KR100850176B1 - Calculating method of numerical middle value of metal layer for overlay measurement and overlay measuring device - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to provide an overlay measuring method and a measuring apparatus which can achieve an accurate overlay measurement by overcoming an overlay measurement error caused by an asymmetrically deposited metal layer.

Accordingly, the present invention provides a method for measuring overlay, comprising the steps of measuring the thickness of the deposited metal layer, measuring the length of the horizontal plane of the deposited metal layer, measuring the length of both slopes of the deposited metal layer, the formula Computing the length of the horizontal portion of the two inclined surface by using, and calculating the median value by adding the horizontal surface length of the metal layer and the horizontal portion of the two inclined surface.

Metal layer, median, slope

Description

Calculating method of numerical middle value of metal layer for overlay measurement and overlay measuring device}

1 is a schematic diagram showing a mother and son formed in a contact layer during overlay measurement of a metal layer to explain the overlay measurement process according to an embodiment of the present invention;

2 is a schematic view showing an overlay measuring apparatus according to an embodiment of the present invention;

3 is a schematic diagram illustrating the difference in median value in overlay measurement according to the prior art.

Explanation of symbols on the main parts of the drawings

103: metal layer L: horizontal plane

B1, B2: Slope C: Horizontal

A: thickness 200: camera

201 support

The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for measuring an overlay between a lower layer and an upper layer in a photolithography process.

As is well known, the semiconductor element has a multilayer structure composed of a plurality of layers. As the integration degree increases, the minimum line width of the pattern required for the manufacturing process becomes smaller as the integration degree increases, and thus, when the fine patterns are connected to each other, a specific layer and a lower portion of the semiconductor layer are formed on or underneath. The accuracy of the overlay with other layers to be formed, ie the accuracy of the alignment, is greatly required.

Therefore, in the normal semiconductor manufacturing process, an overlay measurement pattern is provided for identifying and correcting the alignment state between the layer formed in the previous process and the layer formed through the current process. This overlay measurement pattern is usually installed in a scribe line of a wafer that divides between dies, and is usually composed of a mother formed in the previous layer and a son formed in the current layer to be placed in the mother. It is formed in a box in box structure.

In the overlay measurement pattern of the box in box structure, for example, the mother is formed in the conductive layer pattern in the previous layer, the son is formed in the photosensitive layer pattern in the current layer.

Referring to the conventional overlay measurement method using the overlay measurement pattern of the box-in-box structure as described above, first, by measuring the respective median value of the mother and son by using the overlay measurement equipment, and then calculate the measured values Measure the son's shift.                         

However, the conventional overlay measurement method has a problem that accurate overlay measurement is difficult due to the influence of the bottom pattern, that is, the deposition characteristics of the mother and chemical mechanical polishing (CMP).

3 shows the difference between the median value of the actual contact layer and the median value measured by the overlay device according to the asymmetric metal layer measurement.

In the drawing, reference numeral 101 denotes a mother formed in the contact layer, 102 denotes a tungsten deposited on the formed mother, 103 denotes a metal layer deposited to a predetermined thickness on the tungsten, and 104 a real contact. Represents the median of the mothers formed in the layer, 105 represents the median measured in the overlay equipment by process influence and 106 represents the difference between the actual median 105 and the median read from the overlay equipment.

In other words, when measuring the overlay, the overlay mark is captured by a CCD camera that is generally perpendicular to the wafer, and then the degree of alignment between the lower layer and the current layer is measured. As a result, the metal layer is deposited to cause a difference between the median value of the actual contact layer and the value measured by the overlay equipment, thereby causing a difference in the degree of overlay alignment after the lithography process and the etching process.

This incorrect overlay measurement results in poor overlay accuracy.

 Accordingly, the present invention has been made to solve the above problems, to provide an overlay measuring method and measuring apparatus that can be achieved by accurate overlay measurement by overcoming the overlay measurement error caused by the asymmetrically deposited metal layer Has its purpose.

In order to achieve the object as described above, the present invention is to measure the thickness and the oblique length of the deposited metal layer to correct the median value of the asymmetrically deposited metal layer.

Method for calculating the median value of the metal layer for overlay measurement according to the embodiment, the first step of measuring the thickness of the metal layer forming a trench type step; A second step of measuring a length of an area where the metal layer forms a horizontal plane inside the step; A third step of measuring a length of an area where the metal layer forms an inclined surface in the step; A fourth step of calculating a length of a horizontal plane when the metal layer area forming the inclined plane of the step is vertically projected by using the measured value of the first step and the measured value of the third step; And a fifth step of calculating the median value of the entire length of the step using the measured value of the second step and the calculated value of the fourth step.

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

delete

On the other hand, in the overlay measuring apparatus including a camera for photographing the wafer in order to solve the overlay measurement error, the support structure in which the camera is mounted to the structure to be rotatable with respect to the wafer so that the camera can be rotated to shoot both inclined surfaces of the metal layer It is characterized by.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram illustrating a mother and son formed in a contact layer during overlay measurement of a metal layer to explain the overlay measurement process according to an embodiment of the present invention, Figure 2 is an overlay measurement according to an embodiment of the present invention A schematic diagram showing the device.

First, as shown in FIG. 1, the metal layer 103 may be asymmetrically deposited due to the deposition characteristics of the lower contact pattern and the chemical mechanical polishing (CMP). In this case, the accurate overlay on the metal layer 103 may be observed. Difficulties occur in the measurement, but through this measuring method, an accurate median value of the metal layer 103 can be obtained.
That is, the metal layer 103 forms a trench type step by the structure of the two mother and the tungsten layer between the mother layer formed in the lower layer, the trench type serves as a son.
However, as shown in FIG. 1, when the inclined surface lengths B1 and B2 of both side ends of the trench step are different, it is difficult to reflect the inclined surface lengths B1 and B2 in the calculation of the median value of the son. The median of the sons is calculated based on the area L where the layer 103 forms a horizontal plane.
The median value of the sons calculated as described above is added to the position of the end point of the right inclined plane B1 or the end point of the left inclined plane B2 and calculated as a coordinate value.
On the other hand, the median value between the mothers is added to the position of the mothers and calculated as coordinate values, and the median coordinates of the son and the median coordinates of the mother are compared to each other to determine whether the overlay.
However, since the length of the right inclined plane B1 of the step and the length of the left inclined plane B2 are different, the median value of the horizontal plane L inside the step is the end point of the right inclined plane B1 or the end of the left inclined plane B2. The median coordinate value of the son of the son varies depending on which of the two references is used.
Therefore, accurate comparison with the median coordinate value of the mother is impossible.

의 수식에 의하여 계산될 수 있다.
참고로, 상시 수식은 피타고라스 정리에 의한 것이다.
제5단계로서, 상기 제4단계에서 계산된 2개의 계산치와 상기 제2단계의 측정치를 합산한 후 2로 나눈다. 따라서, 상기 트렌치형 단자, 즉 아들자의 중앙값을 계산할 수 있으며, 아들자의 중앙값은 우측 경사면(B1) 또는 좌측 경사면(B2)의 시작점의 위치에 가산됨으로써 어미자와 비교 가능한 중앙값 좌표수치를 얻을 수 있다.For this reason, the embodiment calculates the median value based on the start point of the right inclined plane B1 and the start point of the left inclined plane B2 of the step.
Therefore, the median coordinate values of the sons can be calculated by adding the calculated median of the sons to the position of the starting point of the right inclined plane B1 or the starting point of the left inclined plane B2. As a fixed value, an accurate comparison with the median coordinate value of the mother is possible.
As a first step, the thickness A of the metal layer 103 forming the trench type step is measured.
As a second step, the length of the region L of which the metal layer 103 forms a horizontal plane inside the step is measured.
In a third step, the lengths of the regions B1 and B2 of the inclined surface of the metal layer 103 are measured in the stepped portions.
As a fourth step, the length of the horizontal plane C when the areas B1 and B2 of the metal layer 103 constituting the inclined surface on both sides of the step are vertically projected is calculated.
Referring to FIG. 1, only the horizontal plane C when the right inclined plane B1 is vertically projected is illustrated, but the horizontal plane when the left inclined plane B2 is vertically projected is also calculated in the same manner.
For example, "the length of the horizontal plane C in the case where the areas B1 and B2 of the metal layer 103 forming the inclined plane are vertically projected" uses the measured value of the first step and the measured value of the third step. Can be calculated.
The length of the "horizontal plane C when the right inclined plane B1 is vertically projected" and the length of the "horizontal plane when the left inclined plane B2 is vertically projected" are each,
"

It can be calculated by the formula of.
For reference, the constant equation is based on the Pythagorean theorem.
As a fifth step, the two calculation values calculated in the fourth step and the measured values of the second step are summed and divided by two. Therefore, the median value of the trench type terminal, that is, the son, may be calculated, and the median value of the son may be added to the position of the start point of the right inclined plane B1 or the left inclined plane B2 to obtain a median coordinate value comparable to the mother.

As shown in FIG. 2, the camera 200 is used to measure the respective lengths. The camera 200 is positioned on the wafer 108 and the inclination surface of the camera 200 along with the horizontal plane L is measured. The structure is rotatable so as to correspond to (B1, B2) at right angles.

To this end, the apparatus has an elliptical camera support 201 in which the camera 200 is installed and is curved concave toward the wafer 108 so that the camera 200 installed on the support 201 can be mounted on the wafer 108. The structure is rotatable.

Therefore, the horizontal L length measurement step of the metal layer 103 is performed in a state where the camera 200 is disposed at a right angle with respect to the wafer 108, and the length of the inclined surfaces B1 and B2 is measured in the support 201. The camera 200 is rotated according to the rotation operation of the camera 200 so that the camera 200 is disposed at a right angle with respect to the inclined surfaces B1 and B2.

delete

delete

delete

delete

It can be seen that the present invention provides an overlay measuring method having a significantly innovative function as described above. While exemplary embodiments of the present invention have been shown and described, various modifications and other embodiments may be made by those skilled in the art. Such modifications and other embodiments are all considered and included in the appended claims, without departing from the true spirit and scope of the invention.

According to the method for calculating the median value of the metal layer and the overlay measuring device for overlay measurement according to the present invention as described above, it is possible to drastically reduce the overlay measurement error and thus to implement accurate overlay measurement. The yield and reliability of the product can be improved.

Claims (3)

In the overlay measurement method, A first step of measuring a thickness of a metal layer forming a trench type step; A second step of measuring a length of an area where the metal layer forms a horizontal plane inside the step; A third step of measuring a length of an area where the metal layer forms an inclined surface in the step; A fourth step of calculating a length of a horizontal plane when the metal layer area forming the inclined plane of the step is vertically projected by using the measured value of the first step and the measured value of the third step; And a fifth step of calculating a median value of the entire length of the step using the measured value of the second step and the calculated value of the fourth step. The method of claim 1, wherein in the fourth step of calculating the length of the horizontal plane, "The length of the horizontal plane when the said metal layer area | region which forms the inclined surface of the step | projection is perpendicularly projected" "

Method of calculating the median value of the metal layer for overlay measurement, characterized in that calculated by the formula of. An overlay measuring apparatus comprising a camera for photographing a wafer, The support on which the camera is installed has an elliptical shape and is concavely curved toward the wafer, so that the camera installed on the support can be rotated with respect to the wafer.

Images