CN105353042B - A kind of monocrystalline silicon internal flaw tim e- domain detection imaging method based on SAFT - Google Patents
A kind of monocrystalline silicon internal flaw tim e- domain detection imaging method based on SAFT Download PDFInfo
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- CN105353042B CN105353042B CN201510666805.4A CN201510666805A CN105353042B CN 105353042 B CN105353042 B CN 105353042B CN 201510666805 A CN201510666805 A CN 201510666805A CN 105353042 B CN105353042 B CN 105353042B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
Abstract
The invention discloses a kind of monocrystalline silicon internal flaw tim e- domain detection imaging method based on SAFT, includes the following steps: that phase array transducer is moved along scanning of a surface, obtains the echo-signal that each data collection point disperses accordingly by probe；Echo summation is overlapped to certain point, this point regards a unit as by treated, point-by-point to complete entire two dimension or three-dimensional surface；When sample point is in a plane, two-dimensional cartesian grid is mapped it to；When sample point is in a solid space, three-dimensional cartesian grid is mapped it to, so that it is determined that suspected defects region；Describe the defect characteristic in gained suspected defects region with 6dB-drop method.The present invention is clearly discernible out two and is spaced the hole that small and diameter is 0.8mm, it is found that the quantization of the size and orientation of natural defect is in close proximity to the cutting sample that actual measurement goes out.Effectively increase the spatial resolution and measurement accuracy of defect.
Description
Technical field
The present invention relates to detection technical field of imaging, and in particular to a kind of monocrystalline silicon internal flaw time domain inspection based on SAFT
Survey imaging method.
Background technique
With the fast development of photovoltaic industry and semiconductor industry, demand rapid growth of the whole world to silicon, and monocrystalline silicon material
Material in process of production, crystal bar, crucible in multi-dimensional complicated motion process due to heating temperature, rotation, tensile speed relationship,
The defects of will form bubble, impurity, crackle inside silicon rod.Monocrystalline silicon silicon rod will be generated when being cut into silicon wafer and largely be cut
Cut waste material.Therefore, before slicing process starts, the position of defect, size in silicon rod are nondestructively found, to protection equipment, is reduced more
Tool changing tool bring cost and raising working efficiency etc. have very important meaning.
In recent years, with the development of transducer technology, substantially increase the centre frequency of ultrasonic transducer, flexibility and
The development of reliability, especially phase array transducer greatly reduces the detection time of big material block.Therefore, in many Ministry of Industry
Door, ultrasonic wave nondestructive evaluation is just at the standardized tool for ensuring quality and safety.Under regular situation, in defect area echo width
Spend it is maximum under the conditions of, by distance-gain-size (DGS) method, carried out the measurement that defect is shown, DGS method can react scarce
Size is fallen into, but physical orientation, shape and the degree of defect cannot be assessed, therefore forecasting fatigue and assessment of the integrity of structure will appear
Biggish measuring uncertainty.The uncertainty of measurement and the uncertainty of material property finally will affect the evaluation of material
Knot.Therefore, the uncertainty for reducing evaluation, the accuracy for improving defectoscopy become the key of detection, use imaging method
Degree, orientation and the shape feature for describing defect are a kind of effective detection means.
With the enhancing of centre frequency and the increase of frequency bandwidth, the spatial resolution of ultrasonic non-destructive assessment is generally improved.
High-frequency ultrasonic it is main by decay, infiltration is limited and signal-to-noise ratio reduce limitation.In fact, the check and evaluation of defect very great Cheng
Data acquisition and post-processing technique are additionally depended on degree.In order to improve the resolution ratio of single transducer, synthetic aperture is proposed
Focusing technology (SAFT).The ultrasound of earliest synthetic aperture focusing technology is applied to improve the lateral resolution of airborne radar system
Rate, theory are to synthesize large-scale effective aperture by large-area scanning antenna to improve resolution ratio.For using SAFT's
Industrial ultrasonic nondestructive evaluation applications need complete waveform echo data, therefore, can be reserved for phase information.When with single transducing
When device carries out synthetic aperture focusing technology, it is necessary to from different observation angles, very carefully manually by incidence angle, that is, penetrate
Beam axis is adjusted to vertical with defect reflection device.And phased-array transducer is used, it can be to avoid this inconvenience, because phased array senses
Device can preset the incidence angle in range with automatically scanning.If the position for ignoring sensor is disregarded, substantially it was determined that working as
When sweep spacing between angle is sufficiently small, some incidence angles are perpendicular to or substantially perpendicular to defect reflection device.Recently, SAFT is being used
In terms of carrying out signal processing, the development of industrial ultrasonic image enhancement has attracted many concerns.Most of research, for visualization
Purpose stresses the theoretical side for studying signal processing, and defect or characteristic are relatively obvious, and also have a few studies.
Summary of the invention
For scarce inside the monocrystalline silicon that there are the real industrial application of small-sized defect, the present invention provides a kind of based on SAFT
Fall into tim e- domain detection imaging method.
To achieve the above object, the technical scheme adopted by the invention is as follows:
Monocrystalline silicon internal flaw tim e- domain detection imaging method based on SAFT, includes the following steps:
S1, phase array transducer is moved along scanning of a surface, each data collection point is obtained by probe and is dispersed accordingly
Echo-signal；
S2, echo summation is overlapped to the certain point that step S1 is obtained, this point regards a unit as by treated, point by point
Complete entire two dimension or three-dimensional surface；
S3, when sample point is in a plane, map it to two-dimensional cartesian grid；When sample point is in a solid
When space, three-dimensional cartesian grid is mapped it to, so that it is determined that suspected defects region；
S4, the defect characteristic for describing gained suspected defects region with 6dB-drop method.
Wherein, the 6dB-drop method specifically comprises the following steps:
Step 1: finding out peak point in flaw echo as defect center；
Step 2: the mesh coordinate of each peak value is indicated, until peak value is down to 6dB；
Step 3: using region growing algorithm search rebuild grid in connected domain, if be connected, by its neighborhood include into
Come, connects its coordinate and form defect.
The invention has the following advantages:
It is clearly discernible out two and is spaced the hole that small and diameters are 0.8mm, find the size and orientation of natural defect
Quantization is in close proximity to the cutting sample that actual measurement goes out.Effectively increase the spatial resolution and measurement accuracy of defect.
Detailed description of the invention
Fig. 1 is SATF schematic diagram in the embodiment of the present invention；
In figure,Probe；■ defective locations；Rebuild grid；The beam of defective locations；The same phase of defective locations
It is total.
Fig. 2 is the echo amplitude that SAFT is generated in the embodiment of the present invention.
Fig. 3 is the mesh reconstruction schematic diagram in the embodiment of the present invention under different resolution.
Fig. 4 is mapping graph of the sampled point in reconstruction grid in the embodiment of the present invention.
Fig. 5 is the monocrystalline silicon experimental material schematic diagram for having 2 holes in the embodiment of the present invention.
Fig. 6 is actual measured results in the embodiment of the present invention.
Specific embodiment
In order to which objects and advantages of the present invention are more clearly understood, the present invention is carried out with reference to embodiments further
It is described in detail.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, it is not used to limit this hair
It is bright.
The embodiment of the invention provides a kind of monocrystalline silicon internal flaw tim e- domain detection imaging method based on SAFT, including such as
Lower step
As shown in Figure 1, S1, moving phase array transducer along scanning of a surface, passes through probe and obtain each data collection point
The echo-signal dispersed accordingly；The flaw echo of generation some incidence angle (shown in dotted line) in Fig. 1 at A and the production from B, C from
Each position can be regarded as an aperture element by raw coincidence.
S2, echo summation is overlapped to certain point, this point regards a unit as by treated, point-by-point to complete entire two dimension
Or three-dimensional surface.In this way, constituting the virtual large aperture (dotted line at A, B, C tri- as shown in figure 1 centered on defective locations in two-dimensional surface
It is shown).The size of virtual large aperture refers to the distance from A to C, in fact, if range setting is swept rationally in the angle popped one's head in,
The size of virtual aperture is more much bigger than the size of probe.If virtual aperture concentrates on central point, summation can obtain biggish
Echo amplitude, however the central point if virtual aperture has been staggered can obtain echo amplitude less than normal (as shown in Figure 2).Defect institute
In place's echo-signal enhancing, the noise of material granule and the noise of data collection system reduce, to improve defect area
Signal-to-noise ratio.
S3, when sample point is in a plane, map it to two-dimensional cartesian grid；When sample point is in a solid
When space, three-dimensional cartesian grid is mapped it to, so that it is determined that the resolution parameter setting of suspected defects area grid is true
Possess effect phase information.SAFT vertical resolution ratio should be equidistant with the sampling interval, and unrelated with aperture；Horizontal resolution
Rate should be equal with the mobile step-length of probe.As Fig. 3 vertical resolution is very important parameter.Select excessively high resolution ratio can
There is cavity in the grid that reconstruction can be will lead to, and too low resolution ratio may eliminate effective phase information.
Based on mapping of the sample point in grid is the geometry by the setting of phase array transducer and scanning surface,
Illustrated herein using two-dimensional grid and plane, indicates a grid cell with (i, j) in Fig. 4.The size M*N, i=of grid
1 ..., M, j=1 ..., N. vertical resolution are set as equal with sample point gap length, and horizontal resolution is set as and probe edge
The step-length of planar movement is equal, and p indicates that, along the position of scanning surface, q represents the position in vertical direction, and r indicates sample point to changing
The position of energy device.Assuming that p=1 ..., P, q=1 ..., Q, r=1 ..., the incident angle of the ultrasound of R, α (q) expression q instruction, in order to
Facilitate calculating, it is assumed that physical coordinates and mesh coordinate are in same origin, if the upper left corner of grid is origin, physical location is
(0,0).As shown in figure 4, can be classified as with the physical location of (p, q, r) representative sample point:
X (p, q, r)=L (r) sin (α (q))+S (p)
Y (p, q, r)=L (r) cos (α (q))
(1) in formula, L (r) is distance of the sample point r to energy converter, and S (p) is length of the point p along the plane of scanning motion, it is assumed that sound
Speed is u, and the sampling interval is Δ t, and step delta s can be acquired easily:
L (r)=ru Δ t/2
S (p)=p Δ s+x0 (2)
In formula, x0It is the lateral shift popped one's head in home position, is not necessarily 0, such as x0=5mm refers to the original of probe
Beginning to deviate is 5mm in the horizontal direction.
By the position (x, y) of sample point and grid resolution, (Δ x, Δ y), each sample point can be mapped in grid
In.The mesh coordinate of sample point (x, y) are as follows:
Wherein:Refer to the maximum integer less than or equal to z
The fundamental formular of SAFT algorithm can be expressed simply with following equation:
In formula, K is the set for being mapped in the sample point of grid cell (i, j), and v (p, q, r) is returning for sample point (p, q, r)
Wave-amplitude.It is relatively difficult to directly search K, but iteration whole sample point, then their echo amplitude value is accumulated in corresponding net
In lattice unit.The algorithm steps are as follows:
(1) resolution ratio of Δ x and Δ y are determined；Grid is rebuild in initialization, and initial value is set as 0；
(2) mesh index (i, j) of each sample point (p, q, r) is calculated with formula (1)-(3), then accumulates grid list
Member value V (i, j)=V (i, j)+v (p, q, r).
(3) when each grid cell has a value V (i, j), the visualization of grid is realized.
S4, the defect characteristic for describing gained suspected defects region with 6dB-drop method, treatment process are as follows:
Step 1: finding out peak point in flaw echo as defect center, i.e., V (i, j) is scarce in mesh coordinate (i, j)
Fall into the maximum value in range；
Step 2: the mesh coordinate of each peak value is indicated, until peak value is down to 6dB；
Step 3: using region growing algorithm search rebuild grid in connected domain, if be connected, by its neighborhood include into
Come, connects its coordinate and form defect.
Embodiment 1
There are 2 artificial foramen among the single crystal silicon material block of selection, as shown in Figure 5.This block cylindrical material diameter is
152.4mm long 120mm.Two hole same sizes, diameter are 0.8mm, and deep 12mm is divided into 2mm between adjacent.Using
The phased-array transducer of 10MHz acquires data.Angle (share 21 incidence angles) of the probe with 1.0 ° of step-length from -10 ° to+10 °
Scanning.Step-length along scan path is 0.1mm.With the length increment of every 0.1mm, it is super that this structure can obtain totally 21 A
Scanning element.Have recorded 802 anchor points altogether along scan path, that is to say, that overlay length 80.2mm.Sampling interval is 10-8
Second, ultrasonic propagation velocity is 9408m/s per second in monocrystalline silicon silicon.Using reconstruction method, the resolution ratio of grid can be calculated, is set as every
Pixel (x, y) (0.0297mm, 0.1mm).By the minimum value and maximum value in domain 1,1 range, make the grid specification of clip
Change, then visualizes grid using color look up table.After standardization, the maximum value of grid is 1, and minimum value is -1.
The actual diameter contrast table of table 1 SAFT measurement result and flat hole.
Table 1 show the measurement result of SAFT and the actual diameter in flat hole.As it can be seen from table 1 the measurement knot of SAFT
Fruit is greater than the actual size of hole, and relative error is about 13.4-25.9%.
The phase information that traditional phased array detects is limited or no record.In order to compare SAFT and tradition side
The difference of method has selected the same sensor to acquire data with traditional set-up mode.Similarly, using the phased array of 10MHz
Sensor acquires data, and scanning range is set as -10 ° to+10 ° angles, and step-length is 1.0 °, totally 21 incidence angles.The echo received
Data are adjusted, and without saving phase information.Its reconstructed results cannot effectively distinguish two circular cavities.
Embodiment 2
Natural defect verifying
By have natural defect single crystal silicon material block, further study SAFT rebuild and measurement method it is effective
Property.Verification step includes:
(1) material block is detected using phased-array transducer.Detection uses the phased-array transducer of 10MHz, and range is set as
From -20 ° of angles to+20 ° of angles, step-length is 2.0 °, totally 21 incidence angles.Linear movement of the sensor at the top of material block；
(2) data are handled with the method proposed, so that it is determined that suspicious defect area；
(3) it determines suspicious region, describes defect characteristic with 6dB-drop method；
(4) it passes through detection plane and cuts material block, specifically measure actual defect geometry structure；
(5) authentic testing and SAFT are compared as a result, the validity of SAFT method can be determined.
The line of demarcation of the local peaking point and 6dB-drop in this region can be found by region growth method.Point of defect
The length of boundary line long axis is 0.93mm, and the length of short axle is 0.15mm, and the inclination angle of defect is shown in Table 2.
2 SAFT measurement result of table is with practical natural flaw contrast table
After testing with the above analysis, material block is separated across detection faces.The long axis length that actual measurement obtains is
0.8mm is slightly less than the result that SAFT is obtained.For conservative effect, it is believed that it is reasonable that SAFT result, which is greater than physical length,.
When evaluating defect, initial crack size can be used as with SAFT result, certain safety margins can be provided.It also found when detection
There are other high-density regions, this is because interface and reflective as a result, as seen in usual ultrasound image.One of allusion quotation
The artifacts of type are characterized in typically exhibiting out the geometrical pattern of rule, the almost the same band-like and line style such as density.However, day
Right defect, and may be more much smaller than artifacts often without specific pattern.In order to distinguish in mechanization detection process
Artificial and natural defect can use signal filtering technique to rebuild grid to eliminate or reduce artifacts.Alternatively, it is also possible to
Proximity index quantity in the set obtained using region growing algorithm, the threshold value of size can be used to reject comprising excessively connecting
Connect the combination of index.
In conclusion SAFT can identify the hole of spacing very little, moreover it is possible to be assessed in the case where relative error very little
Flaw size, and traditional reconstruction cannot identify each hole.This method can be widely used in existing Ultrasonic NDT
In practice, to improve the accuracy and reliability of fault in material feature description.
The above is only a preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
For member, without departing from the principle of the present invention, it can also make several improvements and retouch, these improvements and modifications are also answered
It is considered as protection scope of the present invention.
Claims (2)
1. the monocrystalline silicon internal flaw tim e- domain detection imaging method based on SAFT, which comprises the steps of:
S1, phase array transducer is moved along scanning of a surface, time that each data collection point disperses accordingly is obtained by probe
Wave signal；
S2, echo summation is overlapped to the certain point that step S1 is obtained, this point regards a unit as by treated, point-by-point to complete
Entire two-dimensional surface；
S3, when sample point is in a plane, map it to two-dimensional cartesian grid；So that it is determined that suspected defects region；
A grid cell, the size M*N, i=1 ..., M, j=1 ... of grid, N, vertical resolution setting are indicated with (i, j)
To be equal with sample point gap length, horizontal resolution is set as equal along the step-length of planar movement with probe, and p is indicated along scanning surface
Position, q represents the position in vertical direction, and r indicates sample point to the position of energy converter, it is assumed that p=1 ..., P, q=1 ...,
Q, r=1 ..., R, α (q) indicate the incident angle of the ultrasound of q instruction, calculate for convenience, it is assumed that physical coordinates and mesh coordinate exist
Same origin, if the upper left corner of grid is origin, physical location is (0,0), with the physical bit of (p, q, r) representative sample point
It sets, can be classified as:
X (p, q, r)=L (r) sin (α (q))+S (p)
Y (p, q, r)=L (r) cos (α (q)) (1)
In formula, L (r) is distance of the sample point r to energy converter, and S (p) is length of the point p along the plane of scanning motion, it is assumed that velocity of sound u is adopted
Δ t is divided between sample, step delta s can be acquired easily:
L (r)=ru Δ t/2
S (p)=p Δ s+x0 (2)
In formula (2), x0It is the lateral shift popped one's head in home position；
By the position (x, y) of sample point and grid resolution (Δ x, Δ y), each sample point can be mapped within a grid,
The mesh coordinate of sample point (x, y) are as follows:
The fundamental formular of SAFT algorithm can be expressed simply with following equation:
In formula (4), K is the set for being mapped in the sample point of grid cell (i, j), and v (p, q, r) is returning for sample point (p, q, r)
Wave-amplitude, direct search K is relatively difficult, but iteration whole sample point, then their echo amplitude value is accumulated in corresponding net
In lattice unit, steps are as follows:
(1) resolution ratio of Δ x and Δ y are determined；Grid is rebuild in initialization, and initial value is set as 0；
(2) mesh index (i, j) of each sample point (p, q, r) is calculated with formula (1)-(3), then accumulates grid cell value
V (i, j)=V (i, j)+v (p, q, r)；
(3) when each grid cell has a value V (i, j), the visualization of grid is realized；
S4, the defect characteristic for describing gained suspected defects region with 6dB-drop method.
2. the monocrystalline silicon internal flaw tim e- domain detection imaging method according to claim 1 based on SAFT, which is characterized in that
The 6dB-drop method specifically comprises the following steps:
Step 1: finding out peak point in flaw echo as defect center；
Step 2: the mesh coordinate of each peak value is indicated, until peak value is down to 6dB；Step 3: being looked into using region growing algorithm
The connected domain rebuild in grid is looked for, if be connected, its neighborhood is included, its coordinate is connected and forms defect.
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| CN106093205B (en) * | 2016-05-31 | 2019-04-09 | 大连理工大学 | A kind of thick-walled structure defect inspection method based on oblique incidence ultrasound synthetic aperture focusing |
| CN108459088A (en) * | 2018-05-09 | 2018-08-28 | 北京领示科技有限公司 | A kind of three-dimensional conversion of phased-array ultrasonic signal data and fusion method |
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| CN111579646B (en) * | 2020-05-29 | 2021-07-06 | 中国地质大学（北京） | In-situ nondestructive testing method for stone cultural relic fracture |
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