1 is a diagram of a first embodiment of an irradiation system set vertically in accordance with the present invention;

2 is an illustration of the irradiation system of FIG. 1 set to be inclined at a first angle;

3 is a view of the irradiation system of FIG. 1 set to be inclined at a second angle;

4 shows a second embodiment of a system according to the invention in which a tilt is provided after a scanning element.

5 is a diagram of a tilt irradiation regulator that may be used in accordance with the present invention.

6 is a view of the tilt irradiation regulator of FIG. 5 used with the autofocus device.

7 is a diagram of another form of inclined irradiation regulator that may be used in accordance with the present invention.

8A and 8B are views irradiated in both directions upon defect detection.

9 is a view of a survey embodiment of the present invention set to be inclined.

10 is a view of the irradiation embodiment of FIG. 9 set vertically;

1 is a first embodiment of the present invention. The laser 100, such as an argon laser or other suitable high density laser beam source, provides a light beam that is used to scan the surface of the semiconductor wafer or substrate 105 received by the vacuum chuck. Conventional optical device 110 is used to shape a light beam and may include, for example, a beam expander and a cylindrical lens (not shown). The above-described device and its operating principle are well known and will not be described in detail here.

A mechanism for scanning a laser beam is provided. As is well known, these laser beam scanning mechanisms are Galvanometer's scanning plane mirrors, rotary and polygon mirrors, acoustic-optical deflectors (AODs), or any other method for imparting the laser scan movement required for a laser beam. A mechanism is shown, which is shown in FIG. 1 by reference numeral 120 and will hereinafter be described the same as scanning element 120. In addition, a mechanism is provided for deflecting the scanned beam towards a desired optical channel (eg, a vertical or oblique irradiation channel). The deflection mechanism may include, for example, a movable mirror capable of rotating the beam toward one of the channels, a mirror on a linear actuator moving in and out of the light path, or an AOD. Although various configurations and combinations of scanning mechanisms and detection mechanisms are described in further detail below, the above described examples are not limiting and many other combinations and subcombinations for the scanning and deflection mechanisms may be provided in accordance with the present invention. .

In one basic configuration, as is known to those skilled in the art, the scanning element 120 is coupled to a motor 126 that can adjust the mirror angle by a slight increase in response to the scanning command signal from the scanning controller 115. And a galvanometer scanning plane mirror rotated by it. In this embodiment, the scanning mechanism and the deflection mechanism are preferably integrated into a single element. The scan begins around a number of central positions, each corresponding to a deflection of the scanned beam in the desired direction along the vertical and oblique irradiation channels. These two irradiation channels are shown in FIGS. 1 and 2, which illustrate one central position corresponding to a vertical irradiation path or channel and another central position corresponding to an inclined irradiation channel, respectively.

The scanning element 120 deflects the light beam in a predetermined direction towards the semiconductor wafer or substrate 105 or toward an optical element such as the objective lens 130 or the mirror 140. The scanning may for example be performed along a first axis, such as the X axis, while the wafer is moved by a scanning stage (not shown) along a second axis perpendicular to the first axis, such as the Y axis. Other combinations of processor variables, such as scanning speed, length of scanning lines, spacing between adjacent lines, and spot size of light beams, can be used to implement the present invention as desired by the user.

In the position shown in FIG. 1, the tilt angle of the scanning element 120 including the galvanometer scanning plane mirror is such that the beam is perpendicular to the beam (eg, along the Z axis perpendicular to the X and Y axes). 105). In a method known to those skilled in the art and not described in detail herein, the optical relay 106 includes a pair of lenses used to relay light between the scanning element 120 and the objective lens 130 and is scanned on the wafer. Focus the beam. The dark field detector 160 preferably includes four optical multiplexer tubes (PMTs) manufactured by Hamamatsu, Japan, or light scattered with features that are tilted relative to the X and Y axes of the wafer in a manner known to those skilled in the art. For detection, the photodiode detector includes a photodiode detector spaced at 90 ° from each other and disposed at an angle of about 45 ° with respect to the X and Y axes of the wafer 105. More or fewer PMTs or photodiodes may be used and the placement of such detectors may also be varied to optimize dark field detection depending on the particular application. As shown in FIG. 1, the mirror 140, the objective lens 150, the first mirror 170, the second mirror 180, and the actuator 190 are not included in the optical path of the scanning light beam.

FIG. 2 illustrates the tilt irradiation mode system of FIG. 1. In this mode, the tilt of the scanning element 120 planar mirror is changed to deflect the scanned beam towards the mirror 140 through the optical relay 107. The mirror 140 deflects the light towards and passing through the objective lens 150. Actuator 190 introduces one of the plurality of mirrors 170, 180 into the beam path. Although only two mirrors are shown in FIG. 2, the present invention may preferably include two or more mirrors. Each mirror 170, 180 is connected to a movable actuator arm 175, 185, respectively. The mirror 180 deflects the light beam toward the wafer 105 at an oblique angle that receives incident light from the scanning mirror 120 and all intermediate optical elements located therein and provides oblique irradiation.

As shown in FIGS. 2 and 3, in order to change the irradiation angle, the actuator 190 introduces another mirror, that is, mirror 170, intercepts the light beam output from the scanning mirror, and selects the deselected mirror 180. Put it in. The irradiation angle is changed as shown in FIG. 3 by inserting a mirror 170 having a different inclination or angle from the deselected mirror (ie, the mirror 180). Multiple mirrors aligned at a predetermined angle are used to direct the direction of the incident light beam from each mirror previously aligned at somewhat different angles to the same location on the wafer 105. Alternatively, a single mirror may be used in place of the mirrors 170, 180, which mirror are selectively tilted at a desired angle with respect to a selected axis with respect to the incident light beam, thereby obtaining the required irradiation angle, whereby the wafer 105 The position of the irradiation spot incident on the image is changed.

4 illustrates another variation of the present invention, wherein the scanning element comprises an acousto-optic deflector (AOD) 145 mirror 125 manufactured by US Crystal Technologies, Inc. (CTI). As is known to those skilled in the art, the AOD scanning element 145, for example, adjusts the optical index of refraction of the selected acoustooptic crystal, deflects the light beam and directs the direction of the incident light beam through and through the path between the wafers 105. It includes a conversion portion for generating sound waves to change. The mirror 125 sets the direction of the light beam output from the optics 110 to the AOD scanning element 145. Optionally, laser 100 and optics 110 may be arranged to directly input a light beam into an AOD scanning element or rotatable mirror 145. Inclined illumination is provided by actuator 195, which introduces a deflection mirror 186 into the scanning beam to deflect the scanning beam towards mirror 140, the scanning beam being shown in FIGS. 1-3. Follow a path similar to To provide vertical illumination, actuator 195 subtracts deflection mirror 186 from the optical path of the light beam output by AOD scanning element 145.

1-4 provide an actuator to selectively insert a deflection mirror into the optical path to achieve the desired irradiation angle. Similarly, according to the foregoing and the embodiments shown in FIGS. 5-7, one or more actuators can selectively insert multiple objective lenses into the optical path, and individually or in combination with the objective lens, the glass wedge ( Optional glass wedges can be inserted. As shown in Figs. 5-7, these glass wedges are inserted below the objective lens 130 (shown in Figs. 1-4) to deflect the irradiation beam perpendicular to the substrate in a direction inclined to the substrate. As will be appreciated by those skilled in the art, the objective lens shown on each deflection element in FIGS. 5-7 described below need not necessarily be the same as the objective lens 130 shown, and for similar purposes, It may be placed at any position.

Thus, according to the foregoing, oblique irradiation can be obtained from the vertical irradiation scanning beam by introducing different optical deflection elements, such as prisms or reflective glass wedges, into the vertical irradiation scanning beam. This may be accomplished, for example, using the actuator 195 and the movable actuator arm 185, or in any other way that can be appreciated by those skilled in the art of introducing optical elements into the optical path.

For example, the optical deflection element may include a partially reflected glass wedge 500 disposed below the objective lens 130, as shown in FIG. 5. The selection of the appropriate wedge shape and the refractive index of the glass make it possible to focus the oblique irradiation at the same distance and position as the irradiated light provided vertically along the A-axis corresponding to the center of the objective lens 130. In other words, Fig. 5 shows a preferred configuration in which the inclined irradiation focus coincides with the vertical irradiation focus. In this aspect of the invention, the glass wedge is formed of SFL6 glass, but other modified glass wedges may use other conventional glass, such as BK7. The vertex angle α of the glass wedge is 30 °, the width H of the upper surface is 10.88 mm, and the length L of the leftmost surface is 18.8 mm. As shown in FIG. 5, the end E may be selectively removed by shading the end E to facilitate positioning of the glass wedge 500 relative to the substrate. 5 shows an optical deflection element according to the invention and should not be construed to limit or describe the exact dimensions.

The original inverse focal length B is 15.8 mm and the object inverse focal plane of the objective lens 130 is located at a distance D, 4 mm from the top of the glass wedge. The distance T of the leftmost surface of the glass wedge in the main ray passing from the objective lens through the center of the aperture stop of the optical system is 8.08 mm. In the above configuration, the numerical aperture NA of the lens is selected to be 0.125. However, NA in the range of about 0.04 to 0.125 may be used based on the selected parameter.

Right angled triangular prisms are used in this respect, but other forms of irregular polygons may also be used in accordance with the present invention. In addition, the foregoing dimensions only specify one particular embodiment of a glass wedge that provides tilted illumination and many other combinations of materials, angles, and dimensions can be used to achieve the aforementioned results in accordance with the present invention. In other words, in this embodiment, a vertex angle of 30 ° is selected to form an angle of incidence of 60 °, but other angles of incidence may be obtained using the geometry and characteristics of different wedges 500 using the principles described above and It is to be understood that one exemplary parameter relates to a particular embodiment and does not limit the technical spirit of the invention disclosed herein. In addition, although it is described that the glass wedge 500 may be disposed below the objective lens 130, other modification configurations may be preferably used. For example, the glass wedge 500 may be integrated into the objective lens 130 or embodied in a common structure and placed simultaneously in the incident irradiation light.

As shown in FIG. 5, the light output from the objective lens 130 is reflected at a mirror surface 520, such as but not limited to a reflective aluminum or aluminum alloy coating, and is obliquely focused on the vertical irradiation focus. Light scattered back to the bright field detector through the prism and the objective lens can be used and collected for inspection purposes. In addition, all light diffused in all directions by the wafer or specimen can be collected and used for processing.

In automated inspection systems, autofocus mechanisms are preferred. Some autofocus systems that can be used in vertical illumination configurations utilize light reflected back through the objective lens. This autofocus mechanism can be accommodated by a modified one-way tilt irradiation regulator. In a modified regulator, the autofocus prism 600 shown in FIG. 6 may be provided to the glass wedge 500 of FIG. 5 autofocusable by the second light path. In accordance with the embodiment of FIG. 5, one or more actuators selectively insert different objective lenses into the light path, and selectively or individually with the glass wedge 500 into the light path, either objective lens and / or autofocus prism 600. Can be inserted by

In this embodiment, the mirror surface 520 on the glass wedge 500 is replaced with a reflective coating 620 that transmits some of the incident light. Next, brightfield reflection in the vertical direction may be at least partially retransmitted to the objective lens 130 through the reflective coating 620 to enable brightfield detection and autofocus. In FIG. 5, a portion of the incident light from the objective lens 130 is transmitted through the reflective coating 620, and the remaining portion of the light is transmitted along the inclined irradiation path shown. For example, light transmitted through reflective coating 620 may comprise about 5-10% of the light, and the remaining portion of the light along the oblique irradiation path correspondingly comprises 90-95% of the light. The autofocus prism 600 can be configured to match the focal height of the vertical illumination and the oblique irradiation individually or together with the low power cylindrical lens 630, as shown in FIG. However, the system is not limited to autofocus based on irradiation path optics and is also well suited to autofocus based on other principles such as PSD in reflected light paths. For example, autofocus can be performed when the detector is positioned to detect and utilize incident light reflected from the wafer and the first irradiation beam is tilted in a manner known to those skilled in the art. In addition, the system of the present invention can be operated with or without autofocus.

In addition, as shown in FIG. 7, inclined illumination can be provided in both directions by replacing the glass edge of FIG. 5 with a three-section adjuster 790 comprising glass wedges 700, 710, and 720. Surface 730 is covered with a 100% reflective coating, such as an aluminum or aluminum alloy layer. Surface coating 740 penetrates a specific portion of s-polarized light and p-polarized light (hereinafter denoted as s ₇₄₀ % and p ₇₄₀ % reflecting the transmittance of incident light components, respectively) and reflects the remaining untransmitted light components. Is a polarizing beamsplitter coating provided at the interface of sections 700 and 710. In this embodiment, the polarization of the incident light is controlled to include both s and p polarizations through the use of quarter wave plates or half wave plates. Surface coating 740 is provided to transmit a greater proportion of s-polarized light (i.e., s ₇₄₀ %> p ₇₄₀ %) than p-polarized light. Surface coating 750 provides polarization provided at the interface of sections 710 and 720 that transmits approximately s ₇₅₀ % s polarization and p ₇₅₀ % p polarization and reflects the remaining light components that are not transmitted at s ₇₅₀ %> p ₇₅₀ %. Beamsplitter coating. Thus, the oblique beam 705 emerging from section 700 is mainly s polarized, while the oblique beam 725 emerging from section 720 is primarily p polarized. By this embodiment, one preferred configuration uses a surface coating ₇₄₀ with s ₇₄₀ = 99% and p ₇₄₀ = 1%, and a surface coating _{750 with} s ₇₅₀ = 1% and p ₇₅₀ = 99%. . In general, surface coatings can be used to transmit all desired or light components and are not limited to the above-described embodiments.

In addition, surface coatings 740 and 750 may include multiple layers adjacent to each other, where the functionality of the coatings 740 and 750 is divided by multiple layers. For example, the s polarizing beamsplitter coating 740 may utilize one or more layers, the combination of layers forming the desired polarization level. Thus, the first s-polarization beamsplitter coating 740 having the first polarization ratio is provided with a second polarization ratio provided only after forming the polarization level required for the first s-polarization beamsplitter coating 740. S polarizing beamsplitter coating 741 (not shown) can be used.

Optionally, surface coatings 740 and 750 can be replaced by a half wave plate and polarizing beamsplitter coating. For example, instead of the s polarizing beamsplitter coating 740, a p polarizing beamsplitter may be disposed between two half wave plates. As is known to those skilled in the art, the first half wave plate rotates the input polarization by 90 degrees, changes s- to p- and vice versa. The p-polarizing beamsplitter coating transmits p- (originally s-) and the second half-wave plate rotates the input polarization by another 90 degrees and converts the input p polarization to the output s polarization. This embodiment also contemplates other combinations of wavelength plates, such as quarter wave plates, and / or polarizing beamsplitter coatings that can achieve the desired output polarization ratio. One polarization ratio suitable for use in the system of the present invention is approximately 99: 1.

The 3-section adjuster 790 is introduced into the optical path by the actuator 190 and the movable actuator arm 185 to deflect incident light toward the wafer or substrate at an oblique angle and to conform to the center of the objective lens 130. The oblique irradiation is focused at the same interval and at the same position as the irradiation light provided in the vertical direction along the A axis. In this aspect of the invention, the glass wedge is composed of SFL6 glass, but other variations of the three-section regulator 790 may utilize other conventional glass, such as BK7. The vertex angle α of the glass wedge is 30 degrees, the width H of the upper surface is 10.88 mm, and the length L of the leftmost surface is 18.8 mm. As shown in FIG. 7, the end E can be selectively removed by shading the end E, which facilitates the placement of the glass wedge relative to the substrate.

The original inverse focal length B is 15.8 mm and the object inverse focal plane of the objective lens 130 is disposed at a distance of 4 mm from the top of the three-section adjuster 790. The distance T from the leftmost or rightmost surface of the glass wedges 700 and 720 to the principal ray passing through the center of the aperture stop of the optical system from the objective lens 130 is 8.08 mm. The numerical aperture NA of the lens is 0.125. However, NA in the range of about 0.04 to 0.125 based on the selected parameter can be used. 7 shows a regulator 790 for deflecting a light beam in accordance with the present invention and should not be construed as limiting the exact dimensions.

This limited dimension represents only one specific embodiment of the glass wedges 700, 710 and 720 used together to provide tilted illumination and many other combinations of materials, angles, and dimensions are used to achieve the aforementioned results of the present invention. The example parameters may be used and are not limited to one specific embodiment only. In addition, even when the first irradiation beam is tilted, the three-section adjuster 790 enables the continuous use of the autofocus system, as described above and as known to those skilled in the art. Further, according to the embodiments described above, one or more actuators can selectively insert other objective lenses into the optical path and optionally select a three-section adjuster 790 in the optical path individually or in combination with the objective lens and / or focusing device. Can be inserted by

In the configuration of FIG. 7, the output light from the objective lens 130 is reflected at the mirror surface 730 and is inclinedly focused on the vertical irradiation focus. Specular reflections from each beam 705, 725 return to the path of the opposing polarization beam. For example, the oblique beam 705 is specular reflected to the surface 775, or to morphological features on or within the particles or therein. This reflective beam 705 is directed to the mirror surface 730 on the rightmost side of the wedge 720 by the mirror surface coating 730 directly or in opposing direction towards the surface coating 750. Reflected. As noted above, surface coating 750 transmits about 1% of the s-polarized portion and about 99% of the p-polarized component of beam 705 and this portion of reflective beam 705 is p-polarized beamsplitter coating 750. Through). Similarly, a portion of reflective beam 725 is transmitted through s polarizing beamsplitter coating 740. This transmitted portion continues through the objective lens to the bright field detector and autofocus. In addition to other mechanisms of autofocus, autofocus can be achieved by demonstrating that the device consists of a single scan line rather than double.

In addition, since the two polarizations are transmitted in opposite directions, the scattered light has a polarization dependence of the azimuth angle which can help in defect identification. For example, as described above, bidirectional irradiation using s and p polarizations allows for the identification of the height of the microscopic defects on and within the transparent substrate 810, as shown in FIGS. 8A and 8B. As shown in FIG. 8A, because the incident beams overlap, an image of the small feature 800 on the surface of the substrate 810 appears at one location in the image resulting from another dark field perspective. However, as shown in FIG. 8B, if the feature 800 is below or above the substrate surface, the image is doubled, which means that the incident beams 820, 830 are separated and the feature 800 is scanned during scanning. Because it is investigated once. Although the effects shown in FIGS. 8A and 8B are generally not mentioned because the vertical spacing from the feature to the substrate surface is required to be comparable or greater than the spot size, useful information is provided because of the effects described above. Also, the noisy underlayer will be flattened because the signal consists of two superimposed noise images added incompatible to reduce noise. Also, because the polarization of the bidirectional beams 820, 830 is orthogonal, the beam will not form a known interference pattern.

Another embodiment of the present invention is shown in FIG. 9 where the laser irradiation is provided at an angle, but may be redirected to be irradiated vertically. In particular, the laser 900 outputs a light beam to the optics 910, shaping the beam and providing scanning deflection using, for example, an AOD scanning element or mirror (not shown). Optics 910 may include, for example, beam expanders and cylindrical lenses (not shown) or other types of optical elements known to those skilled in the art. In addition, an optical relay may be provided to transmit light from the laser 900 to the objective lens 960 and the dark field detector 950 collects scattered light from the wafer 905, as known to those skilled in the art. It can be used to be able to detect particles and defects. When vertical irradiation is required, the actuator 920 introduces a deflection mirror and deflects the light toward the mirror 930 up to the selected substrate coordinate through the optical relay 108 and the objective lens 960, as shown in FIG. 10. As shown, the first optical path includes a portion incident on the substrate 905.

As will be appreciated by those skilled in the art, the system provides a scanning beam arranged to scan the entire wafer in a vertical or inclined mode. In addition, with the help of the scanning controller 115, the system can be adjusted to provide selective vertical or oblique scanning of individual portions of the wafer, for example, to improve defect detection in these areas. In particular, the invention as set forth in the claims enables detailed examination of the particular coordinates of interest and the testing of the entire wafer in the preferred perspective view.

Accordingly, the present invention provides an apparatus that can selectively or preferably use vertical scanning radiation or oblique scanning radiation to optimize the inspection characteristics of the scanned layer during wafer inspection. While various obvious embodiments of materials, equipment, and methods are described herein in order not to unnecessarily obscure the present invention, several specific embodiments are described herein to provide a thorough understanding of the present invention known to those skilled in the art. Preferred embodiments of the present invention and several various embodiments are shown and described, and it should be understood that the present invention is capable of modification and combination without departing from the scope of the present invention.

Claims (34)

An inspection system for irradiating at variable angles, A light source for providing a light beam; A scanner for scanning deflecting the light beam to provide a scanning beam approaching the substrate at a first angle; And A deflection element that deflects the scanning beam to approach the substrate at a second angle and is selectively insertable into an optical path of the scanning beam, Inspection system for irradiation at variable angles. The method of claim 1, Wherein the first angle is perpendicular to the substrate Inspection system for irradiation at variable angles. The method of claim 2, The second angle is inclined to the substrate, Inspection system for irradiation at variable angles. The method of claim 3, wherein The scanner comprising one of a scanning mirror, a rotating mirror, a polygon mirror, and an acoustic-optical deflector, Inspection system for irradiation at variable angles. The method of claim 4, wherein The deflection element comprises a mirror connected to an actuator arm, Inspection system for irradiation at variable angles. The method of claim 4, wherein The deflection element comprises a plurality of movable mirrors, Inspection system for irradiation at variable angles. The method of claim 6, The movable mirror is arranged to direct the scanning beam of the second angle to a focal position that matches a focal position of the scanning beam approaching the substrate at the first angle, Inspection system for irradiation at variable angles. The method of claim 4, wherein The deflection element comprises a glass optical element comprising a first mirror surface on a first side and a second mirror surface on a second side, and The scanning beam enters a third side and is reflected obliquely from the first mirror surface and the second mirror surface towards the substrate at the second angle; Inspection system for irradiation at variable angles. The method of claim 8, The focal position of the oblique beam approaching the substrate from the second angle when the deflection element is in the optical path is the focal point of the vertical beam approaching the substrate from the first angle when the deflection element is not in the optical path. Consistent with the location, Inspection system for irradiation at variable angles. The method of claim 8, The first mirror surface is a partial mirror surface that transmits a portion of incident light and reflects a portion of the incident light, and The second glass optical element is for focusing light transmitted through the first mirror surface onto the same coordinates of the substrate irradiated by the scanning beam reflected by the second mirror surface to the substrate at the second angle. Disposed adjacent the first mirror surface, Inspection system for irradiation at variable angles. The method of claim 10, The focal position of the oblique beam approaching the substrate from the second angle when the deflection element is in the optical path is the focal point of the vertical beam approaching the substrate from the first angle when the deflection element is not in the optical path. Consistent with the location, Inspection system for irradiation at variable angles. The method of claim 4, wherein The deflection element comprises a first optical element, a second optical element, and a third optical element, One side of the second optical element is adjacent to the first optical element and the other side of the second optical element is adjacent to the third optical element, The light incident on the deflection element comprises both s and p polarized light at a selectable ratio using at least one of a quarter wave plate and a half wave plate, an s polarizing beamsplitting element is provided between the first optical element and the second optical element, a p-polarizing beamsplitting element is provided between the second optical element and the third optical element, The scanning beam incident on the second optical element is output obliquely toward the substrate as s polarization and p polarization from the first optical element and the second optical element, respectively, and The focal point of the two oblique output beams is matched on the substrate, Inspection system for irradiation at variable angles. The method of claim 12, The focal position of the oblique beam approaching the substrate from the second angle when the deflection element is in the optical path is the focal point of the vertical beam approaching the substrate from the first angle when the deflection element is not in the optical path. Consistent with the location, Inspection system for irradiation at variable angles. A substrate inspection system for irradiating at variable angles, A light source for providing a light beam; A scanning element including a portion incident to the substrate and outputting the light beam to the substrate along a first optical path forming a first angle with respect to the substrate; And A deflection element selectively introduced into said first lightpath to include said portion incident to said substrate and output said light beam to said substrate along a second lightpath forming a second angle with respect to said substrate, The first angle is different from the second angle, Substrate inspection system for irradiation at variable angles. The method of claim 14, The first angle is inclined to the substrate and the second angle is perpendicular to the substrate Substrate inspection system for irradiation at variable angles. The method of claim 14, The second angle is inclined to the substrate and the first angle is perpendicular to the substrate Substrate inspection system for irradiation at variable angles. The method of claim 14, The deflection element is selectively introduced into the first light path by an actuator, Substrate inspection system for irradiation at variable angles. The method of claim 14, The scanning element comprises one of a scanning mirror, a rotating mirror, a polygonal mirror and an acoustic-optical deflector, Substrate inspection system for irradiation at variable angles. The method of claim 17, The deflection element comprises a glass optical element comprising a first mirror surface on a first side and a second mirror surface on a second side, The scanning light beam is introduced at a third side and is reflected obliquely from the first mirror surface and the second mirror surface towards the substrate at the second angle, Substrate inspection system for irradiation at variable angles. The method of claim 19, The focal position of the oblique beam approaching the substrate from the second angle when the deflection element is in the first optical path is determined from the first angle to the substrate when the deflection element is not in the first optical path. Matching the focal position of the approaching vertical beam, Substrate inspection system for irradiation at variable angles. The method of claim 19, The first mirror surface is a partial mirror surface that transmits a portion of incident light and reflects a portion of the incident light, and The second glass optical element is for focusing light transmitted through the partial mirror surface onto the same coordinates of the substrate irradiated by the scanning beam reflected by the second mirror surface to the substrate at the second angle. Disposed to be movable adjacent to the first mirror surface, Substrate inspection system for irradiation at variable angles. The method of claim 21, The focal position of the oblique beam approaching the substrate from the second angle when the deflection element is in the first optical path is determined from the first angle from the first angle when the deflection element is not in the first optical path. Matching the focal position of the approaching vertical beam, Substrate inspection system for irradiation at variable angles. The method of claim 16, The deflection element comprises a first optical element, a second optical element, and a third optical element, One side of the second optical element is adjacent to the first optical element and the other side of the second optical element is adjacent to the third optical element, an s polarizing beamsplitting element is provided between the first optical element and the second optical element, a p-polarizing beamsplitting element is provided between the second optical element and the third optical element, and The scanning beam incident on the second optical element is output obliquely toward the substrate as s-polarized and p-polarized light from the first and second optical elements, respectively, Substrate inspection system for irradiation at variable angles. The method of claim 23, wherein The focal position of the oblique beam approaching the substrate from the second angle when the deflection element is in the first optical path is determined from the first angle from the first angle when the deflection element is not in the first optical path. Matching the focal position of the approaching vertical beam, Substrate inspection system for irradiation at variable angles. delete A deflection element used in a substrate inspection system for irradiating at variable angles, A first deflection surface of the first surface of the deflection element; A second deflection surface of the second surface of the deflection element, The first deflection surface and the second deflection surface each comprise a mirror surface, The first deflection surface is disposed at an angle with respect to the second deflection surface, An irradiation beam input to the deflection element from a first direction and impinging on a deflection surface of one of the first deflection surface and the second deflection surface from the deflection surface of one of the first deflection surface and the second deflection surface; Deflected to the deflection surface of the other of the first deflection surface and the second deflection surface and output from the deflection element in a second direction, The first direction is perpendicular to the substrate to be inspected and the second direction is inclined to the substrate to be inspected, Deflection element used in substrate inspection systems for irradiating at variable angles. A deflection element used in a substrate inspection system for irradiating at variable angles, A first deflection surface of the first surface of the deflection element; A second deflection surface of the second surface of the deflection element, The first deflection surface and the second deflection surface each comprise a mirror surface, The first deflection surface is disposed at an angle with respect to the second deflection surface, An irradiation beam input to the deflection element from a first direction and impinging on a deflection surface of one of the first deflection surface and the second deflection surface from the deflection surface of one of the first deflection surface and the second deflection surface; Deflected to the deflection surface of the other of the first deflection surface and the second deflection surface and output from the deflection element in a second direction, The first direction is inclined to the substrate to be inspected, and the second direction is perpendicular to the substrate to be inspected, Deflection element used in substrate inspection systems for irradiating at variable angles. The method of claim 26, The focal position of the oblique radiation beam output from the deflection element corresponds to the focal position of the incident radiation beam input to the deflection element. Deflection element used in substrate inspection systems for irradiating at variable angles. The method of claim 26, Further comprising an optical element disposed adjacent to a partial mirror surface having a focal position that matches the focal position of the oblique irradiation beam output from the deflection element in the second direction, Deflection element used in substrate inspection systems for irradiating at variable angles. The method of claim 26, Third deflection surface; A fourth deflection surface; An s polarizing beamsplitting element provided in the primary optical path including the first deflection surface and the second deflection surface; Further comprising a p-polarized beamsplitting element provided in the secondary optical path including the third deflection surface and the fourth deflection surface, The third deflection surface and the fourth deflection surface each comprise a mirror surface, The third deflection surface is disposed at an angle with respect to the fourth deflection surface, A scanning beam incident on the deflection element from the first direction perpendicular to the substrate is output to at least one of the primary optical path and the secondary optical path, and A portion of the scanning beam output from the first optical path is output in a first oblique direction and a portion of the scanning beam output from the second optical path is output in a second oblique direction, Deflection element used in substrate inspection systems for irradiating at variable angles. The method of claim 30, Further comprising a polarizing element for controlling the polarization of the scanning beam incident on the deflection element, The scanning beam is controlled to include s and p polarization, Deflection element used in substrate inspection systems for irradiating at variable angles. The method of claim 30, A focal position of the first optical path corresponds to a focal position of the second optical path, Deflection element used in substrate inspection systems for irradiating at variable angles. The method of claim 26 or 27, Wherein the deflection element comprises a prism; Deflection element used in substrate inspection systems for irradiating at variable angles. The method of claim 30, Wherein the deflection element comprises a plurality of prisms, Deflection element used in substrate inspection systems for irradiating at variable angles.

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