Manufacturing method of face-down bonding interconnection three-dimensional electrode of infrared focal plane array detector

Abstract

The invention relates to a method for manufacturing a face-down bonding interconnection three-dimensional electrode of an infrared focal plane array detector, which comprises the following steps of: (1) spin-coating photoresist on an infrared detector chip, exposing by using a mask plate, and developing to form a three-dimensional glue hole; (2) plating a composite metal film on the surface of the chip; (3) spin-coating a protective photoresist, performing ultraviolet light weak flooding exposure on the chip, developing to remove a thin layer of photoresist on the surface of the protective photoresist, and exposing the top composite metal film; (4) etching to remove the top composite metal film; and (5) removing photoresist by using an organic solvent to obtain the three-dimensional electrode. The method is good in process compatibility, the manufactured three-dimensional electrode is good in consistency, and the method is suitable for large-area production.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor devices, and in particular relates to a method for manufacturing three-dimensional electrodes for reverse soldering interconnection of an infrared focal plane array detector. Background Art

[0002] Infrared focal plane detectors have great application prospects in the fields of military, science, medical and health, and are developing in the direction of large array, multi-band, high resolution, miniaturization and low cost. Reducing the pixel pitch is the main method to achieve large array detectors, but the small pixel pitch brings great challenges to the flip-chip interconnection technology. The commonly used indium column flip-chip technology can hardly meet the interconnection requirements of large arrays above 1k×1k.

[0003] Patents and literature have published and reported a new type of three-dimensional metal microtube bump flip-chip interconnection technology, that is, preparing a three-dimensional microtube electrode on the detector chip. During flip-chip interconnection, the microtube electrode is inserted into the indium electrode on the readout circuit. Since the thickness of the microtube electrode side wall is very small, the indium electrode will not expand during interconnection. In addition, since the bump contact area is reduced, the pressure required for flip-chip interconnection is also greatly reduced. Therefore, the new type of metal microtube bump interconnection technology is very suitable for large-area array and small pixel pitch infrared focal plane array detectors.

[0004] Patent CN 109727950 A uses thick film photolithography to make microtube model holes, uses magnetron sputtering to sputter a layer of Au / Pt / Au composite film on the surface of the microtube model holes, applies thick photoresist, and uses mechanical polishing to flatten the chip surface to remove the top of the microtube structure to form a microtube array. The problem with this process is that the mechanical polishing height accuracy and uniformity are poor. The design height of the microtube electrode is only a few microns. For a 2-inch wafer, the mechanical polishing height accuracy error and the height deviation of the entire wafer are usually 2 to 5μm. The larger the wafer size, the worse the uniformity. Therefore, it is not ideal to use mechanical polishing to make microtube electrodes.

[0005] Patent CN 107845693 A and literature (Zhang Yi et al. Preparation and application of micro-tube electrodes of HgCdTe infrared detector chips, Laser and Infrared, 49: 1350-1352; Wang Geqing et al. Preparation and application of three-dimensional electrodes of infrared detectors with 7.5μm pixel spacing, Infrared, 45: 12-19.) use photoresist photolithography to make three-dimensional shapes on the chip, then sputter alloy, perform metal etching on the chip sputtered with alloy, select a suitable etching angle to remove excess metal, and after acetone cleaning, obtain a complete micro-tube electrode array. However, this production method has certain limitations, and an ion beam etching device with a tilting substrate function must be selected. Ion beam etching equipment is not as popular as reactive ion (RIE) etching equipment and inductively coupled plasma (ICP) etching equipment, and commonly used RIE etching and ICP etching do not have the function of tilting the substrate, and only some models of ion beam etching equipment have this function. In addition, the high-energy bombardment of the ion beam during ion beam etching can easily cause lattice damage on the chip surface, causing inevitable electrical damage to the device. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for manufacturing three-dimensional electrodes for reverse soldering interconnection of infrared focal plane array detectors, so as to obtain three-dimensional electrodes with good consistency and suitable for large-area production.

[0007] The present invention provides a method for manufacturing three-dimensional electrodes of an infrared focal plane array detector by reverse soldering interconnection, comprising the following steps:

[0008] (1) Spin-coating photoresist on the infrared detector chip, exposing it with a mask plate, and developing it to form three-dimensional resist holes;

[0009] (2) Plating a composite metal film on the chip surface;

[0010] (3) Spin-coating a protective photoresist, performing weak ultraviolet flood exposure on the chip, and developing to remove the thin layer of photoresist on the surface of the protective photoresist to expose the top composite metal film;

[0011] (4) etching and removing the top composite metal film;

[0012] (5) Use organic solvent to remove the glue to obtain a three-dimensional electrode.

[0013] Preferably, the photoresist in step (1) is a positive photoresist, and its thickness is greater than the height of the three-dimensional electrode.

[0014] More preferably, the thickness of the photoresist is 3-10 μm.

[0015] Preferably, in step (1), the mask plate is a chrome plate processed with a hollow pattern array, and the mask plate determines the size of the three-dimensional glue hole; the cross-section of the three-dimensional glue hole is an inverted trapezoid.

[0016] More preferably, the hollow pattern of the mask is circular with a diameter of 3 to 10 μm.

[0017] Preferably, the method of coating the composite metal film in step (2) comprises electron beam evaporation or magnetron sputtering.

[0018] More preferably, the method for coating the composite metal film in step (2) is magnetron sputtering, which provides better coverage of the side walls of the coating.

[0019] Preferably, the material of the composite metal film in step (2) includes multiple materials selected from titanium, platinum, gold, silver, aluminum and chromium; the thickness of the composite metal film is 0.5 to 2 μm, which is sufficient to support a three-dimensional electrode structure.

[0020] Preferably, the protective photoresist in step (3) is a positive photoresist.

[0021] Preferably, in the step (3), the thickness of the protective photoresist deposited at the bottom of the three-dimensional glue hole is greater than the thickness of the protective photoresist on the top plane, the thickness of the protective photoresist covering the sidewalls of the three-dimensional glue hole gradually decreases from bottom to top, and the thickness of the protective photoresist is the smallest at the top corner of the three-dimensional glue hole.

[0022] Preferably, in the step (3), the thin layer of photoresist on the surface of the protective photoresist is exposed by controlling the exposure time, and the thickness of the thin layer of photoresist is greater than the thickness of the protective photoresist at the top of the three-dimensional glue hole before exposure, and less than the thickness of the protective photoresist at the bottom of the three-dimensional glue hole before exposure; the exposure time is 2 to 10 seconds.

[0023] Preferably, the etching method in step (4) includes one of wet etching, inductively coupled plasma (ICP) etching or reactive ion etching (RIE) etching.

[0024] Beneficial Effects

[0025] The method of the present invention utilizes the characteristic that the protective photoresist is deposited thicker in the three-dimensional glue hole, so that after the top photoresist is removed by weak flooding exposure, the protective photoresist is still retained in the three-dimensional glue hole, thereby preventing the composite metal film at the bottom and side wall of the three-dimensional glue hole from being etched. The method adopts commonly used process equipment, has good process compatibility, and has good consistency in the manufactured three-dimensional electrode, which is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall process of the manufacturing method of the present invention.

[0027] Figure 2 This is a scanning electron microscope image of a three-dimensional electrode manufactured in an embodiment of the present invention.

[0028] Figure numerals: 1-chip, 2-photoresist, 3-mask, 4-three-dimensional glue hole, 5-composite metal film, 6-protective photoresist, 7-thin layer photoresist, 8-three-dimensional electrode. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0030] Example

[0031] This embodiment provides a method for manufacturing three-dimensional electrodes of an infrared focal plane array detector by reverse soldering. The process flow is as follows: Figure 1 As shown, it includes the following steps:

[0032] (1) Spin-coat AZ6130 positive photoresist 2 on the infrared detector chip 1 using a coating machine at a speed of 1500 rpm for 30 seconds. After coating, place the coating on a hot plate at 100°C for soft baking for 3 minutes. The thickness of the photoresist 2 is about 4 μm. Use a SUSS photolithography machine and a mask plate 3 to expose the chip 1 to ultraviolet light for 36 seconds. The mask plate 3 is a chrome plate with a hollow circular array and a circular diameter of 6 μm. Then develop to form a three-dimensional glue hole 4. Due to the characteristics of positive photoresist, the bottom width of the three-dimensional glue hole 4 is slightly smaller than the top width after development, and the side wall is slightly inclined, which is conducive to the composite metal film 5 covering the side wall;

[0033] (2) A titanium-gold (TiAu) composite metal film 5 is plated on the surface of the chip 1 by magnetron sputtering. The sidewall coverage of the magnetron sputtering coating is better. The Ti film thickness is 1000nm, the Au film thickness is 150nm, and the total thickness of the TiAu film is 1150nm, which can support the three-dimensional electrode 8 structure;

[0034] (3) Spin-coat AZ5214 positive protective photoresist 6 on the surface of chip 1 using a glue spreader at a speed of 1500 rpm for 30 seconds. After coating, place the coating on a hot plate at 100°C for soft baking for 2 minutes. The protective photoresist 6 deposited on the bottom of the three-dimensional glue hole 4 is thicker than the protective photoresist 6 on the top plane of the three-dimensional glue hole 4. The thickness of the protective photoresist 6 covering the sidewalls gradually decreases from bottom to top, and the thickness of the protective photoresist 6 is the smallest at the top corner of the three-dimensional glue hole 4. Without a mask plate, use a SUSS photolithography machine to perform weak ultraviolet flood exposure on the chip 1 for 5 seconds. Then develop and remove the thin layer of photoresist 7 on the surface of the protective photoresist 6 to expose the top composite metal film 5;

[0035] (4) Etching to remove the top composite metal film 5. Since the protective photoresist 6 is retained on the bottom and sidewalls of the three-dimensional glue hole 4, etching will only remove the composite metal film 5 on the top plane of the three-dimensional glue hole 4. The TiAu composite metal film 5 is etched by wet etching. The advantage of wet etching is that it does not require etching equipment and is easy to operate. First, etch Au for 30 seconds with iodine-potassium iodide etchant, and then etch Ti for 80 seconds with BOE etching solution. The exposed composite metal film 5 is completely etched away;

[0036] (5) The three-dimensional electrode 8 was obtained by removing the adhesive with acetone in a water bath at 55°C. Figure 2 It is a scanning electron microscope image of the three-dimensional electrode 8. The three-dimensional electrode 8 is in the shape of a cylindrical cup with good consistency. The electrode height is about 3.6 μm, the top diameter is about 6.0 μm, and the bottom diameter is about 5.5 μm.

Claims

1. A method for manufacturing three-dimensional electrodes for inverted solder connection of infrared focal plane array detectors, comprising the following steps: (1) Spin-coating a photoresist (2) on an infrared detector chip (1), exposing it with a mask plate (3), and developing it to form a three-dimensional resist hole (4); (2) coating a composite metal film (5) on the surface of the chip (1); (3) spin coating a protective photoresist (6), performing weak ultraviolet flood exposure on the chip (1), and developing and removing a thin layer of photoresist (7) on the surface of the protective photoresist (6) to expose the top composite metal film (5); (4) etching and removing the top composite metal film (5); (5) Use organic solvent to remove the glue to obtain a three-dimensional electrode (8).

2. The manufacturing method according to claim 1, characterized in that: The photoresist (2) in the step (1) is a positive photoresist, and its thickness is greater than the height of the three-dimensional electrode (8).

3. The manufacturing method according to claim 2, characterized in that: The thickness of the photoresist (2) is 3 to 10 μm.

4. The manufacturing method according to claim 1, characterized in that: In the step (1), the mask plate (3) is a chrome plate processed with a hollow pattern array; the cross section of the three-dimensional glue hole (4) is in the shape of an inverted trapezoid.

5. The manufacturing method according to claim 1, characterized in that: The method of coating the composite metal film (5) in step (2) comprises electron beam evaporation or magnetron sputtering.

6. The manufacturing method according to claim 1, characterized in that: The material of the composite metal film (5) in the step (2) includes multiple materials selected from titanium, platinum, gold, silver, aluminum, and chromium; the thickness of the composite metal film (5) is 0.5 to 2 μm.

7. The manufacturing method according to claim 1, characterized in that: The protective photoresist (6) in the step (3) is a positive photoresist.

8. The manufacturing method according to claim 1, characterized in that: In the step (3), the thickness of the protective photoresist (6) deposited at the bottom of the three-dimensional glue hole (4) is greater than the thickness of the protective photoresist (6) on the top plane, the thickness of the protective photoresist (6) covering the side wall of the three-dimensional glue hole (4) gradually decreases from the bottom to the top, and the thickness of the protective photoresist (6) at the top corner of the three-dimensional glue hole (4) is the smallest.

9. The manufacturing method according to claim 1, characterized in that: In the step (3), the thin layer of photoresist (7) on the surface of the protective photoresist (6) is exposed by controlling the exposure time, the thickness of the thin layer of photoresist (7) being greater than the thickness of the protective photoresist (6) at the top of the three-dimensional glue hole (4) before exposure, and less than the thickness of the protective photoresist (6) at the bottom of the three-dimensional glue hole (4) before exposure; the exposure time is 2 to 10 seconds.

10. The manufacturing method according to claim 1, characterized in that: The etching method in step (4) includes one of wet etching, inductively coupled plasma etching or reactive ion etching.

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