Method for forming an evaluation pattern and method for evaluating positional variation

Abstract

The present invention provides a method for forming an evaluation pattern and a method for evaluating position variation, wherein the evaluation pattern can accurately measure the effect of pattern density on the beam irradiation position. A method for forming an evaluation pattern according to one aspect of the present invention comprises the steps of: irradiating a charged particle beam onto a sample and drawing a plurality of first patterns having different pattern densities; and drawing a plurality of second patterns having different pattern densities such that they are combined with at least some of the plurality of first patterns to make their respective pattern densities equal, thereby forming a plurality of evaluation patterns having equal pattern densities.

Description

Technology Field

[0001] The present invention relates to a method for forming an evaluation pattern and a method for evaluating positional variation. Background Technology

[0002] With the high integration of LSIs, the circuit line width required for semiconductor devices is becoming finer year by year. To form desired circuit patterns on semiconductor devices, a method is employed in which a high-precision original pattern formed on quartz is reduced and transferred onto a wafer using a reduction projection exposure device. For high-precision original patterns, so-called electron beam lithography technology is utilized, in which a pattern is formed by exposing a resist using an electron beam drawing device.

[0003] As an electron beam lithography device, for example, a multi-beam lithography device is known that utilizes multiple beams to irradiate many beams at once and improves throughput. In this multi-beam lithography device, for example, an electron beam emitted from an electron source forms a multi-beam through an aperture member having multiple apertures, blanking control is performed on each beam, and each unshielded beam is reduced by an optical system and irradiated onto a substrate placed on a movable stage.

[0004] A multi-beam drawing device irradiates multiple beams at once and connects the beams formed by passing through the same or different openings of an aperture member to draw a pattern of a desired geometric shape. Accordingly, the shape of the entire beam array irradiated onto the substrate (hereinafter referred to as the "beam array shape") is displayed with the connection precision of the drawn shape.

[0005] It is known that the beam array shape changes (rotates, expands, and contracts) depending on the irradiation dose. Since the irradiation dose depends on the pattern density, the extent to which the pattern density affects the beam array shape (the irradiation positions of multiple individual beams of a multi-beam system) is investigated in advance, and the correction amount for the irradiation dose or irradiation position during product pattern drawing is calculated.

[0006] Conventionally, as shown in FIG. 9, for example, an evaluation pattern was drawn including cross-shaped position measurement patterns (81) arranged at equal intervals and a plurality of density adjustment patterns (82) arranged between the position measurement patterns (81) and having different densities from each other, and after etching and developing, the position of the position measurement patterns was measured and the effect of the pattern density on the beam irradiation position was investigated.

[0007] However, in this conventional evaluation pattern, the position measurement pattern (81) and the density adjustment pattern (82) are separate, and the pattern density of the position measurement pattern (81) itself cannot be changed, and it was difficult to accurately estimate the effect that the pattern density has on the beam irradiation position.

[0008] In addition, the density adjustment pattern (82) surrounding each position measurement pattern (81) has a different pattern density. Since the measuring device that performs position measurement of the position measurement pattern (81) uses light, there was a problem in that if the surrounding conditions of the position measurement pattern are different, the influence on the reflection of light also changes, and the position measurement precision may deteriorate.

[0009] Since the tension of the light-blocking film on the substrate changes according to the pattern density of the density adjustment pattern (82), there were cases where the position of the pattern was deviated due to this during the etching and developing process.

[0010] As such, in conventional evaluation patterns, it was difficult to accurately measure the influence of pattern density on the beam irradiation position.

[0011] The present invention is made in light of the aforementioned conventional reality and aims to provide a method for forming an evaluation pattern and a method for evaluating position variation that can accurately measure the influence of pattern density on the beam irradiation position.

[0012] A method for forming an evaluation pattern according to one aspect of the present invention comprises the steps of: irradiating a charged particle beam onto a sample and drawing a plurality of first patterns having different pattern densities; and drawing a plurality of second patterns having different pattern densities such that they are combined with at least some of the plurality of first patterns to make their respective pattern densities equal, thereby forming a plurality of evaluation patterns having the same pattern density.

[0013] According to the present invention, an evaluation pattern can be formed that can accurately measure the effect of pattern density on the beam irradiation position. Brief explanation of the drawing

[0014] FIG. 1 is a schematic diagram of a drawing device according to an embodiment of the present invention. Figure 2 is a schematic diagram of an aperture member. Figure 3 is a conceptual diagram illustrating an example of a drawing operation. FIGS. 4(a) to FIGS. 4(c) are drawings illustrating a method for measuring pattern density-dependent beam irradiation position variation. Figure 5 is a diagram illustrating a method for drawing evaluation patterns. Figure 6 is a diagram illustrating a method for drawing evaluation patterns. Figure 7 is a diagram illustrating a method for drawing evaluation patterns. Figure 8 is a diagram illustrating the drawing method and measurement method of the evaluation pattern. Figure 9 is a diagram illustrating a method of drawing an evaluation pattern according to a comparative example. Specific details for implementing the invention

[0015] This application enjoys priority based on Japanese Patent Application No. 2025-009298 (filing date: January 22, 2025). By referring to this basic application, this application includes all the contents of the basic application.

[0016] In the following embodiments, a configuration using an electron beam is described as an example of a charged particle beam. However, the charged particle beam is not limited to an electron beam and may be a beam using charged particles such as an ion beam.

[0017] FIG. 1 is a conceptual diagram showing the configuration of a drawing device in an embodiment. In FIG. 1, the drawing device (100) is equipped with a drawing unit (150) and a control unit (160). The drawing device (100) is an example of a multi-charged particle beam drawing device. The drawing unit (150) is equipped with an electron tube (102) and a drawing chamber (103).

[0018] Inside the electron barrel (102), an electron source (201), an illumination lens (202), a molding aperture array substrate (203), a blanking aperture array substrate (204), a reduction lens (205), a limiting aperture member (206), an objective lens (207), and deflectors (208 and 209) are arranged.

[0019] An XY stage (105) is disposed within the drawing room (103). On the XY stage (105), a sample (101), such as a mask that becomes a substrate to be drawn during drawing, is disposed. The sample (101) is, for example, an exposure mask used when manufacturing a semiconductor device, a semiconductor substrate (silicon wafer) on which the semiconductor device is manufactured, mask blanks, etc. A mirror (210) for measuring the position of the XY stage (105) is further disposed on the XY stage (105).

[0020] The control unit (160) has a control calculator (110), a deflection control circuit (130), a stage position detector (139), and a memory device (140) such as a magnetic disk device. Drawing data is stored in the memory device (140) (memory unit).

[0021] A drawing data processing unit (112) and a drawing control unit (114) are arranged within the control calculator (110). The functions of the drawing data processing unit (112) and the drawing control unit (114) may be composed of hardware such as electrical circuits, or software such as programs that execute these functions. Alternatively, they may be composed of a combination of hardware and software. Information input to and output from the drawing data processing unit (112) and the drawing control unit (114), as well as information being processed, are stored in a memory not shown at each time.

[0022] FIG. 2 is a conceptual diagram showing the configuration of a molded aperture array substrate (203). In the molded aperture array substrate (203), openings (22) are formed in a matrix shape with a predetermined array pitch, with m columns in the vertical (y-direction) × n columns in the horizontal (x-direction) (m, n≥2). For example, 512 × 512 openings (22) are formed in the horizontal and vertical (x, y-directions). Each opening (22) is formed, for example, in a rectangular or circular shape with the same dimensions. A multi-beam (20) is formed by a portion of an electron beam (200) passing through each of these multiple openings (22).

[0023] In the blanking aperture array substrate (204), a passage hole (opening) for passing each individual beam of the multi-beam is opened at a position corresponding to each opening (22) of the molded aperture array substrate (203) shown in FIG. 2. Then, in the vicinity of each passage hole, a set of two electrodes (blanker: blanking deflector) for blanking deflection is arranged interposed with the corresponding passage hole.

[0024] FIG. 3 is a conceptual diagram for explaining an example of a drawing operation. As shown in FIG. 3, the drawing area (30) of the sample (101) is virtually divided into a plurality of rectangular stripe areas (32) with a predetermined width in the y-direction, for example. Each stripe area (32) becomes a drawing unit area. First, the XY stage (105) is moved to adjust the position so that an irradiation area (34) capable of being irradiated by one multi-beam (20) is positioned at the left end of the first stripe area (32) or further to the left, and drawing is initiated.

[0025] When drawing the first stripe area (32), the XY stage (105) is moved, for example, in the -x direction, to proceed with drawing in the relative +x direction. The XY stage (105) moves continuously at a predetermined speed. After the drawing of the first stripe area (32) is finished, the stage position is moved in the -y direction, and the irradiation area (34) is adjusted to be located in the relative +y direction at the right end or further right of the second stripe area (32), and this time, the XY stage (105) is moved, for example, in the +x direction, to perform drawing in the same way toward the -x direction.

[0026] Drawing time can be shortened by alternately changing the direction, such as drawing in the +x direction in the third stripe area (32) and drawing in the -x direction in the fourth stripe area (32). However, it is not limited to cases where drawing is done by alternately changing the direction; it is also acceptable to proceed with drawing in the same direction when drawing each stripe area (32). In one shot, a multi-beam formed by passing through each opening (22) of the molded aperture array substrate (203) forms a plurality of shot patterns equal to the maximum number of openings (22) at once.

[0027] A drawing data processing unit (112) reads drawing data from a memory device (140) and performs a multiple-stage data conversion process to generate shot data. In the shot data, the drawing surface of the sample (101) is defined as whether or not to irradiate each irradiation area, for example, divided into a grid-shaped plurality of irradiation areas by beam size, and the irradiation time.

[0028] Tracking control by beam deflection is initiated so that the drawing positions of each individual beam of the multi-beam (20) simultaneously follow the movement of the XY stage (105). Specifically, a stage position detector (139) measures the position of the XY stage (105) by irradiating a laser onto a mirror (210) and receiving reflected light from the mirror (210). The measured position of the XY stage (105) is output to a control calculator (110). The drawing control unit (114) outputs a control signal to a deflection control circuit (130) based on shot data and stage position information.

[0029] In the deflection control circuit (130), deflection amount data (tracking deflection data) for beam deflection to follow the movement of the XY stage (105) is calculated in accordance with the movement of the XY stage (105). The tracking deflection data, which is a digital signal, is converted into an analog signal and applied to the deflector (208) as a tracking deflection voltage.

[0030] The drawing unit (150) performs tracking control and irradiates each corresponding beam of the ON beam among the multi-beams (20) at each corresponding drawing position of each beam at each corresponding drawing time within the preset maximum drawing time. Specifically, it operates as follows.

[0031] An electron beam (200) emitted from an electron source (201) (emission unit) illuminates the entire molded aperture array substrate (203) almost vertically by means of an illumination lens (202). As a portion of the electron beam (200) passes through a plurality of openings (22) installed in the molded aperture array substrate (203), a plurality of electron beams (multi-beams) (20), for example, in a rectangular shape, are formed. The multi-beams (20) pass through each corresponding blanker of the blanking aperture array substrate (204). Each blanker deflects each beam of the multi-beams (20) that pass through individually so that the beam is ON only during the calculated drawing time (irradiation time) and the beam is OFF otherwise (performs blanking deflection).

[0032] The multi-beam (20) passing through the blanking aperture array substrate (204) is reduced by the reduction lens (205) and moves toward the central opening formed in the limiting aperture member (206). Here, the individual beam deflected to be beam OFF by the blanker of the blanking aperture array substrate (204) is positioned away from the central opening of the limiting aperture member (206) (blanking aperture member) and is shielded by the limiting aperture member (206). Meanwhile, the individual beam not deflected by the blanker of the blanking aperture array substrate (204) passes through the central opening of the limiting aperture member (206). Blanking control is performed by the ON / OFF of the individual blanking mechanism, and ON / OFF is controlled for each individual beam.

[0033] In this way, the limiting aperture member (206) shields the individual beams that are deflected to the beam OFF state by the individual blanking mechanism. Then, a beam of one shot is formed by the beam passing through the limiting aperture member (206) from the time the beam is turned ON until the beam is turned OFF.

[0034] The multi-beam (20) passing through the limiting aperture member (206) is focused by the objective lens (207) to form a pattern image of the desired reduction ratio, and is deflected in the same direction all at once by the deflector (209) and irradiated to each drawing position (irradiation position) on the sample (101) of each beam.

[0035] The multi-beam (20) irradiated at once is ideally arranged at a pitch that is the arrangement pitch of a plurality of apertures of the molded aperture array substrate (203) multiplied by the aforementioned desired reduction ratio. The drawing device (100) irradiates a plurality of individual beams at once and draws a pattern of a desired geometric shape by connecting the individual beams to fill the beam pitch. Therefore, the beam array shape has a significant influence on the drawing precision. The beam array shape (the irradiation position of the plurality of individual beams) changes depending on the irradiation amount. Since the irradiation amount changes according to the pattern density, it is necessary to measure the influence of the pattern density on the beam irradiation position and correct the beam irradiation position or the irradiation amount of the individual beams.

[0036] A method for measuring pattern density-dependent beam irradiation position variation is described.

[0037] First, a plurality of position measurement patterns (P1) and a first density adjustment pattern (P2a), such as shown in (a) of FIG. 4, are drawn on the sample (101).

[0038] The position measurement pattern (P1) is, for example, a cross shape.

[0039] The first density adjustment pattern (P2a) is placed in the area between the position measurement patterns (P1). For example, the first density adjustment pattern (P2a) is placed in a rectangular area surrounded by four position measurement patterns (P1). The pattern shape of the first density adjustment pattern (P2a) is not particularly limited and may be a line and space pattern or a contact hole pattern. The pattern density of the first density adjustment pattern (P2a) varies from area to area. For example, the pattern density is lowered as it goes toward the right side of FIG. 4 (a).

[0040] After drawing a position measurement pattern (P1) and a first density adjustment pattern (P2a) on the front surface or a predetermined area of ​​the drawing area of ​​the sample (101), a second density adjustment pattern (P2b) as shown in (b) of FIG. 4 is drawn. The second density adjustment pattern (P2b) is placed so as to overlap with the placement area of ​​the first density adjustment pattern (P2a).

[0041] The second density adjustment pattern (P2b) has a different pattern density for each region, and the change in pattern density is reversed compared to the first density adjustment pattern (P2a). For example, the pattern density is made higher towards the right side of Fig. 4 (b).

[0042] By overlapping the first density adjustment pattern (P2a) and the second density adjustment pattern (P2b) with each other, a pattern (P2) is formed in each region such that the pattern density is the same, as shown in (c) of FIG. 4.

[0043] After drawing an evaluation pattern consisting of a position measurement pattern (P1), a first density adjustment pattern (P2a), and a second density adjustment pattern (P2b), development and etching treatments are performed, and the position of the position measurement pattern (P1) is measured using a position measuring device (not shown).

[0044] Since the position measurement pattern (P1) is drawn together with the first density adjustment pattern (P2a), it is drawn at a position affected by the pattern density. Meanwhile, when measuring the position, the pattern (P2) has the same pattern density, and the surrounding conditions of the position measurement pattern (P1) are the same. Since the influence of the pattern (P2) on the reflection of light used for position measurement is also the same, the position of the position measurement pattern (P1) can be measured with high precision.

[0045] In this way, according to the present embodiment, the variation in beam irradiation position dependent on pattern density can be accurately measured.

[0046] Using FIG. 5, a method for drawing an evaluation pattern to measure pattern density-dependent beam irradiation position variation according to a separate embodiment is described.

[0047] First, a plurality of position measurement patterns (P11a to P11d) are drawn on the sample (101). The position measurement patterns (P11a to P11d) are dot patterns with different pattern densities. In the example shown in FIG. 5, the pattern density is P11a <P11b<P11c<P11d으로 되어 있다.

[0048] After drawing the position measurement patterns (P11a~P11d), the density adjustment patterns (P12a~P12c) are drawn. The density adjustment patterns (P12a~P12c) are grid-shaped and are arranged to surround the position measurement patterns (P11a~P11c).

[0049] The density adjustment patterns (P12a to P12c) have different pattern densities. In the example shown in Fig. 5, the pattern densities are P12a > P12b > P12c.

[0050] A dot pattern (P13) is obtained by combining a position measurement pattern (P11a) and a density adjustment pattern (P12a). A dot pattern (P13) with the same pattern density is also obtained by combining a position measurement pattern (P11b) and a density adjustment pattern (P12b). Additionally, a dot pattern (P13) with the same pattern density is obtained by combining a position measurement pattern (P11c) and a density adjustment pattern (P12c).

[0051] In addition, in this example, since the position measurement pattern (P11d) has the same pattern density as the dot pattern (P13), there is no need to combine density adjustment patterns.

[0052] After drawing a plurality of dot patterns (P13) (evaluation patterns) consisting of position measurement patterns (P11a~P11d) and density adjustment patterns (P12a~P12c), developing and etching treatments are performed, and the position of the dot (pattern edge) of the dot pattern (P13) is measured using a position measuring device (not shown).

[0053] The position measurement patterns (P11a~P11d) each have different pattern densities and are drawn at positions affected by the pattern density. Meanwhile, when measuring the position of a dot, since the pattern edges of the dot pattern (P13) are P11a~P11d, the results at positions affected by the pattern density of P12a~P12c are not visible, and the results at positions affected by the pattern density of P11a~P11d are measured. All dot patterns (P13) have the same pattern density, and the surrounding conditions of the dot are the same. Therefore, the beam irradiation position variation dependent on pattern density can be accurately measured.

[0054] Using FIG. 6, a method for drawing an evaluation pattern to measure pattern density-dependent beam irradiation position variation according to a separate embodiment is described.

[0055] First, position measurement patterns (P21a, P21b) are drawn on the sample (101). The position measurement patterns (P21a, P21b) are line and space patterns with different line widths. By controlling the line width of the line and space patterns, the pattern density can be changed arbitrarily. The position measurement patterns (P21a, P21b) are patterns with different pattern densities.

[0056] After drawing the position measurement pattern (P21a, P21b), the density adjustment pattern (P22a, P22b) is drawn. The density adjustment pattern (P22a, P22b) is a line and space pattern, and the line portion (61a, 61b) is placed between the two line portions (60a, 60b) of the position measurement pattern (P21a, P21b).

[0057] Specifically, one line section (61a) of the density adjustment pattern (P22a) is placed between two line sections (60a) of the position measurement pattern (P21a), and one line section is formed. The spacing between the two line sections (60a) is equal to the line width of the line section (61a).

[0058] Likewise, one line section (61b) of the density adjustment pattern (P22b) is placed between two line sections (60b) of the position measurement pattern (P21b), and one line section is formed. The spacing between the two line sections (60b) is equal to the line width of the line section (61b).

[0059] A line and space pattern (P23) is obtained by combining a position measurement pattern (P21a) and a density adjustment pattern (P22a). A line and space pattern (P23) with the same pattern density is obtained by combining a position measurement pattern (P21b) and a density adjustment pattern (P22b). For example, a line and space pattern with a pattern density of 50% is drawn by combining a position measurement pattern (P21a) and a density adjustment pattern (P22a), and a line and space pattern with a pattern density of 50% is drawn by combining a position measurement pattern (P21b) and a density adjustment pattern (P22b).

[0060] After drawing a plurality of line and space patterns (P23) (evaluation patterns) consisting of position measurement patterns (P21a, P21b) and density adjustment patterns (P22a, P22b), development and etching treatments are performed, and the position of the pattern edge of the formed line and space pattern (P23) is measured by a position measuring device (not shown).

[0061] The position measurement patterns (P21a, P21b) each have different pattern densities and are drawn at positions affected by the pattern density. Meanwhile, when measuring the position of the pattern edge, since the pattern edge of the dot pattern (P23) is P21a and P21b, the result at the position affected by the pattern density of P22a and P22b is not visible, and the result at the position affected by the pattern density of P21a and P21b is measured. The line and space pattern (P23) all have the same pattern density and the surrounding conditions are the same. Therefore, the beam irradiation position variation dependent on pattern density can be accurately measured.

[0062] In the example shown in FIG. 6, a position measurement pattern (P21a, P21b) with pattern edges as measurement targets is drawn in the first pass, and a density adjustment pattern is drawn in the second pass; however, the position measurement pattern and the density adjustment pattern may be drawn in the first and second passes, respectively. A method for drawing such an evaluation pattern is explained using FIG. 7.

[0063] First, a position measurement pattern (P31a) and a density adjustment pattern (P32b) are drawn on the sample (101). The position measurement pattern (P31a) and the density adjustment pattern (P32b) are line and space patterns.

[0064] After drawing the position measurement pattern (P31a) and the density adjustment pattern (P32b), the density adjustment pattern (P32a) and the position measurement pattern (P31b) are drawn. The density adjustment pattern (P32a) and the position measurement pattern (P31b) are line and space patterns. The pattern density of the position measurement pattern (P31b) is different from that of the position measurement pattern (P31a).

[0065] One line section (72a) of the density adjustment pattern (P32a) is placed between two line sections (71a) of the position measurement pattern (P31a). Additionally, one line section (72b) of the density adjustment pattern (P32b) is placed between two line sections (71b) of the position measurement pattern (P31b).

[0066] By combining the position measurement pattern (P31a) and the density adjustment pattern (P32a), a line and space pattern (P33) is obtained. By combining the density adjustment pattern (P32b) and the position measurement pattern (P31b), a line and space pattern (P33) with the same pattern density is obtained.

[0067] By measuring the edge position of the line portion of the line and space pattern (P33), the beam irradiation position affected by the pattern density of the position measurement pattern (P31a) and the beam irradiation position affected by the pattern density of the position measurement pattern (P31b) can be measured simultaneously.

[0068] In the above embodiment, an example was described in which the position measurement pattern and the density adjustment pattern are drawn in two separate passes (two passes), but they may be drawn in three or more separate passes. By combining multiple drawing patterns, a pattern of the same shape (same pattern density) is finally formed.

[0069] Multiple patterns with different densities may be prepared and appropriately combined to form multiple evaluation patterns with the same pattern density, and by changing the measurement location of the evaluation pattern, the edge position of the line portion affected by multiple densities may be measured.

[0070] For example, six types of patterns (P41 to P46) with different densities, as shown in FIG. 8, are prepared. By drawing patterns (P41, P43, and P44) in sequence and combining them, an evaluation pattern with a pattern density of 50% is obtained. Additionally, by drawing patterns (P42 and P43) in sequence and combining them, an evaluation pattern with a pattern density of 50% is obtained. Pattern (P46) alone becomes an evaluation pattern with a pattern density of 50%.

[0071] By an evaluation pattern such as that shown in Fig. 8, the edge position of the line portion affected by six different types of densities can be measured.

[0072] In the above embodiment, a drawing device using a multi-beam was described, but it may also be applied to a drawing device using a single beam.

[0073] Furthermore, the present invention is not limited to the above embodiments, and may be embodied by modifying the components during the implementation phase without departing from the gist thereof. Additionally, various inventions can be formed by appropriate combinations of a plurality of components disclosed in the above embodiments. For example, some components may be deleted from the entire set of components shown in the embodiments. Furthermore, components spanning different embodiments may be appropriately combined. Explanation of the symbols

[0074] 20 : Multi-beam 100 : Drawing device 101 : Sample 102 : Electronic barrel 103 : Drawing Room 110 : Control Calculator 150 : Drawing Department 160 : Control unit 200: Electron beam 201 : Electronic source 202 : Lighting Lens 203: Molded Aperture Array Substrate 204: Blanking Aperture Array Board

Claims

Claim 1 A method for forming an evaluation pattern, comprising: a process of irradiating a charged particle beam onto a sample and drawing a plurality of first patterns having different pattern densities; and a process of drawing a plurality of second patterns having different pattern densities such that each pattern density becomes the same by combining at least some of the plurality of first patterns, thereby forming a plurality of evaluation patterns having the same pattern density. Claim 2 A method for forming an evaluation pattern according to claim 1, comprising a process of drawing a plurality of first patterns and drawing a plurality of position measurement patterns for performing position measurement, wherein each of the plurality of position measurement patterns is disposed between each of the plurality of first patterns. Claim 3 A method for forming an evaluation pattern according to claim 1, wherein the plurality of first patterns are each grid-shaped, and the plurality of second patterns are each grid-shaped patterns surrounding the grid-shaped first patterns. Claim 4 A method for forming an evaluation pattern according to claim 1, wherein the plurality of first patterns and the plurality of second patterns are each line patterns, and one of the plurality of first patterns is installed between one of the plurality of second patterns. Claim 5 A method for forming an evaluation pattern according to claim 1, wherein the plurality of first patterns or the plurality of second patterns are divided and drawn according to different pattern densities. Claim 6 A method for evaluating position variation that measures pattern density-dependent position variation using an evaluation pattern described in any one of claims 1 to 5.

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