JP2009128007A - Inspection device, inspection method and memory medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely discriminate the presence of the adhesion of residue in inspecting the presence of the adhesion of the residue consisting of an organic component to the surface of a resist pattern by applying an electron beam to a substrate which the resist pattern and an antireflection film being an organic film containing silicon overlie in this order from the upper side. <P>SOLUTION: The secondary electrons discharged from the inside of the substrate is pushed back to the substrate by applying a negative bias voltage across the substrate and a detection means for detecting the electrons discharged from the substrate while the reflected electrons discharged from the pole surface layer of the substrate are allowed to arrive at the detection means. By this constitution, even in the case where the residue is extremely thin or in the case where the width of the resist pattern is narrow, the residue can be precisely detected. Further, since an image based on the composition of a substance is obtained in the reflected electrons, the residue can be precisely detected even in the case where composition of the residue and that of the antireflection film are near. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technical field in which a substrate or a reticle provided with a mask layer on which a pattern is formed is irradiated with an electron beam in a vacuum atmosphere to inspect defects in the pattern.

In a semiconductor device manufacturing process, for example, there is an optical inspection method for a defect inspection method for a resist pattern formed on a semiconductor wafer (hereinafter referred to as a wafer). In this method, the line width of the resist pattern is, for example, 32 nm or less. Then, there is a case where the defect of the pattern cannot be detected.
Therefore, there is a scanning electron microscope (SEM) type inspection method using an electron beam as a method for inspecting a defect of the pattern when the line width of the pattern is 32 nm or less, for example, 15 nm (for example, see Patent Document 1).

  As shown in FIG. 6, this SEM type inspection method irradiates an electron beam (primary electrons) onto the wafer W on the mounting table 102 from the electron emission unit 101 provided on the upper side of the vacuum vessel 100. In this method, secondary electrons emitted from the surface layer of the wafer W are detected by the detector 103 and the intensity distribution is examined to inspect the resist pattern for defects. Due to the incidence of the electron beam, reflected electrons from which the electron beam is elastically reflected from the wafer W and secondary electrons whose energy is smaller than that of the electron beam due to heat generation or transition inside the wafer W are emitted. However, as shown in FIG. 7, since the amount of secondary electrons emitted from the wafer W is larger than that of the reflected electrons, such an inspection apparatus uses secondary electrons to detect defects. Note that the energy of the secondary electrons is approximately 1000 eV or less regardless of the energy of the irradiated electron beam.

  For example, as shown in FIGS. 8A and 8B, an insulating film 111 as a film to be etched, an antireflection film 113 mainly made of an organic component for preventing reflection at the time of exposure, and a silicon layer 110, and For example, when a pattern including a line-shaped opening 114 is formed by performing exposure and development on the wafer W on which the photoresist mask 116 that is an organic film is laminated in this order from the lower side, an opening is formed. There is a possibility that the residue 115 of the photoresist mask 116 adheres in the portion 114. Since such residue 115 may be transferred to the pattern of the film to be etched in the subsequent etching, it is necessary to grasp the adhesion state of the residue 115 by inspection. Therefore, in order to inspect the presence or absence of the adhesion of the residue 115, the SEM type inspection apparatus is used.

By the way, when unevenness such as the above-described opening 114 is formed on the surface of the wafer W, when the wafer W is irradiated with an electron beam as shown in FIG. ), An edge effect that increases the amount of secondary electrons emitted from the edge portion appears. For this reason, it is necessary to correct the pattern image based on the luminance information of the secondary electrons. In this case, when the wiring density increases and the opening width of the opening 114 decreases, the edges approach each other and the luminance based on each edge effect Since these peaks overlap, it is difficult to correct the pattern image, and as a result, it is difficult to detect the residue 115 with high accuracy.
Further, since the arrival depth of the electron beam becomes deeper as the acceleration voltage of the electron beam is increased, secondary electrons are emitted from a depth position corresponding to the arrival depth of the electron beam. For this reason, in the opening 114, a portion where the residue 115 is attached is not transmitted through the residue 115, and a portion where the residue 115 is not attached is reached in the lower layer of the photoresist mask 116. The acceleration voltage has to be adjusted, and therefore it is very difficult to adjust the acceleration voltage. For this reason, when the thickness of the residue 115 is reduced, a luminance difference between a portion where the residue 115 is attached and a portion where the residue 115 is not attached cannot be made large, and the detection of the residue 115 becomes difficult.

In addition, since the antireflection film 113 on the lower layer side of the photoresist mask 116 has more carbon than the photoresist mask 116, a luminance difference is generated between the photoresist mask 116 and the antireflection film 113, but both are organic materials. Therefore, the luminance difference is small as shown in FIG. Recently, in order to increase the etching selectivity, some antireflection film 113 contains a minute amount of an inorganic component such as silicon. However, even in this case, the luminance difference does not become so large, and the residue 115 is also removed. It is not easy to discriminate.
Patent Document 2 describes a technique for irradiating a wafer W with an electron beam and detecting reflected electrons emitted from the wafer W, but does not describe the above problem.

JP 2002-216698 A JP-A-5-264464

  This invention is made | formed in view of such a situation, The objective is test | inspecting the adhesion of the residue on the pattern of a mask by irradiating the to-be-inspected object which has a mask layer with an electron beam. In doing so, an object is to provide a technique capable of inspecting for the presence or absence of residue with high accuracy.

The inspection apparatus of the present invention is
In an inspection apparatus for inspecting the presence or absence of a residue on the pattern by irradiating an electron beam to an object to be inspected in which the mask layer on which the pattern is formed and the lower layer film are laminated in this order from the upper side,
A vacuum vessel in which a mounting table for mounting the object to be inspected is provided;
Evacuation means for evacuating the inside of the vacuum vessel;
An electron emission portion for irradiating an electron beam to the object to be inspected on the mounting table;
An electron detection means for detecting reflected electrons emitted from the object to be inspected;
A reverse bias, which is provided between the electron detection means and the object to be inspected, is applied with a reverse bias voltage which is a negative voltage in order to push back secondary electrons emitted from the object to be inspected back to the object to be inspected. And an electrode.
The mask layer is preferably a resist layer.
The lower layer film is preferably an antireflection film containing an organic component as a main component, and preferably further contains at least one of silicon and a compound containing oxygen and silicon.

The inspection method of the present invention comprises:
In the inspection method for inspecting the presence or absence of residues on the pattern by irradiating the inspection target layered in this order from the upper side with the mask layer on which the pattern is formed and the lower layer film,
Placing the object to be inspected on a mounting table in a vacuum vessel, and evacuating the vacuum vessel;
Irradiating the inspection object with an electron beam;
In order to push back the secondary electrons emitted from the object to be inspected back to the object to be inspected, a negative voltage is applied between the object to be inspected and an electron detection means for detecting reflected electrons emitted from the object to be inspected. Applying a reverse bias voltage of
And a step of detecting reflected electrons emitted from the object to be inspected.

The storage medium of the present invention is
A storage medium for storing a program that runs on a computer,
The program has a group of steps so as to execute the inspection method.

  According to the present invention, by irradiating an electron beam to an object to be inspected in which a mask layer on which a pattern is formed and a lower layer film are stacked in this order from above, the presence or absence of residues on the pattern is determined. In inspecting, secondary electrons emitted from the object to be inspected by applying a reverse bias voltage, which is a negative voltage, between the object to be inspected and the electron detecting means for detecting electrons emitted from the object to be inspected. Is pushed back toward the object to be inspected, and the reflected electrons emitted from the surface layer of the object to be inspected are detected. For this reason, the edge effect peculiar to the secondary electrons is eliminated, and a clear image can be obtained even in a region where the opening width of the pattern is narrow. Therefore, the presence or absence of a residue can be detected with high accuracy. In addition, since information on the surface layer of the object to be inspected can be obtained by using the reflected electrons reflected on the surface layer of the object to be inspected, even a thin residue can be detected with high accuracy. Furthermore, by using the reflected electrons reflected from the surface layer of the object to be inspected, information from the surface layer of the object to be inspected can be acquired even if the acceleration voltage is changed. The voltage can be easily adjusted. Furthermore, by using reflected electrons, information based on the composition of the surface layer of the object to be inspected can be obtained, so even a slight difference in composition can be determined, and the composition between the residue and the lower layer film Even when the secondary electrons have a small luminance difference between the residue and the lower layer film, a large luminance difference can be obtained, and the residue can be detected with high accuracy.

  An example of the inspection apparatus of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing an example of an inspection apparatus. This inspection apparatus includes an atmospheric transfer chamber 23, two load lock modules 22, 22 arranged side by side, a vacuum transfer chamber 21 having a pentagonal cross section, and, for example, one SEM type from the front side in FIG. The inspection modules 30 are arranged in this order, and each is configured to be airtightly connected through the gate valve G.

  At the front side of the atmospheric transfer chamber 23, a wafer carrier 200 (hereinafter referred to as a carrier) 200, which is a hermetically sealed substrate transfer container capable of storing a plurality of, for example, 25 wafers W to be inspected, is attached. For example, two loading / unloading ports 24 are provided at two locations. Each of these loading / unloading ports 24 is provided with a shutter (not shown). When the carrier 200 is attached to the loading / unloading port 24, the shutter is detached and the inside of the carrier 200 communicates with the atmospheric transfer chamber 23 in an airtight manner. Is configured to do. The atmospheric transfer chamber 23 is provided with an articulated transfer arm mechanism 27 for transferring the wafer W between the carrier 200 and the load lock module 22 so as to be rotatable and reciprocated around a vertical axis. The transport arm mechanism 27 can travel on the rail 28 along the arrangement of the two carriers 200 arranged side by side.

The load lock module 22 is an area for switching the interior between an air atmosphere and a vacuum atmosphere to wait for the wafer W. The load lock module 22 includes a mounting table 71 for mounting the wafer W, an exhaust valve, and a leak valve (both are (Not shown).
The vacuum transfer chamber 21 is provided with a transfer arm mechanism 50 which is a substrate transfer means for transferring the wafer W between the inspection module 30 and the load lock module 22 so as to be able to rotate and advance and retract. The rotation center of the mechanism 50 is disposed at the approximate center of the vacuum transfer chamber 21.

  Next, the SEM type inspection module 30 will be described with reference to FIG. In FIG. 2, reference numeral 31 denotes a vacuum container, and a mounting table 32 for mounting the wafer W is provided in the lower part of the vacuum container 31. The mounting table 32 is configured to be moved in the horizontal direction by an XY drive mechanism 33. An electrostatic chuck 34 for holding the wafer W is provided on the surface of the mounting table 32, and the wafer W is transferred to and from the transfer arm mechanism 50 described above inside the mounting table 32. Elevating pins (not shown) for performing are provided. Inside the mounting table 32, a cooling mechanism 36 is provided for cooling the wafer W that is heated by electron beam irradiation. The cooling mechanism 36 is configured such that, for example, a refrigerant circulates between the outside of the vacuum vessel 31 and a back supplied to the back surface of the wafer W from a gas supply port (not shown) opened on the top surface of the mounting table 32. The heat exchange between the cooling mechanism 36 and the wafer W is quickly performed by the side gas. A power source 35 for applying a negative voltage to the wafer W is connected to the mounting table 32 in order to reduce the speed of the electron beam (primary electrons) emitted in the vicinity of the wafer W.

In addition, an electron emitting unit 60 for irradiating the wafer W with an electron beam is provided on the ceiling of the vacuum vessel 31 so as to face the mounting table 32. A power supply 61 for applying a negative voltage is connected to the electron emission unit 60, and a difference in voltage applied to the power supply 61 and the power supply 35 of the mounting table 32 described above is applied to the wafer W. This is the acceleration voltage of the irradiated electron beam. Further, a scanning lens 62 for converging the electron beam emitted from the electron emission unit 60, an aperture 63 for restricting the electron beam passing range, and the electron beam are scanned between the electron emission unit 60 and the mounting table 32. A scanning coil 64 is provided in this order from the upper side. The aperture 63 and the scanning coil 64 are grounded. Further, between the mounting table 32 and the scanning coil 64, a ring shape is formed so as to surround an extension line of the central axis of the electron emission portion 60 in order to detect reflected electrons emitted from the wafer W by irradiation of the electron beam. Electron detection means 69 composed of the formed electrodes is provided. The electron detector 69 is connected to a power source 80 that applies a positive voltage of, for example, 10 kV in order to attract the reflected electrons emitted from the wafer W. Between the electron detection means 69 and the wafer W, a reverse bias electrode 81 to which a negative voltage is applied is provided in a ring shape in order to push back secondary electrons emitted from the wafer W to the wafer W side. Yes. Here, as shown in FIG. 7 described above, the energy of the reflected electrons is larger than the energy of the secondary electrons. Therefore, a negative voltage (reverse bias) is applied so that the energy of the reflected electrons that are going to pass through the reverse bias electrode 81 is not lost and the energy of the secondary electrons is lost. In this example, since a voltage of −10 kV is applied to the wafer W by the power source 35, electrons having an energy of, for example, 1000 eV or less are transferred to the wafer W by setting the reverse bias voltage to, for example, −11 kV by the negative voltage power source 82. Will be pushed back to the side.
An exhaust port 66 is formed at the bottom of the vacuum vessel 31, and a vacuum pump 67, which is a vacuum exhaust means, is connected to the exhaust port 66 via a valve V1. A transfer port 68 is formed in the side wall of the vacuum vessel 31, and the wafer W is carried into the vacuum vessel 31 through the transfer port 68.

  The inspection apparatus is provided with a control unit 2 composed of, for example, a computer. The control unit 2 includes a program, a memory, a data processing unit including a CPU, and the like. The control unit 2 sends a control signal to each unit of the inspection apparatus from the control unit 2 and instructs the program to proceed with an inspection method described later ( Each step) is incorporated. Further, for example, the memory includes an area in which values of inspection parameters such as an acceleration voltage of an electron beam irradiated on the wafer W, a pressure at the time of inspection, and a temperature are written, and when the CPU executes each instruction of the program, The inspection parameter is read out, and a control signal corresponding to the parameter value is sent to each part of the inspection apparatus. This program (including programs related to processing parameter input operations and display) is stored in the storage unit 8 such as a computer storage medium such as a flexible disk, a compact disk, a hard disk, or an MO (magneto-optical disk) and installed in the control unit 2. The

Next, an inspection method using the above-described inspection apparatus will be described. First, the wafer W, which is an object to be inspected to which this inspection method is applied, will be described. For example, as shown in FIG. 3A, the wafer W includes a silicon layer 11, an insulating film 12 as a film to be etched, a carbon film 13 containing carbon as a hard mask, and reflection during exposure. An antireflection film 14 as a lower layer film and a resist pattern 15 as a mask layer are laminated in this order from the lower side. The antireflection film 14 has a higher carbon content than the resist pattern 15, and in this example, a small amount of silicon, which is an inorganic component, is mixed in to increase the etching selectivity with respect to the insulating film 12 that is the film to be etched. Has been.
In the resist pattern 15, for example, a pattern including a line-shaped opening 16 is formed by exposure and development. In the opening 16, as shown in FIG. 17 is attached. This residue 17 is attached during development.

  First, the carrier 200 storing a plurality of wafers W is attached to the loading / unloading port 24, and a shutter (not shown) is opened. Then, one wafer W is taken out from the inside of the carrier 200 by the transfer arm mechanism 27, and this wafer W is mounted on the mounting table 71 of the load lock module 22 in the atmosphere. Next, after the atmosphere in the load lock module 22 is switched from an air atmosphere to a vacuum atmosphere, the wafer W is transferred into the inspection module 30 by the transfer arm mechanism 50 and mounted on the mounting table 32.

  Thereafter, the wafer W is electrostatically adsorbed and the temperature is adjusted to a predetermined temperature, and the inside of the vacuum vessel 31 is set to a predetermined degree of vacuum. Further, the voltages of the power supplies 35 and 61 described above are adjusted to −10 kV and −12 kV, respectively, so that the acceleration voltage of the electron beam supplied to the wafer W becomes 5 keV or more. In addition, as described above, a negative voltage, for example, -11 kV is applied to the negative voltage power source 82 of the reverse bias electrode 81, and a positive voltage, for example, 10 kV is applied to the power source 80 in order to draw the reflected electrons into the electron detecting means 69. To do.

When the wafer W is irradiated with an electron beam, reflected electrons and secondary electrons are emitted from the wafer W as shown in FIG. Since a reverse bias voltage of −11 kV is applied to the reverse bias electrode 81 and a voltage of −10 kV is applied to the wafer W, the electrons from the wafer W toward the reverse bias electrode 81 have an energy of 1000 eV or less. Passes through a region surrounded by the reverse bias electrode 81, and electrons having energy lower than 1000 eV are pushed back to the wafer W side. Therefore, as shown in FIG. 5, the secondary electrons are pushed back to the wafer W side, but the reflected electrons are attracted to the electron detection means 69 and arrive, and information corresponding to the composition of the surface layer of the wafer W is detected by the electron detection means. 69 is transmitted.
Thereafter, the wafer W is moved in the horizontal direction by the mounting table 32, and similarly, the surface of the wafer W is sequentially scanned. As a result, a data processing unit (not shown) creates a map of the reflected electron brightness at each position on the wafer W, compares each brightness with a preset threshold value, and determines the presence or absence of the residue 17. Then, the wafers W are unloaded in the order reverse to the order of loading into the inspection module 30.

  According to the above-mentioned embodiment, the residue 17 adhering in the opening 16 is detected by irradiating the substrate on which the resist pattern 15 and the antireflection film 14 are laminated in this order from the upper side. In doing so, secondary electrons emitted from the inside of the wafer W are pushed back to the wafer W side, while reflected electrons emitted from the surface layer of the wafer W are detected. For this reason, as shown in FIG. 4B, the edge effect peculiar to the secondary electrons is eliminated, and a clear image can be obtained even in a region where the opening width of the resist pattern 15 is narrow. It can be detected. Moreover, since information on the surface layer of the wafer W can be obtained by using the reflected electrons reflected on the surface layer of the wafer W, even the thin residue 17 can be detected with high accuracy. Further, in the case of secondary electrons, since the arrival depth of the electron beam changes when the acceleration voltage is changed, the depth position of the information to be obtained changes, and accordingly, the acceleration voltage of the electron beam that can observe the surface layer of the wafer W Is difficult to adjust the acceleration voltage. On the other hand, by using the reflected electrons reflected on the surface layer of the wafer W, information from the surface layer of the wafer W can be acquired even if the acceleration voltage is changed, so that the adjustment range of the acceleration voltage is widened. It becomes easy to adjust.

  In addition, as described above, even if the antireflection film 14 contains a small amount of silicon, the resist pattern 15 and the antireflection film 14 are made of an organic substance, so the composition is close and the residue 17 can be discriminated by secondary electrons. However, since the reflected electrons that can be discriminated even with a slight difference in composition are used, as shown in FIG. 4C, the difference between the residue 17 and the antireflection film 14 is obtained. The brightness difference becomes large, and the residue 17 can be detected with high accuracy from this point. Further, the compound contained in the antireflection film 14 is not limited to silicon, but may be a compound containing oxygen and silicon such as SiO (silicon oxide) and SiOCH (silicon oxide containing carbon and hydrogen). A plurality of these compounds may be used.

  Even if the composition of the residue 17 and the antireflection film 14 is completely different, if the residue 17 is very thin, it is difficult to detect the residue 17 with secondary electrons. However, with reflected electrons, even in such a case, the presence or absence of the residue 17 can be detected with high accuracy. Therefore, in the present invention, not only the composition of the residue 17 and the antireflection film 14 is close, but the antireflection film 14 may be, for example, a metal film or an inorganic film. Further, the resist pattern 15 is not limited to an organic material but may be an inorganic material. Furthermore, the inspection method of the present invention may be applied to a reticle used in a developing device when forming a pattern.

It is a cross-sectional view which shows the inspection apparatus concerning embodiment of this invention. It is a vertical side view which shows an example of the SEM type inspection module in embodiment of this invention. It is a longitudinal cross-sectional view which shows an example of the to-be-inspected object applied to the inspection method of this invention. It is a schematic diagram which shows a mode that the board | substrate surface is observed in said test | inspection module. It is a schematic diagram which shows a mode that reflected electrons are detected in said test | inspection module. It is a longitudinal cross-sectional view which shows an example of the conventional inspection apparatus. It is explanatory drawing about the energy of a secondary electron and a reflected electron. It is a longitudinal cross-sectional view which shows an example of the to-be-inspected object test | inspected in the said conventional test | inspection apparatus. It is a schematic diagram which shows a mode that a to-be-inspected object is test | inspected in the said conventional inspection apparatus.

Explanation of symbols

14 Antireflection film 15 Resist pattern 16 Groove 17 Organic substance 30 Inspection module 31 Vacuum container 32 Mounting table 35 Power supply 60 Electron emission part 69 Electron detection means 81 Reverse bias electrode 82 Negative voltage power supply

Claims (9)

In an inspection apparatus for inspecting the presence or absence of a residue on the pattern by irradiating an electron beam to an object to be inspected in which the mask layer on which the pattern is formed and the lower layer film are laminated in this order from the upper side,
A vacuum vessel in which a mounting table for mounting the object to be inspected is provided;
Evacuation means for evacuating the inside of the vacuum vessel;
An electron emission portion for irradiating an electron beam to the object to be inspected on the mounting table;
An electron detection means for detecting reflected electrons emitted from the object to be inspected;
A reverse bias, which is provided between the electron detection means and the object to be inspected, is applied with a reverse bias voltage which is a negative voltage in order to push back secondary electrons emitted from the object to be inspected back to the object to be inspected. An inspection apparatus comprising: an electrode.   The inspection apparatus according to claim 1, wherein the mask layer is a resist layer.   The inspection apparatus according to claim 1, wherein the lower layer film is an antireflection film containing an organic component as a main component.   The inspection apparatus according to claim 3, wherein the antireflection film includes at least one of silicon and a compound containing oxygen and silicon. In the inspection method for inspecting the presence or absence of residues on the pattern by irradiating the inspection target layered in this order from the upper side with the mask layer on which the pattern is formed and the lower layer film,
Placing the object to be inspected on a mounting table in a vacuum vessel, and evacuating the vacuum vessel;
Irradiating the inspection object with an electron beam;
In order to push back the secondary electrons emitted from the object to be inspected back to the object to be inspected, a negative voltage is applied between the object to be inspected and an electron detection means for detecting reflected electrons emitted from the object to be inspected. Applying a reverse bias voltage of
And a step of detecting reflected electrons emitted from the object to be inspected.   The inspection method according to claim 5, wherein the mask layer is a resist layer.   The inspection method according to claim 5, wherein the lower layer film is an antireflection film containing an organic component as a main component.   The inspection method according to claim 7, wherein the antireflection film contains at least one of silicon and a compound containing oxygen and silicon. A storage medium for storing a program that runs on a computer,
A storage medium comprising a group of steps so that the program executes the inspection method according to any one of claims 5 to 8.

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