CN102569258A - Sample structure and measuring method for CDSEM (critical dimension scanning electronic microscope) - Google Patents

Abstract

The invention provides a sample structure and measurement method of a critical dimension scanning electron microscope. The method adds an auxiliary pattern with a fixed position on the sample. When measuring the critical dimension of the sample, by grabbing the auxiliary pattern as a template, a The relationship between the auxiliary pattern and the relative position coordinates of the pattern to be measured on the sample and the setting of the CD recipe, so that when measuring the pattern to be measured, CDSEM can search for the auxiliary pattern on the sample, and then use the coordinates of the auxiliary pattern as a reference, according to the coordinates of the auxiliary pattern and the sample The relationship between the relative position coordinates of the pattern to be measured can realize the accurate positioning of the pattern to be measured and the repeated availability of CD recipes, and improve the efficiency of CDSEM measurement.

Description

A sample structure and measurement method of critical dimension scanning electron microscope

technical field

The invention relates to the technical field of equipment in the semiconductor manufacturing process, in particular to a sample structure and measurement method of a critical dimension scanning electron microscope (Critical Dimension Scanning Electronic Microscope, CDSEM).

Background technique

At present, in the manufacture of semiconductor devices, a critical dimension scanning electron microscope (Critical Dimension Scanning Electronic Microscope, CDSEM) is used to measure the critical dimension (Critical Dimension, CD) of the pattern made on the wafer. With the development of semiconductor manufacturing technology, the CD of semiconductor devices is getting smaller and smaller. In order to ensure the accuracy of the pattern on the wafer after photolithography, after the pattern on the mask is transferred to the wafer after exposure and development, the wafer with the pattern will be placed on the CDSEM machine, and the CDSEM machine will be controlled by the CDSEM control system to measure the photolithography. After the CD of the pattern, the CDSEM machine will feed back the CD of the obtained pattern to the CDSEM control system to confirm whether the CD of the pattern meets the design requirements of large-scale integrated circuits (IC), so as to understand the accuracy of lithography. In the manufacture of semiconductor devices, the most concerned is the CD of some specific patterns on the wafer, such as the CD of the hole, device width (line) and device spacing (space) patterns, these specific patterns are defined as the pattern to be tested . Take the hole pattern as the pattern to be tested as an example. Generally, the pattern to be tested on the wafer is divided into one area according to the size of the pitch (pitch), for example, the hole pattern with the same pitch. The pitches correspond to different regions.

In the prior art, as shown in Figure 1, the steps of CDSEM to the CD measuring method of pattern on wafer are as follows:

Step 101, select a characteristic pattern in a certain area on the wafer, and record the characteristic pattern as a template;

In this step, after the wafer is put into the CDSEM machine, the CDSEM machine is first controlled by the CDSEM control system to select and capture the characteristic pattern of a certain area on the wafer, specifically, the characteristic pattern with identifiable and distinguishing features can be captured, and then , storing the captured feature pattern as a template in the CDSEM control system. This step is a prior art and will not be repeated here.

Step 102, in the wafer pattern area having the same pitch as the characteristic pattern, determine the relative position coordinates of a reference pattern and the characteristic pattern, and establish a CD measurement recipe (recipe);

In this step, taking the CD measurement of the hole pattern as an example, the CDSEM machine is controlled by the CDSEM control system, and a hole pattern is found in the wafer pattern of the same pitch as a reference pattern, and the distance between the reference pattern and the characteristic pattern is determined by the existing technology. Relative position coordinates; according to the needs of the reference pattern CD measurement, configure the corresponding CDSEM machine control parameters for the reference pattern CD measurement, and store them in the CDSEM control system as the CD measurement recipe; the CDSEM machine control parameters in the CD measurement recipe include: CDSEM The angle, depth, distance, etc. that the probe of the machine moves during the CD measurement process, wherein the moving distance of the probe refers to the distance between the reference pattern and the characteristic pattern, and the steps of configuring the control parameters of the CDSEM machine are prior art. This will not be repeated here.

Step 103, search for the same first pattern as the template pattern on the wafer, take the coordinates of the first pattern as the origin, and locate the first pattern to be measured on the wafer according to the relative position coordinates determined in step 102, and follow the established CD recipe The CD of the first pattern to be tested is measured.

In this step, the CDSEM control system controls the CDSEM machine to scan the pattern on the wafer to find the first pattern that is the same as the template. It should be noted that the first pattern can be a characteristic pattern or other templates other than the characteristic pattern. Figures with the same pattern; positioning is performed with the coordinates of the first pattern as the origin, and when the coordinates of the displacement from the origin are the relative position coordinates of the reference pattern and the characteristic pattern, it is positioned at the position of the first hole pattern to be measured; in the same In the area of the pitch, due to the particularity and repeatability of semiconductor process manufacturing, the relative position coordinates between the first pattern on the wafer and the first hole pattern to be measured are the same as the relative position coordinates between the feature pattern and the reference pattern, Therefore, the relative position coordinates between the feature pattern and the reference pattern can be repeatedly used to locate the first hole pattern to be measured. The CD measurement of the first hole pattern to be measured adopts the CD measurement recipe established in step 102, and the CDSEM control system can control the CDSEM machine to complete the entire first hole pattern to be measured according to the CDSEM machine control parameters in the stored CD measurement recipe. CD measurement process, and then the CDSEM machine will feed back the obtained CD data of the first hole pattern to be tested to the CDSEM control system, and the CDSEM control system can determine whether the CD of the first hole pattern to be tested meets the IC design requirements. In the wafer pattern area of the same pitch, the CD measurement of other hole patterns to be measured can be completed only by repeating step 103 .

Due to different semiconductor manufacturing processes and IC designs, the pattern to be tested on the same wafer is divided into different areas according to the pitch. Taking the hole pattern as an example, the distance between the hole and the hole in different areas is different, and the holes and other areas on the wafer are different. The spacing of the patterns is also different. In the prior art, the CDSEM method for measuring CD has the following defects. On the one hand, it is often impossible to find the same first pattern as the template pattern in the regions of different pitches; on the other hand, even if the same first pattern as the template pattern is found , but due to the difference in the pitch of the wafer pattern, the relative position coordinates between the first pattern and the pattern to be measured will also change, so the relative position coordinates between the reference pattern and the characteristic pattern cannot be used to accurately locate the pattern to be measured, and it is impossible to Accurately measure the CD of the pattern to be tested in the pattern area of the wafer with different pitches. Based on the above two aspects, when measuring the CD of the pattern to be tested, it is often necessary to manually find the correct position of the pattern to be tested and create a new recipe, which reduces the CDSEM. s efficiency.

Contents of the invention

In view of this, the technical problem solved by the present invention is: in the CD measurement process of the critical dimension scanning electron microscope, it is often necessary to manually locate the pattern to be measured, which reduces the measurement efficiency of the CDSEM.

In order to solve the above problems, the technical solution of the present invention is specifically implemented in the following way:

A sample structure of a critical dimension scanning electron microscope, the sample structure comprising:

An auxiliary pattern and a pattern to be measured, and the relative position coordinates of the auxiliary pattern and the pattern to be measured are fixed.

The auxiliary pattern is a cross, a rectangle, a circle or a triangle.

The distance between the auxiliary pattern and the pattern to be tested is less than or equal to 10 microns.

The maximum length of the auxiliary pattern along the x-axis or y-axis ranges from 50 to 5000 nm.

A method for measuring a critical dimension scanning electron microscope, measuring a sample with the auxiliary pattern, after the critical dimension scanning electron microscope machine grabs the auxiliary pattern, record the auxiliary pattern in the critical dimension scanning electron microscope control system as The template is used to establish and store the relative position coordinates of the pattern to be measured and the auxiliary pattern, and set the key dimension measurement prescription of the pattern to be measured. The method also includes:

The critical dimension scanning electron microscope control system controls the critical dimension scanning electron microscope machine to find the auxiliary pattern on the sample according to the graphics of the template; according to the relative position of the pattern to be measured and the auxiliary pattern Coordinates, using the coordinates of the auxiliary pattern as the origin of the reference coordinates, locate the pattern to be measured; control the CD scanning electron microscope to measure the critical dimension of the pattern to be measured according to the critical dimension measurement prescription of the pattern to be measured.

It can be seen from the above technical solution that the present invention provides a sample structure and measurement method of a critical dimension scanning electron microscope. After adding an auxiliary pattern with a fixed position on the sample, the relative positional relationship between the auxiliary pattern and the pattern to be measured is realized. The accurate positioning of the measurement pattern improves the efficiency of the measurement of the critical dimension of the sample.

Description of drawings

Fig. 1 is the flow chart of CDSEM to the CD measuring method of pattern on wafer in the prior art;

Fig. 2 is a schematic diagram of auxiliary patterns on the wafer to be tested in the present invention;

FIG. 3 is a flow chart of the CDSEM method for CD measurement of patterns on a wafer according to the present invention.

Detailed ways

In order to make the object, technical solution, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples.

A sample structure and measurement method for critical dimension scanning electron microscopy.

During the manufacturing process of the photomask, an auxiliary pattern is firstly added on the photomask, and the relative positional coordinate relationship between the auxiliary pattern and other patterns on the photomask can be obtained from the IC design data provided in the prior art.

In this embodiment, the sample measured by the CD scanning electron microscope is a wafer, and the pattern on the wafer is obtained by transferring the pattern on the photomask to the wafer after exposure and development. In addition to the pattern corresponding to the IC design data as in the prior art, the patterns on the wafer also have auxiliary patterns, which can be any identifiable figures such as crosses, rectangles, circles or triangles. In this embodiment, as shown in FIG. 2, the auxiliary pattern 201 is a cross-shaped structure, and the distance between the auxiliary pattern 201 and the pattern to be tested is less than or equal to 10 microns, for example, 1 micron, 5 microns and 10 microns, to ensure The distance between the auxiliary pattern 201 and the pattern to be measured is included in the scope of the probe movement distance that can be set in the CD measurement recipe (recipe), and it is also necessary to ensure that the position of the auxiliary pattern 201 on the wafer 200 will not be different from that in the prior art. The pattern positions corresponding to the IC design data overlap, destroying the original IC design. The maximum length of the auxiliary pattern 201 along the x-axis or y-axis ranges from 50 to 5000 nm, for example, 50 nm, 2000 nm and 5000 nm, wherein the x-axis corresponds to the transverse direction and the y-axis corresponds to the longitudinal direction.

As shown in Figure 3, the steps of a method for measuring a key dimension scanning electron microscope in the present invention are as follows:

Step 301, select the auxiliary pattern 201 on the wafer 200, record the auxiliary pattern 201 as a template in the CDSEM control system, and store the relative position coordinates of the hole pattern 202 on the wafer 200 and the auxiliary pattern 201;

In this embodiment, the hole pattern on the wafer 200 is used as the pattern to be tested. In this step, after the wafer 200 is put into the CDSEM machine, at first the CDSEM control system is used to control the CDSEM machine to grab the auxiliary pattern 201 on the wafer 200. In this embodiment, the auxiliary pattern 201 on the wafer 200 is grabbed. Pattern 201, then, store this auxiliary pattern 201 in the CDSEM control system as a template, and the specific operation steps of grabbing the auxiliary pattern 201 are prior art, and will not be repeated;

Step 302, setting CD measurement recipe;

In this step, according to the needs of CD measurement, the corresponding CDSEM machine control parameters are configured in the CDSEM control system as a CD measurement prescription, which includes, this step is a prior art, and will not be repeated here.

Step 303, find the auxiliary pattern 201 on the wafer 200 according to the pattern of the template, and locate the hole pattern 202 according to the relative position coordinates of the hole pattern 202 and the auxiliary pattern 201;

In this step, taking the CD measurement of a hole pattern 202 on the wafer as an example, first scan the pattern on the wafer 200 by the CDSEM control system, and use the pattern of the template as a reference to search for the same pattern as the pattern of the template on the wafer 200, wherein , because the pattern of the template is exactly the pattern of the auxiliary pattern 201 captured, the same pattern as the image of the template found on the wafer 200 is the auxiliary pattern 201; then, with the coordinates of the auxiliary pattern 201 as the reference coordinates, according to the hole pattern The relative position coordinates of 202 and auxiliary pattern 201 locate the precise position of the hole pattern, wherein the relative position coordinates of hole pattern 202 and auxiliary pattern 201 are obtained from the IC design data provided in the prior art and stored in the CDSEM machine In the control system; in the semiconductor manufacturing process, the pattern on the mask is determined by the IC design data and design rules (Design Rule) provided by the customer. In the present invention, the specific position coordinates of the auxiliary pattern 201 are also fixed. Therefore, when the pattern on the photomask is transferred to the wafer 200, the relative position coordinates between the hole pattern and the auxiliary pattern 201 will not change due to the difference in pitch. Therefore, each hole pattern can use the reference coordinates as the origin, and achieve precise positioning through the displacement of the relative position coordinates.

Step 304 , the CDSEM control system controls the CDSEM machine to measure the CD of the hole pattern 202 on the wafer 200 according to the CD measurement prescription.

In this step, the CDSEM machine control system controls the CDSEM machine to measure the hole pattern 202CD according to the CDSEM machine control parameters in the CD measurement prescription, thereby greatly improving the CD measurement efficiency of the CDSEM.

For all patterns to be measured on the wafer, it is only necessary to repeat steps 303 and 304 to perform CD measurement on different patterns to be measured.

The invention provides a sample structure of a critical dimension scanning electron microscope. The sample has an auxiliary pattern and a pattern to be measured, and the position of the auxiliary pattern relative to the pattern to be measured is fixed. When the coordinates of the auxiliary pattern are used as the reference coordinates, the The positioning of the pattern to be measured can be realized according to the relative position coordinate relationship between the reference coordinates and the pattern to be measured of the sample, which greatly shortens the positioning time of the pattern to be measured and improves the CD measurement efficiency of the CDSEM.

The invention provides a scanning electron microscope measurement method for key dimensions. On the one hand, because the pattern of the template is the auxiliary pattern to grab, the method will not fail to find the same pattern; The relative position coordinates of the pattern and the auxiliary pattern have been determined, so the position of the auxiliary pattern is used as the reference coordinate, and the precise positioning of the pattern to be measured can be realized according to the relative position coordinates of the pattern to be measured and the auxiliary pattern, without manual positioning, which greatly shortens the The positioning time of the pattern to be measured is shortened, and the CD measurement efficiency of the CDSEM is improved.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (5)

1. the sample structure of a critical size scanning electron microscopy is characterized in that, this sample structure comprises:

Auxiliary patterns and pattern to be measured, and the relative position coordinates of said auxiliary patterns and pattern to be measured immobilizes.

2. structure according to claim 1 is characterized in that, said auxiliary patterns is cross, rectangle, circle or triangle.

3. structure according to claim 1 is characterized in that the spacing of said auxiliary patterns and said pattern to be measured is smaller or equal to 10 microns.

4. structure according to claim 1 is characterized in that, said auxiliary patterns is 50 to 5000 nanometers along the maximum length scope of x axle or y axle.

5. the method for measurement of a critical size scanning electron microscopy; Measure sample according to claim 1, it is characterized in that, after critical size scanning electron microscopy board grasps said auxiliary patterns; The said auxiliary patterns of record is as template in critical size scanning electron microscopy control system; The relative position coordinates of setting up and storing pattern to be measured and said auxiliary patterns, and the critical size that pattern to be measured is set measures and writes out a prescription, this method also comprises:

Critical size scanning electron microscopy control system is controlled said critical size scanning electron microscopy board and on said sample, is found said auxiliary patterns according to the figure of said template; According to the relative position coordinates of said pattern to be measured and said auxiliary patterns, be the initial point of reference coordinate with the coordinate of said auxiliary patterns, locate pattern to be measured; Measure the critical size of the prescription said critical size scanning electron microscopy measurement of control pattern to be measured according to the critical size of said pattern to be measured.

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