KR19980016832A - Focus level measurement method using phase inversion overlay key - Google Patents

Abstract

The present invention provides a method for measuring a focus level in manufacturing a semiconductor device. This method includes forming phase inversion overlay keys in a field of a mask using a non-180 ° phase inversion mask manufacturing method, and performing a photolithography process using a mask in which phase inversion overlay keys are formed. Forming, observing the shape of these patterns to calculate the in-field focus level, and correcting the focus leveling of the stepper based on the calculated result. Therefore, since the focus level in the field can be measured accurately, focus leveling correction can also be performed accurately.

Description

How to measure the focus level using the phase reversal overlay key

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor, and more particularly, to a method of measuring a focus level using a phase shift overlay key.

The shorter the wavelength of light used in the photo lithography region, the higher the resolution, but the smaller the depth of focus (DOF).

It is very important in the photographic process to keep all the parts in the stepper lens field in the same focus as possible. Thus, an in-field focus is controlled by introducing a tool called leveling in the i-line stepper. In order to correct the leveling, focus information in the field is required. As a method of measuring the focus change in the field, each individual observes a real pattern with a scope and compares the profile. However, this is a situation where the error due to individual differences of view is large and not quantified.

An object of the present invention is to change the focus level in a field by using a phenomenon in which the pattern of an aerial image of a non-180 ° phase inversion mask (PSM) shifts in proportion to the change in focus. The present invention provides a method for measuring focus level that can be quantified.

1 is a cross-sectional view illustrating a non 180 ° phase shift mask.

FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 3D show simulation results of a photolithography process using the mask of FIG. 1.

3 is a plan view illustrating a non-180 ° phase inversion mask in which a phase inversion overlay key is formed in a field.

4A, 4B, and 4C are diagrams for describing a result of a photolithography process using the mask of FIG. 3.

In order to achieve the above object, the focus level measuring method according to the present invention comprises the steps of forming the phase inversion overlay keys in the field of the mask by a non-180 ° phase inversion mask manufacturing method; Performing a photolithography process using a mask on which the phase inversion overlay keys are formed to form patterns corresponding to the phase inversion overlay keys on a substrate, respectively; Observing the shape of the patterns to calculate an in-field focus level; And correcting the focus leveling of the stepper based on the calculated result.

In this case, the phase inversion overlay keys are formed in the top left, bottom left, top right, bottom right and center of the field, and are box-shaped and frame-shaped. It is preferable to form in either shape.

Hereinafter, with reference to the accompanying drawings, it will be described in more detail the present invention.

1 is a cross-sectional view of a non 180 ° phase shift mask, 10 quartz, 12 0.4 chromium (Cr), 14 90 ° inversion, and 16 Represents an area where the phase is not inverted, that is, an 0 ° inversion area.

(A) (b) (c) and (d) of FIG. 2 are simulation results of the photolithography process using the mask of FIG. 1, and (a) shows three kinds of focal positions. (b) shows an aerial image when defocus is (0), (c) shows an aerial image when defocus is (-), and (d) shows a defocus. (+) Shows the aerial image.

Referring to FIG. 2, when the photographing process is performed using the non-180 ° phase reversal mask, it may be seen that the pattern of the aerial image is proportionally shifted according to the focus. That is, when the defocus is (0), the aerial image is formed at the center of the center (see (b) of FIG. 2), and when the defocus is (-), the aerial image is formed by moving to the right centering on the center of the center (see FIG. (c)), when the defocus is (+), it is formed by moving to the left centering on the center of gravity (see (d) of FIG. 2).

The present invention utilizes the above phenomenon to form a phase shift overlay key in a field so that a focus error component is represented by an overlay error component so that the focus error component and the overlay error are generated. Quantify the relationship with the components and easily obtain focus level information using current automated metrology tools.

3 is a plan view illustrating a non-180 ° phase inversion mask in which a phase inversion overlay key is formed in a field. Reference numeral 30 denotes a 180 ° inversion area, 32 a phase inversion overlay key, and 34 a 0 ° inversion area.

Phase inversion overlay keys 32 are formed in the Top Left, Bottom Left, Top Right, Bottom Right and Center of the field, and are boxed or framed. To form.

(A) (b) and (c) of FIG. 4 are diagrams for explaining the result of the photolithography process using the mask of FIG. 3, and (a) shows an aerial pattern when the defocus is (0). (B) shows the aerial pattern when the defocus is (+), and (c) shows the aerial pattern when the defocus is (-).

After performing the photolithography process using the non-180 ° phase reversal mask of FIG. 3, the focus level in the field can be easily seen by observing the shape of the pattern formed on the substrate (see FIG. 4). After this, the information about this focus level is analyzed and the leveling of the stepper is adjusted.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical idea of the present invention.

In the photolithography process for manufacturing a semiconductor device, since the focus level in the field can be accurately measured, the focus leveling correction can also be performed accurately, thereby improving the profile of the pattern formed on the substrate.

Claims (3)

Forming phase inversion overlay keys in a field of the mask with a non-180 ° phase inversion mask fabrication method; Performing a photolithography process using a mask on which the phase inversion overlay keys are formed to form patterns corresponding to the phase inversion overlay keys on a substrate, respectively; Observing the shape of the patterns to calculate an in-field focus level; And And correcting the focus leveling of the stepper based on the calculated result. The method of claim 1, wherein the phase inversion overlay keys, Focus level measurement method using a phase inversion overlay key, characterized in that formed in the upper left, lower left, upper right, lower right and the center of the field. The method of claim 1, wherein the phase inversion overlay keys, A focus level measurement method using a phase inversion overlay key, characterized in that formed in any one of a box shape and a frame shape.