JP4701460B2 - Inspection apparatus, inspection method, and pattern substrate manufacturing method - Google Patents

Description

  The present invention relates to an inspection apparatus, an inspection method, and a pattern substrate manufacturing method.

  In general, a defect inspection method for a mask on which a pattern is formed includes a comparison inspection method (generally referred to as a die-to-database comparison method) between a mask pattern and design data, and a pattern comparison inspection method for two chips (generally, Two methods are widely known, which are referred to as “Die-to-die comparison methods”. In either method, a small part of the mask pattern (hereinafter referred to as an observation region) is enlarged by an objective lens, and the enlarged optical image is detected by a CCD camera for inspection. However, when a CCD camera is used, a system called TDI (Time Delay Integration) described below is often used. For this reason, this CCD camera is widely called a TDI camera or a TDI sensor.

  As a light source for illuminating the observation region, a laser that continuously operates in the ultraviolet region or a point light source lamp having a spectrum in the ultraviolet region is used. An illumination method for irradiating ultraviolet light extracted from these lasers and lamps from the side opposite to the objective lens with respect to the mask is called transmitted illumination. On the other hand, an illumination method for illuminating the mask from the objective lens side is called reflected illumination. These two illumination methods are used because the way they are viewed (that is, the way the image captured by forming an optical image of the illuminated pattern on a TDI camera or the like) is different, so the types of defects that can be detected, etc. This is because they are different.

JP2009-223095 Semiconductor MIRAI Project Results Report Page 158 2008 Proc. of SPIE Vol. 6349, 63493G, 2006

  Here, a configuration of an optical system of reflected illumination in a general mask inspection apparatus will be described with reference to FIG. FIG. 10 shows a case where a laser device (not shown) is used as the inspection light source. When linearly polarized laser light generated from the laser device enters the inspection optical system, the linearly polarized light is set as an S wave. When this S wave enters the PBS (polarization beam splitter), it reflects and travels downward. The S wave is called linearly polarized light in the polarization direction that is efficiently reflected by the PBS. Next, the laser light is converted into circularly polarized light by passing through the quarter-wave plate. Here, the illumination light is clockwise circularly polarized light. This circularly polarized light passes through the objective lens and is irradiated onto the pattern surface of the mask. The reflected light from the pattern surface has a reverse polarization direction, that is, a counterclockwise circular polarization. Then, the reflected light passes through the objective lens and again passes through the quarter wavelength plate. By doing this, the light is returned to linearly polarized light, but this time it becomes a P wave. For this reason, reflected light permeate | transmits PBS. The P wave, which is reflected light from the pattern surface, passes through the projection lens and reaches the TDI camera. At this time, the pattern surface of the mask is projected onto the TDI camera by the objective lens and the projection lens. As a result, an enlarged image in the field of view of the objective lens is picked up, and defect inspection can be performed.

  On the other hand, the EUV mask reflects X-rays having a wavelength of 13.5 nm, which is exposure light, and is used for exposure. For this reason, the EUV mask is called a reflective mask. A cross-sectional structure of a general EUV mask is shown in FIG. As shown in FIG. 11, a Mo / Si multilayer film is formed on the low expansion glass. In the Mo / Si multilayer film, for example, 40 to 50 Mo films and Si films are formed. The Mo / Si multilayer film reflects X-rays. A buffer layer (and a protective film) is formed on the Mo / Si multilayer film. Further, an absorber that absorbs X-rays is provided on the buffer layer. Thus, the EUV mask has a laminated structure in which an absorber that does not reflect X-rays is formed on a Mo / Si multilayer film that reflects X-rays. With this EUV mask, pattern exposure can be performed on the wafer.

  A conventional mask inspection apparatus can be used for EUV mask pattern inspection. However, since the EUV mask does not transmit light, the major difference is that it can be inspected only by reflected illumination as an illumination method. That is, the reflected light from the Mo / Si multilayer film on the pattern surface irradiated with the reflected illumination light is detected. And by projecting the optical image of a pattern surface on a TDI camera, a pattern shape is imaged and a defect inspection is performed.

  When an EUV mask is inspected using a conventional mask inspection apparatus as it is, there is a problem that it is difficult to obtain high contrast. That is, in the reflected illumination, as described above, the circularly polarized illumination light is applied to the mask. In this case, it becomes difficult to make illumination light reach the patterned Mo / Si multilayer film in the EUV mask. The reason is that an absorber having a thickness equivalent to the width of the pattern in which the Mo / Si multilayer film is exposed is attached. With circularly polarized light, it is considered that such a narrow pattern width cannot be efficiently advanced, and the pattern shape cannot be imaged with high contrast.

  Specifically, according to Non-Patent Document 2, the thickness of the absorber is 90 nm, and the buffer layer below it is 10 nm. For example, in a half-pitch 22 nm generation device, the minimum line width on a quadruple mask is 88 nm. From this, it is considered that the total thickness of the absorber and the protective film is about the same as the pattern width.

  Note that Non-Patent Document 1 shows a configuration in which special polarized illumination having a polarization direction in the radial direction of the beam is used in place of conventional circularly polarized illumination with low contrast. This has been reported to improve contrast. In this special polarized illumination, laser light whose polarization direction is directed in the radial direction from the center of the cross section of the beam is used (hereinafter referred to as radial polarized illumination). For this reason, it is said that high contrast can be obtained regardless of the orientation of the mask pattern as compared with the circular polarization of illumination light in a conventional general mask inspection apparatus. For example, Patent Document 1 discloses a method for forming radially polarized illumination.

  However, a general mask pattern is linear in the vertical direction or the horizontal direction. For this reason, in the radially polarized illumination that faces in all directions, the proportion of the light quantity that improves the contrast is low. As a result, the effect of improving contrast is reduced. Furthermore, in order to realize radial polarization illumination, a special wave plate divided in the azimuth direction is required as shown in Patent Document 1 below. For this reason, there also existed a problem that cost became high.

An object of the present invention is to provide an inspection apparatus, an inspection method, and a pattern substrate manufacturing method capable of obtaining high contrast with a simple configuration.
It is to provide a manufacturing method.

  The inspection apparatus according to the first aspect of the present invention uses an objective lens (for example, the objective lens 7 according to an embodiment of the present invention) and a first region that is a part of the field of view of the objective lens as a first polarization. Reflective illumination optical system for illuminating with linearly polarized light in a direction and illuminating a second region different from the first region with a linearly polarized light having a second polarization direction different from the first polarization direction in the field of view of the objective lens (For example, a reflective illumination optical system 51 according to an embodiment of the present invention) and a first detector that detects reflected light reflected by a sample in the first region (for example, a TDI camera according to an embodiment of the present invention) 11a) and a second detector (for example, a TDI camera 11b according to an embodiment of the present invention) that detects reflected light reflected by the sample in the second region. Thereby, since it can illuminate with the light of a different polarization direction, it can test | inspect with high contrast.

  An inspection apparatus according to a second aspect of the present invention is the inspection apparatus described above, wherein the first polarization direction and the second polarization direction are orthogonal to each other. Thereby, a sample having a vertical and horizontal pattern can be inspected with high contrast.

  An inspection apparatus according to a third aspect of the present invention is the above-described inspection apparatus, wherein the reflective illumination optical system is disposed at a position conjugate with the sample, and changes the polarization state of a part of the illumination light. 1 half-wave plate (for example, the half-wave plate 4 according to the embodiment of the present invention) and the first half-wave plate to the objective lens, and reflected by the sample The first light branching unit (for example, the half mirror 6, the half mirror 41, or the PBS 20 according to the embodiment of the present invention) on which the reflected light is incident through the objective lens is provided. Thereby, the utilization efficiency of light can be improved with a simple configuration.

  An inspection apparatus according to a fourth aspect of the present invention is the inspection apparatus described above, wherein the first half-wave plate is inserted in a half of the optical path. Thereby, a linearly polarized beam can be easily generated.

  An inspection apparatus according to a fifth aspect of the present invention is the inspection apparatus described above, wherein the first light branching unit reflects light according to a polarization state (for example, in the embodiment of the present invention). A first quarter-wave plate (for example, an implementation of the present invention) in which the reflective illumination optical system is provided between the wave plate and the polarizing beam splitter, and the illumination light is circularly polarized. A quarter-wave plate 5a) according to the embodiment, and a second polarized light that is provided between the objective lens and the polarization beam splitter and is made circularly polarized by the first quarter-wave plate into linearly polarized light. A quarter-wave plate (for example, a quarter-wave plate 5b according to an embodiment of the present invention) and the polarization beam splitter to the first and second photodetectors; 2 The reflected light incident on the photodetector is linearly polarized. Third quarter wave plate (e.g., such a quarter-wave plate 5c to the embodiment of the present invention) and are those comprising a.

  An inspection apparatus according to a sixth aspect of the present invention is the above-described inspection apparatus, wherein the reflective illumination optical system is a second light that branches the illumination light into a first light beam and a second light beam. Branch means (for example, the half mirror 6b according to the embodiment of the present invention) and a second half-wave plate (for example, the present invention) that changes the polarization state of the first light beam branched by the light branch means. And a means for superimposing the first light beam so that the first light beam propagates close to the second light beam on the wavelength plate (for example, the present invention). And a mirror 3d) according to the fourth embodiment.

  An inspection apparatus according to a seventh aspect of the present invention is the inspection apparatus described above, wherein the second half-wave plate changes a polarization state of the entire first light beam. is there. This

  An inspection apparatus according to an eighth aspect of the present invention is the above-described inspection apparatus, wherein the reflective illumination optical system divides illumination light and enters the first region, and the first beam A third light branching unit (for example, a half mirror 40 according to the fourth embodiment of the present invention) that generates a second light beam propagating in a direction different from that of the first light beam, and a polarization state of the second beam And a third half-wave plate (for example, the first / half-wave plate 4 according to Embodiment 4 of the present invention) and a position conjugate with the sample, and from the third half-wave plate Means for making the second light beam incident on the second region via the third light branching means (for example, the mirror 40c according to the fourth embodiment of the present invention).

  An inspection method according to a ninth aspect of the present invention includes illuminating a first region that is a part of the field of view of the objective lens with linearly polarized light in a first direction, and the first region within the field of view of the objective lens. Illuminating a second region different from the first region with linearly polarized light having a second polarization direction different from the first polarization direction, and reflecting light reflected by the sample in the first region to the objective A step of detecting with a first detector through a lens, and a step of detecting reflected light reflected by the sample in the second region with the second detector through the objective lens. .

  The inspection method according to a tenth aspect of the present invention is the inspection method described above, wherein at least one of the first direction and the second direction is along a pattern provided on the sample. It is a feature.

  According to an inspection method of an eleventh aspect of the present invention, there is provided a pattern substrate manufacturing method comprising: an inspection step for inspecting a photomask by the above inspection method; and a defect for correcting a defect of the photomask inspected by the inspection step. A correction step; an exposure step of exposing the substrate through the photomask corrected in the defect correction step; and a development step of developing the exposed substrate.

  According to the present invention, an inspection apparatus, an inspection method, and a pattern substrate manufacturing method capable of obtaining high contrast with a simple configuration are provided.

It is a block diagram of the optical system of the EUV mask inspection apparatus which is 1st embodiment. It is explanatory drawing of the polarization state in an EUV mask inspection apparatus. It is a block diagram which shows the other plan of the partial optical arrangement | positioning in an EUV mask inspection apparatus. It is explanatory drawing of the illumination area | region of an EUV mask inspection apparatus. It is a block diagram of the optical system of the EUV mask inspection apparatus which is 2nd embodiment. It is a block diagram of the optical system of the EUV mask inspection apparatus which is 3rd embodiment. It is a graph which shows the characteristic of the half mirror in an EUV mask inspection apparatus. It is a block diagram of the optical system of the EUV mask inspection apparatus which is 4th embodiment. It is a graph which shows the transfer characteristic of the half mirror 40 in an EUV mask inspection apparatus. It is a block diagram of the reflective illumination of a normal mask inspection apparatus. It is a cross-sectional structure diagram of a general EUV mask.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows preferred embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same contents.

Embodiment 1 FIG.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Below, the inspection apparatus concerning this embodiment is demonstrated using FIGS. In the present embodiment, an inspection apparatus that inspects an EUV mask will be described as an example. FIG. 1 is a configuration diagram of the entire illumination optical system of the inspection apparatus of the present invention. FIG. 2 is an explanatory diagram of a polarization state in the EUV mask inspection apparatus. FIG. 3 is a diagram schematically showing the relationship between the illumination area of the inspection apparatus and the inspection area. As shown in FIG. 1, the inspection apparatus illuminates the EUV mask 8 using a reflective illumination optical system 51 having lenses 1b, 1c, and 1d, a mirror 3a, a half mirror 6, and the like.

  Laser light L1 that is illumination light from a laser device (not shown) is emitted. As the laser light, light having an ultraviolet wavelength of about 0.2 μm can be used. The laser beam L1 is incident on the homogenizer 2 by the lens 1a and proceeds while repeating total reflection inside the laser beam L1. By doing so, a beam having a uniform light intensity distribution is formed on the exit surface of the homogenizer 2. The laser beam L1 passes through the lens 1b after being emitted from the homogenizer 2. Thereby, the laser beam L2 is returned to a parallel beam.

  The laser beam L2 passes through the lens 1c and is folded back by the mirror 3a. The laser beam L3 reflected by the mirror 3a reaches the position where the half-wave plate 4 is placed. However, the half-wave plate 4 is arranged so that only half of the beam cross section of the laser light L3 passes. That is, the half-wave plate 4 is inserted up to half of the optical path. The optical position of the half-wave plate 4 is a conjugate position with the exit surface of the homogenizer 2. That is, the optical image of the exit surface of the homogenizer 2 is projected onto the half-wave plate 4 by the lens 1b and the lens 1c.

  The laser beam L4 that has passed through the position of the half-wave plate 4 passes through the lens 1d. The laser beam L4 that has passed through the lens 1d enters the half mirror 6. In the half mirror 6, the laser beam L4 is divided into two parts by reflection and transmission. In the present invention, since the laser beam that passes through the half mirror 6 is not used, it is not shown. The reflectance and transmittance will be described later with reference to FIG.

  The laser beam L7 reflected from the half mirror 6 passes through the objective lens 7. The laser beam L8 collected by the objective lens 7 is incident on the EUV mask 8. Then, the upper pattern surface 8b of the EUV mask 8 is irradiated like the laser beam L8.

  Laser light L8 as reflected light generated by irradiating the pattern surface 8b (Note that the above-described laser light L8 has traveled downward in the figure, and this time it travels upward in the figure, but propagates in the same space. Therefore, the same symbol is used) passes through the objective lens 7. Hereinafter, the laser light reflected by the EUV mask 8 may be referred to as reflected light. The reflected light refracted by the objective lens 7 passes through the half mirror 6. The laser beam L9 that has passed through the half mirror 6 passes through the projection lens 9. The reflected light refracted by the projection lens 9 reaches the position of the space division mirror 10. Here, half of the beams that do not hit the space division mirror 10 reach the TDI camera 11a, and the laser light that strikes the space division mirror 10 reaches the TDI camera 11b. That is, the space division mirror 10 spatially separates the reflected light. The separated two reflected lights reach the sensor surfaces 12a and 12b of the TDI cameras 11a and 11b, respectively.

  Note that an area where the laser beam L8 is irradiated on the pattern surface 8b of the EUV mask 8 is an observation area (illumination area). This observation area is projected onto the sensor surface 12a or the sensor surface 12b by a projection optical system including the objective lens 7 and the projection lens 9.

  Here, the polarization direction of the laser light will be supplementarily described with reference to FIG. Only half of the beam cross-section of the laser beam L3 passes through the half-wave plate 4. The laser beam L4 immediately after the half-wave plate 4 is arranged such that two laser beams that are close to each other in the orthogonal polarization directions are arranged. These are S wave and P wave. Here, the expressions S-wave and P-wave are used, but they are simply used to distinguish two types of light whose polarization directions are orthogonal. The laser light L4 combined with these S and P waves enters the half mirror 6 after passing through the lens 1d.

  The half mirror 6 reflects about 70% and transmits about 30% when the incident laser beam is an S wave. When the incident laser beam is a P wave, about 30% is reflected and about 70% is transmitted. As a result, in the laser light L7 reflected by the half mirror 6 and traveling downward, the S wave is about 70% and the P wave is about 30%. These S wave and P wave pass through the objective lens 7 and irradiate the pattern surface 8b.

  The optical position of the half-wave plate 4 is a conjugate position with the pattern surface 8 b of the EUV mask 8. That is, the position at which two laser beams that are close to each other in the orthogonal polarization directions are formed is an optical position conjugate with the pattern surface 8b, that is, a position where a field stop is generally disposed. A position where two laser beams that are close to each other in the orthogonal polarization direction are formed is projected onto the pattern surface 8b by the projection optical system formed by the objective lens 7 and the lens 1d. As a result, two linearly polarized laser beams L8 that are orthogonal to each other are irradiated onto adjacent different areas on the pattern surface 8b. That is, as shown in FIG. 3, a P-wave illumination area and an S-wave illumination area are formed in the field of view of the objective lens 7. A rectangular inspection area is formed in each, and this area is projected onto the TDI cameras 11a and 11b. Then, defect inspection is performed based on images acquired by the TDI cameras 11a and 11b.

  Next, the reflected light from the pattern surface 8b, that is, the laser light L8 traveling upward, is in a polarization state in which the P wave and the S wave are combined. The reflected light passes through the objective lens 7 and then enters the half mirror 6 again. The ratio of transmitting through the half mirror 6 is about 30% for the S wave and about 70% for the P wave, as described above. On the other hand, as described above, the laser beam L7 has an S wave of about 70% and a P wave of about 30%. Therefore, in the laser light L9 that can be transmitted through the half mirror 6, about 21% (= 70% × 30%) of the S wave and the P wave constituting the laser light L4 for both the S wave and the P wave. ) And the same ratio. As a result, the amount of light received by the TDI camera 11a is substantially equal to the amount of light received by the TDI camera 11b.

  Here, the reflectances of the P wave and S wave in the half mirror 6 are Rp and Rs, respectively. Further, it is assumed that the reflectance on the pattern surface of the EUV mask is 100%. Further, regarding the power of the laser beam L4 obtained by combining the P wave and the S wave before entering the half mirror 6, both the P wave and the S wave are set to 1.0. Then, the P-wave power Pp and the S-wave power Ps in the laser light L9 that passes through the half mirror 6 and travels toward the TDI cameras 11a and 11b are obtained by the following equations 1 and 2. In the following expression, the loss at the half mirror 6 is ignored.

Pp = Rp × (1−Rp) (Formula 1)
Ps = Rs × (1−Rs) (Formula 2)

  On the other hand, since Rs = 1−Rp, the power of the laser light L9 toward the TDI cameras 11a and 11b is expressed by the following equation.

  Pp + Ps = 2.0 × Rp × (1−Rp) (Formula 3)

  Therefore, the ratio (hereinafter referred to as transmission efficiency, expressed as η) to the power of the laser light L4 before the laser light L9 enters the half mirror 6 is expressed by the following formula 4.

  η = Rp × (1−Rp) (Formula 4)

  In Equation 4, a maximum value of 0.25 is obtained when Rp = 0.50. This is the theoretical maximum value in this embodiment using a half mirror. Therefore, as in the above-described embodiment, when the reflectance and transmittance are away from 50%, the transmission efficiency decreases. Therefore, the reflectance and transmittance are preferably as close to 50% as possible. However, in general, the P wave is likely to pass through the optical material. For this reason, in a half mirror that can be actually manufactured, it is difficult to increase Rp to about 50%. Therefore, Rp will be about 30%.

  Similarly to a general mask inspection apparatus, the objective lens 7 and the projection lens 9 are arranged so that the pattern surface 8b is projected onto the TDI camera 11a. In the present embodiment, the space division mirror 10 is disposed immediately before the TDI camera 11a. Therefore, the pattern surface 8b is projected also to the TDI camera 11b. Therefore, orthogonally linearly polarized light (that is, P wave and S wave) irradiated to different adjacent areas on the pattern surface 8b can be projected onto each of the two TDI cameras 11a and 11b.

  As described above, in the inspection apparatus of the present invention, different areas on the mask can be illuminated with each of two orthogonally polarized laser beams. Furthermore, each region can be observed by each of two different TDI cameras. Therefore, when the pattern surface 8b is composed of orthogonal vertical and horizontal patterns, inspection can be performed with reflected illumination having a polarization direction parallel to each pattern. For example, illumination is performed so that the vertical and horizontal patterns of the mask 8 are parallel to the polarization direction. Thereby, imaging can be performed with high contrast, and inspection sensitivity is improved.

  As shown in FIGS. 1 and 3, one TDI camera 11a inspects a P-wave illumination area, and the other TDI camera 11b inspects an S-wave illumination area. The inspection area by the TDI cameras 11a and 11b is included in the illumination area. That is, the illumination area is larger than the inspection area. By illuminating as described above, it is possible to image with high contrast. Thereby, inspection sensitivity improves and it can test | inspect correctly. Therefore, productivity can be improved. In addition, the amount of light in the inspection area by the S wave illumination and the inspection area by the P wave illumination can be made substantially equal.

  In the EUV mask inspection apparatus shown in FIG. 1 or FIG. 2, the half-wave plate 4 is arranged in half of the optical path to divide it into S wave and P wave. The half-wave plate 4 is disposed at a position conjugate with the pattern surface 8b. However, it is also possible to divide the laser light into P waves and S waves with different optical configurations. A different optical configuration when forming the laser beam L4 including the P wave and the S wave will be described with reference to FIG.

  Here, the laser beam L3 is first incident on the half mirror 6b as a P wave. Thereby, the laser beam L3 is divided into two parts in terms of transmission and reflection. That is, the half mirror 6b splits the illumination light into two light beams. The laser beam L12, which is a P wave that has passed through the half mirror 6b, passes through the half-wave plate 4b and is therefore converted to an S wave. The S wave is reflected by the mirrors 3c and 3d. The entire laser beam L12 branched by the half mirror 6b passes through the half-wave plate 4b. Therefore, the polarization state of the entire laser beam L12 is changed by the half-wave plate 4b.

  On the other hand, the P-wave laser beam L13 reflected by the half mirror 6b is reflected by the mirror 3b. The laser beam L13 reflected by the mirror 3b passes near the mirror 3d. This laser beam L13 travels in parallel to the S wave reflected by the mirror 3d as shown in FIG. As a result, a laser beam L4 close to linearly polarized light in two orthogonal directions is formed. Further, the optical position where the two laser beams are brought close to each other by the mirror 3d may be set as the position of the field stop. That is, the mirror 3d is disposed at a position conjugate with the pattern surface 8b.

  As a feature of the present embodiment, a normal circular half-wave plate larger than the beam cross section of the laser beam L12 can be used as the half-wave plate 4b. And there exists the feature which can perform fine adjustment of a crystal axis direction by rotating the half-wave plate 4b. The optical configuration shown in FIG. 4 may be arranged instead of the half-wave plate 4 shown in FIG.

  As described above, the inspection apparatus includes an inspection light source that generates linearly polarized laser light, at least one half-wave plate, at least one half mirror, at least one spatial division mirror, and two units. Imaging devices such as TDI cameras (in the following description, these are represented as TDI cameras as representative). These are optically arranged as follows.

  First, one laser beam taken out from the inspection light source is divided into two, and only one of them is passed through the half-wave plate. Therefore, it is possible to form two laser beams that are close to each other with mutually orthogonal polarization directions. These are made incident on the same half mirror. Unlike the PBS, the half mirror has linearly polarized incident light, and reflection and transmission occur simultaneously regardless of the direction of polarization of the linearly polarized light. From this, at least a part can be directed to the objective lens, and the mask can be irradiated through the objective lens.

  The optical position where two laser beams that are close to each other in the orthogonal polarization directions are formed is conjugate with the pattern surface of the mask. Thereby, an optical position for forming two laser beams that are close to each other in the polarization directions orthogonal to each other is projected onto the pattern surface by the projection optical system including the objective lens. That is, on the pattern surface, two linearly polarized laser beams orthogonal to each other are irradiated to different adjacent illumination areas. For example, as shown in FIG. 3, in the field of view of the objective lens 7, the left half is proved by the P wave and the right half is illuminated by the S wave. Therefore, the laser light can efficiently travel within the pattern width regardless of whether the pattern is in the vertical or horizontal direction.

  Next, the reflected light from the pattern surface passes through the objective lens 7 and then enters the half mirror 6 again. First, the laser beam can be advanced in a direction different from the direction in which the laser beam enters the half mirror 6. Therefore, two TDI cameras 11a and 11b may be arranged in that direction. At this time, similarly to a general mask inspection apparatus, the objective lens 7 and the projection lens 9 may be arranged so that the pattern surface is projected onto one of the two TDI cameras 11a and 11b. Furthermore, a laser beam may be split by disposing a space dividing mirror 10 immediately before the TDI cameras 11a and 11b. By doing so, the other TDI cameras 11a and 11b can also reach the laser beam. Therefore, the pattern surface can be projected onto the two TDI cameras. As a result, the reflected light of each linearly polarized illumination light applied to different adjacent areas on the pattern surface can reach each of the two TDI cameras. Further, by reducing the spread angle of the reflected light, it is possible to dispose the space dividing mirror 10 at a position other than the position conjugate with the pattern surface 8b.

  As described above, in the present invention, the adjacent illumination regions on the pattern surface are respectively illuminated with two orthogonally polarized laser beams. And the optical image of an adjacent illumination area is imaged with a different camera. Each optical image obtained in this way is observed by each of two different cameras. The laser light incident on the EUV mask that is the sample is a laser light having an orthogonal polarization direction. That is, one half of the visual field of the objective lens 7 is illuminated with linearly polarized light in the first direction, and the other half is illuminated with linearly polarized light in the second direction orthogonal to the first direction. Therefore, the laser light can efficiently travel within the pattern width regardless of whether the pattern is in the vertical or horizontal direction. That is, the polarization direction of one of the laser beams is a direction along the pattern. In other words, illumination is performed so that the polarization axis of linearly polarized light is along the pattern direction. Thereby, a pattern shape can be imaged with high contrast.

Embodiment 2. FIG.
Next, Embodiment 2 according to the present invention will be described in detail with reference to FIG. FIG. 5 is a configuration diagram showing a part of the optical system in the EUV mask inspection apparatus. In the EUV mask inspection apparatus, components equivalent to those in the inspection apparatus shown in FIG. Therefore, the details are omitted as appropriate.

  In the present embodiment, a PBS (polarizing beam splitter) 20 is used instead of the half mirror 6. The PBS 20 reflects or transmits light according to the polarization state of incident light. Further, three quarter wavelength plates 5a, 5b, and 5c are added. The quarter wavelength plate 5 a is disposed between the lens 1 d and the PBS 20. The quarter wavelength plate 5 b is disposed between the objective lens 7 and the PBS 20. The quarter wavelength plate 5 c is disposed between the projection lens 9 and the PBS 20.

  As in the first embodiment, only half of the beam cross section of the laser light L3 passes through the half-wave plate 4. The laser beam L4 immediately after passing through the half-wave plate 4 is such that two laser beams that are close to each other in the polarization directions orthogonal to each other are arranged. Therefore, these can be divided into S wave and P wave. The laser light L4 mixed with these S wave and P wave passes through the quarter wavelength plate 5a. By doing so, both the S wave and the P wave are circularly polarized. However, the crystal axis direction of the quarter wave plate 5a is set at an angle rotated by 45 degrees from the polarization directions of the S wave and P wave. As a result, the S wave and the P wave are converted into counterclockwise circularly polarized light (indicated as left circularly polarized light) and clockwise circularly polarized light (indicated as right circularly polarized light). Here, the expressions S-wave and P-wave are used, but they are simply used to distinguish two types of light whose polarization directions are orthogonal.

  In this embodiment, the half mirror used in the EUV mask inspection apparatus shown in FIG. 1 is not used, but PBS 20 is used instead. In general, when circularly polarized light is used, PBS can be divided into two almost accurately in terms of power by transmission and reflection. From this, about half of the power of the laser light L5b including the left circularly polarized light and the right circularly polarized light is reflected by the PBS 20. Thereby, both left circularly polarized light and right circularly polarized light can be directed to the objective lens 7. However, it passes through the quarter-wave plate 5 b before entering the objective lens 7. For this reason, the left circularly polarized light and the right circularly polarized light are again converted into linearly polarized light. At this time, the laser beam L7b is returned to the laser beam L7b having two orthogonal polarization directions such as P wave and S wave. These S wave and P wave pass through the objective lens 7 and irradiate the pattern surface 8b.

  The optical position of the half-wave plate 4 is an optical position conjugate with the pattern surface of the EUV mask 8. That is, the position where the two laser beams L4 that are close to each other in the orthogonal polarization directions (referred to as P wave and S wave) are formed is an optical position conjugate to the pattern surface 8a of the EUV mask 8, that is, generally a field stop. Is the position where is placed. That is, the projection optical system formed by the objective lens 7 and the lens 1d projects a position where two laser beams that are close in orthogonal polarization directions are formed on the pattern surface 8b. As a result, two linearly polarized laser beams L8 (that is, a P wave and an S wave) orthogonal to each other are irradiated onto adjacent different areas on the pattern surface 8b (see FIG. 4).

  Next, the reflected light from the pattern surface 8b will be described. This reflected light is in a polarization state in which the P wave and the S wave are combined. The reflected light passes through the objective lens 7 and then passes again through the second quarter-wave plate 5b. For this reason, the laser beam L7b is again converted into circularly polarized light. The circularly polarized light is in a polarization state in which right circularly polarized light and left circularly polarized light are combined. Since the laser beam L7b traveling upward is circularly polarized light, half the power is transmitted through the PBS 20. The circularly polarized laser beam L9b that has passed through the PBS 20 passes through the third quarter-wave plate 5c. From this, the laser beam L10 is again converted into linearly polarized light. At that time, the P wave and the S wave are in a polarization state.

  In addition, as in the first embodiment shown in FIG. 1, the space division mirror 10 is disposed immediately in front of the two TDI cameras 11a and 11b. By doing so, different illumination areas adjacent to each other on the pattern surface 8b (that is, illumination areas irradiated with the P wave and S wave) can be projected onto the two TDI cameras 11a and 11b, respectively. In addition, PBS may be used instead of the space division mirror 10, or S wave and P wave may be branched.

  In the EUV mask inspection apparatus of this embodiment, PBS 20 is used instead of the half mirror 6 as in the conventional mask inspection apparatus. Accordingly, the basic configuration of the optical system of the conventional mask inspection apparatus is hardly changed, and it can be used by simply adding two quarter-wave plates. That is, when PBS 20 is incident, it is converted into circularly polarized light, which makes it possible to achieve a reflectance of 50% (that is, a transmittance of approximately 50%) for both left-handed circularly polarized light and right-handed circularly polarized light. Here, it is assumed that the reflectance at the EUV mask 8 is 100%. The power of the laser beam L9b toward the TDI cameras 11a and 11b is about 50% of the power of the laser beam L5b immediately before entering the PBS 20, that is, about 25%. Therefore, the power is increased from about 21% of the transmission efficiency in the case of the inspection apparatus of the first embodiment described above. That is, the theoretical maximum value of transmission efficiency when a half mirror is used is obtained. Note that, instead of powering up, the power of the laser device of the inspection light source can be lowered and the life of the optical components in the laser device can be extended.

Embodiment 3 FIG.
Next, a third embodiment of the EUV mask inspection apparatus of the present invention will be described with reference to FIG. The basic configuration of the inspection apparatus shown in FIG. 6 is the same as that of the inspection apparatus shown in FIG. In the present embodiment, the half mirror and the method of entering the half mirror are different from those in the first embodiment. Here, a half mirror 31 and a mirror 30 are provided instead of the half mirror 6 shown in the first embodiment. Therefore, description of other configurations is omitted as appropriate.

  First, the laser beam L4 in which the S wave and the P wave are mixed passes through the lens 1d and then enters the mirror 30. The mirror 30 reflects the incident laser beam L4. The laser beam L30 turned back by the mirror 30 enters the half mirror 31. The half mirror 31 is a thin quartz plate whose front surface is uncoated and whose back surface is coated with an antireflection film. The laser beam L30 is incident on the half mirror 31 at a large angle of about 83 degrees.

FIG. 7 shows the characteristics of the half mirror. FIG. 7 is a graph showing the relationship between the incident angle of the half mirror 31 and the reflectance. As can be seen from the characteristics of the half mirror 31 shown in FIG. 7 (that is, the reflectance characteristics at the uncoated surface of the quartz plate), when the incident angle is about 83 degrees, the reflectance of the P wave is about 35%, The reflectance is about 65%. In this way, by making the laser beam incident on the half mirror 31 obliquely, the P wave and the S wave can be incident on the objective lens 7 with high reflectivity.
As in the first embodiment, the laser beam L7 is collected by the objective lens 7 and enters the EUV mask 8. The laser beam L7 reflected by the EUV mask 8 enters the half mirror 31 through the objective lens 7.

  As a result, in the laser light L9 after passing through the half mirror 31 again, the S-wave has a reflectivity of about 65% when initially incident, and a transmittance of about 35% when incident again. , Approximately 23% (= 0.65 × 0.35). On the other hand, with respect to the P wave, the reflectance at the first incidence is about 35%, and the transmittance at the time of incidence again is about 65%, so this is also about 23% (= 0.35 × 0.65). )

  As described above, the inspection apparatus according to the present embodiment is configured such that the incident angle to the half mirror 31 can be increased. Specifically, the incident angle of the illumination light with respect to the half mirror 31 is preferably 80 degrees or more. Thereby, an uncoated quartz plate can be applied, and an expensive coating is not required. Thus, the component cost can be reduced.

Embodiment 4 FIG.
Next, an inspection apparatus according to Embodiment 4 will be described with reference to FIG. The basic configuration of the inspection apparatus shown in FIG. 8 is the same as that of the inspection apparatus shown in FIG. In the present embodiment, the half mirror and the method of entering the half mirror are different from those in the first embodiment.

  In the present embodiment, the half mirror 40 is arranged at the position of the half mirror 6 shown in the first embodiment. The first half mirror 40 divides the illumination light to generate a first beam and a second light beam that propagates in a direction different from the first light beam. Further, the mirror 40c is disposed at the position of the half-wave plate 4 shown in the first embodiment. Further, in order to use the light that has passed through the half mirror 40, a mirror 40a, a mirror 40b, a half-wave plate 4, a lens 1e, and the like are provided.

  First, the laser beam L4, which is linearly polarized only with P waves, enters the lens 1d after passing through the position of the field stop. A mirror 40c is disposed at the position of the field stop. The mirror 40c is disposed close to the optical path. The mirror 40c. The laser beam L4 is hardly blocked. Therefore, the laser beam L4 passes through the vicinity of the mirror 40c and enters the lens 1d. The laser light L4 enters the half mirror 40 after passing through the lens 1d. The laser beam L4 is divided into two parts by the half mirror 40, which is reflected and transmitted. That is, a first light beam reflected by the half mirror 40 and a second light beam transmitted through the half mirror 40 are generated. The reflected laser beam L7 (first light beam) passes through the objective lens 7 and irradiates the pattern surface 8b of the EUV mask 8 as in the first embodiment. The laser beam L4 is incident on the P-wave illumination region shown in FIG.

  On the other hand, the laser light L40 (second light beam) transmitted through the half mirror 40 is reused by the mirrors 40a, 40b, 40c and the like. Specifically, the laser beam L40 that has passed through the half mirror 40 is reflected by the mirrors 40a and 40b and passes through the half-wave plate 4. The laser beam L41 that has passed through the half-wave plate 4 is converted into an S wave. Then, after passing through the lens 1e, the laser light L40 is incident again on the mirror 40c disposed at the position of the field stop. The laser beam L40 is reflected by the mirror 40c, passes through the lens 1d, and enters the half mirror 40. The half mirror 40 reflects about 50%. The pattern surface 8 b of the EUV mask 8 is irradiated through the objective lens 7 reflected by the half mirror 40. The mirror 40 c is disposed at a position conjugate with the EUV mask 8. Then, the second light beam is reflected by the mirror 40 c, so that the polarization state of the second light beam is changed by the half-wave plate 4, and then the EUV mask 8 is passed through the mirror 40 c and the half mirror 40. Is incident on. This second light beam is incident on the illumination area of the S wave shown in FIG.

  As a characteristic of the half mirror 40 in this embodiment, the reflectance and transmittance with respect to the S wave are about 50%. The reflectance of the P wave is about 25% (transmittance is about 75%). The reason for selecting these reflectances will be described later. Further, the power of the first laser beam L3 is set to 1. Further, it is assumed that the reflectance at the EUV mask 8 is 100%. The power of the P wave constituting the laser beam L10 directed to the TDI cameras 11a and 11b is approximately 19% of a product of approximately 25% and approximately 75% with respect to the power of the laser beam L3. On the other hand, the power of the S wave is about 50% of the laser light L40, which is about 75% of the power of the laser light L3, and further about 50%. Therefore, the power of the S wave is still about 19%. As a result, the total power of both the P wave and the S wave constituting the laser beam L10 is about 38%, which is more than the theoretical maximum value of 25% of the transmission efficiency in the configuration shown in the first, second, and third embodiments. It is a feature of this embodiment that it can be increased.

  Here, the transmission efficiency of the present embodiment will be supplementarily described. Assume that the reflectance of the EUV mask on the pattern surface is 100% assuming that the reflectances of the P wave and S wave in the half mirror 40 are Rp and Rs, respectively. Further, the power of the laser beam L3 before entering the half mirror 40 is set to 1.0. The P-wave power Pp and the S-wave power Ps in the laser light L10 directed to the TDI cameras 11a and 11b are obtained by the following equations.

Pp = Rp × (1−Rp) (Formula 5)
Ps = (1-Rp) × Rs × (1-Rs) (Formula 6)
However, since it is necessary to make Pp and Ps equal, the following equation is established.
Rp = Rs × (1-Rs) (Formula 7)
That is, since Rp is a function of Rs, Pp is also expressed as Rs as follows.
Pp = Rs * (1-Rs) * (1-Rs + Rs ^ 2)) (Formula 8)
This is represented in a graph as shown in FIG. At Rs = 0.50, Pp takes the maximum value (in this case, Rp = 0.25), and Pp = 0.1875. Therefore, since the sum of Pp and Ps is 0.375, the theoretical maximum value of transmission efficiency is about 38%.

Other Embodiments In the above description, the sample to be inspected is described as being the EUV mask 8, but the sample is not limited to the EUV mask 8. For example, the sample may be a pattern substrate. Further, in the above-described embodiment, the inspection area is imaged using the TDI cameras 11a and 11b, but may be imaged using a photodetector (camera) other than the TDI camera. Thus, it is suitable for an inspection apparatus that inspects using the reflective illumination optical system 51.

  Furthermore, the polarization direction of the linearly polarized light that illuminates the EUV mask 8 is not limited to the orthogonal direction. That is, the illumination may be performed in two different directions. Moreover, it is preferable to make a polarization direction follow a pattern. That is, it is preferable to make the polarization direction parallel to the pattern direction.

  The above-described inspection apparatus is not limited to the inspection of the EUV mask, and any pattern substrate having a pattern can be used. For example, examples of the sample to be inspected include a color filter substrate in addition to a photomask.

  A photomask is inspected using the above-described inspection apparatus to detect a photomask defect. Then, a defect-free photomask is manufactured by correcting the defect of the photomask. Thereby, the productivity of the photomask can be improved. A substrate having a photosensitive resin is exposed using such a photomask having no defect. Then, the exposed substrate is developed with a developer. Thereby, the photosensitive resin can be patterned with high accuracy. Therefore, a patterned substrate on which the photosensitive resin is patterned can be manufactured with high productivity. Further, when the photosensitive resin is a resist, the conductive film and the insulating film are etched through the patterned photosensitive resin. Thereby, productivity of pattern boards, such as a wiring board and a circuit board, can be improved.

1a lens 1b lens 1c lens 1d lens 1e lens 2 homogenizer 3a mirror 3b mirror 3c mirror 3d mirror 4 1/2 wave plate 4b 1/2 wave plate 5a 1/4 wave plate 5b 1/4 wave plate 5c 1/4 wave plate 6 Half mirror 6a Half mirror 7 Objective lens 8 EUV mask 8b Pattern surface 9 Projection lens 10 Spatial division mirror 11a TDI camera 11b TDI camera 20 PBS
30 mirror 31 half mirror 40 half mirror 40a mirror 40b mirror 40c mirror 51 reflective illumination optical system

Claims (10)

An objective lens;
A first half-wave plate disposed at a position conjugate with the sample and changing the polarization state of a part of the illumination light, and disposed between the first half-wave plate and the objective lens; First light branching means for reflecting light reflected by the sample through the objective lens, and the first region that is a part of the field of view of the objective lens is a straight line in the first polarization direction. A reflective illumination optical system that illuminates with polarized light and that illuminates a second region different from the first region within the field of view of the objective lens with linearly polarized light in a second polarization direction orthogonal to the first polarization direction;
A first detector for detecting reflected light reflected by the sample in the first region;
A second detector for detecting reflected light reflected by the sample in the second region,
The first light branching means is a polarization beam splitter that reflects light according to a polarization state;
The reflected illumination optical system is
A first quarter-wave plate provided between the first half-wave plate and the polarization beam splitter, which makes the illumination light circularly polarized;
An inspection apparatus comprising: a second quarter-wave plate that is provided between the objective lens and the polarization beam splitter and converts the illumination light that has been circularly polarized by the first quarter-wave plate into linearly polarized light.   A third quarter-wave plate provided between the polarizing beam splitter and the first and second photodetectors, and configured to linearly polarize reflected light incident on the first and second photodetectors; An inspection apparatus according to claim 1.   The inspection apparatus according to claim 1, wherein the first half-wave plate is inserted in a half of the optical path. An objective lens;
A first half-wave plate disposed at a position conjugate with the sample and changing the polarization state of a part of the illumination light, and disposed between the first half-wave plate and the objective lens; First light branching means for reflecting light reflected by the sample through the objective lens, and the first region that is a part of the field of view of the objective lens is a straight line in the first polarization direction. A reflective illumination optical system that illuminates with polarized light and that illuminates a second region different from the first region within the field of view of the objective lens with linearly polarized light in a second polarization direction orthogonal to the first polarization direction;
A first detector for detecting reflected light reflected by the sample in the first region;
A second detector for detecting reflected light reflected by the sample in the second region,
An inspection apparatus in which the first half-wave plate is inserted in a half of the optical path. Illuminating a first region that is part of the field of view of the objective lens with linearly polarized light in a first polarization direction by a reflective illumination optical system;
Illuminating a second region different from the first region in the field of view of the objective lens with linearly polarized light in a second polarization direction orthogonal to the first polarization direction by the reflective illumination optical system;
Detecting the reflected light reflected by the specimen Te said first region odor, the first detector through the objective lens,
Detecting reflected light reflected by the sample in the second region with a second detector via the objective lens,
The reflective illumination optical system is disposed at a position conjugate with the sample, and changes from a polarization state of a part of the illumination light to the objective lens. A first light branching unit that is disposed between and reflected by the sample is incident through the objective lens;
The first light branching means is a polarization beam splitter that reflects light according to a polarization state;
The reflected illumination optical system is
A first quarter-wave plate provided between the first half-wave plate and the polarization beam splitter, which makes the illumination light circularly polarized;
An inspection method comprising: a second quarter-wave plate that is provided between the objective lens and the polarization beam splitter and converts the illumination light that has been circularly polarized by the first quarter-wave plate into linearly polarized light.   A third quarter-wave plate provided between the polarizing beam splitter and the first and second photodetectors, and configured to linearly polarize reflected light incident on the first and second photodetectors; An inspection method according to claim 5.   The inspection method according to claim 5 or 6, wherein the first half-wave plate is inserted in a half of the optical path. Illuminating a first region that is part of the field of view of the objective lens with linearly polarized light in a first polarization direction by a reflective illumination optical system;
Illuminating a second region different from the first region in the field of view of the objective lens with linearly polarized light in a second polarization direction orthogonal to the first polarization direction by the reflective illumination optical system;
Detecting the reflected light reflected by the specimen Te said first region odor, the first detector through the objective lens,
Detecting reflected light reflected by the sample in the second region with a second detector via the objective lens,
The reflective illumination optical system is disposed at a position conjugate with the sample, and changes from a polarization state of a part of the illumination light to the objective lens. A first light branching unit that is disposed between and reflected by the sample is incident through the objective lens;
An inspection method in which the first half-wave plate is inserted in a half of the optical path. 9. The inspection method according to claim 5, wherein at least one of the first polarization direction and the second polarization direction is along a pattern provided on the sample. . An inspection step for inspecting a photomask by the inspection method according to any one of claims 5 to 9,
A defect correcting step of correcting defects of the photomask inspected by the inspecting step;
An exposure step of exposing the substrate through the photomask corrected in the defect correction step;
And a developing step for developing the exposed substrate.

Images