JP2658317B2 - Mask substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding the improvement of the configuration of a mask substrate used for checking a reticle in a stepper, it is possible to detect a finer reticle defect with a plurality of metal layers having different etching characteristics. A stepper that irradiates ultraviolet rays emitted from an ultraviolet light source onto a reticle, and irradiates the mask substrate mounted on a stage with ultraviolet light that is not blocked by a light-shielding film of the reticle. Mask substrate used for checking
A plurality of light-shielding films are formed in a plurality of regions on the surface of the transparent substrate.

[Industrial applications]

The present invention relates to an improvement in the configuration of a mask substrate used for checking a reticle in a stepper.

A mask substrate used for checking a reticle in a conventional stepper, for example, a glass wafer that has the same shape as a semiconductor substrate and has a light-shielding film formed on the surface of a transparent substrate or a light-shielding film formed on the surface of a transparent substrate for a mask The light-shielding film of the mask substrate described above is generally formed from a single metal layer.

In the future semiconductor device in which the element forming part is miniaturized and densified, a single metal layer is used when detecting a common defect of a reticle or mask pattern and evaluating the size and quality of a transfer pattern. Therefore, it has become impossible to keep up with pattern miniaturization with the capability of the current surface inspection apparatus.

In view of the above circumstances, there is a demand for a mask substrate that can be used for checking a reticle having dimensions and quality that can be used in the manufacture of future semiconductor devices in which the element formation portion is miniaturized and increased in density. .

[Conventional technology]

A conventional mask substrate used for checking a reticle and a surface inspection method using the substrate will be described with reference to FIGS.

As shown in FIG. 4, the conventional mask substrate 11 is formed by forming a single metal, for example, a Cr light shielding film 11b made of chromium (Cr) on the surface of a transparent substrate 11a by vapor deposition or the like.

In order to check the reticle using the mask substrate 11, a stepper whose structure is schematically shown in FIG.
A light-shielding film pattern formed on the surface of the mask substrate 11 using a reticle 12 as shown in FIG. 5 (a) is observed by a surface inspection device and evaluated by a comparative inspection method.

FIG. 3 shows a schematic structure of a stepper, in which ultraviolet rays emitted from an ultraviolet light source 4 are made incident on a reticle 2 in units of two chips as shown in FIG. 5 (a), and a reticle pattern of this reticle. The ultraviolet light which is not shielded by the light is reduced by the reduction lens 5 and is irradiated on the mask substrate 1 mounted on the movable object 6 by the XY table 7 to form a light shielding film pattern on the surface thereof.

In the surface inspection apparatus, defects are detected by comparing light-shielding film patterns formed by different reticle patterns indicated by arrows in FIG. 5B formed on the surface of the mask substrate 11.

Since the light-shielding film patterns to be compared are formed by the normal reticle pattern 12a and the defective reticle pattern 12b of the reticle 12, respectively, the normal reticle pattern 12a and the normal reticle pattern 12a are detected by detecting the difference between these light-shielding film patterns to be compared. The difference from the defect reticle pattern 12b can be detected.

[Problems to be solved by the invention]

In the above-described conventional method for detecting a defect using a surface inspection apparatus using a mask substrate, since the defect detection capability of the surface inspection apparatus is 0.5 μm or more, the conventional light-shielding film is formed from a single metal layer. 0.5 for mask substrate
μm or less cannot be detected. Therefore, when a two-chip reticle is used and one chip has a defect of 0.5 μm or less, no defect is detected by the surface inspection device. There was a problem that the rate became 50%.

An object of the present invention is to provide a mask substrate that includes a plurality of metal layers having different etching characteristics from the above-described situation and that can detect finer reticle defects.

[Means for solving the problem]

The mask substrate of the present invention is a stepper that irradiates ultraviolet rays emitted from an ultraviolet light source to a reticle and irradiates the mask substrate mounted on a stage with ultraviolet light that is not shielded by a light shielding film of the reticle. A plurality of light-shielding films are formed in a plurality of regions on the surface of the transparent substrate.

[Action]

That is, in the present invention, a plurality of light-shielding films are formed in a plurality of regions on the surface of the transparent substrate of the mask substrate. The exposed state is different due to the difference in the characteristic characteristics, so that a dimensional difference occurs in the formed light-shielding film pattern, and the dimensional difference in the light-shielding film pattern between the metals due to the difference in the etching rate of each metal layer in the etching process after exposure. This causes defects to appear remarkably larger than in the past, making it possible to detect defects that could not be detected in the past.

〔Example〕

A mask substrate used for checking a reticle and a surface inspection method using the substrate according to an embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, a mask substrate 1 of the present invention includes a Cr light-shielding film made of a plurality of metals, for example, chromium (Cr), aluminum (Al), and copper (Cu) in a plurality of regions on the surface of a transparent substrate 1a. 1b, an Al light shielding film 1c, and a Cu light shielding film 1d are formed by vapor deposition or the like.

In order to check the reticle using the mask substrate 1, a light-shielding film pattern formed on the surface of the mask substrate 1 is observed with a surface inspection device using a stepper having a schematic structure shown in FIG. It is evaluated by the law.

The stepper used in this embodiment is the same stepper as the conventional one shown in FIG. 3, and is a reticle 2 in which ultraviolet light emitted from the ultraviolet light source 4 is divided into two chips as shown in FIG. 2 (a). UV light which is not blocked by the normal reticle pattern 2a or the defective reticle pattern 2b of the reticle 2 is radiated to the mask substrate 1 mounted on the stage 6, and the surface thereof is irradiated with the normal light shielding film pattern 3a or the defective light shield. The film pattern 3b is formed.

In the surface inspection apparatus, a defect is detected by comparing the light-shielding film patterns shown in FIG. 2B formed on the surface of the mask substrate 1.

The light-shielding film pattern in this case is formed by the normal reticle pattern 2a and the defective reticle pattern 2b of the reticle 2, respectively. In the case of a pinhole as shown in the figure, the pinhole of the Al light-shielding film 1c is replaced by the Cr light-shielding film. Since the diameter is larger than the pinhole of 1b by 0.3 μm or more, pinholes not found in the Cr light-shielding film 1b can be found in the Al light-shielding film 1c.

As described above, even if the light-shielding film pattern is formed by the same reticle pattern of the reticle 2 which has not conventionally been compared, if the material of the light-shielding film is different, a difference occurs in the dimensions. It can be adopted as a comparison object.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, there is an advantage in that a very simple configuration can be improved to detect a fine defect that could not be detected by a surface inspection apparatus in the past. In addition, it is possible to provide a mask substrate that can be expected to improve reliability.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment according to the present invention, FIG. 2 is a view showing a surface inspection method using a mask substrate according to an embodiment of the present invention, FIG. 3 is a view showing a schematic structure of a stepper, FIG. FIG. 5 is a diagram showing a conventional mask substrate, and FIG. 5 is a diagram showing a surface inspection method using a conventional mask substrate. In the figure, 1 is a mask substrate, 1a is a transparent substrate, 1b is a Cr light shielding film, 1c is an Al light shielding film, 1d is a Cu light shielding film, 2 is a reticle, 2a is a normal reticle pattern, 2b is a defect reticle pattern, and 3a is normal. A light shielding film pattern, 3b is a defect light shielding film pattern, 4 is an ultraviolet light source, 5 is a reduction lens, 6 is a stage, and 7 is an XY table.

Claims (1)

(57) [Claims] 1. A stepper that irradiates ultraviolet rays emitted from an ultraviolet light source onto a reticle and irradiates a mask substrate mounted on a stage with ultraviolet light that is not shielded by a light-shielding film of the reticle. A mask substrate to be used, wherein a plurality of light shielding films are formed in a plurality of regions on a surface of a transparent substrate (1a).