Wafer level infrared optical window with deep cavity

Abstract

The application discloses a wafer-level infrared optical window with a deep cavity and relates to the field of infrared optical windows. The wafer-level infrared optical window with a deep cavity comprises a wafer, a wafer-level infrared window unit with a deep cavity is formed on the surface of the wafer, and four cross alignment marks are punched by laser on the periphery of the wafer. All photoetching patterns of the application are formed on a plane, thereby avoiding the problems of uneven spin coating of photoresist and difficult photoresist removal caused by photoetching on the wafer with the deep cavity. The application uses the photoetching method to form patterns in the whole process, thereby avoiding the problem of pattern edge divergence caused by the use of mechanical masks to form patterns in the deep groove. Furthermore, the application can meet the miniaturization requirement of the wafer-level infrared window with a deep cavity, the size of a single optical window can reach microns at the minimum, the size range of the optical window unit can be set to 500 um-5 mm, and it is difficult for general mechanical masks to complete the preparation of small-size optical windows under this specification.

Description

Technical Field

[0001] This invention relates to the field of infrared optical windows, and particularly to a wafer-level infrared optical window with a deep cavity. Background Technology

[0002] Currently, infrared detection technology has wide applications in security, military, industry, agriculture, environment, and food safety. Existing infrared focal plane detector packaging windows mainly adopt a small-piece unit manufacturing process, which is costly, complex, and has low yield even in large-scale mass production. This invention provides a wafer-level infrared optical window fabrication method with a deep cavity, meeting the production needs of miniaturized and integrated optical windows. Furthermore, the getter module is made during the fabrication of the optical window, forming a deep cavity cap, eliminating the need for subsequent welding of the cover plate module, reducing process complexity and shortening the process cycle.

[0003] Content of this invention

[0004] The purpose of this invention is to provide a wafer-level infrared optical window with a deep cavity, mainly solving the problem of miniaturized optical window integration and production. The smallest window module can reach the micrometer level, and the size of the optical window is determined during the design of the photomask. The size range of the optical window unit can be set from 500um to 5mm. It is generally difficult to complete the fabrication of such small-sized optical windows using mechanical masking and deposition. Furthermore, it features an integrated getter and deep cavity cap for the optical window.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a wafer-level infrared optical window with a deep cavity, including a specific method for fabricating the wafer-level infrared optical window with a deep cavity, wherein the specific method for fabricating the wafer-level infrared optical window with a deep cavity is as follows: planar wafer → making alignment marks → spin coating photoresist on the wafer surface, exposure, and development to form an infrared optical thin film pattern → depositing an infrared optical film → fabricating a getter pattern according to the spin coating photoresist, exposure, and development method → ​​depositing getter → again spin coating photoresist, exposure, and development to form a welding ring pattern around the infrared window unit → electroplating titanium as a base layer, electroplating copper for the deep cavity, electroplating a titanium adhesive layer, and electroplating a gold layer for welding → removing the photoresist protective layer → completing the wafer-level infrared optical window with a deep cavity.

[0006] Preferably, a cross alignment mark is made on the wafer surface using laser etching to etch the alignment mark into a cross shape. The size and position of the alignment mark correspond to the alignment mark on the chip wafer to be packaged. The purpose is to enable light leakage from the alignment cross, which facilitates the alignment of the infrared optical window wafer and the chip wafer.

[0007] Preferably, after the wafer is cleaned, photoresist is spin-coated with a thickness of 50-100 μm, and then exposed and developed to create an infrared film pattern on the wafer surface.

[0008] Preferably, the method for depositing the infrared film and getter is vacuum evaporation deposition, including magnetron sputtering deposition, vacuum thermal evaporation deposition, and electron beam deposition, with the infrared film thickness in the range of 1-10 μm.

[0009] Preferably, the infrared film is deposited on the photoresist mask created during the fabrication of the infrared film pattern and alignment marks. The thickness of the infrared film is in the range of 1-10 μm. After the film is deposited, the photoresist is removed. The infrared film can be an antireflection film, a cut-off film, or a bandpass filter. The photoresist is removed after the process is complete.

[0010] Preferably, after the infrared film is completed, photoresist is spin-coated, and the pattern of getter is created by exposure and development. The getter is then deposited with a thickness of 2 μm and the components of the getter are titanium, zirconium, and vanadium. After completion, the photoresist is removed.

[0011] Preferably, after the getter is completed, photoresist is spin-coated, exposed, and developed to create the pattern of the electroplated copper deep cavity. Titanium is plated by magnetron sputtering for the base layer with a thickness of 30 nm. Copper with a thickness of 100 μm is electroplated on the surface of the titanium as the main body of the deep cavity. 30 nm of titanium is electroplated for the bonding layer, and 800 nm of gold is electroplated for welding.

[0012] The technical effects and advantages of this invention are as follows: All photolithographic patterns in this invention are fabricated on a plane, avoiding the problems of uneven photoresist spin coating and difficult photoresist removal caused by photolithography on a pre-prepared deep cavity wafer. This invention uses photolithography to fabricate patterns throughout the entire process, avoiding the problem of pattern edge derivation caused by using mechanical masks to fabricate patterns in deep trenches. It can also meet the miniaturization requirements of wafer-level packaging windows with deep cavity infrared technology. The size of a single optical window can be as small as the micrometer level, and the size range of the optical window unit can be set from 500um to 5mm. It is generally difficult to complete the fabrication of small-sized optical windows of this specification using mechanical mask coating. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the deep cavity wafer-level integrated optical window forming of the present invention.

[0014] Figure 2 for Figure 1 A schematic diagram of the structure of the wafer-level infrared optical window unit 2 with deep cavity.

[0015] Figure 3 for Figure 2 Cross-sectional view of the optical window unit.

[0016] Figure 4 A schematic diagram illustrating the fabrication steps of a wafer-level infrared optical window with a deep cavity according to the present invention.

[0017] Figure 1In the middle: 1. Wafer; 2. Wafer-level infrared optical window unit with deep cavity; 3. Hollowed-out cross alignment mark. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Specific implementation examples:

[0020] This embodiment provides a method for fabricating a wafer-level infrared optical window with a deep cavity, comprising the following steps:

[0021] S1. Create alignment marks;

[0022] On the surface of wafer 1, cross alignment marks are made. Using laser etching, alignment marks 3 are etched into a light-leaking cross shape, the size and position of which correspond to the alignment marks on the chip wafer to be packaged.

[0023] S2. Spin-coating photoresist, exposure, and development to create infrared film patterns;

[0024] The wafer with alignment marks is cleaned in S1. Photoresist is spin-coated onto the wafer surface with a thickness of 50um-100um. Infrared film patterns are created on the wafer surface by exposure and development. The size of the infrared film patterns can be set to 500um-5mm.

[0025] S3. Deposit an infrared film;

[0026] After the infrared film pattern is fabricated in S2, the infrared film 21 is deposited by vacuum thermal evaporation. The infrared film types are antireflection film, cut-off film, and bandpass filter film. The thickness of the infrared film is in the range of 1-10um. The deposition method is vacuum evaporation deposition, including magnetron sputtering deposition, vacuum thermal evaporation deposition, and electron beam deposition. After the deposition is completed, the photoresist is removed.

[0027] S4. Spin-coating photoresist, exposure, and development to create getter patterns;

[0028] Based on the completion of infrared film 21, photoresist is spin-coated onto the wafer surface with a thickness of 50um-100um, and then exposed and developed to create a pattern for depositing getter.

[0029] S5. Plating getter;

[0030] Based on the completed S4 getter pattern, getter 22 is deposited by vacuum deposition with a thickness of 2µm. The getter components are titanium, zirconium, and vanadium. After completion, the photoresist is removed.

[0031] S6. Spin-coat photoresist, expose, and develop to create a square frame deep cavity pattern around the optical window;

[0032] Based on the completion of S5 getter, spin-coating photoresist with a thickness of 50um-100um is performed, followed by exposure and development to create a square frame pattern for the electroplated copper deep cavity.

[0033] S7. Electroplating forms a titanium underlayer;

[0034] After the square frame deep cavity pattern around the S6 optical window is completed, titanium 23 is electroplated as a base layer with a thickness of 30nm to enhance the adhesion between the wafer and the subsequent copper deep cavity.

[0035] S8. Electroplated copper deep cavity;

[0036] Based on the S7 titanium base layer, a 100µm thick copper 24 plating is applied as the main body of the deep cavity.

[0037] S9. Electroplated titanium adhesive layer, electroplated gold welding layer;

[0038] Based on the completion of the S8 copper deep cavity body, titanium 25 is electroplated for bonding copper and subsequent gold layers, with a titanium thickness of 30nm, and gold 26 is electroplated for welding, with a gold thickness of 800nm.

[0039] S10. Remove the photoresist to complete the fabrication of the wafer-level optical window with deep cavity.

[0040] After S9 electroplating is completed, the photoresist is removed to complete the fabrication of the wafer-level optical window with deep cavity.

[0041] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wafer level infrared optical window with deep cavity, comprising a wafer (1), characterized in that: The surface of the wafer (1) is made with a wafer-level infrared window unit (2) with a deep cavity, and the periphery of the wafer (1) has four cross alignment marks (3) punched by laser; the specific manufacturing method of the wafer-level infrared optical window with a deep cavity is as follows: planar wafer (1) → making alignment marks → spin coating photoresist on the wafer surface, exposing, developing infrared optical film pattern → plating infrared optical film → plating getter pattern according to the spin coating photoresist, exposing and developing method → plating getter → again according to the spin coating photoresist, exposing and developing infrared window unit peripheral solder ring layer pattern → electroplating titanium as a primer, electroplating copper deep cavity, electroplating titanium adhesive layer and electroplating gold layer for soldering → removing photoresist protective layer → completing wafer-level infrared optical window with a deep cavity; the surface of the wafer (1) is laser-etched with four crosses as alignment marks, which are used for alignment with the chip wafer during packaging and cutting alignment after packaging. The thickness of the spin-coated photoresist is 50-100um; After spin coating photoresist on the wafer surface, exposing and developing infrared optical film pattern, plating infrared film, the thickness of the infrared film is in the range of 1-10um, the size of the infrared film is in the range of 500um-5mm, the type of the infrared film is antireflection film, cutoff film, bandpass filter film, and the photoresist is removed after completion; on the basis of the completion of the infrared film, spin coating photoresist, exposing and developing method is used to make plating getter pattern, and the getter is plated, the getter composition is titanium, zirconium and vanadium, the getter thickness is 2um, and the photoresist is removed after completion; on the basis of the completion of the getter, spin coating photoresist, exposing and developing method is used to make electroplating copper deep cavity pattern, electroplating 30nm thick titanium as a primer, electroplating copper 100um as a deep cavity main body, electroplating titanium 30nm as an adhesive layer, and electroplating gold 800nm for soldering, and the photoresist is removed after completion, and the wafer-level optical window with a deep cavity is prepared.

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