JPH0833655B2 - Photomask correction method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a black defect repairing method for a photomask used for manufacturing a semiconductor device such as an LSI.

[Conventional technology]

For example, a method of manufacturing a photomask using a conventional photomask material used in the manufacturing process of LSI will be described with reference to FIGS. 3 and 4.

FIG. 3 is a cross-sectional view showing this conventional photomask material, which is a thin film 2 of about 100 nm thickness such as MoSi or Cr for shielding light on a glass substrate 1 such as quartz which transmits light. Has been formed.

FIG. 4 is a process sectional view showing a process of correcting a black defect (residual defect) on a photomask made of the conventional photomask material shown in FIG. 3 with a focused ion beam. Here, 3 is an LSI pattern formed of the light shielding thin film 2 formed on the glass substrate 1, 4 is a black defect formed of the light shielding thin film 2 during the fabrication of the photomask, 5
Is a focused ion beam (also referred to as FIB) for removing the black defect 4 by sputtering, and 6 is damage generated on the glass substrate 1 when the black defect 4 is repaired.

That is, in the conventional method, the photomask material shown in FIG. 3 is used, and a normal mask process is applied to this photomask material to form a semiconductor element on the glass substrate 1 as shown in FIG. 4 (a). A photo mask having a pattern 3 for Then, in order to highly accurately correct the black defect 4 generated on the photo mask during the process, a spatter removing method using a finely squeezed FIB 5 is used. General FIB5 conditions are: Ga ⁺ as ion species, accelerating voltage 25KV, beam diameter 0.2 μm ^φ ,
A beam current of 500 pA is used. Further, the black defect 4 is composed of the light shielding thin film 2 similarly to the pattern 3, and is generally
It is a MoSi film or Cr film with a thickness of about 100 nm. To remove this black defect 4 under the above conditions, 10 ¹⁷ pieces /
Irradiation with Ca ⁺ ions of about cm ² is sufficient. As a result, the black defect 4 disappears completely as shown in FIG. 4 (b).

[Problems to be Solved by the Invention]

However, in such a conventional photomask repairing method, after the black defect is repaired, the depth of the repaired portion of the glass substrate 1 is reduced to 50 mm.
Damage 6 of about nm remains (Fig. 4 (b)). This damage 6 is caused by irradiated Ga ⁺ ions penetrating into the glass substrate, and constituent atoms (Mo, Si or Cr) of the light shielding thin film 2 hit by Ga ⁺ ions penetrating into the glass substrate 1. , There are crystal defects in the glass generated by these ions and atoms. Therefore, the light transmittance at the location where this damage 6 occurs is about 40 for a normal glass substrate.
%descend. Therefore, when the pattern is transferred onto the wafer by using this photomask, there is a problem in that the damaged portion is also transferred.

The present invention has been made to solve the above problems, and obtains a photomask material and a photomask repairing method that do not damage a glass substrate even when a black defect on the photomask is repaired by a focused ion beam. The purpose is to

[Means for solving the problem]

In the photomask material according to the present invention, the first buffer film formed on the glass substrate and the buffer film formed on the buffer film have a dry etching selectivity and a second light shielding film. It is composed of the light shielding thin film.

Further, the photomask repairing method of the present invention, when producing a photomask using the photomask material described above, only the light shielding thin film among the black defects composed of the buffer film and the light shielding thin film generated at that time is focused ion. After repairing with a beam, the damaged buffer film in the repaired portion is removed by dry etching.

[Action]

In the photomask repairing method of the present invention, the damage due to the integrated ion beam is absorbed by the buffer film, so that the glass substrate is never damaged.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a photomask material used in a photomask repairing method according to an embodiment of the present invention. As shown in FIG. 1, the photomask material of this embodiment comprises a glass substrate 1, a light shielding thin film 2, and a buffer film 7 provided between the glass substrate 1 and the light shielding thin film 2. There is. In this case, the light shielding thin film 2 may be a MoSi or Cr film used in a normal photomask material.
The buffer film 7 may be any film as long as it has etching selectivity with respect to the light shielding thin film 2. For example, the MoSi film and the Cr film have etching selectivity and have a long-standing track record as a photomask material, so a combination of these is convenient. That is, for etching the MoSi film, CF ₄ + O ₂ gas, C
Dry etching with CCl ₄ + O ₂ is commonly used for etching r films. Here, for simplification, a method of manufacturing a photomask when a Cr film is used as the light shielding thin film 2 and a MoSi film is used as the buffer film 7 will be described with reference to FIG.

FIG. 2 shows FIB of black defects on a photomask formed by applying a mask process to the photomask material of FIG.
FIG. 6 is a process sectional view showing a process of correcting with. Here, the Cr film 2 has a thickness of about 100 nm as in the conventional photomask, and the MoSi film 7 has a thickness of about 50 nm to absorb damage. Further, the same reference numerals in the drawings indicate the same or corresponding parts. When manufacturing the photomask of this embodiment, as a mask process,
As shown in FIG. 1, a MoSi film 7 is formed between the glass substrate 1 and the Cr film 2.
A resist pattern is formed by a normal process on the photomask material formed by using as a buffer film, and the Cr film 2 is replaced with CCl ₄
After dry etching with + O ₂ gas, the MoSi film 7 is then removed.
Dry etching is performed with CF ₄ + O ₂ gas (Fig. 2 (a)). However, in the figure, 3 indicates the pattern of the LSI formed on the glass substrate 1, and 4 indicates black defects.

Then, in order to correct (remove) the black defect 4, the FIB 5 is irradiated as shown in FIG. At this time, as FIB5 conditions, Ga ⁺ is used as the ion species, and the irradiation is performed with an acceleration voltage of 25 KV, a beam diameter of 0.2 μm ^φ , and a beam current of 500 pA. In order to remove the spatter of the Cr film 2 having a film thickness of 100 nm under this condition, it is sufficient to irradiate about 10 ¹⁷ pieces / cm ² of Ga ⁺ ions. At this time, the second
As shown in FIG. 6B, damage 6 occurs in the lower MoSi film 71.
Occurs. Since the MoSi film 71 has a thickness of about 50 nm, no damage occurs in the glass substrate 1. Then, by dry etching with CF ₄ + O ₂ gas, the MoSi film 71 in the portion irradiated with FIB5 is removed. At this time, since the MoSi film 7 in the pattern 3 portion is covered with the Cr film 2, it remains without being removed. As a result, as shown in FIG. 2C, the black defect correction of the photo mask is completed. Therefore, the glass substrate 1 of this photomask is not damaged.

Although Cr is used for the light shielding thin film 2 in the above embodiment, any thin film capable of shielding light may be used. Although MoSi is used as the buffer film 7, any thin film having etching selectivity with respect to the light shielding thin film 2 may be used.

In addition, the thickness of the light-shielding thin film and the buffer film should be 10
Although the thickness is set to 0 nm and 50 nm, any number may be used as long as the film thickness can achieve the result. In addition, the etching method and conditions of these thin films may be other than those in the above embodiment.
The condition of B may be any as long as it can correct the black defect.

〔The invention's effect〕

As described above, according to the present invention, the photomask material is
A two-layer structure in which a thin film for light shielding and a buffer film are provided on a glass substrate, and when a photomask is produced using this photomask material, a black defect formed at that time, which consists of the buffer film and the thin film for light shielding Of these, only the light shielding thin film was repaired with an integrated ion beam, and the buffer film in the repaired portion was etched away by dry etching, so black defects were repaired by FIB that did not damage the glass substrate. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a sectional view of a photomask material used in a photomask repairing method according to an embodiment of the present invention, and FIG. 2 is for repairing a black defect generated when a photomask is manufactured using the photomask material of FIG. FIG. 3 is a process sectional view for explaining an example of the method, FIG. 3 is a sectional view of a conventional photomask material, and FIG. 4 is a process sectional view showing a conventional photomask repairing method. 1 ... Glass substrate, 2 ... Light shielding thin film (Cr film), 3
…… Pattern, 4 …… black defect, 5 …… focused ion beam (FIB), 6 …… damage, 7 …… buffer film (MoSi film).

Claims (1)

[Claims] 1. A buffer film formed on a glass substrate, and a light-shielding thin film having a dry etching selectivity between the buffer film and the buffer film formed on the buffer film. When a photomask is manufactured using the photomask material described above, only the light shielding thin film is repaired by the focused ion beam among the black defects including the buffer film and the light shielding thin film generated at that time, and then the repair is performed. A method of repairing a photomask, characterized in that the buffer film in a portion is removed by dry etching.