A sealing method for metal dewar window of infrared detector

Abstract

A sealing method of metal dewar window for infrared detector, relates to photoelectric technology field, and specifically includes the following steps: using cleaning agent to clean the dewar window, and then carrying out plasma cleaning; depositing a layer of metal Cr or Ti as a primer on the surface and side wall of the dewar window; simultaneously sputtering and depositing metal Ni and metal In on the primer to form a Ni-In alloy layer, and sputtering and depositing a layer of Au as a protective layer on the surface of the alloy layer; using a glue spinner to uniformly coat a layer of photoresist on the dewar window after sputtering and depositing the metal, and uniformly coating photoresist on the side wall of the dewar window to protect the metal layer sputtered and deposited on the side wall; using a gold removal liquid to remove Au without photoresist covering, using an etching liquid to remove the corresponding part of the welding layer and the primer; removing the photoresist and cleaning the dewar window; using indium solder to weld the dewar window and the metal dewar window support; the application can reduce the production cost while ensuring the air tightness of the metal dewar.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronic technology, in particular to a sealing method of metal Dewar window for infrared detector. BACKGROUND

[0002] It is known that Dewar is a kind of thin-walled container with double or multi-layer structure, which is one of the most important basic components in infrared detector, plays a crucial role in refrigeration of the detector, and provides a clean vacuum environment for the chip, and is the main carrier for connecting the chip and other components; with the development of infrared detector, metal Dewar is widely used in various infrared detectors, especially large array infrared focal plane detectors, due to its strong durability, easy processing, high dimensional accuracy and other advantages.

[0003] The air tightness of Dewar affects the heat leakage of the device, and is related to the stability, flow rate, start-up time and other indicators of the refrigerator, and the working life of the detector also directly depends on the maintenance of the vacuum degree of the Dewar, and the sealing quality of the metal Dewar window has a crucial influence on the air tightness of the metal Dewar, and to ensure the reliability of the metal Dewar, the sealing quality of the metal Dewar window must be ensured.

[0004] At present, the sealing technology of metal Dewar window mostly adopts the method of vacuum evaporation of Cr / Au metal layer on the window for welding, wherein the Au layer is the welding layer, and the thickness is generally not less than 1 μm; however, the energy of evaporated atoms or molecules is about 0.1-1 electron volt, and the energy is small, so the adhesion of the film layer deposited by evaporation method to the substrate is weak, the welding effect is poor, and the phenomenon of metal Dewar leakage is easy to occur, in addition, the use of Au layer as the welding layer has high cost.

[0005] Therefore, it has important practical significance to solve the sealing problem of metal Dewar window of infrared detector and reduce the production cost. SUMMARY

[0006] In order to overcome the deficiencies in the background art, the present application discloses a sealing method of metal Dewar window for infrared detector, which realizes the purpose of improving the sealing quality of metal Dewar window of infrared detector and reducing the production cost.

[0007] In order to achieve the purpose of the application, the present application adopts the following technical scheme:

[0008] A sealing method of metal Dewar window for infrared detector, specifically comprising the following steps:

[0009] Step 1, cleaning the Dewar window with cleaning agent to remove surface attached dirt;

[0010] Step 2, plasma cleaning the Dewar window cleaned in step 1;

[0011] Step 3, the Dewar window in the previous step is deposited with a layer of metal Cr or Ti as a primer layer on the surface and the side wall by magnetron sputtering;

[0012] Step 4, after the previous step, metal Ni and metal In are sputter-deposited on the primer layer to form a Ni-In alloy layer as a welding layer;

[0013] Step 5, after the previous step, a layer of Au is sputter-deposited on the surface of the welding layer as a protective layer to prevent the welding layer from being oxidized;

[0014] Step 6, after the previous step, a photoresist is uniformly coated on the metal-deposited Dewar window by a spinner, and the photoresist is developed by photolithography to obtain a pattern required for metalization; meanwhile, the photoresist is uniformly coated on the side wall of the Dewar window to protect the sputter-deposited metal layer on the side wall;

[0015] Step 7, after the previous step, the Au in the part without the photoresist is removed by an Au removing solution, and then the corresponding part of the welding layer and the primer layer is removed by an etching solution;

[0016] Step 8, the photoresist in step 6 is removed, and the Dewar window is cleaned to complete the metalization of the Dewar window;

[0017] Step 9, the Dewar window and the metal Dewar window support are welded by indium soldering to complete the sealing of the metal Dewar window and the metal Dewar.

[0018] In the sealing method of the metal Dewar window for an infrared detector, the cleaning agent in step 1 is acetone and isopropyl alcohol, and the cleaning sequence is: first cleaning with acetone, and then cleaning with isopropyl alcohol.

[0019] In the sealing method of the metal Dewar window for an infrared detector, the specific steps of the plasma cleaning in step 2 are: a, the window is placed in a vacuum chamber and the chamber is vacuumed to a pressure less than 5×10 -5 Pa, the window is heated to 150-200℃ and kept for 1 hour; b, oxygen is introduced into the chamber, the pressure in the chamber is maintained at 1-3 Pa, the loading power is 200-300 W, and oxygen plasma cleaning is performed for 5-10 minutes; c, stop introducing oxygen into the chamber, and vacuum the chamber to a pressure less than 5×10 -5 Pa, then introduce argon into the chamber, maintain the pressure in the chamber at 1-3 Pa, and perform Ar + ion bombardment cleaning for 5-10 minutes.

[0020] In the sealing method of the metal Dewar window for an infrared detector, the thickness of the primer layer of metal Cr or Ti in step 3 is 30-60 nm, and the purity of the target material used is ≥ 99.99%.

[0021] In the sealing method for a metal Dewar window for an infrared detector, the thickness of the Ni-In alloy welding layer described in step 4 is 800-1200 nm, the power ratio of the sputtered metal Ni to the sputtered metal In during sputtering deposition of the Ni-In alloy welding layer is 1:0.6-0.9, and the purity of the target material used is ≥99.99%.

[0022] In the sealing method of the metal Dewar window for the infrared detector, the thickness of the protective layer Au in step 5 is 30-60 nm, and the purity of the target material used is ≥99.99%.

[0023] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0024] 1. The sealing method of the metal Dewar window for an infrared detector described in the present invention adopts a magnetron sputtering deposition method to deposit the metal film layer. Since the atomic energy of magnetron sputtering is 1 to 10 electron volts, the plated film layer is tightly bonded to the substrate, has strong adhesion, is dense, and has good uniformity, which can effectively improve the reliability of the window welding; using a metal Ni-In alloy as the welding layer can significantly reduce production costs, and the metal Ni-In alloy and indium solder can form a stable alloy, ensuring the welding quality.

[0025] 2. The sealing method for the metal Dewar window for an infrared detector of the present invention achieves metallization of the window by using a photolithography process, with high manufacturing precision, which can meet the high-precision requirements of infrared detectors. According to tests, the present invention can achieve good sealing effects for metal Dewar windows of various materials, such as Si, Ge, sapphire, quartz, etc., ensuring the airtightness of the metal Dewar and a high yield rate. It can fully meet the sealing requirements of the metal Dewar window of the infrared detector. The window and the metal Dewar window bracket are firmly sealed. After testing, the leakage rate of the sealed metal Dewar is less than 3.47×10 -14 atm*cc / sec, meeting usage requirements.

[0026] 3. The sealing method of the metal Dewar window for infrared detectors described in the present invention uses a metal Ni-In alloy as the welding layer and Au as the protective layer. The Au layer thickness is only 30-60nm, which can effectively reduce the use of Au, reduce production costs, and improve economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the metal Dewar window structure after metallization;

[0028] Figure 2 It is the photoresist pattern after photolithography development;

[0029] In the figure: 1, Dewar window; 2, primer layer; 3, welding layer; 4, protective layer; 5, photoresist. DETAILED DESCRIPTION

[0030] The application can be explained in detail by the following examples, and the purpose of the disclosure is to protect all technical improvements within the scope of the application.

[0031] Example 1

[0032] The sealing method of the metal Dewar window for infrared detector according to the application specifically comprises the following steps:

[0033] Step 1, clean the Dewar window 1 with acetone and isopropyl alcohol, the cleaning sequence is: first clean the surface with acetone to remove attached dirt, and then use isopropyl alcohol to remove residual acetone;

[0034] Step 2, plasma clean the Dewar window 1 cleaned in step 1; the specific steps of plasma cleaning are: a, place the window in a vacuum chamber and vacuum the chamber to a pressure less than 5×10 -5 Pa, heat the window to 150℃ and maintain for 1 hour; b, introduce oxygen into the chamber, maintain the pressure in the chamber at 1 Pa, load power of 200 W, and perform oxygen plasma cleaning for 5 minutes; c, stop introducing oxygen into the chamber, and vacuum the chamber to a pressure less than 5×10 -5 Pa, then introduce argon into the chamber, maintain the pressure in the chamber at 1 Pa, load power of 200 W, and perform Ar + ion bombardment cleaning for 5 minutes;

[0035] Step 3, deposit a layer of metal Cr or Ti as the primer layer 2 on the surface and sidewall of the Dewar window 1 in the previous step by magnetron sputtering; the thickness of the metal Cr of the primer layer 2 is 30 nm, and the purity of the target material used is ≥99.99%;

[0036] Step 4, based on the previous step, simultaneously sputter and deposit metal Ni and metal In on the primer layer 2 to form a Ni-In alloy layer as the welding layer 3; the thickness of the Ni-In alloy welding layer 3 is 800 nm, and the power ratio of sputtering metal Ni to sputtering metal In when sputtering and depositing the Ni-In alloy welding layer 3 is 1:0.6, and the purity of the target material used is ≥99.99%;

[0037] Step 5, based on the previous step, sputter and deposit a layer of Au as the protective layer 4 on the surface of the welding layer to prevent oxidation of the welding layer, and the thickness of the protective layer 4 Au is 30 nm, and the purity of the target material used is ≥99.99%;

[0038] Step 6, after the metal is sputtered and deposited, a photoresist 5 is uniformly coated on the metal-coated Dewar window by using a spinner, and the photoresist 5 is developed by photolithography to obtain a pattern required for the metalization, and the photoresist pattern developed by photolithography is shown in Fig. 5; meanwhile, the photoresist is uniformly coated on the side wall of the Dewar window to protect the metal layer sputtered and deposited on the side wall; Figure 2

[0039] Step 7, after the above step, the Au without the photoresist covering is removed by using a gold removal solution, and then the solder layer 3 and the primer layer 2 in the corresponding part are removed by using an etching solution;

[0040] Step 8, the photoresist in Step 6 is removed, and the Dewar window 1 is cleaned to complete the metalization of the Dewar window 1; the structure of the Dewar window after the metalization is shown in Fig. 6; Figure 1

[0041] Step 9, the Dewar window is soldered with the metal Dewar window support by using indium solder to complete the sealing of the Dewar window and the metal Dewar.

[0042] Example 2

[0043] The sealing method of the metal Dewar window for the infrared detector comprises the following steps:

[0044] Step 1, the cleaning agent for the Dewar window 1 is acetone and isopropyl alcohol, and the cleaning sequence is: first, the acetone is used to clean and remove the surface-attached dirt, and then the isopropyl alcohol is used to remove the residual acetone;

[0045] Step 2, the Dewar window 1 cleaned in Step 1 is subjected to plasma cleaning; the specific steps of the plasma cleaning are as follows: a, the window is placed in a vacuum chamber, and the chamber is vacuumized to a pressure less than 5*10 -5 Pa, the window is heated to 160℃ and kept for 1 hour; b, oxygen is introduced into the chamber, the pressure in the chamber is maintained at 2 Pa, the loading power is 250 W, and the oxygen plasma cleaning is performed for 7 minutes; c, the oxygen introduction into the chamber is stopped, the chamber is vacuumized to a pressure less than 5*10 -5 Pa, argon is introduced into the chamber again, the pressure in the chamber is maintained at 2 Pa, the loading power is 220 W, and the Ar + ion bombardment cleaning is performed for 7 minutes;

[0046] Step 3, the Dewar window 1 in the above step is subjected to the magnetron sputtering to deposit a metal Ti layer as a primer layer 2 on the surface and the side wall; the thickness of the metal Ti primer layer 2 is 40 nm, and the purity of the target material used is ≥ 99.99%;

[0047] ​​Step 4, after the step, sputtering deposition of metal Ni and metal In on the primer layer 2 to form a Ni-In alloy layer as the welding layer 3; the thickness of the Ni-In alloy welding layer 3 is 900 nm, the power ratio of sputtering metal Ni and sputtering metal In is 1:0.7 when sputtering deposition is performed, and the purity of the target material used is ≥99.99%;

[0048] Step 5, after the step, sputtering deposition of a layer of Au as a protective layer 4 on the surface of the welding layer to prevent oxidation of the welding layer, the thickness of the protective layer 4 Au is 40 nm, and the purity of the target material used is ≥99.99%;

[0049] Step 6, after the step, uniform coating of a layer of photoresist 5 on the sputtered metal Dewar window using a glue spinner, and photoresist 5 is developed to obtain the required pattern for metalization, and the photoresist pattern developed is shown in the accompanying Figure 2 At the same time, the photoresist is uniformly coated on the side wall of the Dewar window to protect the sputtered metal layer on the side wall;

[0050] Step 7, after the step, Au is removed from the part not covered by photoresist using a gold removal solution, and then the welding layer 3 and the primer layer 2 are removed from the corresponding part using an etching solution;

[0051] Step 8, remove the photoresist described in step 6, and clean the Dewar window 1 to complete the metalization of the Dewar window 1; the structure of the Dewar window after metalization is shown in the accompanying Figure 1 ;

[0052] Step 9, use indium solder to weld the Dewar window and the metal Dewar window support to complete the sealing of the Dewar window and the metal Dewar.

[0053] Example 3

[0054] The sealing method of the metal Dewar window for an infrared detector according to the present application specifically comprises the following steps:

[0055] Step 1, the cleaning agent for the Dewar window 1 is acetone and isopropanol, and the cleaning sequence is: first, use acetone to clean and remove surface-attached dirt, and then use isopropanol to remove residual acetone;

[0056] Step 2, after the Dewar window 1 is cleaned in step 1, it is subjected to plasma cleaning; the specific steps of plasma cleaning are: a, place the window in a vacuum chamber and vacuum the chamber to a pressure of less than 5×10 -5 Pa, heat the window to 180℃ and maintain for 1 hour; b, introduce oxygen into the chamber, maintain the pressure in the chamber at 3 Pa, load a power of 270 W, and perform oxygen plasma cleaning for 9 minutes; c, stop introducing oxygen into the chamber, and vacuum the chamber to a pressure of less than 5×10-5 Pa, again into the chamber, the chamber pressure maintained at 3Pa, load power 250W, Ar + ion bombardment cleaning 9 minutes;

[0057] Step 3, the Dewar window 1 in the above step is deposited on the surface and the sidewall with a metal Cr as a primer layer 2 by magnetron sputtering; the thickness of the primer layer 2 of the metal Cr is 50 nm, and the purity of the used target material is ≥ 99.99%;

[0058] Step 4, after the above step, metal Ni and metal In are sputtered and deposited on the primer layer 2 to form a Ni-In alloy layer as a welding layer 3; the thickness of the Ni-In alloy welding layer 3 is 1100 nm, the power ratio of sputtered metal Ni to sputtered metal In is 1:0.8 when the Ni-In alloy welding layer 3 is sputtered and deposited, and the purity of the used target material is ≥ 99.99%;

[0059] Step 5, after the above step, a layer of Au is sputtered and deposited on the surface of the welding layer as a protective layer 4 to prevent the welding layer from being oxidized; the thickness of the protective layer 4 of Au is 50 nm, and the purity of the used target material is ≥ 99.99%;

[0060] Step 6, after the above step, a layer of photoresist 5 is uniformly coated on the metal sputtered and deposited Dewar window by using a glue spinner, and the photoresist 5 is subjected to photoetching to obtain a pattern required for metallization, and the photoresist pattern subjected to photoetching is as shown in the accompanying drawings; meanwhile, the photoresist is uniformly coated on the sidewall of the Dewar window to protect the metal layer sputtered and deposited on the sidewall; Figure 2

[0061] Step 7, after the above step, the Au part not covered by the photoresist is removed by using a gold removal liquid, and then the welding layer 3 and the primer layer 2 of the corresponding part are removed by using an etching liquid;

[0062] Step 8, the photoresist described in step 6 is removed, and the Dewar window 1 is cleaned to complete the metallization work of the Dewar window 1; the structure of the Dewar window after the metallization work is as shown in the accompanying drawings; Figure 1

[0063] Step 9, the Dewar window and the metal Dewar window support are welded by using an indium solder, and the sealing of the Dewar window and the metal Dewar is completed.

[0064] Example 4

[0065] The sealing method of the metal Dewar window for the infrared detector comprises the following steps:

[0066] ​​Step 1, the cleaning agent for the Dewar window 1 is acetone and isopropyl alcohol, and the cleaning sequence is: first, use acetone to clean and remove the surface attached dirt, and then use isopropyl alcohol to remove the residual acetone;

[0067] Step 2, the Dewar window 1 cleaned in step 1 is plasma cleaned; the specific steps of plasma cleaning are: a, place the window in the vacuum chamber and vacuum the chamber to a pressure less than 5x10 -5 Pa, heat the window to 200℃ and maintain for 1 hour; b, introduce oxygen into the chamber, maintain the pressure in the chamber at 3Pa, load power 300W, and perform oxygen plasma cleaning for 10 minutes; c, stop introducing oxygen into the chamber, and vacuum the chamber to a pressure less than 5x10 -5 Pa, then introduce argon into the chamber, maintain the pressure in the chamber at 3Pa, load power 300W, and perform Ar + ion bombardment cleaning for 10 minutes;

[0068] Step 3, deposit a layer of metal Ti as a primer layer 2 on the surface and sidewall of the Dewar window 1 in the previous step by using a magnetron sputtering method; the thickness of the primer layer 2 of metal Ti is 60nm, and the purity of the target material used is ≥99.99%;

[0069] Step 4, based on the previous step, simultaneously sputter and deposit metal Ni and metal In on the primer layer 2 to form a Ni-In alloy layer as a welding layer 3; the thickness of the Ni-In alloy welding layer 3 is 1200nm, and the power ratio of sputtered metal Ni to sputtered metal In during sputter deposition of the Ni-In alloy welding layer 3 is 1:0.9, and the purity of the target material used is ≥99.99%;

[0070] Step 5, based on the previous step, sputter and deposit a layer of Au as a protective layer 4 on the surface of the welding layer to prevent oxidation of the welding layer; the thickness of the protective layer 4 of Au is 60nm, and the purity of the target material used is ≥99.99%;

[0071] Step 6, based on the previous step, uniformly coat a layer of photoresist 5 on the metal sputtered and deposited Dewar window using a glue spinner, and develop the photoresist 5 to obtain the required pattern for metallization, and the photoresist pattern developed by photolithography is shown in the accompanying drawings; at the same time, uniformly coat photoresist on the sidewall of the Dewar window to protect the sputtered and deposited metal layer on the sidewall; Figure 2

[0072] Step 7, based on the previous step, use gold removal liquid to remove the Au without photoresist covering, and then use etching liquid to remove the corresponding part of the welding layer 3 and the primer layer 2;

[0073] ​Step 8, remove the photoresist described in step 6, clean the Dewar window 1, and complete the metallization work of the Dewar window 1; the structure of the Dewar window after the metallization work is as shown in the attached figure. Figure 1 As shown;

[0074] Step 9: Use indium welding to weld the Dewar window and the metal Dewar window bracket to complete the sealing of the Dewar window and the metal Dewar.

[0075] The metal Dewar after the window is encapsulated is tested for leakage rate by a high vacuum leak detector. The metal Dewar window and the metal Dewar are firmly sealed by Examples 1-4, and the leakage rate is less than 3.47×10 -14 atm*cc / sec, meeting usage requirements.

[0076] The parts not described in detail in this invention are prior art.

[0077] The embodiments selected herein for the purpose of disclosing the invention are presently considered suitable, but it should be understood that the invention is intended to include all variations and modifications of the embodiments that fall within the scope of the concept and invention.

Claims

1. A method for sealing a metal Dewar window for an infrared detector, characterized by: Specifically include the following steps: Specifically include the following steps: Step 1: Clean the Dewar window with a cleaning agent to remove dirt attached to the surface; Step 2: Plasma clean the Dewar window after cleaning in step 1. The specific steps of plasma cleaning are as follows: a. Place the window in a vacuum chamber and evacuate the chamber to a pressure less than 5×10 -5 Pa, heat the window to 150℃~200℃ and keep it for 1 hour; b. introduce oxygen into the chamber, maintain the pressure in the chamber at 1~3Pa, load power 200~300W, and perform oxygen plasma cleaning for 5~10 minutes; c. stop introducing oxygen into the chamber and evacuate the chamber until the pressure is less than 5×10 -5 Pa, then introduce argon into the chamber, maintain the pressure in the chamber at 1~3Pa, load power 200~300W, and perform Ar + Ion bombardment cleaning for 5 to 10 minutes; Step 3: deposit a layer of metal Cr or Ti as a base layer on the surface and sidewalls of the Dewar window in the previous step by magnetron sputtering; Step 4: Continuing from the previous step, metal Ni and metal In are simultaneously sputter-deposited on the base layer to form a Ni-In alloy layer as a welding layer; the thickness of the Ni-In alloy welding layer is 800-1200 nm, and the power ratio of the sputtered metal Ni to the sputtered metal In during the sputtering deposition of the Ni-In alloy welding layer is 1:0.6-0.9, and the purity of the target material used is ≥99.99%; Step 5: Continuing from the previous step, a layer of Au is sputtered and deposited on the surface of the welding layer as a protective layer to prevent the welding layer from oxidation; the thickness of the protective layer Au is 30-60nm, and the purity of the target material used is ≥99.99%; Step 6: Continuing from the previous step, a layer of photoresist is evenly coated on the Dewar window where the metal is sputtered and deposited using a coating machine, and the photoresist is photolithographically developed to obtain the pattern required for metallization; at the same time, the sidewalls of the Dewar window are evenly coated with photoresist to protect the metal layer sputtered and deposited on the sidewalls; Step 7: Continuing from the previous step, use a gold removal solution to remove the Au in the portion not covered by the photoresist, and then use an etching solution to remove the corresponding portion of the solder layer and the base layer; Step 8, removing the photoresist described in step 6, cleaning the Dewar window, and completing the Dewar window metallization work; Step 9: Use indium welding to weld the Dewar window and the metal Dewar window bracket to complete the sealing of the metal Dewar window and the metal Dewar.

2. The sealing method for a metal Dewar window for an infrared detector according to claim 1, wherein: The cleaning agents in step 1 are acetone and isopropyl alcohol. The cleaning order is: first use acetone to clean, then use isopropyl alcohol.

3. The sealing method for a metal Dewar window for an infrared detector according to claim 1, wherein: The thickness of the underlying metal Cr or Ti in step 3 is 30-60 nm, and the purity of the target material used is ≥99.99%.

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