JP3737193B2 - Pattern correction method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photomask pattern correcting method, and more particularly to a photomask pattern correcting method for correcting a defect or the like of a mask pattern formed on a photomask to obtain a normal mask pattern.
[0002]
[Prior art]
A mask pattern of a photomask called a reticle is made of a chrome film and is created by using a photolithography technique. When the mask pattern is formed, as shown in FIG. 3, in addition to the chrome film to be left as a regular mask pattern, Unnecessary chromium film residues (black defects) may remain. Since the chromium film residue is transferred as it is and causes defects in wiring and contact holes, it must be removed.
[0003]
In such a case, the reticle is reproduced by removing only the defective chromium film residue by laser irradiation or FIB (Focused Ion Beam) irradiation without recreating the reticle from the beginning.
In the case of laser irradiation, as shown in FIGS. 6A and 6B, the chromium film 3 is heated and evaporated by irradiating the chromium film residue 3 in the defective portion with laser light.
[0004]
In the case of FIB irradiation, as shown in FIG. 7A, the chromium film residue 3 is physically skipped by colliding metal ions with the defective chromium film residue 3 shown in FIG. 6A. In this case, metal ions are implanted into the surface layer of the transparent substrate 1, but the implanted layer 5 decreases the transmittance of exposure light, and therefore, as shown in FIG. By irradiating the FIB in the contained gas), only that portion is etched and removed.
[0005]
[Problems to be solved by the invention]
However, in the case of laser irradiation, as shown in FIG. 6 (b), the transparent substrate 1 is also evaporated by heat for evaporating the chromium film residue 3, and a concave portion 4a is formed on the surface thereof. The thickness of 1 is thinner than the other parts. Also in the case of FIB irradiation, as shown in FIG. 7 (b), a recess 4b is formed in the trace from which the metal ion implantation layer 5 is removed, and the thickness of the transparent substrate 1 is smaller than that of the other portions. It is getting thinner.
[0006]
By the way, in order to cope with the miniaturization of the pattern, when the exposure light for transferring the pattern is also shortened and i-line (366 nm) and g-line (254 nm) are used, a slight amount of the surface of the transparent substrate of the reticle is slightly increased. Unevenness causes scattering of exposure light. In addition, slight variations in the overall thickness of the transparent substrate 1 cause a phase shift or focus shift of the exposure light transmitted through the transparent substrate 1. These cause problems such as abnormalities in the cross-sectional shape of the mask on the conductive film and the insulating film, and reduce the dimensional accuracy of the mask.
[0007]
The present invention was created in view of the above-described problems of the conventional example, and is a reticle that can suppress irregularities on the surface of the transparent substrate and fluctuations in the thickness of the transparent substrate caused by correcting the pattern on the reticle. A pattern correction method is provided.
[0008]
[Means for Solving the Problems]
The above-mentioned problem is the first aspect of the present invention, when there is an unnecessary light-shielding film residue on the transparent substrate after the light-shielding film pattern is formed on the transparent substrate, the portion not covered with the pattern and the light-shielding film residue Etching the transparent substrate, retreating the surface, removing the light shielding film residue, partially removing the surface layer of the transparent substrate from which the light shielding film residue was removed, and retreating the surface And a pattern correction method comprising the step of substantially matching the height of the surface with the height of the surface retreated by the etching,
The step of removing the light shielding film residue according to the second invention is a method of irradiating a laser beam and evaporating the light shielding film residue by heat, and the pattern correction method according to the first invention Solved by
The step of removing the light shielding film residue, which is a third aspect of the invention, is to irradiate a focused ion beam and cause particles to collide with the light shielding film residue to be scattered. Is solved by the pattern correction method of
In the fourth aspect of the invention, the step of partially removing the surface layer of the transparent substrate from which the light shielding film residue has been removed includes irradiating the transparent substrate from which the light shielding film residue has been removed with laser light, Solved by the pattern correction method according to any one of the first to third inventions, wherein the surface layer is partially evaporated,
The step of partially removing the surface layer of the traced transparent substrate from which the light shielding film residue has been removed is a fifth aspect of the invention, in which a focused ion beam is applied to the traced transparent substrate from which the light shielding film residue has been removed in a fluorine-containing gas. This is solved by the pattern correction method according to any one of the first to third inventions, wherein the surface layer is partially removed by irradiation and etching.
[0009]
In the pattern correction method of the present invention, the surface of the transparent substrate that is not covered with the pattern and the light shielding film residue is etched in advance before the defect is corrected.
In the subsequent defect correction, as one method, laser light is irradiated and the light shielding film residue is evaporated by the heat. In this case, simultaneously with the residue of the light shielding film, a part of the transparent substrate under the residue is also evaporated so that the height of the surface coincides with the height of the surface that has been retracted in advance. As another method, a focused ion beam is irradiated, and the light shielding film residue is physically scattered. In this case, since the light shielding film residue is only removed, the transparent substrate of the removal trace remains as it is. Thereafter, the surface layer of the transparent substrate as a removal trace is removed, and the height of the surface is made to coincide with the height of the surface that has been retracted in advance.
[0010]
As a result, in any case, the surface of the transparent substrate in the portion not covered with the pattern becomes substantially flat after the defect is corrected, so that the thickness of the transparent substrate in that portion does not change depending on the location and is uniform. Become.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
(1) First Embodiment of the Present Invention The left side of FIGS. 1A to 1C is a sectional view showing a reticle pattern correcting method according to the first embodiment of the present invention. . 1A and 1C are plan views, and a sectional view taken along line II-II corresponds to a sectional view on the left side. Further, FIG. 3 shows a flowchart of a reticle pattern correcting method. In this method, defects are corrected by irradiation with laser light and reproduced.
[0012]
First, a transparent substrate 11 made of a quartz plate having a size of 5 × 5 inches and a thickness of 2.3 mm is prepared (P1), and a chromium film (light shielding film) having a film thickness of about 100 nm is formed thereon.
Next, after forming a photoresist film on the chromium film, the wiring pattern is transferred. Subsequently, the photoresist film is developed using a developing solution to form a mask (not shown).
[0013]
Next, according to the mask, the chromium film is etched using carbon tetrachloride gas to leave a chromium film 12 corresponding to the reticle pattern as shown in FIG. 1A (P2). At this time, it is assumed that an unnecessary chromium film residue (light shielding film residue, black defect) 13 is left in addition to the chromium film (pattern) 12 to be left.
Next, a defect inspection of the reticle pattern is performed (P3). Since there is a chromium film residue 13, as shown in FIG. 1B, the pattern 12 and the chromium film residue 13 are not covered by the dry etching using an aqueous solution of hydrofluoric acid or CF ₄ gas (etching species). The surface layer 14 of the substrate 11 is removed by a thickness of about 40 nm (P4). This thickness of 40 nm corresponds to the thickness at which the transparent substrate 11 is evaporated at the same time when the chromium film residue 13 is evaporated by heat in a later step. The portion of the transparent substrate 11 covered with the chromium film 12 and the chromium film residue 13 remains without being etched.
[0014]
Next, in order to correct the pattern, as shown in FIG. 1C, laser beam with an output of 5 mJ is irradiated to heat and evaporate the unnecessary chromium film residue 13 (P5). At this time, a laser beam having a minimum energy necessary for evaporating the chromium film residue 13 is irradiated for a time necessary for removing the transparent substrate 11a having a thickness equal to the thickness of the surface layer 14 previously removed. To do. Thereby, the unnecessary chromium film 13 is removed, and the transparent substrate 11a under the unnecessary chromium film residue 13 is also evaporated by the heat of about 40 nm. For this reason, since the surface of the transparent substrate 11a substantially coincides with the surface of the transparent substrate 14 that has been removed in advance, the surface of the transparent substrate 11 that is not covered with the pattern 12 is substantially flat. In addition, since the surface of the transparent substrate 11 is flattened, the thickness of the transparent substrate 11 in a portion not covered with the pattern 12 does not change depending on the location and becomes uniform. In FIG. 4, 21 is a laser light source, 22 is a lens system for focusing the laser beam or focusing on the surface of the transparent substrate 11, and 23 is a mounting table for the reticle 10.
[0015]
Thereafter, other inspections such as dimensional inspection and arrangement accuracy are performed (P6). If there is no defect, the manufacture of the reticle 10 is completed.
As described above, according to the first embodiment, the surface layer of the transparent substrate 11 that is not covered with the chromium film 12 and the chromium film residue 13 is etched in advance before the defect is corrected, and the surface is retreated. Therefore, the unevenness of the surface of the transparent substrate 11 in the portion not covered with the pattern 12 after the defect correction is flattened. In particular, when the thickness of the surface layer of the transparent substrate 11 to be etched is made substantially equal to the thickness of the surface layer of the transparent substrate 11 to be removed at the time of defect correction, the surface becomes substantially flat, and the thickness of the transparent substrate 11 It becomes uniform regardless of the location.
[0016]
Accordingly, when a wiring pattern or the like is transferred onto a semiconductor substrate using this reticle, the exposure light is scattered on the surface of the reticle transparent substrate 11 even if the exposure light is shortened in order to cope with the miniaturization of the pattern. In addition, it is possible to suppress the occurrence of a phase shift or a focus shift of the exposure light transmitted through the transparent substrate 11. Accordingly, it is possible to prevent a decrease in the dimensional accuracy of the resist mask formed on the object to be patterned.
[0017]
In the first embodiment, the laser beam is used to correct the defect and remove the surface layer of the transparent substrate by a necessary thickness after the defect correction. However, the surface layer of the transparent substrate after the defect correction is used. The removal may be performed by irradiating a focused ion beam in a fluorine-containing gas. In this case, the surface layer of the transparent substrate has already been removed to some extent after the defect has been corrected by laser light irradiation, but further fine adjustment of the etching amount is required to align the height of the surface with the height of the surface that has been retracted in advance. It can be carried out.
[0018]
(2) Second Embodiment of the Present Invention FIGS. 2A and 2B are cross-sectional views showing a reticle pattern correcting method according to a second embodiment of the present invention. 2A and 2B are plan views, and a sectional view taken along line II-II corresponds to a sectional view on the left side. In this method, defects are corrected by FIB irradiation and reproduced. This will be described with reference to the flowchart of FIG.
[0019]
Assume that the steps P1 to P4 in FIG. 3 have already been completed, and there is an unnecessary chromium film residue 13 in addition to the pattern 12. The steps from P1 to P4 in FIG. 3 are the same as the steps shown in FIGS. 1A and 1B of the first embodiment, and thus description thereof is omitted.
Next, using the FIB apparatus shown in FIG. 5, as shown in FIG. 2A, the defect portion is irradiated with a metal ion beam having a beam current density of 1 A / cm ² , and the chromium film residue 13 is physically scattered. (P5). At this time, metal ions are implanted into the surface layer of the transparent substrate 11. In FIG. 5, 31 is a metal ion source, and beryllium (Be ⁺ ), boron (B ⁺ ), aluminum (Al ⁺ ), silicon (Si ⁺ ), gallium (Ga ⁺ ), etc. are used as metal ions. . Reference numeral 32 denotes a lens system for focusing the beam or focusing on the surface of the transparent substrate 11, and 33 is a mounting table for the reticle 10.
[0020]
Subsequently, in order to remove the metal ion implantation layer 15, XeF ₂ gas (fluorine-containing gas) is introduced onto the transparent substrate 11 and irradiated with a metal ion beam. As a result, the fluorine active species are separated from the XeF ₂ gas, and only the beam irradiation region of the transparent substrate 11 begins to be etched. At this time, the beam irradiation time is adjusted so that the transparent substrate 11a having a thickness equal to the thickness of the surface layer 14 removed in the step of FIG. As a result, the transparent substrate 11a under the chrome film residue 13 is removed by about 40 nm, and the surface of the transparent substrate 11a substantially coincides with the surface of the transparent substrate 14 previously removed. The surface of 11 becomes flat. In addition, since the surface of the transparent substrate 11 is flattened, the thickness of the transparent substrate 11 in a portion not covered with the pattern 12 does not change depending on the location and becomes uniform.
[0021]
Thereafter, another inspection similar to that of the first embodiment is performed (P6), and if there is no defect, reticle fabrication is completed.
As described above, according to the second embodiment, before removing the chromium film residue 13 by irradiation with the metal ion beam, the transparent substrate 11 is previously provided by the thickness for removing the metal ion implantation layer 15. The surface layer 14 is removed, and the surface is receded. For this reason, the surface of the transparent substrate 11 that is not covered with the pattern 12 after the metal ion implantation layer 15 is removed becomes substantially flat, and the thickness of the transparent substrate 11 becomes uniform regardless of the location.
[0022]
Accordingly, when a wiring pattern or the like is transferred onto a semiconductor substrate using this reticle, the exposure light is scattered on the surface of the reticle transparent substrate 11 even if the exposure light is shortened in order to cope with the miniaturization of the pattern. In addition, it is possible to suppress the occurrence of a phase shift or a focus shift of the exposure light transmitted through the transparent substrate 11. Accordingly, it is possible to prevent a decrease in the dimensional accuracy of the resist mask formed on the object to be patterned.
[0023]
In the second embodiment, XeF ₂ gas is used as the fluorine-containing gas, but the present invention is not limited to this.
In the step of FIG. 2B, the surface layer is removed by etching by irradiating the transparent substrate where the light shielding film residue is removed in the fluorine-containing gas with a focused ion beam. In this case, defect correction and metal ion implantation layer removal can be performed in the same focused ion beam apparatus, but in some cases, they may be performed in separate apparatuses. That is, defect correction is performed using a focused ion beam, and then the surface layer of the transparent substrate is removed using a laser beam.
[0024]
Further, in the above description, a reticle is used as a photomask. However, the present invention is not limited to this, and can be applied to anything as long as a light shielding film is formed on a transparent substrate. .
[0025]
【The invention's effect】
As described above, in the pattern correction method of the present invention, before the defect is corrected, the surface of the transparent substrate that is not covered with the pattern and the light shielding film residue is etched in advance to recede the surface, and after the defect is corrected. The receding surface is made to substantially coincide with the surface receded by etching in advance. Therefore, after the defect is corrected, the surface of the portion of the transparent substrate that is not covered with the pattern becomes substantially flat, and the thickness of the transparent substrate in that portion does not change depending on the location, and becomes uniform.
[0026]
Thereby, scattering of the exposure light on the surface of the transparent substrate can be prevented, and a phase shift and a focus shift of the exposure light transmitted through the transparent substrate can be prevented. Therefore, when the mask is formed by transferring the photomask pattern to the photoresist formed on the conductive film or the insulating film by exposure, the cross-sectional shape of the mask is made normal and the dimensional accuracy of the mask is improved. Can do.
[Brief description of the drawings]
FIGS. 1A to 1C are a cross-sectional view and a plan view showing a reticle pattern correcting method according to a first embodiment of the present invention.
FIGS. 2A and 2B are a cross-sectional view and a plan view showing a reticle pattern correcting method according to a second embodiment of the present invention.
FIG. 3 is a flowchart showing a reticle pattern correction method according to an embodiment of the present invention;
FIG. 4 is a schematic diagram showing a laser beam irradiation apparatus used in a reticle pattern correction method according to an embodiment of the present invention.
FIG. 5 is a schematic diagram showing a focused ion beam irradiation apparatus used in a reticle pattern correction method according to an embodiment of the present invention.
6A and 6B are a sectional view and a plan view showing a reticle pattern correcting method according to a conventional example.
7A and 7B are a cross-sectional view and a plan view showing a reticle pattern correcting method according to another conventional example.
[Explanation of symbols]
10 reticle,
11, 11a transparent substrate,
12 Chromium film (pattern) to be left
13 Unnecessary chromium film (light-shielding film residue, black defect),
14 Surface removed previously,
15 Metal ion implantation layer,
21 laser light source,
22, 32 lens system,
23, 33 mounting table,
31 Metal ion source.

Claims (5)

After the pattern of the light shielding film is formed on the transparent substrate, when there is an unnecessary light shielding film residue on the transparent substrate, the transparent substrate in the portion not covered with the pattern and the light shielding film residue is etched and the surface is retracted. A process of
Removing the light shielding film residue;
Removing the surface layer of the transparent substrate from which the light-shielding film residue has been removed, retreating the surface thereof, and making the height of the surface substantially coincide with the height of the surface retreated by the etching The pattern correction method characterized by this. The pattern correction method according to claim 1, wherein the step of removing the light shielding film residue includes irradiating a laser beam and evaporating the light shielding film residue by heat. The pattern correction method according to claim 1, wherein the step of removing the light shielding film residue includes irradiating a focused ion beam to cause particles to collide with the light shielding film residue to be scattered. The step of partially removing the surface layer of the transparent substrate from which the light shielding film residue has been removed includes irradiating the transparent substrate from which the light shielding film residue has been removed with laser light, and partially evaporating the surface layer by heat. The pattern correction method according to claim 1, wherein the pattern correction method is a method. The step of partially removing the surface layer of the transparent substrate from which the light-shielding film residue has been removed includes irradiating the surface of the transparent substrate from which the light-shielding film residue has been removed in a fluorine-containing gas with a focused ion beam and etching the surface layer. 4. The pattern correcting method according to claim 1, wherein the pattern is partially removed.

Images