CN116525480A - Microscopic image-based automatic detection method for forming quality of laser grid line - Google Patents

Abstract

The invention provides a microscopic image-based automatic detection method for forming quality of a laser grid line, which comprises the following steps: acquiring measurement data: performing a laser grating line forming process test, and acquiring grating line surface height data by a three-dimensional morphology measuring tool and storing the data as digital quantity; and (3) providing measurement indexes: equivalent shielding width, equivalent conductive area and dimensionless equivalent aspect ratio; and writing a computer program to realize automatic measurement of the measurement index. The invention can rapidly detect whether the forming quality of the grid line is qualified or meets the expectations, and has great significance for the engineering application of the process parameter exploration optimization and the laser grid line forming technology.

Description

Microscopic image-based automatic detection method for forming quality of laser grid line

Technical Field

The invention belongs to the field of laser grating line forming, and particularly relates to an automatic laser grating line forming quality detection method based on microscopic images.

Background

The laser transfer printing technology is a novel non-contact printing technology, and mainly refers to a technology of coating a required material on a specific carrier, scanning a specified track by adopting high-power density laser, and transferring the material from the carrier to a receptor.

In the aspect of forming the grid line of the photovoltaic cell, the method mainly comprises a laser pattern transfer technology (Pattern Transfer Printing, PTP), laser-induced forward transfer (laser-induced forward transfer, LIFT) and the like. The electrode grid lines of the photovoltaic cells can be formed continuously and uniformly.

In the existing photovoltaic cell grid line forming technology, the screen printing technology still dominates. The height, width and height-width ratio are traditional indexes for measuring the forming quality of the grid line. However, the indexes have the problems of non-uniform standard, complicated measurement steps, dependence on manpower, strong measurement subjectivity and incomplete response of measurement data to linear quality.

Chinese patent application CN201110399370.3 (solar cell grid line characteristic detector) discloses a hardware device for grid line detection, focusing on the construction of the device, and not describing a specific method and theoretical basis; although the Chinese patent application CN201110428486.5 (a method for evaluating the aspect ratio of the secondary grid line of the crystalline silicon solar cell) considers the quality of the grid line formation represented by the width of the grid line, an automatic measurement method is not provided, and the defects of manual intervention and strong subjectivity cannot be overcome; chinese patent application CN201910597052.4 (a method, a device and equipment for detecting thickness abnormality of a grid line of a solar cell) provides a method and equipment for measuring the quality of the grid line, mainly faces to the detection of the whole solar cell, and refers to the concept of the width of the grid line, but does not provide an automatic measuring method of the quantifiable width of the grid line; chinese patent application CN202011232285.3 (silicon crystal solar cell electrode grid line printability evaluation method and application thereof) provides concepts of grid line cross section and printing fullness, but only provides a calculation formula, and does not provide a feasible measurement algorithm, and the formula depends on traditional measurement indexes such as line width, line height and the like, so that the defects of manual intervention and strong subjectivity can not be solved.

Disclosure of Invention

In order to solve the technical problems, the invention provides an automatic detection method for forming quality of a laser grid line based on microscopic images, which abandons the concepts of fuzzy concepts of line width, line height and the like, strong subjectivity and larger measurement error, and utilizes microscopic imaging technology and computer program to provide three quantifiable evaluation indexes of equivalent shielding width (unit is mum), equivalent conductive area (unit is mum < 2 >) and dimensionless equivalent aspect ratio on the concept of regional average equivalence to measure the forming quality of the grid line.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a microscopic image-based automatic detection method for forming quality of laser grid lines comprises the following steps:

s100, acquiring measurement data: performing a laser grating line forming process test, and acquiring grating line surface height data by a three-dimensional morphology measuring tool and storing the data as digital quantity;

s200, providing measurement indexes: three quantifiable indicators are proposed from the measurement data: equivalent shielding width in μm and equivalent conductive area in μm ² Dimensionless equivalent aspect ratio;

s300, automatic measurement of measurement indexes is carried out, and the whole flow processing speed is less than 1S.

Further, the S100 includes:

s101, aiming at the forming requirement of the grid line, selecting matched laser grid line forming process parameters, and forming a required grid line on a substrate;

s102, setting the field size to 1024 x 1024pixels by using a three-dimensional morphology measuring tool capable of outputting digital image signals; the position of the measured grid line is moved to enable the grid line to be clearly positioned in the center of a field of view and corrected and leveled;

s103, adjusting the magnification of the measuring tool to enable the display width of the observed laser grid line to be in a range of 256-512 pixels and enable the display width of the base plane to be in a range of 512-768 pixels;

s104, acquiring the height data H of the inner surface of the field of view ₀ (i, j) and recording the magnification k and the maximum height h _max ；H ₀ (i, j) is a 1024 x 1024 matrix, the unit of an internal element is μm, wherein i and j are indexes in two directions of an image, and the values are 1-1024; k is in pixel/μm; h is a _max Is H ₀ Maximum values of elements in (i, j) in μm;

s105, normalized height data H (i, j) is expressed as formula H (i, j) =255 (H) ₀ (i，j)/h _max ) Calculating and rounding, wherein the value is 0-255, and the matrix is stored as 1024 x 1024 in the form of unsigned shaping, namely, uint 8; the data is further compressed using a lossless compression algorithm at the time of data storage.

Further, the S200 includes:

s201, selecting a shielding width as a reference for measuring the width of the grid line;

s202, defining an equivalent shielding width w, wherein the unit is μm and comprises the following steps:

in an ideal state, a straight line perpendicular to the grid line is made on the substrate plane and is intersected with the formed grid line to form a straight line segment, and the straight line segment is defined as a shielding width w ₀ The unit is mu m; calculating the length m of each grid line segment before and after the sampling point, namely sampling the total length of 2m+1, and defining the average value of the shielding width of each grid line segment as an equivalent shielding width w;

s203, defining equivalent conductive area a in μm ² Comprising:

forming a plane perpendicular to the gate line and perpendicular to the substrate, intersecting the formed gate line to form a contour curve section, forming a closed pattern with the straight line section in S202, defining the area of the closed pattern as a conductive areaa ₀ In μm ² The method comprises the steps of carrying out a first treatment on the surface of the Taking a grid line segment with the length of 2m+1, and taking the average value of the conductive areas of the grid line segment as an equivalent conductive area a;

s204, defining an equivalent aspect ratio r, comprising:

dividing the equivalent conductive area a in S203 by the square of the equivalent shielding width w in S202 to obtain a dimensionless equivalent aspect ratio r, wherein the dimensionless equivalent aspect ratio r is used for reflecting the shape of the grid line:

further, the S300 includes:

s301, selecting a sampling length m and a calculation position x:

in the normalized height data H (i, j), the i direction is defined as the gate line direction, and the j direction is the direction perpendicular thereto; x is the i coordinate of the calculated point, and the value range is (m+ 1,1024-m);

s302, calculating an equivalent shielding width w, wherein the unit is μm:

wherein i epsilon (x-m, x+m) and j epsilon (x-m, x+m);

H ₁ (i, j) is an intermediate parameter for calculating the equivalent occlusion width w, the numerical meaning is that the area occluded by the grid line is marked as 1, the non-occluded area is marked as 0, and the formula can be expressed as follows:

s303, calculating an equivalent conductive area a with the unit of mu m ² ：

Wherein i is E (x-m, x+m), i>0,

S304, calculating a dimensionless equivalent height-width ratio r:

s305, taking m as 12, calculating variances of w (x), a (x) and r (x) in S302-S304, and defining w as _s 、a _s 、r _s The method comprises the steps of carrying out a first treatment on the surface of the When the w (x), a (x) and r (x) distribution accords with the 3 sigma rule, the measurement data are valid; when the rule of 3 sigma is not met, the measurement error is too large or the grid lines are uneven and continuous, and the sample is re-measured or judged to be unqualified;

s306, after judging the validity of the data, taking the equivalent shielding width w, the equivalent conductive area a and the dimensionless equivalent aspect ratio r in the sampling range as final output results, and defining the final output results as w _m 、a _m 、r _m ：

S307, 3 indexes of any morphology of the grid line are defined in S302-S304, a computer program is written for calculation, and the validity of the measurement data is judged through S305; and outputting a final test result by S306 in the case that the data is valid.

The beneficial effects are that:

the invention provides three indexes, namely three measurement indexes of equivalent width, equivalent area diagram and equivalent height and width, which are clearly defined, have practical physical significance, are easy to automatically measure, and solve the problems of fuzzy standard, dependence on manpower and complicated measurement. The invention can rapidly detect whether the forming quality of the grid line is qualified or meets the expectations, and has great significance for the engineering application of the process parameter exploration optimization and the laser grid line forming technology.

Drawings

FIG. 1a, FIG. 1b is a visual pictorial representation of stored data; wherein, fig. 1a is a gray scale image, and fig. 1b is a three-dimensional morphology image;

FIG. 2 is a schematic diagram of a shielding line width and a gate line cross-sectional area;

FIG. 3 is a graph of a smooth surface profile for different sample lengths m;

FIG. 4 is an equivalent width diagram of a gate line under different processes;

FIG. 5 is an equivalent area diagram of a gate line under different processes;

FIG. 6 is an equivalent aspect ratio diagram of a gate line under different processes;

fig. 7 is a graph of gate line surface profile for different processes.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

The invention discloses a microscopic image-based automatic detection method for forming quality of a laser grid line, which comprises the following steps:

s100, acquiring measurement data: performing a laser grating line forming process test, and acquiring grating line surface height data by a three-dimensional morphology measuring tool and storing the data as digital quantity;

s200, providing measurement indexes: three quantifiable indicators are proposed from the measurement data: equivalent shielding width in μm and equivalent conductive area in μm ² Dimensionless equivalent aspect ratio;

s300, writing a computer program to realize automatic measurement of the measurement index proposed in the step S200, wherein the whole flow processing speed is less than 1S.

Specifically, the step S100 includes the following steps:

s101, aiming at the forming requirement of the grid line, an operator selects matched laser grid line forming process parameters from a process parameter library to perform a laser grid line forming experiment according to experience or process parameter library, and forms a required grid line on a substrate;

s102, setting the field size to 1024 x 1024pixels by using a three-dimensional morphology measuring tool capable of outputting digital image signals; the position of the measured grid line is moved to enable the grid line to be clearly positioned in the center of a field of view and corrected and leveled;

s103, adjusting the magnification of the measuring tool to enable the display width of the observed laser grid line to be in a range of 256-512 pixels and enable the display width of the base plane to be in a range of 512-768 pixels;

s104, acquiring the height data H of the inner surface of the field of view ₀ (i, j) and recording the magnification k and the maximum height h _max ；H ₀ (i, j) is a matrix of 1024 x 1024, the unit of the internal element is μm, wherein i and j are indexes of the image in two directions, namely, the i direction is defined as the direction of a grid line, the j direction is a direction perpendicular to the i direction, the values are 1-1024, and the subsequent matrix related to the measurement height adopts the definition; k is in pixel/μm; h is a _max Is H ₀ Maximum value of element in (i, j) in μm

S105, expressed as H (i, j) =255 (H ₀ (i，j)/h _max ) Normalized height data H (i, j) is calculated and rounded up to a value of 0 to 255 and stored as a 1024 x 1024 matrix in unsigned shaped (uint 8) form. The 255-level precision in the height direction can meet the measurement requirement. The data is transferred from double type to uint8, so that the storage space can be reduced to 1/8, and the calculation speed is faster. As shown in fig. 1a and 1b, fig. 1a is a visual image of gray scale of stored data, and fig. 1b is a three-dimensional height image drawn according to the stored data. An experimenter can quickly judge the forming quality of the grid line from the graph 1a by experience without three-dimensional rendering of the graph 1b. The S105 is the basis of the subsequent rapid detection algorithm.

The step S200 includes the steps of:

s201, selecting a shielding width:

the section of the grid line is not a regular rectangle, and the width of the grid line is defined unevenly in the current index. Because the surface of the substrate cannot interact with the outside after the grid line is shielded, the equivalent grid line width is defined based on the shielding width, the method accords with engineering practice, and a definition standard of the universal grid line width is provided in practice.

S202, defining an equivalent shielding width w (unit is μm):

in an ideal state, a straight line perpendicular to the grid line is made on the substrate plane and is intersected with the formed grid line to form a straight line segment, and the straight line segment is defined as a shielding width w ₀ In micrometers (μm). In actual measurement, the shielding width of the gate line is greatly floated. In order to eliminate the error, the gate segments with the length of m (i.e. 1/2 sampling length) are respectively taken before and after the sampling point to calculate, the total sampling length is 2m+1, and the average value of the shielding width is defined as the equivalent shielding width w, so that the measurement error caused by the selected position can be effectively avoided.

S203, defining equivalent conductive area a, (unit is μm) ² )：

Within the scope of the art, the gate line conductivity can be considered to be area dependent only. Forming a plane perpendicular to the gate line on the substrate plane, intersecting the formed gate line to form a contour curve section, forming a closed pattern with the straight line section in S202, defining the area of the closed pattern as the conductive area a ₀ In micrometers (μm) ² ). The grid line segment with the length of 2m+1 is taken, and the average value of the conductive areas is defined as the equivalent conductive area a, so that the measurement error caused by the selected position can be effectively avoided. The definition of the equivalent shielding width w and the equivalent conductive area a is shown in fig. 2.

S204, defining an equivalent aspect ratio r (dimensionless):

dividing the equivalent conductive area a in S203 by the square of the equivalent shielding width w in S202 can obtain a dimensionless equivalent aspect ratio r, which can reflect the shape of the grid line. The value is close to 0 when the grid line is flat, and is close to 1 when the grid line is full. In the sense of a mathematical definition of the term, the value of r should be (1, ++ infinity A kind of electronic device. In practical engineering application, the r value is difficult to break through 1 at present, and the r value is more than 0.4, which is pursued by industry.

The step S300 includes the steps of:

s301, selecting a sampling length m and a calculation position x:

in the normalized height data H (i, j), the i direction is defined as the gate line direction, and the j direction is the direction perpendicular thereto; x is the i coordinate of the calculated point, and the value range is (m+ 1,1024-m). Too small value of m plays a role in smoothing data and reducing errors, and too large value of m can lead to smooth transition and loss of key information. As shown in fig. 3, the data smoothing schematic diagram can be seen that, among the 1024 data points, 12 data before and after the data is fetched can meet the requirement. Taking m=12 in this example, a single sample can have 1000 data points for calculation.

S302, calculating an equivalent shielding width w (unit is μm):

h1 (i, j) is an intermediate parameter, expressed as:

s303, calculating the equivalent conductive area a (in μm ² )：

S304, calculating a dimensionless equivalent height-width ratio r:

s305, taking m as 12, calculating variances of w (x), a (x) and r (x) in S302-S304, and defining w as _s 、a _s 、r _s The method comprises the steps of carrying out a first treatment on the surface of the At w (x), a (x)) When the r (x) distribution accords with the 3 sigma rule, the measurement data are valid; when the rule of 3 sigma is not met, the measurement error is too large or the grid lines are uneven and continuous, and the sample is re-measured or judged to be unqualified;

s306, after judging the validity of the data, taking the equivalent shielding width w, the equivalent conductive area a and the dimensionless equivalent aspect ratio r in the sampling range as final output results, and defining the final output results as w _m 、a _m 、r _m ：

S307, 3 indexes describing the morphology of any part of the grid line, namely an equivalent shielding width w, an equivalent conductive area a and a dimensionless equivalent aspect ratio r are defined in S302-S304, and the effectiveness of measurement record is judged by S305; and outputting a final test result by S306 in the case that the data is valid. The formula is easy to write as a computer program, and can be calculated and finished in 1s on a common household computer through practical tests. So far, the equivalent shielding width w, the equivalent conductive area a and the dimensionless equivalent aspect ratio r of three grid line evaluation indexes in one sampling interval defined by the invention are all described.

Fig. 4, 5, 6, and 7 are results plotted using the method described in the present invention S200. Eight experiments were performed with equally spaced changes to a critical process parameter, the results of which are shown in fig. 4, fig. 5, fig. 6, and fig. 7. As can be seen from fig. 4 to fig. 6, as the parameter increases, the equivalent width of the gate line increases approximately linearly, and the equivalent area of the gate line increases approximately linearly, but the equivalent aspect ratio has a rapid decreasing trend, which indicates that the parameter should be within a reasonable range and cannot be set to a too large value. Fig. 7 is a graph of the surface profile of the gate line according to S301, and it can be seen that the gate line has a double peak from the fourth experiment, which should be avoided in engineering applications. The three evaluation indexes provided by the invention can reflect the experimental results relatively truly, comprehensively judge whether the forming quality accords with the expectation, and further improve forming equipment and optimize process parameters.

It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (4)

1. The automatic detection method for the forming quality of the laser grid line based on the microscopic image is characterized by comprising the following steps of:

s100, acquiring measurement data: performing a laser grating line forming process test, and acquiring grating line surface height data by a three-dimensional morphology measuring tool and storing the data as digital quantity;

s200, providing measurement indexes: three quantifiable indicators are proposed from the measurement data: equivalent shielding width in μm and equivalent conductive area in μm ² Dimensionless equivalent aspect ratio;

s300, automatic measurement of measurement indexes is carried out, and the whole flow processing speed is less than 1S.

2. The automatic detection method for forming quality of laser grid line based on microscopic image according to claim 1, wherein the step S100 comprises:

s101, aiming at the forming requirement of the grid line, selecting matched laser grid line forming process parameters, and forming a required grid line on a substrate;

s102, setting the field size to 1024 x 1024pixels by using a three-dimensional morphology measuring tool capable of outputting digital image signals; the position of the measured grid line is moved to enable the grid line to be clearly positioned in the center of a field of view and corrected and leveled;

s103, adjusting the magnification of the measuring tool to enable the display width of the observed laser grid line to be in a range of 256-512 pixels and enable the display width of the base plane to be in a range of 512-768 pixels;

s104, acquiring the height data H of the inner surface of the field of view ₀ i, j, and recording the magnification k and the maximum height h _max ；H ₀ i and j are 1024 x 1024 matrixes, the unit of an internal element is mu m, wherein i and j are indexes in two directions of an image, and the values are 1-1024; k is in pixel/μm; h is a _max Is H ₀ The maximum value of the elements in i, j is expressed in mu m;

s105, normalized height data H (i, j) is expressed as formula H (i, j) =255 (H ₀ (i,j)/h _max ) Calculating and rounding, wherein the value is 0-255, and the matrix is stored as 1024 x 1024 in the form of unsigned shaping, namely, uint 8; the data is further compressed using a lossless compression algorithm at the time of data storage.

3. The automatic detection method for forming quality of laser grid line based on microscopic image according to claim 2, wherein S200 comprises:

s201, selecting a shielding width as a reference for measuring the width of the grid line;

s202, defining an equivalent shielding width w, wherein the unit is μm and comprises the following steps:

in an ideal state, a straight line perpendicular to the grid line is made on the substrate plane and is intersected with the formed grid line to form a straight line segment, and the straight line segment is defined as a shielding width w ₀ The unit is mu m; calculating the length m of each grid line segment before and after the sampling point, namely sampling the total length of 2m+1, and defining the average value of the shielding width of each grid line segment as an equivalent shielding width w;

s203, defining equivalent conductive area a in μm ² Comprising:

forming a plane perpendicular to the gate line and perpendicular to the substrate, intersecting the formed gate line to form a contour curve section, forming a closed pattern with the straight line section in S202, defining the area of the closed pattern as a conductive area a0 in μm ² The method comprises the steps of carrying out a first treatment on the surface of the Taking a grid line segment with the length of 2m+1, and taking the average value of the conductive areas of the grid line segment as an equivalent conductive area a;

s204, defining an equivalent aspect ratio r, comprising:

dividing the equivalent conductive area a in S203 by the square of the equivalent shielding width w in S202 to obtain a dimensionless equivalent aspect ratio r, wherein the dimensionless equivalent aspect ratio r is used for reflecting the shape of the grid line:

4. the automatic detection method for forming quality of laser grid line based on microscopic image according to claim 3, wherein the step S300 comprises:

s301, selecting a sampling length m and a calculation position x:

in the normalized height data H (i, j), the i direction is defined as the gate line direction, and the j direction is the direction perpendicular thereto; x is the i coordinate of the calculated point, and the value range is (m+1, 1024-m);

s302, calculating an equivalent shielding width w, wherein the unit is μm:

wherein i epsilon (x-m, x+m) and j epsilon (x-m, x+m);

H ₁ (i, j) is an intermediate parameter for calculating the equivalent occlusion width w, the numerical meaning is that the area occluded by the grid line is marked as 1, the non-occluded area is marked as 0, and the formula can be expressed as follows:

s303, calculating an equivalent conductive area a with the unit of mu m ² ：

Wherein i is E (x-m, x+m), i>0，

S304, calculating a dimensionless equivalent height-width ratio r:

s305, taking m as 12, calculating variances of w (x), a (x) and r (x) in S302-S304, and defining the variances as ws, as and rs; when the w (x), a (x) and r (x) distribution accords with the 3 sigma rule, the measurement data are valid; when the rule of 3 sigma is not met, the measurement error is too large or the grid lines are uneven and continuous, and the sample is re-measured or judged to be unqualified;

s306, after judging the validity of the data, taking the equivalent shielding width w, the equivalent conductive area a and the dimensionless equivalent aspect ratio r in the sampling range as final output results, and defining the final output results as w _m 、a _m 、r _m ：

S307, 3 indexes describing the morphology of any part of the grid line are defined in S302-S304, a computer program is written for calculation, and the validity of the measurement data is judged through S305; and outputting a final test result by S306 in the case that the data is valid.