JPH05272926A - Step-difference measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure the step difference without contact on the surface having minute irregularities. CONSTITUTION:In a step-difference measuring apparatus having a cofocal-point optical system 4, a stage 20, on which an object 5 is mounted, can be moved in the direction orthogonal to incident/reflected light 2 with a driving part 21. The light irradiation position on the object 5 is moved into the direction orthogonal to the incident/reflected light 2, and the intensity of the reflected light through the cofocal-point optical system 4 is detected. Thus, the changing waveform of the intensity of the continuous reflected light with respect to the irregularities of the surface of the object 5 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type step measuring device for measuring the depth of fine irregularities on a surface.

[0002]

2. Description of the Related Art In recent years, a step difference measuring device using a confocal optical system has been used to measure a step difference of fine irregularities on a surface without contacting the surface of an object with a needle or the like.
An example of this conventional step measurement will be described with reference to the drawings. FIG. 4 shows the principle of a conventional confocal level difference measuring apparatus, in which 1 is a light source, 5 is an object, and 2 is incident / reflected light that is incident on and reflected from the surface of the object 5 from the light source 1. 9
Is a pinhole, and 11 is a lens. 6 is a light receiver, 10
Is a beam splitter. 3 is a focal plane of the present optical system.

The operation of the step measuring device configured as described above will be described. First, as shown in FIG.
When the focal plane 3 coincides with the surface of the object 5, the light source 1
The emitted light is focused by the pinhole 9, and the light passing through the pinhole 9 is focused on the surface of the object 5 by the lens 11. Similarly, the light reflected on the surface of the object 5 is focused on the pinhole 9 by the lens 11, and almost all the light passes through the pinhole 9. The light passing through the pinhole 9 is reflected by the beam splitter 10 and enters the light receiver 6.

On the other hand, as shown in FIG.
Is not coincident with the surface of the object 5, the incident light 12 emitted from the light source 1 and passing through the pinhole 9 and the lens 11 is not focused on a single point on the surface of the object 5, and the reflected light on the object 5 is not reflected. 13 spreads when it reaches the pinhole 9 through the lens 11. That is, only a part of the light reflected after entering the surface of the object 5 passes through the pinhole 9.

As described above, in the confocal optical system, the brightness of the object 5 differs depending on whether the surface of the object 5 coincides with the focal plane 3. By utilizing this property, it is possible to accurately grasp whether or not the focal plane 3 of the optical system and the surface of the object 5 are coincident with each other.

FIG. 5 is a schematic view of a conventional confocal optical system step measuring apparatus using the above-mentioned principle of confocal. 1 is a light source,
Reference numeral 5 is an object, 2 is incident / reflected light, and 4 is an abbreviated confocal optical system. Reference numeral 14 is an observation section. According to the above-mentioned principle, the image seen through the observation unit 14 looks bright at the position where the focal plane 3 and the surface of the object 5 coincide.
Therefore, the distance between the object 5 and the optical system 4 is changed so that the bottom surface and the upper surface of the step to be measured become bright, and at that time, the distance between the both objects and the optical system. The size of the step can be measured by measuring the difference.

[0007]

However, in the above-mentioned structure, the lateral resolution of the optical system, which is determined by the spread of light on the focal plane, is limited, and when the width of the unevenness on the surface of the object 5 becomes small. However, there is a problem in that the step cannot be measured due to the above limit of resolution.

The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to accurately measure even fine steps of unevenness in a confocal optical system step measuring device. ..

[0009]

In order to solve the above problems, in a step measuring apparatus of the present invention, a step measuring apparatus having the above confocal optical system is provided with a position for irradiating light on the surface of an object. And a function of moving the irradiation position on the surface of the object and receiving the reflected light from the object to change the intensity into an electric signal.

That is, according to the first aspect of the invention, the light source for irradiating the object with light and the light receiving means for receiving the reflected light from the object of the light emitted from the light source through the confocal optical system. And means for changing the focal length of the optical system or changing the distance between the object and the optical system, and means for measuring the length of the change in the focal length or the change in the distance to the object. A moving means for moving the irradiation position on the surface of the object by the light source in a direction orthogonal to the irradiation light; and an object received by the light receiving means when the irradiation position on the surface of the object is moved by the moving means. And means for converting the intensity of the reflected light from the object into an electric signal.

[0011]

In the present invention, because of the above-described structure, a continuous change in the reflected light on the surface in the direction orthogonal to the light can be obtained as an electric signal. Therefore, the irradiation position on the surface of the object can be clearly defined from the waveform of the signal. can do. Further, by changing the distance between the focal plane and the object while observing the waveform of the continuous signal, it is possible to clarify the measurement position and obtain the distance at which the portion coincides with the focal plane. That is, in the present invention, even when the width of the unevenness of the step of the object is small,
Since the measurement position can be accurately determined and the distance to the focal plane can be accurately adjusted, the step can be accurately measured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A step measuring apparatus according to an embodiment of the present invention will be described below with reference to the drawings (note that since the basic configuration of the confocal optical system step measuring apparatus has been described with reference to FIG. Are denoted by the same reference numerals, and detailed description thereof will be omitted). FIG. 1 is a schematic view of a step measuring apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a light source for irradiating the object 5 with light, 2 is incident light reflected by the surface of the object 5 due to irradiation from the light source 1, 3 is a focal plane, 4 is a confocal optical system, and 6 is reflected light. Is a light receiver for receiving light via the confocal optical system 4. In addition to the light receiving function, the light receiver 4 has a built-in function for converting the intensity of the reflected light from the received object 5 into an electric signal. There is.

Reference numeral 20 denotes a stage on which the object 5 is set, 21
Is a drive unit that is drivingly connected to the stage 20 and drives the target object 5. The target object 5 installed on the stage 20 is
The drive unit 21 can move in the direction perpendicular to the incident / reflected light 2 together with the stage 20, and the drive unit 21 can move the light source 1
This constitutes a moving means for moving the irradiation position on the surface of the object 5 in the direction orthogonal to the irradiation light.

The object 5 can be brought into contact with and separated from the confocal optical system 4 including the light source 1 and the light receiver 6 together with the stage 20 and the driving section 21, and this allows the object 5 and the optical system 4 to be separated from each other. It is configured to change the distance between and. At that time, the length of change in the distance between the optical system 4 and the object 5 can be measured. The light emitted from the light source 1 is incident on the surface of the object 5 and is reflected, and the incident / reflected light 2 passes through the confocal optical system 4. Also,
The reflected light is detected by the light receiver 6, and the light intensity of the light is converted into an electric signal by the light receiver 6. That is, the light receiver 6 is
When the irradiation position on the surface of the target object 5 is moved by the light receiving means for receiving the reflected light from the target object 5 of the light emitted from the light source 1 to the target object 5 through the confocal optical system 4, and the drive unit 21. And means for converting the intensity of the reflected light from the object 5 received by the light receiving means into an electric signal.

The operation of the step measuring device configured as described above will be described. FIG. 2 is an enlarged view of a stepped portion on the surface of the target object 5 shown in FIG. 1. As shown in FIG. 2A, the spot size of the incident / reflected light 2 is a stepped portion on the surface of the target object 5. Since it is larger than the width of the convex portion 7 and the concave portion 8 of
The level difference on the surface of the object 5 cannot be measured as it is. In this embodiment, the irradiation position of the light on the object 5 is set to the stage 2
Driven by the drive unit 21 of 0 (see FIG. 2).
2B), a state in which the convex portion 7 is included in the width of the incident / reflected light 2 occurs as shown in FIG. 2B. Further, when the stage 20 moves further, FIG.
As shown in (c), a state in which the concave portion 8 is included in the width of the incident / reflected light 2 also occurs. At that time, the distance between the object 5 and the focal plane 3 is kept constant, and when the focal plane 3 is close to the surface of the convex portion 7 as shown in FIG. 2B, the light receiver 6 in the case of FIG. The reflected light detected by is the strongest and the weakest in the case of FIG. Therefore, when the surface step of the object 5 has a repeating pattern as shown in FIG. 2, the change in the received light intensity with respect to the displacement in the direction perpendicular to the incident light is as shown in FIG. That is, the reflected light is the strongest when the incident light illuminates the center of the convex portion 7, and the weakest when the incident light illuminates the center of the concave portion 8.
Here, when the object 5 is moved from the optical system 4 and the distance to the focal plane 3 is changed while observing the electric signal of FIG. 3 output from the light receiver 6, the height of the signal waveform of FIG. Changes, so that the highest position is when the focal plane 3 and the surface of the convex portion 7 coincide with each other. On the contrary, the focal plane 3 is changed to the object 5
When it is made to coincide with the vicinity of the concave portion 8, the signal waveform is inverted, and the received light intensity becomes the highest when the center of the concave portion 8 is irradiated. Therefore, by changing the distance between the focal plane 3 and the object 5 as described above, The distance at which the focal plane 3 coincides with the concave portion 8 is obtained. The step can be measured by obtaining the difference between these distances.

Therefore, according to this embodiment, the object 5
By moving the position of irradiating light on the surface in the direction orthogonal to the light and changing the intensity of the reflected light to an electric signal to measure the step, even if there is a minute uneven step, the measurement location is accurate. Can be specified and the step can be accurately measured.

The light irradiation position and the distance between the focal plane and the object are not limited to the case where the position of the object is moved as in the above-mentioned embodiment, but are determined by optical means such as a mirror or a lens system. It may be changed by changing the focal length of the optical system.

[0018]

As described above, according to the present invention,
A step measuring device with a confocal optical system has the function of moving the position of irradiating light on the object surface in the direction orthogonal to the light, and receiving the reflected light while moving the irradiation position on the object surface. By providing the function of changing the intensity into an electric signal, it is possible to accurately specify the measurement location and accurately measure the step even with fine irregularities.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of a step measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the position of incident / reflected light with respect to an object for explaining the operation in the embodiment.

FIG. 3 is a graph showing the relationship between displacement in the direction perpendicular to incident light and received light intensity for explaining the operation in the example.

FIG. 4 is a schematic diagram showing the principle of a confocal step difference measuring device.

FIG. 5 is a schematic view of a conventional step measuring device.

[Explanation of symbols]

 1 light source 2 incident reflected light 3 focal plane 4 confocal optical system 5 object 6 light receiver 7 convex portion 8 concave portion 20 stage 21 drive unit (moving means)

Claims (1)

[Claims] 1. A light source for irradiating an object with light, a light receiving means for receiving reflected light of the light emitted from the light source onto the object through a confocal optical system, and a focus of the optical system. A means for changing the distance or changing the distance between the object and the optical system, a means for measuring the length of change in the focal length or the distance between the object and the surface of the object by a light source. Moving means for moving the irradiation position in the direction orthogonal to the irradiation light, and converting the intensity of the reflected light received by the light receiving means when the irradiation position on the surface of the object is moved by the moving means into an electric signal. A step measuring device comprising: