KR20070101908A - Method of manufacturing photomask for focus drilling exposure - Google Patents

Abstract

A method for manufacturing a photo mask for a focus drilling exposure method is provided to manufacture a photo mask with a uniform critical dimension of a target pattern by performing an OPC(Optical Proximity Correct) for a random pitch and a size. A method for manufacturing a photo mask for a focus drilling exposure method includes the steps of: setting the layouts of target patterns to be formed on a wafer(100); arranging the test patterns for the target patterns(110); extracting rule parameters by exposing the test patterns in a focus drilling method(120); performing an OPC for the target patterns to be formed on the wafer by using mask bias rule data(130); and manufacturing the photo mask with data from the OPC performance for obtaining a uniform critical dimension of the target patterns(140).

Description

Method of manufacturing photomask for focus drilling exposure

1 is a flowchart illustrating a method of manufacturing a photomask using a focus drilling exposure technique according to the present invention.

FIG. 2 is a diagram illustrating a pattern having various pitches and sizes disposed on a test mask.

3 is a view illustrating an exposure apparatus using the focus drilling exposure technique of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly, to a mask fabrication method for a focus drilling exposure method.

In general, a semiconductor device such as a DRAM (DRAM) is composed of a large number of fine patterns, and such fine patterns are formed through a photolithography process. In order to form a fine pattern using a photolithography process, first, a photoresist film is coated on the target film to be patterned. Next, a normal exposure process is performed to change the solubility of a portion of the photoresist film. The development process is performed to remove portions of which the solubility is not changed or not, thereby forming a photoresist film pattern exposing a part of the surface of the target film. Subsequently, the target film pattern can be formed by removing the exposed portion of the target film by etching using the photoresist film pattern as an etching mask and then removing the photoresist film pattern.

In such a photolithography process, resolution and depth of focus (DOF) are known as important variables in forming a fine pattern. Depth of focus (DOF) represents a limit of the defocus value that guarantees the dimensional accuracy of the pattern, it can be expressed as shown in Equation 1 below.

[Equation 1]

DOF = K × λ / NA ² (NA is the numerical aperture of the exposure apparatus, λ is the wavelength of the light source)

At this time, the value of the depth of focus becomes smaller as the wavelength? Is shorter or as the numerical aperture NA is higher. When the depth of focus is small, it is preferable that the value of the depth of focus is large because it becomes difficult to form a fine pattern while decreasing the process margin.

Currently known techniques for increasing the depth of focus (DOF) can be divided into two categories. One is a technique of controlling exposure of a wavelength emitted from a laser, and the other is a technique of exposing by moving a wafer stage. Among these, exposure techniques using a wafer stage include a method of double exposure by changing the position of the wafer stage and a focus drilling method of scanning the wafer stage by tilting it at a predetermined angle.

On the other hand, in the process of using a focus drilling method (Focus drilling) method to improve the margin of the depth of focus (DOF), the mask bias (mask bias) is changed depending on the pitch (pitch) of the pattern. Because of these phenomena, photomasks with conventional exposure techniques cannot be applied to focus drilling techniques. Therefore, a problem may arise in that a mask having to be masked for each pitch needs to be manufactured.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a method for manufacturing a mask for a focus drilling exposure method capable of forming a mask implementing a pattern having a desired critical dimension by reflecting information related to mask bias in a manufacturing process of a photomask. have.

In order to achieve the above technical problem, the mask manufacturing method for the focus drilling exposure method according to the present invention, the step of setting the layout of the target pattern to be formed on the wafer; Extracting rule parameters by performing exposure using a focus drilling method on the test pattern for the target pattern; Performing optical access correction (OPC) on the target pattern using the rule parameters; And fabricating a mask to form the optical access correction (OPC) layout.

The extracting of the rule parameters may include: setting a layout of test patterns having different sizes and pitches; Exposing the test patterns using a focus drilling method; It is preferable to include the step of generating the mask bias rule data by measuring the critical dimension and the space of the exposed test patterns.

In addition, prior to the step of extracting the rule parameter, placing a wafer on the wafer stage of the exposure apparatus; And setting an inclination of the wafer stage required in the exposure method using the focus drilling method by measuring an offset range that is a limit range of focus that can increase a process margin during exposure while changing the inclination of the wafer stage. It is desirable to.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification.

Depth of focus (DOF) represents the limit of the focus value that guarantees the precision of the pattern. As the depth of focus decreases, the depth of focus becomes large because the process margin becomes smaller and it becomes difficult to form a fine pattern. It is desirable to have.

Among the techniques for improving the depth of focus (DOF), a mask manufacturing method for a focus drilling method that can form a pattern having a desired threshold dimension on the photomask by controlling the mask bias in the focus drilling exposure method Will be described.

1 is a flowchart illustrating a method of manufacturing a mask for a focus drilling exposure method according to the present invention. FIG. 2 is a diagram illustrating a pattern having various pitches and sizes disposed on a test mask. 3 is a view illustrating an exposure apparatus using the focus drilling exposure method of the present invention.

First, referring to FIGS. 1 and 2, first, a layout of a target pattern to be formed on a wafer is set (step 100). Next, test patterns 200 for a target pattern are disposed (step 110), and a rule parameter is extracted by performing exposure using the focus drilling method on the test patterns 200 (step 120). .

Here, in order to extract rule parameters, first, layouts of test patterns 200 having different sizes and pitches are set on the wafer. Next, exposure is performed on the test patterns 200 using a focus drilling method, and a rule parameter is extracted by measuring a threshold dimension 210 and a space 220 of the exposed test patterns 200 and extracting a mask bias. Create rule data.

Specifically, as shown in FIG. 2, first, the layout of various test patterns 200 is set on the photomask for testing, from a pattern having a small size and a pitch to a large pattern. In this case, the pitch includes a critical dimension 210 and a space 220.

Next, the test patterns 200 are exposed by using a focus drilling method. The focus drilling exposure method is a method in which the wafer stage is tilted at a predetermined angle and scanned.

As shown in FIG. 3, the exposure apparatus for the focus drilling exposure method includes a slit 300 including an opening through which light is transmitted from a light source, and a pattern to be formed on a wafer, for example, test patterns ( 200, see FIG. 2) is transferred to the photomask 310, the lens 320 to form an image on the wafer (w) by using the light transmitted from the light source, and the wafer (w) It comprises a wafer stage 330. In this case, the wafer stage 330 may be inclined at a predetermined angle, and may move in one direction.

Exposure using the focus drilling method is performed on the test patterns 200 using the exposure apparatus as described above.

To this end, the test wafer w is first placed on the wafer stage 330 of the exposure apparatus. Next, the wafer stage 330 is moved to have a predetermined first tilt 340, and then light is transmitted from the light source to measure the first focus. Subsequently, the wafer stage 330 is moved to have the second slope 350, and then the light is transmitted from the light source to measure the second focus. As such, the optimized offset range is set while varying the inclination of the wafer stage 330. The optimized offset range is a limit range of focus that can increase the process margin during exposure. Next, the wafer stage 330 is exposed and scanned in one direction while the wafer stage 330 is fixed to the inclination required by the method using the focus drilling exposure.

In addition, rule parameters are extracted by measuring the critical dimension 210 and the space 220 of the exposed test pattern 200, and the mask parameters are arranged according to a predetermined rule to prepare mask bias rule data. do. The critical dimension 210 and the space 220 of the exposed test patterns 200 may be measured after the pattern is etched, measured in a state in which a photosensitive film is covered, or in a state in which patterns are formed on a wafer.

Next, using the mask bias rule data thus prepared, optical proximity correction (OPC) of the target pattern to be formed on the wafer is performed (step 130).

Next, using a focus drilling exposure method by fabricating a mask with data subjected to optical proximity correction (OPC) (step 140), a critical dimension of a desired target pattern may be uniformly obtained.

In the mask fabrication method for the focus drilling exposure method according to the present invention, mask mask rule data is generated by extracting rule parameters and performing optical proximity close correction (OPC) of the pattern according to the data, thereby changing the photomask according to the change of the mask bias. It is possible to reduce the number of modifications to the resource. In addition, since the mask bias factor is already reflected by performing the optical proximity correction (OPC) according to the mask bias rule data, the mask bias factor may not be considered, and thus the critical dimension of the target pattern may be eliminated. The mask which has a uniform can be manufactured.

As described so far, according to the mask fabrication method for the focus drilling exposure method according to the present invention, a data file related to mask bias is created before the photomask fabrication, and optical proximity correction (OPC) for random pitch and size is executed. In this way, a mask having a uniform critical dimension of the target pattern can be produced.

Claims (3)

Setting a layout of a target pattern to be formed on the wafer; Extracting rule parameters by performing exposure using a focus drilling method on the test pattern for the target pattern; Performing optical access correction (OPC) on the target pattern using the rule parameters; And And manufacturing a mask to form the optical access correction (OPC) layout. The method of claim 1, wherein the extracting of the rule parameters comprises: Setting a layout of test patterns having different sizes and pitches; Exposing the test patterns using a focus drilling method; A method of manufacturing a mask using a focus drilling exposure method, comprising: generating mask bias rule data by measuring critical dimensions and spaces of exposed test patterns. The method of claim 1, wherein before the extracting of the rule parameter, Placing the wafer on a wafer stage of the exposure apparatus; And Measuring an offset range which is a limit range of a focus that can increase a process margin during exposure while changing an inclination of the wafer stage, and setting the inclination of the wafer stage required by an exposure method using the focus drilling method; Mask manufacturing method using the focus drilling exposure method characterized in that.

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