JPH05332741A - Surface form measuring device - Google Patents

Abstract

PURPOSE:To measure the irregularity of a surface without deteriorating measuring resolution by providing a beam scanner for scanning a light point, an imaging lens for observing and imaging in a direction different from light emission, a focus member, a light detector, and a phase measuring instrument to measure the phase of the output signal of the light detector. CONSTITUTION:A beam scanner 1 changes the beam emitted from a light source 1a by semiconductor laser into a parallel light by a collimator lens 1b to scan it on a material 2 to be measured by a rotating mirror 1c and a f-theta lens 1d. The beam reflected by the material 2 to be measured is imaged on a focus plate 4 by an imaging lens 3. A light detector 5 detects the light transmitted by the focus plate 4 and outputs a light intensity signal S5. A phase measuring instrument 6 detects the phase of the signal S5 and generates a signal S6. The focus plate 4 has a band light permeable part and non-permeable part alternately formed thereon. When the material 2 to be measured has irregularities. Since the moving speed of a light point on the focus plate 4 is changed, when the material 2 to be measured has irregularities, and the phase of the light intensity signal is also changed, the irregularity information can be provided at high speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface shape measuring device for measuring the surface shape of an object to be measured.

[0002]

2. Description of the Related Art Conventionally, various devices have been proposed for measuring the contour or shape of the surface of an object using an optical device. FIG. 8 is a schematic view showing an apparatus for performing shape measurement by the light-section method. Light that spreads in a fan shape from the light projector 7 is projected toward the line AB on the surface of the DUT 2, and the light receiver 8 receives the light. It is designed to receive reflected light. Then, an image of the line AB as shown in the screen 9 can be obtained from the light receiver 8. The shape of this line AB represents the uneven state of the DUT 2.

[0003]

FIG. 9 is an explanatory view showing the path of the light in FIG. 8, and the light emitted from the projector 7 and reflected by the DUT 2 is reflected by the lens 8a in the light receiver 8. It is designed to be detected by the photodetector 8b. Assuming that the positions of the reflection points on the DUT 2 are a ₁ , b ₁ and c ₁ as shown in the figure, the image forming positions of the respective points are a ₂ , b ₂ and c ₂ .

That is, the measurement range in the height direction of the DUT 2 is a range between b _{1 and} c _{1 in} FIG. Therefore, when it is attempted to measure the position shapes of the object to be measured 2 near the point b ₁ or the point c _1, if these shapes are tilted, image formation by the photodetector 8b is no longer possible. Sometimes.

As described above, in order to prevent the measurable range from being substantially narrowed, it is conceivable to change the focal length of the lens 8a and adjust the mounting position of the photodetector 8b. The unevenness resolution of the container 8 is deteriorated.

In order to detect the screen 9 shown in FIG. 8 by the photodetector 8b, a photodetector capable of detecting a two-dimensional light intensity distribution must be used. In such a photo-detecting element, it generally takes several tens of milliseconds to detect information on one screen, and high-speed measurement cannot be performed.

The present invention has been made based on the above-mentioned circumstances. The measurable range in the height direction can be widened without deteriorating the measurement resolution and the unevenness information on the surface of the object to be measured can be obtained at high speed. An object is to provide a surface profile measuring device that can be obtained.

[0008]

In order to achieve the above object, the invention corresponding to claim 1 is a beam scanner for projecting a light spot on an object to be measured and scanning the light spot, and the object to be measured. One reflected light from the above light spot, which is observed from a direction different from that of the projected light to form an image, and one image forming lens, which is placed on the image forming surface of this image forming lens and is capable of transmitting light, Modulate the light intensity 1
Each of the focus members includes a photodetector that receives the light transmitted through the focus member, and a phase measuring device that measures the phase of the output signal of the photodetector.

Further, in order to achieve the above-mentioned object, claim 2
The invention corresponding to, a light beam scanner for projecting a light spot on the object to be measured and scanning the light spot, and observing reflected light from the light spot on the object to be measured from a direction different from the light projection. An imaging lens that forms an image, a beam splitter that splits the light from the imaging lens, a plurality of focus members that can respectively transmit the light split by the beam splitter, and that modulate the light intensity, It comprises a plurality of photodetectors for receiving the light transmitted through each focusing member, and a plurality of phase measuring devices for measuring the phase of the output signal of each photodetector.

Further, in order to achieve the above object, the invention according to claim 3 is a beam scanner for projecting a light spot on an object to be measured and scanning the light spot, and the light spot on the object to be measured. A plurality of imaging lenses for observing the reflected light from a different direction from the projected light and forming an image, and a plurality of imaging lenses that are placed on the imaging surface of each of the imaging lenses and can transmit light and modulate the light intensity. Of the focus members, a plurality of photodetectors for receiving the light transmitted through the focus members, and a plurality of phase measuring devices for measuring the phases of the output signals of the photodetectors.

[0011]

According to the inventions according to claims 1, 2 and 3, the light beam projector projects the light spot onto the object to be measured and scans at a constant speed, and the imaging lens reflects the object to be measured. The light spot is imaged on the focus member, the light spot is scanned on the object to be measured, the light spot imaged on the focus member also moves, and the direction of light projection by the light beam scanner and the light reception by the imaging lens Since the directions are different, the moving speed of the light spot on the focusing member changes depending on the surface roughness of the object to be measured. Since the light transmissive portions and the light non-transmissive portions such as lattice stripes are alternately formed on the focusing member, the light intensity received by the photodetector is modulated by the focusing member.
Moreover, the phase changes due to the unevenness of the object to be measured. Therefore, the surface roughness of the object to be measured can be measured by measuring the phase of the output signal of the photodetector.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a block diagram showing the configuration of the first embodiment of the present invention, and FIG. 1B is a focusing screen.

The light beam scanner 1 collimates a light beam emitted from a light source 1a of a semiconductor laser by a collimator lens 1b to make it a parallel light beam, and a rotary mirror 1c and an f-θ lens 1
The object 2 to be measured is scanned by d. The light beam reflected by the DUT 2 is imaged on the focusing member, for example, the focusing screen 4 by the imaging lens 3. The photodetector 5 detects the light transmitted through the focusing screen 4 and generates a light intensity signal S5. Phase measuring device 6
Detects the phase of the light intensity signal S5 and outputs the phase signal S6. As shown in FIG. 1B, the focusing screen 4 has strip-shaped light transmitting portions and light non-transmitting portions alternately formed at equal intervals.

Here, as the rotating mirror 1c, a high-speed one having a scanning time of several tens of microseconds can be used. Further, since the photodetector 5 only needs to detect the intensity of light with a single element, a very high-speed photodetector with a response time of several tens of nanoseconds can be used. Next, with reference to FIG. 2, the manner in which the moving speed of the light spot on the focusing screen 4 changes when the object to be measured has irregularities will be described.

FIG. 2A shows that, when the object 2 to be measured is a plane, the light spots on the object 2 to be measured are A ₁ , B ₁ , C ₁ , and
Move to D ₁ . These are imaged by the imaging lens 3 on A ₂ , B ₂ , C ₂ and D ₂ on the focusing screen 4. Here, since the DUT 2 is a flat surface, the light spot on the focusing screen 4 moves at a constant speed.

In FIG. 2B, when the object 2 to be measured has irregularities, the light spots on the object 2 to be measured are E ₁ , F ₁ ,
Move to G ₁ and H ₁ . These are imaged by the imaging lens 3 on E ₂ , F ₂ , G ₂ and H ₂ on the focusing screen 4.
Here, since the DUT 2 is higher from F ₁ to G ₁ , the light spot on the focusing screen 4 is between F ₂ and G ₂ ,
Slow down.

FIG. 3 shows the shape of the DUT 2, the light intensity signal,
It shows a phase signal. When the DUT 2 is flat as in (a), the phase of the light intensity signal is constant and the phase signal is also constant. Further, when there is unevenness as in (b), the phase of the light intensity signal is delayed at the convex portion of the measured object. That is, the phase signal indicates the uneven shape of the DUT 2. Further, FIG. 4 shows the relationship between the scanning speed, the pitch of the grating, the projection / reception angle, the measured height and the phase of the light intensity signal. Ray B is the scanning ray, z
Light is projected parallel to the axis (height direction). When the scanning speed is v, the light beam B is represented by x = vt (1). The lattice image G is an image of a lattice that can be formed by an imaging lens. Although the lattice image is not actually formed, the image position of the lattice is shown for convenience of explanation. Here, when the light receiving angle θ and the pitch of the lattice image are p, the lattice image G is expressed by z = (x−np) tan θ (where n is an integer) (2).

Now, assuming that the x-axis is the surface of the object to be measured, the scanning light beam B is reflected on the x-axis, but when this reflection position intersects the lattice image (for example, position A),
The light transmitted through the reticle is minimized. That is, according to the equations (1) and (2), the optical signal intensity becomes the minimum when z = (vt-np) tan θ (3). Since the light intensity signal is a periodic function of time t, when the light intensity signal is approximated by acos (ωt−φ) + b (a and b are arbitrary constants) (4), the angular velocity ω and the phase φ are = (2π) × v ÷ p (5) φ = (2π) × z ÷ ptan θ (6) Therefore, the height z can be obtained from the phase φ by z = (ptan θ / 2π) × φ + nptan θ (7).

However, the value of z has a measurement period of ptan θ, and the value of an integral multiple of ptan θ is uncertain. Therefore, the measurement cycle ptan is
When there is no step difference of ½ or more of θ, the uncertainty can be removed by the continuity from the adjacent data, and the shape measurement can be performed.

Next, a second embodiment of the present invention will be described.
FIG. 5 shows that even if the step of the measured object is large,
This is an example in which measurement can be performed with the same measurement accuracy as that of the example.

As shown in FIG. 5, in the first embodiment described above, a beam splitter 3A, a focusing screen 4a having a pattern with a pitch different from the pitch of the lattice fringes in FIG. 1, a photodetector 5a, and a phase measurement. One set is added to each of the containers 6a. Here, a beam splitter 3A is placed between the imaging lens 3 and the focusing screen 4 to form an image on the two focusing plates 4 and 4a. The transmitted light from the two focusing screens 4 and 4a is detected by the corresponding photodetectors 5 and 5a, and the respective phases are measured. The value of the measurement period ptan θ is increased by these two phase outputs. Combined measurement period p ₀
tan θ is the grating pitch p ₁ , p ₂ (p ₁ <p ₂ )
Then, 1 / p ₀ tan θ = 1 / p ₁ tan θ−1 / p ₂ tan θ (8) Expression (8) indicates that the synthetic pitch p ₀ is an interval in which the phases of the two gratings match. Therefore, if the unevenness is within 1/2 of the combined measurement cycle p ₀ tan θ, measurement can be performed without any uncertainties.

Next, a third embodiment of the present invention will be described with reference to FIG.
Will be described. In the second embodiment described above, one imaging lens 3 is used to combine the measurement cycles, but this embodiment is a case where two imaging lenses 3 and 3a are used. In this case, a synthetic measurement cycle can be obtained even if two different light receiving angles θ ₁ and θ ₂ are created. This combined measurement period P ₀
Is obtained as follows by the light receiving angles θ ₁ , θ ₂ , and the grating pitches p ₁ , p ₂ . 1 / p ₀ = 1 / p ₁ tan θ ₁ −1 / p ₂ tan θ ₂ (9)

In the third embodiment, the number of lenses is three.
However, since the beam splitter 3A is not used as in the first embodiment, the amount of light received by the photodetectors 5 and 5a increases. In the third embodiment, p ₁ t
an θ ₁ <p ₂ tan θ ₂ , even if p ₁ and p ₂ are equal,
The same effect as described above can be obtained.

Further, if a structure using three or more sets of the focusing screen, the photodetector, and the phase detector of the third embodiment, a larger synthetic period can be obtained, so that the measurement accuracy is not deteriorated. Wide measurement range can be obtained.

Next, a fourth embodiment will be described with reference to FIG. In FIG. 7, the light receiving direction is different from that in FIGS. 1, 5, and 6. That is, the beam scanner 1 is placed on the DUT 2.
The light spot scanned by the focusing lens 4 is focused by the imaging lens 3.
Image on top. In this case, the light spot on the focusing screen 4 moves in the x direction by scanning, and moves in the y direction as shown in FIG. 7C due to the surface unevenness of the DUT 2. Therefore, by arranging the lattice stripes of the focusing screen 4 obliquely as shown in the plan view of FIG. 7A and the front view of FIG. 7B,
Phase modulation is performed by periodic fluctuations in light intensity and surface irregularities of the DUT 2. Therefore, by measuring the phase of the light intensity signal S5, the surface unevenness information of the DUT 2 can be obtained.

The lattice fringe pattern of the focusing screens 4 and 4a in the above-mentioned embodiment is a case where the respective grating pitches are equal, but this can be changed by arbitrarily changing the grating pitch of each focusing screen 4 or 4a. Various modifications such as gradually changing can be implemented.

[0027]

According to the present invention, the light spot is scanned on the object to be measured, the reflected light is imaged on the grating, the phase of the intensity change of the transmitted light is determined, and the measured object is determined from this phase. Since the unevenness accuracy of the object surface is calculated, it is possible to provide a surface shape measuring device capable of widening the measurable range in the height direction without deteriorating the measuring accuracy and performing high-speed measurement.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a surface profile measuring apparatus of the present invention and a diagram showing a focusing screen.

FIG. 2 is a diagram showing the shape of the DUT of FIG. 1 and velocity fluctuations of a light spot on a focusing screen.

FIG. 3 is a diagram showing the relationship between the shape of the DUT of FIG. 1 and a light intensity signal and a phase signal.

FIG. 4 is a diagram for explaining the measurement principle of the present invention.

FIG. 5 is a block diagram showing a second embodiment of the surface profile measuring apparatus of the present invention.

FIG. 6 is a block diagram showing a third embodiment of the surface profile measuring apparatus of the present invention.

FIG. 7 is a block diagram showing a fourth embodiment of the surface profile measuring apparatus of the present invention.

FIG. 8 is a diagram for explaining an example of a conventional surface profile measuring apparatus.

FIG. 9 is a diagram for explaining the problem of FIG. 8;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ray-scanner, 1a ... Light source, 1b ... Collimator lens, 1c ... Rotating mirror, 1d ... f-theta lens, 2 ... DUT, 3, 3a ... Imaging lens, 3A ... Beam splitter, 4, 4a ... Focus plate, 5, 5a ... Photodetector, S5, S
5a ... Light intensity signal, 6, 6a ... Phase measuring device, S6, S6
a ... Phase signal, 7 ... Emitter, 8 ... Photoreceiver, 9 ... Image obtained.

Claims (3)

[Claims] 1. A light beam scanning device for projecting a light spot on an object to be measured and scanning the light spot, and observing reflected light from the light spot on the object to be measured from a direction different from the projection direction. One image-forming lens that forms an image, one focus member that is placed on the image-forming surface of this image-forming lens and that can transmit light, and that modulates the light intensity, and the light that passes through this focus member A photodetector for receiving light, and a phase measuring device for measuring the phase of the output signal of the photodetector, for measuring the phase of change in light intensity of the transmitted light of the light spot imaged on the focusing member. The surface profile measuring apparatus is characterized in that the unevenness information of the object to be measured is obtained. 2. A light beam scanner for projecting a light spot on the object to be measured and scanning the light spot; and a reflected light from the light spot on the object to be measured being observed from a direction different from that of the light projection. An imaging lens for forming an image, a beam splitter for splitting the light from the imaging lens, a plurality of focus members each capable of transmitting the light split by the beam splitter, and modulating the light intensity, A plurality of photodetectors for receiving the light transmitted through the focusing member, and a plurality of phase measuring devices for measuring the phase of the output signal of each photodetector. A surface profile measuring device, characterized in that the profile information of the object to be measured is obtained by measuring the phase of the change in the light intensity of the transmitted light at the point. 3. A light beam scanner for projecting a light spot on the object to be measured and scanning the light spot, and an image formed by observing reflected light from the light spot on the object to be measured from a direction different from that of the light projection. A plurality of image forming lenses, a plurality of focus members that are placed on the image forming surfaces of the respective image forming lenses and can transmit light, and that modulate the light intensity, and a light beam that has passed through the respective focus members. A plurality of photodetectors, and a plurality of phase detectors for measuring the phase of the output signal of each photodetector, and of the change of the light intensity of the transmitted light of the light spot imaged on each of the focusing members. A surface profile measuring apparatus, characterized in that the profile information of the object to be measured is obtained by measuring the phase.