JP2008191403A - Photomask, manufacturing method of electronic device using same, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask with which fine repetitive patterns and a thick pattern can precisely be both formed and a manufacturing method of the electronic device using the same, and an electronic device. <P>SOLUTION: The thick-line pattern 2C of the photomask 10 extends in parallel to the repetitive patterns 2a and 2b, and has a larger line width W1 than a line pattern 2a and a space pattern 2b. The line width W1 of the thick-line pattern 2c is within a range of P1×(n±0.25), where P1 is the pitch of the line pattern 2a and (n) is an integer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photomask, an electronic device manufacturing method using the same, and an electronic device, and in particular, a photomask used for forming a pattern including a repetitive pattern and a thick pattern, and an electronic device manufacturing method using the photomask. And an electronic device obtained thereby.

  In recent years, miniaturization of semiconductor circuit patterns is largely due to the progress of photolithography technology, which has been mainly brought about by shortening the wavelength of the exposure light source. However, studies on pattern miniaturization by methods other than the increase in the price of exposure apparatuses and the shortening of the wavelength have been conducted in various fields. For example, due to the advancement of the lens diameter by the scanner type exposure technology, the modified illumination technology, the super-resolution mask technology, etc., there is currently a tendency to reduce the processing dimensions while maintaining the exposure wavelength. From the 0.18 μm (180 nm) generation, a reversal phenomenon has occurred in which the processing dimension falls below the exposure wavelength (KrF excimer laser: 248 nm).

  As a technique for forming a fine pattern having a wavelength equal to or smaller than the wavelength of light used for exposure, use of a phase shift mask such as a halftone phase shift mask or a modified illumination technique is well known. A technique using a phase shift mask is a technique that uses a special mask that, for example, creates a part that inverts the phase of light at the exposure wavelength on the mask and increases the contrast of the optical intensity on the imaging surface by the optical interference effect. It is.

  In the modified illumination technique, the shape of illumination is optimized so that all patterns can be stably formed with respect to the dimensions and two-dimensional shapes of complex circuit patterns designed on the mask. By illuminating the mask surface using such shaped illumination, it is possible to increase the optical intensity contrast of all patterns on the imaging surface.

  A typical example is annular illumination in which the center of the illumination optical system is shielded in a circular shape. In this annular illumination, techniques such as optimizing the outer contour radius (outer diameter R1) and inner contour radius (inner diameter R2) have been taken. In addition, in quadropole illumination (four-point illumination), it has been possible to optimize the sizes of the four openings.

Techniques using such phase shift masks and modified illumination techniques are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 11-8179 and 6-313964.
Japanese Patent Laid-Open No. 11-8179 JP-A-6-313964

The Rayleigh equation representing the optical resolution is shown as equation (1) below.
R = k1 · (λ / NA) (1)
In the above formula (1), R is the pattern resolution, λ is the exposure wavelength, NA is the lens numerical aperture, and k1 is the process factor.

  Here, it is assumed that a fine repetitive pattern having a process factor k1 of less than “0.3” and a thick line pattern or space pattern having a process factor k1 of “0.9 to 1.5” level are patterned. In this fine circuit pattern resist pattern, it may be required that the repetitive pattern and the thick line pattern or space pattern coexist.

  For example, a simple MOS (Metal Oxide Semiconductor) transistor structure with a small leakage current may be formed on the substrate by connecting a control gate and a floating gate below the control gate. In this case, it is necessary to increase the line widths of these wiring patterns in consideration of the occurrence of positional deviation due to mask misalignment in the pattern connecting the control gate and the floating gate. Also, when a contact hole is formed on the control gate in a later step and connected to an upper layer aluminum wiring or the like, it is necessary to form a thick wiring pattern in order to form the control gate as a contact pad.

  Similarly, a contact hole for directly connecting the semiconductor substrate and the aluminum wiring may be formed while avoiding the control gate. In this case, it is necessary to form a wide space pattern in order to prevent an electrical short circuit (short circuit) due to contact between the contact hole and the control gate. For this reason, a thick line or space having a process factor k1 of “0.9 to 1.5” level is required.

  In the prior art described above, it is difficult to stably resolve the fine circuit pattern no matter how the illumination shape is optimized. For example, when the NA is “0.85” at an ArF wavelength (193 nm), the process factor k1 is “0.28” when the repetitive pattern is 65 nm L / S (line and space). In this case, if a phase shift mask technique having a characteristic that the process factor k1 is less than “0.3” is used, a fine repetitive pattern can be processed with high accuracy. However, a thick line pattern having a process factor k1 of “0.9 to 1.5” cannot be processed with high accuracy. As described above, it has been extremely difficult to accurately process both the fine repetitive pattern and the thick line pattern.

  This is because when a phase shift mask suitable for a fine repetitive pattern is used, a phase mismatch associated with the principle of the phase shift mask that inevitably arises from the arbitraryness of the pattern occurs. This is because a problem of remaining will occur. In order to avoid this, a negative resist is generally used. However, there is no negative resist material with good resolution characteristics for ArF wavelength, and even if such a material is present, the circuit configuration is inevitable. This is because the resolving power between the same phases that is generated automatically is insufficient.

  It is also conceivable to use a double exposure technique. In this method, as the first exposure process, an exposure process using the outermost lens periphery is performed on the first region of the resist on which a fine repetitive pattern is formed by two-point illumination by two-point illumination. Thereafter, as a second exposure process, an exposure process using normal illumination is performed on the second region of the resist where the thick line pattern is formed. However, the space between the last line pattern and the thick line pattern of the fine repeating pattern must be about 1.0 to 1.5 times the space size in the repeating pattern. Therefore, in the above-described method having two exposures, it is extremely difficult to satisfy the above restrictions when an overlay error occurs. The same is true for wide space patterns.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a photomask capable of accurately forming both a fine repetitive pattern and a thick pattern, and a method of manufacturing an electronic device using the photomask. And an electronic device.

  A photomask according to an embodiment of the present invention includes a substrate and a light shielding film pattern. The substrate is transparent to exposure light. The light shielding film pattern is for blocking the transmission of exposure light, and is formed on the surface of the substrate. The light shielding film pattern has a repetitive pattern and a thick pattern. In the repeated pattern, the line pattern and the space pattern are alternately repeated. The thick pattern extends so as to run in parallel with the repetitive pattern, and has a larger width than the line pattern and the space pattern. When the pitch of the line pattern is P1, and n is an integer, the width W1 of the thick pattern is in the range of P1 × (n ± 0.25).

  According to the present embodiment, when the pitch of the line pattern is P1 and n is an integer, the width W1 of the thick pattern is in the range of P1 × (n ± 0.25). For this reason, the spatial periodicity of the repetitive pattern can be broken in the thick pattern, the depth of focus can be improved, and both the repetitive pattern and the thick pattern can be formed with high accuracy.

The principle and embodiments of the present invention will be described below with reference to the drawings.
(principle)
First, with respect to the principle of the present invention, the photomask 10 shown in FIG. 1 is obliquely illuminated using a two-point illumination (two-lens illumination) stop 114 shown in FIG. The case of transferring to the photosensitive member (for example, photoresist) 23 of the electronic device 20 or the film 22 to be processed will be described.

  FIG. 1 is a cross-sectional view (a) and a plan view (b) schematically showing the structure of a photomask for explaining the principle of the present invention. Referring to FIGS. 1A and 1B, this photomask 10 has a transparent substrate 1 and a light shielding film pattern 2. The transparent substrate 1 is made of a material that is transparent to exposure light. The light shielding film pattern 2 is made of a material that is formed on the surface of the transparent substrate 1 and that can block the transmission of exposure light. The light-shielding film pattern 2 may be a halftone phase shift film that has a transmittance of, for example, about 6% and inverts the phase of transmitted light to an opposite phase.

  The light shielding film pattern 2 has a repeated pattern region and a thick pattern region. The repeated pattern area and the thick pattern area are adjacent to each other with the space pattern 2d interposed therebetween.

In the repetitive pattern region, a repetitive pattern is formed in which line patterns 2a having a fine line width W _L1 and space patterns 2b having a fine line width W _S1 are alternately arranged. In this repeated pattern region, the line patterns 2a are arranged at a predetermined pitch P1 (= W _L1 + W _S1 ). The line pattern 2a is a pattern in which the light shielding film remains, and the space pattern 2b is a blank pattern in which the light shielding film is removed.

A thick line pattern 2c is formed in the thick pattern region. The thick line pattern 2c has a line width W1 wider than the line width W _L1 of the line pattern 2a and the line width W _S1 of the space pattern 2b. The thick line pattern 2c extends so as to run in parallel with the line pattern 2a and the space pattern 2b of the repeated pattern in plan view.

  In the photomask 10, repeated patterns are arranged on both sides of the thick line pattern 2c in plan view. That is, the first repetitive pattern portion is arranged on one side of the thick line pattern 2c, and the second repetitive pattern portion is arranged on the other side of the thick line pattern 2c.

FIG. 2 is a plan view schematically showing the configuration of a two-point illumination stop for explaining the principle of the present invention. Referring to FIG. 2, the two-point illumination stop 114 has two openings 114a. The two openings 114a of the two-point illumination stop 114 are preferably arranged on the outer peripheral side as much as possible. In the two-point illumination stop 114, the inner sigma σ _in is 0.75, for example, and the outer sigma σ _out is 0.95, for example.

Here, the inner sigma σ _in and the outer sigma σ _out are the radii of the inscribed circle and the circumscribed circle of the opening 114a when the radius of the entire illumination stop 114 is 1, respectively. By arranging the opening 114 a in this way, intense illumination can be realized using the two-point illumination stop 114. Note that the intense illumination in this specification means that σ _in / σ _out is 3/4 or more.

  FIG. 3 is a cross-sectional view (a), (c) and a plan view (b) schematically showing the configuration of an electronic device for explaining the principle of the present invention. 3A and 3B show a state in which the photoconductor pattern 23 is present. FIG. 3C shows a state in which the film 22 to be processed is patterned using the photoconductor pattern 23 as a mask and the photoconductor pattern 23 is removed.

  With reference to FIGS. 3A and 3B, the electronic device 20 that has been subjected to the exposure by the oblique illumination and the subsequent development has substrates 21 and 22 and a photoreceptor pattern 23. . The substrate has a base layer 21 and a film 22 to be processed formed on the base layer 21. The photoreceptor pattern 23 is formed on the film 22 to be processed, and is made of, for example, a positive type photoresist.

  The photoreceptor pattern 23 has a pattern corresponding to the light shielding film pattern 2 of the photomask 10 shown in FIG. That is, the photoconductor pattern 23 has the repeated patterns 23a, 23b and the thick line pattern 23c corresponding to the repeated patterns 2a, 2b and the thick line pattern 2c of the photomask 10 shown in FIG. The photoconductor pattern 23 also has a space pattern 23d corresponding to the space pattern 2d of the photomask 10 shown in FIG.

  The repeated pattern region in which the repeated patterns 23a and 23b are formed and the thick pattern region in which the thick line pattern 23c is formed are adjacent to each other with the space pattern 23d interposed therebetween.

In the repetitive pattern region, line patterns 23a having a fine line width W _L2 and space patterns 23b having a fine line width W _S2 are alternately and repeatedly arranged. A thick line pattern 23c having a line width W2 wider than the line width W _L2 of the line pattern 23a and the line width W _S2 of the space pattern 23b is formed in the thick pattern region. The thick line pattern 23c extends in parallel with the line pattern 23a and the space pattern 23b.

  With reference to FIG. 3C, the light-shielding film pattern 2 shown in FIG. 1 is transferred to the processing film 22 by patterning the processing film 22 by etching or the like using the photoconductor pattern 23 having the above shape as a mask. A pattern (hereinafter referred to as a “transferred pattern”) is formed. That is, the pattern of the film 22 to be processed includes the transferred repeated patterns 22a and 22b and the transferred thick line pattern 22c, to which the repeated patterns 2a and 2b and the thick line pattern 2c of the photomask 10 shown in FIG. Yes. Further, the film pattern 22 to be processed also has a space pattern 22d to which the space pattern 2d of the photomask 10 shown in FIG. 1 is transferred.

  The transferred repetitive pattern region in which the transferred repetitive patterns 22a and 22b are formed and the transferred thick pattern region in which the transferred thick line pattern 22c is formed are adjacent to each other with the transferred space pattern 22d interposed therebetween.

In the repetitive transfer pattern region, a transfer line pattern 22a having a fine line width W _L2 and a transfer space pattern 22b having a fine line width W _S2 are alternately and repeatedly arranged. In the transferred repeat pattern region, the transferred line pattern 22a is arranged at a predetermined pitch P2 (= W _L2 + W _S2 ). In the thick transferred pattern region, a transferred thick line pattern 22c having a line width W _L2 wider than the line width W _L2 of the transferred line pattern 22a and the line width W _S2 of the transferred space pattern 22b is formed. The transferred thick line pattern 22c extends in parallel with the transferred line pattern 22a and the transferred space pattern 22b.

  In the electronic device 20, the transferred repeat pattern is arranged on both sides of the transferred thick line pattern 22 c in plan view. That is, the first transferred repetitive pattern portion is arranged on one side of the transferred thick line pattern 22c, and the second transferred repetitive pattern portion is arranged on the other side of the transferred thick line pattern 22c.

The present inventor completely performs two-light interference between the projected image of the electric field and the light intensity (= the square of the electric field) when exposed by the two-point illumination shown in FIG. 2 using the photomask 10 having the pattern layout shown in FIG. As a result, what kind of interference occurs is simply Fourier series simulated. Here, the amplitude intensity ratio of each frequency by Fourier transform is not obtained. Further, in FIG. 1, the line width W _L1 of the line pattern 2a and the line width W _{S1 of the} space pattern are each 65 nm (repetitive pitch P1 of the line pattern 2a (= W _L1 + W _S1 ) is 130 nm), and the line of the thick line pattern 2c The simulation was performed by changing the width W1. The results are shown in FIG. 4 and FIG.

  FIG. 4A is a diagram showing the shape of the photoconductor pattern 23 when the line width W2 of the thick line pattern 23c is an odd multiple (three times) of half the repeat pitch P2 of the line pattern 23a (half pitch: 65 nm). FIG. 6B is a diagram (b) showing a projected image (notation E) and light intensity (notation int) of an electric field. In FIG. 4, the photoconductor pattern of FIG. 4A is shown so as to correspond to the projected image and the light intensity of FIG.

  Referring to FIG. 4A, when the line width W2 of the thick line pattern 23c is an odd multiple of the half pitch (P2 / 2), the hatched portion at the lower right in the center of the thick line pattern 23c is a blank pattern (that is, Space pattern), the spatial periodicity is maintained from the left side to the right side of the thick line pattern 23c in the figure. In other words, by setting the hatched portion at the center of the thick line pattern 23c to the lower right as a blank pattern, the repeated pattern on the right side of the thick line pattern in the drawing and the repeated pattern on the left side in the drawing are continuously connected at substantially the same pitch. become.

  Since the spatial periodicity is maintained as described above, as shown in FIG. 4B, the waveform of the light intensity in each of the repeated patterns on the left side and the right side of the thick line pattern in the center portion of the thick pattern region. overlap. As a result, the light intensity is higher at the center of the thick pattern area than at the other areas. As a result, the optical image becomes bright in the thick pattern region shown in FIG. 4A, the photoresist 23 is resolved, and the thick line pattern 23c cannot be formed with high accuracy.

  On the other hand, FIG. 5 is a diagram showing the shape of the photoconductor pattern 23 when the line width W2 of the thick line pattern 23c is an even multiple (four times) of half (half pitch: 65 nm) of the repeat pitch P2 of the line pattern 23a. It is a figure (b) which shows a) and the projection image (notation E) and light intensity (notation int) of an electric field. In FIG. 5, the photoconductor pattern of FIG. 5A is shown to correspond to the projected image and the light intensity of FIG.

  Referring to FIG. 5A, when the line width W2 of the thick line pattern 23c is an even multiple of the half pitch (P2 / 2), the spatial periodicity is seen from the repeated pattern on the left side of the thick line pattern 23c. In order to keep it, it is necessary that the right downward hatching portion of the thick line pattern 23c is a blank pattern. On the other hand, in order to maintain the spatial periodicity as seen from the repeated pattern on the right side of the thick line pattern 23c in the drawing, the left downward hatched portion of the thick line pattern 23c needs to be a blank pattern.

  As described above, the spatial periodicity is inconsistent in the repeated patterns on the left side and the right side in the drawing of the thick line pattern 23c. For this reason, as shown in FIG. 5B, the waveform of the light intensity in each of the repeated patterns on the left side and the right side in the diagram of the thick line pattern is inverted in the thick pattern region. Thereby, the light intensity in the thick pattern region is lower than in the case of FIG. As a result, it is possible to suppress the brightening of the optical image in the thick pattern region shown in FIG. 5A, and it is possible to form the thick line pattern 23c with high accuracy.

  As described above, in order to effectively leave the thick line pattern 23c in the thick pattern region, it can be said that how to destroy the spatial periodicity is a key. In order to effectively destroy the spatial periodicity, the phase difference (θ) of the wavelength (2P) of the electric field wave in the repetitive pattern on the left side and the right side of the thick line pattern 23c is half pitch (P / 2). If it is, it will be understood. From this, it can be seen that the line width W1 of the thick line pattern 2c in the photomask 10 shown in FIG. 1 may be an even multiple of half (half pitch) of the repeating pitch P1 of the line pattern 2a.

  From the above, when n is an integer, the relationship between the line width W1 of the thick line pattern 2c and the repetition pitch P1 of the line pattern 2a satisfies the formula W1 = (P1 / 2) × 2n = P1 × n. Good.

  Further, if the line width W1 of the thick line pattern 2c is within the range of P1 × (n ± 0.25), the effect of the above even multiple is obtained. Because, if the line width W1 of the thick line pattern 2c is within the range of (P1 / 2) × (2n ± 0.5), the line width W1 of the thick line pattern 2c is an odd multiple (2n + 1) of half of the repetition pitch P1. This is because the value is closer to an even multiple (2n), and the effect of breaking the spatial periodicity becomes significant.

  Therefore, also in the electronic device 20 (FIG. 3C) manufactured using the photomask 10 (FIG. 1), when the repetition pitch of the transferred line pattern 22a is P2, and n is an integer, The line width W2 of the transferred thick line pattern 22c falls within the range of W2 = P2 × (n ± 0.25).

  In addition, the inventor calculated the change in the light intensity inside the thick line pattern when the phase difference θ was continuously changed by the following equation. The result is shown in FIG.

Appearance Light = [sin (π · x / P) + sin {(π · x / P) −θ}] ²
The origin of the phase shift amount in FIG. 6 indicates a state where the wavelength of the wave of the electric field of the repeated pattern on the left side and the right side of the thick line pattern 23c is shifted by ¼ wavelength as shown in FIG. The state where the phase shift amount is 0.5 in FIG. 6 indicates a state where the wavelength of the electric field wave of the left and right repetitive patterns of the thick line pattern 23c is shifted by ½ wavelength as shown in FIG.

  In the state of FIG. 5 (the origin of the phase shift amount), the light intensity is 0.25. Usually, the light intensity is about 1.5 to 1.6 times the light intensity so that the resist pattern is not broken. Is used. Therefore, the light intensity is preferably about 0.25 × 1.6≈0.4. In order to obtain the light intensity of about 0.4, a phase shift amount of 0.1 is necessary from the relationship of FIG.

  As described above, the line width W1 of the thick line pattern 2c in the photomask 10 of FIG. 1 is in the range of W1 = P1 × (n ± 0.1) in order to obtain an appropriate light intensity while destroying the spatial periodicity. It is preferable to be within.

  Therefore, also in the electronic device 20 (FIG. 3C) manufactured using the photomask 10 (FIG. 1), the line width W2 of the transferred thick line pattern 22c is W2 = P2 × (n ± 0). Within the range of .1).

The following first to fourth embodiments are made based on the above principle.
(Embodiment 1)
FIG. 7 is a diagram showing a cross-sectional configuration (a) of a photomask, a cross-sectional configuration (b) of an electronic device, and an optical simulation result (c) of light intensity at each position of a pattern in a comparative example of the present invention. FIG. 8 is a diagram showing the cross-sectional configuration (a) of the photomask, the cross-sectional configuration (b) of the electronic device, and the optical simulation result (c) of the light intensity at each position of the pattern in the first embodiment of the present invention. . Note that various lines (lines indicating 0 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, and 300 nm) shown in the graphs of FIGS. 7 and 8 represent the amount of focus deviation from the best focus (0 nm). Yes.

  The configuration of the photomask 10 of the present embodiment shown in FIG. 8A is such that a repeated pattern is arranged only on one side of the thick line pattern 2c, compared to the configuration of the photomask 10 shown in FIG. Is different. In addition, the line width W1 of the thick line pattern 2c in the photomask 10 of the present embodiment is an even multiple (for example, four times) of half (half pitch) of the repeat pitch P1 of the line pattern 2a.

  In addition, the configuration of the electronic device 20 of the present embodiment shown in FIG. 8B is also on one side of the thick line pattern 23c as compared with the configuration of the electronic device 20 shown in FIGS. 3A and 3B. The only difference is that repeated patterns are arranged. Further, the line width W2 of the thick line pattern 23c in the electronic device 20 of the present embodiment is an even multiple (for example, four times) of half (half pitch) of the repetitive pitch P2 of the line pattern 23a.

  The other configurations of the photomask 10 and the electronic device 20 of the present embodiment other than the above are substantially the same as the configurations shown in FIGS. 1 and 3, and thus the same elements are denoted by the same reference numerals. The description is omitted.

  The inventor performed a simulation on the intensity distribution of the optical image when the optical image of the photomask 10 in the present embodiment is formed. This will be described below.

  In each of FIG. 7B and FIG. 8B, the repetitive pattern composed of the line pattern 23a and the space pattern 23b of the photoconductor 23 is set to a 130 nm pitch (65 nm L / S), and between the repetitive pattern and the thick line pattern 23c. The width of the space pattern 23d was 65 nm. The line width W2 of the thick line pattern 23c is 195 nm (65 × 3 nm) which is an odd multiple of 65 in FIG. 7B, and 260 nm (65 × 4 nm) which is an even multiple of 65 in FIG.

  Using a photomask 10 (FIGS. 7A and 8A) having a light-shielding film pattern 2 corresponding to the pattern layout of these photoreceptors 23, the exposure wavelength is ArF wavelength (193 nm), and the numerical aperture (NA) ) Was 0.85, and the simulation was performed under the condition that the illumination was two-point illumination.

  As a result, as shown in FIG. 7C, when the line width W2 of the thick line pattern 23c is 195 nm, repeated spatial periodicity appears in the thick pattern region when the focus is shifted. Therefore, the optical image at the center of the thick pattern region becomes bright and the resist is resolved. On the other hand, as shown in FIG. 8C, when the line width W2 of the thick line pattern 23c is 260 nm, the reversal of the image at the time of defocusing can be suppressed more than when it is 195 nm.

This will be described with reference to FIGS. 7B and 8B.
As shown in FIG. 7B, when the thick line pattern 23c is 195 nm (65 × 3 nm), in order to maintain the spatial periodicity when viewed from the repeated pattern on the right side of the thick line pattern 23c, It is necessary that the hatching part of the lower right is a blank pattern. On the other hand, if there is a repeating pattern similar to that on the right side on the left side of the thick line pattern 23c, in order to maintain spatial periodicity when viewed from the virtual left side repeating pattern, It is necessary that the hatching part of the lower right is a blank pattern. That is, assuming that the right-down hatched portion in the thick line pattern 23c is a blank pattern, the spatial periodicity of the repetitive pattern on the right side of the thick line pattern 23c in the figure matches the repetitive pattern on the lower layer on the left side in the figure. For this reason, inversion of the image in the thick line pattern 23c is promoted.

  On the other hand, when the thick line pattern 23c shown in FIG. 8B is 260 nm (65 × 4 nm), in order to maintain the spatial periodicity as seen from the repeated pattern on the right side of the thick line pattern 23c, It is necessary that the hatching part of the lower right is a blank pattern. On the other hand, if there is a repeating pattern similar to that on the right side on the left side of the thick line pattern 23c, in order to maintain spatial periodicity when viewed from the virtual left side repeating pattern, It is necessary that the hatching part with the left-down hatching is a blank pattern. As described above, the spatial periodicity is inconsistent in the repeated pattern on the right side and the virtual left side of the thick line pattern 23c. For this reason, inversion of the image in the thick line pattern 23c is suppressed.

  Similar simulations were performed when the line width W2 of the thick line pattern 23c was 325 nm (65 × 5 nm) and 390 nm (65 × 6 nm). The results are shown in FIGS.

  When the line width W2 of the thick line pattern 23c shown in FIG. 9B is 325 (65 × 5) nm, the light intensity of the optical image is partially in the thick line pattern at the time of defocusing as shown in FIG. 9C. Is getting higher. In contrast, when the line width W2 of the thick line pattern 23c shown in FIG. 10B is 390 (65 × 6) nm, as shown in FIG. It can be seen that the light intensity of the inverted optical image is suppressed. The reason why the light intensity can be suppressed in the pattern layout of FIG. 10 as compared with the case of FIG. 9 can be explained in the same manner as described above.

  As described above, even when the repeated pattern is arranged only on one side of the thick line pattern 2c as shown in FIGS. 8A and 10A, the line width W1 of the thick line pattern 2c is equal to the half pitch ( If it is an even multiple of P1 / 2), the thick line pattern 2c can be accurately transferred to the electronic device.

  Referring to FIGS. 8B and 10B, generally, as the line width W2 of the thick line pattern 23c increases, the light shielding efficiency increases, as shown in FIGS. 8C and 10C. However, the depth of focus tends to increase. However, in a trade-off, the resolution of the space pattern 23d adjacent to the thick line pattern 23c tends to decrease. For example, FIG. 11 shows a graph in which the relationship between the line width W2 of the thick line pattern 23c and the depth of focus (DOF) is obtained from the optical simulation result.

  Referring to FIG. 11, in the focal depth simulation, only the thick line pattern 23c is focused on, and the space pattern 23d between the thick line pattern 23c and the repetitive pattern is ignored. As described above, in general, the depth of focus should improve as the line width W2 of the thick line pattern 23c increases. However, in the simulation results, when there is a repeated pattern only on one side of the thick line pattern 23c as in the present embodiment, the depth of focus when the line width W2 of the thick line pattern 23c is 260 nm (65 × 4 nm) is The line width W2 is as high as the depth of focus when the line width W2 is 325 nm (65 × 5 nm). From this, it was confirmed that the depth of focus is improved when the thick line pattern 23c is an even multiple of the half pitch of the repeated pattern.

  For example, in FIG. 10B, the thicker the thick line pattern 23c, the higher the light shielding efficiency. Therefore, the line pattern 23a adjacent to the thick line pattern 23c is also thickened. As a result, the resolution of the space pattern 23d between the thick line pattern 23c and the repetitive pattern deteriorates, and a so-called bridge phenomenon occurs in which the thick line pattern 23c and the adjacent line pattern 23a are connected.

The present inventor examined the elimination of this bridge. As a result, when the width of the space pattern 23d is 65 nm, which is the line width of the line pattern 23a, as shown in FIG. 10B, the light intensity of the space pattern 23d is shown in FIG. 10C. Increased, preventing bridging. As shown in FIG. 12, when the width of the space pattern 23d is 90 nm, which is 1.38 times the line width of the line pattern 23a, which is 65 nm, as shown in FIG. The light intensity of 23d was further increased, and bridging could be prevented. Therefore, the bridge can be eliminated by setting the width W _S3 of the space pattern 23d to 1.0 to 1.5 times that of the line pattern 23a. It turns out that the effect is not lost either.

  Therefore, in the photomask 10 shown in FIG. 12A, the width of the space pattern 2d is preferably 1.0 to 1.5 times the line width of the line pattern 2a. In the electronic device 20 shown in FIG. 3C, the width of the space pattern 22d is preferably 1.0 to 1.5 times the line width of the line pattern 22a.

  In FIG. 12B, only the line width of the line pattern 23a adjacent to the space pattern 23d is 40 nm.

  In the present embodiment, the thick line pattern 23c has been described as a thick pattern, but the thick pattern may be a thick space pattern 23c as shown in FIG. Also in this case, as described above, when the thick space pattern 23c is an odd multiple of the half pitch of the repetitive pattern, the spatial periodicity is matched, and a line pattern that should not originally exist at the center of the thick space pattern 23c appears. To do. On the other hand, if the thick space pattern 23c is made an even multiple of the half pitch of the repetitive pattern, the spatial periodicity can be destroyed, and the appearance of the line pattern can be prevented.

  Correspondingly, the pattern in the thick pattern region in the photomask 10 may be a thick space pattern 2c as shown in FIG.

  When the dimension of the light shielding film pattern 2 on the photomask 10 is, for example, 260 nm, the finished dimension of the resist pattern obtained by transferring the pattern at the same magnification is about 260 ± 20 nm.

(Embodiment 2)
FIG. 14 is a diagram showing a cross-sectional configuration (a) of a photomask, a cross-sectional configuration (b) of an electronic device, and an optical simulation result (c) of light intensity at each position of a pattern in a comparative example of the present invention. FIG. 15 is a diagram showing the cross-sectional configuration (a) of the photomask, the cross-sectional configuration (b) of the electronic device, and the optical simulation result (c) of the light intensity at each position of the pattern in the second embodiment of the present invention. .

  The configuration of the photomask 10 of the present embodiment shown in FIG. 15A is almost the same as that of the photomask 10 shown in FIG. 1, and repeated patterns are arranged on both sides of the thick line pattern 2c. In addition, the line width W1 of the thick line pattern 2c in the photomask 10 of the present embodiment is an even multiple (for example, four times) of half (half pitch) of the repeat pitch P1 of the line pattern 2a.

  Also, the configuration of the electronic device 20 of the present embodiment shown in FIG. 15B is almost the same as the configuration of the electronic device 20 of the first embodiment shown in FIG. 7B, and is arranged on both sides of the thick line pattern 23c. Repeat pattern is arranged. Further, the line width W2 of the thick line pattern 23c in the electronic device 20 of the present embodiment is an even multiple (for example, four times) of half (half pitch) of the repetitive pitch P2 of the line pattern 23a.

  Note that the configuration of each of the photomask 10 and the electronic device 20 of the present embodiment is almost the same as the configuration shown in FIGS. 1 and 3, and therefore, the same components are denoted by the same reference numerals, and the description thereof is omitted. Is omitted.

  The inventor performed a simulation on the intensity distribution of the optical image when the optical image of the photomask 10 in the present embodiment is formed. This will be described below.

  In both FIG. 14B and FIG. 15B, the line width of the line pattern 23a and the width of the space pattern 23b of the photoconductor 23 are set to 65 nm. The line width W2 of the thick line pattern 23c is 195 nm (65 × 3 nm) which is an odd multiple of 65 in FIG. 14B, and 260 nm (65 × 4 nm) which is an even multiple of 65 in FIG.

  Using a photomask 10 (FIGS. 14A and 15A) having a light-shielding film pattern 2 corresponding to the pattern layout of these photoreceptors 23, the exposure wavelength is ArF wavelength (193 nm), and the numerical aperture (NA) ) Was 0.85, and the simulation was performed under the condition that the illumination was two-point illumination.

  As a result, when the size of the thick line pattern is 195 nm as shown in FIG. 14C, repeated spatial periodicity appears in the thick line pattern 23c when the focus is shifted. Therefore, the optical image at the center of the thick line pattern where the resist should be left is brightened and the resist is resolved. On the other hand, when the dimension of the thick line pattern 23c shown in FIG. 15C is 260 nm, the spatial periodicity is mismatched between the left and right of the thick line pattern 23c. Can also be suppressed. Further, in this case, the depth of focus is improved as compared with the case of 195 nm (65 × 3 nm) which is an odd multiple.

  FIGS. 16 and 17 show the results of a similar simulation when the line width W2 of the thick line pattern 23c is 325 nm (65 × 5 nm) and 390 nm (65 × 6 nm).

  When the line width W2 of the thick line pattern 23c shown in FIG. 16B is 325 nm (65 × 5 nm), as shown in FIG. 16C, the light intensity of the optical image is partially in the thick pattern region at the time of defocusing. Is getting higher. On the other hand, when the line width W2 of the thick line pattern 23c shown in FIG. 17B is 390 nm (65 × 6 nm), as shown in FIG. It can be seen that the light intensity of the inverted optical image is suppressed and the depth of focus is improved. The reason why the light intensity can be suppressed more than in the case of FIG. 17 in the pattern layout of FIG. 16 can be explained in the same manner as described above.

  Furthermore, referring to FIG. 11, when there are repeated patterns on both sides of the thick line pattern 23c as in the present embodiment, the depth of focus when the line width W2 of the thick line pattern 23c is 260 nm (65 × 4 nm), It becomes higher than the depth of focus when the line width W2 is 325 nm (65 × 5 nm). From this, it was confirmed that the depth of focus is improved when the line width W2 of the thick line pattern 23c is an even multiple of the half pitch of the repetitive pattern. This is because by arranging 65 nm L / S repetitive patterns on both sides of the thick line pattern 23c, the spatial periodicity from the left and right becomes obvious, and the effect of canceling out both spatial periodicities increases. is there.

  Further, by arranging repeated patterns on both sides of the thick line pattern 23c and making the pattern arrangement symmetrical with respect to the thick line pattern 23c, it becomes prominent at the time of defocusing shown in FIGS. 9C and 10C. Misalignment of the thick line pattern or the like can be prevented as shown in FIGS. 16 (c) and 17 (c).

Similarly to the first embodiment, the width of the space pattern 23d is 1.0 times or more and 1.5 times or less that of the line pattern 23a, so that the bridge can be eliminated. The effect of is not lost. As shown in FIG. 17, when the width W _S3 of the space pattern 23d is 65 nm, which is the line width of the line pattern 23a, the light intensity of the space pattern 23d increases as shown in FIG. Bridging could be prevented. As shown in FIG. 18, when the width W _S3 of the space pattern 23d is 90 nm, which is 1.38 times the line width of the line pattern 23a, which is 1.38 times, as shown in FIG. The light intensity of the space pattern 23d is further increased, and bridging can be prevented.

  Therefore, in the photomask 10 shown in FIG. 18A, the width of the space pattern 2d is preferably 1.0 to 1.5 times the line width of the line pattern 2a. In the electronic device 20 shown in FIG. 3C, the width of the space pattern 22d is preferably 1.0 to 1.5 times the line width of the line pattern 22a.

  In FIG. 18B, only the line width of the line pattern 23a adjacent to the space pattern 23d is 40 nm.

  Further, the thick line pattern 2c of the photomask 10 may be formed with a non-resolving dummy pattern having a dimension that does not resolve the photoconductor on the wafer. FIG. 19 shows a photomask cross-sectional configuration (a), an electronic device cross-sectional configuration (b), and an optical simulation result of light intensity at each position of the pattern when a non-resolving dummy space is provided in the thick line pattern of the photomask. It is a figure which shows (c).

Referring to FIG. 19, since the dimension of the non-resolution dummy space 2c ₁ is smaller than the resolution limit dimension of the mask manufacturing technique, it is not resolved on the photoconductor on the wafer. The dimensions of the non-resolution dummy space 2c ₁ are 20 nm to 40 nm on the wafer (80 nm to 160 nm on the quadruple mask). The non-resolving dummy space 2c ₁ is arranged in the thick line pattern 2c at a distance of 0.22 to 0.27 times the line width of the thick line pattern from the edge of the thick line pattern 2c (that is, the edge of the thick pattern region). Has been. In the present embodiment, for example, the line width of the thick line pattern 2c is 260 nm, and the non-resolving dummy space 2c ₁ having a line width of 34 nm is provided 60 nm inside the distance of 0.23 times from the edge of the thick line pattern 2c. The spatial periodicity could be broken more, and the reversal of the image could be suppressed.

  In the present embodiment, the thick line pattern 23c is described as the thick line pattern. However, the thick line pattern may be a thick space pattern 23c as shown in FIG. Also in this case, as described above, when the width of the thick space pattern 23c is an odd multiple of the half pitch of the repeated pattern, the spatial periodicity is matched and should not originally exist in the center of the thick space pattern 23c. A line pattern appears. On the other hand, if the width of the thick space pattern 23c is set to a dimension that is an even multiple of the half pitch of the repetitive pattern, the spatial periodicity can be destroyed and the appearance of the line pattern can be prevented.

  Correspondingly, the pattern in the thick pattern area of the photomask 10 may be a thick space pattern 2c as shown in FIG.

(Embodiment 3)
First, the structure of an electronic device manufactured using the photomask of Embodiment 1 as an electronic device of this embodiment will be described.

  FIG. 21 is a plan view schematically showing the configuration of the electronic device according to the third embodiment of the present invention. Referring to FIG. 21, the electronic device 20 of the present embodiment has a base layer 21 and a film 22 to be processed formed on the base layer 21. The processed film 22 has, for example, a pattern (hereinafter referred to as “transferred pattern”) to which the light shielding film pattern 2 of the photomask 10 shown in FIG. 7A is transferred. In other words, the film pattern 22 to be processed has the repeated transfer patterns 22a and 22b and the thick transfer line pattern 22c. These transferred repeated patterns 22a and 22b are obtained by transferring the repeated patterns 2a and 2b of the photomask 10 shown in FIG. The transferred thick line pattern 22c is obtained by transferring the thick line pattern 2c shown in FIG. The transferred repetitive pattern region in which the transferred repetitive patterns 22a and 22b are formed and the transferred thick pattern region in which the transferred thick line pattern 22c is formed are adjacent to each other with the transferred space pattern 22d interposed therebetween.

In the repetitive transfer pattern area, a transfer line pattern 22a having a fine line width W _L2 and a transfer space pattern 22b having a fine line width W _S2 are alternately and repeatedly arranged. The transferred line patterns 22a are arranged at an equal pitch P2. A thick transferred line pattern 22c is formed in the thick transferred pattern region. The transferred thick line pattern 22c has a line width W _L2 and the line width W linewidth W2 than _S2 of the transfer space pattern 22b of the transfer line patterns 22a. The transferred thick line pattern 22c extends in parallel with the transferred line pattern 22a and the transferred space pattern 22b.

  In the electronic device 20, the transferred repeat pattern is arranged only on one side of the transferred thick line pattern 22c in plan view.

  The line width W2 of the thick line pattern is in the range of P2 × (n ± 0.25). The line width W2 of the thick line pattern is more preferably within a range of P2 × (n ± 0.1).

  Next, a method for manufacturing the electronic device shown in FIG. 21 using the photomask of Embodiment 1 will be described.

  22 is a diagram showing a flowchart of the method for manufacturing the electronic device shown in FIG. 21, and FIG. 23 is a schematic sectional view showing the method for manufacturing the electronic device shown in FIG. 21 in the order of steps. Referring to FIGS. 22 and 23A, first, a photoresist (photoconductor) 23 is applied on a predetermined substrate (step S1). The predetermined substrate here means a substrate in which a film 22 to be processed such as polysilicon, tungsten, a silicon oxide film, a silicon nitride film, and aluminum is formed on a silicon wafer 21 or the substrate itself.

  The photoresist 23 is, for example, a methacrylic chemically amplified positive resist having a film thickness of about 180 nm, and an organic antireflection film (not shown) having a film thickness of, for example, about 78 nm formed on the predetermined substrate. ) Is applied on top.

  Referring to FIGS. 22 and 23 (b), a heat treatment (soft bake) before exposure is performed (step S2). This soft baking is performed at a temperature of about 110 ° C. for about 60 seconds, for example.

  Referring to FIGS. 22 and 23C, for example, an optical image of the photomask 10 shown in FIG. 7A is projected onto the photoresist 23 by intense oblique illumination, and the photoresist 23 is exposed to perform exposure processing. Is executed (step S3). In this exposure process, for example, an ArF excimer laser (wavelength 193 nm) is used as an exposure light source.

  Referring to FIGS. 22 and 23 (d), a heat treatment (PEB (Post Exposure Bake) or post-exposure bake) is performed after the exposure (step S4). The heat treatment is performed, for example, at a temperature of about 110 ° C. for about 60 seconds.

  Referring to FIGS. 22 and 23 (e), thereafter, photoresist 23 is subjected to development processing (step S5), and photoresist 23 is patterned. In this development process, a 2.38 mass% (wt%) aqueous solution of tetramethylammonium hydroxide can be used as a developer. As a result, the photoresist 23 is patterned into the desired pattern. In addition, after the development, in order to dry the moisture, a heat treatment is performed at a temperature of about 115 ° C. for about 60 seconds.

  Referring to FIGS. 22 and 23 (f), film 22 to be processed is patterned by a well-known etching method such as dry etching using photoresist 23 patterned in the above as a mask (step S6). Thereafter, the photoresist 23 is removed by, for example, ashing. Thereby, the pattern of the planar layout shown in FIG. 21 is formed. Further, by repeating the above steps, an electronic device such as a semiconductor device is manufactured.

  In the exposure process (FIG. 23C) of step S3 of the manufacturing method, the projection exposure apparatus shown in FIG. 24 is used. FIG. 24 is a diagram schematically showing a configuration of a projection exposure apparatus used in the above-described electronic device manufacturing method. Referring to FIG. 24, the projection exposure apparatus projects a pattern on photomask 10 onto photoresist 23 on the surfaces of substrates 21 and 22. The projection exposure apparatus has an illumination optical system from the light source 111 to the pattern of the photomask 10 and a projection optical system from the pattern of the photomask 10 to the substrates 21 and 22.

  The illumination optical system includes a lamp 111 as a light source, a reflecting mirror 112, a condenser lens 118, a fly-eye lens 113, a diaphragm 114 for oblique illumination, condenser lenses 116a, 116b, and 116c, and a blind diaphragm 115. And a reflecting mirror 117. The projection optical system includes projection lenses 119a and 119b and a pupil surface stop 125.

  In the exposure operation, the light 111a emitted from the lamp 111 is first reflected by the reflecting mirror 112 to become single wavelength light. Next, the light 111 a passes through the condenser lens 118, enters each fly-eye constituent lens 113 a of the fly-eye lens 113, and then passes through the diaphragm 114.

  Here, the light 111b indicates an optical path created by one fly-eye component lens 113a, and the light 111c indicates an optical path created by the fly-eye lens 113. The light 111a that has passed through the diaphragm 114 passes through the condenser lens 116a, the blind diaphragm 115, and the condenser lens 116b, and is reflected by the reflecting mirror 117 at a predetermined angle.

  The light 111a reflected by the reflecting mirror 117 passes through the condenser lens 116c, and then uniformly irradiates the entire surface of the photomask 10 on which a predetermined pattern is formed. Thereafter, the light 111a is reduced to a predetermined magnification by the projection lenses 119a and 119b, and the photoresist 23 on the substrates 21 and 22 is exposed.

  In addition, the position of the opening in the oblique illumination illumination diaphragm 114 is determined as follows. FIG. 25 is a schematic cross-sectional view showing a state of diffraction of exposure light in a photomask. Referring to FIG. 25, the optical path difference Δ between the exposure light 36 and the exposure light 37 irradiated to the photomask 10 is expressed by the following equation (2).

Δ = d1 + d2 = P · (sin θi + sin θd) = λ (2)
In the above formula (2), P is the pitch of the repetitive pattern of the light shielding film 2, θi is the incident angle of the exposure light, θd is the diffraction angle of the exposure light, and λ is the exposure wavelength as described above. From this equation (2), the ideal optical interference condition is when (λ / P) = sin θi + sin θd.

Here, when λ = 193 nm, NA = 0.85, P = 130 nm (repetitive pattern in which spaces and lines are arranged at a pitch of 65 nm), and iNA = 0.81, inner sigma σ _in and outer The sigma σ _out can be obtained by applying the following equations (3) and (4) using (λ / P) obtained by the equation (2). Note that iNA is the illumination numerical aperture of the projection exposure apparatus, and NA is the numerical aperture of the projection lenses 119a and 119b.

σ _in = {(λ / P) −NA} / NA (3)
σ _out = iNA / NA (4)
As a result, the inner sigma σ _in can be obtained as 0.75 and the outer sigma σ _out can be obtained as 0.95, and the inner sigma σ _in and the outer sigma σ _{out of the} opening 114a shown in FIG. 2 are set.

  Further, when the cut-out angle of the arc of the opening 114a of the illumination system stop for two-point illumination shown in FIG. 2 is increased, the contrast is deteriorated, but the illuminance is improved. Therefore, an optimal value is selected for the cut-out angle according to the trade-off relationship between the two.

  Moreover, the photomask 10 used in the exposure process (FIG. 23C) in step S3 of the manufacturing method is, for example, a halftone (HT) phase shift mask. In this case, the light-shielding film 2 of the photomask 10 shown in FIG. 23C is made of a material having a transmittance of about 6% and reversing the phase of transmitted light to the opposite phase. By adopting an exposure technique using such a halftone phase shift mask, the contrast on the imaging plane can be improved.

  As described above, the exposure process of the repetitive pattern and the thick line pattern is executed by the above-described exposure using the half-tone phase shift mask with the two-point illumination.

  According to the present embodiment, the line width W2 of the thick line pattern 22c shown in FIG. 21 is an even multiple of the half pitch (P2 / 2) of the repetitive pattern. For this reason, a resist pattern for a circuit pattern in which a minute repetitive pattern having a process factor k1 value of 0.3 or less and a thick line pattern having a process factor of 0.9 to 1.5, for example, coexist can be obtained with high accuracy. be able to. Therefore, a desired pattern (such as FIG. 21) including the thick line pattern 22c and the repeated patterns 22a and 22b can be stably formed.

(Embodiment 4)
A method for manufacturing the electronic device shown in FIG. 21 using the photomask of Embodiment 2 will be described.

  26 is a diagram showing a flowchart of the method for manufacturing the electronic device shown in FIG. 21, and FIG. 27 is a schematic sectional view showing the method for manufacturing the electronic device shown in FIG. 21 in the order of steps. The manufacturing method of the present embodiment first passes through step S11 shown in FIGS. 26 and 27A and step S12 shown in FIGS. 26 and 27B.

  Step S11 shown in FIG. 26 and FIG. 27 (a) and step S12 shown in FIG. 26 and FIG. 27 (b) are the same as steps S1 and 22 shown in FIG. 22 and FIG. Since this is almost the same as step S2 shown in FIG.

  Thereafter, referring to FIGS. 26 and 27C, for example, the optical image of photomask 10 shown in FIG. 15A is projected onto photoresist 23 by intense oblique illumination, and photoresist 23 is exposed. In step S13, the first exposure process is executed. In the first exposure process, for example, an ArF excimer laser (wavelength 193 nm) is used as the exposure light source. In the first exposure process, the optical image of the thick line pattern 2 c of the photomask 10 and the optical images of the repeated patterns 2 a and 2 b on both sides thereof are projected onto the photoresist 23.

  Referring to FIGS. 26 and 27D, after the first exposure process, the second exposure process is executed (step S14). In the second exposure process, the optical image of the photomask 30 is projected onto the photoresist 23 by normal illumination, and the photoresist 23 is exposed.

  The photomask 30 used in the second exposure process has a transparent substrate 31 and a light shielding film 32 formed on the transparent substrate 31. The light shielding film 32 shields the projection portion of the thick line pattern previously projected in the first exposure process and the repetitive pattern on one side thereof, and opens the projection portion of the repetitive pattern on the other side of the thick line pattern. Have a good pattern. Further, the light shielding film 32 has an arbitrary pattern (not shown) arranged arbitrarily other than the thick line pattern and the repeated pattern.

  Therefore, the second exposure process exposes the repeated pattern on the other side of the thick line pattern and the portion of the arbitrary pattern. In particular, the repetitive pattern on the other side of the thick line pattern is erased (disappears) by covering exposure.

  In the second exposure process, for example, an ArF excimer laser (wavelength 193 nm) is used as the exposure light source.

  After the first and second exposure processes, step S15 shown in FIGS. 26 and 27 (e), step S16 shown in FIGS. 26 and 27 (f), and step shown in FIGS. 26 and 27 (g). Processing with S17 is performed. These steps S15, S16, and S17 include step S4 shown in FIGS. 22 and 23 (d), step S5 shown in FIGS. 22 and 23 (e), and step S6 shown in FIGS. 22 and 23 (f). Since this is the same, the description thereof is omitted.

  Thereafter, the photoresist 23 is removed by, for example, ashing. Thereby, the pattern of the planar layout shown in FIG. 21 is formed. Further, by repeating the above steps, an electronic device such as a semiconductor device is manufactured.

In the first and second exposure processes (FIGS. 27C and 27D) of steps S13 and S14 of the manufacturing method, the projection exposure apparatus shown in FIG. 24 is used as in the third embodiment. . Similarly to the third embodiment, the arrangement positions of the apertures in the oblique illumination stop 114 used in the first exposure process of step S13 are sigma 0.75 _in inner sigma and sigma _out in outer sigma. It is set to be 0.95.

  According to the present embodiment, the line width of the thick line pattern is an even multiple of the half pitch of the repetitive pattern. For this reason, a resist pattern for a circuit pattern in which a minute repetitive pattern having a process factor k1 value of 0.3 or less and a thick line pattern having a process factor of 0.9 to 1.5, for example, coexist can be obtained with high accuracy. be able to. Therefore, a desired pattern (such as FIG. 21) including the thick line pattern and the repeated pattern can be stably formed.

  In the photomask 10 used for the first exposure process, the repeated patterns 2a and 2b are arranged symmetrically about the thick line pattern 2c. For this reason, it is possible to prevent the positional deviation of the thick line pattern or the like that becomes conspicuous at the time of defocusing, and it is possible to stably form a desired pattern (such as FIG. 21) including the thick line pattern and the repeated pattern.

(Other)
An example of the electronic device manufactured in Embodiment 3 or 4 will be described.

  FIG. 28 is a cross-sectional view (a) and a plan view (b) schematically showing the configuration of the electronic device manufactured in the third or fourth embodiment. FIG. 28A corresponds to a cross section taken along line XXVIIIA-XXVIIIA in FIG.

  Referring to FIG. 28A, this electronic device has a NAND-type FLASH memory configuration. This FLASH memory has a plurality of memory cells. This memory cell has a pair of source / drain regions 207 and 207, a floating gate 203a, and a control gate 206a. The pair of source / drain regions 207 and 207 are formed on the surface of the semiconductor substrate 201 at a distance from each other. Floating gate 203 a is formed on a region sandwiched between a pair of source / drain regions 207, 207 via gate insulating layer 202. The control gate 206a is formed on the floating gate 203a via an inter-gate insulating layer 204a.

  The FLASH memory also has a MOS (Metal Oxide Semiconductor) transistor for controlling the memory cell. This MOS transistor has a pair of source / drain regions 207, a gate insulating layer 202, and gates 203b, 205, and 206b. The pair of source / drain regions 207 and 207 are formed on the surface of the semiconductor substrate 201 at a distance from each other. Gates 203b, 205, and 206b are formed on a region sandwiched between a pair of source / drain regions 207 and 207 with gate insulating layer 202 interposed therebetween. The gates 203b, 205, and 206b serve as select gates, for example. The gates 203b, 205 and 206b are electrically connected between the lower gate 203b formed in the same process as the floating gate 203a, the upper gate 206b formed in the same process as the control gate 206a, and the lower gate 203b and the upper gate 206b. And a connection layer 205 connected to the. The connection layer 205 is formed so as to fill a hole provided in the insulating layer 204b formed in the same process as the inter-gate insulating layer 204a. Thus, by increasing the line width of the gates 203b, 205, and 206b, a simple MOS transistor structure with less leakage current is realized with respect to the semiconductor substrate 201.

  An interlayer insulating layer 208 is formed on the surface of the semiconductor substrate 201 so as to cover the plurality of memory cells and the MOS transistors. In the interlayer insulating layer 208, a plurality of contact holes reaching the upper gate 206b and contact holes reaching the source / drain regions 207 are formed. Conductive layers 209a and 209b are buried in each contact hole. Each of upper layer gate 206b and source / drain region 207 is electrically connected to an upper layer aluminum wiring or the like through conductive layers 209a and 209b.

Referring to FIG. 28B, each of the plurality of control gates 206a has a fine line width W _L2 and runs in parallel in the same direction via a space pattern having a fine line width W _S2 in plan view. It extends like so. The upper gate 206b has a thick line width W2, and extends so as to run in parallel in the same direction as the plurality of control gates 206a in plan view.

  The plurality of control gates 206a and the space pattern therebetween constitute a fine repetitive pattern, and the upper gate 206b constitutes a thick line pattern. The line width W2 of the upper gate 206b is in the range of P2 × (n ± 0.25), where P2 is the pitch of the control gate 206a and n is an integer. The line width W2 of the control gate 206a is more preferably in the range of P2 × (n ± 0.1).

  In the above description, the line pattern including the upper gate 206b is described as the thick line pattern, but a thick space line may be used as the thick line pattern. Such a thick space pattern is necessary to prevent an electrical short circuit due to contact between the contact hole and the control gate when forming a contact hole that directly connects the semiconductor substrate and the aluminum wiring while avoiding the control gate. .

  Even when a thick space pattern is used instead of the thick line pattern, the same effects as those of the first to fourth embodiments can be obtained.

  The transferred pattern manufactured in the third and fourth embodiments may have a repeated pattern area A1 and an arbitrary pattern area A2 as shown in FIG. The repetitive pattern area A1 has a repetitive pattern in which fine line patterns 22a and space patterns 22b are alternately arranged, and a thick line pattern 22c located next to the repetitive pattern. The arbitrary pattern region A2 includes, for example, a contact pad portion 22e connected to the fine line pattern 22a and a contact pad portion 22f connected to the thick line pattern 22c.

  Further, in the transferred pattern manufactured in the third and fourth embodiments, as shown in FIG. 30, the transferred repeated pattern area may be arranged on both sides of the thick transferred pattern area.

  In the transferred pattern manufactured in the third and fourth embodiments, as shown in FIGS. 31 and 32, the contact pad portion 22e connected to the fine line pattern 22a has a fine line pattern 22a line. It may have a dimension that is an even multiple of the width. Further, as shown in FIG. 31, the fine line pattern 22a may be arranged only on one side of the contact pad portion 22e, and the fine line pattern 22a is arranged on both sides of the contact pad portion 22e as shown in FIG. It may be.

  When the electronic device having the pattern layout shown in FIG. 31 is formed by the method of Embodiment 3, a photomask 10 as shown in FIG. 33 is used in the step of FIG. The photomask 10 has a light shielding film pattern 2 including a contact pad pattern 2c having a large width and a line pattern 2a having a fine width disposed only on one side of the contact pad pattern 2c.

  When the electronic device having the pattern layout shown in FIG. 31 is formed by the method of Embodiment 4, a photomask 10 as shown in FIG. 34 is used in the step of FIG. The photomask 10 has a light shielding film pattern 2 including a contact pad pattern 2c having a large width and a line pattern 2a having a fine width disposed on both sides of the contact pad pattern 2c.

  When the electronic device having the pattern layout shown in FIG. 32 is formed by the method of Embodiment 3, a photomask 10 as shown in FIG. 34 is used in the step of FIG.

  The shape of the opening 114a in the illumination system stop 114 shown in FIG. 2 is an example, and other shapes may be used as long as the optical interference condition is satisfied. For example, in addition to two-point illumination, quattropole illumination (quadrupole illumination shown in FIG. 35, cross-pole illumination shown in FIG. 37), or annular illumination shown in FIG. 36 can be used. However, in this embodiment, two-point illumination is most suitable.

  In the above description, the NAND-type FLASH memory has been described as an example of the electronic device. However, the present invention can be applied to other electronic devices such as semiconductor devices, liquid crystal display devices, thin film magnetic heads, and manufacturing methods thereof.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention relates to a photomask used for forming a pattern including a repetitive pattern and a thick line pattern, a method for manufacturing an electronic device using the photomask, and an electronic device obtained thereby.

1A and 1B are a cross-sectional view and a plan view schematically showing a configuration of a photomask for explaining the principle of the present invention. It is a top view which shows roughly the structure of the 2 point | piece illumination stop for demonstrating the principle of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing (a), (c) and a top view (b) which show schematically the structure of the electronic device for demonstrating the principle of this invention. FIG. 6A is a diagram showing the shape of the photoreceptor pattern 23 when the line width W1 of the thick line pattern 2c in FIG. 1 is an odd multiple (three times) of half (half pitch: 65 nm) of the repetition pitch P1 of the line pattern 2a; FIG. 5B is a diagram (b) showing a projected image (notation E) and light intensity (notation int) of an electric field. FIG. 6A is a diagram showing the shape of the photoconductor pattern 23 when the line width W1 of the thick line pattern 2c in FIG. 1 is an even multiple (four times) of half (half pitch: 65 nm) of the repeat pitch P1 of the line pattern 2a; FIG. 5B is a diagram (b) showing a projected image (notation E) and light intensity (notation int) of an electric field. It is a figure which shows the relationship between the phase shift amount of a pattern on either side, and the light intensity of the thick line pattern center. It is a figure which shows the cross-sectional structure (a) of the photomask in the comparative example of this invention, the cross-sectional structure (b) of an electronic device, and the optical simulation result (c) of the light intensity in each position of a pattern. It is a figure which shows the cross-sectional structure (a) of the photomask in Embodiment 1 of this invention, the cross-sectional structure (b) of an electronic device, and the optical simulation result (c) of the light intensity in each position of a pattern. When the line width of the thick line pattern is 325 nm (65 × 5 nm), the photomask cross-sectional configuration (a), the cross-sectional configuration of the electronic device (b), and the optical simulation result (c) of the light intensity at each position of the pattern are shown. FIG. When the line width of the thick line pattern is 390 nm (65 × 6 nm), the cross-sectional configuration of the photomask (a), the cross-sectional configuration of the electronic device (b), and the optical simulation result (c) of the light intensity at each position of the pattern are shown. FIG. It is a figure which shows the graph which calculated | required the relationship between the line width of a thick line pattern, and a focal depth from the optical simulation result. Photomask cross-sectional configuration (a), electronic device cross-sectional configuration (b), and light intensity at each position of the pattern when the width of the space pattern between the repetitive pattern and the thick line pattern is larger than the fine line pattern in the repetitive pattern It is a figure which shows the optical simulation result (c). It is a figure which shows the cross-sectional structure (a) of a photomask when the pattern of a thick pattern area | region is made into a space pattern, and the cross-sectional structure (b) of an electronic device. It is a figure which shows the cross-sectional structure (a) of the photomask in the comparative example of this invention, the cross-sectional structure (b) of an electronic device, and the optical simulation result (c) of the light intensity in each position of a pattern. It is a figure which shows the cross-sectional structure (a) of the photomask in Embodiment 2 of this invention, the cross-sectional structure (b) of an electronic device, and the optical simulation result (c) of the light intensity in each position of a pattern. When the line width of the thick line pattern is 325 nm (65 × 5 nm), the cross-sectional configuration of the photomask (a), the cross-sectional configuration of the electronic device (b), and the optical simulation result (c) of the light intensity at each position of the pattern are shown. FIG. When the line width of the thick line pattern is 390 nm (65 × 6 nm), the cross-sectional configuration of the photomask (a), the cross-sectional configuration of the electronic device (b), and the optical simulation result (c) of the light intensity at each position of the pattern are shown. FIG. Photomask cross-sectional configuration (a), electronic device cross-sectional configuration (b), and light intensity at each position of the pattern when the width of the space pattern between the repetitive pattern and the thick line pattern is larger than the fine line pattern in the repetitive pattern It is a figure which shows the optical simulation result (c). The figure which shows the optical simulation result (c) of the cross-sectional structure (a) of a photomask at the time of providing a dummy pattern in the thick line pattern area | region of a photomask, the cross-sectional structure (b) of an electronic device, and each position of a pattern is there. It is a figure which shows the cross-sectional structure (a) of a photomask when the pattern of a thick pattern area | region is made into a space pattern, and the cross-sectional structure (b) of an electronic device. It is a top view which shows roughly the structure of the electronic device in Embodiment 3 of this invention. It is a figure which shows the flowchart of the manufacturing method of the electronic device shown in FIG. It is a schematic sectional drawing which shows the manufacturing method of the electronic device shown in FIG. 21 in order of a process. It is a figure which shows schematically the structure of the projection exposure apparatus used for the manufacturing method of an electronic device. It is a schematic sectional drawing which shows the mode of diffraction of the exposure light in a photomask. It is a figure which shows the flowchart of the manufacturing method of the electronic device shown in FIG. It is a schematic sectional drawing which shows the manufacturing method of the electronic device shown in FIG. 21 in order of a process. FIG. 6 is a cross-sectional view (a) and a plan view (b) schematically showing the configuration of the electronic device manufactured in the third or fourth embodiment. It is a schematic plan view which shows the pattern layout which has arbitrary pattern areas other than a repeating pattern area. FIG. 6 is a schematic plan view showing a pattern layout in which transferred repeat patterns are arranged on both sides of a thick transferred pattern region. It is a schematic plan view which shows an example of the pattern layout of a contact pad of a small area. It is a schematic plan view which shows the other example of the pattern layout of a contact pad of a small area. FIG. 32 is a schematic plan view showing an example of a pattern layout on the photoreceptor of the small area contact pad shown in FIG. 31. FIG. 32 is a schematic plan view showing another example of a pattern layout on the photoreceptor of the small area contact pad shown in FIG. 31. It is a schematic plan view which shows the structure of the illumination system stop for quadrupole illumination used by exposure processing. It is a schematic plan view which shows the structure of the illumination system aperture | diaphragm for annular illumination used by an exposure process. It is a schematic plan view which shows the structure of the illumination system stop for cross pole illumination used by exposure processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate, 2 Light shielding film, 2a Line pattern, 2b Space pattern, 2c Thick line pattern, 2c ₁ Non-resolution dummy space, 2d Space pattern, 10 Photomask, 20 Electronic device, 21 Underlayer, 22 Processed film, 22a Transfer line pattern, 22b Transfer space pattern, 22c Transfer thick line pattern (pad part), 22d Transfer space pattern, 22e Contact pad part, 23 Photoconductor (photoresist), 23a Line pattern, 23b Space pattern, 23c Thick line Pattern, 23d space pattern, 30 photomask, 31 transparent substrate, 32 light shielding film, 111 lamp, 111 light source, 112 reflector, 113 fly eye lens, 113a fly eye component lens, 114a aperture, 116a, 116b, 116c , 118 condenser lens, 117 reflector, 119a projection lens, 201 semiconductor substrate, 202 gate insulating layer, 203a floating gate, 203b lower gate, 204a inter-gate insulating layer, 204b insulating layer, 205 connection layer, 206a control gate, 206b Upper layer gate, 207 source / drain region, 208 interlayer insulating layer, 209a conductive layer.

Claims (12)

A substrate transparent to the exposure light;
A light-shielding film pattern formed on the surface of the substrate for blocking transmission of the exposure light,
The light shielding film pattern is
A repeated pattern in which a line pattern and a space pattern are alternately repeated;
A thick pattern extending parallel to the repetitive pattern and having a width wider than the line pattern and the space pattern;
A photomask in which a width W1 of the thick pattern is in a range of P1 × (n ± 0.25), where P1 is a pitch of the line pattern and n is an integer.   2. The photomask according to claim 1, wherein a line width W <b> 1 of the thick pattern is in a range of P1 × (n ± 0.1).   The repetitive pattern has a first repetitive pattern portion disposed on one side of the thick pattern in a plan view and a second repetitive pattern portion disposed on the other side of the thick pattern. The photomask according to claim 1 or 2.   The photomask according to claim 1, wherein the thick pattern has a dummy pattern having a dimension that does not resolve on the imaging surface. The light shielding film pattern has a second space pattern between the repetitive pattern and the thick pattern,
5. The width according to claim 1, wherein the width of the second space pattern is a dimension that is not less than 1 and not more than 1.5 times the width of the space pattern in the repetitive pattern. Photo mask. A first exposure step of exposing the photoconductor by projecting the optical image of the photomask according to any one of claims 1 to 5 onto a photoconductor on a substrate by oblique illumination;
Developing the exposed photoreceptor to form the photoreceptor pattern; and
And a step of selectively etching and patterning the substrate using the photoconductor pattern as a mask.   Second exposure step of exposing the photoconductor by projecting an optical image of another photomask onto the photoconductor after the first exposure step using the oblique illumination and before developing the photoconductor The method of manufacturing an electronic device according to claim 6, further comprising: The first exposure step using the oblique illumination exposes the photosensitive body to a projected area of a thick pattern and a projected area of first and second repeated pattern areas sandwiching the projected area of the thick pattern,
8. The electronic device according to claim 7, wherein in the second exposure step, the entire projection area of one of the first and second repetitive pattern areas is exposed and disappeared. 9. Production method. A semiconductor substrate;
A transferred pattern formed on the surface of the semiconductor substrate,
The transferred pattern is
A repeated transfer pattern in which a transferred line pattern and a transferred space pattern are alternately repeated; and
A transferred thick pattern extending in parallel with the transferred repeat pattern and having a width wider than the transferred line pattern and the transferred space pattern;
An electronic device in which a width W2 of the thick pattern to be transferred is within a range of P2 × (n ± 0.2), where P2 is a pitch of the transferred line pattern and n is an integer.   10. The electronic device according to claim 9, wherein a width W1 of the transferred thick pattern is in a range of P1 × (n ± 0.1).   The transferred repetitive pattern includes a first transferred repetitive pattern portion disposed on one side of the transferred thick pattern and a second transferred repeated pattern disposed on the other side of the transferred thick pattern in plan view. It has a pattern part, The electronic device of Claim 9 or 10 characterized by the above-mentioned. The transferred pattern has a second transferred space pattern between the transferred repeated pattern and the transferred thick line pattern,
The width of the second transferred space pattern has a dimension that is not less than 1 and not more than 1.5 times the width of the transferred space pattern in the transferred repeated pattern. The electronic device in any one of.

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