Ultraviolet-to-far infrared broadband microscopic light fluorescence scanning imaging experimental device

Abstract

The utility model discloses an ultraviolet-far infrared broadband microscopic light fluorescence scanning imaging experimental device. The device comprises a periodic modulation module, a modulation pumping module, a surface image detection module, an ultraviolet-far infrared broadband microscopic module, a low-temperature-change sample to be detected, a scanning imaging module, a light detection demodulation module and a computer central control module. The device realizes a light fluorescence microscopic imaging function from ultraviolet to far infrared wave bands. And the spatial resolution can reach the submicron dimension. The method provides a wide characterization wave band for micro-area optical performance morphology test, has the advantages of convenience, no damage, no contact and the like, and is particularly suitable for weak fluorescence performance imaging detection of a semiconductor micro-nano structure.

Description

Technical Field

[0001] The invention relates to the field of microscopic fluorescence imaging, and in particular to an ultraviolet to far infrared wide-band microscopic light fluorescence scanning imaging experimental device, which is particularly suitable for imaging detection of extremely weak 0.3-20 micron band light fluorescence performance of semiconductor microstructures. Background Art

[0002] Microscopic fluorescence scanning imaging characterization has important applications in semiconductor microstructure optoelectronic research, but for a long time only a very narrow band from visible to near-infrared is available, which limits the range of semiconductor types that can be tested. More importantly, due to electromagnetic interference such as environmental radiation and scattering, the dynamic range of semiconductor extremely weak fluorescence signal detection is greatly limited. For example, in the 3-20 micron infrared band, since the thermal radiation background of the environment is usually 2 orders of magnitude stronger than the light fluorescence signal to be detected, and the sensitivity of currently available infrared detectors is 2 orders of magnitude lower than that of the visible band, direct infrared array imaging cannot detect weak infrared fluorescence signals. At the same time, the spatial resolution capability of area array imaging is also greatly limited, especially for microstructures that are smaller than area array pixels.

[0003] Wideband fluorescence from ultraviolet to far infrared not only expands the types of semiconductors that can be detected, but also reflects the optical properties of band gap, shallow energy level and deep energy level impurities / defects in a wide band. The spatial distribution of its fluorescence intensity can provide optical morphologies with different luminescence properties. Therefore, it is necessary to develop a wideband microscopic fluorescence scanning imaging experimental device from ultraviolet to far infrared. Summary of the invention

[0004] In order to solve the above technical problems, the present invention designs an ultraviolet to far-infrared wide-band microscopic light fluorescence scanning imaging experimental device, which includes a periodic modulation module, a modulation pump module, a surface image detection module, an ultraviolet-far-infrared wide-band microscopic module, a low-temperature variable sample to be tested, a scanning imaging module, a light detection demodulation module and a computer central control module, and is characterized in that:

[0005] The periodic modulation module is a function generator with a sine wave or square wave output, and the sine wave or square wave frequency is read by the computer central control module;

[0006] The modulation pump module includes a laser with analog signal modulation function and a spatial filter, the laser output photon energy is higher than the band gap of the sample to be tested, and its modulation signal is provided by the periodic signal output by the function generator;

[0007] The surface image detection module comprises a parallel illumination light source, a first visible beam splitter, a second visible beam splitter and a visible camera, wherein the transmission-reflection ratio of the first visible beam splitter and the second visible beam splitter is 50:50;

[0008] The ultraviolet-far-infrared wide-band microscopy module includes a dichroic beam splitter and a microscope objective lens. The dichroic beam splitter reflects the parallel illumination light source and the laser band, and transmits the light fluorescence band of the sample to be tested. The microscope objective lens is a reflective objective lens, and the working band covers 0.3-20 microns.

[0009] The low-temperature variable test sample comprises a test sample, a microscopic cryostat, a liquid helium storage tank and a liquid helium infusion tube, the microscopic cryostat has an ultraviolet-infrared wide-band optical window, the working distance is smaller than the working distance of the microscope objective lens, and the liquid helium infusion tube connects the microscopic cryostat and the liquid helium storage tank;

[0010] The scanning imaging module includes a multi-dimensional micro-displacement stage and its corresponding multi-dimensional motor controller;

[0011] The optical detection demodulation module includes an optical filter, a photodetector, a signal preamplifier and a spectrum analyzer, and the frequency domain range of the spectrum analyzer includes the frequency of the periodic signal output by the function generator;

[0012] The computer central control module controls the three-dimensional motor controller and collects the intensity signal of the frequency spectrum of the spectrum analyzer corresponding to the output frequency of the function generator, and at the same time monitors the surface morphology image of the sample to be tested output by the camera.

[0013] The main advantages of the present invention are:

[0014] 1. The available wavelengths cover the range from ultraviolet to far infrared, especially the infrared fluorescence performance in the 3-20 micron wavelength range can be scanned and imaged;

[0015] 2. Eliminate electromagnetic interference from the environmental background and enhance the dynamic range of the fluorescence to be measured, especially suitable for weak light fluorescence imaging of semiconductors;

[0016] 3. The spatial resolution depends on the pump wavelength rather than the fluorescence wavelength, so the infrared band also has sub-micron spatial resolution;

[0017] 4. The sample does not require pretreatment, the measurement is non-destructive and non-contact, and it belongs to non-destructive measurement;

[0018] 5. The properties of semiconductors such as impurity / defect distribution can be detected at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A schematic diagram of a wide-band ultraviolet to far-infrared microscopic fluorescence scanning imaging experimental device of the present invention is given. Among them, 1: function generator; 21: laser; 22: spatial filter; 31: parallel illumination light source; 32: first visible beam splitter; 33: second visible beam splitter; 34: visible camera; 41: dichroic beam splitter; 42: microscope objective lens; 51: sample to be tested; 52: microscopic cryostat; 53: liquid helium storage tank; 54: liquid helium infusion tube; 61: multi-dimensional micro-displacement stage; 62: multi-dimensional motor controller; 71: optical filter; 72: photodetector; 73: preamplifier; 74: spectrum analyzer; 8: computer central control module. In the figure, the solid line without arrows indicates the circuit connection, the solid line with arrows indicates the pump laser and its transmission direction, the dotted line with arrows indicates the parallel illumination light and its transmission direction, and the dotted line with arrows indicates the light fluorescence and its transmission direction.

[0020] Figure 2 Taking the optical fluorescence microscopy scanning imaging in the mid-infrared band as an example, the scanning imaging results of optical fluorescence in the 3.3-4.2μm band of an InAs / GaSb superlattice with a size range of 15μm×15μm were measured. DETAILED DESCRIPTION

[0021] The following is based on the attached Figure 1 and attached Figure 2 The present invention is described in detail for the purpose of better illustrating the technical features and functional characteristics of the present invention, rather than limiting the application scope of the present invention.

[0022] First, according to the attached Figure 1 Connect and set up the different optical and electrical components. Turn on the power of the function generator 1, laser 21, parallel illumination source 31, visible camera 34, multi-dimensional motor controller 62, preamplifier 73, spectrum analyzer 74 and computer control module 8, and make sure all of them work normally. At the same time, select a suitable dichroic beam splitter 41 and optical filter 71.

[0023] The sample 51 to be tested is attached to the cold finger of the micro cryostat 52 by means of thermally conductive adhesive. After the micro cryostat 52 is evacuated, the liquid helium in the liquid helium storage tank 53 is input into the micro cryostat 52 by means of the liquid helium infusion tube 54, so as to achieve a variable temperature in the range of 4.2-300K.

[0024] The computer central control module 8 sends instructions to the multi-dimensional motor controller 62 to move the sample 51 to be tested parallel to the transmission direction of the laser and illumination light, so that it moves into the imaging range of the microscope objective 42. It can be seen that the camera 34 can observe a clear real-time image of the sample surface morphology.

[0025] The multi-dimensional motor controller 62 is used to move the sample 51 to be tested in a plane perpendicular to the pump optical axis, and a light fluorescence scanning imaging test area of ​​interest is selected, and the position of the sample 51 to be tested along the pump optical axis is fine-tuned again in the area.

[0026] The output frequency of the function generator 1 and the key parameters such as the gain and bandwidth of the preamplifier 73 are appropriately set to optimize the intensity, signal-to-noise ratio and stability of the output of the spectrum analyzer 74 .

[0027] The area range and spatial resolution of the optical fluorescence scanning imaging are set. The computer central control module 8 is used as a control, and the intensity of the corresponding frequency of the spectrum analyzer 74 is collected after each movement in the area. The imaging of the area is completed by scanning in sequence.

[0028] The principle of the present invention is as follows:

[0029] Take the sinusoidal signal u(t)=u0sin(ω0t+θ1) output by the function generator 1 as an example, as the modulation signal of the laser 21, the laser outputs alternating light intensity:

[0030] I(t)=I0[1+sin(ω0t+θ2)].

[0031] The laser excites the sample 51 to be tested, and the generated fluorescence is

[0032] I PL (t) = σI0[1+sin(ω0t+θ2)].

[0033] Where σ represents the light fluorescence efficiency.

[0034] The signal output by the photoelectric detector 72 after photoelectric conversion and passing through the preamplifier 73 is

[0035] I D (t)=A{σI0[1+sin(ω0t+θ2)]+I B},

[0036] Among them I B is the background electromagnetic interference, is a constant, and A is the photoelectric conversion coefficient of the preamplifier 73. It is input into the spectrum analyzer 74 and converted into a frequency domain expression containing a delta function.

[0037] I(ω)=A(σI0+I B )δ(ω)+AσI0δ(ω-ω0).

[0038] The computer control module 8 reads the intensity corresponding to ω=ω0,

[0039] I(ω=ω0)=AσI0∝σ.

[0040] This eliminates background electromagnetic interference. B By sequentially scanning and recording the spatial micro-region positions and their corresponding frequency intensity values ​​of the spectrometer, forming a three-dimensional array and drawing an equal intensity diagram, a microscopic image of the fluorescence efficiency from ultraviolet to far infrared light can be achieved.

[0041] Figure 2 This is one of the implementation results of the 3.3-4.2μm band mid-infrared light fluorescence scanning imaging of the InAs / GaSb epitaxial superlattice. The selected laser wavelength is 532nm, the photodetector is a liquid nitrogen cooled mercury cadmium telluride detector, the preamplifier is a Stanford SR570 current amplifier, and the test temperature is 77K. It should be noted that this is only an embodiment of the light fluorescence scanning imaging in the mid-infrared band of the present invention, and does not limit the scope of protection of the present invention. By selecting different pump laser wavelengths, beam splitters, filters and dichroic beam splitters applicable bands, and photodetector detection bands, etc., light fluorescence scanning imaging from ultraviolet to far infrared bands can be achieved. Based on the present invention and embodiments, all other inventions and embodiments obtained by technicians in this field without making creative work are within the scope of protection of the present invention.

Claims

1. An ultraviolet to far infrared wideband microscopic light fluorescence scanning imaging experimental device, the device comprises a periodic modulation module, a modulation pump module, a surface image detection module, an ultraviolet-far infrared wideband microscopic module, a low temperature variable sample to be tested, a scanning imaging module, a light detection demodulation module and a computer central control module, characterized in that: The periodic modulation module is a function generator (1) with a sine wave or square wave output, and the sine wave or square wave frequency is read by a computer central control module; The modulation pump module comprises a laser (21) with analog signal modulation function and a spatial filter (22), the laser (21) outputs photon energy higher than the band gap of the sample to be tested, and its modulation signal is provided by a periodic signal output by a function generator (1); The surface image detection module comprises a parallel illumination light source (31), a first visible beam splitter (32), a second visible beam splitter (33) and a visible camera (34), wherein the transmission-reflection ratio of the first visible beam splitter and the second visible beam splitter is 50:50; The ultraviolet-far-infrared wide-band microscopy module comprises a dichroic beam splitter (41) and a microscope objective lens (42). The dichroic beam splitter (41) reflects the wavelength band of the parallel illumination light source (31) and transmits the fluorescence wavelength band of the sample to be tested. The microscope objective lens (42) is a reflective objective lens and has a working wavelength band covering 0.3-20 microns. The low-temperature variable sample to be tested comprises a sample to be tested (51), a microscopic cryostat (52), a liquid helium storage tank (53) and a liquid helium infusion tube (54); the microscopic cryostat has an ultraviolet-infrared wide-band optical window, and a working distance smaller than a working distance of a microscope objective lens (42); and the liquid helium infusion tube (54) connects the microscopic cryostat (52) and the liquid helium storage tank (53); The scanning imaging module comprises a multi-dimensional micro-displacement stage (61) and a corresponding multi-dimensional motor controller (62); The optical detection demodulation module comprises an optical filter (71), a photodetector (72), a preamplifier (73) and a spectrum analyzer (74), wherein the frequency domain range of the spectrum analyzer (74) includes the frequency of the periodic signal output by the function generator (1); The computer central control module (8) controls the multi-dimensional motor controller (62) and collects the intensity signal of the frequency spectrum of the spectrum analyzer (74) corresponding to the output frequency of the function generator (1), and monitors the surface morphology image of the sample to be tested (51) output by the visible camera (34) at the same time.

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