JP4122563B2 - Method for correcting circuit pattern portion of photomask - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for correcting a residual defect in a circuit pattern portion of a photomask used in an exposure apparatus (stepper or the like) in a lithography process when manufacturing a semiconductor device.
[0002]
[Prior art]
Correction of residual defects in circuit pattern portions in current photomasks is performed as follows.
[0003]
(1) First, the FIB (Focused Ion Beam systems) correction technique will be described. As the FIB correction device, there are devices such as those manufactured by Seiko Electronics Industry Co., Ltd. and Micron (USA).
[0004]
As shown in FIG. 4, the FIB correction apparatus includes an ion source 1, a lens 1 </ b> A for focusing an ion beam, an electron gun 2, and a process gas gun 3.
[0005]
The removal of the circuit pattern portion physically removes the circuit pattern portion by emitting a Ga (gallium) ion beam 1B from one portion of the ion source and scanning the ion beam to the circuit pattern region to be removed.
[0006]
The electrons emitted from the electron gun 2 are irradiated to suppress ion beam drift (positional deviation). Since the Ga ion beam 1B emitted from one part of the ion source has a positive charge, the surface of the quartz substrate part 4 is charged with a positive potential by irradiating the quartz substrate part 4 of the insulator with the ion beam. Therefore, when ion beam irradiation is continued, ion beam drift occurs. The electrons emitted from the electron gun 2 electrically neutralize the surface of the quartz substrate portion 4 for the purpose of suppressing beam drift.
[0007]
The process gas gun 3 is not used when residual defects are corrected.
[0008]
(2) Next, a laser correction technique will be described. As the laser correction device, there is a device manufactured by Quantronix (USA) or NEC Corporation.
[0009]
The laser correction apparatus shown in FIG. 5 uses an Nd / YAG laser.
[0010]
A method for removing the circuit pattern portion will be described below. The circuit pattern portion (Cr portion) 13 in the region irradiated with the laser 11 absorbs the irradiated light energy and converts it into thermal energy. The converted thermal energy becomes energy for melting and evaporating the circuit pattern portion (Cr portion) 13. Therefore, the circuit pattern portion (Cr portion) 13 is removed by melting and evaporating. In FIG. 5, 12 is a mirror and 14 is a quartz substrate.
[0011]
[Problems to be solved by the invention]
(1) In the FIB correction technique, when a photomask is irradiated with an ion beam, Cr secondary ions from Cr forming a circuit pattern portion and Si secondary ions from a quartz substrate portion which is a light transmitting portion are generated. . The channeltron for counting the type and number of ions is composed of a Cr secondary ion generated at the time of ion beam irradiation, a Si secondary ion is detected by a channeltron for detecting a Cr secondary ion, and a channeltron for detecting a secondary ion of Si. Count the type and number of ions. The data obtained by counting the number of each ion is taken into a computer and used to create an image image of the photomask using the ion beam irradiation position and the number of secondary ions.
[0012]
However, the above-described FIB correction technique has the following problems.
[0013]
(A) When there are residual defects in the circuit pattern portion, the number of Cr secondary ions for creating an image by a computer can be counted if the film thickness of the residual defect portion is approximately the same as that of the circuit pattern portion. . However, when the number of Cr secondary ions from the residual defect portion is small, that is, when the film thickness of the residual defect portion is a thin film with respect to the circuit pattern portion (halftone defect), the detection and decomposition capability of the channeltron and the computer Due to the limitations of the image processing resolution capability, it is difficult to recognize the shape of the residual defect in the image image of the photomask.
[0014]
(B) In a DRAM with 64 Mb quality requirements regarding the size of defects existing on the photomask, a 0.35 to 0.3 μm DRAM and a 256 Mb DRAM require a 0.25 to 0.2 μm level defect correction. The
[0015]
However, it is difficult to confirm the residual defect portion of the fine image size of the photomask due to the limit of the resolution capability of computer image processing.
[0016]
(C) Quartz is usually used as the substrate material for the light transmitting portion of the photomask. The FIB correction technique is a method of physically removing a defective portion by irradiating an ion beam to a region where the defective portion of the circuit pattern portion is removed and performing beam scanning. Accordingly, Ga ions are implanted into the region irradiated with the ion beam, and the substrate surface is physically sputtered by the ion beam, so that the roughness of the substrate surface is deteriorated.
[0017]
That is, at the time of exposure, the light intensity of the defect correction portion is low because the surface roughness of the defect correction portion is poor. Therefore, at the time of transfer, the defect correcting portion is transferred with the same shape as when a defect exists.
[0018]
(D) The FIB correction technique is a method in which beam scanning is performed only in a region where a defective portion of a circuit pattern portion is removed, and is physically removed. The boundary between the region scanned with the ion beam (residual defective portion of the circuit pattern portion) and the region not scanned (quartz substrate portion) is because the region scanned with the ion beam is physically sputtered. A gap is formed at the boundary (generic name: river bed). This river bed is transferred in the same manner as the defective portion.
(2) Problems in Laser Technology The observation method of this device is an observation method using an optical microscope, unlike the photomask circuit pattern confirmation method image image in the FIB correction device. In addition, reflected light and transmitted light can be used for illumination during observation. In other words, the observation method of the correction apparatus can directly observe the residual defect in the circuit pattern portion.
[0019]
Therefore, even when a Cr thin film is present in a defect defect portion that is a problem in the FIB correcting apparatus (halftone defect), it can be confirmed by using reflected light and transmitted light.
[0020]
However, this laser correction device has the following problems.
[0021]
(A) At the time of setting the laser irradiation region, Nd • YAG laser (λ: 532 nm), that is, light is used as the light source, so the setting of the irradiation region is limited to several microns or more. That is, when the residual defect area is at the submicron level, the irradiation area cannot be set, and the defect cannot be corrected.
[0022]
(B) The correction by this apparatus is performed by melting and evaporating the residual defect portion by laser light. However, when the pattern edge portion is corrected, a bulge of several hundreds of ridges is formed on the pattern edge portion irradiated with the laser. That is, the raised portion of the pattern edge portion becomes a factor that deteriorates the correction accuracy. Incidentally, when the processing accuracy of the laser correction method and the FIB correction method are compared, the correction accuracy by the laser correction method is worse.
[0023]
(C) Correction by this apparatus uses a laser. That is, the laser irradiation area depends on the laser intensity distribution (Gaussian distribution). Therefore, as the laser irradiation area of the correction portion becomes larger, the laser intensity decreases outside (peripheral portion) of the laser irradiation region. As a result, the defect portion outside (peripheral portion) of the laser irradiation region does not completely evaporate but is scattered or altered in the peripheral portion. The defect portion that has been scattered or altered becomes a new residual defect portion.
[0024]
The present invention eliminates the above-described problems and utilizes the advantages of the FIB correction method and the laser correction method to accurately detect a defective portion and improve the defect correction accuracy. It is an object to provide a method for correcting parts.
[0025]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
[ 1 ] In a method of correcting a pattern residual defect portion existing in a circuit pattern portion of a photomask, a carbon film which covers the circuit pattern portion excluding the residual defect portion and exposes a quartz substrate portion in a pattern edge region including the residual defect portion And a step of correcting the residual defect portion by irradiating the residual defect portion region with a laser.
[0026]
[ 2 ] In a method of correcting a pattern residual defect portion existing in a circuit pattern portion of a photomask, a step of forming a new residual defect portion using a carbon film on a circuit pattern portion including the residual defect portion and a quartz substrate portion; And a step of correcting the new residual defect portion by irradiating the residual defect portion region with a laser.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0028]
The correction method of the present invention is superior in the correction accuracy of the residual defect portion, which is an advantage of the FIB correction device, as compared with the laser correction device, and a circuit pattern by a direct observation method using an optical microscope, which is an advantage of the laser correction method. The observation (detection) of the residual defect part of the part is superior to the FIB correction device, and the defect part of the circuit pattern part does not evaporate completely as the laser irradiation area becomes wide, Scattered or altered in the part, but skillfully captures the point that if the carbon film (carbon thin film) formed with the FIB correction device is irradiated with laser, it can be removed around the defective part of the circuit pattern part without being scattered or altered Thus, the circuit pattern portion of the photomask can be corrected.
[0029]
First, a reference example of the present invention will be described.
[0030]
FIG. 1 is a process chart for correcting a circuit pattern portion of a photomask showing a reference example of the present invention.
[0031]
(1) First, as shown in FIG. 1A, the circuit pattern portion 21 formed on the quartz substrate portion 20 has a residual defect (edge residual defect) portion 22. That is, a residual defect (edge residual defect) portion 22 exists outside the circuit pattern portion 21. The size of the residual defect (edge residual defect) 22 is X: 0.3 μm and Y: 0.3 μm. This edge residual defect portion 22 cannot be detected from the computer image of the FIB correction apparatus.
[0032]
(2) Next, as shown in FIG. 1B, a region 23 overlapping with the edge residual defect portion 22 is set using a laser correction device (DRS-II: manufactured by Quantronix and SL453C: manufactured by NEC). To do.
[0033]
(3) Next, as shown in FIG. 1C, the edge residual defect portion 22 is changed to a new defect portion 24 by irradiation with an Nd / YAG laser. The new defect defect portion 24 was set to X: 1.6 μm and Y: 0.7 μm. The size of the new defect part 24 is the size that can be recognized by the computer image in the FIB correction apparatus, the size that can be corrected, and the shape of the new defect part that does not affect the design shape of the circuit pattern part. Considering that there is no limitation on the size and shape of the new defect defect.
[0034]
(4) Next, as shown in FIG. 1 (d), a photomask is set in the FIB correction device (SIR-1000: manufactured by Seiko Denshi Kogyo) and correction is performed. First, the FIB deposition region 25 in which the carbon film is formed on the new defect portion 24 of the circuit pattern portion 21 is determined. In the FIB deposition area 25, the shape and area for forming a carbon film as a correction film on the computer image image of the FIB correction apparatus are set. The FIB deposition region 25 was set so that the new defective defect portion 24 in the circuit pattern portion can be corrected by one time.
[0035]
(5) Next, as shown in FIG. 1 (e), 1300 膜 of carbon film 26 is formed in the FIB deposition region 25. The carbon film 26 to be formed is exposed in an exposure apparatus (stepper or the like) in a lithography process. As long as it is a thin film capable of blocking light source and light intensity, the film thickness value is not relevant.
[0036]
(6) Finally, the light-shielded image of the circuit pattern portion was observed using the transmitted light of the optical microscope (manufactured by Nikon). As a light source of the optical microscope, a mercury lamp was used, and the wavelength was set near (λ: 365 nm) and near the light source wavelength at the time of transfer by a modulation filter. As shown in FIG. 1 (f), the microscopic observation result confirmed that the transferred image was equivalent to a state in which there was no residual defect portion in the circuit pattern portion.
[0037]
In this way, the laser is irradiated to the region overlapping the edge residual defect portion of the circuit pattern portion, so that the edge residual defect portion becomes a new defect defect portion. Thereafter, a carbon film is formed as a light-shielding film on the new defective defect portion of the circuit pattern portion.
[0038]
As described above, according to the reference example, by making the edge residual defect part of the circuit pattern part a new defect defect part,
1. In the image image of the FIB correction apparatus, it becomes possible to detect a defective portion and a position that cannot be detected (confirmed).
[0039]
2. By using the FIB correction device as a tool for correcting minute edge residual defects in the circuit pattern portion, the defect defect accuracy is improved by making the correction film a carbon film by performing the edge defect defect portion with the FIB correction device. It is possible to obtain a good defect-corrected portion with excellent cleaning resistance.
[0040]
3. The existing correction device can be applied as a method for correcting a minute edge residual defect portion of the circuit pattern portion, and the minute edge residual defect portion of the circuit pattern portion can be easily corrected.
[0041]
Next, a first embodiment of the present invention will be described.
[0042]
In this embodiment, the difference in thermal characteristics between Cr, which is the material of the circuit pattern portion, and the carbon film formed by the FIB correction device is used. When the residual defect at the edge of the circuit pattern portion is corrected by the laser correcting device, it can be corrected with high accuracy.
[0043]
Here, Cr as the material of the circuit pattern portion is formed by the FIB correction device with respect to the thermal characteristics of melting point: 2670 ° C., heat of fusion: 14.6 KJ / mol, and thermal conductivity: 90.3 W / m · K. The carbon film has heat resistance in terms of thermal properties: sublimation point: 3370 ° C., sublimation heat: 715 KJ / mol, thermal conductivity: 100 to 130 W / m · K.
[0044]
When the residual defect existing at the edge of the circuit pattern portion is removed by laser correction, the pattern edge portion obtains thermal energy by laser irradiation. Excitement).
[0045]
Therefore, the shape of the edge portion of the circuit pattern changes. That is, the correction accuracy is deteriorated. Therefore, a correction method in which the edge shape at the time of laser irradiation is not disturbed by forming the carbon film formed by the FIB correction apparatus on a part of the circuit pattern portion will be described below.
[0046]
FIG. 2 is a modification process diagram of the circuit pattern portion of the photomask showing the first embodiment of the present invention.
[0047]
(1) First, as shown in FIG. 2A, the circuit pattern portion 31 formed on the quartz substrate portion 30 has a residual defect (edge residual defect) portion 32. That is, the residual defect (edge residual defect) portion 32 exists outside the circuit pattern portion 31. The size of the residual defect (edge residual defect) portion 32 is X: 0.3 μm and Y: 0.3 μm. This edge residual defect portion could not be detected from the computer image of the FIB correction apparatus.
[0048]
(2) Next, as shown in FIG. 2 (b), after setting a photomask on the FIB correction device (SIR-1000: manufactured by Seiko Electronics Industry), a circuit pattern including the edge residual defect portion 32 of the circuit pattern portion 31 An FIB deposition region 33 for forming a carbon film is determined in the edge region of the portion 31. In the FIB deposition region 33, the shape and region for forming a carbon film as a correction film were set on the computer image image of the FIB correction device.
[0049]
The setting of the correction area includes the size that can be set in the computer image of the FIB correction device, the size that can form a carbon film on the shared edge portion in the regular circuit pattern portion and the edge residual defect portion 32, and the circuit pattern portion 31. Considering that the shape does not affect the shape of the carbon film, there are no restrictions on the size and shape of the region where the carbon film is formed.
[0050]
(3) Next, as shown in FIG. 2C, a carbon film 34 was formed in a thickness of 1000 mm in the FIB deposition region 32 using an FIB correction device. In this correction, the carbon film 34 is formed in a thickness of 1000 mm, but there is no problem as long as the carbon film to be formed has a thin film thickness that can be formed into a thin film by the FIB correction apparatus.
[0051]
(4) Next, as shown in FIG. 2 (d), a photomask is set on the laser correction device (DRS-II: manufactured by Quantronix and SL453C: manufactured by NEC), and Nd / YAG is formed in the edge residual defect region. A region 35 for laser irradiation is set. The region 35 to be irradiated with laser is not limited as long as it has a size and shape that does not affect the circuit pattern portion except that the region to be irradiated with laser is set on the edge portion of the regular circuit pattern.
[0052]
(5) Next, as shown in FIG. 2E, the region 35 to be irradiated with laser was irradiated with laser, and the residual defect portion 32 of the circuit pattern portion was removed.
[0053]
(6) Finally, the light-shielded image of the circuit pattern portion was observed using the transmitted light of the optical microscope (manufactured by Nikon). As a light source of the optical microscope, a mercury lamp was used, and the wavelength was set near (λ: 365 nm) and near the light source wavelength at the time of transfer by a modulation filter. As a result of microscopic observation, as shown in FIG. 2 (f), it was confirmed that the transferred image was equivalent to a state in which there was no residual defect portion in the circuit pattern portion.
[0054]
Thus, the carbon film is formed in the circuit pattern portion edge region including the edge residual defect portion of the circuit pattern portion. Thereafter, the edge residual defect portion area of the circuit pattern portion is irradiated with laser to remove the edge residual defect portion.
[0055]
As described above, according to the first embodiment, by forming the carbon thin film in the edge residual defect portion of the circuit pattern portion and the edge portion vicinity region of the circuit pattern portion,
1. In the laser correction device, the correction accuracy at the edge of the circuit pattern portion is improved.
[0056]
2. As a method of correcting the edge residual defect portion of the circuit pattern portion, the existing correction device can be applied, and the edge residual defect portion of the circuit pattern portion can be easily corrected.
[0057]
Next, a second embodiment of the present invention will be described.
[0058]
In this embodiment, a carbon film is formed in an area including a residual defect portion of a circuit pattern portion by an FIB correction device, a new residual defect is produced, and then the residual defect portion and the new residual defect are corrected by a laser correction device. is there.
[0059]
FIG. 3 is a modification process diagram of a circuit pattern portion of a photomask showing a second embodiment of the present invention.
[0060]
(1) First, as shown in FIG. 3A, the circuit pattern portion 41 formed on the quartz substrate portion 40 has a residual defect (edge residual defect) portion 42. That is, a residual defect (edge residual defect) portion 42 exists outside the circuit pattern portion 41. The size of the residual defect (edge residual defect) 42 is X: 0.3 μm and Y: 0.3 μm. This edge residual defect portion could not be detected from the computer image of the FIB correction apparatus.
[0061]
(2) Next, as shown in FIG. 3B, a photomask is set in an FIB correction device (SIR-1000: manufactured by Seiko Denshi Kogyo Co., Ltd.), and the circuit pattern portion including the edge residual defect portion 42 of the circuit pattern portion. 41 and an FIB deposition region 43 for forming a carbon film on the quartz substrate portion 40 is determined. The FIB deposition area 43 was set in the shape and area for forming a carbon film as a correction film on the computer image of the FIB correction apparatus.
[0062]
In addition, the setting of this correction area | region is the size which can be set in the computer image image of a FIB correction apparatus, the size which can form a carbon thin film in the edge part shared in a regular circuit pattern part and an edge residual defect part, and a circuit pattern part. Considering that there is no influence on the shape, there are no restrictions on the size and shape of the region where the carbon film is formed.
[0063]
(3) Next, as shown in FIG. 3C, 1000 Å of carbon film 44 was formed in the FIB deposition region 43. In this modification, 1000 カ ー ボ ン of carbon film 44 is formed. However, there is no problem as long as the formed carbon film 44 has a thin film thickness that can be formed into a thin film by the FIB correction apparatus.
[0064]
(4) Next, as shown in FIG. 3 (d), using a laser correction device (DRS-II: manufactured by Quantronix and SL453C: manufactured by NEC), a portion where the carbon film 44 is formed is formed on the Nd / YAG. A region 45 for laser irradiation is set. The area 45 to be irradiated with laser is the size, shape, and quartz for removing the edge residual defect portion 42 that does not affect the circuit pattern section 41 except that the area to be irradiated with laser is set on the edge section of the regular circuit pattern section 41. There is no limitation on the region to be irradiated as long as the size and shape of the region where the carbon film 44 is formed on the substrate unit 40 are removed.
[0065]
(5) Next, as shown in FIG. 3 (e), the region 45 where the laser film is irradiated is irradiated with the laser to thereby form the residual defect portion 42 of the circuit pattern portion 41 and the carbon film on the quartz substrate portion 40. Then, a modified carbon film region 46 is formed.
[0066]
(6) Finally, the light-shielded image of the circuit pattern portion 41 was observed using the transmitted light of the optical microscope (manufactured by Nikon). As a light source of the optical microscope, a mercury lamp was used, and the wavelength was set near (λ: 365 nm) and near the light source wavelength at the time of transfer by a modulation filter. As a result of microscopic observation, as shown in FIG. 3 (f), it was confirmed that the transferred image was equivalent to a state in which the circuit pattern portion 41 had no residual defect portion 42.
[0067]
In this manner, the carbon film is formed on the circuit pattern portion edge region including the edge residual defect portion of the circuit pattern portion and the quartz substrate portion. After that, the edge residual defect region and the new residual defect portion of the circuit pattern portion are irradiated with laser to remove the residual defect portion.
[0068]
As described above, according to the second embodiment, by forming the carbon film on the edge residual defect portion and the quartz substrate portion of the circuit pattern portion,
1. The laser correction device improves the correction accuracy at the edge of the circuit pattern portion.
[0069]
2. As a method of correcting the edge residual defect portion of the circuit pattern portion, the existing correction device can be applied, and the edge residual defect portion of the circuit pattern portion can be easily corrected.
[0070]
In the first and second actual施例has been described a circuit pattern correcting method of the photomask as an example, the circuit pattern correction technique of the present invention, the correction technique of the photomask of the liquid crystal panel wiring pattern modifications and forming technology It is also applicable to.
[0071]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
[0072]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
[0073]
( 1 ) According to the invention described in claim 1, by forming a carbon film in the edge residual defect portion of the circuit pattern portion and the edge vicinity region of the circuit pattern portion, in the laser correction device, the edge of the circuit pattern portion Correction accuracy is improved.
[0074]
Further, as a method for correcting the edge residual defect portion of the circuit pattern portion, the existing correction device can be applied, and the edge residual defect portion of the circuit pattern portion can be easily corrected.
[0075]
( 2 ) According to the invention described in claim 2 , the correction accuracy at the edge of the circuit pattern portion is improved by forming the carbon film on the edge residual defect portion of the circuit pattern portion and the quartz substrate portion by the laser correcting device.
[0076]
Further, as a method for correcting the edge residual defect portion of the circuit pattern portion, the existing correction device can be applied, and the edge residual defect portion of the circuit pattern portion can be easily corrected.
[Brief description of the drawings]
FIG. 1 is a correction process diagram of a circuit pattern portion of a photomask showing a reference example of the present invention.
FIG. 2 is a process chart for correcting the circuit pattern portion of the photomask according to the first embodiment of the present invention.
FIG. 3 is a correction process diagram of a circuit pattern portion of a photomask showing a second embodiment of the present invention.
FIG. 4 is a schematic diagram of an FIB correction apparatus.
FIG. 5 is a schematic view of a laser correction device.
[Explanation of symbols]
20, 30, 40 Quartz substrate part 21, 31, 41 Circuit pattern part 22, 32, 42 Residual defect (edge residual defect) part 23 Area overlapping with edge residual defect part 24 New defect defect part 25, 43 FIB deposition area 26 34, 44 Carbon film 33 FIB deposition area 35, 45 Laser irradiation area 46 Modified carbon film area

Claims (2)

In a method for correcting a pattern residual defect portion present in a circuit pattern portion of a photomask,
(A) forming a carbon film covering the circuit pattern portion excluding the residual defect portion and exposing the quartz substrate portion in a pattern edge region including the residual defect portion ;
(B) A method of correcting a circuit pattern portion of a photomask, comprising performing a step of correcting the residual defect portion by irradiating a laser to a residual defect portion region. In a method for correcting a pattern residual defect portion present in a circuit pattern portion of a photomask,
(A) forming a new residual defect portion using a carbon film on the circuit pattern portion including the residual defect portion and the quartz substrate portion;
(B) A step of correcting the new residual defect portion by irradiating a laser to the new residual defect portion region.

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