KR20000061438A - Method for measuring critical dimension and overlay in semiconductor fabricate process - Google Patents

Abstract

PURPOSE: A method for measuring the critical dimension and overlapping degree is provided to increase the productivity of articles by reducing the time for measuring the overlapping degree. CONSTITUTION: A wafer is positioned on a critical dimension measuring position. The critical dimension of patterns formed on the wafer is measured. At the same time, an overlapping measuring position of the wafer is calculated based on the predetermined reticle information. The information regarding to the critical dimension is stored. Then, the wafer is moved to the overlapping measuring position. After measuring the overlapping degree of the patterns formed on the wafer, the information regarding to the overlapping is stored. The stored information of the critical dimension and the overlapping of patterns are displayed.

Description

{Method for MEASURING CRITICAL DIMENSION AND OVERLAY IN SEMICONDUCTOR FABRICATE PROCESS}

The present invention relates to a method for testing and evaluating a semiconductor manufacturing process, and more particularly, to an overlapping degree suitable for continuously measuring critical dimension (CD) and overlay of a pattern formed on a semiconductor wafer. The critical dimension measurement method.

As is well known, even if a defect occurs only in one step of the semiconductor manufacturing process, the manufactured semiconductor device cannot be used, and therefore, every process step of the semiconductor manufacturing process involves a test or evaluation of the process result.

Among them, after the photolithography process is completed, the measurement of the critical dimension and the degree of overlap is essential. That is, the photolithography process is a process of accurately transferring the pattern formed on the reticle to the top layer of the photoresist film or wafer, so that the critical dimension measurement to measure whether the size of the pattern is formed correctly and whether the pattern is accurately aligned on the top of the previous pattern Overlap measurements should be made to measure.

Such a critical dimension measurement is usually made by a scanning electron microscope (SEM), and the degree of overlap measurement is made by an overlapping degree measuring device, which will be briefly described with reference to FIGS. 1 and 2. Same as

First, referring to FIG. 5 with reference to FIG. 1, which generally illustrates a process of measuring a critical dimension with an electron scanning microscope, an alignment code for measuring a critical dimension formed on the wafer 100 by the alignment means 110. mark for CD (hereinafter, referred to as a “critical code”) 510, the electron source 120 scans an electron beam on the surface of the wafer 100. The secondary electron detection means 130 detects the secondary electron beam reflected by the sample coated on the surface of the wafer 100, and then converts the detected secondary electron beam into an electrical signal to display means 140 In the display means 140, the received electrical signal is displayed on the screen in synchronization with a scanning period of a monitor (not shown) or the like to measure the critical dimension.

Next, referring to FIG. 5 with reference to FIG. 2, which generally illustrates a process of measuring the degree of overlap with a degree of overlap measurement apparatus, an alignment code for measuring the degree of overlap formed on the wafer 200 by the alignment means 210. When the alignment is performed using the alignment mark for overlay 520, the light source 230 emits a visual beam to irradiate the entire surface of the aligned semiconductor wafer 220. And the pattern formed in the previous step by detecting the reflected light reflected from the surface of the wafer 200 by the reflected light detecting means 230 and converting it into an electrical signal, and then displaying the reflected light by the display means 240. Measure the degree of overlap of the pattern performed in the current step.

The above-described critical dimension measurement process and overlapping degree measurement process are typically performed separately. For example, after the critical dimension measurement by an electron scanning microscope is completed, the semiconductor wafer is moved to the overlapping measuring device to measure the overlapping degree. Doing.

As such, in the related art, the measurement of each of the critical dimension and the degree of overlap is performed separately by individual measuring equipment, which increases the overall process time and causes a decrease in productivity.

The present invention has been made in order to solve the above-described problems, the critical dimension and the degree of overlap measurement that can continuously perform the measurement of the critical dimension and the degree of overlap by unifying the overlapping process in the measurement of the critical dimension and overlapping degree To provide a way.

In order to achieve the above object, in the present invention, in the method for measuring the critical dimension and the overlapping degree of the pattern formed on the wafer with the integrated equipment, the wafer is thresholded based on the threshold code for measuring the critical dimension. A first step of aligning to a dimensional measurement position; A second step of measuring a critical dimension of a pattern formed on the wafer and calculating an overlapping degree measurement position of the wafer based on preset reticle information; A third step of storing information on the critical dimension measured in the second step; A fourth step of moving the wafer to the overlap measurement position calculated in the second step; Measuring a degree of overlap of the patterns formed on the wafer and storing information about the measured degree of overlap; And a sixth step of displaying the information on the stored critical dimension and the information on the overlapping degree.

1 is a diagram generally illustrating a process of measuring a critical dimension with an electron scanning microscope;

Figure 2 is a view showing a process for measuring the overlap in general with the degree of overlap measurement equipment,

3 is a diagram illustrating an apparatus for implementing a method of measuring a critical dimension and a degree of overlap according to the present invention;

4 is a detailed flowchart illustrating a method of measuring a critical dimension and a degree of overlap according to the present invention;

5 shows a relative positional relationship between a critical dimension alignment code and a superimposition measurement alignment code formed on a reticle and both of them according to the invention;

<Description of the code | symbol about the principal part of drawing>

10: light source 20: reflector

30, 60: Lens 40: Fly Eye

50: Aperture 70: Reticle

75 pattern 80 projection lens

90: wafer stage 110: roughness detection sensor (conventional)

120: micom (conventional) 210: power supply block

220: voltage variable block 230: illuminance detection block

240: microcomputer (invention)

Hereinafter, a method of measuring a critical dimension and a degree of overlap according to a preferred embodiment of the present invention will be described with reference to FIGS. 3 to 5 as follows.

3 is a diagram illustrating an apparatus for implementing a method for measuring a critical dimension and a degree of overlap according to the present invention, and FIG. 4 is a detailed flowchart illustrating a method for measuring a critical dimension and a degree of overlap according to the present invention.

First, the core technical idea of the present invention is to measure the critical dimension measurement process and the overlapping degree as in the step of 'critical code alignment → critical dimension measurement → measurement result display → move → overlap code alignment → overlapping measurement → measurement result display'. The overlapping steps in the process were performed separately by separate measuring equipment, such as 'critical code alignment → critical dimension measurement and moving position calculation → overlapping measurement → measurement result display' to reduce the process time. In order to obtain an increase in productivity through the following, the following description focuses on the core technical idea of the present invention.

First, referring to FIG. 3, an apparatus for implementing a method for measuring a critical dimension and an overlapping degree according to the present invention includes a light source 350 for overlapping degree measurement, an overlapping degree measuring means 360 and an electron for threshold dimension measurement. The source 320, the critical dimension measuring means 330, the critical dimension alignment means 340 are individually equipped, and the wafer stage 370, the storage means 380 and the display means 390 are commonly provided, and such And apparatus control means (310) for controlling the entire constituent member.

Among them, the light source 350 for overlapping degree measurement and the overlapping degree measuring means 360 play the same role as the functions in the conventional overlapping degree measurement equipment, and the electron source 320 for threshold dimension measurement and the critical dimension measurement The means 330 and the critical dimension aligning means 340 are the same as the critical dimension measuring operation in the conventional electron scanning microscope, and thus description thereof is omitted.

The wafer stage 370 is placed on the wafer under the control of the apparatus control means 310 on the movement path via the light irradiation region from the light source 350 and the electron beam scanning region from the electron source 320. Move on. At this time, in the present embodiment, the wafer stage 370 includes moving means not shown.

The storage means 380 is composed of a conventional memory, and pre-stored the relative position information of the critical code and the superimposed code, the superimposition measured by the critical dimension information measured by the critical dimension measuring means and the superimposition measure means. The degree information is stored. In this case, the relative position information of the threshold code and the overlap code may be obtained from the reticle information provided from the reticle manufacturer.

The display means 390 includes a cathode-ray tube display unit (CRT) and a signal processing means thereof, and the critical dimension information and the degree of overlap provided by the control of the apparatus control means 310. Information is displayed in images and text.

The apparatus control means 370 calculates the movement position of the stage wafer 370 from the relative position of the predetermined threshold code and the overlapping code and the reduced magnification between the reticle and the pattern, and the stage wafer 370 based on the calculated movement position. By driving control, superimposition by superimposition code replaces measurement alignment. At this time, since it moves directly to the position calculated from the device control means 370, the process time required for alignment will be shortened.

Hereinafter, a process of measuring the critical dimension and the overlapping degree according to the present invention in a device composed of a member that performs the above-described function will be described with reference to FIGS. 3 and 5 with reference to FIG. 4.

First, in a state where a wafer (not shown) is mounted on the wafer stage 370 (S 10), when the switch of the measuring equipment is turned on (S 20), the device control means 310 generates an electron beam. The electron source 320 is controlled to scan while the wafer stage 370 is drive controlled to move the wafer into the electron beam scanning region of the electron source 320. By the control of such device control means 320, the electron source 320 scans the electron beam (S 30), and the wafer stage 370 moves the wafer into the electron beam scanning region (S 40).

Subsequently, by the control of the device control means 310, the critical dimension alignment means 340 performs alignment using the threshold code 510 on the wafer that has entered the electron beam scanning region from the electron source 320. That is, as shown in FIG. 5, the critical code 510 is formed on the reticle 500, and the wafer is aligned at the critical dimension measurement position using the critical code 510 (S 50).

By such alignment, the electron beam scanned from the electron source 320 is scanned on the front surface of the wafer, and the electron beam thus scanned is reflected by the sample applied on the surface of the wafer and emitted into the secondary electron beam. . The critical dimension measuring means 330 detects the secondary electron beam emitted as such, and then detects the detected secondary electron beam by the apparatus control means 310, that is, the measured critical dimension. Information is converted into information (hereinafter referred to as "critical information") and provided to the device control means 310 (S60).

In the device control unit 310, the answer provided by the threshold measurement unit 330 stores the threshold information in a predetermined area of the storage unit 380 (S 70).

On the other hand, during the steps S60 and S70, the device control means 310 overlaps based on the preset position of the threshold code 510 and the overlap code 520 and the reduction ratio between the reticle and the pattern on the wafer. The moving position for measuring the sign is calculated. That is, in the present invention, since the reticle information provided from the reticle manufacturing company or the like, that is, the position information of the superimposed code, the position information of the critical code, the reduced magnification information of the reticle, and the like are stored in the storage unit 380, the device control means. In 310, the moving position of the wafer for measuring the degree of overlap is calculated by the following process.

First, as shown in FIG. 5, the position information (eg, coordinates (x1, y1)) of the threshold code 510 and the position information (eg, coordinates (x2, y2)) of the superimposition code 520. ), The relative position of the overlap code 520 with respect to the threshold code 510 is calculated. For example, the movement amount Δx in the x direction and the movement amount Δy in the y direction with respect to the threshold code 510 are calculated. In another embodiment, a vector consisting of a direction (eg, θ) and a straight line distance L of the position (x2, y2) of the superposition code 520 with respect to the position (x1, y1) of the threshold code 510. It may be calculated as The device control means 310 then reduces the calculated value to a reduction factor (e.g., 1/5) of the pattern on the wafer 500 for the reticle to calculate the final moving position. In other words, the linear distance L / 5 in the direction [theta] formed by the superimposition code 520 with respect to the moving distances [Delta] x / 5 and [Delta] y / 5) or the threshold code 510 in the x and y directions is calculated. S 80)

Subsequently, the device control unit 310 completes storing of the critical information (S90), and when the calculation of the information on the movement position for the overlapping degree measurement is completed (S100), the calculated movement position position information is added to the calculated movement position position information. Drive control of the wafer stage 370 is performed based on this. The wafer stage 370 is precisely transferred to the position for measuring the degree of overlap by the drive control of the apparatus control means 310. At this time, since the wafer is moved in the state where the alignment with respect to the critical dimension is completed, the wafer will be correctly positioned at the alignment position by the superimposition code.

Meanwhile, before or after step S 110, the device control unit 310 controls the electron source 320 to stop scanning of the electron beam, and drives the light source 350 to irradiate light for measuring the overlapping degree. To control. Under the control of such device control means 310, the electron source 320 stops scanning of the electron beam, the light source 350 irradiates the light for measuring the overlapping degree, and the light so irradiated is a wafer. Reflected from the surface of (S 120)

By the control of the device control means 310, the overlapping degree measuring means 360 detects the reflected light reflected from the wafer surface as such, and the detected reflected light is an electrical signal that can be recognized by the device control means 310. In other words, the information is converted into information on the measured degree of overlap (hereinafter, referred to as 'nested information'), and the converted overlap information is provided to the device control means 310 (S 130).

The device control means 310, which has received the overlapping information from the overlapping degree measuring means 360, stores the overlapping information in the storage means 380 (S 140), while storing it in a previous step (i.e., step S 70). The critical information and the overlapping information provided in step S 130 are provided to the display means 390. In the display means 390, the critical information and the superimposition information provided from the device control means 310 are displayed on the screen as an image or a text in synchronization with a scanning period such as a monitor (not shown) (S 150). ).

According to the present invention described above, in the process of unifying the critical dimension measurement and the degree of overlap measurement, by performing the overlapping steps in common, the time required for the process can be shortened, and the production efficiency can be increased. .

Claims (3)

In the method for measuring the critical dimension and the degree of overlap of the pattern formed on the wafer with the integrated equipment, A first step of aligning the wafer to a critical dimension measurement position based on a critical sign for measuring the critical dimension; A second step of measuring a critical dimension of a pattern formed on the wafer and calculating an overlapping degree measurement position of the wafer based on preset reticle information; A third step of storing information on the critical dimension measured in the second step; A fourth step of moving the wafer to the overlap measurement position calculated in the second step; Measuring a degree of overlap of the patterns formed on the wafer and storing information about the measured degree of overlap; And a sixth step of displaying the information on the stored critical dimension and the information on the overlapping degree. The method of claim 1, The reticle information is composed of position information (x1, y1) of critical code, position information (x2, y2) of superimposed code, and reduced magnification information (× 1 / z), The calculating of the overlapping degree measuring position in the second step includes calculating the multiplying reduction factor (x1 / z) by the x-axis movement distance Δx and the y-axis movement distance Δy, respectively. How to measure. The method of claim 1, The reticle information is composed of position information (x1, y1) of critical code, position information (x2, y2) of superimposed code, and reduced magnification information (× 1 / z), The step of calculating the overlap measurement position of the second step, The direction (θ) of the superimposed code with respect to the threshold code and the linear distance L of the superimposed code and the superimposed code are calculated as a moving distance (L / z) multiplied by the reduction factor (× 1 / z). Superposition degree measurement method, characterized in that.