WO2011070890A1

WO2011070890A1 - Inspection device and inspection method

Info

Publication number: WO2011070890A1
Application number: PCT/JP2010/070117
Authority: WO
Inventors: 正樹長谷川; 智一島倉
Original assignee: 株式会社日立製作所
Priority date: 2009-12-07
Filing date: 2010-11-11
Publication date: 2011-06-16
Also published as: JP5635009B2; JPWO2011070890A1

Abstract

Provided is an inspection device wherein an equipotential plane parallel to the surface of a sample is formed, and the sample can be irradiated with ultraviolet light from the underside. The inspection device wherein a sample retained by a holder is irradiated with an electron beam, and the reflected electrons from the sample are detected to inspect the surface of the sample, is provided with an upper electrode (6) and a lower electrode (7), which are in parallel with each other so that a holder (2) for retaining a sample (1) is provided therebetween. The upper electrode (6) has a hole through which the electron beam (5) passes and to which a voltage for accelerating the electron beam (5) to irradiate the sample (1) with the electron beam is applied. The lower electrode (7) has a hole through which the area of the sample (1) irradiated with the electron beam (5) is irradiated with ultraviolet light (8) from the underside of the sample (1) and to which a voltage for decelerating the accelerated electron beam (5) to cause the electron beam to be reflected by the surface of the sample, is applied.

Description

Inspection apparatus and inspection method

The present invention relates to an apparatus and a method suitable for inspecting the presence of foreign matter on a mold used in an insulating substrate, particularly in a nanoimprint technique, and the presence of a shape defect in a pattern formed on the mold.

When the recording density of the magnetic recording medium is increased and high density recording of 1 Tb / in ² (terabit / square inch) level is performed, it is adjacent to writing magnetic information on a conventional uniform magnetic film. Since it becomes difficult to separate recording units, development of a new magnetic recording medium technology called a pattern medium, in which grooves are formed in a magnetic film to spatially separate recording units, is being developed. The manufacturing process of the pattern medium requires a processing technique comparable to semiconductor device manufacturing in which grooves are formed at a pitch of 100 nm or less, but the unit price of a magnetic recording medium is much lower than that of a semiconductor device. The introduction of nanoimprint technology that enables high-precision patterning in large quantities at a low price is promising.

Nanoimprint technology creates a mold that is the pattern prototype in advance with high accuracy, presses this mold over the resist coated on the magnetic film, cures the resist, and then removes the mold. This is a technique for transferring the pattern shape of a mold to a resist pattern. After the pattern transfer, the resist pattern is transferred to the magnetic film pattern by etching as in the semiconductor device process. One of the resist curing processes used in this nanoimprint technology is a method that utilizes a curing action by ultraviolet irradiation. In the UV curable nanoimprint technology, the mold is made of quartz glass that transmits ultraviolet rays because it is necessary to irradiate ultraviolet rays while the mold is pressed.

Since the pattern shape of this quartz glass mold is transferred in large quantities to produce a pattern medium, the pattern shape of this quartz glass mold does not allow any defects. Further, a large amount of replica molds of quartz glass molds are manufactured by nanoimprint technology based on the quartz glass molds, and these replica molds are used for actual pattern medium production. Therefore, quality control of the pattern shape of these replica molds as well as the original quartz glass mold is extremely important.

Defective inspection of the pattern is essential for quality control of the pattern shape of the original quartz glass mold or replica mold. However, since the quartz glass mold is made of quartz glass, it is difficult to apply inspection technology using light, and application of inspection technology using electron beams is expected. As a defect inspection technique using an electron beam, there is a method using a scanning electron microscope (SEM) that scans a converged electron beam. For example, it is a SEM type visual inspection apparatus equipped with an image processing apparatus for comparing acquired SEM images as described in Patent Document 1. However, the SEM type visual inspection apparatus has a great disadvantage that it takes a long time for the inspection.

Therefore, in recent years, a new electron beam application inspection method has been developed which is intended to increase the inspection speed as disclosed in Patent Document 2 and Patent Document 3. These inspection technologies apply a negative potential close to the acceleration voltage of the electron beam applied to the sample, and then irradiate the entire inspection field onto the sample and image the electrons reflected by the sample. Get a statue. However, even if it is referred to as a reflected electron, the technique disclosed in Patent Document 2 applies a negative potential to the sample from the acceleration voltage of the irradiation electron beam and reflects the negative electron potential before the irradiation electron beam collides with the sample. Is an inspection technique that applies a mirror electron microscope (MEM: Mirror Electron Microscope) that forms an image of the emitted electrons. On the other hand, the technique disclosed in Patent Document 3 is, for example, about several V with respect to the acceleration voltage of an irradiation electron beam. This is an inspection technology applying a low energy reflection electron microscope (LEEM) that applies a positive electric potential to the sample and forms an image of the reflected electrons that collide with the sample surface with extremely low energy. .

The reflected electrons in this specification include both mirror electrons and low energy reflected electrons. An electron microscope that forms an image of mirror electrons or low-energy reflected electrons is hereinafter referred to as a reflection imaging electron microscope.

In a defect inspection apparatus using a reflection imaging electron microscope, an electron beam is irradiated, but the energy when electrons are incident on the quartz glass mold surface is several volts or less. Since electrons collide with the surface of the quartz glass mold with such low energy, secondary electrons are not emitted and incident electrons remain on the surface. That is, when the surface of the quartz glass mold is inspected with a reflection imaging electron microscope, the surface of the quartz glass is negatively charged because quartz is an insulator. In the reflection imaging electron microscope, when the surface is negatively charged, the resolution of the electron image is deteriorated, and as a result, the defect detection sensitivity is significantly lowered. In order to remove this negative charge, irradiation with ultraviolet rays is effective. By irradiating ultraviolet rays simultaneously with electron beam irradiation, an electron image can be obtained while removing negative charges. For example, Patent Document 4 discloses a technique for removing the charge generated in the MEM by irradiating ultraviolet rays.

However, in the prior art disclosed in Patent Document 4, ultraviolet rays are introduced from the side of the electron optical column, reflected by the reflecting mirror installed in the electron optical column, and the sample from above. Irradiated. In this ultraviolet irradiation method, since the area of the reflecting surface of the reflecting mirror is limited, the ultraviolet rays emitted from the ultraviolet light source cannot be collected efficiently. Although the amount of electron beam current increases to increase the speed of inspection, the amount of charge on the surface of the generated sample also increases. If a sufficient amount of ultraviolet rays cannot be supplied, this charge cannot be erased, but there is a limit to the amount of ultraviolet rays that can be collected by the reflecting mirror as described above.

In order to supply a sufficient amount of ultraviolet light to the inspection visual field region, it is necessary to bring the ultraviolet light condensing element closer to the irradiated object. This is not possible because there is an objective lens for electron irradiation on the sample surface. Therefore, as described in Patent Document 5, a method of irradiating from the back surface using the fact that the sample is made of quartz glass is suitable. Since ultraviolet rays are transmitted through quartz glass, negative charge on the surface can be removed by irradiation from the back surface. There is a space available on the back of the sample, and an optical element having a large light receiving area capable of collecting sufficient ultraviolet rays can be installed.

JP 05-258703 A Japanese Patent Laid-Open No. 11-108864 JP 2005-228743 A JP 2009-4114 A Japanese Patent Laid-Open No. 2005-174591

In a reflection imaging microscope, since the irradiated electron beam is irradiated in a substantially parallel bundle, the equipotential surface on the surface of the sample must be parallel to the sample. When the sample is a dielectric such as a quartz glass mold, in order to form an equipotential surface parallel to the surface, it is sandwiched between parallel electrodes and the potential above and below is fixed. In order to irradiate ultraviolet rays from the back surface in order to remove the charge at the time of electron beam irradiation, it is necessary to provide a hole for passing ultraviolet rays in the electrode on the back surface side.

During the inspection operation, the quartz glass mold is placed on a stage that moves continuously so that the electron beam irradiates the entire surface. In the configuration of a conventional reflection imaging microscope, even if an electrode is provided on the moving stage and a hole is provided, the position of the hole, that is, the ultraviolet irradiation position is separated from the electron beam irradiation position as the stage moves. Even during movement, it is impossible to keep the back surface opposite to the electron beam irradiation position on the front surface being irradiated with ultraviolet rays.

In addition, even if the quartz glass mold moves during the inspection operation, the back side of the electron beam irradiation position is always irradiated with ultraviolet rays, so that the back surface of the quartz glass mold is exposed before the ultraviolet light collector. If the holes are made larger, the electric field on the quartz glass mold surface will be greatly disturbed.

That is, in the conventional reflection imaging microscope, there is a problem that it is impossible to simultaneously form an equipotential surface parallel to the quartz glass mold surface and to irradiate ultraviolet rays from the back surface.

The object of the present invention is to form an equipotential surface parallel to the surface of the sample and irradiate the sample with ultraviolet rays from the back surface (below), even when the sample is sandwiched between electrodes provided above and below it. It is an object of the present invention to provide an inspection apparatus and an inspection method that can perform inspection.

As an embodiment for achieving the above object, in an inspection apparatus for inspecting the surface of the sample by irradiating the sample held by the holder with an electron beam and detecting reflected electrons from the sample, The upper electrode and the lower electrode are arranged in parallel, and the upper electrode has a hole through which the electron beam passes, and a voltage for accelerating the electron beam and irradiating the sample is applied. The lower electrode has a hole for irradiating ultraviolet rays from the back side of the sample to the sample region irradiated with the electron beam, decelerates the accelerated electron beam, and the sample The inspection apparatus is characterized in that a voltage reflected by the surface is applied.

Also, means for irradiating the insulator flat plate sample with electrons as substantially parallel electron beams, means for forming an electric field for pulling up the electron beam reflected near the surface of the insulator flat plate sample, and the reflected electron beam From the electron image, the electron optical means for obtaining the electron image, the means for moving the insulator flat plate sample with respect to the electron beam so that the shape formed on the insulator flat plate sample can be observed, In an inspection apparatus provided with a means for detecting a desired shape on the insulator flat plate sample and recording the detected location, an electric field is formed to pull up the electron beam reflected near the surface of the insulator flat plate sample. The means includes an electrode that does not move during the inspection operation on the side opposite to the side on which the electron beam of the insulator plate sample is irradiated, and on the side on which the electron beam of the insulator plate sample is irradiated Against The surface, the inspection device characterized by comprising a means for irradiating ultraviolet rays.

Also, means for irradiating the insulator flat plate sample with electrons as substantially parallel electron beams, means for forming an electric field for pulling up the electron beam reflected near the surface of the insulator flat plate sample, and the reflected electron beam Electron optical means for obtaining the electron image, means for moving the insulator plate sample so that the shape formed on the insulator plate sample can be observed, and the desired insulator plate from the electron image In the inspection apparatus provided with means for detecting the shape on the sample and recording the detection location, means for irradiating the surface of the insulator flat plate sample opposite to the side irradiated with the electron beam with ultraviolet rays An inspection apparatus comprising: an electrode made of a conductive material that transmits ultraviolet rays in means for forming an electric field for pulling up the electron beam reflected in the vicinity of the surface of the insulator plate sample. To.

Further, an electron is irradiated on the insulator flat plate sample as a substantially parallel electron beam, and the electron beam reflected in the vicinity of the surface of the insulator flat plate sample is pulled up by an electric field formed on the surface of the insulator flat plate sample. In the inspection method for inspecting the shape formed on the surface of the insulator flat plate sample by obtaining an electron image by means, the insulating plate is opposite to the side irradiated with the electron beam of the insulator flat plate sample. A step of applying a voltage to an electrode independent of the moving stage on which the body plate sample is placed, and a step of irradiating the surface of the insulator plate sample opposite to the side irradiated with the electron beam with ultraviolet rays. And an inspection method characterized by including:

Further, an electron is irradiated on the insulator flat plate sample as a substantially parallel electron beam, and the electron beam reflected in the vicinity of the surface of the insulator flat plate sample is pulled up by an electric field formed on the surface of the insulator flat plate sample. In the inspection method for inspecting the shape of the surface of the insulator plate sample by obtaining an electron image by means, the surface of the insulator plate sample opposite to the side irradiated with the electron beam is irradiated with ultraviolet rays. And a step of applying a voltage to the conductive electrode through which the ultraviolet rays are transmitted on the surface of the insulator flat plate sample opposite to the side irradiated with the electron beam. The inspection method to be used.

By arranging the upper electrode and the lower electrode to be parallel and using a lower electrode provided with a hole through which ultraviolet rays can pass, or by using a conductive thin film having a thickness that allows ultraviolet rays to pass through, the sample surface It is possible to provide an inspection apparatus and an inspection method capable of forming an equipotential surface parallel to the surface and irradiating the sample with ultraviolet rays from the back surface (below).

1 is a main part schematic diagram of an inspection apparatus according to Embodiment 1. FIG. It is a principal part schematic diagram of the inspection apparatus for demonstrating the operation | movement at the time of the to-be-inspected object conveyance in Example 1. FIG. 1 is a schematic diagram of an inspection apparatus using a reflection imaging microscope according to Example 1. FIG. FIG. 2 is a schematic diagram of a main part of an inspection apparatus for explaining a method for removing charge from a sample before inspection in Example 1. FIG. 6 is a schematic diagram of a main part of an inspection apparatus according to a second embodiment. 6 is a schematic diagram of an inspection apparatus according to Embodiment 3. FIG.

In order to irradiate ultraviolet rays from the back side of the quartz glass mold, an electrode provided with micropores for passing ultraviolet rays on the back side of the quartz glass mold is installed separately from the moving stage on which the quartz glass mold is placed, The center position of the microhole was always matched with the central axis of the objective lens of the electron optical system. In addition, a configuration in which the center position of the minute hole and the center axis of the objective lens of the electron optical system are coincident is optimal, but in practice, ultraviolet rays are irradiated so as to cover the electron beam irradiation region (about 100 μmφ). Thus, negative charging can be reduced and prevented.

It is possible to bring the light source closer to the sample by irradiating UV light from the back of the sample, and the intensity of the UV light can be increased. Therefore, UV light that can sufficiently remove the negative charge that occurs when using a high-current electron beam is supplied to the inspection field. As a result, the quartz glass mold can be inspected at high speed.

Hereinafter, the embodiment will be described in detail.

The first embodiment will be described with reference to FIGS. FIG. 1 schematically shows a cross section of a configuration in the vicinity of a quartz glass mold sample. It is different from the actual size ratio for clarity.

The quartz glass mold 1 is placed on a holder 2 made of the same quartz glass as the quartz glass mold 1 or a material having the same dielectric constant, and the holder 2 is placed on the movable stage insulating member 3. It is done. The quartz glass mold 1 used here has a diameter of 2 inches, but is not limited thereto, and may be 2 to 8 inches or larger. When the diameter of the quartz glass mold 1 is sufficiently large, it may be placed directly on the movable stage insulating member 3 instead of being placed on the holder 2. The moving stage insulating member 3 is installed on the moving stage 4.

The holder 2 is configured to hold the periphery of the quartz glass mold 1. Thereby, the ultraviolet rays irradiated to the back surface of the sample are not shielded by the holder 2. Further, the inspection sample is not limited to the quartz glass mold, and may be a replica mold.

The moving stage 4 has a drive mechanism configured to irradiate the entire surface of the quartz glass mold 1 with the electron beam 5 by performing a rotational movement about the center of the quartz glass mold 1 and a rectilinear movement in a plane. Has been.

An upper electrode 6 and a lower electrode 7 are installed so as to sandwich the quartz glass mold 1. The lower surface of the upper electrode 6 and the upper surface of the lower electrode 7 are parallel to the surface of the quartz glass mold 1 in a sufficiently wide area so as to form an equipotential surface parallel to the surface of the quartz glass mold 1. . The upper electrode 6 is provided with a hole (about 100 μm to 1 mm) through which the electron beam 5 passes, and constitutes a part of an objective lens that forms an image of the electron beam reflected near the quartz glass mold 1. . The distance L1 between the upper electrode 6 and the quartz glass mold 1, the positive voltage applied to the upper electrode 6, and the diameter R1 of the passage hole of the electron beam 5 are optimally designed so as to obtain an optimal electron image for inspection. Has been. For example, when forming an equipotential surface, L1> R1 is desirable. In order to avoid scattering of the electron beam, it is desirable that R1 exceeds the diameter of the electron beam 5.

The voltage of the surface of the quartz glass mold 1 is sufficiently slowed down near the surface of the quartz glass mold 1 and collides with the surface with a low energy of about several eV, or reverses just before the surface collides with the surface. In addition, a negative voltage is applied to the lower electrode 7. The lower electrode 7 is provided with a fine hole R2 so that the ultraviolet rays 8 pass through and irradiate the back surface of the quartz glass mold 1. The diameter of the passage hole for the ultraviolet rays 8 is designed to be smaller than the distance between the upper surface of the lower electrode 7 and the surface of the quartz glass mold 1, and the disturbance of the potential on the surface of the quartz glass mold 1 caused by this hole does not affect the electron image. . Further, it is desirable that the diameter R2 of the passage hole for the ultraviolet ray 8 provided in the lower electrode 7 exceeds the diameter of the electron beam so that the negatively charged region can be irradiated with sufficient ultraviolet ray.

The ultraviolet ray 8 is emitted from the ultraviolet light source 9, is collected by the lens 10, and irradiates the back surface of the quartz glass mold 1. The irradiation area of the ultraviolet rays 8 is almost equal to the inspection visual field. The ultraviolet light source 9 in this figure shows the light source for the lens 10. For example, the actual ultraviolet light source may be a tip further apart and introduced by quartz glass fiber.

Since the lens 10 can be installed close to the quartz glass mold 1 and can have a size of several centimeters, the lens 10 receives almost all ultraviolet rays from the ultraviolet light source 9 and collects them in an inspection region of about several hundred microns. Can be light. For this reason, the negative charge on the surface generated when the current amount of the electron beam 5 is increased and a high-speed inspection operation is performed can be removed by irradiating with a sufficient amount of ultraviolet rays.

The lower electrode 7, the lens 10, and the ultraviolet light source 9 are separated from the moving stage 4 so that the center of the ultraviolet passage hole of the lower electrode 7 and the center of the electron beam passage hole of the upper electrode 6 are aligned. ing. Therefore, even when the electron beam 5 is irradiated to various positions of the quartz glass mold 1 by the movement of the moving stage 4, the back side can always be correctly irradiated with the ultraviolet rays 8.

It is desirable that the lower electrode 7, the lens 10 and the ultraviolet light source 9 constitute one unit. For example, when the quartz glass mold 1 or the holder 2 on which the quartz glass 1 is placed is introduced into the inspection apparatus as a sample to be inspected or discharged from the post-inspection apparatus, the moving stage 4 has an electron beam 5. The sample to be inspected moves away from the irradiation position near the introduction port through which the sample is taken in and out of the apparatus.

When moving, the lower electrode 7, the lens 10, and the ultraviolet light source 9 may obstruct the movement due to the structure. In such a case, if the lower electrode 7, the lens 10, and the ultraviolet light source 9 are provided as a single unit, the failure can be avoided by the operation shown in FIG. In FIG. 2, the lower electrode 7, the lens 10, and the ultraviolet light source 9 are used as one lower unit 11. When the inspection is completed, the lower unit 11 is lowered downward by the operation (1), and a space in which the moving stage 4 can move is created. The moving stage 4 moves to the inspection sample introduction port (operation (2)), takes the inspection sample out of the apparatus, receives the next inspection sample, and returns to the position where the electron beam can be irradiated ( Operation (3)). Thereafter, the lower unit 11 moves up (operation (4)), and inspection is started.

Next, the whole nanoimprinted quartz glass mold defect inspection apparatus using the reflection imaging microscope according to this embodiment will be described with reference to FIG. However, FIG. 3 omits a pump for vacuum exhaust, its control device, exhaust system piping, a transport system for the sample to be inspected, and the like. The electron beam trajectory is exaggerated from the actual trajectory for the sake of explanation.

First, the part related to electron beam irradiation will be described. The irradiation electron beam 100a emitted from the electron gun 101 is deflected by the separator 103 while being converged by the condenser lens 102 to form a crossover 100b, and then becomes an electron beam 5 having a substantially parallel bundle on the specimen 104 to be inspected. Is irradiated. Hereinafter, each element will be described. The sample 104 to be inspected shown in FIG. 3 is the quartz glass mold 1 or the holder 2 on which the quartz glass mold 1 is placed.

For the electron gun 101, a Zr / O / W type Schottky electron source having a small light source diameter and a large current value is used, and a lanthanum hexaboride (LaB ₆ ) electron source capable of obtaining a higher current value is used. Other electron sources may be used. Further, a magnetic field superposition type in which a magnetic lens is disposed in the vicinity of the electron source may be used. The voltage and current necessary for the operation of the electron gun, such as the extraction voltage to the electron gun 101, the acceleration voltage of the extracted electron beam, and the heating current of the electron source filament, are supplied and controlled by the electron gun controller 105. .

Although the condenser lens 102 is depicted as one in the drawing, it may be a system in which a plurality of lenses are combined so that an irradiation electron beam with higher parallelism can be obtained. The condenser lens 102 is adjusted so that the electron beam is focused on the back focal plane of the objective lens 106.

The separator 103 is installed to separate the irradiation electron beam directed toward the sample 104 to be inspected and the reflected electron beam returning from the sample 104 to be inspected. In the present embodiment, a separator using an E × B deflector is taken as an example. The E × B deflector can be set so as to deflect the electron beam coming from above and to make the electron beam coming from below go straight. In this case, as shown in the figure, the electron optical column that supplies the irradiation electron beam is tilted, and the electron optical column that forms an image of the reflected electrons stands upright. It is also possible to use a magnetic field sector as a separator. A magnetic field is installed in a direction perpendicular to the optical axis of the electron beam, and the irradiated electron beam is deflected in the direction of the sample 104 to be inspected, and the electrons from the sample 104 to be inspected are deflected in a direction opposite to the direction in which the irradiated electron beam comes. To do. In this case, the optical axis of the irradiation electron beam column and the optical axis of the electron beam imaging column are arranged symmetrically about the optical axis of the objective lens.

When the irradiation electron beam 100a is deflected by the separator, the separator 103 generates aberration. When it is necessary to correct this aberration, when the separator 103 is an E × B deflector, an E × B deflector 120 for aberration correction is arranged. When the separator 103 is a magnetic sector, correction is made by providing an auxiliary coil.

The irradiation electron beam 100 a deflected by the separator 103 is formed on the parallel bundle of electron beams 5 incident perpendicularly to the surface of the sample 104 to be inspected by the objective lens 106. As described above, since the irradiation system condenser lens 102 is adjusted so that the electron beam is focused on the back focal point of the objective lens 106, it is possible to irradiate the specimen 104 with a highly parallel electron beam. A region on the inspection sample 104 irradiated by the irradiation electron beam 100a has a large area such as 2500 μm ² (square micron), 10000 μm ² (square micron), or the like.

The sample 104 to be inspected is placed on the moving stage 4 via the insulating member 3 (not shown in FIG. 3). The moving stage 4 can perform a rotational movement around the center of the quartz glass mold 1 (not shown in FIG. 3) and a linear movement of the quartz glass mold 1 in the radial direction. By moving the moving stage 4 in the radial direction of the quartz glass mold 1 while rotating, the region where the pattern of the quartz glass mold 1 exists is thoroughly inspected. The movement of the moving stage 4 is controlled by the moving stage control device 107 according to the operation during the inspection, the replacement operation of the sample 104 to be inspected described with reference to FIG.

The objective lens 106 is an electrostatic lens composed of a plurality of electrodes or a magnetic lens. In any case, since it is necessary to form an electric field on the surface so that the electron beam reflected in the vicinity of the specimen 104 to be inspected is pulled back to the objective lens, a positive potential can be applied to the position closest to the specimen. The upper electrode 6 described in FIG. 1 is disposed. In this figure, it is included in the objective lens 106 and is not clearly shown.

The lower electrode 7 described with reference to FIG. 1 is arranged so that a negative potential substantially equal to the acceleration voltage of the electron beam is applied to the surface of the specimen 104 to be inspected. In FIG. 3, it is shown as the lower unit 11 described in FIG. The voltage of the lower electrode 7 which is a component of the lower unit 11 is set by the lower unit control device 108 so that the difference between the surface voltage of the sample 104 to be inspected and the acceleration voltage is about several volts or less. The irradiation electron beam 100a is decelerated in front of the sample 104 to be inspected by this negative potential, and is reflected in the opposite direction before colliding with the sample 104 to be inspected depending on the setting of the surface potential or by collision with low energy. Thus, the reflected electrons 100c are obtained.

The trajectory of the reflected electrons 100c reflects the pattern information on the specimen 104 to be inspected, and is taken into the apparatus as an image for defect determination by image formation using the electron imaging optical system. Next, the imaging optical system, image acquisition, and defect determination will be described.

The reflected electrons 100 c form a first image by the objective lens 106. Since the separator 103 is an E × B deflector in this embodiment, the separator 103 is controlled so as not to have a deflection action with respect to the electron beam traveling from below, and the reflected electron 100c travels without being deflected. These images are sequentially formed by the intermediate electron lens 109 and the projection electron lens 110, and finally enlarged and projected on the image detection unit 111. The first image is desirably formed at the center of the separator 103. This is because the influence of the aberration on the image due to the electromagnetic field of the separator 3 can be minimized. In FIG. 3, the projection electron lens 110 is depicted as a single electron lens, but it may be composed of a plurality of electron lenses for high magnification and image distortion correction.

The image detection unit 111 converts the image into an electric signal and sends a potential distribution image formed by the pattern on the surface of the quartz glass mold to the image processing unit 112. The electron optical system controller 113 controls the various electron lenses and the electron optical systems such as the separator 103 described so far.

Next, the image detection unit 111 will be described. For image detection, a fluorescent screen 111a for converting a reflected electron image into an optical image and an optical image detection device 111b are optically coupled by an optical image transmission system 111c. An optical fiber bundle is used as the optical image transmission system 111c. The optical fiber bundle is a bundle of thin optical fibers equal to the number of pixels, and can efficiently transmit an optical image.

Further, when a fluorescent image having a sufficient amount of light can be obtained, the optical transmission efficiency may be lowered. An optical lens is used instead of the optical fiber bundle, and the optical image on the fluorescent plate 111a is optically detected by the optical lens. In some cases, an image is formed on the light receiving surface 111b.

It is also possible to insert an amplification device into the optical image transmission system and transmit an optical image with a sufficient amount of light to the optical image detection device 111b. The optical image detection device 111b converts the optical image formed on the light receiving surface into an electrical image signal and outputs it. A TDI sensor using a time delay integration (TDI) type CCD is used for the optical image detection device 111b.

As described above, the image detection unit 111 uses a detector sensitive to an electron beam in addition to returning an electronic image to an optical image and then outputting the optical image as an image signal. A device that directly outputs an image signal without conversion to an optical image can be used.

The image processing unit 112 includes an image signal storage unit 112a and a defect determination unit 112b. The image signal storage unit 112 a obtains the electro-optical condition, image data, and stage position data from the electro-optical system control device 113, the image detection unit 111, and the stage control device 107, and the image data is stored on the specimen 104 to be inspected. It is stored in relation to the coordinate system. The defect determination unit 112b uses various kinds of defects such as comparison with a preset value or comparison with an adjacent pattern image using image data with coordinates on the inspection sample (quartz glass mold) 104. Defects are determined by a determination method.

The coordinates of the defect and the signal intensity of the corresponding pixel are transferred and stored in the inspection apparatus control unit 114. These defect determination methods are set by the user, or the inspection apparatus control unit 114 selects a method associated with the type of sample to be inspected in advance.

The operating conditions of each part of the apparatus are input / output from the inspection apparatus control unit 114. Various conditions such as an acceleration voltage at the time of generating an electron beam, an electron beam deflection width / deflection speed, a stage moving speed, and an image signal capturing timing from the image detection element are input to the inspection apparatus control unit 114 in advance. The control device is comprehensively controlled and serves as an interface with the user. The inspection apparatus control unit 114 may be composed of a plurality of computers that share roles and are connected by communication lines. In addition, a monitor input / output device 115 is installed.

The above is an overall outline of a quartz glass mold inspection apparatus using a reflection imaging microscope. Next, the preliminary charging removal operation on the quartz glass mold surface and the inspection operation while irradiating with ultraviolet rays will be described.

Since quartz glass is an insulator, there is a possibility that charging will occur before electron beam irradiation is performed during the inspection process. For example, charging occurs during processing of a mold pattern or during conveyance. Even if the surface of the quartz glass mold is charged, it is possible to set the potential of the surface of the quartz glass mold to a desired potential by adjusting the voltage applied to the lower electrode 7, but the distribution of the charged potential Is usually not uniform, and the charge amount may be several hundred volts in voltage. If the charge on the surface of the quartz glass mold is previously removed before the inspection, it is not necessary to change the potential of the lower electrode 7 during the inspection, and a more stable inspection is possible.

The preliminary charge removal operation, in which the charge is previously removed before entering the inspection operation, is performed in the load lock chamber through which the sample to be inspected passes when it is transported from the atmosphere to the main chamber where the inspection operation is performed. Efficient. When the sample to be inspected is carried into the apparatus, the load lock chamber is opened to the atmosphere and the sample to be inspected is introduced, and then the load lock chamber is evacuated and transported to the main chamber maintained in a vacuum. As described above, since the sample to be inspected always stops temporarily in the load lock chamber, the charge is removed at that time.

As a method of removing the charge, a method of neutralizing the charge on the surface of the sample to be inspected by irradiating ions or electrons in a vacuum state, or an ionization by injecting an inert gas and irradiating with ultraviolet rays for inspection A method of neutralizing the charge on the surface of the sample can be used.

Another method is to heat the sample to be inspected. FIG. 4 shows the configuration in the load lock chamber when the specimen to be inspected is heated to remove the charge. The quartz glass mold 1 or the holder 2 on which the quartz glass mold 1 is placed is placed on the ground electrode 201. A heater 202 is provided below the ground electrode 201 to uniformly heat the quartz glass mold 1 and the holder 2. The heating temperature is about 200 ° C to about 400 ° C. An electrode 203 may be provided above the quartz glass mold 1 and the holder 2 and an appropriate voltage may be applied to form an electric field in a direction in which the charged charges are released to the ground electrode 201. The heater 202 is installed on a moving stage 204 in the load lock chamber.

The quartz glass mold from which the surface charge has been removed by the above process is transferred to the main chamber and enters the inspection operation. The pattern of the quartz glass mold for processing the magnetic recording pattern medium is formed along the rotation direction. The starting point of the inspection start is the position of the pattern outermost periphery or innermost periphery. The entire surface of the pattern is inspected by moving the quartz glass mold in the radial direction while rotating the quartz glass mold. During the inspection, the sample is continuously irradiated with the electron beam.

The amount of negative charge generated by electron beam irradiation is proportional to the time during which an electron beam is irradiated to a certain inspection field, so if the speed at which the pattern crosses the inspection field is constant, the negative charge amount is always the same, that is, The amount of ultraviolet rays for removing this negative charge is also constant and convenient. Accordingly, the rotational speed is changed with the movement in the radial direction so that the pattern moving speed at the inspection position is constant.

The ultraviolet rays to be irradiated have a wavelength between about 200 nm and 300 nm, and are wavelengths that allow the quartz glass to pass through and remove the negative charge on the surface of the quartz glass (the quartz glass has energy larger than the energy for holding electrons). . Ultraviolet rays are introduced immediately before the start of inspection, and then an electron beam is irradiated to start inspection. Prior to the inspection, the inspection conditions corresponding to the inspection speed, such as the irradiation ultraviolet ray amount, are determined in advance.

When the inspection of the entire surface of the quartz glass mold is completed, the electron beam irradiation is stopped, and the ultraviolet irradiation is also stopped almost simultaneously, and the discharging operation from the apparatus is executed. The electron beam and ultraviolet light irradiation is stopped from the viewpoint of operational stability of the electron source and ultraviolet light source, not by stopping the electron source and ultraviolet light source itself, but by blocking the ultraviolet light by inserting a shutter, and blocking the electron beam by a blanker. .

According to the present example, the quartz glass mold surface is erased by irradiating the back surface of the quartz glass mold generated by electron beam irradiation with ultraviolet irradiation from the back surface even when the sample is sandwiched between parallel electrodes. Therefore, it is possible to provide an inspection apparatus and an inspection method capable of maintaining a constant electric potential of the quartz glass mold and realizing an inspection of the quartz glass mold at a high speed.

The second embodiment will be described with reference to FIG. The matters described in the first embodiment but not described in the present embodiment can be applied to the present embodiment.

In Example 1, a passage hole was opened in the lower electrode installed on the back side of the quartz glass mold, and ultraviolet rays were irradiated. In this example, an electrode in which a thin conductive film was formed on the surface of quartz glass was used instead of the electrode having a hole.

FIG. 5 is a schematic diagram of a main part of the inspection apparatus according to the present embodiment. The quartz glass mold 1 and the holder 2 are placed on a quartz glass plate 306 having a conductive thin film 305 formed on the upper surface. The conductive thin film 305 is formed to a thickness that does not significantly reduce the ultraviolet transmittance by metal vapor deposition or the like. In this example, platinum (Pt) having a thickness of 10 nm was used as the conductive thin film. Gold (Au) can also be used. In addition, a voltage is applied to the conductive thin film 305 and the surface potential is set so as to reflect the electron beam 5 near the surface of the quartz glass mold 1.

Since the quartz glass plate 306 transmits the ultraviolet light 8, even if the moving stage 4 moves during the inspection, the ultraviolet light 8 can be irradiated on the opposite side of the position irradiated by the electron beam 5, and the conductive thin film 305 allows quartz to be irradiated. The surface potential of the glass mold 1 is stabilized. Since the lower electrode in the first embodiment can be eliminated from the unit installed at the lower part of the moving stage 4 and only the ultraviolet light source 9 and the condenser lens 10 are provided, the size of the entire lower unit can be reduced. Since the interference area with the moving area of the moving stage 4 becomes small, the moving stage 4 can be made small.

As described above, according to the present embodiment, even when the sample is sandwiched between electrodes provided above and below it, an equipotential surface parallel to the sample surface is formed, and ultraviolet light is emitted from the back surface (below). It is possible to provide an inspection apparatus and an inspection method that can irradiate a sample with a sample. Further, by using a conductive thin film as the lower electrode, the structure is simplified, the sample can be easily supported, and the reliability is improved.

The third embodiment will be described with reference to FIG. Note that items described in the first and second embodiments but not described in the present embodiment can be applied to the present embodiment.

The previous examples have been inspection devices that perform negative charge removal by ultraviolet irradiation only from the back side of the quartz glass mold. In the present embodiment, ultraviolet irradiation is performed not only from the rear surface of the quartz glass mold but also from the front surface, and further, high-speed negative charge removal is realized, thereby realizing high-speed inspection.

FIG. 6 is a schematic view of the inspection apparatus according to the present embodiment. In the present embodiment, a condensing reflection mirror 402 is installed in the electron optical column so that the ultraviolet ray 401 is incident on the inspection apparatus 104 described with reference to FIG. An ultraviolet light source 403 is disposed on the side of the cylinder. The ultraviolet ray 401 is reflected and collected by the condensing / reflecting mirror 402, and is simultaneously irradiated onto the region of the sample 104 to be irradiated with the electron beam 5. Accordingly, it is possible to irradiate the ultraviolet rays with further increased intensity together with the ultraviolet rays irradiated from the back surface from the lower unit 11.

According to this example, even when the sample is sandwiched between electrodes provided above and below it, an equipotential surface parallel to the sample surface is formed and the sample is irradiated with ultraviolet rays from the back surface (below) It is possible to provide an inspection apparatus and an inspection method that can be used. Further, since a larger amount of ultraviolet rays can be irradiated to the electron beam irradiation region, the amount of current of the irradiation electron beam can be increased, and a higher-speed inspection can be performed.

DESCRIPTION OF SYMBOLS 1 ... Quartz glass metal mold | die, 2 ... Holder, 3 ... Insulating member, 4 ... Moving stage, 5 ... Electron beam, 6 ... Upper electrode, 7 ... Lower electrode, 8 ... Ultraviolet light, 9 ... Ultraviolet light source, 10 ... Lens, 11 ... Lower unit, 100a ... Irradiated electron beam, 100b ... Crossover, 100c ... Reflected electron, 101 ... Electron gun, 102 ... Condenser lens, 103 ... Separator, 104 ... Sample to be inspected, 105 ... Electron gun control device, 106 ... Objective Lens 107, moving stage control device 108 lower unit control device 109 intermediate electron lens 110 projection electron lens 111 image detecting unit 111a fluorescent plate 111b optical image detecting device 111c optical image transmission 112, image processing unit, 112a, image signal storage unit, 112b, defect determination unit, 113, electron optical system control device, 114, inspection device control unit DESCRIPTION OF SYMBOLS 115 ... Input / output device with monitor, 120 ... Deflector (for aberration correction), 201 ... Ground electrode, 202 ... Heater, 203 ... Electrode, 204 ... Moving stage, 305 ... Conductive thin film, 306 ... Quartz glass plate, 401 ... Ultraviolet 402: Condensing reflector, 403: UV light source.

Claims

In an inspection apparatus that inspects the surface of the sample by irradiating the sample held by the holder with an electron beam, detecting reflected electrons from the sample,
It has an upper electrode and a lower electrode arranged so as to be parallel across the holder,
The upper electrode has a hole through which the electron beam passes and is applied with a voltage for accelerating the electron beam and irradiating the sample.
The lower electrode has a hole for irradiating ultraviolet rays from the back side of the sample to the sample region irradiated with the electron beam, and decelerates the accelerated electron beam and reflects it on the sample surface An inspection apparatus characterized in that is applied.
The inspection apparatus according to claim 1,
The diameter of the hole provided in the said lower electrode is a magnitude | size exceeding the diameter of the said electron beam, The inspection apparatus characterized by the above-mentioned.
The inspection apparatus according to claim 1,
And further comprising a light source for the ultraviolet light and a lens for condensing the ultraviolet light,
The inspection apparatus, wherein the lower electrode, the light source, and the lens move together.
The inspection apparatus according to claim 1,
The inspection apparatus according to claim 1, wherein the hole of the upper electrode allows ultraviolet rays irradiated from above the sample to pass through the region irradiated with the electron beam on the sample.
The inspection apparatus according to claim 1,
Instead of the lower electrode, an inspection apparatus comprising a conductive thin film to which a voltage reflected by the sample surface is applied and which can transmit ultraviolet rays.
Means for irradiating an insulator flat plate sample with electrons as substantially parallel electron beams; means for forming an electric field for pulling up the electron beam reflected near the surface of the insulator flat plate sample; and electrons of the reflected electron beam From the electron image, an electron optical means for obtaining an image, a means for moving the insulator flat plate sample with respect to the electron beam so that the shape formed on the insulator flat plate sample can be observed, In the inspection apparatus provided with means for detecting the shape on the insulator flat plate sample and recording the detection location,
During the inspection operation, the means for forming an electric field for pulling up the electron beam reflected near the surface of the insulator plate sample is opposite to the side irradiated with the electron beam of the insulator plate sample. Including non-moving electrodes,
An inspection apparatus comprising: means for irradiating ultraviolet rays on a surface opposite to the side irradiated with the electron beam of the insulator flat plate sample.
The inspection apparatus according to claim 6, wherein
Ultraviolet light passes through a position corresponding to a position on the insulator plate sample irradiated with the electron beam to the electrode provided on the opposite side of the insulator plate sample to the side irradiated with the electron beam. An inspection apparatus characterized in that a hole is provided.
The inspection apparatus according to claim 7,
The size of the ultraviolet light passage hole is smaller than the distance between the electrode provided on the side opposite to the side irradiated with the electron beam of the insulator plate sample and the surface of the insulator plate sample. Inspection device characterized by
The inspection apparatus according to claim 6, wherein
The electrode provided on the opposite side of the insulator flat plate sample to the side irradiated with the electron beam is in the process of introducing the insulator flat plate sample into the inspection apparatus or discharging it out of the inspection apparatus. An inspection apparatus comprising a mechanism for moving to a position different from the position in the above.
Means for irradiating an insulator flat plate sample with electrons as substantially parallel electron beams; means for forming an electric field for pulling up the electron beam reflected near the surface of the insulator flat plate sample; and electrons of the reflected electron beam Electron optical means for obtaining an image; means for moving the insulator flat plate sample so that the shape formed on the insulator flat plate sample can be observed; In the inspection apparatus provided with means for detecting the shape of and recording the detection location,
Means for irradiating ultraviolet rays on a surface opposite to the side irradiated with the electron beam of the insulator plate sample;
An inspection apparatus comprising: an electrode made of a conductive material that transmits ultraviolet rays, as means for forming an electric field for pulling up the electron beam reflected in the vicinity of the surface of the insulator flat plate sample.
The inspection apparatus according to claim 10, wherein
An inspection apparatus, wherein the electrode made of a conductive material that transmits ultraviolet rays is quartz glass having a conductive thin film formed on a surface thereof.
The inspection apparatus according to claim 6, wherein
An inspection apparatus characterized in that a material of the insulator flat plate sample is quartz glass.
Electrons are irradiated as a substantially parallel electron beam onto an insulator flat plate sample, and the electron beam reflected near the surface of the insulator flat plate sample is pulled up by an electric field formed on the surface of the insulator flat plate sample. In the inspection method for inspecting the shape formed on the surface of the insulator flat plate sample by obtaining an electronic image,
Applying a voltage to an electrode independent of the moving stage on which the insulator flat plate sample is placed on the opposite side of the insulator flat plate sample to the side irradiated with the electron beam;
Irradiating the surface opposite to the side irradiated with the electron beam of the insulator flat plate sample with ultraviolet rays;
The inspection method characterized by including.
The inspection method according to claim 13,
A hole is provided at a position corresponding to a position on the insulator plate sample irradiated with the electron beam on the electrode provided on the opposite side of the insulator plate sample to the side irradiated with the electron beam. An inspection method characterized by passing ultraviolet rays.
Electrons are irradiated as a substantially parallel electron beam onto an insulator flat plate sample, and the electron beam reflected near the surface of the insulator flat plate sample is pulled up by an electric field formed on the surface of the insulator flat plate sample. In an inspection method for inspecting the shape of the insulator flat plate sample surface by obtaining an electronic image,
Irradiating the surface opposite to the side irradiated with the electron beam of the insulator flat plate sample with ultraviolet rays;
Applying a voltage to the conductive electrode through which the ultraviolet rays pass, on the surface of the insulator plate sample opposite to the side irradiated with the electron beam;
The inspection method characterized by including.
The inspection method according to claim 13,
An inspection method, wherein the material of the insulator flat plate sample is an insulator that transmits ultraviolet rays.
The inspection method according to claim 13,
An inspection method, wherein a material of the insulator flat plate sample is quartz glass.