CN103438825B - An angular spectrum scanning illumination array type confocal annular microstructure measurement device and method - Google Patents

Abstract

A kind of angular spectrum scanning confocal annular microstructure measurement device of illumination array formula and method belong to ultraprecise three-dimensional microstructure measuring surface form field; This device comprises angular spectrum scanning illumination path, and the light beam sent from donut light source is successively after imaging len, Amici prism, microcobjective, and parallel radiation is surperficial to tested microstructure sample; Comprise accurate confocal measurement light path, imaging moiety adopts pinhole array to coordinate the structure of imageing sensor; First the method obtains the tomographic map of all pixels under different angular spectrum scanning illumination, then utilizes confocal three-dimensional measurement principle, judges the axial coordinate of each pixel, finally simulate the three-dimensional appearance of tested microstructure sample; This design makes every part of tested microstructure sample can find corresponding optimal illumination angle, improves signal strength detection, reduces ground unrest, and then improves measuring accuracy; Realize measuring at a high speed simultaneously.

Description

An angular spectrum scanning illumination array type confocal annular microstructure measurement device and method

technical field

An angular spectrum scanning illumination array type confocal annular microstructure measuring device and method belongs 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 confocal annular microstructure measurement device and method of angular spectrum scanning illumination array, so that each part of the circularly symmetrical microstructure sample to be measured can find the corresponding optimal illumination angle, avoiding circular Some areas cannot be illuminated or complex reflections are caused by the ups and downs of the surface profile of the sample with a symmetrical microstructure to be measured, which improves the detection signal strength, reduces background noise, and improves measurement accuracy. At the same time, the quasi-confocal measurement optical path uses a pinhole array with an image sensor to achieve high-speed measurement.

The purpose of the present invention is achieved like this:

An array-type confocal annular microstructure measuring device with angular spectrum scanning illumination, comprising an angular spectrum scanning illumination optical path and a quasi-confocal measurement optical path;

The described angular spectrum scanning illumination light path comprises: concentric ring light source, imaging lens, dichroic prism, diaphragm and microscopic objective lens; the light beam emitted from the concentric circular light source passes through imaging lens, dichroic prism and microscopic objective lens successively, parallel to Irradiating onto the surface of a circularly symmetric microstructure sample that moves with the three-degree-of-freedom stage; the three-degree-of-freedom stage moves along the three coordinate axes of the Cartesian coordinate system, wherein the z-axis is the direction of the optical axis;

The quasi-confocal measurement optical path includes: a three-degree-of-freedom stage, a microscope objective lens, a diaphragm, a beam splitting prism, a tube lens, a pinhole array and an image sensor; The light beam reflected by the surface of the microstructure sample passes through the microscopic objective lens, aperture, beam splitter, and tube mirror in sequence, and is imaged to the position of the pinhole array, and is imaged by the image sensor;

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

The concentric ring light source is located at the object plane of the imaging lens, and the image plane of the imaging lens coincides with the rear focal plane of the microscopic objective lens on the plane where the diaphragm is located; the front focal plane of the tube mirror is located at the plane where the pinhole array is located; the pinhole array The pinholes on the pinhole array are closely attached to the pixels of the image sensor, and the number of the pinholes is the same as the pixels of the image sensor, and the positions correspond to each other.

In the aforementioned angular spectrum scanning illumination array type confocal annular microstructure measurement device, the concentric annular light source is an LED array.

The radius difference between two adjacent rings of the concentric ring light source is constant or not.

A method for measuring angular spectrum scanning illumination array confocal annular microstructures, comprising the following steps:

Step a, dividing the thickness of the circularly symmetrical microstructure sample to be tested into N layers;

Step b, adjusting the three-degree-of-freedom stage so that the center of the circularly symmetrical microstructure sample to be measured is located on the optical axis;

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

Step c, according to the number M of concentric rings in the concentric ring light source, and the thickness layer N of the circularly symmetrical microstructure sample to be measured, M×N angular spectrum illumination images are formed;

Step d, define the angular spectrum illumination images between different layers under the same angular spectrum illumination as tomographic images, compare the axial envelope curves between the tomographic images of the same pixel 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 all pixels;

Step e, fitting the three-dimensional shape of the circularly symmetrical microstructure sample to be tested according to all the pixels and their axial coordinates.

In the above method for measuring angular spectrum scanning illumination array confocal annular microstructures, the step c is specifically:

Step c1: adjusting the circularly symmetric microstructure sample to be tested through the three-degree-of-freedom stage, so that each layer in the N layers is placed in the front focal plane of the microscopic objective lens in turn;

Step c2: by sequentially lighting up M rings in the concentric ring light source, forming M angular spectrum illuminations for the circularly symmetrical microstructure sample to be tested;

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

Step c1, step c2;

Step c2, step c1;

Finally, M×N angular spectrum illumination images are formed.

Since the present invention is designed with an illumination optical path, the illumination beam is incident on the surface of the circularly symmetrical microstructure sample in parallel, and the illumination angle of the illumination beam is changed by lighting the ring of the concentric ring light source, and the principle of confocal three-dimensional measurement is used, Fit the three-dimensional shape of the circularly symmetrical microstructure sample to be tested; this design enables each part of the circularly symmetrical microstructure sample to be tested to find the corresponding optimal lighting angle, avoiding the surface profile of the circularly symmetrical microstructure sample itself Some areas cannot be illuminated or have complex reflections caused by high and low fluctuations, which can improve the detection signal strength, reduce background noise, and improve measurement accuracy. At the same time, the quasi-confocal measurement optical path uses a pinhole array with an image sensor to achieve high-speed measurement.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the angular spectrum scanning illumination array type confocal annular microstructure measuring device of the present invention.

Fig. 2 is a diagram of the angular spectrum scanning illumination light path of the angular spectrum scanning illumination array type confocal annular microstructure measuring device of the present invention.

Fig. 3 is a quasi-confocal measurement optical path diagram of the angular spectrum scanning illumination array type confocal annular microstructure measurement device of the present invention.

Fig. 4 is a flow chart of the angular spectrum scanning illumination array type confocal annular microstructure measurement method of the present invention.

In the figure: 1 concentric ring light source, 2 imaging lens, 3 dichroic prism, 4 aperture, 5 microscope objective lens, 6 three-degree-of-freedom stage, 7 tube mirror, 8 pinhole array, 9 image sensor.

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 illumination array type confocal annular microstructure measurement device of this embodiment, the angular spectrum scanning illumination light circuit diagram is shown in Figure 2 , and the quasi-confocal measurement light circuit diagram is shown in Figure 3 .

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

The described angle-spectrum scanning illumination light path comprises: concentric ring light source 1, imaging lens 2, dichroic prism 3, diaphragm 4 and microscopic objective lens 5; 3. After the microscope objective lens 5, it is parallelly irradiated to the surface of the circularly symmetrical microstructure sample that moves with the three-degree-of-freedom stage 6; the three-degree-of-freedom stage 6 is along the three coordinate axes of the Cartesian coordinate system Move, where the z axis is the direction of the optical axis;

Described quasi-confocal measurement optical path comprises: three-degree-of-freedom stage 6, microscope objective lens 5, aperture 4, beam splitting prism 3, tube lens 7, pinhole array 8 and image sensor 9; The light beam reflected by the surface of the circularly symmetrical microstructure sample to be measured by the moving stage 6 passes through the microscope objective lens 5, the aperture 4, the beam splitter 3, and the tube mirror 7 in sequence, and is imaged at the position of the pinhole array 8, and is imaged by the image sensor 9;

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

The concentric ring light source 1 is located at the object plane of the imaging lens 2, and the image plane of the imaging lens 2 coincides with the rear focal plane of the microscopic objective lens 5 on the plane where the diaphragm 4 is located; the front focal plane of the tube lens 7 is located at the pinhole array The plane where 8 is located; the pinhole array 8 is in close contact with the pixels of the image sensor 9, and the number of pinholes on the pinhole array 8 is the same as that of the image sensor 9, and their positions correspond to each other.

The above-mentioned angular spectrum scanning illumination array type confocal ring microstructure measuring device, the concentric ring light source 1 is an LED array, and the left view of the concentric ring light source 1 is drawn above the concentric ring light source 1 in Fig. 1; The radius difference between two adjacent rings of the ring light source 1 is constant.

The flow chart of the angular spectrum scanning illumination array type confocal annular microstructure measurement method in this embodiment is shown in Figure 4, and the method includes the following steps:

Step a, dividing the thickness of the circularly symmetrical microstructure sample to be tested into N layers;

Step b, adjusting the three-degree-of-freedom stage 6 so that the center of the circularly symmetrical microstructure sample to be measured is located on the optical axis;

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

Step c, according to the number M of concentric rings in the concentric ring light source 1, and the thickness layer N of the circularly symmetrical microstructure sample to be measured, M×N angular spectrum illumination images are formed;

Step d, define the angular spectrum illumination images between different layers under the same angular spectrum illumination as tomographic images, compare the axial envelope curves between the tomographic images of the same pixel 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 all pixels;

Step e, fitting the three-dimensional shape of the circularly symmetrical microstructure sample to be tested according to all the pixels and their axial coordinates.

Wherein step c is specifically:

Step c1: adjust the circularly symmetrical microstructure sample to be tested through the three-degree-of-freedom stage 6, so that each layer in the N layers is placed in the front focal plane of the microscopic objective lens 5 in sequence;

Step c2: by sequentially lighting up the M rings in the concentric ring light source 1, forming M angular spectrum illuminations for the circularly symmetrical microstructure sample to be tested;

The step c1 and step c2 form a double cycle, and the sequence of the cycle from outside to inside is: step c2 and step c1, finally forming M×N angular spectrum illumination images.

Specific embodiment two

The difference between this embodiment and the first embodiment is that the radius difference between two adjacent rings of the concentric ring light source 1 is not constant, and its beneficial effect is that it can be more precisely adjusted 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 angular spectrum scanning illumination array type confocal annular microstructure measurement method, the sequence of step c preferably double cycle is step c1 and step c2, finally forming M×N Zhang Angular Spectrum Illumination Image. The fastest step c2 is placed on the innermost layer, and the slowest step c1 is placed on the outermost layer. 3D topography reconstruction efficiency.

Claims (2)

1. the confocal annular microstructure measuring method of angular spectrum scanning illumination array formula, the device used comprises angular spectrum scanning illumination path and accurate confocal measurement light path;

Described angular spectrum scanning illumination path comprises: donut light source (1), imaging len (2), Amici prism (3), diaphragm (4) and microcobjective (5); The light beam sent from donut light source (1) is successively after imaging len (2), Amici prism (3), microcobjective (5), and parallel radiation is to the symmetrical tested microstructure sample surface of circle with Three Degree Of Freedom objective table (6) movement; Described Three Degree Of Freedom objective table (6) moves along three coordinate axis of cartesian coordinate system, and wherein, z-axis is optical axis direction;

Described accurate confocal measurement light path comprises: Three Degree Of Freedom objective table (6), microcobjective (5), diaphragm (4), Amici prism (3), Guan Jing (7), pinhole array (8) and imageing sensor (9); The light beam of the symmetrical tested microstructure sample surface reflection of the circle with Three Degree Of Freedom objective table (6) movement is successively through microcobjective (5), diaphragm (4), Amici prism (3), Guan Jing (7), be imaged onto pinhole array (8) position, and by imageing sensor (9) imaging;

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

Described donut light source (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 diaphragm (4) place plane; The front focal plane of Guan Jing (7) is positioned at pinhole array (8) place plane; Pinhole array (8) and imageing sensor (9) pixel are close to, and the pin hole on pinhole array (8) is identical with the pixel quantity of imageing sensor (9), corresponding before and after position;

Described donut light source (1) is LED array;

The semidiameter of described adjacent two annulus of donut light source (1) is constant or is not constant;

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

Step a, by circle symmetrical tested microstructure sample thickness be divided into N layer;

Step b, adjustment Three Degree Of Freedom objective table (6), make the symmetrical tested microstructure sample of circle be centrally located on optical axis;

The order interchangeable of described step a, step b;

Step c, according to the donut quantity M in donut light source (1), the thickness layering N of the symmetrical tested microstructure sample of circle, forms M × N subtended angle spectrum illumination image;

Steps d, the angular spectrum illumination image defining under identical angular spectrum illumination between different layers are tomographic map, axial envelope curve between the tomographic map of contrast same pixel 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 all pixels;

Step e, according to all pixels and axial coordinate thereof, simulate circle symmetrical tested microstructure sample three-dimensional appearance.

2. the confocal annular microstructure measuring method of a kind of angular spectrum scanning illumination array formula according to claim 1, is characterized in that: described step c is specially:

Step c1: by the symmetrical tested microstructure sample of Three Degree Of Freedom objective table (6) adjustment circle, make the every one deck in N layer be placed in the front focal plane of microcobjective (5) successively;

Step c2: by lighting M annulus in donut light source (1) successively, forms M the angular spectrum illumination to the symmetrical tested microstructure sample of circle;

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

Step c1, step c2;

Step c2, step c1;

Final formation M × N subtended angle spectrum illumination image.