A dewar cooling stage and its preparation method, and infrared detector

Abstract

The present invention provides a Dewar cold stage and a preparation method thereof, and an infrared detector, which relate to the technical field of infrared detectors, and include a cold stage body, wherein the upper surface of the cold stage body is divided into three regions in a herringbone shape, and each of the regions is provided with a plurality of long strip grooves, and the long strip grooves between two adjacent regions are interconnected. The beneficial effect is that by designing the upper surface of the cold stage as a regular etched surface including a plurality of long strip grooves, the glue can more smoothly infiltrate along the long strip grooves during the gluing process, thereby making it difficult to form bubbles, and effectively increasing the bonding strength.

Description

Technical Field

[0001] The invention relates to the technical field of infrared detectors, and in particular to a Dewar cooling stage and a preparation method thereof, and an infrared detector. Background Art

[0002] As one of the core components of infrared detectors, the surface characteristics of the cold stage have an important impact on the performance of the detector. The surface of the cold stage inside the Dewar on the market is flat. The main difference lies in the random roughness of the cold stage surface and the difference in the materials used for the cold stage; and the surface roughness is a key factor affecting the bonding strength and the quality of glue coating. On the one hand, moderate roughness can increase the contact area between the cold stage and the surrounding medium (such as glue), thereby improving the bonding strength. On the other hand, if the roughness is too large, bubbles are easily formed when applying glue. These bubbles will not only reduce the reliability of bonding, but may also become an obstacle to heat conduction, affecting the cooling efficiency of the cold stage, thereby shortening the vacuum life of the product.

[0003] Based on the above problems of random surface roughness, the cold stage surface can be microstructured and processed to have a suitable roughness. The existing methods for microstructuring metal surfaces mainly include:

[0004] 1. Laser processing: Although nanosecond laser processing microstructures has a fast forming speed, an oxide layer of about 10 microns and residual stress will be formed on the surface of the processed part during the etching process. There is almost no oxide on the surface processed by picosecond and femtosecond lasers, but the processing speed is very slow due to the small single pulse energy and weak thermal effect on the processed surface (low laser energy absorption rate).

[0005] 2. Wire cutting: The micro pits on the surface of wire cutting are uncontrollable, the surface structure is irregular, and an obvious oxide layer will also be formed.

[0006] 3. Mechanical processing (such as milling and turning): The machined microstructure surface is limited by the size of the milling cutter and the lane. The processed structure often cannot reach the ten-micron level, and some special structures cannot be processed.

[0007] In summary, how to design and process the microstructure of the cold stage surface and find an optimal roughness balance point has become a technical problem that needs to be solved urgently. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a Dewar cooling stage, comprising a cooling stage body, wherein the upper surface of the cooling stage body is divided into three areas in a herringbone shape, each of the areas is respectively provided with a plurality of long strip grooves, and the long strip grooves between two adjacent areas are interconnected.

[0009] Preferably, the three areas are evenly distributed on the upper surface of the cold stage body.

[0010] Preferably, the elongated grooves in each of the regions are arranged parallel to each other.

[0011] Preferably, each of the long strip-shaped grooves extends from the center of the cold platform body toward the edge.

[0012] Preferably, a plurality of hexagonal bosses are staggeredly distributed on the lower surface of the cold stage body.

[0013] Preferably, an anti-wetting groove is provided in the circumferential direction of the edge of the lower surface of the cold stage body, and each of the hexagonal bosses is located in an area enclosed by the anti-wetting groove.

[0014] The present invention also provides a method for preparing a Dewar cooling stage, which is used to prepare the above-mentioned Dewar cooling stage, comprising:

[0015] Step S1, using infrared laser to etch the upper surface of the cold stage body to form a long strip groove, and while etching, using ultraviolet laser to follow the infrared laser to etch the inner side wall of the long strip groove to remove the oxide layer formed on the inner side wall of the long strip groove;

[0016] Step S2, laser etching is performed on the upper surface of the cold stage body where the long strip grooves are formed, so as to remove the oxide layer on the upper surface of the cold stage body.

[0017] Preferably, in step S1, the light emission time of the ultraviolet laser lags behind the light emission time of the infrared laser by at least 1 millisecond.

[0018] Preferably, in step S2, the laser etching includes:

[0019] Using the ultraviolet laser in step S1 to perform zigzag etching on the upper surface of the cold stage body with a spot overlap rate greater than 80%;

[0020] or

[0021] A cylindrical lens is used to shape the laser light emitted by the picosecond laser into a line laser, and then the line laser is used to cover and scan the upper surface of the cold stage body.

[0022] The present invention also provides an infrared detector, comprising the above-mentioned Dewar cooling stage.

[0023] The above technical solution has the following advantages or beneficial effects:

[0024] 1) By designing the upper surface of the cold stage to be a regular etched surface containing multiple long grooves, the glue can more smoothly infiltrate along the long grooves during the glue coating process, making it difficult to form bubbles, and effectively increasing the bonding strength;

[0025] 2) By designing multiple hexagonal bosses on the lower surface of the cold table, the refrigerant gas can flow quickly between the hexagonal bosses, which significantly accelerates the heat exchange rate between the cold table and the gas;

[0026] 3) By designing a wetting groove on the edge of the lower surface of the cold platen, the solder is effectively prevented from flowing to the location of the hexagonal boss when the Dewar cold platen is brazed with other components, ensuring the heat exchange surface area of ​​the lower surface of the cold platen, and further accelerating the heat exchange rate between the cold platen and the gas;

[0027] 4) Using ultraviolet laser to follow the infrared laser for etching, so that the oxide layer and burrs formed during the infrared laser processing can be quickly removed by the ultraviolet laser and an etched surface with regular corners is formed;

[0028] 5) Ultraviolet laser is used to follow the infrared laser for etching. The entire processing process does not need to be in a vacuum environment or an inert gas environment. At the same time, the effect of vacuum degassing can be achieved, which is equivalent to vacuum heat treatment of the surface of the cold stage, so that the cold stage does not need to be vacuum degassed at high temperature, which can save at least one day of process time. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the upper surface of the cold stage body in a preferred embodiment of the present invention;

[0030] Figure 2 It is a structural schematic diagram of the lower surface of the cold stage body in a preferred embodiment of the present invention;

[0031] Figure 3 In a preferred embodiment of the present invention, it is a schematic diagram of the solder wetting condition when the cold stage is brazed with other components when the lower surface of the cold stage body is not processed;

[0032] Figure 4 In a preferred embodiment of the present invention, it is a schematic diagram of the brazing material wetting condition when the cold stage is brazed with other components when only a hexagonal boss is formed on the lower surface of the cold stage body;

[0033] Figure 5 In a preferred embodiment of the present invention, a schematic diagram of the wetting of solder when the cold platen is brazed with other components when the wetting groove is provided on the lower surface edge of the cold platen body;

[0034] Figure 6 The figure is a schematic flow chart of a method for preparing a Dewar cooling stage in a preferred embodiment of the present invention;

[0035] Figure 7 This is a schematic diagram of etching the inner sidewall of a long strip groove using a beam of ultraviolet laser followed by an infrared laser in a preferred embodiment of the present invention;

[0036] Figure 8 This is a schematic diagram of etching the inner sidewall of a long strip groove using two ultraviolet laser beams followed by an infrared laser in a preferred embodiment of the present invention;

[0037] Fig. 9 This is a schematic diagram of using ultraviolet laser to perform Z-shaped etching on the upper surface of the cold stage body with a spot overlap rate greater than 80% in a preferred embodiment of the present invention;

[0038] Fig.10 This is a schematic diagram of using a line laser to perform coverage scanning on the upper surface of the cold stage body in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.

[0040] In a preferred embodiment of the present invention, based on the above problems existing in the prior art, a Dewar cooling stage is provided. Figure 1 As shown, it includes a cold stage body 1, the upper surface of which is divided into three regions 2 in a herringbone shape, each region 2 is provided with a plurality of long strip grooves 3, and the long strip grooves 3 between two adjacent regions 2 are interconnected.

[0041] Specifically, in this embodiment, the upper surface of the cold table body 1 is a bonding surface and a rapid cooling functional surface. By designing a long groove 3 on the upper surface, the glue can more smoothly infiltrate along the long groove 3 during the bonding and gluing process, making it difficult to form bubbles, while effectively increasing the bonding strength.

[0042] Furthermore, by dividing the upper surface of the cold stage body 1 into three areas 2, and the three areas 2 are evenly distributed on the upper surface of the cold stage body 1, the bonding stress of the glue infiltrated therein can be effectively balanced.

[0043] In a preferred embodiment of the present invention, the long strip-shaped grooves 3 in each region 2 are arranged parallel to each other.

[0044] In a preferred embodiment of the present invention, each of the long strip grooves 3 extends from the center of the cold stage body 1 toward the edge.

[0045] In a preferred embodiment of the present invention, each of the long strip grooves 3 in two adjacent regions 2 is connected to each other, and the angle between two long strip grooves 3 connected to each other is 120°.

[0046] The width of each long strip groove 3 is 3 μm-1000 μm, the depth is 1 μm-1000 μm, and the spacing between two adjacent long strip grooves 2 in the same area 2 is 1 μm-1000 μm.

[0047] Furthermore, the lower surface of the cold stage body 1 is a fast cooling functional surface. In order to allow the refrigerant gas to flow smoothly on the lower surface of the cold stage body 1, in a preferred embodiment of the present invention, Figure 2 As shown, a plurality of hexagonal bosses 4 are staggeredly distributed on the lower surface of the cold stage body 1 .

[0048] Specifically, the hexagonal boss 4 is formed by etching a groove on the lower surface of the cold stage body 1 , the etched groove has a width of 1 μm-500 μm and a depth of 1 μm-500 μm; the side length of the hexagonal boss is 1 μm-500 μm.

[0049] In a preferred embodiment of the present invention, an anti-wetting groove 5 is circumferentially provided on the edge of the lower surface of the cold stage body 1 , and each hexagonal boss 4 is located in the area enclosed by the anti-wetting groove 5 .

[0050] Specifically, Figure 3 As shown in the figure, the solder wetting condition when the cold platen is brazed with other parts without any processing on the lower surface of the cold platen body 1, wherein the grid filled part is the solder wetting area. Figure 4 As shown in FIG. 1 , the solder wetting condition when the microstructure of the hexagonal boss 4 is set on the lower surface of the cold platform body 1, wherein the grid filling part is the solder wetting area. It can be seen that a large area of ​​the solder is wetted at the brazing point on the lower surface of the cold platform body 1, thus affecting the cooling effect. Figure 5 As shown in FIG. 1 , a cold stage body 1 is provided with an anti-wetting groove 5. It can be seen that even if the solder is wetted, it will only wet into the anti-wetting groove 5, and the lower surface of the cold stage body 1 will not be affected. Figure 4 , Figure 5 The anti-wetting groove 5 is provided in the cold stage, and the lower surface area of ​​the cold stage without etching the anti-wetting groove is increased by 40%. Figure 3 , Figure 5 The anti-infiltration groove 5 is provided in the cold stage, and the lower surface area thereof is increased by 300%-500% compared with the untreated cold stage.

[0051] Regarding the upper surface of the cold stage body 1, the surface tensile strength is 40.3 kg without any treatment. After the long strip grooves 3 are etched thereon, the bonding strength is significantly enhanced, as shown in Tables 1 and 2 below:

[0052] Table 1: Comparison of different groove depths when the groove width of the long groove is 50 microns

[0053] Groove depth (μm) 10 50 100 200 Tensile strength(kg) 47.1 76.4 84.6 88.7

[0054] As can be seen from Table 1, due to the narrow groove width, the inside of the groove cannot be completely wetted when the depth is 100μm or more. Therefore, the bonding strength does not increase significantly when the depth is greater than or equal to 100μm.

[0055] Table 2: Comparison of different groove depths when the groove width of the long groove is 100 microns

[0056] Groove depth (μm) 10 50 100 200 Tensile strength(kg) 49.5 79.1 112.7 127.1

[0057] It can be seen from Table 2 that, due to the increase in the groove width relative to Table 1, the bonding strength increases significantly at a depth of 100 μm, but the surface bonding strength at a depth of 200 μm increases slightly.

[0058] For the lower surface of the cooling platform body 1, the surface cooling rate is 277.6s without any treatment. After the grooves are etched to form the hexagonal boss 4 with a side length of 200μm, the cooling efficiency is significantly enhanced, as shown in Tables 3 and 4 below:

[0059] Table 3: Comparison of different groove depths when the etching groove width is 50 microns

[0060] Groove depth (μm) 10 50 100 200 Cooling time(s) 270.1 241.5 239.0 237.4

[0061] Table 4: Comparison of different groove depths when the etching groove width is 100 microns

[0062] Groove depth (μm) 10 50 100 200 Cooling time(s) 275.4 258.9 253.7 251.0

[0063] It can be seen from Tables 3 and 4 that the 50 μm groove width results in more hexagonal bosses and a greater increase in surface area, so that the refrigerant gas is in more complete contact with the lower surface of the cold platform, and the cooling rate is faster than that of the 100 μm groove width microstructure with the same depth.

[0064] In summary, the Dewar cooling table of the present invention can allow the glue to fully infiltrate the microstructure formed by the long strip grooves on the upper surface; significantly enhance the bonding strength, and provide gain for rapid cooling of the chip by forming a microstructure through the hexagonal bosses on the lower surface.

[0065] The present invention also provides a method for preparing a Dewar cooling stage, which is used to prepare the above-mentioned Dewar cooling stage. Figure 6 As shown, including:

[0066] Step S1, using infrared laser to etch the upper surface of the cold stage body to form a long strip groove, and while etching, using ultraviolet laser to follow the infrared laser to etch the inner side wall of the long strip groove to remove the oxide layer formed on the inner side wall of the long strip groove;

[0067] Step S2 , laser etching is performed on the upper surface of the cold stage body where the long strip grooves are formed, so as to remove the oxide layer on the upper surface of the cold stage body.

[0068] Specifically, in this embodiment, the infrared laser is responsible for quickly etching the groove, and the ultraviolet laser is responsible for removing the oxide layer and burrs on the sidewall of the groove.

[0069] The parameters of the infrared laser are preferably wavelength: 1064nm, pulse width: 5-200ns, average power: 10-20w, spot diameter after focusing: 5-50μm, pulse frequency: 20-50kHz, scanning speed: 20-5000mm / s.

[0070] The infrared laser is responsible for quickly etching the rough shape of the groove. Each groove can be formed with only one etching (groove width is 1μm-60μm). If the designed groove width is greater than 60μm, multiple etchings are required, and the etching width can reach 60μm each time. The groove depth is 1μm-1000μm, and a single etching can reach 200μm.

[0071] The parameters of the ultraviolet laser are preferably an ultraviolet light source with a wavelength of 200-355nm, a pulse width of 10fs-10ps (shorter than the metal electron-phonon coupling time of about 10ps, and almost no thermal effect); average power: 10-20w, spot diameter after focusing: 2-10μm, pulse frequency: 50-100kHz, scanning speed: 20-5000mm / s.

[0072] The ultraviolet laser is responsible for removing the oxide layer formed on the sidewalls of the etched trench. There are two removal schemes:

[0073] A kind of Figure 7 As shown, only one ultraviolet laser beam, through 100kHz high frequency pulse, realizes the groove to follow the infrared laser etching back and forth (one pulse on the left, one pulse on the right, and so on).

[0074] Another kind of Figure 8 As shown, two beams of ultraviolet laser (which can be two ultraviolet lasers or two beams of ultraviolet laser formed by the same laser through a beam splitter) etch both sides of the groove at the same time. This method has a higher upper limit on the etching rate.

[0075] Among them, due to the thermal effect of the infrared laser, the absorption rate of the side wall to the ultraviolet laser will increase significantly, which greatly enhances the etching rate of the ultraviolet laser. The ultraviolet laser cannot etch synchronously with the infrared laser, otherwise, even after the ultraviolet laser etching, a layer of oxide layer with a thickness of about 2μm will still be formed on the fresh surface exposed. Therefore, in step S1, the emission time of the ultraviolet laser lags behind the emission time of the infrared laser by at least 1 millisecond.

[0076] The single UV laser etching depth is 1-100μm. If the trench is thick, the trench sidewall shaping can be achieved through high-frequency multiple etching. The etching width is 2-10μm, which is consistent with the thickness of the oxide layer formed on the sidewall.

[0077] After the trench etching is completed, laser etching is also used to remove the oxide layer on the vertical surface of the cold stage. In a preferred embodiment of the present invention, in step S2, the laser etching includes:

[0078] Select the ultraviolet laser used for side oxide removal for etching, such as Fig. 9 As shown, the upper surface of the cold stage body is etched in a zigzag shape by using the ultraviolet laser in step S1 with a spot overlap rate greater than 80%;

[0079] or

[0080] like Fig.10 As shown, a cylindrical lens is used to shape the laser emitted by the picosecond laser into a line laser, and then the line laser is used to cover and scan the upper surface of the cold stage body. Among them, the wavelength of the picosecond laser is preferably 370-650nm. The line laser can achieve coverage scanning of the entire surface of the cold stage through unidirectional movement of the y-axis or x-axis, and can remove oxides on the entire surface and splashed molten metal microspheres. Compared with the use of ultraviolet lasers for etching to remove the oxide layer on the side, this method has a faster etching rate.

[0081] The present invention also provides an infrared detector, comprising the above-mentioned Dewar cooling stage.

[0082] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. A Dewar cooling stage, characterized in that: It comprises a cooling platform body, the upper surface of which is divided into three areas in a herringbone shape, each of which is respectively provided with a plurality of long strip grooves, and the long strip grooves between two adjacent areas are interconnected.

2. The Dewar cooling stage according to claim 1, characterized in that: The three areas are evenly distributed on the upper surface of the cold stage body.

3. The Dewar cooling stage according to claim 1, characterized in that: The long strip grooves in each of the regions are arranged parallel to each other.

4. The Dewar cooling stage according to claim 3, characterized in that: Each of the long strip grooves extends from the center of the cold platform body toward the edge.

5. The Dewar cooling stage according to claim 1, characterized in that: A plurality of hexagonal bosses are staggeredly distributed on the lower surface of the cold stage body.

6. The Dewar cooling stage according to claim 5, characterized in that: An anti-wetting groove is provided in the circumferential direction of the edge of the lower surface of the cold stage body, and each of the hexagonal bosses is located in the area enclosed by the anti-wetting groove.

7. A method for preparing a Dewar cooling stage, characterized in that: For preparing the Dewar cooling stage as claimed in any one of claims 1 to 6, comprising: Step S1, using infrared laser to etch the upper surface of the cold stage body to form a long strip groove, and while etching, using ultraviolet laser to follow the infrared laser to etch the inner side wall of the long strip groove to remove the oxide layer formed on the inner side wall of the long strip groove; Step S2, laser etching is performed on the upper surface of the cold stage body where the long strip grooves are formed, so as to remove the oxide layer on the upper surface of the cold stage body.

8. The preparation method according to claim 7, characterized in that: In the step S1, the emission time of the ultraviolet laser lags behind the emission time of the infrared laser by at least 1 millisecond.

9. The preparation method according to claim 7, characterized in that: In the step S2, the laser etching includes: Using the ultraviolet laser in step S1 to perform zigzag etching on the upper surface of the cold stage body with a spot overlap rate greater than 80%; or A cylindrical lens is used to shape the laser light emitted by the picosecond laser into a line laser, and then the line laser is used to cover and scan the upper surface of the cold stage body.

10. An infrared detector, characterized in that: The method comprises a Dewar cooling stage as claimed in any one of claims 1 to 6.

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