JP5311326B2 - Photomask, pattern forming method, and electronic device manufacturing method - Google Patents

Description

  The present invention relates to a photomask, a pattern forming method, and an electronic device manufacturing method.

  Unlike the line pattern, hole pattern formation in photolithography requires the electromagnetic field to be localized two-dimensionally, so that miniaturization is difficult in principle. Furthermore, when the hole pattern is formed of a positive photoresist, the effective contrast of the image is essentially reduced.

  In particular, since there is no effective super-resolution technique for forming minute isolated holes, it is difficult to form them with a high process margin. For this reason, the formation of minute isolated holes is one of the factors that suppress the miniaturization of devices.

  On the other hand, in the regularly arranged hole patterns, the image quality of the formed optical image is inferior to that of the dense line pattern which is a one-dimensional pattern due to the above-mentioned principle restrictions. However, there is a super-resolution technique represented by the modified illumination method. For this reason, the application of a high-resolution photoresist having excellent separation performance makes it possible to form highly dense fine holes with a high process margin.

  On the other hand, in the formation of a dark spot image, as disclosed by the inventors of the present case (see Patent Document 1 and Non-Patent Document 1), a phase cancellation image using a phase shift mask under optimal deformation illumination is applied. Thus, an excellent image quality can be obtained in a randomly arranged pattern.

Further, a mask pattern for generating an optimum image is (automatically) generated, and techniques corresponding to random patterns include those described in Non-Patent Documents 2 and 3.
JP 2004-251969 A S. Nakao et al., "Zero MEF Hole Formation with Atten-PSMand Modified Illumination", Proc. Of SPIE Vol. 5040 (2003), pp. 1258-1269 R. Socha et al., "Contact Hole Reticle Optimization by Using Interference Mapping Lithography (IMLTM)", Proc. Of SPIE Vol. 5377 (2004), pp.222-240 DS Abrams et al., "Fast Inverse Lithography Technology", Proc. Of SPIE Vol. 6154 (2006), pp.61541J-1-J-9

  In forming a hole pattern in a random arrangement using a phase-inverted image by a conventional phase shift mask, a negative photoresist is required as described in Patent Document 1 and Non-Patent Document 1. However, in ArF excimer laser exposure, which is the current state-of-the-art technology, there is no negative photoresist having excellent characteristics. For this reason, the conventional method has a problem that it is difficult to obtain characteristics sufficient for practical use at an ArF excimer laser wavelength.

  In the methods disclosed in Non-Patent Documents 2 and 3, since a complicated mask pattern is generated, it is difficult to manufacture a photomask.

  The present invention has been made in view of the above problems, and its object is to form a randomly arranged hole pattern with a simple photomask configuration and high focus tolerance under the application of a positive photoresist. It is to provide a photomask, a method of forming a pattern, and a method of manufacturing an electronic device.

The photomask in this embodiment includes a transparent substrate, a halftone phase shift film, and a light shielding film. The halftone phase shift film is formed on the transparent substrate and has a plurality of openings. The light shielding film is formed on the halftone phase shift film and forms a plurality of light shielding portions. When a lattice formed by intersecting a plurality of vertical lines and a plurality of horizontal lines in a plan view is assumed, a specific lattice point among the plurality of lattice points of the lattice opens a halftone phase shift film exposed from the light shielding film. By leaving the halftone phase shift film without forming a halftone phase shift film, a halftone phase shift film is formed at portions other than the plurality of lattice points . An opening is formed in each of the four lattice points adjacent in the diagonal direction of the unit lattice with respect to the specific lattice point that is the halftone phase shift portion. A light-shielding portion is formed at each of two lattice points adjacent in the vertical line direction and two lattice points adjacent in the horizontal line direction with respect to a specific lattice point set as the halftone phase shift portion.

  By using the photomask of the present embodiment described above, a hole pattern in a random arrangement can be formed with a simple photomask configuration and high focus tolerance under the application of a positive photoresist in ArF excimer laser exposure. The present inventor has found that this is possible. Thereby, the said objective can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view schematically showing a configuration of a photomask in one embodiment of the present invention. FIG. 2 is a schematic sectional view taken along line II-II in FIG. Referring mainly to FIG. 2, the photomask PM of the present embodiment has a transparent substrate TS, a halftone phase shift film HT, and a light shielding film LS.

  The transparent substrate TS is made of a material transparent to the exposure light so as to transmit the exposure light. The halftone phase shift film HT is formed on the transparent substrate TS and has a plurality of openings OP that expose a part of the surface of the transparent substrate TS. The halftone phase shift film HT is configured such that the phase of the exposure light transmitted through the halftone phase shift film HT is different from the phase of the exposure light transmitted through the opening OP (for example, a phase different by 180 °). ing. The transmittance of the halftone phase shift film HT is preferably 10% or more and 30% or less.

  The light shielding film LS is formed on the halftone phase shift film HT. The light shielding film LS forms a plurality of light shielding portions SP in plan view. The light shielding film LS is configured to block the transmission of exposure light, and is made of, for example, chromium (Cr).

  Referring mainly to FIG. 1, a virtual lattice in which a plurality of vertical lines VL and a plurality of horizontal lines HL intersect is set on the surface of the photomask PM in plan view. This lattice is, for example, a square lattice. And the opening part OP and the light-shielding part SP are regularly arrange | positioned alternately by several lattice point LP of the grating | lattice. This arrangement pattern (checkered pattern) is taken as a basic pattern. In this basic pattern, the halftone phase shift film HT is sandwiched between the opening OP and the light shielding part SP in plan view.

  In the present embodiment, in the basic pattern, at least one lattice point LP among the plurality of lattice points LP to be the opening OP is a halftone phase shift portion HTP (broken line portion in the figure). In the halftone phase shift part HTP, the halftone phase shift film HT is left without an opening being formed at a position indicated by a broken line in the drawing of the halftone phase shift film HT.

  An opening OP is formed in each of the four lattice points LP adjacent to each other in the diagonal DL direction of the unit lattice (for example, a region surrounded by a thick line in the drawing) with respect to the lattice point LP which is the halftone phase shift portion HTP. ing. In addition, a light shielding portion SP is formed at each of two lattice points LP adjacent to each other in the vertical line VL direction and two lattice points LP adjacent to each other in the horizontal line HL direction with respect to the lattice point LP as the halftone phase shift portion HTP. ing.

In the above pattern, when the area of the opening OP is A _0P , the area of the halftone phase shift portion HTP is A _HT , and the light transmittance of the halftone phase shift portion HTP is T, the area of the opening OP is A _{0P. Satisfies} the relationship of A _{0P ≈A HT} × T ^1/2 .

  When the virtual grating pitch is P, the wavelength of exposure light applied to the photomask is λ, and the numerical aperture of the exposure system in the projection exposure apparatus is NA, the grating pitch P is 0.6 × λ / NA. <P <0.7 × λ / NA is satisfied.

  The photomask of this embodiment can be applied to either an isolated arrangement of hole patterns, a dense arrangement, or a random arrangement including both an isolated arrangement and a dense arrangement. This will be described below.

  FIG. 3 is a plan view schematically showing a configuration of a photomask according to an embodiment of the present invention, in which hole patterns can be randomly arranged. Referring to FIG. 3, the photomask PM of the present embodiment includes a portion where halftone phase shift portions HTP are isolated and a portion where they are densely arranged so as to form a randomly arranged hole pattern. have.

  The dense arrangement of the halftone phase shift portions HTP is an arrangement in which two or more halftone phase shift portions HTP are arranged in succession with the light shielding portion SP in at least one of the vertical line VL direction and the horizontal line HL direction. . The isolated arrangement of the halftone phase shift part HTP is an arrangement in which an opening OP is provided with the light shielding part SP sandwiched between the vertical line VL direction and the horizontal line HL direction of the halftone phase shift part HTP. is there.

  In both the dense arrangement and the isolated arrangement of the halftone phase shift portions HTP, the four lattice points LP adjacent to each other in the diagonal DL direction of the unit lattice UL with respect to the lattice points LP as the halftone phase shift portions HTP. Each has an opening OP. In addition, a light shielding portion SP is formed at each of two lattice points LP adjacent to each other in the vertical line VL direction and two lattice points LP adjacent to each other in the horizontal line HL direction with respect to the lattice point LP as the halftone phase shift portion HTP. ing.

  Further, in the dense arrangement of the halftone phase shift units HTP, the distance between two halftone phase shift units HTP arranged closest to each other among the plurality of halftone phase shift units HTP is more than twice the lattice pitch. is there.

  As described above, in the photomask PM according to the present embodiment, the halftone phase shift portion HTP is arranged in a random arrangement including a dense arrangement and an isolated arrangement, so that a random arrangement of minute hole patterns (opening diameters) will be described later. 80 nm or less hole pattern) can be resolved into the photoresist.

  Next, a pattern design method using optical proximity correction (OPC: Optical Proximity Correction) in the photomask of this embodiment will be described by taking an example in which OPC is performed on the mask pattern of FIG.

  When image formation / exposure is performed with a mask pattern that is merely a halftone phase shift portion HTP (bright spot portion), leaving the portion of the halftone phase shift film to be the opening OP shown in FIG. Depending on the situation of the surrounding bright spot, the size of the formed image will be different, and as a result, holes of different sizes will be formed. In a typical advanced device, the size of the fine hole is mainly limited to one type, and it is necessary to make the size the same. Therefore, OPC is required, but in this embodiment, simple and highly accurate correction is possible by two-stage OPC.

  First, as a first-stage OPC, a rule-based OPC for correcting a design pattern based on a correction rule (OPC rule) obtained in advance is performed. That is, first, coarse correction is performed based only on the arrangement rule (situation).

  FIG. 4 is a schematic plan view showing the configuration of the mask pattern after rough correction is performed. Referring to FIG. 4, in the rule-based OPC, the planar shape of the light shielding part SP located adjacent to the halftone phase shift part HTP (bright spot part) is corrected.

  In this correction, the light shielding portion SP sandwiched between the two halftone phase shift portions HTP is set to the original light shielding pattern (that is, the pattern shape of the light shielding portion SP in the basic pattern). Further, the light-shielding part SP sandwiched between the halftone phase shift part HTP and the opening OP is left with only the half pattern part closer to the halftone phase shift part HTP from the pattern shape of the light-shielding part SP in the basic pattern. The half pattern portion on the side close to the opening OP is removed.

  By executing such a simple rule-based OPC, the dimensions of the bright spot images for hole formation obtained from the corrected mask pattern are roughly the same.

  FIG. 5 is a schematic plan view showing an example of a mask pattern in the photomask according to the present embodiment in which the above rough correction (rule-based OPC) is performed. Referring to FIG. 5, this mask pattern is a mask pattern for forming holes on the radiation from the vicinity of the center of the figure, and is densely arranged near the center of the figure and is isolated on the outside. .

  Next, as the second stage OPC, model-based OPC is performed in which a design pattern is corrected by a simulator that models a phenomenon in the lithography process. That is, by further modifying the pattern of the light-shielding part SP located next to the halftone phase shift part HTP (bright spot part), the difference between the predicted dimension based on the process model and the desired dimension is reduced below a certain level. In addition, fine correction is performed.

  FIG. 6 is a schematic plan view showing the configuration of the mask pattern after precise correction is performed. Referring to FIG. 6, in the model-based OPC, when the image size of the bright point image is large, the planar size of the light shielding portion SP adjacent to the halftone phase shift portion HTP is increased, and the image size of the bright point image is increased. Is small, the planar dimension of the light shielding part SP adjacent to the halftone phase shift part HTP is reduced.

  Further, the position of the light-shielding part SP adjacent to the halftone phase shift part HTP is moved to the target halftone phase shift part HTP side as necessary. In the light-shielding part SP adjacent to the halftone phase shift part HTP, the dimension or position in the long side direction of the sparse corrected rectangle is changed as necessary.

  According to the above-described two-stage OPC, the rough correction at the first stage has made an approximate correction. Therefore, the convergence of the model-base OPC at the second stage is ensured, and a small number of sequential adjustments (iteration ) Can correct the desired accuracy, so that the correction processing time can be shortened and the accuracy can be improved.

  As described above, the two-stage OPC corrects the planar shape of the light shielding portion SP located adjacent to the halftone phase shift portion HTP. Therefore, the light shielding portion not adjacent to the light shielding portion SP adjacent to the halftone phase shift portion HTP. SP may have different shapes in plan view.

  Further, as a result of performing the first stage correction, among the light shielding portions SP adjacent to the halftone phase shift portion HTP, the light shielding portions SP adjacent to the two halftone phase shift portions HTP and one halftone phase shift portion HTP. Adjacent light shielding portions SP may have different shapes in plan view.

  Next, a pattern formation method (electronic device manufacturing method) using the photomask of this embodiment will be described.

  7 to 11 are schematic cross-sectional views illustrating a pattern forming method (electronic device manufacturing method) using a photomask in one embodiment of the present invention in the order of steps. Referring to FIG. 7, a film to be processed PF is formed on the surface of a base substrate SB such as a semiconductor substrate. A positive photoresist PR is applied on the film PF to be processed.

  Referring to FIG. 8, an exposure process using photomask PM shown in FIGS. 1 and 2 is performed. In this exposure, for example, ArF excimer laser light (wavelength 193 nm) is used as exposure light. By this exposure, a bright spot image is formed at a position corresponding to the halftone phase shift portion HTP, and the photoresist PR in the bright spot image portion is resolved.

  Referring to FIG. 9, the exposed photoresist PR is developed to remove the exposed portion of the bright spot image. Thereby, a hole pattern HP1 is formed in the photoresist PR, and a part of the surface of the film PF to be processed is exposed from the hole pattern HP1.

  Referring to FIG. 10, for example, anisotropic etching is performed on the surface of film to be processed PF exposed from hole pattern HP1 using patterned photoresist PR as a mask. By this etching, a hole pattern HP2 is formed in the film PF to be processed, and a partial surface of the base substrate SB is exposed from the hole pattern HP2. Thereafter, photoresist PR is removed by, for example, ashing.

  Referring to FIG. 11, the surface of the film PF to be processed is exposed by removing the photoresist PR.

  In the above description, the case where the hole pattern HP2 is formed in the processed film PF on the base substrate SB has been described. However, the hole pattern HP2 may be formed on the surface of the base substrate SB without the processed film PF. .

  Next, a projection exposure apparatus used in the exposure process of FIG. 8 in the pattern forming method will be described.

  FIG. 12 is a schematic view showing a state in which the photomask according to one embodiment of the present invention is attached to the projection exposure apparatus. Referring to FIG. 12, the projection exposure apparatus projects a mask pattern on photomask PM onto a photoresist on substrate (for example, wafer) WA. The projection exposure apparatus includes an illumination optical system from a light source (not shown) to the pattern of the photomask PM and a projection optical system from the pattern of the photomask PM to the substrate WA.

  The illumination optical system mainly includes a light source (not shown), a fly-eye lens FR, an illumination stop IA, and a condenser lens CR. The projection optical system mainly includes projection lenses PR1 and PR2 and a pupil surface stop PA.

  In the exposure operation, light (for example, ArF excimer laser light) emitted from a light source first enters each fly-eye constituent lens of the fly-eye lens FR, and then passes through the illumination stop IA. The light that has passed through the illumination stop IA passes through the condenser lens CR and then uniformly irradiates the entire surface of the photomask PM. Thereafter, the light diffracted by the pattern of the photomask PM is reduced to a predetermined magnification by the projection lenses PR1 and PR2, and the photoresist on the substrate WA is exposed.

  In the present embodiment, it is preferable that illumination of the photomask PM is performed by modified illumination instead of normal illumination in the exposure process of FIG. As the modified illumination, quadrupole illumination is preferably used. That is, as shown in FIG. 13, a quadrupole illumination stop IA having four transmission portions IAa and having a shape obtained by rotating the cross pole illumination by 45 ° is preferably used as the illumination stop IA in FIG.

As shown in FIG. 14, the quadrupole illumination has a center σ (= r ₁ / r ₀ ) of 0.8 to 0.9 and a radius σ (= r ₂ / r ₀ ) of 0.2. The following is appropriate. Here, r ₀ is the radius of the illumination stop IA, r ₁ is the distance between the center of the illumination stop IA and the center of the transmission part IAa, and r ₂ is the radius of the transmission part IAa.

  In the photomask PM of the present embodiment, as shown in FIG. 1, a halftone phase shift unit HTP is arranged at a specific lattice point LP, and four lattices adjacent to the specific lattice point LP in the diagonal DL direction. The opening OP is disposed at the point LP, and the light shielding portions SP are disposed at four lattice points LP adjacent to the specific lattice point LP in the vertical line VL direction and the horizontal line HL direction. Thereby, by irradiating the photomask PM with ArF excimer laser light to expose the positive photoresist PR, a fine bright spot image can be formed at a location corresponding to the halftone phase shift portion HTP, and The positive photoresist PR can be resolved with the bright spot image. Thereby, a hole pattern HP1 having a minute opening diameter (opening diameter of 80 nm or less) can be formed in the photoresist PR with a high focus tolerance.

  Further, based on a mask pattern composed of a plurality of openings OP regularly arranged at lattice points and a plurality of light-shielding portions SP, a part of the openings OP is changed to a halftone phase shift portion HTP. The above-mentioned fine bright spot image can be generated with the configuration of the photomask.

  Further, by appropriately combining the arrangement of the halftone phase shift part HTP, the opening OP, and the light shielding part SP as shown in FIG. 3, holes having a random arrangement including a dense arrangement and an isolated arrangement are provided. A pattern can be formed.

  As described above, in ArF excimer laser exposure, a positively arranged hole pattern can be formed with a simple photomask configuration and high focus tolerance under the application of a positive photoresist.

  In the present embodiment, the layout of the opening OP and the light shielding portion SP is limited on the lattice point LP, and the types of pattern arrangement environments are limited. Therefore, OPC can be easily performed.

  In the present embodiment, the case where the shape of the unit lattice UL of the lattice composed of the plurality of vertical lines VL and the plurality of horizontal lines HL is a square (that is, a square lattice) is described, but the shape of the unit lattice UL is a rectangle. May be.

  In the present embodiment, the case where the planar shape of each of the opening OP and the light shielding portion SP is rectangular (for example, a square) has been described. However, the planar shape of each of the opening OP and the light shielding portion SP is not rectangular. It may be rectangular or circular, and may have a shape with rounded corners of a rectangle.

  In the configuration of the photomask PM of the present embodiment shown in FIG. 2, the configuration in which the light shielding film LS is formed on the halftone phase shift film HT has been described. However, the halftone phase shift film is formed on the light shielding film LS. HT may be formed.

  Moreover, it is preferable from the point of the ease of making that the planar shape of each of several opening part OP is the same. Further, the planar shape of the light shielding part SP may be appropriately set by the above OPC. In this case, the light shielding part SP may be displaced from the lattice point LP and not positioned on the lattice point LP. In this specification, the light shielding part SP including the light shielding part SP displaced from the lattice point LP is formed at the lattice point LP. This is referred to as a light-shielding portion SP.

  An electronic device manufactured using the photomask of this embodiment is not limited to a semiconductor device, and may be a liquid crystal display device, a thin film magnetic head, or the like.

  As a result of intensive studies, the present inventor has used the above-described photomask PM to form a randomly arranged hole pattern with a simple photomask configuration and high focus under the application of a positive photoresist in ArF excimer laser exposure. I found out that it can be formed with tolerance. The contents and results of the study are described below.

  First, the inventor obtained an optical image by calculation when the mask pattern shown in FIG. 15 was formed. In the mask pattern shown in FIG. 15, the opening OP and the light-shielding part SP are arranged in a checkered pattern in the halftone phase shift film HT in a plan view, as in the photomask PM shown in FIGS. No halftone phase shift portion HTP was formed. Since the other configuration of this mask pattern is substantially the same as the configuration of the photomask shown in FIGS. 1 and 2, the same elements are denoted by the same reference numerals and description thereof will not be repeated.

The optical conditions at the time of imaging are as follows: exposure light is ArF excimer laser light (wavelength 193 nm), the numerical aperture NA of the exposure system is 1.07, and the illumination stop is quadrupole illumination (center σ0.84 / radius σ0.10). ). In the above pattern, the area A _0P of the opening OP satisfies the relationship of A _{0P ≈A HT} × T ^1/2 .

  FIG. 16 shows an optical image obtained by optical image calculation when the mask pattern shown in FIG. 15 is formed. Referring to FIG. 16, in this optical image, the light intensity (relative intensity) of the image is low at a location corresponding to light shielding portion SP in FIG. 15 and high at a location corresponding to opening OP. The contrast of the light intensity is outstanding. However, the light intensity of the image is in the range of 0.02 to 0.04, the light intensity is 0.04 or less even at the highest light intensity, and it is sufficiently darker than the bright spot image shown later. ing. Therefore, the positive photoresist is not resolved at the light intensity of this image, and the positive photoresist remains completely and cannot be patterned.

  Next, the present inventor obtained an optical image when the mask pattern shown in FIG. 17 is formed by calculation. In the mask pattern shown in FIG. 17, one half of the opening OP of the mask pattern shown in FIG. 15 is not opened, and the halftone phase shift film HT is left to form a halftone phase shift portion HTP. Further, the OPC was performed on the light shielding part SP adjacent to the halftone phase shift part HTP. Thereby, for the light-shielding part SP adjacent to the halftone phase shift part HTP, only the half pattern part closer to the halftone phase shift part HTP from the pattern shape of the light-shielding part SP in the basic pattern is left, and the opening OP The half pattern portion on the side close to is removed.

As the optical conditions at the time of image formation, the exposure light is ArF excimer laser light (wavelength 193 nm), the numerical aperture NA of the exposure system is 1.07, and the illumination stop is quadrupole illumination (center σ0.84 / Radius σ0.10). In the above pattern, the area A _0P of the opening OP satisfies the relationship of A _{0P ≈A HT} × T ^1/2 .

  FIGS. 18A to 18C show optical images obtained by optical image calculation when the mask pattern shown in FIG. 17 is formed. FIG. 19 is a diagram showing a distribution of light intensity (Relative Intensity) at a position (Horizontal Position) passing through a bright spot image of the obtained optical image, with focus as a parameter. FIG. 20 is a diagram in which the dimension of the bright spot image of the obtained optical image, that is, Image CD (Critical Dimension) is plotted with respect to the focus, and the slice level (amount inversely proportional to the exposure amount) is shown as a parameter. FIG.

  Referring to FIGS. 18A to 18C, in this optical image, the light intensity of the image is highest at a position corresponding to the halftone phase shift portion HTP in FIG. A point image was formed. The light intensity of the isolated bright spot image is about 0.2, which is higher than the surrounding intensity, and is high enough to sufficiently resolve the positive photoresist.

  18A to 18C and FIG. 19, an isolated bright spot having a light intensity of about 0.2 even when the focus is varied from 0.00 μm to 0.10 μm from the best focus. An image was obtained. From this, it can be seen that a fine isolated bright spot image having excellent focus characteristics is formed.

  In FIG. 19, the focus was shifted from the best focus by 0 μm, 0.02 μm, 0.04 μm, 0.06 μm, 0.08 μm, and 0.10 μm, respectively, but the light intensity distributions at the respective shift amounts were similar. Distribution was shown. For this reason, the light intensity distribution at each shift amount is collectively shown as one curve in FIG.

  Referring to FIG. 20, it can be seen from the image size (Image CD) obtained by the slice level method that a hole with a diameter of ˜60 nm can be formed with a CD-DOF (Depth Of Focus) of ˜0.20 μm.

  From the above results, the imaging performance of isolated fine holes obtained by imaging the mask pattern shown in FIG. 17 is considered to be the world's highest level at the present time.

  Furthermore, the present inventor obtained an optical image when the mask pattern shown in FIG. 21 is formed by calculation. The mask pattern shown in FIG. 21 has the same structure as the dense arrangement of the mask pattern shown in FIG.

As for the optical conditions for imaging, the exposure light is ArF excimer laser light (wavelength 193 nm), the numerical aperture NA of the exposure system is 1.07, and the illumination aperture is 4 as in the mask pattern imaging shown in FIG. Multipole illumination (center σ0.84 / radius σ0.10) was used. In the above pattern, the area A _0P of the opening OP satisfies the relationship of A _{0P ≈A HT} × T ^1/2 .

  FIGS. 22A to 22C show optical images obtained by optical image calculation when the mask pattern shown in FIG. 21 is formed. FIG. 23 is a diagram showing the light intensity distribution at a position passing through a plurality of bright spot images of the obtained optical image, with focus as a parameter. FIG. 24 is a diagram in which the size of the bright spot image of the obtained optical image, that is, Image CD is plotted with respect to the focus, and the slice level is a parameter.

  Referring to FIGS. 22A to 22C, also in this optical image, the light intensity of the image is the highest at the location corresponding to the halftone phase shift portion HTP in FIG. An image was formed. Further, a bright spot portion is formed corresponding to each of the plurality of halftone phase shift portions HTP arranged densely, and an arrangement in which a plurality of bright spot portions are densely obtained is obtained. The light intensity of each of the plurality of bright spot images is about 0.2, which is larger than the surrounding area, and is high enough to resolve a positive type photoresist.

  Further, referring to FIGS. 22A to 22C and FIG. 23, an isolated bright spot having a light intensity of about 0.2 even if the focus is varied from 0.00 μm to 0.10 μm from the best focus. An image was obtained. From this, it can be seen that a fine dense bright spot image having excellent focus characteristics is formed.

  In FIG. 23, the focus was shifted from the best focus by 0 μm, 0.02 μm, 0.04 μm, 0.06 μm, 0.08 μm, and 0.10 μm, respectively, but the light intensity distribution at each shift amount was similar. Distribution was shown. For this reason, the light intensity distribution at each shift amount is collectively shown as one curve in FIG.

  Referring to FIG. 24, it can be seen from the image size (Image CD) obtained by the slice level method that a hole with a diameter of ˜60 nm can be formed with CD-DOF (Depth Of Focus) of ˜0.20 μm.

  Based on the above results, the imaging performance of dense micro holes obtained by imaging the mask pattern shown in FIG. 21 is considered to be the world's highest level at the present time.

  As described above, the present inventor has intensively studied to the extent that a positive photoresist can be resolved by setting at least one of a plurality of openings of a basic pattern having a checkered pattern as a halftone phase shift portion HTP. The present inventors have found that a randomly arranged fine bright spot image having a light intensity of 10 nm can be formed with a simple photomask configuration and a high focus tolerance.

  Although the present inventor cannot clearly explain the reason why the above effect can be obtained, it is presumed that light beams having different diffraction orders have the opposite effect on the contrast of the image at the time of defocusing. .

  In any of the mask patterns of FIG. 17 and FIG. 21, any one of the four openings OP adjacent to the halftone phase shift portion HTP in the diagonal direction of the unit cell is also used as the halftone phase shift portion HTP. When changed, the imaging characteristics deteriorated greatly.

  Further, if one of the four light shielding portions SP adjacent to the halftone phase shift portion HTP in each of the vertical line direction and the horizontal line direction of the grating is deleted, the imaging characteristics are greatly deteriorated.

  From the above, it can be seen that the halftone phase shift portion HTP needs to be arranged at least twice the grating pitch P.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. 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.

  Although the present invention is considered to be mainly targeted for pattern formation of logic devices that are mostly sparse patterns, it is widely used as a photomask, pattern formation method, and electronic device manufacturing method for pattern formation in a random arrangement. It can be applied particularly advantageously.

It is a top view which shows roughly the structure of the photomask in one embodiment of this invention. It is a schematic sectional drawing in alignment with the II-II line of FIG. It is a top view which shows schematically the structure of the photomask in one embodiment of this invention, Comprising: The structure which can arrange | position a hole pattern at random. It is a schematic plan view which shows the structure of the mask pattern after rough correction was implemented. It is a schematic plan view which shows an example of the mask pattern in the photomask of this Embodiment which performed rough correction | amendment (rule base OPC). It is a schematic plan view which shows the structure of the mask pattern after delicate correction | amendment was implemented. It is a schematic sectional drawing which shows the 1st process of the formation method (electronic device manufacturing method) using the photomask in one embodiment of this invention. It is a schematic sectional drawing which shows the 2nd process of the formation method (electronic device manufacturing method) using the photomask in one embodiment of this invention. It is a schematic sectional drawing which shows the 3rd process of the formation method (electronic device manufacturing method) using the photomask in one embodiment of this invention. It is a schematic sectional drawing which shows the 4th process of the formation method (electronic device manufacturing method) using the photomask in one embodiment of this invention. It is a schematic sectional drawing which shows the 5th process of the formation method (electronic device manufacturing method) using the photomask in one embodiment of this invention. It is the schematic which shows a mode that the photomask in one embodiment of this invention was attached to the projection exposure apparatus. It is a top view which shows an example of the illumination stop used for quadrupole illumination. It is a figure of the illumination stop used for quadrupole illumination for demonstrating center (sigma) and radius (sigma). It is a top view which shows the mask pattern which arrange | positions an opening part and a light-shielding part in a halftone phase shift film so that a checkered pattern may be made in planar view, and does not form a halftone phase shift part. It is a figure which shows the optical image calculated | required by the optical image calculation at the time of imaging the mask pattern shown in FIG. It is a top view which shows the structure of the mask pattern which has the halftone phase shift part of an isolation arrangement. It is a figure which shows the optical image calculated | required by the optical image calculation at the time of imaging the mask pattern shown in FIG. It is the figure which showed the distribution of the light intensity (Relative Intensity) in the position (Horizontal Position) which passes the bright point image of the optical image obtained from the mask pattern shown in FIG. 17 as a parameter. It is the figure which plotted the dimension of the bright spot image of the optical image obtained from the mask pattern shown in FIG. 17, ie, Image CD (Critical Dimension), with respect to the focus, and uses the slice level (amount inversely proportional to the exposure amount) as a parameter. FIG. It is a top view which shows the structure of the mask pattern which has a halftone phase shift part of a dense arrangement. It is a figure which shows the optical image calculated | required by the optical image calculation at the time of imaging the mask pattern shown in FIG. It is the figure which showed the distribution of the light intensity in the position which passes through the several bright point image of the optical image obtained from the mask pattern shown in FIG. 21 as a parameter. It is the figure which plotted the dimension of the bright spot image of the optical image obtained from the mask pattern shown in FIG. 21, ie, Image CD, with respect to a focus, and showed the slice level as a parameter.

Explanation of symbols

  CR condenser lens, DL diagonal line, FR fly-eye lens, HL horizontal line, HP1, HP2 hole pattern, HT halftone phase shift film, HTP halftone phase shift part, IA illumination stop, IAa transmission part, LP lattice point, LS light shielding Film, OP opening, PF film to be processed, PM photomask, PR photoresist, PR1, PR2 projection lens, SB base substrate, SP light shielding unit, TS transparent substrate, UL unit lattice, VL vertical line, WA substrate.

Claims (9)

A transparent substrate;
A halftone phase shift film formed on the transparent substrate and having a plurality of openings;
A light shielding film formed on the halftone phase shift film and forming a plurality of light shielding portions;
The halftone phase shift in which a specific lattice point among a plurality of lattice points of the lattice is exposed from the light shielding film when a lattice formed by intersecting a plurality of vertical lines and a plurality of horizontal lines in a plan view is assumed. By leaving the halftone phase shift film without opening the film as a halftone phase shift portion, and the halftone phase shift film is formed in a portion other than the plurality of lattice points,
The opening is formed in each of the four lattice points adjacent in the diagonal direction of the unit lattice with respect to the specific lattice point that is the halftone phase shift portion,
The light-shielding portion is formed at each of two lattice points adjacent in the vertical line direction and two lattice points adjacent in the horizontal line direction with respect to the specific lattice point that is the halftone phase shift portion. A photomask.   The photomask according to claim 1, wherein the transmittance of the halftone phase shift film is 10% or more and 30% or less. A plurality of halftone phase shift units including the halftone phase shift unit , and a distance between two halftone phase shift units disposed closest to each other among the plurality of halftone phase shift units is a lattice pitch; The photomask according to claim 1 or 2, wherein the photomask is twice or more.   The light-shielding part adjacent to the halftone phase shift part and the light-shielding part not adjacent to the halftone phase shift part have different shapes in plan view. The photomask described.   Among the light shielding portions adjacent to the halftone phase shift portion, the light shielding portions adjacent to the two halftone phase shift portions and the light shielding portion adjacent to the one halftone phase shift portion are in a plan view. The photomask in any one of Claims 1-4 which has a mutually different shape. The process of forming a bright spot image in the position of the said halftone phase shift part by exposing the positive type photoresist on a board | substrate with the exposure light which illuminated the said photomask in any one of Claims 1-5. When,
Forming a hole pattern in a portion where the light spot image of the photoresist is exposed by developing the exposed photoresist.   When the lattice pitch is P, the wavelength of the exposure light is λ, and the numerical aperture of the exposure system is NA, the lattice pitch P is 0.6 × λ / NA <P <0.7 × λ / NA. The method of forming a pattern according to claim 6, wherein the pattern is satisfied.   The pattern forming method according to claim 6 or 7, wherein illumination applied to the exposure is quadrupole illumination.   The manufacturing method of an electronic device which manufactures an electronic device with the pattern formation method in any one of Claims 6-8.

Images