Photomask, method of manufacturing photomask, and plasma etching chamber system

The present invention relates to a photomask, and more particularly to an extreme ultraviolet mask, and methods and devices for producing the extreme ultraviolet mask.

In order to satisfy the excellent performance and low price required by consumers, it is required to make the size of the pattern formed on the semiconductor substrate smaller. In order to satisfy such technical requirements, the wavelength of the light source used in the lithography process is gradually shortened.

For example, the lithographic process goes beyond the past g-line (436 nm) and i-line (365 nm) and uses light in the current deep ultraviolet band, and will now use extreme ultraviolet (EUV). ) Band light is expected to be used in next-generation lithography processes.

On the other hand, since light in the polar ultraviolet band is absorbed by most refractive optical materials, polar ultraviolet lithography generally uses a reflective optical system instead of a refractive optical system. To do. By using such a reflective optical system in EUV lithography, the path of light incident on and reflected by the EUV photomask is formed so that it is not perpendicular to the upper surface of the photomask. For example, the path of incident light or reflected light can be inclined by about 6 ° with respect to the normal of the upper surface of the photomask.

However, due to such a slanted light path, the sidewalls of the light-shielding pattern (ie, the absorber pattern) formed on the photomask can act as obstacles that impede the passage of light. .. Such a current situation is generally referred to as a shadowing effect, and a pattern shape transferred to the same wafer such as a decrease in contrast characteristics and a distortion of critical dimension (CD). May induce deformation and HV bias problems.

<p><patcit num="1"><text>U.S. Pat. Nos. 4,309,267</text></patcit></p>

<p> The present invention has been made in view of the above problems, and an object of the present invention is to provide a photomask that provides improved properties in the shadow effect. Another object of the present invention is to provide a method for producing a photomask capable of alleviating the shadow effect. Yet another object of the present invention is to provide a plasma etching chamber system that can be utilized for improving the shadow effect in EUV photomasks.</p>

<p> In order to achieve the above object, the present invention provides a method for manufacturing a photomask including a step of inclined etching. The solution 1 corresponding to claim 1 includes a step of forming an upper film on a photomask substrate and then patterning the upper film to form an upper pattern having an inclined side wall. At this time, the step of patterning the upper film includes a step of anisotropically etching the upper film using charged particles that move in parallel to the first direction inclined to the upper surface of the upper film. According to the second solution according to claim 2, the photomask substrate can be fixed while the upper film is patterned. In the solution 3 corresponding to claim 3, the shape of the cross section of the upper pattern can be a parallelogram.</p><p> According to the third solution according to claim 4, the photomask substrate can rotate about a rotation axis parallel to the normal of the upper surface thereof while the upper film is patterned. In solution 5, the photomask substrate rotates at a discrete angle about the axis of rotation while the upper film is patterned. In the solution 6, it is possible to continuously rotate around the rotation axis. In the solution 7, the cross-sectional shape of the upper pattern can be a reversed trapezoidal cross-section.</p><p> According to the solution 8 corresponding to claim 5, the upper film may contain a substance that absorbs extreme ultraviolet rays. In the solution 9 corresponding to claim 6, a step of forming a multilayer film capable of functioning as a Bragg reflector against extreme ultraviolet rays is formed on the photomask substrate before the upper film is formed. Further can be included. According to the solution 10 corresponding to claim 7, a buffer film can be further formed on the photomask substrate before the upper film is formed. In this case, the buffer film can contain at least one substance having etching selectivity with respect to the upper film.</p><p> According to the solution 11 corresponding to claim 8, after the upper pattern is formed, the step of forming the absorption pattern by using the upper pattern as a mold and the step of removing the upper pattern to form the side wall of the absorption pattern. The exposure step and can be further carried out. In the solution 12, in the step of forming the absorption pattern, an absorption film that fills the space around the upper pattern is formed on the result product in which the upper pattern is formed, and then the absorption film is front-etched. A step of exposing the upper surface of the upper pattern can be included.</p><p> According to the solution 13 corresponding to claim 9, the step of patterning the upper film is arranged so as to incline the photomask substrate on which the upper film is formed in the plasma etching chamber that produces the charged particles. Can include stages of etching. In the solution 14, the plasma etching chamber includes a Faraday cage that controls the direction of movement of the charged particles, and a position control unit that controls the angle between the photomask substrate and the first direction. be able to. In the solution 15, the position control unit may include a rotation control unit that controls the rotation of the photomask substrate with respect to the rotation axis.</p><p> The photomask according to the solution 16 according to claim 10 includes a photomask substrate, an absorption pattern arranged on the photomask substrate, and a multilayer film arranged between the absorption pattern and the photomask substrate. , Can be included. At this time, the upper surface and one side wall of the absorption pattern can form an acute angle.</p><p> According to the solution 17, the upper surface of the absorption pattern and the side wall different from the one side wall can form an obtuse angle. In this case, the cross section of the intersection region between one of the planes perpendicular to the upper surface of the photomask substrate and the absorption pattern can be a parallelogram. According to the solution 18, a buffer film can be further formed between the absorption pattern and the multilayer film. In the solution 19, the buffer film can extend from below the absorption pattern to the side surface of the absorption pattern. The thickness of the buffer film or the thickness of the multilayer film can be thicker under the absorption pattern than around the absorption pattern. In the solution 20, the buffer film can be formed of a substance having etching selectivity with respect to the absorption pattern.</p><p> The photomask according to the solution 21 according to claim 11 includes a photomask substrate, an absorption pattern arranged on the photomask substrate, and a multilayer film arranged between the absorption pattern and the photomask substrate. , The absorption pattern can have at least one side wall forming an obtuse angle with its top surface.</p><p> According to the solution 22, at least two side walls of the absorption pattern can form an obtuse angle with the upper surface of the absorption pattern. According to the solution 23, at least one of the corners of the absorption pattern can have a rounded side wall. According to the solution 24, at least one pair in the side wall of the absorption pattern can be formed such that at least one of the corners of the absorption pattern defines a recess in the shape of a right-angled triangular pyramid. In this case, the side wall of the absorption pattern that defines the recessed portion can be formed perpendicular to the upper surface of the photomask substrate.</p><p> According to the solution 25, a buffer film can be further formed between the absorption pattern and the multilayer film. In the solution 26, the thickness of the buffer film or the thickness of the multilayer film can be thinner at the center of the absorption pattern than at the edges of the absorption pattern.</p><p> The present invention provides a plasma etching chamber system capable of realizing inclined etching. The plasma etching system of the solution 27 corresponding to claim 12 includes a chuck on which the substrate is loaded, a plasma generation unit for ionizing the etching gas, and a position control unit for controlling the position of the chuck. At this time, the position control unit may include an inclination angle control unit that controls the angle of the upper surface of the chuck with respect to the motion direction of the etching gas ionized in the plasma generation unit.</p><p> According to one aspect of the solution 28, the system can further include an ion direction control unit that controls the direction of motion of the ionized etching gas. In the solution 29, the ion direction control unit may include a Faraday cage. According to the solution 30, the position control unit may further include a rotation control unit that controls the rotation of the substrate with respect to a rotation axis parallel to the upper surface of the substrate. The rotation control unit can be configured so that the chuck can be rotated while the etching process is performed. According to the solution 31, the tilt angle control unit can be configured to be able to variably control the angle of the upper surface of the chuck in the range of -60 to 60 °.</p>

<p> According to aspects of the invention, the absorption pattern of the photomask is formed to have a sloping side wall. Thereby, the photomask according to the present invention can provide an improved technical effect in association with the shadow effect.</p>

<figref num="1">It is a figure for schematically explaining the plasma etching chamber by one Embodiment of this invention.</figref><figref num="2">It is a figure for schematically explaining the plasma etching chamber by one Embodiment of this invention.</figref><figref num="3">It is a figure for demonstrating the position control part of the plasma etching chamber by one Embodiment of this invention.</figref><figref num="4A">It is a figure for demonstrating the method of inclined etching by embodiment of this invention.</figref><figref num="4B">It is a figure for demonstrating the method of inclined etching by embodiment of this invention.</figref><figref num="5">It is a process flowchart for demonstrating the manufacturing method of the photomask by 1st Embodiment of this invention.</figref><figref num="6">It is a perspective view for demonstrating the manufacturing method of the photomask by 1st Embodiment of this invention.</figref><figref num="7">It is a perspective view for demonstrating the manufacturing method of the photomask by 1st Embodiment of this invention.</figref><figref num="8">It is a perspective view for demonstrating the manufacturing method of the photomask by 1st Embodiment of this invention.</figref><figref num="9">It is a process flowchart for demonstrating the manufacturing method of the photomask by 2nd Embodiment of this invention.</figref><figref num="10">It is a perspective view for demonstrating the manufacturing method of the photomask by 2nd Embodiment of this invention.</figref><figref num="11">It is a perspective view for demonstrating the manufacturing method of the photomask by 2nd Embodiment of this invention.</figref><figref num="12">It is a perspective view for demonstrating the manufacturing method of the photomask by 2nd Embodiment of this invention.</figref><figref num="13">It is a perspective view for demonstrating the manufacturing method of the photomask by 2nd Embodiment of this invention.</figref><figref num="14">It is a perspective view for demonstrating the manufacturing method of the photomask by 2nd Embodiment of this invention.</figref><figref num="15">It is a process flowchart for demonstrating the manufacturing method of the photomask by the 3rd Embodiment of this invention.</figref><figref num="16">It is a perspective view for demonstrating the manufacturing method of the photomask by 3rd Embodiment of this invention.</figref><figref num="17">It is sectional drawing for demonstrating one technical feature of the photomask produced by the manufacturing method of embodiment of this invention.</figref><figref num="18">It is sectional drawing for demonstrating one technical feature of the photomask produced by the manufacturing method of embodiment of this invention.</figref><figref num="19">It is sectional drawing for demonstrating one technical feature of the photomask produced by the manufacturing method of embodiment of this invention.</figref><figref num="20">It is sectional drawing for demonstrating one technical feature of the photomask produced by the manufacturing method of embodiment of this invention.</figref><figref num="21">It is sectional drawing for demonstrating one technical feature of the photomask produced by the manufacturing method of embodiment of this invention.</figref><figref num="22">It is sectional drawing for demonstrating one technical feature of the photomask produced by the manufacturing method of embodiment of this invention.</figref><figref num="23">It is sectional drawing for demonstrating one technical feature of the photomask produced by the manufacturing method of embodiment of this invention.</figref>

The above objectives, other objectives, features and advantages of the present invention should be readily understood through the following desirable embodiments in connection with the accompanying drawings. However, the present invention is not limited to the embodiments described herein, but can be embodied in other embodiments. By the way, the embodiments introduced here are provided so that the disclosed contents are thorough and complete, and the ideas of the present invention can be fully conveyed to those skilled in the art.

When it is mentioned herein that any film is on a different film or substrate, it can be formed directly on the different film or substrate, or a third film can be interposed between them. means. Also, in the drawings, the thickness of the membrane and region is exaggerated for effective explanation of the technical content. Also, in various embodiments of the present specification, terms such as first, second, and third have been used to describe various regions, membranes, etc., but these regions, membranes are referred to by such terms. It should not be limited. These terms have only been used to distinguish a given area or membrane from other areas or membranes. Therefore, the membrane quality referred to in any one embodiment may be referred to as the second membrane quality in other embodiments. Each embodiment described and illustrated herein also includes a detailed complementary embodiment thereof.

&lt;Plasma etching chamber&gt; In the following, a method of obliquely etching an upper film on a photomask substrate (hereinafter, referred to as substrate) to form an upper pattern having inclined side walls will be described. Such an etching step can be performed in a plasma etching chamber, and the inclined etching method can be variously classified according to the relative position and direction between the substrate and the plasma etching chamber. In order to more clearly explain such a method of inclined etching, here, the plasma etching chamber according to the embodiment of the present invention will be described first, and then the relative position between the substrate and the plasma etching chamber will be described. And a brief definition for the direction.

1 and 2 are diagrams for schematically explaining a plasma etching chamber according to an embodiment of the present invention. Referring to FIGS. 1 and 2, the plasma etching chamber 200 includes a chuck on which a substrate is loaded, a plasma generator 210, an accelerator 220, an alignment device 230 as an ion direction control unit, and the chuck. It is provided with a position control unit 240 for controlling the position and direction of the above. The plasma generator 210 and the accelerator 220 can each include a low frequency RF power source and a coupled electrode to the low frequency power source, respectively, and bring the process gas supplied to the plasma etching chamber 200 into a plasma state 205. After making it, it is configured to increase the kinetic energy of the plasma ions. According to this embodiment, the plasma generator 210 and the accelerator 220 can be substantially identical to the configurations used in a typical plasma etching chamber. The alignment device 230 controls the traveling direction of the ions. In this embodiment, the alignment device 230 is a Faraday cage that includes a grid.

The position control unit 240 is configured to control the position and direction of the chuck. Specifically, a predetermined position of the plasma etching chamber 200 is selected as a reference point O for defining the position of the chuck. In this case, the position of the chuck is a Cartesian coordinate system defined by three orthogonal axes (for example, x-axis, y-axis, and z-axis), and the specific position P of the chuck and the reference point O are It can be described by three Cartesian coordinates (ie, x, y, z) that represent the distance between.

Since the chuck is regarded as a rigid body having a finite volume and an invariant shape, the direction of the chuck can rotate in each of three independent directions. For example, the upper surface of the chuck can rotate about the normal of the upper surface of the chuck, and hereinafter, the first angle θ is used to express the degree of such rotation. Further, the upper surface of the chuck can be rotated about one axis (for example, x-axis or y-axis) parallel to the upper surface, and the second angle φ is hereinafter such rotation. Used to express degree. In this embodiment, the normal line on the upper surface of the chuck corresponds to the "rotation axis".

The position control unit 240 is configured to be able to control the position coordinates (x, y, z) and the rotation angles θ and φ. Therefore, as shown in FIG. 3, the position control unit 240 controls the position coordinates (x, y, z) of the chuck to each of the x--coordinate control unit 241, y--coordinate control unit 242. , Z-coordinate control unit 243, θ-angle control unit 244 as a rotation control unit that controls the rotation angles θ and φ of the chuck, and φ-angle control unit 245 as an inclination angle control unit. it can. The arrangement of the coordinates and angle control units 241 to 245 can be variously modified from the structure illustrated in FIG.

According to one embodiment of the present invention, the φ-angle control unit 245 is configured so that the second angle φ can be variably adjusted in the range of -60 ° to 60 °. In this case, as shown in FIG. 4A, the second angle φ determines the angle between the normal N of the upper surface of the substrate and the traveling direction DI of the ions, and will be described in detail later. In addition, the upper pattern can be formed to have an inclined side wall. As shown in FIG. 4B, the θ-angle control unit 244 is configured so that the substrate can be freely rotated within a range of 0 to 360 °.

According to an embodiment of the present invention related to the method of inclined etching, during the etching step, the second angle φ is fixed to one angle selected within the range of 1 ° to 60 °, and the first angle θ. Can be varied within a predetermined angular range selected within the range 0-360 °. The first angle θ is a plurality of angles (eg, 0 °, 45 °, 90 °) that are continuously changed or discontinuous within a predetermined range (for example, 0 to 90 ° or 0 to 360 °). , 180 °, 270 °, etc.).

When the first angle θ is fixed, the upper pattern has side walls tilted in a particular direction, but when the first angle θ is continuously or discontinuously changed, the upper pattern has a plurality. It is formed so as to have a side wall inclined in the direction. The direction in which the inclined side wall is formed depends on the method of changing the first angle θ.

&lt;Manufacturing method-First embodiment&gt; FIG. 5 is a process flowchart for explaining a method for manufacturing a photomask according to the first embodiment of the present invention. 6 to 8 are perspective views for explaining a method for manufacturing a photomask according to the first embodiment of the present invention.

With reference to FIGS. 5 and 6, the multilayer film 20 is formed on the photomask substrate 10 (hereinafter referred to as substrate) (S1). The substrate 10 can be formed of a material having low thermal expansion properties, such as glass. The multilayer film 20 can include a plurality of thin films constituting a Bragg reflector so that the reflectance of EUV radiation used in the EUV exposure system can be improved. .. According to one embodiment, the multilayer film 20 can include molybdenum films and silicon films that are alternately laminated, and the number of the thin films is approximately 40 to 60. The molybdenum film is formed to a thickness of about 2.8 nm, the silicon film can be formed to a thickness of about 4.0 nm or 4.1 nm, but the thickness of the thin film is the wavelength of the extreme ultraviolet rays used. It can be selected differently from the illustrated value in consideration of such factors.

A buffer film 30 and an upper film 40 are sequentially formed on the multilayer film 20 (S2 and S3). The upper membrane 40 can be formed into one of the substances capable of absorbing extreme ultraviolet light. According to one embodiment, the top film 40 can be formed on a conductive absorber such as a tantalum nitride film (TaN). However, the material for the upper film 40 is not limited to the exemplified tantalum nitride film and can be variously deformed. The buffer film 30 can be used as an etching stop film in the subsequent etching step of patterning the upper film 40, and can be a silicon nitride film, a silicon oxide film, or the like according to one embodiment. According to the modified embodiment, the top film 40 can be formed directly on the multilayer film 20 without the buffer film 30. Subsequently, a mask pattern 50 for patterning the upper film 40 is formed on the upper film 40. According to one embodiment, the mask pattern 50 can be a photoresist pattern.

Referring to FIGS. 5 and 7, the mask pattern 50 is used as an etching mask to pattern the top film 40 to form an top pattern 45 that exposes a portion of the top surface of the buffer film 30. According to the modified embodiment, the buffer film 30 can also be etched during this step or subsequent etching steps, in which case the buffer pattern 35 exposing the upper surface of the multilayer film 20 as shown in FIG. It is formed.

According to this embodiment, the upper pattern 45 is formed through a method of inclined etching so as to have an inclined side wall defining a first undercut region 91. The inclined etching can be performed in the plasma etching chamber 200 described with reference to FIGS. 1 to 3. More specifically, the step of forming the upper pattern 45 includes a step (S4) of loading the substrate 10 on which the upper film 40 and the mask pattern 50 are formed on the chuck of the plasma etching chamber 200.

Subsequently, by operating the position control unit 240, the positions and directions x, y, z, θ, and φ of the chuck are adjusted (S5), and the mask pattern 50 is used as the etching mask to make the upper film 40 different. After forming the upper pattern 45 by anisotropic etching (S6a), the substrate 10 on which the upper pattern 45 is formed is unloaded from the plasma etching chamber 200 (S7). After that, the mask pattern 50 can be selectively removed to expose the upper surface of the upper pattern 45. FIG. 8 illustrates the result of removing the mask pattern 45.

According to this embodiment, the step of forming the upper pattern 45 (S6a) is performed under the condition that the position and direction of the substrate 10 are stopped relative to the plasma etching chamber 200. That is, while the upper film 40 is etched, the position coordinates x, y, z and the rotation angles θ, φ of the chuck do not change from the initial values.

At this time, the first angle θ is a predetermined plane (that is, the z-axis) in which the long axis (main axis) of the mask pattern 50 includes the normal line N of the upper surface of the substrate 10 and the axis parallel to the plasma ion direction DI (that is, the z-axis). For example, it can be selected to be arranged in a direction that vertically penetrates the xz plane). That is, the long axis of the mask pattern 50 can be arranged parallel to the y-axis. In this case, as shown in FIG. 8, only the pair of side walls facing the upper pattern 45 are formed to selectively incline, and the cross section of the upper pattern 45 intersecting the xz plane is a parallelogram. ..

&lt;Manufacturing method-Second embodiment&gt; FIG. 9 is a process flowchart for explaining a method for manufacturing a photomask according to the second embodiment of the present invention. 10 to 14 are perspective views for explaining a method for manufacturing a photomask according to the second embodiment of the present invention. According to this embodiment, the upper pattern is used as a mold for forming the absorption pattern, and the substrate is rotated during the etching process for forming the upper pattern. The description of the technical features that overlap with the above-described first embodiment, excluding such differences, will be omitted.

With reference to FIGS. 9 to 10, the multilayer film 20 is formed on the photomask substrate 10 (hereinafter referred to as substrate) (S1), and the upper film 40 is formed on the multilayer film 20 in order (S3). Subsequently, after forming a mask pattern 50 for patterning the upper film 40 on the upper film 40, the upper surface of the multilayer film 20 is patterned by using the mask pattern 50 as an etching mask to pattern the upper film 40. Form an upper pattern 45 that exposes a portion. Although not shown, a buffer film can be formed on the multilayer film 20 before the upper film 40 is formed as in the above embodiment. The technical features associated with the substrate 10, the multilayer film 20, the buffer film, and the mask pattern 50 are substantially the same as those of the first embodiment described above, or are modified within the technical knowledge of those skilled in the art. be able to.

On the other hand, according to this embodiment, the upper membrane 40 is used as a template for forming an absorption pattern. For this reason, in the present embodiment, the upper film 40 can be formed of at least one of different substances from a substance suitable for use in the absorption pattern (eg, tantalum nitride film). For example, the upper film 40 is, but is not limited to, a silicon oxide film, a silicon nitride film, a silicon oxide nitride film, and a silicon film.

The step of patterning the upper film 40 can include a step of inclined etching performed in the plasma etching chamber 200 described above. More specifically, the inclined etching steps include a loading step (S4) for the substrate 10, a chuck position and orientation adjusting step (S5), a patterning step for the upper film 40 (S6b), and an unloading step (S7). ) And can be included. The loading step (S4), chuck position and orientation adjusting step (S5), and unloading step (S7) of the substrate 10 can be substantially the same as the first embodiment described above.

On the other hand, according to the present embodiment, in the patterning stage (S6b) of the upper film 40, the position coordinates of the substrate 10 and the second angle φ are fixed, and the first angle θ is a plurality of discontinuous angles (for example, 0 °). , 45 °, 90 °, 180 °, 270 °, etc.). For example, FIGS. 10 and 11 show the results of gradient etching performed under conditions where the first angle θ is 0 ° and 90 ° and the second angle φ is from 0 ° to a predetermined angle.

At this time, in order to more clearly explain one technical idea of the present invention, the mask pattern 50 is a projection P of the ion direction DI on the upper surface of the substrate 10 as shown in FIG. It is assumed to have a portion 51 parallel to and a portion 52 perpendicular to.

Referring to FIG. 10, since the second angle φ is not 0 °, the upper pattern 45 is formed to have an inclined side wall that defines the first undercut region 91 under the mask pattern 50. In this case, since the inclined etching step is performed under the condition that the first angle θ is fixed at 0 °, only the pair of side walls facing the upper pattern 45 is selectively selected as in the first embodiment described above. It can be formed to be inclined to.

Referring to FIG. 11, when the inclined etching is performed under the condition that the first angle θ is 90 °, the upper pattern 45 is performed twice under the condition that the first angle θ is 0 ° and 90 °. Since the slope etching is performed, a second undercut region 92 is formed on one side wall of the upper pattern 45 adjacent to the first undercut region 91 formed above. When the second angle φ is fixed, the side wall inclinations of the first undercut region 91 and the second undercut region 92 are substantially the same, and the value thereof is substantially the same as that of the second angle φ. Is the same as.

On the other hand, when the difference between the first angles θ in the two inclined etching steps is the same as the angle between the parallel portion 51 and the vertical portion 52 of the mask pattern 50, it is shown in FIG. At the inward cross-point of the parallel portion 51 and the vertical portion 52, the unetched residual portion 99 is formed by the two inclined etchings described in detail.

Referring to FIG. 12, the above-mentioned gradient etching step is performed under the condition that the first angle θ is 180 ° and 270 ° and the second angle φ is a predetermined angle other than 0 °. In this case, as shown, a third undercut region 93 having an inclined side wall is formed on one side wall of the upper pattern 45 adjacent to the second undercut region 92, and is adjacent to the third undercut region 93. A fourth undercut region 94 with an inclined side wall can be formed on one side wall of the upper pattern 45.

With reference to FIG. 13, the mask pattern 50 can be removed to expose the upper surface of the upper pattern 45. In this case, as shown in FIG. 13, the upper pattern 45 will have a Reversed Trapezoidal cross-section or an inverted truncated pyramid shape.

With reference to FIGS. 9 and 14, the upper pattern 45 is used as a mold to form the absorption pattern 100 (S8). The step S8 for forming the absorption pattern 100 includes a step of forming an absorption film on the product on which the upper pattern 45 is formed and a step of etching the absorption film to expose the upper surface of the upper pattern 45. be able to. In this case, the absorption pattern 100 is formed around the upper pattern 45. After that, the upper pattern 45 is removed around the absorption pattern 100 (S9).

The absorbing film can contain one of the substances capable of absorbing extreme ultraviolet rays. According to one embodiment, the absorbent film can be formed on a conductive absorber such as a tantalum nitride film (TaN), but for this reason the material is not limited to the tantalum nitride film exemplified. It can be transformed in various ways.

The step of etching the absorbent film can be carried out using front etching (etch-back) or chemical mechanical polishing techniques. The step S9 of removing the upper pattern 45 can be performed using an etching recipe that has etching selectivity for the absorption pattern 100. That is, the etching recipe for this stage can be selected so that the etching of the absorption pattern 100 can be minimized and the upper pattern 45 can be selectively removed, the upper pattern 45 being such an etching selection. It is selected among the substances that can embody the sex.

On the other hand, according to the present embodiment, since the upper pattern 45 has a pyramid-shaped cross section cut by turning over as described above, the absorption pattern 100 formed by using this as a mold is shown in FIG. As such, it can have a truncated pyramid shape cross section. That is, the side wall of the absorption pattern 100 can be inclined at an angle of (2π-φ) with respect to the normal line N of the upper surface of the substrate 10. Here, φ is the second angle that expresses the degree to which the upper surface of the chuck of the plasma etching chamber rotates about one axis parallel to the upper surface.

According to the present embodiment, at least one of the corners of the absorption pattern 100 can have a recessed portion 105 in the shape of a right-angled triangular pyramid. At this time, the recessed portion 105 is defined by the side wall of the absorption pattern 100, and the side wall of the absorption pattern 100 that defines the recessed portion 105 can be substantially perpendicular to the upper surface of the photomask substrate 10. Further, the depressed portion 105 is a result of the remaining portion 99 formed in the upper pattern 100 being transferred to the absorption pattern 100. As shown, when the absorption pattern 100 is in the bar-shape, the recess 105 is formed in the square of the absorption pattern 100.

On the other hand, when the remaining portion 99 is excessively etched in the above-mentioned inclined etching step, the size of the depressed portion 105 is reduced. For example, the top of the recess 105 can be formed at a height lower than the top surface of the absorption pattern 100. According to one embodiment, the size and shape of the recess 105 can be adjusted as a means to improve the optical proximity effect (OPE).

&lt;Manufacturing method-Third embodiment&gt; FIG. 15 is a process flowchart for explaining a method for manufacturing a photomask according to the third embodiment of the present invention. FIG. 16 is a perspective view for explaining a method for manufacturing a photomask according to the third embodiment of the present invention.

Excluding the difference in the manufacturing method related to the step of patterning the upper film 40 (S6c), the photomask manufacturing method according to the present embodiment is the photo according to the second embodiment described with reference to FIGS. 9 to 14. It is substantially the same as the method for manufacturing a mask. Therefore, for the sake of brevity, the description of the technical features that overlap with the second embodiment described above will be omitted.

With reference to FIGS. 15 and 16, in the step S6c of patterning the upper film 40, the position coordinates of the substrate 10 and the second angle φ are fixed, and the first angle θ is a condition that continuously changes within a predetermined range. It is carried out below. The range of the first angle θ can be selected in consideration of the required product characteristics and the like. That is, according to the present embodiment, the first angle θ can be continuously changed as a function of time within a predetermined angle range (for example, 0 to 360 °). According to one embodiment, the angular velocity (dθ / dt) of the first angle θ can be 0.001 rpm (rev / min) to 10 rpm.

Due to such continuous rotation, the remaining portion 99 shown in FIGS. 11 to 13 is not formed at the inner intersection of the upper pattern 45 formed by the present embodiment. That is, the inner corner of the upper pattern 45 according to the present embodiment is formed in a round shape. As a result, the absorption pattern 100 according to the present embodiment formed by using the upper pattern 45 as a mold can have rounded corners as shown in FIG.

FIG. 17 is a cross-sectional view for explaining the technical features of the photomask manufactured by the manufacturing method of the first embodiment of the present invention described above. With reference to FIG. 17, a first recess region 88a can be formed that results in non-uniformity in the thickness of the thin film (eg, buffer film 30 or multilayer film 20) below the top pattern 45. In the case of the first embodiment, since the inclined etching is performed under the condition that the substrate 10 is fixed, the first recess region 88a can be offset from the upper pattern 45.

According to the first embodiment described above, since the upper pattern 45 is used for the absorption pattern, the first recess region 88a of the photomask according to the first embodiment is formed around the absorption pattern (that is, the upper pattern 45). Can be done.

17 to 22 are cross-sectional views for explaining a technical feature of the photomask manufactured by the manufacturing method of the second embodiment of the present invention described above. Referring to FIGS. 17-20, according to the second embodiment, the tilt etching is performed under conditions where the substrate 10 rotates at 0 °, 90 °, 180 ° and 270 °. Therefore, around the upper pattern 45, a second recess region 88b (shown in FIG. 18), a third recess region 88c (shown in FIG. 19), and a fourth recess region 88b (shown in FIG. Recess regions 88d (shown in FIG. 20) can be formed in sequence.

According to the second embodiment described above, the upper pattern 45 is used as a template for forming the absorption pattern 100, so that the absorption pattern 100 is formed on the fourth recess region 88d. As a result, as shown in FIG. 21, the thin film under the absorption pattern 100 (ie, the buffer film 30) has a thinner thickness at the center of the absorption pattern 100 than at the edges.

According to a modified embodiment of the present invention, after removing the mask pattern 50 and the upper pattern 45, the buffer film 30 around the absorption pattern 100 can be etched to expose the upper surface of the multilayer film 20. In this case, as shown in FIG. 22, a buffer pattern 35 whose edge thickness is thicker than its central portion can be locally formed under the absorption pattern 100.

According to another modified embodiment of the invention, the top pattern 45 can be formed directly on the multilayer film 20 without the buffer film 30. In this case, the upper surface of the multilayer film 20 becomes non-uniform, but the non-uniform region as shown in FIG. 23 is formed under the absorption pattern 100, which has a substantial effect on the quality of the photomask. Do not give. That is, according to the second embodiment described above, the step of forming the separate buffer film 30 can be omitted.

On the other hand, in the case of the third embodiment described above, since the region to be etched changes depending on the rotation angle, it is possible to form a recess region that provides a non-uniform upper surface similar to the second embodiment. However, the recess area according to the third embodiment may not be in the shape of a staircase.

10: Substrate, 40: Top film, 45: Top pattern, 50: Mask pattern, 200: Plasma etching chamber