TWI398623B - Measurement method of interference system - Google Patents

Description

Measurement method of interference system

The invention relates to a measuring method, in particular to a measuring method of an interference system.

In the field of measurement technology, there are many measurement methods widely used, and the interference system is one of them. In general, the interference system can be used to measure the two-dimensional and three-dimensional surface topography of the object to be tested. .

Please refer to the first figure, the first picture is a schematic diagram of the object to be tested. The white light interferometry system applies the principle of optical interference. First, the white light illumination system emits parallel light through the collimating lens, and after 45-degree spectroscopic reflection, it enters the interference microscope objective lens, and the microscope objective beam divides the incident light into two lights, one through Referring to the specular reflection, the other is reflected by the object to be tested 100 placed on the scanning platform, and the last two reflected lights are again combined and interfered by the difference in optical path difference, and the interference image is then focused by the 45-degree beam splitter and the imaging objective lens. Imaging on an image sensing device.

By interfering with the movement of the microscope objective or the scanning platform along the vertical scanning path D1, the image sensing device can receive a series of interference images generated by different optical path differences, and the computer can be used for each of the interference images. A pixel is analyzed to obtain a surface topography of the object 100 to be tested.

Please refer to the second figure, which is a two-dimensional topographic image with interference fringes. Although the white light interference system measures the object to be tested 100, the surface topography height information of the object to be tested 100 can be obtained through the above analysis manner, and the three-dimensional topographic image of the object to be tested 100 is obtained by the height information. Since the interference microscopy lens produces an interference phenomenon when focusing, the two-dimensional topographical image I0 received by the image sensing device contains the interference fringe S, and the topography boundary of the object to be tested 100 cannot be clearly distinguished.

However, in order to solve the problem that the two-dimensional topographic image I0 contains interference fringes S, two methods are developed, one of which is to obtain a plurality of interference images by vertical scanning in the interference system, and to obtain a plurality of interference images by a plurality of interference images. After obtaining the three-dimensional topographic image of the object to be tested 100, the position of the image sensing device is adjusted to the two reflected light without causing interference of the light, so as to avoid the interference fringe S in the two-dimensional topographic image I0. However, the three-dimensional topographic image and the two-dimensional topographical image I0 of the test object 100 are respectively obtained by different scanning processes, so the measurement method is more complicated than the conventional measurement method. .

Another measurement method is that the interference system obtains a plurality of interference images by vertical scanning, and obtains a three-dimensional shape image of the object 100 by a plurality of interference images, and then replaces the interference microscope objective with a non-interference display. The micro objective lens avoids the generation of light interference and avoids the interference fringe S contained in the two-dimensional topographic image I0. However, this measurement method requires not only an unnecessary scanning process but also more than the conventional measurement method. The preparation of a set of non-interfering microscope objectives also adds to the cost of the hardware.

Accordingly, the main object of the present invention is to provide a measurement method for an interference system. The purpose of the measurement method is to obtain an interference-free stripe without increasing the hardware cost and the image flow of the sample to be tested. A two-dimensional image of the object.

An interference system measuring method is used for vertical scanning of an object to be measured by an interference system along a vertical scanning path, and a plurality of interference images are sequentially generated at a plurality of scanning heights of the vertical scanning path to utilize the interference images. To generate a two-dimensional topographic image, the measuring method comprises the steps of: sampling each pixel point in each interference image to obtain an interference region area of each interference image, and using the scanning height corresponding to the interference image Establishing a height-interference area correspondence ratio information with the interference area area; using the height-interference area correspondence ratio information, extracting relative peaks in the interference area area corresponding to the interference images, thereby extracting a scan height corresponding to the relative peak value, and It is defined as a feature height; and the interference image of the first predetermined number of sheets of the feature height and the height of the adjacent feature is superimposed to generate a two-dimensional topographic image.

Compared with the conventional interference system measurement method, the present invention can obtain a two-dimensional image of the object to be tested without interference fringes directly after obtaining an interference image by vertical scanning in the interference system. There is no need to increase the cost of hardware or to carry out additional image processing of the object to be tested, which not only saves costs, but also makes the measurement process relatively simple.

The specific embodiments of the present invention will be further described by the following examples and drawings.

The invention relates to a measuring method, in particular to a measuring method of an interference system. The invention is illustrated by the following description of the preferred embodiments of the invention, and is not intended to limit the invention. The contents of this preferred embodiment are detailed below.

Please refer to the first figure first. The first picture is a schematic diagram of the object to be tested. The measuring method of the interference system of the present invention is used for vertically scanning the object to be tested 100 along the vertical scanning path D1 of the interference system, and sequentially generating a plurality of interference images respectively at a plurality of scanning heights of the vertical scanning path D1. These interference images are utilized to generate a two-dimensional topographic image; wherein the type of interference system has no effect on the measurement method of the present invention, and the interference system may be a Mirau white light interferometer, a Michelson white light interferometer, a Linnik white light interferometer or the like. A common interferometer.

Please continue to refer to the third figure, the third figure is the height-interference area correspondence ratio information. The measuring method of the interference system of the present invention comprises several steps. First, each pixel point in each interference image must be sampled to obtain the interference area of each interference image, and corresponding to each interference image. The scan height and the interference area area establish a height-interference area correspondence ratio information. Taking the object to be tested 100 of the first figure as an example, since the top surface 11 of the object to be tested 100 occupies most of the area of the upper view, the height is In the interference area correspondence ratio information, the scanning height corresponding to the top surface 11 and the adjacent scanning height are displayed to occupy a considerable area, and in this embodiment, in order to facilitate the operator's observation, each scanning height can be correspondingly The area of the interference area is shown as a percentage state.

Then, using the height-interference area correspondence ratio information, a relative peak is obtained in the areas of the interference regions corresponding to the interference images, thereby obtaining the scanning height corresponding to the relative peak, and defining the feature height H1.

Please refer to the fourth and fifth figures. The fourth figure is a schematic diagram of the scanning sampling points of the interference system in an interference wave packet range. The fifth figure is to extract some interference images from all the interference images to be superimposed. schematic diagram. After the feature height H1 is determined, the interference image of the feature height H1 and the first predetermined number of frames of the adjacent feature height H1 can be extracted from all the interference images to perform numerical processing to generate a two-dimensional image. Preferably, in the embodiment, the numerical processing is an image superimposing process; further, in the preferred embodiment, if the interfering system scans the object 100 vertically along the vertical scanning path D1. In the range of one interference wave packet of the vertical scanning path D1, a second predetermined number of interference images are generated, in other words, a second predetermined number of samples are taken within the range of one interference wave packet. Then, the first predetermined number of sheets described above may be equal to half of the second predetermined number of sheets.

Please also refer to the sixth figure. The sixth picture is a schematic diagram of the two-dimensional shape image without interference fringes. For example, when the interference system samples 11 scanning heights in an interference wave packet and generates 11 interference images, after obtaining the feature height H1, the feature height H1 can be extracted from all the interference images. The interference image Ibase is superimposed on the interference image Ibase and the interference images I1 to I10 of the top and bottom of the adjacent feature height H1 to obtain a two-dimensional topographic image Ieng without interference fringes.

In addition, in the preferred embodiment, the process of superimposing the interference image Ibase and the interference images I1~I10 is mainly for the gray of each interference image I1~I10 and the interference image Ibase at each pixel. The difference of the order value is superimposed on the pixel corresponding to the two-dimensional topographical image Ieng, and the grayscale value of the two-dimensional topographical image Ieng pixel is divided by the number of sampling points in one interference wave packet, in this embodiment In the middle, by dividing 11 to normalize the gray scale range of the two-dimensional topographic image Ieng, a two-dimensional topographic image Ieng without interference fringes can be created by using multiple interference images.

In summary, compared with the conventional interference system measurement method, the present invention can obtain the two-dimensional interference image without interference fringes directly after obtaining a plurality of interference images by vertical scanning in the interference system. The shape image Ieng does not need to increase the hardware cost or perform additional image processing of the object to be tested, which not only saves cost, but also makes the measurement process simple.

In addition, the measuring method of the interference system of the present invention is not limited to the superimposing action of the interference image on a feature height H1. In the above embodiment, the object to be tested 100 has a groove, so in the third figure The height-interference area correspondence ratio information can be clearly found, and the relative peak value also has a relative peak value at another scanning height. Therefore, the relative peak value also corresponds to a feature height H2, and the measurement method can correspond to the interference image corresponding to the feature height H2. The interference images of the first predetermined number of sheets above and below the feature height H2 are superimposed to obtain a two-dimensional topographic image without interference fringes at the feature height H2 of the object to be tested; further, when to be tested When the object 100 has two or more characteristic heights H1 and H2, the interference images corresponding to the feature heights H1 and H2 and the interference images of all the first predetermined number of upper and lower levels of the feature heights H1 and H2 may be superimposed to obtain Another two-dimensional topographic image without interference fringes.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed.

100. . . Analyte

11‧‧‧ top surface

D1‧‧‧ vertical scan path

I0‧‧‧ two-dimensional image

Ibase‧‧ Interference image

I1~I10‧‧‧ interference image

Ieng‧‧‧ two-dimensional image

S‧‧‧ interference fringe

H1, H2‧‧‧ feature height

The first figure is a schematic diagram of the object to be tested;

The second figure is a two-dimensional topographic image with interference fringes;

The third figure is the height-interference area correspondence ratio information;

The fourth figure is a schematic diagram of the scanning sampling points of the interference system in an interference wave packet range;

The fifth figure is a schematic diagram of superimposing partial interference images from all interference images;

The sixth picture is a schematic diagram of a two-dimensional topographic image without interference fringes.

Ibase. . . Interference image

I1～I10. . . Interference image

Ieng. . . Two-dimensional image

Claims (6)

A method for measuring an interference system is used for performing an vertical scan of an object to be tested along a vertical scanning path by an interference system, and sequentially generating a plurality of interference images after a plurality of scanning heights of the vertical scanning path By using the interference images to generate a two-dimensional topographic image of the object to be tested without interference fringes, the method includes the following steps: (a) sampling each pixel in each interference image to Obtaining an interference region area of the interference image, and establishing a height-interference area correspondence ratio information by using the scanning height corresponding to the interference image and the interference region area; (b) using the height-interference area correspondence ratio information, Extracting a relative peak from the areas of the interference regions corresponding to the interference images, thereby capturing the scan height corresponding to the relative peaks and defining it as a feature height; and (c) capturing the feature height A numerical process is performed on the interference image adjacent to a first predetermined number of sheets above and below the height of the feature to generate the two-dimensional topographic image. The method for measuring an interference system according to claim 1, wherein the numerical processing is an image overlay processing. The method for measuring an interference system according to claim 1, wherein the height-interference area correspondence ratio information is used to record at each scanning height, and the area of the interference region in the corresponding interference image is occupied. Area percentage. The method for measuring an interference system according to claim 1, wherein when the interference system performs the vertical scanning of the object to be tested along the vertical scanning path, an interference wave packet is applied to the vertical scanning path. A second predetermined number of interference images are generated within the range. The method for measuring an interference system according to claim 1, wherein the first predetermined number of sheets is equal to half of the second predetermined number of sheets. A method for measuring an interference system is used for performing an vertical scan of an object to be tested along a vertical scanning path by an interference system, and sequentially generating a plurality of interference images at a plurality of scanning heights of the vertical scanning path. By using the interference images to generate a two-dimensional topographic image, the method includes the following steps: (d) sampling each pixel in each interference image to obtain an interference region area of the interference image, and And using the scan height corresponding to the interference image to establish a height-interference area correspondence ratio information; (e) using the height-interference area correspondence ratio information, the interference regions corresponding to the interference images Extracting at least two relative peaks in the area, thereby extracting the scan heights corresponding to the relative peaks and defining them as at least two feature heights; and (f) extracting the feature heights and the heights of the adjacent features The first predetermined number of interference images of the upper and lower sides are superimposed to generate the two-dimensional topographic image.