A flip-chip package and its preparation method

Abstract

The present invention discloses a flip-chip packaged chip and its preparation method, belonging to the field of semiconductor material technology. The chip preparation includes: initial oxidation of an epitaxial wafer, thinning treatment, stress relief etching, double-sided photolithography, front-side etching, front film lamination, back-side etching, film tearing, adhesive removal, phosphorus pre-diffusion, phosphorus re-diffusion, P+ ring photolithography etching, boron implantation, first annealing, N++ photolithography etching, Ni evaporation, silicide formation, silicide etching, Ti and Al evaporation, Al etching, passivation, passivation photolithography etching, pad metal evaporation, pad metal photolithography etching, and second annealing. By improving the chip preparation process, such as adjusting the epitaxial wafer, back-side etching, phosphorus pre-diffusion, and phosphorus re-diffusion processes, a flip-chip packaged chip with a low forward voltage drop and a back label pattern that is not easily misaligned can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to a flip-chip packaged chip and a preparation method thereof. Background Art

[0002] Flip-chip packaging technology uses a planar process to create lead-free solder joints on the input / output (I / O) terminals of an integrated circuit chip. The chip's solder joints are first aligned and mounted to the pads on the substrate. A solder reflow process is then used to form solder balls between the chip and substrate pads. Finally, underfill glue is applied to the gap between the chip and substrate to achieve electrical, thermal, and mechanical connections. Because the chip's functional area is placed upside down against the substrate, interconnected via solder bumps, the chip's placement is opposite to that of traditional packaging, where the functional area faces upward. This is why it's called a flip-chip.

[0003] The conventional preparation method of flip-chip package chip includes the following steps: initial oxidation, N+ single-side photolithography etching, phosphorus pre-diffusion, phosphorus re-diffusion, P+ ring photolithography etching, boron implantation, first annealing, N++ photolithography etching, Ni evaporation, silicide formation, silicide etching, Ti and Al evaporation, Al etching, passivation, passivation photolithography etching, pad metal evaporation, pad metal photolithography etching, front film protection, back thinning, film tearing, double-sided photolithography, front film protection, back photolithography etching, and film tearing.

[0004] However, the flip-chip packaged chips prepared by the above preparation method usually have problems such as large forward voltage drop (VF) and easy misalignment and unclear back-label patterns (such as Figure 1 shown).

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The object of the present invention is to provide a flip-chip package chip and a preparation method thereof, so as to solve or improve the above-mentioned technical problems.

[0007] The present invention can be achieved like this:

[0008] In a first aspect, the present invention provides a method for preparing a flip-chip package chip, comprising the following steps: performing initial oxidation on an epitaxial wafer, thinning treatment, stress relief etching, double-sided photolithography, front-side etching, front-side film lamination, back-side etching, film tearing, adhesive stripping, phosphorus pre-diffusion, phosphorus re-diffusion, P+ ring photolithography etching, boron implantation, first annealing, N++ photolithography etching, Ni evaporation, silicide formation, silicide etching, Ti and Al evaporation, Al etching, passivation, passivation photolithography etching, pad metal evaporation, pad metal photolithography etching, and second annealing;

[0009] Among them, the doping concentration of the epitaxial wafer is 7.0×10 18cm -3 to 7.6×10 18 cm -3 , the thickness of the epitaxial wafer is 4.7μm~5.1μm;

[0010] The etching solution used for backside etching is hydrofluoric acid, nitric acid, phosphoric acid and acetic acid in a volume ratio of (0.8~1.2):(0.8~1.2):(2.8~3.2):(3.8~4.2); the backside etching temperature is 8℃~12℃, and the backside etching time is 8min~12min;

[0011] Phosphorus pre-diffusion includes: conducting at 1080° C. to 1120° C., first introducing oxygen at a flow rate of 3.8 L / min to 4.2 L / min for 2.5 minutes to 3.5 minutes, then introducing a phosphorus source for 52 minutes to 58 minutes, and then introducing oxygen at a flow rate of 3.8 L / min to 4.2 L / min for 4.8 minutes to 5.2 minutes;

[0012] Phosphorus rediffusion includes: at 1040°C~1060°C, first introducing oxygen at a flow rate of 3.8L / min~4.2L / min for 8min~12min, then introducing oxygen and hydrogen at flow rates of 3.8L / min~4.2L / min and 4.8L / min~5.2L / min respectively for 58min~62min, and then introducing oxygen at a flow rate of 3.8L / min~4.2L / min for 8min~12min.

[0013] In an optional embodiment, the initial oxidation includes: at 1040°C to 1060°C, first introducing oxygen at a flow rate of 4.8 L / min to 5.2 L / min for 8 min to 12 min, then introducing oxygen and hydrogen at flow rates of 4.8 L / min to 5.2 L / min and 5.8 L / min to 6.2 L / min respectively for 88 min to 92 min, then introducing oxygen at a flow rate of 4.8 L / min to 5.2 L / min for 8 min to 12 min, then introducing nitrogen carrying trichloroethylene at a flow rate of 3.8 L / min to 4.2 L / min for 18 min to 22 min, and then introducing oxygen at a flow rate of 4.8 L / min to 5.2 L / min for 8 min to 12 min.

[0014] In an optional embodiment, the stress relief corrosion reagent is nitric acid, hydrofluoric acid, acetic acid and water in a volume ratio of (38-42): (0.8-1.2): (1.8-2.2): (18-22), and the stress relief corrosion is carried out at room temperature for 880s-920s;

[0015] and / or, the front side etching is performed with a volume ratio of hydrofluoric acid to ammonium fluoride of 5.5:1 to 6.5:1, and the front side etching is performed at 23° C. to 28° C. for 580 s to 620 s;

[0016] and / or, the etching reagent used for the P+ ring photolithography etching is hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:1, and the P+ ring photolithography etching is performed at 23° C. to 28° C. for 580 s to 620 s;

[0017] and / or, the etching reagent used for N++ photolithography etching is hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:1, and the N++ photolithography etching is performed at 23° C. to 28° C. for 580 s to 620 s;

[0018] and / or, the etching agent used for silicide etching is aqua regia, and the silicide etching is performed at 74° C. to 76° C. for 8 min to 12 min;

[0019] and / or, the etching reagent used for Al etching is acetic acid, phosphoric acid, and nitric acid in a volume ratio of (7.5-16.2):(67.8-73):(0.5-2.6), and the Al etching is performed at 46° C.-48° C. for 280 s-320 s;

[0020] And / or, the etching reagent used for the passivation photolithography etching is an etching solution and acetic acid in a volume ratio of 1.8:1 to 2.2:1, wherein the etching solution is composed of hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:1, and the passivation photolithography etching is performed at 23° C. to 28° C. for 100 s to 140 s;

[0021] And / or, the pad metal photolithography etching includes NiAg etching and Ti anti-corrosion, wherein the NiAg etching solution used for NiAg etching is glacial acetic acid and acetic acid in a volume ratio of (48.81~50.81):(18.23~20.23), and the NiAg corrosion is carried out at 18°C~20°C for 640s~660s; the Ti etching solution used for Ti anti-corrosion is hydrofluoric acid, nitric acid and glacial acetic acid in a volume ratio of (1.87~2.17):(8.6~9.2):(3.2~4.2); the Ti corrosion is carried out at 16°C~20°C for 6s~10s.

[0022] In an alternative embodiment, the boron implantation dose is 1.8×10 15 cm -2 to 2.2×10 15 cm -2 ;The energy of boron injection is 48KeV~52KeV.

[0023] In an optional embodiment, the first annealing includes: conducting at 1075° C. to 1085° C., first introducing oxygen at a flow rate of 4.8 L / min to 5.2 L / min for 8 min to 12 min, then introducing oxygen and hydrogen at flow rates of 4.8 L / min to 5.2 L / min and 5.8 L / min to 6.2 L / min, respectively, for 62 min to 68 min, then introducing oxygen at a flow rate of 4.8 L / min to 5.2 L / min for 8 min to 12 min, then introducing nitrogen carrying trichloroethylene at a flow rate of 3.8 L / min to 4.2 L / min for 8 min to 12 min, and then introducing oxygen at a flow rate of 4.8 L / min to 5.2 L / min for 4.8 min to 5.2 min;

[0024] And / or, the second annealing is performed at 415° C. to 425° C. for 28 min to 32 min.

[0025] In an optional embodiment, Ni is evaporated by cold evaporation, the evaporation rate is 9Å / s~11Å / s, and the thickness of the Ni layer formed after Ni evaporation is 490Å~510Å.

[0026] In an optional embodiment, the silicide is formed at 480° C. to 520° C. for 28 min to 32 min, and nitrogen is introduced at a flow rate of 11 L / min to 13 L / min during the silicide formation process.

[0027] In an optional embodiment, the evaporation of Ti and Al is carried out at 145° C. to 155° C., and the thickness of the Al layer formed after the evaporation of Ti and Al is 19500Å to 20500Å, and the thickness of the Ti layer formed is 1450Å to 1550Å.

[0028] In an optional embodiment, the passivation is performed at 480° C. to 520° C. to form a silicon dioxide layer with a thickness of 4000 Å to 5000 Å.

[0029] In an optional embodiment, the pad metal evaporation is carried out at 145°C~155°C, and the thickness of the Ag layer formed after the pad metal evaporation is 39500Å~40500Å, the thickness of the Ni layer formed is 4950Å~5050Å, and the thickness of the Ti layer formed is 1450Å~1550Å.

[0030] In a second aspect, the present invention provides a flip-chip package chip, which is prepared by the preparation method of any one of the aforementioned embodiments.

[0031] The beneficial effects of the present invention include:

[0032] The present invention improves the preparation process of the flip-down package chip by comparing with the prior art. It directly adopts a double-sided photolithography machine for alignment at the front end of the preparation, and directly carves out the back mark, which can effectively solve the problem of the shift of the photolithography back mark pattern. The present invention adopts hydrofluoric acid, nitric acid, phosphoric acid and acetic acid with a volume ratio of (0.8~1.2): (0.8~1.2): (2.8~3.2): (3.8~4.2) to carry out back etching, which can effectively improve the problem of unclear back mark. The phosphorus pre-diffusion and phosphorus re-diffusion methods provided by the present invention are conducive to improving the problem that the VF of the existing flip-down package chip is too large.

[0033] The preparation method provided by the present invention can obtain a flip-chip packaged chip with low forward voltage drop and clear and complete back label patterns. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a finished product image of a flip-chip packaged chip in the prior art;

[0036] Figure 2 This is a finished product picture of the flip-chip packaged chip in Example 1 of the present application. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0038] The flip-chip packaged chip and its preparation method provided by the present invention are described in detail below.

[0039] The preparation method of the flip-chip package chip proposed by the present invention comprises the following steps: initial oxidation of the epitaxial wafer, thinning treatment, stress relief corrosion, double-sided photolithography, front-side corrosion, front-side film lamination, back-side corrosion, film tearing, adhesive removal, phosphorus pre-diffusion, phosphorus re-diffusion, P+ ring photolithography corrosion, boron implantation, first annealing, N++ photolithography corrosion, Ni evaporation, silicide formation, silicide corrosion, Ti and Al evaporation, Al corrosion, passivation, passivation photolithography corrosion, pad metal evaporation, pad metal photolithography corrosion and second annealing.

[0040] By improving the preparation process of flip-chip packaged chips compared to existing technologies, a double-sided photolithography machine is used for alignment at the front end of the preparation to directly etch out the back logo, which can effectively solve the problem of shifting of the photolithography back label pattern.

[0041] The following is a detailed description of each of the above steps.

[0042] S1: Initial oxidation of the epitaxial wafer.

[0043] In this step, the epitaxial wafer commonly used in the prior art is replaced. Specifically, the resistivity of the epitaxial wafer commonly used in the prior art is 0.85Ω·cm~0.93Ω·cm, and the doping concentration of the epitaxial wafer is 5.2×10 18 cm -3 to 5.6×10 18 cm -3 , with a thickness of 5.0μm~5.5μm. The present invention replaces the epitaxial wafer with a doping concentration of 7.0×10 18 cm -3 to 7.6×10 18 cm -3 , epitaxial wafers with a thickness of 4.7μm~5.1μm.

[0044] Replacing the epitaxial wafer can help improve the problem of large VF of flip-chip packaged chips.

[0045] Initial oxidation includes: at 1040°C to 1060°C (such as 1040°C, 1050°C or 1060°C), first introducing oxygen at a flow rate of 4.8L / min to 5.2L / min (such as 4.8L / min, 5.0L / min or 5.2L / min, etc.) for 8min to 12min (such as 8min, 10min or 12min), and then simultaneously introducing oxygen and hydrogen at a flow rate of 4.8L / min to 5.2L / min (such as 4.8L / min, 5.0L / min or 5.2L / min, etc.) and 5.8L / min to 6.2L / min (such as 5.8L / min, 6.0L / min or 6.2L / min, etc.) for 88min to 92min (such as 88min, 90min or 92min) respectively. n, etc.), then introduce oxygen at a flow rate of 4.8L / min~5.2L / min (such as 4.8L / min, 5.0L / min or 5.2L / min, etc.) for 8min~12min (such as 8min, 10min or 12min), then introduce nitrogen carrying trichloroethylene at a flow rate of 3.8L / min~4.2L / min (such as 3.8L / min, 4.0L / min or 4.2L / min, etc.) for 18min~22min (such as 18min, 20min or 22min, etc.), and then introduce oxygen at a flow rate of 4.8L / min~5.2L / min (such as 4.8L / min, 5.0L / min or 5.2L / min, etc.) for 8min~12min (such as 8min, 10min or 12min).

[0046] In some typical embodiments, at 1050°C, oxygen is first introduced at a flow rate of 5.0 L / min for 10 minutes, then oxygen and hydrogen are simultaneously introduced at flow rates of 5.0 L / min and 6.0 L / min, respectively, for 90 minutes, then oxygen is introduced at a flow rate of 5.0 L / min for 10 minutes, then nitrogen carrying trichloroethylene is introduced at a flow rate of 4.0 L / min for 20 minutes, and then oxygen is introduced at a flow rate of 5.0 L / min for 10 minutes.

[0047] S2: Thinning treatment.

[0048] The back side is thinned to about 300 mm using a thinning machine.

[0049] S3: Stress relief corrosion.

[0050] This step can be performed at room temperature for 880s to 920s (e.g., 880s, 900s, or 920s). The etching reagent used in this step can be nitric acid, hydrofluoric acid, acetic acid, and water in a volume ratio of (38-42):(0.8-1.2):(1.8-2.2):(18-22).

[0051] In some typical embodiments, stress relief corrosion is performed at room temperature for 900 seconds. The corrosion reagent used in this step consists of nitric acid, hydrofluoric acid, acetic acid and water in a volume ratio of 40:1:2:20.

[0052] S4: Double-sided lithography.

[0053] This step can refer to the relevant existing technology and will not be described in detail or limited here.

[0054] S5: Front corrosion.

[0055] This step can be performed at 23°C to 28°C (e.g., 23°C, 25°C, or 28°C) for 580s to 620s (e.g., 580s, 600s, or 620s). The etching reagent used in this step can be hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:1 (e.g., 5.5:1, 6.0:1, or 6.5:1).

[0056] In some typical embodiments, the front side etching is performed at 25° C. for 600 s, and the etching reagent used in this step is composed of hydrofluoric acid and ammonium fluoride in a volume ratio of 6.0:1.

[0057] In this paper, a mixture of hydrofluoric acid and ammonium fluoride in a volume ratio of 6.0:1 is defined as BOE, the same below.

[0058] S6: Front film.

[0059] The film applied in this step is a UV film.

[0060] S7: Backside corrosion.

[0061] This step can be performed at 8°C to 12°C (such as 8°C, 10°C, or 12°C) for 8 minutes to 12 minutes (such as 8 minutes, 10 minutes, or 12 minutes). The etching solution used in this step can be hydrofluoric acid, nitric acid, phosphoric acid, and acetic acid in a volume ratio of (0.8-1.2):(0.8-1.2):(2.8-3.2):(3.8-4.2).

[0062] In some typical embodiments, the back side etching is performed at 10° C. for 10 minutes. The etching solution used in this step is composed of hydrofluoric acid, nitric acid, phosphoric acid and acetic acid in a volume ratio of 1.0:1.0:3.0:4.0.

[0063] It should be noted that in the prior art, the etching solution used for back etching is usually hydrofluoric acid, nitric acid, phosphoric acid, and acetic acid in a volume ratio of 40.0:1.0:2.0:20.0, and is usually carried out at room temperature for 24 hours. This method takes a long time to etch, the etching is uneven, and it is easy to cause the back label to be unclear. By using the above-mentioned etching solution provided by the present invention for back etching, the problem of unclear back label can be effectively improved.

[0064] S8: Tear off the film.

[0065] This step is to tear off the UV film attached to S6.

[0066] S9: Remove glue.

[0067] This step can be carried out with sulfuric acid and hydrogen peroxide in a volume ratio of 3:1.

[0068] S10: Phosphorus pre-diffusion.

[0069] This step can be performed at 1080° C. to 1120° C. (e.g., 1080° C., 1100° C., or 1120° C.), first introducing oxygen at a flow rate of 3.8 L / min to 4.2 L / min (e.g., 3.8 L / min, 4.0 L / min, or 4.2 L / min), for 2.5 to 3.5 minutes (e.g., 2.5 minutes, 3.0 minutes, or 3.5 minutes), then introducing a phosphorus source for 52 to 58 minutes (e.g., 52 minutes, 55 minutes, or 58 minutes), and then introducing oxygen at a flow rate of 3.8 L / min to 4.2 L / min (e.g., 3.8 L / min, 4.0 L / min, or 4.2 L / min), for 4.8 to 5.2 minutes (e.g., 4.8 minutes, 5.0 minutes, or 4.2 minutes). The phosphorus source can be phosphorus oxychloride. Phosphorus oxychloride is carried in by nitrogen, and the nitrogen flow rate is 0.4L / min~0.45L / min (such as 0.4L / min, 0.42L / min or 0.45L / min, etc.).

[0070] In some typical embodiments, phosphorus pre-diffusion is performed at 1100°C by first introducing oxygen at a flow rate of 4.0 L / min for 3.0 minutes, then introducing a phosphorus source for 55 minutes, and then introducing oxygen at a flow rate of 4.0 L / min for 5.0 minutes. Phosphorus oxychloride is introduced with nitrogen at a flow rate of 0.42 L / min.

[0071] S11: Phosphorus redistribution.

[0072] This step can be carried out at 1040°C to 1060°C (such as 1040°C, 1050°C or 1060°C), firstly introducing oxygen at a flow rate of 3.8L / min to 4.2L / min (such as 3.8L / min, 4.0L / min or 4.2L / min) for 8min to 12min (such as 8min, 10min or 12min), and then introducing oxygen at a flow rate of 3.8L / min to 4.2L / min (such as 3.8L / min, 4.0L / min or 4.2L / min) for 8min to 12min (such as 8min, 10min or 12min), respectively. Oxygen and hydrogen are introduced simultaneously at a flow rate of 4.8 L / min to 5.2 L / min (such as 4.8 L / min, 5.0 L / min or 5.2 L / min) for 58 min to 62 min (such as 58 min, 60 min or 62 min, etc.), and then oxygen is introduced at a flow rate of 3.8 L / min to 4.2 L / min (such as 3.8 L / min, 4.0 L / min or 4.2 L / min) for 8 min to 12 min (such as 8 min, 10 min or 12 min, etc.).

[0073] In some typical embodiments, phosphorus rediffusion is carried out at 1050°C, firstly oxygen is introduced at a flow rate of 4.0 L / min for 10 minutes, then oxygen and hydrogen are introduced simultaneously at flow rates of 4.0 L / min and 5.0 L / min respectively for 60 minutes, and then oxygen is introduced at a flow rate of 4.0 L / min for 10 minutes.

[0074] It should be noted that the phosphorus pre-diffusion and phosphorus re-diffusion methods provided by the present invention, combined with the replacement of the epitaxial wafer, can effectively improve the problem of large VF of the existing flip-chip packaged chips.

[0075] S12: P+ ring photolithography etching.

[0076] This step can be performed at 23°C to 28°C (such as 23°C, 25°C, or 28°C) for 580s to 620s (such as 580s, 600s, or 620s). The etching reagent used in this step can also be hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:1 (such as 5.5:1, 6:1, or 6.5:1).

[0077] In some typical embodiments, the P+ ring photolithography etching is performed at 25° C. for 600 seconds, and the etching reagent used in this step is BOE.

[0078] S13: Boron injection.

[0079] In this step, the dose of boron implantation can be 1.8×10 15 cm -2 to 2.2×10 15 cm -2(e.g. 1.8×10 15 cm -2 , 2.0×10 15 cm -2 or 2.2×10 15 cm -2 The boron implantation energy can be 48KeV~52KeV (such as 48KeV, 50KeV or 52KeV, etc.).

[0080] In some typical embodiments, the boron implantation dose is 2.0×10 15 cm -2 , the boron implantation energy is 50KeV.

[0081] S14: first annealing.

[0082] This step can be performed at 1075°C to 1085°C (e.g., 1075°C, 1080°C, or 1085°C), first introducing oxygen at a flow rate of 4.8 L / min to 5.2 L / min (e.g., 4.8 L / min, 5.0 L / min, or 5.2 L / min), for 8 min to 12 min (e.g., 8 min, 10 min, or 12 min), and then simultaneously introducing oxygen and hydrogen at flow rates of 4.8 L / min to 5.2 L / min (e.g., 4.8 L / min, 5.0 L / min, or 5.2 L / min), and 5.8 L / min to 6.2 L / min (e.g., 5.8 L / min, 6.0 L / min, or 6.2 L / min), respectively, for 62 min to 68 min (e.g., 62 min, 65 min, or 68 min). , then introduce oxygen at a flow rate of 4.8L / min~5.2L / min (such as 4.8L / min, 5.0L / min or 5.2L / min, etc.) for 8min~12min (such as 8min, 10min or 12min, etc.), then introduce nitrogen carrying trichloroethylene at a flow rate of 3.8L / min~4.2L / min (such as 3.8L / min, 4.0L / min or 4.2L / min, etc.) for 8min~12min (such as 8min, 10min or 12min, etc.), and then introduce oxygen at a flow rate of 4.8L / min~5.2L / min (such as 4.8L / min, 5.0L / min or 5.2L / min, etc.) for 4.8min~5.2min (such as 4.8min, 5.0min or 5.2min, etc.).

[0083] In some typical embodiments, the first annealing is carried out at 1080° C., first, oxygen is introduced at a flow rate of 5.0 L / min for 10 minutes, then oxygen and hydrogen are introduced simultaneously at flow rates of 5.0 L / min and 6.0 L / min, respectively, for 65 minutes, then oxygen is introduced at a flow rate of 5.0 L / min for 10 minutes, then nitrogen carrying trichloroethylene is introduced at a flow rate of 4.0 L / min for 10 minutes, and then oxygen is introduced at a flow rate of 5.0 L / min for 5.0 L / min.

[0084] S15: N++ photolithography etching.

[0085] This step can be performed at 23°C to 28°C (e.g., 23°C, 25°C, or 28°C) for 580s to 620s (e.g., 580s, 600s, or 620s). The etching reagent used in this step is hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:1 (e.g., 5.5:1, 6.0:1, or 6.5:1).

[0086] In some typical implementations, N++ photolithography etching is performed at 25° C. for 600 seconds, and the etching reagent used in this step is BOE.

[0087] S16: Steaming.

[0088] This step can be performed by cold evaporation, and the evaporation rate can be 9Å / s~11Å / s (such as 9Å / s, 10Å / s or 11Å / s, etc.), and the thickness of the Ni layer formed after evaporation of Ni is 490Å~510Å (such as 490Å, 500Å or 510Å, etc.).

[0089] In some typical embodiments, Ni evaporation is performed by cold evaporation with an evaporation rate of 10 Å / s, and the thickness of the Ni layer formed after Ni evaporation is 500 Å.

[0090] S17: forming silicide.

[0091] This step can be carried out at 480°C to 520°C (such as 480°C, 500°C or 520°C, etc.) for 28min to 32min (such as 28min, 30min or 32min, etc.), and nitrogen is introduced at a flow rate of 11L / min to 13L / min (such as 11L / min, 12L / min or 13L / min, etc.) during the formation of the silicide.

[0092] In some typical embodiments, the silicide formation is performed at 500° C. for 30 minutes, and nitrogen is introduced at a flow rate of 12 L / min during the silicide formation process.

[0093] S18: Silicide corrosion.

[0094] This step can be performed at 74° C. to 76° C. (eg, 74° C., 75° C., or 76° C.) for 8 min to 12 min (eg, 8 min, 10 min, or 12 min). The etching reagent used in this step can be aqua regia.

[0095] In some typical embodiments, the silicide etching is performed at 75° C. for 10 minutes, and the etching reagent used is aqua regia.

[0096] S19: Ti and Al evaporate.

[0097] This step can be carried out at a temperature of 145°C to 155°C (such as 145°C, 150°C or 155°C, etc.). The thickness of the Al layer formed after evaporation of Ti and Al can be 19500Å to 20500Å (such as 19500Å, 20000Å or 20500Å, etc.), and the thickness of the Ti layer formed can be 1450Å to 1550Å (such as 1450Å, 1500Å or 1550Å, etc.).

[0098] In some typical embodiments, Ti and Al are evaporated at 150° C., and the thickness of the Al layer formed after the evaporation of Ti and Al is 20,000 Å, and the thickness of the Ti layer formed is 1,500 Å.

[0099] S20: Al corrosion.

[0100] This step can be performed at 46°C to 48°C (such as 46°C, 47°C, or 48°C) for 280s to 320s (such as 280s, 300s, or 320s). The etching reagent used in this step can be acetic acid, phosphoric acid, and nitric acid in a volume ratio of (7.5-16.2):(67.8-73):(0.5-2.6).

[0101] In some typical embodiments, Al corrosion is performed at 47° C. for 300 s, and the corrosion reagent used in this step is acetic acid, phosphoric acid, and nitric acid in a volume ratio of 10:70:1.5.

[0102] S21: Passivation.

[0103] This step can be performed at 480°C to 520°C (eg, 480°C, 500°C, or 520°C) to form a silicon dioxide layer with a thickness of 4000Å to 5000Å (eg, 4000Å, 4500Å, or 5000Å).

[0104] In some typical embodiments, the passivation is performed at 500° C. to form a silicon dioxide layer with a thickness of 4000 Å to 5000 Å.

[0105] S22: Passivation photolithography etching.

[0106] This step can be performed at 23°C to 28°C (e.g., 23°C, 25°C, or 28°C) for 100 seconds to 140 seconds (e.g., 100 seconds, 120 seconds, or 140 seconds). The etching reagent used in this step can be an etching solution and acetic acid in a volume ratio of 1.8:1 to 2.2:1 (e.g., 1.8:1, 2.0:1, or 2.2:1). The etching solution can be composed of hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:1 (e.g., 5.5:1, 6.0:1, or 6.5:1).

[0107] In some typical embodiments, the passivation photolithography etching is performed at 25° C. for 120 seconds. The etching reagent used in this step is an etching solution and acetic acid in a volume ratio of 2.0:1, wherein the etching solution is BOE.

[0108] S23: Pad metal evaporation.

[0109] This step can be performed at 145°C~155°C (such as 145°C, 150°C or 155°C, etc.). The thickness of the Ag layer formed after the pad metal is evaporated can be 39500Å~40500Å (such as 39500Å, 40000Å or 40500Å, etc.), the thickness of the Ni layer formed can be 4950Å~5050Å (such as 4950Å, 5000Å or 5050Å, etc.), and the thickness of the Ti layer formed can be 1450Å~1550Å (such as 1450Å, 1500Å or 1550Å, etc.).

[0110] In some typical embodiments, the pad metal is evaporated at 150° C., and the thickness of the Ag layer formed after the pad metal evaporation is 40,000 Å, the thickness of the Ni layer formed is 5,000 Å, and the thickness of the Ti layer formed is 1,500 Å.

[0111] S24: Pad metal photolithography corrosion.

[0112] This step includes NiAg corrosion and Ti anti-corrosion, wherein the NiAg corrosion solution used for NiAg corrosion can be glacial acetic acid and acetic acid in a volume ratio of (48.81-50.81):(18.23-20.23), and the NiAg corrosion can be carried out at 18°C-20°C (such as 18°C, 19°C or 20°C) for 640s-660s (such as 640s, 650s or 660s); the Ti corrosion solution used for Ti anti-corrosion can be hydrofluoric acid, nitric acid and glacial acetic acid in a volume ratio of (1.87-2.17):(8.6-9.2):(3.2-4.2), and the Ti corrosion can be carried out at 16°C-20°C (such as 16°C, 18°C ​​or 20°C) for 6s-10s (such as 6s, 8s or 10s).

[0113] In some typical embodiments, the pad metal photolithography etching includes NiAg etching and Ti anti-corrosion, wherein the NiAg etching solution used for NiAg etching is glacial acetic acid and acetic acid in a volume ratio of 50:20, and the NiAg corrosion is carried out at 19°C for 650s; the Ti etching solution used for Ti anti-corrosion is hydrofluoric acid, nitric acid and glacial acetic acid in a volume ratio of 2:9:4, and the Ti corrosion is carried out at 18°C ​​for 8s.

[0114] S25: Second annealing.

[0115] This step can be performed at 415°C to 425°C (eg, 415°C, 420°C, or 425°C) for 28 min to 32 min (eg, 28 min, 30 min, or 32 min).

[0116] In some typical embodiments, the second annealing is performed at 420° C. for 30 minutes.

[0117] Furthermore, intermediate testing, dicing and packaging can be carried out as needed.

[0118] Correspondingly, the present invention also provides a flip-chip package chip, which is prepared by the above preparation method.

[0119] In some optional implementations, the VF of the flip-chip package can be reduced from 0.54V to 0.46V.

[0120] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0121] Example 1

[0122] This embodiment provides a flip-chip package chip, and the preparation method thereof is as follows:

[0123] S1: Initial oxidation of the epitaxial wafer.

[0124] The doping concentration of the above epitaxial wafer is 7.3×10 18 cm -3 , thickness is 4.9μm.

[0125] The initial oxidation includes: at 1050°C, first introducing oxygen at a flow rate of 5.0 L / min for 10 minutes, then introducing oxygen and hydrogen at a flow rate of 5.0 L / min and 6.0 L / min respectively for 90 minutes, then introducing oxygen at a flow rate of 5.0 L / min for 10 minutes, then introducing nitrogen carrying trichloroethylene at a flow rate of 4.0 L / min for 20 minutes, and then introducing oxygen at a flow rate of 5.0 L / min for 10 minutes.

[0126] S2: Thinning treatment.

[0127] The back side is thinned to about 300 mm using a thinning machine.

[0128] S3: Stress relief corrosion.

[0129] This step was performed at room temperature for 900 seconds. The etching reagent used in this step consisted of nitric acid, hydrofluoric acid, acetic acid, and water in a volume ratio of 40:1:2:20.

[0130] S4: Double-sided lithography.

[0131] S5: Front corrosion.

[0132] This step was performed at 25° C. for 600 s, and the etching reagent used in this step was BOE.

[0133] S6: Front film.

[0134] The film applied in this step is a UV film.

[0135] S7: Backside corrosion.

[0136] This step is carried out at 10° C. for 10 minutes. The etching solution used in this step is composed of hydrofluoric acid, nitric acid, phosphoric acid and acetic acid in a volume ratio of 1.0:1.0:3.0:4.0.

[0137] S8: Tear off the film.

[0138] This step is to tear off the UV film attached to S6.

[0139] S9: Remove glue.

[0140] This step is carried out using sulfuric acid and hydrogen peroxide in a volume ratio of 3:1.

[0141] S10: Phosphorus pre-diffusion.

[0142] This step was carried out at 1100°C, with oxygen introduced at a flow rate of 4.0 L / min for 3.0 minutes, followed by a phosphorus source for 55 minutes, and then oxygen introduced at a flow rate of 4.0 L / min for 5.0 minutes. Phosphorus oxychloride was carried by nitrogen at a flow rate of 0.42 L / min.

[0143] S11: Phosphorus redistribution.

[0144] This step was carried out at 1050°C. Oxygen was first introduced at a flow rate of 4.0 L / min for 10 minutes, oxygen and hydrogen were then introduced simultaneously at flow rates of 4.0 L / min and 5.0 L / min, respectively, for 60 minutes, and oxygen was then introduced at a flow rate of 4.0 L / min for 10 minutes.

[0145] S12: P+ ring photolithography etching.

[0146] This step was performed at 25° C. for 600 s, and the etching reagent used in this step was BOE.

[0147] S13: Boron injection.

[0148] In this step, the dose of boron implantation is 2.0×10 15 cm -2 , the boron implantation energy is 50KeV.

[0149] S14: first annealing.

[0150] This step is carried out at 1080°C. First, oxygen is introduced at a flow rate of 5.0 L / min for 10 minutes, then oxygen and hydrogen are introduced simultaneously at flow rates of 5.0 L / min and 6.0 L / min respectively for 65 minutes, then oxygen is introduced at a flow rate of 5.0 L / min for 10 minutes, then nitrogen carrying trichloroethylene is introduced at a flow rate of 4.0 L / min for 10 minutes, and then oxygen is introduced at a flow rate of 5.0 L / min for 5.0 minutes.

[0151] S15: N++ photolithography etching.

[0152] This step was performed at 25° C. for 600 s, and the etching reagent used in this step was BOE.

[0153] S16: Steaming.

[0154] This step is carried out by cold evaporation with an evaporation rate of 10Å / s. The thickness of the Ni layer formed after evaporation is 500Å.

[0155] S17: forming silicide.

[0156] This step was carried out at 500° C. for 30 minutes, and nitrogen was introduced at a flow rate of 12 L / min during the formation of the silicide.

[0157] S18: Silicide corrosion.

[0158] This step was carried out at 75° C. for 10 min, and the etching reagent used was aqua regia.

[0159] S19: Ti and Al evaporate.

[0160] This step is carried out at 150°C. After evaporation of Ti and Al, the thickness of the Al layer formed is 20,000Å, and the thickness of the Ti layer formed is 1,500Å.

[0161] S20: Al corrosion.

[0162] This step was performed at 47° C. for 300 s. The etching reagent used in this step was acetic acid, phosphoric acid, and nitric acid in a volume ratio of 10:70:1.5.

[0163] S21: Passivation.

[0164] This step was performed at 500°C to form a silicon dioxide layer with a thickness of 4500Å.

[0165] S22: Passivation photolithography etching.

[0166] This step is performed at 25° C. for 120 seconds. The etching reagent used in this step is an etching solution and acetic acid in a volume ratio of 2.0:1, wherein the etching solution is BOE.

[0167] S23: Pad metal evaporation.

[0168] This step is carried out at 150°C. After the pad metal is evaporated, the thickness of the Ag layer formed is 40,000Å, the thickness of the Ni layer formed is 5,000Å, and the thickness of the Ti layer formed is 1,500Å.

[0169] S24: Pad metal photolithography corrosion.

[0170] This step includes NiAg corrosion and Ti anti-corrosion, wherein the NiAg corrosion solution used for NiAg corrosion is glacial acetic acid and acetic acid in a volume ratio of 50:20, and the NiAg corrosion is carried out at 19°C for 650s; the Ti anti-corrosion solution is hydrofluoric acid, nitric acid and glacial acetic acid in a volume ratio of 2:9:4, and the Ti corrosion is carried out at 18°C ​​for 8s.

[0171] S25: Second annealing.

[0172] This step was carried out at 420°C for 30 min.

[0173] S26: intermediate testing, dicing and packaging.

[0174] The actual picture of the finished product is as follows Figure 2 shown.

[0175] Example 2

[0176] This embodiment provides a flip-chip package chip, and the preparation method thereof is as follows:

[0177] S1: Initial oxidation of the epitaxial wafer.

[0178] The doping concentration of the epitaxial wafer is 7.0×10 18 cm -3 , thickness is 4.7μm.

[0179] The initial oxidation includes: at 1040°C, first introducing oxygen at a flow rate of 4.8 L / min for 12 minutes, then introducing oxygen and hydrogen at a flow rate of 4.8 L / min and 5.8 L / min respectively for 92 minutes, then introducing oxygen at a flow rate of 4.8 L / min for 12 minutes, then introducing nitrogen carrying trichloroethylene at a flow rate of 3.8 L / min for 22 minutes, and then introducing oxygen at a flow rate of 4.8 L / min for 12 minutes.

[0180] S2: Thinning treatment.

[0181] The back side is thinned to about 300 mm using a thinning machine.

[0182] S3: Stress relief corrosion.

[0183] This step was performed at room temperature for 880 seconds. The etching reagent used in this step consisted of nitric acid, hydrofluoric acid, acetic acid, and water in a volume ratio of 38:0.8:1.8:18.

[0184] S4: Double-sided lithography.

[0185] S5: Front corrosion.

[0186] This step was performed at 23° C. for 620 s. The etching reagent used in this step was hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1.

[0187] S6: Front film.

[0188] The film applied in this step is a UV film.

[0189] S7: Backside corrosion.

[0190] This step is carried out at 8° C. for 12 minutes. The etching solution used in this step is composed of hydrofluoric acid, nitric acid, phosphoric acid and acetic acid in a volume ratio of 0.8:0.8:2.8:3.8.

[0191] S8: Tear off the film.

[0192] This step is to tear off the UV film attached to S6.

[0193] S9: Remove glue.

[0194] This step is carried out using sulfuric acid and hydrogen peroxide in a volume ratio of 3:1.

[0195] S10: Phosphorus pre-diffusion.

[0196] This step was carried out at 1080°C, with oxygen introduced at a flow rate of 4.2 L / min for 3.5 minutes, followed by a phosphorus source for 52 minutes, and then oxygen introduced at a flow rate of 3.8 L / min for 5.2 minutes. Phosphorus oxychloride was carried by nitrogen at a flow rate of 0.4 L / min.

[0197] S11: Phosphorus redistribution.

[0198] This step was carried out at 1040°C. Oxygen was first introduced at a flow rate of 3.8 L / min for 12 minutes, then oxygen and hydrogen were introduced simultaneously at flow rates of 3.8 L / min and 4.8 L / min respectively for 62 minutes, and then oxygen was introduced at a flow rate of 3.8 L / min for 12 minutes.

[0199] S12: P+ ring photolithography etching.

[0200] This step was performed at 23° C. for 620 s. The etching reagent used in this step was hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1.

[0201] S13: Boron injection.

[0202] In this step, the dose of boron implantation is 1.8×10 15 cm -2 , the boron implantation energy is 48KeV.

[0203] S14: first annealing.

[0204] This step is carried out at 1075°C. First, oxygen is introduced at a flow rate of 4.8 L / min for 12 minutes, then oxygen and hydrogen are introduced simultaneously at flow rates of 4.8 L / min and 5.8 L / min for 68 minutes, respectively. Then, oxygen is introduced at a flow rate of 4.8 L / min for 12 minutes, then nitrogen carrying trichloroethylene is introduced at a flow rate of 3.8 L / min for 12 minutes, and then oxygen is introduced at a flow rate of 4.8 L / min for 5.2 minutes.

[0205] S15: N++ photolithography etching.

[0206] This step was performed at 23° C. for 620 s. The etching reagent used in this step was hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1.

[0207] S16: Steaming.

[0208] This step was carried out by cold evaporation with an evaporation rate of 9Å / s. The thickness of the Ni layer formed after evaporation was 510Å.

[0209] S17: forming silicide.

[0210] This step was carried out at 480° C. for 32 minutes, and nitrogen was introduced at a flow rate of 11 L / min during the formation of the silicide.

[0211] S18: Silicide corrosion.

[0212] This step was carried out at 74° C. for 12 minutes, and the etching reagent used was aqua regia.

[0213] S19: Ti and Al evaporate.

[0214] This step was carried out at 145°C. The thickness of the Al layer formed after the evaporation of Ti and Al was 19500Å, and the thickness of the Ti layer formed was 1450Å.

[0215] S20: Al corrosion.

[0216] This step was performed at 46° C. for 320 seconds. The etching reagent used in this step was acetic acid, phosphoric acid, and nitric acid in a volume ratio of 7.5:67.8:0.5.

[0217] S21: Passivation.

[0218] This step was performed at 480°C to form a 4000Å thick silicon dioxide layer.

[0219] S22: Passivation photolithography etching.

[0220] This step is performed at 23° C. for 140 seconds. The etching reagent used in this step is an etching solution and acetic acid in a volume ratio of 1.8:1, wherein the etching solution is hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1.

[0221] S23: Pad metal evaporation.

[0222] This step is carried out at 145°C. After the pad metal is evaporated, the thickness of the Ag layer formed is 39500Å, the thickness of the Ni layer formed is 4950Å, and the thickness of the Ti layer formed is 1450Å.

[0223] S24: Pad metal photolithography corrosion.

[0224] This step includes NiAg corrosion and Ti anti-corrosion, wherein the NiAg corrosion solution used for NiAg corrosion is glacial acetic acid and acetic acid with a volume ratio of 48.81:18.23, and the NiAg corrosion is carried out at 18°C ​​for 660s; the Ti anti-corrosion solution is hydrofluoric acid, nitric acid and glacial acetic acid with a volume ratio of 1.87:8.6:3.2, and the Ti corrosion is carried out at 16°C for 10s.

[0225] S25: Second annealing.

[0226] This step was carried out at 415°C for 32 min.

[0227] S26: intermediate testing, dicing and packaging.

[0228] Example 3

[0229] This embodiment provides a flip-chip package chip, and the preparation method thereof is as follows:

[0230] S1: Initial oxidation of the epitaxial wafer.

[0231] The doping concentration of the above epitaxial wafer is 7.6×10 18 cm -3 , thickness is 5.1μm.

[0232] The initial oxidation includes: at 1060°C, first introducing oxygen at a flow rate of 5.2 L / min for 8 minutes, then introducing oxygen and hydrogen at a flow rate of 5.2 L / min and 6.2 L / min respectively for 88 minutes, then introducing oxygen at a flow rate of 5.2 L / min for 8 minutes, then introducing nitrogen carrying trichloroethylene at a flow rate of 4.2 L / min for 18 minutes, and then introducing oxygen at a flow rate of 5.2 L / min for 8 minutes.

[0233] S2: Thinning treatment.

[0234] The back side is thinned to about 300 mm using a thinning machine.

[0235] S3: Stress relief corrosion.

[0236] This step is carried out at room temperature for 920 seconds. The etching reagent used in this step consists of nitric acid, hydrofluoric acid, acetic acid and water in a volume ratio of 42:1.2:2.4:22.

[0237] S4: Double-sided lithography.

[0238] S5: Front corrosion.

[0239] This step was performed at 28° C. for 580 s. The etching reagent used in this step was hydrofluoric acid and ammonium fluoride in a volume ratio of 6.5:1.

[0240] S6: Front film.

[0241] The film applied in this step is a UV film.

[0242] S7: Backside corrosion.

[0243] This step is carried out at 12° C. for 8 minutes. The etching solution used in this step is composed of hydrofluoric acid, nitric acid, phosphoric acid and acetic acid in a volume ratio of 1.2:1.2:3.2:4.2.

[0244] S8: Tear off the film.

[0245] This step is to tear off the UV film attached to S6.

[0246] S9: Remove glue.

[0247] This step is carried out using sulfuric acid and hydrogen peroxide in a volume ratio of 3:1.

[0248] S10: Phosphorus pre-diffusion.

[0249] This step was carried out at 1120°C, with oxygen introduced at a flow rate of 3.8 L / min for 2.5 minutes, followed by a phosphorus source for 58 minutes, and then oxygen at a flow rate of 4.2 L / min for 4.8 minutes. Phosphorus oxychloride was carried by nitrogen at a flow rate of 0.45 L / min.

[0250] S11: Phosphorus redistribution.

[0251] This step was carried out at 1060°C. Oxygen was first introduced at a flow rate of 4.2 L / min for 8 minutes, then oxygen and hydrogen were introduced simultaneously at flow rates of 4.2 L / min and 5.2 L / min respectively for 58 minutes, and then oxygen was introduced at a flow rate of 4.2 L / min for 8 minutes.

[0252] S12: P+ ring photolithography etching.

[0253] This step was performed at 28° C. for 580 s. The etching reagent used in this step was hydrofluoric acid and ammonium fluoride in a volume ratio of 6.5:1.

[0254] S13: Boron injection.

[0255] In this step, the dose of boron implantation is 2.2×10 15 cm -2 , the boron implantation energy is 52KeV.

[0256] S14: first annealing.

[0257] This step is carried out at 1085°C. First, oxygen is introduced at a flow rate of 5.2 L / min for 8 minutes, then oxygen and hydrogen are introduced simultaneously at flow rates of 5.2 L / min and 6.2 L / min respectively for 62 minutes, then oxygen is introduced at a flow rate of 5.2 L / min for 8 minutes, then nitrogen carrying trichloroethylene is introduced at a flow rate of 4.2 L / min for 8 minutes, and then oxygen is introduced at a flow rate of 5.2 L / min for 4.8 minutes.

[0258] S15: N++ photolithography etching.

[0259] This step was performed at 28° C. for 580 s. The etching reagent used in this step was hydrofluoric acid and ammonium fluoride in a volume ratio of 6.5:1.

[0260] S16: Steaming.

[0261] This step was carried out by cold evaporation with an evaporation rate of 11Å / s. The thickness of the Ni layer formed after evaporation was 490Å.

[0262] S17: forming silicide.

[0263] This step was carried out at 520° C. for 28 minutes, and nitrogen was introduced at a flow rate of 13 L / min during the formation of the silicide.

[0264] S18: Silicide corrosion.

[0265] This step was carried out at 76° C. for 8 minutes, and the etching reagent used was aqua regia.

[0266] S19: Ti and Al evaporate.

[0267] This step was carried out at 155°C. The thickness of the Al layer formed after the evaporation of Ti and Al was 20500Å, and the thickness of the Ti layer formed was 1550Å.

[0268] S20: Al corrosion.

[0269] This step was performed at 48° C. for 280 seconds. The etching reagent used in this step was acetic acid, phosphoric acid, and nitric acid in a volume ratio of 16.2:73:2.6.

[0270] S21: Passivation.

[0271] This step was performed at 520°C to form a 5000Å thick silicon dioxide layer.

[0272] S22: Passivation photolithography etching.

[0273] This step was performed at 28° C. for 100 s. The etching reagent used in this step was an etching solution and acetic acid in a volume ratio of 2.2:1, wherein the etching solution was hydrofluoric acid and ammonium fluoride in a volume ratio of 65:1.

[0274] S23: Pad metal evaporation.

[0275] This step is carried out at 155°C. After the pad metal is evaporated, the thickness of the Ag layer formed is 40500Å, the thickness of the Ni layer formed is 5050Å, and the thickness of the Ti layer formed is 1550Å.

[0276] S24: Pad metal photolithography corrosion.

[0277] This step includes NiAg corrosion and Ti anti-corrosion, wherein the NiAg corrosion solution used for NiAg corrosion is glacial acetic acid and acetic acid in a volume ratio of 50381:20.23, and the NiAg corrosion is carried out at 20°C for 640s; the Ti anti-corrosion solution is hydrofluoric acid, nitric acid and glacial acetic acid in a volume ratio of 2.17:9.2:4.2, and the Ti corrosion is carried out at 20°C for 86s.

[0278] S25: Second annealing.

[0279] This step was carried out at 425°C for 28 min.

[0280] S26: intermediate testing, dicing and packaging.

[0281] Test example

[0282] The forward voltage drop test was performed on the flip-chip packaged chips prepared in Examples 1 to 3. The results are shown in Table 1.

[0283] Table 1 Forward voltage drop results

[0284]

[0285] It can be seen from Table 1 that the flip-chip packaged chip prepared by the preparation method provided by the present invention has a lower forward voltage drop, which is significantly lower than the 0.54V of the conventional flip-chip packaged chip.

[0286] In summary, the preparation method provided by the present invention can obtain a flip-chip packaged chip with a low forward voltage drop and a clear and complete back label pattern.

[0287] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a flip-chip package, characterized in that: The following steps are involved: The epitaxial wafer is subjected to initial oxidation, thinning, stress relief etching, double-sided photolithography, front etching, front film lamination, back etching, film tearing, resist stripping, phosphorus pre-diffusion, phosphorus re-diffusion, P+ ring photolithography etching, boron implantation, first annealing, N++ photolithography etching, Ni evaporation, silicide formation, silicide etching, Ti and Al evaporation, Al etching, passivation, passivation photolithography etching, pad metal evaporation, pad metal photolithography etching and second annealing; Wherein, the doping concentration of the epitaxial wafer is 7.0×10 18 cm -3 to 7.6×10 18 cm -3 , the thickness of the epitaxial wafer is 4.7 μm~5.1 μm; The etching solution used for backside etching is hydrofluoric acid, nitric acid, phosphoric acid and acetic acid in a volume ratio of (0.8~1.2):(0.8~1.2):(2.8~3.2):(3.8~4.2); the backside etching temperature is 8℃~12℃, and the backside etching time is 8min~12min; Phosphorus pre-diffusion includes: conducting at 1080° C. to 1120° C., first introducing oxygen at a flow rate of 3.8 L / min to 4.2 L / min for 2.5 minutes to 3.5 minutes, then introducing a phosphorus source for 52 minutes to 58 minutes, and then introducing oxygen at a flow rate of 3.8 L / min to 4.2 L / min for 4.8 minutes to 5.2 minutes; Phosphorus rediffusion includes: at 1040°C~1060°C, first introducing oxygen at a flow rate of 3.8L / min~4.2L / min for 8min~12min, then introducing oxygen and hydrogen at flow rates of 3.8L / min~4.2L / min and 4.8L / min~5.2L / min respectively for 58min~62min, and then introducing oxygen at a flow rate of 3.8L / min~4.2L / min for 8min~12min.

2. The preparation method according to claim 1, characterized in that The initial oxidation includes: under the condition of 1040℃~1060℃, first introducing oxygen at a flow rate of 4.8L / min~5.2L / min for 8min~12min, then introducing oxygen and hydrogen at a flow rate of 4.8L / min~5.2L / min and 5.8L / min~6.2L / min respectively for 88min~92min, then introducing oxygen at a flow rate of 4.8L / min~5.2L / min for 8min~12min, then introducing nitrogen carrying trichloroethylene at a flow rate of 3.8L / min~4.2L / min for 18min~22min, and then introducing oxygen at a flow rate of 4.8L / min~5.2L / min for 8min~12min.

3. The preparation method according to claim 1, characterized in that The corrosion reagents used for stress relief corrosion are nitric acid, hydrofluoric acid, acetic acid and water in a volume ratio of (38~42):(0.8~1.2):(1.8~2.2):(18~22), and the stress relief corrosion is carried out at room temperature for 880s~920s.

4. The preparation method according to claim 1, characterized in that The etching reagent used for the front side etching is hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:

1. The front side etching is performed at a temperature of 23° C. to 28° C. for 580 s to 620 s.

5. The preparation method according to claim 1, characterized in that The etching reagent used for the P+ ring photolithography etching is hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:

1. The P+ ring photolithography etching is performed at 23° C. to 28° C. for 580 s to 620 s.

6. The preparation method according to claim 1, characterized in that The etching reagent used for N++ photolithography etching is hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:

1. The N++ photolithography etching is performed at 23° C. to 28° C. for 580 s to 620 s.

7. The preparation method according to claim 1, characterized in that The etching reagent used for silicide etching is aqua regia, and the silicide etching is carried out at 74°C to 76°C for 8min to 12min.

8. The preparation method according to claim 1, characterized in that The corrosion reagents used for Al corrosion are acetic acid, phosphoric acid and nitric acid in a volume ratio of (7.5~16.2):(67.8~73):(0.5~2.6). Al corrosion is carried out at 46℃~48℃ for 280s~320s.

9. The preparation method according to claim 1, characterized in that The etching reagent used for the passivation photolithography etching is an etching solution and acetic acid in a volume ratio of 1.8:1 to 2.2:1, wherein the etching solution is composed of hydrofluoric acid and ammonium fluoride in a volume ratio of 5.5:1 to 6.5:

1. The passivation photolithography etching is carried out at 23°C to 28°C for 100s to 140s.

10. The preparation method according to claim 1, characterized in that The pad metal photolithography etching includes NiAg etching and Ti anti-corrosion, wherein the NiAg etching solution used for NiAg etching is glacial acetic acid and acetic acid with a volume ratio of (48.81~50.81):(18.23~20.23), and the NiAg corrosion is carried out at 18℃~20℃ for 640s~660s; the Ti etching solution used for Ti anti-corrosion is hydrofluoric acid, nitric acid and glacial acetic acid with a volume ratio of (1.87~2.17):(8.6~9.2):(3.2~4.2); Ti corrosion is carried out at 16℃~20℃ for 6s~10s.

11. The preparation method according to claim 1, characterized in that The dose of boron implantation is 1.8×10 15 cm -2 to 2.2×10 15 cm -2 ;The energy of boron injection is 48KeV~52KeV.

12. The preparation method according to claim 1, characterized in that The first annealing includes: conducting at 1075°C~1085°C, first introducing oxygen at a flow rate of 4.8L / min~5.2L / min for 8min~12min, then introducing oxygen and hydrogen at flow rates of 4.8L / min~5.2L / min and 5.8L / min~6.2L / min respectively for 62min~68min, then introducing oxygen at a flow rate of 4.8L / min~5.2L / min for 8min~12min, then introducing nitrogen carrying trichloroethylene at a flow rate of 3.8L / min~4.2L / min for 8min~12min, and then introducing oxygen at a flow rate of 4.8L / min~5.2L / min for 4.8min~5.2min.

13. The preparation method according to claim 1, characterized in that The second annealing is carried out at 415℃~425℃ for 28min~32min.

14. The preparation method according to claim 1, characterized in that Ni was evaporated by cold evaporation with an evaporation rate of 9Å / s~11Å / s. The thickness of the Ni layer formed after evaporation was 490Å~510Å.

15. The preparation method according to claim 1, characterized in that Ti and Al evaporation is carried out at 145°C~155°C. The thickness of the Al layer formed after Ti and Al evaporation is 19500Å~20500Å, and the thickness of the Ti layer formed is 1450Å~1550Å.

16. The preparation method according to claim 1, characterized in that The silicide is formed at 480° C. to 520° C. for 28 min to 32 min, and nitrogen is introduced at a flow rate of 11 L / min to 13 L / min during the silicide formation process.

17. The preparation method according to claim 1, characterized in that Passivation is performed at 480°C to 520°C to form a silicon dioxide layer with a thickness of 4000Å to 5000Å.

18. The preparation method according to claim 1, characterized in that The pad metal evaporation is carried out at 145℃~155℃. The thickness of the Ag layer formed after the pad metal evaporation is 39500Å~40500Å, the thickness of the Ni layer formed is 4950Å~5050Å, and the thickness of the Ti layer formed is 1450Å~1550Å.

19. A flip-chip package, characterized in that: Prepared by the preparation method according to any one of claims 1 to 18.

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