Medium and far infrared high-reflective film and preparation method thereof

Abstract

The invention provides a middle and far infrared high-reflective film and a preparation method thereof, and the film comprises a first insulating layer, a first adhesion layer, a metal reflection layer, a second adhesion layer and a second insulating layer which are sequentially connected from bottom to top. The first insulating layer and the second insulating layer have high transmittance in the middle and far infrared band and insulate and isolate the laser chip from the upper electrode and the lower electrode, and the metal reflecting layer reflects middle and far infrared laser. According to the invention, the high-reflection film is evaporated on the rear cavity surface of the laser chip, and the high-reflection characteristic of the Au layer is utilized, so that the reflectivity of the whole film system structure in the middle-infrared band of 4-6 [mu] m is greater than 95%, and the reflectivity in the far-infrared band of 8-14 [mu] m is greater than 99%. The total thickness of the film system structure does not exceed 1.3 mu m and is far smaller than that of a conventional medium high-reflection film, and the risk that the film layer falls off is reduced. In addition, the design of the two insulating layers avoids the short circuit of the upper electrode and the lower electrode of the laser chip, and can be suitable for the laser chips of normal bonding and flip-chip bonding.

Description

Technical Field

[0001] The invention relates to the technical field of electrical components, and in particular to a mid- and far-infrared high-reflection film and a preparation method thereof. Background Art

[0002] Usually, the back cavity surface of high-power semiconductor laser chips needs to be evaporated with a high-reflective film. The main function of the high-reflective film is to increase the single-sided output light power of the laser chip, and to prevent the oxidation of the cavity surface, thereby improving the stability and reliability of the laser. In the selection of high-reflective film materials, not only is the film material required to have high reflectivity at the target wavelength, but it is also required to have good adhesion to the cleavage surface of the laser chip, and have good stress matching and thermal matching with the cleavage surface material, so as to avoid the film layer from falling off or cracking. For visible light and near-infrared semiconductor lasers, a multi-layer dielectric film with alternating high and low refractive indices with a thickness of λ / 4 is usually used as a high-reflective film. However, for mid- and far-infrared semiconductor lasers, due to the longer wavelength, in order to achieve a high reflectivity of more than 90%, the total thickness of the dielectric film needs to be very thick, which increases the internal stress and is easy to fall off from the cavity surface. On the other hand, this dielectric film can only have high reflectivity at a specific wavelength, and cannot achieve high reflection in a wide spectrum range.

[0003] Therefore, there is a need for a dielectric film that can achieve high reflection in a wide spectral range and is not easy to fall off. Summary of the invention

[0004] The present invention is to solve the problem of thickness and reflection range of mid-infrared high-reflection film, and provides a mid-infrared high-reflection film and a preparation method thereof. The film system structure of the mid-infrared high-reflection film is: first insulating layer / first adhesion layer / metal reflection layer / second adhesion layer / second insulating layer, wherein the first insulating layer and the second insulating layer are both Y2O3 with a thickness of 300-500nm, the first adhesion layer and the second adhesion layer are both Cr with a thickness of 1-5nm, and the metal reflection layer is Au with a thickness of 100-200nm. The high-reflection film is evaporated on the rear cavity surface of the laser chip, and the high reflection characteristics of the Au layer are used to make the reflectivity of the entire film system structure greater than 95% in the 4-6μm mid-infrared band and greater than 99% in the 8-14μm far-infrared band. The total thickness of the film system structure of the present invention does not exceed 1.3μm, which is much smaller than the conventional medium high-reflection film, reducing the risk of film layer shedding. In addition, the design of the two insulating layers avoids short circuits between the upper and lower electrodes of the laser chip, and can be applied to laser chips for positive welding and flip-chip welding.

[0005] The present invention provides a mid-to-far infrared high reflection film, comprising a first insulating layer, a first adhesion layer, a metal reflection layer, a second adhesion layer and a second insulating layer connected in sequence from bottom to top, wherein the first insulating layer is connected to the cavity surface of the laser chip;

[0006] The first insulating layer and the second insulating layer have high transmittance in the mid-infrared and far-infrared bands and insulate and isolate the laser chip from the upper electrode and the lower electrode; the first adhesive layer is connected between the first insulating layer and the metal reflective layer to improve the adhesion between the first insulating layer and the metal reflective layer; the second adhesive layer is connected between the second insulating layer and the metal reflective layer to improve the adhesion between the second insulating layer and the metal reflective layer; and the metal reflective layer reflects the mid-infrared and far-infrared lasers;

[0007] The thickness of the first insulating layer and the second insulating layer are both greater than the thickness of the metal reflective layer, and the thickness of the metal reflective layer is both greater than the thickness of the first adhesive layer and the second adhesive layer;

[0008] The light emitted from the laser chip cavity surface passes through the first insulating layer and the first adhesive layer in sequence and then reaches the metal reflective layer, and the metal reflective layer reflects light;

[0009] The thickness of the mid- and far-infrared high-reflection film is less than 1.3μm.

[0010] The mid-to-far infrared high reflection film of the present invention is preferably such that when the mid-to-far infrared high reflection film has internal stress, the compressive stress of the first insulating layer and the second insulating layer can balance the tensile stress of the first adhesion layer, the metal reflection layer and the second adhesion layer;

[0011] The thickness of the first insulating layer and the second insulating layer are both 300-500 nm, the thickness of the first adhesion layer and the second adhesion layer are both 1-5 nm, and the thickness of the metal reflective layer is 100-200 nm.

[0012] In the mid-to-far infrared high reflective film described in the present invention, as a preferred embodiment, the materials of the first insulating layer and the second insulating layer are both Y2O3, the material of the metal reflective layer is Au, and the materials of the first adhesion layer and the second adhesion layer are both Cr.

[0013] The mid-to-far infrared high reflection film described in the present invention is preferably prepared on the cavity surface of the laser chip by evaporation, and the cavity surface of the laser chip is the rear cavity surface of the laser chip.

[0014] The mid-to-far infrared high reflection film described in the present invention can be used for semiconductor laser chips in face-down welding and flip-chip welding as a preferred embodiment.

[0015] The method for preparing a mid-to-far infrared high-reflection film of the present invention comprises the following steps:

[0016] S1. Clean the parts to be plated: Use dust-free cloth and anhydrous ethanol to clean and wipe the rear cavity surface of the laser chip to remove impurities and oil stains on the end surface of the parts to be plated;

[0017] S2. Fix the plated part on the fixture and place it in the vacuum chamber. Evacuate the vacuum chamber to 5×10 -3 Pa;

[0018] S3, turn on the ion source and Ar gas to clean the surface of the workpiece to be plated, and turn off the ion source and working gas after the cleaning is completed;

[0019] S4, continue to vacuum to 2~3×10 -3 Pa, and heat the workpiece to be plated to 100-150° C., and sequentially plate a first insulating layer, a first adhesion layer, a metal reflective layer, a second adhesion layer, and a second insulating layer on the surface of the workpiece to be plated, and monitor the thickness of the film layer;

[0020] S5. After the coating is completed, the vacuum chamber is cooled to room temperature and then the vacuum is broken, and the plated parts are taken out. A mid-to-far infrared high-reflection film and a preparation method thereof are completed.

[0021] The method for preparing a mid-to-far infrared high reflective film of the present invention is preferably such that in step S3, during cleaning, the vacuum degree is 2×10 -1 Pa, ion energy is 1000eV, and cleaning time is 2min.

[0022] The method for preparing a mid-to-far infrared high-reflective film described in the present invention is, as a preferred embodiment, in step S4, the coating rate of the first insulating layer and the second insulating layer is 0.5-0.9 nm / s, the coating rate of the first adhesion layer and the second adhesion layer is 0.8-1.2 nm / s, and the coating rate of the metal reflective layer is 1-1.5 nm / s; the film thickness is monitored by a crystal oscillator method.

[0023] The method for preparing a mid-to-far infrared high-reflective film described in the present invention is, as a preferred embodiment, in step S4, the coating rates of the first insulating layer and the second insulating layer are lower than the coating rates of the first adhesion layer and the second adhesion layer, and the coating rates of the first adhesion layer and the second adhesion layer are lower than the coating rate of the metal reflective layer.

[0024] The method for preparing a mid-to-far infrared high-reflective film described in the present invention is, as a preferred embodiment, the coating rates of the first insulating layer and the second insulating layer are both 0.5nm / s, the coating rates of the first adhesion layer and the second adhesion layer are both 0.8nm / s, and the coating rate of the metal reflective layer is 1.2nm / s.

[0025] The present invention uses a gold reflective layer to achieve high reflectivity, and only one or two hundred nanometers of gold layer is needed to achieve high reflection. The entire film system of the present invention is a structure of an insulating layer + an adhesive layer + a high reflective layer + an adhesive layer + an insulating layer. The application scenario of this film system is as a high reflective film on the end face of a laser chip, so an insulating layer needs to be added to prevent the chip from short-circuiting. The adhesive layer is to improve the adhesion between the insulating layer and the metal layer to prevent the film layer from falling off or cracking.

[0026] The insulating layer in the present invention is made of Y2O3 material. On the one hand, the material has high transmittance and low absorption in the mid- and far-infrared bands. On the other hand, the Y2O3 film layer is compressive stress, which can balance the tensile stress of the Cr / Au / Cr metal material layer and avoid film cracking caused by excessive stress.

[0027] The Cr adhesion layer has a certain absorption in the mid- and far-infrared bands, so it should not be too thick, and 1-5nm is used. In order to sufficiently balance the tensile stress of the Cr / Au / Cr metal material layer, the thickness of Y2O3 is set to 300-500nm.

[0028] The present invention has the following advantages:

[0029] (1) The present invention utilizes the high reflectivity of the Au layer to make the entire film structure have high reflectivity in a wide spectrum range. Specifically, the reflectivity in the 4-6 μm mid-infrared band is greater than 95%, and the reflectivity in the 8-14 μm far-infrared band is greater than 99%.

[0030] (2) The total thickness of the film structure of the present invention does not exceed 1.3 μm, which is much smaller than the conventional dielectric high-reflection film, reducing the risk of film shedding. In addition, the design of two insulating layers avoids short circuits between the upper and lower electrodes of the laser chip, and is suitable for both face-up and flip-chip laser chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of a mid-to-far infrared high reflection film;

[0032] Figure 2 The present invention is a flow chart of a method for preparing a mid-to-far infrared high-reflective film;

[0033] Figure 3 Schematic diagram of the reflectivity results of a mid-to-far infrared high-reflective film and its preparation method.

[0034] Reference numerals:

[0035] 1. First insulating layer; 2. First adhesion layer; 3. Metal reflective layer; 4. Second adhesion layer; 5. Second insulating layer. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0037] Example 1

[0038] A mid-to-far infrared high-reflection film and a preparation method thereof, which is plated on the back cavity surface of a laser chip, such as Figure 1As shown, the film structure from inside to outside is: first insulating layer 1 / first adhesion layer 2 / metal reflective layer 3 / second adhesion layer 4 / second insulating layer 5. The first insulating layer 1 and the second insulating layer 5 are both Y2O3, the first adhesion layer 2 and the second adhesion layer 4 are both Cr, and the metal reflective layer 3 is Au. The thickness of each layer of the film structure is as follows: the thickness of the first insulating layer 1 and the second insulating layer 5 is 400nm, the thickness of the first adhesion layer 2 and the second adhesion layer 4 is 2nm, and the thickness of the metal reflective layer 3 is 150nm. The total thickness of the entire film system is 954nm.

[0039] like Figure 2 As shown, the present invention provides a method for preparing a mid-to-far infrared high-reflection film, comprising the following steps:

[0040] Step 1: Clean the part to be plated. Use a dust-free cloth and anhydrous ethanol to clean and wipe the rear cavity surface of the laser chip to remove impurities and oil stains on the end surface of the part to be plated.

[0041] Step 2: Fix the plated part on the fixture, place it in the vacuum chamber, and evacuate to 5×10 -3 Pa.

[0042] Step 3: Turn on the ion source and Ar gas to clean the surface of the plated part. The specific cleaning parameters are: vacuum degree 2×10 -1 Pa, ion energy 1000eV, cleaning time 2min. After cleaning, turn off the ion source and working gas.

[0043] Step 4: Continue to vacuum until 2-3×10 -3 Pa, and heat the part to be plated to 100-150℃, and perform evaporation in sequence according to the film structure and thickness. The coating rate of Y2O3 is 0.5nm / s, the coating rate of Cr is 0.8nm / s, and the coating rate of Au is 1.2nm / s. The film thickness is monitored by the crystal oscillator method.

[0044] Step 5: After coating, wait for the vacuum chamber to cool to room temperature, break the vacuum, and take out the plated parts.

[0045] So far, the preparation of a mid-to-far infrared high-reflective film of the present invention has been completed.

[0046] The reflectivity test of the mid-to-far infrared high-reflective film in this embodiment at different wavelengths (2-20 μm) was tested using an infrared spectrophotometer. The results are as follows: Figure 3 As shown, the reflectivity in the 4-6 μm mid-infrared band is greater than 95%, and the reflectivity in the 8-14 μm far-infrared band is greater than 99%.

[0047] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A mid-to-far infrared high reflection film, characterized in that: It comprises a first insulating layer (1), a first adhesive layer (2), a metal reflective layer (3), a second adhesive layer (4) and a second insulating layer (5) which are connected in sequence from bottom to top, wherein the first insulating layer (1) is connected to the cavity surface of the laser chip; The first insulating layer (1) and the second insulating layer (5) have high transmittance in the mid-infrared and far-infrared bands and insulate the laser chip from the upper electrode and the lower electrode; the first adhesive layer (2) is connected between the first insulating layer (1) and the metal reflective layer (3) to improve the adhesion between the first insulating layer (1) and the metal reflective layer (3); the second adhesive layer (4) is connected between the second insulating layer (5) and the metal reflective layer (3) to improve the adhesion between the second insulating layer (5) and the metal reflective layer (3); and the metal reflective layer (3) reflects the mid-infrared and far-infrared lasers; The thickness of the first insulating layer (1) and the second insulating layer (5) are both greater than the thickness of the metal reflective layer (3), and the thickness of the metal reflective layer (3) is both greater than the thickness of the first adhesive layer (2) and the second adhesive layer (4); The light emitted from the cavity surface of the laser chip passes through the first insulating layer (1) and the first adhesive layer (2) in sequence and then reaches the metal reflective layer (3), and the metal reflective layer (3) reflects light; The thickness of the mid- and far-infrared high-reflection film is less than 1.3 μm.

2. A mid-to-far infrared high reflective film according to claim 1, characterized in that: The mid- and far-infrared high-reflection film has internal stress, and the compressive stress of the first insulating layer (1) and the second insulating layer (5) can balance the tensile stress of the first adhesive layer (2), the metal reflective layer (3), and the second adhesive layer (4); The thickness of the first insulating layer (1) and the second insulating layer (5) are both 300-500 nm, the thickness of the first adhesion layer (2) and the second adhesion layer (4) are both 1-5 nm, and the thickness of the metal reflective layer (3) is 100-200 nm.

3. A mid-to-far infrared high reflective film according to claim 1, characterized in that: The materials of the first insulating layer (1) and the second insulating layer (5) are both Y2O3, the material of the metal reflective layer (3) is Au, and the materials of the first adhesion layer (2) and the second adhesion layer (4) are both Cr.

4. A mid-to-far infrared high reflective film according to claim 1, characterized in that: The mid-to-far infrared high-reflection film is prepared on the laser chip cavity surface by evaporation, and the laser chip cavity surface is the laser chip rear cavity surface.

5. The mid-to-far infrared high reflective film according to claim 1, characterized in that: The mid-to-far infrared high-reflection film can be used for semiconductor laser chips in face-down welding and flip-chip welding.

6. The method for preparing a mid-to-far infrared high reflective film according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Clean the parts to be plated: Use dust-free cloth and anhydrous ethanol to clean and wipe the rear cavity surface of the laser chip to remove impurities and oil stains on the end surface of the parts to be plated; S2, fix the plated piece on the fixture and place it in the vacuum chamber, evacuate to 5×10 -3 Pa; S3, turn on the ion source and Ar gas to clean the surface of the workpiece to be plated, and turn off the ion source and working gas after the cleaning is completed; S4, continue to vacuum to 2~3×10 -3 Pa, and heating the workpiece to be plated to 100-150° C., sequentially plating the first insulating layer (1), the first adhesion layer (2), the metal reflective layer (3), the second adhesion layer (4) and the second insulating layer (5) on the surface of the workpiece to be plated, and monitoring the film thickness; S5. After the coating is completed, the vacuum chamber is cooled to room temperature and then the vacuum is broken, and the plated parts are taken out. A mid-to-far infrared high-reflection film and a preparation method thereof are completed.

7. The method for preparing a mid-to-far infrared high reflective film according to claim 6, characterized in that: In step S3, during cleaning, the vacuum degree is 2×10 -1 Pa, ion energy is 1000eV, and cleaning time is 2min.

8. The method for preparing a mid-to-far infrared high reflective film according to claim 6, characterized in that: In step S4, the coating rates of the first insulating layer (1) and the second insulating layer (5) are 0.5 to 0.9 nm / s, the coating rates of the first adhesion layer (2) and the second adhesion layer (4) are 0.8 to 1.2 nm / s, and the coating rate of the metal reflective layer (3) is 1 to 1.5 nm / s; the film thickness is monitored by a crystal oscillator method.

9. The method for preparing a mid-to-far infrared high reflective film according to claim 6, characterized in that: In step S4, the coating rates of the first insulating layer (1) and the second insulating layer (5) are lower than the coating rates of the first adhesive layer (2) and the second adhesive layer (4), and the coating rates of the first adhesive layer (2) and the second adhesive layer (4) are lower than the coating rate of the metal reflective layer (3).

10. A mid-to-far infrared high reflective film and a preparation method thereof according to claim 9, characterized in that: The coating rates of the first insulating layer (1) and the second insulating layer (5) are both 0.5 nm / s, the coating rates of the first adhesion layer (2) and the second adhesion layer (4) are both 0.8 nm / s, and the coating rate of the metal reflective layer (3) is 1.2 nm / s.

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