TW202120913A - Optical measuring method - Google Patents

Abstract

The present invention discloses an optical measuring method for measuring a surface of an object. The method comprises the following steps. First, an input light beam is provided. Then, a spatial light modulator, having a plurality of pixels, is provided in the light path of the input light beam, and the plurality of pixels selectively convert the input light beam into a testing light beam. The spatial light modulator can be controlled to activate a first pixel group among the plurality of pixels for not modulating the input light beam, and the first pixel group corresponds to a positioning mark on the surface of the object. Then, a first surface image and a second surface image, corresponding to the surface of the object, are obtained at a first time and a second time respectively. Then, the first surface image and the second surface image are aligned according to the positioning marks therewithin.

Description

Optical measurement method

The present invention relates to an optical measurement method, in particular to an optical measurement method for analyzing the surface image of an object.

After the product is manufactured, it will go through a certain test procedure to check the quality of the product. Generally speaking, people will rely on manpower to check whether the appearance of the product is defective, or by observing the appearance of the product to determine whether the function is normal. However, the structure of some products is relatively detailed, and sometimes it is impossible to require personnel to detect defects with the naked eye. Traditionally, when the naked eye cannot tell whether there is a defect, the appearance of the product can be captured with the help of a camera, and the appearance of a specific area of the product can be checked by zooming in on the captured image. For example, after wafer epitaxy is completed, the surface of the wafer is often photographed by a camera, and the epitaxial quality of each component in the wafer is checked by the surface image of the wafer.

Due to the very small size of the components in the wafer, the surface image often needs to have a relatively high resolution in order to check the epitaxial quality in detail. However, in order to improve the image resolution, the method of combining multiple images into a single image is often used. However, due to the vibration of the camera or the displacement of the wafer, the captured surface image is offset and the resolution is not good. Happening. Therefore, the industry needs a new optical measurement method that can effectively calibrate the surface image when the surface image is offset, so as to improve the resolution of the surface image.

The invention provides an optical measurement method, which avoids the positioning mark of the object when the structured light is projected onto the surface of the object. In this way, when shooting the surface image of the object, it will be found that the positioning mark is not interfered by the structured light, making the surface image easier to perform subsequent alignment and correction procedures.

The present invention provides an optical measurement method for measuring the surface of an object. The optical measurement method includes the following steps. First, provide input light. On the optical path of the input light, a spatial light modulator is provided. The spatial light modulator has a plurality of pixels for selectively modulating the input light into a test light. In addition, the spatial light modulator is controlled so that the first pixel group of the plurality of pixels does not modulate the input light, and the first pixel group corresponds to the position of the positioning mark on the surface. And, the first surface image and the second surface image of the surface are obtained at the first time and the second time respectively. And, according to the positioning marks in the first surface image and the second surface image, the first surface image and the second surface image are aligned.

In some embodiments, the plurality of pixels of the spatial light modulator may correspond to a first pattern at a first time, and the plurality of pixels of the spatial light modulator may correspond to a second pattern at a second time. In addition, the step of aligning the first surface image and the second surface image according to the positioning marks in the first surface image and the second surface image includes the following steps. First, locate the positioning mark in the first surface image, and generate the first coordinate accordingly. In addition, the positioning mark in the second surface image is positioned, and the second coordinate is generated accordingly. In addition, the first coordinate and the second coordinate are compared, and the first offset value is calculated. And, according to the first offset value, the second surface image is compensated so that the second surface image is aligned with the first surface image.

In some embodiments, the first surface image may correspond to the first imaging range of the surface, and the second surface image may correspond to the second imaging range of the surface, and the first imaging range is not equal to the second imaging range. In addition, in the step of aligning the first surface image and the second surface image, it is further possible to set the area where the first image capturing range and the second image capturing range overlap on the surface as the intersection image capturing range. In addition, it is possible to remove data outside the intersection of the first surface image and the second surface image.

In some embodiments, the optical measurement method may further include the following steps. First, the initial surface image of the surface can be obtained in advance. In addition, the position of the positioning mark in the initial surface image can be calculated, and the calculation result can be generated accordingly. Moreover, the first pixel group may be selected from the plurality of pixels according to the calculation result, so that the first pixel group corresponds to the position of the positioning mark in the initial surface image. In addition, the first pixel group may correspond to the non-projection range on the surface, the area of the non-projection range is larger than the area of the positioning mark, and the center position of the non-projection range may be substantially equal to the center position of the positioning mark.

In summary, the optical measurement method provided by the present invention avoids the positioning mark of the object when the structured light is projected onto the surface of the object. In addition, the optical measurement method provided by the present invention can use positioning marks to overlap surface images taken multiple times. Since the positioning marks are not interfered by structured light, the surface images taken multiple times are easier to perform subsequent alignment and correction procedures.

The features, objectives and functions of the present invention will be further disclosed below. However, the following are only examples of the present invention, and should not be used to limit the scope of the present invention, that is, all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention will still be the essence of the present invention. Without departing from the spirit and scope of the present invention, it should be regarded as a further implementation aspect of the present invention.

Please refer to FIGS. 1 and 2A together. FIG. 1 is a schematic diagram of an optical measurement system according to an embodiment of the present invention, and FIG. 2A is a schematic diagram of an object surface according to an embodiment of the present invention. As shown in the figure, the optical measurement method disclosed in the present invention can be applied to the optical measurement system 1, and the optical measurement system 1 can be used to detect an object 20. Here, the object 20 may be a wafer or a carrier board for loading the component 200 under test. The component under test 200 is disposed on the surface 20a of the object 20, and can be a chip, a die, a panel, or a circuit, which is not limited in this embodiment. In addition, the surface 20a of the object 20 may also have a positioning mark 202. In practice, the positioning mark 202 may be used to align the object 20 during detection. In addition, the optical measurement system 1 shown in FIG. 1 may have a light source 10, a lens 11, a beam splitting unit 12, a lens 13, a spatial light modulator 14, a lens 15, an image capture device 16, and a processing unit 17. , The optical architecture of the optical measurement system 1 is described below.

The light source 10 is used to provide input light. Although FIG. 1 shows that the light source 10 is a point light source, this embodiment is not limited. For example, the light source 10 may also be a surface light source. In addition, the light source 10 may be a white light source or a non-coherent light source, so the input light can be a white light light or a non-coherent light source. Here, the input light provided by the light source 10 enters the lens 11, and the function of the lens 11 is to convert the input light from the point light source into parallel light. Those with ordinary knowledge in the relevant technical field should understand that the light source 10 is roughly at the focal position of the lens 11, so that the input light passing through the lens 11 can be roughly regarded as a plane light. Of course, if the light source 10 is originally a parallel surface light source, the lens 11 may not be required in practice.

In addition, a beam splitting unit 12 and a spatial light modulator 14 may also be provided on the optical path of the input light. In the example shown in FIG. 1, the spatial light modulator 14 can be disposed between the lens 11 and the beam splitting unit 12, and the spatial light modulator 14 can convert at least part of the input light into test light, wherein the test light can be For example, the first structured light. In practice, the beam splitting unit 12 may be an optical beam splitter, which can reflect the test light from the spatial light modulator 14 to the lens 13 so that the test light can irradiate the object 20 through the lens 13. In an example, the input light and the test light modulated by the spatial light modulator 14 may be in the same direction, and the test light reflected by the light splitting unit 12 may be in a direction perpendicular to the input light.

The spatial light modulator 14 may have a plurality of pixels, and the plurality of pixels may be arranged in an array form. Each "pixel" referred to herein can be composed of liquid crystals, and the plurality of pixels can be selected in a light-transmissive state or a non-transparent state, so as to determine whether the test light can pass or the ratio of passing. For example, the spatial light modulator 14 can determine which pixels are turned on or partially turned on, and which pixels are turned off according to the control command cmd provided by the processing unit 17. In one example, the spatial light modulator 14 in FIG. 1 may have a transmissive pixel array, and the transmissive pixel array may have a liquid crystal layer (not shown), which is controlled by the control command cmd. The rotation direction of the liquid crystal in the liquid crystal layer determines the proportion of test light that can pass through a specific pixel. To facilitate the description of the spatial light modulator 14 of this embodiment, please refer to FIG. 1, FIG. 2A and FIG. 2B together. FIG. 2B is a schematic diagram of the spatial light modulator according to an embodiment of the present invention. As shown in the figure, the spatial light modulator 14 may have a plurality of pixels 140 arranged in an array, and the pixels 140 may be controlled by a control command cmd to adjust the proportion of test light passing through.

In an example, there is a spatial correspondence between the plurality of pixels 140 and the surface 20a of the object 20. For example, any pixel 140 can correspond to a specific position on the surface 20a. Conversely, any position on the surface 20a can also correspond to a specific pixel 140 in the spatial light modulator 14. After the corresponding relationship between the plurality of pixels 140 and the surface 20a is established, some of the pixels 140 can be defined as the first pixel group 142, and the first pixel group 142 will roughly correspond to the position of the positioning mark 202 on the surface 20a . In practice, in the spatial light modulator 14 provided in this embodiment, the first pixel group 142 can be regarded as an area where the test light is not modulated, that is, the pixels 140 in the first pixel group 142 can pass all the test light. For example, the first pixel group 142 corresponds to a non-projection range on the surface 20a, the center position of the non-projection range is approximately equal to the center position of the positioning mark 202, and the area of the non-projection range is slightly larger than that of the positioning mark 202. Occupies area.

Taking a practical example, if it is known that a batch of similar objects 20 is to be repeatedly detected, the processing unit 17 may pre-store the correspondence between the pixels 140 and the surface 20a, and may also pre-store the position of the positioning mark 202. In other words, since the processing unit 17 pre-stores the correspondence between the pixels 140 and the surface 20a, it is possible to find out which pixels 140 correspond to the surrounding area of the positioning mark in the initial surface image. Then, the processing unit 17 sets a plurality of pixels 140 corresponding to the area around the positioning mark in the initial surface image as the first pixel group 142. In one example, in order to quickly complete the step of setting the first pixel group 142, the resolution of the initial surface image may be low or not fully focused, as long as the processing unit 17 can see the positioning marks in the initial surface image. , Which can meet the scope of the initial surface image of this embodiment.

On the other hand, this embodiment does not limit the spatial light modulator 14 to have a transmissive pixel array. For example, the spatial light modulator 14 may also have a reflective pixel array. For example, if the pixel 140 has a reflective structure, the pixel 140 may be composed of a liquid crystal layer and a mirror. Here, the pixel 140 can also determine the proportion of the test light reflected by the mirror by controlling the rotation direction of the liquid crystal in the pixel. In addition, the reflective pixels 140 may have no liquid crystal layer but only a mirror. For example, each pixel 140 may be a small mirror. The control command cmd can determine which pixels 140 can reflect the test light to the surface 20a. Similarly, even though the pixels 140 have a reflective structure, the first pixel group 142 can still be regarded as an area where the test light is not modulated, that is, the pixels 140 in the first pixel group 142 can allow all the test light to be reflected to the surface. 20a. In addition, the spatial light modulator 14 may be used in conjunction with a polarizer. However, since the function and use of the polarizer can be understood by those with ordinary knowledge in the technical field, and it is not the focus of the present invention, it is not here. To repeat.

After being reflected by the surface 20 a of the object 20, the test light can pass through the lens 13 and be directed to the spectroscopic unit 12 again. Due to the optical characteristics of the light splitting unit 12, the light from the lens 13 can directly penetrate the light splitting unit 12 and enter the lens 15 and then is focused by the lens 15 and guided to the image capturing device 16. In one example, the image capturing device 16 may be disposed on one side of the beam splitting unit 12 to receive the reference light reflected from the lens 13 and the light reflected from the surface 20 a of the object 20. In one example, in order to clearly see the surface 20a at a certain height, the image capturing device 16 may capture multiple surface images of the object 20 at multiple consecutive time points to improve the resolution of the surface image.

For example, the image capturing device 16 can obtain the first surface image of the surface 20a at the first time, and the image capturing device 16 can obtain the second surface image of the surface 20a at the second time. The first time and the second time can be It is two shooting time points one after another, and this embodiment is not limited here. For the convenience of description, please refer to FIGS. 1, 2A, 2B, 3A and 3B together. FIG. 3A is a schematic diagram of a first surface image according to an embodiment of the present invention, and FIG. 3B is a schematic diagram of a first surface image according to an embodiment of the present invention. A schematic diagram of the second surface image of an embodiment. As shown in the figure, at the first time, the spatial light modulator 14 can modulate the test light into the first structured light, so that the image capturing device 16 can shoot the first structured light and irradiate the surface 20a to obtain the first surface image 3. In practice, since the first structured light may have a specific pattern, if the positioning mark 202 on the surface 20a is also projected on the specific pattern, it may be difficult to distinguish in the first surface image 3. Therefore, the spatial light modulator 14 of this embodiment will control the pixels 140 in the first pixel group 142 so that the pixels 140 in the first pixel group 142 do not modulate the test light, so that the positioning mark 202 on the surface 20a will not be affected. A specific pattern is projected.

In other words, because the pixels 140 in the first pixel group 142 do not modulate the test light, the positioning marks 30 in the first surface image 3 are not projected on the first structured light, so that the positioning marks 30 can be read easily and clearly take out. In addition, since other pixels 140 outside the first pixel group 142 normally modulate the test light, other parts on the surface 20a of the object 20 (for example, the device under test 200) are projected on the first structured light. The object 20 can also be detected normally.

Similarly, at the second time, the spatial light modulator 14 can modulate the test light into the second structured light, so that the image capturing device 16 can shoot the second structured light and irradiate the surface 20a to obtain the second surface image 4. Here, the second structured light may have a different phase from the first structured light, or the second structured light may have a different pattern from the first structured light, which is not limited in this embodiment. As mentioned above, the spatial light modulator 14 of this embodiment also controls the pixels 140 in the first pixel group 142 so that the pixels 140 in the first pixel group 142 do not modulate the test light, so that the positioning mark on the surface 20a 202 will not be projected on the second structured light. Since the pixels 140 in the first pixel group 142 do not modulate the test light, the positioning marks 40 in the second surface image 4 can also be read out easily and clearly.

In a practical example, when the image capturing device 16 successively shoots the first surface image 3 and the second surface image 4, some undesirable factors may cause the object 20 to shift relative to the image capturing device 16 . At this time, the processing unit 17 of this embodiment can receive the first surface image 3 and the second surface image 4, and use the positioning mark 30 in the first surface image 3 and the positioning mark 40 in the second surface image 4 to convert The first surface image 3 and the second surface image 4 are aligned. Please refer to FIG. 4. FIG. 4 is a schematic diagram illustrating the offset of the positioning mark according to an embodiment of the present invention. As shown in the figure, assuming that the positioning mark 30 in the first surface image 3 defines a center point A, the processing unit 17 may give the center point A a coordinate (a1, a2) for the convenience of calculation. Similarly, the processing unit 17 can find the positioning mark 40 in the second surface image 4, and give the center point B a coordinate (b1, b2) in the same coordinate system.

When the coordinates of the center point A and the center point B are not the same, it can be known that the image capturing device 16 or the object 20 vibrated between the first time and the second time, causing the object 20 to deviate from the image capturing device 16 shift. Therefore, the processing unit 17 may first determine the degree of deviation between the center point A and the center point B (that is, the first offset value). The first offset value may be b1-a1 in the first direction, and in the second direction. The direction can be b2-a2. Then, the processing unit 17 may choose to use the first surface image 3 as a basis to translate the second surface image 4 based on the first offset value. For example, moving the entire second surface image 4 in the first direction-(b1-a1), and in the second direction-(b2-a2), so that the second surface image 4 can overlap the first surface image 3. In this way, the processing unit 17 completes the alignment operation of the first surface image 3 and the second surface image 4.

In an example, the processing unit 17 may not calculate the offset degree of the positioning mark 30 and the positioning mark 40 based on the center point A and the center point B. For example, the processing unit 17 may also select other points or lines that are conveniently defined to calculate the The first offset value. In addition, if there is a relative rotation between the object 20 and the image capturing device 16, the processing unit 17 can also calculate the respective positions of the positioning mark 30 and the positioning mark 40 based on a combination of multiple points, points and lines or lines and lines. Angle to determine the degree of rotation of the positioning mark 30 and the positioning mark 40. In other words, the first offset value may not only be used to indicate the degree of translation, but also may be used to indicate the degree of rotation, which is not limited in this embodiment.

In addition, since the shooting range of the image capturing device 16 should be fixed, if the object 20 is offset relative to the image capturing device 16 between two shots, those with ordinary knowledge in the technical field should understand that the image The range of the frame captured by the capture device 16 should be slightly different these two times. That is, the first surface image 3 may correspond to the first imaging range of the surface 20a, and the second surface image 4 may correspond to the second imaging range of the surface 20a, and the first imaging range is not equal to the second imaging range. On the other hand, since the first image capturing range is not equal to the second image capturing range, the processing unit 17 can also crop the first surface image 3 and the second surface image 4, leaving only the first image capturing range and the second image capturing range. The image content at the overlap (intersection acquisition range). In practice, even if the object 20 is shifted relative to the image capturing device 16, it will not shift too much, and most of it will be within an acceptable level. Therefore, the cut-out parts of the first surface image 3 and the second surface image 4 are also the edges of the image frame, and will not affect the purpose of detecting the device under test 200.

In one example, after the processing unit 17 completes the alignment operation of the first surface image 3 and the second surface image 4, it is also possible to combine the first surface image 3 and the second surface image 4, so that the combined surface image can have more High resolution, and can show complete details. Of course, this embodiment does not limit the processing unit 17 to only align two surface images. For example, if the image capture device 16 continuously captures multiple surface images, the processing unit 17 can also align or combine these surface images in sequence.

It is worth mentioning that the processing unit 17 does not necessarily have to store the correspondence between the pixels 140 and the surface 20a in advance, and it does not have to store the positions of the positioning marks 202 in advance. For example, if different objects are frequently detected, the processing unit 17 may first allow the image capturing device 16 to capture an initial surface image of the surface 20a of the object 20 before the formal test. Then, the processing unit 17 can calculate the position of the positioning mark 202 in the initial surface image to generate a calculation result accordingly. In addition, the processing unit 17 may select the first pixel group 142 from the plurality of pixels 140 according to the calculation result, so that the first pixel group 142 corresponds to the position of the positioning mark in the initial surface image.

In order to explain the steps of the optical measurement method of the present invention again, please refer to FIGS. 1 to 5 together. FIG. 5 shows a flowchart of the optical measurement method according to an embodiment of the present invention. As shown in the figure, in step S50, the light source 10 provides input light. In step S52, a spatial light modulator 14 is provided on the optical path of the input light. The spatial light modulator 14 has a plurality of pixels 140 for selectively modulating the input light into a test light. In step S54, the processing unit 17 may control the spatial light modulator 14 so that the first pixel group 142 of the plurality of pixels 140 does not modulate the input light, and the first pixel group 142 corresponds to the position on the surface 20a of the object 20 Mark the location of 202. Then, in step S56, the image capturing device 16 obtains the first surface image 3 and the second surface image 4 of the surface 20a at the first time and the second time, respectively. Then, in step S58, the processing unit 17 can align the first surface image 3 and the second surface image 4 according to the positioning marks 30 and the positioning marks 40 in the first surface image 3 and the second surface image 4. The details of other steps of the optical measurement method of the present invention have been described in detail in the foregoing embodiment, and will not be repeated here.

In summary, the optical measurement method provided by the present invention avoids the positioning mark of the object when the structured light is projected onto the surface of the object. In addition, the optical measurement method provided by the present invention can use positioning marks to overlap surface images taken multiple times. Since the positioning marks are not interfered by structured light, the surface images taken multiple times are easier to perform subsequent alignment and correction procedures.

1: Optical measurement system 10: light source 11: lens 12: Spectroscopic unit 13: lens 14: Spatial light modulator 140: pixels 142: The first pixel group 15: lens 16: Image capture equipment 17: Processing unit 20: Object 20a: surface 200: component under test 202: Positioning mark 3: The first surface image 30: Positioning mark in the image 4: Second surface image 40: Positioning mark in the image A, B: The center point of the positioning mark in the image cmd: control command S50~S58: Step flow

FIG. 1 is a schematic diagram of an optical measurement system according to an embodiment of the present invention.

2A is a schematic diagram showing the surface of an object according to an embodiment of the invention.

FIG. 2B is a schematic diagram of a spatial light modulator according to an embodiment of the invention.

FIG. 3A is a schematic diagram of a first surface image according to an embodiment of the invention.

FIG. 3B is a schematic diagram of a second surface image according to an embodiment of the invention.

FIG. 4 is a schematic diagram showing the offset of the positioning mark according to an embodiment of the present invention.

FIG. 5 is a flowchart showing the steps of an optical measurement method according to an embodiment of the present invention.

S50~S58: Step flow

Claims (8)

An optical measurement method for measuring a surface of an object. The optical measurement method includes: Provide an input light; On an optical path of the input light, a spatial light modulator is provided, the spatial light modulator has a plurality of pixels, and the pixels are used for selectively modulating the input light into a test light; Controlling the spatial light modulator so that a first pixel group of the pixels does not modulate the input light, and the first pixel group corresponds to the position of a positioning mark on the surface; Acquiring a first surface image and a second surface image of the surface at a first time and a second time respectively; and Aligning the first surface image and the second surface image according to the positioning mark in the first surface image and the second surface image. The optical measurement method according to claim 1, wherein the step of aligning the first surface image and the second surface image according to the positioning mark in the first surface image and the second surface image includes : Positioning the positioning mark in the first surface image to generate a first coordinate accordingly; Positioning the positioning mark in the second surface image to generate a second coordinate accordingly; Compare the first coordinate with the second coordinate to calculate a first offset value; and According to the first offset value, the second surface image is compensated so that the second surface image is aligned with the first surface image. The optical measurement method according to claim 1, wherein the first surface image corresponds to a first image capturing range of the surface, the second surface image corresponds to a second image capturing range of the surface, and the first image capturing The range is not equal to the second imaging range. The optical measurement method according to claim 3, wherein the step of aligning the first surface image and the second surface image further comprises: Setting the area where the first imaging range and the second imaging range overlap on the surface as an intersection imaging range; and Remove the data of the first surface image and the second surface image outside the intersection image capturing range. The optical measurement method described in claim 1, further including: Obtaining an initial surface image of the surface in advance; Calculate the position of the positioning mark in the initial surface image to generate a calculation result; and According to the calculation result, the first pixel group is selected from the pixels so that the first pixel group corresponds to the position of the positioning mark in the initial surface image. The optical measurement method according to claim 5, wherein the first pixel group corresponds to a non-projection range on the surface, and the area of the non-projection range is larger than the area of the positioning mark. The optical measurement method according to claim 6, wherein the center position of the non-projection range is substantially equal to the center position of the positioning mark. The optical measurement method according to claim 1, wherein the pixels of the spatial light modulator correspond to a first pattern at the first time, and the pixels of the spatial light modulator correspond to a first pattern at the second time. Two patterns.

Images