JP2015225257A - Photomask inspection method and photomask manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photomask inspection method and a photomask manufacturing method, capable of obtaining the optical concentration of a photomask light shielding region pattern with high accuracy.SOLUTION: A light shielding region with a light shielding region pattern 15 of a photomask 10 is formed and a transparent region 14 where a transparent substrate 13 is exposed are irradiated with excimer laser light 21a, 21b, having the same wavelength as exposure light. The light intensity distribution of each of first transmission light 22a passing through the light shielding region and second transmission light 22b passing through the transparent region is measured by an imaging device. The light intensity distributions of the first transmission light 22a and the second transmission light 22b thus measured are compared to obtain the optical concentration of the light shielding region pattern 15.

Description

  The present invention relates to a photomask used for manufacturing a semiconductor element, and more particularly to a photomask inspection method and a photomask manufacturing method.

  In order to realize high integration and miniaturization of semiconductor elements, a pattern is transferred onto a wafer using a photomask by an optical projection exposure apparatus using ArF excimer laser light with an exposure wavelength of 193 nm as exposure light. Photolithographic techniques are used.

Here, in the manufacture of semiconductor elements, usually, an exposure area in which a mask pattern of a photomask is formed is projected to be reduced to ¼ and transferred onto a resist provided on a wafer (for example, Patent Document 1). ).
Therefore, for example, as shown in FIG. 8, in the photomask 100, a light-shielding region pattern is formed on the outer periphery of the exposure region 101 in order to prevent a problem that the resist positioned at the boundary portion when performing multi-face transfer is subjected to multiple exposure. 105 is provided.
In the example shown in FIG. 8, a mask pattern 102 is provided in the exposure region 101, and a region where the mask pattern 102 is not provided in the exposure region 101 is a transparent region 104 where the transparent substrate 103 is exposed. ing.

FIG. 9 is a flowchart showing an example of a conventional photomask manufacturing method. Usually, a photomask is formed by processing a photomask blank provided with a material layer (referred to as a light shielding material layer) constituting a light shielding region pattern on a transparent substrate to form various patterns including the light shielding region pattern. Manufactured.
As shown in FIG. 9, conventionally, the optical density of the light-shielding region pattern of the photomask is measured using a spectrophotometer in the state of the photomask blank before the various pattern formation steps (S103). And obtained by measuring the light intensity of the transmitted light of the light shielding material layer (for example, Patent Document 2)

Japanese Patent No. 3664332 JP 2006-78807 A

  However, the optical density of the light shielding region pattern of the photomask that has undergone various manufacturing processes including the cleaning process may be different from the optical density of the light shielding material layer in the state of the photomask blank before the formation of the various patterns. More specifically, the optical density of the light-shielding region pattern of the photomask may be smaller than the optical density of the light-shielding material layer in the photomask blank state due to damage received from various manufacturing processes.

  Therefore, in order to more accurately obtain the optical density of the light shielding region pattern of the photomask, the light shielding region of the light shielding region can be obtained using light having the same wavelength as the exposure light in the state of the photomask that has undergone various manufacturing processes including the cleaning process. It is necessary to measure the light intensity of the transmitted light.

  Here, in the light shielding area, the part where the optical density needs to be guaranteed is a part close to the exposure area. Usually, various kinds of alignment marks are provided in the light shielding area, so that the light intensity of the transmitted light is measured. It is desirable that the spot diameter of the light used for is a small size, for example, a spot diameter of 500 μm or less, preferably 100 μm or less.

However, since the spot diameter of light in a spectrophotometer is usually as large as about 10 mm, it is not suitable for photomask measurement.
In the case of a spectrophotometer, light of a desired wavelength (same wavelength as exposure light) is obtained by demultiplexing the light of the deuterium lamp with a diffraction grating and eliminating unnecessary light. The energy of light that can be produced is only small. Therefore, there is a problem that if the spot diameter is reduced by any method, the measurement accuracy is also lowered.

  The present invention has been made in view of the above circumstances, and provides a photomask inspection method and a photomask manufacturing method capable of accurately obtaining the optical density of the light shielding region pattern of the photomask. With the goal.

  As a result of various studies, the inventor irradiates the light shielding region where the light shielding region pattern of the photomask is formed and the transparent region where the transparent substrate is exposed to each other by irradiating the light shielding region with an excimer laser beam having the same wavelength as the exposure light. Each light intensity distribution of the first transmitted light to be transmitted and the second transmitted light to be transmitted through the transparent region is measured by the image sensor, and the measured light intensity distributions of the first transmitted light and the second transmitted light are compared. Thus, the present invention has been completed by finding that the above problem can be solved by obtaining the optical density of the light shielding region pattern.

  That is, the invention according to claim 1 of the present invention is a photomask inspection method having a light shielding area pattern for shielding exposure light on a transparent substrate, wherein the light shielding area pattern of the photomask is formed. The region and the transparent region where the transparent substrate is exposed are respectively irradiated with excimer laser light having the same wavelength as the exposure light, and the first transmitted light that passes through the light shielding region and the second transmitted light that passes through the transparent region. Each light intensity distribution of the light-shielding region pattern is measured by the image sensor, and the light intensity distributions of the first transmitted light and the second transmitted light measured by the image sensor are compared, and the optical density of the light-shielding region pattern is compared. This is a photomask inspection method characterized in that

  The invention according to claim 2 of the present invention is the photomask according to claim 1, wherein a spot diameter of the excimer laser light irradiated to the light shielding region is 100 μm or less. Inspection method.

  The invention according to claim 3 of the present invention is characterized in that the first transmitted light and the second transmitted light are measured by an image sensor after being magnified by a magnifying lens. 2. A photomask inspection method according to 2.

  In the invention according to claim 4 of the present invention, the first transmitted light and the second transmitted light are respectively applied to a fluorescent plate, and the light emitted from the fluorescent plate is measured by an imaging device, thereby 4. The photomask inspection method according to claim 1, wherein each light intensity distribution of the first transmitted light and the second transmitted light is measured. 5.

  According to a fifth aspect of the present invention, there is provided a process for forming a light shielding region pattern for shielding exposure light on a transparent substrate, and the photomask according to any one of the first to fourth aspects. A method of manufacturing a photomask, comprising sequentially obtaining the optical density of the light shielding region pattern using an inspection method.

  The invention according to claim 6 of the present invention is characterized by comprising a cleaning step after the step of forming the light shielding region pattern and before the step of obtaining the optical density of the light shielding region pattern. The photomask manufacturing method according to claim 5.

According to the photomask inspection method of the present invention, the optical density of the light shielding region pattern of the photomask can be obtained with high accuracy.
Moreover, according to the photomask manufacturing method of the present invention, it is possible to guarantee the optical density of the light shielding region pattern in the state of the photomask that has undergone various manufacturing processes.

It is a figure explaining an example of the inspection method of the photomask concerning the present invention. It is a figure which shows the structural example of the test | inspection apparatus used for the test method of the photomask which concerns on this invention. It is a figure explaining the other example of the inspection method of the photomask which concerns on this invention. It is a flowchart which shows an example of the manufacturing method of the photomask which concerns on this invention. It is a schematic process drawing which shows an example of the manufacturing method of the photomask which concerns on this invention. FIG. 6 is a schematic process diagram illustrating an example of a method for manufacturing a photomask according to the present invention following FIG. 5. 4 is a graph showing measurement results in Example 1. It is a figure explaining an example of a photomask, (a) is a schematic plan view, (b) is AA sectional drawing of (a). It is a flowchart which shows an example of the manufacturing method of the conventional photomask.

  Hereinafter, a photomask inspection method and a photomask manufacturing method according to the present invention will be described.

<Photomask inspection method>
First, a photomask inspection method according to the present invention will be described.
FIG. 1 is a diagram for explaining an example of a photomask inspection method according to the present invention.
For example, as shown in FIG. 1, in the photomask inspection method according to the present invention, the exposure light is respectively applied to the light shielding region where the light shielding region pattern 15 of the photomask 10 is formed and the transparent region 14 where the transparent substrate 13 is exposed. Each of the light intensity distributions of the first transmitted light 22a that is irradiated with excimer laser beams 21a and 21b having the same wavelength as that of the first transmitted light and transmitted through the light shielding region and the second transmitted light 22b that is transmitted through the transparent region is image sensor (not shown). ) And the respective light intensity distributions of the first transmitted light 22a and the second transmitted light 22b measured by the image sensor, and the optical density of the light shielding region pattern 15 is obtained.
As the imaging element, a CCD (Charge Coupled Device) or the like can be used.

  FIG. 1 shows an example in which excimer laser beams 21a and 21b are irradiated from the film surface side (light shielding region pattern 15 side) of the photomask 10, but in the photomask inspection method according to the present invention, However, the present invention is not limited to this mode, and a mode in which excimer laser beams 21a and 21b are irradiated from the back surface side (transparent substrate 13 side) of the photomask 10 may be used.

  As described above, in the photomask inspection method according to the present invention, in the state of the photomask that has undergone various manufacturing steps, the first transmitted light that passes through the light shielding region using light having the same wavelength as the exposure light, Each light intensity distribution of the second transmitted light that passes through the transparent region is measured by an image sensor such as a CCD, and the measured light intensity distributions of the first transmitted light and the second transmitted light are compared to block light. Since the optical density of the area pattern is acquired, the optical density of the light shielding area pattern can be acquired more accurately.

  In addition, as described above, in the photomask inspection method according to the present invention, the first transmitted light 22a that passes through the light-shielding region of the photomask 10 and the second transmitted light 22b that passes through the transparent region 14 are measured. Excimer laser beams 21a and 21b having the same wavelength as the exposure light (for example, 193 nm) are used. That is, the light used for the measurement does not include light having an unnecessary wavelength, such as light from a deuterium lamp when a spectrophotometer is used.

  Therefore, there is no energy loss due to eliminating light of unnecessary wavelength, and higher energy is obtained than the light obtained by demultiplexing the light of the conventional deuterium lamp, thus suppressing the decrease in measurement accuracy, The spot diameter of the excimer laser beams 21a and 21b can be made 100 μm or less. And since a spot diameter can be made small, the optical density of the light shielding area | region pattern 15 nearer to the exposure area | region 11 can be acquired correctly.

In addition, in the photomask inspection method according to the present invention, unlike the photomultiplier tube used in the conventional spectrophotometer, the first measurement is performed with an image sensor such as a CCD, and the first resolution is obtained according to the number of pixels. Each light intensity distribution of the transmitted light 22a and the second transmitted light 22b can be measured.
Therefore, by comparing the distribution curves of the light intensity of the first transmitted light 22a that passes through the light shielding area and the light intensity of the second transmitted light 22b that passes through the transparent area 14, a more accurate light shielding area pattern can be obtained. A value of 15 optical densities can be obtained.

  More specifically, for example, in the light intensity distribution of the first transmitted light 22a, a value in a range where the numerical variation near the center of the spot diameter is small is set as the light intensity of the first transmitted light 22a. In the light intensity distribution of the transmitted light 22b, a value in a range where the numerical variation near the center of the spot diameter is small is set as the light intensity of the second transmitted light 22b, and the difference between the two is taken, so that the optical of the light-shielding region pattern 15 can be more accurate. A concentration value can be obtained.

  Here, in the photomask inspection method according to the present invention, the first transmission light 22a and the second transmission light 22b can be measured by an image pickup device such as a CCD without enlarging the first transmission light 22a and the second transmission light 22b. More preferably, the light 22a and the second transmitted light 22b are magnified by a magnifying lens and then measured by an imaging device such as a CCD. This is because by magnifying with a magnifying lens, the light intensity distribution can be measured with higher accuracy even with an image sensor such as a CCD having a large pixel size.

  In the present invention, the range of magnification by the above magnifying lens is not particularly limited as long as the light intensity distribution can be measured with high accuracy, but as a suitable range, for example, enlarging to 100 to 200 times is mentioned. Can do.

FIG. 2 is a diagram showing a configuration example of an inspection apparatus used in the photomask inspection method according to the present invention.
As shown in FIG. 2, the inspection apparatus 30 has an excimer laser light source 31, a condenser lens 32, a magnifying lens 33, and a CCD 34.
The photomask 10 to be measured is disposed between the condenser lens 32 and the magnifying lens 33. Although illustration is omitted, the inspection apparatus 30 also includes a photomask moving mechanism, and the photomask moving mechanism can irradiate a desired portion of the photomask 10 with excimer laser light.

  In the inspection apparatus 30, the excimer laser light 41 emitted from the excimer laser light source 31 is irradiated as a parallel light 42 having a predetermined spot diameter to a desired light-shielding region or transparent region of the photomask 10, and the transmitted light 43 is enlarged. The light intensity distribution of the transmitted light 44 magnified by the lens 33 is measured by the CCD 34.

  Further, in the photomask inspection method according to the present invention, as shown in FIG. 3, the first transmitted light 22a is applied to the fluorescent plate 51, and the light emitted from the fluorescent plate (first emitted light 52a) is applied to the CCD 53. You may measure with. Similarly, the second transmitted light 22 b may be applied to the fluorescent plate 51, and the light emitted from the fluorescent plate (second emitted light 52 b) may be measured by the CCD 53.

A CCD that can measure light having the same wavelength as the exposure light (for example, 193 nm), such as the first transmitted light 22a and the second transmitted light 22b, is generally expensive, but as described above, the first transmitted light 22a In addition, by applying the second transmitted light 22b to the fluorescent plate 51, it is possible to generate radiated light (first radiated light 52a and second radiated light 52b) having a wavelength that can be measured by a cheaper CCD.
By measuring the first radiated light 52a and the second radiated light 52b, a desired light intensity distribution can be measured even when a cheaper CCD is used.

<Photomask manufacturing method>
Next, a method for manufacturing a photomask according to the present invention will be described.
FIG. 4 is a flowchart showing an example of a photomask manufacturing method according to the present invention.
As shown in FIG. 4, in the photomask manufacturing method according to the present invention, first, a photomask blank provided with a light shielding material layer on the main surface is prepared (S1), and then the prepared photomask blank is prepared. Various patterns including the light shielding area pattern are formed by processing (S2), and then the optical density of the formed light shielding area pattern is obtained by using the photomask inspection method according to the present invention (S4).

As described above, in the photomask manufacturing method according to the present invention, the optical density of the light shielding region pattern is obtained using the photomask inspection method according to the present invention after various pattern forming steps including the light shielding region pattern. The process of acquiring.
Therefore, as before, the transmitted light of the light shielding material layer was measured in the state of the photomask blank before forming various patterns, and the optical density calculated from the measured value was used as the optical density of the light shielding area pattern of the photomask. Compared to the case, the optical density of the light shielding region pattern of the actually formed photomask can be obtained more accurately.
Thereby, according to the photomask manufacturing method of the present invention, it is possible to guarantee the optical density of the light shielding region pattern in the state of the photomask that has undergone various manufacturing processes.

Further, in the photomask manufacturing method according to the present invention, as shown in FIG. 4, after the formation of various patterns including a light shielding region pattern, the photomask is washed (S3), and then the photomask according to the present invention described above. It is more preferable to obtain the optical density of the formed light shielding region pattern using a mask inspection method (S4).
This is because it is possible to guarantee the optical density of the light shielding region pattern of the photomask in a state just before shipment after the cleaning process.

  The above-described photomask manufacturing method according to the present invention will be described in more detail with reference to FIGS. Here, FIG. 5 and FIG. 6 are schematic process diagrams showing an example of a photomask manufacturing method according to the present invention.

  In the photomask manufacturing method according to the present invention, as shown in FIG. 5A, first, a photomask blank 60 provided with a light shielding material layer 61 on a transparent substrate 13 is prepared.

Next, a resist 63 is formed on the light shielding material layer 61 (FIG. 5B), followed by pattern drawing and development using an electron beam 71 or the like (FIG. 5C), and a resist pattern 63P. Is formed (FIG. 5D).
Here, the resist pattern 63P includes a resist pattern 63a that forms the mask pattern 12 and a resist pattern 63b that forms the light shielding region pattern 15.

  Next, the light shielding material layer 61 exposed from the resist pattern 63P is dry-etched (FIG. 6E), and then the resist pattern 63P is removed (FIG. 6F), and the mask pattern 12 is formed on the transparent substrate 13. A photomask 10 having a light shielding region pattern 15 is obtained.

  Next, the photomask 10 obtained in the above step is washed, and then, as shown in FIG. 6G, the region where the light shielding region pattern 15 of the photomask 10 is formed and the transparent region where the transparent substrate 13 is exposed. 14 are irradiated with excimer laser beams 21a and 21b having the same wavelength as the exposure light, respectively, and the respective light intensity distributions of the first transmitted light 22a that passes through the light shielding region and the second transmitted light 22b that passes through the transparent region 14 are shown. The optical density of the light shielding region pattern 15 is obtained by measuring with an image pickup device such as a CCD and comparing the measured light intensity distributions of the first transmitted light 22a and the second transmitted light 22b.

  As mentioned above, although each embodiment was described about the inspection method of a photomask and the manufacturing method of a photomask which concern on this invention, this invention is not limited to the said embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same function and effect regardless of the case. Are included in the technical scope.

  The present invention will be described more specifically with reference to the following examples.

[Example 1]
(Manufacture of photomasks)
A photomask blank having a chromium (Cr) film having a thickness of 70 nm as a light shielding material layer on a transparent substrate having an outer shape of 152 mm × 152 mm and a thickness of 6.35 mm was prepared.
Next, an electron beam resist was applied onto the chromium film (Cr), and pattern drawing and development were performed with an electron beam drawing apparatus to form a desired resist pattern.
Next, the chromium film exposed from the resist pattern is dry-etched with a mixed gas of chlorine and oxygen to form a desired mask pattern and a light-shielding region pattern. The photomask of Example 1 was obtained.

(Measurement of optical density)
Excimer laser light having a wavelength of 193 nm and a spot diameter of 80 μm is irradiated to the light-shielding region and the transparent region of the photomask obtained as described above, respectively, and the first transmitted light that passes through the light-shielding region and the first light that passes through the transparent region. Each of the two transmitted lights was magnified 150 times with an optical lens and then measured with a CCD.
The results are shown in FIG. The light intensity distribution shown in FIG. 7 is a light intensity distribution within a radius of 5 μm from the center of the spot diameter of the first transmitted light, where the value of the light intensity of the second transmitted light is 1. Is shown.

(Evaluation)
As shown in FIG. 7, the obtained light intensity values are stably in the range of 0.0011 to 0.0012. This is because the transmittance of the light shielding region pattern is 0.11% to 0.12%. In other words, the optical density of the light shielding region pattern is in the range of 2.9 to 3.0.
That is, it was confirmed that the optical density of the light-shielding region pattern of the photomask that has undergone various manufacturing steps can be obtained with high accuracy by the photomask inspection method according to the present invention.

DESCRIPTION OF SYMBOLS 10 Photomask 11 Exposure area | region 12 Mask pattern 13 Transparent substrate 14 Transparent area 15 Light-shielding area pattern 21a, 21b Excimer laser beam 22a 1st transmitted light 22b 2nd transmitted light 30 Inspection apparatus 31 Excimer laser light source 32 Condenser lens 33 Magnifying lens 34 CCD
41 Excimer laser light 42 Parallel light 43, 44 Transmitted light 51 Fluorescent plate 52a First emitted light 52b Second emitted light 53 CCD
60 Photomask blank 61 Light shielding material layer 61P Light shielding material pattern 63 Resist 63P Resist pattern 71 Electron beam 100 Photomask 101 Exposure region 102 Mask pattern 103 Transparent substrate 104 Transparent region 105 Light shielding region pattern

Claims (6)

A photomask inspection method having a light shielding region pattern for shielding exposure light on a transparent substrate,
Irradiating a light shielding region where the light shielding region pattern of the photomask is formed and a transparent region where the transparent substrate is exposed, respectively, with an excimer laser beam having the same wavelength as the exposure light;
Each light intensity distribution of the 1st transmitted light which permeate | transmits the said light-shielding area | region and the 2nd transmitted light which permeate | transmits the said transparent area | region is measured with an image pick-up element, respectively.
A method for inspecting a photomask, comprising: comparing optical intensity distributions of the first transmitted light and the second transmitted light measured by the imaging device to obtain an optical density of the light shielding region pattern. .   The photomask inspection method according to claim 1, wherein a spot diameter of the excimer laser light applied to the light shielding region is 100 μm or less.   3. The photomask inspection method according to claim 1, wherein the first transmitted light and the second transmitted light are measured by an imaging device after being magnified by a magnifying lens. 4.   Each of the first transmitted light and the second transmitted light is measured by applying the first transmitted light and the second transmitted light to the fluorescent plate and measuring the light emitted from the fluorescent plate with an imaging device. The photomask inspection method according to any one of claims 1 to 3, wherein the light intensity distribution is measured. Forming a light shielding region pattern for shielding exposure light on a transparent substrate;
The step of acquiring the optical density of the light shielding region pattern using the photomask inspection method according to claim 1,
A method for manufacturing a photomask, comprising: sequentially. 6. The method of manufacturing a photomask according to claim 5, further comprising a cleaning step after the step of forming the light shielding region pattern and before the step of acquiring the optical density of the light shielding region pattern.

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