JP2792318B2 - Polarization analysis method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention separates and detects changes in the polarization state of reflected light from an object (measurement object) on which light is incident, and based on the results, optical constants (including thickness) of the object. More specifically, the present invention relates to a polarization analysis method and an apparatus for obtaining an ellipsometric parameter necessary for measuring an optical system, specifically, a technique for determining the attitude of an optical system including a beam splitter in the inspection and measurement of a subject, and an attitude based on the determination result. The present invention relates to a polarization analysis method and a device therefor with a focus on control technology.

[0002]

2. Description of the Related Art Conventionally, as a film thickness measuring apparatus using an ellipsometry method (ellipsometry) for measuring the thickness and refractive index of a thin film of several thousand angstroms or less, for example, Japanese Patent Laid-Open No. Japanese Patent No. 26410, which has recently been developed so that it can be measured online in an improved form, is disclosed in, for example, JP-A-62-293104.
JP-A-63-36105, JP-A-64-2850
There is one disclosed in Japanese Patent Application Laid-Open Publication No. 9-No.

[0003] As is clear from the above-mentioned literatures, the polarization reflectance ratio ρ of an object, for example, a thin film, can be determined by equation (1) by causing light to enter the object and performing polarization analysis. .

[0004]

(Equation 1) Here, R _p is the reflectance of the component (p component) parallel to the plane of incidence of the electric field vector, R _s is the reflectance of the component (s component) perpendicular to the plane of incidence of the electric vector, and the amplitude ratio tan ψ Ψ and Δ determined by the phase difference Δ are so-called ellipso parameters. The polarization reflectance ratio ρ indicates a change in the state of polarization when incident light is reflected on the surface of the subject, and has a fixed relationship with the thickness d of the thin film on the surface. Therefore, the characterization of the subject can be performed by obtaining the ellipsometric parameters by the ellipsometry.

As a film thickness measuring apparatus using such a method, for example, Japanese Patent Application Laid-Open Nos. 55-26410 and
Japanese Patent Publication No. -28509 discloses a well-known ellipsometry. The former relates to a high-speed ellipsometer (polarization analyzer) using a rotating analyzer in the optical system, and the latter relates to a high-speed compact ellipsometer in which the optical system does not include a movable part. In particular, the simplification of the optical system by removing the movable portion as in the latter case contributes to the improvement of the reliability and the size and weight of the apparatus, and the measurement accuracy is improved because the measurement error is reduced. In addition, since the optical calculation can be simplified, the measurement can be speeded up and the apparatus can be reduced in cost. In this sense, the applicant of the present invention filed Japanese Patent Application No. Hei.
No. 029296 has been filed, and a simple, small, and lightweight high-speed ellipsometer has been proposed.

As described above, ellipsometry observes the change in the polarization state when light is reflected on the surface of an object, and measures the optical constant of the substance itself, or the optical constant and the film thickness of a thin film attached to the substance. Methods and apparatuses that fall under the category of "optical devices". Despite the technology that began at the end of the last century, it has only recently come to the limelight in the industrial world because it has been applied as a technology that meets the needs of the high-tech industry as described above. Optical devices other than the ellipsometer for the so-called high-tech technology in this field include a semiconductor wafer distortion evaluation device (Japanese Patent Application Laid-Open No. 55-150248), a laser radar (Japanese Patent Application Laid-Open No. 56-120970), and a surface inspection device ( JP-A Nos. 55-113942 and 56-85
No. 31).

[0007]

However, irrespective of whether the optical system of the optical device includes a movable part or not, for example, the vertical movement of the measuring head unit including the optical system and the loading stage of the subject. For the imbalance of the entire optical system, fine adjustment of the measuring head and the optical system is indispensable. For this reason, some optical elements (analyzer,
A manual fine adjustment function is mounted on a polarizer, a beam splitter, or the like, or a distance adjustment mechanism between the measurement head and the loading stage is provided. Such a mechanism is used to adjust the optical path between the photodetector and the optical axis visually before measurement, or to manually adjust while looking at the output value displayed on the screen after the signal from the photodetector is processed. These adjustments require experience and intuition, take time,
There is a drawback that the reproducibility is lacking in measurement because the adjustment method differs depending on the person. Further, even if the measurement device is adjusted in a state close to the ideal, the state cannot be maintained continuously even during the measurement. For example, if the flatness of the subject or its loading stage is not constant, a slight shift occurs in the optical path, making it impossible to perform optimal measurement. Such a problem occurs when one subject is continuously measured at multiple points.
This is particularly noticeable when the relative positional relationship between the loading stage and the measuring head moves continuously at high speed.

In order to suppress these problems, an optical analyzer having a large light receiving area for reflected light can be used.
There is a limit in the area, which is a result that goes against recent demands for downsizing and simplification. It is also possible to install a condenser lens at the front of the photodetector and collect the reflected light without leakage, and make the reflected light incident on the detector. .

On the other hand, for example, even if a measurement error occurs, if the cause can be quantified, a correction value corresponding to the quantified value is determined, a necessary correction coefficient is multiplied to the measured value in calculation, or an optical system or a measuring head is used. It can be fine-tuned mechanically in real time. In this sense, the specification of the amount of deviation of the posture of the optical system from the ideal state is important for high-accuracy measurement.

Further, in various optical elements in the optical system, an undesired light component may be generated at the time of light reflection or refraction. For example, when light incident on a beam splitter is emitted from the inside to the outside, the light is split into a transmitted light component and a reflected light component on an emission surface depending on the emission angle. The latter reflected light component exits from the other exit surface of the beam splitter, but the unexpected exit light becomes a disturbance of the detector and hinders the measurement. The occurrence of such unexpected light components can be avoided to some extent by modifying the processing and arrangement of each optical element constituting the optical system.However, depending on the polarization analysis method, despite such a modification,
There is a problem that it cannot be completely avoided.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and effectively utilizes the characteristics of existing device elements without excessively complicating the device, thereby making it possible to shift the optical system in the ellipsometer. A polarization analysis method and apparatus that are advantageous for so-called on-line measurement in which it is necessary to establish a technique for determining the amount and an optimization technique for ellipsometry based on the amount of deviation, and particularly to optimize the detection of reflected light from a photodetector in real time. The purpose is to provide.

[0012]

According to the present invention, there is provided an ellipsometry comprising: means for extracting a plurality of light components from reflected light of light incident on an object to be measured by an optical system having a beam splitter;
It has means for detecting and analyzing the extracted light components to determine the ellipsometric parameters, and means for detecting light leakage from the beam splitter and controlling the attitude of the optical system from its position. In this method, the light leakage is made to exit perpendicularly from the inside to the outside at the exit surface of the beam splitter, and means for causing the detection position of the light component to follow the target position based on the position information of the light leakage. May be adopted. Then, the means for determining the ellipsometric parameter makes the polarized light incident on the measurement object at a predetermined angle, extracts four different polarization components from the reflected light of the measurement object, and extracts the four polarization components thus extracted. May be calculated based on three light intensities among the above light intensities.

Further, the polarization analyzing means according to another aspect of the present invention is characterized in that polarized light is made incident on a measurement object at a predetermined angle, and reflected light of the measurement object is converted into four different polarization components by an optical system. And ellipsometric parameters are obtained based on the light intensities of three of the four polarized light components extracted, and the remaining one polarized light component is detected to determine the attitude of the optical system from its position. It is.

Next, an ellipsometer according to the present invention comprises an optical system having a light source for irradiating an object to be measured with incident light, a beam splitter for extracting a plurality of light components from reflected light from the object to be measured, and A plurality of detectors for detecting light components;
A measurement unit that analyzes the detection results from the plurality of detectors to determine the ellipsometric parameter, and a light leakage position determination unit that detects light leakage from the beam splitter and determines the position of light leakage,
A calculating unit for determining the attitude of the optical system based on the leaked light position information. Here, the beam splitter may have an emission surface from which light leaks vertically from inside to outside, and the calculation unit may determine the relative positional relationship between the measurement target and the optical system. Frequently, the optical system does not have a movable part, and the optical system and the plurality of detectors can be fixed in a predetermined positional relationship, and based on the output from the arithmetic unit, It may have a driving means for relatively adjusting the positional relationship with a plurality of detectors.

Further, the optical device according to the present invention has a beam splitter, means for detecting the position of light leakage from the beam splitter, and a posture for determining the posture of the optical device based on the output of the position detecting means. Determining means for controlling the optical device to a target attitude based on the output of the attitude determining means, if necessary. The optical device having the beam splitter includes a light source unit that causes polarized light to enter a measurement target at a predetermined angle, and a non-polarization beam splitter that branches reflected light reflected by the measurement target into two different directions. An optical member that extracts two different polarization components from each of the lights split by the non-polarization beam splitter, and finally extracts four polarization components from the reflected light of the measurement target; Four light receivers for detecting the light intensities of the respective polarized components, and an ellipsometric parameter of elliptically polarized light in the reflected light based on three of the four light intensities detected from the four light receivers. And an operation unit for calculating the following.
Further, the polarization analyzer includes a first optical system in which the plurality of optical members extract respective polarization components in + 90 ° and 0 ° directions with respect to a reference direction from one of the lights split by the non-polarization beam splitter. And a second optical system that extracts each polarization component in the + 45 ° and −45 ° directions with respect to the reference direction from the other light split by the non-polarization beam splitter. It is also desirable that a wave plate is inserted in an incident optical path or a reflected optical path with respect to the measurement object.

The above-mentioned ellipsometer comprises a light source unit for causing polarized light to enter a measurement object at a predetermined angle, and a compound beam splitter for extracting four different polarization components from the reflected light reflected by the measurement object. Four light receivers for detecting the light intensity of each polarization component extracted by the composite beam splitter, and reflection based on three of the four light intensities detected from the four light receivers. It is preferable to include a calculation unit that calculates an ellipsometric parameter of elliptically polarized light in the light. Among them, the composite beam splitter converts reflected light from a measurement target into reflected light and transmitted light on an incident surface. A non-polarizing glass to be branched and one end fixed to the non-polarizing glass, and extracting each polarization component in + 90 ° and 0 ° directions with respect to a reference direction from the reflected light of the non-polarizing glass. A polarizing beam splitter, and a polarizing beam splitter that is bonded to the transmitting surface of the non-polarizing glass for transmitting the transmitted light, and extracts, from the transmitted light of the non-polarizing glass, polarized components in + 45 ° and −45 ° directions with respect to a reference direction And a non-polarizing glass that splits the reflected light from the measurement target into reflected light and transmitted light on the incident surface, and one end of the non-polarized glass. A first polarizing beam splitter fixed to extract each polarized component in + 45 ° and −45 ° directions with respect to a reference direction from the reflected light of the non-polarized glass; and a light-emitting surface of the transmitted light of the non-polarized glass. It may be constituted by a second polarizing beam splitter which is joined and extracts each polarization component of + 90 ° and 0 ° with respect to the reference direction from the transmitted light of the non-polarizing glass.

As described above, the present invention positively utilizes light leakage unavoidably generated in an optical system during optical analysis. More specifically, the present invention is one of the components of the optical system of an optical device. It is characterized in that light leaked from a certain beam splitter is used for detecting the attitude of the optical system. Here, the light leakage occurs during a process in which a plurality of components are extracted from the reflected light by such an optical system and detected by each detector, and the reflected light component which is minimum required to obtain various optical information Other reflected light components. In the case of ellipsometry, this would mean a light component that does not contribute to the ellipsometric parameter determination.

That is, the light leaked from the beam splitter due to the reflected light from the object irradiated with the light is emitted perpendicularly to the emission surface from the inside to the outside, so that the influence of the leaked light on other detectors is reduced. In this method, light leakage is detected, and the optimum posture of the optical system is determined from the detected position. Also, based on the leaked light position information, the detection position, that is, the detection position of the reflected light component is calculated, and based on the calculation result, the optical system is formed in a plane perpendicular to the subject including the reflected light and a plane perpendicular thereto. By rotating, a method of always following and maintaining the detection position of the reflected light at the target position during the measurement is used, so that the fine adjustment of the measuring head and the optical system of the entire optical system can be automatically performed. .

[0019]

First, among various optical devices or optical analysis methods having the above-described configuration, the principle of operation of a polarization analysis method and a method of measuring ellipso parameters using the device will be described as preferred embodiments. I do. In the present invention, when light polarized from the light source unit is incident on the measurement target at a predetermined angle φ, the reflected light reflected by the measurement target has elliptically polarized light having a predetermined shape determined by the thickness of the measurement target.
Since the ellipsometric parameters ψ and Δ are determined by the amplitude ratio tan の between the P component and the S component of the reflected wave from the measurement object and the phase difference Δ, they are determined from the elliptical shape and the degree of inclination of the ellipse from the reference line. Therefore, if at least three light intensities obtained by projecting an ellipse in each direction are obtained, the ellipse is uniquely determined. Therefore, as shown in FIG. 11, for example, even if projections from four directions are obtained, one of them is discarded, and projections from the remaining three directions are obtained, the ellipse is uniquely defined.

Therefore, in the ellipsometric parameter measuring method of the present invention, the reflected light having the elliptically polarized light reflected by the object to be measured is split into two directions by the non-polarizing beam splitter, and further separated from the light in each of the split directions. Polarized components in two directions are extracted. Therefore, finally, four polarization components having different polarization directions are obtained and converted into respective light intensities. Since these four light intensities are values obtained by projecting the above-mentioned ellipse from different directions, the amplitude ratio tan に よ る and the phase difference Δ by the ellipsometric parameter ψΔ are obtained by using any three of these four light intensities. I get it. It is clear from the above description that the ellipsometric parameter can be obtained even when only three polarization components are extracted by the optical system.

When the above four polarization components are extracted, the light intensity having the smallest value which can be regarded as having a large degree of error among the four light intensities is discarded, and the three light intensities are increased. Since the calculation is performed using the intensity, the accuracy of the calculated ellipsometric parameters ψ and Δ is improved.

The polarization direction of each polarization component is + 90 °, 0 °, + 45 ° and −45 ° with respect to a reference direction in which the plane of incidence of the incident light with respect to the object to be measured is the azimuth of 0 ° (P direction).
The calculation of the ellipsometric parameters ψ and Δ is simplified by setting to °.

Further, four different polarization components are extracted from the reflected light reflected by the object to be measured by a composite beam splitter composed of one optical component. As described above, by using the composite beam splitter, the number of optical components can be reduced, and the entire ellipsometer can be manufactured to be small and lightweight.

This composite beam splitter is composed of non-polarizing glass and first and second polarizing beam splitters. In the composite beam splitter having such a configuration, the reflected light from the measurement target is split into transmitted light and reflected light on the surface of the non-polarizing glass. Then, from the reflected light,
+ 90 ° with respect to the reference direction by the polarizing beam splitter
And two polarization components at 0 ° are extracted. Similarly, two polarized components of + 45 ° and −45 ° with respect to the reference direction are extracted from the transmitted light by the second polarizing beam splitter. Therefore, four different polarization components are extracted from the reflected light.

Further, the first polarization beam splitter extracts each polarization component in the + 45 ° and −45 ° directions from the reflected light, and the second polarization beam splitter extracts each polarization component in the + 90 ° and 0 ° directions from the transmitted light. Can also be extracted.

Next, in another embodiment of the present invention, the light leakage from the beam splitter is detected and the attitude of the optical system is determined from the position of the light leakage, so that another optical system is added to the existing optical system. There is no need to provide an element, and it is only necessary to detect the position of light leakage and determine the attitude of the optical system.
The device only needs a light leakage position determination unit and a calculation unit for the attitude of the optical system. For this reason, if an optical system having a beam splitter is used, it is possible to avoid the need for a heavy-weighted ellipsometer. The attitude of the optical system is determined as a relative positional relationship between the subject and the optical system. In this case, if the leaked light is emitted vertically from the inside to the outside on the emission surface of the beam splitter,
This light leakage is only a transmitted light component and can prevent new light leakage from occurring. For this reason, basically, light leakage having a small intensity can be effectively used for determining the attitude of the optical system, and another light leakage does not disturb the detector.

Based on the attitude of the optical system determined as described above, the detection of the reflected light component can be optimized.
In this case, the detection position of the reflected light component can follow the target value in real time. Specifically, based on the calculated attitude of the optical system, the optical system is rotated in a plane perpendicular to the subject including the incident light and / or in a plane perpendicular thereto,
The positional relationship between the reflected light component and the plurality of detectors can be relatively adjusted.

In the case of an ellipsometer in which the optical system has no movable part and the optical system and the plurality of detectors are fixed in a predetermined positional relationship, the attitude of the optical system is measured. It is the attitude of the head and the attitude of the detector. Therefore, optimizing the detection of the reflected light component based on the attitude of the optical system is nothing less than optimizing the detection position of the reflected light component and the positional relationship between the optical system and the subject. Such fixed ellipsometry techniques are extremely lightweight, compact, and allow for highly accurate and fast ellipsometric parameter determination. Therefore, with the method of determining the attitude of the optical system according to the present invention, the attitude of the optical system can be determined and the attitude can be optimally controlled based on the technique while maintaining the features of the polarization analysis technique.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 In this embodiment, means for detecting light leakage from a beam splitter and controlling the attitude (displacement of an optical axis) of an optical system from the position of the light leakage will be described. FIG. 1 is a schematic configuration diagram showing an optical system of one embodiment of a polarization analyzer according to the present invention.

The light t 0 polarized from the semiconductor laser light source 14 through the polarizer 15 is incident on the sample surface 13. Note that the measurement object or the specimen used so far is hereinafter referred to as a sample surface. The light t0 incident on the sample surface 13 is reflected on the sample surface 13 to become reflected light r0, and the unpolarized beam splitter 6
7 is incident. The non-polarization beam splitter 67 is made of, for example, a non-polarization glass plate. The reflected light r0 is split into a reflected light r1 and a transmitted light t1 at the surface d1 of the non-polarization beam splitter 67. Analyzer 2 at 0 ° for reflected light r1
1 to light t3, and the light intensity I1 of the detector 23
a. On the other hand, the transmitted light t1 is split at the back surface d2 of the beam splitter 67 into a light t2 transmitted outside the non-polarization beam splitter 67 and a light r2 reflected inside the non-polarization beam splitter 67. The transmitted light t2 is −45 ° and +45 by the Wollaston prism 22, which is an analyzer.
The light becomes polarized light t4 and t5, and is detected by the detectors 23b and 23c as light intensities I2 and I3. The light r2 reflected in the non-polarization beam splitter 67 is transmitted from the exit surface d3 to the outside of the non-polarization beam splitter 67 as light leakage. This is referred to as light leakage m. This leaked light m is transmitted to the position detector 24.
To detect.

Further, the reflected light t3, t
In an optimal state of the optical system in which the light beams 4 and t5 are incident on the centers of the detectors 23a, 23b and 23c, the light exit surface is perpendicular to the traveling direction of the light r2 reflected by the back surface d2 of the non-polarizing beam splitter 67. Set d3. That is, the reflected light r2 only transmits through the exit surface d3, and the influence of the reflection on the detector is prevented. Then, the transmitted light leak light m is made incident on the center of the position detector 24 installed outside the non-polarizing beam splitter 67. By doing so, in the optimal state of the optical system in which the reflected light from the sample surface 13 is incident on the centers of all the detectors, the leaked light m is made incident on the center of the position detector 24 and there is no extra leaked light. You can prevent it.

Now, for example, as shown in the detailed view of FIG. 2, when the light leakage m does not exit perpendicularly from the exit surface d3 of the non-polarizing beam splitter 67a, if the optical system is previously optimally adjusted in that state. For example, the optimum adjustment state can be maintained by always maintaining the detection position of the light leakage m in that state. Therefore, the light leakage m is equal to the emission surface d3 of the non-polarization beam splitter 67a.
Even when the light is not emitted perpendicularly from the light source, the present invention can be applied without any problem. However, new reflected light r3 generated due to the light leakage m not being emitted vertically is emitted by the light intensity detectors 23a and 23a.
3b, 23c and light leak m without affecting the position detector 24.
Is assumed to be detectable by the position detector 24.

In the above description, the non-polarizing beam splitter is specified as the beam splitter. However, the position detection does not detect the polarization state of the reflected light, but simply detects the position information. Therefore, the light leakage may or may not be polarized, and the beam splitter used in the present invention is not limited to a non-polarization beam splitter,
Any beam splitter may be used.

The present invention can be applied to any optical system as long as it includes a beam splitter. Therefore, as the optical system, a different type of polarization analyzer (for example, Japanese Patent Application Laid-Open No. 64-28509) may be used. Gazette). That is, as shown in another embodiment 7 of FIG.
A non-polarizing beam splitter 25a is used instead of the Wollaston prism 22 as an analyzer for the 5 ° and + 45 ° polarized components, and further, r1 is made incident on the non-polarizing beam splitter 25b, and each light is analyzed by the analyzers 26a, 26b, and 26c. +
Polarizing light into 45 °, -45 °, and 0 ° components, and condensing lens 7
The light is condensed by the detectors 23a, 23b and 7c.
It is also possible to use an optical system for detecting at b and 23c. Further, the Wollaston prisms 22, 22a as shown in FIG.
Is used, the detected light intensity is four components instead of three components, that is, since the optical system of the 4CH ellipsometer also includes the beam splitter, the present invention can be applied. In addition,
The 4CH ellipsometer will be described in another embodiment.

Next, the position detecting means will be described. Detectors used for the position detector 24 include, for example, a multi-division type photodiode and a two-dimensional position detection photodiode PSD. As a multi-segmented photodiode, for example, there is a four-segmented photodiode, in which four photodiodes are arranged on two-dimensional coordinates corresponding to the first to fourth quadrants, and the area irradiated with light is provided. Each output value is different. However, since the area ratio and the output value take a proportional relationship, absolute position information cannot be obtained.
For example, the center position is a position where all output values are the same. Mathematically, the output values from the four photodiodes corresponding to the first to fourth quadrants are represented by I1, I2, I3 and I4.
Assuming that the center of each diode is located at the vertex of a square with a distance L of one side, for example, formulas (2) and (3) are considered as a method of obtaining rough positional information near the center. Can be

[0036]

(Equation 2)

[0037]

(Equation 3) Here, X and Y are displacements from the center of the four-division type photodiode, and the signals I1, I2, I3, and I3 based on the light intensity.
When I4 is very small, it is also possible to appropriately amplify by using an amplifier.

A two-dimensional position detector photodiode P
The SD is classified into, for example, a double-sided type, a surface type, and an improved surface type, each of which has four electrodes. Using the light intensity from two sets of electrodes facing each other of the PSD, for example, X1, X2 and Y1, Y2, the double-sided type and the surface type are obtained by the formulas (4) and (5), and the improved surface type is obtained by the formula (6). And (7), two-dimensional coordinates, for example, X and Y can be calculated.

[0039]

(Equation 4)

[0040]

(Equation 5)

[0041]

(Equation 6)

[0042]

(Equation 7) Where L is the distance between two electrodes facing each other,
X and Y indicate displacements in the X and Y directions from the center of the PSD. When the signals X1, X2, Y1, and Y2 based on the light intensity are small, it is possible to appropriately amplify the signals using an amplifier.

When a PSD element is used as the position detector 24, there may be a case where there is no linearity between the detection position of the light to be detected and the output signal of the element. In such a case, a correction circuit is added in the position signal processing unit 31a (see FIG. 9) or the position determination unit, which is one of the functions of the personal computer, so that the nonlinearity of the output signal as described above is linearly adjusted. After the correction, the subsequent signal processing can be performed.

FIG. 5 shows a system view of the entire view of the apparatus, and FIG. 6 shows a block diagram of the apparatus configuration. The components are an ellipsometer main body 50 including a position detecting device, an A / D converter 5 for taking in position information into a personal computer.
1. a personal computer 52 that performs control arithmetic processing;
It comprises a D / A converter 53 for converting an output value calculated by a personal computer 52 into an analog signal, and an actuator unit 54 for driving an ellipsometer, that is, an ellipsometer body 50.

First, a method of controlling the reflected light incident on the detector to be always at the target position will be described.

The position of the ellipsometer from the position detector 24 is appropriately amplified and taken into a personal computer 52 through an A / D converter 51 as a digital value. Here, the position signal is converted into position information, and the difference between the position signal and the previously input target value is calculated by the personal computer 52. Based on the result of the calculation, the deviation is calculated under appropriately set conditions. Is always set to 0 and digital / PID control is performed, and output using the D / A converter 53. The output value is amplified by an amplifier and the
To slightly move the ellipsometer body 50,
Feedback control is performed so that the reflected light incident on the detector always reaches the target position. FIG. 7 is a flowchart showing the above process. In addition, the control method may be analog PID control, and is not limited to PID control, and may be any suitable control that makes the deviation zero.

Next, the mechanism for slightly moving the ellipsometer main body 50 and the actuator section 54 will be described in detail. FIGS. 8A and 8B are schematic explanatory views showing the attitude control means of the apparatus, wherein FIG. 8A is a front view including a partial cross section, and FIG. 8B is a side view. In FIG. 8, the ellipsometer main body 50 is semi-fixed by a method such as pinning at point a. For example, the shaft 55 is attached from the point a of the ellipsometer main body 50. Then, a bearing 57 is attached to the fixing plate 56, and the shaft 55 of the ellipsometer may be inserted into the bearing 57. By doing so, the ellipsometer main body 50 can perform a rotational movement in the direction indicated by the arrow in the figure around the point a in a plane parallel to the paper surface. The same applies to the fixed plate 5 including the ellipsometer.
6, the fixing plate 56 including the ellipsometer main body 50 can rotate around a certain point in a plane perpendicular to the plane of the drawing. If the ellipsometer body 50 and the fixed plate 56 set in this way are driven by the servomotor 58 via the ball screw 57a, the servomotor 58 is driven by the output from the D / A converter 53 amplified by the amplifier. The rotational movement is converted into a linear movement by the ball screw 57, and the ellipsometer main body 50 can be moved in the horizontal direction on the paper and the vertical direction on the paper. The ellipsometer main body 50 is, for example, a spring 59.
The tip of the ball screw 57 is always brought into contact with a certain load by using a method such as the above. However, in the figure, only the actuator unit 54 for driving in the horizontal direction on the paper is shown.

As described above, the signal from the position detector 24 causes the main body 50 of the ellipsometer to move in the left-right direction and the vertical direction on the paper, and the reflected light can always be set to the target position.

Embodiment 2 In this embodiment, three leaked light components among the four polarized light components separated from the beam splitter of the first embodiment are used for the measurement of the ellipsometer parameter, but the remaining one polarized light is used. Means for detecting the component and controlling the attitude of the optical system from the position will be described. FIG. 9 is a configuration block diagram showing one embodiment.

In the figure, reference numeral 33 denotes an ellipsometer main body housed in a case made of a light metal material. In this main body, linearly polarized incident light 15 emitted from a light source 16 composed of a semiconductor laser light source 14 and a polarizer 15 is reflected on the sample surface 13. This reflected light 18 is split by a non-polarizing beam splitter 19 into a reflected light 20a and a transmitted light 20b. The polarization beam splitter 21 separates the reflected light 20a into polarization components in directions of 90 ° and 0 ° with respect to the reference direction, and enters the light receiving units 23a and 23b. On the other hand, the polarization beam splitter 22 converts the transmitted light 20b into + with respect to the reference direction.
The light is separated into polarized light components in the 45 ° and −45 ° directions, and is incident on the light receivers 23c and 23d. The light receivers 23b, 23c,
23d sends the light intensities I2, I3 and I4 to the signal processing unit 31. Then, in the case of the present embodiment, the light receiver 23a employed as the position detecting detector sends the light intensity I1 to the position signal processing unit 31a.

As described above, first, the light intensities I1, I3, and I4 output from the ellipsometer main body 33 are converted into digital values by the signal processing section 31, and then input to the personal computer 32 as an arithmetic section. You.
The personal computer 32 performs a predetermined calculation using the input light intensities I2, I3, and I4 to calculate the ellipsometric parameters ψ and Δ. Further, using the calculated ellipsometric parameters ψ and Δ, for example, the film thickness d of the subject 13 to be measured is calculated using a predetermined arithmetic expression. When the calculation processing of the film thickness d at one measurement point is completed, the personal computer 32 moves the XY movement table 34 on which the measurement target is mounted, and starts measurement at the next measurement point on the subject 13. The method for calculating the ellipsometric parameters will be described in a third embodiment. The moving table is not limited to the XY moving table but may be an rθ moving table.

On the other hand, the light intensity I1 input to the position signal processing section 31a is used for adjusting the optical axis of the apparatus, and the output thereof is a personal computer (hereinafter abbreviated as a personal computer).
32, the personal computer 32 controls the attitude of the optical system by operating the actuator 35 and the XY movement table 34. Software suitable for the purpose of the present apparatus has been developed for the personal computer 32, and one of them is configured with the above-mentioned ellipso parameter calculation unit. The other systematically incorporates a position determination unit, a posture calculation unit, a posture adjustment amount determination unit, and a signal output unit to an actuator of the optical system. Note that the signal processing unit 31 and the position signal processing unit are formed on a board substrate as one unit.

In the above-described apparatus configuration, the same multi-division type photodiode or two-dimensional position detection photodiode PSD as the position detector 24 shown in the first embodiment may be used as the light receiver 23a for position determination. . For example,
In the case of the detector 23a using a photodiode divided into four in the first to fourth quadrants, X and Y are calculated using the above equations (2) and (3), and the position is calculated based on the position information. The attitude of the optical system is calculated from the determined value, and a deviation (deviation) from a reference attitude amount serving as a target amount is obtained to obtain an attitude adjustment amount. Here, the reference posture amount may be stored in advance, or may be changed as needed by the keyboard / display unit 36 as needed.

In this way, 4
One polarization component I1 of the two polarization components is detected by the detector 23.
a position signal processing unit 3 which inputs the output to a as position information
The microcomputer 32 calculates the posture adjustment amount by using the output from the microcomputer 1a as a position signal and determines the posture adjustment amount.
By outputting a signal to a movable adjustment section (not shown) of the XY moving table 34 and, if necessary, the position adjustment of the ellipsometer 33 is performed by, for example, PID control. As a result, the optimal adjustment of the optical axis of the optical system before the measurement can be automatically achieved in a short time without relying on human experience, and the ellipsometric parameters with higher reproducibility can be measured.

Embodiment 3 In this embodiment, some basic configuration examples of an optical device having a beam splitter to which a leaked light position detecting means can be applied by utilizing light leaked from a beam splitter will be described using an ellipsometer as an example. The optical system mode will be described.

FIG. 10 is an internal configuration diagram of the ellipsometer main body. For example, a laser beam having a single wavelength output from the semiconductor laser light source 14 is converted into linearly polarized light by the polarizer 15. Therefore, the semiconductor laser light source 14
The polarizer 15 forms a light source unit 16. The incident light 17 converted into linearly polarized light is incident on the sample surface 13 from the light source unit 16 at an angle φ. Then, the reflected light 18 reflected by the subject (hereinafter referred to as the sample surface) 13 changes from linearly polarized light to elliptically polarized light shown in FIG. 11 due to the presence of the film on the sample surface 13, and is incident on the non-polarized beam splitter 19. .

The non-polarizing beam splitter 19 is made of, for example, a non-polarizing glass plate. Then, the incident reflected light 18 is split into two lights 20a and 20b while maintaining the elliptically polarized state without being polarized at all. The reflected light 20a is incident on the first polarization beam splitter 21. The transmitted light 20 b that has passed enters the second polarizing beam splitter 22.

The first and second polarizing beam splitters 21,
Numeral 22 has the same structure, for example, a Glan-Thompson prism, a Glan-Taylor prism, or the like, which separates incident elliptically polarized light into two orthogonal polarization components and transmits transmitted light and reflected light, respectively. Output as It should be noted that a Wollaston prism or the like that separates transmitted light into two components at an angle may be used.

The first polarization beam splitter 21 as the first optical system is arranged such that the direction of polarization of the transmitted light 21 a of the first polarization beam splitter 21 is parallel to the plane of incidence of light on the sample surface 13. Is +90 in the counterclockwise direction as viewed from the light receiver 23a side with respect to the above-described reference direction in which the azimuth is 0 °.
° is positioned. Then, the polarization direction output from the first polarization beam splitter 21 is +9.
The transmitted light 21a at 0 ° is incident on the light receiver 23a. The reflected light 21b having the polarization direction of 0 ° output from the first polarization beam splitter 21 is incident on the light receiver 23b.

Further, the second polarization beam splitter 22 as the second optical system is positioned so that the polarization direction of the transmitted light 22a of the second polarization beam splitter 22 is + 45 ° with respect to the reference direction. Have been. Then, the transmitted light 22a having the polarization direction of + 45 ° output from the second polarization beam splitter 22 is incident on the light receiver 23c. The reflected light 22b output from the second polarizing beam splitter 22 and having a polarization direction of -45 ° is incident on the light receiver 23d.

Therefore, the light intensity I1 (one channel) of the reflected light 18 projected on the vertical axis of the elliptically polarized light shown in FIG. 11 by the transmitted light 21a incident on the light receiver 23a is obtained. Further, the light intensity I2 (two channels) projected on the horizontal axis of the elliptically polarized light is obtained by the reflected light 21b incident on the light receiver 23b. Further, the light intensity I3 (3 channels) projected on a line inclined by + 45 ° with respect to the horizontal axis of the elliptically polarized light by the transmitted light 22a incident on the light receiver 23c.
Is obtained. Then, the light intensity I4 (4 channels) projected on a line inclined by −45 ° with respect to the horizontal axis of the elliptically polarized light is obtained by the reflected light 22b incident on the light receiver 23d.

That is, the reflected light 18 from the sample surface 13 has the respective light intensities I1, I2, I3 and I4, respectively.
The light is separated into polarization components in four directions of °, 0 °, + 45 °, and -45 °.

As described above, the ellipsometric parameters ψ and Δ for specifying the elliptically polarized light using the three light intensities of the four light intensities I1 to I4 are respectively set according to the following conditions A to D. It is calculated by the equations (8) to (11).

Condition A: When light intensity I1 is minimum (I2
(Calculated using I3 and I4)

[0065]

(Equation 8) However, the amplitude transmittance σ3 of the non-polarizing beam splitter 19 is a unique value, and test light having a known linearly polarized light or elliptically polarized light is incident on the non-polarizing beam splitter 19, and the true ellipsometric parameters ψ and Δ Is calculated in advance from the amount of deviation.

Condition B: When light intensity I2 is minimum (I1,
(Calculated using I3 and I4)

[0067]

(Equation 9)

Condition C: When light intensity I3 is minimum (I1,
(Calculated using I2 and I4)

[0069]

(Equation 10)

Condition D: When light intensity I4 is minimum (I1,
(Calculated using I2 and I3)

[0071]

[Equation 11]

An embodiment of an actual reference ellipsometer will now be described. FIG. 12 is a configuration block diagram showing the entire ellipsometer including the optical system of the embodiment shown in FIG. In the figure, reference numeral 10 denotes an ellipsometer main body housed in a case formed of a light metal material. This ellipsometer body 10
The light intensities I1, I2, I3, and I4 output from are represented by A /
After being converted into a digital value by the D converter 11, the digital value is input to a personal computer 12 as an arithmetic unit.
The personal computer 12 uses the remaining three light intensities obtained by discarding the lowest light intensity among the input light intensities I1, I2, I3, and I4 as described above to calculate the ellipsometric parameters ψ and Δ. calculate. Further, using the calculated ellipsometric parameters ψ and Δ, for example, a film thickness d of the sample surface 13 to be measured is calculated using a predetermined arithmetic expression.

Here, the A / D converter 11 time-divisionally converts the light intensities I1, I2, I3, and I4 and sequentially performs A / D conversion. The conversion time of one light intensity is about 10 μse
c. Therefore, including the calculation time in the personal computer 12, the measurement time of the ellipsometric parameters ψ and Δ and the film thickness d at one sampled measurement point on the sample surface 13 is about 100 μsec. Since the light intensities I1, I2, I3, and I4 are simultaneously measured and held by the voltage holding circuit, even if the sample surface 13 moves at a high speed, it is possible to cope with the problem.

Personal computer 1 as arithmetic unit
2 is an ellipsometer body 10 according to the flowchart of FIG.
Then, the film thickness d on the sample surface 13 is calculated from the four light intensities I1 to I4, which are digital values input through the A / D converter 11 from.

That is, when the flowchart of FIG. 13 is started, four light intensities I1 to I4 are read. Next, the minimum light intensity of the four light intensities is discarded. And the rest 3
A search is made as to which of the conditions A to D the two light intensities match. Then, an expression indicating the searched condition is selected, and the ellipso parameter ψ, Δ
Is calculated. When the ellipsometric parameters ψ, Δ, are obtained,
The film thickness d on the sample surface 13 is calculated using a formula separately.

In the ellipsometer configured as described above, the light intensity having the smallest value, which is considered to have the largest degree of error among the four measured light intensities I1 to I4, is discarded. Then, the ellipsometric parameters ψ and Δ are calculated using the remaining three light intensities having a large value regarded as having a small degree of error. Therefore, the accuracy of the calculated ellipsometric parameters ψ and Δ is improved.

As described above, since the light intensity under the best condition is always selected and used for the calculation, the ellipsometric parameters ψ and Δ
In comparison with a three-channel (3CH) ellipsometer as shown in FIGS. 1 and 3 in which three light intensities I1 to I3 fixed in advance are used for the calculation, the measurement accuracy is always higher than a certain level. Can be maintained. That is, the fluctuation of the measurement accuracy due to the measurement object and the measurement conditions is small, and the stable measurement accuracy can be always maintained.

FIG. 14 shows the ellipsometric parameters of the phase difference Δ calculated by the rotation analyzer method and the values calculated by the example apparatus when the film thickness was measured on a large number of silicon wafers having various film thicknesses d. FIG. 4 is a diagram illustrating a relationship between a phase difference Δ and an ellipso parameter. FIG. 14A shows an experimental result using the 4CH ellipsometer of the example, and FIG. 14B shows an experimental result using the 3CH ellipsometer.

As shown in the figure, in the 3CH ellipsometer of FIG. 14B, the phase difference Δ at which one of the three light intensities I1 to I3 becomes extremely small is 0.
In the vicinity of ° and 180 °, the difference from the phase difference Δ calculated by the rotation analyzer method is large.

On the other hand, in the 4CH ellipsometer of FIG. 14A, one of the four light intensities I1 to I4 whose extremely small value described above is removed, so that the phase difference Δ Is near 0 ° and 180 °, the error from the phase difference Δ calculated by the rotation analyzer method is reduced.

The basic form of the optical system and the method of calculating the ellipsometric parameters by using the ellipsometer of the optical device as shown in the embodiment of FIG. 10 have been described as an example. Therefore, when the non-polarizing beam splitter 67 having the shape shown in FIG. 1 of the first embodiment and the position detector 24 are provided instead of the non-polarizing beam splitter 19 shown in the apparatus of FIG. In the same manner as the analyzing means shown in Example 1, a position detecting means for detecting a position of light leakage from the beam splitter, an attitude determining means for determining an attitude of the apparatus by using an output of the position detecting means, The attitude control means for controlling the target attitude can be easily applied.

Hereinafter, an ellipsometer is mainly used as an example of an optical device which can be applied in place of the beam splitter and the position detector serving as measuring members of the position determining means for light leakage, which are the basis of such attitude determining means and attitude controlling means. Therefore, the points of several different configurations will be described with reference to the drawings.

FIG. 15 is a diagram showing a schematic configuration of an ellipsometer according to another embodiment of the present invention. The same parts as those in FIG. 10 are denoted by the same reference numerals. The same applies to the apparatus described in the following Example 4. Therefore, the description of the overlapping part will be omitted.

In this embodiment, the reflected light 20a of the non-polarizing beam splitter 19 is converted by the first polarizing beam splitter 21 into + 45 ° and −45 ° with respect to the reference direction.
The polarized light component is separated into the polarization components in the ° direction, and the transmitted light 20b of the non-polarization beam splitter 19 is split into the second polarization beam splitter 22.
Thus, the light is separated into polarized light components in directions of 90 ° and 0 ° with respect to the reference direction. And in this embodiment,
The light intensities of the light receivers 23c and 23d become I1 and I2,
The light intensities of the light receivers 23a and 23b are I3 and I4.
Even in such a configuration, the respective light intensities I1 to I4 of the four polarization components in each direction obtained by shifting the reflected light 18 from the sample surface 13 by 45 ° with respect to the reference direction can be obtained as in FIG. Therefore, substantially the same effects as those of the above-described embodiment can be obtained. And in order to detect the position of light leakage,
Instead of the non-polarizing beam splitter 19, one having the same configuration as the non-polarizing beam splitters 67 and 67a in FIGS. 1 and 2 may be provided. The position detector 24 is also provided.

In the embodiment shown in FIG. 16, the light source unit 16 in the ellipsometer of FIG.
A quarter-wave plate 40 is inserted in the optical path of the incident light 17 with respect to 3. By inserting the quarter-wave plate 40 in this manner, it is possible to convert the incident light 17 entering the sample surface 13 from linearly polarized light to circularly polarized light. Therefore,
The measurement range of the film thickness d can be shifted as compared with the ellipsometer of FIG. Then, instead of the non-polarizing beam splitter 19, a beam splitter 67 and a position detector 24 similar to those described above are provided for detecting the position of polarized light.

Further, in the embodiment shown in FIG.
As a first optical system that separates the reflected light 20a of the non-polarization beam splitter 19 into polarization components in different directions, a first non-polarization beam splitter 41 and a reference direction of the reflection light of the first non-polarization beam splitter 41 are provided. 90 °
An analyzer 43a for extracting the polarized component in the directional direction and an analyzer 43b for extracting the polarized component in the 0 ° direction of the light transmitted through the first non-polarizing beam splitter 41 are provided.

Further, as a second optical system for separating the transmitted light 20b of the non-polarization beam splitter 19 into polarization components in different directions, the second non-polarization beam splitter 42 and the reflection of the second non-polarization beam splitter 42 + 45 ° of light
An analyzer 44a for extracting a polarized component in the direction and an analyzer 44b for extracting a polarized component in the −45 ° direction of the light transmitted through the second non-polarizing beam splitter 42 are provided.

As described above, the polarization beam splitters 21 and
Even if a combination optical system of a non-polarizing beam splitter and an analyzer is used instead of 2, some corrections in the formulas for calculating the ellipsometric parameters Δ and ψ are required, but the same effect as in the embodiment of FIG. 10 is obtained. be able to.

The embodiment shown in FIG. 18 differs from the embodiment shown in FIG. 17 in that the directions of polarization of the analyzers 43a and 43b corresponding to the first non-polarizing beam splitter 41 are + 45 °,
Set to -45 °, the second non-polarizing beam splitter 42
The polarization directions of the analyzers 44a and 44b corresponding to
° and 0 °. Even with such a configuration, it is possible to obtain substantially the same effects as in the embodiment of FIG.

The embodiment shown in FIG. 19 differs from the embodiment shown in FIG. 17 in that, similar to the embodiment shown in FIG. 16, a quarter-wave plate 40 is inserted in the optical path of the incident light 17 from the light source section 16 to the sample surface 13. I have. Therefore, substantially the same effects as in the embodiment of FIG. 16 can be obtained.

17 to 19, any of the non-polarizing beam splitter 19, the first non-polarizing beam splitter 41, and the second non-polarizing beam splitter 42 can be used to detect the position of light leakage. Instead, the non-polarizing beam splitter 67 or 67a and the position detector 24 may be provided.

FIG. 20 is a schematic diagram showing a schematic configuration of an ellipsometer according to still another embodiment of the present invention. The same parts as those in the embodiment of FIG. 10 are denoted by the same reference numerals. Therefore, the detailed description of the overlapping part will be omitted.

The reflected light 18 from the sample surface 13 is split by the non-polarizing beam splitter 19 into reflected light 20a and transmitted light 20b. The reflected light 20a enters the analyzer 45. The analyzer 45 extracts the polarization component of the reflected light 20a in the direction of 0 ° and makes it incident on the light receiver 23b. The light receiver 23b is at 0 °
The light intensity I2 of the polarization component in the direction is output. On the other hand, the transmitted light 20b of the non-polarizing beam splitter 19 is
6 is incident on the incident surface. The non-polarizing glass 46 is formed of, for example, a prism having a triangular cross section. And
The incident surface of the polarization beam splitter 47 is joined to the exit surface opposite to the entrance surface. The mounting angle is set so that the transmitted light 20b is incident on the incident surface at a Brewster angle θ. As is well known, light incident at a Brewster angle θ is separated into reflected light 46a reflected on the incident surface and transmitted light 46b entering the inside. The reflected light 46a has only a polarization component that is polarized in a direction parallel to the incident surface (reflection surface), that is, in a direction at 90 ° to the reference direction. Therefore, the light intensity I1 of the reflected light 46a is
3a.

The transmitted light 46b transmitted through the non-polarized glass 46 and maintained in the elliptically polarized state enters the polarization beam splitter 47 from the opposite exit surface. In this case, the transmitted light 4
The cross-sectional shape of the non-polarizing glass 46 is set so that the angle of the non-polarizing glass 46 with respect to the emission surface of the non-polarizing glass 6b is perpendicular. The polarization beam splitter 47 is set at an angular position around the optical axis such that the incident transmitted light 46b is separated into polarization components of + 45 ° direction and −45 ° direction with respect to the reference direction. + 45 °
The light intensity I3 of the polarization component in the direction is detected by the light receiver 23c, and the light intensity I4 of the polarization component in the -45 ° direction is detected by the light receiver 23c.
It is detected at d.

Therefore, the sample surface 13 having elliptically polarized light
90 °, 0 °, + 45 °,-in reflected light 18 from
Each light intensity I1 to I4 of each polarization component in the 45 ° direction is obtained from each of the light receivers 23a to 23d. Therefore, although it is necessary to slightly modify the equations for calculating the ellipsometric parameters Δ and ψ due to different optical systems, it is possible to obtain substantially the same effect as the embodiment shown in FIG. Also in this case, an alternative member of the beam splitter for detecting light leakage is the non-polarization beam splitter 19 as described above, and the same effect can be achieved by using the non-polarization beam splitter 67 or 67a instead.

Embodiment 4 In this embodiment, there is shown an optical system which separates the reflected light from the object to be measured into four different polarized light components and obtains the ellipsometric parameters from the light intensities of the four polarized light components. Several components to which the position determining means is added will be described in the same manner as in the third embodiment.

FIG. 21 is an internal configuration diagram of such a four-channel ellipsometer main body 1. As shown in FIG. For example, output 1
A laser beam having a single wavelength output from a laser light source 75 of a semiconductor laser of 0 mmW is converted by a polarizer 76 into linearly polarized light of + 45 ° with respect to a reference direction. Therefore,
The laser light source 75 and the polarizer 76 constitute a light source unit 77. The incident light 78 converted into linearly polarized light is incident on the sample surface 74 from the light source unit 77 at an angle φ. The reference direction is a direction in which the incident surface of the incident light 78 with respect to the sample surface 74 has an azimuth of 0 °.

The reflected light 7 reflected on the sample surface 74
FIG. 9 shows that the film on the sample surface 74 is
The beam becomes the elliptically polarized light shown in FIG.
0 is incident. The non-polarization beam splitter 80 is made of, for example, a non-polarization glass plate. Then, the incident reflected light 79 is split into two lights 81a and 81b without being polarized at all and maintaining the elliptically polarized state. The reflected light 81a is incident on the first polarization beam splitter 83 via the quarter-wave plate 82a. Further, the transmitted light 81b that has passed directly enters the second polarization beam splitter 84.

The first and second polarization beam splitters 83,
84 has the same configuration, for example, is composed of a Glan-Thompson prism, a Glan-Taylor prism, etc., and separates incident elliptically polarized light into two orthogonal polarization components, which are orthogonal to each other, as transmitted light and reflected light, respectively. Output.
It should be noted that a Wollaston prism or the like that separates transmitted light into two components at an angle may be used.

Then, the first polarization beam splitter 83
Is the transmitted light 83 of the first polarization beam splitter 83
Positioning is such that the polarization direction of a is + 45 ° with respect to a reference direction in which the incident surface of the incident light 78 on the sample surface 74 has an azimuth of 0 °. Then, the transmitted light 83 having the polarization direction of + 45 ° output from the first polarization beam splitter 83 is output.
a is incident on the light receiver 85a. The light receiver 85a outputs a signal corresponding to the light intensity I1 of the received polarization component, and the reflected light 83b output from the first polarization beam splitter 83 and having a polarization direction of -45 ° is necessarily a light receiver. 85b and is converted into light intensity I2.

Further, the second polarization beam splitter 84
Is transmitted light 84 of the second polarizing beam splitter 84.
Positioning is performed such that the polarization direction of a is + 45 ° with respect to the reference direction. Then, the transmitted light 84a having the polarization direction of + 45 ° output from the second polarization beam splitter 84 is incident on the light receiver 85c, and is converted into the light intensity I3. In addition, the reflected light 84b output from the second polarizing beam splitter 84 and having a polarization direction of -45 ° is incident on the light receiver 85d, and is converted into light intensity I4.

Since the quarter-wave plate 82a is interposed in the optical path of the reflected light 81a entering the first polarization beam splitter 83, the elliptically polarized reflection enters the first polarization beam splitter 83. The polarization direction of the light 81a changes by a predetermined angle. Therefore, the values of the polarization components incident on the respective light receivers 85a to 85d are different.

Then, using these four light intensities I1 to I4, the ellipsometric parameters ψ and Δ for specifying the elliptically polarized light in FIG. 22 are calculated by equation (12).

[0104]

(Equation 12) However, the polarization reflectance ratio σ _{R of} the non-polarizing beam splitter 80
And the polarization transmittance ratio σ _T is a unique value. A test light having a known linearly polarized light or elliptically polarized light is incident on the non-polarizing beam splitter 80, and is inversely calculated from the deviation from the true ellipsometer parameters ψ and Δ. Beforehand.

In calculating the phase difference Δ, a quadrant (zone) is determined according to the following positive and negative conditions of σ _T (I1-I2) and σ _R (I3-I4).

That is, σ _T (I1-I2) = A, σ _R
If (I3-I4) = B, the following is obtained.

(1) When A> 0 and B> 0, the first quadrant (0 ° <
Δ <90 °) (2) If A> 0, B <0, the second quadrant (90 ° <
Δ <180 °) (3) If A <0, B> 0, the third quadrant (180 ° <
Δ <270 °) (4) If A <0, B <0, the fourth quadrant (270 ° <
(Δ <360 °) Therefore, it is possible to simultaneously determine which quadrant from the first quadrant to the fourth quadrant the calculated phase difference Δ belongs to.
It can be accurately determined whether the true value of the phase difference Δ obtained as a result is Δ or (360 ° −Δ), (90 ° −Δ),.

Therefore, when the amplitude ratio tan ψ and the ellipso parameter of the phase difference Δ including the belonging quadrant are obtained,
The film thickness d on the sample surface 74 is calculated using a predetermined formula.

With the ellipsometer configured as described above, the four intensities I1, I2, I3, and I4 detected at the same time by the photodetectors 85a, 85b, 85c, and 85d, respectively.
Since the ellipsometric parameters ψ and Δ are calculated almost instantaneously in the personal computer 3 using the equation (12), the film thickness d on the sample surface 84 is also calculated almost instantaneously.

Therefore, even if the object to be measured is moving at a high speed, the film thickness d at the designated measurement point can be measured. Therefore, the incident light 7 from the light source 77
In a state where the object 8 is output, while the measurement object is moved at a constant speed, the light intensities I1 to I4 are read at a constant period to calculate the ellipsometric parameters ψ, Δ and the film thickness d. For example, the film thickness d of the surface of a continuously moving strip-shaped product on an inspection line in a factory can be continuously measured online.

Further, as shown in FIG. 21, the elliptically polarized reflected light from the sample surface 74 is separated into four polarization components having different conditions, and the light intensity of each polarization component is read at the same timing. As with a conventional ellipsometer, a rotating analyzer or a ４
There is no need to provide a wave plate insertion / removal mechanism. Therefore, all the optical components can be configured only with the fixed member, and the movable device is not used, so that the entire apparatus can be configured to be small and lightweight. Therefore, it can be installed in a narrow place such as a manufacturing site, and the applicable range can be expanded.

Further, the phase difference Δ can be obtained with high accuracy regardless of the range of the value. For example, when the incident light on the sample surface 74 is linearly polarized light in the conventional apparatus, the measurement accuracy at a value of Δ in the vicinity of 90 ° or 270 ° is very poor as compared with other places, but in the ellipsometer of the present invention, Even if Δ is a value near 90 ° or 270 °, accurate measurement can be performed.

For example, in the ellipsometer shown in FIG. 21, incident light 78 is made incident on a sample surface 74 having various known film thicknesses d to produce reflected light 79 having various shapes of elliptically polarized light. The ellipsometric parameters of each elliptically polarized light were measured. As a result, for each phase difference Δ from 0 ° to 360 °, the absolute error could be suppressed to a maximum of 1.5% and an average of 1.0%. The measurement error of the amplitude ratio tan ψ was about 5%.

FIG. 23 is a diagram showing a schematic configuration of an ellipsometer according to another embodiment of the present invention. 1 are given the same reference numerals. The same applies to the following embodiments in the fourth embodiment. Therefore, the description of the overlapping part will be omitted. In this embodiment, the 波長 wavelength plate 82
b is inserted into the optical path of the transmitted light 81b from the non-polarizing beam splitter 80 that enters the second polarizing beam splitter 84. Then, the 波長 wavelength plate 8 in FIG.
2a has been removed.

In the ellipsometer configured as described above, the polarization direction of the transmitted light 81b incident on the second polarization beam splitter 84 changes, and as a result, different polarization components are respectively applied to the light receivers 85a to 85d. Incident. Therefore, the same operation as the embodiment of FIG. 21 can be obtained.

In the ellipsometer shown in FIG. 24, the same quarter-wave plate 82a as in FIG. 21 is inserted into the optical path incident on the first polarizing beam splitter 83, and the optical path incident on the second polarizing beam splitter 84 is changed. The half-wave plate 99b is inserted. Even with such a configuration,
Since a predetermined difference occurs in the polarization direction of each of the elliptically polarized light incident on each of the polarization beam splitters 83 and 84, different polarization components are incident on the respective light receivers 85a to 85d. Therefore, substantially the same effects as in the previous embodiment can be obtained. In addition, since the reflected light 81a and the transmitted light 81b output from the non-polarized beam splitter 80 can be moved in the same polarization direction by an amount corresponding to a quarter-wave plate, the measurement range of the film thickness d can be shifted. It is.

FIGS. 25, 26, and 27 show a quarter-wave plate 82c on the optical path of incident light 78 and reflected light 79 on the sample surface 74 in each of the ellipsometers shown in FIGS. 21, 23, and 24, respectively. , 82d, or 1
This is an embodiment in which the half-wave plates 99c and 99d are inserted. As described above, by inserting the wavelength plate into the entrance path and the reflection path of the sample surface 74, the phase difference between the P-polarized light and the S-polarized light of the incident light 8 can be arbitrarily changed.

In FIG. 28, a non-polarizing beam splitter and an analyzer are used as two sets of optical systems for extracting different changed components of the reflected light 81a and the transmitted light 81b of the non-polarizing beam splitter 80, respectively.

That is, the reflected light 81a is
A first non-polarizing beam splitter 100 incident through the second non-polarizing beam splitter 2a, and an analyzer 102 for extracting a + 45 ° polarization component of the reflected light from the first non-polarizing beam splitter 100
a and the first non-polarizing beam splitter 100
Analyzer 10 for extracting the polarized light component of the transmitted light in the -45 direction.
2b is provided.

Further, the second light, on which the transmitted light 81b is directly incident,
The non-polarizing beam splitter 101, the analyzer 103a that extracts the + 45 ° polarization component of the reflected light of the second non-polarizing beam splitter 101, and the −45 of the transmitted light of the second non-polarizing beam splitter 101 An analyzer 103b for extracting a polarization component in the ° direction is provided.

As described above, the same effect as that of the embodiment shown in FIG. 21 can be obtained by using the combination optical system of the non-polarization beam splitter and the analyzer instead of the polarization beam splitter.

FIGS. 29, 30, 31, 32, and 33
The ellipsometers shown in FIGS. 23, 24, 25,
Each of the polarization beam splitters 83 and 84 in the ellipsometer of each embodiment described in FIGS. 26 and 27 is replaced with each of the non-polarization beam splitters 100 and 10 described in the embodiment of FIG.
1 and each analyzer 102a, 102b, 102a, 10
3b. Therefore, it is possible to obtain substantially the same effect as the embodiment of FIGS.

FIG. 34 is a schematic diagram showing a schematic configuration of an ellipsometer according to still another embodiment of the present invention. In this embodiment, the first polarization beam splitter 106
The orientation of the first polarization beam splitter 106 is fixed so that the polarization direction of the transmitted light 106a output from the first polarization direction is oriented at −45 ° with respect to the above-described reference direction.
Then, the second polarization beam splitter 1 is arranged such that the polarization direction of the transmitted light 107a output from the second polarization beam splitter 107 is oriented at 0 ° with respect to the reference direction.
07 is fixed. So naturally,
The polarization direction of the reflected light 106b of the first polarization beam splitter 106 is oriented in the + 45 ° direction, and the polarization direction of the reflected light 107b of the second polarization beam splitter 107 is oriented in the 90 ° direction. Therefore, each of the light receivers 85a, 85b, 85c, 8
The polarization direction of the light incident on 5d is −45 °, + 45 °,
It faces 0 ° and 90 °.

Therefore, the ellipsometers ψ and Δ are calculated using the light intensities I1 to I4 obtained from the light receivers 85a to 85d. Therefore, substantially the same effects as those of the embodiment of FIG. 21 can be obtained.

FIGS. 35, 36, 37, 38, and 39
The ellipsometers shown in FIGS. 23, 24, 25,
As shown in FIG. 34, the attitude angle of each of the polarization beam splitters 83 and 84 in the ellipsometer of each embodiment shown in FIGS. 26 and 27 is -45 with respect to the reference direction.
°, + 45 °, 0 °, and 90 °. Therefore, it is possible to obtain substantially the same effect as the embodiment of FIGS.

FIGS. 21 to 3 except for the above described FIG.
In the optical system of No. 9, instead of any one of the non-polarization beam splitter 80, the first non-polarization beam splitter 100, and the second non-polarization beam splitter 101, the optical system shown in FIG.
If the non-polarizing beam splitter 67 or its equivalent is disposed and the position detector 24 is provided, the position of the non-polarizing beam splitter 67 is determined using the light leaked from the beam splitter provided in the optical system, and the first embodiment is performed. 3 can be applied to the attitude control means.

Fifth Embodiment In this embodiment, the optical system according to the other embodiment is the same as that of the first to third embodiments except that the non-polarizing beam splitter used in the optical system is replaced with the first embodiment.
4 illustrates an optical system to which the beam splitter capable of measuring the position of light leakage according to the present invention used in No. 4 can be applied. Since these are all related to the published patent publications by the same applicant as the present applicant, only the drawings are presented, and the detailed description is omitted.

FIGS. 40 and 41 show Japanese Patent Application Laid-Open No. 64-28509.
FIG. 1 shows an optical system of a film thickness measuring apparatus shown in FIGS. 42 and FIG.
FIG. 1 is an optical system of a film thickness measuring apparatus shown in FIGS. FIG. 44 shows an optical system of the film thickness measuring apparatus shown in FIG. 1 of JP-A-63-36105. Optical flats (beam splitter sections) 13a to 13d shown in FIGS. 40 and 41, and 13a to 13d shown in FIGS. 42 and 43.
The optical non-polarizing beam splitter 67 of FIG. 1 or FIG. 2 or its equivalent with the position detector 24 in place of the optical flat of 13c and any of the optical flats of 29a to 29c shown in FIG. If a functional product is provided, light leakage from the beam splitter of the optical system can be used as in the first to fourth embodiments, and application as position determining means of the optical system is possible.

[0129]

As described above, according to the present invention, the reflected light of light incident on the object to be measured is separated into light components of a plurality of optical paths by a beam splitter of an optical system (optical device). Means for detecting and analyzing the ellipsometric parameters and determining the position of the light leakage by detecting light leakage from the beam splitter, and controlling the attitude of the optical system based on this, In some cases, instead of using the leaked light from the beam splitter, the reflected light is separated into, for example, four different polarization components, and the ellipso parameter is calculated based on the three light components having the highest intensity among the four polarization components. Since the position of the optical system is controlled from the position by detecting one light component of the optical system, the position of the optical system is determined by this light leakage or one polarization component. Attitude control can now be carried out automatically. In this way, it is possible to automatically adjust the optical system as an ellipsometer to the optimal state, improve the measurement accuracy of ellipso parameters and required items to be measured based on them, and save time and effort in adjusting the optical axis. Compared with the required conventional analysis means, the effect of contributing to significantly shortening the measurement time is great.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an optical system according to an embodiment of the present invention.

FIG. 2 is a detailed view of a non-polarization beam splitter in which light leakage does not exit vertically.

FIG. 3 is a schematic diagram showing another optical system embodiment (3CH) of the present invention.

FIG. 4 is a schematic configuration diagram showing another optical system embodiment (4CH) of the present invention.

FIG. 5 is an overall view system configuration diagram of the apparatus of the present invention.

FIG. 6 is a block diagram of an apparatus configuration of the present invention.

FIG. 7 is a flowchart of the polarization analysis method of the present invention.

FIGS. 8A and 8B are schematic explanatory views showing attitude control means of the ellipsometer of the present invention, wherein FIG. 8A is a front view and FIG. 8B is a side view.

FIG. 9 is a configuration block diagram showing another embodiment of the present invention.

FIG. 10 is a schematic configuration diagram showing an optical system according to still another embodiment of the present invention.

FIG. 11 is an explanatory diagram of elliptically polarized light in which incident linearly polarized light is reflected on a sample surface.

12 is a block diagram showing a configuration of an entire ellipsometer including the optical system of the embodiment shown in FIG. 10;

FIG. 13 is a flowchart of the polarization analysis method of the present invention using a personal computer.

FIG. 14 is a diagram showing a relationship between an elliptical parameter of a phase difference Δ calculated by a rotation analyzer method at the time of film thickness measurement and an ellipso parameter of a phase difference Δ calculated by an example apparatus. (A) is the measured value corresponding to the case of 4CH and (b) is the measured value corresponding to the case of 3CH.

FIG. 15 is a schematic configuration diagram of a 4CH optical system according to another embodiment of the present invention.

FIG. 16 is a schematic configuration diagram of a 4CH optical system according to still another embodiment.

FIG. 17 is a block diagram showing another 4CH optical system embodiment.

FIG. 18 is a block diagram showing another 4CH optical system embodiment.

FIG. 19 is a configuration diagram showing another optical system example also having a 波長 wavelength plate.

FIG. 20 is a configuration diagram showing still another 4CH optical system embodiment of the present invention.

FIG. 21 is a configuration diagram showing still another 4CH optical system embodiment of the present invention.

FIG. 22 is a diagram showing elliptically polarized light reflected from the optical system of the example.

FIG. 23 is a configuration diagram showing still another 4CH optical system embodiment of the present invention.

FIG. 24 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 25 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 26 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 27 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 28 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 29 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 30 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 31 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 32 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 33 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 34 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 35 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 36 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 37 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 38 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 39 is a configuration diagram of still another 4CH optical system embodiment.

FIG. 40 is a configuration diagram of the optical system shown in FIG. 1 of JP-A-64-28509, showing that the beam splitter of the present invention is applicable.

FIG. 41 is a configuration diagram of the optical system shown in FIG. 3 of JP-A-64-28509.

FIG. 42 is a configuration diagram of the optical system shown in FIG. 1 of JP-A-62-293104.

FIG. 43 is a configuration diagram of the optical system shown in FIG. 3 of JP-A-62-293104.

FIG. 44 is a configuration diagram of the optical system shown in FIG. 1 of JP-A-63-36105.

[Explanation of symbols]

13,74 Sample surface (subject) 14,75 Semiconductor laser light source 15,76 Polarizer 16,77 Light source 17,78 Incident light 18,79 Reflected light 19,41,42,67,67a, 80,100,10
1 Non-polarizing beam splitters 20a, 81a Reflected light 20b, 81b Transmitted light 21, 83, 106 Polarizing beam splitters 22, 84, 107 Polarizing beam splitters 23a, 23b, 23c, 23d, 85a, 85b, 8
5c, 85d Light receiver 24 Position detector 31 Signal processing unit 31a Position signal processing unit 32, 52 Personal computer 10, 33, 50 Ellipsometer main body 34 XY movement table 35 Actuator 36 Keyboard display means 51 A / D converter 52a Digital control operation 53 D / A converter 54 Actuator unit 55 Shaft 56 Fixed plate 57 Bearing 57a Ball screw 58 Servo motor 59 Spring 81a Reflected light 81b Transmitted light 82a, 82b, 82c, 82d Quarter wave plate 99c, 99d 1/2 wave plate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-294227 (JP, A) JP-A-2-129503 (JP, A) JP-A-64-28509 (JP, A) JP-A-63-1988 186104 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01B 11/00-11/30 G01N 21/00-21/01 G01N 21/17-21/61

Claims (20)

(57) [Claims] 1. A means for extracting a plurality of light components from an optical system having a beam splitter from reflected light of light incident on a measurement object, and detecting and analyzing the extracted light components to determine ellipsometric parameters. And a means for detecting light leakage from the beam splitter and controlling the attitude of the optical system from the position of the light leakage. 2. The polarization analysis method according to claim 1, wherein said leaked light is emitted vertically from inside to outside at an emission surface of said beam splitter. 3. The polarization analysis method according to claim 1, further comprising means for causing a detection position of the light component to follow a target position based on the information on the position of the light leakage. 4. The means for determining the ellipsometric parameter extracts four polarized components different from each other from reflected light of the measurement object obtained by making polarized light incident on the measurement object at a predetermined angle, and extracting the extracted components. 2. The polarization analysis method according to claim 1, wherein the calculation is performed based on three light intensities of the four polarized light components. 5. A polarized light is incident on a measurement object at a predetermined angle, and four mutually different polarization components are extracted from reflected light of the measurement object via an optical system having a beam splitter, and are extracted. Calculating ellipsometric parameters based on the light intensities of three of the four polarized light components;
A polarization analysis method characterized by detecting one remaining polarization component and controlling the attitude of the optical system from the position. 6. A light source unit for irradiating incident light on a measurement target,
An optical system having a beam splitter for extracting light components of a plurality of optical paths from reflected light from the measurement object, a plurality of detectors for detecting the light components, and analyzing detection results from the plurality of detectors A measurement unit for determining ellipso parameters;
Polarization analysis, comprising: a light leakage position determination unit that detects light leakage from the beam splitter and determines the position of the light leakage; and a calculation unit that determines the attitude of the optical system based on the position information of the light leakage. apparatus. 7. The polarization analyzer according to claim 6, wherein the beam splitter has an emission surface from which the leaked light is emitted vertically from inside to outside. 8. The apparatus according to claim 6, wherein the calculation unit determines a relative positional relationship between the measurement target and the optical system.
An ellipsometer as described. 9. The optical system according to claim 6, wherein the optical system has no movable part, and the optical system and the plurality of detectors are fixed in a predetermined positional relationship. An ellipsometer according to any one of the preceding claims. 10. A driving unit for relatively adjusting a positional relationship between the light component and the plurality of detectors based on an output from the arithmetic unit.
An ellipsometer according to any one of the above. 11. The optical system according to claim 1, wherein the optical system is configured to control a plane perpendicular to a measurement target including the incident light and / or
10. The polarization analyzer according to claim 9, further comprising a driving unit that rotates in a plane perpendicular to the driving unit and relatively adjusts a positional relationship between the light component and the plurality of detectors. 12. An optical device to which a beam splitter is attached, further comprising a position detecting means for detecting a position of light leaked from the beam splitter. 13. The optical device according to claim 12, further comprising: attitude determining means for determining an attitude of the optical apparatus based on an output of the position detecting means. 14. The optical apparatus according to claim 12, further comprising: attitude control means for controlling the optical apparatus to a target attitude based on an output of the attitude determination means. 15. An optical device including the beam splitter, wherein the light source unit causes polarized light to enter a measurement target at a predetermined angle, and the light reflected by the measurement target is split into two different directions. A non-polarizing beam splitter,
An optical member that extracts two different polarization components from each light branched by the non-polarization beam splitter, and finally extracts four polarization components from the reflected light of the measurement target;
Four light receivers for detecting the light intensity of each polarized light component extracted by the optical member, and the reflected light based on three of the four light intensities detected from the four light receivers. The optical device according to claim 12, 13 or 14, further comprising a calculation unit for calculating an ellipsometric parameter of elliptically polarized light in (1). 16. The first optical system, comprising: a first optical system that extracts, from one of the lights split by the non-polarization beam splitter, polarization components in + 90 ° and 0 ° directions with respect to a reference direction. And a second optical system that extracts, from the other light split by the non-polarizing beam splitter, polarization components in + 45 ° and −45 ° directions with respect to the reference direction. The polarization analyzer according to claim 15. 17. The apparatus according to claim 1, wherein a wave plate is inserted in an incident light path or a reflected light path with respect to the object to be measured.
An ellipsometer according to claim 5 or claim 16. 18. A light source unit that causes polarized light to enter a measurement target at a predetermined angle, a composite beam splitter that extracts four different polarization components from light reflected by the measurement target, and the composite beam splitter. Four light receivers for detecting the light intensities of the respective polarization components extracted in the above, and elliptically polarized light in the reflected light based on three of the four light intensities detected from the four light receivers 16. An ellipsometer according to claim 15, further comprising a calculation unit for calculating the ellipsometric parameter of 19. The non-polarizing glass, wherein the composite beam splitter branches reflected light from a measurement target into reflected light and transmitted light at an incident surface, and one end is fixed to the non-polarized glass.
+90 from the reflected light of the non-polarized glass with respect to the reference direction
A first polarizing beam splitter for extracting each polarization component in the 0 ° and 0 ° directions, and joined to an exit surface of the transmitted light of the non-polarized glass, and + 45 ° with respect to a reference direction from the transmitted light of the non-polarized glass 19. The polarization analyzer according to claim 18, further comprising a second polarization beam splitter for extracting each polarization component in a direction of -45 degrees. 20. The non-polarizing glass, wherein the composite beam splitter branches reflected light from a measurement target into reflected light and transmitted light on an incident surface, and one end is fixed to the non-polarized glass.
From the reflected light of the non-polarized glass, +45 with respect to the reference direction
A first polarizing beam splitter for extracting each of the polarization components in the directions of ° and -45 °, and a first polarizing beam splitter joined to an outgoing surface of the transmitted light of the non-polarized glass, and +90 relative to a reference direction from the transmitted light of the non-polarized glass 19. The polarization analyzer according to claim 18, further comprising a second polarization beam splitter that extracts each polarization component in the directions of ° and 0 °.