JPH0875414A - Infinitesimal position measuring device - Google Patents

Abstract

PURPOSE: To provide an infinitesimal position measuring device capable of relatively simply measuring the thickness of the layer of a layered sample from sub-micron to several mm. CONSTITUTION: A laser diode 12 applied with a constant forward current by a laser diode driving power source 16 emits a fixed quantity of light. The light forms a light spot in a sample S via a confocal optical system 20. The reflected light from the sample S is again returned to the light source 12 via the confocal optical system 20. A piezo-stage 26 scans the position of the confocal optical system 20 in the optical axis Z-direction, and the light quantity fed back to the light source 12 is increased when the light spot hits the boundary surface in the sample S. The increase of the light output is detected by a photo-diode 14. An arithmetic control device 30 calculates the positions of boundary surfaces in the optical axis Z-direction of the sample S from the position of the confocal optical system 20 by the scanning means 26 when the light output is doubled and calculates the distance between the boundary surfaces from the positions of the boundary surfaces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro position measuring device for measuring the position of a boundary surface of a sample.

[0002]

2. Description of the Related Art As a minute position measuring device for measuring the position of a boundary surface of a sample, a device for measuring a dimension of a sample which is a relative position of a plurality of boundary surfaces of the sample (hereinafter, referred to as There is known a "small size measuring device") and a device for obtaining the shape of the sample by measuring the distribution of the position of the boundary surface of the sample (hereinafter referred to as "small shape measuring device").

As a conventional minute dimension measuring device, there is an ellipsometer for measuring the thickness dimension of a layer of a sample having a layer structure. In the ellipsometer, polarized light is obliquely incident on the sample surface and the change in polarization of reflected light is measured to calculate and output the layer thickness dimension and the refractive index. As a conventional minute dimension measuring apparatus, there is also an apparatus that measures the thickness dimension of a layer by utilizing the interference of white light. This device is composed of an optical system of a Michelson interferometer, and vibrates a reference mirror of the Michelson interferometer to interfere the reflected light from each layer with the reference light. The layer thickness dimension is measured from the position of the reference mirror where the intensity of the interference light is the highest. On the other hand, as a conventional minute shape measuring apparatus, there are a contact type three-dimensional shape measuring machine and an optical non-contact displacement type. A contact-type three-dimensional shape measuring instrument generally moves a needle onto the surface of a sample and measures the shape of the sample based on position information of the needle. Further, in the optical non-contact displacement type, in general, a laser beam is focused and irradiated on the sample surface, and the lens is moved up and down to scan the sample surface while performing autofocusing. The shape of the sample is measured from the vertical position of the lens and the sample feed.

[0004]

However, these conventional minute dimension measuring devices cannot measure the dimension in the range from submicron to several millimeters. Therefore, for example, it was not possible to measure a liquid crystal cell gap of about 10 microns. The ellipsometer also has a problem that the layer thickness in the vicinity of the surface of the sample having the multilayer structure can be measured, but the layer thickness in the deep layer portion cannot be measured. In addition, the device utilizing the interference of light has a drawback that it is vulnerable to disturbance such as vibration and that it takes time to set the optical system. In addition, the conventional micro-shape measuring device cannot measure the shape of each layer of the sample having the layered structure at the same time.

Therefore, an object of the present invention is to measure the position of the boundary surface of the sample even in units of sub-microns to several millimeters, and to relatively easily measure the position of each of the plurality of boundary surfaces of the sample having the multilayer structure. Since it is possible to measure the thickness dimension from sub-micron to several millimeters, which was impossible in the past, it is possible to measure the dimension and shape of each layer of a sample with a multilayer structure relatively easily without contact. It is an object of the present invention to provide a micro position measuring device that enables the measurement.

[0006]

SUMMARY OF THE INVENTION Therefore, according to the present invention, a light source having a multiplying function and a confocal system along the optical axis direction of the light from the light source are provided so that the light from the light source is prevented. A confocal optical system for focusing and irradiating a sample having at least one boundary surface and for returning reflected light from the sample to the light source, and a relative position of the sample with respect to the confocal optical system A scanning unit that moves in the axial direction, a detection unit that detects the output state of the light source that varies depending on the amount of reflected light from the sample that returns and enters the light source, a detection result of the detection unit, and the scanning unit. A boundary surface of the sample, which comprises a calculating means for calculating the position of the at least one boundary surface of the sample in the optical axis direction based on the relative position of the sample with respect to the confocal optical system. For measuring position It provides a small position measurement device.

Here, it is preferable that the calculating means includes a relative position calculating means for calculating a relative position of the at least one boundary surface of the sample in the optical axis direction with respect to the minute position measuring device.

Here, at least one boundary surface of the sample means, if the sample has a pair of surfaces facing each other along the optical axis direction (hereinafter referred to as "external boundary surface"), these two boundary surfaces. The outer boundary surface. In particular, the sample is
In the case of a multilayer structure in which a plurality of layers are stacked along the optical axis direction, the at least one boundary surface is a boundary surface of the plurality of layers (hereinafter, referred to as “internal boundary surface”). And the pair of outer boundary surfaces.

When the sample has a plurality of boundary surfaces along the optical axis direction, the calculating means calculates the relative position of each of the plurality of boundary surfaces in the optical axis direction. Therefore, it is preferable to include dimension calculation means for calculating the distance between the boundary surfaces.

The scanning means includes a first scanning means for moving the relative position of the sample with respect to the confocal optical system in the optical axis direction, and a relative position of the sample with respect to the confocal optical system for the light. It comprises a second scanning means for moving in a direction orthogonal to the axis, the first scanning means scanning the relative position of the sample with respect to the confocal optical system in the optical axis direction at a predetermined scanning cycle. The second scanning means moves the relative position of the sample with respect to the confocal optical system in a direction orthogonal to the optical axis at a cycle slower than the scanning cycle of the first scanning means, The calculation means may include a distribution calculation means for calculating the distribution of the position of the at least one boundary surface of the sample in the optical axis direction in the direction orthogonal to the optical axis direction.

It is preferable that the light source is provided with a constant state drive source for maintaining it in a constant drive state, and the detecting means is a light detecting means for detecting an output light amount of the light source. More preferably, the light source preferably comprises a laser diode and a laser diode drive power source for applying a constant drive current thereto. In this case, it is preferable that the light detecting means is a light detector for detecting the output light of the laser diode. Here, the light source may further include a drive current control device, and control may be performed to maintain the oscillation of the laser diode under appropriate conditions according to the amount of light reflected from the sample.

Further, the light source may be provided with a feedback drive source for performing a feedback drive so that the output light amount becomes constant, and the detection means may detect the drive state of the feedback drive source. More preferably, the light source is a laser diode, and a laser diode drive power source for applying a drive current to the laser diode,
A photodetector for detecting the output light of the laser diode, and a feedback control device for feedback-controlling the drive current applied to the laser diode by the laser diode drive power source based on the detection result of the photodetector. preferable. Further, the detection means detects the drive current value that is feedback-controlled by the feedback control device.

[0013]

In the microposition measuring apparatus of the present invention having the above-mentioned structure, the confocal optical system focuses the light from the light source onto the sample having at least one boundary surface, and
The reflected light from the sample obtained by the irradiation is returned and made incident on the light source. The scanning means moves the relative position of the sample with respect to the confocal optical system in the optical axis direction. When the light from the confocal optical system is focused and irradiated on the at least one boundary surface of the sample with such movement, the amount of reflected light from the sample increases. As a result, the amount of reflected light from the sample that returns and enters the light source increases. Here, since the light source has an amplifying function, its output state changes. The detecting means detects the change in the output state. The calculation means calculates the position of the at least one boundary surface of the sample in the optical axis direction based on the detection result of the detection means and the relative position of the sample with respect to the confocal optical system by the scanning means.

Here, when the calculating means includes the relative position calculating means, the relative position calculating means includes the minute position measuring device in the optical axis direction of the at least one boundary surface of the sample. Calculate the relative position to.

Here, when the sample has a plurality of boundary surfaces along the optical axis direction, the light from the confocal optical system is moved by the scanning means so that each of the plurality of boundary surfaces. The amount of reflected light from the sample increases each time the sample is focused and irradiated. Therefore, the calculation means determines the position of each of the plurality of boundary surfaces of the sample in the optical axis direction based on the detection result of the detection means and the relative position of the sample with respect to the confocal optical system by the scanning means. Calculate Here, when the calculating means includes the dimension calculating means, the dimension calculating means calculates a distance between the boundary surfaces which is a relative position of the plurality of boundary surfaces of the sample. Here, when the sample has a pair of external boundary surfaces facing each other along the optical axis direction, the dimension calculating means calculates the distance between the pair of external boundary surfaces to calculate the optical axis of the sample. Find the dimension in the direction. Further, when the sample has a multi-layer structure having a pair of outer boundary surfaces and a plurality of inner boundary surfaces, the dimension calculation means calculates a distance between the pair of outer boundary surfaces and the plurality of inner boundary surfaces. Then, the layer thickness of each layer in the optical axis direction of the sample is obtained.

When the scanning means comprises the first scanning means and the second scanning means, the first scanning means determines the relative position of the sample with respect to the confocal optical system by the optical axis. Scanning in the predetermined scanning cycle. The second scanning means is
The relative position of the sample with respect to the confocal optical system is moved in a direction orthogonal to the optical axis at a cycle slower than the scanning cycle of the first scanning means. The distribution calculation means of the calculation means calculates the distribution of the position of the at least one boundary surface of the sample in the optical axis direction in the direction orthogonal to the optical axis direction.

Here, when the light source is provided with a constant state drive source for maintaining it in a constant drive state,
The light source outputs a constant amount of light. When the confocal optical system focuses and irradiates the at least one boundary surface of the sample with the scanning by the scanning unit, the amount of reflected light from the sample increases. As a result, the amount of reflected light from the sample that returns and enters the light source increases.
Here, since the light source has an amplification function, the output light amount thereof increases. The light detecting means detects the increase in the output light amount. The calculation means calculates the position of the at least one boundary surface of the sample in the optical axis direction, based on the detection result of the light detection means and the relative position of the sample with respect to the confocal optical system by the scanning means. . In particular, when the light source comprises a laser diode and a laser diode drive power source for applying a constant drive current to the laser diode, and the photodetection means comprises a photodetector for detecting the output light of the laser diode, The photodetector detects the output light of the laser diode which is controlled by the reflected light from the sample that is returned and incident on the laser diode. Here, when the light source is provided with a drive current control device, the drive current control device adjusts the value of the constant drive current according to the amount of light reflected from the sample, thereby Keep the oscillation of the diode in proper condition.

On the other hand, when the light source has a feedback drive source, the light source is always fed back so as to output a constant amount of light. When the light from the light source is focused and irradiated on the at least one boundary surface of the sample by the confocal optical system, the amount of reflected light from the sample increases, and the amount of reflected light returning to the light source and incident increases. To do. Here, since the light source has an amplification function, the output light amount thereof increases. The feedback drive source changes its drive state in order to reduce the output light amount as the output light amount increases. The detection means detects the change in the driving state. The calculating means calculates the position of the at least one boundary surface of the sample in the optical axis direction based on the detection result of the detecting means and the relative position of the sample with respect to the confocal optical system by the scanning means. In particular, when the light source is composed of a laser diode, a laser diode driving power source, a photodetector, and a feedback control device, the laser diode changes the output light amount according to the light amount of the reflected light that returns from the sample. The photodetector detects a variation in the amount of output light, and the feedback control device feedback-controls the laser diode drive power source based on the detection result of the photodetector to apply a drive current to the laser diode. Adjust. The detection means detects this drive current value.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

First, the first embodiment of the present invention will be described. The first embodiment of the present invention is a minute position measuring device (a minute dimension measuring device) for measuring the positions of a plurality of boundary surfaces of a sample and measuring the relative distances between the boundary surfaces. . For example, when the sample has a pair of surfaces (external boundary surfaces) facing each other, the positions of these two external boundary surfaces can be measured, and the dimension of the sample, which is the distance (relative position) between them, can be obtained. When the sample has a multi-layer structure formed by stacking a plurality of layers, the positions of the boundary surface (inner boundary surface) of the plurality of layers and a pair of outer boundary surfaces are measured, and the distance between them (relative It is possible to obtain the thickness dimension of each layer which is (position).

The outline of the minute position measuring apparatus will be briefly described with reference to FIG. Micro position measuring device 1 of this embodiment
Mainly includes a laser diode 12 as a light source having a multiplication function, and a laser diode drive power source 16 as a constant drive state drive source for driving the light source 12 in a constant drive state,
A confocal optical system 20 forming a confocal system along the optical axis Z direction of the light from the light source 12, and a piezo as a scanning means for moving the relative position of the sample S with respect to the confocal optical system 20 in the optical axis Z direction. The stage 26, the photodiode 14 as a light detecting means for detecting the output light quantity of the light source 12 which is reflected by the sample and is changed by the return light which is returned and incident on the light source 12 by the confocal optical system 20, and the detection result of the photodiode 14. Based on the relative position of the sample S with respect to the confocal optical system 20 by the scanning means 26, the positions of a plurality of boundary surfaces of the sample S in the optical axis Z direction are calculated, and the distance between them is calculated and controlled as an arithmetic means. A device 30 is provided.

According to the minute position measuring apparatus 1 of the present embodiment having such a configuration, the laser diode 12 driven by the laser diode driving power source 16 in a constant driving state.
Outputs a constant amount of light. This light forms a light spot in the sample S by the confocal optical system 20. The reflected light from the sample returns to the light source 12 via the confocal optical system 20 again. The scanning means 26 moves the position of the confocal optical system 22 to the optical axis Z.
When the light spot strikes the boundary surface in the sample, the amount of light returning to the light source 12 increases. Here, since the light source 12 has a multiplication function, its light output is multiplied as the amount of the returned light is increased. The photodiode 14 detects this increase in the light output. The calculation / control device 30 calculates the position of each boundary surface in the optical axis Z direction of the sample from the position of the confocal optical system 20 by the scanning means 26 at the time when the light output is multiplied. Arithmetic / control device 30
Further calculates the distance between the boundary surfaces from the position of each boundary surface.

The minute position measuring apparatus 1 of this embodiment will be described in more detail below. In the minute position measuring apparatus 1 of this embodiment, a laser diode and a photodiode built in the LD package 10 are used as the light source 12 and the photodetector 14. In general, a laser diode package incorporates a photodiode for monitoring the optical output of the built-in laser diode in order to suppress output fluctuations due to temperature changes and the like. In this embodiment, this photodiode is used as the photodetector 14 for detecting the output light amount of the laser diode 12. A constant forward current is applied to the laser diode 12 from the laser diode drive power supply 16. On the other hand, the photodiode 14 is connected via an amplifier 18 to an arithmetic / control device 30 composed of, for example, a microcomputer. The arithmetic / control device 30 receives the detection signal (hereinafter, referred to as “optical output signal”) output from the photodiode 14 and amplified by the amplifier 18.

Collimator lens 22 and objective lens 24
Form a confocal optical system 20 along the optical axis Z of the laser diode 12. The collimator lens 22 collimates the laser light output from the laser diode 12 into a substantially parallel light,
It is fixed at a position separated by a predetermined distance (focal length). The objective lens 24 has a function of receiving substantially parallel light from the collimator lens 22 and forming a spot image at a position separated by the focal length f thereof. On the other hand, fixed base 3
4 is fixedly arranged facing the objective lens 24 along the optical axis Z direction. A sample S having a plurality of boundary surfaces is placed on the surface of the fixed table 34. Here, sample S
Are arranged so that their boundary surfaces are lined up along the optical axis Z direction.

The objective lens 24 is fixedly arranged on the piezo stage 26, and is reciprocally scanned in the optical axis Z direction while facing the sample S arranged on the fixed base 34. That is, the piezo stage 26 includes a piezoelectric element (not shown) arranged so as to vibrate in the optical axis Z direction.
A piezo driver 28 is connected to the piezoelectric element on the piezo stage 26 and applies a drive voltage to it. The piezo driver 28 oscillates the piezoelectric element by scanning the drive voltage to reciprocally scan the piezo stage 26 in the optical axis Z direction. Here, the position of the piezo stage 26 in the optical axis Z direction is determined by the drive voltage applied to the piezo stage 26 of the piezo driver 28. The piezo driver 28 is connected to the arithmetic / control device 30, and calculates / controls a signal indicating the drive voltage applied to the piezo stage 26, that is, a position signal indicating the position of the piezo stage 26 in the optical axis Z direction. Output to 30. As this position signal, for example,
The distance z from the surface of the fixed table 34 to the piezo stage 26 (that is, the distance between the objective lens 24 of the confocal optical system 20 and the sample S) can be indicated.

In the minute position measuring apparatus 1 having such a configuration, the laser light of the constant light amount emitted from the laser diode 12 in the laser diode package 10 is made into substantially parallel light by the collimator lens 22, and the objective lens 24 causes the sample S to pass through the sample S. Connect the spot image to. The reflected light from the sample S returns to the laser diode 12 via the objective lens 24 and the collimator lens 22. The photodiode 14 for monitoring the laser diode output in the laser diode package 10 detects the fluctuation of the output light amount of the laser diode 12.

Since the collimator lens 22 and the objective lens 24 form the confocal optical system 20, the returning light from the portion other than the position where the laser spot image is formed in the sample is efficiently reflected by the laser diode 12. Cut by the opening. Therefore, when the objective lens 24 is scanned in the optical axis direction, the laser spot is a boundary surface of different substances which is a high reflectance portion in the sample S (an external boundary surface which is a surface of the sample or an internal boundary when the sample is a multilayer film). When it hits the surface, a large amount of reflected light returns to the laser diode 12. This large amount of reflected light amplifies and fluctuates the laser diode oscillation, so that the output light amount of the laser diode 12 increases. The photodiode 14 detects the changed optical output and outputs an optical output signal indicating the detection result. The optical output signal is amplified by the amplifier 18 and then input to the arithmetic / control device 30.

The arithmetic / control device 30 synchronizes the optical output signal with the position signal of the piezo driver 28 and controls the display device 32 to establish the relationship between the moving distance of the objective lens 24 and the output light amount of the laser diode 12. Is displayed. For example, when the display device 32 is an oscilloscope, it may be triggered by a position signal to display an optical output signal. As a result, the reflected light from each boundary surface of the sample is obtained as a pulsed light output signal. Arithmetic / control device 30
Is the optical output signal and the position signal, and the pulse-shaped optical output signal (more specifically, the apex, the center of gravity, or the minimum differential value of the pulse-shaped optical output signal) of the objective lens 24 when it is obtained. By obtaining the moving distance, the relative position of each boundary surface of the sample S with respect to the objective lens 24 is obtained. here,
Since the sample S has a plurality of boundary surfaces (at least two outer boundary surfaces) in the optical axis Z direction, a plurality of (the same number as the boundary surfaces) pulse-shaped light is reflected from the plurality of boundary surfaces. It is obtained as an output signal. The calculation / control device 30 calculates the distance between the boundary surfaces by calculating the distance between the vertices of the pulses, the distance between the centers of gravity of the pulses, or the distance between the positions of the minimum differential values of the pulses as the distance between the pulses. Therefore, the dimension of the sample S can be obtained by obtaining the distance between the two surfaces (external boundary surfaces) of the sample S facing each other.
When the sample S has a multilayer film structure, the layer thickness of each layer can be obtained by obtaining the distance between the adjacent boundary surfaces.

The present inventors actually manufactured the minute position measuring apparatus 1 of this embodiment, and measured the forward current value applied to the laser diode 12 of the laser diode drive power source 16 and the reflected light from one boundary surface. The measurement was performed in order to investigate the relationship with the full width at half maximum of the pulsed optical output signal formed by.
As a result, as shown in FIG. 2, it was confirmed that the full width at half maximum was smallest when a forward current having a value slightly lower than the oscillation threshold value was applied to the laser diode 12. In a laser diode driven by a forward current slightly lower than the oscillation threshold value, when the amount of light returned to the laser diode exceeds a certain level, the light emitting diode (LE
From the state where the characteristics of D) are dominant, the laser diode (L
The characteristic of D) shifts to a dominant state, and the output light amount with respect to the incidence of light on the laser diode extremely increases. In other words, the output of the laser diode becomes non-linear with respect to a large amount of returned light from the sample. Therefore, the change in the light amount when the light feedback amount is small does not appear so much, and the change in the light amount when the light feedback amount is large is emphasized. As a result, the sub-pulse generated due to the influence of the aberration of the optical system can be efficiently suppressed, the half width of the pulse signal can be narrowed, and the measurement accuracy can be improved. Therefore, in the minute position measuring apparatus 1 of this embodiment, the laser diode drive power supply 16 sets the forward current applied to the laser diode 12 to a value slightly lower than the oscillation threshold value.

However, the peak value of the amount of light returned to the laser diode 12 differs depending on the boundary state (especially reflectance) of the sample. Therefore, how much the forward current value applied to the laser diode 12 is made lower than the oscillation threshold depends on the sample. Therefore, it is preferable that the forward current value applied to the laser diode 12 is finely adjusted according to the sample to be measured, and the half-width is always minimized for any sample. Therefore, it is preferable to provide a drive current value setting device 17 connected to the amplifier 18 and the laser diode drive power source 16 as shown by the dotted line in FIG. The drive current value setting device 17 is composed of a microcomputer or the like, and includes an amplifier 18 and a laser diode 1
This is for receiving the optical output signal indicating the output light amount of 2 and setting the forward current value to be applied to the laser diode 12 by the laser diode drive power supply 16 based on the value. More specifically, the drive current value setting device 17 is
First, an appropriate forward current value is initially set, and the laser diode drive power supply 16 is controlled to apply the forward current of the initial set value to the laser diode 12. In this state, laser light is emitted while scanning the objective lens 24 to perform trial measurement. The drive current value setting device 17 receives the optical output signal from the amplifier 18, and from the signal waveform,
The drive current value having the smallest half width is calculated. After that, the drive current value setting device 17 controls the laser diode drive power supply 16 to apply the set value of the forward current to the laser diode 12 to perform actual measurement. The drive current value setting device 17 may be directly connected to the photodiode 14 and the optimum drive current value may be calculated based on the current value of the direct current component of the photodiode 14.

According to the minute position measuring apparatus 1 of the present embodiment having such a configuration, it is judged that the extreme increase (pulse) of the output light quantity of the laser diode 12 is the increase of the feedback light by each boundary surface of the sample. You can That is, it can be judged that each boundary surface of the sample has reached the focal position of the objective lens 24 when the output light amount is extremely increased. Therefore, the arithmetic / control device 30 receives the optical output signal and the position signal which are synchronized with each other, obtains a time point when the optical output signal forms a pulse indicating an extreme increase in the output light quantity, and obtains the position signal obtained at this time point. Ask for. Where this position signal is
The position of each boundary surface of the sample is shown. For example, when the position signal indicates the distance z between the lens 24 and the surface of the fixed base 34, as shown in FIG. 1, the distance zf obtained by subtracting the focal length f of the lens 24 from this z is the fixed base 34. This is because the distance between the surface and each boundary surface is shown. Therefore, the distance between the boundary surfaces of the sample can be calculated based on the position signal z indicating the position of each boundary surface.

The configuration of the arithmetic / control unit 30 and its arithmetic operation will be specifically described below with reference to FIGS. 1 and 3 to 8. The arithmetic / control device 30 is a CPU (not shown).
And a ROM that stores various programs and the like, a RAM that temporarily stores calculation results and the like, and a microcomputer that includes an analog / digital converter and the like. When the arithmetic / control device 30 receives the analog optical output signal output from the amplifier 18 and the analog position signal sent from the piezo driver 28, the arithmetic / control device 30 converts these into digital signals by the analog / digital converter. Convert. The arithmetic / control device 30 further generates a data pair composed of individual synchronized optical output data and position data by matching the phases of these digitized optical output signal and position signal. In the following, each optical output data and position data will be referred to as I (i) and Z (i) (i is an integer), and a data pair consisting of these will be referred to as a data pair (I (i), Z (i)). ). In addition, a data pair (I (i), Z
(i)) is once stored in the RAM. The arithmetic / control device 30 reads the data pair stored in the RAM,
As shown in FIG. 3, the pulse signal waveforms formed by these data pairs may be displayed on the display device 32 with the horizontal axis representing the position (Z (i)) and the vertical axis representing the light intensity (I (i)). .

The arithmetic / control unit 30 also performs the following arithmetic processing on the read data pair, so that the characteristic points (apex position and barycentric position) of each of a plurality of pulse signal waveforms formed by the data pair are formed. , Or the minimum differential value position)
Is calculated to calculate the distance between the feature points. In this calculation, the calculation / control device 30 obtains the piezo effective scanning section (the scanning section excluding about 5% of the folded portion) of all the data pairs obtained in all the scanning sections of the piezo stage 26. The data pair is read from the RAM and used for calculation.
The positions of both ends of the piezo effective scanning section are
Let Z (e1) (i = e1) and Z (e2) (i = e2) (e1 <
e2). In this case, the number N of data pairs used for calculation is N
= e2-e1 + 1. More specifically, the arithmetic / control device 30 performs the threshold value determination process shown in the flowchart of FIG. 4 and the pulse-pulse separation process shown in the flowchart of FIG.
Either the pulse vertex calculation process, the pulse center of gravity point calculation process, or the pulse minimum differential value point calculation process shown in the flowchart of FIG. 8 is performed. The calculation / control device 30 then calculates the characteristic points of each pulse (vertices, centroids, or
Calculate the distance between the minimum differential value points). Here, in the threshold value determination process, the threshold value necessary for distinguishing a pulse indicating an extreme increase in the output light amount obtained by the increase of the feedback light due to the boundary surface of the sample and a subpulse indicating the aberration of the optical system or the like. Determine Ith. Further, in the pulse-pulse separation processing, a plurality of pulses obtained corresponding to a plurality of boundary surfaces of the sample S are separated for each pulse. In the pulse vertex calculation process, the pulse centroid calculation process, and the pulse minimum differential value point calculation process, respectively, the vertex of each pulse,
The center of gravity and the minimum differential value point are calculated.

In the threshold value determining process, as shown in FIG. 4, first, in step S1, i is set to an initial value e1. Next, in step S2, I (i) (that is, I (e1)) is read from the RAM. Furthermore, in step S3,
The maximum value Imax and the total sum Iint are initialized to I (i) (= I (e1)). So in this case Imax = I (e1), Iint =
It becomes I (e1). Next, i is incremented by 1 (step S4), and in step S5, I is read from the RAM again.
Read (i). At step S6, the current I (i) is set in Iint.
Is added. Further, in step S7, I (i) is compared with I (i-1) read last time, and if I (i) is larger, Im
Replace ax with I (i) (step S8). On the other hand, I (i) is
If it is less than or equal to I (i-1), leave Imax unchanged. Next, in step S9, it is determined whether or not i is smaller than e2. If i is smaller than e2, the process returns to step S4 and steps S4 to S9 are repeated. On the other hand, when i reaches e2 (in the case of “Yes” in step S9), in step S10, the total light amount data I obtained in the effective scanning section I
The total value Iint of is divided by the number of data N to obtain the average value Iave. Further, in step S11, the threshold value Ith is calculated by the following mathematical expression, and the processing is ended. Ith = 0.1 (Imax-Iave) + Iave = 0.1Imax + 0.9Iave

In the pulse-pulse separation processing, as shown in FIG. 5, first, in step S21, i is set to the initial value e1 and j is set to 0 as the pulse number. Next, in step S22, I (i) is read from the RAM.
And Z (i) (that is, I (e1), Z (e1)). Then, in step S23, the read I (i) is compared with the threshold value Ith obtained in the threshold value determining process. If I (i) is smaller than the threshold value Ith (step S23
Is "Yes"), it is possible to determine that this I (i) does not form a pulse. Therefore, set the pulse determination value f to 0 to determine whether I (i) is located in the pulse. Yes (step S24). Then, in step S25, i is incremented by 1. Next, in S26, it is determined whether or not i has reached e2. If e2 or less, the process returns to step S22 and I (i), Z (i) is read. On the other hand, when i reaches e2 (“No” in step S26), the process ends.

As described above, I (i) and Z (i) are read while incrementing i, and when I (i) exceeds the threshold value Ith for the first time (step S23 is "Yes"). , In step S27, the currently set pulse judgment value f
Determines whether is zero. When I (i) exceeds the threshold value Ith for the first time, f is still set to 0 (step S
27 is “Yes”), and it can be determined that I (i) is located within the pulse for the first time. Therefore, in step S28, j is incremented by 1, and k indicating the number of the optical output data I (i) forming each pulse is initialized to 0, and the pulse determination value f is changed to 1. Next, step S29
Then, the code number k is incremented by 1, and step S30
Then, I (i) is stored in the RAM as M (j, k) indicating that it is the kth signal in the jth pulse. Then, in step S25, i is incremented by 1 and i is increased to e2.
If it has not reached (N in step S26)
o ”), I (i) and Z (i) are read again. If I (i) read in this way is again above the threshold value Ith (“ No ”in step S23), the current The set pulse judgment value f is 1 (“N” in step S27).
o ”), only the code number k of the signal is incremented by 1 (step S29), and I (i) is stored in the RAM again as M (j, k) (step S30). (i)
However, when it becomes smaller than the threshold value Ith again (“Yes” in step S23), the pulse determination value f is reset to 0 (step S24), and i is incremented by 1 (step S25).

Through the above processing, only the light output data I (i) forming the pulse are stored in the RAM. More specifically, the kth optical output data I (i) forming the jth pulse is stored in the RAM as M (j, k) data.
Stored in.

In the pulse vertex calculation process, as shown in FIG. 6, in steps S41 to S50, the j-th pulse is formed by performing the same process as steps S21 to S30 of the pulse-pulse separation process. The kth optical output data Ii is stored in the RAM as M (j, k) data. Next, in step S51, the k-th optical output data M (j, k)
And the previous optical output data M (J, k-1),
Only when M (j, k) is larger (in step S51, "
Yes ”), which is the maximum (apex) value P of the j-th pulse
Stored in RAM as max (step S52), M
Zi corresponding to I (i) which is (j, k) is stored in the RAM as the peak position Pz (j) of the j-th pulse (step S5).
3). As a result, i reaches e2 (in step S46, "
Yes ”), the maximum value Pmax (j) in the optical output data M (j, k) forming each j-th pulse is obtained, and the maximum optical output data Pmax (j ), That is, the position data at the time when the pulse peak was obtained
Pz (j) is determined and stored in RAM. The apex position Pz (j) of each j-th pulse thus obtained indicates the position of each j-th boundary surface of the plurality of boundary surfaces of the sample. Therefore, the calculation / control device 30 calculates the distance between the adjacent boundary surfaces of the sample S by calculating the distance Pz (j) -Pz (j-1) between the vertex positions of the adjacent pulses.

On the other hand, in the pulse center-of-gravity point calculation process, as shown in FIG. 7, by performing the same processes as steps S21 to S28 of the pulse-pulse separation process in steps S60 to S67, the optical output data I (i The following processing is performed only for the pulse forming the j-th pulse of That is, when the optical output data Ii exceeds the threshold value Ith for the first time and enters the j-th pulse (step S66).
, "Yes"), the weighted sum Sum (j, 0) is initialized to 0 (step S68), the pulse code k is incremented by 1 (step S69), and the following mathematical expression is calculated.
The weighted sum Sum (j, k) as the calculation result is stored in the RAM. Sum (j, k) = Sum (j, k-1) + I (i) * z (i) Next, set the current code number k as Kmax (j) and the current pulse number j as Jmax. Then, Z (i) corresponding to the current I (i) is set as Zk (j, k) (step S
71).

By repeating the above processing for each jth pulse while incrementing i by 1 in step S64, at the time point when i reaches e2 in step S65, each jth pulse is , All the position data Z (i) that compose this, corresponding optical output data
The sum ΣI (i) * Z (i) of the values weighted by I (i) is Sum (j, Kma
x) and stored in RAM. Also,
Jmax is set as the total number of pulses. Furthermore, all position data Z (i) that make up each j-th pulse are Zk
It is stored in the RAM as (j, k).

Next, in step S72, j is set to 1
Is set to step S73 for the first pulse.
The following formula is calculated with. MSum (j) = Sum (j, Kmax (j)) / 2 That is, in step S73, for each j-th pulse, all the position data Z (i) constituting it are converted into the corresponding optical output data I (i). ) Sum of values weighted by Sum (j, Kmax
MSum (j), which is half the value of (j)) (= ΣI (i) * Z (i) / 2), is obtained. Next, the code k is first set to 1 (step S74), and the corresponding Sum (j, k) stored in the RAM is stored.
And the obtained MSum (j) are compared (step S75).
Then, the comparison is repeated (step S75) while incrementing the code number k by 1 (step S76) until Sum (j, k) exceeds MSum (j). Sum (j, k) is MSum (j)
If it exceeds ("Yes" in step S75), the following mathematical expression is calculated to obtain the barycentric position ZG (j) of each j-th pulse. ZG (j) = Zk (j, k-1) + {Zk (j, k) -Zk (j, k-1)} {MSum (j)-
Sum (j, k-1)} / {Sum (j, k)-Sum (j, k-1)} Then, increment j by 1 until the current j reaches the total pulse number Jmax (step S78). While (step S79), by repeating steps S73 to S77, the barycentric position ZG (j) of each j-th pulse is obtained and stored in the RAM. The center-of-gravity point position ZG (j) of each j-th pulse thus obtained also indicates the position of each j-th boundary surface of the plurality of boundary surfaces of the sample.
Therefore, the arithmetic / control device 30 calculates the distance ZG (j) -ZG (j-1) between the centers of gravity of adjacent pulses by
The distance between the adjacent boundary surfaces of the sample S is calculated.

In the pulse minimum differential value point calculation processing, as shown in FIG. 8, in steps S90 to S97, the optical output data I ( The following processing is performed only for the pulse forming the j-th pulse in i). That is, the optical output data I (i) is the threshold Ith for the first time.
When it enters the j-th pulse beyond (step S96
Then, "Yes"), and the minimum difference value Dmin (j) is I (i) -I (i-1)
Initially set to (step S98), pulse code k is set to 1
Increment (step S99). And each j
I (i) -I (i-1) is calculated as the difference value D (j, k) with respect to the kth optical output data I (i) of the th pulse (step S
100). Then, the absolute value of the difference value D (j, k) with respect to the kth optical output data I (i) of each jth pulse (ABS (D (j,
k))) is compared with the minimum difference value Dmin (j) (step S1).
01). If ABS (D (j, k)) is smaller ("Yes" in step S101), the difference value D for this k-th optical output data I (i) is set as the minimum difference value Dmin (j). (j,
k) is set (step S102). Further, Z (i) corresponding to the kth optical output data I (i) is set as the minimum difference value position ZD (j) of each jth pulse.

By repeating the above-mentioned processing for each j-th pulse while incrementing i by 1 in step S94, when i reaches e2 in step S95, for each j-th pulse. , The position ZD (j) having the smallest difference value is obtained and stored in the RAM. The position ZD (j) of the minimum differential value of each j-th pulse obtained in this way is also j
The position of the th boundary surface is shown. Therefore, the calculation
The control device 30 determines the minimum difference value inter-point distance ZD of adjacent pulses.
By calculating (j) -ZD (j-1), the distance between the adjacent boundary surfaces of the sample S is obtained.

FIG. 9 shows a liquid crystal cell gap measuring device embodying the minute position measuring device 1 of the present embodiment. This liquid crystal cell gap measuring device measures the liquid crystal cell gap of the liquid crystal display module and at the same time makes it possible to observe the microscope image thereof.

As shown in FIG. 9, in this liquid crystal cell gap measuring device, the laser diode package 10, the amplifier 18, the collimator lens 22, and the objective lens 24 are used.
The piezo stage 26 on which the
It is located on the 2nd. The piezo stage 26 is provided so as to be capable of vibrating in the optical axis Z direction with respect to the microscope holder 52. A sample table 54 for mounting a liquid crystal display module, which is a sample S, is provided on the microscope holder 52 so as to be finely adjustable in the optical axis Z direction. As the objective lens 24, an infinite lens barrel length correction type,
Alternatively, it is possible to use a finite lens barrel length correction type concave lens having a focal length obtained by inverting the positive / negative of the optical lens barrel length at the exit pupil side end surface. In order to increase the resolution of measurement, it is desirable to use the objective lens 24 having a large numerical aperture NA. In this specific example, a position sensor 27 is newly provided on the piezo stage 26 to detect the position of the piezo stage 26 in the optical axis Z direction (for example, the distance z of the piezo stage 26 from the fixed base 34). ing. The position sensor 27 is driven by a piezo driver 28 together with the piezo stage 26.

On the microscope holder 52, a light source 50 for picking up a microscope image, a condenser lens system 46, an image forming lens 44, and a video camera 48 are further provided. The beam splitter 40 is provided to reflect the laser light from the collimator lens 22 to guide it to the objective lens 24 and to return the laser light reflected by the liquid crystal display module S to the laser diode package 10. The beam splitter 40 is preferably a polarization beam splitter or a dichroic mirror so that the laser light from the laser diode package 10 and the laser light reflected by the liquid crystal cell S can be efficiently reflected. Further, another beam splitter 42 is provided so as to reflect the light from the condenser lens system 46 and guide it to the objective lens 24. This light is reflected by the liquid crystal display module S and carries the image thereof. The beam splitters 40 and 42 also play a role of transmitting the light from the objective lens 24 carrying the image of the liquid crystal display module and guiding it to the video camera 48. Monitor 3
3 is connected to the video camera 48 and displays the image captured by the video camera 48.

In the optical system configured as described above, the light from the light source 50 for capturing a microscope image is condensed by the condenser lens system 46, reflected by the beam splitter 42, further transmitted through the beam splitter 40, The liquid crystal display module S is illuminated. This light is reflected by the liquid crystal display module S and carries the microscope image thereof. The microscope image-carrying light passes through the beam splitters 40 and 42 and is imaged by the imaging lens 44 on the imaging surface of the video camera 48. The liquid crystal display module image thus captured by the video camera 48 is displayed on the screen of the monitor 33. The laser light from the laser diode package 10 is collimated by the collimator lens 22 into a parallel light flux, which is then bent 90 degrees by the beam splitter 40 and directed toward the objective lens 24. The laser light reflected by the liquid crystal display module S is reflected by the beam splitter 4
It is reflected at 0 and returns to the laser diode package 10. Here, the objective lens 24 is the piezo stage 2
6 vibrates in the optical axis Z direction together with 6, the amount of light returned to the laser diode 12 fluctuates corresponding to the distance between the sample S and the objective lens 24 when the sample enters the focal depth of the objective lens. The beam splitters 40 and 42 of the laser light reflected by the liquid crystal display module S are
The leaked light that has passed through is captured by the video camera 48 as a laser beam spot, and is displayed almost at the center of the screen of the monitor 33.

In this specific example, the arithmetic / control unit 30 comprises a computer 300 as an arithmetic unit and a controller 301 as a control unit. The computer 300 is for performing the arithmetic processing of FIGS. The controller 301 is a microcomputer in which the piezo driver 28 and the laser diode drive power supply 16 are integrated. The controller 301 is further provided with an analog / digital converter for receiving an analog optical output signal output from the amplifier 18 and an analog position signal output from the position sensor 27 and converting them into a digital signal. Has been. Controller 30
On the outer surface of 1, the piezo driver 28 is powered on to apply a voltage to the piezoelectric element of the piezo stage 26 and to start driving the position sensor 27, and the laser diode drive power source 1
Laser diode switch 3 for powering on 6
04, a piezo scan switch 306 for causing the piezo driver 28 to scan the voltage applied to the piezo stage 26, and a light source switch 3 for turning on the light source 50.
08, a warning lamp 310 indicating that the laser diode 12 is in a lighting state, and a piezo indicator 312 indicating that the piezo driver 28 is in a voltage scanning state are provided.

The operation method of this specific example having the above-mentioned configuration will be described below.
explain. First, the operator sets the liquid crystal display module, which is a sample, on the sample table 54, and turns on the piezo drive power switch 302. The piezo driver 28 applies a voltage to the piezoelectric element of the piezo stage 26 and
The driving of the position sensor 27 is started. As a result, the position sensor 27 outputs the position signal of the piezo stage to the controller 3
Start sending to 01. Next, the operator turns on the laser diode switch 304. Then, the warning lamp 310 is turned on and the laser diode 12 is turned on. The operator further selects the piezo scan switch 306.
Turn on. The piezo driver 28 starts scanning the drive voltage applied to the piezoelectric element of the piezo stage. The operator further turns on the light source switch 308,
The light source 50 is turned on. As a result, the sample image captured by the video camera 48 as a normal microscope image is displayed on the monitor 3.
The image is displayed on three screens, and at the same time, the laser beam spot is also displayed almost at the center of the monitor screen. The controller 301 outputs the amplifier 18 from the photodiode 14.
The optical output signal amplified by and the position signal output from the position sensor 27 are received and AD-converted. The controller 301 further aligns and synchronizes the phases of the digitally converted optical output signal and the position signal, and then the computer 30
Send to 0. Computer 300 is further illustrated in FIGS.
By performing the calculation process shown in FIG. 8, the peak position, the center of gravity position, or the minimum differential value position, which is the characteristic point of the signal waveform, is calculated, and the distance between them is calculated to obtain the liquid crystal cell gap.

The present inventors manufactured the minute position measuring device shown in FIG. 9 and conducted a measurement experiment of the cell gap of the liquid crystal display module. The laser diode 12 of the laser diode package 10 has a wavelength of 670n.
A m power of 5 mW was used. Then, the laser diode 12 is set to 0.5 mA from the oscillation threshold value.
It was driven a little lower. Furthermore, so that the applied voltage to the piezo stage 26 performs a sine wave drive scan at 30 Hz,
The piezo driver 28 was controlled. The scanning length of the piezo stage could be set up to 100 μm at maximum by setting the piezo applied voltage at 100 V at maximum. Furthermore, when an objective lens having a numerical aperture of NA 0.9 is used as the objective lens 24, the pulse half width is 0.4 μm.
The pulse peak position reading accuracy is 0.1μ.
The accuracy was as high as m or less, and good measurement could be performed.

Next, a second embodiment of the present invention will be described with reference to FIG. Similarly to the first embodiment, the second embodiment also measures a position of a plurality of boundary surfaces of a sample and measures a relative position of the sample, that is, a minute position measuring device (a minute size measuring device). Device).

In the minute position measuring device 1 of this embodiment, the feedback control device 15 is provided and the laser diode 12 is provided.
Performs feedback control (auto power control) so that it always outputs a constant amount of light. That is, in this embodiment, the feedback control device 15 is connected to the laser diode drive power supply 16 and the amplifier 18. The feedback control device 15 includes a comparison circuit and the like, receives the optical output signal output from the photodiode 14 and amplified by the amplifier 18, and feedback-controls the laser diode drive power supply 16 based on the optical output signal to control the laser diode 12 The drive current (forward current) applied to is adjusted. That is, the applied forward current of the laser diode drive power source 16 is feedback-controlled so that the laser diode 12 outputs a constant amount of light. The laser diode drive power supply 16 is also connected to the arithmetic and control unit 30, and outputs a signal indicating a forward current applied to the laser diode 12 (hereinafter, referred to as “driving current signal”).
Output to the arithmetic / control device 30. The feedback response frequency of the feedback control device 15 is the drive frequency and stroke of the piezo driver 28, the objective lens 2
It is determined according to the numerical aperture of 4 and the oscillation wavelength of the laser diode 12. Also in the case of the present embodiment, it is preferable that the power of the automatic power control (forward current) is initialized to be lower than the oscillation threshold of the laser diode 12 by several percent. This is because the sub-peak of the signal output can be suppressed as in the first embodiment.

In such a structure, the piezo stage 2
When the laser spot hits the boundary surface in the sample in accordance with the scanning of 6, the reflected light is largely returned to the laser diode 12, the laser diode oscillation is amplified and changed, and the output light amount of the laser diode 12 increases. Photodiode 14
Detects the increased optical output and outputs an optical output signal. The optical output signal is amplified by the amplifier 18 and then input to the feedback control device 15. The feedback control device 15 uses the laser diode drive power source 1
By reducing the forward current value 6 applied to the laser diode 12, the increase in the light emission amount of the laser diode due to the increase in the feedback light to the laser diode 12 is suppressed, and feedback control is performed so that the light emission amount becomes constant. As described above, in the present embodiment, the light emission amount itself is constant, but the drive current changes. Therefore, the position of the boundary in the sample is measured by measuring this drive current.

In this embodiment, the arithmetic / control unit 30 receives the analog drive current signal output from the laser diode drive power source 16 and the analog position signal output from the piezo driver 28, and converts these signals into analog / digital signals. After that, by matching the phases, a data pair (D (i), Z (i)) composed of the synchronized drive current data D (i) and the position data Z (i) is obtained. The arithmetic / control device 30 controls the display device 32 to display the relationship between the moving distance Z (i) of the objective lens 24 and the drive current D (i) of the laser diode 12, as shown in FIG. As a result, the reflected light from the boundary surface of the sample is obtained as a downward pulsed drive current signal. The calculation / control device 30 further calculates the drive current data and the position data, and the objective lens 24 of the objective lens 24 when the downward pulse (more specifically, the vertex of the downward pulse, the center of gravity, or the minimum differential value) is obtained. By obtaining the moving distance, the relative position of the boundary surface of the sample S with respect to the objective lens 24 is obtained. Since the sample S has a plurality of boundary surfaces in the optical axis Z direction, the reflected light from the plurality of boundary surfaces is obtained as a plurality of downward pulsed drive current signals. Therefore, the arithmetic / control device 30 is similar to the first embodiment in that
As the distance between the downward pulses, the dimension of the sample is obtained by calculating the pulse vertex interval, the pulse centroid interval, or the pulse minimum differential value position interval.

In the arithmetic processing performed by the arithmetic / control unit 30 of this embodiment, the drive current data D is used instead of the optical output data I (i).
It is substantially the same as the arithmetic processing shown in FIGS. 4 to 8 except that (i) is used. More specifically, in this embodiment, it is determined that the extreme decrease in the laser diode drive current is due to the increase in the feedback light due to the boundary surface of the sample. Arithmetic / control device 3
0 receives the drive current signal and the position signal which are synchronized with each other, obtains the time when the drive current signal forms a downward pulse showing its extreme decrease, and obtains the position of each boundary surface from the position signal obtained at this time. . Furthermore, the distance between each boundary surface is calculated.

The present inventors have embodied the present embodiment and manufactured a liquid crystal cell gap measuring device having a structure similar to that of FIG. The objective lens 24 having a numerical aperture NA of 0.65 and the laser diode 12 having a wavelength of 670 nm are used, and the piezo stage 26 is driven by a piezo driver 28 at 20 Hz, 40 Hz.
Scanned in μm strokes. The initial setting value of the power of the auto power control is set to be a few percent lower than the oscillation threshold value of the laser diode 12. In addition, the feedback response of the feedback control device 15 is set to hundreds of tens of kilohertz. As a result, good results were obtained.

According to this embodiment, feedback (auto power control) is applied so that the light emission amount of the laser diode is always constant, and the drive current of the laser diode is extracted as a signal. Therefore, the laser diode can always be driven so as to have a constant output without exceeding its rated output, so that the load on the laser diode can be reduced and the temperature change in the external environment and the influence of heat generation of the laser diode itself. Can be suppressed.

In the first and second embodiments, the arithmetic / control unit 30 calculates the characteristic points of each pulse to obtain the position of each boundary surface, and then calculates the distance between the boundary surfaces. However, the position of the boundary surface with respect to the minute position measuring device may be simply obtained by performing the arithmetic processing of FIGS. For example, when the position signal z indicates the distance between the objective lens 24 and the surface of the fixed base 34, the obtained vertex position Pz (j) of each j-th pulse, the center of gravity position ZG (j), or , By calculating the focal length f from the minimum differential value position ZD (j), the distance of each j-th boundary surface from the surface of the fixed base 34 can be obtained.

Further, according to the pulse-pulse separation processing of FIG. 5, it is possible to store only the data of the pulse portion and use this data for other processing. However, this process may be omitted. That is, after performing the threshold value determination process of FIG. 4, any of the processes of FIGS. 6 to 8 may be directly performed without performing the pulse-pulse separation process of FIG. Further, although any of the processes of FIGS. 6 to 8 may be performed, it is sufficient to obtain the vertex position by the process of FIG. 6 when the signal output has little noise, but FIG. It is preferable to obtain the position of the center of gravity by the processing of.

Further, when the reflectances of a plurality of boundary surfaces of the sample are largely different depending on the boundary surfaces, the height of the pulse formed by the optical output signal emitted from the photodiode 14 is considerably different. In such a case, in order to reduce the difference in pulse height, the amplifier 18 may be a log amp to suppress signal variations. This is because the log amp can make the output logarithmic with respect to the input.

In the first and second embodiments, the sample S is scanned by the objective lens 24.
The sample S may be scanned. FIG. 12 shows a configuration when the piezo stage 26 is changed so as to move and scan the sample S. In this figure, the objective lens 24 is fixed on the XYZ stage 80 so that the relative position between the objective lens 24 and the sample S can be finely adjusted.

In the first and second embodiments described above, the position of the sample boundary surface in the one-dimensional (Z-axis) direction is measured. However, according to the present invention, the position of the sample boundary surface in the one-dimensional direction is two. It can also be measured dimensionally. The third example is
This is a two-dimensional scanning minute position measuring device which is capable of two-dimensional measurement by applying the configuration of the first embodiment. That is, the third embodiment is a minute position measuring apparatus (minute shape measuring apparatus) capable of obtaining the shape of the sample by measuring the distribution of the position of the boundary surface of the sample.

The third embodiment of the present invention will be described below with reference to FIGS.
This will be described with reference to 15. As shown in FIGS. 13 and 14, the optical system of this two-dimensional scanning minute position measuring apparatus is mounted on a Z stage 104 which is slidable in the Z axis direction with respect to the microscope holder 52. Also, sample S
Is mounted on the XY stage 102 that is movable in the X-axis and Y-axis perpendicular to the Z-axis with respect to the microscope holder 52, so that the optical system and the sample can be easily aligned.
In this device, a galvanometer mirror 96 and a pupil relay lens 90 are provided between the collimator 22 and the objective lens 24. The galvanometer mirror 96 is for deflecting the laser light from the collimator 22 in the X-axis direction orthogonal to the Z-axis. The pupil relay lens 90 forms an image of the exit pupil of the objective lens 24 on the galvanometer mirror 96, and further forms a laser light spot at the image point position of the objective lens 24. Furthermore, between the galvanometer mirror 96 and the pupil relay lens 90, 3
A 0 ° prism 92 is provided. The 30 ° prism 92 forms a branched optical path that guides a part of the laser light reflected by the sample S and returned through the objective lens 24 and the pupil relay lens 90 to the camera lens 94 of the video camera 95. The video camera 95 is for confirming the position on the sample S irradiated with the laser light. The objective lens 24 is attached to the revolver 98, and the type can be selected according to the sample.

In this structure, the laser light emitted from the laser diode 12 is collimated by the collimator 22, and the galvanometer mirror 96, the 30 ° prism 92,
After entering the objective lens 24 through the pupil relay lens 90,
A spot is formed on the sample S. The reflected light from the sample S traces back the above optical path and returns to the laser diode 12. The galvanometer mirror 96 scans the laser light on the sample in the X-axis direction perpendicular to the optical axis direction Z.
Here, the galvanometer mirror 96 scans the laser light in the X-axis direction orthogonal to the optical axis Z at a cycle slower than the scanning cycle of the piezo driver 26 in the Z-axis direction by the piezo driver 28. The calculation / control device 30 uses the optical output signal from the photodiode 14 in the laser diode package 10, the position signal in the X-axis direction of the galvanometer mirror 96, and the position signal in the Z-axis direction of the piezo stage 26 to detect the light of the sample. The distribution state of the cross-sectional shape in the axial (Z-axis) direction in the X-axis direction is displayed on the display device.

FIG. 15 is an explanatory diagram showing signal processing in this two-dimensional micro position measuring device. Now, it is assumed that the surface of the sample is distributed along the X-axis direction as shown in FIG. In this case, when the laser light is scanned in the optical axis Z direction in the two-dimensional micro position measuring device while scanning in the X direction,
The signal can be observed as a series of pulses as shown in FIG. By connecting the peak points as the characteristic points of this pulse by the arithmetic processing shown in FIGS. 4 to 6, the surface shape of the sample can be obtained as shown in FIG. When the sample has a pair of external boundary surfaces, the distribution state of the sample shape in the X-axis direction can be obtained from the distribution state of each boundary surface in the X-axis direction. Furthermore, when the sample has a multilayer structure,
From the distribution state of each boundary surface in the X-axis direction, the distribution state of the shape of each layer of the sample in the X-axis direction can be obtained. It is needless to say that a similar two-dimensional micro position measuring device can be constructed by applying the configuration of the second embodiment.

The present invention is not limited to the minute position measuring apparatus of the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above embodiment, a laser diode is used as the light source,
It is not limited to this. Any light source having a multiplication function may be used. For example, a laser or a maser may be used. further,
A light source to which a fiber amplifier is added may be used.

The means for adjusting the distance between the sample and the objective lens is not limited to the piezo stage using the piezoelectric element. For example, a fine movement stage may be used for measuring a relatively long distance, or a piezo stage and a fine movement stage may be used together. Furthermore, as the photodiode 14 for detecting the output light of the laser diode 12,
As described in the above specific example, it is preferable to use the monitoring photodiode built in the laser diode package 10. However, the photodiode 1
4 is used as a monitor as usual, a half mirror is provided in the beam optical path between the laser diode 12 and the photodiode 14 to split the light, and the split light is detected by a separately provided photodiode. The result may be used for measurement. Further, as the characteristic point of the pulse, other than the peak point of the pulse, the center of gravity point, the minimum differential value point,
Various points can be considered.

[0068]

As is clear from the above description, in the minute position measuring apparatus of the present invention, the confocal optical system focuses the light from the light source onto the sample having at least one boundary surface. At the same time, the reflected light from the sample obtained by the irradiation is returned and made incident on the light source. The scanning means moves the relative position of the sample with respect to the confocal optical system in the optical axis direction. When the light from the confocal optical system is focused and irradiated on the at least one boundary surface along with the movement, the amount of reflected light from the sample increases. As a result,
The amount of reflected light from the sample that returns and enters the light source increases. Here, since the light source has an amplifying function, its output state changes. The detecting means detects the change in the output state. The calculation means calculates the position of the at least one boundary surface of the sample in the optical axis direction based on the detection result of the detection means and the relative position of the sample with respect to the confocal optical system by the scanning means. According to such a minute position measuring device, the position of the boundary surface of the sample can be measured in units of submicrons to several millimeters, and the position of each boundary surface of the sample having the multilayer structure can be measured relatively easily. Therefore, it is possible to measure the thickness dimension from sub-micron to several millimeters, which has been impossible in the past, and the dimension and shape of each layer of the sample having the multilayer structure can be relatively easily measured without contact.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a micro position measuring device according to a first embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a forward current applied to a laser diode and a pulse half width of an optical output signal obtained in the minute position measuring apparatus of FIG.

3 is an explanatory diagram showing a pulse signal waveform formed by a data pair consisting of position data and optical output data obtained by the micro position measuring device of FIG. 1. FIG.

FIG. 4 is a flowchart showing a threshold value determination process performed by a calculation / control device of the microposition measuring device of FIG.

5 is a flowchart showing a pulse-pulse separation process performed by the arithmetic / control device of the microposition measuring device of FIG.

6 is a flowchart showing a pulse vertex calculation process performed by a calculation / control device of the microposition measuring device of FIG.

7 is a flow chart showing a pulse centroid calculation process performed by the calculation / control device of the microposition measuring device of FIG.

8 is a flowchart showing a pulse minimum differential value point calculation process performed by the calculation / control device of the minute position measuring device of FIG. 1. FIG.

9 is an explanatory diagram showing a configuration of a liquid crystal cell gap measuring device that embodies the minute position measuring device of FIG. 1. FIG.

FIG. 10 is an explanatory diagram showing a configuration of a minute position measuring apparatus according to a second embodiment of the present invention.

11 is an explanatory diagram showing a pulse signal waveform formed by a data pair composed of position data and drive current data obtained by the minute position measuring device of FIG.

FIG. 12 is a perspective view showing a modified example in which a sample is placed on a piezo stage.

13 is a cross-sectional explanatory view showing a configuration of a two-dimensional scanning micro-position measuring device of a third embodiment of the present invention configured by applying the micro-position measuring device of FIG.

14 is a perspective view of the two-dimensional scanning minute position measuring device of FIG.

15A is a diagram showing a cross-sectional shape of the surface of the sample, and FIG. 15B is a series of pulse signals obtained as a result of measuring the sample with the two-dimensional scanning minute position measuring device of FIG. FIG. 4C is a graph showing the cross-sectional shape of the surface of the sample, which is obtained by connecting the peak points of the pulse shown in FIG.

[Explanation of symbols]

 1 Micro Position Measuring Device 12 Laser Diode 14 Photodiode 15 Feedback Control Device 16 Laser Diode Driving Power Supply 20 Confocal Optical System 26 Piezo Stage 30 Arithmetic / Control Device

Claims (1)

[Claims] 1. A light source having a multiplication function, and a confocal system configured along an optical axis direction of light from the light source,
A confocal optical system for focusing and irradiating light from the light source onto a sample having at least one boundary surface, and returning reflected light from the sample to the light source, and the sample for the confocal optical system. Means for moving the relative position of the light source in the optical axis direction, a detection means for detecting the output state of the light source that varies depending on the amount of light reflected from the sample that is returned to the light source, and the detection means. A calculation means for calculating the position in the optical axis direction of the at least one boundary surface of the sample based on the result and the relative position of the sample with respect to the confocal optical system by the scanning means. ,
A micro position measuring device for measuring the position of the boundary surface of a sample.