Semiconductor laser cavity surface coating method and chip

Abstract

The invention relates to the technical field of lasers, and provides a semiconductor laser cavity surface coating method and a chip. The method comprises the following steps: after pre-cleaning the front cavity surface of a laser chip, evaporating a front protective layer on the front cavity surface of the laser chip; overturning the laser chip to a rear cavity surface, pre-cleaning the rear cavity surface of the laser chip, and evaporating a rear protection layer on the rear cavity surface of the laser chip; overturning the laser chip to the front cavity surface, introducing a first mixed gas into the ion source auxiliary equipment, and evaporating an antireflection film on the front cavity surface of the laser chip by using the first mixed gas; wherein the first mixed gas comprises O2 and Ar, and the proportion of Ar in the first mixed gas is 5%-20%; and turning over the laser chip to the rear cavity surface, and evaporating a high-reflection film on the rear cavity surface of the laser chip. According to the invention, the mixed gas of O2 and Ar is used as the evaporation gas of the antireflection film of the front cavity surface, and the front cavity surface and the rear cavity surface are switched, turned and coated, so that the stability of the ESD threshold value of the obtained chip is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser, in particular to a semiconductor laser cavity surface coating method and chip. BACKGROUND

[0002] Semiconductor laser has the characteristics of small volume, light weight, high electro-optical conversion efficiency, high reliability, long life, etc., and has become the most promising product in the photoelectric industry. However, the laser cleavage surface as the resonant cavity surface, after the laser is cleaved, if not timely coated, the dangling bond on the surface of the laser will encounter low-density water vapor or oxygen, not only will form a defect center, reduce the loss threshold of the cavity surface film, but also prone to film peeling problem in packaging, especially when the heat sink uses AuSn solder to package the device, the welding temperature is relatively high, generally at 250-360℃, and when the film with low adhesion is welded quickly, the film layer is prone to peeling.

[0003] In the prior art, in addition to meeting the spectral characteristics of different chips, the semiconductor laser end face coating also needs to bear the reliability requirement. At present, vacuum cleavage and coating can obtain a laser with high performance, but there are disadvantages of expensive equipment and complex operation technology; although the film layer quality of electron cyclotron resonance sputtering is high, the equipment is expensive, the operation is complex, the deposition speed is slow, and the production efficiency is low, which cannot meet the production demand. Another method is to coat a very thin silicon layer as a passivation layer on the cavity surface before coating the antireflection film and the high-reflection film, but this often leads to poor film adhesion, film peeling, and decline of electro-static discharge (ESD) and photoelectric performance of the chip, affecting the actual use of the product. Actual test shows that the ESD threshold of the chip coated by the existing process technology is extremely unstable, which further leads to uneven service life of the semiconductor laser chips in mass production.

[0004] Therefore, it is urgent to overcome the defects of the prior art in the technical field. SUMMARY

[0005] The technical problem to be solved by the present application is that the ESD threshold of the chip coated by the existing process technology is unstable.

[0006] The present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a semiconductor laser cavity surface coating method, which uses a coating device to coat the front and rear cavity surfaces of a laser chip, and the method comprises the following steps:

[0008] Pre-cleaning the front cavity surface of the laser chip, and evaporating a protective layer on the front cavity surface of the laser chip;

[0009] flip the laser chip to the back cavity surface, pre-clean the back cavity surface of the laser chip, and evaporate a back protective layer on the back cavity surface of the laser chip;

[0010] flip the laser chip to the front cavity surface, introduce a first mixed gas into the ion source auxiliary device, and evaporate an anti-reflection film on the front cavity surface of the laser chip using the first mixed gas; wherein the first mixed gas comprises O2 and Ar, and the proportion of Ar in the first mixed gas is 5% to 20%;

[0011] flip the laser chip to the back cavity surface, and evaporate a high-reflection film on the back cavity surface of the laser chip.

[0012] Preferably, the pre-cleaning of the front and back cavity surfaces of the laser chip specifically comprises:

[0013] introduce a second mixed gas into the ion source auxiliary device, set the anode voltage of the ion source auxiliary device to 180 to 185 V and the anode current to 2.5 to 3.5 A, and use the ion source auxiliary device to pre-clean the front and back cavity surfaces of the laser chip; wherein the second mixed gas comprises N2 and Ar, and the proportion of Ar in the second mixed gas is 0% to 10%.

[0014] Preferably, the pre-cleaning of the front and back cavity surfaces of the laser chip lasts for 300 to 400 seconds.

[0015] Preferably, the high-reflection film comprises, in order from the back protective layer to the direction away from the back protective layer, a first low-reflection film, a first high-reflection film, a second low-reflection film, a second high-reflection film, a third low-reflection film, and a third high-reflection film; wherein the evaporation temperature used when evaporating the first, second, and third high-reflection films is 200 to 230°C.

[0016] Preferably, the material of the first low-reflection film is Al2O3, the materials of the second and third low-reflection films are SiO2, and the materials of the first, second, and third high-reflection films are Ti3O5; the evaporation of the high-reflection film on the back cavity surface of the laser chip specifically comprises:

[0017] introduce the first mixed gas into the ion source auxiliary device, set the anode voltage of the ion source auxiliary device to 140 to 150 V and the anode current to 2.0 to 2.5 A, evaporate the first low-refraction film at an evaporation temperature of 200 to 230°C and an evaporation speed of 4.0 to 5.0 A / s until the thickness of the first low-refraction film reaches 120 to 130 nm;

[0018] The O2 is introduced into the ion source auxiliary equipment, the anode voltage of the ion source auxiliary equipment is set to 140-150V, the anode current is 4.5-5.0A, the first high reflectivity film is evaporated at the evaporation temperature of 200-230℃ and the evaporation rate of 1.5-2.0A / s, and the evaporation is continued until the thickness of the first high reflectivity film reaches 130-140nm;

[0019] The second low refractive index film is evaporated at the evaporation temperature of 200-230℃ and the evaporation rate of 4.0-5.0A / s, and the evaporation is continued until the thickness of the second low refractive index film reaches 220-230nm;

[0020] The second high reflectivity film, the third low reflectivity film and the third high reflectivity film are evaporated in sequence.

[0021] Preferably, before the front cavity surface of the laser chip is pre-cleaned, the method further comprises:

[0022] The laser chip is cleaved into a bar, and the bar is sent into a film coating equipment, the machine cavity of the film coating equipment is vacuumed to 8.0x10-6Torr, and the machine cavity temperature is set to 200-230℃, so that the bar is baked in the machine cavity for 30-60min. -6 Torr, and the machine cavity temperature is set to 200-230℃, so that the bar is baked in the machine cavity for 30-60min.

[0023] Preferably, the material of the front protective layer is SiN x ; the front protective layer is evaporated on the front cavity surface of the laser chip, and specifically comprises:

[0024] NH3 is introduced into the machine cavity of the film coating equipment, the flow rate of NH3 is 10-15sccm;

[0025] N2 is introduced into the ion source auxiliary equipment, the anode voltage of the ion source auxiliary equipment is set to 180-185V, the anode current is 3.0-3.5A, the front protective layer is evaporated at the evaporation rate of 1.5-2.0A / s, and the evaporation is continued until the thickness of the front protective layer reaches 80-90nm.

[0026] Preferably, the material of the antireflection film is Al2O3; the antireflection film is evaporated on the front cavity surface of the laser chip using the first mixed gas, and specifically comprises:

[0027] The first mixed gas is introduced into the ion source auxiliary equipment, the anode voltage of the ion source auxiliary equipment is set to 140-150V, the anode current is 2.0-2.5A, the antireflection film is evaporated at the evaporation temperature of 200-230℃ and the evaporation rate of 4.0-5.0A / s, and the evaporation is continued until the thickness of the antireflection film reaches 100-110nm.

[0028] Preferably, the material of the rear protective layer is SiN x ; the rear protective layer is evaporated on the rear cavity surface of the laser chip, and specifically comprises:

[0029] The NH3 is introduced into the machine cavity of the coating equipment, and the flow rate of the NH3 is 10-15sccm;

[0030] The N2 is introduced into the ion source auxiliary equipment, the anode voltage of the ion source auxiliary equipment is set to 180-185V, the anode current is 3.0-3.5A, the back protective layer is evaporated at a deposition rate of 1.5-2.0A / s, and the thickness of the back protective layer reaches 90-95nm.

[0031] In the second aspect, the application further provides a semiconductor laser chip, which is obtained by coating the front cavity surface and the back cavity surface of the semiconductor laser chip by using the semiconductor laser cavity surface coating method in any one of the first aspect.

[0032] The application uses the mixed gas of O2 and Ar as the evaporation gas of the front cavity surface anti-reflection film, and switches and turns over the coating of the front and back cavity surfaces, that is, the evaporation of each film layer is sequentially performed in the order of first coating the front protective layer of the front cavity surface, then coating the back protective layer of the back cavity surface, then coating the anti-reflection film of the front cavity surface, and finally coating the high reflection film of the back cavity surface, so as to improve the stability of the ESD threshold of the obtained chip. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments of the application. Obviously, the drawings described below are only some embodiments of the application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0034] Figure 1 is a flowchart of the first semiconductor laser cavity surface coating method provided by the embodiments of the application;

[0035] Figure 2 is a test result diagram of the ESD threshold in the semiconductor laser cavity surface coating method provided by the embodiments of the application;

[0036] Figure 3 is a test result diagram of the reflectivity in the semiconductor laser cavity surface coating method provided by the embodiments of the application;

[0037] Figure 4 is a flowchart of the second semiconductor laser cavity surface coating method provided by the embodiments of the application;

[0038] Figure 5 is a flowchart of the third semiconductor laser cavity surface coating method provided by the embodiments of the application;

[0039] Figure 6is a film layer surface roughness test result schematic diagram in a semiconductor laser cavity surface coating method provided by the embodiment of the present application;

[0040] Figure 7 is a film layer surface schematic diagram in a semiconductor laser cavity surface coating method provided by the embodiment of the present application;

[0041] Figure 8 is a film layer surface schematic diagram in another semiconductor laser cavity surface coating method provided by the embodiment of the present application;

[0042] Figure 9 is a stress test result schematic diagram in a semiconductor laser cavity surface coating method provided by the embodiment of the present application;

[0043] Figure 10 is a structure schematic diagram of a semiconductor laser chip front cavity surface provided by the embodiment of the present application;

[0044] Figure 11 is a structure schematic diagram of a semiconductor laser chip rear cavity surface provided by the embodiment of the present application. DETAILED DESCRIPTION

[0045] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0046] In the description of the present application, the orientation or position relationship indicated by the terms "inner", "outer", "longitudinal", "transverse", "upper", "lower", "top", "bottom" and the like is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and does not require the present application to be constructed and operated in a particular orientation, therefore should not be understood as a limitation on the present application.

[0047] The terms "first", "second", and the like in the present application are only for the purpose of description, and should not be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features limited by "first", "second" and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "multiple" is two or more.

[0048] In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as there is no conflict.

[0049] Embodiment 1:

[0050] Embodiment 1 of the present application provides a semiconductor laser cavity surface coating method, using a coating device to coat the front cavity surface and the rear cavity surface of a laser chip, as shown in Figure 1 The method comprises the following steps:

[0051] In step 201, the front cavity surface of the laser chip is pre-cleaned, and a front protective layer is evaporated on the front cavity surface of the laser chip.

[0052] In step 202, the laser chip is flipped to the rear cavity surface, the rear cavity surface of the laser chip is pre-cleaned, and a rear protective layer is evaporated on the rear cavity surface of the laser chip.

[0053] In step 203, the laser chip is flipped to the front cavity surface, a first mixed gas is introduced into the ion source auxiliary device, and the front cavity surface of the laser chip is evaporated with the first mixed gas to form an anti-reflection film; wherein the first mixed gas comprises O2 and Ar, and the proportion of Ar in the first mixed gas is 5% to 20%.

[0054] In step 204, the laser chip is flipped to the rear cavity surface, and a high-reflection film is evaporated on the rear cavity surface of the laser chip.

[0055] In order to make the advantages of the present application more clear and obvious, the prior art coating method is also briefly described in this embodiment. The coating method in the prior art is to flip the laser chip after coating the front cavity surface of the laser chip (including coating the protective layer and the anti-reflection film), and then coat the rear cavity surface of the laser chip. When evaporating the anti-reflection film on the front cavity surface of the laser, O2 is used for evaporation, that is, O2 is introduced into the ion source auxiliary device as the evaporation gas to evaporate the anti-reflection film on the front cavity surface. According to experiments, the ESD threshold of the laser chip produced by the prior art is unstable, and the ESD threshold of each chip in the same batch fluctuates greatly. In order to solve this problem, a control experiment is conducted in this embodiment, which includes multiple control groups.

[0056] As in the optional embodiment, the control experiment includes 6 control groups, as follows:

[0057] The first control group: using O2 as the evaporation gas of the front cavity anti-reflection film, after coating the front cavity surface of the laser chip, flipping the laser chip, and coating the rear cavity surface of the laser chip.

[0058] The second control group: using Ar as the evaporation gas of the front cavity anti-reflection film, after coating the front cavity surface of the laser chip, flipping the laser chip, and coating the rear cavity surface of the laser chip.

[0059] The third control group: using the first mixed gas as the evaporation gas of the front cavity surface anti-reflection film, after the film coating on the front cavity surface of the laser chip is completed, the laser chip is flipped, and the rear cavity surface of the laser chip is coated.

[0060] The fourth control group: using O2 as the evaporation gas of the front cavity surface anti-reflection film, after the evaporation of the front protective layer on the front cavity surface of the laser chip is completed, the laser chip is flipped, the rear protective film on the rear cavity surface of the laser chip is evaporated, then the laser chip is flipped again, the anti-reflection film on the front cavity surface of the laser chip is evaporated, and after the completion, the laser chip is flipped again, and the high-reflection film on the rear cavity surface of the laser chip is evaporated.

[0061] The fifth control group: using Ar as the evaporation gas of the front cavity surface anti-reflection film, after the evaporation of the front protective layer on the front cavity surface of the laser chip is completed, the laser chip is flipped, the rear protective film on the rear cavity surface of the laser chip is evaporated, then the laser chip is flipped again, the anti-reflection film on the front cavity surface of the laser chip is evaporated, and after the completion, the laser chip is flipped again, and the high-reflection film on the rear cavity surface of the laser chip is evaporated.

[0062] The sixth control group: using the first mixed gas as the evaporation gas of the front cavity surface anti-reflection film, after the evaporation of the front protective layer on the front cavity surface of the laser chip is completed, the laser chip is flipped, the rear protective film on the rear cavity surface of the laser chip is evaporated, then the laser chip is flipped again, the anti-reflection film on the front cavity surface of the laser chip is evaporated, and after the completion, the laser chip is flipped again, and the high-reflection film on the rear cavity surface of the laser chip is evaporated.

[0063] The six control groups are consistent in other processes and parameters in the chip film coating process except for the above-mentioned different processes and parameters.

[0064] After the laser chips corresponding to the above six control groups are prepared, a corresponding number of laser chips with qualified other performance indicators are selected from each batch for ESD threshold value testing. In this embodiment, 12 chips with qualified other performance indicators are selected from each batch of laser chips for ESD threshold value testing, and the obtained ESD threshold values of each chip are as shown in Table 1. Figure 2

[0065] ​Taking the 12 chips of each batch as an example, the standard deviation of the ESD threshold of each batch of chips is calculated as follows: the standard deviation of the first control group is 264.00, and the average value is 833; the standard deviation of the second control group is 400.76, and the average value is 1033; the standard deviation of the third control group is 328.91, and the average value is 1050 (ESD threshold less than 500 is used to participate in the calculation of standard deviation and average value); the minimum standard deviation of the fourth control group is 419.60, and the average value is 1083 (ESD threshold less than 500 is used to participate in the calculation of standard deviation and average value); the standard deviation of the fifth control group is 290.64, and the average value is 1058; the standard deviation of the sixth control group is 57.74, and the average value is 1183.

[0066] Comparing the first control group (standard deviation 264.00, average value 833), the second control group (standard deviation 400.76, average value 1033) and the third control group (standard deviation 328.91, average value 1050), it can be found that when O2 is used as the evaporation gas of the front cavity surface anti-reflection film, the ESD threshold of each chip is more uniform than when Ar is used as the evaporation gas of the front cavity surface anti-reflection film, and the average value of the ESD threshold of each chip when the first mixed gas is used as the evaporation gas of the front cavity surface anti-reflection film is higher (i.e. the ESD threshold is higher) than when O2 is used as the evaporation gas of the front cavity surface anti-reflection film.

[0067] Comparing the first control group (standard deviation 264.00, average value 833) with the fourth control group (standard deviation 419.60, average value 1083), comparing the second control group (standard deviation 400.76, average value 1033) with the fifth control group (standard deviation 290.64, average value 1058), and comparing the third control group (standard deviation 328.91, average value 1050) with the sixth control group (standard deviation 57.74, average value 1183), it can be found that the ESD threshold of the chip obtained by the method of turning over after the front protective layer film is deposited, then depositing the back protective layer, then turning over, then depositing the anti-reflection film on the front cavity surface, then turning over, and then depositing the high-reflection film on the back cavity surface is more uniform, and the average value of the ESD threshold of the chip obtained by the method of turning over three times is relatively higher.

[0068] Comparing the six control groups together, it can be found that the ESD threshold of the chip obtained by the sixth control group is the most uniform, and the lowest ESD threshold is 1000V, which meets the requirement of the minimum ESD threshold of 500V, so the optimal implementation method is the sixth control group, i.e. the film deposition method described in the embodiment.

[0069] The embodiment uses a mixed gas of O2 and Ar as the evaporation gas of the front cavity surface anti-reflection film, and makes the front and rear cavity surfaces switch to flip the film, that is, the evaporation of each film layer is sequentially performed in the order of first evaporating the front protective layer of the front cavity surface, then evaporating the rear protective layer of the rear cavity surface, then evaporating the anti-reflection film of the front cavity surface, and finally evaporating the high-reflection film of the rear cavity surface, thereby improving the stability of the ESD threshold of the obtained chip.

[0070] In the preferred embodiment, the front cavity surface of the laser chip is pre-cleaned, specifically including: introducing a second mixed gas into the ion source auxiliary device, setting the anode voltage of the ion source auxiliary device to 180-185V and the anode current to 2.5-3.5A, and using the ion source auxiliary device to pre-clean the front cavity surface of the laser chip; wherein the second mixed gas comprises N2 and Ar, and the proportion of Ar in the second mixed gas is 0%-10%. The pre-cleaning time of the front cavity surface of the laser chip is 300-400s. The proportion of Ar in the second mixed gas is actually greater than or equal to 0% and less than or equal to 10%, and when the proportion of Ar is 0%, the second mixed gas is actually N2.

[0071] In actual application scenarios, the rear cavity surface of the laser chip is also pre-cleaned using the preferred embodiment.

[0072] The embodiment uses the second mixed gas for pre-cleaning, thereby improving the adsorption of the film, improving the strength of the film layer, and avoiding film layer peeling.

[0073] The preferred embodiment is also obtained through experiments, specifically including:

[0074] The first control group: the cavity surface of the laser chip is not pre-cleaned, and the evaporation of the front protective layer or the rear protective layer is directly performed.

[0075] The second control group: the cavity surface of the laser chip is pre-cleaned using the second mixed gas, and then the subsequent evaporation process is performed.

[0076] The third control group: the cavity surface of the laser chip is pre-cleaned using Ar, and then the subsequent evaporation process is performed.

[0077] The three control groups are consistent in other processes and parameters in the chip film coating process except for the above-mentioned different processes and parameters.

[0078] After the laser chips corresponding to the above three control groups are prepared, the strength of the film layer is tested by using the method of pasting adhesive tape on the surface of the film layer and tearing the adhesive tape, and the following results are obtained:

[0079] The chip prepared by the first control group was completely stripped off the film layer at the tearing position after the tape was torn, and the chip substrate was exposed. The chip prepared by the second control group did not appear to be stripped off the film layer after the tape was torn. The chip prepared by the third control group appeared to be partially stripped off the film layer, and the chip substrate was not exposed. It can be seen from the tearing experiments of the above three control groups that after the second mixed gas is used to pre-clean the cavity surface of the laser chip, the strength of the film layer of the chip obtained by coating is the highest, and the anti-falling effect is the best, that is, the above-mentioned preferred embodiment.

[0080] In actual use, the chip rear cavity surface may also be affected by water vapor, causing the reflectivity to change. To solve this problem, the embodiment also provides a preferred embodiment, that is, the high-reflectivity film comprises, in order from the rear protective layer to the direction away from the rear protective layer, a first low-reflectivity film, a first high-reflectivity film, a second low-reflectivity film, a second high-reflectivity film, a third low-reflectivity film, and a third high-reflectivity film; wherein the evaporation temperature used when evaporating the first high-reflectivity film, the second high-reflectivity film, and the third high-reflectivity film is 200-230°C.

[0081] The material of the high-reflectivity film is Ti3O5. In this embodiment, high-reflectivity films are evaporated under different temperature conditions to obtain a plurality of chip experimental pieces. The different temperature conditions include 80-110°C, 110-140°C, 140-170°C, 170-200°C, and 200-230°C (in actual use, 90°C, 130°C, 160°C, 190°C, and 220°C are used). After the chips obtained under each temperature condition are immersed in a 100°C high-temperature deionized water solution for 60 minutes, the reflectivity of the high-reflectivity film of the rear cavity surface of each chip is tested, and the results are as shown in Figure 3 The curve marked as initial is the reflectivity curve of the chip without water boiling. The curves of 190°C, 220°C, and initial are relatively close, and the same line is used for marking in Figure 3 In actual values, there is a small difference, as shown in the following table. It can be seen that the reflectivity changes significantly at 90°C and 130°C, and the reflectivity of the chip obtained under the conditions of 160°C, 190°C, and 220°C is less affected by water boiling (i.e., close to the initial curve). This embodiment also provides specific reflectivity data at some wavelengths, as shown in the following table:

[0082]

[0083] It can be seen that the reflectivity of the chip obtained under the condition of 200-230°C (i.e., the high-reflectivity film evaporated at 220°C) is almost not affected by water boiling. It can be considered that the high-reflectivity film evaporated under the condition of 200-230°C has good compactness and strong water vapor isolation effect.

[0084] In a specific application scenario, as shown in Figure 11 The material of the first low reflectivity film is Al2O3, the material of the second low reflectivity film and the third low reflectivity film is SiO2, and the material of the first high reflectivity film, the second high reflectivity film and the third high reflectivity film is Ti3O5; the high reflectivity film is deposited on the back cavity surface of the laser chip, as shown in Figure 4 The specific steps include:

[0085] In step 301, a first mixed gas is introduced into the ion source auxiliary device, the anode voltage of the ion source auxiliary device is set to 140-150V, the anode current is set to 2.0-2.5A, the first low refractive index film is deposited at a deposition temperature of 200-230℃ and a deposition rate of 4.0-5.0A / s, and the thickness of the first low refractive index film is 120-130nm.

[0086] In step 302, O2 is introduced into the ion source auxiliary device, the anode voltage of the ion source auxiliary device is set to 140-150V, the anode current is set to 4.5-5.0A, the first high reflectivity film is deposited at a deposition temperature of 200-230℃ and a deposition rate of 1.5-2.0A / s, and the thickness of the first high reflectivity film is 130-140nm.

[0087] In step 303, the second low refractive index film is deposited at a deposition temperature of 200-230℃ and a deposition rate of 4.0-5.0A / s, and the thickness of the second low refractive index film is 220-230nm.

[0088] In step 304, the second high reflectivity film, the third low reflectivity film and the third high reflectivity film are sequentially deposited; the manufacturing process of the second high reflectivity film and the third high reflectivity film is consistent with that of the first high reflectivity film, i.e. step 302, and the thickness of the film layer is also consistent, i.e. the thickness of the second high reflectivity film and the third high reflectivity film is 130-140nm; the manufacturing process of the third low reflectivity film is consistent with that of the second low refractive index film, i.e. step 303, and the thickness of the film layer is also consistent, i.e. the thickness of the third low reflectivity film is 220-230nm.

[0089] Before pre-cleaning the front cavity surface of the laser chip, the method further includes:

[0090] The laser chip is cleaved into a bar, and the bar is sent into a film coating device; the machine cavity of the film coating device is vacuumed to 8.0×E -6 Torr, and the machine cavity temperature is set to 200-230℃, so that the bar is baked in the machine cavity for 30-60min.

[0091] The material of the front protective layer is SiN x The front protective layer is evaporated on the front cavity surface of the laser chip, and specifically includes the following steps.

[0092] NH3 is introduced into the machine cavity of the film coating equipment, the flow rate of NH3 is 10-15sccm, N2 is introduced into the ion source auxiliary equipment, the anode voltage of the ion source auxiliary equipment is set to 180-185V, the anode current is 3.0-3.5A, the front protective layer is evaporated at an evaporation rate of 1.5-2.0A / s, and the thickness of the front protective layer reaches 80-90nm.

[0093] The material of the antireflection film is Al2O3, the antireflection film is evaporated on the front cavity surface of the laser chip using the first mixed gas, and specifically includes the following steps.

[0094] The material of the rear protective layer is SiN x The rear protective layer is evaporated on the rear cavity surface of the laser chip, and specifically includes the following steps.

[0095] Embodiment 2:

[0096] Based on the method described in embodiment 1, the specific application scenarios are combined, and the implementation process in the specific scenario of the application is described by the technical description in the related scenario.

[0097] The semiconductor laser cavity surface coating method provided in the embodiment is as shown in Figure 5 The semiconductor laser cavity surface coating method provided in the embodiment is as shown in

[0098] In step 401, the evaporation chamber of the electron beam evaporation coating machine is cleaned in advance, the film layer on the crucible is gently scraped off, and then sucked by a dust collector, and the surrounding of the crucible is checked to ensure that there is no slag falling in the ion source, the used Al2O3, SiO2, Ti3O5 and Si coating materials in the crucible must be removed before coating, and new materials are filled, and the crucible is confirmed to be sufficient, the semiconductor laser chip is cleaved into a bar, and then the bar is placed and fixed by a clamp, the clamp with the bar is placed on the workpiece disc fan of the electron beam evaporation equipment, then the coating pot fan is installed in the self-rotating support, and the automatic vacuum program of the equipment is started.

[0099] In step 402, the process parameters are loaded, the automatic coating program is started, and the coating equipment is vacuumed to below 8.0*E - 6 After the vacuuming, the equipment is baked at 200-230℃ for 30-60 minutes, the ion source auxiliary equipment is started, process gas N2 and Ar are introduced, the proportion of Ar is 0%-10%, the anode voltage of the ion source is 180-185V, the anode current is 2.5-3.5A, the front cavity surface of the semiconductor laser chip is pre-cleaned, the processing time is 300-400s, the unstable oxide and air carbon contamination during cleaving and bar setting are removed, and an activated surface is provided to facilitate thin film nucleation and growth.

[0100] In step 403, after the processing, the front cavity surface is evaporated with SiN x As the front protective layer, NH3 is introduced into the cavity, the flow rate of NH3 is 10-15sccm, pure N2 is introduced into the ion source as the process gas, the anode voltage is 180-185V, and the anode current is 3.0-3.5A. SiN x The evaporation rate is 1.5-2.0A / s, and the film thickness is 80-90nm.

[0101] In step 404, the automatic flipping device is opened, the laser chip is flipped, and the rear cavity surface is pre-cleaned first after the flipping. The ion source auxiliary equipment is started, N2 and Ar are introduced, the proportion of Ar is 0-10%, the anode voltage is 180-185V, and the anode current is 2.5-3.5A. After the processing, the next step is to evaporate SiN x , the process parameters are consistent with those of the front protective layer, i.e. NH3 is introduced into the cavity, the flow rate of NH3 is 10-15sccm, pure N2 is introduced into the ion source as the process gas, the anode voltage is 180-185V, and the anode current is 3.0-3.5A. SiN x The evaporation rate is 1.5-2.0A / s, and the film thickness is 90-95nm.

[0102] In step 405, the automatic flipping device is opened, the laser chip is flipped, and optical thick Al2O3 is evaporated on the front cavity surface as an anti-reflection film to form a SiN x / Al2O3 structure. The Al2O3 evaporation temperature is 200-230℃, the evaporation rate is 4.0-5.0A / s, the thickness is 100-110nm, O2 and Ar are introduced into the ion source as the gas, the proportion of Ar is 5%-20%, the anode voltage of the ion source is 140-150V, and the anode current is 2.0-2.5A.

[0103] In step 406, after the antireflection film is plated, the automatic turnover device is opened, the laser chip is turned over, and the high-reflection film is evaporated after being turned over, that is, Al2O3, Ti3O5, SiO2, Ti3O5, SiO2 and Ti3O5 are evaporated on the SiN x layer of the back cavity surface, wherein Al2O3 and SiO2 are low-refractive-index films, Ti3O5 is a high-refractive-index film, and together they form a high-reflection film, forming a SiN x / Al2O3 / Ti3O5 / SiO2 / Ti3O5 / SiO2 / Ti3O5 structure, wherein the evaporation temperature of the high-reflection film is 200-230°C; the evaporation rate of Al2O3 and SiO2 is 4.0-5.0 A / s, the ion source process gas is O2 and Ar, the proportion of Ar is 0-10%, the anode voltage is 140-150V, and the anode current is 2.0-2.5A; the evaporation rate of Ti3O5 is 1.5-2.0 A / s, the ion source process gas is O2, the anode voltage is 140-150V, and the anode current is 4.5-5.0A. The thickness of Al2O3 is 120-130nm, the thickness of SiO2 is 220-230nm, and the thickness of Ti3O5 is 130-140nm.

[0104] In step 407, after the high-reflection film is plated, the interface cavity display temperature is observed to be less than 120°C, and the "break vacuum" key on the operation interface is pressed; the film plating chamber starts to be inflated, and after inflation is completed, the film plating chamber door is automatically opened, the fixture containing the Bar strip is taken out, the Bar strip is taken out of the fixture, and the laser Bar strip is divided into single laser chips for aging life and ESD tests.

[0105] The present embodiment also provides the following control groups to embody the advantages of the above-mentioned embodiments, specifically including:

[0106] First control group:

[0107] (1) Clean the evaporation chamber of the electron beam evaporation film plating machine in advance, gently scrape off the film layer on the crucible, then use a dust collector to suck it up, and check to ensure that the crucible around is clean, there is no slag falling in the ion source, the used Al2O3, SiO2, Ti3O5 and Si plating materials in the crucible must be removed before plating, new materials are filled, it is confirmed that the crucible film material is sufficient, the semiconductor laser chip is cleaved into a Bar strip and fixed with a fixture, the fixture containing the Bar strip is placed on the workpiece disc fan of the electron beam evaporation equipment, then the plating pot fan is installed in the self-rotating support, and the automatic vacuum program of the equipment is started.

[0108] (2) Load the process parameters, start the automatic film plating program, and the film plating equipment is vacuumed to less than 8.0 x E -6After baking at 200-230℃ for 30-60 minutes, the ion source auxiliary equipment is started, N2 is introduced, the anode voltage of the ion source is 180-185V, the anode current is 2.5-3.5A, the cavity surface of the semiconductor laser chip is pre-cleaned for 300-400 seconds, and the unstable oxide and air carbon contamination during cleaving and bar setting are removed, and an activated surface is provided to facilitate film nucleation and growth;

[0109] (3) After the treatment, the next step is to evaporate SiN x As a front protective layer, NH3 is introduced into the cavity, the flow rate of NH3 is 10-15sccm, the ion source introduces pure N2 as a process gas, the anode voltage is 180-185V, and the anode current is 3.0-3.5A. SiN x The evaporation rate is 1.5-2.0A / s, and the film thickness is 80-90nm. SiN x After evaporation, optical thick Al2O3 is continuously evaporated as an antireflection film, forming a SiN x / Al2O3 structure, the Al2O3 evaporation temperature is 200-230℃, the evaporation rate is 4.0-5.0A / s, the thickness is 100-110nm, the ion source introduces O2 as a gas, the anode voltage of the ion source is 140-150V, and the anode current is 2.0-2.5A. The cavity surface is the front cavity surface of the semiconductor laser chip.

[0110] (4) After the antireflection film is evaporated, the automatic turnover device is opened, and the evaporation of the high reflection film is carried out. First, the rear cavity surface is pre-cleaned, the ion source auxiliary equipment is started, N2 and Ar are introduced, the proportion of Ar is 0-10%, the anode voltage is 180-185V, and the anode current is 2.5-3.5A. After the treatment, the next step is to evaporate SiN x As a rear protective layer, the process parameters are the same as those in the front protective layer. SiN x The evaporation rate is 1.5-2A / s, and the film thickness is 90-95nm. SiN x The Al2O3 and SiO2 on the rear cavity surface are evaporated as low refractive index films, and Ti3O5 is evaporated as a high refractive index film to form a high reflection film, forming a SiN x / Al2O3 / Ti3O5 / SiO2 / Ti3O5 / SiO2 / Ti3O5 structure, wherein the evaporation temperature of the back film layer is 200-230℃; the evaporation rate of Al2O3 and SiO2 is 4.0-5.0A / s; the ion source process gas is O2 and Ar, the proportion of Ar is 0-10%, the anode voltage is 140-150V, and the anode current is 2.0-2.5A; the evaporation rate of Ti3O5 is 1.5-2.0A / s, the ion source process gas is O2, the anode voltage is 140-150V, and the anode current is 4.5-5.0A. The thickness of Al2O3 is 120-130nm, the thickness of SiO2 is 220-230nm, and the thickness of Ti3O5 is 130-140nm.

[0111] (5) After the high-reflection film is plated, the interface cavity display temperature is observed to be less than 120℃, and then the "break vacuum" key on the operation interface is pressed; the film plating chamber starts to be inflated, and after the inflation is completed, the film plating chamber door is automatically opened, the fixture containing the Bar strip is taken out, the Bar strip is taken out of the fixture, and the laser Bar strip is divided into single laser chips for aging life and ESD tests.

[0112] The second control group: on the basis of the first control group, the pre-cleaning process of the front cavity surface and the back cavity surface is removed.

[0113] The third control group: on the basis of the first control group, the ion source gas used in the pre-cleaning process is changed from pure N2 to N2 and Ar, and the proportion of Ar is 0%-10%.

[0114] The fourth control group: the ion source gas used in the pre-cleaning process is changed from pure N2 to Ar.

[0115] The fifth control group: on the basis of the first control group, the ion source process gas used for the front cavity surface Al2O3 anti-reflection film is changed from pure O2 to pure Ar.

[0116] The sixth control group: on the basis of the first control group, the ion source process gas used for the front cavity surface Al2O3 is changed from pure O2 to O2 and Ar, and the proportion of Ar is 5%-20%.

[0117] The seventh control group: the evaporation temperature of the back cavity surface Ti3O5 is in the range of 90-230℃, and a comparison and reference test is performed every 30℃.

[0118] The eighth control group: after the SiN x of the front cavity surface is plated, the automatic turning process is started to pre-clean the back cavity surface, the SiN x process is performed, then the turning is continued to complete the anti-reflection film process of the front cavity surface, after the anti-reflection film process is completed, the turning is started again to complete the high-reflection film process of the back cavity surface, and the whole process is turned three times.

[0119] The ninth control group: the film system structure of the front cavity surface is changed to: Sub / SiN x / SiO2 / Ti3O5, the film layer thickness is 80 / 64 / 247 nm respectively, and the film system structure of the rear cavity surface is changed to Sub / SiN x / SiO2 / Ti3O5 / SiO2 / Ti3O5 / SiO2 / Ti3O5, the film layer thickness is 90 / 110 / 150 / 236 / 150 / 236 / 150 nm; a plurality of Ti3O5 evaporation temperature reference tests are performed, and the temperature is 90-230 °C.

[0120] The above nine control groups are all adjusted through experiments, the tooling value is corrected, the thickness is calculated by using TFC software, the AR reflectivity of the InP wafer is ensured to be less than 0.2%, and the HR reflectivity is 89±0.5%. Meanwhile, the wafer of each case is subjected to high-temperature (380 °C) baking, 100 °C water boiling for one hour, and 3M adhesive tape sticking and pulling experiments; and the surface morphology of the wafer is analyzed by using an atomic force microscope (AFM).

[0121] In the high-temperature baking experiment, the nine control groups are all heated and baked by using a 380 °C hot plate, and the thin films do not fall off or burst.

[0122] In the 3M adhesive tape sticking and pulling experiment, the thin film plated in the first control group does not fall off before and after the 3M adhesive tape is stuck to the surface; the thin film plated in the second control group falls off on the rear cavity surface after the 3M adhesive tape is stuck to the surface, and most of the plated thin film is exposed to the substrate surface, which indicates that the adhesion of the thin film without the pre-cleaning process scheme is poor; the thin film plated in the third control group does not fall off; the thin film plated in the fourth control group falls off on the rear cavity surface after the 3M adhesive tape is stuck and pulled; the thin films plated in the fifth, sixth, seventh and eighth control groups pass the firmness test under the condition of pre-cleaning; and the thin films plated in the ninth control group fall off on the front and rear cavity surfaces after the 3M adhesive tape is stuck and pulled.

[0123] In the water boiling experiment, the thin film plated in the seventh control group is immersed in a 100 °C deionized water solution and heated for 60 min under the condition that the temperature is 90 °C and 130 °C, the thin film discolors, and the reflectivity change is as shown in Figure 3 The rest of the control groups do not change before and after water boiling, which indicates that the temperature of Ti3O5 has an effect on the denseness of the thin film, and the thin film plated under the condition that the temperature is 200-230 °C has good denseness and strong water vapor isolation effect.

[0124] After obtaining the above conclusions, parameters with better film performance were selected for subsequent comparative reference experiments: the film structure remained unchanged; the pre-cleaning conditions were fixed as follows: ion source gas N2 and Ar, with the Ar ratio being 0% to 10%; and the process temperature was fixed as 200 to 230℃.

[0125] The tenth control group: the Al2O3 ion source gas at the front cavity surface was O2.

[0126] Eleventh control group: The Al2O3 ion source gas at the front cavity surface was replaced with pure Ar.

[0127] The twelfth control group: the Al2O3 ion source gas on the front cavity surface was changed to O2 and Ar.

[0128] The thirteenth control group: the Al2O3 ion source gas on the front cavity surface was O2; the number of flips was 3.

[0129] The fourteenth control group: the Al2O3 ion source gas on the front cavity surface was changed to pure Ar; the number of flips was changed to 3.

[0130] The fifteenth control group: the Al2O3 ion source gas on the front cavity surface was changed to O2 and Ar; the number of flips was changed to 3.

[0131] The coated laser strips from the tenth to fifteenth control groups were cleaved into individual dies. Twelve qualified dies were selected from each control group and subjected to TO packaging for ESD threshold testing. The ESD threshold of the laser chip should not be lower than 500V. The test results were as follows: Figure 2 The ESD threshold data shown is as follows, Figure 2 Control group 1 is the tenth control group, and so on. Figure 2 Control group 6 was the fifteenth control group.

[0132] Furthermore, AFM testing was performed on the tenth to fifteenth control groups, and the obtained test data are as follows: Figure 6 As shown, the difference in roughness variation is small; among them, the AFM of the front and rear cavity surfaces of the thin film deposited in the fifteenth control group is as follows. Figure 7 and Figure 8 As shown, the fifteenth control group has an inP substrate on the anterior cavity surface with Rq = 1.35 nm and Ra = 1.05 nm; and an inP substrate on the posterior cavity surface with Rq = 7.57 nm and Ra = 2.47 nm.

[0133] Therefore, it can be seen that the coating method of the present invention performs ion cleaning on the cavity surface before coating, which improves the bonding strength between the thin film and the cavity surface. Then, the reliability of the laser is improved by optimizing the subsequent evaporation temperature, ion source process gas and process.

[0134] The eleventh control group has good individual test data (1000V) in the ESD threshold test, but the variation range is large, and the fifteenth control group does not reach 1400V in the ESD overall test, but the overall variation range is small, and the test is stable. In the stress test of the tenth to fifteenth control groups, it is found that the performance is improved compared with the existing process in terms of stress. When a chip with very high ESD threshold is needed, the process described in the thirteenth control group can be used, and the obtained chip is tested and selected to obtain a chip with very high ESD threshold, such as a chip with an ESD threshold of 1800V, but the yield of the chip with very high ESD threshold is low due to the instability of the ESD threshold of the chip; when a large number of chips with stable ESD threshold are needed, the process described in the fifteenth control group can be used, so as to obtain a chip with an ESD threshold stable between 1000-1200V.

[0135] In actual use, the first control group and the fifteenth control group are also subjected to cavity surface stress tests, and the test results are as shown in Figure 9 It can be seen that with the change of the process, the aggregation density and deformation of the film of the fifteenth control group change, resulting in the overall stress of the film of the fifteenth control group becoming smaller, so that the stability of the overall film is improved to a certain extent.

[0136] On the basis of the above-mentioned embodiments, the present embodiment also provides a semiconductor laser chip, which is coated on the front cavity surface and the rear cavity surface of the semiconductor laser chip using the semiconductor laser cavity surface coating method of embodiment 1 or embodiment 2 to obtain, as shown in Figure 10 and Figure 11 .

[0137] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for coating a semiconductor laser cavity surface, characterized in that, The front cavity surface and the rear cavity surface of the laser chip are coated by using a coating device, and the method comprises the following steps: The front cavity surface of the laser chip is pre-cleaned, and a front protective layer is evaporated on the front cavity surface of the laser chip; The laser chip is flipped to the rear cavity surface, the rear cavity surface of the laser chip is pre-cleaned, and a rear protective layer is evaporated on the rear cavity surface of the laser chip; The laser chip is flipped to the front cavity surface, a first mixed gas is introduced into the ion source auxiliary device, and the front cavity surface of the laser chip is evaporated with the first mixed gas to form an anti-reflection film; wherein the first mixed gas comprises O2 and Ar, and the proportion of Ar in the first mixed gas is 5% to 20%; The laser chip is flipped to the rear cavity surface, and a high-reflection film is evaporated on the rear cavity surface of the laser chip.

2. The method according to claim 1, wherein The pre-cleaning of the front cavity surface of the laser chip specifically comprises the following steps: A second mixed gas is introduced into the ion source auxiliary device, the anode voltage of the ion source auxiliary device is set to 180 to 185 V, the anode current is set to 2.5 to 3.5 A, and the front cavity surface of the laser chip is pre-cleaned by using the ion source auxiliary device; wherein the second mixed gas comprises N2 and Ar, and the proportion of Ar in the second mixed gas is 0% to 10%.

3. The method according to claim 2, wherein The pre-cleaning time of the front cavity surface of the laser chip is 300 to 400 seconds.

4. The method of claim 1, wherein the semiconductor laser is a vertical external cavity surface emitting laser (VECSEL). The high-reflection film comprises, from the side close to the rear protective layer to the side far from the rear protective layer, a first low-reflection film, a first high-reflection film, a second low-reflection film, a second high-reflection film, a third low-reflection film, and a third high-reflection film; wherein the evaporation temperature used when evaporating the first high-reflection film, the second high-reflection film, and the third high-reflection film is 200 to 230 DEG C.

5. The method according to claim 4, wherein The material of the first low-reflection film is Al2O3, the materials of the second low-reflection film and the third low-reflection film are SiO2, and the materials of the first high-reflection film, the second high-reflection film, and the third high-reflection film are Ti3O5; the evaporation of the high-reflection film on the rear cavity surface of the laser chip specifically comprises the following steps: A first mixed gas is introduced into the ion source auxiliary device, the anode voltage of the ion source auxiliary device is set to 140 to 150 V, the anode current is set to 2.0 to 2.5 A, a first low-refraction film is evaporated at an evaporation temperature of 200 to 230 DEG C and an evaporation speed of 4.0 to 5.0 A / s until the thickness of the first low-refraction film reaches 120 to 130 nm; O2 is introduced into the ion source auxiliary device, the anode voltage of the ion source auxiliary device is set to 140 to 150 V, the anode current is set to 4.5 to 5.0 A, a first high-reflection film is evaporated at an evaporation temperature of 200 to 230 DEG C and an evaporation speed of 1.5 to 2.0 A / s until the thickness of the first high-reflection film reaches 130 to 140 nm; A second low-refraction film is evaporated at an evaporation temperature of 200 to 230 DEG C and an evaporation speed of 4.0 to 5.0 A / s until the thickness of the second low-refraction film reaches 220 to 230 nm; A second high-reflection film, a third low-refraction film, and a third high-reflection film are evaporated in sequence.

6. The method of claim 1, wherein the semiconductor laser is a distributed feedback (DFB) laser. Before the pre-cleaning of the front cavity surface of the laser chip, the method further comprises the following steps: The laser chip is cleaved into a bar, and the bar is sent into a coating equipment. The chamber of the coating equipment is vacuumed to 8.0×E -6 Torr, and the chamber temperature is set to 200-230℃. The bar is baked in the chamber for 30-60min.

7. The method of claim 1, wherein the semiconductor laser is a vertical external cavity surface emitting laser (VECSEL). The material of the front protective layer is SiN x The method of evaporating the front protective layer on the front cavity surface of the laser chip specifically comprises: The NH3 is introduced into the machine cavity of the coating equipment, and the flow rate of the NH3 is 10-15sccm; The N2 is introduced into the ion source auxiliary equipment, the anode voltage of the ion source auxiliary equipment is set to 180-185V, the anode current is 3.0-3.5A, the front protective layer is deposited at a deposition rate of 1.5-2.0A / s, and the deposition is continued until the thickness of the front protective layer reaches 80-90nm.

8. The method of claim 1, wherein the semiconductor laser is a vertical external cavity surface emitting laser (VECSEL). The material of the anti-reflection film is Al2O3; the method for depositing the anti-reflection film on the front cavity surface of the laser chip using the first mixed gas specifically comprises: The first mixed gas is introduced into the ion source auxiliary equipment, the anode voltage of the ion source auxiliary equipment is set to 140-150V, the anode current is 2.0-2.5A, the anti-reflection film is deposited at a deposition temperature of 200-230℃ and a deposition rate of 4.0-5.0A / s, and the deposition is continued until the thickness of the anti-reflection film reaches 100-110nm.

9. The method of claim 1, wherein the semiconductor laser is a vertical external cavity surface emitting laser (VECSEL). The material of the rear protective layer is SiN x The method for evaporating the rear protective layer on the rear cavity surface of the laser chip specifically comprises: The NH3 is introduced into the machine cavity of the coating equipment, and the flow rate of the NH3 is 10-15sccm; The N2 is introduced into the ion source auxiliary equipment, the anode voltage of the ion source auxiliary equipment is set to 180-185V, the anode current is 3.0-3.5A, the back protective layer is deposited at a deposition rate of 1.5-2.0A / s, and the deposition is continued until the thickness of the back protective layer reaches 90-95nm.

10. A semiconductor laser chip, characterized by The front cavity surface and the back cavity surface of the semiconductor laser chip are coated by using the semiconductor laser cavity surface coating method in any one of claims 1-9.

Images