KR20060104825A - Method of manufacturing a photo mask - Google Patents

Abstract

The present invention relates to a method for manufacturing a photomask, and after measuring the CD change of the device pattern is converted into an amount of energy change or transmittance change, to form a material layer that can control the transmittance in the mask in preparation for 100% transmittance or a glass substrate The photomask fabrication method can reduce the cost of manufacturing the mask compared to the method of manufacturing a new mask by feeding back the data of the existing wafer state by forming a pinhole to correct the CD change.

Photo mask, CD change, transmittance change

Description

Method of manufacturing a photo mask

1 is a process flowchart illustrating a method of manufacturing a photomask according to an embodiment of the present invention.

2 to 8 are diagrams for convenience of explanation of each step of FIG.

<Explanation of symbols for the main parts of the drawings>

101 glass substrate 102 light shielding film

103 MoSiN film 104 CrON film

100: cell area 200: peripheral area

300: mask 400: lens

500 wafer 600 device pattern

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a photo mask, and more particularly to a method of manufacturing a photo mask capable of correcting a change in a critical dimension (hereinafter, referred to as "CD") of a pattern formed on a wafer.

BACKGROUND OF THE INVENTION A semiconductor device manufacturing process requires a plurality of photolithography processes to form devices on a semiconductor substrate. Furthermore, in order to form a highly integrated circuit, a photo mask having a fine pattern is required, and the pattern must be free of defects. The CD size required for high integration of semiconductor devices has already reached the limit of the resolution of exposure equipment. In this situation, CD uniformity of the photo mask for patterning a predetermined material layer is very important.

Meanwhile, in order to manufacture a photomask used for photolithography, it is common to perform the following series of processes using electron beam lithography. First, a light shielding film and an electron beam resist are sequentially formed on a transparent substrate made of a material such as quartz or glass. An exposure apparatus is used to expose the electron beam to the electron beam resist in a desired pattern. Then, the exposed electron beam resist is developed using a development apparatus. The light shielding film is etched using the electron beam resist pattern formed according to a desired pattern as a mask to form a light shielding film pattern. Thereafter, the photomask is completed by removing the electron beam resist pattern.

The photomask manufactured as described above has a problem in that a light shielding film pattern having a line width different from that of a CD is formed due to various factors in the manufacturing process, and the uniformity of the pattern line width is reduced. As such, when the photolithography process is performed using a photomask whose pattern line width is changed or uniformity is reduced due to the process, the line width of the pattern on the wafer is also changed or the uniformity is reduced. The photomask with the changed pattern line width or the reduced uniformity becomes a cause of defects in the semiconductor device, thereby increasing the manufacturing cost by reducing the process yield.

Representative causes of the change of the pattern line width are the fogging effect and the loading effect. The fogging effect refers to a change in line width caused by scattering exposure of the electron beam resist by the electron beam reflected from the inside or the surface of the electron beam resist and the lower portion of the objective lens of the electron beam irradiator. In addition, the loading effect means that when the light shielding film is etched, a line width change occurs in which a line width of a portion having a large loading density (density of an area where the light shielding layer is exposed due to electron beam stress is removed) is larger than a line width of a portion having a small loading density. Say.

There are various methods to improve the CD uniformity, but in particular, the manufacturing of the mask is made by changing the light shielding film pattern by dividing the number of electron beam irradiation, the etching method of the electron beam equipment, and the energy of the electron beam by specific regions. The method is mainly used. Of course, these methods are generally used together, but there are many manufacturing difficulties and large differences in the performance and form of the equipment. In order to improve the uniformity of the cell area of the device, it is calculated by adjusting the fogging value although it depends on the data. OPC) simulation and continuous feedback to mask fabrication and wafer results to set up optimal mask conditions. However, the above method is expensive to manufacture a mask, and the reliability is high in the case of the existing i-line (365 nm wavelength), KrF (248 nm wavelength), but a lot of difficulties in the recent ArF (193 nm wavelength). Suffer. In particular, when the CD change tolerance for the pattern near 70 nm is within 10 nm, it is greatly influenced by the Mask Error Factor (MEF) value, and the exposure of the peripheral area is focused on the patterning of the cell. Despite the large design rules, many problems, such as collapse and bridge, are occurring.

It is an object of the present invention to provide a photomask manufacturing method which can improve CD uniformity while reducing mask manufacturing cost.

Another object of the present invention is to provide a photomask manufacturing method that can improve CD uniformity by forming a material layer capable of controlling transmittance on the back surface of a glass substrate on which a light shielding film pattern is formed.

In order to achieve the above object, the present invention intends to improve CD uniformity by the following method. First, a device pattern is formed on a wafer using a mask in which cell and peripheral areas are determined, the cell area of the device pattern is divided into a plurality of areas, and then CDs are measured for each area. The CD measured value is calculated as the amount of change in energy or change in transmittance, and the CD is corrected by applying a material having a different transmittance to one surface of the glass substrate on which the light shielding film is not formed according to the change amount. In general, the CD value tends to increase or decrease toward an edge with respect to the center of the device pattern. A large CD can be seen as having more or less energy exposed than a small area of the CD, thereby compensating the CD by compensating for the intensity of light passing through the portion with a material having a different transmittance.

On the other hand, as the cell pattern becomes smaller, there are many cases of patterning at the limit of the exposure equipment. In this case, exposure conditions for only cell patterns are set (especially directional exposure conditions are selected). Incidentally, the peripheral area is caused to suffer from pattern collapse and bridge due to exposure conditions that do not match the orientation of the device pattern. In this case, a method of compensating the exposure condition and energy difference by applying a material to adjust transmittance in a specific peripheral region or etching the glass substrate.

According to one or more exemplary embodiments, a method of manufacturing a photomask may include: manufacturing a mask in which a cell region and a peripheral region are determined by patterning a light shielding film on a glass substrate; Forming a plurality of device patterns in which a cell region and a peripheral region are defined on a wafer using the mask; Calculating the CD uniformity according to the line width of the measurement pattern by dividing the device pattern into a plurality of areas, measuring line widths in each area, and grouping areas having the same line width; Configuring the device pattern into a matrix of energy and focus and then calculating the measured CD uniformity as an energy change amount; Exposing based on 100% transmittance and comparing the difference with respect to CD for each region, and converting the CD change into transmittance accordingly; And forming a material layer capable of controlling transmittance on one surface of the glass substrate on which the light shielding film is not formed according to the converted transmittance, and patterning the same to adjust transmittance for each region.

According to another aspect of the present invention, there is provided a method of manufacturing a photomask, including: forming a light shielding film on a glass substrate and patterning the first mask to determine a cell region and a peripheral region; Forming a plurality of device patterns in which a cell region and a peripheral region are defined on a wafer using the first mask; Calculating the CD uniformity according to the line width of the measurement pattern by dividing the device pattern into a plurality of areas, measuring line widths in each area, and grouping areas having the same line width; Preparing a second mask having a different transmittance of the glass substrate and calculating the CD uniformity as a change in transmittance; Exposing based on 100% transmittance and comparing the difference with respect to CD for each region, and converting the CD change into transmittance accordingly; And forming a material layer capable of controlling transmittance on one surface of the glass substrate on which the light shielding film of the first mask is not formed according to the converted transmittance, and patterning the same to adjust transmittance for each region. .

According to still another aspect of the present invention, there is provided a method of manufacturing a photomask, including: forming a light shielding film on a glass substrate and patterning the same to form a mask in which cell regions and peripheral regions are determined; Forming a plurality of device patterns in which a cell region and a peripheral region are defined on a wafer using the mask; Calculating the CD uniformity according to the line width of the measurement pattern by dividing the device pattern into a plurality of areas, measuring line widths in each area, and grouping areas having the same line width; Configuring the device pattern into a matrix of energy and focus and then calculating the measured CD uniformity as an energy change amount; Exposing based on 100% transmittance and comparing the difference with respect to CD for each region, and converting the CD change into transmittance accordingly; And forming a pinhole by etching a predetermined region of the glass substrate according to the converted transmittance, thereby controlling the transmittance equally for each region.

According to still another aspect of the present invention, there is provided a method of manufacturing a photomask, including: forming a light shielding film on a glass substrate and patterning the first mask to determine a cell area and a peripheral area; Forming a plurality of device patterns in which a cell region and a peripheral region are defined on a wafer using the first mask; Calculating the CD uniformity according to the line width of the measurement pattern by dividing the device pattern into a plurality of areas, measuring line widths in each area, and grouping areas having the same line width; Preparing a second mask having a different transmittance of the glass substrate and calculating the CD uniformity as a change in transmittance; Exposing based on 100% transmittance and comparing the difference with respect to CD for each region, and converting the CD change into transmittance accordingly; And forming a pinhole by etching a predetermined region of the glass substrate according to the converted transmittance, thereby controlling the transmittance equally for each region.

The matrix sets the pattern center region to a predetermined energy and focus, and sets the pattern center region by changing energy and focus up, down, left, and right.

The material layer capable of adjusting the transmittance is formed by stacking a MoSiN film and a CrON film.

The transmittance is controlled by controlling the thickness of the MoSiN film and the CrON film and the composition of Mo and Cr.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

1 is a flowchart illustrating a method of manufacturing a photomask according to the present invention, and FIGS. 2 to 8 are diagrams for convenience of description at each step of the flowchart.

Step 11: After forming the light shielding film 102 on the glass substrate 101 as shown in Fig. 2 (a) and patterning. As a result, a mask 300 in which the cell region 100, the peripheral region 200, and the like are determined as illustrated in FIG. 2B is manufactured.

Step 12: Using the mask 300 as shown in FIG. 3, the projection is reduced to, for example, one quarter on the wafer 500 through a predetermined lens 400, and developed. As a result, a plurality of device patterns 600 in which cell regions and peripheral regions are determined are formed on the wafer 500.

Step 13: As shown in FIG. 4, the cell pattern of one device pattern is divided into a plurality of areas, the line widths in each area are measured, and the areas of the same line width are grouped to map CD uniformity according to the line width of the measurement pattern. Expressed as In the CD uniformity map, the regions of the same hatching have the same line width, and the CD uniformity decreases as more differently hatched regions exist.

Step 14: As shown in FIG. 5, the device pattern is composed of a matrix of energy and focus, and then the measured CD uniformity is calculated as an energy change amount. Here, the matrix increases the energy by 5 mJ toward the left side of the pattern center region based on 20 mJ of energy and the focus of 0 μm, and decreases the energy by 5 mJ toward the right side of the pattern center region. In addition, the focus is increased by 0.05 μm toward the top, and the focus is increased by 0.05 μm toward the bottom. On the other hand, a mask in which the transmittance of the glass substrate is formed differently is manufactured as shown in FIG. 6, and the measured CD change is expressed as a change in transmittance.

Step 15: As shown in FIG. 7, a table comparing the differences of CDs for respective regions by exposure based on 100% transmittance is constructed, and the change in CD is converted into energy and transmittance accordingly.

Step 16: A light blocking film 102 is formed on the glass substrate 101 as shown in FIG. 8, and a material for controlling transmittance, for example, a MoSiN film 103 and a CrON film 104 is laminated on the patterned mask. By adjusting the transmittance for each area equally. Here, the laminated film of the MoSiN film and the CrON film is used as a material for controlling the transmittance in the halftone mask, and the transmittance of 6 to 8% is controlled. Therefore, by adjusting the composition and thickness of Mo and Cr affecting the transmittance can be formed on the glass substrate 101 to control the transmittance. It is known that defects generated during formation and patterning of the transmittance regulating material of the glass substrate 101 are not a problem up to a size of 100 μm. Transmittance of the exposure light other than the MoSiN film 103 and the CrON film 104 can be controlled, and both materials can be formed and patterned.

On the other hand, instead of forming a material layer that can control the transmittance in the portion that needs to control the transmittance by another method of the present invention by using a scattering interference when the exposure light is irradiated by forming a pinhole by etching a glass substrate to a certain size You can adjust the intensity.

In addition, the exposure energy difference compared to the cell region may be determined using the energy and focus matrix as shown in FIG. 5 or the transmittance division mask as shown in FIG. 6 through the inspection on the wafer in the collapse and bridge portions of the peripheral region. You can correct it.

As described above, according to the present invention, after measuring the CD change of the device pattern, it is converted into an energy change or transmittance change, and the CD change is corrected by forming a material layer capable of adjusting the transmittance in the mask in preparation for 100% transmittance. The cost of mask manufacturing can be reduced compared to the method of manufacturing a new mask by feeding back the data of the existing wafer state.

Claims (7)

Forming a light shielding film on the glass substrate and patterning the same to form a mask in which a cell region and a peripheral region are determined; Forming a plurality of device patterns in which a cell region and a peripheral region are defined on a wafer using the mask; Calculating the CD uniformity according to the line width of the measurement pattern by dividing the device pattern into a plurality of areas, measuring line widths in each area, and grouping areas having the same line width; Configuring the device pattern into a matrix of energy and focus and then calculating the measured CD uniformity as an energy change amount; Exposing based on 100% transmittance and comparing the difference with respect to CD for each region, and converting the CD change into transmittance accordingly; And And forming and patterning a material layer capable of adjusting transmittance on one surface of the glass substrate on which the light shielding film is not formed according to the converted transmittance, thereby controlling the transmittance equally for each region. Forming a light shielding film on the glass substrate and patterning the first mask to determine a cell area and a peripheral area; Forming a plurality of device patterns in which a cell region and a peripheral region are defined on a wafer using the first mask; Calculating the CD uniformity according to the line width of the measurement pattern by dividing the device pattern into a plurality of areas, measuring line widths in each area, and grouping areas having the same line width; Preparing a second mask having a different transmittance of the glass substrate and calculating the CD uniformity as a change in transmittance; Exposing based on 100% transmittance and comparing the difference with respect to CD for each region, and converting the CD change into transmittance accordingly; And Forming a material layer capable of controlling transmittance on one surface of the glass substrate on which the light shielding film of the first mask is not formed according to the converted transmittance, and patterning the same to adjust transmittance for each region equally Mask manufacturing method. The method of claim 1, wherein the matrix sets the pattern center region to a predetermined energy and focus, and changes the energy and the focus up, down, left, and right based on the matrix. The method of claim 1, wherein the material layer capable of adjusting transmittance is formed by stacking a MoSiN film and a CrON film. The method of claim 4, wherein the transmittance is controlled by controlling the thickness of the MoSiN film and the CrON film and the composition of Mo and Cr. Forming a light shielding film on the glass substrate and patterning the same to form a mask in which a cell region and a peripheral region are determined; Forming a plurality of device patterns in which a cell region and a peripheral region are defined on a wafer using the mask; Calculating the CD uniformity according to the line width of the measurement pattern by dividing the device pattern into a plurality of areas, measuring line widths in each area, and grouping areas having the same line width; Configuring the device pattern into a matrix of energy and focus and then calculating the measured CD uniformity as an energy change amount; Exposing based on 100% transmittance and comparing the difference with respect to CD for each region, and converting the CD change into transmittance accordingly; And And forming a pinhole by etching a predetermined region of the glass substrate according to the converted transmittance, thereby controlling the transmittance equally for each region. Forming a light shielding film on the glass substrate and patterning the first mask to determine a cell area and a peripheral area; Forming a plurality of device patterns in which a cell region and a peripheral region are defined on a wafer using the first mask; Calculating the CD uniformity according to the line width of the measurement pattern by dividing the device pattern into a plurality of areas, measuring line widths in each area, and grouping areas having the same line width; Preparing a second mask having a different transmittance of the glass substrate and calculating the CD uniformity as a change in transmittance; Exposing based on 100% transmittance and comparing the difference with respect to CD for each region, and converting the CD change into transmittance accordingly; And And forming a pinhole by etching a predetermined region of the glass substrate according to the converted transmittance, thereby controlling the transmittance equally for each region.

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