JP2010272528A - Method and apparatus for inspecting surface of sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve throughput of a semiconductor inspection apparatus using an electron beam. <P>SOLUTION: An apparatus for inspecting a surface of a sample includes: an electron source 14,6 for applying electron beams toward the specimen; a sample stage 14,22 for holding the specimen; a detector 14,4 for detecting electrons obtaining information about the surface of the sample by an irradiation of the electron beams toward the specimen; an image processing unit 14,5 for creating an image of the surface of the sample based on the electrons detected by the detector 14,4; and a Wiener filter 14,3 for separating a secondary electron optical system including from the sample stage 14,22 to the detector 14,4 from a primary electron optical system including from the electron source 14,6 to the sample stage 14,22. Emission electrons emitted from the surface of the sample forms a crossover in the Wiener filter 14,3 while the electron beams emitted from an electron gun 14,6 forms a crossover in the Wiener filter 14,3. Each position of the crossovers of the primary electron optical system and the secondary electron optical system differs on the Wiener filter 14,3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inspection apparatus for inspecting a defect or the like of a pattern formed on the surface of an inspection object using an electron beam, for example, when detecting a defect of a wafer in a semiconductor manufacturing process. To capture secondary electrons, reflected electrons (including mirror electrons), backscattered electrons, transmitted electrons, etc. that change according to the surface properties, and form image data, and then inspect based on the image data The present invention relates to an inspection apparatus for inspecting a pattern or the like formed on the surface of an object with high throughput, and a device manufacturing method for manufacturing a device with high yield using such an inspection apparatus. The present invention also relates to a detection apparatus using a projection method using a surface beam and a device manufacturing method using the apparatus.

In the semiconductor process, the design rule is about to reach the age of 100 nm, and the production form is changed from mass production of small varieties represented by DRAM to SOC (Silicon on
chip), and is shifting to high-mix low-volume production. Along with this, the number of manufacturing processes increases, and it is essential to improve the yield for each process, and defect inspection due to the process becomes important.

  As semiconductor devices are highly integrated and patterns are miniaturized, inspection devices with high resolution and high throughput are required. In order to investigate defects on a wafer substrate of 100 nm design rule, it is necessary to look at pattern defects and particle / via defects in wirings having a line width of 100 nm or less and their electrical defects, and therefore a resolution of 100 nm or less is required. In addition, since the amount of inspection increases due to an increase in manufacturing process due to high integration of devices, high throughput is required. In addition, as the number of devices increases, the inspection apparatus is also required to have a function of detecting a contact failure (electrical defect) of a via that connects wirings between layers. Currently, optical defect inspection devices are mainly used. However, in terms of resolution and contact defect inspection, instead of optical defect inspection devices, defect inspection devices using electron beams will be used in the future. Expected to become mainstream. However, the electron beam type defect inspection apparatus has a weak point, which is inferior to the optical method in terms of throughput.

  Therefore, development of an inspection apparatus capable of detecting electric defects with high resolution and high throughput is required. The resolution in the optical system is said to be limited to 1/2 of the wavelength of the light to be used, and is about 0.2 μm in the case of visible light that has been put into practical use.

  On the other hand, in a method using an electron beam, a scanning electron beam method (SEM method) is usually put into practical use, with a resolution of 0.1 μm and an inspection time of 8 hours / piece (200 mm wafer). The electron beam method is also characterized by being capable of inspecting electrical defects (wire disconnection, conduction failure, via conduction failure, etc.), but a defect inspection device with a very low inspection speed and a high inspection speed. Development is expected.

  By the way, in general, an inspection apparatus is expensive and has a lower throughput than other process apparatuses. Therefore, after an important process at present, for example, after etching, film formation, or CMP (chemical mechanical polishing) flattening process. Etc. are used.

  A scanning (SEM) type inspection apparatus using an electron beam will be described. The SEM inspection apparatus narrows the electron beam (this beam diameter corresponds to the resolution), scans it, and irradiates the sample in a line shape. On the other hand, by moving the stage in the direction perpendicular to the scanning direction of the electron beam, the observation region is irradiated with the electron beam in a planar shape. The scanning width of the electron beam is generally several 100 μm. A secondary electron from a sample generated by irradiation of the finely focused electron beam (referred to as a primary electron beam) is detected by a detector (scintillator + photomultiplier (photomultiplier tube) or semiconductor type detector (PIN diode type). Etc.). The coordinates of the irradiation position and the amount of secondary electrons (signal intensity) are combined and imaged and stored in a storage device, or an image is output on a CRT (CRT).

  The above is the principle of SEM (scanning electron microscope), and a defect in a semiconductor (usually Si) wafer in the process is detected from an image obtained by this method. The inspection speed (corresponding to the throughput) is determined by the amount of primary electron beam (current value), the beam diameter, and the response speed of the detector. The beam diameter is 0.1 μm (which may be considered to be the same as the resolution), the current value is 100 nA, the detector response speed is 100 MHz, and the inspection speed is said to be about 8 hours per 20 cm diameter wafer in this case. ing. A serious problem is that the inspection speed is extremely slow (1/20 or less) compared to the optical system. In particular, a device pattern with a design rule of 100 nm or less formed on a wafer, that is, detection of a shape defect such as a line width of 100 nm or less or a via having a diameter of 100 nm or less, or an electrical defect, and a high speed of dust of 100 nm or less. Detection is required.

Scanning inspection apparatuses using electron beams are disclosed in, for example, Patent Documents 1 to 3.
JP 2002-26093 A (3rd, 4th page, FIG. 2) Japanese Patent Laid-Open No. 2002-161948 (page 4-6, FIG. 1) JP 2000-161932 A (page 7-9, FIG. 2)

  In the SEM inspection apparatus described above, the above inspection speed is considered to be almost the limit, and a new method is necessary to further increase the speed, that is, to increase the throughput.

  Also, depending on the inspection, defects such as the boundary between the memory cell portion and the random logic portion in the inspection after lithography, or the memory cell portion where the pattern is densely packed and the line width is very thin are used. You may want to inspect only the critical parts that are likely to occur. In other words, the priority of high throughput is higher than the high accuracy of full-scale inspection, and the inspection accuracy is such that it is necessary to properly inspect only critical parts and satisfy a certain degree of accuracy, There are cases where the locations that are likely to occur are limited, and if only those locations are inspected, sufficient inspection accuracy may be ensured. In such cases, it would be convenient if there was a method that could selectively inspect only critical portions. Yes, it can meet the demand for high throughput.

  Therefore, an object of the present invention is to provide an inspection method, an inspection apparatus, and the like that can meet the demand for high throughput.

  One embodiment of the present invention is an electron beam apparatus, which is configured to irradiate an electron beam toward a sample, and to obtain electrons obtained from the surface of the sample by irradiation of the electron beam toward the sample. A detector for detecting, means for generating an image based on electrons obtained from the detector and obtaining information on the surface of the sample, and control means for selectively inspecting an arbitrary portion of the sample surface . The image generation means performs a process of combining the detected electrons as an image.

  Electrons that have obtained information on the surface of the sample are at least one of secondary electrons, reflected electrons, backscattered electrons, and transmitted electrons generated from the sample, or mirror electrons reflected near the surface of the sample, Or it is desirable that it is a transmission electron which permeate | transmits a sample.

  One aspect of the present invention is a sample surface inspection method, comprising: selecting an arbitrary region on the sample surface as a region to be inspected; irradiating an electron beam toward the selected region to be inspected; The method includes a step of detecting electrons that have obtained information, a step of generating an image of a sample surface based on the detected electrons, and a step of performing a comparison inspection by comparing the generated image with a reference image.

  The step of selecting an arbitrary region on the sample surface as the region to be inspected is performed based on a preset recipe command.

  The step of selecting an arbitrary region on the sample surface as the region to be inspected is selected in units of stripes when inspecting the substrate.

  The step of irradiating the selected region to be inspected with the electron beam is performed while moving the electron beam or the sample so that the electron beam relatively moves on the sample.

  Further, the step of detecting the electrons obtained from the sample surface information is detected by projecting onto a projection surface composed of a plurality of pixels.

  The step of irradiating the selected region to be inspected with an electron beam is performed using an electron beam having an area including a plurality of pixels on the detector in the electron beam irradiation region.

  Further, in the step of comparing and comparing the synthesized image with a reference image, an image of a die in the same stripe as the synthesized image is used as a reference image.

  One aspect of the present invention is a sample surface inspection method, in which an arbitrarily selected small region on a sample is inspected using an electron beam, and an image of the small region is obtained. A step of identifying a large area and a region where many defects are estimated on the entire surface of the sample from a region having many defects identified in the small area, and a step of identifying and estimating that there are many defects on the entire surface of the sample Irradiating an electron beam to the region to be inspected and inspecting the sample surface.

  One embodiment of the present invention is a sample surface inspection apparatus, which is directed to an electron gun that irradiates an electron beam toward a sample, a sample stage that holds the sample, and the electron beam directed to the sample. A detector for detecting electrons obtained from the surface information of the sample by irradiation, means for generating an image of the sample surface based on the electrons detected by the detector, and comparing the generated image with a reference image And a control means for controlling so as to selectively inspect an arbitrary area on the sample surface.

  In this apparatus, an arbitrary region on the sample surface is selected based on a recipe command.

  In this apparatus, an arbitrary area on the sample surface is selected in units of stripes at the time of inspection.

  In this apparatus, the control means controls the electron beam by deflection of the electron beam or movement of the stage so that the electron beam irradiates the stripe on the sample.

  In the present apparatus, the detector is a CCD sensor or a TDI-CCD sensor.

  In this apparatus, the electron gun irradiates a sample with an electron beam having an irradiation area including a plurality of pixels.

  In the present apparatus, the stage continuously moves in at least one direction on the xy plane during inspection.

  This device identifies an area with many defects from an image of an arbitrary small area on the sample, calculates the positional relationship with the die of the area with many defects, and identifies an area that is estimated to have many defects in the entire sample. The operation means is further provided.

  Another aspect of the present invention is a device manufacturing method comprising: a. Providing a wafer; b. Performing a wafer process, c. Inspecting the processed wafer using the inspection method described above, d. Repeat steps b and c, e. Assemble the device.

  With the inspection method or inspection apparatus of the present invention, it is possible to inspect defects of a substrate such as a wafer with high throughput.

It is a figure which shows the whole structure of a semiconductor inspection apparatus. It is a figure which shows the structure of a test | inspection part. It is a figure which shows the structure of a test | inspection part. It is a figure which shows the structure of a test | inspection part. It is a figure which shows the structure of a test | inspection part. It is a figure which shows the structure of a test | inspection part. It is a figure which shows the main structures of a test | inspection part. It is a front view which shows the semiconductor inspection apparatus of this Embodiment. It is a top view which shows the semiconductor inspection apparatus of this Embodiment. It is a figure which shows the structural example of a cassette holder. It is a figure which shows a mini-environment apparatus. It is a figure which shows a loader housing. It is a figure which shows an electron optical system. It is a figure which shows an electron optical system. It is a figure which shows the shape of a sample irradiation dome. It is a figure which shows operation | movement of a control system. It is a figure which shows operation | movement of a control system. It is a figure which shows operation | movement of a control system. It is a figure which shows operation | movement of a control system. It is a figure which shows operation | movement of a control system. It is a figure which shows operation | movement of a control system. It is a figure which shows operation | movement of a control system. It is a figure which shows the alignment procedure. It is a figure which shows the alignment procedure. It is a figure which shows the alignment procedure. It is a figure which shows a defect inspection procedure. It is a figure which shows a defect inspection procedure. It is a figure which shows a defect inspection procedure. It is a figure which shows a defect inspection procedure. It is a figure which shows a defect inspection procedure. It is a figure which shows a defect inspection procedure. It is a figure which shows a defect inspection procedure. It is a figure which shows the structure of a control system. It is a figure which shows the structure of a user interface. It is a figure which shows a test | inspection procedure. It is a figure which shows a test | inspection procedure. It is a figure which shows the setting of inspection object die | dye. It is a figure which shows the setting of the to-be-inspected area | region inside die | dye. It is a figure which shows a test | inspection procedure. It is a figure which shows a test | inspection procedure. It is a figure which shows the example of a scan in case the inspection die | dye in an inspection procedure is one. It is a figure which shows a test object. It is a figure which shows the selective test | inspection of this invention. It is a figure which shows the selective test | inspection of this invention. It is a figure which shows the selective test | inspection of this invention. It is a figure which shows the selective test | inspection of this invention. It is a figure which shows an electron beam apparatus. It is a figure which shows the primary electron irradiation method. It is a figure which shows the structure which connected the inspection apparatus to the manufacturing line. It is a figure which shows the example of the semiconductor device manufacturing method using an test | inspection apparatus. It is a figure which shows the detail of a lithography process.

  Embodiments of a semiconductor inspection apparatus according to the present invention will be described below in detail with reference to the drawings.

1. Overall Configuration First, a preferable overall configuration of the semiconductor inspection apparatus will be described.

  FIG. 1 shows the overall configuration of the inspection apparatus. The inspection apparatus includes inspection apparatus main bodies 1 and 1, power supply racks 1 and 2, control racks 1 and 3, film formation apparatuses 1 and 4, etching apparatuses 1 and 5, image processing units 1 and 6, and the like. A roughing pump such as a dry pump is placed outside a clean room. The main parts inside the inspection apparatus main body are composed of an electron beam optical column, a vacuum transfer system, a main housing that houses a stage, a vibration isolation table, a turbo molecular pump, and the like.

  The control system includes two CRTs and a command input function (such as a keyboard). The electron beam column is mainly composed of an electron optical system, a detection system, an optical microscope, and the like. The electron optical system includes an electron gun, a lens, and the like, and the transfer system includes a vacuum transfer robot, an atmospheric transfer robot, a cassette loader, various position sensors, and the like.

  Here, the film forming apparatus, the etching apparatus, and the cleaning apparatus (not shown) are arranged side by side near the inspection apparatus main body, but these may be incorporated in the inspection apparatus main body. These are used, for example, for suppressing charge of the sample or for cleaning the sample surface. When the sputtering method is used, both functions of controlling film and etching can be provided by one unit.

Although not shown, depending on the intended use, the related devices may be installed side by side near the inspection apparatus main body, or the related apparatuses may be incorporated into the inspection apparatus main body and used. Or you may incorporate an inspection apparatus in those related apparatuses. For example, a chemical mechanical polishing apparatus (CMP) and a cleaning apparatus may be incorporated in the inspection apparatus main body, or a CVD (chemical vapor deposition) apparatus may be incorporated in the inspection apparatus. Advantages such as saving the number of units for conveyance and shortening the conveyance time can be obtained.

  Similarly, the inspection apparatus main body may be incorporated in a film forming apparatus such as a plating apparatus. It can also be used in combination with a lithographic apparatus.

1-1) Main chamber, stage, vacuum transfer system exterior In FIGS. 2, 3, and 4, main components of the inspection unit of the semiconductor inspection apparatus are shown. The inspection unit of the semiconductor inspection apparatus includes an active vibration isolation base 2. 1 for blocking vibration from the external environment, a main chamber 2. 2 serving as an inspection room, and an electron optical device 2. 3, an XY stage 3, 1 for wafer scanning mounted inside the main chamber, a laser interference measurement system 3, 2 for controlling the operation of the XY stage, and a vacuum transfer system 2, 4 attached to the main chamber, They are arranged in a positional relationship as shown in FIGS. 2 and 3 show active vibration isolation units 3 and 3, surface plates 3 and 4, load lock chambers 3 and 5, transfer chambers 3 and 6, vacuum transfer robots 3 and 7, TMP for tube exhaust, Detection system exhaust TMP3 • 9 and the like are shown. The inspection unit of the semiconductor inspection apparatus further includes an exterior 4 · 1 for enabling environmental control and maintenance of the inspection unit, and is arranged in a positional relationship as shown in FIG.

1-1-1) Active anti-vibration table Active anti-vibration table 2.1 is equipped with welding surface plate 2, 4 on active anti-vibration unit 2, 3, and is an inspection room on this surface plate. The main chambers 2 and 2, the electron optical devices 2 and 3 installed on the upper part of the main chamber, and the vacuum transfer systems 2 and 4 associated with the main chamber are held. Thereby, the vibration from the external environment in a test | inspection part can be suppressed now.

1-1-2) Main chamber The main chambers 2 and 2 hold a turbo molecular pump directly in the lower part in order to realize the degree of vacuum (10 ⁻⁴ Pa or less), which is an inspection environment. An accurate XY stage 3. 1 is provided inside to shield the magnetism from the outside.

  In addition, in order to control the XY stage with high accuracy, a stage position measurement system using a laser interferometer is installed. The interferometer 5 · 1 is arranged in a vacuum in order to suppress measurement errors, and in this embodiment, in order to make the vibration of the interferometer itself, which is a direct measurement error, zero, the rigid chamber wall Directly fixed. FIG. 5 shows the motors 5 and 2 for driving the XY axes, and further shows the magnetic fluid seals 5 and 3, mirrors 5 and 4, and ball screws 5 and 5.

1-1-3) XY stage The XY stage 3.1 is configured to scan a wafer with high accuracy in a vacuum. The strokes of X and Y are, for example, 200 mm to 300 mm for 200 mm wafers and 300 mm to 600 mm for 300 mm wafers, respectively.

  A θ stage is installed on the XY stage for wafer alignment in vacuum. In the θ stage in this embodiment, two ultrasonic motors for driving and a linear scale for position control are arranged. Various cables connected to the movable part that performs the X, Y, and θ operations are clamped by cable bearers respectively held by the X stage and the Y stage, and then to the outside of the main chamber through feedthroughs installed on the chamber walls. Connected with.

1-2) Laser interferometry system The laser interferometer system is a laser optical system having an optical axis parallel to the X axis and the Y axis, the extension line of which corresponds to the inspection position, and an interferometer 5. 1. The optical system in the present embodiment is arranged in a positional relationship as shown in FIGS. The laser beam emitted from the laser 6. 1 installed on the welding surface plate is raised vertically by the vendor 6. 2 and then bent parallel to the measurement surface by the vendor 7. Furthermore, after being distributed for X-axis measurement and Y-axis measurement by splitters 6 and 4, they are bent parallel to Y-axis and X-axis by vendors 7 and 3 and 6 and 6, respectively, and introduced into the main chamber. Is done. 6 and 7 show several targets 7 and 2.

1-3) Inspection unit exterior The inspection unit exterior 6.1 is provided with a function as a frame structure for maintenance. In the present embodiment, a double-sided crane that can be stored is mounted on the upper part. The crane is attached to a transverse rail, and the transverse rail is further installed on a traveling rail (vertical). While the traveling rail is normally housed, the traveling rail rises as in maintenance, and the vertical stroke of the crane can be increased. As a result, the electron optical devices 2 and 3, the main chamber top plate, and the XY stage 3.1 can be attached to and detached from the back of the device by a crane built in the exterior during maintenance. In another embodiment of the crane built into the exterior, a crane structure with a rotatable cantilever shaft is provided.

  Further, the exterior of the inspection unit can also function as an environmental chamber. This provides a magnetic shielding effect along with temperature and humidity management as required.

2. Embodiment Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the inspection target is a substrate, that is, a wafer having a pattern formed on the surface.

2-1) Transport System FIGS. 8 and 9 show the main components of the semiconductor inspection apparatus according to the present invention in elevation and plan views. The semiconductor inspection apparatus 8. 1 includes a cassette holder 8. 2 for holding a cassette containing a plurality of wafers, a mini-environment apparatus 8. 3, a loader housing 8. 5 constituting a working chamber, and a wafer. A loader 8 and 7 for loading from a cassette holder 8 and 2 onto a stage device 8 and 6 disposed in the main housing 8 and 4 and an electro-optical device 8 and 8 attached to a vacuum housing are shown. 8 and FIG. 9 are arranged in a positional relationship.

  The semiconductor inspection apparatus 8. 1 further includes a precharge unit 8 9 disposed in the vacuum main housing 8 4, a potential application mechanism for applying a potential to the wafer, an electron beam calibration mechanism, and a stage device. Optical microscopes 8 and 11 constituting alignment control devices 8 and 10 for positioning the wafer are provided.

2-1-1) Cassette Holder The cassette holder 8. 2 is a cassette 8 or 12 (for example, SMIF manufactured by Assist Corp.) in which a plurality of (for example, 25) wafers are stored in a state of being arranged in parallel in the vertical direction. , A closed cassette such as FOUP) is held (two in this embodiment). The cassette holder 8. 2 has a structure suitable for the case where the cassette is transported by a robot or the like and automatically loaded into the cassette holder 8. 2, and suitable for the case where it is manually loaded. An open cassette structure can be arbitrarily selected and installed. Further, in the cassette holder of the example of FIG. 10, the box main body 10.1, the substrate transport box 10.2, the substrate carry-in / out door 10.3, the lid 10.4, the ULPA filter 10.5, the chemical filter 10.6, Fan motors 10 and 7 are provided.

2-1-2) Mini-Environment Device In FIGS. 8 to 11, the mini-environment device 8. 3 includes a housing 11. 2 and a mini-environment space that constitute a mini-environment space 11. A gas circulation device 11.3 for controlling the atmosphere by circulating a gas such as clean air in the 11.1 and a part of the air supplied in the mini-environment space 11.1 are collected and discharged. Discharge devices 1 1 and 4 and pre-aligner 1 1 and 5 disposed in the mini-environment space 1 1 and coarsely positioning a substrate to be inspected, that is, a wafer, are provided.

The housings 11 and 2 have top walls 11 and 6, bottom walls 11 and 7, and peripheral walls 11 and 8 that surround the four circumferences, and have a structure that blocks the mini-environment space 11 and 1 from the outside.
Entrances 8 and 15 are formed in portions of the peripheral walls 11 and 8 of the housings 11 and 2 adjacent to the cassette holders 8 and 2. A shutter device having a known structure may be provided in the vicinity of the entrances 8 and 15 so that the entrances 8 and 15 are closed from the mini-environment device side.

  The pre-aligner 11.5 placed in the mini-environment space 11.1 is an orientation flat formed on the wafer (refers to a flat portion formed on the outer periphery of a circular wafer, hereinafter referred to as an orientation flat), a wafer One or more V-shaped notches or notches formed on the outer periphery of the wafer are optically or mechanically detected to determine a rotational position about the wafer axis OO of about ± 1 degree. Positioning is performed in advance with accuracy.

2-1-3) Main Housing In FIGS. 8 to 9, the main housing 8, 4 constituting the working chamber 8, 16 includes a housing body 8, 17, and the housing body 8, 17 includes the base frame 8 18 is supported by a housing support device 8/20 mounted on a vibration isolating device, ie, an anti-vibration device 8/19. The housing support devices 8 and 20 include frame structures 8 and 21 assembled in a rectangular shape. The housing bodies 8 and 17 are disposed and fixed on the frame structures 8 and 21, and the bottom walls 8 and 22, the top walls 8 and 23, the bottom walls 8 and 22, and the tops placed on the frame structures are fixed. The working chambers 8 and 16 are isolated from the outside by being provided with peripheral walls 8 and 24 which are connected to the walls 8 and 23 and surround the four sides. In this embodiment, the bottom walls 8 and 22 are made of a relatively thick steel plate so as not to be distorted by weighting by a device such as a stage device mounted thereon. It may be.

2-1-4) Loader Housing In FIG. 8 to FIG. 9 and FIG. 12, the loader housings 8 and 5 are housing main bodies 9 and 2 constituting first loading chambers 9 and 2 and second loading chambers 9 and 3, respectively. 4 is provided. The housing main body 9 · 4 is a partition that divides the bottom wall 12 · 1, the top wall 12 · 2, the peripheral wall 12 · 3 surrounding the four circumferences, the first loading chamber 9 · 2 and the second loading chamber 9 · 3. Walls 9 and 5 are provided so that both loading chambers can be isolated from the outside. The partition walls 9 and 5 are formed with openings, that is, entrances and exits 12 and 4 for exchanging wafers between both loading chambers. In addition, entrances 9 and 6 and 9 and 7 are formed at portions of the peripheral walls 12 and 3 adjacent to the mini-environment device and the main housing.

2-1-5) Loader The loader 8 or 7 includes a robot-type first transfer unit 11 or 14 disposed in the housing 11 or 2 of the mini-environment device 8 or 3, and a second loading chamber 9 or 3 is a robot-type second transfer unit 9.

The first transport units 11 and 14 have multi-node arms 11 and 16 that are rotatable about the axis O ₁ -O ₁ with respect to the drive units 11 and 15. As the multi-node arm, an arbitrary structure can be used, but in this embodiment, the multi-node arm has three portions which are rotatably attached to each other. Grip devices 9 and 13 are attached to the tips of the arms 11 and 16. The arms 11 and 16 are provided together with the shafts 11 and 17 and the lifting mechanisms 11 and 18.

  The first transfer units 11 and 14 transfer between the wafers accommodated in the cassette and the pre-aligner 1 1 and 5 and transfer between the pre-aligner 1 1 and 5 and the second loading chamber 9 2.

  The second transfer units 9 and 12 are basically the same in structure as the first transfer unit, and are different only in that the wafer is transferred between the wafer rack and the stage apparatus mounting surface.

2-1-6) Stage device The stage devices 8 and 6 include a fixed table 8 and 32 disposed on the bottom walls 8 and 22 of the main housings 8 and 4 and a Y direction (on the drawing in FIG. Y table 8, 33 that moves in the vertical direction), X table 8, 34 that moves in the X direction (left and right in FIG. 1) on the Y table, and rotary tables 8, 35 that can rotate on the X table. And holders 8 and 36 disposed on the rotary tables 8 and 35, respectively. The wafer is releasably held on the wafer placement surfaces 9 and 14 of the holders 8 and 36. The holders 8 and 36 may have a known structure capable of releasably gripping the wafer mechanically or by an electrostatic chuck method. The stage devices 8 and 6 are held by the holders on the mounting surfaces 9 and 14 by operating a plurality of tables as described above using a servo motor, an encoder, and various sensors (not shown). High precision in the X, Y, and Z directions (up and down in FIG. 8) with respect to the electron beam emitted from the electron optical device, and in the direction around the axis perpendicular to the wafer support surface (θ direction) It can be positioned with. FIG. 9 shows servo motors 9, 14, 9, 15 and encoders 9, 17, 9, 18 for the stage device.

  For positioning in the Z direction, for example, the position of the mounting surface on the holder may be finely adjusted in the Z direction. In this case, the reference position of the mounting surface is detected by a position measuring device (laser interference distance measuring device using the principle of an interferometer) using a fine-diameter laser, and the position is controlled by a feedback circuit (not shown). Instead, the position of the notch or orientation flat of the wafer is measured to detect the planar position and rotation position of the wafer with respect to the electron beam, and the rotation table is rotated by a stepping motor capable of controlling a minute angle.

  It is also possible to standardize the signal obtained by inputting the rotation position of the wafer with respect to the electron beam and the X and Y positions in advance to the signal detection system or the image processing system. Further, the wafer chuck mechanism provided in the holder is configured so that a voltage for chucking the wafer can be applied to the electrode of the electrostatic chuck. It is comprised so that it may position by pressing down. The wafer chuck mechanism includes two fixed positioning pins and one pressing crank pin. The clamp pin is configured to realize automatic chucking and automatic release, and constitutes a conduction portion for applying voltage.

  In this embodiment, the table that moves in the left-right direction in FIG. 9 is the X table and the table that moves in the up-down direction is the Y table. However, the table that moves in the left-right direction in FIG. The table that moves to X may be the X table.

2-2) Wafer transfer method Next, wafer transfer from the cassettes 8 and 12 supported by the cassette holders 8 and 2 to the stage devices 8 and 6 disposed in the working chambers 8 and 16 is performed in order. This will be described (see FIGS. 8 to 12).

  As described above, the cassette holder 8 or 2 has a structure suitable for manually setting a cassette, and a cassette holder having a structure suitable for automatically setting a cassette. In this embodiment, when the cassettes 8 and 12 are set on the lifting tables 8 and 13 of the cassette holders 8 and 2, the lifting tables 8 and 13 are lowered by the lifting mechanisms 8 and 14, and the cassettes 8 and 12 are moved in and out. 8.15. When the cassette is aligned with the entrance / exit 8/15, a cover (not shown) provided on the cassette is opened, and a cylindrical cover is provided between the cassette and the entrance / exit 8/15 of the mini-environment device 8/3. Arranged to block the inside of the cassette and the mini-environment space from the outside. Since these structures are publicly known, detailed description of the structure and operation is omitted. In addition, when the shutter device which opens / closes the entrance / exit 8/15 is provided in the mini-environment device 8/3 side, the shutter device operates to open the entrance / exit 8/15.

  On the other hand, the arms 11 and 16 of the first transport units 11 and 14 are stopped in a state facing in either the direction M1 or M2 (in this description, the direction of M1). One of the wafers stored in the cassette is received at the leading end. In this embodiment, the vertical position adjustment of the arm and the wafer to be taken out from the cassette is performed by the vertical movement of the driving units 11 and 15 of the first transfer units 11 and 14 and the arms 11 and 16. The lifting / lowering table of the cassette holder may be moved up and down or both.

When the receipt of the wafer by the arms 11 and 16 is completed, the arm contracts and operates the shutter device to close the entrance / exit (when the shutter device is present), and then the arms 11 and 16 rotate around the axis O ₁ -O _1. It will be in the state which can move and expand | extend toward the direction M3. Then, the arm extends and is placed on the tip or held by the chuck, and the wafer is placed on the pre-aligner 11, 5, and the pre-aligner 11, 5 rotates the wafer in the direction of rotation (the central axis perpendicular to the wafer plane). Rotation direction) is positioned within a predetermined range. When the positioning is completed, the transfer units 11 and 14 receive the wafer from the pre-aligner 11.5 at the tip of the arm and then contract the arm so that the arm can be extended in the direction M4. Then, the doors 8 and 27 of the shutter devices 9 and 8 are moved to open the entrances 8 and 25 and 8 and 37, and the arms 11 and 16 are extended to move the wafers to the wafer racks 9 and 11 in the first loading chamber 9 and 2. Place on the upper or lower side. In addition, before opening the shutter devices 9 and 8 and delivering the wafers to the wafer racks 9 and 11 as described above, the entrances 12 and 4 formed in the partition walls 9 and 5 are the doors 9 of the shutter devices 9 and 10. -It is closed in an airtight state by 19. The shutter devices 9 and 8 are provided with sealing materials 8 and 26 and drive devices 8 and 28, respectively.

  In the wafer transfer process by the first transfer units 11 and 14, clean air flows in a laminar flow from the gas supply units 11 and 9 provided on the housing of the mini-environment devices 8 and 3 (downflow). ) To prevent dust from adhering to the upper surface of the wafer during transfer. The conduits 11 and 11 are provided together with the gas supply units 11 and 9. Part of the air around the transport unit (in this embodiment, air that is mainly contaminated with about 20% of the air supplied from the supply unit) is sucked from the suction ducts 11 and 12 of the discharge devices 11 and 4 to be outside the housing. To be discharged. The remaining air is recovered through recovery ducts 11 and 10 provided at the bottom of the housing and returned to the gas supply units 11 and 9 again.

  When a wafer is placed on the wafer racks 9 and 11 in the first loading chambers 9 and 2 of the loader housings 8 and 5 by the first transfer units 11 and 14, the shutter devices 9 and 8 are closed, and the loading chamber 9 -Seal the inside of 2. Then, after the inert gas is expelled in the first loading chamber 9. 2 and the air is expelled, the inert gas is also discharged and the inside of the loading chamber 9. The vacuum atmosphere of the first loading chamber 9.2 may be a low vacuum level. When the degree of vacuum in the loading chambers 9 and 2 is obtained to some extent, the shutter devices 9 and 10 are operated to open the shutters 9 and 5 of the entrances 12 and 4 that have been sealed by the doors 9 and 19, and the second transfer unit The arms 9 and 12 of the 9 and 12 are extended to receive one wafer from the wafer racks 9 and 11 by the gripping device at the tip (mounted on the tip or gripped by a chuck attached to the tip). When the receipt of the wafer is completed, the arm contracts, and the shutter devices 9 and 10 operate again to close the doorway 12 and 4 with the doors 9 and 19.

  Before the shutter devices 9 and 10 are opened, the arms 9 and 20 can be extended in advance in the direction N1 of the wafer racks 9 and 11. Further, before the shutter devices 9 and 10 are opened as described above, the doors 9 and 9 and 9 and 1 are closed by the doors 9 and 9 of the shutter devices 8 and 29, so that the inside of the second loading chamber 9 and 3 is working. Communication with the chambers 8 and 16 is blocked in an airtight state, and the second loading chambers 9 and 3 are evacuated. The shutter devices 8 and 29 are provided with sealing materials 30 and 30 and drive devices 13 and 31, respectively.

When the shutter devices 9 and 10 close the entrances 12 and 4, the inside of the second loading chamber 9 and 3 is evacuated again, so that the vacuum is higher than that in the first loading chamber 9 and 2. Meanwhile, the arms of the second transfer units 11 and 14 are rotated to a position where they can extend toward the stage devices 8 and 6 in the working chambers 8 and 16. On the other hand, in the stage devices 8 and 6 in the working chambers 8 and 16, the Y tables 8 and 33 have the center lines X _{0 to} X ₀ of the X tables 8 and 34 and the rotation axes O _{2 of} the second transport units 9 and 12. 9 moves upward in FIG. 9 to a position substantially coincident with the X-axis line X ₁ -X ₁ passing through −O ₂ , and the X tables 8 and 34 move to a position approaching the leftmost position in FIG. Waiting in this state. When the second loading chamber 9 · 3 becomes substantially the same as the vacuum state of the working chamber 8 · 16, the door 9 · 9 of the shutter device 8 · 29 moves to open the entrances 9 · 7 and 9 · 1 and the arms extend. Then, the tip of the arm holding the wafer approaches the stage device 8 or 6 in the working chamber 8 or 16. Then, the wafer is placed on the placement surfaces 9 and 14 of the stage devices 8 and 6. When the placement of the wafer is completed, the arm contracts, and the shutter devices 8 and 29 close the entrances 9 and 7 and 9 and 1.

  Since the stage has a mechanism that applies a reverse bias potential (retarding potential) to the wafer, when the arm goes to or gets the wafer from the stage, the arm is at the same potential as or close to the stage, or the arm is at a floating potential. Thus, a mechanism for avoiding problems such as discharge due to potential short-circuiting is provided. As another embodiment, when the wafer is transferred onto the stage device, the bias potential to the wafer may be turned off.

  When controlling the bias potential, the potential may be turned off until the wafer is transported to the stage, and the bias potential may be applied after the wafer is transported and placed on the stage. When the bias potential is applied, the tact time may be set in advance, and may be applied according to the preset time. Alternatively, the sensor detects that the wafer is placed on the stage and applies the detection signal as a trigger. You may make it do. Further, it may be detected that the shutter devices 8 and 29 close the entrances 9 and 7 and 9 and 1 and the detection signal is applied as a trigger. Further, when an electrostatic chuck is used, it may be confirmed that the chuck is attracted to the electrostatic chuck, and a bias potential may be applied using this as a trigger.

  The operation until the wafers in the cassettes 8 and 12 are transferred onto the stage device has been described above. However, the wafers that have been placed on the stage devices 8 and 6 and completed processing are transferred from the stage devices 8 and 6 to the cassettes 8 and 12. To return to the inside, the reverse operation is performed. In addition, since a plurality of wafers are placed on the wafer racks 9 and 11, the wafers are transferred between the wafer racks 9 and 11 and the stage devices 8 and 6 by the second transfer units 9 and 12. The first transfer units 11 and 14 can transfer the wafers between the cassette and the wafer racks 9 and 11, and can efficiently perform the inspection process.

  Specifically, when there are already processed wafers A and unprocessed wafers B in the wafer racks 9 and 11, first, the unprocessed wafers B are moved to the stage apparatuses 8 and 6. During this time, the processed wafer A is moved from the wafer rack to the cassettes 8 and 12 by the arm, and the unprocessed wafers C are extracted from the cassettes 8 and 12 by the arm and positioned by the pre-aligner 1 1 and 5. Move to 2 wafer racks 9 and 11.

  In this way, in the wafer racks 9 and 11, the processed wafer A can be replaced with the unprocessed wafer C while the wafer B is being processed. Further, depending on how to use such an apparatus for performing inspection and evaluation, a plurality of stage apparatuses 8 and 6 are placed in parallel, and a plurality of wafers are moved from one wafer rack 9 or 11 to each apparatus. One wafer can be processed simultaneously.

According to the above embodiment, the following effects can be obtained.
(1) An overall configuration of a mapping projection type inspection apparatus using an electron beam is obtained, and an inspection object can be processed with high throughput.
(2) Inspecting the inspection object while monitoring the dust in the space by providing a sensor for observing the cleanliness by supplying a clean gas to the inspection object in the mini-environment space to prevent the adhesion of dust. Can do.
(3) Since the loading chamber and the working chamber are integrally supported via the vibration preventing device, it is possible to supply and inspect the inspection target to the stage device without being affected by the external environment.

2-3) Electron optical system
2-3-1) Outline The electron optical systems 8 and 8 are provided in the lens barrels 8 and 38 fixed to the housing main bodies 8 and 17, and are schematically illustrated in FIG. And an electron optical system including a secondary electron optical system (hereinafter simply referred to as a secondary optical system) 13.2 and a detection system 13.3. The primary optical system 13. 1 is an optical system that irradiates the surface of the wafer W to be inspected with an electron beam. The electron gun 13. 4 that emits an electron beam and the primary electron beam emitted from the electron gun 13. Comprising a lens system 13,5 comprising an electrostatic lens for focusing the light, a Wien filter or E × B separator 13,6, and an objective lens system 13,7, as shown in FIG. Arranged in order with 13.4 at the top. The lenses constituting the objective lens systems 13 and 7 of this embodiment are deceleration electric field type objective lenses. In this embodiment, the optical axis of the primary electron beam emitted from the electron guns 13 and 4 is oblique with respect to the irradiation optical axis (perpendicular to the wafer surface) irradiated to the wafer W to be inspected. It has become. Electrodes 13 and 8 are arranged between the objective lens systems 13 and 7 and the wafer W to be inspected. The electrodes 13 and 8 have an axisymmetric shape with respect to the irradiation optical axis of the primary electron beam, and the voltage is controlled by the power supplies 13 and 9.

  The secondary optical systems 13 and 2 include lens systems 13 and 10 including electrostatic lenses that pass secondary electrons separated from the primary optical system by the E × B deflectors 13 and 6. The lens systems 13 and 10 function as a magnifying lens that magnifies the secondary electron image.

  The detection systems 13 and 3 include detectors 13 and 11 and image processing units 13 and 12 arranged on the image planes of the lens systems 13 and 10.

  The incident direction of the primary beam is usually the E direction of the E × B filter (the reverse direction of the electric field), and this direction is the same as the integration direction of the integration type line sensor (TDI: time delay integration). The TDI integration direction may be different from the primary beam direction.

Hereinafter, specific embodiments will be described.
It is an example of an inspection apparatus mainly composed of a vacuum chamber, a vacuum exhaust system, a primary optical system, a secondary optical system, a detector, an image processor, and a control computer. An example is shown in FIG.

Secondary optics for guiding the primary optical system 14. 1 for irradiating the sample with an electron beam and electrons emitted from the sample surface, for example, secondary electrons, reflected electrons, backscattered electrons, etc. to the detector. There is a system 14.2. The secondary optical system is a mapping projection optical system. To separate the primary and secondary systems,
An E × B beam separator 14.3 is used. The electronic image signals detected by the detectors 14 and 4 are converted into optical signals and / or electric signals and processed by the image processors 14 and 5. At this time, an image can be satisfactorily formed even if the number of electrons incident on the detector is 200 or less in an area corresponding to one pixel. Of course, it is needless to say that an image can be satisfactorily formed even when there are 200 or more pixels in one pixel region.

The electron gun 14. 6, which is a component of the primary optical system, uses LaB ₆ as a heat filament, and draws electrons from the cathode by Wehnelt and extraction electrodes 14 and 7. Thereafter, the beam is converged to the apertures 14 and 9 by the two-stage A lenses (Einzel lenses) 14 and 8 to form a crossover. Thereafter, the light passes through the two-stage aligners 14 and 10, the apertures 14 and 11, the three-stage quadrupole lenses 14 and 12, and the three-stage aligners 14 and 13, enters the beam separator, and is deflected toward the sample surface. 14 and 14, the apertures 14 and 15, and the P lens (objective lens) 14 and 16 of the secondary optical system, and the sample surface is irradiated almost perpendicularly.

The apertures 14 and 9 pass through a beam region having high uniformity at crossover and high brightness, and the apertures 14 and 11 define an incident angle of the beam to the quadrupole lens 14. 10 is used for adjustment to make the beam enter the center of the optical axis of the apertures 14 and 11 and the quadrupole lenses 14 and 12. The quadrupole lenses 14 and 12 are used to change the shape of the beam by changing the trajectory in two directions of the beam, for example, the X and Y directions. For example, in the sample irradiation beam shape, it is possible to change the ratio of the circular, elliptical, rectangular, rectangular / elliptical shape in the x and y directions (see FIG. 14-2). After passing through the quadrupole lens, it is adjusted by the aligners 14 and 14 so as to pass through the centers of the apertures 14 and 15 and the P lenses (objective lenses) 14 and 16, and enters the sample surface. At this time, the shape of the irradiation beam can be symmetrically formed with respect to at least one of the two axes. The beam shape may be asymmetric. The energy of the beam applied to the sample surface is finally determined by the voltage difference between the cathode and the sample surface. For example, when the cathode is -5.0 kV and the sample surface is -4 kV,
The irradiation beam energy is 1 keV (see FIG. 14-1).

  In this case, the voltage error is ± 10 V and the energy error is ± 20 eV. When secondary electrons are used as detection electrons, when the beam irradiation energy is 1.5 keV ± 10 eV to 5 keV ± 10 eV, the sample is in a negatively charged state, and secondary electrons from that state are emitted from the sample. The image is enlarged and imaged by the secondary system and guided to the detection system. When the irradiation energy is 50 ± 10 eV to 1500 eV ± 10 eV, the sample surface is positively charged, and the emitted secondary electrons are guided to the detection system. Positive charging can operate with relatively low damage, but is more susceptible to charge-up effects or non-uniform surface potential due to charge-up. In the operation with negative charging, it is easy to obtain a stable image, and the distortion of the image due to the effect of charge-up or uneven surface potential due to charge-up can be made smaller than that of positive charge.

Further, there are cases where the positions of the apertures 14 and 15 are operated by shifting the positions of the crossover between the secondary system and the primary system. For example, the secondary system forms a crossover of secondary electrons on the center of the optical axis of the secondary system, and the crossover of the primary system is shifted by 50 to 500 μm from the center of the optical axis of the secondary system (X, Y may be formed and operated. As a result, the two crossovers of the primary system and the secondary system at the apertures 14 and 15 do not overlap, and the current density can be relaxed. Therefore, the blur due to the space charge effect when the amount of beam current is large can be increased. It becomes possible to suppress. This is effective, for example, when the primary system irradiation beam current density is 1 × 10 ⁻³ A / cm ² or more. When the current density is lower than that, there is little influence even if the optical axis centers are the same.

  One or more kinds of secondary electrons, reflected electrons, and backscattered electrons are used as the emitted electrons from the sample surface. For example, when the incident beam energy is 1000 eV ± 10 eV, the emission energy from the sample surface is approximately 0 to 10 eV, 1000 eV ± 10 eV, and 10 to 1000 eV, respectively.

  A focused ion beam (FIB) may be used instead of the electron beam. As the FIB source, a liquid metal Ga ion source is generally used, but other liquid metal ion sources using a metal that is easily liquefied, ion sources of different systems, for example, a duoplasmatron using a discharge, and the like can be used.

  As a sample, various samples are used from a chip of about 10 × 10 mm to a 2, 4, 6, 8, 12 inch wafer. In particular, it is effective for detecting a wiring pattern having a line width of 100 nm or less, a via defect having a diameter of 100 nm or less, and dust, and is convenient for detecting these electrical defects. As the sample, a Si wafer, a semiconductor device wafer obtained by processing Si, a wafer subjected to micromachining, a liquid crystal display substrate, a hard disk head processed wafer, or the like is used.

  In the secondary optical system 14. 2, there is a mapping projection optical system for imaging and guiding the emitted electrons from the sample, for example, secondary electrons, reflected electrons, and backscattered electrons to the detection system at a magnification. The example used is described. Examples of the lens configuration of the column include P lenses (objective lenses) 14 and 16, apertures 14 and 15, aligners 14 and 14, beam separators 14 and 3, P lenses (intermediate lenses) 14 and 17, and aligners 14 and 18. , Apertures 14 and 19, P lenses (projection lenses) 14 and 20, aligners 14 and 21, and a microchannel plate (MCP) unit. Hermetic quartz glass is installed on the top flange of the column. A relay lens and a two-dimensional charge coupled device (2D-CCD) are installed on the top thereof, and an image formed on the phosphor screen is formed on the 2D-CCD sensor.

  The emitted electrons from the sample surface form a crossover at the apertures 14 and 15 by the P lenses (objective lenses) 14 and 16, and form an image at the center of the beam separator 14.3. It is effective to operate under the condition that the image is formed at the center of the beam separator because the influence of the aberration of the secondary beam generated in the beam separators 14 and 3 can be reduced. This is because, for example, when the beam is passed through E × B, the amount of deflection and aberration differ depending on the image height, so that the aberration experienced by the imaging component can be minimized by imaging. It is. The same can be said for the primary system. In the primary system, not only the imaging conditions are formed on the sample but also the imaging point is formed near the center of the beam separator. This is effective in reducing the aberration of the primary beam and minimizing uneven current density on the sample.

  Aligners 14 and 14 are used to adjust the beam to the center of the P lens (intermediate lens) 14 and 17 at the top. In order to adjust the beam to the center of the P lens (projection lens) 14 and 20 located upstream thereof, aligners 14 and 18 are used. There are aligners 14 and 21 to adjust the beam to the center of the MCP at the top. The magnification of the P lens (objective lens) 14 and 16 is 1.5 to 3 times, the magnification of the P lens (intermediate lens) 14 and 17 is 1.5 to 3, and the magnification of the P lens (projection lens) 14 and 20 is 30. ~ 50. In order to achieve these magnifications, adjustment is performed by applying a voltage corresponding to each magnification to each lens. In order to finely adjust the focus, a dedicated focus correction lens is incorporated in a P lens (objective lens) system, and focusing is achieved by fine adjustment of the voltage applied to the electrode. Further, when both the apertures 14 and 15 and the apertures 14 and 19 form a crossover, the apertures 14 and 15 are used for the backlight cut, and the apertures 14 and 19 determine the aberration and contrast. It can also be used to fulfill

  As the sizes, for example, the apertures 14 and 15 and the apertures 14 and 19 can be used in a range of φ30 to φ2000 μm, preferably φ30 to φ1000 μm, more preferably φ30 to φ500 μm. At this time, when aberrations, transmittance, and contrast characteristics are mainly determined by the apertures 14 and 15, the apertures 14 and 15 are, for example, φ30 to φ500 μm, and the apertures 14 and 19 are φ1000 to φ2000 μm. When the aberration, transmittance, and contrast characteristics are mainly determined by the apertures 14 and 19, for example, the apertures 14 and 19 are used at φ30 to φ500 μm, and the apertures 14 and 15 are used at φ1000 to φ2000 μm.

  In some cases, stig electrodes are provided above and below the P lenses (intermediate lenses) 14 and 17. This is used to correct astigmatism generated by the beam separator 14. For example, it is possible to use a stig having an electrode configuration of 4, 6, and 8 poles. For example, different voltages can be applied to the electrodes of each of the eight music pieces and used to correct astigmatism and spherical aberration.

  Further, in the lens operation when the backscattered electron image and the backscattered electron are used, if the P lens (projection lens) 14 and 20 at the final stage uses a deceleration lens (negative voltage application lens), noise reduction of secondary electrons is performed. Effective. Usually, the amount of secondary electrons is about 10 to 1000 times larger than the amount of reflected electrons, which is particularly effective when imaging using reflected electrons and backscattered electrons is performed. For example, when the cathode voltage of the primary electron source is −4 kV and the sample potential is −3 kV, the reflected electron energy from the sample is 1 keV, and the detector voltage is the installation potential. The energy difference between electrons is 1 keV. At this time, in the negative voltage lens operation of the P lens (projection lens) electrode, it is possible to use a condition in which the center voltage passes the reflected electrons and cuts off the secondary electrons. These conditions can be obtained by simulation.

The beam separators 14 and 3 use E × B in which an electric field and a magnetic field are orthogonal, or a separator that uses only the magnetic field B. In the example of E × B, an E electrode that forms an electric field distribution and a magnetic pole that has a magnetic pole surface orthogonal to the E electrode and forms a magnetic flux density distribution in an orthogonal direction. For example, when the optical axis of the secondary system is perpendicular to the sample surface, the incident beam of the primary system can be set at 10 to 90 degrees with respect to the axis of the secondary system. At this time, the primary system is E × B,
It is deflected so that it can vertically enter the sample surface, and the emitted electrons from the sample surface are guided by E × B in the optical axis direction, that is, the vertical direction from the sample surface. This is achieved by the voltage applied to the E electrode and the magnetic flux density formed by the B magnetic pole. For example, a magnetic flux density distribution is formed in parallel with a pair of E electrodes from ± 2 kV ± 1 V and a pair of B magnetic poles. For example, a magnetic flux density in the magnetic pole direction of 1 to 60 G ± 1 G is generated at the center of E × B. (See FIG. 14-1).

  E × B can also be applied when the deflection relationship between the primary system and the secondary system is reversed. That is, a primary system incident beam source is provided directly above the sample, and a secondary system detector is provided in a direction that forms an angle of 10 to 80 degrees with the primary system axis. The system beam can be incident perpendicularly to the sample without applying a deflection force, and can be guided toward the detector by applying a deflection force to the electrons (secondary system beam) emitted from the sample.

  The detectors 14 and 4 are introduced into an electron multiplier such as an MCP, and the fluorescent electrons are irradiated with the multiplied electrons to form a fluorescent image. The fluorescent screen is one in which a fluorescent material is coated on one side of a glass plate such as quartz glass. This fluorescent image is picked up by a relay lens system and a two-dimensional CCD. The relay lens system and CCD are installed at the top of the column. Hermetic glass is installed on the top flange of the column, separating the vacuum environment inside the column from the external atmospheric environment, and reducing the distortion and contrast degradation of the fluorescent image to form an image on the CCD. Can be imaged efficiently.

An integrated line image sensor (TDI-CCD) camera can also be used instead of the CCD. In this case, TDI imaging can be performed while moving the stage on the stage, for example, in the E electrode direction or the B magnetic pole direction. For example, when the number of TDI integrated stages is 256, the number of 2048 pixels / stage per stage, the element size is 15 × 15 μm, and the MCP imaging magnification with respect to the sample surface is 300 times, the line / space is 0.1 / 0. .1μ
When m, the sample surface size is 30/30 μm on the MCP surface. When the relay lens magnification is 1 ×, 30 μm is imaged with two element sizes. At this time, electrons emitted from a sample position corresponding to one element, that is, a sample size of 0.05 × 0.05 μm, are accumulated during the stage movement by the number of stages of 256 elements, and the total acquired light quantity can be increased and imaged. This is particularly effective when the stage speed is high, such as for a line rate of 100 kHz to 600 kHz. This is because when the line rate is high, the number of acquired electrons per element, that is, the acquired light intensity per element of the TDI sensor decreases, so that integration is performed to increase the final acquired light intensity, and contrast and S This is because / N can be increased. The line rate is 0.5 kHz to 100 MHz, preferably 1 kHz to 50 MHz, more preferably 20 kHz to 10 MHz. Correspondingly, the video rate is also used at 1 to 120 MHz / tap, preferably 10 to 50 MHz / tap, more preferably 10 to 40 MHz / tap per tap. The number of taps is 1 or more and 520 or less, preferably 4 or more and 256 or less, more preferably 32 or more and 128 or less.

CCDs and TDI sensors / cameras having low noise and high sensitivity characteristics are used. For example, it can be set at 100 to 100000 DN / (nJ / cm ² ), but among these, it is efficient when used at 1000 to 50000 DN / (nJ / cm ² ). In addition, 10
When used at 000 to 50000 DN / (nJ / cm ² ), high quality images can be obtained with good S / N even at high line rates.

  In addition, when an image is acquired using a CCD or TDI sensor, the area of the number of pixels × the number of stages of these sensors can be used in a state where they substantially coincide with the irradiation area of the primary beam, which is efficient. In addition, noise is reduced. As for the noise, there are those in which electrons from a part having a high image height other than the area used for imaging reach the detector as noise. In order to reduce them, it is effective to reduce the beam irradiation of parts other than the effective visual field. Image information acquired by the CCD and TDI sensors is converted into an electrical signal and processed by an image processor. By this image processing, cell-to-cell, Die to Die, Die to Any Die images are compared, and defect inspection can be performed. For example, pattern defects, particle defects, potential contrast defects (for example, wiring or plating electrical connection defects).

As the stages 14 and 22, a stage installed by a combination of one or more of X, Y, Z and a moving mechanism is used.
The MCP has a function of amplifying incoming electrons, and the emitted electrons are converted into light by a fluorescent screen. If the number of incident electrons is sufficiently large and does not need to be multiplied, the operation can be performed without MCP. It is also possible to use a scintillator instead of the fluorescent screen. This light signal (or image signal) is transmitted to the TDI at a predetermined magnification in the case of a relay lens, and is transmitted to the TDI or formed as an image in the case of FOP by a factor of 1 (transmitting the optical signal on a one-to-one basis). A photomal amplifies an optical signal and converts it into an electrical signal, and a multiphotomal is a plurality of photomals arranged.

Image processor The image processor has functions such as image comparison, defect detection, defect classification, and image data recording.

  In the electron beam inspection apparatus described above, the irradiation beam shape of the primary beam can be an irradiation beam shape that is symmetric with respect to the X and Y axes at least one axis or more. This makes it possible to form an acquired image with low aberration and low distortion on the electron incident surface of the detector by a beam centered on the optical axis.

  Further, when a CCD or TDI is used as a detector, an S / N sufficient for an incident amount of electrons of 200 or less per pixel area in the formation of one pixel on an area corresponding to one pixel, for example, MCP. And can be used for image processing and defect detection. This is because, for example, in a projection projection optical system, by defining the size of the apertures 14, 15 or 14, 19, noise reduction and aberration reduction effects can be generated. For example, an aperture having a diameter of 30 μm to 1000 μm is installed. As a result, an S / N improvement can be realized, and a high-quality image with high resolution can be acquired in the area of 200 electrons / 1 pixel.

  TDI performs integration for the number of stages along the moving direction of the stage. In this embodiment, 256 stages of integration are performed. The number of integration stages is 114 to 8192, preferably 114 to 4096, and more preferably 512 to 4096. Even if the illuminance unevenness of the primary beam is slightly in the integration direction and the signal electrons from the sample are also uneven, the unevenness is averaged by the effect of integration, and the detected electronic information is constant and stable. Become. Accordingly, the moving direction of the stage can be determined in consideration of the direction in which the illuminance unevenness of the primary electron beam is likely to occur, so that the direction in which the uneven illuminance is likely to coincide with the integration direction of TDI. Although the use of TDI enables continuous image acquisition, the CCD may be used to scan the stage in a step-and-repeat manner, and image acquisition may be performed.

  When the surface of the sample is enlarged by electrons and an image is formed on the detector, if the resolution of the image is about one pixel of CCD or TDI, the aberration or blur of the secondary optical system should be within one pixel. Is desirable. When the signal electrons are deflected at E × B, aberration and blur increase. Therefore, in the present embodiment, in the secondary optical system, signal electrons such as secondary electrons, reflected electrons, and backscattered electrons are expressed as E ×. In B, it is set so as to go straight without applying a deflection force. That is, the central axis of the secondary optical system is a straight line that passes through the center of the visual field of the sample, the E × B center, and the center of the detector.

  It should be noted that it is sufficient that the image of the secondary optical system is not blurred even if it is other than the above-described embodiment, and it goes without saying that the present invention includes it.

2-4) Control system The control system is mainly composed of a main controller, a control controller, and a stage controller. The main controller is equipped with a man-machine interface, through which operator operations are performed (various instructions / commands, recipe input, inspection start instructions, automatic and manual inspection mode switching, manual inspection mode, etc. Input of all necessary commands at the time). In addition, communication with the host computer in the factory, control of the evacuation system, sample transfer of wafers, alignment control, command transmission to other control controllers and stage controllers, reception of information, etc. are also performed by the main controller. . In addition, acquisition of image signals from an optical microscope, stage vibration correction function that feeds back stage fluctuation signals to the electron optical system to correct image deterioration, and the Z direction of the sample observation position (axial direction of the secondary optical system) It has an automatic focus correction function that detects the displacement, feeds back to the electron optical system, and automatically corrects the focus. Transmission / reception of a feedback signal and the like to the electron optical system and transmission / reception of a signal from the stage are performed via a control controller and a stage controller, respectively.

  The control controller is mainly responsible for control of the electron optical system (control of a high-precision power source for an electron gun, a lens, an aligner, a Wien filter, etc.). Specifically, each operation mode, such as ensuring that the irradiation area is always irradiated with a constant electron current even when the magnification changes, and automatically setting the voltage to each lens system and aligner corresponding to each magnification. Control (interlocking control) such as automatic voltage setting for each lens system and aligner corresponding to is performed.

  The stage controller mainly controls the movement of the stage to enable precise movement in the X and Y directions in the order of μm (± 5 μm or less, preferably ± 1 μm or less, more preferably ± 0.5 μm or less). ing. In this stage, the rotational direction control (θ control) is also performed within an error accuracy of about ± 10 seconds, preferably within ± 1 second, more preferably within ± 0.3 seconds. The configuration of the control system will be specifically described below.

2-4-1) Configuration and function This apparatus captures and displays a specified position of a wafer with an electron microscope or an optical microscope, and functions to detect and classify defects by imaging the specified position of a wafer with an electron microscope, And a function of imaging and displaying the position where the defect is detected with an electron microscope or an optical microscope. In addition, for the realization and maintenance of the above functions, electron optical system control, vacuum system control, wafer transfer control, component unit single operation, imaging function, automatic defect inspection processing, apparatus abnormality detection, apparatus activation / And a stop processing function.

The auxiliary functions are as follows.
(1) Electro-optical system control function (a) Lens voltage application control (a-1) Interlocking control (a-2) Voltage application by application function (a-3) Multipole lens interlocking voltage application (a-4) Wobble control (B) Electron beam output adjustment (b-1) Preheat (Gun)
(B-2) Heat up (Gun)
(B-3) Emission current control (BIAS control)
(2) Vacuum system control function (a) Individual chamber evacuation / atmosphere release (b) Specified chamber batch evacuation / atmosphere release (3) Wafer transfer control function Step operation of the following operation / Fully automatic operation (a) Wafer load ( b) Wafer unload (4) Single component operation function (5) Imaging function Select the following two input systems to perform imaging:
(A) CCD camera ・ Optical microscope low magnification (pixel size: 2.75 μm / pix)
・ High magnification of optical microscope (pixel size: 0.25 μm / pix)
(B) TDI camera (b-1) TDI-still
(B-2) TDI-scan
EB × 80 (pixel size: 0.2 μm / pix)
EB × 160 (pixel size: 0.1 μm / pix)
EB × 320 (pixel size: 0.05 μm / pix)
EB × 480 (pixel size: 0.03 μm / pix).

  Furthermore, there is a user mode designation function as a function for restricting items that can be operated according to the skill and knowledge level of the operator to prevent accidents due to erroneous operations. This user mode is designated by a user ID and password that are input when a GUI (Graphical User Interface) is started.

The user mode includes a maintenance mode, recipe creation mode, and operator mode. Operation is performed in maintenance mode during start-up work and maintenance work after device installation, and operations and procedures required in recipe creation mode when creating recipes At the time of automatic defect inspection, inspection is performed using a recipe already created in the operator mode. The relationship between each user mode and the device operation form is as shown in FIG. here,
Maintenance mode. . . . Single component operation, wafer transfer, vacuum system control, electron optical system control, observation (light microscope imaging, TDI imaging), defect inspection, review recipe creation mode. . . . . Wafer transfer, observation (optical microscope imaging, TDI imaging), defect inspection, review operator mode. . . . . Automatic defect inspection (automatic control of necessary functions such as wafer transfer) and review.

  In this apparatus, there are apparatus constants and recipes as variable parameters necessary for operation. An apparatus constant is defined as a parameter that absorbs an error inherent to the apparatus (such as an attachment error), and a recipe is defined as a parameter that defines various conditions for automatically performing defect inspection. The device constant is set at the time of start-up work and after maintenance work, and is basically not changed thereafter.

  Recipes are classified into transport recipes, alignment recipes, die map recipes, focus map recipes, and inspection recipes, and defect inspection is performed according to these recipes, so setting work is performed before the inspection process is performed, and multiple patterns are set. Saved.

  As a procedure for creating a recipe, the first step is to transfer the wafer onto the stage (wafer load) as shown in FIG. After installing the wafer cassette in the system, a wafer search is performed to detect the presence / absence of each slot in the cassette, and the wafer size, notch / orientation type, (when loaded on the stage) The notch direction is designated, and the wafer is loaded by the procedure shown in FIGS. These conditions are stored in the transfer recipe. The arrangement direction of the dies on the wafer loaded on the stage does not necessarily coincide with the scanning direction of the TDI camera (FIG. 19). In order to make this coincide, an operation of rotating the wafer on the θ stage is required, and this operation is called alignment (FIG. 20). In the alignment recipe, the alignment execution condition after being loaded on the stage is stored.

  A die map (FIG. 21) showing the arrangement of the dies is created at the time of alignment, and the die size and the position of the origin die (which is the starting point indicating the position of the die) are stored in the die map recipe.

2-4-2) Alignment Procedure As an alignment (positioning) procedure, first, coarse positioning is performed at a low magnification of the optical microscope, and then detailed positioning is performed by an EB image at the high magnification of the optical microscope.

A. Image taken with optical microscope at low magnification (1) <Specifying first, second, third search die and specifying template>
(1-1) First Search Die Designation and Template Designation The user moves the stage so that the lower left corner of the die located below the wafer is located near the center of the camera. get. This die is a die serving as a positioning reference, and the coordinates of the lower left corner are the coordinates of the feature points. In the future, we will measure the exact position coordinates of any die on the substrate by performing pattern matching on this template image. As the template image, an image that has a unique pattern within the search area must be selected.

  In this embodiment, the lower left corner is the pattern matching template image acquisition position. However, the present invention is not limited to this, and an arbitrary position in the die may be selected as the feature point. However, in general, it is preferable to select any of the four corners because the corners are easier to specify the coordinates than the points on the inside of the die or on the sides. Similarly, in the present embodiment, the pattern matching template image is acquired for the die located below the wafer, but it is natural that any die may be selected so that alignment can be easily performed.

(1-2) Second search die designation The die next to the right of the first search die is the second search die, and the stage is moved by the user operation so that the lower left corner of the second search die is located near the center of the camera. After the position is determined, the exact coordinates of the pattern of the second search die that matches the template image specified by the first search die by automatically performing pattern matching using the template image acquired in (1-1) above. Get the value.

  In the present embodiment, the die on the right side of the first search die is described as an example of the second search die. However, the second search die of the present invention is not limited to this. . In short, it is only necessary to select a point that can accurately grasp the positional relationship of the die in the row direction from the reference point that grasps the position map of the accurate feature point by pattern matching. Therefore, for example, the die next to the left of the first search die can be used as the second search die.

(1-3) Third search die designation The die next to the second search die is the third search die, and the stage is moved by the user operation so that the lower left corner of the third search die is located near the center of the camera. After the position is determined, the exact coordinates of the pattern of the third search die that matches the template image specified by the first search die by automatically performing pattern matching using the template image acquired in (1-1) above Get the value.

  In the present embodiment, the upper die adjacent to the second search die is described as an example of the third search die. However, it goes without saying that the third search die of the present invention is not limited to this. In short, it is only necessary to be able to grasp the positional relationship including the distance of the coordinates of the specific point of the die in the column direction with reference to the die that grasped the exact coordinates of the feature points. Therefore, the die adjacent to the upper side of the first search die can be preferably applied as an alternative.

(2) <Light microscope low magnification Y direction pattern matching>
(2-1) From the relationship between the pattern match coordinates (X2, Y2) of the second search die and the pattern match coordinates (X3, Y3) of the third search die (dX, dY) Is calculated.
dX = X3-X2
dY = Y3-Y2

(2-2) Using the calculated movement amount (dX, dY), move the stage to the coordinates (XN, YN) where the pattern of the adjacent die on the first search die exists (expected).
XN = X1 + dX
YN = Y1 + dY
* (X1, Y1): Coordinates of the pattern of the first search die

  (2-3) After moving the stage, pick up an image at a light microscope low magnification, and execute a pattern match using a template image, thereby obtaining exact coordinate values (XN, YN) of the currently observed pattern, 1 is set as the initial value of the number of detected die (DN).

(2-4) The amount of movement (dX, dY) from the pattern coordinates (X1, Y1) of the first search die to the coordinates (XN, YN) of the pattern currently being imaged is calculated.
dX = XN-X1
dY = YN-Y1

  (2-5) The stage is moved starting from the first search die by a movement amount (2 * dX, 2 * dY) twice the calculated movement amount (dX, dY).

  (2-6) After moving the stage, the image is picked up at low magnification, and pattern matching is executed using the template image, thereby updating the exact coordinate values (XN, YN) of the currently observed pattern, The number of detected signals is doubled. See FIG. 22 for this.

  (2-7) The steps (2-4) to (2-6) are repeatedly executed toward the upper part of the wafer until the Y coordinate value specified in advance is exceeded.

  In the present embodiment, an example has been described in which a double movement amount is repeated in order to increase accuracy, reduce the number of times of processing (number of repetitions), and shorten the processing time. However, there is a problem in accuracy. If the processing time is to be further reduced, it may be executed at a high magnification of an integral multiple such as 2 or more, such as 3 or 4 times. Conversely, if there is no problem, the movement may be repeated with a fixed movement amount in order to further improve the accuracy. In any of these cases, it goes without saying that this is also reflected in the detected number.

(3) <Light microscope low magnification θ rotation>
(3-1) The amount of movement from the pattern coordinates (X1, Y1) of the first search die to the exact coordinate values (XN, YN) of the last searched die pattern and the number of dies detected so far ( DN) is used to calculate the rotation amount (θ) and the Y-direction die size (YD) (see FIG. 23).
dX = XN-X1
dY = YN-Y1
θ = tan ⁻¹ (dX / dY)
YD = sqrt ((dX) ² + (dY) ² ) / DN
* Sqrt (A) = √A
(3-2) The θ stage is rotated by the calculated rotation amount (θ).

B. Imaging with optical microscope high magnification (1) The same procedure as (1) for optical microscope low magnification is executed using an optical microscope high magnification image.
(2) The same procedure as in (2) for light microscope low magnification is executed using a light microscope high magnification image.
(3) The same procedure as (3) for light microscopic low magnification is executed.
(4) <Tolerance value check after optical microscope magnification θ rotation>

(4-1) [First search die, light magnifying power template specification]
The coordinates (X′1, Y′1) of the first search die after rotation are calculated from the coordinates (X1, Y1) before rotation and the rotation amount (θ), and the stage is moved to the coordinates (X′1, Y′1). After moving and locating, get a template image for pattern matching.
X′1 = x ₁ * cos θ−y ₁ * sin θ
Y′1 = x ₁ * sin θ + y ₁ * cos θ
(4-2) Light microscope high magnification Y direction pattern matching

  By moving in the Y direction by dY from the coordinates (X′1, Y′1) of the first search die after rotation, the exact coordinate values (XN, YN) of the currently observed pattern are obtained by executing pattern matching. get.

(4-3) A movement amount (dX, dY) from the coordinates (X′1, Y′1) of the first search die after rotation to the coordinates (XN, YN) of the pattern currently being imaged is calculated.
dX = XN−X′1
dY = YN−Y′1

  (4-4) The stage is moved from the first search die as a starting point by a movement amount (2 * dX, 2 * dY) twice the calculated movement amount (dX, dY).

  (4-5) After moving the stage, the image is captured at optical magnification, and the pattern matching is executed using the template image, thereby updating the exact coordinate values (XN, YN) of the currently observed pattern.

  (4-6) Steps (4-3) to (4-5) are repeatedly executed toward the upper portion of the wafer until the Y coordinate value designated in advance is exceeded.

(4-7) Calculate the rotation amount of θ Move from the coordinate (X′1, Y′1) of the first search die after rotation to the exact coordinate value (XN, YN) of the die pattern searched last The rotation amount (θ) is calculated using the amount.
dX = XN-X1
dY = YN-Y1
θ = tan− ¹ (dX / dY)

(4-8) Light microscopic magnification θ allowable value check It is confirmed that the rotation amount (θ) calculated in (4-7) is within a predetermined value or less. If not, the steps (4-1) to (4-8) are executed again after the θ stage is rotated using the calculated rotation amount (θ). However, if it does not fall within the allowable range even if (4-1) to (4-8) are repeatedly executed a specified number of times, the process is interrupted as an error.

C. EB image alignment (1) <Y search first die, EB template designation>
The same procedure as that in (1) for optical magnification is performed using the EB image.
(2) <EB Y-direction pattern matching>
A procedure similar to that in (2) of the optical magnification is executed using the EB image.
(3) <EB θ rotation>
A procedure similar to that in (3) of the optical magnification is performed using the EB image.
(4) <Allowable value check after EB θ rotation>
A procedure similar to that in (4) of the optical magnification is performed using the EB image.
(5) If necessary, execute (1) to (4) using a high-magnification EB image.
(6) An approximate value of the X direction die size (XD) is calculated from the coordinates (X1, Y1) of the first search die and the coordinates (X2, Y2) of the second search die.
dX = X2-X1
dY = Y2-Y1
XD = sqrt ((dX) ² + (dY) ² )
* Sqrt (A) = √A

D. Die map recipe creation (1) <X search first die, EB template designation>
Move the stage by user operation so that the lower left corner of the die located at the left edge of the wafer is located near the center of the TDI camera, and after determining the position, obtain a template image for pattern matching. As the template image, an image that has a unique pattern within the search area must be selected.

(2) <EB X direction pattern matching>
(2-1) Using the approximate X-direction die size (XD), move the stage to the coordinates (X1 + XD, Y1) where the pattern of the die next to the X search first die exists (and is expected).

  (2-2) After moving the stage, an EB image is captured with a TDI camera, and pattern matching is executed using a template image to obtain exact coordinate values (XN, YN) of the currently observed pattern, Further, 1 is set as the initial value of the number of detected die (DN).

(2-3) X Search The movement amount (dX, dY) from the pattern coordinates (X1, Y1) of the first die to the coordinates (XN, YN) of the pattern currently being imaged is calculated.
dX = XN-X1
dY = YN-Y1

  (2-4) The stage is moved from the X search first die as the starting point by a movement amount (2 * dX, 2 * dY) twice the calculated movement amount (dX, dY).

  (2-5) After moving the stage, an EB image is captured by the TDI camera, and pattern matching is executed using the template image, thereby updating the exact coordinate values (XN, YN) of the currently observed pattern. Double the number of detected dies.

  (2-6) Steps (2-3) to (2-5) are repeatedly executed in the right direction of the wafer until the X coordinate value designated in advance is exceeded.

(3) <Calculate X-direction tilt>
Using the amount of movement from the pattern coordinates (X1, Y1) of the first die of the X search to the exact coordinate values (XN, YN) of the last searched die pattern, and the number of dies detected so far (DN) The stage direct error (Φ) and the X-direction die size (XD) are calculated.
dX = XN-X1
dY = YN-Y1
Φ = tan− ¹ (dY / dX)
XD = sqrt ((dX) ² + (dY) ² ) / DN
* Sqrt (A) = √A

(4) <Die map creation>
Thus, the X direction die size (XD) is obtained, and the die map (ideal die arrangement information) is created together with the Y direction die size (YD) obtained when the rotation amount (θ) is calculated in advance. To do. The die map shows the ideal die placement. On the other hand, the die on the actual substrate is affected by the mechanical error of the stage (components such as guides and assembly errors), the error of the interferometer (for example, due to the problem of assembly of mirrors, etc.) and the image distortion due to charge-up. However, it is not always possible to observe the ideal arrangement, but the error between this actual die position and the ideal arrangement on the die map is grasped, and this error is taken into account and automatically corrected. While doing the inspection, try to do it.

E. Focus recipe creation procedure Next, a focus recipe creation procedure will be described. The focus recipe stores information on an optimum focus position at a mark position on a plane of a sample such as a substrate or various conditions related to the focus position in a predetermined format such as a table. In the focus map recipe, a focus condition is set only at a specified position on the wafer, and a focus value between the specified positions is linearly complemented (see FIG. 24). The focus recipe creation procedure is as follows.
(1) A focus measurement target die is selected from a die map.
(2) Set a focus measurement point in the die.
(3) The stage is moved to each measurement point, and the focus value (CL12 voltage) is manually adjusted based on the image and the contrast value.

  The die map created by the alignment process is ideal position information calculated from the die coordinates at both ends of the wafer, and an error occurs between the die position on the die map and the actual die position due to various factors (FIG. 25). reference). A procedure for creating a parameter for absorbing this error is called fine alignment, and error information between the die map (ideal die arrangement information) and the actual die position is stored in the fine alignment recipe. The information set here is used at the time of defect inspection. In the fine alignment recipe, the error is measured only for the die designated on the die map, and the error between the designated dies is linearly complemented.

F. Fine alignment procedure (1) An error measurement die for fine alignment is designated from a die map.
(2) The reference die is selected from the error measurement target die, and the position of this die is set to a point where the error from the die map is zero.
(3) The lower left corner of the reference die is imaged with a TDI camera, and a pattern matching template image is acquired.
* Select a unique pattern in the search area as a template image. (4) Acquire the coordinates (X0, Y0) at the lower left (on the die map) of the neighboring error measurement die and move the stage. After the movement, an image is taken with a TDI camera, and pattern matching is executed using the template image of (3), thereby obtaining exact coordinate values (X, Y).
(5) The error between the coordinate value (X, Y) acquired by pattern matching and the coordinate value (X0, Y0) on the die map is stored.
(6) Execute (4) to (5) for all error measurement target dies.

2-4-3) Defect Inspection As shown in FIG. 26, the defect inspection is performed by setting the conditions of the electron optical system (setting the imaging magnification, etc.) and moving the stage while irradiating the electron beam to perform TDI scan imaging. (FIG. 27) is performed, and according to the set inspection conditions (array inspection conditions, random inspection conditions, inspection area), defect inspection is performed in real time by the inspection dedicated processing unit (IPE).

  In the inspection recipe, the conditions of the electron optical system, the inspection target die, the inspection area, the inspection method (random / array), and the like are set (A and B in FIG. 28).

  In addition, in order to acquire a stable image for defect inspection, EO correction that suppresses blurring of a captured image due to positional deviation, speed unevenness, and the like, and an error between an ideal die map arrangement and an actual die position are absorbed. Die position correction and focus adjustment that complements the focus value of the entire area of the wafer using focus values measured in advance at finite measurement points are simultaneously performed in real time.

  In the defect inspection scanning operation, in addition to inspecting the entire area of the inspection target die (FIG. 29), as shown in FIG. 30, thinning inspection can be performed by adjusting the step movement amount in the direction perpendicular to the scanning direction. (Reduced inspection time). Furthermore, although the inspection time can be shortened by simple thinning inspection, since the area where the thinning inspection is performed is not necessarily an important area for inspection, a critical area that is particularly important for inspection is arbitrarily selected. It is also possible to inspect. Thereby, while shortening the inspection time, it is possible to properly inspect important areas and to ensure the accuracy more efficiently.

  After the inspection is completed, the number of defects, the position of the die containing the defect, the defect size, the position of the defect in each die, the defect type, the defect image, and the comparison image are displayed on the display as the inspection result. It is possible to confirm and reproduce past test results by saving to a file.

  By selecting and specifying various recipes during automatic defect inspection, the wafer is loaded according to the transfer recipe, the wafer is aligned on the stage according to the alignment recipe, focus conditions are set according to the focus map recipe, and inspection is performed according to the inspection recipe. And the wafer is unloaded according to the transfer recipe (A and B in FIG. 31).

2-4-4) Control system configuration This apparatus includes a plurality of controllers as shown in FIG. The main controller controls the GUI unit / sequence operation of the device (EBI), receives operation commands from the factory host computer or GUI, and gives necessary instructions to the VME controller and IPE controller. The VME controller manages the operation of the equipment (EBI) components and gives instructions to the stage controller and the PLC controller according to instructions from the main controller. The IPE controller acquires defect inspection information from the IPE node computer, classifies the acquired defects, and displays an image according to an instruction from the main controller. The IPE node computer acquires an image output from the TDI camera and performs defect inspection.

  In response to an instruction from the VME controller, the PLC controller drives a device such as a valve, acquires sensor information, and performs abnormality monitoring such as a vacuum degree abnormality that requires constant monitoring. Upon receiving an instruction from the VME controller, the stage controller moves in the XY directions and rotates the wafer installed on the stage.

  By configuring such a distributed control system, it is not necessary to change the software and hardware of the host controller by keeping the interface between the controllers the same when the terminal device configuration device is changed. Further, even when the sequence operation is added / modified, it is possible to flexibly cope with the configuration change by minimizing the change of the upper software and the hardware.

2-4-5) User Interface Configuration FIG. 33 shows a device configuration of the user interface unit.
(1) Input unit A device that accepts input from a user, and includes a “keyboard”, “mouse”, and “joy pad”.
(2) Display unit A device that displays information to the user, and consists of two monitors.
Monitor 1: Display the acquired image with CCD camera or TDI camera Monitor 2: GUI display

About the coordinate system This device defines the following three coordinate systems.
(1) Stage coordinate system [X _S , Y _S ]
Reference coordinate system for position indication during stage position control With the lower left corner of the chamber as the origin, the X coordinate value increases in the right direction and the Y coordinate value increases in the upward direction.
There is only one coordinate system in the apparatus.
The position (coordinate value) indicated in the stage coordinate system is the center of the stage (wafer center).
That is, when the coordinate value [0, 0] is specified in the stage coordinate system, the stage center (wafer center) moves so as to overlap the origin of the stage coordinate system.
The unit is [μm], but the minimum resolution is λ / 1024 (≈0.618 [μm]).
* Λ: Wavelength of the laser used in the laser interferometer (λ ≒ 632.991 [μm])

(2) Wafer coordinate system [X _W , Y _W ]
Reference coordinates for designating the observation (imaging / display) position on the wafer The X coordinate value increases in the right direction and the Y coordinate value increases in the upward direction with the wafer center as the origin.
The position (coordinate value) indicated in the wafer coordinate system is the imaging center of the imaging device (CCD camera, TDI camera) selected at that time.
There is only one coordinate system in the apparatus.
The unit is [μm], but the minimum resolution is λ / 1024 (≈0.618 [μm]).
* Λ: Wavelength of the laser used in the laser interferometer (λ ≒ 632.991 [μm])

(3) Die coordinate system [X _D , Y _D ]
Reference coordinates for defining the observation (imaging / display) position in each die The X coordinate value increases in the right direction and the Y coordinate value increases in the upper direction with the lower left corner of each die as the origin. This coordinate system exists for each die. The unit is [μm], but the minimum resolution is λ / 1024 (≈0.618 [μm]).
* Λ: Wavelength of the laser used in the laser interferometer (λ ≒ 632.991 [μm])

    The dies on the wafer are numbered (numbered), and the die that serves as a reference for numbering is called the origin die. By default, the die closest to the wafer coordinate system origin is set as the origin die, but the position of the origin die can be selected by the user's specification.

* The relationship between the coordinates specified by the user interface and the stage movement direction is as follows.
(1) Joystick & GUI arrow button The direction indicated by the joystick and the GUI arrow button is regarded as the direction that the operator wants to see, and the stage is moved in the direction opposite to the indicated direction.
Example)
Direction: Right . . . Stage movement direction: Left (image moves to the left = field of view moves to the right)
Direction: Up ... Stage movement direction: Down (Image moves down = Field of view moves up)

(2) Directly inputting coordinates on the GUI The coordinates directly input on the GUI are regarded as a place the operator wants to see on the wafer coordinate system, and the stage is moved so that the corresponding wafer coordinates are displayed at the center of the captured image. .

2-5) Inspection Next, the inspection procedure will be described with reference to FIG. First, a general inspection procedure will be described, and then a selective inspection will be described. In general, a defect inspection apparatus using an electron beam is expensive and has a lower throughput than other process apparatuses. Therefore, an important process (e.g., etching, film formation, or After the CMP (Chemical Mechanical Polishing) flattening process, etc., and in the wiring process, it is used for a finer wiring process part, that is, one or two steps of the wiring process, the gate wiring process of the previous process, and the like. In particular, it is important to find shape defects and electrical defects such as wiring having a design rule of 100 nm or less, that is, a line width of 100 nm or less, and via holes having a diameter of 100 nm or less, and feeding back to the process.

  The wafer to be inspected is positioned on the ultra-precision XY stage through the atmospheric transfer system and the vacuum transfer system, and then fixed by an electrostatic chuck mechanism or the like, and thereafter, defect inspection or the like is performed according to the procedure of FIG. . First, as necessary, the position of each die is confirmed and the height of each location is detected and stored by an optical microscope. In addition to this, the optical microscope acquires an optical microscope image of a desired location such as a defect and is used for comparison with an electron beam image. Next, the conditions of the electron optical system are set, and the information set by the optical microscope is corrected using the electron beam image to improve the accuracy.

  Next, recipe information corresponding to the type of wafer (after which process, whether the wafer size is 200 mm or 300 mm, etc.) is input to the apparatus. Hereinafter, specification of the inspection area, setting of the electron optical system, inspection conditions, etc. After setting, etc., defect inspection is usually performed in real time while acquiring images. In the case of general wafer entire surface inspection, cell-to-cell comparison, die comparison, etc. are inspected by a high-speed information processing system equipped with an algorithm, and the results are output to a CRT or the like if necessary. To remember.

  Defects include particle defects, shape abnormalities (pattern defects), and electrical (disconnections such as wiring or vias and poor conduction) defects, etc., which can be distinguished from each other, the size of defects, and killer defects (use of chips). It is also possible to automatically classify critical defects that are impossible) in real time. In particular, it is effective for classifying the defects such as wiring having a line width of 100 nm or less and vias having a diameter of 100 nm or less. Detection of an electrical defect is achieved by detecting a contrast abnormality. For example, a place with poor conduction is normally positively charged by electron beam irradiation (about 500 eV), and the contrast is lowered, so that it can be distinguished from a normal place. The electron beam irradiation means in this case is a low potential (energy) electron beam generation means (thermoelectron generation, UV / photoelectron) provided to make contrast due to potential difference stand out separately from the electron beam irradiation means for normal inspection. ). Before irradiating the inspection target region with the inspection electron beam, this low potential (energy is, for example, 100 eV or less) electron beam is generated and irradiated. In the case of a projection method that can be positively charged by irradiating an inspection electron beam, it is not necessary to provide a low-potential electron beam generating means depending on the specifications. Further, it is possible to detect a defect from a difference in contrast caused by applying a positive or negative potential to a sample such as a wafer with respect to a reference potential (which occurs because the flowability varies depending on the forward direction or reverse direction of the element).

  The contrast due to the potential difference may be converted into an image of a signal effective for displaying the potential contrast data and displayed. The potential contrast image can be analyzed to identify structures that are at voltages higher or lower than expected, ie, poor insulation or poor conduction or defects. For example, a potential contrast image is acquired from each different die on the wafer, and the defect is recognized by detecting the difference. In addition, by generating image data equivalent to the potential contrast image of the die to be inspected from design data such as CAD data, and detecting the difference between this image data and the potential contrast image acquired from the die to be inspected on the wafer. Recognize defects.

  It can also be used for line width measurement equipment and alignment accuracy measurement. Information on wafers to be inspected, for example, cassette numbers, wafer numbers (or lot numbers), etc., are all stored and managed in what position and state they are currently in. Therefore, there is no trouble that the inspection is mistakenly performed twice or more or the inspection is not performed.

2-6) Inspection method
2-6-1) Overview The basic flow of inspection is shown in FIG. First, after carrying the wafer including the alignment operation 35.1, a recipe in which conditions and the like related to the inspection are set is created (35.2). At least one type of recipe is required for a wafer to be inspected, but a plurality of recipes may exist for one wafer to be inspected in order to cope with a plurality of inspection conditions. Further, when there are a plurality of wafers to be inspected with the same pattern, a plurality of wafers may be inspected with one kind of recipe. The path 35.3 shown in FIG. 35 indicates that when an inspection is performed with a recipe created in the past, it is not necessary to create a recipe immediately before the inspection operation. In FIG. 35, an inspection operation 35.4 performs a wafer inspection according to the conditions and sequence described in the recipe. Defect extraction is performed immediately every time a defect is discovered during an inspection operation,
a) Operation to perform defect classification (35.5) and add extracted defect information and defect classification information to result output file b) Operation to add extracted defect image to image-only result output file or file c) Position of extracted defect The operation for displaying the defect information on the operation screen is executed almost in parallel.
When inspection is completed for each wafer to be inspected,
a) Operation to close and save result output file b) Operation to send inspection result when communication from outside requests inspection result c) Operation to discharge wafer is executed almost in parallel.

  When the setting for continuously inspecting the wafer is made, the next wafer to be inspected is transported and the series of operations are repeated.

Hereinafter, the details of the flow in FIG. 35 will be described.
(1) Recipe creation A recipe is a setting file for conditions related to inspection, and can be saved. The equipment is set up using the recipe at the time of inspection or before inspection, but the conditions related to the inspection described in the recipe in the case of general wafer entire inspection are:
a) Inspection target die b) Die internal inspection area c) Inspection algorithm d) Detection conditions (conditions necessary for defect extraction such as inspection sensitivity)
e) Observation conditions (magnification, lens voltage, stage speed, inspection order, and other conditions necessary for observation).

  Among these, as shown in FIG. 36, the operator designates the die to be inspected on the die map screen displayed on the operation screen as shown in FIG. In the example of FIG. 36, the die 1 on the wafer end surface and the die 2 that is clearly determined to be defective in the previous process are grayed out and deleted from the inspection target, and the remainder is used as the inspection target die. It also has a function of automatically specifying an inspection die based on the distance from the wafer end face and the quality information of the die detected in the previous process.

  In addition, as shown in FIG. 37, the setting of the inspection area inside the die is performed by the operator using the optical microscope or the EB microscope with respect to the die internal inspection area setting screen displayed on the operation screen. Specify with an input device such as a mouse based on the image. In the example of FIG. 37, a region 37.1 pointed to by a solid line and a region 37.2 pointed to by a broken line are set.

  In the region 37.1, almost the entire die is set as a setting region. The inspection algorithm is an adjacent die comparison method (die-die inspection), and details of detection conditions and observation conditions for this region are set separately. In the area 37.2, the inspection algorithm is an array inspection (inspection), and details of detection conditions and observation conditions for this area are set separately. That is, a plurality of inspection areas can be set, and each inspection area can be set with its own inspection algorithm and inspection sensitivity. In addition, the inspection areas can be overlapped, and different inspection algorithms can be simultaneously processed for the same area.

(2) Inspection operation The inspection is performed by subdividing the wafer to be inspected into a scan width as shown in FIG. The scanning width is substantially determined by the length of the line sensor, but is set so that the end portions of the line sensor slightly overlap. This is in order to determine the continuity between the lines when the detected defects are finally integrated, and to secure a margin for image alignment when performing the comparative inspection. The overlapping amount is about 16 dots for a 2048 dot line sensor.

  A scanning direction and a sequence are schematically shown in FIG. That is, in order to shorten the inspection time, a bidirectional operation A and a unidirectional operation B due to machine limitations can be selected by the operator.

  It also has a function of automatically calculating and inspecting the operation of reducing the scanning amount based on the inspection target die setting of the recipe. FIG. 40 shows an example of scanning when there is one inspection die 40. 1, and unnecessary scanning is not performed. FIG. 41 shows a cell part 40 • 2 and a random part 40 • 3.

2-6-2) Selective Inspection Method Hereinafter, the selective inspection method will be described. The selective inspection does not inspect the entire surface of the wafer, but is performed only in an arbitrary region to be inspected, for example, a pattern is densely formed and a defect is likely to occur or a particularly important region on the chip. It is possible to significantly reduce the inspection time while inspecting important parts properly.

  Specifically, the inspection is performed as follows. First, as described above, a sample (various substrates including a wafer) is transported and placed on the stage of the inspection apparatus. Next, sample alignment called alignment is performed. First, pattern matching or the like is performed on the pattern formed on the sample, the rotation angle of the sample is adjusted, and the position of the θ deviation is corrected. Next, the deviation of the die on the xy plane is stored, and the inspection is performed while correcting the deviation.

  Each sample is inspected based on a recipe in which various inspection conditions are designated in advance. In other words, in principle, various setting values of the inspection device, such as acceleration voltage, beam current, lens setting voltage, and operating conditions such as which region of the sample to be inspected are determined based on the recipe. Follow the inspection.

  Therefore, if the operator of the inspection device knows the processing process of the sample before the inspection and it is clear which part to inspect for each sample, specify the inspection area in the recipe. And inspecting based on the designation. Usually, the entire surface inspection is performed on the sample, and even if the thinning inspection is performed as shown in the right side of FIG. 30, only regular stage movement and deflection such as every other one are performed. As usual, in the present invention, since it is necessary to flexibly inspect according to the designation of the recipe of the critical part, the coordinates of the inspected area are designated and the designated coordinates are inspected.

  In this case, taking lithography as an example, as shown in FIG. 42, the boundary portion between the memory cell portion and the random logic portion may be inspected, so that the stripe including this boundary portion is inspected.

  Referring to FIG. 42, a plurality of dies 2 are arranged on the wafer 1. A low pattern density region 3 and a high pattern density region 4 are arranged on the wafer 1. For example, the low pattern density region 3 corresponds to a random logic portion, and the high pattern density region 4 corresponds to a memory cell portion.

  In the present embodiment, as shown in the figure, an inspection omitted area 5 which is an area where inspection is omitted is provided. Then, the stripe-shaped inspected area 6 is set at the boundary between the low pattern density area 3 and the high pattern density area 4.

  The beam used in the present invention is not only a beam diameter for one pixel as in the SEM, but, for example, a wide beam having an imaging region of 2048 pixels in width is used. Thus, it is possible to inspect a region having a considerably wide width. For example, the image width can be about twice the scanning width of the SEM. In addition, a TDI-CCD is used as a detector, and the stage can be inspected by moving the stage continuously in the same direction as the stripe in synchronization with the integrated speed of TDI. In addition, the inspection can be performed in a short time. Therefore, if the x coordinate of the stripe including the critical part can be designated, the selective inspection can be executed at a very high speed.

Although an example has been described in which only one stripe is required at the boundary portion, if necessary, two or more stripes may be set in order to inspect the periphery of the boundary a little more widely. The coordinates of the recipe can be arbitrarily set by the operator, but the width of the die is constant, so if the x coordinate of one boundary and the width of the die are known, it is automatically calculated for all dies. It is possible to calculate boundary coordinates. When creating a recipe, the driver often knows the past defect history, so from the analysis result of the history, if you specify and inspect the place where it is expected that there are many defects, Efficient and relatively accurate inspection can be performed. For example, since the pattern density changes greatly at the boundary region between the cell portion having a high pattern density and the random portion having a relatively small pattern density, a proximity effect correction error occurs when the pattern is formed on the sample by EB lithography. Even in the case where pattern formation is performed using optical lithography, an OPC (Optical Proximity Correction) correction error is likely to occur. In this case, the boundary region between the cell portion and the random portion (usually x If the coordinate) is designated as the inspection area, an efficient inspection can be performed. You may perform a simulation experiment etc. suitably for prediction of a location with many defects. In addition, if there is a region that the pattern designer thinks that a defect is particularly likely to occur or a region that is considered particularly important in the pattern, the region may be designated as an inspection region. For example, if the pattern is dense and the line width is narrow, and there is a portion with a small design margin, it may be designated as the inspection area. Note that the entire inspection of the sample and the selective inspection based on the recipe may be switched depending on the mode.

  Further, FIG. 42 shows inspected regions 7, 9, and 10 in addition to the striped inspected region 6. The inspection area 7 is an area in which inspection is selectively performed by continuous movement of the stage, beam scanning, or a combination of both. The inspection area 7 corresponds to a defect occurrence area 8 which is an area where defects are expected to occur frequently. The inspection area 9 is also an area in which inspection is performed by continuous movement of the stage, beam scanning, or a combination of both. Furthermore, in the present embodiment, the inspection may be performed by a step-and-repeat method. In addition, the region to be inspected 10 is an example of a region which is a low pattern density region but is selectively inspected, and this is also included in the present embodiment.

  In addition, as shown in FIG. 43, instead of a recipe, first, a preliminary inspection is performed on a predetermined small area on the sample, and the result is analyzed to estimate an area expected to have many defects in the die. The region may be selectively inspected. As shown in the center of FIG. 43, the small area to be preliminarily inspected may be inspected on the entire surface with the stripe width for one or two rows of dies or as shown on the left side of FIG. For example, it may be performed for 2 dies and 2 columns (4 total). Images are acquired for these small areas, and a wafer map is created. It is possible to designate a portion to be inspected selectively from the wafer map created here, thereby performing the inspection. Since the entire inspection location is determined from the inspection results of the actual small area on the same sample, it is possible to select the inspection location in a form that reflects the status of the previous processing process, and more flexibility in accordance with the current situation Is possible. Note that this selection is also convenient in terms of operation if a wafer map is displayed on the screen and designation can be made by enclosing the area to be inspected with a rectangle by clicking or dragging the area to be inspected. is there.

  Furthermore, the selection of those areas to be inspected may be automatically processed. For example, when an image of a small area is acquired, a template of the pattern to be inspected is previously stored in a memory, a difference between this and the small area image is taken, a location exceeding a predetermined threshold is specified, and the specified location In other words, an algorithm for determining the inspection region so as to include the most frequent defect candidate portions may be prepared.

  Further, as shown in FIG. 44, even if a fine test pattern 23 for inspection is formed on the scribe line 21 around the die 20, and a stripe including the test pattern 23 is designated as an inspection region. Good. In FIG. 44, test patterns 23 are arranged at four corners of the die 20 including the memory cell portion 24. If a pattern that is finer than the actual pattern in the die is formed as a test pattern and this pattern is inspected and there are no defects, the actual pattern in the die is likely to be processed without defects. This is also an effective selective test. In particular, if test patterns are formed at the four corners on the outside of the die and these are inspected and there are no defects, the test pattern is evenly distributed over the entire sample, so there is a possibility that the entire sample is free of defects. It can be estimated to be high.

  In the present invention, the inspection optical system adopts a mapping optical system, and a TDI-CCD is used as a detector. Therefore, as described above, the stage is continuously moved to inspect continuously in units of stripes. This inspection method is the most suitable inspection method for this equipment, but the stage movement is a step-and-repeat method, and only critical areas are spot-selected and inspected. Is also possible.

  Electrons used for inspection directly irradiate the sample with a primary electron beam, and in addition to secondary electrons, reflected electrons, and backscattered electrons emitted from the sample, a reverse electric field is applied in the vicinity of the sample, and the primary electron beam is applied to the sample. Electrons reflected before collision (also referred to as mirror electrons) may be used. Furthermore, it is possible to inspect with the transmitted electrons that have passed through the sample. These can be adapted by changing the lens and retarding settings as needed, or by adding / changing necessary hardware.

  The inspected image is once captured in the memory, and the image stored in the memory is compared with the next captured image, that is, before and after the same stripe die. Alternatively, a comparative inspection is performed by comparing stripes on the same or different samples or stripes of design data.

In order to shorten the inspection time, a thinning inspection or a sampling inspection may be performed. In this method, a thinning rate or a sampling rate is determined in advance, and the stripes are inspected at intervals of several rows according to this thinning rate. Because it is mechanically determined the stripe to be the inspection area, it can not be said that the critical part is necessarily inspected, and in terms of accuracy, it is inferior to the selective inspection described above, but the inspection time is shortened realizable. In addition, since it is easy to specify the region to be inspected, this inspection is also effective if the most important is to shorten the inspection time. In the case of the mapping projection type inspection apparatus used in the present invention, the stripe width of one row is much wider than that of the SEM, so that the inspection time can be considerably shortened.

  As described above, the selective inspection method and apparatus of the present invention is preferably applied to an inspection apparatus using a mapping projection type electron beam, but an inspection apparatus adopting another method. It is also applicable to. If an arbitrary region to be inspected is set, the stripe may be inspected using a narrowed beam of SEM type. Also, if the inspection speed is slow in the single beam SEM method, for example, the number of beams is increased to make a multi-beam irradiation source, and each raster is simultaneously scanned with a plurality of beams as shown in FIG. Image synthesis may be performed in consideration of the beam position.

  FIG. 45 illustrates a case where a place where a large number of defects are expected to be generated is selectively inspected with multi-beams. The scanning start point and the scanning end point are determined so that all nine beams scan the stripe width 30, and the nine beams are scanned simultaneously, and the secondary electrons from each scanning point are mutually detected by the nine detectors. Detection is performed without crosstalk, and an SEM image is synthesized from signals from each detector. The SEM images of the regions 31, 32, and 33 set separately are compared, and a portion of the image of the region 32 that is different from the region 31 and the region 33 is a defect candidate.

  Furthermore, the projection type inspection apparatus used in the present invention may adopt a multi-beam method. In addition to the large beam diameter itself, which is a projection projection type, the sample is further irradiated with a plurality of beams, so that the inspection time can be greatly shortened. A projection type multi-beam inspection apparatus is shown in FIG. The four electron beams 46.2 (46.3 to 46.6) emitted from the electron gun 46.1 are shaped by the aperture stop 46.7, and the two-stage lenses 46.8, 46.9 (lens system). 46.50), an image is formed in an ellipse of 10 .mu.m.times.12 .mu.m on the deflection center plane of the Wien filter 46.10. The electron beam is raster-scanned by the deflectors 46 and 11 in the direction perpendicular to the paper surface of the drawing, and is imaged so as to uniformly cover a rectangular area of 1 mm × 0.25 mm as a whole of the four electron beams. A plurality of electron beams deflected by an E × B separator (Wien filter) 46 and 10 are crossed over by an NA aperture, reduced to 1/5 by lenses 46 and 20, and a sample W is covered by 200 μ × 50 μm, Irradiated and projected so as to be perpendicular to the sample surface (called Koehler illumination). The E × B separators 46 and 10 include electrodes 46 and 52 and magnets 46 and 53. The four secondary electron beams 46 and 12 having information of the pattern image (sample image F) emitted from the sample are lenses 46 and 11, 46 and 13, 46 and 14 (lenses 46 and 13, lenses 46 and 14). Is magnified by the lens systems 46 and 51) and formed on the MCP 46 and 15 as a rectangular image (enlarged projection image F ′) synthesized by the four electron beams 46 and 12 as a whole. The enlarged projection image F ′ by the secondary electron beams 46 and 12 is sensitized 10,000 times by the MCP 46 and 15, converted into light by the fluorescent part, and synchronized with the continuous moving speed of the sample by the TDI-CCD 46 and 16. It is acquired as a continuous image by the image display units 46 and 17 and output to a CRT or the like.

  The electron beam irradiation unit needs to irradiate the sample surface with the electron beam in a rectangular or elliptical shape with as little uniformity as possible and with less irradiation unevenness. Irradiation is necessary.

  The primary electron beam irradiation method of this embodiment mode is shown in FIG. The primary electron beam 47.1 is composed of four electron beams 47.2 to 47.5, and each beam has an elliptical shape of 2 μm × 2.4 μm, each having a rectangular shape of 200 μm × 12.5 μm. The areas are raster-scanned and added together so that they do not overlap to irradiate a rectangular area of 200 μm × 50 μm as a whole. The beam 46.2 arrives at 46.2 'in a finite time, and then returns to the position immediately below 46.2 shifted by the beam spot diameter (10 μm) with almost no time loss. Move parallel to 2-46.2 'and immediately below 46.2' (in the direction of 46.3 '), and this is repeated until 1/4 of the rectangular irradiation area indicated by the dotted line in the figure (200 μm × 12.5 μm) After scanning, return to the first point 47.1 and repeat this at high speed.

  The other electron beams 47 and 3 to 47 and 5 are repeatedly scanned at the same speed as the electron beams 47 and 2 to uniformly irradiate a rectangular irradiation region (200 μ × 50 μm) as a whole at high speed.

  As long as the irradiation can be performed uniformly, the raster scan may not be performed. For example, scanning may be performed so as to draw a Lissajous shape. Therefore, the moving direction of the stage need not be the direction A shown in the figure. That is, it is not necessary to be perpendicular to the scanning direction (the high-speed scanning direction in the horizontal direction in the figure).

  In this embodiment, the unevenness of electron beam irradiation can be irradiated at about ± 3%. The irradiation current was 250 nA per electron beam, and 1.0 μA was obtained with four electron beams as a whole on the sample surface (twice as compared with the conventional method). By increasing the number of electron beams, current can be increased and high throughput can be obtained. Further, since the irradiation point is smaller than the conventional one (about 1/80 in area) and moved, the charge-up can be suppressed to 1/20 or less of the conventional one.

  The electron detected in the present invention may be anything as long as it obtains information on the surface of the substrate. For example, by forming a reverse electric field in the vicinity of the substrate, it does not directly collide with the substrate, but near the substrate. Mirror electrons that are reflected on the substrate (also referred to as reflected electrons in a broad sense) or transmitted electrons that pass through the substrate may be used. In particular, when mirror electrons are used, the electrons do not directly collide with the sample, so that there is an advantage that the influence of charge-up is extremely small.

  When mirror electrons are used, a negative potential lower than the acceleration voltage is applied to the sample to form a reverse electric field near the sample. This negative potential is preferably set to a value such that most of the electron beam is returned near the surface of the substrate. Specifically, it may be set to a potential lower by 0.5 to 1.0 V or more than the acceleration voltage of the electron gun. For example, in the case of the present invention, when the acceleration voltage is −4 kV, the voltage applied to the sample is preferably set to −4.00 kV to −4.050 kV. More desirably, it is preferably −4.005 kV to −4.020 kV, and more preferably −4.005 kV to −4.010 kV.

3) Embodiment of Production Line FIG. 48 shows an example of a production line using the apparatus of the present invention. Read out information such as the lot number of the wafer to be inspected by the inspection apparatus 48. 1, the history of the manufacturing apparatus via the production from the memory provided in the SMIF or FOUP 48 2, or the lot number is read from the SMIF, FOUP or It can be recognized by reading the ID number of the wafer cassette. During the transfer of the wafer, the amount of moisture is controlled to prevent the metal wiring from being oxidized.

  The defect inspection apparatus 48.1 can be connected to a production line network system. Through this network system 48.3, a production line control computer 48.4 for controlling the production line, each manufacture. Information such as the lot number of the wafer to be inspected and the inspection result can be sent to the apparatus 48.5 and another inspection apparatus. The manufacturing apparatus includes lithography-related apparatuses such as exposure apparatuses, coaters, curing apparatuses, developers, etc., film forming apparatuses such as etching apparatuses, sputtering apparatuses, and CVD apparatuses, CMP apparatuses, various measuring apparatuses, other inspection apparatuses, and review apparatuses. Etc. are included.

  FIG. 49 is a flowchart showing an example of a semiconductor device manufacturing method using the electron beam apparatus according to the embodiment of the present invention. The semiconductor device manufacturing method of FIG. 49 includes the following main steps. (1) Wafer manufacturing process 49 • 1 for manufacturing wafer 49 • 2 or wafer preparation process for preparing wafer 49.2, (2) Mask manufacturing process 49 • for manufacturing mask (reticle) 49 • 12 used for exposure 11 or a mask preparation step for preparing a mask, (3) a wafer processing step 49, 3 for performing necessary processing on the wafer, and (4) a chip assembly for cutting out chips formed on the wafer one by one and making them operable. Steps 49, 4 and (5) Chip inspection step 49, 6 for inspecting the completed chip 49, 5 and a step of obtaining a product (semiconductor device) 49, 7 composed of chips that have passed the inspection. Each of these main processes includes several sub-processes. The right part of FIG. 49 shows a sub-process of the wafer processing process 49 · 3.

  Among the main processes (1) to (5), the main process that has a decisive influence on the performance of the semiconductor device is the wafer processing process 49. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as memories and MPUs. This wafer processing step includes the following steps. (6) Thin film forming steps 49 and 14 for forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film for forming an electrode portion (using CVD or sputtering). (7) Oxidation steps 49 and 14 for oxidizing the thin film layer and the wafer substrate. (8) Lithography steps 49 and 13 for forming a resist pattern using a mask (reticle) for selectively processing a thin film layer, a wafer substrate, or the like. (9) Etching steps 49 and 14 for processing a thin film layer and a substrate according to a resist pattern (for example, using a dry etching technique). (10) Ion / impurity implantation diffusion steps 49 and 14. (11) Resist stripping step. (12) An inspection process for inspecting the processed wafer. The wafer processing steps 49 and 3 are repeated as many times as necessary to manufacture a semiconductor device that operates as designed.

  The flow chart of FIG. 49 shows the above (6), (9) and (10) together as one block 49/14, which includes an additional wafer inspection process 49/15, and further repeats the block 49. 16. By using the inspection apparatus of the present invention in the inspection process for inspecting the processed wafer of (12) above, even a semiconductor device having a fine pattern can be inspected with good throughput, and 100% inspection can be performed, and the product yield can be obtained. It is possible to improve and prevent shipment of defective products.

  FIG. 50 is a flowchart showing details of the lithography steps 49 and 13 in the manufacturing method of FIG. As shown in FIG. 50, the lithography steps 49 and 13 include (13) a resist coating step 50 and 1 for coating a resist on the wafer on which the circuit pattern is formed in the preceding step, and (14) an exposure step for exposing the resist. 50.2, (15) development step 50.3 for developing the exposed resist to obtain a resist pattern, and (16) annealing step 50.4 for stabilizing the developed resist pattern. The semiconductor device manufacturing process, the wafer processing process, and the lithography process are well known.

  The preferred embodiments of the present invention have been described above. As described mainly with reference to FIGS. 42 to 45, a selective inspection is performed in the present embodiment. Depending on the intended use of the inspection device, not only the entire surface of the sample but also only the critical areas that require inspection can be selectively inspected, keeping the inspection accuracy at a certain level. The inspection time can be greatly shortened. When the area to be inspected is limited, only a desired area can be inspected, so that only a necessary area can be inspected efficiently.

Further, since the projection method is adopted and the TDI-CCD is used as the detector, it is possible to inspect while continuously moving the stage. There is no need to worry about the influence of vibration after moving the stage of step-and-repeat, which is often found in partial inspection, and inspection can be performed in the same way as full-surface inspection. In addition, since the irradiation area of the beam is wide, the critical area can be covered with a single stripe, and high throughput and high inspection accuracy can be realized.

  In this way, the present embodiment meets the demand for high throughput and enables inspection with high inspection accuracy.

  The inspection method and inspection apparatus according to the present invention can be used in a semiconductor manufacturing process or the like and are useful.

DESCRIPTION OF SYMBOLS 1 Wafer 2 Dies 3 Low pattern density area 4 High pattern density area 5 Inspection omission area 6, 7, 9, 10 Inspection area 8 Defect occurrence area 20 Die 21 Strive line 22 Test pattern 23 Memory cell part

Claims (4)

An inspection device for inspecting the surface of a sample,
An electron gun that irradiates the sample with an electron beam;
A sample stage for holding the sample;
A detector for detecting electrons obtained from the surface of the sample by irradiation of the electron beam toward the sample;
Means for generating an image of the sample surface based on the electrons detected by the detector;
A Wien filter that separates a primary electron optical system from the electron gun to the sample stage and a secondary electron optical system from the sample stage to the detector;
With
The electron beam emitted from the electron gun forms a crossover in the Wien filter, and the emitted electron emitted from the sample surface forms a crossover in the Wien filter, and the primary electron optical system and the 2 The sample surface inspection apparatus, wherein the position of the crossover of the secondary electron optical system is different on the Wien filter. The secondary electron optical system includes a first aperture disposed between the sample stage and the Wien filter, and a second aperture disposed between the Wien filter and the detector,
The sample surface inspection apparatus, wherein the size of the second aperture is larger than the size of the first aperture.   The sample surface inspection apparatus according to claim 1, wherein the detector detects mirror electrons reflected before the primary electron beam collides with the sample. A method for positioning a semiconductor wafer using the sample surface inspection apparatus according to claim 1,
Positioning the die present in the wafer with an optical microscope;
Increasing the magnification of the optical microscope and positioning the die;
Positioning the die based on an image of the sample surface generated based on the electrons detected by the detector;
A positioning method comprising: