KR20060124342A - Data compensation method of wafer inspection system - Google Patents

Abstract

The data compensation method for acquiring information about a pattern on a wafer includes acquiring first optical signal data from a reference wafer using a wafer inspection system, and then setting the first optical signal data and predetermined reference optical signal data of the reference wafer. Compute the difference data. After acquiring the second optical signal data from the wafer to be inspected using the wafer inspection system, the second optical signal data is compensated using the difference data. Therefore, the time taken for the second optical signal data compensation can be reduced, and an error of the second optical signal data can be prevented.

Description

Method for compensating data of wafer inspection system

1 is a conceptual diagram illustrating a schematic configuration of a wafer inspection system.

2 is a conceptual diagram illustrating a schematic configuration of a light control unit and a light detection unit using a spectroscopic ellipsometer.

3 is a flowchart illustrating a data compensation method of a wafer inspection system according to an exemplary embodiment of the present invention.

4 is a graph for explaining comparison of spectral data.

5 is a graph illustrating a difference of spectral data according to an embodiment.

6 is a graph for explaining a difference of spectral data according to another embodiment.

7 is a graph for explaining differences in spectral data in a steady state.

8 is a graph for explaining the difference in spectral data after compensation.

Explanation of symbols on the main parts of the drawings

100: stage 200: light control unit

300: light detection unit 400: storage unit

500: central processing unit 600: control unit

700: display unit 900: wafer inspection system

The present invention relates to a data compensation method of a wafer inspection system, and to a data compensation method for compensating spectral data used to obtain information of a pattern.

In recent years, as the degree of integration of semiconductor integrated circuits is improved, design rules, contact areas, or critical dimenstion of semiconductor devices have been continuously reduced, and thus the size of defects detected is becoming smaller. It has become difficult to detect. Examples of fatal defects worsened by the reduction of the critical number of water include voids in the interlayer insulating film deposited after forming a film on a wafer, and a bridge failure of contacts for wiring or stacked capacitance. .

Many of these defects are due to the pattern defects generated during the pattern formation process. Therefore, the thickness of the pattern or the thickness or width of the pattern formed by exposure or etching is measured by measuring the thickness of the deposited film in each unit process for semiconductor device manufacturing. And inspecting whether there is any defect. That is, it is determined whether the measured quantities are within the allowable process range, and if the deviation is allowed within the process, the process condition is changed to block the pattern defect, thereby preventing a fatal defect due to the pattern defect in advance.

In order to inspect whether the pattern has been completed, a SEM measurement method using a scanning electron microscope (SEM) or an optical measurement method for analyzing light reflected from a pattern is widely used. In order to measure the thickness of the pattern, an SE measurement method using a spectroscopic ellipsometer (hereinafter referred to as SE) is used.

In the SE measurement method, the reliability of the data is considerably higher than that of the conventional method, and the measurement of the thin film (Thin film), which was previously impossible, is possible to some extent. However, since the SE measurement method is based on a complex calculation formula that requires a lot of calculations, the SE equipment reacts very sensitively and thus has a disadvantage of affecting the obtained data even if the detected light signal changes only slightly.

In addition, in order to obtain the same data in each SE facility, the optical signals of each SE facility must be identical to each other. However, the optical signal is slightly different for each SE facility, causing a difference in data between the SE facilities.

In this case, the data derived from the SE facility is different from the actual data. Therefore, not only the quality of the process can be reduced but also the yield of the semiconductor device manufacturing process can be reduced.

On the other hand, there is a problem that it takes a lot of time to find the cause of the SE facility even if it finds an abnormality of the SE facility using the difference between the data derived from the SE facility and the actual data.

An object of the present invention for solving the above problems is to provide a data compensation method that can more accurately identify the information on the pattern.

According to a preferred embodiment of the present invention for achieving the object of the present invention, the data compensation method of the wafer inspection system after obtaining the first optical signal data from the reference wafer using the wafer inspection system, the first optical The difference data is calculated by comparing signal data with preset reference optical signal data of the reference wafer. Next, after acquiring the second optical signal data from the wafer to be inspected using the wafer inspection system, the second optical signal data is compensated using the difference data.

Using the data compensation method of the wafer inspection system according to the present invention configured as described above can quickly compensate the optical signal data obtained during the inspection of the wafer, it is possible to obtain accurate information by inspecting the wafer using the compensated optical signal data have.

Hereinafter, a data compensation method of a wafer inspection system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram illustrating a schematic configuration of a wafer inspection system.

Referring to FIG. 1, a wafer inspection system 900 includes a stage 100 for supporting a wafer W, a dimming unit 200 for irradiating inspection light to the wafer W, and a portion of the wafer W. FIG. A photodetector 300 generating optical signal data for the formed pattern, a storage unit 400 storing reference optical signal data and result data for the wafer W, and performing compensation and calculation of the optical signal data It includes a central processing unit 500, the stage 100 and the control unit 600.

In an embodiment, the stage 100 drives the support unit 110 and the support unit 110 to fix and support the wafer W on which a predetermined pattern is formed to adjust the position of the wafer W. It is provided with a drive unit 120 for. In an embodiment, the wafer W is a semiconductor wafer for manufacturing a semiconductor device, and the pattern may be a photoresist pattern or a mask pattern of an etching process. The support unit 110 is formed of a flat plate having an upper surface to fix and support the wafer W to obtain data on a pattern formed through a predetermined process. The driving unit 120 is connected to the lower surface of the support unit 110 to move the position of the support unit 110 to change the position of the wafer (W) fixed to the upper surface of the support unit 110. Adjust In one embodiment, the drive unit 120 includes a transfer mechanism that can move in three dimensions, the operation of which is controlled by a drive driver 130 electrically connected to the drive unit 120. The operation of the driving driver 130 is controlled by the control unit 600. Therefore, the position of the wafer W is adjusted by the controller 600.

The dimming unit 200 irradiates the inspection light to the surface of the wafer (W) fixed to the support unit 110, the light detector 300 detects the reflected light reflected from the surface of the wafer (W) Inspection optical signal data for the pattern is generated.

In one embodiment, the dimming unit 200 includes a light source 210 for generating light and a beam splitter 220 for forming the light generated by the light source 210 into slit light. The detection unit 300 includes a detection lens 310 for detecting the reflected light reflected from the surface of the wafer W and a detection unit 320 for generating the optical signal data from the reflected light via the detection lens 310. Include.

In one embodiment, the light source 210 is a laser light source such as a fluoride krypton (KrF) excimer laser light source, an argon fluoride (ArF) excimer laser light source, a fluorine (F ₂ ) excimer laser light source or an argon (Ar) laser light source. The light includes ultraviolet (Ultra violet ray) or deep ultra violet (Deep Ultra Violet ray) generated from the light source. In addition, as an embodiment, the beam splitter 220 is formed of a lens combination consisting of a pair of concave lens 222 and convex lens 224, and increases the measurement speed for the pattern characteristics of the inspection target pattern.

The detection lens 310 is formed of an objective lens having a predetermined aperture ratio to collect the reflected light, and the detection unit 320 processes the reflected light detected from the detection lens 320 to generate the optical signal data. do. In one embodiment, the detection lens 320 includes an image sensor (charge coupled sensor, CCD sensor). The CCD sensor 320 converts a change in free charge amount according to the amount of light detected into an electrical signal, detects the reflected light, and converts the reflected light into an electrical signal. Optical characteristics such as the intensity or frequency of the reflected light change according to the physical characteristics of the pattern formed on the wafer (W). That is, the optical characteristics of the reflected light change depending on the line width, thickness, and the like of the pattern. Since the electrical signal output by the CCD sensor 320 is proportional to the amount of reflected light, the CCD sensor 320 uniquely represents the intensity of the reflected light. Therefore, the inspection optical signal data may be the intensity of the reflected light that can be measured by the CCD sensor 320.

The light dimming unit 200 and the light detecting unit 300 are spectroscopic ellipsometers capable of measuring the thickness of the pattern in a non-destructive manner as well as a general pattern structure analysis optical device having the structure as described above. SE) may be used. That is, the polarized light reflected from the surface of the wafer W is decomposed into horizontal and vertical components, and an intensity ratio or a phase difference between the two components is used as optical signal data.

2 is a conceptual diagram illustrating a schematic configuration of a light control unit and a light detection unit using the SE.

Referring to FIG. 2, the dimming unit 200 includes a light source 210 for generating light and a polarizer 240 for forming light generated by the light source as polarized light, and the light detector 300 includes the wafer. A detection lens 310 for detecting the reflected light reflected from the surface of (W), a component decomposition unit 330 for decomposing the light passing through the detection lens 310 into horizontal and vertical polarization components, and the horizontal and vertical polarization And a detection unit 320 for calculating the intensity ratio or phase difference of the components. The polarizer 240 supplies polarized light to the surface of the wafer W by passing only light waves oscillating in a specific direction among the light generated by the light source. In an embodiment, the component decomposition unit 330 uses a prism, and the reflected light passing through the prism is decomposed into a vertical polarization component and a horizontal polarization component. The detection unit 320 calculates intensity ratios (Ψ) and phase differences (Δ) of the vertical and horizontal polarization components by conventional spectroscopic ellipsometry theory. In this case, the optical signal data uses either the tangent of the intensity ratio Ψ or the cosine of the phase difference cosΔ.

The storage unit 400 includes a first storage unit 410 and a second storage unit 420.

The first storage unit 410 stores reference optical signal data. The reference optical signal data serves as reference data for performing the data compensation method according to the present invention, is measured by a separate process, and is preset and stored. The reference optical signal data is obtained using the wafer inspection system and the reference wafer in normal operation.

The second storage unit 420 stores the result processed by the central processing unit 500.

The CPU 500 includes a comparison unit 510, a compensation unit 520, and a calculation unit 530.

The comparison unit 520 compares the reference optical signal data stored in the first storage unit 410 with the optical signal data acquired by the light detector 300, and calculates a difference. The compensation unit 520 compensates for the difference. The calculation unit 530 calculates and processes the compensated optical signal data.

In detail, the central processing unit 500 compares the reference optical signal data stored in the storage unit 400 with the optical signal data obtained by the light detection unit 300 in the comparison unit 510. The reference optical signal data is transmitted from the first storage unit 400 to the comparison unit 510. The comparison unit 510 calculates a difference when there is a difference between the reference optical signal data and the optical signal data acquired by the light detector 300 as a result of the comparison.

The difference calculated by the comparison unit 510 is compensated by the optical signal data in the compensation unit 520. The comparison in the comparison unit 510 is performed only once, and then the compensation unit 520 compensates the difference calculated by the comparison unit 510 equally every time the optical signal of the wafer W is acquired.

The calculation unit 530 calculates the compensated optical signal data to obtain information about the pattern on the wafer W. The information about the pattern obtained by the calculation unit 530 is stored in the second storage unit 420.

 The stage 100, the dimming unit 200, the light detecting unit 300, the storage unit 400, and the central processing unit 500 form a substrate pattern inspection apparatus by organically functioning by the control unit 600. . Preferably, the display unit 700 may further include a display unit 700 for visually displaying the processing result of the central processing unit 500. In one embodiment, the display includes a computer monitor.

The processing result of the central processing unit 500 is controlled by the control unit 600 and displayed on the display unit 700. Therefore, the operator can easily check the information on the data compensation and inspection target.

3 is a flowchart illustrating a data compensation method of a wafer inspection system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, first, the reference wafer W is loaded into the stage 100 to set a compensation value of the optical signal data. Light is irradiated from the dimming part 200 to the reference wafer (W). The light detector 300 detects the light reflected from the reference wafer (W). Therefore, the first optical signal data is obtained (S100).

The first optical signal data obtained by the light detector 300 is transmitted to the comparison unit 510 of the central processing unit 500. Meanwhile, reference optical signal data stored in the first storage unit 410 of the storage unit 400 is also transmitted to the comparison unit 510. The comparison unit 510 calculates difference data by comparing the first optical signal data with the reference optical signal data (S200).

In the above, the reference optical signal data and the first optical signal data are spectral data.

4 is a graph for comparing first spectrum data with reference spectrum data.

In FIG. 4, A is reference spectral data, and B is first spectral data. In FIG. 4, it can be seen that the reference spectrum data and the first spectrum data are different near the wavelength of 400 nm.

However, as shown in FIG. 4, when the reference spectrum data and the first spectrum data differ, this indicates an error state of the wafer inspection system. Therefore, it is not possible to obtain accurate information on the pattern of the wafer W by using the wafer inspection system. And it takes a lot of time to check the error of the wafer inspection system.

Therefore, the compensation unit 520 compares the first optical signal data with the reference optical signal data to calculate difference data. The difference data is calculated according to the wavelength.

5 is a graph illustrating difference data between first spectrum data and reference spectrum data, according to an exemplary embodiment.

Referring to FIG. 5, C represents difference data from the first spectrum data based on reference spectrum data. As shown in FIG. 4, since the reference spectrum data value is generally larger than the first spectrum data value, the difference data value is generally negative.

6 is a graph for explaining difference data between first spectrum data and reference spectrum data according to another exemplary embodiment.

Referring to FIG. 6, D represents difference data from the reference spectrum data based on the first spectrum data. As shown in FIG. 4, since the reference spectral data value is generally larger than the first spectral data value, the difference data value is generally positive.

7 is a graph for explaining the difference data between the first spectrum data in the steady state and the reference spectrum data.

When the reference spectrum data and the first spectrum data are substantially the same, the difference data value becomes almost zero (zero) as shown in FIG. 7. In this case, when the pattern of the wafer W is inspected using the wafer inspection system, accurate information on the pattern of the wafer W can be obtained without compensation for optical signal data.

8 is a graph for explaining difference data between compensated first spectrum data and reference spectrum data.

As shown in FIG. 8, when the first spectrum data is compensated using the difference data, the difference data with the reference spectrum data is calculated, and the value is almost zero. Therefore, the compensated first spectrum data may be determined to be substantially the same as the reference data. Therefore, it is determined that the data of the pattern obtained by compensating the first spectral data obtained in the faulty wafer inspection system and the pattern data obtained by computing the spectral data obtained in the normal wafer inspection system are substantially the same. can do.

Since the difference data shown in FIG. 4 is based on reference spectrum data, a negative value of the difference data is compensated for when compensating the first spectrum data.

Since the difference data shown in FIG. 5 is based on the first light spectrum data, the difference data is compensated as it is when the first spectrum data is compensated.

When the calculation of the difference data is completed, the wafer 100 is loaded into the stage 100 to inspect the pattern. Light is irradiated from the dimming part 200 to the inspection wafer W. The light detector 300 detects light reflected from the inspection wafer W. Therefore, the second optical signal data is obtained (S300).

The second optical signal data obtained by the light detector 300 is transmitted to the compensation unit 520 of the central processing unit 500. The compensation unit 520 compensates by adding the calculated difference data to the second optical signal data (S400).

The compensation unit 520 always compensates for the data difference to the second optical signal data detected by the light detector 300.

Thereafter, the compensated second optical signal data is calculated in the calculation unit 530 to obtain information about the pattern of the inspection wafer W. Therefore, accurate information about the pattern of the wafer W can be obtained in the wafer inspection system.

As described above, the data compensation method of the wafer inspection system according to the preferred embodiment of the present invention compares the reference optical signal data to calculate the difference data, and then uses the calculated difference data to obtain the light obtained in the wafer inspection system. Compensate signal data. Therefore, even if there is an abnormality in the optical signal data obtained by the wafer inspection system, it is possible to obtain accurate data on the wafer by compensating for this. In addition, the time required for compensation of the optical signal data can be reduced.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can.

Claims (4)

Obtaining first optical signal data from a reference wafer using a wafer inspection system; Calculating difference data by comparing the first optical signal data with preset reference optical signal data with respect to the reference wafer; Acquiring second optical signal data from a wafer to be inspected using the wafer inspection system; And And compensating for the second optical signal data using the difference data. The method of claim 1, wherein when the difference data is calculated based on the reference optical signal data, a negative value of the difference data is compensated for in the second optical signal data. . The method of claim 1, wherein when the difference data is calculated based on the first optical signal data, the value of the difference data is compensated to the second optical signal data as it is. . The method of claim 1, wherein the optical signal data is spectral signal data.

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