KR20140104667A - A three dimensional shape measuring apparatus - Google Patents

Abstract

The present invention relates to a three dimensional shape measuring device and, more specifically, to a three dimensional shape measuring device capable of measuring the accurate shape even when the inclination of the surface of a sample (08) is higher than the numerical aperture (NA) of an optical system without mutual influence, even when light is not well reflected due to the very high roughness of the surface, and even when the light is not well reflected due to the characteristics of a material in spite of the smooth surface by coupling a white scanning interferometer (WSI) for acquiring light interference data on the sample (08) and an extended depth of focus (EDF) for acquiring noninterference light data on the sample (08) with multiple light splitters (02, 04, 09) and linear polarizers (01, 05, 07, 10, 14). The present invention can accurately measure the shape even when the inclination of the surface of the sample is higher than the NA of the optical system, even when the light is not well reflected due to the very high roughness of the surface, and even when the light is not well reflected due to the characteristics of the material in spite of the smooth surface since the present invention enables large area measurement, satisfies the faster inspection time than a confocal device, and has the higher spatial resolution than a Moire or laser-based inspection solution.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a three-

More particularly, the present invention relates to a three-dimensional shape measuring apparatus, and more particularly, to a three-dimensional shape measuring apparatus, in which, when a slope of a sample surface is larger than a numerical aperture (NA) of an optical system, Dimensional shape measurement apparatus capable of accurately and rapidly inspecting a three-dimensional shape measurement even when reflection is not performed due to the nature of materials, thereby achieving a spatial resolution higher than that of a moiré laser-based inspection solution.

Currently, integration and miniaturization of semiconductor, display, smart phone, LED and other industrial fields are progressing from the economic and technical point of view.

Improvement of the yield of products made by using such an integration and refinement process is very important in terms of reduction of production cost.

Improvement of production yield is achieved by minimizing defects, and it is essential to properly check whether the process is proceeding properly. However, it is a reality that the proper inspection technique according to the miniaturization is still unsatisfactory.

In particular, the shape of the surface is an important factor that can affect the properties of the formed device. Therefore, the shape inspection is an important indicator for judging good products and defects.

For example, demand for three-dimensional inspection such as solder ball shape inspection in a wafer level package field, via hole inspection on a PCB, and shape inspection of a bump formed on a sapphire substrate by an LED process is increasing, but the resolution, , And the ability to test according to the surface condition of the sample.

Commonly used non-contact shape inspection solutions include WSI (White Scanning Interferometer) (eg, No. 0785802), confocal microscope (eg, No. 0992029), moiré (eg, No. 0663323) , Laser triangulation (for example, patent No. 0406843), and the like.

Among them, WSI generally uses tungsten halogen and LED as a light source and has a microscope-based optical structure. When it is configured with a low optical magnification for large area measurement, a numerical aperture (hereinafter referred to as "NA" ), It is almost impossible to measure the sample if the surface of the sample is tilted or the surface is rough and the reflection does not occur well.

In addition, the precision is as high as sub-nanometer to sub-micrometer, but since it takes hundreds of images while performing mechanical scanning, the inspection time is somewhat slow and it is vulnerable to external vibration because it uses light interference phenomenon.

In contrast, the confocal microscope measures only the intensity of light, so it is relatively robust to vibration, but the scanning time is relatively slow because of the scanning in the horizontal and vertical directions. The precision is relatively high at the submicrometer level and the laser is used as the light source However, the intensity of the light is greatly reduced by the fine pinhole located at the front end of the detector.

For this reason, a photodiode or a photomultiplier tube (PMT) is used as a detector for improving the detection power. In principle, since co-focal is used, objective lenses with high NA are used and scanning is possible in the horizontal direction There are few restrictions on the field of view (FOV).

In addition, Moiré and laser triangulation have advantages over WSI or confocal microscopy, which have a wide measurement range and fast inspection time, but there are many technical deficiencies to inspect bumps and microstructures due to low spatial resolution.

Since spatial resolution and inspection time have conflicting characteristics, some compromise is needed in the optical structure for high spatial resolution and high speed inspection.

On the other hand, the EDF (Extended Depth of Focus) is relatively less known than the main three-dimensional measurement solution, and can be seen in terms of sub-micrometer accuracy and performs scanning on the vertical axis as well as WSI or confocal. In the EDF, the position of the image corresponding to the optimum focus state is found for each pixel from the acquired 2D images, and the position of the image corresponds to the relative height of the object to be measured.

Since EDF uses non-coherent 2D images, non-coaxial external illumination can be used even when the surface is relatively strong, tilted and rough, and does not reflect well. However, the degree of focus can be used only if there is a texture on the surface of the sample.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and it is an object of the present invention to provide a method and apparatus for measuring a large area (10 mm x 10 mm or more) A WSI-based optical system having a high spatial resolution. When the slope of the sample surface is larger than the NA of the optical system, the surface roughness is too large and the reflection is not good. Dimensional shape measuring device that can not measure the shape of a target object but can overcome it and measure a shape.

The present invention provides a WSI (White Scanning Interferometer) for acquiring optical interference data for the sample (08), an EDF (Extended Depth of Field) for acquiring interferenceless optical data for the sample (08) Focus) is combined with a plurality of optical splitters (02,04,09) and linear polarizers (01,05,07,10,14) so that the slope of the sample (08) surface is less than the numerical aperture (NA) Dimensional shape measuring apparatus is characterized in that when the surface roughness is too large and the reflection is not good, the surface is smooth but the accurate shape can be measured even when the reflection is not good due to the nature of the material. to provide.

At this time, the WSI includes a first linear polarizer 01 for linearly polarizing unpolarized light radiated from a coaxial illumination; A part of the linearly polarized light is transmitted, and a part of the light is reflected by the first light splitter (02); An objective lens 03 for collecting light transmitted through the first optical splitter 02; A second light splitter (04) for reflecting and transmitting the light transmitted through the objective lens (03); A second linear polarizer (07) for linearly polarizing the light transmitted through the second light splitter (04) and irradiating it with a sample (08); A fourth linear polarizer (05) for linearly polarizing the light reflected by the second light splitter (04); A reference mirror (06) for reflecting light passing through the fourth linear polarizer (05) to generate an optical path difference with light transmitted through the second optical splitter (04) to induce optical interference; And a third linear polarizer (10) for linearly polarizing the light reflected from the sample (08) and the reference mirror (06) and guiding the light to the first detector (12) through the first imaging lens (11) It is also characterized by being.

In addition, the first and third linear polarizers (01, 10) are polarizers which transmit only light in a 45 ° direction; The second linear polarizer 07 is a polarizer that transmits only light in the 90 占 direction; The fourth linear polarizer 05 is a polarizer that transmits only light in the 0 占 direction.

The EDF further includes a fifth linear polarizer (14) for linearly polarizing the light reflected from the sample (08) of the light reflected from the third optical splitter (09) so as to pass therethrough; A mirror 15 for vertically reflecting the polarized light through the fifth linear polarizer 14; And a second imaging lens 16 which collects the light reflected through the mirror 15 and makes it detectable through the second detector 17. [

The fifth linear polarizer 14 is also a polarizer that transmits only light in the 0 ° direction.

According to the present invention, it is possible to measure a large area and satisfy the inspection time faster than the confocal, but has a higher spatial resolution than the Moirena or laser-based inspection solution, and if the slope of the sample surface is larger than the NA of the optical system, When the reflection is not good, the surface is smooth, but it has an advantage that the accurate shape can be measured even when the reflection is not good due to the nature of the material.

1 is an exemplary diagram of a three-dimensional shape measuring apparatus according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Before describing the present invention, the following specific structural or functional descriptions are merely illustrative for the purpose of describing an embodiment according to the concept of the present invention, and embodiments according to the concept of the present invention may be embodied in various forms, And should not be construed as limited to the embodiments described herein.

In addition, since the embodiments according to the concept of the present invention can make various changes and have various forms, specific embodiments are illustrated in the drawings and described in detail herein. However, it should be understood that the embodiments according to the concept of the present invention are not intended to limit the present invention to specific modes of operation, but include all modifications, equivalents and alternatives falling within the spirit and scope of the present invention.

Prior to explanation, shape measurement is easy if the optical magnification of the WSI optical system for surface shape inspection is relatively high and the NA is higher than the slope of the sample surface.

However, in the case of an optical system configured to measure a large area, a surface having a low magnification and a low relative NA is not well-measured.

Such as a so-called round bump with a curved surface.

Since such a problem is not a good measure in principle, the present invention is configured to solve this problem by combining EDF (Extended Depth of Focus), which is another shape measuring method.

That is, the EDF also has a microscopic-based optical structure, and therefore, it is inevitably affected by NA of the system as described above. However, the EDF is principally a method of measuring the shape using interference or non-coherent light, so an external illumination system can be used differently from WSI.

With this concept in mind, a preferred embodiment according to the present invention will be described with reference to Fig.

As shown in FIG. 1, a three-dimensional shape measuring apparatus according to the present invention is a combination of a WSI and an EDF, including a plurality of optical splitters and a polarizer, and follows a basic optical system of WSI.

Therefore, the following description explains the three-dimensional shape measuring apparatus of the present invention in a form of sequentially explaining along the light path.

That is, the light originating from the coaxial illumination maintains 45 degrees through the first linear polarizer 01 to linearly polarize the non-polarized incident light.

Then, the linearly polarized light is reflected through the first optical splitter 02 and passes through the objective lens 03.

Thereafter, reflection and transmission are performed in the second optical splitter 04 constituting the Michelson optical system, and one light is divided into two.

Here, for convenience of explanation, the transmitted light is referred to as a first light ray, and the reflected light is referred to as a second light ray.

Then, the transmitted first light beam is changed to 90 degrees by the polarizer 07 positioned at 90 degrees, incident on the sample 08 for measurement, and then re-reflected to the second linear polarizer 07, Passes through the second light splitter 04, the objective lens 03, the first light splitter 02 and the third light splitter 09 in order and reaches the third linear polarizer 10 positioned at 45 degrees.

The second light beam reflected by the second light splitter 04 is transmitted through the fourth linear polarizer 05 positioned at 0 占 and oscillates at 0 占 and is reflected by the reference mirror 06, Reaches the third linear polarizer 10 while sequentially passing through the polarizer 05, the second optical splitter 04, the objective lens 03, the first optical splitter 02 and the third optical splitter 09 in this order.

The first ray of light at this point oscillates at 90 [deg.] And the second ray oscillates at 0 [deg.].

After passing through the third linear polarizer 10, the third linear polarizer 10 is positioned at 45 degrees, and both the first light beam and the second light beam are vibrated in the direction of 45 degrees. And is picked up by the first detector 12 by the first imaging lens 11. [

That is, optical interference data by the WSI device is obtained.

In this case, although part of the light reflected from the surface of the sample 08 is incident on the first detector 12 by the non-coaxial illumination 13, it does not affect the interference, .

On the other hand, the configuration for the EDF apparatus is as follows. As described above, the first light beam and the second light beam are respectively reflected from the sample 08 and the reference mirror 06 to reach the third optical splitter 09.

At this time, the transmitted first and second light beams are directed to the first detector 12, and the reflected first and second light beams are directed to the fifth linear polarizer 14.

Here, the first light ray and the second light ray have mutual coherence but do not interfere with each other because the vibration direction is kept perpendicular.

Therefore, even if the fifth linear polarizer 14 is not provided, the second detector 17 can obtain a non-interference image.

However, the second light beam by the reference mirror 06 acts as a background light, which reduces the overall sharpness of the image. As a result, in order to obtain a clear 2D image, the second linear beam must be removed, so that the fifth linear polarizer 14 is positioned in the 0 ° direction to pass only the first beam and remove the second beam.

Then, the second light beam passing through the mirror 15 and the second imaging lens 16 reaches the second detector 17 and is scratched.

At this time, the light reflected from the sample 08 by the non-coaxial illumination 13 can be detected by the second detector 17, and in particular, the surface tilt of the sample 08 can be detected by the NA of the optical system, 03) can be utilized by an EDF method using a 2D image, thereby overcoming the limitations of the existing WSI.

In addition, the present invention requires the use of two detectors while measuring the area of the same sample (08). Thus, an alignment device 18 for alignment of the second detector 17 can be added to the second detector 17.

As described above, the apparatus according to the present invention, that is, the optical system is a combination of a WSI (white light scanning interferometer) and a surface shape measuring device called EDF (Extended Depth of Focus), which can not simply be realized, Can be obtained only through carefully planned designs by applying a number of linear polarisers to remove unnecessary information. In other words, it can not be obtained simply by pasting two existing optical systems.

To summarize, WSI uses well-known interference of light, which is the strongest interfering signal in each pixel from a series of interference images taken along the optical axis (here, vertical axis) And the height of the sample surface corresponding to the pixel. The EDF is also the best focusing point for each pixel using non-coherent images taken while moving the optical system or a part of the optical system along the optical axis The present invention is capable of measuring the shape of the surface by finding the position to be judged. The present invention is capable of measuring a large area by having a special connection structure for mutual coupling so that only these advantages can function, Although satisfactory, it has higher spatial resolution than Moirner laser based inspection solution. If the slope of the surface is larger than the optical system NA, if the surface roughness is too large reflection does not easily achieved, but a so that the correct shape even if the nature of the reflection of only the material surface is smooth and does not easily made to measure.

01: first linear polarizer 02: first light splitter
03: objective lens 04: second optical splitter
05: fourth linear polarizer 06: reference mirror
07: second linear polarizer 08: sample
09: Third optical splitter 10: Third linear polarizer
11: first imaging lens 12: first detector
14: fifth linear polarizer 15: mirror
16: second imaging lens 17: second detector
18: Alignment device

Claims (5)

A WSI (White Scanning Interferometer) for acquiring optical interference data for the sample 08 and an EDF (Extender Depth of Focus) for acquiring interferenceless optical data for the sample 08 are divided into a plurality of optical splitters 02, ) And the linear polarizers (01, 05, 07, 10, 14), and the slope of the sample (08) surface is larger than the NA (Numerical Aperture) of the optical system without mutual influence, the surface roughness is too large, Dimensional shape measuring device is configured so that the accurate shape can be measured even when the surface is smooth but the reflection is not good due to the nature of the material.
The method of claim 1,
In the WSI,
A first linear polarizer (01) for linearly polarizing unpolarized light emitted from a coaxial illumination;
A part of the linearly polarized light is transmitted, and a part of the light is reflected by the first light splitter (02);
An objective lens 03 for collecting light transmitted through the first optical splitter 02;
A second light splitter (04) for reflecting and transmitting the light transmitted through the objective lens (03);
A second linear polarizer (07) for linearly polarizing the light transmitted through the second light splitter (04) and irradiating it with a sample (08);
A fourth linear polarizer (05) for linearly polarizing the light reflected by the second light splitter (04);
A reference mirror (06) for reflecting light passing through the fourth linear polarizer (05) to generate an optical path difference with light transmitted through the second optical splitter (04) to induce optical interference;
And a third linear polarizer 10 for linearly polarizing the light reflected from the sample 08 and the reference mirror 06 and guiding the light through the first imaging lens 11 to the first detector 12, Dimensional shape measuring device.
The method of claim 2,
The first and third linear polarizers (01, 10) are polarizers that transmit only light in a 45 ° direction;
The second linear polarizer 07 is a polarizer that transmits only light in the 90 占 direction;
And the fourth linear polarizer (05) is a polarizer that transmits only light in the 0 占 direction.
The method of claim 2,
The EDF,
A fifth linear polarizer 14 for linearly polarizing the light reflected from the sample 08 among the light reflected from the third optical splitter 09 so as to pass only the light reflected from the sample 08;
A mirror 15 for vertically reflecting the polarized light through the fifth linear polarizer 14;
And a second imaging lens (16) that collects the light reflected through the mirror (15) and makes it detectable through the second detector (17).
The method of claim 4,
And the fifth linear polarizer (14) is a polarizer that transmits only light in the 0 占 direction.

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