TWI461839B - Photomask and method of manufacturing the same, pattern transfer method, and pellicle - Google Patents

Description

Photomask and manufacturing method thereof, pattern transfer method and film

The present invention relates to a photomask, a pattern transfer method, and a pellicle. More particularly, the present invention relates to a reticle that can be advantageously used to manufacture display devices such as liquid crystal display panels.

In an exposure apparatus for manufacturing a liquid crystal display panel or the like, an ultrahigh pressure mercury lamp is generally used as a light source for exposure. The ultrahigh pressure mercury lamp has a light source comprising a plurality of peak wavelengths of i-line (365 nm), h-line (405 nm), and g-line (436 nm). Using the light source, the transfer pattern formed on the photomask is transferred to the photoresist film on the transfer target, and the formed photoresist pattern is used as an etching mask for film formation on the object to be transferred. The film is processed on the film. A liquid crystal display panel is manufactured using the series of light lithography processes.

An exposure mask is described in Japanese Patent No. 4413414 (Patent Document 1). There is described an exposure mask which is obtained by absorbing light of the first wavelength of light having a mixed wavelength of light having first, second, and third wavelengths emitted from a light source by a filter. And absorbing the light of the second wavelength from the transmitted light from the filter, transmitting the light of the third wavelength, irradiating the photoresist, and exposing the light, and forming an absorption on the entire surface of the exposure mask The film or substrate of the second wavelength light.

In recent years, the high resolution of the display device has been advanced, and the pixel size of the pixel formed in the liquid crystal display panel has been increased. Get pushed forward. In other words, along with the improvement in the quality of the display image quality, it is necessary to reduce the size of the element during the formation of an element for performing operations such as switching or orientation of the liquid crystal. When the transfer pattern formed on the photomask is transferred by using the projection type exposure apparatus, the necessity of realizing pattern transfer with higher resolution is also gradually produced. In particular, in an exposure apparatus that performs double exposure, it is difficult to reduce the minimum resolution line width as compared with an exposure apparatus that performs reduction exposure, and thus an improvement in the minimum resolution limit is expected.

Further, regarding the relationship between the pattern resolution (the minimum line width at which the image can be resolved) and the exposure wavelength when the optical system is used, the following expression representing the resolution limit of Rayleigh can be considered as a reference.

F=k ₁ λ/NA

Here, F: minimum line width, k ₁ : (coefficient, so-called k1 factor), λ: wavelength of exposure light, NA: aperture ratio of optical system with respect to the object to be transferred.

According to the above formula, if the wavelength of the exposure light is shortened, the minimum line width of the solvable image can be reduced.

When pattern transfer is performed using a plurality of peak wavelengths (hereinafter, also referred to as multi-wavelength) exposure light sources of the ultrahigh pressure mercury lamp as described above, the resolution may be caused by chromatic aberration of the optical system of the exposure apparatus or the like. Deterioration.

For this reason, in order to achieve a single wavelength or short wavelength of exposure light, for example, when a mechanism for selectively switching the desired wavelength of exposure light is provided in the exposure apparatus, by selecting an exposure Exposure with light and switching to light of a desired wavelength can improve the solution of the transfer pattern Image degree.

However, depending on the device, when the functions cannot be attached due to limitations in optical design, or even if the design is achievable, there are the following problems: the modification with the addition of functions requires cost. Or during the retrofit period, the device must be stopped for a long time. In general, the size of the exposure apparatus used in the manufacturing process of the large-sized substrate for a liquid crystal panel is very large, so that the modification or condition change of the apparatus as described above becomes a large burden for the liquid crystal panel manufacturer. Therefore, it is expected that the resolution of the pattern to be miniaturized can be increased without making a great effort to change the exposure apparatus.

On the other hand, when the optical filter disclosed in the above Patent Document 1 is provided in the photomask, there are the following problems.

When the exposure light is irradiated to the filter, there is a problem that heat is generated by the absorbed light, and the temperature of the mask rises. Therefore, the thermal expansion of the mask affects the dimensional accuracy at the time of pattern transfer.

The present invention provides a method for solving the above problems, and an object thereof is to provide a photomask capable of improving the resolution of a transfer pattern when using a light source for exposure of a plurality of wavelengths in the past, a method for manufacturing the same, a pattern transfer method, and a protection method membrane.

In order to solve the above problems, the present invention has the following constitution.

(Composition 1)

A reticle for illuminating a pattern transfer with exposure light having a wavelength region including a plurality of peak wavelengths, and The photomask has a transparent substrate, a transfer pattern formed on the transparent substrate, and a wavelength selection mechanism. The wavelength selection means reduces the light transmission amount of the specific wavelength by reflecting a specific wavelength included in the exposure light irradiated to the photomask.

(constituent 2)

A photomask according to claim 1, characterized in that the wavelength selecting means is composed of a dielectric multilayer film in which a plurality of dielectric layers having different refractive indices are laminated.

(constitution 3)

A photomask according to claim 1 or 2, wherein the specific wavelength includes a g line or an h line.

(construction 4)

In the photomask of the third aspect, the transmittance of the i-line in the wavelength selecting means is 60% or more.

(Constituent 5)

In the photomask of the third or fourth aspect, the reflectance of the h line and the g line in the wavelength selecting means is 70% or more.

(constituent 6)

A photomask according to any one of the first to fifth aspects, wherein the wavelength selection means has a transmittance of 70% or more with respect to any wavelength in a range of from 500 nm to 650 nm.

(constituent 7)

A reticle comprising any one of the components 1 to 6, characterized in that: the wave The long selection mechanism is formed on a surface of the transparent substrate opposite to the surface on which the transfer pattern is formed.

(Composition 8)

A photomask according to claim 1, wherein the photomask has a protective film mounted on a front surface of the photomask on a side on which the transfer pattern is formed, and the wavelength selection mechanism is provided on the protective film.

(constituent 9)

The photomask of the ninth aspect, wherein the transfer pattern has at least a light transmitting portion and a phase adjusting portion, and transmits the light through the light transmitting portion of any one of the i line, the h line, and the g line The difference between the phase of the light and the phase of the light transmitted through the phase adjustment portion is 180 degrees ± 10 degrees.

(construction 10)

In the photomask of the ninth aspect, the transfer pattern includes a light shielding portion, a light transmission portion, and a phase adjustment portion, and the phase adjustment portion is formed by etching the transparent substrate to a specific depth.

(Structure 11)

A pattern transfer method characterized by using an exposure apparatus using exposure light of a plurality of peak wavelengths and a photomask configured as any one of 1 to 10 to pattern a transfer target Transfer.

(construction 12)

A protective film which is mounted on a photomask having a transfer pattern for pattern transfer by exposing exposure light having a wavelength region including a plurality of peak wavelengths, and The protective film comprises: a pellicle frame; a film for a film attached to the film frame; and a wavelength selection mechanism; wherein the wavelength selection mechanism reduces the specific wavelength by reflecting a specific wavelength included in the exposure light irradiated to the mask The light passes through.

(construction 13)

In the protective film of the configuration 12, the wavelength selecting means is formed of a dielectric multilayer film formed on the film for a protective film and laminated with a plurality of dielectric layers having refractive indices different from each other.

(construction 14)

The protective film of the 12 or 13 is characterized in that the specific wavelength includes a g line or an h line.

(construction 15)

A protective film comprising any one of 12 to 14 characterized in that, in the wavelength selecting means, a transmittance of the i-line is 60% or more.

(construction 16)

A protective film comprising any one of 12 to 15 characterized in that the reflectance of the g-line and the h-line in the wavelength selecting means is 70% or more.

(Construction 17)

A coating film comprising any one of 12 to 16 wherein, in the wavelength selecting means, the transmittance at any wavelength in the range of 500 nm to 650 nm is 70% or more.

(Composition 18)

A protective film comprising any one of 12 to 17 characterized in that: The film for a film contains quartz glass.

(Composition 19)

A pattern transfer method characterized in that it uses an exposure apparatus equipped with a photomask configured as any one of 12 to 18 and using exposure light including a plurality of peak wavelengths The photoresist pattern is transferred to the photoresist film on the transfer target.

The photomask of the present invention has a wavelength selection mechanism that reflects a specific wavelength of the exposure light that is irradiated to the region where the transfer pattern is formed, whereby the light transmission amount of the specific wavelength can be reduced, thereby eliminating the need for a large exposure apparatus. With the modification, the transfer pattern on the reticle can be transferred at a higher resolution than the previous one. That is, on the one hand, the previous exposure light source or exposure device can be used, on the one hand, it is possible to have different wavelength selection functions in each of the reticle.

Hereinafter, the form for carrying out the invention will be described in detail.

As described in the above configuration 1, the photomask of the present invention is used for pattern transfer using exposure light having a plurality of wavelength regions including peak wavelengths, and the photomask has a transparent substrate and is formed in the transparent layer. a transfer pattern on the substrate and a wavelength selection mechanism.

That is, the photomask of the present invention is a photomask used for irradiating light having a plurality of peak wavelengths to the photomask by the exposure device, and the transmitted light of the transfer pattern possessed by the photomask is The object to be transferred is exposed. The wavelength selection mechanism of the photomask of the present invention is reflected by reflecting a specific wavelength included in the exposure light irradiated to the photomask. The light transmission intensity of the above specific wavelength is lowered, and as a result, the light transmission amount is lowered. That is, the wavelength selection mechanism reduces the amount of transmission at a specific wavelength, and the reduction is mainly achieved by reflection of light.

The peak wavelength refers to the wavelength at which the light intensity appears as a peak.

In addition, the term "specific wavelength" as used herein refers to a wavelength at which a transfer pattern of a photomask is transferred when an exposure device is used to reduce the wavelength of the transfer of the pattern, and may also be referred to as a wavelength of a transmission reduction target. .

The wavelength selecting mechanism of the present invention may be an optical filter that can selectively transmit light in other wavelength regions by selectively having a higher reflectance with respect to a specific wavelength in the wavelength region of the exposure light. Relatively higher than the above specific wavelength. Further, the wavelength selecting mechanism of the present invention mainly reduces the amount of light transmitted at the specific wavelength by reflection. Here, "mainly by reflection" means that the degree of decrease in the amount of transmission due to reflection of light is greater than the degree of decrease in the amount of transmission due to absorption of light.

For example, a particular wavelength can include an h-line, a g-line. Thereby, the light transmission intensity of the other wavelength region (hereinafter also referred to as the selected wavelength region) is selectively made higher than the transmission intensity of the specific wavelength described above. The selected wavelength region preferably includes an i-line, and for example, can be set to have a wavelength of 365 ± 10 nm. In the wavelength selection mechanism of the present invention, when the exposure light including the i-line, the h-line, and the g-line is used, the wavelength selection region (preferably, the wavelength region including the i-line and not including the h-line or the g-line) may be selected. It exhibits a transmittance higher than a specific wavelength (for example, an h line or a g line). Preferably, the wavelength selection mechanism of the present invention is one of the g-line (436 nm), the h-line (405 nm), and the i-line (365 nm) included in the exposure light of the exposure apparatus used. The reflectance is lower than any of the h line and the g line The transmittance of the i-line is higher than either the h-line or the g-line.

Preferably, the wavelength selecting means according to the present invention has a transmittance (ratio of transmission intensity to incident intensity) of 60% or more in a selected wavelength region in the light wavelength region for exposure. For example, the transmittance may be 60% or more at a selected wavelength (for example, an i-line) included in the wavelength region. More preferably 70% or more.

Further, the transmittance at the specific wavelength (for example, the h-line or the g-line) in the wavelength region of the exposure light is preferably 40% or less. Further, it is preferably 20% or less.

Further, in the wavelength selection mechanism of the present invention, the decrease in transmittance at a specific wavelength in the wavelength range of the exposure light is mainly achieved by reflection of light. For example, the reflectance in the wavelength region may be 70% or more.

Further, as the selected wavelength included in the selected wavelength region, the i-line is selected, and the reflectance at the specific wavelength (for example, the reflectance of the h-line and the g-line) may be 70% or more.

In the following description, the wavelength selecting means has a component that is transmitted or a component that is absorbed as a component other than the reflection with respect to the light for exposure.

Here, when the amount of exposure light irradiated to the wavelength selecting means is set to 100%, the amount of reflection by the wavelength selecting means is expressed as a percentage as a reflectance (R%), and the wavelength selecting means is used. The amount of absorption is expressed as a percentage and as the absorption rate (D%), and the amount of the wavelength selective mechanism transmitted is expressed as a percentage as a transmittance (T%). At this time, the total value of each of R, D, and T is 100 (%) of the amount of exposure light irradiated to the wavelength selecting means.

In the wavelength selection mechanism of the present invention, the specific wavelength of the exposure light to be irradiated is mainly reduced by the reflection of light, and the term "reflection mainly by light" means satisfying and reflecting and transmitting. When the rate and the absorption rate are related to the above conditions, the reflectance is greater than the absorption rate (R > D).

Further, in the reduction of the amount of light transmitted by the wavelength selecting means of the present invention, it is preferable that the light for exposure transmitted through the transmittance T has a degree of preventing exposure to the photoresist film of the transfer target. The exposure amount (or intensity), and the transmittance is preferably 40% or less. Further preferably, it is 20% or less. Regarding the exposure light reflected by the wavelength selecting means, for example, when the intensity of the exposure light irradiated to the wavelength selecting means is 100%, the reflectance is preferably 70% or more. Further preferably, the reflectance is 90% or more. At this time, it is preferable that the wavelength selecting means uses a material which itself absorbs less light for exposure, and for example, it is preferable that the absorption rate is 10% or less. Further preferably, the absorption rate is 5% or less. The reflectance R (%), the transmittance (T%), and the absorptance (D%) can be obtained for each desired wavelength by the following method.

The measurement of the reflectance R (%) can be carried out using a spectrophotometer.

Further, the measurement of the transmittance (T%) can be carried out, for example, using a spectrophotometer in the same manner as the measurement of reflected light.

Further, regarding the absorption rate (D%), for example, when the exposure light irradiated to the wavelength selecting means is 100%, the reflectance (R%) and the transmittance (T%) can be used according to the following relationship. It is obtained by the formula (1).

Absorption rate (D%) = 100% - reflectance (R%) - transmittance (T%) (1)

Exposure device for manufacturing a liquid crystal display panel by expanding each exposure The transfer area shortens the exposure time, which is advantageous for manufacturing the takt time. At this time, the exposure magnification is equal to that of the pattern formed on the reticle, and the minimum resolution line width is larger than the case where the reduction exposure is performed, and the limit is about 3 to 4 μm. However, due to the improvement in product performance in recent years, it is required to reduce the resolution line width. The reason for this is that, for example, by setting the minimum resolution line width to 2 to 3 μm or less, the degree of freedom in designing the liquid crystal display panel can be greatly expanded, so that the existing equipment or the current process can be used to manufacture high. Performance, high-performance LCD panel.

In the photolithography step in the manufacture of the liquid crystal display panel, an ultrahigh pressure mercury lamp is used as the light source for exposure, and the i line, the h line, and the g line emitted from the ultrahigh pressure mercury lamp are mainly used as the exposure light for sensitizing the photoresist. . The exposure of the transfer pattern can be improved by performing exposure using the shortest wavelength of the exposure light including the plurality of peak wavelengths. Further, by performing exposure using only a single wavelength, the influence of the chromatic aberration of the optical system of the exposure apparatus can be reduced, and the resolution of the transfer pattern can be improved. Moreover, when the photomask used is a phase shift mask, the phase shift effect can be effectively exerted by using a single wavelength of light, and further, when a single wavelength is selected from a shorter wavelength, A further improvement in the resolution of the transfer pattern is achieved.

Therefore, by providing the wavelength selection mechanism having such a wavelength selection function on the reticle, not only the reticle of the transfer pattern but also the two regions having different transmittances of the exposure light (binary mask) Photo mask) or the multi-step mask in which the transfer pattern is formed by three or more regions of the light transmittance for exposure, and the resolution of the transfer pattern can be easily and at low cost. Moreover, the phase shift mask can also achieve an improved resolution of the transfer pattern at a low cost.

1 is a cross-sectional view showing the configuration of a photomask (second-order photomask) of the present invention, and (a) shows a case where a wavelength selection mechanism is provided on the opposite side of a formation surface of a transfer pattern of a transparent substrate, (b) The case where the wavelength selection mechanism is provided on the transfer pattern forming surface is shown, and (c) shows the case where the wavelength selection mechanism is provided on the protective film attached to the photomask. The transfer pattern 2 is formed on the transparent substrate 1, and further, the wavelength selection mechanism 3 of the present invention is formed at a specific position.

When a wavelength selecting mechanism is directly provided on the photomask, for example, a wavelength selecting mechanism composed of a dielectric multilayer film as will be described below may be provided on a surface of the photomask on which the transfer pattern is formed (the front side of the mask) ( Figure 1 (b); or on the opposite side (back of the mask) (in the case of Figure 1 (a)). On the transfer pattern forming surface of the mask, irregularities are generated due to the film thickness of the pattern-forming film. Therefore, the ease of film formation of the dielectric multilayer film, the variation in film thickness, or the influence of the step on the control of optical properties are considered. It is advantageous to form a film on the back side of the mask. When the wavelength selection mechanism is formed on the back surface of the transparent substrate of the reticle, the back surface of the reticle is defocused during exposure, and therefore, the defect is temporarily not caused when the dielectric multilayer film is temporarily defective. Printing, so it is better.

Alternatively, the wavelength selective mechanism of the present invention can be disposed on a protective film disposed on the photomask. In order to allow the film to have a function of selecting a specific wavelength and transmitting it, for example, the film for a film may have a wavelength selection function, or a substance having a wavelength selection function may be formed as a film on a film for a film (hereinafter, Also known as the film base). Wherein, formed on the substrate In the method of selecting a substance for the wavelength selection function, it is preferable to suppress the temperature rise of the substrate or the substance formed on the substrate due to light absorption under irradiation with strong light such as exposure light. Therefore, the present invention which reduces the transmission of a specific wavelength by reflection is advantageous. Further, an organic material containing nitrocellulose or acetylcellulose or the like which has been used as a film for a film as a substrate can be used as a substrate, and a substance having a wavelength selective function can be formed as a film on the surface thereof. .

Further, as shown in Fig. 1(c), a film 4 (base) for the film for attachment to the film frame 5 can be made of a glass material, and a dielectric material to be described later is formed on the film 4 for the film. A wavelength selection mechanism 3 composed of a multilayer film. In this case, compared with the above organic material, it is advantageous in terms of light transmittance at a selected wavelength, or straightness, resistance, and the like. The wavelength selection mechanism 3 can be formed on either one of the front and back surfaces of the film 4 for a film. As the glass material constituting the film 4 for a film, it is preferable to use a quartz glass having a high transmittance with respect to a short-wavelength side (for example, an i-line) in a wavelength region of the light for exposure.

In the case where the wavelength selecting means of the present invention is provided on the film, as a more advantageous aspect, in order not to directly process the mask, the case where the wavelength selecting means can be attached or detached can be cited. Thereby, it is possible to change the presence or absence of the wavelength selection mechanism or the exchange of the optical characteristics with respect to one photomask. Further, since the film is attached to a photomask that has been cleaned by cleaning or the like, it is not necessary to clean the mask after the film is attached. Therefore, it is advantageous in that it does not cause a physical or chemical burden on the wavelength selection mechanism due to cleaning or the like.

Moreover, it is desirable that the integrated layer of the dielectric multilayer film of the present invention is relative to The surface perpendicular to the irradiation direction of the exposure light is -5 or more and +5 or less, and is a distribution of the inclination of the entire surface of the dielectric multilayer film.

Further, it is preferably -2.5 or more and +2.5 or less. The reason for this is that when the inclination of the dielectric multilayer film is within the above range, the distribution of the spectral characteristics is substantially suppressed, so that more favorable pattern transfer characteristics can be obtained.

The wavelength selective mechanism of the present invention is composed of a dielectric multilayer film in which a plurality of dielectric layers having different refractive indices from each other are laminated.

The dielectric multilayer film can, for example, transmit or reflect only a wavelength side longer than a certain wavelength. Moreover, only a specific wavelength can be transmitted.

Here, the plural means any number of two or more layers. For example, a dielectric multilayer film in which two layers having different refractive indices from each other are alternately laminated may be used. Alternatively, three or more layers having refractive indexes different from each other may be laminated in a fixed arrangement order.

Fig. 2 is a cross-sectional view showing a configuration example in a case where the wavelength selecting mechanism of the present invention is formed of a dielectric multilayer film.

In the present invention, as described above, the transmittance of the specific wavelength in the wavelength region of the exposure light used for the pattern transfer is lowered by reflection, whereby the light transmittance characteristics can be adjusted. For example, as shown in FIG. 2, as the wavelength selecting means, a dielectric multilayer film which is alternately laminated on the substrate 31 (transparent substrate for a photomask or a film for a protective film, etc.) and having different refractions can be used. The two dielectric materials (high refractive index material 32 and low refractive index material 33 having a lower refractive index). As a dielectric material which can be used in an ultraviolet region including i-line, h-line, and g-line, for example, Nb ₂ O ₅ (antimony pentoxide), ZrO ₂ (zirconia), or the like can be used as the high refractive index material. For the low refractive index material, for example, SiO ₂ or the like can be used. The dielectric multilayer film used in the present invention preferably has an absorption ratio in the ultraviolet region of 10% or less and a high resistance in the ultraviolet region.

In the wavelength selection mechanism composed of such a dielectric multilayer film, since the refractive index of the dielectric material of the laminated layer is different, a fresnel reflection occurs at the boundary of the dielectric film layer, and The refractive index and the thickness of each of the dielectric film layers are adjusted to an appropriate value, and the interference state of the Fresnel reflection waves generated at the respective boundaries of the plurality of layers is enhanced as a mirror. Therefore, the dielectric multilayer film utilizes Freyne reflection, which makes the absorption of light extremely low, so that the problem of the prior optical filter in which the light transmittance characteristics are adjusted by absorption of light can be solved.

The thickness or the number of layers of each of the dielectric film layers forming the dielectric multilayer film can be obtained by simulation based on parameters such as a wavelength region and a reflectance at which transmittance is to be reduced by reflection. Optical design has a high degree of freedom and can be advantageously used in the present invention.

Further, the method of laminating the low refractive index material and the high refractive index material in the dielectric multilayer film may include a configuration in which a plurality of low refractive index materials and a high refractive index material are combined as one unit, and This unit is repeatedly laminated. There are a plurality of units combined, and they may be formed by stacking in a fixed sequence.

The dielectric material can be laminated on the substrate by a film formation method such as vacuum evaporation or sputtering.

For example, when the transmittance of the i-line is maintained while maintaining the transmittance of the specific wavelength of the h-line and the g-line, the transmittance is lowered (refer to the reflectance characteristic curve of FIG. 3). A dielectric multilayer film having a high reflectance of the h-line and a dielectric multilayer film having a high reflectance of the g-line are laminated to form a dielectric multilayer film having a relatively high transmission intensity of the i-line. Alternatively, a dielectric multilayer film having a high reflectance in the two regions including the h line and the g line may be formed to relatively increase the transmittance of the i line. As described above, by forming the dielectric multilayer film by reflecting light in a wavelength region not to be transmitted, a wavelength selecting mechanism having various optical characteristics can be constructed, and thus the dielectric multilayer film is suitable as the wavelength selecting mechanism of the present invention. .

Further, in the exposure apparatus for manufacturing a liquid crystal display panel or the like, in order to shorten the exposure time as much as possible and to shorten the processing yield of the product, the exposure light is designed to be irradiated with light per unit area of the irradiation region. The energy is very large, and when the wavelength selecting means uses a material having a large light absorption, the absorbed light is converted into heat, whereby the temperature of the wavelength selecting means is raised by irradiating the exposure light. Therefore, if the temperature of the photomask rises, the accuracy of the transfer pattern is likely to deteriorate.

A cooling device for controlling the temperature of the photomask is provided in the exposure device. However, depending on the optical characteristics of the wavelength selection mechanism, the amount of light absorption changes, and the amount of heat generated also changes. In view of such a situation, the photomask of the present invention which reduces the transmittance of exposure light by reflection of a specific wavelength is less advantageous in heat generation.

In the wavelength selecting mechanism of the present invention, the transmittance of the selected wavelength (for example, the i-line) is preferably 60% or more. If the desired wavelength region has a transmittance of 60% In the above, the energy necessary for the photoresist to be exposed is ensured, so that the increase in the yield by the increase in the exposure time can be prevented. Further, the transmittance unevenness in the mask surface of the wavelength selecting means is preferably ±10% or less. Further, it is preferably ±5% or less, and more desirably ±1% or less. The reason for this is that, by setting the transmittance unevenness to the above range, the in-plane distribution of the light for exposure light is made uniform, and the accuracy of the transfer pattern is also uniform.

In the wavelength selecting mechanism of the present invention, light of a specific wavelength (for example, an h line or a g line) is reflected, and in this case, the reflectance is preferably 70% or more. The reflectance is further preferably 90% or more. The reason for this is that when the reflectance is in the range, the exposure light transmitted through the wavelength selective mechanism is attenuated, and even if the light in the other wavelength region is not exposed to the photoresist, it is preferably obtained. The effect of the present invention. Further, the reflectance unevenness in the mask surface of the wavelength selecting means is preferably ±10% or less.

Further, in the photomask, a defect inspection is performed in order to confirm whether or not a defect occurs on the pattern surface. In the defect inspection, there is a defect inspection for photographing a pattern surface by a CCD (Charge Couple Device) or the like, or a visual inspection using an optical microscope. In the defect inspection device, it is convenient to use light in the visible light region as the inspection light. Further, as an autofocus mechanism used in the defect inspection device, a visible laser such as a helium neon laser (633 nm) or a semiconductor laser is used. Therefore, in order not to hinder such optical defect inspection, the wavelength selecting means of the present invention preferably has a certain degree of transmittance at a wavelength of light for inspection outside the wavelength region of the exposure light. For example, it is desirable to have light penetration in one of the visible light regions Too much. For example, it is desirable that the transmittance is 70% or more at any wavelength in the wavelength range of 500 nm to 650 nm. More preferably, the transmittance of visible light used for inspection light or autofocusing in the above wavelength region is preferably 70% or more. When the wavelength selection mechanism is designed to have such transmittance characteristics, the defect inspection of the photomask of the present invention in which the wavelength selection mechanism is formed can be performed with high precision, and the quality of the completed photomask can be ensured.

Further, the exposure wavelength of the exposure apparatus to be used is preferably 500 nm or less.

The present invention is suitably used for a photomask having a so-called binary mask including a transfer pattern of a light-shielding portion and a light-transmitting portion, or a light-shielding portion, a light-transmitting portion, and a semi-transmissive portion for exposure A transfer pattern of a plurality of regions having different light transmittances, and a multi-step mask having a stepped shape formed on the photoresist on the transfer target.

Further, the present invention is also suitable for a photomask (phase shift mask) having a phase shift effect. In a reticle having a phase shift effect, the nature of the exposure light used for exposure has a large influence on the accuracy of the transferred pattern. When the wavelength selection mechanism of the present invention is used, the wavelength region contributing to the transfer can be limited, so that the effect of improving the resolution can be obtained by the phase shift effect.

A phase shift mask having improved light transmittance and a depth of focus and having improved transfer characteristics by controlling the phase of the light is configured to have a light transmitting portion and a phase adjusting portion, and the phase adjusting portion is used for exposure The phase of the light is substantially 180 degrees out of phase with the exposure light transmitted through the light transmitting portion. because The exposure light that has passed through the light transmitting portion and the exposure light that has passed through the phase adjustment portion interfere with each other, whereby the resolution or the depth of focus can be improved. As the phase shift mask to which the present invention is applied, a Levenson-type phase shift mask having a etched on a substrate, a chromeless phase shift mask, or the like is included. The term "roughly 180 degrees" means a range of 180 ± 10 degrees.

In order to further improve the effect of such a phase shift mask, it is advantageous to define a wavelength region that facilitates pattern transfer by the wavelength selection mechanism of the present invention, and to interfere with light generated by the edge of the pattern. Improve the contrast. In this case, it is preferable to select a shorter wavelength light, and for example, it is preferable to use the h line as compared with the g line, and it is desirable to use the i line as compared with the h line.

[Examples] (Example 1)

Here, as a specific embodiment of the photomask of the present invention, a Levenson-type phase shift mask having a substrate etching will be described.

Fig. 4 is a cross-sectional view showing the manufacturing steps of the above-described Levenson type phase shift mask. This manufacturing process will be described.

A reticle substrate was prepared using a quartz substrate 10 having a size of 1220 mm × 1400 mm and a thickness of 13 mm and a light-shielding film 11 was formed on the substrate (the Cr film was set to 100 nm, and oxidation of 10 nm was formed thereon). The chromium layer is used as a low-reflection layer, and a positive resist is applied to the light-shielding film 11 at a thickness of 1000 nm by a method such as spin coating or CAP coating. Thereby, the first photoresist film 12 is formed (Fig. 4(a)).

Then, the first resist film 12 is subjected to specific drawing exposure by a laser plotter, and an inorganic alkaline aqueous solution such as KOH or TMAH (Tetra Methyl) is supplied to the first resist film 12 by a method such as a sputtering method. The developing solution such as Anmonium Hydroxide or tetramethylammonium hydroxide aqueous solution is developed to form a first photoresist pattern 12a covering a predetermined completion region of the light shielding portion and the phase shift portion (Fig. 4(b)).

Then, the first photoresist pattern 12a is used as a mask, and the light-shielding film 11 is etched by an etchant such as a mixed solution of cerium ammonium nitrate and perchloric acid to form a light-shielding film pattern 11a (Fig. 4(c)). Thereafter, the remaining first photoresist pattern 12a is removed using a photoresist stripping solution or the like (Fig. 4(d)).

Next, a second photoresist film of the same material as described above is formed on the entire surface of the substrate on which the light-shielding film pattern 11a is formed by spin coating or CAP coating at a thickness of 1000 nm (for convenience) For the sake of reference, the same reference numeral "12" as the first resist film is used (Fig. 4(e)).

Next, the second resist film 12 is subjected to specific drawing exposure by a laser plotter, and a developing solution is supplied to the photoresist film by a method such as a sputtering method to perform development, thereby forming a cover phase shift. The second photoresist pattern 12b in the region other than the portion (Fig. 4(f)).

Next, the light-shielding film pattern 11a is etched by using the second photoresist pattern 12b as a mask to remove the light-shielding film pattern in the region where the phase shift portion is to be formed (FIG. 4(g)). Then, the second photoresist pattern 12b and the light-shielding film obtained by etching the second photoresist pattern 12b as a mask are used as a mask, and the substrate is etched by using an etchant containing hydrofluoric acid or the like. The quartz substrate 10 is etched, and the etching is performed until the depth of phase shift of 180 degrees with respect to the exposure light transmitted through the light transmitting portion, thereby forming the phase shifting portion 10a (FIG. 4) (h)). Thereafter, the remaining second photoresist pattern 12b is removed using a photoresist stripper or the like to complete the pattern (Fig. 4(i)).

Next, the wavelength selection mechanism of the present invention is formed.

Specifically, a high refractive index material (using Nb ₂ O ₅ ) and a low refractive index material (using SiO ₂ ) are alternately applied to the back surface of the mask (the surface opposite to the pattern forming surface) by sputtering. A film is formed to form a dielectric multilayer film. The deposited film thickness and the number of layers are determined based on the wavelength region to be reflected. Specifically, by combining a high refractive index material in a film thickness range of 40 nm to 80 nm with a low refractive index material and alternately stacking 22 layers, the h line and the light having a longer wavelength are reflected, thereby reducing The transmittance of this wavelength region. Thereby, the transmittance of the i-line becomes relatively larger than the h-line and the g-line.

In this way, a Levenson-type phase shift mask (Fig. 4(j)) which is an embodiment of the present invention is completed.

In the present embodiment, the formation of the wavelength selecting means including the dielectric multilayer film is performed on a surface (mask back surface) different from the pattern forming surface of the photomask.

Further, as shown in Fig. 5, in the present invention, as the wavelength selecting means, it can be used for the function of the protective film. For example, a film having a thickness of 1 mm attached to the film frame 15 as a film 14 for a film (base) is prepared as described above, and is formed on the surface in the same manner as described above. The dielectric multilayer film is designed to have the same wavelength selection mechanism 13, and the film is attached to the photomask (Fig. 4(i)) which has completed the above pattern, thereby completing the present invention. The mask of the attached film.

Next, the reticle (Fig. 4(j)) completed in the manner described above was used to verify the resolution. As shown in FIG. 6, the mask has the following pattern as a pattern for resolution verification.

That is, a line and space pattern of the Levenson-type phase shift pattern is provided, in which the light-transmitting portion having the phase shift amount of 0 degrees is alternately arranged next to the light-shielding portion (A) B) A phase shifting portion (C) having a phase shift amount of 180 degrees. The line and the gap pattern are arranged in such a manner that the distance between the adjacent center line of the light shielding portion A and the phase shift portion C is the same as the distance between the adjacent center lines of the light shielding portion A and the light transmission portion B, and The width of each of the light shielding portion A, the light transmitting portion B, and the phase shift portion C is also the same as the value of the distance from the center line. Here, the distance between the center lines is in the range of 1.5 μm to 3.0 μm, and a plurality of lines and gap patterns of a plurality of sizes are formed in units of 0.1 μm. For example, a distance between the center lines of 2.0 μm can be referred to as a 2.0 μm line and gap pattern.

In order to form a pattern on the object to be transferred in the same size as the pattern on the photomask, the following conditions are set.

The exposure conditions for both the regions remaining in the region after the development of the photoresist film as an etch mask and the region where the photoresist film is completely removed after development are irradiated through the mask to The transmittance of the light for exposure of the light to be transferred of the transfer target is such that the minimum transmittance of the region where the film remains is set to satisfy 11% or less, and the transmittance of the removed region is set to 40% or more is satisfied (further, the photoresist on the transfer target is a positive photoresist). When the above conditions are not met, In the case where exposure is performed using an actual photomask, unevenness in line width generated in the mask surface or unevenness in illumination of exposure light occurs (see Fig. 7).

Further, as a flow condition of the transfer target, an area of the photoresist film which is actually exposed through the photomask by development (an area where the transmittance of the exposure is 40% or more) is over-developed. ) will enlarge the area, and its expansion is 0.2 μm at each edge. Further, it is assumed that the enlarged region is further enlarged by 0.25 μm at each edge of the line width formed on the transfer target by etching. That is, the width of the exposed region is enlarged (0.2 × 2 + 0.25 × 2) = 0.9 μm at both edges due to development and etching.

Moreover, the optical conditions of the exposure light when patterning to the object to be transferred using the photomask of the present embodiment are set to NA=0.083 and σ=0.9, and when the wavelength selection mechanism of the present embodiment is provided, The light intensity ratio of the exposure light is set to g/h/i=0/0/100, and the exposure magnification is set to 1.0, and the transmittance of the light-shielding portion A of the mask is set to 0%. The transmittance of B is set to 100%, the phase shift amount is set to 0 degree, the transmittance of the phase shift portion C is set to 100%, and the phase shift amount is set to 180 degrees.

According to the above conditions, the light intensity curve of the transmitted light is obtained for the line and gap pattern of 1.5 μm to 3.0 μm of the mask, and is plotted in units of 0.1 μm. At this time, the exposure light that has passed through the reticle is imaged by a photographing mechanism provided with a CCD (imaging element), and a light intensity curve is obtained from the obtained image information. An emulator is used in which an exposure light and an imaging optical system are provided which approximate optical characteristics to an actual exposure apparatus. The inspection light and the inspection optical system are irradiated to the photomask by the inspection light passing through the inspection optical system, whereby the same transfer image as that obtained by the actual exposure device is imaged by an imaging mechanism such as a CCD.

By the light intensity curve obtained as described above, a 2.0 μm line and gap pattern can be selected as the condition for satisfying the pattern formation described above.

According to the transmission curve of the 2.0 μm line and the gap pattern (refer to FIG. 7), in the transfer target, the minimum transmittance of the region where the photoresist film is to remain is 10%, and the transmittance of the region where the photoresist is to be removed is removed. It is 40% or more, and the conditions for simultaneously achieving the residual and complete removal of the photoresist film are satisfied. Further, the width of the region having the transmittance of 40% or more is 1.1 μm. Therefore, as described above, the line width is enlarged by 0.9 μm from the area actually exposed by the development flow and the etching flow, and the exposed region is finally A line width of 2.0 μm was formed on the object to be transferred.

According to the above, based on the transmittance curve and by simulation, it was confirmed that the 2.0 μm line and gap pattern formed on the mask of the present embodiment can form a line and gap pattern of 2.0 μm on the object to be transferred.

Further, as another embodiment of the present invention, a substrate etching type phase shift mask (chrome-free type) having no light-shielding film pattern was produced, and the resolution was verified in the same manner as in the present example, and as a result, it was confirmed that the improvement was possible. The effect of resolution.

(Comparative Example 1)

The same resolution is verified for a photomask (see Fig. 4(i)) in which the wavelength selecting mechanism of the present invention is not provided. Furthermore, the wavelength intensity ratio of the exposure light is set to g/h/i=34.8/32.1/33.1, in addition to the above implementation The transmission curve of the 2.0 μm line and gap pattern was obtained in the same manner (refer to the black circle in FIG. 7).

As a result, it was found that the exposed conditions for both the regions remaining in the photoresist film after the development as the etching mask and the regions where the photoresist was completely removed after the development were not able to be satisfied The transmittance of the light for exposure of the mask is such that the minimum transmittance of the region where the film remains is 11% or less and the transmittance of the removed region is 40% or more, and 2.0 μm formed on the mask. The line and gap patterns do not form a 2.0 μm line and gap pattern on the transferred body.

(Example 2)

A binary mask as shown in FIG. 1(a) in which a wavelength selecting means including the same dielectric multilayer film as in Example 1 is formed on the back surface of the reticle is produced, and the line and gap pattern pair is used in the same manner as in the first embodiment. The resolution of the transfer pattern was evaluated. As a result, based on the transmittance curve and confirmed by simulation, it was possible to transfer a pattern having a line width of 2.8 μm.

(Comparative Example 2)

The second-order photomask produced in the same manner as in the second embodiment except that the above-described wavelength selection mechanism was not provided was subjected to the evaluation of the resolution of the transfer pattern in the same manner as in the first embodiment. As a result, it was confirmed by the simulation based on the transmittance curve that the pattern of less than 3.0 μm was not resolved.

According to the results of the above Example 2 and Comparative Example 2, the present invention has an effect of reducing the line width of the transfer by about 7%.

It is clear from the above that the wavelength selection mechanism of the present invention can transmit a necessary wavelength region in the wavelength of light for exposure, and on the other hand, The transmittance (cutoff light) is lowered in the wavelength region. The light cutoff is mainly achieved by the reflection of light, so that the generation of heat due to light absorption can be suppressed, and the dimensional change of the transfer pattern caused by the temperature rise of the film for the mask or the film can be suppressed or Material degradation.

Further, as the wavelength selecting means of the present invention, a suitable dielectric multilayer film can be applied, thereby having a degree of freedom in optical design such as selectively turning off a desired wavelength region from the wavelength of light for exposure. Further, it is advantageous to manufacture or manage the photomask by selecting a wavelength selection mechanism that ensures transmission of light in a wavelength region (for example, a range of 500 nm to 650 nm) necessary for inspection.

When the wavelength selecting mechanism of the present invention is disposed on the protective film mounted on the photomask, the convenience of attaching the wavelength selecting function to the photomask or the convenience of disassembly and replacement can be obtained.

Further, in the photomask of the present invention, the same transfer pattern can be transferred between the plurality of exposure apparatuses by the same mask regardless of whether or not an exposure apparatus having a wavelength selection function is used.

It is clear from the above that when pattern transfer is performed using an exposure apparatus having exposure light of a plurality of peak wavelengths, according to the present invention, pattern transfer with higher resolution can be realized compared to the prior method, for example, When the electrode portion having a fine line and gap pattern formed by patterning a conductive film such as an ITO (Indium Tin Oxide) film used in a liquid crystal display panel is formed, the present invention is suitably used. Alternatively, in a TFT (Thin Film Transistor) used in a liquid crystal display panel, the present invention is suitably used when a pattern of a thin line width resolution is required as a channel of a transistor portion.

1‧‧‧Transparent substrate

2‧‧‧Transfer pattern

3‧‧‧wavelength selection mechanism

4‧‧‧ film for film protection

5‧‧‧ film frame

10‧‧‧Transparent substrate

11‧‧‧Shade film

12‧‧‧Photoresist film

13‧‧‧Wavelength selection agency

14‧‧‧ film for film

15‧‧‧film frame

31‧‧‧ base

32‧‧‧High refractive index material

33‧‧‧Low-refractive index material

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing the configuration of a photomask according to the present invention, wherein (a) shows a case where a wavelength selecting mechanism is provided on the opposite side of a forming surface of a transfer pattern of a transparent substrate, and (b) shows a transfer pattern. The formation surface is provided with a wavelength selection mechanism, and (c) is a case where a wavelength selection mechanism is provided on the protective film attached to the photomask.

Fig. 2 is a cross-sectional view showing the configuration of a wavelength selecting mechanism of the present invention formed by dielectric multilayer film.

Fig. 3 is a view showing an example of reflectance characteristics obtained by the wavelength selecting means of the present invention.

4(a) to 4(j) are cross-sectional views showing the steps of manufacturing the substrate-etched Levenson type phase shift mask of the present invention.

Fig. 5 is a cross-sectional view showing a Levenson-type phase shift mask of the film-mounting type of the present invention.

Fig. 6 is a view showing a pattern for verifying the resolution of the reticle of the first embodiment.

Fig. 7 is a view showing the result of verification of the resolution of the reticle of the first embodiment.

1‧‧‧Transparent substrate

2‧‧‧Transfer pattern

3‧‧‧wavelength selection mechanism

4‧‧‧ film for film protection

5‧‧‧ film frame

Claims (23)

A reticle for illuminating a pattern transfer with exposure light having a wavelength region including a plurality of peak wavelengths, wherein the reticle includes a transparent substrate and a transfer pattern formed on the transparent substrate And a wavelength selecting means for reducing the light transmission amount of the specific wavelength by reflecting a specific wavelength included in the exposure light that is irradiated onto the photomask. A photomask according to claim 1, wherein said wavelength selecting means is constituted by a dielectric multilayer film in which a plurality of dielectric layers having different refractive indices from each other are laminated. The reticle of claim 2, wherein the specific wavelength comprises a g-line or an h-line. The photomask of claim 3, wherein the transmittance of the i-line in the wavelength selection mechanism is 60% or more. The photomask of claim 3, wherein the reflectance of the h line and the g line in the wavelength selection mechanism is 70% or more. The photomask of claim 3, wherein the transmittance in any of the wavelength selection ranges of from 500 nm to 650 nm is 70% or more. A photomask according to claim 2, wherein said wavelength selecting means is formed on a surface of said transparent substrate opposite to a surface on which said transfer pattern is formed. The photomask of claim 2, wherein the photomask comprises a protective film mounted on a front surface of the photomask on a side on which the transfer pattern is formed, and the wavelength selection mechanism is disposed in the protective film. The photomask of claim 2, wherein the transfer pattern includes at least a light transmitting portion and a phase adjusting portion, and in any one of the i line, the h line, and the g line, a phase of light transmitted through the light transmitting portion The difference in phase of the light transmitted through the phase adjustment unit is 180 degrees ± 10 degrees. The photomask of claim 9, wherein the transfer pattern includes a light shielding portion, a light transmitting portion, and a phase adjustment portion, and the phase adjustment portion is formed by etching the transparent substrate to a specific depth. A photomask according to claim 2, which is a photomask for manufacturing a display device. The photomask of claim 1, wherein the transfer pattern is a pattern for manufacturing a display device, and the wavelength selection mechanism is configured to reflect a g line or an h line included in the exposure light irradiated onto the photomask. The light transmission amount of the above-mentioned g-line or h-line is 70% or more at any wavelength in the range of 500 nm to 650 nm. The photomask of claim 1, wherein the transfer pattern is a pattern for manufacturing a display device, and the wavelength selection mechanism is composed of a dielectric multilayer film in which a plurality of dielectric layers having different refractive indices are laminated. The electrical multilayer film comprises a high refractive index material comprising Nb ₂ O ₅ or ZrO ₂ and a low refractive index material comprising SiO ₂ . A pattern transfer method characterized by using an exposure apparatus using exposure light of a plurality of peak wavelengths and a photomask according to any one of claims 1 to 13 for pattern transfer onto a transfer target Printed. A protective film, characterized in that it is mounted on a photomask, and the photomask includes a transfer pattern for pattern transfer using exposure light having a wavelength region including a plurality of peak wavelengths, and the protective pattern The film includes: a film frame; a film for a film attached to the film frame; and a wavelength selection mechanism; and the wavelength selection mechanism is included in the exposure light to be irradiated onto the mask The specific wavelength reflects, and the light transmission amount of the above specific wavelength is lowered. The protective film according to claim 15, wherein the wavelength selecting means is formed of a dielectric multilayer film formed on the film for a protective film and laminated with a plurality of dielectric layers having refractive indices different from each other. The film of claim 16, wherein the specific wavelength comprises a g-line or an h-line. The protective film of claim 17, wherein the transmittance of the i-line in the wavelength selecting means is 60% or more. The protective film of claim 17, wherein the reflectance of the g-line and the h-line in the wavelength selecting means is 70% or more. The protective film of claim 15, wherein the wavelength selective mechanism is composed of a dielectric multilayer film having a plurality of dielectric layers having different refractive indices from each other, the dielectric multilayer film comprising a high refractive index material and low refraction. Rate material, the high refractive index material comprising Nb ₂ O ₅ or ZrO ₂ , the low refractive index material comprising SiO ₂ . The protective film of claim 15, wherein the wavelength selection mechanism reduces the light transmission amount of the g-line or the h-line by reflecting the g-line or the h-line, and 500 The transmittance at any wavelength in the range of nm to 650 nm is 70% or more. The film of claim 16, wherein the film for the film comprises quartz glass. A pattern transfer method characterized by using a photomask provided with a protective film according to any one of claims 15 to 22 and using an exposure device including exposure light of a plurality of peak wavelengths to form a resist pattern Transfer to the photoresist film on the transfer target.