Laser detector suitable for strong sunlight environment and preparation method thereof

Abstract

The invention relates to a laser detector suitable for a strong sunlight environment and a preparation method thereof, and belongs to the field of photoelectric detectors. The laser detector comprises a first sub-detector and a second sub-detector which are opposite in polarity, the first sub-detector is used for detecting sunlight and laser signals, the second sub-detector is used for detecting sunlight signals, and the first sub-detector and the second sub-detector eliminate sunlight interference by outputting sunlight current signals which are equal in magnitude and opposite in direction. The detector further comprises a first electrode, a second electrode and a third electrode, the third electrode is connected with the first sub-detector and the second sub-detector, the first electrode is connected with the first sub-detector, and the second electrode is connected with the second sub-detector. And the polarities of voltages connected to the first electrode and the second electrode are opposite. Sunlight currents generated by the two sub-detectors are basically consistent to offset each other, and only small light currents generated by laser signals are output, so that the detector can maintain the optimal working voltage.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric detection devices and relates to a laser detector suitable for a strong sunlight environment and a preparation method thereof. Background Art

[0002] The laser detector measures the target by detecting the echo signal of the target object irradiated by the laser. The detector is usually connected in series with a sampling resistor and extracts the AC signal through a DC blocking capacitor, such as Figure 1 As shown. After receiving light, the detector generates photocurrent, which flows through the sampling resistor and is converted into a voltage signal. The DC part of the voltage signal will be filtered out by the DC blocking capacitor, and only the AC part enters the back-end circuit through the DC blocking capacitor. In actual work, the light entering the detector includes signal light and ambient light. The signal generated by the pulsed laser is an AC signal, while the ambient light is usually DC and will be suppressed, allowing the circuit to extract the weak laser signal.

[0003] However, when the laser detector is in a strong sunlight environment, the strong sunlight will cause the detector to output a very large photocurrent. This large current causes the voltage divider of the sampling resistor to rise rapidly, and the voltage difference between the two ends of the detector drops significantly, causing the detector to deviate from the optimal operating voltage. When the sunlight is strong enough, it may even cause the potential at the sampling point to be equal to the potential at the high voltage end of the detector. The detector is in a zero bias state, and the detector cannot maintain a high gain, and thus cannot detect the laser AC signal. Although reducing the resistance of the sampling resistor can reduce the voltage divider generated by the sampling resistor, reducing the sampling resistor will also reduce the amplitude of the extracted laser signal. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a laser detector suitable for strong sunlight environment and a preparation method thereof, by setting two sub-detectors to offset the photocurrent generated by sunlight, thereby achieving high-precision detection of laser.

[0005] To achieve the above-mentioned objectives, on one hand, the present invention provides a laser detector suitable for a strong sunlight environment, which includes a first sub-detector and a second sub-detector with opposite polarities, wherein the first sub-detector is used to detect sunlight and laser signals, and the second sub-detector is used to detect sunlight signals, and the first sub-detector and the second sub-detector eliminate sunlight interference by outputting sunlight current signals of equal magnitude and opposite directions.

[0006] In addition, the laser detector further comprises a first electrode, a second electrode and a third electrode, the third electrode is connected to the first sub-detector and the second sub-detector respectively, the first electrode is connected to the first sub-detector, and the second electrode is connected to the second sub-detector. The polarities of the voltages connected to the first electrode and the second electrode are opposite.

[0007] Furthermore, the first sub-detector includes a first P+ contact area, a first absorption area located on the surface of the first P+ contact area, a first N+ contact area located on the surface of the first absorption area, and a first filter film located on the surface of the first N+ contact area. The first electrode is located on the surface of the first N+ contact area, adjacent to the first filter film. The first filter film can transmit sunlight and laser signals.

[0008] Furthermore, the second sub-detector includes a second N+ contact area, a second absorption area located on the surface of the second N+ contact area, a second P+ contact area located on the surface of the second absorption area, and a second filter film located on the surface of the second P+ contact area. The second electrode is located on the surface of the second P+ contact area and is adjacent to the second filter film. The second filter film only transmits sunlight signals.

[0009] Furthermore, an isolation groove is provided between the first sub-detector and the second sub-detector for insulation.

[0010] In another aspect, the present invention provides a method for preparing a laser detector suitable for a strong sunlight environment, the method comprising:

[0011] Obtaining a clean P-type single crystal silicon wafer, and growing a silicon oxide dielectric layer on the P-type single crystal silicon wafer;

[0012] An isolation groove pattern is formed by photolithography and etching of a silicon oxide dielectric layer, and an isolation groove is formed by etching single crystal silicon using the silicon oxide dielectric layer as a hard mask, and then silicon oxide is deposited to fill the isolation groove;

[0013] Forming an N+ contact region pattern of the first sub-detector by photolithography and etching the silicon oxide dielectric layer, and performing impurity implantation to form a first N+ contact region;

[0014] Forming a P+ contact region pattern of the second sub-detector by photolithography and etching the silicon oxide dielectric layer, and performing impurity implantation to form a second P+ contact region;

[0015] Depositing dielectric film layers on the surfaces of the first N+ contact region and the second P+ contact region respectively, and forming a first filter film and a second filter film by photolithography and etching the dielectric film layers; wherein the first filter film can transmit sunlight and laser, and the second filter film can only transmit sunlight. Specifically, by setting multiple dielectric film layers and designing the thickness and material of each dielectric film layer, the filter film can only transmit light of a specific wavelength band;

[0016] Depositing metal on the surfaces of the first N+ contact region and the second P+ contact region respectively, and forming a first electrode and a second electrode by photolithography and etching;

[0017] Back thinning of P-type monocrystalline silicon wafer;

[0018] The back side forms a P+ contact region pattern of the first sub-detector by photolithography, and performs impurity implantation to form a first P+ contact region;

[0019] The back side is formed with a pattern of an N+ contact region of the second sub-detector by photolithography, and an impurity is implanted to form a second N+ contact region;

[0020] Metal is deposited on the surfaces of the first P+ contact region and the second N+ contact region, and a third electrode is formed by photolithography and etching.

[0021] The body concentration range of the first P+ contact region, the first N+ contact region, the second P+ contact region, and the second N+ contact region is 1×10 18 cm -3 ~1×10 20 cm -3 .

[0022] Furthermore, the passband width and transmittance of the second filter film must satisfy:

[0023]

[0024] Wherein, T1(λ) represents the transmittance of the first filter film, T2(λ) represents the transmittance of the second filter film, f(λ) represents the solar spectrum, η(λ) represents the detector quantum efficiency; λ1 represents the starting wavelength of the first filter film passband, λ2 represents the cut-off wavelength of the first filter film passband, λ3 represents the starting wavelength of the second filter film passband, and λ4 represents the cut-off wavelength of the second filter film passband.

[0025] The beneficial effects of the present invention are as follows: the present invention designs two sub-detectors, wherein the transmission band of one sub-detector includes the laser wavelength, and the corresponding photocurrent generated includes sunlight and laser signals, while the transmission band of the other sub-detector does not include the laser wavelength, and the corresponding photocurrent generated includes only sunlight; in addition, the present invention suppresses the adverse effects of strong sunlight by making the photocurrents generated by sunlight output by the two sub-detectors basically consistent, thereby offsetting each other.

[0026] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0028] Figure 1This is the circuit principle of a traditional laser detector;

[0029] Figure 2 A schematic diagram of the structure of a laser detector provided by an embodiment of the present invention;

[0030] Figure 3 for Figure 2 The circuit principle of the laser detector shown;

[0031] Figure 4 A flow chart of the preparation of a laser detector provided in one embodiment of the present invention;

[0032] Figure 5 This is a comparison chart of IV curves of different laser detectors.

[0033] Figure numerals: 1-first electrode; 2-second electrode; 3-third electrode; 4-isolation groove; 51-first P+ contact area; 52-first absorption area; 53-first N+ contact area; 54-first filter film; 61-second N+ contact area; 62-second absorption area; 63-second P+ contact area; 64-second filter film. DETAILED DESCRIPTION

[0034] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0035] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0036] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0037] Embodiment 1

[0038] This embodiment provides a laser detector suitable for strong sunlight environment, such as Figure 2 As shown, it mainly includes two sub-detectors. The first sub-detector includes a first P+ contact area 51, a first absorption area 52 located on the upper surface of the first P+ contact area 51, a first N+ contact area 53 located on the upper surface of the first absorption area 52, and a first filter film 54 located on the upper surface of the first N+ contact area. The second sub-detector includes a second N+ contact area 61, a second absorption area 62 located on the upper surface of the second N+ contact area 61, a second P+ contact area 63 located on the upper surface of the second absorption area 62, and a second filter film 64 located on the upper surface of the second P+ contact area 63. In addition, the laser detector also includes a first electrode 1 arranged on the upper surface of the first N+ contact area 53, a second electrode 2 arranged on the upper surface of the second P+ contact area 63, and a third electrode 3 arranged on the lower surface of the first P+ contact area 51 and the lower surface of the second N+ contact area 61.

[0039] The first filter film and the second filter film are narrowband filters of different wavelengths. The transmission band of the first filter film includes the laser wavelength, and the corresponding photocurrent generated by the first sub-detector includes sunlight and laser signals; the transmission band of the second filter film does not include the laser wavelength, and the corresponding photocurrent generated by the second sub-detector only includes sunlight. The passband width and transmittance of the second filter film need to be designed according to the solar spectrum and the quantum efficiency of the sub-detector, which can be shown in the following formula:

[0040]

[0041] In the formula, T1(λ) is the transmittance of the first filter film, T2(λ) is the transmittance of the second filter film, f(λ) represents the solar spectrum, and η(λ) represents the detector quantum efficiency. λ1 is the starting wavelength of the first filter film passband, λ2 is the cutoff wavelength of the first filter film passband, λ3 is the starting wavelength of the second filter film passband, and λ4 is the cutoff wavelength of the second filter film passband.

[0042] Under this condition, the photocurrents generated by sunlight in the two sub-detectors are basically the same, and then cancel each other out, and no photocurrent generated by sunlight will flow out. When the laser signal is irradiated onto the detector, since the first filter film can transmit the laser and the second filter film cannot transmit the laser, only the first sub-detector outputs the photocurrent generated by the laser signal. However, this current is small and will not cause the voltage division of the sampling resistor to rise rapidly, so the laser detector can maintain the optimal operating voltage. The equivalent circuit diagram of the laser detector when it is working is as follows: Figure 3 shown.

[0043] like Figure 5 As shown, the IV curves of the laser detector described in this embodiment and the traditional laser detector under simulated sunlight can be clearly seen that the photocurrent output by the laser detector provided in this embodiment is smaller than the photocurrent of the traditional laser detector, and as the light intensity increases, the difference in the photocurrent output by the two becomes larger and larger.

[0044] Embodiment 2

[0045] This embodiment provides a method for preparing the laser detector described in embodiment 1, such as Figure 4 As shown, the method includes:

[0046] (1) Prepare a clean P-type single crystal silicon wafer with a resistivity of ≥1000Ω·cm;

[0047] (2) growing a silicon oxide dielectric layer;

[0048] (3) forming an isolation groove pattern by photolithography and etching the dielectric layer, and forming an isolation groove by etching silicon using the silicon oxide dielectric layer as a hard mask;

[0049] (4) filling the isolation trench by depositing a silicon oxide dielectric layer;

[0050] (5) The N+ contact region pattern of the first sub-detector is formed by photolithography and etching of the dielectric layer, and a large dose of phosphorus is implanted to form the N+ contact region, wherein the body concentration range of the N+ contact region is 1×10 18 cm -3 ~1×10 20 cm -3 ;

[0051] (6) The P+ contact area pattern of the second sub-detector is formed by photolithography and etching of the dielectric layer, and a P + The contact area, where the P+ contact area body concentration range is 1×10 18 cm -3 ~1×10 20 cm -3 ;

[0052] (7) depositing a dielectric film layer required for the first filter film, and forming a first filter film corresponding to the first sub-detector by photolithography and etching the dielectric film layer;

[0053] (8) depositing a dielectric film layer required for the second filter film, and forming a second filter film corresponding to the second sub-detector by photolithography and etching the dielectric film layer;

[0054] (9) depositing metal aluminum on the front side, and forming a first electrode and a second electrode by photolithography and etching;

[0055] (10) Back side thinning of silicon wafer;

[0056] (11) The back side is photolithographically formed into a P+ contact region pattern of the first sub-detector, and a large dose of boron is implanted to form a P+ contact region, wherein the body concentration of the P+ contact region is in the range of 1×10 18 cm -3 ~1×10 20 cm -3 ;

[0057] (12) The N+ contact region pattern of the second sub-detector is formed by photolithography on the back side, and a large dose of phosphorus is implanted to form the N+ contact region, where the body concentration of the N+ contact region is in the range of 1×10 18 cm -3 ~1×10 20 cm -3 ;

[0058] (13) Metal aluminum is deposited on the back to form the third electrode.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A laser detector suitable for strong sunlight environment, characterized in that: It comprises a first sub-detector and a second sub-detector with opposite polarities, wherein the first sub-detector is used to detect sunlight and laser signals, and the second sub-detector is used to detect sunlight signals, and the first sub-detector and the second sub-detector eliminate sunlight interference by outputting sunlight current signals of equal magnitude and opposite directions; It also includes a first electrode, a second electrode and a third electrode; the third electrode is connected to the first sub-detector and the second sub-detector respectively, the first electrode is connected to the first sub-detector, and the second electrode is connected to the second sub-detector; wherein the polarities of the voltages connected to the first electrode and the second electrode are opposite.

2. The laser detector according to claim 1, characterized in that: The first sub-detector includes a first P+ contact region, a first absorption region located on the surface of the first P+ contact region, a first N+ contact region located on the surface of the first absorption region, and a first filter film located on the surface of the first N+ contact region; The first electrode is located on the surface of the first N+ contact area; the first filter film transmits sunlight and laser signals.

3. The laser detector according to claim 1, characterized in that: The second sub-detector includes a second N+ contact area, a second absorption area located on the surface of the second N+ contact area, a second P+ contact area located on the surface of the second absorption area, and a second filter film located on the surface of the second P+ contact area; the second electrode is located on the surface of the second P+ contact area; the second filter film transmits the sunlight signal.

4. The laser detector according to any one of claims 1 to 3, characterized in that: An isolation groove is provided between the first sub-detector and the second sub-detector for insulation.

5. A method for preparing a laser detector suitable for a strong sunlight environment, characterized in that: The method includes: Obtaining a clean P-type single crystal silicon wafer, and growing a silicon oxide dielectric layer on the P-type single crystal silicon wafer; An isolation groove pattern is formed by photolithography and etching of a silicon oxide dielectric layer, and an isolation groove is formed by etching single crystal silicon using the silicon oxide dielectric layer as a hard mask, and then silicon oxide is deposited to fill the isolation groove; Forming an N+ contact region pattern of the first sub-detector by photolithography and etching the silicon oxide dielectric layer, and performing impurity implantation to form a first N+ contact region; Forming a P+ contact region pattern of the second sub-detector by photolithography and etching the silicon oxide dielectric layer, and performing impurity implantation to form a second P+ contact region; Depositing dielectric film layers on the surfaces of the first N+ contact region and the second P+ contact region respectively, and forming a first filter film and a second filter film by photolithography and etching the dielectric film layers; the first filter film transmits sunlight and laser, and the second filter film transmits sunlight; Depositing metal on the surfaces of the first N+ contact region and the second P+ contact region respectively, and forming a first electrode and a second electrode by photolithography and etching; Back thinning of P-type monocrystalline silicon wafer; The back side forms a P+ contact region pattern of the first sub-detector by photolithography, and performs impurity implantation to form a first P+ contact region; The back side is formed with a pattern of an N+ contact region of the second sub-detector by photolithography, and an impurity is implanted to form a second N+ contact region; Metal is deposited on the surfaces of the first P+ contact region and the second N+ contact region, and a third electrode is formed by photolithography and etching.

6. The method according to claim 5, characterized in that The body concentration ranges of the first P+ contact region, the first N+ contact region, the second P+ contact region and the second N+ contact region are all 1×10 18 cm -3 ~1×10 20 cm -3 .

7. The method according to claim 5, characterized in that The passband width and transmittance of the second filter film must meet the following requirements: Wherein, T1(λ) represents the transmittance of the first filter film, T2(λ) represents the transmittance of the second filter film, f(λ) represents the solar spectrum, η(λ) represents the detector quantum efficiency; λ1 represents the starting wavelength of the first filter film passband, λ2 represents the cut-off wavelength of the first filter film passband, λ3 represents the starting wavelength of the second filter film passband, and λ4 represents the cut-off wavelength of the second filter film passband.

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