Electron beam lithography data processing method, lithography method, and imprint mold manufacturing method

Abstract

To provide a method for obtaining a patterned shape that maintains good circularity by drawing at high speed even for a design including circular patterns of multiple sizes, including those of less than 100 nm.SOLUTION: An electron beam drawing data processing method for creating drawing data for drawing using electron beam drawing from design data of an array holes or a pillar in which circular patterns with different diameters are mixed includes the steps of assigning a trapezoidal, rectangular, or triangular pattern smaller than the circular pattern to the drawing data at the centroid of the circular pattern on the design data, assigning a different layer to the drawing data for each size of the circular pattern on the design data, and allocating a Dose amount and a Focus value corresponding to each diameter size for each of the different allocated layers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electron beam lithography data processing method for forming an array hole, a lithography method, and a method for manufacturing an imprint mold. [Background technology]

[0002] Known devices that can quickly draw fine patterns of 1 μm or less using electron beams include variable shaped beam devices (hereafter referred to as VSB devices), character projection type electron beam devices (hereafter referred to as CP devices), and point beam type electron beam devices (hereafter referred to as PB devices) (Figure 5).

[0003] The VSB machine uses two shaped apertures with rectangular openings and a shaping deflector placed between them to shoot an arbitrarily and variably shaped rectangular beam onto an electron beam resist material, and by shooting the electron beam while successively changing the rectangular size of the electron beam, it is possible to draw fine patterns at high speed.

[0004] Unlike a VSB machine, a CP machine cannot change the shaped beam size by adjusting the shot position on the second shaping aperture using a shaping deflector, but it can shoot a beam that matches the opening shape of the second shaping aperture onto the electron beam resist material. Therefore, even if a pattern has a complex shape, for example, it can be written with a single shot, and in some cases it can be written faster than a VSB machine.

[0005] Furthermore, by providing various aperture shapes within the plane of the second shaping aperture, multiple complex shapes can be drawn in a single shot, and in some cases drawing can be even faster than with a VSB machine.

[0006] The PB machine shoots a circular beam that passes through a single shaped aperture with a circular opening onto an electron beam resist material, and patterns the shape by arranging each shot in an arbitrary order, so any number of patterns can be formed by connecting small beams, even if the shape is complex.However, in this case, since one shape is formed using multiple small beams, the increase in drawing time becomes a major problem.

[0007] Now, when attempting to form multiple circular patterns of different sizes on the same surface, VSB and PB machines divide (fracture) each circular CAD data into multiple drawable figures and then draw them in a circular shape. As a result, the number of shots increases, which increases the electron beam irradiation time during drawing and the settling time during drawing (the time it takes for the electron optical system to stabilize and the time it takes for data to be expanded), resulting in a significant increase in drawing time.

[0008] In addition, there is a trade-off between the roundness of the shape and the writing time, and if an attempt is made to improve the roundness, finer divided shots are required, which further increases the writing time.

[0009] In response to this, a technique has been proposed for realizing a circular shape with a single shot rectangular beam by utilizing the blurring (beam blur) of the electron beam even when a VSB machine is used (see Patent Document 1 below).

[0010] On the other hand, if multiple circular apertures are prepared in a CP machine, it is possible to shoot circular patterns of multiple different sizes.However, if you want to change the manufacturing process conditions or product specifications in the process of improving the manufacturing process or product, it may be necessary to prepare a new aperture mask with the appropriate aperture diameter, which poses a problem in terms of procurement time and cost.

[0011] In a PB machine, it is possible to shoot circular patterns of different sizes, just like a CP machine, by appropriately selecting from the multiple circular opening apertures that the PB machine has. However, because the number of selectable circular opening apertures and their opening sizes are limited, a pattern size adjustment method that can complement the dimensions in between is required.

[0012] Generally, the pattern size can be adjusted within a certain range by adjusting the dose of the electron beam, but if the dose is too low, poor resist penetration and poor resolution occur, and conversely, if the dose is too high, edge roughness deteriorates, so in practice the range becomes even narrower than that. In other words, there is a limit to the adjustment range of pattern size that can be adjusted by dose alone.

[0013] In response to this, a method has been proposed in which charged particle beams formed with multiple circular apertures of different sizes are overlapped at the same position for exposure, thereby increasing the range of variation in the size of the circular pattern (see Patent Document 2 below). [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-253965 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-41903 Summary of the Invention [Problem to be solved by the invention]

[0015] However, with the technology of Patent Document 1, the opening size is limited to 100 nm to 250 nm, and sufficient circularity is not obtained.

[0016] Furthermore, in the technology of Patent Document 2, it is necessary to perform drawing by accurately overlapping beams in the same position on hundreds of thousands to billions of figures, but since it is difficult to ensure the reproducibility of alignment, it is difficult to maintain the patterned circular shape as a perfect circle.

[0017] The present invention has been made to address the above-mentioned problems, and aims to provide a means for quickly and quickly drawing a patterned shape that maintains good circularity, even for designs that include circular patterns of multiple sizes, including those less than 100 nm. [Means for solving the problem]

[0018] As a means for solving the above-mentioned problems, the invention described in claim 1 is an electron beam lithography data processing method for creating lithography data for lithography using electron beam lithography from design data of an array hole or pillar in which circular patterns of different diameters are mixed, the method comprising: a step of allocating a trapezoidal, rectangular or triangular pattern smaller than the circular pattern to the drawing data at the center of gravity of the circular pattern on the design data; allocating different layers to the drawing data for each size of the circular pattern on the design data; This is an electron beam lithography data processing method characterized by including a step of assigning a dose amount and a focus value for each of the different assigned layers so that each circular pattern can be drawn with a single circular beam in accordance with the size of each diameter.

[0019] The invention described in claim 2 is an electron beam lithography method characterized by using lithography data created by the electron beam lithography data processing method described in claim 1 to lithograph electron beam resist coated on a substrate using a circular beam.

[0020] The invention described in claim 3 is a method for manufacturing a nanoimprint mold, characterized in that the substrate is processed using an electron beam resist pattern produced by the electron beam lithography method described in claim 2. [Effects of the Invention]

[0021] According to the present invention, by limiting the number of shots assigned to a desired circular pattern to one, multiple shots are not required, and an increase in beam irradiation time during drawing can be suppressed. In addition, by reducing the number of rectangles in the electron beam drawing data, an increase in settling time during drawing can be suppressed. These two points make it possible to significantly reduce drawing time compared to the usual case where a PB machine is used.

[0022] Furthermore, because a PB machine uses one circular beam to form one circular pattern, it is possible to form a circular pattern that is closer to a perfect circle compared to when a VSB or PB machine uses multiple shots.

[0023] Furthermore, by combining focus adjustment with dose adjustment, the pattern size can be adjusted by utilizing the expansion of the circular beam diameter that occurs due to focus shift relative to the substrate surface being irradiated with the electron beam. This makes it possible to expand the pattern size adjustment range compared to conventional methods without increasing or decreasing the dose beyond its limit. [Brief explanation of the drawings]

[0024] [Figure 1] An image of all layers and design shapes superimposed. [Figure 2] An image of the layout of design data. [Figure 3] An image of the center (center of gravity) of each shape. [Figure 4] An image of the layout with a rectangle assigned to each shape. [Figure 5] Examples of various electron beam lithography methods. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described.

[0026] <Drawing data processing method> An image of the layout of the design data is shown in Figure 2. This figure shows the layout of design data for three types of circular patterns with different diameters (circular pattern 1, circular pattern 2, and circular pattern 3, in order from smallest to largest).

[0027] From this design data, graphic information consisting of size and position information for each circular pattern is extracted using a design tool such as DRC (Design Rule Check) software.

[0028] From the graphic information, square shapes smaller than one shot are derived at the center of gravity of each pattern (Fig. 3) by assigning them to three types of layers corresponding to circular patterns 1, 2, and 3, respectively, for different circular dimensions (Fig. 4), and stored in a Stream file such as GDSII or OASIS.

[0029] Next, the Stream file is used as input and different Dose Shots are created for each layer. Drawing data with assigned ranks is prepared. The Dose Shot Rank is a symbol that specifies the amount by which the Dose amount is modulated, and each Dose Shot Rank contains information on how much the Dose amount should be increased or decreased by. In other words, by changing the Dose Shot Rank assigned to each layer, it is possible to assign different Dose amounts to each layer.

[0030] <Drawing method> The graphic data group, with its assigned dose and shot rank for each layer, is converted into a format usable by the PB machine. The appropriate writing setting parameters, such as dose, focus value, probe current value, and aperture, are then entered into the writing job file, which is then compiled into a file ready for writing and writing. The optimal focus is determined by checking the focus value and the diameter of the written pattern obtained at the set focus value for at least three points, determining the correlation between the focus value and the pattern diameter, and then calculating the desired focus from a function plot of the set focus value and dimensional variation. Electron beam writing is performed on an electron beam resist material coated on a substrate made of silicon or silicon oxide, followed by appropriate baking and development processes to form a resist pattern (Figure 1). The circular area irradiated by the electron beam is hatched in this figure.

[0031] Although the square figures 11, 12 and 13 shown in Figures 1 and 4 are shown as rectangles here, this does not represent the shape of the electron beam to be drawn, but rather represents the data that can be drawn in one shot.

[0032] In actual drawing, a circular beam is formed using the circular aperture of the PB machine for each of these square graphic data, and one shot of drawing is performed for one circular pattern using the drawing data.

[0033] The drawing conditions for each shot are based on the drawing data prepared in advance, and specific different electron beam conditions are applied corresponding to each of the circular shapes 1, 2 and 3 having different sizes.

[0034] This makes it possible to quickly draw a group of shapes containing a mixture of circular patterns of different sizes in a single shot while maintaining high circularity.

[0035] The electron beam resist may be either a positive type, i.e., the part irradiated with an electron beam is removed by development, or a negative type, i.e., the part not irradiated is removed by development. Therefore, if the resist is a positive type, the resist shape formed will be a hole shape, and if it is a negative type, the resist shape will be a pillar shape.

[0036] <Method for forming an imprint mold> The resist pattern can be used to form an imprint mold. The electron beam resist used here may be a chemically amplified resist or a non-chemically amplified resist, and may not require baking after drawing.

[0037] The formed resist pattern may then be subjected to nickel electroforming, or may be used as a mask material for etching the substrate. In the former case, the nickel pattern itself, which is the inverse of the resist pattern, becomes the master mold, while in the latter case, the pattern is transferred to the substrate by etching, and then the resist is peeled off, leaving the substrate with the transferred pattern as the master mold. Etching can be done by either dry etching or wet etching.

[0038] In addition, two metal layers are used as the substrate, and the first metal layer directly under the resist layer is formed by the resist pattern. The turn can be used as a mask for etching, which then functions as a hard mask to further etch the underlying second metal layer, and after peeling off the first metal layer, the second metal layer itself can be used as a master mold.

[0039] This process makes it possible to fabricate imprint molds without being affected by the type of electron beam resist, the size of the pattern to be formed, whether it is a hole or pillar, or the material of the mold. [Explanation of symbols]

[0040] 1 Circular Pattern 1 2 Circular Pattern 2 3 Circular Pattern 3 4. Center position of each shape 11 Square shape corresponding to circular pattern 1 12 Square shape corresponding to circular pattern 2 13 Square shape corresponding to circular pattern 3

Claims

1. 1. An electron beam lithography data processing method for creating lithography data for lithography using electron beam lithography from design data of an array hole or pillar including a mixture of circular patterns with different diameters, the method comprising: a step of allocating a trapezoidal, rectangular or triangular pattern smaller than the circular pattern to the drawing data at the center of gravity of the circular pattern on the design data; allocating different layers to the drawing data for each size of the circular pattern on the design data; A method for processing electron beam lithography data, comprising a step of assigning a dose and focus value for each of the different assigned layers so that each circular pattern can be drawn with a single circular beam in accordance with the size of each diameter.

2. 2. An electron beam lithography method, comprising: drawing with a circular beam on an electron beam resist applied to a substrate, using lithography data prepared by the electron beam lithography data processing method according to claim 1.

3. A method for manufacturing a nanoimprint mold, comprising processing the substrate using an electron beam resist pattern produced by the electron beam lithography method according to claim 2.

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