CN103969220A - Method for detecting dynamic optical properties of UV (Ultraviolet) glue in curing process - Google Patents

Abstract

The invention belongs to the field of optoelectronic devices and manufacturing technology, and specifically relates to a method for detecting dynamic optical characteristics in the curing process of UV glue, which includes the following steps: preparing a micro waveguide cavity, pouring UV glue into it; The glass sheet of the film is bonded to the waveguide cavity to form a double-sided metal-clad waveguide structure waveguide; the incident light path is built, and the UV lamp is cured from one side; the position-sensitive detector is used to detect in real time when the laser propagates in the waveguide structure and undergoes total reflection. Lateral displacement; where the lateral displacement is greatly enhanced when the laser propagates in the waveguide structure and generates a guided mode, that is, the mode number corresponding to the sharp peak of the lateral displacement, the known incident angle, and the mode of the waveguide structure The intrinsic equation deduces the dynamic change of the dielectric constant of the UV glue, and then the dynamic change of the refractive index of the UV glue can be calculated. The advantage is that the method of the invention is simple and effective.

Description

A method for detecting dynamic optical characteristics of UV glue curing process

technical field

The invention belongs to the technical field of design and manufacture of optoelectronic devices, and in particular relates to a method for detecting dynamic characteristics of UV glue curing process.

Background technique

With the rapid development of microelectronics technology, the integration of integrated chips is getting higher and higher, and its characteristic line width is getting smaller and smaller. It is becoming more and more difficult and costly to prepare nano-micro components close to nanometer precision by traditional semiconductor technology. high. The nanoimprint technology that appeared in the mid-1990s does not need various expensive and complicated optical systems and electron beam exposure, and can produce various nano-pattern structures on large-area wafers with high precision and in large quantities through precise replication and low-cost. In recent years, various optical nanoscale and micro-scale components with superior performance have been prepared based on UV-cured nanoimprint technology, such as subwavelength grating filters, polarizers, and optical integrated chips.

In UV-curable nanoimprint technology, curing glue is the core material used in the preparation of components, and the evolution of mechanical and optical properties during the molding process has a decisive impact on the performance of components including optical uniformity. Therefore, the dynamic quantitative detection of the evolution of material optical properties (mainly refractive index) during the curing process of cured glue under different intensities of ultraviolet light is of great significance.

The curing glue currently used in the market has a small change in refractive index before and after curing, and due to the introduction of ultraviolet light sources, it is difficult for the traditional ellipsometry to complete such measurement tasks. It is necessary to rely on optical principles to carry out independent measurement optical design and build.

Contents of the invention

In view of the problems existing in the above-mentioned prior art, the present invention adopts a double-sided metal-clad waveguide structure, and detects the dynamic optical characteristics of the UV glue curing process by measuring the lateral displacement of the laser reflected light when the incident light is totally reflected to excite the waveguide mode. . Its method is simple and effective.

The double-sided metal-clad waveguide structure is a special type of optical waveguide structure. Compared with the traditional dielectric waveguide structure, it has a stronger ability to confine the electromagnetic field, and the effective refractive index range of the guided mode is larger, and it can start from zero. In this way, it can be obtained from free space without resorting to coupling devices such as prisms or gratings. Electromagnetic field energy can be coupled into the waveguide. When the thickness of the double-sided metal-clad waveguide waveguide layer reaches the submillimeter scale, the waveguide can accommodate thousands of guided modes. When coupling with free space, if the incident angle is large, the mode density in the waveguide is quite large, and the attenuation of total reflection The total reflection absorption peaks of the (Attenuated Total Reflecton, ATR) spectrum overlap each other and cannot be distinguished, but when the incident angle is small, a series of discrete guided modes can be excited, that is, ultra-high-order guided modes. The double-sided metal-clad waveguide has an enhanced Goose-Hanchen effect near the attenuated total reflection peak, and the resulting Goose-Hanchen displacement can reach the order of hundreds of microns or even millimeters.

In the present invention, we use the waveguide cavity where the sample is placed as the waveguide layer, and the light wave propagates in the waveguide layer in the form of an oscillating field. The energy of the light wave is concentrated here, and the interaction with the medium of the waveguide layer is very strong. The incident light energy in the sensitive area enhances the GH shift and improves the detection sensitivity.

The technical solution of the present invention is specifically described as follows.

A method for detecting the dynamic optical characteristics of the UV glue curing process, which uses a double-sided metal-clad waveguide structure waveguide for detection, specifically comprising the following steps:

Step a. adopt the magnetron sputtering method to plate the noble metal films with different thicknesses on the two glass sheets respectively;

Step b. Using photolithography to fabricate a submillimeter-scale fence on a thicker noble metal film as a waveguide cavity;

Step c. Clean the above-mentioned device with alcohol, after drying, inject UV glue into the waveguide cavity, cover the glass sheet covered with thinner precious metal film on the waveguide cavity, and the precious metal film of the upper glass sheet contacts the UV glue to form The waveguide cavity is a double-sided metal-clad waveguide structure waveguide with a waveguide layer;

Step d. Using a clamp to fix the above-mentioned waveguide structure;

Step e. Collimate the laser beam at an angle When it is incident on the upper glass sheet, total reflection occurs at the interface between the upper glass and the upper noble metal film, and the position of the reflected light of the laser beam is detected and received by a position sensitive detector;

Step f. The UV light whose beam width is slightly larger than the size of the fence is incident on the UV glue of the waveguide cavity from below, and its intensity is modulated according to the curing time of the cured glue;

Step g. Adjust the optical path so that the laser reflected from the interface between the upper glass and the upper noble metal film of the double-sided metal-clad waveguide is vertically incident on the position-sensitive detector probe to detect the laser reflected light during the curing process of UV glue in real time. Calculate the distance between the changing light spot and its initial position, the initial position is the position of the reflected light spot when no guided mode is generated before curing;

Step h. According to the position where the laser beam is totally reflected in the waveguide structure and the guided mode is greatly enhanced, that is, the mode number corresponding to the sharp peak of the lateral displacement, the known incident angle , the dielectric constant of the noble metal film and glass, and the mode eigenequation of the waveguide, inversely deduce the dynamic change of the dielectric constant of the UV glue, and then calculate the dynamic change of the refractive index of the UV glue.

In the above step e, the He-Ne laser emits the initial beam first, and then the initial beam passes through a polarizing prism to become a TE or TM beam, and then passes through a spatial filter to filter out high-order components before outputting, and finally incident on the upper glass plate.

In the above step e, when the laser beam is incident, firstly calculate through matlab simulation to obtain the angle at which multiple sharp peaks of lateral displacement can be observed during the UV glue curing process The theoretical value, and then conduct an angle scan in a small range around the theoretical value, and select it based on the results of the position sensitive detector.

In the above step h, when the laser beam is incident, the dynamic change of the UV glue dielectric constant is calculated by the mode eigenequation of the waveguide, and the mode eigenequation is is the propagation constant of the waveguide layer perpendicular to the direction of the noble metal film, d is the thickness of the waveguide layer, m is the mode number, is the phase shift when the laser light is totally reflected at the interface between the waveguide layer and the noble metal film.

The present invention first prepares the composite waveguide structure, puts the UV glue to be tested into the waveguide cavity, uses the laser collimated beam to incident on the upper surface, and excites the waveguide mode inside the UV glue, thus resulting in the evanescent wave with more energy of the incident light Transitioning into the waveguide mode causes a large enhancement of the lateral displacement at total reflection, so that within-error readings can be taken on the PSD. At the same time, since the lateral displacement is related to factors such as the wavelength and angle of the incident light, it is necessary to design a corresponding waveguide structure so that multiple waveguide modes can be excited during the curing process of UV glue, so that multiple lateral displacements can be observed on the PSD. Sharp peak, and then use the corresponding mode number, and the known incident angle, the dielectric constant of the noble metal film and glass, and the mode eigenequation of the waveguide to inversely deduce the dynamic change of the dielectric constant of the UV glue, and then it can be calculated. Dynamic changes in the refractive index of UV glue. The method of the invention is simple, and is very effective for measuring the process in which the refractive index will change dynamically.

Description of drawings

Figure 1 is a measurement light path diagram: 101 is a He-Ne laser, 102 is a polarizer, 103 and 108 are variable aperture diaphragms, 104 is UV light, 105 is a waveguide sample, 106 is an optical synchronous tracking turntable, and 107 is a sample 109 is a PSD probe, 110 is a PSD, and 111 is a computer.

2 is a schematic diagram of the waveguide structure of the present invention: 201 is a waveguide cavity, 202 is an upper layer of silver metal film, 203 is an upper layer of glass, 204 is a lower layer of metal silver film, and 205 is a lower layer of glass.

Fig. 3 is the lateral displacement that embodiment 1 simulation obtains Angle of incidence with incident light relationship diagram.

FIG. 4 is a graph showing the relationship between the Goose-Hanchen displacement and the dielectric constant of the waveguide layer obtained through the simulation of Embodiment 2. FIG.

Detailed ways

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

Example 1

Step a. The waveguide structure is shown in Fig. 2, and the lower layer metal silver film 204 with a thickness of 500 nm is produced on the lower layer glass 205 with a radius of 30 mm, a thickness of 1 mm, and a surface roughness of wavelength level by using the magnetron sputtering method. On the same upper glass 203 substrate, an upper metal silver film 202 with a thickness of 40nm is fabricated;

Step b. Using photolithography to make a fence with a height of 200 microns on the lower metal silver film 204 as the waveguide cavity 201;

Step c. Clean the two devices with alcohol, after drying, pour a certain amount of UV glue into the waveguide cavity 201, cover the waveguide cavity 201 with the upper glass 203, and ensure that the upper metal silver film 202 is in contact with the UV glue, cover Be careful to avoid the generation of air bubbles during the process;

Step d. Fixing the two glass plates with a clamp;

Step e. The measurement optical path is shown in Figure 1. The laser light emitted by the He-Ne laser 101 passes through the polarizer 102 and becomes a TE or TM beam, and then passes through the first adjustable circular aperture diaphragm 103 to spatially filter out the high-order components and then output it. on the waveguide sample 105; UV light 104 is incident on the waveguide sample for curing; the optical synchronous tracking turntable 106 and the sample stage 107 are programmed and controlled by the computer 111, which is convenient for angle scanning; the second adjustable aperture diaphragm 108 selects the desired reflection light spot.

He-Ne laser 101 corresponding wavelength , after being collimated, it is incident on the upper glass 203, so that total reflection occurs at the interface between the upper glass 203 and the upper metal silver film 202, and the PSD probe 109 is used to receive the reflected light;

Step f. To measure the lateral displacement Angle of incidence with incident light It is necessary to change the size of the incident angle, and the other parameters are constant, so turn off the UV lamp, the UV glue of the waveguide layer is not cured, and its dielectric constant is fixed as ;

Step g. Use PSD 110 to detect the relationship between the position coordinates of the reflected light spot vertically incident on the probe PSD109 and the incident angle, and calculate the distance between the changed light spot and the initial position. The initial position is the position of the reflected light spot when no guided mode is generated before curing ;

Step h. Next, use matlab to simulate, and the parameters are: the thickness of the waveguide layer 201 d=200 μm, the refractive index , corresponding to the dielectric constant ; The dielectric constant at the wavelength 632.8nm corresponding to the upper layer silver film 202 and the lower layer silver film 204 , the upper metal silver film 202 thickness h=40nm; glass refractive index , the dielectric constant ;

Step i. Calculations found that the waveguide can generate 951 guided modes in the TM mode, that is, from the 0th order mode to the 950th order mode, and the mode number m can be up to 950. The larger the order of the known mode, the corresponding angle (angle in the waveguide layer) and (the angle of incidence in the air) is smaller, you can choose m=945, when , the calculated corresponding , . At the same time, in order to make the incident light totally reflect at the interface between the upper metal silver film 202 and the glass, θ should not be less than . After considering the above factors, the relationship between the GH displacement and the incident angle θ is shown in Figure 3. It can be found that the GH displacement at the interface between the glass and the upper silver film is significantly enhanced when the guided mode is generated in the waveguide.

Example 2

Step a. The waveguide structure is shown in Fig. 3, using the magnetron sputtering method to make a lower layer metal silver film 204 with a thickness of 500nm on the lower layer glass 205 with a radius of 30mm, a thickness of 1mm, and a surface roughness of wavelength level, and another layer of silver film 204 with a thickness of 500nm. On the same upper glass 203 substrate, an upper metal silver film 202 with a thickness of 40nm is fabricated;

Step b. Using photolithography to make a fence with a height of 200 microns on the lower metal silver film 204 as the waveguide cavity 201;

Step c. Clean the two devices with alcohol, after drying, pour a certain amount of UV glue into the waveguide cavity 201, cover the waveguide cavity 201 with the upper glass 203, and ensure that the upper metal silver film 202 is in contact with the UV glue, cover Be careful to avoid the generation of air bubbles during the process;

Step d. Fixing the two glass plates with a clamp;

Step e. The measurement optical path is shown in Figure 1, and the He-Ne laser 101 corresponds to the wavelength , after collimation, the angle It is incident on the upper glass 203, so that total reflection occurs at the interface between the upper glass 203 and the upper metal silver film 202, and the PSD probe 109 is used to receive the reflected light;

Step f. The UV light whose beam width is slightly larger than the size of the fence is incident on the UV glue of the waveguide cavity 201 from below, and its intensity is modulated according to the curing time of the cured glue;

Step g. Detect the position coordinates of the reflected light spot vertically incident on the PSD probe 109 on the PSD 110 as the curing process changes, and calculate the distance between the changed light spot and the initial position. The initial position is the result of the reflected light spot when no guided mode is produced before curing. position;

Step h. Use matlab to simulate below, and the waveguide structure parameters are the same as in Embodiment 1;

Step i. To measure the lateral displacement and the dielectric constant of the waveguide layer It is necessary to study the waveguide structure before and after curing. The angle corresponding to the different mode ordinal number m in the process of changing from 2.2620 to 2.3134 is as follows.

Step j. Fix the angle of incidence in air , with the progress of the curing process, we can observe multiple enhanced GH shift peaks starting from m=941 through PSD110, that is, the sharp peak of lateral displacement, and then we can carry out the waveguide layer dielectric corresponding to each peak. Calculation of electric constant. For each mode at a fixed angle of incidence The corresponding dielectric constants of the waveguide layer are calculated, and the results are shown in the table below.

m 941 942 943 944 945 946 947 948 949 950 2.2665 2.2712 2.2760 2.2807 2.2854 2.2901 2.2949 2.2996 2.3044 2.3091

Step k. Make the relationship between the GH displacement and the dielectric constant of the waveguide layer as shown in FIG. 4 .

Claims (4)

1. a method that detects UV glue curing process dynamics optical characteristics, is characterized in that, it adopts double-sided metal coated

Waveguiding structure waveguide detects, and specifically comprises the following steps:

Step a. adopts magnetron sputtering method on two blocks of glass sheet, to plate respectively the different noble metal film of thickness;

Step b. adopts photoetching method on thicker noble metal film, to make the fence of submillimeter yardstick, as waveguide cavity;

Step c is cleaned above-mentioned device with alcohol, after drying, UV glue is injected to waveguide cavity, the glass sheet of coated thinner noble metal film is covered in waveguide cavity, the noble metal film contact UV glue of upper glass plate, the coated waveguiding structure waveguide of double-sided metal that formation waveguide cavity is ducting layer;

Steps d. adopt fixture that above-mentioned waveguiding structure is fixed;

Step e. collimates laser beam, incides on upper glass plate with angle q, allows upper strata glass and noble metal film interface, upper strata that total reflection occurs, and the catoptrical position of laser beam is surveyed and received with Position-Sensitive Detector;

Step f. incides width of light beam the UV glue of waveguide cavity from below less times greater than the UV light of fence size, and its intensity is according to modulating the set time of curing glue;

Step g. regulate light path, the laser vertical that makes to reflect in the time that the upper strata glass of the coated waveguide of double-sided metal, with noble metal film interface, upper strata, total reflection occurs incides Position-Sensitive Detector pops one's head in, the position coordinates of laser reflection light in real-time detection UV glue curing process, calculate the hot spot of variation and the distance of its initial position, initial position is flare present position while not producing guided mode before solidifying;

There is according to lateral shift the pattern ordinal number that sharp peak place is corresponding in step h., known incident angle q, the specific inductive capacity of noble metal film and glass, the pattern eigen[value of waveguide, the anti-dynamic change of releasing UV glue specific inductive capacity, and then calculate the dynamic change that obtains UV glue refractive index.

2. method according to claim 1, it is characterized in that: in step e, first send incipient beam of light by He-Ne laser instrument, incipient beam of light becomes TE or TM light beam after by a polaroid afterwards, after spatial filtering filtering high order component, export again, finally incide on upper glass plate.

3. method according to claim 1, it is characterized in that, in step e, during with laser beam incident, first by matlab simulation calculation, obtain in UV glue curing process, observing the theoretical value of the angle q of multiple lateral shift sharp peak, then carry out angle scanning among a small circle near theoretical value, selected by Position-Sensitive Detector result.

4. method according to claim 1, is characterized in that: in step h, and during with laser beam incident, UV glue

The dynamic change of specific inductive capacity calculates by the pattern eigen[value of waveguide, and pattern eigen[value is , for ducting layer is perpendicular to the propagation constant of noble metal film direction, d is ducting layer thickness, and m is pattern ordinal number, phase shift while there is total reflection for laser in ducting layer and noble metal film interface.