TWI522608B - Transmittance measurement apparatus for photomask and transmittance measurement method - Google Patents

Description

Transmissivity measuring device for mask and transmittance measuring method

The present invention relates to a transmittance measuring apparatus and a transmittance measuring method for measuring a transmittance of a measuring object having a light-transmitting region.

In order to reduce the cost by reducing the number of masks in a manufacturing step of an electronic component such as a liquid crystal panel, a so-called multi-step mask having at least one semi-transmissive film pattern applied to a previous monochromatic pattern is used ( Japanese Patent Laid-Open Publication No. 2009-258250 (hereinafter referred to as Patent Document 1)). Control of the transmittance of such a semi-transmissive film pattern is critical in managing the quality of the multi-level mask. Therefore, in the quality management of the multi-step mask, the reference mask was produced using the same composition as the actually patterned semi-transmissive film, and the transmittance was measured to evaluate the transmittance of the semi-transmissive film pattern.

Japanese Patent No. 4,358,848 (hereinafter referred to as Patent Document 2) describes a method for measuring the transmittance of a specific region (pixel of a color filter) of a sample. In the transmittance measurement method described in Patent Document 2, the light to be detected is collected in the measurement target region of the sample to measure the transmitted light intensity, and the transmittance of the region is calculated based on the measured intensity.

However, the semi-transmissive film pattern is complicated and finely formed on a transparent substrate having a large area, and thus it is difficult to manufacture at a uniform transmittance, and there may be a case where the transmittance from the reference mask is inconsistent. Moreover, the light transmittance in the stage in which only the semi-transparent film is formed is implemented as a plurality of processes The light transmittance of a patterned reticle finish sometimes does not exhibit the same penetration rate. Therefore, in order to manage the reticle, it is preferable to actually measure the transmittance of the semi-transmissive film pattern formed at any position on the reticle irrespective of the surrounding pattern.

When the method of measuring the transmittance of the above-described Patent Document 2 is developed and the light to be collected is collected on the multi-step mask, it is considered that the transmittance of the fine semi-transmissive film pattern can be measured. For example, if the light to be detected is collected on the semi-transmissive film pattern and the light is detected by the photodetector, it is considered that the penetration of the fine semi-transparent film pattern can be measured without being affected by the transmittance of the surrounding pattern. rate.

However, in the case of implementing the above-described transmittance measuring method, it is assumed that not only direct light directly penetrating the multi-step mask but also internal reflected light in which the transparent substrate is mixed is detected by the photodetector. The internal reflected light is defined as light that is emitted from the transparent substrate after the internal reflection component generated when the transparent substrate is emitted is again internally reflected by the transfer pattern forming surface of the transparent substrate. The internally reflected light also includes multiple reflected light that repeatedly reflects the internal reflection of the exit surface of the transparent substrate and the transfer pattern forming surface.

The reflectance in the transfer pattern forming surface changes in accordance with the pattern drawn on the transfer pattern forming surface. When the above reflectance changes, the amount of detected light detected by the photodetector also changes. That is, the transmittance of the semi-transmissive film pattern measured by the photodetector varies depending on the pattern on the transfer pattern forming surface, so that it is difficult to accurately measure.

The present invention has been made in view of the above circumstances, and its object is to provide a A transmittance measuring apparatus that preferably suppresses an error caused by internal reflected light and accurately measures the transmittance of the measurement target region.

A transmittance measuring apparatus according to one aspect of the present invention, which is characterized in that the light source device includes a light source device that emits light to be inspected, and a first optical system that collects the light to be detected to form a light spot on the measurement target a second optical system that condenses the light to be detected passing through the measurement target to form a conjugate image of the light spot; the aperture is disposed near the formation position of the conjugate image; and the light detecting mechanism detects the penetration aperture The light to be examined.

According to the present invention, it is possible to guide the direct light that has passed through the measurement target without internal reflection to the light detecting mechanism without causing light leakage by the aperture being substantially cut off from the internal reflected light generated when the inspection light penetrates the measurement target. . Since the change in the transmittance of the pattern depending on the measurement target is substantially suppressed, for example, the transmittance of the fine semi-transmissive film pattern can be accurately measured. In other words, according to the present invention, there is provided a transmittance measuring apparatus which preferably suppresses an error caused by internally reflected light and accurately measures the transmittance of a measurement target region.

In order to make the function of penetrating direct light and the function of shielding the internally reflected light sufficient, the aperture diameter of the aperture may be equal to or larger than the diameter of the conjugate image, and less than the internal reflection light generated when the inspection light penetrates the measurement object. The beam path at the location.

In order to better utilize the function of penetrating direct light and shielding the internal reflected light, the aperture may have an opening diameter in the range of 2 to 400 times the diameter of the conjugate image.

In order to form a tiny spot on the object to be measured, the light source device may also be a shot. The formation of light of a specific wavelength.

Further, a method for measuring a transmittance of a form of the present invention is a method for measuring a transmittance of a photomask having a semi-transparent pattern formed by patterning at least a semi-transparent film on a transparent substrate, and including The above method for measuring the transmittance of a semi-transmissive film pattern by the transmittance measuring device.

The photomask to be measured by the present invention is a multi-step mask which has a semi-transmissive pattern formed by patterning a semi-transparent film on the transparent substrate and a light-shielding film pattern in which the light-shielding film is patterned. The light transmissive portion, the light shielding portion and the semi-penetrating portion are included.

Hereinafter, a transmittance measuring apparatus according to an embodiment of the present invention will be described with reference to the drawings.

The transmittance measuring apparatus according to the present embodiment is a device for measuring the transmittance of the reticle, and is configured to preferably measure the transmittance of the fine semi-transmissive film pattern formed on the transparent substrate. 1 and 2 are block diagrams showing the configuration of the transmittance measuring apparatus 100 of the present embodiment. 1 shows the configuration of the entire transmittance measuring device 100, and FIG. 2 shows the configuration of a part of the transmittance measuring device 100.

As shown in FIG. 1, the transmittance measuring apparatus 100 includes a light projecting unit 1 and a light receiving unit 4. Between the light projecting unit 1 and the light receiving unit 4, the mask 8 to be measured is attached to the light projecting unit 1 side with the measurement target surface (transfer pattern forming surface). In the present embodiment, the photomask 8 is a so-called multi-step mask for manufacturing a liquid crystal panel in which a semi-transparent film pattern is formed on a transparent substrate in addition to a monochromatic pattern.

Further, as described below, the transmittance measuring apparatus and method of the present invention are not limited to the photomask for manufacturing a liquid crystal panel, and are not limited to the multi-step mask.

The light projecting unit 1 includes a light source device 2 and a first condensing lens system 3. The light source device 2 includes a laser light source that emits a specific single wavelength of the detected light. The light source device 2 may also include other forms of light sources such as LEDs (Light Emitting Diodes).

Further, the light source device 2 may be configured to combine a wavelength selective filter that selectively transmits light of a specific wavelength to a light source that emits light having a wide wavelength range, such as a mercury lamp, a halogen lamp, or a xenon lamp. . For example, the light source device 2 emits the detected light having a wavelength of 405 nm. The light source device 2 includes a collimating lens that converts the emitted light from the light source into collimated light and is efficiently guided to the first collecting lens system 3.

In the present invention, the light source can be selected depending on the use of the subject. In the case where the subject whose transmittance is measured is a photomask for a liquid crystal panel, it is preferable to use a light source included in the exposure machine used when the transfer pattern of the photomask is transferred to the transfer target. The wavelength in the wavelength is the wavelength of the detected light. For example, one of i-ray (365 nm), g-ray (405 nm), and h-ray (436 nm) is used as a representative wavelength, and a mercury lamp, a halogen lamp, a xenon lamp, an LED light source, or the like that can emit the representative wavelength is used. .

Also, laser light typically has a substantially Gaussian distribution of light intensity in the beam. That is, the light intensity at the center of the light beam (near the optical axis) decreases with a relatively large extent away from the optical axis (along the peripheral portion) on a plane perpendicular to the optical axis. On the other hand, in the above-mentioned lamp or LED including a plurality of wavelengths, there is no intensity distribution like the laser light, and the light intensity in the light beam depends on the light. The shape of the source and the optical system used to form the beam. In this case, in order to have a light intensity distribution similar to that of laser light, a filter (for example, an apodization filter) for adjusting the light distribution of the light beam may be included.

In the case of using a mercury lamp, a halogen lamp, a xenon lamp or the like as a light source, it is preferable to use a combination of wavelength-selective filters for selectively penetrating light of a desired wavelength from light of a plurality of wavelengths. On the other hand, in the case of a light source that emits light of a specific wavelength like a laser light source or an LED, it is also possible to configure not to provide a wavelength selective filter. It is also advantageous to use a light source device equipped with a plurality of LEDs of a single wavelength or a laser source. In this way, the transmittance can be measured for different wavelengths by switching a plurality of light sources using a single wavelength different from each other. Moreover, light of a single wavelength emitted from the LEDs or laser light sources is preferred because it is easily condensed by the optical system and the diameter of the light beam can be reduced.

When such a light source having high directivity is used, an optical element such as a beam expander (not shown) may be used to amplify the diameter (beam diameter) of the emitted light beam to a specific magnification, and introduce it into the first concentrated light described below. Lens system 3. Further, when a laser light source is used as the light source, it is preferable that the oscillation mode is a single mode, and the shape of the beam diameter is preferably a circle or an ellipse.

The first condensing lens system 3 sufficiently corrects aberrations so that minute spots can be formed on the measurement target region 11 of the reticle 8. The first condensing lens system 3 has a NA of 0.4, for example, and condenses the detection light having a wavelength of 405 nm emitted from the light source device 2 on the measurement target region 11 at a spot diameter of 2.0 μm or less. In the present specification, when the intensity distribution of the light source is Gaussian like a laser light, a range having an intensity of 1/e ² (about 13.5% of the peak) or more is defined as a spot diameter, and the intensity of the light source is used. When a lamp or LED that is not distributed in a Gaussian distribution is used, a range of 86.4% or more of the concentrated light amount is defined as a spot diameter. In addition, in this specification, the path which is not clearly described as "radius" means "diameter".

The light projecting unit 1 is configured to be movable in a plane parallel to the transfer pattern forming surface of the mask 8 (ie, in a plane perpendicular to the optical axis) by a moving mechanism (not shown), and can be finely adjusted to the liquid crystal panel. The relative position of the optical axis direction of the reticle 8 is used. For example, when the measurement target region 11 is a semi-transmissive film pattern, the light projecting unit 1 is adjusted in parallel with the transfer pattern forming surface in such a manner that the light collecting point of the first collecting lens system 3 comes to the semi-transmissive film pattern. The position in the in-plane and optical axis directions.

Further, the light receiving unit 4 is also movably moved by a moving mechanism (not shown). The light projecting unit 1 and the light receiving unit 4 are preferably integrally moved with respect to the reticle 8 via the interlocking mechanism.

The light to be illuminated on the semi-transmissive film pattern penetrates the reticle 8. As shown by the broken line in FIG. 2, a part of the light is internally reflected when the light is emitted from the transparent substrate of the mask 8, and is internally reflected again on the transfer pattern forming surface, and then emitted from the transparent substrate. The direct light (solid line in FIG. 2) that penetrates the mask 8 without internal reflection is incident on the light receiving unit 4, and such internal reflected light (dashed line in FIG. 2) is also incident on the light receiving unit 4.

The light receiving unit 4 includes a light amount detector 5, a second collecting lens system 6, and an aperture 7. The NA of the photomask 8 side of the second concentrating lens system 6 is preferably larger than the NA of the light beam condensed on the measurement target region 11 of the reticle 8 by the first condensing lens system 3, to effectively obtain Concentrating a lens system 3 and collecting it All beams of the light being examined.

In the present embodiment, the diaphragm 7 is disposed at a position where the image conjugated with the condensed point of the first condensing lens system 3 on the measurement target region 11 is formed by the second condensing lens system 6. Therefore, the direct light in the detected light penetrating the measurement target region 11 is formed at the position of the aperture 7 to form a conjugate image of a minute spot and penetrates the aperture 7 (solid line in FIG. 2), but the internal reflected light is tied to Unlike the positional imaging of direct light, it spreads at the position of the aperture 7, so it is mostly obscured by the aperture 7 (dashed line in Fig. 2). Therefore, in the light amount detector 5, only direct light is substantially detected.

The condensing angle of the detected light of the first concentrating lens system 3 is defined as θ (unit: deg), the thickness of the reticle 8 is defined as t (unit: mm), and the refractive index of the reticle 8 is defined as n, and when the imaging magnification of the conjugate image of the second condensing lens system 6 is defined as m, the beam radius L (unit: mm) of the internally reflected light at the position of the aperture 7 is expressed by the following formula (1) Said.

L=2tan θ. (t/n)m.........(1)

Furthermore, the thickness of the semi-transmissive film pattern is very thin compared to the thickness of the transparent substrate and is computationally negligible. In the present embodiment, for convenience, the beam radius L is calculated by using the thickness and the refractive index of the transparent substrate alone as the thickness t and the refractive index n of the mask 8.

When the opening radius of the diaphragm 7 is defined as r (unit: mm), the area ratio Sr of the beam of the internally reflected light at the position of the diaphragm 7 to the opening of the diaphragm 7 is expressed by the following formula (2).

Sr=r ² /L ² ...(2)

Arriving into the aperture of all the examined light that will penetrate the measurement target region 11 When the ratio of the internally reflected light of 7 is defined as the internal reflection transmittance Ix, the ratio of the internal reflected light reaching the light amount detector 5 among all the detected light that has passed through the measurement target region 11 (hereinafter referred to as "internal" The reflection transmittance Iy") is represented by the following formula (3). Furthermore, the internally reflected light is a light beam having the same intensity distribution.

Iy=Ix. Sr.........(3)

Here, the aperture 7 is required to have a function of allowing direct light to pass through and a function of shielding internal reflected light. In order to make both functions sufficient, the aperture diameter of the aperture 7 is equal to or greater than the conjugate image path (direct light path) SP formed at the position of the aperture 7, and smaller than the beam diameter (beam radius L × 2) of the internally reflected light. That is enough. Furthermore, in the present specification, the conjugate image diameter is the same as the spot diameter, and in the case where the intensity distribution of the light source such as laser light is Gaussian, it will have a range of intensity of 1/e ² (about 13.5% of the peak) or more. The conjugate image diameter is defined as a conjugate image diameter when a light source whose intensity distribution is not a Gaussian distribution lamp or an LED is used, and a range of 86.4% or more of the concentrated light amount is defined as a conjugate image diameter.

When the position where the conjugate image is formed and the center of the opening of the diaphragm 7 are eccentric due to an assembly error or the like, the conjugate image is blocked by the aperture 7. Further, depending on the product specifications, it is preferable to further reduce the internal reflected light reaching the light amount detector 5. In order to suppress the amount of shielding, it is necessary to design the opening diameter of the diaphragm 7 to be large, and in order to reduce the internal reflected light reaching the light amount detector 5, it is necessary to design the opening diameter of the diaphragm 7 to be small. In order to satisfy these opposite requirements, it is preferable to design the opening diameter of the diaphragm 7 to be in the range of 2 to 400 times the conjugate image diameter SP.

When the opening diameter is twice the conjugate image diameter SP, the diaphragm 7 shields a portion of the outer portion of the spot diameter (1/e ² ) of the direct light that penetrates the first condensing lens system 3 from light. As a result, direct light having a light amount of about 99.97% reaches the light amount detector 5. That is, when the position where the conjugate image is formed and the center of the opening of the diaphragm 7 are eccentric due to an assembly error or the like, only the edge portion of the conjugate image having a low intensity is shielded by the aperture 7. That is, since the loss of direct light is slight, it does not substantially affect the measurement of the transmittance of the semi-transmissive film pattern.

If the measurement accuracy required in the technical field of the photomask is taken as a reference, the internal reflected light reaching the light amount detector 5 is preferably suppressed to 1/100 or less by the aperture 7. In other words, the opening radius r of the diaphragm 7 may be designed to be 1/10 or less of the beam radius L of the internally reflected light according to the formula (2) so that the area ratio Sr is 1/100 or less. For example, when tan θ = 0.4, t = 6.0, n = 1.47, and m = 4, L = 13.32 according to the formula (1). In order to make the area ratio Sr 1/100, according to the formula (2), r=1.332. When the spot diameter on the measurement target region 11 of the first condensing lens system 3 is 2.0 μm, since m=4, the conjugate image diameter SP is 8.0 μm. Since the area ratio Sr is 1/100 or less, since the opening radius r is 1.332 mm and the radius of the conjugate image diameter SP is 4.0 μm, the aperture diameter of the aperture 7 must be about 333 times or less of the conjugate image diameter SP. However, if the measurement accuracy required for the mask of the low-cost version is lower than the above-described example, the allowable range of the mechanical arrangement deviation or the optical system for measurement is lowered in the measurement apparatus having the lower measurement accuracy required. The aberration correction performance allows the aperture diameter of the aperture 7 to be 400 or less times the conjugate image diameter SP.

Further, in the present embodiment, the diaphragm 7 is disposed at a position where the image conjugated with the condensed point of the first condensing lens system 3 on the measurement target region 11 is formed by the second condensing lens system 6. However, according to the present invention, not only The case where the aperture 7 is located at a position completely conjugate with the condensing point of the first condensing lens system 3 includes the case of being disposed on the front side or the rear side thereof. That is, before the detected light collected by the second collecting lens system 6 is incident on the light amount detector, the diaphragm 7 can shield a part of the light beam, thereby adjusting the light beam. This means that, in accordance with the present invention, the diaphragm 7 is disposed in the vicinity of the formation position of the image conjugated to the condensed point of the first condensing lens system 3 on the measurement target region 11. For example, it is preferably located in a region including a formation position of the conjugate image and within 1000 μm in the optical axis direction.

Preferably, the aperture 7 is disposed at a position within a specific tolerance within a central value of a position conjugate with the condensing point. The allowable arrangement error of the aperture 7 with respect to the conjugate point is considered by the aperture diameter of the aperture 7 (the conjugate image shielding amount of the aperture 7 caused by the assembly error or the like) or the allowable degree of the internal reflection light detected by the light amount detector 5, etc. And decided.

According to research by the inventors, for example, when the reflectance of the light to be examined on the surface of the subject is 80% and the reflectance of the back surface is 4%, the aperture diameter of the aperture 7 is the beam path of the internally reflected light. 1/2, the influence of the measurement error on the transmittance of the internally reflected light can be about 1% or less.

The light amount detector 5 is assumed to have a Si photodiode or a photomultiplier tube or the like. In order to measure the amount of light transmitted through the measurement target region 11 with high precision, the light amount detector 5 may be provided, for example, on the inner surface of the integrating sphere. The integrating sphere exerts an effect of causing light incident from the entrance port (penetrating light beam) to be spatially integrated by the diffuse reflection of the inner wall surface of the ball to be uniform and incident on the light amount detector.

The light amount data detected by the light amount detector 5 is input to the arithmetic unit 9. The arithmetic unit 9 calculates the transmittance T (unit: %) of the mask 8 based on the input light amount data. Here, the transmittance Tb (unit: %) of the transparent substrate alone before forming the film is measured in advance using the transmittance measuring device 100, and stored in the memory of the arithmetic unit 9. The arithmetic unit 9 calculates the transmittance Ta (unit: %) of the semi-transmissive film pattern on the measurement target region 11 by the following formula (4).

Ta=T/Tb.........(4)

Further, in the transmittance measuring apparatus of the present invention, a diaphragm opening adjustment mechanism (not shown) for adjusting the aperture opening diameter may be provided. Further, it may include a diaphragm position variable mechanism that adjusts the position of the aperture in the optical axis direction. For example, consider the case where there are a plurality of reticles having different thicknesses. In this case, the position at which the conjugate image is formed varies depending on the thickness of the reticle, which may affect the measurement accuracy. In this case, the above-described aperture position variable device can be used to improve the measurement accuracy.

Further, the transmittance measuring apparatus of the present invention may further include means for adjusting the position of the diaphragm in the vertical direction with respect to the optical axis direction.

Fig. 3 is a view showing a transfer pattern forming surface of the photomask 8. Here, a photomask for a liquid crystal panel is shown. 4(a) and 4(b) are enlarged views showing regions R ₁ and R ₂ in Fig. 3, respectively. As shown in FIGS. 3 and 4, the pattern is not formed on the transfer pattern forming surface. The region R ₁ located at the center of the reticle 8 is a portion corresponding to the pixel, so that the pattern is small and the ratio of the penetration region is large. The region R ₂ located near the outer periphery of the photomask 8 is a wiring portion, and therefore the pattern is large and the ratio of the light shielding film pattern is large. Since the ratio of region R ₂ of the light-shielding film pattern is large, so compared to the inner regions R ₁ and the reflected light increases. Hereinafter, a specific example will be specifically described using a comparative example.

(Comparative example)

In Figs. 4(a) and 4(b), the transmittance Ta of the semi-transmissive film itself was 45.0%, and the transmittance Tb of the transparent substrate was 96.0%. According to the formula (4), the transmittance T of the mask 8 is 0.45 × 0.96 × 100 = 43.2%, and the internal reflectance when the internal reflected light is internally reflected on the transfer pattern forming surface (irradiation from the back of the transparent substrate) The average value of the reflectance of the region of the reflected light beam is 5.0% in the example of Fig. 4(a), and 40.0% in the example of Fig. 4(b), the internal reflection transmittance Ix is: 0.45 × (1 - 0.96) × 0.05 × 100 = 0.09% 0.45 × (1 - 0.96) × 0.40 × 100 = 0.72%.

In the case where the second condensing lens system 6 and the diaphragm 7 are not present, the transmittance T of the reticle 8 measured by the light amount detector 5 is the transmittance T + the internal reflection transmittance Ix, and thus is shown in Fig. 4 (a In the case of 43.29%, it is 43.92% in the example of Fig. 4(b). As a result, in the case where the second condensing lens system 6 and the diaphragm 7 are not present, the transmittance T which should be the same value varies depending on the surrounding pattern on the measurement target region 11, so that the semi-transparent film is hindered. Determination of the penetration rate of the pattern. Further, in each of the comparative examples and the respective embodiments described later, since the amount of light is extremely small, the multiple reflected light is not considered, and the characteristics of the invention are easily grasped.

[Example 1]

In the first embodiment, the specifications of the respective elements constituting the transmittance measuring device 100 are as follows. Further, in the first embodiment and the second embodiment described later, the photomask 8 to be measured is in the comparative example and each of the examples. The same, so the respective values of the transmittances T, Ta, Tb and the internal reflection transmittance Ix refer to the values of the comparative examples.

The light source device 2 ... emits the collimated light having a wavelength of 405 nm, and the first concentrating lens system 3...NA is 0.4 (tan θ = 0.43 of the formula (1)) 5...Si photodiode second concentrating lens system 6...aspherical lens aperture with a focal length of 30 mm 7...opening 20 μm pinhole mask 8... Synthetic quartz with thickness t=7.0 mm (refractive index at wavelength 405 nm n=1.46966) The second collecting lens system 6 is arranged in the first collecting lens system 3 The spot is 4 times the aperture 7 (i.e., m = 4).

In the first embodiment, according to the formula (1), the beam radius L is 16.38 mm. According to the formula (2), the area ratio Sr is 3.72E-7. The mark E represents the power of the exponent based on the number 10 and the number to the right of E. According to the formula (3), the internal reflection transmittance Iy at the time of the half-transmission film pattern in the light-transmitting regions R ₁ and R ₂ is as follows.

0.09×(3.72E-7)×100=3.35E-6

0.72 × (3.72E-7) × 100 = 2.68E-5

When the second concentrating lens system 6 and the aperture 7 are disposed, the transmittance T of the reticle 8 measured by the light amount detector 5 is the transmittance T + the internal reflection transmittance Iy, and thus is shown in FIG. 4 (a). Any of (b) is roughly 43.2%. In the first embodiment, by arranging the second condensing lens system 6 and the diaphragm 7, it is possible to guide the direct light to the light amount detector 5 without causing light leakage. By cutting off the internally reflected light, the change in the transmittance caused by the surrounding pattern on the measurement target region 11 can be substantially suppressed. Therefore, the transmittance measurement of the fine semi-transmissive film pattern is accurately performed.

[Embodiment 2]

In the second embodiment, the specifications of the respective elements constituting the transmittance measuring device 100 are as follows.

Light source device 2... YAG laser with a wavelength of 355 nm (Yttrium-Aluminum-Garnet Laser) + beam expander (collimator) First concentrating lens system 3...NA is 0.65 (tan θ = 0.86 of the formula (1)) microscope objective light quantity detector 5... photomultiplier tube second concentrating lens system 6... lens system aperture 7 composed of two pieces of focal length 50 mm... Opening is 1.5 mm reticle 8... Synthetic quartz having a thickness t = 12.0 mm (refractive index at wavelength 355 nm n = 1.47604) The second concentrating lens system 6 is disposed at the condensing point of the first concentrating lens system 3 at the aperture 7 is 3 times the position (ie m=3).

In the second embodiment, according to the formula (1), the beam radius L is 41.95 mm. According to the formula (2), the area ratio Sr is 3.20E-4. According to the formula (3), the internal reflection transmittance Iy at the time of the half-transmission film pattern in the light-transmitting regions R ₁ and R ₂ is as follows.

0.09×(3.20E-4)×100=0.003

0.72×(3.20E-4)×100=0.023

The transmittance T of the photomask 8 measured by the light amount detector 5 is as shown in Fig. 4(a). The middle is 43.203%, which is 43.223% in the example of Figure 4(b). In the second embodiment, by arranging the second condensing lens system 6 and the diaphragm 7, the direct reflection light can be guided to the light amount detector 5 without causing the light leakage, and the internal reflection light can be substantially cut off. The change in the transmittance caused by the surrounding pattern on the area 11 is suppressed to a minimum. Therefore, the transmittance measurement of the fine semi-transmissive film pattern is accurately performed.

The above is the description of the embodiments of the present invention. The present invention is not limited to the above-described configuration, and various modifications can be made without departing from the spirit and scope of the invention. For example, the present invention is not limited to the transmittance measuring device in which the measurement target is a mask, and may be applied to a transmittance measuring device that measures the transmittance of a measurement target having another form of a light-transmitting region.

Further, as described in the present embodiment, the present invention includes a method for measuring a transmittance, and examples of the measurement include a semi-transmissive film pattern obtained by patterning a semi-transparent film formed on a transparent substrate. Further, by further including a light shielding film pattern, the effects of the present invention are remarkable in a multi-step mask including a light shielding portion, a penetration portion, and a semi-transmissive portion. The transmittance of the semi-transparent film is preferably from 5 to 80% with respect to the exposure light.

By performing exposure and development on the photoresist film formed on the transfer target by using such a photomask, the exposure amount can be partially different, and a photoresist pattern having a different remaining film amount portion can be formed. In this case, the step of previously using the two masks can use one mask, so that the number of masks used can be reduced, and the production efficiency of the liquid crystal panel or the like is improved.

Further, a fourth-order or more multi-step mask including a plurality of semi-transmissive portions formed by two or more types of semi-transmissive film patterns having different light transmittances has been proposed. This hair It is effective in ensuring the penetration rate of such a plurality of semi-penetrating portions.

For the photomask for a liquid crystal panel, for example, a portion corresponding to a source and a drain of a TFT (thin film transistor) may be formed as a light shielding portion, and a portion corresponding to a channel portion between the source and the drain may be adjacent. A multi-step mask partially formed as a semi-transmissive portion. In recent years, with the miniaturization of the pattern of the TFT channel portion and the like, a fine pattern is more and more required in the multi-step mask, which corresponds to a portion of the channel width in the TFT channel portion pattern, that is, a semi-transparent between the light shielding films. The width of the section also tends to be fine. Such miniaturization is effective for improving the brightness or the reaction speed of the liquid crystal panel. In order to achieve miniaturization, the transmittance management of the fine pattern portion is crucial.

Further, the present invention can be effectively applied to a reticle in which only a semi-transparent film is formed on a transparent substrate and a specific pattern is formed thereon, and the transmittance of the fine pattern of the semi-transmissive portion can be accurately measured.

The measurement object of the present invention is exemplified by a line width of 0.5 μm or more and 10 μm or less in the semi-transmissive pattern. Further, when the thickness is 1 μm or more and 7 μm or less, and more preferably 2 μm or more and 7 μm or less, the effect of the present invention is remarkable.

In the above description, the photomask for a liquid crystal panel is exemplified, but the use of the photomask is not limited thereto. The transmittance measuring apparatus and method of the present invention are also applicable to the measurement of the transmittance of a photomask for other purposes, and can exert a beneficial effect. For example, a mask for a display device such as an organic EL (Electro Luminescence) or the like, a photomask for an imaging device, and a photomask for an integrated circuit may be used in addition to the liquid crystal. Depending on the application, the semi-transmissive film utilizes interference by inverting the phase of the transmitted light. A photomask (a photomask with a phase shift of 180 degrees ± 30 degrees for a representative wavelength of transmitted light) or a photomask that does not substantially utilize an interference effect (for a representative wavelength of transmitted light, the phase shift amount is 60 degrees or less) The effect of the present invention can be advantageously obtained in any of the reticle.

1‧‧‧Lighting unit

2‧‧‧Light source device

3‧‧‧First Condenser Lens System

4‧‧‧Light receiving unit

5‧‧‧Light quantity detector

6‧‧‧Second condenser lens system

7‧‧‧ aperture

8‧‧‧Photomask

9‧‧‧ arithmetic device

11‧‧‧Target area

100‧‧‧Density measuring device

L‧‧‧ beam radius

T‧‧‧thickness

R ₁ ‧‧‧Area

R ₂ ‧‧‧ area

Θ‧‧‧concentrating angle

Fig. 1 is a block diagram showing the configuration of a transmittance measuring apparatus according to an embodiment of the present invention.

Fig. 2 is a block diagram showing the configuration of a transmittance measuring apparatus according to an embodiment of the present invention.

Fig. 3 is a view showing a transfer pattern forming surface of a photomask to be measured.

4(a) and 4(b) are views showing a transfer pattern forming surface of a photomask to be measured.

3‧‧‧First Condenser Lens System

5‧‧‧Light quantity detector

6‧‧‧Second condenser lens system

7‧‧‧ aperture

8‧‧‧Photomask

11‧‧‧Target area

L‧‧‧ beam radius

T‧‧‧thickness

Θ‧‧‧concentrating angle

Claims (15)

A transmittance measuring device for a photomask, comprising: a light source device that emits the detected light; and a first optical system that collects the detected light to form a light spot on the transfer pattern of the photomask; a second optical system that condenses the detection light that has passed through the photomask to form a conjugate image of the light spot; the aperture is disposed near a position where the conjugate image is formed; and the light detecting mechanism detects the wear a light that passes through the aperture of the aperture; wherein the aperture of the aperture is equal to or larger than a diameter of the conjugate image, and is smaller than a beam of internal reflected light generated at a position of the aperture when the inspection light penetrates the measurement target The diameter is within the range of 2 to 400 times the diameter of the conjugate image. The light transmittance measuring apparatus for a photomask according to claim 1, wherein the light to be detected concentrated on the transfer pattern is on a plane perpendicular to the optical axis, and the light intensity in the center of the light beam is relatively larger than the peripheral portion. The transmittance measuring apparatus for a photomask according to claim 1 or 2, wherein the first optical system includes a number of apertures (NA) for concentrating the inspection light with a spot diameter of 2.0 μm or less in the transfer pattern. The transmittance measuring apparatus for a photomask according to claim 1 or 2, wherein a number of apertures (NA) of the mask side of the second optical system is larger than a beam of light concentrated on the transfer pattern by the first optical system The number of openings (NA) is large. The transmittance measuring apparatus for a photomask according to claim 1 or 2, wherein the photomask forms a transfer pattern on the transparent substrate, and the transparent substrate has a thickness of 6 mm or more. A light transmittance measuring apparatus for a photomask according to claim 1 or 2, wherein said light source means emits light of a single wavelength. The transmissivity measuring device for a photomask according to claim 1 or 2, wherein the light source device is a laser light source. A light transmittance measuring apparatus for a photomask according to claim 1 or 2, wherein said light source means comprises a filter for adjusting a light intensity distribution in the light beam. A method for measuring a transmittance of a photomask having a semi-transparent pattern formed by patterning at least a semi-transparent film on a transparent substrate, and the method for measuring the transmittance of the photomask is as claimed in claim 1 The photomask is used to measure the transmittance of the semi-transparent pattern by a transmittance measuring device. The method for measuring a transmittance of a photomask according to claim 9, wherein the light to be detected concentrated on the transfer pattern is on a plane perpendicular to the optical axis, and the light intensity at the center of the light beam is relatively larger than the peripheral portion. The method for measuring the transmittance of a photomask according to claim 9 or 10, wherein the photomask has a thickness of 6 mm or more. A method of measuring a transmittance of a photomask according to claim 9 or 10, wherein said transparent substrate comprises quartz. A method of measuring a transmittance of a photomask according to claim 9 or 10, wherein said semi-transmissive pattern comprises a line width portion of 0.5 to 10 μm. A method of measuring a transmittance of a photomask according to claim 9 or 10, wherein said photomask is a photomask for manufacturing a display device. The method for measuring the transmittance of a photomask according to claim 9 or 10, wherein the photomask is a multi-step mask, which has a semi-transparent pattern formed by patterning a semi-transparent film on the transparent substrate and is shielded from light. The film is patterned into a light shielding film pattern, and includes a light transmitting portion, a light blocking portion, and a semi-transmissive portion.