JP2004354084A - Substrate inspection apparatus, substrate inspection method, and manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate inspection apparatus for acquiring a detection image having an improved contrast without any distortion. <P>SOLUTION: A substrate inspection system 1 comprises a primary optical system 10 for generating electron beams for irradiating the substrate S as primary beams Bp; an electron detection section 30 that detects secondary electrons, or the like, generated from the substrate S by receiving irradiation with the primary beams Bp, and outputs a one-dimensional or two-dimensional image signal on the surface of the substrate S; and a two-dimensional optical system 20 for forming an image at the electron detection section 30 with secondary electrons, or the like, generated from the substrate S as secondary beams 18s. In the substrate inspection system 1, a laser beam irradiator 70 for irradiating a part wherein the secondary beams 18s on the surface of the substrate S are generated with the laser beams L is further provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a substrate inspection apparatus, a substrate inspection method, and a method of manufacturing a semiconductor device, and is directed to, for example, observation or inspection of a semiconductor pattern or the like using an electron beam.
[0002]
[Prior art]
Inspection using an electron beam has recently been performed to inspect a semiconductor pattern for defects and the like.For example, a rectangular electron beam is generated by an electron beam irradiation means and irradiated on a sample as a primary beam. A secondary beam composed of at least one of a secondary electron, a reflected electron and a backscattered electron generated according to a change in the shape / material / potential of the surface is enlarged and projected on an electron detection unit by a mapping projection optical unit, A technique for obtaining a sample surface image has been developed (for example, Patent Document 1). Furthermore, in addition to this method, the primary beam is deflected by a Wien filter, which is an electron beam deflecting means, and is made incident perpendicularly to the sample surface, and the secondary beam is made to travel straight through the same Wien filter to perform projection optical projection. There has been proposed a method of introducing the means (for example, Patent Document 2).
[0003]
[Patent Document 1]
JP-A-7-24939
[Patent Document 2]
JP-A-11-132975
[0004]
[Problems to be solved by the invention]
However, for example, in the inspection process disclosed in Patent Document 2, when a primary beam is irradiated to a sample, a local difference occurs in the charging state of the sample surface due to the shape and material of the sample surface or a layer near the surface. There is a problem that the inspection characteristic of the device is deteriorated due to a local difference in potential. This will be described with reference to the drawings. In the following drawings, the same portions are denoted by the same reference numerals, and the description thereof will not be repeated.
[0005]
As shown in FIG. 15, when portions 202 and 204 having different potentials exist on the surface of the sample S, the upper region R near the boundary surfaces C1 and C2 between the portions 202 and 204 is formed._D1, R_D2Then, a potential gradient not parallel to the surface of the sample S is generated. These potential gradients are undesired with respect to the secondary beams emitted from near the boundaries C1 and C2 when the secondary beams are controlled by the secondary optical system of the inspection apparatus and imaged on the detection surface of the detector. This causes an excessive deflection action, hinders proper image formation, and causes distortion of a detected image and a decrease in contrast. Such a phenomenon is particularly prominent in the inspection of LSI (Large Scale Integrated circuit) wiring patterns. In the LSI wiring, the portion 202 shown in FIG.₂This is because the portion 204 corresponds to a conductor such as tungsten (W) and the potential difference from the conductor portion increases when the insulator is charged when the electron beam is irradiated.
[0006]
Such a local potential difference is not limited to a case where interfaces between different materials are close to each other. For example, as shown in FIG. 16, even when the metal wiring portion 212 and the inter-wiring insulator portion 214 exist on the sample S of the integrated circuit wafer, the total secondary electron emission ratio σ of the insulator portion 214 becomes 1 or more. When a primary beam is irradiated with incident energy, the surface of the insulator 214 is positively charged. Such an incident energy is such that, for example, the material of the insulator portion 214 is SiO 2₂Then, it is about 50 to about 1 keV. At this time, a local potential gradient not parallel to the surface of the sample S is generated near the boundary 216 between the metal wiring portion 212 and the insulator portion 214. The potential gradient is such that the trajectory of the secondary beam emitted from the point P2 in the metal wiring portion near the boundary 216 and the point P4 in the insulator portion is controlled by the secondary optical system of the apparatus and forms an image on the detection surface of the detector. Function as an undesired deflection when the electron beam orbit TJ_IP2And TJ_IP4Deviates from the ideal trajectory for performing accurate mapping projection such as_RP2And TJ_RP4It becomes a curved orbit like. As a result, appropriate imaging of the secondary beam is hindered, which causes distortion of the detected image from the secondary beam and a decrease in contrast.
[0007]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a board inspection apparatus and a board inspection method for realizing acquisition of a detected image having no distortion and excellent contrast, and a semiconductor device using the board inspection method. It is to provide a manufacturing method of.
[0008]
[Means for Solving the Problems]
The present invention solves the above problems by the following means.
[0009]
That is, according to the present invention,
Electron beam irradiation means for generating an electron beam and irradiating the substrate to be inspected as a primary beam,
An electron beam that detects at least one of secondary electrons, reflected electrons, and backscattered electrons generated from the substrate under irradiation of the electron beam and outputs a signal that is a one-dimensional image or a two-dimensional image of the substrate surface. Detecting means;
Mapping projection optical means for forming an image on the electron beam detection means as at least one of the secondary electrons, the reflected electrons and the backscattered electrons as a secondary beam,
An electromagnetic wave irradiating unit that generates an electromagnetic wave, and irradiates the electromagnetic wave to a location where the secondary beam is generated on the substrate surface,
The board inspection apparatus provided with this is provided.
[0010]
According to the present invention,
Electron beam irradiation means for generating an electron beam and irradiating a substrate to be inspected having an insulator formed on its surface under conditions where the insulator is negatively charged,
An electron beam that detects at least one of secondary electrons, reflected electrons, and backscattered electrons generated from the substrate under irradiation of the electron beam and outputs a signal that is a one-dimensional image or a two-dimensional image of the substrate surface. Detecting means;
Mapping projection optical means for forming an image of the secondary electrons, at least one of the reflected electrons and the backscattered electrons on the electron beam detection means,
The board inspection apparatus provided with this is provided.
[0011]
According to the present invention,
A step of generating an electron beam and irradiating the substrate to be inspected as a primary beam,
The step of projecting at least one of secondary electrons, reflected electrons and backscattered electrons generated from the substrate under irradiation of the electron beam as a secondary beam to form an image,
Detecting the image-formed secondary beam, and outputting a signal that is a one-dimensional image or a two-dimensional image of the substrate surface,
A step of generating an electromagnetic wave and irradiating the electromagnetic wave to a place where the secondary beam is generated on the surface of the substrate,
There is provided a substrate inspection method comprising:
[0012]
According to the present invention,
An electron beam irradiation step of generating an electron beam and irradiating the substrate to be inspected having the insulator formed on the surface under conditions where the insulator is negatively charged,
The step of projecting at least one of secondary electrons, reflected electrons and backscattered electrons generated from the substrate under irradiation of the electron beam as a secondary beam to form an image,
Detecting the image-formed secondary beam, and outputting a signal that is a one-dimensional image or a two-dimensional image of the substrate surface,
There is provided a substrate inspection method comprising:
[0013]
Furthermore, according to the present invention,
A method for manufacturing a semiconductor device using the above-described substrate inspection method is provided.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, some embodiments of the present invention will be described with reference to the drawings.
[0015]
(1) First embodiment of substrate inspection apparatus
FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of the board inspection apparatus according to the present invention. The substrate inspection apparatus 1 shown in FIG. 1 includes a primary optical system 10, a Wien filter 41, a secondary optical system 20, an electron detection unit 30, an image signal processing unit 58, a host computer 60, a display unit 62, a stage 43, and a stage driving device. 47, various control units 16, 17, and 51 to 57, and a laser light irradiation device 72 and a power supply 74 which are characteristic in this embodiment.
[0016]
The primary optical system 10 includes an electron gun unit 11 and a multi-stage quadrupole lens system 15. The electron gun section 11 is a LaB having a rectangular electron emission surface having a major axis of 100 to 700 μm and a minor axis of 15 μm.₆It has a linear cathode 112, a Wehnelt electrode 114, an anode 116 for extracting an electron beam, and a deflector 118 for adjusting the optical axis. The acceleration voltage, emission current, and optical axis of the primary beam Bp are controlled by the electron gun controller 16. The electron gun controller 16 is connected to the host computer 60 and receives a control signal therefrom. The multi-stage quadrupole lens 15 is controlled by the multi-stage quadrupole lens controller 17 and converges the primary beam Bp emitted from the linear cathode 112 so that its trajectory is obliquely incident on the Wien filter 41. Control. The multi-stage quadrupole lens controller 17 is also connected to the host computer 60 and receives a control signal therefrom.
[0017]
The Wien filter 41 receives a control signal from the host computer 160 via the Wien filter control unit 53, deflects the primary beam Bp incident from the primary optical system 10, and makes the primary beam Bp incident substantially perpendicularly to the surface of the sample S. . The primary beam Bp that has passed through the Wien filter 41 receives a lens action by the cathode lens 21 that is a rotationally symmetric electrostatic lens, and irradiates the surface of the sample S vertically.
[0018]
The sample S is set on the stage 43, and a negative voltage can be applied by the stage voltage controller 51 via the stage 43. This mechanism reduces incident damage to the sample S due to the primary beam Bp, and secondary electrons, reflected electrons, and backscatter generated by irradiation of the primary beam Bp according to changes in the shape / material / potential of the surface of the sample S. The purpose is to improve the energy of the secondary beam Bs composed of electrons. The stage 43 receives a control signal from the stage driving device 47 and moves in the present embodiment, for example, in the direction Dss indicated by the arrow in FIG. 1, whereby the surface of the sample S is scanned by the primary beam Bp.
[0019]
FIG. 2 shows a more specific configuration of the Wien filter 41, and its operating principle is shown in FIG. 3 and FIG. As shown in FIG. 2, the field of the Wien filter 41 has a structure in which the electric field E and the magnetic field B are orthogonal to each other in a plane (XY plane) perpendicular to the optical axis (Z axis) of the secondary optical system. In this case, only the electrons satisfying the Wien condition qE = vB (q is the particle charge and v is the speed of the straight-moving electron) are caused to travel straight on the incident electron beam Bp. In the substrate inspection apparatus 1, as shown in FIG. 3, a force FB caused by a magnetic field and a force FE caused by an electric field act on the primary beam Bp in the same direction, so that the primary beam Bp is perpendicularly incident on the sample S. Is deflected. On the other hand, as shown in FIG. 4, FB and FE act on the secondary beam Bs in the opposite directions, and the secondary beam Bs is deflected because the Wien condition FB = FE is satisfied. The light travels straight without entering the secondary optical system 20.
[0020]
Returning to FIG. 1, the secondary optical system 20 includes a rotationally symmetric electrostatic lens, a cathode lens 21, a second lens 22, a third lens 23, and a fourth lens 24, and a section between the Wien filter 41 and the cathode lens 21. It includes an aperture stop 25 disposed in a plane 9 perpendicular to the optical axis As of the secondary optical system, and a field stop 26 provided between the second lens 22 and the third lens 23. The cathode lens 21, the second lens 22, the third lens 23, and the fourth lens 24 are controlled by a cathode lens controller 52, a second lens controller 54, a third lens controller 55, and a fourth lens controller 56, respectively. , The secondary beam Bs is projected and imaged. The cathode lens control unit 52, the second lens control unit 54, the third lens control unit 55, and the fourth lens control unit 56 are connected to the host computer 60 and receive various control signals. In the apparatus configuration shown in FIG. 1, an aperture stop 25 is arranged at a position on the horizontal plane 9 in order to suppress the chromatic aberration of magnification of the secondary beam Bs, so that the secondary beam Bs is transmitted between the cathode lens 21 and the second lens 22. One image is formed in combination. Further, in this configuration, the irradiation area of the primary beam Bs on the sample S is limited by the aperture stop 25. As a solution, the primary beam Bp opens in the space from the aperture stop 25 to the sample S. The trajectory of the primary beam Bp is controlled so as to have a focal point on the angular stop 25, and a Koehler illumination system is adopted in which a lens effect is given by the cathode lens 21 and then the sample S is irradiated almost perpendicularly.
[0021]
The electronic detection unit 30 includes an MCP (Micro Channel Plate) detector 31, a fluorescent plate 32, a light guide 33, and an imaging device 34 such as a CCD (Charge Coupled Device). The secondary beam Bs incident on the MCP detector 31 is amplified by the MCP and irradiates the fluorescent screen 32. The imaging device 34 detects a fluorescent image generated by the fluorescent plate 32 via the light guide 33 and sends a detection signal to the image signal processing unit 58. The image signal processing unit 58 processes the detection signal and supplies it to the host computer 60 as image data representing a one-dimensional image or a two-dimensional image. The host computer 60 processes the supplied image data and displays the image on the display unit 62, saves the image data, detects the presence or absence of a defect in the sample S using various image processing, and detects the defect. If so, the degree is evaluated and output.
[0022]
The laser light irradiation device 70 is installed near the secondary optical system 20 and generates a laser beam to irradiate the sample S, thereby reducing a local potential difference on the surface of the sample S. The laser light irradiation device 70 forms an electromagnetic wave irradiation unit in the present embodiment, and includes a laser light source 72 that generates the laser light L and a power supply 74 that supplies power to the laser light source 72. The laser optical axis AL is defined by an intersection IP between the surface of the sample S and the optical axis As of the secondary optical system.₀, And the laser light L emitted from the laser light source 72 irradiates the center of the inspection area on the surface of the sample S irradiated with the primary beam Bp. The adjustment of the laser beam axis AL is performed by, for example, using a laser detection sensor such as a laser power meter at the intersection IP.₀And monitor the output and adjust the laser light source to maximize the value.
[0023]
During the inspection, when the primary beam Bp is irradiated on the surface of the sample S, there is a local difference in the amount of charge on the surface of the sample S depending on the shape and material of the surface of the sample S or a layer near the surface. In particular, when an insulator is present on the surface of the sample S, the charge amount is large, and the charges (electrons and holes) often stay without being able to move (neutralize).
[0024]
Therefore, in the present embodiment, by irradiating the laser light L from the laser light source 72, the staying charges or the charges in the vicinity thereof absorb the energy of the laser light L, thereby being in a movable state. Even if the charge amount of the entire insulator does not change, it is possible to reduce local charging at a charged portion on the sample surface and reduce a local potential difference.
[0025]
As a method of reducing such a local potential difference, more specifically,
1) A method of irradiating an electromagnetic wave having energy capable of making the entire charged portion of the insulator conductive.
2) A method of irradiating an electromagnetic wave which is given energy so that electrons and holes captured by a localized level of an insulator can move.
Other
3) A method of reducing electrification near the boundary between dissimilar materials existing on the sample surface
Is mentioned. Hereinafter, these methods will be described as first to third embodiments of the substrate inspection method according to the present invention.
[0026]
(2) First and second embodiments of the board inspection method
FIG. 5 is an explanatory diagram of the first and second embodiments of the substrate inspection method according to the present invention. The left surface of the insulator IS1 is locally charged by positive charges. Further, on the right surface of the insulator IS1, the electrons and holes are trapped at the localized levels and stay there. Note that the capture of electrons and holes by such local charging and localized levels can occur not only in the insulator portion but also in the semiconductor portion.
[0027]
FIG. 6 shows an energy band diagram of the insulator IS1. In order to move the electric charge locally charged to the insulator IS1, a laser beam (electromagnetic wave) L1 having energy equal to or larger than the band gap Eg of the insulator is irradiated and the electrons are irradiated as shown in the left part of FIG. -An electron-hole pair may be generated to bring the insulator IS1 into a conductive state. The wavelength λ1 of the laser beam L1 required for achieving such a state needs to satisfy λ1 <hc / Eg, where h is the Planck constant and c is the light speed. For example, if the insulator IS1 is made of silicon dioxide SiO₂When the energy gap Eg = 9 (eV), the longest wavelength λm of the laser light L1 having energy equal to or larger than the energy gap is:
λm = hc / Eg = 137 (nm)
It is.
[0028]
Further, as shown in the right part of FIG. 5, the insulator IS1 has localized levels LL1 and LL2 (see the left part of FIG. 6) for capturing electrons and holes, and the electrons trapped therein. e2 and holes HL2 have a great influence on the charged state of the insulator IS1. The electrons e2 and holes HL2 captured by the localized levels LL1 and LL2 are irradiated with laser beams L2 and L3, respectively, as shown in FIG. The holes HL2 are respectively moved. As a result, it is possible to reduce local electrification caused by capture to the local potential and reduce a local potential difference. More specifically, as shown in FIG. 6, a laser beam (electromagnetic wave) L2 having energy equal to or greater than the difference Ee between the localized level LL1 where the electron e2 is captured and the conduction band bottom level Ec is irradiated. The captured electrons e2 can move. The wavelength λ2 of the laser beam L2 necessary for achieving such a state needs to satisfy λ2 <hc / Ee. Similarly, if a laser beam (electromagnetic wave) L3 having energy equal to or greater than the difference Eh between the localized level LL2 at which the hole HL2 is captured and the valence band top level Ev is irradiated, the captured hole HL2 moves. It becomes possible. The wavelength λ3 of the laser beam L3 necessary for achieving such a state needs to satisfy λ3 <hc / Eb. The shorter the wavelength of the laser beam, the larger the scale and cost of the device, but generally, λ1 <λ2 and λ1 <λ3. Therefore, the insulator IS1 due to the movement of the trapped electrons e2 and the holes HL2 described above. If there is no problem in the performance of the device due to the reduction in local charging, the size and cost of the laser beam irradiation device 70 can be reduced. As a result, the cost and size of the apparatus can be further reduced.
[0029]
(3) Third embodiment of substrate inspection method
The present embodiment is a method for reducing the charge of the insulator near the boundary between the insulator and the conductor or near the boundary between the insulator and the semiconductor. Even if only the inspection method of the third embodiment is used, Since the local potential difference near the boundary is reduced, it is possible to suppress the distortion of the secondary beam detection image and the decrease in contrast without making the charged portion of the insulator conductive. For example, when the insulator is positively charged, electrons can be transferred (injected) from a metal or semiconductor to the insulator to neutralize the positive charge. In the example shown in FIG. 7, the laser beam L4 is irradiated on the boundary C3 between the metal ML and the insulator IS2 to move electrons from the metal ML to the insulator IS2.
[0030]
FIG. 8 shows an energy band diagram of a metal-insulator junction. A laser beam (electromagnetic wave) L4 having energy equal to or more than the energy eφ of the contact potential barrier at the boundary between the metal ML and the insulator IS2 is irradiated on the above-described boundary C3, and electrons e4 in the metal ML are moved to the insulator IS2. Just fine. The wavelength λ4 of the laser beam L4 necessary for achieving such a state needs to satisfy λ4 <hc / Eb. Here, for example, the conductor is silicon Si, and the insulator is silicon dioxide SiO₂And Si-SiO₂When the potential barrier Eb of the contact portion is 3.5 (eV), the longest wavelength λm of the laser beam L4 having energy equal to or higher than the potential barrier is:
λm = hc / Eg = 354 (nm)
It is.
[0031]
Generally, since λ1 <λ4, if there is no problem in the performance of the device by neutralizing the positive charge of the insulator IS2 near the boundary, the size and cost of the laser beam irradiation device 70 should be reduced. Therefore, a small-sized apparatus can be provided at a lower cost.
[0032]
In the present embodiment, the laser light irradiation device 70 is used to reduce a local potential difference on the surface of the sample S. However, a device that irradiates other electromagnetic waves according to the material or shape of the sample to be inspected, For example, an X-ray irradiation device or an ultraviolet lamp may be used.
[0033]
(4) Second Embodiment of Board Inspection Apparatus
FIG. 9 is a block diagram showing a schematic configuration of a second embodiment of the board inspection apparatus according to the present invention. The features of the substrate inspection apparatus 2 shown in the figure are that additional electron beam irradiation apparatuses 80 and 90 for generating and irradiating the sample S with the electron beams EB1 and EB2 respectively, a CAD data storage unit 68, and an electron beam irradiation condition processing The device further comprises a device 66 and an electron beam irradiation condition storage device 64. Other configurations of the board inspection apparatus 2 are substantially the same as those of the board inspection apparatus 1 shown in FIG.
[0034]
When inspecting the sample surface, the electron beam irradiation device 80_SSOn the other hand, an arbitrary point in the imaging region is defined by an intersection IP between the optical axis As of the secondary optical system and the surface of the sample S.₀Rather than the optical axis A of the electron beam from the electron beam device 80 itself._EB1Of intersection between the sample and the surface of sample S₁Is arranged at a position where the light passes first. Similarly, the electron beam irradiating device 90 moves the stage scan direction D_SSIn contrast, an arbitrary point in the photographing area is₁Rather than the electron beam optical axis A of the electron beam device 90 itself._{EB 2}Of intersection between the sample and the surface of sample S₂Is arranged at a position where the light passes first. With such an arrangement, the potential difference on the sample surface can be reduced by the electron beam devices 80 and 90 before the signal of the secondary electron image on the sample surface is acquired by the electron detection unit 30. Hereinafter, in the present embodiment, the intersection IP₂, Intersection IP₁, And intersection IP₀An example in which the sample surface moves in the following order will be described.
[0035]
The electron beam irradiation device 80 includes a W filament 82, a Wehnelt electrode 84, and an anode 86. The W filament 82 has a coil shape and generates an electron beam EB1. In the present embodiment, the W filament 82 is arranged so that the electron beam EB1 is irradiated on the surface of the sample S vertically. The Wehnelt electrode 84 controls the emission amount of the electron beam EB1 emitted from the W filament 82. The anode 86 extracts the electron beam EB1 emitted from the W filament 84. The W filament 82, Wehnelt electrode 84, and anode 86 are all connected to and controlled by an electron gun controller 88.
[0036]
Similarly, the electron beam irradiation device 90 includes a W filament 92 for generating an electron beam EB2, a Wehnelt electrode 94, and an anode 96. These components are a W filament 82 of the electron beam irradiation device 80, a Wehnelt electrode 84 and the anode 86 are arranged in the same manner and exhibit the same function. Therefore, these components will not be described in detail.
[0037]
The CAD data storage device 68 stores layout pattern data of the sample S to be inspected and data of electrical characteristics of each layout pattern. The electron beam irradiation condition processing device 66 uses the data stored in the CAD data storage device 68 to calculate the irradiation conditions of the primary beam Bp and the electron beams EB1 and EB2 before the inspection. The electron beam irradiation condition storage device 64 stores the calculation result of the electron beam irradiation condition processing device 66.
[0038]
(5) Fourth embodiment of the board inspection method according to the present invention
First, the principle of the substrate inspection method according to the present embodiment will be described.
[0039]
In order to solve the problems of distortion of the detected image of the secondary beam and lowering of the contrast, it is only necessary to reduce the potential gradient on the sample surface which causes these problems. Explaining with the example shown in FIG. 16, if the surface of the sample S is irradiated with the primary beam Bp under the condition that the insulator portion 214 is negatively charged, the potential difference between the metal wiring portion 212 and the insulator portion 214 can be reduced. good. Normally, a contact potential is generated at the contact portion between the metal and the insulator, and the insulator has a positive potential of several volts more than the metal even when the primary beam Bp is not irradiated. Therefore, the primary beam Bp may be applied under the condition that the insulator is negatively charged.
[0040]
The condition that the insulator is negatively charged means, for example, that the primary beam is irradiated with incident energy at which the total secondary electron emission ratio σ from the insulator is less than 1, and the value of the incident energy at that time is as follows: For example, as shown in FIG.₂If it is 214, it is about 1 keV or more or about 50 eV or less as shown in FIG. Increasing the amount of secondary electrons (here, secondary electrons including reflected electrons and backscattered electrons) generated by electron beam irradiation increases the amount of signal for forming an image. Time becomes shorter. That is, the inspection time can be shortened. Conventionally, a method of setting the total secondary electron emission ratio δ to 1 or more has been used in consideration of the inspection throughput. However, in the present embodiment, the insulator is negatively charged by setting the total secondary electron emission ratio σ <1 contrary to the related art. Thereby, the accuracy of the detected image can be improved. Hereinafter, the step of irradiating the electron beam under the condition that the insulator is negatively charged is referred to as step 1.
[0041]
According to the above-described step 1, for example, with respect to the sample S illustrated in FIG. 16, the potential of the insulator 214 gradually decreases from the initial state of + several V with respect to the metal wiring 212, and is illustrated in FIG. 11. Thus, the potential becomes the same as that of the metal wiring portion 212. The secondary beam trajectories Bsp2 and Bsp4 in this state are ideal electron beam trajectories TJ for performing accurate mapping projection._IP2, TJ_IP4And the same respectively. As a result, it is possible to obtain a detected image without distortion or contrast reduction.
[0042]
However, if the step of minimizing the surface potential difference of the sample S is performed prior to the step of acquiring the inspection image, it takes time to equalize the potential difference on the sample surface, and the inspection throughput is reduced. I will. Therefore, as will be described in detail later, an electron beam separate from the primary beam for observation Bp is used, and in parallel with the irradiation of the primary beam Bp, immediately before the irradiation of the primary beam Bp, a separate electron beam is applied to the inspection area on the surface of the sample S. By previously irradiating the electron beam, the surface potential difference in that area is made as small as possible, so that the waiting time is almost eliminated, and the problem of a decrease in throughput can be solved. In the present embodiment, the pre-processing using the electron beams EB1 and EB2 is performed using the additional electron beam irradiation devices 80 and 90, respectively. Hereinafter, this pretreatment step is referred to as step 2.
[0043]
In Steps 1 and 2, the difference in the dose of the electron beam required to minimize the surface potential difference is caused by the layout pattern and electrical characteristics of the metal wiring portion 212 and the insulator portion 214 on the surface of the sample S. There is a problem that occurs. For example, in a region where the occupation ratio of the metal wiring portion 212 is large, a large amount of electrons leak from the insulator portion 214 to the metal wiring portion 212, so that a large amount of electron beam irradiation is required until the surface potential difference is minimized. . Further, depending on whether or not the metal wiring portion 212 and the substrate S are conductive, a difference occurs in the amount of electron leakage from the insulator portion 214. These problems cause image distortion and defocus due to non-uniform surface potential in the same visual field when imaging the surface of the sample S. In order to avoid this problem, more specific irradiation conditions under the condition that the insulator portion 214 is negatively charged, for example, electrons per unit area of the substrate S in accordance with the above-described layout pattern and electric characteristics. What is necessary is just to adjust the total current amount of the beam and the incident energy of the electron beam to the sample. For example, in a region where the occupation ratio of the metal wiring portion 212 is large, a region where the metal wiring portion 212 is electrically connected to the substrate, or the like, the amount of electrons leaking from the insulator portion 214 is large. It is preferable that the total current amount of the beam is made larger than that in the other regions, and that the electron beam irradiation can be performed with incident energy at which the total secondary electron emission efficiency σ becomes smaller.
[0044]
It is also effective to irradiate the electron beam under the condition that the insulator becomes positively charged before the step 1 as a method for making the surface potential of the sample uniform. Hereinafter, such a pretreatment step is referred to as step 3.
[0045]
FIG. 12 is a diagram for explaining a problem when the primary beam Bp is excessively irradiated on the surface of the sample S under the above-described negative charging condition. If the primary beam Bp is excessively irradiated on the insulator 214, the insulator 214 may be negatively charged as shown in FIG. In the same image at the time of imaging the surface of the sample S, even if the surface potential is made uniform in other regions, the insulating portion may be formed depending on the layout pattern and the electrical characteristics in the region shown in FIG. A case is considered in which the 214 becomes a negatively charged state and becomes a negative potential with respect to the potential of the metal wiring portion 212, and the uniform state of the surface potential is rather broken. Even in such a case, similar to the case of the positive charging shown in FIG. 16, a local potential gradient not parallel to the surface of the sample S near the boundary 216 between the metal wiring portion 212 and the insulator portion 214. Occurs. This potential gradient is generated when the secondary electrons emitted from the point P2 in the metal wiring portion near the boundary 216 and the point P4 in the insulator portion are controlled by the secondary optical system 20 to form an image on the MCP detector 31. Ideal electron beam trajectory TJ to perform accurate projection by improper deflection_IP2, TJ_IP4From the beam trajectory TJ_RP6, TJ_RP8It becomes a curved orbit like. In such a case, the primary beam Bp is irradiated beforehand on the surface of the sample S under the condition that the insulator portion 214 is positively charged before the process of Step 1, and a region (for example, the metal wiring portion 212) that is likely to be negatively charged in Step 1 The region where the occupation ratio is small, or the region where the metal wiring portion 212 is not electrically connected to the substrate, etc.) is positively charged before other regions in Step 3. By such a process, it is possible to avoid the problem that the surface potential locally varies depending on the pattern layout and the electrical characteristics on the surface of the sample S when imaging the surface of the sample S in step 1.
[0046]
The board inspection apparatus 2 shown in FIG. 9 operates according to such an inspection principle. Hereinafter, the characteristic operation of the board inspection apparatus 2 will be described more specifically.
[0047]
First, prior to the inspection, the electron beam irradiation condition processing device 66 fetches the layout pattern data and the electrical characteristic data of the sample S from the CAD data storage device 68, and the observation target portion on the sample S, that is, the imaging region, Intersection IP between optical axis As and sample S surface₀Is set, the irradiation conditions of the primary beam Bp and the electron beams EB1 and EB2 at the respective positions of the stage 43 are set so that the surface potential in the imaging region is made uniform or the surface potential difference is minimized. calculate. This calculation result is stored in the electron beam irradiation condition storage device 64.
[0048]
Next, after the start of the inspection, the host computer 60 refers to the current position information of the stage 43 supplied from the stage driving device 47, and determines the irradiation conditions of the electron beam EB2, the electron beam EB1, and the primary beam Bp at the stage position. It is extracted from the electron beam irradiation condition storage device 64. Further, the host computer 60 transmits these irradiation condition data to the electron beam device control unit 98, the electron beam device control unit 88, the electron gun control unit 16 and the multiple quadrupole lens control unit 17, and transmits the data to the electron beam device 90. , The electron beam device 80 and the primary optical system 10 are respectively controlled to adjust the irradiation conditions of the electron beam EB2, the electron beam EB1, and the primary beam Bp. As the irradiation conditions, for example, the following five cases are considered as shown in FIG.
[0049]
(Case 1) The primary beam Bp is irradiated under the condition that the insulator is negatively charged. The electron beams EB1 and EB2 are not irradiated.
(Case 2) The primary beam Bp is irradiated under the condition that the insulator is negatively charged. The electron beam EB1 is irradiated under the condition that the insulator is negatively charged. The electron beam EB2 is not irradiated.
(Case 3) The primary beam Bp is irradiated under the condition that the insulator is negatively charged. The electron beam EB1 is irradiated under the condition that the insulator is positively charged. The electron beam EB2 is not irradiated.
(Case 4) The primary beam Bp is irradiated under the condition that the insulator is negatively charged. The electron beam EB1 is irradiated under the condition that the insulator is negatively charged. The electron beam EB2 is irradiated under the condition that the insulator is positively charged.
(Case 5) The primary beam Bp is irradiated under the condition that the insulator is negatively charged. The electron beam EB1 is irradiated under the condition that the insulator is positively charged. The electron beam EB2 is irradiated under the condition that the insulator is negatively charged.
[0050]
As described above, by inspecting the sample S under the optimum conditions for uniformizing the surface potential of the sample adopted by the electron beam irradiation condition processing device 66, it is possible to obtain a highly accurate detection image without image distortion and defocus. Can be.
[0051]
In the above description, the form using two additional electron beam devices for uniforming the surface potential has been described. However, the present invention is not limited to this. For example, an additional electron beam device such as a substrate inspection device 3 shown in FIG. Even when only one beam device is provided or when three or more additional electron beam devices are provided (not shown), the above-described method can be similarly applied.
[0052]
(6) Semiconductor device manufacturing method
By using the above-described substrate inspection process in the process of manufacturing a semiconductor device, the substrate can be inspected with high accuracy, so that the semiconductor device can be manufactured with a higher yield.
[0053]
Although the embodiments of the present invention have been described above, it is apparent that the present invention is not limited to the above embodiments, but can be variously applied within the technical scope thereof. For example, in the above-described embodiment, the stage scanning type substrate inspection apparatus has been described. However, it is needless to say that the present invention can also be applied to a beam scanning type substrate inspection apparatus using a deflector. The present invention is also applicable to a board inspection apparatus provided.
[0054]
【The invention's effect】
As described in detail above, the present invention has the following effects.
[0055]
That is, according to the present invention, it is possible to obtain an inspection image in which distortion and a decrease in contrast at a boundary where a local potential difference occurs on the sample surface are suppressed, so that the inspection accuracy can be further improved.
[0056]
Further, according to the present invention, a semiconductor device can be manufactured with a higher yield because a substrate inspection method capable of obtaining an inspection image with high accuracy is used.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of a substrate inspection apparatus according to the present invention.
FIG. 2 is a perspective view showing a specific configuration of a Wien filter included in the substrate inspection apparatus shown in FIG.
FIG. 3 is an explanatory view of the operation principle of the Wien filter shown in FIG.
FIG. 4 is an explanatory view of the operation principle of the Wien filter shown in FIG.
FIG. 5 is a schematic diagram illustrating a first embodiment and a second embodiment of a substrate inspection method according to the present invention.
6 is an explanatory diagram of an energy band of the insulator shown in FIG.
FIG. 7 is a schematic diagram illustrating a third embodiment of the substrate inspection method according to the present invention.
FIG. 8 is an explanatory diagram of an energy band at a joint between a metal and an insulator shown in FIG. 7;
FIG. 9 is a block diagram showing a second embodiment of the board inspection apparatus according to the present invention.
FIG. 10: SiO₂6 is a graph illustrating an example of a relationship between an incident energy of an electron beam and a total secondary electron emission ratio in the first embodiment.
FIG. 11 is an explanatory diagram of an effect of the fourth embodiment of the substrate inspection method according to the present invention.
FIG. 12 is a diagram for explaining a problem when the primary beam is excessively irradiated on the insulator on the sample surface under the negative charging condition.
13 is a table showing combinations of electron beam irradiation conditions of the substrate inspection apparatus shown in FIG.
FIG. 14 is a block diagram showing a third embodiment of the board inspection apparatus according to the present invention.
FIG. 15 is an explanatory diagram of a problem of a conventional board inspection method.
FIG. 16 is an explanatory view of another problem of the conventional board inspection method.
[Explanation of symbols]
1-3 Board inspection device
9 Aperture position surface
10. Primary optical system
11 electron gun
15 Multi-stage quadrupole lens
16 electron gun controller
17 Multi-stage quadrupole lens controller
20 Secondary optics
21 Cathode lens
22 Second lens
23 Third lens
24 Fourth lens
25 Aperture angle aperture
26 Field stop
30 electron detector
31 MCP detector
32 fluorescent plate
33 Light Guide
34 Image sensor
41 Wien filter
41a, 41b electrodes
41c, 41d Magnetic pole
43 stages
47 Stage drive
51 Stage voltage controller
52 Cathode lens controller
53 Wien filter controller
54 Second lens control unit
55 Third lens control unit
56 Fourth lens control unit
57 MCP detection system controller
58 Image signal processing unit
60 Host computer
62 Display
64 Electron beam irradiation condition storage device
66 Electron beam irradiation condition processing equipment
68 CAD data storage device
70 Laser beam irradiation device
72 Laser light source
74 power supply
80,90 Electron beam irradiation device
82,92 W filament
84,94 Wehnelt electrode
86,96 anode
88,98 electron gun controller
112 linear cathode
114 Wehnelt electrode
116 anode
118 deflector
212 metal wiring
214 Insulator
216 border
A_EB1, A_EB2  Optical axis of electron beam
AL laser beam axis
As Secondary optical system optical axis
Bp primary beam
Bs secondary beam
C1, C2 boundary
CB conduction band
e1 to e4 electron
HL1 to HL4 holes
IL2, IL4 equipotential line
IS1, IS2 insulator
IP₀  Intersection between the optical axis of the secondary optical system and the sample surface
IP₁, IP₂  Intersection between the optical axis of the electron beam and the sample surface
L, L1 to L4 laser light
LL1, LL2 localized level
ML metal
S sample
TJ_IP2, TJ_IP4  Ideal electron beam orbit
VB valence band

Claims (27)

Electron beam irradiation means for generating an electron beam and irradiating the substrate to be inspected as a primary beam,
An electron beam that detects at least one of secondary electrons, reflected electrons, and backscattered electrons generated from the substrate under irradiation of the electron beam, and outputs a signal that is a one-dimensional image or a two-dimensional image of the substrate surface. Detecting means;
Mapping projection optical means for forming an image on the electron beam detection means as a secondary beam at least one of the secondary electrons, the reflected electrons and the backscattered electrons,
Electromagnetic wave irradiating means for generating an electromagnetic wave and irradiating the electromagnetic wave to a place where the secondary beam is generated on the substrate surface,
A substrate inspection device comprising: The electromagnetic wave irradiating means irradiates the electromagnetic wave such that a region where the electromagnetic wave irradiates the surface of the substrate and a region where the primary beam irradiates the surface of the substrate overlap with each other. A substrate inspection apparatus according to item 1. The substrate inspection apparatus according to claim 1, wherein the electromagnetic wave irradiation unit irradiates the surface of the substrate with the electromagnetic wave substantially simultaneously with the irradiation of the primary beam. The substrate inspection apparatus according to claim 1, wherein the wavelength of the electromagnetic wave is determined based on a band gap or a localized level of a material on a surface of the substrate. The surface of the substrate is formed of a plurality of different materials,
The substrate inspection apparatus according to claim 1, wherein a wavelength of the electromagnetic wave is determined based on a height of a potential barrier generated at a contact portion of the different materials. Electron beam irradiation means for generating an electron beam and irradiating a substrate to be inspected having an insulator formed on the surface under conditions where the insulator is negatively charged,
An electron beam that detects at least one of secondary electrons, reflected electrons, and backscattered electrons generated from the substrate under irradiation of the electron beam, and outputs a signal that is a one-dimensional image or a two-dimensional image of the substrate surface. Detecting means;
Mapping projection optical means for forming an image of at least one of the secondary electrons, the reflected electrons and the backscattered electrons on the electron beam detection means,
A substrate inspection device comprising: The condition under which the insulator is negatively charged is a ratio of the total amount of the secondary electrons, the reflected electrons and the backscattered electrons emitted from the substrate to the amount of electrons incident on the substrate, and all the secondary electrons. The substrate inspection apparatus according to claim 6, wherein the condition is that the emission ratio is less than 1. The substrate inspection apparatus according to claim 6, further comprising an electron beam irradiation condition control unit that controls the electron beam so that a surface potential difference in a desired region of the substrate is minimized. The substrate further has at least one of a metal and a semiconductor formed on the surface,
The electron beam irradiation condition control means may include a total current amount of the electron beam per unit area of the substrate surface or the electron beam according to at least one pattern layout or electrical characteristics of the metal, the semiconductor, and the insulator. 9. The substrate inspection apparatus according to claim 8, wherein incident energy to said substrate is controlled. The electron beam irradiation means,
First electron beam irradiation means for generating the electron beam and irradiating the inspection target area of the substrate as a primary beam;
Second electron beam irradiation means for generating the electron beam and irradiating the inspection target area prior to the irradiation of the primary beam;
The substrate inspection apparatus according to any one of claims 6 to 9, further comprising: The method according to claim 10, further comprising a third electron beam irradiation unit that generates the electron beam under a condition that the insulator is positively charged, and irradiates the substrate with the electron beam prior to the irradiation of the primary beam. Board inspection equipment. The electron beam irradiation means irradiates the inspection area of the substrate with the electron beam as a primary beam,
The apparatus further includes a second electron beam irradiation unit configured to generate the electron beam under the condition that the insulator is positively charged and to irradiate the inspection target area before the irradiation of the primary beam.
The substrate inspection apparatus according to any one of claims 6 to 9, wherein: 13. The substrate inspection apparatus according to claim 11, wherein the condition under which the insulator is positively charged is a condition under which the total secondary electron emission ratio exceeds 1. A step of generating an electron beam and irradiating the substrate to be inspected as a primary beam,
A step of projecting at least one of secondary electrons, reflected electrons and backscattered electrons generated from the substrate under irradiation of the electron beam as a secondary beam to form an image,
Detecting the image-formed secondary beam, and outputting a signal that is a one-dimensional image or a two-dimensional image of the substrate surface,
Generating an electromagnetic wave, and irradiating the electromagnetic wave to a location on the substrate surface where the secondary beam is generated,
A board inspection method comprising: The substrate inspection method according to claim 14, wherein the electromagnetic wave irradiates the surface of the substrate substantially simultaneously with the irradiation of the primary beam. The trajectory of the electromagnetic wave is controlled such that an area where the electromagnetic wave irradiates the surface of the substrate and an area where the primary beam irradiates the surface of the substrate overlap, and the trajectory of the electromagnetic wave is controlled. The board inspection method described. 17. The substrate inspection method according to claim 14, wherein the wavelength of the electromagnetic wave is determined based on a band gap or a localized level of a material on a surface of the substrate. The surface of the substrate is formed of a plurality of different materials,
17. The substrate inspection method according to claim 14, wherein the wavelength of the electromagnetic wave is determined based on a height of a potential barrier generated at a contact portion between the different materials. An electron beam irradiation step of generating an electron beam and irradiating the substrate to be inspected having an insulator formed on the surface under conditions where the insulator is negatively charged,
A step of projecting at least one of secondary electrons, reflected electrons and backscattered electrons generated from the substrate under irradiation of the electron beam as a secondary beam to form an image,
Detecting the image-formed secondary beam, and outputting a signal that becomes a one-dimensional image or a two-dimensional image of the substrate surface,
A board inspection method comprising: The condition under which the insulator is negatively charged is a ratio of the total amount of the secondary electrons, the reflected electrons and the backscattered electrons emitted from the substrate to the amount of electrons incident on the substrate, and all the secondary electrons. 20. The method according to claim 19, wherein the emission ratio is less than 1. 21. The substrate inspection method according to claim 19, further comprising an electron beam irradiation condition control step of controlling the electron beam such that a surface potential difference in an inspection target area of the substrate is minimized. The substrate further has at least one of a metal and a semiconductor formed on the surface,
The electron beam irradiation condition control step may include a step of controlling a total current amount of the electron beam per unit area of the substrate surface or the electron beam according to at least one pattern layout or electrical characteristics of the metal, the semiconductor, and the insulator 22. The substrate inspection method according to claim 21, further comprising a step of controlling incident energy on the substrate. The electron beam irradiation step,
A first electron beam irradiation step of generating the electron beam and irradiating the inspection target area of the substrate as a primary beam;
A second electron beam irradiation step of generating the electron beam and irradiating the inspection target area prior to the irradiation of the primary beam;
The substrate inspection method according to any one of claims 19 to 22, comprising: 24. The method according to claim 23, further comprising a third electron beam irradiation step of generating the electron beam under the condition that the insulator is positively charged, and irradiating the substrate with the electron beam prior to the irradiation of the primary beam. Board inspection method. The electron beam irradiation step is a first electron beam irradiation step of irradiating the inspection target area of the substrate with the electron beam as a primary beam,
Generating an electron beam under the condition that the insulator is positively charged, and further comprising a second electron beam irradiation step of irradiating the inspection target area prior to irradiation of the primary beam,
The substrate inspection method according to claim 19, wherein: 26. The substrate inspection method according to claim 24, wherein the condition under which the insulator is positively charged is a condition under which the total secondary electron emission ratio exceeds 1. A method of manufacturing a semiconductor device using the substrate inspection method according to claim 14.

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