JPH0646298B2 - Photomask manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a photomask used for patterning a semiconductor device.

[Conventional technology]

FIG. 3 is a diagram showing a conventional process for correcting a pattern defect of a photomask. FIG. 3 (a) is a top view of the photomask. The metal mask pattern 1 is formed by depositing a metal mask pattern material such as Cr or MoSi on a quartz glass substrate 2 and patterning it into an F shape. Reference numeral 3 is a pattern defect portion generated at a place where a pattern should not be originally present. FIG. 3 (a) is a top view of the photomask showing this state. Reference numeral 4 is a focused ion beam for removing pattern defects, and 5 is a portion (hereinafter referred to as "stain") in which the ions of the focused ion beam 4 penetrate into the quartz glass substrate 2.

Next, the removal of the pattern defect portion 3 will be described with reference to FIGS. 3B to 3D which are sectional views of the photomask. Third
In the figure (b), for example, Ga ⁺
The focused ion beam 4 is irradiated. Focused ion beam 4
Is irradiated onto the pattern defect portion 3 with energy of several keV to several tens keV, and the mask material of the pattern defect portion 3 is removed by sputter etching. During irradiation of the focused ion beam 4, the absorption current generated from the irradiated portion of the focused ion beam 4 and the secondary electrons or secondary ions are monitored in advance to show that the mask material of the pattern defect portion 3 has disappeared. Irradiation of the focused ion beam 4 is stopped upon detecting a change in the signal of secondary electrons or secondary ions. The focused ion beam 4 is an energy beam, and its energy is distributed with a spread of several hundred eV to several keV. Therefore, when all the metal mask pattern material of the pattern defect portion 3 is removed, Ga ⁺
Penetrate into the quartz glass substrate 2 to form stains 5 in which the network structure of quartz glass is disturbed. This state is shown in FIG. 3 (c). Generally, glass having a disordered network structure has a low optical transmittance. Therefore, when the photomask on which the stain 5 remains is used in the wafer transfer process, that portion is transferred as a shadow and becomes a pattern defect on the wafer. In order to prevent this, it is necessary to remove the stain 5.

Therefore, the stain 5 is wet-etched using a buffered hydrofluoric acid solution or the like. In this case, the network structure of the quartz glass in the portion of the stain 5 is disturbed, but the quartz glass other than the stain 5 is not disturbed because Ga ⁺ does not enter, and as a result, the stain 5 is not disturbed. Since the etching rate is higher, only the portion of the stain 5 is wet-etched. Therefore, a step is formed between the stain 5 and other parts. Further, even after the stain 5 is removed, its surface is not completely flat. This state is shown in FIG. 3 (d).

[Problems to be Solved by the Invention]

The conventional photomask manufacturing method is performed as described above, and since the stain 5 is removed by the wet etching process, a step is generated on the quartz glass substrate 2 after the removal and the removal trace of the stain 5 is completely flat. It doesn't. Therefore, when the wafer transfer process is performed using this photomask, light is diffusely reflected at the removal trace of the stain 5 and a pattern defect occurs on the wafer.

The present invention has been made to solve the above-described problems, and it is an object of the present invention to obtain a photomask manufacturing method in which a step is not formed on a glass substrate after removing stains and the surface is completely flat after the removal. To aim.

[Means for Solving the Problems]

The photomask manufacturing method according to the present invention comprises the steps of preparing a glass substrate made of glass having a non-disturbed network structure, and forming a glass layer made of distorted glass on the main surface of the glass substrate. A step, a step of forming a mask pattern on the glass layer, a step of removing a pattern defect generated when forming the mask pattern by irradiating a focused ion beam, the glass other than the mask pattern portion And a step of removing the layer.

[Action]

In the present invention, even if stains are generated by the focused ion beam irradiation, the stains are removed together with the glass layer, so that after the stains are removed, no step is formed on the glass substrate, and the stain removal traces become flat.

〔Example〕

FIG. 1 is a view showing an embodiment of the present invention, in which FIG. 1 (a) is a top view of a photomask and FIG. 1 (b) is a sectional view thereof. In the figure, the structural difference from the conventional photomask of FIG. 2 is that a glass layer (hereinafter referred to as a surface glass layer) made of a disordered glass between the quartz glass substrate 2 and the metal mask pattern 1 is formed. 7) is provided. The surface glass layer 7 is formed on the quartz glass substrate 2 by S by a CVD method, a vacuum deposition method, a sputter deposition method, or the like.
It is formed by depositing an iO ₂ film, and its thickness is about several hundred Å. Other structures are similar to those of the conventional example.

Next, a method of correcting a pattern defect on the photomask will be described with reference to FIG. The Ga ⁺ focused ion beam 4 having an energy of several KeV to several tens KeV is used to remove the pattern defect portion 3 by the sputter etching as in the conventional case (FIG. 2 (b)). In this case, the focused ion beam 4 is an energy beam as described above,
The energy distribution (several hundred eV to several Ke as described above)
Ga ⁺ is a surface glass layer 7 depending on the V spread).
Invades the area, and that part becomes stain 5 (Fig. 2
(c))). At this time, the depth of ion penetration is several hundred Å or less in consideration of ion energy and energy distribution, so that Ga ⁺ does not reach the quartz glass substrate 2 (Fig. 2 (c)). Next, the stain 5 is removed together with the surface glass layer 7 by wet etching using a buffered hydrofluoric acid solution or the like (FIG. 2 (d)). Surface glass layer 7
Of course, the mesh structure is distorted, and the etching rate for hydrofluoric acid is larger than that of the quartz glass substrate 2, so that the quartz glass substrate 2 is selectively etched. Therefore, the flat quartz glass substrate 2 is exposed after the stain 5 is removed. Therefore, even when this photomask is used in the wafer transfer process, light is not diffusely reflected by the stain 5 as in the conventional case, and the shadow of the stain 5 is not transferred. Therefore, pattern defects on the wafer do not occur. Moreover, since the thickness of the surface glass layer 7 is several hundred Å, the side etching amount just below the mask pattern is several hundred Å or less, and the minimum mask pattern size is generally at least submicron (5,000 to 10,000 Å). Considering this, the influence on the mask pattern can be ignored. Further, since the surface glass layer 7 has good adhesion to the quartz glass substrate 2 and the metal mask pattern 1, it is possible to prevent the metal mask pattern 1 from peeling off.

In the above embodiment, the quartz glass substrate 2 was used as the glass substrate, and the glass layer made of glass having a disordered network structure was formed by depositing a thin SiO ₂ film on the quartz glass substrate 2. Not limited to.

It is also doped with an impurity such as G _a at the surface glass layer 7 formed.

The surface glass layer 7 may be formed by implanting ions such as G _a a quartz glass substrate 1 over the entire surface.

〔The invention's effect〕

As described above, according to the present invention, a glass layer made of disordered glass having a mesh structure is formed on the main surface of the glass substrate,
After that, a mask pattern is formed on the glass layer, and then pattern defects generated when the mask pattern is formed are removed by irradiating a focused ion beam, and then the glass layer other than the mask pattern portion is removed,
Even if stains are generated by the focused ion beam irradiation, the stains are removed together with the glass layer.Therefore, after the stains are removed, there is no step on the glass substrate, and it is possible to obtain a photomask with a flat stain removal trace. Light is not diffusely reflected on the photomask in the wafer transfer process, and as a result, pattern defects are not generated on the wafer.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a process of repairing pattern defects of the photomask shown in FIG. 1, and FIG. 3 is a process of repairing pattern defects of a conventional photomask. FIG. In the figure, 1 is a metal mask pattern, 2 is a quartz glass substrate, and 7 is an amorphal glass layer. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A step of preparing a glass substrate made of glass having a non-disturbed network structure; a step of forming a glass layer made of glass having a distorted network structure on the main surface of the glass substrate; Forming a mask pattern on the layer, removing pattern defects generated when forming the mask pattern by irradiating a focused ion beam, and removing the glass layer other than the mask pattern portion And a photomask manufacturing method comprising: