KR101009808B1 - Inspection apparatus, inspection method, and storage medium - Google Patents

Abstract

In the present invention, the presence or absence of adhesion of residues composed of organic components on the pattern by irradiating an electron beam to a substrate in which a resist pattern and an antireflection film, which is an organic film containing silicon, is laminated in this order from above. In the inspection, the presence of residues is determined with high precision.

By applying a negative bias voltage between the substrate and the detection means for detecting the electrons emitted from the substrate, the secondary electrons emitted inside the substrate are returned to the substrate side, while being emitted from the polar surface layer of the substrate. The reflected electrons reach the detection means. This makes it possible to detect the residue with high accuracy even when the residue is very thin or when the width of the pattern is narrow. In addition, since the image based on the composition of the substance is obtained by the reflected electrons, the residue can be detected with high accuracy even when the composition of the residue and the anti-reflection film are similar.

Description

Inspection device, inspection method and storage medium {INSPECTION APPARATUS, INSPECTION METHOD, AND STORAGE MEDIUM}

TECHNICAL FIELD This invention relates to the technical field which irradiates an electron beam in a vacuum atmosphere with respect to the board | substrate or reticle provided with the mask layer in which the pattern was formed, and performs the defect inspection of the said pattern.

In the manufacturing process of a semiconductor device, for example, there is an optical inspection method for a defect inspection method of a resist pattern formed on a semiconductor wafer (hereinafter referred to as a wafer), but the line width of the resist pattern is, for example, 32 nm or less. In this case, a defect in the pattern may not be detected.

Then, as a method which can inspect the defect of a pattern in which the line width of a pattern is 32 nm or less, for example, 15 nm, there exists a SEM (Scanning Electron Microscope) type | mold inspection method using an electron beam (for example, refer patent document 1). .

In this SEM type inspection method, as shown in FIG. 6, an electron beam (primary electron) is irradiated to the wafer W on the mounting table 102 from the electron emission unit 101 provided above the vacuum vessel 100. The detector 103 detects secondary electrons emitted from the surface layer of the wafer W and examines the intensity distribution, thereby performing defect inspection of the resist pattern. Due to the incidence of the electron beams, the reflected electrons which the electron beams reflect elastically from the wafer W and the secondary electrons whose energy is smaller than the electron beams due to heat generation or transition inside the wafer W are emitted, as shown in FIG. 7. Since secondary electrons are emitted more from the wafer W than reflective electrons, such inspection apparatus uses secondary electrons for defect detection. Moreover, the energy of this secondary electron is set to about 1000 eV or less irrespective of the energy of the electron beam to irradiate.

For example, as shown in FIGS. 8A and 8B, on the silicon layer 110, an insulating film 111 which is a film to be etched, and an antireflection film composed mainly of an organic component for preventing reflection during exposure Exposure and development are performed on the wafer W in which the 113 and the organic photoresist mask 116 are stacked in this order from the lower side, for example, to form a pattern including the linear opening 114. In this case, the residue 115 of the photoresist mask 116 may adhere to the opening 114. Since the residue 115 may be transferred to the pattern of the etching target film in the subsequent etching, the adhesion state of the residue 115 should be grasped by inspection. Therefore, in order to inspect the presence or absence of adhesion of this residue 115, the SEM-type inspection apparatus is used.

By the way, when the unevenness | corrugation, such as the opening part 114 mentioned above, is formed in the surface of the wafer W, when an electron beam is irradiated with respect to this wafer W as shown to FIG. 9 (a), it is as shown to FIG. 9 (b). Similarly, an edge effect appears in which the amount of secondary electrons emitted from the edge portion increases. For this reason, it is necessary to correct the pattern image based on the luminance information of the secondary electrons. In that case, when the wiring density becomes high and the opening width of the opening 114 is narrowed, the edges become closer and the peaks of the luminance based on the respective edge effects are increased. Because of the overlap, correction of the pattern image becomes difficult, and as a result, it is difficult to detect the residue 115 with high accuracy.

In addition, since the arrival depth of the electron beam becomes deeper as the acceleration voltage of the electron beam is increased, the secondary electrons are emitted from a position having a depth corresponding to the arrival depth of the electron beam. For this reason, in the opening part 114, the photoresist mask 116 does not permeate | transmit the residue 115 with respect to the site | part to which the residue 115 adhered, and about the site | part to which the residue 115 is not attached. It is necessary to adjust the acceleration voltage so as to reach the lower layer of, and thus the adjustment of the acceleration voltage is very difficult. For this reason, when the thickness of the residue 115 becomes thin, the luminance difference between the site | part to which the residue 115 adhered and the site | part to which it is not attached is not largely obtained, 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 difference in luminance occurs between the photoresist mask 116 and the antireflection film 113, Since all are organic substances, the luminance difference is small, as shown in Fig. 9C. In recent years, a small amount of an inorganic component such as silicon is contained in the antireflection film 113 in order to increase the etching selectivity. However, even in this case, the luminance difference does not become very large. Is not easy.

Patent Literature 2 discloses a technique for irradiating an electron beam to the wafer W to detect reflected electrons emitted from the wafer W, but the above-described problem is not described.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2002-216698

[Patent Document 2] Japanese Unexamined Patent Application Publication No. 5-264464

This invention is made | formed in view of such a situation, The objective is to test the presence or absence of the residue on the pattern of a mask by irradiating an electron beam with respect to the to-be-tested object which has a mask layer, and to examine the presence or absence of a residue with high precision. It is to provide technology that can.

The inspection apparatus of the present invention is a test apparatus for inspecting the presence or absence of a residue on the pattern by irradiating an electron beam to a mask layer having a pattern formed thereon and an inspected object whose lower layer film is laminated in this order from above. A vacuum vessel provided therein, a vacuum exhaust means for evacuating the inside of the vacuum vessel, an electron emitting portion for irradiating an electron beam to the subject under test on the mount, and the reflection emitted from the subject under test. A reverse bias, which is a negative voltage, provided between the electron detecting means for detecting electrons and the secondary electrons provided between the electron detecting means and the inspected object and returned from the inspected object to the inspected object side; And a reverse bias electrode to which a voltage is applied.

It is preferable that the said mask layer is a resist layer.

It is preferable that the said underlayer film is an antireflection film which has an organic component as a main component, and it is preferable to contain at least one of the compound containing silicon, oxygen, and silicon.

In the inspection method of the present invention, in the inspection method for inspecting the presence or absence of a residue on the pattern by irradiating an electron beam to the mask layer on which the pattern is formed and the inspected object in which the lower layer film is laminated in this order from above, the inspected object is vacuumed. Mounted on a mounting table in a container, evacuating the inside of the vacuum container, irradiating an electron beam to the inspected object, and returning secondary electrons emitted from the inspected object to the inspected object side; And applying a reverse bias voltage as a negative voltage between the object under test and the electron detecting means for detecting the reflected electrons emitted from the object under test, and then detecting the reflected electrons emitted from the object under test. It features.

The storage medium of the present invention is a storage medium for storing a program running on a computer, wherein the program is characterized in that a step group is configured to execute the inspection method.

According to the present invention, when inspecting the presence or absence of a residue on the pattern by irradiating an electron beam to the test object in which the patterned mask layer and the lower layer film are laminated in this order from above, the test object is released from the test subject and the test subject. A negative bias voltage, which is a negative voltage, is applied between the electron detecting means for detecting the electrons to return the secondary electrons emitted from the inspected object to the inspected object side to detect the reflected electrons emitted from the surface layer of the inspected object. . Therefore, the edge effect peculiar to the secondary electrons is eliminated, and a clear image is obtained even in a region where the opening width of the pattern is narrow, so that the presence or absence of a residue can be detected with high precision. In addition, since the information on the surface layer of the inspected object can be obtained by using the reflected electrons reflected from the surface layer of the inspected object, even a thin residue can be detected with high accuracy. Further, by using the reflected electrons reflected from the surface layer of the object under test, information from the surface layer of the object under test can be obtained even if the acceleration voltage is changed, so that the adjustment range of the acceleration voltage becomes wider and the acceleration voltage can be easily adjusted. . In addition, since the information based on the composition of the surface layer of the object under test can be obtained by using the reflected electrons, even a slight difference in composition can be discriminated, and the composition between the residue and the underlayer film is similar, and the secondary electrons are used. Even if the luminance difference between the residue and the underlayer film is small, a large luminance difference can be obtained, and the residue can be detected with high accuracy.

An example of the inspection apparatus of this invention is demonstrated with reference to FIG. 1 and FIG. 1 is a cross-sectional view showing an example of an inspection apparatus. The inspection apparatus includes, from the lower end of FIG. 1, an air transport chamber 23, two load lock modules 22 and 22 arranged on the left and right, a vacuum transport chamber 21 whose cross section is pentagonal, and, for example, 1. A large SEM type inspection module 30 is arranged in this order, and each is configured to be hermetically connected through the gate valve G.

On the lower side of the drawing of the air | atmosphere conveyance chamber 23, the wafer carrier (henceforth a carrier) 200 called FOUP which is a sealed type | mold board | substrate conveyance container which can accommodate a plurality of wafers W which are 25 to-be-tested objects can be attached. Carry-in / out port 24 for doing so is provided in two places, for example. These carry-out ports 24 are each provided with a shutter not shown, and when the carrier 200 is attached to the carry-in / out port 24, these shutters will be separated, and the inside of the carrier 200 and the atmospheric conveyance chamber 23 will be made. It is configured to communicate confidentially. In addition, in the air transport chamber 23, a carrier arm mechanism 27 having a multi-joint structure for transferring the wafer W freely rotates and retracts about the vertical direction axis between the carrier 200 and the load lock module 22. This conveyance arm mechanism 27 is capable of traveling on the rail 28 according to the arrangement of the two carriers 200 arranged on the left and right sides.

The load lock module 22 is an area for switching the inside into an atmospheric atmosphere and a vacuum atmosphere to wait for the wafer W, a mounting table 71 for mounting the wafer W, an exhaust valve and a leak valve (both not shown). Not included).

In the vacuum conveyance chamber 21, the conveyance arm mechanism 50 which is a board | substrate conveyance means for conveying the wafer W between the inspection module 30 and the load lock module 22 is provided freely, and this conveyance arm mechanism is provided. The rotation center of 50 is arrange | positioned in the substantially center of the vacuum conveyance chamber 21. As shown in FIG.

Next, the SEM-type inspection module 30 will be described with reference to FIG. 2. In FIG. 2, reference numeral 31 denotes a vacuum container, and a mounting table 32 for mounting a wafer W is provided below the vacuum container 31. The mounting table 32 is configured to be movable in the horizontal direction by the X-Y drive mechanism 33. The surface of the mounting table 32 is provided with an electrostatic chuck 34 for holding the wafer W, and inside the mounting table 32, the wafer W is transferred between the carrying arm mechanism 50 described above. Lift pins (not shown) are provided. Inside the mounting table 32, a cooling mechanism 36 for cooling the wafer W heated by the irradiation of the electron beam is provided. The cooling mechanism 36 is configured such that, for example, the refrigerant is circulated between the outside of the vacuum container 31 and the wafer W is opened from a gas supply port (not shown) which is opened on the upper surface of the mounting table 32. The heat exchange between the cooling mechanism 36 and the wafer W is performed quickly by the back side gas supplied to the back surface. The mounting table 32 is connected to a power supply 35 for applying a negative voltage to the wafer W in order to slow down the speed of the electron beam (primary electron) emitted near the wafer W.

Moreover, the electron emission part 60 for irradiating an electron beam to the wafer W is provided in the ceiling part of the vacuum container 31 so that the mounting table 32 may be opposed. A power source 61 for applying a negative voltage is connected to the electron emission unit 60, and the power source 61 is applied to the power source 61 and the power source 35 of the mounting table 32 described above. The difference in voltage becomes the acceleration voltage of the electron beam irradiated to the wafer W. In addition, between the electron emission unit 60 and the mounting table 32, a converging lens 62 for converging the electron beam emitted from the electron emission unit 60, and an aperture controlling the passage range of the electron beam ( 63) and the scanning coil 64 for scanning an electron beam is provided in this order from above. These apertures 63 and scan coils 64 are grounded. Moreover, between the mounting table 32 and the scanning coil 64, in order to detect the reflected electron emitted from the wafer W by irradiation of an electron beam, it was formed in ring shape so that the extension line of the center axis of the electron emission part 60 may be enclosed. Electronic detection means 69 made of electrodes is provided. The electron detection means 69 is connected to a power supply 80 that applies a positive voltage of 10 kV, for example, to attract reflected electrons emitted from the wafer W. Between this electron detection means 69 and the wafer W, in order to return secondary electrons discharged from the wafer W to the wafer W side, a reverse bias electrode 81 to which a negative voltage is applied is provided in a ring shape. Here, as shown in FIG. 7 described above, the energy of the reflected electrons is larger than that of the secondary electrons. Therefore, a negative voltage (reverse bias) is applied so that the energy of the reflected electrons to pass through the reverse bias electrode 81 is not lost and also 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 supply 35, the reverse bias voltage is set to, for example, -11 kV by the negative voltage power supply 82, so that the energy is, for example, 1000 eV. The following electrons are sent back to the wafer W side.

The exhaust port 66 is formed in the bottom part of the vacuum container 31, and the vacuum pump 67 which is a vacuum exhaust means is connected to this exhaust port 66 via the valve V1. The conveyance port 68 is formed in the side wall of the vacuum container 31, and the wafer W is carried in into the vacuum container 31 via this conveyance port 68. As shown in FIG.

In this test | inspection apparatus, the control part 2 which consists of computers is provided, for example. The control unit 2 is provided with a data processing unit comprising a program, a memory, a CPU, and the like. The control unit 2 sends a control signal from the control unit 2 to each unit of the inspection apparatus to advance the inspection method described later (each Step) is built-in. Further, for example, the memory has an area in which inspection parameter values such as acceleration voltage of the electron beam irradiated to the wafer W, pressure during inspection, temperature, and the like are written, and these inspection parameters are set when the CPU executes each instruction of the program. The control signal is read and sent to each part of the inspection apparatus according to the parameter value. This program (including a program related to input operation and display of processing parameters) is stored in a storage unit 8 such as a computer storage medium, such as a flexible disk, a compact disk, a hard disk, and an MO (magnet) disk. It is installed in (2).

Next, the inspection method using the inspection apparatus mentioned above is demonstrated. First, the wafer W which is the inspection object 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. The antireflection film 14, which is an underlayer film, and the resist pattern 15, which is a mask layer, are laminated in this order from the lower side in order to prevent the damage. Since the anti-reflection film 14 has more carbon content than the resist pattern 15, and in this example, the etching selectivity is large with respect to the insulating film 12 which is an etching target film, a trace amount of silicon which is an inorganic component is mixed.

In the resist pattern 15, for example, a pattern formed of a linear opening 16 is formed by exposure and development. In the opening 16, as shown in Fig. 3B, a resist pattern ( The residue 17 of 15 is attached. This residue 17 is attached at the time of development.

First, the carrier 200 in which the plurality of wafers W are housed is attached to the carrying in and out ports 24, and a shutter (not shown) is opened. And one wafer W is taken out from the carrier 200 by the conveyance arm mechanism 27, and this wafer W is mounted in the mounting base 71 of the load lock module 22 of an atmospheric atmosphere. Subsequently, after switching the atmosphere in the load lock module 22 from the atmospheric atmosphere to the vacuum atmosphere, the transfer arm mechanism 50 transports the wafer W into the inspection module 30 and mounts it on the mounting table 32.

Thereafter, the wafer W is electrostatically adsorbed, the temperature is adjusted to a predetermined temperature, and the inside of the vacuum container 31 is set to a predetermined vacuum degree. In addition, the voltages of the power sources 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 is 5 keV or more. In addition, as described above, in order to apply a negative voltage, for example, -11 kV to the negative voltage power supply 82 of the reverse bias electrode 81, and to attract the reflected electrons to the electron detecting means 69, the power source ( A positive voltage, for example 10 kV, is applied to 80).

When the electron beam is irradiated onto the wafer W, as shown in Fig. 4A, the reflected electrons and the secondary electrons are emitted from the wafer W. 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 energy of 1000 eV or less of the electrons directed from the wafer W toward the reverse bias electrode 81 is reversed. Electrons with energy lower than 1000 eV passing through the region surrounded by the bias electrode 81 are sent back to the wafer W side. Therefore, as shown in FIG. 5, although the secondary electrons are sent back to the wafer W side, the reflected electrons are attracted and reached by the electron detection means 69, and the information corresponding to the composition of the surface layer of the wafer W has the electron detection means. To (69).

Thereafter, the wafer W is moved in the horizontal direction by the mounting table 32, and the surface of the wafer W is similarly sequentially scanned. As a result, a data processing unit (not shown) creates a map of the luminance of reflected electrons at each position on the wafer W, compares each luminance with a preset threshold value, and determines the presence or absence of the residue 17. . Then, the wafer W is carried out in the reverse order to that carried in the inspection module 30.

According to the above-described embodiment, the resist pattern 15 and the anti-reflection film 14 are irradiated with electron beams to the substrate stacked in this order from above, thereby detecting the residue 17 adhered in the opening 16. The secondary electrons emitted from the inside of the wafer W are sent back to the wafer W side, and the reflected electrons emitted from the surface layer of the wafer W are detected. For this reason, as shown in FIG.4 (b), since the edge effect peculiar to secondary electrons disappears, and a clear image is obtained also in the area | region of the opening width of the resist pattern 15, the residue 17 was highly accurate. The presence or absence of can be detected. In addition, since the surface layer information of the wafer W can be obtained by using the reflected electrons reflected from the surface layer of the wafer W, even a thin residue 17 can be detected with high accuracy. Moreover, in the case of secondary electrons, since the arrival depth of an electron beam changes when an acceleration voltage is changed, the depth position of the information obtained will change, and therefore the setting range of the acceleration voltage of the electron beam which can observe the surface layer of the wafer W is narrow, It is difficult to adjust the acceleration voltage. On the other hand, by using the reflected electrons reflected from the surface layer of the wafer W, since information from the surface layer of the wafer W can be obtained even if the acceleration voltage is changed, the adjustment range of the acceleration voltage becomes wider, and thus the acceleration voltage can be easily adjusted. do.

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 material, and thus the composition is similar, and the residue is caused by the secondary electrons. Although the luminance difference is not obtained to the point that (17) can be discriminated, since the reflected electrons that can be discriminated even with a small composition difference are used, as shown in Fig. 4C, the residue 17 and the antireflection film 14 The luminance difference between and becomes large, and the residue 17 can be detected with high precision also from this point. The compound included in the antireflection film 14 is not limited to silicon, but may be a compound containing oxygen and silicon such as SiO (silicon oxide), SiOCH (carbon oxide and hydrogen-containing silicon oxide), and the like. It may be a plurality of these compounds.

On the other hand, even when the composition of the residue 17 and the anti-reflection film 14 is completely different, when the residue 17 is very thin, detection of the residue 17 becomes difficult by the secondary electrons. However, even with such reflection electrons, 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 similar, but also the antireflection film 14 described above may be, for example, a film made of a metal film or an inorganic material. In addition, as said resist pattern 15, it is not limited to an organic substance, It may be an inorganic substance. In addition, you may apply the test method of this invention to the reticle used by a developing apparatus, when forming a pattern.

1 is a cross-sectional view showing an inspection apparatus according to an embodiment of the present invention,

2 is a longitudinal side view showing an example of an SEM-type inspection module in the embodiment of the present invention;

3 is a longitudinal sectional view showing an example of a test subject applied to the test method of the present invention;

4 is a schematic diagram showing the appearance of the substrate surface observed in the inspection module,

5 is a schematic diagram showing a state in which reflected electrons are detected in the inspection module;

6 is a longitudinal sectional view showing an example of a conventional inspection apparatus;

7 is an explanatory diagram of energy of secondary electrons and reflected electrons;

8 is a longitudinal sectional view showing an example of an inspected object inspected by the conventional inspection device;

9 is a schematic diagram showing the state in which the inspected object is inspected in the conventional inspection device.

Explanation of the sign

14 antireflection film 15 resist pattern

16: opening 17: organic matter

30: inspection module 31: vacuum vessel

32: mount 35: power

60 electron emission unit 69 electron detection means

81: reverse bias electrode 82: negative voltage power supply

Claims (9)

In the inspection apparatus which inspects the presence or absence of the residue on the said pattern by irradiating an electron beam with the mask layer in which the pattern was formed, and the to-be-tested object laminated | stacked in this order from the upper layer film, A vacuum container in which a mounting table on which a test subject is mounted is provided, Vacuum evacuation means for evacuating the inside of the vacuum vessel; An electron emission unit for irradiating an electron beam to the object under test on the mounting table; Electron detecting means for detecting reflected electrons emitted from the object under test; A reverse bias electrode provided between the electron detecting means and the inspected object and to which a reverse bias voltage as a negative voltage is applied to return secondary electrons emitted from the inspected object to the inspected object side; Inspection apparatus comprising a. The method of claim 1, And said mask layer is a resist layer. The method according to claim 1 or 2, The underlayer film is an antireflection film containing an organic component as a main component. The method of claim 3, wherein The anti-reflection film includes any one or both of silicon and a compound containing oxygen and silicon. In the inspection method which inspects the presence or absence of the residue on the said pattern by irradiating an electron beam with the mask layer in which the pattern was formed, and the to-be-tested object laminated | stacked in this order from the upper layer film, Mounting the inspected object on a mounting table in a vacuum container and evacuating the inside of the vacuum container; Irradiating an electron beam to the inspected object; Applying a reverse bias voltage, which is a negative voltage, between the object under test and the electron detecting means for detecting the reflected electrons emitted from the object under test to return secondary electrons emitted from the object under test to the object under test; , Subsequently, detecting the reflected electrons emitted from the object under test Inspection method comprising a. The method of claim 5, And said mask layer is a resist layer. The method according to claim 5 or 6, The underlayer film is an antireflection film containing an organic component as a main component. The method of claim 7, wherein The anti-reflection film includes any one or both of silicon and a compound containing oxygen and silicon. A storage medium for storing a program running on a computer, The program comprises a step group configured to execute the inspection method according to claim 5 or 6.

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