CN103411559B - Based on the accurate confocal microstructure measuring method of angular spectrum scanning of matrix lamp - Google Patents

Abstract

The angular spectrum scanning quasi-confocal microstructure measurement device and method based on array illumination belong to the field of ultra-precise three-dimensional microstructure surface topography measurement; After the prism and the microscope objective lens, it is irradiated in parallel to the surface of the microstructure sample to be tested, and different LEDs in the LED array correspond to different angular spectrum illuminations; this method first obtains tomographic images of all pixels under different angular spectrum scanning illuminations, and then uses Confocal three-dimensional measurement principle, judging the axial coordinates of each pixel, and finally fitting the three-dimensional shape of the microstructure sample to be tested; this design enables each part of the microstructure sample to be tested to find the corresponding optimal illumination angle , to avoid some areas that cannot be illuminated or complex reflections caused by the ups and downs of the surface profile of the microstructure sample to be measured, improve the detection signal strength, reduce background noise, and improve measurement accuracy.

Description

Quasi-confocal Microstructure Measurement Method Based on Array Illumination

technical field

The invention relates to an angular spectrum scanning quasi-confocal microstructure measurement device and method based on array illumination, belonging to the field of ultra-precise three-dimensional microstructure surface topography measurement.

Background technique

The processing and application of microstructures are mainly reflected in three aspects: microelectronics technology, microsystem technology and micro-optical technology, such as typical applications such as computer chips, biochips and microlens arrays. The common feature of the above-mentioned technologies is that they have a three-dimensional structure, and the size of the functional structure is on the order of micron, submicron or nanometer. development of related industries. With the rapid development of micromachining technology, instruments capable of rapid and non-destructive three-dimensional detection of such samples will have great application prospects.

U.S. Patent US3013467 discloses a confocal imaging technology for the first time. This invention obtains the axial detection ability of the sample contour by introducing the confocal imaging technology of the three-point optical conjugation of point light source, point illumination and point detection. Cooperate with the movement of the stage in the horizontal direction to realize three-dimensional measurement. Chinese patent CN1395127A discloses a confocal microscopic measurement system. The invention utilizes confocal technology and introduces an interference optical path into the confocal optical path to obtain a highly sensitive interferometric signal and realize high-precision measurement of the axial direction of the sample. US Patent US6282020B1 discloses a confocal microscope system based on a scanning galvanometer. The invention utilizes the confocal principle and introduces the galvanometer scanning technology to obtain the ability of converging the illumination spot to move at high speed on the sample surface, realize fast confocal detection, and improve the measurement speed. However, the above three methods converge parallel light beams to the surface of the sample for illumination through a microscope objective lens. When measuring a three-dimensional sample, due to the ups and downs of the surface profile of the sample itself, the converged illumination beam is blocked, which will cause some areas to be unavailable. Illumination or complex reflections will cause the attenuation of the detection signal strength and the enhancement of background noise, which will reduce the measurement accuracy or even make it impossible to measure.

Contents of the invention

In order to solve the above problems, the present invention discloses a quasi-confocal microstructure measurement device and method based on array illumination, so that each part of the microstructure sample to be measured can find the corresponding optimal illumination angle, avoiding the Some areas cannot be illuminated or undergo complex reflections due to the ups and downs of the surface profile of the microstructure sample itself, which improves the detection signal strength, reduces background noise, and improves measurement accuracy.

The purpose of the present invention is achieved like this:

An angular spectrum scanning quasi-confocal microstructure measurement device based on array illumination, including an angular spectrum scanning illumination optical path and a quasi-confocal measurement optical path;

The described angular spectrum scanning illumination optical path comprises: LED array, imaging lens, dichroic prism, first aperture and microscopic objective lens; After the light beam sent from LED array passes through imaging lens, dichroic prism and microscopic objective lens in turn, it is irradiated in parallel to The surface of the microstructure sample to be measured moves axially with the stage;

The quasi-confocal measurement optical path includes: stage, microscope objective lens, first aperture, dichroic prism, tube mirror, second aperture, scanning lens, two-dimensional scanning galvanometer, focusing lens, pinhole and detection The light beam reflected by the surface of the microstructure sample that moves axially with the stage passes through the microscope objective lens, the first aperture, the beam splitting prism, the tube lens, the second aperture, the scanning lens, the two-dimensional scanning galvanometer, The focusing lens is imaged to the position of the pinhole and imaged by the detector; the two-dimensional scanning galvanometer performs two-dimensional rotation on the plane where it is located or in a plane parallel to it, with two directions perpendicular to each other as rotation axes;

The angular spectrum scanning illumination light path and the quasi-confocal measurement light path share a dichroic prism, a first diaphragm and a microscope objective lens;

The LED array is located on the object plane of the imaging lens, and the image plane of the imaging lens coincides with the rear focal plane of the microscope objective lens on the plane where the first diaphragm is located; the front focal plane of the tube mirror coincides with the rear focal plane of the scanning lens on the second The plane where the second diaphragm is located; the pinhole is located at the front focal plane of the focusing lens, and is close to the detector.

In the aforementioned angular spectrum scanning quasi-confocal microstructure measurement device based on array illumination, the LED arrays are arranged in horizontal and vertical directions or in two directions at 45° and 135° to the horizontal direction.

The LED arrays are arranged at equal intervals or at unequal intervals.

The above-mentioned angle-spectrum scanning quasi-confocal microstructure measurement device based on array illumination is provided with a cross axis or a spherical cage type universal joint in the direction that the two-dimensional scanning galvanometer deviates from the beam propagation direction.

The angular spectrum scanning quasi-confocal microstructure measurement method based on array illumination comprises the following steps:

Step a, dividing the thickness of the tested microstructure sample into N layers;

Step b, setting a total of P spatial positions for the two-dimensional scanning galvanometer;

The order of described step a, step b can be exchanged;

Step c. According to the number M of LEDs in the LED array, the thickness layer N of the microstructure sample to be tested, and the spatial position P of the two-dimensional scanning galvanometer, M×N angular spectrum illumination images are formed, and each angular spectrum illumination image pixel The number is P;

Step d, define the angular spectrum illumination images between different layers under the same angular spectrum as tomographic images, compare the axial envelope curves between the tomographic images at the same spatial position under M angular spectrum illuminations, and select the best The envelope curve close to the fourth power of the sinc function, according to the principle of confocal three-dimensional measurement, judge the axial coordinates of P spatial position points;

Step e, fitting the three-dimensional shape of the microstructure sample to be tested according to the P spatial position points and their axial coordinates.

In the method for measuring the quasi-confocal microstructure based on array illumination, the described step c is specifically:

Step c1: adjusting the microstructure sample to be tested through the stage, so that each layer in the N layers is placed in the front focal plane of the microscope objective lens in turn;

Step c2: M LEDs in the LED array are sequentially turned on to form M angular spectrum illuminations for the microstructure sample to be tested;

Step c3: by adjusting the P spatial positions of the two-dimensional scanning galvanometer, the acquisition of the illumination image by the detector is realized;

The step c1, step c2, and step c3 form a triple cycle, and the cycle sequence from outside to inside is one of the following sequences:

Step c1, step c2, step c3;

Step c1, step c3, step c2;

Step c2, step c1, step c3;

Step c2, step c3, step c1;

Step c3, step c1, step c2;

Step c3, step c2, step c1;

Finally, M×N angular spectrum illumination images are formed, and the number of pixels in each angular spectrum illumination image is P.

Since the present invention is designed with an illumination optical path, the illumination beam is incident on the surface of the microstructure sample in parallel, and the illumination angle of the illumination beam is changed by lighting different LEDs in the LED array, and the confocal three-dimensional measurement principle is used to fit the The three-dimensional shape of the microstructure sample to be tested; this design enables each part of the microstructure sample to be tested to find the corresponding optimal lighting angle, avoiding the undulation of the surface profile of the microstructure sample itself. Illumination or complex reflections can increase the detection signal strength and reduce background noise, thereby improving measurement accuracy.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the angular spectrum scanning quasi-confocal microstructure measurement device based on the array illumination of the present invention.

Fig. 2 is a diagram of the angular spectrum scanning illumination light path of the angular spectrum scanning quasi-confocal microstructure measurement device based on the array illumination of the present invention.

Fig. 3 is a diagram of the quasi-confocal measurement light path of the angular spectrum scanning quasi-confocal microstructure measurement device based on the array illumination of the present invention.

Fig. 4 is a flow chart of the method for measuring quasi-confocal microstructures based on array illumination in the present invention.

In the figure: 1LED array, 2 imaging lens, 3 dichroic prism, 4 first aperture, 5 microscope objective lens, 6 stage, 7 tube mirror, 8 second aperture, 9 scanning lens, 10 two-dimensional scanning galvanometer , 11 focusing lenses, 12 pinholes, 13 detectors.

Detailed ways

The specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The so-called angular spectrum scanning illumination is to illuminate the surface of the microstructure sample to be measured with a parallel beam and realize continuous or discrete change of the incident angle of the parallel light through a scanning mechanism or other technical means. The description of this illumination method in the frequency domain is the angle Spectrum scanning illumination.

The confocal measurement method is to use the three-point optical conjugate method of point illumination, point object and point detection to realize the measurement ability of the optical axis direction, and then complete the three-dimensional measurement. The quasi-confocal measurement method mentioned in this patent is: use angular spectrum scanning illumination instead of point illumination, while retaining the optical conjugate of point object and point detection. This method not only retains the three-dimensional measurement capability of confocal measurement, but also introduces angular spectrum scanning illumination to improve the detection signal strength, reduce background noise, and improve measurement accuracy.

Specific embodiment one:

Figure 1 shows the structural diagram of the angular spectrum scanning quasi-confocal microstructure measurement device based on array illumination in this embodiment, Figure 2 shows the angular spectrum scanning illumination light path, and Figure 3 shows the quasi-confocal measurement light path.

The measurement device includes an angular spectrum scanning illumination optical path and a quasi-confocal measurement optical path;

The described angular spectrum scanning illumination light path includes: LED array 1, imaging lens 2, dichroic prism 3, first aperture 4 and microscopic objective lens 5; Behind the microscope objective lens 5, parallel irradiation is carried out to the surface of the microstructure sample to be measured which moves axially with the stage 6;

The quasi-confocal measurement optical path includes: a stage 6, a microscope objective lens 5, a first aperture 4, a dichroic prism 3, a tube lens 7, a second aperture 8, a scanning lens 9, and a two-dimensional scanning galvanometer 10 , focusing lens 11, pinhole 12 and detector 13; The light beam reflected by the surface of the measured microstructure sample that moves axially with the stage 6 passes through the microscopic objective lens 5, the first diaphragm 4, the beam splitting prism 3, the tube mirror in sequence 7. The second diaphragm 8, the scanning lens 9, the two-dimensional scanning vibrating mirror 10, and the focusing lens 11 are imaged to the position of the pinhole 12 and imaged by the detector 13; Or in a plane parallel to it, take the two directions perpendicular to each other as the rotation axis to perform two-dimensional rotation;

The angular spectrum scanning illumination light path and the quasi-confocal measurement light path share the dichroic prism 3, the first diaphragm 4 and the microscope objective lens 5;

The LED array 1 is arranged at equal intervals in the horizontal and vertical directions, and is positioned at the object plane of the imaging lens 2, and the left view of the LED array 1 is drawn above the LED array 1 in Fig. 1; the image plane of the imaging lens 2 and The rear focal plane of the microscope objective lens 5 coincides with the plane where the first diaphragm 4 is located; the front focal plane of the tube mirror 7 and the rear focal plane of the scanning lens 9 coincide with the plane where the second diaphragm 8 is located; the pinhole 12 is located at the plane of the focusing lens 11 The front focal plane is close to the detector 13.

The above-mentioned angular spectrum scanning quasi-confocal microstructure measurement device based on array illumination is provided with a motorized cross axis in the direction that the two-dimensional scanning galvanometer 10 deviates from the beam propagation direction, so as to realize the control of the spatial position of the two-dimensional scanning galvanometer 10 .

The flow chart of the method for measuring the quasi-confocal microstructure based on array illumination and angular spectrum scanning in this embodiment is shown in Figure 4. The method includes the following steps:

Step a, dividing the thickness of the tested microstructure sample into N layers;

Step b, setting the two-dimensional scanning galvanometer 10 to have a total of P spatial positions;

Step c, according to the number M of LEDs in the LED array 1, the thickness layer N of the microstructure sample to be tested, and the spatial position P of the two-dimensional scanning galvanometer 10, M×N angular spectrum illumination images are formed, and each angular spectrum illumination The number of image pixels is P;

Step d, define the angular spectrum illumination images between different layers under the same angular spectrum as tomographic images, compare the axial envelope curves between the tomographic images at the same spatial position under M angular spectrum illuminations, and select the best The envelope curve close to the fourth power of the sinc function, according to the principle of confocal three-dimensional measurement, judge the axial coordinates of the spatial position point;

Step e, fitting the three-dimensional shape of the microstructure sample to be tested according to the P spatial position points and their axial coordinates.

Wherein step c is specifically:

Step c1: adjust the microstructure sample to be measured through the stage 6, so that each layer in the N layers is placed in the front focal plane of the microscope objective lens 5 in sequence;

Step c2: M LEDs in the LED array 1 are sequentially turned on to form M angular spectrum illuminations for the microstructure sample to be tested;

Step c3: by adjusting the P spatial positions of the two-dimensional scanning galvanometer 10, the acquisition of the illumination image by the detector 13 is realized;

The step c1, step c2, and step c3 form a triple cycle, and the order of the cycle from outside to inside is: step c1, step c3, and step c2.

Specific embodiment two:

The difference between this embodiment and the specific embodiment 1 is that in the described angular spectrum scanning quasi-confocal microstructure measurement device based on array illumination, the LED array 1 is arranged at unequal intervals in the horizontal and vertical directions, and its beneficial effect is that it can be The direction is adjusted more precisely within a certain range of illumination angle spectrum.

Specific embodiment three:

The difference between this embodiment and the specific embodiment 1 is that in the described angular spectrum scanning quasi-confocal microstructure measurement device based on array illumination, the LED arrays 1 are arranged at equal intervals in two directions of 45° and 135° from the horizontal direction. , the beneficial effect is that the diagonal spectrum can be uniformly adjusted in this direction.

Specific embodiment four:

The difference between this embodiment and the specific embodiment 1 is that in the array illumination-based angular spectrum scanning quasi-confocal microstructure measurement device, the LED array 1 is arranged at unequal distances in two directions of 45° and 135° from the horizontal direction. The beneficial effect is that the direction can be adjusted more precisely within a certain range of illumination angle spectrum.

Specific embodiment five:

The difference between this embodiment and the specific embodiment 1 is that in the array illumination-based angle-spectrum scanning quasi-confocal microstructure measurement method, step c is preferably in the order of three cycles of step c3, step c1, and step c2; the execution speed The fastest step c2 is placed in the innermost layer, and the slowest step c3 is placed in the outermost layer, which can reduce the time spent on the angular spectrum illumination image and improve the three-dimensional shape reconstruction efficiency of the microstructure sample under test.

Claims (2)

1., based on the accurate confocal microstructure measuring method of angular spectrum scanning of matrix lamp, the device used comprises angular spectrum scanning illumination path and accurate confocal measurement light path;

Described angular spectrum scanning illumination path comprises: LED array (1), imaging len (2), Amici prism (3), the first diaphragm (4) and microcobjective (5); The light beam sent from LED array (1) is successively after imaging len (2), Amici prism (3), microcobjective (5), and parallel radiation is to the tested microstructure sample surface moved axially with objective table (6);

Described accurate confocal measurement light path comprises: objective table (6), microcobjective (5), the first diaphragm (4), Amici prism (3), Guan Jing (7), the second diaphragm (8), scanning lens (9), two-dimensional scanning mirrors (10), condenser lens (11), pin hole (12) and detector (13); The light beam of the tested microstructure sample surface reflection moved axially with objective table (6) is successively through microcobjective (5), the first diaphragm (4), Amici prism (3), Guan Jing (7), the second diaphragm (8), scanning lens (9), two-dimensional scanning mirrors (10), condenser lens (11), be imaged onto pin hole (12) position, and by detector (13) imaging; Described two-dimensional scanning mirrors (10), in its place plane or plane in parallel, with orthogonal both direction for rotating shaft, carries out two-dimensional rotary;

Described angular spectrum scanning illumination path and accurate confocal measurement light path share Amici prism (3), the first diaphragm (4) and microcobjective (5);

Described LED array (1) is positioned at the object plane of imaging len (2), and the picture plane of imaging len (2) and the back focal plane of microcobjective (5) coincide with the first diaphragm (4) place plane; The front focal plane of Guan Jing (7) and the back focal plane of scanning lens (9) coincide with the second diaphragm (8) place plane; Pin hole (12) is positioned at the front focal plane of condenser lens (11), is close to detector (13);

Described LED array (1) is for horizontal vertical direction arrangement or from the horizontal by 45 ° and 135 ° of both direction arrangements;

Described LED array (1) is equidistantly arrangement or unequal-interval arrangement;

Deviate from the direction of beam propagation at two-dimensional scanning mirrors (10), be provided with joint spider or rzeppa joint;

It is characterized in that: said method comprising the steps of:

Step a, the thickness of tested microstructure sample is divided into N layer;

Step b, total P the locus of setting two-dimensional scanning mirrors (10);

The order interchangeable of described step a, step b;

Step c, according to the LED quantity M in LED array (1), the thickness layering N of tested microstructure sample, the locus P of two-dimensional scanning mirrors (10), form M × N subtended angle spectrum illumination image, and every subtended angle spectrum illumination image number of pixels is P;

Steps d, the angular spectrum illumination image defining under identical angular spectrum between different layers are tomographic map, axial envelope curve between the tomographic map of contrast same spatial location under M angular spectrum illumination, pick out closest to the quadruplicate enveloping curve of sinc function, according to confocal three-dimensional measurement principle, judge the axial coordinate of P locus point;

Step e, according to P locus point and axial coordinate thereof, simulate the three-dimensional appearance of tested microstructure sample.

2. the accurate confocal microstructure measuring method of the scanning of the angular spectrum based on matrix lamp according to claim 1, is characterized in that: described step c is specially:

Step c1: adjust tested microstructure sample by objective table (6), makes the every one deck in N layer be placed in the front focal plane of microcobjective (5) successively;

Step c2: form M the angular spectrum illumination to tested microstructure sample by M the LED lighted successively in LED array (1);

Step c3: by P locus of adjustment two-dimensional scanning mirrors (10), realize detector (13) to the collection of illumination image;

Described step c1, step c2, step c3 form three and recirculate, and circular order is from outside to inside followed successively by one in following order:

Step c1, step c2, step c3;

Step c1, step c3, step c2;

Step c2, step c1, step c3;

Step c2, step c3, step c1;

Step c3, step c1, step c2;

Step c3, step c2, step c1;

Final formation M × N subtended angle spectrum illumination image, every subtended angle spectrum illumination image number of pixels is P.