JP2012008219A - Multi-tone photomask, photomask blank for multi-tone photomask, and pattern transfer method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more surely prevent a semi-translucent film from being etched.SOLUTION: A light shielding part is formed by laminating the semi-translucent film, an etching stopper film, and a light shielding film in this order on a transparent substrate, and a semi-translucent part is formed by forming the semi-translucent film on the transparent substrate, and a translucent part is formed by exposing the transparent substrate, and the etching stopper film has a film thickness being 1.5 or more times as thick as a surface roughness of the semi-translucent film.

Description

  The present invention relates to a multi-tone photomask used for manufacturing a flat panel display (hereinafter referred to as FPD) such as a liquid crystal display device, a method for manufacturing the multi-tone photomask, and the multi-tone The present invention relates to a pattern transfer method using a photomask.

  A thin film transistor (hereinafter referred to as TFT) substrate for FPD uses a photomask in which a transfer pattern composed of a light-shielding portion and a light-transmitting portion is formed on a transparent substrate. For example, photolithography is performed 5 to 6 times. It has been manufactured through a process. In recent years, in order to reduce the number of photolithography processes, a multi-tone photomask in which a transfer pattern including a light shielding portion, a semi-translucent portion, and a translucent portion is formed on a transparent substrate has been used. For example, the light-shielding portion of the multi-tone photomask is formed by forming a semi-transparent film, an etching stopper film, and a light-shielding film in this order on a transparent substrate. The light-transmitting part can be formed by exposing the transparent substrate.

JP 2002-189281 A

  The transfer pattern of the above-described multi-tone photomask is formed by etching each film using, for example, an etching solution or an etching gas. For example, first, a photomask blank in which a semi-transparent film, an etching stopper film, a light shielding film, and a first resist film are laminated in this order on a transparent substrate is prepared. Then, drawing and development are performed on the first resist film to form a first resist pattern that covers the formation region of the light shielding portion, and the light shielding film and the etching stopper film are sequentially etched using the first resist pattern as a mask. Next, the first resist pattern is removed to form a second resist film, and the second resist film is drawn and developed to cover the light shielding portion formation region and the semi-transparent portion formation region. Form. Further, the semi-transparent film is etched using the second resist pattern as a mask to remove the second resist pattern.

  Alternatively, after preparing the photomask blank, drawing and development are performed on the first resist film to form a first resist pattern that covers the areas other than the light-transmitting portion formation region, and the light-shielding film and etching are performed using the first resist pattern as a mask. The stopper film and the semi-transparent film are sequentially etched. Next, the first resist pattern is removed to form a second resist film, and the second resist film is drawn and developed to form a second resist pattern that covers the formation region of the light shielding portion. Further, the light shielding film and the etching stopper film are etched using the second resist pattern as a mask, and finally the second resist pattern is removed. In any of the above steps, the etching stopper film functions to prevent the underlying semi-transparent film from being etched in the light shielding film etching step.

  When there is no such etching stopper film, if there is not sufficient etching selectivity between the two laminated films (here, the semi-transparent film and the light-shielding film), a predetermined pattern is formed on each film. Can not be applied. For example, it is generally necessary that the etching selectivity with respect to the etchant of the light shielding film is about 10 (the etching rate of the light shielding film is 10 times that of the semitransparent film) or more between the light shielding film and the semitransparent film. In this case, the materials for the light-shielding film and the semi-transparent film cannot be freely selected considering only their optical characteristics. In other words, a multi-tone photomask (and a blank for it) provided with an etching stopper film has an advantage that the degree of freedom in selecting materials for the semi-transparent film and the light-shielding film is increased. The etching stopper film ensures a necessary etching selectivity between the light shielding film on the upper layer side and the semi-transparent film on the lower layer side depending on the material. That is, if there is a sufficient etching selection ratio, the etching stopper film has a sufficient function even if the film thickness is small.

  By the way, even if the etching stopper film thickness is appropriately designed in consideration of the etching selectivity, the base semi-transparent film that should be protected by the etching stopper film in the etching process of the light shielding film is uniform. In some cases, the etching was partially performed. That is, it has been found that the semi-transparent film may disappear after the light shielding film is etched in the above-described process.

  An object of the present invention is to more reliably prevent the semi-transparent film on the lower layer side of the etching stopper film from being etched in the etching process of the light shielding film and improve the accuracy of the transfer pattern to be formed. To do.

  A first aspect of the present invention is a multi-tone photomask in which a predetermined transfer pattern including a light shielding portion, a semi-translucent portion, and a light transmitting portion is formed on a transparent substrate, and the light shielding portion includes: A semi-transparent film, an etching stopper film, and a light-shielding film are laminated on the transparent substrate in this order, and the semi-transparent portion is formed by forming the semi-transparent film on the transparent substrate. The optical part is formed by exposing the transparent substrate, and the etching stopper film has a thickness of 1.5 times or more the value of the surface roughness Rmax of the semi-transparent film on the lower layer side of the etching stopper film. This is a multi-tone photomask.

  A second aspect of the present invention is the multi-tone photomask according to the first aspect, wherein the semi-translucent film is made of a material containing chromium.

  A third aspect of the present invention is the multi-tone photomask according to the first or second aspect, wherein the etching stopper film is formed on the upper side of the semi-translucent film by sputtering.

  A fourth aspect of the present invention is the multi-tone photomask according to any one of the first to third aspects, wherein the etching stopper film is made of a material containing metal silicide.

  According to a fifth aspect of the present invention, in the multi-tone photomask according to any one of the first to fourth aspects, the surface roughness of the semi-transparent film is 10 to 20 mm in maximum height Rmax. It is.

  A sixth aspect of the present invention is the multi-tone photomask according to any one of the first to fifth aspects, wherein the thickness of the etching stopper film is equal to or less than the thickness of the semi-transparent film.

  A seventh aspect of the present invention is a photomask blank for a multi-tone photomask having a predetermined transfer pattern including a light-shielding part, a semi-translucent part, and a translucent part. An optical film, an etching stopper film, and a light shielding film are formed in this order. The semi-transparent film is made of a material containing chromium, and the etching stopper film is on the lower layer side of the etching stopper film. Is a photomask blank for a multi-tone photomask having a film thickness of 1.5 times or more the value of the surface roughness Rmax.

  An eighth aspect of the present invention is the photomask blank for a multi-tone photomask according to the seventh aspect, wherein the etching stopper film is formed on the upper layer side of the semi-translucent film by sputtering.

  A ninth aspect of the present invention is the photomask blank for a multi-tone photomask according to the seventh or eighth aspect, wherein the etching stopper film is made of a material containing metal silicide.

  A tenth aspect of the present invention is the multi-tone photomask according to any one of the seventh to ninth aspects, wherein the surface roughness of the semi-transparent film is 10 mm or more and 20 mm or less at the maximum height Rmax. Photomask blank.

  The eleventh aspect of the present invention is the photomask blank for a multi-tone photomask according to any one of the seventh to tenth aspects, wherein the film thickness of the etching stopper film is equal to or less than the film thickness of the semi-transparent film. It is.

  According to a twelfth aspect of the present invention, the exposure film is irradiated with the exposure light through the multi-tone photomask according to any one of the first to sixth aspects. A pattern transfer method including a step of transferring the transfer pattern onto the resist film.

  According to the multi-tone photomask, the photomask blank for the multi-tone photomask, and the pattern transfer method using the multi-tone photomask according to the present invention, in the etching process of the light shielding film, the lower layer of the etching stopper film It can prevent more reliably that the semi-transparent film in the side will be etched, and can improve the precision of the pattern for transfer formed.

1 is a partial cross-sectional view of a multi-tone photomask according to an embodiment of the present invention. It is sectional drawing which shows the pattern transfer method using the multi-tone photomask which concerns on one Embodiment of this invention. It is a flowchart of the manufacturing process of the multi-tone photomask which concerns on one Embodiment of this invention. It is a schematic diagram which shows the relationship of the film thickness of each film | membrane which the multi-tone photomask which concerns on one Embodiment of this invention has. It is a figure which shows the mode of manufacture of the multi-tone photomask which concerns on a prior art example. It is a schematic diagram which shows the covering state of the etching stopper film | membrane formed on the semi-transparent film of the multi-tone photomask which concerns on a prior art example.

  The present invention provides a multi-tone in which a translucent film and a light-shielding film are formed on a transparent substrate, and each is subjected to predetermined patterning to form a translucent part, a semi-transparent part, and a light-shielding part. It relates to a photomask. That is, it is necessary to independently pattern the laminated films having different optical characteristics, and at this time, an etching process is required so as not to damage other films on the lower layer side. Therefore, an etching stopper film is provided between the semi-transparent film and the light shielding film.

  Here, the film formed on the transparent substrate is not limited to the above three kinds of films. In addition to these films, films having other functions may exist within the range where the effects of the present invention can be obtained. For example, a second etching stopper film that prevents damage to the transparent substrate may be provided between the transparent substrate and the semi-transparent film. Further, the semi-transparent film may be a single film, or a plurality of films may be laminated. For example, in a photomask having four or more gradations having two or more semi-transparent portions, two or more semi-transparent films having different exposure light transmittances are stacked on a transparent substrate, and an etching stopper film is formed thereon. It may be formed. Alternatively, the etching stopper film of the present invention may be interposed between two or more semi-transparent films. Furthermore, the multi-tone photomask of the present invention may have a different semi-transparent film pattern formed on the light shielding film pattern.

  When a multi-tone photomask of the present invention is to be obtained using a photomask blank in which a translucent film, an etching stopper film, and a light shielding film are formed on a transparent substrate, the semitransparent film and the light shielding film are used. Since no etching selectivity is required between the two films, both films can be formed of similar materials. For example, the light shielding film can be a film containing chromium (Cr) as a main component, and the semi-transparent film can be made of a chromium (Cr) compound. At this time, as described above, when the etching process of the light shielding film formed on the semi-transparent film is performed, the underlying semi-transparent film that should be protected by the etching stopper film is partially etched and disappears. There was a case. According to the inventor's earnest research, the phenomenon is derived from the surface roughness of the semi-transparent film, and a gap is generated in the etching stopper film deposited thereon, and the wet etchant acts from this part. Was found. In other words, the etchant of the light-shielding film acts on the semi-transparent film starting from the part where the side surface of the surface irregularity of the semi-transparent film is not sufficiently recovered by the etching stopper film at the time of film formation and is slightly exposed. It turned out that. This is a phenomenon that should be particularly noted in wet etching, which is isotropic etching.

  The surface roughness of the semi-transparent film is somewhat different depending on the material and the film forming method. However, it is possible to design a photomask such as determining the film thickness of the etching stopper film based on the numerical value (for example, the surface roughness due to the Rmax maximum height) by evaluating the surface roughness. . And the inventor obtained the knowledge that the above-mentioned subject can be solved by prescribing the film thickness of the etching stopper film according to the surface roughness of the semi-transparent film that is the base of the etching stopper film. . The present invention has been made based on such knowledge obtained by the inventor.

<One Embodiment of the Present Invention>
Hereinafter, an embodiment of the present invention will be described mainly with reference to FIGS. 1 to 3. FIG. 1 is a partial cross-sectional view of a multi-tone photomask 10 according to this embodiment. FIG. 2 is a cross-sectional view showing a pattern transfer method using the multi-tone photomask 10. FIG. 3 is a flowchart of the manufacturing process of the multi-tone photomask 10 according to this embodiment.

(1) Configuration of Multi-tone Photomask A multi-tone photomask 10 shown in FIG. 1 is used for manufacturing a thin film transistor (TFT) substrate for a flat panel display (FPD) such as a liquid crystal display device. However, FIG. 1 illustrates a laminated structure of a multi-tone photomask, and an actual pattern is not necessarily the same.

  The multi-tone photomask 10 has a configuration in which a predetermined transfer pattern including a light shielding part 110, a semi-transparent part 115, and a translucent part 120 is formed on a transparent substrate 100. The light shielding unit 110 is formed by laminating a semi-transparent film 101, an etching stopper film 102, and a light shielding film 103 on the transparent substrate 100 in this order. The semi-transparent portion 115 is formed by forming the semi-transparent film 101 and the etching stopper film 102 on the transparent substrate 100 in this order, and the translucent portion 120 is formed by exposing the transparent substrate 100. In addition, a film having other functions may be interposed.

The transparent substrate 100 includes, for example, quartz (SiO ₂ ) glass, SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , RO (R is an alkaline earth metal), R ₂ O (R ₂ is an alkali metal), or the like. It is configured as a flat plate made of low expansion glass or the like. The main surface (front surface and back surface) of the transparent substrate 100 is configured to be flat and smooth by polishing or the like. The transparent substrate 100 can be a square having a side of about 2000 mm to 2400 mm, for example. The thickness of the transparent substrate 100 can be set to about 3 mm to 20 mm, for example.

  The translucent film 101 is made of, for example, a material containing chromium (Cr), and is made of a chromium compound such as chromium nitride (CrN), chromium oxide (CrO), chromium oxynitride (CrON), chromium fluoride (CrF), or the like. be able to. The semi-transmissive film 101 is a sputtered film formed by sputtering, for example, as will be described later, and the surface of the semi-transmissive film 101 has a certain surface roughness. The surface roughness of the semi-transparent film 101 is, for example, 10 to 20 mm at the maximum height Rmax.

The translucent film 101 can be etched using a chromium etching solution made of pure water containing, for example, ceric ammonium nitrate ((NH ₄ ) ₂ Ce (NO ₃ ) ₆ ) and perchloric acid (HClO ₄ ). It is configured as follows. Further, the semi-transparent film 101 has an etching resistance to a fluorine (F) -based etching solution (or etching gas).

The etching stopper film 102 is preferably made of a material having resistance to an etchant for a chromium-based film. In addition to SiO ₂ and SOG, a metal material such as molybdenum (Mo) or tantalum (Ta) and silicon It can be composed of a metal silicide containing (Si) or a material thereof such as a nitride, oxide, carbide, or oxynitride thereof. Specifically, a metal silicide compound made of MoSix, MoSiN, MoSiON, MoSiCON, TaSix, or the like can be used. As will be described later, the etching stopper film 102 can be a sputtered film formed by sputtering, for example. In the multi-tone photomask 10 of the present invention, the etching stopper film 102 may not remain in the semi-translucent portion 115, but the etching stopper film 102 may partially or completely remain. . In that case, the exposure light transmittance of the etching stopper film 102 is preferably 80% or more, more preferably 90% or more.

  The film thickness of the etching stopper film 102 is set according to the surface roughness of the semi-transparent film 101. When the surface roughness of the semi-transparent film 101 is defined by, for example, the maximum height Rmax, the film thickness of the etching stopper film 102 is 1.5 times or more the surface roughness of the semi-transparent film 101, preferably 2.0. It is configured to be more than twice. Specifically, when the surface roughness of the semi-transparent film 101 defined by the maximum height Rmax is within a range of, for example, 10 mm or more and 20 mm or less, the film thickness of the etching stopper film 102 is at least 15 mm or more, preferably For example, it can be about 50 mm or more.

  In the present embodiment, the etching stopper film 102 is configured to be etched using a fluorine (F) -based etchant (or etching gas). The etching stopper film 102 has etching resistance to the above-described chromium etching solution, and functions as an etching stopper layer when the light shielding film 103 is etched using the chromium etching solution as described later. That is, since the etching stopper film 102 having etching resistance is hardly etched, the underlying semi-transparent film 101 is prevented from being etched. As described above, since the film thickness of the etching stopper film 102 is adjusted according to the surface roughness of the underlying semi-transparent film 101, the semi-transparent film 101 has a predetermined surface roughness. In addition, since the etching stopper film 102 formed by sputtering sufficiently covers the semi-transparent film 101, it is possible to suppress a part of the semi-transparent film 101 from being etched.

  In the present embodiment, the light shielding film 103 is substantially made of chromium (Cr). If a chromium compound (CrO, CrC, CrN or the like) is laminated on the surface of the light shielding film 103 (not shown), the surface of the light shielding film 103 can have a light reflection suppressing function. The light shielding film 103 is configured to be etched using the above-described chromium etching solution.

  The light shielding unit 110, the semi-transparent unit 115, and the translucent unit 120 each have a transmittance within a predetermined range with respect to light having a representative wavelength among exposure light in the range of, for example, i-line to g-line. It is configured as follows. That is, the light shielding unit 110 is configured to shield the exposure light (light transmittance is approximately 0%), and the light transmitting unit 120 is configured to transmit the exposure light approximately 100%. The translucent part 115 has, for example, a transmittance of exposure light of 5% or more and 80% or less (when the transmittance of the sufficiently wide translucent part 120 is 100%. The same applies hereinafter), more preferably 10% or more. It is comprised so that it may reduce to 60% or less. Note that i-line (365 nm), h-line (405 nm), and g-line (436 nm) are main emission spectra of mercury (Hg). The representative wavelength here is any wavelength of i-line, h-line, and g-line. More preferably, it is desirable to satisfy the above transmittance for all wavelengths of i-line to g-line.

(2) Pattern Transfer Process Using Multi-tone Photomask FIG. 2 illustrates a partial cross-sectional view of a resist pattern 302p formed on the transfer target 30 by a pattern transfer process using the multi-tone photomask 10. The resist pattern 302p is formed by irradiating the positive resist film 302 formed on the transfer target 30 with exposure light through the multi-tone photomask 10 and developing it. The transferred object 30 includes a substrate 300 and an arbitrary processed layer 301 such as a metal thin film, an insulating layer, and a semiconductor layer, which are sequentially stacked on the substrate 300, and the positive resist film 302 is the processed layer 301. It is preliminarily formed with a uniform thickness on the top. In addition, each layer which comprises the to-be-processed layer 301 may be comprised so that it may have tolerance with respect to the etching liquid (or etching gas) of the upper layer of each layer.

  When the above-described exposure light is irradiated to the positive resist film 302 via the multi-tone photomask 10, the exposure light is not transmitted through the light shielding unit 110, and the exposure light is sequentially emitted from the semi-translucent unit 115 and the translucent unit 120. The amount of light increases step by step. Then, the positive resist film 302 has a thickness that decreases in order in the regions corresponding to the light-shielding portion 110 and the semi-transparent portion 115 and is removed in the region corresponding to the transparent portion 120. In this manner, resist patterns 302p having different thicknesses are formed on the transfer target 30 in stages.

  When the resist pattern 302p is formed, the processing target layer 301 exposed in a region not covered with the resist pattern 302p (region corresponding to the light transmitting portion 120) is sequentially etched away from the surface side. Then, the resist pattern 302p is ashed (reduced) to remove the thin region (the region corresponding to the semi-translucent portion 115), and the newly exposed layer 301 to be etched is sequentially removed. As described above, by using the resist pattern 302p having different thicknesses in steps, the conventional process for two photomasks is performed, the number of masks can be reduced, and the photolithography process can be simplified.

(3) Multi-tone photomask manufacturing method The present invention can be applied to a multi-tone photomask according to the following manufacturing process. That is,
1) A method for manufacturing a multi-tone photomask, wherein a predetermined transfer pattern including a light-shielding part, a semi-translucent part, and a translucent part is formed on a transparent substrate,
A step of preparing a photomask blank in which a semi-transparent film, an etching stopper film, a light shielding film, and a first resist film are laminated in this order on the transparent substrate;
Drawing and developing the first resist film to form a first resist pattern that covers a formation region of the light shielding portion;
A first etching step of sequentially etching the light-shielding film and the etching stopper film using the first resist pattern as a mask;
Forming a second resist film on the photomask blank subjected to the first etching step after removing the first resist pattern;
Drawing and developing the second resist film to form a second resist pattern covering the formation region of the light-shielding portion and the formation region of the semi-translucent portion;
Etching the semi-transparent film using the second resist pattern as a mask to partially expose the transparent substrate; and
Removing the second resist pattern,
The method for manufacturing a multi-tone photomask, wherein the etching stopper film has a film thickness of 1.5 times or more a surface roughness Rmax of the semi-translucent film that is a base of the etching stopper film.
Or
2) A method for manufacturing a multi-tone photomask, wherein a predetermined transfer pattern including a light-shielding part, a semi-translucent part, and a translucent part is formed on a transparent substrate,
A step of preparing a photomask blank in which a semi-transparent film, an etching stopper film, a light shielding film, and a first resist film are laminated in this order on the transparent substrate;
Drawing and developing the first resist film to form a first resist pattern that covers a formation region of the light-shielding portion and the semi-transparent portion;
A first etching step of sequentially etching the light-shielding film, the etching stopper film, and the semi-transparent film using the first resist pattern as a mask;
Forming a second resist film on the photomask blank subjected to the first etching step after removing the first resist pattern;
Drawing and developing the second resist film, and forming a second resist pattern covering the formation region of the light shielding portion;
Etching the light shielding film and the etching stopper film using the second resist pattern as a mask to partially expose the semi-transparent film; and
Removing the second resist pattern,
The method for manufacturing a multi-tone photomask, wherein the etching stopper film has a film thickness of 1.5 times or more a surface roughness Rmax of the semi-translucent film that is a base of the etching stopper film.

  Next, a manufacturing method of the multi-tone photomask 10 according to the present embodiment will be described based on the above 1) with reference to FIG.

(Photomask blank preparation process)
First, as illustrated in FIG. 3A, a semi-transparent film 101, an etching stopper film 102, and a light shielding film 103 are formed in this order on a transparent substrate 100, and a first resist film 104 is formed as the uppermost layer. A photomask blank 10b is prepared. The first resist film 104 can be composed of a positive photoresist material or a negative photoresist material. In the following description, it is assumed that the first resist film 104 is formed from a positive photoresist material. The first resist film 104 can be formed using, for example, a slit coater or a spin coater.

  Further, when the photomask blank 10b is prepared, the semi-transparent film 101, the etching stopper film 102, the light-shielding film 103, and the optical characteristics, etc. of the semi-transparent film 101, the etching film 103, and the etching are adjusted so as to have desired values as described above. The material and thickness of the stopper film 102 and the light shielding film 103 are selected. Further, when the surface roughness of the semi-transparent film 101 is defined by, for example, the maximum height Rmax, the thickness of the etching stopper film 102 is 1.5 times or more the surface roughness of the semi-transparent film 101, preferably 2 The film thickness of the etching stopper film 102 is selected so as to be 0 times or more.

  In addition, it is considered necessary not to excessively increase the film thickness of the etching stopper film 102 in consideration of not deteriorating the shape accuracy (particularly the line width) of the semi-transparent film pattern 101p by etching, which will be described later. Specifically, the thickness of the etching stopper film 102 is preferably less than or equal to the thickness of the semi-transparent film 101. This is because if the thickness of the etching stopper film 102 is too large, the etching time for etching the etching stopper film 102 becomes long, and the side etching of the etching stopper film 102 also proceeds during this time. This tendency is remarkable in wet etching. Next, when the semi-transparent film 101 on the lower layer side of the etching stopper film 102 is etched, the etching proceeds using the etching stopper film 102 as a mask. If the pattern shape accuracy of the semi-translucent film 101 deteriorates and is remarkable, the allowable range of the line width accuracy of the device to be obtained cannot be achieved. The film thickness of the semi-transparent film 101 differs depending on the setting value of the exposure light transmittance of the semi-transmissive part 115. The etching stopper film 102 is more preferably 1/6 times to 1 time the film thickness of the semi-translucent film 101.

The semi-transparent film 101 and the etching stopper film 102 are formed by, for example, sputtering in the process of manufacturing the photomask blank 10b. For example, the semi-transparent film 101 containing chromium nitride (CrN) as a main component uses a large sputtering apparatus, and a chromium (Cr) target disposed in a processing chamber of the apparatus is combined with an argon (Ar) gas and a nitrogen (N) source. A film is formed by sputtering with a mixed gas such as nitrogen (N ₂ ) gas. The semi-transparent film 101 to be formed is, for example, a difference in film composition due to a difference in flow rate of each gas introduced into the processing chamber, a film formation time, a film formation temperature, or the like, or the transparent substrate 100 underlying the semi-transparent film 101 This surface roughness has a predetermined surface roughness. However, the surface roughness of the semi-transparent film 101 in this embodiment is within a range that does not affect the optical characteristics such as the transmittance of the semi-transparent film 101. In FIG. 3A and the following (b) to (g), the surface roughness is exaggerated in order to visually express the state of the surface roughness of the semi-translucent film 101.

  Further, for example, the etching stopper film 102 mainly composed of MoSix uses a large sputtering apparatus or the like, and a target made of molybdenum (Mo) and silicon (Si) with a predetermined mixing ratio disposed in a processing chamber of the apparatus is argon. The film is formed by sputtering with (Ar) gas or the like. At this time, for example, the flow rate of each gas introduced into the processing chamber, the film formation time, the film formation temperature, and the like are adjusted to form the etching stopper film 102 having a predetermined film thickness.

  FIG. 4 schematically shows the relationship between the thicknesses of the respective films when the semi-transparent film 101, the etching stopper film 102, and the light shielding film 103 are laminated on the transparent substrate 100 in this order. In the drawing, the surface roughness of the semi-transparent film 101 is represented by a surface roughness curve S1, and the average surface roughness of the semi-transparent film 101 is represented by a surface roughness average line S2. The surface roughness of the etching stopper film 102 is represented by a surface roughness curve s1, and the average surface roughness of the etching stopper film 102 is represented by a surface roughness average line s2.

  As shown in FIG. 4, the translucent film 101 formed on the transparent substrate 100 has a predetermined surface roughness defined by, for example, the maximum height Rmax. The maximum height Rmax is represented by the difference between the maximum height and the minimum height within a predetermined reference length of the surface roughness curve S1 of the semi-transparent film 101, and conforms to, for example, JIS-B-601. be able to.

  The etching stopper film 102 formed on the semi-transparent film 101 is a film having a surface roughness of the semi-transparent film 101, for example, 1.5 times or more, more preferably 2.0 times or more of the maximum height Rmax. Has a thickness. Thereby, the surface of the semi-transparent film 101 can be more reliably covered with the etching stopper film 102 regardless of the surface roughness of the semi-transparent film 101 on the lower layer side. Therefore, the etching of the semi-transparent film 101 can be more reliably prevented in the etching process of the light shielding film 103 described later.

(First resist pattern forming step)
Next, as illustrated in FIG. 3B, the photomask blank 10 b is drawn with a laser drawing machine or the like, the first resist film 104 is exposed, and a developer is supplied to the first resist film 104. Then, development is performed to form a first resist pattern 104p that covers the formation region of the light shielding portion 110. In addition, the formation area of the light-shielding part 110 is an area where the light-shielding part 110 is to be formed in the subsequent process. The same applies to the formation region of the semi-translucent portion 115 described below.

(First etching process)
Next, using the formed first resist pattern 104p as a mask, the light shielding film 103 is etched to form the light shielding film pattern 103p. The light shielding film 103 can be etched by wet etching in which the chromium etching solution is supplied to the light shielding film 103 by a spray method or the like. At this time, the underlying etching stopper film 102 functions as an etching stopper layer. That is, the semi-transparent film 101 which is a lower layer of the etching stopper film 102 is protected. FIG. 3C illustrates a state where the light shielding film pattern 103p is formed. As described above, since the film thickness of the etching stopper film 102 is adjusted according to the surface roughness of the semi-transparent film 101, the semi-transparent film 101 is etched in the etching process of the light shielding film 103. Can be prevented more reliably.

  Subsequently, using the first resist pattern 104p or the light shielding film pattern 103p as a mask, the etching stopper film 102 is etched to form an etching stopper film pattern 102p, and the semi-transparent film 101 is partially exposed. Etching of the etching stopper film 102 can be performed by supplying a fluorine (F) -based etching solution (or etching gas) to the etching stopper film 102. At this time, the underlying semi-transparent film 101 functions as an etching stopper layer. The state in which the etching stopper film pattern 102p is formed is illustrated in FIG. Note that when the etching stopper film 102 is etched using the light shielding film pattern 103p as a mask, the first resist pattern 104p may be removed in advance.

(Second resist film forming step)
Then, after removing the first resist pattern 104p, a second resist film 105 is formed on the entire surface of the photomask blank 10b having the light shielding film pattern 103p and the etching stopper film pattern 102p. The first resist pattern 104p can be removed by bringing a stripping solution or the like into contact with the first resist pattern 104p. The second resist film 105 can be formed using, for example, a slit coater or a spin coater. The state in which the second resist film 105 is formed is illustrated in FIG.

(Second resist pattern forming step)
Next, drawing is performed by a laser drawing machine or the like, the second resist film 105 is exposed, a developing solution is supplied to the second resist film 105 and development is performed, and the formation region of the light shielding portion 110 and the semi-transparent portion 115 are exposed. A second resist pattern 105p that covers each of the formation regions is formed.

(Second etching process)
Subsequently, the semi-transparent film 101 is etched using the second resist pattern 105p as a mask to form the semi-transparent film pattern 101p, and the transparent substrate 100 is partially exposed. Etching of the semi-transparent film 101 can be performed by supplying the above-described etching solution for chromium to the exposed surface of the semi-transparent film 101. FIG. 3F illustrates a state where the second etching process has been performed.

(Second resist pattern removal step)
Then, the second resist pattern 105p is removed, and the manufacture of the multi-tone photomask 10 according to this embodiment is completed. The second resist pattern 105p can be removed by bringing a stripping solution or the like into contact with the second resist pattern 105p. A state where the second resist pattern is removed is illustrated in FIG.

  In addition, each film | membrane raw material quoted so far is not limited to the above-mentioned thing.

(4) Effects according to the present embodiment According to the present embodiment, the following one or more effects are achieved.

(A) According to this embodiment, the etching stopper film 102 has a film thickness that is 1.5 times or more the surface roughness of the semi-transparent film 101 that is the base. Thereby, even if the semi-transparent film 101 which is the base has a predetermined surface roughness, sufficient coverage of the etching stopper film 102 is obtained, and the surface of the semi-transparent film 101 on the lower layer side is more Thus, the semi-transparent film 101 can be more reliably prevented from being etched in the first etching step. Therefore, the accuracy of the transfer pattern to be formed can be improved.

  FIG. 5 shows how the multi-tone photomask 20 according to the conventional example is manufactured. As shown in FIG. 5A, a semi-transparent film 201, an etching stopper film 202, and a light shielding film 203 are formed in this order on a transparent substrate 200 in a photomask blank 20b used for manufacturing the multi-tone photomask 20. As a result, the first resist film 204 was formed on the uppermost layer. The thickness of the etching stopper film 202 included in the photomask blank 20b is based on the etching selectivity of the light shielding film 203 and the etching stopper film 202 with respect to the chromium etching solution, and when the time required for etching the light shielding film 203 ends, the etching stopper film 202 is provided. Is set to remain for a predetermined thickness.

  However, like the above embodiment, the semi-transparent film 201 made of CrN is formed by sputtering and has a columnar crystal shape. It has been found by the inventors that such a crystal shape is prominently observed in a film containing Cr. In this crystal structure, the vertical dimension of the formed crystal has a correlation with the surface roughness of the semi-transparent film 201. The inventors have found that a surface state of Rmax of 10 to 20 cm is formed. This is shown in FIG.

  The sputtering method can be used for film formation on an uneven surface, but generally has a directivity during film formation as compared with chemical vapor deposition or physical vapor deposition without using a high voltage. As described above, in the formation of the etching stopper film 202 according to the conventional example, when a target composed of molybdenum (Mo) and silicon (Si) having a predetermined mixing ratio is sputtered with argon (Ar) gas or the like, the target is beaten from the target. The released mixture of molybdenum and silicon reaches the surface of the semi-transparent film 201 with a certain degree of directivity. That is, the mixture of molybdenum and silicon is most easily deposited in the film thickness direction on the surface of the semi-transparent film 201. Therefore, if the surface of the semi-transparent film 201 is uneven, the film growth on the side surface is delayed, and in the case of remarkable, as shown in FIG. 6, the etching stopper film 202 is formed in a partially interrupted state. There was a case. FIG. 5A described above shows a state in which the etching stopper film 202 is interrupted.

  A first resist pattern 204p is formed on the photomask blank 20b on which such an etching stopper film 202 is formed (see FIG. 5B), and the light shielding film 203 is etched as shown in FIG. 5C. Then, the chromium etching solution permeates from the discontinuous portion of the etching stopper film 202 exposed by removing the light shielding film 203, and the semi-transparent film 201 that is the base of the etching stopper film 202 is partially etched. That is, the semi-transparent film 201 cannot be reliably etched.

  When the second resist pattern 205p is removed through the steps shown in FIGS. 5D to 5F in the same manner as in the above-described embodiment, for example, as shown in FIG. A multi-tone photomask 20 having a semi-translucent portion in which a part of the film pattern 201p is interrupted is manufactured. In the semi-transparent portion of the multi-tone photomask 20, a predetermined transmittance or the like cannot be obtained.

  However, according to this embodiment, since the film thickness of the etching stopper film 102 is adjusted according to the surface roughness of the underlying semi-transparent film 101, the surface of the semi-transparent film 101 is made to be etched by the etching stopper film 102. It can cover more reliably and can prevent more reliably that the translucent film | membrane 101 will be etched in a 1st etching process.

  In addition, when the semi-transparent film 101 has a composition other than CrN, or when it contains other elements in addition to CrN, the shape and size of this crystal structure may change, but its surface roughness On the other hand, it was found that the problem that the translucent film 101 disappears when the light shielding film 103 is etched can be almost completely prevented if an overlap of about 0.5 times is anticipated. That is, the etching stopper film 102 having a film thickness 1.5 times or more than the value of Rmax of the semi-transmissive film 101 is used.

<Other Embodiments of the Present Invention>
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change variously in the range which does not deviate from the summary.

In the embodiment described above, the etching stopper film 102 mainly composed of MoSix has been mainly described. However, the material of the etching stopper film 102 is not limited to this. For example, SiO ₂ or tantalum silicide (TaSix ), Tungsten silicide (WSix), nickel silicide (NiSix), etc., as long as they have etching resistance to the etching solution or etching gas of the semi-transparent film 101.

  In the above-described embodiment, the semi-transparent film 101 and the etching stopper film 102 are formed by sputtering, but may be formed by other methods. However, the film formation method by sputtering generally has an advantage that it is cheaper and simpler than the method by CVD or the like. Further, in the formation of the etching stopper film 102, since the coating characteristics (coverage) generally tend to be inferior to those of CVD or the like, the effect of the present invention is remarkable.

DESCRIPTION OF SYMBOLS 10 Multi-gradation photomask 100 Transparent substrate 101 Semi-light-transmitting film 102 Etching stopper film 103 Light-shielding film 110 Light-shielding part 115 Semi-light-transmitting part 120 Light-transmitting part

Claims (12)

A multi-tone photomask in which a predetermined transfer pattern including a light shielding portion, a semi-transparent portion, and a translucent portion is formed on a transparent substrate,
The light shielding part is formed by laminating a semi-transparent film, an etching stopper film, and a light shielding film in this order on the transparent substrate,
The semi-transparent portion is formed by forming the semi-transparent film on the transparent substrate,
The translucent part is formed by exposing the transparent substrate,
The multi-tone photo, wherein the etching stopper film has a film thickness of 1.5 times or more the value of the surface roughness Rmax of the semi-translucent film on the lower layer side of the etching stopper film mask. The multi-tone photomask according to claim 1, wherein the semi-transparent film is made of a material containing chromium. The multi-tone photomask according to claim 1, wherein the etching stopper film is formed on an upper layer side of the semi-translucent film by sputtering. The multi-tone photomask according to any one of claims 1 to 3, wherein the etching stopper film is made of a material containing metal silicide. 5. The multi-tone photomask according to claim 1, wherein the semi-transparent film has a surface roughness of 10 to 20 mm in maximum height Rmax. 6. The multi-tone photomask according to claim 1, wherein a thickness of the etching stopper film is equal to or less than a thickness of the semi-transparent film. A photomask blank for a multi-tone photomask having a predetermined transfer pattern including a light-shielding part, a semi-translucent part, and a translucent part,
A translucent film, an etching stopper film, and a light shielding film are formed in this order on the transparent substrate,
The semi-translucent film is made of a material containing chromium,
The multi-tone photo, wherein the etching stopper film has a film thickness of 1.5 times or more the value of the surface roughness Rmax of the semi-translucent film on the lower layer side of the etching stopper film Photomask blank for mask. The photomask blank for a multi-tone photomask according to claim 7, wherein the etching stopper film is formed on the upper layer side of the semi-translucent film by sputtering. 9. The photomask blank for a multi-tone photomask according to claim 7, wherein the etching stopper film is made of a material containing metal silicide. The photomask blank for a multi-tone photomask according to any one of claims 7 to 9, wherein the surface roughness of the semi-translucent film is 10 to 20 mm in maximum height Rmax. . The photomask blank for a multi-tone photomask according to any one of claims 7 to 10, wherein the thickness of the etching stopper film is equal to or less than the thickness of the semi-transparent film. The transfer pattern is transferred to the resist film by irradiating the resist film formed on the transfer object with the exposure light through the multi-tone photomask according to claim 1. A pattern transfer method comprising the step of:

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