Cavity surface coating structure and method of InP-based semiconductor laser chip

Abstract

The invention relates to the technical field of cavity surface coating of semiconductor laser chips, in particular to a cavity surface coating structure and method of an InP-based semiconductor laser chip, and the method comprises the following steps: S001, cleaving the semiconductor laser chip into bars, fixing the bars by using a special clamp, and transferring the bars into electron cyclotron resonance coating equipment for vacuumizing; s002, starting an automatic cleaning coating program, and when vacuum pumping reaches a required value, automatically performing plasma pre-cleaning treatment on the cavity surface of the chip by an electron cyclotron resonance ion source; s003, after the first protective film Si layer is plated, the laser chip clamp is transferred to an electron beam evaporation coating equipment platform to continue vacuumizing; according to the semiconductor laser chip cavity surface coating method provided by the invention, the semiconductor laser is cleaned by using the electron cyclotron technology, the high antireflection film and the high reflectivity film are evaporated by using the electron beam evaporation coating equipment, high-temperature heating is not needed in the whole coating process, and laser chip electrode degradation caused by high temperature can be effectively avoided; and the efficiency is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of cavity surface coating of semiconductor laser chips, and in particular to a cavity surface coating structure and method of an InP-based semiconductor laser chip. Background Art

[0002] Semiconductor lasers are exposed to wind and rain for a long time, and are affected by rapid changes in high and low temperatures due to their working environment. The film layer of the laser chip is prone to wrinkles, cracks, and peeling. These abnormal chips will accelerate the aging of the laser and reduce the service life of the laser. More seriously, due to the large difference in the expansion coefficients of the substrate and film materials of most laser chips, the high temperature generated by the operation of the laser will cause gaps between the cavity surface and the film layer, and water vapor and oxygen in the air will more easily corrode the cavity surface, eventually causing the laser to fail.

[0003] Therefore, it is crucial to select suitable coating materials and coating equipment and design and manufacture a film system with a dense structure and strong film reliability to improve the quality and reliability of semiconductor lasers. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a cavity surface coating structure and method for an InP-based semiconductor laser chip.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A cavity surface coating method for an InP-based semiconductor laser chip, comprising: S001. Cleave the semiconductor laser chip into strips, then fix them with a special fixture and transfer them into the electron cyclotron resonance coating equipment to evacuate; S002, start the automatic cleaning and coating program, and when the vacuum is drawn to the required value, the electron cyclotron resonance ion source automatically performs plasma pre-cleaning treatment on the cavity surface of the chip, and then coats the first Si layer of the protective layer on the cavity surface of the laser chip; the cavity surface of the chip in this step is the light-emitting cavity surface and the backlight cavity surface of the semiconductor laser; S003. After coating the first protective film Si layer, the laser chip fixture is transferred to the electron beam evaporation coating equipment platform to continue vacuuming; S004. Start the automatic coating program. When the vacuum is drawn to 2.6E-05Pa, heat the temperature to 150℃ and keep it warm for more than 60 minutes. The electron beam evaporation coating equipment automatically coats a high anti-reflection film system on the light-emitting cavity surface of the chip. The high-transmittance film system includes a first Si layer coated on the light-emitting cavity surface, and an Al2O3 layer / Si layer / Al2O3 layer coated on the Si layer in sequence. After coating the high-transmittance film, the equipment automatically turns over and continues to coat a high-reflection film system on the backlight cavity surface. The high-reflection film system includes a first Si layer coated on the backlight cavity surface, and an Al2O3 layer / Si layer / Si layer / Al2O3 layer coated on the Si layer in sequence. After coating, the equipment automatically deflates air and cools down to room temperature to complete the semiconductor laser chip cavity surface coating process.

[0006] Furthermore, in the S002, the specific process of the plasma pre-cleaning treatment is: when the vacuum reaches 5.0E-5Pa, use a plasma process gas Ar flow rate of 10sccm, a N2 flow rate of 20sccm, an ion source power of 300W, and a cleaning time of 120S.

[0007] Furthermore, in the S002, the plasma gas of the first Si layer plated is Ar, the ion source power is 500W, the RF power is 500W, the Si layer thickness is 9-11nm, and the conditions of the first Si layer on the light-emitting surface and the backlight surface are consistent.

[0008] Furthermore, in the S004, the process of electron beam evaporation coating equipment to coat the high anti-reflection film system is as follows: pre-melting the film materials Al2O3 and Si, the ion source plating Ar flow rate is 20sccm, the ion source anode voltage is 100V, the anode current is 3A, the cathode current is 22A, and Al2O3 layer / Si layer / Al2O3 layer are evaporated in sequence to complete the evaporation of the high anti-reflection film system.

[0009] Furthermore, in the S004, the process of plating the high-reflection film system is: pre-melting the film materials Al2O3 and Si, the ion source plating Ar flow rate is 20sccm, the ion source anode voltage is 100V, the anode current is 3A, the cathode current is 22A, and Al2O3 layer / Si layer / Al2O3 layer / Si layer / Al2O3 layer are evaporated in sequence to complete the evaporation of the high-reflection film system.

[0010] Furthermore, in S004, the Al2O3 thin film evaporation rate is 3A / S, and the Si thin film evaporation rate is 1.2A / S.

[0011] A structure prepared by a cavity surface coating method of an InP-based semiconductor laser chip, comprising: In the S001, the semiconductor laser chip is cleaved into Bar strips, which can be performed in a dust-free environment; In the step S002, an electron cyclotron resonance ion source is used to clean the light-emitting cavity surface and the backlight cavity surface of the chip. The plasma generated by electron cyclotron resonance has the advantages of high density and low energy. In the S003, a first layer of protective film Si is plated on the Bar light-emitting cavity surface and the backlight cavity surface by using electron cyclotron resonance coating technology; In the above S004, after the protective film is coated, the fixture is transferred to the electron beam evaporation coating equipment, and the required high anti-reflection film and high reflectivity film are coated on the Bar light emitting cavity surface and the backlight cavity surface using electron beam evaporation technology.

[0012] The beneficial effects of the present invention are: This scheme uses an electron cyclotron resonance ion source to perform plasma cleaning on the light-emitting surface and the backlight surface of the laser. Compared with the Hall source and the Kaufman source, the electron cyclotron resonance ion source has the characteristics of high density and low energy. The high density can effectively clean the cavity surface, and the low energy will not cause damage to the cavity surface of the laser chip during the cleaning process.

[0013] The present invention uses electron cyclotron resonance to plate the first Si layer of the protective film on the front and rear light-emitting surfaces of the chip. The thermal expansion coefficient of the grown Si film is close to that of the InP substrate material, and the high temperature generated by the laser chip will not cause a gap between the film layer and the substrate. At the same time, the Si layer plated by electron cyclotron resonance technology has excellent compactness and corrosion resistance, which can effectively protect the chip cavity surface and avoid performance and reliability failure problems caused by oxidation of the chip cavity surface.

[0014] The present invention adopts electron beam evaporation coating equipment to evaporate high antireflection film and high reflectivity film. The method has low coating temperature, high deposition rate, high equipment utilization, good film density, and high coating reliability and stability.

[0015] The semiconductor laser chip cavity surface coating method provided by the present invention utilizes electron cyclotron technology to clean the semiconductor laser, and utilizes electron beam evaporation coating equipment to evaporate high anti-reflection film and high reflectivity film. No high-temperature heating is required during the entire coating process, which can effectively avoid the problems of laser chip electrode degradation and efficiency reduction caused by high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic flow chart of the coating structure of the present invention; Figure 2 It is a schematic diagram of the film system of the light-emitting cavity surface and the backlight cavity surface of the present invention; Figure 3 It is a curve diagram of the reflectivity test results of the high antireflection film structure of the present invention on the InP companion film; Figure 4 It is a curve diagram of the reflectivity test results of the high reflective film structure of the present invention on the InP companion film.

[0017] In the figure: Al2O3-1, the first Al2O3 layer; Al2O3-2, the second Al2O3 layer; Al2O3-3, the third Al2O3 layer; Al2O3-4, the fourth Al2O3 layer; Al2O3-5, the fifth Al2O3 layer; Si-1, first Si layer; Si-2, second Si layer; Si-3, third Si layer; Si-4, fourth Si layer. DETAILED DESCRIPTION

[0018] 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.

[0019] Example: Refer to Figure 1-2 , a cavity surface coating method for an InP-based semiconductor laser chip, comprising: S001. Cleave the surface of the semiconductor laser chip, place the cleaved bar in a special fixture, and quickly put it into the cleaned electron cyclotron coating equipment to evacuate; at the same time, put the InP substrate companion sheet with the same epitaxial material as the laser chip to monitor the stability of the film thickness and reflectivity data during the coating process; S002, start the automatic cleaning and coating program, when the vacuum is drawn to the required value, the electron cyclotron resonance ion source automatically performs plasma pre-cleaning treatment on the cavity surface of the chip, and after the cleaning is completed, the equipment continues to automatically plate the first Si layer of the protective layer on the light-emitting cavity surface of the laser chip; the cavity surface of the chip in the step is the light-emitting cavity surface and the backlight cavity surface of the semiconductor laser, the equipment does not start heating during the ion source pre-cleaning and coating of the protective film Si layer, after the electron cyclotron resonance coating of the light-emitting cavity surface is completed, it is turned over to the backlight cavity surface, the plasma performs ion source pre-cleaning treatment on the backlight cavity surface of the chip, and the first Si layer is plated on the backlight cavity surface of the chip, and the equipment does not start heating during the ion source pre-cleaning and coating of the protective film Si layer, and the thickness of the first Si layer is 10nm; S003. Clean the electron beam evaporation coating equipment in advance to ensure that the equipment is in a vapor deposition state. After coating the first protective film Si layer, transfer the laser chip fixture to the electron beam evaporation coating equipment platform to continue vacuuming. S004. Start the automatic coating program. When the vacuum is drawn to 2.6E-05Pa, the temperature is heated to 150℃ and kept warm for more than 60 minutes. The electron beam evaporation coating equipment automatically coats the high anti-reflection film system on the light-emitting cavity surface of the chip. The high-transmittance film system includes the first Si layer coated on the light-emitting cavity surface, and the Al2O3 layer / Si layer / Al2O3 layer coated on the Si layer. After coating the high-transmittance film, the equipment automatically turns over and continues to coat the high-reflection film system on the backlight cavity surface. The high-reflection film system includes the first Si layer coated on the backlight cavity surface, and the Al2O3 layer / Si layer / Al2O3 layer / Si layer / Al2O3 layer coated on the Si layer. After the coating is completed, the equipment automatically deflates and cools down to room temperature, completing the semiconductor laser chip cavity surface coating process.

[0020] Specifically, in S002, the specific process of plasma pre-cleaning treatment is: when the vacuum reaches 5.0E-5Pa, use plasma process gas Ar flow rate 10sccm, N2 flow rate 20sccm, ion source power 300W, and cleaning time 120S.

[0021] Furthermore, in S002, the plasma gas of the first Si layer deposited is Ar, the ion source power is 500W, the RF power is 500W, the Si layer thickness is 9-11nm, and the conditions of the first Si layer on the light-emitting side and the backlight side are the same.

[0022] Furthermore, in S004, the process of electron beam evaporation coating equipment to coat high antireflection film system is as follows: pre-melting the film materials Al2O3 and Si, the ion source plating Ar flow rate is 20sccm, the ion source anode voltage is 100V, the anode current is 3A, the cathode current is 22A, and Al2O3 layer / Si layer / Al2O3 layer are evaporated in sequence, wherein the thicknesses are 26.8nm, 20.9 nm, and 179.3nm respectively.

[0023] Moreover, in S004, the process of plating the high-reflection film system is as follows: pre-melting the film materials Al2O3 and Si, the Ar flow rate of the ion source plating aid is 20sccm, the anode voltage of the ion source is 100V, the anode current is 3A, the cathode current is 22A, and Al2O3 layer / Si layer / Al2O3 layer / Si layer / Al2O3 layer are evaporated in sequence, wherein the thicknesses are 204.5nm, 67.9nm, 204.5nm, 67.9nm, and 145.5nm respectively.

[0024] Finally, in S004, the machine temperature is heated to 150°C and kept constant for more than 60 minutes. The Al2O3 film evaporation rate is 3A / S, and the Si film evaporation rate is 1.2A / S. At the same time, the Al2O3 and Si materials need to be pre-melted before coating to ensure that the coating rate is stable and controllable.

[0025] A structure prepared by a cavity surface coating method of an InP-based semiconductor laser chip, comprising: In S001, the semiconductor laser chip is cleaved into Bar strips, which can be performed in a dust-free environment. As a further embodiment, after cleavage, the chip is placed in an electron cyclotron resonance chamber and evacuated within one hour to prepare for the next step. In S002, an electron cyclotron resonance ion source is used to clean the light-emitting cavity surface and the backlight cavity surface of the chip. The plasma generated by electron cyclotron resonance has the advantages of high density and low energy. The specific process conditions for cleaning are: when the equipment vacuum reaches 5.0E-5Pa, the microwave power is 300W, the argon gas flow rate is 20sccm, and the cleaning time is 120S; In S003, the electron cyclotron resonance coating technology is used to coat the first layer of protective film Si on the Bar light-emitting cavity surface and the backlight cavity surface; the coating process conditions are: microwave power 500W, RF radio frequency power 500W, argon gas flow rate 40sccm, and the coating thickness is 9~11nm; In S004, after the protective film is coated, the fixture is transferred to the electron beam evaporation coating equipment, and the required high anti-reflection film and high reflectivity film are coated on the Bar light-emitting cavity surface and the backlight cavity surface using electron beam evaporation technology. The electron beam evaporation coating process conditions are vacuum reaching 2.6E-5Pa, coating temperature 150°C, ion source assisting Ar flow rate of 20sccm, ion source anode voltage of 100V, anode current of 3A, and cathode current of 22A. The high anti-reflection film system on the light-emitting cavity surface includes a first Al2O3 layer, a second Si layer, and a second Al2O3 layer coated on the Si layer, wherein the thicknesses are 26.8nm, 20.9nm, and 179.3nm, respectively. The high-reflection film system on the backlight cavity surface includes a third Al2O3 layer, a third Si layer, a fourth Al2O3 layer, a fourth Si layer, and a fifth Al2O3 layer plated on the Si layer, wherein the thicknesses are 204.5nm, 67.9nm, 204.5nm, 67.9nm, and 145.5nm, respectively.

[0026] like Figure 3 and Figure 4 As shown, the reflectivity of the high-transmittance film and high-reflection film layer tested by monitoring the InP companion film deposition as completed in the above steps, it can be seen from the test curve that the reflectivity of the high-transmittance film at a wavelength of 1270nm is 0.1%, and the reflectivity of the high-reflection film at a wavelength of 1270nm is 90.0%.

[0027] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0028] The standard parts used in the present invention can all be purchased from the market, and special-shaped parts can be customized according to the description in the specification and the drawings. The specific connection methods of each part adopt conventional means such as mature bolts, rivets, welding, etc. in the prior art. The machinery, parts and equipment all adopt conventional models in the prior art, and the circuit connection adopts the conventional connection method in the prior art, which will not be described in detail here.

[0029] 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 method for coating the cavity surface of an InP-based semiconductor laser chip, characterized in that: include: S001. Cleave the semiconductor laser chip into strips, then fix them with a special fixture and transfer them into the electron cyclotron resonance coating equipment to evacuate; S002, start the automatic cleaning and coating program, and when the vacuum is drawn to the required value, the electron cyclotron resonance ion source automatically performs plasma pre-cleaning treatment on the cavity surface of the chip, and then coats the first Si layer of the protective layer on the cavity surface of the laser chip; the cavity surface of the chip in this step is the light-emitting cavity surface and the backlight cavity surface of the semiconductor laser; S003. After coating the first protective film Si layer, the laser chip fixture is transferred to the electron beam evaporation coating equipment platform to continue vacuuming; S004. Start the automatic coating program. When the vacuum is drawn to 2.6E-05Pa, heat the temperature to 150℃ and keep it warm for more than 60 minutes. The electron beam evaporation coating equipment automatically coats a high anti-reflection film system on the light-emitting cavity surface of the chip. The high-transmittance film system includes a first Si layer coated on the light-emitting cavity surface, and an Al2O3 layer / Si layer / Al2O3 layer coated on the Si layer in sequence. After coating the high-transmittance film, the equipment automatically turns over and continues to coat a high-reflection film system on the backlight cavity surface. The high-reflection film system includes a first Si layer coated on the backlight cavity surface, and an Al2O3 layer / Si layer / Si layer / Al2O3 layer coated on the Si layer in sequence. After coating, the equipment automatically deflates air and cools down to room temperature to complete the semiconductor laser chip cavity surface coating process.

2. The cavity surface coating method of an InP-based semiconductor laser chip according to claim 1, characterized in that: In the above S002, the specific process of plasma pre-cleaning treatment is: when the vacuum reaches 5.0E-5Pa, use plasma process gas Ar flow rate 10sccm, N2 flow rate 20sccm, ion source power 300W, and cleaning time 120S.

3. The method for coating the cavity surface of an InP-based semiconductor laser chip according to claim 1, characterized in that: In the S002, the plasma gas of the first Si layer plated is Ar, the ion source power is 500W, the RF power is 500W, the Si layer thickness is 9-11nm, and the conditions of the first Si layer on the light-emitting surface and the backlight surface are consistent.

4. The method for coating the cavity surface of an InP-based semiconductor laser chip according to claim 1, characterized in that: In the above S004, the process of coating the high anti-reflection film system by the electron beam evaporation coating equipment is as follows: pre-melting the film materials Al2O3 and Si, the ion source assisting Ar flow rate is 20sccm, the ion source anode voltage is 100V, the anode current is 3A, the cathode current is 22A, and Al2O3 layer / Si layer / Al2O3 layer are evaporated in sequence to complete the evaporation of the high anti-reflection film system.

5. The method for coating the cavity surface of an InP-based semiconductor laser chip according to claim 1, characterized in that: In the S004, the process of plating the high-reflection film system is: pre-melting the film materials Al2O3 and Si, the ion source plating Ar flow rate is 20sccm, the ion source anode voltage is 100V, the anode current is 3A, the cathode current is 22A, and Al2O3 layer / Si layer Al2O3 layer / Si layer / Al2O3 layer are evaporated in sequence to complete the evaporation of the high-reflection film system.

6. The method for coating the cavity surface of an InP-based semiconductor laser chip according to claim 1, characterized in that: In the S004, the Al2O3 thin film evaporation rate is 3A / S, and the Si thin film evaporation rate is 1.2A / S.

7. A structure prepared by using the cavity surface coating method of an InP-based semiconductor laser chip according to any one of claims 1 to 6, characterized in that: include: In the step S001, the semiconductor laser chip is cleaved into Bar strips in a dust-free environment; In the step S002, an electron cyclotron resonance ion source is used to clean the light-emitting cavity surface and the backlight cavity surface of the chip. The plasma generated by electron cyclotron resonance has the advantages of high density and low energy. In the S003, a first layer of protective film Si is plated on the Bar light-emitting cavity surface and the backlight cavity surface by using electron cyclotron resonance coating technology; In the above S004, after the protective film is coated, the fixture is transferred to the electron beam evaporation coating equipment, and the required high anti-reflection film and high reflectivity film are coated on the Bar light emitting cavity surface and the backlight cavity surface using electron beam evaporation technology.

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