KR20060086198A - Methods for inspecting photomasks - Google Patents

Abstract

It provides a photomask inspection method. Critical dimensions are measured in addition to defect inspection, which inspects the entire area of the photomask. In this way, the critical dimension of many light blocking patterns can be measured over the entire area of the photomask. As a result, the uniformity of critical dimensions over the entire photomask can be measured more precisely.

Description

Photomask inspection method {METHODS FOR INSPECTING PHOTOMASKS}

1 is a diagram showing inspection equipment used in embodiments of the present invention.

2 is a flowchart illustrating a photomask inspection method according to an embodiment of the present invention.

3 is a plan view illustrating a photomask for explaining a photomask inspection method according to an exemplary embodiment of the present invention.

4 is a flowchart illustrating a photomask inspection method according to another exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating light intensities for explaining a photomask inspection method according to another exemplary embodiment.

TECHNICAL FIELD The present invention relates to an inspection method, and more particularly, to a method for inspecting a photomask used in a semiconductor process.

Typically, photomasks are used to selectively inject light into a photosensitive film coated on a wafer in a photolithography process of a semiconductor device. The photomask has a light blocking pattern made of chromium, which is a material that blocks light, on the surface of the transparent substrate. As a result, light exposed through the photomask is selectively scanned onto the photosensitive film on the wafer.

Since shading patterns define semiconductor patterns formed on a wafer, critical dimensions such as the line width of the shading patterns and / or the spacing between the shading patterns are very important.

Typically, the critical dimension of the light blocking patterns is measured by a scanning electron microscope, or an edge diffraction detection device using an optical system or a laser. In this case, after the operator moves the field of view to a designated position in the photomask, the critical dimension of the light shielding pattern is measured by means of measuring the critical dimension. That is, in the case of measuring the critical dimension with a scanning electron microscope or edge refraction detection equipment or the like, the critical dimension is measured by the operator, so that the point for measuring the critical dimension in the photomask can be very limited. Because of this, it may be difficult to predict the uniformity of the critical dimensions of the light shielding patterns in the photomask.

As the trend toward higher integration of semiconductor devices is intensified, the importance of uniformity of critical dimensions of light shielding patterns in a photomask is very important. For this reason, there is a need for a method that can more accurately measure the uniformity of the critical dimensions of the light blocking patterns in the photomask.

 An object of the present invention is to provide a photomask inspection method capable of accurately measuring the uniformity of critical dimensions of patterns on a photomask.

Another object of the present invention is to provide a photomask inspection method capable of precisely measuring the uniformity of critical dimensions of patterns on a photomask and at the same time detecting defects on the photomask.

It provides a photomask inspection method for solving the above technical problem. An inspection method according to an exemplary embodiment of the present invention may be a method of inspecting a photomask including a plurality of unit regions having patterns having the same shape as each other using inspection equipment capable of defect inspection and critical dimension measurement. This method may include the following steps. The inspection apparatus recognizes a plurality of critical dimension measurement points included in each unit region, captures images of the unit regions, and spreads the images over the photomask in an image to image manner. Perform a defect check for the During the defect inspection, the critical dimension of light blocking patterns of the recognized critical dimension measurement points in each unit area is measured.

According to another exemplary embodiment of the present invention, an inspection method includes a stage capable of horizontal movement, and detection means for measuring the intensity of inspection light that is scanned from a light source and passes through a photomask, and the inspection apparatus stores a database of light blocking patterns of the photomask. It may be a method of inspecting the photomask using. The method stores defect thresholds of inspection light in the inspection equipment and performs defect inspection in a database to image manner in which the entire area of the photomask is scanned. The intensity of the inspection light detected by the detection means during the defect inspection calculates a critical dimension of the light shielding patterns throughout the photomask from the moving distance of the stage with respect to an area which is constantly larger than the threshold intensity and / or a smaller area. .

In detail, the critical dimension of the region where the intensity of the detected inspection light is continuously greater than the threshold intensity may be an interval between the shading patterns, and the threshold dimension of the region where the intensity of the detected inspection light is continuously smaller than the threshold intensity. May be line widths of the light blocking patterns.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed subject matter is thorough and complete, and that the spirit of the present invention to those skilled in the art will fully convey. Therefore, the shape of the elements in the drawings are exaggerated to emphasize a clearer description. Portions denoted by like reference numerals denote like elements throughout the specification.

(First embodiment)

1 is a diagram showing inspection equipment used in embodiments of the present invention.

Referring to FIG. 1, the test equipment includes a main body 50 and a control unit 60. The main body 50 includes a stage 10, a light source 30, and a detection means 40. The stage 10 is loaded with a photomask 20, it is possible to move horizontally in two dimensions. The stage 10 may be configured to hold an edge of the photomask 20. As a result, both the top and bottom surfaces of the photomask 20 loaded on the stage 10 may be exposed. The photomask 20 is transparent, and light blocking patterns made of chromium or the like are disposed on a surface thereof.

The light source 30 scans inspection light toward the photomask 20. The light source 30 may be disposed under the loaded photomask 20. The detection means 40 detects the inspection light via the photomask 20. In particular, the detecting means 40 is a means for detecting the intensity, phase, and / or wavelength of the inspection light via the photomask 20. It is preferable that the detection means 40 detects the inspection light transmitted through the photomask 20. Thus, the detection means 40 is preferably disposed above the loaded photomask 20.

The detection means 40 may obtain an image of the surface state of the photomask 20 from the detected intensity, phase, and / or wavelength of the inspection light. The detection means 40 may comprise imaging means such as a camera or the like capable of imaging the obtained image.

The controller 60 exchanges a predetermined electrical signal with the main body 50. The control unit 60 receives data about the position or / and the movement distance of the stage 10 and the data detected by the detecting means 40 to correspond to a surface state corresponding to each position of the photomask 20. To obtain an image. In addition, the controller 60 may calculate the critical dimensions of the light blocking patterns according to the difference between the contrast and / or the color in the obtained image. The controller 60 includes a storage device that stores various types of data and images.

The inspection equipment may further include display means 70 connected to the controller 60 to represent various types of data and images.

One method of inspecting the photomask 20 using the inspection equipment having the above-described structure will be described with reference to the flowchart of FIG. 2.

2 is a flowchart illustrating a photomask inspection method according to an embodiment of the present invention, and FIG. 3 is a plan view illustrating a photomask for describing a photomask inspection method according to an embodiment of the present invention.

1, 2, and 3, the photomask 20 preferably includes a plurality of unit regions 25. Each of the unit regions 25 includes various types of light blocking patterns. Light blocking patterns disposed in one unit area 25 are disposed at the same shape and position as light blocking patterns of a neighboring unit area 25. In other words, in the photomask 20, a group of various light blocking patterns is repeatedly arranged in a matrix form.

The unit region 25 may form one semiconductor chip. That is, light blocking patterns corresponding to a plurality of semiconductor chips may be illustrated in the photomask 20. Alternatively, the unit region 25 may be a region in which light blocking patterns repeated in one semiconductor chip are repeated.

One method of inspecting this type of photomask 20 will be described.                     

First, among the light blocking patterns in each unit area 25, critical dimension measurement points including a light blocking pattern for measuring a critical dimension are designated. In particular, it is preferable to designate a plurality of said critical dimension measurement points in each said unit area 25. The light shielding patterns to be measured in the critical dimension measuring points in each unit region 25 may be different from each other or may have the same shape.

Recognize the critical dimension measurement points to the inspection equipment (S100). It is preferable to make the inspection equipment recognize the light shielding pattern to be measured at the critical dimension measurement point in the form of an image.

Subsequently, defect inspection of the entire area of the photomask 20 and critical dimensions are measured in an image-to-image manner (S110). The image-to-image method is a method of capturing an image of each unit region 25 and comparing images of neighboring unit regions 25 to each other to recognize different portions as defects.

The defect inspection and measuring the critical dimension (S110) will be described in detail. The light source 30 scans the inspection light into the photomask 20, and the detection means 40 picks up an image of the selected first unit area 25 of the photomask 20. In this case, the detection means 40 may capture an image by scanning the first unit area 25. While the detection means 40 captures an image of the first unit area 25, the inspection equipment measures the critical dimension of the light shielding patterns in the recognized critical dimension measurement points. The control part 60 which received the signal of the said detection means 40 and the signal of the stage 10 calculates the critical dimension of the light shielding pattern in the said critical dimension measuring point.

Subsequently, the stage 10 moves the photomask 20, and the detection means 40 picks up an image of the second unit area 25. At this time, the inspection equipment measures the critical dimension of the light blocking patterns in the critical dimension measurement points of the second unit area 25. In this way, the inspection equipment captures images of the unit regions 25 across the photomask 20 and measures the critical dimensions of the light shielding patterns in the critical dimension measurement points of the respective unit regions 25. Measure

The inspection equipment compares the captured images to find defects in the photomask 20. These defects may be displayed on the display means 70 of the inspection equipment corresponding to the position of the photomask 20. In addition, the display means 70 may display the measured critical dimensions according to the position of the photomask 20.

According to the method for inspecting the photomask 20 described above, the defect inspection for inspecting the entirety of the photomask 20 using the images of the unit areas 25 is performed, and the photomask 20 is performed. The critical dimension of the selected shading patterns in < RTI ID = 0.0 > As a result, the critical dimensions of the light blocking patterns may be measured for each unit area 25 of the photomask 20. As a result, the uniformity of the light blocking patterns of the photomask 20 may be measured more precisely. In addition, the defect inspection and the measurement of the critical dimension can be performed at the same time, thereby shortening the manufacturing time of the photomask and improving productivity.

(2nd Example)                     

In this embodiment, another method of inspecting a photomask using the inspection equipment of FIG. 1 is disclosed.

4 is a flowchart illustrating a photomask inspection method according to another exemplary embodiment of the present invention, and FIG. 5 is a diagram illustrating light intensity for describing the photomask inspection method according to another exemplary embodiment of the present invention.

1, 4 and 5, the threshold intensity 300 of the inspection light is stored in the inspection apparatus described with reference to FIG. 1 (S200). The inspection apparatus stores a database of light blocking patterns 27 of the photomask 20. The database may be stored in the controller 50 of the inspection equipment. The threshold intensity 300 of the inspection light corresponds to a reference compared with the intensity of the inspection light detected by the detection means 40.

Defect inspection and critical dimensions of the database to image method are measured (S210). The database-to-image method is a method of inspecting defects in the photomask 20 by comparing the shape of the light blocking patterns 27 detected by the inspection apparatus with the stored database.

Specifically, the photomask 20 is loaded on the stage 10, and the inspection light is scanned from the light source 30 to the loaded photomask 20. At this time, the detection means 40 detects the intensity of the inspection light via the photomask 20. Of course, the detection means 40 may further detect the phase and / or the wavelength of the inspection light via the photomask 20. The inspection equipment moves the stage 10 to scan the entire area of the photomask 20. At this time, the inspection equipment compares the data detected by the detection means 40 with the database and inspects the defects on the photomask 20.

The photomask 20 is divided into a first region a in which the light blocking pattern 27 exists and a second region b in which the light blocking pattern 27 does not exist. Since the light blocking pattern 27 blocks light, the intensity of the inspection light detected through the first region a is smaller than the intensity of the inspection light detected via the second region b. The threshold intensity 300 is preferably a value between the intensity of the inspection light detected through the first region a and the intensity of the inspection light detected through the second region b.

While performing the defect inspection through the scanning, the controller 60 calculates critical dimensions of light blocking patterns throughout the photomask 20.

More specifically, as shown in FIG. 3, the detected inspection light is continuously smaller than the threshold intensity 300 in the first region a. On the contrary, the detected inspection light is continuously larger than the threshold intensity 300 in the second region b. Accordingly, the controller 60 calculates the moving distance of the stage 10 with respect to a region where the detected intensity of the inspection light is continuously smaller than the threshold intensity 300, thereby reducing the line width of the light shielding pattern 27. Can be calculated. In addition, the controller 60 calculates a moving distance of the stage 10 with respect to a region in which the intensity of the detected inspection light is continuously larger than the threshold intensity 300, thereby preventing the gap between the light blocking patterns 27. Can be calculated. The line width of the light blocking pattern 27 and the spacing of the light blocking patterns 27 are included in a critical dimension.

The inspection equipment may display on the display means 70 the defects found by the defect inspection and / or the critical dimensions measured from the light shielding patterns 27.

According to the method for inspecting the photomask described above, the critical dimension of the light blocking patterns 27 is measured while scanning the entire area of the photomask 20. Accordingly, the critical dimension of the light blocking patterns 27 disposed in the entire area of the photomask 20 may be measured. As a result, the uniformity of the critical dimensions of the photomask 20 can be measured very precisely. In addition, by simultaneously performing the defect inspection and the measurement of the critical dimension, it is possible to significantly reduce the photomask manufacturing time to improve productivity.

As described above, according to the present invention, while performing defect inspection over the entirety of the photomask, the critical dimensions of the light shielding patterns are measured. Accordingly, the uniformity of the light blocking patterns can be measured more precisely. In addition, by simultaneously performing defect inspection and measurement of critical dimensions, it is possible to shorten the manufacturing time of the photomask and improve productivity.

Claims (3)

Claims [1] A method for inspecting a photomask composed of a plurality of unit regions having patterns of the same shape using each other using inspection equipment capable of defect inspection and critical dimension measurement Recognizing, by the inspection equipment, a plurality of critical dimension measurement points included in each unit area; Capturing images of the unit areas to perform defect inspection over the entire photo mask in an image to image manner; And During the defect inspection, measuring a critical dimension of a light shielding pattern of the recognized critical dimension measurement point in each unit region. A method of inspecting a photomask using an inspection apparatus that includes a stage capable of horizontally moving and detecting an intensity of inspection light scanned from a light source via a photomask, wherein a database of light blocking patterns of the photomask is stored. , Storing a threshold intensity of inspection light in the inspection equipment; Performing defect inspection in a database to image manner scanning the entire area of the photomask; And Calculating the critical dimension of the light shielding patterns throughout the photomask from the moving distance of the stage with respect to an area where the intensity of the inspection light detected by the detection means during the defect inspection is continuously greater than the threshold intensity and / or less than the threshold intensity; A photomask inspection method comprising the steps. The method of claim 2, The critical dimension of the region where the intensity of the detected inspection light is continuously greater than the threshold intensity is the interval between the light blocking patterns, and the critical dimension of the region where the intensity of the detected inspection light is continuously smaller than the threshold intensity is the size of the shading patterns. A photomask inspection method, characterized in that the line width.

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