Electron Beam Inspection Equipment

Abstract

To perform highly accurate inspection by suppressing concentration of electric fields in a space between a substrate, to which a retarding voltage is applied, and a support pin.SOLUTION: An electron beam inspection device according to an aspect of the present invention comprises: an optical system which irradiates a surface of a substrate with a primary electron beam; a beam separator for splitting, from the primary electron beam, a secondary electron beam which is emitted due to the irradiation of the substrate with the primary electron beam; a detector which detects the split secondary electron beam; a movable stage on which the substrate is mounted; a support base which supports the substrate on the stage; and an application unit which applies a predetermined first voltage to the substrate. The support base includes a plurality of support pins supporting the substrate from a lower side, the support pin includes a columnar insulator and a metal film provided in the insulator, and a predetermined second voltage is applied to the metal film.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electron beam inspection apparatus. [Background technology]

[0002] As LSIs become more highly integrated, the circuit line width required for semiconductor devices is becoming finer year by year. To form the desired circuit pattern on a semiconductor device, a method is adopted in which a high-precision original pattern formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure tool.

[0003] Improving yield is essential for the manufacturing of LSIs, which are very costly to manufacture. As the dimensions of LSI patterns formed on semiconductor wafers become finer, the dimensions that must be detected as pattern defects are also becoming extremely small. Therefore, the importance of pattern inspection equipment that can inspect defects in ultra-fine patterns transferred onto semiconductor wafers is increasing.

[0004] A known method for inspecting pattern defects is to compare a measurement image of a pattern formed on a substrate such as a semiconductor wafer or a lithography mask with design data or a measurement image of the same pattern on the substrate. For example, there is a "die to die inspection" that compares measurement image data of the same pattern at different locations on the same substrate, and a "die to database inspection" that generates design image data (reference image) based on design data for a pattern design and compares it with a measurement image that is the measurement data obtained by photographing the pattern. If the compared images do not match, it is determined that there is a pattern defect.

[0005] Progress is being made with the development of inspection equipment that scans the surface of the substrate to be inspected with an electron beam, detects secondary electrons emitted from the substrate when the electron beam is irradiated, and obtains a pattern image. Progress is also being made with the development of equipment that uses multiple beams as an inspection equipment that uses electron beams.

[0006] To improve the resolution, a method is known in which the acceleration voltage of the electron beam is increased while a negative voltage (retarding voltage) is applied to the substrate to be inspected, thereby decelerating the electron beam just before the substrate. The substrate to be inspected is placed on a movable stage and supported by multiple support pins.

[0007] Conventionally, electric fields are concentrated in the space between the substrate to which the retarding voltage is applied and the support pins, which can induce discharges. When discharges occur, the trajectory of the electron beam changes, causing problems such as a deterioration in inspection accuracy. In addition, when a large discharge occurs, there is a possibility that the device will be damaged. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2000-223542 A [Patent Document 2] JP 2013-239386 A [Patent Document 3] JP 2015-185529 A Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide an electron beam inspection apparatus that suppresses concentration of an electric field in the space between a substrate to which a retarding voltage is applied and a support pin, thereby enabling highly accurate inspection. [Means for solving the problem]

[0010] An electron beam inspection device according to one aspect of the present invention includes an optical system for irradiating a primary electron beam onto a substrate, a beam separator for separating a secondary electron beam emitted as a result of the primary electron beam being irradiated onto the substrate from the primary electron beam, a detector for detecting the separated secondary electron beam, a movable stage on which the substrate is placed, a support table for supporting the substrate on the stage, and an application unit for applying a predetermined first voltage to the substrate. The support table has a plurality of support pins for supporting the substrate from below, the support pins including a columnar insulator and a metal film provided within the insulator, and a predetermined second voltage is applied to the metal film. Effect of the Invention

[0011] According to the present invention, it is possible to suppress the concentration of an electric field in the space between a substrate to which a retarding voltage is applied and a support pin, thereby enabling inspection to be performed with high accuracy. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a pattern inspection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of a shaping aperture array substrate. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. 2 is a schematic diagram of a support pin and a substrate. [Figure 6] 11 is a schematic diagram of a support pin and a substrate according to a comparative example. [Figure 7] 10A to 10C are diagrams illustrating a manufacturing method of the support pin. [Figure 8] FIG. [Figure 9] 10A to 10C are diagrams illustrating a manufacturing method of the support pin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] 1 is a schematic diagram of a pattern inspection apparatus 100 according to this embodiment. This pattern inspection apparatus 100 irradiates a substrate to be inspected with multiple electron beams and captures a secondary electron image.

[0015] 1, the pattern inspection apparatus 100 includes an image acquisition mechanism 150 and a control circuit 160. The image acquisition mechanism 150 includes an electron beam column 102 (electron lens barrel) and an inspection chamber 103. In the electron beam column 102, an electron gun 201, an electromagnetic lens 202, a shaping aperture array substrate 203, an electromagnetic lens 205, an electrostatic lens 210, a collective blanking deflector 212, a limiting aperture substrate 213, an electromagnetic lens 206, an electromagnetic lens 207 (objective lens), a main deflector 208, a sub-deflector 209, a beam separator 214, a deflector 218, an electromagnetic lens 224, and a multi-detector 222 are arranged.

[0016] A stage 105 movable in the XYZ directions is placed in the inspection chamber 103. A substrate 101 (sample) to be inspected is placed on the stage 105. The substrate 101 includes an exposure mask substrate and a semiconductor substrate such as a silicon wafer. When the substrate 101 is a semiconductor substrate, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. When the substrate 101 is an exposure mask substrate, a chip pattern is formed on the exposure mask substrate. The chip pattern is composed of a plurality of graphic patterns. The chip pattern formed on the exposure mask substrate is exposed and transferred onto the semiconductor substrate a plurality of times, thereby forming a plurality of chip patterns (wafer dies) on the semiconductor substrate.

[0017] The substrate 101 is placed on a stage 105 with its pattern-formed surface facing upward. The stage 105 is provided with a voltage application unit 50 that applies a retarding voltage to the upper surface (pattern-formed surface) of the substrate 101. The substrate 101 is supported from below by a support stand D (see FIG. 3), which will be described later.

[0018] A mirror 216 is arranged on the stage 105 to reflect a laser beam for laser length measurement irradiated from a laser length measurement system 111 arranged outside the inspection room 103 .

[0019] The multi-detector 222 is connected to a detection circuit 106 outside the electron beam column 102. The detection circuit 106 is connected to a chip pattern memory 123.

[0020] In the control system circuit 160, a control computer 110 that controls the entire inspection apparatus 100 is connected via a bus 120 to a position circuit 107, a comparison circuit 108, a reference image creation circuit 112, a stage control circuit 114, a lens control circuit 124, a blanking control circuit 126, a deflection control circuit 128, a storage device 109 such as a magnetic disk device, a monitor 117, a memory 118, and a printer 119.

[0021] The deflection control circuit 128 is connected to the main deflector 208, the sub-deflector 209, and the deflector 218 via a DAC (digital-analog conversion) amplifier (not shown).

[0022] The chip pattern memory 123 is connected to the comparison circuit 108 .

[0023] The stage 105 is driven by a driving mechanism 142 under the control of a stage control circuit 114. The stage 105 is movable in the horizontal direction and in the rotational direction. The stage 105 is also movable in the height direction.

[0024] The laser measurement system 111 measures the position of the stage 105 based on the principle of laser interferometry by receiving the reflected light from the mirror 216. The movement position of the stage 105 measured by the laser measurement system 111 is notified to a position circuit 107.

[0025] The electromagnetic lens 202 , the electromagnetic lens 205 , the electromagnetic lens 206 , the electromagnetic lens 207 (objective lens), the electrostatic lens 210 , the electromagnetic lens 224 , and the beam separator 214 are controlled by a lens control circuit 124 .

[0026] The electrostatic lens 210 is composed of, for example, three or more stages of electrode substrates each having an opening in the center, and the middle stage electrode substrate is controlled by the lens control circuit 124 via a DAC amplifier (not shown). A ground potential is applied to the upper and lower stage electrode substrates of the electrostatic lens 210.

[0027] The collective blanking deflector 212 is composed of two or more electrodes, and each electrode is controlled by the blanking control circuit 126 via a DAC amplifier (not shown).

[0028] The sub-deflector 209 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via a DAC amplifier. The main deflector 208 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via a DAC amplifier. The deflector 218 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via a DAC amplifier.

[0029] A high-voltage power supply circuit (not shown) is connected to the electron gun 201, and an acceleration voltage from the high-voltage power supply circuit is applied between a filament (cathode) (not shown) and an extraction electrode (anode) inside the electron gun 201. In addition, a voltage is applied to another extraction electrode (Wehnelt) and the cathode is heated to a predetermined temperature, whereby a group of electrons emitted from the cathode are accelerated and emitted as an electron beam 200.

[0030] 2 is a conceptual diagram showing the configuration of the shaping aperture array substrate 203. The openings 203a are two-dimensionally formed at a predetermined arrangement pitch in the x and y directions in the shaping aperture array substrate 203. Each opening 203a is rectangular or circular (including oval) and has the same dimensional shape.

[0031] An electron beam 200 emitted from an electron gun 201 (emission source) is refracted by an electromagnetic lens 202 and illuminates the entire shaping aperture array substrate 203. A plurality of apertures 203a are formed in the shaping aperture array substrate 203 as shown in Fig. 2, and the electron beam 200 illuminates an area including the plurality of apertures 203a. Each part of the electron beam 200 irradiated to the positions of the plurality of apertures 203a passes through each of the plurality of apertures 203a, thereby forming a multi-beam MB (multi-primary electron beams).

[0032] The multibeam MB is refracted by the electromagnetic lenses 205 and 206, and while repeating image formation and crossover, it passes through a beam separator 214 arranged at the crossover position of each beam of the multibeam MB and proceeds to the electromagnetic lens 207 (objective lens). Then, the electromagnetic lens 207 focuses the multibeam MB on the substrate 101. The multibeam MB focused (compressed) on the surface of the substrate 101 (sample) by the electromagnetic lens 207 is deflected collectively by the main deflector 208 and the sub-deflector 209, and each beam is irradiated at its respective irradiation position on the substrate 101. Since a retarding voltage (first voltage) is applied to the substrate 101, the multibeam MB decelerates just before the substrate 101.

[0033] When the entire multibeam MB is deflected collectively by the collective blanking deflector 212, it moves out of position from the center hole of the limiting aperture substrate 213 and is blocked by the limiting aperture substrate 213. On the other hand, the multibeam MB not deflected by the collective blanking deflector 212 passes through the center hole of the limiting aperture substrate 213 as shown in Fig. 1. Blanking control is performed by turning the collective blanking deflector 212 on and off, and the beams are turned on and off collectively.

[0034] When the multi-beam MB is irradiated onto a desired position on the substrate 101, a bundle of secondary electrons (multi-secondary electron beams 300) including reflected electrons corresponding to each beam of the multi-beam MB (multi-primary electron beams) is emitted from the substrate 101.

[0035] The multiple secondary electron beams 300 emitted from the substrate 101 pass through an electromagnetic lens 207 and proceed to a beam separator 214 .

[0036] The beam separator 214 generates electric and magnetic fields in perpendicular directions on a plane perpendicular to the direction in which the central beam of the multi-beam MB travels (the central axis of the orbit). The electric field exerts a force in the same direction regardless of the direction in which the electrons travel. In contrast, the magnetic field exerts a force according to Fleming's left-hand rule. Therefore, the direction of the force acting on the electrons can be changed depending on the direction in which the electrons enter.

[0037] The force due to the electric field and the force due to the magnetic field cancel each other out for the multi-beam MB entering the beam separator 214 from above, and the multi-beam MB travels straight downward. In contrast, the force due to the electric field and the force due to the magnetic field act in the same direction on the multi-secondary electron beams 300 entering the beam separator 214 from below, and the multi-secondary electron beams 300 are bent obliquely upward and separated from the multi-beam MB.

[0038] The multiple secondary electron beams 300 bent obliquely upward and separated from the multiple beam MB are deflected by the deflector 218, refracted by the electromagnetic lens 224, and projected onto the multiple detector 222. In Fig. 1, the trajectory of the multiple secondary electron beams 300 is shown in a simplified manner without being refracted.

[0039] The multi-detector 222 detects the projected multiple secondary electron beams 300. The multi-detector 222 has, for example, a diode-type two-dimensional sensor (not shown). Then, at the position of the diode-type two-dimensional sensor corresponding to each beam of the multi-beam MB, each secondary electron of the multiple secondary electron beams 300 collides with the diode-type two-dimensional sensor, and the electrons are multiplied inside the sensor, and secondary electron image data is generated for each pixel by the amplified signal.

[0040] The detection data of the secondary electrons detected by the multi-detector 222 (measurement image: secondary electron image: inspection image) is output in the order of measurement to the detection circuit 106. In the detection circuit 106, an A / D converter (not shown) converts the analog detection data into digital data, which is stored in the chip pattern memory 123. In this manner, the image acquisition mechanism 150 acquires a measurement image of the pattern formed on the substrate 101.

[0041] The reference image creation circuit 112 creates a reference image for each mask die based on the design data that is the basis for forming a pattern on the substrate 101, or the design pattern data defined in the exposure image data of the pattern formed on the substrate 101. For example, the reference image creation circuit 112 reads out the design pattern data from the storage device 109 through the control computer 110, and converts each figure pattern defined in the read out design pattern data into binary or multi-value image data.

[0042] The figures defined in the design pattern data are, for example, based on rectangles and triangles, and the figure data stored defines the shape, size, position, etc. of each pattern figure using information such as the coordinates (x, y) at the reference position of the figure, the length of the sides, and a figure code that serves as an identifier to distinguish the type of figure, such as a rectangle or triangle.

[0043] When the design pattern data that will become the graphic data is input to the reference image creation circuit 112, it is expanded into data for each graphic, and the graphic code indicating the graphic shape of the graphic data, graphic dimensions, etc. are interpreted. Then, it is expanded into binary or multi-value image data of the design pattern as a pattern to be arranged within a square with a grid of a predetermined quantization dimension as a unit, and output.

[0044] In other words, the design data is read, the inspection area is virtually divided into squares with a predetermined unit size, the occupancy rate of the figure in the design pattern is calculated for each square, and n-bit occupancy data is output. For example, it is preferable to set one square as one pixel. Then, 1 / 2 8If a resolution of (=1 / 256) is to be given, a small area of ​​1 / 256 is allocated for the area of ​​the figure placed within the pixel to calculate the occupancy rate within the pixel. Then, the occupancy rate data of 8 bits is output to the reference image creation circuit 112. The grid (inspection pixels) can be aligned with the pixels of the measurement data.

[0045] Next, the reference image creation circuit 112 applies appropriate filtering to the design image data of the design pattern, which is the image data of the figure. The optical image data as the measurement image is in a state where a filter has been applied by the optical system, in other words, in an analog state that changes continuously. Therefore, by also applying filtering to the image data of the design pattern, which is the design side image data whose image intensity (grayscale value) is a digital value, it is possible to match it with the measurement data. The image data of the created reference image is output to the comparison circuit 108.

[0046] The comparison circuit 108 compares the measured image (inspection image) measured from the substrate 101 with the corresponding reference image. Specifically, the aligned inspection image and reference image are compared pixel by pixel. The two are compared pixel by pixel according to predetermined judgment conditions using a predetermined judgment threshold, and the presence or absence of a defect, such as a shape defect, is judged. For example, if the gradation value difference for each pixel is greater than the judgment threshold Th, it is judged to be a defect candidate. Then, the comparison result is output. The comparison result may be stored in the storage device 109 or memory 118, may be displayed on the monitor 117, or may be printed out from the printer 119.

[0047] In addition to the above-mentioned die-database inspection, die-die inspection may be performed. When die-die inspection is performed, measurement image data obtained by capturing the same pattern at different locations on the same substrate 101 are compared. For this purpose, the image acquisition mechanism 150 acquires measurement images, which are secondary electron images of one graphic pattern (first graphic pattern) and the other graphic pattern (second graphic pattern), from the substrate 101 on which the same graphic patterns (first and second graphic patterns) are formed at different locations, using a multi-beam MB (electron beam). In this case, the acquired measurement image of one graphic pattern becomes a reference image, and the acquired measurement image of the other graphic pattern becomes an image to be inspected. The acquired images of one graphic pattern (first graphic pattern) and the other graphic pattern (second graphic pattern) may be in the same chip pattern data, or may be separated into different chip pattern data. The inspection method may be the same as that of the die-database inspection.

[0048] Next, the support base D that supports the substrate 101 on the stage 105 will be described with reference to Fig. 3 to Fig. 5. As shown in Fig. 3, the support base D has a flat base 1 and a plurality of support pins 2 protruding upward from the base 1. For example, three support pins 2 protrude from the base 1, supporting the substrate 101 at three points.

[0049] 4, the support pin 2 is cylindrical with a convex curved tip (upper end), and a metal film 20 is provided midway along the height direction. For example, the metal film 20 is disposed in a direction perpendicular to the height direction, in other words, parallel to the main surface (upper surface) of the base 1. Wiring 21 extends vertically from the lower surface of the metal film 20, allowing any voltage to be applied to the metal film 20. Other than the metal film 20 and the wiring 21, the support base D is made of an insulator.

[0050] The diameter of the support pin 2 is about 5 to 15 mm, and the height of the support pin 2 (the height from the main surface of the base 1 to the tip of the support pin 2) is about 15 to 30 mm. The height of the metal film 20 from the main surface of the base 1 is preferably about 30% or more of the height of the support pin 2.

[0051] 5, a voltage (second voltage) is applied to the metal film 20 via the wiring 21 so that the metal film 20 and the surface of the substrate 101 have the same potential. The voltage applied to the metal film 20 is controlled by, for example, a stage control circuit 114.

[0052] As a comparative example, as shown in FIG. 6, when a substrate 101 is supported by a support pin 3 made only of an insulator without including a metal film, an electric field may concentrate in the space between the tip of the support pin 3 and the substrate 101 to which a retarding voltage is applied, causing a discharge.

[0053] On the other hand, in this embodiment, the metal film 20 of the support pin 2 and the surface of the substrate 101 are at the same potential, so that the concentration of the electric field in the space between the tip of the support pin 2 and the substrate 101 is suppressed, preventing the occurrence of discharge and enabling high-precision inspection.

[0054] The support pin 2 can be produced by joining a tip body 2a and a base body 2b, as shown in Fig. 7. The tip body 2a has a flat circular bottom surface, a side surface rising from the periphery of the bottom surface, and a convex curved surface continuing to the upper end of the side surface, and a metal film 20a is provided on the bottom surface.

[0055] The base end body 2b is cylindrical, and a metal film 20b is provided on the upper surface of the base end body 2b. A wiring 21 is provided at the central axis of the base end body 2b, and the upper part of the wiring 21 is connected to the metal film 20b. The wiring 21 can be made of titanium, silver, or the like.

[0056] Examples of insulating materials used for the tip body 2a and the base body 2b include sapphire, cordierite, steatite, alumina, yttria, silicon carbide, aluminum nitride, and zirconia.

[0057] Metal films 20a, 20b can be formed on the bottom surface of the tip body 2a and the top surface of the base body 2b by, for example, coating, vapor deposition, sputtering, etc. The metal films 20a, 20b can be made of, for example, a silver-copper-titanium alloy and brazed.

[0058] The metal film 20a on the bottom surface of the tip body 2a and the metal film 20b on the top surface of the base body 2b are joined together to form the tip body 2a and the base body 2b, thereby forming the support pin 2. There are no particular limitations on the method for joining the metal films 20a and 20b, and for example, a known heat-resistant inorganic adhesive may be used, or solid-state bonding or diffusion bonding may be used.

[0059] A conductive adhesive such as silver paste may be used to form the metal film 20 and to bond the tip body 2a and the base body 2b together.

[0060] In the support pin 2 shown in FIG. 4, the end of the metal film 20 is exposed on the side surface of the support pin 2, and therefore an electric field is generated on the surface (in the creeping direction) of the support pin 2, which may cause discharge.

[0061] 8, it is preferable to provide the metal film 22 so that the end is not exposed on the side surface of the support pin 2. The distance (depth) t between the side surface of the support pin 2 and the metal film 20 is preferably 0.3 mm or more and 2 mm or less.

[0062] By making the metal film 22 and the surface of the substrate 101 at the same potential, it is possible to suppress the concentration of an electric field in the space between the tip of the support pin 2 and the substrate 101, and to more effectively suppress the generation of an electric field on the surface (in the creepage direction) of the support pin 2. This makes it possible to prevent the generation of discharge and to perform highly accurate inspection.

[0063] The support pin 2 shown in FIG. 8 can be produced, for example, by joining a tip body 2c and a base body 2d as shown in FIG.

[0064] The tip body 2c has a downwardly protruding protrusion 24 provided at the center of a circular bottom surface 25 (lower surface). A side peripheral surface rises from the periphery of the bottom surface 25, and a convex curved surface is connected to the upper end of the side peripheral surface. A metal film 22a is provided on the tip surface (lower end surface) of the protrusion 24.

[0065] The base end body 2d is cylindrical, and has a recess (recess) 26 at the center of its upper surface. A metal film 22b is provided on the bottom surface of the recess 26. A wiring 21 is provided at the central axis position of the base end body 2d, and an upper portion of the wiring 21 is connected to the metal film 22b.

[0066] The protrusion 24 of the tip body 2c is fitted into the recess 26 of the base body 2d, and the bottom surface 25 of the tip body 2c is brought into contact with the top surface 27 of the base body 2d. By joining the tip body 2c and the base body 2d, the support pin 2 shown in FIG.

[0067] In the above embodiment, the inspection device using multiple beams has been described, but a single beam may also be used.

[0068] It is preferable to have the metal films 20, 22 of the support pin 2 and the surface of the substrate 101 at the same potential, but even if there is a slight potential difference, the concentration of the electric field in the space between the support pin 2 and the substrate 101 can be suppressed compared to the configuration shown in Figure 6.

[0069] The present invention is not limited to the above-described embodiment, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0070] 1 Pedestal 2 Support pin 2a Tip body 2b Proximal body 20 Metal Film 21 Wiring 100 Pattern inspection device 101 Substrate 105 Stages

Claims

1. an optical system for irradiating a primary electron beam onto a substrate; a beam separator that separates a secondary electron beam emitted as a result of the primary electron beam being irradiated onto the substrate from the primary electron beam; a detector for detecting the separated secondary electron beam; a movable stage on which the substrate is placed; a support base for supporting the substrate on the stage; an application unit that applies a predetermined first voltage to the substrate; Equipped with the support table has a plurality of support pins that support the substrate from below, The support pin includes a columnar insulator and a metal film provided within the insulator, Electron beam inspection apparatus, characterized in that a predetermined second voltage is applied to the metal film.

2. 2. The electron beam inspection system of claim 1, wherein the first voltage and the second voltage are the same.

3. 3. The electron beam inspection device according to claim 1, wherein the metal film is covered with the insulator.

4. the metal film is disposed in a direction perpendicular to a height direction of the support pin, 4. The electron beam inspection device according to claim 3, wherein the distance between the side surface of the support pin and the end of the metal film is 0.3 mm or more and 2 mm or less.

5. the insulator has a base end body having a recess formed on an upper surface thereof and a tip end body having a protrusion formed on a lower surface thereof, the recess and the protrusion being fitted together, 5. The electron beam inspection device according to claim 3, wherein the metal film is provided between a bottom surface of the recess and a lower end surface of the protrusion.

Images