JP2018006100A - Ultraviolet ray irradiation apparatus and vacuum vessel equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove contaminants on a sample surface in the observation, analysis, etc. of a sample.SOLUTION: A spot irradiation type excimer lamp 100 is arranged in a sample chamber 40 of a scanning electron microscope 10, and mounted to a sample chamber side wall 40S by a support member 120 that comprises a fixed part 122 and a connecting part 124. The mounting position of the excimer lamp 100 is adjusted such that a light emitting surface 105 of the excimer lamp faces a sample surface 50S.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus for removing contaminants attached to a sample to be observed and analyzed by a scanning electron microscope or the like, and more particularly to contaminant removal by ultraviolet irradiation.

  When a sample (for example, a semiconductor integrated circuit, a reticle, or the like) is observed and analyzed using a scanning electron microscope or the like, the sample is placed in a sample chamber that is a vacuum vessel and observed and analyzed. At this time, contaminants such as carbon compounds adhere to and accumulate on the sample surface due to the sample being left in the atmosphere, gas diffusion from the vacuum container, or irradiation of primary electrons. If contamination (contamination) occurs, it becomes an obstacle to observation and analysis, so it is necessary to remove the contamination.

  As a method for removing contaminants, a method of irradiating a sample with ultraviolet light is known (see Patent Document 1). There, a vacuum container different from the sample chamber is provided, a sample is arranged, and a lamp unit for irradiating ultraviolet light is arranged adjacent to the vacuum container. Then, ultraviolet light is irradiated into the sample chamber through the irradiation window of the vacuum vessel.

  By irradiating the sample surface with ultraviolet rays, molecular bonds of contaminants are broken, oxygen remaining in the vacuum vessel is activated, and ozone is generated, thereby removing contaminants. The support for supporting the sample is installed so that it can be raised and lowered, and its height, that is, the distance from the lamp unit is adjusted according to the sample.

JP 2002-195965 A

  When the sample chamber is irradiated from the outside of the sample chamber through the irradiation window, the ultraviolet light is attenuated by irradiating the portion where the contaminants are not attached, and the contamination removal yesterday is reduced. In addition, ultraviolet light is also irradiated to the part of the sample surface outside the irradiation target area and to which no contaminant is attached, causing unnecessary gas generation and sample damage. Furthermore, ultraviolet rays are irradiated to components such as a sample stage installed in the sample chamber, causing unnecessary gas emission and component deterioration.

  Therefore, it is required to suppress sample damage and generation of unnecessary gas without lowering the contaminant removal function in the sample contaminant removal process by ultraviolet irradiation.

  The ultraviolet irradiation device of the present invention includes an ultraviolet light source that emits ultraviolet light from an ultraviolet light emitting surface, a sample chamber in which a sample is disposed, and a support member that supports the ultraviolet light source so that the ultraviolet light emitting surface faces the sample. The ultraviolet light radiation surface is exposed in the sample chamber at a position closer to the sample than the sample chamber wall.

  Instead of illumination where the ultraviolet light source radiates the sample chamber as a whole, it is possible to irradiate ultraviolet light in an appropriate range by providing a configuration for irradiating the desired range. Become. For example, considering that the ultraviolet light is irradiated only on the contaminant removal portion, it is possible to position the ultraviolet light source so as to irradiate a predetermined region of the sample surface with the ultraviolet light.

  The arrangement of the ultraviolet light source is arbitrary on condition that the radiation surface is exposed to the inside of the sample chamber. For example, an ultraviolet light source may be installed in the sample chamber, and the support member can be configured to connect to the inner wall of the sample chamber.

  As a configuration of the ultraviolet light source, any light source can be applied, and a light source having an ultraviolet light emitting surface facing in one direction can be applied. For example, the ultraviolet light source can be constituted by an excimer lamp having a bottomed cylindrical outer tube with the ultraviolet light emitting surface as a bottom and emitting ultraviolet light from the ultraviolet light emitting surface along the lamp axis. .

  For such an excimer lamp, in consideration of lamp heating during ultraviolet irradiation, efficient ultraviolet irradiation, and the like, the outer tube is surrounded, and at least one of conductivity, ultraviolet light reflection characteristics, and thermal conductivity is included. It can comprise so that it may provide the lamp attachment member which has these. There is no blocking member between the lamp and the sample, and if the lamp is placed inside the sample chamber, which is a vacuum vessel, so that ultraviolet light from the lamp is directly irradiated onto the sample surface, it is insulated by vacuum. As a result, the luminous efficiency is lowered due to the overheating of the lamp, and the contaminant removal function is lowered. Therefore, by providing at least one of conductivity, ultraviolet light reflection characteristics, and thermal conductivity, it is possible to prevent the lamp from being overheated. The lamp mounting member can be formed of a member that covers or houses the lamp portion, such as a housing or a container. In addition, it is possible to provide such an attachment member also about light sources other than an excimer lamp.

  In consideration of simplifying the configuration of the excimer lamp, the lamp mounting member can be configured as an outer electrode of the excimer lamp having conductivity. Further, in order to efficiently derive light from the ultraviolet light emitting surface, an ultraviolet light reflecting member may be provided on the inner surface of the lamp mounting member. In consideration of preventing the lamp from overheating, a heat conductive member may be provided on the lamp mounting member. Furthermore, a heat insulating member may be provided so as to cover the lamp mounting member.

  The configuration of the supporting member is arbitrary, and it is desirable that the supporting member can be effectively adjusted to a light source posture in which the ultraviolet light emitting surface is directed to the sample. In the support member, it is possible to provide an adjustment mechanism capable of changing at least one of the direction of the ultraviolet light emitting surface with respect to the sample surface and the distance between the ultraviolet light emitting surface and the sample surface.

  For example, the support member can support the ultraviolet light source so that the angle of the ultraviolet light source with respect to the inner wall of the sample chamber can be adjusted. In addition, a support member having a fixing portion fixed to the inner wall of the sample chamber and a connecting portion for connecting the light source holding portion to the inner wall of the sample chamber is configured, and the angle of the ultraviolet light source with respect to the connecting portion can be adjusted. You may make it support by a connection part.

  According to another aspect of the present invention, there is provided a sample contaminant removal method by ultraviolet irradiation, wherein an excimer lamp that emits ultraviolet light from an ultraviolet light emitting surface is directed to a sample chamber in which the sample is disposed, In the state where the ultraviolet light emitting surface is exposed to the internal space of the sample chamber at a position closer to the sample than the inner wall of the sample chamber, ultraviolet light is irradiated from the ultraviolet light emitting surface toward the sample. Such a sample contaminant removal method can be applied to various apparatuses including a sample chamber such as an electron microscope and a vacuum vessel.

  An apparatus (vacuum container apparatus) provided with a vacuum container according to another aspect of the present invention can be applied to various apparatuses including a sample chamber such as an electron microscope, and includes a vacuum container in which a sample is disposed and ultraviolet light. An ultraviolet light source that radiates from the ultraviolet light emitting surface; and a support member that supports the ultraviolet light source so that the ultraviolet light emitting surface faces the sample disposed in the vacuum container. It is exposed at a position closer to the sample than the inner wall of the vacuum vessel.

  According to the present invention, sample contaminants can be effectively removed in sample observation, analysis, and the like.

It is the figure which showed the schematic structure centering on the sample chamber of the scanning electron microscope which is this embodiment. It is the top view which looked at the excimer lamp from the light emission surface side. FIG. 3 is a cross-sectional view of an excimer lamp along III-III ′ in FIG. 2. FIG. 3 is a cross-sectional view of the excimer lamp along IV-IV ′.

  Hereinafter, an electron microscope equipped with an ultraviolet irradiation device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration centering on a sample chamber of a scanning electron microscope according to the present embodiment. FIG. 2 is a plan view of the excimer lamp viewed from the light emitting surface side.

  The scanning electron microscope 10 includes a lens barrel 20 including an electron gun, a focusing lens, a scanning deflector, an objective lens (all not shown), a secondary electron detector 30, and a sample chamber 40. In the sample chamber 40, a sample (for example, a reticle or a semiconductor circuit) 50 to be observed is mounted on a support base 60.

  The lens barrel 20 that emits the primary electron beam is attached in a state in which the tip 20B is fitted in the center of the upper wall 40A of the sample chamber 40. The secondary electron detector 30 for detecting secondary electrons emitted from the sample 50 is attached to the side of the lens barrel tip 20B through the upper wall 40A.

  The lower wall 40B of the sample chamber 40 is provided with an exhaust pipe 42 connected to a vacuum pump (not shown) for evacuating the inside of the sample chamber 40. The exhaust pipe 42 allows the sample chamber 40 to have a primary electron beam. The vacuum container is maintained in a high vacuum state through which the secondary electron beam can pass.

  The preliminary exhaust chamber 45 adjacent to the sample chamber 40 is connected to the sample chamber 40 via an opening 41 formed in the side wall 40S of the sample chamber 40, and a gate valve (not shown) opens and closes the opening 41. . The sample 40 can be taken in and out by the opening 46 formed in the side wall of the preliminary exhaust chamber 45, and the opening 46 is opened and closed by an on-off valve (not shown). An exhaust pipe 47 connected to a vacuum pump (not shown) for evacuating is formed on the lower wall of the preliminary exhaust chamber 45.

  The primary electron beam emitted from the electron gun in the lens barrel 20 is focused on the surface 50S of the sample 50 through the focusing lens and the objective lens, and is scanned with respect to a predetermined region of the sample surface 50S by the scanning deflector. . Secondary electrons emitted from the sample surface 50 </ b> S by scanning are detected by the secondary electron detector 30. By applying conventionally known image processing to the detected secondary electron signal, the surface shape of the sample 50 is imaged and the sample image is displayed on a monitor (not shown).

  A cylindrical excimer lamp 100 is disposed inside the sample chamber 40 and is supported by a support member 120 attached to the sample chamber side wall 40S. The excimer lamp 100 that emits light by dielectric barrier discharge or capacitive discharge is formed of a single light source here, and irradiates 172 nm ultraviolet light in one direction along the lamp axis from the light emitting surface 105. It is configured as a mold lamp.

  The excimer lamp 100 is disposed in the vicinity of the corner of the upper wall 40A that does not hinder the irradiation of the electron beam from the lens barrel 20 and the detection of the secondary electrons of the secondary electron detector 30. Here, the light emitting surface 105 is a sample. It is positioned so as to face the surface 50S. That is, the excimer lamp 100 is positioned so that the ultraviolet light is irradiated obliquely upward with respect to the sample surface 50S.

  The support member 120 that supports the excimer lamp 100 includes a fixing portion 122 that is fixed to the sample chamber side wall 40S and a connecting portion 124, and is formed of a material having thermal conductivity such as a metal such as aluminum. The support member 120 supports the excimer lamp 100 so that the position and posture of the excimer lamp 100 in the sample chamber 40 can be adjusted.

  Specifically, the connecting portion 124 is fixed to the fixing portion 122 so that the attachment angle can be adjusted, and is fixed by tightening a screw (not shown) on the shaft B1. On the other hand, the connecting portion 124 holds the excimer lamp 100 on one side surface thereof, and the excimer lamp 100 is fixed to the connecting portion 124 by tightening a screw (not shown) on the shaft B2.

  Accordingly, by adjusting the angles of the connecting portion 124 and the excimer lamp 100 around the two axes B1 and B2, the attitude of the excimer lamp 100 in the sample chamber 40, more specifically, the light emitting surface 105 with respect to the sample surface 50S is adjusted. An angle and its distance interval are set.

  The excimer lamp 100 includes a cylindrical lamp mounting member 110 on the outer peripheral portion thereof, and the light source portion of the excimer lamp 100 is provided in the internal space 40T of the sample chamber 40 except for the light emitting surface 105 and the sealing portion 100B on the opposite side. I try not to expose it. Here, the lamp mounting member 110 is configured by integrating a pair of semi-cylindrical members with fastening screws (not shown).

  FIG. 3 is a cross-sectional view of the excimer lamp taken along the line III-III 'of FIG. FIG. 4 is a cross-sectional view of the excimer lamp taken along IV-IV ′ in FIG. 3.

  Excimer lamp 100 includes an inner tube 130 and an outer tube 140 made of a dielectric material such as quartz glass. The outer tube 140 has a flat light emitting surface 105 and a sealing portion 100B formed by welding and forming with the inner tube 130 by the outer tube diameter, and accommodates the inner tube 130 inside the tube.

  In the vicinity of the center of the inner wall of the inner tube 130, a strip-like inner electrode 120 'such as Mo is embedded, and the inner electrode 120 is connected to the feeder line 120L. The arc tube composed of the inner tube 130 and the outer tube 140 forms a discharge space 135, and a rare gas such as Xe or a mixed gas of a rare gas and a halogen gas is enclosed in the discharge space 135.

  The lamp mounting member 110 of the excimer lamp 100 described above is configured as an outer electrode here, and is connected to the ground side. On the inner surface of the lamp mounting member 110, a thin-film (foil-shaped) ultraviolet reflecting member (not shown) such as an aluminum film is provided. The lamp mounting member 110 is made of a metal having thermal conductivity and conductivity, such as aluminum or copper.

  Excimer lamp 100 is controlled to be turned on by light source control device 150 shown in FIG. The excimer lamp 100 can be repeatedly turned on and off for a short time, and the lighting time and the like can be set according to an input operation by an operator or the like.

  Hereinafter, removal of sample contaminants by ultraviolet light irradiation will be described.

  The excimer lamp 100 is positioned at a desired position by adjusting the attachment angle of the connecting portion 124 to the fixed portion 122 and the attachment angle to the excimer lamp 100. Specifically, the desired angle and distance interval of the light emitting surface 105 with respect to the sample surface 50S are determined so that the predetermined area is irradiated with ultraviolet rays with respect to the sample surface 50S. Further, the gas in the sample chamber 40 is made to contain oxygen.

  When a voltage is applied to the outer electrode (lamp mounting member) 110 and the inner electrode 120 of the excimer lamp 100, dielectric barrier discharge (or capacitive discharge) occurs in the discharge space 135. As described above, since the aluminum film is formed on the inner surface of the lamp mounting member 110, the ultraviolet light radiated in the radial direction is repeatedly reflected by the aluminum film. As a result, the ultraviolet light is emitted from the light emitting surface 105 of the excimer lamp 100. Is emitted along the lamp axis and irradiated onto a predetermined region of the sample surface 50S.

  Since the excimer lamp 100 is disposed in the internal space 40T of the sample chamber 40, the light emission surface 105 is exposed in the internal space 40T. That is, the light emitting surface 105 is exposed to the internal space 40T. There is no blocking member between the light emitting surface 105 and the sample 50, and the sample surface 50S is directly irradiated with ultraviolet light.

  An excimer lamp 100, which is a spot irradiation lamp, is arranged near the corner of the upper wall 40A in the sample chamber 40 and irradiated with ultraviolet light, whereby a space between the light emitting surface 105 and the irradiation target region of the sample surface 50S is obtained. Thus, no other member inside the sample chamber such as the lens barrel tip 20B enters, and the ultraviolet light is not irradiated outside the irradiation target region of the sample surface 50S.

  The excimer lamp 100 can be irradiated with ultraviolet rays having a desired wavelength (here, 172 nm) by being lit at an appropriate temperature. When the excimer lamp 100 is overheated, the contaminant removal function is degraded. Further, due to lamp overheating, cracks due to the difference in thermal expansion occur in the sealing portion 100B, and the lamp may be damaged.

  However, since both the lamp mounting member 110 of the excimer lamp 100 and the support member 120 (the fixing portion 122 and the connecting portion 124) connected thereto have thermal conductivity, the heat generated by the lamp lighting is generated by the lamp mounting member 110, The excimer lamp 100 is prevented from overheating by being quickly transmitted to the sample chamber inner wall 40S through the connecting portion 124 and the fixing portion 122.

  In order to discharge the excimer lamp 100 uniformly along the lamp axis direction, the conductivity of the inner electrode 120 and the outer electrode 110 is increased to such an extent that it is not necessary to consider the influence of electrical resistance along the lamp axis direction ( It is necessary to reduce the electrical resistance). In the present embodiment, the lamp mounting member 110 is configured as an external electrode, and is opposed to the inner electrode 120 along the lamp axis at an equal distance as a whole. There is no UV illuminance.

  When ultraviolet rays are irradiated onto a predetermined region of the sample surface 50S, active oxygen and ozone are generated in the vicinity of the sample surface 50S by oxygen remaining in the sample chamber 40, and the molecular bonds of contaminants are broken by the ultraviolet irradiation. Molecules such as hydrocarbons decomposed by this photolytic action react with activated oxygen and ozone to be removed as water and carbon dioxide.

  During spot irradiation with ultraviolet rays, the ultraviolet light emitted from the light emitting surface 105 of the excimer lamp 100 is applied to devices, members, etc. in the sample chamber 40 such as the lens barrel tip 20B and the secondary electron detector 30. Not. Therefore, unnecessary gas release and member deterioration do not occur. Then, by repeatedly performing short-time irradiation of the excimer lamp 100, the generation of active oxygen and ozone is precisely controlled, and ultraviolet irradiation is performed for a required time in a predetermined irradiation region.

  As a result, pollutants are removed while suppressing unnecessary oxygen release due to generation of active oxygen exceeding the required amount, generation of ozone, damage to a portion of the sample surface 50S where the contaminants are not deposited, and the like.

  The shape of the lamp mounting member is not limited to a cylindrical shape. Also, the excimer lamp holding structure may be configured to support the excimer lamp so that either the angle with respect to the sample chamber wall or the angle with respect to the excimer lamp can be adjusted. You may connect mechanically, thermally, and electrically.

  Regarding the ultraviolet light reflecting structure of the lamp mounting member, instead of providing an ultraviolet light reflecting member such as an aluminum film on the inner surface of the lamp mounting member, the inner surface of the outer electrode is mirror-finished. It can also be finished. Further, regarding the conductivity of the lamp mounting member, an outer electrode may be provided between the ultraviolet light reflecting member provided on the inner peripheral surface of the lamp mounting member and the lamp mounting member. The lamp mounting member can be provided so as to have any one of thermal conductivity, conductivity, and reflection characteristics.

  Regarding the heat radiation of the lamp heat, the heat may be transmitted to the outside of the sample chamber instead of transmitting the heat to the sample chamber wall. Further, the outer periphery of the lamp mounting member may be covered with a heat insulating member to prevent the member in the sample chamber from being heated and releasing gas. Examples of the heat insulating member include polyimide, glass, and ceramics.

  With respect to the irradiation region on the sample surface, it is possible to make the entire sample an irradiation region without setting a partial region as the irradiation region. By adjusting the ultraviolet light irradiation angle of the spot irradiation type excimer lamp and the distance between the surface and the sample surface, the irradiation region may be set according to the size of the sample. Further, the irradiation region can be appropriately changed by adjusting the size of the spot irradiation type excimer lamp and the size of the light emitting surface.

  It is also possible to use an ultraviolet radiation source other than the excimer lamp, and it is possible to use a spot irradiation type light source that irradiates in a certain direction from the light emission surface. Further, the configuration is not limited to the configuration in which the entire light source such as an excimer lamp is arranged inside the sample chamber. At least the light emission surface is closer to the sample than the inner wall of the sample (projects toward the inner space side than the wall surface of the sample chamber) What is necessary is just to comprise so that exposure may be carried out. Since the light emitting surface is not configured to be formed on the sample chamber wall (irradiation window or the like), the light emitting surface can be determined at an arbitrary position.

  In this embodiment, it is composed of an electron microscope in which an excimer lamp is arranged in the sample chamber. However, a pretreatment chamber or a dedicated ultraviolet irradiation chamber is provided separately from the sample chamber, and ultraviolet irradiation is performed there. In addition, the present invention can be applied to an apparatus other than an electron microscope that can observe, analyze, or measure a sample, or a vacuum container apparatus that performs ultraviolet irradiation treatment or ozone treatment.

  As described above, according to the present embodiment, the spot irradiation type excimer lamp 100 is arranged in the sample chamber 40 of the scanning electron microscope 10, and the sample chamber side wall 40 </ b> S is provided by the support member 112 including the fixing portion 122 and the connecting portion 124. Attach to. Then, the excimer lamp mounting position is adjusted so that the light emitting surface 105 faces the sample surface 50S. The ultraviolet light emitted from the light emitting surface 105 irradiates a predetermined region of the sample surface 50S. Prevents sample damage, deterioration of members in the sample chamber, unnecessary gas release, and simple configuration, so it can be installed in equipment and equipment such as an electron microscope with limited space around the sample chamber. .

10 Scanning electron microscope 40 Sample chamber 50 Sample 50S Sample surface 100 Excimer lamp (ultraviolet light source)
105 Light emitting surface (ultraviolet light emitting surface)
110 Lamp mounting member 120 Support member 122 Fixed portion 124 Connecting portion

Claims (15)

An ultraviolet light source that emits ultraviolet light from the ultraviolet light emitting surface;
A sample chamber in which the sample is placed;
A support member that supports the ultraviolet light source so that the ultraviolet light emitting surface faces the sample;
The ultraviolet irradiation apparatus, wherein the ultraviolet light emitting surface is exposed in the sample chamber at a position closer to the sample than the sample chamber wall.   The ultraviolet irradiation apparatus according to claim 1, wherein the ultraviolet light source is positioned so as to irradiate a predetermined region of the sample surface with ultraviolet light. The ultraviolet light source is installed in the sample chamber;
The ultraviolet irradiation apparatus according to claim 1, wherein the support member is connected to an inner wall of the sample chamber.   The ultraviolet light source is an excimer lamp having a bottomed cylindrical outer tube with the ultraviolet light emitting surface as a bottom, and emitting ultraviolet light from the ultraviolet light emitting surface along a lamp axis. The ultraviolet irradiation device according to claim 1.   The ultraviolet irradiation according to claim 4, wherein the excimer lamp includes a lamp mounting member that surrounds the outer tube and has at least one of conductivity, ultraviolet light reflection characteristics, and thermal conductivity. apparatus.   The ultraviolet irradiation device according to claim 5, wherein the lamp mounting member has conductivity and is configured as an outer electrode of the excimer lamp.   The ultraviolet irradiation device according to claim 5 or 6, wherein the lamp mounting member is provided with an ultraviolet light reflecting member on an inner surface thereof.   The ultraviolet irradiation device according to claim 5, wherein the lamp mounting member includes a heat conductive member.   The ultraviolet irradiation device according to claim 5, wherein a heat insulating member is provided so as to cover the lamp mounting member.   The support member has an adjustment mechanism capable of changing at least one of an orientation of the ultraviolet light emitting surface with respect to a sample surface and a distance interval between the ultraviolet light emitting surface and the sample surface. The ultraviolet irradiation device according to claim 1.   The ultraviolet irradiation apparatus according to claim 10, wherein the support member supports the ultraviolet light source so that an angle of the ultraviolet light source with respect to an inner wall of the sample chamber can be adjusted. The support member has a fixed portion fixed to the inner wall of the sample chamber, and a connecting portion for connecting a light source holding portion to the inner wall of the sample chamber;
The ultraviolet irradiation device according to claim 10 or 11, wherein the ultraviolet light source is supported by the connecting portion such that an angle with respect to the connecting portion is adjustable. For the sample chamber where the sample is placed, an excimer lamp that emits ultraviolet light from the ultraviolet light emitting surface is installed so that the ultraviolet light emitting surface faces the sample,
The ultraviolet light emitting surface is irradiated from the ultraviolet light emitting surface toward the sample while being exposed to the internal space of the sample chamber at a position closer to the sample than the inner wall of the sample chamber. Sample contaminant removal method by UV irradiation. A vacuum vessel in which the sample is placed;
An ultraviolet light source that emits ultraviolet light from an ultraviolet light emitting surface;
A support member that supports the ultraviolet light source so that the ultraviolet light emitting surface faces a sample disposed in the vacuum vessel;
The vacuum container apparatus, wherein the ultraviolet light emitting surface is exposed in the vacuum container at a position closer to the sample than the inner wall of the vacuum container. An electron microscope comprising the vacuum container device according to claim 14.

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