KR102509303B1 - Apparatus for measuring surface profile and control method of thereof - Google Patents

Abstract

The present invention is a surface shape measuring device for measuring the surface shape of a measurement object, comprising: a light source for emitting light; a light splitting unit directing the light to the object to be measured; an optical interference module for irradiating light from the light splitting unit onto the object to be measured and forming an interference fringe based on the light reflected from the object to be measured; an imaging module for forming an image of the interference fringe emitted from the optical interference module with an imaging unit; an imaging unit that captures an image of an interference fringe formed through the imaging module; a first transfer unit that approaches and separates the imaging unit so that a separation distance between the imaging module and the imaging unit is adjusted; It relates to a surface shape measuring device including a control module that generates and analyzes surface shape data of the object to be measured based on the interference fringes captured by the imaging unit and feedback-controls the transfer unit. The surface shape measuring device of the present invention can easily compensate for the difference in light path caused by the change in the working distance of the imaging lens, and has excellent measurement reliability.

Description

Surface shape measuring device and its control method {APPARATUS FOR MEASURING SURFACE PROFILE AND CONTROL METHOD OF THEREOF}

The present invention relates to a surface shape measuring device and a control method thereof, and more particularly, to a surface shape measuring device capable of more precise measurement and shortening the measurement time for measuring the surface shape of a measurement object, and a control method thereof It is about.

In general, there is a process of applying a thin film layer on the surface of an opaque metal layer among semiconductor and LCD (Liquid Crystal Display) manufacturing processes. methods have been proposed.

As one of the methods for measuring the surface shape of the thin film layer, white-light scanning interferometry (WSI) has been proposed.

The basic measurement principle of white light scanning interferometry uses short coherence length characteristics of white light. This uses the principle that an interference signal is generated only when the reference light and the measurement light separated by a beam splitter, which is an optical splitter, experience almost the same optical path difference.

Therefore, when observing the interference signal at each measurement point in the measurement area while moving the measurement object in the direction of the optical axis by a transport means such as a PZT actuator at minute intervals of several nanometers, the optical path difference at each point is the same as that of the reference mirror. A short interfering signal is generated at the point where

When the location of the interference signal is calculated at all measurement points within the measurement area, information on the 3D shape of the measurement surface is obtained, and the surface shape of the measurement object is measured from the obtained 3D information.

The structure of the interference lens used in the most widely known white light scanning interferometry includes the Michelson interferometer, the Mirau interferometer, and the Linick interferometer.

A surface shape measuring device using a conventional white-light scanning interferometry collects interference fringes formed through an interference lens through a single imaging lens into an imaging unit, but in some cases, two or more An imaging lens may be employed. As an example, when two imaging lenses are employed, a fixed imaging lens may be installed at the bottom and an adjustable imaging lens may be installed at the top. The magnification of the interference fringes collected through the fixed imaging lens can be adjusted based on different conditions such as distance and radius of curvature between the fixed imaging lens and the adjustable imaging lens.

Korean Patent Registration No. 10-0943406 is an invention related to "a self-compensation device at the location of an interference generator for compensating for a difference in an optical path caused by a change in the working distance of an objective lens according to a change in temperature in an interference lens." It is an invention related to a method for compensating for a difference in an optical path when a change in the working distance of an interference lens occurs according to

A surface shape measuring device including an interference lens and an imaging lens is not only the method for compensating for the optical path difference according to the change in the working distance of the interference lens mentioned in Korean Patent Registration No. 10-0943406, but also the change in the working distance of the imaging lens. A solution for how to compensate for the optical path difference occurring along the way is also needed.

The present inventors have completed the present invention by providing a surface shape measuring device capable of more easily compensating for a difference in an optical path according to a change in the working distance of an imaging lens.

An object to be solved by the present invention is to provide a surface shape measuring device capable of precisely measuring by compensating for a difference in an optical path caused by a change in the working distance of an imaging lens and a control method thereof.

An object to be solved by the present invention is to provide a surface shape measuring device capable of easily compensating for a difference in an optical path caused by a change in the working distance of an imaging lens and a control method thereof.

The above and other objects of the present invention can all be achieved by the present invention described below.

One aspect of the present invention is a surface shape measuring device for measuring the surface shape of a measurement object, comprising: a light source for emitting light; a light splitting unit directing the light to the object to be measured; an optical interference module for irradiating light from the light splitting unit onto the object to be measured and forming an interference fringe based on the light reflected from the object to be measured; an imaging module for forming an image of the interference fringe emitted from the optical interference module with an imaging unit; an imaging unit that captures an image of an interference fringe formed through the imaging module; a first transfer unit that approaches and separates the imaging unit so that a separation distance between the imaging module and the imaging unit is adjusted; and a control module that generates and analyzes surface shape data of the object to be measured based on the interference fringes captured by the imaging unit and feedback-controls the transfer unit.

In addition, the imaging module includes a fixed imaging lens and one or more adjustable imaging lenses, and the adjustable imaging lens can move in the z-axis direction within the optical interference module to adjust the magnification of the interference fringe.

In addition, the first transfer unit includes a position sensor for detecting a working distance (T) between the optical interference module and the imaging unit; an actuator that approaches and separates the imaging unit from the optical interference module; and an output unit which controls driving of the actuator and outputs information on the operating distance detected by the position sensor to the control unit.

In addition, it may include a second transfer unit that approaches and separates one of the optical interference module and the measurement object from the other so that the separation distance between the optical interference module and the measurement object is adjusted.

In addition, the control module controls the light source, the imaging unit, the first transfer unit, and the second transfer unit so that the surface shape data is generated according to white-light scanning interferometry (WSI). can

Another aspect of the present invention is a method for controlling the above-described surface shape measuring device, comprising: forming a focus of an optical interference module (S10); Adjusting the magnification of the optical imaging module (S20); and compensating for the optical path difference (S30), wherein the compensating for the optical path difference (S30) causes the imaging unit to match the imaging distance (T) and the working distance (L) of the optical imaging module. It is to provide a control method of a surface shape measuring device characterized in that the light path difference is compensated for by moving in a vertical direction with respect to the optical imaging module.

The surface shape measuring device and its control method of the present invention can easily compensate for the difference in optical path caused by the change in the working distance of the imaging lens, and has excellent measurement reliability.

1 shows a surface shape measuring device according to one embodiment of the present invention.
FIG. 2 schematically shows a specific example in which the imaging distance T of the optical imaging module and the working distance L1 from the center of the adjustable imaging lens to the imaging unit are the same.
3 shows a specific example in which the working distance L2 from the center of the adjustable imaging lens to the imaging unit is greater than the imaging distance T of the optical imaging module.
4 shows a specific example in which the imaging distance T of the optical imaging module is greater than the working distance L3 from the center of the adjustable imaging lens to the imaging unit 50.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Here, in describing the present invention, even if the embodiments are different, the same reference numerals are used for the same components, and the descriptions are omitted if necessary.

1 shows a surface shape measuring device 100 according to one embodiment of the present invention. Referring to FIG. 1 , the surface shape measuring device 100 includes a light source 10, a light splitting unit 20, an optical interference module 40, an optical imaging module 60, an imaging unit 50, and a first transfer unit ( 70), a second transfer unit 90 and a control unit 80.

The light source 10 emits light. Here, the light source 10 according to the present invention may include at least one LED 12 (Light Emitting Diode) emitting white light.

The light emitted from the light source 10 is incident to the light splitter 20 through a pinhole (not shown) formed in the fixing member and the convex lens 11 . The light splitting unit 20, for example, a beam splitter, reflects the incident light at an angle of about 45° with respect to the incident direction, and directs it toward the object to be measured 30. The light splitter 50 according to the first embodiment of the present invention may have a non-polarized cube shape capable of separating incident light at a ratio of approximately 50:50.

Light reflected by the light splitting unit 20 and directed toward the object to be measured 30 is incident to the optical interference module 40 . Here, as the optical interference module 40 according to the present invention, any one of a Michelson optical interference module, a Linnik optical interference module, and a Mirau optical interference module may be used.

The light interference module 40 directs light incident from the light splitting unit 20 toward the reference mirror and the object to be measured 30 . Then, the optical interference module 40 forms an interference pattern by the light reflected from the object to be measured 30 and the reference mirror, and makes the formed interference pattern incident to the imaging unit 50 .

The imaging unit 50 captures an interference fringe generated by the optical interference module 40 and emitted through the light splitting unit 20 . Here, an optical imaging module 60 may be provided between the light splitting unit 20 and the imaging unit 50 to condense the interference fringe to the imaging unit 50 .

The controller 50 generates surface shape data of the object to be measured 30 using the data transmitted from the imaging unit 40 . Here, the control unit 80 according to the present invention generates surface shape data for the surface shape of the measurement object 30 according to white-light scanning interferometry (WSI). For this purpose, the light source 10, Controls the imaging unit 50, the first transfer unit 70 and the second transfer unit 90 to be described later.

The second transfer unit 90 includes a PZT actuator that approaches and separates the optical interference module 40 from the measurement object 30 and a PZT driver that controls the movement of the PZT actuator according to a command from the control unit 80. For example, the position sensor detects information about the position of the PZT actuator, that is, information about the separation distance between the optical interference module 40 and the measurement target 30, and the control unit 80 detects the separation distance detected by the position sensor. The feedback control of the second transfer unit 90 is performed by using the information about.

For the application of the white light scanning interferometry, the control unit 80 performs nanoscale scan control in the vertical direction of the optical interference module 40 by the PZT actuator, that is, in the direction of approaching and separating from the measurement object 30. In order to improve the precision and measurement speed of the shape measuring device, scan precision and fast control speed are required in controlling the second transfer unit 90 .

The optical imaging module 60 is composed of a fixed imaging lens 61 and an adjustable imaging lens 62. The interference fringes generated by the optical interference module 40 are imaged by the imaging unit 40 through the optical imaging module 60 . The fixed imaging lens 61 is a single-magnification lens and can be fixedly coupled to the barrel of the optical imaging module 60, and the adjustable imaging lens 62 is a z in the optical interference module 60 to adjust the magnification of the interference fringe. It can move in the axial direction. A plurality of adjustable imaging lenses 62 may be provided, and the magnification of the interference pattern may be easily adjusted through a combination of various imaging lenses.

A method of compensating for an optical path difference by adjusting an imaging distance between an optical imaging module and an imaging unit will be described with reference to FIGS. 2 to 4 . In the present invention, the imaging distance (T) means the distance from the center of the adjustable imaging lens 62 to the point where the interference fringe is formed, and the working distance (L) is the center of the adjustable imaging lens 62 It means the spaced distance to the part 50.

FIG. 2 schematically shows a specific example in which the imaging distance T of the optical imaging module and the working distance L1 from the center of the adjustable imaging lens to the imaging unit are the same, and FIG. 3 is the imaging distance T of the optical imaging module. ) shows a specific example in which the working distance L2 from the center of the adjustable imaging lens to the imaging unit is greater than that of the adjustable imaging lens, and FIG. It shows a specific example greater than the working distance (L3) of

Referring to FIG. 2 , when the imaging distance T and the working distance L1 are the same, an interference fringe having a desired magnification is formed in the imaging unit, and a clear interference fringe image can be secured after imaging.

On the other hand, when the working distance L2 is greater than the imaging distance T of the optical imaging module 60 as shown in FIG. 3, or the working distance L3 is greater than the imaging distance T of the optical imaging module 60 as shown in FIG. ) is small, it is not possible to secure a clear interference fringe image at a desired magnification. Therefore, in order to compensate for the optical path difference, it is necessary to adjust the distance between the optical imaging module 60 and the imaging unit 50, that is, the working distances L2 and L3. As an example, as shown in FIG. 3 , when the working distance L2 is greater than the imaging distance T of the optical imaging module 60, the imaging distance T and separation distance L2 of the optical imaging module 60 are the same. In order to do so, the optical path difference may be compensated for by vertically moving the optical imaging module 60 in the direction where the imaging unit 50 is located. However, since changing the position of the optical imaging module 60 in this way requires fine adjustment of the order of microns or less, there is a limit to manual control, and even if manual control is possible, the optical imaging module and the optical path affect each other. Since the focal position of the optical interference module that affects the light changes, there is a problem in that it is impossible to precisely measure the desired surface shape.

As another example, when the imaging distance T of the optical imaging module 60 is greater than the working distance L3 as shown in FIG. In order to make the imaging distance T and the working distance L3 of ) the same, the optical path difference may be compensated for by vertically moving the optical imaging module 60 in the direction where the optical splitting unit 20 is located, but in the case of FIG. 3 Similarly, since the focal position of the optical interference module changes, there is a problem in that it is impossible to precisely measure the desired surface shape.

The surface shape measuring device 100 of the present invention maintains the focal length of the optical interference module 40 and at the same time compensates for the optical path difference of the optical imaging module 60 by using the imaging unit 50 as the optical imaging module 60 A first transfer unit 70 for approaching or spaced apart in the vertical direction is provided. The control unit 80 analyzes the interference fringe image received from the imaging unit 50 and controls the first transfer unit 70 in feedback when it is determined that the optical path difference needs to be compensated. Feedback control by the controller is repeatedly performed until the imaging distance (T) and the working distance (L) of the optical imaging module 60 become the same through the driving of the first transfer unit. It is possible to obtain a clear interference fringe image of the magnification.

As one specific example, the first transfer unit 70 includes a position sensor for detecting a working distance (T) between the optical interference module and the imaging unit; an actuator that approaches and separates the imaging unit 50 from the optical interference module 60; An output unit which controls driving of the actuator and outputs information on the operating distance detected by the position sensor to the control unit 80; may include.

A method for controlling a surface shape measuring device according to an embodiment of the present invention includes forming a focus of an optical interference module (S10); Adjusting the magnification of the optical imaging module (S20); Feedback control step of the control unit (S30); and an optical path difference compensating step (S40).

In the step of forming the focus of the optical interference module (S10), while the control unit observes the interference signal at each measurement point within the measurement area of the object to be measured by the optical interference module, a short interference signal is generated at each point where the same optical path difference as that of the reference mirror occurs. This step is to generate an interference fringe by controlling the driving of the second transfer unit 90 so as to occur. At this time, only when the focus of the optical interference module 40 is accurately focused on the measurement reference plane can an interference fringe that can be accurately measured be secured. To this end, the control unit 80 feedback-controls the second transfer unit 90 using information on the separation distance between the optical interference module and the object to be measured.

Adjusting the magnification of the optical imaging module 60 (S20) is a step of adjusting the magnification of the interference fringe generated by the optical interference module 40 by controlling the adjustable imaging lens 62 of the optical imaging module 60.

In the optical path difference compensating step (S30), in order to make the imaging distance T and the working distance L of the optical imaging module the same, the imaging unit 50 is vertically moved in the direction where the optical imaging module 60 is located, thereby reducing the optical path It is a step to compensate for the difference. The control unit 80 analyzes the interference fringe image received from the imaging unit 50 and controls the first transfer unit 70 in feedback when it is determined that the optical path difference needs to be compensated. The feedback control of the controller 80 is repeatedly performed by driving the first transfer unit 70 until the imaging distance T and the working distance L of the optical imaging module 60 are matched, and when the feedback control is completed, measurement is performed. It is possible to obtain a clear interference fringe image at the desired magnification.

After the step of compensating for the optical path difference, the measurement of the surface shape is completed by detecting shape data from the interference fringe image obtained from the imaging unit.

As described above, the surface shape measuring device of the present invention can easily and quickly compensate for the difference in light path caused by the change in the working distance of the imaging lens, and has excellent measurement reliability.

It should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims to be described later rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts thereof are included in the scope of the present invention. should be interpreted

10: light source 11: convex lens
20: light splitter 30: object to be measured
40: optical interference module 50: imaging unit
60: optical imaging module 61: fixed imaging lens
62: adjustable imaging lens 70: first transfer unit
80: control unit 90: second transfer unit

Claims (6)

In the surface shape measuring device for measuring the surface shape of a measurement object,
The surface shape measuring device,
a light source that emits light;
a light splitting unit directing the light to the object to be measured;
an optical interference module for irradiating light from the light splitting unit onto the object to be measured and forming an interference fringe based on the light reflected from the object to be measured;
an optical imaging module for forming an image of the interference fringe emitted from the optical interference module with an imaging unit;
an imaging unit that captures an image of an interference fringe formed through the optical imaging module;
a first transfer unit configured to adjust a separation distance between the optical imaging module and the imaging unit, and adjust the separation distance by moving the imaging unit to and from the optical imaging module;
a second transfer unit which approaches and separates one of the optical interference module and the measurement object from the other so that a separation distance between the optical interference module and the measurement object is adjusted; and
A control module for feedback-controlling the first transfer unit by generating and analyzing surface shape data of the object to be measured based on the interference fringes captured by the imaging unit;
The optical imaging module includes a fixed imaging lens and one or more adjustable imaging lenses, wherein the adjustable imaging lens has a movable structure within the optical imaging module to adjust the magnification of an interference fringe;
The first transfer unit,
a position sensor for detecting a working distance between the optical interference module and the imaging unit;
an actuator for moving the imaging unit to and from the optical imaging module; and
An output unit which controls driving of the actuator and outputs information on the operating distance detected by the position sensor to the control module;
The control module controls the light source, the imaging unit, the first transfer unit and the second transfer unit so that the surface shape data is generated according to the white light scanning interferometry, so that the following imaging distance and the following working distance are the same Surface shape measuring device, characterized in that feedback control by repeatedly performing the movement of the first transfer unit:
Imaging distance: the distance from the center of the adjustable imaging lens to the point where the interference fringe is formed
Working distance: the separation distance from the center of the adjustable imaging lens to the imaging unit.
According to claim 1,
The surface shape measuring device, characterized in that the adjustable imaging lens of the optical imaging module moves in the z-axis direction within the optical interference module to adjust the magnification of the interference fringes.
delete delete delete As a control method of the surface shape measuring device of claim 1 or 2,
Focus formation step of the optical interference module (S10); Adjusting the magnification of the optical imaging module (S20); And compensating for the optical path difference (S30),
In the step of compensating for the optical path difference (S30), the optical path difference is compensated for by moving the imaging unit in a vertical direction with respect to the optical imaging module so that the imaging distance T and the working distance L of the optical imaging module match. A control method of a surface shape measuring device, characterized in that for.

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