JP2012248676A - Euv mask and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EUV mask including an ultrafine auxiliary pattern, and to provide a manufacturing method therefor.SOLUTION: A reflective layer 102 reflecting EUV light is formed by laminating a high transmittance/low reflection layer and a low transmittance/high reflection layer alternately on a substrate 101. An absorption layer 105 which absorbs EUV light is then formed on the reflective layer 102. Subsequently, the absorption layer 105 is processed in the shape of a main pattern 107 being transferred onto the transferred surface, and an auxiliary pattern 108 not transferred to the transferred surface is formed near the main pattern 107. In the step for forming the auxiliary pattern 108, a solid solution of the high transmittance/low reflection layer and the low transmittance/high reflection layer is formed by irradiating the reflective layer 102 with an electron beam 204.

Description

  The present invention relates to an EUV (Extreme Ultra Violet) mask and a manufacturing method thereof.

  In recent years, with the increase in the degree of integration of semiconductor devices, the dimensions of individual elements have been miniaturized, and the widths of wirings and gates constituting each element have also been miniaturized.

  In the manufacture of a semiconductor integrated circuit, a process of processing a wafer by transferring a circuit original plate called a reticle to a photosensitive resin called a resist is fundamental. Then, by repeating this basic process, a semiconductor integrated circuit is manufactured.

  In the transfer process, an exposure device called a stepper or a scanner is used. Conventionally, a method has been employed in which light is used as a transfer light source, and a circuit pattern on a reticle is projected onto a wafer while being reduced to about one-fourth to one-fifth. In order to miniaturize a semiconductor integrated circuit, it is necessary to improve the resolution performance in this transfer process. Here, if the aperture coefficient of the imaging optical system is NA and the wavelength of the light source is λ, the resolution dimension is proportional to (λ / NA). Therefore, the exposure resolution can be reduced by improving the aperture coefficient NA or shortening the wavelength λ.

However, since the depth of focus is proportional to (λ / NA ² ), if the aperture coefficient NA is increased, the exposure resolution can be reduced, but the depth of focus decreases. For example, the depth of focus in a fine pattern corresponding to a design rule of 100 nm or less is about 0.35 μm. With the progress of miniaturization, the depth of focus is expected to become even shallower in the future. Therefore, a modified illumination method has been proposed in which light is incident on the reticle from an oblique direction so that the depth of focus is increased.

  On the other hand, development of EUV lithography technology using EUV (Extreme Ultra Violet) light with a short wavelength (λ = 13 to 14 nm) is also in progress. Although the aperture coefficient NA of EUV lithography is smaller than that of photolithography, the resolution is approximately 2.0 to 1.5 times the wavelength, so that a resolution dimension of 30 nm or less is possible.

  Patent Document 1 describes a method for manufacturing an EUV mask. According to this, first, a reflective film is formed by laminating a multilayer film made of molybdenum and silicon with a desired number of layers on a low thermal expansion glass substrate by sputtering or the like. Next, a buffer film is formed on the reflective layer. The buffer film has a function of reducing damage received by the multilayer film during patterning of the absorption layer and defect correction. Next, a thin film serving as an absorption layer is formed on the buffer film by sputtering or the like. Then, a resist is applied on the thin film, and baking is performed, followed by drawing with an electron beam. Thereafter, after post-baking after drawing, development is performed to form a resist pattern, and the thin film is dry-etched using the resist pattern as a mask. Next, the resist is removed to obtain an EUV mask.

  By the way, since the line width of the pattern has become narrow and has approached the resolution limit, a super-resolution technique has been proposed in which an auxiliary pattern is provided around the main pattern to improve the resolution of the main pattern. At this time, the auxiliary pattern is used only to compensate for the optical proximity effect that occurs when the main pattern is projected. Examples of the auxiliary pattern include Scattering Bar. The auxiliary pattern is designed with dimensions and transmittance that do not resolve itself, and is arranged in the vicinity of the main pattern. Patent Document 2 describes a method for manufacturing an auxiliary pattern.

JP 2004-260056 A JP 2002-323746 A Japanese Patent Application Laid-Open No. 64-33030 US Pat. No. 3,498,876

The resolution (R) is expressed by the following equation using the process coefficient (k).

  In the above equation, the coefficient (k) is a value reflecting the degree or ability of fluctuating depending on the complexity of the transfer pattern related to the photolithography conditions, the process recipe when performing the photolithography process, and the like.

  In the next generation EUV exposure apparatus, for example, it is assumed that k = 0.4 to 0.5, NA = 0.33 to 0.5, and λ = 13.5 nm. In this case, it is considered that the resolution on the mask surface is about 60 nm and the resolution on the sample surface is about 15 nm. The auxiliary pattern required in this generation is considered to have a dimension of 15 nm or less on the mask.

  As described in Patent Document 1, an electron beam lithography apparatus is used for manufacturing a mask used in a state-of-the-art semiconductor integrated circuit from the viewpoint of pattern fineness. However, it is difficult to form an auxiliary pattern having the above dimensions due to blur caused by the electron optical system, the process, and the resist. Hereinafter, this point will be described in detail.

  In mask production, since throughput is required in addition to resolution, a resist with high resolution and high sensitivity is required. Specifically, a chemically amplified resist is used. The chemically amplified resist contains a photoacid generator, and the acid generated by the photoreaction serves as a catalyst to remove protecting groups that have insolubilized the resist resin component in the heating step after exposure. As a result, the exposed portion is solubilized in the alkaline developer, and a fine pattern is formed.

  In the chemically amplified resist, even if a small amount of acid is generated by exposure, the reaction proceeds in a chain manner due to thermal diffusion, so that it can be exposed with high sensitivity, that is, with a very small exposure amount. However, it is known that effective image blur occurs due to this thermal diffusion. This is because the solubility distribution pattern in the developer after heating depends on the acid distribution that changes due to thermal diffusion. Therefore, in order to predict the dimension of the resist pattern, it is important to quantitatively determine the blur of the optical image. In the case of a chemically amplified resist currently used, there is a blur of about 10 to 20 nm at one edge. Therefore, even if an auxiliary pattern having a dimension of 15 nm or less is formed on the mask, it is difficult to form a latent image of the pattern on the resist. Even if a latent image can be formed, it is more difficult to form a resist pattern because a sufficient contrast cannot be ensured by the development process.

  The present invention has been made in view of these points. That is, an object of the present invention is to provide an EUV mask having an ultrafine auxiliary pattern and a method for manufacturing the same.

  Other objects and advantages of the present invention will become apparent from the following description.

A first aspect of the present invention includes a substrate,
A reflective layer that is formed on a substrate and reflects EUV light by a structure in which high transmittance / low reflection layer and low transmittance / high reflection layer are alternately laminated;
An EUV mask formed on the reflective layer and having an absorbing layer for absorbing EUV light,
The absorption layer is processed into the shape of the main pattern transferred to the transfer target surface,
Near the main pattern, an auxiliary pattern that is not transferred to the transfer target surface is formed,
The auxiliary pattern is characterized by comprising a solid solution of a high transmittance / low reflection layer and a low transmittance / high reflection layer.

  In the first aspect of the present invention, the high transmittance / low reflection layer is preferably made of silicon, and the low transmittance / high reflection layer is preferably made of molybdenum.

The second aspect of the present invention includes a step of alternately stacking a high transmittance / low reflection layer and a low transmittance / high reflection layer on a substrate to form a reflection layer that reflects EUV light;
Forming an absorption layer for absorbing EUV light on the reflective layer;
Processing the absorbent layer into the shape of the main pattern transferred to the transfer target surface;
Forming an auxiliary pattern that is not transferred to the transfer target surface in the vicinity of the main pattern,
In the step of forming the auxiliary pattern, the present invention relates to a method for manufacturing an EUV mask, wherein a solid solution of a high transmittance / low reflection layer and a low transmittance / high reflection layer is formed by irradiating the reflective layer with an electron beam.

In the second aspect of the present invention, the high transmittance / low reflection layer is made of silicon, and the low transmittance / high reflection layer is made of molybdenum,
It is preferable to form a solid solution of silicon and molybdenum by irradiating the electron beam to set the temperature of the reflective layer to 400 ° C. or higher.
In this case, the temperature of the reflective layer is preferably 500 ° C. or lower.

  According to the present invention, an EUV mask having an ultra-fine auxiliary pattern and a manufacturing method thereof are provided.

It is an example of the EUV mask substrate in this Embodiment. (A)-(d) is a schematic diagram which shows the manufacturing method of the EUV mask in this Embodiment. It is a block diagram of the electron beam drawing apparatus in this Embodiment. It is explanatory drawing of the drawing method by an electron beam.

  Since EUV light has a short wavelength, there is no substance that forms a lens that transmits and refracts it. For this reason, it is not possible to use a conventional transmissive refractive optical system such as photolithography using visible light or ultraviolet light. Therefore, in EUV lithography, a reflective optical system, that is, a reflective photomask and a mirror are used. Further, in order to avoid interference between the illumination optical system that guides the EUV light from the light source to the EUV mask and the imaging optical system that guides the light having the pattern information reflected by the EUV mask to the wafer, the light is inclined with respect to the mask. An illumination system that makes the light incident is adopted. The incident angle can be set to 6 ° from the normal direction, for example. For example, a conductive chromium film is formed on the back surface of the EUV mask, and EUV light is incident obliquely from the front surface while the back surface is held by an electrostatic chuck method.

  For the above reason, a general EUV mask has a structure in which a reflective layer that reflects EUV light and an absorption layer that absorbs EUV light are formed in this order on a low thermal expansion glass substrate. As the reflection layer, a layer having a high transmittance and a low reflection (also referred to as a high transmittance / low reflection layer) and a layer having a low transmittance and a high reflection (also referred to as a low transmittance / high reflection layer) are alternately provided. A multilayer reflective film having an increased light reflectivity when EUV light is irradiated onto the layer surface is used. On the other hand, as the absorption layer, a material having a high absorption coefficient for EUV light, for example, a material mainly composed of tantalum is used.

  Below, the manufacturing method of the EUV mask by this Embodiment is demonstrated.

  First, an EUV mask substrate is prepared.

  In the EUV mask substrate, for example, a reflective layer that reflects EUV light and an absorption layer that absorbs EUV light are formed in this order on a low thermal expansion glass substrate, and a resist is further formed on the absorption layer. Is.

  As the reflective layer, a multilayer reflective film with high light reflectance when EUV light is irradiated on the surface of the layer by alternately laminating a high transmittance / low reflection layer and a low transmittance / high reflection layer is used. Is done. For example, a reflection layer is formed by using a multilayer reflection film in which two layers of a molybdenum layer as a low transmittance / high reflection layer and a silicon layer as a high transmittance / low reflection layer are laminated. Can do. The film thickness of molybdenum can be 3 nm, for example. The film thickness of silicon can be 4 nm, for example.

  As the absorption layer, a material having a high absorption coefficient for EUV light, for example, a material mainly composed of tantalum is used.

  A buffer film made of a material such as CrN or ruthenium can be provided between the reflective layer and the absorbing layer. The buffer film has a function as a protective film that reduces damage received by the reflective layer during patterning of the absorption layer and defect correction. Further, a cap film made of silicon may be provided between the buffer film and the reflective layer.

  FIG. 1 is an example of an EUV mask substrate.

The optical characteristics of the substrate 101 are not limited, but a low thermal expansion material is used. For example, titanium-doped silicate glass and Cu ₂ O—CuO—ZnO—Al ₂ O ₃ —SiO ₂ -based copper zinc aluminum silicate glass are suitable. The thermal expansion coefficient of titanium-doped silicate glass is << 100 ppb / K, which is known as a material having a thermal expansion close to zero (NZTE; Near Zero Thermal Expansion) (for example, Japanese Patent Laid-Open No. 64-33030). See the publication.) Cu ₂ O—CuO—ZnO—Al ₂ O ₃ —SiO ₂ -based copper zinc aluminum silicate glass is also known to have a low thermal expansion coefficient of 15 × 10 ⁻⁷ / K at the maximum. (See U.S. Pat. No. 3,498,876).

  In FIG. 1, a reflective layer 102 is formed on a substrate 101 by laminating a large number of two-layer films made of molybdenum and silicon. Since EUV light is easily absorbed by the material, it is not reflected by a normal mirror surface. However, according to the reflective layer 102 using light interference, EUV light can be reflected. However, the reflective layer 102 needs to have a uniform thickness, and it is necessary to pay sufficient attention to prevent foreign matters from being placed on the substrate 101 and from entering foreign matters during film formation. In addition, the foreign matter absorbs EUV light or scatters and causes a line width defect and a phase defect.

  In the reflective layer 102, the thickness of the molybdenum film can be 3 nm, for example, and the thickness of the silicon film can be 4 nm, for example. For example, the reflective layer 102 can be a film having a thickness of about 300 nm in which 40 to 50 layers of two-layer films of molybdenum and silicon are stacked. In this case, the reflectance of EUV light by the reflective layer 102 is 60% to 70%.

  A cap film 103 is formed on the reflective layer 102. The cap film 103 can be a film made of silicon, for example. The cap film 103 is the uppermost layer in the recess of the EUV mask and has a function of protecting the reflective layer 102.

A buffer film 104 is formed on the cap film 103. The buffer film 104 can be, for example, a film made of CrN or ruthenium. It is also possible to SiO ₂ film. As described above, the buffer film 104 has a function as a protective film that reduces damage to the reflective layer during patterning of the absorption layer 105 and defect correction. Further, it also has a function as an etching stopper for the absorption layer 105. The buffer film 104 preferably has a high inspection contrast using visible light. The exposure contrast by EUV light is determined by the absorber laminated film including the absorption layer 105 and the buffer film 104.

  An absorption layer 105 is formed on the buffer film 104. As the absorption layer 105, for example, a TaN film, a TaBN film, or a TaGeN film can be used. Moreover, the film thickness of the absorption layer 105 can be about 40-70 nm, for example. The absorption layer 105 has high exposure contrast by EUV light, high inspection contrast using ultraviolet light, good stress controllability during film formation, good etching processability, and further, Various characteristics such as non-ionization by irradiation are required.

  A resist 106 is formed on the absorption layer 105. The resist 106 is formed using a material having sensitivity to an electron beam.

  Next, electron beam lithography is performed on the EUV mask substrate to process the absorption layer 105 and the buffer film 104 into a predetermined pattern. Here, the predetermined pattern refers to a main pattern such as an LSI (Large Scale Integration) circuit pattern, and does not include an auxiliary pattern provided for the purpose of improving the resolution of the main pattern. In the present embodiment, the auxiliary pattern is formed in a step different from the main pattern, as will be described later. When the main pattern is drawn with an electron beam, it is preferable to draw a pattern alignment mark, which is necessary in the auxiliary pattern forming step.

  In the electron beam lithography process, as shown in FIG. 2A, first, a predetermined pattern is drawn on the resist 106 with an electron beam. Next, the resist 106 is developed to form a resist pattern. Next, the lower layer films (the absorption layer 105 and the buffer film 104) are etched using this resist pattern as a mask. Thereafter, the resist pattern that has become unnecessary is peeled off. Through the above steps, as shown in FIG. 2B, the absorption layer 105 and the buffer film 104 are processed into a main pattern 107 having a desired shape.

  After the main pattern is formed, an auxiliary pattern is formed. The auxiliary pattern is a pattern provided for the purpose of improving the resolution of the main pattern, and is formed as a portion where incident light is not reflected.

  The thickness and area of the auxiliary pattern are variously set depending on the thickness and area of the main pattern. In addition, the auxiliary pattern can be arranged on both sides (two directions) of the main pattern or around the main pattern (four directions). For example, when the main pattern is a one-dimensional pattern such as a line and space, the auxiliary pattern can be arranged on both sides of the main pattern. On the other hand, when the main pattern is a two-dimensional pattern such as a contact hole, the auxiliary pattern can be arranged around the main pattern.

  When the auxiliary pattern is formed by the electron beam lithography method, the auxiliary pattern is also drawn in the step of drawing the main pattern on the resist 106. Then, the absorption layer 105 and the buffer film 104 are processed into these pattern shapes. Specifically, a main pattern and an auxiliary pattern are drawn on the resist 106 with an electron beam, and then the resist 106 is developed to form a resist pattern, and then the absorbing layer 105 and the buffer film 104 are formed using the resist pattern as a mask. Etch. Thereafter, when the resist pattern is peeled off, the absorption layer 105 and the buffer film 104 processed into the main pattern and the auxiliary pattern are obtained. However, with this method, it is difficult to form an ultrafine auxiliary pattern due to blurring of the optical image caused by the resist. The reason is that a resist pattern having a shape corresponding to the target auxiliary pattern cannot be obtained.

  Therefore, in the present embodiment, the auxiliary pattern is formed without using the electron beam lithography technique. Hereinafter, this method will be described in detail.

  First, as shown in FIG. 2C, an electron beam is irradiated to a portion where an auxiliary pattern is formed. Specifically, the absorption layer 105 (or the absorption layer 105 and the buffer film 104) is removed by the above-described electron beam lithography process, and the cap film 103 is exposed in a predetermined region near the main pattern 107. Is irradiated with an electron beam. At this time, the alignment of the pattern is performed using the alignment mark drawn together with the drawing of the main pattern 107 so that the electron beam is irradiated to a desired position.

  A reflective layer 102 is provided below the cap film 103. As described above, the reflective layer 102 is formed by alternately laminating a high transmittance / low reflection layer and a low transmittance / high reflection layer, thereby increasing the light reflectance when the EUV light is irradiated on the surface of the layer. A multilayer reflective film. When the multilayer reflective film reaches a predetermined temperature or higher due to the irradiation of the electron beam, the structure of the part changes locally and EUV light is not reflected. Therefore, this portion can function as an auxiliary pattern. FIG. 2 (d) is a diagram schematically showing how the auxiliary pattern 108 is formed by direct irradiation with an electron beam.

  For example, when a multilayer reflective film in which 40 layers of two layers of molybdenum and silicon are stacked is used, an electron beam is irradiated to a portion where an auxiliary pattern is to be formed so that the temperature of the portion becomes a predetermined temperature or higher. . Then, a solid solution of molybdenum and silicon is formed, and the light incident on this portion is not reflected. That is, according to this method, a phase defect portion in which the structure of the multilayer reflective film is locally disturbed can be formed without using a resist. Therefore, there is no need to consider a reduction in resolution due to resist blur.

  Further, according to the above method by direct irradiation with an electron beam, it is possible to form an ultrafine auxiliary pattern. For example, in the case of a variable shaping type electron beam drawing apparatus, a shot having a size and shape prepared according to a pattern figure is formed by a shaping deflector. Specifically, after the electron beam emitted from the electron gun is shaped into a rectangular shape by the first aperture, it is projected onto the second aperture by the shaping deflector to change the beam shape and dimensions. . Thereafter, the light is deflected by the sub-deflector and the main deflector, and is irradiated onto the mask placed on the stage. Here, the electron beam shot can be formed in units of 0.1 nm. Therefore, it is sufficiently possible to form an auxiliary pattern having a dimension of 15 nm or less by irradiating an extremely limited portion on the mask with an electron beam and changing the film structure of this portion.

  In order to form a solid solution of molybdenum and silicon, the reflective layer 102 needs to be locally heated to 400 ° C. or higher. Therefore, the irradiation amount of the electron beam is set to a value such that the temperature of the reflective layer 102 is 400 ° C. or higher. In general, the exposure dose in each electron beam lithography process is adjusted so that the exposure dose per irradiation is set to a temperature lower than 250 ° C. from the viewpoint of preventing resist scattering. On the other hand, the auxiliary pattern forming process is after the resist is peeled off, and it is not necessary to consider the scattering of the resist. Therefore, it is possible to irradiate the electron beam to a temperature necessary for forming the solid solution.

  As described above, the temperature control when forming the solid solution need not be as strict as when the resist is irradiated with the electron beam. However, if the temperature becomes too high, the silicon diffuses and there is a possibility that a solid solution is formed in a place other than the place where the auxiliary pattern is to be formed. Therefore, the temperature rise due to the electron beam irradiation needs to be within a temperature range in which the diffusion of silicon is suppressed, and specifically, the temperature is preferably 500 ° C. or lower.

  As described above, according to the present embodiment, the reflective layer is irradiated with an electron beam to locally disturb the film structure. Since this part does not reflect incident light, it can function as an auxiliary pattern. That is, in this method, since the auxiliary pattern is formed without using a resist, it is not necessary to consider a reduction in resolution caused by the resist, and an ultrafine auxiliary pattern can be formed.

  FIG. 3 shows an example of an electron beam drawing apparatus used for drawing a main pattern and forming an auxiliary pattern in the present embodiment.

  As shown in FIG. 3, a stage 3 on which a sample 2 is installed is provided in the sample chamber 1 of the electron beam lithography apparatus. Sample 2 is the above-described EUV mask substrate, and in this embodiment, a main pattern or the like is drawn on the resist with an electron beam, or the reflective layer is irradiated with an electron beam to locally raise the temperature. To do.

  The stage 3 is driven in the X direction and the Y direction by the stage drive circuit 4. The moving position of the stage 3 is measured by a position circuit 5 using a laser length meter or the like.

  An electron beam optical system 10 is installed above the sample chamber 1. The optical system 10 includes an electron gun 6, various lenses 7, 8, 9, 11, 12, a blanking deflector 13, a shaping deflector 14, a beam scanning main deflector 15, and a beam scanning sub deflector. 16 and two beam shaping apertures 17, 18 and the like.

  FIG. 4 is an explanatory diagram of a drawing method using an electron beam. As shown in this figure, the pattern 51 drawn on the sample 2 is divided into strip-shaped frame regions 52. Drawing with the electron beam 54 is performed for each frame region 52 while the stage 3 continuously moves in one direction (for example, the X direction). The frame area 52 is further divided into sub-deflection areas 53, and the electron beam 54 draws only necessary portions in the sub-deflection areas 53. The frame area 52 is a strip-shaped drawing area determined by the deflection width of the main deflector 15, and the sub-deflection area 53 is a unit drawing area determined by the deflection width of the sub-deflector 16.

  Positioning of the reference position of the sub deflection area is performed by the main deflector 15, and drawing in the sub deflection area 53 is controlled by the sub deflector 16. That is, the main deflector 15 positions the electron beam 54 in a predetermined sub-deflection region 53, and the sub-deflector 16 determines the drawing position in the sub-deflection region 53. Further, the shape and size of the electron beam 54 are determined by the shaping deflector 14 and the beam shaping apertures 17 and 18.

  Drawing of the main pattern and the like on the resist on the EUV mask substrate is performed as follows. That is, the sub-deflection area 53 is drawn while the stage 3 is continuously moved in one direction, and when drawing of one sub-deflection area 53 is completed, the next sub-deflection area 53 is drawn. When drawing of all the sub-deflection areas 53 in the frame area 52 is completed, the stage 3 is stepped in a direction orthogonal to the direction in which the stage 3 is continuously moved (for example, the Y direction). Thereafter, the same processing is repeated, and the frame area 52 is sequentially drawn.

  The sub-deflection region is a region where the electron beam 54 is scanned by the sub-deflector 16 at a speed higher than that of the main deflection region, and is generally a minimum drawing unit. When the inside of the sub deflection region is drawn, a shot having a size and shape prepared according to the pattern figure is formed by the shaping deflector 14. Specifically, the electron beam 54 emitted from the electron gun 6 is shaped into a rectangular shape by the first aperture 17, and then projected onto the second aperture 18 by the shaping deflector 14. Change the dimensions. Thereafter, as described above, the electron beam 54 is deflected by the sub-deflector 16 and the main deflector 15 and is applied to the sample 2 placed on the stage 3.

  The electron beam shot can be formed in units of 0.1 nm, for example. Therefore, it is possible to irradiate an extremely limited part on the mask with an electron beam and raise the temperature of this part locally. In the present embodiment, when the auxiliary pattern is formed, an electron beam is irradiated to a predetermined region of the reflective layer to change the film structure of this portion. Thereby, for example, even a fine auxiliary pattern having a dimension of 15 nm or less can be formed.

  It is determined as follows what pattern of the shape and size of the sample 2 is shot at which position and at what dose. This determination method is basically the same for both the main pattern and the auxiliary pattern.

  The pattern data drawn on the sample 2 is first created as CAD data by a designer (user). Next, the CAD data is converted into design intermediate data in a hierarchical format such as OASIS. The design intermediate data stores design pattern data created for each layer and formed on each mask. Here, generally, the electron beam drawing apparatus is not configured to directly read OASIS data. That is, unique format data is used for each manufacturer of the electron beam drawing apparatus. For this reason, the OASIS data is converted into format data unique to each electron beam drawing apparatus for each layer and then input to the apparatus.

  In FIG. 3, reference numeral 20 denotes an input unit, which is a part where format data is input to the electron beam drawing apparatus through a magnetic disk as a storage medium. Since the figure included in the design pattern is a basic figure of a rectangle or a triangle, for example, the coordinates (x, y) at the reference position of the figure, the length of the side, a rectangle, a triangle, etc. Information such as a graphic code serving as an identifier for discriminating between graphic types, and graphic data defining the shape, size, position, etc. of each pattern graphic is stored.

  Furthermore, a set of figures existing in a range of about several tens of μm is generally called a cluster or a cell, and data is hierarchized using this. In the cluster or cell, arrangement coordinates and repeated description when various figures are arranged alone or repeatedly at a certain interval are also defined. The cluster or cell data is further arranged in a strip-shaped region called a frame or stripe having a width of several hundreds μm and a length of about 100 mm corresponding to the total length of the photomask in the X direction or Y direction. .

  The graphic pattern division processing is performed in units of the maximum shot size defined by the size of the electron beam, and the coordinate position, size, and irradiation time of each divided shot are also set. Then, drawing data is created so that a shot is formed according to the shape and size of the graphic pattern to be drawn. The drawing data is divided into strip-shaped frames (main deflection areas) and further divided into sub-deflection areas. That is, the drawing data of the entire chip has a data hierarchical structure including a plurality of strip-shaped frame data according to the size of the main deflection area and a plurality of sub deflection area units smaller than the main deflection area in the frame. .

  In the electron beam drawing apparatus, it is necessary to perform correction processing for changing the beam irradiation amount so that the pattern size after drawing becomes the same as the size of the design data. Factors that cause pattern dimension variation include proximity effect, fogging effect, and loading effect. In order to correct the dimensional variations caused by these, parameters necessary for correction are experimentally determined for each phenomenon. And the correction process based on this correction parameter is performed by the drawing data correction unit 31 of FIG. The drawing data correction unit 31 includes a dimension correction map creation unit 31a, a correction dose calculation unit 31b that calculates a correction dose corresponding to the dimension correction map, and an electron beam dose at a predetermined position of the mask from the correction dose. A dose calculation unit 31c to be obtained. Here, the correction dose can be at least one of a proximity effect correction dose, a fog correction dose, and a loading effect correction dose.

  Each correction parameter is input from the input unit 20 in FIG. 3 and sent to the dimension correction map creation unit 31 a of the drawing data correction unit 31. In addition, as already described, the input unit 20 also receives drawing data converted into format data unique to the electron beam drawing apparatus. The drawing data read from the input unit 20 by the control computer 19 is temporarily stored in the pattern memory 21 for each frame region 52. The pattern data for each frame area 52 stored in the pattern memory 21, that is, the frame information composed of the drawing position, the drawing graphic data, and the like are sequentially sent to the drawing data correction unit 31, and a plurality of pieces of frame information are taken into consideration. Perform dimension correction.

  The irradiation amount calculation unit 31c of the drawing data correction unit 31 also calculates the irradiation amount when forming the auxiliary pattern of the present embodiment. For example, in the case of using a multilayer reflective film in which 40 layers of two layers of molybdenum and silicon are stacked, the temperature needs to be 400 ° C. or higher in order to form these solid solutions. In the irradiation amount calculation unit 31c, the irradiation amount necessary to obtain this temperature is obtained. Since the thickness and area of the auxiliary pattern are variously set depending on the thickness and area of the main pattern, the irradiation amount can be changed according to the required thickness and area of the auxiliary pattern.

  The frame information corrected by the drawing data correction unit 31 is sent to the pattern data decoder 22 and the drawing data decoder 23 which are data analysis units.

  Information from the pattern data decoder 22 is sent to a blanking circuit 24 and a beam shaper driver 25. Specifically, blanking data based on the data is created by the pattern data decoder 22 and sent to the blanking circuit 24. Desired beam size data is also created and sent to the beam shaper driver 25. Then, a predetermined deflection signal is applied from the beam shaper driver 25 to the shaping deflector 14 of the optical system 10 to control the size of the electron beam 54.

  The deflection control unit 30 in FIG. 3 is connected to a settling time determination unit 29, the settling time determination unit 29 is connected to a sub deflection region deflection amount calculation unit 28, and the sub deflection region deflection amount calculation unit 28 is a pattern data decoder. 22 is connected. The deflection control unit 30 is connected to a blanking circuit 24, a beam shaper driver 25, a main deflector driver 26, and a sub deflector driver 27.

  The output of the drawing data decoder 23 is sent to the main deflector driver 26 and the sub deflector driver 27. Then, a predetermined deflection signal is applied from the main deflector driver 26 to the main deflector 15, and the electron beam 54 is deflected and scanned to a predetermined main deflection position. Further, a predetermined sub deflection signal is applied from the sub deflector driver 27 to the sub deflector 16, and drawing in the sub deflection area 53 is performed.

  The electron beam lithography technique described above has an essentially excellent resolution because the electron beam used is a charged particle beam. Further, since a large depth of focus can be secured, there is an advantage that dimensional variation can be suppressed by controlling the beam. Therefore, it is suitable for manufacturing a reticle that is becoming finer, and a fine circuit pattern or the like can be formed with high accuracy.

  Also, an ultrafine auxiliary pattern can be formed by irradiating an electron beam without passing through a resist and locally disturbing the film structure of the reflective layer. According to this method, it is not necessary to consider the resolution reduction caused by the resist, and the electron beam shot can be formed in units of 0.1 nm, so that an ultra-fine auxiliary pattern can be formed. Can do.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, although the electron beam is used in the above embodiment, the present invention is not limited to this, and the present invention can also be applied to the case where another charged particle beam such as an ion beam is used.

DESCRIPTION OF SYMBOLS 1 Sample chamber 2 Sample 3 Stage 4 Stage drive circuit 5 Position circuit 6 Electron gun 7, 8, 9, 11, 12 Various lenses 10 Optical system 13 Blanking deflector 14 Molding deflector 15 Main deflector 16 Sub deflector 17 First aperture 18 Second aperture 19 Control computer 20 Input unit 21 Pattern memory 22 Pattern data decoder 23 Drawing data decoder 24 Blanking circuit 25 Beam shaper driver 26 Main deflector driver 27 Sub deflector driver 28 Sub deflection area deflection Amount calculation unit 29 Settling time determination unit 30 Deflection control unit 31a Dimension correction map creation unit 31b Correction dose calculation unit 31c Dose calculation unit 31 Drawing data correction unit 51 Pattern to be drawn 52 Frame region 53 Sub deflection region 54, 204 Electronic Beam 101 Substrate 102 Picolinimidate 103 cap film 104 buffer film 105 absorbing layers 106 resist 107 main pattern 108 auxiliary pattern

Claims (5)

A substrate,
A reflective layer that is formed on the substrate and reflects EUV light by a structure in which a high transmittance / low reflection layer and a low transmittance / high reflection layer are alternately laminated;
An EUV mask formed on the reflective layer and having an absorbing layer for absorbing EUV light,
The absorption layer is processed into the shape of the main pattern transferred to the transfer target surface,
In the vicinity of the main pattern, an auxiliary pattern that is not transferred to the transfer target surface is formed,
The EUV mask according to claim 1, wherein the auxiliary pattern comprises a solid solution of the high transmittance / low reflection layer and the low transmittance / high reflection layer.   2. The EUV mask according to claim 1, wherein the high transmittance / low reflection layer is made of silicon, and the low transmittance / high reflection layer is made of molybdenum. A step of alternately stacking a high transmittance / low reflection layer and a low transmittance / high reflection layer on a substrate to form a reflection layer that reflects EUV light;
Forming an absorption layer for absorbing EUV light on the reflective layer;
Processing the absorbent layer into the shape of the main pattern transferred to the transfer target surface;
Forming an auxiliary pattern not transferred to the transfer target surface in the vicinity of the main pattern,
In the step of forming the auxiliary pattern, the reflective layer is irradiated with an electron beam to form a solid solution of the high transmittance / low reflection layer and the low transmittance / high reflection layer. Production method. The high transmittance / low reflection layer is made of silicon, and the low transmittance / high reflection layer is made of molybdenum,
4. The method of manufacturing an EUV mask according to claim 3, wherein a solid solution of the silicon and the molybdenum is formed by irradiating an electron beam to raise the temperature of the reflective layer to 400 ° C. or higher. 5. The method of manufacturing an EUV mask according to claim 4, wherein the temperature of the reflective layer is 500 ° C. or less.

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