CN115325963B - Wafer surface three-dimensional shape measuring device and measuring method thereof - Google Patents
Wafer surface three-dimensional shape measuring device and measuring method thereof Download PDFInfo
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- CN115325963B CN115325963B CN202211239997.7A CN202211239997A CN115325963B CN 115325963 B CN115325963 B CN 115325963B CN 202211239997 A CN202211239997 A CN 202211239997A CN 115325963 B CN115325963 B CN 115325963B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
- G01B11/254—Projection of a pattern, viewing through a pattern, e.g. moiré
Abstract
The invention discloses a device and a method for measuring the three-dimensional topography of a wafer surface, and belongs to the technical field of wafer detection. The measuring device comprises an optical measuring module, the optical measuring module comprises a high-speed camera assembly, a transverse switching module, a piezoelectric displacement assembly and a GPU image card processing module, an external trigger module is embedded in the high-speed camera assembly, the external trigger module is matched with the piezoelectric displacement assembly and used for triggering the high-speed camera assembly to take a picture, the GPU image card processing module is used for processing interference fringe image information collected by the high-speed camera assembly, the measuring device guarantees measuring accuracy based on a white light interference measuring principle, and the measuring method is used for assisting interference measurement automatic focusing and image analysis through an algorithm. In summary, the present invention provides a device and a method for completely measuring the three-dimensional topography of a wafer surface, which is helpful for high-efficiency and high-precision measurement and evaluation of the wafer surface.
Description
Technical Field
The invention belongs to the technical field of wafer detection, and particularly relates to a device and a method for measuring the three-dimensional topography of a wafer surface.
Background
Wafers are basic raw materials in semiconductor devices, most of the electronic products are manufactured by the wafers at present, and the performance of the electronic products has great influence on the semiconductor industry. In production, the three-dimensional surface micro-topography has the most direct influence on the evaluation of many technical performances of engineering parts, and the measurement of the three-dimensional surface micro-topography of the wafer surface is more important as the evaluation parameters of the three-dimensional surface are more and more emphasized because the evaluation parameters of the three-dimensional surface can comprehensively and truly reflect the surface characteristics of the parts and measure the quality of the surface. The quality of the surface quality of the wafer can be comprehensively evaluated by measuring the three-dimensional morphology, and the quality of the processing method and the reasonability of design requirements are further confirmed, so that the high-quality surface of the wafer can be processed by guiding the processing and optimizing the processing technology in turn, and the realization of the use function of the wafer is ensured.
The difference of the surface appearance of the traditional mechanical part is that the surface of the wafer is a three-dimensional complex structure consisting of microstructure units, and the wafer is required to have higher transverse resolution and longitudinal resolution, larger measurement depth and measurement range while measuring parameters such as surface profile, geometric dimension, position deviation and the like. In addition, the production and manufacturing of the wafer have the characteristics of nano scale, difficult direct contact, micro surface effect, large positioning error influence, large interference of dust or foreign matters on the measurement result, large optical diffraction influence and the like. Therefore, the three-dimensional measurement of the wafer surface always faces the practical problem that the precision and the efficiency cannot be considered at the same time, and a high-precision and high-efficiency measurement method and a device are urgently needed to solve the problem of the three-dimensional measurement of the wafer surface.
In the existing optical 3D measuring method, a plurality of measuring methods are derived based on the optical basic principle, namely refraction, reflection, scattering and interference principles, and the measuring accuracy is different. The optical measurement method can be divided into coordinate point measurement, line profile scanning measurement and surface aperture measurement according to the measurement form, and the measurement methods have different characteristics and different applicability.
The coordinate point scanning measurement mainly uses the irradiation of a focused light beam to measure the profile of a measured surface, which typically represents a color confocal measurement sensor, and the longitudinal vertical resolution of the color confocal measurement sensor is high and reaches the nanometer level, but the horizontal resolution is limited by the geometric size of a light spot emitted by a measuring head, and the transverse resolution is usually submicron or micron level. The problem of low scanning efficiency generally exists in current coordinate type scanning measurement, and the requirement of high-efficiency measurement of the wafer cannot be met.
In order to solve the problem of slow scanning efficiency of coordinate points and improve the measuring speed, the line scanning measuring technology is developed, the basic principle is that linear scanning light is adopted to carry out light strip coverage scanning measurement on the surface of an object, and a related light strip extraction and calibration algorithm is adopted to realize one-time scanning reconstruction of three-dimensional surface profile information of the object to be measured. However, a general problem of line scanning measurement is the principle-level-determined micrometer-scale absolute measurement accuracy, which makes it unsuitable for nanoscale microscopic surface profile measurement, typically represented by a line laser sensor.
No matter coordinate point scanning measurement or line scanning measurement, a sensor needs to be carried on for scanning movement based on movement of a displacement table, and various shafting movement errors are introduced into a system displacement table, so that the final surface profile measurement accuracy is poor. In order to reduce the measurement system error caused by the introduction of a shafting, a single-view field area is introduced to scan and measure, and field measurement of one area is realized by one-time measurement.
Surface interferometry is a nano-scale measurement method currently accepted in the industry, such as white light interferometry. According to the objective lens with different multiplying powers, high-precision measurement of local areas with different view field sizes can be achieved. However, the problem of interferometry is that the field of view is limited by the constraint of the interference objective, and the test field of view of microscopic measurement is only hundreds of microns, which is not suitable for three-dimensional high-efficiency scanning measurement of the surface of a large-size wafer.
In conclusion, the conventional detection means has no good wafer three-dimensional measurement capability, the application range of the measurement system has great limitation, and the requirement of complete measurement of the three-dimensional morphology of the surface of the nanoscale and ultrafast wafer cannot be met. Therefore, a set of measuring system capable of accurately detecting the three-dimensional topography of the surface of the wafer is researched, the surface of the wafer is efficiently and accurately measured and evaluated, problems occurring in the machining process are found and analyzed in time, the machining process is further perfected, the machining quality of the surface of the wafer is improved, a reference can be provided for analyzing the relation between the performance of the wafer and the topography of the surface, and meanwhile the performance of the wafer is enhanced and the production efficiency is improved.
Disclosure of Invention
The purpose of the invention is as follows: in order to solve the defects of the existing method for measuring the three-dimensional topography of the surface of the wafer, the invention is designed from two aspects of algorithm control and a hardware device, on one hand, the invention provides a high-precision high-efficiency automatic complete measuring method for the three-dimensional topography of the surface of the wafer, and on the other hand, the invention provides a measuring device suitable for the measuring method.
The technical scheme is as follows: a wafer surface three-dimensional appearance measuring device comprises a measuring frame, a high-precision three-dimensional motion module and an object stage assembly, wherein the high-precision three-dimensional motion module is arranged on the measuring frame, the object stage assembly is arranged on the motion module and used for bearing a wafer to be measured, the motion X axis and the motion Y axis of the high-precision three-dimensional motion module are matched and used for carrying the object stage assembly to carry out plane motion,
the system comprises a high-precision three-dimensional motion module, a photoelectric conversion module and a power supply module, wherein the optical measurement module is mounted on a motion Z axis of the high-precision three-dimensional motion module and comprises an infinite imaging lens cone assembly, a light source assembly, a high-speed camera assembly, a transverse switching module, a piezoelectric displacement assembly and a GPU image card processing module; the light source assembly is arranged at a light inlet of the infinite imaging lens cone assembly, and is matched with the infinite imaging lens cone assembly and the interference objective lens assembly on the transverse switching module to form an interference fringe image on the wafer to be detected; the high-speed camera assembly is arranged at an observation port of the infinite imaging lens cone assembly and used for collecting interference fringe images, the high-speed camera assembly is embedded with the external trigger module, the external trigger module is matched with the piezoelectric displacement assembly arranged on the transverse switching module and used for triggering the high-speed camera assembly to take pictures, and the GPU image card processing module is used for processing the high-speed camera assembly to collect the interference fringe images.
Furthermore, the interference objective lens assembly on the transverse switching module comprises a microscopic interference objective lens assembly and a large-view-field interference objective lens assembly, the length and the width of a measurement view field of the large-view-field interference objective lens assembly are respectively L and W, the measurement view field is in millimeter level, and the transverse resolution is not less than 4 μm.
Furthermore, the GPU image card processing module comprises a graphics pipeline, and the graphics pipeline is used for real-time parallel high-speed calculation and reconstruction processing of the three-dimensional topography of the surface of the wafer.
Further, unlimited long formation of image lens cone subassembly includes the primary light way, sends out light way and reflection path, the primary light way includes the relay mirror, micro-interference objective assembly or big visual field interference objective assembly and relay mirror collineation set up, it is equipped with aperture diaphragm, plano-convex lens, speculum one, plano-convex lens and beam splitter one in proper order along light direction of transfer on the road to send out light, the light source subassembly sets up in aperture diaphragm department, reference reflector, speculum two and beam splitter two have been set gradually along light direction of transfer on the reflection road.
Further, the light source assembly comprises an LED light source and a light source control circuit board, and the light source control circuit board is used for controlling the LED light source.
Furthermore, the measuring frame comprises a marble gantry and a marble base, the marble gantry is installed on the marble base, the X axis and the Y axis of the movement of the high-precision three-dimensional movement module are installed on the marble base, and the optical measuring module is installed on the Z axis of the movement.
A measuring method of a device for measuring the three-dimensional topography of a wafer surface comprises the following steps:
step 1: feeding; supplying the wafer to be tested to the objective table assembly through an automatic feeding device;
step 2: automatic focusing; switching the optical measurement module to a large-view-field interference objective lens assembly to perform scanning measurement on the wafer to be measured, and acquiring surface images of the wafer to be measured at different Z-direction heights by the high-speed camera assembly to obtain the clearest acquisition position Z1 so as to realize automatic focusing of interference measurement;
and step 3: automatic measurement path planning; carrying a wafer to be measured and an optical measurement module to perform relative measurement position scanning movement based on a high-precision three-dimensional movement module, and realizing path planning of the scanning movement;
and 4, step 4: automatically identifying the scanning range of the interference image; under the planning of a measurement path, an optical measurement module moves to an automatic focusing position Z1, the Z-direction position of the optical measurement module is adjusted at equal steps along the same direction, the surface images of the wafer to be measured at different heights are obtained, the surface images of the wafer to be measured captured in the adjustment process are processed, a gray value mark bit is obtained, the distribution condition of the gray value mark bit on the surface images of different wafers is obtained, low-pass filtering processing is carried out, the initial image position and the final image position of fringes in an interference image are determined, and automatic identification of the interference image is completed;
and 5: three-dimensional resolving reconstruction of interference images; defining the surface images of the wafer to be detected at different heights captured in the range from the initial image position to the final image position in the step 4 as an interference pattern group, respectively processing different interference fringe images in the interference pattern group to obtain an envelope curve of a white light interference light intensity signal under each pixel, processing the envelope curves to obtain coherent peak positions under all pixels, and forming the three-dimensional topography of the surface of the wafer of the sub-field of view under the large-field-of-view interference object lens assembly;
step 6: splicing the three-dimensional measurement data of the surface appearance of the wafer completely; scanning and measuring the three-dimensional topography according to the measuring path, converting the height data of the sub-field of view into image data, extracting the positions of the characteristic points in the image to obtain the position relation of the surface topography in the horizontal direction, and realizing the complete splicing of the three-dimensional topography measuring data of the surface of the wafer by using an image fusion method;
and 7: switching an optical measurement module to the micro-interference objective lens assembly to perform local amplification measurement on a specific position of the complete wafer surface three-dimensional morphology, performing parameter analysis and evaluation on the obtained wafer surface three-dimensional morphology, and storing a measurement result;
and 8: and (5) blanking the wafer to be measured through the automatic feeding device, and finishing measurement.
Further, the step 2 of judging the definition of the surface images at different height positions is based on a Tenengrad gradient method, and the gradient of the wafer surface image in the horizontal direction and the gradient of the wafer surface image in the vertical direction, which are acquired by the high-speed camera assembly, are respectively calculated in real time by using a Sobel operator, so that an average gradient value of the wafer surface image is obtained, and the definition is represented by the average gradient value.
Further, step 2 comprises:
step 21: establishing a measurement coordinate system through a wafer surface three-dimensional shape measuring device, and carrying and moving an optical measurement module to a focusing position Z1 through a moving Z axis;
step 22: the movement X axis and the movement Y axis carry the wafer to be measured to the starting point of the measuring path, the coordinates of the starting point are (-phi/2, phi/2), wherein phi is the diameter of the wafer to be measured;
step 23: and designing and generating a measuring path according to the size of the field of view of the high-speed camera component, wherein the measuring path is of an S-shaped grid structure and traverses the whole surface of the wafer to be measured, the size of the field of view of the high-speed camera component is L multiplied by W, and the distance between the measuring paths is W.
Has the advantages that: the method is based on the white light interferometry principle, and on the basis of ensuring the measurement accuracy, the large-view-field interferometer component is adopted to carry out splicing measurement on the three-dimensional topography of the surface of the wafer, so that the problem of high-accuracy complete scanning measurement of the three-dimensional topography of the surface of the wafer is effectively solved.
On the basis of ensuring the measurement precision, in order to improve the measurement efficiency, on one hand, starting from the automatic measurement of white light, the high-speed camera is controlled by the external trigger module to collect the surface images of the wafer to be measured at different heights, and the position Z1 of the clearest surface image of the wafer to be measured is analyzed by an algorithm, so that the automatic focusing of the interference measurement is realized, and the efficiency is higher compared with the traditional manual interference fringes; on the other hand, the GPU image card processing module is integrated in the optical measurement module, so that multiple data processing can be performed in parallel and high-speed calculation and reconstruction can be realized, and the efficiency of wafer three-dimensional measurement is realized.
In summary, the invention provides a device and a method for completely measuring the three-dimensional topography of the surface of a wafer, which are beneficial to high-efficiency and high-precision measurement and evaluation of the surface of the wafer.
Drawings
FIG. 1 is a schematic structural diagram of a wafer surface three-dimensional topography measuring apparatus according to the present invention;
FIG. 2 is a schematic view of the wafer surface three-dimensional topography measuring apparatus of the present invention with the optical measuring module removed;
FIG. 3 is a schematic diagram of the internal structure of the optical measurement module of the present invention;
FIG. 4 is an optical path diagram of an optical measurement module of the present invention;
FIG. 5 is a survey routing diagram of the present invention;
FIG. 6 is a measurement flowchart of the method for measuring the three-dimensional topography of the surface of a wafer according to the present invention.
Reference numerals: 1. a marble gantry; 2. an optical measurement module; 3. an object stage assembly; 4. a wafer to be tested; 5. a Z axis of motion; 6. an X-axis of motion; 7. motion Y axis, 8 marble base; 9. a high-speed camera component; 10. a light source assembly; 11. a microscopic interferometer objective lens assembly; 12. a large field of view interferometric objective lens assembly; 13. an infinity imaging barrel assembly; 14. GPU image card processing module; 15. a transverse switching module; 16. a piezoelectric displacement assembly; 17. an aperture diaphragm; 18. a plano-convex lens; 19. a first reflecting mirror; 20. a first beam splitter; 21 a reference mirror; 22. a relay lens; 23. a sub-field of view; 24. measuring a path; 25. a second reflecting mirror; 26. and a second beam splitter.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present invention.
Example 1:
in order to provide a high precision measuring device for the three-dimensional topography of the wafer surface, embodiment 1 is proposed,
as shown in fig. 1-2, a device for measuring the three-dimensional topography of the surface of a wafer comprises a measuring frame, a high-precision three-dimensional motion module installed on the measuring frame, and an objective table component 3 arranged on the motion module, wherein the objective table component 3 is used for bearing a wafer 4 to be measured, and a motion X-axis 6 and a motion Y-axis 7 of the high-precision three-dimensional motion module are matched and used for carrying the objective table component 3 to perform plane motion.
Wherein, the measuring rack includes marble longmen 1 and marble base 8, and marble longmen 1 installs on marble base 8, and the motion X axle 6 and the motion Y axle 7 of high accuracy three-dimensional motion module are installed on marble base 8, and optical measurement module 2 is installed on motion Z axle 5.
As shown in fig. 3, an optical measurement module 2 is mounted on a movement Z axis 5 of the high-precision three-dimensional movement module, the optical measurement module 2 includes an infinite imaging lens barrel assembly 13, a light source assembly 10, a high-speed camera assembly 9, a transverse switching module 15, a piezoelectric displacement assembly 16 and a GPU image card processing module 14, and an interference objective lens assembly alternately matched with a light outlet of the infinite imaging lens barrel assembly 13 is arranged on the transverse switching module 15; the light source assembly 10 is installed at a light inlet of the infinity imaging lens barrel assembly 13, and the light source assembly 10 is matched with the infinity imaging lens barrel assembly 13 and the interference objective lens assembly on the transverse switching module 15 and is used for forming an interference fringe image on the wafer 4 to be measured; the high-speed camera assembly 9 is arranged at an observation port of the infinite imaging lens cone assembly 13 and used for collecting interference fringe images, the high-speed camera assembly 9 is internally embedded with an external trigger module, the external trigger module is matched with a piezoelectric displacement assembly 16 arranged on the transverse switching module 15 and used for triggering the high-speed camera assembly 9 to take pictures, and the GPU image card processing module 14 is used for processing the high-speed camera assembly 9 to collect the interference fringe images.
The interferometer objective assembly on the transverse switching module 15 comprises a microscopic interferometer objective assembly 11 and a large-view-field interferometer objective assembly 12, the measurement view field range of the large-view-field interferometer objective assembly 12 is 35mm multiplied by 35mm, and the transverse resolution is 4 mu m. The traditional white light interferometry principle is traditionally applied to microscopic measurement, a view field is only hundreds of microns, the view field cannot be matched with a large-diameter wafer, and the large-view-field interferometer component 12 amplifies the monitoring view field, so that the high-efficiency measurement is assisted, and the method is suitable for large-diameter wafer detection.
The GPU graphics card processing module 14 includes a graphics pipeline for real-time parallel high-speed calculation and reconstruction processing of the three-dimensional topography of the wafer surface.
As shown in fig. 4, the infinity imaging lens barrel assembly 13 includes a main light path, a light emitting path and a reflecting path, the main light path includes a relay lens 22, the microscopic interference objective assembly 11 or the large field of view interference objective assembly 12 is arranged collinearly with the relay lens 22, the light emitting path is provided with an aperture stop 17, a plano-convex lens 18, a first reflector 19, a plano-convex lens 18 and a first beam splitter 20 in sequence along a light transmission direction, the light source assembly 10 is arranged at the aperture stop 17, and the reflecting path is provided with a reference reflector 21, a second reflector 25 and a second beam splitter 26 in sequence along the light transmission direction. The infinity imaging barrel assembly 13 is used to create parallel rays between the objective lens and the barrel lens.
The light source assembly 10 includes an LED light source and a light source control circuit board for controlling the LED light source.
Example 2:
in order to provide the measuring method of the measuring device for the three-dimensional topography of the surface of the wafer in the embodiment 1 and realize the high-efficiency measurement, the embodiment 2 is provided,
a measurement method based on a three-dimensional topography measurement apparatus of a wafer surface, as shown in fig. 6, the measurement method includes the following steps:
step 1: the measurement is started, and the wafer 4 to be measured is firstly fed onto the objective table component 3 through the automatic feeding device.
Step 2: the method comprises the steps of switching an optical measurement module 2 to a large-view-field interference objective assembly 12, scanning and measuring the surface of a wafer 4 to be measured, carrying the optical measurement module 2 by a moving Z shaft 5 to carry out lifting scanning movement, collecting the surface image of the wafer 4 to be measured by a high-speed camera assembly 9 in real time, calculating the gradient of the surface image of the wafer 4 to be measured in the horizontal direction and the vertical direction collected by the high-speed camera assembly 9 by utilizing a Sobel operator based on a Tenengrad gradient method to obtain the average gradient value of the surface image of the wafer 4 to be measured, representing the definition by the average gradient value, judging the definition of different positions to obtain the position Z1 of the surface image of the wafer 4 to be measured with the clearest, completing automatic focusing of interference measurement, and carrying the optical measurement module 2 to move to the position Z1 during subsequent measurement so as to be continuously unfolded in the subsequent steps.
And step 3: carrying a wafer 4 to be measured and an optical measurement module 2 to carry out automatic measurement path 24 planning based on a high-precision three-dimensional motion module, wherein the process comprises the following steps: firstly, a measuring coordinate system is established through a wafer surface three-dimensional shape measuring device, after an optical measuring module 2 finishes automatic focusing to obtain a clear surface image of a wafer 4 to be measured, the optical measuring module 2 is carried by a high-precision moving Z shaft 5 to move to a focusing position Z1; then, the wafer 4 to be measured is carried to the coordinate position of (-phi/2, phi/2) by the movement X-axis 6 and the movement Y-axis 7, namely the starting point of the scanning measurement path 24, wherein phi is the diameter of the wafer 4 to be measured; finally, a scanning path of the wafer 4 to be measured is planned and generated, as shown in fig. 5, an S-shaped grid-like measurement path 24 is designed and generated according to the size L × W of the field of view of the high-speed camera assembly 9, the distance between the paths is W, the whole surface of the wafer 4 to be measured is traversed, and high-speed scanning with low time consumption is achieved in terms of scanning efficiency.
And 4, step 4: under the planning of the automatic measurement path 24, the optical measurement module 2 moves to an automatic focusing position Z1, the Z-direction position of the optical measurement module 2 is adjusted at equal steps along the same direction, the surface images of the wafer 4 to be measured at different heights are obtained, gaussian filtering and edge operator identification processing are carried out on the surface images of the wafer 4 to be measured captured in the adjustment process to obtain a gray value zone bit, the distribution conditions of the zone bit on the surface images of different wafers are obtained, low-pass filtering processing is carried out, the initial image position and the final image position of the fringe in the interference image are determined through quadratic polynomial and composite exponential function fitting, and automatic identification of the interference image is completed.
And 5: after the scanning range of the interference image is identified, the optical measurement module 2 is carried by a motion Z-axis 5 and moves at a constant speed from top to bottom along the vertical direction, the optical measurement module gradually approaches to a wafer 4 to be detected, meanwhile, an external trigger module triggers a high-speed camera through the variation of voltages along the upper edge and the lower edge and the like, the surface images of the wafer 4 to be detected at different heights captured from the initial image position to the final image position in the step 4 are defined as an interference image group, different interference fringe images in the interference image group are respectively processed, namely, the images in the interference image group are subjected to forward and inverse Fourier transform twice to obtain an envelope curve of a white light interference light intensity signal under each pixel in the interference image, then the position of a peak point of the envelope curve, namely a coherent peak point, is obtained, the coherent peak points under all the pixels in the interference image are connected to form a three-dimensional topography of the wafer surface of a sub-field 23, and the three-dimensional calculation and reconstruction of the interference image is completed.
And 6: scanning and measuring the surface three-dimensional topography of the wafer 4 to be measured according to the automatic measurement path 24, converting the height data of the three-dimensional topography of the surface of the wafer in the sub-field 23 into image data, extracting the positions of the feature points in the image by adopting an SIFT algorithm to obtain the position relation of the surface topography in the horizontal direction, and realizing the complete splicing of the measured data of the three-dimensional topography of the surface of the wafer by utilizing an image fusion method.
And 7: and switching the optical measurement module 2 to a microscopic interferometer component 11, carrying out local amplification measurement on the specific position of the three-dimensional topography of the surface of the complete wafer, carrying out parameter analysis and evaluation on the obtained three-dimensional topography of the surface of the wafer, and storing the measurement result.
And 8: and finally, discharging the wafer 4 to be measured through the automatic feeding device, and finishing measurement.
By the measuring device and the measuring method, the high-precision and high-efficiency scanning measurement of the three-dimensional topography of the surface of the large-size wafer can be truly realized, and the scanning yield of the 12-inch wafer is more than or equal to 25wph. The problem of prior art, measurement system can't compromise simultaneously and measure the requirement with high accuracy on a large scale is solved.
The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the embodiments, and various equivalent changes can be made to the technical solution of the present invention within the technical scope of the present invention, and these equivalent changes are all within the protection scope of the present invention.
Claims (9)
1. A method for measuring the three-dimensional topography of a wafer surface is characterized by comprising the following steps:
step 1: feeding; feeding the wafer (4) to be tested onto the objective table assembly (3) through an automatic feeding device;
step 2: automatic focusing; the optical measurement module (2) is switched to the large-view-field interference objective lens assembly (12) to scan and measure the wafer (4) to be measured, the high-speed camera assembly (9) collects surface images of the wafer (4) to be measured at different Z-direction heights to obtain the clearest collection position Z1, and automatic focusing of interference measurement is achieved;
and step 3: automatic measurement path planning; carrying a wafer (4) to be measured and an optical measurement module (2) to perform relative measurement position scanning movement based on a high-precision three-dimensional movement module, and realizing path planning of the scanning movement;
and 4, step 4: automatically identifying the scanning range of the interference image; under the planning of a measurement path, the optical measurement module (2) moves to an automatic focusing position Z1, the Z-direction position of the optical measurement module (2) is adjusted at equal steps along the same direction, the surface images of the wafer (4) to be measured at different heights are obtained, the surface image of the wafer (4) to be measured captured in the adjustment process is processed to obtain a gray value mark bit, the distribution condition of the gray value mark bit on the surface images of different wafers is obtained, low-pass filtering processing is carried out, the initial image position and the final image position of a fringe in an interference image are determined, and the automatic identification of the interference image is completed;
and 5: three-dimensional resolving reconstruction of interference images; defining the surface images of the wafer (4) to be detected at different heights captured in the range from the initial image position to the final image position in the step (4) as an interference pattern group, respectively processing different interference fringe images in the interference pattern group to obtain an envelope curve of a white light interference light intensity signal under each pixel, processing the envelope curves to obtain coherent peak positions under all pixels, and forming the three-dimensional appearance of the surface of the wafer under the sub-field (23) of the large-field interference object lens assembly (12);
and 6: splicing the three-dimensional measurement data of the surface appearance of the wafer completely; scanning and measuring the three-dimensional topography according to the measuring path (24), converting the height data of the sub-field of view (23) into image data, extracting the positions of the characteristic points in the image to obtain the position relation of the surface topography in the horizontal direction, and realizing the complete splicing of the three-dimensional topography measuring data of the wafer surface by using an image fusion method;
and 7: switching the optical measurement module (2) to a microscopic interference objective lens assembly (11) to perform local amplification measurement on the specific position of the three-dimensional topography of the surface of the complete wafer, performing parameter analysis and evaluation on the obtained three-dimensional topography of the surface of the wafer, and storing a measurement result;
and 8: and (4) blanking the wafer (4) to be measured through an automatic feeding device, and finishing measurement.
2. The method of claim 1, wherein: and 2, judging the definition of the surface images at different height positions in the step 2, namely calculating the gradients of the horizontal direction and the vertical direction of the surface image of the wafer acquired by the high-speed camera assembly (9) in real time by utilizing a Sobel operator based on a Tenengrad gradient method to obtain an average gradient value of the surface image of the wafer, and representing the definition by using the average gradient value.
3. The method of claim 1, wherein: the step 2 comprises the following steps:
step 21: a measurement coordinate system is established through a wafer surface three-dimensional shape measurement device, and an optical measurement module (2) is carried by a motion Z shaft (5) to move to a focusing position Z1;
step 22: the movement X axis (6) and the movement Y axis (7) carry the wafer (4) to be measured to the starting point of the measuring path (24), and the coordinates of the starting point are (-phi/2, phi/2), wherein phi is the diameter of the wafer (4) to be measured;
step 23: and designing and generating a measuring path (24) according to the size of the view field of the high-speed camera assembly (9), wherein the measuring path (24) is of an S-shaped grid structure, the whole surface of the wafer (4) to be measured is traversed, the size of the view field of the high-speed camera assembly (9) is L multiplied by W, and the distance between the measuring paths (24) is W.
4. The measuring device for the wafer surface three-dimensional topography measuring method according to any one of claims 1 to 3, comprising a measuring frame, a high-precision three-dimensional motion module mounted on the measuring frame, and a stage assembly (3) arranged on the motion module, wherein the stage assembly (3) is used for carrying a wafer (4) to be measured, and the motion X axis (6) and the motion Y axis (7) of the high-precision three-dimensional motion module are matched for carrying the stage assembly (3) to perform planar motion, characterized in that: an optical measurement module (2) is mounted on a motion Z axis (5) of the high-precision three-dimensional motion module, the optical measurement module (2) comprises an infinite imaging lens cone assembly (13), a light source assembly (10), a high-speed camera assembly (9), a transverse switching module (15), a piezoelectric displacement assembly (16) and a GPU image card processing module (14), and an interference objective lens assembly alternately matched with a light outlet of the infinite imaging lens cone assembly (13) is arranged on the transverse switching module (15); the light source assembly (10) is installed at a light inlet of the infinity imaging lens barrel assembly (13), and the light source assembly (10) is matched with the infinity imaging lens barrel assembly (13) and an interference objective lens assembly on the transverse switching module (15) and is used for forming an interference fringe image on the wafer (4) to be detected; the high-speed camera assembly (9) is arranged at an observation port of the infinite imaging lens cone assembly (13) and used for collecting interference fringe images, an external trigger module is embedded in the high-speed camera assembly (9) and matched with a piezoelectric displacement assembly (16) arranged on a transverse switching module (15) and used for triggering the high-speed camera assembly to take pictures, and the GPU image card processing module (14) is used for processing the interference fringe images collected by the high-speed camera assembly (9).
5. The measuring apparatus according to claim 4, wherein the measuring apparatus comprises: the interference objective lens assembly on the transverse switching module (15) comprises a microscopic interference objective lens assembly (11) and a large-view-field interference objective lens assembly (12), the length and the width of a measurement view field of the large-view-field interference objective lens assembly (12) are L and W respectively, the measurement view field is in millimeter level, and the transverse resolution is not less than 4 mu m.
6. The measuring apparatus according to claim 4, wherein the measuring apparatus comprises: the GPU image card processing module (14) comprises a graphic pipeline, and the graphic pipeline is used for real-time parallel high-speed calculation and reconstruction processing of the three-dimensional topography of the surface of the wafer.
7. The measuring apparatus according to claim 5, wherein: infinity formation of image lens cone subassembly (13) are including the primary light way, give out light way and reflection road, the primary light way includes relay (22), micro-interference objective assembly (11) or big visual field interference objective assembly (12) and relay (22) collineation setting, it is equipped with aperture diaphragm (17), plano-convex lens (18), speculum (19), plano-convex lens (18) and beam splitter (20) in proper order to follow light conduction direction on the luminescence road, light source subassembly (10) set up in aperture diaphragm (17) department, be equipped with reference reflector (21), speculum two (25) and beam splitter two (26) in proper order along light conduction direction on the reflection road.
8. The measuring apparatus according to claim 4, wherein the measuring apparatus comprises: the light source assembly (10) comprises an LED light source and a light source control circuit board, wherein the light source control circuit board is used for controlling the LED light source.
9. The measuring apparatus according to claim 4, wherein the measuring apparatus comprises: the measuring rack comprises a marble gantry (1) and a marble base (8), the marble gantry (1) is installed on the marble base (8), a movement X axis (6) and a movement Y axis (7) of the high-precision three-dimensional movement module are installed on the marble base (8), and the optical measuring module (2) is installed on a movement Z axis (5).
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