KR20090072823A - Apparatus of inspecting mask - Google Patents

Abstract

An apparatus of inspecting mask is provided to improve the photo lithography process by improving the mask inspection. The mask test equipment comprises a stage(210), a supporting shaft(230), and a support bar(250) and an optical sensor(310). The mask(100) is settled in the stage. A mask pattern(103) is formed on the mask substrate(101). The supporting shaft moves the stage while supporting the stage. The support bar supports the supporting shaft. The test light is irradiated the optical sensor on the surface of mask. The foreign material of the mask surface is inspected by the optical sensor using the scattered light from the surface of mask.

Description

Mask inspection equipment {Apparatus of inspecting mask}

TECHNICAL FIELD The present invention relates to the manufacture of semiconductor devices, and more particularly, to equipment for inspecting defects on a mask.

A pattern transfer process for integrating a semiconductor device on a wafer is performed by lithography. Prior to the lithography process, a mask pattern having a pattern layout to be transferred onto a wafer is formed on a transparent substrate to fabricate a photo mask. After fabricating the photo mask, optical particle inspection on the surface of the photo mask is performed before the photo mask is shipped to the subsequent exposure process. The optical foreign material inspection is a process of finally checking whether there is a foreign material or scratches on the mask, and after such foreign material inspection, the mask is shipped as a product.

Foreign material inspection on such a mask is performed depending on the visual inspection of the operator. The operator irradiates the inspection light onto the mask through a light emitter and visually grasps the state of the light reflected from the mask surface to determine whether there is a foreign material, a scratch or the like on the mask. The worker grasps the mask with a jig and moves up, down, left, and right, and irradiates the inspection light from the transmitter onto the mask. In the mask pattern region in which foreign substances or scratches are present on the mask, light scattering is relatively increased compared to zero in which a normal pattern in which no foreign substances or scratches exist. The amount and state of light reflected from the mask surface by the light scattering caused by the foreign matter and scratches are different. This phenomenon caused by light scattering is visually confirmed by an operator to identify defects such as foreign matter and scratches on the mask.

The method of determining whether there is an abnormality of the mask once again depending on the naked eyes of the worker has a vulnerability that the inspection result may vary according to the worker's condition. That is, it may be missed without grasping the abnormal state caused on the mask according to the condition of the operator, the working skill, and the working environment. As a result, it is difficult to reliably detect and remove foreign matters that may adversely affect the defects in the subsequent exposure process and cause defects, thereby limiting the provision of a high quality mask. When foreign material detection fails in such a light inspection, when the mask is shipped, a repeating defect (RD) is caused in the exposure step of the wafer fab. Therefore, since the remanufacturing of the mask is performed according to the defect check in the subsequent process, the turn-around time (TAT) in the manufacturing process may be increased.

Moreover, since the mask state is inspected by the worker's manual work, there is a possibility that the mask may drop when the worker grabs the mask with the jig and moves around. In this case, cracking and damage of the mask may be caused. In addition, since the foreign material inspection depends on the naked eyes of the worker, the reflected light scattered by the foreign matter and scratches adversely affects the naked eyes of the worker, which may cause a health problem of the eyesight of the worker.

The present invention is to provide a mask inspection equipment that can perform a foreign material inspection on the surface of the manufactured mask more reliably.

One aspect of the invention is a stage on which a mask to be inspected is mounted; A support shaft supporting the stage and moving the stage in front, rear, left and right directions; A support on which the support shaft is installed; And a photo sensor for irradiating inspection light to the mask surface mounted on the stage to detect the degree of light scattering due to foreign matter on the mask surface.

The stage may be installed as a vacuum adsorption stage for vacuum adsorption and fixing the mounted mask.

The support shaft may be installed as a multi-joint support shaft having four degrees of freedom.

The optical sensor may be introduced into a direct reflection type sensor in which a light emitting unit for irradiating the inspection light and a light receiving unit for receiving reflected light reflected from the surface of the mask by irradiation of the inspection light are arranged side by side.

It includes a light transmitting unit having an illumination system for irradiating illumination for visual inspection on the mask surface, the light sensor may be installed at the entrance of the illumination system.

Embodiments of the present invention can provide a mask inspection equipment that can perform a foreign material inspection on the surface of the manufactured mask more reliably.

In an embodiment of the present invention, a stage for seating a manufactured mask is introduced, and a support shaft for supporting the stage has a multi-joint support shaft structure for freely moving the stage up, down, left, and right, and may exist on a mask. Alternatively, a mask inspection apparatus incorporating an optical sensor to detect scratches by a scattering effect of light is presented. A light transmitting unit for irradiating light onto the mask to allow visual inspection together with the light sensor can also be introduced.

In addition, the light transmitting unit may be configured to include an illumination system for emitting light to be used as the inspection light, the light sensor is installed at the entrance of the illumination system to detect the scattered light on the mask surface and to alert the operator by detecting a warning sound when a defect is detected. can do. As a result, defect detection by the optical sensor can be performed together with the visual inspection of the operator, thereby overcoming the detection limit by the visual inspection of the operator, so that the detection of the mask foreign material can be confirmed more reliably and more accurately.

By using the mask inspection equipment configured as described above, the light scattering effect due to the foreign material or the scratch may be detected to identify various defects that may exist on the mask, and the manufactured mask may be shipped.

1 and 2 are diagrams schematically illustrating a mask inspection apparatus in an embodiment of the present invention.

Referring to FIG. 1, a mask inspection apparatus according to an embodiment of the present invention may include a mask pattern 103 formed of a chromium (Cr) light shielding layer, a phase shift layer, or the like on a transparent substrate 101. And a stage 210 on which the mask 100 formed by the photomask manufacturing process is mounted. The stage 210 may be configured as a vacuum adsorption mask for fixing the mask 100 by vacuum adsorption so that the mounted mask 100 does not escape from the movement of the stage 210. To this end, a stage 210 may be provided with a suction port for evacuating the vacuum, and a passage through which the vacuum for vacuum suction may be applied, a vacuum pump, and the like may be provided through the suction port.

The stage 210 is connected to a support shaft 230 that implements at least four degrees of freedom to support the stage 210, and to position the mask 100 when the mask 100 is inspected. Move the position of left, right, front and back to move. The support shaft 230 is connected to the connecting shaft 231 through the joint portion 233 to implement three degrees of freedom, and the connecting shaft 231 is connected to the rotation shaft 235. The joint part 233 implements a fastening structure that can flow, including a bearing. The rotating shaft 235 is installed on the support 250 to enable 360 ° rotation. The structure of the support shaft 230 may be configured similar to the joint structure of the robot arm. The movement of the support shaft 230 may be controlled at the operator's intention by a joystick or a remote controller. The support 250 may have a built-in pump for vacuum adsorption, and a control unit 251 for turning on / off vacuum adsorption of the stage 210 may be installed.

An optical sensor that detects defects such as foreign matter or scratches on the surface of the mask 100 by the degree of surface light scattering by irradiating inspection light to the surface of the mask 100 mounted on the stage 210 at a position opposite to the stage 210 ( photo sensor: 310). The optical sensor 310 may be installed in the optical sensor support 350, and as shown in FIG. 2, may be installed as a direct reflective optical sensor. The light sensor 310 includes a light emitting part 311 for irradiating inspection light onto a mask 100, which is an object to be inspected, and a light receiving unit 312 for receiving reflected light reflected from the surface of the mask 100 by irradiation of inspection light. It can be introduced into a disposed direct reflective sensor.

The direct reflection type sensor (or diffuse reflection type sensor) is configured to be embedded in one body case of the light emitting unit 311 and the light receiving unit 312 like a mirror reflective sensor. Accordingly, there is an advantage that wiring is easy to install, pre-adjustment such as optical axis alignment is unnecessary, and inspection can be performed on almost any inspection object including a transparent body.

Since the optical sensor 310 irradiates the inspection light to the surface of the mask 100 to be inspected and the amount of reflected light varies depending on the scattering degree, the optical sensor 310 detects the amount of reflected light and determines that the defect is generated when the amount is lower than the reference level. It may be configured to inform the defect detection. Since a foreign material or scratch on the surface of the mask 100 scatters incident inspection light, the presence of the foreign material or scratch reduces or changes the amount of reflected light received. By using this point, it is possible to check whether foreign matter and scratches are generated on the surface of the mask 100.

The optical sensor 310 may be installed in the light transmitting unit 320. Transmitting unit 320 may be configured to include an illumination system for irradiating the light for visual inspection on the surface of the mask (100). In this case, the optical sensor 310 may be installed at the inlet of the light transmitting unit 320 of the illumination system. The introduction of such a light transmitting portion 320 also enables the visual inspection of the operator, thereby further increasing the reliability and accuracy of defect detection.

As described above, when detecting defects such as foreign matter and scratches on the mask by using the mask inspection equipment according to the exemplary embodiment of the present invention, it is possible to prevent a defect detection failure due to an operator's mistake. Thus, a high quality mask substantially free of defects can be provided for subsequent exposure procedures. In addition, since the inspection is performed in a state in which the mask 100 is fixed to the stage 210 by adsorption and fixation, the mask may be dropped and damaged when the jig is used. Since the defect can be detected by the optical sensor 310, it is possible to prevent a decrease in the eyesight of the operator due to visual inspection.

1 is a view schematically showing a mask inspection equipment according to an embodiment of the present invention.

2 is a view provided to explain a photo sensor of the mask inspection equipment according to an embodiment of the present invention.

Claims (5)

A stage on which a mask to be inspected is mounted; A support shaft supporting the stage and moving the stage in front, rear, left and right directions; A support on which the support shaft is installed; And And a photo sensor for irradiating inspection light onto the mask surface mounted on the stage to detect the degree of light scattering due to foreign matter on the mask surface. The method of claim 1, And the stage is installed as a vacuum suction stage for vacuum suction and fixing the mounted mask. The method of claim 1, The support shaft is a mask inspection equipment installed with a multi-joint support shaft having 4 degrees of freedom. The method of claim 1, And the optical sensor is introduced into a direct reflection type sensor in which a light emitting portion for irradiating the inspection light and a light receiving portion for receiving reflected light reflected from the surface of the mask by irradiation of the inspection light are arranged side by side. The method of claim 1, And a light transmitting unit having an illumination system for irradiating illumination for visual inspection on the mask surface, wherein the optical sensor is installed at an entrance of the illumination system.

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