KR20030054781A - Apparatus for overlay measurement and method for measuring overlay using the same - Google Patents

Abstract

PURPOSE: An apparatus for measuring an overlay and a measuring method using the same are provided to prevent an edge detection error due to a damage of an overlay measurement pattern by detecting an edge and a profile of the overlay measurement pattern. CONSTITUTION: An apparatus for measuring an overlay includes a light source(31), the first beam splitter(32), the first optical fiber(33), the second beam splitter(34), a reference mirror(35), a CCD camera(37), the second optical fiber(44), a Z-stage(41), and a photo diode(43). The first beam splitter is used for transmitting or reflecting beams of the light source. The first optical fiber is used for condensing the transmitting beams of the first beam splitter. The second splitter transmits the beams of the first optical fiber to the first and the second paths. The reference mirror is used for transmitting the beams of the first path to the second beam splitter. The CCD camera is used for imaging the beams of the first and the second paths. The second optical fiber is used for condensing the beams of the first beam splitter. The Z-stage includes a fiber-tip(42) to perform a near-field scanning process. The photo diode is used for converting the scanned images of the fiber-tip to electric signals.

Description

Overlay measuring device and overlay measuring method using the same {APPARATUS FOR OVERLAY MEASUREMENT AND METHOD FOR MEASURING OVERLAY USING THE SAME}

The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to an overlay measuring apparatus for accurately measuring an overlay between a previous layer and a current layer, and an overlay measuring method using the same.

In manufacturing a semiconductor device having a laminated structure, alignment between the layers formed in the previous process and the layers formed through the current process is very important. Therefore, in the related art, overlay measurement patterns are provided in each layer to identify and correct an alignment state between a lower layer and an upper layer.

For reference, the overlay refers to the numerical display of the alignment between the layers implemented in the previous process and the layers formed in the current process. In the semiconductor manufacturing process, the measured overlay values are measured. Or by feeding back to exposure equipment, such as a stepper, to improve the degree of overlap between the bottom and top layers.

The overlay measurement pattern is usually installed in a scribe line for dividing the die and the die from the wafer, for example, an outer box formed as a lower layer and an inner box formed as an upper layer. It consists of (Inner Box). Here, the outer box is formed of a lower layer pattern, while the inner box is formed of a photoresist pattern formed through a photolithography process to pattern the lower layer pattern.

1A and 1B are a plan view and a cross-sectional view showing a conventional overlay measurement pattern.

The conventional overlay measurement pattern, as shown in Figure 1a, is formed of a box in box (Box in Box) structure, consisting of an outer box 1 disposed on the outside and the inner box 2 disposed on the inside. do.

In order to form such an overlay measurement pattern, as shown in FIG. 1B, the outer box 1 is formed by forming the recesses 12 in the form of a picture frame in the oxide film 11 such as TEOS or BPSG in the previous process step. ) And by forming a photoresist pattern 14 on the metal film 13 by a photolithography process after the deposition of the metal film 13, which is a medium to be implemented in the current process step, the outer box 1. An inner box 2 disposed therein is formed.

Meanwhile, in the overlay measurement using the overlay measurement pattern as described above, the overlay measurement apparatus as shown in FIG. 2 is conventionally used.

Referring to FIG. 2, a conventional overlay measurement apparatus photographs an overlay measurement pattern implemented on a wafer by an image processing method using an interferometer, and then uses an edge detection algorithm to determine an overlay measurement pattern. Each edge is detected to measure the overlay between the lower and upper layers.

The overlay measuring method using the overlay measuring apparatus as described above will be briefly described as follows.

First, the beam emitted from the light source 21 is incident to the beam splitter 23 through the optical fiber 22, and then transmitted and reflected through the beam splitter 23 so that the first and second paths ( Proceed by dividing into L1, L2).

Then, the beam transmitted and propagated to the first path L1 is reflected by the reference mirror 24 and is incident again to the beam splitter 23, and the beam is reflected and propagated to the second path L2. Is incident on the wafer 25 and then reflected in the overlay measurement pattern and incident back into the beamsplitter 23.

Next, the beams of the two paths L1 and L2 incident to the beam splitter 23 are picked up by the imaging means, that is, the CCD camera 26, and then analyzed according to a specific algorithm to determine the overlay alignment. do.

In Fig. 2, reference numeral 30, which is not explained, denotes a lens.

However, in the conventional overlay measurement method as described above, as shown in FIG. 3, the CMP process is performed by detecting the overlay measurement pattern, that is, each edge of the outer box and the inner box, by the image processing method by the CCD camera. When the overlay box is damaged in the current process technology, which is widely applied, it is difficult to detect edges and thus accurate overlay measurement is not possible. Accordingly, accurate alignment between the wafer and the reticle in the exposure process cannot be achieved, thereby producing a yield. Will cause a decrease.

4 is a diagram illustrating a problem in conventional overlay measurement. Here, reference numeral 1 denotes an outer box, 2 an inner box, 11 an oxide film, 13 a metal film, 14 a photosensitive film pattern, and A denotes an outer box portion to be attacked, respectively.

As shown, as the outer box 1 formed on the oxide film 11 is attacked by the CMP process, the metal film 13 is anisotropically deposited, and at the same time, the profile is smooth. Therefore, it is difficult to detect the edge of the overlay box in the image processing method using a conventional CCD camera.

Accordingly, an object of the present invention is to provide an overlay measuring apparatus and an overlay measuring method using the same, which are designed to solve the above problems, and to enable precise overlay measurement.

1A and 1B are a plan view and a sectional view of a conventional overlay measurement pattern.

2 is a schematic view of a conventional overlay measurement apparatus.

3 is a view for explaining an edge detection method of a conventional overlay measurement pattern.

4 illustrates a problem in conventional overlay measurement.

5 illustrates an overlay measurement apparatus according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

31 light source 32 first beam splitter

33: first optical fiber 34: second beam splitter

35 reference mirror 36 wafer

37: CCD camera 41: Z-page

42 Fiber-Tip 43 Photodiode

44 second optical fiber 50 lens

An overlay measuring apparatus of the present invention for achieving the above object, the light source; A first beam splitter for transmitting and reflecting a beam from the light source; A first optical fiber for condensing and propagating a beam transmitted through the first beam splitter; A second beam splitter which transmits and reflects a beam traveling through the first optical fiber to travel in the first and second paths; A reference mirror which reflects the beam of the first path passing through the second beam splitter and enters the second beam splitter again; A second path transmitted through the second beam splitter and reflected by the second beam splitter, and reflected by the overlay pattern of the wafer and then reentered and transmitted through the second beam splitter A CCD camera for imaging a beam of light; A second optical fiber for condensing and propagating the beam reflected by the first beam splitter; A Z-stage connected to an end of the second optical fiber and attached with a fiber tip for near-field scanning; And a photodiode receiving the image scanned by the fiber tip and outputting the image as an electrical signal.

In addition, the overlay measuring method of the present invention for achieving the above object, the outer box on the wafer using a light source, a beam splitter for transmitting and reflecting the beam from the light source, and a beam separated by the beam splitter And an image capturing means portion for photographing an image of an overlay measurement pattern composed of an inner box, and an overlay measuring apparatus including a near-field scanning means portion for precisely scanning a local portion of the wafer surface. A method of measuring an overlay between a box and an inner box, the method comprising: a first step of detecting respective edges of the outer box and the inner box by image processing by the imaging means; A second step of precisely scanning the local portions of the outer box and the inner box with the near-field scanning means; A third step of correcting the data value obtained in the first step with the data value obtained in the second step; And a fourth step of calculating the final data value obtained in the third step according to a specific edge detection algorithm.

According to the present invention, by introducing a near-field scan method to the existing measurement method, it is possible to overcome the edge detection error of the overlay measurement pattern, so that precise overlay measurement can be made.

(Example)

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

5 is a diagram illustrating an overlay measurement apparatus according to an embodiment of the present invention, which will be described below.

As shown, the overlay measuring apparatus of the present invention includes a light source 31 composed of a He-Ne laser, a first beam splitter 32 that transmits and reflects a beam emitted from the light source 31, and Imaging means portion A for imaging the image of the overlay measurement pattern on the wafer using the beam separated by the first beamsplitter 32 and near-field scanning for precisely scanning the local area of the wafer. And a means part (B).

In this case, the imaging means unit A transmits the first optical fiber 33 for condensing and propagating the beam transmitted through the first beam splitter 32, and the beam propagating through the first optical fiber 33. The second beam splitter 34 reflects and proceeds to the first and second paths, and the beam of the first path passing through the second beam splitter 34 is reflected to enter the second beam splitter 34 again. The reference mirror 35 and the second beam splitter 34 that are re-entered and reflected by the beam of the first path and the second beam splitter 34 that are reflected by the overlay measurement pattern of the wafer 36. And a CCD camera 37 which is a substantial imaging means for imaging the beam of the second path transmitted through the second beam splitter 34 after being re-entered.

The near-field scanning means portion B is a fiber tip 42, which is a substantially scanning means, and a photo that receives an image of the surface of the wafer scanned by the fiber tip 42 and outputs an electrical signal. A diode 43, wherein the fiber tip 42 is fixed to the Z-stage 41, to which the second optical fiber 44 for delivering the focused beam is connected. .

In FIG. 5, reference numeral 50 denotes a lens, which lens 50 is disposed between the first beam splitter 32 and the first optical fiber 33, and the first optical fiber 33 and the second beam splitter 34. Between the second beam splitter 34 and the reference mirror 35, between the second beam splitter 34 and the wafer 36, and between the first beam splitter 32 and the second optical fiber 44. Placed between each).

An overlay measurement method using the overlay measurement apparatus of the present invention having such a configuration is as follows.

First, the image of the outer box and the inner box is picked up from the imaging means unit B according to the existing overlay measuring method, thereby detecting each edge of the outer box and the inner box.

Then, using the near-field scanning means portion B, a precise scanning of the wafer surface is performed, and thereby two-dimensional for an overlay measurement pattern composed of a local portion of the wafer, that is, an outer box and an inner box. Or find a three-dimensional profile.

Subsequently, the center values of the outer box and the inner box obtained by the edge detection method by the image processing are corrected with the respective center values of the outer box and the inner box obtained by the near-field scanning.

Then, by calculating the center value thus corrected according to a specific edge detection algorithm, the degree of overlay alignment between the outer box and the inner box is measured.

By measuring the overlay in this manner, since the data obtained by the conventional image processing is corrected with the data obtained by the near-field scanning method, more accurate overlay measurement is made, and therefore, due to the overlay measurement failure The fall of the manufacturing yield of an element can be prevented.

That is, in the conventional overlay measurement method, when the overlay measurement pattern, in particular, the outer box is damaged by the CMP, an error occurs in edge detection, but the present invention can correct such an error by a near-field scanning method. This allows more accurate overlay measurements.

As described above, the present invention detects the edge of the overlay measurement pattern according to the conventional measurement method, and then detects and corrects the profile of the overlay measurement pattern by the near-field scan method, thereby damaging the overlay measurement pattern. It is possible to overcome the edge detection error caused by.

Therefore, the precise overlay measurement can be made, which can improve the reliability of the exposure process, as well as further improve the manufacturing yield and reliability of the device.

In addition, this invention can be implemented in various changes in the range which does not deviate from the summary.

Claims (4)

Light source; A first beam splitter for transmitting and reflecting a beam from the light source; A first optical fiber for condensing and propagating a beam transmitted through the first beam splitter; A second beam splitter which transmits and reflects a beam traveling through the first optical fiber to travel in the first and second paths; A reference mirror which reflects the beam of the first path passing through the second beam splitter and enters the second beam splitter again; A second path transmitted through the second beam splitter and reflected by the second beam splitter, and reflected by the second beam splitter and reflected again in an overlay measurement pattern of a wafer, and then reentered and transmitted through the second beam splitter A CCD camera for imaging a beam of light; A second optical fiber for condensing and propagating the beam reflected by the first beam splitter; A Z-stage connected to an end of the second optical fiber and attached with a fiber tip for near-field scanning; And And a photodiode receiving the image scanned by the fiber tip and outputting the image as an electrical signal. The method of claim 1, wherein the first beam splitter and the first optical fiber, between the first optical fiber and the second beam splitter, between the second beam splitter and the reference mirror, between the second beam splitter and the wafer, and the first An overlay measuring apparatus according to claim 1, wherein a lens is disposed between each of the first beam splitter and the second optical fiber. An imaging means unit for imaging an image of an overlay measurement pattern consisting of a light source, a beam splitter for transmitting and reflecting a beam from the light source, an outer box and an inner box on a wafer using the beam separated by the beam splitter, and In the method for measuring the overlay between the outer box and the inner box using an overlay measuring device equipped with a near-field scanning means for precisely scanning the local area of the wafer surface, A first step of detecting respective edges of the outer box and the inner box by image processing by the imaging means; A second step of precisely scanning the local portions of the outer box and the inner box with the near-field scanning means; A third step of correcting the data value obtained in the first step with the data value obtained in the second step; And And a fourth step of calculating the final data value obtained in the third step according to a specific edge detection algorithm. 4. The method of claim 3 wherein the imaging means is a CCD camera and the near-field scanning means is a fiber tip.