TWI568989B - Full-range image detecting system and method thereof - Google Patents

Description

Global image detection system and detection method thereof

The present invention relates to a detection system, and more particularly to a global image detection system and a detection method thereof.

As wafers become thinner, wafer warpage can be measured in millimeters (mm). Also, due to the increase in the amount of warpage, when the focus range of the general automatic optical inspection (AOI) system is not large enough and the speed of focusing is not fast enough, the focus of the automatic optical measuring system is not easy, and the detection time is prolonged. The detection results are not good, which affects the subsequent process.

In the prior art, the main focusing modes are divided into active focusing and passive focusing, wherein the passive focusing uses a coarse adjustment and a fine adjustment two-stage focusing, and the active focusing uses the projection of the light generated by the light source through the focusing grating. The objective lens is projected onto the surface of the object, and the raster image reflected by the object surface is phase-aligned with the original raster image to improve the focusing speed. However, the cost of active focusing is relatively high.

The invention relates to a global image detection system and detection thereof The method can overcome the lack of the prior art and improve the detection of the global image to improve the detection speed and accuracy.

According to an aspect of the invention, a global image detection system is provided, comprising a planar light source, an image capturing device, an optical position measuring device, a processing unit and a measuring module. The planar light source is used to project a light image with a periodic change on a test object. The image capturing device is configured to capture an image of the reflected light through one of the objects reflected by the object to be tested. The optical position measuring device is configured to detect relative coordinates of at least three measuring points on the object to be tested to fit a plane. The processing unit is configured to calculate a phase change after the phase shift of the reflected light image, and calculate a relative height distribution of the surface topography of the object to be tested according to the phase change, and calculate an absolute height of the surface topography of the object to be tested relative to the plane Distribution to get an absolute coordinate information. The measurement module detects the surface of the object to be tested based on the absolute coordinate information.

According to an aspect of the invention, a global image detection method is provided, comprising the following steps. A plane light source is projected onto the object to be tested with a periodically varying light image. The image is reflected by one of the reflections of the object to be tested. The relative coordinates of at least three measuring points on the object to be tested are detected to fit an absolute height coordinate system. The phase change after the phase shift of the reflected light image is calculated, and a relative height distribution of the surface topography of the object to be tested is calculated according to the phase change. Calculate an absolute height distribution of the surface topography of the object to be measured in the absolute height coordinate system to obtain an absolute coordinate information. The surface of the object to be tested is detected based on the coordinate information.

In order to better understand the above and other aspects of the present invention, the preferred embodiments are described below, and in conjunction with the drawings, the detailed description is as follows:

10‧‧‧Test object

11‧‧‧Light image

12‧‧‧ stripes

100‧‧‧Global Image Detection System

101‧‧‧Global image detection device

110‧‧‧ planar light source

120‧‧‧Processing unit

121‧‧‧Light Image Control Module

122‧‧‧Image Correction Module

123‧‧‧Computation Module

124‧‧‧ Phase Expansion Module

125‧‧‧ flattening module

130‧‧‧Image capture device

140‧‧‧Light sensing device

150‧‧‧Measurement module

160‧‧‧ Positioning platform

A, B, C‧‧‧ measuring points

θ1‧‧‧Rotation angle

L‧‧‧ distance

‧‧‧‧ angle

Z‧‧‧ Height

(x _o , y _o ) ‧ ‧ center position

(x _n , y _n ) ‧‧‧ alignment slot position

FIG. 1 is a flow chart of a global image detection method according to an embodiment of the invention.

FIG. 2 is a schematic diagram of a global image detection system according to an embodiment of the invention.

FIG. 3 is a schematic diagram of a global image detecting apparatus according to an embodiment.

FIG. 4 is a schematic diagram of an optical image of an embodiment.

FIG. 5 is a flow chart of a global image focusing method according to an embodiment of the invention.

Figure 6 shows the center position of the object to be tested, the position of the alignment groove, and the angle of rotation.

The global image detecting system and the detecting method thereof of the embodiment measure the surface topography and the relative height distribution of the object to be tested (for example, a wafer), and output reference coordinate information (for example, wafer center position and alignment) The position of the groove and the angle of rotation and the resolution of the image, etc., as the movement information of the measurement module (such as optical microscope or optical interferometer) and the positioning platform, shorten the focusing time, and enable the measurement module to do the point-by-point rapid amount Measurement.

Taking the wafer surface inspection as an example, the relative height distribution of the surface topography of the wafer is measured, and the relative height of the surface topography of the wafer and the reference coordinate information are provided to the measurement module to eliminate the traditional measurement. The module needs to perform the focus adjustment steps such as coarse adjustment and fine adjustment, and reduce the fine scan stroke to solve the focus problem caused by wafer warpage.

The embodiments are described in detail below, and the embodiments are only intended to be illustrative and not intended to limit the scope of the invention.

Please refer to FIG. 1 , which illustrates a flow chart of a global image detection method according to an embodiment of the invention. The global image detection method of this embodiment includes the following steps: in step S101, a light image with a periodic change is projected on a test object by a planar light source. In step S102, the reflected light image is reflected from one of the objects reflected by the object to be tested. In step S103, a phase change after the phase shift of the reflected light image is calculated, and a relative height distribution of the surface topography of the object to be tested is calculated according to the phase change. In step S104, relative coordinates of at least three measurement points on the object to be tested are detected to fit a plane. In step S105, an absolute height distribution of the surface topography of the object to be tested relative to the plane is calculated to obtain an absolute coordinate information. In step S106, the surface of the object to be tested is detected based on the absolute coordinate information.

Please refer to FIG. 2, which is a schematic diagram of a global image detection system according to an embodiment of the invention. The global image detection system 100 includes a planar light source 110, a processing unit 120, an image capturing device 130, a light sensing device 140, a measuring module 150, and a positioning platform 160. . The positioning platform 160 is used to carry an object to be tested 10, such as a wafer or a semiconductor substrate. For the arrangement and details of the planar light source 110, the processing unit 120, and the image capturing device 130, please refer to the description of FIGS. 3 and 4 together. Hereinafter, steps S101 to S103 of Fig. 1 will be described with reference to the global image detecting device 101 of Fig. 3.

Referring to FIG. 3 , the processing unit 120 includes an optical image control module 121 , an image correction module 122 , a calculation module 123 , a phase expansion module 124 , and a planarization module 125 . In step S101, the planar light source 110 is configured to project a light image 11 (refer to FIG. 4) having a periodic change on an object to be tested 10, and the light image 11 can be reflected by the object 10 to form a reflected light image. . The reflected light image has the same periodic variation as the light image 11 projected on the object to be tested 10, and the difference is only that when the surface of the object to be tested 10 has no slope change, the reflected light image does not shift or deform, just like the projection. Light image. However, when there is a slight slope change on the surface of the object to be tested 10, the reflected light image may be offset or deformed, and the offset δ y of the reflected light image is positively correlated with the amount of change in the slope of the surface of the object 10 to be tested, such as Relationship (1): δy = L [tan( α + 2 θ ) - tan( α )] (1) where L : distance between the planar light source 110 and the object to be tested 10

α : image capturing device 130 captures the angle of the image

θ: 10 surface slope variation when the object 10 under test surface inclination change amount [theta] is small, the equation can be simplified as ^{δy = 2 Lθ sec 2 α (} 2)

Therefore, the amount of change θ of the slope of the surface of the object 10 to be measured can be calculated by the offset δ y of the reflected light image.

Next, please refer to the optical image 11 of FIG. 4, which is composed of, for example, strips 12 of long strips that change periodically. In another embodiment, the light image may be composed of periodically varying concentric stripes. These light and dark stripes 12 can be generated by the sine wave or square wave of the period 2π by the signal processing in the planar light source 110, and then projected onto the object 10 by the planar light source 110 to form the optical image 11 having a periodic variation. The planar light source 110 is generated, for example, by a flat display, for a flat panel display. The control signal input by the optical image control module 121 is received, and the desired optical image 11 is generated by the brightness change of the plurality of pixel units in the flat display. In an embodiment, the width of each stripe 12 is determined by the number of corresponding pixel units, for example, 10 to 20, and can be determined by controlling the transmittance of liquid crystal molecules in the pixel unit. Stripes or dark stripes.

In step S102, the optical image control module 121 is, for example, a programmable control module for generating the optical image 11 and controlling the optical image 11 to move at least equal intervals along at least one direction with respect to the object 10 to be tested. To produce a phase shift. For example, the light image is moved at equal intervals by a three-step phase shift method or a four-step phase shift method to generate a plurality of light images (for example, six or eight). In Fig. 4, the direction in which the optical image 11 moves can be the direction in which the strips 12 of the strips are arranged (the X direction in the figure). In FIG. 2, after a predetermined number of optical images are generated, the image capturing device 130 can sequentially capture the reflected light images, and the image correcting module 122 performs distortion correction processing on the reflected light images. In addition, in order to obtain a two-dimensional phase map, the optical image control module 121 can respectively generate two orthogonal optical images, and move the optical images along the X direction or the Y direction to generate phase shifts in different directions. Of course, the embodiment is not limited to two orthogonal optical images, and may also be two optical images of any angle.

In the above, the three-step phase shift method needs to take three phase-shifted optical images, and the first image I ₁ and the second image I _{2 are} shifted by 2π/3, and the second image I ₂ and the third image. The phase shift of image I ₃ is 4π/3, and its simultaneous equation is as follows:

Where I ₀ is the intensity of the background light and A is the amplitude of the light wave. The phase value of each coordinate point (x, y) in the light image.

In addition, the four-step phase shift method requires four images of phase-shifted stripes, and the difference between the first image I ₁ and the second image I ₂ is π/2, and the second image I ₂ and the third image The phase shift of I ₃ is π, and the phase shift of the third image I ₃ and the fourth image I ₄ is 3π/2, and the simultaneous equation is as follows:

Where I ₀ is the intensity of the background light and A is the amplitude of the light wave. The phase value of each coordinate point (x, y) in the light image.

In step S103, due to the phase change of each coordinate point (x, y) △ It is proportional to the offset δ y of the reflected light image. Therefore, the calculation module 123 of FIG. 2 can calculate the phase change of each coordinate point (x, y) in the images. To know the surface topography of the object 10 to be tested. If the relation (2) is in the relationship, the phase changes △ The offset δy representing the reflected light image can be expressed as follows:

Where P : the period of the reflected light image

It can be known from the relation (3) that the variation amount θ of the surface slope of the object to be tested 10 can be changed by the phase Δ. Learned. Since the three-step phase shift method or the four-step phase shift method used above is based on the arc tangent (tan ^-1 ) function, and the phase is limited to between -π/2 and π/2, the phase map is not Continuous phase distribution map. To restore the discontinuous phase to the phase of the original continuous 0~Nπ period (N is an integer), the phase expansion operation is required.

Referring to FIG. 3, the phase unwrapping module 124 performs phase unwrapping on the phase values of the respective coordinate points to obtain a phase unwrapping map. In short, the phase unwrapping operation is to solve the problem that the adjacent two phase differences in the phase map exceed a certain limit by adding a subtraction of the difference to eliminate the cut line and restore it to continuous. Phase. Therefore, the phase values of the respective punctuation points in the optical image can be obtained by the phase shift and phase expansion methods.

Then, the planarization module 125 can planarize the phase unwrapped image to obtain a relative height distribution of the surface topography of the object 10 to be tested. In short, the flattening process compares the phase of each coordinate point to the same level to compare the amount of change to facilitate calculation of a relative height distribution of the surface topography of the object 10 to be tested. among them, The relative height distribution of each coordinate point on the object to be tested 10 is represented by Wi(x, y, z).

Referring to FIG. 5, a flowchart of a global image focusing method according to an embodiment of the present invention is illustrated. Steps S201 to S204 are projected as a planar light source 110 in step S201, as in steps S101 to S103 described above. To generate multiple periodic changes in the light image, and to capture multiple periodic changes in the reflected light image. In step S202, the reflected light image is subjected to distortion correction to correct the light image obliquely projected onto the object to be tested 10 to be orthographically projected to the light image of the object to be tested 10. The phase change after the phase shift of the reflected light image is calculated in step S203 to obtain the surface topography of the object 10 to be tested. In step S203, a relative height distribution of the surface topography of the object to be tested 10 is calculated based on the phase unwrapping result, expressed by Wi(x, y, z).

Next, please refer to steps S205 to S207, as in step S104 described above. In step S205, a uniform light image (strips 12 without periodic changes) is projected onto the object to be tested 10 by the planar light source 110, and the image capturing device 130 captures the reflected uniform light image. In step S206, the reflected uniform light image is subjected to distortion correction to correct the uniform light image obliquely projected onto the object to be tested 10 to be uniformly projected onto the uniform light image of the object to be tested 10. Then, according to the relative coordinates of at least three measuring points on the object 10 to be measured, a plane is fitted. As shown in Figure 6. In step S207, the processing unit 120 calculates the center position (x _o , y _o ) of the object to be tested 10 and the position of the alignment slot according to the planes fitted to the coordinate positions of the three measurement points A, B, and C ( The coordinate information such as x _n , y _n ) and the rotation angle θ1 and the image resolution are obtained to obtain a plane coordinate system of the object to be tested 10 . The device for detecting relative coordinates of at least three measuring points A, B, and C on the object to be tested 10 is, for example, a laser sensor or other light sensing device 140 having an optical positioning function, such as the second The figure shows.

Next, in step S208, the center position (x _o , y _o ) and the image resolution are used to link the coordinate coordinate system of the object to be tested 10 with other coordinate systems (for example, the coordinate system and measurement of the positioning platform 160). The coordinate system of the module 150), in addition, the rotation angle θ1 of the alignment groove is used to correct the rotation angle error when the object 10 is placed. In step S209, the height of the measurement module 150 is adjusted based on the absolute coordinate information to detect the surface of the object to be tested 10. Therefore, in FIG. 2, the processing unit 120 can control the positioning platform 160 to move the object to be tested 10 to the target position (x, y) according to the absolute coordinate information, and the measurement module 150 can adjust the height Z according to the absolute coordinate information. To adjust a focal length between the optical microscope or the optical interferometer and the object to be tested 10. In another embodiment, when the equivalent measurement module 150 includes a probe card electrical detection device, the gap between the probe card electrical detection device and the object to be tested 10 can be adjusted according to the absolute coordinate information to enable the detection. The needle card electrical detecting device is in electrical contact with the object to be tested 10.

For the calculation method of absolute coordinate information, please refer to the following. In step S105, after the processing unit 120 obtains the relative coordinates of the three measurement points A, B, and C, the coordinates of the three measurement points are fitted to a plane Q (x, y) according to the following calculation formula. , z), and superimposing the relative height distribution Wi(x, y, z) of the surface topography of the object to be tested 10 on the surface Q(x, y, z) to calculate the surface of the object to be tested 10 An absolute height distribution of the topography relative to the plane Q(x, y, z) yields an absolute coordinate information. This absolute coordinate information can be used as the absolute height coordinate system Zi(x, y, z) of the surface of the actual object 10 to be tested, wherein Zi(x,y,z)=Wi(x,y,z)+Q(x,y,z)-P(xi,yi,zi)

P(xi, yi, zi) is a coordinate of a reference coordinate point in the absolute height coordinate system (for example, one of the three measurement points A, B, and C).

In step S106, after the absolute measurement information is obtained by the equivalent measurement module 150, the surface of the object to be tested 10 can be detected according to the absolute coordinate information, such as focusing, scanning, or performing an electrical detection. The measurement module 150 is, for example, an optical microscope, an optical interferometer, or a probe card electrical detection device. Therefore, in the embodiment, when the global image detecting system 100 corrects the absolute height between the plurality of to-be-measured points (x _i , yi) on the object to be tested 10 and the measuring module 150 through the image height information, the processing is performed. The unit 120 moves the controllable measurement module 150 on the vertical axis and directly reaches the positioning without the need for coarse adjustment to save the focus time or the alignment time of the measurement module 150.

In the global image detecting system and the detecting method thereof disclosed in the above embodiments of the present invention, the processing unit controls the positioning platform to move the object to be tested to a target position according to the absolute coordinate information, and the measuring module can control the height according to the absolute coordinate information. The measurement module moves on the vertical axis and directly reaches the positioning, so the focusing speed is very fast, and it is convenient for quick detection point by point. Compared with the general passive focus, the system uses the coarse adjustment and the fine adjustment two-stage method to obtain the focus quickly, and the cost is relatively low compared with the active focus, thus breaking the bottleneck of the prior art. In addition, the system can measure the surface topography (such as bump height distribution), surface defects and warpage on the object to be tested to meet the various requirements of the system.

In conclusion, the present invention has been disclosed in the above preferred embodiments, and is not intended to limit the present invention. General knowledge in the technical field to which the present invention pertains Various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

10‧‧‧Test object

100‧‧‧Global Image Detection System

110‧‧‧ planar light source

120‧‧‧Processing unit

130‧‧‧Image capture device

140‧‧‧Light sensing device

150‧‧‧Measurement module

160‧‧‧ Positioning platform

Z‧‧‧ Height

Claims (12)

A global image detection system includes: a planar light source for displaying a periodically varying optical image on a test object, wherein the planar light source is generated by a flat display; and an image capture device for capturing The object to be tested reflects a planar light source image; a light sensing device is configured to detect coordinates of at least three measuring points on the object to be tested to fit a plane; and a processing unit for calculating the Offset or deformation offset of the planar light source image, and calculating a relative height distribution of the surface topography of the object to be tested according to the offset, and calculating an absolute surface surface of the object to be tested relative to the plane The height is distributed to obtain an absolute coordinate information; and a measuring module detects the surface of the object to be tested according to the absolute coordinate information. The global image detection system of claim 1, further comprising a positioning platform for carrying the object to be tested, the positioning platform moving the object to be tested to a target position according to the absolute coordinate information. The global image detection system of claim 1, wherein the planar light source projects a uniform optical image to the object to be tested, so that the processing unit obtains a coordinate of a plane coordinate system according to the fitted plane. News. The global image detection system of claim 1, wherein the measurement module comprises an optical microscope or an optical interferometer. The global image detection system of claim 4, wherein the optical microscope or the optical interferometer adjusts the height according to the absolute coordinate information to adjust A focal length between the optical microscope or the optical interferometer and the object to be tested. The global image detection system of claim 1, wherein the measurement module comprises a probe card electrical detection device. The global image detection system of claim 6, wherein the measurement module adjusts a gap between the probe card electrical detection device and the object to be tested according to the absolute coordinate information, so that the probe The needle card electrical detecting device is in electrical contact with the object to be tested. A global image detecting method includes: displaying, by a planar light source, a light image having a periodic change on an object to be tested, wherein the planar light source is generated by a flat display: capturing a planar light source image reflected by the object to be tested Calculating an offset of the offset or deformation of the image of the planar light source, and calculating a relative height distribution of the surface topography of the object to be tested according to the offset; detecting at least three measuring points on the object to be tested Coordinates to fit a plane; calculate an absolute height distribution of the surface topography of the object to be measured relative to the plane to obtain an absolute coordinate information; and detect the surface of the object to be tested according to the absolute coordinate information . The method for detecting a global image according to claim 8 further includes: carrying the object to be tested by a positioning platform, and controlling the positioning platform to move the object to be in a target position according to the absolute coordinate information. The method for detecting a global image according to claim 8 further includes projecting a uniform light image to the object to be tested by the planar light source, and obtaining coordinate information of a plane coordinate system according to the fitted plane. The method for detecting a global image according to claim 8 , wherein when the object to be tested is detected by an optical microscope or an optical interferometer, the method further comprises: adjusting the height according to the absolute coordinate information to adjust the optical microscope or A focal length between the optical interferometer and the object to be tested. The method for detecting a full-field image according to claim 8, wherein the object to be tested is detected by a probe card electrical detecting device, and further comprising: adjusting the probe card electrical detecting device according to the absolute coordinate information; a gap with the object to be tested, so that the probe card electrical detecting device is in electrical contact with the object to be tested.