JP2009117541A - Substrate inspecting method, substrate inspecting device, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for easily discriminating sticking of residues consisting of an organic component when inspecting whether the residues stick on a pattern by irradiating with an electron beam a substrate on which a photoresist mask consisting of an organic film and having the pattern formed, an antireflective film consisting of an organic component, and a metal compound film are stacked in this order. <P>SOLUTION: An acceleration voltage for the electron beam is so calculated that, in an area where residues stick, the reaching depth of the electron beam is at a position shallower than a top surface of the metal compound film, and in an area where residues do not stick yet, the reaching depth of the electron beam is at a position deeper than a reverse surface of the antireflective film, and the substrate is irradiated with the electron beam using the acceleration voltage to obtain a secondary electron image emitted from the substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention irradiates a substrate on which a patterned photoresist mask is formed with an electron beam in a vacuum atmosphere, and thereby inspects defects in the pattern based on secondary electrons emitted from the substrate. It relates to the technical field to be performed.

In the manufacturing process of a semiconductor device, there is an optical inspection method as a defect inspection method for a resist pattern formed on a semiconductor wafer (hereinafter referred to as a wafer). When the line width of the resist pattern is, for example, 32 nm or less. In some cases, 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).

  In this SEM type substrate inspection method, as shown in FIG. 10, an electron beam (primary electron) is irradiated to 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 thereof is examined to examine the presence or absence of deposits attached to the openings of the resist pattern.

  However, the above-described SEM type substrate inspection method has the following problems. For example, as shown in FIGS. 11A and 11B, on the silicon layer 110, an insulating film 111 as a film to be etched, a metal compound film 112 as a hard mask, and reflection at the time of exposure are prevented to improve resolution. By performing exposure and development on the wafer W in which the antireflection film 113 that is an organic film and the photoresist mask 116 that is an organic film are laminated in this order from the lower side, a pattern including, for example, the groove 114 In the case where the organic material 115 is formed, the organic material 115 that is a residue of the photoresist mask 116 may adhere to the groove 114. If a concave portion is formed in the insulating film 111 by the subsequent etching process on the wafer W to which the organic matter 115 is attached, the region to which the organic matter 115 is attached may not be etched to a desired depth. Therefore, it is necessary to inspect for the presence of the organic substance 115.

  By the way, in such a laminated structure, since the photoresist mask 116 and the antireflection film 113 on the lower layer side of the photoresist mask 116 are both organic components, the organic matter 115 that is a residue of the photoresist mask 116 is also included. It is the same organic component as the antireflection film 113. Therefore, in such an inspection method using an electron beam, it is very difficult to discriminate between substances having similar compositions. Therefore, as shown in FIG. Even so, as shown in FIG. 5B, a contrast (luminance difference) to the extent that the organic substance 115 and the antireflection film 113 can be distinguished cannot be obtained.

JP 2002-216698 A

  The present invention has been made in view of such circumstances, and an object thereof is to provide a mask layer on which a pattern is formed, a first film whose components are similar to those of the mask layer, and the first film. Based on the difference in the number of secondary electrons emitted from the substrate by irradiating the electron beam to the substrate laminated in this order from above, the second film whose components are not similar to the film An object of the present invention is to provide a technique capable of reliably detecting the residue when inspecting the presence or absence of the residue on the pattern.

The substrate inspection method of the present invention comprises:
A mask layer on which a pattern is formed, a first film whose component is similar to that of this mask layer, and a second film whose component is not similar to this first film are arranged from above. In the substrate inspection method for detecting the presence or absence of a residue of the mask layer on the pattern based on the number of secondary electrons emitted from the substrate by irradiating an electron beam to the substrates stacked in order,
Inputting substrate information including film thickness information of the first film into a computer;
In the opening portion of the pattern, the electron beam does not reach the second film at a site where the residue exists, but the electron beam reaches the second film at a site where the residue does not exist. A step of obtaining an acceleration voltage of an electron beam by a computer based on the substrate information,
Next, the step of irradiating the substrate with an electron beam at the acceleration voltage determined in this step, measuring the number of secondary electrons emitted from the substrate, and detecting the presence or absence of residues on the pattern based on the measurement results; , Including.

Preferably, the mask layer is a resist mask, and the first film is an antireflection film.
The second film is preferably a metal or a metal compound.
The substrate information preferably includes at least one of material information of the first film, material information of the second film, material information of the mask layer, and film thickness information of the mask layer.
The step of obtaining the acceleration voltage is preferably a step of obtaining the acceleration voltage based on the electron arrival depth obtained from the substrate information.

The substrate inspection apparatus of the present invention is
A mask layer on which a pattern is formed, a first film whose component is similar to that of this mask layer, and a second film whose component is not similar to this first film are arranged from above. In a substrate inspection apparatus that detects the presence or absence of a residue of a mask layer on a pattern based on the number of secondary electrons emitted from the substrate by irradiating an electron beam to the substrates stacked in order,
A vacuum container for inspection having a mounting table for mounting a substrate therein;
Means for inputting substrate information including at least film thickness information of the first film;
In the opening portion of the pattern, the electron beam does not reach the second film at a site where the residue exists, but the electron beam reaches the second film at a site where the residue does not exist. Means for determining the acceleration voltage of the electron beam based on the inputted substrate information,
Means for irradiating the substrate with an electron beam at an acceleration voltage determined by the means;
Means for detecting secondary electrons emitted from the substrate.

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 substrate inspection method.

  According to the present invention, a mask layer on which a pattern is formed, a first film whose components are similar to the mask layer, and a second film whose components are not similar to the first film. When the substrate stacked in this order from above is irradiated with an electron beam and the presence or absence of residues on the pattern is inspected based on the difference in the number of secondary electrons emitted from the substrate, the pattern The electron beam does not reach the second film at the portion where the residue exists, but the electron beam reaches the second film at the portion where the residue does not exist. Since the acceleration voltage of the electron beam is calculated, and the electron beam is irradiated onto the substrate with the acceleration voltage to detect the secondary electrons emitted from the substrate, the presence or absence of a residue can be reliably determined.

  A substrate inspection method according to an embodiment of the substrate inspection apparatus of the present invention will be described. First, the wafer W that is a substrate to which the substrate inspection method is applied will be described. For example, as shown in FIG. 1A, the wafer W includes, for example, a silicon layer 11, an insulating film 12 that is a film to be etched, a metal compound film 13 that is a second film made of TiN that is a hard mask, A structure in which an antireflection film (BARC) 14 as a first film made of an organic component for preventing reflection at the time of exposure and a photoresist mask 15 made of an organic component as a mask layer are laminated in this order from the lower side. It has become. For example, a pattern is formed on the photoresist mask 15 by exposure and development, and a residue 17 which is a resist component generated during development is formed in the opening 16 as shown in FIG. Is attached. Both the photoresist mask 15 and the antireflection film 14 are made of an organic material, and therefore have similar components. On the other hand, the metal compound film 13 is a metal compound as described above, and its composition is not similar to that of the antireflection film 14.

Next, the substrate inspection apparatus of the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view showing an example of the substrate inspection apparatus. This substrate inspection apparatus includes an atmospheric transfer chamber 23, two load lock modules 22 and 22 arranged side by side, a vacuum transfer chamber 21 having a pentagonal cross-sectional shape, and, for example, one SEM in this order from the front side in the figure. The test modules 30 of the type are arranged in this order, and each is configured to be airtightly connected through the gate valve G.
On the front side of the atmospheric transfer chamber 23, a loading / unloading port for mounting a wafer carrier (hereinafter referred to as a carrier) 200 called a FOUP, which is a sealed substrate transfer container capable of storing a plurality of, for example, 25 wafers W. For example, 24 is provided in two places. 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 able to rotate and advance and retract. The arm mechanism 27 can run on the rail 28 along an array of 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. 3, 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. The power source 35 is an electron beam (EB (electron beam) emitted from the vicinity of the wafer W: This is for reducing the speed of the primary electrons).

In addition, an electron emission unit 60 that is a means 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 focusing lens 62 for focusing the electron beam emitted from the electron emission unit 60, an aperture 63 and an electron beam for restricting the passage range of the electron beam are provided between the electron emission unit 60 and the mounting table 32. And a scanning coil 64 for scanning. Further, an electron detection means 69 that is a means for detecting secondary electrons emitted from the wafer W by irradiation of an electron beam is provided between the mounting table 32 and the scanning coil 64.
An exhaust port 66 is formed at the bottom of the vacuum vessel 31, and a vacuum pump 67 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 board inspection apparatus includes a control unit 2 composed of a computer, for example. The control unit 2 includes an input unit 3, a program storage unit 4, a data storage unit 5, a CPU 7, and a memory 6 that are means for inputting board information. First, the reason why the residue 17 attached to the opening 16 of the wafer W can be reliably discriminated in this substrate inspection apparatus will be described below based on the results obtained from the examples described later.

  When the wafer W having the laminated structure shown in FIG. 1 described above is irradiated with an electron beam under a low acceleration voltage, secondary electrons from the surface layer of the wafer W are obtained. The exposed portion of the surface of the wafer W is composed of organic components (photoresist mask 15, antireflection film 14 or residue 17). Here, in general, an electron beam is largely absorbed in a metal compound having electrical conductivity and the amount of secondary electrons emitted is reduced. On the other hand, in an organic material having no electrical conductivity, the amount of absorption is small. Therefore, the amount of secondary electrons emitted tends to increase. Therefore, the amount of secondary electrons obtained from the photoresist mask 15, the antireflection film 14, or the residue 17 is increased in the exposed portion of the surface of the wafer W as compared with a conductive material such as a metal compound. On the other hand, since the photoresist mask 15, the antireflection film 14, and the residue 17 are all made of an organic material and have similar compositions, the secondary mask obtained between the photoresist mask 15, the antireflection film 14, and the residue 17 is obtained. The difference in the number of electrons is extremely small (see FIG. 12B described above).

  For example, when the acceleration voltage of the electron beam is increased with respect to such a wafer W, it is considered that the arrival depth reached by the electron beam becomes deeper. This has been analyzed by simulation using Monte Carlo simulation. Therefore, the obtained secondary electrons are also emitted from the region that enters the inside from the surface layer of the wafer W. For this purpose, the acceleration voltage is gradually increased, and the incident depth of the electron beam is gradually increased, so that the surface of the photoresist mask 15 and the antireflection film 14 (the bottom surface of the opening portion 16) is changed to the inside. A secondary electron image is obtained in accordance with the depth position. And if the depth of the bottom part of the opening part 16 is a uniform depth position, since the arrival depth of an electron beam will become uniform, if the acceleration voltage is raised further, the electron irradiated to the opening part 16 will be carried out. The line passes through the antireflection film 14 uniformly and reaches the upper end surface of the metal compound film 13.

  On the other hand, when the electron beam is irradiated onto the wafer W with an acceleration voltage at which the electron beam reaches the depth position of the upper end surface of the metal compound film 13 in the opening 16 as described above, the opening in the photoresist mask 15 is obtained. In the region where 16 is not formed, the photoresist mask 15 becomes an obstacle, and for example, the electron beam reaches only a depth position in the photoresist mask 15. Accordingly, as described above, the metal compound film 13 emits a small amount of secondary electrons, while the photoresist mask 15 increases the amount of secondary electrons emitted. Therefore, the openings 16 in the photoresist mask 15 are formed. An extremely large luminance difference is obtained between the non-exposed region and the bottom surface of the opening 16. From this, the ridgeline of the opening 16 can be clearly observed by increasing the acceleration voltage so that the electron beam reaches the metal compound film 13. At this time, since the arrival depth of electrons varies, the number of electrons reaching the metal compound film 13 increases as the acceleration voltage of the electron beam is gradually increased. As shown in FIG. 7, the luminance obtained at the opening 16 gradually decreases.

  By the way, as described above, since the residue 17 is attached to the bottom of the opening 16, in the region where the residue 17 is attached, the residue 17 becomes an obstacle and the residue 17 is attached. The reach of the electron beam is shallower than that in the non-existing region. Therefore, even if an electron beam is irradiated with an acceleration voltage reaching the depth position of the upper end surface of the metal compound film 13 in a region where the residue 17 is not attached, the electron beam is irradiated in the region where the residue 17 is attached. Does not reach the metal compound film 13. Therefore, as described above, the amount of secondary electrons emitted from the metal compound film 13 is small, while the amount of secondary electrons emitted from the organic substance such as the residue 17 is large. However, in the region where the residue 17 is not attached, the amount of secondary electrons emitted is reduced, and thus the luminance difference between the two regions is increased.

  As described above, in the opening 16, the reaching depth of the electron beam differs depending on the presence or absence of the residue 17, while the secondary material obtained between the organic substance such as the antireflection film 14 and the residue 17 and the metal compound film 13. The difference in the number of electrons is extremely large. Therefore, as shown in FIG. 4A, in the opening 16, the electron beam reaches the inside of the metal compound film 13 in the region where the residue 17 is not attached, and is reflected in the region where the residue 17 is attached. By adjusting the acceleration voltage of the electron beam so that the electron beam only reaches the inside of the prevention film 14, the difference in luminance increases depending on the presence or absence of the residue 17, as shown in FIG. It is considered that the residue 17 can be easily and reliably identified. In the region where the residue 17 is attached, the acceleration voltage of the electron beam is adjusted so that the electron beam reaches only the photoresist mask 15 or the antireflection film 14, so that the opening 16 of the photoresist mask 15 is formed. In the region where no film is formed, the electron beam is reflected, for example, within the photoresist mask 15 and does not reach the metal compound film 13.

  By the way, when adjusting the acceleration voltage of the electron beam as described above, most of the electron beam needs to pass through the antireflection film 14 in the region where the residue 17 is not attached in the opening 16 as described above. There is. Therefore, it can be seen that, for example, as the antireflection film 14 becomes thicker, the acceleration voltage required to transmit the antireflection film 14 increases. On the other hand, for example, when the film thickness of the antireflection film 14 is constant and the acceleration voltage is gradually increased with respect to the antireflection film 14, the amount of electron beams reaching the metal compound film 13 gradually increases. It can be seen that the number of secondary electrons obtained from the metal compound film 13 gradually decreases. FIG. 5 is a diagram schematically showing a correlation among the thickness of the antireflection film 14 described above, the acceleration voltage of the electron beam, and the amount of secondary electrons emitted from the wafer W. As described above, the luminance level L3 in the opening 16 is changed from the luminance level L1 in the photoresist mask 15 as the thickness of the antireflection film 14 is decreased and the acceleration voltage of the electron beam is increased. The brightness gradually decreases to the luminance level L2 in the metal compound film 13. In this example, each wafer W provided with an antireflection film 14 having a film thickness of t1, t2 or t3 (t1 <t2 <t3) is opened when an electron beam is irradiated with various acceleration voltages. The luminance level L3 of the secondary electrons emitted from the part 16 is shown. Such data D can be obtained by, for example, an experiment performed in advance or the simulation described above.

  Therefore, the film thickness t1 of the antireflection film 14 on the wafer W, the luminance of secondary electrons emitted from the region where the residue 17 is attached, and the luminance of secondary electrons emitted from the region where the residue 17 is not attached. By comparing the set value of the difference dL with this data D, the acceleration voltage of the electron beam necessary for clearly discriminating the residue 17 is obtained. In this example, by setting the acceleration voltage to 800 eV or more with respect to the antireflection film 14 having a film thickness of t2, the luminance set in the region where the residue 17 is attached and the region where the residue 17 is not attached. It can be seen that the difference dL is obtained.

  By the way, such data D is obtained based on the emission amount of secondary electrons, and therefore varies depending on the composition of the photoresist mask 15, the composition of the antireflection film 14, and the composition of the metal compound film 13. It turns out that it becomes a value. Therefore, in this embodiment, the control unit 2 includes data D1, D2,..., Dn obtained by experiments and simulations for such data D in accordance with various combinations of materials in the data storage unit 5. Yes.

  Subsequently, returning to the description of the control unit 2 described above, the input unit 3 is, for example, a keyboard or a touch panel for an operator to input substrate information such as information about the wafer W described above. Material information about the metal compound film 13, the antireflection film 14, and the photoresist mask 15, for example, composition information, density, formula weight, mass number, atomic weight, and the like, and the antireflection film 14 and the photoresist mask 15. The film thickness information and the luminance difference dL between the region where the residue 17 is adhered and the region where the residue 17 is not adhered can be input.

  The program storage unit 4 includes an EB condition calculation program 4A and a defect measurement program 4B, which are means for obtaining the acceleration voltage of the electron beam. The EB condition calculation program 4A uses the information input to the input unit 3 described above and the data D stored in the data storage unit 5 to detect defects 17 in the photoresist mask 15, that is, residues 17 adhering in the openings 16. As described above, the electron difference is set so as to have a preset secondary electron brightness difference dL between the region where the residue 17 is attached and the region where the residue 17 is not attached. This is a program for calculating the acceleration voltage of a line. The luminance difference dL may be set in advance, but may be set by inputting it to the input unit 3 for each lot of wafers W, for example.

  Specifically, the EB condition calculation program 4A uses the material information of the photoresist mask 15, the antireflection film 14 and the metal compound film 13 input to the input unit 3 as data D corresponding to these material information. Read from the storage unit 5. Further, in this data D, as shown in FIG. 5 described above, it is necessary to detect a defect from the film thickness t of the antireflection film 14 input to the input unit 3 and the set value of the luminance difference dL. The minimum acceleration voltage of the electron beam (800 eV in FIG. 5) is obtained. In order to minimize damage to the wafer W due to the electron beam irradiation, the acceleration voltage of the electron beam is preferably set to the lowest level at which the residue 17 can be detected. The EB condition calculation program 4A sets the determination level of the residue 17 from the data D in FIG. 5 and the set value of the luminance difference dL. This determination level is, for example, a value obtained by subtracting half of the set value of the luminance difference dL from the luminance corresponding to the photoresist mask 15.

  The EB condition calculation program 4A is configured to calculate the upper limit value of the acceleration voltage that can inspect defects from the film thickness information of the photoresist mask 15. That is, as can be seen from the graph of FIG. 5, as the acceleration voltage of the photoresist mask 15 is increased, the photoresist mask 15 eventually passes through the photoresist mask 15 and the antireflection film 14 is exposed ( Similar to the opening 16), the luminance decreases. Then, the limit value of the acceleration voltage at which the luminance starts to decrease becomes lower as the film thickness of the photoresist mask 15 becomes thinner. In the same figure, the threshold value approaches or overlaps the luminance decrease region of the antireflection film 14. In that case, depending on the magnitude of the acceleration voltage, the set value of the luminance difference dL may not be sufficiently large. Therefore, the film thickness information of the photoresist mask 15 is input to the input unit 3, and the acceleration voltage immediately before reaching the region where the luminance difference dL described above cannot be sufficiently large is obtained as the upper limit value. In the case where the process for reducing the thickness of the photoresist mask 15 is not performed, the thickness information of the photoresist mask 15 may not be input.

  The defect measurement program 4B is a program for inspecting the wafer W for defects by controlling the operation sequence of the transfer arm mechanism 27, the transfer arm mechanism 50 and the gate valve G, and each part of the inspection module 30. The programs 4A and 4B are stored in the storage unit 8 which is a storage medium such as a hard disk, a compact disk, a magnet optical desk (MO), and a memory card, and installed in the control unit 2 from the storage unit 8.

Next, a substrate inspection method using the above-described substrate inspection apparatus will be described.
First, the carrier 200 storing a plurality of wafers W is attached to the carry-in / out port 24. In addition, for example, the operator can input the material information of the metal compound film 13, the antireflection film 14 and the photoresist mask 15 and the film thickness information of the antireflection film 14 and the photoresist mask 15 with respect to the input unit 3. The luminance difference dL is input. Then, a shutter (not shown) of the carry-in port 24 is opened, one wafer W is taken out from 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. 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. The above-described EB condition calculation program 4A reads the data D (see FIG. 5) corresponding to the material information of the metal compound film 13, the antireflection film 14 and the photoresist mask 15 from the data storage unit 5, and this The acceleration voltage of the electron beam is calculated by comparing the data D with the film thickness information of the antireflection film 14 and the set value of the luminance difference dL.

  Then, as shown in FIG. 4A, the defect measurement program 4B irradiates the wafer W with the electron beam at the calculated acceleration voltage, and the secondary electrons emitted from the wafer W are detected by the electron detection means 69. Detect by. As described above, the defect measurement program 4B sets, for example, a value obtained by subtracting half of the set value of the luminance difference dL from the luminance value corresponding to the photoresist mask 15 as a threshold value. The threshold value is compared with the above luminance. If the luminance is lower than this threshold value, for example, “no defect” is determined, and if the luminance is higher than the threshold value, for example, “defect” is determined.

Next, the wafer W is sequentially moved in the horizontal direction by the mounting table 32, and similarly the luminance of secondary electrons emitted from the surface of the wafer W is detected, and this luminance is compared with a threshold value. Thus, an inspection result map corresponding to the presence or absence of adhesion of the residue 17 at each coordinate position of the wafer W is obtained.
Then, the wafers W are unloaded in the order reverse to the order of loading into the inspection module 30.

According to the above-described embodiment, the wafer W on which the photoresist mask 15, the antireflection film 14, and the metal compound film 13 are laminated in this order from the upper side is irradiated with an electron beam. In detecting the residue 17 adhering in the opening 16 based on the difference in the number of secondary electrons emitted from W, in the region where the residue 17 is attached, the electron beam is transmitted only to the antireflection film 14. On the other hand, in the region where the residue 17 is not attached, the brightness difference of the secondary electrons is increased so that the residue 17 can be clearly identified by setting the acceleration voltage to transmit the electron beam to the metal compound film 13. Therefore, the presence or absence of the residue 17 can be reliably detected by irradiating the wafer W with this acceleration voltage with an electron beam and measuring the luminance of secondary electrons emitted from the wafer W.
In calculating the acceleration voltage, the data D is stored in advance in the data storage unit 5 and the data D is compared with the input information. Therefore, the inspection time is shortened, and therefore the throughput is increased. In addition, the damage caused by the irradiation of the electron beam onto the wafer W can be reduced.

  By the way, the same effect as in the present invention can be obtained by irradiating the wafer W with an electron beam at a low acceleration voltage first and then gradually increasing the acceleration voltage until a brightness difference is obtained so that the residue 17 can be discriminated. However, in such a method, it is considered that the measurement time becomes longer and the damage caused by the increase of the electron beam irradiation amount on the wafer W is considered to increase. Therefore, the acceleration voltage is calculated in advance as described above. It is preferable to keep it.

In the above example, a plurality of data D1, D2,... Dn are stored in the data storage unit 5, and the information input to the input unit 3 is collated with the data D, so that Although the acceleration voltage is calculated, the control unit 2 has simulation means based on the above-described Monte Carlo simulation, and the acceleration voltage of the electron beam is calculated each time based on the information input to the input unit 3. May be. Further, the acceleration voltage may be calculated based on the data D, and the acceleration voltage may be calculated with higher accuracy by this simulation.
In addition to TiN, the metal compound film 13 may be other inorganic material such as a metal compound film other than TiN or a metal film as long as it has a composition capable of obtaining a luminance difference from an organic material. Specifically, Ti etc. can be mentioned, for example. Further, the present invention can be applied to the metal compound film 13 as long as it is a film mainly composed of an inorganic component other than the organic component and has a composition capable of obtaining a luminance difference from the residue 17. In the present invention, the mask layer and the first film are not limited to organic substances, and may be applied if the composition is similar to each other, that is, the amount of secondary electron emission is equal. . Therefore, the mask layer and the first film may be a film mainly containing an inorganic component, and the second film may be a film mainly containing an organic component.

  In the above example, film quality information about the photoresist mask 15, the antireflection film 14, and the metal compound film 13 is input to the input unit 3. For example, information about whether the film is an organic film or an inorganic film. You may make it input only. Furthermore, the difference between the number of secondary electrons obtained from the photoresist mask 15 and the number of secondary electrons obtained from the metal compound film 13 is extremely large. Therefore, the number of secondary electrons obtained from the residue 17 and the metal compound film 13 are obtained. If the number of secondary electrons to be generated is also extremely large, the material information of the photoresist mask 15 may not be input to the input unit 3.

In addition, the brightness | luminance of the secondary electron obtained when an electron beam is irradiated has the characteristic which has a peak in a specific acceleration voltage. Since such characteristics differ depending on the material, in the above example, the amount of secondary electrons emitted from the organic component increases (the luminance is high), and the amount of secondary electrons emitted from the metal compound film 13. However, since the brightness of the secondary electrons obtained may be reversed, the value to be compared with the data D stored in the data storage unit 5 is not the absolute value of the brightness. It is preferable to set the luminance difference dL.
As the above-mentioned data D, as shown in FIG. 5 described above, the acceleration voltage and the luminance of the electron beam are respectively set on the X axis and the Y axis, and the film thickness is variously changed on the graph. As shown in FIG. 6, for example, the graph may be redrawn by setting the film thickness of the antireflection film 14 to the X axis.

  Next, an experiment conducted to confirm how the brightness of the secondary electrons obtained changes when the acceleration voltage of the electron beam applied to the wafer W is gradually increased will be described. In the following experiment, a wafer W having the same stacked structure as that of FIG. 1 described above was used.

(Experimental example 1)
A predetermined pattern was formed on the photoresist mask 15 of the wafer W described above. At this time, the metal compound film 13, the antireflection film 14 and the photoresist mask 15 were laminated so that their film thicknesses were 40 nm, 80 nm and 150 nm, respectively. Further, regarding the material of each film, the metal compound film 13 was TiN, the antireflection film 14 was SiOCH, and the photoresist mask 15 was polymethacrylate.
The wafer W was irradiated with an electron beam by gradually increasing the acceleration voltage from 600 eV to 1600 eV in the inspection module 30 described above. And the change of the quantity (luminance) of the secondary electron obtained in the photoresist mask 15 and the surface (opening part 16) of the antireflection film 14 was measured.

  As a result, as shown in FIG. 7, substantially the same level of secondary electron brightness was obtained at 600 eV or less. Therefore, it was found that with such a low acceleration voltage, the brightness difference between the photoresist mask 15 and the antireflection film 14 is small, and even if the residue 17 or the like is adhered, it cannot be determined.

  On the other hand, when the acceleration voltage was increased, the brightness was hardly changed in the photoresist mask 15, but the brightness was lowered in the antireflection film 14, and thus the brightness difference between the two was increased. From this, as described above, as the acceleration voltage is increased, the arrival depth of the electron beam becomes deeper, and the amount of the electron beam that passes through the antireflection film 14 and reaches the metal compound film 13 at the opening 16 is increased. It is considered that the luminance gradually increased, and therefore the amount of electron beams absorbed by the metal compound film 13 gradually increased and the luminance decreased. On the other hand, on the surface of the photoresist mask 15, it is considered that the photoresist mask 15 hinders the electron beam from reaching only the upper layer of the lower surface of the antireflective film 14, so that the luminance is not lowered. From this, it is considered that the luminance difference between the photoresist mask 15 and the antireflection film 14 (opening 16) has increased as described above.

  Then, at an acceleration voltage of 1400 eV or higher, the luminance difference between the two does not increase any more. Therefore, at this acceleration voltage (1400 eV), the electron beam completely reaches the depth position where the metal compound film 13 is formed at the opening 26. It is thought that it reached. In FIG. 7, the luminance is shown as a gray level.

  The SEM image obtained in this experiment is shown in FIG. When the acceleration voltage was 800 eV, the photoresist mask 15 and the antireflection film 14 on the surface layer of the wafer W were observed as shown in FIG. On the other hand, at 1300 eV, the photoresist mask 15 was confirmed as it was as shown in FIG. 5B, but it was found that the metal compound film 13 on the lower layer side of the antireflection film 14 can be confirmed at the opening 16. Therefore, a very large luminance difference is produced between the photoresist mask 15 and the opening 16. If the electron beam continues to be irradiated, correct evaluation cannot be performed due to charge-up or damage to the film. FIGS. 6A and 6B are schematic diagrams showing SEM images taken of different regions. .

(Experimental example 2)
Next, the wafer W having holes formed in the photoresist mask 15 was irradiated with an electron beam while gradually increasing the acceleration voltage in the same manner. At this time, the metal compound film 13, the antireflection film 14 and the photoresist mask 15 were laminated so that their film thicknesses were 40 nm, 80 nm and 150 nm, respectively. Further, regarding the material of each film, the metal compound film 13 was TiN, the antireflection film 14 was SiOCH, and the photoresist mask 15 was polymethacrylate.

  9A and 9B show SEM images when the wafer W is observed in the same manner with acceleration voltages of 800 eV and 1300 eV. In this wafer W, as in the above example, a sufficient luminance difference was not obtained at 800 eV, but an extremely clear image was obtained at 1300 eV. In FIG. 9 as well, the imaging area is changed in (a) and (b).

  From the above, in the wafer W having such a laminated structure, the reaching depth of the electron beam is the extreme surface layer of the wafer W at an acceleration voltage of 800 eV, while the single film of the antireflection film 14 is completely transmitted at 1300 eV. In addition, it was found that the reaching depth is such that it does not pass through the laminated film of the photoresist mask 15 and the antireflection film 14. Therefore, in the case where the residue 17 is attached to the opening 16 in the wafer W, the acceleration voltage is set in the range of 800 eV to 1300 eV, and the SEM image is observed, so that the residue 17 can be clearly identified. I knew that I could distinguish. Even when the acceleration voltage of the electron beam was increased, almost no change in luminance was observed for the contour (edge) of the photoresist mask 15.

It is a longitudinal cross-sectional view which shows an example of the board | substrate applied to the board | substrate inspection method of this invention. It is a cross-sectional view which shows the board | substrate inspection apparatus concerning embodiment of this invention. It is explanatory drawing which shows an example of the inspection module of said board | substrate inspection apparatus. It is a schematic diagram which shows the mode of the board | substrate when test | inspecting the said board | substrate. It is a characteristic view which shows an example of the data stored in the data storage part in said test | inspection module. It is a characteristic view which shows an example of the data stored in the data storage part in said test | inspection module. It is a characteristic view showing the brightness | luminance difference obtained in the Example of this invention. It is the schematic diagram which copied the SEM image obtained in said Example. It is the schematic diagram which copied the SEM image obtained in said Example. It is a longitudinal cross-sectional view which shows an example of the conventional board | substrate inspection apparatus. It is a longitudinal cross-sectional view which shows an example of the board | substrate test | inspected in the said conventional board | substrate inspection apparatus. It is a schematic diagram which shows a mode that a board | substrate is test | inspected in the said conventional board | substrate inspection apparatus.

Explanation of symbols

2 Control section 3 Input section 4 Program storage section 4A EB condition calculation program 4B Defect measurement program 5 Data storage section D Data 11 Silicon layer 12 Insulating film 13 Metal compound film 14 Antireflection film 15 Photoresist mask 16 Opening 17 Residue 30 Inspection Module 31 Vacuum vessel 35 Power supply 61 Power supply 69 Electron detection means

Claims (16)

A mask layer on which a pattern is formed, a first film whose component is similar to that of this mask layer, and a second film whose component is not similar to this first film are arranged from above. In the substrate inspection method for detecting the presence or absence of a residue of the mask layer on the pattern based on the number of secondary electrons emitted from the substrate by irradiating an electron beam to the substrates stacked in order,
Inputting substrate information including film thickness information of the first film into a computer;
In the opening portion of the pattern, the electron beam does not reach the second film at a site where the residue exists, but the electron beam reaches the second film at a site where the residue does not exist. A step of obtaining an acceleration voltage of an electron beam by a computer based on the substrate information,
Next, irradiating the substrate with an electron beam at the acceleration voltage determined in this step, measuring the number of secondary electrons emitted from the substrate, and detecting the presence or absence of residues on the pattern based on the measurement results; The board | substrate inspection method characterized by including these.   The substrate inspection method according to claim 1, wherein the mask layer is a resist mask, and the first film is an antireflection film.   The substrate inspection method according to claim 1, wherein the second film is a metal or a metal compound.   The substrate inspection method according to claim 1, wherein the substrate information includes material information of the first film.   5. The substrate inspection method according to claim 1, wherein the substrate information includes material information of the second film.   The substrate inspection method according to claim 1, wherein the substrate information includes material information of the mask layer.   The substrate inspection method according to claim 1, wherein the substrate information includes film thickness information of the mask layer.   8. The substrate inspection method according to claim 1, wherein the step of obtaining the acceleration voltage is a step of obtaining the acceleration voltage based on an electron arrival depth obtained from the substrate information. . A mask layer on which a pattern is formed, a first film whose component is similar to that of this mask layer, and a second film whose component is not similar to this first film are arranged from above. In a substrate inspection apparatus that detects the presence or absence of a residue of a mask layer on a pattern based on the number of secondary electrons emitted from the substrate by irradiating an electron beam to the substrates stacked in order,
A vacuum vessel for inspection having a mounting table for mounting a substrate therein;
Means for inputting substrate information including at least film thickness information of the first film;
In the opening portion of the pattern, the electron beam does not reach the second film at a site where the residue exists, but the electron beam reaches the second film at a site where the residue does not exist. Means for determining the acceleration voltage of the electron beam based on the inputted substrate information,
Means for irradiating the substrate with an electron beam at an acceleration voltage determined by the means;
And a means for detecting secondary electrons emitted from the substrate.   The substrate inspection apparatus according to claim 9, wherein the mask layer is a resist mask, and the first film is an antireflection film.   The substrate inspection apparatus according to claim 9, wherein the second film is a metal or a metal compound.   The substrate inspection apparatus according to claim 9, wherein the substrate information includes material information of the first film.   The substrate inspection apparatus according to claim 9, wherein the substrate information includes material information of the second film.   The substrate inspection apparatus according to claim 9, wherein the substrate information includes material information of the mask layer.   The substrate inspection apparatus according to claim 9, wherein the substrate information includes film thickness information of the mask layer. A storage medium for storing a program that runs on a computer,
9. A storage medium, wherein the program includes a group of steps so as to execute the substrate inspection method according to claim 1.

Images