KR100437823B1 - align measurement using overlay pattern - Google Patents

Abstract

The present invention relates to an overlay pattern for measuring the degree of alignment to prevent overlapping degree deterioration, an outer box formed of two pairs to have a space of 1um or less and each width of 1um or less, and the inside of the outer box It characterized in that it comprises an inner box formed in a matrix form with a constant distance and step with the outer box.

Description

Align measurement using overlay pattern

The present invention relates to an overlay pattern for measuring alignment, and more particularly to an overlay pattern for measuring alignment suitable for removing WIS (Wafer Induced Shift).

As the pattern size becomes smaller in the lithography process, the required overlay budget is also decreasing. As the semiconductor generation progresses, it is necessary to verify and solve the overlay error deterioration phenomenon which may be caused by the metallic film at a time when the use of the metallic film is increasing.

WIS is a superposition alignment degradation caused by asymmetrical deposition properties of such highly reflective metallic films (eg, W, Al, poly-Si, etc.).

As a kind of trick by film reflection, the existing overlap alignment detection box cannot avoid this error and cannot reflect the actual overlap alignment value. Thus, even if the measurement meets the overlay spec, it may actually deviate from the spec.

On the other hand, in general, the overlay measurement method is a box-in-box type is used to measure the overlay between the two layers, the box-in-box type features a hollow inner box and a smaller inner box than the outer box In the outer box to measure the overlay between the two layers.

Hereinafter, referring to the accompanying drawings, a conventional overlay pattern for measuring alignment is as follows.

FIG. 1A is a plan view illustrating a conventional overlay pattern for measuring alignment, and FIG. 1B is a cross-sectional view taken along line IV-IV of FIG. 1A.

As shown in FIGS. 1A and 1B, an outer mark 11 having a width of 1 μm or more, and a constant distance and step between the outer box 11 and the outer box 11 are formed inside the outer box 11. And an inner mark 12 formed in a matrix form.

That is, the outer box 11 is a box in which an overlay pattern for measuring the degree of alignment for measuring alignment accuracy between a preceding process and a subsequent process is used as an overlay measurement target, and the inner box 12 is a current layer (for example, Photoresist).

On the other hand, the metal film 13 deposited by PVD and CVD is formed on the side of the outer box 11 which is asymmetrically formed when the sputter source is on the side when viewed from a semiconductor substrate (not shown). .

Accordingly, when the outer box 11 having a width of 1 μm or more is used as described above, asymmetry when the metal film of PVD (Physical Vapor Deposition) method is deposited is displayed on the edge of the box.

In this case, in the overlay error measurement method dx = (d2-d1) / 2, the wrong distance of B1 and B2 is used instead of A1 and A2 which should be actually reflected when measuring the actual distance of the measuring equipment.

Therefore, A and B make an error in overlapping degree.

That is, when the overlay is measured between the edge of the inner box 12 and the edge of the metal film 13 formed on the side of the outer box 11, the metal film 13 formed on the side of the outer box 11 is asymmetrically. Because it is formed, it is measured shift more than actually.

On the other hand, in the conventional method of forming the overlay pattern for measuring the degree of alignment, after forming the hollow outer box 11, the inner box 12 is formed inside the outer box 11 to form a xenon lamp (Zenon). The light generated from the lamp is measured using a microscope.

Such light measures the accuracy of the alignment of the overlay pattern using the signal reflected from the edges of the outer box 11 and the inner box 12 to measure the accuracy between the preceding process and the subsequent process.

However, the above-described conventional alignment pattern measurement overlay problem has the following problems.

In other words, A1 and A2 themselves do not represent the exact position of the edge, so that an incorrect dx value is calculated.

The present invention has been made to solve the conventional problems as described above, the overlay for measuring the degree of alignment to prevent the overlapping degree degradation by using a geometrical properties and narrow space contrast detection method The purpose is to provide a pattern.

1A is a plan view showing an overlay pattern for measuring a conventional alignment degree

FIG. 1B is a cross-sectional view taken along line IV-IV of FIG. 1A

Figure 2a is a plan view showing an overlay pattern for measuring the alignment degree according to the present invention

FIG. 2B is a cross-sectional view taken along line VI-VI of FIG. 2A

3A to 3F are graphs showing differences in superposition alignment components of overlay patterns for measuring alignment in accordance with the present invention.

Explanation of symbols for main parts of the drawings

21: outer box 22: inner box

23: metal film

The overlay pattern for measuring the degree of alignment according to the present invention for achieving the above object is an outer box formed by pairing two to have a space of 1um or less and each width of 1um or less, and the outer box and the inside of the outer box; It characterized in that it comprises an inner box formed in a matrix form at regular intervals and steps.

Hereinafter, referring to the accompanying drawings, the overlay pattern for measuring the alignment degree according to the present invention will be described in detail.

FIG. 2A is a plan view illustrating an overlay pattern for measuring alignment according to the present invention, and FIG. 2B is a cross-sectional view taken along the line VI-VI of FIG. 2A.

2A and 2B, the outer box 21 is formed to be paired to have a space of 1 μm or less and each width is 1 μm or less, and the outer box 21 is fixed to the inside of the outer box 21. It consists of an inner box 22 formed in a matrix form with a gap and a step.

That is, the outer box 21 is a box indicating the position of the previous layer, and the inner box 22 is a current layer (for example, photoresist).

On the other hand, the metal film 23 deposited by PVD and CVD is deposited on the outer box 21.

Here, the spacer of the outer box 21 is sized by the type, thickness and deposition property of the metal film 23 deposited by PVD and CVD.

Therefore, as the metal film 23 is deposited in the appropriately selected space, the asymmetry of the deposition is alleviated, and the average is measured because the space measuring two edges, not the edges, is measured when measuring with a measuring device. The effect allows for a more accurate physical location.

That is, the measurement method dx = (C2-C1) / 2 of the box according to the present invention, and since C2 and C1 represent actual distances, accurate overlap alignment can be measured.

On the other hand, Table 1 is the experimental data of the overlay pattern for measuring the alignment degree according to the present invention.

In other words, it shows an example of the selection of the appropriate space for the Pt deposition thickness and the WIS detection capability.

Thickness Space width (μm) 500 0.2 (2_2d) 1000 0.25 (2_25d) 1500 0.3 (2_3d) 2000 0.4 (2_4d) 2500 0.5 (2_5d) 3000

The component in which the WIS appears in the actual overlap alignment is the wafer scale component of the system offset component.

The experiment used Pt deposited by sputtering method. Pt thickness was classified from 500Å to 500Å by 3000Å and the size of space was 0.2㎛, 0.25㎛, 0.3㎛, 0.4㎛, 0.5㎛.

3A to 3F are graphs showing differences in overlapping arrangement components of overlay patterns for measuring alignment in accordance with the present invention.

That is, FIGS. 3A and 3B are X and Y scale components, FIGS. 3C and 3D are X shift and Y shift components, and FIGS. 3E and 3F are X rotation and Y rotation components.

As shown in Figures 3a to 3f, the value other than the scale component appears to be almost unchanged as expected, and it can be seen that the scale component value extracted as the space size decreases increases and then becomes constant.

The constant point becomes the size of the maximum space where the WIS can be detected under the conditions of the thickness and the step of the metal film used. 2500 Å, 3000 Å shows that it can already detect at 0.5 μm.

Therefore, a novel type of alignment measurement overlay pattern according to the present invention can eliminate WIS caused by asymmetrical deposition of a highly reflective metal film.

Although the existing overlap alignment detection boxes have a width or space of more than 1 μm and cannot use WIS detection or removal due to the edge contrast detection method, the present invention eliminates WIS by using a narrow space and space contrast of less than 1 μm. can do.

The narrow space geometry reduces the tendency of asymmetric deposition, and the use of space contrast can prevent WIS due to the average effect.

The size of the space is determined by the thickness of the film to be deposited, the deposition properties, and the step height of the overlay pattern for measuring the degree of alignment. The space size for various conditions is evaluated to have a margin for process application.

As described above, the overlay pattern for measuring the degree of alignment according to the present invention has the following effects.

In other words, when the speed and capacity of semiconductors need to be finely patterned and strict overlay error management is required, an overlay error different from the actual one may be applied due to WIS.

Accurate WIS detection was difficult unless the pattern was etched, but WIS detection on photoresist patterning prevents or reduces invisible overlay error buckets.

Claims (2)

Two outer pairs to have a space of 1um or less and each outer box formed of 1um or less, An overlay pattern for measuring alignment degree, comprising an inner box formed in a matrix form at regular intervals and steps with the outer box in the outer box. The overlay pattern as claimed in claim 1, wherein the size of the space is determined by the thickness of the film to be deposited, the deposition property, and the step height of the overlay pattern for measuring the degree of alignment.