JP3154808B2 - Mask, mask repair apparatus and mask repair method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask and a focused ion beam irradiating apparatus which cause less damage due to focused ion beam irradiation.

[0002]

2. Description of the Related Art In a lithography process of a semiconductor device, a pattern is transferred to a resist on a silicon substrate by irradiating ultraviolet light or the like from above a photomask in which a metal pattern such as chromium is formed on a glass substrate.

[0003] However, the pattern of the photomask is not always perfect, and a white defect in which a part of the pattern is lost,
In many cases, a black defect or the like in which chromium remains in an unnecessary portion occurs.

A mask having such a defect needs to be repaired, and a black defect has conventionally been removed by a laser. However, in recent years, miniaturization of patterns has progressed, and there have been cases where laser resolution of about 1 μm cannot be used. In order to solve this problem, a mask is corrected using a focused ion beam (FIB) irradiation apparatus as shown in FIG. The FIB apparatus includes an ion beam generating and focusing mechanism 91 and a mask driving mechanism 93 that horizontally mounts the mask 92. An ion beam 96 is emitted from the central axis direction 95 of the ion beam generating and focusing mechanism 91 to the mask upper surface in a vertical direction. . FIGS. 10A and 10B schematically show a method of correcting a defect of a mask by the FIB. A black defect 23 occurs on the transparent substrate 21 on which the light-shielding pattern 22 is formed. The black defect 23 is vertically irradiated with an ion beam 96 from the focused ion beam apparatus shown in FIG.
3 is removed. However, at this time, in the region 24 below the black defect 23 on the transparent substrate 21, the density of the ions used in the FIB becomes high, and therefore, as shown in FIG. There is a problem that the transmittance of the removed portion is reduced.

On the other hand, after the correction by the FIB, the entire surface of the transparent region on the transparent substrate is subjected to plasma etching or FIB irradiation in a reactive gas atmosphere to thereby provide the above-described high-density ion layer. Is removed,
It is reported that the transmittance is almost the same as before the correction. However, adding the above steps to increase the transparency of the FIB irradiation area may cause a new white defect, and the introduction of the reactive gas may contaminate the apparatus and reduce the function, There is a problem that the system becomes complicated.

[0006]

In order to prevent a decrease in the transmittance of the ion irradiation region of the photomask after the correction by the FIB, a plasma etching process is performed after the FIB process, or the FIB irradiation is performed in a reactive gas atmosphere. When,
New white defects may occur. Furthermore, the introduction of the reactive gas causes problems such as contamination of the apparatus and deterioration of the function.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a photomask, a focused ion beam irradiation apparatus, and a repairing method which cause less damage after repair of a mask defect by focused ion beam irradiation. To provide.

[0008]

Means for Solving the Problems In order to solve the above problems, a first invention is to provide a translucent layer having a desired thickness and a desired transmittance formed on an upper layer of a transparent substrate, And a light-shielding film provided in the photomask.

The second invention has a mask driving mechanism for mounting a mask and an ion beam generating mechanism capable of irradiating an ion beam from a direction inclined at a desired angle from a normal direction of the mask. A mask repair apparatus using a focused ion beam is provided.

[0010]

When a transparent substrate is previously irradiated with ions of an appropriate type and the dose becomes a certain amount, a translucent layer is formed such that the change in light transmittance is saturated. In this translucent layer, F
When IB irradiation is performed, the dose of ions in the irradiation region increases, but the light transmittance is saturated, so that the light transmittance of the previously formed translucent layer does not decrease.

Further, the FIB is oblique to the mask.
Irradiation, the sputtering rate increases, and the depth of the region on the substrate into which ions are implanted becomes shallower. Therefore, FIB
Since the region where the ion density is high formed on the substrate surface by the irradiation becomes shallower than the case of the vertical irradiation, the decrease in the light transmittance of the FIB irradiation part can be reduced as compared with the case of the conventional vertical irradiation. . In addition, 25 from the normal direction of the mask
This effect becomes remarkable when FIB irradiation is performed at an angle of more than degrees.

[0012]

【Example】

 (Example 1)

The present embodiment will be described below in detail with reference to the drawings. In the case of correction by the FIB, according to the research of the inventor, the light transmittance of the transparent substrate of the photomask saturates at a certain value with respect to the ion implantation amount. FIG. 2 is a graph showing the relationship between the implantation amount of Ga ions and the transmittance of the substrate when the irradiation with FIB is performed with the acceleration voltage of Ga ions set to 30 kev. Dose 10 ¹⁷ ions / cm ² Above this, the light transmittance of the substrate becomes almost constant at about 80%.

Therefore, ions are implanted in advance into the transparent substrate to form a translucent layer having a density higher than the above value.
By correcting the mask by IB, even if the ion density in the FIB-irradiated portion increases, the light transmittance of the transparent substrate is saturated and does not decrease, and the light transmittance of the entire transmission region is kept uniform. be able to.

FIG. 1A is a sectional view showing one embodiment of the present invention. A translucent film 2 is formed on a transparent substrate 1, and a light-shielding film 3 made of Cr is formed thereon. Before depositing the light-shielding film 3 on the transparent substrate 1, the semi-transparent film 2 is formed by ion-implanting the entire surface of the transparent substrate 1 until the density becomes equal to or higher than the ion implantation amount at which the light transmittance is constant.

FIG. 1B schematically shows a case where a photomask according to the present invention is repaired using FIB. Numeral 5 indicates an ion beam, and numeral 6 indicates damage to the substrate surface due to FIB irradiation. FIG. 1C is a diagram showing a distribution of light transmittance of the photomask. Since the damage 6 on the substrate surface is included in the translucent film 2, the light transmittance of the transmission region in the photomask shown in FIG. There is no change in comparison, and it is uniform. The light transmittance of this transmissive area is less than 100% because it is the saturated light transmissivity of the translucent film 2. However, if the light transmissivity of all the transmissive areas is uniform, it is ideal to increase the exposure amount. Distribution of light transmittance is obtained.

The present invention is not limited to the above embodiment. For example, a halftone type phase shift mask in which the light shielding film is a translucent film 33 as shown in FIG. 3 and a translucent layer 32 is formed on a transparent substrate 31 as shown in FIG. A translucent layer 42 may be formed on a transparent substrate 41 of a self-aligned phase shift mask having a film 44 deposited thereon. In short, if a translucent layer is formed in advance on a transparent substrate that may be damaged in accordance with the removal of the light-shielding portion by FIB, a decrease in transmittance due to damage to the substrate can be prevented.

The type of ions to be implanted into the substrate to form the translucent layer does not need to be the same as the ions used for the FIB. It suffices that the ions are irradiated until the decrease in light transmittance is saturated. (Embodiment 2) Hereinafter, a second embodiment will be described in detail with reference to the drawings.

FIG. 5 is a diagram showing one embodiment of the FIB apparatus of the present invention. In this apparatus, when the mask 52 is mounted, the mask driving mechanism 53 on which the mask is placed is made horizontal, and when the ion beam is irradiated, the mask driving mechanism 53 can be inclined by θ with respect to the ion beam generated from the ion beam generation and convergence mechanism 51. . As a result, the ion beam 54 is incident on the mask at an angle θ from its normal 56. Using glass and glass with Cr as samples, measurement wavelength 4
At 36 nm, the incident angle of the ion beam is 10 degrees, 15 degrees.
FIG. 6 shows changes in the light transmittance of the ion irradiation part when the angles were changed to degrees, 30 degrees, and 45 degrees. At 15 degrees, the decrease in light transmittance at the corrected portion of the mask is almost the same as at 0 degrees in the conventional method, but at 30 degrees, the decrease in light transmittance is small, and
At 5 degrees, the decrease in light transmittance is greatly improved, and a light transmittance substantially equal to that of the portion not irradiated with the ion beam can be obtained. As shown by the dotted line in the figure, when the glass with Cr was used as a sample, the light transmittance of 80% in the conventional method was 85% at 25 degrees.
%, Which indicates that setting θ to 25 degrees or more is effective. Since it is often difficult to increase θ in terms of device design, it is desirable to set θ to a small value as long as the required light intensity transmittance can be obtained.

Further, as shown in FIG.
When there is a black defect 73 on the transparent substrate 71 on which
When the ion beam is incident from the direction of 75, a part of the light shielding pattern is sputtered, and a new defect is generated. In order to avoid this, the ion beam must be irradiated from the direction of 74. For this reason, the mask driving mechanism 53 in FIG. 5 can be rotated in a horizontal state when the mask is mounted, and may be rotated by a desired angle φ with respect to the normal direction 56 of the mask.

As described above, the angle of incidence θ of the ion beam with respect to the mask driving circuit and the rotation angle φ with respect to the normal line of the mask so that the black defect can be removed without damaging the necessary light shielding film using the apparatus of the present invention. By appropriately setting, it is possible to prevent damage to the portion of the substrate irradiated with the ion beam and to remove defects effectively.

FIG. 8 is a diagram showing another embodiment of the FIB apparatus of the present invention. The purpose of this apparatus is the same as that described above, and is to arbitrarily adjust the incident angle θ of the mask with respect to the ion beam and the rotation angle φ of the mask with respect to the normal line. In this apparatus, the mask 52 and the mask driving circuit 53 are perpendicular to the ion beam generating mechanism 81 and the ion beam incident direction 85. To change the incident angle θ of the ion beam 84 with respect to the mask 52, a deflector is used. 82 is used. In order to adjust the rotation angle φ with respect to the normal 86 of the mask, it is desirable to have a function of rotating the mask and the mask driving circuit.

FIG. 5 shows an ion beam generating and focusing mechanism 81.
In contrast, the apparatus has a function of tilting the mask driving circuit 53 and the mask 52 by θ. On the contrary, the ion beam generating and focusing mechanism has a function of tilting the θ by the mask driving circuit and the mask, and a function of rotating the mask. It may be a device provided.

The ion beam is irradiated onto the mask by an ion focusing mechanism having an electrostatic field or a static magnetic field between the ion source and the objective lens, or a mass spectrometry mechanism combining the ion beam and the ion beam. A device having a function of bending the traveling direction to an arbitrary direction may be used. In short, the incident angle θ of the ion beam with respect to the mask driving circuit and the rotation angle φ with respect to the normal line of the mask so that the black defect can be removed without damaging the necessary light shielding film.
Any device having a function of appropriately setting is possible.

[0025]

As described above, the photomask of the present invention forms a semi-transparent film having an ion density at which the decrease in light transmittance is saturated on a transparent substrate. Thus, a photomask having a uniform light transmittance in the transmission region can be obtained even after the defect is corrected, while suppressing a decrease in the light transmittance of the removed portion.

Further, the mask repair apparatus of the present invention has a function of irradiating the mask with an ion beam at an arbitrary angle, and inclining the ion beam with respect to the mask by at least 25 degrees from the normal direction of the mask. By performing the irradiation, the decrease in the light transmittance of the irradiated portion due to the ion irradiation can be made smaller than that at the time of normal incidence.

[Brief description of the drawings]

FIG. 1 is a view showing defect correction of a photomask of the present invention by FIB.

FIG. 2 is a diagram showing a relationship between an ion irradiation amount and transmittance.

FIG. 3 is a sectional view of a halftone type phase shift mask of the present invention.

FIG. 4 is a sectional view of a self-aligned phase shift mask of the present invention.

FIG. 5 is a structural view of an FIB defect repair apparatus according to the present invention.

FIG. 6 is a diagram showing a relationship between an ion irradiation angle and transmittance.

FIG. 7 is a schematic view of an FIB defect repair method according to the present invention.

FIG. 8 is a structural diagram of an FIB defect repair apparatus according to the present invention.

FIG. 9 is a structural diagram of a conventional FIB defect repair apparatus.

FIG. 10 is a diagram showing defect correction by conventional FIB.

[Explanation of symbols]

1, 21, 31, 41, 71 ... Transparent substrate 2, 32, 4
2 ... translucent layer 3, 22, 43, 72 ... light shielding film 4, 2
3, 73: black defect 6, 24: FIB irradiation area 5, 54, 74, 75, 96: ion beam 33, 4
4: Phase shifter 52, 92 ... Mask 53, 93 ...
Mask driving mechanism 56, 86: Normal direction of mask 51, 81, 91 ... Ion beam generation and focusing mechanism 55,
85, 95: Central axis direction of ion beam generation and focusing mechanism

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsuya Okumura 1 Komagi Toshiba-cho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Inside the Toshiba Tamagawa Plant (72) Inventor Satoshi Masuda 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Address Toshiba Corporation Tamagawa Factory (56) References JP-A-4-1648 (JP, A) JP-A-4-131185 (JP, A) JP-A-4-5655 (JP, A) JP-A-4-4 136854 (JP, A) JP-A-3-144645 (JP, A) JP-A-3-259256 (JP, A) JP-A-4-155339 (JP, A) JP-A-1-107257 (JP, A) JP-A-59-208830 (JP, A) JP-A-61-66349 (JP, A) JP-A-1-124857 (JP, A) JP-A-1-280759 (JP, A) JP-A-2-37346 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03F 1/08 H01 L 21/027

Claims (5)

(57) [Claims] 1. A transparent substrate, a semi-transparent layer having a desired thickness formed by irradiating the transparent substrate with ions until the decrease in light transmittance of the transparent substrate is substantially eliminated, and a predetermined thickness on the semi-transparent layer. And a light-shielding film provided at the position. 2. A mask repair method according to claim 1, wherein the defect on the photomask is removed by a focused ion beam. 3. A mask driving mechanism for mounting a mask, and an ion beam generating mechanism capable of irradiating an ion beam from a direction inclined at a desired angle from a normal direction of the mask. Mask repair device using focused ion beam. 4. The mask repair apparatus using a focused ion beam according to claim 3, wherein said ion beam generating mechanism has a function of inclining at a desired angle. 5. A mask for removing defects of a mask by irradiating an ion beam from a direction inclined at least 25 degrees from a normal direction of the mask using the mask repair apparatus according to claim 3. How to fix.